Abstract:
The a modular system for locating and clamping a workpiece in space is provided that includes positioning blade including a riser mount having a plurality of first mounting-bores and a plurality of first positioning-bores. A clamp mount is provided on the blade that includes a plurality of second mounting-bores and a plurality of second positioning-bores. The first positioning-bores have a predetermined positional relationship to the second positioning-bores. A locator arm is also provided on the blade, and has a plurality of third positioning-bores where the third positioning-bores comprise a predetermined position relative to the first positioning-bores and the second positioning-bores. A system for positioning and clamping a workpiece is also provided that includes in combination the foregoing positioning blade mounted on structure for elevating the workpiece, e.g., a riser, and structure for clamping the workpiece. A kit for forming a variety of fixtures for positioning and clamping a workpiece is also provided that includes a plurality of position determining modules where each module includes a positioning blade having a different set of positional locations for its positioning-bores.

Description:
This application claims priority from provisional patent application Ser. No. 60/218,396, filed Jul. 14, 2000, entitled Modular System and Fixture for Positioning and Clamping a Workpiece. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to workpiece positioning and fixating systems, and more particularly to a modular apparatus and system for positioning and clamping a workpiece. 
     BACKGROUND OF THE INVENTION 
     Workpiece positioning and clamping systems are well known in the art. For example, U.S. Pat. No. 4,655,445, issued to Morse discloses an apparatus for selectively positioning a workpiece adjacent to a guide on a substantially planar work surface of a power tool assembly. The positioning apparatus is adapted to selectively position the workpiece at selected ones of a plurality of predetermined lateral offsets with respect to a cutter. The positioning apparatus includes an indexing member having a plurality of index holes and an elongated index pin element. The indexing member is affixed to either the workpiece or the guide, and the pin element is affixed to the other of the workpiece or the guide, so that the workpiece may be positioned adjacent to the indexing member and the guide, with the pin element extending through and interferingly engaging one of the index holes. This apparently permits the generation of a succession of cuts in a workpiece which are substantially uniformly spaced along a reference axis. 
     U.S. Pat. Nos. 4,500,079 and 4,801,225, issued to Morghen disclose a removable and replaceable locating pin adapted to locate a workpiece on a tooling fixture for machining. The locating pin is adapted to cooperate with a workpiece for positioning the workpiece in various directions of restraint. The locating pin is provided with manually actuatable locking means that permit easy adjustment or removal of the specific locator pin as a particular machining operation may require. 
     U.S. Pat. No. 4,896,086, issued to Miyahara, et al., discloses a method and apparatus for positioning a workpiece to a pallet on a working line. The line transports plural kinds of workpieces. Plural positioning pins are provided at various locations on each pallet to enable all the workpieces to be carried by the pallets. Each positioning pin has a set position and a reset position. All positioning pins are first reset to the reset position, thereafter, a selected positioning pin is set to the set position to accommodate a particular kind of workpiece. The positioning of the workpiece is accomplished by fitting a positioning hole defined by the selected workpiece onto the selected positioning pin. 
     U.S. Pat. No. 4,968,012, issued to Haddad, et al., discloses a modular workpiece holding apparatus for locating and holding a workpiece in a predetermined position. The apparatus includes a base having a plurality of external faces, each with a plurality of bores arranged in an X-Y grid pattern of parallel rows. The bores alternate vertically and horizontally between first and second different diameter bores. A riser is mounted at a predetermined position on the base by bushings and fasteners extending between the riser and the bores in the base. The bushings in each riser are arranged in diagonally opposed pairs such that one pair of bushings engages the first diameter bores in the base, while the second opposed pair of bushings engages the second enlarged diameter bores in the base. A workpiece attachment member is mounted on the mounting head end of each riser to locate and hold a workpiece. The mounting head of each riser is axially in line with the riser mounting base or offset from the riser mounting base. Each bushing includes an internal bore having a threaded end portion and an enlarged, coaxial, smooth portion. Each fastener includes a plurality of threads adjacent one end and an unthreaded portion extending from the threaded end so as to be movably retainable within a bushing in the riser mounting base after the threaded end portion of the fastener is threaded through the threaded end of the bore in the riser mounting base. 
