Abstract:
A clamp and method for locating a clamping workpiece in predetermined location are disclosed. The clamp includes a clamp body, a driving member, a workpiece-locating pin and a clamping member. The driving member is moveable in a first linear direction at least partially inside the clamp body. The workpiece-locating pin is moveable in a second direction substantially perpendicular to the first direction and at least partially externally projects from the body. The clamping member is moveable relative to the workpiece-locating pin in the first direction when moving between a retracted position and a clamping position.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
   The present invention relates generally to a clamp and more specifically to a sealed locking pin locator clamp. 
   Automated or powered clamps have been used to secure workpieces, such as sheet metal automotive vehicle body panels, polymeric parts and the like in checking fixtures, gauging stations, molding stations and punching machines. Some 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. 5,884,903 entitled “Powered Clamp Gauging Apparatus” which issued on Mar. 23, 1999; U.S. Pat. No. 5,165,670 entitled “Retracting Power Clamp” which issued on Nov. 24, 1992; U.S. Pat. No. 5,190,334 entitled “Powered Clamp with Parallel Jaws” which issued on Mar. 2, 1993; and U.S. Pat. No. 6,378,855 entitled “Locking Pin Clamp” which issued on Apr. 30, 2002; all of which are incorporated by reference herein. 
   It has also become desirable to prevent the gripping arm from opening and releasing the workpiece if there is a loss of fluid pressure. Gripper 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 preferred embodiment of a sealed locking pin locator clamp employs a piston head operably advancing in a first linear direction, a clamp body, a driving member coupled to the piston head, a workpiece-locating pin movably coupled to the driving member and a clamping member movably coupled to the driving member. The driving member is moveable in a first direction in concert with the piston head. The driving member is moveable at least partially inside of the body. The workpiece-locating pin is moveable in a second direction substantially perpendicular to the first direction. The workpiece-locating pin at least partially externally projects from the body. The clamping member is moveable relative to the workpiece-locating pin in the first direction when moving from a retracted position to a clamping position. 
   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 perspective view showing a first embodiment sealed locking pin locator clamp with a pair of clamping members shown in a clamping position; 
       FIG. 2  is a perspective view of the first embodiment sealed locking pin locator clamp showing the clamping members in a retracted position; 
       FIG. 3  is an exploded perspective view showing the first embodiment sealed locking pin locator clamp; 
       FIG. 4  is a cross-sectional view, taken along line  4 — 4  of  FIG. 2 , showing the first embodiment sealed locking pin locator clamp in an unclamped position; 
       FIG. 5  is a cross-sectional view, taken along line  5 — 5  of  FIG. 2 , showing the first embodiment sealed locking pin locator clamp in the unclamped position; 
       FIG. 6  is a cross-sectional view, like that of  FIG. 4 , showing the clamp in an intermediate position between the unclamped and clamped positions; 
       FIG. 7  is a cross-sectional view, like that of  FIG. 5 , showing the first embodiment sealed locking pin locator clamp in the intermediate position of  FIG. 6 ; 
       FIG. 8  is a cross-sectional view, like that of  FIGS. 4 and 6 , showing the first embodiment sealed locking pin locator clamp in a clamped position; 
       FIG. 9  is a cross-sectional view, like that of  FIGS. 5 and 7 , showing the first embodiment sealed locking pin locator clamp in a clamped position; and 
       FIG. 10  is an exploded perspective view showing a first embodiment collar, locating pin and clamping member subassembly as well as a second embodiment collar, locating pin and clamping member subassembly. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
   Referring to  FIGS. 1–9 , a first preferred embodiment of a sealed locking pin locator clamp  20  of the present invention is used to locate or gauge and then clamp a workpiece  22 . A clamp body  24  may be fixed to a stationary mount or table  26  by way of threaded screws and/or dowels (not shown). Alternatively, clamp body  24  may be secured to an end effector (not shown) of a robotic arm. Thus, workpiece  22  may be moved relative to the stationary mounted clamp  20  or clamp  20  may be moved relative to a stationarily mounted workpiece  22 . 
