Patent GB-191502012-A (GB)
Title: Improvements in or relating to Means for Controlling the Temperature of Heated Bodies.
Inventor: KIRKLAND THOMAS
IPC: H05B1/02
Filed: 1915-02-08
Abstract: 2012. Kirkland, T., and Kiernan, T. J. R. Feb. 8. Actuating.-In a gas, steam. or hot-air heating system employing t w o distinct heaters each provided with a device for switching the heat on or off, a control apparatus is provided comprising means for switching both heaters off manually, and a thermometric regulation by which one heater is automatically switched off at a predetermined upper temperature, and the other heater is automatically switched off at a higher predetermined temperature and remains switched off until switched on manually. In the following arrangement s, switches controlling electric heaters may be replaced by valves controlling gas &c. Fig. 4 shows the electric circuits for an arrangement in which two electric heaters B, S are regulated by a mercury thermometer 0 through electro-magnetic devices E', E<2>. The contact member C of the switch for etch heater is carried by a plunger B<1> or S' fitted with a collar C', Fig. 2, adapted to be engaged by a spring-pressed hook D forming the armature of the corresponding electro-magnet E<1> or E'. Each plunger is pressed down manually to place the corresponding heater in circuit, and is raised by a spring F to open the switch when released from the hook D either manually or automatically. The manual release is effected by pressing down a spring plunger H which bears on a spring-controlled pivoted arm J carrying two pins J<3>, one bearing against each hook D. The automatic release is effected by the closing of a circuit in the bore of the thermometer and through the electro-magnet E' or E' when the mercury contacts with the wire O<2> or O<3>. Fig. 5 shows a modified arrangement employing an air thermometer Q in which the switch B' controlling the heater B is opened and closed automatically according as the temperature rises above or falls below that corresponding to the position of the wire Q<2>, unless the temperature rises above that corresponding to the position of the wire Q<3>, whereupon both switches B', S<2> are opened and can only be closed manually. The temperature corresponding to the wire Q<2> may be varied by the use of multiple contacts and a selector switch. In case of breakage of the thermometer, the mercury falls into a cavity fitted with three terminals and completes the circuits for closing both switches. To avoid sparking at the wire Q<2> in the thermometer tube, the coil of the electro-magnet E<1> may be provided with a potentiometer device and a non-inductive shunt. In another modification employing a mercury thermometer, the switch B' is a double-throw switch and trembling of the switch arm and sparking in the thermometer tube are prevented by the provision of an additional electro-magnetic device and a potentiometer resistance. Fig. 9 shows a further modification employing expansible capsules R, R<1> as the heat-seusitive elements for operating the switch or valve devices S<2>, B' respectively. At the lower of the two upper temperatures, the capsule R<1> operates the lever T of the device B' through a pin-and-slot connexion at T<3> and against the action of a spring T'. At the higher of the two upper temperatures, the capsule R operates the hook D to allow the spring F to operate the device S', whereupon the device B', being under master control from the device S', is also operated and both devices can then only be restored manually.