Abstract:
The present invention is directed toward a seatback assembly that includes a backrest comprising shapeable material and an adjustable support, the backrest being attached to the adjustable support, the adjustable support being adjustable to alter the curvature of the backrest from top to bottom and then fix the backrest in place, thus shaping the backrest.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/848,343, filed Sep. 29, 2006, the disclosure of which is incorporated herein by reference. 
     
     BACKGROUND OF INVENTION 
       [0002]    The present invention generally relates to wheelchairs and, more particularly, to wheelchair seat systems which are adaptable to the anatomical structure of the user and/or adjustable to achieve support-related objectives for a given user. 
         [0003]    In general, wheelchair seat systems include cushions that are constructed from flexible material. However, the flexible material does not provide optimum support or comfort for the user. Foam and air filled seat cushions have been developed to provide improved support for users requiring special support, such as paraplegics or users having spinal deformities or muscular atrophy, but these seat cushions are difficult to adjust to accommodate specific needs and proportions of individual users and do not encourage proper control of body position. Furthermore, users often become oversensitive to pressures against their skin and bodies so that it is desirable to develop a support cushion that exerts low pressures against a user&#39;s body and skin. 
         [0004]    What is needed is a seat system that not only conforms to the shape of the user&#39;s body, but also provides stabilizing forces that allow for postural control. Such a seat system should provide a stable platform to permit improved control of body position and posture. Furthermore, such a seat system must be durable and able to withstand extensive use for extended periods of time. 
       SUMMARY OF INVENTION 
       [0005]    The present invention is directed toward a seatback assembly that includes a backrest comprising shapeable material and an adjustable support, the backrest being attached to the adjustable support, the adjustable support being adjustable to alter the curvature of the backrest from top to bottom and then fix the backrest in place, thus shaping the backrest. 
     
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0006]      FIG. 1  is a partially cutaway front perspective view of a shapeable wheelchair seatback assembly having an exemplary backrest with wings, ribs and slots that promote backrest flexibility and the shapeability of the seatback assembly. 
           [0007]      FIG. 2  is a front elevational view of an alternative backrest generally having webs instead of slots. 
           [0008]      FIG. 3  is a rear elevational view of the alternative backrest shown in  FIG. 2 . 
           [0009]      FIG. 4  is an enlarged perspective view of a coupling for attaching a seatback assembly to a rigid support. 
           [0010]      FIG. 5  is a side elevational view of an adjustable support for shaping the backrest. 
           [0011]      FIGS. 6-9  are diagrammatic representations of the seatback assembly in alternative positions. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring now to the drawings, there is a perspective view in  FIG. 1  of a seatback assembly, generally indicated at  10 , having a backrest  12 , an adjustable support  14  and a coupling  16  for attaching the seatback assembly  10  to a rigid support  18 . 
         [0013]    An example of a backrest  12  is described in U.S. Pat. No. 7,032,971, the disclosure of which is hereby incorporated by reference into this specification. The backrest  12  may be of molded plastics, such as nylon, and may have the general shape of a shield bowed in a forward direction (when viewed in vertical section) and may have side wings  20  curving further in a forward direction. There may be two closed end slots  22  extending vertically and symmetrically, one proximate each side of a vertical center line and stopping short of the top and bottom edges of the backrest  12 . There could be thin webs or membranes or other suitable structure, instead of the slots  22 , making narrow zones of weakness, but for ease of manufacture slots may be preferred. 
         [0014]    Reinforcing ribs  24  may extend horizontally across the backrest  12  spanning the slots  22 , and in doing so, may form bridges  26 . The reinforcing ribs  24  may be integrally molded with the backrest  12 . The reinforcing ribs  24  shown start about one-third of the way up the backrest  12 , although another starting point may be suitable for carrying out the invention. Towards the bottom of the backrest  12 , the reinforcing ribs  24  may be clustered closer together than towards the top, although such clustering may be an optional characteristic. Outside the slots  22  in the wings  20  of the backrest  12 , horizontal slots  28  may alternate with the ribs  24 . 
         [0015]    Beyond the upper ends of the slots  22 , there may be more slots, such as the upper slots  30  shown. These slots  30  may extend down from the upper edge of the backrest  12 , and may include, for example, two outer slots and one central slot, which is slightly longer than two outer slots, and which may be just inward of the slots  22 . 
         [0016]    On the rear face of the backrest  12 , in the central zone  32  of the backrest  12  between the slots  22 , there may be fixing points, such as the four fixing points  34  shown, where the backrest  10  may be attached to the adjustable support  14 . The arrangement of the fixing points  34  may be symmetrical with respect to a vertical center line of the backrest  12 , with one pair near the top of a central zone  32  of the backrest and another pair near the bottom of the central zone  32 . The fixing points  34  of each pair may be quite close together so that the backrest  12  can be secured to the adjustable support  14  at a narrow interface with the backrest  12 , whereby the adjustable support  14  may be a narrow supporting spine or frame supported from the rear of the seat assembly  10 . While these fixing points  34  may be fixed, the rest of the backrest  12  can move slightly under the constraints imposed by the stiffness of the backrest material and the ribs  24  and the amount of freedom allowed by the slots  22 . But, in particular, there is a capacity to “ripple” or alter the curvature of the backrest  10  from top to bottom or vice versa by adjusting the adjustable support  14 , as will become more apparent in the description that follows, and fix the backrest  10  in place, thus shaping the backrest  12  and the seatback assembly  10 . 
