WO2024170582A1

WO2024170582A1 - Assembly for casting molten metal comprising a sand casting mould, a short-shroud, and a mould / shroud coupling mechanism, casting installation and method for casting a molten metal part

Info

Publication number: WO2024170582A1
Application number: PCT/EP2024/053648
Authority: WO
Inventors: David Hrabina
Original assignee: Foseco International Ltd
Current assignee: Foseco International Ltd
Priority date: 2023-02-14
Filing date: 2024-02-13
Publication date: 2024-08-22
Anticipated expiration: 2025-08-14
Also published as: AU2024223622A1; EP4665521A1; CN222221130U; MX2025009364A; KR20250150033A; CN118492353A

Abstract

The invention refers to a kit-of-parts and an assembly comprising a sand casting mould (2) for casting metal parts, a short-shroud (9) comprising a short-shaft (10), and a mould ! shroud coupling mechanism (14). The mould (2) comprises a bore (7) extending over a bore length (d7) from a bore inlet to the inlet (6i) of a housing (6) in fluid communication with cavities defining the shape of the metal parts. The mould / shroud coupling mechanism (14) is configured for receiving and maintaining the short-shroud (9) in a shroud casting position with the short-shaft inserted in the bore (7) separated from the housing inlet §6i) by a shaft-free distance (d710 > 0), wherein k = d710 / d7 is preferably comprised between 0.2 and 0.8.

Description

ASSEMBLY FOR CASTING MOLTEN METAL COMPRISING A SAND CASTING MOULD, A SHORT-SHROUD, AND A MOULD / SHROUD COUPLING MECHANISM, CASTING INSTALLATION AND METHOD FOR CASTING A MOLTEN METAL PART

TECHNICAL FIELD

[0001] The current invention refers to a mould assembly comprising a sand casting mould, a short shroud, and a mould / shroud coupling mechanism for coupling the short shroud to the sand casting mould in a shroud casting position. The use of a short shroud rather than known long shrouds substantially reduces the cost of casting metal in a shrouded metal stream in foundry applications, because saving substantial amounts of expensive refractory material forming the shroud.

BACKGROUND OF THE INVENTION

[0002] In foundry, metal parts are produced by casting a metal from a nozzle of a ladle into a bore leading to a cavity of a sand casting mould defining the geometry of the part to be cast. One of the main challenges of such metal casting processes is avoiding the entrainment of air as the metal is cast into the bore. This can lead to defects, including air bubbles and oxide films, which result in cracks in the casting.

[0003] To avoid entrainment of air it is known in the art to protect molten steel from air entrainment and bi-film formation during the casting process by using a shroud, extending along a whole length of the bore. A sealing gasket can be applied to an inlet of the shroud to prevent air from being drawn into the metal stream at the contact interface between the ladle nozzle and the shroud. This gasket also has the advantage of protecting the nozzle and shroud from mechanical damage upon bringing them into contact, since ceramic materials are brittle. An outlet of the shroud is introduced in a housing, possibly provided with a filter unit to prevent solid particles to flow into the mould cavity. A mould I shroud coupling mechanism is used to ensure a reproducible and stable positioning of the shroud in the bore of the sand casting mould.

[0004] A system for casting molten metals is disclosed in EP3463715. This system includes,

• a sand casting mould comprising a casting cavity having an inlet and a bore extending between an upper surface of the mould and the inlet,

• a shroud comprising a shroud base and a hollow shaft, wherein the shroud base is located outside of the mould adjacent to the upper surface, and the hollow shaft is housed in the bore and is movable therein.

[0005] To form a sealing contact between the nozzle and the shroud base, EP3463715 B1 proposes a mould / shroud coupling mechanism comprising a lifting mechanism located at the upper surface of the mould. The lifting mechanism comprises concentrically arranged first and second collars, wherein the first collar is fixed to the upper surface of the mould and the second collar is rotatably coupled to the upper surface of the mould and supports the shroud base of the shroud. A bayonet system comprising a follower engaged in a ramped slot allows the second collar to be lifted relative to the upper surface of the mould by rotation, thus causing a linear motion of the shroud. The rotation of the bayonet system is carried out by an operator. Once the shroud base is in contact with the nozzle, the lifting mechanism does not move anymore during the whole duration of the casting operation, ensuring a stable and reproducible process. The lack of moving liberty of the shroud during casting can, however, also be a problem, since the flow of molten metal through the shroud causes vibrations which propagate to the contact area between the nozzle and the shroud base, which can cause wear or even cracks in the refractory materials. Furthermore, fixing a bayonet requires the intervention of a human operator, thus increasing cost and safety risks when operated at a height over the workshop floor.

[0006] To solve this issue, an alternative mould / shroud coupling mechanism is proposed in PCT/EP2022/072007 wherein the first and second collars are coupled by means of springs, such that upon application of a vertical load onto the shroud sitting on the first collar, the shroud is driven downwards in the bore forming a dynamic seal between nozzle and shroud inlet as well as between the shroud outlet and the filter housing.

[0007] Casting metal parts in foundry applications with a shroud as described above is highly advantageous in that air entrainment onto the shrouded metal stream is substantially reduced. This solution, however, increases the cost of the process, since the shrouds are made of refractory materials which are more expensive than any material used in sand casting moulds.

[0008] The present inventions proposes a solution for producing metal parts in foundry, which gathers the advantages of shrouded casting assemblies as discussed supra, at a much lower cost.This and other advantages of the present invention are described in more details in continuation..

SUMMARY OF THE INVENTION

[0009] The appended independent claims define the present invention. The dependent claims define preferred embodiments. In particular, the present invention concerns a kit-of-parts for casting molten metals comprising a short shroud, a sand casting mould, and a mould I shroud coupling mechanism?

[0010] The short shroud comprises,

• a shroud base attached to a proximal end of a short-shaft of shaft length (d10) measured along a Z-axis, and having,

• a shroud bore extending along the Z-axis from a shroud inlet opening at the shroud base to a shroud outlet opening at a downstream end of the short-shaft, wherein the sand casting mould comprises,

• a casting cavity having a cavity inlet,

• a housing selected among a filter housing and a diverter housing, having a housing outlet in fluid communication with the cavity inlet and a housing inlet (6i) in fluid communication with,

• a bore extending over a bore length (d7) along the Z-axis between a bore inlet opening at an upper surface of the sand casting mould and a bore outlet opening at a downstream end at a level of the housing inlet, the downstream end comprising a bore choke, wherein • the bore choke forms a bore constriction defining the bore outlet which opens in the housing with a reduction of a bore diameter of at least 10% along the Z-axis in a flow direction, wherein the mould / shroud coupling mechanism comprises,

• a seat member configured for receiving the shroud base and holding the short-shroud in a shroud casting position wherein the downstream end of the short-shaft (10) is inserted in the bore,

[0011] The shaft length (d10) is shorter than the bore length (d7), (i.e., d10 < d7), such that in the shroud casting position, the downstream end of the short-shaft is separated from the housing inlet by a shaft-free distance (d710) which is proportional to the bore length (d7) by a proportionality factor (k) (i.e., d710 = k d7), wherein the proportionality factor (k) is preferably at least 20% (i.e., k > 0.2), more preferably at least 35% (i.e., k > 0.35), and wherein the proportionality factor (k) is preferably not more than 90% (i.e., k < 0.9), more preferably not more than 80% (i.e., k < 0.8), more preferably more than 70% (i.e., k < 0.7), most preferably not more than 60% (i.e., k < 0.6). In terms of absolute values, a penetration depth (= d7 - d710) of the short-shaft (10) in the bore (7) at the shroud casting position is preferably at least equal to 3 cm, (i.e., d7 - d710 > 3 cm) more preferably at least equal to 5 cm (i.e., d7 - d710 > 5 cm), most preferably at least equal to 10 cm (i.e., d7 - d710 > 10 cm). With 5 cm < d7 - d710 < 3 cm, it is preferred to provide a sealing material (e.g. a gasket) between the bore (7) and the short-shaft (10) to ensure air tightness of the gap formed between the two.

[0012] In a preferred embodiment, the mould I shroud coupling mechanism comprises:

• a base member fixed relative to the upper surface,

• a seat member configured for receiving the shroud base and holding the short-shroud (9) in the shroud casting position,

[0013] The base member and seat member each comprises a central hole aligned with one another to define a lead-in towards the bore for the shroud. The seat member is coupled to the base member by at least one compliant element such that the seat member is separated from and movable relative to the base member from a seat rest position to a seat casting position upon application of a load parallel to the Z-axis onto the seat member which deforms the at least one compliant element so as to drive a short-shroud sitting in the seat member to reach the shroud casting position.

[0014] The compliant element preferably comprises,

• one or more resilient elements including a spring, preferably a spiral spring, or an elastomeric material at a process temperature, extending between the seat member and the base member, or

• a free-flowing material enclosed in one or more bags configured for deforming upon application of the load onto the seat member.

[0015] The mould I shroud coupling mechanism preferably comprises at least three resilient elements, preferably at least three spiral springs, extending between the seat member and the base member. The at least three resilient elements are preferably equally spaced apart around a circumference of the central holes of the seat member and the base member.

[0016] To strengthen the wall of the bore, it is preferably lined by a lining over at least a portion of the bore length (d7), preferably over the whole bore length (d7). The lining material can be selected from chamotte (or grog) preferably composed of high-fired clay, sand core material, or cellulose material.

[0017] The present invention also concerns a sand casting mould assembly comprising, the short-shroud and the sand casting mould as defined supra, with the shroud base of the short-shroud sits on the seat member with the short-shaft of the short-shroud inserted in the bore with the downstream end separated from the housing inlet.

[0018] In a preferred embodiment, the mould I shroud coupling mechanism comprises compliant elements as discussed supra. In this embodiment, the mould I shroud coupling mechanism is configured,

• at the seat rest position, to maintain the downstream end of the short-shaft separated from the housing inlet by a distance greater than the shaft-free distance (d710) and

• at the seat casting position, to maintain the short-shroud at the shroud casting position, with the downstream end of the short-shaft separated from the housing inlet by a distance substantially equal to the shaft-free distance (d710), upon application of the load parallel to the Z-axis.

[0019] The present invention also concerns a casting installation comprising,

• the short-shroud and the sand casting mould as defined supra,

• a ladle comprising a nozzle provided at a base of the ladle for dispensing molten metal out of the ladle, wherein the nozzle is configured for reversibly and sealingly engaging into the shroud inlet of the short-shroud. The ladle is configured for being displaced relative to the sand casting mould, such as o to position the nozzle substantially aligned along the Z-axis over the mould / shroud coupling mechanism and o to be lowered along the Z-axis until the nozzle is engaged in the shroud inlet of the short-shroud which is in the shroud casting position with the downstream end of the short-shaft being outside of and separated from the housing inlet by the shaft-free distance (d710).

[0020] In a preferred embodiment, the casting installation comprises a ladle / shroud coupling mechanism configured for reversibly gripping the short-shroud to the nozzle, preferably without forming a seal between the shroud inlet and the nozzle. The ladle I shroud coupling mechanism comprises, o a base adapter, fixed relative to the shroud base of the short-shroud, the base adapter comprising holding means, and o a nozzle adapter, fixed relative to the base of the ladle or to the nozzle, and configured for engaging the holding means of the base adapter to reversibly lock the short-shroud (9) to the nozzle in a locked position.

