CLOCK No. 12
Details of Mechanism
This Master clock has a seconds-heating pendulum, and is designed to furnish half-minute and seconds impulses. The former are effected by means of a count-wheel A having 30 teeth on its periphery. This wheel is propelled by means of a
paw B attached to the pendulum rod C, which rotates the count wheel A one tooth for each complete swing to and fro of the pendulum.
On the count-wheel A are two indentations diametrically opposite each other, which permit the pawl B to drop lower and engage the push rod D at every half minute. This push rod is attached to a contact spring E which, on being closed, permits an electric impulse to be sent out at every half minute.
At the top of the pendulum rod C and near to its point of suspension a
fitment is attached which alternately closes a contact on either side, sending
out one electric impulse every second. These two contacts FF are connected in
The pendulum is maintained in vibration by means of an electromagnet M, having extended pole pieces N, embracing the pendulum rod. Situated above these and attached to the pendulum rod is an iron armature P. The electromagnet M is energized by currents from a 4-volt battery controlled by the contacts Q.
So long as the are of oscillation of the pendulum lies outside a pre-determined minimum, the detent R trails over the notched agate S attached to the pendulum rod. When the arc has declined to the minimum the detent R engages in the notch, and on the return swing of the pendulum, acts as a toggle, raising the contact spring X so that the driving battery is momentarily joined to M, thus giving an impulse to the pendulum.
The clock must be vertical, and to ensure this a register T is provided at the lower extremity of the clock case, such that when the clock is in the correct position the point V is directly over T.
A rating nut W is provided, by means of which the clock call be adjusted to have. a slight gaining rate not exceeding 14 seconds per day.
The arrangement of contact springs adopted is such that the external circuit
closed through a resistance before the battery spring breaks its contact. This
lever prevents sparking at the main contact.
Last revised: July 05, 2020