WO2003028967A1

WO2003028967A1 - A press, apparatus and method for moulding

Info

Publication number: WO2003028967A1
Application number: PCT/EP2002/010958
Authority: WO
Inventors: Giuliano Mari
Original assignee: DECORATERRE Sas DI MARI GIULIANO EC
Current assignee: DECORATERRE Sas DI MARI GIULIANO EC
Priority date: 2001-10-01
Filing date: 2002-09-30
Publication date: 2003-04-10
Anticipated expiration: 2004-04-01
Also published as: ITFI20010178A1

Abstract

Press, apparatus and method for moulding comprising a mould (4) for forming a semi-finished body (8), comprising an elastic forming membrane (7) which acts on the body (8) and deformable by pressurized-fluid means so as to compress said body (8) against said mould (4).

Description

A PRESS, APPARATUS AND METHOD FOR MOULDING Field of the invention

The present invention relates to the sector of production of articles by moulding, preferably earthenware articles, but also articles made of plaster of Paris, plastic mixtures or synthetic materials, or even foodstuffs such as chocolate, dough for making bread, artistic cakes.

In particular, the invention is aimed at the automatic production of artistic objects such as vases and ornamental objects in general or articles made of plaster of Paris, picture frames, mouldings and the like, which are characterized by a high decorative quality and geometrical complexity. Prior art

As is known, the production of moulded articles, in particular earthenware articles, is currently carried out using manual or semi-automatic processes. In manual production, celadonite (green earth of Verona), presenting the appropriate degree of humidity, is spread inside plaster moulds which are then opened for extraction of the product, for example a vase, which is to be sent onto the subsequent drying and baking steps.

In semi-automatic production, metal moulds are used, in which a positive mould compresses the celadonite set inside a negative mould to form the product. Next, the negative mould is opened, for example in segmented fashion, to enable extraction of the product, which is to be sent on for drying and baking. Using currently known techniques, the quality of the decorations on the product are considerably limited by the curvatures that can be obtained, which are in all cases very rounded, and by the fact that they present a relatively poor resemblance to the original.

Alternatively, limited decorations may be obtained by pinching the semi-finished product or by applying decorations to the surface. In the latter case, in addition to the relative simplicity and limited nature of the decorations that can be achieved, the result is to incur in an evident increase in overall costs of manufacture, as well as problems of brittleness of the decorations themselves Object of the invention A first purpose of the present invention is to propose an automatic or semi- automatic method and apparatus, which are capable of overcoming the drawbacks of known moulding systems.

A second purpose is to obtain an industrial production of decorated products made of earthenware, plaster of Paris, or synthetic material presenting a quality that is comparable to what can be achieved by a skilled craftsman.

Summary of the invention

The above purpose is achieved by a method and apparatus according to the main claims.

Further purposes are achieved using a method and apparatus according to the dependent claims.

Brief description of the drawings

The advantages of the invention will emerge clearly to a person skilled in the art from the ensuing description and from the annexed drawings, which are provided purely by way of non-limiting example, and in which: - Figure 1 illustrates a first step of fabrication (smooth green vase) of a decorated vase according to the invention;

- Figures 2a and 2b illustrate the subsequent steps for obtaining a decorated vase using a press according to the invention;

- Figures 3a and 3b illustrate a plan view and a cross-sectional elevation of an apparatus for producing decorated vases according to the invention;

- Figures 4 to 8 illustrate the succession of production steps, numbered from zero to nine, for making a vase using the press according to the invention;

- Figures 9a to 9c illustrate a second embodiment of the press with double inner/outer membrane in successive steps of production of an article; and - Figures 10 to 13 illustrate the sequence of the steps for producing an article using the press shown in Figures 9a to 9c, the said steps being numbered from ten to seventeen.

Detailed description of the invention

With reference to Figures 1 to 8, there is now described, by way of example, a preferred embodiment of an apparatus according to the invention for the production of decorated earthenware vases.

