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Patent Searching and Data


Title:
ROLLER SUPPORT
Document Type and Number:
WIPO Patent Application WO/2020/141322
Kind Code:
A1
Abstract:
A roller support system (14) for a printing machine, comprising: a plurality of spindles (16, 18), each spindle defining a spindle axis (17, 19) and being configured to support a roller (6, 8) for rotation about each spindle axis, and a support member (20) supporting the plurality of spindles, wherein the support member is configured to rotate about a support axis (36) so as to selectively position a first one of the plurality of spindles in a printing position and a second one of the plurality of spindles in a non-printing position.

Inventors:
CLEMENTS BEN (GB)
CLEMENTS TREVOR (GB)
THOMPSON CHRIS (GB)
Application Number:
PCT/GB2020/050004
Publication Date:
July 09, 2020
Filing Date:
January 03, 2020
Export Citation:
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Assignee:
EMERSON & RENWICK LTD (GB)
International Classes:
B41F5/24; B41F9/18; B41F13/20; B41F13/38; B41F13/40
Foreign References:
GB1382352A1975-01-29
US20160101616A12016-04-14
DE202014008836U12014-12-08
EP3137300B12017-12-06
Attorney, Agent or Firm:
MARKS & CLERK LLP (GB)
Download PDF:
Claims:
CLAIMS:

1. A roller support system for a printing machine, comprising:

a plurality of spindles, each spindle defining a spindle axis and being configured to support a roller for rotation about each spindle axis, and

a support member supporting the plurality of spindles,

wherein the support member is configured to rotate about a support axis so as to selectively position a first one of the plurality of spindles in a printing position and a second one of the plurality of spindles in a non-printing position.

2. A roller support system according to claim 1 , wherein the spindles are mounted to the support member such that angular movement of the spindles relative to one another about the support axis is substantially prevented.

3. A roller support system according to any preceding claim, wherein the spindles are mounted to the support member such that movement of the spindles in the radial direction relative to the support axis is substantially prevented.

4. A roller support system according to any preceding claim, wherein the first and second spindles are positioned diametrically opposite one another relative to the support axis.

5. A roller support system according to any preceding claim, wherein the support member is configured such that every 180 ° of rotation of the support member about the support axis selects which one of the first and second spindles is in the printing position and which one of the first and second spindles is in the non-printing position.

6. A roller support system according to any preceding claim, wherein the support member comprises a plate to which the spindles are mounted.

7. A roller support system according to claim 6, wherein the plate is generally cylindrical.

8. A roller support system according to claim 6 or 7, wherein each spindle has an associated roller drive unit, the drive units being supported by the plate.

9. A roller support system according to any preceding claim, wherein the printing machine defines a printing zone, wherein the spindles extend into the printing zone so as to support the rollers for rotation within the printing zone, and wherein the support member is positioned outside of the printing zone.

10. A roller support system according to any preceding claim, further comprising a movable support frame, wherein the support member is supported for rotation about the support axis by the support frame, the support frame being mounted to the printing machine so that the orientation of the support frame is rotationally frozen relative to the printing machine.

11. A roller support system according to claim 10, further comprising a support member drive unit configured to cause rotation of the support member relative to the support frame.

12. A roller support system according to claim 11 , wherein the support member drive unit comprises a pinion wheel and the support member comprises an annular gear in engagement with the pinion wheel.

13. A roller support system according to any of claims 10 to 12, wherein the support frame is displaceable relative to the printing machine within a plane normal to the support axis.

14. A roller support system according to any of claims 10 to 13, wherein the support frame is supported for linear movement relative to the printing machine.

15. A roller support system according to any of claims 10 to 14, further comprising an actuator configured to cause movement of the support frame relative to the printing machine.

16. A roller support system according to any preceding claim, wherein the support member supports the plurality of spindles for radial movement relative to the support axis.

17. A printing machine comprising the roller support system of any preceding claim.

18. A method of supporting a plurality of rollers in a printing machine, comprising: providing a first spindle defining a first spindle axis and a second spindle defining a second spindle axis,

providing a support member supporting the first and second spindles, supporting a first roller for rotation about the first spindle axis using the first spindle and a second roller for rotation about the second spindle axis using the second spindle, and

rotating the support member about the support axis so as to selectively position the first spindle in a printing position and the second spindle in a non-printing position.

19. A method according to claim 18, wherein the method further comprises displacing the support member relative to the printing machine. 20. A method according to claim 18 or 19, wherein the method further comprises displacing the first and/or second spindles in a radial direction relative to the support axis.

Description:
Roller Support

The present invention relates to a roller support system for a printing machine, a printing machine comprising a roller support system, and to a method of supporting a plurality of rollers in a printing machine.

