Patent Publication Number: US-6902159-B2

Title: Sealed pin locating and clamping apparatus

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
   The present invention relates generally to a clamp and, more particularly, to a fluid powered, sealed pin locating and clamping apparatus. 
   Powered clamps have been commonly used to secure workpieces, such as sheet metal automotive body panels, polymeric parts and the like in checking fixtures, gauging stations, welding station, punching stations and other locations within a manufacturing environment. Many existing clamps are powered by hydraulic or pneumatic fluid pressure. For example, reference should be made to the following U.S. Patents, which have been invented by Sawdon: U.S. Pat. No. 6,502,880 entitled “Pin Part Locator” which issued on Jan. 7, 2003; U.S. Pat. No. 6,378,855 entitled “Locking Pin Clamp” which issued on Apr. 30, 2002; U.S. Pat. No. 5,190,330 entitled “Powered Clamp with Parallel Jaws” which issued on Mar. 2, 1993; all of which are incorporated by reference herein. 
   It is desirable to prevent a clamping arm from opening and releasing the workpiece if there is a loss of fluid pressure. Prior constructions employing such a feature are disclosed in U.S. Pat. No. 5,871,250 entitled “Sealed Straight Line Gripper” which issued to Sawdon on Feb. 16, 1999 and U.S. Pat. No. 5,853,211 entitled “Universal Gripper” which issued to Sawdon et al. on Dec. 29, 1998. These patents are also incorporated by reference herein. 
   In accordance with the present invention, a sealed pin locating and clamping apparatus includes a body, an actuator moveably supported by the body, a pin mounted to the body and a clamping member drivingly coupled to the actuator. The actuator includes a first rod having an internal cavity and a second rod rotatably positioned within the internal cavity. A portion of the pin is positioned within a cam slot formed in the second rod. The clamping member is drivingly coupled to the actuator such that the second rod rotates in response to linear movement of the first rod to position the clamping member. 
   The sealed pin locating and clamping apparatus of the present invention is highly advantageous over traditional clamps in that the clamp includes a clamping member contained within a precise slot of a locating pin. The clamping member is moveable in response to the application of pressurized fluid to a sealed chamber. This design eliminates exposing the inner mechanism to contamination such as weld flash, metal shavings or coatings on the metal which may rub off when parts are loaded over the pin locator clamp. Additionally, the clamping member is rotatable from a position inside the pin to a position outside the pin such that the workpiece may be freely positioned over the pin when the clamping member is retracted and firmly held in place when the clamping member is extended. 
   In addition, the present invention optionally includes a self-locking mechanism which does not allow the clamping mechanism to retract if fluid actuation pressure is lost. 
   Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
       FIG. 1  is a side elevational view showing a sealed pin locating and clamping apparatus constructed in accordance with the teachings of the present invention; 
       FIG. 2  is a perspective view of the sealed pin locating and clamping apparatus; 
       FIG. 3  is a exploded perspective view of the sealed pin locating and clamping apparatus; 
       FIG. 4  is a side view cross-sectional view of the sealed pin locator clamp having a clamping member in an extended position; 
       FIG. 5  is a bottom view of the sealed pin locator clamp; 
       FIG. 6  is a partial top view depicting the location of the clamping members when in the extended position; 
       FIG. 7  is a partial top view depicting the location of the clamping members when in the retracted position; and 
       FIG. 8  is a partial cross-sectional view depicting an alternate embodiment sealed pin locating clamping apparatus. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
   Referring to  FIGS. 1-7 , a sealed pin locating and clamping apparatus or clamp  10  of the present invention is used to locate or gauge and then clamp a workpiece  12  in a work station such as a moving assembly line, in a start-stop manufacturing station or in an off-line work cell. A clamp body  14  is coupled to a base  16  which in turn may be mounted to a table or attached to an end effector secured to a robotic arm. A seal  18  is positioned between body  14  and base  16 . Clamp body  14  includes a rectangular section  20  and a cylindrical section  22 . Rectangular section  20  of body  14  is preferably machined with a NAAMS hole pattern on one or more sides. The bottom of body  14  also includes a hole pattern to aid in mounting pin clamp  10 . Furthermore, cylindrical section  22  may be used to mount clamp  10  if so desired. In use, workpiece  12  may be moved relative to a stationarily mounted clamp  10  or clamp  10  may be moved relative to a stationarily mounted workpiece. 
