IE48987B1 - Method and apparatus for casting ceramic ware - Google Patents

Abstract

An installation for slip casting cistern tanks comprises a plurality of moulds (10) in a line on a support structure (19) each carried by transport means (18) for movement along the support; the moulds have a female part (11) with a cavity (14) for shaping the tank sides and bottom and a male part (12) with a core (15) for shaping the inside of the tank. The moulds are arranged so that the tanks are cast on their sides with the open tops of the tanks facing along the line of moulds. Each mould unit may include mould parts at one side of or above the tank mould for casting a tank cover.

Description

This invention relates to an installation for casting from ceramic material in slip form tanks having side walls, a bottom wall and an open top, and to a method of casting such tanks. By tank is meant any relatively deep vessel or container of which the depth (i.e. the height of the side walls)· is greater than the smallest dimension of the open top. The invention is particularly, although not exclusively, applicable to the casting of cistern tanks for water closets.

Cistern tanks for water closets are conventionally cast in an upright position, that is, with the open top of the tank uppermost. Thus, for casting, the female part of the tank-casting mould conventionally has its cavity presented upwardly and the male part which includes the core for shaping the inside of the tank is assembled with and separated from the female part by movement in a generally vertical direction. , The mould parts are made of plaster which during casting absorbs the moisture from the slip. After a predetermined casting time the mould parts are separated by lifting the male part, i.e. the core, out of the female part. This lifting of the core is a laborious operation if done manually because the core is quite heavy not only owing to the weight of the core itself but also owing to the weight of moisture absorbed by it. The lifting of the core can be carried out or assisted by mechanical lifting mechanisms but this requires an adequately strong framework to be provided above the mould, A further problem associated with conventional 5 casting of cistern tanks is that very strong clamps have to be provided to hold the core precisely in place in the female mould part to prevent the core being displaced when the mould is filled with slip owning to the buoyancy forces exerted on the core. However, the plaster from which the mould parts are made is brittle and not particularly strong so that the clamps have to be very carefully designed to achieve the required large clamping forces without fracturing the mould parts. The clamping forces required can be reduced by making the core heavier but this makes lifting of the core more difficult.

Conversely, if the weight of the core is reduced to make lifting easier, for example by making the core hollow, the buoyancy is increased making stronger clamping forces necessary. The solution for reducing the clamping forces and for making lifting easier are therefore not compatible.

According to a first aspect of the present invention there is provided an installation for casting from ceramic material in slip form, tanks, such as cistern tanks for water-closet suites, each having side walls, a bottom wall and an open top, the height dimension of the side walls from the bottom wall and an open top, the height dimension of the side walls from the bottom wall to the open top being greater than the smallest dimension of the open top, the installation comprising: a plurality of moulds arranged in a generally horizontal line on a support structure, each mould consisting of a female part having a cavity for shaping the external surfaces of the side walls and bottom wall of a tank to be cast and a male part having a core which is adapted to be located in the cavity of the female part for shaping the internal surfaces of the side walls and bottom wall of the tank, and means for clamping the moulds each in a closed condition for casting, the mould parts being carried by transport means enabling them to be moved along the support structure in a direction longitudinally of the line of moulds for separating and closing the mould parts, the mould parts being arranged on the transport means so that the tanks are each cast in a position in which the said height dimension of the side walls is aligned in the longitudinal direction of the line of moulds and so that the open top faces in a direction generally parallel to the longitudinal direction of the line of moulds.

Advantageously, all the moulds are oriented in the same direction so that in each case the end of each female mould part which shapes the bottom of the tank lies adjacent the top of the male part of the next adjacent mould in the line. Advantageously, adjacent mould parts of adjacent moulds are connected together, preferably rigidly. This has the advantages that the buoyancy forces occurring when the moulds are filled, are withstood more effectively, and also that during emptying, when the female part of one mould is moved along the line, the male part of the next mould with its core is simultaneously drawn away from its corresponding female mould part.

Preferably all the moulds in the line are clamped together by a common clamping arrangement comprising an abutment at one end of the line and a pressure applying device at the other end.

