Abstract:
This disclosure relates to a landing gear system that includes a landing gear strut rotatable between stowed and deployed positions. A lock-stay is connected to the landing gear strut and is movable between locked and unlocked conditions. An unlock actuator is connected to the lock-stay and includes first and second members movable relative to one another. The first member is movable between first and second positions that correspond to the locked and unlocked conditions. A controller is in communication with the unlock actuator and is configured to command the unlock actuator between the first and second positions in response to an input. The second member is permitted to free-drive relative to the first member between the stowed and deployed positions with the lock-stay in the unlocked condition.

Description:
[0001]    This application is a divisional application of U.S. patent application No. 12/131,996, which was filed on Jun. 3, 2008, now U.S. Pat. No. 8,123,161, which issued on Feb. 28, 2012. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates to an aircraft landing gear unlock actuator. More particularly, this disclosure relates to an unlock actuator that when mechanically jammed will not prevent the landing gear from fully deploying. 
         [0003]    Aircraft employ landing gear arrangements that must be reliably deployed from a stowed position during landing. In one type of arrangement, the landing gear is rotated about a pivot by an extend/retract actuator. A lock-stay is biased over-center to lock the landing gear in a deployed position. 
         [0004]    To retract the landing gear, an unlock actuator pulls the lock-stay from over-center, which enables the extend/retract actuator to retract the landing gear to the stowed position. During the locking and unlocking sequence, it is possible for the unlock actuator to experience a mechanical jam. It is important that any mechanical jam does not prevent the landing gear from fully deploying during the next landing gear deploy cycle. What is needed is a jam tolerant unlock actuator that enables the landing gear to be fully deployed regardless of a mechanical jam. 
       SUMMARY 
       [0005]    This disclosure relates to a landing gear system that includes a landing gear strut rotatable between stowed and deployed positions. A lock-stay is connected to the landing gear strut and is movable between locked and unlocked conditions. An unlock actuator is connected to the lock-stay and includes first and second members movable relative to one another, in one example. The first member is movable between first and second positions that correspond to the locked and unlocked conditions. A controller is in communication with the unlock actuator and is configured to command the unlock actuator between the first and second positions in response to an input. The second member is permitted to free-drive relative to the first member between the stowed and deployed positions with the lock-stay in the unlocked condition. 
         [0006]    These and other features of the application can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Other advantages of the example embodiment can be understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0008]      FIGS. 1A-1D  schematically illustrate the landing gear in deployed and locked, deployed and unlocked, retracting and stowed positions, respectively. 
           [0009]      FIG. 2  is a schematic view of a control system for the extend/retract and unlock actuators. 
           [0010]      FIG. 3  is a perspective cross-sectional view of the unlock actuator. 
           [0011]      FIG. 4  is a flow chart depicting a retract and deploy cycle in the event of a mechanical jam. 
           [0012]      FIGS. 5A-10B  schematically illustrate the unlock actuator throughout the retract and deploy cycles with a mechanical jam. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    A retracting cycle of a landing gear  10  is illustrated in  FIGS. 1A-1D .  FIG. 1A  depicts the landing gear  10  in a fully deployed position and locked.  FIG. 1B  depicts the landing gear  10  in a fully deployed position and unlocked.  FIG. 1C  depicts the landing gear  10  while it is being retracted.  FIG. 1D  depicts the landing gear  10  in a stowed position. 
         [0014]    The landing gear  10  includes a strut  14  supporting wheels  16 . The strut  14  is rotatable about a pivot, which is provided by an airframe  12 , in response to an extend/retract actuator applying a force to an arm  19 . A linkage  20  connects a lower portion of the strut  14  to the airframe  12 , for example. A lock-stay  22  is interconnected between the linkage  20  and the strut  14  to lock the landing gear  10  in the fully deployed position until the pilot retracts the landing gear. 
