Abstract:
The invention concerns a structure for maintaining a body part, the structure consisting of assembled frame members, at least one of the frame members being a tubular beam ( 1 ) provided on the outside with at least a groove ( 7 ) extending longitudinally. The invention also concerns a template for drilling said beam.

Description:
The present invention relates to a structure for holding bodywork parts. 
   BACKGROUND OF THE INVENTION 
   In car bodywork assembly lines, subassemblies (such as the subframe, the sides of the body, the rear skirt, . . . ) are positioned relative to one another and relative to welding robots. By their very nature, bodywork parts are deformable on being subjected to stresses, so the tooling used for making bodywork of determined and reproducible shape performs two functions: firstly it constitutes framework for each deformable subassembly for the purpose of stiffening it to enable it to be handled by the handling robots, and secondly it constitutes a stable interface enabling positioning to be precise in a fixed frame of reference associated with the welding robots. 
   Such tools are generally constituted by a structure for holding a bodywork part, which structure comprises members assembled to one another together with auxiliary elements secured to the members for the purposes, for example, of positioning the part in the structure, of holding the part in the structure, of positioning the structure relative to another structure, of making a connection with the handling robot, . . . . 
   These members are formed by beams made from metal bars of lengths that are determined as a function of the dimensions of the part to be held. With the bars used, it is difficult to have beams that are sufficiently rigid and lightweight for this purpose. 
   The beams are usually assembled to one another and to the auxiliary elements by welding. This means that they are relatively time-consuming and difficult to make, given the deformations caused by welding, and their fabrication also requires specialized personnel. Furthermore, repairs and additions of auxiliary elements need to be performed by the specialized personnel and with very great care so as to avoid spoiling the shape of the structure. In order to limit deformation, it is common practice to make use of beams and of auxiliary elements of considerable thickness, to the detriment of lightness. 
   It is also possible to make an assembly by bolting. However it is difficult to position the various beams and auxiliary elements relative to one another prior to assembling them together. An assembly made in this way is generally not sufficiently rigid. Furthermore the beams must be of relatively great thickness in order to allow fixing screws to penetrate sufficiently, and as a result the beams are relatively heavy. 
   However, tool weight is an important parameter governing the dimensions of the robots that are to handle the tools, and having an influence on the cost of such robots. 
   OBJECTS OF SUMMARY OF THE INVENTION 
   According to the invention, a holding structure is provided that is made up of assembled-together members, with at least one of the members being a tubular beam provided on the outside with at least one longitudinally-extending spline. 
   Thus, the spline can be used as means for stiffening the beam in bending, as an angular positioning marker for an element fixed on the beam, as means for preventing an element fixed on the beam from moving in rotation, and as a zone for anchoring a screw (the spline forming local extra thickness, and thus enabling a screw to be engaged over a depth that is sufficient, while still making it possible to conserve weight that is relatively low). It is thus possible to obtain a structure that is relatively lightweight, robust, and rigid, and that is easy to implement. 
   Preferably, the tubular beam has a plurality of splines that are angularly distributed in regular manner around the beam and that present a section that is substantially circular and symmetrical about at least one diameter thereof. 
   This increases the number of options for fixing and orienting beams and elements that are to be fixed thereon. 
   In a particular embodiment, at least one spline has at least one flank arranged to constitute an angular reference face. 
   It is then possible to obtain accurate positioning for elements that are to be fixed on the beam. 
   It is then advantageous for the structure to include at least one auxiliary element provided with means enabling it to be fixed to the beam, and for said means to include a face for bearing against the reference face and presser means for pressing the bearing face against the reference face, the bearing face preferably being formed by a side wall of a groove formed in the auxiliary element to receive the spline, and the presser means comprising at least one wedging device for being inserted between the flank of the spline opposite from the reference face and the facing side wall of the groove. 
   This ensures that the auxiliary element is positioned effectively and firmly relative to the beam. 
   Also advantageously, the wedging device comprises a chock and at least one sloping wedge disposed so that the slope of the wedge co-operates with the corresponding ramp on the chock and so that the chock and the wedge present parallel opposite faces, one for bearing against the flank of the spline opposite from the reference face and the other for bearing against the side wall of the facing groove, the wedge being mounted to slide relative to the chock and the wedging device including means for adjusting the position of the wedge relative to the chock. 
   This method of pressing the bearing face against the reference face is then particularly simple and effective. 
