Patent ID: 7980270

Claim:
A spool valve in a housing including at least one first aperture, the spool valve comprising: at least two rings through which an axis passes, each one of the at least two rings including symmetrical oppositely facing sides and a first radial inner surface, a first one of the at least two rings comprising a plurality of projections extending toward a second one of the at least two rings, the plurality of projections including a second radial inner surface that has a greater radius than the first radial inner surface; the first one of the at least two rings including at least one first pin on a first oppositely facing side that engages the at least one first aperture of the housing in order to couple the first one of the at least two rings to the housing, and at least one second pin on a second oppositely facing side that engages at least one second aperture of the second one of the at least two rings in order to couple the at least two rings together; a spool movable along the axis, the spool including a first end and a second end, the spool including an internal aperture along the axis, the spool having a first position in which fluid moves through the valve in a first manner; and a second position in which fluid moves through the valve in a second manner different than the first manner; friction between the spool and the at least two rings being reduced when the spool passes through the at least two rings due to the second radial inner surface having the greater radius than the first radial inner surface; a piston rod at least partly positioned in the internal aperture of the spool, the piston rod movable with respect to the spool along the axis, the piston rod including a first stop and a second stop, the first stop engaging and disengaging with the first end of the spool, the second stop engaging and disengaging with the second end of the spool; and a chamber located between the spool and at least one of the at least two rings.