WO2025010069A1

WO2025010069A1 - Pulp molding seals

Info

Publication number: WO2025010069A1
Application number: PCT/US2023/027031
Authority: WO
Inventors: Sébastien CADALEN; Pau PALLARES VENDRELL
Original assignee: Hewlett Packard Development Co LP
Current assignee: Hewlett Packard Development Co LP
Priority date: 2023-07-06
Filing date: 2023-07-06
Publication date: 2025-01-09
Anticipated expiration: 2026-01-06

Abstract

In an example, a pulp molding apparatus includes a pulp molding screen. In some examples the pulp molding apparatus further includes a pulp molding form to support the pulp molding screen and through which fluid can drain during a fluid drainage process of an object being molded on the pulp molding screen. The pulp molding apparatus may include a seal which, in use of the apparatus, is between the pulp molding screen and the pulp molding form and is to define a first fluid drainage zone and a second fluid drainage zone, wherein the first and second fluid drainage zones have different fluid drainage characteristics.

Description

PULP MOLDING SEALS

BACKGROUND

[0001] Objects may be formed from a pulp or slurry of material in a pulp moulding process. The pulp or slurry may comprise a mixture of solid material (for example formed from recycled cardboard and/or paper) and a liquid such as water. A pulp moulding die, which may include a screen and a main body, also referred to as a form, may be immersed in a pulp such that a solid material in the pulp accumulates on the screen to form an object in an intended shape.

BRIEF DESCRIPTION OF DRAWINGS

[0002] Figs. 1A and 1 B are a cross section and a top down view of an example of a pulp moulding apparatus respectively;

[0003] Fig. 2 is another cross section of an example pulp moulding apparatus;

[0004] Fig. 3 is a flowchart of an example of a method for forming a molded pulp object;

[0005] Fig. 4 is a flowchart of another example of a method for forming a molded pulp object;

[0006] Fig. 5 is a cross section of an example of a component of a pulp moulding apparatus; and

[0007] Figs. 6A to 6E are cross sections of examples of forms of a pulp moulding apparatus.

DETAILED DESCRIPTION

[0008] A moulded pulp object may be an object formed using a pulp moulding process. Pulp moulding processes comprise covering a screen of a pulp moulding die with a slurry or pulp. The pulp moulding die may comprise a screen and a form which supports the screen. The slurry, or pulp, may comprise a liquid (e.g. water), and a solid, fibrous material. The screen of the pulp moulding die may comprise a surface having a shape which corresponds to the shape of a surface of an object to be formed using the die. The die may be submersed in a bath of the slurry to cover the screen of the die.

[0009] The screen of the pulp moulding die may comprise fluid pathways, such as channels, holes or pores. Holes may be hollow passages through the screen through which material may flow from one side of the screen to another side of the screen. Pores may be small holes or porous zones in the surface which allow the liquid component of the slurry to pass through, but are sufficiently small that the solid, fibrous material accumulates on the surface of the screen to form the object. Channels may be recesses on a surface through which a fluid may flow. In some examples pressure may be reduced behind the die to suck the liquid through the fluid pathways in the screen and to suck the fibrous material towards the surface of the screen. In some examples, a reduced pressure may be insufficient to dry the fibrous material, and therefore additional drying may be achieved by a further drying process, for example by heating the material to cause evaporation of the liquid or by application of pressure. The drying may take place in an oven or between heated metal dies.

[0010] Prior to drying, the object may be transferred from the pulp moulding die to a transfer apparatus. This transfer may comprise supplying air through the screen of the pulp moulding die to blow the object from the pulp moulding die to the transfer apparatus. At least partially concurrently, air may be drawn into holes of the transfer apparatus to suck the object towards the transfer apparatus.

[0011] The fibrous material may retain a significant amount of moisture. Therefore, the object may be subjected to a drying procedure subsequent to transfer to the transfer apparatus. In some examples the object is removed from the transfer apparatus for drying, for example in a drying oven or a heated die. In some examples, removing the object from the transfer apparatus comprises reversing the direction of air through the holes of the transfer apparatus to blow the part off the transfer apparatus, in some examples directly into a drying apparatus, such as a heated die or in other examples onto a conveyor apparatus which transports the object to a drying apparatus, such as an oven. [0012] Pulp molded objects may be described in terms of their mass per unit area. If a larger quantity of fibrous material is accumulated on the screen when forming the object, then that object will have a higher mass per unit area. A higher mass per unit area may correspond to a greater thickness and/or a higher density. The mass per unit area may also be referred to as ‘grammage’ or ‘basis weight’ of the object and may be measured in grams per squared metre (g/m²). The mass per unit area may be determined by calculating a product of the density (i.e. mass per unit volume) of a portion of the object (e.g. measured in g/m³) with a thickness of the portion of the object (e.g. measured in m). In some examples, the thickness of an object may be increased by drawing a larger quantity of liquid through the screen causing more fibrous material to accumulate on the screen. In some examples, as the amount of fibrous material accumulated on the screen increases, the thickness of the object also increases while the density (i.e. mass per unit volume) of the object may remain relatively constant.

