Abstract:
A weld gun for performing a welding operation on a workpiece includes a pair of opposing arms, at least one arm movable relative to the opposing arm to apply pressure to the workpiece during a welding operation. A pair of identical or mirror image side plates support components of the weld gun to establish critical dimensions of the components relative to one another, while preventing tolerance buildup of critical dimensions at critical points. A guide block is connected to one of the opposing arms. The guide block has a non-circular aperture formed therein. An electrode adapter has a non-cylindrical rod portion slidably received in the noncircular aperture formed in the guide block for preventing rotation of the electrode adapter. A hose fitting is attachable directly to a rear end of the electrode adapter for communicating with an inlet water port and an outlet water port formed in the electrode adapter for providing a routing of coolant directly through the electrode adapter only.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of U.S. Serial No. 60/370,816 filed on Apr. 8, 2002, which is incorporated by reference herein in its entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to weld guns and more particularly to weld guns especially suitable for use in industrial automotive applications.  
         BACKGROUND OF THE INVENTION  
         [0003]    Weld guns are in common usage in many industrial applications and in particular in automotive applications. Whereas a myriad of weld gun designs have been proposed and/or utilized commercially, there is still a need for a simpler weld gun design, providing a less expensive cost of assembly; for a weld gun design that is easier to service, thereby reducing servicing costs; and for a weld gun design that provides a longer life, thereby reducing replacement costs. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:  
         [0005]    [0005]FIGS. 1, 2 and  3  are perspective views of the weld gun according to the present invention;  
         [0006]    [0006]FIGS. 4, 5 and  6  are elevational, plan, and end views of the weld gun according to the present invention;  
         [0007]    [0007]FIG. 7 is a cross-sectional view of the weld gun according to the present invention;  
         [0008]    [0008]FIGS. 8 and 9 are fragmentary perspective views of the weld gun according to the present invention;  
         [0009]    [0009]FIGS. 10 and 11 are elevational and plan views of side plates used in the weld gun according to the present invention;  
         [0010]    [0010]FIGS. 12 and 13 are plan and elevational views of a base plate used in the weld gun according to the present invention;  
         [0011]    [0011]FIGS. 14, 15, and  16  are elevational, plan, and end views of a cap adapter used in the weld gun according to the present invention;  
         [0012]    FIGS.  17 - 35  are perspective views of component parts of the weld gun according to the present invention;  
         [0013]    [0013]FIGS. 36, 37 and  38  are plan, elevational, and end views of an electrode adapter used in the weld gun according to the present invention; and  
         [0014]    [0014]FIG. 39 is a perspective view of a servo motor optionally utilizable in the weld gun of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    A weld gun assembly  10  according to the invention can include the following illustrated major component parts: a transformer  12 ; a base plate  14 ; at least one transformer mounting strap  16 ; a slide block  18 ; at least one side plate  20 ; at least one rail  22 ; a positioning cylinder  24 ; a clevis bracket  25 ; a spring lock  26 ; a spring cup  28 ; a threaded rod  30 ; an equalizing spring  32 ; a power cylinder  34 ; an electrode adapter  38 ; a guide block  40 ; a moveable cap adapter  42 ; a first cap  44 ; an electrode holder  46 ; a stationery cap adapter  48 ; a hose fitting  50 ; a second cap  52 ; at least one transformer terminal  54 ,  56 ; at least one shunt  58 ,  60 ; at least one shunt adapter  62 ,  64 ,  66 ; at least one nut  68 ,  70 ,  72 ; and a cooling tube  80 .  
         [0016]    Main body transformer  12  is of known form and can have a monolithic rectangular configuration including a top face  12   a  and side faces  12   b . Base plate  14  (FIGS. 12 and 13) can have a rectangular configuration generally corresponding to the configuration and dimensions of the top face  12   a  of the transformer  12 . Base plate  14  can include a pair of slots  14   a  proximate the front end of the plate  14  and a rectangular opening  14   b  proximate the rear end of the plate  14 . Transformer mounting straps  16  (FIG. 28) can be fixedly secured to the side face  12   b  of the transformer  12  and can include a notch  16   a  proximate the upper end of the strap  16  receiving a side edge  14   c  of the base plate  14  so as to mount the base plate  14  in overlying relation to the upper face  12   a  of the transformer  12  but spaced from the upper face  12   a.    
         [0017]    Slide block  18  (FIG. 30) can have an “H” shaped cross-sectional configuration defining opposed longitudinal guide grooves or keyways  18   a . Slide block  18  is fixed to the upper face of base plate  14 . Slide block  18  can be formed of aluminum and can include chrome plated equalizing keyways. Side plates  20  (FIGS. 10 and 11) can be identical to one another and disposed on opposite sides of the slide block  18 . Each side plate  20  can include a main body portion  20   a , a front pedestal portion  20   b , an intermediate pedestal portion  20   c , and a rear strap portion  20   d  terminating in a rear end  20   e . Side plates  20  can preferably be formed of stainless steel. Rails  22  can be secured to the inboard faces of strap portions  20   d  and can be slidably received in the opposed keyways  18   a  of slide block  18  to mount the side plates  20  for sliding equalizing movement on the slide block  18 .  
