GB2330109A

GB2330109A - Casting machine

Info

Publication number: GB2330109A
Application number: GB9721709A
Authority: GB
Inventors: William David Dunsmore
Original assignee: Porvair PLC
Current assignee: Porvair PLC
Priority date: 1997-10-13
Filing date: 1997-10-13
Publication date: 1999-04-14
Also published as: GB9721709D0

Abstract

A ceramic pressure casting machine is provided with a main frame and affords a plurality of mould cavity defining means arranged in a row and defining a plurality of mould cavities, the mould cavity defining means being afforded by porous moulds. Means are provided for supplying slip to the mould cavities and for applying gas or liquid pressure or suction to the mould cavities directly or via the porous moulds or both. Each mould cavity is defined by two side moulds, at least one upper mould and at least one lower mould, the side moulds being carried on side mould carriages 110, each side mould carriage providing a side mould for two different mould cavities and each upper and lower mould being carried on an upper/lower mould carriage 50. Each mould cavity is defined by two side mould carriages and one upper/lower mould carriage, the carriages being suspended from overhead support means which are carried by, or are part of, the main frame and are moveable therealong along the direction of the row. Means (40, Fig 3) are provided for holding the moulds closed during casting. The machine is designed for casting articles such as toilet bowls.

Description

CASTING MACHINE The present machine relates to casting machines for casting ceramic articles from ceramic slip under pressure.

The articles with which the invention is concerned are large complex articles exemplified by toilet bowls, urinals, squatting pans and bidets.

According to the present invention there is provided a ceramic pressure casting machine provided with a main frame and affording a plurality of mould cavity defining means arranged in a row, defining a row of a plurality of mould cavities, the mould cavity defining means being afforded by porous moulds, means being provided for supplying slip to the mould cavities and for applying gas or liquid pressure or suction to the mould cavities directly or via the porous moulds or both, each mould cavity being defined by two side moulds and at least one upper mould and at least one lower mould, the side moulds being carried on side mould carriages, each side mould carriage providing a side mould for two different mould cavities, the upper and lower moulds being carried on an upper/lower mould carriage, each mould cavity being defined by two side mould carriages and one upper/lower mould carriage, the carriages being suspended from overhead support means which are carried by, or are part of, the main frame and are moveable therealong along the direction of the row, and means for holding the moulds closed during casting.

In a preferred form of the invention means for holding the moulds closed in an up and down direction, e.g. vertically, are carried on each upper/lower mould carriage and act between the carriage and the upper or lower mould or both, whereby such mould closure forces do not act on the main frame.

Preferably restraint means are provided to restrain expansion of each mould cavity from expansion in three directions at right angles,restraint in two directions being provided by means located on the said mould carriages.

The restraint means preferably comprise first restraint means acting along the direction of the row, e.g. horizontally, second restraint means acting transverse to the row, e.g. horizontally, and third restraint means acting transverse to the row but at right angles to the second restraint, e.g. vertically, the second and third restraints being located on the said mould carriages, the restraining forces being accommodated within the said mould carriages.

The transverse horizontal restraint means are preferably located on each of the side mould carriages. The transverse vertical restraint means are preferably located on each of the upper/lower mould carriages.

The first restraint is preferably provided by applying pressure to the row of moulds along the length of the row.

The pressure is preferably applied by having a fixed plate at one end of the row and pressure applying means at the other end of the row arranged to urge the row towards the fixed plate. Thus pressure is applied to the whole row of side mould carriages from one end and the pressure is transmitted through the carriages from end to end.

The second restraint is preferably provided by side reinforcing frames disposed along the opposed side faces of the row of mould defining means and secured to each other via transverse plates or beams between adjacent side moulds, each reinforcing frame extending over two adjacent side moulds, and means limiting outward movement of the said frames, e.g. tie rods extending through non functional parts of the porous side moulds but not through the mould cavity.

