Patent GB-925239-A (GB)
Title: Improvements in or relating to methods and apparatus for establishing and maintaining a substantially uniform temperature within an enclosed space
Inventor: SUTTON MYER S
IPC: F25B27/00
Filed: 1960-11-30
Abstract: 925,239. Automatic temperature control systems. THERMO KING CORPORATION. Nov. 30, 1960, No. 41235/60. Class 38 (4). [Also in Group XIII] A storage space 10 is cooled or heated by a heat pump at a relatively high rate of heat transfer when its temperature is above or below a predetermined range, respectively, and, when the temperature is within the range, it is continuously and alternately cooled and heated at a lower rate by the heat pump. As shown in Fig. 1, a compressor 14 is driven by an I.C. engine 44 normally running at full speed but adapted to be run at reduced speed when a throttle control device is actuated by energization of a solenoid 50. The compressor supplies refrigerant to condenser 18 and evaporator 30 in the storage space. The compressor outlet is connected direct to the evaporator by a pipe 34 including a normally-closed valve 36 adapted to be opened when a solenoid 42 is energized. A thermal element 54 responsive to the temperature of space 10 actuates a pivoted arm 64 carrying cams 66, 68, 70 which operate switches 78, 80, 82 mounted on an arm 74 which is adjustable about pivot 76. Arm 74 is adjusted along scale 72 to alter the set level of the predetermined temperature range. As shown, the temperature in space 10 is too low and switches 78, 80 are closed and switch 82 is open. Valve 36 is held open by energization of solenoid 42 through switch 80 so that hot gas is supplied to the evaporator to heat space 10 ; the engine 44 is at full speed. When the lower limit of the temperature range in space 10 is reached, cam 70 closes switch 82 and solenoid 50 is energized through switches 78, 82 so that the compressor operates at reduced speed and heat is supplied at reduced rate to the evaporator. When the upper limit of the temperature range in space 10 is reached, switch 80 is opened by cam 68 so that valve 36 closes and heat is abstracted from space 10 at a low rate. Subsequently, the space 10 is alternately heated and cooled at a low rate within the range. If, however, the temperature in space 10 should rise above the range, switch 78 will be opened by cam 66 so that solenoid 50 will be de-energized so that the compressor runs at full speed and heat is abstracted from space 10 at a high rate. A fan may circulate air over evaporator 30. In a modified form, Fig. 4, evaporator 30 is located in an air duct 11 communicating with space 10, adapted to be closed by dampers 98 when a solenoid 100 is energized, and through which air is circulated by a continuously running fan 96. An additional thermal element 126 responsive to evaporator temperature is provided. The engine 44 normally runs at reduced speed but runs at full speed when solenoid 50 is energized. Arm 74 carries normally open and closed switches 78a, 80a and an arm 102 adapted to open a normally-closed switch 82a when the temperature setting is below 28 ‹ F. In the condition shown, the set temperature is above 28 ‹ F. (so that the switch 82a is closed) and the space 10 is too cold. Current from source 84 and wire 128 flows through closed switches 80a, 82a to actuate relay 110 with two results: (1) current flows from line 128 through line 140, solenoid 42 to open valve 36, lines 142, 144 and switch 112 of relay 110; (2) a relay 118 is actuated by current from line 128 through switch 114 of relay 110, this resulting in energization of solenoid 50 through line 148 and switch contacts 122b of relay 118 so that engine 44 runs at full speed to heat space 10 at a high rate. When the temperature reaches the preset range cam 68 opens switch 80a so that relays 110, 118 fall out. The falling out of relay 118 causes closing of dampers 98 by energization of solenoid 100 through line 150 and contacts 122a of relay 118, de-energization of solenoid 50 so that engine 44 runs at reduced speed, and connection, through switch 120 of relay 118, of solenoid 42 in series with thermal switch 126 so that heat or cold will be supplied to evaporator 30 at a reduced rate as long as the temperature in space 10 is within the preset range. Should the temperature in space 10 rise above the preset range, cam 66 closes switch 78a so that relay 104 is actuated, this causing actuation of relay 118 through line 138. This causes de-energization of solenoids 42, 100, so that valve 36 is closed and dampers 98 are opened, and energization of solenoid 50 so that engine 44 runs at full speed, thus causing maximum cooling of space 10. When the temperature of space 10 has again been brought within the preset range, switch 78a is opened so that the dampers 98 close, the engine runs at reduced speed and valve 36 comes under the control of thermal switch 126 to give alternate heating and cooling of the evaporator. If the preset temperature were below 28‹ F., however, projection 102 holds switch 82a open in all conditions so that the space 10 can never be heated at the high rate.