Abstract:
A drive clutch for connecting a drive shaft ( 12 ) with an exchangeable cylinder ( 10 ) of a printing machine, such that, at one end of the cylinder ( 10 ), a locking part ( 24 ) is provided and that, in or on the drive shaft, a spanner ( 32 ) is disposed, which has a recess ( 38 ), which opens up radially and into which the locking part ( 24 ) can be introduced positively, and that the spanner ( 32 ) can be retracted axially, in order to pull the cylinder ( 10 ) with the help of the locking part ( 24 ) against the end of the drive shaft ( 12 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a drive clutch for connecting a drive shaft with an exchangeable cylinder of a printing machine. 
     It is frequently necessary to exchange cylindrical, rotatable elements, such as printing cylinders, inking rollers and the like of printing machines. These exchangeable, cylindrical elements are referred to in an abbreviated fashion in this application as “cylinders”. 
     Robots are known, with which the generally relatively heavy cylinders can be lifted out of their bearings in the machine frame after the appropriate cap pieces of the bearing have been opened or removed. If the cylinders are driven over mutually meshing gearwheels, the engagement of the teeth is cancelled automatically when the cylinder is lifted out of its bearings. Recently, however, driving systems are increasingly being used, for which the cylinders and rollers of a printing machine, instead of being driven by gearwheel transmissions synchronously with the help of a single driving motor, are driven by a separate driving motor, which is provided for each cylinder and which is seated directly on a drive shaft connected coaxially with the cylinder in question. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to provide a drive clutch which, on the one hand, permits the cylinder to be driven precisely directly and, on the other, to be exchanged easily. 
     Pursuant to the invention, this objective is accomplished owing to the fact that a locking part is provided at one end of the cylinder and that, in or on the drive shaft, a spanner is disposed, which has a radially opening recess, into which the locking part can be introduced positively, and that the spanner can be retracted axially, in order to pull the cylinder with the help of the locking part against one end of the drive shaft. 
     During the operation of the printing machine, the cylinder is tensioned axially with the help of the spanner against the end of the drive shaft, so that a positive or preferably predominantly frictional connection between the drive shaft and the cylinder is created. For exchanging the cylinder, the spanner is moved into a release position, in which the locking part can radially leave the recess of the spanner. Accordingly, the cylinder can be uncoupled from the drive shaft in a very simple manner, in that it is moved, with the help of the robot, radially in the direction, in which the recess of the spanner opens up. By reversing this course of motion, the new cylinder with its locking part can be introduced into the spanner and then, by retracting the spanner, tensioned once again against the end of the drive shaft, so that the driving connection is restored. 
     The inventive drive clutch is intended, particularly for printing machines, in which, although the cylinder is driven over the drive shaft, which is connected coaxially with the cylinder, the cylinder itself is directly supported in the machine frame. Since the bearings in this case have a relatively large diameter, the drive clutch, which naturally must have a certain minimum diameter, can adjoin the bearing site of the cylinder directly or even mesh somewhat with the end face of the cylinder, so that a very small construction is achieved. Moreover, it proves to be advantageous that the cylinder is stressed by the drive clutch axially with the drive shaft. The clutch therefore behaves in a stiff manner in the axial direction and in the direction of rotation, so that the side register and the longitudinal register can be adjusted precisely. On the other hand, in the radial direction, the clutch can be somewhat elastic. This has the advantage that the axis of rotation of the cylinder is defined precisely by the mounting in the machine frame and a slight eccentricity in the drive shaft, resulting from installation inaccuracies, can be compensated, as also described in the European patent application 98 121 059 of the applicant. 
     Preferably, the mutual facing ends of the cylinder and of the drive shaft together form a friction clutch which, in a particularly preferred embodiment, is combined with a positively meshing clutch, especially a single tooth clutch. In this case, the single tooth clutch serves to hold the cylinder in a defined angular position in relation to the drive shaft, so that the longitudinal register can be adjusted with the help of an angle sensing device, which is disposed at the drive shaft or directly at the motor. However, the driving torque is transferred mainly by the friction clutch. 
     Preferably, the spanner is tensioned elastically in the clamped position and can be moved into the release position with the help of an actuating rod extending axially through the hollow drive shaft. When the drive shaft is connected coaxially with the motor shaft or formed in one piece with the latter, the actuating rod can extend through the whole of the motor and optionally also through the angle sensing device. For loosening the clutch, the free end of the actuating rod can then be acted upon by a tappet, which is actuated pneumatically or hydraulically and does not need to participate in the rotation of the drive shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, an example of the invention is explained in greater detail by means of the drawing, in which 
     FIG. 1 shows an axial section through the end of a cylinder of a printing machine 
     FIG. 2 shows a section in the plane II—II in FIG. 1, 
     FIG. 3 shows an axial section through a drive clutch, 
     FIG. 4 shows an end view of the drive clutch, 
     FIG. 5 shows the drive clutch of FIG. 3 during the connection of the cylinder of FIG.  1  and 
     FIG. 6 shows the drive clutch and the end of the cylinder in the connected state. 
