Abstract:
A selectively lockable assembly includes a body, a pin, a locking member, and a plunger that is configured to selectively urge the locking member against the pin to lock the pin with respect to the body. The locking member is keyed to the body in a manner to prevent or limit rotation of the locking member and thereby limit movement of the pin under load. A corresponding clamp is also provided.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to locking mechanisms and reconfigurable clamps incorporating locking mechanisms. 
       BACKGROUND OF THE INVENTION 
       [0002]    Clamps are used extensively to temporarily locate sheet metal parts during the fabrication of sheet metal parts, usually by spot welding, into vehicle bodies or body subassemblies. Clamps are typically specific to one vehicle body style and to one location on that body style. Thus due to variations in external sheet metal, the same clamp cannot be used on a broad range of vehicle bodies even when general similarities exist between them. Thus the number of vehicle body variants which can be fabricated on a particular body assembly line is restricted. 
       SUMMARY OF THE INVENTION 
       [0003]    A selectively lockable assembly includes a body, a pin that is selectively movable with respect to the body, an actuator member that is selectively movable in first and second directions with respect to the body, and a locking member that is operatively connected to the body such that the body restricts rotation of the locking member in at least one direction. The actuator member is configured to urge the locking member against the pin when the actuator member is urged in one of the first and second directions. The locking member being urged against the pin locks the pin with respect to the body. The selectively lockable assembly improves upon prior art lockable assemblies by preventing rolling of the locking member with respect to the body and the pin, thereby enhancing the fastening of the pin with respect to the body. 
         [0004]    A reconfigurable clamp is also provided. The clamp includes a body, a plurality of pins that are operatively connected to the body and that are selectively movable with respect to the body, an actuator member that is operatively connected to the body and that is selectively movable with respect to the body in first and second directions, and a locking member. The locking member is operatively connected to the body such that the body restricts rotation of the locking member in at least one direction. The actuator member is configured to urge the locking member against at least one of the pins when the actuator member is urged in one of the first and second directions. 
         [0005]    The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a schematic, perspective view of a clamp assembly having a plurality of pins; 
           [0007]      FIG. 2  is a schematic, cross-sectional bottom view of the clamp assembly of  FIG. 1 ; 
           [0008]      FIG. 3  is a schematic, cross-sectional side view of the clamp assembly of  FIG. 1 ; 
           [0009]      FIG. 4  is a schematic, perspective view of a locking element in the clamp assembly of  FIG. 1 ; 
           [0010]      FIG. 5  is a schematic, sectional side view of the clamp assembly of  FIG. 1 ; 
           [0011]      FIG. 6  is a schematic, fragmentary sectional view of the clamp assembly of  FIG. 1  with one of the pins in a first position; and 
           [0012]      FIG. 7  is a schematic, fragmentary sectional view of the clamp assembly of  FIG. 1  with the pin of  FIG. 6  in a second position. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0013]    Referring to  FIGS. 1 and 2 , a reconfigurable clamp  10  is schematically depicted. The clamp  10  includes a body  12 , which, in the embodiment depicted, is generally cylindrical, but which may be characterized by other shapes within the scope of the claimed invention. The clamp  10  also includes a plurality of pins  14 A-F that are selectively movable with respect to the body  12 . The clamp  10  also includes a pin  14 G that is fixed with respect to the body  12 . The body  12  defines a plurality of elongated holes  16 A-F, each of which at least partially contains a respective one of the pins  14 A-F. 
         [0014]      FIG. 3  is a schematic, cross-sectional view of the clamp  10 , which depicts pins  14 C,  14 F and holes  16 C,  16 F. It should be noted that pins  14 C,  14 F are representative of all of the movable pins  14 A-F, and that holes  16 C,  16 F are representative of all of holes  16 A-F. The holes  16 C,  16 F extend through the body  12  from the tip  18  of the body  12  to the base  20  of the body  12 . In the embodiment depicted, the pins  14 C,  14 F are generally cylindrical. The holes  16 C,  16 F are generally cylindrical. Each hole  16 C,  16 F is characterized by a respective segment  22  that has a uniform diameter. Each pin  14 C,  14 F is characterized by a respective segment  26  that has a uniform diameter and that is positioned within a respective one of segments  22 . The diameter of segments  22  is slightly larger than the diameter of segments  26  so that the surfaces defining segments  22  restrict the movement of the pins  14 C,  14 F to substantially linear translation in either a first direction D 1  or a second direction D 2 , which is opposite the first direction D 1 . As used herein, directions D 1  and D 2  are relative to the clamp  10 . Each pin  14 A-F is capable of individual motion in the first or second direction without inducing motion in any of the other pins  14 A-F. 
