| Hydraulic lock for axial motion output device -> Monitor Keywords |
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Hydraulic lock for axial motion output deviceRelated Patent Categories: Pumps, Motor Driven, Electric Or Magnetic Motor, Reciprocating Rigid Pumping MemberHydraulic lock for axial motion output device description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070081909, Hydraulic lock for axial motion output device. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 60/685,358, filed May 27, 2005, the disclosure of which is hereby incorporated by reference in its entirety. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The subject invention relates to control of hydraulic systems. More specifically, the invention relates to fuel metering systems for gas turbine engines, and more particularly, to a hydraulic lock for an axial motion output device used in a fuel metering system of a gas turbine engine. [0004] 2. Background of the Related Art [0005] Hydraulic axial motion output systems are an essential part of any engine fuel metering system. Typically, in aircraft applications, servo-controlled axial motion output devices, such as axially acting pistons, are used to schedule fuel flow and to position variable geometry actuation systems. These systems are typically driven with an electro-mechanical device that functions by way of a varying electronic input signal. Often times, as a required safety measure, it is necessary to "freeze" the position of the axial motion output device in the event of an electronic signal failure. This is typically referred to as "fail fixed." [0006] Since they act on a varying electrical signal input, the tendency for these types of output devices is to fail to a position corresponding to a low electrical signal. This is commonly referred to as "failing down," and is not a preferred condition in instances where the metered fuel flow in the last commanded position is critical for the continued safe control of an aircraft. It is desired, therefore to provide a system that achieves a "fail fixed" condition for an axial motion output device, which is adapted to override the effect of a decaying electrical signal that would otherwise result in a "fail down" condition. [0007] The subject invention is directed to a new and useful system that is adapted and configured to achieve a "fail fixed" condition for an axial motion output device of a fuel metering system, in the event of an electrical signal failure, by frictionally or otherwise physically engaging the axial motion output device, thus overriding the effect of a decaying electrical signal. SUMMARY OF THE DISCLOSURE [0008] The subject invention is directed to a system for locking the axial position of a servo-controlled axial motion output device upon the loss of an electrical input signal to the fuel metering system. The system includes a locking device operatively associated with the output device and adapted for movement between a neutral position in which the output device can move freely relative to the locking device and a locking position in which the locking device frictionally or otherwise physically engages the output device with a sufficient amount of force to prevent further movement of the output device upon loss of an electrical input signal. [0009] In an embodiment of the subject invention, the locking device is a ring of expandable or otherwise deformable material, such as a metallic, elastomeric or plastic material, that surrounds an outer periphery of the output device, and which is constrained about its outer diameter such that axial compression of the locking device causes the material to exert a radially inwardly directed force on the outer periphery of the output device, thus locking the axial position thereof. In an embodiment of the subject invention, the ring of material is a deformable metallic ring having a generally toroidal configuration that is constrained about its outer diameter in such a manner so as to facilitate the radially inward expansion thereof when it is compressed under a generally axially applied load. [0010] In an embodiment of the subject invention, the system further comprises means for moving the locking device from the neutral position to the locking position. The means for moving the locking device preferably includes a locking piston configured to generally axially compress the ring of expandable or otherwise deformable material. The locking piston is preferably in fluid communication with a normally regulated source of high-pressure fluid, and is thus hydraulically energized. Upon the loss of an electrical input signal, the normally regulated source of high-pressure fluid exerts a motive force on the locking piston. This causes the locking piston to load or otherwise exert an axially directed compressive force on the ring of expandable or otherwise deformable material, causing it to frictionally engage the output device and prevent it from moving, thus locking its output position. [0011] In accordance with another aspect of the invention, a system is provided for locking the axial position of an axial motion output device upon the loss of an electrical input signal, having a locking element, a piston and an electrically actuated element. The locking element is configured to engage a shaft of the axial motion output device and is adapted and configured to frictionally engage a surface of the shaft when pressure is applied to the locking element in a predetermined manner. The locking element can have a substantially toroidal shape, and can be made of metal, plastic or an elastomer, depending on the implementation. Depending on the implementation of the invention, the locking element can be configured to deform in response to an applied axially-oriented load, and expand in a radial direction relative to the axial motion output device to frictionally engage the axial motion output device and secure an axial position thereof. [0012] The piston is configured and adapted for applying pressure to the locking element. The electrically actuated element has a normal operating range and a failure position, to which the electrically actuated element moves upon loss of an electric signal. The electrically actuated element permits passage of pressurized fluid to the piston when in a failure position. The electrically actuated element can be an electrically variable flow control device, which adjusts pressure controlling a position of the axial motion output device. Further, depending on the implementation, the electrically actuated element can be a torque motor having a movable flapper arm. A spring can be provided and configured to move the flapper arm into the failure position upon loss of an electrical signal to the electrically actuated element. [0013] The shaft of the axial motion output device can include a fuel metering element, and/or can be adapted and configured to actuate an external device. If desired, flow restriction elements can be provided in hydraulic lines to adjust fluid flow therethrough. [0014] In accordance with still another aspect of the invention, a method of securing an axial motion output device upon loss of an electric control signal is provided. The method includes providing a locking element, piston and electrically actuated element. [0015] The locking element is configured to engage a shaft of the axial motion output device and is adapted and configured to frictionally engage a surface of the shaft when pressure is applied to the locking element in a predetermined manner. The piston is configured and adapted for applying pressure to the locking element. The electrically actuated element has a normal operating range and a failure position, to which the electrically actuated element moves upon loss of an electric signal. The electrically actuated element permits passage of pressurized fluid to the piston when in a failure position. [0016] The method further comprises diverting a pressurized fluid flow to the piston when the electrically actuated element is in a failure position. The pressurized fluid flow moves the piston, which causes the locking element to frictionally engage a surface of the shaft, inhibiting axial movement of the shaft. [0017] The method can further include, depending on the implementation, applying an axially-oriented load to the locking element, causing the locking element to expand in a radial direction relative to the axial motion output device, and frictionally engage the axial motion output device, securing an axial position thereof. [0018] These and other features of the new and useful hydraulic lock for an axial motion output device will become more readily apparent from the following enabling description of the subject invention, taken in conjunction with the drawings accompanying the subject disclosure. BRIEF DESCRIPTION OF THE DRAWINGS [0019] So that those having ordinary skill in the art to which the subject invention appertains will more readily appreciate how to make and use the hydraulic locking system disclosed herein, preferred embodiments thereof will be described herein with respect to the drawings, wherein: [0020] FIG. 1 is a cross-sectional view illustrating the failing fixed implementation of a hydraulic locking device in accordance with a preferred embodiment of the subject invention in conjunction with a typical fuel metering arrangement; and Continue reading about Hydraulic lock for axial motion output device... Full patent description for Hydraulic lock for axial motion output device Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Hydraulic lock for axial motion output device patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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