| 摘要 |
A valve arrangement for a mining support frame ram having a ram setting piston surface connection A' and ram lowering a ring surface connection B'. The valve arrangement includes a housing 21 having a first, piston surface, connection A', a second, ring surface, connection B', a third connection A for receiving fluid from a ram setting fluid source, a fourth, ram lowering connection B ram and a return connection R. A first unlockable check valve 12 has a supply port, a piston surface port and a port communicating with the lowering connection B for unlocking the first check valve in the event of a pressure rise due to a rock burst. The housing further contains a second unlockable check 14 valve having a port communicating with said return connection R, a piston surface port and a port communicating with said fourth connection B for unlocking said check valve in the event of a pressure rise due to a rock burst. |