In a printing press, an image is typically printed onto a substrate using an image roller. Typically, an outer surface of the image roller is wrapped with a plate or sleeve having a physical impression of the image that is desired to be printed onto the substrate. It is often necessary to change the image that is being printed, for example once a particular printing job has been completed. In order to do so, the printing press must be stopped and the image roller removed so that the plate or sleeve can be replaced with a new plate or sleeve carrying the next image. In a typical printing press, one image roller is required per printing colour of the final image. A full colour printing press may comprise seven or more different colours of ink. As such, when the printed image is to be changed it may be necessary to replace seven or more image rollers, and therefore the time taken to change all of the image rollers can be relatively lengthy. When the press is stopped, it is no longer generating revenue for the operator, and therefore frequent or prolonged stoppages may add to the overall running cost of the printing press.

It is an object of the present invention to obviate or mitigate one or more problems of the prior art, whether identified herein or elsewhere. It is a further object of the invention to provide an improved and/or alternative system and method for supporting and/or changing a roller of a printing press, and in particular an image-carrying roller of a printing press.

According to a first aspect of the invention there is provided a roller support system for a printing machine, comprising: a plurality of spindles, each spindle defining a spindle axis and being configured to support a roller for rotation about each spindle axis, and a support member supporting the plurality of spindles, wherein the support member is configured to rotate about a support axis so as to selectively position a first one of the plurality of spindles in a printing position and a second one of the plurality of spindles in a non-printing position. Because the roller support system comprises a plurality of spindles, at least one of the spindles can be used for printing whilst the other spindle is not being used for printing. The non-printing spindle can be loaded with a roller having the next image that is desired to be printed. When the printing job has finished, the support member is rotated so as to move the printing spindle (i.e. the first spindle) out of the printing position to a non-printing position and to move the non-printing spindle (i.e. the second spindle) to the printing position. Roller changeover between consecutive printing jobs is therefore straightforward and quick, since the roller for the next printing job can be pre-loaded onto the non-printing spindle before the initial printing job has stopped. The roller support system therefore saves time and money between printing operations. Furthermore, because roller changeover occurs primarily due to rotation, roller changeover is mechanically simple to control and there are fewer moving parts compared to alternative systems. Use of rotation also provides the advantage that roller changeover occurs with relatively few frictional losses compared, for example, to sliding systems. In addition, because the support member is rotatable, only one actuator needs to be used to cause rotation of all of the plurality of spindles and therefore there are fewer actuators which might fail and cause the system to be inoperable.

Typically, in the non-printing position, any roller supported by the non-printing spindle will not contact the substrate being printed and may be spaced apart from the impression roller and/or any other rollers of the printing machine. Because the roller of the non-printing spindle does not engage the substrate or the impression roller, replacement of the non-printing roller is easier. The time taken to change the image being printed by the printing machine is therefore reduced, thus saving costs. Furthermore, because the time taken to change the image is reduced, the amount of substrate that is potentially wasted is also reduced thus saving further costs. In some instances it may be possible to replace the non-printing roller whilst the printing machine is still running, thus reducing machine downtime even further (although in such instances it is recommended that appropriate safety equipment is used by the operator). Furthermore, the operator can plan ahead for a roller changeover that is expected to occur at a future time, and can place the next image roller in position on the non-printing spindle so that it is ready to go when the current printing job has finished. The changeover process can therefore be automated such that roller changeover can occur even without the presence of the operator. As such, the time between printing jobs can be reduced such that the printing machine can run almost continuously. This effect is enhanced when more than two spindles are used, as three or more printing jobs can be run in succession without the need for the operator to physically interact with the printing machine.

By“printing position” it is meant any position in which a roller supported by the spindle may be used to transfer an image onto a substrate. Typically, this will be when the spindle causes the roller to engage a substrate between an outer surface of the roller and the impression roller. By“non-printing position” it is meant any position of the spindle in which the roller is not used to transfer an image onto the substrate. The term “selectively position” is intended to encompass any movement or change to the configuration of the support member in which the spindle that is in the printing position can be moved out of the printing position and replaced with another, different, spindle. However, any such movement must comprise at least some rotation of the support member about the support axis. In particular, in addition to rotation, the support member and/or the spindles may also, but not necessarily, undergo translational movement when changing the spindle that is in the printing position. The term “connecting” is intended to encompass both direct connection and indirect connection. For example, the spindles may be mounted directly to the support member, or may be mounted to the support member via one or more intermediate components, including for example, bearings, tracks, rails, fixtures etc. The term“support axis” is intended to encompass an axis generally parallel to the spindle axes. The support axis may be positioned at the centrepoint of the plurality of spindles.

