Apparatus for threading an intermediate transfer member of a printing system

Abstract

A printing system is described that has an intermediate transfer member in the form of a seamed endless belt for transporting an ink image from an image forming station, at which an ink image is deposited on the intermediate transfer member, to an impression station, where the ink image is transferred onto a printing substrate. The belt has along its edges formations of a greater thickness than the belt. The formations are received in channels to guide the belt and maintain the belt under lateral tension. Two drive members are provided, each located within a respective one of the channels. The two drive members are connected for movement in synchronism with one another and each has a respective laterally projecting gripper shaped for form locking engagement with the formations on a leading end of a strip from which the intermediate transfer member is to be formed. Rotation of the drive members during installation of a new intermediate transfer member serves to thread the strip through the printing system by pulling the strip from its leading end.

Claims

1. A printing system having an intermediate transfer member in the form of an endless belt for transporting an ink image from an image forming station, at which an ink image is deposited on the intermediate transfer member, to an impression station, where the ink image is transferred onto a printing substrate, the belt having along its edges formations of a greater thickness than the belt, which formations are received in channels to guide the belt and maintain the belt under lateral tension, the printing system further comprises two endless drive members, each located within a respective one of the channels, the two drive members being connected for movement in synchronism with one another and each having a respective laterally projecting gripper shaped for form locking engagement with the formations on a leading end of a strip from which the intermediate transfer member is to be formed, rotation of the drive members during installation of a new intermediate transfer member being operative to thread the strip through the printing system by pulling the strip from its leading end.

2. A printing system as claimed in claim 1, wherein a support plate is provided in the printing system for supporting ends of the strip that are to be joined to one another at a seam in order to convert the strip into an endless belt, the support plate not contacting the intermediate transfer member subsequent to installation.

3. A printing system as claimed in claim 1, wherein the strip has a V-shaped leading edge.

4. A printing system as claimed in claim 3, wherein the leading edge is formed as part of a leader that is separably connected to one end of the strip.

5. A printing system as claimed in claim 4, wherein the end of the strip connected to the leader and the opposite ends of the strip are formed with rebates for receiving a joining tape to form a seam.

6. A printing system as claimed in claim 1, wherein the opposite ends of the strip are joined at a seam while maintaining the thickness of the intermediate transfer member uniform throughout its length.

7. A printing system as claimed in claim 1, wherein the drive members are in the form of chains or toothed belts.

8. A method of installing an intermediate transfer member in a printing system having an intermediate transfer member in the form of an endless belt for transporting an ink image from an image forming station, at which an ink image is deposited on the intermediate transfer member, to an impression station, where the ink image is transferred onto a printing substrate, the belt having along its edges formations of a greater thickness than the belt, which formations are received in channels to guide the belt and maintain the belt under lateral tension, which method comprises: (a) providing an elongate strip of a length exceeding the circumference of the intermediate transfer member, (b) connecting a leading end of the strip to two grippers projecting laterally from two drive members that are each disposed within a respective one of the two channels by engaging formations on a leading end of the strip with the two grippers, (c) rotating the drive members in synchronism with one another to thread the leading end of the strip through the stations of the printing system, and (d) joining the ends of the strip to one another to form an endless intermediate transfer member after the strip has been threaded through the printing system.

9. A method as claimed in claim 8, wherein the strip has a separable leader and the ends of the strip are rebated and wherein, after separating the leader from the remainder of the strip, the ends of the strip are joined to one another by adhering a tape within the rebates in the ends of the strip to form a seam while maintaining the uniformity of the thickness of the intermediate transfer member.

10. A method as claimed in claim 8, wherein the drive members are in the form of chains or toothed belts.

11. A method of installing an intermediate transfer member in a printing system having an intermediate transfer member in the form of an endless belt for transporting an ink image from an image forming station, at which an ink image is deposited on the intermediate transfer member, to an impression station, where the ink image is transferred onto a printing substrate, which method comprises: (a) providing an elongate strip of predetermined length corresponding to the circumferential length of the intermediate transfer member, (b) threading the strip through the printing system, (c) providing rebates along the end edges, and (d) joining the end edges to one another by means of a tape that is recessed within the rebates and secured to the ends of the strip, so to form a seam having substantially the same thickness as the strip.

