Device for clamping the trailing edge of a printing plate in a plate cylinder of a rotary printing machine

Information

  • Patent Grant
  • 6487967
  • Patent Number
    6,487,967
  • Date Filed
    Wednesday, December 13, 2000
    23 years ago
  • Date Issued
    Tuesday, December 3, 2002
    21 years ago
Abstract
A device for clamping the trailing edge of a printing plate in a plate cylinder of a rotary printing machine includes a torsion bar disposed in a cylinder gap formed in the plate cylinder and extending in axial direction thereof, clamping elements affixed to the torsion bar and cooperating with holding elements for clamping the printing plate, and actuators provided on both sides of the plate cylinder for stretching the printing plate in axial direction. The torsion bar is of bipartite construction, and the actuators, respectively, are mounted so as to be displaceable axially independently of one another.
Description




BACKGROUND OF THE INVENTION




Field of the Invention




The invention relates to a device for clamping the trailing edge of a printing plate in a plate cylinder of a rotary printing machine, including a torsion bar disposed in a cylinder gap extending in the longitudinal direction of the plate cylinder, and braced against cheeks of the plate cylinder, clamping elements cooperating with holding elements affixed to the torsion bar, for clamping the printing plate, and an actuator provided on the torsion bar for stretching the printing plate in axial direction, the torsion bar being rotatably mounted in a support bearing at the center of the cylinder.




A conventional embodiment of this type is disclosed in the published German Patent Document DE 42 44 279 A1, wherein a printing plate, when clamped, is adjustable to changes in the printing image by stretching the substrate to be processed. With this known construction, the trailing edge of the printing plate, as viewed in axial direction, can be stretched towards both sides from a support bearing arranged at the center. In addition, in this heretofore known construction, it is possible to stretch only one or the other side, so that in the event of a single-sided application of ink to the printing substrate, a matching or adjusted stretching of the trailing edge of the plate can be performed.




In practice, the problem often occurs that the printing plate has to be compressed small amounts in the end region thereof. This option is not provided in the devices heretofore known in the prior art.




SUMMARY OF THE INVENTION




It is accordingly an object of the invention to provide a device for clamping the trailing edge of a printing plate in a plate cylinder of a rotary printing press with which, in addition to stretching the trailing edge of the printing plate, end compression is also possible.




With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for clamping the trailing edge of a printing plate in a plate cylinder of a rotary printing machine, comprising a torsion bar disposed in a cylinder gap formed in the plate cylinder and extending in axial direction thereof, clamping elements affixed to the torsion bar and cooperating with holding elements for clamping the printing plate, and actuators provided on both sides of the plate cylinder for stretching the printing plate in axial direction, the torsion bar being of bipartite construction, and the actuators, respectively, being mounted so as to be displaceable axially independently of one another.




In accordance with another feature of the invention, each of the actuators is a hollow screw.




In accordance with a further feature of the invention, the clamping device includes a cup spring arranged between each of the actuators, respectively, and the torsion bar.




In accordance with an added feature of the invention, the hollow screw is formed with a through bore for accommodating the torsion bar free of contact therein.




In accordance with an additional feature of the invention, the hollow screw is formed with an external thread cooperating with a threaded bore formed in a cheek of the plate cylinder.




In accordance with yet another feature of the invention, the clamping device includes roller bearings wherein the torsion bar is rotatably and axially adjustably mounted.




In accordance with a concomitant feature of the invention, the torsion bar has a torsionally weak construction, and the clamping elements are individually affixed to the torsion bar.




An advantage of the invention is, in particular, that the trailing edge of the printing plate can be manipulated in many ways. For example, it is possible to stretch or to compress the printing plate in specific regions.




In an advantageous embodiment of the invention, a hollow screw, respectively braced against one of the cylinder cheeks, is provided as an actuator for applying axial actuating forces in both axial directions, and a spring, preferably a cup spring, arranged between the hollow screw and the actuating shaft, eliminates play resulting from production operations from the printing-plate stretching and compressing device.




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 clamping the trailing edge of a printing plate in a plate cylinder of a 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.




The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein:











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a diagrammatic side elevational view of a sheet-fed rotary printing machine with a plate cylinder for incorporating therein the clamping device according to the invention;





FIG. 2

is an enlarged fragmentary view of

FIG. 1

showing, in cross section, the plate cylinder with a cylinder channel thereof, and a clamping/holding element for a printing plate;





FIG. 3

is a fragmentary longitudinal sectional view of the plate cylinder, showing the cylinder gap therein with a stretching and compressing device according to the invention;





FIG. 4

is an enlarged fragmentary view of

FIG. 3

, more clearly showing an actuating element for actuating shafts; and





FIG. 5

is an enlarged fragmentary view of

FIG. 3

, more clearly showing a bearing location for the actuating shafts.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring now to the drawings and, first, particularly to

FIG. 1

thereof, there is shown therein a rotary printing machine


1


, for example, for processing sheets


7


, having a feeder


2


, at least one printing unit


3


,


4


and a delivery


6


. The sheets


7


are taken from a sheet pile


8


and are fed, separated or overlapped, over a feed table


9


to the printing units


3


and


4


. The latter include, in a conventional way, a respective plate cylinder


11


;


12


. Each of the plate cylinders


11


and


12


has a device


13


,


14


for affixing or fastening flexible printing plates. In addition, to each plate cylinder


11


;


12


, there is assigned a device


16


;


17


for semiautomatic or fully automatic printing-plate changing.




