| 主权项 |
1. A piston pump comprising a piston chamber-forming body and a piston element reciprocally slidable relative the body about an axis,
the piston element including a sleeve portion and a tube portion, the sleeve portion disposed coaxially about the axis annularly about the tube portion, the tube portion coaxially slidable along the axis relative the sleeve portion, the tube portion having an elongate discharge passageway and a discharge outlet, the sleeve portion coaxially slidable relative the body along the axis between a retracted position and extended position, the tube portion captured for axial movement between the sleeve portion and the body such that relative outward sliding of the tube portion on the sleeve is limited to an outer position relative the sleeve portion by engagement of an outwardly directed stop surface on the tube portion with an inwardly directed stop surface on the sleeve portion and relative inward sliding of the tube portion relative the body is limited to an inner position relative the body by engagement of an inwardly directed stop surface of the tube portion with an outwardly directed stop surface on the body, in sliding of the sleeve portion inwardly relative the body from the extended position toward the retracted position, the sleeve portion moves the tube portion inwardly from the outer position to the inner position with, when the tube portion is in the inner position relative the sleeve portion, the sleeve portion is in a partially retracted position intermediate the extended position and the retracted position, in sliding of the sleeve portion inwardly from the partially retracted position to the retracted position the sleeve portion moves inwardly relative both the body and the tube portion, a fluid compartment selected from the group consisting of a fluid compartment defined between the body and the tube portion and a fluid compartment defined between the body, the tube portion and the sleeve, the fluid compartment in communication with a fluid in a reservoir by a one-way valve permitting fluid flow outwardly from the reservoir to the fluid compartment but preventing fluid flow inwardly, an air compartment selected from the group of an air compartment defined between the tube portion and the sleeve portion and an air compartment defined between the sleeve portion and the body, on sliding of the sleeve portion inwardly from the extended position to the partially retracted position with the sleeve portion moving the tube portion inwardly from the outer position to the inner position, a volume of the fluid compartment is reduced discharging fluid from the fluid compartment as a fluid stream through the passageway of the tube portion and out the discharge opening, on sliding of the sleeve portion inwardly from the partially retracted position to the retracted position, a volume of the air compartment is reduced discharging air from the air compartment into the fluid stream in the elongate discharge passageway, on sliding of the sleeve portion outwardly from the fully retracted position to the partially retracted position, the volume of the air compartment increases drawing air into the air compartment, and on sliding of the sleeve portion outwardly from the partially retracted position toward the extended position, the tube portion moves outwardly toward the outer position and the volume of the fluid chamber increases drawing fluid from the fluid reservoir past the one-way valve into the fluid chamber. |
