GB633440A - Improvements in and relating to light sensitive signalling devices - Google Patents

Abstract

633,440. Visible signalling-apparatus. LONDEX, Ltd., and BESSON, A. P. June 2, 1947, No. 14519. [Class 118 (ii)] [Also in Group XL (b)] A flashing signal controlled by a photo-cell so that it operates only when the ambient illumination reaches a predetermined low level has its timing mechanism stepped by an electromagnetic relay which also derives a high voltage from a low voltage supply for application to the photo-cell circuit. As shown, a timing camshaft 1 is rotated by a self-interrupting relay 5 which rocks a cradle 2 carrying a pawl which rotates the shaft through a ratchet-wheel 3. The speed of the shaft is maintained constant by a geared eddy current disc 7 and a spring 6 loaded by the rocking of the cradle and attached to the periphery of an eccentric cam to maintain its torque constant. When the relay interrupts it closes a circuit containing a condenser 15 and rectifier 36, this condenser being charged to a high voltage by the surge produced in the relay coil. This high voltage is applied to a circuit comprising a further condenser 17 and a photo-cell 18 which conducts if the day is sufficiently bright. In this case, on closure of contacts 21 by a cam on the timing shaft, a relay 19 will open the circuit to the flashing lamp 20. If the day is dull, relay 19 will fail to operate and the lamp will flash its characteristic signal by a cam 27. The contacts of relay 19 are normally held open by a lever 23 and released by a cam 25 just prior to the closure of contacts 21 by cam 22.