Abstract: A brushless slip ring includes a housing, a plurality of annular spaces disposed in the housing and spaced apart along a common longitudinal axis, and a cageless assembly of electrically conductive spherical balls freely rotatably disposed in each of the spaces. Each of the spaces is formed between radially inner and outer electrically conductive surfaces of a rotor and stator, respectively, and a pair of axially spaced retainer rings. The spherical balls conduct electrical current between the outer and inner surfaces. The balls are rigid and harder than the inner and outer surfaces and are arranged in an annular row. The balls occupy substantially the entire circumference of the space and are freely circumferentially movable relative to one another within the space for making contact with one another.

Abstract: An electric resistance welder comprises a frame and a movable arm mounted to the frame for gravitational movement relative thereto. A movable electrode is carried at an end of the movable arm. A stationary electrode is spaced opposite the movable electrode to accommodate a plurality of workpieces therebetween, with the movable electrode resting against the workpieces and gravitationally biased toward the stationary electrode. An electric pulse is conducted through the electrodes and workpieces for heating and softening the workpieces to enable the arm to accelerate toward the stationary electrode at the acceleration of gravity, whereby the movable electrode collapses the workpieces toward one another. A stop is arranged to be engaged by the arm for terminating travel of the arm when the movable electrode has traveled a predetermined distance toward the stationary electrode, and subsequent to termination of the electric pulse.