Cistern tanks are generally of a box shape with generally planar walls though these may be curved slightly, with the side walls at the front and back being wider than the lateral walls. In a preferred construction of the installation the moulds are arranged so that the tanks are cast with the longest dimension of the cross-section generally vertical, i.e. with the narrow lateral walls of the tank one above the other and the front and back side walls generally vertically arranged.

This makes the lateral width of each line smaller than if the tanks are cast with the front and back side walls above each other, and the tanks are cast in a more suitable position for drying.

According to a development of the invention, the female and male mould parts include extensions disposed either laterally or above the tank-forming mould portions, which extensions form male and female mould parts defining for each mould unit a discrete mould cavity for casting a cover to fit on the open top of the tank. The male and female cover-casting mould parts are so arranged that the cover-casting cavity is opened or closed simultaneously with the opening or closing of the tank mould cavity.

This development affords production advantages in that the tanks and their covers can all be cast in the same casting cycle and the covers assembled directly with their respective tanks as soon as they are removed from the moulds, still in the green condition.

For increased productivity it may further be possible to arrange on a single support structure two lines, side by side, of tank moulds, or of combined tank and cover moulds, each pair of two side-by-side moulds being opened and closed simultaneously. Alternatively, it may be possible to arrange for each mould unit to include two tank moulds, or two combined tank and cover moulds, one above the other. - 7 According to a second aspect of the present invention there is provided a method of casting, from ceramic material in slip form, tanks, such as cistern tanks for water-closet suites, each having side walls, a bottom wall and an open top, the height dimension of the side walls from the bottom wall to the open top being greater than the smallest dimension of the open top, in an installation comprising a plurality of moulds arranged in a generally horizontal line on a support structure, each mould consisting of a female part having a cavity for shaping the external surfaces of the side walls and bottom wall of a tank to be cast and a male part having a core which is adapted to be located in the cavity in the female part for shaping the internal surfaces of the side walls and bottom wall, the moulds being arranged so that the tanks are each cast in a position in which the said height dimension of the side walls is aligned in the longitudinal direction of the line of moulds and so that the open top faces in a direction generally parallel to the longitudinal direction of the line of moulds, the method comprising closing all the moulds in the line, filling the moulds with slip and allowing a casting time to elapse, opening all the moulds of the line to draw the cores out of contact with the soft cast tanks in the female mould parts by an amount at least sufficient to ensure that the tanks do not bind on the cores when they shrink during an initial drying period, allowing a predetermined initial drying time to elapse, then removing the cast tanks from each mould in turn.

By allowing the predetermined initial drying time to elapse with the moulds at least partially open, the tanks are permitted to dry and harden sufficiently to enable them to be handled; during this initial drying shrinkage occurs but because the core has been withdrawn, the green cast tank does not shrink onto the core.

Conveniently the initial opening of the moulds by a small amount is carried out by applying air pressure at a suitable region between the male and female parts of all the moulds; it may be possible to open all the moulds simultaneously in this way.

In the case where the installation includes moulds which are each adapted to cast both a tank and a cover, in separate mould cavities within the same mould unit, it may be advantageous if after the mould units are all closed and clamped, the cover-casting cavities are all filled before filling of the tank cavities commences; it may even be desirable to allow a delay after completion of the filling of the cover-casting cavities before filling the tank cavities. Casting of the covers before the tanks in this way provides a longer casting time for the - 9 covers so that when the tanks and covers are removed from each mould unit in turn, the covers will be in a sufficiently hard condition to allow them to be placed directly onto the open top of the tank.

Advantageously, releasable sucker-type devices are used for lifting each' cover off the male part of the cover-casting mould and for carrying it to the tank for assembly with the latter.

The invention may be carried into practice in a 10 number of ways but certain specific embodiments will now be described by way of example with reference to the accompanying drawings in which:Figure 1 is a diagrammatic side view of part of an installation in accordance with the invention for casting cistern tanks for water closets,· Figure 2 is a perspective view of two adjacent moulds of the line of moulds shown in Figure 1; Figure 3 is a perspective view similar to that shown in Figure 2 of a second embodiment wherein each 20 mould has a tank-casting cavity and a cover-casting cavity; Figure 4 is an end view of a line of moulds such as shown in Figure 3; Figure 5 is a perspective view of one of the 25 mould parts shown in Figure 3 looking in the other direction along the line of moulds; Figure 6 is a view of a cover being removed from the moulds of Figures 3 and 5; Figure 7 is a diagrammatic plan view of a double line of combined tank and cover casting moulds side-by-side; Figure 8 is an end view of the double line of moulds shown in Figure 7; Figure 9 is an end view of a further embodiment showing a double line of combined tank and cover casting moulds arranged one above the other; and Figure 10 is a perspective view of a former for removing the tanks from the moulds after casting.

