Patent GB-1170969-A (GB)
Title: A System for Controlling Secondary Clocks from a Master Clock Location.
Inventor: DURIS RUDOLPH MARTIN
IPC: G04C13/03
Filed: 1967-06-28
Abstract: 1,170,969. Electric clocks. EDWARDS CO. Inc. June 28, 1967 [Dec.27, 1966], No.29761/67. Heading G3T. In a system for controlling a secondary clock by a master clock 10, the secondary clock has first resetting means 15 and second resetting means, the first resetting means being operable to drive the secondary clock a variable amount depending on the duration of a power failure and the second resetting means being operable at an instant determined by the master clock to drive the secondary clock to a predetermined setting, switching means comprising a relay RE and a contact 45 being controllable by the master clock to render the first or the second resetting means operative. A device 11 which registers the length of time that power is cut off is associated with the master clock so that in the event of a power failure a switch contact 13 is made and a contact 12 broken. When the power is restored, power is supplied to both the reset drive motor 15 and a normal drive motor 14, the motor 15 driving a gear 28 of a differential 28-30 to add to the normal rate of rotation of a minute hand M. The normal rotation of the minute hand M is provided by the gear 29 rotated by the motor 14, the gear 29 rotating a minutes sleeve 27 by rotation of a spider sleeve 31. The reset motor 15 drives the gear 28 at a speed greater than time keeping speed and at the same time the device 11 is driven in reverse at a similar speed until it shows a zero indication, the contact 13 then being opened. During the resetting operation, the reset motor 15 is energized through the contact 45 of the relay RE, a reset solenoid RS therefore remaining de-energized. The master clock 10 is also reset by operating its reset motor at the same time as the secondary clock motor is operated. To provide an hourly resetting of the secondary clock, a clutch 49 is secured by a pin 55 to a clutch disc 48. A detent 49a is held away from a toothed wheel SEC by the pressure on the clutch of an arm 21a of a spring biased lever 21 pivoted at 60. At a given time, for example 58 minutes past each hour, the master clock energizes a relay 1HR so that a contact 18 is opened to cut off the A.C. supply to the relay RE and a D.C. pulse is applied to a wire 20 through a contact 63. The contact 45 therefore switches over to enable the reset solenoid RS to be energized. The D.C. pulse causes the solenoid to rotate the lever 21 until a detent 65 on the lever engages a slot 66 on a latch 22. The movement of the arm 21a allows the detent 49a of the spring loaded clutch to engage the wheel SEC which is driven at the rate of the seconds hand S. The clutch disc 48 is therefore quickly rotated and the end 50a of a spring 50 engages a slot 53 in a disc 52, after one revolution of the disc 48 if the secondary clock is on time or before one revolution of the secondary clock is slow. A detent 21c of the lever is raised out of a notch 67 of the disc 48 to allow rotation of the disc 48 and a projecting portion of the clutch 49 raises the latch 22 away from the detent 65 of the arm 21a about eight seconds after the start of the hourly correction to position the lever for a twelve hour correction. A stop 69 on the lever co-operates with a detent 68 to maintain the seconds hand in the 60 second position during hourly and twelve hourly resetting operations. Toprovide a correction once every twelve hours, a second pulse is transmitted by closure of a contact 63a by the master clock about eight seconds after the first pulse. Since the detent 65 is disengaged from the latch 22, the solenoid RS can fully actuate the lever 21. A detent 70 on the lever 21 therefore engages a notch 71 in a latch 23 pivoted at 72 so that, since the clutch 49 cannot be disengaged from the wheel SEC whilst the latch 23 engages the lever 21, the clutch makes several revolutions for the twelve hour correction until the hour hand H indicates the same hour as the master clock. At the termination of the correction the latch 23 engages a pin 74 on the hour wheel HR to disengage the detent 70 from the notch 71 thus permitting the returning of the resetting devices to their normal positions on rotation of the disc 48 to the position shown in Fig.1.