Abstract:
In an apparatus for adapting the pressing force of a control roller on a control can in a sheet-processing machine by a torsion spring, the apparatus either changes the effective spring length or the spring stiffness as a function of the rotational speed of the sheet-processing machine. The spring can be a torsion spring rod with an actuator setting the spring force by changing the prestress. A stiffening element can be connected to the torsion spring rod and set the spring force by changing the spring stiffness of the torsion spring rod.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Field of the Invention:  
         [0002]     The present invention relates to an apparatus for adapting the pressing force of a control roller on a control cam in a sheet-processing machine.  
         [0003]     In, for example, roller-controlled gripper devices in sheet-fed rotary presses, there is a problem that the control rollers provided for controlling the grippers, for example, are subjected to very high forces, in particular, at higher processing speeds and, therefore, high rotational speeds, which forces lead to the control rollers lifting off the control cams. This results in undefined gripper movement and increased wear of the control rollers. As a rule, this problem can be countered by the pressing forces of the control rollers on the control cams being matched to the highest processing speed.  
         [0004]     German Published, Non-Prosecuted Patent Application DE 199 56 369 A1 shows a gripper of a sheet-processing machine that is controlled by a control roller that interacts with a control cam. The pressing force of the control roller on the control cam can be set manually. However, the result of this is that a high setting of pressing forces is also very high at low and medium processing speeds, and, therefore, the control rollers and also the control cam are subject to increased wear.  
       SUMMARY OF THE INVENTION  
       [0005]     It is accordingly an object of the invention to provide a speed-dependent pressing force that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that permits automatic adaptation of the pressing force of control rollers and control cam to different operating conditions.  
         [0006]     With the foregoing and other objects in view, there is provided, in accordance with the invention, an apparatus for adapting a pressing force of a control roller on a control cam, including a prestressed spring having a force, the force of the spring to be set as a function of a rotational speed of a sheet-processing machine.  
         [0007]     With the objects of the invention in view, there is also provided an apparatus for adapting a pressing force of a control roller on a control cam, including a prestressed spring having a force, the force of the spring to be regulated as a function of the pressing force between the control roller and the control cam.  
         [0008]     It is a particular advantage of the invention that the service lives of the elements involved in the gripper control, such as control rollers and/or control cams, are increased.  
         [0009]     In accordance with another feature of the invention, provision is made to increase the prestressing force of a spring that produces the pressing force as a function of rotational speed, for example, by prestressing a torsion spring. The actuating devices provided are actuating measures that can be driven hydraulically, pneumatically, magnetically, or electrically.  
         [0010]     Further advantageous refinements relate to the configuration of speed-dependent pressure generators for supplying the actuating elements. In such a case, for example, a pressure generator or, else, a speed-controlled swash plate pump or a pressure transformer operating with centrifugal force can be provided.  
         [0011]     In accordance with a further feature of the invention, an electric pump is driven as a function of the rotational speed of the sheet-processing machine, for example, by the control computer.  
         [0012]     In accordance with an added feature of the invention, the pressing force is adapted by changing the spring rate or spring stiffness of the gripper system, for example, when a torsion spring is used, by increasing the spring stiffness by changing the length of the twistable proportion of the torsion spring as a function of the machine rotational speed by the form-fitting connection to a displaceable element.  
         [0013]     In accordance with an additional feature of the invention, provision is made to configure the elements that have elasticity in a manner that saves overall space by connecting them in parallel.  
         [0014]     In accordance with yet another feature of the invention, provision is made to control the adaptation of the pressing force of the spring system as a function of the actual pressing force between control roller and control cam, for example, measured by strain gages.  
         [0015]     In accordance with yet a further feature of the invention, the spring is a torsion spring rod having a prestress and an actuator is connected to the torsion spring rod and sets the spring force by changing the prestress of the torsion spring rod.  
         [0016]     In accordance with yet an added feature of the invention, the spring is a torsion spring rod having a spring force and a spring stiffness and a stiffening element is connected to the torsion spring rod and sets the spring force by changing the spring stiffness of the torsion spring rod.  
         [0017]     In accordance with yet an additional feature of the invention, the stiffening element has a holder surrounding the torsion spring rod and the holder is secured against rotation and displaced axially.  
         [0018]     In accordance with again another feature of the invention, there is provided an actuating motor connected to the stiffening element and displacing the stiffening element along the torsion spring rod.  
         [0019]     In accordance with again a further feature of the invention, the torsion spring rod is a plurality of torsion spring rods operatively connected in parallel with one another and the control roller is part of a cam-controlled gripper system in which the torsion spring rod, applies the pressing force.  
         [0020]     In accordance with again an added feature of the invention, a gear wheel coupling operatively connecting the torsion spring rods to one another.  
         [0021]     In accordance with again an additional feature of the invention, there is provided an actuator connected to at least one of the torsion spring rods for rotating the at least one of the torsion spring rods.  
         [0022]     In accordance with still another feature of the invention, the actuator has a hydraulically actuated operating cylinder.  
