Patent GB-540087-A (GB)
Title: Improvements in or relating to temperature and like control systems
IPC: G05D23/19
Filed: 1940-02-29
Abstract: 540,087. Automatic control systems for heating buildings. VUILLE, B. A., and WATFORD ELECTRIC & MANUFACTURING CO., Ltd. (Queyras, J. F. Augier-). Feb. 29, 1940, No. 3822. [Class 38 (iv)] [Also in Group XXXVIII]  Temperature.-The heat supply to a building is controlled by outside temperature responsive means so as to vary in accordance with one of a family of laws each calculated to maintain a different inside temperature, other conditions remaining the same, and inside temperature responsive means progressively adjusts the system to operate on a higher or lower laws so long as the temperature in the building is below or above that desired. The system may be combined with means to start or stop it or to change from night to day operation and vice versa at a time interval after the operation of a time switch depending on the outside temperature. The system is described as applied to heat control means of the following types : steam or water supply varied progressively, electrical or steam heating periodically cut in and out for variable periods, and electric fans circulating air heated by hot water which are cyclically controlled and operate in sequence in each cycle to avoid a heavy instantaneous demand for heat. A Wheatstone bridge comprises a resistance Re varying with outside temperature and a resistance Rf varied in accordance with the temperature of heating water or steam or in accordance with the varying setting of heat control means so that the bridge is balanced where the rate of heat supply has a certain relation to the outside temperature. A resistance R5 is varied to change this relation or " law " as determined by a second bridge containing a resistance Rr responsive to inside temperature ; this resistance may comprise a series connection of resistances in different rooms. A resistance Rx may be manually varied to adjust the law of the bridge according to the design and operation of the installation. A galvanometer relay 10 responsive to the first bridge controls a reversible motor M 1 through a relay system, such for example as is described in Specification 501,017, which includes resetting means for the relay 10. This motor may determine the opening of a valve or the position of a pair of contacts in relation to a constantly driven actuator (two arrangements of which are described) whereby the period of closure in each cycle of a circuit controlling the supply of heat is determined ; in the latter case one motor also makes a corresponding adjustment of a resistance replacing Rf and rebalancing the bridge. The second bridge controls a reversible motor M2 determining the value of the resistance R5 and contains a resistance Ry which may be manually adjusted. Fig. 5 shows a modification of the first bridge for a system in which law relays 50 ... 53 control current supply to four unit heaters each comprising a fan for circulating air over a heating element. A cycling contactor closes and opens switches C5, C6 so that the relays (and fans) operate in twelve minute cycles, successively, twice displaced by three minutes. The valve of a resistance R13, divided into four parts of ratio 1:1:3:6 is changed every quarter of a minute by switches C 1 ... C4 appropriately operated by the contactor so that in the first quarters of each succeeding minute it is progressively changed by equal steps and the progression is repeated with a time displacement of 3“ minutes in the second, third and four quarters. Thus the galvanometer relay contacts 11 which controls the relays 50 ... 53 operates to eliminate a variable part of each complete fan cycle which corresponds with the outside temperature (resistance Re) and is modified by the room temperature (resistance R5). Another arrangement of the bridge uses four circular rheostats with 90 degrees phase displaced arms in parallel with the resistance Re. These rheostats are continuously driven in synchronism with the contactor and with switches which connect the bridge current supply to the rheostat arms in turn. To switch on or off a control system or to change it from a night condition of operation to a day condition and vice versa a third bridge may be used having a resistance RE subject to outside temperature and a resistance Rt which is progressively varied by a motor M3 intermittently energized through a commutator 30 on the closure of the contacts TS of time switch. The galvanometer relay contacts 22 will then close to energize a relay 2 or open to de-energize it after period determined by the outside temperature according to the direction in which the motor M3 is set to run. A change beween day and night operation would be obtained by a switch operating on a resistance R9 in parallel with a bridge resistance.