Abstract:
A workpiece securing apparatus or clamp includes a piston, a coupling or transmission mechanism, and an unlock device. In another aspect of the present invention, the unlock device is rotatable to move the coupling mechanism. Still another aspect of the present invention provides a mechanism which converts linear movement of a piston to rotary motion of a hub and workpiece interfacing arm.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
         [0001]    The present invention relates generally to workpiece securing apparatuses and more specifically to a powered clamp with an unlocking feature.  
           [0002]    Pneumatically powered clamps have been used to secure workpieces, such as sheet metal panels for automotive vehicles, during welding, gauging or other industrial manufacturing operations. One such device is disclosed in U.S. Pat. No. 5,884,903 entitled “Powered Clamp and Gauging Apparatus” which issued to the present inventor on Mar. 23, 1999. This patent is incorporated by reference herein.  
           [0003]    On occasion, there is a need to manually assist retracting movement of the piston rod, slide, link, hub and arm. One conventional resetting device is shown in U.S. Pat. No. 5,845,897 entitled “Toggle Lever Clamp Device for Automobile Body Fabrication” which issued to Tunkers on Dec. 8, 1998. In another clamp, a non-rotating, linearly moving and unthreaded, spool-type reset button has been employed to manually retract a slide and to serve as a supplemental stop. These resetting devices, however, project from an end of the clamp and are prone to undesired contact with passing workpieces or other machinery. Furthermore, these traditional, linearly moving resetting devices also serve as stops for the slide. Notwithstanding, manufacturing plant contamination settling on the greased spool or threads may inadvertently alter the stop location relative to the clamp housing after continuous use.  
           [0004]    In accordance with the present invention, a workpiece securing apparatus or clamp includes a piston, a coupling or transmission mechanism, and an unlock device. In another aspect of the present invention, the unlock device is rotatable to move the coupling mechanism. Still another aspect of the present invention provides a mechanism which converts linear movement of a piston to rotary motion of a hub and workpiece interfacing arm. In yet another aspect of the present invention, a rotational axis of the unlock device is generally parallel to a rotational axis of the arm  
           [0005]    The clamp securing apparatus of the present invention is advantageous over traditional devices in that the present invention does not elongate the overall length of the apparatus. Furthermore, the unlock device does not project outside of the nominal width of the apparatus for one form of the invention. Moreover, the unlock device of the present invention is more reliably sealed to the adjacent housing as compared to conventional devices, thereby minimizing containment intrusion. Additionally, the tolerances and positioning of the unlock device do not impact the stopping location of the mechanism and arm, in another form of the invention. 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  
       [0006]    [0006]FIG. 1 is a partially fragmented, side elevational view showing a first preferred embodiment of a clamp of the present invention;  
         [0007]    [0007]FIG. 2 is a cross-sectional view, taken along line  2 - 2  of FIG. 1, showing the first preferred embodiment clamp;  
         [0008]    [0008]FIG. 3 is an exploded perspective view showing an unlock device employed in the first preferred embodiment clamp;  
         [0009]    FIGS.  4 - 6  are a series of fragmentary, longitudinal-sectional views showing the first preferred embodiment clamp in various positions;  
         [0010]    [0010]FIG. 7 is a diagrammatic side view showing a second preferred embodiment clamp of the present invention;  
         [0011]    [0011]FIG. 8 is an elevational view, taken in the direction of arrows  8 - 8  in FIG. 7, showing the unlock device employed in the second preferred embodiment clamp;  
         [0012]    [0012]FIG. 9 is a side elevational view showing the unlock device employed in the second preferred embodiment clamp;  
         [0013]    [0013]FIG. 10 is a diagrammatic side view showing a first alternate embodiment clamp of the present invention; and  
         [0014]    [0014]FIG. 11 is a fragmentary perspective view showing a second alternate embodiment clamp of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    A first preferred embodiment of an automatically powered clamp  21  of the present invention is shown in FIGS.  1 - 4 . Clamp  21  includes a single piece housing  23 , a transmission or coupling mechanism  25 , a piston  27  and an unlock device  29 . Transmission mechanism  25  further includes a longitudinally elongated piston rod  31  secured to piston  27 , a slide  33  mounted to an opposite end of piston rod  31 , a straight link  35  having a first end pivotably coupled to slide  33 , a crank  37  pivotably coupled to a second end of link  35  and a hub  39  secured to crank  37 . Piston  27  is advanced and retracted in a linear manner by pneumatic-fluid pressure applied to the corresponding face of piston  27  within a piston cylinder  41 . Concurrently, piston rod  39  and slide  33  are linearly advanced and retracted along a longitudinal axis  43  within a bore  45  of housing  23 . A workpiece interfacing arm  51  is adjustably secured to hub  39  by way of multiple dowel pins  53 , and a central nut and bolt assembly  55 . Thus, linear advancing of piston  27 , piston rod  31  and slide  33  along longitudinal axis  43  causes rotation of link  35 , such that crank  37 , hub  39  and arm  51  are rotated about a hub rotational axis  57 , extending in a transverse and generally perpendicular direction to longitudinal centerline  43 . Accordingly, arm  51  is operable to interface with and secure multiple sheet metal workpieces  59  against a stationary structure or fixed second arm (not shown). The piston, transmission mechanism and arm work substantially in accordance with the clamp disclosed in U.S. Pat. No. 5,884,903.  
         [0016]    Unlock device  27  includes a driving formation  71  located between generally circular journalling segments  73 . In the first preferred embodiment, driving formation  71  is a generally straight and narrow wall with opposite flat faces  75  bordered by a pair of curved edges  77 . A groove  81  is disposed in each journalling segment  73  to receive an elastomeric O-ring  83 . A hexagonal tool receptacle  85  is further depressed in each outboard end of unlock device  29 .  
