GB2218656A

GB2218656A - Method of and apparatus for patterning solid workpieces

Info

Publication number: GB2218656A
Application number: GB8811963A
Authority: GB
Inventors: Stephen Paul Blake
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-05-20
Filing date: 1988-05-20
Publication date: 1989-11-22
Also published as: GB8811963D0

Abstract

A stencil for use in the patterning of a workpiece of wood or glass by blasting with particulate etching material, comprises a patterned metal layer having a rubber or plastics layer on the side towards which the impacting etching material such as sand is directed in use.

Description

Method of and Apparatus for Patterning Solid Workpieces This invention relates to a method of and apparatus for forming a pattern on a solid workpiece, more particularly a workpiece of wood or glass.

The term "pattern" is used herein generically, and includes letter and figure configurations, pictures, logos, decorative motifs and designs and all possible combinations thereof.

Sand blasting is a well known technique with various applications, for example as a preliminary step to be taken in the restoration of antique furniture, or for cleaning wood beams or the like or for aging new wood to impart an antique appearance. In complete contrast, the technique is also employed for etching automobile glass with a security code or the like by blasting the sand on to the glass through a small, thin metal stencil. It is therefore practicable to pattern a wood or glass workpiece with a more complex design through a suitable complex metal stencil.In the etching of glass with a security code, however, where the thin metal stencil is stamped out by machine (in the form of individual characters which are then assembled in a frame), etching is effected by directing an extremely fine etching powder through the stencil under a relatively low blasting pressure of about 80 p.s.i., and the method is practicable only because relatively slight or shallow etching is required.

The technique would make no impression on wood, and could not be used for decorative patterning of glass, e.g.

mirrors. For effective patterning of wood or glass, using a very much higher blasting pressure, a much thicker gauge metal stencil would be required, expensive and time consuming to produce and yet even then having a very limited life possibly of only a single usage.

According to one aspect of the present invention, there is provided a method of patterning a solid workpiece, more particularly a workpiece of wood or glass, according to which a particulate etching material such as sand or bead is blasted on to the workpiece through a stencil which comprises a layer of rigid sheet material such as metal and, on the side towards which the sand is blasted, a layer of rubber, synthetic rubber, synthetic resin or plastics material.

Especially in the patterning of wood, the use of rubber or a material having rubber-like properties is greatly preferred, as blasting with etching material under a relatively high pressure is essential. However, for the fine etching of glass, where a somewhat smaller blasting pressure may sometimes be sufficient, a non-resilient plastics or synthetic resin material may be employed to protect the metal stencil layer, e.g. an electrostatically deposited epoxy coating.

According to another aspect of the invention, there is provided, for use in patterning a rigid workpiece by blasting with a particulate etching material, a stencil cut through with the required pattern and comprising a layer of rigid sheet material and a backing layer of rubber, rubber-like plastics or synthetic resin material for facing the impacting etching material.

The principle underlying the invention is that the backing layer of the stencil is able to withstand the impacting sand or other etching material substantially without damage, whilst at the same time protecting from damage the underlying rigid layer which provides support for the backing layer.

In this connection, it has to be appreciated that, although the rubber, rubber-like, or plastics backing layer is able to withstand the impacting etching material, it is not in itself suitable for use as a stencil without the underlying rigid support. Commonly, moreover, the presence of the rigid layer, e.g. sheet metal, cut with the required pattern, is necessary to provide support and to serve as a guide for stencilling of the backing layer with the same pattern. For this purpose, an unpatterned sheet of backing layer is applied to the patterned rigid layer by use of a suitable adhesive, such as a cyano-acrylate adhesive, and the backing layer is then cut through to conform to the underlying rigid stencil.

It will also be understood that it is not essential for the final stencil to be flat, because use of a suitable metal as the rigid layer can make it possible to shape and/or contour the composite layer stencil to match the shape and/or contour of the workpiece to be patterned.

Moreover, if the workpiece, e.g. of wood, is painted or otherwise surface treated, the relief pattern formed by the method and apparatus of the invention can be of contrasting shades or colours, since the etching material will also remove the surface treatment at the etched areas of the pattern.

The invention is further exemplified in the following description, which also discloses three methods by which the composite layer stencil can be produced.

In one example, a rigid metal plate, for example a copper or zinc plate, is directly or indirectly marked with a required ornamental pattern, as by drawing on architect's paper applied over the plate, and the metal plate is manually cut in accordance with the pattern to form a stencil. Sheet rubber or equivalent sheet rubber-like synthetic material, such aspso-called sheathing rubber of 16 gauge, is then adhered to one face of the metal stencil by use of a suitable adhesive, and the rubber layer is then cut through using the metal plate stencil as a support and guide. The result is a composite layer stencil suitable for use in particulate blasting of a rigid workpiece which may be of wood or glass, for example.