     U.S. Pat. No. 5,026,033, issued to Roxy, discloses a universal system for support and positioning a workpiece for use with a device such as an inspection system. A plurality of individual alignment devices are inserted into predetermined holes of a platform having a matrix of holes. Individual alignment devices support, clamp, datum point position, and provide reference points. Each alignment device includes stanchions of varying length. These stanchions appear to be capable of being connected to each other. Once an alignment device is positioned in a hole, it can be fine tuned in all directions to get an exact location, so that workpieces of widely varying types, shapes and sizes can be positioned using the same set of alignment devices. 
     U.S. Pat. No. 5,044,616, issued to Jakob discloses a locating device for positioning a workpiece on a processing apparatus. A first embodiment includes a base and a fixture plate with positioning means between the base and the fixture plate. An abutment defines a fixed reference point for locking the fixture plate on the base through a clamping mechanism. The clamping mechanism also includes release cylinders so that the fixture plate can be quickly interchanged for introducing a new workpiece. A second embodiment includes a base structure that comprises a first clamping unit and a second clamping unit that support a fixture plate. First positioning means secured to each clamping unit cooperate with second positioning means secured to the fixture plate. Clamping means engage and lock the fixture plate in position. The clamping means include locking members that are slidably disposed in channels in the blocks. 
     U.S. Pat. No. 5,226,638, issued to Ausillio discloses a clamp having slip plane positioning capability that enables a clamp nose and an attached pressure foot, which are initially non-permanently attached to a clamp arm, to be brought into a final predetermined coordinate position before the clamp nose is fixedly attached to the clamp arm. The clamp nose has a pressure foot mounted at one end. An open-ended slot is formed at the other end of the clamp nose and slidingly engages opposed side walls of one end of the clamp arm. A fastener threadingly extends through a portion of the clamp nose binding the slot into engagement with the clamp arm to non-permanently attach the clamp nose to the clamp arm. The clamp nose and the pressure foot are positionally adjusted with respect to the clamp arm, at final assembly, to bring the pressure foot into a predetermined coordinate position before the clamp nose is fixedly secured to the clamp arm. 
     U.S. Pat. No. 5,362,036, issued to Whiteman discloses a modular welding fixture for positioning a workpiece. The fixture includes a base table having an array of openings through the surface and an array of locator mounting holes colocated in spaced relationship, with respect to the openings, to accommodate at least one vertical end locator having a base plate that is removably mountable to the base table at preselected positions. The locator has means for locating and holding at least a portion of a workpiece. The fixture further includes at least one horizontal locator having a base plate that is removably mountable to the base table at preselected positions, and the base plate includes means for locating and holding at least a portion of a workpiece. 
     U.S. Pat. No. 5,415,383, issued to Ausillio discloses a clamp having slip plane positioning capability that enables a clamp nose and an attached pressure foot, which are initially non-permanently attached to the clamp arm, to be brought into a final predetermined coordinate position before the clamp nose is fixedly attached to the clamp arm. The clamp nose has a pressure foot mounted at one end. An open-ended slot is formed at the other end of the clamp nose and slidingly engages opposed side walls of one end of the clamp arm. In one embodiment, a fastener threadingly extends through a portion of the clamp nose surrounding the slot, and into engagement with the clamp arm to non-permanently attach the clamp nose to the clamp arm. In another embodiment, aligned bores and slots are formed in adjoining surfaces of the clamp nose and the clamp arm so as to receive fasteners therethrough to non-permanently mount the clamp nose on the clamp arm. The clamp nose and the pressure foot attached thereto are positionally adjusted with respect to the clamp arm at final assembly to bring the pressure foot into a predetermined coordinate position before the clamp nose is fixedly secured to the clamp arm. 