   Clamp  20  includes a piston  28 , a first piston cylinder  30 , a second piston cylinder  32 , a piston rod  34 , a control member  36 , a locating pin  38 , a pair of clamping members  40 , and a collar  42 . Clamp body  24  includes a first longitudinally elongated internal bore  44  having a central axis  46  and a second transversely elongated internal bore  48  having a central axis  50 . 
   Locating pin  38  is a substantially cylindrically shaped hollow member having an outer cylindrical surface  52  at its midsection, an arcuate taper  54  and at a distal end, a first shoulder  56  and a second shoulder  58  at its proximal end. A pair of ribs  60  axially extend from second shoulder  58 . The preferred embodiment includes bore ribs  60  circumferentially spaced apart from one another at ninety-degree intervals. 
   Piston rod  34  includes a substantially cylindrical body  62  having a circular flange  64  positioned at a distal end  66 . A pair of perpendicularly oriented slots  68  extend through circular flange  64  and a portion of body  62 . Slots  68  are sized and positioned to receive ribs  60  of locating pin  38 . Piston rod  34  also includes a unitary working portion  70  that contains an aperture  72  adjacent a proximal end  74 . Locating pin  38  and piston rod  34  are slidably positioned within clamp body  24  and are moveable along central axis  46 . 
   A blind bore  76  of locating pin  38  and slotted circular flange  64  of piston rod  34  define a cavity  78  in which control member  36  is slidably positioned. Control member  36  is substantially cylindrically shaped and includes a distal end  80  and a proximal end  82 . Two pair of camming surfaces  84  are formed on distal end  80 . A pair of generally “T” shaped rails  86  are spaced apart from camming surfaces  84 . Rails  86  are shaped to guide and retain clamping members  40 . Specifically, each clamping member  40  includes a clamping surface  88 , a pair of camming surfaces  90  and a slot  92  sized and shaped to receive one of rails  86 . Each clamping member  40  is slidably positioned within a window transversely extending through locating pin  38 . Clamping members  40  and control member  36  are sized and shaped such that relative movement between control member  36  and locating pin  38  causes clamping members  40  to move between extended and retracted positions. Workpiece  22  is operably clamped between clamping members  40  and a collar  42 . 
   A cross rod  96  transversely extends through an aperture  98  extending through control member  36 . Another aperture  100  extends through proximal end  82  in a direction orthogonal to aperture  98 . The rotational orientation of clamping members  40  relative to clamp body  24  may be varied by ninety degrees if alternate aperture  100  is used to house cross rod  96 . A screw  101  couples cross rod  96  to control member  36 . 
   A pair of upper keepers  102  are positioned around first shoulder  56  and are coupled to a pair of lower keepers  104  to rigidly interconnect locating pin  38  and piston rod  34 . Furthermore, control member  36  is trapped within cavity  78  but free to translate a predefined linear stroke. Cap screws  106  couple upper keepers  102  to lower keepers  104 . It should be appreciated that each of the lower keepers  104  are spaced apart from one another to allow cross rod  96  to travel therebetween during clamp operation. 
   Collar  42  is coupled to clamp body  24  by threaded fasteners  108 . Collar  42  and clamp body  24  define a cavity  110 . A subassembly  112  including locating pin  38 , control member  36 , piston rod  34 , upper keepers  102  and lower keepers  104  is at least partially slidably positioned within first bore  44  and cavity  110 . A portion of locating pin  38  extends through an aperture  114  extending through collar  42 . 
   A pair of springs  116  are positioned within spring seats  118  formed within clamp body  24 . Slots  120  axially extend through clamp body  24  and are positioned adjacent to spring seats  118  to allow cross rod  96  to travel freely therein. 
