Piezoelectric driven diaphragm micro-pump

Claim 1

A pump having an inlet and an outlet and comprising: a sealed variable volume chamber; a flexible tube inside said variable volume chamber and connected to said inlet and outlet; a piezoelectric means forming a wall of said chamber for varying the volume of said chamber; an essentially non-compressible liquid within said chamber to transmit forces created inside said chamber to said flexible tube during the volume variation of said chamber; solenoid valve means for controlling the flow of fluid through said inlet and outlet; and control means connected to said piezoelectric means and said solenoid valve means for electrically activating said piezoelectric means and said solenoid valve means in a desired sequence to pass fluid from said inlet to said flexible tube and to pump fluid from said flexible tube to said outlet, said control means comprising an oscillator means for providing an electric signal output of a selectively fixed frequency, adjustable valve opening duration means for controlling the time duration of activation of said solenoid valve means, a step-up transformer having the secondary connected across said piezoelectric means and the primary adapted to alternately conduct current in opposite directions according to said oscillator output signal, first switch means activated by said oscillator output signal for providing current in alternate, opposite directions to said primary, and second switch means for activating said valve opening duration means according to said oscillator frequency; whereby the volume of fluid pumped by and through said flexible tube is a function of the selectively fixed oscillator output frequency and the adjustable time duration of activation of said solenoid valve means.