Abstract:
A device for preventing a spring-loaded control roller from being lifted off a control cam therefor in a gripper control system in a sheet processing machine, includes a support mechanism disposed separately from the gripper control system. The support mechanism impresses an additional force upon the control roller in critical regions.

Description:
BACKGROUND OF THE INVENTION  
       FIELD OF THE INVENTION  
         [0001]    The invention relates to a device for sustaining a contact force of a control roller against a control cam appertaining thereto.  
           [0002]    When mechanically controlled grippers are installed on sheet guiding cylinders in printing presses, it is conventional for the grippers and gripper mechanisms, which are disposed on the sheet-guiding cylinders, such as impression cylinders, transfer cylinders, turning or reversing cylinders, storage cylinders, feed cylinders, and so forth, to be controlled cyclically by control rollers operating in conjunction with corresponding control cams. One or more spring elements ensure contact between the control rollers and the control cams. At high press speeds, the control rollers tend to lift away or jump from the control cams.  
           [0003]    German Patent 1 611 240 describes how to prevent jumping of the control rollers by providing forced control with inner and outer cams. Such devices are difficult to assemble and exhibit incorrectable play between the inner cam and the control roller, and between the control roller and the outer cam.  
           [0004]    European Patent Application EP 0 908 314 A1 describes a device wherein a spring, which is provided for pressing the control roller against a control cam, acts upon the control roller via a torque transmission mechanism. Through the use of that feature, the spring force acting on the control roller is sought to be approximately equal at the high and low points. It is impossible, however, separately and independently to control the forces of the control roller at the high and low points.  
         SUMMARY OF THE INVENTION  
         [0005]    It is accordingly an object of the invention to provide a device for sustaining a contact force of a control roller against a control cam appertaining thereto, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which prevents the lifting of a control roller from a control cam, the contact forces of which in critical regions are individually adjustable.  
           [0006]    With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for preventing a spring-loaded control roller from being lifted off a control cam thereof in a gripper control system in a sheet processing machine. The device comprises a support mechanism disposed separately from the gripper control system for impressing an additional force upon the control roller in critical regions.  
           [0007]    In accordance with another feature of the invention, the support mechanism includes two pivotably mounted levers, and a spring element having a spring force applied to the levers.  
           [0008]    In accordance with a further feature of the invention, one of the levers carries a support roller. The other of the levers carries a further control roller.  
           [0009]    In accordance with an added feature of the invention, the device further includes a further control cam. The further control roller is to be brought into active contact with the further control cam.  
           [0010]    In accordance with an additional feature of the invention, the further control cam is displaceably disposed.  
           [0011]    In accordance with yet another feature of the invention, the support roller is to be brought into active contact with an element of the gripper control system.  
           [0012]    In accordance with yet a further feature of the invention, the device further includes an actuating element and a connection therefrom to a control unit of the sheet processing machine. The further control curve is remotely displaceable by the actuating element via the connection to the control device of the sheet processing machine.  
           [0013]    In accordance with yet an added feature of the invention, the force of the spring element is adjustable.  
           [0014]    In accordance with yet an additional feature of the invention, the gripper control system includes a torsion spring for generating a contact force between the control roller and the control cam.  
           [0015]    In accordance with still another feature of the invention, the device further includes a control lever for the control roller. The control lever has a tooth connection for effecting a pivoting motion of a gripper shaft.  
           [0016]    In accordance with still a further feature of the invention, the gripper control system further includes a helical spring for generating a pressure force between the control roller and the control cam.  
           [0017]    In accordance with still an added feature of the invention, the control roller is disposed as a forerunning roller.  
           [0018]    In accordance with still an additional feature of the invention, the control roller is disposed as a follower roller.  
           [0019]    In accordance with another feature of the invention, the sheet processing machine is a printing press.  
           [0020]    In accordance with a further feature of the invention, the support mechanism includes a pivotably mounted lever carrying a support roller for bringing the support roller into active contact with an element of the gripper control system.  
           [0021]    In accordance with a concomitant feature of the invention, the element is a control lever formed with a control contour on a support surface cooperating with the support roller.  
           [0022]    A particular advantage of the invention is that an additional contact force acts precisely in the critical region wherein the control roller tends to lift and not in other regions. In that way, it is possible to reduce the wear at the control roller and the control cam and to improve the service life or durability thereof.  
           [0023]    A spring-loaded support mechanism cooperating with an additional control cam ensures a precise setting or application of the roller forces at the critical regions, for example when respectively opening and closing the grippers.  
           [0024]    Other features which are considered as characteristic for the invention are set forth in the appended claims.  
           [0025]    Although the invention is illustrated and described herein as embodied in a device for sustaining a contact force of a control roller against an appertaining control cam, 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.  
           [0026]    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. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    [0027]FIG. 1 is a diagrammatic, side-elevational view of a rotary printer wherein a roller control according to the invention may be embodied;  
         [0028]    [0028]FIG. 2 is an elevational view of a first exemplary embodiment of the roller control according to the invention;  
         [0029]    [0029]FIG. 3 is an elevational view of a second exemplary embodiment having a follower control roller;  
         [0030]    [0030]FIG. 4 is an elevational view of a third exemplary embodiment having a forerunning control roller; and  
         [0031]    [0031]FIG. 5 is an elevational view of a fourth exemplary embodiment of the roller control according to the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]    Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a rotary printing press, for example a printing press  1  to which a sheet  7  is fed, including a feeder  2 , at least one printing unit  3  or  4  and a delivery  6 . The sheets  7  are removed from a sheet pile or stack  8  and fed to the printing units  3  and  4  individually or in a shingled formation by way of a feedboard or feed table  9 . The printing units  3  and  4  include, in a conventional manner, plate cylinders  11  and  12 , respectively. The respective plate cylinders  11  and  12  include a respective device  13  and  14  for fastening flexible printing plates thereon. Moreover, respective devices  16  and  17  for automatic or semi-automatic printing-plate exchange are allocated to the plate cylinders  11  and  12 , respectively.  
