Abstract:
A telescoping aircraft door is disclosed having first and second panels that slide relative to one another to extend and retract as the door closes and opens, respectively. The first panel is hinged to the door frame in a traditional manner, and the second panel is fixed to the door frame by a linkage that limits the arc of the second panel. By selecting the location and length of the linkage, the relative movement of the two panels can be predictably controlled to reduce the depth of the door when closed and the length of the door when opened.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims priority from U.S. Application No. 62/023,530, filed Jul. 11, 2014, the content of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     The interior of a commercial aircraft typically includes several compartments, such as crew changing quarters, lavatories, galleys, and the like. In each case, ingress and egress of these compartments are typically through a door or panel that walls off the compartment when in use. Doors of this type include both sliding doors and swinging doors. Each of these types of doors have inherent drawbacks. Namely, swinging or hinged doors occupy a large amount of cross-aisle space when the door is open and the design of the aircraft must account for the free space needed to accommodate the arc of the door as it transitions open. Conversely, sliding doors occupy twice the depth space to achieve the same closure area. Both of these shortcomings add unnecessary weight and/or occupy space that could be used for better purposes. Thus, there is a need for an improved door for use in an aircraft that overcomes the shortcomings of the prior art. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a two panel door having a first panel hinged to the door frame and a second panel coupled to the frame by a linkage that includes a rotating arm. The rotating arm reduces the arc traveled by the second panel (and thus the door in general) and results in a door with less width, weight, and covers the same area without unduly monopolizing cross-aisle space. The door when opened is roughly half as wide as when it is closed, allowing for a more narrow aisle or, alternatively, leaving more aisle space available for cross traffic. In narrow aisle aircraft, the use of a bi-fold door can be replaced with the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevated perspective view of a first embodiment of the present invention; 
         FIG. 2A  is a top view of the telescoping panel door of the present invention in the extended, closed position; 
         FIG. 2B  is a top view of the telescoping panel door of  FIG. 2A  in a partially open position; 
         FIG. 2C  is a top view of the telescoping panel door of  FIG. 2A  approximately half way open; 
         FIG. 2D  is a top view of the telescoping panel door of  FIG. 2A  in a substantially open position; and 
         FIG. 2E  is a top view of the telescoping panel door of  FIG. 2A  in the fully open position; 
         FIG. 3  is an elevated, perspective view of the first and second panels; and 
         FIG. 4  is a perspective view looking upward at the linkage between the second panel and the door frame. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a first preferred embodiment of a telescoping door of the present invention in which a door for an aircraft, vessel, or other vehicle is disclosed. The door  10  of the present invention comprises at least two panel, including a first panel  12  connected to the door frame  14  via a hinge or set of hinges, such as the piano hinge  16 , and a second panel  18  that is slidingly engaged with the first panel  12  and extends therefrom. The first panel  12  is attached to the frame  14  in a pivoting arrangement and a width of the first panel is selected to be sufficient to approximately span one half of the width of the doorway. A handle or release lever  20  is provided in the first panel  12  to assist in opening and closing the door  10 . The first panel  12  is also provided with preferably two horizontal grooves or slots  22 , 24 , as set forth more fully below. The operation of the first panel  12  is relatively simply, swinging about its fixed point on the hinge or hinges  16  between on open position and a closed position, where the closed position locates the first panel  12  in the doorway where it occupies approximately one half of the door frame area. 
     The second panel  18  of the telescoping door  10  is attached to the first panel through a wheel  23  and slot arrangement where the wheels are captured on tracks in the horizontal slots  22 , 24  or grooves, such that the second panel  18  is carried by the wheels  24  to move relative to the first panel  12  in a sliding or telescoping relationship. It should be noted that the wheels  23  of the second panel  18  can be replaced with other structure that allow the second panel  18  to glide or extend outward from the first panel  12  without undue friction or resistance (e.g., drawer slides) and is not limited to any particular mode of sliding/rolling/shifting engagement. If the second panel  18  is sized to be approximately the same width as the first panel  12 , when fully extended away from the first panel  12  (in the direction away from the hinged connection on the first panel) the second panel  18  will cooperate with the first panel  12  to completely cover and occlude the door frame  14  in a reliable manner. That is, the first and second panels  12 , 18  have a combined width that when fully extended close the doorway when the door  10  is closed by virtue of the full extension of the second panel  18  along and within the horizontal grooves or slots  22 , 24  of the first panel  12 . 
     To extend and retract the second panel  18  from the first panel  12  as discussed above, the second panel  18  is connected along an upper edge  26  to the door frame  14  by a linkage such as a rigid bar  28 . The bar  28  is fixed at a first end  30  to the second panel  18  at an inner edge  32  that is closest to the piano hinge  16 , and is fixed at a second end  34  in a pivoting connection to the door frame approximately at approximately one quarter of the distance between the sides of the door frame, closest to the side  36  with the hinge that connects the first panel  12  (See  FIG. 2 ). 