         [0018]    Positioning cylinder  24  can be carried by clevis bracket  25  which in turn can be mounted on a reduced thickness platform mounting portion  14   d  at the rear of base plate  14 . Spring block  26  can be positioned between the rear ends  20   e  of side plates  20  to fixedly interconnect the rear ends of the side plates. Spring cup  28  (FIG. 26) can have a generally cup shaped configuration and can define a socket  28   a  sized to receive one end of spring  32 .  
         [0019]    Threaded rod  30  (FIG. 32) can be fixedly secured at its rear end  30   a  to the piston of positioning cylinder  24  and can include a threaded portion  30   b  extending forwardly through a central aperture  26   a  in spring block  26  and through a central aperture  28   b  in the rear wall of spring cup  28 . Nuts  68 ,  70  can be received on threaded portion  30   b  and can engage opposite side faces of spring block  26  to lock the spring block with respect to the threaded rod. A further nut  72  can be received on threaded portion  30   b  and can engage the rear wall of the spring cup  28  to adjustably mount the spring cup on the forward end of the threaded rod  30 . Equalizer spring  32  can have a coil configuration and can be received at its front end  32   a  in a socket  18   b  in the rear face of slide block  18  and at its rear end  32   b  in the socket  28   a  of spring cap  28 .  
         [0020]    Power cylinder  34  can preferably be an air cylinder and can include a cylinder body  74  slidably mounting a piston (not shown), and a piston rod  36 . The forward end  74   a  of the cylinder  74  can be fixedly mounted between the pedestal portions  20   c  of spaced side plates  20 . Electrode adapter  38  (FIGS. 18, 35,  36  and  37 ) can include a monolithic, generally rectangular main body rear portion  38   a  and a forward rod portion  38   b  of rectangular cross-section. Main body portion  38   a  can include a socket  38   c  at its rear end receiving the front end  36   a  of piston rod  36 . Main body portion  38   a  can be split at  38   d  and  38   e  to facilitate the grasping of the front end  36   a  of the piston rod  36  using fasteners  78 . Adapter  38  can include a longitudinal bore  38   f  communicating with a transverse “in” bore  38   g  and a counterbore  38   h  communicating with a transverse “out” bore  38   i . A tube  80  can be positioned in bore  38   f  to communicate with “in” bore  38   g . Guide block  40  (FIG. 19) can be fixedly positioned between pedestal portions  20   b  of the spaced side plates  20  and can slidably receive the rod portion  38   b  of electrode adapter  38  via a square central passage  48   a  drilled at the corners  48   b  to facilitate the sliding movement of rod portion  38   b  in the guide block. Moveable cap adapter  42  can be fixedly mounted on the front end  38   j  of the rod portion  38   b  of electrode adapter  38  and first welding cap  44  can be fixedly positioned on the front end of the cap adapter  42 .  
         [0021]    It should be understood that, in known manner, the cooling tube  80  (FIG. 36) can extend forwardly through cap adapter  42  and into proximity with welding cap  44  and can be positioned in spaced relation to an interior bore of adapter  42  allowing cooling fluid to flow through “in” port  38   g  and through cooling tube  80  and into proximity with cap  44 , whereafter the cooling fluid can leave the cap and flow around the cooling tube back through adapter  42  and rod portion  38   b  for discharge through “out” port  38   i.    
         [0022]    Electrode holder  46  (FIG. 27) can have a generally rectangular configuration and can be fixedly positioned between the front ends  20   f  of side plates  20  beneath holder  40 . Electrode holder  46  can define a central aperture  46   a  for fixed receipt of stationary cap adapter  48 . As seen in FIG. 8, electrode holder  46  can preferably be sandwiched between insulator plates  82  (FIG. 29) which can be formed for example of a mica or similar insulating material.  
         [0023]    Stationary cap adapter  48  (FIGS. 14, 15 and  16 ) can be shaped depending on the particular gun configuration being employed. In the illustrated configuration of the welding gun, adapter  48  can have a tubular U-shaped configuration with a rear end  48   a  of the adapter positioned in and passing through the aperture  46   a  of electrode holder  46  and the other end  48   b  of the adapter  48  mounting the second welding cap  52 . A central tube  84  can be positioned within a central bore  48   c  of adapter  48  and can extend through the adapter so as to provide, in known manner, means for introducing cooling fluid into the adapter for delivery to the welding cap and means for returning cooling fluid outside of the tube back to a cooling fluid discharge.  
