| 摘要 |
<p>1427455 Automatic control of temperature CONTROLS CO OF AMERICA 5 March 1974 [16 March 1973 15 Jan 1974] 9802/74 Heading G3R [Also in Divisions F2 and F4] In a refrigeration system comprising a compressor 10, condenser 14, expansion valve 18 and evaporator 22, the temperature of the refrigerated space is sensed by a thermistor 30 connected in one arm of a bridge circuit, the arm being adjustable e.g. by a resistor 36 to pre-set the desired temperature, and a signal from the bridge circuit is used to control a valve 26 between the compressor and the evaporator, to control the evaporator pressure and thus the space temperature. As shown the valve 26 is normally open (during temperature pulldown) and operates to reduce the flow from the evaporator to the compressor when the set temperature is reached. The valve may alternatively be a normally closed valve (126), Fig. 4 (not shown) operative to by-pass hot refrigerant back from the compressor outlet to the evaporator. The valve 26 is a sleeve valve in which a bi-metal stack (76) Fig. 2 (not shown) operates the sleeve (86) against the force of a spring (88) when heated by a heater 74 receiving the amplified control signal. The system may be applied to the control of an air-curtain type refrigerated display case (98), Fig. 5 (not shown), the thermistor 30 being in the air-curtain and the bridge arm containing a second resistor (104) which can be shunted by a switch (106) for defrosting or at shop closing time.</p> |
