A simple, manually operated mechanical device will ensure a smooth and predictable motion when feeding filler wire into a molten weld pool in gas tungsten arc welding (GTAW). This device simplifies and/or reduces the requirements for a dexterous hand to hold and manipulate filler wire. This device will grant, to the GTAW process, a level of consistency and integrity heretofore unknown.

At present, GTAW is performed manually by trained welders. The most common version of the GTAW process for aerospace-related hardware involves the addition of filler wire in a molten weld pool. The diameter of the filler wire can range from 1/64 to 3/16 in. (0.4 to 4.8 mm). Traditionally, a welder uses one hand to hold and/or manipulate a welding torch while manipulating the wire with the other hand. To ensure the consistency and integrity of a weld, a welder must feed the filler wire into the molten weld pool in a selective and specific fashion in coordination with manipulation of the torch. In other words, the repeatability and reliability of manual GTAW is highly contingent on the human factor; that is, the welder's skill in manipulating a welding torch while simultaneously feeding filler wire into a molten weld pool. Clearly, the manual feeding of filler wire is a skill that requires physical dexterity (hand, finger, wrist) as well as precise hand/eye coordination. Not surprisingly, wide variations in hand, wrist, and finger movements have been observed from welder to welder and from time to time.

The present manually operated weld-filler-wire feeder is a means of reducing reliance on the welder's dexterity while increasing consistency and integrity. The wire feeder includes a metal frame with a knurled roller wheel mounted on a polyimide (Vespel or Torlon) bushing that promotes low-friction movement. This roller is attached to the center of the long axis of the metal frame. The frame ends are turned up as tabs perpendicular to the long axis where they protrude slightly above the top of the roller. Holes near the edge in each tab are aligned with each other and are centered on the width of the roller. These holes are then positioned where the inside diameter of the roller is approximately tangent to a point central to the holes. On the side of the frame opposite the roller, a loop (ring) is attached tangentially to the frame with a rivet that allows the loop to rotate about its attachment point. The loop is there to assist the welder in holding the device.

A length of filler wire is threaded through the holes in the end tabs by the welder, who aligns the wire across the roller. A small amount of tension is needed to keep the wire in contact with the roller so that it remains fixed in the frame when tilted out of plane and thumb pressure is briefly released from the wire. Because too much tension can cause undue friction and impede the pushing of the wire across the roller, to accommodate wires of different diameters, the welder can bend the frame very slightly up or down to apply the right amount of pressure against the roller. The device is then lightly grasped in the hand normally used to hold wire. The welder's index or middle finger is placed through the loop, and the frame is moved to place the device in a comfortable position across the upper palm and lower portion of the fingers. The thumb is then brought over the top of the wire and placed so it can be moved from near the back of the frame, across the roller, and toward the front of the frame. The wire is thus fed through the device at a steady rate to a predictable location; that is, in axial alignment with the holes and the roller.

In assuring a smooth, steady feeding of filler wire to a predictable location, this manually operated weld-filler-wire feeder advances the state of the art of GTAW. By overcoming the human-dexterity problems associated with manually feeding filler wire during GTAW, this device assures both consistency among welders and consistency between jobs performed by the same welder at different times. Because of its simplicity, the use of this device is easily learned, regardless of the user's previous skill or hand size. Because this device contains fewer parts than do other devices designed for the same purpose, it can be manufactured economically. Because it can be adapted to numerous filler wire diameters and can hold and manipulate multiple wires at the same time, its usefulness is assured across a broad spectrum. Of particular interest to the U.S. space program is the ability of this device to hold multiple wires simultaneously and thus to facilitate the welding of reactive alloys. An added benefit of this device is that it will keep wire clean by minimizing hand or glove contact. The device is expected to offer benefits wherever GTAW is performed - not only in the space program, but also in commercial settings.

This work was done by Daniel J. Rybicki of Lockheed Martin for Johnson Space Center.

This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to

the Patent Counsel
Johnson Space Center
(281) 483-0837

Refer to MSC-23026.