GB2076338A - Decoration of ceramic or other ware - Google Patents

Abstract

A method and apparatus for decorating ceramic or other ware involves deforming a body 10 of for example silicone rubber against a support surface 18 with a pattern defining screen 22 interposed between the body 10 and the surface 18 so that printing medium 20 applied to the surface 18 is expressed through the screen 22 and onto the body 10 to form a pattern. The body 10 is subsequently deformed against the article 16 to be decorated in order to transfer the printed pattern to the article. If the screen is sufficiently rigid, there may be no need for the support surface. <IMAGE>

Description

SPECIFICATION Decoration of ceramic ware This invention relates to the decoration of ceramic or other ware, such as glassware.

One known method of decorating ceramic ware is by means of direct silk screen printing wherein a screen having a pattern-defining area is brought into superimposed relation with the article, printing medium is deposited onto the upper face of the screen and a squeegee is brought into contact with the upper face of the screen and rotated to express the printing medium through the pattern-defining area and onto the article. In order to produce a well defined pattern on the article, the conventional practice is to maintain a small gap between the screen and the article so that the screen only contacts the article locally in the vicinity of the squeegee.

The application of this method is limited to flat surfaces of the article, e.g. the central circular area of a plate or saucer, or to generally conical surfaces of relatively large apex angle, e.g. the outer annular shoulder of plate or relatively shallow side walls of dishes. The method cannot be used for example to print the curved transition between the flat central area and the outer annular shoulder of a plate or other surfaces having significant curvature.

Thus, the patterns produced by the known silk screen printing method cannot extend beyond the periphery of the central flat area of a plate and into the transition portion.

Moreover where for example the pattern is to be applied to the central flat area and the annular shoulder of a plate, these steps have to be carried out separately. Furthermore, because the squeegee rotates about the axis of symmetry of the article a small zone at the centre of the article must be left unprinted and to some extent this places constraints on the type of pattern that can be used insofaras the design has to be devised in such a way that the unprinted zone does not detract from the aesthetic appeal of the design.

Although the known method suffers from the above mentioned limitations and drawbacks, it has important advantages, for example the colour or colours employed may be applied in substantial amounts in sharp, clean, high contrast patterns and rapid rates of production are possible with high quality results.

Attempts have been made to effect printing on curved sections of ceramic ware by applying the printed pattern to a so-called "bomb" comprising soft deformable and resilient body of, for example, silicon rubber which, when pressed against the ware, deforms to complement the contour of the ware at least in the area to be printed so that, when the bomb is raised, the printed pattern is transferred from the bomb to the ware. In one method which has been adopted commercially, the printed pattern is applied to the bomb by means of a plate engraved or photo-etched with the desired pattern. The printing medium is spread over the plate so as to enter the depressions therein, the plate is doctored or scraped to removed excess printing medium and the bomb is then pressed against the plate to conform to the surface thereof and thereby effect transfer of the pattern onto the bomb.

This method suffers from the drawback that two transfer steps are involved, i.e. transfer of the pattern from the plate to the bomb and then from the bomb to the ware. Also there are limitations on the amount of printing medium that can be transferred from the plate to the bomb and, in general, it is not possible with this method to achieve the same decorative effect as can be attained by the silk screen printing method initially described.

More recently, attempts have been made to incorporate silk screen printing into the transfer method described above. Thus, instead of using an engraved or photo etched plate, the desired pattern is applied to a flat substrate by silk screen printing and the bomb is then pressed against the substrate to effect transfer of the pattern to the bomb, the bomb thereafter being pressed against the ware to transfer the pattern to the ware. Although this modification allows large amounts of printing medium to be transferred to the bomb, it has not been possible to obtain high quality results because blurring of the pattern has tended to occur possibly as a result of the large quantities of printing medium being transferred coupled with the fact that two steps are necessary.

The object of the present invention is to provide an improved method by means of which ceramic ware having curved contours may be printed.

According to the present invention we provide a method of decorating ceramic or other ware comprising contacting an article of ceramic or other ware with a soft deformable and resilient body to which a pattern has been applied directly by screen printing with the body deformed into face to face contact with a pattern defining area of the screen.

Thus, in accordance with the invention, the pattern is applied directly to the body thereby avoiding the two step transfer procedure used in the prior art. Moreover, in contrast with conventional silk screen printing practice where the screen is separated from the article to be printed by a small gap and is only contacted locally with the article by the action of the squeegee, in accordance with the invention, the body is deformed into face to face contact with the print defining area.

Contrary to expectations, a sharp well defined pattern can be printed onto said body despite the substantial face to face contact between the body and the screen during printing and it is thought that this surprising result is attributable at least in part to the manner in which the body and screen separate in that the body disengages from the screen with a rolling motion sothat the area of contact between the body and the screen decreases progressively.

