Abstract:
Apparatuses and methods consistent with the present inventive concept relate to a clamping device which is connectable with a shaft having a longitudinal axis and four longitudinal surfaces extending in a direction parallel to the longitudinal axis, the clamping device including: a base member having two substantially perpendicular surfaces, the base member being configured to contact two adjacent longitudinal surfaces of said four longitudinal surfaces of said shaft, wherein said base member extends along the shaft in the direction parallel to the longitudinal axis; and a plurality of clamping elements, the plurality of clamping elements being coupled to said base member, wherein each of the plurality of clamping elements is flexible in a direction substantially perpendicular to the longitudinal axis of the shaft, and the plurality of clamping elements is operable to exert clamping pressure on the two adjacent longitudinal surfaces of said shaft opposing the base member. 
     Patrick Brewster 19

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Patent Application 61/604468 filed on Feb. 28, 2012. 
     
    
     BACKGROUND 
       [0002]    The present inventive concept relates to a positioning apparatus including a polygonal shaft and at least one mating device, which are connectable and configured to clamp onto the shaft. 
         [0003]    In any application requiring linear motion, such as machinery, optics, or medical devices, uniaxial positioning systems may be utilized to provide the required motion. Uniaxial positioning systems are typically composed of dovetail assemblies, shafts and mating bearings or rails and mating carriages, and typically include a means to propel and/or brake the moveable components. Often a mechanism that exerts a clamping pressure onto the shaft is used as the brake. Uniaxial positioning systems composed of shafts generally make use of bearings with rolling elements, such as balls; or sliding elements, such as low-friction liners. The latter are typically known as plain bearings. 
         [0004]    Round shafts are often utilized due to ease of manufacture of both the shaft and mating components. However, two round shafts are required to restrict the motion to one linear axis, and the use of two shafts presents numerous problems and costs. For example, the alignment of the shafts must be extremely accurate to avoid binding of the sliding components. However, in the related art, the use of two shafts incurs both the cost of the hardware required to mount them, and the cost of achieving or compensating for the lack of necessary alignment. Furthermore, dual-shaft assemblies may be too large for applications with particular dimensional constraints. 
         [0005]    A single polygonal shaft, on the other hand, when coupled with appropriate mounting hardware and at least one sliding bearing or clamping device with a mating aperture, can provide uniaxial motion. The use of such a system eliminates the aforementioned costs related to dual-shaft systems, and consumes less space than an equivalent dual-shaft system. Square or hexagonal shafts are typically preferred due to manufacturing ease and commercial availability. 
         [0006]    A related art V-block with clamping accessory, such as shown in  FIGS. 1 and 2 , can clamp onto and slide along a square shaft. However, the clamping force is applied by a set-screw, which presents numerous problems. First, a set-screw applies its pressure in one location, which may create an indentation or otherwise damage the shaft surface. Second, the set-screw, when loose, is free to deflect in the direction of travel. As a result, the set-screw may bind and chatter when the V-block slides along the shaft. 
         [0007]    A related art square shaft clamp can also clamp onto and slide along a square shaft. However, the clamping force is applied primarily to the two corners of the shaft closest to the pinch bolt, potentially resulting in shaft damage and an unsatisfactory clamping engagement. 
         [0008]    Still other related art includes a square shaft clamp, which can clamp onto and slide along a square shaft, and it applies the clamping force over a large surface area of the shaft. However, because the base member and clamping elements form an aperture that is larger than the shaft profile, the shaft is not forced into repeatable alignment with the base member upon tightening of the pinch bolt. Therefore true uniaxial motion is not achieved. Furthermore, the clamping elements are free to move slightly in the direction of travel when the pinch bolt is loose. As a result, the clamping elements may bind and chatter when the device slides along the shaft. 
         [0009]    Other related art discloses a clamp for a square shaft that is actuated by one pinch bolt. However, the clamping pressure is transferred from the pinch bolt and nut to the housing, then to the clamping elements, and finally to the shaft. The deformation of the housing and clamping elements that is necessary to achieve clamping engagement is unpredictable and unrepeatable. Therefore, a consistent positional relationship between the shaft and the device is not maintained through repeated actuations of the pinch bolt. This consistent positional relationship is critical in linear motion applications. 
         [0010]    Still other related art discloses a similar clamp for a square shaft that is actuated by two pinch bolts. Although effective, the operation of two pinch bolts is burdensome to the user. 