In a preferred embodiment each side mould carriage carries two side moulds arranged back to back and secured to a strong rigid support plate which extends from side to side between their opposed rear faces and up above their top edges, the opposed sides of the moulds are reinforced by two reinforcing frames which extend along the whole of each of the two sides of the two moulds and are secured to the end faces of the support plate between the two side moulds, and there is provided means limiting outward movement of the said reinforcing frames, e.g. at least one tie rod for each mould extending through the mould and securing the two reinforcing frames to each other, whereby expansion forces generated within the mould cavity during casting are balanced and compensated for, so that the risk of rupturing of the moulds is lessened or eliminated.

The third restraint is preferably provided by the upper and lower moulds being urged towards each other by clamping means carried on each upper/lower mould carriage. The clamping means e.g. hydraulic cylinders, are preferably arranged to exert clamping pressure in only one direction, preferably in a downwards direction.

In one form of the invention the lower mould is fixed to its mould carriage and the upper mould is mounted on the carriage and is movable vertically and is provided with extensible pressure transmitting means adapted to cooperate with pressure exerting means located on the said mould carriage.

The extensible pressure transmitting means may be shoot bolts mounted on a platen which carries the upper mould and activatable e.g. by hydraulic cylinders to move from a retracted to an extended position. The pressure exerting means may be hydraulic cylinders each adapted to engage a respective shoot bolt when the bolt is in an extended position.

The upper mould is preferably also adapted to be movable between an open position and a raised position which facilitates access to the cast item. This may be achieved by means of a long stroke e.g. pneumatic cylinder, preferably mounted vertically on the upper and lower mould carriage, with its piston connected via a wire and pulleys to the upper mould platen so that retraction of the piston raises the upper mould and extension of the piston lowers it.

In the specific description herein the upper/lower mould carriage is referred to as the rim/slipper mould carriage, the upper mould being the rim mould and the lower mould being the slipper mould.

The invention may be put into practice in various ways and one specific embodiment will be described to illustrate the invention with reference to the accompanying drawings in which: Figure 1 is a diagrammatic side elevation of a machine for pressure casting ceramic sanitary ware, in particular toilet bowls for water closets, with the moulds closed; Figure 1A is an enlarged view of the headstock end of Figure 1; Figure 1B is an enlarged view of the tail stock end of Figure 1; Figure 2 is a diagrammatic end elevation of the same embodiment also enlarged; Figure 3 is a side elevation of the tailstock end of the machine showing the components separated and with certain parts cut away; Figure 4 is similar to Figure 3 and shows other components, namely two rim/slipper carriage assemblies, one with the top platen shown raised and the other with the platen lowered, and two side mould carriage assemblies located alternately between them, the carriages being in the separated state with an exaggerated degree of separation; it should be noted that each mould cavity is provided by two side mould carriages and one rim/slipper carriage assembly; Figure 5A is an end elevation (looking along the axis of the machine) of a rim /slipper carriage assembly with the top platen raised; Figure 5B is an end elevation (looking along the axis of the machine) of a rim /slipper carriage assembly with the top platen lowered; Figure 6A is an end elevation (looking along the axis of the machine) of a side mould carriage assembly; Figure 6B is a plan view of the moulds of two side mould carriage assemblies shown juxtaposed to each other as they are in the closed mould state; Figure 6C is similar to Figure 6B but shows the end half mould at the headstock end; Figure 6D is a view similar to Figure 2 and shows the connection of end half mould to the headstock; Figure 7 is a scrap detail side elevation of part of Figure 4 showing the relationship of the shoot bolts, the side frame and the hydraulic cylinders on an enlarged scale; and Figure 8 is a scrap detail end elevation of part of Figure 5B showing the relationship of the shoot bolts and the hydraulic cylinders on an enlarged scale.

The structure of the machine will be described first then its mode of operation.

The machine is designed for pressure casting large ceramic articles of complex shape such as toilet bowls and will be described with reference thereto but it will be understood that it is not limited in its usefulness to the production only of toilet bowls.

The machine has a fixed headstock assembly 10 and a fixed tailstock 20 which are connected at a high level by an overhead beam affording a pair of twin track overhead beams 25 and 30 each of which have an inner track 26, 31 and an outer track 27,32, and at low level by two base beams 28 and 33 located below a floor grill 29. The beams are designed to support moulds for up to 10 toilet bowls as can be seen from Figure 1. The mould cavities are provided by cavity defining mould parts which are carried on carriage assemblies. These are suspended from the beams 25 and 30.

