Claims
- 1. A fluid flow control servo valve comprising:
- a valve housing having a generally cylindrical bore extending therethrough;
- a supply port extending into said valve housing for receiving working fluid from an external pump;
- a return port extending into said valve housing for returning working fluid from said valve housing to a tank;
- an isolated pilot port extending into said valve housing and being separated from said supply port and said return port for receiving pilot pressure; a generally cylindrical valve spool dimensioned to be slidingly received within said valve housing bore, said cylindrical valve spool having
- an internal passageway axially extending throughout the length of said valve spool,
- an internally enlarged zone at one end of said valve spool forming a first chamber, and
- an internally enlarged zone at the other end of said valve spool forming a second chamber;
- first fixed orifice means mounted within said internal passageway in said generally cylindrical valve spool generally at said one end of said valve spool and providing fluid communication between said internal passageway and said first chamber;
- fixed aperture means coaxially fashioned within said internal passageway in said generally cylindrical valve spool generally at said other end of said valve spool and having internal dimensions greater than the internal dimensions of said first fixed orifice means at said one end of said valve spool and providing fluid communication between said internal passageway and said second chamber;
- said valve spool being exteriorly fashioned with first and second cylindrical land areas at opposite ends of said valve spool and third and fourth cylindrical land areas axially spaced intermediate said first and second land areas, each of said cylindrical land areas being dimensioned to intimately contact said valve housing in sliding engagement within said bore of said valve housing, said cylindrical land areas forming
- first and second cylindrical end grooves between said first and third and fourth and second cylindrical land areas, respectively, and
- a third cylindrical central groove between said third and fourth cylindrical land areas;
- first passage means extending through said valve housing and connecting said first and second cylindrical end grooves to said return port such that hydraulic fluid within either of said first or second cylindrical end grooves may be returned to tank;
- second passage means extending through said valve housing from said supply port to said third cylindrical central groove for delivering pressurized hydraulic fluid into said cylindrical bore;
- third and fourth passage means extending through said valve housing for respectively and selectively communicating said first and second cylindrical end grooves to a load and said third central groove to a load, depending on the position of said valve spool relative to said valve housing;
- first and second cylindrical grooves in said valve housing radially projecting outwardly from said cylindrical bore of said valve housing and being located at the axial extremities respectively of said third cylindrical land area on said valve spool;
- third and fourth cylindrical grooves in said valve housing radially projecting outwardly from said cylindrical bore of said valve housing and being located at the axial extremities respectively of said fourth cylindrical land area on said valve spool;
- said third and fourth cylindrical land areas of said valve spool being axially dimensioned such that a null position may be established wherein the passage of hydraulic fluid from said third cylindrical central groove of said valve spool into said second cylindrical groove radially projecting into said valve housing and from said fourth cylindrical groove radially projecting into said valve housing into said second cylindrical end groove in said valve spool will be blocked while concomitantly the passage of hydraulic fluid from said third cylindrical central groove of said valve spool into said third cylindrical groove radially projecting into said valve housing and from said first cylindrical groove radially projecting into said valve housing into said first cylindrical end groove in said valve spool will be blocked;
- aperture means generally radially projecting into said generally cylindrical valve spool for fluidically connecting said internal passageway of said valve spool with said first passage means through said valve housing such that hydraulic fluid within said internal passageway of said valve spool may be returned to tank through said return port in said valve housing;
- cap means releasably mounted upon said valve housing and extending into said valve housing in a posture coaxial with respect to said generally cylindrical valve spool and adjacent to said internally enlarged zone at said other end of said valve spool forming a second chamber;
- washer means mounted generally transversely across said cap means and adjacent to said second chamber;
- first compression spring means mounted within said second chamber and extending coaxially within said valve spool between said washer means and an internal ledge of said second chamber, said first compression spring means being axially dimensioned to normally bias said valve spool away from a mechanical null position of said third and fourth cylindrical land areas of said valve spool with respect to said first, second, third, and fourth cylindrical grooves radially projecting into said valve housing;
- end gland means releasably mounted upon said valve housing and extending into said valve housing in a posture generally coaxial with respect to said generally cylindrical valve spool and adjacent to said internally enlarged zone at said one end of said valve spool forming a first chamber;
- piston means mounted for translation within said end gland means and coaxially aligned with respect to said generally cylindrical valve spool and extending adjacent to said first chamber;
- second compression spring means mounted within said first chamber and extending coaxially within said one end of said valve spool between one side of said piston means and an internal ledge of said first chamber, said second compression spring means being axially dimensioned to normally bias said valve spool in a direction opposing the bias of said first compression spring means; mechanical adjustment means connected to said end gland means and abutting against the other side of said piston means for selectively translating said piston means to mechanically react said second compression spring means against said first compression spring means and mechanically bring said valve spool to a null position within said cylindrical bore of said valve housing such that hydraulic fluid is blocked from flowing from said third central groove of said valve spool to either of said second or third cylindrical grooves radially projecting outwardly from said cylindrical bore of said valve housing and from said first cylindrical groove radially projecting outwardly from said cylindrical bore into said first cylindrical end groove of said valve spool and from said fourth cylindrical groove radially projecting outwardly from said cylindrical bore into said second cylindrical end groove of said valve spool;
- fifth passage means extending through said valve housing for fluidically connecting said isolated pilot port to said first chamber formed at said one end of said valve spool;
- second fixed orifice means positioned within said fifth passage means and being dimensioned to be equal to said first fixed orifice means mounted within said internal passageway generally at said one end of said valve spool;
- sixth passage means extending through said valve housing for fluidically connecting said isolated pilot port to said second chamber formed at said other end of said valve spool;
- third fixed orifice means positioned within said sixth passage means and being dimensioned to be equal to said first and second fixed orifice means;
- said first and second chambers formed at the ends of said valve spool being operable to receive intermediate control pressure from said isolated pilot port through said fifth passage means and second fixed orifice means and said sixth passage means and said third fixed orifice means, respectively;
- electro-magnetic force motor means coaxially mounted within said cap means, said force motor means having
- a generally cylindrical force motor stem mounted for selective reciprocation within said force motor means, said force motor stem having an outer, planar end surface operably extending adjacent to but spaced from said fixed aperture means coaxially fashioned at said other end of said valve spool,
- said fixed aperture means comprising a nozzle pressed into said internal passageway of said generally cylindrical valve spool at said other end thereof, said nozzle having
- a planar annular outer surface disposed opposite to and mutually parallel with said planar end surface of said force motor stem, such that the annular zone between said planar end of said force motor stem and said planar annular surface on said fixed aperture means constitutes fourth orifice means of variable area; and
- means connecting said electro-magnetic force motor means to said cap means for axially adjusting said force motor means and said force motor stem such that, in an electro-magnetic null position of said force motor means, the area of said fourth orifice means may be operably set to equal the area of said first, second, and third fixed orifice means, such that said valve spool will be fluidically balanced in a null position when said force motor means is in a null position.
Parent Case Info
This is a continuation of application Ser. No. 44,440, filed June 1, 1979, now abandoned. That application was a continuation of application Ser. No. 815,467, filed July 12, 1977, now abandoned.
Foreign Referenced Citations (1)
Number |
Date |
Country |
2307209 |
Nov 1976 |
FRX |
Continuations (2)
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Number |
Date |
Country |
Parent |
44440 |
Jun 1979 |
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Parent |
815467 |
Jul 1977 |
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