GB2191444A

GB2191444A - Improvements in printing

Info

Publication number: GB2191444A
Application number: GB08713470A
Authority: GB
Inventors: Geoffrey Thomas Dargavel
Original assignee: MASCOPRINT DEV Ltd
Current assignee: MASCOPRINT DEV Ltd
Priority date: 1986-06-10
Filing date: 1987-06-09
Publication date: 1987-12-16
Also published as: EP0252610A1; GB8713470D0; GB8614034D0; WO1987007562A1; KR880701185A; JPH01500580A

Description

1 GB2191444A 1 SPECIFICATION complicated, however, and thus relatively ex

pensive. Moreover, it is not a straightforward Improvements in printing matter to ensure that each and every pad ap plies the optimum pressure to the associated This invention relates to printing and is con- 70 key.

cerned in the most important example with It is an object of this invention to provide printing upon surfaces which are not flat. an improved printing method and an improved In a number of applications printed matter is printing apparatus which simplify the applica required to withstand repeated handling or tion of sublimation inks, especially to non-flat other forms of wear. With computer keys, for 75 surfaces.

example, it is essential that the character on Accordingly, the present invention consists, the key should remain distinct throughout the in one aspect, in printing apparatus for print expected life of the keyboard. Because of this ing with sublimation ink upon a rigid surface requirement, keys have often been produced of an article, comprising a support for the arti in the past, not by a printing process, but by 80 cle, means for applying sublimation ink in the a two-stage moulding procedure. The first required image to the surface, a flexible, heat stage produces the body of the key in the resistant membrane, vacuum means for draw background colour with the hollowed outline ing the membrane by suction closely toward of the character. The second moulding stage the surface over the applied ink to apply pres forms the character in the chosen colour. As 85 sure thereto and means for applying heat to will be apparent, this is an expensive proce- said surface through the membrane.

dure. Advantageously, the support comprises a In an attempt to overcome this problem, it chamber adapted to receive at least that por has been proposed to use sublimation inks. tion of the article which is associated with These are applied to the key surface in the 90 said surface the chamber having a rim which form of a transfer and are then heated so that engages in use said membrane; the vacuum the ink sublimates and enters the substrate in means being adapted to evacuate said cham the nature of a dye. A character printed in ber.

this manner is indelible and with suitably cho- Preferably, said means for applying heat sen inks, substrates and process parameters, 95 comprise infra-red heating means.

the desired durability can be achieved. Suitably, the means for applying ink com The upper surface of a computer key is of- prises a transfer.

ten concave and to ensure that the ink is In one form of the invention, the membrane transferred over the entire character, it is is formed of silicone rubber.

necessary to apply a degree of pressure. It 100 In another aspect, the present invention has been proposed for this purpose to use a consists in printing apparatus for printing with form of resilient pad. To speed up the printing sublimation ink upon the keys of an assem operation, it is desirable to apply, simultane- bled keyboard; comprising a support for the ousiy with the application of pressure, the keyboard, means for applying sublimation ink necessary heat for the sublimation process. 105 in the form of characters to the upper sur Considerable difficulties have been experienced faces of the respective keys, a flexible, heat hitherto in applying the correct amounts of resistant membrane, vacuum means for draw heat and pressure. With silicone rubber pads, ing by suction the membrane into intimate for example, the additives that are necessary contact with the upper surfaces of the respec to achieve sufficient heat conductivity tend to 110 tive keys over the applied ink and means for reduce the resilience of the pad to the point applying heat to said upper surfaces through where it can no longer properly conform to the membrane.

curved surfaces or surfaces which depart from Advantageously, the apparatus further com predetermined tolerances. These difficulties are prises an apertured template locatable over experienced not only with computer keys but 115 the keyboard with the keys received in the also with a variety of other applications where apertures of the template so as to restrain the durability of sublimation inks is required. movement of the keys and to limit travel of There is a further problem that arises with the membrane.

computer keys in that once the keys have In a further aspect. the present invention been printed, they require to be assembled in 120 consists in a method of printing with sublima the keyboard in the correct arrangement. As- tion ink upon a rigid surface, comprising the sembly is therefore extremely labour intensive. steps of applying the ink to the surface, draw There would be considerable simplification of ing a flexible heatresistant membrane towards the procedure if printing of the keys could be said surface through suction so as to apply achieved after assembly of the keys in the 125 pressure to said ink; and applying heat to ef keyboard. Some work has already been done fect sublimation of the ink.

