Abstract:
A torch-mounted power controller mounts to the handle of a welding torch and includes a control lever that is operated by the user&#39;s finger. The control lever is arranged to allow the user to hold the torch with a normal grip. Power supply to the welding torch is controlled by applying finger pressure to a control lever. A voltage control circuit is operatively connected to the control lever and controls the amount of power supplied responsive to the movement of the control lever.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 61/729,655, filed Nov. 26, 2012, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to TIG welding equipment and, more particularly, to a torch-mounted, fingertip welding controller for a TIG welder. 
     BACKGROUND 
     Probably every operator who has ever used a TIG torch has wanted a true fingertip controller for the welding current. The prior art offers numerous examples of torch-mounted controllers that purport to offer such control. Examples of torch-mounted controllers in the prior art are U.S. Pat. No. 6,051,808 to Kleppen, U.S. Pat. No. 4,227,066 to Bulwidas, and U.S. Pub. No. 2005/0023263 A1 to Bilde. 
     The prior art torch-mounted welding controllers have proved unsatisfactory so that most TIG operators still prefer to use a foot pedal control whenever possible Controllers taught in the prior art have the following problems:
         They require the operator to alter his normal, preferred grip on the torch in order to reach the control with one or more fingers. In some cases, as with trigger type schemes, the grip required will be completely foreign to most operators.   Once the operator&#39;s finger has found the control knob or trigger, activation requires a large range of motion, involving many muscles of the hand; in fact, with many controllers you can&#39;t go from off to full power in one smooth motion, but must finger the controller repeatedly.   Many of these controllers require a fair amount of finger pressure, because they work by friction between the finger and a knob or belt.   Operation of the controller interferes with the operator&#39;s main task, which is maintaining an exact and very close height of the torch and electrode above the weld puddle.       

     Accordingly, there remains a need for a troch-mounted welding controller that overcomes one or more of these problems. 
     SUMMARY 
     The present disclosure relates to a torch-mounted power controller for an electric arc welder. Although intended primarily for tungsten inert-gas (TIG) welding, it could be used in other welding processes such as metal inert-gas (MIG) or plasma welding. The welding controller comprises a control lever that mounts to the handle of a welding torch and is operated by the user&#39;s finger. The control lever is arranged to allow the user to hold the torch with a normal grip. In some embodiments, the control lever includes a pivot and extends forwardly from the pivot so as to lie directly beneath the user&#39;s finger. Power supply to the welding torch is controlled by applying finger pressure to the control lever. A voltage control circuit is operatively connected to the control lever and controls the amount of power supplied responsive to the movement of the control lever. 
     In some embodiments, the voltage control circuit comprises a sequentially-switched resistor network including two or more voltage control switches and two or more series connected resistors arranged as a voltage divider. When finger pressure is applied to the control lever, the voltage control switches are sequentially actuated as the control lever is depressed. 
     In some embodiments, a contactor circuit is provided to activate the power supply for the welding torch. The contactor circuit is configured to activate the power supply when finger pressure is applied to the control lever. In one embodiment, the contactor circuit comprises a contactor switch activated by the control lever when finger pressure is applied to the control lever. The contactor switch may be arranged to be activated prior to activation of one of the voltage control switches, at the same time as a first one of the voltage control switches, or after a first one of the voltage control switches. 
     The welding controller according to various embodiments described herein provides the user with fingertip control of the welding power supply from off to full power or levels in between. The embodiments herein described further provide a degree of fine control without altering the operator&#39;s normal grip on the torch, and without requiring a large range of finger motion or pressure that could disturb the position of the torch electrode relative to the weld puddle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a torch-mounted, welding controller according to a first embodiment. 
         FIG. 2  is a section view of a torch-mounted, welding controller according to the first embodiment. 
         FIG. 3  is a schematic diagram of an exemplary control circuit of the torch-mounted, welding controller according to the first embodiment. 
         FIG. 4  is a perspective view of a torch-mounted, welding controller according to a second embodiment. 
         FIG. 5  is a section view of a torch-mounted, welding controller according to the second embodiment. 
         FIG. 6  is a schematic diagram of an exemplary control circuit of the torch-mounted, welding controller according to the second embodiment. 
