EP0146199A1

EP0146199A1 - Method and machine for applying decalcomanias

Info

Publication number: EP0146199A1
Application number: EP84303886A
Authority: EP
Inventors: Wilfred Roberts; Kenneth Marshall
Original assignee: British Ceramic Research Association Ltd
Current assignee: British Ceramic Research Association Ltd
Priority date: 1983-06-17
Filing date: 1984-06-08
Publication date: 1985-06-26
Also published as: JPS6071256A; GB8316546D0

Abstract

@ Articles (38) of ceramic ware are heated and then a portion of a sheet (2) of thermo-plastics material carrying a design motif (4) is pressed into engagement with the article by a silicone rubber pad (33), to apply the design to the ware. In order to facilitate handling of a strip of the thermo-plastics material, during printing of the motifs and subsequent unrolling of the strip, the strip is initially provided with a paper backing (3). An automatic machine is described in which the paper is stripped off by a blade (19), and the plastics strip is carried to an application station (5) by a reciprocable carriage (12). A reciprocable carrier (26) is movable transversely of the carriage through the application station for alternately bringing a perforating assembly (6a, 6b) and a transfer application assembly (7a, 7b) into position at the application station.

Description

This invention relates to decalcomanias, commonly called 'decals', and in particular to a method of applying decals to articles such as articles of ceramic ware, to a novel decal for use in the method, and to an apparatus for applying such decals.
Waterslide transfers or decals are used for the decoration of ceramics, glass and vitreous enamal products. A major part of tableware on-glaze decoration for example is effected by such means. These transfers are conventionally produced by printing the decoration motif in ceramic colours onto the surface of a paper coated with a water soluble gum. Silk-screening or lithography are the methods used for printing. The motif after printing is overprinted with a coat of a clear plastics lacquer.
Similar transfers, not necessarily printed in ceramic colours can also be used to decorate plastics.
To apply the decoration, the printed sheet is soaked in water which releases both the motif and plastics coating as the gum dissolves. The plastics coating retains the motif and now acts as its support during application to the ware. The transfer is placed on the ware and squeegeed into the correct position. The gum retained on the back of the plastics film acts both as a lubricant, when wet, to allow the transfer to be moved easily to the correct position, and as an adhesive once the correct position for the transfer is located. The plastics coating is sufficiently pliable at ambient temperatures to allow the motif to be moulded to complex shapes.
Decoration of ceramic bisque or clay ware can also be performed by means of transfers but in this case the gum layer on the back of the plastics carrier is insufficient to act either as a lubricant or an adhesive due to the very porous nature of the substrate. Various patents have described means of overcoming this problem typical of which is British Patent Specification No. 1 338 323. Lubrication and adhesion are achieved according to this specification by first applying to the very porous substrate a thin liquid coating of a film forming adhesive medium. This can be for example a carboset resin in butyl oxitol, thickened to prevent rapid penetration of the substrate pores by means of a water solution of a cellulose derivative. The transfer is applied over the wet adhesive medium which stays liquid long enough to allow the transfer to be slid easily into the correct position. The transfer is next squeegeed down removing excess medium. The medium then acts as a solvent adhesive on the plastics carrier of the transfer anchoring it firmly to the ware where positioned.
The application of these transfers particularly in the case of ceramics is generally carried out by hand which means that decoration by transfer is labour intensive and unsuited to a modern production line. Mechanised methods of decoration are available as an alternative to decoration by transfer, for example off-set printing from an inked gravure design plate as in British Patent Specifictaion No. 735 637 or silk screening either direct or by an intermediate surface as described in British Patent Specification No. 1 602 225. Whilst these methods are able to produce multi-colour designs they are generally limited to printing in a maximum of four colours due to the expense and complexity of the equipment. On the other hand transfer printing carried out by accepted paper printing techniques has no such limitations on colour and can produce designs which are wide ranging in colour, tone and definition. Thus although other methods of decoration will be used because of their more immediate integration into a mechanised production flow line, there will always remain a need for the sophistication and quality of transfer decoration.
Attempts have been made in the past to mechanise transfer decoration but none of the systems so far devised has gained universal acceptance. Probably the better known are the Zeidler British Patent Specification 1 411 961 and Netzsch Ibercalco systems which are designed to apply transfers of the water slide type described above. It is this attempt to operate with water slide transfers, which are more suited to hand application, which is the major reason for their lack of acceptance. Water slide transfers, as previously described, need water for their release and this, combined with the complex backing paper removal systems, reacts unfavourably on machine reliability.