         [0015]    In  FIG. 1A , the landing gear  10  is shown locked in the fully deployed position. The example lock-stay  22  includes first and second links  21 ,  23  pivotally secured to one another at a joint D, best shown in  FIG. 1B . One end of the first link  21  is connected to the strut  14  at pivot B. A portion of the second link  23  is connected to the linkage  20  at pivot C. A biasing member  26  is arranged between the lock-stay  22  and the linkage  20  to bias the lock-stay  22  to the locked position shown in  FIG. 1A . An unlock actuator  24  is interconnected between the linkage  20  and lock-stay  22  to pull the joint D from over-center, as depicted by the arrow in  FIG. 1B  (from the locked position shown in  FIG. 1A ), so that the extend/retract actuator  18  can move the landing gear  10  to a stowed position. 
         [0016]    For the example unlock actuator  24 , once the lock-stay  22  has been moved from over-center, the unlock actuator  24  free-drives. That is, the lock-stay  22  is no longer moved under the power of the unlock actuator  24 , but rather, the extend/retract actuator  18  moves the lock-stay  22  and unlock actuator  24  as the landing gear  10  is stowed. 
         [0017]    A controller  32  is used to control the operation of the landing gear and sense the location of various components. The controller  32  can be hardware and/or software and constructed as single or multiple units. For example, a lock position sensor  28  communicates with the controller  32  to detect the lock-stay  22  in a locked position, as shown schematically in  FIG. 1A . The stowed position sensor  30  communicates with the controller  32  and detects the position of a portion of the landing gear  10  to ensure that the landing gear is fully stowed. 
         [0018]    Other sensors can be used to detect faults in the operation of the landing gear. For example, position sensors  50  are associated with the unlock actuator  24  to determine positions of components within the unlock actuator  24 , as shown in  FIG. 2 . The position sensors  50  are in communication with the controller  32  and are used to evaluate whether a fault has occurred. Input and output devices  31 ,  33  are also in communication with the controller  32 . The input device  31  includes one or more pilot initiated controls, for example. The output device  33  includes a fault indicator or a position indicator, for example. 
         [0019]    Referring to  FIGS. 2 and 3 , the unlock actuator  24  includes a body that houses a motor  38 . The motor  38  drives a screw  42  through gears  40 , for example. A finger tube  44  is driven axially by the screw  42 . A guide  46  is housed within the finger tube  44  and supports a rod  48 . The finger tube  44  and rod  48  are coaxial with one another in the example. During normal operation, the finger tube  44  and rod  48  remain nested with one another. Ends  34  are provided by the body  36  and rod  48 . The ends  34  are interconnected between the linkage  20  and lock-stay  22 . As shown in  FIG. 2 , the position sensors  50  detect the axially position of the finger tube  44 . The actual position of the finger tube  44  relative to a commanded position can indicate a mechanical jam and trigger a fault. 
         [0020]    Referring to  FIG. 3 , one end of the screw  42  is supported by a bearing  52 . An end of the finger tube  44  includes a nut  54  that is threadingly received by the screw  42 . A sleeve  56  is positioned within the body  36  and provides a stop  58  that limits the axial travel of the finger tube  44 . In the example, the axial distance that the finger tube  44  can travel from “stop to stop” corresponds to the distance needed to pull the lock-stay  22  from over-center to the unlocked condition. 
         [0021]    An end of the finger tube  44  includes first and second sets of fingers  62 ,  64 . In the example, the first set of fingers  62  includes hooks  66  that cooperate with a lip  60  provided by one side of the guide  46  (shown in  FIG. 5B ). The first set of fingers  62  are moved radially inward when the first set of fingers  62  engage an annular tapered collar  74 . The first set of fingers  62  extend axially beyond the second set of fingers  64 . Referring to  FIG. 5B , the guide  46  includes a key  70  that is received by a slot  72  that extends axially along a portion of the finger tube  44 . The key and slot  70 ,  72  cooperate with one another to prevent rotation of the guide  46  and rod  48 . 