         [0024]    Hose fitting  50  (FIGS. 14 and 35) can include a threaded forward end  50   a  adapted to be threadably received in a threaded bore  48   c  in the rear end  48   a  of adapter  48  and can further include an “in” port  50   b  and an “out” port  50   c . It should be understood that “in” port  50   b  can be configured to communicate with cooling tube  84  proximate the rear end  84   a  of that tube and “out” port  50   c  can be configured to communicate with an annular area outside of the tube end  84   a  to receive the return fluid flow.  
         [0025]    Transformer  12 , in known manner, can include terminals  54  and  56  positioned on the front face  12   c  of the transformer. Shunt adapter  62  (FIGS. 8 and 21) can have an L-shaped configuration and can be fixedly and electrically secured to the front face of terminal  54 . Shunt  58  (FIGS. 2 and 24) can have a U-shaped configuration and can extend between adapter  62  and the underface of the main body portion  38   a  of electrode adapter  38 . It can be seen that adapter  62  and shunt  58  can coact to provide an electrical flow path from transformer terminal  54  to electrode holder  38  to deliver electric power to welding cap  44 .  
         [0026]    Shunt  58  can be of the laminated copper type and should be understood to provide flexibility as between the connection with the adapter  62  and the underface of block  38   a . Adapter  64  (FIGS. 2 and 22) can have a T-shaped configuration including a T-bar portion  64   a  fixedly and electrically secured to transformer terminal  56  and a stem portion  64   b . Adapter  66  (FIGS. 2 and 20) can have an L-shaped configuration and can define a central aperture  66   a  proximate the upper end  66   b  of the adapter. Aperture  66   a  can be intended to fit over the rear end  48   a  of adapter  48  as the rear end  48   a  projects rearwardly beyond the rear face of holder  46 . The upper end of the adapter  66  can be fixedly secured to the rear end  48   a  of adapter  48  using a suitable fastener coacting with a split  66   c  to facilitate the squeezing engagement of adapter  66  with the rear end  48   a  of the adapter  48 . This arrangement can allow the hose fitting  50  to readily and threadably access the rear end of adapter  48  without interference from the upper end of adapter  66  and without interference from electrode holder  46 . Shunt  60  (FIGS. 8 and 23) can electrically interconnect adapter  66  and adapter  64  and, in known matter, can have a laminated copper construction to provide a flexible electrical interconnection between terminal  56  and welding cap  52  via adapter  64 , shunt  60 , adapter  66 , and adapter  48 .  
         [0027]    In typical operation of the welding gun according to the present invention, the gun can be attached to a robot (as for example by attaching the robot to the side face  12   b  of the transformer); gross adjustment of the overall welding gun can be performed using the robot; fine adjustment of the overall welding gun can be performed using positioning cylinder  24 ; and adjustment of the space or gap between the welding caps  52 / 54  to grip the item to be welded can be achieved using power cylinder  34  in combination with equalizing spring  32 . Specifically, once the caps of the open gun have been positioned on opposite sides of the article to be welded, power cylinder  34  can be fired to bring cap  44  into engagement with one face of the article whereafter continued extending movement of piston rod  36  allows equalizing spring  32  to act to bring the cap  52  into engagement with the other face of the article to be welded.  
         [0028]    The welding gun according to the present invention can provide many important advantages as compared to prior known welding guns. The square rod portion  38   b  of the electrode adapter can be slidably received in the square opening in the guide block  40  to preclude unwanted rotation of the electrode adapter. The design allows the ready interchange of the power cylinder  34  with a servo motor, such as for example the servo motor  100  shown in FIG. 39. The use of the identical side plates  20  to establish all of the critical dimensions of the components of the gun can insure that tolerances will be maintained on all of the critical dimensions and at all of the critical points. The use of the identical side plates  20  further can simplify reconfiguration of the gun since the shape and configuration of the side plates can be changed to accommodate a different welding requirement while continuing to use much of the same components of the welding gun in the new configuration. The rod portion  38   b  of the adapter  38  can be chrome treated to enhance work characteristics and reject weld splatter. The use of insulating plates  82  to embrace the electrode holder  46  can allow a metal to metal configuration at the arm engagement and the holder to prevent rotation of the arm under usage. The design can allow dual attachment points of the electrode adapter or shunt adapter to allow for a new attachment point after a wear failure or electrical arcing failure. The use of the hose fitting  50  attached directly to the rear end of electrode adapter  48  for coaction with tube  84  can simplify the connection of the inlet water and the outlet water to the electrode adapter  48  and specifically avoids complex routing of the coolant through the gun frame. The design of electrode adapter  38  can allow the in and out ports in the adapter main body portion  38   a  to communicate directly with the central bore in the adapter as well as with the central tube to simplify electrode construction and provide a more direct routing of the in and out coolant, thereby avoiding complex routing of the coolant though the gun frame.  
         [0029]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.