Flow detector

Claim 1

A flow detector for detecting and monitoring the dynamic characteristics of particulate matter as it is conveyed pneumatically within a conduit, said flow detector comprising a conduit segment formed of a hard material and having a wall subject to vibration in response to particles striking said wall as the particles flow through the conduit segment, said conduit segment having an internal cross section corresponding to that of a conduit of which said conduit segment is a part, a vibrational excitable piezoelectric transducer which generates an output voltage having an amplitude at a preselected transducer resonant frequency on the order of 3.1 KHz being of at least one order of magnitude greater than its voltage output at all other frequencies, the resonant frequency of said transducer excited by the vibration amplitude of said wall regardless of the vibratory frequency of said wall or the impact of particles thereon for a selected desired particle mass flow rate per unit of time, and means mounting said transducer in operative engagement with said wall, said transducer being of a cantilevered beam type with said beam effective length being adjusted to resonate at said preselected frequency, with the mass of said beam and the mechanical mounting of said beam being selected to cause said piezoelectric transducer to generate little or no voltage at frequencies other than said preselected resonant frequency, and said beam being shaped to vibrate in a plane at a right angle to a longitudinal axis of said flow segment and the length of said beam being parallel to said axis to reduce excitation of said beam by forces acting on said conduit segment wall other than those induced by particles flowing through said conduit segment.