Device for correcting the register of sheet overprints in a sheet-fed rotary printing machine

Device for correcting the register of a sheet-overprint and for compensating for a distorted sheet in a sheet-fed rotary printing machine by deforming the leading edge of the sheet on a travel path thereof before the leading edge enters a printing unit, including an adjustable bending device for bending, in rhythm with a printing cycle of the machine, a support beam extending transversely to the travel path of the sheet and carrying a plurality of mutually adjacent sheet grippers, includes a pregripper device for executing swinging movements about a stationary axis and an axis adjustable into a given position, respectively, the pregripper device including a gripper fly forming the support beam for the sheet grippers, and respective rigid levers supporting the gripper fly at least at both ends thereof on a gripper-fly shaft, the bending device being cooperatively engageable with the pergripper device and being formed of a single adjustable deforming stop disposed substantially midway between the respective ends of the gripper fly and fixed to a frame of the machine, the bending device and theh pregripper device, except for the sheet gripper thereof, being located below the sheet travel path, the gripper fly, at a substantially midwise location thereof between the levers, being deformably engageable with the single adjustable deforming stop before the ends of the gripper fly, during a return swing thereof, have reached a zero setting in which the sheet grippers take over a sheet.

The invention relates to a device for correcting the register of a sheet 
overprint and for compensating for a distorted sheet in a sheet-fed rotary 
printing machine by deforming the leading edge of the sheet on a travel 
path thereof before the leading edge enters a printing unit, including an 
adjustable bending device for bending, in rhythm with a printing cycle of 
the machine, a support beam extending transversely to the travel path of 
the sheet and carrying a plurality of mutually adjacent sheet grippers. 
These generic features of a device for correcting register and for 
compensating for distorted sheets have become known heretofore from U.S. 
Pat. No. 4,466,350 wherein a sheet transfer cylinder provided with these 
features is described. A bending device engages the middle of a 
gripper-fly shaft of a sheet transfer cylinder so that it bends the 
gripper-fly shaft in rhythm with the operating cycle of the machine. The 
leading edge of a sheet is thereby deformed in the middle thereof in or 
opposite to the direction of rotation of the cylinder. The bending device 
is formed of a movable arrangement of a middle gripper-fly shaft bearing 
and a cam mechanism including a cam roller and a restoring or return 
spring, the cam roller having an instantaneous position of rotation 
adjustable by a control shaft which, in accordance with the suggestion in 
the aforementioned patent, is formed by the gripper-fly shaft. Relatively 
high costs are entailed in providing such a bending device. Above all, 
such a bending device is disadvantageous in that an adjustment in the 
deformation of the leading edge of the sheet cannot be effected during the 
operation of the machine, so that it is necessary to stop the machine 
repeatedly in the make-ready phase in order to perform register 
corrections by deforming the leading edge of the sheet. 
U.S. Pat. No. 2,577,099 shows a register-correcting device wherein the 
gripper-bridge or fly shaft is firmly held at the ends thereof in a sheet 
transfer cylinder, and is also bent in the middle thereof either in or 
opposite the direction of travel of the sheet. In this regard, the 
gripper-bridge shaft is of tubular construction and is supported on a pair 
of rollers in the middle of a channel formed in the sheet transfer 
cylinder, the pair of rollers having axes of rotation which assume varying 
angular positions with respect to the axis of the gripper-bridge shaft the 
rollers of the pair thereof being pressable individually against the 
gripper-bridge shaft, by means of an eccentric mechanism or formed as a 
bending or flexure rod which is directly deformable by an eccentric 
mechanism. Such a control mechanism for the bending device is also quite 
costly and is, above all, not controllable during operation of the 
machine. 
In German Prosecuted Application (DE-AS) 23 14 302 and German Patent 11 75 
695, devices for deforming the leading edge of a sheet for the purpose of 
effecting a register correction are described wherein the gripper-fly or 
bridge shaft is subdivided, and the adjacent ends of the shaft portions 
are mounted in a movable slide which is adjustable by means of specific 
structural members. These devices, as well, are non-economical and are not 
adjustable during operation of the machine. 
Reference is also made to the heretoforeknown possibility of adjusting 
gripper pad bars and front stops, respectively, which are provided in the 
grippers of sheet transfer cylinders for the purpose of deforming the 
leading edge of a sheet, in accordance with German Patent 1,909,795 and 
German Published Non-Prosecuted Application DE-OS 35 04 435. With the 
devices known therefrom, the leading edge of a sheet is already deformed 
during the alignment thereof at the gripper pad bar and at the front 
stops, respectively, of the grippers in a sheet feeding cylinder, and 
thereby brought to a smooth or uniform abutment thereat. 
