Narrow groove welding gas diffuser assembly and welding torch

A diffuser assembly is provided for narrow groove welding using an automatic gas tungsten arc welding torch. The diffuser assembly includes a manifold adapted for adjustable mounting on the welding torch which is received in a central opening in the manifold. Laterally extending manifold sections communicate with a shield gas inlet such that shield gas supplied to the inlet passes to gas passages of the manifold sections. First and second tapered diffusers are respectively connected to the manifold sections in fluid communication with the gas passages thereof. The diffusers extend downwardly along the torch electrode on opposite sides thereof so as to release shield gas along the length of the electrode and at the distal tip of the electrode. The diffusers are of a transverse width which is on the order of the thickness of the electrode so that the diffusers can, in use, be inserted into a narrow welding groove before and after the electrode in the direction of the weld operation.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention generally relates to automatic Gas Tungsten Arc
 Welding (AGTAW or GTAW) and, more particularly, to narrow groove welding
 torches for such welding, and to gas diffusers thereof.
 2. Related Art
 The AGTAW process uses welding equipment which, for a given set of welding
 parameters (current, voltage, travel speed and the like) performs the weld
 with minimal adjustments or corrections by the welding operator. As
 discussed below, particular problems are presented in providing a weld
 joint in a narrow groove in thick plates or heavy wall pipes.
 Typically, a weld prep is determined by a joint geometry which requires the
 least amount of welding and therefore, reduces distortion and material
 stresses. However, it is also necessary that the joint geometry provide
 good accessibility for the welding torch. Welding thick plates or heavy
 wall pipes requires a weld joint design which allows the welding torch, or
 at least the electrode thereof, to be placed in the joint and the work
 angle of the torch adjusted into the side wall to assure a good weld
 tie-in as a series of weld beads are deposited layer by layer until the
 joint is filled.
 One technique for welding thick plates requires the adjacent surfaces to be
 machined or otherwise prepared in advance in order to provide a "V" notch
 having a large volume to accommodate the welding torch. Unfortunately,
 while more maneuvering room is provided, multiple (24-150) weld beads per
 layer are required to fill the large volume created for the welding torch.
 Therefore, the welding process requires additional setup and machining
 time, preparation, filler material and shielding gas. In addition, the
 multiple bead layers are subject to distortion and internal stresses that
 result in decreased weld quality.
 In an effort to reduce welding time and cost, a joint design which requires
 a minimal amount of welding is preferable. Narrow groove welding is a
 process wherein successive single bead weld layers are applied directly on
 top of one another in a narrow groove or joint, thus requiring a minimal
 amount of root opening on the order of 0.250 inches and a 0.degree. side
 wall.
 Briefly considering the difficulties created by the geometry and
 restrictiveness of the narrow grooves of the type just described, the
 welding torch or associated hardware must be modified to weld the entire
 joint from the surface since such a joint design provides insufficient
 room to angle or maneuver the torch in the joint. In addition, it is
 difficult to obtain the amount of shield gas in the weld joint necessary
 to protect the molten weld pool and electrode from atmospheric
 contamination. Moreover, in an approach where a long bare electrode is
 inserted into the groove and an associated diffuser is placed outside of
 the weld joint, there can be problems with the amount of Argon shield gas
 used to protect the weld pool and electrode. For example, in a confined
 area or work space, the shield gas rapidly replaces the oxygen available
 to the welding operator, thereby creating a safety concern. More
 generally, the high volume of shield gas required also adds to the cost of
 the weld.
 SUMMARY OF THE INVENTION
 According to the invention, there is provided a diffuser assembly for
 narrow groove welding, as well as a welding torch assembly utilizing the
 diffuser assembly. An advantage to the invention is that the diffuser
 assembly can be used with any conventional or commercially available
 automatic gas tungsten arc welding torch.
 In accordance with a first aspect of the invention, a diffuser assembly is
 provided for narrow groove welding using an automatic gas tungsten arc
 welding torch including a tungsten electrode, the diffuser assembly
 comprising:
 a manifold adapted for adjustable mounting on the welding torch, said
 manifold including a central opening for receiving the welding torch, a
 shield gas inlet, and laterally extending manifold sections in
 communication with said gas inlet, the manifold sections each having a gas
 passage therein such that shield gas supplied to the inlet passes to the
 gas passages of the manifold sections; and
 first and second tapered diffusers respectively connected to the manifold
 sections of the manifold in fluid communication with the gas passages
 thereof and extending, in use, downwardly along the torch electrode on
 opposite sides thereof so as to release shield gas along the length of the
 electrode and at the distal tip of the electrode, the diffusers being of a
 transverse width which is less than that of the manifold sections and
 which is on the order of the thickness of the electrode so that the
 diffusers connected to the manifold can, in use, extend into a narrow
 welding groove before and after the electrode in the direction of the weld
 operation.
