Abstract:
A clamping device ( 1 ) is disclosed for one or several workpieces ( 2 ), especially bodywork parts. The clamping device ( 1 ) includes one or several clamps ( 4 ) which can be positioned on a clamping table. Several parts can be displaced along at least one axis. The clamps ( 4 ) comprise a positioning device ( 13 ) and a fixing device ( 10 ). The positioning device ( 13 ) has a height adjustment system ( 21 ) and/or angle adjustment system ( 22 ) and/or lateral adjustment system ( 4   b ). To allow for stepless adjustment over a wide range the positioning device ( 13 ) has a coarse adjustment system ( 43 ) and a fine adjustment system ( 44 ). The fixing device ( 10 ) can be configured as a clamping device ( 35 ) and simultaneously include the lateral adjustment system ( 4   b ).

Description:
FIELD OF THE INVENTION 
     The present invention pertains to a clamping apparatus for workpieces, especially body parts with one or more tensioner, which can be positioned on a said clamping table. The tensioners have a plurality of tensioner parts, which are guided adjustably in relation to one another along at least one axis and which have a positioning device ( 13 ) with a vertical adjustment device and a fixing device for the mutual adjustment. 
     BACKGROUND OF THE INVENTION 
     Such a clamping apparatus has been known from DE-A 197 16 874. It comprises one or more tensioners, which can be positioned on a clamping table and with which the workpiece, e.g., body parts of vehicles, can be clamped. The workpiece can then be welded or machined in another way by an industrial robot or the like. The tensioners are of a multipart design and comprise a foot part, a middle part and a head part, which are guided adjustably relative to another along at least one axis. A positioning apparatus with vertical adjustment apparatus and a fixing device are present for the mutual adjustment. The vertical adjustment apparatus comprises one or more adjusting screws between the parts of the tensioner. The foot part may also be fastened to the clamping table via a spacer placed under it. The fixing device comprises an elongated hole guide with two clamping screws. Moreover, the positioning apparatus may also comprise an angle adjustment apparatus with an additional pivot bearing between the parts of the tensioner. As an alternative, it is also possible to use a bent middle part. The lower adjusting screw for the vertical adjustment apparatus is reserved for the supplier and is used to set a fixed basic length of the clamping unit specified by the user. Only the upper adjusting screw between the middle part and the head part is then accessible to the customer and user. He can then perform a fine adjustment within a narrow range by apparatus of this adjusting screw. The tensioners are accurately positioned according to the user&#39;s specifications and hold the workpiece in the specified position. Inaccurate workpieces (pilot run) as well as warping during machining may make it necessary to adjust the clamping points. This adjustment can be carried out by the customer with the prior-art tensioner only with the upper adjusting screw and in a range limited by the screw. The inaccuracies inherently existing in adjusting screws must be accepted here. The tensioner as a whole can be adjusted vertically continuously by apparatus of the adjusting screws. 
     WO 96/38265 shows another clamping unit, which comprises a bracket, a clamping frame, a centering piece and a support that can be fastened thereto. This clamping unit has a fixed, predetermined length, which is determined by the length of the support cut as needed. The support may assume different angular positions in relation to the foot-side bracket, which can be achieved by dividing the clamping frame and the centering piece into mutually independent components and by apparatus of correspondingly shaped connection surfaces. 
     U.S. Pat. No. 2,497,943 discloses another clamping unit for sewing machines, typewriters, electric motors or the like for repair purposes. It has a pivotable bracket with clamping jaws for this purpose, which can be adjusted by apparatus of a spindle. 
     Clamping pallets for workpieces on machine tools or gaging machines have been known from DE-A 195 36 341, DE-A 42 43 370 and DE-A 38 01 813. The tensioners have clamping claws, which are vertically adjustable by apparatus of adjusting screws, toothed plates or the like. Finally, a clamping unit with a plurality of clamping parts that are angularly adjustable in relation to one another has been known from GB-A 1 466 434. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     The object of the present invention is therefore to provide a more flexible clamping apparatus. 