         [0033]    The sheet pile  8  lies on a controllably liftable pile or stack plate  10 . Removal of the sheets  7  commences from the top of the pile  8  by a so-called suction head  18  which, among other things, has a number of lifting and dragging suckers  19  and  21  for singling or individually separating the sheets  7 . Furthermore, blowing or blast devices  22  are provided for loosening the top sheet layers, and scanning or feeling elements  23  are provided for tracking or readjusting the sheet pile. A number of lateral and rear stops are provided for aligning the sheet pile  8 , particularly the top sheet  7  of the sheet pile  8 .  
         [0034]    Any or all of the cylinders guiding the sheets and, therefore, carrying grippers, including a feed cylinder  31 , impression cylinders  32  and  33 , a transfer cylinder  34 , a storage drum  36 , and a reversing or turning drum  37 , can be furnished with a support mechanism  38  according to the invention.  
         [0035]    [0035]FIG. 2 illustrates the support mechanism  38  in the vicinity or region of the face of a respective cylinder carrying the grippers. At least one conventional gripper or pincers gripper  42  is disposed on a gripper shaft  43  which is pivotably mounted on the cylinder. A nose  44  of the gripper  42  works together with a gripper seat  46  for the purpose of transporting the sheet. The gripper shaft  43  has a gearwheel or first toothed segment  47  mounted thereon, the teeth of the gearwheel or toothed segment  47  meshing with a second toothed segment  48  which is disposed on the end of a control lever  49  pivotably mounted on the cylinder. A rotatably mounted control roller  50 , which is disposed on the opposite end of the control lever  49 , cooperates with a stationary control cam  51 . A bearing location  52  for the control lever  49  has a torsion spring  53  which is constructed as a torsion bar spring and which ensures a minimum required pressure force of the control roller  50  on the control cam  51 . In order to increase the supporting force up to a maximum required contact force, the control lever  49  is formed with a radially outwardly directed support surface  55  in the vicinity or region of the control roller  50 , which can be brought into supportive contact with a support roller  54  of the support mechanism  38  in critical regions. The support roller  54  is rotatably mounted at the end of a first support lever  56 , which is pivotably mounted on the cylinder. A second support lever  57  has the same mounting location on the cylinder as does the first support lever  56 , and carries an adjustable prestressed compression spring  58  at the end thereof, which acts upon the first support lever  56  in the region of the support roller  54 . Also disposed at the end of the second support lever  57  is a rotatably mounted control roller  59 , which cooperates with a stationary control cam  61 . The control cam  61  is disposed in critical regions, such as in the gripper opening region, for example. In this regard, the cam  61  acts with the control contour thereof upon the support roller  54  via the control roller  59 , the support lever  57  and the spring  58 , so that the support roller  54 , being spring loaded, influences the support surface  55  of the control lever  49  and thereby increases the overall spring power resulting from the force of the torsion spring  53  and the spring  58 . Due to these measures, the control roller  50  is prevented from being lifted off from the control cam  51 . In order to modify the timing and the force, respectively, of the action of the support mechanism  38 , the support cam  61  is pivotably mounted, and is remotely displaceable with the aid of an actuating element such as a motor  62  and connecting lines  63  to the control device or machine control unit  64  of the printing machine  1 .  
         [0036]    Outside the operating range or region of the control cam  61 , the support roller  54  is separated from the support surface  55 . In this region (approximately 330° machine angle), the support lever  57  abuts a stop  60 , so that the control roller  50  is pressed against the control cam  51  with considerably less force. The service life thereof is thereby increased.  
         [0037]    In the second exemplifying embodiment according to FIG. 3, the gripper shaft  43  is pivotable by a double-armed lever or bell crank  66  which is fastened to the gripper shaft  43 , and has a first arm carrying the rotatably mounted control roller  50 , and a second arm holding a helical spring  68  which is fixed to the cylinder and is braced against the second arm.  
         [0038]    In the region of the control roller  50  which cooperates with the control cam  51 , a support surface  55  is formed on the lever  66  and cooperates with the support roller  54  of the support mechanism  38 . The control roller  50  is disposed in front of, i.e., preceding, the gripper shaft  43  in the direction of cylinder rotation as a so-called forerunning roller. A spring-supported gripper opening process is thereby produced.  
         [0039]    In a third exemplifying embodiment, the control roller  50  is constructed as a so-called follower roller. A spring-supported gripper closing process is thereby produced.  
         [0040]    In a fourth exemplifying embodiment, as shown in FIG. 5, the support roller  54  is rotatably mounted on an end of the lever  56 , and the other end of the lever located opposite the support roller  54  is pivotably mounted on the frame of the sheet-processing or printing machine  1 . The support surface  55  of the control lever  49  has a control cam contour  69 . A prestressed spring  71  acts upon the lever  56  from above and moves it against a stationary stop  60  and into a waiting or maintenance position. The force of the spring  71  is remotely adjustable by the printing-machine control via a stationary drive  62 , for example, a servomotor. Upon the rotation of the gripper-carrying cylinder, the support roller  54  enters onto the active region of the control contour  69  applied to the control lever  49 . The support roller  54  is displaced counter to the force of the spring  71  by the contour  69  of the support surface  55 , so that the desired supporting force acts between the support roller  54  and the support surface  55 , which prevents the control roller  50  from lifting off from the control cam  51 . The support mechanism  38  described in the various exemplifying embodiments is always disposed in the region of an end face of the gripper-carrying cylinder, preferably between the end face of the cylinder and the side frame of the sheet processing or printing machine.