US 4,227,443 AGranted

Fail-fixed servovalve

AssigneeGeneral Electric Company

InventorPeter D. Toot

Life of this patent

Estimating the term…

Abstract

A fail-fixed servovalve is provided for use in a digital control system. The servovalve is comprised of a deflecting means which deflects a jet pipe in response to an electrical input signal. Fluid flowing through the jet pipe causes a spool to translate within a sleeve, thereby allowing pressurized fluid to flow through selected ports within the sleeve to control the movement of an output piston. The output of the servovalve is essentially linear over the primary range of digital input currents with the output being zero when the input current is either zero or in excess of the maximum rated current for the servovalve.

Claims8

Dependent claims

A servovalve system comprising:

a sleeve having a plurality of ports therethrough, one of said ports receiving an inlet flow of pressurized fluid, at least one of said ports communicating pressurized fluid to a relatively lower pressure sump, and at least two of said ports comprising separate output ports;
a jet pipe for discharging a jet of pressurized fluid received from said inlet port;
means for producing an electrical input signal having rated input current values from zero to a maximum rated value;
deflecting means responsive to said electrical input signal for deflecting the jet pipe;
a pair of receiver conduits in flow communication with opposite ends of the sleeve and disposed to receive fluid discharged from the jet pipe, wherein:
said conduits receive equal amounts of said jet pipe fluid when the jet pipe is in a balanced flow deflected position,
a first of said conduits receives more of said jet pipe fluid when the jet pipe is located between a non-deflected position and the balanced flow deflected position, and
the second of said conduits receives more of said jet pipe fluid when the jet pipe is located between the balanced flow deflected position and a fully deflected position;
a spool movable solely by fluid pressure and disposed within the sleeve to axially translate in the direction of lower sleeve end pressure, said spool having a plurality of circumferentially relieved areas interspaced between a plurality of circumferential lands;
feedback means connected to said jet pipe and said spool;
a servopiston unit having a piston translatably disposed within a bore, each side of said piston respectively being in fluid communication with one of said two separate output ports in said sleeve;
and
passage means, formed by the translation of the spool within the sleeve causing selected relieved areas to interconnect selected sleeve ports with said two output ports for:
delivering pressurized fluid to a first side of the piston and porting pressurized fluid away from the second side of the piston when the spool translates between a position near a first end of the sleeve and the midpoint of its axial stroke within the sleeve;
delivering pressurized fluid to the second side of the piston and porting pressurized fluid away from the first side of the piston when the spool translates between a position near the second end of the sleeve and the midpoint of its axial stroke within the sleeve;
and
delivering no pressurized fluid to and porting no pressurized fluid away from the servopiston unit to lock the unit in place when the spool is located near either end of the sleeve at a respective one of a first and second extreme position or is at the midpoint of its axial stroke within the sleeve;
wherein:
when no electrical input signal is applied to the deflecting means the jet pipe is in said non deflected position and the spool is at the first extreme position within the sleeve;
when an electrical input signal is applied to the deflecting means the jet pipe is in a proportionally deflected position and the spool moves proportionally from the first extreme position toward the second extreme position as the magnitude of the electrical signal is increased;
and
when a maximum rated electrical input signal is applied to the deflecting means the jet pipe is in said fully deflected position and the spool is at the second extreme position.

19 more elements

Dependencies are inferred from the claim text.

patentgrep

Loading patent…

Abstract

A servovalve system comprising:

a sleeve having a plurality of ports therethrough, one of said ports receiving an inlet flow of pressurized fluid, at least one of said ports communicating pressurized fluid to a relatively lower pressure sump, and at least two of said ports comprising separate output ports;
a jet pipe for discharging a jet of pressurized fluid received from said inlet port;
means for producing an electrical input signal having rated input current values from zero to a maximum rated value;
deflecting means responsive to said electrical input signal for deflecting the jet pipe;
a pair of receiver conduits in flow communication with opposite ends of the sleeve and disposed to receive fluid discharged from the jet pipe, wherein:
said conduits receive equal amounts of said jet pipe fluid when the jet pipe is in a balanced flow deflected position,
a first of said conduits receives more of said jet pipe fluid when the jet pipe is located between a non-deflected position and the balanced flow deflected position, and
the second of said conduits receives more of said jet pipe fluid when the jet pipe is located between the balanced flow deflected position and a fully deflected position;
a spool movable solely by fluid pressure and disposed within the sleeve to axially translate in the direction of lower sleeve end pressure, said spool having a plurality of circumferentially relieved areas interspaced between a plurality of circumferential lands;
feedback means connected to said jet pipe and said spool;
a servopiston unit having a piston translatably disposed within a bore, each side of said piston respectively being in fluid communication with one of said two separate output ports in said sleeve;
and
passage means, formed by the translation of the spool within the sleeve causing selected relieved areas to interconnect selected sleeve ports with said two output ports for:
delivering pressurized fluid to a first side of the piston and porting pressurized fluid away from the second side of the piston when the spool translates between a position near a first end of the sleeve and the midpoint of its axial stroke within the sleeve;
delivering pressurized fluid to the second side of the piston and porting pressurized fluid away from the first side of the piston when the spool translates between a position near the second end of the sleeve and the midpoint of its axial stroke within the sleeve;
and
delivering no pressurized fluid to and porting no pressurized fluid away from the servopiston unit to lock the unit in place when the spool is located near either end of the sleeve at a respective one of a first and second extreme position or is at the midpoint of its axial stroke within the sleeve;
wherein:
when no electrical input signal is applied to the deflecting means the jet pipe is in said non deflected position and the spool is at the first extreme position within the sleeve;
when an electrical input signal is applied to the deflecting means the jet pipe is in a proportionally deflected position and the spool moves proportionally from the first extreme position toward the second extreme position as the magnitude of the electrical signal is increased;
and
when a maximum rated electrical input signal is applied to the deflecting means the jet pipe is in said fully deflected position and the spool is at the second extreme position.

19 more elements