Process and device for the qualitative assessment of processed sheets

Information

  • Patent Grant
  • 6192140
  • Patent Number
    6,192,140
  • Date Filed
    Tuesday, February 17, 1998
    26 years ago
  • Date Issued
    Tuesday, February 20, 2001
    23 years ago
Abstract
The quality of processed or printed sheets is assessed while the sheets are supported on the periphery of a drum. The surface of each drum is provided with sheet leading and trailing end gripper systems which are circumferentially, and axially shiftable with respect to each other. Each sheet to be inspected is stretched tightly on the periphery of its supporting drum before the quality of the printing or other processing done to the sheet is assessed.
Description




FIELD OF THE INVENTION




The present invention relates to a method and a device for the qualitative assessment of processed sheets.




DESCRIPTION OF THE PRIOR




DE 32 20 098 C2 describes a numbering machine with a device for the qualitative assessment, by means of two testing cylinders, of the front and reverse sides of sheets to be numbered.




It is a limitation of this prior art device that no guide elements for holding the sheets on the testing cylinders are provided.




DE 42 23 555 A1 discloses a drum for transporting sheets in a reversing device of a sheet-fed rotary printing press. This drum is provided with grippers for gripping the front edge of the sheets, and with displaceable suction elements for stretching the rear edge of the sheet tight.




SUMMARY OF THE INVENTION




It is the object of the present invention to create a method and a device for the qualitative assessment of processed sheets.




This object is attained in accordance with the present invention by providing at least one drum which receives the sheet to be inspected. This drum passes the sheet by an image recording device, and is provided with a first holding device that grips the leading end of the sheet. At least one second holding device is also provided on the drum and holds the trailing end of the sheet. The two holding devices stretch the sheet tightly both circumferentially and axially on the surface of the drum prior to the inspection of the sheet. Once the sheet has been gripped and stretched, one page on the sheet can be inspected.




By means of the method or the device in accordance with the present invention, it is possible in an advantageous manner to prevent false measurements because of sheets having creases or being dished or otherwise deformed. The dependability of the image inspection is considerably increased, in particular in case of sheets having creases.




The arrangement of two drums, both of which have two holding devices for stretching the sheets tight, in particular makes a dependable inspection of the front and reverse sides of the sheets after their processing is finished possible.











BRIEF DESCRIPTION OF THE DRAWINGS




The device for the qualitative assessment of processed sheets in accordance with the present invention is represented in the drawings and will be described in more detail in what follows.




Shown are in:





FIG. 1

, a schematic lateral view of a device for the qualitative assessment of printed sheets;





FIG. 2

, a schematic plan view of a drum.











DESCRIPTION OF THE PREFERRED EMBODIMENT




A device generally at


1


, for the qualitative assessment of processed sheets


5


has been installed in a sheet-processing machine. In the present preferred embodiment, this is a sheet-fed rotary printing press, which imprints sheets of paper


5


on their front and reverse sides


2


,


3


.




For reasons of simplification, only the sheet transport device downstream of the print units, as far as the deposit of the sheets


5


on stacks


4


,


6


,


7


in a delivery device


8


, has been represented.




Processed sheets


5


are understood to be, for example, sheets


5


which have been printed, embossed or provided with a pattern in other ways.




A first chain conveyor


9


is arranged following a printing cylinder, not represented. The chains


11


of this chain conveyor


9


first extend horizontally in the vicinity of the floor, and then vertically as far as across the stacks


4


,


6


,


7


of the delivery device


8


, to a first chain wheel


10


. Chain gripper devices


12


are fastened on these chains


11


. Following the vertical portion of this first chain conveyor


9


, horizontally extending chains


13


of a second chain conveyor


14


are arranged, on which chain gripper devices


16


are also provided. These chains


13


are reversed by two chain wheels


15


,


20


. A first drum


17


is arranged to work together with these chain gripper devices


16


, and a second drum


18


directly cooperates with it. Following this, a third chain conveyor


19


, with chains


38


is arranged directly above the stacks


4


,


6


,


7


, which conveys the sheets


5


to the stacks


4


,


6


,


7


of the delivery device


8


. The chains


38


are reversed by means of three chain wheels


39


,


41


,


42


. In the present preferred embodiment, chain gripper systems


21


of the third chain conveyor


19


can selectively deposit the sheets


5


on one of the three stacks


4


,


6


,


7


. For example, inspected sheets


5


, which do not comply with the present quality requirements, are deposited on one (in the example the left stack


7


) of the three stacks


4


,


6


,


7


.




