Abstract:
The subject matter of this specification can be embodied in, among other things, a track lock assembly that includes a pawl assembly comprising a pawl arm extending from a pawl axis and configured to engage a slot in a slider assembly, a cam arm extending from the pawl axis and having a pawl cam, and a compliant member, and a position lock assembly comprising a first lock arm extending from a lock axis and an actuator configured to urge rotation of the first lock arm between a lock locked position and a lock unlocked position, the first lock arm configured to engage and retain the cam arm in a pawl locked position when the first lock arm is in the lock locked position and disengage the cam arm in the lock unlocked position such that the compliant member is able to urge the pawl assembly to a pawl unlocked position.

Description:
TECHNICAL FIELD 
       [0001]    This instant specification relates to locking mechanisms. 
       BACKGROUND 
       [0002]    Contemporary aircraft engines may include a thrust reverse actuation system to assist in reducing aircraft speed during landing. Typical thrust reversers include a movable element that when in the active position reverses at least a portion of the air flow passing through the engine. During maintenance of such areas of the engine the movement of the movable part is inhibited for safety; currently, this is done manually by a user near the equipment that controls the hydraulic flow to the movable element. 
       SUMMARY 
       [0003]    In general, this document describes locking mechanisms. 
         [0004]    In a first aspect, a track lock assembly includes a pawl assembly comprising a pawl arm extending from a pawl axis and configured to engage a slot in a slider assembly, a cam arm extending from the pawl axis substantially opposite the pawl arm and having a pawl cam, and a compliant member configured to urge rotation of the pawl about the pawl axis from a pawl locked position, such that the pawl arm is engaged in the slot and the pawl cam is disengaged from a slider cam extending from the slider assembly, to a pawl unlocked position such that the pawl arm is biased away from the slot and the pawl cam is biased toward contact with the slider cam extending from the slider assembly, and a position lock assembly comprising a first lock arm extending from a lock axis and an actuator configured to urge rotation of the first lock arm between a lock locked position and a lock unlocked position, the first lock arm configured to engage and retain the cam arm in the pawl locked position when the first lock arm is in the lock locked position and disengage the cam arm in the lock unlocked position such that the compliant member is able to urge the pawl assembly to the pawl unlocked position. 
         [0005]    Various embodiments can include some, all, or none of the following features. The slider assembly can be configured to slide the slider cam and the slot substantially perpendicular to the pawl axis such that movement of the slider assembly urges contact between the slider cam and the lock cam and rotation of the pawl assembly into the pawl locked position. The track lock assembly can include a sensor configured to provide a first indication when the lock assembly is in the lock locked position and provide a second indication when the position lock assembly is in the lock unlocked position. The track lock assembly can include a manual lock assembly having a first configuration which does not affect movement of the position lock assembly, and a second configuration in which the position lock assembly is urged into the lock unlocked position. 
         [0006]    In a second aspect, a method of locking a track includes providing a track lock assembly proximal a slider assembly, the track lock assembly having a pawl assembly having a pawl cam and a pawl arm configured to pivot together about a pawl axis between a pawl locked position and a pawl unlocked position, and a position lock assembly configured to selectably permit or prevent movement of the pawl assembly between the pawl locked position and the pawl unlocked position. The method also includes sliding the slider assembly in a first direction perpendicular to the pawl axis. contacting a slider cam to the pawl cam in the pawl unlocked position, urging, by contact between the slider cam and the pawl cam, rotational movement of a distal end of the pawl arm into the slot, and contacting a slot end with the distal end as to interfere with sliding of the slider in the first direction. 