[0013] The quantity of moisture to be removed from the fibrous material may depend on the amount of material the object comprises. For example, an object which is formed from a larger quantity of material may initially retain more moisture and therefore may take a longer time and/or more energy to dry relative to an object comprising less material. Reducing the quantity of fibrous material used to form the object may also reduce the amount of energy and/or time taken when drying the object. To reduce the quantity of fibrous material used to form the object the thickness and/or density can be reduced (i.e. lower mass per unit volume). However, either of these changes can result in an object which is weaker and therefore more susceptible to damage.

[0014] In order to reduce the total mass of an object, localised regions of the object could be formed from a relatively thin layer of fibrous material while structural regions of the object could be formed from a relatively thick layer of fibrous material. In some examples, the localised regions may be non-structural regions, in order to reduce the mass without significantly adversely affecting the strength or functionality of the object. However, pulp molding processes form a continuous layer of fibrous material on the screen and therefore it is challenging to form a molded pulp object comprising regions of different thickness.

[0015] Fig. 1 A shows a cross section of an example of a pulp molding apparatus 100, which may be used for forming objects using a pulp moulding process. Fig. 1 B shows a top down view of this example pulp molding apparatus 100, wherein the cross section illustrated in Fig. 1A is along the dotted line ‘a’ of Fig. 1 B. [0016] Moulded pulp objects may be formed from fibrous materials suspended in a slurry. The fibrous material may be a paper or card, for example recycled paper such as newsprint, cardboard or virgin fibers. Various objects may be formed using pulp moulding, for example packaging for eggs, packaging for electronic devices, bed pans or cup carriers. In this example the molded pulp object to be formed is a bowl-shaped object, however in other examples the pulp molding apparatus 100 may have a different shape to form other molded pulp objects.

[0017] The pulp molding apparatus 100 comprises a pulp molding screen 102 and a pulp molding form 104 to support the pulp molding screen 102. During a fluid drainage process of an object being molded on the pulp molding screen 102 a fluid may drain through pulp molding form 104. The screen 102 has a surface which may comprise a plurality of holes, pores (small holes or porous zones) and/or channels (e.g. recesses along a surface) through which a fluid may flow. In some examples the surface of the screen may comprise a mesh. In this example the screen 102 is separable from the form 104 (i.e. main body of the pulp molding apparatus). The form 104 may comprise an element which provides structural support for the screen 102 which helps it to maintain its shape while forming an object. Although not shown in Figs. 1A and 1 B, the form 104 may comprise features to support the form, for example structures protruding from the form 104 towards the screen 102. The form 104 may also comprise fluid drainage pathways 112 (e.g. holes or channels) through which fluids may flow to and from the screen 102.

[0018] The pulp molding apparatus 100 also comprises a seal 106 which, in use of the apparatus 100, is between the pulp molding screen 102 and the pulp molding form 104. The seal 106 defines a first fluid drainage zone 108 and a second fluid drainage zone 110, wherein the first and second fluid drainage zones 108, 110 have different fluid drainage characteristics. A portion of the screen 102 and a corresponding portion of the form 104 may be located within the first fluid drainage zone 108, and in this example the central portion of the screen 102 and the form 104 located within the region defined by the seal 106 are in the first fluid drainage zone 108. The remaining portions towards the outer edges of the screen 102 and form 104 are in the second fluid drainage zone 110. The second fluid drainage zone 110 comprises a flat rim portion 110a at an outer edge of the screen 102 and form 104, and a curved portion 110b between the flat rim portion 110a and the seal 106.

[0019] In some examples the seal 106 may be attached to, or attachable to, the screen 102 and/or the form 104. For example the screen 102 and/or the form 104 may comprise grooves or channels to receive the seal 106, or they may comprise locating pins or clips to hold the seal in place. In some examples the seal 106 may be attached to the screen 102 or the form 104, for example using an adhesive or a fastener. In some examples, the seal 106 may be attached to, or attachable to, the form 104 rather than the screen 102. In such examples the form 104 may be relatively more robust.

[0020] In this example the seal 106 has a circular cross section, however in other examples the seal 106 may have a different cross sectional shape e.g. elliptical, square, rectangular, semi-circular, trapezoidal or any other suitable shape.

[0021] In use of the apparatus 100, the apparatus 100 may be submerged in a slurry comprising a liquid and fibrous material. A reduced, or negative, pressure may be applied to a back side 116 of the form 104, i.e. the side of the form 104 facing away from the screen 102. This causes a reduced pressure to form in the fluid drainage pathways 112. The fluid drainage pathways 112 may be in fluid communication with a space 114 (i.e. a gap), between the screen 102 and the form 104. The space 114 may allow a relatively constant pressure to form between the screen 102 and the form 104 within each zone 108, 110. The relatively constant pressure may result in the properties of the formed object being relatively consistent within each zone. In contrast, if the space 114 did not exist, or is too small, more fibrous material may accumulate in the vicinity of the fluid drainage pathways 112 of the form relative to parts of the screen 102 which are further from the fluid drainage pathways 112 of the form 104. Therefore, in some examples, the space 114 may be dimensioned to allow for the relatively constant pressure condition to occur. In some examples the space 114 provides a space of at least 0.1 mm between the pulp molding screen 102 and the pulp molding form 104 (e.g. at least 0.1 mm, at least 0.2mm or at least 0.4mm), for example a space in the range 0.1 mm to 0.7mm, 0.2mm to 0.7mm or 0.4mm to 0.7mm.