These heretofore known means which are formed differently from the 
initially described state of the art do not, however, eliminate the 
aforementioned disadvantages. 
All of the devices according to the state of the art exhibit a common 
feature, namely, that the means for deforming the leading edge of the 
sheet are arranged on a rotatingly driven cylinder, with a gripper system 
disposed in an axial channel formed at the peripheral surface of this 
cylinder and swingable about a gripper-fly shaft mounted eccentrically to 
the cylinder axis. Thus, practice and the literature clearly indicate a 
direction towards limiting the construction of such means to rotating 
cylinders and a necessity for accepting a costly production without having 
any possibility of performing a simple adjustment of the means during the 
operation of the machine. 
It is accordingly an object of the invention to provide a bending device 
for deforming the leading edge of a sheet for the purpose of correcting 
the register and for compensating for distorted or stressed sheets, 
respectively, in a gripper system for taking over sheets in a sheet-fed 
rotary printing machine, which is primarily adjustable during operation of 
the machine, and requires a least possible number of additional structural 
members. 
With the foregoing and other objects in view, there is provided, in 
accordance with the invention, a device for correcting the register of a 
sheet-overprint and for compensating for a distorted sheet in a sheet-fed 
rotary printing machine by deforming the leading edge of the sheet on a 
travel path thereof before the leading edge enters a printing unit, 
including an adjustable bending device for bending, in rhythm with a 
printing cycle of the machine, a support beam extending transversely to 
the travel path of the sheet and carrying a plurality of mutually adjacent 
sheet grippers, comprising a pregripper device for executing swinging 
movements about a stationary axis and an axis adjustable into a given 
position, respectively, the pregripper device including a gripper fly 
forming the support beam for the sheet grippers, and respective rigid 
levers supporting the gripper fly at least at both ends thereof on a 
gripper-fly shaft, the bending device being cooperatively engageable with 
the pregripper device and being formed of at least one adjustable stop 
fixed to a frame of the machine, the gripper fly, at a substantially 
midwise location thereof between the levers, being engageable with the one 
adjustable stop before the ends of the gripper fly, during a return swing 
thereof, have reached a zero setting in which the sheet grippers take over 
a sheet. 
An essential feature which distinguishes the invention over the state of 
the art is thus the construction of the bending device at the gripper fly 
or bridge of a pregripper device which executes swinging movements about 
an axis which is stationary with respect to the machine frame yet possibly 
adjustable in the position thereof, the gripper fly thereof being 
supported only at both ends thereof by means of rigid i.e. stiff against 
flexure, levers on a gripper-fly shaft. The bending device per se is 
formed then only of a stop which is fixed to the machine frame yet is able 
to be adjusted in height, and is engageable by the gripper fly at a middle 
location thereof before the ends of the gripper fly, during a return swing 
thereof, have reached a zero setting thereof in which the sheet grippers 
take over a sheet. Because the stop is disposed on a part of the machine 
frame, it is adjustable at any time, even when the machine is in 
operation. This constitutes an essential advantage of the device according 
to the invention of the instant application over all of the constructions 
of the prior art described hereinbefore. Moreover, the stop, in its 
simplest form, may be constructed as or on an adjusting screw or setscrew 
which is screwed into a thread formed in a member fixed to the machine 
frame. End stops for the gripper fly are generally unnecessary, however, 
stops may also be provided on the machine frame for the ends of the 
gripper fly, the stops being engageable, if necessary or desirable, by the 
gripper fly in the zero setting thereof. If the middle stop for the 
gripper fly is withdrawn behind a rectilinear connection line between the 
two end stops, the bending device is ineffective. If a register correction 
should be necessary, the middle stop is shifted with respect to the 
rectilinear connection line so that the middle of the gripper fly engages 
the middle stop before the ends of the gripper fly reach the zero setting 
thereof and the outer stops, respectively, so that the gripper fly is 
slightly bent around the middle stop. Such a gripper fly operates with 
gripper pad bars so that when the bending device is adjusted, the sheet 
projects farther into the grippers at the ends of the gripper fly than in 
the middle thereof and, initially, for the purpose of tensioning the sheet 
during motion of the pregripper device, the lateral sides of the sheet are 
accelerated to a greater extent than in the middle, as in the case of 
other hereinaformentioned conventional devices. 
