GB792145A - Improvements in and relating to devices for obtaining a mechanical movement from theaction of an electric current - Google Patents

Abstract

792,145. Temperature-responsive actuating-elements. TECHNOGRAPH PRINTED CIRCUITS, Ltd. May 20, 1954 [May 20, 1953], No. 14179/53. Class 64(2) [Also in Groups XX and XXIX] Heat from an electric current passing through a flat conductor 19 such as a printed strain gauge, e.g. produced as in Specification 639,178 [Group XXXVI], is distributed asymmetrically in an elastic member such as a bimetal (so that the high expansion part gets the greater share of heat) or such as a bar or disc loaded for snap-action (externally as in Fig. 13 or by inherent bowing) and the elastic member therefore bends or changes its convexity. In the bimetal shown in Fig. 8, an electric heater 19 is sandwiched between a brass layer 42 and a steel layer 43. It is electrically insulated from the brass layer by a layer 23 and thermally and electrically insulated from the steel by a layer 46. Two bimetals may be arranged to counteract the effect of ambient temperature, having their free ends joined by spring means, Fig. 6 (not shown), or, as in Fig. 7, the free end of one bimetal 37 may be attached to a sliding block in which is mounted another bimetal 38 bending in the opposite direction with temperature change. Either or each of the bimetals has a heater 19, which can be energized to deflect the free end of bimetal 38. In the case of the loaded, non-bimetallic members, the elastic member may be a metallic bar in two parts 21, Fig. 4, sandwiching the heater 19 and its electric insulation 23; it may be a simple bar 56, Fig. 13, or a bar in two parts 14,15, Fig. 2, with a sandwiched heat-insulating layer 16 and in either of these cases the heater 19 is mounted on a face of the bar but electrically insulated from it by a layer 18. In the case of a two-part bar, there may be heaters on two opposite faces, Fig. 14, (not shown), or a central layer of heat insulation, Fig. 15 (not shown), may have on each side, a heater, electrical insulation, then, outermost, the one or the other part of the bar, one heater being energized at a time. The bar is secured at one end or its middle, Fig. 9 (not shown), to allow movement of the free end or ends. In Fig. 13, heating causes bowing of the bar to be reversed and this position is then held, by the pressure of the spring 61 producing the bowing, when the heating ceases. Instead of a bar, a disc 54, Fig. 11, with a spiral or double spiral heater 19 may be used and may be radially loaded to produce bowing. To produce the differential expansion which changes the form, one part of the member may have a heat-insulating or heat-reflecting layer 25, Fig. 4; and the other part may have a heat-radiating surface. One part may be cooled by a flowing liquid 26 and the deformation used as an indication of the liquid flow or temperature. A heat-insulating layer may 'be placed adjacent one face of the sandwiched heater 19 and act also as its electric insulation at that'face, Fig. 10 (not shown). During the operation of the member, the heater 19 may function as a resistance thermometer or strain gauge (see Group XXXVIII). Specification 741,384 also is referred to.