WO1993022117A1

WO1993022117A1 - Mould, in particular, for the shaping of unfired ceramic products

Info

Publication number: WO1993022117A1
Application number: PCT/IT1993/000042
Authority: WO
Inventors: Domenico Pellacani
Original assignee: International Stampi S.R.L.
Priority date: 1992-04-29
Filing date: 1993-04-27
Publication date: 1993-11-11
Also published as: DE4391896C2; DE4391896T1; ITMO920062A0; IT1259950B; ITMO920062A1

Abstract

The present invention relates to a mould, in particular, for shaping unfired ceramic products. It can be used to make products of complex geometric shape using vertical-action presses, in which the surface of an upper buffer (3) in each cell (9) is so shaped that it can be superimposed by vertical displacement onto the surface of a fixed lower buffer (6) in such a way that the two surfaces almost meet. The 'soft' material is fed at room temperature through loading inlets (111) located in plates (11) which form the sides of each cell (9) and are in turn attached to a matrix (10) constituting the lower, mobile part of the mould. Feeding of the soft material through the loading inlets (111) into the cell (9), the form of which is defined above by the upper buffer (3), below by the lower buffer (6) and on each side by the plates (11), occurs while the cell is closed.

Description

i„ DESCRIPTION

»

MOULD, IN PARTICULAR, FOR THE SHAPING OF UNFIRED CERAMIC PRODUCTS.

The present invention relates to a mould, in particular, for shaping unfired ceramic products. Specifically, but not exclusively, it can be used for making unfired ceramic products of complex geometric shape in vertical presses by moulding materials (clays, pulverised 5 preparations, etc.) usually used in the ceramics industry for the production of tiles.

One of the most frequent problems encountered in making ceramic products by moulding powders (powdered preparations, etc.) of ceramic material is that of ensuring a high level of homogeneity in the

1 o distribution of density within the body of the moulded product.

It is important that density is homogenous in order to limit, over and above the inevitable shrinkage, differential deformation and possible breakage during firing. A high level of uniformity is difficult to achieve even with the simpler

15 forms of flat tiles, which generally have an upper smooth face and an opposite face presenting various reliefs (imprints) and of different size as a result of the presence of delivery angles, etc. Another factor which can cause a lack of homogeneity in the density of the moulded product is the system of distribution of the clay, pulverised preparation or ceramic material in powdered form in the individual cells, indeed distribution mechanisms are frequently found which use mechanisms which are notable to guarantee uniform distribution of the layers of pulverised material for the entire length of their run. Depending on the case, this problem is overcome by adjusting the distribution in order to obtain the maximum uniformity possible.

As far as moulding products of more complex shape is concerned, such as roof tiles or any forms which do not have two flat, parallel surfaces, the systems currently in use are particularly inefficient in ensuring that the density of the moulded product will be sufficiently constant to guarantee that the subsequent firing process will be successful.

This situation severely limits the use of vertical pressing in the manuføcture of ceramic products of complex geometric shape (roof tiles, etc.). The present invention, as detailed in the claims, aims to overcome the short-comings and difficulties of the process by providing a mould to make unfired ceramic products from so-called "soft material", in which the feed occurs while the cell is closed and the product is then moulded by vertical action pressing. An advantage of the present invention is that it can be easily applied to standard vertical-action presses.

A further advantage of the invention is the possibility of complete automation the pressing cycle. The other features and advantages of the invention can be seen in the detailed description that follows of a preferred but not exclusive realisation of the invention itself, illustrated in a non-binding example

A t by the attached drawings, in which: 5 • figure 1 shows a schematic section in vertical plane ll-ll of the following figure 2;

• figure 2 shows a scaled-down, schematic section in plane l-l of figure 1 ;

• figure 3 shows an enlarged, schematic section in plane Ill-Ill of 10 figure 2;

• figure 4 shows a working design of the mould, indicating schematically the various functions and the connections between the various oleodynamic and pneumatic parts which make up the mould;

15 • figure 5 a different operative configuration of the invention in the same section as figure 1.

With reference to the cited figures, 101 indicates an upper, mobile part of the mould attached to a mobile cross-bar 102 of a vertical-action press. The upper part 101 bears two upper buffers 3, solidly fixed to

20 two upper supports 2.

A lower, fixed part of the mould 120 which supports two lower buffers 6 is anchored to the bench of the press 121.

The structure of the mould is completed by a lower part or matrix 10 that can be displaced vertically with respect to a lower fixed part 120, to

25 which it is connected by dual effect hydraulic cylinders 20 with axes in the vertical plane. Plates 11 are solidly attached to the matrix 10 and serve as side walls of individual cells 9, the form of which is further defined above by an upper buffer 3 and below by a lower buffer 6. The overall form of each cell 9 is primarily defined by the shape of the two facing surfaces of the upper buffer 3 and the lower buffer 6. The upper buffer 3 represents the surface which will come into contact with the s material to be moulded, and is so shaped that it can be superimposed by vertical displacement onto the corresponding surface of the lower buffer (6) in such a way that the two surfaces almost meet. Thus, the vertical distance between the two facing surfaces of the upper buffer 3 and the lower buffer 6 is practically constant for the entire cell. 0 On the plan, the overall form of each cell 9 is rectangular, defined by four plates 11 fixed to the matrix 10 in which loading inlets 111 and outlets 112 are located. In particular, the loading inlets 111 are located in three plates on three adjoining sides, and are fed via pipes 45 located in the body of the matrix 10 from a distributor 23 also attached 5 to the matrix 10.

