Patent Publication Number: US-9416569-B1

Title: Latch assembly

Description:
TECHNICAL FIELD 
     The present disclosure relates to a latch assembly, and more particularly, to a latch assembly for an access panel on an aircraft body. 
     BACKGROUND 
     An aircraft body has access panels that serve as doors providing access to internal compartments. For example, a forward access panel is a tool-operated, inwardly opening plug type door that provides access to the equipment bay located in the nose of the aircraft. Other examples include access panels at the wing to fairing structure and other locations on the aircraft body. In each case the access panel has one or more latch assemblies. Such a latch assembly includes a latch member that is movable into and out of a latching position securing the access panel in a closed position. The latch member is located at the inside of the access panel, and is not visible from the outside of the aircraft. 
     SUMMARY 
     In an embodiment, a latch assembly may be configured for use with a first structure having an outer surface and a second structure that is movable relative to the first structure. The latch assembly may include a latch member and a visual indicator device. The latch member may be movable into and out of a latching position securing the second structure to the first structure. The visual indicator device may be movable between a retracted position not protruding outward from the outer surface of the first structure and an extended position protruding outward from the outer surface. A linkage may be operatively connected between the latch member and the visual indicator device to move the visual indicator device from the retracted position to the extended position under the influence of the latch member when the latch member is moved out of the latching position. 
     In another embodiment a vehicle, such as an aircraft, may have a first body panel with an outer surface and a second body panel that is movable relative to the first body panel. A latch member may be movable pivotally into and out of a latching position securing the second body panel to the first body panel. A visual indicator device may have a longitudinal axis, and may be movable longitudinally between a retracted position not protruding outward from the outer surface of the first body panel and an extended position protruding outward from the outer surface. A mechanism may include a helical cam and a cam follower. The cam follower may be engaged between the latch member and the indicator device to move the indicator device longitudinally upon movement of the latch member pivotally, whereby the mechanism can move the indicator device between the retracted and extended positions upon movement of the latch member into and out of the latching position. 
     In yet another embodiment, a method for indicating an unlatched condition of first and second structures that are movable relative to one another may include moving a latch member out of a latching position securing the structures together, and moving a visual indicator device under the influence of the latch member. The visual indicator device may be moved relative to an outer surface of the first structure from a non-protruding position to a protruding position under the influence of the latch member when the latch member is moved out of the latching position. 
     Other objects and advantages of the disclosed latch assembly for aircraft access panel will be apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of the disclosed latch assembly, shown mounted on an aircraft access door panel, taken from outside the aircraft body. 
         FIG. 2  is a perspective view of the embodiment of  FIG. 1 , showing the latch assembly in unlatched position. 
         FIG. 3  is an exploded, perspective view of the embodiment of  FIG. 1 . 
         FIG. 4  is a side view, partly in section, of the embodiment of  FIG. 1 , showing the latch assembly in unlatched position. 
         FIG. 5  is a view similar to  FIG. 4 , showing parts in latched position. 
         FIG. 6  is a perspective view of the embodiment of  FIG. 1 , taken from inside the aircraft body. 
         FIG. 7  is a perspective view of another embodiment of the disclosed latch assembly. 
         FIG. 8  is a perspective view of the motion limiting feature detail of the embodiment of  FIG. 7 . 
         FIG. 9  is a perspective view of other parts of the embodiment of  FIG. 7 . 
         FIG. 10  is a perspective view of yet another embodiment of the disclosed latch assembly. 
         FIG. 11  is a perspective view of a part of the embodiment of  FIG. 10 . 
         FIG. 12  is a perspective view of another part of the embodiment of  FIG. 10 . 
         FIG. 13  is a sectional view of a part of the embodiment of  FIG. 10 . 
         FIG. 14  is a side view of the part shown in  FIG. 13 . 
         FIG. 15  is a sectional view showing interconnected parts of the embodiment of  FIG. 10 . 
         FIG. 16  is a perspective view of the embodiment of  FIG. 10 , showing parts in different positions. 
