| 摘要 |
<p>1. Device permitting a cyclic automatic reversal of a double-action jack, characterized in that the information which triggers the reversal is taken from the draining chamber of the jack by a probe means (11, 12, 12A, 15) which ascertains the state of flow and the state of absence of flow from this draining chamber and triggers the reversal at a zero flow.</p> |
