Patent GB-644438-A (GB)
Title: Improvements in or relating to time delay apparatus for controlling an electric circuit
IPC: G04F3/06
Filed: 1947-10-06
Abstract: 644,438. Time switches. SHARMAN, G. A. Oct. 6, 1947, Nos. 26822/47 and 7762/48. [Class 38(v)] A time switch is first set by moving a pointer 5 over a dial 4 and then the contacts 26a, 27a controlled thereby are closed, to initiate the set time interval, by pressing a plunger 28. At the end of the interval the contacts open and the switch resets in readiness for a further operation by again pressing the plunger. In Figs. 1-3, a spindle 7 rotatable by the pointer 5 has a collar 8 engaging a spring 9 by which it is frictionally held. A setting plate 10 on the spindle 7 has a projection 11, against which a spiral spring 17 urges a stud 12 on a disc 13 secured to a trip spindle 14 coaxial with the spindle 7. A synchronous motor 23 drives the spindle 14 through a differential gear comprising a planet wheel 18 secured to the spindle 14 and meshing with contrate sun wheels 20, 19, respectively driven by the motor gear train 22, and freely rotatable on the spindle 14. In use, the pointer 5 is moved to the desired time setting and the stud 12 follows the projection 11, the differential gear 18, 19, 20 idling during this movement. To initiate the set time interval, the plunger 28 is pressed, manually or electromagnetically, to flex the contact blades 26, 27 whereby a tongue 25 on the blade 26 engages a serrated disc 24 integral with the sun wheel 19, to lock the latter against rotation, and a spring-loaded latch 29 moves to hold the blade 26 flexed. On release of the plunger 28, the stem 28b thereof permits the blade 27 to move back and close the circuit to the driving motor 23 and also the circuit to be controlled. The motor 23 now drives the stud 12 back to the zero position where the stud 12 engages a tail 29a on the latch 29 which releases the blade 26 to open the contacts, and the tongue 25 disengages the disc 24 so that the differential gear can idle while the spring 17 returns the stud 12 into engagement with the projection 11 in readiness for a further operation. In an alternative construction (not shown) the drive between the motor 23 and the stud 12 is effected by axially displacing the spindle 14 so that a .gear thereon engages a member of the motor gear train 22, the spindle being displaced by a pivoted, spring-loaded fork which co-operates with the blade 26 so that the gears engage when the blade 26 is flexed. In a modification, Fig. 4, (not shown) the contacts can be manually closed for any desired time by the projection 11 engaging an abutment on blade 27 when the pointer 5 is rotated a little beyond its normal maximum time-setting position, in which condition, although the motor 23 is energized, the differential gear idles since the disc 24 is not engaged by the tongue 25. In a further construction, Fig. 5, the drive between the motor 23 and stud 12 is effected by mounting a pinion 33a of the gear train 22 on an arm 34 pivoted at 35, the free end of the arm being held by a spring in engagement with a hook 26b on the blade 26, so that when the plunger 28 is depressed, the pinion 33a engages a gear 36 on the spindle 14. The spindle 7 may be tubular and receive an extension of the spindle 14 carrying a pointer indicating the amount of delay which has expired, Figs. 7, 8, (not shown). An additional contact blade may be mounted above and engaged by the blade 26 to close an alarm circuit at the end of the time interval, Fig. 9 (not shown).