         [0007]    Various implementations can include some, all, or none of the following features. The method can also include locking, by the position lock assembly, the pawl assembly in the pawl locked position such that the distal end of the pawl arm is within the slot. The method can also include unlocking, by the position lock assembly, the pawl assembly, rotating the pawl assembly to the pawl unlocked position such that the distal end of the pawl arm is removed from the slot, and sliding the slider assembly in a second direction opposite the first direction perpendicular to the pawl axis. The pawl assembly can include a compliant member configured to urge the pawl assembly into the pawl unlocked position, and urging, by contact between the slider cam and the pawl cam, rotational movement of a distal end of the pawl arm into the slot can also include biasing the compliant member, and rotating the pawl assembly to the pawl unlocked position such that the distal end of the pawl arm is removed from the slot can include urging, by the compliant member, rotation of the pawl assembly to the pawl unlocked position such that the distal end of the pawl arm is removed from the slot. The method can also include providing a manual lock assembly having a first configuration which does not affect movement of the position lock assembly, and a second configuration in which the position lock assembly is urged into the lock unlocked position, and configuring the manual lock assembly into the second configuration to urge the position lock assembly into the lock unlocked position. The method can also include providing a sensor configured to identify the lock locked position and the lock unlocked position, providing, by the sensor, a first indication when the lock assembly is in the lock locked position, and providing, by the sensor, a second indication when the lock assembly is in the lock unlocked position. The method can also include unlocking, by the position lock assembly, the pawl assembly, wherein the pawl arm includes an angular pawl face at a distal end opposite the pawl axis, sliding the slider assembly in a second direction opposite the first direction perpendicular to the pawl axis, wherein the slot includes a slot end having an angular end face that is complimentary to the angular pawl face, and contacting the angular end face with the angular pawl face as to urge rotation of the pawl assembly to the pawl unlocked position such that the distal end of the pawl arm is removed from the slot. 
         [0008]    In a third aspect, a track lock assembly includes a pawl assembly having a pawl arm extending from a pawl axis and configured to engage a slot in a slider assembly, a cam arm extending from the pawl axis substantially opposite the pawl arm and having a pawl cam, and a compliant member configured to urge rotation of the pawl about the pawl axis from a pawl locked position such that the pawl arm is engaged in the slot and the pawl cam is disengaged from a slider cam extending from the slider assembly to a pawl unlocked position such that the pawl arm is biased away from the slot and the pawl cam biased toward contact with the slider cam extending from the slider assembly, and a position lock assembly comprising an actuator configured to selectably engage the pawl assembly to retain the pawl assembly in the pawl locked position and disengage the pawl assembly which does not affect movement of the pawl assembly between the pawl locked position and the pawl unlocked position. 
         [0009]    Various embodiments can include some, all, or none of the following features. The slider assembly can be configured to slide the slider cam and the slot substantially perpendicular to the pawl axis such that movement of the slider assembly urges contact between the slider cam and the lock cam and urges rotation of the pawl assembly into the pawl locked position. The track lock assembly can include a sensor configured to provide a first indication when the lock assembly is engaged with the pawl assembly and provide a second indication when the position lock assembly is disengaged from the pawl assembly. The track lock assembly can include a manual lock assembly having a first configuration which does not affect engagement of the position lock assembly with the pawl assembly, and a second configuration in which the position lock assembly is urged into engagement with the pawl assembly. The pawl arm can include an angular pawl face at a distal end opposite the pawl axis, and the slot can include a slot end having an angular end face that is complimentary to the angular pawl face. 
         [0010]    The systems and techniques described herein may provide one or more of the following advantages. First, a system can provide a light weight tertiary mechanism to prevent inadvertent in-flight deployment of a transcowl assembly. Second, the system can reduce the bulk, weight, and/or complexity associated with the large solenoids and/or reduction gearboxes generally used in direct-drive type tertiary locks for transcowl assemblies. Third, the system can use motion of a transcowl assembly to actuate the tertiary lock, rather than use electrical power to actuate a direct action solenoid or motor as with direct-drive type tertiary locks. Fourth, the system can reduce actuator stroke and/or power consumption by powering an actuator to baulk a locking element instead of actuating it. 
         [0011]    The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a block diagram that shows an example of a track lock system in an unlocked configuration. 
           [0013]      FIG. 2  is a block diagram that shows an example of a track lock system in a locked configuration. 
           [0014]      FIG. 3  is a block diagram that shows another example of a track lock system in a locked configuration. 
           [0015]      FIG. 4  is a block diagram that shows another example of a track lock system in an unlocked configuration. 
