Patent GB-754972-A (GB)
Title: Improvements relating to electrical time switches
IPC: G04C23/16
Filed: 1954-06-14
Abstract: 754,972. Time switches. GENERAL ELECTRIC CO. June 14, 1954 [June 19, 1953], No. 17425/54. Class 38(5) A switching device for closing contacts at a pre-set time and in which the contacts may also be manually operated "on" and "off", the device being set for automatic operation by movement of the manual "on" "off" knob to a third "auto" position, comprises a synchronous electric motor 9 having an output shaft 14 which drives through gears 15, 16 a shaft 17, carrying a second hand 3.. The minute hand 4 connected to a shaft 18 is driven from gear 19 attached to the shaft 17, the gear 19 meshing with a gear 20 freely mounted on a shaft 21, a spring clutch 22 fixed to the shaft 21 bearing against the gear 20 and a gear 23 fixed to the shaft driving a gear 24 fixed to the shaft 18. The hour hand 5 and its shaft 25 are driven from gear 26 attached to the shaft 18, the gear 26 driving a gear 27 freely mounted on the shaft 21 and connected to a gear 28 which drives a gear 29 fixed to the shaft 25. The pointer 1 is set to the time at which the contacts are to be closed with reference to the hour numerals 8, by a knob 32 connected to a shaft 36 slidable within the shaft 21, the knob being pushed in to engage a key 35 on the shaft 36 with a slot 37 in a shaft 38 connected to a gear 39, rotation of the knob then causing the gear 39 to rotate a gear 34 connected to the pointer shaft 33. The hands 4, 5 may be adjusted to indicate the correct time by pulling the knob 32 to engage the key 35 with a slot 40 in the shaft 21, the clutch 22 slipping so that the gear 20 does not rotate when the knob is turned. The opposed faces of the hour gears 29 and pointer gear 34 have double-sloped cam projections 43, 42, respectively, which co-operate to move the gear 29 away from the gear 34, the shaft 25 being slidable on the shaft 18 for this purpose and the gear 28 being elongated so that the gear 29 always remains in engagement therewith. The initial angular extent between the projections 42, 43 is determined by the setting of pointer 1 and the gear 29 is biased towards the gear 34 by an insulating arm 44 urged towards the gear 29 and also upwardly by a hairpin spring 45 fixed in a plate 53 and received in a notch 59 in the arm 44. A slot 55 in the arm 44 receives a blade 50 carrying contacts 51 at its free end, the contacts 51 cooperating with the arms 48, 49 of a fixed U-shaped contact 47, whereby whenever the arm 48 or 49 is engaged by a contact 51 the circuit is completed to an outlet 46 connected across the supply 12. A knob 2 having "on", "off", and "auto" positions operates a shaft 60 having projections 61, 62, the shaft being biased axially by a spring 67 to hold the projection 62 in one of three depressions 64...66 in a mounting plate 31, the depressions corresponding to the three knob positions. The projection 61 co-operates with a catch 63 on the arm 44 so that when the knob 2 is moved to the "on" position the arm 44 is moved down to close the contacts 51, 49 and the engagement of the projection 62 and the depression 66 holds the contacts closed until the knob is moved to the central "off" position whereupon the spring 45 lifts the arm 44 to open the contacts 51 which are maintained in this condition by the engagement between 62, 65. When the knob 2 is moved to the "auto" position to separate 61, 63, upward movement of the arm 44 is prevented by a projection 57 thereon engaging the end of a slot 58 in the plate 31; however, at the preset time when the projections 42, 43 engage the arm 44 is tilted by the gear 29 and the.projection 57 leaves the slot 58 whereby the spring 45 can lift the arm and close contacts 48, 51, the latter remaining in this condition until the knob 2 is moved to the "off" position. When the knob is "off" the spring 45 in unable to close the contacts in the event of the arm 44 being tilted by the gear 29.