   First piston cylinder  30  and second piston cylinder  32  are attached to clamp body  24 . Each piston cylinder has an internal chamber accessible to second bore  48  and they are elongated coaxially with axis  50 . An open end  122  of each piston cylinder is inserted into second bore  48  and secured in its respective fully installed position relative to body  24  by way of a pair of circumferentially compressible roll pins  124 . Ends of each roll pin are stationarily secured in openings  126  in clamp body  24  while a middle portion of each roll pin  124  engages a circular groove  128  machined in each piston cylinder. Accordingly, each of the first and second piston cylinders  30  and  32  may be rotated 360 degrees relative to clamp body  24  on axis  50 , even after being fully inserted and attached to the clamp body. This feature allows fluid carrying tubes, hoses, and fittings which may be attached to an inlet  130  to be repositioned free of any obstructions in the factory or to improve tube routing by minimizing bends. 
   Piston  28  is configured to have a pair of opposed piston head portions  132  and  134  and a driving or camming member  136  mounted therebetween. Piston  28  is movably located inside second bore  48 , first piston cylinder  30  and second piston cylinder  32 . An elastomeric O-ring or other shaped seal  138  is secured within a groove  140  in each piston head portion  132  and  134 . A camming slot  142  is internally located in camming member  136  of piston  28 . Camming slot  142  preferably has a closed loop configuration defined by a first elongated segment  144  elongated in generally the same direction as axis  50 . Axis  50  also defines the advancing and retracting direction of piston  28  within second bore  48 . More specifically, an elongated axis of first segment  144  is approximately offset nine degrees from axis  50 . Camming slot  142  further includes a second camming segment  146  angularly offset from first segment  144 . 
   A pin assembly  148  is secured to proximal end  74  of piston rod  34 . Pin assembly  148  includes a pair of outboard rollers  150  which are rotatably coupled to a central elongated pivot pin  152  by way of snap rings  154 . Outboard rollers  150  longitudinally travel within longitudinally elongated slots  156  machined within clamp body  24 . Outboard rollers  150  are maintained in their outboard positions by an inward flange  158  offset from each longitudinally elongated slot  156 . 
   A middle roller  160  is journaled around an intermediate portion of pivot pin  152  and lies within a camming slot  162  of piston  28 . Middle roller  160  is laterally trapped between a lateral face  164  of working portion  70  and an inwardly stepped face  166  of driving member  136 . Pivot pin  152  is rotatably secured within aperture  72  of piston rod  34 . Camming slot  142  and pin assembly  148  define a camming mechanism. Plates  167  are coupled to body  24  with fasteners  169  to sealingly cover slots  156 . In an alternate embodiment shown in  FIG. 3 , a proximity switch  171  may be coupled to body  24  in place of plate  167  to sense the position of piston  28 . 
   Clamp body  24 , first piston cylinder  30  and second piston cylinder  32  are preferably machined on a lathe from aluminum bar stock having a circular cross-sectional shape. As such, the outer and inner surfaces of these parts predominantly have circular-cylindrical shapes with secondary holes in the slots machined therein. Piston  28 , locating pin  38 , collar  42 , piston rod  34  and control member  36  are preferably machined on a lathe from steel bar stock having a circular cross-sectional shape with other grooves and holes being machined thereafter. Clamping members  40  are either cast or machined from steel components. 
     FIG. 10  depicts collar  42 , locating pin  38  and clamping members  40  from first embodiment clamp  20  previously described. Also depicted in  FIG. 10  are a second embodiment collar  200 , a locating pin  202  and clamping members  204 . Collar  200 , locating pin  202  and clamping members  204  define a replacement set of components  206  which may replace collar  42 , locating pin  38  and clamping members  40  as a group to define a second embodiment clamp assembly. A proximal end  208  of locating pin  202  is substantially similar to the proximal end of locating pin  38 . Specifically, the outer diameter of first shoulder  56  is the same size as the outer diameter of a first shoulder  210  of locating pin  202 . In similar fashion, the dimensions associated with second shoulder  58  in ribs  60  are equivalent to the shape and dimensions of a second shoulder  212  and ribs  214  of second embodiment locating pin  202 . In this manner, locating pin  202  mates with piston rod  34 , upper keepers  102  and lower keepers  104  in the manner previously described. Collar  200  includes an aperture  216  sized to receive the increased outer diameter of locating pin  202 . Replacement set  206  is shown to include a locating pin  202  having an outer diameter approximately twice the size of locating pin  38 . One skilled in the art will appreciate that this size ratio is merely exemplary and that a family of replacement sets may be constructed to allow a user of the sealed locking pin locator clamp to quickly change the size of the locating pin if the workpiece to be clamped so requires. In the manufacturing environment, it is beneficial to be able to quickly change the clamping tooling to provide flexibility for clamping a number of different workpieces having differently sized apertures extending therethrough. Locating pin  202  includes a blind bore  218  similarly sized to blind bore  76  to accommodate common control member  36 . 
   The operation of the first embodiment sealed locking pin locator clamp  20  of the present invention may be observed with reference to  FIGS. 4–9 . When a pressurized fluid is applied against piston head portion  132 , piston  28  is advanced in a first direction along axis  50 . This action begins to move clamping members  40  from their fully retracted positions within the internal cavity of locating pin  38 , as shown in  FIG. 4 , to an extended position as shown in  FIG. 6 . This initial advancing movement from  FIGS. 4 and 5  to  FIGS. 5 and 6  is achieved by sliding pin assembly  148  down the steeply inclined leading segment of camming slot  142 . Pivot pin  152  drives piston rod  34  and locating pin  38  downwardly. At this time, control member  36  is biased toward an upward most position in relation to the Figures by springs  116 . Relative motion occurs between locating pin  38  and control member  36  in the form of control member  36  further entering blind bore  76 . Camming surfaces  84  of control member  36  engage camming surfaces  90  of clamping members  40  thereby driving the clamping members from their retracted position to the extended position depicted in  FIG. 6 . During the remaining stroke of piston  28 , clamping members  40  remain in the fully extended position. 
   Further advancement of piston  28  causes pin assembly  148  to ride along second camming segment  146 . This portion of piston advancement is depicted as movement between the intermediate position depicted in  FIGS. 6 and 7  to the clamped position shown in  FIGS. 8 and 9 . During this portion of piston movement, middle roller  160  engages second camming segment  146 . Also, cross rod  96  is moved from its seat against a pair of screws  168  that are coupled to clamp body  24 . Specifically, two ribs  60  of locating pin  38  engage cross rod  96  as locating pin  38  is being driven further downwardly by piston rod  34  and pin assembly  148 . Springs  116  are compressed while locating pin  38 , control member  36 , piston rod  34  and clamping members  40  are translated as a unit. Accordingly, clamping surfaces  88  of clamping members  40  are drawn into contact with workpiece  22  to clamp the workpiece between clamping members  40  and collar  42 . 
   In the clamping position shown in  FIGS. 8 and 9 , middle roller  160  engages a corresponding detent  169  formed along camming surface  146 . Specifically, camming surface  146  has slight indentations or detents  169  where cam rollers  160  find a locking position which prevents unlocking even under vibration when fluid pressure is lost or undesirably reduced. Piston  28  is retracted by applying fluid pressure against the opposite piston head portion  134  to provide a reversal of the above-discussed motions. 
   An extension portion  170  is coupled to one end of piston  28  and extends through an aperture  172  extending through an end wall  174  of first piston cylinder  30 . A pair of seals  176  engage extension portion  170  and first piston cylinder  30  to restrict ingress of contamination and egress of pressurized fluid. A knob  178  is coupled to an end of extension portion  170 . If pressurized fluid is unavailable, a user may cause clamp  20  to function as previously described by simply grasping knob  178  and imparting a force sufficient to slide piston  28  as previously described. If a manual override feature is not desired, piston  28  may be configured without extension portion  170  without departing from the scope of the present invention. 
   Furthermore, the foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations may be made therein without department from the spirit and scope of the invention as defined in the following claims.