GB695819A - A timing device for producing control signals spaced by accurately determined intervals - Google Patents

Abstract

695,819. Time switches. MINISTER OF SUPPLY. Nov. 12, 1951 [Nov. 17, 1950; March 3, 1951], Nos. 28124/50 and 5195/51. Class 38(v) [Also in Group XVIII] Rotation by hand through a predetermined angle of a knob 12 on a shaft 13 winds up a spring 20, rotates an escapement wheel 16, and by means of a cam arm 18 closes the circuit to a synchronous motor 22; on release of the knob 12 the spring 20 slowly returns the wheel 16 at a rate determined by the oscillation of a pallet 45 engaging the wheel 16, the oscillation of the pallet 45 being caused by a snail cam 44 driven by the motor. The motor drives the shaft 41 carrying the cam 44 by means of a dog clutch 32, 33 and at the beginning of the movement a pin 34 on the shaft 41 moves past a weighted spring blade 35, the return movement of the latter operating a bell crank lever 40, 42 and releasing a spring contact 46 to operate a "start" signal. The motor continues to run releasing the escapement wheel 16 step by step until the original position of the wheel 16 and shaft 13 is reached whereupon an arm 17 on the shaft restores the contact blade 46 operating a "stop" signal and the cam arm 18 breaks the motor circuit. Time setting is effected by operation of a knob 8 which frees a member 9 from a fixed toothed wheel 10 and allows a ring 3 to be moved relative to a fixed dial 7. The ring 3 carries a stop 19 engagable by an arm 15 on the shaft 13 and so limiting the angular movement of the knob 12. Fig. 1 (5195/51) shows a modified form of escapement in which a pallet 45a operated in the same manner as the pallet 45 is carried by a lever 60 pivoted at 63. Normally the lever 60 is held pressed against a stop 68 by a spring 66, but it can be hand operated if desired to release the escapement wheel 16a at a greater rate than that provided by the automatically operated pallet 45a. In this case the tooth 62 of the pallet 45a and a tooth 64 co-operate to form an additional pallet, movement of which releases the wheel.