         [0023]     In accordance with still a further feature of the invention, the operating cylinder has an operating chamber and a stationary pump to be driven by a control computer as a function of the rotational speed of the sheet-processing machine is pressurizes the operating chamber.  
         [0024]     In accordance with still an added feature of the invention, there are provided a cylinder bearing the torsion spring rod, the operating cylinder having an operating chamber, and a hydraulic pump pressurizing the operating chamber and being driven by the cylinder bearing the torsion spring rod.  
         [0025]     In accordance with still an additional feature of the invention, a first feed line connects the pump to the operating chamber, an oil reservoir is fixed to the cylinder bearing the torsion spring rod, a second feed line connects the pump to the oil reservoir, and a restrictor connects the first feed line to the second feed line.  
         [0026]     With the objects of the invention in view, in a sheet-processing machine operating with a rotational speed and having a control roller and a control cam, there is also provided an apparatus for adapting a pressing force of the control roller on the control cam, including a prestressed spring having a force, the force of the spring being set as a function of the rotational speed of the sheet-processing machine.  
         [0027]     With the objects of the invention in view, there is also provided a sheet-processing machine, including a sheet-processing assembly operating with a rotational speed, the sheet-processing assembly having a control roller and a control cam, the control roller contacting the control cam with a pressing force, and an apparatus for adapting the pressing force of the control roller on the control cam, the adapting apparatus having a prestressed spring having a force, the force of the spring being set as a function of the rotational speed of the sheet-processing assembly.  
         [0028]     With the objects of the invention in view, in a sheet-processing machine having a control roller and a control cam, there is also provided an apparatus for adapting a pressing force of the control roller on the control cam, including a prestressed spring having a force, the force of the spring being regulated as a function of the pressing force between the control roller and the control cam.  
         [0029]     With the objects of the invention in view, there is also provided a sheet-processing machine, including a sheet-processing assembly having a control roller and a control cam, the control roller contacting the control cam with a pressing force, and an apparatus for adapting the pressing force of the control roller on the control cam, the adapting apparatus having a prestressed spring having a force, the force of the spring being regulated as a function of the pressing force between the control roller and the control cam.  
         [0030]     Other features that are considered as characteristic for the invention are set forth in the appended claims.  
         [0031]     Although the invention is illustrated and described herein as embodied in a speed-dependent pressing force, it is, nevertheless, not intended to be limited to the details shown because 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.  
         [0032]     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  
       [0033]      FIG. 1  is a diagrammatic cross-sectional view of a sheet-processing rotary press according to the invention;  
         [0034]      FIG. 2  is a fragmentary, diagrammatic, cross-sectional view of a sheet-transporting cylinder;  
         [0035]      FIG. 2A  is a partially block circuit and partially cross-sectional view of a first exemplary embodiment for driving a hydraulic actuator according to the invention;  
         [0036]      FIG. 2B  is a diagrammatic cross-sectional view of a second exemplary embodiment for driving the hydraulic actuator according to the invention;  
         [0037]      FIG. 3  is a diagrammatic cross-sectional view of a third exemplary embodiment of a way to change the spring stiffness of the gripper system according to the invention; and  
         [0038]      FIG. 4  diagrammatic cross-sectional view of a fourth exemplary embodiment according to the invention with regulated pressing force.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]     Referring now to the figures of the drawings in detail and first, particularly to  FIG. 1  thereof, there is shown a machine  1  that processes sheets  7 , for example, a press, having a deliverer  2  (also referred to as a delivery), at least one printing unit  3  and  4  and a deliverer  6 . The sheets  7  are taken from the sheet stack  8  and, separated or overlapping, are supplied over a feed table  9  to the printing units  3  and  4 . The units  3 ,  4  each contain a plate cylinder  11 ,  12  in the known way. The plate cylinders  11 ,  12  each have an apparatus  13 ,  14  for fixing flexible printing plates. Furthermore, each plate cylinder  11 ,  12  is associated with an apparatus  16 ,  17  for the semiautomatic or fully automatic printing plate change.  
         [0040]     The sheet stack  8  rests on a stack board  10  that can be raised under control. The sheets  7  are removed from the top side of the sheet stack  8  by what is referred to as a suction head  18  that, inter alia, has a number of lifting and dragging suckers  19 ,  21  for separating the sheets  7 . Furthermore, blower devices  22  are provided for loosening the upper layers of sheets, and sensing elements  23  for tracking the stack. To align the sheet stack  8 , in particular, the upper sheets  7  of the sheet stack  8 , a number of lateral and rear stops  24  are provided.  
         [0041]     The sheets are transported through the sheet-processing machine by gripper systems  29  disposed on the transport cylinders  24 ,  26 ,  27 ,  28 . The construction of these gripper systems is substantially the same and will, therefore, be described only by using the transfer cylinder  27 .  