         [0015]    Referring again to  FIG. 1 , each pin  14 A-F includes a respective end, or tip  30 A-F. Each of the pins  14 A-F in  FIG. 1  is depicted in a respective extended position in which the tip of each pin is a predetermined distance outside the holes  16 A-F and from the tip  18  of the body  12 . Referring again to  FIG. 3 , a spring  32  is positioned within hole  16 C between a base plate  34  and pin  14 C and urges the pin  14 C in the first direction D 1  to its extended position. Similarly, a spring  32  is positioned within hole  16 F between base plate  34  and pin  14 F and urges the pin  14 F in the first direction D 1  to its extended position. Springs (not shown) identical to the springs shown at  32  are also in holes  16 A,  16 B,  16 D,  16 E between the base plate  34  and a respective one of pins  14 A,  14 B,  14 D,  14 E to bias the pins  14 A,  14 B,  14 D,  14 E in their respective extended positions. 
         [0016]    Hole  16 C includes a section  36  having a diameter greater than the diameter of section  22 . A lip  38  is formed in the body  12  where segment  22  and segment  36  meet. Pin  14 C includes a wide section  40  that has a diameter greater than the diameter of section  22 , but less than the diameter of section  36 . Section  40  of pin  14 C is within section  36  of hole  16 C. Thus, section  36  of hole  16 C is wide enough to accommodate translation of section  40  therein. However, the lip  38  and the section  40  are sufficiently positioned to contact each other when the pin  14 C is in its extended position. Thus, the physical part interference between section  40  and the lip  38  prevents movement of the pin  14 C in the first direction D 1  beyond the extended position. Each pin  14 A-F also includes a respective tapered portion  43 , which, in the embodiment depicted, decreases in diameter in the second direction D 2 . 
         [0017]    The body  12  also defines a central hole  42 , which, in the embodiment depicted, is cylindrical and has a common centerline with the body  12 . In the embodiment depicted, the pins  14 A-F and holes  16 A-F are equidistant from the hole  42  and thus are arranged about a circle having the hole  42  at its center. An actuator member  44  is located within the central hole  42 . The actuator member  44  is a plunger that is selectively movable in the first and second directions D 1 , D 2 . A spring  48  urges the actuator member  44  in the second direction D 2 . More specifically, the spring  48  is within the hole  42  between a closed end of the hole  42  and a collar  52 , and urges the collar  52  in the second direction D 2 . The collar  52  acts on a lip  56  formed on the actuator member  44  and thereby transfers the force of the spring  48  to the actuator member  44 . 
         [0018]    The actuator member  44  is characterized by a tapered portion  58  that decreases in diameter in the second direction D 2 . The tapered portion  58  in the embodiment depicted is frustoconical, i.e., has the shape of a frustum of a cone. The tapered portion is characterized by outer surface  62 . 
         [0019]    The clamp  10  further includes a member  66  that is configured to selectively contact the actuator member  44  and to cause the actuator member  44  to move in the first direction D 1 , against the force of spring  48 . In the embodiment depicted, member  66  is operatively connected to a pneumatic actuator, as shown at  70  in  FIG. 5 . Other devices or techniques of moving actuator member  44  may be employed within the scope of the claimed invention. For example, the clamp  10  may include a servomotor or solenoid to move the actuator member  44 , the actuator member  44  may be manually moved (such as via a mechanical linkage), etc. 
         [0020]    Referring again to  FIG. 2 , the body  12  defines three lateral apertures, or holes  74 A,  74 B,  74 C, each of which extends laterally from the outer surface of the clamp body  12  to the central hole  42 . Each of the lateral holes  74 A,  74 B,  74 C is also open to a respective two of the holes  16 A-F such that two of the pins  14 A-F are accessible from one of the lateral holes  74 A,  74 B,  74 C. Thus, each hole  74 A,  74 B,  74 C interconnects the central hole  42  and a two of the holes  16 A-F. 
         [0021]    More particularly, in the embodiment depicted, at least a portion of each of the of the lateral holes  74 A,  74 B,  74 C is coextensive with a portion of two of the holes  16 A-F. Portions of hole  74 A are coextensive with portions of holes  16 A and  16 F. Portions of hole  74 B are coextensive with portions of holes  16 B and  16 C. Portions of hole  74 C are coextensive with holes  16 D and  16 E. 
         [0022]    The clamp  10  also includes three locking members  78 A,  78 B,  78 C. Each of the locking members  78 A,  78 B,  78 C is at least partially located within a respective one of the holes  74 A,  74 B,  74 C. Referring to  FIG. 4 , locking member  78  is representative of locking members  78 A,  78 B,  78 C. Locking member  78  includes a substantially spherical portion  82  and a generally polygonal portion  86 . In the embodiment depicted, the generally polygonal portion  86  has a form approximating that of a rectangular parallelepiped. The spherical portion  82  and the polygonal portion  86  are interconnected by a cylindrical or rod-like portion  88 , one end of which terminates on the surface of the spherical portion  82  while the other end terminates on one face of the polygonal portion  86 . As shown in  FIG. 4 , the portions  86 ,  88  may exhibit features such as chamfers and rounded corners to enable a smoother transition and blending of their individual geometries. 
         [0023]    Referring again to  FIG. 2 , portion  82  of member  78 A is between actuator member  44  and pins  14 A,  14 F such that portion  82  of member  78 A contacts surface  62  of the actuator member  44  and the tapered portions  43  of pins  14 A,  14 F. Portion  88  of member  78 A is between pins  14 A,  14 F. Portion  86  of member  78 A is in hole  78 A such that the movement of member  78 A is restricted, as will be explained in more detail. Portion  82  of member  78 B is between actuator member  44  and pins  14 B,  14 C such that portion  82  of member  78 B contacts surface  62  of the actuator member  44  and the tapered portions  43  of pins  14 B,  14 C. Portion  88  of member  78 B is between pins  14 B,  14 C. Portion  86  of member  78 B is in hole  74 B such that the movement of member  78 B is restricted. Portion  82  of member  78 C is between actuator member  44  and pins  14 D,  14 E such that portion  82  of member  78 C contacts surface  62  of the actuator member  44  and the tapered portions  43  of pins  14 D,  14 E. Portion  88  of member  78 C is between pins  14 D,  14 E. Portion  86  of member  78 C is in hole  74 C such that the movement of member  78 C is restricted. 
         [0024]    In the embodiment depicted, the body  12  of the clamp  10  also defines holes  90 . Each hole  90  is opposite a respective one of holes  74 A-C, and may facilitate maintenance of the clamp  10  by providing access to the locking members  78 A-C. 
         [0025]    Referring to  FIG. 5 , hole  74 B and locking element  78 B are schematically depicted. Hole  74 B is representative of holes  74 A,  74 C. Locking element  78 B is representative of locking elements  78 A,  78 C. The locking member  78 B and the hole  74 B are configured such that interaction between the body  12  and the locking member  78 B prevents rotation of the locking member  78 B with respect to the body  12  in at least two directions. 
         [0026]    Referring to  FIGS. 4 and 5 , the polygonal portion  86  functions as a polygonal key, interacting with the body  12  inside hole  74 B to prevent rotation of the member  78 B about axis A 1 . That is, the perimeter  92  of the polygonal portion  86  interacts with the surface of the body  12  that defines the hole  74 B such that the body  12  prevents the rotation of the locking member  78 B about axis A 1 . A portion of the spherical portion  82  protrudes outward from the lateral hole  74 B into the central hole  42  to contact surface  62  of the actuator member  44 . Another portion of the spherical portion  82  remains in the lateral hole  74 B. The height of the lateral hole  74  is only marginally larger than the diameter of the spherical portion  82  and the height of the polygonal portion  86 ; thus the surface of the body  12  that defines the hole  74 B also prevents rotation of the locking member  78 B about axis A 2 . Axes A 1  and A 2  are perpendicular to each other and are perpendicular to the first and second directions D 1 , D 2 . The surfaces of the body  12  that define hole  74 B also prevent movement of the locking member  78 B in either the first direction D 1  or the second direction D 2 . 
         [0027]    Referring again to  FIGS. 2 ,  3 , and  5 , the spring  48  exerts a force on the actuator member  44  in the second direction via the collar  52 . The surface  62  of the actuator member  44  is angled relative to the second direction D 2  such that the actuator member  44  transfers the force from the spring  48  to the spherical portions  82  of the locking members  78 A-C. The force exerted on the spherical portions  82  by the surface  62  includes a lateral component, i.e., a component that is orthogonal to the first and second directions D 1 , D 2 , and that urges the spherical portions  82  away from the central hole  42  and into the tapered portions  43  of the pins  14 A-F, thereby locking the pins  14 A-F with respect to the body  12 . Thus, the actuator member  44  and the locking members  78 A-C are part of a locking mechanism  93  that selectively prevents movement of the pins  14 A-F relative to the body. Each locking member  78 A,  78 B is prevented from rotating about an axis that is parallel to the first and second directions D 1 , D 2  by the surface  62  and two of the pins  14 A-F acting thereon. Thus, in the embodiment depicted, the locking members  78 A-C are prevented from rotating, and their movement is limited to lateral translation. 
