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A valve combining in a single unit a multiplicity of functions including isolation, thermal and pressure relief, return check and bypass. The valve includes a pair of spool valves, one slidably positioned within the other, disposed with a bore in a housing and interconnected with system pressure and

A valve combining in a single unit a multiplicity of functions including isolation, thermal and pressure relief, return check and bypass. The valve includes a pair of spool valves, one slidably positioned within the other, disposed with a bore in a housing and interconnected with system pressure and return and an appropriate control valve.

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In a hydraulic control circuit for providing flow of fluid under pressure between a source and return thereof to a load responsive to positioning of a control valve the improvement of a combination valve means in a unitary housing interposed between said control valve and said source/return for prov

In a hydraulic control circuit for providing flow of fluid under pressure between a source and return thereof to a load responsive to positioning of a control valve the improvement of a combination valve means in a unitary housing interposed between said control valve and said source/return for providing a plurality of functions normally provided by a plurality of separate valves, said valve means comprising: (A) a housing defining a first bore therein; (B) a first spool valve having lands and grooves slidably disposed within said first bore and defining a second bore therein; (C) a second spool valve reciprocally disposed within said second bore and closing said second bore at a first position; (D) a first poppet means disposed adjacent one end of said second bore and urged thereagainst to close said second bore at a second position displaced from said first position thereby defining a first closed chamber within said first spool valve between said first poppet and said second spool valve; (E) first passageway means for connecting said fluid pressure source to said first closed chamber; (F) a second poppet means disposed adjacent the opposite end of said second bore and urged thereagainst to close said opposite end of said second bore thereby defining a second closed chamber within said first spool valve between said second spool valve and said second poppet, said second spool valve engaging said second poppet means; (G) second passageway means for connecting said return to said second poppet means; (H) third and fourth passageway means for connecting said first poppet and said second chamber to said control valve; (I) said first and second poppets normally blocking communication of said third and fourth passageways with said first and second passageways respectively in the absence of said fluid under pressure and permitting communication therebetween upon the application of fluid under pressure to said first chamber.