Abstract:
A hinge assembly for attaching a door structure to an aircraft fuselage is provided. The door structure is linked to the aircraft body structure by way of a programmable mechanical linkage that is attached to the hinge member. The programmable mechanical linkage is actuated along the hinge member so as to maintain the door structure attached thereto in a controlled angular relationship relative to the longitudinal axis of the aircraft fuselage through its attachment to the fixed aircraft frame.

Description:
BACKGROUND 
   1. Field of the Invention 
   This invention relates generally to aircraft door assemblies and, more particularly, to a hinge mechanism for connecting an aircraft door to a fuselage. 
   2. Related Art 
   An important part of any door assembly is the hinge assembly that connects the door to the adjacent aircraft fuselage structure. One particular type of hinge assembly is arranged so that, when the door is opened, the door physically separates from the surrounding structure and is translated out and away from the body while the door itself maintains a relatively parallel orientation to the longitudinal axis of the aircraft fuselage. The hinge also translates the door forward to provide a clear opening into the aircraft as the door swings away from the body. When the door is completely open, the inside face of the door is adjacent the outer skin of the aircraft. 
   Many hinge assemblies used with translating-motion-type aircraft doors include both a structural hinge for securing the door to the aircraft and a mechanical linkage that provides a second door-to-fuselage connection. The mechanical linkage is employed to control the rotational orientation of the door along its vertical axis so that, as the door is moved away from the fuselage, the door remains generally parallel to the outer skin of the aircraft. If the movement of the door was not controlled, the door would swing free at the end of the hinge and be difficult to maneuver and/or strike the outer skin of the fuselage. 
   What is needed is a mechanism configured to use a small number of fittings and links to provide a more rigid linkage with less overall stretching or flex than existing systems. 
   SUMMARY 
   The invention provides a hinge assembly for connecting an aircraft door to a fuselage. The hinge assembly of this invention includes a horizontally oriented programmable mechanism with linkage rods and pivot fittings that functions as the interface between the aircraft door structure and the aircraft fuselage, and that physically connects the aircraft door structure to the aircraft fuselage. 
   In one aspect of the invention, three linkage rods and two pivot fittings are employed to create a programmable mechanical linkage between the rigid aircraft structure and the moving door structure. As the door structure is opened, one end of the hinge assembly pivots toward the doorway frame while the other end pushes the door structure away from the aircraft body. This motion drives the programmable mechanical linkage through its actuation path and thereby drives the door position as the hinge swings open. 
   A pivot fitting positioned closest to the door structure attachment pin provides an interface point for the Emergency Power Actuation System (EPAS)/Snubber cylinder. The inclusion of the EPAS/snubber system in this manner should allow for simplification and possibly reduced costs of the EPAS components. The invention incorporates a concept where the EPAS cylinder and the door snubber are combined into one component serving both purposes. 
   The hinge assembly of the present invention provides the necessary motion control for the door structure through the opening motion. At all times, it controls the relative orientation of the door structure to the aircraft body, and rigidly constrains the door while in the fully open position. The mechanism provides for a smooth translating motion through the use of length-adjustable links, pins, and pivot fittings. 
   The mechanism of the present invention reduces or eliminates problems typically associated with chain systems, such as tensioning, lubrication and corrosion. 
   Advantageously, the present invention includes relatively simple components, such as simple and common rods, pins, small machined fittings, bushings, and bearings. Thus, the need for complex machining or manufacturing practices is reduced or eliminated. 
   The present invention provides a lighter design, fewer components, reduced component costs, reduced rigging requirements at installation, greater control of door structure(reduced door play throughout motion travel), than chain-type systems. Overall, the mechanism of the present invention is less complex, and easier to fabricate and install than chain-type systems. 
   Additional advantages, objects, and features of the invention will be set forth in part in the detailed description which follows. It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings are included to provide further understanding of the invention, illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention. In the drawings, the same components have the same reference numerals. The illustrated embodiment is intended to illustrate, but not to limit the invention. The drawings include the following Figures: 
       FIG. 1  is a perspective view of a hinge assembly in accordance with an embodiment of the present invention; 
       FIG. 2  is a top view of said hinge assembly of  FIG. 1  in accordance with an embodiment of the present invention; 
       FIGS. 3A-3J  are simplified perspective views of components of the hinge assembly of  FIG. 1  in accordance with an embodiment of the present invention; and 
       FIGS. 4A-4F  are simplified top views illustrating the translation of a door translating using the hinge assembly of  FIG. 1  in accordance with an embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a perspective view of a hinge assembly  100  in accordance with an embodiment of the present invention. Hinge assembly  100  includes components which allow it to perform in its intended manner. Many of these components are common to mechanical systems, such as pins, fasteners, brackets and the like. The following description shall describe selected components and their arrangement and combination needed to understand the invention. 
