GB2027634A

GB2027634A - Casting ceramic material

Info

Publication number: GB2027634A
Application number: GB7832838A
Authority: GB
Original assignee: Ideal Standard GmbH
Current assignee: Ideal Standard GmbH
Priority date: 1978-08-09
Filing date: 1978-08-09
Publication date: 1980-02-27
Also published as: ES251212U; IT7946862A0; FR2432922A1; ES251212Y; BR7905103A; NL7906075A; IT1166251B; GR66830B; SE7906611L; BE878133A; DE2931975A1

Abstract

A mould for casting ceramic slip material comprises a portion 15, 16, 17, which is adapted for casting a hollow region in the article, such as a box flush-water rim 31 of a water closet bowl, having projections 30 made of non-casting material the free ends of which project into the mould cavity where the hollow cast region will be formed, the projections being removable after casting to leave precise, clean holes or slots in the wall of the hollow region. The projections which may be located in core pieces 15, 16, 17, for forming the bowl of a w.c., may be made of resilient material so that they flex during removal to avoid damaging the soft cast material. <IMAGE>

Description

SPECIFICATION A mould for casting ceramic material This invention relates to a mould for casting ceramic material in slip form and particularly, although not exclusively, for casting articles of sanitary ware of vitreous china.

It is known to form a hole in an article during casting by providing a metal or plastic peg our rod in a mould which forms a bridge across the mould cavity between opposite walls, the peg or pin being removed after casting either separately or with one of the mould parts to leave the cast hole in the article.

According to the present invention there is provided a mould for casting ceramic material in slip form in which at least a portion of the mould is adapted for casting a hollow cast region in the article cast in the mould, that portion of the mould being provided with one or more projections the or each or which is in the form of a peg, pin, spigot, or rib, and is made of a material against which slip will not cast, the or each projection projecting into the mould cavity so that its free end or edge lies within that region of the cavity where the hollow cast region will be formed in the article the or each projection being removable from the article, after casting, to leave a hole or slot in the wall of the hollow cast region of the article.

The or each projection may be rigid provided that the mould design permits it to bè removed in a direction exactly:corresponding to the line of projection of the hole or slot, or the or each projection may be flexible.

Furthermore, the or each projection may be parallel sided, tapered or of other varying crosssection, and when in the form of a peg, pin or spigot it may be circular in cross-section or any other cross-sectional shape provided it can be withdrawn from the article after casting; such removal may be facilitated or made possible by the projection being made of an elastically flexible material. If the or each projection is in the form of a rib which may be straight or curved then a corresponding straight or curved slot will be formed in the wall of the hollow cast region of the article.

The or each projection may be fixed to or in a part of the mould, or loosely located in or on a part of the mould, and it may be separate from or joined to other projections. Moreover, the or each projection may be adapted so that after casting it can be removed or withdrawn from the article either before, or after, or at the same times as, the adjacent mould portion, i.e. that part ofthe mould which forms the wall of the hollow cast region of the article, is removed or separated from the article.

The invention is particularly applicable to the casting of a box-section flushing water rim for a water-closet bowl, bidet or urinal, either when such a rim is cast separately for subsequent assembly with a separately cast bowl portion or when such a rim is cast integrally with the bowl. In either case, the flushing water rim in the finished product is to have a series of small holes or slots spaced around the underside of the rim for directing flushing water downwardly around the inside surface of the bowl in use of the water closet. Hitherto, such holes or slots have been made in the rim immediately after casting while the article is still in the green condition.Thus, in conventional practice a separately cast rim is cast in a suitably shaped mould to form a hollow cast, unperforated (apart from an outlet aperture for draining excess slip from the hollow cast region) box-section rim, and then when the mould has been opened the holes are punched at the desired spacing around the rim. This punching is done either by a machine which makes all the holes simultaneously or the holes are punched individually by an operator using a template to ensure that the holes are punched in the correct position.

Where the flushing water rim is cast integrally with the bowl, again it is conventionally cast unperforated (apart from the excess slip drain aperture) and then with the mould in a position in which the water closet is upright and the top mould part and inner core pieces removed, the operator punches the holes in the rim by pushing a tubular punch upwardly from underneath the rim and turning it so that it bores out the small hole, the operation being repeated successively around the rim, again usinga tempjate in the form of an.

oval ring with holes spaced around it; the alternative to a tubular punch is to use a solid pointed punch which is simply pushed into the soft rim wall.

These previous methods have several disadvantages: first, with a tubular punch it is difficult, and with å solid punch it is impossible, to make the holes cleanly because the punch, on entry pushes the softs cast material in slightly around where the hole is formed, and with a solid punch there remains on the inside of the flush rim.

a jagged edge around the hole as a result of the punch breaking through the cast wall. Whilst this jagged ring, or indeed the deformed hole opening underneath the rim, cannot be seen in use, they adversely affect the flushing characteristics.

