Liquid dispensing pump

Claim 1

A liquid dispensing pump powerable by a pressurized liquid, comprising: (a) a pump housing having therein a pumping and pressurizing chamber, said chambers being physically divided from each other; (b) means movable within the housing for transferring a pressure in the pressurizing chamber to the pumping chamber and for reducing the volume of the pumping chamber; (c) a liquid inlet to the pumping chamber, said inlet having a valve for directing liquid flow into the pumping chamber; (d) a liquid outlet from the pumping chamber, said outlet having a valve for directing liquid flow from the pumping chamber; (e) a liquid source line having an upstream end adapted to be connected to a source of liquid under pressure, a normally closed control valve which upon being opened and operable for permitting a flow of liquid under pressure through said source line, a flow restrictor downstream of said control valve for backing up at least part of the source pressure during flow of liquid therethrough, and an outlet for discharge of liquid flowing through said restrictor; (f) a pressurizable power conduit having an inlet end fluidly connected to said source line in between the control valve and the restrictor, a second end fluidly connected to the pressurizing chamber, and a check valve for permitting a flow of liquid under pressure from said source line through the conduit to the pressurizing chamber and for precluding reverse flow of liquid from the pressurizing chamber back to the source line from whence the liquid came; and (g) an open drain fluidly connecting the pressurizing chamber to atmosphere, said drain being sized with respect to said power conduit to form a greater restriction to flow of power liquid therethrough than does said power conduit, for permitting flow of power liquid through the drain during an operative pressurization of the pressurizing chamber of only a fractional portion of the power liquid passing through said power conduit during such pressurization, and for draining from said pressurizing chamber the remainder of the power liquid passed through said power conduit during such operative pressurization, upon termination of an operative pressurization of said power conduit, said drain being a capillary aperture sized for retaining by capillary action a prime of liquid within the power conduit and pressurizing chamber.