The embodiment shown in Figures 1 and 2 comprises an installation for casting cistern tanks for water closets. A plurality of similar moulds 10 are arranged in a generally horizontal line. Each mould has a female part 11 defining a casting cavity 14 with casting surfaces for shaping the external surfaces of the sides and bottom of the tank and a male part 12 having a core 15 which locates inside the cavity 14 of the female part 11 at a predetermined distance from the casting surface of the latter corresponding to the wall thickness of the tank to be cast; the core being shaped to cast the inside surfaces of the sides and bottom of the tank. As is conventional, each core has a slight taper, or draw, towards the bottom of the tank to enable it to be withdrawn from the tank after casting. The terms sides and bottom as applied to a tank to be cast refer to its position in normal use as part of a water-closet suite.

The top of each tank as cast will be open, though in use a removable cover rests on the top of the tank.

As will be appreciated from Figures 1 and 2 the moulds 10 are arranged, in the line, so that each casting cavity is oriented such that each tank is cast not in its upright position, as in conventional casting, but resting on one side as it were, with the open top of the tank facing in a direction generally horizontally, parallel with the longitudinal direction of the line.

Each tank to be cast is of conventional shape with the front and back walls (in the use position) being wider than the lateral side walls. In the arrangement in Figures 1 and 2, the moulds are disposed with their casting cavities arranged such that the tanks are cast with the longest axis of their cross-section generally vertically, that is, with each tank resting on one of its narrow, lateral side walls with the front and back tank walls arranged generally upright. It will of course be appreciated that in practice the front, back and lateral side walls of each tank may be somewhat curved according to the particular design of tank but such curvature is usually slight.

It may be possible to arrange the moulds so that the tanks are cast resting on the front or back wall i.e. rotated through 90° about a longitudinal axis parallel to the line from the position shown in Figure 2, but this may present difficulties as will be discussed below.

The moulds 10 are arranged end to end along the line, the top of each male part 12 being rigidly connected to the bottom” of the female part 11 of the next adjacent mould in the line. Each set of rigidly joined male and female mould parts is carried on a respective trolley 18 provided with rollers or other runners enabling it to be moved easily along tracks 19 provided on a support structure; as will be clear from Figures 1 and 2, the core 15 and the rigidly joined female part 11 of the neighbouring mould project beyond the trolley 18 in opposite directions making a stable arrangement. The length of the tracks 19 is somewhat longer than the line of moulds to allow for an opening space to permit removal of each cast tank, in turn. The complete line of moulds 10, of which there may be thirty or more, is provided with an overall mould clamping arrangement (not shown) comprising an abutment at one end of the line and a pressure applying device, e.g. a screw or a hydraulic or pneumatic piston at the other end of the line.

Running along the line below the support structure is a slip supply line 21 with branch pipes 22 connected to inlet pipes 23 of the respective moulds.

Each inlet pipe 23 leads via a respective internal duct to an opening 24 at a position corresponding to the centre of the bottom of each tank where a hole will be formed in the finished tank for flushing water to flow out of the tank. Disposed opposite this slip inlet opening 24, in the bottom of the core 15 is a further opening 26 covered with a 200 grade wire mesh which does not allow liquid slip to pass through it, this further opening 26 communicating with a duct 27, shown in dash-dot lines, leading up inside the core 15 and out of the male part 12 to one side of the line. The cores 15 may be hollow, as is conventional in known tank casting moulds, in which case the ducts 27 will be afforded partly by tubes, for example of plastics, extending up inside the hollow cores. The ducts 27 are all connected externally by respective flexible pipes 30 to a manifold air-presure line 31 extending along the line above the moulds. Alternatively, the ducts 27 may terminate at openings at the side in the top of each male mould part.

