Abstract:
A welding fixture clamp includes a stationary clamp jaw having a first guide surface and a pivotal clamp jaw having a second guide surface. The second guide surface slides relative to the first guide surface as the pivotal clamp jaw pivots about the pivot axis. Side shields are secured to one of the pivotal clamp jaw and the stationary clamp jaw to extend over the other one of the pivotal clamp jaw and the stationary clamp jaw to shield the first guide surface and the second guide surface from weld splatter and debris. A pivot pin connects the side shield to the stationary clamp jaw and operatively connects the pivotal clamp jaw to the stationary clamp jaw to pivot about the pivot axis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 61/691,836 filed Aug. 22, 2012, the disclosure of which is hereby incorporated in its entirety by reference herein. 
    
    
     TECHNICAL FIELD 
     This invention disclosure relates to automation clamps that are used to hold sheet metal parts together while welding operations are performed. 
     BACKGROUND 
     Automation clamps generally have two clamping jaws that are opened and closed by a hydraulic or pneumatic cylinder. In operation, the jaws are opened to load and unload parts and closed to hold the parts together as they are welded. Some welding processes typically produce weld splatter that accumulates on anything that is in the vicinity of the welding operation. Accumulations of weld splatter can interfere with the operation of automation clamps and can interfere with opening and closing the clamps. 
     Automation clamps and mounting brackets are traditionally fabricated from metal plates. Weld splatter fuses to the metal plates and is difficult to remove from the surface of the plates. Pivot points on metal automation clamps may become fouled by weld splatter and debris and may require servicing or replacement. Problems and service interruptions caused by automation clamps can result in expensive downtime and costly repairs. 
     End effector automation clamps are attached to robot arms to reach in and hold parts together. The weight of metal automation clamps requires robots that are specified to perform operations with the load capacity to manipulate the clamps. The cost of automation systems may also be reduced by using robots that have lower weight capacities if the weight of automation clamps can be reduced. 
     This disclosure is directed to solving the above problems and other problems relating to automation clamps. 
     SUMMARY 
     According to one aspect of this disclosure, a welding fixture clamp is provided that has a stationary clamp jaw that includes a first guide surface and a pivotal clamp jaw that includes a second guide surface that conforms to at least a part of the first guide surface. At least one side shield is secured to or provided on one of the pivotal clamp jaw and the stationary clamp jaw to extend over the other one of the pivotal clamp jaw and the stationary clamp jaw to shield the first guide surface and the second guide surface from weld splatter and debris. A pivot pin connects the side shield to the stationary clamp jaw and operatively connects the pivotal clamp jaw to the stationary clamp jaw to pivot about a pivot axis. The second guide surface moves relative to the first guide surface as the pivotal clamp jaw pivots about the pivot axis. 
     According to another aspect of this disclosure, a first side shield may be fixedly secured to a first side of the pivotal clamp jaw and a second side shield may be fixedly secured to a second side of the pivotal clamp jaw. The first side shield may extend over a first side of the pivotal clamp jaw and the second side shield may extend over a second side of the pivotal clamp jaw. The pivot pin may pivotally connect the first side shield to a first side of the stationary clamp jaw and may pivotally connect the second side shield to the second side of the stationary clamp jaw. 
     The first side shield and the second side shield may each have convex cylindrical ends that are generated about the pivot pin and enclose a protected area on the stationary clamp jaw that includes the first guide surface and the second guide surface. The first side shield may define a first blind hole facing the first side of the stationary clamp jaw and the second side shield may define a second blind hole facing the second side of the stationary clamp jaw. The pivot pin may extend outwardly from the first side of the stationary clamp jaw and second side of the stationary clamp jaw. 
     The first guide surface may be a convex cylindrical surface that is generated about the pivot pin and the second guide surface may be a concave cylindrical surface generated about the pivot pin. The concave cylindrical surface may at least partially cover the convex cylindrical surface when the first and second clamp jaws are closed. 