Second, because the template is held by the operator whilst he is also carrying out the punching, the exact positioning of the holes can vary and is dependent on operator skill and care.

Third, the template does not always guide the line of the punch so that the punch may be inserted obliquely to the proper direction again adversely affecting the flushing characteristics. Fourth, punching of the holes is in any case an awkward operation, and therefore time consuming, because the operator has to reach inside the bowl in order to punch the holes upwardly whilst at the same time he has to take care not to damage the inside surface of the still soft bowl.

Even where the holes are punched by a machine in the separately cast rim, the punching is a discrete operation and the holes are still not cleanly formed.

In accordance with the invention the holes in the flush water rim are formed cleanly, and at exactly determined spacing and alignment, during casting by providing a series of pins or pegs on or in that part of the mould which forms the underside wall of the flushing rim. In practice the pegs will be provided on or in core pieces which form the inside surface of the bowl and the underneath of the rim and they project upwardly by an amount greater than the wall thickness of the rim. If one or more slots are to be formed in the rim in addition to or instead of the holes, then a rib or ribs will be provided in addition to or in place of the pegs.

1n a preferred feature of the invention the pins, pegs, spigots or ribs are each made of an elastically flexible material so that when the mould part (e.g. core piece) on or in which the pegs or ribs are fixed is removed the pegs or ribs can flex slightly during withdrawal and thereby avoid damage to the sides and edges of each hole or slot. This feature even allows withdrawal of the pegs in a direction slightly inclined to the line of the hoie, without damage being caused and thus also allows a core piece to have a plurality of pegs projecting at somewhat different angles.

In an alternative preferred feature, the pins, pegs or spigots, made of an elastically flexible material, are removably located in the mould part; for example a plurality of pegs, joined together in a common brace or joining strip, may project through respective holes in the mould part. In this case the pegs would be withdrawn from the article and from the mould part before the latter is separated from the article.

The invention may be carried into practice in a number of ways but certain specific embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a side view looking into a mould in accordance with the invention, for casting a water closet bowl with an integral flushing water rim; Figure 2 is a view of the rim mould part of the mould of Figure 1 with its inner core and a number of separate core pieces assembled thereon; Figure 3 shows one of the side core pieces removed from the assembly of Figure 2; Figure 4 is a sectional detail view of part of the mould during casting; Figures 4A and 4B show details of an alternative embodiment of the invention; Figure 5 is a cut away view of a water closet bowl cast in the mould of Figure 1 showing the core pieces prior to removal;; Figure 6 is a detail of Figure 5 showing holes in the flushing water rim; and Figure 7 shows a section of a mould for casting a separate flushing water rim.

The mould shown in Figure 1 is shaped for casting a water closet bowl having an integral box-section flushing water rim, a bowl portion arid an integral S or P trap. The mould comprises two side parts 10, only one of which is shown, which are substantially symmetrical relative to a vertical parting plane and which each shape half the exterior of the closet bowl, a lower core or slipper 11, a rim mould part 12 which fits over the side parts 10 and which has an integral core 13 which projects down into the mould cavity to form the inside surface of part of the bowl, and five loose core pieces 14, 15, 16, 17 and 18 which fit around the core 1 3 and which shape the upper part of the inside of the bowl and the underneath wall of the box section rim.

The loose core pieces 14 to 18 are shaped to conform, with the core 13, to the contours of the inside of the bowl and they seat into an annular step-shaped recess 1 9 - see Figure 2 - in the core 13, the core pieces 14 to 18 being held during casting by respective spring attachments 20 to the rim mould part 13; the spring attachments 20 are simpiy coiled springs extending through holes 21 in the rim mould part 13 one end being attached to the associated core piece and the other end carrying a small cross bar 22 which is pulled through the hole 21 and turned to seat across the hole 21 and so hold the spring under tension.This type of spring attachment is conventional and is merely one way of holding the loose core pieces 14 to 18; other methods such as wire loops and wedges, or screw-threaded bolts, could be used.

The core pieces comprise an elongate backwall piece 14, and four under-rim pieces 1 5 to 18, namely piece 1 5 which fits on top (relative to the upright position of the cast article as shown in Figure 1) of the back-wall piece 14 and is held by the spring tension acting on the piece 14, two roughly segment-shaped side pieces 16 and 1 8 and a roughly wedge-shaped front piece 1 7. The four under-rim pieces 1 5 to 18 each have a plurality of short flexible, rubber pegs 30 projecting upwardly from the surface of the respective core piece which forms the underneath wall of the rim; these pegs 30 are stuck into suitable holes in the core pieces though in other embodiments they may be cast in when the core pieces are cast.The pegs 30 on the two side pieces 16 and 18 and the front piece 17 are all identical, there being thirty-seven pegs in total in this particular embodiment, at regular spacing around the rim; the four pegs 30 on the back piece 1 5 are slightly larger in diameter than the pegs 30 on the core pieces to provide correspondingly larger diameter holes in the flushing rim for the larger flow of water at the back of the bowl. These four larger diameter pegs could be replaced by a single rib extending the same length as the line of four pegs, to form a single slot instead of the four holes.