       SUMMARY 
       [0011]    The present inventive concept includes a clamping device which is capable of clamping onto and sliding along a mating polygonal shaft. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows an end view of a related art clamping device typically referred to as a V-block. 
           [0013]      FIG. 2  shows a perspective view of a related art clamping device typically referred to as a V-block. 
           [0014]      FIG. 3  shows an end view of a related art clamping device. 
           [0015]      FIG. 4  shows a perspective view of a related art clamping device. 
           [0016]      FIG. 5  shows an end view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0017]      FIG. 6  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0018]      FIG. 7  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0019]      FIG. 8  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0020]      FIG. 9  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0021]      FIG. 10  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0022]      FIG. 11  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0023]      FIG. 12  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0024]      FIG. 13  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0025]      FIG. 14  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0026]      FIG. 15  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0027]      FIG. 16  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0028]      FIG. 17  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0029]      FIG. 18  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0030]      FIG. 19  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0031]      FIG. 20  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0032]      FIG. 21  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0033]      FIG. 22  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0034]      FIG. 23  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0035]      FIG. 24  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0036]      FIG. 25  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0037]      FIG. 26  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0038]      FIG. 27  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0039]      FIG. 28  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0040]      FIG. 29  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0041]      FIG. 30  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0042]      FIG. 31  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0043]      FIG. 32  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0044]      FIG. 33  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0045]      FIG. 34  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0046]      FIG. 35  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0047]      FIG. 36  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0048]      FIG. 37  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0049]      FIG. 38  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0050]      FIG. 39  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0051]      FIG. 40  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0052]      FIG. 41  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0053]      FIG. 42  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0054]      FIG. 43  shows an end view of the shaft of an exemplary embodiment consistent with the inventive concept. 
           [0055]      FIG. 44  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0056]      FIG. 45  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0057]      FIG. 46  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0058]      FIG. 47  shows an end view of the shaft of an exemplary embodiment consistent with the inventive concept. 
           [0059]      FIG. 48  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0060]      FIG. 49  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0061]      FIG. 50  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0062]      FIG. 51  shows an end view of the shaft of an exemplary embodiment consistent with the inventive concept. 
           [0063]      FIG. 52  shows a perspective view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0064]      FIG. 53  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0065]      FIG. 54  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0066]      FIG. 55  shows an end view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0067]      FIG. 56  shows an end view of the shaft of an exemplary embodiment consistent with the inventive concept. 
           [0068]      FIG. 57  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0069]      FIG. 58  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0070]      FIG. 59  shows an end view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0071]      FIG. 60  shows an end view of the shaft of an exemplary embodiment consistent with the inventive concept. 
           [0072]      FIG. 61  shows an end view of another exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0073]      FIG. 62  shows a detail view of an exemplary embodiment consistent with the inventive concept. The shaft is shown. 
           [0074]      FIG. 63  shows an end view of an exemplary embodiment consistent with the inventive concept. The shaft is not shown. 
           [0075]      FIG. 64  shows an end view of the shaft of an exemplary embodiment consistent with the inventive concept. 
       
    
    
     DETAILED DESCRIPTION 
       [0076]    As shown in  FIGS. 5 ,  6 , and  7  an exemplary embodiment includes a shaft  60 , a base member  70 , and clamping elements  80 ,  90  that may be composed of one solid piece of material. Further, the shaft  60  may be square, such as shown. The clamping elements are spaced by gap  140 . Pinch bolt  100  passes through bolt hole  160  in clamping element  80  and mates with threaded hole  162  in clamping element  90 . Recesses  151  may be provided at the junction of the clamping elements and the base member to allow the clamping elements to pivot with ease at live hinge points  150 . 
         [0077]    The configuration of the base member and clamping elements is such that an aperture  130 , with geometry that mates with the shaft  60 , is provided. More particularly, each interior surface of the base member mates with one of two adjacent sides of the shaft, while each interior surface of the clamping elements mates with one of the two remaining sides of the shaft. The dimensional relationship between the aperture and the shaft is such that the gaps  141  offer a minimal clearance, permitting unlimited linear, but limited rotational motion along the shaft axis when the pinch bolt is loose. 