     
    
    
     DETAILED DESCRIPTION 
     As partially shown in  FIG. 1 , a vehicle body  10  may include first and second relatively movable structures  12  and  14 . The first structure  12  in this example may include a door panel, and the second structure  14  in this example may include a panel surround  14 . An edge  16  of the panel surround  14  may define an opening  19  in which the door panel  12  may be received in the closed position of  FIG. 1 . The vehicle may be, for example, an aircraft, a spacecraft, a land vehicle or a marine vehicle. On an aircraft body, the door panel  12  may be a forward access panel any other suitable door panel that is mounted on hinges or otherwise supported for movement relative to the respective panel surround  14 . 
     A latch assembly  20  beside the opening  19  operates to latch the door panel  12  securely in the closed position, and to unlatch the door panel  12  for movement inward from the opening  19 . When the latch assembly  20  unlatches the door panel  12  from the panel surround  14 , a visual indicator device  22  moves from the recessed position of  FIG. 1  to the extended position of  FIG. 2 . This provides a visual indication that the door panel  12 , although still located in the closed position in the opening  19 , is not secured by the latch assembly  20 . 
     As shown in  FIG. 3 , this embodiment of the latch assembly  20  has parts including a latch member in the form of a latch pin  30 . The latch pin  30  may have an elongated cylindrical rod  32  projecting from a ring-shaped head  34 . The head  34  may have apertures  37  for receiving a fastener  38 . 
     The parts shown in  FIG. 3  further include a shaft  40  with a cylindrical shape centered on an axis  45 . A pair of flanges  50  and  52  may be spaced apart along the axis  45 . A passage  55  for the fastener  38  may extend transversely through the shaft  40  above the flanges  50  and  52  for attachment of the latch pin  30  to the shaft  40 . A helical slot  57  may extend partially along the length of the shaft  40  beneath the flanges  50  and  52 . 
     As further shown in  FIG. 3 , other parts of the latch assembly  20  in this embodiment include a body  60  and the visual indicator device  22 . The visual indicator device  22  may be a sleeve that fits over the shaft  40  beneath the flanges  50  and  52 . The body  60  may have a cylindrical portion  64 , and may include a mounting plate  66  with fastener openings  69 . An axially extending slot  71  may reach partly along the length of the cylindrical portion  64 . 
     When the parts shown in  FIG. 3  are interconnected in the latch assembly  20 , the sleeve  22  and the shaft  40  are received coaxially within the cylindrical portion  64  of the body  60 . A pin  74  may extend through an aperture  75  in the sleeve  22 . The pin  74  may project radially inward from the sleeve  22  into the helical slot  57  on the shaft  40 . The pin  74  may also project radially outward from the sleeve  22  into the axially extending slot  71  on the body  60 . 
     More specifically, the parts shown in  FIG. 3  are interconnected as shown in  FIGS. 4 and 5 . An O-ring  76  may be received between the flanges  50  and  52  to provide a seal between the shaft  40  and the body  60 . A spring washer  80  may be received axially between the first flange  50  and the body  60 . A tool engagement feature  82  at the end of the shaft  40  can receive a driving tool for the user to rotate the shaft  40  about the axis  45 . In this manner the user can move the latch pin  30 , which in the illustrated embodiment is fixed to the shaft  40 , pivotally about the axis  45  between a unlatched position, as shown in  FIG. 4 , and a latching position, as shown in  FIG. 5 . 
     When the user rotates the shaft  40  to move the latch pin  30  pivotally, the shaft  40  rotates relative to the body  60 , but the pin  74  in the slot  71  blocks the sleeve  22  from rotating relative to the body  60 . The helical groove  57  then acts as a cam, with the pin  74  acting as a cam follower, to drive the sleeve  22  along the axis  45  as the shaft  40  rotates about the axis  45 . The shaft  40 , the pin  74 , and the body  60  in the illustrated embodiment thus act together as a linkage mechanism that moves the sleeve  22  along the axis  45  as the latch pin  30  moves pivotally about the axis  45 . When the latch pin  30  is moved back and forth between the latching position of  FIG. 5  and the unlatched position of  FIG. 4 , the sleeve  22  is moved longitudinally back and forth between a retracted position received fully within the body  60  ( FIG. 5 ) and an extended position projecting outward from the body  60  ( FIG. 4 ). 
