Valve seal breakaway device

摘要

A spool valve has a seal-carrying spool movable in a valve bore terminated at one end by an end wall. A stem projects toward the end wall from an end of the spool. A hollow cylinder member is mounted coaxially on the stem via a radially inwardly extending flange which slidably receives the stem. A spring is coaxially mounted on the stem and is biased to urge the cylinder member away from the spool. A stop near the end of the stem retains the cylinder member on the stem and maintains a minimum preload in the spring. When the spool is in a position near the end wall, the end wall engages the cylinder member and moves it away from the stop, thereby compressing the spring so that the spring will be biased to move the spool away from the end wall.