Abstract:
A moving amount detection apparatus for a movable body includes a press member, detection body, and potentiometer. The press member is provided to either one of a bracket and plate cylinder. The moving amount of the plate cylinder is to be controlled. The detection body is connected to the press member. The potentiometer is provided to the remaining one of the bracket and plate cylinder and detects the moving amount of the plate cylinder on the basis of a displacement of the plate cylinder relative to the detection body. One of the press member and potentiometer displaces in accordance with movement of the plate cylinder.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a moving amount detection apparatus for detecting the moving amount of a movable body.  
           [0002]    Generally, a printing press has a plate registration unit for moving a plate cylinder in circumferential and lateral directions in order to set the register of a plate mounted on the plate cylinder in the circumferential and lateral directions. A plate registration unit of this type has a detection apparatus for detecting the position of the plate cylinder (movable body) by detecting the moving amount of the plate cylinder. A conventional moving amount detection apparatus for a plate cylinder has a plate cylinder the movement of which can be adjusted in the axial direction, and a direct coupled type potentiometer for linearly detecting the movement of the plate cylinder in the axial direction, as disclosed in Japanese Utility Model Laid-Open No. 64-42135. The direct coupled type potentiometer has a detection body which moves against the spring force of a compression coil spring when it is urged by a press member movable together with the plate cylinder.  
           [0003]    In this arrangement, when the motor of the plate registration unit is driven to move the plate cylinder in the axial direction so that the register of the plate cylinder is set, the displacement amount of the detection body which follows the plate cylinder is detected by the direct coupled type potentiometer. Thus, the position of the plate cylinder is detected, and the driving operation of the motor is stopped at a preset position.  
           [0004]    In the conventional moving amount detection apparatus described above, when the press member moves in a direction to urge the detection body into the direct coupled type potentiometer, the detection body is directly urged by the press member against the spring force of the compression coil spring. When the press member moves in a direction to extend the detection body from the potentiometer, the detection body extends to follow the spring force of the compression coil spring.  
           [0005]    If the moving amount detection apparatus has not been in use for a long period of time, or ink, paper dust, powder, or the like attaches to that portion of the detection body which slides on the potentiometer, sometimes the detection body does not extend correctly despite the spring force of the compression coil spring. More specifically, when the press member moves in a direction to extend the detection body, the detection body does not extend and thus does not follow the movement of the press member. In this case, the moving amount of the detection body cannot be detected correctly, so correct position control of the movable body cannot be performed, and the reliability decreases.  
         SUMMARY OF THE INVENTION  
         [0006]    It is an object of the present invention to provide a moving amount detection apparatus for a movable body, which correctly detects the moving amount of a movable body to enable correct position control of the movable body.  
           [0007]    In order to achieve the above object, according to the present invention, there is provided a moving amount detection apparatus for a movable body, comprising an operational member provided to either one of a stationary member and a movable body a moving amount of which is to be controlled, a detection body connected to the operational member, and detection means, provided to the remaining one of the stationary member and the movable body, for detecting the moving amount of the movable body on the basis of a displacement of the movable body relative to the detection body, wherein one of the operational member and the detection member displaces in accordance with movement of the movable body. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a partially cutaway side view of a moving amount detection apparatus for a plate cylinder in a printing press according to an embodiment of the present invention; and  
         [0009]    [0009]FIG. 2 is a side view showing the main part of the moving amount detection apparatus shown in FIG. 1. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]    The present invention will be described in detail with reference to the accompanying drawings.  
         [0011]    [0011]FIG. 1 shows a moving amount detection apparatus for a plate cylinder in a printing press according to an embodiment of the present invention. Referring to FIG. 1, a direct coupled type potentiometer  1  with a circular cylindrical detection body  1   a  which is linearly movable forward/backward is fixed to a holder  4  through a hexagonal adjuster bolt  3  in a bracket  2  fixed to a frame (not shown), such that a projection height T from the bracket  2  can be adjusted.  
         [0012]    The adjuster bolt  3  has a male screw portion  3   a  formed at its one end and a female screw portion  3   b  formed at its other end. With the male screw portion  3   a  of the adjuster bolt  3  threadably engaging with a threaded portion  2   a  of the bracket  2 , when a nut  5  is fastened, the adjuster bolt  3  is fixed to the bracket  2  to be upright from it.  