The term“the support member is configured to rotate about a support axis so as to selectively position a first one of the plurality of spindles in a printing position and a second one of the plurality of spindles in a non-printing position” is intended to encompass that the support member is rotatable about the support axis between: (i) a first configuration in which a first spindle is in a printing position and a second spindle is in a non-printing position, and (ii) a second configuration in which the first spindle is in the non-printing position and the second spindle is in the printing position. The support member may further be configured so that the spindles to rotate about the support axis simultaneously.

The spindles exhibit a first degree of rotation about their spindle axes and a second degree of rotation about the support axis. In addition to being supported for rotation about the support axis, the support member may also be supported for translational movement so the support axis is displaceable. For example, the support member could be supported by a mechanism which causes the spindles to rotate about the support axis at the same time that the support axis undergoes translational movement. Such a mechanism may comprise one or more cams, rails, rotational or linear actuators or the like.

The spindles may be mounted to the support member such that angular movement of the spindles relative to one another about the support axis is substantially prevented. Because movement of the spindles relative to one another is prevented, the spindles rotate in unison about the support axis and therefore the angular positions of all of the spindles can be predicted with greater accuracy by a control unit. However, in such embodiments the spindles may still be free to move radially inwards and outwards from the support axis.

The spindles may be mounted to the support member such that movement of the spindles in the radial direction relative to the support axis is substantially prevented. Movement of the spindles in the radial direction relative to the support axis may be prevented. The spindles are therefore positioned at a constant distance from the support axis regardless of their angular position. As such, the positions of the spindles can be accurately predicted by a control unit, and hence control over the changeover operation is simplified. Where both the angular position of the spindles and the radial positions of the spindles are constrained, no relative movement between the spindles is permitted and therefore it is easier to predict the position of the spindles when the support member is rotated. This ensures that the spindles reach the correct printing position.

The first and second spindles may be positioned diametrically opposite one another relative to the support axis. Because the two spindles are diametrically opposite one another, the region of clear space between the spindles is maximised. This provides a greater region within which the operator can work when replacing the roller of the spindle in the non-printing position, and thus improves the ease of use and the safety of the roller support system and the printing machine.

The support member may be configured such that every 180 ° of rotation of the support member about the support axis selects which one of the first and second spindles is in the printing position and which one of the first and second spindles is in the non- printing position. The support member may be configured to rotate through 180 ° to select which one of the first and second spindles is in the printing position and which one of the first and second spindles is in the non-printing position. The roller support system may comprise any number of spindles, spaced equidistantly apart from one another relative to the support axis. For example, the roller support system may comprise two spindles, spaced around 180 ° apart from one another relative to the support axis, or three spindles spaced around 120 ° apart from one another relative to the support axis.

The support member may comprise a plate to which the spindles are mounted. The term“plate” is intended to encompass a generally planar sheet of material having a relatively narrow thickness in relation to its width and/or length. The angular position of the spindles must be accurately controlled to so that the image printed by the roller is in the correct position on the substrate. The plate forms a stable and strong base for the spindles, and helps to prevent the spindles from moving out of position such that the position of the spindles and rollers can be more accurately controlled. Furthermore, the use of a plate makes it easy to modify the support member so as to change the number of spindles. For example, a third spindle could be fitted to the support member to provide extra capacity but without the need to replace the support member itself. Because the spindles are mounted to the same base, movement of the spindles relative to one another is prevented and therefore positioning of the spindles is more accurate.

The plate may be generally cylindrical. Because the plate is generally cylindrical, any loads experienced by the plate are evenly distributed throughout the material of the plate. That is to say, a cylinder is the optimum plate shape for distributing loads. By evenly distributing any load, the support member is stiffer and less likely to flex in a manner which might move the spindle out of position. As such, when the support member is cylindrical, the shape of the support member helps to improve control and accuracy over the spindle and roller positions, improving print registration and quality.

Each spindle may have an associated roller drive unit, the drive units being supported by the plate. The drive units may comprise a drive motor and an encoder, and may be mounted to the plate via a bracket. Because the drive units are supported by the plate and the plate provides a stiff and stable base, the drive units are better able to control the rotational positions of the rollers and spindles. The printing machine may define a printing zone, wherein the spindles extend into the printing zone so as to support the rollers for rotation within the printing zone, and wherein the support member is positioned outside of the printing zone. That is to say, the support member does not extend into the printing zone. As such, the only components of the roller support system that extend into the printing zone are the spindles and the rollers. This provides a greater area of clear space within which the operator can work when it is necessary to change the rollers of the plurality of spindles. The increased region of clear space makes it easier and safer for the operator to replace the rollers.

