GB2109307A - A platen printing machine - Google Patents

Abstract

One or more platens 12 are mounted on a movable turret 10 which steps each platen in succession between a loading station 17a first printing station 14, a second printing station 15 and an unloading station 18. As shown, the loading, printing and unloading operations are performed substantially simultaneously on sheet material on respective platens, though the printing operations are staggered slightly to avoid smudging of the impressions. The stations may be arranged around the turret or facing an axial end of the turret (Figure 5 not shown). instead of rotating between the various stations, the platens may be subjected to a translational movement (Figures 5 and 7 not shown). <IMAGE>

Description

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GB 2 109 307 A

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SPECIFICATION A platen printing machine

5 The present invention relates to a process for printing and also to printing machines. In particular it relates to processes and machines for printing pre-cut blanks, such as small tickets or cards, for example, visiting cards.

10 None of the current methods for printing small cards is entirely satisfactory.

In one method of printing visting cards, a number of cards are printed simultaneously on a single large sheet, by offset printing. The whole card can subse-15 quently be subjected to thermographic treatment, for which powder is applied to the card and adhered to the printed characters, the surplus being removed, either by hand or semi-rriechanically. Heat is then applied. After the heat treatment, during which 20 the powder fuses, the printing on the card gains a simulated raised effect. In order thereafter to cut the cards with reasonable accuracy each sheet has to be guillotined separately, or stacked with only one or two other sheets for guillotining, and this is a 25 relatively slow procedure.

The cleanness and accuracy of the cut will depend on the guillotine used. Furthermore there may be some inaccuracy in aligning the sheet for printing all the cards according to a required grid and there is a 30 second possibility of error in the alignment of the guillotine, which could result in misaligned printing and/or variation in card to card sizes.

In fact, it is desirable to print visting or other small cards in pre-cut form. Free-cut blanks can be purch-35 ased in packets in a wide variety of sizes; in each pack there is a high degree of accuracy in card to card size and the edges of the cards are clearly cut. This means that the printed cards can be neatly stacked to give good presentation to the purchaser. 40 However, in the past, it has been found very expensive to print individual small cards, especially where it is desired to print close to the edges, because of difficulties in handling the cards.

A major disadvantage common to the known 45 printing methods is that they are not readily adaptable for two-colour printing and thermography. In the methods described above, it wold be necessary to print a card with ink of one colour, coat it with powder and partially thermograph the card until the 50 powder sticks to the ink, and then to print the card with another colour, apply powder again and thermograph the two colours, which would be very time consuming. There would also be difficulties in ensuring alignment of the two impressions. 55 Accordingly, the invention proposes a platen printing machine having a plurality of printing stations, at least one platen, and means for bringing printing stations and platen(s) into registration, whereby a plurality of impressions can be made on a 60 sheet material held on the platen without removal between registrations.

Preferably the platen is mounted on a rotatable turret. The printing stations may be distributed circumferentially around the turret, or they may be 65 arranged around the axis of rotation but facing an axial end of the turret.

The turret preferably has a plurality of platens, the actual number corresponding to the number of functions to be performed, i.e. separate printing 70 steps and loading and unloading.

In order that the invention shall be clearly understood, several exemplary embodiments thereof will now be described with reference to the accompanying drawings, in which:

75 Figure 1 shows a schematic plan view of a multi-platen turret arrangement according to the invention;

Figure 2 shows a perspective view of a complete printing machine according to the invention; 80 Figure 3 shows in plan view a cross-section through the turret platen of the printing machine;

Figure 4 shows a vertical elevation of one platen face; and

Figures 5, 6 and 7 show three variations, illus-85 trated schematically, of a printing machine according to the invention.

Figure 1 shows, in plan view and schematically only, a multi-platen turret for a printing machine. The turret 10 is mounted for rotation about a vertical 90 axis 11 and incorporates four platens 12, which receive sheet material for printing, for example individual cards 13. The machine is designed to print in two colours on each card, and has two printing stations 14,15. The print heads are moved towards 95 and away from the platens as indicated by the arrows 16. On a third side of the turret 10 is a magazine and feed device 17 which supplies the cards 13 one by one to the platen. After printing, the cards are released from the fourth side of the turret 100 and carried away at 18. Any suitable means may be employed for holding the cards on the platens, and in this particular case, the platens have the form of vacuum pads, a suction being maintained from within the turret so long as the cards are to be held 105 on the platens.

