GB2107255A - A platen printing machine - Google Patents

Abstract

A rotating turret block 56 has a plurality of platen plates 58 for carrying cards etc to be printed, the cards being retained on the platen by suction; the suction is applied to the cards via a central sleeve 52, radial bores 53 and a circumferential slot 54 in the sleeve, radial bores 55 in the turret block, recesses 57 and fine bores 60 in each platen plate. A card is located on a single platen throughout the printing process, the platen being moved in succession between a loading station, one or more printing stations and an unloading station (at the left in Fig 3) where the suction is removed from the card. In modifications the platens may be arranged on the axial end face of a rotatable turret (Fig 5 not shown) or on a member which is capable of relative reciprocating motion to one or more printing stations. <IMAGE>

Description

SPECIFICATION A platen printing machine 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.

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

In one method of printing visiting cards, a number of cards are printed simultaneously on a single large sheet, by offset printing. The whole card can subsequently be subjected to thermographic treatment, for which powder is applied to the card and adheres to the printed characters, the surplus being removed, either by hand or semi-mechanically. Heat is then applied. After the heat treatment, during which 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 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 second possibility of error in the alignment of the guiliotine, which could result in misaligned printing and/or variation in card to card sizes.

In fact, it is desirable to print visiting or other small cards in pre-cutform. Pre-cut blanks can be purchased 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 cleanly cut. This means that the printed cards can be neatly stacked to give good presentation to the purchaser.

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. In one printing method using pre-cut cards, cards are positioned by hand on a letter press machine where they are held by edge grippers or the like which reduce the area available for printing. After the printing operation the cards are manaully removed.

The feed and removal of cards to a platen using edge grippers is very inconvenient, both for letterpress printing and other systems.

The invention aims to provide an improved platen in printing machines which avoids these disadvantages.

Accordingly, the invention provides a platen printing machine comprising a platen having internal passages communicating between an external connection and the front surface of the platen, and suction means connected to the external connection, whereby a sheet material to be printed can be held on the platen by suction for printing.

The front surface of the platen is preferably covered by a platen plate having a plurality of bores communicating with said internal passages.

The platen plate may be covered by a sheet of porous material which is preferably also resilient.

The machine preferably comprises a plurality of platens arranged around a rotatable turret, the turret having an axially-extending central sleeve and the platens having respective radiallyextending bores which communicate, at least part of the time with the central sleeve.

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: 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; 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, illustrated 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 axis 1 1 and incorporates four platens 12, which receive sheet material for printing, for example individual cards 1 3. The machine is designed to print in two colours on each card, and has two printing stations 14, 1 5. The print heads are moved towards and away from the platens as indicated by the arrows 16. On a third side of the turrent 10 is a magazine and feed device 1 7 which supplies the cards 13 one by one to the platen.After printing, the cards are released from the fourth side of the turret and carried away at 1 8. 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 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 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 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 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 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 device 35, a conveyor 36, a heater 37 and a cooling fan 38. The finished cards discharge into a tray 39. When released from the fourth platen, the cards slide down an inclined plate 40 and are then moved on edge by a conveyor belt 41 in the direction of the 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 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 steps of 900. At each dwell, the four platens are located accurately in the four stations, with their surfaces precisely vertical. The support 44 for the turret 24 is relatively massive so that the turret can withstand the operation of the printing heads 32, 33. 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: 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 900, 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 900, a third card is applied to the platen, the 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 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 vacuum system for retaining the cards on each platen, which permits extremely rapid and convenient operation. Although movement of the turret 24 under the action of a print head is minimised by the support 44, some slight movement is inevitable. Therefore, the operations of the print head 32, 33 are made nonsynchronous, 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 between the two operations to allow the turret 24 to resume its stationary central position before the second impression is made.

The construction of the turret 24 will now be described with reference to Figures 3 and 4. The 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 which communicates with the three bores 53. The slot 54 extends around exactly 2700.

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 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 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 2700 of rotation of the turret at full effect, and is only removed completely over the last approximately 50 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 and the vacuum effect on the platen then at that station is removed completely. The platen is then at the discharge station of the printing machine.

In order to further distribute the vacuum effect uniformly over the surface of each platen, a replaceable 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 under the name "Vyon" of Porvair Limited. This material has a further advantageous feature. This is that it retains a slight transverse curve, due to a sizeing operation carried out at one surface only of the sheet. This has the advantage that, although nominally flat on the platen plate 58, once the 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 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 and possible ('flare out'). Moreover, a constant line on one edge of the platen can be used as the datum line for mounting all printing material, thus simplifying feed and alignment. The area not covered by a biank can be masked off by sticky tape. In principle, other arrangements can be adopted to allow multiple printing using one or more platens, without release of the material to be printed between impression. 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 shown in Figure 5.

In this case, a turret 70 is arranged for rotation about a horizontal axis 71. Again the turret indexes through 900, but the four platens 72 are arranged spaced at 900 on a single flat plane 73.

The four stations are again feed, print one, print two, 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 to and fro on a carriage 83, but not towards and 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 retained on the belt. A first 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 from the effect of the vacuum platen 91,so that it is discharged at the point 96.

Claims (11)

Claims

1. A platen printing machine comprising a platen having internal passages communicating between an external connection and the front surface of the platen, and suction means connected to the external connection, whereby a sheet material to be printed can be held on the platen by suction for printing.

2. A machine according to claim 1 wherein the front surface of the platen is covered by a platen plate having a plurality of bores communicating with said internal passages.

3. A machine according to claim 2 wherein the front surface of the platen plate is covered with a sheet of porous material.

4. A machine according to claim 3 wherein said porous material is resilient.

5. A machine according to any preceding claim comprising a plurality of platens arranged around a rotatable turret, the turret having an axiallyextending central sleeve and the platens having respective radially-extending bores which communicate, at least part of the time with the central sleeve.

6. A machine according to claim 5 having n platens and in which the turret is intermittently rotated to permit different functions to be formed substantially simultaneously at each platen, the central sleeve having aperture means which communicate with the radially-extending bores of n-i of the platens at a single time.

7. A machine according to claim 6 wherein the following functions are performed substantially simultaneously; a loading operation at a first platen, respective printing operations at one or more further platens, and an unloading operation at a last platen the radially-extending bore of which is not in communication with the sleeve.

8. A machine according to any of claims 1 to 4 comprising a plurality of platens arranged on an axial end surface of a rotatable turret, and one or more printing stations being arranged to face the platens.

9. A machine according to any of claims 1 to 4 wherein the platen is mounted to reciprocate in a first direction relative to one or more printing stations which are mounted to move in a relatively perpendicular direction.

10. A machine according to claim 1 or 2 wherein a continuous belt of porous material passes in front of the platen to move a sheet material therealong.

11. A platen printing machine substantially as herein described with reference to Figs. 1 to 4, Fig. 5, Fig. 6, or Fig. 7 of the accompanying drawings.