[0022] The seal 106 may divide the space 114 into the first and second zones 108, 110. Due to the configuration of the fluid drainage pathways 112 in each of the zones 108 and the relative isolation of the zones 108, 110 caused by the seal 106, a different pressure may exist in each of the first and second zones 108, 110.

[0023] If the form 104 comprises fluid drainage pathways 112 in one zone with a lower resistance to fluid flow, more fluid will flow through this zone causing a larger quantity of fibrous material to accumulate on the screen 102 in this zone. Similarly, the portion of the screen 102 in the zone with higher resistance to fluid flow will accumulate less fibrous material. Some fluid which has passed through the screen 102 will be constrained, by the seal 106, to pass through the high resistance zone. In the absence of the seal 106, the amount of fibrous material in each zone may be more similar, as that fluid could instead flow to the low resistance zone and drain through the fluid drainage pathways 112 therein. Furthermore, depending on the configuration of the fluid drainage pathways 112, in use of the apparatus, different pressures may exist in the first and second zones 108, 110 of the space 114. This in turn may result a greater amount of fibrous material being deposited in that zone than is the case with the seal 106 in place. In this way, a molded pulp object may be formed which has variable mass per unit area. In some examples the mass per unit area may vary by 10% to 20%, or up to 50% between the first and second fluid drainage zones 108, 110.

[0024] In this example the first fluid drainage zone 108 is at the centre of the pulp molding apparatus 100 and the second fluid drainage zone 110 is at the edge of the pulp molding apparatus 100. The object to be formed has a bowl form. In this example the seal 106 is in the form of a closed loop and encloses the first fluid drainage zone 108. The central portions of the screen 102 and the form 104 which are within the region defined by the seal 106 are considered to be within the first fluid drainage zone 108. The portion of the screen 102 and the form 104 which lie outside the first fluid drainage zone 108, i.e. the flat rim portion 110a and the curved portion 110b, are in the second fluid drainage zone 110, which in this example encircles the first fluid drainage zone 108.

[0025] In this example, the seal 106 defines two zones, however, in other examples the apparatus 100 may comprise more than one seal which may define more than two zones. In this example the seal 106 forms a closed loop however in other examples the seal may take different shapes, for example the second zone may not encircle the first zone.

[0026] The seal 106 may be formed from a material which provides sufficient compressibility, which is deformable and elastic. In some examples the seal 106 comprises a silicone material, for example a silicone sponge. In other examples the seal may comprise a rubber or elastomer material. The seal may be formed using an extrusion process to create a seal 106 with a consistent cross section along its length. In some examples the seal 106 may be a composite object and comprise several different materials, for example the seal 106 may comprise a compressible, deformable material (e.g. silicone, rubber or elastomer) and a stiffening member to maintain the shape of the seal 106, which may be made from metal or plastic. [0027] In some examples the seal 106 may permanently separate the first and second fluid drainage zones 108, 110 (i.e. it may not be readily removed from between the screen 102 and form 104). In some examples the seal 106 may be formed by bonding a region of the screen 102 and a region of the form 104 together. For example, a portion of the screen 102 and the form 104 may be glued using an adhesive, or they may be welded together. In some examples the screen 102 and/or the form 104 may comprise features, such as protrusions, ridges or channels to facilitate such bonding. For example, such features may protrude from the screen 102 and/or the form 104 to contact the other of the screen 102 and/or the form 104 along a linear region to separate the first and second fluid drainage zones 108, 110 and this region may be bonded (e.g. glued or welded) to provide the seal 106.

[0028] In some examples the apparatus 100, the screen 102 and/or the form 104 may be formed from a metallic material. In some examples they may be manufactured using machining techniques, such as CNC (Computer Numerical Control) milling. The screen 102 may be a woven mesh formed from a plurality of fine metal wires. The openings in the screen 102 may be around 0.1 mm to around 0.6mm, for example 0.5mm.

[0029] In some examples, at least one of the screen 102 and the form 104 are generated by additive manufacturing, such as three-dimensional (3D) printing. In some examples the apparatus 100 further comprises a transfer apparatus, to which an object is transferred to after it is formed on the screen. The transfer apparatus may also be generated using additive manufacturing.

[0030] Additive manufacturing techniques may generate a three-dimensional object, such as the screen 102, the form 104 or the transfer apparatus through the solidification of a build material. In some examples, the build material is a powder-like granular material, which may for example be a plastic, ceramic or metal powder and the properties of generated objects may depend on the type of build material and the type of solidification mechanism used. Build material may be deposited, for example on a print bed and processed layer by layer, for example within a fabrication chamber.