           [0016]      FIG. 5  is a block diagram that shows another example of a track lock system in an unlocked configuration. 
           [0017]      FIG. 6  is a block diagram that shows an example of a track lock system reset to a locked configuration. 
           [0018]      FIG. 7  is a block diagram that shows another example of a track lock system reset to a locked configuration. 
           [0019]      FIG. 8  is a block diagram that shows an example of a track lock system in a manually unlocked configuration. 
           [0020]      FIG. 9  is a block diagram that shows an example of another track lock system. 
           [0021]      FIG. 10  is flow chart that shows an example of a process for locking a track lock system. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    This document describes locking mechanisms. More specifically, this document describes electric baulking type track lock tertiary lock mechanisms, for example, for use in thrust reverser actuation systems for cascade type turbofan and turbojet thrust reversers, and for variable fan nozzle (VAFN) actuation systems. In general, the locking mechanisms described in this document can directly lock the slider of a cascade type thrust reverser. The track lock tertiary locks described herein are generally lighter and more compact when compared to pin type locks. 
         [0023]      FIG. 1  is a block diagram that shows an example of a track lock system  100  in an unlocked configuration. The track lock system  100  is located proximal to a slider assembly  10  that includes a slot  20  formed in a surface  21  of the slider assembly  10 . The slider assembly  10  is configured to move linearly. 
         [0024]    The track lock system  100  includes a pawl assembly  110 . In the present example, the pawl assembly  110  of the track lock system  100  is shown in an unlocked configuration. The pawl assembly  110  includes a pawl arm  112  extending from a pawl axis  116 , and a cam arm  114  extending from the pawl axis  116  substantially radially opposite the pawl axis  116  (e.g., about 90 degrees to about 180 degrees apart). The pawl assembly  110  is configured to pivot at least partly about the pawl axis  116 . The track lock system  100  is arranged relative to the slider assembly  10  such that movement of the slider assembly  10  is substantially perpendicular to the rotation of the pawl axis  116 . 
         [0025]    The pawl arm  112  includes a distal end  117  that can be pivoted about the pawl axis  116  into contact with the surface  21  and the slot  20 , as will be discussed further in the description of  FIG. 2 . The cam arm  114  includes a cam  118  extending substantially perpendicular to the cam arm  114  toward the slider assembly  10 . The cam  118  is configured to contact a cam  119  as the slider assembly  10  is moved. 
         [0026]      FIG. 2  is a block diagram that shows an example of the track lock system  100  in a locked configuration. In the illustrated example, the slider assembly  10  has been moved, as indicated by arrow  200 , relative to the track lock assembly  100  and relative to the position of the slider assembly  10  illustrated in  FIG. 1 . 
         [0027]    Movement of the slider assembly  10  is urged by movement of external fixtures or equipment to which the slider assembly  10  is connected. For example, the slider assembly  10  may be affixed to, or part of, a transcowl assembly. As the transcowl assembly is urged to move by hydraulic, electric, pneumatic, or other force, the slider assembly  10  is urged to move as well. 
         [0028]    Movement of the slider assembly  10  brings the cam  119  into contact with the cam  118 . Contact between the cam  119  and the cam  118  causes the pawl assembly  110  to pivot about the pawl axis  116 , as indicated by the arrow  202 . Rotation of the pawl axis  116  causes the pawl arm  112  to extend into the slot  20  and bring the distal end  117  into contact or near-contact with the slot  20 , transitioning from a pawl unlocked configuration to a pawl locked configuration. 
         [0029]    Rotation of the pawl assembly  110  also brings the cam arm  114  into interfering contact with a lock arm  152  of a position lock assembly  150  in a lock locked configuration. As will be discussed in more detail in the descriptions of  FIGS. 4-8 , the position lock assembly  150  can be actuated between the lock locked configuration that can hold the pawl assembly  110  in the pawl locked configuration, and a lock unlocked configuration that does not interfere with movement of the pawl assembly  110  between the pawl unlocked configuration and the pawl locked configuration. 