[0021] For example, the holding means of the base adapter can comprise holding pegs and the nozzle adapter can comprise either,

• fastening hooks configured for reversibly engaging the holding pegs and are preferably configured to be self-engaging with the holding pegs, or

• a bayonet coupling element configured for interacting with the one or more holding pegs to reversibly lock the shroud to the nozzle in the locked position.

[0022] In a preferred embodiment, the mould I shroud coupling mechanism comprises compliant elements as discussed supra. In this embodiment, the downstream end of the short-shaft reaches the casting position separated from the housing inlet by the shaft-free distance (d710) by applying the load parallel to the Z-axis onto the seat member.

[0023] The present invention also concerns a method for casting a molten metal with the casting installation of any one of claims 8 to 11 , comprising the following steps.

• lowering the ladle along the Z-axis until the nozzle is engaged in sealing contact in the shroud inlet and the short-shroud, with the shroud base sitting on the seat member is in the shroud casting position, with the downstream end being outside of and separated from the housing inlet by the shaft-free distance (d710),

• allowing the molten metal to flow from the ladle to the casting cavity through the nozzle the short-shroud, and the housing.

[0024] In a preferred embodiment, the mould I shroud coupling mechanism comprises compliant elements as discussed supra. In this embodiment, the ladle is lowered along the Z-axis until the nozzle) engaged in the shroud inlet applies a load parallel to the Z-axis onto the shroud base sitting on the seat member, thus moving along the Z-axis the seat member relative to the base member against the compliant elements, and forming a sealing contact between the nozzle and the shroud inlet of the short-shroud which is in the shroud casting position, with the downstream end being outside of and separated from the housing inlet by the shaft-free distance (d710).

[0025] In this embodiment, the short-shroud is first accommodated in the sand casting mould with the seat member receiving the shroud base and holding the short-shroud with the downstream end being outside of and separated from the housing inlet by a distance greaterthan the shaft-free distance (d710) to form a sand casting mould assembly as described supra. The nozzle us then engaged into the shroud inlet by lowering vertically the ladle, and forming the sealing contact between the nozzle and the short-shroud by further lowering the ladle for the nozzle to apply the load onto the shroud base to move the short-shroud towards the housing inlet to the shroud casting position with the downstream end being separated from the housing inlet by the shaft-free distance (d710).

[0026] Alternatively, the nozzle ican be engaged into the shroud inlet of the short-shroud and the short-shroud is gripped to the nozzle with the ladle / shroud coupling mechanism by engaging: • the holding means of the base adapter fixed to the shroud inlet of the short-shroud with,

• the nozzle adapter fixed to the base of the ladle or to the nozzle. such as to lock the short-shroud (9) to the nozzle (12) in a locked position,

[0027] The short-shroud locked to the nozzle can be positioned substantially aligned along the Z-axis above the mould / shroud coupling mechanism and lowered along the Z-axis until the shroud base sits on the seat member with the short-shroud in the bore and the downstream end separated from the housing inlet by a distance greater than the shaft-free distance (d710). At this point, the ladle can be lowered further along the Z-axis until the short-shroud reaches the shroud casting position with the downstream end (10d) being outside of the housing inlet separated therefrom by the shaft-free distance (d710), thereby forming the sealing contact between the short-nozzle and the short-shroud. Metal casting can start.

BRIEF DESCRIPTION OF THE FIGURES

[0028] The invention is explained in continuation in detail with reference to the following drawings.

Figure 1 shows steps of a metal casting method with the casting installation according to an embodiment of the invention.

Figure 2 shows steps of a metal casting method with the casting installation according to an alternative embodiment of the invention comprising a ladle / shroud coupling mechanism (140).

Figure 3 shows a perspective view of an embodiment of a mould I shroud coupling mechanism suitable for the invention.

Figure 4 shows a cross-section along the lines IV-IV in Figure 3, of the mould I shroud coupling mechanism and of the short-shroud accommodated therein.

Figure 5 shows a perspective view of a casting installation according to the invention, wherein the nozzle of the ladle is located vertically above the short-shroud in the shroud casting position, wherein the shroud base is received in the seat member of the mould I shroud coupling mechanism. The ladle is not represented for sake of clarity.

Figure 6 shows a cross-sectional view of the casting installation of Figure 5, wherein the nozzle is reversibly and sealingly engaging into the shroud base, in spite of a slight in coaxiality misalignment with the bore axis.

Figure 7a-7c show cross-sectional views of the mould / shroud coupling mechanism and the nozzle in a casting installation according to the invention, (7a) as the ladle moves above the mould, aligning the nozzle with the shroud inlet, (7b) as the ladle is lowered to bring the nozzle close to or in contact with the shroud inlet, and (7c) as the ladle is further lowered to press the compliant elements to form a sealing contact..

Figure 8 shows a perspective bottom view of the seat member of the mould I shroud coupling mechanism according to an embodiment of the invention. Figure 9a show cross-sectional views of the ladle / shroud coupling mechanism in the casting installation according to an embodiment of the invention, before gripping the short-shroud to the nozzle.

Figure 9b shows a cross-sectional view of the ladle / shroud coupling mechanism in the casting installation of Figure 9a, with the short-shroud coupled, albeit not sealed to the nozzle and holding the short-shroud vertically above the mould / shroud coupling mechanism.

Figure 9c shows a cross-sectional view of the ladle / shroud and mould / shroud coupling mechanism in the casting installation of Figure 9a, wherein the base adapter is received in the seat member of the mould / shroud coupling mechanism holding the short-shroud, and wherein the compliant element is in a rest state.

Figure 9d shows a cross-sectional view of the ladle / shroud and mould / shroud coupling mechanism in the casting installation of Figure 9a, wherein the ladle is further lowered vertically with the short-shroud gripped to the nozzle until the nozzle applies a load onto compliant members, thus forming a sealing contact between the nozzle and the short-shroud.

Figure 10 shows a view of the ladle / shroud coupling mechanism in the casting installation of Figure 9a, before gripping the short-shroud in the shroud casting position to the nozzle.

Figure 11 shows a view of the ladle / shroud coupling mechanism in the casting installation of Figure 10, with the short-shroud gripped to the nozzle in the shroud casting position.

Figure 12 shows a detailed cross-sectional view of the ladle / shroud coupling mechanism of Figure 10.

Figure 13 shows a detailed cross-sectional view of the ladle / shroud coupling mechanism of Figure 1 1 .

Figure 14 shows a detailed view of the ladle / shroud coupling mechanism in the casting installation according to the invention, with the short-shroud coupled to the nozzle and vertically translating (up or down) the ladle and the short-shroud coupled thereto above the mould.

Figure 15 shows a detailed cross-sectional view of the casting installation comprising the ladle / shroud coupling mechanism according to the invention, with the short-shroud gripped to the nozzle and in the shroud casting position.

Figure 16a-16f shows various embodiments of the compliant element in the invention.

Figure 17a-17h shows various embodiments of the kit-of-parts of the invention.

Figure 18a shows an example of long-shroud of the prior art, with a long shaft of long shaft length d10L.

Figure 18b shows an example of short-shroud of the invention with a short shaft of shaft length d10. Figure 18c shows a top view of a long-shroud and a short-shroud according to Figures 18a and 18b.

Figure 18d graphically shows the material weight saving as a function of the shaft length (d10) of the shrouds illustrated in Figurres 18a and 18b, expressed in terms of the proportionality factor, k, defined as k = d10 / d10L, with k =0 (i.e., d10 = 0) to 100% (i.e., d10 = d10L).

DETAILED DESCRIPTION OF THE INVENTION

[0029] In a first aspect, the invention concerns a kit-of-parts for casting molten metals comprising a short-shroud (9), a sand casting mould (2), and a mould I shroud coupling mechanism. as illustrated e.g., in Figures 17(a) to 17(c).

[0030] As illustrated e.g., in Figures 4, 9a and 17a to 17h, the short-shroud (9) comprises a shroud base (11) attached to a proximal end of a short-shaft (10) of shaft length (d10) measured along a Z-axis. The short-shroud has a shroud bore extending along the Z-axis from a shroud inlet (9i) opening at the shroud base (11) to a shroud outlet (9o) opening at a downstream end (10d) of the short-shaft. The short-shaft (9) suitable for the present invention differs from prior art shrouds in that the short-shaft (10) has a substantially shorter shaft length (d10) as prior art shrouds, as discussed in detail below.

[0031] As shown e.g., in Figures 5, 6, and 17a to 17h, the sand casting mould (2) comprises,

• a bore (7) in fluid communication with the cavity (3),

• a housing (6) comprising a housing inlet (6i) and a housing outlet (6o) and

• one or more casting cavities (3),

[0032] The bore (7) extends over a bore length (d7) along the Z-axis between a bore inlet opening at an upper surface (8) of the sand casting mould and a bore outlet opening at a downstream end. The downstream end comprises a bore choke (7c) which forms a bore constriction defining the bore outlet which opens in the housing (6) with a reduction of a bore diameter of at least 10% along the Z-axis in a flow direction.

[0033] The housing (6) is selected among a filter housing and a diverter housing. In both cases, the housing comprises a single housing inlet (6i) in fluid communication with the bore outlet, and one or more housing outlets (6o) in fluid communication with the one or more cavities (3). It is configured for distributing the flow of the molten metal traversing the housing from the housing inlet (6i) to the one or more housing outlets (6o) connected to the casting cavities. The housing (6) can be a filter housing comprising a filter element for filtering and eliminating solid impurities in the flow of molten metal.

[0034] The one or more casting cavities (3) have a geometry defining the geometry of the part to be cast. Each of the one or more casting cavities (3) comprises a cavity inlet (4) in fluid communication with the housing outlet (6o). Figures 5 and 6 show a mould (2) comprising a single cavity (3), whilst Figures 15 and 17a to 17h show moulds comprising several cavities (3).

[0035] In use, molten metal is cast through the bore inlet, it flows into the housing and fills the one or more cavities (3). If the molten metal is cast directly into the bore (7) without any specific protection from exposure to the atmosphere, oxide inclusions are formed and entrained in the flowing melt, forming defects in the cast metal part. This problem was solved to a great extent by using a shroud which extends from the bore inlet all the way down the bore length (d7) into the housing (6) through the housing inlet (6i), thus forming a continuous flow path substantially sealed from the atmosphere extending from the ladle to the cavity (3). This is described e.g., in EP3463715 and in PCT/EP2022/072007 discussed supra, and such shrouds are available on the market as Hollotex® from Foseco. The shroud must sit on a mould I shroud coupling mechanism to ensure that it is repeatedly and stably maintained in a shroud casting position. As the kit-of-parts of the present invention also comprises a shroud, namely a short-shroud, it must also comprise a mould / shroud coupling mechanism (14) to accommodate and maintain the short-shroud (9) in the shroud casting position.

[0036] The mould / shroud coupling mechanism (14) suitable for the present invention comprises a seat member (15) configured for receiving the shroud base (11) and holding the short-shroud (9) in a shroud casting position wherein the downstream end (10d) of the short-shaft (10) is inserted in the bore.

