Patent GB-382663-A (GB)
Title: Improvements in or relating to electromagnetic light valves
IPC: G02F1/01
Filed: 1931-07-30
Abstract: 382,663. Current and pressure meters. ELECTRICAL RESEARCH PRODUCTS Inc., 195, Broadway, New York, U.S.A.- (Assignees of Wente, E. C.; 245, West 104th Street, New York, U.S.A.) July 30, 1931, No. 21806. Convention date, Oct. 4, 1930. [Class 37.] In an electro-magnetic light valve, the vibratory ribbons carrying the current are mounted on a frame so as, to position them in the magnetic field, the ribbons being tensioned before being actually secured to the frame, so that special tensioning means carried by the e frame is dispensed with. The light valve, shown comprises a frame having sides 1, 2, Fig. 2, and cross pieces 3, 4. A polepiece 5 having an aperture 6 has attached to it by screws 8, 9 a conductor-supporting member 7, with the interposition of a shim 10. A second polepiece 11 having an aperture 12, Fig. 5, has secured thereto spacing members 13, 14. The apertures 6, 12 are held in alignment by screws 17, 18, and pins 23, 24, Fig. 3, which engage holes in the spacing members 13, 14. Two horseshoe permanent magnets 25, 26 are clamped between the sides 1, 2, by screws 27, 28. The conducting ribbons 33, 34 are mounted on the non-magnetic support 7 before the valve is assembled. On the top surface of the support 7 are cut channels into which are fastened by an insulating compound gold strips 39, 40, which are connected to terminals 29, 30, Fig. 2,. The strip 40 is divided, the parts being separated by insulating-material 41. The ribbons 33, 34 are separately tensioned on adjusting devices so as to have a supersonic natural frequency of vibration, which is the same for each ribbon. A greater length of ribbon than that finally secured to the support 7 is mounted on the adjusting device and is tuned to the desired frequency reduced in the ratio of the tested length to the final length. The two parts of the adjusting device are placed together by means of adjusting screws so that the ribbons are accurately spaced, the support 7 is adjusted under them, and the ribbons are secured by insulating bars 43, 44, Fig. 2. The polepiece 5 fits into the cut-out portion 45, Fig. 3, of the support 7. Metal spacing-pieces 46, 47, defining the gap between the polepieces, are secured to the support 7, and prevent excessive movement of the ribbons and also provide increased damping. A cylindrical lens in the form of a. glass rod 52, Fig. 5, is mounted at the outer end of the aperture 12 in the polepiece 11. The rod 52 has a diameter of about 1/16 in. and is positioned so as to give an image of the ribbons on the film one quarter the size of the opening between the ribbons 33, 34. Transverse corrugations 53 are provided in the lateral surfaces of the apertures 6, 12, to reduce specular reflection of stray light. The sides of the apertures are made flat and parallel and are polished to reflect light on to the ribbons. A condensing lens system 57 projects light rays from a source of light on to the ribbons 33, 34. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the application to string galvanometers and oscillographs. This subject-matter does not appear in the Specification as accepted.