GB1602225A

GB1602225A - Printing

Info

Publication number: GB1602225A
Application number: GB2227778A
Authority: GB
Original assignee: Service Engineers Ltd
Current assignee: Service Engineers Ltd
Priority date: 1978-05-25
Filing date: 1978-05-25
Publication date: 1981-11-11
Also published as: JPS552089A

Description

(54) IMPROVEMENTS IN OR RELATING TO PRINTING (71) We, SERVICE (ENGINEERS) LIMI TED, a British Company of Leek New Road, Cobridge, Stoke on Trent, Staffordshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention is concerned with improvements in or relating to printing, and more particularly with off-set screen printing processes and machines for decorating articles of ceramic ware.

Screen printing machines have been introduced into the ceramic ware industry for decorating articles of tableware, both flatware and holloware, by the direct application of colour through the screen onto the ware.

Another process which is well established for decorating such tableware is by means of an off-set printing machine comprising a deformable pad, for example of gelatine, in the shape of an inverted dome which transfers colour from an intaglio plate to the ware. The plate may be engraved or etched.

Both the foregoing processes, direct screen printing and off-set printing from an intaglio plate, offer an advantage over other, traditional, ways of decorating, for example transfer pressing and hand painting, in that, while both processes call for skill in the preparation of the screens or plates, as is also required in making transfers, they do not call for such highly skilled operatives in the pottery where the ware is decorated.

The arranging of transfers on the ware, even if a machine is used to press them on rather than rub them in by hand, requires considerable skill and care.

A problem inherent in direct screen printing on articles of tableware arises from the surface contours which it is customary for such ware to assume. Direct screen printing onto a truly flat central area of a piece of so-called flatware or onto a cylindrical surface of a piece of holloware, presents no such problem, but most articles of flatware have a contoured radial profile and the walls of cups are more commonly nonuniform in diameter than uniform, and it is difficult to provide for the required deformation of the screen during application of the colour without leaving any such undesired marks as indicate whereabouts on the surface the operation of applying the colour began and finished.

Direct off-set printing from an intaglio plate by means of a deformable pad has the advantage that the decoration is uniform all over the area of the ware engaged by the pad without evident discontinuities, but the preparation of the plates from which the pad takes the colour, and which requires a high quality plating operation to ensure the surfaces can withstand the wear to which they are subject by the doctor blade, is becoming increasingly expensive compared with modern processes for preparing screens.

It has been proposed in United Kingdom Patent Specification 737 461 to apply colour by screen printing onto an intermediate flat surface, and then to transfer the colour from such surface directly onto a piece of ware by means of a deformable gelatine off-set printing pad in the shape of an inverted dome, thus to obtain the advantages of screen printing to obtain the desired design in colour and of the pad to apply the colour to the ware without discontinuity. The teaching of that specification is that the intermediate surface must be non-absorbent, preferably of rustless metal or a sheet of glass although any non-absorbent flat sheet may be used, with the implication that paper would be unsuitable, at any rate unless it were non-absorbent.

An off-set screen printing process as described in said specification has not, so far as we are aware, been used industrially, and laboratory trials carried out by the applicant company resulted in unsatisfactory products due to the spreading of colour and the loss of definition of the design as successive prints were obtained.

It is accordingly one of the objects of the present invention to provide an improved off-set screen-printing process suitable, for example, for the application of designs to the contoured surfaces of articles of ceramic tableware.

It is another of the objects of the present invention to provide an improved off-set screen-printing machine which enables successive designs in colour to be applied uniformly to the ware without significant loss of definition.

