Abstract:
An aircraft seat has an adjustable armrest in which the armrest platform is supported by a hinged attachment to an armrest support member. The hinged attachment between the armrest platform and the arm support member is located at the wrist-end of the arm support member near the aircraft control stick. The armrest platform and the armrest support are locked into position by means of telescoping struts that are controlled at the wrist-end of the arm platform member. The telescoping struts can be selectively locked to create triangular and/or quadrilateral trusses that lock the armrest firmly into position and may include springs or other elements to bias the armrest platform up and forward so that the armrest “floats” when the telescoping struts re released.

Description:
BACKGROUND OF THE INVENTION 
     Modern aircraft with side stick controllers typically require that the pilot seating include an armrest that is adjustable to accommodate multiple operators to position their arm to safely and comfortably operate the side stick controller. Once in this position, the armrest must then be securely locked in its new location. Prior art pilot seating has conventionally included an adjustable armrest that is pivoted near the occupant&#39;s elbow. The pivot is then movable vertically along the axis of the seat back. This type of armrest is cumbersome to use because must first be adjusted vertically to accommodate the occupant&#39;s elbow height, then the angle adjusted so that the occupant&#39;s hand is located at the appropriate position relative to the side stick controller. Additionally, because the locking mechanisms must be robust, in order to resist in-flight acceleration, landing and crash loads, prior art aircraft seating often have locks that permit only relatively coarse adjustment (e.g., ratchets) or are unnecessarily slow and cumbersome to use (e.g., screw or worm drives). 
     Because the ultimate purpose of the armrest is to position the pilot&#39;s hand appropriately relative to the fixed side stick controller, what is needed is a pilot seat having an adjustable armrest that is not constrained to tilt about a pivot fixed at the pilot&#39;s elbow, but which freely floats (e.g., can be tilted about an axis through the pilot&#39;s wrist or any other location) and can be smoothly and effortlessly locked into position. 
     SUMMARY OF THE INVENTION 
     The present invention comprises an aircraft seat with an adjustable armrest. According to an illustrative embodiment, the armrest platform is supported by a hinged attachment to an armrest support member. The armrest support member, rather than the armrest platform is hinged to the seat frame near the seat back. The hinged attachment between the armrest platform and the arm support member is located at the wrist-end of the arm support member near the aircraft control stick. This arrangement enables a user to raise and lower, then tilt the armrest from a position near the side stick controller rather than tilting from a pivot near the seat back. The armrest platform and the armrest support are locked into position by means of telescoping struts that are controlled at the wrist-end of the arm platform member. The telescoping struts can be selectively locked to create triangular and/or quadrilateral trusses that lock the armrest firmly into position and may include springs or other elements to bias the armrest platform up and forward so that the armrest “floats” when the telescoping struts re released. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawing figures in which like references designate like elements and, in which: 
         FIG. 1  is a rear perspective view of a prior art aircraft pilot seat; 
         FIG. 2  is a rear perspective view of an aircraft seat with adjustable armrest in accordance with features of the present invention; 
         FIG. 3  is a schematic view of the adjustable armrest of  FIG. 1  in its fully lowered and tilted back position; 
         FIG. 4  is a schematic view of the adjustable armrest of  FIG. 1  in its fully raised and tilted forward position; and 
         FIG. 5  is a cross-sectional view of a locking mechanism to lock the telescoping struts shown in its locked position; 
         FIG. 6  is a cross-sectional view of a locking mechanism to lock the telescoping struts shown in its unlocked position; 
         FIG. 7  is an exploded view of the locking mechanism of  FIG. 5 ; and 
         FIG. 8  is a perspective view of a barrel nut used in the locking mechanism of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     The drawing figures are intended to illustrate the general manner of construction and are not necessarily to scale. In the detailed description and in the drawing figures, specific illustrative examples are shown and herein described in detail. It should be understood, however, that the drawing figures and detailed description are not intended to limit the invention to the particular form disclosed, but are merely illustrative and intended to teach one of ordinary skill how to make and/or use the invention claimed herein and for setting forth the best mode for carrying out the invention. 