   Hinge assembly  100 , includes hinge member  102  which provides the structural support member that connects a door structure (not shown) to an aircraft fuselage (not shown). In one embodiment, hinge member  102  includes two primary pivot points: 1) between hinge member  102  and the aircraft fuselage at end  120  and 2) between hinge assembly  100  and the door structure at the end  122 . 
   Hinge member  102  provides the attach points for the remaining components of hinge assembly  100 . For example, mounted to hinge member  102  are door-to-hinge attach fitting  104  (hereinafter, “door fitting  104 ”), pivot fitting-final drive  106  (hereinafter “pivot member  106 ”), pivot fitting-hinge elbow  114  (hereinafter “pivot member  114 ”), EPAS cylinder  108 , pin door-to-hinge  110  (hereinafter “door pin  110 ”),and a programmable mechanical linkage assembly, including a long, adjustable link rod  112  (hereinafter “link rod  112 ”) in the middle, a frame-side link rod  116  (hereinafter “link rod  116 ”), and a door-side link rod  202  (hereinafter “link rod  202 ”). 
   Hinge member  102  provides additional features necessary to the function of the door structure, such as a door hold-open mechanism and attachment points for lining components, and the like. As illustrated in  FIG. 2 , in one embodiment, hinge member  102  provides unique features including: pivot point ‘D’ for pivot member  114 , pivot point ‘E’ for pivot member  106 , attach point ‘L’ for EPAS cylinder  108 . 
   As shown in  FIG. 3A , recessed areas are provided, such as areas  310  and  312 , to allow motion of the mechanism through hinge member  102 . Location of all the attach points on hinge member  102  contribute to the programmability and operation of hinge assembly  100 . The location of pivot point ‘D’, for example, maintains proper clearance between hinge member  102  and the outer aircraft skin when the door is in the full open position. 
   Referring again to  FIG. 1 , door fitting  104  (see also  FIG. 3B ), provides an interface between hinge member  102  and the door structure. 
   As shown in  FIGS. 1 and 2 , hinge assembly  100  also includes pivot member  106 , which provides a pivot to transfer motion from link rod  112  into link rod  202  which drives into door fitting  104 . Additionally, pivot member  106  provides a connection point for EPAS cylinder  108 . (All members described in further detail below). 
   Pivot member  106  (see also  FIG. 3E ) also acts as an attachment point between EPAS cylinder  108  (see also  FIG. 3F ) and programmable mechanical linkage. EPAS cylinder  108  is primarily used in emergency situations to provide force to open the aircraft door. For example, in emergency operation, if the inside door operating handle is actuated and the door structure is lifted beyond specified stops, EPAS cylinder  108  is engaged to drive the door structure completely open very quickly. The force output by EPAS cylinder  108  is driven into pivot member  106  which then provides two motion inputs: 1) through link rod  202  to drive the door position relative to the hinge, and 2) through link rod  112 /pivot member  114 /link rod  116  linkage path back to the aircraft frame to pull the hinge and door assembly to a full open position. 
   In another embodiment, EPAS cylinder  108  can provide damping for the door motion during operations. For example, if the speed of the door opening or closing motions becomes too great, the impact when the door structure contacts the aircraft fuselage (during closing) or when it contacts the frame stop (when opening) could cause damage. For that reason, the EPAS cylinder  108  includes a snubber feature to damp, or restrict the speed of motion to an acceptable level. 
   By varying the geometry of pivot member  114  and pivot member  106 , the mechanical linkage has been tailored to yield a desired motion (i.e. Programmed). Thus, the parameters of pivot member  114  and pivot member  106  contribute considerably to the use and programmability of hinge assembly  100 . 
   As shown in  FIG. 2 , door fitting  104  acts as a connection between the programmable mechanical linkage assembly (described below) of hinge assembly  100  and the door structure. Generally, the translational motion transmitted through the programmable mechanical linkage is converted into rotational motion of the door structure via door fitting  104  as it pivots about the axis of door pin  110  which connects door fitting  104  to hinge member  102 . 
   Hinge assembly  100  also includes three link rods as part of the programmable mechanical linkage. Link rod  116  ( FIG. 3I ) connects between the attach fitting-hinge to body  118   b  (hereinafter, “body fitting  118   b  ”) and pivot member  114 . Link rod  112  ( FIG. 3G ) connects between pivot member  114  and pivot member  106 . Link rod  202  ( FIG. 3H ) connects between pivot member  106  and door fitting  104 . 