   Clamp  10  includes an actuator assembly  24  having a moveable locating pin assembly  26 . A pair of selectively radially extendable clamping members  28  are positioned within slots  30  extending through locating pin assembly  26 . Clamping members  28  are selectively moveable in a radial direction between a first position where clamping members  28  are positioned substantially entirely within slots  30  and a second position where clamping members  28  extend at least partially from slots  30  beyond an external surface  32  of locating pin assembly  26 . As will be described in greater detail hereinafter, clamping members  28  are positioned in the second or extended position when actuator assembly  24  is in a retracted position as depicted in  FIGS. 4 and 6 . Linear motion of actuator assembly  24  from the retracted position to an extended position, causes locating pin assembly  26  to axially translate and also move clamping members  28  from the second position to the first position inside locating pin assembly  26 . Accordingly, workpiece  12  may be loaded over locating pin assembly  26  when actuator assembly  24  is in the extended position and clamping members  28  are in the first position not extending beyond external surface  32 . Once workpiece  12  is positioned over locating pin assembly  26 , actuator assembly  24  is moved from the extended position toward the retracted position where clamping members  28  outwardly extend from external surface  32 . Locating pin assembly  26  translates until clamping members  28  engage an upturned flange  34  of workpiece  12 . 
   Body  14  includes a stepped bore  36  having a first bore portion  38 , a second bore portion  40  and a third bore portion  42 . First bore portion  38  is substantially cylindrical and extends inwardly from a first end  44  of body  14 . Second bore portion  40  is substantially cylindrical and coaxially aligned with first bore portion  38 . Third bore portion  42  extends inwardly from a second end  46  of body  14  and is also substantially coaxially aligned with first bore portion  38  and second bore portion  40 . A stop face  48  is formed at the intersection of first bore portion  38  and second bore portion  40 . A land  50  is formed at the intersection of second bore portion  40  and third bore portion  42 . 
   Actuator assembly  24  includes a piston  52 , a piston rod  54 , a cam rod  56 , a drive pin  58 , a substantially hollow, cylindrically shaped, extension tube  60  and a locating pin  62 . Piston  52  is a substantially cylindrical member having a body  64 , a reduced size forward section  66  and a reduced size rearward section  68 . A pair of annular grooves  70  are formed in an outer surface of body  64 . Seals  72  are positioned within grooves  70  to define a first chamber  74  between body  64  and base  16 . A second chamber  76  is formed between body  64  and stop face  48 . Ports  77  communicate with first chamber  74  and second chamber  76  to facilitate the supply of pressurized fluid to translate actuator assembly  24  between the retracted and extended positions. Forward section  66  of piston  52  includes a pocket  78  in receipt of a first end  80  of piston rod  54 . A seal  82  sealingly interconnects piston rod  54  and piston  52 . A threaded fastener  84  mounts piston rod  54  to piston  52 . 
   Piston rod  54  is a substantially cylindrical member including a blind bore  86  extending inwardly from a second end  88 . A keyway  90  axially extends along piston rod  54  in communication with blind bore  86 . A key  92  is fixed to body  14  and slidingly disposed with keyway  90  to allow axial movement of piston rod  54  relative to body  14 . Key  98  may be cylindrically shaped as shown or may alternately include any number of cross-sectional shapes such as a square or rectangle. Relative rotational movement between piston rod  54  and body  14  is restricted. Second end  88  of piston rod  54  includes a necked section  94  and a radially extending flange  96 . 
