Abstract:
A seat, particularly for aircraft, has a backrest with a high pivot. Such a backrest permits a range of supported semi-reclining seating positions without inconveniencing an occupant of the next rearward seat row. The seat also permits selection of seat pan length to suit the height of the occupant.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority, under 35 U.S.C. §119, of United Kingdom Patent Application No. 0809952.5, filed May 30, 2008, which designated the U.S. and was published in English, the entire disclosure of which is hereby incorporated herein by reference in its entirety. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    n/a 
       FIELD OF THE INVENTION 
       [0003]    This invention relates to a pivoting backrest of a seat, and is particularly, though not exclusively, intended for use in passenger vehicles such as aircraft. 
       BACKGROUND OF THE INVENTION 
       [0004]    Prolonged sitting without substantial change of position is bad practice, and may result in stiffness and pain. Especially in the case of aircraft, such prolonged sitting has been identified as a cause of blood clots in the lower leg, which can in turn have serious medical consequences. Passengers are encouraged to move limbs, and adopt different positions, but this is rather difficult where seating is cramped, such as in economy class. More generously proportioned seating leads to an increase in ticket price and may in fact be revisited by those passengers seeking low cost travel. 
         [0005]    U.S. Pat. No. 5,058,954 describes a reclining seat/backrest which in the reclined condition offers little support against the occupant sliding down the inclined surface. Furthermore the backrest moves rearwardly, and may encroach unacceptably on the occupant of the next rearward seat. In theory, however, this seat configuration allows an occupant to straighten the legs. 
         [0006]    U.S. Pat. No. 5,536,067 describes a chair with a split seat pan, which may give better clearance for the upper thighs, yet retain sufficient support for the buttocks. 
         [0007]    U.S. Pat. No. 5,722,726 discloses a multi-component aircraft seat intended to permit the occupant to adopt a semi-reclined position. 
         [0008]    U.S. Pat. No. 6,659,552 proposes an inflatable seat portion which supports the lumbar region in an aircraft seat, and allows the occupant to straighten the legs. 
         [0009]    U.S. Pat. No. 7,195,316 is a mechanical substitute similar to U.S. Pat. No. 6,659,552, and in which the seat back and seat pan move together to a reclined position without encroaching on the next rearward occupant. In order to allow leg space for the occupant, the seat pan is divided and the front portion hinges down. Thus this seat has a sloping backrest and short seat pan in the reclined condition, which permits an occupant to straighten the legs. 
         [0010]    The latter proposal is mechanically complex, and has numerous movable components and pivots. There is also a risk of broken or damaged parts, for example the split seat pan may be uncomfortable in the normal position. 
         [0011]    What is required is a lightweight and simple seat construction suitable for close seat pitch, and which permits an occupant to comfortably adopt different postures. 
       SUMMARY OF THE INVENTION 
       [0012]    According to the invention there is provided a seat comprising a mounting, a seat pan on the mounting, a frame on the mounting, a backrest pivoted on the frame about a high transverse axis with respect to the seat pan, and a latch to restrain said backrest at a desired angular position relative to said frame. 
         [0013]    In practice many occupants of economy seating tend to adopt a position in which the buttocks are forward on the seat pan, in order to try and straighten the legs; sometimes this forward positioning is inadvertent. The present invention allows the back to be supported in such a position, which is more comfortable for the occupant and has less risk of causing pain. 
         [0014]    The mounting is provided for fixing the seat to a substrate, and the frame supports the backrest. The frame may be fixed with respect to the mounting, or may be relatively movable—for example as part of a seat reclining mechanism. 
         [0015]    In one embodiment the seat pan is fixed; in such a seat, a moving backrest with a single pivot axis may suffice. The occupant selects a desired rake and latches the backrest to the seat frame. The rake may be changed on demand, and may provide a range of seat configurations from full sitting to semi-reclining. 
         [0016]    In another embodiment the seat pan is movable in a generally fore and aft direction for example on a latchable sliding mechanism. In such a configuration, the seat pan slides independently of the backrest. 
         [0017]    In this configuration, the seat pan length can be selected to give the degree of buttock support which the occupant desires. 
         [0018]    In another configuration a reclining seat is provided with a high pivot backrest according to the invention. In this configuration, the backrest maybe moved forward in the reclined position of the seat to give a shorter seat pan length with greater reclining angle. 
         [0019]    Preferably, the transverse axis is above mid-height of the backrest, and most preferably. above three-quarter height. A head rest may be provided on the seat back, or made integral therewith. For the purposes of this specification, a seat back terminates at average passenger shoulder height. 
         [0020]    When latched close to the forward end of a seat pan, for example with 20% or less of the seat pan exposed, the seat permits semi-reclining of the occupant with the buttocks supported on the ledge provided by the exposed seat pan portion. In this position the occupant&#39;s back is supported and the occupant&#39;s legs are substantially straight, thus avoiding prolonged bending of the body at the pelvis which may give rise to lower back pain. 
         [0021]    It will be understood that a seat according to the invention is relatively inexpensive compared with prior art proposals, and it can be mechanically simple. The high pivot seat allows a close seat pitch, as required in economy seating, and does not encroach upon the next rearwards row. 
         [0022]    A further advantage of the invention is that the seat back may be adjusted for normal sitting with several different lengths of seat pan; thus the seat permits comfortable accommodation of both short and tall passengers. 