[0037] The gist of the present invention is that the short-shaft (10) has a shaft length (d10) which is shorterthan the bore length (d7), i.e., d10 < d7. It follows that contrary to the prior art shrouded systems discussed supra, in the shroud casting position, the downstream end (10d) of the short-shaft is separated from the housing inlet (6i) by a shaft-free distance (d710) which is greater than zero. The shaft-free distance (d710) can be defined as being proportional to the bore length (d7) by a proportionality factor (k < 1). For example, the proportionality factor (k) can be at least 30%, preferably at least 40%, more preferably at least 50% (i.e., d710 = k d7, preferably with k > 0.3, preferably with k > 0.4, more preferably with k > 0.5).

[0038] To ensure a tight interface between the short-shaft (10) and the bore wall, the short-shaft (10) must penetrate at least over a certain distance in the bore (7). For example, the proportionality factor (k) can be not more than 90% (i.e., k < 0.9), preferably not more than 80% (i.e., k < 0.8), more preferably more than 70% (i.e., k < 0.7), most preferably not more than 60% (i.e., k < 0.6). The proportionality factor (k) being smaller than unity requires the short-shaft (10) to have a length (d10) such that it does not penetrate the bore (7) over the whole bore length (d7). A penetration depth of the short-shaft (10) in the bore (7) at the shroud casting position can be defined as being equal to (d7 - d710). The penetration depth is preferably at least equal to 3 cm, (i.e., d7 - d710 > 3 cm) more preferably at least equal to 5 cm (i.e., d7 - d710 > 5 cm), most preferably at least equal to 10 cm (i.e., d7 - d710 > 10 cm).

[0039] A shroud having a short-shaft (10) of shaft length (d10) as shown in Figure 18b, smaller than the shaft length (d10L) of prior art shrouds (which must be greater than d7) as shown in Figure 18a, is advantageous in that substantially less refractory material is required for producing a short-shroud than a state-of-the-art shroud. The cost of the most expensive expendable accessory of the shrouded metal casting foundry process is reduced proportionally. Also the the weight of the short-shroud is reduced proportionally, which facilitates handling thereof. Another advantage of short-shrouds (9) is illustrated in Figure 2, wherein at station (1 a) a short-shroud (9) is coupled to the nozzle (12) below the ladle (103) which is moved around the workshop. Moving the ladle with a short-shroud (9) coupled thereto is substantially easier than with a long shroud as in the prior art (cf. e.g., PCT/EP2022/072007). SHORT-SHROUD (9)

[0040] As shown in Figure 15, during casting, the molten metal contained in a ladle (103) is dispensed through a nozzle (12) located in a lower portion of the ladle (103), whence it flows into the cavities (3) through the short-shroud (9), the shroud-free distance (d710) of the bore (7), the housing (6), and the feeding channels (5). The short-shroud (9) comprises a shroud base (11) attached to a proximal end of a shaft (10) which is hollow with a shroud bore opening at a shroud inlet (9i) in the shroud base and extending to a shroud outlet (9o) opening at a distal end (10d) of the hollow shaft.

[0041] The gist of the present invention is to replace long shrouds (9L) described in the prior art (e.g., EP3463715 and PCT/EP2022/072007) extending along the whole bore length (d7) from the bore inlet to the housing inlet (6i), by a short-shroud (9) whose shroud outlet (9o) is separated from the housing intlet (6i) by a shaft-free distance (d710). This reduction of the shaft length (d10) yields corresponding savings of expensive material and thus costs reduction, whilst keeping the advantages described in the foregoing documents.

[0042] The shroud base (11) of the short-shroud (9) of the present invention is identical to the shroud base of long-shaft shrouds described in the cited prior art. The shroud inlet (9i) is thus shaped as to receive the nozzle (12) and to form therewith a sealed interface. As for the long shrouds of the prior art, the nozzle (12) of the ladle (103) must be sealingly engaged in the shroud inlet (9i) to prevent air from being sucked through the interface the interface between the nozzle and the shroud inlet (9i) into the flow of molten metal and, at the same time, to prevent molten metal from leaking therethrough. The sealing contact between nozzle (12) and the shroud inlet (9i) is made possible by mating the complementary geometries of the nozzle tip and the shroud inlet. The shroud inlet can have a geometry of a cup, either curved ortrunco-conical, and the nozzle tip can have a corresponding protruding mating geometry. Pressure can be applied at the interface through the movement along the Z-axis of the ladle (103) which drives the nozzle tip into the mating shroud inlet (9i). If required, a sealing joint or gasket can be applied to ensure an enhanced sealing of the interface. Static seals or dynamic seals between the moving nozzle (12) and the shroud inlet (9i) can be formed . Dynamic seals can include intumescent sealing materials, e.g. a gasket lodged in the shroud inlet, as described for sliding gates in WO2013/088249 A2. As represented in Fig. 17e-17h, the shroud bore of the short-shroud (9) may be equipped with a lining insert (9L). Such lining insert (9L) is advantageously crafted from an expendable material, selected for its durability under the specific conditions of a single sand casting operation and its efficacy in keeping the shroud bore largely free from molten metal residues. This expendable material could, for example, be a composition of cellulose, chosen grades of minerals, and a binder. As an alternative, the insert may be composed of a refractory material. The thickness of this lining insert (9L) is generally in the range of 3mm to 10mm. This is in contrast to the wall thickness of the short shroud (9) itself, which is typically between 15mm and 20mm. With this configuration, the short-shroud (9) can be efficiently reused across multiple sand casting operations. This is made possible by the simple replacement of the lining insert (9L) following each operation, enabling the repeated use of a singular short-shroud (9). Moreover, the lining insert (9L) advantageously includes an integrated gasket (9g) designed to seamlessly interface with the nozzle (12) of the ladle (103). However, the integration of a gasket (9g) may not be necessary if the lining insert (9L) inherently possesses the requisite mechanical properties to accommodate the nozzle (12). This is particularly applicable when the insert comprises materials like cellulose. Additionally, to enhance the short-shroud's (9) resistance to molten metal leakage and thermal shocks, a metal can (not depicted in the figures) may line its outer surface. The lining insert (9L) offers versatile mounting options. It can be pre-assembled onto the short-shroud (9) prior to its integration into the sand casting mould assembly, as demonstrated in Figures 17e and 17f. Alternatively, the insert (9L) can be mounted onto the short-shroud (9) subsequent to the short-shroud's installation within the sand casting mould assembly, a process illustrated in Figures 17g and 17h.

[0043] The short-shroud (9) of the present invention differs from the long shrouds (9L) of the cited prior art in that the long-shaft of long shaft length, d10L > d7 of the latter, is replaced by a short-shaft (10) of shaft length d10 < d7 < d10L. The shaft length of both long and short-shrouds is defined as the portion of the shroud comprising the shroud outlet (9o) and whose bore has a substantially constant hydraulic diameter (Dh10), wherein the hydraulic diameter is defined as a ratio 4A / P, wherein A is the cross-sectional area and P the perimeter of the bore. The hydraulic diameter (Dh) of a circular crosssection is equal to the diameter of the bore.

[0044] Figures 18a and 18c show an example of long-shroud of the cited prior art, with a simplified geometry, comprising a shroud base (11) with a cylindrical portion of diameter (Dhi) followed by a trunco-conical shaped shroud inlet (9i) with smaller diameter (Dh10) attached to a cylindrical long-shaft (10) of length (d10L) with constant bore diameter (Dh10). This simplified geometry is reasonably representative of actual shroud geometries and suffices forthe purpose of showing the saving in material when shortening the shaft length (d10). The wall thickness (tw) is constant. Figure 18b shows a corresponding short-shroud (9) according to the present invention, with identical shroud base (11) and with a short-shaft of same diameter but shorter shroud length (d10), with d10 = a x d10L. Examples of values of the different dimensions of the long-shroud (9L) are listed in Table 1 , with corresponding calculated weight (m9L) considering a refractory material of density, p = 2.4 g I cm³. With a shaft-length of 100 cm, the long-shroud (9L) of Figure 18a weighs about 11 kg.

Table 1: examples of values of the dimensions of the long shroud of Figure 18a

[0045] Figure 18b shows a corresponding short-shroud (9) according to the present invention. Since the short-shroud (9) differs from the long-shroud of Figure 9a solely by the shorter shaft length d10 < d10L, the top view of the shroud of Figure 9c is identical for both long- and short-shrouds of Figures 9a and 9b. The shaft length (d10) of the short-shaft (10) according to the invention is shorter than the long shaft length (d10L) of the long-shroud. The shroud length (d10) can be expressed as being proportional to the long shaft length (d10L) by a proportionality factor (a) as, d10 = a x d10L < d10L, with a < 1 , and with a preferably comprised between 0.2 and 0.8 (as indicated in Figure 18a), more preferably between 0.35 and 0.6. Figure 18d illustrates graphically the relative weight reduction ((m9L - m9) I m9L) between the weight (m9) of the short-shroud (9) and the weight (m9L) of the long-shroud (9L) as a function of the proportionality factor, a = d10 / d10L. The light shaded area identifies the preferred range 0.2 < a < 0.8 (i.e., d10 = 20 to 80 cm) yielding a weight reduction between 75 and 20%, respectively. The short-shroud (9) therefore weighs between 2 and 7.9 kg instead of 11 kg. The dark shaded area identifies the more preferred range, 0.35 < a < 0.6 (i.e., d10 = 40 to 60 cm), yielding a weight reduction between 60 and 40%, respectively. The short-shroud (9) therefore weighs between 3.9 and 6.4 kg instead of 11 kg. This has the advantage of reducing the cost of the dispensable shrouds and also greatly eases handling of the shrouds by the operators.

[0046] The short-shroud (9) is made of a refractory material, such as for example fused silica, aluminagraphite materials, or other materials well known in the art. The outer wall of the shroud base (11) can have a conical shape with sloping shoulders (23) which rest on the seat member (15). In one embodiment, the shoulder rests on a filling (22) filling up a space between a sleeve of the seat member (15) and the shroud base as shown in Figure 4. Alternatively, the shoulder of the shroud rests directly on the seat element, as shown in Figures 9c, 9d 12, and 13.

[0047] The main goal of the long-shaft of the long-shroud (9L) of the cited prior art, is to span the distance separating the tip of the nozzle (12) from the housing inlet (6i), to prevent the flowing metal melt from contacting air between the ladle (103) and the cavity (3) of the mould (2). Protecting the molten melt from contact with air can also be achieved with a short-shroud (9), whose short-shaft does not reach the housing inlet (6i), separated therefrom by the shaft-free distance (d710) by ensuring a sealed contact between the short-shaft (10) and the bore (7).

[0048] A simple way of forming a seal between the short-shaft (10) and the bore (7) is to dimension the short-shaft (10) so as to leave only a thin gap between the short-shaft (10) and the wall of the bore (7) when the short-shroud (9) is at the shroud casting position. Upon filling the bore (7) with molten metal as it flows through the nozzle (12) and short-shroud (10), some metal flows into the gap between the short-shaft (10) and the wall of the bore (7) which is cold, and freezes forming a solid layer sealing the bore (7) from the atmosphere. To enhance the sealing, a sealing gasket or a sealing material can be provided to seal the gap from the atmosphere. Again, beside sealing materials well known in the art and, in particular if a mould/shroud coupling mechanism (14) comprising compliant or resilient elements, a dynamic seal can be formed using intumescent materials as described in WO2013/088249.