   The invention also provides a template for drilling the beam, which template comprises a body provided with means for releasably fixing it on the beam, and with at least one drilling bushing arranged to extend over a spline of the beam when the template is in position on the beam, said means including a groove which is formed in the body and which possesses a first side wall forming a bearing face for pressing against a first flank of the spline, presser means for pressing the bearing face against the first flank, the presser means comprising a wedging device received between a second flank of the spline and a facing second side wall of the groove. 
   This enables holes to be drilled and tapped in a manner that is very accurate in each of the splines of the beam so as to make it possible subsequently to fix other beams and/or elements thereto. 

   
     BRIEF DESCRIPTION OF THE INVENTION 
     Other characteristics and advantages of the invention will appear on reading the following description of a particular, non-limiting embodiment of the invention. 
     Reference is made to the accompanying drawings, in which: 
       FIG. 1  is a fragmentary perspective view of a first structure in accordance with the invention; 
       FIG. 2  is a side view of the structure; 
       FIG. 3  is a section on plane III of  FIG. 1 ; 
       FIG. 4  is a section on plane IV of  FIG. 1 ; 
       FIG. 5  is a fragmentary perspective view of a second structure in accordance with the invention; 
       FIG. 6  is a fragmentary section view of said structure on plane VI of  FIG. 5 ; 
       FIG. 7  is a perspective view of a template for drilling a beam of the  FIG. 1  structure; and 
       FIG. 8  is a section of the template in position on the beam. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention is described herein in an application to handling a bodywork part (not shown), e.g. in an assembly line for motor vehicle bodywork. In particular, the structure shown in  FIGS. 1 to 4  is intended to constitute a lateral tool for manipulating a left-hand body side, said tool being arranged specifically to co-operate with a second lateral tool for manipulating a right-hand body side and with a rear tool for manipulating the rear skirt of the bodywork. 
   A complete holding structure may comprise a plurality of beams that are assembled to one another by means of auxiliary link elements fixed to the beams so as to hold them at predetermined angles and positions, and also fixed on the beams, auxiliary elements for positioning the bodywork part within the structure, auxiliary elements for holding the bodywork part as positioned in this way, auxiliary elements for fixing the structure to an arm of a handling robot, auxiliary elements for positioning the structure in the assembly line or relative to other structures, auxiliary elements for making releasable connections to said other structures, . . . . The holding structure is not shown in full in the figures, only one or a few beams and a few auxiliary elements appearing in the drawings so as to illustrate a few possible characteristic configurations. 
   With reference to  FIGS. 1 to 4 , the first holding structure of the invention comprises a beam given overall reference  1  and auxiliary elements referenced  2 ,  3 ,  4 ,  5 , and  6 . 
   The beam  1  is tubular, of circular section, and it is provided with splines  7  which extend along the outside surface  8  of the beam  1 . In this case, the splines  7  are fitted onto the outside surface  8  of the beam  1  by welding, however the splines  7  could be made integrally with the beam  1 , e.g. by extrusion. There are eight splines  7  and they are disposed at 45° intervals relative to one another. The beam  1  is thus symmetrical. 
   Each spline  7  has two substantially parallel flanks  9 ,  10  and a top face  11 . Some of the splines, referenced  7 ′ in order to distinguish them from the others, include a respective flank  9 ′ that has been machined accurately so as to constitute a reference surface. It is possible for the beam  1  to have only a single spline  7 ′. 
   Tapped holes  12  (visible in  FIGS. 3 and 4 ) and a hole for receiving a pin are made radially through the beam  1  from the top surfaces  11  of the splines  7 . 
   The auxiliary element  2  has one end provided with means  13  (described below) enabling it to be releasably fixed on the beam  1 , and an opposite end provided with a female V-shape  14  for co-operating with a male V-shape of the rear tool structure to ensure that these two structures are positioned relative to each other. 
   Each auxiliary element  5  has one end provided with means  13  for releasably fixing it to the beam  1 , and an opposite end  19  arranged for fixing either positioning members and/or holding members for the bodywork part, or for positioning the structure. By way of example, these members can be clamping means, positioning or indexing fingers or studs, . . . . 
   The means  13  comprise a soleplate  22  for bearing against two splines  7  disposed at 90° from each other on either side of a spline  7 ′. The soleplate  22  has holes  23  that receive fixing screws  24  with transverse clearance, the screws being engaged in the tapped holes  12  in the splines  7 , and a hole having a pin engaged therein (not shown in the figures) and received in the hole provided for this purpose in the splines. A groove  25  is formed in the soleplate  22  to receive the spline  7 ′. The groove  25  is defined laterally by walls  26 ,  27  that are spaced apart from each other by a distance that is greater than the distance between the flanks  9 ′ and  10 ′ of the spline  7 ′. The wall  27  is machined to form a reference surface for positioning the auxiliary element in co-operation with the flank  9 ′. 