   A feature to vary the length of link rod  112  provides the programmable mechanical linkage a method for accommodating manufacturing tolerances of hinge assembly  100 , and its individual component parts, during the rigging of the door structure and hinge assembly  100  into the aircraft. 
   Again referring to  FIGS. 1 and 2 , pivot member  114  (see also  FIG. 3D ) acts as a pivot to transfer motion from link rod  116  into link rod  112  ( FIG. 3G ) which provides a direct link to body fitting  118   b  ( FIG. 3J ) which is rigidly attached to the airplane body frame. 
   Many of the links and fittings making up the present invention may have multiple component parts making up each item. For example, the linking rods may have spherical bearings in the end of each rod. The pivot fittings and the hinge member may have bushings pressed in at each joint. 
   In one embodiment, link rods  116 ,  114  and  202  may all be adjustable, and thus may include a tube with an adjustable length rod on each end, which facilitates multiple usages. Adjusting the length of any link rod also contributes to the programmability of the mechanism. 
   Having thus described components of hinge assembly  100 , the location of pivot points between the components of hinge assembly  100 , as shown in the embodiment of  FIG. 2 , are now described. Pivot point ‘A’ is provided between hinge member  102  and body fittings  118   a  and  118   b . Pivot point ‘B’ is provided between hinge member  102  and door fitting  104  as connected by door pin  110 . Pivot point ‘C’ is provided between link rod  116  and body fitting  118   b . Pivot point ‘D’ is between hinge member  102  and pivot member  114 . Pivot point ‘E’ is provided between hinge member  102  and pivot member  106 . Pivot point ‘F’ is provided between link rod  202  and door fitting  104 . Pivot point ‘G’ is provided between link rod  116  and pivot member  114 . Pivot point ‘H’ is provided between pivot member  114  and link rod  112 . Pivot point ‘I’ is provided between link rod  112  and pivot member  106 . Pivot point ‘J’ is provided between pivot member  106  and link rod  202 . Pivot point ‘K’ is provided between EPAS cylinder  108  and pivot member  106 . Pivot point ‘L’ is provided between EPAS cylinder  108  and hinge member  102 . 
   The operation of the door and hinge assemblies is represented in  FIGS. 4A-4E . As shown in  FIG. 4A , door structure  302  (shown dashed for clarity) can be opened by manually rotating a door handle (not shown) to unlock door structure  302 , and manually applying a force to move door structure  302  open. In emergencies, the rotation of the door handle causes EPAS cylinder  108  to create the force that translates door  302  open. EPAS cylinder  108  is activated by a door system that does not form part of the present invention and thus is not described here. As noted above, EPAS cylinder  108  operates only to open door  302  during an emergency situation. 
   Referring now to FIGS.  2  and  4 A- 4 F, when a door structure that is attached to an aircraft fuselage by hinge assembly  100  is opened, hinge member  102  rotates about hinge pivot point ‘A’ and end  122  is translated outward, causing end  122  of hinge member  102  (and the complete door assembly) to be swung away from the aircraft body. The programmable mechanical linkage controls the orientation of the door assembly around pivot point ‘B’ on hinge member  102  as the door is opened and translated away from the body. Thus, when the door is fully opened, the inside of the door structure is adjacent the outer skin of the aircraft while the door has been translated out away from, and forward of, the door opening in the aircraft body. 
   When the door structure is closed, hinge assembly  100  is pulled in the opposite direction. As a result, the door structure is translated in the opposite direction. Thus, when the door structure is moved into the door opening, it is correctly seated. 
   As shown in  FIGS. 4A-4F , when hinge assembly  100  is made to open, door structure  302  initially moves generally away from the aircraft fuselage  400  so that door structure  302  clears the door opening. When hinge assembly  100  rotates about pivot point ‘A’ as door structure  302  moves open, the linkage pivot points ‘D’ and ‘C’ move closer together, which causes the programmable mechanical linkage to actuate. Link rod  116  drives pivot member  114  to rotate about pivot ‘D’. Pivot member  114  then drives link rod  112 , which rotates pivot member  106  about pivot point ‘E’. Pivot member  106  drives link rod  202 , which rotates door structure  302  about pivot point ‘B’ (by rotating door fitting  104  which is rigidly attached to door structure  302 ), which controls the alignment of door structure  302  relative to hinge member  102 . 
   It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.