US Patent 7980270 Spool valve apparatus and method

Some embodiments of the present invention provide a spool valve having a spool axially movable within a sleeve of two or more stacked rings having projections extending therebetween. One or more seals on the spool can slide across surfaces of the stacked rings in movement of the spool to different positions corresponding to different states of the valve. In some embodiments, one or more of the stacked rings can have projections extending toward and contacting an adjacent ring of the sleeve, thereby maintaining desired axial positions of the rings relative to one another while providing apertures through which fluid can flow and supporting surfaces for each seal as it slides from one ring to another.