   A wedging device given overall reference  28  is received between the flank  10 ′ and the facing wall  26 . The wedging device  28  (more clearly visible in  FIG. 7 , where it is shown mounted on the drilling template) comprises a chock  29  and two wedges  30 . The chock  29  has a soleplate  31 , and on its opposite side two ramps  32  disposed in such a manner that these surfaces form a triangle. Each wedge  30  comprises on the side a soleplate  33 , and on the opposite side a slope  34 , together with a heel  35  at the thick end of the wedge  30 . The wedges  30  are disposed so that the slopes  34  co-operate with the corresponding ramps  32  and so that the soleplates  31 ,  33  bear firstly against the flank  10 ′ and secondly against the facing wall  26 , the heels  35  forming rims that extend over the ends of the facing chocks  29 . A screw (not shown) is mounted to turn in each heel  35  and is engaged in a tapped hole formed in the corresponding end of the chock  29  so as to enable each wedge  30  to be caused to slide relative to the chock  29 , thereby moving the soleplates  31 ,  33  further apart to a greater or lesser extent (the wedges  30  are thus adjustable in position relative to the chock  29 ). The wedging device thus enables the wall  27  to be pressed firmly against the flank  9 ′. The angular positioning of the auxiliary element is accurate and is maintained even when large forces are exerted on said element. Because of the clearance that exists between the soleplate  22  and the fixing screws  24 , said screws do not oppose positioning of the element. The pin provides positioning in a direction parallel to the spline. 
   The auxiliary element  3  is a leg possessing one end fitted with means  13  enabling it to be releasably fixed to the beam  1  (said means being identical to those described above), and an opposite end  15  that is arranged to bear against the ground or to co-operate with another beam  1  via means that are not shown but that are of the same type as the means  13 . 
   The auxiliary element  4  is a bracket whose top is provided with means  16  enabling it to be releasably fixed to the beam  1 , whose first branch has a free end  17  arranged to bear on the ground or to co-operate with another beam  1  via means that are not shown but that are of the same type as the means  13 , and a second branch with a free end  18  that is arranged to bear against and be fixed to a corresponding bracket secured to the structure of the righthand lateral tool. 
   The means  16  comprise a soleplate  36  extending over 180° to bear against three splines  7  disposed at 90° intervals to one another, with two of these splines  7  lying on either side of the spline  7 ′. The soleplate  36  includes holes  37  that receive fixing screws  24  with transverse clearance, said screws being engaged in the tapped holes  12  in the splines  7 . A groove  38  is formed in the soleplate  36  to receive the spline  7 ′. The groove  38  is defined laterally by walls  39  and  40  that are spaced apart from each other by a distance that is greater than the distance between the flanks  9 ′ and  10 ′ of the spline  7 ′, the wall  40  being machined to form a bearing surface pressed against the flank  9 ′. 
   A wedging device  28  identical to that described above is housed between the flank  10 ′ and the facing wall  39 . 
   The auxiliary element  6  has one end provided with means  20  for releasably fixing it to the beam  1 , and an opposite end  21  arranged to be fixed either to members for positioning and/or holding the bodywork part, or to members for positioning the structure. 
   The means  20  comprise a soleplate  40  for bearing against the top faces  11  of two splines  7  that are at 90° from each other, a pin (not shown) that is inserted in the corresponding radial holes of the soleplate and the spline to serve mainly for positioning the auxiliary element longitudinally relative to the beam, and fixing screws  24  passing through the soleplate  40  and engaged in the tapped holes  12  of the splines  7 . This element is not required to withstand large forces so there is no need to provide special means for holding it in position other than the fixing screws engaged in the tapped holes  12 . 
   The structure made in this way is completely modular, the beams  1  and the auxiliary elements  2 ,  3 ,  4 ,  5 , and  6 , being easy to assemble and disassemble. In addition, the structure is rigid, relatively light in weight, and easy to repair, it being possible to change quickly any components that might become damaged. 
   It should be observed that when two auxiliary elements have respective soleplates that extend over less than 180° (i.e. which overlie no more than four splines), these two auxiliary elements can be located in the same plane extending transversely to the beam (see for example  FIG. 3 ). 
   The holes made in the auxiliary elements  2 ,  3 ,  4 ,  5 , or  6  are preferably all spaced apart by the same distance. This makes it easy to implant an auxiliary element between auxiliary elements that have already been mounted on the beam, and increases modularity. 
