Abstract:
An apparatus for clamping and releasing a drive wheel on a shaft, includes a spring device which encloses the shaft annularly to provide a direct clamping connection with the shaft. The spring device is connected to the drive wheel which can be a chain sprocket or a gearwheel. A sheet-processing machine and a sheet-fed rotary printing press, 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 2008 057 679.4, filed Nov. 17, 2008; the prior application is herewith incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to an apparatus for clamping or releasing a drive wheel on a shaft. The invention also relates to a sheet-processing machine and a sheet-fed rotary printing press having the apparatus. 
         [0003]    In order to ensure that a gearwheel or chain sprocket can be rotated with respect to its bearing point, for example in order to set a phase offset with respect to a second gearwheel or chain sprocket, the gearwheel or chain sprocket firstly has to be released. 
         [0004]    Numerous apparatuses for that purpose are known from the prior art. 
         [0005]    For example, German Patent DE 44 47 863 C2 discloses an apparatus for clamping or releasing a clamping connection of a gearwheel which is disposed on a bearing journal. An axially acting spring device, which is provided for clamping, achieves a radial clamping action through conically configured clamping elements, as a result of which the gearwheel is clamped on the bearing journal. 
         [0006]    During clamping and releasing of the clamping connection, wear of the clamping elements occurs as a result of sliding on the conical face under load. 
       SUMMARY OF THE INVENTION 
       [0007]    It is accordingly an object of the invention to provide an apparatus for clamping or releasing a drive wheel on a shaft, a sheet-processing machine and a sheet-fed rotary printing press, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which provide for low wear. 
         [0008]    With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for clamping or releasing a drive wheel on a shaft. The apparatus comprises a spring device to be deflected axially. The spring device annularly encloses the shaft, the spring device has a clamping face acting directly on the shaft in radial direction, the spring device has an inner ring and an outer ring coaxially surrounding the inner ring, and spokes or struts couple the inner ring and the outer ring to one another. 
         [0009]    It is a particular advantage of the radially acting clamping device that it can be clamped or released virtually without wear. 
         [0010]    In accordance with another feature of the invention, the clamping device has a spring device in the form of a disk spring which is disposed on a shaft or a journal in such a way that it can be rotated but is fixed in terms of displacement. 
         [0011]    In accordance with a further feature of the invention, the disk spring has an inner ring (bearing ring) which is connected to an outer ring through the use of radially disposed struts or spokes and the outer ring is disposed in such a way that it can be displaced in an axially resilient manner with respect to the inner ring, with the struts or spokes generating the spring force. 
         [0012]    In accordance with a concomitant feature of the invention, the outer ring is preferably configured to be thicker than or at least as thick as the inner ring. 
         [0013]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0014]    Although the invention is illustrated and described herein as embodied in an apparatus for clamping or releasing a drive wheel on a shaft, a sheet-processing machine and a sheet-fed rotary printing press, 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. 
         [0015]    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 
         [0016]      FIG. 1  is a diagrammatic, longitudinal-sectional view of a sheet-fed rotary printing press; 
           [0017]      FIG. 2  is a cross-sectional view of a drive wheel clamped on a shaft; and 
           [0018]      FIG. 3  is a fragmentary, perspective view of a spring device with a radial clamping face. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen a machine which processes sheets  7 , for example a printing press  1 , having a feeder  2 , at least one printing unit  3 ,  4  and a delivery  6 . The sheets  7  are removed from a sheet stack  8  and are fed individually or overlapped to the printing units  3 ,  4  over a feed table  9 . In a known manner, the printing units  3  and  4  each include a respective plate cylinder  11 ,  12  and a respective blanket cylinder  15 ,  20  which interact in each case with the latter. The plate cylinders  11 ,  12  each have a respective clamping apparatus  13 ,  14  for fastening flexible printing plates. Moreover, each plate cylinder  11 ,  12  is associated with a respective apparatus  16 ,  17  for semiautomatic or fully automatic printing plate changing. 
         [0020]    The sheet stack  8  lies on a stack board  10  which can be raised in a controlled manner. The sheets  7  are removed from the upper side of the sheet stack  8  through the use of a so-called suction head  18  which has, inter alia, a number of lifting and dragging suckers  19 ,  21  for separating the sheets  7 . Moreover, blowing devices  22  are provided for loosening the upper sheet layers and sensing elements  23  are provided for stack tracking. A number of lateral and rear stops  24  are provided for aligning the sheet stack  8 , in particular the upper sheets  7  of the sheet stack  8 . 
         [0021]    The delivery  6  has a chain gripper system  26 , in which gripper bars  27  that are spaced apart from one another in the sheet transport direction are disposed on chains  28  which are guided in parallel in order to grip the sheet  7  at the front edge. A further chain pair  29 , which is disposed parallel to the chains  28 , has gripper bars  31  for gripping the rear sheet edge. The chains  28 ,  29  are deflected endlessly about drive wheels, for example chain sprockets  32 ,  33  and  34 . The chain sprockets  33 ,  34  are seated on a common shaft  36  seen in  FIG. 2 . The chain sprocket  33  is seated fixedly on the shaft  36 , while the chain sprocket  34  is disposed on the shaft  36  in such a way that it can be engaged. 
         [0022]    In order to ensure that the gripper bars  31  for the rear sheet edge can be set to the format length of the sheet to be processed, the drive gearwheel or chain sprocket  34  can be rotated with respect to the shaft  36 . To this end, the chain sprocket  34  is connected fixedly to an annular spring element  37 . The spring element  37  encloses the shaft  36  coaxially and has a clamping face  38  which is in radial clamping connection with a clamping face  39  of the shaft  36 . 
         [0023]    The chain sprocket  34  has a cylindrical recess  41 , in which a working piston  42  is guided axially. A working space  43  between the piston  42  and the cylinder  41  can be loaded through a rotary inlet  44  with a working medium, for example a pneumatic fluid, for moving the piston  42  into a position in which it provides a clamping connection between the sprocket  34  and the shaft  36  as seen in  FIG. 2 . 
         [0024]    The spring element  37  has an inner ring  46  and an outer ring  47 . The rings  46 ,  47  are disposed coaxially and are connected to one another through the use of a number of spokes or struts  48 . As is seen in  FIG. 3 , the spokes or struts  48  have a large length relative to their diameter, that is to say a length L of the struts or spokes  48  is at least 5 times as large as a diameter or width B thereof (L=at least 5B). 
         [0025]    The spokes or struts  48  are disposed at an axial end  46 . 1  of the inner ring  46  and extend in the radial direction obliquely to the outside, where they are disposed at an axial end  47 . 2  of the outer ring  47 . The inner ring  46 , the outer ring  47  and the spokes or struts  48  are configured in one piece. The inner ring  46  has a thickness D 1  which is less than or equal to a thickness D 2  of the outer ring  47  (D 1 ≦D 2 ). 
         [0026]    In one preferred embodiment, the spring element  37  is inverted, as a result of which pressure loading of the working space leads to a release of the clamping connection. 
         [0027]    The invention has been described by using a bearing seat of a chain sprocket  34  on a shaft  36 . It goes without saying that the invention also includes the seating of a gearwheel on a shaft or a crown gear on a hub, etc.