In its simplest construction and, in accordance with another feature of the 
invention, the one adjustable stop for the gripper fly is disposed on a 
crossbar of the machine frame. 
In accordance with an added feature of the invention, the one adjustable 
stop is formed on a setscrew threadedly secured on the crossbar. 
In accordance with an additional feature of the invention, there are 
provided additional stops fixed to the machine frame for engaging the ends 
of the gripper fly on a rectilinear connecting line, the one adjustable 
stop being adjustable in a travel direction of the sheet along the travel 
path thereof so as to project beyond the rectilinear connecting line. 
In accordance with a further feature of the invention, the additional stops 
are adjustable. 
In accordance with another conceivable embodiment of the invention, the 
middle stop for the gripper fly is supported on the gripper-fly shaft in 
order to permit a delay of several degrees of swing. In this regard, in 
accordance with yet another feature of the invention, the one adjustable 
stop is formed as a roller braced against the gripper-fly shaft and 
adjustable in spacing from the axis of the gripper-fly shaft. 
In accordance with further features of this embodiment, the 
register-correcting device includes another lever firmly connected at an 
end thereof to the gripper fly and extending substantially parallel to and 
midwise between the rigid levers disposed at the ends of the gripper fly, 
the other lever at the other end thereof having a self-aligning bearing 
disposed eccentrically to the axis of the gripper-fly shaft and connected 
to the gripper-fly shaft so as to be fixed against rotation relative 
thereto, the roller forming the one adjustable stop being mounted on the 
other lever. 
In accordance with yet an added feature of the invention, there is provided 
a ring turnably mounted on the gripper-fly shaft, a cam formed at the 
periphery of the ring, the roller forming the one adjustable stop being 
engageable with the cam and adjustable thereby in spacing from the 
gripper-fly shaft. 
In accordance with yet an additional feature of the invention, the 
register-correcting device provides an adjusting screw secured to the 
machine frame so as to be fixed against displacement in axial direction, 
the ring being connected to the adjusting screw. 
In accordance with a concomitant feature of the invention, the 
register-correcting device includes a stop lever fixed to the machine 
frame and adjustable to a tension-free zero setting of the gripper fly, 
the other lever being cooperatively engageable with the stop lever. 
When the device is disengaged, the roller remains free, and the lever is 
pressed against the contact screw by a spring. 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a 
device for correcting the register of sheet overprints in a sheet-fed 
rotary printing machine, it is nevertheless not intended to be limited to 
the details shown, since various modifications and structural changes may 
be made therein without departing from the spirit of the invention and 
within the scope and range of equivalents of the claims.

Referring now to the figures of the drawing and, first, particularly to 
FIG. 1 thereof, there is shown therein a pregripper device which takes 
over a sheet 1, which is to be printed, from a feed table 2 whereon the 
sheet has been aligned at non-illustrated front and side lays. The 
pregripper device accelerates the travel of the sheet 1 to printing speed 
and transfers it to a transfer cylinder 3. The pregripper device is driven 
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 being forced by a spring 7 
against the cam 4. By suitably designing the cam 4, the sheet 1 is 
accelerated to printing speed by the device as the sheet 1 is being 
transferred to the cylinder 3, while the pregripper device after a 
suitable delay in the last phase of motion, slowly returns to its starting 
or zero position in which it takes over a new sheet from the delivery 
table 2. In the embodiment illustrated in FIGS. 1 and 2, a gripper bridge 
or fly 8, which extends across the width of the machine and has a U-shaped 
cross section, is fastened at the ends thereof to respective ends of 
levers 9 which are resistant to bending, the levers 9 being, in turn, 
fastened at the respective opposite ends thereof to a rocking shaft 10 of 
the pregripper device. A device for bending the gripper fly 8, in 
accordance with the invention, is made up of a stop 12 adjustably disposed 
on a crossbar 11 of a frame of the machine and cooperating with an 
opposing or counter-stop 13 located on the gripper fly 8. In the 
embodiment illustrated in FIGS. 1 and 2, the stop 12 is formed on an 
adjusting screw or setscrew 14 which can be screwed into the transversely 
extending crossbar 11 or another structural member of the machine frame, 
the setscrew 14 having a free end formed with a knurled head or other 
means for applying or connecting a tool or motor thereto. Further 
necessarily or desirably adjustable stops 15 and 16 are provided in the 
vicinity of the ends of the gripper fly 8 and cooperate with respective 
counter-stops 17 and 18 on the gripper fly 8. In their simplest form, the 
stops 15 and 16 are "mushroom heads", and the counter-stops 17 and 18 are 
formed on adjusting screws or setscrews. In this arrangement or embodiment 
of the inventive device, the stop 12 can be withdrawn by its setscrew 14 
to a location behind a non-illustrated rectilinear connecting line which 
extends through planes of contact of the stops 15 and 16, on the one hand, 
with the counter-stops 17 and 18, on the other hand, so that no bending of 
the gripper fly 8 occurs. For the purpose of effecting a register 
correction, the stop 12 can be advanced beyond this non-illustrated 
rectilinear connection line, while the machine is in operation, by 
suitably actuating or manipulating the setscrew 14 so that bending of the 
gripper fly 8 to a greater or lesser extent is effected, as is indicated 
in phantom in FIG. 2. Depending upon the extent of bending, grippers 20 in 
the gripper fly 8, which are movable about a swivel axis 19 of the gripper 
fly 8, extend farther into the sheet 1 at the lateral edges thereof than 
the grippers 20 in the middle of the gripper fly 8, so that, during the 
movement of the pregripper device, a greater acceleration of the sheet 1 
occurs at the lateral edges of the sheet 1 than at the middle thereof, 
with a consequent tensioning of the sheet 1. 
