GB1260387A - Transducers - Google Patents

Abstract

1,260,387. Piezoelectric transducers. PIONEER ELECTRONIC CORP. 23 Jan., 1969, No. 3981/69. Heading H4J. An audio transducer comprises a sheet of molecularly oriented high molecular weight polymeric piezoelectric flexible material having electrodes on two opposite surfaces. A potential difference across the electrodes results in or from mechanical strain in the sheet at an oblique angle to the direction of molecular orientation of the material. Suitable natural materials are collagen (animal tendon), silk fibre and wood cellulose. Synthetic materials include poly-8- methyl L glutamate and poly-8-benzyl glutamate. There may be a square sheet rigidly held at two opposite corners and resiliently held at the other two corners (Figs. 3, 4, not shown). Two sheets of the material in the same plane may act to provide a monaural gramophone pickup (Fig. 7, not shown), or two sheets at right angles (Fig. 9) may provide a stereo pickup. Another stereo pickup has four diagonally arranged sheets with the stylus at the centre (Fig. 10, not shown). A loud-speaker has a V-shaped sheet 51 (Fig. 12) of the material, the apex of the sheet being connected to the apex 59a of a conical diaphragm 59. Alternatively the sheet 51 is planar. A sonar receiver or transmitter comprises a sheet 61 of the material, opposite ends of which are secured to a frame 60 (Fig. 16). Hollow cylindrical members 81a, 81b (Fig. 19) formed from the sheet material are sealed at opposite ends to walls 87 and have between them a diaphragm 86. The diaphragm may be apertured and if a valve is provided at each aperture a flute-like sound is produced. Alternatively the ends of the cylindrical members may be open and one may be coupled to a horn (98), Fig. 20 (not shown), to provide a loud-speaker. A sheet 102 (Fig. 21) of the material may be secured at two opposite edges to walls 104 on a base-plate 101, spongy material or fluid 103 imparting resiliency. A number of sheets 102 may be mounted side by side on a common baseplate 101 (Fig. 22, not shown) to provide a multistereo acoustic effect. Instead of the sheet being curved as in Fig. 21 it may be angled along its centre line, being supported by a resilient upright (123), Fig. 25 (not shown). A multidirectional loud-speaker has sheets 132 of the material supported by resilient struts 133 about a base 131 (Fig. 26). Alternatively a sheet of the material is formed into a tube to provide an omnidirectional loud-speaker (Figs. 23, 24, not shown).