     Referring again to  FIGS. 1 and 2 , the latch assembly  20  in this embodiment may be mounted on the door panel  12 . One or more additional latch assemblies  20  may also be mounted on the door panel  12 . As shown in greater detail in  FIG. 6 , the body  60  of each latch assembly  20  may be fastened to a mounting boss  90  at the inside of the door panel  12 . The latch pin  30  in each latch assembly  20 , when in the latching position as shown in  FIG. 6 , may engage a bracket  92  on the panel surround  14  to secure the door panel  12  to the panel surround  14 , but the latch pin  30  is not visible from outside of the vehicle body  10 . 
     In each latch assembly  20 , the cylindrical portion  64  of the body  60  may fit closely into an aperture  95  in the door panel  12  as shown in  FIG. 1 , and may be flush with, or recessed from, the adjacent outer surface  96  of the door panel  12 . The shaft  40  is preferably perpendicular to the plane of the outer surface  96  at the aperture  95 . The tool engagement feature  82  at the end of the shaft  40  may be accessible in the aperture  95 , and also may be flush or recessed at the outer surface  96  so as not to protrude outward. Preferably, the sleeve  22  also does not protrude from the outer surface  96  of the door panel  12  when in the retracted position shown in  FIG. 1 . However, the sleeve  22  is moved outward through the aperture  95  to protrude from the outer surface  96  when moved to the extended position of  FIG. 2 . In this manner the sleeve  22  provides a visual indication that the latch pin  30  has been moved out of the latching position. Return movement of the sleeve  22  inward through the aperture  95  to the recessed position of  FIG. 1  provides a corresponding visual indication that the latch pin  30  has been moved back to the latching position. 
     An additional feature of the latch assembly  20  is a spring-biased over-center mechanism that acts between the latch pin  30  and the shaft  40 . As shown in  FIGS. 4 and 5 , the body  60  may have a cam profile with a center point  102  between two ramp surfaces  104  and  106 . As the latch pin  30  begins to move from the latching position toward the unlatched position, the rod  32  may slide upward along the first ramp surface  104  toward the center point  102 . This lifts the shaft  40  such that the upper flange  50  on the shaft  40  presses the spring washer  80  upward against the body  60 . The resulting stress in the spring washer  80  provides resistance that biases the rod  32  back down the ramp surface  106  toward the latching position. A reversed over-center effect biases the rod  32  toward the unlatched position when the rod  32  is located on the second ramp surface  104  at the other side of the center point  102 . 
     Another embodiment of a latch assembly  120  is shown in  FIG. 7 . This latch assembly  120  may have many parts that are the same or substantially the same as corresponding parts of the latch assembly  20  described above, as indicated by the use of the same reference numbers for such parts in the drawings. However, the latch assembly  120  differs from the latch assembly  20  by omitting the visual indicator device  22 , and by including a motion limiting structure and a torsion spring  124 . 
     As best shown in  FIG. 8 , the motion limiting structure may provide a circumferentially extending slot  129  at the inner end of the body  60 . Stop surfaces  130  and  132  may be located at opposite ends of the slot  129 . A stop member  134  ( FIG. 8 ) on the head  34  of the latch pin  30  may extend into the slot  129  for movement circumferentially throughout a range defined between the stop surfaces  130  and  132  at the opposite ends of the slot  129 . 
     A first end  140  of the torsion spring  124  may engage the shaft  40 , as shown in  FIG. 9 . A second end  142  of the torsion spring  124  may engage the cylindrical portion  64  of the body  60 , as shown in  FIG. 7 . In the assembled condition of  FIG. 7 , the stop member  134  on the latch pin  30  abuts the second stop surface  132  in the slot  129 . The torsion spring  124 , which may be either stressed or unstressed in the condition of  FIG. 7 , can then apply a spring force resisting rotation of the shaft  40  about the axis  45  upon movement of the stop member  134  away from the second stop surface  132 . 
     When this embodiment of a latch assembly  120  is mounted a door panel  12  as described above with reference to  FIG. 6 , it is placed such that the latch pin  30  takes its latched position in the condition of  FIG. 7 . The torsion spring  124  can then apply the spring force to resist movement of the latch pin  30  pivotally out of the latching position, and to bias the latch pin  30  back toward the latching position. 
     Yet another embodiment of a latch assembly  200  is shown in  FIG. 10 . This latch assembly  200  may include a latch member  202 , a shaft  204 , and a body  206 . 
