Fluid handling – Systems – Multi-way valve unit
Patent
1986-06-20
1987-08-04
Michalsky, Gerald A.
Fluid handling
Systems
Multi-way valve unit
13762525, 13762566, F15B 1302
Patent
active
046839143
DESCRIPTION:
BRIEF SUMMARY
This invention relates to slide valves and more particularly to slide valves which control the passage of a fluid, which may be either a gas or a liquid.
Slide valves, which are also known as spool valves, commonly comprise a cylinder in which a spool or piston is free to move relative to apertures or ports formed in the cylinder wall so as to provide passages for a fluid or cut off a supply of fluid. The spool or piston is formed with one or more annular grooves which are wide enough to allow the passage of fluid between two laterally spaced ports in the cylinder. To either side of each annular groove and set into the major diameter of the spool or piston are sealing elements such as "O" seals which define a pressure tight region between them. Typically, a common inlet port is connected to a laterally offset outlet port by an annular groove formed in the spool. By moving the spool laterally, the outlet port will be closed to the passage of fluid by the sealing element being interposed between the inlet and outlet port. The corresponding sealing element may, in this position, expose a second port to the annular groove and allow the passage of fluid through the second port.
However, slide valves of this nature have poor endurance characteristics because the sealing elements mounted on the spool or piston are subjected to wear each time they pass a port in the cylinder. Moreover the sealing action of the spool or piston is not positive in that the flow of fluid is first restricted by the major diameter of the spool passing a port and then finally terminated by the seal element passing that port.
Other known spool valves consists of a precision-ground spool or piston arranged to slide in a finely machined and honed cylindrical bore with a minimum clearance between the parts in order to minimise leakage. The construction of such a valve is however expensive due to the accurate machining and close tolerances required. Moreover, because of the metal-to-metal sliding contact as the valve operates, the valve is subject to wear and also requires lubrication.
A desired operational requirement in spool valves is that the spool action should be free from inertia to enable consistent response to pilot signals.
The first described example of a known spool valve has high friction characteristics due to the number of sealing elements incorporated in the spool rubbing on the bore of the cylinder. This results in hysterisis in response to pilot signals.
In the second described example of a known spool valve, the sealing elements are eliminated and friction is confined to the contacting surfaces of the spool and cylinder bore. Hysterisis in this case is relative to wear and lubrication characteristics of the valve.
It is an object of the present invention to provide an improved construction of slide valve which alleviates the disadvantages of known construction.
From one aspect the invention provides a slide valve for controlling the passage of a fluid comprising a valve body having valve ports and a slide slidable relative to the valve body for controlling the opening, interconnection and closing of the valve ports, wherein the slide carries a sealing member for sealing off one or more of the valve ports, said sealing member being floatingly located in the slide and being urged into its sealing position by means of fluid pressure applied through at least one of the ports.
From another aspect the invention provides a slide valve comprising a valve body having valve ports and a slide mounted within and slidable relative to the valve body for controlling the opening, interconnection and closing of the valve ports, wherein the slide carries a sealing member which is floatingly located in a location in said slide, said sealing member including one or more galleries to provide interconnection between two or more ports in one or more defined positions of the slide and said sealing member having at least one sealing surface for sealing off one or more of the ports in one or more defined positions of the slide, said sealing member b
REFERENCES:
patent: 3227180 (1966-01-01), Tissot-Dupont
patent: 3610285 (1971-10-01), Passaggio
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