   A pair of semi-circular keepers  98  removably interconnect second end  88  of piston rod  54  with a first end  100  of extension tube  60  to define a portion slots  30 . First end  100  includes a necked section  102  and radially extending flange  104  similar to piston rod  54 . 
   Locating pin  62  includes a bulbous end  106  and a hollow sleeve  108 . Hollow sleeve  108  is positioned within extension tube  60 . A pair of pin retainers  110  transversely extend through one wall of extension tube  60  and hollow sleeve  108 . Pin retainers  110  terminate short of cam rod  56  to allow the cam rod to rotate freely within a cavity  111  defined by hollow sleeve  108  and blind bore  86 . First end  100  includes a lug  112  positioned within a slot  114  formed in second end  88  of piston rod  54 . Lug  112  acts to prevent relative rotation between extension tube  60  and piston rod  54 . 
   A pair of diametrically opposed slots  116  are formed on a second end  118  of extension tube  60 . Slots  116  define a portion of slots  30 . Each slot  116  includes an aperture  120  for receipt of a pin  122 . Each pin  122  rotatably interconnects a clamping member  28  to extension tube  60 . Pins  122  also act to couple locating pin  62  and extension tube  60 . 
   Cam rod  56  is a substantially cylindrical member axially captured but free to rotate within cavity  111 . Cam rod  56  includes a serpentine slot  124  in receipt of drive pin  58 . Slot  124  is positioned proximate a first end  126 . A pair of flutes  128  are formed at a second end  130  of cam rod  56 . It should be appreciate that drive pin  58  is positioned within a slot  131  and is trapped between body  14  and a support  132 . Accordingly, drive pin  58  does not rotate or translate in conjunction with actuator assembly  24 . As actuator assembly  24  translates drive pin  58  travels within slot  124  and causes cam rod  56  to rotate. 
   Support  132  is coupled to body  14  and at least partially encompasses actuator assembly  24 . Specifically, support  132  includes a substantially cylindrical body  134  and a radially extending flange  136 . Support  132  is positioned within third bore portion  42 . Flange  136  is supported on land  50 . Support  132  includes a clamping surface  137  where at least a portion of workpiece  12  is supported. One skilled in the art will appreciate that the length of body  134  may be varied to account for packaging concerns within the work cell or the geometry of workpiece  12 . The length of extension tube  60  may be accordingly varied to construct a properly proportioned clamp  10 . An aperture  138  extends axially through body  134  and flange  136 . A pair of fastener apertures  140  extend through flange  136 . Aperture  138  is sized to guide actuator assembly  24  but allow relative movement of actuator assembly  24  to support  132 . This slip-fit interconnection also serves to maintain the location of keepers  98  during operation. A pair of fasteners  142  fix support  132  to body  14 . 
   Based on the construction previously described a serviceable subassembly is defined to include locating pin  62 , extension tube  60 , clamping members  28 , pin retainers  110  and pins  122 . During operation of clamp  10 , bulbous end  106  may become worn or damaged thus requiring replacement. Similarly, clamping members  28  may become worn. The subassembly may be replaced by removing fasteners  142  and the coupling support  132  from body  14 . With support  132  removed, access to keepers  98  is provided. Upon removal of keepers  98 , the subassembly may be replaced without further disassembly of clamp  10 . The new subassembly is simply aligned with piston rod  54  while keepers  98  interconnect the replacement subassembly with piston rod  54 . Support  132  is axially positioned over keepers  98  and the remainder of actuator assembly  24 . Once fasteners  142  have been reinstalled, clamp  10  is operable again. 
   As best shown in  FIGS. 6 and 7 , each clamping member  28  includes an arcuate arm portion  146  and a dog  148 . Each flute  128  includes a first face  150  and a second face  152  selectively engageable with dog  148 . During movement of actuator assembly from the retracted position to the extended position, cam rod  56  rotates to cause first face  150  to engage dog  148 . Based on the positioning of pin  122  relative to cam rod  56 , a torque is applied to each clamping member  28  to cause clamping members to retract within locating pin  62  toward the first position. The retracted or first position is depicted in FIG.  7 . When actuator assembly  24  is moved from the extended position toward the retracted position, cam rod  56  rotates to place second face  152  in contact with dog  148 . This motion imparts a torque to each clamping member  28  to cause arcuate arm portion  146  to extend outwardly beyond external surface  32  and place the clamping member in the second position as shown in FIG.  6 . Locking pin assembly  26  translates to draw clamping member  28  into contact with workpiece  12 . 