[0049] The shroud outlet (9o) may comprise one or more apertures for dispensing molten metal in the bore (7).

MOULD/SHROUD COUPLING MECHANISM (14)

[0050] For receiving and maintaining the short-shroud (9) in the shroud casting position during the duration of a casting operation, the mould according to the invention is equipped with a mould / shroud coupling mechanism (14). The type of mould / shroud coupling mechanism is not critical for the present invention, as long as it fulfils the dual function of receiving the short-shroud (9) and of maintaining it in the shroud coupling position during the whole duration of the casting operation. The following types of mould I shroud coupling mechanisms (14) are, however, preferred: (1) with compliant elements, and (2) lifting coupling.

MOULD / SHROUD COUPLING MECHANISM (14) - WITH COMPLIANT ELEMENTS

[0051] A preferred type of mould I shroud coupling mechanism (14) comprises compliant elements (17) as shown e.g., in Figures 3 and 4. As shown in Figure 6, the mould I shroud coupling mechanism (14) is configured for accommodating the shroud (9) of a casting installation (1) in a shroud casting position defined as the short-shaft (10) being accommodated in the bore (7) with the distal end (10d) thereof separated from the housing inlet (6i) by the shaft-free distance (d710). During a casting operation, the molten metal flows out of the ladle through the nozzle (12) sealingly engaged in the shroud inlet (9i) in the shroud casting position. The molten metal then flows through the short-shaft (10) and along the bore (7) before entering into the housing (6) via the bore outlet at the bore choke (7c) and flows out of the housing through the housing outlet (6o) into the feeding channels to fill the casting cavities (3).

Base Member (16) and Seat Member (15)

[0052] As shown in Figures 3 and 4, the mould / shroud coupling mechanism (14) comprises a base member (16) fixed to the upper surface (8) of the mould (2), and a seat member (15) configured for receiving the shroud base (11) and holding the short-shroud (9) in the shroud casting position. As shown in Figures 3 and 4, the seat member (15) is coupled to the base member (16) by at least one compliant element (17) such that the seat member (15) is separated from the base member (16) when the mould / shroud coupling mechanism (14) is in a rest state, and movable relative to the base member (16) and preferably towards the base member (16) upon application of a load onto the seat member (15) along the Z-axis, which deforms the at least one compliant element (17) to reduce an rest distance (hO) to a casting distance (hi) separating the seat member (15) from the base member (16). The compliant elements (17) are described in more detail in continuation and are defined as elements that deform significantly along the Z-axis when a load is applied along the Z-axis.

[0053] The compliant elements (17) are configured for deforming under application of the vertically (i.e., along the Z-axis) and downwardly oriented load by the nozzle (12) of the ladle (103) onto the shroud base (11) received in the seat member (15), to drive both seat member (15) and short-shroud (9) down from a rest distance (hO) from the bore inlet to a casting distance (hi < hO), wherein the short-shroud (9) reaches the shroud casting position with the shroud outlet (9o) separated from the housing inlet (6i) by the shaft-free distance (d710). Upon releasing the load along the Z-axis from the short-shroud (9) and seat member (15), the seat member can either return to its rest distance (hO) from the bore inlet, if the compliant elements (17) are elastic elements; remain at the casting distance (hi) if the compliant elements (17) are plastic elements, or return with delay either at the rest distance (hO) or at some point between the casting and rest distances (hi , hO) if the compliant elements (17) are viscoelastic elements. [0054] With the preferred embodiment of the mould / shroud coupling mechanism (14) comprising compliant elements (17), it is not necessary to manually adapt the position of the short-shroud (9) received in the seat member (15) relative to the nozzle (12) to engage the shroud inlet (9i) with the nozzle (12) of the ladle (103). In one embodiment of the present invention, the short-shroud is coupled to the mould at the rest distance (hO) from the bore inlet, i.e., with the shroud base resting on the seat member (15) of the mould / shroud coupling mechanism (14), with the short-shaft (10) housed in the bore (7) and the shroud outlet (9o) separated from the housing inlet (6i) by a distance larger than d710 (the shroud outlet (9o) is actually separated by a distance [d710 + (hO - hi)] from the housing inlet (6i)). At the rest state, the shroud base (11) rests on the seat member (15) which is maintained at the rest distance (hO) from the base member (16) by the reaction force of the so biased compliant element (17). The nozzle (12) of the ladle (103) is lowered to engage the shroud inlet (9i) simply by first moving the ladle to align it along the Z-axis with and above the shroud inlet (9i) and subsequently lowering the ladle (103) along the Z-axis until the nozzle engages the shroud inlet (9i), as illustrated in Figures 7a and 7b. In Figure 7a, the nozzle is aligned along the Z-axis with and located at a distance from the shroud inlet (9i). Then, the ladle is lowered i.e., moved downwardly along the Z-axis towards the shroud base (11) such that the nozzle engages the shroud inlet (9i) of the shroud, as illustrated in Figure 7b. At this stage, the nozzle and the shroud inlet (9i) are not coupled so as to form a sealing contact. To sealingly engage the nozzle into the shroud inlet (9i) and prevent air and molten metal from leaking through the gap between the nozzle and the shroud inlet (9i), the ladle is then further lowered as illustrated in Figure 7c, such that the nozzle contacts and applies a load along the Z-axis onto the shroud base (11) resting on the seat member (15) of the mould I shroud coupling mechanism (14), causing the seat member (15) to move towards the base member (16) from the rest distance (hO) to the casting distance (hi), by deforming the compliant element (17) so that, on the one hand,

• the a sealing contact can be formed between the nozzle and the shroud inlet (9i) and, on the other hand,

• the short-shroud (9) reaches the shroud casting position with the shroud outlet (9o) being separated from the housing inlet (6i) by the shaft-free distance (d710).

[0055] As shown in Figure 7c, the movement of the seat member (15) relative to the base member (16) driven by the downward translation of the ladle and rendered possible by the deformation of the compliant elements (17) reduces the distance by (hO - hi) between the seat member (15) and the base member (16), moving from the rest distance (hO) to the casting distance (hi) (with hi < hO).

[0056] Another advantage of the mould / shroud coupling mechanism (14) comprising compliant elements (17) is to absorb energy generated by movements between the nozzle and short-shroud caused e.g., by impacts upon lowering the ladle (103) or by vibrations during the casting operation. This reduces wear caused by friction between moving elements.

[0057] The mould / shroud coupling mechanism (14) in the mould of the invention preferably allows for also compensating a lateral and / or a tilting misalignment between the nozzle and the shroud inlet (9i), as shown in Figure 6. Lateral misalignments can occur when lowering down the ladle for engaging the nozzle into the shroud inlet (9i). Without compliant element (17) in the mould / shroud coupling mechanism (14) as is the case to date, a lateral misalignment can prevent the formation of a sealing contact between the nozzle and the shroud inlet (9i) or may cause important material stresses to compensate this misalignment for establishing the sealing contact. In the present invention, lateral misalignment is compensated by the the compliant element, thereby reducing material stresses and potential failures in the casting installation.

[0058] As illustrated in Figures 3, 4 and 5, the base member (16) and seat member (15) of the mould / shroud coupling mechanism (14) according to the invention, can each comprise a central hole aligned with one another and with the bore inlet to define a lead-in path towards the bore (7) for the short-shroud (9). In Figures 3, 4 and 5, the base member (16) has a central hole (20) which is circular and forms a lead-in path to the bore (7) through which the short-shaft (10) of the short-shroud (9) can penetrate into the bore (7) until the shroud base (1 1) rests on the seat member (15) which is at rest position, as shown in Figure 4. As will be discussed below, the short-shroud can be introduced into the bore (7) by a human operator, as shown in Figure 1 (1 a), or by lowering the ladle with the short-shroud attached thereto, shown in Figure 2(1 a), 2(1) and 2(2).

[0059] In one embodiment, wherein the short-shroud sits on the seat member (15) before the ladle is lowered to establish contact between the nozzle and the shroud inlet (9i) (cf. Figure 1 (1 a)&(1), and 7a), the seat member (15) can be formed by a sleeve (21) provided with arms (18) distributed about a circumference of the sleeve and extending radially outwards therefrom, as illustrated in Figures 3 & 4. Centering pins (19) can be used to centre the compliant elements.

[0060] The geometry of the sleeve can mate the geometry of the outer wall of the shroud base (11), so as to snugly receive the shroud base (1 1). Alternatively, as shown in Figures 4 and 7a, the shroud base (11) can be snugly received by the seat-member (15) by filling a seating gap with a filling (22), preferably made of moulding sand, forming a seat on which a shoulder (23) of the shroud base (11) rests when the shroud (9) is in the casting position. The filling (22) of moulding sand may comprise an organic binder such as furan, alkaline - phenolic binders. Also, other binders, for example inorganic binders or clay minerals may be used.

[0061] A preferred embodiment of the mould I shroud coupling mechanism (14) with compliant elements (17) is represented in Figure 3. It comprises a seat member (15) comprising a sleeve configured for receiving and holding the shroud base (11). The seat member is coupled to the base member (16) by means of compliant members (17) in the form of spiral springs (17s). The seat member (15) has three radially outwardly extending arms (18) which are uniformly distributed around a circumference of the sleeve at a radial distance to an axis of symmetry of the drive-through. A person skilled in the art may appreciates that the seat member can have any other shape, for example can be disk shaped and the number of outwardly extending arms can vary.

[0062] The base member (16) is preferably rigidly fixed to the upper surface (8) of the mould (2). For examples, the base member can be coupled with an adhesive (organic or mineral), or with fastening means such as screws, rivets, and the like. Alternatively, the base member (16) can sit in a mating recess and held in place by gravity and by the load parallel to the Z-axis applied by the nozzle (12). The latter embodiment has the advantage that the mould / shroud coupling mechanism can easily be removed before breaking the mould (2) to extract the cast metal part. It suffices that the central hole (20) of the base member remains concentric with the bore (7) during the whole casting operation. The base member also comprises three radially outwardly extending arms (18) which are aligned with the corresponding arms of the seat member (15). The compliant element (17) is formed by three spiral springs (17s) sandwiched between the arms of the seat member and of the base member.

[0063] Figure 3 shows three spiral springs (17s) which are preferred compliant elements (17). The compliant elements (17) can, however, have other configurations, some examples of which are illustrated in Figures 16a to 16f and discussed in more detail in the next section.

[0064] When the shroud base (11) of the short-shroud (9) sits in the seat member (15), the compliant elements (17) (e.g., the spiral springs (17s) maintain the seat member (15) at the rest distance (dO) (cf. Figures 4 and 7b). Upon lowering the ladle (103) the nozzle engages the shroud inlet (9i) and applies the load along the Z-axis onto the seat member (15) which deforms the compliant elements (17) and drives the seat member to the casting distance (hi) and the short-shroud (9) to the shroud casting position with the shroud outlet (9o) separated from the housing inlet (6i) by the shaft-free distance (d710). At this stage, a sealed contact is formed between the nozzle (12) and shroud inlet (9i) by the mating geometries of the two elements and by the application of the load between the two, and optionally by a sealing member. Metal melt can be cast through the nozzle and short-shroud (9), which fills the bore (7) and flows into the housing (6) and into the cavities (3). The thin gap between the short-shaft (10) and the bore wall is rapidly filled with metal that freezes in contact with the cold mould and forms a seal. Optionally, a seal member (e.g., a gasket) can be used to ensure sealing of the thin gap.

