Abstract:
An air insert is designed for a proper fit into a cushion pelvic loading area that has sloped walls for positioning and properly supporting the human pelvis. The air insert may be segmented, or pre-contoured by the manufacturer, so as to be designed for a proper fit into the PLA. The seat cushion and the insert will provide comfort and support to the users.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/008,802, filed Dec. 21, 2007, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates in general to wheelchair seats and more particularly, to wheelchair seat cushions that reduce pressure point concentrations against the contacting portions of a user&#39;s body. 
     Medical practitioners have long known that excessive contact pressure against a user&#39;s body over a period of time may create a harmful condition for the user&#39;s skin. This condition is especially true where a user is confined to a wheelchair creating prolonged contact with the user&#39;s trochanters or the bony prominences of the user&#39;s buttocks. When seated, the user&#39;s weight must be properly distributed in order to reduce the pressure on the bony prominences of the user&#39;s buttocks. Resilient seat cushions are often employed to increase the supporting surface exposed to the user. Fluid, air, foam and other types of resilient cushions are used to minimize the pressure on the bony prominences. 
     Many resilient seat cushions lack enough support, when used alone, to prevent the user&#39;s weight from excessively compressing, or bottoming out, the cushion. Seat cushion bases, often structured as foam bases, may include a pelvic loading area (PLA) to provide better support and stability to the user. Support is improved by directing load to the tissue supporting the user&#39;s trochanters. The PLA of the foam base may be formed with sloped walls to locate a seat cushion insert. Sloped walls may help to distribute the load between the user&#39;s ischial tuberosities (IT) and trochanters. Because of the sloped walls, however, it may be difficult to place an insert into the PLA without overlapping or folding of the insert. Thus, it would be desirable to provide a seating system that improves the support and load distribution of a user&#39;s weight. 
     SUMMARY OF THE INVENTION 
     Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a wheelchair and a seat cushion assembly having a contoured support base and a fluid-filled cushion insert. 
         FIG. 2A  is a sectional view of the contoured support base that includes a pelvic loading area (PLA) having sloped walls. 
         FIG. 2B  is a rear perspective view of the contoured support base of  FIG. 2A . 
         FIG. 3  is a top plan view of a prior art insert having cells uniformly sized, shaped and oriented. 
         FIG. 4  is a rear perspective view of the prior art insert of  FIG. 3 . 
         FIG. 5  is a top plan view of a cushion insert, laid out on a generally flat surface, having regions with cells that are not uniformly sized, shaped and oriented. 
         FIG. 6  is a rear perspective view of the cushion insert and the regions shown in  FIG. 5 . 
         FIG. 7  is a top plan view of the cushion insert shown in  FIG. 5 , wherein the regions of the insert are oriented so that they may be disposed along the bottom, sloped walls and radii corners of the PLA of the contoured support base. 
         FIG. 8  is a rear perspective view of the cushion insert shown in  FIG. 7 . 
         FIG. 9  is a rear elevational view of the cushion insert shown in  FIG. 7 . 
         FIG. 10  is a rear perspective view of the cushion insert shown in  FIG. 7  disposed in the PLA of the foam base. 
         FIG. 11  is a top plan view of another embodiment of a cushion insert that is pre-contoured for disposition along the bottom, sloped walls and radii corners of the PLA. 
         FIG. 12  is a rear perspective view of the pre-contoured cushion insert shown in  FIG. 11 . 
         FIG. 13  is a rear elevational view of the pre-contoured air insert shown in  FIG. 11 . 
         FIG. 14  is a rear perspective view of the pre-contoured cushion insert shown in  FIG. 11  and disposed in the PLA of a foam base. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, there is illustrated in  FIG. 1  an embodiment of a wheelchair and a pelvic loading area (PLA) seat cushion assembly, indicated generally at  1 . The wheelchair and PLA seat cushion assembly  1  includes a wheelchair, indicated generally at  2 , and a PLA seat cushion assembly, indicated generally at  10 . The wheelchair  2  is known in the art and intended to represent but one environment applicable for use with the PLA cushion assembly  10 . However, the PLA cushion assembly  10  is not limited to use with wheelchairs. On the contrary, the various embodiments of the PLA cushion assembly may be used in any environment and for the purposes described herein. For example, the wheelchair  2  may include variations such as power driven wheelchairs, and may further include other personal mobility vehicles, such as scooters. 
     The wheelchair  2  is illustrated having a frame  3  that supports a seat bottom  4  and a seat back  5 . The seat bottom  4  is illustrated as a sling seat, which is known in the art, though any seat structure may be used if desired. The frame  3  further supports a pair of drive wheels  6  and a pair of front casters  7 . A pair of foot rests  8  (only one shown) may be provided to support the user&#39;s feet, though such is not required. The PLA cushion assembly  10  is shown removed from the wheelchair  2  and typically is located on the seat bottom  4 . The PLA cushion assembly  10  may also be provided for use between the seat back  5  and the user, if so desired. The PLA cushion assembly  10  is shown with the rear side view exposed and is preferably oriented on the seat bottom  4  as indicated by the dashed lines. The PLA cushion assembly  10  includes a contoured support base, indicated generally at  12  and further shown as a foam base, and a fluid-filled cushion insert, indicated generally at  13 . Though described in the context of foam, the contoured support  12  may be made from any material capable of accommodating a pelvic loading area  14  and supporting a fluid-filled, cushion insert  13 . Materials used to form the contoured support base  12  may include open and closed cell foams, plastics, and the like. 
