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(11) | EP 0 919 345 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | A process for preparing a mould with replaceable stamping surface for clay manufactured articles |
| (57) A process for preparing moulds for manufacturing clay articles, provided with a replaceable
moulding surface that can be replaced when worn out, provides the forming of a negative
(3) in said mould (1) of a material capable of being drawn that is then spray coated
with a mixture (7) comprising from 85% to 90% of tungsten carbide and from 15% to
10% of cobalt carbide, such coating imparting to the sheet (3) very good properties
of hardness and wear resistance for the molding of the clay articles. |
[0001] The present invention refers to a process for preparing moulds with a replaceable moulding surface for manufacturing clay articles.
[0002] It is known that the preparation of moulds to be used with presses for manufacturing clay articles is very laborious because of the nature of the material to work on and the consequent strong wear of the moulds.
[0003] Such moulds are made of steel, and the steel has to be subjected to a special heat treatment in order to maintain for a long time a surface hard and strong enough for the intended uses.
[0004] To overcome these drawbacks, at present a technique has been used in which positives of the clay article to be moulded are built on the upper and lower faces of the moulds, and then a setting resin, such as an epoxy resin or the like, is poured between said positives and through the casting formed in this way one obtains the negative of the article to be mould.
[0005] This is a remarkable improvement with respect to the above mentioned conventional technique, nevertheless the main drawback of this technique is the wear of the membrane, of rubber or similar material, that is usually interposed between the mould and the clay.
[0006] It is an object of the present invention to overcome the drawback due to the wear of the membrane interposed between the mould and the clay, by using a replaceable moulding component in lieu of the membrane.
[0007] The above object of the present invention is achieved through a process as claimed in claim 1.
[0009] According to a first embodiment of the invention, a negative of metal sheet or other material capable of being drawn is formed in the mould, such negative is secured to the mould by proper means, and is subsequentely spray coated with a mixture containing from 85% to 90% of tungsten carbide and from 15% to 10% of cobalt carbide. This coating imparts to the material capable of being drawn and reproducing the shape of the article, very good properties of hardness together with very good properties of wear resistance in the moulding process.
[0010] According to a second embodiment of the invention the negative to be coated is formed on replaceable blocks or inserts inside the mould, secured to the mould by proper means, and such a negative is then sprayed with the above mentioned tungsten carbide and cobalt carbide mixture.
[0011] According to a preferred embodiment, the mixture for coating the sheet material capable of being drawn and constituting the negative is formed by 88% of tungsten carbide and 12% of cobalt carbide.
[0012] The invention will now be disclosed with particular reference to the attached exemplary and non limiting drawings, in which:
Fig. 1 is a schematic view illustrating a first embodiment of the invention; and
Fig. 2 is a schematic view illustrating a second embodiment of the invention.
[0013] With reference to the Figures, numeral 1 indicates a mould, 3 a sheet of a resilient material adapted to be drawn that has been formed with the profile of the clay article to be manufactured, 5 the means for securing such sheet 3 to the upper mould 1.
[0014] After the sheet 3 has been fsstened to the mould 1, the sheet is sprayed to form a coating with a mixture 7 comprising from 85% to 90% of tungsten carbide and from 15% to 10% of cobalt carbide. Such coating imparts to the sheet 3 very good properties of hardness and wear resistance for the molding of the clay article (not shown in the drawings).
[0015] After a number of moulding processes, the sheet 3, although protected by the coating 7, worns out and can be replaced with a new sheet in the mould 1.
[0016] This way one achieves an easy and simple way to replace the active surface of the mould, which is not possible with the conventional methods.
[0017] Fig. 2 illustrates a second embodiment of the invention, that is similar to that of Fig. 1, but for the sheet 3 being applied to a support 9 that in turn can be fitted in the mould as shown in Fig. 1.
1. A process for preparing a mould for manufacturing clay articles and provided with
a replaceable moulding surface, characterized in that it comprises the steps of:
- forming in said mould (1) a negative (3) of a material capable of being drawn;
- fastening said negative (3) to the mould (1) through fastening means (5);
- coating said negative (3) with a mixture (7) comprising from 85% to 90% of tungsten carbide and from 15% to 10% of cobalt carbide.
2. A process according to claim 1, characterized in that said negative (3) is directly
fastened to said mould (1).
3. A process according to claim 1, characterized in that said negative (3) is formed
on a replaceable support (9) fastened to said mould (1) through fastening means (5).
4. A process according to the preceding claims, characterized in that said coating mixture
(7) comprises 88% of tungsten carbide and 12% of cobalt carbide.
5. A process according to the preceding claims, characterized in that said material capable
of being drawn is a metal sheet.
6. A process according to the preceding claims, characterized in that said coating is
applied by spraying.