     U.S. Pat. No. 5,481,811, issued to Smith discloses a modular system for the support and positioning of a workpiece for use with an inspection system. The modular system includes a base having a plurality of exterior faces, at least some of which have an array of equally spaced holes forming a grid pattern. At least one riser is attached to the base cube by a fastener, which can be inserted into the riser by defeating an outwardly biased locking member at the inner end of the fastener, extending through the riser and into the holes of the base cube. The fastener is used to provide positive location and fastening of the risers to the base cube. Functions of individual risers include support, clamping, datum point positioning and providing reference points. 
     U.S. Pat. No. 5.516.089, issued to Seniff et al., discloses a workpiece locating unit that is receivable in a T-slot formed in a workpiece supporting table member. It provides a pin or other locating device cooperable with a locating feature on a workpiece to aid in accurately positioning the workpiece on the work supporting surface of the table member. The unit has four corners each providing an abutment surface for engagement with one or the other of two vertical slot surfaces. Two diagonally opposite ones of the abutment surfaces are rigid and the other two diagonally opposite ones of the abutment surfaces are resilient. The resilient abutment surfaces resiliently engage the two vertical surfaces of the slot and urge the unit about a vertical axis to hold the rigid abutment surfaces engaged with the vertical slot surfaces eliminating lateral looseness between the unit and the table member and providing accurate positioning of the locating device of the unit as the unit is moved from one position to another along the length of the slot. 
     These and other prior art positioning and clamping systems often require multiple fixtures and component parts to be on hand in order to accommodate multiple parts that are to be positioned in any given manufacturing shift. This requires extensive inventories of clamps and associated fixtures, as well as, well trained and technically sophisticated personnel to properly select and operate them. This adds to the cost and complexity of such systems. Also such prior art positioning and clamping systems do not lend themselves to a modular design, that is in conformance with NAAM standards, and that allows for fine adjustments of position of a clamped workpiece through the selection of easily identifiable and assembled modular parts. As a consequence, there has been a long felt need for a workpiece positioning and clamping system that avoids the foregoing problems in the prior art. 
     SUMMARY OF THE INVENTION 
     The present invention provides a modular system for locating and clamping a workpiece in space. One aspect of the present invention provides a positioning blade comprising a riser mount having a bottom edge surface, a first side edge surface, a second side edge surface, a top edge surface, and including a plurality of first mounting-bores and a plurality of first positioning-bores defined through the riser mount between the edge surfaces. A clamp mount is provided on the blade that projects outwardly from the first side edge surface, and includes a plurality of second mounting-bores and a plurality of second positioning-bores. The first positioning-bores comprise a predetermined positional relationship to the second positioning-bores. A locator arm is also provided on the blade and projects outwardly from the second side edge surface. The locator arm has a plurality of third positioning-bores where the third positioning-bores comprise a predetermined position relative to the first positioning-bores and the second positioning-bores. 
     A system for positioning and clamping a workpiece is also provided that includes in combination the foregoing positioning blade mounted on means for elevating the workpiece, e.g., a riser, and means for clamping the workpiece. 
