| 摘要 |
<p>Disclosed is an assembly for unseating a seated traveling valve ball (75), and pumps utilizing such an assembly. The assembly generally includes a tubular member having therein a piston (40) with an actuator (41) 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 an engaging member (141) suitable to strike the seated ball asymmetrically with respect to the vertical axis through the center line of the ball.</p> |