The roller support system may further comprise a movable support frame, wherein the support member is supported for rotation about the support axis by the support frame, the support frame being mounted to the printing machine so that the orientation of the support frame is rotationally frozen relative to the printing machine. In such embodiments, because the support frame is movable, the support frame is able to move the support member, the spindles and the rollers towards or away from the other components of the printing machine (which many include, for example, an impression roller, an anilox roller, a substrate etc.). As such, the spindles and rollers can be moved to a position in which the spindles and rollers will not accidentally contact the other components of the printing machine when the support member is rotated about the support axis. By“rotationally frozen” it is meant that movement of the support frame is constrained such that it is not able to rotate relative to the printing machine. As such, the support frame provides a first degree of articulation between the support frame and the support member (so as to control the angular position of the support member), and a second degree of articulation between the printing machine and the support frame (so as to control the translational position of the support member).

The roller support system may further comprise a support member drive unit configured to cause rotation of the support member relative to the support frame. The support member drive unit is therefore able to control the angular position of the spindles about the support axis to determine which spindle is in the printing position. The support member drive unit may comprise a drive motor and/or encoder.

The support member drive unit may comprise a pinion wheel and the support member comprises an annular gear in engagement with the pinion wheel. It will be appreciated that, in general, toothed connections such as gears avoid slipping which may make determining the precise angular position of the support member more difficult. As such, the annular gear and pinion eliminate the possibility of slip and therefore provide improved control over the angular position of the support member.

The support frame may be displaceable relative to the printing machine within a plane normal to the support axis. In such embodiments, because the support frame is displaceable normal to the support axis, the rollers and spindles can be lifted away from the other components of the printing machine so that they do not accidentally engage or otherwise interfere with the other components when the support member is rotated. As such, there is no need for any ink fountains, anilox rollers or impression rollers etc. to also be displaceable. Furthermore, by moving the support frame in a plane normal to the support axis, the spindles and rollers remain generally parallel to the other components of the printing machine, and in particular with any ink fountains, anilox and/or impression rollers. By keeping the spindles and rollers generally parallel to the other components it is easier to ensure that the spindles and rollers return to the correct position after every changeover operation.

The support frame may be supported for linear movement relative to the printing machine. For example, the support frame may be mounted to a side wall of the printing machine by a linear support means. The linear support means may comprise rails, sliders, or slots or the like. The linear movement may be substantially vertical (i.e. opposite to the action of gravity).

The roller support system may further comprise an actuator configured to cause movement of the support frame relative to the printing machine. The actuator may permit the support frame, support member, spindles and rollers to be moved away from the other components of the printing machine automatically so that the support member can rotate.

The support member may support the plurality of spindles for radial movement relative to the support axis. That is to say, the spindles may be movable both rotationally around the support axis and linearly towards or away from the support axis. Because the spindles can be moved radially relative to the support axis, the spindles are able to retract in the radial direction so that they avoid accidentally engaging the other components of the printing machine when the support member is rotated. The spindles may be supported for movement in the radial direction by slots or rails or the like.

According to a second aspect of the invention there is provided a printing machine comprising the roller support system of the first aspect of the invention. The printing machine may be, for example, a flexographic printing machine or a gravure printing machine.

According to a second aspect of the invention, there is provided a method of supporting a plurality of rollers in a printing machine, comprising: providing a first spindle defining a first spindle axis and a second spindle defining a second spindle axis, providing a support member supporting the first and second spindles, supporting a first roller for rotation about the first spindle axis using the first spindle and a second roller for rotation about the second spindle axis using the second spindle, and rotating the support member about the support axis so as to selectively position the first spindle in a printing position and the second spindle in a non-printing position.

The printing machine may comprise a roller support system according to the first aspect of the invention, such that the first and second spindles and the support member may be part of the roller support system according to the first aspect of the invention. It will be appreciated that additional components of movement other than rotation may be employed to change which of the first and second spindles is in the printing position and which is in the non-printing position. However, at least one of the components of movement required to select which of the first and second spindles is in the printing position and which is in the non-printing position is rotational movement about the support axis. The step of “rotating” is intended to encompass rotating the support member about the support axis between: (i) a first configuration in which the first spindle is in a printing position and the second spindle is in a non-printing position, and (ii) a second configuration in which the first spindle is in the non-printing position and the second spindle is in the printing position.

The method may further comprise displacing the support member relative to the printing machine. The displacement may comprise linear movement, for example vertical movement. The method may further comprise displacing the first and/or second spindles in a radial direction relative to the support axis. The method may further comprise displacing one or more other rollers or components of the printing machine, for example an anilox roller, impression roller or an ink fountain.

