GB1559321A - Arc-welding torches - Google Patents

Description

(54) IMPROVEMENTS IN ARC-WELDING TORCHES (71) We, FOSTER WHEELER POWER PRODUCTS LIMITED, a British Company, of Greater London House, Hampstead Road, London NW1 7QN, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to non-consumable electrode bore welding torches.

The torch described in our Patent No.

934,485 has been extremely successful in making bore welds. In the particular construction of torch shown in that Patent, the rotatable stem which carries the electrode, is fixed to a rotatable brass distributor to which water, inert gas and power are supplied from a stationary housing. In order to insulate the distributor it is rotably mounted in bushes of insulating material. However, the seals provided between the distributor and bushes have sometimes been less than perfect in operation, both giving poor sealing action and erratic rotation of the distributor, and we now belive that this is because the insulating material of the bushes does not provide a very satisfactory surface for these seals to bear against.

According to the present invention, therefore, there is provided a bore arc welding torch in which a non-consumable electrode is carried by a rotatable stem, a distributor joined to the stem is rotatably positioned within a metal body, and means are provided for rotating the stem and distributor relative the body during the making of a weld, and in which the distributor has a first metal part acting as a commutator for cooling water to cool the electrode, this first metal part being insulated from a second metal part of the distributor acting as a commutator for the welding current by an electrically insulating material part, the stem having inner and outer tubes providing passages for the cooling water to pass along the stem to cool the electrode and return along the stem, the inner tube being of electrically insulating material to prevent conduction between the first and second metal parts of the commutator and the outer tube being of electrically conductive material and arranged to conduct the welding current to the electrode.

An advantage of such a torch is that suitable seals such as O-ring seals can be provided where necessary between the distributor and the outer metal body and these seals can function well because they bear against a metal surface. Therefore erratic rotation of the distributor and stem can be avoided and also excellent sealing can be given so avoiding the risks of water leakage.

The metal parts of the distributor and the outer metal body are preferably made of brass since this can be given a good surface finish and so cooperate well with rubber O-ring seals, The second metal part preferably receives the welding current by means of a brush connected to a stationary current outlet in the body which bears against a cylindrical outer surface of the metal part. This second part also preferably acts as a commutator for the inert shielding gas supply which passes through a stationary inlet bore in the metal body to an annular recess in the second metal part from whence it passes via a bore in this part to a passage along the stem to escape in the region of the welding electrode to blanket the weld region.

Means are required to rotate the stem and distributor so that the tip of the nonconsumable electrode can be orbited around the weld region during the making of a weld.

This rotation can be achieved by means of a worm and worm-wheel. Preferably, however, the distributor is driven directly by a miniature electric motor supported by the torch body through reduction gearing. This has the advantage of avoiding trailing Bow den cables and the slightly erratic rotation which can be caused by such Bowden cable drives and can lead to less than perfect welds.

In order to keep the speed of rotation of the stem accurate and even, a tachometer is preferably provided to monitor the drive and keep it constant.

Preferably the torch body carries an electric motor for rotating a stem projecting from the body and carrying a welding electrode, the speed of the electric motor being controlled by means of a tachometer so as to keep this substantially constant.

The rotatable stem preferably has an outer ceramic tube within which the inert gas is arranged to flow and within which the inner and outer tubes for the cooling water are positioned. This ceramic tube has a hole in it near its outer end through which the electrode projects. Surrounding this ceramic tube over part of its length is desirably a metal sleeve which fits into the bore of the part to be welded so locating the stem axially within that bore. This metal sleeve desirably has a bush or the like fitted over it to abut the end of that member and so locate the tip of the electrode with the butt weld. This bush can carry an electrical contact which completes a circuit when the bush contacts that member to be welded so giving a remote signal that the torch is positioned ready to make a weld.

The bore welding torch according to the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a sectional elevation through the torch; Fig. 2 is a section on the line B - B of Fig. 1; and Fig. 3 is a section on the line C - C of Fig. 1.

The bore welding torch 10 shown in the drawings comprises a body 12 in which is rotatably positioned, a distributor 14. An electric motor 18 is supported by the body 12 for rotating the distributor 14 and stem 16.

The stem 16 has an outer ceramic tube 20 within which are concentric outer and inner tubes 22 and 24. The outer tube 22 is of electrically conductive material such as copper or beryllium copper and fixed to and closing its outer end is a copper plug 26. In a bore in this copper plug is clamped by a grub screw 29 a non-consumable electrode 30 whose tip projects through a hole 20a in the ceramic tube 20. The inner tube 24 is made of electrically insulating material such as nylon and its end stops short of the plug 26 so defining a path for cooling water to pass along the stem past the plug and back along the stem.