         [0030]    The pawl axis  116  includes a compliant member  160 , such as a spring, that provides a torque that urges the pawl assembly  110  toward the pawl unlocked configuration. Contact between the cam  119  and the cam  118  also causes rotation of the pawl assembly  110  against the bias of the compliant member  160  (e.g., partly winds the spring). With the position lock assembly  150  in the lock locked configuration, the position lock assembly  150  resists the torque of the compliant member  160  and keeps the pawl assembly  110  in the pawl locked configuration as will be discussed in the description of  FIGS. 3 and 7 . With the position lock assembly  150  in the lock unlocked configuration, the compliant member  160  is able to torque the pawl assembly  110  into the pawl unlocked configuration (e.g., partly unwind the spring  160 ) as will be discussed in the description of  FIGS. 4-5 . 
         [0031]    Referring briefly to  FIG. 7 , which will be described in more detail later in this description, a block diagram shows another example of the track lock system  100  in which the cam  119  is not in contact with the cam  118 . The pawl assembly  110  is kept in the pawl locked configuration due to mechanical interference between the cam arm  114  and the lock arm  152 , which is in the lock locked position. 
         [0032]      FIG. 3  is a block diagram that shows another example of the track lock system  100  in the locked configuration. In this example, the track lock system  100  is preventing inadvertent in-flight deployment of the slider assembly  10 . In the illustrated example, the slider assembly  10  has been moved, as indicated by arrow  300 , relative to the track lock assembly  100  and relative to the position of the slider assembly  10  illustrated in  FIG. 2 . 
         [0033]    In the illustrated example, the cam  119  has moved out of contact with the cam  118 . Interference between the lock arm  152  and the cam arm  114  resists the torque provided by the compliant member  160 , and holds the pawl assembly  150  in the pawl locked configuration. As the slider assembly  10  continues to move, the distal end  117  of the pawl arm  112  contacts a slot end  22  of the slot  20 . Contact between the distal and  117  and the slot end  22  resists further movement of the slot assembly  10  as indicated by the arrow  300 . 
         [0034]      FIG. 4  is a block diagram that shows another example of the track lock system  100  in the unlocked configuration. In the illustrated example, the slider assembly  10  has been moved, as indicated by arrow  400 , relative to the track lock assembly  100  and relative to the position of the slider assembly  10  illustrated in  FIG. 2 . 
         [0035]    In the illustrated example, (e.g., as compared to  FIG. 7 ), the position lock assembly  150  has been put into the lock unlocked configuration. The position lock assembly  150  includes the lock arm  152  which extends from a lock axis  156 , a switch arm  154  that extends from the lock axis  156  substantially opposite from the lock arm  152  (e.g., approximately 180 degrees apart). The lock axis  156  can be partly rotated to cause the position lock assembly  150  to move between the lock locked configuration and the lock unlocked configuration. 
         [0036]    Movement of the position lock assembly  150  is urged by a solenoid  170 . The solenoid  170  includes a plunger  172  that is connected to the lock arm  152 , although in some embodiments the plunger  172  could be connected to the switch arm  154  or any other appropriate part of the position lock assembly  150 . When energized, the solenoid  170  and the plunger  172  urge movement of the position lock assembly  150  from the lock locked configuration to the lock unlocked configuration, as indicated by the arrow  410 . 
         [0037]    In the lock unlocked configuration, the lock arm  152  is moved out of contact with the cam arm  114 . When the position lock assembly  150  is in the lock unlocked configuration, the pawl assembly  110  is able to be urged toward the pawl unlocked position by the compliant member  160 , as indicated by the arrow  420 . For example, as the slider assembly  10  moves from the position illustrated in  FIG. 2  to the position illustrated in  FIG. 4 , the cam  119  moves away from contact with the cam  118 . The cam  118 , as urged by torque provided by the compliant member  160 , follows the contour of the cam  119 , which lets the pawl assembly  110  rotate the distal end  117  out of the slot  20  to a position above the surface  21 . 