to this end. It has been suggested, for.exam- Advantageously, the ink is applied by posi pie, to employ an array of resilient pads which tioning a transfer over the surface.

are aligned one each with the keys of the Preferably, heat is applied radiantly. The in keyboard. A printing machine of this type is 130 vention will now be described by way of 2 GB2191444A 2 example with reference to the accompanying that the transfer 32 closely conforms to the drawings in which: shape of the keys and particularly to the con Figure 1 is a sectional view through part of cave upper surface of the key which is to the printing apparatus according to this inven- receive the printed character.

tion, 70 After an appropriate time interval, the heat Figure 2 is a somewhat diagrammatic side lamps are energised to cause the upper sur view of the printing apparatus according to faces of the keys to rise in temperature to the this invention, and level required for sublimation to take place.

Figures 3a and 3b are sectional views illus- After a further interval the lift table is re- trating stages in the method of this invention. 75 tracted and the keyboard withdrawn from the There is shown in Figure 1 an open box 10 box. With the transfer 32 based on a plastics having a port 12 through which it may be film, the further desirable effect is seen of a connected to a vacuum pump (not shown). softening and increase in flexibility of the The base of the box is provided with suitably transfer. This further improves the degree of shaped and positioned lugs 80 contact between the key and the ink of the A template 16 is formed with an array of transfer.

apertures 18 corresponding exactly with the It will be appreciated that the use of a flexi position of the keys in the keyboard. This ble membrane and suction to apply the re template is hinged to the box 10 so that it quired pressure offers considerable mechanical may be moved to a closed position in which 85 simplification over arrangements of individual each key projects through and is a reasonably pressure pads and the like. This should lead close fit within the corresponding template to economies in manufacturing of the appara aperture 18. tus. It is also felt that because of the ability of It is well known that sublimation inks can the heat lamps to reach working temperature be applied in the form of a transfer which has 90 very quickly, the cycle time of the apparatus been prepared by a silk screen or other suit- should be reduced. Moreover, it is believed able printing process. The transfer is usually that the upper surface of the keys can be formed on paper. For this invention, it is pretaken to the required temperature without heat ferred to use a transfer which has been damage to the remainder of the keyboard or printed by a silk screen technique on to a 95 electronic circuitry contained within the key substrate in the form of a plastics film. The board. There exists the option, of course, of transfer is positioned above the keyboard with printing the keys before the circuitry is added accurate location being achieved by means of to the keyboard.

pins 20 provided on the box engaging within The ability to print the keys in situ offers pre-punched holes in the transfer. In the preconsiderable advantages. Firstly, a large num sent example, the transfer is intended to lie ber of keys are printed at the same time lead above the template but the reverse arrange- ing to reductions in manufacturing time. Sec ment is also possible. ondly and perhaps more importantly, the ma Referring now to Figure 2, the box 10 con- jority of keys in the original assembly of the taining the keyboard and transfer and with the 105 keyboard are indistinguishable and can be sup template in the closed position, is placed on a plied from a single feed. This represents a lift table 22 of a form conventional in the considerable simplification over the conven printing industry. A thin sheet of silicone rub- tional technique where each keyboard must be ber 24 is held in a horizontal plane above the provided with the correct key character at the lift table by means of a frame 26 shown 110 correct position.

schematically in the Figure. Above the mem- Whilst the apparatus and method according brane 24 there is positioned an array of infra- to this invention offer considerable advantages red heat lamps 28. in the particular application which has been Under automatic control, the lift table 22 is described by way of example, there are many raised until the edges of the box 10 contact 115 other instances where the technique could of the membrane 24, as shown in this position, fer important advantages. Examples are the the membrane 24 will be extended through its printing of plastics containers, housings for contact with the keys 30 which project from electronic apparatus household goods or nov the box. A vacuum is then applied at port 12 elty items. These are of course taken from a to draw the membrane towards the upper sur- 120 very large list of possibilities.