         [0023]    Although the invention is illustrated and described herein as embodied in a seat with pivoting backrest, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0024]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    Other features of the invention will be apparent from the following description of a preferred embodiment shown by way of example in the accompanying drawings in which: 
           [0026]      FIG. 1  is a diagrammatic illustration from the side of a conventional aircraft seat; 
           [0027]      FIG. 2  is a diagrammatic illustration of the seat of  FIG. 1  with a person shown in a typical slumped seating position; 
           [0028]      FIG. 3  is a diagrammatic illustration from the side of a seat according to the invention in a reclined configuration; 
           [0029]      FIG. 4  is a diagrammatic illustration of the seat of  FIG. 3  with the seat in a long seat pan configuration; 
           [0030]      FIG. 5  is a diagrammatic illustration of the seat of  FIG. 3  with the seat in a short seat pan configuration; 
           [0031]      FIG. 6  is a diagrammatic illustration of the seat of  FIG. 3  with a movable seat pan; and 
           [0032]      FIG. 7  is a diagrammatic illustration of the seat of  FIG. 3  retrofitted on a reclining seat. 
       
    
    
       [0033]    Aspects of the invention are disclosed in the following description and related drawings directed to specific embodiments of the invention. Alternate embodiments may be devised without departing from the spirit or the scope of the invention. Additionally, well-known elements of exemplary embodiments of the invention will not be described in detail or will be omitted so as not to obscure the relevant details of the invention. 
         [0034]    Before the present invention is disclosed and described, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. 
         [0035]    While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figures, in which like reference numerals are carried forward. The figures of the drawings are not drawn to scale. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    With reference to  FIG. 1 , a conventional aircraft seat  10  comprises a seat pan  11  and a backrest  12 . Not shown in  FIG. 1  is the usual seat frame, leg(s), armrests and headrest. The seat frame supports the seat pan and backrest; typically in an economy seat, the seat pan is fixed, and the backrest is pivoted at the lower end to allow a limited amount of reclining (as shown in dotted outline  13 ). 
         [0037]    As illustrated in  FIG. 1 , the backrest provides support for the occupant&#39;s back, and the seat pan provides support for the thighs. Necessarily, the length of seat pan (fore and aft) is a compromise and may not be comfortable for very short or very tall occupants. 
         [0038]      FIG. 2  illustrates in somewhat exaggerated form a common posture adopted by an occupant during a long haul flight in an economy seat. The buttock region moves toward the front end of the seat pan in order that the occupant can straighten the legs  14 , but as a consequence much of the occupant&#39;s back and spine region  15  is unsupported and thus may result in lower back pain. 
         [0039]    The invention is illustrated in  FIG. 3 . A backrest  22  is pivoted on a seat frame at the high end; as illustrated a pivot axis  24  is at the very top of the backrest  22 , but it need not be. The seat pan  21  can be attached to the seat frame, and may be movable as further described below. 
         [0040]    For take-off and landing, and if desired by the occupant, the backrest is fixed in a conventional upright position, as illustrated in dotted outline  24 . 
         [0041]    However, when permitted, the occupant may pull the lower end of the backrest  22  forward so as to permit full straightening of the legs  14  whilst ensuring that the back and spine region  15  is fully supported. The occupant&#39;s buttocks are supported by a short protruding portion of the seat pan  21 , typically 25% or less of the overall fore and aft length. 
         [0042]    Any suitable measures for latching the backrest  22  can be used, for example spring loaded plungers on either side of the backrest  22  may engage in non-illustrated rails having plunger receiving apertures at suitable spacings. The occupant merely moves to the front of the seat pan  21 , and eases the backrest  22  forward. A motorized motion is relatively simple to configure because a single moving seat part is provided—for example a screw jack in either armrest may be sufficient. 
         [0043]      FIGS. 4 and 5  illustrate how the adjustable backrest allows a comfortable length of seat pan  26  for both tall ( FIG. 4 ) and short ( FIG. 5 ) occupants. 
         [0044]      FIG. 6  illustrates a movable seat pan variant in which a seat pan  31  is slidable fore and aft. The seat pan  31  is moved by the occupant, and is latchable at a desired fore and aft position. A backrest  34  is independently latchable so as to give a range of seating positions. This configuration allows a sloping backrest with a full length seat pan, at the expenses of reduced leg room. 
         [0045]      FIGS. 7   a  to  7   d  illustrate the affect of the invention applied to a reclining seat of the kind usually provided for business class travelers. 
         [0046]      FIG. 7   a  shows a reclining seat  41  in the upright condition, and  FIG. 7   b  illustrates a high pivot backrest  42  in rear and forward conditions. 
         [0047]      FIG. 7   c  shows the seat  41  in the reclined condition, and  FIG. 7   d  shows the affect of pivoting the high pivot backrest  42  to give a shorter seat pan  43  with additional reclining of the backrest  42 . It will be understood that, in this embodiment, the reclining mechanism of the seat  41  incorporates the pivot frame of the backrest. 
         [0048]    As is clear from the drawings, variation of backrest angle does not substantially reduce the space available for the next rearward passenger. 
         [0049]    Although the invention has been described in relation to aircraft seats, it will be understood that it is applicable to transportation seating generally, and may also be suitable for buses, trains and the like. 
         [0050]    The foregoing description and accompanying drawings illustrate the principles, preferred embodiments and modes of operation of the invention. More specifically, the seat with pivoting backrest according to the present invention has been described. However, the invention should not be construed as being limited to the particular embodiments discussed above. Additional variations of the embodiments discussed above will be appreciated by those skilled in the art as well as for applications, unrelated to inventory, that require encrypted identification of parts. 
         [0051]    The above-described embodiments should be regarded as illustrative rather than restrictive. Accordingly, it should be appreciated that variations to those embodiments can be made by those skilled in the art without departing from the scope of the invention as defined by the following claims.