Patent GB-417204-A (GB)
Title: Improvements in or relating to electrical indicating and controlling systems
IPC: G05D23/20
Filed: 1933-04-13
Abstract: 417,204. Regulating combustion. BAILEY METER CO., 1050, Ivanhoe Road, Cleveland, Ohio, U.S.A.-(Assignees of Ryder, J. D. ; 11448, Euclid Avenue, Cleveland, Ohio, U.S.A.) April 13, 1933, No. 11093. Convention date, April 14, 1932. [Class 51 (i).] In a system for indicating, recording, and regulating the temperature of a furnace, two motors are controlled in accordance with the variations of temperature through the medium of thermionic apparatus, one of the motors effecting regulation of the temperature and the other operating an indicator. The system is similar to that described in Specification 417,203 wherein a thermocouple 4 is connected in a Wheatstone bridge circuit which when disturbed positions a galvanometer pointer 23 so that it makes contact with one or other of the cam-operated contacts 24, 25 to control the electric motors 5, 13 through the intermediary of thermionic valves 17, 18. The valves are oppositely connected and are arranged normally to supply alternating current to the motors which remain stationary due to the equal and opposite torques developed by the alternate half waves. Operation of the galvanometer contact 23 into engagement with contact 24 or 25 stops the operation of the corresponding valve in order that unidirectional current may be produced in the motor circuits to cause rotation in the appropriate direction. The motor 5 operates an indicator arm 9 which co-operates with a scale 10 and a recording chart 11 and also controls a contact 20A which co-operates with the resistance 20 to rebalance the bridge. Corrections for the varying temperature of the cold junction of the thermocouple are introduced into the bridge circuit by a thermometric contact device 64. The bridge circuit is periodically standardized against a standard cell 61, which is switched into the bridge circuit by a cam-operated switch 52. Standardisation is effected by a motor-controlled variable resistance 22. The motor 13 controls the fuel supply valve 3 of the furnace and the system is capable of regulating the temperature of the furnace within relatively wide limits. In the modification shown in Fig. 2, the system is arranged to maintain a constant temperature in the furnace. Instead of operating the motors 5, 13 simultaneously under the control of common thermionic discharge apparatus, the motors are switched alternately into the bridge circuit by switch 67 and are controlled by individual thermionic apparatus 72, 73 ; 76, 77. The temperature at which the furnace operates is predetermined by the variable resistance apparatus 87, 88, 92. The pointer 9 of the indicating apparatus carries a cam which is set to position a mercury switch 94 in its neutral position when the indicator records the predetermined temperature. The mercury switch controls a motor 84 which adjusts resistances 78, 79 in accordance with departures from normal temperature. A further resistance 81 included in the bridge is controlled by the regulating motor 13 which balances the bridge and regulates the fuel supply to maintain the temperature at the value predetermined by the setting of the device 92. Automatic switches 106, 107 are provided for limiting the travel of the motor 13. Contacts 105, 108 also are provided so that in the extreme limits of the travel of the valve, a short-circuit across resistance 109 is opened and the sensitivity of the galvanometer decreased.