The two drums


17


,


18


respectively, as seen also in

FIG. 2

, each consist essentially of a first drum base body


22


with first segments


23


, a second drum base body


24


with second segments


26


, and first holding devices


27


and second holding devices


28


. The holding devices can be respectively embodied as gripper or suction devices. The first drum base body


22


is seated by means of hollow shaft journal in lateral frames of the delivery device


8


. A shaft


29


is pivotably seated in this hollow shaft journal. The second segments


26


extending in the circumferential direction are fastened next to each other on this shaft


29


. The second holding device


28


is arranged, displaceable in the circumferential direction and the axial direction, in the area of the ends of the segments


26


. This second holding device


28


is constituted by a plurality of suction devices


28


, arranged next to each other in the axial direction, which can be charged with suction air in a controlled manner.




The first holding device


27


in the form of controllable grippers


27


, arranged next to each other in the axial direction, is provided at the beginning of the first drum base body


22


. First


23


and second segments


26


are arranged meshing in a comb-like manner, so that a cylinder-shaped peripheral surface


31


is formed. The distance between suction devices


28


and grippers


27


in the circumferential direction, i.e. a length


131


of the surface


31


in the circumferential direction, can be adapted to a length


11


of the sheets


1


to be processed. To this end the first


23


and second segments


26


are pivotable in the circumferential direction and can be fixed in place following the process of setting the length of surface


31


. In the present preferred embodiment, each drum


17


,


18


is designed as a “double-size” drum


17


,


18


, i.e. two first


27


and two second holding devices


28


with the associated elements


23


,


26


are arranged on the circumference, offset by 180° in respect to each other.




Each one of these two drums


17


,


18


has been assigned its own inspection device. Essentially this inspection device, as shown in

FIG. 1

, consists of an illumination device


32


,


33


and an image recording device


34


,


36


. In the present preferred embodiment, a plurality of stroboscopic flashes


37


is provided as the illumination device


32


,


33


, which are arranged in such a way that an even illumination of the sheet


5


to be inspected takes place. This means that an angle and a distance of the light outlet surface of the stroboscopic flashes


37


are matched to the surface


31


of the drum


17


,


18


and to the lens of the image recording device


34


,


36


.




The respective image recording device


34


,


36


consists of at least one planar CCD camera, preferably of two planar CCD cameras


34


,


36


, arranged next to each other in the axial direction of the drum


17


,


18


. Preferably four individual recordings, corresponding to each quadrant, are taken of each sheet


5


to be inspected, which are again superimposed on each other to form a whole image in an evaluation device connected downstream of the planar CCD cameras


34


,


36


. This whole image is then evaluated, for example in a method corresponding to the method described in DE 42 06 366 A1.




Two successive images per sheet


5


to be inspected are recorded by each one of the two planar CCD cameras


34


,


36


.




However, it is also possible to record a single image of the sheets


5


by means of a single planar CCD camera.




The inspection device is disposed downstream of the transfer area from the second chain conveyor


14


and the first drum


17


in such a way that, after stretching, the sheet


5


to be inspected is located in the evaluation area of the planar CCD camera


34


. The second inspection device is arranged in the same way between the transition area from the first drum


17


to the second drum


18


, or respectively the second drum


18


and the third chain conveyor


19


.




