Abstract:
A device for the assembly of at least two standard elements (EB) of a precision mechanical structure by means of a linking element, where the first standard element includes a reference surface, while the second standard element includes a bearing surface which has to be positioned with precision in an orthonormal coordinate system associated with the aforementioned reference surface, given that the connection between the linking element and at least one of said standard elements (EB) includes: two contact faces provided on said linking element and said standard element (EB) respectively, a clamp composed of two half collars, held together by tightening means, and presenting shapes which interlock with the corresponding shapes of said linking element and of said standard element (EB) in such a way that the clamping of the two half collars causes the application and the centring of the two aforementioned contact faces against each other.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This present invention concerns a device for the assembly of standard elements intended for the creation of precision mechanical structures.  
         [0003]     2. Description of Related Art  
         [0004]     It applies in particular, but not exclusively, to the creation of tools for the gripping of mechanical parts intended in particular for the automobile industry. It is usable in particular on assembly lines for parts of the bodywork of automobiles which require gripping tools or grippers, which are firmly attached to fixed supports or mobile supports such as the heads of robots. It is used to position, with precision and in a repeatable manner, the aforementioned mechanical parts during their assembly on automobile assembly lines. It also allows said grippers to conform to the nature of the mechanical parts to be processed and to the type of operation to be performed on said mechanical parts.  
         [0005]     We know in fact that such grippers are designed and manufactured to order in accordance with the nature of the mechanical parts to be processed, and in particular with their geometry, with the type of operation to be performed, and especially with the trajectories to be followed by said mechanical parts.  
         [0006]     These grippers are generally manufactured in steel or aluminium alloy tubing, or in aluminium alloy bar. The dimensions of these connecting elements are determined by the loads to be supported and by the precision of the positioning required. As such, they therefore constitute tools which have to be matched to specific requirements, and which necessitate a high degree of rigidity combined with the lowest possible mass. As a consequence, their production cost is high, because the process is one which can be described as artisanal, given the diversity of the mechanical parts to be employed. In addition, in the event of failure or of damage, the stocking of such grippers constitutes an additional cost, greatly increasing their repair costs.  
         [0007]     In order to remedy these drawbacks, the invention proposes to create grippers from arms which are firmly attached to a support block, such arms being implemented in the shape of an assembly of sections of extruded aluminium alloy bar which has been processed so as to obtain the desired shape.  
         [0008]     This solution allows the weight of the gripper to be reduced while also providing a certain rigidity that guarantees the required precision and repeatability. It also results in less costly maintenance, in view of the ability to replace any defective elements. Finally, it allows the gripper to be reconfigured in order to make it compatible with different mechanical parts.  
         [0009]     The drawback of this type of gripper results from the method of assembly of the bar sections, which is performed using assembly bolts and centring pins. Such an assembly method leads to high production costs for the pin housings and for the threaded orifices, as well as high assembly costs for the mating of the pins with their housings and the number of tightening operations necessary.  
         [0010]     Given the problems mentioned above, the invention particularly has the aim of facilitating the assembly operations and reducing the costs associated with the production and assembly operations.  
       SUMMARY OF THE INVENTION  
       [0011]     To this end, it propose a device for the assembly of at least two standard elements of a precision mechanical structure by means of a linking element, where the first standard element includes a reference surface while the second standard element includes a bearing surface which has to be positioned with precision in a orthonormal coordinate system associated with the aforementioned reference surface, characterised in that the connection between the linking element and at least one of said standard elements includes: 
        two contact faces provided on said linking element and said standard element respectively,     a clamp composed of two half collars, held together by tightening means, presenting shapes which interlock with the corresponding shapes of said linking element and of said standard element in such a way that the tightening of the two half collars causes the application and the centring of the two aforementioned contact faces against each other.        
 
         [0014]     Advantageously, the contact faces of the aforementioned standard elements and connecting elements which have to be associated will be composed of end cheek-plates, of circular shape, which may or may not include angular positioning elements such as at least a flat part or an assembly of the tenon/mortise type or at least one cylindrical pin mounting.  