         [0078]    When the pinch bolt is tightened, the clamping elements flex at live hinge points  150 , and gaps  141  diminish in size, restricting rotational motion. With further tightening, the clamping elements make contact with the shaft and force the shaft into locking engagement and repeatable alignment with the base member. 
         [0079]      FIGS. 8 ,  9 , and  10  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 5 ,  6 , and  7 , except that the shaft orientation is different and the base member  71  and clamping elements  81 ,  91  are shaped accordingly. 
         [0080]      FIGS. 11 and 12  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 5 ,  6 , and  7 , except that the clamping elements include set-screws  111 , the tips of which make contact with the shaft upon actuation of the pinch bolt  100 . When the pinch bolt is loose, the user may adjust the set-screws to achieve the desired running clearance between the shaft  60  and the clamping device. Nuts  121  may be provided to lock the set-screws in their desired positions. The provision of the set-screws allows this embodiment to accommodate a range of shaft sizes or dimensional tolerances, and permits the inner surfaces of the clamping elements to be manufactured with a rough finish or imprecise dimensions. These virtues may reduce manufacturing costs and expand usefulness. Set-screws are commercially available with special tips such as rolling balls, as shown in  FIGS. 11 and 12 , or low-friction pads. The manufacturer or one skilled in the art may designate the optimal type, quantity, and placement of the set-screws. 
         [0081]      FIGS. 13 ,  14 , and  15  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 5 ,  6 , and  7 , except that the clamping elements  80 ,  90  are provided with clamping pads  180 ,  181  which are free to pivot at live hinge points  152  by virtue of recesses  153 . The provision of pivoting clamping pads ensures that the clamping pressure exerted on the shaft  60  is evenly distributed and widespread. 
         [0082]      FIGS. 16 ,  17 , and  18  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 5 ,  6 , and  7 , except that four sliding elements  190  are adhered or coupled to the interior surfaces of the base member  70  and clamping elements  80 ,  90 , providing four sliding surfaces which mate with the four sides of shaft  60 . The sliding elements may be composed of any suitable low-friction material such as polytetrafluoroethylene, polyoxymethylene, a blend thereof, or brass. The provision of sliding elements allows the clamping device to slide freely along the shaft. 
         [0083]      FIGS. 19 and 20  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 5 ,  6 , and  7 , except that a commercially available cam mechanism  101  is used to move the clamping elements  80 ,  90  into locking engagement with the shaft  60 . The manufacturer or one skilled in the art may substitute any such device, including but not limited to a hydraulic, pneumatic, or electromagnetic piston, in place of the cam mechanism. 
         [0084]      FIGS. 21 and 22  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 5 ,  6 , and  7 , except that two clamping devices are ganged together by pinch bars  200 ,  201 , and actuated by a single pinch bolt  102 . Pinch bolt  102  passes through bolt hole  168  in pinch bar  200 , and mates with threaded hole  169  in pinch bar  201 . The pinch bars may be coupled to clamping elements  80 ,  90  by any appropriate means. 
         [0085]      FIGS. 23 ,  24 , and  25  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 5 ,  6 , and  7 , except that the base member  72  and clamping elements  82 ,  92  are separate components. Clamping elements  82 ,  92 , which are preferably formed from sheet metal, may be coupled to base member  72  with coupling screws  110  or other appropriate means, such as welding. Pinch bolt  100  passes through bolt hole  160  in clamping element  82 , bolt hole  161  in clamping element  92 , and mates with threaded nut  120  affixed to clamping element  92 . 
         [0086]      FIGS. 26 ,  27 , and  28  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 23 ,  24 , and  25 , except that clamping elements  83 ,  93  are formed and provided with slots  167  such that gaps  141  may be adjusted by loosening coupling screws  110  and moving the clamping elements to the desired position in respect to base member  73 . This adjustability allows this embodiment to accommodate a range of shaft sizes or dimensional tolerances, and allows the dimensional accuracy of the components to be less exact than that of a non-adjustable embodiment. 
         [0087]      FIGS. 29 ,  30 , and  31  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 23 ,  24 , and  25 , except that clamping elements  84 ,  94  are reinforced by gussets  210 . The gussets prevent undesired excess deformation or damage of the clamping elements upon actuation of the pinch bolt  100 , especially if the pinch bolt is over-tightened. The provision of the gussets may allow the clamping elements to be fabricated from thinner material than an unreinforced embodiment, which in turn may reduce manufacturing costs. 
