GB671053A - Improvements in or relating to electric time switches - Google Patents

Abstract

671,053. Actuation of switches. BRITISH THERMOSTAT CO., Ltd. June 13, 1950. [June 13, 1949] No. 15702/49. Class 38 (v). [Also in Group XX] A time switch, particularly for prolonging the operation of a camera mounted in an aircraft after an associated gun has ceased firing, comprises motor driven cams 5, 6 which operate switches at predetermined times, e.g. as in Specification 642,878, the cams being fixed to a sleeve 7 which is loosely mounted on a shaft 3 and are only driven thereby when an electromagnetically-operated clutch is operative on de-energization of the magnet 8. The latter has a disc armature 9 which, when the magnet is de-energized, is pushed to the left, Fig. 3, by a spring 10 so as to engage teeth 13 on cam 5 and on a part 11 fast on the shaft. On energization of the magnet by closure of a pushbutton 25, Fig. 4, the armature is moved to the right and a spring 14 disengages the clutch so that a spring 18 can return the cams to their normal position as determined by an adjustable stop 23 and an abutment 22 on cam 6, the spring 18 having one end fixed to sleeve 7 and the other fixed at 19 to the casing. At the same time the gun (not shown) is fired and a relay 27 energized to close contacts 28 in parallel with a switch 15a operated by cam 5, thereby starting the camera 29. When the button 25 is released, the magnet 8 is de-energized and the cams are clutched to the shaft and the motor runs until its circuit is broken at the end of a time cycle at a switch 15 operated by a cam 6. The relay 27 is de-energized during this period, but the camera circuit is completed by switch 15a, being opened thereby at the end of the cycle.