GB2290260A

GB2290260A - Device for correcting the register on a sheet-fed rotary printing machine

Info

Publication number: GB2290260A
Application number: GB9512426A
Authority: GB
Inventors: Andreas Henn
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1994-06-18
Filing date: 1995-06-19
Publication date: 1995-12-20
Anticipated expiration: 2015-06-19
Also published as: GB9512426D0; FR2721550B1; GB2290260B; DE9409890U1; FR2721550A1

Description

1 - 2290260 Device for correcting the register on a sheet-fed rotary

printing machine The invention relates to a device for correcting the register on a sheet- fed rotary printing machine by deforming the leading edge of a respective sheet by means of a gripper bridge, said gripper bridge supporting the gripper shaft and being bendable approximately in the middle of said gripper bridge when taking over the sheets to be conveyed, said gripper bridge comprising an adjusting means acting on the gripper shaft/gripper bridge in the stroke with the sheet sequence, with said gripper shaft/gripper bridge being supported, on both sides thereof, in the sheet- conveying device.

A known embodiment of this type (DE 88 16 641 U1) shows such a device provided at the sheet feeder of a printing machine, with the gripper bridge being bent, by means of an adjustable stop, when being in a position in which the sheets are taken over. Thus, the sheets to be conveyed are gripped by the gripper bridge being in a bent condition and the leading edge of each sheet is deformed when pivoting the gripper bridge so that, after having corrected the leading sheet edges as desired, said sheets are transferred to the subsequent cylinder. The bending of the gripper shaft/gripper bridge is effected prior to the gripper gripping the respective leading sheet edge. It is thus possible to correct the sheet register in order to obtain a perfect print result.

Proceeding from this state of the art it is the object of the present invention to effect a register correction of the sheets to be conveyed without additional torque fluctuations increasing the load of the drive of the printing machine. Moreover, the device is to provide a 2 simple possibility of register correction on each sheetconveying cylinder.

According to the invention, this object is achieved in that the adjusting means bending the gripper shaft/gripper bridge is designed as a piezoelectric actuator, in that said actuator is braced against a supporting surface of the sheet-conveying device and bends the gripper shaft/gripper bridge, and in that the control voltage required for the actuator is adjustable via the voltage supply. Due to this solution the respective sheet-conveying device may be actuated without any additional torque fluctuations and the forces necessary for the bending may be effective within the sheet-conveying device so that there do not occur any additional torsional and bending moments. Furthermore, already available machines may be retrofitted with the above-described equipment, and its simple configuration does not require a complicated structional design, thus avoiding high costs.

Due to the piezoelectric actuator used, it is not difficult at all to effect the required bending of the gripper bridge of some tenths of a millimeter and to adjust said bending very precisely via the voltage supply so that even adjustments in the micrometer range may be carried out. While the machine is in operation, the pressman may thus influence the respective register very sensitively, and at any time he may reproduce the values set.

A preferred embodiment of the present invention is now described by way of example with reference to the accompanying drawings, in which:- FIG. 1 is a vertical sectional view of a pre-gripper of a sheet-fed rotary printing machine; and is a top view of the pre-gripper shown in Fig. 1.

FIG. 2 v 3 The pre-gripper shown in the drawing has grippers 20 which take a sheet 1 to be printed from a feed table 2 on which the sheet has been aligned by means of front lays and side lays (not illustrated). The pre-gripper accelerates the sheet 1 to printing speed and transfers it to a transfer cylinder 3. The pre-gripper is drivne by a cam 4, shown in Fig. 1, via a roller lever 5 having a roller 6 rotatably mounted on a free end thereof and forced against the cam 4 by means of a spring 7. By suitably designing the cam 4, the pre-gripper accelerates the sheet 1 to printing speed as said sheet is transferred to the cylinder 3, while, after a suitable delay in the last phase of motion, the pre-gripper slowly returns to the othe end position and reaches its zero position in which a new sheet 1 is taken from the f eed table 2.

A U-shaped section gripper bridge 8 extends transversely across the cylinder width and is fastened at its two ends to two levers 9 which are resistant to bending, said levers 9, in turn, being fastened at the opposite ends thereof to a pivoting shaft 10 of the pre-gripper. In its sheet takeover position, gripper bridge 8 abuts with stops 17 against counter-stops 18, said stops 17 being provided on supports 11 which, in turn, are fastened to a side frame of the printing machine.

A third lever 9 is secured on the gripper bridge shaft 10 approximately midway between the first two levers 9, said further lever 9 having a supporting surface 12 below the U- shaped gripper bridge 8. A piezoelectric actuator 13 is fixed on the supproting surface 12 by means of screws 14. In the region of a recess 16 in the U-shaped gripper bridge 8, a base 15 of the actuator 13 penetrates the lower part of the gripper bridge 8 so that said actuator 13 directly acts on a side of the gripper bridge 8 and, given a respective voltage supply, bends said gripper bridge 8. A shaft 19 for the sheet grippers 20 is fixed in the U-shaped gripper bridge 8 via supporting bearings 21, and hence, the shaft 19 4 is bent at the same time as the gripper bridge 8.

In Fig.2, the bending of the gripper shaft 19 and gripper bridge a is shown in an exaggerated manner; in practice, it is quite sufficient to bend the gripper shaft/gripper bridge only slightly by some tenths of a millimetre. Via a voltage supply 22, the actuator may be supplied with a very sensitively adjustable control voltage so that even in the micrometre range a bending may be effected. Thus, the pressman may easily cope with "narrow printing and fanningout".

By using sensors to scan the position of the leading sheet edge it is possible to provide, in connection with the piezoelecgric actuator, a closed loop position control system by means of which each individual sheet may be accurately placed in a predetermfined position. Moreover, it is also possible to correct stochastic deviations from a mean sheet position.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

CLAIMS.

1. A rotary printing machine having a pre-gripper f or correcting the register of a sheet to be transferred to a cylinder by deforming the leading edge of the sheet, comprising a gripper bridge supporting a gripper shaft, on both ends thereof, which is bendable at an approximate central location thereof when taking over the sheet to be transferred, a piezoelectric actuator acting on the gripper shaf t/gripper bridge during take over of the sheet, and wherein said actuator is braced against a supporting surf ace and bends said gripper shaft/gripper bridge, and wherein a control voltage for said actuator is adjustable via a voltage supply.

2. A rotary printing machine having a pre-gripper f or correcting the register of a sheet to be transferred to a cylinder, substantially as hereinbefore described with reference to the accompanying drawings.