         [0013]    The holder  4  to which the potentiometer  1  is fixed is fixed to the adjuster bolt  3  through a bolt  6  threadably engaging with the female screw portion  3   b  of the adjuster bolt  3 . The holder  4  has a window  4   a  through which the detection member  1   a  passes. In this arrangement, when the fastened nut  5  is loosened and the screwed amount of the male screw portion  3   a  of the adjuster bolt  3  with respect to the threaded portion  2   a  of the bracket  2  is changed, the projection height T of the adjuster bolt  3  from the bracket  2  can be changed. Therefore, a distance D between the potentiometer  1  and a press member  8  (to be described later) serving as an operational member can be adjusted.  
         [0014]    The press member  8  is fixed to the end shaft of a plate cylinder  20 , serving as a movable body through a bracket or the like, to oppose the potentiometer  1 . When the plate cylinder  20  is moved in the axial direction for the purpose of plate register adjustment, the press member  8  moves (is displaced) together with the plate cylinder  20  in the axial direction (direction of arrows A-B) of the plate cylinder  20 . As shown in FIG. 2, the press member  8  has a circular recess  8   a  in its surface opposing the potentiometer  1 , and a through hole  8   b , through which the detection body  1   a  of the potentiometer  1  is to movably extend, is formed in the bottom of the recess  8   a . Regarding the coupling arrangement of the plate registration unit, plate cylinder, and press member, the description in Japanese Utility Model Laid-Open No. 64-42135 is incorporated in this specification.  
         [0015]    A snap ring  10  is axially mounted around the detection body  1   a  corresponding to the recess  8   a  and extending through the through hole  8   b , and a washer  13  loosely fitted on the detection body  1   a  is interposed between the snap ring  10  and the bottom surface of the recess  8   a . A pair of spring guides  9  and  11  are slidably supported on the detection body  1   a , and a compression coil spring  12  is elastically mounted on the detection body  1   a  between the spring guides  9  and  11 . In this arrangement, the spring force of the compression coil spring  12  urges the spring guide  11  against the snap ring  10  so as to bias the detection body  1   a  in a direction to separate from the bracket  2 . In other words, the detection body  1   a  of the potentiometer  1  is biased by the spring force of the compression coil spring  12  through the snap ring  10  in an extending direction (direction of arrow B), and is locked by the press member  8  through the washer  13 .  
         [0016]    A snap ring  14  is axially mounted around the distal end of the detection body  1   a  projecting from the press member  8 . A washer  15  is loosely fitted on the detection body  1   a  between the snap ring  14  and press member  8 , and a clearance δ is set between the washer  15  and press member  8 . When the snap rings  10  and  14  are mounted to be erroneously inclined with respect to a direction perpendicular to the detection body  1   a , the clearance δ prevents the press member  8  from being inclined. In other words, the backlash caused by inclination of the snap rings  10  and  14  is absorbed by the clearance δ and does not adversely affect the press member  8 .  
         [0017]    In this arrangement, along with movement of the press member  8 , when the press member  8  urges the washer  15  as will be described later, or when the washer  13  urges the press member  8 , the detection body  1   a  is not inclined with respect to the axial direction. Hence, an excessive load can be prevented from acting on the detection body  1   a  to fracture it. Since the detection body  1   a  moves in the axial direction, it can move smoothly, and the accurate moving amount of the press member  8  can be detected.  
         [0018]    The operation of the moving amount detection apparatus with the above arrangement will be described.  
         [0019]    When a motor (not shown) is driven by a control unit (not shown) in order to perform register adjustment of the plate cylinder  20 , the press member  8  also moves together with the plate cylinder  20  in the axial direction (direction of arrows A-B) of the press member  8 . When the press member  8  moves in a direction to move the detection body  1   a  backward, i.e., in the direction of an arrow A, the detection body  1   a  moves in the direction of arrow A through the washer  13  and snap ring  10  against the spring force of the compression coil spring  12 , and is retracted into the potentiometer  1 . When the moving amount of the detection body  1   a  in the direction A reaches a preset plate register adjustment amount, the driving operation of the motor is stopped, so the movement of the plate cylinder  20  is stopped and the movement of the press member  8  is also stopped.  
         [0020]    When the press member  8  moves in the extending direction of the detection body  1   a , i.e., in the direction of arrow B, the detection body  1   a  is extended by the spring force of the compression coil spring  12  to follow the press member  8 . In other words, with the washer  13  being urged against the bottom surface of the recess  8   a  of the press member  8 , the compression coil spring  12  biases the detection body  1   a  in the extending direction through the spring guide  11  and snap ring  10 . Thus, the detection body  1   a  moves in the direction of arrow B together with the press member  8 .  
