Abstract:
A cam mechanism includes a control cam and a control roller rolling on the control cam to produce a deflection of the control roller. The control cam and the control roller each have a respective anti-twist safeguard, protection or device interacting with each other and being constructed, for example, as a toothing system. An alignment cylinder for sheets and a sheet processing machine are also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority, under 35 U.S.C. § 119, of German Patent Application DE 10 2009 014 058.1, filed Mar. 20, 2009; the prior application is herewith incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a cam mechanism for producing a deflection, stroke or travel of a control roller rolling on a control cam. 
         [0003]    Since, in a control cam-control roller mechanism, it is primarily a matter of the control roller experiencing a deflection resulting from the control contour of the control cam, it is normally completely sufficient if the control roller has a relatively small circumference in relation to the control cam and the circumference or the length of the control cam is an integer multiple of the circumference of the control roller, in order to achieve reproducible results with a satisfactory accuracy. 
         [0004]    In a cam mechanism for actuating a pregripper in a sheet processing machine, which is known from German Patent DE 43 16 599 C2, corresponding to U.S. Pat. No. 5,544,546, a rotating control cam interacts with a control roller disposed on the pregripper. 
         [0005]    In that case, the circumference of the control cam is an integer multiple of the circumference of the control roller. 
         [0006]    However, in devices of that type, as a result of fabrication inaccuracies, circularity errors or slippage, it is possible for the point of contact between the control cam and the control roller to vary, in particular in the two “sheet acceptance” and “sheet transfer” functional positions of the pregripper, as a result of a rotational angle offset between the control cam and the control roller. 
       SUMMARY OF THE INVENTION 
       [0007]    It is accordingly an object of the invention to provide a cam mechanism having a control cam and a control roller, an alignment cylinder and a sheet processing machine, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which avoid any rotational angle offset between a control cam and a control roller, in particular in the area of the functional positions. 
         [0008]    With the foregoing and other objects in view there is provided, in accordance with the invention, a cam mechanism, comprising a control cam, and a control roller rolling on the control cam to produce a deflection of the control roller. The control cam and the control roller each have a respective anti-twist safeguard, protection or device interacting with each other. 
         [0009]    It is a particular advantage of the invention that the control cam has an anti-twist safeguard, protection or device with respect to the control roller, in particular in the area of functional positions. As a result of this measure, a point of contact between the control cam and the control roller in the area of the functional positions can be reproduced unambiguously. In this way, circularity errors, fabrication tolerances, slippage and play in the bearings remain constant and thus without any influence. 
         [0010]    In a preferred embodiment, provision is made for the control cam and the control roller to each have an intermeshing toothing system. This can preferably be disposed in each case parallel to the running surface of the control cam and the control roller. 
         [0011]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0012]    Although the invention is illustrated and described herein as embodied in a cam mechanism having a control cam and a control roller, an alignment cylinder and a sheet processing 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. 
         [0013]    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 SEVERAL VIEWS OF THE DRAWING 
       [0014]      FIG. 1  is a diagrammatic, longitudinal-sectional view of a sheet processing machine, in particular a printing press; 
         [0015]      FIG. 2  is an enlarged, fragmentary longitudinal-sectional view of a feed cylinder having a toothed cam drive according to the invention for front lays; 
         [0016]      FIG. 3  is a fragmentary, plan view of a cam mechanism according to the invention having a toothed ring-gear wheel anti-twist safeguard, protection or device; 
         [0017]      FIG. 4  is a front-elevational view of a further exemplary embodiment having a chain-sprocket anti-twist safeguard, protection or device; 
         [0018]      FIGS. 5A and 5B  are respective front-elevational and side-elevational views of a further exemplary embodiment having a pin wheel anti-twist safeguard, protection or device; and 
         [0019]      FIGS. 6A and 6B  are respective front-elevational and side-elevational views of a further exemplary embodiment having a driver-stop anti-twist safeguard, protection or device. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen a machine, for example a printing press  1 , 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 stack  8  and, separated or in overlapping formation, are fed over a feed table  9  to the printing units  3 ,  4 . The latter each contain, in a known manner, a plate cylinder  11 ,  12  and a blanket cylinder  15 ,  20  interacting therewith in each case. The plate cylinders  11 ,  12  each have a clamping and tensioning apparatus  13 ,  14  for fixing flexible printing plates. Furthermore, each plate cylinder  11 ,  12  is assigned an apparatus  16 ,  17  for semiautomatic or fully automatic printing plate change. 
         [0021]    The sheet stack  8  rests on a stack board  10  that can be raised under control. The removal of the sheets  7  is carried out from the top of the sheet stack  8  through the use of a so-called suction head  18  which, amongst other things, has a number of lifting and dragging suckers  19 ,  21  for separating the sheets  7 . Moreover, blowing devices  22  are provided in order to loosen the upper sheet layers, as are sensing elements  23  for stack tracking. A number of side and rear stops  24  are provided in order to align the sheet stack  8 , in particular the upper sheets  7  of the sheet stack  8 . 
         [0022]    At the end of the feed table  9  which, in particular, is a suction belt table, there is disposed a printing unit cylinder, e.g. a feed cylinder  26 , which grips the sheets  7  at their leading edge and transfers them to a downstream cylinder  27 , for example an impression cylinder. 
