Patent GB-1531903-A (GB)
Title: Electrical bistable position indicating device
IPC: G09F11/23
Filed: 1976-03-10
Abstract: 1531903 Alphanumeric displays WIDENS ELAUTOMATIK AB 10 March 1976 [19 March 1975] 09478/76 Heading G5C [Also in Division H1] A bistable indicating device (Figs. 1a, 1b, not shown) comprises a rotatable tubular outer casing pivotable on end supports; half the longitudinal surface of the casing being painted, e.g. black and half, e.g. red exposed through a window of a panel so that either colour is exhibited by rotation of the casing through approximately 180 degrees. A magnetic coil within the casing is pulsed to interact with a permanent magnet to rotate the casing, and plural devices may be arranged to exhibit successive letters or digits. In an embodiment (Figs. 2a, 2b, 2c) the casing 1 pivotal on supports 2 encloses a concentric magnetizable core 3 trunnioned on the supports which has sector shaped part cylindrical pole shoes 4a extending therefrom. A coil 5a is interposed between the core and the pole shoes and the core is insulatedly split at 6 into two parts so that the coil is energizable over the trunnions and conductors 8a. A permanent magnet ring 7a encircles coil 5a so that on current pulsing the latter its field interacts with that of the permanent magnet to rotate the outer casing which is retained by the permanent magnet on de-energization, and is restored to its former position on reverse pulsing. In a modification (Figs. 3a, 3b, not shown) the pole shoes may be sector-shaped end plates of the core, a coil surrounds the core between the endplates, and axially magnetized disc permanent magnets are provided within the opposite ends of the casing with through holes for the core mounting trunnions. In a further modification (Figs. 4a, 4b) the casing 1 surrounds a coil 5c on a core 3c; the core being provided with axially extending sector shaped part cylindrical pole shoes 4c. The core and coil are cast into an insulant body 11 carried on end support 2. At the end of body 11 remote from support 2 a cylindrical radially polarized permanent magnet 7c is mounted on a spacer 10 and is attached at its other end to the end of outer casing 1 so as to project beyond the pole shoes 4c; the ends being carried on the other support 2. Pulse energization again rotates the magnet and the casing through approximately 180 degrees. In a further embodiment (Figs. 5a, 5b, 5c) the outer casing 1 of transparent material is fixed and within it a cylinder 13 is concentrically and rotatably positioned with its longitudinal surface painted in bi-coloured portions. The cylinder 13 is mounted on the outer casing at one end on shaft 14 and at the other surrounds a coil 5d on core 3d with part cylindrical sector shaped pole shoes 4d. An axially magnetized permanent disc magnet 7d attached to inner cylinder 13 is mounted on the shaft 12 axial of coil 5d. Pulse energization rotates the magnet and inner cylinder through approximately 180 degrees by interaction of the coil and magnet fields as before. An electromagnetic or photoelectric contact adjacent the outer casing may be provided to develop a control signal on rotation through the appropriate angle. The outer casing may be sealed. The rotational angle may be restricted to, e.g. 90 degrees and any distinctive colours or tones may be employed.