Abstract:
A clamp employs a workpiece-clamping member, a clamp body, and a driving member. A further aspect of the present invention provides a camming mechanism to couple a clamping member to a camming member. Still another aspect of the present invention employs a piston and a clamping member wherein the piston advances in a direction generally perpendicular to a direction of movement of the clamping member.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates generally to a clamp and more specifically to a fluid powered, locking pin clamp. 
     Automated or powered clamps have been commonly used to secure workpieces, such as sheet metal automotive vehicle body panels, polymeric parts and the like in checking fixtures, gauging stations, welding stations and punching machines. 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. 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; and U.S. Pat. No. 5,190,334 entitled “Powered Clamp with Parallel Jaws” which issued on Mar. 2, 1993; all of which are incorporated by reference herein. 
     It has recently become desirable to prevent a 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 clamp employs a workpiece-clamping member, a clamp body, and a driving member. In another aspect of the present invention, a fluid actuated piston is operable to drive a clamping member. A further aspect of the present invention provides a camming mechanism to couple a clamping member to a camming member. Still another aspect of the present invention employs a piston and a clamping member wherein the piston advances in a direction generally perpendicular to a direction of movement of the clamping member. A detent arrangement is provided on a camming surface in yet another aspect of the present invention, in order to deter inadvertent unclamping of a workpiece if the desired fluid pressure is not present. Another aspect of the present invention, allows a clamping member to retract into a hollow locating pin extending from a clamp body. A method of operating a clamp is also provided. 
     The locking pin clamp of the present invention is highly advantageous over traditional clamps in that the moving clamping member of the present invention can be maintained in its clamping position even during loss of piston fluid pressure. This eliminates undesired opening of the clamping member which can lead to inadvertent dropping and damage of the workpiece. The present invention is also advantageous in that the clamping member can be retracted into a locating pin whereby the workpiece can first be located relative to the clamp body and then clamped against the clamp body, in a single, compact and multi-functional package; thus, the clamping member does not need to be remotely located away from the target locating pin. Furthermore, the present invention allows for four point equidistant locating or gauging against the workpiece even when openings are provided in the locating pin for passage of the clamping member. This four point locating and contacting against the workpiece provides accurate workpiece-to-pin alignment that coincides with the typically designed geometric tolerancing and dimensioning characteristics of the workpiece. 
     The specific perpendicular orientation of the piston movement relative to the general direction of clamping member movement advantageously encourages locking of the clamping member in the clamping position if fluid pressure is not present. Moreover, this generally perpendicular arrangement is resistant to being back driven and is further maintained in the clamping position by use of a set of detent formations located along a camming surface. Another advantage of the present invention is the ability to rotate one or more piston cylinders 360 degrees relative to the body even after the piston cylinder is fully installed in the body. This allows for convenient routing of fluid carrying tubes and fittings to the piston cylinders free of adjacent obstructions in the manufacturing facility. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view showing the first preferred embodiment of a locking pin clamp of the present invention; 
     FIG. 2 is a perspective view showing the first preferred embodiment locking pin clamp; 
     FIG. 3 is a top elevational view showing the first preferred embodiment locking pin clamp; 
     FIG. 4 is a side elevational view, 90 degrees to that of FIG. 1, showing the first preferred embodiment locking pin clamp; 
     FIG. 5 is an exploded perspective view showing the first preferred embodiment locking pin clamp; 
     FIG. 6 is a cross sectional view, taken along line  6 — 6  of FIG. 3, showing the first preferred embodiment locking pin clamp; 
     FIG. 7 is a perspective view showing the first preferred embodiment locking pin clamp, with a clamp body removed; 
     FIG. 8 is a fragmentary perspective view showing a second preferred embodiment of the locking pin clamp of the present invention, with the body and a piston removed; 
     FIG. 9 is a perspective view showing a camming mechanism for the piston employed in the first preferred embodiment locking pin clamp; 
     FIG. 10 is a partially fragmentary side elevational view showing a clamping member of the first preferred embodiment locking pin clamp, disposed in a clamping position; 
     FIG. 11 is a partially fragmentary side elevational view showing the clamping member of the first preferred embodiment locking pin clamp, disposed in an intermediate movement position; 
     FIG. 12 is a partially fragmentary side elevational view showing the clamping member of the first preferred embodiment locking pin clamp, disposed in a retracted position; 
     FIG. 13 is a side elevational view showing the third preferred embodiment of a locking pin clamp of the present invention; and 
     FIG. 14 is a cross sectional view, like that of FIG. 6, showing the third preferred embodiment locking pin clamp. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-7, a first preferred embodiment of a locking pin clamp  21  of the present invention is used to locate or gauge and then clamp a workpiece  23  on a moving assembly line, in a start-and-stop manufacturing station, or in an off-line work cell. A clamp body  25  is affixed to a stationary mount or table  27  by way of two threaded screws  28  and two adjustable dowels (not shown) or can be attached to an end arm effector  29  secured to a robotic arm. Thus, workpiece  23  can be moved relative to the stationarily mounted clamp  21  or clamp  21  can be moved relative to a stationarily mounted workpiece  23 . 