In the example described, the press is located in an integrated work unit for the production of decorated earthenware vases; however, it is understood that a press according to the invention can be introduced into production lines that are organised in different ways. In the example described there are provided: - a traditional press 1 for the production of smooth green vases, preferably of the type with a negative mould that can be opened in segmented fashion (Figure 1);

- a transfer system 2 for transferring the semi-finished green vase 8 from a first workstation to a second workstation;

- a press 3 according to the invention, comprising a negative mould 4 for forming decorations, preferably a mould of the type that can be opened in segmented fashion, located in said second workstation and mounted on a frame 15 that can move in a vertical direction. The press 3 further comprises a bag-like element 7 made of an elastic membrane which is designed to copy the inner surface of the vase and is mounted on a membrane-carrying positive mould 10 fixed to a fixed support 9, which is set at the top and aligned with the vase and with the negative mould 4 for forming decorations. In addition, clinching fasteners are provided for controlled clamping of said mobile frame 15 of the decoration mould 4 to said fixed support 9 and for keeping them stably joined together; and

- a system 6 for moving the decorated vase which is to undergo possible subsequent steps of fabrication, the said system comprising a frame with a mobile cross member 61 which is able to slide between said second press 3 and a loading surface 62.

Provided according to the invention are means (which in themselves are of a known type and consequently will not be described any further herein) for controlled blowing of a fluid or semi-fluid under pressure (for example, a gas, a liquid, a gel or a flow of grit or balls) into said bag.

Preferably, the fluid under pressure is hydraulic oil, and said means envisage a hydraulic power unit and automatically controlled solenoid valves.

In particular, in the example described, the hydraulic power unit supplies the controls for the following purposes: a) raising/lowering of the mobile frame 15; b) opening/closing of the negative mould 4 in segmented fashion; c) opening/closing of sectors of the fasteners for clinching the frame 15 to the support 9; and d) supply of fluid under pressure to the elastic forming membrane 7.

From the structural point of view, in a preferred example of embodiment, the hydraulic power unit is made up of a metal tank of adequate capacity to meet the functional requirements, a vane pump of variable capacity, a three-phase, four- pole electric motor, and filtering units for suction and discharge, as well as hydraulic accessories. A controlled panel set above the hydraulic power unit preferably groups together the electric distributors, flow regulators and pressure regulators, etc. associated to the external-connection block for the hydraulic actuators.

In the example described, the actuators, which are to be moved sequentially and/or simultaneously, are for the following purposes: a) raising/lowering of the mobile frame 15: 1 double-acting hydraulic cylinder; b) opening/closing of the negative mould 4 in segmented fashion: 2 double- acting hydraulic cylinders; c) opening/closing of sectors of the fasteners for clinching the frame 15 to the support 9: 4 double-acting hydraulic cylinders; and d) supply of fluid under pressure to the elastic forming membrane 7: 2 double- acting hydraulic cylinders, plus 1 elastic membrane of dimensions similar to the internal geometry of the specific vase.

During automatic operation, the hydraulic power unit supplies the actuators described in the foregoing point by means of electric distributors and the valves of the control panel according to the control logic resident in a programmable controller.

Preferably, each actuator is equipped with proximity sensors and/or some other sensing device designed to interact with the central control unit. A particularly advantageous solution has been adopted for pressurizing and emptying the elastic membrane 7 by means of two distinct inlet/suction ducts 41 , 42, the said operation of pressurizing and emptying the said membrane being designed to press the wall of the green vase 8 against the negative decorations of the mould 4. According to the above solution, the hydraulic circuit enables a continuous change of the oil introduced into the membrane, thus preventing any deposit of sludge, which would be produced if this solution were not adopted. The elastically deformable bag or membrane can conveniently be purged using a continuous and/or temporary purging device, with recovery, in the tank, of the oil that has formed an emulsion with the air, particularly during the first operating step of a new moulding operation.

Pressurization of the elastic membrane is obtained rapidly and at a high pressure according to the parameters set, which depend upon the configuration of the decorations that are to be produced, without representing any limit to the values that are needed for the valves or the specific object that is to be decorated. Emptying of the elastically deformable membrane or bag, at the end of the decoration operation is carried out at the top of the membrane-carrying positive mould 10 by suction of the oil introduced during the step of decoration carried out by exerting pressure and, consequently, whilst all the hydraulic circuits are working under more or less high positive pressure. Instead, in the emptying step, it is necessary to operate in conditions of negative pressure.