As is readily apparent from FIG. 1, the sheet 1 is fed along a travel path 
over the feed table 2 and is intercepted by the pregripper device which 
includes the grippers 20, the gripper fly 8, the levers 9, the rocking 
shaft 10 and the cam 4, all of which, except for the gripping portion of 
the grippers 8, are located below the sheet travel path and the feed table 
2. Furthermore, the bending device formed of the crossbar 11, the 
deforming stop 12 and the end stops 15 and 16 engaging the counterstops 17 
and 18 provided on the gripper fly 8 is also located below the sheet 
travel path and the feed table 2. Thus, before the sheet 1 actually enters 
the printing unit represented by the transfer cylinder 3, the register 
thereof is corrected, and distortions therein are compensated for by 
deforming the leading edge thereof by means of the device according to the 
invention. By locating the pregripper device and the bending device below 
the sheet travel path and the feed table, the pressman has an unobstructed 
view of the traveling sheet 1 before it enters the printing unit. 
Another embodiment of the device for correcting the register of sheet 
overprints in a sheet-fed rotary printing machine according to the 
invention is illustrated in FIGS. 3 and 4. In this embodiment, the stop is 
formed of a roller 21 which is braced by a spring 31 against a cam 24 and 
freely rotatably mounted on a further lever 22, which is disposed midwise 
between the ends of the gripper fly 8 somewhat parallel to the two levers 
9, resistant to bending, which are shown in FIG. 4. One end of the lever 
22 is firmly connected to the gripper fly 8, and the other end thereof has 
a self-aligning bearing 23 thereon which is connected to the shaft 10 of 
the gripper fly 8 eccentrically to the axis of the shaft 10 and so as to 
be fixed against relative rotation therewith. Because the roller 21 is 
adjustable in its spacing from the axis of the gripper-fly shaft 10, a 
bending device is formed by means of which the gripper fly 8 can be 
deformed via the lever 22. For the purpose of adjusting the spacing of the 
roller 21 from the axis of the gripper-fly shaft 10, a cam 24 is provided 
in the embodiment of FIGS. 3 and 4, which is formed at the periphery of a 
ring 25 which is turnable about the axis of the gripper-fly shaft 10. This 
ring 25 is turnable by a setscrew 26 which is held in the machine frame in 
a manner so as not to be axially displaceable, the setscrew 26 having a 
nut 27 threaded therein which is connected oscillatingly displaceably with 
the ring 25. By means of the setscrew 26, the cam 24 can be turned into 
the range of the roller 21 serving as a stop, so that the roller 21, when 
the gripper fly 8 swings back, comes to a stop earlier, and the gripper 
fly 8 thereby becomes deformed. To stop or inactivate the bending device, 
the cam 24 is moved out of the range of motion of the roller 21, as is 
illustrated in FIG. 3. The lever 22 which is connected to the middle of 
the gripper fly 8 cooperates with another stop lever 28 which is mounted 
on the gripper-fly shaft 10 so as to be fixed against relative rotation 
therewith. A respective adjustable stop screw 29 and 30 are provided on 
the lever 29 and the lever 22, the stop screw 29 and 30 having respective 
heads by which they are in contact with one another and by which they are 
adjustable or settable to a tension-free zero setting of the gripper fly 
8. When the bending device is stopped or inactive, both heads, 
respectively, of the screws 29 and 30 are held together by a spring 31.