Abstract:
The invention concerns a device for securing workpieces with at least one clamping bar and a block suction apparatus disposed on the clamping bar. The block suction apparatus is secured to a slide which can be transported in the longitudinal direction of the clamping bar. The block suction apparatus can be lifted from the surface of the clamping bar.

Description:
[0001]    This application claims Paris Convention priority of DE 100 55 379.6 filed Nov. 8, 2000 the complete disclosure of which is hereby incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    The invention concerns a device for securing workpieces, in particular, plate-shaped workpieces, with at least one clamping bar and at least one slide which can be transported on the clamping bar, to transport at least one block suction apparatus in the longitudinal direction of the clamping bar, and a driving device for the at least one slide.  
           [0003]    EP 0 687 521 A1 discloses a device for fixing workpieces, wherein the workpiece is disposed on a plurality of block suction devices and is retained thereby. These block suction devices are disposed on slides which can be transported in a first direction. The block suction devices themselves can also be transported on the slides and have a drive therefor. The device is disadvantageous in that a plurality of drives is required for transporting the block suction devices.  
           [0004]    It is the object of the invention to provide a device of the above-mentioned type with a reduced number of drives.  
         SUMMARY OF THE INVENTION  
         [0005]    This object is achieved in accordance with the invention with a device of the above-mentioned type in that the slide comprises a coupling by means of which the slide can be coupled to the drive device and be decoupled from same at the desired position.  
           [0006]    In the inventive device, the slide is connected to the drive device by means of a coupling such that the slide is transported by the drive device in the longitudinal direction of the clamping bar only if it is coupled thereto. When the coupling is released, the drive device does not change the position of the slide. The drive device can be used for other purposes, e.g. for transporting other slides whose coupling is coupled to the drive device. In accordance with the invention, the drive device is used not only for transporting one single slide but for transporting several slides.  
           [0007]    In a further development, the coupling is formed as a clamping device. This clamping device permits coupling of the slide to or decoupling from the drive device in a reliable and straightforward fashion. This can be effected pneumatically, hydraulically or electromagnetically. A coupling which is pneumatically actuated by underpressure is thereby preferred since the clamping bar is usually provided with pneumatic lines. Tapping of the underpressure is therefore straightforward.  
           [0008]    In a preferred embodiment, the drive device comprises a drive motor and a circulating drive belt. This drive belt, which can be driven by the drive motor in both directions of circulation, serves for transporting the slide on the clamping bar. Towards this end, the drive belt is guided through or past the slide such that it can be connected to the slide by means of the coupling. Either of the two sides of the drive belt can be coupled to the slide to permit transport of the slide in both directions. For several slides, it is possible to transport one slide in one direction while simultaneously transporting the other slide in the other direction without having to change the direction of rotation of the drive motor.  
           [0009]    In a preferred embodiment, the slide is provided with a sprocket via which the drive belt, formed as a toothed belt, is guided. The sprocket has the substantial advantage that it can be connected to the toothed belt without slippage. The sprocket itself is secured on the slide in a rotatable but otherwise stationary fashion.  
           [0010]    The clamping device preferably comprises a clamping block which can be pressed against the sprocket or onto the toothed belt. This clamping block prevents idle running of the sprocket independent of the position of the toothed belt or sprocket, thereby connecting the slide to the toothed belt.  
           [0011]    A further feature of the invention provides that the at least one block suction apparatus can be lifted from the clamping bar by means of the coupling. This has the advantage that the block suction apparatus seal no longer contacts the clamping bar to prevent damage to the seal during the transport process. Processing remnants lying on the surface of the clamping bar can no longer damage the seal during transport of the block suction apparatus.  
           [0012]    Further advantages, features and details of the invention can be extracted from the dependent claims and the following description which describes in detail a particularly preferred embodiment with reference to the drawing. The features shown in the drawing and recited in the claims and in the description can be essential to the invention either individually or collectively in any arbitrary combination. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0013]    [0013]FIG. 1 shows a perspective view of a clamping bar with indicated slide; and  
         [0014]    [0014]FIG. 2 shows an enlarged perspective representation of the slide. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    [0015]FIG. 1 shows a perspective representation of a clamping bar, designated in its totality with  10 , on which one or more block suction apparatus  12  can be transported. The clamping bar comprises one slide  14  for each block suction apparatus, wherein FIG. 1 shows only one of these slides  14 . FIG. 1 also shows a drive device, referred to in its totality with  16 , which is formed by a drive motor  18 , an angular gear  20  with a transmission gearing and a drive belt  22 . This drive belt  22  embraces a drive wheel  24  having an outer toothing and driven by the angular gear  20 . The drive belt  22  is designed as toothed belt  26 .  
         [0016]    This slide  14 , shown in an enlarged representation in FIG. 2, is guided on corresponding guide rails  30  on the clamping bar  10  via pulleys  28 . The slide  14  is furthermore provided with a vertical plate  32  on which guiding rollers  34  and a sprocket  36  are rotatably disposed. The toothed belt  26  comprises an upper side  38  and a lower side  40 . The upper side  38  is guided by the two upper guiding rollers  34  whereas the lower side  40  is guided about the sprocket  36  through an angle a. The teeth of the sprocket  36  thereby engage in the teeth (not shown) of the toothed belt  26 . The sprocket  36  is disposed on the plate  32  in a freely rotatable fashion such that it is driven via the toothed belt  26  without slippage.  
         [0017]    The plate  32  is connected to a base plate  42  on which the two pulleys  28  are rotatably disposed. A lifting plate  44  is located below the base plate  42  and is held at a separation from the base plate  42  by means of springs  46 . Underpressure drives  48  for the lifting plate  44  are located between the base plate  42  and the lifting plate  44 . These underpressure drives  48  can move the lifting plate  44  against the force of the spring  46  in the direction of the base plate  42  to thereby displace a braking arm  50 , provided on the lifting plate  44 , such that a clamping block  52  presses the lower side  40  of the drive belt  22  against the sprocket  36  thereby blocking the rotation of the sprocket  36 . The slide  14  is then coupled to the lower side  40  of the drive belt  22 . As the drive belt  22  is driven by the drive motor  18 , the slide  14  is carried along in the running direction of the lower side  40 . When the slide  14  has assumed the desired position on the clamping bar  10 , the clamping is released by displacement of the lifting plate  44  towards the bottom i.e. away from the base plate  42 . The clamping block  52  is thereby removed from the drive belt  22  and the sprocket  36  can be rotated without hindrance. The slide  14  remains in this position.  
         [0018]    [0018]FIG. 1 also shows that the lifting plate  44  is connected to the block suction apparatus  12  via a connecting leg  54 . This connecting leg  54  serves for carrying along the block suction apparatus  12  in the transport direction (double arrow  56 ) and for lifting the block suction apparatus  12  from the upper side  58  of the clamping bar  10  during transport. The block suction apparatus  12  is lifted when the lifting plate  44  is lifted and the drive belt  22  is clamped to the sprocket  36 .  
         [0019]    In accordance with the invention, several slides  14  can be connected to the drive belt  22  independent of one another. Several slides  14  and therefore several block suction apparatus  12  can then be transported on the clamping bar  10  independently of one another using one single drive device  16 .  
         [0020]    If the upper side  38  of the drive belt  22  is coupled to a given slide  14 , that slide  14  and therefore also the associated block suction apparatus  12  are transported in the opposite direction for a same rotational direction of the drive motor  18 .