12. A method as claimed in claim 11, wherein the end edges of the strip are rebated prior to threading of the strip through the printing system.

13. A method as claimed in claim 11, wherein a leader is releasably secured to one of the two rebated ends of the strip to assist in threading the strip through the printing system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a section through a support system of an intermediate transfer member;

(3) FIG. 2 is a perspective view of one end of the support system shown in FIG. 1;

(4) FIG. 3 is a section through one of the guide channels of the intermediate transfer member with one of the drive members running alongside the formations on the lateral edges of the intermediate transfer member;

(5) FIG. 4 is a detail of FIG. 3 drawn to an enlarged scale;

(6) FIG. 5 shows the leading end of a strip that is threaded through a printing system to form an intermediate transfer member; and

(7) FIG. 6 shows the manner in which the ends of a strip may be joined at a seam while maintaining the thickness of the intermediate transfer member uniform throughout its length.

(8) It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate identical components but may not be referenced in the description of all figures.

DETAILED DESCRIPTION OF THE DRAWINGS

(9) An intermediate transfer member support system 10 shown in FIGS. 1 and 2 comprises two lateral frames 12 and 14, arranged one on each side of the intermediate transfer member 18, and various support, drive and tensioning rollers 16 extending transversely between the two frames 12 and 14 to constrain the intermediate transfer member to follow a closed loop and pass through the various stations of the printing system. The remainder of the printing system and more details of the intermediate transfer member support system are well documented in the prior art and need not therefore be repeated in the present context. Essentially, in the region designated 20 the intermediate transfer member passes beneath an image forming station where ink is deposited on the intermediate transfer member to form an image. The intermediate transfer member rotates clockwise as viewed to carry the ink image to the region designated 22, where the wet image is heated to evaporate the ink carrier and leave behind a tacky resin film. Along its lower run, the intermediate transfer member passes through one or more impression stations where it is pressed against a substrate, so that the tacky film separates from the intermediate transfer member and is transferred to the surface substrate.

(10) The intermediate transfer member support system 10 is designed to ensure that the intermediate transfer member remains substantially flat and taut as it passes the regions 20 and 22 and as it approaches the nip of the impression stations. In order to achieve this objective, the edges of the intermediate transfer member 18 have formations 30 in the form of zipper teeth, shown in FIGS. 3 and 4, that have a greater thickness than the transfer member 18 and are received in C-shaped guide channels 32 secured to the lateral frames 12 and 14. The guide channels 32 are shown in FIG. 1 and their position in the support system is shown in FIG. 2. Further details of the formations 30 and the guide channels 32 are disclosed WO2013/132418 and are shown in FIGS. 11 and 12 of that publication. It is to be understood that the guide channels may have any alternative cross section shape, as long as the lateral formations and the guide channels are compatible and suitable to guide the intermediate transfer member and maintain it under lateral tension while the printing system is operating.

(11) The intermediate transfer member 18 is installed by threading a strip 18 through the printing system and connecting its ends to one another by means of a seam, in order to form a seamed endless loop. The present disclosure is concerned with simplifying this task, which needs to be carried out, not only during manufacture, but from time to time during use as the intermediate transfer member is subjected to wear.

(12) The installation of a new or replacement intermediate transfer member 18 is made difficult by the fact that its lateral formations 30 need to be introduced into the guide channels 32 and, as can be seen in FIG. 1, these need not be continuous. Because they maintain the intermediate transfer member under lateral tension, engagement of the formations 30 in the guide channels 32 creates drag and makes threading of the strip 18 from which the intermediate transfer member more difficult.

(13) To mitigate this problem, in the disclosed embodiment, two endless drive members, in the form of chains 50 passing over sprockets 52 are provided alongside the edges of the intermediate transfer member 18, preferably within the enclosed cross section of the C-shaped channels 32. Reference to chains passing over sprockets is intended herein to include the equivalent of toothed belts passing over toothed pulleys. Each of the chains 50 has a respective laterally projecting gripper 54, most clearly shown in FIG. 4, that engages the formations 30 of the intermediate transfer member strip 18 at its leading end in a form locking manner. After the gripper 54 has engaged the formations on the leading edge of the strip 18, the two endless chains 50 are driven to pull the strip 18 by its leading end, in the direction shown by the arrows in FIG. 3, through the various stations of the printing system. To ensure that the two chains 50 move in synchronism, two of their drive sprockets 52 are mounted on a common axle that is connected either to a crank for manual operation, or to a suitable motor if threading is automated.