[0031] In some examples, selective solidification is achieved through directional application of energy, for example using a laser or electron beam which results in solidification of build material where the directional energy is applied. In other examples, at least one print agent may be selectively applied to the build material, and may be liquid when applied. For example, a fusing agent (also termed a ‘coalescence agent’ or ‘coalescing agent’) may be selectively distributed onto portions of a layer of build material in a pattern derived from data representing a slice of a three-dimensional object to be generated (which may for example be determined from structural design data). The data may be derived from a digital or data model of the object, e.g. object model data provides a data, or virtual, model of an object to be generated. The fusing agent may have a composition which absorbs energy such that, when energy (for example, heat) is applied to the layer, the build material to which it has been applied heats up, coalesces and solidifies, upon cooling, to form a slice of the three-dimensional object in accordance with the pattern.

[0032] When the screen 102 or form 104 are generated using additive manufacturing the openings in the screen 102 or form 104 may be formed by partially fusing build material in portions of the screen 102 or form 104. The partially fused build material may allow fluids (gases and liquids such as water and air) to pass through while preventing solid material (such as the fibrous materials used in pulp moulding) from passing through. In other examples, the openings may comprise holes, pores (i.e. small holes) or channels though the screen 102 or the form 104.

[0033] Fig. 2 shows a cross section of another example of a pulp molding apparatus 200, which may be used for forming objects using a pulp moulding process. The pulp molding apparatus 200 comprises a screen 202 and seal 206 as described in relation to the corresponding elements of Figs. 1A and 1 B. The pulp molding apparatus 200 also comprises a form 204. The form 204 comprises the features of the form 104 described in relation to Figs. 1A and 1 B.

[0034] As described in relation to Figs. 1 A and 1 B, the seal 206 separates the apparatus into a first zone 208 and a second zone 210 wherein each zone has different fluid drainage characteristics. In this example the fluid drainage characteristics comprise a fluid drainage rate. For example, when a constant pressure is applied to the back side 216 of the form 204 i.e. the side 216 of the form 204 facing away from the screen 202, the fluid drainage rate is different in each zone. In this example the different fluid drainage rates may result in different quantities, densities or thickness of fibrous material to accumulate on the first and second zones of the screen 202.

[0035] In this example the first zone 208 of the form 204 comprises first fluid drainage pathways 212 and the second zone 210 of the form 204 comprises second fluid drainage pathways 214. The fluid drainage pathways 212, 214 may be any pathways which allow fluid to pass from one side of the form 204 to an opposing side of the form 204. For example the fluid drainage pathways 212, 214 may be channels, openings, pores, holes, orifices or passages. The fluid drainage pathways 212, 214 may be hollow or may comprise a porous material through which fluid may flow. For example the fluid drainage pathways 212, 214 may comprise partially solidified build material which allows fluid to flow through, but which may provide some resistance to the flow relative to a hollow fluid drainage pathway.

[0036] The fluid drainage pathways 212, 214 may have different fluid drainage characteristics in each zone. In this example the first fluid drainage pathways 212 have a higher resistance to the flow of fluid than the second fluid drainage pathways 214 and therefore the fluid drainage rate is lower in the first fluid drainage zone 108 relative to the second fluid drainage zone 110. This is at least partially because the first fluid drainage pathways 212 have a smaller cross sectional area than the second fluid drainage pathways 214. Furthermore, the form 204 comprises fewer (e.g., two) first fluid drainage pathways 212 in the first zone 208 whereas the form comprises more (e.g., six) second fluid drainage pathways 214 in the second zone 210. In some examples, the zones may have a different number of fluid drainage pathways 214 per unit area. Each of these features results in the form 204 having a lower resistance to the flow of fluid through the second zone 210 of the form 204 relative to the flow of fluid through the first zone 208 of the form 204.

[0037] In other words, the characteristics of the fluid drainage pathways 212, 214 may comprise at least one of: different dimensions (e.g. cross sectional area, width, circumference, diameter or length), different shapes (e.g. cross sectional shape, shape of the path such as straight or curved), different structures, different spacing between fluid drainage pathways, different densities (i.e. total number of fluid drainage pathways by unit area (e.g. per cm²) of the surface of the form 204), different porosities (e.g. a fluid drainage pathway may be partially obscured by a porous material), different orientations, total number of fluid drainage pathways in each zone, or any other feature which may affect resistance to flow of a fluid.

[0038] Fig. 2 shows a cross section of the apparatus 200 after a pulp molded object 216 has been formed on the screen 202 of the apparatus 200. Due to the shape of the screen 202 and the form 204, the formed object 216 is a bowl-shaped object 216. In this example the object 216 has a lower mass per unit area in the first fluid drainage zone 208 relative to the mass per unit area of the object 216 in the second fluid drainage zone 210. As illustrated, this results in the base of the bowl-shaped object 216 being thinner than the other portions of the object 216. The object 216 has a lower mass per unit area in the first fluid drainage zone due to the reduced fluid flow rate through the relatively small first fluid drainage pathways 212 compared with the relatively high fluid flow rate through the relatively large second fluid drainage pathways 214. Such an object 216 has a lower total mass than a similar object formed with a constant thickness and mass per unit area equal to that in the second fluid drainage zone 210. Therefore, this object may be formed with less material and may be dried more quickly and using less energy.