     An actuator may be pivotally connected to the stationary clamp jaw at a fixed location relative to the pivot axis. The actuator may also be pivotally connected to the pivotal clamp jaw to move in a range of locations disposed on an arc generated about the pivot axis. 
     The welding fixture clamp may be provided in combination with an L-bracket that is fixedly attached to the welding fixture to support the welding fixture clamp. Alternatively, the welding fixture clamp may be provided in combination with a robot with the welding fixture clamp functioning as an end effector of the robot. 
     According to another aspect of this disclosure, a clamp assembly is disclosed for a welding fixture that prevents the accumulation of weld splatter on surfaces of the clamp assembly that can interfere with opening and closing the clamp assembly. A first clamp jaw includes a convex guide surface. A second clamp jaw is pivotal about a pivot axis and includes a concave guide surface that slides over the convex guide surface when the second clamp jaw pivots about the pivot axis. A first side shield is secured to the first clamp jaw and extends partially over a first side of the second clamp jaw. A second side shield is secured to the first clamp jaw and extends partially over a second side of the second clamp jaw. A pivot pin connects the first clamp jaw to the first and second side shields. An actuator is attached to the first and second clamp jaws to open and close the clamp jaws by pivoting the second clamp jaw relative to the first clamp jaw. 
     According to another aspect of this disclosure, the first and second side shields may each have a blind hole facing the first and second sides of the second clamp jaw, and the pivot pin may extends outwardly from the first and second sides of the second clamp jaw. 
     According to another aspect of this disclosure, the first and second side shields may each have convex ends that enclose a protected area on the second clamp jaw that is centered relative to the axis. 
     According to another aspect of this disclosure, the convex guide surface may be a cylindrical guide surface generated about the pivot axis and the concave guide surface may be a cylindrical guide surface generated about the pivot axis. 
     According to another aspect of this disclosure, the convex cylindrical guide surface may be at least partially covered by the concave cylindrical guide surface when the first and second clamp jaws are closed. 
     According to another aspect of this disclosure, the actuator may be pivotally connected to the first clamp jaw at a fixed pivot point relative to the pivot axis. The actuator may be pivotally connected to the second clamp jaw at a location that moves through a range of locations that are disposed on an arc generated about the pivot axis. 
     According to another aspect of this disclosure, the clamp assembly may be provided in combination with a welding fixture, and may further comprise an L-bracket fixedly attached to the welding fixture. 
     According to another aspect of this disclosure, the clamp assembly may be provided in combination with a robot having a first end effector attachment part, and may further comprise a second end effector attachment part that is configured to be attached to the first end effector attachment part. 
     According to another aspect of this disclosure, the clamp assembly and supporting structures may be fabricated from nylon plates that resist the accumulation of weld splatter and are lighter weight. 
     These and other aspects of the disclosure will be more fully described with reference to the attached drawings in the following detailed description of the illustrated embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a rear/side perspective view of an automation clamp for a welding fixture; 
         FIG. 2  is a front/side perspective view of an automation clamp for a welding fixture; 
         FIG. 3  is an exploded perspective view of an automation clamp for a welding fixture; 
         FIG. 4  is a side elevation view of a closed automation clamp for a welding fixture; 
         FIG. 4A  is a cross-sectional view taken along the line  4 A- 4 A in  FIG. 4 ; 
         FIG. 4B  is a cross-sectional view taken along the line  4 B- 4 B in  FIG. 4 ; 
         FIG. 5  is a side elevation view of an open automation clamp for a welding fixture; 
         FIG. 6  is an exploded perspective view of an L-bracket automation clamp for a welding fixture; 
         FIG. 7  is a side elevation view of a closed L-bracket automation clamp for a welding fixture; and 
         FIG. 8  is a side elevation view of an open L-bracket automation clamp for a welding fixture. 
     
    
    
     DETAILED DESCRIPTION 
     The illustrated embodiments are disclosed with reference to the drawings. However, it is to be understood that the disclosed embodiments are intended to be merely examples that may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but as a representative basis for teaching one skilled in the art how to practice the disclosed concepts. 
