Abstract:
An adjusting device is mounted for rotation about a central axis and can be axially actuated. The adjusting device can be displaced or shifted between an inoperative position and at least one working position by an axially displaceable fluid-driven piston.

Description:
FIELD OF THE INVENTION 
   The present invention is directed to an adjusting element and an ejecting device for a mandrel. The adjusting element is rotatably supported around a center axis and can be axially actuated. 
   BACKGROUND OF THE INVENTION 
   Clamping mandrels usable for the rotatable support of paper rolls, such as are used in connection with web-fed rotary printing presses, are known from U.S. Pat. No. 4,149,682, U.S. Pat. No. 4,951,894 and U.S. Pat. No. 4,715,553. Ejecting devices are provided on the clamping mandrels, by use of which the tube on which the paper web is wound can be stripped off the clamping mandrels. Spring elements, that are provided on the ejecting device, are elastically prestressed in the course of inserting the clamping mandrel into the tube. When the clamping mandrel is pulled back out of the tube for changing the paper web, the prestress of the spring elements assures that the tube is stripped off the two oppositely located clamping mandrels. 
   The disadvantage of this type of structure of an ejecting device lies in that the force, by which the tube can be stripped off the clamping mandrel, is limited by the type of construction of the spring elements. It is moreover necessary to overcome the prestress of the spring elements in the course of inserting the clamping mandrels into the tube. 
   A clamping mandrel is known from DE 28 14 338 A1, in which a displaceable ring, which can rotate together with the mandrel, is arranged between the detent flange of the mandrel and the tube. An actuating device, which is fixed in place on a frame, is provided for ejecting the tube. Claws are provided on the actuating device, wherein the ring can freely rotate in one position of the claws, namely the position of rest, and is not in engagement with the claws. In the course of operating the actuating device the claws are pressed against the ring, so that the tube can be stripped off the clamping mandrel. 
   It is disadvantageous in connection with the actuating device known from DE 28 14 338 A1 that, because of its mechanical drive mechanism, the ejecting device requires a large structural volume. 
   U.S. Pat. No. 2,949,313 discloses an adjusting element which is rotatably seated around its center axis and which can be axially actuated. The adjusting element can be displaced between a position of rest and at least one working position by use of an axially displaceable, fluid-driven piston. 
   SUMMARY OF THE INVENTION 
   It is the object of the present invention to provide an adjusting element. 
   In accordance with the present invention, the object is attained by providing an adjusting device which is rotatable about a central axis. The adjusting device is axially displaceable by use of an axially displaceable fluid driven piston. The adjusting device is displaceable between a position of rest and at least one working position. In the rest position of the adjusting device the piston does not contact the adjusting device in the working position of the adjusting element, it is in contact with the piston. Movement of the piston to its rest position can be accomplished by use of a magnetic element. An ejector device, for stripping a tube off a mandrel of the adjusting device can be provided. 
   The advantages which can be achieved by the present invention lie, in particular, in that a pressure-charged piston is employed for driving the ejecting arrangement. Since the pressure-containing fluid, which may be, for example, compressed air or hydraulic fluid, can be conducted to the piston head above the piston through conduits, whose geometry can be arbitrarily designed, clamping mandrels of very compact design are possible. It is furthermore possible to generate very high stripping forces by selecting a correspondingly high working pressure. 
   To reduce the technical outlay, in the course of constructing the clamping mandrel, it is advantageous if the piston for stripping off the tube is driven by use of the fluid. Elastic spring elements, for example helical springs, can be used for restoring the piston into the initial position. 
   Since the ejecting arrangement has an element, which can be rotated along with the clamping mandrel, and a fixed element, which two elements must be brought into engagement with each other, there is the danger that increased wear may occur in the area of contact between the rotatably seated element and the stationary element of the ejecting arrangement. Therefore, the embodiment of the ejecting arrangement is to be selected so that the second element can be switched between a position of rest and at least one working position. In the position of rest, the first element is completely separated from the second element by a gap, while in the working position the first element comes to rest against the second element, so that forces for actuating the second element can be transmitted. 
   Magnetic elements can be particularly advantageously employed for restoring the second element out of at least one working position. The attracting forces, emanating from a magnetic element, act in a contactless manner over an air gap, and in this way they can automatically retract the stationary second element, for example an actuating piston, in a particularly simple manner. 
