WO1994026526A1

WO1994026526A1 - Printing apparatus

Info

Publication number: WO1994026526A1
Application number: PCT/GB1994/000939
Authority: WO
Inventors: Ian Gaylor; Steven Buckby
Original assignee: Prestek Limited
Priority date: 1993-05-06
Filing date: 1994-05-03
Publication date: 1994-11-24
Also published as: GB9309363D0; GB2283706B; AU6578694A; GB2283706A; GB9500251D0

Abstract

A printing apparatus (10) of the kind which comprises a plurality of elements which can selectively be operated, for example under computer control, to effect printing as the elements are moved relative to a substrate, comprises a body, a print head (11) mounting each of the elements of the selectively operable elements, a motive means (21) and a transmission (23, 24) whereby the print head (11) can be moved in a first direction relative to a body of the apparatus and to the substrate between beginning of, and end of, printing positions, during which movement printing is effected, and relative to the body of the apparatus generally towards and away from a substrate transverse to the first direction, the transmission comprising at least one flexible drive member (23, 24) carrying the print head (11) and driven by the motive means (21) to cause movement of the print head (11) at least in the first direction, so that the print head (11) is permitted to float to a limited extent by virtue of the inate flexibility of the drive member (23, 24).

Description

Title: Printing Apparatus Description of Invention

This invention relates to a printing apparatus and more particularly to a printing apparatus comprising a plurality of elements which can selectively be operated, for example under computer control, to effect printing as the elements are moved relative to a substrate.

Such a printing apparatus will hereinafter be referred to as being "of the kind specified".

According to one aspect of the invention we provide a printing apparatus of the kind specified comprising a body, a print head mounting each of the elements of the selectively operable elements, a motive means and a transmission whereby the print head can be moved in a first direction relative to a body of the apparatus and to the substrate between beginning of, and end of, printing positions, during which movement printing is effected, and relative to the body of the apparatus generally towards and away from a substrate transverse to the first direction, the transmission comprising at least one flexible drive member carrying the print head and driven by the motive means to cause movement of the print head at least in the first direction.

Thus the print head is permitted to float to a limited extent by virtue of the inate flexibility of the drive member.

Hence a printing apparatus in accordance with the invention may be used to print information on a substrate which is not exactly planar and flat, the floating print head accommodating unevenness in the surface of the substrate.

In a preferred arrangement, the flexible drive member comprises an endless driven loop member such as a belt driven via a pulley which may, in turn be driven for example from a shaft. A pair of such endless loop members or other flexible drive members may extend generally parallel to one another with the print head carried between them. Where the drive members comprise endless loop members, these may each be driven from a respective pulley mounted on a common shaft. The print head may be guided during its motion in the first direction by a guide means which may provide some restriction to the amount of float which would otherwise be permitted by the transmission.

For example, the print head may be connected to a roller which runs on an elongate guide member during movement of the print head in the first direction, the guide member preferably being of such configuration, as generally circular, in cross section so that in response to floating of the print head the roller is permitted to roll about a central axis of the guide member.

The transmission may include a further endless loop member which is clamped to the print head to add rigidity to the mounting of the print head on the transmission. The further endless loop member may be driven from the common drive shaft along with the first, and where provided, second, flexible drive members.

The print head may be movable at least towards the substrate by virtue of an actuator being actuated. For example, the actuator may comprise an air operated piston or other linear actuator which moves against the guide member where provided, so as to cause movement of the print head towards the substrate such movement being permitted by the inate flexibility of the transmission.

The elements of the print head when operated preferably produce heat, and the substrate may itself be heat sensitive whereby printing can be effected thereon.

Preferably though, the printing apparatus is of the so called hot foil type in which foil is fed through the apparatus and contacted by the thermal printing elements of the print head which when the elements are energised, transfer the foil onto the substrate such that printing may be effected on the substrate.

The foil may be fed through the apparatus as a continuous web, from a feed spool, via a web guide path, to a take up spool. Preferably, at least the take up spool is driven from the motive means to advance the web of foil through the apparatus, only when the print head is undergoing some movement during which printing is not effected.