It will be appreciated that any of the above-described advantages or optional features of the first aspect of the invention may be applied equally to the second and/or third aspects of the invention.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

Figure 1 is a perspective front view of a portion of a printing machine comprising a roller support system in accordance with a first embodiment of the present invention;

Figure 2 is a perspective rear view of the printing machine of Figure 1 ;

Figures 3A to 3D are sequential first to fourth steps of a method of changing a roller of a printing machine in accordance with the first embodiment of the invention; and

Figures 4A to 4D are sequential first to fourth steps of a method of changing a roller of a printing machine in accordance with a second embodiment of the invention.

Figure 1 shows a portion of a flexographic printing machine 2 comprising an ink fountain 4, an anilox roller 5, a first image roller 6, a second image roller 8, an impression roller 10, and a printable substrate 12. The printing machine 2 further comprises a side wall 38 which separates a printing zone 11 from a non-printing zone 13. The printing zone 11 is the portion of the printing machine 2 in which the printing process is conducted. The ink fountain 4, anilox roller 5, image rollers 6, 8, impression roller 10 and the substrate 12 are positioned in the printing zone 11. The first and second image rollers 6, 8 have upon their surfaces respective image plates or sleeves containing a physical impression of the image desired to be printed. During use, rotation of the anilox roller 5 transfers ink from the ink fountain 4 to the anilox roller 5. The surface of the anilox roller 5 comprises a large number of equally-sized microscopic cells which receive a metered dose of ink from the ink fountain 4. As the anilox roller 5 rotates, it transfers the ink to the image plate or sleeve of the first image roller 6. The first image roller 6 is rotated and presses the substrate 12 against the impression roller 10 so as to transfer the image to the substrate 12. For full colour printing, the above process is repeated for each different colour of ink required, which may comprise seven or more colours. The substrate 12 is fed continuously through the printing machine 2 as a web, and is typically collected on a spool at the end of the printing machine 2 or may be fed to a further processing apparatus such as a die cutter.

As shown in Figures 1 and 2, the printing machine 2 comprises a roller support system 14 which supports the first and second image rollers 6, 8. The roller support system 14 comprises a first spindle 16, a second spindle 18, a support member 20, a first drive unit 28 and a second drive unit 30. The roller support system 14 is generally positioned in the non-printing zone 13, however the first and second spindles 16, 18 extend from the non-printing zone 13 to the printing zone 11 through a circular aperture 15 formed in the side wall 38. The first spindle 16 supports the first image roller 6 for rotation about a first spindle axis 17 and the second spindle 18 supports the second image roller 8 for rotation about a second spindle axis 19. The spindles 16, 18 comprise bearings which permit an outer surface of the spindle 16, 18 to rotate whilst an inner part of the spindle remains stationary. The support member 20 is a generally cylindrical plate, and the first and second spindles 16, 18 are mounted to the support member 20 on diametrically opposite sides of a support axis 36 and at an equal distance from the support axis 36. In alternative embodiments the support member 20 may have any construction that is suitable for supporting the first and second spindles 16, 18, such as for example a frame-like construction or a plate having a non-cylindrical shape.

The first and second drive units 28, 30 are mounted to the support member 20 by brackets 29 on the opposite side of the support member 20 to the first and second image rollers 6, 8. The support member 20 comprises apertures (not shown) through which the first and second spindles 16, 18 are passed so that the first drive unit 28 is connected to the first spindle 16 and the second drive unit 30 is connected to the second spindle 18. The first drive unit 28 is therefore operable to drive the first spindle 16 and the second drive unit 30 is operable to drive the second spindle 18. Preferably the first and second drive units 28, 30 are directly connected to the first and second spindles 16, 18 without any intermediate transmission components such as drive belts, gears, clutches or the like. By directly connecting the first and second drive units 28, 30 to the first and second spindles 16, 18 the rotational positions and speeds of the first and second spindles can be more accurately controlled so as to improve the alignment of the final printed image. The first and second drive units 28, 30 may comprise a drive motor of any suitable motor type, such as for example AC or DC electric motors. The drive units 28, 30 preferably also comprise encoders so that that precise rotational position of the image rollers 6, 8 and spindles 16, 18 about the spindles axes 17, 19 are known. The drive units 28, 30 are electrically connected to and controlled by a control unit (not shown).