       FIG. 2  shows a sequence of the two panels  12 , 18  as the door  10  transitions from fully closed in  FIG. 2 a    to fully open in  FIG. 2 e   . In the first frame ( FIG. 2A ), the telescoping door  10  is fully closed and lies in the plane of the doorway. The depth (or thickness) of the door  10  is a single panel for the entire door&#39;s length except for where the two panels are joined together, creating space on both sides of the door itself. In the second frame ( FIG. 2B ), the door  10  is slightly ajar as it begins to open. 
     One can see that the first panel  12  is hinged to the door frame  14  and moves in a predictable arc about the hinged connection. However, the second panel  18  is prevented from following the same arc due to the fixed connection of the inner edge  32  with the door frame via the linkage  28 . As a result, the second panel  18  is retracted or constrained along the first panel  12  within the horizontal grooves or slots  22 , 24 , and the door “shortens” in length as a result. 
     In the third frame ( FIG. 2C ), the door  10  is approximately half way open and the second panel  18  is further withdrawn or retracted into the first panel as the door continues to shorten. The fixed connection of the linkage  28  at the second panel  18  pulls the second panel along the first panel  12  such that the combined width (negating overlap) of the first and second panels is effectively halved. 
     In the fourth frame ( FIG. 2D ), the first panel  12  is opened more than half way, and the second panel  18  has almost completely moved in alignment with the first panel such that the door&#39;s width is significantly reduced. Finally, in the last frame, the linkage  28  has retracted the second panel  18  into complete alignment with the first panel  12  such that there is essentially no overlap between the two panels  12 , 18 . The width of the door  10  now coincides with the width of the first panel  12  as the second panel  18  is hidden behind the first panel. When used as a lavatory door, for example, the telescoping door of the present invention when closed extends only approximately half way into the lavatory as compared with a traditional door, yielding greater mobility and comfort to the occupant without any loss of function. 
       FIG. 3  illustrates the first and second panels  12 , 18  in the closed (extended) position. The horizontal slot  22  in the first panel is shown, and the wheel  23  or other engagement mechanism is shown in shadow that couple the two panels  12 , 18  together. A pivoting extension  50 , such as a coat hook, can be positioned just adjacent the edge of the second panel. When the extension  50  is seated inside the first panel  12 , the second panel  18  is free to slide back and forth as shown in  FIG. 2  as the door transitions from opened to closed. However, with the extension pivoted out of the plane of the first panel  12 , the second panel  18  is blocked from sliding across the surface of the first panel  12  by the interference of the extension  50 . Thus, a reliable and efficient locking mechanism can be formed using a dual purpose coat hook  50  or the like. 
       FIG. 4  illustrates the linkage  28  between the second panel  18  and the door frame  14 . The linkage  28  connects the second panel  18  at a top edge  26  with a pin or other mechanical arrangement that allows for rotation of the linkage  28  about the connection so that the linkage can track the second panel  18  as it rotates around the primary hinge  16 . The bar, rod, or other structure that forms the linkage  28  is connected to the door frame  14  or an immediate adjacent location by a similar pivoting coupling that allows for the linkage  28  to swivel at the fixed location. As the door  10  opens, the linkage  28  limits the travel of the second panel  18  from the fixed connection point of the bar, thereby causing the second panel  18  to slide along the horizontal grooves  22 ,  24  from an extended position to a retracted position as the first panel  12  swings in an arc away from the fixed connection point. In this manner, the length of the door  10  automatically shortens to (roughly) half of its extended length in the open position. 
     The horizontal grooves or slots  22 ,  24  on the first panel  12  establish tracks or raceways that permit a smooth rolling or sliding motion across their surfaces, so that the second panel  18  can move easily and freely along the first panel. This is particularly important where there is only one linkage  28  maneuvering the second panel  18  at the top  26  of the door  10 , because friction or sticking of the track will cause issues with torquing or twisting of the panels with a resultant loss of effectiveness. 
     The result is a two panel door for an aircraft compartment that has a first panel hingedly connected to a door frame, the first panel having a width of approximately half of a door frame to which it is mounted, and a second panel mounted on the first panel for sliding translation thereon, the second panel extending parallel to the first panel in a sliding arrangement. The first panel is coupled to the door frame via a hinge and the second panel is coupled to the door frame via a linkage, the linkage fixing a distance that the second panel can extend from the door frame as the first panel swings about its hinged connection is a circular arc. The two panel door operates such that the ends of the panels  60 , 32  are adjacent in the closed configuration and the faces  62 , 64  of the panels  12 ,  18  are adjacent to each other in the open configuration. 
     It will be apparent from the foregoing that while particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.