The carriage assemblies consist of rim/slipper carriage assemblies 50 and side mould carriage assemblies 110, which are arranged alternately along the length of the machine, as can be seen most clearly from Figure 4. The assemblies 110 provide the sides and most of the mould walls and the assemblies 50 provide the top and bottom mould walls.

Figure 3 shows a finished cast piece 90 located on a bottom platen 61.

The assemblies 50 and 110 are carried by wheeled trolleys 51 and 111 which run along the machined tracks of the beams 25 and 30. The trolleys provide for easy movement of the moulds along the beams by means of an automatic powered mould movement system. Each trolley 51 has two pairs of wheels 52 and 53 which run on the outer tracks 27 and 32. Each trolley 111 has two pairs of wheels 112 and 113 which run on the inner tracks 26 and 31. This permits the assemblies 50 to run past the assemblies 110 without catching on them and thus allows for the side mould assemblies 110 to nest within the rim/slipper assemblies 50.

A single closing force is used to hold the moulds closed in the longitudinal direction. This is done by squeezing the row of side mould assemblies between the headstock 10 and a pressure plate 40 at the tailstock 20.

The pressure plate 40 is carried by a plate 35 which hangs down from a wheeled trolley 36 which runs on the inner tracks 26 and 31 of the beams 25 and 30.

A hydraulic cylinder 42 with a piston 41 is located in the tailstock on the centre line of the mould assemblies.

The cylinder 42 is itself mounted on a piston and cylinder (not shown) so that it can be retracted down towards the base of the assembly (see Figure 1 and 1B).

Located between the piston 41 and the centre of the pressure plate 40 is an adjustable tube 46 itself hung from the beams 25 and 30 by rods 43 which are connected to a wheeled trolley 44 which runs on the inner tracks 26 and 31.

The adjustable tube 46 is adjustable lengthwise and is maintained level by adjustment of the rod 43 and the trolley 44 is fixed to the trolley 36 by means of a rigid tie bar (not shown). The adjustable tube 46 is located with its axis on the centre line. When it is wished to close the moulds the piston 41 is extended, it engages the adjustable tube 46 and pushes it into contact with the centre of the pressure plate 40 and this movement is continued until the moulds are closed and the desired closing force is exerted spread evenly through the moulds. The tail stock has at its centre around the centre line a hole (not shown) of such a size as to be able to accomodate the adjustable tube 46.

Thus when one wishes to open the moulds the piston 41 is retracted into the cylinder 42 which is lowered downwards out of the way of the adjustable tube 46. The tube 46 is then slid along the beams 25 and 30 into the hole in the tailstock 20. This leaves room for an operator to remove the cast pieces.

The side mould carriage assemblies 110 will now be described in more detail, with reference to Figures 4, 6A and 6B. Figure 4 is a side view and shows the suspension on the beams; it also shows the reinforcement of the sides of the moulds. Each assembly 110 provides two side moulds 115 and 120 arranged back to back which define the shape of the opposing side faces of complete mould cavities 119. The partial mould cavities are shown in Figures 4, 6B and 6C as 117 and 118.

When the elements of the multipart mould have been closed together the side mould 115 from one assembly 110 and the side mould 120 from the neighbouring assembly 110 provide respectively the male mould and the female mould for a complete mould cavity e.g. 119B (see Figure 6B).

Where the cavity 119 is symmetrical e.g. as in the present case, the side moulds 115 and 120 constitute complementary moulds of mirror image shape (see Figure 6B).

Thus each assembly 110 carries in a back to back arrangement a side mould 115 for one mould cavity e.g. 119B and a complementary side mould 120 for an adjacent mould cavity e.g. 119A.

Each mould has a porous plastics structure with appropriate gas and liquid inlets and drains as is conventional and is located in a metal e.g. steel case, which extends round its back and sides but not its top and bottom edges. The steel case is bolted to a strong metal e.g.steel support plate 123 which extends up and across between the two moulds and which is secured via a strong suspension plate 124 to the trolley 111. Side reinforcing frames 127 having five cross members 128 and four vertical members 129 extend across the sides of the two adjacent moulds 115 and 120. Fixing bolts 131 secure the side frames 127 to the support plate 123, being located in screw threaded holes in the end faces of the plate 123.

The side frames attached to the support plates 123 and the moulds are reinforced against pressure generated inside the moulds rupturing the sides of the moulds by mould tie rods 135 which extend through holes drilled in the side frames, the metal casing of the mould and the porous non functional parts of the porous mould, but not through the mould cavity. The side frames are thus connected to each other from opposite faces of the mould cavity and can be pretensioned by adjusting the bolts on the ends of the tie rods. The moulds have their porous mould surfaces in contact as can be seen in Figure 6B, but excess pressure on the porous structures is avoided by providing stops or shims 140 between the opposing end faces of the side reinforcement frames (see Figures 4 and 6B).

The closing pressure exerted by the piston 41 is transmitted through the array of moulds by the contacting edges 140 of the side frames 126 and 127.

The end moulds 150 have a slightly different structure; three faces of the mould cavity are provided in the same way as for the rest of the moulds, but the fourth face, a side face, is provided differently. The porous mould is the same but the reinforcing side frames 151,152 are of L shape, the leg 153,154 of each side frame extending outwardly and being attached e.g. by bolts 155 to a thick rigid plate 160 which extends across from one side frame 170 of the main frame to the other 171 on either side of the longitudinal axis of the machine. The same tie rods 135 are provided. This plate 160 is attached e.g. bolted or welded respectively to the headstock 10. The reinforcing members 128 are web shaped at one end and extend across the leg of the L shape so as to reinforce the two parts of the L shape.

A similar arrangement is used at the tailstock end of teh machine, the half mould being secured to the pressure plate 40 in the same way.

In Figure 6D the tie rods 135 have been omitted so as not to obscure the view of the bolts 155.

Alternatively a strong rigid plate which may be integral with the side frames and which extends across the back of the porous mould may be used instead and this plate is attached to the headstock at one end and to the tail stock for the mould at the other end.

The rim/slipper carriage assemblies 50 will now be described in more detail, with reference to Figures 3, 4, 5A and 5B. Figure 4 is a side view and shows the suspension on the beams; it also shows the assemblies in the open and in the closed positions. Each assembly carries a base or slipper mould 55 and a top or rim mould 70 and frame 71. The assembly has two side frames 56 and 57 having arms 58 and 59 which extend from the base right up to the trolley 51. The base mould is attached via its external metal reinforcing frame 63 to a machined horizontal surface on a fixed bottom platen 61 which extends between the bottom ends of the side frames 56 and 57 and is rigidly attached to the arms 58 and 59 of each side frame 56 and 57. The top end of the carriage has a cross beam 65, at the ends of which are the trolleys with the wheels running on the outer machined tracks 27 and 32 of the beams. The rim mould 70 is attached via its external metal reinforcing frame 71 to an upper movable platen 72 which is provided with guide rollers 66,67,68,69 which run along the outside longitudinal faces of the arms 58 and 59 (see Figure 4) of each of the side frames 56 and 57.

Movement of the upper platen between the closed position (see Figure 5B) and the open position (see Figure 5A) is achieved by use of a long stroke pneumatic cylinder 75 mounted on the side frame 56. Its piston is connected via a wire cable 76 and two pulleys 77 and 78 to the top of the upper platen 72 which can thus be raised and lowered by operation of the cylinder whilst providing a compact array.

The separation between the upper and lower platens is designed to be sufficient to give enough clearance to enable the casting to be removed from the mould, that is to enable the casting to be raised high enough to clear the top of the slipper mould. The separation shown has also been designed to be enough to accommodate all currently known models of toilet bowls. Clamping of the top mould relative to the bottom mould and the side moulds is achieved by outwardly extendable means engagable by actuators able to exert downwards clamping force on the upper mould. This is done in this embodiment by providing shoot bolts 80 and 81 mounted in bearings 82 on the upper surface of the top platen 72 actuatable by pneumatic cylinders 83 and 84. The shoot bolts are positioned to extend out between the arms 58 and 59 into the path of a pair of short stroke hydraulic cylinders 86 and 87 also located between the arms 58 and 59, and positioned so that they can engage the shoot bolts and force the rim moulds down into sealing and clamping engagement with the rest of the moulds (see Figure 5B).

Adjustable stops (not shown) are provided between the slipper mould frame 63 and the bottom edges 137 and 138 of the side reinforcing frames 126 and 127. Similar stops are provided between the rim mould frame 71 and the top edges 147 and 148 of the side reinforcing frames 126 and 127.

These stops prevent the porous moulds being crushed while ensuring that adequate clamping occurs between the contacting porous mould faces. The clamping force is largely transmitted through the metal frames 71 and 63 and the side frames 126 and 127.

The upper platen can be safely secured in the raised position (see figure 5A) by extending the shoot bolts 80 and 81 so that they engage in a cut out 85 in a transverse member 89 attached between the arms 58 and 59 of the side frames 56 and 57.

It will be appreciated that each mould cavity is defined by one rim/slipper carriage and two side mould carriages The moulds are clamped longitudinally by the piston 41 acting on the pressure plate 40, and vertically by the individual clamping of the cylinders 86 and 87 on the shoot bolts 80 and 81. Horizontal transverse restraint against pressures generated in the mould cavity is provided by the side frames 126 and 127, which are connected to each other via the transverse plates 123 and the bolts 131 and by the mould tie rods 135. Accordingly the pressure generated inside the moulds is balanced in three dimensions, longitudinally, vertically and transversely of the length of the row of moulds.

The machine main frame and its hydraulic system are designed to exert mould closing forces of up to 700kn.

Typically this closing force will allow a casting pressure of the order of 10 Kg/sq cm.

In general for large complex ceramic objects casting pressures in the range 5 to 15 or 20 or even 25 kg/sq cm have been used. Lower pressures, result in extended casting times while higher pressures above 25 kg/sq cm, such as 40 kg/sq cm and above, require increased strength in the machinery and moulds. A convenient balance of these factors indicates a range of 5 to 15 kg/sq cm as being desirable.

A manifold is provided for feeding slip to the moulds and connection to individual moulds is by means of flexible hoses. A slip handling circuit is provided which comprises a heated and insulated storage tank, high and low pressure air driven diaphragm pumps, a pulsation damper and interconnecting pipework. The slip casting pressure is adjusted by means of an air pressure regulator in the air supply line to the high pressure pump. Automatic valves are provided to route slip to the moulds during the fill part of the cycle and from the moulds back to the storage tank during the drain part of the cycle.

Separate piping manifolds are provided to distribute compressed air to the moulds for consolidating and releasing the cast pieces. These manifolds and associated control valves are supported by the beams 25 and 30. Connections to individual moulds is by flexible hoses with quick release couplings.

The operation of the machine will now be described.

Mould closure is automatic, the machine operator initiating an automatic process cycle. The moulds are moved to the closed position. The moulds are clamped longitudinally by the piston 41 acting on the pressure plate 40, and vertically by the individual clamping of the cylinders 86 and 87 on the shoot bolts 80 and 81. Horizontal transverse restraint against pressures generated in the mould cavity is provided by the side reinforcing frames or plates 126 and 126 connected by the bolts 131 to the support plate 123 and by the mould tie rods 135. Accordingly the pressure generated inside the moulds is balanced in three dimensions, longitudinally, vertically and transversely of the length of the row of moulds.

Whilst the invention is not dependant on the accuracy or otherwise of any theory it is thought that the row of bolts 131 may act as a fulcrum so that outward force exerted on the mould 115 in one mould cavity e.g. 119B in Figure 6B can be transferred by the reinforcing side frame or plate 126 or 127 to balance the equivalent force exerted on the mould 120 in the adjacent mould cavity 119A, the same balancing being available for the mould cavity 119C, the side frames 126 and 127 being retained by the tie rods 135.

The reinforcing frames 126 and 127 may be considered to act as a link between adjacent moulds. The row of moulds may therefore in effect work together as a single assembly and not as a discrete series of individual units which are independant of each other. This enables the size and complexity of the machine to be lessened.

The moulds are then filled with slip. The initial filling duty is by a low pressure, high flow pump, after a short duration purge of the slip manifold in which the slip is routed back to the slip tank. At the end of the purge period, slip is transferred from the heated storage tank via automatically controlled valves to the mould cavity.