         [0088]      FIGS. 32 ,  33 , and  34  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 23 ,  24 , and  25 , except that clamping elements  85 ,  95  are formed so as to mate with a portion of the curved surfaces of cylindrical pinch blocks  220 ,  221 . Pinch bolt  100  passes through bolt hole  163  in pinch block  220 , bolt hole  160  in clamping element  85 , bolt hole  161  in clamping element  95 , and mates with threaded hole  164  in pinch block  221 . The cylindrical pinch blocks are free to rotate about their axes, thereby distributing the clamping force of the pinch bolt over a large portion of the clamping element surfaces. 
         [0089]      FIGS. 35 ,  36  and  37  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 23 ,  24 , and  25 , except that spacing element  170  is affixed to clamping element  82  and positioned such that pinch bolt  100  is in between the spacing element and aperture  130 . The spacing element is fabricated and installed such that it protrudes from clamping element  82  toward clamping element  92  across gap  140 , and the distance of protrusion is substantially less than the dimension of gap  140 . The spacing element serves as a stop for the clamping elements, allowing the clamping elements to move into locking engagement with the shaft, but preventing undesired excess deformation or damage of the clamping elements that may result from over-tightening of the pinch bolt. The spacing element may alternatively be installed such that it protrudes from clamping element  92  toward clamping element  82 . 
         [0090]      FIGS. 38 ,  39 , and  40  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 23 ,  24 , and  25 , except that set bolt  112 , spacing washer  171  and set nut  122  are provided. Set bolt  112  passes through bolt hole  165  in clamping element  86 , spacing washer  171  positioned between the clamping elements  86 ,  96 , bolt hole  166  in clamping element  96 , and mates with threaded set nut  122  affixed to clamping element  96 . The set bolt, spacing washer and set nut assembly is positioned such that pinch bolt  100  is in between the spacing washer and aperture  130 . The spacing washer, which is substantially smaller in length than the dimension of gap  140 , serves as a stop for the clamping elements, allowing the clamping elements to move into locking engagement with the shaft, but preventing undesired excess deformation or damage of the clamping elements that may result from over-tightening of the pinch bolt. The set bolt and set nut allow the user to adjust the running clearance of the device by setting gaps  141  to their desired maximum size. 
         [0091]      FIGS. 41 ,  42 ,  43 , and  44  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 5 ,  6 , and  7 , except that shaft  61  is hexagonal and base member  74  and clamping elements  87 ,  97  are shaped accordingly. The configuration of the base member and clamping elements is such that an aperture  131 , with geometry that mates with the shaft  61 , is provided. More particularly, inner base member surfaces  240  and  241  mate with shaft surfaces  230  and  231 , respectively, while inner clamping element surfaces  242  and  243  mate with shaft surfaces  234  and  233 , respectively. Inner base member surfaces  244  and  245  are spaced from shaft surfaces  235  and  232  by gaps  142  and  143 , respectively. The dimensional relationship between the aperture and the shaft is such that gaps  141  offer a minimal clearance, permitting unlimited linear, but limited rotational motion along the shaft axis when the pinch bolt  100  is loose. 
         [0092]    When the pinch bolt  100  is tightened, the clamping elements flex at live hinge points  150 , and gaps  141  diminish in size, restricting rotational motion. With further tightening, the clamping elements make contact with the shaft and force the shaft into locking engagement and repeatable alignment with the base member. 
         [0093]      FIGS. 45 ,  46 ,  47 , and  48  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 41 ,  42 ,  43 , and  44 , except that the shaft orientation is different and base member  75  and clamping elements  88 ,  98  are shaped accordingly. The configuration of the base member and clamping elements is such that an aperture  132 , with geometry that mates with the shaft  61 , is provided. More particularly, inner base member surfaces  250  and  251  mate with shaft surfaces  230  and  232 , respectively, while inner clamping element surfaces  252  and  253  mate with shaft surfaces  235  and  233 , respectively. Inner base member surface  254  is spaced from shaft surface  231  by gap  144 , and inner clamping element surfaces  255  are spaced from shaft surface  234  by gap  145 . 
