Electric arc welding

#The present invention relates generally to electric arc welding and more particularly to a new and improved manual arc welding system for unskilled welders which is provided with an automatic feed system for advancing filler wire into the arc or weld puddle.

#In presently existing hand welding systems using the tungsten inert gas (TIG) process an arc welding gun or torch is manipulated in one hand while a discrete length of filler wire held in the other hand is manipulated and dipped intermittently into the arc or molten weld puddle to form the weld. Present manual welding systems have many drawbacks and disadvantages, for example welding speeds are reduced because of the requirement for hand manipulation and feeding of the filler wire into the arc or molten weld puddle. Moreover, welding speed is reduced because the weld process must be stopped when each discrete length of filler wire become too short for convenience. The welder is required to throw away the short piece and pick up a new piece of weld filler wire before continuing the weld. Another disadvantage is that inclusions and foreign matter are created in the weld because of stoppage of the welding process and when this happens gouging out and rewelding of the area is required. Another difficulty encountered in present processes is the possibility of the welder grabbing the wrong type of filler wire and hence costly systems of color coding and identifying the discrete lengths of filler wire have been initiated to reduce the possibility of the wrong type of filler rod being used. However, even with marking and coding systems a welder often inadvertently reaches and grabs the wrong type of filler material thereby spoiling the weld joint and weakening the weld.

#Hand manipulation and feeding of the filler wire causes contamination in the weld due to dirt, grease or salt present on the operator's hand and the full length of each piece of filler wire is not available because the short stub portion gets too hot to handle and is either thrown away (stub losses sometimes reach as high as 30% of the total quantity of filler material used) or time must be taken to weld the stub to a new piece of filler before proceeding. One of the most difficult problems with the presently existing hand welding systems is the requirement for a high degree of operator skill and training in addition to a high level of manual dexterity needed to produce high quality welds. It is difficult to make high quality welds in tight corners and cramped spaced when both hands are required. The present invention overcomes the aforementioned disadvantages of presently existing manual welding systems and it is therefore an object of the present invention to provide a new and improved arc welding system. More specifically it is an object of the present invention to provide a new and improved manual arc welding system wherein only one hand is required and feeding of the filler wire into the arc or weld puddle is automatically controlled.

#For a better understanding of the invention reference should be had to the following detailed description taken in conjunction with the drawings in which:

#FIG. 1 is a longitudinal cross-sectional view, partially broken away, of a new and improved manual arc welding torch constructed in accordance with the features of the present invention, and

#FIG. 2 is a schematic diagram of a control circuit for an automatic weld filler wire feed system constructed in accordance with the features of the present invention.

#Briefly, the foregoing and other objects and advantages of the present invention are disclosed in an embodiment by way of illustration and not limitation which comprises a manual arc welding torch having a head supporting a nonconsumable electrode for establishing an arc between the lower end of the electrode and a workpiece. Annular nozzle means is provided for supplying an inert gas shield around the longitudinal axis of the electrode and arc and electrical conductor means is provided for supplying electrical current to the electrode for said arc. The torch includes handle means and control means for controlling the feed of weld filler wire toward intersection with a longitudinal axis of the electrode on a feed path which intersects the axis at an acute included angle from the front. The feeding means includes means for advancing the filler wire along said feed path in repetitive incremental advancing strokes between alternate periods of dwell. Means is provided for selectively controlling the feed velocity, the length of time or duration of each advancing stroke, and the length of dwell or idle time between successive strokes. Means is provided for continuous feeding of the filler wire if desired.

#Referring now more particularly to the drawings, therein is illustrated a new and improved manual arc welding torch constructed in accordance with the features of the present invention and referred to generally by the reference numeral 10. The torch 10 is adapted to use the tungsten inert gas process, commonly known at TIG welding, and includes an elongated, hollow tubular body 12 having an axial bore extending therethrough and an outwardly extending radial flange 14 spaced intermediate the upper and lower ends thereof. The body 12 of the torch is adapted to support an elongated, nonconsumable tungsten electrode 16 extended through the axial bore and the lower end of the electrode is adapted to establish and maintain an arc with a workpiece spaced therebelow which is to be welded. For the purpose of supporting the electrode in coaxial alignment within the bore of the body 12, the lower end of the axial bore is formed a frustroconical shaped wedging surface 20 and a threaded section 18 extending upwardly thereof. An elongated tubular electrode holder 22 is adapted to be threaded into the threaded section 18 and for this purpose includes threaded upper end portion 24. The electrode holder is formed with a plurality of longitudinal slots which form deflectable fingers 25 adjacent the lower end and each finger has an enlarging tapered lower end portion which bears against the frustroconical surface 20 of the tubular body. When the electrode holder 22 is tightened in the threaded bore section 18, the fingers 25 are biased inwardly against the electrode to firmly hold and establish electrical contact therewith. The upper end portion of the electrode extends upwardly into the hollow axial bore of the torch body or housing 12 and one or more radially spaced centering lands 26 are provided in the bore to coaxially align the electrode. The longitudinal slots in the holder 22 and the spaces between the lands 26 permit the passage of inert gas downwardly through the hollow bore of the body to form an inert gas shield around the electrode and the arc which is established between the lower end thereof and a workpiece. In order to guide the gas flow downwardly from the lower end of the body 12 to form the inert gas shield, there is provided a tubular gas nozzle having an upper end portion formed with a slightly tapered frustroconical bore adapted to slip onto a similarly tapered outer surface 29 on the lower end portion of the tubular body 12 below the radial flange 14. The tubular gas nozzle 28 is formed of an electrically nonconductive and relatively inert Pyrex glass or ceramic material. At the upper end, the tubular body 12 is connected to a gas supply conduit 30 for supplying inert gas (for example, a mixture of Helium and Argon) to shield the arc and weld puddle as is known.

#In order to provide for cooling of the torch body 12 and carrying away the intense heat generated in the region of the arc and weld puddle, the torch 10 is provided with an annular upper body or sleeve 36 having an inside diameter substantially equal to the outer diameter of the radial flange portion 14 on the body 12. The upper end of the sleeve 36 is closed by an integral end wall 38 having a central opening therein for the upper end portion of the tubular body structure which is connected to the gas tube 30. Suitable sealing means, such as brazing, is used to seal between the upper end wall 38 of the sleeve 36 and the upper section or tubular stem of the body 12. At the lower end, the sleeve 36 is similarly sealed and joined to the outer surface of the radial flange portion 14 thus forming an annular cooling chamber 40 around the body intermediate the ends for the circulation of coolant water. The coolant water is directed into the torch head from a supply tube 42 and after it passes through the chamber 40, the water is discharged through a water discharge tube 44. The water tubes 42 and 44 are attached to the upper end wall 38 of the outer housing sleeve 36 and are sealed into the opening ports of the wall, as by brazing.