US Patent 4,355,643
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
The present invention comprises a vacuum cup having a concave undersurface on which is mounted a doppler flow transducer. A vacuum tube is in communication with the undersurface of the cup and is capable of removing the air from beneath the suction cup so as to permit the suction cup to be clamped over an artery or other vessel. The device is used by activating the transducer to cause it to transmit a sound signal into the artery. The secondary or echo sounds created by this sound signal are sensed by the transducer and the transducer converts these secondary sound signals into electrical signals which are transmitted to means for analyzing the signals so as to determine the velocity of fluid flow within the vessel.
Laughlin, Donald E. and Krumm, Paul J. Vacuum cup doppler flow transducer and method for using same. US Patent 4,355,643 filed March 05, 1980 and issued October 26, 1982. https://ir.uiowa.edu/patents/30