         [0094]      FIGS. 49 ,  50 ,  51 , and  52  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 5 ,  6 , and  7 , except that shaft  62  is pentagonal and base member  76  and clamping elements  89 ,  99  are shaped accordingly. The configuration of the base member and clamping elements is such that an aperture  133 , with geometry that mates with the shaft  62 , is provided. More particularly, inner base member surfaces  270  and  271  mate with shaft surfaces  260  and  262 , respectively, while inner clamping element surfaces  272  and  273  mate with shaft surfaces  264  and  263 , respectively. Inner base member surface  274  is spaced from shaft surface  261  by gap  146 . The dimensional relationship between the aperture and the shaft is such that the gaps  141  offer a minimal clearance, permitting unlimited linear, but limited rotational motion along the shaft axis when the pinch bolt  100  is loose. 
         [0095]    When the pinch bolt  100  is tightened, the clamping elements flex at live hinge points  150 , and gaps  141  diminish in size, restricting rotational motion. With further tightening, the clamping elements make contact with the shaft and force the shaft into locking engagement and repeatable alignment with the base member. 
         [0096]      FIGS. 53 ,  54 ,  55 , and  56  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 5 ,  6 , and  7 , except that shaft  63  is heptagonal and base member  77  and clamping elements  40 ,  50  are shaped accordingly. The configuration of the base member and clamping elements is such that an aperture  134 , with geometry that mates with the shaft  63 , is provided. The base member is formed so as to mate with and contact shaft surfaces  283  and  284  and to be spaced from shaft surfaces  282  and  285  by gaps  290  and  291 , respectively. The clamping elements  40 ,  50  are formed so as to mate with shaft surfaces  281 ,  286 , respectively, and to be spaced from shaft surface  280  by gap  292 . The dimensional relationship between the aperture and the shaft is such that the gaps  141  offer a minimal clearance, permitting unlimited linear, but limited rotational motion along the shaft axis when the pinch bolt  100  is loose. 
         [0097]    When the pinch bolt  100  is tightened, the clamping elements flex at live hinge points  150 , and gaps  141  diminish in size, restricting rotational motion. With further tightening, the clamping elements make contact with the shaft and force the shaft into locking engagement and repeatable alignment with the base member. 
         [0098]      FIGS. 57 ,  58 ,  59 , and  60  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 53 ,  54 ,  55 , and  56 , except that base member  78  is formed so as to mate with and contact shaft surfaces  282  and  285  and to be spaced from shaft surfaces  283  and  284  by gap  293 . The clamping elements  40 ,  50  are formed so as to mate with shaft surfaces  281 ,  286 , respectively, and to be spaced from shaft surface  280  by gap  292 . The configuration of the base member and clamping elements is such that an aperture  135 , with geometry that mates with the shaft  63 , is provided. The dimensional relationship between the aperture and the shaft is such that the gaps  141  offer a minimal clearance, permitting unlimited linear, but limited rotational motion along the shaft axis when the pinch bolt  100  is loose. 
         [0099]    When the pinch bolt  100  is tightened, the clamping elements flex at live hinge points  150 , and gaps  141  diminish in size, restricting rotational motion. With further tightening, the clamping elements make contact with the shaft and force the shaft into locking engagement and repeatable alignment with the base member. 
         [0100]      FIGS. 61 ,  62 ,  63 , and  64  show an embodiment consistent with the inventive concept that is similar to that shown in  FIGS. 53 ,  54 ,  55 , and  56 , except that base member  79  is formed so as to mate with and contact shaft surfaces  283  and  285  and to be spaced from shaft surface  284  by gap  296 . The clamping elements  41 ,  51  are formed so as to mate with shaft surfaces  281 ,  280 , respectively, and to be spaced from shaft surfaces  282 ,  286  by gaps  294 ,  295 , respectively. The configuration of the base member and clamping elements is such that an aperture  136 , with geometry that mates with the shaft  63 , is provided. The dimensional relationship between the aperture and the shaft is such that the gaps  141  offer a minimal clearance, permitting unlimited linear, but limited rotational motion along the shaft axis when the pinch bolt  100  is loose. 
         [0101]    When the pinch bolt  100  is tightened, the clamping elements flex at live hinge points  150 , and gaps  141  diminish in size, restricting rotational motion. With further tightening, the clamping elements make contact with the shaft and force the shaft into locking engagement and repeatable alignment with the base member. 
         [0102]    Although various exemplary embodiments have been described herein, those skilled in the art will understand that additional implicit variations and combinations may exist which lie within the scope and spirit of the inventive concept.