Patent GB-490011-A (GB)
Title: Improvements in or connected with automatic overload switches
IPC: H01H71/20
Filed: 1937-02-04
Abstract: 490,011. Electrically-released switches. ZAHRADNIK, E., and HITSCHMANN, H. Feb. 4, 1937. No. 3323. [A Specification was laid open to inspection under Sect. 91 of the Acts, Aug. 6, 1937.] [Class 38 (v)] A reclosable automatic switch comprises a depressible plunger contact held in depressed position by a movable locking member itself held in resting position by a fusible body when in set condition, a spring being operative, on release of the locking member when the body is fused, to move the contact-part proper of the plunger inwardly of the switch, and initiates movement of the locking member from its initial resting position to a position in which the switch may be reclosed upon solidification of the fusible body simply by depressing the plunger. Fig. 1 shows a cartridge-shaped switch adapted for insertion in a socket, and comprising a metal casing 1 and pin 2 the protruding end of which serves as one contact. An opening-spring 6 bears on a collar 8 fast on the pin 2 and also on a sleeve 21 carrying circularly-arranged spring tongues 20, which are provided with lugs 23 urged by collar 22 on pin 2 to engage a split ring 19. A coil 12 is housed in a fusible mass 11 in a recess in an insulating cylinder 9, and is connected between conducting members 13, 14, the circuit being normally from casing 1 through member 13, coil 12, member 14, tongues 20, and sleeve 21 to pin 2. When the mass 11 is solid, it retains in place an insulating member 15 urged downwards by a weak spring 17 and acting as a locking member. On overload, spring 6 overpowers spring 17, and lifts pin 2, member 15, and tongues 20, but owing to expansion of the ring 19 on the conical surface of 9, the lugs 23 slip past that ring, and spring 17 restores the member 15 which is again held by the solidified mass 11. To reclose, pin 2 is depressed into contact again, whereupon the lower edge of collar 22 engages the sleeve 21 and restores the lugs 23 into engagement with ring 19. The pin 2 is then released and returns to the position shown, but without breaking circuit, since it co-operates with a follow-on spring contact. In a modification, Fig. 2, a split or resilient ring 25 is placed in a groove 24 in the pin 2 and located between the upper flange of the locking member 15 and a beading 26 on the member 14. On overload the part 28 of the pin pushes upwards and spreads the ring, which slips into the wider groove 27 and allows 15 to restore. In reclosing, the part 28 is forced through the ring into the position shown. Figs. 3, 4 show a form having a rotary cylindrical locking member 31 (shown developed in Fig. 4) provided with a series of slots 30 which co-operate with pins 29 on the pin 2. Member 31 is rotatable about bushing 14 fixed in a guide member 32 and housing an insulating coil-holder 34 in which is the mass 11. The coil 12 is connected to closure 35 and to bushing 14, which is slotted at 33a adjacent slots 33 in the guide 32 to allow movement of pins 29. Figs. 3, 4 respectively show the parts in open and closed position. On overload pins 29 are forced up the right-hand side of slot 33a and rotate the member 31 until the lower ends of the operative slots 30 coincide with edges 37 of slots 33. The member 31 being again held, reclosure is effected by again depressing the pin 2, whereupon 29 travel down the same slots 30 to the edge 37, then travel down this edge to the guide surface 36. When the pressure is removed, the pin 2 rises until the pins 29 are again in the position of Fig. 4, but at the next slots 30.