Electrohydraulic servo valve
First Claim
1. An electrohydraulic servo valve, comprising:
- a first stage servo unit having a drive assembly adapted to move a forked clevis member from a null position to alternatively open and close first and second nozzle orifices such that when the first nozzle orifice is open flow is permitted between a pressure port and a control port and when the second nozzle orifice is open flow is permitted between the control port and a return port; and
a second stage valve unit having a sliding valve member and having an inlet port in communication with the first stage control port, a flow port and a pressure port, wherein flow from the second stage pressure port to the flow port is controlled by the sliding valve member;
whereby the clevis member and the sliding valve member are linked by a feedback spring such that movement of the sliding valve member imparts a feedback force to the feedback spring to return the clevis member to the null position such that movement of the sliding valve member is proportional to an input signal to the drive assembly.
1 Assignment
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Accused Products
Abstract
A two, three or four-way valve includes two stages each with working valve components linked by a feedback spring so that a first stage servo unit is auto-nulling and the stroke of the valve member in a second stage valve unit is proportional to the input current to the first stage. An inherently balanced clevis member in the first stage controls flow of pressurized control media, which in combination with direct pressure flow, controls the position of a spool member in the second stage. The spool in turn controls pressure flow to a either one or two metering or input/output flow ports. Transient movement of the clevis due to change in input current to a magnetic servo drive assembly is opposed by bending of the feedback spring arising from the associated movement of the spool, which returns the clevis to its centered null position and stops the spool.
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Citations
22 Claims
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1. An electrohydraulic servo valve, comprising:
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a first stage servo unit having a drive assembly adapted to move a forked clevis member from a null position to alternatively open and close first and second nozzle orifices such that when the first nozzle orifice is open flow is permitted between a pressure port and a control port and when the second nozzle orifice is open flow is permitted between the control port and a return port; and
a second stage valve unit having a sliding valve member and having an inlet port in communication with the first stage control port, a flow port and a pressure port, wherein flow from the second stage pressure port to the flow port is controlled by the sliding valve member;
whereby the clevis member and the sliding valve member are linked by a feedback spring such that movement of the sliding valve member imparts a feedback force to the feedback spring to return the clevis member to the null position such that movement of the sliding valve member is proportional to an input signal to the drive assembly. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A four-way electrohydraulic servo valve, comprising:
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a servo first stage unit including;
a valve housing having pressure, control and return ports;
a magnetic drive assembly disposed in the valve housing selectively pulling an armature toward opposite sides of a main axis a flexure pivot disposed about the main axis and having a movable part mounted to the armature and a non-moving part fixed to the housing to allow pivoting of the actuator member with respect to the main axis;
a clevis member mounted to the armature and the movable part of the flexure pivot at one end and having a forked end defining two prongs symmetrical about the main axis, the clevis being pivotal about the flexure pivot in response to movement of the armature such that the clevis member moves from a null position to alternatively open and close first and second nozzle orifices;
a feedback spring mounted to the clevis member; and
a spool valve second stage unit having a spool disposed in a valve housing having an inlet port in communication with the first stage control port, a pressure port, a return port and two input/output ports, wherein the spool valve is linked to the clevis member by the feedback spring disposed through the first stage control port and the second stage inlet port;
whereby movement of the spool valve imparts a feedback force to the feedback spring to return the clevis member to the null position such that movement of the spool is proportional to an input signal to the drive assembly.
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22. An electrohydraulic servo valve, comprising:
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a first stage servo unit having a drive assembly adapted to move a clevis member from a null position to alternatively open and close first and second nozzle orifices such that when the first nozzle orifice is open flow is permitted between a pressure port and a control port and when the second nozzle orifice is open flow is permitted between the control port and a return port; and
a second stage valve unit having a sliding valve member and having an inlet port in communication with the first stage control port, a flow port and a pressure port, wherein flow from the second stage pressure port to the flow port is controlled by the sliding valve member;
whereby the clevis member and the sliding valve member are linked by a feedback member such that movement of the sliding valve member imparts a feedback force to the feedback member to return the clevis member to the null position such that movement of the sliding valve member is proportional to an input signal to the drive assembly.
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Specification