Controllable-force wire advance arrangement for electric-arc welding applications

A force-adjustable wire advancing mechanism for converting rotations of a motor shaft to a linear advance of a wire electrode into an arc-welding system is described. A pair of skewed rollers are carried in the front part of a two-part feed housing on a pair of radially reciprocable pistons, which in their innermost positions are effective to engage the rollers with the wire to advance the wire as the housing is rotated. In order to bring the rollers into operative position, a motion-translating element fixedly connected to the rear part of the housing and to the motor shaft is threaded onto a rear surface of the front part of the housing, and includes an integral outer conical guiding element that is cooperable with like ends of a pair of two-armed levers pivotally supported in the housing. A pair of biasing springs urge the pistons outwardly against the opposite ends of the levers, and a second pair of rollers are carried in recesses on the first ends of the levers for engagement with the opposed portions of the conical guiding element. With this arrangement, relative turning movement of the front and rear parts of the housing will cause the conical element to move axially with respect to the front part of the housing, thereby varying the force by which the levers force the skewed rollers, via the pistons, against the advancing wire.