Patent GB-1431356-A (GB)
Title: Pickup cartridge
IPC: H04R17/04
Filed: 1973-07-20
Abstract: 1431356 Stereophonic pick-ups MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 20 July 1973 [21 July 1972] 34757/73 Heading H4J A 45-45 degree stereophonic pick-up has two transducers slidably coupled to a stylus arm by a resilient coupler secured to the stylus arm at a point along the length of the arm. The pick-ups described are for playing 4-channel discrete gramophone records having a frequency range up to 50 kHz. The transducers are piezoelectric or piezoresistive. They may be of semi-conductor material such as silicon or germanium. A stylus arm 9 (Fig. 2b) is embraced by a circular coupler 11 of butyl rubber or plastics material. Transducers 12a, (12b), Fig. 2a (not shown), are of rectangular strip form, are mutually perpendicular and in use are at 45 degrees to the surface of a gramophone record 7. Each transducer is held by a butyl rubber damper 13 secured to a case 14. The circular coupler 11 touches the inner surfaces of the transducers 12a, (12b). The stylus 8 of diamond has a titanium base and the stylus arm 9 is a titanium or aluminium tube. Stylus pressure and output sensitivity are determined by the position of the coupler 11 along the length of stylus arm 9 (see Figs. 4a, 4b, not shown). The coupler may consist of three portions 11a, 11b, 11c (Fig. 4c) each of different hardness, the stylus arm support structure 10 being movable in the axial direction A. Each transducer, such as transducer 12a may contact portion 11a to give maximum stylus pressure and maximum output, or may contact portion 11b as shown, or may contact portion 11c to give minimum stylus pressure and minimum output. The stylus arm support structure 10 may include a filament of phosphor bronze or nylon 10a in a cylindrical support 10b. In Fig. 4c (and Fig. 5a, not shown) the coupler 11 engages an edge portion of each transducer 12, or engages a surface of each transducer (12), Fig. 5b (not shown) or the coupler engages each transducer 12 in parallel relation (Fig. 5c, not shown). The edge of the coupler which engages each transducer may be curved (Fig. 6a, not shown) or the coupler may be of elliptical cross-section (Fig. 6b, not shown). Other couplers are of square section (Fig. 7a, not shown) or part-circular section devoid of mass in the lower portion (Fig. 7b, not shown) or heart-shaped (Fig. 7c, not shown). Another coupler has an outer portion (11a) Fig. 8b (not shown), of resilient material such as butyl rubber and an inner portion (11b) of synthetic resin. Unwanted portions of the coupler may be removed to minimize the resilient material (Fig. 8c, not shown). A stylus arm support 10 (Fig. 9) may be of resilient material and secured to a removable stylus holder 17. The transducers 12a, 12b (Fig. 10) are inserted into rectangular openings in dampers 13a, 13b which are held by a support 20. In an alternative arrangement the dampers (13c, 13d), Figs. 11a, 11b (not shown), are hollow or solid cylinders of resilient material each held between a transducer and the casing. Another arrangement (Fig. 12) has a coupler 11 with a frusto-conical face engaging one end of each transducer 12, the stylus 8 being on the opposite side of the coupler 11 to the transducers 12. A filament 10c extends through a flange 9b of the stylus arm 9 and is secured in a hole 10c in a support 10b by a screw 10e. A stylus arm damper 10f is interposed. In further embodiments (Fig. 13a, not shown) the end of each transducer 12 carries a wing (22) and the coupler 11 engages the end of the wing (22). Such coupler may be spherical (Fig. 13b, not shown) bevelled (Fig. 13c, not shown) or an O- ring (Fig. 13d, not shown). In place of the wing (22) a cushion (23), Figs. 14a, 14b (not shown), of resilient material may engage the coupler.