    
    
     DETAILED DESCRIPTION 
     In FIG. 1, one end of a cylinder  10 , for example, a printing cylinder or an inking roller of a printing machine is shown, which is to be connected to a drive shaft  12  with the help of the drive clutch shown in FIG.  3 . An end section of the cylinder  10 , shown in section in FIG. 1, forms a bearing surface  14  and serves to mount the end of the cylinder  10  in question in a bearing  16  (FIG.  3 ), which is disposed in a frame of the printing machine that is not shown. 
     On the front side of the cylinder  10 , adjoining the bearing surface  16 , a friction ring  18  is disposed, which is interrupted at one place on its periphery by a protruding coupling tooth  20 . 
     A cylindrical extension  22  protruding coaxially from the end of the cylinder  10  carries at the free end a locking part  24  which, as can be recognized in FIG. 2, is in the shape of a circular disk. 
     The drive shaft  12 , shown in FIG. 3, carries at its end, facing the bearing  16 , a friction ring  26  which, when the cylinder  10  is connected, forms a friction clutch together with the friction ring  18  of the cylinder. The friction ring  26  is interrupted at one place on its periphery by a notch  28 , which can be engaged by and accurately fits the coupling tooth  20  so that, in the connected state, the angular position of the cylinder  10  is fixed precisely in relation to the angular position of the drive shaft  12 . 
     The drive shaft  12  is constructed as a hollow shaft, through which a continuous actuating rod  30  passes axially. At the end of the actuating rod  30 , a spanner  32  is fastened, which can be shifted with the help of the actuating rod  30  axially into an end section of the drive shaft  12 . The spanner is fixed by a bolt  34 , which engages a longitudinal groove  36  of the spanner, so that it cannot rotate in the drive shaft  12 . The spanner  32  has a recess  38 , which is U-shaped in cross section and opens radially in the direction of the notch  28 , that is, towards the top in FIGS. 3 and 4. The recess  38  is bounded at the free end of the spanner by a front wall  40 , in which a U-shaped slot  42 , which also opens in the upwards direction, is formed. 
     At its end, opposite the spanner  32 , the actuating rod  30  has a plate  44  and is tensioned towards the left in FIG. 3 by a spring  46 , so that it has the tendency to retract the spanner  32  into the interior of the drive shaft  12 . In the state shown in FIG. 3, the plate  44  is held by a pneumatically or hydraulically actuated tappet  48  against the force of the spring  46  in a position, in which the spanner  32  protrudes out of the open end of the drive shaft  12 . When in this state, the cylinder  10  is placed with the help of a robot, which is not shown, from above into the bearing  16 , the locking part  24  enters the recess  38  and the extension  22  is placed in the slot  42  of the front wall  40 . This state is shown in FIG.  5 . 
     Subsequently, the tappet  48  is retracted, so that the spring  46  is relieved and shifts the actuating rod  30  and the spanner  32  towards the left. At the same time, the locking part  24  is taken hold of by the front wall  40  of the spanner  32  and the cylinder  10  is pulled axially in the bearing  16  against the end of the drive shaft  12 , so that the friction rings  26  and  18  are brought into firm frictional contact with one another, as shown in FIG.  6 . At the same time, the coupling tooth  20  enters the corresponding notch  28 . In this way, a connection, rigid in the axial direction and in the peripheral direction, is established between the drive shaft  12  and the cylinder  10 . 
     The drive shaft  12 , of which only the respective end sections are shown in the drawing, can at the same time form the rotor of a driving motor, which is not shown, so that the drive shaft  12  and also the actuating rod  30  pass axially through the housing of this driving motor. In addition, the drive shaft  12  can also engage a mechanism (not shown) for adjusting the side register, and an angle sensing device for measuring the angular position of the cylinder  10  can be integrated in the motor for adjusting the longitudinal register. All adjustment motions for adjusting the longitudinal register and the side register are transferred by the inventive drive clutch free from backlash to the cylinder  10 . 
     After the cylinder  10  has been coupled to the drive shaft  12  in this manner, the bearing  16  is closed with the help of a bearing cover  50 . The axis of rotation of the cylinder  10  is then defined precisely by the bearing  16 , which is attached to the frame. If a slight eccentricity develops between the drive shaft  12  and the cylinder  10  as a result of dimensional tolerances during the manufacture or installation of the motor housing, this eccentricity can be compensated for owing to the fact that the friction rings  26  and  18  work radially somewhat against one another. The coupling tooth  20  also engages free from backlash only in the peripheral direction; however, in the radial direction, it engages the associated notch of the drive shaft with backlash. In this way, the transfer of radial forces and/or bending moments to the cylinder  10  is prevented. 
     When the cylinder  10  is to be exchanged, the bearing cover  50  is opened or removed and the actuating rod  30  is shifted with the help of the tappet  48  once again into the release position. At the same time, the end wall  40  of the spanner  32  can engage the end surface of the cylinder  10  and shift the cylinder into an axial position, in which the locking part  24  lies outside of the drive shaft  12 , so that the cylinder  10 , with the help of a robot, can be lifted upward out of the bearing  16 .