| 摘要 |
The plunger of the pump has a radially extending lug near its upper end which can be inserted down into a notch in the stationary pump collar when the plunger is fully depressed, so that when the plunger is then rotated in a clockwise direction relative to the collar, the lug is brought under an overhanging ledge on the collar to releasably lock the plunger in its fully depressed position. In order to deter unlocking, the lug of the plunger and the interior wall of the collar are provided with mutually interengageable structures that permit the lug to be rotated substantially without significant resistance into a final or fully locked up position against a shoulder beneath the ledge but to be held in such fully locked up position against unlocking movement unless substantial, counterclockwise-directed force is applied. Interengaging ramp surfaces on the collar and the lug slide against one another during movement of the lug into its locked up position, while abrupt, blocking surfaces thereafter oppose one another to prevent unlocking rotation unless significant force is applied to override the blocking action. The underside of the retaining ledge of the collar is also provided with a depending abutment adjacent the notch which lies in the path of travel of the lug during attempted unlocking rotation to thereby block access of the lug to the notch unless the plunger is first depressed a sufficient amount to permit passage of the lug under the abutment. |
