Automatic reciprocation of a reversible fluid pressure unit and switching valve therefor

A fluid pressure switching valve, comprising:

• a) an elongated hollow valve body having closed ends,
• b) an elongated spool member reciprocative longitudinally in the valve body,
• c) first and second longitudinally spaced fluid passageways in the spool member,
• d) first and second fluid pressure delivery ports spaced apart longitudinally in the valve body for registration each with a different one of the first and second fluid passageways in the spool member, the first and second fluid pressure delivery ports being arranged for communication with the opposite sides of the movable component of a reversible fluid pressure drive unit,
• e) a fluid pressure inlet port in the valve body arranged for registration with the first fluid passageway in the spool member at one limit of longitudinal reciprocation of the spool member and with the second fluid passageway in the spool member at the other limit of longitudinal reciprocation of the spool member, the fluid pressure inlet port being arranged for communication with a fluid pressure source having an exhaust side,
• f) first and second fluid exhaust ports spaced apart longitudinally in the valve body for registration each with a different one of the first and second fluid passageways in the spool member when the fluid pressure inlet port is in registration with the other of the first and second fluid passageways in the spool member,
• g) an exhaust conduit communicating with the exhaust ports and arranged for communication with the exhaust side of the fluid pressure source,
• h) lock means operatively associated with the valve body and spool member and operable by exhaust fluid pressure in the exhaust conduit to lock the spool member against reciprocation within the valve body and operable when exhaust fluid pressure is absent in the exhaust conduit to release the spool member for movement within the valve body, and
• i) means communicating the opposite ends of the valve body alternately with a source of fluid pressure for reciprocating the spool member.

An automatically reciprocative fluid pressure drive unit, comprising the combination of

• a) a reversible fluid pressure drive unit having a movable component reciprocative within and relative to a housing,
• b) fluid pressure servicing ports in the housing communicating with opposite sides of said movable component at the opposite ends of reciprocation of said movable component,
• c) a fluid pressure switching valve, comprising:
• 1) an elongated hollow valve body having closed ends,
• 2) an elongated spool member reciprocative longitudinally in the valve body,
• 3) first and second longitudinally spaced fluid passageways in the spool member,
• 4) first and second fluid pressure delivery ports spaced apart longitudinally in the valve body for registration each with a different one of the first and second fluid passageways in the spool member,
• 5) a fluid pressure inlet port in the valve body arranged for registration with the first fluid passageway in the spool member at one limit of longitudinal reciprocation of the spool member and with the second fluid passageway in the spool member at the other limit of longitudinal reciprocation of the spool member, the fluid pressure inlet port being arranged for communication with a fluid pressure source having an exhaust side,
• 6) first and second fluid exhaust ports spaced apart longitudinally in the valve body for registration each with a different one of the first and second fluid passageways in the spool member when the fluid pressure inlet port is in registration with the other of the first and second fluid passageways in the spool member,
• 7) an exhaust conduit communicating with the exhaust ports and arranged for communication with the exhaust side of a fluid pressure source,
• 8) lock means operatively associated with the valve body and spool member and operable by exhaust fluid pressure in the exhaust conduit to lock the spool member against reciprocation within the valve body and operable when exhaust fluid pressure is absent in the exhaust conduit to release the spool member for movement within the valve body,
• 9) means communicating the opposite ends of the valve body alternately with a source of fluid pressure for reciprocating the spool member,
• d) a secondary switching valve comprising:
• 1) an elongated hollow valve body having closed ends,
• 2) an elongated spool member reciprocative longitudinally in the valve body,
• 3) first and second longitudinally spaced fluid passageways in the spool member,
• 4) first and second fluid pressure delivery ports spaced apart longitudinally in the valve body for registration each with a different one of the first and second fluid passageways in the spool member, the first and second fluid pressure delivery ports communicating with the opposite sides of the reversible fluid pressure drive unit,
• 5) a fluid pressure inlet port in the valve body arranged for registration with the first fluid passageway in the spool member at one limit of longitudinal reciprocation of the spool member and with the second fluid passageway in the spool member at the other limit of longitudinal reciprocation of the spool member, the fluid pressure inlet port being arranged for communication with a fluid pressure source having an exhaust side,
• 6) first and second fluid exhaust ports spaced apart longitudinally in the valve body for registration each with a different one of the first and second fluid passageways in the spool member when the fluid pressure inlet port is in registration with the other of the first and second fluid passageways in the spool member,
• 7) an exhaust conduit communicating the exhaust ports with the lock means of the switching valve, and
• 8) first and second connecting conduits communicating the first and second fluid pressure delivery ports of the switching valve with the opposite ends of the hollow body of the secondary switching valve.