Head valve bumper
Exhaust is open
Head valve closed
Resevoir of high pressure air
Return chamber
Hole in cilinder wall
Fig. 1
Exhaust sealed by head valve bumper
Driving stroke
Fig. 2
Exhaust still closed
Air flows into return chamber
Fig. 3
2
Bumper
Air released from above head valve
Piston is sealed against bumper
Port between head valve and trigger valve
Resevoir of high pressure air
Trigger valve released
Passage for air release from head valve
Head valve open
Trigger valve actuated
Head valve open
End of stroke trigger still pulled
Trigger valve still actuated