Patent GB-629094-A (GB)
Title: Apparatus for regulating the temperature of an enclosed space
IPC: B61D27/00
Filed: 1946-05-27
Abstract: 629,094. Automatic control systems. VAPOR CAR HEATING CO., Inc. May 27, 1946, No. 16090. Convention date, Oct. 19, 1945. [Class 38 (iv)] Temperature.-An apparatus for regulating the temperature of an enclosed space comprises a pair of temperature control means including thermostats and associated relays, and a third relay, actuated by the relay associated with the second means, to add heat to the thermostat associated with the first means to adjust its operating temperature setting. In this way, it is arranged that, while it is in a satisfied or unsatisfied state, the second thermostat dominates the first to keep it closed in spite of its own low surrounding temperature. The application of the invention to the heating or cooling of a railway carriage is shown in Fig. 1, Fig. 3 showing a control circuit. Heating and cooling means.-A blower 19 is arranged to pass air through two coolers and a heater, both controlled as below, and into the carriage through openings 20, 21, 22. The evaporators No. 1 and No. 2 of the cooling means are fed from a common compressor 34 and controlled by valves 36 and 37 respectively. The heater 10 is fed with steam controlled by a normally closed valve 15 opened by a solenoid 17. In addition to the " overhead " heater 10 there are several " floor " heaters, of which 23 and 26 are shown, having radiating fins 28 and fed through solenoid controlled valves 30, 33 from a common valve 39 which is operated through a solenoid 38 by the control system. The floor heaters are controlled by the thermostats such as A situated near each floor heater, subject to the domination of an " overhead " thermostat K which is at breathing level, and also controls the " overhead " heater 10. The coolers No. 1 and No. 2 are controlled by thermostats L and S respectively. When the thermostat L is operating, the motor thermostat K is heated by a current-carrying coil so as to prevent the simultaneous operation of the heaters. Normal control of heaters.-To operate the regulator for normal service, switches 1-8, 63 and 63a are closed, 9 being left open. This starts the blower motor 77 and passes air through the " overhead " heaters and coolers into the carriage. If the air temperature is under 76 F. and the thermostat K is unsatisfied, the coil 44 of relay E is energized to make contact 56 as shown in Fig. 3. Solenoid 17 is then energized and the overhead heater 10 is supplied with steam whilst simultaneously a circuit through resistance 59 and auxiliary heater 40 of thermostat K is established. In addition to these two circuits, the closing of the contacts 56 of the relay E energizes the solenoids 51 of the normally closed floor heater relays F, G, H and I, thus de-energizing the solenoids 30, 30a, 31, 32, and 33, and allowing the floor heater steam valves to open under the control of their individual thermostats A, B, C and D respectively. When the temperature of the carriage plus the auxiliary heat added to the thermostat K by the coil 40 is sufficient to cause it to function, the coil 44 of relay E is short-circuited through wires 42a, 45a and the contacts 56 of relay E are opened, thus deenergizing the coil 17 to shut off the overhead heaters and simultaneously de-energizing the relays F, G, H, I to shut off the floor heaters. The de-energization of the relay E closes its contacts 66, thus supplying current to the auxiliary heaters 70, 70b, 70c, 70d, of the floor heater thermostats and causes them to close, thus allowing the relays F, G, H, I to remain de-energized when the thermostat K opens, due to the falling temperature, and causes steam to be supplied to the overhead heater. In this way, the floor heaters can only be operated during the operation of the overhead heater, and they are under the control of their thermostats subject to the overhead thermostat K being unsatisfied. Control of cooling means. Cooler No. 1 control.-If the temperature outside the carriage rises to 50 F. a thermostat J closes and energizes a relay P which transfers the dominant control from the overhead heater thermostat K to the cooler thermostat L when the carriage temperature rises to 76 F. At this temperature the contacts of thermostat L are closed and the coil 94 of a relay Q is energized through resistances 97 and the closed contacts of relay P. Closure of relay Q energizes solenoid 38 to shut off all steam to the heaters and also energizes a solenoid 117 which closes a relay M to direct an additional current through the auxiliary heater of thermostats K, L, through resistances 122, 129 respectively. In parallel with these circuits is the coil 118 of relay R which is closed to start the compressor 34 of the coolers. Energization of the relay Q also completes the circuit through solenoid 115 of the cooler No. 1 inlet valve 36, this circuit being energized through a delaying switch mechanism 113 for holding the circuit closed for a fixed period after the cir cuit is otherwise broken to prevent repeated cycling of the cooling system. Addition of auxiliary heat to the thermostat L holds its contacts closed until the carriage temperature falls to 74 F. and thus also prevents frequent cycling of the cooling means. The heat added to thermostat K also depresses its operating temperature to 74 F. and delays its opening for about ¢ hour after the thermostat L has opened, thus permitting resumption of the heating function. Thus in this case also the action of the relay Q of thermostat L is to add heat to thermostat K by means of relay M. Cooler No. 2 control.-If, in spite of the operation of cooler No. 1 the temperature continues to rise, thermostat S will close between 76 and 78 F. depending on the amount of auxiliary heat supplied to its auxiliary heater 125 which is in series with that of thermostat L. This energizes coil 132 of a relay T whose contact 138 completes the circuit of the solenoid 136, which opens the valve 37 of cooler No. 2. If thermostat L fails to function, thermostat S will close all circuits except that operating the valve 36 of cooler No. 1, and thus it provides a safeguard against complete failure of the cooling system. In the normal way, however, the cooler No. 2 is allowed to cycle freely under the influence of thermostat S which is dominated by thermostat L through relay M. Controlling the temperature when the carriage is out of service.-When the carriage is to be taken out of service its temperature is only maintained high enough, by using the floor heaters alone, to prevent freezing of the pipes &c. This is achieved by closing only switches 63 and 9, which directs additional current through resistance 61 to the auxiliary heater of the thermostat to set this down to a suitable stand-by temperature. The overhead heater cannot function since switch 8 controlling its solenoid 17 is open. When the temperature falls to a suitable value, the thermostat K opens and allows relay E to close contact 66 and so energize the floor heaters as described before, the auxiliary heat added to the floor thermostats being insufficient to allow them to operate at the stand-by temperature. The resultant rising temperature plus the additional heat added to the thermostat K causes it to close and de-energize relay E to close contact 56 and shut off the floor heaters as described.