         [0015]     In addition, at least two connecting elements can be assembled by means of junction elements associated with transition elements, where said junction elements can be of cubic or prismatic shape so as to position the connecting elements, in relation to each other, in accordance with orthogonal or oblique directions respectively. Said transition elements will be firmly attached to the junction elements by means of tightening elements, and positioned by means of an assembly of the tenon/mortise type. The association of the linking element to the transition element is effected by clamps composed of half collars hinged to each other at one of their ends and with clamping means at the other end.  
         [0016]     Likewise, the standard element, which includes the bearing surface, can be of the non-adjustable or adjustable type. In the second case, the aforementioned bearing surface can be positioned in relation to the end cheek-plate with at least one degree of freedom.  
         [0017]     Furthermore, the linking element, composed of a connecting section and two end cheek-plates can be of different lengths, and can therefore satisfy the requirements of the needs expressed. It can also include orifices which are positioned in parallel with the principal axis of said linking element so as to allow the passage of fluid circuits, electrical circuits or control devices.  
         [0018]     Thus the assembly of standard elements composed of connecting elements of different lengths, associated with adjustable and non-adjustable standard elements, where the connecting elements can be held together by junction elements allowing them to be positioned in different directions, can constitute a gripper that includes multiple bearing surfaces referenced in relation to a reference surface or in relation to at least one other bearing surface constituting the aforementioned reference surface.  
         [0019]     These different standard elements will be designed so as to satisfy the requirements of precision, rigidity and low mass which are necessary for the creation of grippers. Thus, for example, the connecting elements will be created from extruded aluminium-alloy bar. The adjustable standard elements will include precise positioning devices in translation or in rotation. The clamps composed of half collars will be in shape conformity with the end cheek-plates, complying with the precision and rigidity requirements. This will also apply to the assembly of the tenon/mortise type, allowing association of the standard elements and transition elements.  
         [0020]     Methods for the implementation of the invention will be described below, as non-limited examples, with reference to the appended figures, in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is a perspective view of a basic element, shown in exploded form.  
         [0022]      FIG. 2  is a perspective view of a linking element.  
         [0023]      FIG. 3  is a perspective view of non-adjustable terminal elements.  
         [0024]      FIG. 4  is a perspective view of adjustable terminal elements.  
         [0025]      FIG. 5  is a perspective view of junction elements.  
         [0026]      FIG. 6  is a perspective view of a junction element associated with transition elements.  
         [0027]      FIG. 7  is a perspective view of clamps.  
         [0028]      FIG. 8  is an example of the assembly of standard elements. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]     In the example shown in  FIG. 1 , the basic element EB essentially includes a top plate EB 1 , of rectangular shape, a bottom plate EB 2  of rectangular shape identical to that of the top plate EB 1 , an inspection plate EB 3  associated with the bottom plate EB 2 , and a certain number of basic transition elements EB 4 , of which there are  8  in the present case, positioned between the top plates EB 1  and bottom plates EB 2 .  
         [0030]     Thus, by means of the top plate EB 1 , the basic element EB is used to fix the assembly of standard elements according to the invention, constituting a gripper, to a fixed support or a mobile support such as the head of a robot.  
         [0031]     The top surface of the aforementioned top plate EB 1  will constitute the so-called reference surface of the gripper.  
         [0032]     The top plate EB 1 , includes grooves EB 11 , positioned in parallel with the large dimension of said top plate EB 1 , and cut into the top face of said top plate EB 1 . Said grooves EB 11 , also include circular orifices EB 12  passing through the plate at the bottom of the groove.  
         [0033]     The aforementioned bottom plate EB 2 , identical in length and width to those of the top plate EB 1 , includes a rectangular opening EB 21  which acts as an access door, and this rectangular opening EB 21  is associated with a plate EB 3 , of corresponding shape and fixed solidly to said bottom plate EB 2  by appropriate means. The aforementioned bottom plate EB 2  also includes circular orifices EB 22 , passing through the wall of said bottom plate EB 2 , the axes of which are co-linear with the axes of the circular orifices EB 12  in the top plate EB 1 .  