For this purpose, the stencil is located over the workpiece, with the metal stencil layer against the workpiece surface to be patterned. Using conventional sand blasting equipment, for example similar to that used in antique furniture restoration, the workpiece is then sand blasted through the stencil. Sand blasting is continued for the period necessary to etch the pattern to a required depth.

The rubber backing layer of the stencil is preferably sufficiently larger in outside dimensions than the metal stencil plate that it provides a curtain surrounding the stencil area in order to protect from damage the area of the workpiece adjacently surrounding the area to be patterned.

The copper plate could be replaced by a plate of another suitable metal or possibly the rigid stencil plate may be constituted by a plate of hard plastics material. One example of suitable material for the backing layer is 16 gauge sheathing rubber, but the use of other materials with rubber-like properties is possible.

In another example, the metal stencil plate is formed by a substantially conventional line blocking technique.

For this purpose, the required pattern is formed as a negative image thereof on a transparent film, which is then applied over a zinc plate bearing a light-sensitive layer, the plate and film being drawn tightly together by a known evacuation technique. The zinc plate is then irradiated through the film with U/V light, thereby to fix the light-sensitive layer at the area where the light is incident. The film is removed from the plate, and the non-fixed areas of the light sensitive layer are washed off. The plate is then treated with nitric acid, -again in a manner known from line blocking techniques, but unconventionally the treatment is maintained until the acid has eaten right through the plate to form a stencil.

The plate is then cleaned up by hand to remove any burrs and generally sharpen up the stencil image.

The rubber backing layer is then applied to the thus formed rigid stencil plate so that the pattern is seen the correct way round when viewed through the said backing layer, which as before is cut right through in conformity with the underlying stencil plate.

Use of the composite stencil is the same as that described with reference to the first method of stencil manufacture.

Blasting with bead or other suitable particulate etching material, appropriate to a workpiece of wood or glass, may be used instead of sand.

For the fine patterning of glass, where a somewhat lower blasting pressure may be practicable than in the patterning of wood, the composite layer stencil may be produced by applying an epoxy resin coating to the metal stencil plate.

The coating may be deposited by a conventional electrodeposition method, where the final thickness of the coating is readily controllable by adjustment of the speed and duration of deposition.

This composite layer stencil may be used for the fine patterning of glass in the same manner as the stencils previously described, facing the epoxy coating towards the incident etching material in order to protect the underlying metal stencil layer.

It is to be noted that by surface treatment of the workpiece prior to pattern etching, so a multi-colour or multitexture pattern can be produced. It is also to be noted that it is possible, by use of a suitable material for the rigid plate, to produce a non-flat stencil which conforms to a curved or contoured area of a workpiece which is to be patterned.

Claims

1. A method of patterning a solid workpiece, more particularly a workpiece of wood or glass, according to which a particulate etching material such as sand or bead is blasted on to the workpiece through a stencil which comprises a layer of rigid sheet material and, on the side towards which the sand is blasted, a layer of rubber, synthetic rubber, synthetic resin or plastics material.

2. A method according to claim 1, wherein the rigid stencil layer is a metal layer.

3. A method according to claim 1 or claim 2, wherein, for the patterning of wood, a rubber or a material having rubber-like properties is employed on the one side of the rigid stencil layer.

4. A method according to claim 1 or claim 2, wherein, for the fine etching of glass, a non-resilient plastics or synthetic resin material is employed on the one side of the rigid stencil layer.

5. A method according to claim 4, wherein the nonresilient material is an electrostatically deposited epoxy coating.

6. A stencil for use in patterning a rigid workpiece by blasting with a particulate etching material, the stencil being cut through with the required pattern and comprising a layer of rigid sheet material and a backing layer of rubber, rubber-like plastics or synthetic resin material for facing the impacting etching material.

7. A stencil according to claim 6, which is non-planar.

8. A method of producing the stencil of claim 6 or claim 7, wherein the rigid stencil layer is cut with the required pattern, and serves both to support and act as a guide for stencilling of the backing layer with the same pattern.

9. A method according to claim 9, wherein an unpatterned sheet of backing layer is applied to the patterned rigid layer by use of an adhesive and the backing layer is then cut through to conform to the underlying rigid stencil layer.

10. A method of patterning a workpiece substantially as hereinbefore described.

11. A stencil and method of production thereof substantially as hereinbefore described.