It will be appreciated that once the print head has moved from the beginning to end of printing, positions, the print head must be returned to the beginning of printing position. It is during this return movement only that preferably the web of foil is advanced through the apparatus.

The invention will now be described with reference to the accompanying drawings in which :

FIGURE 1 is a side illustrative view of a printing apparatus in accordance with the invention, without a foil carrying web being shown, for clarity.

FIGURE 2 is an underneath plan view of the printing apparatus of figure 1, showing the foil carrying web.

FIGURE 3 is a front illustrative view of a printing apparatus in accordance with the invention, again without the web, for clarity.

Referring to the drawings, there is shown a printing apparatus 10 comprising a print head assembly 1 1 which mounts a plurality of individually energisable thermal printing elements, preferably provided on an edge of the print head assembly 11, in a row. The print head assembly 11 is movable relative to a web 12 which carries foil, whilst the thermal printing elements are individually selectively energised under computer control, thus to cause foil to be removed from the web 12 and deposited onto a substrate (not shown) to the right hand side of the apparatus 10 as seen in figure 1. The substrate may for example by a label, which is subsequently applied to an article, or may be the article itself, which labels/articles are carried past the printing apparatus 10 on a conveyor for example, and are temporarily halted at the printing apparatus 10 whilst printing thereon is effected.

In this way, information can be printed, in foil, on the substrate.

The web 12 carrying the foil is provided on a spool 14 carried on a hub 15, the web 12 passing around a web guide path comprising rollers 16, 17,18,19, and then on to a take up spool 20. Both the feed spool 14 and take up spool 20 are driven, as hereinafter explained, from a motive means 21 which is in this example, a stepper motor.

The print head assembly 11 is driven for movement relative to the web 12 by the motor 21 via a transmission which also serves to carry the print head assembly 11. The transmission comprises a pair of generally parallel spaced apart flexible drive members comprising belts 23,24, each of which is entrained about a first pair of rollers 25,26, and a second pair of rollers 27,28.

The first pair of rollers 25,26, are mounted on respective generally parallel and vertical drive shafts 30,31, with shaft 31 being driven via a belt 32 or chain drive or otherwise as required, from an output shaft 33 of the motor 21.

The second pair of rollers 27,28, are each mounted on respective generally parallel and vertical shafts 34,35, via bearings so that the rollers 27,28, are free to rotate relative to their respective shafts 34,35.

As can be seen from figure 1, the print head assembly is of generally rectangular configuration, and is clamped at its top and bottom edges 38,39, via clamps 36,37, (see figure 3) to the belts 23,24, between the rollers 34,35, so that upon operation of the motor 21 drive is transmitted from the drive shaft 33 of the motor to each of the belts 23,24, via the shaft 31, and hence the print head assembly 11 is caused to move either in the direction indicated by arrow A, relative to the web 12, or an opposite direction depending upon the sense of rotation of the output shaft 33 of the motor 21.

To give rigidity to the mounting of the print head assembly 1 1, the print head assembly 1 1 is also clamped at its rear edge 40 to a third belt 41 as shown at 42 in figure 2, the third belt 41 being driven in synchronism with belts 23,24, from shaft 31, but being entrained only about the shafts 31 and 30.

The print head assembly 11 also carries at its rear edge 40, a guide roller 44 which is rotatable about a generally vertical axis transverse to the direction A of movement of the print head assembly 1 1. The roller 44 bears on a generally horizontal post 46 of generally circular cross section, the post being mounted via a lever arm 47 for rotation about a horizontal axis 48 generally parallel to but spaced from the post 46, on a bearing 50 which is fixed relative to a body of the printing assembly 10.

Hence as the printing assembly 11 moves from side to side in the direction of arrow A, or oppositely, the print head assembly 11 is guided for movement via the guide roller 44 and post 46.

The print head assembly 11 is able to float during its movement by virtue of the inate flexibility of belts 23,24, and 41, and the roller 44 can thus move bodily about post 46 to accommodate such floating whilst continuing to guide the print head assembly 1 1.