         [0017]    An alternative backrest  12 ′ is illustrated in perspective views shown in  FIGS. 2 and 3 , with similar parts similarly referenced. Much of the difference lies in having webs  36  and  44  instead of the slots  28  and  30  and in adding webs  38  and  42  and scored lines  40 . For example, horizontal webs or elongate membranes  36  may alternate with the ribs  24 . The webs  36  may be created by thinning and/or corrugating material on both sides of the backrest  12 ′. Webs  38  may also be provided in a central zone  32  of the backrest  12 ′ between the slots  22 . These webs  38  may be created by the provision of horizontal grooves in the front side of the backrest  12 ′. The webs  38  may be discontinuous, and may further be aligned with some of the webs  36  between the ribs  24 . Between the webs  38 , over part of the central zone  32 , lines  40  may be scored parallel to the webs  38  in the backrest  12 ′, whereby the lines  40  may give a bit of extra flexibility. 
         [0018]    Beyond the upper ends of the slots  22 , there may be another intermittent web  42 , which may be visible on both sides of the backrest  12 ′, and above the intermittent web  42 , there may be more webs or elongate corrugated membranes  44  extending down from the upper edge of the backrest  12 ′, for example, one central and slightly longer than the two others, which may be just inward of the slots  22 . 
         [0019]    Although it is not necessary for practicing the invention, the former backrest  12  may give greater flexibility to the lower part of the central zone  32 , with the upper part remaining relatively stiff, as compared to the latter backrest  12 ′. While the lower part may ripple quite easily, the upper part may have more limited capacity to deform. To maintain these different characteristics between the upper and lower parts, the material of the upper part could be thicker than that of the lower part, or, as shown in  FIG. 3 , at least some of the ribs  24  spanning the upper part may be joined by further vertical ribs  46 , which may be substantially symmetrical with respect to the vertical center line of the backrest  12 ′. The vertical ribs  46  shown extend between the two uppermost reinforcing ribs  24  and incorporate the upper fixing points  34 , which may also be incorporated in a short transverse rib. This may reinforce the backrest  12 ′ in the upper zone of attachment. There may be similar reinforcement in the lower zone. Such vertical ribs  46  may have a very short vertical extent and thus should not affect the ability of the backrest  12 ′ to ripple above the second lowermost reinforcing rib  24 . 
         [0020]    It will be understood that the number, size and distribution of ribs  24 , slots  22  and  28 , webs  36 ,  38 ,  42  and  44 , and lines  40  can vary from what is shown, to tailor the flexibility of the backrests  12  and  12 ′ with some precision. It should also be understood that the slots  22 , though shown as straight and parallel, may be varied, for example by having them slightly divergent or curved. 
         [0021]    Referring back to  FIG. 1 , the seatback assembly  10  is attached to a rigid support  18 , which may be in the form of laterally spaced seatback posts or canes, or a single supporting spine or narrow frame, upstanding from the rear of the seat. The seatback assembly  10  may be attached in any suitable manner, such as, for example, by the coupling  16  shown in the enlarged perspective view in  FIG. 4 . It should be understood that this coupling  16  is shown for exemplary purposes and that other couplings, or other forms of fasteners, may be suitable for carrying out the invention. 
         [0022]    The coupling  16  may have a first coupling element  50  that may be in the form of a tube clamp, which is structured to clamp the coupling  16  to the laterally spaced seatback posts, or other suitable rigid support  18 . Such an element  50  may be structured to be separated into parts  52 ,  54 , which can be joined together and tightened upon the rigid support  18  by cap screws, or other suitable fasteners  56 . Upon loosening the fasteners  56 , the coupling element  50  can be adjusted relative to the rigid support  18 , such as by raising or lowering the coupling element  50  relative to the rigid support  18 . 
         [0023]    A second coupling element  57  may be in the form of a tube clamp as well. This coupling element  57  is structured to support the adjustable support  14  for pivotal movement about a laterally extending axis. Such an element  57  may be in the form of a collar having a threaded member  58  passing therethrough. The threaded member  58  may be provided with a knob  59 , which functions as a hand grip for conveniently tightening and loosening the threaded member  58  by hand, without the aid of tools. Upon loosening the threaded member  58 , the adjustable support  14  may be pivoted about the laterally extending axis to change the general orientation of the adjustable support  14 . Once a desired orientation has been achieved, the threaded member  58  can be tightened into engagement with the adjustable support  14  so that the adjustable support  14  is prevented from pivoting relative to the coupling element  57 . The effect of this pivotal adjustment will become clear in the description that follows. 