     With reference to the figures and in particular,  FIG. 1 , conventional aircraft pilot seating such as prior art seat  10  are often equipped with adjustable armrests such as armrest  12 . Typically adjustable armrest  12  is adjusted first by releasing lever  14  which enables the pivot  16  to be moved vertically relative to seat back  18  of seat  10 . This adjustment positions the pivot  16  at a comfortable elevation relative to the pilot&#39;s elbow, but may not position armrest  12  so that the pilot&#39;s hand is in the proper location for a side stick controller. Accordingly, a second adjustment such as thumbwheel  20  must be provided to enable the tilt angle of armrest  12  to be adjusted. The tilt angle must be self-locking. Accordingly, thumbwheel  20  is often a screw drive mechanism that is slow and cumbersome to operate. Additionally, since pivot  16  is not located exactly at the pilot&#39;s elbow, adjustment of the armrest may be a sequential process in which the armrest is iteratively tilted, then raised or lowered and tilted again in order to achieve the proper location. 
     With reference to  FIGS. 2-8  and in particular  FIGS. 2-4 , an aircraft seat  30  having an adjustable armrest  28  incorporating features of the present invention comprises a seat frame  32  having a seat back portion  34  and a seat pan portion  36 . An arm support member  38  is attached by means of a hinge  40  to seat frame  32  proximal seat back  34 . An arm platform member  42  is attached by means of a hinge  46  to the free end  44  of arm support member  38 . An armrest pad  48  is secured (e.g., with screws) to arm platform member  42 . Armrest pad  48  extends from wrist-end  50 , which is proximal the side stick controller of the aircraft (not shown) to elbow end  52 , which is proximal seat back portion  34 . Arm support member  38  and arm platform member  42  are preferable made of a lightweight aluminum or titanium alloy but may be constructed of any suitably rigid lightweight material including composites. 
     With particular reference to  FIGS. 3 ,  4  and  7 , vertical adjustment of arm platform member  42  is achieved by rotating arm support member  38  about hinge  40 , thus raising or lowering arm platform member  42 . Arm support member  38  can be selectively locked into position by means of a telescoping strut  54  which is attached by a hinge  56  to seat frame  32 . The free end  58  of telescoping strut  54  telescopes through a locking mechanism  60  described more fully hereinafter. Telescoping strut  54 , arm support member  38 , arm platform member  42  and seat frame  32  form a quadrilateral linkage, and in particular a trapezoidal linkage which, due to the unequal lengths of the linkage arms, forms a rigid truss when telescoping strut  54  is prevented from telescoping through locking mechanism  60 . For example, in the illustrative embodiment, the effective length of arm support member  38  is 7½ to 11½ inches, preferably about 9½ inches, the effective length of arm platform member  42  is 1 to 3 inches, preferably about 2 inches, the effective length of seat frame  32  is 2 to 6 inches, preferably about 4 inches (but is not the same length as the effective length of arm platform member  42  so as to ensure the linkage cannot form a parallelogram) and the effective length of telescoping strut  54  varies from about 7½ to about 13½ inches, and preferably varies from about 9½ to 11½ inches depending on the relative positions of arm support member  38  and arm platform member  42 . As used herein “effective length” means the distance between the attachment points of the frame member in question. For example the effective length of arm support member  38  is the distance from hinge  40  to hinge  46 , the effective length of seat frame  32  is the distance from hinge  40  to hinge  56 , and the effective length of telescoping strut  54  is the distance from hinge  56  to locking mechanism  60 . 
     The tilting of arm platform member  42  is achieved by rotating arm platform member  42  about hinge  46 . Arm platform member  42  can be selectively locked in place about hinge  46  by means of a second telescoping strut  62  which is attached to arm support member  38  by means of a hinge  64 . The free end  66  of telescoping strut  62  telescopes through locking mechanism  60  in a manner more fully described hereinafter. Telescoping strut  62 , arm support member  38  and arm platform member  42  form a triangular linkage which becomes a triangular truss that prevents arm platform member from rotating when telescoping strut  62  is prevented from telescoping through locking mechanism  60 . For example, in the illustrative embodiment, the effective length of arm support member  38  is 7½ to 11½ inches, preferably about 9½ inches, the effective length of arm platform member  42  is 1 to 3 inches preferably about 2 inches, and the effective length of telescoping strut  62  varies from 4 to 9 inches and preferably varies from about 6 to 7¼ inches. 
