GB2108417A

GB2108417A - Arc welding apparatus

Info

Publication number: GB2108417A
Application number: GB08230605A
Authority: GB
Inventors: Roy Neville
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-10-27
Filing date: 1982-10-26
Publication date: 1983-05-18
Also published as: GB2108417B

Abstract

A welding tool comprises a solenoid body 1 wound with a coil of wire 2 about a hollow core 3. A central core contains a fixed iron part 4 and a movable iron part 5. The core part 5 has a threaded brass studding 6 connected thereto and which passes with clearance through the part 4 to connect with a conducting leaf 7 which is in series with the solenoid coil and serves as a mechanically flexible welding current feed to a welding electrode holder 8 via the studding 6 and the part 5. The studding is adjustable to adjust an air gap 9 between the two iron parts 4, 5. A spring 10, normally urging the electrode holder 8 and the part 5 away from the part 4, is further stressed when the air gap is adjusted in the closing direction. In operation, when the electrode is brought into contact with the work the solenoid retracts the electrode momentarily to strike the arc. The arc breaks and the electrode is repeatedly returned to the work by the spring 10. <IMAGE>

Description

SPECIFICATION An improved electric arc welding tool This invention relates to an improved electric arc welding tool, such as that described in G.B. 996126 which operates to strike an arc and maintain a succession of arcs to enable efficient welding operation to be performed without a high degree of skill from an operator. In such a tool a sustained heavy current drain is avoided and the tool is suitable for use on low voltage supplies where difficulty would otherwise be experienced in rapidly striking and maintaining an arc.

The known constructions of tool have an electromagnetic means arranged to retract an electrode holder in opposition to a restoring means which urges the holder towards the workpiece, the electromagnetic means having an energising circuit which is completed through the electrode and workpiece by mutual contact of these whereby the electrode will be retracted to strike an arc and break the circuit and the restoring means will then restore the electrode to make contact with the workpiece, resulting in a succession of arcs between the electrode and workpiece.

The electro-magnetic means is a solenoid having a core arranged to move and in electrical connection with the electrode holder; the core is in electrical contact throughout the whole of its movement with the electric current feed to the tool. The energising current for the solenoid is provided by a winding through which the current to the tool is fed. In such an arrangement it is difficult to arrive at the correct balance between coil winding and current. Welding thick metals requires high current with a coil of heavy gauge wire and few turns, whereas light gauge welding using low current needs a coil with a large number of turns and thinner gauge wire. The resulting tool to a large extent is therefore a compromise with heavy wire wound tool unsuitable for light work and the thin wire tool unsuitable for heavy work.It was not possible hitherto to provide a single tool for the current range 15 to 150 Amps.

It is an object of this invention to provide an improved construction for the solenoid of such a welding tool in which a wider range of currents can be used with a single solenoid winding.

According to this invention there is provided a welding tool generally as hereinbefore described wherein the solenoid includes a core of magnetic material with a first part fixed to the solenoid coil structure and a second part fixed to the electrode holder and movable with respect to the solenoid, the first and second parts being spaced longitudinally by an air gap and a current carrying connection of the second part passing through the first part and connected to the electric feed to the tool.

The air gap is preferably within the solenoid structure and with this arrangement the fixed core part ensures adequate magnetic flux when low currents are used to provide sufficient attraction.

The construction according to this invention enables the minimum number of turns to be used which reduces manufacturing costs and gives a lower coil resistance and hence less heating. The increased efficiency allows tools built to carry heavy currents to be usable and efficient at low currents when magnetism is weak.

An embodiment according to the invention is shown by way of example only in the accompanying drawings which show a cross-section through the solenoid part only of a welding tool, other parts of the tool being omitted. In the drawings: Figure 1 shows a first embodiment, and Figure 2 shows a second embodiment being a modification of the first.

Referring to Figure 1 of the drawings, a solenoid comprises a body 1 wound with a coil of wire 2 about a central hollow core 3. The core contains a fixed iron core part 4 and a movable iron core part 5. The core part 5 has a threaded brass studding 6 connected thereto and which passes with clearance through the core part 4 to connect with a conducting leaf 7 serving as a mechanically flexible current feed to the welding tool holder 8 via the studding 6 and core part 5. The studding is adjustable and provides an air gap 9 between the two iron core parts. By this means magnetic attraction is increased at lower weld currents. The tool holder 8 and core part 5 are normally urged away from the core part 4 by a return spring 10 and the tension in this spring will be increased when the studding 6 is adjusted to close the gap.

Another feature of the construction is that the tool may be arranged as a self-striking, arc-restoring STATIC electrode holder. If a weak return spring 10 is used, then welding current passing through the coil will hold the two iron cores 4 and 5 together solidly. In this form the role is as a static electrode holder. Should the arc break the electrode will move forward to make electrical contact and then draw away restoring the arc.

Although the known prior art tool has such qualities the elctrode tends to float about and to some operators this is undesirable. In the invention herein the tool becomes truly static during the actual welding process.

In Figure 2 the arrangement is generally similar and like references are used, but in this case the studding 6 is extended at 11 and a spring 12 is provided around the extended portion and lying between the connection to leaf 7 and a knurled adjusting nut 13. This nut provides for simple adjustment of the air gap 9 whilst the spring 12 provides tension sufficient to lock the nut 13 and prevent movement during use.

A quick means of adjustment is-provided by the above which allows the operator to easily find the optimum setting for given welding electrodes, metals/thicknesses and currents/voltages.

