Patent GB-425872-A (GB)
Title: Improvements relating to apparatus for detecting suspended matter in fluids
IPC: G01N21/53
Filed: 1934-08-23
Abstract: 425,872. Smoke detectors. KIDDE & CO., Inc., W., 60, West Street, Bloomfield, New Jersey, U.S.A. Aug. 23, 1934, No. 24308. Convention date, Sept. 1, 1933. [Class 47 (i)] In a system for detecting smoke or other suspended matter in fluids of the kind employing a light-sensitive element normally illuminated by a source of light, means is provided for maintaining a constant voltage at the light source, for giving an alarm if the light source fails or if its voltage fluctuates beyond certain limits, and for preventing operation of the smoke alarm elements due to failure of the light source or decrease of its voltage. Further, means is provided for breaking the circuit of the voltage-regulating means if the light source fails. The main supply terminals, at which the voltage may fluctuate, are shown at E, O. Regulated positive voltage for energizing the source of light 112 is obtained from the regulator terminal III (L<1>) the negative terminal being IV (L<2>). A light-sensitive element 113, of the type adapted to generate an E.M.F. when illuminated, is connected in circuit with a galvanometer relay M.G.R., which is balanced so long as normal illumination of the element 113 persists. When smoke occurs, the relay M.G.R., closes a contact 121 to close circuit through, and energize, a relay 123. The armature 128 of the latter then closes the energizing circuit of the smoke alarm gong 118 and lamp 119. Failure of the light source causes de-energization of a relay 105 which is in circuit with it. Contact 104 of this relay then opens to break the circuit of the smoke alarms 118, 119 and so prevent a false alarm, and also to break circuit to the terminal L2 so as to prevent overloading of the voltageregulating elements. Contact 116 closes to close the energizing circuit of a trouble bell 44 and lamp 45. The unregulated positive voltage at E is applied to a regulating rheostat W which is controlled by a motor 13, 14. This motor is controlled through the intermediary of a galvanometer relay GR which is arranged in a Wheatstone bridge system including two neon glow tubes G, T and a series of resistances A .. D. The galvanometer is arranged between a point S of constant voltage and a point F at which fluctuations in the mains voltage are effective. Consequently, such fluctuations cause movement of the galvanometer armature. If the voltage falls, the armature closes a circuit at 3 to energize a relay 1. The armature 10 of this relay then closes circuit at 8 to cause energization of the motor field 13, and the armature 20 closes circuit at 18 to energize a relay 21. This closes, at 25, a circuit through the motor armature 14. The motor then drives the rheostat W to regulate the voltage at terminal L<1>. When the normal voltage has been re-established the contact at 3 is opened and the motor stops. The relay 1 also opens a normallyclosed contact 108 in the energizing circuit of the smoke alarms 118, 119, so that these alarms cannot function until normal voltage has been re-established. If the voltage rises, the galvanometer relay GR closes circuit at 32 to energize a relay 31, the armature 37 of which closes circuit at 35 to energize the motor field 13. Since the relay 21 is not energized, the motor armature circuit is closed at 38, so that the current through the motor is reversed and the rheostat W is oppositely driven to reduce the voltage. Limit switches 40<1>, 40<11>, and 41 are associated with the relays 21 and 31 and act to break the motor circuit when the rheostat reaches either limit of movement, and also to ensure that the energizing circuit of the smoke alarms 118, 119 remains open at such times. When the limit switches function, they close an energizing circuit through the trouble bell 44 and lamp 45.