The difficulties involved with water release when attempting to mechanise transfer application are acknowledged by the effort that has been devoted to the development of heat or pressure release transfers. A typical system is described in British Patent Specification No. 1 387 754.
However, an essential of all such transfer systems is that the transfer and its paper backing support need to contact the work piece before the paper is released by the application of heat and or pressure. This limits the use of such transfers to flat or cylindrical items which is a major limitation. Again such systems have failed to gain general acceptance.
The present invention has resulted from attempts to devise a system for automatically applying decals to complex shapes and which avoids the disadvantages of the previous methods described.
According to one aspect of the invention a method of applying a colour design to an article comprises applying the colour design to a portion of a sheet of thermo-plastics material, and urging said sheet portion into engagement with the surface of the article, the temperature of the sheet portion when engaged with the article being so arranged as to render said sheet portion plastically deformable.
Preferably the article is heated to render the sheet portion plastically deformable on engagement therewith. The use of a heated article also induces tack in the sheet portion.
The sheet portion is preferably urged into engagement with the article by a resiliently deformable pad.
The pad is preferably of substantially dome shape, so that a central part of said sheet portion initially contacts the article, but on further movement of the pad towards the article a progressively increasing area of the sheet portion is forced into contact with the article as the dome is resiliently deformed.
The pad is preferably formed of a soft silicone rubber.
The sheet portion is preferably applied to the article with that side carrying the colour adjacent to the article, particularly in the case of decals for ceramic ware which are subsequently to be fired, thereby removing the risk of design disruption when the plastics film burns away.
The sheet portion is preferably detached from the parent sheet by the pad as the pad moves towards the article, and to facilitate this the sheet is preferably perforated.
The parent sheet is preferably in strip form and is provided with a series of design motifs which are longitudinally spaced apart. Each motif is encircled by perforations prior to the pad being applied to the motif.
It is preferred to perforate the strip after the design motifs have been applied thereto, but it may be possible if desired to perforate the strip prior to application of the motifs.
It is preferred to perforate the strip with the design motif in position at the application station at which the motif is applied to the ware, to avoid any problems in obtaining registration of the perforations and the motif.
The use of a strip facilitates a continuous automatic process in which the strip is indexed past an application station where the successive sheet portions are detached from the strip and applied to articles successively positioned there.
The parent sheet is conveniently supported by a paper backing during application of the design to the sheet and to facilitate storage and handling of a roll of the sheet in strip form. However, it may be possible to apply the design to an un-backed plastics sheet.
The paper backing may be arranged to be separable from the sheet strip by a simple mechanical stripping operation without the use of water, heat or pressure. This is facilitated by the addition of a release agent to the sheet such as those described in British Patent Specification No. 1 524 960.
The use of a sheet in strip form enables continuous multi-colour printing processes to be employed for applying the design motifs.
According to a second aspect of the invention a machine for applying designs to articles comprises an application station provided with means for locating an article to be decorated, means for conveying a strip of thermo-plastic sheet material carrying design motifs through the application station, a resilient pad and means for urging the resilient pad against the strip to press a portion of the strip against the article located at the application station.
Preferably the machine comprises a perforating assembly for perforating the strip and means for conveying the perforating assembly from an inoperative position displaced from the application station to an operative position at the application station, to enable the strip to be perforated whilst at the application station and prior to application of the pad.
The means for conveying the perforating assembly preferably comprises a carrier which also carries the pad and the pad applying means, and the carrier is arranged to reciprocate transversely of the direction of movement of the strip through the application station.
According to a third aspect of the invention a decalcomania comprises a design motif carried by a thermo-plastics sheet, the motif having been applied to the sheet by printing onto the sheet.
An automatic machine for applying decalcomanias to articles of ceramic ware and in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which:-

Figure 1 shows a roll of decalcomanias in accordance with the invention;
Figure 2 is a longitudinal cross-section on the line 2-2 of Figure 3 of the film transport assembly of the machine;
Figure 3 is a plan view of the film transport assembly of Figure 2;
Figure 4 is a side elevation of the punch and transfer application rig of the machine, and showing the film transport assembly sectioned on the line 4-4 of Figure 3; and
Figure 5 is a cross-sectional view of a modified support for an article of clayware, suitable for use in the machine of Figure 2 to 4.