In the figures, the print head assembly 1 1 is shown in a start position spaced away from a substrate, but with the web 12 carrying the foil, entrained over an edge of the print head assembly 1 1 mounting the thermal printing elements.

To bring the print head assembly 1 1 into contact with the substrate to effect printing, the print head assembly 1 1 is moved in a direction indicated by arrow B which is transverse to the direction of movement of the print head assembly 11 during printing, as indicated by arrow A.

Movement in direction B is achieved by means of an air cylinder and piston arrangement 50, which, when actuated, rotates the guide post 46 about axis 48, thus to urge the print head assembly 11 towards the substrate, against a restoring force supplied by the inate resilience and flexibility of the drive belts 23,24,41. The piston 50 is arranged to retain the print head assembly 11 in its extended position against the restoring force of the belts 23,24,41 whilst the print head assembly 11 moves from the beginning, to end of printing positions in direction of arrow A, to effect printing on the substrate.

At the end of printing, when the print head assembly 11 is in its end of printing position, the piston 50 is deactuated and the print head assembly 11 is moved in an opposite direction to arrow B by the restoring force of the belts 23,24,41, away from the substrate and, by actuating the motor 21 in an opposite sense of rotation, the assembly 11 is moved back to the start position shown in the drawings in a direction opposite to the direction of arrow A. The hub 15 of the supply spool 14 of the web 12 is driven from the motor 21 via a gear train and capstan arrangement, 53,54, from the driven shaft 31. Similarly, the take up spool 20 is driven via the gear train and capstan arrangement 53,54.

The gear train and capstan arrangement 53,54, includes a one way clutch such that the spools 14 and 20 are only rotated, in an anti-clockwise direction as shown in figure 2, when the print head assembly 11 is being returned to the start position by movement in a direction opposite to that indicated by arrow A.

The hub 15 of spool 14 at least, preferably includes some mechanism for maintaining a constant tension on the web 12 around its entire guide path. It will be appreciated that as the print head assembly 1 1 is extended by actuation of the piston 50, the spool 14 will need to permit a small extra amount of web 12 to be fed out, and that when the piston 50 is deactuated, and the print head assembly 11 moves in a direction opposite to the direction indicated by arrow B, the spool 20 needs to be able to take up any slack in the web 12.

Further features of the printing apparatus are as follows.

In this embodiment described, the spools 14 and 20 are carried by a cartridge 55 which can be removed from the body of the printing apparatus 10 to facilitate replenishing the printing apparatus 10 with web 12.

The web guide path includes a peeler bar over which the web 12 passes immediately after passing over the print head assembly 1 1, the bar being operable to ensure proper separation of foil to be deposited on the substrate, and remaining web 12.

The belt 41 is maintained under strong tension by means of a tensioning roller 59 and the belts 23,24, can also be kept under constant tension by tensioning rollers 60.

When the cartridge 55 carrying the spools 14 and 20 is removed, a micro switch 61 is tripped so that there is no risk of the mechanism of the printing apparatus 10 being actuated without the cartridge 55 being in position. In the event that the web feed spool 14 becomes empty, an electronic sensor carried by a clamp 62 around which the web 12 passes, will signal the lack of web 12 to an operator, and/or disable printing apparatus 10.

The amount of movement of the print head assembly 11 in a direction opposite to that of arrow A i.e. the return movement, is restricted by means of a microswitch carried on a clamp means 63 which senses the print head assembly 11 when returned to its start position immediately to stop motor 21.

Various modifications may be made without departing from the scope of the invention.

The printing apparatus 10 may be used in other orientations to that described, as appropriate to the position and orientation of the substrate.

For example, although the printing apparatus 10 described has been of the type which utilises a web 12 carrying foil which is deposited by means of thermal print elements onto a substrate, the invention may be applied to any other printing apparatus having a plurality of selectively operable printing elements to effect printing, for example, directly onto a heat sensitive or other substrate.

Although in the arrangement described, the print head assembly 11 is carried by three drive belts 23,24,41, in another arrangement, less than three drive belts, or more than three drive belts, may be provided.

