GB810971A - Improvements in and relating to electro-mechanical transducers - Google Patents

Abstract

810,971. Gramophone pick-ups. COSMOCORD Ltd., and KELLY, S. March 25, 1955 [Dec. 29, 1953], No. 36044/53. Class 40 (4)] In a piezo-electric transducer a single piezoelectric element is attached to part of an element of non-piezo-electric material, the thicknesses of the two elements being such that their compliances for transducing motion are approximately the same, the second element having also a part for attachment to a support, and an intermediate portion shaped so as to increase the compliance of the second element with regard to the supporting part. As shown in the gramophone pick-up of Figs. 1, 2, a Rochelle salt plate 10, 0 degree X-cut and of rectangular shape is cemented to the portion 11a of the polystyrene mounting 11, the thickness of which is so related to that of the plate 10 that the two have equal compliances. The forward portion of the mounting 11 forms a shoulder 11b of roughly double thickness, from the centre of which extends forwardly a cylindrical spigot 11c which enters an opening in a plate 12, supported from a body 13 so that the spigot 11c forms a front bearing for the transducer element. At the rear end the portion 11dis secured to the body 13, and portions 11d and 11a are joined by the section 11e which is reduced in height and thickness so as to make it torsionally compliant. A stylus 15 is mounted in a straight carrier 16 inserted in a boring in the shoulder 11b. If desired, the portion 11a may be moulded with a marginal lip thus forming a recess to receive the plate 10. A thin sealing plate of polystyrene of, say 5 mils. thickness, may then be used to cover the recess. Cementing of this plate in position ensures that the crystal is embedded in a waterproof insulating medium. In the modification of Figs. 3, 4 the shoulder 11b is extended to form a drive lug 11f, and a plate 17 is secured to the bottom face of body 13, into a hole in which is fitted a grommet 19 of compliant, lossy material. The stylus 21 is carried by a carrier 22 of wire, or the like, the rear end of which fits into the grommet 19, while the end of lug 11f is split or notched to receive the carrier 22. Alternative stylus mountings are described with reference to Figs. 5 to 7 (not shown). A pick-up cartridge of the turn-over type using an element and drive similar to that of Figs. 3, 4 is shown in Fig. 8. The two-part moulded casing 30 (not shown), 31 is held together by rivets 32, 33 which also hold the front bearing pivot member 34 which is intended to be carried in a bearing bush in a frame as shown in Specification 760,787. The mounting 36 is preferably made of polythene. Specification 799,329 also is referred to.