Improvements in or relating to temperature regulating devices

摘要

606,436. Automatic control systems for air heating devices. HANNAH, S. H. Sept. 28, 1945, No. 25252. [Class 38 (iv)] In an air or other fluid temperature regulating system, electric heaters are cumulatively switched into or out of circuit, at a controlled rate, by a switching device associated with a single temperature responsive device. At the commencement of the heating process, the minimum temperature contacts 1 of the thermometer will be closed, the switch SS is in the extreme clockwise position, as shown. On closing the start button STB the main contactor coil M and relay TRR are energized, thus energizing the main heater MH, which is continuously in circuit and a relay, HR, whereby all the subsidiary regulating contacts are operated so that all the auxiliary heaters RH1 &c. are initially employed. On the air temperatures rising to the predetermined upper limit, the thermometer arm 3 makes at contact 2, the high temperature relay TRL and the solenoid LS are energized, the latter with D.C. from the rectifier R. The relay coil HR is de-energized, the contacts IHR, IHR, &c. are opened, but the coils HI, H2, &c. remain energized through contacts H11, H21, &c. which comprise a differential system effecting a reduction in the tendency of the system to heat. The switch SS is rotated in an anticlockwise direction, by the solenoid LS, thereby cutting out auxiliary heaters by interruption of the subsidiary contacts H6 &c. at a rate set by an adjustable time-lag fitted to solenoid LS, until the relay TRL opens. Continuous back and forward movement of the switch S, under the control of the switch arm 3 maintains the system air temperature between the limits. Upon completion of the work, the stop button SPB is pressed and all heater circuits are broken. A circuit, through contact 18 of switch SS contacts SSR1, SSR11 to the rectifier R remains closed and the relay RS is energized and rotates SS to the extreme clockwise position, wherein the contacts SSR1 are separated and the system is completely deenergized. In alternative arrangements, the selector switch may be operated by an electric motor and the heaters switched direct from the switch itself.