In one convenient arrangement, the screen printing operation is effected by deforming said body against a support surface with the screen interposed between the body and the surface and the pr:nting medium being supplied to the screen at the face opposite to the face coRtacted by said planar body. The support surface is preferably planar and the screen is preferably supported at its periphery in spaced relation to said support surface so that the action of deforming the body against the support surface also deflects the screen against the support surface. The support surface may be fixed and said body may be mounted for movement towards and away from the support surface; however other arrangements are possible, e.g. the relative movement required to deform the body may be effected with the body fixed and the support surface being movable towards the body.

In the preferred embodiment, the printing.

medium is supplied to the screen in the form of a film or layer which is engaged by the screen as the body deforms against the screen. Thus, the film or layer of printing medium is conveniently provided on said support surface so that, as the body and support surface move relatively towards one another, the screen engages said film or layer. Means, eg a doctoring blade, may be provided to ensure that the film or layer has a predetermined thickness prior to each printing opera tion As the body deforms against the screen and the support surface, it will be appreciated that if the periphery of the screen is spaced from the support surface by a fixed amount, the inclination of that portion of the screen beyond the area of contact with the body will gradually increase.This may be undesirable and preferably the arrangement is such that the angle of inclination remains substantially constant as the area of contact between said body and the screen increases. This may be achieved for example by progressively reducing the spacing between the screen and the support surface as the area of contact increases. Likewise, this spacing may be progressively increased as the area of contact decreases during separation of the body from the screen.

Although in the preferred embodiment, a support surface is provided against which the body is deformed (with the screen interposed), it is envisaged that such a support surface may be unnecessary if the screen is made sufficiently taut or rigid to enable said body to deform to a substantially flat condition against the screen. A relevant factor in this respect will be the composition of said body because the degree of tautness or rigidity required of the screen will be dependent on how readily the body is able to deform to the flat condition.

In practice, where multi-coloured printing is required, the body may be cooperable with a number of screens in the aforesaid manner, the screens being supplied with printing media of different colour. Where thermoplastic printing media are to be used, the support surface (or each support surface) may incorporate a heater to maintain the printing medium in fluid condition.

In order to promote further understanding of the invention, one embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic view of apparatus used in carrying out the method of the invention, the bomb being shown in the position it assumes following printing of a pattern on a plate; Figure 2 is a view similar to Fig. 1 but showing the bomb in readiness for receiving a pattern for transfer to the plate.

Figure 3 shows the bomb being pressed against the silk screen which in turn is pressed against a backing support; and Figure 4 shows the bomb being pressed against a plate to effect printing of the pattern on the latter.

The apparatus is depicted diagammatically in the drawings and only those parts are shown that are essential to an understanding of the invention. The apparatus comprises a so-called bomb 10, i.e. a soft deformable and resilient, rotationally symmetric body of for example silicon rubber, which when pressed against another surface, e.g. a flat surface or an article of ceramic ware having curved and/or flat sections, is capable of deforming to a shape complementary to that of the surface.

The bomb 10 is mounted on mechanism (not shown) for moving it vertically (arrow 12) and, horizontally (arrow 14). The shape of the bomb will in general vary according to the contour of the articles to be printed.

The bomb 10 is movable horizontally between a print receiving station (Figs. 2 and 3) and a print applying station (Figs. 1 and 4).

At the print applying station, means (not shown) may be provided for feeding articles 1 6 of ceramic ware, one at a time, beneath the bomb such that the axes of symmetry of the article and the bomb are substantially coaxial. At the print receiving station, there is provided a silk screen printing assembly comprising a flat bed 1 8 to which a film 20 of printing medium is applied and a screen 22 of, for example, nylon mounted under tension within a frame 24 which is supported above the bed 1 8. The frame 24 may be circular and arranged with its axis lying substantially co-axial with the axis of the bomb 10 when the latter is in the print receiving station. As usual, the screen 22 is provided with a pattern defining area (not depicted) corresponding to the desired pattern to be applied to the ceramic ware.The printing medium may be one conventionally used in the decoration of ceramic ware and where the medium is a thermoplastic material the bed 1 8 may incorporate means for heating the same to maintain the medium through it.

A doctoring blade or like device (not shown) may be associated with the bed 1 8 to maintain the film 20 of preselected thickness, in conjunction with means for supplying the printing medium on to the bed 1 8. A scraper or other device (not shown) may be provided to remove excess printing medium from the screen, e.g. from the underside thereof, in readiness for each print receiving operation of the bomb.

To transfer the printed pattern onto the bomb, the latter is lowered so that it contacts the screen 22 and presses it against the flat bed 1 8 (see Fig. 2). As a result, the pattern defining area of the screen 1 8 enters the film 20, thereby causing the openings in the screen to fill with printing medium. The bomb 10 is then raised to the position shown in Fig.