     According to the invention, a clamping apparatus is provided for workpieces, especially body parts. The clamping apparatus comprising one or more tensioners, which can be positioned on a clamping table. The tensioners have a plurality of tensioner parts, which are guided adjustably in relation to one another along at least one axis and which have a positioning apparatus with a vertical adjustment device and a fixing device for the mutual adjustment. The vertical adjustment has a coarse adjustment device and a fine adjustment device, wherein the coarse adjustment device has a grid-like mount and a hinge pin on one tensioner part and the fine adjustment device has a support and optionally one or more fitting plates and a fixing device for supporting the hinge pin on the other tensioner part. 
     In the clamping apparatus, the individual tensioners have a multipart design in themselves and are adjustable along at least one translatory and/or rotary axis, i.e., especially vertically and/or in at least one lateral direction and/or in at least one angle. For an exact adjustment, they have a positioning means and a fixing device, wherein these means may be structurally separate or combined. As a result, the tensioners can be adjusted vertically and/or angularly as desired to compensate distortion and warping phenomena. The tensioners are thus changed in themselves. Disassembly and repositioning of the tensioners is not necessary. 
     The clamping apparatus has the advantage that a small number of standard elements are sufficient for a broad field of application. Continuous vertical, lateral and/or angular adjustment is possible with high accuracy and reproducibility. 
     Two possibilities of adjustment, namely, a coarse adjustment and a fine adjustment for highly accurate adjustment that nevertheless covers a broad range, are possible for vertical adjustment. A grid-like mount with a stepwise adjustment in greater increments in combination with suitable, accurately fitting supports offers advantages at least for the vertical adjustment in terms of handling, precision and the manufacturing and assembly efforts. The supports may be designed as disks and have an additional lateral mobility for the lateral adjustment. 
     The clamping apparatus makes possible a simple adjustment at the manufacturer or at the site of installation. Furthermore, it is possible to prepare the foot part and the adjusting part of the tensioners from simple stock parts without project-specific machining. The accurate setting of the tensioners is performed only by means of the positioning and fixing device. 
     The preferred fixing device with the clamping apparatus has the advantage that it can also be used as a positioning device for the lateral adjustment at the same time. By placing a wedge part or a pressure piece against a corner area of the component member or adjusting part being guided, force is introduced obliquely, which ensures better fixation. As a result, it is possible, in particular, to support the adjusting part in a plurality of directions or axes. Additional fixations may be eliminated. The adjusting part can be accurately positioned by means of distance plates and fitting plates. Moreover, the position of the adjusting part can be statically defined. 
     The fixing device allows tolerance errors on the component members and the parts of the clamping apparatus and as a result it always ensures reliable fixation in the correct position. By inserting distance plates and fitting plates, shim rings or other similar positioning elements, particularly accurate mutual positions of the component members can also be set and secured. 
     For the lateral adjustment, additional lateral mobilities may be available at the other positioning means. These may be advantageously provided in the area of the supports and hinge pins. Furthermore, it is favorable to arrange a positive-locking plug-in connection between the support and the hinge pin and, in addition, to provide a fixation. This is practical for accurate positioning and prevents the loss of parts during disassembly or reassembly. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a schematic top view of a clamping table with a clamping apparatus and a clamped workpiece; 
     FIG. 2 is a side view of an individual tensioner with a vertical adjustment means; 
     FIG. 3 is a front view of the tensioner according to arrow III in FIG. 2; 
     FIG. 4 is a vertical adjustment device of the tensioner according to FIGS. 2 and 3; 
     FIG. 5 is a view showing an operating position of a tensioner with a vertical and angular adjustment device; 
     FIG. 6 is a view showing another operating position of a tensioner with a vertical and angular adjustment device; 
     FIG. 7 is a view showing another operating position of a tensioner with a vertical and angular adjustment device; 
     FIG. 8 is a side view of a variant of the embodiment of FIGS. 5 through 7 with another angular adjustment device; 
     FIG. 9 is a front view of the variant of the embodiment of FIGS. 5 through 7 with another angular adjustment device showing an operating position; 
     FIG. 10 is a view of the variant of the embodiment of FIGS. 5 through 7 with another angular adjustment device showing another operating position; 
     FIG. 11 is a side view of a variant of the tensioner with another fixing device and a lateral adjustment device; 
     FIG. 12 is a sectional view through the arrangement shown in FIG. 11 corresponding to the section line XII—XII; 
     FIG. 13 is a view showing a variant of FIG. 12; and 
     FIG. 14 is a variant of the support according to FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings in particular, FIG. 1 shows a schematic top view of a clamping table  3 , on which one or more workpieces  2  are clamped with one or more tensioners  4  in the exact position needed for machining. The workpiece  2  is preferably a body part of a vehicle. In the embodiment shown, it is a vehicle door. The tensioners  4  are mounted on the clamping table  3  at suitable points in a fixed or adjustable manner. The workpiece  2  is machined by an industrial robot (not shown) or by another suitable device in the clamped position. This may be, e.g., a welding operation. 