   With reference to  FIGS. 5 and 6 , the second holding structure in accordance with the invention comprises three beams  1  that are entirely identical to the beam described above, auxiliary elements given overall references  50 ,  51 , and  52  for interconnecting the beams  1  rigidly to one another, and auxiliary elements given overall references  53  and  54  for positioning the structure relative to a stand  55 . 
   The auxiliary elements  50 ,  51  are arranged to fix two beams  1  to each other in such a manner that they form an angle of 90°. Each auxiliary element  50 ,  51  comprises two respective soleplates  56  &amp;  57  and  58  &amp;  59  for bearing against two splines  7  disposed at 90° relative to each other on either side of a spline  7 ′ having a reference flank. The soleplate  56  &amp;  57  and  58  &amp;  59 , and the associated fixing means are identical to the fixing means  13  and to the soleplate  12  as described above. The soleplates  56  &amp;  57  and  58  &amp;  59  extend in directions that form an angle of 90° relative to each other. 
   The auxiliary element  52  comprises an arm  60  provided at each end with means  61  for releasably fixing it to two beams  1  in order to hold them parallel to each other. The means  61  are identical to the fixing means  13 . 
   The auxiliary elements  53  are identical to the auxiliary element  6  and each of them is fixed to one of the parallel beams  1  in the same manner as the auxiliary element  6 . Each auxiliary element  53  has a free end provided with a housing  62  for receiving a pilot  63  secured to the stand  55 . The auxiliary elements  52  and  53  extend substantially in the same plane extending transversely to the beam  1 . 
   The auxiliary element  54  is identical to the auxiliary element  6  and is fixed to one of the beams  1  in the same way. The auxiliary element  64  has a free end provided with a fork  64  for sliding along a rail  65  secured to the stand  55 . 
   The tapped holes  12  and the smooth hole for the pin are made in the splines  7  by means of a drilling template shown in  FIGS. 7 and 8 , and given overall reference  100  in these figures. 
   The template  100  comprises a body  101  provided with means  102  enabling it to be releasably fixed on the beam  1 , and drilling bushings  103  disposed to extend over a spline for drilling when the template is in position on the beam  1 . 
   The means  102  comprise a soleplate  104  for bearing against the top faces  11  of two splines  7  for drilling that are disposed at 90° from each other on either side of another spline  7  used or positioning the template  100 . A groove  105  is formed in the soleplate  104  to receive said spline  7 . The groove  105  is defined laterally by walls  106  and  107  that are spaced apart by a distance that is greater than the distance between the flanks  9  and  10  of the spline  7 . The wall  107  is machined to form a reference surface for angularly positioning the auxiliary element  2  in co-operation with the flank  9  of the spline  7  used for positioning. A wedging device  28  identical to those described above is received between the flank  10  and the facing wall  106 . 
   The means  102  further comprise clamping means  108  of the “grasshopper” type for bearing against the top faces  11  of two splines  7  opposite from the splines  7  that are to be drilled so as to press the soleplate  104  against the top faces  11  of the two splines  7  that are to be drilled. Other clamping means could be used. 
   The template  100  is put into place on a spline  7  and is positioned along it by using positioning means. The positioning means may be constituted merely by measuring a distance from a predetermined reference point on the beam or by using a longitudinal positioning template. 
   When the template  100  is in position, the drilling bushings  103  extend over the splines  7  for drilling. 
   The template  100  may be arranged to enable more than two splines  7  to be drilled, and may optionally be made in two parts so as to enable all of the splines to be drilled. 
   It should be observed that the retaining spline for positioning the template  100  on the beam  1  is preferably a spline  7 ′ so as to make use of the flank  9 ′ thereof in order to ensure accurate positioning of the template. Drilling bushings may also be provided for drilling the spline(s) used for positioning. 
   Naturally, the invention is not limited to the embodiments described above, but on the contrary it covers any variant using equivalent means to reproduce the essential characteristics specified above. 
   In particular, the number of splines and the way in which they are arranged can be different from those shown, the beam  1  need not be symmetrical, or it may be symmetrical about only one of its diameters. 
   In addition, means other than the described wedging device could be used for pressing the reference wall of the groove against the reference flank  9 ′ of the spline  7 ′, for example a clamping device using an eccentric. 
   Furthermore, the beam  1  may have a plurality of splines  7 ′ each with a respective flank  9 ′ arranged to form a positioning reference. 
   Clamping means, e.g. analogous to those of the template  100 , may also be used for fixing auxiliary elements to the beams. The auxiliary elements could also bear against one spline only.