     A kit for forming a variety of fixtures for positioning and clamping a workpiece is also provided that includes a plurality of position determining modules wherein each module comprises a positioning blade having a different set of positional locations for its positioning-bores. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the present invention will be more fully disclosed in, or rendered obvious by, the following detailed description of the preferred embodiment of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein: 
     FIG. 1 is a perspective view of a plurality of modular systems and fixtures for positioning and clamping a workpiece formed in accordance with the present invention, positioned upon a platform shown in phantom and holding a partially broken-away workpiece; 
     FIG. 2 is a perspective view of a modular system and fixture for positioning and clamping a workpiece formed in accordance with one embodiment of the present invention; 
     FIG. 3 is a side elevational view of the modular system and fixture for positioning and clamping a workpiece shown in FIG. 2; 
     FIG. 4 is a perspective view of a modular positioning blade formed in accordance with the present invention; 
     FIG. 5 is a perspective view of an alternative embodiment of modular positioning blade; 
     FIG. 6 is a perspective view of another alternative embodiment of modular positioning blade including a transition portion; 
     FIG. 7 is a perspective view of yet another alternative embodiment of modular positioning blade with transition portion; 
     FIG. 8 is a further embodiment of a modular positioning blade with an alternative transition portion; 
     FIG. 9 is a perspective view of another modular positioning blade; 
     FIG. 10 is a perspective view, partially in phantom, of a modular system and fixture for positioning and clamping a workpiece having a modular positioning blade mounted on a riser with a clamping assembly assembled to a portion of the modular positioning blade; 
     FIG. 11 is a perspective view, partially in phantom, of an alternative embodiment of the modular system and fixture for positioning and clamping a workpiece shown in FIG. 10; 
     FIG. 12 is a perspective view, partially in phantom, of a further alternative embodiment of the modular system and fixture for positioning and clamping a workpiece of the present invention; 
     FIG. 13 is a perspective view, partially in phantom, of yet another alternative embodiment of the modular system and fixture for positioning and clamping a workpiece of the present invention; 
     FIG. 14 is a perspective view, partially in phantom, of another alternative embodiment of the modular system and fixture for positioning and clamping a workpiece of the present invention; 
     FIG. 15 is a perspective view, partially in phantom, of another alternative embodiment the modular system and fixture for positioning and clamping a workpiece of the present invention; 
     FIG. 16 is a perspective view, from a rear side, of a fully assembled modular system and fixture for positioning and clamping a workpiece in accordance with the present invention; 
     FIG. 17 is a broken-away view of a portion of a clamp assembly used in connection with the present invention; 
     FIG. 18 is a partially broken-away, perspective view of a portion of a modular positioning blade and clamp assembly; and 
     FIG. 19 is a partially, broken-away, perspective view of a portion of a clamp assembly showing an alternative positioning of pressure feet. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This description of preferred embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms including “inwardly” versus “outwardly,” “longitudinal” versus “lateral” and the like are to be interpreted relative to one another or relative to an axis of elongation, or an axis or center of rotation, as appropriate. Terms concerning attachments, couplings and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. In the claims, means-plus-function clauses are intended to cover the structures described, suggested, or rendered obvious by the written description or drawings for performing the recited function, including not only structural equivalents but also equivalent structures. 
     Referring to FIGS. 1-4, a modular system and fixture for positioning and clamping a workpiece  5  comprises a riser  7 , a modular positioning blade  9 , and a clamp assembly  11 . More particularly, riser  7  includes a mounting plate  18  and a seat plate  21 , with a stiffening support  23  fastened between them to add to the rigidity and ability of riser  7  to support significant loads. Modular positioning blade  9  is mounted to a top portion  24  of each riser  7 . A plurality of positioning-bores  25  and mounting-bores  26  are defined in top portion  24  of each riser  7  (FIG.  16 ). Positioning-bores  25  are accurately sized and shaped, and selectively and precisely located in top portion  24  for operatively locating modular positioning blade  9  on riser  7 , via dowel pins  27 . Conventional fasteners, e.g., bolts  28  or the like, are positioned through mounting-bores  26  so as to fasten modular positioning blade  9  to top portion  24  of riser  7 . 
     A plurality of risers  7  are often mounted on a platform  12  in a predetermined matrix of holes having an adequate distance from each other such that risers  7  can be positioned to clamp virtually any size or shape workpiece. For example, a typical workpiece clamped with the present invention may be an automobile roof, hood, trunk lid, or side panel (shown generally in FIG. 1, and identified by reference numeral  30 ). Of course, other non-automotive parts may also be clamped with the present invention. The dimensions and general shape of risers  7  are subject to industry agreed upon standards, with specific tolerance allowances, which would be known to those skilled in the art. 