     The tensioners  4  have clamping elements that may have any desired design. In the embodiment shown, two clamping jaws  6  are provided, which are mounted movably, especially pivotably in relation to one another and receive between them and clamp two body panels  2  with fittingly machined clamping surfaces. They are actuated by a suitable drive  5 . The drive  5  may have any desired design. It is preferably designed as a remotely controllable motor drive or as a hydraulic or pneumatic and likewise remotely controllable cylinder. The clamping elements are arranged at the adjusting part  9 . 
     The individual tensioners  4  are multipart tensioners in the manner described below and are adjustable along at least one translatory and/or rotary axis. They are preferably adjustable vertically and/or in at least one lateral direction and/or in at least one angle. The possibilities of adjustment may be combined as described and may also be used individually. 
     The position of the tensioner may be changed continuously while maintaining the position on the clamping table  3 . Machining-related errors on the workpiece  2  can be anticipatorily compensated with this adjustment. The tensioners  4  are deliberately set with a deviation from their specified desired position. For example, the tensioners  4  may be set slightly higher and/or with an angular deviation in order to compensate a warping caused by welding or the like as a result and to absorb and compensate a lowering of the workpiece  2  in the clamped area that occurs in this process. The workpiece  2  will then have the desired shape after the machining. 
     FIGS. 2 and 3 show a side view and a front view of an individual tensioner. The tensioner  4  is a multipart tensioner in itself and comprises, e.g., a foot part  7  and at least one adjusting part  9  adjustably arranged thereon. The foot part  7  has, e.g., a base  8 , which is fastened, e.g., screwed, on the clamping table  3  in the specified position. In the embodiment shown, the adjusting part  9  comprises a vertically directed plate, which is adjustably guided in a suitable manner at the foot part  7 . The guide  12 ,  12 ′ may be, e.g., a groove guide engaging itself in a positive-locking manner or the like. In deviation from the embodiment shown, the tensioner  4  may also comprise more than two parts  7 ,  9 . 
     To adjust the adjusting part  9  in relation to the foot part  7 , a fixing device or fixing means  10  and a positioning device or positioning means  13  are provided, which may have various suitable designs. The positioning device  13  permits continuous adjustment of the parts  7 ,  9  over a broad range of adjustment and has a coarse adjustment means  43  and a fine adjustment means  44  for this. 
     In the exemplary embodiment shown, the fixing device  10  comprises a vertical elongated hole guide  12  in one of the two clamping parts  7 ,  9  and two or more clamping screws  11 . In one embodiment, not shown, sleeve-like sliding blocks, which engage fitting countergrooves on the contact surfaces of the tensioner parts  7 ,  9  facing one another, may be arranged, e.g., clamping screws  11 . 