         [0023]    As is seen in  FIG. 2 , an alignment cylinder  28 , which is driven at the speed of the feed cylinder  26 , is provided underneath the feed cylinder  26 , approximately tangentially to a feed plane E formed by the feed table  9 . A number of front lay supports  30  having front lay stops  31  are disposed on a common pivot shaft  29 , spaced apart from one another transversely with respect to the sheet transport direction. The pivot shaft  29  is pivotably mounted on the cylinder body of the alignment cylinder  28 . 
         [0024]    A respective stop  32  is provided at an end of each front lay support  30 , which is opposite the front lay stop  31 , for a mating stop formed as a roller  33 . The mating stop  33  is seated in such a way that it can rotate at a first end of a double-armed cam lever  34 , which is pivotably mounted on the alignment cylinder  28 . A control roller  36  of a cam mechanism  41  is mounted so as to continue to rotate about its rotational axis on a second end of the double-armed lever  34 . The control roller  36 , which is disposed so as to be stationary, is in operative contact with a contour of a control cam  37  of the cam mechanism  41 . A compression spring  38 , which is supported on the alignment cylinder  28 , presses with prestress on the front lay support  30 , so that the front lay  31  is pivoted out of the periphery of the alignment cylinder  28  under the force of the spring  38 . In this case, the control roller  33  is in continuous contact with the stop  32  of the front lay support  30  and controls the movement of the front lay  31 . 
         [0025]    In order to align a leading sheet edge, the front lays  31  are pivoted out of the periphery of the alignment cylinder  28  as far as the plane E. Through the use of transport systems disposed on the feed table  9 , for example a suction belt, the sheet  7  is conveyed towards the front lays  31  at a speed V 1  which is greater than a speed V 2  of the front lays  31  in the sheet transport direction. In this case, the sheet  7  is aligned in the sheet transport direction and with respect to a skewed position. 
         [0026]    Following the completion of the alignment phase, the sheet is picked up by transport grippers  39  of the feed cylinder  26 . A speed V 3  of the transport grippers  39  is then synchronized with the speed V 2  of the stops, that is to say the speeds V 2 =V 3  at the time of closure of the grippers  39 . 
         [0027]    During the alignment phase, the front lays  31  are moved translationally along an imaginary extension—plane E—of the feed table  9 . The sheet is aligned in the transport direction and also with respect to a skewed position on the front lays  31  during the alignment phase and is then gripped by the transport grippers  39  of the feed cylinder  26 . Following the closure of the transport grippers  39 , the front lays  31  dip into the periphery of the alignment cylinder  28 , until, shortly before reaching the plane E, they are pivoted out of the periphery of the alignment cylinder  28  into the plane E in order to align the next sheet  7 . 
         [0028]    In order to ensure that the control roller  36  always rolls on the control cam  37  without slippage, provision is made for both the control cam  37  and the control roller  36  to each be assigned a respective toothing system  42 ,  43  with the same tooth modulus. In this case, a pitch circle of the toothing systems  42 ,  43  preferably lies at the height of the contour of the control cam  37 . The toothing systems can, for example, be gear wheels or toothed rings, which are disposed on respective hubs  44 ,  46  of the control cam  37  and the control roller  36 , as seen in  FIGS. 2 and 3 . Elements  42 ,  43  thus each form an anti-twist device. 
         [0029]    In an exemplary embodiment according to  FIG. 4 , provision is made for a chain  47  to be disposed on the hub  44  of the control cam  37  and to mesh with a sprocket  48  disposed axially parallel to the control roller  36 . 
         [0030]    In this case, the number of engagement points of the chain  47  is an integer multiple of the teeth of the sprocket  48 . Elements  47 ,  48  thus each form an anti-twist device. 
         [0031]    In an exemplary embodiment according to  FIGS. 5A and 5B , provision is made for the control cam  37  to be assigned a cam element  51  matched to the contour of the control cam  37  and having engagement points  49  (for example drilled holes) on the hub  44 . Of course, the drilled holes  49  can also be introduced directly into the hub  44 . 
         [0032]    A pin wheel  52  is assigned axially parallel to the control roller  36  in such a way that pins  53 , for example bolts, engage in the drilled holes  49  in the cam element  51 . The number of drilled holes  49  in the cam element  51  is an integer multiple of the number of bolts  53  on the pin wheel  52 . Elements  51 ,  52  thus each form an anti-twist device. 
         [0033]    In an exemplary embodiment according to  FIGS. 6A and 6B , provision is made for the control cam  37  to be assigned stops  56  only in the area of functional points a and to serve to calibrate the control roller  36  in relation to control cam  37 . A driver  57 , which is fixed to the control roller  36 , comes into contact with the stop  56  of the control cam at the respective functional points a and if necessary rotates the control roller  36  so far as to come into a position defined by the stop  56  and the driver  57 . Elements  56 ,  57  thus each form an anti-twist device. 
         [0034]    All of the exemplary embodiments relate to a control cam which is disposed in such a way as to be stationary. However, the invention can also be applied to control cams that can be driven in rotation.