GB700233A - Devices for converting mechanical vibrations to electrical variations - Google Patents

Abstract

700,233. Transducers, semi-conductive amplifiers. WESTERN ELECTRIC, CO., Inc. Aug. 12, 1949 [Aug. 19, 1948], No. 21022/49. Class 40 (4) [Also in Group XXXVI] Means for convertingmechanical vibrations into electrical variations comprises a semiconductor amplifier having' at least three electrodes, the contact between one of which and the semi-conductive body being varied in accordance with the vibrations. In a first embodiment (Fig. 1), the semi-conductor amplifier is a block 1 of germanium having emitter and collector electrodes 4 and 5 and a base electrode 6 which may be a plated metal film. The normal sharp point contact of the emitter is replaced by a substantially spherical one of about 2-20 mils. diameter, preferably of carbon or of a silicon compound such as quartz with a tough carbon skin coated thereon. This contact is mounted on one end of a light stiff rod 10 driven by a diaphragm 11. The variations in the pressure of this contact on the surface 2 change the contact area and the spacing between the emitter and collector electrodes and corresponding variations are produced in the collector current. To prevent the output from being noisy, the block surface is smoothly polished either mechanically, electrolytically or both. The same construction may be adapted to act as a reproducer for lateral-cut records by arranging that the contact 4 is varied under the control of a stylus. Fig. 2 (not shown). In the embodiment of Fig. 4 the emitter and collector electrodes 24, 25 are placed on-opposite sides of a block 21 of semi-conductor material with concave surfaces at the thinnest part thereof and a circumferential metal ring 26 serves as the base electrode. The spherical electrode 24 is considerably larger than that of Fig. 1, e.g. 10- 100 mils diameter, but the operation is similar. In the Fig. 5, embodiment for reproducing hill-and-dale records the point of contact of the electrode 24 is altered, but its pressure and contact area are not. Axial movement of the stylus 33 is transmitted by the rod 35 (restrained to move vertically) and the electrode 24 slides over the surface of the semi-conductor block 21 thus altering the distance between the emitter and collector electrodes. To reduce wear in this type of embodiment a Boiling or rocking movement of the .emitter electrode may be employed as shown in Fig. 6. The emitter electrode is a sector of a sharp-edged disc 44 the diameter of which is slightly less than that of the concave surface of the block. It is held in a normal rest position in which its point of contact is slightly misaligned with the collector electrode 25 by a restoring spring 46 serving also as an electrical connection, and is rocked under control of the applied vibrations. Specifications 472,101, 632,942, [ Group XXXVI], 632,980, [Group XL (c)], 694,021, 694,022, [Group XXXVI], 694,023, 694,024, 694,025, 694,026 and 700,232 are referred to.