Referring to Figure 1, this diagramatically shows a roll 1 of decals suitable for use in the machine of Figure 2. The roll 1 comprises a film 2 of thermo-plastics material supported on a paper layer 3. The film 2 contains a suitable release agent to enable the film 2 to be stripped or peeled mechanically from the paper layer 3, as indicated, without the use of water or heat. The film 2 has been previously printed on its upper surface in the drawing with a series of longitudinally spaced apart design motifs 4 in ceramic colours. The printing is performed by any convenient method but the strip form of the film 2 enables conventional continuous multi-colour printing processes to be employed. The paper layer 3 supports the film 2 during printing and generally facilitates handling of the film.
Figures 2 to 4 diagramatically show a machine for automatically applying decals to articles of complex shape. The machine essentially comprises a film transport assembly shown in Figures 2 and 3 for transporting film from a supply roll 1 to an operating station 5, and a punch and transfer application rig, shown in Figure 4, which extends at right angles to the film transport assembly for alternately positioning at the operating station 5 a film perforating assembly 6a, 6b and a transfer application assembly 7a, 7b.
The film transport assembly comprises an elongate reciprocating carriage 8 guided by rollers 9 which engage with longitudinal side members 10 of the carriage, the side members 10 being connected by transverse end members 11. Side members 10 incorporate respective upwardly facing elongate vacuum grippers 12 which extend for the full length of members 10 and which enable the film to be held by the carriage and drawn from the supply roll 1 as the carriage is moved to the right in Figures 2 and 3.
A fixed rectangular bed 13 mounted on a table 13' lies in the space between carriage side members 10 and is provided towards one end with a pair of upwardly facing suction pads 14, and at its other end, at the operating station 5, with a circular hole 15 surrounded by an upwardly facing annular suction pad 16.
The supply roll 1 is as shown in Figure 1, and film 2 supported by paper 3 passes through tensioning rollers 17, with the film 2 on the underside, and along the upper surface of the carriage 8 to a return roller 18 at which a separating blade 19 ensures separation of paper 3 from film 2. The paper 3 proceeds to a rewind spool 20, and the sheet 2 extends further along the carriage 8 and through the operating station 5 to a scrap film position 21. The scrap film position 21 has a series of fixed downwardly facing suction pads 22 for holding the margins of the scrap film.
The operation of the film transport assembly will now be described. The film 2 is supported by the paper backing 3 until just prior to the film reaching the operating station 5, in order to minimise the risk of stretching the film, which would distort the design motifs 4. Starting with carriage 8 in the position shown in full outline in Figure 2, and at the stage when perforation and transfer application has just taken place at the operating station 5, suction is applied to the vacuum grippers 12 to grip the margins of the sheet 2 along the full length of the carriage 8, and, with no suction applied to pads 14, 16 and 22, the carriage 8 is driven fully to the right, to bring the front end of the carriage into the scrap film position 21, as indicated in broken outline 8' in Figure 2. The forward movement of the carriage draws the film 2 with backing paper 3 from roll 1, paper 3 is separated from the film 2 at roller 18 and proceeds to rewind spool 20, which is lightly driven through a slipping clutch. Once the carriage has moved fully to the right, suction is applied to pads 14, 16 and 22 to hold the sheet 2 firmly whilst the punching and film transfer operations are performed at operating station 5, as will be further described.
The vacuum supply to grippers 12 is then disconnected to de-activate the grippers 12, and the carriage is returned to its original position shown in full outline in Figure 2, the pads 14, 16 and 22 holding the film whilst the carriage returns.
This sequence of carriage movements and film gripping operations ensures that a precise indexing of the film 2 is achieved by each reciprocation of the carriage thereby enabling each design motif 4 to be precisely positioned at the operating station 5. The travel of the carriage 8 is preferably made adjustable to permit different spacings of the design motifs 4.
The punch and transfer application rig will now be described with reference to Figure 4. A fixed cross frame 23 extends transversely through the operating station 5, beneath the top of table 13', and is supported on legs 24. The cross frame 23 comprises horizontally spaced parallel guide bars 25 on which is slidably mounted a carrier frame 26 mounting the film perforating assembly 6a, 6b and the transfer application assembly 7a, 7b. A pneumatic ram 26' controls sliding movement of the frame 26, which is shown in Figure 4 in its extreme leftwards position in which the perforating assembly 6a, 6b is located at the operating station 5. The perforating assembly 6a, 6b comprises an upper perforating unit 6a positioned above the carriage 8 comprising a horizontal punch plate 27 provided with a ring of downwardly projecting perforating pins 28, and a lower unit 6b comprising a horizontal die plate 29 provided with corresponding holes to receive the pins 28.