         [0034]     A certain number of basic transition elements EB 4  are located between the aforementioned top plates EB 1  and bottom plates EB 2 . In the present case, there are  8  of these.  
         [0035]     Each basic transition element EB 4  includes a parallelepiped element EB 41 , a cheek-plate of circular section EB 42  and a connecting element EB 43 , joining the body element EB 41  to the cheek-plate EB 42  of circular section. In addition each body element EB 41  includes two circular, orifices EB 45  whose axes are parallel to the axes of orifices EB 12  and EB 22 .  
         [0036]     Thus, taken in pairs, the aforementioned orifices EB 45 , EB 22  and EB 12 , have a co-linear axis, and are used to join the different basic elements EB 4  between the top plates EB 1  and bottom plates EB 2  by means of cylindrical bushings EB 5  and shoulder-headed bolts EB 6 .  
         [0037]     In fact, the aforementioned cylindrical bushings EB 5  include a cylindrical part EB 51  that fits into in the circular orifice EB 12  of the top plate EB 1 , and the circular orifice EB 45  of the basic transition element EB 4 , a shoulder EB 52  of rectangular or square section that fits into a corresponding shape in the groove EB 11  of the top plate EB 1 , and a threaded orifice EB 53  whose axis is co-linear with that of the cylindrical part EB 51 .  
         [0038]     In addition, the aforementioned shoulder-head bolts EB 6  include a head EB 61  which bears onto the bottom surface of the bottom plate EB 2 , and a threaded part EB 62  that screws into the threaded orifice EB 53  of the corresponding cylindrical bushing EB 5 .  
         [0039]     Furthermore, each of said cheek-plates EB 42  of the basic transition elements EB 4  includes, on its periphery, at least one indentation EB 46  whose width is equal to the diameter of the hinging swivel-pin of the clamps, which will be described later.  
         [0040]     In the example shown in  FIG. 2 , the linking element EL is composed of a length EL 1  of circular section, and two cheek-plates EL 2  and EL 3 , also of circular section. The axes of symmetry of the length EL 1 , and of the cheek-plates EL 2  and EL 3 , are co-linear with the principal axis ΔEL of the linking element EL). The distance separating the two external faces of the cheek-plates EL 2  and EL 3  determines the length of the linking element EL.  
         [0041]     Thus, several lengths will be provided in this way, separated by a constant or variable distance, allowing the length combinations necessary for the gripper design.  
         [0042]     In addition, each of said cheek-plates includes, at its periphery, at least one indentation EL 4  whose width is equal to the diameter of the hinging swivel-pin of the clamps to be described later. The aforementioned indentation EL 4  is used to position the linking element EL angularly in relation to the element that will be associated with it.  
         [0043]     Advantageously, the linking element will include orifices EL 5  positioned in parallel with the axis ΔEL. Their section can be circular or any other shape. Their purpose is to reduce the mass of the linking element EL, though without compromising the rigidity of said linking element EL. They can also be used to accommodate fluid circuits, electrical circuits or control devices that have to pass through the linking element EL. In addition, the section of the linking element EL 1  can be square, polygonal, or any other shape, so as to constitute, with the orifices EL 5 , a compromise between a minimum surface area and a maximum principal moment of inertia along the two orthogonal directions of inertia.  
         [0044]     In the example shown in  FIG. 3 , the non-adjustable terminal elements ETA, ETB, and ETC, are composed essentially of a cheek-plate ET 1 , of circular section, centred on the principal axis AET, and including on their periphery at least one indentation ET 7  whose width is equal to the diameter of the hinging swivel-pin of the clamps to be described later, of a body element ET 2  and ET 3 , that includes a bearing surface, rectangular or circular respectively, and a body element ET 4 , ET 5  and ET 6  constituting the link between the cheek-plates ET 1  and the body element constituting the bearing surfaces.  
