The slide valve includes a pre loaded spring, capable in {TAIL ~ the absence} of other force of moving the slide valve to {HEAD ~ its closed position} to lock the member against movement 
The slide valve includes a pre loaded spring , capable in { TAIL ~ the absence } of other force of moving the slide valve to { HEAD ~ its closed position } to lock the member against movement
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH