Axially Displaceable Roller in a Printing Unit

Field of the Invention

The present invention concerns a method for dismounting as well as mounting a replaceable sleeve on a rotatable and radially displaceable roller which is a roller for a printing unit in a printing machine, e.g. a flexo-printing machine. The invention furthermore concerns such a printing machine with at least one printing unit, wherein the roller at a first end is provided with a first shaft end in a first bearing and at the other end is provided with a second shaft end in a second bearing, where these bearings are arranged in two radially displaceable slides on the printing machine, and where the roller can be released from the printing machine at one end of the roller by the roller being displaced axially in its longitudinal direction prior to dismounting a sleeve, whereby the roller is withdrawn from engagement with one radially displaceable slide.

Background of the Invention It is common knowledge to use rollers with different exchangeable surfaces in connection with printing machines. Such exchangeable surfaces may be so-called sleeves which are cylindric shells mounted on a mandrel which constitutes the innermost part of a roller for a printing machine. Examples of such sleeves are i.a. known from EP 1 361 073, EP 0 787 597 and EP 0 732 201. These sleeves may be with an internal conical shape or with cylindric shape. In order to mount and dismount the sleeves, the inner part of the roller may advantageously be with a number of openings through which compressed air is conducted during mounting and dismounting. By the outflowing air is obtained a supporting layer of air allowing the sleeve to be positioned in a correct and precise position. This solution requires that the sleeve is elastic, or that at least the inner part of the sleeve is elastic. The sleeve may therefore be entirely or partly elastic. The sleeve may e.g. be of a rubber material, possibly several different layers with different properties. Another solution is an outer layer which is very rigid and one or more inner layers which are elastic and compressible during mounting.

Such sleeves require that the roller on which they are to be mounted is released at one end, and that the bearing pedestal on which the roller is seated during operation, is

removed prior to mounting or replacement of the sleeve on the roller. This is typically provided by dismounting the pedestal, or at least releasing it from the machine so much that access to the machine is obtained from the operator side of the machine. This disassembling of the machine is, however, rather inexpedient, as disassembling and subsequent assembling are cost-increasing processes that advantageously could be omitted. At the same time, the construction of the machine itself is complex, cumbersome and costly.

From 1,338,417 is known another solution where the roller is displaced in axial direction in order thereby to be drawn out of one bearing pedestal. After release from the pedestal, the roller is pivoted, as in the other pedestal at the other end of the roller there is provided a device allowing the roller to pivot out and form an angle relative to the normal position. Thus is provided access for mounting and dismounting a sleeve on the roller. However, this solution has the drawback that the device allowing turning or pivoting of the roller is a complex design since it is very important that no play or other imprecise features occur in the device/bearing pedestal. This solution is, as mentioned, complex as well, but also cost-increasing for the process and for the machine.

Object of the Invention It is thus the object of the invention to indicate a solution to the above mentioned problems where replacement of a sleeve on a roller can be effected rapidly, precisely and without actual disassembly of the machine.

Description of the Invention

As mentioned in the introduction and as specified in the preamble of claim 1, the invention concerns a method for dismounting as well as mounting a replaceable sleeve on a rotatable and radially displaceable roller which is a roller for a printing unit in a printing machine, e.g. a flexo-printing machine. The invention furthermore concerns such a printing machine with at least one printing unit, wherein the roller at a first end is provided with a first shaft end in a first bearing and at the other end is provided with a second shaft end in a second bearing, where these bearings are arranged in two radially displaceable slides on the printing machine, and where the roller can be released from the printing machine at one end of the roller by the roller being

displaced axially in its longitudinal direction prior to dismounting a sleeve, whereby the roller is withdrawn from engagement with one radially displaceable slide.

The method and the printing unit according to the invention are adapted such that the roller is provided with displacing means, and by these it is displaced in its longitudinal direction prior to dismounting a sleeve, whereby the roller is drawn out of engagement with the one fixed and radially displaceable slide. The axial displacement is preferably between 30 and 80 mm, more specifically between 40 and 60 mm. The new feature according to the invention is that the slide and the roller are displaced radially in relation to each other, whereafter the sleeve can be released and dismounted by being drawn off the roller in its longitudinal direction. By mounting a sleeve, process is reversed as a matter of course.

By this solution is achieved a more rapid replacement of the sleeve, and the mechanical solution itself may be designed much more stable, as the slide at the released end of the roller is not to be designed such as to be readily disassembled or such that the slide at the other end of the roller has to be adapted to turning or pivoting the roller to a side. Therefore, this is a fixed slide which only can be moved in radial direction. Such a solution is cheaper to make as well as being more robust and stable. Moreover, minor inaccuracies do not arise after disassembling and assembling which otherwise entail fine adjustment before restarting the machine. In another embodiment, the slide may be adapted to be pivoted aside after releasing the roller from the slide in order to provide space for replacing the sleeve. Alternatively, both a radial displacement and a pivoting movement of the slide can be applied at the first end of the roller.