     The positioning means  13  is designed as a vertical adjustment device or vertical adjustment means  21  in the exemplary embodiment according to FIGS. 2 through 4. The coarse adjustment device or coarse adjustment means  43  is provided here in the adjusting part  9  as a grid-like mount  14 , which makes possible vertical adjustment at greater increments. The mount  14  comprises, e.g., a vertical row of holes, wherein the openings in the hole grid are preferably located at equally spaced locations from one another. A hinge pin  15 , which is supported on the foot part  7  via the fine adjustment means  44 , may be introduced into the mount  14  in the needed position. The fine adjustment means  44  comprises a support  16  and optionally one or more additional fitting plates  17  here. The support  16  may have a predetermined standard thickness. The fitting plate  17  may be ground or otherwise machined to an individual size. As an alternative, it may also be formed from a set of a plurality of prepared fitting plates, so-called shims. Continuous vertical adjustment is possible within the increment of the hole grid  14  by means of the support  16  and the fitting plates  17 . 
     In one variant, not shown, the coarse adjustment means  43  or the mount  14  is designed as a groove grid. The mounting is brought about here by means of a sliding block, which is inserted into the mount  14  at a particular, desired height. 
     FIGS. 5 through 7 show a clamping apparatus  1 , in which the positioning means  13  is designed as an angular adjustment device or angular adjustment means  22 . 
     In FIGS. 5 through 7, the angular adjustment means  22  comprises a rotating unit  23 , which is adjustable around an axis of rotation  25  that is essentially horizontal and extends at right angles to the principal plane of the adjusting part  9 . The embodiment according to FIGS. 8 through 10 shows a variant in which the angular adjustment means  22  is designed as a tilting unit  30 , which has a tilt axis  26  that is essentially horizontal and extends along the principal plane of the adjusting part  9 . The axes  25 ,  26  are directed at right angles to one another. The clamping apparatus  1  may have a rotating unit  23  and/or a tilting unit  30  and optionally additionally a vertical adjustment means  21  of the above-described type. 
     The rotating unit  23  according to FIGS. 5 through 7 permits a continuous or incremental rotation of the adjusting part  9  in relation to the foot part  7 . To do so, a rotary guide  27  is arranged between the foot part  7  and the adjusting part  9 . As is illustrated in two variants in FIG. 6, the rotary guide  27  may have an elongated hole guide  28  bent around the axis of rotation  25  and/or a plurality of individual holes  29  arranged in a circular arc around the axis of rotation  25 . The axis of rotation  25  is formed by a preferably central hole in the foot part  7 . 
     The rotary guide  27  cooperates with the fixing means  10  and utilizes the clamping screws  11  for the angular adjustment. The lower clamping screw  11  forms the axis of rotation  25  and is inserted into the corresponding hole of the foot part. The upper clamping screw  11  is inserted into the rotary guide  27 ,  28 ,  29  and is set to the desired angle. The elongated hole guide  12  is located in the adjusting part  9 . This part can be additionally adjusted vertically at a given angular position by means of the elongated hole guide  12 . For example, a vertical adjustment means  21  corresponding to the above-described exemplary embodiments may be used for this purpose. 
     The foot part  7  may have a rotary support  24  for the vertical adjustment means  21 . In the embodiment shown with three angular positions predetermined by means of individual holes  29 , the rotary support  24  comprises a bent base, which has a support surface parallel to the base  8  in the middle area for the upright position according to FIG.  5 . On the two adjoining flank areas, the base is beveled corresponding to the selected angular position. The support  16  with its fitting plates  17 , the cam  18  or the stop  19  can be supported on the rotary support  24 . The angular and vertical adjustment is fixed by means of the clamping screws  11 . 
     FIGS. 8 through 10 show three different designs of the tilting unit  30 . In the variant shown in FIGS. 8 and 9, the tilting unit  30  comprises a tilting base  31  with the tilt axis  26  arranged at the end. In addition, a flange  32  is articulated to the tilt axis  26 . The tilted position is obtained by rotating the tilting base  31  in relation to the flange  32 . The desired angular adjustment and the fixation are performed by means of an adjusting element  33  between the tilting base  31  and the flange  32 , which is designed, e.g., as an adjusting screw and has an oblique guide for the tilting base  31  and for the accurate setting of the desired tilt angle. 
