GB444673A - Improvements in and relating to regulating devices - Google Patents

Abstract

444,673. Automatic control of temperature, fluid pressure, &c. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. March 14, 1935, Nos. 7959, 7960, and 7961. Convention dates, March 14, 1934, Jan. 16, 1935, and Jan. 23, 1935. [Class 38 (iv)] In an automatic regulation arrangement having means responsive to deviation of the variable from a standard value which causes operation of restoring means, thermal. means are provided for producing a return action having a characteristic which is a reproduction of the characteristic of the regulating process. In the form shown in Fig. 1, deviation of temperature in a furnace 1 causes unbalance of a Wheatstone bridge 3 supplying a galvo 4, which controls by a motor 13 the fuel valve 14. To prevent hunting, the bridge is temporarily reset by an amount depending on the deviation of temperature. The amount of a resistance wire 17 in two arms of the bridge is varied by a mercury column in a U-tube, the ends of which communicate with chambers 19, 20 containing heaters, one or the other of which is supplied with an impulse depending on the extent of the deviation. Rate of transfer of heat between the two chambers is determined by the position of a screen 25. In a modification, separate temperature sensitive resistances connected in the bridge are associated with the heaters. In another modification, Fig. 5, for adjusting the valve 40 in a pipe line in response to pressure of the fluid, a lever 33 is moved by a manometer 31 to close the circuit of a reversible motor 38 which adjusts the valve. The pivot of the lever 33 is carried by the centre diaphragm 51 of a manometer having compartments 46, 47 containing heaters 44, 45 and a readily vaporizable substance 52. When a deviation occurs one of the heaters is energized and the pivot is temporarily shifted by an amount depending on the deviation. In a modification of this the contacts 34, 35 are mounted on a plate coupled to the movable partition 51. In a further modification, Fig. 6, energy to the heating winding 67 of an electric furnace is supplied through a grid controlled valve 64, the grid potential of which is varied by the unbalancing of a bridge 70 to give control of the temperature. Two arms of the bridge contain temperature sensitive resistances 73, 74 which are mounted in a vessel 76 containing a heater 75 supplied with current proportional to the load current. One resistance is screened from the heater to give a lag in its response such as to cause temporarily balancing of the bridge.