In the alternative embodiment shown in Figures 4A and 4B the pegs 30 are not struck or cast into the core pieces but are removably located in respective holes 50 in the core pieces by insertion from-below via an undercut portion 51 of the core piece. In this way a series of pegs 30 can be joined together on a common base strip 52, those pegs and the base strip 52 comprising an integrally moulded flexible element.

In a specific construction, all the pegs 30 project beyond the casting surface of the core piece by approximately 1 8 mm and the smaller diameter pegs on the core pieces 16, 17, 18 are approximately 6.5 mm in diameter, all the pegs being made of rubber or other elastically flexible material.

For casting operation, the mould is assembled and filled with slip under pressure, and a casting time is then allowed to elapse whilst the water from the slip is absorbed by the plaster of the mould parts. For this casting stage the mould may be positioned upright, as shown in Figure 1, or inverted.

During the casting time the wall thickness of the cast article will build up and then after a predetermined time the excess slip is drained from the mould via a suitable aperture. The box-section rim 31 (see Figure 4 or Figure 4A) will also be drained via an aperture at the back of the rim leaving a cast wall thickness of for example 1 0-12 mm. Around the rim 31 in the underneath wall, slip will, of course, not have cast where the pegs 30 are located. As shown in Figures 4 and 4A, the pegs 30 project into the mould cavity such that their free ends lie within the hollow cast region inside the box rim.

After draining, the mould is opened and the article removed; this is done in the upright position of the article. First the spring attachments 20 are released and the rim mould part 12 with its integral main core 1 3 is lifted off; this leaves the five loose core pieces 14 to 18 resting around the inside of the bowl as shown in Figure 5. In the case where the pegs 30 are fixed into the core pieces, the procedure then is as follows: the backwall core piece 14 is drawn towards the centre of the bowl and when it is clear of the core piece 15 it is lifted out, and the core piece 1 5 is then drawn down at an appropriate angle to draw the four larger diameter rubber pegs 30 out of the four corresponding holes in the rim; when the pegs 30 are free of the holes the core piece 1 5 is lifted out.Next, the front core piece 1 7 is drawn down at an appropriate angle to draw the smaller diameter pegs 30 out of their corresponding holes and when the pegs 30 are clear, that core piece 17 is then lifted out. In this regard it will be appreciated that the side faces 32 of the wedge-shaped core piece 71, and the corresponding side faces of the back core piece 1 5 must be aligned such as to allow those pieces to be drawn down, to free the pegs 30, without dislodging the side core pieces 16 and 18.

Finally the two side core pieces 1 6 and 18 are removed in turn, again by first drawing each piece downwardly to withdraw the pegs 30 from the holes in the rim.

Owing to the fact that the pegs 30 are somewhat flexible it is not necessary for all the pegs in each core piece to be precisely parallel or indeed for the withdrawal direction to be very precisely aligned, because on withdrawl the pegs 30 flex slightly without disturbing the soft china clay material around the holes.

With ail the core pieces 14 to 18 removed the side mould parts 10 can then be separated and the article removed.

In the alternative case where the pegs 30 are removably located in the core pieces as illustrated in Figures 4A and 4B, the procedure is first to remove the sets of pegs 30 by withdrawing each set on its base strip 52 down in the undercut portion 51 thereby to withdraw the pegs 30 from the wall of the hollow cast region 31 and from the holes 51 in the core piece. When all the sets of pegs have. been removed in this way, then the core pieces can be removed in turn in the conventional way. Whilst sets of pegs have been referred to, it will be appreciated that it may be possible to provide all the pegs 30 on a single element in the form of a complete ring.

As shown in Figure 6, the quality of the holes 33 formed in the rim 31 is greatly superior to that of the holes formed by the methods used hitherto.

The upper and lower edges of each hole are cleanly formed and the position and alignment is consistent for all the holes. By contrast, two holes 35 are illustrated in Figure 6 which have been punched with a solid punch, showing the resulting jagged edges. Furthermore, by forming the holes in accordance with the invention no subsequent punching operations are needed at all for these holes.

An advantage of using the sets of pegs joined to a common base strip is that such an element would have a very long useful life and could be used with successive mould parts which have to be replaced after a number df castings.

The embodiments shown in Figures 1 to 6 relate.to a water closet bowl with a straight wash action, the holes in the flushing rim being directed directly down the sides of the bowl. It would be possible, however, to use the same principle of projecting pegs for making holes to produce a swirl action. In this case, the pegs 30 would all be inclined in the same direction, roughly at the same helix angle to a verical axis. In this case the core pieces would be designed for removal by turning them as the pegs are withdrawn down from the holes in the rim.