1. A welding tool of the kind as herein described and wherein the solenoid includes a core of magne The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION An improved electric arc welding tool This invention relates to an improved electric arc welding tool, such as that described in G.B. 996126 which operates to strike an arc and maintain a succession of arcs to enable efficient welding operation to be performed without a high degree of skill from an operator. In such a tool a sustained heavy current drain is avoided and the tool is suitable for use on low voltage supplies where difficulty would otherwise be experienced in rapidly striking and maintaining an arc. The known constructions of tool have an electromagnetic means arranged to retract an electrode holder in opposition to a restoring means which urges the holder towards the workpiece, the electromagnetic means having an energising circuit which is completed through the electrode and workpiece by mutual contact of these whereby the electrode will be retracted to strike an arc and break the circuit and the restoring means will then restore the electrode to make contact with the workpiece, resulting in a succession of arcs between the electrode and workpiece. The electro-magnetic means is a solenoid having a core arranged to move and in electrical connection with the electrode holder; the core is in electrical contact throughout the whole of its movement with the electric current feed to the tool. The energising current for the solenoid is provided by a winding through which the current to the tool is fed. In such an arrangement it is difficult to arrive at the correct balance between coil winding and current. Welding thick metals requires high current with a coil of heavy gauge wire and few turns, whereas light gauge welding using low current needs a coil with a large number of turns and thinner gauge wire. The resulting tool to a large extent is therefore a compromise with heavy wire wound tool unsuitable for light work and the thin wire tool unsuitable for heavy work.It was not possible hitherto to provide a single tool for the current range 15 to 150 Amps. It is an object of this invention to provide an improved construction for the solenoid of such a welding tool in which a wider range of currents can be used with a single solenoid winding. According to this invention there is provided a welding tool generally as hereinbefore described wherein the solenoid includes a core of magnetic material with a first part fixed to the solenoid coil structure and a second part fixed to the electrode holder and movable with respect to the solenoid, the first and second parts being spaced longitudinally by an air gap and a current carrying connection of the second part passing through the first part and connected to the electric feed to the tool. The air gap is preferably within the solenoid structure and with this arrangement the fixed core part ensures adequate magnetic flux when low currents are used to provide sufficient attraction. The construction according to this invention enables the minimum number of turns to be used which reduces manufacturing costs and gives a lower coil resistance and hence less heating. The increased efficiency allows tools built to carry heavy currents to be usable and efficient at low currents when magnetism is weak. An embodiment according to the invention is shown by way of example only in the accompanying drawings which show a cross-section through the solenoid part only of a welding tool, other parts of the tool being omitted. In the drawings: Figure 1 shows a first embodiment, and Figure 2 shows a second embodiment being a modification of the first. Referring to Figure 1 of the drawings, a solenoid comprises a body 1 wound with a coil of wire 2 about a central hollow core 3. The core contains a fixed iron core part 4 and a movable iron core part 5. The core part 5 has a threaded brass studding 6 connected thereto and which passes with clearance through the core part 4 to connect with a conducting leaf 7 serving as a mechanically flexible current feed to the welding tool holder 8 via the studding 6 and core part 5. The studding is adjustable and provides an air gap 9 between the two iron core parts. By this means magnetic attraction is increased at lower weld currents. The tool holder 8 and core part 5 are normally urged away from the core part 4 by a return spring 10 and the tension in this spring will be increased when the studding 6 is adjusted to close the gap. Another feature of the construction is that the tool may be arranged as a self-striking, arc-restoring STATIC electrode holder. If a weak return spring 10 is used, then welding current passing through the coil will hold the two iron cores 4 and 5 together solidly. In this form the role is as a static electrode holder. Should the arc break the electrode will move forward to make electrical contact and then draw away restoring the arc. Although the known prior art tool has such qualities the elctrode tends to float about and to some operators this is undesirable. In the invention herein the tool becomes truly static during the actual welding process. In Figure 2 the arrangement is generally similar and like references are used, but in this case the studding 6 is extended at 11 and a spring 12 is provided around the extended portion and lying between the connection to leaf 7 and a knurled adjusting nut 13. This nut provides for simple adjustment of the air gap 9 whilst the spring 12 provides tension sufficient to lock the nut 13 and prevent movement during use. A quick means of adjustment is-provided by the above which allows the operator to easily find the optimum setting for given welding electrodes, metals/thicknesses and currents/voltages. CLAIMS

tic material with a first part fixed to the solenoid coil structure and a second part fixed to the electrode holder and moveable with respect to the solenoid, thefirst and second parts being spaced longitudinally by an air gap and a current carrying connection of the second part passing through the first part and connected to the electric feed to the tool.

2. Atool as claimed in Claim 1, wherein the air gap is within the solenoid structure.

3. A tool as claimed in Claim 1 or 2, wherein the current carrying connection of the second part comprises a nut adjustable thereon with respect to a fixed abutment of the coil body whereby the air gap may be adjusted by means of the nut.

4. Atool as claimed in Claim 3, wherein the studding extends beyond the nut and connects with the electric feed, a spring being provided between the feed and the nut.

5. Atool as claimed in any preceding Claim, wherein the first and second core parts are urged apart by spring means, the tension of which is increased as the air gap is reduced.

6. Awelding tool embodying the improvements as claimed in any preceding Claim.

7. A welding tool solenoid assembly as described herein and as shown in Figure 1 or Figure 2 of the drawings.