Abstract:
A device ( 10 ) for storing and dispensing endless machining belts for a robotic installation, comprising a support ( 16 ) rotating about a vertical axis ( 14 ) and having radial arms ( 12 ), each equipped with means for locating a machining belt, and means for the stepwise rotation of the rotating support, in order to bring each arm in turn to a station where the belt may be fitted onto a robot arm ( 40 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a device for storing and dispensing endless machining belts, especially grinding belts, for a machining installation comprising a robot arm. 
         [0002]    The robot arm is equipped with one or more machining belts which must be regularly replaced to change the type of belt used or to replace a worn belt with a new one. 
       DESCRIPTION OF THE PRIOR ART 
       [0003]    Document FR-A1-2677289 discloses a machining installation comprising a dispenser of endless grinding belts comprising a plurality of belt support platforms mounted in a vertical cage with a vertical and horizontally mobile system for extending the platforms from the cage one after the other toward a robot arm. One problem with that dispenser is its complexity and the large number of operations that have to be carried out to change one abrasive belt on the robot, with the result that belt changes are time-consuming and can require the intervention of an operator. 
       SUMMARY OF THE INVENTION 
       [0004]    It is a particular object of the invention to provide a simple, effective and inexpensive solution to this problem. 
         [0005]    To this end, the invention provides a device for storing and dispensing endless machining belts for a robotic installation, comprising means for supporting a plurality of machining belts and means for locating these belts on the supporting means, in which device the supporting and locating means comprise a support rotating about a vertical axis and having radial arms, each equipped with means for locating a machining belt, and means for the stepwise rotation of the rotating support, in order to bring each arm in turn to a station where the belt may be fitted onto a robot arm. 
         [0006]    The star configuration of the device of the invention means that changing a belt on a robot arm takes little time and very few operations, because all that is required is to rotate the support of the radical arms a fraction of a revolution to present a new belt in a position where this belt can be picked up by the robot arm. 
         [0007]    The device comprises for example twelve radial arms set out at regular intervals around the vertical axis. 
         [0008]    In accordance with another feature of the invention, the belt locating means comprise retractable pins guided in housings in the arms and engaged in the ends of the belts, and return springs urging these pins toward their belt holding position. 
         [0009]    The locating pins are engaged in the belt carried by the radial arm and make it possible to keep this belt in a position in which the belt is slightly tensioned, so that the belts are stored on the radial arms in the same position. It is therefore no longer necessary for an operator to check that the belts are correctly positioned in the device. The retractable pins are permanently urged by the return springs toward their belt holding position. 
         [0010]    The top ends of the belt locating pins form contact surfaces that are pushed by the bottom ends of two pulleys of a robot arm to depress the pins and engage the belt on the pulleys of the robot. 
         [0011]    The fitting of a belt to the robot arm is done automatically by placing the robot arm in such a way that the pulleys push down on the pins to depress the pins and release a belt. The pulleys of the robot arm which are engaged in the ends of the belt are then moved further apart from each other so that the belt is tensioned between the pulleys. The robot arm can then move away with the belt to perform machinery operations. 
         [0012]    Each radial arm may comprise for example an elongate plate supporting the edges of a belt and comprising orifices at its ends for the locating pins to pass through. 
         [0013]    This plate preferably comprises an elongate guide slot extending between the two edges of the belt, to allow the descent of part of the robot arm and facilitate the positioning of the latter when the pulleys of the arm are being moved apart from one another. 
         [0014]    The device preferably comprises at least one sensor for detecting the presence of machining belts on the radial arms. The sensor can detect the presence of a belt on the radial arm present in the station where belts are fitted to the robot arm. If this radial arm is not carrying a belt, the rotating support is turned one step so that a new radial arm is situated in the fitting station and the sensor can detect the presence of a belt on this arm. If there is still no belt, the operation is repeated until a belt is found in the fitting station. 
         [0015]    An operator can intervene on the device to install new belts. This operation may also be carried out by an automatic unit. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0016]    The invention will be understood more clearly and other advantages and features of the invention will become apparent from the following description, which is given by way of non-restrictive example with reference to the appended drawings in which: 
           [0017]      FIG. 1  is a schematic top view of the device for storing and dispensing endless machining belts according to the invention; 
           [0018]      FIGS. 2 and 3  are schematic perspective views of a radial arm of the device seen in  FIG. 1 ; 
           [0019]      FIGS. 4-6  are highly schematic side views of a radial arm of the device according to the invention, and illustrate steps in a process of fitting a belt to a robot arm. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Referring initially to  FIG. 1 , this shows in schematic form an embodiment of the device  10  according to the invention for storing and dispensing endless machining belts for a machining installation comprising a robot arm  40 . 
         [0021]    The device  10  comprises a plurality of belt supporting and locating arms  12  that extend radially around a vertical axis  14  and that are distributed at regular intervals about this axis  14 . The radial arms  12  are fixed by screws  15  or the like to a circular platform  16  rotated stepwise about the axis  14  by drive means. The device also includes a base for supporting and guiding the rotary platform  16 . 
         [0022]    In the example illustrated, the radial arms  12  are twelve in number and the platform is turned stepwise in steps of 300. 
         [0023]    The machining belts may be of any type such as grinding belts for example. Belts mounted on the robot arm  40  must be replaced at regular intervals, especially to replace a worn belt with a new one. The stepwise rotation of the platform  16  is controlled by a robot arm control unit so that the platform is rotated in response to the needs of the robot arm for belts. 