The plates 27, 28 are each mounted on respective vertical slide bars 30 and are vertically movable with respect to carrier frame 26 by respective vertical rams 31 mounted on frame 26. In order to carry out a perforating operation the lower ram 31 is operated to bring the plate 29 into the hole 15 and in engagement with the underside of the film 2, which is held in position by suction applied to pad 16, and the upper ram 31 is operated to bring the punch plate 27 down against the upper surface of the film, the perforating pins 28 punching through the film to form a circle of perforations around the motif.
The transfer application assembly comprises a workpiece support unit 7b mounted on a vertical ram 32 carried by frame 26, and a dome-shaped pressure pad 33 of silicone rubber is carried by a backing plate 34 and is vertically movable by a further ram 35 carried by frame 26. The vertical movement of plate 34 is guided by slide bars 36. Workpiece support unit 7b comprises a support plate 37 provided with a vacuum supply, not shown, for holding the article 38 on the plate 37, and centring arms 39 for the articles.
Suitable automatic means of known type, not shown, is provided for loading and unloading the support unit 7b with a heated article 38, this operation being performed when the unit 7b is in the retracted condition shown and displaced as shown from the operating station 5.
Following perforation of the sheet 2 by the perforating assembly 6a, 6b the units 6a and 6b are retracted upwards and downwards respectively by rams 31 and the ram 26 is contracted to move the frame 26 fully to the right in Figure 4 to bring the transfer application assembly 7a, 7b to the operating station 5, whereupon the ram 32 is operated to raise unit 7b until the article is positioned closely adjacent to the underside of the perforated film held by suction pad 16. Ram 35 is then operated to move the pad 33 quickly downwards to punch through the sheet 2, detaching the motif .carrying portion of the film, as assisted by the perforations, which portion is then carried by the pad 33 to the article 38. This film portion is then progressively deformed by the pad to the shape of the article as the pad spreads out over the article, and due to the heat in the article the film portion develops tack and sticks firmly to the contoured surface of the article.
Since the sheet 2 is continuously held by pad 16 throughout the perforation operation and the punching operation of pad 33, the perforated portion of the sheet 2 is necessarily in register with the pad 33 when the pad 33 is punched downwards. This is an advantage over a possible arrangement in which the film is first perforated at a stationary perforating station and is then advanced to a stationary transfer application station.
Following application of the transfer to the article the rams 32 and 35 are retracted and ram 26' is extended to move frame 26 to its leftward position in Figure 4. As soon as the pad 33 and article 38 have been retracted from the hole 15 the sequence of film advancing operations is commenced by the film transport assembly so that by the time that the perforating assembly 6a, 6b has been positioned at the operating station 5 a fresh motif carrying portion of film 2 has been positioned at station 5. The procedure is then repeated.
It will be appreciated that the machine is provided with a master controller, not shown, which provides the timing for the various machine operations.
As will be clearly understood from the above description, the method and apparatus embodying the invention provide a mechanical transfer application means which can be equally and effectively used for glazed ceramics, either glazed, or vitreous or porous bisque ware, or for glass, vitreous enamel or plastics articles, removing all need to use water or solvent lubricant- adhesives.
The method can also be applied equally to ceramic clayware. The centring device required for glost and bisque items is replaced by a soft silicone rubber support for the clay piece. Figure 5 illustrates diagramatically how this is effected where 40 is the clay piece and 41 is the rubber support. By this method the pressure pad is able to apply the transfer without breaking the clay pieces.
Having applied the transfers, ceramic ware, either glost, bisque or clayware can be processed in the normal ceramic manner to produce a decorated item. In the case of bisque and clayware which has to be subsequently glazed it will be found of advantage to add a proportion of glaze or ground frit to the thermo-plastic film to enable it to be both wetted by a glaze and to act as a bridge between substrate and glaze as the film burns away.
By way of illustration to demonstrate the principles of the invention and not to imply any limitations, the following examples for film and pressure pad are given.

