GB504157A - Improvements in or relating to welding pliers - Google Patents

Abstract

504,157. Control systems for resistance welding. KELLER & KNAPPICH, GES. April 19, 1938, No. 11794. [Class 38 (iv)] [Also in Group XXII] In a hand-operated electric-butt welding pliers having a pair of handles 17, 20 pivoted together at 19, the wires 1, 2 to be welded are secured in jaws to arms 7, 8, the arm 8 being integral with the handle 17 and the arm 7 being screwed to a spindle 23 passing freely through a socket 22 on arm 8. The arms are separated by a spring 40 and are connected by toggle links 31, 32 and the spindle 23 passes through the handle 20 and carries a nut 28 between which and a bracket 26 on the handle 20 is placed the upset pressure spring 29. On pressing together the handles the spring 29 is compressed and spring contacts 50, 49 and 46, 45 in control circuits are closed, the former by engaging a nose 48 on a nut fixed to the spindle 23 and the latter by an insulating sleeve 47. The welding current is applied through flexible leads from a transformer 64, Fig. 7. The primary circuit of the transformer 64 is controlled by a pair of contactors, the coils 55, 53 of which are connected at one end to the switch contacts 46 through the secondary 52 of a control transformer. The contact 40 and contact 45 are conductively connected together via the handle 20. When the contacts 49, 50 and 45, 46 are closed, the coil 53 is energized by way of a normally closed contact 54, thus closing the contacts 56-59. The coil 55 is thus energized through contact 58 and the contacts 60, 61, 63 are closed to connect the welding current. The coil 53 at tHis stage remains energized by way of contact 59 and contacts 49, 50, when the contacts 49, 50 open by withdrawal of the nose 48, the coil 53 is de-energized and the contacts 56-59 open. The coil 55 still remains energized by way of contact 63 and remains so until the handles are cleared by a spring 40a and the contacts 45, 46 thus opened.