         [0024]    The device also includes one or more detectors  17  for detecting the presence of belts on the radial arms  12 : these detectors transmit signals to the robot arm control unit. 
         [0025]    Each radial arm  12  (more clearly visible in  FIGS. 2 and 3 ) comprises means for supporting a belt  18  and means for locating this belt on the support means in such a way that the belt can be picked up directly by the robot arm without operator assistance. 
         [0026]    The locating means comprise an elongate parallelepiped-shaped box  20  having a large upper face  22  at whose longitudinal ends are two orifices  24  for two retractable cylindrical pins  26  to pass through. The belt  18  will be wrapped around these pins  26 . 
         [0027]    The pins  26  are approximately parallel to and at a distance from each other, the distance between the pins being such that the belt  18  wrapped around the pins is in an elongated or slightly tensioned condition in which it comprises two long belt portions that are approximately straight, mutually parallel, and close together. 
         [0028]    Return springs (represented schematically by dashes  28 ) are held inside the box  20  and extend between the bottom face of the box and the bottom ends of the pins  24  so as to tend to push these pins out of the box, into their belt holding position. Means are provided to limit the movement of the pins into and out of the box, through the orifices  24 . 
         [0029]    The top ends of the pins  26  form contact surfaces on which a robot arm can push, as will be described later in more detail. 
         [0030]    The means of supporting a belt on the radial arm  12  comprise a flat elongate plate  30  whose dimensions in terms of breadth and length are approximately the same as those of the upper face  22  of the box  20 , and which is fixed over the top of and at a distance from this face by means of screws  32 . The distance between the plate  30  and the face  22  of the box is determined for example by tubes  34  of predetermined length engaged around the screws and mounted between the plate  30  and the upper face  22  of the box  20 . 
         [0031]    At the longitudinal ends of the plate  30  are two orifices  36  for the pins  26  to pass through, the inside diameter of these orifices being greater than the outside diameter of the pins. 
         [0032]    The pins  26  can be moved axially between first and second positions and are permanently urged toward the first position by the return springs  28 . 
         [0033]    In the first position, shown in  FIG. 2 , the top end parts of the pins  26  pass through the orifices  36  of the plate  30  and project above this plate. In this position the pins are engaged in the machining belt  18  placed on the plate  30  and keep this belt in an elongate or slightly tensioned condition. 
         [0034]    In the second position, shown in  FIG. 3 , the pins  26  have been pushed down beneath the plate  30  and are no longer engaged in the belt  18 , which is resting on the plate and is therefore free to be picked up by a robot arm. The distance between the plate and the box  20  is such that the pins no longer project above the plate when the pins are in their second position. 
         [0035]    As will be described in more detail below with reference to  FIGS. 4-6 , the movement of the pins from their first position to their second is caused mechanically by the robot arm. 
         [0036]    The robot arm  40 , shown partially and highly schematically in  FIG. 4 , comprises an actuator  42  whose cylinder  44  is mounted on the robot arm and whose piston  46  is connected to a driven pulley  48  mounted so as to rotate freely on a spindle perpendicular to the longitudinal axis of the actuator. The robot arm also has a drive pulley  50  which extends parallel to the first pulley, behind the actuator, and whose axis is parallel to the axis of the actuator  42 . This pulley  50  is turned by a motor mounted on the robot arm. 
         [0037]    In a first step of fitting a belt  18  to the robot arm, shown in  FIG. 4 , the actuator  42  of the robot arm is in a retracted position in which the distance between the axes of the pulleys  48 ,  50  is approximately equal to the distance between the axes of the pins  26 . The robot arm  40  is positioned above a radial arm  12  of the device on which a belt is fitted ( FIG. 1 ), until the pulleys  48 ,  50  are aligned with the pins  26 . The robot arm  40  is then moved vertically toward the radial arm  12  until the pulleys  48 ,  50  of the robot arm engage in the belt  18  and move the pins  26  from their first position to their second by pushing on the top ends of the pins ( FIG. 5 ). The piston  46  of the actuator is then extended to move the pulleys  48 ,  50  further apart until the belt  18  is tensioned between the pulleys. The belt can then be removed to carry out machining work ( FIG. 6 ). The pins  26  are returned to their first position by the return springs  28 . A new belt  18  can be placed on the pins  26  by an operator or by an automatic unit. 
         [0038]    The control unit of the robot arm controls the movement of the robot arm and of the platform  16  in response to information transmitted by the sensor  17 . The platform  16  is driven stepwise about the axis  14  until a radial arm  12  fitted with a belt is in a predetermined belt pick-up position, so that the belt can be fitted on the robot arm by carrying out the steps shown in  FIGS. 4-6 . 
         [0039]    As is visible in  FIGS. 1-3 , the plate  30  of each radial arm  12  may include an elongate slot  51  extending along the edges of the belt  18  and connected at one end to one of the aforementioned orifices  36  through which the pins  26  can pass, in such a way as to facilitate the engagement of the actuator  42  of the robot arm in the belt  18  and guide the actuator piston  46  as it extends. 
         [0040]    In one particular illustrative embodiment of the invention, the device also comprises a vertical wall  52  separating the device shown in  FIG. 1  into two groups of six radial arms each, one group being accessible to one robot arm  40  and the other group being accessible to an operator for the purpose of installing new machining belts. Each time the platform  16  turns one step about the axis  14 , one of the radial arms  12  of the first group moves into the second group, and one of the arms  12  of the second group moves into the first group.