         [0024]    Now, with reference to  FIG. 5 , there is illustrated a side elevational view of an adjustable support  14 . The support  14  generally includes a primary support member  60 , a secondary support member  62 , tertiary support members  64 ,  66 , and couplings  68 ,  70 ,  72 ,  74 . 
         [0025]    The primary support member  60  extends laterally relative to the rigid support  18  and is supported for pivotal movement by one or more couplings  16 . The secondary support member  62  extends transversely, perpendicularly or otherwise, from the primary support member  60 , and may be supported in fixed relation to the primary support member  60  so that upon pivoting the primary support member  60 , the secondary support member  62  pivots along the line A-A in  FIG. 5 . Alternatively, the primary support member  60  may be held in a fixed position and the secondary support member  62  may pivot in relation to the fixed primary support member  60 . 
         [0026]    The tertiary support members  64 ,  66  extend forwardly from the secondary support member  62 . Although two tertiary support members  64 ,  66  are shown, one member  64 ,  66  may be suitable for carrying out the invention. The tertiary support members  64 ,  66  may be coupled at one end for pivotal movement along the lines B-B relative to the secondary support member  62  and at another end to the backrest fixing points  34  to permit pivotal movement of the backrest  12  along the lines C-C. In the exemplary embodiment shown, an upper tertiary support member  64  is coupled to an upper end of the secondary support member  62  and a lower tertiary support member  66  is coupled to a lower end of the secondary support member  62 . 
         [0027]    The tertiary support members  64 ,  66  are coupled to the secondary support member  62  by a first set of couplings  68 ,  70  and to the backrest fixing points  34  by a second set of couplings  72 ,  74 . The couplings are structured to be tightened to prevent the tertiary support members  64 ,  66  from pivoting relative to the secondary support member  62  and prevent the backrest  12  from pivoting relative to the tertiary support members  64 ,  66 . Each coupling, for example, may be in the form of a threaded fastener that, when tightened, applies a clamping force between the tertiary support members  64 ,  66  and the secondary support member  62  and between the backrest  12  and the tertiary support members  64 ,  66  to prevent pivotal movement. The threaded fasteners may be provided with a knob or lever  76 , which functions as a hand grip for conveniently tightening and loosening the threaded fastener by hand, without the aid of tools. Alternatively, the couplings may be comprised of a cam lever that is displaceable to apply a clamping force. It should be understood that these are merely examples of couplings that may be suitable for practicing the invention and that the invention may be practiced with other couplings. 
         [0028]    The operation of the shapeable wheelchair seatback assembly  10  is best understood with reference to the diagrammatic representations shown in  FIGS. 6-9 . By comparing  FIGS. 6 and 7 , it should be clear that pivotal movement of the secondary support member  62  (i.e., along the line A-A when viewing  FIG. 5 ) has the effect of causing general fore and aft movement of the upper and lower portions of the backrest  12 . Pivotal movement of tertiary support members  64 ,  66  relative to the secondary support member  62  (i.e., along the lines B-B when viewing  FIG. 5 ) has the effect of causing general vertical movement of the upper and lower portions of the backrest  12 . Pivotal movement of backrest  12  relative to the tertiary support members  64 ,  66  (i.e., along the lines C-C) has the effect of causing angular movement of the upper and lower portions of the backrest  12 . By combining various pivotal movements, the backrest  12  can be shaped as desired. Once a desired shape is achieved, the couplings can be tightened to fix the backrest  12  in position. 
         [0029]    It should be appreciated that the exemplary shapeable seatback assembly  10  may be described in terms of a four bar assembly, wherein the four bars comprise three support members, like the secondary and tertiary support members, and a flexible backrest, all pivotally moveable relative to one another and configured to be fixed in a desired position. 
         [0030]    It should be also appreciated that the shapeable seatback assembly  10  shown and described herein is an exemplary assembly. The invention is not limited to the assembly shown and described above. For example, one or more couplings may be provided for effecting pivotal movement to shape the backrest accordingly and that all the couplings shown and described need not be necessary for practicing the invention. 
         [0031]    It should further be appreciated that the invention is not limited to the primary, secondary and tertiary support members shown but may be practiced with more or less support members than shown and described. For example, though not shown, the invention may be practiced with other support members, which are pivotally movable, similar to the support members described above, and corresponding couplings that function to fix the support members in place. 
         [0032]    Although the support members are not described in detail, the support members may take on any suitable shape and may be configured in any suitable manner. For example, the invention is not intended to be limited to the linear support members shown but instead may be practiced with curved support members. Moreover, each support member may be in the form of a tubular member, or a single or multi-leaf member, wherein the multi-leaf members may include plural leafs held in spaced relation by spacers. 
         [0033]    The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.