Abstract:
A plant for assembly of bodies ( 15 ) with work stations ( 16 ) and means ( 12 ) for conveying bodies between work stations comprises reference members ( 17 ) assembled transitorily on the conveyance means to support the body on the conveyance means during transfer between work stations and grasping devices ( 27 ) assembled in the work stations for grasping the reference members ( 17 ) and positioning them accurately while temporarily disengaging them from the conveyance means to accurately position the body supported on the reference members in the station space. The reference members ( 17 ) comprise means ( 39,40 ) for grasping the body and holding it steadily against them when operated by actuators ( 44 ) assembled in the station.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a body or car processing plant with an innovative device for holding and centering bodies in processing stations. Processing is understood below to mean all processing operations such as welding, finishing and assembly of parts and completion with mechanical members, glass et cetera and dressing the car which can be performed on members such as motor car bodies or the like from purposeful as well as known work stations. By the term ‘bodies’ is meant cars in the completion stage and not only naked bodies.  
           [0002]    In processing plants the need to report and accurately hold the position of the members being processed once they have reached an operating station is known. During body processing in the station there are however possible undesired movements which can be caused by the thrusts applied to the body by the processing equipment itself.  
           [0003]    In the prior art, holding clamps arranged in the station for grasping the body have been proposed but they are cumbersome, can obstruct processing and have to be shaped and positioned purposely for the particular body model.  
           [0004]    The general purpose of the present invention is to remedy the above mentioned shortcomings by making available a body processing plant in which the precision positioning members also fulfill the function of holding the body without further encumbrances in the station and with no need of independent holding members in the individual stations but keeping the individual conveyance devices simple and economical.  
         SUMMARY OF THE INVENTION  
         [0005]    In view of this purpose it was sought to provide in accordance with the present invention a body or car processing plant with work stations and means of conveying bodies between work stations comprising reference members assembled on the conveyance means to support the body on the conveyance means during transfer between work stations characterized in that the reference members comprise means for grasping the body or car in completion and holding it steadily against them when operated by actuators mounted in the station. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    To clarify the explanation of the innovative principles of the present invention and its advantages compared with the prior art there is described below with the aid of the annexed drawings a possible embodiment thereof by way of non-limiting example applying said principles. In the drawings:  
         [0007]    [0007]FIG. 1 shows a diagrammatic view of part of a body conveyance and processing plant having devices in accordance with the present invention,  
         [0008]    [0008]FIG. 2 shows a partially cross sectioned side elevation view of a positioning and holding device in accordance with the present invention,  
         [0009]    [0009]FIG. 3 shows an enlarged view of a detail of the device of FIG. 2, and  
         [0010]    [0010]FIGS. 4 and 5 show different operating positions of the device of FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]    With reference to the figures FIG. 1 partially illustrates a plant designated as a whole by reference number  10  comprising a conveyance plant made up of an overhead rail  11  on which run conveyance means  12  which are advantageously conveyors or self-propellers and have motors  13  and bearing hangers  14  for supporting the bodies  15  to be processed e.g. welded. The hanger conveyors convey the bodies or cars among a plurality of work stations or cells of which one designated by reference number  16  is shown in FIG. 1. A similar conveyor system and the processing equipment in the stations are well known to those skilled in the art and are therefore not further described or shown.  
         [0012]    To support the body the hanger  14  comprises a frame  19 ,  20  with arms  18  from which support or reference members  17  on which the body is rested project above.  
         [0013]    As may be seen better in FIGS. 2 and 3 each support  17  includes a vertical stem  22  with a positioning pin  35  at its top end. The pin  35  has a tapered end—conical for example—and is designed to engage with minimal side play in an appropriate reference seat  23  in the body  15 . At the base of the coupling pin  35  the stem  22  defines a table  34  for supporting the body. The combination of the table  34  and the pin  35  supplies a precise positioning reference for the body with respect to the stem  22 .  
         [0014]    As may be seen in FIG. 2 and enlarged in FIG. 3 the stem  22  is hollow and inside it are a pair of rods  37 ,  38  extending along the axis of the stem to end above in a clamp  39 ,  40  each and below in a handling end pivoted at  46  to a sleeve  47  mounted in a running manner on the outside of the stem  22 .  
