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A spool valve includes a housing having a spring-enclosing portion and a spool-enclosing portion aligned along a longitudinal axis. A spool is mounted for reciprocal axial movement in the housing and a piston is fixed to one end of the spool. The spool-enclosing portion supports a stationary bushing

A spool valve includes a housing having a spring-enclosing portion and a spool-enclosing portion aligned along a longitudinal axis. A spool is mounted for reciprocal axial movement in the housing and a piston is fixed to one end of the spool. The spool-enclosing portion supports a stationary bushing having a bore receiving an opposite control end of the spool, the bushing formed with a first plurality of radially-oriented passages opening into an annular groove formed in the bore, the groove having sloped side edges. The spool supports plural ring-seals arranged to engage the sloped side edges of the annular groove and thereby seal off the radially-oriented passages when the spool is in a neutral position. Movement of the spool is adjustably limited in one direction and dampened in both axial directions.

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1. A spool valve comprising: a housing including a spring-enclosing portion and a spool-enclosing portion aligned along a longitudinal axis;a spool mounted for reciprocal axial movement in said spool-enclosing portion;a piston fixed to one end of the spool;said spool-enclosing portion supporting a s

1. A spool valve comprising: a housing including a spring-enclosing portion and a spool-enclosing portion aligned along a longitudinal axis;a spool mounted for reciprocal axial movement in said spool-enclosing portion;a piston fixed to one end of the spool;said spool-enclosing portion supporting a stationary bushing having a bore receiving an opposite control end of the spool, the bushing formed with a first plurality of radially-oriented passages opening into an annular groove formed in said bore said groove having sloped side edges said first plurality of radially-oriented passages aligned with a first radial port provided in said spool-enclosing portion;a sealed chamber on one side of said piston defined by a diaphragm engaged with one side of said piston and an end face of said spool-enclosing portion, said sealed chamber in communication with a second radial port provided in said spool-enclosing portion; a spring supported in said spring-enclosing portion engaged between a distal end of said spring-enclosing portion and the other side of said piston; andsaid opposite end of the spool supporting plural ring-seals arranged to engage the sloped side edges of the annular groove and thereby seal off said radially-oriented passages when said spool is in a neutral position, and to resiliently engage said sloped side edges upon axial movement of the spool in either of two opposite, axial directions to thereby resist axial movement away from said neutral position. 2. The spool valve of claim 1 wherein said plural ring-seals comprise side-by-side O-rings. 3. The spool valve of claim 1 wherein said plural ring-seals comprise a pair of axially-separated O-rings. 4. The spool valve of claim 1 wherein a dampening device is located axially between said one side of said piston and said end face of said spool-enclosing portion. 5. The spool valve of claim 4 wherein said dampening device comprises an O-ring. 6. The spool valve of claim 1 wherein said spool-enclosing portion is provided with another port at a distal end of said spool-enclosing portion; and a restrictor device including an axially-slidable pin for regulating movement of said spool in a direction away from said spring-enclosing portion; wherein said axially-slidable pin is detached from but engageable with said spool at one end of said axially-slidable pin. 7. The spool valve of claim 6 wherein movement of said axially-slidable pin is controlled by a selectively adjustable cam engageable with an opposite end of said axially-slidable pin. 8. The spool valve of claim 6 wherein movement of said axially-slidable pin is controlled by a selectively adjustable screw engageable with an opposite end of said axially-slidable pin. 9. The spool valve of claim 8 wherein a damper is inserted between said selectively-adjustable screw and said opposite end of said axially-slidable pin. 10. The spool valve of claim 9 wherein said damper comprises plural O-rings. 11. The spool valve of claim 9 wherein said damper comprises plural, stacked Belleville washers. 12. The spool valve of claim 9 wherein said damper comprises a coil spring. 13. The spool valve of claim 1 wherein said bushing has a length dimension corresponding to substantially a length of said spool-enclosing portion. 14. The spool valve of claim 13 wherein said bushing is formed with another plurality of radially-oriented passages axially-spaced from said first plurality of radially-oriented passages and in radial alignment with a third radial port provided in said spool-enclosing portion. 15. The spool valve of claim 6 wherein a dampening device is located axially between said one end of said piston and said end face of said spool-enclosing portion. 16. A spool valve comprising: a housing including a spring-enclosing portion and spool-enclosing portion;a spool mounted for reciprocal axial movement in said spool-enclosing portion;a piston fixed to one end of the spool, a sealed chamber on one side of said piston defined by a diaphragm engaged with one side of said piston and an end face of said spool-enclosing portion, said sealed chamber in communication with a port provided in said spool-enclosing portion; a spring supported in said spring-enclosing portion engaged between a distal end of said spring-enclosing portion and the other side of said piston;said spool-enclosing portion supporting a stationary bushing having a bore receiving an opposite control end of the spool, the bushing formed with a first plurality of radially-oriented passages opening into said bore, said first plurality of radially-oriented passages aligned with a first radial port provided in said spool-enclosing portion;a restrictor device including an axially-slidable pin for regulating movement of said spool in a direction toward said axially-oriented port; wherein said axially-slidable pin is detached from but engageable with said spool at one said end of said axially-slidable pin and engageable at an opposite end with an adjustable stop aligned with said longitudinal axis. 17. The spool valve of claim 16 wherein said adjustable stop comprises a rotatably adjustable cam. 18. The spool valve of claim 16 wherein said adjustable stop comprises a screw. 19. The spool valve of claim 18 wherein a damper is inserted between said screw and said opposite end of said axially-slidable pin. 20. The spool valve of claim 19 wherein said damper comprises a coil spring, plural O-rings or plural Belleville washers. 21. A spool valve of comprising: a housing including a spring-enclosing portion and a spool-enclosing portion aligned along a longitudinal axis;a spool mounted for reciprocal axial movement in said spool-enclosing portion;a piston fixed to one end of the spool;said spool-enclosing portion supporting a stationary bushing having a bore receiving an opposite control end of the spool, the bushing formed with a first plurality of radially-oriented passages opening into said bore, said first plurality of radially-oriented passages aligned with a first radial port provided in said spool-enclosing portion;a sealed chamber on one side of said piston defined by a diaphragm engaged with one side of said piston and an end face of said spool-enclosing portion, said sealed chamber in communication with a second radial port provided in said spool-enclosing portion; a spring supported in said spring-enclosing portion engaged between a distal end of said spring-enclosing portion and the other side of said piston; anda dampening device located axially between said one side of said piston and said end face of said spool-enclosing portion,wherein said spool-enclosing portion is provided with another port at a distal end of said spool-enclosing portion, said another port oriented at an acute angle relative to said longitudinal axis; and wherein a restrictor device is provided including an axially-slidable pin for regulating movement of said spool in a direction toward said axially-oriented port, said axially-slidable pin detached from but engageable with said spool at one end of said axially-slidable pin and engageable at an opposite end with an adjustable screw aligned with said longitudinal axis. 22. The spool valve of claim 21 wherein a damper is inserted between said adjustable screw and said opposite end of said axially-slidable pin. 23. The spool valve of claim 22 wherein said groove is formed with sloped side edges, said opposite end of the spool supporting plural ring-seals arranged to engage said sloped side edges and thereby seal off said radially-oriented passages when said spool is in a neutral position, and to resiliently engage said sloped side edges upon axial movement of the spool in either of two opposite directions to thereby resist movement away from said neutral position.