   Serpentine slot  124  is shaped to include a substantially straight longitudinally extending section  153 . Drive pin  58  is positioned in section  153  when actuator assembly  24  is in the fully retracted position. At this time, clamping members  28  are in their second or extended positions. If a loss of pressurized fluid should occur, clamping members  28  will be retained in the second position because cam rod  56  is restricted from rotation due to the positioning of drive pin  58  in longitudinally extending section  153  as previously described. If an operator wishes to move clamping member  28  from their second positions to their first positions without the aid of pressurized fluid, locating pin  62  is manually drawn toward the extended position. Locating pin  62  includes an aperture  155  for receipt of a tool to assist the operator in translating actuator assembly  24  toward the extended position. As the operator causes the actuator assembly to move, cam rod  56  rotates to cause each arcuate arm portion  146  to retract beneath external surface  32 . At this time, workpiece  12  may be removed from clamp  10 . 
     FIG. 4  shows an alternate retention device to maintain force on workpiece  12  should pressurized fluid become unavailable. Optional spring  157  (shown in broken lines) biasedly urges actuator assembly  24  toward the fully retracted position. Clamping members  28  remain in their second positions and are urged into contact workpiece  12 . The force provided by spring  157  may be overcome by an operator manually moving actuator assembly  24  toward the extended position as previously described. 
   A proximity switch assembly  154  is configured to signal an electronic controller (not shown) or a user when piston  52  is located near the top or bottom of first bore portion  38 . More particularly proximity switch assembly  154  includes a housing  156 , an access plate  158 , a first sensor head  160 , a second sensor head  162  and wire  164  interconnecting the sensor heads and housing  156 . First sensor head  162  is positioned within a first transverse bore  166 . First transverse bore  166  extends from first bore portion  38  to a switch pocket  168  formed in body  14 . Second sensor head  162  is positioned within a second transverse bore  170 . Second transverse bore  170  is in communication with first bore portion  38  and pocket  168 . First sensor head  160  and second sensor head  162  are positioned to detect the presence or absence of piston  52 . Each sensor head outputs a signal when the piston is within a predetermined proximity of an end face of the sensor head. In this manner, a controller or an operator is notified that clamping member  28  is in the first position, second position or somewhere therebetween depending on the signals output from proximity switch assembly  154 . 
     FIG. 8  depicts an alternate embodiment sealed pin locating and clamping apparatus  200 . Clamp  200  is substantially similar to clamp  10 . Accordingly, like elements will retain their reference numerals as previously introduced. Clamp  200  includes a locating pin assembly  202  including an enlarged locating pin  204 . Enlarged locating pin assembly  202  is used in conjunction with piston rod  54 , cam rod  56  and keepers  98 . A modified support  206  includes an enlarged bore  208  for receipt of the differently sized components. A sleeve  210  fills the gap between the increased size bore  208  and extension tube  60 . Enlarged clamping members  212  pivot about pins  122 . A pair of pin retainers  214  interconnect sleeve  210  to extension tube  60  and locating pin  204 . By constructing clamps  10  and  200  in this manner, one skilled in the art will appreciate that any number of differently sized pins may be used with a common clamp body and actuator assembly. 
   It should be appreciated that the embodiment shown is merely exemplary in nature and that a number of variations may be made without departing from the scope of the present invention. Specifically, the actuator may include an electric motor in lieu of the piston arrangement depicted. Additionally, functioning embodiments of the clamp need not include an actuator assembly including a serviceable subassembly. Therefore, the clamp could be further simplified by reducing the number of components required.