833,295. Welding by pressure. SCIAKY, D. Sept. 12, 1957 [Oct. 29, 1956], No. 28757/57. Class 83 (4). In a resistance welding-machine having a fixed lower electrode 16 and an upper movable electrode 14 carried by a vertically reciprocable arm, a gauging device is provided for detecting the upward movement of the movable electrode consequent upon melting and expansion of weld metal during welding, and comprises a cylinder 36 fixed to the arm, the cylinder forming the base of the device and having an upstanding tubular support 40, a piston 43 in the cylinder, a sleeve 50 in telescoping relation with the support and connected to the piston, a push-rod 60 suspended from the frame of the machine and having its lower portion extending within the support, a gripping element 55 fixed to the support and having telescoping relation with the push-rod, and an actuating member 62 for the gripping element fixed to the sleeve and in telescoping relation with the gripping element, the reciprocating movements of the piston being imparted to the sleeve to locate the member in either an operative or an inoperative position with respect to the gripping element. A spot welder comprises the fixed electrode 16 and the movable electrode 14 on a carrier 30 secured to a plate 27 movable by a plunger 26 in a cylinder 25, current being supplied to the movable electrode by bars 31 connected to one side of the secondary. A plate 34 is bolted to the plate 27 to support the cylinder 36 of the gauging device. The piston 43, Fig. 2, is pressed downwardly by a spring 45 and the cylinder 36 has a pressure fluid inlet 37 and a top cover 38 with the integral tubular push-rod support 40. The rod 46 of the piston 43 extends into the support 40 and is connected by a cross-pin 51, slidable in vertical slots in the support 40, to the sleeve 50 slidable on the support and carrying a nut 62 about the upper slit end of a collet 55, screwed into the upper end of the support 40, and surrounding the push-rod 60 depending from a container 61 fixed to a stationary arm 24 of the welder. The nut 62 does not close the upper flexible end of the collet when the piston 43 is in its normal lower position. The push-rod is connected by a hardened steel ball 83 and springs 85, 86 to a lever 71 in the container 61 pivoted at 72, 73 or 74 and carrying an adjustable screw 77 at the other end, the lever normally abutting a stop 81. The screw 77 engages a cantilever beam 88 clamped between blocks 90, 91 and carrying compression strain gauges 93 on its upper side and tension strain gauges 95 on its under side. In operation the electrode 14 is raised by the piston 26, the piston 43 being in its normal lower position so that the rod 60 can slide freely in the collet. The workpieces are placed between the electrodes and electrode 14 is lowered until a maximum pressure is exerted on the work. This pressure is somewhat reduced and pressure medium admitted to cylinder 36 to raise the piston 43 and thus the collet nut 62 which closes the split collet to grip the rod 60. The welding current is applied and melting of metal in the weld area is accompanied by expansion and upward movement of the electrode 14 and thus of the rod 60 to pivot the lever 71. The beam 88 is deflected and the strain gauges produce a voltage output. The operation of the welder may be automatically controlled. Specifications 811,338 and 833,294 are referred to.