In a casting operation, the mould parts 11 and of all the moulds in the line are closed and clamped together by the overall clamping arrangement. With the air pressure line 31 closed, slip is fed under pressure via the casting line 21 simultaneously to all the mould cavities, the air displaced from each cavity passing through small vent channels which, once each cavity is full, become blocked with slip and play no further part.

A casting time of for example one hour is then allowed to elapse, the slip being kept under pressure at least in the first part of the casting time to provide for topping up of slip to replace the volume of moisture absorbed by the plaster of the mould parts.

When the casting time has elapsed, the slip feed line 21 is closed, the mould clamping arrangement is released, and the air manifold 31 line opened to admit air under pressure to act along the duct 27 within each core and through the fine wire mesh at the opening 26. This pressure, applied simultaneously to all the moulds, causes air to enter between each core 15 and the tank and causes all the moulds 10 to open slightly e.g. by about 10 cms. Alternatively, where the ducts 27 terminate at openings in the top” of each male part, air may be applied to each mould in turn using an air nozzle. The air pressure alone may be sufficient to cause the opening of each mould or the separation may be assisted by an operator pulling the moulds open. The moulds may be opened up to the depth of each core; however the important point is to open all the moulds by an amount at least sufficient to ensure that the tanks do not bind on the cores when they shrink during an initial drying period.

With all the moulds 10 now partially open, a drying time is allowed to elapse when the still soft tanks will begin to harden. Such hardening is accompanied by slight shrinkage but since the core 15 in each case has been drawn away from inside of the tank the latter will not shrink onto the core. During this drying time, air may be blown into the moulds to promote faster drying.

The air may be heated. The ducts 27 through which mould opening air pressure is applied may be utilised for admitting drying air in this way.

When the drying time has elapsed (half one hour will probably be sufficient), the operator then fully opens each mould in turn and removes the respective tank. This is done by pulling the core 15 of the first mould in the line right out of the female part 11 and moving it far enough along the line to permit the tank to be withdrawn from the female part 11. The operator then pushes a former, such as is shown in Figure 10, into the inside of the tank and lifting slightly carefully draws the tank out. When it is clear of the mould part 11, the operator tips it to an upright position on a rack nearby. He then proceeds to empty the next mould, pulling the just emptied female part 11 and the integrally connected male part 12 of the next mould along the line to open the next mould and allow access to the tank therein.

Instead of manually lifting each tank out of the female mould part, a mechanical lifting and removal device may be provided.

The construction of each mould can be different from that shown where each comprises just two mould parts? for example it may be advantageous to make each female mould part in divided form whereby part of it could be removed to facilitate removal of the cast tank, e.g. in a vertical direction.

It will be appreciated that during the initial drying stage when all the moulds are partially open the lateral side wall of the tank which is uppermost in the mould has to be strong enough to support its own weight without sagging. This presents no difficulty with the arrangement shown where the lateral, narrow side walls are uppermost since the width of these walls is small. If the moulds were to be cast in a position rotated through 90° about the longitudinal axis of the line, the wider front or back walls of the tanks would be uppermost and being generally horizontal they would tend to sag during drying. Whether such sagging occurs of course depends on the size and shape of the tanks. It may be possible to prevent sagging by allowing a longer casting time or by providing support for the uppermost wall when the moulds are opened for the initial drying period.

Figure 3, 4 and 5 show an advantageous embodiment in which each mould carries at one side of the line additional mould parts for casting cistern tank covers. Thus each female mould tank casting part 11 carries a male mould part 40 of a cover casting mould and the top of each male mould tank-casting part 12 carries the corresponding female mould part 41 of the cover-casting mould. The cover-casting male and female parts 40 and 41 are arranged so that their parting plane lies in the same plane as the parting plane of the male and female tank-casting parts 12 and 11 so that the two cavities of each mould unit are opened and closed simultaneously. Each male and female cover-casting mould part 40 and 41 is supported by a strengthening rib or gusset 43 at the back.

As shown in Figure 4, the combined mould units are arranged on a respective trolley 18 slightly offset laterally to the side at which the tank-casting mould cavities lie to facilitate access by the operator for removal of the tanks when cast.