   In general it is advantageous, in connection with devices which have a rotatably supported and axially actuable adjusting element, which adjusting element can be displaced by an axially displaceable, fluid-driven piston between a position of rest and at least one working position, if the axially displaceable, fluid driven piston can be returned from its working position into its position of rest by use of at least one magnetic element. It is possible, in this way, to prevent wear in the contact zone between the fixed piston and the rotatably supported seated adjusting element in a simple way. As long as it is not needed, the piston is automatically retracted, in a simple manner, by the magnetic element and is dependably maintained in its retracted position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the present invention is represented in the drawings and will be described in greater detail in what follows. 
     Shown are in: 
       FIG. 1 , a cross-sectional, side elevation view of a clamping mandrel in accordance with the present invention, 
       FIG. 2 , a detail view taken at X in FIG.  1  and showing the clamping mandrel in a first operating state, and in 
       FIG. 3 , a detail view taken at X in FIG.  1  and showing the clamping mandrel in a second operating state. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A clamping mandrel  01  in accordance with the present invention is represented in FIG.  1 . Clamping mandrel  01  is fastened in a frame  02 , shown in a broken-off manner, of a roll changer, which is not further represented. A multi-part shaft  07  is rotatably supported in rolling bearings  04 ,  06  in the housing  03  of the clamping mandrel  01 , which housing  03  is fixedly connected with the frame  02 . 
   On the left side of the housing  03 , as seen in  FIG. 1 , the multi-part shaft  07  extends to the outside of the housing  03  and constitutes a clamping cylinder  08 , on which a schematically represented tube  09  can be fixed in place. To fix the tube  09  in place on the clamping mandrel  01 , toggle levers, located at clamping cheeks  11  of the clamping cylinder  08 ,are pushed radially outward by the use of plate springs and compression springs. An adjusting element  12  of the multipart shaft  07 , for example an actuating shaft  12 , can be axially displaced in a hollow shaft  13  of the multipart shaft  07 for actuating the clamping cheeks  11 , so that the clamping cheeks  11  are pushed radially outward by positive engagement with spreading elements  14  which are carried at the left or outboard end of the actuating shaft  12 . 
   The tube  09 , which is engaged by the clamping cylinder  08  supports a rolled-up web, such as, for example a paper web. 
   For stripping an empty or used tube  09  off the clamping cylinder  08 , a stripping ring  10  of the clamping cylinder  08 , including an ejecting arrangement with several actuating elements  16 , for example rotatable elements  16 , for example ejecting bolts  16 , is provided. In this case, the ejecting bolts  16  are arranged in such a way on a hollow shaft  13 , which is part of the multipart shaft  07 , so that the one end of the stripping ring  10  can come to rest against the front or end face of the tube  09 . To accomplish the removal of the tube  09  from the clamping cylinder  08 , the ejecting bolts  16  are synchronously moved axially out, together with the stripping ring  10 , from the free end of the multipart shaft  07 . In the course of this movement, they push the tube  09  axially off the clamping cylinder  08 . Care should be taken that the ejecting bolts  16  and the stripping ring  10  are seated to be axially displaceable on the hollow shaft  13  and, together with the hollow shaft  13 , rotate in the housing  03  around the center axis  17 . 
   A non-rotatable element, for example a ring-shaped piston  18 , which can be charged with a pressure medium via a pressure line  19 , is used for actuating the ejecting bolts  16 . The functioning of the actuation of the ejecting bolts  16  by use of the piston  18  will be explained by utilization of  FIGS. 2 and 3 , which represent the detail X in  FIG. 1  in an enlarged manner. 
   The piston  18  and the right end of the ejecting bolt  16  can be seen in cross section in FIG.  2 . In connection with the operation of the ejecting bolt  16 , it should be noted that the piston  18 , together with the housing  03 , an intermediate element  21  and the outer ring of the rolling bearing  06 , are fixed in place in relation to the frame  02 , while the ejecting bolt  16 , together with the hollow shaft  13 , can rotate around the center axis  17  of the clamping mandrel  01 . The ring-shaped piston  18  can be sealed by simple seals or seal rings  24 ,  26 , which are structured in the manner of piston rings. 