2, returned to the print applying station (Fig.

1) and then lowered into contact with the article (Fig. 4). During lowering of the bomb 10 relative to the bed 18, the bomb deforms itself and the screen 22 against the bed 1 8 with a rolling action such that the peripheral line bounding the circular area of contact between the bomb and screen moves outwardly in a progressive manner. Likewise when the bomb is raised from the bed 1 8 and screen 22, a similar rolling action occurs with the area of contact progressively decreasing.

Such rolling action of the bomb also takes place during contact of the bomb with the article 1 6 and in this manner the printed pattern is applied from the screen to the bomb and subsequently from the bomb to the article without any substantial loss of definition.

It will be observed that during the silk screen printing process operations described above no squeegee is employed in order to express the printing medium through the screen and onto the bomb. It would appear that the bomb itself acts in the manner of a squeegee during contact with the screen but, in contrast with conventional silk screen printing techniques, where the squeegee only contacts the screen locally, the deformed bomb makes extended surface contact with the screen. As previously mentioned, such extended contact would normally be expected to result in excessive biurring of the pattern applied to the body but surprisingly experiment has shown that the body is printed with a sharp and well defined pattern even where relatively large amounts of printing medium are being used.

For the reason previously mentioned, the arrangement may be such. that the spacing between the frame 24 and the bed 1 8 can be controlled according to the area of contact between the bomb and the screen. Thus, during raising and lowering of the bomb, the frame 24 may be moved downwardly or upwardly so as to maintain the angle of inclination of that portion of the screen beyond the area of contact substantially constant.

As described above, there is only a single print receiving station but, in practice, where multi-coloured printing is required, there will be a number of print receiving stations so that the bomb may be printed with different coloured printing mediums. Alternatively, there may be a single print receiving station and a number of screen and bed assemblies movable into and out of the print receiving station according to which colour is to be printed onto the bomb.

Various other modifications of apparatus described above will be readily apparent to those skilled in the art, eg the arrangement may be such that the bomb is vertically movable and remains in one location, the screens and articles being movable into and out of that location in a suitable sequence.

Although the invention has been described with reference to ceramic ware specifically, it will be appreciated that the invention is also applicable to other materials, eg glassware.

Claims (14)

1. A method of decorating ceramic or other ware comprising contacting an article of ceramic or other ware with a soft deformable and resilient body to which a pattern has been applied directly by screen printing with the body deformed into face to face contact with a pattern defining area of the screen.

2. A method as claimed in Claim 1 in which the screen printing operation is effected by deforming said body against a support surface with the screen interposed between the body and the surface, the printing medium being supplied to the screen at the face opposite to the face contacted by the said body. a

3. A method as claimed in Claim 2 in which said support surface is planar.

4. Apparatus as claimed in Claim 2 or 3 in which the screen is supported at its periphery in spaced relation to said support surface so that the action of deforming the body against the support surface also deflects the screen against the support surface.

5. A method as claimed in any one of Claims 1 to 4 in which the printing medium is supplied to the screen in the form of a film or layer which is engaged by the screen as the body deforms against the screen.

6. A method as claimed in Claim 5 when appendent to any one of Claims 2 to 4 in which the film or layer of printing medium is provided on said support surface so that, as the body and support surface move relatively towards one another, the screen engages said film layer.

7. A method as claimed in Claim 5 or 6 including means for providing a film or layer of predetermined thickness prior to each printing operation.

8. A method as claimed in any one of Claims 1 to 7 in which the arrangement is such that the angle of inclination of that portion of the screen beyond the area of contact with the body remains substantially constant as the area of contact between said body and the screen increases.

9. A method as claimed in Claim 8 when appendent to any of Claims 2 to 4 in which said angle of inclination is maintained constant by progressively reducing the spacing between the screen and said support surface as the area of contact increases.

10. A method as claimed in any one of Claims 1 to 9 for multicoloured printing wherein patterns of different coloured printing media are applied to said body by successively contacting the body with the pattern defining area of a number of screens in the aforesaid manner, each screen being supplied with printing media of different colour.

11. A method as claimed in Claim 2 or any one of Claims 3 to 10 when appendent to Claim 2 in which said support surface (or each support surface, incorporates a heater to maintain thermoplastic printing media in fluid condition.

12. Apparatus for decorating ceramic or other ware comprising means for applying a film or layer of printing medium to a support surface, a screen having a pattern defining area in superimposed relation to the support surface, a soft deformable and resilient body for contact with the pattern defining area of the screen and means for effecting deformation of the body against said support surface with the pattern defining area of said screen interposed therebetween whereby subsequent deformation of the body against the article to be decorated effects transfer of the printed pattern from the body to the article.

A A method of decorating ceramic or other ware substantially as hereinbefore described with reference to the accompanying drawings.

14. Apparatus for decorating ceramic or other ware substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.