         [0028]    The clamp  10  is reconfigurable; that is, the locking mechanism  93  is selectively releasable so that the positions of the pins  14 A-F with respect to the body  12  are selectively variable.  FIGS. 6 and 7  schematically depict operation of the locking mechanism  93  during reconfiguration of the clamp  10 , i.e., during repositioning of the pins with respect to the clamp body  12 . Although only pin  14 C is shown in  FIGS. 6 and 7 , it should be noted that the interaction between pin  14 C and the locking mechanism  93  is identical to the interaction between the other selectively movable pins  14 A-B,  14 D-F and the locking mechanism  93 . 
         [0029]    Referring to  FIG. 6 , pin  14 C is shown in its extended position. Spring  48  urges actuator member  44  in the second direction D 2 ; in turn, surface  62  of the actuator member  44  drives spherical portion  82  of locking member  78 B outward and against the tapered portion  43  of pin  14 C, thereby locking pin  14 C with respect to the body  12 . Friction between the spherical portion  82  of the locking member  78 B and the pin  14 C prevents movement of the pin  14 C in the first direction D 1 . It should be noted that, in the embodiment depicted, the force exerted by the spring (shown at  32  in  FIG. 3 ) is sufficient to overcome friction between the pin  14 C and the body  12 , but is not sufficient to overcome the friction between the locking element  78 B and the pin  14 C. 
         [0030]    The pin  14 C is prevented from moving in the second direction D 2  due to friction between the locking member  78 B and the pin  14 C, and also because the tapered portion  43  is angled relative to the second direction D 2  such that movement of the pin  14 C in the second direction causes the locking member  78 B to exert a reaction force on the pin  14 C in the first direction. 
         [0031]    It should be noted that, if spherical balls are used in place of locking elements  78 A-C, then the balls could rotate, or “roll,” relative to the body and to the pins, and thus the pins may “drift” from their intended positions. The locking members  78 A-C, by being keyed to the body  12 , are prevented from rolling in a direction that would compromise the ability to lock the pins  14 A-F with respect to the body  12 . 
         [0032]    To unlock the pin  14 C, and thereby to permit translation of the pin  14 C in either the first or the second direction D 1 , D 2 , the actuator member  44  is moved in the first direction D 1 . More specifically, in the embodiment depicted, the actuator (shown at  70  in  FIG. 5 ) exerts a force on member  66  (shown in  FIGS. 3 and 5 ), which transmits the force to the actuator member  44 . The force exerted by the actuator  70  is sufficient to overcome the bias of the spring  48 , and the actuator member  44  moves in the first direction to the position shown in phantom at  44 A. Correspondingly, surface  62  moves in the first direction D 1  to the position shown in phantom at  62 A. 
         [0033]    The taper of surface  62  is such that movement of the actuator member  44  in the first direction D 1  increases the distance between surface  62  and the tapered portion  43 , and thus the spherical portion  82  of the locking member  78 B. Thus, locking member  78 B is not tightly wedged between the surface  62  and the tapered portion  43  of the pin, thereby permitting relative movement of the pin  14 C relative to the body  12 . Thus, when the surface is at the position shown at  62 A, the locking member  78 B can move laterally, away from the pin  14 C (and pin  14 B) to the position shown in phantom at  78 BB in  FIG. 5 ; correspondingly, the spherical portion  82  of the locking member  78 B moves laterally, further into the central hole  42 , to the position shown in phantom at  82 A in  FIG. 6 , where it does not contact the pin  14 C, or, if contact occurs between the spherical portion  82  and the pin  14 C, the friction therebetween is low. 
         [0034]    Thus, movement of the member  44  to the position shown at  44 A unlocks the pin  14 C with respect to the body  12 , and the pin  14 C is selectively movable. In an exemplary use, the clamp  10  is employed by a robotic arm or other fixture to manipulate or hold sheet metal components for vehicle bodies. In prior art systems, a robotic arm or other fixture would require a new clamp, or significant machining of a clamp, to handle sheet metal components having different shapes or contours. The clamp  10  is reconfigurable such that the clamp  10  can be used for sheet metal components of differing contours and shapes. 
