Flight lock actuator with dual energy sources

Abstract

A flight lock actuator that can be powered by two sources of stored energy when aircraft power has been switched off. A mechanical energy storage means and an electrical energy storage means provide a fully redundant energy storage system that stores sufficient energy to complete the actuator's extension stroke when aircraft power is removed. The actuator has a motor control system that limits the stroke velocity for both the extension and retraction strokes, including a damper feature capable of effectively braking the actuator during the back-driven extension stroke.

What is claimed is:  
     
         1 . A method for providing improved reliability in an aircraft door flight lock actuator comprising: 
 storing energy in a mechanical energy storage means and an electrical energy storage means;    powering the actuator using the energy stored in the mechanical energy storage means and the electrical energy storage means to complete an unlocking stroke in the absence of aircraft power; and    controlling a linear velocity of the actuator.    
     
     
         2 . The method defined in  claim 1 , wherein storing energy in the mechanical energy storage means comprises deforming a compression coil spring during a powered locking stroke of the actuator.  
     
     
         3 . The method defined in  claim 1 , wherein storing energy in the electrical energy storage means comprises charging at least one capacitor during a powered locking stroke of the actuator, and during a subsequent powered stall of the actuator.  
     
     
         4 . The method defined in  claim 1 , wherein storing energy in the electrical energy storage means comprises charging a rechargeable battery during a powered locking stroke of the actuator, and during a subsequent powered stall of the actuator.  
     
     
         5 . The method defined in  claim 1 , wherein the mechanical energy storage means and the electrical energy storage means are fully redundant.  
     
     
         6 . The method defined in  claim 1 , wherein controlling the linear velocity of the actuator comprises: 
 sensing a rotational speed of an actuator motor;    sensing a first current supplied to the motor;    reducing the first current if the rotational speed is higher than a maximum speed, or if the first current is higher than a maximum current.    
     
     
         7 . The method defined in  claim 6 , wherein controlling the linear velocity of the actuator further comprises: 
 shunting a second current generated by the motor into a damper circuit to place an electrical load on the motor if the first current is substantially zero and the rotational speed is higher than the maximum speed.    
     
     
         8 . The method defined in  claim 6 , wherein sensing the rotational speed of the motor comprises measuring a frequency of a Hall effect sensor signal.  
     
     
         9 . The method defined in  claim 6 , wherein sensing the rotational speed of the motor comprises measuring a back electromotive force generated by the motor.  
     
     
         10 . The method defined in  claim 6 , wherein reducing the first current comprises reducing a voltage supplied to the motor.  
     
     
         11 . The method defined in  claim 6 , wherein reducing the first current comprises pulse-width-modulating a power signal supplied to the motor.  
     
     
         12 . A system for providing improved reliability in an aircraft door flight lock actuator comprising apparatus for: 
 storing energy in a mechanical energy storage means and an electrical energy storage means;    powering the actuator using the energy stored in the mechanical energy storage means and the electrical energy storage means to complete an unlocking stroke in the absence of aircraft power; and    controlling a linear velocity of the actuator.    
     
     
         13 . The system defined in  claim 12 , wherein the apparatus for storing energy in the mechanical energy storage means comprises apparatus for deforming a compression coil spring during a powered locking stroke of the actuator.  
     
     
         14 . The system defined in  claim 12 , wherein the apparatus for storing energy in the electrical energy storage means comprises apparatus for charging at least one capacitor during a powered locking stroke of the actuator, and during a subsequent powered stall of the actuator.  
     
     
         15 . The system defined in  claim 12 , wherein the apparatus for storing energy in the electrical energy storage means comprises apparatus for charging a rechargeable battery during a powered locking stroke of the actuator, and during a subsequent powered stall of the actuator.  
     
     
         16 . The system defined in  claim 12 , wherein the apparatus for storing energy in the mechanical energy storage means and the electrical energy storage means are fully redundant.  
     
     
         17 . The system defined in  claim 12 , wherein the apparatus for controlling the linear velocity of the actuator comprises apparatus for: 
 sensing a rotational speed of an actuator motor;    sensing a first current supplied to the motor;    reducing the first current if the rotational speed is higher than a maximum speed, or if the first current is higher than a maximum current.    
     
     
         18 . The system defined in  claim 17 , wherein the apparatus for controlling the linear velocity of the actuator further comprises apparatus for: 
 shunting a second current generated by the motor into a damper circuit to place an electrical load on the motor if the first current is substantially zero and the rotational speed is higher than the maximum speed.    
     
     
         19 . The system defined in  claim 17 , wherein the apparatus for sensing the rotational speed of the motor comprises apparatus for measuring a frequency of a Hall effect sensor signal.  
     
     
         20 . The system defined in  claim 17 , wherein the apparatus for sensing the rotational speed of the motor comprises apparatus for measuring a back electro-motive force generated by the motor.  
     
     
         21 . The system defined in  claim 17 , wherein the apparatus for reducing the first current comprises apparatus for reducing a voltage supplied to the motor.  
     
     
         22 . The system defined in  claim 17 , wherein the apparatus for reducing the first current comprises apparatus for pulse-width-modulating a power signal supplied to the motor.  
     
     
         23 . A linear actuator comprising: 
 a brushless electric motor for rotating a shaft in either rotational direction;    a ball screw assembly for converting rotation of the shaft to linear motion of a follower member and vice versa, the follower member moving in either linear direction with the respective rotational direction of the shaft;    control circuitry for selectively powering the motor to rotate in either rotational direction; and    a mechanical energy storage assembly for resiliently urging the follower member to move in a predetermined one of its linear directions, the motor being powerful enough to overcome the resilient urging of the storage assembly when the control circuitry powers the motor to produce motions of the follower member opposite the predetermined one linear direction.    
     
     
         24 . The linear actuator defined in  claim 23  further comprising: 
 electrical energy storage circuitry for storing electrical energy during powering of the motor to produce motion of the follower member opposite the predetermined one linear direction, the control circuitry being adapted to selectively use electrical energy from the storage circuitry to power the motor to produce motion of the follower member in the predetermined one linear direction.  
 
     
     
         25 . The linear actuator defined in  claim 23  further comprising: 
 a first shock absorbing stop for stopping motion of the follower member in the predetermined one linear direction adjacent a first location.  
 
     
     
         26 . The linear actuator defined in  claim 25  further comprising: 
 a second shock absorbing stop for stopping motion of the follower member opposite the predetermined on linear direction adjacent a second location.  
 
     
     
         27 . The linear actuator defined in  claim 23  wherein the control circuitry comprises: 
 circuit components for limiting the speed of the motor.  
 
     
     
         28 . The linear actuator defined in  claim 27  wherein the circuit components comprise: 
 circuitry for selectively applying electrical current generated by the motor to an electrical load to thereby retard the motor.