The ceramic material (technically described as "soft"), for example, pulverised preparations and similar substances, is fed into the distributor 23 from a hopper or loading tank 24 via flexible pipes 27. If the piezometric pressure from the hopper 24 is insufficient, a device .25 0 can be used to feed the "soft" material under pressure through the distributor 23 to the cells 9.

The shape and size of the pipes 45 are such as to give the minimum loss of pressure. At the same time, both the horizontal and vertical dimensions of the loading inlets 111 are as large as possible. In 5 particular, the.vertical dimension of the loading inlets 111 is equal to the distance at which the facing surfaces of the upper buffer 3 and the lower buffer 6 are placed when the cell 9 is filled prior to the pressing operation.

The outlets 112 are also of good size. Unlike the loading inlets 111 , these contain filters 8 made of porous, synthetic material, for example ceramic material or synthetic bronze, which, from a physical point-of- view, constitute a lateral limiting surface together with the rest of the plate n.

The outlets 112 containing the filters 8 are connected to vertical pipes 44 located in the plates 11, and flow through openings 47 to the outside in correspondence to the upper surface of the matrix 10. Corresponding openings 48 located in the horizontal surface that will come into contact with the corresponding horizontal surface of the said matrix 10 can be tightly superimposed on the openings 47. The openings 48 are located at the end of pipes 49 which flow into a collector 51 in turn connected to a suction device, indicated in its entirety as 50.

The function of this suction device is to create a decompression in the cell as the latter is fed, so facilitating the flow and even distribution of the "soft" material in the cell. In the form illustrated, the suction device 50 is realised with a two-stage ejector system 32.

Each pipe 44 is connected to a small diverting valve 13 which links the inlets 111 either to the suction device 50 or to a pipe 52 which is located in the body of the matrix 10 and can be fed with compressed air. Normally a spring 14 closes the small valve 13 in the pipe 52. Feeding compressed air into the pipe 52 pushes back the spring 14 and the moving part of the small valve 13 closes the connection to the upper part of the pipe 44. Passing compressed air to the filters 8 in the opposite direction to the suction cleans the filters once the product has been moulded. In order to facilitate the extraction of the moulded product, the surfaces of the plates 11, which are connected at the top to the inlets 111 and outlets 112, are inclined at a pre-set delivery angle. The sides of the lower buffers 6 have stop plates 7 which can be moved perpendicularly with respect to the displacement of the matrix 10 by "cup" springs 46 which constantly press the stop plates 7 against the facing surface of the plates 11.

The main function of the stop plates 7 is to close the loading inlets 111 and the outlets 112 after the cell has been fad and to rest perfectly against the surface of the plates 11 for the entire pressing process. For this reason, the vertical size of the stop plates 7 is not less than the maximum vertical size of the inlets 111 and outlets 112.

Obviously, in order to guarantee a perfect closure, the vertical displacement of the matrix 10 is not less than the height of the outlets

112.

The operative cycle of the mould can be easily illustrated by reference to the functional scheme in figure 4. The "soft" ceramic material is fed continuously, or at least at a frequency corresponding to that of the pressing process of the unfired product, from the hopper 24 via flexible pipes 27 to the distributor 23, possibly with the support of the device 25 to provide extra pressure. The material flows through pipes 45 into the cells 9 which are closed prior to feeding by an initial lowering of an upper part 101 of the mould. The filling of the cells 9 with the "soft" material is facilitated and rendered sufficiently uniform by activating the system which decompresses the cells by suction through the outlets 112 containing the filters 8. In the feeding configuration shown in figure 1, the suction is obviously applied at the moment the cell closes. The effectiveness of the suction through the filters 8 is dependent on keeping the filters free of blockage. In order to maintain the efficiency of the filters 8, compressed air fed along the pipes 52 is passed through the filters 8 prior to the closing of the cells on each cycle. The compressed air for this cleaning is fed by an electric valve 39 through flexible tubes 41 which in turn are directly connected to the pipes 52. The same source of compressed air, in combination with a pressure regulator 42 and an electric valve 34, feeds the suction device 50 which drives the ejectors 32 In the loading configuration, once the individual cell 9 closes, the decompression system effecting suction across the filters 8 is activated by an electric valve 30 which is connected to a collector 51 by a flexible tube 28. The valve 30 is in turn connected to the ejector system 32 of the suction device 50 through an air filter 31. The in-coming air is expelled through a silenced exhaust 33.

