Hydraulic lock for axial motion output device

Abstract

A system for locking the axial position of an axial motion output device upon the loss of an electrical input signal 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 engages the output device with a sufficient amount of force to prevent further movement thereof upon the loss of an electrical input signal.

1 . A system for locking the axial position of an axial motion output device upon the loss of an electrical input signal comprising: 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 engages the output device with a sufficient amount of force to prevent further movement thereof upon the loss of an electrical input signal.  
   
   
       2 . A system as recited in  claim 1 , further comprising means for moving the locking device from the neutral position to the locking position.  
   
   
       3 . A system as recited in  claim 2 , wherein the locking device is a ring of material surrounding an outer periphery of the output device and constrained about its outer diameter such that generally axial compression of the material causes the ring of material to exert a radially inwardly directed force on the outer periphery of the output device.  
   
   
       4 . A system as recited in  claim 3 , wherein the means for moving the locking device includes a locking piston configured to exert a generally axially directed compressive force on the ring of material.  
   
   
       5 . A system as recited in  claim 4 , wherein the locking piston is in fluid communication with a normally regulated source of high-pressure fluid.  
   
   
       6 . A system as recited in  claim 5 , wherein upon the loss of an electrical input signal, the normally regulated source of high-pressure fluid exerts a motive force on the locking piston, causing the locking piston to exert a compressive force on the ring of material.  
   
   
       7 . A system for locking the axial position of an axial motion output device upon the loss of an electrical input signal comprising: 
 a locking element for engaging a shaft of the axial motion output device, the locking element being adapted and configured to frictionally engage a surface of the shaft when pressure is applied to the locking element in a predetermined manner;    a piston for applying pressure to the locking element; and    an electrically actuated element having 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 in a failure position permitting passage of pressurized fluid to the piston.    
   
   
       8 . The system of  claim 7 , wherein the locking element is a substantially toroidal element.  
   
   
       9 . The system of  claim 7 , wherein the locking element is made of a metal, plastic or elastomer.  
   
   
       10 . The system of  claim 7 , wherein the locking element is configured to deform in response to an axially applied 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.  
   
   
       11 . The system of  claim 7 , wherein the electrically actuated element is an electrically variable flow control device, which adjusts pressure controlling a position of the axial motion output device.  
   
   
       12 . The system of  claim 7 , wherein the electrically actuated element is a torque motor having a movable flapper arm.  
   
   
       13 . The system of  claim 12 , wherein a spring is configured to move the flapper arm into the failure position upon loss of an electrical signal to the electrically actuated element.  
   
   
       14 . The system of  claim 7 , wherein the shaft of the axial motion output device includes a fuel metering element.  
   
   
       15 . The system of  claim 7 , wherein the shaft of the axial motion output device is adapted and configured to actuate an external device.  
   
   
       16 . The system of  claim 7 , wherein flow restriction elements are provided in hydraulic lines to adjust fluid flow therethrough.  
   
   
       17 . A method of securing an axial motion output device upon loss of an electric control signal, the method comprising: 
 providing a locking element for engaging a shaft of the axial motion output device, the locking element being adapted and configured to frictionally engage a surface of the shaft when pressure is applied to the locking element in a predetermined manner;    providing a piston for applying pressure to the locking element;    providing an electrically actuated element having 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 in a failure position permitting passage of pressurized fluid to the piston;    diverting a pressurized fluid flow to the piston when the electrically actuated element is in a failure position, the pressurized fluid flow moving the piston, which causes the locking element to frictionally engage a surface of the shaft, inhibiting axial movement of the shaft.    
   
   
       18 . The method of  claim 17 , further comprising: 
 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.