         [0045]     Thus, as an example, three types of non-adjustable terminal elements ETA, ETB and ETC, shown in  FIG. 3 , are used respectively to obtain a rectangular bearing surface containing the principal axis ΔET, a rectangular bearing surface that is offset in relation to the principal axis ΔET, and a circular bearing surface on the principal axis ΔET.  
         [0046]     In addition, as an example, four orifices ET 8  are created perpendicularly to the aforementioned bearing surfaces, providing the connection between the mechanical part to be processed and the assembly according to the invention, constituting the gripper.  
         [0047]     In the example shown in  FIG. 4 , the adjustable terminal elements ETRA, ETRB, ETRC and ETRD are composed essentially of a cheek-plate ETR 1 , of circular section, centred on the principal axis ΔETR, and include on their periphery at least one indentation ETR  16  whose width is equal to the diameter of the hinging swivel-pin of the clamps to be described later, of a body element ETR 2 , ETR 3 , ETR 4  and ETR 5  firmly attached to the corresponding cheek-plate ETR 1 , and of a mobile element ETR 6 , ETR 7 , ETR 8  and ETR 9  respectively in relation to the aforementioned element ETR 2 , ETR 3 , ETR 4  and ETR 5  including either a circular bearing surface or a rectangular bearing surface.  
         [0048]     The first example of an adjustable terminal element ETRA includes a cheek-plate ETR 15  of circular section, attached to the mobile element ETR 6 , and constituting the bearing surface of the terminal element ETRA. Said mobile element ETR 6  is able to pivot around an axis perpendicular to the principal axis ΔETR by means of a shaft ETR 7  mounted to rotate in the fixed element ETR 2 . Thus the axis of symmetry of the cheek-plate ETR 15  is able to pivot in the plane containing the principal axis ΔETR by an angle greater than 90° on either side of said principal axis ΔETR. Advantageously, the cheek-plate ETR 15  can include, on its periphery, at least one indentation ETR 16  whose width is equal to the diameter of the hinging swivel-pin of the clamps to be described later. Moreover, the locking into angular position of the mobile element ETR 6  in relation to the fixed element ETR 2  will be effected by means of a pin placed in at least one circular orifice ETR 11  located around the axis of rotation of said mobile element ETR 6 .  
         [0049]     The second example of an adjustable terminal element ETRB includes a cheek-plate ETR 15  of circular section, attached to a mobile element ETR 7 , and constituting the bearing surface of the terminal element ETRB. Said mobile element ETR 7  is able to slide in parallel with the principal axis ΔETR. Thus the axis of symmetry of the cheek-plate ETR 15  will be co-linear with the principal axis ΔETR. Advantageously, the cheek-plate ETR 15  can include, on its periphery, at least one indentation ETR 16  whose width is equal to the diameter of the hinging swivel-pin of the clamps to be described later. In addition, the locking of the mobile element ETR 7  in a longitudinal position in relation to the fixed element ETR 3  will be effected by means of a dowel pin placed in at least one circular orifice ETR 11  placed perpendicularly to the principal axis ΔETR.  
         [0050]     The third example of an adjustable terminal element ETRC includes a mobile element ETR 8  in relation to the fixed element ETR 4 , and constituting the bearing surface of the terminal element ETRC. Said mobile element ETR 8  is able to slide perpendicularly to the principal axis ΔETR. In addition, the locking of the mobile element ETRB in a transverse position in relation to the fixed element ETR 4  will be effected by means of a shoulder-headed screw ETR 13 , thread mounted in the mobile element ETR 8  and which is able to slide in at least one oblong orifice ETR 14  whose longitudinal axis is perpendicular to the principal axis ΔETR. Also, as an example, four orifices ETR 1   7  are created perpendicularly to the aforementioned bearing surface, allowing the connection to be made between the mechanical part to be processed and the assembly according to the invention, constituting the gripper.  