face of the keys and to force the ink bearing The invention has been described by way of transfer 32 closely toward the keys. In this example only and numerous modifications are way, the required amount of pressure can be possible without departing from the scope of applied to the transfer 32 and the ink it car- the invention. The membrane could for inries. The template serves the dual purposes in 125 stance be supported in other ways and differ- this procedure of minimising sideways dis- ent techniques employed for drawing the placement of the keys and limiting the travel membrane closely toward the surface to be of the membrane downwardly into the spaces printed. Whilst the use of transfers is felt to between the keys. The position reached is be preferable, the sublimation ink could be ap- that shown in Figure 3b and it will be seen 130 plied in other ways. The ink might for 3 GB2191444A 3 example be in powdered form. The use of mation of the ink.

radiant heat has the mentioned advantage of 9. A method of printing with sublimation ink simple and fast acting control but alternatives upon a rigid surface as claimed in claim 8 will suggest themselves to one skilled in the wherein the ink is applied by positioning a art. 70 transfer over the surface.

10. A method of printing with sublimation

Claims

CLAIMS ink upon a rigid surface as claimed in claim 9

1. Printing apparatus for printing with subli- wherein the heat is applied radiantly.

mation ink upon a rigid surface of an article, 11. A method of printing with sublimation comprising a support for the article, means for 75 ink upon a rigid surface as claimed in either applying sublimation ink in the required image claim 9 or claim 10 wherein said transfer is to the surface, a flexible, heat-resistant mem- printed by a silk screen technique on to a brane, vacuum means for drawing the mem- substrate in the form of a plastics film.

brane by suction closely toward the surface 12. A method of printing with sublimation over the applied ink to apply pressure thereto 80 ink upon a rigid surface as claimed in claim 11 and means for applying heat to said surface wherein said transfer is a thin sheet of silicone through the membrane. rubber

2. Printing apparatus for printing with subli- 13. A method of printing with sublimation mation ink upon a rigid surface of an article as ink upon a rigid surface as claimed in any one claimed in claim 1 wherein the support com- 85 of the preceding claims 8 to 12 wherein the prises a chamber adapted to receive at least heat is provided by means of an array of in that portion of the article which is associated fra-red heat lamps with said surface, the chamber having a rim 14. An item having an uneven surface or a which in use, engages said membrane. plurality of non-co-planar surfaces on which a

3. Printing apparatus for printing with subli- 90 marking has been printed using apparatus as mation ink upon a rigid surface of an article as claimed in any one of the preceding claims 1 claimed in either claim 1 or claim 2 wherein to 7.

said means for applying heat comprises infra- 15. An item having an uneven surface or a red heating means. plurality of non-co-planar surfaces on which a

4. Printing apparatus for printing with subli- 95 marking has been printed by the method mation ink upon a rigid surface of an article as claimed in any one of the preceding claims 8 claimed in any one of the preceding claims to 13.

wherein the means for applying ink comprises 16. A keyboard having a plurality of keys a transfer. printed using apparatus claimed in any one of

5. Printing apparatus for printing with subli- 100 the preceding claims 1 to 7 or by a method mation ink upon a rigid surface of an article as as claimed in any one of the preceding claims claimed in any one of the preceding claims 8 to 13. wherein the membrane is formed of silicone rubber. Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd, Dd 8991685, 1987. 40

6. Printing apparatus for printing with subli- Published at The Patent Office, 25 Southampton Buildings, mation ink upon the keys of an assembled London, WC2A l AY, from which copies may be obtained.

keyboard comprising a support for the keyboard, means for applying sublimation ink in the form of characters to the upper surfaces of the respective keys, a flexible, heat-resistant membrane, vacuum means for drawing by suction the membrane into intimate contact with the upper surfaces of the respective keys over the applied ink and means for applying heat to said upper surfaces through the membrane.

7. Printing apparatus for printing with sublimation ink upon the keys of an assembled keyboard as claimed in claim 6 wherein the apparatus further comprises an apertured template locatable over the keyboard with the keys received in the apertures of the template so as to restrain movement of the keys and to limit travel of the membrane.

8. A method of printing with sublimation ink upon a rigid surface, comprising the steps of applying the ink to the surface, drawing a flexible heat-resistant membrane towards said surface through suction so as to apply pressure to said ink; and applying heat to effect subli-