There is hereinafter described in detail to illustrate the invention by way of example in its machine aspects an off-set screen printing machine suitable for decorating articles of ceramic flatware, comprising a frame, a deformable transfer pad, in the shape of an inverted dome, mounted for vertical reciprocation on the frame, screenprinting means including a screen support and squeegee mounted for vertical reciprocation on the frame in side-by-side relationship to the transfer pad, and a table mounted for horizontal reciprocation on the frame and itself having mounted on it a ware support and means for supporting a roll of sheet material to be used to provide an intermediate surface in the printing operation. This illustrative machine comprises means for moving the pad, screen and table in such a manner that, in a cycle of operation of the machine, first registration is effected between the screen and the intermediate surface and colour is applied through the screen to said surface, then registration is effected between the pad and the intermediate surface and the colour is picked up from said surface by the pad, and then registration is effected between the ware support and the pad and the colour is transferred from the pad to an article on the ware support. The roll-supporting means of the illustrative machine comprises a dispensing roll and a take-up roll for the sheet material, both mounted on the reciprocable table, as also is a hard flat perforate platform on which a portion of material between the dispensing and take-up rolls and which is to be engaged by the pad rests in the operation of the machine.

In the operation of the illustrative machine the under side of the platform is arranged to be subject to reduced air pressure at least for an initial period during ascent of the pad so as to hold the sheet of material in place by suction when adhesion to the pad would otherwise tend to raise it, and preferably also during application of colour to the material through the screen.

The aforementioned take-up roll of the illustrative machine is arranged to be powerdriven in steps of variable length so that, without undue waste of sheet material, a fresh area can be brought into register with the screen for each application of colour thereto after engagement with the pad to pick up the colour previously applied.

The illustrative machine is thus suitable for use in carrying out a production process, itself illustrative of the invention in its process aspects, in which the machine operates continuously, the pad in alternate strokes engaging the intermediate surface provided by the sheet material and a contoured surface of an article of ware on the ware support, a fresh application of colour being applied through the screen to a fresh portion of the sheet material at the same time as the pad is engaging the ware. The suction by which the sheet material is held on the platform is always released, of course, for the feed step of the sheet material.

In carrying out the illustrative process there is thus no risk of excessive build up of colour on the intermediate surface, since the surface to which the colour is applied through the screen in a cycle of operation is always free from residual colour left over from a previous cycle. Successive designs in colour are thus obtained without significant loss of definition.

The sheet material used to provide the intermediate surface in carrying out the illustrative process is one which can be regarded as significantly not non-absorbent, but on the other hand not sufficiently absorbent to result in loss of definition of the design by spontaneous spreading of the colour over the surface. Paper is the preferred material, for use as the intermediate surface in carrying out a process in accordance with the invention because there are suitable "half-sized" papers (i.e. papers which are not completely sized to seal them not as porous as blotting paper) which are cheap enough to be thrown away after being used once, which is far more practical than providing an intermediate surface of a nondisposable kind which would have to be cleaned after each pick-up of colour: also, paper is commonly available in roll form, which is more convenient to handle than separate sheets, which, however, can be used, if desired. The paper should not, of course, have been sealed to render it nonabsorbent, at least not on the side that is going to be used, but must be strong enough not to tear under the conditions of use. The kind of paper used in photographic reproduction machines and sold under the brand names "RONEO" and "XEROX" is technically very suitable, but less expensive papers of similar strength and absorbency are no doubt available.

The illustrative machine may be used for single colour applications and when a gelatine pad is used only cold colours would be suitable. A silicone rubBer pad could be used for hot colours if desired. The illustrative machine may also be used in conjunction with other similar machines for decoration of ware in more than one colour, with the application of talcum powder, for example, to the freshly applied colour before applying another one.

Whereas the sheet material used to provide the intermediate surface in the operation of the illustrative machine is advanced step-by-step in a straight path to provide a fresh area for the subsequent application of further colour, the roll of material being thrown away after it has been used up, the material could be fed in a zig-zag path to allow closer "packing" of the area contaminated by residual colour and thus economises in material. Alternatively, it is contemplated that instead of using a dispensible material for this purpose, means could be provided for cleaning the contaminated area before a subsequent application of colour.