     Referring to FIGS. 2-15, modular positioning blade  9  preferably comprises a planar metal or polymer plate, and includes a riser mount  32 , a clamp mount  34 , and a locator arm  36 . Referring to FIGS. 4-9, riser mount  32  is often generally rectilinearly shaped, and includes a bottom edge surface  40 , side edge surfaces  42 , 43 , a top edge surface  45 , multiple mounting-bores  48 , and multiple positioning-bores  50 . Riser mount  32  is typically arranged to be below clamp mount  34  and locator arm  36 , with top edge surface  45  arranged on an incline so as to provide a transition between clamp mount  34 , locator arm  36 , and riser mount  32 . Thus, when mounted to riser  7 , modular positioning blade  9  is oriented such that riser mount  32  is arranged below locator arm  36  and clamp mount  34 . 
     In some embodiments, a transition portion  38  interconnects riser mount  32  with clamp mount  34  and locator arm  36 . Mounting-bores  48  are sized and shaped to receive fasteners, such as bolts  28  or the like. Mounting-bores  48  are often arranged in parallel rows extending along riser mount  32 . In some embodiments, additional mounting bores  48  and positioning-bores  50  are located trough transition portion  38  of modular positioning blade  9  to secure and position additional fixtures, tools and/ or locators (FIGS. 6,  7 ,  12  and  13 ). 
     Positioning-bores  50  are accurately sized and shaped, and selectively and precisely located on riser mount  32  so as to operatively receive dowel pins  27 , and thereby to selectively and precisely position modular positioning blade  9  and clamp arm assembly  11  on riser  7 . Positioning-bores  50  are often arranged within the parallel rows of mounting-bores  48 , and may be defined through riser mount  32  alone, or through riser mount  32  and transition portion  38 . Advantageously, positioning-bores  50  may be located at varying, predetermined fixed distances from bottom edge surface  40 . Also, a variety of modular positioning blades  9  may be provided, each having positioning-bores  50  located at different predetermined positions along the length of riser mount  32  or transition portion  38 , e.g., in ten, fifteen or twenty millimeter increments as measured from bottom edge surface  40 . This feature allows for a family or kit to be provided comprising a plurality of individual modular positioning blades  9 , each having a differently positioned set of positioning-bores  50 . 
     Clamp mount  34  projects outwardly from a top portion of side edge surface  42 , and includes mounting-bores  58  and positioning-bores  60 . Mounting-bores  58  are sized and shaped to receive fasteners, such as bolts  28  or the like, and are often arranged in parallel rows along clamp mount  34 . Positioning-bores  60  are accurately sized and shaped, and selectively and precisely located on clamp mount  34  so as to operatively receive dowel pins  27 , and thereby to selectively and precisely position clamp arm assembly  11  relative to riser  7 . Positioning-bores  60  are often arranged within the parallel rows of mounting-bores  58 . 
     Advantageously, positioning-bores  60  may be located at varying, predetermined fixed distances from positioning-bores  50 , so as to establish their true position relative to riser  7 . Also, positioning-bores  50  and positioning-bores  60  are preferably arranged in mutually parallel relation to one another. A variety of modular positioning blades  9  may be provided, each having positioning-bores  60  at different predetermined positions along the length of clamp mount  34 , e.g., in ten, fifteen, and twenty millimeter increments. 
     Locator arm  36  projects outwardly relative to a top portion of side edge surface  43 , and includes a top surface  65 , a bottom surface  66 , and a front face  67 . A plurality of longitudinally extending through-bores  68  are defined between top surface  65  and bottom surface  66 , and are sized and shaped to receive a releasable fastener, such as a bolt  70  or the like. Through-bores  68  are sized, shaped, and selectively located on top surface  65  of locator arm  36  so as to operatively position a portion of clamp assembly  11 , as will hereinafter be disclosed in further detail. Advantageously, through-bores  68  may be located at varying, predetermined fixed distances from positioning-bores  60 . Positioning-bores  50  and positioning-bores  60  are preferably arranged in substantially perpendicular relation to through-bores  68 . 