         FIG. 7  illustrates a control circuit for a torch-mounted welding controller according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, a welding controller  10  according to exemplary embodiments of the disclosure is shown. Similar reference numbers are used in the Figures to indicate similar elements. 
       FIG. 1  illustrates a welding controller  10  according to a first embodiment attached to a typical TIG welding torch  12 . The welding controller  10  comprises a controller housing  20 , a control lever  30  pivotally connected to the housing  20 , and a control circuit  40  contained within the housing  20  for controlling the power supplied to the welding torch. The controller housing  20  comprises a base  22  and cover  24  detachably secured to the base  22 . The controller housing  20  is attached to the torch handle by a clamp  26 , although other methods for securing the housing  20  to the torch handle could be used. The control lever  30  is connected to the housing  20  by a pivot  36 . The outer end  32  of the control lever  30  extends forwardly from the housing  20  towards the torch head. The inner end  34  of the control lever  30  extends into the housing  20 . The housing  20  is positioned on the torch handle so that the control lever  30  lies directly under the user&#39;s finger. This arrangement allows the user to hold the torch  12  with a normal grip. The user can exert a varying downward pressure on the control lever  30  with an index finger or middle finger to control the power supply to the welding torch. As will be described in more detail below, the inner end  34  of control lever  30  activates a series of switches in the control circuit  40  to control the power to the welding torch  12 . 
       FIG. 3  illustrates an exemplary control circuit  40  which is mounted to circuit board  28  and connected by a cable  42  to the welding power supply. The control circuit  40  comprises a contactor circuit  44  and a voltage control circuit  50 . The contactor circuit  44  comprises a contactor switch  46  that completes an AC circuit to activate the welding power supply. The voltage control circuit  50  comprises a plurality of voltage control switches  54 ,  56 ,  58  and resistors  62 ,  64 ,  66 , and  68  arranged as a voltage divider. The resistors  62 ,  64 ,  66 , and  68  are connected in series between a nominal +10 volt (DC+) input and ground (GND). The voltage control switches  54 ,  56 ,  58  are connected between respective pairs of the resistors  62 ,  64 ,  66 , and  68  and arranged to supply a variable control voltage (DC OUT) at an output of the voltage control circuit  40 . 
     In one exemplary embodiment, the contactor switch  46  and voltage control switches  54 ,  56 ,  58  comprise sub-miniature snap action switches which are mounted to the circuit board  28  ( FIG. 2 ) in the housing  20 . Sequential activation of the switches  46 ,  54 ,  56 , and  58  is achieved by their placement in the housing  20  as shown in  FIG. 2 . As the control lever  30  is depressed, the activation plungers of the switches  46 ,  54 ,  56 ,  58  are contacted by the inner end of the control lever  30  to sequentially activate the switches  46 ,  54 ,  56 , and  58 . 
     In operation, the contactor switch  46  is closed first to activate the welding power supply when pressure is applied to the control lever  30 . The switches  54 ,  56  and  58  are closed sequentially in that order as the control lever  30  is further depressed. As switches  54 ,  56 ,  58  are activated; the control voltage (DC OUT) output to the welding power supply is taken from successively higher points in the voltage divider network. This arrangement allows for very fine fingertip control of the welding power supply. In one embodiment, the voltage levels correspond to 25% power, 50% power, 75% power and 100% power. 
       FIG. 4  illustrates a welding controller  10  according to a second embodiment attached to a typical TIG welding torch  12 . In this embodiment, the welding controller  10  comprises a controller housing  20  and a control circuit  40  contained within the housing  20  for controlling the power supplied to the welding torch. The controller housing  20  comprises a base  22  and a cover  24 . The controller housing  20  is attached to the torch handle by a clamp  26 , although other methods for securing the housing  20  to the torch handle could be used. The cover  24  in this embodiment is pivotally secured to the base  22  by a pivot  36  and functions as the control lever. The cover  24  extends forwardly from the pivot  36  towards the head of the torch  12 . The housing  20  is positioned on the torch handle so that the cover  24  lies directly under the user&#39;s finger. This arrangement allows the user to hold the torch  12  with a normal grip. The user can exert a varying downward pressure on the cover  24  with an index finger or middle finger to control the power supply to the welding torch  12 . As seen in  FIG. 5 , the cover  24  engages and activates a series of switches in the control circuit  40  to control the power to the welding torch  12 . 