     The latch member  202  ( FIG. 11 ) may include an arm  210  and a bolt  212 . An end portion  214  of the arm  210  may have a bore  215  with a non-circular cross section. The shaft  204  ( FIG. 12 ), which may have a longitudinal central axis  217 , may have a major portion  218  with a non-circular cross section, and may further have a cylindrical head  220  with a tool engagement feature  222  at the outer end. A locator pin  226  may extend transversely through the major portion  218  near the inner end. 
     The body  206  ( FIGS. 13 and 14 ) may have first and second compartments  227  and  229 , both of which are open at opposite sides of the body  206 . A pair of passages  233  may communicate the first compartment  227  with the inner and outer ends  234  and  236  of the body  206 . A locator structure  238  at the inner end  234  may have a first pair of notches  240  on a first transverse axis  241 , and a second pair of notches  244  on a second transverse axis  245 . The second transverse axis  245  may be perpendicular to the first transverse axis  241 , and may be spaced inward from the first transverse axis  241 . 
     As shown in  FIG. 15 , the end portion  214  of the arm  210  may be received in the first compartment  227  in the body  206 . The major portion  218  of the shaft  204  may extend through the bore  215  in the arm  210 , and may project through the passages  233 . In this arrangement, the shaft  204  may carry the arm  210  pivotally about the axis  217  when the shaft  204  rotates about the axis  217  relative to the body  206 . The shaft  204  may also be movable along the axis  217  relative to both the arm  210  and the body  206 . A spring  248  may be compressed between the body  206  and the head  220  to bias the shaft  204  outward along the axis  217 . 
     In use, a mounting flange  250  on the body  206  may be fastened to a mounting boss on the inside of an aircraft panel structure beside an opening for an access door panel. In a fully unlatched position, as shown in  FIGS. 10 and 15 , the latch member  202  may be contained within the body  206 . The locator pin  226  on the shaft  204  may then rest in the first notches  240  on the body  206 . The head  220  of the shaft  204  may then project longitudinally outward from the body  206  along the axis  217 . 
     A user may move the latch member  202  to a latching position, as shown in  FIG. 16 , by first pushing the shaft  204  axially inward against the bias of the spring  248  until the locator pin  226  is moved inward beyond the locator structure  238  on the body  206 . The user may next rotate the shaft  204  90° to move the locator pin  226  into alignment with the second notches  244 , and allow the spring  248  to move the shaft  206  back outward until the locator pin  226  rests in the second notches  244 . The bolt  212  is then engaged with a bracket on the adjacent panel to secure the panels from movement relative to one another. 
     When the latch member  202  is moved to the latching position of  FIG. 16 , the head  220  of the shaft  204  is retracted fully into the body  206 . Reversing these movements will move the latch member  204  back out of the latched position, and will move the head  220  back outward of the body  206 . The head  220  is thus movable between retracted and extended positions with reference to an outer surface of an aircraft body panel to serve as a visual indicator device for an unlatched condition of a door panel. 
     Also shown in  FIG. 16  is a ramp surface  252  at the bracket on the adjacent panel. The ramp surface  252  may be inclined downward along the path of movement of the bolt  212  from the latching to the unlatched position of the latch member  204 . This promotes sliding movement of the bolt  212  downward along the ramp surface  252  under the influence of the spring  248 . Such movement can return the latch member  204  to the unlatched position, with actuation of the head  220  as a visual indicator device, if the latch member  204  has not been moved fully to the latching position in which the bolt  212  securely engages the bracket. 
     In each of the illustrated embodiments of a latch assembly, all parts of the latch assembly, with the exception of a visual indictor device, preferably remain flush with, or recessed from, the adjacent outer surface of the door panel throughout the entire range of movement of the latch member between the lathing and unlatched positions. Additionally, supporting the latch member for movement pivotally about the axis of the shaft provides the latch member with a range of movement in a plane that is parallel to the outer surface, rather than perpendicular to the outer surface, and thereby reduces the depth of the latch assembly relative to the door panel and the opening in the surround panel. 
     While the methods and forms of apparatus disclosed herein may constitute preferred aspects of the disclosed latch assembly, it is to be understood that the invention is not limited to these precise forms and methods, and that changes may be made therein without departing from the scope of the invention.