Patent GB-815298-A (GB)
Title: Improvements relating to electrical measuring and control systems
Inventor: HOLLOWAY DOUGLAS ROWLAND
IPC: G05B11/01
Filed: 1955-06-24
Abstract: 815,298. Electric correspondence control. ELECTROFLO METERS CO. Ltd. June 25, 1956 [June 24, 1955], No. 18332/55. Class 40 (1). In an electrical measuring and control system, means for measuring the duration of a variable condition from a selected predetermined value and for applying to said condition a correction whose magnitude varies according to the deviation comprises relatively movable electrical elements one of which is movable in response to variation in said condition and to another of which is imparted a cyclical movement over a predetermined band of movement about the spatial position corresponding to the selected value, provision being made for adjusting or changing the position about which the cyclical movement occurs, in relation to the range of movement of the first named element. As shown the invention is applied to the electrical measuring and controlling system disclosed in Specification 616,551 and which comprises a valve oscillator having tuned anode and grid coils L1, L2 mounted side-by-side on a support in a common plane and the distance between which is such that the coupling between them is insufficient to sustain oscillation, oscillation being controlled by a coupling coil X carried on an arm B connected to the moving coil of a known type of moving-coil instrument I, the coil X increasing the coupling between the coils L1 and L2 over a part of its range of movement above that necessary to sustain oscillations. The oscillations are used to control relays or thyratrons and the system may form part of a temperature control apparatus for example. According to the present invention the coils L1, L2 are given a cyclical movement for varying their position between two limiting values at which critical coupling occurs which is sufficient to permit oscillations to commence. The coils L1, L2 are attached by means of a bracket 2 to an arm 1 which is rockable on a pivot 4. Fixed to the arm 1 is a bar 10 which engages a rotary cam 11 driven by an electric motor in a casing 12. The arm 1 is loaded by a bow spring 13 into engagement with the cam. A frame 6 is also mounted on the pivot 4 which supports the arm 1 and this may be secured in any desired position to vary the mean position of the coils L1, L2 relative to the coupling coil X by means of an arcuate rod 7 engaged by a spring-loaded friction wheel 8. The .extent of movement of the arm 1 can be varied by changing the cam 11 or alternatively a linkage may be interposed between the cam 11 and arm 10 which can be adjusted for varying the extent of movement. The speed of the motor driving the cam can also be altered to vary the frequency of the cyclical movement. In a modification the coils L1, L2 can co-operate with a vane of electrically conducting material instead of with the coil X. The cyclical movement of the coils L1, L2, as shown is in the plane of the coils and parallel to the movement of the coupling coil X but alternatively it can be at right angles to the movement of the coupling coil X or perpendicular to the plane of the coils L1, L2.