GB1444966A - Electromechanical vibration pick-ups and methods of their manufacturing - Google Patents

Abstract

1444966 Gramophone pick-ups THOMSON-BRANDT 8 Oct 1973 [10 Oct 1972] 46799/73 Heading H4J A vibration pick-up, such as a stereophonic gramophone pick-up of the general type shown in Fig. 1 and comprising a transistor 7 secured to a beam 3 is made by fixing the transistor 7 to the beam 3 and subsequently cutting the beam 3 to divide it into two parts connected by the transistor 7. The transistor 7 acts similarly to a strain gauge. A ceramic beam (Fig. 4) of alumina, of initial thickness b, has a thinned part 11, thickness c, formed by machining. A tranverse slot 13 is formed by a diamond wheel or ultrasonic machining. The surfaces adjacent the slot 13 are smoothed and coated with gold film 16, 17 (Fig. 5). Film 17 has an extended portion 18. Two side coatings 19, 20 are also provided. Coatings 19, 20 are connected by leads (31), Fig. 6 (not shown), to the transistor 7 and extend to a damping block 5 for connection to circuitry (not described). The transistor 7 is soldered across the slot 13 (Fig. 7) by a gold-silicon solder. The beam is assembled in a housing 6 in a manner similar to that shown in Fig. 1. The side of the slot 13 is then cut using a laser beam, thereby separating the two parts 10, 11. The laser beam also cuts through the housing 6. In another embodiment (Fig. 9, not shown) one side of the beam 3 is adhered to a glass base (26) and the other side is abraded to provide a thinned part 11 and the slot 13. The beam is then unstuck and assembled in a housing 6. The laser cut is then carried out at the base of the slot 13.