GB2080725A

GB2080725A - A method of producing plates having a festooned rim and tools for performing the method.

Info

Publication number: GB2080725A
Application number: GB8122765A
Authority: GB
Original assignee: Erich Netzsch GmbH and Co Holding KG
Current assignee: Erich Netzsch GmbH and Co Holding KG
Priority date: 1980-07-25
Filing date: 1981-07-23
Publication date: 1982-02-10
Also published as: DE3028296C2; IT1138102B; IT8123140A0; DE3028296A1; GB2080725B

Abstract

A plate or other flat or planar article of crockery 12 having a festooned rim, and a relief embossed in the upper side of the plate, is moulded in a powdery, granular or pasty ceramic material. The moulded article 30 has a thickened rim portion 22 which begins at the underside of the rim zone 14, projects radially outwards beyond the outer contour 16 of the finished plate or other article of flat or planar crockery, and in axial view has a plain, in particular circular, perimeter 24. The outer contour 16 of the relief is embossed up to the thickening 22, and the thickened portion 22 is worked off in an operation following the moulding. A two part mould for moulding the article 30 and an abrading tool for removing the thickened portion 22 are also disclosed. <IMAGE>

Description

SPECIFICATION A method of producing plates having a festooned rim and tools for performing the method The invention relates to a method of producing plates or other flat or planar articles of crockery having a festooned rim, by moulding a powdery, granular or pasty ceramic material, in which a relief is embossed in the upper side of the plate. The subject matter of the invention moreover encompasses tools for performing the method.

The pressing, in particular isostatic pressing, of plates and other flat or planar articles of crockery made of powdery or granular ceramic material has been known for a long time (DE-PS 379391 and DE-OS 1684041) and it is also known that plates having a festooned rim be produced by isostatic pressing (Keramische Zeitschrift, Vol. 31, Issue 10, P.

603-604). It is furthermore known that after pressing and as soon as the press mould has been opened, moulded articles made of powdery or granular ceramic material are subject to varying degrees of expansion, depending on their composition. Thus, above all flat plates of large diameter are exposed to the danger of jamming against the one orthe other mould part, with the almost inevitable consequence that when the plate is removed its rim is damaged.

For plates having a plain perimeter, this danger has been obviated by special contouring of the press mould in the plate rim region.

On the other hand, for plates having a festooned rim, the danger of the rim jamming and then crumbling away is so much greater than the known provisions have not yet led to satisfactory results on an industrial scale.

It is, therefore, an object of the invention to develop a method of the type described at the outset in such a manner that the danger of the festooned rim of the moulded plate or of other articles of flat or planar crockery being damaged is substantially reduced, if not completely eliminated. Another object of the invention is to devise tools suitable for performing the method of the invention.

As far as the method is concerned, the object is attained according to the invention in that moulded articles are moulded exhibiting a thickening which begins at the underside of their rim zone, projects radially outwards beyond the axial section profile of the finished plate or other flat or planar article of crockery, and in an axial view has a plain, in particular circular, perimeter, that the outer contour of the relief is embossed up to the thickening, and that the thickening is worked off in an operation following the moulding.

When the article moulded according to the invention expands, the outer contour of the relief, that is to say the rim of the finished plate, is no longer in danger of breaking but at most only the thickening.

Since the thickening is in any case worked off in a subsequent operation, it can break away without the finished plate suffering any damage.

In the interest of there being as little impurity as possible in the moulding tool area, it is desirable though that the thickening does not crumble away either, or as little as possible. The method according to the invention is therefore preferably performed in such a manner that the thickening produced during moulding tapers radially outwards. A thickening of this shape facilitates release of the moulded article from the mould parts of the moulding tool. This applies particularly when, in accordance with a further development of the invention, the upper side and underside of the thickening are composed of faces at least approximately corresponding to the surfaces of a double cone.

The thickening is preferably worked off by machining, i.e., with one or more lathe, milling or grinding tools.

To perform the moulding as the first method step in the invention, there is preferably used a moulding tool exhibiting two mould parts axially movable in relation to and towards one another, one of which determines the upper side and the other the underside of the moulded article. In the invention, such a moulding tool is preferably devised in such a way that projections for embossing the relief are formed only on the mould part determining the upper side of the moulded article and that both mould parts have a plain edge zone around the projections.

In such a moulding tool, the mould part determining the upper side of the moulded article may exhibit, in a known manner, a chamber which is defined by a membrane and can be filled with a fluid under pressure for isostatic pressing of the moulded article. In the invention such a moulding tool is preferably developed further in that the mould part determining the upper side of the moulded article is coated with an elastomer layer which is compressed during the isostatic pressing and pushes the pressed moulded article away when the chamber is released from pressure.

The elastomer layer is preferably thicker in the zone of the thickening of the moulded article than in the other zones of the latter.

To work off the thickening as the second step of the method in the injection, a cleaning tool having a rotary-driven cylinder made of foam plastics and covered with a laminar abrasive agent, such as emery cloth, is particularly suitable.