As is known, the limit of suction of a liquid is represented by the phenomenon of cavitation (i.e., the formation of air bubbles in the suctioned liquid), this being a threshold which would definitively rule out any possibility of recovering the oil. Consequently, the circuit may advantageously envisage the adoption of two hydraulic cylinders, where one functions as an active actuator (with appropriately calibrated positive pressures), and the other functions as a "single-bodied syringe" for continuous multicycle operation, which enables suction of the oil, up to recomposition of the membrane, irrespective of the volume of oil that is to be recovered. The suction cycle is interrupted automatically, without the presence of sensors and without producing any cavitation.

The hydraulic power unit thus far described meets the requirements of production both of a vase of small size and of a vase of very large size, without any need to personalize the calibrations of its components in so far as the functional parameters of said components have been selected to cover the specific production range, precisely by exploiting the functional elasticity of the said components.

In greater detail, and with reference to Figures 2a and 2b, in a preferred embodiment of a press 3 for making decorations according to the invention, the elastically deformable membrane or bag 7 takes the form of a shroud or cowling set around a positive mould 10 and constrained thereto by means of a top flange 11 fixed to the top face of the positive mould 10 by means of screws 12. The elastically deformable membrane or bag 7 can be realised with any elastic material suitable for the purposes to be reached and the materials which have to be pressed, for example synthetic materials, plastics, resins or even thin metal plates.

The edge of the elastic membrane is gripped between the flange and the positive mould and, preferably, a tight seal is guaranteed by a gasket 13, for example, of the O-ring type. At the centre, the flange 11 and the positive mould 10 are traversed by a channel 14, into which the liquid is sent under pressure via inlet means of a type that is in itself traditional.

Advantageously, passing through the positive mould 10 there are made grooves 19, which are arranged radially so as to set the channel 14 in communication with the outer surface of the positive mould. If necessary, the grooves may proceed along the corresponding generatrices of the positive mould 10, whilst at the bottom, between the mould and the green vase, a free margin is left to enable even better distribution of the fluid.

In operation, the green vase is formed in a traditional way using the traditional press 1 and transferred to the workstation of the decoration mould 4. Once the vase 8 has been set in position, the mould 4 closes on the vase, and the frame 15 rises, causing the membrane 7, supported by the support 9 and by the positive mould 10, to enter the vase 8.

Once the frame 15 has been clamped to the support 9 by means of the fastening clamps 18, an appropriate amount of fluid under pressure is introduced through the channel 14 and runs through the grooves of the positive mould 10 and swells the membrane, which presses against the inner walls of the vase 8 until it brings about copying, on the outer wall of the vase 8, of the decorations 23 made on the inner face of the negative mould 4. Once the moulding step is completed, the fluid is recalled by the hydraulic system, with opening of the fasteners 18 and descent of the frame 15. The negative mould 4 opens, and the formed vase 8' is transferred by the system 6 for carrying out movement onto a pallet 16 for being sent onto subsequent drying and baking steps.

Advantageously, the fluid exerts a uniform hydrostatic pressure inside the membrane, which consequently expands, so pressing against the inner surface of the vase to which it is associated. In turn, the vase, under the action of the uniform hydrostatic pressure exerted by the elastic membrane, is deformed in a precise way so as to adapt to the decorations of the mould.

In addition, the possibility of reaching high hydrostatic pressures is not dangerous for the integrity of the vase, whilst it enables perfect filling of decorations such as bas-reliefs and niches with a very high precision as compared to what is possible using normal processes adopted in the handicrafts industry, and in an absolutely evenly distributed way over the entire surface.

A further advantage lies in the reduction of the porosity of the pressed material, which favours the subsequent steps of drying and baking.

With reference to Figures 9a to 9c, a further embodiment of the invention is now described, in which the press 30 is, as regards many of its components, equivalent to the press 3 described above, but is provided with a second compliant membrane 70 for external containment of the product 80.

In the figures, components that are equivalent have been assigned the same reference numbers. In greater detail, in this embodiment there is provided a second membrane, this time external to the product and having the shape of a cylindrical sleeve closed against the inner walls of the forming mould 40 by means of pressure-tight seals 44, 45.