       FIG. 6  illustrates an exemplary control circuit  40  according to the second embodiment. The control circuit  40 , which is mounted to circuit board  28  ( FIG. 5 ), and connected to the welding power supply by a cable  42 . The control circuit  40  comprises a contactor circuit  44  and a voltage control circuit  50 . The contactor circuit  44  comprises a contactor switch  46  that completes an AC circuit to activate the welding power supply. The voltage control circuit  50  comprises a plurality of voltage control switches  52 ,  54 ,  56 ,  58  and resistors  62 ,  64 ,  66 , and  68  arranged as a voltage divider. Compared to the first embodiment, the voltage control circuit  50  includes an additional voltage control switch  52  not present in the first embodiment. The resistors  62 ,  64 ,  66 , and  68  are connected in series between a nominal +10 volt (DC+) input and ground (GND). Voltage control switch  52  is connected between resistor  62  and ground and voltage control switches  54 ,  56 ,  58  are connected between respective pairs of the resistors  62 ,  64 ,  66 , and  68  to supply a variable control voltage (DC OUT) at an output of the voltage control circuit  40  as the switches  52 ,  54 ,  56  and  58  are activated. 
     In one exemplary embodiment, the switches  46 ,  52 ,  54 ,  56 ,  58  comprise sub-miniature snap action switches which are mounted to the circuit board  28  in the housing  20 . Sequential activation of the switches  46 ,  52 ,  54 ,  56  and  58  is achieved by their placement in the housing  20  as shown in  FIG. 5 . As the control lever  30  is depressed, the activation plungers of the switches  46 ,  54 ,  56 ,  58  are contacted by the inner surface of cover  24  to sequentially activate the switches  46 ,  52 ,  54 ,  56 , and  58 . 
     In operation, the contactor switch  46  and voltage control switch  52  are arranged to be closed at the same time. In other embodiments, the contactor switch  46  could be arranged to close either before or after the voltage control switch  52 . The voltage control switch  52  in this embodiment extends the range of the output voltage to 0 volts to accommodate certain welding power supplies that expect the control voltage to go to ground or 0 volts when the contactor switch  44  is open. The switches  54 ,  56  and  58  are closed sequentially in that order as the cover  24  is further depressed. As switches  52 ,  54 ,  56  and  58  are activated; the control voltage (DC OUT) output to the welding power supply is taken from successively higher points in the voltage divider network. This arrangement allows for very fine fingertip control of the welding power supply. 
     In the previous embodiments, the switches  46 ,  52 ,  54 ,  56  and  58  are closed mechanically by movement of the control lever  30  or cover  24 .  FIG. 7  illustrates an alternate embodiment of the control circuit  40 . The control circuit  40  in this embodiment comprises a contactor circuit  44 , digital controller  80  and sensor  82 . The contactor circuit  44  comprises a contactor switch  46  that is operated by a relay  48 . The relay  48  is, in turn, activated by the digital controller  80 . A battery  84  provides power to the digital controller  80 . A +DC reference voltage is supplied by the welding power supply to the digital controller  80 . The sensor  82  detects the movement or position of the control lever (e.g., control lever  30  or cover  24 ) and supplies an analog input signal to the digital controller  80 . The sensor  82  may comprise a capacitive, inductive, magnetic, or optical sensor. Sensor  82  could also comprise a pressure transducer or other electro-mechanical transducer. The welding power supply also supplies a reference voltage (+DC) to another analog input of the digital controller  80 . Based on a comparison of the analog input signal from the sensor  82  and the +DC reference voltage, the digital controller  80  activates the relay  48  to close the contactor switch  46  and provides a DC control voltage (DC OUT) to the welding power supply via an analog output. 
     Other implementations of a welding controller  10  based on a switched resistance network are easily imagined, and will not be enumerated here, except to suggest the most obvious, which would substitute some other means of sequential switching for the standard snap-action switches of the present implementation. 
     While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention as claimed.