Patent GB-462985-A (GB)
Title: Improvements in oscillographs
IPC: G01R13/04
Filed: 1935-09-18
Abstract: 462,985. Phonographic recorders; circuits for electrostatic instruments. PITZELBACHER, W. Sept. 18, 1935, No. 25926. [Class 40 (iv)] [Also in Groups XXXVI and XL] An oscillograph for sound - recording, picture transmission or television, comprises two electrodes 1, 3, at least one of which is of a semi - conducting material and the other is pivotally mounted and inclined at an angle to the plane of the other. One electrode may be a resilient metal strip 3 secured at one end 2 to the other electrode 1 which has a curved surface forming an angle alpha with the free end of the strip which also carries the recording member. The electrodes are connected to a source of polarizing voltage 7 and to an input transformer 5. Alternatively, the metal strip 3 may be clamped at one end between two semi-conducting electrodes which are electrically connected in series. The free end of the strip 3 is connected by a biassing spring to a support and is electrically connected through an input transformer secondary with the mid-point of a potential divider which is supplied from a biassing voltage. The two semi-conducting electrodes are connected to opposite poles of the biassing voltage. In a modification, Fig. 3, the movable electrode 15 is pivoted on or about the fixed electrode 14 and may have an extended balancing portion 17, and a spring or other restraining means. In such an arrangement the stationary semi-conducting member 24, Fig. 4, is secured to a pivoted frame 23, 26 which can be adjusted to vary the angle alpha between the member 24 and the oscillating member 20 which latter is secured to heads 21 mounted in bearings on the frame 26, 23. A spring (not shown) controls the motion of the member 20. In a further modification, the movable member consists of two superposed metal plates supported along a central axis by bands, filaments or other torsional carriers. Each half of the movable member is associated with a stationary semi-conducting member arranged preferably on opposite faces of the plate. Each half of the movable member is provided with an optical shutter and these control the passage of a beam of light to the sound track on a film. The casing of the device may, it is stated, be filled with a gas for increasing the field strength. Similarly, two movable members may co-operate with a single fixed semiconducting member. In the arrangement in Fig. 7, the stationary member 24 is fixed by a post 53 in a block 54 of insulating material, and the movable member 20 is held by pins 60 engaging bearings secured to the member 20. Arms 57 on the member 20 engage a stretched string 63 which provides the restoring force. The member 20 may alternatively be pivoted on knife-edges and tensioned by a helical spring or by a bowed strip spring which is twisted in and arranged in the pivotal axis. Further arrangements are described in which the movable member is a flat plate and is mounted between cheeks which are carried by one or more stretched strings and are pivoted on knife edges or the movable member is held at two adjacent corners by tubular torsion members which are fixed to a frame or one corner may be provided with a pivot and the other with a torsion tube. The movable member may carry a recording member or a mirror or may itself be silvered. Where magnetic restoring forces are used, the currents induced by the oscillations are utilized to control relay or for monitoring. Specifications 151,997 and 239,741, [both in Class 37], are referred to.