         [0017]    An aperture  91  is transversely elongated through housing  23  above and slightly rearward of hub pivot axis  57 , as illustrated. Unlock device  29  is rotatably located within aperture  91  and is inboard of the nominal faces  93  of housing  23 . Hence, unlock device  29  does not project beyond or increase any external dimension of the clamp housing. O-rings  83  provide a reliable seal between journalling segment  73  of unlock device  29  and housing  23 . Furthermore, a snap ring  95  is disposed on one side of unlock device  29  to retain unlock device within aperture  91  while still allowing it to rotate. An Allen wrench tool  97 , or alternately a screw driver if tool receptacle  85  has a Phillips or flat head shape, can be removably inserted into either tool receptacle  85 . Furthermore, a depressed abutment formation  101  is located within a transverse top side of slide  33 . Abutment formation  101  has a lead-in surface with a relatively gentle angle of about 30 degrees from longitudinal centerline  43 , but has a much steeper trailing abutment surface with an angle of about 70 degrees from the longitudinal centerline. Alternately, abutment formation can be located in a top or bottom side of the piston rod.  
         [0018]    FIGS.  4 - 6  show the operational interface between unlock device  29  and transmission mechanism  25 . In the event that transmission mechanism  25  is undesirably locked in a generally over-center position as shown in FIG. 4, the Allen wrench tool can be inserted in the externally accessible tool receptacle  85  (see FIG. 2) in order to rotate unlock device  29  about its transverse pivot axis  103 . When unlock device  29  is manually rotated from the initial contact position of FIG. 4 to the rotated position of FIG. 5, driving formation  71  pushes against the trailing abutment surface of abutment formation  101 , thereby manually retracting slide  33 , piston rod  31  and the piston in a linear direction. Further continued rotation of unlock device  29  from the position shown in FIG. 5 to that in FIG. 6 further drivingly retracts transmission mechanism  25  and then allows clearance between driving formation  71  of locking device  29  and adjacent portions of transmission mechanism  25 . Thereafter, the retracting pneumatic pressure can freely take over to completely retract the transmission mechanism and clamping arm, or alternately, the clamping arm itself can be manually rotated to obtain full retraction.  
         [0019]    A second preferred embodiment clamp of the present invention is shown in FIGS.  7 - 9 . In this embodiment, a rotatable unlock device  229  has a somewhat triangular shaped driving formation  271  defined by a pair of flat faces  275  having a relative angle of about 75 degrees and joined at an apex. A circular section  277  joins the opposite ends of faces  275 . Flat faces  275  operably contact against and retractingly drive a component  225  associated with a transmission mechanism, such as a slide or piston rod, when unlock device  229  is manually rotated. Locking rings  295  transversely secure unlock device  229  within the corresponding transverse aperture through housing  223 . O-rings (not shown) are also employed to ensure the complete sealing of the housing to internally retain grease while exclude airborne contaminants such as dirt, dust, weld splatter and the like.  
         [0020]    A tool receptacle located on each end employs a pair of diagonally located wedge-shaped structures  301  and  303  which are spaced apart from each other to allow entry of a removable tool such as an Allen wrench  297  or screw driver shaft therebetween. Recessed sections  305  are spaced between structures  301  and  303  in order to allow unobstructed movement of tool  297  within a 90 degree range of lost motion before recontacting structures  301  and  303 . In this exemplary embodiment, structures  301  and  303  outwardly project beyond the nominal face of the clamp housing in order to allow external accessibility of the tool. Alternately, a ramp angle can also be employed on structures  301  and  303  to ensure only retracted rotational engagement of the tool with the unlock device.  
         [0021]    Referring now to FIG. 10, a first alternate embodiment of a clamp  401  of the present invention employs a rack and pinion interface between a transmission mechanism  425  and an unlock device  429 . A linearly slidable slide  433  has a toothed rack  467  which is enmeshed with gear teeth  469  circumferentially projecting around a central driving formation of unlock device  429 . Unlock device  429  is rotatable about a transverse centerline generally parallel to the rotational centerline of a hub  439  and generally perpendicular to a longitudinal axis of slide  433  and a piston rod  431 . Insertion and manual rotation of an Allen wrench tool or the like within a tool receptacle  485  serves to rotate the gear-like unlock device  429 . This allows for a manual override retraction or advancing movement of transmission mechanism  425 . Notwithstanding, unlock device  429  is free spinning during normal pneumatic powered actuation of the piston, transmission mechanism  425  and the attached workpiece clamping arm.  
         [0022]    A second alternate embodiment clamp  501  of the present invention is shown in FIG. 11. This clamp  501  includes a lever arm  503  projecting from each end of a rotatable unlock device  529 . Unlock device  529  can be constructed like any of the previously disclosed embodiments. Lever arms  503 , however, upwardly project above a nominal external face  531  of a housing  523 . Thus, a tool, such as a hammer, can manually impact against a front or rear edge  505  of lever arm  503  to rotate unlock device  529  and move the transmission.  
         [0023]    While various embodiments of the powered clamp have been disclosed, it should be appreciated that other variations may fall within the scope of the present invention. For example, an electromagnetic device, such as an electric motor, can be coupled to the unlock device to allow automatically powered rotation thereof. Furthermore, the presently disclosed clamp also includes grippers and other members having movable parts which can engage or interface with one or more workpieces. The features of the present invention are also applicable for hydraulically powered devices as well as the disclosed pneumatic ones. Other linkages and cams can further be added to or replace for the components disclosed with the present transmission mechanism. Moreover, the presently disclosed housing can also have a circular or various other external shapes. While various materials and angles have been disclosed, it should be appreciated that other materials and angles may be readily 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.