Compliant Elements (17)

[0065] The at least one compliant element (17) of the mould / shroud coupling mechanism of the embodiment discussed supra allows dynamically moving the short-shroud (9) to the shroud casting position by deformation thereof upon application of a load along the Z-axis. The load is applied by lowering the ladle (103) along the Z-axis until the nozzle (12) contacts the shroud inlet (9i) and applies a force thereon. Compliant elements (17) are elements that deform significantly along the Z-axis when a load is applied along the Z-axis. The compliant elements (17) can show an elastic behaviour, a viscoelastic behaviour, or a purely plastic behaviour.

[0066] Elastic elements are compliant elements (17) that can absorb energy when they are deformed elastically, and instantly release that energy upon unloading. A mould / shroud coupling mechanism comprising elastic elements can be used several times with different moulds (2) without replacing the elastic elements since they return to their rest state after use, ready for being used again. Examples of elastic elements include spiral springs (17s) as shown e.g., in Figures 3, 4, 16a, 16b, or blade springs as shown in Figure 16e.

[0067] Viscoelastic elements are compliant elements (17) having an elastic modulus (E’) and a loss modulus (E”). Upon release of a load, viscoelastic elements do not recover their initial geometry, or they do with a time delay. Only the latter type of viscoelastic elements can be used several time in different casting operations. Example of viscoelastic elements include elastomeric materials such as rubber, as illustrated in Figure 16d, or a hydraulic or pneumatic damper as shown in Figure 16c, which can be modelled with a spring and dashpot arranged in parallel.

[0068] Plastic elements are compliant elements (17) which, upon release of a load, are unable to recover, even partially, their original geometry. For example, this is the case of a compliant element, such a beam, which is configured for deforming substantially plastically upon application of a load along the Z-axis. This can also be the case as illustrated in Figure 16f, of free-flowing material enclosed in one or more bags or flexible containers configured for viscously deforming upon application of the load onto the seat member (15). The free-flowing material can be a particulate material such as sand or the like, which can absorb energy by opposing a viscous flow to the load applied by the nozzle onto the shroud and seat member (15). The compliant element can also comprise disposable elements configured for being destroyed or crushed by plastic deformation upon application of the load, Upon release of the load, the plastic elements maintain their deformed configuration. Plastic elements must either be reshaped or removed and replaced by new, undeformed plastic elements each time the mould I shroud coupling mechanism (14) is to be used again.

[0069] Because of the ready availability of spiral springs (17s), their resistance to casting conditions, and the fact that they can be re-used several times without any repair between two successive uses, spiral springs (17s) are the preferred compliant elements (17). Elastic elements are also more suitable for maintaining a sealing contact between the shroud inlet (9i) and nozzle (12) during a casting operation in the event of the ladle (103) and nozzle (12) moving slightly up and down due to vibrations during the casting.

[0070] Preferably, the mould I shroud coupling mechanism (14) comprises at least three resilient elements, preferably at least three spiral springs (17s), extending between the seat member (15) and the base member (16), wherein the at least three resilient elements are preferably equally spaced apart around a circumference of the central holes of the seat member (15) and the base member (16), as illustrated in Figures 3, 4 and 5. Preferably, the at least three spiral springs which are preferably uniformly distributed, extend between the seat member (15) and the base member (16). This design has the advantage that the compliant elements (17) will not be heated up excessively by the molten metal flowing through the shroud bore from the shroud inlet (9i) to the hollow shaft of the shroud during the casting process.

MOULD / SHROUD COUPLING MECHANISM (14) WITH LIFTING MECHANISM

[0071] A mould I shroud coupling mechanism (14) comprising a lifting coupling system suitable for use in the present invention is described in EP3463715 and is referred to in continuation simply as a “lifting mechanism”. The lifting mechanism comprises a seat member (15) in the form of an inner collar which sits concentrically within an outer collar forming the base member (16). The inner collar comprises an annular seat configured receiving and supporting the shroud base (1 1) with the short-shaft passing through a central hole and the bore inlet to be inserted in the bore (7). Two pegs and a handle extend radially out of and are distributed over an exterior surface of the inner collar.

[0072] The base member (16) formed by the outer collar comprises a cylindrical wall surrounding an annular base. The base 70 is mounted on the upper surface of the mould in the same way as the base member of the mould / shroud coupling mechanism with compliant members discussed supra, i.e., glued, screwed, or simply laid on top of the upper surface of the mould, preferably within a mating recess preventing any lateral movements (over the plane normal to the Z-axis, defining the upper surface of the mould.

[0073] The cylindrical wall of the outer collar are cut away so as to provide at least two ramped or spiral surfaces rising by a distance (hi - hO) over a given azimuthal angle, from a rest position at hO, to a casting position at hi from the upper surface of the mould. The inner collar is inserted within the outer collar with the pegs thereof resting on the ramped surfaces of the outer collar at the rest position hO. By rotating the inner collar using the handle, the pegs travel along the ramped surfaces, causing the inner collar, and thus the short-shroud 9 supported by the inner collar, to be lifted upwardly until reaching the casting position hi . The inner and outer collars thus function as a cylindrical cam, with the pegs constituting followers.

[0074] Unlike the mould / shroud coupling mechanism with compliant elements discussed supra, the lifting mechanism drives the short-nozzle away from the housing inlet (6i) to reach the shroud casting position. At the rest position, the shroud outlet (9o) is therefore closer to the housing inlet (6i) separated therefrom by a distance, d710 - (hi - hO), than at the shroud casting position, wherein it is separated from the housing inlet by the shaft-free distance (d710).

[0075] In use, the ladle (103) and nozzle (12) are lowered along the Z-axis until contacting or almost contacting the shroud inlet (9i) without forming a sealed contact. The seal contact being formed by lifting the shroud inlet (9i) over the nozzle (12) by rotating the inner collar relative to the outer collar as explained supra.

[0076] The mould I shroud coupling mechanism with compliant elements discussed supra is preferred to the lifting mechanism for the following reasons. First, it allows for more automation, as the compliant elements provide a dynamic, self-regulated sealing contact mechanism requiring no other human intervention than lowering the ladle to engage the nozzle into the shroud opening. Second, as explained in more detail in continuation, the lifting mechanism can only be used by first inserting the short-shroud into the bore (7) followed by lowering the ladle as illustrated in Figure 1. The mould / shroud coupling mechanism with compliant elements also afford the possibility of coupling the short-shroud directly to the nozzle, and driving the short-shaft (10) into the bore (7) by controlling the displacements of the ladle (103) and nozzle (12) thereof.

SAND CASTING MOULD (2)

[0077] The mould (2) is a sand casting mould made of compacted sand with a binder. It comprises a bore (7) extending from a bore inlet to a bore outlet located in a bore choke (7c) and opening in a housing inlet (6i) leading to the housing (6). The sand casting mould (2) comprises one or more cavities (3) fluidly connected to the housing (6) by feeding channels (5). If the sand casting mould comprises more than one cavity, a single feeding channel (5) can be coupled to the housing outlet (6o) and branch off towards the different cavities as illustrated in Figures 17a and 17c. Alternatively, several feeding channels (5) can be coupled to corresponding housing outlets (60), each one leading to a different cavity as illustrated in Figure 17b. Finally, as shown in Figure 15, several feeding channels can be coupled to corresponding housing outlets (6o) and each feeding channel branching towards different cavities. Venting channels (13) can be provided for venting the cavities to maintain the pressure substantially constant in the headspace as they are being filled with molten metal. The cavities (3) with corresponding feeding channels (5) of the sand casting mould of the present invention are identical to the ones currently used and are well known to the skilled person. They are therefore not discussed in more details in continuation.

Bore (7)

[0078] The bore (7) extends from the bore inlet to the housing inlet (6i), over a bore length (d7). The bore portion excluding the choke (7c) is preferably cylindrical, with a circular cross-section, or is slightly tapered getting thinner in the flow direction, with a tapering angle of preferably not more than 2 deg, more preferably not more than 1 deg. The downstream end of the bore (87) is formed by a choke (7c) the bore choke (7c) forming a bore constriction defining the bore outlet with a reduction of a bore diameter of at least 10% along the Z-axis in the flow direction. The bore outlet opens in the housing inlet (6i). The choke (7c) allows pressure to build up in the bore (7) so that the bore gets entirely filled with molten metal during the casting operation, reducing air entrapment and formation of a turbulent flow.

[0079] The bore wall can be formed by the compacted sand forming the bulk of the mould (2), as illustrated in Figures 17a and 17e. This is the cheapest solution. The sand forming the bore wall can, however, be eroded by the fast flowing molten metal, entraining sand particles with it into the housing (6). If the housing comprises a filter unit, the sand particles can be retained, but at the expenses of pressure loss. To reduce or even avoid the risk of erosion, the bore wall can be lined by a lining (7s) over the whole bore length (d7), as shown in Figure 17b, or over a portion only of the bore length (d7), as shown in Figures 17c and 17g. The lining material must be cheaper than the refractory material forming the short-shroud (9), else the material and cost savings achieved with the use of short-shrouds would be cancelled by the additional material and cost required for forming the lining (7s). The lining (7s) sole function is to prevent sand particles to be eroded and entrained in the metal flow. Any cheap material forming a compact surface resisting erosion during one casting operation can be used for forming the lining (7s). For example, any one of chamotte (or grog) preferably composed of high-fired clay, sand core material, or cellulose material can advantageously be used to form the lining (7s) as it is cheap and forms a compact surface resistant to erosion by the flowing metal. In an alternative embodiment, the bore (7) features a dual-material lining approach. Specifically, the downstream segment of the bore length (d7) is lined with a first material, as depicted in lining (7s). In contrast, the upstream segment of the bore length (d7) is lined with a second material (7m), characterized by high dimensional accuracy relative to the first material. This dual-material lining configuration is illustrated in Figures 17d, 17f, and 17h. The primary role of the second material (7m) is to ensure an effective seal in the gap between the short shroud (9) and the bore (7). This second material is not limited to a specific type and may include various substances such as moulding sands, ceramics, or core sands. The key criterion for selecting this material is its capability to be dimensionally accurate to a degree that guarantees an optimal seal.

Housing (6)

[0080] The housing (6) is in fluid communication with the bore outlet, allowing molten metal to flow directly from the bore (7) into the housing (6) through the bore outlet and the housing inlet (6i). The housing (6) can be a diverter, guiding the flow of molten metal towards feeding channels (5) leading to corresponding cavities (3), like a manifold. The housing also serves to stabilize the flow of molten metal, eliminating turbulent flow to yield a more laminar flow before it fills the one or more cavities (3).

[0081] Preferably, the housing (6) is a filter housing provided with a filter unit to prevent solid particles to flow into the feeding channels (5) and into the mould cavities (3), as illustrated with a checkered element in the housings (6) of Figures 17a to 17c.