         [0021]    Despite the movement of the press member  8  in the direction of arrow B, if the detection body  1   a  does not extend because ink, paper dust, powder, or the like is clogged in a portion C between the potentiometer  1  and detection body  1   a , that is, if the stationary frictional force generated by the ink, paper dust, or the like is larger than the spring force of the compression coil spring  12  (temporary locked state), only the press member  8  moves in the direction of arrow B. The press member  8  moves slightly by an amount corresponding to the clearance δ to abut against the washer  15 , and then biases the detection body  1   a  in the direction of arrow B through the washer  15  and snap ring  14 . Thus, the temporarily locked detection body  1   a  is forced to start moving in the direction of arrow B, so that it moves smoothly at the portion C.  
         [0022]    Along with the forced movement of the detection body  1   a , the compression coil spring  12  is extended by its own spring force to urge the washer  13  against the bottom surface of the recess  8   a  of the press member  8  again through the spring guide  11  and snap ring  10 . Thus, the washer  13  is restored to a normal state wherein it is urged by the compression coil spring  12  against the press member  8 , and the washer  13  and press member  8  integrally move by a predetermined amount in the direction of arrow B.  
         [0023]    When the detection body  1   a  is locked and the press member  8  has moved in the direction of arrow A, the detection body  1   a  is biased in the compression direction of the compression coil spring  12  through the washer  13  and snap ring  10 , so the detection body  1   a  is unlocked in the same manner as that described above.  
         [0024]    In this embodiment, when the press member  8  moves in a direction to bias the compression coil spring  12 , even if the detection body  1   a  does not extend, the movement of the press member  8  is transmitted to the detection body  1   a  through the snap ring  14 . This forcibly moves the detection body  1   a , so the detection body  1   a  moves reliably to follow the press member  8 . As a result, the moving amount of the press member  8  can be detected reliably, so that plate register adjustment of the plate cylinder  20  is performed reliably, and the reliability of plate register adjustment is improved.  
         [0025]    After the press member  8  moves, the washer  13  is urged against the press member  8 , in the same manner as in the state before the press member  8  starts moving, and the relative position relationship between the press member  8  and detection body  1   a  becomes identical to that obtained before the press member  8  starts moving. Despite the clearance δ between the press member  8  and washer  15 , the moving amount of the press member  8  becomes equal to that of the detection body  1   a , and the detection body  1   a  correctly detects the moving amount of the press member  8 .  
         [0026]    When the distance D between the potentiometer  1  and press member  8  is to be adjusted, the fastened nut  5  is loosened, and the fastened bolt  6  is loosened to separate the holder  4  from the adjuster bolt  3  to which it has been fixed. Subsequently, the adjuster bolt  3  is rotated clockwise/counterclockwise by a spanner or the like, thereby adjusting the projection height T of the adjuster bolt  3 . When adjustment is ended, the nut  5  is fastened to fix the adjuster bolt  3  to the bracket  2 , and the bolt  6  is fastened to fix the holder  4  to the adjuster bolt  3 . In this manner, when detecting the moving amount of the press member  8  with the detection body  1   a , the distance D between the potentiometer  1  and press member  8  can be adjusted to the optimal value. Therefore, the detection body  1   a  can detect the moving amount of the press member  8  correctly and reliably.  
         [0027]    In the above embodiment, the potentiometer  1  is fixed to the bracket  2  as a stationary side, and the press member  8  is provided to the plate cylinder  20  side as the detection target side. Alternatively, the potentiometer  1  may be provided to the plate cylinder  20  side, and the press member  8  may be fixed to the bracket  2 .  
         [0028]    In the above embodiment, the compression coil spring  12  urges one washer  13  against the press member  8  with its spring force, so the detection body  1   a  moves to follow the movement of the press member  8 . Alternatively, no clearance δ may be provided between the press member  8  and the other washer  15 , but the press member  8  may be sandwiched by the two washers  13  and  15 , and the press member  8  and detection body  1   a  may be directly connected to each other through the two washers  13  and  15 . In this case, the compression coil spring  12  becomes unnecessary.  
         [0029]    The above embodiment exemplifies a case in the printing press wherein plate register adjustment of the plate cylinder  20  is controlled by the potentiometer  1 . However, the present invention is not limited to this, but can also be applied to position detection apparatuses for various types of movable bodies that move linearly.  
         [0030]    As has been described above, according to the present invention, as the operational member moves, the detection body is also forced to move. Thus, the detection body is moved reliably. As a result, the reliability of the position detection precision for the movable body is improved. Since the distance between the detection means and operational member can be adjusted, detection can be performed correctly and reliably.