         [0051]     The fourth example of an adjustable terminal element ETRD includes a mobile element ETR 9  in relation to the fixed element ETR 5 , and constituting the bearing surface of the terminal element ETRD. Said mobile element ETR 9  is able to slide perpendicularly to the principal axis, ΔETR and along the principal axis ΔETR. In addition, the locking in the transverse position and in the longitudinal position of the mobile element ETR 9  in relation to the fixed element ETR 5  will be effected by means of at least one bolt ETR 13 , which is able to slide in two oblong orifices ETR 14  whose longitudinal axes are perpendicular and parallel to the principal axis ΔETR respectively. Advantageously, the locking in the transverse position and in the longitudinal position of the mobile element ETR 9  in relation to the fixed element ETR 5  will be effected by means of a dowel pin placed in at least one circular orifice ETR 11  positioned perpendicularly to the principal axis ΔETR. Also, as an example, four orifices ETR 17  are created perpendicularly to the aforementioned bearing surface, providing the connection between the mechanical part to be processed and the assembly according to the invention, constituting the gripper.  
         [0052]     In the example shown in  FIG. 5 , the junction element EJA is composed essentially of a principal prismatic element, and the junction elements EJB, EJC, EJD, EJE, EJF, EJG, and EJH are composed essentially of a principal cubic element. Thus the bearing faces of the prism or of the cube can receive at least one transition element ETT which will be described later. In fact the aforementioned junction element EJA is able to receive two junction elements ETT. The bearing faces make an angle which can vary between 0° and 90°, and preferably equal to 30°, or 45°, or 60°.  
         [0053]     The aforementioned junction elements EJB, EJC, EJD, EJE, EJF, EJG and EJH can receive 2, 3, 3, 4, 4, 5 and 6 junction elements ETT respectively, corresponding to the different possible combinations, given the six faces of a cube.  
         [0054]     In the example shown in  FIG. 6 , the junction element EJ is composed essentially of a principal cubic element. Each of the six faces of said principal cubic element EJ includes a mortise EJ 1  whose longitudinal axis contains the centre of the corresponding face and whose length is equal to the length of said corresponding face.  
         [0055]     In addition, each of the six faces of said principal cubic element EJ includes a threaded circular orifice EJ 2  whose principal axis is perpendicular to the corresponding face, and contains the centre of said corresponding face.  
         [0056]     Thus, each of the six faces of the principal cubic element EJ can receive a transition element ETT, which is composed of a cheek-plate ETT 1  of circular section, a pin mounting ETT 2 , and a connecting element ETT 5 , which can be of circular section, linking said cheek-plate ETT 1  to said tenon ETT 2 .  
         [0057]     The assembly composed of the cheek-plate ETT 1 , the tenon ETT 2  and the connecting element ETT 5 , is traversed by a circular orifice ETT 4  whose principal axis contains the centre of said cheek-plate ETT 1 .  
         [0058]     The tenon ETT 2  will be of a shape to correspond with the mortise EJ created in the bearing face of the junction element EJ receiving the corresponding transition element ETT.  
         [0059]     A shoulder-head screw ETT 3  will bear upon the external face of the cheek-plate ETT 1 , and will hold the transition element ETT by a tightening operation on the threaded part of the screw ETT 3  in the threaded circular orifice EJ 2 .  
         [0060]     Advantageously, the same principle for attaching the transition element ETT to the prismatic-type junction element can be applied to the two faces of said junction element.  
         [0061]     In the example shown in  FIG. 7 , five types of clamp BRA, BRB, BRC, BRD and BRE are proposed as examples. Clamps BRA and BRB are composed of two half collars associated with a swivel-pin. Clamps BRC, BRD and BRE are composed of two half collars associated with two swivel-pins.  
         [0062]     In addition, said half collars are tightened at the end opposite to that including either two-. swivel-pins of a locking device, or by a bolt bearing upon the two half collars, or by a shoulder-head screw, hinged on one of the two half collars and bearing upon the other half-collar.  
         [0063]     Each of the two half collars includes a throat of trapezoidal section and of a shape that corresponds with the two cheek-plates of circular section corresponding to the two elements which have to be brought together. These elements can be connecting elements EL, non-adjustable terminal elements ET, adjustable terminal elements ETR, transition elements ETT associated with junction elements EJ, or basic transition elements associated with the basic element EB.  
