FLEXTENSIONAL TRANSDUCER WITH VARIABLE BEAM PATTERN AND FREQUENCY CONTROL

摘要

A flextensional transducer for use in the instrumentation of an oil well drill bit includes a stack of piezoceramic elements arranged to define a longitudinal axis and to move longitudinally in response to an electric signal, and a plurality of flexible, generally arcuate longitudinal ribs directly or indirectly connected to the piezo stack so that the ends of the ribs move longitudinally in response to the longitudinal movement of the piezo stack. This longitudinal movement of the ends of the ribs causes the middle portions of the ribs to flex radially, thus producing acoustic waves. The transducer is designed to operate in the hostile environment of the drilling bit of an oil well, and operates effectively at temperatures of at least -40°C to 150°C. The transducer provides sound waves at a frequency of about 15 KHz, with a -6dB bandwidth of 5KHz to 25 KHz and at a sound pressure of at least 2 kPa. The piezoceramic elements may be made of a material having a base formula of : PbxSr( 1-X)(Mn1/3Sb2/3)(1-y)(ZrzTi1-z)yO3 wherein x is in the range of 0.95 to 0.99; wherein y is in the range of 0.92 to 0.97; and wherein z is in the range of 0.45 to 0.55; with the composition further including one or more dopants selected from the group consisting of : PbO, CeO2, SnO2, Sm2O3, TeO2, MoO3, Nb2O5, SiO2, CuO, CdO, HfO2, Pr2O3, and mixtures thereof.