         [0038]    The position lock assembly  150  also includes a switch  180 . The switch  180  includes a plunger  182  that can contact the switch arm  154 , although in some embodiments the plunger  182  could be connected to the lock arm  152  or any other appropriate part of the position lock assembly  150 . The plunger  182  is configured to actuate the switch  180  such that the switch  180  an provide an first output signal at a signal port  184  when the position lock assembly  150  is in the lock locked position and provides a second output signal at the signal port  184  when the position lock assembly  150  is in the lock unlocked position. In some embodiments, the signal output port  184  can be in communication with an indicator light, a controller, a buzzer, or any other appropriate external device (e.g., Electronic Engine Controller (EEC), Full Authority Digital Engine Controller (FADEC)) that has a state that can be altered when the position lock assembly  150  enters and exits the lock locked configuration. 
         [0039]      FIG. 5  is a block diagram that shows another example of the track lock system  100  in the unlocked configuration. In the illustrated example, the slider assembly  10  has been moved, as indicated by arrow  500 , relative to the track lock assembly  100  and relative to the position of the slider assembly  10  illustrated in  FIG. 4 . With the distal and  117  positioned out of the slot  20 , the slider assembly  10  can continue to move without causing interference between the pawl arm  112  and the slot end  22 . 
         [0040]      FIG. 6  is a block diagram that shows an example of the track lock system  100  reset to the locked configuration. In the illustrated example, the slider assembly  10  has been moved, as indicated by arrow  600 , relative to the track lock assembly  100  and relative to the position of the slider assembly  10  illustrated in  FIG. 5 . 
         [0041]    In the illustrated example, the solenoid  170  has been de-actuated to cause the plunger  172  to extend, causing the position lock assembly  150  to partly rotate, as indicated by the arrow  610 , about the lock axis  156  to the lock locked position. In the lock locked position, the switch arm  154  contacts the plunger  182 , actuating the switch  180  to provide a signal at the signal port  184  to indicate that the position lock assembly  150  is in the lock locked configuration. 
         [0042]    As the slider assembly  10  moves (e.g., under hydraulic power), the cam  119  contacts the cam  118 . The cam  118  follows the cam  119 , transferring energy from the lateral movement of the slider assembly  10  into rotational movement of the pawl assembly  110 , as indicated by arrow  620 . Contact between the pawl  119  and the pawl  118  rotates the pawl assembly  110  against the bias of the compliant member  160  and into the pawl locked configuration. With the position lock assembly  150  in the lock locked configuration, the lock arm  152  interferes with movement of the cam arm  114 , holding the lock assembly  110  in the pawl locked configuration. In some implementations, the solenoid  170  could be energized again to cause the position lock assembly  150  to release the pawl assembly  110  to the unlocked configuration. 
         [0043]      FIG. 7  is a block diagram that shows another example of the track lock system  100  reset to the pawl locked configuration. In some implementations, the pawl locked configuration may be the normal in-flight and/or on-ground position of the track lock system  100 . In the illustrated example, the cam  119  is not in contact with the cam  118 . The compliant member  160  provides a bias that urges rotation of the pawl assembly  110  toward the pawl unlocked position and removal of the distal end  117  from the slot  20 . The pawl assembly  110  is kept in the locked configuration due to mechanical interference between the cam arm  114  and the lock arm  152 , which is in the lock locked position. 
         [0044]    The position lock assembly  150  includes a manual override assembly  190 . The manual override assembly  190  is configurable to an override inactive configuration and an override active configuration. The manual override assembly  190  is a rotary assembly in which an override arm  192  is offset from the axis of rotation of the manual override assembly  190 . In the override inactive configuration, the override arm  192  is offset such that an override arm  192  does not interfere with the movement of a plunger arm  192  that is coupled to the plunger  172 . For example, as the solenoid  170  is energized and de-energized, the plunger  172  moves along its major axis and the plunger arm  192  moves with the plunger  172 , not contacting the override arm  192 . 
         [0045]      FIG. 8  is a block diagram that shows an example of the track lock system in a manually unlocked configuration. In the illustrated example, the manual override assembly  190  has been rotated into the override active configuration, as indicated by arrow  810 . As the manual override assembly  190  is rotated, the manual override arm  192  is moved into contact with the plunger arm  192  and urges movement of the plunger  170  (e.g., and in turn, the position lock assembly  150 ) into the lock unlocked configuration, as indicated by the arrow  820 . For example, as the solenoid  170  is energized and de-energized, contact between the manual override arm  192  and the plunger arm  194  prevents the plunger  172  from moving along its major axis out of the lock unlocked configuration. 