     Referring to  FIGS. 1 and 2 , a clamp assembly is generally indicated by reference numeral  10 . The clamp assembly  10  is intended primarily to be used in conjunction with a welding fixture  12 , but may be used in other non-welding applications for holding parts together. The welding fixture  12  may have one or more robots  14  that are used to manipulate and position one or more clamp assemblies  10 . The clamp assembly  10  may also be referred to as an end effector of the robot  14 . 
     A first clamp jaw  16  engages a part  18  with a second clamp jaw  20 . The first clamp jaw  16  and second clamp jaw  20  pivot relative to each other about a pivot axis X. 
     A first side shield  24  partially covers a first side  26  of the first clamp jaw  16 . The first side shield  24  is secured to a first side  28  of the second jaw  20 . With specific reference to  FIG. 2 , a second side shield  30  partially covers a second side  32  of the first clamp jaw  16 . The second side shield  30  is secured to the second side  34  of the second jaw  20 . 
     With continuing reference to  FIGS. 1 and 2  and with particular reference to  FIG. 3 , the clamp assembly  10  is shown in an exploded perspective view. The first clamp jaw  16  and second clamp jaw  20  are pivotally connected at a pivot axis X. The first side shield  24  is connected to the first side  28  of the second clamp jaw  20 . The second side shield  30  is connected to the second side  34  of the second jaw  20 . The first side shield  24  and second side shield  30  extend toward and partially cover the first side  26  of the first clamp jaw  16  and the second side  32  of the first clamp jaw  16 . 
     A pivot pin  36  is inserted to extend through a hole  38  formed in the first clamp jaw  16 . The pivot pin  36  extends outwardly from both sides of the hole  38 . The pivot pin  36  is received in a first blind hole  40  formed in the first side shield  24 . The pivot pin  36  is also received in a second blind hole  42  formed in the second side shield  30 . 
     An actuator  44 , such as a hydraulic cylinder, a pneumatic cylinder, or the like is attached to the first clamp jaw  16  and second clamp jaw  20 . The actuator  44  functions to pivot the second jaw  20  relative to the first clamp jaw  16 . 
     The first clamp jaw  16  includes a convex guide surface  48  that is a circular surface generated about the pivot axis X. A concave guide surface  50  is provided on the second clamp jaw  20 . The concave guide surface  50  moves relative to the convex guide surface  48 . The guide surfaces  48 ,  50  are slightly spaced apart from each other (i.e., on the order of 1 mm) or the concave guide surface  50  may slide on the convex surface  48 . When the clamp assembly  10  is closed, the second clamp jaw  20  covers the convex guide surface  48  with the concave guide surface  50  to prevent weld splatter from accumulating on the guide surfaces  48  and  50 . 
     The first side shield  24  and second side shield  30  have convex ends  52 . The convex ends  52  have a convex surface that is generated about the pivot axis X. A protected area  54  is provided on both sides of the first clamp jaw  16  that are shielded from weld splatter by the first side shield  24  and second side shield  30 . The side shields  24 ,  30  also enclose the pivot pin  36  and protect the circular area  54 , and guide surfaces  48  and  50  from weld splatter. 
     The actuator  44  is connected at a fixed pivot point  58  to the first clamp jaw  16 . A pivot connector  60  connects the actuator  44  to the second clamp jaw  20 . The pivot connector  60  moves in an arcuate path about the pivot axis X when the actuator  44  moves the second clamp jaw  20 . 
     Referring to  FIGS. 4 ,  4 A,  4 B and  5 , operation of the clamp assembly  10  is explained in greater detail. With specific reference to  FIG. 4 , the clamp assembly  10  is shown in its closed position with the first clamp jaw  16  and second clamp jaw  20  clamped together by operation of the actuator  44 . The first side shield  24  is attached to the first side  28  of the second clamp jaw  20 . The first side shield  24  covers a portion of the first clamp jaw  16 . The first side shield  24  is secured by a pin connector  68  to the second clamp jaw  20  and the second side shield  30 . 
