GB450844A - Improvements in and relating to electro-optical switches - Google Patents

Abstract

450,844. Control systems for incandescent lamps. GEFFCKEN, H., 9, K÷nig- Albert-Strasse, Naunhof, near Leipsic, and RICHTER, H., 3, Wiederitzscherstrasse, Leipsic, Germany. Jan. 21, 1935, No. 2024. Convention date, Jan. 20, 1934. [Class 38 (iv)] [See also Group XL] In photocell apparatus for switching lamps on at night and off in the morning, the sensitivity is changed at each operation so that switching-off is effected at a lesser strength of daylight than that by which switching- on is effected ; and delay mechanism is provided to prevent the occurrence of hunting. The change may be produced by an alteration of circuits or by interposition of screens before the photocell. In the arrangement shown in Fig. 1, in which the lamp-controlling relay 5 is controlled through a valve 4 by a photocell 1, the parts 2 and 3 being resistances, the sensitivity is altered by switches 6 and 8 under the control of a delay-producing mechanism 9 utilizing a wiper contact or a thermal or electrostatic timing-device. In the arrangement shown in Fig. 2, the pendulum 20, which turns the lamp on and off by means not shown, closes contacts 16 in one position and contacts 15 in another ; in this way it controls the connections of a bridge of which the valve 4 and relay 12 are members, and so determines the sensitiveness of the relay. When the illumination of the photocell 1 increases in the morning, relay 12 causes relay 18 to move the pendulum 20 into the position shown, switching off the lamps. At the same time it closes contact 16 and opens contact 15, so as to alter the balance of the bridge and decrease the sensitivity of the device. This change of sensitivity causes relay 12 to reverse and pendulum 20 to be released, coil 17 being now energized instead of coil 18. But the latter now engages the toothed wheel 23 and holds it until the daylight has increased sufficiently to re-energize the relay 18 at the new threshold of sensitivity. The wheel 23 then revolves until a stop 26 carried by it engages a tooth 25 on the pendulum 20. A similar process in the reverse sense takes place at night. Fluctuation of the illumination during the rotation of the wheel 23 causes the pendulum 20 to fall back and lock the wheel temporarily.