Abstract: Ultrasonic transducers spring biased into seating engagement in a pair of opposed spot welding tips transmit and receive ultrasonic waves and associated circuitry measures the time of flight between the transducers which is a function of tip separation, workpiece temperature and nugget size which are indicators of the progress of a weld. The rate of change of flight time is measured and the weld current is adjusted early in the weld cycle to maintain a preset rate of weld growth. The weld current is terminated later in the cycle if the transit time rate falls below another preset value. Otherwise the weld current and termination time follow a standard schedule.

Abstract: A freestanding luminaire includes a floor-supported frame having a base adapted to rest on the floor, an overhead beam arrangement and an upright member connected at its lower end to the base and at its upper end to the beam arrangement so as to support it in a cantilevered fashion over a work surface. The beam arrangement includes a central longitudinally extending beam and a plurality of cross beams attached to the central beam at spaced locations therealong and extending in transverse relationship to the longitudinal extent of the central beam. The central beam is attached at one end to the upper end of the upright member of the frame and extends in transverse relationship outwardly therefrom. The luminaire also includes a plurality of lamps being preferably of the type which use fluorescent tubes, mounted to and extending between the cross beams.