Patent GB-1068069-A (GB)
Title: Improvements in or relating to automatic temperature control systems
Inventor: STEGHART FRITZ LUDWIG FELIX
IPC: G05D23/275
Filed: 1964-10-12
Abstract: 1,068,069. Automatic temperature control. SATCHWELL CONTROLS Ltd. Oct. 12, 1965 [Oct. 12, 1964; Dec. 3, 1964; Dec. 9, 1964; April 2, 1965], Nos.41495/64, 49246/64, 50152/64, and 14171/65. Heading G3R. A system for automatically and selectively controlling the heating and cooling effect of a heating and cooling system comprises a heat exchanger which may be supplied with either heating or cooling fluid, the rate of heat transfer being controlled by a thermostatic device responsive to the temperature to be controlled, the means for changing from a heating to a cooling effect being incorporated in the power supply to the system. A space to be heated includes a heat exchanger 20 which is supplied with heating or cooling fluid by way of conduits 202, 203 and a valve 204 operated by a thermal motor 205 comprising an expansible wax device. A master controller (not shown) is operable to select the supply of heating or cooling fluid and is such as to make terminal 206 the positive terminal of a D. C. supply when heating fluid is being supplied but when cooling fluid is being supplied terminal 207 is made positive. Energization of the wax device 205 is controlled in an ON-OFF manner by a thermostatic device 208 which includes a bimetallic strip 209 associated with a heating element 210 when the system is used for heating and a heating element 211 when the system is operating as a cooling system. When the system is used in a heating mode and when the controlled temperature is below the set temperature the bimetal strip 209 will make on contact 216. In this position both the heating element 210 and the wax device 205 will be energized. The subsequent heating causes the wax in the device 205 to expand causing the valve 204 to open to admit heating fluid to the heat exchanger 201. Heat generated by the element 210 causes the bimetal strip 209 to warp so that its engagement with contact 216 is broken whereupon the element 210 and the wax device are de-energized the wax device then tending to close the valve 204 and the bimetal strip to re-close with contact 216, the cooling of the strip 209 taking place quickly compared with the cooling of the wax. Closing of the strip 209 with contact 216 causes re-energization of the heating element 210 and the wax device 205 repeating the cycle. As the temperature of the space containing the heat exchanger 201 increases the cooling time of the strip 209 increases and the heating time thereof decreases and the valve 204 will become more and more closed until the temperature of the space is stabilized. Cooling of the space is effected in a similar manner using a cooling fluid in the heat exchanger and a heating element 211 for the bimetal strip 209 which in this case cooperates with contact 217. An auxiliary heating element 212 is provided to apply a thermal bias to the strip 209 so that the thermostatic device 208 operates at a lower temperature during heating than during cooling of the space at any set point of the bimetal strip 209. In other embodiments the energizing winding of the device 205 may be in two sections and the device 205 may be replaced by an electric fan driving air over the heat exchanger.