[0039] After the pulp molded object 216 is formed on the screen 202 it may be transferred to a transfer apparatus by expelling or ‘blowing’ air through the first and second fluid drainage pathways 212, 214 towards the screen 202 and through the screen 202 to push the object 216 away from the screen 202 and towards a transfer apparatus (not shown). In some examples the different fluid drainage rates in the first and second first and second zones 208, 210 may not substantially affect the transfer process, however the position of the first and second fluid drainage pathways 212, 214 of the form 204 may be selected to ensure an effective transfer.

[0040] Fig. 3 is an example of a method 300, which comprises a method for forming a molded pulp object.

[0041] The method 300 comprises, in block 302, providing a seal between a screen and a form of a pulp molding apparatus to define a first zone and a second zone of the screen. The screen and form of the pulp molding apparatus may be a screen and form as described in relation to Figs. 1 and/or 2. The first zone and second zone of the screen may correspond to the first and second fluid drainage zones as described in relation to Figs. 1 and/or 2.

[0042] The method 300 comprises, in block 304, forming a first portion of a molded pulp object with a first mass per unit area on the first zone of the screen and comprises, in block 306, forming a second portion of molded pulp object with a second mass per unit area on the second zone of the screen. The first and second portions of the molded pulp object may be formed concurrently. For example the screen and form may be submersed in a pulp comprising a liquid and a fibrous material. The liquid may then be drawn through the screen causing fibrous material to accumulate on the screen forming the first and second portions of the object on the first and second zones of the screen respectively.

[0043] The flow rate of liquid through the screen may be different in each of the zones which may cause different quantities of fibrous material to accumulate in each zone resulting in relative differences in thickness and/or density. [0044] Fig. 4 is an example of a method 400, which comprises a method for forming a molded pulp object. The method may be carried out, at least in part, by processing circuitry, which may comprise at least one processor. In some examples the processing circuitry may be part of, or associated with, an additive manufacturing apparatus. Fig. 4 provides an example of the method 300 of Fig. 3.

[0045] The method 400 comprises, in block 402, forming at least one of the screen and form using additive manufacturing. Forming the screen and/or the form using additive manufacturing may allow the features of these components described herein to be formed in a relatively simple and cost effective manner. For example, characteristics of the fluid drainage pathways, such as the size, shape, spacing, porosity, number, orientation of fluid drainage pathways may be readily varied between different parts of the screen or form. Furthermore, additive manufacturing may allow features to be incorporated into the form and/or screen to receive or secure a seal, as described below.

[0046] The method 400 comprises, in block 302, providing a seal between a screen and a form of a pulp molding apparatus to define a first zone and a second zone of the screen, as described in relation to Fig. 3. In some examples the form also comprises a first zone and a second zone corresponding to the first and second zones of the screen

[0047] Blocks 404 to 408 are an example of forming the first and second portions of the molded pulp object as described in relation to blocks 304, 306 of Fig. 3. The method 400 comprises, in block 404, submersing the screen in a slurry comprising a liquid and a fibrous material. The method 400 comprises, in block 406, drawing the liquid, at least in part, through the screen and the form by applying a uniform pressure to fluid drainage pathways in both the first and second zones of the form. The uniform pressure may be a reduced, or negative, pressure applied to a back side of the form (i.e. a side facing away from the screen). For example, the first and second zones of the back side of the form may be in communication, for example they may be connected to the same vacuum pump(s) or there may be a single cavity on the back side of the form acting as a negative pressure plenum. A space between the pulp molding screen and the pulp molding form (e.g. providing a space of at least 0.4mm, at least 0.2mm or at least 0.1 mm), for example a space in the range 0.1 mm to 0.7mm, 0.2mm to 0.7mm or 0.4mm to 0.7mm, may allow a relatively constant pressure to form within the space in each of the first and second zones. The different zones of the form may have different fluid drainage characteristics, which may lead to a different pressure forming in each of the first and second zones of the space. [0048] The method 400 comprises, in block 408, accumulating the fibrous material on the screen to form the first and second portions of the molded pulp object. The reduced, or negative, pressure applied to the back side of the form may cause the liquid component of the slurry to be drawn through the screen resulting in the solid, fibrous material accumulating on the screen to form the object. The different zones of the form may have different fluid drainage characteristics which cause the first mass per unit area to be different from the second mass per unit area, for example as illustrated in Figs. 6B to 6E.

[0049] Fig. 5 shows a cross section of an example of a component 500 of a pulp molding apparatus, which may be used for forming objects using a pulp moulding process. The component 500 may be a screen or a form of a pulp molding apparatus, for example as described in relation to Figs. 1 and/or 2. However, in this example the component 500 is substantially flat and therefore may be used to form a substantially flat pulp molded object. However, in other examples the component 500 may have another shape and may be used to form pulp molded objects of different shapes.

