GB520357A - Improvements in or relating to piezo-electric pick-ups - Google Patents

Abstract

520,357. Gramophone pick-ups. WEBSTER ELECTRIC CO. Oct. 19, 1938, No. 30264. Convention date Jan. 21. [Class 40 (iv)] [Also in Group XL] In a pick-up of the piezo-electric type, the crystal assembly is contained in a chamber formed by two separate housing members of flexible resilient material adapted to be clamped together. The crystal unit, which comprises two plates 30, 31 of Rochelle salt separated by a metal foil 32 and covered on the outside by metal foils 33, 34 which are coated with asphalt lacquer, is supported by resilient members 94, 95 in a chamber 54 formed by two similar members 35, 36 of rubber which are clamped together by a metal casing 82. The rubber members 35, 36 are formed with co-operating grooves in which are located sleeves 100, 101 for the leads to the crystal and further grooves which form bearing surfaces for the horizontal arms of a cruciform needle-carrier. The members 35, 36 are shaped to form a recess 64 adjacent the upper part of the needle-carrier and a clearance 123 is left between the arm carrying the needle and the metal case 82. The vibrations of the needle are transmitted to the crystal unit 29 by extensions. 78, 79 of the arm 66 forming a U-shaped recess in which the unit is resiliently clamped by means of a rubber strip 81. The ends of the sleeves 37, 38 are pinched together and soldered to connectors 104, 105 attached to the metal foils 33, 34. Cotter pins 103 are secured within the sleeves and have the leads soldered to their outer ends. In a modification, Fig. 3 (not shown) the eyes of the pins are within the chamber and the legs of the pins pass through the sleeves and may be inserted in a connecting jack. In alternative connecting arrangements the insulated cores of a twin cable are soldered to the inner ends of the sleeves, Fig. 4 (not shown), or connecting members passing through the sleeves and soldered at their inner ends are formed with screw terminals, Fig. 5 (not shown), or have eyes to which the external connecting'leads are connected and soldered, Fig. 12 (not shown). In the construction shown in Fig. 9, in which the needle is inserted from the top of the casing, the groove 59 extends beyond the top of the metal casing, is provided with a metal lining 121 and has a frusto-conical portion 99 leading to the needle socket.