The invention provides, in one of its several aspects, a repetitive production process for applying a design in colour to contoured surfaces of a succession of articles comprising a repeated cycle of operations wherein, in each cycle, the design in colour is applied by screen printing to an intermediate surface and then transferred from said surface to the contoured surface of an article by a deformable dome-shaped transfer pad, the intermediate surface for each cycle being free form residual colour left over from a previous cycle.

The invention also provides, in another of its several aspects, an off-set screenprinting machine suitable for use in decorating articles of ceramic ware, comprising means for supporting a screen to enable a design in colour to be applied by a screen-printing process to an intermediate surface, a ware support for supporting an article to which the design in colour is to be applied, and a deformable dome-shaped transfer pad for transference of the design in colour from the intermediate surface to the article, the machine being operable cyclically in such a manner that in each cycle of operation first registration is effected between the screen and the intermediate surface and the design in colour is applied through the screen to the surface, second registration is effected between the transfer pad and the intermediate surface and the design in colour is picked up from the surface by the pad, and third registration is effected between the ware support and the pad and the design in colour is transferred from the pad to an article on the ware support, the machine comprising means arranged to provide for said first registration in each cycle of operation an intermediate surface that is free or substantially free of residual colour from a previous cycle.

There now follows a description, to be read with reference to the accompanying drawing, of the illustrative machine and illustrative process aforementioned. It will be realised that this illustrative machine and the illustrative process have been selected for description to illustrate the invention by way of example and not of limitation.

The accompanying drawing is a perspective view of the illustrative machine with parts broken away.

The illustrative machine comprises a frame 10 arranged to stand on the floor and having a table top 12 from which corner pillars 14 stand up to support a horizontal upper plate 16 of the frame.

A pad support 18 and screen support 20 are mounted side-by-side on the plate 16 for vertical reciprocation. Thus, the pad 18 includes two sleeve portions 22 slidable on vertical posts 24 depending from the plate 16. Mounted on top of the plate 16 is a hydraulic cylinder 26 from which a piston rod 28 projects downwardly through the plate 16 and is secured to the support 18.

Mounted on a flat under surface of the support 18 is a deformable gelatine pad 30 in the shape of an inverted dome.

The screen support 20 also has two sleeve portions, 32, slidable on posts 34 depending from the under side of the plate 16. A piston rod 36 of a pneumatic cylinder 38 secured to the under side of the plate 16 is connected to the support 20. The support 20 is in the form of an open U-shaped bracket laid on its side so that one branch of the U provides a lower one of two parallel horizontal arms 40 on which a screen 42, consisting of a design-bearing mesh 44 mounted in a frame 46, is secured in a horizontal position.

Mounted on a horizontal bar 48 constituting part of the frame 10 of the illustrative machine and disposed behind the support 20 are two forwardly projecting horizontal guide posts 50 on which a slide 52 is carried for to-and-fro reciprocation under the influence of a hydraulic cylinder 54. A horizontal shaft 56 is rockable about its axis in bearings 58 supported below the slide 52 and adjustable heightwise by screwed knobs 60. A rocker arm 62 secured to one end of the shaft 56 beyond its bearing is arranged to be actuated to rock the shaft through a small angle by a doubleacting pneumatic cylinder 64. Mounted in an inclined position an the shaft 56 is a bracket 66 which carries a support 68 for a squeegee 69. The squeegee 69 can thus be raised off and lowered onto the screen 42 by rocking the shaft 56 upon actuation of the cylinder 64.

A carriage 70 of the illustrative machine is mounted to slide horizontally from side to side on hexagonal guide bars 72. Such reciprocation is effected by a hydraulic cylinder 74 disposed in a transverse channel 76 of the table top 12, a piston rod (not shown) of the cylinder 74 being secured to the carriage 70.

