Patent GB-1308473-A (GB)
Title: Transducers
IPC: H04R21/04
Filed: 1970-05-11
Abstract: 1308473 Piezoresistive devices MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 11 May 1970 [9 May 1969 (4)] 22718/70 Heading H1K [Also in Division H4] A transducer comprising a substrate having a deposited film of semi-conductor piezoresistive material includes a viscous material for imposing a stress on the substrate and on the film. The viscous material is preferably a silicon base grease. The semi-conductor material comprises silicon, germanium or indium antimonide and is vacuum evaporated on a substrate of polyimide, polyamide or mica. Electrodes of nickel, chromium or gold are also vacuum evaporated. A microphone (Fig. 21) includes a diaphragm 314 connected to a semi-conductor film. The film is deposited on a substrate to form an element 315, the opposite ends of which are in recesses 318, 318<SP>1</SP> of a mounting block 316. Viscous material 319, 319<SP>1</SP> is disposed in the recesses. Alternatively, a generally flat diaphragm 314 (Fig. 22) is fixed to a movable drive member 323 to define opposed recesses 322, 322<SP>1</SP>. A fixed member 324 carries semi-conductor elements 315, 315<SP>1</SP> which extend into the recesses 322, 322<SP>1</SP>, viscous material 319, 319<SP>1</SP> being interposed. One typical stereophonic pickup (Figs. 6, 8) has a cantilever stylus arm 14 supported by wire 15 to a cylindrical support 17 mounted in a main support block 21. An insulating film substrate 19 is clamped between a drive member 18 and a damping sleeve 20. The block 21 has front and rear recesses 22, 24 joined by a bore 25 in which fits support 17. Terminal rods 26 extend through the block 21 and are wired to pins 28. The damping sleeve 20 fits into an extension 23 of recess 22. The insulating film substrate 19 has two perpendicular arms each carrying two semi-conductor piezoresistive elements 36, 36<SP>1</SP> and 37, 371. Each pair of elements is connected together at the outer ends and the inner ends are connected to electrodes 34, 34<SP>1</SP>, 35, 35<SP>1</SP>, which are in turn connected to rods 26. The arms are located in the recess 22. This is filled with flowable viscous material. A front cap 39 is provided. An alternative substrate (Fig. 10, not shown) carries a single semiconductor element (47, 48) on each arm (29, 30). Another substrate (Fig. 11, not shown) has a cut-out (49) instead of an opening 31 and the inner ends of the semi-conductor elements are electrically connected together. In another stereophonic pickup (Figs. 12 to 14, not shown) the substrate is of cruciform shape with two semi-conductor piezo resistive elements on each arm. The wire (17) is dispensed with and the substrate fits on the reduced front part (137) of a cylindrical support (136). Alternative cruciform substrates have a single semi-conductor element on each arm (Figs. 15, 16, not shown). In yet another stereophonic pickup (Figs. 17 to 20, not shown) the substrate has two arms (221, 222) each carrying two semi-conductor elements. The arms (221, 222) are bent back to be parallel with the axis of the stylus arm and are contained in recesses in a cylindrical body (223). The recesses are filled with viscous material.