     In the embodiment according to FIG. 8, the flange  32  is directed essentially vertically and is fastened to the foot part  7  by means of the fixing device  10 . A vertical adjustment means  21  may be present. The tilt axis  26  is located at the top edge of the flange  32 . The tilting base  31  is again fastened to the adjusting part  9  by means of a fixing device  10 . Longitudinal or vertical adjustment means  21  may be present here as well. The adjusting part  9  is pivoted by the tilting unit  30  in relation to the foot part  7 . 
     In the variant according to FIG. 9, the tilting unit  30  is located between the base  8  and the clamping table  3 , wherein the tensioner  4  as a whole can be pivoted in relation to the clamping table  3  around the tilt axis  26 , which is essentially parallel to the table. The flange  32  is fastened to the clamping table  3 . The tilting base  31  is connected to the base  8 . The adjusting element  33  is directed vertically here. It is directed essentially horizontally in FIG.  8 . 
     In the third variant according to FIG. 10, the tilting unit  30  comprises a wedge piece  34 , which is arranged between the foot part  7  and the adjusting part  9 . The wedge piece  34  has sloped fastening surfaces corresponding to the desired tilted position for the tensioner parts  7 ,  9 . In the embodiment shown, the adjusting part  9  is tilted in relation to the foot part  7 . A vertical adjustment means  21  may be additionally present at one or both fastening points here as well. As an alternative, the wedge piece  34  may also be arranged between the base  8  and the clamping table  3 . 
     The various designs of the rotary unit  23  and the tilting unit  30  may be combined or interchanged with one another. 
     FIGS. 11,  12  and  13  show two variants of the fixing device  10 . It is also used as a positioning device  21  for the lateral adjustment  46  at the same time and may be otherwise combined with any other desired positioning means  13 . The fixing device  10  preferably acts is in two axes. It is designed as a clamping device  35 , which acts on the guided and adjustable adjusting part  9 . 
     To make possible the lateral adjustment  46 , an additional lateral mobility  47  is present in the area of the vertical adjustment means  21 . FIG. 14 shows an example for this. 
     In the exemplary embodiment according to FIGS. 11 and 12, the clamping device  35  has at least one, preferably strip-shaped clamping wedge  36 , which extends along the groove-like guide  12 ′ and has one or more detachable fastening elements, preferably in the form of clamping screws  11 , for fixation. The clamping wedge  36  has an oblique wedge surface  37 , with which it can be pressed against a corner area  38  of the guided adjusting part  9 . FIG. 12 shows the cross section of this arrangement. The clamping wedge  36  is preferably guided on its rear side located opposite the wedge surface  37  at a parallel side wall of the guide groove  12 ′ and is supported laterally there. 
     The clamping wedge  36  is brought into contact by means of the clamping screws  11 , which are preferably present as two more screws and are plugged into corresponding openings in the clamping part  36 . The clamping screws  11  engage a thread in the foot part  7 , which is arranged at the bottom of the guide groove  12 ′. This bottom also forms a guide surface  41  for the adjusting part  9 . The clamping wedge  36  expands to the outside, so that it is pressed against the corner area  38  during the turning of the clamping screws  11 . 
     The guided and adjustable adjusting part  9  is supported on two surfaces  41 ,  42  of the guide groove  12 ′ which are located diagonally. These guide surfaces  41 ,  42  are preferably located obliquely opposite the wedge surface  37 . An oblique force component at the corner  38  is transmitted by the oblique wedge surface  37  to the adjusting wedge  9 , which ensures pressing on both guide surfaces  41 ,  42  located diagonally. 
     The shaft of the adjusting part  9  to be clamped preferably has an essentially rectangular cross section, wherein one or more corner areas  38  may be beveled or rounded. The two guide surfaces  41 ,  42  are correspondingly also arranged at right angles to one another. The guide surfaces  41 ,  42  may be formed directly by the guide groove  12 ′ or the foot part  7 . 
