GB538118A - Improvements in automatic electric regulators - Google Patents

Abstract

538,118. Thermal switches. DAVIS, N. R., WETHERILT, J. N., and SUN-VIC CONTROLS, Ltd. Dec. 18, 1939, No. 32453. [Class 38 (v)] [Also in Groups XXXV and XIII] In the operation of a regulator which intermittently closes an electric circuit or changes the relation between condenser plates in the control circuit of a space discharge tube a change in relation between the mean position of an element 1 and an element 6 responsive to a regulated quantity occurs which causes a change in the said quantity. In order to prevent this the comparison contact 2 is caused to change its position in a direction in accordance with the average value of the interrupted current. As shown the element 6 is responsive to a temperature controlled by a heating element 14 supplied through the contact elements 1, 2 which are bimetallic and heated by windings 8, 9 in parallel with each other and with the element 14. The auxiliary contact element 2 is arranged to take a mean temperature varying with the average value 7 the current in the winding 9. The element 1 turns about the axis 4 with change in the controlled temperature. In modification, one of the companion contacts is carried by the temperature responsive element and the other by a bimetallic strip which turns about a fixed axis under the control of the auxiliary bimetallic element. In other modifications, the bimetallic element 1 is carried by an auxiliary bimetallic: element rigidly supported at one end and bending in the opposite direction to the element 1 on heating. The two elements may be heated by windings, e.g. in series with one another, but the auxiliary element may be heated conductively from the element 1 in order to attain the mean temperature required. The heat storage capacity of this auxiliary element may be variable for adjustment purposes. Fig. 6 shows the element 2 supported by a member 33 containing a quantity of mercury which may be removed from a plugged aperture to change the thermal capacity. Lagging 34 covers the auxiliary element 2 and the member 33. Since the elements 1, 2 move in opposite directions they may be arranged also to compensate changes in ambient temperature. The invention is not restricted to regulators in which the intermittent current is produced by thermal means.