Between the mould 40 and the membrane 70 a gap 46 is left, which can be filled with fluid under pressure, the said fluid being introduced through the ducts 43. Also in this case, automatic management of the steps of introduction and suction of the fluid in the membranes 7, 70 is envisaged. With reference also to Figures 10 to 14, the manufacture of the products that can be made using this apparatus envisages picking-up of a pre-formed object from a traditional press, where the smooth vase is produced, with appropriately chosen wall thickness to allow for the subsequent dilation, which has already been described with reference to the decoration press 3. Advantageously, this embodiment of the invention enables the production of articles characterized by an even very large undercut, for example an amphora that is very pot-bellied and has a narrow neck.

In particular, the hydraulic power unit is equipped also with proportional valves and electronic pressure transducers, such as to render convenient management of the dynamic parameters using a PLC, in so far as the protocols inherent in the rational dilation of the earth require objective self-learning processes, which may vary significantly and are linked to the different configurations of the vases, of the earths, etc. The invention further comprises a method for the production of articles made of earthenware or other mouldable materials.

In the example of the production of an earthenware vase using the apparatus described above with reference to Figures 1 to 8, the method comprises the following steps:

- Step "0": forming of the smooth green vase in a traditional press; - Step "1": transfer of the formed smooth vase 8, either automatically or manually, to the workstation of the forming negative mould, which is at this point in the open configuration;

- Step "2": raising of the mobile frame, with the negative mould in the closed configuration; - Step "3": raising of the frame of the forming negative mould up to end-of-travel until the support carrying the elastic membrane is made to penetrate inside the vase;

- Step "4": clinching of the mobile frame to the fixed support of the membrane;

- Step "5": introduction of fluid under pressure into the membrane; - Step "6": discharge of the pressure, and suction of the oil from the membrane;

- Step "7": release of the fasteners clinching of the mobile frame to the fixed support of the membrane; - Step "8": descent of the mobile frame, with the negative mould closed;

- Step "9": end of cycle, with opening of the negative mould, discharge of the product formed, and transfer to possible drying and baking steps;

According to the invention, the products obtained are characterized by low porosity and high characteristics of hardness as compared to traditional products.

Thanks to the above characteristics, the product presents a better behaviour during drying and baking, and ageing is markedly reduced.

Preferably, said step of forming is moreover a step of decoration of the product.

According to a second embodiment, with particular reference to the steps described in detail in Figures 10 to 13 and to the apparatus of Figures 9a-9c, the method comprises the following steps:

- Step "10": on a traditional press, using a negative mould, which can open in segmented fashion, and a rotating positive mould, a smooth green vase 80 is produced, the wall of which presents variable thicknesses in the direction of the vertical axis such as to have a greater thickness in the area where there is to be the subsequent perimetral dilation. The aforesaid thicknesses vary continuously as is required for the reserve of pasty material (celadonite) according to the final thicknesses that the finished amphora is to have;

- Step "11": the smooth vase 80 thus produced is transferred, either by automatic pick-up or by manual pick-up, on to a press 30;

- Step "12": negative mould 40 closed;

- Step "13": mobile frame 15 of the negative mould 40 at top end-of-travel, and positive mould 10 with elastic membrane in the depressurized condition inserted inside the smooth green vase; clinching clamps 18 activated to fasten the frame 15 to the positive mould 10, the elastic membrane 70 for containing the vase externally being depressurized;

