Patent GB-623995-A (GB)
Title: Temperature control system
IPC: G05D23/275
Filed: 1946-04-18
Abstract: 623,995. Automatic systems for temperature control. VAPOR CAR HEATING CO., Inc. April 18, 1946, No. 11964. Convention date, April 16, 1945. [Class 38 (iv)] A system for controlling the temperature within an enclosed space such as a railway car, and comprising a primary heater A located near the floor, a secondary heater B, and a cooling element C, each associated with a thermostat and relay for controlling its operation, is characterised by the thermostat F of the primary heater being provided with an electric auxiliary heater 45 which is connected through the relay of the secondary heater B so as to reduce the functional setting of thermostat F when the thermostat H of the secondary heater functions, and an auxiliary heater 79 provided for thermostat H is connected through the relay of the cooling element to reduce the heating current and thereby raise the temperature at which thermostat H operates when the cooler is functioning. The heating medium, such as steam, is fed through a solenoidcontrolled valve 40, Fig. 3, to the primary heater A, the solenoid being normally energized to hold the valve closed against the action of a spring 41 before the system is rendered operative by the manual closure of a switch 15. The supply of steam to the secondary heater B is controlled by a solenoid-operated valve 57 which is normally held closed by a spring and operated by the closure of a relay contact 55 under the control of thermostat H. An outside thermostat L is associated with a relay M for rendering the primary heater and controls therefor inoperative when the outside temperature rises to a predetermined minimum. Operation of the switch 15 closes the circuit of a blower motor D and energizes relay M to close the circuit through the coil 31 of the primary heater relay, whereupon the relay operates to de-energize a solenoid 36 and open the valve 40. Steam is thus fed to the primary heater A until its thermostat F operates to short-circuit the relay coil and close the valve 40. The period of time during which valve 40 remains open is determined by the co-operative functioning of the secondary heat thermostat H and relay I which control the current supply to the auxiliary heater 45 of the primary heat thermostat F. An over-riding control to maintain valve 40 open is provided by a manual switch 46 which can be closed to hold a relay G open. Simultaneously with the opening of valve 40 by closure of switch 15 the valve 57 of the secondary heater B is opened by the energization of its relay coil 50. This valve is held open until coil 50 is short-circuited by thermostat H, whereupon relay contact 55 is opened and an associated contact 54 is released to close a circuit from the line 18 through the auxiliary heater 45 of the primary heat thermostat F and also through a shunt connected heating coil 66 of a heat motor R, Fig. 1. This heat motor, which may be of known type, e.g. a bimetallic spiral, operates a valve Q to byepass a portion of the air around the cooler C, the amount being dependent on the temperature within the car. The auxiliary heater 45 and coil 66 of the heat motor are thus effective only when the secondary heat thermostat has operated to shut off radiator B, with the result that the heat added to the primary thermostat F causes it to short-circuit relay G to close the primary heat valve 40. This action takes place cyclically. An auxiliary heating coil 79 is provided on the secondary heat thermostat H whereby it is caused to operate at a temperature lower than that at which it would otherwise respond. This added heat can be varied for day and night conditions by connecting the heating coil 79 alternatively in series with one or the other of two resistances 77, 82 by a switch 75. The manner of operation of thermostat H is also dependent upon whether the air cooler is operative. The control exercised by thermostat H is accelerated by supplying a small additional current to the heating coil 79 during the periods that its relay contact 55 is closed to open the valve 57, this current being fed through a shunt circuit comprising a lead 60, and resistance 84 connected to coil 79. The additional heat is switched off immediately thermostat H operates, resulting in a cyclic action which opens and closes the valve 57 to admit bursts of steam until the temperature is sufficient to maintain the thermostat in its operative condition. When the cooling system is inoperative a still further current is fed to the heater coil 79 of thermostat H through a lead 107, contact 108 of the inoperative relay K, and resistance 110. This adds a further 3 ‹ F. to the temperature of the thermostat H, so that assuming it is constructed to function normally at 78‹ F., with the switch 75 in its " day '' setting and the cooler inoperative, the thermostat is at a room temperature setting of 72‹ F. actual, whereas the " night " setting will be 74‹ F. Cooling control. Operations of the cooler C are controlled by a relay K with its associated thermostat J connected in a circuit comprising relay M which is held inoperative until the outside temperature rises above 40‹ F. and operates thermostat L. Thermostat J would normally function at 76‹ F., but is adjusted to a lower room temperature by a heating coil 84a which can be connected in series with either of two resistances 88 and 92 by a switch 86, the resistance 88 being dimensioned to add 3‹ F. to the heater for " day " operation, and 92 dimensioned to add 1‹ F. for " night, " operation. The thermostat operates to close a contact 98 to start the cooler operating and also opens contact 108 to open the circuit through resistance 110 and the auxiliary heater 79 of the secondary heat thermostat H and thereby removes 3‹ F. of auxiliary heat from that thermostat and raises its functional setting.