On the carriage 70 of the illustrative machine is a ware support 80 with centring arms 82 and a vacuum holder 84 for centring and holding a circular piece of flatware in a conventional manner not further described herein. On the carriage 70 is also mounted means 90 for supporting a roll of paper 92. The means 90 comprises a hard flat perforate platform 94 upon which a portion of the paper rests, the roll being initially placed on a dispensing roll (not visible in the drawing) behind the platform and disposed low enough for the paper to be drawn taut over the platform by a take up roll 96 to which the leading end of the paper is attached. The roll 96 is arranged to be driven step-by-step by an electric motor 98 which can be switched on and off at adjustable step lengths by switching means (not shown) controlled by a rotatable metering device riding on the paper (and thus not influenced by the gradually increas ing diameter of the roll as the paper is rolled up). In the illustrative machine, this metering device takes the form of a presser roller 100 which also serves to assist the holding of the paper down onto the plat form. (The roller 100 of the illustrative machine does not have a continuous cylin drical surface over its whole length, but is relieved at intervals at 102 to avoid its picking up, as it will be seen hereinafter - would otherwise be likely, an undue amount of excess colour as the paper is wound up).

Gearing 97 from the motor 98 to the roll 96 is only partially visible in the drawing, being concealed behind a bracket 104 of the means 90.

Provision (not visible in the drawing) is also made in the roll-supporting means 90 of the illustrative machine for reducing air pressure under the platform 94 so that the paper laid over it is held down by suction, especially when, as hereinafter described, the pad 30 is raised to pick up colour from the paper. control means (not shown) Electrical control means (not shown) operates pneumatic and hydraulic valves of the illustrative machine in suitable sequence so that, in the cycle of operation of the machine from a condition in which the rollsupporting means 90 is in register below the screen support 20 and a piece of ware ready to be decorated is on the support 80 in register below the pad 30 (which has colour on it which it has just picked up from the paper), the cylinders 26 and 38 are actuated to bring the pad 30 down in an operating stroke to impress the design in colour onto the ware and to lower the support 20 so that an under side of the screen frame 46 bears on the paper, which is preferably also subject at this time to suction to hold it steady on the platform 94. While the pad is executing its operating stroke, the short descent of the support 20 taking negligible time compared with the stroke of the pad support, the squeegee 69 is rocked down onto the screen 42 and executes an operating stroke (under the influence of the cylinder 54) across the screen (from front to rear of the illustrative machine). The squeegee is raised and brought forward again and the support 26 is raised to lift it clear of the deposited colour. (A reservoir of colour is maintained on the screen by hand, or by automatic feed, if preferred).

The pad 30 is also raised after impressing the design on the ware, and when both screen support 20 and pad 30 are clear, the carriage 70 moves to the right hand end of its stroke to its position shown in the drawing under the influence of the cylinder 74.

The ware support 80 is now in a loading and unloading position where the piece of ware bearing the design is replaced by a fresh piece, either by hand or automatically.

At this stage, the portion of paper to which the design (indicated as 110 in the drawing) has been applied is in register and below the pad 30. The pad 30 is now brought down again (while the screen support 20 remains up) into pressing engagement with the paper, thus, on its ascent to pick up the design from the paper. When it is clear of the paper, the carriage returns to the left (viewing the drawing) and during this movement, the take-up roll 96 is actuated by the motor 98 to advance the paper a measured step as determined by the roller 100 so that residual colour left on the paper is moved away from the area covered by the design on the screen 42, a fresh portion of paper thus being placed in register with the screen ready for application of the next design.

The roll of paper is wound up on the roll 96 and, when it is finished, is replaced by a fresh one on the dispensing roll. The old roll is then thrown away. The relieving of the roller 100 at 102 militates against the build up of an undue amount of residual colour on the roller.

The illustrative machine thus enables designs to be printed reliably and uniformly on successive pieces of ware by screen printing without discontinuity of the design itself and with few interruptions in the output of production.