 Preferably, the diffuser sections each have a shape comprising a right
 triangle with a right angle portion disposed adjacent to the central
 opening.
 In accordance with a second aspect of the invention, a torch assembly is
 provided for narrow groove welding, the torch assembly comprising:
 a conventional automatic gas tungsten arc torch comprising torch body, and
 an adjustable electrode connected to the torch body and positioned to
 extend into a narrow welding groove, the electrode having a distal tip
 end; and
 a diffuser assembly mounted on the torch, the diffuser assembly comprising
 a manifold having a shield gas inlet, and first and second gas passages
 therein connected to the inlet; and first and second tapered diffusers
 respectively connected to said first and second gas passages of said
 manifold, and disposed before and after said electrode in the direction of
 the weld operation, the diffusers tapering down along the electrode to an
 area near the tip end of the electrode so as to release shield gas along
 the length of the electrode and in the area of the tip end, and the
 diffusers being of a transverse thickness on the order of that of the
 electrode so as to enable the diffusers to extend into a narrow welding
 groove before and after the electrode.
 Since, as indicated above, the diffusers of the invention are thin enough
 to be placed in a weld joint wherein they are disposed on opposite sides
 of, i.e., before and after, the welding electrode, the invention can be
 used with a very narrow, steep welding groove. For example, with a
 specific implementation of the invention, a narrow groove joint with a
 1.degree. side wall and a 0.250 inch root opening , or with a 0.degree.
 side wall and 0.3125 inch root opening, can be welded to a depth of 4.00
 inches. In addition, by placing the diffusers into the weld joint, the
 amount of shield gas necessary to protect the weld pool is greatly
 reduced.
 Further features and advantages of the present invention will be set forth
 in, or apparent from, the detailed description of preferred embodiments
 thereof which follows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring to FIG. 1, a welding torch assembly 10 includes a conventional
 AGTAW or GTAW torch 12 comprising a cylindrical torch body 14 and an
 elongated electrode 16. The electrode 16 is adjustable or repositionable
 with respect to the torch body 14 in order to maintain the minimum
 extension of the electrode necessary to weld. The torch 12 is mounted in a
 diffuser assembly 18 which basically comprises a manifold 20 and a pair of
 diffusers 22. The manifold 20 includes a central support member or sleeve
 24 defining a central passage in which the torch body 14 is received and
 laterally extending manifold sections 26, 28 are disposed on opposite
 sides of support sleeve 24. Manifold 20 further includes a central section
 30 to which is connected a shield gas inlet 32 through an inlet pipe 32a
 mounted on a mounting plate 32b affixed to central manifold section 30.
 The diffuser assembly 18 is also adjustable or repositionable on the torch
 body 14 in order to enable the diffusers 22 to be retracted from a joint
 as weld layers L are deposited as shown in FIG. 2.
 The diffusers 22 are of a triangular or tapered shape as shown in FIG. 1
 and are in fluid communication with the gas passages in manifold 20 so
 that shield gas supplied to gas inlet 32 passes through inlet pipe 32a to
 central manifold section 30 and thence to lateral sections 26 and 28 and
 ultimately to diffusers 22. The sides of the diffusers 22 that face and
 are parallel to the electrode 16 are open and provide for the release of
 the shield gas along the length and distal end of the electrode 16.
 Preferably, the electrode 16 comprises a tungsten electrode, while the
 triangular-shaped diffusers 22 and manifold 20 are preferably formed from
 stainless steel sheet metal.
 FIG. 2 shows the diffuser assembly 18 mounted on the torch body 14 in use
 in welding a narrow groove G in a block B. In operation, during welding,
 the torch body 14, and the manifold 20, remain outside the narrow groove
 G, while the electrode 16 and the triangular-shaped diffusers 22 extend
 into the narrow groove. The diffusers 22 are positioned in the narrow
 groove such that one diffuser is behind, and one diffuser is in front of,
 the electrode 16 as the latter travels through the joint. The electrode 16
 is positioned to reach or extend to, the bottom of the weld, and both the
 electrode 16 and diffuser assembly 18 are repositioned with respect to the
 weld joint depth, as necessary due to the amount of weld metal deposited.
 Although the invention has been described above in relation to preferred
 embodiments thereof, it will be understood by those skilled in the art
 that variations and modifications can be effected in these preferred
 embodiments without departing from the scope and spirit of the invention.