Embodiments of the invention are described below with the help of schematic drawings, in which Figure 1 is a perspective partial view of a moulded plate having a festooned rim and cut along the plate axis, Figures 2a to 2c are partial plan views of various festooned plate rims, Figures 3 is an axial section through a moulding tool for the isostatic pressing of moulded articles as per Figures 1 and 2a to 2c made of powdery or granular ceramic material, Figure 4 is an enlarged axial section through part of a modified moulding tool for the isostatic pressing of moulded articles, Figure 5 is an axial section through a moulding tool for rolling moulded articles as per Figures 1 and 2a and 2c made of pasty ceramic material, Figure 6 is a side view of an apparatus for cleaning moulded articles of the type shown in Figures 1 and 2a to 2c, and Figure 7is an enlarged axial section through parts of a cleaning tool belonging to an apparatus as per Figure 5.

The illustrated devices and the method that can be performed with them have the purpose of producing plates 12 fro powdery, granular or pasty ceramic material, the plate rim zone 14 exhibiting a relief having an outer contour 16 diverging from the form of a circle. In accordance with Figure 2a the outer contour 16 may have, by way of example, ar) arcuate pattern or in accordance with Figure 2b a pattern of arcs and serrations or in accordance with Figure 2c a pattern of serrations of different height measured in a radial direction of the plate 12. Accordingly, the outer contour 16 of the finished plate 12 has indentations 18 of the same depth, as illustrated in Figures 2a and 2b, or indentations 18 and 20 of varying depth, as per Figure 2c. In Figure 1 the sectional area of the plate 12 is shown hatched and within this area indentations 18 and 20 are indicated by broken lines.

The plate 12 is not moulded as such, but during moulding is given a thickening 22 which begins at the underside of the plate rim zone 14, extends outwards in a radial direction beyond the outer contour 16 - of whatever shape - in such a way as to cover all indeMations 18 and 20 from the underside of the plate, and has a plain perimeter 24 that is circular in the illustrated example. The thickening 22 has an upper side 26 and an underside 28, both of which are likewise completely plain and at least approximately correspond to the surfaces of a double cone coaxial with the plate 12.

The plate 12 is moulded together with the thickening 22 as unitary moulded article 30.

In the event that the moulded article 30 is to be produced from powdery or granular material, the moulding tool is provided which is shown in Figure 3 and has two mould parts 32 and 34. An elastomer layer 36 is coated, for instance vulcanized, on mould part 32 and is firmly adherent thereto. The surface of said layer is complementary to the upper side 38 of the entire moulded article 30, that is to say is devised to mould the entire plate 12 including the outer contour 16 of the relief at the plate rim zone 14, as well as the upper side 26 of the thickening 22. To mould the relief with its outer contour 16 which will later border the finished plate 12, the layer 36 has projections 40 indicated in Figure 3 and corresponding to the indentations 18 and 20 of one of the plate shapes as per 2a to 2c.

The mould part 34 has the function of moulding the underside 42 of the moulded article 30. For this purpose the mould part 34 has an elastomer membrane 44 whose major portion is complementary to the entire underside 42 of the moulded article 30 and rests on a correspondingly shaped insert 46 of nonyielding material. The edge of membrane 44 rests on a frame 48 belonging to the mould part 34 and is clamped so as to be mechanically fixed and fluid-proof between said frame and a clamping ring 50 bolted thereto. The insert 46 has ducts 52 through which a fluid under high pressure can be conducted when the mould parts 32 and 34 assume their closing position shown in Figure 3.The fluid cone ducted through ducts 52 creates a chamber 54 between the membrane 44 and the insert 46, the fluid pressure in said chamber being evenly distributed so that the moulded article 30 is eastatically pressed.

The moulding tool shown in Figure 3 furthermore comprises afilling slide 56 annularlysurrounding the mould part 32 and having a feed duct 58. The mould parts 32 34 and the filling slide 56 are fixed to parts movable relative to one another of a press of known design and can be moved by the latter relative to one another in such a way that the pressed moulded article 30 is removed and the thus vacated space is closed again, yet in a manner that it can be filled with powdery ceramic materfal bythe feed duct 58, as is known parse The modified mould tool partly illustrated In Figure 4 differs from the illustratBd in Figure 3 In that it is devised to press a moulded article 30 whose thickening 22 tapers radially outwards even more distinctly.There is a smooth transition between the upper side 26 of the thickening 22 an'dtheupper side of plate 12, that is to say without any step. Conse- quently, even more distinctly than is the case in the embodiment of Figure 3, the upper side 26 of the thickening 2 has the effect of an rnollned face which, as the moulded article expands during and directly after separation of the mould parts 32 and 34, slides radially outwards on the complementary annular inclined face of layer 36, whembythe moulded article is pushed away from mould part 32 in the direction of the horizontal axis af the two mould parts.

In both of the embodiments in Figures 3 and 4this axial pushing away of the moulded article 30 is also brought about or promoted in that the elastomer of which layer 36 is made is compressed in the axial direction during the isostatic pressing, above all in the somewhat thickened edge zone of the layer 36, that is to say has become somewhat thinner, and as the mould parts 32 and 34 separate now re-assumes it original thickness.