WHAT WE CLAIM IS: 1. A repetitive production process for applying a design in colour to contoured surfaces of a succession of articles comprising a repeated cycle of operations wherein,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. reciprocation is effected by a hydraulic cylinder 74 disposed in a transverse channel 76 of the table top 12, a piston rod (not shown) of the cylinder 74 being secured to the carriage 70. On the carriage 70 of the illustrative machine is a ware support 80 with centring arms 82 and a vacuum holder 84 for centring and holding a circular piece of flatware in a conventional manner not further described herein. On the carriage 70 is also mounted means 90 for supporting a roll of paper 92. The means 90 comprises a hard flat perforate platform 94 upon which a portion of the paper rests, the roll being initially placed on a dispensing roll (not visible in the drawing) behind the platform and disposed low enough for the paper to be drawn taut over the platform by a take up roll 96 to which the leading end of the paper is attached. The roll 96 is arranged to be driven step-by-step by an electric motor 98 which can be switched on and off at adjustable step lengths by switching means (not shown) controlled by a rotatable metering device riding on the paper (and thus not influenced by the gradually increas ing diameter of the roll as the paper is rolled up). In the illustrative machine, this metering device takes the form of a presser roller 100 which also serves to assist the holding of the paper down onto the plat form. (The roller 100 of the illustrative machine does not have a continuous cylin drical surface over its whole length, but is relieved at intervals at 102 to avoid its picking up, as it will be seen hereinafter - would otherwise be likely, an undue amount of excess colour as the paper is wound up). Gearing 97 from the motor 98 to the roll 96 is only partially visible in the drawing, being concealed behind a bracket 104 of the means 90. Provision (not visible in the drawing) is also made in the roll-supporting means 90 of the illustrative machine for reducing air pressure under the platform 94 so that the paper laid over it is held down by suction, especially when, as hereinafter described, the pad 30 is raised to pick up colour from the paper. control means (not shown) Electrical control means (not shown) operates pneumatic and hydraulic valves of the illustrative machine in suitable sequence so that, in the cycle of operation of the machine from a condition in which the rollsupporting means 90 is in register below the screen support 20 and a piece of ware ready to be decorated is on the support 80 in register below the pad 30 (which has colour on it which it has just picked up from the paper), the cylinders 26 and 38 are actuated to bring the pad 30 down in an operating stroke to impress the design in colour onto the ware and to lower the support 20 so that an under side of the screen frame 46 bears on the paper, which is preferably also subject at this time to suction to hold it steady on the platform 94. While the pad is executing its operating stroke, the short descent of the support 20 taking negligible time compared with the stroke of the pad support, the squeegee 69 is rocked down onto the screen 42 and executes an operating stroke (under the influence of the cylinder 54) across the screen (from front to rear of the illustrative machine). The squeegee is raised and brought forward again and the support 26 is raised to lift it clear of the deposited colour. (A reservoir of colour is maintained on the screen by hand, or by automatic feed, if preferred). The pad 30 is also raised after impressing the design on the ware, and when both screen support 20 and pad 30 are clear, the carriage 70 moves to the right hand end of its stroke to its position shown in the drawing under the influence of the cylinder 74. The ware support 80 is now in a loading and unloading position where the piece of ware bearing the design is replaced by a fresh piece, either by hand or automatically. At this stage, the portion of paper to which the design (indicated as 110 in the drawing) has been applied is in register and below the pad 30. The pad 30 is now brought down again (while the screen support 20 remains up) into pressing engagement with the paper, thus, on its ascent to pick up the design from the paper. When it is clear of the paper, the carriage returns to the left (viewing the drawing) and during this movement, the take-up roll 96 is actuated by the motor 98 to advance the paper a measured step as determined by the roller 100 so that residual colour left on the paper is moved away from the area covered by the design on the screen 42, a fresh portion of paper thus being placed in register with the screen ready for application of the next design. The roll of paper is wound up on the roll 96 and, when it is finished, is replaced by a fresh one on the dispensing roll. The old roll is then thrown away. The relieving of the roller 100 at 102 militates against the build up of an undue amount of residual colour on the roller. The illustrative machine thus enables designs to be printed reliably and uniformly on successive pieces of ware by screen printing without discontinuity of the design itself and with few interruptions in the output of production. WHAT WE CLAIM IS:

1. A repetitive production process for applying a design in colour to contoured surfaces of a succession of articles comprising a repeated cycle of operations wherein,

in each cycle, the design in colour is applied by screen printing to an intermediate surface and then transferred from said surface to the contoured surface of an article by a deformable dome-shaped transfer pad, the intermediate surface for each cycle being free from residual colour left over from a previous cycle.