The casting operation is generally similar to that described above for the embodiment of Figures 1 and 2. Thus all the tank-casting cavities and all the covercasting cavities are filled with slip (separate slip supply lines may be provided for filling the cover-casting cavities on the one hand, and the tank-casting cavities on the other, particularly if the covers are to be hollow cast so that draining of excess slip is carried out after the casting time), a casting time is allowed to elapse, the moulds are all opened partially by air pressure and an initial drying time is allowed to elapse, after which the cast articles are removed. Each tank is removed, as described previously and after placing it on the rack nearby, the cover 44 from the same mould unit is removed by using a releasable suction cup device 45 as shown in Figure 6 and this cover 44 is then placed directly onto the open top of the tank; it may be possible to carry out all further operations without having to remove the cover from the tank.

In an alternative procedure, the cover-casting cavities of the whole line of moulds may be filled with slip before the tank-casting cavities are filled, and a casting time may be allowed to elapse before the tanks are cast. This will mean that the covers are at a more advanced stage when the moulds are eventually opened and the covers will therefore be somewhat firmer when they are removed.

The embodiments shown in Figures 7 and 8 is for increased production wherein two lines of combined tank and cover casting moulds 50A and 50b, each having a tankcasting cavity 52 and a cover-casting cavity 53, are arranged side-by-side along the same support structure, a single trolley 51 supporting the integral or rigidly joined side-by-side mould parts of adjacent moulds. Thus a single opening movement opens four mould cavities simultaneously, two tank and two cover casting cavities. With this embodiment twice as many tanks and covers are cast in a single casting cycle.

An alternative embodiment for increased production is shown in Figure 9 wherein instead of the double line of moulds being arranged side-by-side, the two lines are arranged one above the other. Thus each mould unit comprises an upper tank-casting mould 54, an upper cover-casting mould 55, a lower tank-casting mould 56 and a lower cover-casting mould 57; corresponding upper and lower mould parts are made integrally or are rigidly joined together.

With all the embodiments, lifting of the heavy cores for removing cast tanks is completely done away with and moreover the clamping of the entire line of moulds by an overall clamping arrangement presents no difficulty; in any case the required clamping forces are less than was previously required because with the orientation of the mould cavities so that the tanks are cast on their sides, the buoyancy forces acting on the mould parts when the cavities are filled with slip act differently and are resisted more effectively by the mould constructions.

In general, developments in recent years in the ceramic sanitary-ware casting industry have been to make casting installations more compact so that more moulds can be cast in each casting cycle and attended by a single operator. The present invention is in this regard contrary to modern trends in that the moulds take up more floor space. However, it has been found that the advantages to the operator and in the mould constructions of the particular arrangement of moulds according to the invention outweigh the increased space requirements, and furthermore the increased space requirements can be offset by the double line arrangements of moulds side-by-side or one above the other.

Claims (16)

1. An installation for casting from ceramic material in slip form, tanks , such as cistern tanks for water-closet suites, each having side walls, a bottom wall and an open top, the height dimension of the side walls fron the bottom wall to the open top being greater than the smallest dimension of the open top, the installation comprising; a plurality of moulds arranged in a generally horizontal line on a support structure, each mould consisting of a female part having a cavity for shaping the external surfaces of the side walls and bottom wall of a tank to be cast and a male part having a core which is adapted to be located in the cavity of the female part for shaping the internal surfaces of the side walls and bottom wall of the tank, and means for clamping the moulds each in a closed condition for casting, the mould parts being carried by transport means enabling them to be moved along the support structure in a direction longitudinally of the line of moulds for separating and closing the mould parts, the mould parts being arranged on the transport means so that the tanks are each cast in a position in which the said height dimension of the side walls is aligned in the longitudinal direction of the line moulds and so that the open top faces in a direction generally parallel to the longitudinal direction of the line of moulds.

2. An installation as claimed in claim 1, in which all the moulds are oriented in the same direction so that in each case the end of each female mould part which shapes the bottom of the tank lies adjacent the 'top' of the male part of the next adjacent mould in the line.

3. An installation as claimed in claim 1 or claim 2 in which adjacent mould parts of adjacent moulds are connected together, preferably rigidly.

4. An installation as claimed in any one of claims 1 to 3, in which all the moulds in the line are clamped together by a common clamping arrangement comprising an abutment at one end of the line and a pressure applying device at the other end.