On completion of the initial deposition of a film of slip on the surface of the mould cavity a second slip pump takes over. This pump increases the pressure inside the cavity to the preset value needed for the casting, which is of the order of 10 kg/sq.cm, or more broadly in the range 5 to 15 or 5 to 20 kg/sq cm. The set pressure is maintained throughout the casting part of the machine cycle.

If a drain cast item is being produced, at the end of the set casting time the high pressure slip pump is closed down. The slip inlet valve is left open and acts as a drain and is connected directly to the slip storage tank. Liquid slip is displaced from the mould by the introduction of compressed air. At the end of the drain period the slip inlet valve is closed.

The air pressure within the mould is increased to the preset consolidation pressure, which is typically of the order of 4 kg/sq cm, e.g. 2 to 5 kg/sq cm. Water is displaced from the cast clay into the pore structure of the moulds and is drained therefrom. This results in some drying of the cast piece.

At the end of the consolidation period the slip inlet valve is opened briefly to drain any remaining slip back to the slip tank. The drained cavity is then brought back to atmospheric pressure.

The vertical hydraulic pressure is removed from each of the top platens and then the longitudinal hydraulic pressure is removed from the row of moulds. Release air is applied to the rim moulds 70 simultaneously so that all release together. The rim moulds 70 and their platens 72 are then raised to the safe position shown in Figure 5A and the shoot bolts 80 and 81 extended so that they engage in the cut out 85 in the side arms 56 and 57 and hold the platen 72 raised.

The moulds are opened in sequence from the tailstock end of the machine. Air is introduced into the side mould half located on the pressure plate. Water is displaced from the cavity face of the mould and the cast surface separates from the mould surface. The air is immediately switched off and the pressure plate moved back (to the right in Figure 1 and 1B and as shown in Figure 3). The cast piece is supported on the slipper mould (as shown in Figure 3). Separation from the other side mould is then carried out as previously described. Finally separation from the slipper mould is carried out by supplying compressed air to the slipper mould and the casting is removed by raising it clear of the mould.

It will be appreciated that each mould cavity is defined by one rim/slipper carriage and two side mould carriages.

Accordingly the next mould to the left in Figure 3 is then opened using the same sequence as described already, and this repeated up to the headstock end of the machine.

It will be appreciated that the top and bottom moulds for each mould cavity are located within the individual structural frame 56,57,65,61 of the rim/slipper mould carriage assembly 50 which thus only has to be strong enough to accommodate the vertical closing forces needed for that individual mould cavity, which are typically of the order of 70 tonnes. Thus none of the vertical forces needed to hold the moulds closed is transferred to the main frame of the machine constituted by the headstock 10, beams 25 and 30, tailstock 20 and base frame 33, which can accordingly be made of lighter construction.

The main frame of the machine thus merely has to support the weight of the suspended mould assemblies which for ten such assemblies is of the order of 30 tonnes rather than the vertical closing forces; which if this arrangement was not used would be of the order of 700 tonnes. In addition the main frame has to accommodate the longitudinal horizontal closing force, which being spread over all 10 mould cavities only needs to be of the order of 50-70 tonnes.

The tie rod arrangement 135 for providing means limiting outward movement of the side reinforcing frames 126 and 127 also enables the side reinforcement of the moulds to be less substantial than otherwise would be needed, and being located on the suspended side mould carriages also does not impose any load on the main frame of the machine.

In a further aspect of the invention a ceramic pressure casting machine affords a plurality of mould cavity defining means arranged in a row, defining a row of a plurality of mould cavities, the mould cavity defining means being afforded by porous moulds, means being provided for supplying slip to the mould cavities and for applying gas or liquid pressure or suction to the mould cavities directly or via the porous moulds or both, each mould cavity being defined by two side moulds and at least one upper mould and at least one lower mould, the side moulds being carried on side mould carriages, each side mould carriage providing a side mould for two different mould cavities, the upper and lower moulds being carried on an upper/lower mould carriage, each mould cavity being defined by two side mould carriages and one upper/lower mould carriage, the carriages being suspended from overhead support means and moveable therealong along the direction of the row, side reinforcing frames being disposed along the opposed side faces of the row of mould defining means and secured to each other via transverse plates or beams between adjacent side moulds, each reinforcing frame extending over two adjacent side moulds and there being provided means limiting outward movement of the said frames, e.g. tie rods extending through non functional parts of the porous side moulds but not through the mould cavity.