     Referring to  FIG. 4A , the first and second side shields  24  and  30  are shown to be secured to the second clamp jaw  20  and first clamp jaw  16 . The first and second side shields  24 ,  30  and the first and second clamp jaws  16 ,  20  are preferably formed from nylon plates or other similar plastic material that has sufficient durability and rigidity to function as a clamp. The plastic material used should resist damage or accumulation of weld splatter. Alternatively, the parts may be molded from a durable polymer or machined from other suitable materials. The side shields  24 ,  30  are shown as being assembled to the second clamp jaw  20  but, alternatively, one or both of the side shields  24 ,  30  could be molded with the clamp jaw  20  in one piece. 
     Pivot pin  36  is received in a hole  38  formed through the first clamp jaw  16 . Pin  36  is received in the first and second blind holes  40 ,  42  formed in the first side shield  24  and second side shield  30 , respectively. The side shields  24 ,  30  are secured by the pin connector  68  to the second clamp jaw  20 . The pin connector  68  may be a nut and bolt, a pin and cotter pin connection, or the like. 
     Referring to  FIG. 4B , the connection of the first clamp jaw  16  to the actuator is illustrated. A pivot connection  60  is used to connect the first clamp jaw  16  to the actuator  44 . The pin connector  68  is shown connecting the first side shield  24  and second side shield  30  to opposite sides of the first clamp jaw  16 . 
     Referring to  FIG. 5 , the clamp assembly  10  is shown in its open position with the second clamp jaw  20  being pivoted away from the first clamp jaw  16  by the actuator  44 . The first side shield  24  is shown attached to the second clamp jaw  20  to overlap a part of the first clamp jaw  16 . The second clamp jaw  20  is pivoted about the pivot axis X. The pin connection  60  to the actuator  44  is moved by the actuator in an arcuate path around the pivot axis X. Actuator  44  pivots about the fixed pivot point  58  on the first clamp jaw  16 . The clamp assembly  10  is adapted to function as an end effector and may be connected to a robot (indicated in  FIG. 1 ) at an end effector attachment area  64 . 
     Referring to  FIGS. 6-8 , the clamp assembly  10  is shown attached to an L-bracket  70  that is secured to a weld fixture base  72  or other part of a weld fixture. The L-bracket  70  holds the clamp assembly  10  in a fixed location on the welding fixture  12 . The first clamp jaw  16  and second clamp jaw  20  are shown in their closed position in  FIG. 7  and in their open position in  FIG. 8 . The second clamp jaw  20  pivots about the pivot axis X as it moves between the positions illustrated in  FIGS. 7 and 8 . The second side shield  30  is secured to the second clamp jaw  20  and covers the pivot pin  36  (shown in  FIG. 6 ) that is received in the hole  38  in the first clamp jaw  16  and in the second blind hole  42  formed in the second side shield  30 . The actuator  44  is extended to move the first clamp jaw  16  into engagement with the second clamp jaw  20  as shown in  FIG. 7 . The actuator  44  is refracted to pivot the first clamp jaw  16  relative to the second clamp jaw  20 . An end stop  74  and locator  76  are provided on the second clamp jaw  20  to locate one or more parts  18  (shown in  FIG. 1 ) to be clamped between the first clamp jaw  16  and the second clamp jaw  20 . 
     The L-bracket  70  may be formed of nylon material. By forming the L bracket  70 , the first clamp jaw  16  and second clamp jaw  20  from nylon, substantial weight savings can be obtained. Reducing the weight of the weld fixture  72  reduces the total weight of the weld fixture  72  and allows the fixture to be moved with conventional material handling and equipment and may eliminate the need to move the welding fixture  12  with a crane. In addition to the larger parts, the side shields  24 ,  30 , end stop  74  and other locator  76  may also be formed of nylon to reduce the total weight of the welding fixture  12 . 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the disclosed apparatus and method. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure as claimed. The features of various implementing embodiments may be combined to form further embodiments of the disclosed concepts.