Thermo-plastics peelable film

100 parts: polymethacrylate
0.5 to 2.0 parts: silicone-glycol block copolymer fluid.
Film thickness in the range 1 to 3 thousandths of an inch.

Pressure pad

A condensation cured silicone rubber where the basic polydimethylsiloxane polymer has been extended by the addition of silicone fluid to give a rubber having a Shore 00 hardness in the range 30 to 50.
The backing support paper can be any suitable for the printing process, non-absorbent and compatible with the thermo-plastic film. Silicone coated papers are preferred since these prevent any tendency to sticking whilst the paper and thermo-plastic film are in roll form.
With thermo-plastic films of the type examplified above typical temperatures for the ware on application of the film are in the range 40 - 60°C.

Claims

1. A method of applying a colour design (4) to an article (38; 40) characterised by the steps of applying the colour design to a portion of a sheet (2) of thermo-plastics material, and urging said sheet portion into engagement with the surface of the article, the temperature of the sheet portion when engaged with the article being so arranged as to render said sheet portion plastically deformable.

2. A method as claimed in claim 1 in which the article is heated to render the sheet portion plastically deformable on engagement therewith.

3. A method as claimed in claim 1 or claim 2 in which the sheet portion is urged into engagement with the article by a resiliently deformable pad (33).

4. A method as claimed in claim 3 in which the pad is of substantially dome shape, so that a central part of said sheet portion initially contacts the article, but on further movement of the pad towards the article a progressively increasing area of the sheet portion is forced into contact with the article as the dome is resiliently deformed.

5. A method as claimed in claim 3 or claim 4 in which the pad is formed of a soft silicone rubber.

6. A method as claimed in any of claims 3 to 5 in which the sheet portion is detached from the parent sheet by the pad as the pad moves towards the article.

7. A method as claimed in claim 6 in which the sheet is perforated prior to the application of the pad to the sheet.

8. A method as claimed in claim 7 in which the sheet is perforated by providing perforations which encircle each motif (4).

9. A method as claimed in claim 7 or claim 8 in which the strip is perforated after the design motifs have been applied thereto.

10. A method as claimed in claim 9 in which the perforations are made in the strip with the design motif in position at an application station (5) at which the motif is applied to the article.

11. A method as claimed in any of the preceding claims in which the article is an article of ceramic ware.

12. A method as claimed in any of the preceding claims in which the sheet portion is applied to the article with that side carrying the colour adjacent to the article.

13. A method as claimed in any of the preceding claims in which the parent sheet is supported by a paper backing (3) during application of the design to the sheet, the paper backing being removed prior to application of the sheet to the article.

14. A method as claimed in claim 13 as appended to any of claims 7 to 10 in which the paper backing is removed prior to the formation of the perforations.

15. A method as claimed in claim 13 or claim 14 in which the paper backing is arranged to be separable from the sheet strip by a mechanical stripping operation without the use of water, heat or pressure.

16. A method as claimed in claim 15 in which the paper is treated with a release agent to facilitate the stripping.

17. A machine for applying colour designs to articles (38; 40) comprising an application station (5) provided with means (37, 39) for locating an article to be decorated, characterised by means (8) for conveying a strip of thermo-plastic sheet material (2) carrying design motifs (4) through the application station, a resilient pad (33), and means (35) for urging the resilient pad against the strip to press a portion of the strip against the article located at the application station.

18. A machine as claimed in claim 17 characterised by a perforating assembly (6a, 6b) for perforating the strip and means (26, 26') for conveying the perforating assembly from an inoperative position displaced from the application station to an operative position at the application station, to enable the strip to be perforated whilst at the application station and prior to application of the pad.

19. A machine as claimed in claim 18 in which the means for conveying the perforating assembly comprises a carrier (26) which also carries the pad and the pad applying means, and the carrier is arranged- to reciprocate transversely of the direction of movement of the strip through the application station.