In a preferred embodiment of the invention, the axial displacement of the roller in its longitudinal direction includes a displacement of at least part of the other slide in which the second end of the roller is suspended by the second bearing. This may be where the roller at the second end is seated in a displaceable bearing housing in the second slide, where the bearing housing is displaceable in axial direction of the roller, and where the bearing housing and the shaft end are preferably with more than one bearing. As mentioned, the bearing housing may be with more than one bearing,

entailing the advantage that the roller can be released at the first end without requiring support of the roller during replacement of the sleeve. Such a support is space- demanding and cumbersome to handle as it must not interfere with the sleeve during the replacement. Another advantage of using more than one bearing is that it is easier to ensure a precise disposition of the two slides opposite each other after replacing a sleeve.

By the way, the displaceable bearing housing in the second slide also has the function that it is used for regulating the lateral position of the roller relative to other printing units in a printing machine. It is important that successive prints are placed exactly over each other, both in longitudinal and transverse direction of the print. This displacing mechanism may advantageously be the same which is used for both regulation of the side register and for disassembly by replacement of a sleeve.

In principle, the solution is simple as a printing machine is typically with a displaceable device which only is used for controlling the side register. This displaceable device may easily be extended by a suitable length, e.g. 50 mm. Actually, the solution can be realised in that the prior art side displacement rails are purchased with the said additional length and subsequently incorporated in the actual slide. It is thus a rather simple solution that may readily be performed.

The radial movement of the two slides is effected by means which already are on a printing machine as these are equipped with displacement means in radial direction, by which respective rollers in a printing unit in a printing machine are mutually adjusted. This is usual in that rollers with the same diameter are not always used and because during reconfiguration of the machine it may be necessary to create space.

In a variant of the invention, the axial movement of the roller may be intended for the first bearing at the first end of the roller being drawn out of the first slide by the said axial movement. At the first slide, the printing machine is provided with means for receiving, retaining and releasing one or more bearings that remain secured on the first shaft end of the roller during separation of the roller from the slide.

Another variant is where the first shaft end at the first end of the roller is drawn out of the first bearing, which e.g. may be a needle bearing, by the axial movement. By this solution, the printing machine is provided at the first slide with one or more permanently mounted bearings, where the first shaft end of the roller is provided with means for receiving, retaining and releasing one or more bearings.

Alternatively, the said means for retaining and releasing the bearing/bearings in relation to either the shaft end or the slide may be arranged on or in connection with the bearing/bearings.

The invention as described above may advantageously be used in replacing the sleeve on printing cylinders with cliches, but may also be used in connection with replacing sleeves on screen rollers/anilox rollers.

Description of the Drawing The invention is described in the following with reference to the drawing, wherein:

Fig. 1 shows a roller in a printing unit in operating position.

Fig. 2 shows a roller in a printing unit in axially displaced position.

Detailed Description of the Invention In Fig. 1 is seen a roller 1 which at its first end 2 is provided with a shaft end 3 that is seated in a recess 5 via a bearing 4 in a first slide 6. This first slide 6 is on the side of the printing machine called the operator side. This is of course the side from which the machine is operated.

At the second end 7 of the roller appears a somewhat longer shaft end 8 which is here suspended by two bearings 9 in a recess 10. The recess 10 is in a displaceable bearing housing 11 which may be displaced in axial direction of the roller in the second slide 12. The bearing housing 11 is displaced with a spindle arrangement 13 which is shown here with a handwheel 14 for operating the spindle and thereby the axial displacement of the roller 1. This regulation may of course also be performed automatically, e.g. by an electric motor.

At the end of the second shaft end 8 is mounted a coupling 15 which via a gear 16 forms connection with the driving motor 17.

In Fig. 2 is seen the same variant of the invention as in Fig. 1, but here shown with the roller 1 in an axially displaced position where the shaft end 3 is drawn free of the bearing 4 and thereby of the first slide 6. This axial displacement is effected by using the spindle arrangement 13 connected with the displaceable bearing housing 11. As it appears from Fig. 2, the roller 1 comes with the displaceable bearing housing 11, coupling 15, gear 16 and motor 17, and disassembly of any parts is thus not required. A subsequent radial displacement of the first slide 6 relative to the second slide 12 may then be performed whereby free access to the roller 1 is provided.