The mode of operation of the device in accordance with the present invention is as follows:




The chain gripper devices


12


of the first chain conveyor


9


take over the printed sheets


5


from a printing cylinder, not represented. The inspection of the front


2


and reverse side


3


of the sheets


5


only takes place after printing, i.e. following complete processing, as the last work step prior to deposition in the sheet processing machine. These chain gripper devices


12


convey the sheets


5


first in the horizontal, then in the vertical direction to the second chain conveyor


14


arranged above the stacks


4


,


6


,


7


, and transfer the sheets


5


to the first drum


17


. In the process, the grippers


27


of the first drum


17


grip the beginning of the sheet


5


to be inspected. After approximately one-half rotation of the drum


17


, the end of each of the sheets


5


reaches the area of the suction devices


28


, which are thereupon charged with suction air and in this way grasp the end of the sheets


5


. Subsequently, the suction devices


28


perform a movement both in the circumferential direction and the axial direction of the drum


17


and in this manner tightly stretch the sheet


5


. Now the sheet


5


lies, free of creases, on the first drum


17


. In the present example, the reverse side


3


of the sheets


5


faces away from the drum


17


and points in the direction toward the planar CCD cameras


34


. Now the stroboscopic flashes


37


illuminate the sheet


5


for the first time, and the two planar CCD cameras


34


record the two adjoining individual images of the forward half of the sheets


5


. The sheet


5


is stretched tight before the first single image is recorded. After a rotation of the drum


17


corresponding to one-half length of the sheet


5


, the two successive individual images of the rear half of the sheet


5


are recorded. Only after all individual images, or respectively the total image, of the sheet


5


has been recorded, the sheet


5


is then transferred to the second drum


18


for inspecting the front side


2


of the sheet


5


.




The grippers


27


of the first drum


17


transfer the beginning of the sheet


5


to the grippers


27


of the second drum


18


. In this way the sheet is conveyed by the second drum


18


and the reverse side


3


of the sheet


5


, which faced to the outside on the first drum


17


, moves inward to overlie the surface


31


of the second drum


18


, so that the front side


2


of the sheet


5


now faces to the outside. As soon as the suction devices


28


of the first


17


and the second drum


18


come into the transfer area (i.e. into the area of the common centers of the two drums


17


,


18


), the suction air for the suction devices


28


of the first drum is turned off and the suction devices


28


of the second drum


18


are charged with suction air. By means of this, the end of the sheet


5


is grasped by the suction devices


28


of the second drum


18


. Subsequently, the suction devices


28


of the second drum


18


are moved in the circumferential direction and in the axial direction of the second drum


18


. Here the suction force generated by the suction devices


28


on the end of the sheet


5


is designed to be such that, although the sheet


5


is stretched tightly, the sheet


5


begins to slide on the suction devices


28


before the tear resistance of the sheet


5


is overcome.




Only after the sheet


5


has been completely stretched tight on the second drum


18


, are individual images of the forward half of the front side


2


of the sheet


5


recorded. Thereafter, the two individual images of the rear half of the sheet


5


are recorded. Here, too, the beginning of the sheet


5


is only transferred to the chain gripper devices


21


of the third chain conveyor


19


after the entire image of the sheet


5


has been completely recorded. The third chain conveyor


19


is triggered by the evaluation device of the inspection device in such a way, that it selectively deposits the inspected sheets


5


which satisfy the quality requirements on the first


4


or second stack


6


, while the inspected sheets


5


, which do not meet the quality requirements, are deposited on the third stack


7


.




It is also possible for the sheets


5


to be inspected not to be directly transferred from the first drum


17


to the second drum


18


, but to be transferred by means of interposed conveying means, for example further drums. In this case, the interposed conveying means are arranged in such a way, that the first side


3


of sheet


5


faces toward the outside on the first drum


17


, and on the second drum the second side


2


of sheet


5


faces outward.




In place of the drums


17


,


18


, which stretch the sheets


5


tight, a chain conveyor can also be provided with two holding devices cooperating in pairs, for example. These holding devices are arranged so they perform a relative movement which stretches the sheets


5


, wherein respectively one holding device grasps the beginning and one holding device the end of each of the sheets


5


.




