GB734453A - Method of making circuit connections to a transducer unit - Google Patents

Abstract

734,453. Piezo-electric transducers. CLEVITE CORPORATION. May 6, 1953 [May 17, 1952], No. 12601/53. Class 40 (8). A multiplate transducer comprising plates of, e.g., barium titanate with an inner electrode between two of the plates is connected, for purposes of polarization, to an external circuit by pressing one edge of the transducer against a conductor to effect contact with the inner electrodes, the outer electrodes being insulated from the conductor by a non-conducting margin along the edge. Small sheets of barium titanate may be prepared by the dipping and firing processes described in Specification 663,424. These sheets are trimmed and cut into strips having a width equal to the desired length of the transducer. Each strip is provided with a conductive coating by dipping the strip in a suspension of a powder containing silver particles and a vitreous binder in a suitable vehicle such as toluol. The edges and a narrow margin along one side (the outer side) of each strip are wiped clean and the conductive coating is fired. The inner side of each strip is then tinned and the strips sweated together in pairs. Finally the strip is cut along its narrow dimension to produce a number of transducers 23, Fig. 2, each having two plates 24, 25 joined by an inner electrode 26 extending to the lower edge and having also two outer electrodes 27, 32 spaced from the lower edge by a margin 28. At this point in the process leads 31, 33 are connected to the outer electrodes. In order to apply a polarizing voltage to the transducer plates a number of transducers are mounted in an insulated holder 36 by means of rows 'of phosphor-bronze spring contacts 38, 39 which hold the lower edge of each transducer in contact with a corresponding yieldable conductor 42 having a terminal 44. The members 42, which may consist of metallic brushes or rubber pads pigmented with acetylene black, contact the edge of the inner electrodes 26 but are insulated from the outer ones by the margins 28. The holder 36 is adapted to clip into a further holder 46 having rows of spring contacts 48, 49 which contact the springs 38, 39 and are connected in parallel through resistors 52, 53 (# 10 M#) to a terminal 57. A polarization voltage of, e.g., 20 kv./in. is applied for 10 or 15 minutes across the terminals 44, 57. The holders may be immersed in oil at a desired temperature during this time. To test the effectiveness of the polarization a voltmeter is connected between the terminal 44 and each of the contacts 38, 39 in turn. Wherever a short-circuit occurs a voltage lower than the full polarization voltage will be registered since a portion of this voltage will be dropped across one of the resistors 52, 53. The holders may be tested for continuity with the transducers in position by means of an A.C. voltage applied across the terminals 44, 57. U.S.A. Specification 2,486,560 is referred to.