Patent GB-432932-A (GB)
Title: Improvements relating to electrically driven turret clocks, high duty or power current time switches and the like
IPC: G04C3/16
Filed: 1934-08-28
Abstract: 432,932. Electrically - driven clocks and time-switches. LANDIS & GYR AKT.- GES., 1, Hofstrasse, Zug, Switzerland. Aug. 28, 1934, No. 24749. Convention date, Sept. 8, 1933. [Class 139] Clock hands or a time-switch are normally driven by an A.C. synchronous motor 3 and a reserve auxiliary movement 14, during A.C. supply failure, drives a device 24, 22 which registers the period of current failure so that on current again flowing, the elapsed time is made good by the synchronous motor drive. The rotor 2 normally drives a shaft 1, wheel 5, train 6, 7, and reduction train 9 leading to the hands 31. A spring 4 pulls shaft 1 up bodily so that wheels 5 and 6 mesh, and the stray flux of motor 3 rotates armature lever 12 counterclockwise about pivot 12<a> so that its left hand end brakes the balance 13 of the auxiliary movement 14. The driving spring of the latter is wound up during the normal A.C. motor drive by ratchet and pawl 26 and eccentric 27 on a wheel 29 of the train 9. In a differential gear 17, sun-wheel 19 is connected through friction coupling 20 with the train 9, sun-wheel 18 (loose on shaft 23), is connected to movement 14 and the shaft 23 of the planet wheel 21 carries an arm 24 coacting with a bell-crank 25, 22. When the A.C. supply fails, shaft 1 stops, spring 11 pulls lever 12 clockwise so that balance 13 is freed and part 15 is depressed to cause wheel 5 to engage wheel 8, and the movement 14 drives sun-wheel 18 and arm 24. As soon as the arm 24 leaves the end of arm 22 the arm 25 rocks couhter-clockwise to lock the part 15 down and the arm 24 rotates farther away from arm 22 as the current failure continues. When current is restored, the motor 3 and shaft 1 drive the hands 31 at increased speed (e.g. ten times normal speed), through train 5, 8, 9 and also through coupling 20, drive the differential 17 backwards so that arm 24 is rotated backwards until, after an angle corresponding to the period of failure, the arm 24 rocks arms 22, 25 clockwise to release part 15. Shaft 1 is then raised by spring 4 so that wheel 5 returns into mesh with wheel 6 for normal drive ; and lever 12 is rocked counterclockwise and stops the balance 13. Instead of driving the hands 31 at higher speed, when the A.C. supply is restored, by cutting out the gear train 6, 7, the synchronous motor may have two rotors of different speeds ; at current failure one rotor is brought out of, and the other rotor into, the rotary field of the rotor. In a modification, Fig. 2, the synchronous motor 3 is driven from an A.C. supply and drives one side 35 of a differential gear 34. The auxiliary movement 14 drives one side 43 of a second differential gear 42 and a motor 38, fed from a D.C. supply 51, drives the other side 36 and 45 of each differential gear. During A.C. supply failure, movement 14 rotates a disc 49 so that the insulated spot 47 leaves the contact blade 48 and the circuit 50 is closed to drive the motor 38 which thereupon rotates the clock hands through gears 37, 36, 39 and also through the lower differential returns disc 49, so that spot 47 breaks the circuit 50. Movement 14 then moves disc 49 again, so that whilst the A.C. supply fails the motor 38 is energized intermittently.