The roller support system 14 further comprises a gear wheel 22, four bearing units 24, a support frame 26, a third drive unit 40 and a linear actuator 44. The gear wheel 22 is attached to the support member 20 via fasteners so as to rotationally freeze the support member 20 relative to the gear wheel 22. The gear wheel 22 is generally annular in shape, and defines a smooth radially inner surface 32 and an outer surface comprising a plurality of teeth 34. Each bearing unit 24 comprises at least one bearing wheel 25 which engages the inner surface 32 of the gear wheel 22 so as to support the gear wheel 22 and the support member 20 for rotation about the support axis 36. In alternative embodiments, any suitable means may be used in addition to or in place of the bearing units 24 to support the support member 20 for rotation. For example, the support member 20 may comprise an axle extending parallel to the support axis 36 that is supported for rotation by bearings. The bearing units 24 and the third drive unit 40 are attached to the support frame 26. The third drive unit 40 is connected to a pinion wheel 42 which meshes with the teeth 34 of the gear wheel 22 so that the third drive unit 40 drives rotation of the support plate 20 about the support axis 36. The third drive unit 40 preferably comprises a servo or stepper motor; however the third drive unit 40 may comprise any suitable motor type and/or additional position encoders. The third drive 40 unit is also electrically connected to and controlled by the control unit.

Although not shown in the figures, the support frame 26 is attached by rails to the side wall 38 of the printing machine 2 such that the support frame 26 is movable in the vertical direction. The linear actuator 44 is fixedly attached to the side wall 38 and comprises an extension rod 46 connected to the support frame 26 so that the linear actuator 44 can raise or lower the position of the support frame 26. In the present embodiment, the linear actuator 44 is pneumatically powered, however in alternative embodiments the linear actuator 44 may be powered by any suitable means, for example a lead screw driven by an electric motor or the like.

With additional reference to Figures 3A to 3D, a method of operating the roller support system 14 will now be described. In normal operation, as shown in Figure 3A, the first image roller 6 engages the anilox roller 5 and the substrate 12 against the impression roller 10. In such a configuration, the first image roller 6 is said to be in a printing position as it is supplied with ink and is able to transfer an image onto the substrate 12. Conversely, the second image roller 8 is said to be in a non-printing position as it is not in contact with the substrate 12 or a source of ink, and therefore does not act to print an image onto the substrate.

When it is desired to change the image being printed, the linear actuator 44 is extended to move the support frame 26 vertically upwards. Movement of the support plate 26 carries the support member 20, the first and second spindles 16, 18 and hence the first and second image rollers 6, 8 vertically upwards as shown by arrow 46 in Figure 3B. Next, the third drive unit 40 is activated so as to cause the support member 20 to rotate about the support axis 36. The support member 20 carries the first and second spindles 16, 18 and hence the first and second image rollers 6, 8 so that the first and second spindles 16, 18 are rotated through 180 ° relative to the support axis 36 as shown by the arrow 48 in Figure 3C. It is important that the support frame 26 is displaced far enough upwards that the first and second image rollers 6, 8 are free to rotate about the support axis 36 without accidentally engaging the anilox roller 5 or the impression roller 10 (or indeed any other rollers that may be present in the printing machine).

Once the support member 20 has been rotated, the second image roller 18 is in the position previously occupied by the first image roller 6 and the first image roller 6 is in the position previously occupied by the second image roller 8. The linear actuator 44 is then retracted so as to cause the support frame 26 to move vertically downwards so that the second image roller 8 is brought into contact with both the anilox roller 5 and the impression roller 10, as shown by the arrow 50 in Figure 3D. The second image roller 8 is now in the printing position and the printing operation can resume with a new image. The first image roller 6 is in the non-printing position, and can be removed so that may be replaced with another image roller carrying the next image that is desired to be printed by the printing machine 2.

When it is desired to change the image being printed for a subsequent time, the steps described above and illustrated in Figures 3A to 3D are repeated. The support member 20 may be driven so that it only rotates in one direction during each subsequent changeover sequence. However, in some embodiments the support member 20 and the support frame 26 may comprise mechanical stops configured to limit rotational movement of the support member 20 so that the printing position of the first and second spindles 16, 18 can be controlled with greater accuracy. In such embodiments, the direction of rotation of the support member 20 may be reversed for each subsequent changeover sequence (i.e. so that the support member 20 is driven in the opposite direction to that shown by arrow 48 in Figure 3C).