     Clamp  21  includes a hollow locating pin  31 , a clamping member  33 , a piston  35 , a pair of piston cylinders  37  and a collar  39 . Clamp body  25  has a first longitudinally elongated internal bore  51  having a central axis  52  and a second transversely elongated internal bore  53  having a central axis  54 . A shoulder  55  transversely extends around the base of locating pin  31  and is bolted onto a working end of body  25 . Accordingly, locating pin  31  outwardly extends in an elongated manner from body  25  such that an internal hollow cavity  57  (see FIG. 10) is elongated coaxial with axis  52 . Locating pin  31  has a circular-cylindrical external side surface  61  interrupted by a pair of longitudinally elongated openings  63 . Openings  63  are spaced away from each other and separated by a solid remaining portion  65  of external side surface  61 ; this remaining portion  65  serves as one of four equidistant contact points, the others being defined as points  67 ,  69  and  71 , which coincide with the geometric tolerancing and dimension characteristics of a hole in workpiece  23 . A distal end  73  of locating pin  31  has an arcuate taper to ease installation of workpiece  23  in a snugly fitting manner around side surface  61 . A circular-cylindrical collar is bolted onto the external surface of shoulder  55  to partially surround a proximal end of locating pin  31 . Workpiece  23  is operably clamped between collar  39  and clamping member  33 . 
     Clamping member  33  has a pair of bifurcated and spaced apart clamping arms  81 , which have curved portions that end in clamping surfaces  83 . Clamping member  33  further has a unitary working portion  85  that contains a camming slot  87  and a hole  89  adjacent a distal end. Working portion  85  is movably positioned in first bore  51  of body  25 . Clamping member  33  has a generally J-shaped side view configuration. 
     A solid pivot pin assembly  91  is stationarily affixed to body  25  by engagement of a bolt head  93  in an undercut of pin assembly  91  while a threaded section  95  of the bolt engages a threaded aperture in body  25 . Pin assembly  91  is preferably a single stepped cylindrical pin, but it may also include rollers, bearings or other parts. Pin assembly  91  passes through camming slot  87  of clamping member  33 . Camming slot  87  includes a first camming segment  101  (see FIG. 11) generally elongated in the direction of axis  52 , which is also the elongated direction of clamping member  33 . Camming slot  87  further has a second segment  103  angularly offset from first segment  101 . Pin assembly  91  and camming slot  87  define a first camming mechanism. 
     A pair of piston cylinders  37  are attached to body  25 . Each cylinder  37  has an internal chamber accessible to second bore  53  and they are elongated coaxially with axis  54 . Open end  111  of each piston cylinder  37  is inserted into second bore  53  and secured in its respective fully installed position relative to body  25  by way of a pair of circumferentially compressible roll pins  113 . Ends of each roll pin are stationarily secured in openings  115  in body  25  while a middle portion of each roll pin  113  engages in a circular groove  117  machined in each piston cylinder  37 . Accordingly, each piston cylinder  37  can be rotated 360 degrees relative to body  25 , even when fully inserted and attached to body  25 . This allows fluid carrying tubes, hoses and fittings which are attached to an inlet  121  to be repositioned free of any obstructions in the factory or to improve tube routing by minimizing bends. 
     As can best be observed in FIGS. 5,  6 ,  9  and  10 , piston  35  is configured to have a pair of opposed piston heads  131  and  133  and a driving or camming member  135  mounted therebetween. Piston  35  is movably located inside of second bore  53  and piston cylinders  37 . An elastomeric O-ring or other shaped seal  137  is secured within a groove  139  in each piston head  131  and  133 . A camming slot  141  is internally located in camming member  135  of piston  35 . Camming slot  141  preferably has a closed looped configuration defined by a first elongated segment  143  elongated in generally the same direction as axis  54 . Axis  54  also defines the advancing and retracting direction of piston  35  within second bore  53 . More specifically, an elongated axis of first segment  143  is approximately 9 degrees offset from axis  54 . Camming slot  141  further has a second camming segment  145  angularly offset from first segment  143 . Four detented step-like formations  147  are machined as part of one side of first camming segment  143 . Each detent formation  147  provides approximately {fraction (1/5,000)} of an inch of a step relative to the adjacent one. 
     A second pin assembly  161  is secured to the distal end of clamping member  33 . Pin assembly  161  includes a pair of outboard rollers  163  which are affixed onto a central elongated pivot pin  165  by way of snap rings  167 . Outer rollers  163  longitudinally travel within longitudinally elongated slots  169  machined in body  25 . Outer roller  163  are maintained in their outboard positions by an inward flange  171  offset from each longitudinally body slot  169 . 
     A middle roller  181  is journalled around an intermediate portion of pivot pin  165  and rides within camming slot  141  of piston  35 . Middle roller  181  is laterally trapped between an inwardly stepped lateral face  183  of clamping member  33  and an inwardly stepped face  185  of camming member  135  adjacent camming slot  141 . There is clearance between the secondary slot in stepped face  185  and pivot pin  165 . Pivot pin  165  is rotatably secured within aperture  89  of clamping member  33 . Camming slot  141  and second pin assembly  161  define a second camming mechanism. 