SAND CASTING MOULD ASSEMBLY

[0082] The invention also concerns a mould assembly comprising the mould (2), the mould / shroud coupling mechanism (14) and the short-shroud (9) as defined supra, with the should base (1 1) of the short-shroud (9) sitting on the seat member (16) of the mould / shroud coupling mechanism (14) and with the downstream end (10d) of the short-shaft (10) inside the bore (7) and outside of the housing inlet (6i). This configuration of the sand casting mould assembly is suitable for carrying out a casting process as illustrated in Figure 1 , wherein the short-shroud (9) is first coupled to the sand casting mould (2) via the mould / shroud coupling mechanism (14). The shroud base (11) is generally located outside of the mould, i.e., above and adjacent to the upper surface (8) of the mould, and the short-shaft (10) is engaged in the bore (7). At the rest position, the downstream end of the short-shaft is separated from the housing inlet by a gjven distance. If the mould / shroud coupling mechanism does not allow any movement of the short-shroud along the Z-axis when the shroud base (11) sits on the seat member (15), then the given distance is d710, and the short shroud is in the shroud casting position. If, like the two types of mould I shroud coupling mechanisms (14) described supra (with compliant elements (17) and with lifting mechanism) allow for an up and down movement of the short-shaft relative to the bore (7) between a rest position (hO) and a casing position (hi), the given distance is d710 + |h0 - h1 |. The short-shroud can be moved into the shroud casting position, with the downstream end (10d) of the short-shaft (10) at the shaft-free distance (d710) from the housing inlet (6i) as described above, viz.,

• by applying a load along the Z-axis towards the sand casting mould (2) to reduce the distance to d710, if the mould / shroud coupling mechanism (14) comprises compliant elements (17), or

• by rotating the inner collar to increase the distance to d710, if the mould / shroud coupling mechanism (14) comprises a lifting mechanism.

[0083] In the shroud casting position as shown in Figure 5 the shrt-shaft is separated from the housing inlet (6i) by the shaft-free distance d710. Molten metal is supplied to the casting cavity (3) through a flowing path extending from the ladle (103) to the casting cavities flowing sequentially though the nozzle (12) short-nozzle, the short-shroud (9), the bore (7), the housing (6), the feeding channels (5) and into the cavities. Like with the long-shrouds of the cited prior art, the flowing path is substantially air-tight and prevents re-oxidation of the metal by protecting it from the atmosphere. The bore (7) extends along the Z-axis and is so dimensioned as to receive the short-shroud (9) with as thin a gap as possible between the bore wall and the short-shaft, while still allowing linear movement along the Z-axis of the short-shroud (9) within the bore (7). As explained above, as the bore (7) fills in with molten metal, some will flow through the thin gap and freeze or solidify in contact with the cold sand casting mould material, thus creating a sealed joint. Optionally, a joint material can be applied as a paste or as a gasket to ensure a perfect seal between the short-shaft (10) and the bore wall.

[0084] In an embodiment of the mould assembly according to the invention, the short-shroud (9) is fixed to the seat member (15), either by gravity or with a filling (22) of moulding sand filling an annular gap between the shroud base (11) and the seat member (15) and defining a seat for the shroud base

(11), as illustrated in Figure 4.

[0085] In a preferred embodiment of the invention, a gasket is placed in the shroud inlet (9i) enhancing a sealing contact between the nozzle (12) and the shroud inlet (9i). The gasket may for example be formed by a plasticized clay or by an intumescent material.

CASTING INSTALLATION

[0086] The invention also concerns a casting installation comprising the sand casting mould (2), the short-shroud (9), the mould / shroud coupling mechanism (14), and the ladle (103) equipped with the nozzle (12) provided at a base ofthe ladle (103) for dispensing molten metal out ofthe ladle. The nozzle

(12) is configured for reversibly and sealingly engaging into the shroud inlet (9i). The ladle (103) is configured for being displaced relative to the sand casting mould (2), such as to position the nozzle (12) substantially vertically (along the Z-axis) above the mould I shroud coupling mechanism (14) and the bore inlet (9i), and to be lowered vertically along the Z-axis until the nozzle (12) is sealingly engaged in the shroud inlet (9i) with the shroud (9) in the shroud casting position. Depending on the type of mould / shroud coupling mechanism (14) used, the short-shroud (9) is either already in the shroud casting position before the nozzle (12) engages the shroud inlet (6i) or is brought into the shroud casting position either by applying the load along the Z-axis onto the seat member (15) thus deforming the compliant elements (17) or by rotating the inner collar to activate the lifting mechanism. The casting installation may comprise a gasket which is preferably located in the shroud inlet (9i). In the casting installation, the short-shroud (9) may be fixed to the seat member, preferably with the filling (22), or may be detachable and removable from the seat member (15).

[0087] To enhance the sealing contact between the nozzle (12) and the shroud inlet (9i), the nozzle tip and the shroud inlet (9i) preferably have mating geometries of the type male-female geometry. For example, the nozzle (12) can have a protruding trunco-conical geometry and the shroud inlet (12) have a mating trunco-conical cup shape as shown e.g., in Figures 3, 4, 7a. Alternatively, the nozzle (12) can form a protruding spherical cap and the shroud inlet (9i) form a spherical cup as shown in Figures 5 and 6. These types of male I female geometries allow for a moderate tilting of the nozzle relative to the short-shroud (9). These geometries are also self-centring, correcting any small deviation from alignment of the nozzle relateive to the short-shroud (9).

[0088] Application of a load at the interface between the nozzle and the shroud inlet (9i) is also important to ensure a tight contact. If a mould / shroud coupling mechanism comprising compliant elements (17) is used, the load can be applied when lowering the ladle and engaging the nozzle tip into the shroud inlet (9i) and pressing the compliant elements (17). If a mould / shroud coupling mechanism with a lifting mechanism is used, load is applied by lifting along the Z-axis the shroud inlet (9i) over the nozzle top. The use of compliant elements is preferred because it reduces the risk of impacts upon lowering the nozzle into the shroud inlet (9i) and can also absorb vibrations of the ladle and nozzle during a casting operation...

LADLE / SHROUD COUPLING MECHANISM (140)

[0089] A preferred embodiment of the casting installation according to the invention comprises a ladle / shroud coupling mechanism (140) configured for reversibly gripping the short-shroud (9) to the nozzle (12), preferably without forming a seal between the shroud inlet (9i) and the nozzle (12).

[0090] As illustrated in Figures 2 and 9a, this allows moving the ladle with the short-shroud suspended thereto, which is advantageous when the shroud can be reused for multiple castings in a row, e.g. as illustrated in Figure 2. When performing a series of subsequent castings with a same ladle and shroud (9), the shroud can for example be disengaged from the bore of a first mould after completing casting of metal in the first mould by lifting the ladle upward (see Figure 2 - step 4). Then, the ladle is translated horizontally for positioning the shroud above the bore of a second mould (see Figure 2 - step 5). Then, the ladle is lowered downward (see Figure 2(1)) until the shroud reaches the casting position (see Figure 2 (2) and a subsequent casting can be performed into the second mould. This operation can be repeated as long as the shroud is in casting conditions. After that, the spent shroud can be removed (see Figure 2 - step 1 b) and a new shroud loaded to the ladle (see Figure 2 - step 1 a). This ladle / shroud coupling mechanism allows a same shroud to be repeatedly used several times for multiple castings. It also saves operator workload as the coupling between the ladle, shroud, and mould can be performed by the operator commanding the ladle positioning system alone. Between two castings with a same shroud, the shroud heated by a previous casting in a mould does not need to be manipulated by an operator to position it in the casting position in the subsequent mould, thus increasing safety.

[0091] Gripping the shroud to the nozzle can also be done with the long-shrouds of the cited prior art, as described in PCT/EP2022/072007 but using short-shrouds (9) instead is greatly advantageous in that the ladle needs not be lifted as high to remove a long-shaft from the bore, and translating a ladle with a short-shroud attached thereto across a workshop is easier and less dangerous than doing the same with a long-shroud.

[0092] As shown in Figure 9a, the ladle I shroud coupling mechanism (140) comprises a base adapter (140b) which is fixed to the shroud base (11) and comprises holding means. The base adapter (140b) is generally made of metal and is fixed to the shoulder of the shroud with an adhesive filling (113) such as a cement or the like. The ladle / shroud coupling mechanism (140) also comprises a nozzle adapter (140n) which is fixed to a base of the ladle (103) or to the nozzle (12) and is configured for engaging the holding means of the base adapter (140b) to reversibly lock the short-shroud (9) to the nozzle (12) in a locked position. The unlocked and locked positions of the ladle / shroud coupling mechanism (140) are represented in Figures 10 and 11 , respectively. The base of the ladle is the lowest part of the ladle in use. The nozzle adapter (140n) is preferably mounted at the base of a bottom-pour-ladle.

[0093] The base adapter (140b) and nozzle adapter (140n) are complementary to one another and are configured to releasably and loosely engage one another in the locked position. One important aspect of the ladle / shroud coupling mechanism (140) according to the invention is that the base adapter (140b) and nozzle adapter (140n) are configured to loosely engage one another in a locked position. That means that the shroud inlet (9i) and nozzle adapters engage each other in the locked position with sufficient play relative to each other so that they can be articulated to a certain extent relative to one another. This design allows for relative movement of the short-shroud and the ladle when the short-shroud is attached to the ladle so that the risk of damaging the shroud while inserting the short-shaft (10) into the bore (7) of the mould is significantly reduced. In the locked position, it is preferred that no sealing contact is formed between the nozzle and the shroud inlet (9i).

[0094] In a preferred embodiment of the ladle / shroud coupling mechanism represented in Figures 10 and 11 , the holding means of the base adapter (140b) comprise holding pegs (109) and the nozzle adapter (140n) comprises fastening hooks (107) configured for reversibly engaging the holding pegs (109) and preferably configured to be self-engaging with the holding pegs (109). The self-engaging fastening hooks allow for gripping the shroud to the ladle easily. For example, this allows using the ladle to pick up a shroud held in the casting position in a first mould (2) according to the invention as illustrated in Figure 10, by lowering the ladle so as to engage the holding means of the base adapter with the nozzle adapter as illustrated in Figure 11 and 15, and then lift the ladle to remove the shroud from the bore as illustrated in Figure 14 and 16.

[0095] Turning to Figure 12, the base adapter (140b) can comprise a sleeve like element with a truncated bearing surface (114) resting on a sloping edge (115) in a central hole (25) of the seat member (15) forming a seat for the base adapter (140b). The base adapter (140b) snugly sits in the seat member (15) but is only held by the force of gravity. On the outer circumference of the base adapter (140b), two, three, or four holding pegs (109) extend outwards in the radial direction. The holding pegs (109) may be engaged by fastening hooks (107) attached to the nozzle adapter (140n) which is attached to the ladle base plate (105).

[0096] The nozzle adapter (140n) is designed as a socket surrounding the nozzle (12). At the side attached to the ladle (103), also referred to as the proximal side, the first coupling member (11) comprises a bayonet ring (106) engaging the ladle base plate (105). The nozzle adapter (140n) is detachably connected to the ladle (103). At the other end of the nozzle adapter (140n), also referred to as the distal end, the nozzle adapter (140n) comprises a plurality of studs (111) on which the fastening hooks (107) are rotatably attached.

[0097] While lowering the nozzle (12) into the shroud inlet (9i), the nozzle adapter (140n) and the base adapter (140b) are engaged with each other. Coupling and locking of the nozzle and base adapters can be achieved into different ways. The fastening hooks (107) can be self-engaging. A ramped surface (112) of the fastening hooks (107) slides over the holding pegs (109) so that the fastening hooks (107) catch the holding pegs (109).

