GB2215329A - Moulding process - Google Patents

Abstract

There is disclosed a moulding process for moulding objects using a centrifugal moulding technique and a method of forming a rotary mould for use in such a technique. The rotary mould is formed by providing a model having a surface of revolution, and applying mouldable material to said surface and shaping the material so that the surface of the model takes up any required shape and/or pattern which is to be transferred to an open-topped rotary mould, the material being of such a nature that it is capable of being shaped and of maintaining its shape during subsequent transfer of its shape from the model. Then the shape of the model is transferred to the side wall and to the base of an open-topped rotary mould, whereby the rotary mould can be used to form a body of revolution in a centrifugal moulding technique when settable material is introduced into the mould.

Description

MOULDING PROCESS This invention relates to a moulding process for moulding articles produced using a centrifugal moulding technique Centrifugal moulding has been used for many years to produce objects of glass, and involves the use of an opentopped mould which is rotated at progressively increasing speed after a charge of molten glass has been introduced into the mould. The molten glass is thrown against the side wall of the mould and gradually climbs up the side wall while taking-up the shape imparted to it by the shaping of the side wall. This process is carefully controlled so that the glass takes up the required shape while it is still flowable and then is allowed to set while the speed of the mould is reduced to zero.

The centrifugal moulding technique enables a variety of designs of glass objects to be made, which are capable of formation by rotary casting, and includes bowls, plates and vases. The design appeal of the products is dependent upon the quality and design of the mould, and therefore a succession of products of readily repeatable quality can be obtained on a production line basis, once the mould has been formed. This is a considerable economic and technical advantage of the centrifugal moulding technique, over conventional glass blowing techniques, in which the quality of design of each article which is produced is dependent entirely upon the skill on each occasion of the glass blower.

The centrifugal moulding technique would also be applicable to the production of articles of ceramic material.

The production of the mould is therefore central to the centrifugal moulding technique, and presently this is carried out often by using a wooden model of regular shape e.g. hemi or part spherical, and which has its external surface carved with a required shape to be imparted ultimately to the product to be moulded. Thereafter, the wooden model design is transferred to a plaster mould, and then to an aluminium or copper mould which forms the rotary mould to be used in the centrifugal moulding technique.

The design applied initially to the wooden model is ultimately transferred to the product moulded by the rotary mould.

Clearly, subject to the exercise of a satisfactory level of craftsmanship in the transfer of the design from the wooden model to the plaster mould, and then to the metal rotary mould, the quality of the design applied to the product is dependent upon the design expertise in application initially to the wooden model.

However, given that the model is formed with suitable external shaping by carving with a chisel or other tool, very great care has to be taken to ensure that too much wood is not removed at any given position, since this cannot readily be rectified, and will of course result in deviation from the required external appearance of the product ultimately derived from the wooden model. Also, of course, once the design on the wooden model has been carved, there is very little scope for design variations to be made, other than by way of small adjustments in removing additional material at any one place or another.

The invention therefore seeks to provide an improved centrifugal moulding technique in which the production of the initial design on a wooden or other solid starting model is facilitated.

According to one aspect of the invention there is provided a moulding process for moulding objects produced using a centrifugal moulding technique and which comprises the steps of: providing a model having a surface of revolution; applying mouldable material to said surface and shaping the material so that the surface of the model takes up any required shape and / or pattern which is to be transfer red to the side wall and / or base of an open-topped rotary mould, the material being of such a nature that it is capable of being shaped and of maintaining its shape during subsequent transfer of the shape from the model; introducing a settable material into the rotary mould; and rotating the mould about a substantially vertical axis so as to cause the settable material to move under centrifugal action into engagement with the base and with the side wall of the mould and to form a moulded object as a body of revolution, and causing or allowing the material to set during and / or after reduction of the speed or rotation of the mould to zero.

Thus, a moulding process according to the invention enables a model to be shaped readily with any required shape and / or pattern, and if the shape being built-up is found to be unsatisfactory, further mouldable material may be applied and / or removed as necessary, which allows shaping to be resumed until any required final appearance has been achieved. This therefore gives considerably more freedom to the designer in creating new designs, than is presently available via the use of conventional wooden models.

Preferably, the shape of the model is transferred indirectly to the side wall and the base of the rotary mould, in that an intermediate process step is involved, which comprises application of the shape of the model to a plaster mould, pressing of the plaster mould into a sand press so that the relief pattern is transferred to the sand and then pouring of molten material (usually metal and preferably copper or aluminium) into the sand mould to form the rotary mould having its side wall and its base formed with a shape and / or pattern ultimately derived from the model.

However, it is within the scope of this invention for the model shape to be transferred to the rotary mould by other process steps.

Conveniently, the model is solid and may be made of wood, having a hemi or part spherical external surface of revolution. The preferred mouldable material applied to the model is clay modelling material, though other material may be used provided it can be readily shaped, and then maintain its shape during a subsequent shape-transferring step.

The objects which may be made by the invention include any bodies of revolution, such as plates, bowls, lampstands and vases, and they may be made of glass or ceramic material.

According to a further aspect of the invention there is provided a method of forming a rotary mould for use in a centrifugal moulding technique and which comprises the steps of: providing a model having a surface of revolution; applying mouldable material to said surface and shaping the material so that the surface of the model takes up any required shape and / or pattern which is to be transferred to an open-topped rotary mould, the material being of such a nature that it is capable of being shaped and of maintaining its shape during subsequent transfer of its shape from the model; and indirectly transferring the shape of the model to the side wall and the base of an open topped rotary mould which is formed by a casting process, whereby the rotary mould can be used to form a body of revolution by a centrifugal moulding technique when settable material is introduced into the mould.

