Sperry Corporation

Ford New Holland, Inc.

Peter G Mitchell

Carl E Bohman

Ronald T Sheehan

Charles G Bagg

William H Kent

An agricultural harvesting machine having a cutting element movably supported thereon is provided with a height sensor including a transmitter and a receiver mounted for movement with the cutting element. The transmitter directs bursts of sound waves in the range of about 5 KHz toward the ground and echoes of the bursts are picked up by the receiver, the elapsed time between transmission and reception being an indication of the height of the cutting element above the ground. To distinguish between echoes of the bursts and environmental noise picked up by the receiver, the bursts are encoded by transmitting them in pairs, the bursts of a pair being of fixed duration and separated by a fixed interval of time. The duration of each signal and the time spacing between signals is checked and if they are not of the correct duration or are not separated by the fixed interval of time they are rejected as noise. The time between transmission and reception of a burst is measured to provide an indication of the height of the cutting element. The measured height is compared with a reference or desired height and the difference value is used to control movement of the cutting element to the desired height.

Distance measurement and control using coded sonic signals

For use in transmitting acoustic waves propagated along a well drilling string, a piezoelectric transducer is provided operating in the relatively low loss acoustic propagation range of the well drilling string. The efficiently coupled transmitting transducer incorporates a mass-spring-piezoelectric transmitter combination permitting resonant operation in the desired low frequency range.

Resonant acoustic transducer system for a well drilling string

An illustrative embodiment of the invention provides an acoustic sensor for detecting stones and other hard foreign objects mixed within crop material in a harvesting machine susceptible to damage thereby. The acoustic sensor comprises a sensing surface disposed within an input path in the harvesting machine for impacting engagement with the flow of crop material therein and an acoustic sensing device coupled to the sensing surface for detecting acoustic vibrations induced within the sensing surface as a result of impact therewith by stones and other foreign objects mixed within the crop material. The sensor provides electrical signals in response to the acoustic vibrations indicative of the impact of the crop material and the foreign objects with the sensing surface and includes isolation means for obviating the effects of extraneous acoustical signals of the same character as the foreign object impacting signals to accentuate the foreign object impacting signals and thereby reduce the false alarm signals.

Growing community of inventors

Concord, MA, United States of America

Peter G Mitchell