US 4,056,125 AGranted

Extended life structure for spool valve

AssigneeThe Bendix Corporation

InventorVernon L. McNabb

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Abstract

Multiple path means for a fluid flow control device is shown in connection with a typical spool type servo valve wherein the spool member moves within a stationary sleeve to control fluid flow to a piston in a cylinder. The multiple path means includes a series of stacks of washer-like elements or disks which are positioned in radial bores in the valve sleeve and which disks cooperate when the spool number moves a small distance from null to define a restricted path across the stack in which flow is forced through a series of alternating chambers and orifices with measured pressure drops across the orifices. Further movement of the spool member away from null opens a large parallel flow path. Since many servo valves have comparatively short travel and since both control and wear problems of such valves tend to be most serious near null, the restricted flow path is utilized to minimize abrupt step flow gains with the usual accompanying wear around null.

Claims3

Dependent claims

In a flow control valve wherein a spool valve member having a plurality of lands is moveable within a sleeve to cause said lands to open and close radially directed fluid passageways through the sidewalls of said sleeve,

at least some of said passageways including cylindrical chambers and fine radial passageways communicating said chambers with the inside of said sleeve, and
a stack of laminar disk members positioned in said cylindrical chambers, said stack including disks of a first group including a central opening of large area and disks of a second group including an orifice of limited area each of which introduces a substantial pressure drop thereacross, said stack comprising alternate disks of said first group and said second group with a disk of said first group positioned at the bottom of said cylindrical chamber such that its opening communicates with one of said fine passageways, said sleeve also including large openings axially displaced from said fine passageways such that as said spool valve member moves past said fine passageways it begins to uncover said large openings.

Dependencies are inferred from the claim text.