A complete printing machine embodying a multi-platen turret is shown in Figure 2. The machine has a base frame 20 mounted on castors 21. The machine has two main sections, the first being the printing 110 section 22, and the second being a thermographic glazing section 23. The section 22 employs a multi-platen turret 24, as described in principle with reference to Figure 1, the details of which will be described later with reference to Figure 3 and 4. The 115 machine has a main switch box 25, a control board 26 and compressors and vacuum pumps 27. A magazine 30 is arranged to hold pre-cut blanks for printing. A transfer mechanism 31 is arranged to extract blanks singly from the magazine 30 and to 120 supply them one by one to the first platen of the turret 24. The second and third platens of the turrets 24 lie adjacent first and second printing heads 32,33. Each print head has a separate ink reservoir 34 containing different colour inks. The fourth platen of 125 the turret lies at the discharge station, and a card previously printed is here released for passage through the thermographic section 23 of the machine.

The thermographic section incorporates a dusting 130 device 35, a conveyor 36, a heater 37 and a cooling

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GB 2 109 307 A

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fan 38. The finished cards discharge into a tray 39. When released from the fourth plate, the cards slide down an inclined piate 40 and are then moved on edge by a conveyor belt 41 in the direction of the 5 arrow. A hopper 42 contains a glazing powder which is carried upwards by a belt conveyor 43. The glazing powder is tipped off the top of the conveyor 43 onto the card passing below so that the powder for the thermographic process adheres to the still wet ink. A 10 small vibrator causes the excess powder to be shaken off. The remainder of the thermographic process is entirely conventional, and will not be further described.

In operation, the turret 24 is indexed accurately in 15 steps of 90°. At each dwell, the four platens are located accurately in the four stations, with their surfaces precisely vertical. The support 44 forthe turret 24 is relatively massive so that the turret can withstand the operation of the printing heads 32,33. 20 These heads and their ink reservoirs, together with the necessary inking mechanisms and formes are of conventional design, and will also not be described in detail.

The operation of the machine is as follows: 25 Starting from an initial dwell, a first card is removed from the magazine 30 and applied by the transfer mechanism 31, which preferably operates with vacuum suction pads, to the platen at that time facing it. The turret 24 is then indexed through 90°, 30 bringing the card to the first printing station. During the next dwell, a second card is applied to the next platen, and a first impression by print head 32 is made on the first card. The turret 24 indexes again through 90°, a third card is applied to the platen, the 35 second card is printed for the first time by the first print head 32 and the first first card is printed for the second time by the second print head 33. After a third index movement, the first card is brought to the discharge station and is allowed to drop off onto the 40 conveyor 41. At this stage, all four platens of the turret 24 are now in operation, and a fourth indexing movement brings the now empty first platen back to its starting position to receive a fresh card.

As will be described later, the turret 24 employs a 45 vacuum system for retaining the cards on each platen, which permits extremely rapid and convenient operation. Although movement of the turret 24 underthe action of a print head is minimised by the support 44, some slight movement is inevitable. 50 Therefore, the operations of the print heads 32,33 are made non-synchronous, so that movement of the platen caused by one head does not cause smudging of an impression made simultaneously by the second print head. A delay is introduced be-55 tween the two operations to allow the turret 24 to resume its stationary central position before the second impression is made.

The construction oftheturret 24 will now be described with reference to Figures 3 and 4. The 60 sectional view in Figure 3 shows the turret to be of basically square cross-section. The turret block 56 has a vertical central bore 50 with a liner 51. It is mounted for rotation on a vertical sleeve 52 having three radial bores 53 and an external milled slot 54 65 which communicates with the three bores 53. The slot 54 extends around exactly 270°.

Communicating with the bores 53 and the slot 54 are four horizontal radial bores 55 in the turret block

56. The bores 55 communicate with a recess or 70 series of recesses 57 covering the four vertical surfaces of the block 56. A platen plate 58 is bolted onto each face of the block 56 and covers the slot(s)

57. The platen plate 58 has a large number of fine bores 60 distributed over its entire area. Thus, a

75 suction or vacuum applied to the central sleeve 52 is transmitted via bores 53,55 and recesses 57 to provide a uniform suction effect over the entire area of the platen plate 58. This suction effect is maintained through 270° of rotation oftheturret at full 80 effect, and is only removed completely over the last approximately 5° of rotation when the bore 55a on the left of Figure 3 becomes completely cut off from the slot 54. In its final indexed position, an exhaust bore 61 comes into communication with the exterior 85 and the vacuum effect on the platen then at that station is removed completely. That platen is then at the discharge station of the printing machine.