[0098] Alternatively, the base adapter (140b) may be rotated so that upon lowering of the ladle (103) the holding pegs (109) are placed between the fastening hooks (107) and then upon rotation of the base adapter (140b), locking of the holding pegs (109) within the fastening hooks (107) is achieved.

[0099] Once coupled as shown in Figure 13 the ladle (103) with the shroud (9) hanging on the ladle can be lifted up for being inserted in a second mould for second casting with the same shroud.

[00100] In another embodiment of the ladle / shroud coupling mechanism (140), the holding means of the base adapter (140b) comprises one or more holding pegs (109) and the nozzle adapter (140n) comprises a bayonet coupling element configured for interacting with the one or more holding pegs to reversibly lock the short-shroud (9) to the nozzle (12) in the locked position.

[00101] The nozzle adapter (140n) can be in the form of a sleeve like member which at one end and/or at both ends may be configured as a bayonet coupling element. The nozzle adapter (140n) may enclose the nozzle and may be releasably attached to a ladle baseplate (105) as illustrated in Figure 12 and 13. For example, at one end the nozzle adapter (140n) can be configured as a bayonet ring (106) engaging a corresponding structure at the ladle baseplate.

[00102] In an embodiment of the ladle I shroud coupling mechanism according to the invention the base adapter and/or the nozzle adapter are rotatable around a longitudinal axis in order to allow at least disengagement of the base and nozzle adapters by rotating either the base adapter or the nozzle adapter around said longitudinal axis.

[00103] In the casting installation according to the invention, the seat member (15) of the mould I shroud coupling mechanism (14) is configured for receiving the base adapter (140b) and holding the short-shroud (9) with the short-shroud (10) inserted in the bore (7). The base adapter (140b) is preferably fixed to the short-shroud (9) with an adhesive material (113) as represented in Figures 12 and 13. Preferably, the outer wall of the shroud base (11) can have the shape of a truncated cone; forming shoulders (23) resting on and being held in the adhesive material (113). The adhesive material can be a filling or packing of moulding sand can preferably comprise a binder (organic or inorganic). The base adapter may be designed as a sleeve like element.

[00104] Preferably, as illustrated in Figure 2(2a) & (2), the casting installation according to the invention allows coupling of the ladle with the short-shroud (9) in situ, i.e., when the short-shroud is inserted in the bore (7) of the sand casting mould. A separate station for attaching the short-shroud to the ladle as shown in Figure 2(1 a) is thus not essential. The short-shaft (10) of the short-shroud (9) is first inserted into the bore and the ladle is brought down along the Z-axis to engage the nozzle in the shroud opening (9i) as explained above with reference to Figure 1 (1 a) &(1) and casting can start. Contrary to the embodiment of Figure 1 , as the nozzle (12) engaged the shroud opening (9i), the base and shroud adapters (140b, 140n) can lock each other to grip the short-shroud (9) to the nozzle (12). At the end of the casting operation, as the ladle is driven up and away from the sand casting mould (2), instead of staying in the bore (7), the short-shroud (9) is gripped to the nozzle and is withdrawn together with the ladle, ready for use in a next casting operation with a new sand casting mould (2). This operation can be repeated as long as the short-shroud (9) is in good operational conditions. When it is worn and must be discarded, the short-nozzle is ungripped and disposed of. A new short-shroud (9) can be inserted in the next sand casting mould for the next casting operation.

[00105] In the existing art, the so-called Harrison process suggested by the Harrison Steel Castings Company involves attaching a fused silica shroud below the nozzle of a bottom pour ladle. The mould is provided with a side riser for receiving the shroud. Below the side riser a pouring well is provided which feeds into the casting cavity. With the shroud attached, the ladle is aligned over a mould and then lowered so as to insert the shroud into the side riser. The stopper rod is then moved into the open position so that molten metal contained in the ladle flows through the nozzle and the shroud into the mould. Once the mould is filled, the stopper is closed. The ladle is lifted until the shroud is clear of the mould and is then moved over to the next mould to repeat the process. For attaching the shroud below the nozzle of the bottom-pour-ladle the ladle is first secured in an attachment station and then the shroud is fixedly attached to a shroud holder assembly which is connected to the ladle baseplate.

[00106] One drawback of said rigid and fixed attachment of the shroud to the nozzle is that clearing the nozzle by oxygen lancing is almost impossible. As the material of choice for the shroud is fused silica, inserting the shroud into the side riser of the mould while being attached to the bottom of the ladle is a difficult and critical manoeuvre since even the slightest tilting of the shroud may result in destruction of the shroud. Using a short-shroud (9) instead is advantageous when moving the ladle around the workshop with a shroud protruding out of the bottom thereof.

METHOD WITHOUT LADLE / SHROUD COUPLING MECHANISM (140)

[00107] The invention also concerns a method for casting a molten metal with the casting installation according to the invention. In a first embodiment of the method illustrated in Figure 1 , the casting installation does not comprise the ladle / shroud coupling mechanism (140). The short-shaft (10) of the short-shroud (9) is inserted into the bore (7) with the shroud base (11) sitting on the seat member (15), before the ladle approaches the mould. In use, the Z-axis is substantially vertical. The short-shroud (9) can be inserted in the mould (2) by an operator as illustrated in Figure 1 (1 a) or using one or more dedicated appliances or a robot. As illustrated in Figures 5 and 6, the shroud base (11) sits on the seat member (15) and the short-shaft (10) is inserted in the bore (7) with the downstream end (10d) of the short-shaft (10) situated at a distance from the housing inlet (6i).

[00108] After step 1 a in Figure 1 , the mould assembly is ready for receiving the molten metal. As illustrated in steps (1) ² (2) of Figure 1 and in Figure 7a, a ladle (103) loaded with molten metal is brought above a first sand casting mould (2) equipped with the short-shroud (9) (e.g., with a crane) with the nozzle (12) in alignment along the Z-axis with the shroud inlet (9i). The ladle (103) is then lowered until the nozzle (12) engages the shroud inlet (9i) as illustrated in Figures 1 (2) and 7b. The short-shroud (9) is brought to the shroud casting position by moving it along the Z-axis by a distance |h0 - hi |, either by applying a load along the Z-axis on the compliant element (17) of the mould / shroud coupling mechanism (14) or by actuating the lifting mechanism to lift the short-nozzle into tight contact with the nozzle depending on which type of mould / shroud coupling mechanism is used.

[00109] As the short-shroud (9) is in the shroud casting position in tight contact with the nozzle, casting of the metal into the mould can start as illustrated in Figure 1 (3). The nozzle is opened, thereby allowing the molten metal to flow from the ladle (103) to the casting cavity (3) through the nozzle (12), the short-shroud (9), and the housing (6) of the first sand casting mould. Once the casting cavity is full as illustrated in Figure 1 (3) & (4), the nozzle can be closed to stop the flow of molten metal and the ladle can be retrieved ready to move over a next mould for starting a new casting operation as shown in Figure 1 (5) & (1). The short-shroud (9) remains inserted in the bore (7) is not gripped to the ladle and remains inserted in the bore (7) of the first mould.

[00110] The sand casting mould is broken to remove the cast metal part as shown in Figure 1 (6). The mould / shroud coupling mechanism (14) is also recovered for further use with a new mould. If the mould / shroud coupling mechanism comprises a lifting mechanism or an elastic element, it can be re-used directly without any further operations. If the compliant element is a plastic element or a viscoelastic element, it may require replacement or re-shaping of the compliant element (17) before re-using the mould / shroud coupling mechanism.

[00111] The ladle is available for a subsequent casting into a second mould, as illustrated in Figure 1 (5) & (1).

METHOD WITH LADLE / SHROUD COUPLING MECHANISM (140)

[00112] In a second embodiment of the invention illustrated in Figure 2, the casting installation comprises the ladle / shroud coupling mechanism (140). The nozzle (12a is provided with the nozzle adaptor (140n) and the short-shroud (9), equipped with the base adapter (140b) can either ,

• be inserted in the bore (7) as described with reference of the embodiment of Figure 1 and illustrated in Figure 2(2a), or it can

• be fixed to the nozzle (12) by an operator or a robot as shown in Figure 2(1 a) and as described supra.

[00113] The ladle (103a) with or without gripping the short-shroud (9) is moved to bring the nozzle (12) above (along the Z-axis) the bore inlet, and lowered so that, either

• the nozzle (12) engages the shroud inlet (9i) and at the same time the nozzle adapter (140n) grips the base adapter (140b), as shown in Figure 2(2a) & (2) or

• the nozzle (12) with the short-shroud (9) locked thereto is lowered to insert the short-shaft (10) into the bore (7) until the shroud base (11) sits on the seat member (15) of the mould / shroud coupling mechanism (14), as shown in Figure 2(1) & (2).

[00114] At this stage, the short-shroud (9) can be moved to the shroud casting position with the shroud inlet (9i) forming a tight contact with the nozzle (12a and with the downstream end (1 Od) of the short-shaft (9) at the shaft-free distance (d710) from the housing inlet (6i). It the mould I shroud coupling mechanism (14) comprises compliant elements (17) this is achieved by applying a load along the Z-axis with the nozzle (12) and ladle (103) to lower the seat member (15) and the short-shroud (9) by a distance (hO -h1). If the mould / shroud coupling mechanism (14) comprises a lifting mechanism, then this is achieved by lifting the short-shroud (9) by a distance (hi - hO) by activating the lifting mechanism (e.g., by rotating the seat member (15) (= inner collar) over the ramping surface of the base member (16) (= outer collar)).

[00115] As shown in Figure 2(3), the nozzle is opened, allowing the molten metal to flow from the ladle (103) to the one or more cavities (3) through the nozzle (12), the short-shroud (9), and the housing (6) of the first sand casting mould (2). When the one or more cavities (3) are filled with metal, as shown in Figure 2(4) & (5), the nozzle is closed, and the ladle (103) can be removed by lifting it along the Z-axis away from the mould. Since the short-shroud (2) is locked to the nozzle (12), the short-shroud (9) is thereby extracted from the bore (7) and removed together with the ladle, ready for use for a next casting operation or, if worn, ready for being dispensed.

[00116] As shown in Fire 2(6), when the metal as solidified, the sand casting mould (2) can be broken to extract the metal part. The mould / shroud coupling mechanism (14) is recovered and can be used again with a new sand casting mould (2), if necessary after replacing or re-shaping deformed plastic or viscoelastic elements. A new sand casting mould can be used for a new metal casting process according to the present invention (cf. Figure 2(1) or (2a)).

[00117] Figure 2 shows how easy it is for the ladle (103) to travel across a workshop with the short-shroud (9) locked to the nozzle (12), contrary to a ladle attached to a long-shroud instead. Both mould / shroud coupling mechanism (14) and short-shroud (9) can be recovered and used again for several other casting operations, thus substantially reducing the cost of the process.

