Reciprocable device with switching mechanism

A reciprocable device comprising:

• a housing having a chamber therein;
• a reciprocable member in the chamber and having first and second faces exposable to a driving fluid under pressure to reciprocate the reciprocable member in the chamber;
• a valve having first and second states for controlling the supply and exhaust of the driving fluid under pressure to and from the first and second faces whereby the reciprocable member can be reciprocated in said chamber;
• an actuator for drivingly coupling the reciprocable member and the valve;
• a bistable spring device having first and second states and a neutral position between said states thereof;
• said bistable spring device being coupled to said actuator such that said reciprocable member can move the bistable spring device from one of its states through the neutral position, with the resilience of the bistable spring device at least assisting in moving the bistable spring device from its neutral position to the other state thereof, movement of said bistable spring device to said other state at least assisting in switching the valve from one of its states to another so that the reciprocable member reverses direction;
• said valve including a valve housing having an interior wall surface defining a valve chamber and a spool valve body slidably mounted within the valve chamber for movement between first and second positions which correspond to the first and second states of the valve, respectively;
• and
• said interior wall surface having first and second spaced lands thereon and an undercut annular groove between the first and second lands, said valve body having a sealing surface, said sealing surface traveling from sealing engagement with one of the lands of the valve chamber across the undercut annular groove to another of the lands of the valve chamber as the valve body moves from one of the positions to the other of the positions.