A moulding process according to the invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective illustration of a starting model for producing a rotary mould for use in a centrifugal moulding technique according to the invention; Figure 2 is a perspective illustration of the application of any predetermined surface shape or pattern to the wooden model; Figure 3 is a perspective illustration of a plaster mould derived from the shaped model shown in Figure 2; Figure 4 is a perspective illustration of a rotary mould for use in a centrifugal moulding technique, made of metal, and which has been derived from the plaster mould shown in Figure 3; and, Figure 5 is a perspective side illustration of a typical glass or ceramic object which can be formed using a rotary mould in a moulding process according to the invention.

Referring now to the drawings, there will be described one example of a moulding process for moulding objects of revolution using a centrifugal moulding technique, and also a method of making a rotary mould for use in the centrifugal moulding technique.

Referring first to Figure 1, there is shown a model which is designated generally by reference 10 and which is preferably solid and made of wood, having an initial hemi or part spherical external surface 11. The model 10 may be formed generally similarly to existing wooden models used to produce rotary moulds, but which have hitherto been shaped externally by carving. The model 10 with the part spherical surface 11 has a peripheral flange 12 on which there is arranged a dome shaped structure 13. At the top of the dome 13 there is a circular mounting boss 14, which ultimately will form the base and the centre of rotation of the rotary mould derived from the model.

As shown in Figure 2, mouldable material 15 in the form of modelling clay is applied to the surface 11 and is shaped so as to impart to the combined surface of the model 10 any required shape and / or pattern which is to be transferred subsequently, by an indirect process, to the side wall and base of an open-topped rotary mould. As shown in Figure 2, the moulding clay 15 has been shaped into a series of spirals 16 which start at the base 14 at the top of the dome 13, and terminate adjacent to the flange 12. Upon subsequent transfer of this shape to the side wall of a rotary mould, an object of revolution can be formed during a centrifugal moulding technique, which will have its external surface shaped in conformance with this initial shape applied to the model 10.Evidently, the material 15 can be readily shaped into any required shape, and altered as may be required to suit the requirements of the designer, and which may involve the application of additional material. This material is also capable of maintaining any given shape during the subsequent transfer of the shape of the model to a plaster mould 17, as shown in Figure 3.

Thereafter, the plaster mould 17 is pressed into a sand press (not shown) so as to transfer the relief pattern to the sand, and molten material, such as copper or aluminium for preference, and poured into the sand mould so as to form an open-topped rotary mould 18 as shown in Figure 4, having a base 19 corresponding with base 14 of the wooden model 10, and a vertical axis of rotation 20 which passes through the centre of the base 19. The side wall of the rotary mould 18 is formed with spiral shaping 21 which has been derived ultimately from the wooden model by indirect transfer via the plaster mould, and this then forms the outer wall of a body of revolution formed by introduction of a settable material, which will usually be molten glass or ceramic material, into the rotary mould.

The mould 18 is then rotated about its axis 20 so as to cause the molten material to move under centrifugal action into engagement with the side wall of the mould, and to form a body of revolution, which is then caused or allowed to set during reduction of speed or rotation of the mould to zero. The object can then be removed, and the process repeated.

Glass or ceramic objects, such as plates, bowls, lampstands and vases can be formed using the centrifugal moulding technique disclosed herein. By way of example only, Figure 5 illustrates a glass vase 22 which may be formed by the centrifugal moulding technique.

The technique disclosed herein for forming a rotary mould for use in centrifugal casting may also be used to form a mould (a double mould) for use in the glass-blowing of objects such as bottles or glasses.

Claims (10)

1. A moulding process for moulding objects produced using a centrifugal moulding technique and which comprises the steps of: providing a model having a surface of revolution, applying mouldable material to said surface and shaping the material so that the surface of the model takes up any required shape and / or pattern which is to be transferred to the side wall and / or base of an open rotary mould, the material being of such a nature that it is capable of being shaped and of maintaining its shape during subsequent transfer of the shape from the model to the mould; transferring the shape of the model to the side wall and the base of an open rotary mould, whereby the rotary mould can be used to form a body of revolution in a centrifugal moulding technique when settable material is introduced into the mould; introducing a settable material into the rotary mould; and, rotating the mould so as to cause the settable material to move under centrifugal action into engagement with the base and with the side wall of the mould and to form a moulded object as a body of revolution, and causing or allowing the material to set during and / or after reduction of the speed of rotation of the mould to zero.

2. A process of forming a rotary mould for use in a centrifugal moulding technique and which comprises the steps of: providing a model having a surface of revolution; applying mouldable material to said surface and shaping the material so that the surface of the model takes up any required shape and / or pattern which is to be transferred to an open rotary mould, the material being of such a nature that it is capable of being shaped and of maintaining its shape during subsequent transfer of its shape from the model to the mould; and, transferring the shape of the model to the side wall and the base of an open rotary mould, whereby the rotary mould can be used to form a body of revolution in a centrifugal moulding technique when settable material is introduced into the mould.

3. A process according to Claim 1 or 2, in which the shape of the model is indirectly transferred to the side wall and the base of an open-topped rotary mould.

4. A process according to Claim 3, in which the indirect transfer of the shape of the model to the side wall and the base of the open-topped rotary mould takes place via a casting process.

5. A process according to any one of the preceding claims, in which the model is made of wood.

6. A process according to any one of the preceding claims, in which the model has a hemi or part spherical external surface of revolution.

7. A process according to any one of the preceding claims, in which the mouldable material is clay modelling material.

8. A process according to any one of the preceding claims, in which the settable material is molten glass or molten ceramic material.

9. A process according to Claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.

10. A moulded object formed by a process according to any one of the preceding claims.