     Referring to FIG. 1-3 and  10 - 19 , clamp assembly  11  includes a lower pressure foot  75 , an upper pressure foot  80 , a fluid operated cylinder  85 , and a pivotal clamp arm  90 . More particularly, lower pressure foot  75  is mounted to top surface  65  of locator arm  36 , and includes a leg  77  and an anvil  81  that are joined together so as to form an “L”-shaped support. Anvil  81  includes a rearwardly radiused end surface  84 , and joins leg  77  at a right angle at the other end. Leg  77  includes at least one trough-bore  89  that is sized and shaped to receive releasable fastener  70  to thereby releasably fasten lower pressure foot  75  to locator arm  36 . Radiused end surface  84  of anvil  81  comprises a curvature that corresponds to, and is complementary with, the curvature present in workpiece  30 . Upper pressure foot  80  is releasably mounted to the under side of pivotal clamp arm  90 , and includes a leg  87  and an anvil  91  that are joined together so as to form an “L”-shaped support. Anvil  91  may include a rearwardly radiused end surface, or may have another surface profile as needed for a particular task. Leg  87  joins anvil  91  at a right angle, and includes at least one through-bore that is sized and shaped to receive releasable fastener  70  to thereby releasably fasten upper pressure foot  80  to pivotal clamp arm  90 . It will be understood that pressure feet  75 , 80  may have various other shapes and configurations, as required for a particular workpiece, without departing from the scope of the present inventions 
     Referring to FIGS. 16 and 17, fluid operated cylinder  85  includes a closed chamber formed within a cylindrical body  108 . End caps  112  and  114  are mounted on opposite ends of cylindrical body  108  and are interconnected by connecting rods  116 . A piston (not shown) is mounted in cylindrical body  108  of fluid operated cylinder  85 . The piston is moved by the bidirectional application of pressurized fluid to opposite sides of it. The pressurized fluid causes a piston rod  120  that is connected to one end of the piston, and extending outwardly from one end of cylinder  108  through end cap  119 , to reciprocate in extendible and retractable linear directions with respect to fluid operated cylinder  85 . 
     A mounting plate  122  is fixedly connected to end cap  119 , and has a central aperture through which piston rod  120  slidably extends. Mounting plate  122  supports a pair of spaced, plate-like support members  125  and  128 . Each of support members  125  and  128  includes a number of spaced mounting-bores  130  which are used to receive fasteners  28  for fixedly mounting support members  125  and  128  to clamp mount  34 . Bores  130  are arranged to correspond in position with mounting-bores  58  of clamp mount  34 , and are sized and shaped to receive fasteners  28 . At least a pair of positioning-bores  131  extend through support members  125  and  128 , and are arranged to correspond in position to positioning-bores  60  on clamp mount  34 . A pair of spaced, strip-like covers  136  and  138  are disposed between support members  125  and  128  and are welded to support plate  125  on opposite sides of piston rod  120 . An additional cover member  140  is disposed in an overlapping end arrangement with cover member  138 . 
     The linear reciprocal, bidirectional movement of piston rod  120  is converted to pivotal movement of clamp arm  90  by an assembly including a tubular sleeve  142  having an internally threaded bore at one end that threadingly engages a threaded adapter  144  mounted on the exterior end of piston rod  120 . An opposed end portion  146  of tubular sleeve  142  has a flattened shape with a central bore extending therethrough which receives a pivot pin  148 . Cover member  140  is fixedly attached to the flattened portion of sleeve  142  and is movable. Also mounted to pivot pin  148  is a first end of a link  150 . A second end of link  150  is fixed to a pivot pin  152  extending between the support plates  125  and  128 . 