The sheet pile


8


rests on a pile board


10


which can be raised under control. Removal of the sheets


7


takes place from the top of the sheet pile


8


by a so-called suction head


18


which has a number of lifting and dragging suckers


19


and


21


, respectively, for separating the sheets


7


. Furthermore, blowing or blast devices


22


for loosening the upper layer of sheets, and sensing elements


23


for tracking the sheet pile


8


are provided. In order to align the sheet pile


8


, in particular, the top sheets


7


of the sheet pile


8


, a number of lateral and rear stops


24


are provided.




The plate cylinders


11


and


12


are identical in design terms, and therefore the invention will be described hereinbelow only with reference to the plate cylinder


11


, which has, at the ends thereof, cylinder cheeks or so-called Schmitz or bearer rings


26


and


27


-between which a cylinder gap


28


extends. Arranged in the cylinder gap is a two-part torsion bar


29


,


30


which are mounted by first ends thereof, respectively, in the cylinder cheeks


26


and


27


, and by second ends thereof in a central support


31


in the cylinder gap


28


. The central support


31


is in the form of a bushing and carries loose radial bearings


32


and


33


, respectively, wherein the second ends of the torsion bars


29


and


30


are supported. The loose radial bearings


32


and


33


therefore permit a rotational movement of the torsion bars


29


and


30


, as well as a displacement of the latter in the support


31


. The support


31


is screwed firmly to the plate cylinder


11


in the cylinder gap


28


. The first ends of the torsion bars


29


and


30


are mounted so that they are pivotable, respectively, by a needle bearing


34


in the cylinder cheeks


26


and


27


. At the outer end thereof, the respective torsion bar


29


,


30


bears a stop plate


36


, which is supported via an axial bearing


37


on an actuating element formed as a hollow screw


38


. The hollow screw


38


has a through bore


39


to accommodate the end of the respective actuating shaft


29


,


30


without contact, and is formed with an external thread


41


, with which the respective hollow screw


38


is screwed into a threaded hole


42


formed in the respective cylinder cheek


26


,


27


. The hollow screw


38


is supported via a disk spring


43


and a further axial bearing


44


at the end of a stop


46


fixed to the respective actuating shaft


29


,


30


. In addition to the stop


46


, printing-plate clamping pads


47


, respectively, distributed at a small distance from and located adjacent one another are firmly seated on the actuating shaft


29


,


30


. The pads


47


, respectively, have a holder


48


, whereon a clamping element in the form of a clamping gripper


49


is arranged so that it is pivotable, and cooperates with the printing-plate clamping pad


47


. A compression spring


51


braced against or supported on the plate cylinder


11


acts upon the clamping gripper


49


and therefore applies both the clamping force to the clamping gripper


49


and, in the clamping position, a clamping force to the printing-plate clamping pad


47


, as well. An actuating element


52


supported on or braced against the plate cylinder


11


, for example, in the form of pneumatic bellows, acts upon the printing-plate clamping pad


47


, counter to the force of the compression spring


51


, and thus releases or unclamps the printing plate


50


.




An additional clamping screw


53


is, respectively, arranged in a through bore


54


formed in the clamping gripper


49


and, with the thread thereof, respectively, engages in a threaded bore


56


formed in the printing-plate clamping pad


47


.




Through the intermediary of the clamping screws


53


, the printing plate


50


is partially specially affixed along the axial length of the printing-plate cylinder


11


, in order then to be able to perform a stretching or compression of the printing plate


50


by axial movement of the torsion bar


29


;


30


between the partial affixing locations. The part of the printing plate


50


which is clamped in only by the force of the compression spring


51


is therefore able to perform a relative movement, in particular, in the axial direction, with respect to the clamping device. Stretching or compression of the printing plate


50


can therefore be effected in each region located between a printing-plate clamping pad


47


which is arranged on the torsion bar


29


, and a printing-plate clamping pad


47


which is arranged on the torsion bar


30


.



Claims
  • 1. A device for clamping a trailing edge of a printing plate in a plate cylinder of a rotary printing machine, comprising a torsion bar adapted to be disposed in a cylinder gap formed in the plate cylinder and extending in axial direction thereof, clamping elements affixed to said torsion bar and being immovably mounted relative to said torsion bar, said clamping elements cooperating with a plurality of holding elements for clamping the printing plate, and actuators provided on both sides of the plate cylinder for stretching the printing plate in an axial direction, said torsion bar being of bipartite construction, and said actuators, respectively, being mounted to said torsion bar so as to be displaceable axially independently of one another.
  • 2. The clamping device according to claim 1, wherein each of said actuators is a hollow screw.
  • 3. The clamping device according to claim 1, including a cup spring arranged between each of said actuators, respectively, and said torsion bar.
  • 4. The clamping device according to claim 2, wherein said hollow screw is formed with a through bore for accommodating the torsion bar free of contact therein.
  • 5. The clamping device according to claim 2, wherein said hollow screw is formed with an external thread adapted to cooperate with a threaded bore formed in a cheek of the plate cylinder.
  • 6. The clamping device according to claim 1, including roller bearings wherein said torsion bar is rotatably and axially adjustably mounted.
Priority Claims (1)
Number Date Country Kind
199 60 073 Dec 1999 DE
US Referenced Citations (4)
Number Name Date Kind
3858512 Simeth Jan 1975 A
5168810 Kojima Dec 1992 A
5694854 Becker Dec 1997 A
5709149 Weber Jan 1998 A