Patent ID: 9140246
Filing Date: 2015-09-22
Classification: F04B

Abstract:
1. A pressure controlled pump for pumping a viscous liquid from a reservoir, said pump comprising: a pump body adapted for positioning above said reservoir; an elongate tube extending downward from an upper end connected to the body, past an upper portion and a lower portion, to a lower end when the body is positioned above said reservoir; an elongate core slidably received in the tube and extending vertically downward from the body into the liquid when the body is in position above the reservoir, the core having a longitudinal axis extending between an upper end mounted on the body and a lower end opposite the upper end; a stepper motor mounted on the body having a selectively rotatable output shaft extending vertically above the liquid in the reservoir when the body is in position; a transmission operatively connected to the stepper motor output shaft for effecting reciprocating relative motion between the tube and the core so the elongate core moves between a relative raised position and a relative lowered position as the stepper motor output shaft rotates in one direction to effect an upward pumping stroke and in an opposite direction to effect a downward pumping stroke; an inlet check valve mounted inside the tube defining with the tube an expansible and contractible lower pump chamber, the inlet check valve being oriented to open during each upward pumping stroke permitting viscous liquid to enter said lower pump chamber; an annular upper chamber defined in part by the tube and the core above the lower pump chamber and having a cross-sectional area half as large as that of said lower pump chamber; a lateral passage in the core connecting the lower pump chamber to the annular upper chamber having a check valve oriented to open during each downward pumping stroke; an outlet passage connected to the annular upper chamber so viscous liquid flows from the annular upper chamber and through the outlet passage during each upward pumping stroke and each downward pumping stroke; a pressure monitor in fluid communication with liquid in the outlet passage for measuring pressure of said liquid; and a control operatively connected between the pressure monitor and the stepper motor for controlling operation of the stepper motor in response to a signal from the pressure monitor, the control adjusting stepper motor output shaft speed in response to the signal from the pressure monitor, said control controlling operation of the stepper motor to deliver a predetermined quantity of viscous liquid through the outlet by effecting a selected number of upward pumping strokes and downward pumping strokes, said control thereby delivering the predetermined quantity of viscous liquid at a preselected pressure.