[0050] The component 500 comprises a first fluid drainage zone 502 and a second fluid drainage zone 504. The component 500 further comprises a seal 506 defining the first fluid drainage zone 502 and the second fluid drainage zone 504 of the component 500. In this example the first fluid drainage zone 502 is illustrated on the left of the seal 506 and the second fluid drainage zone is illustrated on the right of the seal 506.

[0051] The first and second fluid drainage zones 502, 504 may have different fluid drainage characteristics. In this example the component 500 comprises first fluid drainage pathways 508 in the first fluid drainage zone 502 and second fluid drainage pathways 510 in the second fluid drainage zone 504. The fluid drainage pathways 508, 510 may allow fluid to pass from one side of the component 500 to the other side of the component 500. For example when the component 500 is a screen fibrous material may accumulate on the screen while the fluid drainage pathways allow liquid to pass through the screen. In examples wherein the component 500 is a form, the fluid drainage pathways 508, 510 may allow the liquid which has passed through the screen to pass through the form. The fluid drainage pathways 508, 510 may be channels, openings, pores, holes, orifices or passages through the component 500.

[0052] To provide the different fluid drainage characteristics in each zone, the first fluid drainage pathways 508 and the second fluid drainage pathways 510 may comprise different characteristics, for example different dimensions (e.g. cross sectional area, width, circumference, diameter or length), different shapes (e.g. cross sectional shape, shape of the path such as straight or curved), different structures, different spacing between fluid drainage pathways, different densities (e.g. number of fluid drainage pathways per unit area), different porosities (e.g. a fluid drainage pathway may be partially obscured by a porous material), different orientations, different total number of fluid drainage pathways in each zone, or any other feature which may affect resistance to flow of a fluid.

[0053] In some examples the component 500 may further comprise features to receive, align, engage or retain the seal 506. For example, the component 500 may comprise a channel into which the seal 506 is located or it may comprise locating pins or clips to hold the seal 506 in an intended position. In some examples the seal may be fixed to the component 500, for example using an adhesive. In such examples the seal 506 may be permanently attached to the component 500 however in other examples the seal may be separable from the component 500.

[0054] The seal 506 may be formed from a material which provides sufficient compressibility, which is deformable and elastic, for example silicone (e.g. a silicone sponge) or rubber and may be formed using an extrusion process to create a seal 506 with a consistent cross section along its length. In some examples the seal 506 may be a composite object and comprise several different materials, for example the seal 506 may comprise a compressible, deformable material (e.g. silicone, rubber) and a stiffening member to maintain the shape of the seal 506, which may be made from metal or plastic.

[0055] In this example the seal 506 has a circular cross section, however in other examples the seal 506 may have a different cross sectional shape e.g. elliptical, square, rectangular, semi-circular or any other suitable shape.

[0056] In some examples a component 500 of a pulp molding apparatus may comprise different types of fluid drainage pathways in a single fluid drainage zone. For example a single fluid drainage zone may comprise fluid drainage pathways with different shapes, dimensions, porosities, or the like.

[0057] In some examples the component 500 may comprise more than one seal 506 and/or may comprise more than two fluid drainage zones which may each have different fluid drainage characteristics. When the component 500 comprises more than two fluid drainage zones, some of the zones may have the same fluid drainage characteristics such that portions of the pulp molded object formed in those zones will have a similar mass per unit area. [0058] Figs. 6A to 6E show cross sections of example components 620, 640, 660, 680 of a pulp molding apparatus, which may be used for forming objects using a pulp moulding process. The components 600, 620, 640, 660, 680 are similar to the component 500 described in relation to Fig. 5, however each of these examples illustrate fluid drainage pathways with different characteristics. In each of the examples shown in Figs. 6A to 6E the component 620, 640, 660, 680 is a form of a pulp molding apparatus.

[0059] Fig. 6A shows an example of a form 600 and a screen 612 of a pulp molding apparatus. A seal 606 is also provided between the form 600 and the screen 612 to define a first fluid drainage zone 602 and a second fluid drainage zone 604. As described previously, the form 600 comprises fluid drainage pathways 608 in the first and second fluid drainage zones 602, 604. In this example the form 600 comprises a channel 614 in which the seal 606 is located. The channel may ensure that the seal 606 is located in the intended position and may prevent it from moving from this position during a pulp molding operation. In other examples the screen 612 may comprise such a channel instead of, or in addition to, the form 600. However, in this example, the screen comprises a protrusion 616 which is arranged such that when the screen 612 is arranged on the form 600 the protrusion 616 contacts, and may compress, the seal 606 ensuring effective sealing is achieved. In some examples the protrusion 616 may be provided on the form 600 rather than the screen 612.

[0060] In each of the examples shown in Figs. 6B to 6E fluid drainage is provided by holes, pores and/or channels in the form 620, 640, 660, 680 and the different fluid drainage characteristics are provided by different dimensions, different spacing, different shapes and/or different porosities of the holes, pores and/or channels in the first fluid drainage zones 622, 642, 662, 682 and second fluid drainage zones 624, 644, 664, 684.