2. A process according to claim 1 in which said intermediate surface is constituted by a roll of sheet material which is advanced step-by-step between successive applications of colour to present a fresh area for each application.

3. A process according to claim 2 in which said intermediate surface is one which, while not sufficiently absorbent to result in loss of definition of the design by spontaneous spreading of the colour over the surface, is significantly not nonabsorbent.

4. A process according to claim 3 in which said intermediate surface is paper.

5. An off-set screen-printing machine suitable for use in decorating articles of ceramic ware, comprising means for supporting a screen to enable a design in colour to be applied by a screen-printing process to an intermediate surface, a ware support for supporting an article to which the design in colour is to be applied, and a deformable dome-shaped transfer pad for transference of the design in colour from the intermediate surface to the article, the machine being operable cyclically in such a manner that in each cycle of operation first registration is effected between the screen and the intermediate surface and the design in colour is applied through the screen to the surface, second registration is effected between the transfer pad and the intermediate surface and the design in colour is picked up from the surface by the pad, and third registration is effected between the ware support and the pad and the design in colour is transferred from the pad to an article on the ware support, the machine comprising means arranged to provide for said first registration in each cycle of operation an intermediate surface that is free or substantially free of residual colour from a previous cycle.

6. A machine according to claim 5 in which said means arranged to provide an intermediate surface comprises means for supporting a roll of sheet material to be used to provide the intermediate surface, and means whereby after the pad has picked up colour from the intermediate surface, in each cycle of operation, the roll of sheet material can be advanced by a long enough step to bring a fresh area of the material into registration with the screen for 4be next application of colour through the screen.

7. A machine according to claim 6 in which the means whereby the roll of sheet material can be advanced is actuated automatically to advance the roll between successive applications of colour thereto.

8. A machine according to claim 7 comprising a dispensing roll to support the roll of sheet material to be used as the intermediate surface and a power-driven take-up roll on which the sheet material is to be wound up for advancing the sheet material a step at a time after each engagement thereof by the pad and before the application of further colour thereto by the screen.

9. A machine according to any one of claims 6 to 8 comprising means for varying the length of step of advancement of the sheet material.

10. A machine according to claim 9 comprising a presser roller which engages the upper surface of the sheet material adjacent the take-up roll, the presser roller engaging the material only at spaced apart intervals across its width.

11. A machine according to any one of claims 6 to 10 in which the roll-supporting means comprises a hard flat perforate platform on which the sheet material of the roll is supported when it is engaged from above by the pad, and means is provided to reduce the air pressure beneath the platform at least for an initial period during ascent of the pad after engaging the intermediate surface to hold the sheet material by suction on to the platform.

12. A machine according to claim 11 comprising means whereby suction is applied to the under side of said sheet of material, in the operation of the machine, also when the colour is applied through the screen.

13. A machine according to any one of claims 6 to 12 comprising a frame on which the pad, in the shape of an inverted dome, and the screen are mounted for vertical reciprocation in side-by-side relationship, and a horizontally reciprocable table on which the ware support and the rollsupporting means are mounted, means being provided to move the table to-and-fro when the pad and screen are in raised positions to bring the intermediate surface into register with the screen and pad alternately.

14. A production process for applying a design in colour to contoured surfaces of a succession of articles by off-set screen printing carried out substantially as hereinbefore described with reference to the accompanying drawing.

15. An off-set screen-printing machine suitable for use in decorating articles of ceramic ware constructed arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawing.