| 摘要 |
Disclosed is an assembly for unseating a seated traveling valve ball, and pumps utilizing such an assembly. The assembly generally includes a tubular member having therein a piston with an actuator for engaging the ball. Mechanical advantage is provided either by providing a sealing area of the piston that is greater than the sealing area of the seat valve and/or by providing a engaging member suitable to strike to seated ball asymmetrically with respect to the vertical axis through the center line of the ball.
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