         [0035]    Referring to  FIG. 7 , to reconfigure the clamp  10  for a particular sheet metal contour, a representative piece of sheet metal  94  is pressed against the tips  30 A-F of the pins  14 A-F when the pins  14 A-F are unlocked, i.e., when the actuator member  44  is in the position shown at  44 A in  FIG. 6 . The axis of advance of the sheet metal part  94  should be such as to locate the point of contact between the fixed pin  14 G and the sheet metal part  94  at a predetermined location on the sheet metal part  94 , which is preferably a location of minimal local curvature. The sheet metal part  94  will continue to contact and displace the pins  14 A-F until the sheet metal part  94  contacts the fixed pin  14 G and the relative motion between the sheet metal part  94  and the clamp body  12  ceases. Preferably at the point when contact occurs between the sheet metal part  94  and the fixed pin  14 G, the sheet metal part  94  will contact all of the plurality of movable pins  14 A-F. 
         [0036]    The sheet metal  94  will move each pin  14 A-F in the second direction D 2 , against the bias of the springs shown at  32  in  FIG. 3 , to a respective position in which the tips  30 A-F approximate the contour of the sheet metal  94 . Thus, in  FIG. 7 , pin  14 C has been moved in the second direction D 2  by the sheet metal  94  from its extended position to the position shown in  FIG. 7 . It should be noted that the stationary pin  14 G is used as a reference location capable of identifying the location of the clamped sheet metal  94  in the reference frame of the tooling and thus for specifying the operating location of the clamp  10 . 
         [0037]    After the pin  14 C has been moved to the position shown in  FIG. 7 , then the actuator (shown at  70  in  FIG. 5 ) is deactivated, and the spring  48  urges the actuator member  44  in the second direction D 2  until the actuator member  44  is in the position shown in  FIG. 7  and driving the spherical portion  82  of locking member  78 B against pin  14 C (and pin  14 B), thereby to lock the pins  14 C and  14 B with respect to the body  12 . It should be noted that the locking element  78 B in  FIG. 7  contacts tapered portion  43  at a wider portion of the tapered portion  43  in  FIG. 7  than in  FIG. 6 ; accordingly, the locking element  78 B is closer to the centerline of hole  42  in  FIG. 7  than in  FIG. 6 . Thus, once the pneumatic actuator is deactivated and the spring  48  moves the actuator member  44  in the second direction D 2 , the locking element  78 B prevents the actuator member  44  from returning to its original position shown at  44  in  FIG. 6 . Since all three locking members  78 A-C may move laterally as a result of pin movement, the actuator member  44  is movable laterally, such as to the position shown at  44 B, in order to find a location such that it acts on all three locking members  78 A-C. Thus, the actuating member  44  is not rigidly connected to the collar (shown at  52  in  FIG. 3 ) or to the member (shown at  66  in  FIG. 3 ). 
         [0038]    It should be noted that the locked condition is achieved through the urging of actuator spring  48 , without the need for any action of the actuator (shown at  70  in  FIG. 5 ). Thus the locking action may be achieved without the application of external power to the reconfigurable clamp  10 . Hence the reconfigurable clamp  10  maintains its geometry even in the case of a power failure which incapacitates the external source of power. The locking members  78 A-C may be hardened to limit deformation during stress. In an exemplary embodiment, springs (not shown) may be used to bias the locking members  78 A-C into contact with surface  62  of the actuator member  44 . The springs shown at  32  and  48  are depicted as compression coil springs; however, those skilled in the art will recognize other spring configurations that may be employed within the scope of the claimed invention. In an exemplary embodiment, the springs  32 ,  48  are plunger springs. Pin  14 G is depicted as a member attached to the body  12 ; however, within the scope of the claimed invention, the pin  14 G may be part of the body  12 . 
         [0039]    In the above description it has been assumed that the transfer of the shape of the sheet metal part  94  to be supported and the clamp  10  is achieved through contact between the sheet metal part  94  and the reconfigurable clamp  10 . Alternatively, a solid block into which a representation of the relevant section of the sheet metal part  94  has been rendered may also be used. Such a procedure may be desirable if it is desired to set the form of the reconfigurable clamp  10  off-line and bring it to the operating location with the shape already preset. 
         [0040]    In alternative embodiments, and within the scope of the claimed invention, the tapered portions  43  on the movable pins  14 A-F may be oriented such that the diameter of the tapered portions  43  increase in the second direction D 2 , instead of in the first direction D 1  as shown. Similarly, and within the scope of the claimed invention, the tapered portion  58  on the actuator member  44  may be oriented such that the diameter of the tapered portion  58  increases in the second direction D 2 , instead of in the first direction D 1  as shown. 
         [0041]    While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.