         [0064]     In a more precise manner, the aforementioned clamp BRA includes two half collars BR 1  and BR 1 ′, hinged at one of their ends by means of a swivel-pin BR 2 , where the length of the aforementioned swivel-pin BR 2  is greater than the width of said half collars BR 1  AND BR 1 ′. In addition the axis ΔBR 1  of said swivel-pin BR 2  is parallel to the central axis ΔBR of the clamp BRA.  
         [0065]     A bolt BR 3 , whose principal axis ΔBR 2  is perpendicular to the central axis ΔBR of the clamp BRA, bears upon the ends of the two half collars opposite to the aforementioned swivel-pin BR 2 .  
         [0066]     This type of clamp can be used essentially in the case where the respective angular positioning of the two cheek-plates, corresponding to the two elements which have to be brought together, is not necessary.  
         [0067]     The aforementioned clamp BRB includes two half collars BR 1  AND BR 1 ′, hinged at one of their ends by means of a swivel-pin BR 2 , where the length aforementioned swivel-pin BR 2  is at least equal to the width of said half collars BR 1 , BR 1 ′. In addition, the axis ΔBR 1  of said swivel-pin BR 2  is parallel to the central axis ΔBR of the clamp BRB.  
         [0068]     A bolt BR 3 , whose principal axis ΔBR 2  is perpendicular to the central axis ΔBR of the clamp BRB bears upon the ends of the two half collars opposite to the aforementioned swivel-pin BR 2 .  
         [0069]     In addition, the ends of the two half collars associated with the aforementioned swivel-pin BR 2  are pierced so as to free the corresponding portion of the aforementioned swivel-pin BR 2 .  
         [0070]     This type of clamp can essentially be used in the case where respective angular positioning of the two cheek-plates, corresponding to the two elements which have to be brought together, is necessary. In this case, the aforementioned corresponding portion of the swivel-pin BR 2  will slot into an indentation, described previously, machined into the two cheek-plates.  
         [0071]     The aforementioned clamp BRC includes two half collars BR 5  and BR 5 ′, hinged at one of their ends by means of two swivel-pins BR 4  and BR 4 ′, where the length of the aforementioned swivel-pins BR 4  and BR 4 ′ is at least equal to the width of said half collars BR 5  and BR 5 ′. In addition the axes ΔBR 1  and ΔBR 1 ′ of said swivel-pins BR 4  and BR 4 ′ are parallel to the central axis ΔBR of the clamp BRC. The swivel-pins BR 4  and BR 4 ′ are held apart by a shim BR 9  which has a flat surface oriented toward the central axis ΔBR and parallel to said central axis ΔBR.  
         [0072]     A locking device, including a threaded sleeve BR 8 , hinged on the end of one of the two half collars opposite to the aforementioned swivel-pins BR 4  and BR 4 ′, by means of an axle BR 6 , and a shoulder-head screw BR 7  bearing upon the end of the other of the two half collars opposite to the aforementioned swivel-pins BR 4  and BR 4 ′, employs a tightening operation on the aforementioned shoulder-head screw BR 7  in the threaded sleeve BR 8 , to tighten the two half collars BR 5  and BR 5 ′. This type of clamp can essentially be used in the case where the respective angular positioning of the two cheek-plates, corresponding to the two elements which have to be brought together, is necessary in this case, the aforementioned shim BR 9  will press against a flat part machined on the two cheek-plates.  
         [0073]     The aforementioned clamp BRD includes two half collars BR 5  and BR 5 ′, hinged at one of their ends by means of two swivel-pins BR 4  and BR 4 ′, where the length of the aforementioned swivel-pins BR 4  and BR 4 ′ is at least equal to the width of said half collars BR 5  and BR 5 ′. In addition the axes ΔBR 1  and ΔBR 1 ′ of said swivel-pins BR 4  and BR 4 ′ are parallel to the central axis ΔBR of the clamp BRC. The swivel-pins BR 4  and BR 4 ′ are held apart by two shims BR 10  and BR 10 ′, which are not shown.  