The distributor 14 consists of a first brass portion 34 insulated by a Tufnol (Registered Trade Mark) portion 36 from a second brass portion 38. The inner end of the nylon tube 24 is fixed to the portion 34 while the inner end of the tube 22 is fixed to the portion 38.

The inner end of the ceramic tube 20 is clamped to the second portion 38 by means of a grub screw 40.

The first brass portion 34 acts as a commutator for the supply of cooling water. A water inlet and a water outlet (not shown) are provided through the body 12 in line with annular recesses 42 and 44 in the portion 34.

Bores 42a and 44a lead from these recesses 42 and 44 respectively to the end of the tube 24 and to a bore 46 in the portion 34 surrounding the tube 24 which provides an annular passage through the portions 34 and 36 to the end of the tube 22. Annular recesses 52, 54 and 56 alternate with the recesses 42 and 44 in the portion 34 and these contain O-ring seals 52a, 54a and 56a. These O-ring seals bear against the body 12 which can be of brass and so they can provide excellent seals and also do not stick and lead to erratic rotation of the distributor 12 and stem 16 during welding.

The body 12 has an inset portion 12a of insulating material. Through this and the body 12 is provided an inert gas inlet 60 (see Fig. 3). This is in line with an annular recess 62 in the portion 38 which is in communication with a bore 64 through portion. The bore 64 leads to the inner end of the ceramic tube 20 and inert gas can pass along the passage defined between the tube 20 and the metal tube 22 to the hole 20a where it leaves the stem to blanket the region of the weld.

Bearing against the outer surface of the portion 38 is a copper carbon brush 66 which is also in contact with the end of a welding current supply lead 68 urged against the brush 66 by a spring 70. Welding current then passes from the portion 38 along the tube 22 to the plug 26 and electrode 30. The current path is insulated from the body 12 by the inset portion 12a, the portion 36 and the nylon tube 24.

Surrounding the projecting portion of the ceramic tube 20 is a metal sleeve 72. This has an outside diameter such that it will just fit within the bore of the header, tube plate or the like to be butt welded and align the stem 16. An insulating bush 74 fits over the inner end of the sleeve 72 and this bush has an inset electrical ring contact 76. When the stem 16 is inserted into a bore, the contact 76 can be arranged to complete an electrical circuit to a control panel (not shown) once the stem has been inserted fully and the electrode is correctly aligned with the weld to be made.

The end of the distributor 14 is in the form of a shaft (not shown) and extends into a worm-reduction gear box 80. This box has an input spindle 82 carrying a cog 84 (see Fig. 2) meshing with a cog 86 on an output spindle 88 of a reduction gear 90. This reduction gear 90 is integrally formed with the drive motor 18 which is supported by the body 12.

In this way when the motor 18 operates, the distributor 14 and stem 16 are rotated.

The motor 18 also has an output shaft 92 at its upper end and this is joined to a tachometer 94 by a flexible coupling 96. This tachometer 94 also supported on the body 12 is used to maintain the speed of rotation of the motor constant in the conventional manner.

Power for actuating the motor 18 and tachometer 94 is supplied by a lead (not shown) which for ease of assembly fits into a socket 88 from which electrical leads pass to the motor and tachometer.

As will be appreciated the bore welding torch of the invention is quite simple and has a number of advantages including a very accurate and even speed of rotation of the stem 16 during welding.

WHAT WE CLAIM IS: 1. A bore arc welding torch in which a non-consumable electrode is carried by a rotatable stem, a distributor joined to the stem is rotatably positioned within a metal body, and means are provided for rotating the stem and distributor relative the body during the making of a weld, and in which the distributor has a first metal part acting as a commutator for cooling water to cool the electrode, this first metal part being insulated from a second metal part of the distributor acting as a commutator for the welding current by an electrically insulating material part, the stem having inner and outer tubes providing passages for the cooling water to pass along the stem to cool the electrode and return along the stem, the inner tube being of electrically insulating material to prevent conduction between the first and second metal parts of the commutator and the outer tube being of electrically conductive material and arranged to conduct the welding current to the electrode.

2. A bore welding torch as claimed in Claim 1 wherein the torch body carries an electric motor for rotating a stem projecting from the body and carrying a welding electrode, the speed of the electric motor being controlled by means of a tachometer so as to keep this substantially constant.

3. A bore welding torch as claimed in either Claim 1 or 2 in which rotary seals are provided between the distributor and outer metal body.

