Patent GB-901706-A (GB)
Title: Improvements in or relating to temperature control apparatus
IPC: G05D23/30
Filed: 1958-08-14
Abstract: 901,706. Automatic temperature-control systems. MINNEAPOLIS - HONEYWELL REGULATOR CO. Aug. 14, 1958 [Aug. 15, 1957], No. 26178/58. Class 38 (4). In an automatic temperature-control system in which at least two heating and/or cooling devices are individually controlled by an equal number of thermostats which cause them to operate for varying periods of time over different temperature ranges, the control-points of the two thermostats are brought together automatically as the transition point between the ranges is approached. In Fig. 7 the temperature of a space is maintained constant by heaters 182, 183 and coolers 190, 191 which are respectively brought into operation as required by relays 194, 213, 223, 224 under the control of bimetallic switch thermostats 193, 212, 222, 233. The thermostats have identical basic operating temperatures which are modified by auxiliary heaters associated with them. If one space heater 183 is being operated intermittently by thermostat 212 to keep temperature constant and the on/off time is increasing, the average energization of a heater 200 for thermostat 193 decreases to raise the operating temperature of thermostat 193. The arrangement is progressive until, when thermostat 212 is permanently on, both heater thermostats have the same operating temperatures. Intermittent operation of the second space heater 182 then commences and the energization of a heater 251 for thermostat 212 progressively increased with increase in the on/off time of thermostat 193 to raise the operating temperature of thermostat 212 and thus maintain it closed. At the same time increasing energization of a heater 250 for thermostat 193 provides compensation to maintain its operating temperature constant. The opening of contacts 236 of relay 213 whenever space heating is taking place ensures that the coolers cannot operate. If space heater 183 is operating intermittently with decreasing on/off time, the increasing on/off time of contacts 236 increases the average energization of a heater 252 for thermostat 222 to lower its operating temperature progressively until, when thermostat 212 is permanently off, thermostats 212, 222 have the same operating temperatures. Intermittent operation of one space cooler 190 then commences and the energization of a heater 230 for thermostat 212 is progressively increased with increase in the on/off time of thermostat 222 to lower the operating temperature of thermostat 212. At the same time increasing energization of a heater 254 for thermostat 233 reduces the operating temperature of the latter until, when thermostat 222 is permanently on, both cooler thermostats have the same operating temperature. Intermittent operation of the second space cooler 191 then commences and the energization of a heater 241 for thermostat 222 progressively increased to reduce the operating temperature of the latter and thus maintain it closed. The operating temperature of thermostat 233 is maintained approximately constant by virtue of a heater 254. Modifications involving two or three heaters or coolers only are described.