     Body  25  and piston cylinders  37  are preferably machined on a lathe from aluminum bar stock having a circular cross sectional shape. Thus, the outer and inner surfaces of these parts predominantly have circular-cylindrical shapes with secondary holes and slots machined therein. Piston  35 , locating pin  31  and collar  39  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 member  33  is preferably laser cut from a sheet of steel and then milled for the extra slots and apertures. 
     The second preferred embodiment of locking pin clamp  21  of the present invention is shown in FIG.  8 . In this embodiment, one of the cover plates  201  (see FIG. 5) of the first preferred embodiment is removed and replaced by a switch package  203 . Switch package  203  includes a three-dimensionally shaped housing or cover  205  within which is secured a pair of proximity switch sensors  207  and  209 . Sensors  207  and  209  are of an inductive type such as that which can be purchased from Turck Inc. or Namco. Housing  205  is fastened to the outside of clamp body  25  (see FIG. 5) by bolts such that sensing portions of sensors  207  and  209  are exposed to one of more of the inner bores of body  25 . Housing  205  is sealed against body  25  thereby allowing the parts internal to body  25  and housing  205  to be greased and sealed for a longer life and improved durability. Sensors  207  and  209  inductively sense the location of the adjacent outer roller  163  and thereby send the appropriate electrical or fiber optic signal to the fluid control unit that controls the amount and direction of pneumatic pressure applied within the piston cylinders. The electrical or fiber optic cables are connected via the coaxial or fiber optic connector  211  projecting from housing  205 . 
     The third preferred embodiment of a locking pin clamp  321  is shown in FIGS. 13 and 14. This embodiment is similar to the first preferred embodiment except that a clamping member  333  has a single clamping arm  381  with a curved portion that ends in a single clamping surface  383 . Clamping member  333  further has a working portion  385  that contains a camming slot  387  and a hole  389  adjacent a distal end. Working portion  385  is movably positioned in a first bore  351  of a body  325 . Clamping member  333  has a generally J-shaped side view configuration. Furthermore, a locating pin  331  has a generally pointed distal end projecting above a single longitudinally elongated opening  363  in locating pin  331 . Opening  363  is laterally offset from a longitudinal centerline of locating pin  331  thereby providing four equally spaced locating points for a workpiece. 
     The operation of the first preferred embodiment locking pin clamp  21  of the present invention can be observed with reference to FIGS. 10-12. When pneumatic air pressure is applied against piston head  133 , piston  35  is advanced in a first direction along axis  54 . This will move clamping member  33  from the fully retracted position within the internal cavity of locating pin  31 , as shown in FIG. 12, to an intermediate rotated position, as shown in FIG.  11 . This initial advancing movement from FIG. 12 to that of FIG. 11, is achieved by sliding pin assembly  161  down the steeply inclined leading segment of camming slot  141 . Concurrently, clamping member  33  is moved from a fully extended position, along the steeply inclined segment of camming slot  87 , downward and further into body  25  by interfacing with pin assembly  91 . This double camming mechanism arrangement causes an approximately 5 degree rotation of clamping member  33  relative to body  25  such that clamping surfaces  83  of clamping member  33  pass through openings  63  and are externally accessible beyond locating pin  31  and body  25 . 
     Further advancement of piston  35  causes pin assemblies  161  and  91  to further ride along their respective camming slots  141  and  87 . This drives clamping member  33  to a fully clamping position, as illustrated in FIG. 10 (with collar  39  removed for clarity). Approximately ten millimeters of linear movement is achieved in the longitudinal direction, generally perpendicular to axis  54 , between the fully retracted and fully clamping positions. In the clamping position of FIG. 10, middle roller  181  of pin assembly  161  engages the corresponding detent formation  147  (see FIG.  9 ). This detent-to-camming arrangement, in addition to the somewhat perpendicular movement geometries, encourage clamping member  33  to maintain its clamping (or partial clamping) position engaging the workpiece even if pneumatic pressure is lost or undesirably reduced. Piston  35  is retracted by applying pneumatic pressure against the opposite piston head  131  to provide a reversal of the above discussed motions. 
     While various embodiments of the locking pin clamp have been disclosed, it will be appreciated that other modifications may be made without departing from the spirit of the present invention. For example, a piston rod can be employed between the piston heads and the camming member. Furthermore, many of the pin assemblies and camming slots can be reversed between the interfacing parts. Moreover, the clamping member can have other shapes such that the clamping surface has a different orientation relative to the piston advancing direction. The clamping, piston, piston cylinder and camming configurations can be used without a locating pin although the preferred embodiment of the present invention is optimized with the locating pin arrangement to provide enhanced advantages. While various materials, shapes and manufacturing processes have been disclosed, it will be appreciated that others can be also employed. It is intended by the following claims to cover these and any other departures from the disclosed embodiments which fall within the true spirit of this invention.