4. A bore welding torch as claimed in any of the preceding claims in which the metal parts of the distributor and outer body are made of brass.

5. A bore welding torch as claimed in any of the preceding claims wherein the second metal part of the distributor receives welding current by means of a brush connected to a stationary current outlet in the body which bears against a cylindrical outer surface of the metal part.

6. A bore welding torch as claimed in any of the preceding claims in which the second part of the distributor also acts as a commutator for the inert shielding gas supply which passes through a stationary inlet bore in the metal body to an annular recess in the second metal part from whence it passes via a bore in this part to a passage along the stem to escape in the region of the welding electrode to blanket the weld region.

7. A bore welding torch as claimed in any of the preceding claims in which the distributor is driven relative to the body by an electric motor which is supported by the body of the torch.

8. A bore welding torch as claimed in any of the preceding claims having an outer ceramic tube within which the inert gas is arranged to flow and within which the inner and outer tubes for the cooling water are positioned.

9. A bore welding torch as claimed in Claim 8 in which a metal sleeve surrounds the ceramic tube over part of its length to fit into the bore of the part to be welded.

10. A bore welding torch as claimed in Claim 9 in which a bush is fitted over the metal sleeve and carries an electrical contact to complete a circuit to signal when the torch is correctly positioned within a bore.

11. A bore welding torch substantially as hereinbefore described with reference to the accompanying drawings.

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

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. motor 18 which is supported by the body 12. In this way when the motor 18 operates, the distributor 14 and stem 16 are rotated. The motor 18 also has an output shaft 92 at its upper end and this is joined to a tachometer 94 by a flexible coupling 96. This tachometer 94 also supported on the body 12 is used to maintain the speed of rotation of the motor constant in the conventional manner. Power for actuating the motor 18 and tachometer 94 is supplied by a lead (not shown) which for ease of assembly fits into a socket 88 from which electrical leads pass to the motor and tachometer. As will be appreciated the bore welding torch of the invention is quite simple and has a number of advantages including a very accurate and even speed of rotation of the stem 16 during welding. WHAT WE CLAIM IS:

1. A bore arc welding torch in which a non-consumable electrode is carried by a rotatable stem, a distributor joined to the stem is rotatably positioned within a metal body, and means are provided for rotating the stem and distributor relative the body during the making of a weld, and in which the distributor has a first metal part acting as a commutator for cooling water to cool the electrode, this first metal part being insulated from a second metal part of the distributor acting as a commutator for the welding current by an electrically insulating material part, the stem having inner and outer tubes providing passages for the cooling water to pass along the stem to cool the electrode and return along the stem, the inner tube being of electrically insulating material to prevent conduction between the first and second metal parts of the commutator and the outer tube being of electrically conductive material and arranged to conduct the welding current to the electrode.

2. A bore welding torch as claimed in Claim 1 wherein the torch body carries an electric motor for rotating a stem projecting from the body and carrying a welding electrode, the speed of the electric motor being controlled by means of a tachometer so as to keep this substantially constant.

3. A bore welding torch as claimed in either Claim 1 or 2 in which rotary seals are provided between the distributor and outer metal body.

4. A bore welding torch as claimed in any of the preceding claims in which the metal parts of the distributor and outer body are made of brass.

5. A bore welding torch as claimed in any of the preceding claims wherein the second metal part of the distributor receives welding current by means of a brush connected to a stationary current outlet in the body which bears against a cylindrical outer surface of the metal part.

6. A bore welding torch as claimed in any of the preceding claims in which the second part of the distributor also acts as a commutator for the inert shielding gas supply which passes through a stationary inlet bore in the metal body to an annular recess in the second metal part from whence it passes via a bore in this part to a passage along the stem to escape in the region of the welding electrode to blanket the weld region.

7. A bore welding torch as claimed in any of the preceding claims in which the distributor is driven relative to the body by an electric motor which is supported by the body of the torch.

8. A bore welding torch as claimed in any of the preceding claims having an outer ceramic tube within which the inert gas is arranged to flow and within which the inner and outer tubes for the cooling water are positioned.

9. A bore welding torch as claimed in Claim 8 in which a metal sleeve surrounds the ceramic tube over part of its length to fit into the bore of the part to be welded.

10. A bore welding torch as claimed in Claim 9 in which a bush is fitted over the metal sleeve and carries an electrical contact to complete a circuit to signal when the torch is correctly positioned within a bore.

11. A bore welding torch substantially as hereinbefore described with reference to the accompanying drawings.