Abstract:
A portable welder including a housing, a power supply contained within the housing, a welding cable having a proximal end and a distal end, the proximal end of the welding cable being electrically connected to the power supply, a welding electrode that extends from the distal end of the welding cable, and a control system that adjusts welding current delivered to the welding electrode from the power supply based on user input.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. Provisional Patent Application Ser. No. 60/796,835, filed May 1, 2006. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to welders, and in particular to self-contained portable welders having an internal power supply.  
       BACKGROUND OF THE INVENTION  
       [0003]     Arc welding is used to join two metal work pieces either by melting the metal work pieces directly or by melting a metal electrode between the metal work pieces using heat generated from an arc of high electricity formed between the work pieces and the metal electrode. The metal electrode is designed to conduct current generated by an arc welder to sustain the arc and to provide filler metal to form the weld.  
         [0004]     There are numerous arc-welding devices known in the art, most of which include bulky and relatively heavy housing units that must be connected to a power source, such as a wall outlet or the battery of a vehicle. For example, U.S. Pat. No. 5,410,126 to Miller discloses a wire feed welder that is described as being “portable”. However, the welder of Miller requires an external source of power, which may either be utility power or a battery power source, such as a car battery. Thus, although the Miller welder can be relocated to and used at different work sites as long as an external power source is available, it is not portable in the sense that it does not allow the user to weld at various work sites without being tethered to a power source.  
         [0005]     Accordingly, there is a need for a truly portable and self-contained welder that allows a user to relocate the welder from one work site to another without requiring an external power source to power the welder.  
       SUMMARY OF THE INVENTION  
       [0006]     A portable welder according to an exemplary embodiment of the present invention includes a housing, a power supply contained within the housing, and a welding cable having a proximal end and a distal end. The proximal end of the welding cable is electrically connected to the power supply. A welding electrode extends from the distal end of the welding cable. A control system adjusts welding current delivered to the welding electrode from the power supply based on user input.  
         [0007]     In at least one embodiment, the power supply comprises at least one battery.  
         [0008]     In at least one embodiment, the at least one battery is a Sealed-Lead Acid (SLA) battery.  
         [0009]     In at least one embodiment, the at least one battery is an Absorbed Glass Matt (AGM)-type SLA battery.  
         [0010]     In at least one embodiment, the portable welder further comprises a ground cable electrically connected to the at least one battery.  
         [0011]     In at least one embodiment, the control system comprises a welding control electrical circuit.  
         [0012]     In at least one embodiment, the welding control electrical circuit comprises a potentiometer that is adjusted by the user to control current delivered to the welding electrode from the power supply.  
         [0013]     In at least one embodiment, the portable welder further comprises a wire feed motor that drives the welding electrode through the welding cable.  
         [0014]     In at least one embodiment, the portable welder further comprises a welding gun disposed at the distal end of the welding cable.  
         [0015]     In at least one embodiment, the wire feed motor is contained within the welding gun.  
         [0016]     In at least one embodiment, the wire feed motor is contained within the housing.  
         [0017]     In at least one embodiment, the welding electrode is a stick electrode.  
         [0018]     In at least one embodiment, the housing comprises a handle for transporting the portable welder.  
         [0019]     These and other features of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of this invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     Various exemplary embodiments of this invention will be described in detail, with reference to the following figures, wherein:  
         [0021]      FIG. 1  is an elevation view of a portable welder according to an exemplary embodiment of the present invention;  
         [0022]      FIG. 2  is a block diagram showing internal components of the portable welder of  FIG. 1 ; and  
         [0023]      FIG. 3  is a diagram showing a current control circuit used in the portable welder of  FIG. 1 .  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0024]     Various exemplary embodiments of the present invention are directed to a portable welder that is lightweight enough for a user to easily transport the welder and perform welding jobs while still holding the welder either in hand or, for example, connected to a utility belt worn by the user. The welder according to the present invention is fully self-contained in that it includes an internal power supply which, in a preferred embodiment, includes one or more batteries. Thus, a user can simply remove the inventive portable welder from a storage shelf, charge the batteries in the welder, and walk to a work site with the welder to perform a welding operation.  
         [0025]      FIG. 1  is an elevation view of a portable welder, generally designated by reference number  1 , according to an exemplary embodiment of the present invention. The portable welder  1  includes a housing  10  preferably made of a light-weight material, such as, for example, plastic. The housing  10  includes a handle portion  12  for ease of transport. The housing may also be equipped with attachments (not shown), such as hooks or straps, which allow the housing  10  to be hung from the user&#39;s utility belt or from an object nearby the work site while the portable welder  10  is in use.  