- Step "14": simultaneous filling of the internal elastic membrane 7 and the external elastic membrane 70 of the vase by means of a single supply with hydraulic oil at low pressure up to complete filling thereof, leaving the drainage points inside and outside the vase open for expelling the air present on the outside of the walls of the vase itself; automatic separation of the two hydraulic circuits, for the internal elastic membrane and the elastic membranes for external containment of the vase, and progressive increase of the pressure in the internal elastic membrane, as well as simultaneous prevention of leakage of oil from the elastic membrane for external containment of the vase. Once the pre-set pressure for achieving dilation of the vase has been reached, the discharge of the oil present in the elastic membranes for external containment of the vase is activated by means of automatic control of pressure and flow, whilst oil at a pre-set constant pressure and free flow is introduced into the internal elastic membrane. The step described above proceeds up to complete dilation of the specific vase. Then, the outlet of the oil from the elastic membranes for external containment of the vase is closed, and the pressure inside the internal elastic membrane is raised up to a pre-set value required for compacting any micro-wrinkles or micro-ridges of the celadonite produced during the dilation step. Then, the supplies to the two sets of elastic membranes, i.e., the internal one and the external one, are set to simultaneous discharge, preferably via two distinct circuits; - Step "15": once pressure has been released from the two sets of elastic membranes, the step of suction of the oil from the internal elastic membrane starts, and continues until all the oil has been emptied out completely; - Step "16": the fastening clamps for clinching the mobile frame to the fixed positive mould are released; - Step "17": lowering of the mobile frame, opening of the negative mould 40 in segmented fashion, in the sectors of which the elastic membranes 70 for external containment of the vase are housed.

At this point, the product 80 is finished and stands free on a plate provided in the negative mould 40, ready to be picked up either automatically or manually and to be transferred, for instance, to a decoration press or onto a pallet for the drying step.

As already said above, it is important to stress the fact that a press according to the present invention can be used for moulding whatever kind of material ranging from metal plats to soft materials as foodstuffs, in fact the peculiar embodiment of the press allows the application of pressure ranging from few bars up to 1.000 bars or more. With the press according to the invention, for example, it is even possible to prepare sinters of metals, glass powders etc. Moreover the press can be easily dimensioned for the production of huge artefacts or for very small ones.

Claims

1. A press for moulding comprising a mould (4, 40) for forming a semi-finished body (8, 80), characterized in that it comprises an elastic forming membrane (7) which acts on the body (8, 80) and is deformable by pressurized-fluid means so as to compress said body against said mould.

2. The press according to Claim 1 , in which the elastic membrane (7) is set between the outer surface of a supporting element (10) and inner walls of said body (8).

3. The press according to Claim 2, in which said element (10) consists of a positive mould (10) carried by a fixed support (9), and the elastic membrane (7) is in the form of a bag set precisely and in a pressure-tight way inside said positive mould (10).

4. The press according to Claim 3, in which said elastic membrane is closed on said positive mould (10) by means of a flange connection (11, 12) with a pressure- tight gasket (13).

5. The press according to Claim 3, in which said pressurized-fluid means comprise means for introducing fluid under pressure into a central through channel (14), which is made so that it traverses the positive mould (10), and into a plurality of surface grooves (19) made in the positive mould (10), which communicate with said channel and are set over at least part of the surface of contact between the positive mould (10) and the membrane (7) for uniform transmission of the flow of fluid under pressure.

6. The press according to Claim 5, in which said grooves are arranged in a regular way over the entire surface of contact between the positive mould (10) and the elastic membrane (7).

7. The press according to Claim 5, in which said pressurized fluid means comprise means for suctioning the fluid present in the elastic membrane (7).

8. The press according to Claim 1 , in which said forming mould (4) is a negative mould for forming vases, which can be opened in segmented fashion.

9. The press according to Claim 8, comprising a frame (15), which can move in a vertical direction and is fixed to the negative mould (4) and is able to carry the negative mould (4) from a lowered position up to a position in which the positive mould (10) is inserted inside the forming mould (4).

10. The press according to Claim 9, comprising clinching fasteners (18) for controlled clamping of the frame (15) to the support (9).

11. The press according to Claim 8, comprising an ejector for extracting the finished vase (8') from the negative mould (4).

12. The press according to Claim 7, comprising means for continuous change of the oil introduced into the membrane (7).

^• 13. The press according to at least one of the preceding claims, characterized in that said negative mould (4) is a mould for decorating the product.

14. The press according to at least one of the preceding claims, characterized in that it comprises a second elastic forming membrane (70), which acts between the negative mould (40) and the body (80) and is deformable by pressurized-fluid means so as to form said body (80) on the outside.

15. The press according to Claim 14, in which said second elastic membrane is set on the outside of the product in the form of a cylindrical sleeve closed against the inner walls of the forming mould (40) by means of pressure-tight seals (44, 45).

16. The press according to Claim 15, in which between the negative mould (40) and the membrane (70) there is left a gap (46), which can be filled with fluid under pressure introduced by means of ducts (43).