         [0046]    With the position lock assembly  150  in the lock unlocked configuration, as effected by the manual override assembly  190  or by actuation of the solenoid  170 , the pawl assembly  110  is able to rotate into the pawl unlocked configuration, as indicated by the arrow  830 . In some embodiments, the manual override assembly  190  may be configured to put the position lock assembly  150  into the lock locked configuration, to put the position lock assembly  150  into the lock unlocked configuration, to not interfere with operation of the solenoid  170 , or to perform any combination of these actions. 
         [0047]    In some embodiments, the position lock assembly  150  may be a clutch assembly or any other appropriate assembly that can selectably prevent and permit rotation of the pawl axis  116 . For example, a clutch may be provided on the pawl axis. When the clutch is inactive, the pawl axis  116  may be permitted to pivot. When the clutch is active, the pawl axis  116  may be mechanically blocked from permitting movement of the pawl assembly  110 . 
         [0048]      FIG. 9  is a block diagram that shows an example of another track lock system  900 . The track lock system  900  includes a pawl assembly  910 . In the present example, the pawl assembly  910  of the track lock system  900  is shown in an unlocked configuration. The pawl assembly  910  includes the pawl arm  112  extending from the pawl axis  116 , and the cam arm  114  extending from the pawl axis  116  substantially radially opposite the pawl axis  116 . The pawl assembly  910  is configured to pivot at least partly about the pawl axis  116 . The track lock system  900  is arranged relative to the slider assembly  10  such that movement of the slider assembly  10  is substantially perpendicular to the rotation of the pawl axis  116 . 
         [0049]    The pawl arm  112  includes a distal end  917  that can be pivoted about the pawl axis  116  into contact with the surface  21  and the slot  20 , as was discussed previously in the description of  FIG. 2 . The distal end  917  includes an angular face  918  that is configured to contact an angular slot end  922  of the slot  20 . As the slider assembly  10  moves, the distal end  917  of the pawl arm  112  contacts the angular slot end  922 . Contact between the distal end  917  and the angular slot end  922  resists further movement of the slot assembly  10  as indicated by the arrow  901 . 
         [0050]    When the position lock assembly  150  is unlocked under normal operating conditions, the compliant member  160  will rotate the distal  917  out of the slot  20 . Under abnormal operating conditions, however, the pawl assembly  910  may not be able to rotate under the urging of the compliant member  160  alone. For example, in an aircraft application, icing may occur on the outer surface of the aircraft, including the slider assembly  10  (e.g., ice buildup in the slot  20 ) and/or the pawl assembly  910 , and resist the bias of the compliant member  160 . Under conditions in which the pawl assembly  910  is prevented from moving by the bias of the compliant member  160  alone, as the slider assembly  10  moves as indicated by the arrow  901 , the angular face  918  may be brought into sliding contact with the angular slot end  922 . As the slider assembly  10  continues to move (e.g., under hydraulic power), the relative movement of the angular slot end  922  to the angular face  918  may provide additional force that can urge rotation of the pawl assembly  910  to the unlocked configuration. In some embodiments, the relative movement of the angular slot end  922  to the angular face  918  under the power of the slider assembly  10  may also serve to clear ice or other debris out of the slot  20 . 
         [0051]      FIG. 10  is flow chart that shows an example of a process  1000  for locking a track lock system. In some implementations, the process  1000  can be used with the track lock system  100  of  FIGS. 1-9 . 
         [0052]    At  1010 , a track lock assembly is provided proximal a slider assembly. The track lock assembly includes a pawl assembly having a pawl cam and a pawl arm configured to pivot together about a pawl axis between a pawl locked position and a pawl unlocked position, and a position lock assembly configured to selectably permit or prevent movement of the pawl assembly between the pawl locked position and the pawl unlocked position. For example, the track lock assembly  100  can be provided near enough to the slider assembly  10  that the pawl arm  112  can reach the slot  20 . 
