GB574169A - Improvements in or relating to electric clocks - Google Patents

Abstract

574,169. Electric clocks. DENTON', L. E. Oct. 19, 1943, No. 17196. [Class 139] In an electrically-maintained time-mechanism, a lever is rocked by the balance-wheel spring as the latter commences to wind or unwind, the rocking movement continuing until the lever engages one of a pair of fixed electric contacts,. further movement of the spring then causing flexing in the normal manner. The lever 6, Fig. 1, mounted to rock about a horizontal arbor 7 has its lower end forked at 8 to embrace the outside convolution of the spring 9 of a balance wheel 2. As the spring 9 expands and contracts, the upper end of the lever 6 plays between the adjustable screw contacts 10, 11. When the lever 6 closes the contact 11, Fig. 14, the charging circuit for a condenser 17 is completed through an electromagnet 19 which operates clock hands through ratchet mechanism 22. On the return swing of the balance wheel 2, the contact 10 is closed and the condenser 17 discharges through the contact 10 and the winding of an electromagnet 5 which attracts a bar 3 secured to the balance wheel staff 1 to impart a maintaining impulse to the balance wheel. The arbor 7 and the fixed electric contacts 10, 11 are mounted in a housing 12 which can be turned for regulating purposes about the axis of the staff 1 and which is extended as an arm 13 with an index 14 turned over a fixed plate 15 bearing a regulating scale. In a modification, Fig. 6, the outside convolution of the balance spring is anchored to the contact arm 6 which is bent over at right angles to engage the contacts 10, 11. In a further modification, Figs. 7, 8, the balance wheel 2 has a rim of non-magnetic material with an inset 24 of soft iron which passes between the polepieces 4a and 4b of the electromagnet 5 providing the maintaining impulses. In this arrangement, the outer end of the balance spring 9 is secured in an arbor 25 which carries the contact lever 6, the arbor 2 turning about its axis and rocking the lever 6 as the balance spring 9 oscillates. In the modification shown in Fig. 13, the fixed electric contacts 10, 11 are placed on the same side of the lever 6 which is pivoted at its centre to an arbor 7.