         [0042]      FIG. 2  shows a gripper bar, as it is known, which is mounted such that it can be pivoted in a cylinder channel  31  of the transfer cylinder  27 . The gripper bar substantially includes a gripper tube  32  that carries a number of grippers  33  disposed beside one another at intervals. At its first end, the gripper tube  32  bears a control lever  34  for a control roller  36  that, under the force of a torsion spring  37 , is in operating contact with a control cam  38  configured to be stationary. The torsion spring  37  is a torsion spring rod that is surrounded coaxially by the gripper tube  32  and, at the end facing the control roller  36 , is firmly connected to the gripper tube  32 . At the other end, the torsion spring  37  projects out of the gripper tube  32  and, between a bearing point  39  for the torsion spring rod  37  and the gripper tube  32 , bears a gear wheel  41 .  
         [0043]     The gear wheel  41  meshes with a further gear wheel  42 , which is fixed to a second torsion spring  43  and, in particular, a torsion spring rod, disposed parallel to the first. The second torsion spring  43  has a first rotatable mounting  44  and, on the opposite side, a fixed clamping device  46 .  
         [0044]     The second torsion spring  43  bears an actuator  47  that can be driven as a function of the rotational speed of the sheet-processing machine and can be actuated accordingly, which effects twisting of the two torsion spring rods  37  and  43 . The torsion spring rods  37 ,  43  are installed such that they are stressed with respect to each other so that the control roller  36  is pressed with slight pressure against the control cam  38  when the machine is at a standstill. As the rotational speed increases, the actuator  47  brings about twisting of the torsion spring  43  and, thus, through the gear wheel connection  42 ,  41 , twisting of the torsion spring  37  and, respectively, a higher pressing force of the control roller  36  on the control cam  38 .  
         [0045]     The actuator  47  operates electrically, magnetically, pneumatically, or, preferably, hydraulically.  
         [0046]     For such a purpose, as illustrated in  FIG. 2A , an externally disposed hydraulic pump  49  that can be driven electrically is provided that, as a function of rotational speed from the control computer  51  of the sheet-processing machine, pressurizes the actuator  47  through, for example, a rotary leadthrough. As illustrated in  FIGS. 2A and 2B , the actuator  47  substantially includes an operating cylinder  52 , whose cylinder body  53  is fixed to the cylinder  27  at the mounting position of the fixed clamping device  46 . The operating cylinder  52  has a piston  54  that is fixed against rotation in its cylinder body and that, by a pin  55 , engages in an oblique groove  56  in a second cylinder  57 . The second cylinder  57  is connected to the torsion spring rod  43  such that the axis  58  of the torsion spring  43  is identical to the mid-axis  58  of the operating cylinder  53 . Loading the operating chamber  59  (see  FIG. 2B ) formed between the cylinder body  53  and piston  54  leads to a translation or displacement of the piston  54  and twisting of the second cylinder  57  and of the torsion spring rod  43 , produced through the pin  55  and inclined groove  56 .  
         [0047]     A further possible way of driving or pressurizing the actuator  47 , in particular, the operating cylinder  52 , is shown by  FIG. 2B . An axial piston pump  63  disposed in a stationary manner on a frame wall  62  of the sheet-processing machine  1  is driven by the rotation of the cylinder journal  64  (for example, drive of the swash plate) and supplies the operating cylinder  52  through a line  66  with an operating medium, preferably, hydraulic oil. A second line  67  connects a hydraulic oil reservoir  69  disposed in the cylinder  27  to the axial piston pump  63 . The lines  66 ,  67  are connected to a line in which a restrictor  68  is incorporated. The volume flow delivered by the pump  63  produces a back-pressure region upstream of the restrictor  68 , the back-pressure region being used to drive the operating cylinder  53 .  
         [0048]     In a third exemplary embodiment, according to  FIG. 3 , provision is made to make the stiffness of the entire spring system variable by changing the twistable length of the torsion spring rod  43  as a function of the rotational speed of the sheet-processing machine. The torsion spring rod  43 , formed as a square, is, in this case, surrounding coaxially with a clearance fit by a holder  71  that can be moved axially. The holder  71  is mounted so as to be fixed against rotation and is driven by a threaded bore mechanism  72  driven by a motor  73  that can be driven by the machine controller  51 .  
         [0049]     A displacement of the holder  71  in the direction of the fixed clamping device  46  lengthens the twistable length of the torsion spring rod  43 , which means that the spring stiffness of the entire gripper system decreases and the pressing force of the control roller  36  on the control cam  38  is reduced. As the machine rotational speed increases, the holder  71  is moved in the opposite direction, which means that the spring stiffness of the gripper system is increased and the pressing force of the control roller  36  on the control cam  38  increases.  
         [0050]     In a fourth exemplary embodiment according to  FIG. 4 , provision is made to dispose, on the control lever  34 , a force sensor, for example, a strain gauge (DMS)  74 , which is connected to the control computer  51  and determines the pressing force with which the control roller  36  is pressed onto the control cam. By using predefined data in the form of characteristic curves or formulas, the control computer  51  uses the measured data to determine the actuating values for the actuator  47 .  
         [0051]     This application claims the priority, under 35 U.S.C. § 119, of German patent application No. 10 2004 014 868.6, filed Mar. 26, 2004; the entire disclosure of the prior application is herewith incorporated by reference.