17. An apparatus for automatic moulding of earthenware products and the like, comprising at least one unit (20) for supplying raw material to at least one first press (1) for the production of a smooth semi-finished product (8), the said apparatus being characterized in that it further comprises:

- means (2) for transferring said semi-finished product (8) to at least one second forming press (3, 30) according to one or more of Claims 1 to 16 for the manufacture of finished products (8');

- means for transferring said finished product (8') to possible subsequent processes; and

- means for automatic or semi-automatic control of said supply (20), said presses (1 , 3, 30) and said transfer means (2, 6).

18. The apparatus according to Claim 17, in which said means (2) for transferring the semi-finished product (8) consist of a pick-up arm (21 ) rotating between the workstation of said first press (1) and the workstation of said second press (3, 30).

19. The apparatus according to Claim 17, in which said means for transferring the decorated product (8') consist of a frame with mobile cross member (61), which can slide between said second press (3, 30) and a loading surface (62).

20. The apparatus according to Claim 17, in which said control means comprise a hydraulic power unit with programmable control logic.

21. The apparatus according to Claim 17, in which said control means comprise:

- at least one double-acting hydraulic cylinder (a) for raising/lowering the mobile frame (15); - at least one double-acting hydraulic cylinder (b) for opening/closing, in segmented fashion, a negative mould (4, 40) of said second press;

- at least one double-acting hydraulic cylinder (c) for opening/closing sectors of the fastening clamps for clinching the frame (15) to the support (9); and

- at least one double-acting hydraulic cylinder (d) for supplying the elastic forming membrane or bag (7) and/or the external elastic membrane (70) with fluid under pressure.

22. The apparatus according to Claim 21 , in which said hydraulic actuators are equipped with proximity sensors controlled by the central control unit.

23. The apparatus according to Claim 17, comprising means for continuous change of the oil introduced into the membrane (7) and/or sent to the membrane

(70).

24. The apparatus according to Claim 23, in which said means consist of two double-acting hydraulic cylinders (d), where the first cylinder functions as active actuator, and the second cylinder functions as single-bodied syringe for suction of the oil introduced into the membrane.

25. The apparatus according to Claim 17, comprising a device for purging the hydraulic circuit.

26. A method for moulding products, comprising a step of moulding a semifinished product in a forming mould by means of pressure exerted on said semi- finished product by at least one elastically deformable membrane.

27. The method according to Claim 26, in which said forming is obtained by pressure exerted on the inner walls of said semi-finished product, said method further comprising a step of containment of the forming of the semi-finished product by means of pressure exerted on the outside of said semi-finished product by at least one second elastically deformable membrane.

28. The method according to Claim 26, comprising the following steps: - obtaining the smooth semi-finished product in a press;

- transfer of the semi-finished product, either automatically or manually, to the workstation of a forming mould;

- raising of a mobile frame, with the negative mould in closed configuration;

- raising of the frame of the decoration mould to end-of-travel until the support carrying the elastic membrane is made to penetrate inside the semi-finished product;

- clinching of the mobile frame to the fixed support of the membrane;

- introduction of fluid under pressure inside the membrane;

- discharge of the pressure, and suction of oil from the membrane; - release of the fasteners for clinching the mobile frame to the fixed support of the membrane;

- lowering of the mobile frame, with the negative mould closed;

- end of cycle, with opening of the negative mould and discharge of the decorated product.

29. The method according to Claim 28, in which:

- following upon said clinching of the mobile frame to the fixed support of the membrane, there is envisaged the step of simultaneous filling, by introduction of fluid under pressure, of a second elastic membrane 70 for external containment of the vase; and there are moreover envisaged the steps of: - discharge of the fluid under pressure which acts on the external membrane, starting from the attainment of a pre-set pressure value for carrying out forming of the vase up to the end of forming of the vase;

- closing of the outlet for the oil from the external membrane, and raising of the pressure in the internal elastic membrane until a pre-set value of compacting of any possible micro-wrinkles or ridges produced in the vase during the forming step is reached;

- simultaneous discharge of the fluid contained in the internal membrane and the external membrane, preferably via two distinct circuits.