     For lateral adjustment  46  and for setting a defined lateral position of the adjusting part  9  in relation to the guide groove  12 ′ and the foot part  8 , one or more distance plates  39  and optionally also one or more fitting plates  17  may be placed under one or both guide surfaces  41 ,  42 . The thicker distance plates  39  ensure the coarse adjustment  44  and the thinner fitting plates  17  the fine adjustment  43 . FIG. 12 shows this arrangement based on the example of the lateral guide sure  42 . The adjusting part  9  is in contact with the distance plate  39 , and the adjusting part forms the guide surface  42  and in turn supported in an adjustable position on the adjacent side wall of the guide groove  12 ′ via one or more fitting plates  17 . Due to the bevel or rounding, the adjusting part  9  is not located in the corner area between the guide surfaces  41 ,  42 , so that no position errors can occur here. 
     In addition, a clamping plate  40 , which can be detachably fastened to the foot part  7  with a clamping screw  11  or the like, may be present on the side located opposite the clamping wedge  36 . The angular clamping plate  40  presses the free surface of the adjusting part  9  from the outside and additionally presses it against the guide surface  41  and additionally secures the component  9  against separation in the adjacent corner area. However, the clamping plate  40  may alternatively also be omitted. 
     FIG. 13 shows a design variant to FIG.  12 . The right-hand clamping screw  11  is directed obliquely in relation to the guide groove  12 ′ here and has, instead of the clamping wedge  36 , a pressure piece  45 , e.g., in the form of a plate or a disk, which is pressed by the screw head against the correspondingly oblique corner areas  38  of the adjusting part  9  and of the foot part  7  and of the guide groove  12 ′. The guide groove  12  is open on the right-hand side in this variant. 
     The lateral mobility  47  in the area of the vertical adjustment means  21 , which mobility is necessary for the lateral adjustment  46 , may be designed in various ways. In the simplest embodiment shown in FIG. 11, the hinge pin  15  and the support  16  or the fitting plates  17  can slide in relation to one another in the direction of the lateral mobility  47 . The hinge pin  15  lies only loosely on the top side of the support  16  here. 
     FIG. 14 shows a variant of this. The support  16  is designed as a large, parallelepipedic block, which has an opening  48  for passing through the hinge pin  15 , which opening is designed as an elongated hole guide  48  provided along the lateral mobility  47  here. In addition, the support  16  is provided with a fixing means  49 , e.g., a clamping screw, with which it can be fastened to the foot part  7  through the fitting plate  17 . An elongated hole guide  48  in the direction of the lateral mobility  47  may also be present for the fixation  49 . Similar fixing means may also be present in the case of the above-described supports in the other exemplary embodiments. One or more fitting plates  17  are located under the support block  16  in the above-described manner. 
     As a modification of the exemplary embodiments shown, the lateral mobility  47  may also have any other desired design. For example, the hinge pin  15  may be mounted movably in a suitable elongated hole guide at the mount  14 , in which case the opening  48  in the support block  16  is designed as a cylindrical hole. 
     Various modifications of the exemplary embodiments shown are possible; e.g., a multi-step vertical adjustment may be provided. In addition, the tensioners  4  may optionally also be adjusted laterally in relation to the clamping table  3 . This can be achieved, e.g., by means of a correspondingly modified fixing and positioning means  10 ,  13 . Furthermore, the fixing device  10  and the positioning means  13  may also have any other desired suitable design. In addition, the design and the mutual arrangement and guiding of the tensioner parts  7 ,  9  may be varied. For example, the shape and the arrangement of the guide groove  12 ′ as well as of the guide surfaces  41 ,  42  may vary. Another type of guide may also be present instead of the slideway shown. The shapes of the tensioner parts  7 ,  9  are also variable. The clamping wedge  36  may, e.g., co-rotate and then press the adjusting part  9  against the guide axis or the axis of rotation. Furthermore, a plurality of clamping wedges  36  may be present. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.