Patent GB-621486-A (GB)
Title: Improvements in and relating to magnetic-field responsive devices
IPC: G01R33/02
Filed: 1944-01-19
Abstract: 621,486. Magnetic tests. SPERRY GYROSCOPE CO., Inc. Jan. 19, 1944, No. 1084. Convention date, Jan. 19, 1943. [Class 37] [Also in Group XXXVIII] The core of a flux valve comprises a pair of similar core members of magnetic material lying in parallel planes, each arranged to form a substantially closed magnetic circuit arranged so that corresponding parts of the two members are spaced in the direction normal to the two planes, the exciting winding comprising similar windings for the corresponding parts of the core member but arranged to produce flux in opposite directions in the corresponding parts, and the pick-up coil or coils being each disposed on a part of the core comprising two corresponding parts of the core members which are encircled together by the coil. As shown in Fig. 2, the core of the flux valve is formed of two parallel regular polygons each made up of flat strips 31a, 32a, and fastened to a non-magnetic support by bolts 40. Exciting coils 33a, 34a are wound about the strips 31a, 32a forming the two polygons and are connected so that the flux in the two polygons is in opposite directions. Wound about each pair of strips 31a, 32a and their exciting coils 33a, 34a is a secondary or pick-up coil 35a. In the absence of an externally applied field, zero voltage is induced in each pick-up coil 35a since the effects of the opposite fluxes cancel one another, but a voltage is produced in the presence of an external field depending on the orientation of the axis of the coil 35a with respect to the field. The flux valve may be rotatable about the axis of a central shaft or column 36. Fig. 3 shows a system which may be used as a remote indicating compass or as a position repeating system. This includes a flux valve transmitter 61 comprising a toroidal core 62 wound with an exciting winding (not shown) and pick-up coils 63a, 63b, 63c, 63d, &c. The external magnetic field may be either the earth's field or the field of a circular magnet 64. The receiver or repeater 66 is provided with a core 67 and secondary coils 68a, 68b, &c., connected as shown to the flux valve coils so that a flux is produced along a diameter corresponding to the position of the rotor 64 or the earth's field. A magnetic armature 69 aligns itself with the diametral flux and provides a remote indication of the orientation of the field to which the transmitter 61 is exposed. To avoid sense ambiguity the armature 69 may be provided with a coil 71 excited at a frequency double that used for exciting the core 62 of the transmitter 61. This may be derived from an oxide rectifier connected to the source feeding the exciting coils of the transmitter. The Specification as open to inspection under Sect. 91 comprises also the following subjectmatter. A toroidal core 11, Fig. 1 (Cancelled), is wound with a continuous exciting winding 12 supplied with alternating current. This winding may be a uniformly-wound coil or a number of separate coils. A circulating periodicallyvarying flux is produced in the core, creating a varying permeance. A number of secondary or pick-up coils 16, 17, 18, 19, are also wound on the core 11, diametrically opposite pairs of coils being connected in series opposition so that the resultant voltage induced in each pair is zero in the absence of an external field. In the presence of a field in the direction of the arrow 20 the voltages induced in the coils 16, 17 will be differentially varied so as to produce a resultant output of a frequency twice that of the exciting flux and having a phase sense corresponding to the component of the applied field along the direction 20. Similarly a pair of coils 18, 19 produce a double-frequency output voltage in the presence of a component of the field in the direction 21. In the example shown in Fig. 2 (Cancelled), the flux valve 10 is wound with a single exciting winding 12 and nine pairs of opposed secondary coils 20a, 20b, &c., which are connected to a signal or synchro transformer 22 having a stator 23 carrying eighteen poles 23a, 23b, &c., each wound with a corresponding coil 24a, 24b, &c. The coils 20a, 20b, 24a, 24b, &c., are arranged in polyphase star connection as shown. The rotor 28 of the transformer 22 carries a distributed two-pole winding in which is induced an E.M.F. of the same frequency as the flux valve output and an amplitude corresponding to the relative angular displacement between the orientation of the flux valve 10 and the rotor 28 and a phase sense, corresponding to the sense of this displacement. This voltage may be employed as described in Specifications 638,971 and 638,972 to provide an indication of, or control action from, the direction of the external magnetic field. The core may be formed of straight laminations joined by screws so as to form a twelve-sided polygon. Each side carries an exciting coil and a pick-up coil, and the whole is built up on a non-magnetic base, for example of synthetic resin. In the flux valve shown in Fig. 11 (Cancelled), the core is in the form of an equilateral triangle, each leg 1, 2, 3 of which consists of two strips which may be in contact or spaced apart. The legs may be in contact with each other at the vertices, as shown, or they may be slightly spaced. Collector horns 17 may be provided or these may be dispensed with. The legs 1, 2, 3 are provided with exciting windings (not shown) connected in series so that the flux flows in the same direction round the triangular core for any instantaneous value. Each core leg also carries two pick-up windings 8, 9, 10, 11, 12, 13, which are star connected in pairs as shown. The windings of the flux valve may be connected to a receiver with star-connected windings. This subject-matter does not appear in the Specification as accepted.