When the cells 9 have been filled, the matrix 10 is lowered by cylinders 20 to the height necessary to securely locate the inlets 111 of the plates 11 below the bottom of the cells 9 so that the stop plates 7 can completely close the inlets. In this position, the electric valve 30 is closed in order to stop the suction, and pressing by displacement of the upper mobile part 101 is effected. The displacement involves the lowering of the upper buffers 3 with respect to the fixed lower buffers 6.

The method of closing the inlets 111 and outlets 112, realised as described, allows the whole system to be seen as a three-way diverting valve far each cell and two positions with double hydraulic driving to change from open to closed and vice versa.

Once pressing has occurred, the upper, mobile part 101 retracts to the upper point of rest, while the matrix 10 is further lowered to the lower point of rest, again by the cylinders 20, in order to remove the moulded product The retraction of the upper part 101 and the lowering of the matrix 10 opens a space large enough far an arm, not shown in the figures, with suction cups 35 to lift the moulded product off the lower buffer 6 and out of the mould. - The device can use suction cups 35 designed in such a way as to avoid breaking the unfired product and connected to the suction device by means of a dividing electric valve 37. The product is released from the suction cups 35 by disactivating the suction while at the same time feeding compressed air to the cups through an electric valve 38. When the product has been extracted, the mould is ready for the next cycle which begins by lowering the upper, mobile part 101 into the closed configuration of the cells 9 shown in figure 2. Obviously numerous modifications of a practical and applied nature can be made to the construction details of the invention without infringing the protection of the inventive idea as claimed below.

Claims

CLAIMS 1) Mould, in particular far shaping unfired ceramic products, comprising:

- a central, upper, mobile part (101) attached to a mobile cross¬ bar (102) of a press (vertical-action); the stated upper part (101) supporting at least an upper buffer or half-section of a mould (3);

- a lower, fixed part (120) anchored to a fixed bench (121) of the press; the stated part (120) supporting at least a lower buffer or half-section (6);

- a lower part or matrix (10), vertically displaceable with respect to the stated lower, fixed part (120), bearing plates (11) which function as side walls defining the farm of individual cells (9);

- the stated cells (9), the form of which being further defined above by the stated upper buffer (3) and below by the stated lower buffer (6); characterised by the fact that the surface of each upper buffer (3) which comes into contact with the material to be moulded is so shaped that it can be superimposed by vertical displacement onto the corresponding surface of the stated lower buffer (6) in such a way that the two surfaces almost meet, and that in correspondence to the stated plates (11) of the said matrix (10) loading inlets (111) for the "soft" material are located, which are fed through pipes (45) located in the said matrix (10), themselves fed from a hopper or external loading tank (24); with at least part of the said plates (11) presenting outlets (112), containing filters (8) connected to a suction device (50); with stop plates (7) connected to the side of the lower buffers (6) in such a way that they can be moved perpendicularly with respect to the displacement of the matrix (10) by springs (46), the action of . which is such as to press the stop plates against the stated plates

(11); the stated stop plates (7) being of a size in the direction of displacement of the matrix (10) at least and not less than the maximum size in the same direction of the said inlets (111). 2) Mould as in claim 1 , characterised by the fact that the dimensions of the stated inlets (111) and outlets (112) in a vertical direction is almost equal to the distance between the facing surfaces of the stated upper buffer (3) and the stated lower buffer (6) which define the single cell (9) and are filled with "soft" ceramic material prior to the pressing process.

3) Mould as in claim 1 , characterised by the fact that the stated plates (11) present respective surfaces connected above to the stated inlets (111) and outlets (112) and inclined at a pre-set delivery angle. 4) Mould as in claim 1 , in which the entire perimeter of each stated cell (9) is laterally defined by the said plates (11); the outlets (112) containing the stated filters (8) being connected to vertical pipes (44) which are located in the plates (11) and flow through openings (47) to the outside on the upper surface of the stated matrix (10); it being possible to firmly superimpose onto the stated openings (47) corresponding openings (48) of pipes (49) located in supports (2) of - li ¬

the upper part (101) and flowing into collectors (51) connected to the stated suction device (50).

5) Mould, as in claim 1 , characterised by the fact that it comprises on each stated pipe (44) a diverting valve (13) able to connect alternatively the stated outlets (112) containing filters (8) with openings (47) or with pipes (52) located in the body of the matrix (10) which can be fed, as required, with compressed air; the said diverting valve (13) normally being kept in a position by a spring (14) such that the pipe (44) is open and the pipe (52) is closed, so long as compressed air is not fed into the said pipe (52).

6) Mould, as in claim 5, characterised by the fact that the said pipes (45) come from a distributor (23) solidly attached to the matrix (10) and fed with "soft" ceramic material from a hopper or loading tank

(24) through flexible pipes (27). 7) Mould, as in claim 6, characterised by the fact that it comprises immediately downstream from the hopper (24) a pressurising device

(25) with the function of feeding "soft" ceramic material through the distributor (23) to the cells (9) at a pre-set pressure.