[0061] Fig. 6B shows an example of a form 620 and a screen 632 of a pulp molding apparatus. A seal 626 is also provided between the form 620 and the screen 632 to define a first fluid drainage zone 622 and a second fluid drainage zone 624. As described previously, the form 620 comprises first fluid drainage pathways 628 in the first fluid drainage zone 622 and second fluid drainage pathways 630 in the second fluid drainage zone 624. In this example the form 620 comprises fewer first fluid drainage pathways 628 in the first fluid drainage zone 622 relative to the number of second fluid drainage pathways 630 in the second fluid drainage zone 624. Therefore, the fluid drainage characteristics of the zones will be different due to the different characteristics of the fluid drainage pathways 628, 630 in each zone. In particular, the form 620 comprises first fluid drainage pathways 628 which have a larger spacing and lower total number (i.e. lower number of holes per unit area, or hole density) in the first fluid drainage zone 622 relative to the second fluid drainage zone 624. For example, the fluid drainage pathways 628, 630 may be holes and the spacing between the holes may be 5mm to 50mm, wherein the holes in the first fluid drainage zone 642 have a diameter towards the top of this range (e.g. 30mm to 50mm) and the holes in the second fluid drainage zone 644 have a diameter towards the bottom of this range (e.g. 5mm to 30mm). Therefore, when a similar pressure is applied to the back of the form 620 (i.e. the side facing away from the screen 632), fluid may drain at a higher rate from the second fluid drainage zone 624 relative to the first fluid drainage zone 622 causing fibrous material to accumulate at a higher rate on the screen 632 in the second fluid drainage zone 624.

[0062] Fig. 6C shows an example of a form 640 and a screen 652 of a pulp molding apparatus. A seal 646 is also provided between the form 640 and the screen 652 to define a first fluid drainage zone 642 and a second fluid drainage zone 644. As described previously, the form 640 comprises first fluid drainage pathways 648 in the first fluid drainage zone 642 and second fluid drainage pathways 650 in the second fluid drainage zone 644. In this example the form 640 comprises first fluid drainage pathways 648 with a smaller cross sectional area in the first fluid drainage zone 642 relative to the cross sectional area of the second fluid drainage pathways 650 in the second fluid drainage zone 644. Therefore the fluid drainage characteristics of the zones will be different due to the different characteristics of the fluid drainage pathways 648, 650 in each zone. In particular the fluid drainage pathways 648, 650 may be holes with a diameter in the range 0.5m to 3mm. In some examples the holes in the first fluid drainage zone 642 have a diameter towards the bottom of this range (e.g. 0.5mm to 1.5mm) and the holes in the second fluid drainage zone 644 have a diameter towards the top of this range (e.g. 1 ,5mm to 3mm). Therefore when a similar pressure is applied to the back of the form 640 (i.e. the side facing away from the screen 652), fluid may drain at a higher rate from the second fluid drainage zone 644 relative to the first fluid drainage zone 642 causing fibrous material to accumulate at a higher rate on the screen 652 in the second fluid drainage zone 644.

[0063] Fig. 6D shows an example of a form 660 and a screen 672 of a pulp molding apparatus. A seal 666 is also provided between the form 660 and the screen 672 to define a first fluid drainage zone 662 and a second fluid drainage zone 664. As described previously, the form 660 comprises first fluid drainage pathways 668 in the first fluid drainage zone 662 and second fluid drainage pathways 670 in the second fluid drainage zone 664. In this example the form 660 comprises first fluid drainage pathways 668 with a non-straight path in the first fluid drainage zone 662 and second fluid drainage pathways 670 in the second fluid drainage zone 664 which follow a straight path. Therefore the fluid drainage characteristics of the zones will be different due to the different characteristics of the fluid drainage pathways 668, 670 in each zone. In particular the first fluid drainage pathways 668 have a corner which may impede the flow of fluid relative to the straight path followed by the second fluid drainage pathways 670. In some examples fluid drainage pathways in each zone may comprise different shapes of paths, for example they may be straight or have a corner as shown in Fig. 6C, or they may follow some more convoluted or complex path for example they may contain more than one corner. Furthermore, the relatively complex shape of the first fluid drainage pathways 668 results in them having a longer length compared with the second fluid drainage pathways 670 further impeding the flow of fluid. Therefore when a similar pressure is applied to the back of the form 660 (i.e. the side facing away from the screen 672), fluid may drain at a higher rate from the second fluid drainage zone 664 relative to the first fluid drainage zone 662 causing fibrous material to accumulate at a higher rate on the screen 632 in the second fluid drainage zone 664.

