| 摘要 |
A downhole pump has a master piston having a first side and a second side in a first piston chamber. The first piston chamber has a first inlet and a second inlet for alternatingly applying fluid pressure to the first side of the master piston to move the piston toward the top of a piston stroke, and to the second side of the master piston to move the piston toward the bottom of the piston stroke. A valve is carried by the master piston that relieves fluid pressure from the respective side of the master piston once the top or bottom of the stroke is reached. There is a sequencing valve with a first state that applies fluid pressure to the first inlet and a second state that applies fluid pressure to the second inlet. The sequencing valve switches between the first state and the second state once a drop in pressure occurs. A slave piston is driven by the master piston in a second piston chamber. The second piston chamber has at least one fluid inlet and at least one fluid outlet. |