While a preferred embodiment of a method and device for the qualitative assessment of sheets in accordance with the present invention has been set forth filly and completely hereinabove, it will be apparent to one of skill in the art that a number of changes in, for example, the size of the sheets being printed, the type of printing being performed, the type of printing press being used, and the like could be made without departing from the true spirit and scope of the present invention, which is accordingly to be limited only by the following claims:



Claims
  • 1. A method for accomplishing a qualitative assessment of processing on a sheet including:providing a first image recording inspection and evaluation device including at least a first planar CCD camera facing a first side of a processed sheet to be assessed; locating a first sheet support drum adjacent said first image recording inspection and evaluation device; providing first and second sheet end holding devices on said first sheet support drum; utilizing said first and second sheet end holding devices to grasp leading and trailing ends of a processed sheet supplied to said first sheet support drum; moving at least one of said first and second sheet end holding devices circumferentially and axially on said first sheet support drum; stretching said processed sheet circumferentialy on said first sheet support drum during said circumferential movement of said at least one of said first and second sheet end holding devices of said first sheet support drum; stretching said processed sheet axially on said first sheet support drum during said axial movement of said at least one of said first and second sheet end holding devices of said first sheet support drum; performing a qualitative assessment of said first side of said processed sheet in said first image recording inspection and evaluation device after said circumferential and axial stretching of said processed sheet on said first sheet support drum by taking two successive, circumferentially spaced images of said processed sheet using said first planar CCD camera; providing a second image recording inspection and evaluation device including at least a second planar CCD camera facing a second side of said processed sheet to be assessed; locating a second sheet support drum adjacent said second image recording inspection and evaluation device and after, in a direction of travel of said processed sheet said first sheet support drum; providing first and second sheet end holding devices on said second sheet support drum; utilizing said first and second sheet end holding devices of said second sheet support drum to grasp leading and trailing ends of said processed sheet supplied to said second sheet support drum from said first sheet support drum; moving at least one of said first and second sheet end holding devices of said second sheet support drum circumferentially and axially on said second sheet support drum; stretching said processed sheet circumferentially on said second sheet support drum during said circumferential movement of said at least one of said first and second sheet end holding devices of said second sheet support drum; stretching said processed sheet axially on said second sheet support drum during said axial movement of said at least one of said first and second sheet end holding devices of said second sheet support drum; performing a qualitative assessment of said second side of said processed sheet in said second image recording inspection and evaluation device after said circumferential and axial stretching of said processed sheet on said second sheet support drum by taking two successive, circumferentially spaced images of said processed sheet using said second planar CCD camera; providing a processed sheet delivery device after, in said direction of travel of said processed sheet, said second sheet support drum; locating at least first and second processed sheet receiving stacks in said processed sheet delivery device; directing said processed sheets to said sheet delivery device from said second sheet support drum; and using said first and second image recording inspection and evaluation devices to deposit each said processed sheet on a selected one of said at least first and second processed sheet receiving stacks.
Priority Claims (1)
Number Date Country Kind
196 24 196 Jun 1996 DE
PCT Information
Filing Document Filing Date Country Kind 102e Date 371c Date
PCT/DE97/01201 WO 00 2/17/1998 2/17/1998
Publishing Document Publishing Date Country Kind
WO97/48556 12/24/1997 WO A
US Referenced Citations (6)
Number Name Date Kind
4448121 Uno et al. May 1984
5086698 Wirz Feb 1992
5186107 Wieland Feb 1993
5241907 Dörsam et al. Sep 1993
5317390 Bolza-Schunemann et al. May 1994
5471309 Bolza-Schünemann Nov 1995
Foreign Referenced Citations (7)
Number Date Country
32 020 098 Dec 1982 DE
42 23 555 Feb 1993 DE
42 06 366 Feb 1993 DE
42 17 942 Dec 1993 DE
44 36 583 Apr 1996 DE
0 317 665 May 1989 EP
0 576 824 Jan 1994 EP
Non-Patent Literature Citations (1)
Entry
English Translation of DE 44 36 583 to Butcher, Apr. 1996.