Device for Taking Up the Clearance of Gear Transmissions

The present invention relates to a device for taking up the clearance of gear transmissions, particularly the clearance between the gears of impression cylinders and transfer cylinders of printing machines.

An important condition for the obtaining of a perfect register in printing on paper sheets which are transferred on a multicolor printing press from one printing unit to the following printing units, is to secure an accurate position of the transferred sheets in the pregrippers, on the impression cylinders and on the transfer cylinders.

On a known multicolor printing machine, paper sheets to be printed are transported from one printing unit to the other by means of chains which are provided with grippers. The accurate positioning of the sheet relative to the impression cylinder is secured by means of guide pins which are mounted on the gripper mechanism, and by means of a stop element which is arranged on the impression cylinder.

A disadvantage of this device is that it is not possible to transfer paper sheets by means of the gripper mechanism mounted on chains without use of complex auxiliary equipment where printing on both sides of the sheet with one pass of the sheet through the printing machine is required.

Therefore, on multicolor printing machines, transfer drums are used for the transfer of paper sheets from one printing unit to the following printing unit of the machine. Transfer drums permit the transfer of sheets at high printing speeds.

By use of transfer drums, if they are properly adjusted, it also is possible to turn the sheets of paper. On these printing machines, the transfer drums are driven by chains from one power source.

As a result of clearance or backlash between the teeth of the drive gears, a vibration in the gear mechanism and of the transfer cylinders (drums) is produced, which has a very negative effect on the printing quality.

Known means for the taking up of clearance or backlash between gears are clearance eliminating gears or toothed segments which have teeth of the same width as the teeth, the clearance of which has to be eliminated. The clearance eliminating gears and toothed segments are (turnably) mounted on drive gears and are urged by means of springs between (into) the teeth of the engaging gear, by which the clearance is taken up.

A disadvantage of the mentioned device is in that due to production tolerances of the engaging gear, there is created during rotation of the machine, a turning of the gear for taking up clearance relative to the drive gear, which results in a considerable wear of the teeth of said gears. A further disadvantage is in that the mechanism of such a device is very expensive in production.

A disadvantage of devices with toothed segments is in that at the region of engagement of the spring-urged toothed segments with the drive gears undesirable shocks arise. The intensity of the shocks depends on the turning ratio of the toothed segments relative to the drive gears.

The above-mentioned disadvantages are avoided by a device according to the invention, where on the drive gears are attached toothed segments, the teeth of which have a different width, whereby the single teeth are stepwise with a reduced width in the direction from the center part of the toothed segment in the direction to the outer two end portions of the segment, the reduction of the teeth being gradual and with each given tooth the reduction of width always of the same value in a range of 0.005 to 0.06 mm.

The toothed segments are provided with centering arches which engage with centering recesses provided on the side walls of the drive gears. The toothed segments are fixed on the side walls of the drive gears by means of screws.

An advantage of the device, according to the present invention, is in that by a stepwise taking up of the clearance of the transmission gears of the printing cylinders in relation to the gears of the transfer drums, undesirable shocks which arise during the transfer of the paper sheets from the gripper mechanism of one transfer drum to the gripper mechanisms of the second transfer drum are eliminated. In eliminating these shocks in the printing mechanisms, the printing quality is considerably increased and also the life time of the printing machine.

The invention will now be described in detail with reference to preferred embodiments thereof and to the illustrations on the accompanying drawings, wherein:

FIG. 1 shows schematically an arrangement of the printing cylinders and transfer drums of the printing machine, with the toothed segments which are fixed to the gears,

FIG. 2 is a top view of the device of FIG. 1,

FIG. 3 is a detailed view of the attachment of the toothed segments on the drive gear of the second transfer drum,

FIG. 4 is a sectional view along a plane I--I of the device of FIG. 3; and

FIG. 5 shows a detail of a toothed segment where the teeth have a different width, where the reduction of the width of teeth is beginning from the middle part of the segment and is increasing in the direction to the both end portions of the segment.

The device, according to the invention, consists of a first drive gear 1 which is mounted on the shaft of a first transfer drum 4. On the side wall of the first drive gear 1 is fixed by means of a screw 8, a toothed segment 9 which engages with a gear 10 fixed on the shaft of a first impression cylinder 11. A second drive gear 2 is mounted on the shaft of a second transfer drum 5 which has double the diameter of the first transfer drum 4 and a greater diameter than that of a third transfer drum 6.

On the outer side wall of the second drive gear 2, there are fixed two outer gear segments 15, one located opposite the other, which are in engagement with a gear 17 of the first transfer drum 4. On the inner side wall of the second drive gear 2, there are oppositely mounted two inner gear segments 16 which are in engagement with a gear 18 which is fixed on the shaft of the third transfer drum 6. On the shaft of the third transfer drum 6 also is fixed a third drive gear 3, on which is mounted a second gear segment 12 which engages a gear 13 fixed on the shaft of a second impression cylinder 14.

On the drive gears 1, 2, 3 are provided centering recesses 19, into which engage centering arches 20 which are formed on the gear segments 9, 12, 15 and 16. The gear segments 9, 12, 15, 16 are fixed on the side walls of the drive gears 1, 2, 3 by means of screws 8. Each tooth of the toothed segments 9, 12, 15 and 16 has a different width "A", whereby the teeth of the segments show gradually a reduction of width of a value "x" in the direction of the segments, whereby the value of reduction "x" is in the range of 0.003 to 0.06 mm.

The impression cylinders 11, 14 and transfer drums 4, 5 and 6 are rotationally mounted in side walls 7 of the printing machine.

The operation of the device according to the present invention is as follows:

After the first transfer drum 4 is turned relative to the first impression cylinder 11 to reach a position such that the gripper mechanisms, not illustrated, are in a position approximately on the direct line connecting the centers of the transfer drum 4 and the first impression cylinder 11, the proper circumferential adjustment of the first gear segment 9 is carried out. The centering arch 20 of the first gear segment 9 is turned in the centering recess 19 of the first drive gear 1 in the direction of arrow "II" in such a way, that the middle tooth 21 will completely take up the clearance between the first drive gear 1 and the gear 10 of the first impression cylinder 11. The position of the first gear segment 9 on the first drive gear 1 is then secured by means of the screws 8.

The take-up of clearance between the second drive gear 2 and the gear 17 of the first transfer drum 4 is achieved by turning the outer toothed segments 15. Each of the outer toothed segments 15 has to be individually turned, on the second drive gear 2 in the range of the tooth clearance, in the direction of arrow III. The take-up of clearance of teeth between the second drive gear 2 and the gear 18 of the third transfer drum 6 is carried out by turning of the inner gear segments 16 which are mounted on the second drive gear 2.

The circumferential adjustment of the inner gear segments 16 is carried out in the direction of arrow IV in the range of the clearance between the teeth. The position of the outer toothed segments 15 and of the inner toothed segments 16 is secured by the screws 8.

The take-up of clearance between the third drive gear 3 and the gear 13 of the second impression cylinder 14 is carried out by a circumferential turning of the second toothed segment 12 in the range of the clearance between the teeth, in the direction of arrow "V".

1--first drive gear

2--second drive gear

3--third drive gear

4--first transfer drum

5--second transfer drum

6--third transfer drum

7--side wall

8--screw

9--first toothed segment

10--gear of the first impression cylinder

11--first impression cylinder

12--second toothed segment

13--gear of the second impression cylinder

14--second impression cylinder

15--outer toothed segment

16--inner toothed segment

17--gear of the first transfer drum

18--gear of the third transfer drum

19--centring recess

20--centring arch

21--middle tooth