(14) The intermediate transfer member 18 may in some locations have to be threaded through a gap that is as narrow as 2 mm, while its width may typically be about 1,000 mm. Sagging of the leading edge of the strip 18 being threaded through the printing system can therefore cause a problem. This is mitigated by forming a V-shaped cut-out 60 in the leading edge of the strip in the manner shown in FIG. 5.

(15) Once the strip has been pulled around the entire printing system, and its leading end comes round to the end of the support system shown in FIG. 2, the opposite ends of the strip are laid over a support plate 62 and joined to one another to form a seam, which may, as shown in FIG. 5, extend along an inclined line 64. After the seam has been formed, a tension roller is extended to maintain the intermediate transfer member under the desired longitudinal tension and space it from the grippers 54 that remain stationary during operation of the printing system.

(16) To form the seam, the two ends of the strip 18 may be laid one over the other on the support plate 62 and cut along the inclined line 64. While retained on the support plate 62 with the cut edges in abutting relation, an adhesive tape may be laid over the two ends to create the desired join. Such a method of forming the two ends results in a seam having an increased thickness and in order that it should not create a sudden change in tension as it passes over drive rollers or through an impression station, the cut line 64 may be inclined in the manner illustrated in FIG. 5.

(17) It is alternatively possible to form a seam without increasing the thickness of the intermediate transfer member and this is shown in FIG. 6. In this case, the strip 18 is made to a predetermined length and is attached to a separable leader at its leading end. The leading 19 and trailing 21 ends of the strip 18 proper, would be ground down to form rebates 70 for receiving a tape 75 that is as wide as the two rebates 72. The tape 72 is secured to the two ends of the strip 18 by a layer 74 of adhesive.

(18) In an embodiment where the thickness of the strip 18 is about 550 m, the rebates in the ends of the strip may have a depth of 200 m. The rebates can then accommodate a tape having a thickness of about 150 m leaving 50 m for the thickness of the adhesive layer 74.

(19) The separable leader should be made of a flexible material so that it may follow the path of the intermediate transfer member but it may be made of a stiffer material than the strip 18 so as to have less tendency to sag. The leader may, as shown in FIG. 5, have a V-shaped leading edge and it should have formations that are continuous with the formations on the sides of the strip 18.

(20) It is understood that in addition to the image forming station and the impression station above-mentioned, a printing system may further comprise a treatment station and/or a cleaning station to respectively treat and/or clean the intermediate transfer member, a drying station to evaporate liquid carrier out of the ink image, a cooling or a heating station to modify the temperature of the intermediate transfer member along its path, a finishing station for further processing the printed substrate, and so on. All such stations need not be considered in detail in the present context.

(21) It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

(22) Although the present disclosure has been described with respect to various specific embodiments presented thereof for the sake of illustration only, such specifically disclosed embodiments should not be considered limiting. Many other alternatives, modifications and variations of such embodiments will occur to those skilled in the art based upon Applicant's disclosure herein. Accordingly, it is intended to embrace all such alternatives, modifications and variations and to be bound only by the spirit and scope of the appended claims and any change which come within their meaning and range of equivalency.

(23) In the description and claims of the present disclosure, each of the verbs comprise, include and have, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of features, members, steps, components, elements or parts of the subject or subjects of the verb.

(24) As used herein, the singular form a, an and the include plural references and mean at least one or one or more unless the context clearly dictates otherwise.

(25) Unless otherwise stated, the use of the expression and/or between the last two members of a list of options for selection indicates that a selection of one or more of the listed options is appropriate and may be made.

(26) Unless otherwise stated, adjectives such as substantially and about that modify a condition or relationship characteristic of a feature or features of an embodiment of the present technology, are to be understood to mean that the condition or characteristic is defined to within tolerances that are acceptable for operation of the embodiment for an application for which it is intended.

(27) To the extent necessary to understand or complete the present disclosure, all publications, patents, and patent applications mentioned herein, including in particular the applications of the Applicant, are expressly incorporated by reference in their entirety by reference as is fully set forth herein.