In the configuration of the printing machine 2 shown in Figure 1 the first image roller 6 is being used for printing, such that the first image roller 6 and/or first spindle 16 are said to be in a printing position. In the printing position, the first spindle 16 is supported at its longitudinally opposite ends by cups 21 (only one of which is visible in Figure 1). The cups 21 are formed as flat plates having a shallow, generally u-shaped concavity on an upper surface which receives the first or second spindles 16, 18. The radius of curvature of the cups 21 is generally larger than the radius of the spindles 16, 18, such that when the spindles 16, 18 are received within the cups 21 the cups 21 act to self centre the spindles 16, 18 to the correct position without inhibiting insertion or removal of the spindles 16, 18 from the cups. Put another way, the cups 21 aid alignment of the spindles 16, 18 to the correct printing position. Additionally or alternatively, clamps may be used with or without the cups 21 to hold the spindles 16, 18 in the correct printing position.

By moving the support member 20 in a vertically upwards direction, the first image roller 6 is able to disengage both the anilox roller 5 and the impression roller 10 at the same time so that the first and second spindles 16, 18 can rotate about the support axis 36. However, in alternative embodiments the anilox roller 5 and/or the impression roller 10 may be moved in a plane normal to the support axis 36 so as to bring the anilox roller 5 and/or the impression roller 10 out of contact from the first image roller 6 along any suitable path (for example linear, arcuate etc.). In such embodiments, the support member 20 may also be movable in the plane normal to the support axis 36 (for example, in the horizontal direction) so as to move the first image roller out of contact from the anilox roller 5 and/or the impression roller 10. When the anilox roller 5 and/or the impression roller 10 are displaceable, it may be possible to rotate the support member 20 in situ, without adjusting the elevation of the support member 20 or the radial distance of the spindles 16, 18 relative to the support axis. Because the first and second spindles 16, 18 are on diametrically opposite sides of the support axis 36, the first and second spindles 16, 18 are spaced at the maximum distance apart from one another. This is beneficial when the image roller 6, 8 mounted to the spindles 16, 18 that is in the non-printing position needs to be replaced, as the spacing between the first and second spindles 16, 18 provides clear space around the non-printing spindle for an operator to work within when replacing the non-printing roller. Furthermore, because the support member 20 is a plate that is supported by an annular gear 22, there is no axle extending along the support axis 36 and into the printing zone 11 which may get in the way of the operator when replacing the non printing roller. That is to say, the printing zone 11 is substantially free of obstacles which may complicate replacement of the image rollers 6, 8. Consequently, it is easier for the operator to replace the image roller 6, 8, and therefore the overall downtime for roller changeover will be reduced. Furthermore, the clear space reduces the chance of possible contact between the operator and/or the image roller and other components of the printing machine 2 and therefore the safety of the roller support system 14 is improved. Provided that appropriate safety equipment is used, in some situations it may be possible to replace the image roller on the non-printing spindle whilst the printing machine 2 is in operation (i.e. whilst it is running).

Although the roller support system 14 has been described with two spindles 16, 18 spaced diametrically opposite each other relative to the support axis 36, it will be appreciated that in alternative embodiments the spindles 16, 18 may be placed at any suitable angular position in relation to the support axis (i.e. such that they are not 180 ° apart relative to the support axis 36). Furthermore, the roller support system may comprise more than two spindles, for example three or more spindles. The spindles may be equally spaced about the support axis 36, or may be spaced at irregular angular positions. It will be appreciated that when more spindles are present, a greater number of image changeover operations can be completed without the input of human operators. As such, the printing machine 2 can be left for longer periods without requiring human input. Furthermore, where there are three or more spindles, the roller support system 14 may define different types of non-printing positions. For example, a first non-printing position may be used for physically changing the image roller of a first spindle and a second non-printing position may be used to perform inspection of an already loaded image roller before it is used for printing. Such inspection could be carried out automatically, for example using cameras. This may occur whilst a third spindle is in the printing position and the printing machine 2 is running. Because the support member 20 is a cylindrical plate, the support member 20 is better able to distribute loads and is therefore relatively stiff. The support member 20 is provided with a generally cylindrical central portion 23 of increased thickness so as to further increase the stiffness of the support member 20. It will be appreciated that the thicker the support member 20 the stiffer the support member 20 will be. The brackets 29 holding the drive units 28, 30 for each spindle 16, 18 are mounted to the central portion 23 because it is thicker and provides increased stiffness. Because the support member 20 is stiff, the spindles 16, 18 are less likely to flex or otherwise move out of position in response to external forces. This means that the rotational and axial positions of the image rollers 6, 8 relative to the spindle axes 17, 19 can be better controlled. This improves the registration of the printed image on the substrate 12 (i.e. ensures that the image is printed in the correct position).

Because the spindles 16, 18 are mounted to the support member 20, both spindles 16, 18 share the same base. By mounting the spindles 16, 18 to the same base, there are fewer mechanical interfaces between the spindles 16, 18 which could introduce tolerances that may cause misalignment of the spindles 16, 18 relative to one another. As such, positioning of the spindles 16, 18 is more accurate. Furthermore, because the support member 20 is a plate, the support member 20 acts to prevent angular and radial movement of the spindles 16, 18 relative to one another about the support axis 36.