         [0015]    In an intermediate position between its ends each rod has a slot  41 ,  42  shaped as a cam to run on a pin  43  fastened in the stem. The slot  41 ,  42  has a first vertical upper section and a second lower section inclined outwardly in the direction of the extension of the clamp associated with the rod. The slot is shaped so that when the sleeve  47  is in its lower rest position as shown in FIG. 2 and hence when the pin  43  is in the vertical section of the slot the clamps  39 ,  40  are arranged at the two sides of the positioning pin  35  with the grasping end resting on the positioning table  34  as may be seen in FIG. 3. As shown in dash-dot lines for the left-hand clamp in FIG. 3, by raising the sleeve  47  the cams provided by the slots  41 ,  42  and the pin  43  cause return of the clamps  39 ,  40  into the positioning pin  35 .  
         [0016]    To move the sleeve, actuators  44  are placed in the stations to grasp a corresponding sleeve upon arrival of a body and open or close the clamps as required for body loading, unloading or processing.  
         [0017]    Advantageously as clarified below, the supports  17  are assembled transitorily on the hanger and protrude below with one of their spherical ends  26  to be grasped by grasping and positioning devices  27  arranged in the work stations. For support of the stem  22  on the hanger the stem  22  has a hemispherical fifth wheel  24  resting in a complementary seat  25  in the respective hanger arm  18 . The stem  22  continues downward beyond the seat  25  and ends below in the above mentioned spherical end  26 .  
         [0018]    The grasping devices  27  are made with a pair of movable jaws  28  powered by a kinematic mechanism  36  to close on the lower end of the positioning member  17 .  
         [0019]    Each jaw comprises vertical rollers or bearings  29 ,  30  and a pair of rollers or bearings  31  arranged horizontally.  
         [0020]    The two rollers  31  of the pair of which only one is visible in the FIGS are arranged symmetrically with respect to a vertical plane passing through the two clamps. The rollers  29 ,  30  are designed to be arranged above and below the equatorial diameter of the sphere  26  and the rollers  31  are designed to rest on the sphere  26  side by side and in an intermediate position between the rollers  29 ,  30 . In this manner upon closing of the jaws the center of the sphere  26  is positioned accurately in the device  27 . The holding position is slightly raised over the position of the sphere  26  when the fifth wheel  24  is resting in the hanger seat  25  so that the positioning member  17  is raised and released by the hanger when it is grasped by the jaws  28 . To prevent rotation of the sphere between the jaws and then position the upper end of the stem accurately the jaws have ends  33  which grasp the stem. Advantageously one of the jaws  28  supports the actuator  44  which operates a fork  45  to slide it axially to the stem  22  between the two positions shown respectively in solid and dash-dot lines in FIG. 2. The two positions allow the fork to position itself above or below the sleeve when the jaws are closed.  
         [0021]    In use, to unload a body from the hanger or load a body on the hanger the hanger reaches a station  16  where grasping means  27  grasp the positioning members with the forks  45  lowered and then raise the forks to move the sleeves  47  upwards and draw in the clamps  39 ,  40  as shown in FIG. 4. In this manner a body can be freely placed on or removed from the pins  35 .  
         [0022]    After this the grasping means  27  are opened and the hanger can convey the body among the various processing stations. During conveyance the clamps are rested on the edges of the positioning hole  23  of the body (FIG. 2).  
         [0023]    When the hanger reaches a processing station the grasping means  27  of the station close on the positioning members  17  to raise them from the seats  25  in the hanger and position them accurately with respect to the station. Closing of the jaws is however performed after operation upward of the actuator  44  so that the fork  45  is located over the sleeve  47 . The actuator  44  is then operated downward so that the clamps  39 ,  40  firmly hold the body between them and the supporting table  34  to prevent all possibility of movement of the body with respect to the positioning members.  
         [0024]    After the station has performed the programmed processing the actuator  44  raises the fork  45  and the grasping means  27  are opened so that the hanger can resume its travel towards the next station.  
         [0025]    It is now clear that the predetermined purposes have been achieved to secure safe and accurate holding in accordance with all Cartesian axes. As the body is firmly grasped opposite the support and positioning members  17  the body remains fully accessible for processing in the various stations. In addition since the supporting points are standardizable and to a high degree independent of the body configuration different bodies can be treated without the need of modifying the support and holding structure. Even if body details require modifications in the position of the supports  17  the structure of the supports remains the same since the configuration of the bodies near the positioning holes does not vary significantly. The additional characteristic of using body supports mounted transitorily on the conveyor plant allows high precision regardless of the design and positioning accuracy of the conveyor system.  
         [0026]    Naturally the above description of an embodiment applying the innovative principles of the present invention is given by way of non-limiting example of said principles within the scope of the exclusive right claimed here. For example the structure of the conveyance means can vary depending on specific exigencies. In particular overhead conveyor systems with or without incorporated vertical hoisting members for the load bearing support can be employed as well as skid, roller, chain, push-conveyor et cetera conveyance systems.