Pulsation-free volumetric pump

Claim 1

A pulsation-free reciprocating volumetric pump comprising a pump housing having two plungers providing a combined discharge volume, a cam for driving said plungers, a direct current driving motor connected to said cam, a rotation setting means operatively connected to said driving motor for supplying thereto a predetermined direct current voltage for driving the motor at a predetermined rotational rate, a main amplifier operatively connected to said rotation setteing means for supply thereto as a first input the direct current voltage from the rotation setting means, said main amplifier having an output supplied to said drive motor, a tachogenerator operatively connected to said drive motor for drive thereby and supplying its output voltage as a second input to said main amplifier, and means for compensating for pressure pulsations produced during pumping, said last-named means comprising a pressure detector for detecting the pressure of said combined discharge volume and providing an output signal having a direct current component and an alternating current component representative of said pressure pulsations, means eliminating the direct current component of the pressure detector output signal and passing only the alternating current component, an amplifier circuit for amplifying the alternating current component, and adding means supplied with the direct current voltage from the rotation setting means and with the amplified alternating current component from the amplifier circuit for adding said alternating current component, after phase reversal, to the direct current voltage from the rotation setting means for modifying said first input voltage to said main amplifier in a sense to modify the rotation rate of the drive motor to compensate for said pressure pulsations.