Preferably each side mould carriage carries two side moulds arranged back to back and secured to a strong rigid support plate which extends fro opposed sides of the moulds are preferably reinforced by two reinforcing frames which extend along the whole of each of the two sides of the two moulds and are secured to the end faces of the support plate between the two side moulds.

There is provided means for limiting outward movement of the said reinforcing frames e.g. at least one tie rod for each mould extends through the mould and secures the two reinforcing frames to each other, whereby expansion forces generated within the mould cavity during casting are balanced and compensated for, so that the risk of rupturing of the moulds is lessened.

In a further aspect of the invention a ceramic pressure casting machine affords mould cavity defining means arranged in a row, defining a mould cavity, the mould cavity defining means being afforded by porous moulds, means being provided for supplying slip to the mould cavity and for applying gas or liquid pressure or suction to the mould cavity directly or via the porous moulds or both, the mould cavity being defined by two side moulds and at least one upper mould and at least one lower mould, the side moulds being carried on supports, a first one of which is fixed and the other of which, the second support, is movable along an axis orthogonal to the first support, the upper and lower moulds being carried on an upper/lower mould carriage, the mould cavity being defined by the fixed and movable side moulds and the upper/lower mould carriage, the carriage and the movable side mould being suspended from overhead support means and moveable therealong along the said orthogonal direction and means for holding the mould closed during casting. Preferably restraint means are provided to restrain expansion of the mould cavity from expansion in three directions at right angles.

In another aspect of the present invention a ceramic pressure casting machine affords a plurality of mould cavity defining means arranged in a row, defining a row of a plurality of mould cavities, the mould cavity defining means being afforded by porous moulds, means being provided for supplying slip to the mould cavities and for applying gas or liquid pressure or suction to the mould cavities directly or via the porous moulds or both, each mould cavity being defined by two side moulds and at least one upper mould and at least one lower mould, the side moulds being carried on side mould carriages, each side mould carriage providing a side mould for two different mould cavities, the upper and lower moulds being carried on an upper/lower mould carriage, each mould cavity being defined by two side mould carriages and one upper/lower mould carriage, the carriages being suspended from overhead support means and moveable therealong along the direction of the row, and means for holding the moulds closed during casting.

The said means for holding the moulds closed in a vertical direction are preferably carried on each upper/lower mould carriage and preferably act between the frame of the carriage and the upper mould.

The said means for holding the moulds closed in a horizontal direction preferably act on the side mould carriages.

In another aspect of the present invention a ceramic pressure casting machine has a main frame and affords a plurality of mould cavity defining means arranged in a row, defining a row of a plurality of mould cavities within the main frame, the mould cavity defining means being afforded by porous moulds, means being provided for supplying slip to the mould cavities and for applying gas or liquid pressure or suction to the mould cavities directly or via the porous moulds or both, each mould cavity being defined by two side moulds and at least one upper mould and at least one lower mould, the side moulds being carried on side mould carriages, each side mould carriage providing a side mould for two different mould cavities, the upper and lower moulds being carried on an upper/lower mould carriage, each mould cavity being defined by two side mould carriages and one upper/lower mould carriage, the carriages being suspended from overhead support means which are carried by, or part of, the main frame, the carriages being movable therealong along the direction of the row, and means for holding the moulds closed during casting, the said means for holding the moulds closed in a vertical direction being carried on each upper/lower mould carriage and acting between the frame of the carriage and the upper mould whereby the vertical mould closure forces do not act on the main frame.