As well as providing the force to move the support frame 26 vertically upwards and downwards, the linear actuator 44 may also control the clamping force exerted by the first and/or second image rollers 6, 8 on the substrate 12 and impression roller 10. The clamping force exerted by the linear actuator 44 must be sufficient to cause the ink from the image roller 6, 8 currently being used to the substrate 12. If the clamping force is too high or too low, image quality will be affected. Preferably, the printing press 2 comprises a control unit that is able to adjust the clamping force exerted by the linear actuator 44 during operation of the printing machine 2. In alternative embodiments, a plurality of linear actuators 44 may be provided so as to distribute the load between the linear actuators. For example, a first linear actuator may be provided that is configured to provide an upwards force that is approximately equal to (or just below) the weight of the roller support system 14 due to gravity and so that the roller support system 14 is almost“weightless”. A second linear actuator may be also provided that is configured to urge the roller support system 14 downwards, so as to provide the correct amount of clamping force between the roller 6, 8 in the printing position and the impression roller 10. This type of arrangement makes it easier to make adjustments to the clamping force, as the clamping force and the weight of the roller support system 14 are handled by different actuators. In yet further alternative embodiments, the movement of the linear actuator 44 may be limited so that it does not provide a clamping force between the first and/or second image rollers 6, 8 on the substrate 12 and impression roller 10, and the clamping force may be controlled by other means of any suitable type, such as for example by clamping the spindles 16, 18 to the cups 21.

Use of the gear wheel 22 and pinion 42 ensures that the rotation of the support member 20 about the support axis 36 can be controlled with good accuracy. Although the present embodiment uses a gear wheel 22 and pinion 42 to cause the support member 20 to rotate, it will be appreciated that in other embodiments any suitable means may be used for causing rotation of the support member 20. For example, the support member 20 may be directly driven by an electrical motor, such as a servo motor. Alternatively, any suitable means may be used to cause the support member 20 to rotate about the support axis 36. For example a chain and sprocket, belt and pulley, contact roller, or worm gear arrangement or the like may be used.

As described above, the spindles 16, 18 are positioned at the same radial distance relative to the support axis 36 (i.e. such that they lie on the same pitch circle). However, in alternative embodiments the support member 20 may be configured to permit the radial spacing of the spindles 16, 18 relative to the support axis 36 to be adjusted either separately or simultaneously. In such embodiments, the support member 20 may define a pair of radially extending channels and the spindles 16, 18 may be supported for slidable movement within each channel. Movement of the spindles 16, 18 along the channels may be controlled by linear actuators, such as for example by using a lead screw. Alternatively, the spindles 16, 18 may be supported by rails or the like.

The operation of such an embodiment is described below with reference to Figures 4A to 4D. When it is desired to change the image being printed, the first and second spindles 16, 18 are translated so that they are positioned radially inwards of the anilox roller 5 and the impression roller 10, as shown by the arrows 50 in Figure 4B. Subsequently, the support member 20 is rotated about the support axis 36 as shown by the arrow 52 in Figure 4C, such that the first and second image rollers 6, 8 have swapped positions. Finally, the first and second spindles 16, 18 are moved radially outwards relative to the support axis 36 so that the second image roller 8 engages the anilox roller 5, the substrate 12 and the impression roller 10.

Because the first and second spindles 16, 18 are displaceable relative to the support axis 36 by the support member 20, there is no need for a support frame 26 to be present to move the support member vertically upwards, as such the overall size of the roller support system 14 can be reduced. However, in general the advantages of the embodiment of Figures 4A to 4D remains the same as the advantages of the previously described embodiment, namely that the changeover sequence is simplified for the user so as to reduce the overall downtime of the printing machine 2.

It will be appreciated that any of the above described optional features of the embodiment shown in Figures 1 to 3D may be applied to the embodiment of Figures 4A to 4D. For example, the anilox roller 5 and/or the impression roller 10 and/or the support member 20 may be horizontally displaceable relative to one another.

It will be appreciated that any suitable mechanism for rotating the support member 20 may be used. For example, a system of cams could be used to cause the support member 20 to simultaneously rotate about the support axis 36 and move the support axis 36 in a plane generally parallel to the side wall 38 of the printing machine (i.e. normal to the support axis 36).

Although printing machine has been described as a flexographic printing machine, it will be appreciated that the printing machine 2 may be any printing machine that uses a roller to transfer an image onto a substrate, such as for example gravure printing or the like.




 
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