5. An installation as claimed in any one of claims 1 to 4, in which the moulds are shaped for casting tanks having generally planar walls with the side walls at the front and back being wider than the lateral walls, the moulds being arranged so that the tanks are cast with the longest dimension of the cross-section generally vertical, i.e. with the narrow lateral walls of the tank one above the other and the front and back side walls generally vertically.

6. An installation as claimed in any one of claims 1 to 5, in which for-opening the mould units after casting an air inlet is provided in each mould unit in the end face of the core which shapes the inside surface of the bottom of the tank, the air inlet being connectible to a source of air under pressure via a duct within the core.

7. An installation as claimed in claim 6, in which each air inlet comprises an aperture covered with a perforate screen which does not allow slip to pass through it.

8. An installation as claimed in any one of claims 1 to 7, in which the female and male mould parts include extensions disposed either laterally or above the tankforming mould portions, which extensions form male and female mould parts defining, for each mould unit, a discrete mould cavity for casting a cover to fit on the open top of the tank, the male and female cover-casting mould parts being so arranged that the cover-casting cavity is opened or closed simultaneously with the opening or closing of the tank mould cavity.

9. An installation as claimed in any one of claims 1 to 8, in which each mould unit includes two tank moulds, or two combined tank and cover moulds, side by side, each pair of two side-by-side moulds being opened and closed simultaneously .

10. An installation as claimed in any one of claims 1 to 8, in which each mould unit includes two tank moulds, or two combined tank and cover moulds, one above the other, each pair of moulds one above the other being opened and closed simultaneously.

11. 13. A method of casting, from ceramic material in slip form, tanks, such as cistern tanks for water-closet suites, each having side walls, a bottom wall and an open top, 5 the height dimension of the side walls from the bottom wall to the open top being greater than the smallest dimension of the open top, in an installation comprising a plurality of moulds arranged in a generally horizontal line on a support structure, each mould consisting of a female part having a cavity for shaping the external surfaces of the side walls and bottom wall of a tank to be cast and a male part having a core which is adapted to be located in the cavity in the female part for shaping the internal surfaces of the side walls and bottom wall,· the moulds 15 being arranged so that the tanks are each cast in a position in which the said height dimension of the side walls is aligned in the longitudinal direction of the line of moulds and so that the open top faces in a direction generally parallel to the longitudinal direction of the 20 line of moulds, the method comprising closing all the moulds in the line, filling the moulds with slip and allowing a casting time to elapse, opening all the moulds of the line to draw the cores out of contact with the soft cast tanks in the female mould parts by an amount at least 25 sufficient to ensure that the tanks do not bind on the cores when they shrink during an initial predetermined drying period, allowing a predetermined initial drying time to elapse, then removing the cast tanks from each mould in turn. 30 12. A method as claimed in claim 11, in which the initial opening of the moulds by a small amount is carried out by applying air pressure at a suitable region between the male and female parts of all the moulds. 13. A method as claimed in claim 12, in which all the 35 initial opening of all the moulds is carried out simultaneously.

12. 14. A method as claimed in any one of claims 11 to 13, in which the installation includes moulds which are each adapted to cast both a tank and a cover in separate mould cavities within the same mould unit, wherein after the mould units are all closed and clamped , the cover-casting cavities are all filled before filling of the tank cavities commences.

13. 15. A method as claimed in any one of claims 11 to 14, in which the installation includes moulds which are each adapted to cast a tank and a cover, in separate mould cavities within the same mould unit, wherein after the initial drying , each tank is removed from its mould and placed upright nearby and the associated cover is removed from the same mould unit and is placed onto the open top of the tank, whilst still in the green condition.

14. 16. A method as claimed in claim 15, in which each cover is removed from its mould and placed on its associated tank using a releasable suction holding device.

15. 17. An installation for casting cistern tanks for water-closet suites, or for casting such cistern tanks and covers therefor, substantially as specifically described herein with reference to Figures 1 and 2, or to Figures 3 to 5, or to Figures 7 and 8, or to Figure 9, of the accompanying drawings.

16. 18. A method of casting cistern tanks for water-closet suites, or of casting such cistern tanks and covers therefor, substantially as specifically described herein with reference to Figures 1 and 2, or to Figures 3 to 5, or to Figures 7 and 8, or to Figure 9, of the accompanying drawings.