Claims

CLAIMS 1. A ceramic pressure casting machine provided with a main frame and affording a plurality of mould cavity defining means arranged in a row, defining a row of a plurality of mould cavities, the mould cavity defining means being afforded by porous moulds, means being provided for supplying slip to the mould cavities and for applying gas or liquid pressure or suction to the mould cavities directly or via the porous moulds or both, each mould cavity being defined by two side moulds and at least one upper mould and at least one lower mould, the side moulds being carried on side mould carriages, each side mould carriage providing a side mould for two different mould cavities, the upper and lower moulds being carried on an upper/lower mould carriage, each mould cavity being defined by two side mould carriages and one upper/lower mould carriage, the carriages being suspended from overhead support means whch are carried by, or are part of, the main frame and are moveable therealong along the direction of the row and means for holding the moulds closed during casting.
2. A machine as claimed in claim 1 characterised in that means for holding the moulds closed in an up and down direction are carried on each upper/lower mould carriage and act between the carriage and the upper or lower mould or both, whereby such mould closure forces do not act on the main frame.
3. A machine as claimed in claim 1 or claim 2 characterised in that restraint means are provided to restrain expansion of each mould cavity from expansion in three directions at right angles, restraint in two directions being provided by means located on the said mould carriages.
4. A machine as claimed in claim 3 characterised in that the restraint means comprise first restraint means acting along the direction of the row, e.g. horizontally, second restraint means acting transverse to the row, e.g. horizontally, and third restraint transverse to the row but at right angles to the second restraint means, e.g. vertically, the second and third restraints being located on the said mould carriages, the restraining forces being accommodated within the said mould carriages.
5. A machine as claimed in claim 4 characterised in that the transverse horizontal restraint means is located on each of the side mould carriages.
6. A machine as claimed in claim 4 or claim 5 characterised in that the transverse vertical restraint means is located on each of the upper/lower mould carriages.
7. A machine as claimed in any one of the preceding claims characterised in that the first restraint is provided by applying pressure to the row of moulds along the length of the row.
8. A machine as claimed in any one of the preceding claims characterised in that the second restraint is provided by side reinforcing frames disposed along the opposed side faces of the row of mould defining means and secured to each other via transverse plates or beams between adjacent side moulds, each reinforcing frame extending over two adjacent side moulds and means for limiting outward movement of the said frames e.g. tie rods extending through non functional parts of the porous side moulds but not through the mould cavity.
9. A machine as claimed in anyone of the preceeding claims characterised in that each side mould carriage carries two side moulds arranged back to back and secured to a strong rigid support plate which extends from side to side between their opposed rear faces and up above their top edges, the opposed sides of the moulds being reinforced by two reinforcing frames which extend along the whole of each of the two sides of the two moulds and are secured to the end faces of the support plate between the two side moulds, and there is provided means limiting outward movement of the said reinforcing frames e.g. at least one tie rod for each mould extends through the mould and securing the two reinforcing frames to each other, whereby expansion forces generated within the mould cavity during casting are balanced and compensated for, so that the risk of rupturing of the moulds is lessened.
10. A machine as claimed in anyone of the preceeding claims characterised in that the third restraint is provided by the upper and lower moulds being urged towards each other by clamping means carried on each upper/lower mould carriage.
11. A machine as claimed in claim 10 characterised in that the clamping means, e.g. hydraulic cylinders, are arranged to exert clamping pressure in a downwards direction only.
12. A machine as claimed in anyone of the preceeding claims characterised in that the lower mould is fixed to its mould carriage and the upper mould is mounted on the carriage and is movable vertically and is provided with extensible pressure transmitting means adapted to cooperate with pressure exerting means located on the said mould carriage.
13. A machine as claimed in claim 12 characterised in that the extensible pressure transmitting means are shoot bolts mounted on a platen which carries the upper mould and activatable e.g. by pneumatic cylinders to move from a retracted to an extended position, and the pressure exerting means are hydraulic cylinders each adapted to engage a respective shoot bolt when the bolt is in an extended position.
14. A machine as claimed in anyone of the preceeding claims characterised in that the upper mould is also adapted to be movable between an open position and a raised position which facilitates access to the cast item.
15. A machine as claimed in claim 14 characterised in that the upper mould is movable between an open position and a raised position by means of a long stroke hydraulic cylinder, mounted vertically on the upper/lower mould carriage, with its piston connected via a wire and pulleys to the upper mould platen so that retraction of the piston raises the upper mould and extension of the piston lowers it.