     In the illustrative embodiment, locking mechanism  60  comprises a pillow block  70  that is secured (e.g., by threaded fasteners) to arm platform member  42 . Pillow block  70  includes a longitudinal cylindrical bore  72  adapted to receive a pair of pilot sleeves  74 ,  76  and two transverse bores  92 . Each of the pilot sleeves  74 ,  76  has a cylindrical bore adapted to receive a barrel nut  78 ,  80 . As shown in  FIG. 8 , barrel nut  78  is cross-drilled and threaded with threads  84  matched to threads  86  formed at the end of telescoping strut  62 . A smooth-walled relief  88  is then formed in barrel nut  78  which enables barrel nut  78  to slide smoothly over threads  86  of telescoping strut  62  as long as barrel nut  78  is biased so relief  88  rather than threads  84  engage the threads  86  of telescoping strut  62 . 
     The locking mechanism for telescoping strut  62  is assembled by inserting pilot sleeve  74  into pillow block  70  then inserting barrel nut  78  into pilot sleeve  74  so that relief  88  is lined up with aperture  90  formed in pilot sleeve  74 . Telescoping strut  62  is then passed through the corresponding transverse bores  92  formed in pillow block  70 , aperture  90  formed in pilot sleeve  74  and barrel nut  78 . Aperture  90  in pilot sleeve  74  is sized to approximately the major diameter of threads  86  of telescoping strut  62  so that telescoping strut  62  can slide smoothly through pilot sleeve  74 . Transverse bore  92  in pillow block  70  is elongated to accommodate the change in angular relationship between telescoping strut  62  and pillow block  70  as armrest  28  is raised, lowered and tilted as described herein. 
     Once assembled, locking mechanism  60  can be moved from an unlocked position into a locked position. In the unlocked position, the smooth wall of relief  88  of barrel nut  78  bears against threads  86  of telescoping strut  62  which permits telescoping strut  62  to move smoothly through pillow block  70 . In the locked position, barrel nut  78  is pressed against telescoping strut  62  so that threads  84  of barrel nut  78  engage threads  86  of telescoping strut  62 , which is then pinched between barrel nut  78  and pilot sleeve  74  thus locking telescoping strut  62  firmly into position. The operation of barrel nut  80  and pilot sleeve  76  with respect to telescoping strut  54  is identical and therefore will not be explained in detail. Springs (not shown) co-axial with telescoping struts  54  and  62  that bear against pillow block  70  may be incorporated to bias the armrest  28  upward and tilted back so that armrest  28  “floats” when locking mechanism  60  is released, thus enabling armrest  28  to be adjusted in a single operation by pushing armrest  28  into the desired position and engaging locking mechanism  60 . In the illustrative embodiment, the use of standard thread forms to fabricate threads  84  of barrel nut  78  and threads  86  of telescoping strut  62 , enables production of a very robust locking mechanism, while permitting very precise adjustments at relatively low cost as compared with conventional prior art ratchet and screw drive mechanisms. 
     In the illustrative embodiment, barrel nuts  78  and  80  are urged into their locked position by means of a threaded a locking plunger  94 . A spring, rubber pad or other resilient means may optionally be included to urge the barrel nuts into their released positions when locking plunger  94  is withdrawn. 
     Although certain illustrative embodiments and methods have been disclosed herein, it will be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods may be made without departing from the invention. For example, although in the illustrative embodiment, the telescoping struts telescope by passing through a locking mechanism located at the wrist end of the arm support member, the telescoping struts could pass through locks located at the seat back end of the arm support member or could comprise true telescoping struts that lock at a location intermediate the ends of the struts. Additionally, although the illustrative embodiment employs standard thread forms, nonstandard thread forms and/or non-helical teeth could be substituted without departing from the scope of the invention. Accordingly, it is intended that the invention should be limited only to the extent required by the appended claims and the rules and principles of applicable law. Additionally, as used herein, unless otherwise specifically defined, the terms “substantially,” “about,” or “generally” when used with mathematical concepts or measurements mean within ±10 degrees of angle or within 10 percent of the measurement, whichever is greater.