In orderto further distribute the vacuum effect uniformly over the surface of each platen, a replace-90 able sheet 62 of a porous material is fixed over each platen. In a preferred case, this sheet material is also slightly resilient, and thus provides an ideal platen surface against which to print. A suitable material is known underthe name "Vyon" of Porvair Limited. 95 This material has a further advantageous feature. This is that it retains a slight transverse curve, due to a sizeing operation carried out on one surface only of the sheet. This has the advantage that, although nominally flat on the platen plate 58, once the 100 vacuum is released behind it, it springs naturally due to its curvature, and provides a positive discharge of the card previously held on its surface.

Such a platen system is extremely simple to use, since physical guide members for locating and 105 holding the cards on the platens are unnecessary. Thus the whole area of the cards is available for printing, and lines leading off the edge are possible ('flare out')- Moreover a constant line on one edge of the platen can be used as the datum line for 110 mounting all printing material, thus simplifying feed and alignment. The area not covered by a blank can be masked off by sticky tape.

In principle, other arrangements can be adopted to allow multiple printing using one or more platens, 115 without release of the material to be printed between impressions. In a first variant, it is of course possible to employ a turret having more than four faces, e.g. six, and the turret must then be indexed through the appropriate number of degrees. A second variant is 120 shown in Figure 5. In this case, a turret 70 is arranged for rotation about a horizontal axis 71. Again the turret indexes through 90°, but the four platens 72 are arranged spaced at 90° on a single flat plane 73. The four stations are again feed, print one, print two, 125 and discharge, the latter being arranged at the lowermost station.

A third variant is shown in Figure 6, in which a platen 80 is reciprocated to bring it alternately into register with two printing heads 81,82 which move 130 to and fro on a carriage 83, but not towards and

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away from the platen. A final alternative is shown in Figure 7. Here, a continuous belt 90 passes in front of a fixed but elongated vacuum platen 91. The belt 90 is porous and a card for printing inserted at 92 will be 5 retained on the belt. Afirst print head 93 can then make a first impression, before the card is indexed by movement of the belt to a second position 94. In this position, a second print head 95 can operate. A further movement of the belt will take the card away 10 from the effect of the vacuum platen 91, so that it is discharged at the point 96.

Claims (14)

15 1. A platen printing machine having a plurality of printing stations, at least one platen, and means for bringing printing stations and platen(s) into registration, whereby a plurality of impressions can be made on a sheet material held on the platen without 20 removal between registrations.

2. A machine according to claim 1 wherein the platen is mounted on a rotatable turret.

3. A machine according to claim 2 wherein the printing stations are distributed around the turret.

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4. A machine according to claim 3 and further comprising sheet material loading and/or unloading stations distributed around the turret.

5. A machine according to claim 3 or4wherein the turret has a plurality of platens arranged around

30 its axis, whereby different functions may be performed substantially simultaneously at each platen, the turret being rotated by a predetermined amount before the functions are repeated.

6. A machine according to claim 5 where two of 35 said different functions are the making of afirst impression on a sheet material by a first printing station, and the making of a second impression on a sheet material by a second printing station.

7. A machine according to claim 6 wherein the 40 making of said second impression is separated slightly in time from the making of said first impression.

8. A machine according to any of claims 5 to 7 wherein one of said different functions is the loading

45 of a sheet material to be printed.

9. A machine according to any of claims 5 to 8 wherein one of said different functions is the unloading of a printed sheet material.

10. A machine according to claim 2 wherein the 50 printing stations face an axial end oftheturret.

11. A machine according to claim 1 wherein the printing stations are arranged in a single plane and the platen and the printing stations are capable of relative motion both parallel to and perpendicular to

55 said plane.

12. A machine according to claim 11 wherein the platen is moved perpendicularly to said plane to achieve a first impression on a sheet material by a first printing station, the printing stations are then

60 moved parallel to said plane, and the platen is then again moved perpendicularly to said plane to achieve a second impression on the sheet material by a second printing station.

13. A machine according to claim 11 wherein at 65 least a first printing station is moved perpendicularly to said plane to perform a first impression on a sheet material, the platen is then moved parallel to said plane, and at least a second printing station is then moved perpendicularly to said plane to perform a 70 second impression on the sheet material.

14. A machine according to claim 13 comprising a continuous belt for effecting the movement of the platen parallel to said plane.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1983.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.