         [0053]    At  1020 , the slider assembly is slid in a first direction perpendicular to the pawl axis. For example, the slider assembly  10  can be moved in the direction indicated by arrow  200  of  FIG. 2 . 
         [0054]    At  1030 , a slider cam is contacted to the pawl cam in the pawl unlocked position. At  1040 , contact between the slider cam and the pawl cam urges rotational movement of a distal end of the pawl arm into the slot. For example, when the slider assembly  10  is moved from its position relative to the pawl assembly  110  as shown in  FIG. 1 , to the position shown in  FIG. 2 , the cam  119  contacts the cam  118 . Hydraulic or other mechanical force used to move the slider assembly as indicated by arrow  200 , contact between the cam  119  and the cam  118  causes the pawl assembly to pivot and cause the pawl arm  112  to extend the distal end  117  into the slot  20 . 
         [0055]    At  1050  a slot end is contacted with the distal end as to interfere with sliding of the slider in the first direction. For example, as illustrated in  FIG. 3 , the slider assembly  10  has moved further as indicated by arrow  300 , bringing the slot end  22  into contact with the distal end  117 . 
         [0056]    In some implementations, the process  1000  can also include locking, by the position lock assembly, the pawl assembly in the pawl locked position such that the distal end of the pawl arm is within the slot. For example, the position lock assembly  150  can be put into the lock locked configuration, which can prevent the distal end  117  from being rotated out of the slot  20 . 
         [0057]    In some implementations, the process  1000  can also include unlocking, by the position lock assembly, the pawl assembly, rotating the pawl assembly to the pawl unlocked position such that the distal end of the pawl arm is removed from the slot, and sliding the slider assembly in a second direction opposite the first direction perpendicular to the pawl axis. For example, in the illustration of  FIG. 4 , the solenoid  170  has been actuated to cause the position lock assembly  150  be put into the lock unlocked configuration which allows the compliant member  160  urge rotation of the distal end  117  out of the slot  20  to permit movement of the slider assembly  10  in the direction of arrow  400 . 
         [0058]    In some implementations, the pawl assembly also includes a compliant member configured to urge the pawl assembly into the pawl unlocked position, and the process  1000  can include urging, by contact between the slider cam and the pawl cam, rotational movement of a distal end of the pawl arm into the slot further comprises biasing the compliant member, and rotating the pawl assembly to the pawl unlocked position such that the distal end of the pawl arm is removed from the slot can include urging, by the compliant member, rotation of the pawl assembly to the pawl unlocked position such that the distal end of the pawl arm is removed from the slot. For example, the pawl axis  116  includes the compliant member  160 . The compliant member  160  can be a spring or other elastic device that can provide a bias to pivot the pawl assembly  110  to the unlocked configuration as illustrated in  FIG. 4 . 
         [0059]    In some implementations, the process  1000  can include providing a manual lock assembly having a first configuration which does not affect movement of the position lock assembly and a second configuration in which the position lock assembly is urged into the lock unlocked position, and configuring the manual lock assembly into the second configuration to urge the position lock assembly into the lock unlocked position. For example, the track lock assembly  100  includes the manual override assembly  190 . The manual override assembly  190  can be put in an override inactive configuration as shown in  FIG. 7 , and can be put in an override active configuration as shown in  FIG. 8 . 
         [0060]    In some implementations, the process  1000  can include providing a sensor configured to identify the lock locked position and the lock unlocked position; and provide a second indication when the position lock assembly is in the lock unlocked position, provide, by the sensor, a first indication when the lock assembly is in the lock locked position, and provide, by the sensor, a second indication when the lock assembly is in the lock unlocked position. For example, the position lock assembly  150  includes the switch  180 , which is configured to provide a signal at the signal port  184  to indicate whether the position lock assembly  150  is in the lock locked configuration or in the lock unlocked configuration. 
         [0061]    Although a few implementations have been described in detail above, other modifications are possible. For example, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. In addition, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.