US3431390A - Work-in-circuit arc starting apparatus - Google Patents

Description

March 4, 1969 Af MANZ 3,431,390

WQRK-IN-CIRCUIT ARC STARTING APPARATUS Filed May 20. 1965 DC. A Non-Consumable POWER SOURCE Material INVENTOR AUGUST F. MANZ Jamaal $457 ATTORN United States Patent 3,431,390 WORK-IN-CIRCUIT ARC STARTING APPARATUS August F. Manz, Union, N.J., assignor to Union Carbide Corporation, a corporation of New York Filed May 20, 1965, Ser. No. 457,388 US. Cl. 219-130 6 Claims Int. Cl. B23k 9/00, 9/10 ABSTRACT OF THE DISCLOSURE This invention provides for improving main arc startmg by incorporating into the torch a substantially electrically non-conductive gas cup which is located about the electrode, the cup comprising both nonconductive and conductive material and being directly grounded to the work lfor inhibiting undesirable are starting blocking potentia This invention relates to work-in-circuit are starting apparatus, and more particularly, to non-consumable electrode-inert gas shielded arc welding.

The invention provides for improving main arc starting by making the substantially electrically non-conductive gas nozzle or cup at least partially electrically conductive and grounding the latter to the work, so that undesirable blocking potential is prevented from accumulating on the cup, thus assuring starting of the are even with high frequency.

Prior to the invention, the use of high frequency in starting the main arc presented a problem in that the arc occasionally failed to start.

The main object of this invention is to solve such problems by simple and economical means.

This object is accomplished either by coating a cup that is composed of relatively electrically non-conductive material with material that is conductive, or by providing a cup that is composed of a combination of conductive material as well as non-conductive material, and electrically connecting such conductive material on or in the cup to the work to be welded, by an auxiliary circuit. This bleeds undesirable arc blocking potential from the cup and results in more reliable starting of the main arc.

In the drawing:

FIGURE 1 is a circuit diagram of apparatus illustrative of the invention; and' FIGURES 2 and 3 are enlarged sections of modifications of the cup.

As shown in such drawing, a torch 10 comprising a tungsten electrode 12 and a gas cup 14 is located above the work 16 to be welded in the usual way. Such electrode is connected by lead 18 to a power source 20 that is provided with high-frequency are starting means. The other terminal of such source 20 is connected to the work 16 by a ground lead 22. Inert gas, such as argon 24, is supplied to the torch 10 and flows through cup 14 to protect the operation from the atmosphere.

The cup 10, FIGURE 2, is composed of material 26 that is substantially electrically non-conductive, such as alumina, having an annular coating 28 composed of electrically conductive material, such as graphite. Such coating 28 is connected to the work 16 by a pigtail conductor 30 that is held by place at one end on the cup by a spring clip, not shown.

In operation, the coating 28 and conductor 30 act to bleed from the cup any electrical charge which tends to accumulate thereon to the work while also acting as a relatively high impedance to the main are, thereby preventing any undesirable main arc current from flowing therethrough.

Thus, even with the aid of high frequency to start the main are between the electrode 12 and work 16 in the inert gas stream, undesirable are starting blocking potential buildup on the cup is inhibited, assuring more reliable starting of the main are, even under repetitive starting conditions.

As shown in FIGURE 3, the cup 10a is made by mixing conductive material, such as graphite, or metal, in the form of powder with the alumina powder of the cup, before molding and baking the latter. Thus, the cup contains conductive as well as non-conductive material, and is grounded to the work as pointed out above for the same purpose.

What is claimed is:

1. A non-consumable electrode gas shielded are working system comprising a torch, the electrode of which is connected in circuit with an arc energizing power source, and the Work, which power source includes electrical means for starting such arc, said torch being provided with a substantially electrically non-conductive cup surrounding said electrode for directing the gas about such arc to shield the operation from the atmosphere, said cup being directly grounded to said work for inhibiting undesirable are starting blocking potential.

2. A system as defined by claim 1, in which said are starting means comprises high frequency.

3. A system defined by claim 1, in which said cup comprises a non-conductive core and a coating of conductive material.

4. A system as defined by claim 3, in which said core comprises a ceramic.

5. A gas cup for non-consumable electrode inert gas shielded arc torches, consisting of a composite material of a substantially homogeneous mixture of electrically conductive particles and electrically non-conductive particles.

6. A gas cup as defined by claim 5, in which the nonconductive particles comprises a ceramic.

References Cited UNITED STATES PATENTS 2,620,422 12/1952 Volfi 219- 2,992,320 7/1961 Hill 21975 2,922,023 1/ 1960 Hackman et al 219-l27 RICHARD M. WOOD, Primary Examiner.

J. GREGORY SMITH, Assistant Examiner.

U.S. Cl. X.R. 219

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