         [0026]     The housing  10  includes a power on/off switch  14 , and a control panel  16  that may include various other welding control switches and indicators. In a preferred embodiment, a current control switch  18  is provided in the control panel  16 , the manipulation of which results in adjustment in the current delivered to a welding electrode, as discussed in further detail below.  
         [0027]     A welding cable  20  extends from one side of the housing  10  and a ground cable  30  extends from the opposite side of the housing  10 . A welding electrode  22  extends from a distal end of the welding cable  20 . As is known in the art, current delivered to the electrode  22  creates an arc between the electrode  22  and a work piece, which in turn generates heat that melts the electrode onto the work piece.  
         [0028]     The housing  10  may also include an accessory charger input jack  40  for insertion of an accessory, such as, for example, a flashlight, for charging from an internal power supply, as described in further detail below. In this regard, the housing  10  may include mounts (not shown) for storage of a variety of accessories. The housing  10  also includes a power supply charger jack  50  that receives a plug from a charger (not shown) to charge the internal power supply of the portable welder  1 .  
         [0029]      FIG. 2  is a block diagram showing the internal components of the portable welder  1 . The portable welder  1  includes a battery  100  which supplies power to the portable welder  1 . The battery is preferably a Sealed-Lead Acid (SLA) battery, which may either be an Absorbed Glass Mat (AGM) SLA battery or a Gel Cell SLA battery. However, an AGM-SLA battery is preferred for consistency in operation. Although only one battery  100  is shown in  FIG. 2 , it should be appreciated that any number and combination of different types of batteries may be used to provide the necessary welding power. The battery  100  includes a positive lead  102  and negative lead  104 . The welding cable  20  is electrically connected to the positive lead  102 , and the ground cable  30  is electrically connected to the negative lead  104 . As is known in the art, connection of a welding cable to a positive lead of a battery results in higher temperature welds and therefore deeper penetration. Alternatively, the welding cable  20  may be electrically connected to the negative lead  104  and the ground cable  30  may be connected to the positive lead  102 .  
         [0030]     As the heat of the arc between the electrode  22  and a work piece depends on the current delivered to the electrode during the welding operation, it is important to maintain a constant current in the electrode, even as the voltage varies. Maintaining a stable welding temperature results in a more consistent weld. Thus, the portable welder  1  also includes a current control circuit  110  that maintains the current output from the battery  100  at a user-controlled level selected using the current control switch  18 .  
         [0031]      FIG. 3  is a diagram of the current control circuit  110  according to an exemplary embodiment of the present invention. The current control circuit  110  includes a charging circuit, generally designated by reference number  112 . The charging circuit  112  includes a 115 VAC to 36 VAC step down transformer  114 . A 4-diode bridge rectifier  116  converts the AC voltage output from the transformer  114  to DC voltage.  
         [0032]     The current control circuit  110  further includes three diodes D 1 -D 3  in series that reduce the DC voltage slightly. Two resistors R 1  and R 2  in conjunction with two capacitors C 1  and C 2  form a voltage filter for a line voltage regulator LM317 which outputs a constant voltage. An LM555 oscillator generates a variable duty-cycle square wave signal. The signal is biased to ground through the resistor R 15  and boosted through transistors Q 1  and Q 2 . The boosted signal is then used to drive two high current output drivers Q 3  and Q 4  to generate an R/L output. The R/L output is rapidly switched between being grounded and open for the length of time determined by a 10M OHM potentiometer in the LM555 oscillator, adjusted by the user through the current control switch  18 . Driver resistor banks R 20  and R 21  on the output drivers Q 3  and Q 4  and output resistor bank R 24  on the R/L output equalize the load on the two drivers Q 3  and Q 4  and reduce the maximum current draw.  
         [0033]     The portable welder  1  may be a stick welder, in which case the welding electrode  22  is a stick electrode. Alternatively, the welding electrode  22  may be a wire electrode that extends through the welding cable  20 . In the case of a wire electrode, the portable welder  1  may include a wire feed motor  150  that drives the wire electrode off of a spool as the electrode is consumed. The wire feed motor  150  may be disposed within the housing  10  or within a welding gun  24  disposed at the distal end portion of the welding cable  20 .  
         [0034]     While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.