Patent ID: RE42633

Claim:
In spool valve apparatus having a plurality of respective valves operated sequentially by the rotation of a drive shaft, each spool said valve comprising (a) a cylinder having at least a first fluid port defining a first fluid passage, and (b) a spool having a stem portion and at least one port-blocking portion, said spool being movable axially within the cylinder between first and second positions so that, when said spool is in said first position, said fluids are permitted to move past said stem portion and through said first fluid passage and, when said spool is in said second position, said first fluid passage is blocked, the improvement comprising: a cam track rotated by said drive shaft and having at least two parallel surfaces; and a plurality of cam followers, each cam follower being associated with, and aligned in a predetermined position relative to, a respective one of said spools, and each cam follower being captured between said parallel surfaces of said cam track for relative moving engagement therewith for controlling said axial motion of each respective spool and said sequential operation of said respective spool valves in response to the rotation of said drive shaft; and wherein: said stem portion of each respective spool defines a passageway formed by one of (a) no sidewalls with a central support comprising a non-cylindrical curved surface shaped hydrodynamically, and (b) a pair of sidewalls with said passageway formed therebetween, said central support and said sidewalls having interior surfaces shaped hydrodynamically, said sidewalls being positioned in a predetermined orientation relative to said respective first fluid port of said cylinder to facilitate the flow of fluids past said stem portion and through said first fluid port when said stem portion is aligned therewith.