   The piston  18  is shown in its position of rest in  FIG. 2 , in which rest position of piston  18  the ejecting bolt  16  and the piston  18  are separated by a gap  22 . In the position of rest of the piston  18 , the ejecting bolts  16  can rotate, free of wear and resistance, around the center axis  17 . Magnetic elements  23 , for example permanent magnets  23 , are fastened to the front or end face of the piston  18  which is facing away from, or remote from the ejecting bolts  16 . These magnetic elements  23  pull the piston  18  against the metallic intermediate element  21  and in this way assure that the piston  18  is dependably maintained in its position of rest. The piston  18  is sealed against the housing  03 , or the intermediate element  21 , by operation of the seal rings  24 ,  26 . It is thus possible to exert a force directed in the direction of the ejecting bolt  16  by charging the pressure line  19  with a pressure medium so as to move the ring-shaped piston  18  to the left, as shown in FIG.  3 . 
   In  FIG. 3  the piston  18  is represented in its working position. By supplying pressure medium through the pressure line  19 , the piston  18  is pushed against the ejecting bolt  16 , so that the ejecting bolts  16  and the stripper ring  10  move out to the left, as shown in dashed lines in  FIG. 1  to strip the tube  09  off the clamping cylinder  08 . As soon as the tube  09  has been stripped off, the pressure medium is drained from the pressure line  19 , so that no pressure forces will now act on the piston  18 . 
   Springs  27 , for example helical springs  27 , are provided on each of the ejecting bolts  16 , which helical springs  27  prestress the ejecting bolts  16  against the hollow shaft  13 , A restoring force which, following the draining of the pressure medium out of the pressure line  19 , assures that the ejecting bolts  16  are again automatically retracted, acts on the ejecting bolts  16  because of the prestress by the helical springs  27 . The piston  18  is also pushed back together with the ejecting bolts  16  until the ejecting bolts  16  come into contact with appropriately provided end stops  28 , as shown in FIG.  1 . In this rearmost working position, in which the piston  18  still rests against the ejecting bolt  16 , a gap  29  exists between the piston  18  and the intermediate element  21 , which gap  29  must be bridged to return the piston  18  out of its rearmost working position and into a position of rest. By operation of the permanent magnets  23  provided on the piston  18 , a magnetic force, which is directed toward the right as seen in  FIGS. 2 and 3 , acts on the piston  18 , which magnetic force causes the return of the piston  18  across the gap  29 . At the termination of the actuation of the ejecting bolts  16 , the piston  18  again takes up its position of rest as represented in  FIG. 2 , where it is separated from the ejecting bolts  16  by the gap  22 . 
   For actuating the rotatably seated, axially shiftable ejecting bolts  16 , it is merely necessary to employ the displaceably seated piston  18 . Accordingly, the sealing of the work chamber above the piston  18  is greatly simplified. The walls of the piston  18  constituting the sealing gap, on the one hand, and of the housing  03 , or of the intermediate elements  21 , on the other hand, do not perform any rotationally directed relative movement. 
   The end positions of the piston  18  are detected and determined by sensors. 
   The employment of magnetic elements for uncoupling of a pair of elements can be utilized, for example, also in the actuating device of the clamping cheeks  11 . It can be seen in  FIG. 1  that the actuator shaft  12 , which represents such a rotatably seated actuating element, can be displaced toward the left by operation of an axially displaceable, non rotating piston  31  for actuating the clamping cheeks  11 . For this purpose, a pressure medium is supplied via a pressure line  32  to a cylinder chamber formed by the piston  31  and the housing  03 . The pressure medium assures that the piston  31  is displaced toward the left and in this way displaces the actuator shaft  12  by acting on the front plate  33 , so that as a result the clamping cheeks  11  can be actuated. 
   Following the draining of pressure medium from the pressure line  32 , coil springs  34  assure the return of the actuator shaft  12 , so that the piston  31  is pushed back by the front plate  33 . The return of the actuator shaft  12  is limited by end stops, so that the front plate  33  can push the piston  31  back only up to a defined point, namely the rearmost working position. In this position, the piston  31  still rests against the front plate  33 , which is undesirable because of wear occurring in case of a relative movement between the front plate  33  and the piston  31 . To prevent this wear, magnetic elements  37 , for example a permanent magnet  37 , are provided on the front face of the piston  31  facing away from the front plate  33 , by use of whose magnetic forces the piston  31  can be returned into a position of rest, in which the piston  31  no longer rests against the front plate  33 . 
   While a preferred embodiment of an adjusting element and ejector device in accordance with the present invention has been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that changes in, for example, the overall size of the device, the specific type of working fluid and the like could be made without departing from the true spirit and scope of the invention which is to be limited only by the following claims.