Patent GB-598168-A (GB)
Title: Improvements in and relating to devices sensitive to an external magnetic field
IPC: G01R33/02
Filed: 1944-04-17
Abstract: 598,168. Magnetic tests. SPERRY GYROSCOPE CO., Inc. April 17, 1944, No. 7113. Convention date, April 15, 1943. [Class 37] A flux valve is arranged to provide a signal voltage output in which substantially no component of the exciting current frequency is present. In the construction shown in Figs. 1, 3, and 4 the core 1 is arranged as a closed triangular frame each leg of which comprises laterally spaced parallel members 2, 3 of highly permeable magnetic material such as permalloy. These are joined at their ends by magnetic cores 8 wound with exciting windings 9. On the core member 3 is mounted a secondary or pick-up winding 10. A magnetic shunt 11 is carried by the other leg 2 and extends into close proximity to the coil 10. The exciting coils 9 are connected across an A.C. source 12 and cause fluxes to flow in each core leg 2, 3 in relatively opposite directions as shown by the arrows in Fig. 4. The coil 10 is adjusted lengthwise of the core 3 until the voltages induced by these fluxes neutralize each other and is then fixed in position by sealing compound or by a clamp. Flux collectors or horns 13 may be connected to the upper and lower core sections, their ends being connected together by non-magnetic spacers 14 to prevent a closed magnetic path being formed. Each spacer 14 may be formed of parts 14a, 14b, Fig. 3, having magnetic and non- magnetic properties to reduce the gap in the magnetic circuit. The core may be polygonal instead of triangular. The exciting windings may alternatively be mounted on the upper core leg 2 instead of between the core legs. The pick-up winding may be adjusted longitudinally by a screw and nut, or the magnetic shunt may be adjustable and the pick-up winding fixed. To increase the sensitivity, pick-up coils may be mounted on both the upper and lower core strips. In the construction shown in Fig. 12 the core of the flux valve comprises a single strip or a laminated strip 47 on which are mounted exciting windings 48, 49 arranged to produce oppositely flowing fluxes in the core. A secondary or pick-up winding 50 is mounted over the exciting winding and an annular shunt 51 of magnetic material may be slid over the pick-up winding and adjusted lengthwise thereof. In a modification, Fig. 14, the core comprises spaced strips 52, 53 connected at their ends by magnetic spacers 54 to provide a closed magnetic circuit. Exciting windings 55, 56 produce oppositely flowing exciting fluxes. A magnetic shunt 57, which extends about both core strips and their windings is movable lengthwise, for balancing. Alternatively the exciting coils surround the spacers 54 and the pick-up winding surrounds both strips 52, 53, the shunt surrounding the pick-up coil. Instead of forming the sides of a triangle or polygon the flux valve legs may be radially arranged. The exciting flux may be caused to flow in the collector rings as well as the leg portions in order to effect demagnetisation. The upper and lower core strips and their associated collector rings and coils may be formed as a unit as shown in Fig. 24. The upper and lower core strips 96, 97 have collector rings 96a, 97a formed integrally therewith. Exciting windings 98, 99 are mounted on the strips 96, 97 and a pick-up winding 100 is mounted over both core strips and exciting windings. The strips are fastened together by tubular spacers 101 which are wholly or partially of magnetic material. The flux valve structure is mounted in a casing of non-magnetic or insulating material having pins over which the tubular spacers 101 are fitted.