         [0074]     A locking device, including a threaded sleeve BR 8 , hinged on the end of one of the two half collars opposite to the aforementioned swivel-pins BR 4  and BR 4 ′ by means of an axle BR 6 , and a shoulder-head screw BR 7  bearing upon the end of the other of the two half collars opposite to the aforementioned swivel-pins BR 4  and BR 4 ′, employs a tightening operation on the aforementioned shoulder-head screw BR 7  in the threaded sleeve BR 8  to tighten the two half collars BR 5  and BR 5 ′.  
         [0075]     This type of clamp can essentially be used in the case where the respective angular positioning of the two cheek-plates, corresponding to the two elements which have to be brought together, is not necessary.  
         [0076]     The aforementioned clamp BRE includes two half collars BR 5  and BR 5 ′, hinged at one of their ends by means of two swivel-pins BR 4  and BR 4 ′, where the length of the aforementioned swivel-pins BR 4  and BR 4 ′ is at least equal to the width of said half collars BR 5  and BR 5 ′. In addition the axes ΔBR 1  and ΔBR 1 ′ of said swivel-pins BR 4  and BR 4 ′ are parallel to the central axis ΔBR of the clamp BRC. The swivel-pins BR 4  and BR 4 ′ are held apart by a shim BR 11 .  
         [0077]     A locking device, including a threaded sleeve BR 8 , hinged on the end of one of the two half collars opposite to the aforementioned swivel-pins BR 4  and BR 4 ′ by means of an axle BR 6  and a shoulder-head screw BR 7  bearing upon the end of the other of the two half collars opposite to the aforementioned swivel-pins BR 4  and BR 4 ′, employs a tightening operation of the aforementioned shoulder-head screw BR on the threaded sleeve BR 8  in order to tighten the two half collars BR 5 , BR 5 ′.  
         [0078]     This type of clamp can essentially be used in the case where the respective angular positioning of the two cheek-plates, corresponding to the two elements which have to be brought together, is necessary. In this case, at least one swivel-pin BR 12  fitted to one of the two cheek-plates will allow the other cheek-plate to be positioned.  
         [0079]     In the example shown in  FIG. 8 , an assembly of standard elements according to the invention is proposed, providing an overview if the capabilities provided by the various elements described above.  
         [0080]     A basic element EB is equipped with eight junction elements EJ (shown partially), brought together with the basic element EB by eight basic transition elements (not shown).  
         [0081]     Connecting elements EL 1 , EL 2 , EL 3 , EL 4 , EL 5 , EL 6  and EL 7  are either firmly attached to each other by junction elements EJ 2 , EJ 3 , EJ 4 , EJ 5 , EJ 6  and EJ 7  or firmly attached to the basic element EB.  
         [0082]     A non-adjustable terminal element ET 1  is attached to the basic element EB.  
         [0083]     Adjustable terminal elements ETR 1 , ETR 2 , ETR 3  and ETR 4  are attached to junction elements EJ 3 , EJ 5 , EJ 8  and EJ 9 . Junction elements EJ 1 , EJ 6  and EJ 10  are available for other attachments.  
         [0084]     An adjustable terminal element ETR 5  is attached to another adjustable terminal element ETR 1 .  
         [0085]     The clamps used for the attachments between these different elements are shown partially.  
         [0086]     Thus, this example of a gripper will have five bearing surfaces, positioned and oriented with precision in relation to the reference surface represented by the top surface of the basic element EB.  
         [0087]     Given the possible adjustments offered by the adjustable terminal elements ETR 1 , ETR 2 , ETR 3  and ETR 4 , any finishing work connected with the geometry of the mechanical parts to be processed will thus be facilitated.  
         [0088]     The replacement of elements or the addition of other elements can easily be envisaged without compromising the initial structure.  
         [0089]     The present invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.  
         [0090]     Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.