         [0022]    The operation of the landing gear  10  is schematically illustrated by the flow chart shown in  FIG. 4 . As shown in block  78 , the landing gear  10  is illustrated in a fully deployed position and locked. The lock-stay  22  is biased in the locked position (with the joint D over-center) by the biasing member  26 . Referring to  FIGS. 5A and 5B , the unlock actuator  24  is illustrated in the locked position with a “normally” operating unlock actuator. The finger tube  44  has been axially advanced by the screw  42  with the motor  38  and gears  40  to the position shown. The first set of fingers  62  has been moved radially inwardly by the tapered collar  74  (not shown). With the finger tube  44  in the illustrated axial position, the biasing member  26  is able to move the rod  48  a sufficient axial amount to enable the biasing member  26  to move the lock-stay  22  to the locked position. In the position shown in  FIGS. 5A and 5B , the hooks  66  engage the lip  60  in preparation for pulling the rod  48  to move the lock-stay  22  to an unlocked condition. 
         [0023]    The pilot, for example, provides an input through input device  31  to raise the landing gear, as indicated in block  80 . In response to the pilot&#39;s command to raise the landing gear  10 , the unlock actuator  24  axially moves the finger tube  44  with the screw  42  to retract the rod  48  and move the lock-stay  22  as shown at blocks  82  and  84 . The hooks  66  and lip  60  are interlocked with one another such that the finger tube  44  pulls the rod  48  and remains in engagement with the guide  46  even after the first set of fingers  62  have moved out of engagement with the tapered collar  74 . 
         [0024]    A mechanical jam is illustrated in  FIGS. 6-10B . The mechanical jam depicted (block  86 ) is one in which the screw  42  is unable to retract the finger tube  44  to its axially retracted position, such as if the screw  42  and nut  54  have become frozen to one another, as shown in  FIG. 6 . As illustrated at block  88 , a fault is triggered for example, by position sensors  50  ( FIG. 2 ) indicating that the unlock actuator  24  is malfunctioning and in need of replacement. 
         [0025]    Referring to block  90  and  FIG. 7 , the extend/retract actuator  18  acts upon the landing gear  10  to rotate it to the stowed position. The rod  48  is moved axially inward and is permitted to free-drive relative to the finger tube  44  in response to movement by the extend/retract actuator  18 . In doing so, the hooks and lip  66 ,  60  disengage from one another permitting the first set of fingers  62  to move radially outwardly relative to the guide  46 . The landing gear  10  is fully stowed as indicated at block  92  and the guide  46  and rod  48  are positioned as indicated in  FIG. 8 . 
         [0026]    When the pilot initiates a command to deploy the landing gear  10 , as indicated at block  94 , the landing gear  10  will fully deploy despite the jammed unlock actuator. Referring to block  96  in  FIG. 9 , the extend/retract actuator  18  rotates the landing gear  10  to the deployed position. The rod  48  moves axially outwardly relative to the finger tube  44 . Even with the finger tube  44  stuck in an undesired position, the rod  48  is permitted to free-ride and fully extend in response to movement of the extend/retract actuator  18  to permit the lock-stay  22  to lock. As shown in  FIGS. 10A and 10B , the rod  48  decouples from the finger tube  44 . In one example, the guide  46  is permitted to move past the hooks  66  into space  76  since the hooks  66  are arranged radially outward of the lip  60 . The biasing member  26  biases the lock-stay  22  to the locked position as shown at block  98 . If the pilot commands the landing gear to a stowed position, as indicated at block  100 , the unlock actuator  24  will not permit retraction of the rod  48  and the landing gear  10  will remain locked in the fully deployed position, as indicated at block  102 . Faces  77  of protrusions  68  will engage ends  75  of the second set of fingers  64  ( FIG. 10B ) thereby preventing the guide  46  from again entering the finger tube  44 . A fault will again be sent, as indicated at block  104 . 
         [0027]    In this manner, the landing gear  10  is permitted to cycle from a fully deployed position to a stowed position with a jammed unlock actuator. The landing gear is also permitted to cycle from the stowed position to a fully deployed position once with a jammed unlock actuator  24 , after which replacement of the unlock actuator is required. The landing gear  10  is not permitted to again cycle from the fully deployed position to a stowed position. 
         [0028]    Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.