In Figures 3 and 4 it is moreover clearly to be seen that the elastomer layer 36 is thicker in the zone of the thickening 22 of the moulded article 30 than in the other zones of the latter that later constitute the finished plate 12. However, the layer 36 narrows towards its outer edge, i.e., its cross-section more or less tapers off radially outwards.

In the event that the moulded article 30 is to be produced from pasty ceramic material, the moulding tool illustrated in Figure 5 and having two mould parts 32' and 34' is provided. The mould part 32' has a surface complementary to the upper side 38 of the entire moulded article 30. However, as distinguished from Figures 3 and 4, here the mouddd article 30 is produced with its upper side 38 downwards. Aecordingly, the mould part 32', is disposed atthe bottom and the mould part 34' at the the. Each-of the mould parts 32' and 34' is adapted to be rotary-dhriven about its axis of symmetry 32n and 34", vspttively. ln addition, the mould part 32 is adapted t be tobar - ed and lowered along its axis aF symtryNf "wherefe the mould part34' is adapted te l we}e - point of intersectin-of ith; ; and 34" The mould part 34" has the purpose of molding the underside 42 of the molded article 30.In this respect, the moulding tool shown in Figure 5 is analogous to conventional moulding tools for rolling moulded articles made of pasty ceramic material.

However, like the mould part 32 in Figures 3 and 4, the mould part 32" is devised such that it moulds the plate 12 including the outer contour 16 of the relief and the plate rim zone 14 (see Figure 1), as well as the upper side 26 of the thickening 22.

The thickening 22 protects that part of the moulded article 30 ultimately to constitute the finished plate 12 from damage not only on separation of the mould parts and removal of the moulded article, but also on subsequent handling of the latter.

However, before the moulded article 30 is fired, the thickening 22 has to be worked off in such a way that the outer contour 16 becomes free and only the plate 12 proper remains.

For working off the thickening 22, the apparatus illustrated in Figures 6 and 7 is provided. In accord ante with Figure Gthe moulded article 30 is sucked by vacuum onto a work-holding plate 60 in a manner as is known in cleaning devices. The work-holding plate 60 is mounted on a carriage 64 and is adapted to be rotary-driven by an electromotor 62. The carriage 64 is horizontally reciprocable in the direction of arrow 66 and adjustable in the vertical as per double-ended arrow 68. Cleaning tool 70 is provided for working off the thickening 22 and has a cylinder 72 made of foamed plastics fixed to the shaft of an electromotor 74 and covered with a laminar deformable abrasive agent 76, such as emery cloth.

In Figure 6 the cleaning tool 70 has just finished abrading the thickening 22 of the moulded article 30.

The work-holding plate 60 rotating together with the moulded article 30 will now move to the left, whereby the moulded article 30 is urged against a disc 78 made of sponge-like material, kept wet and rotated by a further electromotor 80 so as to completely clean and rim zone 14 of the plate 12.

The two electromotors 34 and 80 are mounted on a common support 82 also carrying a suction chamber 84 for sucking off the dust produced by the cleaning tool 70, as well as a trough 86 for keeping the disc 78 wet.

wherein the thickening tapers radially outwardly.

4. A method according to Claim 3, wherein the upper side and underside of the thickening at least approximately correspond to the surfaces of a double cone.

5. A method according to any one of Claims 1 to 4, wherein the thickening is worked off by machining.

6. A moulding tool for performing the method according to any one of Claims 1 to 4, comprising two mould parts axially movable in relation to and towards one another, one of which determines the upper side and the other the underside of the moulded article, projections for embossing the relief formed only on that mould part which determines the upper side of the moulded article, and each of the two mould parts having a plain edge zone around the projections.

7. A moulding tool according to Claim 6, wherein the mould part determining the upper side of the moulded article has a chamber which is defined by a membrane and can be filled with a fluid under pressure for isostatic pressing of the moulded article, and is coated with an elastomer layer which is compressed during the isostatic pressing and pushes the pressed moulded article away when the pressure in the chamber is released. P 8. A moulding tool according to Claim 7, wherein the elastomer layer is thicker in the zone of the thickening of the moulded article than in the other zones of the latter.

9. A cleaning tool for performing the method according to Claim 5, comprising a driven rotatable cylinder made of foam plastics which is covered with a laminar abrasive agent such as emery cloth.

10. A method of producing plates or other flat or planar articles of crockery having a festooned rim according to Claim 1 and substantially as hereinbefore described.

11. The apparatus for producing plates or other flat or planar articles of crockery having a festooned rim substantially as hereinbefore described with reference to the accompanying drawings.

Claims

1. Amethodofproducing plates or other flat or planar articles of crockery having a festooned rim, by moulding a powdery, granular or pasty ceramic material, and embossing a relief in the upper side of the plate, the method comprising moulding the articles with a thickening which begins at the underside of their rim zone, projects radially outwards beyond the axial section profile of the finished plate or other article of flat or planar crockery, and in axial view has a plain perimeter embossing the outer contour of the relief up to the thickening, and working offthethickening in an operation following the moulding.

2. A method according to Claim 1, wherein the plain perimeter is circular.

3. A method according to Claim 1 or Claim 2,