     Pivotal clamp arm  90  comprises a first end  154  and a spaced-away second end  156 . First end  154  has a recessed portion which has a central bore that is fixedly mountable about pivot pin  152 . Linear extension and retraction of piston rod  120  due to activation of fluid operated cylinder  85  results in pivotal movement of first end  154 . This causes pivotal movement of pivot pin  152  and the recessed portion of clamp arm  90 . In turn, first end  154  of the clamp arm  90  pivots in one direction and second end  156  pivots in an opposite direction. This arrangement results in second end  156  moving between a first position that is spaced from workpiece  30  and a second position in which clamp arm  90  drives upper pressure foot  80  into firm engagement with a portion of workpiece  30  (FIG. 1) that is supported on radiused surface  84  of lower pressure foot  75  so as to hold workpiece  30  at a predetermined coordinate position. 
     Advantageously, positioning-bores  25  of riser  7  may be located at varying fixed distances from the bottom surface of seat plate  21 , e.g., between one-hundred and five-hundred millimeters, etc., in about five millimeter to about thirty-five millimeter increments, more or less. In this way, positioning-bores  50  and  60  of modular positioning blade  9  may be located at varying fixed distances from the bottom surface of seat plate  21 , e.g., three-hundred, three-hundred and twenty, four-hundred and thirty, five-hundred and forty millimeters, etc., by simply adjusting riser mount  32  upwardly or downwardly relative to top portion  24  of riser  7 . 
     Additionally, the vertical and horizontal location of positioning-bores  50  and  60 , may be more finely adjusted by utilizing an alternative modular positioning blade  9 , as shown in FIGS. 4-9. In this way, radiused surface  84  of pressure foot  75  may be precisely and accurately positioned vertically and/or horizontally in space for supporting and clamping workpiece  30  at a known position above the top surface of platform  12 . Modular system and fixture for positioning and clamping a workpiece  5  may be used not only to clamp and maintain workpiece  30  at a known height, but also can be modified to adjust the horizontal location of workpiece  30  relative to riser  7  by merely adjusting the relative positions of modular blade  9  on riser  7 , clamp assembly  11  on clamp mount  34  of modular blade  9 , and/or pressure feet  75  and  80  on locator arm  36  and clamp arm  90 , respectively. For example, FIG. 13 shows one possible orientation of pressure feet  75 , 80  that can be selected while maintaining modular positioning blade  9  in one position. FIG. 14 represents the use of additional “NC” blocks that are positioned on portions of pressure fee  75 , so as to further provide an alternative position for clamping work piece  30 . Also, as shown in FIG. 16, a rough locator arm  175  and/or piloting pin  180  may be installed on the back side of modular positioning blade  9  in order to initially locate and pilot an edge of workpiece  30  into position for engagement by pressure feet  75 ,  80 . It will be understood that rough locator arm  175  and/or piloting pin  180  may be assembled to modular positioning blade  9 , via mounting bores  48  and positioning-bores  50  located through transition portion  38 . Of course, with the use of each additional embodiment of modular positioning blade  9 , a plurality of precisely and accurately defined locations of pressure feet  75 ,  80  can be achieved without the need for manufacturing custom fixturing or tools to suit that purpose. 
     ADVANTAGES OF THE INVENTION 
     Numerous advantages are obtained by employing the present invention. 
     More specifically, a modular system and apparatus for positioning and clamping a workpiece is provided which avoids all of the aforementioned problems associated with prior art devices. 
     In addition, a modular system and apparatus for positioning and clamping a workpiece is provided which does not require well trained and technically sophisticated personnel to properly operate. 
     Furthermore a modular system and apparatus for positioning and clamping a workpiece is provided which reduces the cost and complexity associated with the accurate positioning of a workpiece, such as a portion of an automobile. 
     Also, a system and apparatus for positioning and clamping a workpiece is provided which incorporates a modular design that allows for fine adjustments of the position of a workpiece through the selection of easily identifiable, standardized modular blades that are easily assembled to accommodate a plurality of required workpiece locations, as well as, a design that provides for multiple clamped positions by simple adjustments to the location of a assembly or pressure feet on a modular blade. 
     It is to be understood that the present invention is by no means limited only to the particular constructions herein disclosed and shown in the drawings, but also comprises any modifications or equivalents within the scope of the claims.