[0064] Fig. 6E shows an example of a form 680 and a screen 692 of a pulp molding apparatus. A seal 686 is also provided between the form 680 and the screen 692 to define a first fluid drainage zone 682 and a second fluid drainage zone 684. As described previously, the form 680 comprises first fluid drainage pathways 688 in the first fluid drainage zone 682 and second fluid drainage pathways 690 in the second fluid drainage zone 684. In this example the form 680 comprises first fluid drainage pathways 688 formed from a porous material and second fluid drainage pathways 690 in the second fluid drainage zone 684 which are hollow (i.e. comprise no solid material). Therefore the fluid drainage characteristics of the zones will be different due to the different characteristics of the fluid drainage pathways 688, 690 in each zone. In particular, solid yet porous material of the first fluid drainage pathways 688 may impede the flow of fluid relative to the hollow second fluid drainage pathways 690 i.e. the flow rate of fluid may be lower through the porous material in the first fluid drainage pathways 688 relative to the flow rate of fluid through the second fluid drainage pathways 690. In some examples fluid drainage pathways in each zone may comprise different materials (or an absence of any material) and therefore may have different porosities. For example when the form 680 is generated using additive manufacturing the different materials may be partially solidified build material which may have a different porosity depending on the degree of solidification. Therefore when a similar pressure is applied to the back of the form 680 (i.e. the side facing away from the screen 692), fluid may drain at a higher rate from the second fluid drainage zone 684 relative to the first fluid drainage zone 682 causing fibrous material to accumulate at a higher rate on the screen 692 in the second fluid drainage zone 684.

[0065] The present disclosure is described with reference to flow charts and/or block diagrams of the method, devices and systems according to examples of the present disclosure. Although the flow diagrams described above show a specific order of execution, the order of execution may differ from that which is depicted. Blocks described in relation to one flow chart may be combined with those of another flow chart.

[0066] While the method, apparatus and related aspects have been described with reference to certain examples, various modifications, changes, omissions, and substitutions can be made without departing from the spirit of the present disclosure. It is intended, therefore, that the method, apparatus and related aspects be limited only by the scope of the following claims and their equivalents. It should be noted that the above- mentioned examples illustrate rather than limit what is described herein, and that those skilled in the art will be able to design many alternative implementations without departing from the scope of the appended claims.

[0067] The word “comprising” does not exclude the presence of elements other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims.

[0068] The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims.

Claims

1. A pulp molding apparatus comprising: a pulp molding screen; a pulp molding form to support the pulp molding screen and through which fluid can drain during a fluid drainage process of an object being molded on the pulp molding screen; and a seal which, in use of the apparatus, is between the pulp molding screen and the pulp molding form and is to define a first fluid drainage zone and a second fluid drainage zone, wherein the first and second fluid drainage zones have different fluid drainage characteristics.

2. A pulp molding apparatus as claimed in claim 1 wherein the seal comprises a silicone material.

3. A pulp molding apparatus as claimed in claim 1 wherein the fluid drainage characteristics comprise a fluid drainage rate.

4. A pulp molding apparatus as claimed in claim 1 wherein the pulp molding form comprises fluid drainage pathways in each of the first and second zones and wherein the fluid drainage pathways have different fluid drainage characteristics in each zone.

5. A pulp molding apparatus as claimed in claim 4 wherein the different characteristics of the fluid drainage pathways in each zone comprise at least one of: different dimensions, different shapes, different structures, different spacing, different densities, different porosities, different lengths, different number of fluid drainage pathways and different orientations.

6. A pulp molding apparatus as claimed in claim 1 further comprising a space of at least 0.1 mm between the pulp molding screen and the pulp molding form.

7. A method comprising: providing a seal between a screen and a form of a pulp molding apparatus to define a first zone and a second zone of the screen; forming a first portion of a molded pulp object with a first mass per unit area on the first zone of the screen; and forming a second portion of molded pulp object with a second mass per unit area on the second zone of the screen.

8. A method as claimed in claim 7 wherein forming the first and second portions of the molded pulp object comprises: submersing the screen in a slurry comprising a liquid and a fibrous material; drawing the liquid through the screen and the form; and accumulating the fibrous material on the screen to form the first and second portions of the molded pulp object.

9. A method as claimed in claim 8 wherein: the form comprises a first zone and a second zone corresponding to the first and second zones of the screen; and the different zones of the form have different drainage characteristics which cause the first mass per unit area to be different from the second mass per unit area.

10. A method as claimed in claim 9 wherein the first and second zones of the form comprise fluid drainage pathways and wherein drawing the liquid through the screen and the form comprises: applying a uniform pressure to the fluid drainage pathways in both the first and second zones of the form.

11. A method as claimed in claim 7 further comprising: forming at least one of the screen and form using additive manufacturing.

12. A component of a pulp molding apparatus comprising: a first fluid drainage zone through which fluid can flow; a second fluid drainage zone through which fluid can flow; and a seal defining the first fluid drainage zone and the second fluid drainage zone of the component, wherein the first and second fluid drainage zones have different fluid drainage characteristics which affect the rate at which fluid flows through the first and second fluid drainage zones.

13. A component of a pulp molding apparatus as claimed in claim 12 wherein the component is a form of a pulp molding apparatus.

14. A component of a pulp molding apparatus as claimed in claim 13 wherein fluid drainage is provided by holes in the form and the different fluid drainage characteristics are provided by different dimensions, different spacing and/or different porosities of the holes in the first and second fluid drainage zones.

15. A component of a pulp molding apparatus as claimed in claim 14 wherein the holes have a diameter in the range 0.5m to 3mm and the spacing between the holes is 5mm to 50mm.