LIST OF REFERENCE NUMERALS

1 Casting installation

2 Sand casting mould

2a Upper part of the mould

2b Lower part of the mould

3 Cavity

4 Cavity inlet

5 Feeding channels

6 Housing

6i Housing inlet

6o Housing outlet

7 Bore

7c choke

7m second lining material

7s lining

8 Upper surface of the mould

9 Short shroud

9i Shroud inlet

9L lining insert of the short-shroud

9g integrated gasket of the lining insert 9o Shroud outlet 10 Short-shaft of the short-shroud 10d downstream end of the short-shaft 11 Shroud base 12 Nozzle 13 Feeder sleeve 14 Mould / shroud coupling mechanism 15 Seat member 16 Base member 17 Compliant element 17s Spiral spring 18 Arm 19 Centring pin 20 Central hole in the base member 21 Sleeve 22 Filling 23 Shoulder 103 Ladle 105 Ladle baseplate 106 Bayonet ring 107 Fastening hooks 109 Holding pegs 111 Studs 112 Ramped surface 113 Adhesive material 114 Bearing surface 115 Sloping edge 140b Base adapter 140n Nozzle adapter a a = d10 / d10L d7 bore length along Z-axis d9 shroud length along Z-axis of short-shroud d9L shroud length along Z-axis of long-shroud d10 shaft length along Z-axis of short-shaft d10L shaft length along Z-axis of long-shaft d11 base height along Z-axis d11a height along Z-axis of cylindrical portion of the shroud base d11 b height along Z-axis of frusto-conical portion of the shroud base d710 shaft-free distance between housing inlet (6i) and downstream end ‘10d) of the short-shaft (10) in the shroud casting position

Dh hydraulic diameter = 4 A / P Dhi Dh of the shroud inlet (9i) Dhix Dhix = Dhi = 2 tw (wherein tw = wall thickness Dh10 Dh of the bore in the short shaft (10). Dh10x Dh10x = Dh10 = 2 tw, wherein tw = wall thickness k k = d710 / s7 tw short shroud wall thickness

Claims

1. Kit-of-parts for casting molten metals comprising a short shroud (9), a sand casting mould (2), and a mould I shroud coupling mechanism wherein the short shroud (9) comprises,

• a shroud base (1 1) attached to a proximal end of a short-shaft (10) of shaft length (d10) measured along a Z-axis, and having

• a shroud bore extending along the Z-axis from a shroud inlet (9i) opening at the shroud base (11) to a shroud outlet (9o) opening at a downstream end (10d) of the short-shaft, wherein the sand casting mould comprises,

• a casting cavity (3) having a cavity inlet (4),

• a housing (6) selected among a filter housing and a diverter housing, having a housing outlet (6o) in fluid communication with the cavity inlet (4) and a housing inlet (6i) in fluid communication with,

• a bore (7) extending over a bore length (d7) along the Z-axis between a bore inlet opening at an upper surface (8) of the sand casting mould and a bore outlet opening at a downstream end at a level of the housing inlet (6i), the downstream end comprising a bore choke (7c), wherein

• the bore choke (7c) forms a bore constriction defining the bore outlet which opens in the housing (6) with a reduction of a bore diameter of at least 10% along the Z-axis in a flow direction, wherein the mould / shroud coupling mechanism (14) comprises,

• a seat member (15) configured for receiving the shroud base (11) and holding the short-shroud (9) in a shroud casting position wherein the downstream end (10d) of the short-shaft (10) is inserted in the bore (7), characterized in that, the shaft length (d10) is shorter than the bore length (d7), (i.e., d10 < d7), such that in the shroud casting position, the downstream end (10d) of the short-shaft is separated from the housing inlet (6i) by a shaft-free distance (d710) which is proportional to the bore length (d7) by a proportionality factor (k) (i.e., d710 = k d7), wherein the proportionality factor (k) is at least 20% (i.e., k > 0.2), more preferably at least 35% (i.e., k > 0.35), and wherein a penetration depth (= d7 - d710) of the short-shaft (10) in the bore (7) at the shroud casting position is at least equal to 3 cm, more preferably at least equal to 5 cm, most preferably at least equal to 10 cm, and in that the mould / shroud coupling mechanism (14) comprises:

• a base member (16) fixed relative to the upper surface (8),

• a seat member (15) configured for receiving the shroud base (11) and holding the short-shroud (9) in the shroud casting position, wherein the base member (16) and seat member (15) each comprises a central hole aligned with one another to define a lead-in towards the bore (7) for the shroud (9), and wherein the seat member (15) is coupled to the base member (16) by at least one compliant element (17) such that the seat member (15) is separated from and movable relative to the base member (16) from a seat rest position to a seat casting position upon application of a load parallel to the Z-axis onto the seat member (15) which deforms the at least one compliant element (17) so as to drive a short-shroud (9) sitting in the seat member (15) to reach the shroud casting position, wherein the compliant element (17) comprises one or more resilient elements including a spring, preferably a spiral spring (17s), extending between the seat member (15) and the base member (16).

2. Kit-of-parts according to claim 2, wherein the mould / shroud coupling mechanism (14) preferably comprises at least three resilient elements, preferably at least three spiral springs (17s), extending between the seat member (15) and the base member (16), wherein the at least three resilient elements are preferably equally spaced apart around a circumference of the central holes of the seat member (15) and the base member (16).

3. Kit-of-parts according to any one of the preceding claims, wherein the bore (7) is defined by a wall which is lined by a lining (7s) over at least a portion of the bore length (d7), preferably over the whole bore length (d7).

4. Kit-of-parts according to claim 3, wherein the lining material is selected from any one of chamotte composed of high-fired clay, sand core material, or cellulose material.

5. Sand casting mould assembly comprising, the short-shroud (9) and the sand casting mould (2) as defined in any one of the preceding claims, wherein the shroud base (11) of the short-shroud (9) sits on the seat member (15) with the short-shaft (10) of the short-shroud (9) inserted in the bore (7) with the downstream end (10d) separated from the housing inlet (5i).

6. Sand casting mould assembly according to claim 5, wherein the mould I shroud coupling mechanism (14) is configured,

• at the seat rest position, to maintain the downstream end (10d) of the short-shaft (10) separated from the housing inlet by a distance greater than the shaft-free distance (d710) and

• at the seat casting position, to maintain the short-shroud at the shroud casting position, with the downstream end (10d) of the short-shaft (10) separated from the housing inlet by a distance substantially equal to the shaft-free distance (d710), upon application of the load parallel to the Z-axis.

7. Casting installation comprising,

• the short-shroud (9) and the sand casting mould (2) as defined in any one of claims 1 to 4,

• a ladle (103) comprising a nozzle (12) provided at a base of the ladle (103) for dispensing molten metal out of the ladle, wherein the nozzle (12) is configured for reversibly and sealingly engaging into the shroud inlet (9i) of the short-shroud (9), and wherein the ladle (103) is configured for being displaced relative to the sand casting mould (2), such as o to position the nozzle (12) substantially aligned along the Z-axis over the mould I shroud coupling mechanism (14) and o to be lowered along the Z-axis until the nozzle (12) is engaged in the shroud inlet (9i) of the short-shroud (9) which is in the shroud casting position with the downstream end (10d) of the short-shaft (10) being outside of and separated from the housing inlet (6i) by the shaft-free distance (d710).

8. Casting installation according to claim 7, comprising a ladle / shroud coupling mechanism (140) configured for reversibly gripping the short-shroud (9) to the nozzle (12), preferably without forming a seal between the shroud inlet (9i) and the nozzle (12), wherein the ladle / shroud coupling mechanism (140) comprises, o a base adapter (140b), fixed to the shroud base (11) of the short-shroud (9), the base adapter (140b) comprising holding means, and o a nozzle adapter (140n), fixed to the base of the ladle (103) or to the nozzle (12), and configured for engaging the holding means of the base adapter (140b) to reversibly lock the short-shroud (9) to the nozzle (12) in a locked position.

9. Casting installation according to claim 8, wherein the holding means of the base adapter (140b) comprises one or more holding pegs (109) and the nozzle adapter (140n) comprises either,

• fastening hooks (107) configured for reversibly engaging the holding pegs (109) and are preferably configured to be self-engaging with the holding pegs (109), or

• a bayonet coupling element configured for interacting with the one or more holding pegs to reversibly lock the shroud (9) to the nozzle (12) in the locked position.

10. Casting installation according to anyone of claims 7 to 9, wherein the downstream end (10d) of the short-shaft reaches the casting position separated from the housing inlet (6i) by the shaft-free distance (d710) by applying the load parallel to the Z-axis onto the seat member (15).

11. Method for casting a molten metal with the casting installation of any one of claims 7 to 10, comprising:

• lowering the ladle (103) along the Z-axis until the nozzle (12) is engaged in sealing contact in the shroud inlet (9i) and the short-shroud, with the shroud base (11) sitting on the seat member (15), is in the shroud casting position, with the downstream end (10d) being outside of and separated from the housing inlet (6i) by the shaft-free distance (d710),

• allowing the molten metal to flow from the ladle (103) to the casting cavity (3) through the nozzle (12), the short-shroud (9), and the housing (6).

12. Method according to claim 11 , wherein the casting installation is according to claim 10, and wherein

• the ladle (103) is lowered along the Z-axis until the nozzle (12) engaged in the shroud inlet (9i) applies a load parallel to the Z-axis onto the shroud base (11) sitting on the seat member (15), thus moving along the Z-axis the seat member (15) relative to the base member (16) against the compliant elements (17), and forming a sealing contact between the nozzle (12) and the shroud inlet (9i) of the short-shroud (9) which is in the shroud casting position, with the downstream end (10d) being outside of and separated from the housing inlet (6i) by the shaft-free distance (d710).

13. Method according to claim 12, wherein,

• the short-shroud (9) is first accommodated in the sand casting mould (2) with the seat member (15) receiving the shroud base (11) and holding the short-shroud (9) with the downstream end (10d) being outside of and separated from the housing inlet (6i) by a distance greater than the shaft-free distance (d710) to form a sand casting mould assembly according to claim 5 or 6, and

• comprising engaging the nozzle (12) into the shroud inlet (9i) by lowering vertically the ladle (103), and forming the sealing contact between the nozzle (12) and the short-shroud (9) by further lowering the ladle (103) for the nozzle (12) to apply the load onto the shroud base (11) to move the short-shroud (9) towards the housing inlet (6i) to the shroud casting position with the downstream end (10d) being separated from the housing inlet by the shaft-free distance (d710).

14. Method according to claim 13, wherein the casting installation is according to claim 8 or 9, and comprising:

• engaging the nozzle (12) into the shroud inlet (9i) of the shroud (9) and gripping the short-shroud (9) to the nozzle (12) with the ladle I shroud coupling mechanism (140) by engaging: o the holding means of the base adapter (140b) fixed to the shroud inlet (9i) of the short-shroud (9) with, o the nozzle adapter (140n) fixed to the base of the ladle (103) or to the nozzle (12), such as to lock the short-shroud (9) to the nozzle (12) in a locked position,

• positioning the short-shroud (9) locked to the nozzle (12) substantially aligned along the Z-axis above the mould / shroud coupling mechanism (14),

• lowering along the Z-axis until the shroud base (11) sits on the seat member (15) with the short-shroud in the bore (7) and the downstream end separated from the housing inlet (6i) by a distance greater than the shaft-free distance (d710).

• Lowering the ladle further along the Z-axis until the short-shroud reaches the shroud casting position with the downstream end (10d) being outside of the housing inlet (6i) separated therefrom by the shaft-free distance (d710), thereby

• forming the sealing contact between the short-nozzle (12) and the short-shroud (9).