In place of drive belts, any other suitable endless loop members, such as chains, could be used to provide a transmission and mounting for the print head assembly 11, or indeed any other suitable flexible drive member or members which is/are able to provide drive to, and a sole means of mounting the print head assembly 11, could be used.

Although it is preferred for single stepper motor 21 to be used as a motive means for the printing apparatus 10, with suitable logic control e.g. utilising a computer, if desired more than one stepper motor 21 or other motive means may be provided. For example a separate motor may be provided to drive the payout and/or take up spools 14,20 for the web 12. Any alternative means to the piston and cylinder arrangement 50 for effecting movement of the print head assembly 11 towards the substrate, may be provided. If desired, the return movement of the print head assembly 11 in a direction oppostiveiy to that of arrow B may be spring assisted or otherwise positively caused.

Claims

1. A printing apparatus comprising a plurality of elements which can selectively be operated to effect printing as the elements are moved relative to a substrate, a body, a print head mounting each of the elements of the selectively operable elements, a motive means and a transmission whereby the print head can be moved in a first direction relative to a body of the apparatus and to the substrate between beginning of, and end of, printing positions, during which movement printing is effected, and relative to the body of the apparatus generally towards and away from a substrate transverse to the first direction, the transmission comprising at least one flexible drive member carrying the print head and driven by the motive means to cause movement of the print head at least in the first direction.

2. An apparatus according to Claim 1 wherein the flexible drive member comprises an endless driven loop member.

3. An apparatus according to Claim 2 wherein the loop member comprises a belt driven from a pulley.

4. An apparatus according to Claim 3 wherein the pulley is driven from a shaft.

5. An apparatus according to any one of Claims 1 to 4 where a pair of such flexible drive members extend generally parallel to one another with the print head carried between them.

6. An apparatus according to any one of the preceding Claims wherein the print head is guided during its motion in the first direction by a guide means which provides some restriction to the amount of float which would otherwise be permitted by the transmission.

7. An apparatus according to Claim 6 wherein the print head is connected to a roller which runs on an elongate guide member during movement of the print head in the first direction.

8. An apparatus according to Claim 7 wherein the guide member is of such configuration in cross section that in response to floating of the print head, the roller is permitted to roll about a central axis of the guide member.

9. An apparatus acording to any one of the preceding claims wherein the transmission includes a further endless loop member which is clamped to the print head to add rigidity to the mounting of the print head on the transmission.

10. An apparatus according to Claim 9 wherein the further endless loop member is be driven from a common drive shaft along with the first, and where provided, second, flexible drive members.

11. An apparatus according to any one of Claims 1 to 10 wherein the print head is movable at least towards the substrate by virtue of an actuator being actuated.

12. An apparatus according to Claim 11 wherein the actuator comprises a linear actuator.

13. An apparatus according to Claim 12 when appendant to Claim 7 wherein the linear actuator moves against the guide member to cause movement of the print head towards the substrate, such movement being permitted by the inate flexibility of the transmission.

14. An apparatus according to any one of the preceding claims wherein the elements of the print head when operated produce heat, and the substrate is heat sensitive whereby printing can be effected thereon.

15. An apparatus according to any one of Claims 1 to 13 wherein the printing apparatus is of the so called hot foil type in which foil is fed through the apparatus and contacted by the thermal printing elements of the print head which when the elements are energised, transfer the foil onto the substrate such that printing may be effected on the substrate.

16. An apparatus according to Claim 15 wherein the foil is fed through the apparatus as a continuous web, from a feed spool, via a web guide path, to a take up spool.

17. An apparatus according to Claim 16 wherein at least the take up spool is driven from the motive means to advance the web of foil through the apparatus, when the print head is undergoing some movement during which printing is not effected.

18. An apparatus according to Claim 17 wherein the web of foil is advanced during return movement of the print head from the end of printing to the beginning of printing positions.

19. A printing apparatus substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

20. Any novel feature or novel combination of features hereinbefore described and/or shown in the accompanying drawings.