Figure 7 shows a second embodiment in which the invention is applied to a mould for forming a separate rim. The mould is annular and shapes the whole of the box section rim and the black portion of the water closet bowl, i.e. that portion to which the seat is mounted, and, in close-coupled models, that portion on which the cistern tank rests. The mould is formed of two parts, an upper part 40 for forming the top and side walls of the box-rim and a lower part 41 for shaping the underneath wall of the box rim. Located at intervals around the rimforming portion of the lower part 41 is a plurality of outstanding rubber pegs 43 which act in the same manner as the pegs 30 of the first embodiment.After casting and draining the excess slip, with the mould either way up, it does not matter, the mould is opened by positioning it with the cast rim upside down and then lifting the lower part 41 directly upwards to withdraw all the pegs 43 from the holes. Again, for a flushing rim designed to provide a swirl action, the pegs will be inclined and the lower part 41 will have to be turned as it is lifted. The separate rim, whilst still in the green condition, is then struck onto a bowl portion to form the complete water closet bowl.

As with the alternative embodiment shown in Figures 4A and 4B, it would be possible to use in place of the individual pegs 43 as shown in Figure 7, one or more sets of pegs joined together on a common base strip 52, the pegs being removably located in respective holes in the lower mould part 41.

Whilst the above embodiments relate to water closets with box rims, it will be appreciated that the invention would be applicable equally to a mould for casting any article having a similar, perforated flushing rim, e.g. urinals or bidets; indeed the invention is even not limited only to moulds for casting such articles but would be applicable to any case where a hole is to be formed in a hollow cast region where formerly the hole had to be punched, provided the mould could be designed appropriately to permit withdrawal of the peg, pin, spigot or rib which forms the hole or slot.

Claims

1. A mould for casting ceramic material in slip form, in which at least a portion of the mould is adapted for casting a hollow cast region in the article cast in the mould, that portion of the mould being provided with one or more projections the or each of which is in the form of a peg, pin spigot, or rib, and is made of a material against which slip will not cast, the or each projection projecting into the mould cavity so that its free end or edge lies within that region of the cavity where the hollow cast region will be formed in the article, the or each projection being removable from the article, after casting, to leave a hole or slot in the wall of the hollow cast region of the article.

2. A mould as claimed in claim 1, in which the or at least one projection is made of flexibly resilient material,

3. A mould as claimed in claim 1, in which the or at least one projection is made of a rigid material.

4. A mould as claimed in any one of claims 1 to 3, in which the or at least one projection is parallel-sided.

5. A mould as claimed in any one of claims 1 to 3, in which the or at least one projection is tapered or of other varying cross-section.

6. A mould as claimed in any one of the preceding claims, in which the or at least one projection is in the form of a rib which is straight or curved.

7. A mould as claimed in any one of the preceding claims, in which the or at least one projection is fixed to or in a part of the mould.

8. A mould as claimed in any one of claims 1 to 6, in which the or at least one projection is removably located in or on a part of the mould.

9. A mould as claimed in claim 8, in which a plurality of projections are provided, the projections being connected to each other.

1 0. A mould for casting a water closet bowl, bidet, urinal or other sanitary-ware article having an integrally cast box rim for distributing flushingwater, wherein that portion of the mould which is adapted for casting the wall of the box rim which is to be perforate in the finished article is provided with a plurality of projections made of a material against which slip will not cast, each projection projecting into the part of the mould cavity which will form the box rim so that its free end lies within that region where the hollow cast region will be formed inside the box rim, all the projections being removable from the article, after casting, to leave a plurality of holes or slots in the wall of the box rim.

1 A mould as claimed in claim 10, in which the projections are provided in core pieces shaped for casting the inside of the bowl and the underside wall of the box rim.

12. A mould as claimed in claim 1 in which the projections are connected together in sets, joined to a common base, each projection being located, removably, in a corresponding hole in the core piece.-

13. A mould for casting a separately cast box rim for flushing-water, to be assembled with a bowl or the like to form a sanitary-ware article such as a water closet bowl, bidet or urinal, wherein that portion of the mould which is adapted for casting the wall of the box rim which is to be perforate in the finished article is provided with a plurality of projections made of a material against which slip will not cast, each projection projecting into the mould cavity so that its free end lies within that region where the hollow cast region will be formed inside the box rim, all the projections being removable from the article, after casting, to leave a plurality of holes or slots in the wall of the box rim.

1 4. A mould for casting ceramic material in slip form substantially as specifically described herein with reference to Figures 1 to 4, 5 and 6, or to those Figures as modified by Figures 4A and 4B, or to Figure 7 of the accompanying drawings.