Open hydraulic circuit for e.g. turret of hydraulic shovel, has jettisoning valve device moving to jettisoning position when selector isolates ducts from pump and tank, and difference between duct pressure and jettisoning pressure changes

摘要

The circuit has a jettisoning valve device (50) adopting a retaining position and a jettisoning position in which it connects main ducts (14, 16) to a jettisoning enclosure (24). The device moves to the jettisoning position when a selector (18) isolates the ducts from a main pump (10) and a tank (20) and a difference between a main duct pressure and a jettisoning pressure which is greater than a boost pressure, changes.