GB1450413A - Encapsulating electrical elongate contact units - Google Patents

Abstract

1450413 Manufacture of encapsulated contact units; turret machines for making sealed electrical devices COMTELCO (UK) Ltd 18 Feb 1974 [20 Feb 1973] 8276/73 Headings H1J and H1N Encapsulation of a contact sub-assembly 16 (e.g. in which two elongate contacts are bridged by a temporary rigid fusible link, Fig. 2 not shown) is achieved by mounting the subassembly concentrically with an encapsulating glass tube 17 with one end of the assembly protruding from the tube, introducing a hollow needle 2H into the tube and passing purge gas through the needle, using a flame to seal a first end of the tube to the sub-assembly, Fig. 6, heating the tube over the length corresponding to the finished capsule, Fig. 7 and using a flame to make a second seal in the tube, Fig. 9, the purge gas being passed until after the second seal is made. The apparatus comprises a turntable 13 with rotatable workheads 12 which are indexed in turn to stations at which the respective operations are carried out, the purge gas needle remains in the tube during movement of the turntable. The workhead is rotated at each work station during the 2-3 seconds that the turntable is stationary. At additional work stations, the parts of the device are placed on a workhead 12, with one end of the contact sub-assembly extending through a hole (12c Fig. 3 not shown) in the workhead beyond the encapsulating tube. The hole has chamfered edges (12D) for guiding the sub-assembly into the hole. The other end of the sub-assembly is bent to assist in maintaining the concentric relationship. At a second workstation purge gas needle 2H is introduced and gas flames preheat the tube (Fig. 4 not shown). At station 3, (Fig. 5) the lower end of thetubeis softened and at the next station, Fig. 6, the seal is completed. At station 5 the tube is heated to 450‹ to drive off contaminants, Fig. 7. At stations 6 and 7 (Figs. 8, 9 not shown) the glass at the vicinity of the upper seal is softened and the seal is made. At 7 or later the purge gas needle is withdrawn. Station 8 provides a slow cooling of the second seal, station 9 cuts the superfluous material from the tube and station 10 smooths off the cut ends (Figs. 10-12 not shown). At station 11 (Fig. 13 not shown) the device is removed and the workhead proceeds to station 1. A pulse of electrical energy melts the temporary bridge linking the contacts in the encapsulated unit. Additional work stations may further prolong cooling of the seals; the cutting off of superfluous material may be done on a separate apparatus. The contact subassembly may have appropriately situated glass beads to assist formation of the seals. By connecting a vacuum line to the open end of the tube before sealing, a reduced pressure may be produced in the capsule.