     Referring now to  FIGS. 2A and 2B , the foam base  12  includes a pelvic loading area (PLA), indicated generally at  14 . The PLA  14  is illustrated as a depression having depression zones. The depression zones are illustrated as a bottom surface  16  and sides  18  that are sloped toward the bottom surface  16 . However, the depression zones may be any surfaces or features such as arcuate sections, radii, bumps or discontinuities that impose a shape requirement onto the cushion insert  13 . The sides  18  are illustrated in an angular orientation relative to the bottom surface  16 . The angular orientation between the bottom  16  and sides  18  is generally an obtuse angle, greater than ninety degrees relative to the bottom  16 . As will be described below, the sides  18  support and contain the cushion insert  13  as the user&#39;s weight is applied thereto. The sloping sides  18  of the PLA  14  may be steeper on one or more sides than the other side or sides of the PLA  14 . Orientations of the boney prominences of the user relative to the PLA  14  are indicated by symbols representing trochanters  20  and ischial tuberosities  22  of the user. The foam base  12  may further include a leg support area  24  extending from the PLA  14 , though such is not required. The leg support area  24  may be generally flat or may be contoured to fit the underside of the user&#39;s thigh when seated. 
     Referring now to  FIGS. 5 and 6 , the cushion insert  13  is illustrated, in a generally flat orientation, prior to insertion in the PLA  14  The cushion insert  13  is illustrated as a generally oval or rectangular structure, though any shape may be used. The general shape of the cushion insert  13  is similar to the shape of the PLA  14 . The cushion insert  13  includes a flexible base portion  26  having first and second notches  28  and  30 , respectively. The notches  28  and  30  are illustrated as being oriented in the corners or a point of transition from one side to another. However, the notches  28  and  30  may be located at any suitable location that facilitates positioning the cushion insert  13  within the PLA  14 . The notches  28  and  30  may alternatively be creased or pleated areas of the flexible base portion  26  that are subsequently folded against the sloped sides  18 , rather than cut out areas as shown. The first notches  28  are shown as being generally triangular in shape, though such is not required. The edges of the first notches  28  are configured to be generally brought together during insertion of the cushion insert  13  into the PLA  14 , as will be described below. The second notches  30  are generally triangular in shape and may include a terminal void  31 , as shown in  FIG. 5 . The terminal void  31  allows the edges of the second notch  30  to be brought together when the cushion insert  13  is inserted into the PLA  14 . As the edges of the second notch  30  are brought together for conformance of the base  26  to the shape of the PLA 14 , the terminal void  31  accommodates a steeper incline of the sides  18  without causing a wrinkle or other discontinuity at the terminal end of the second notch  30 . Such a discontinuity, over time, may cause cracking or other damage to the base  26  or the cells  32 . Further more, discontinuities may also prevent the cushion insert  13  from properly conforming to the shape of the PLA  14 . Once in place, the edges of the notches  28  and  30  may be spaced apart, touching, or overlapping. 
     The cushion insert  13  further includes a plurality of cells, shown generally at  32 , extending from the base portion  26 . The illustrated plurality of cells  32  are hollow and may be fluid filled cells that may include gaseous, liquid, or thixotropic fluids such as, for example, air, nitrogen, water, highly viscous gels, pastes, and the like. The cells  32 , or any number of cells  32 , may be partially or completely filled with fluid. The cells  32  may also be partially or completely filled with more than one type of fluid. Alternatively, the cells  32  may be generally solid foam cells that include interstitial voids that may have fluid contained therein. In the illustrated embodiment of  FIGS. 5 and 6 , the cells  32  are illustrated as elongated columns extending from the base portion  26  and having a generally square cross section. However, any shape may be used. Additionally, the cells  32  may be any size, whether the uniform or non-uniform, relative to other cells. The cells  32  are structured and arranged on the base portion  26  in relative orientations such that, when the cushion insert  13  is positioned in the PLA  14  of the foam base  12 , the top portions of the cells  32  form a substantially planar surface as illustrated in  FIG. 10 . The illustrated orientation of the cells  32  is such that the greater weight distribution of the user falls onto the larger cross sectioned cells and the lower weight concentrations are supported by the cells of smaller cross section. Other configurations can be used. As shown in  FIG. 6  the cells  32  are arranged on the base portion  26  such that the base portion defines regions. The cells  32  further include axes, such as axes A, B, C, D, and E that define a centerline or other feature consistent between the cells  32 . 
     As shown in  FIGS. 5 and 6 , the cushion insert  13  includes side regions  34  and  36 . The side region  34  is shown having first row cells  38   a  and  38   b  and second row cells  38   c  that have axes B that are oriented at an acute angle, α, relative to the base portion  26  when the insert  13  is placed on a flat surface. The side region  36  is shown having first row cells  40   a  and  40   b  and second row cells  40   c  that also have axes D and are also oriented at an acute angle relative to the base portion  26 , though opposite in direction from the cells of side region  34 . Though shown as having two rows of cells, the side regions  34  and  36  may have any number of cells arranged in any pattern or orientation, including a random orientation. The first row cells  38   a ,  38   b  and  40   a ,  40   b  are illustrated as different sized cells, though such is not required. The cells  38   b  and  40   b  are shown as a smaller size than the cells  38   a  and  40   a , respectively, in order to provide support at the point where the notches  28  are folded. The first row cells  38   a ,  38   b  and  40   a ,  40   b  are oriented relative to the base  26  at a similar angle as the second row cells  38   c  and  40   c , respectively, though such is not required. The first and second row cells  38   a ,  38   b ,  38   c  and  40   a ,  40   b ,  40   c  are generally angled outwardly, toward the outer perimeter of the cushion insert  13 . The first row cells  38   a ,  38   b  and  40   a ,  40   b  have a shorter standout or height from the base portion  26 , in the unfolded position, than the second row cells  38   c  and  40   c , respectively. The shorter standout of the first row cells  38   a ,  38   b  and  40   a ,  40   b  and the longer standout of the second row cells  38   c  and  40   c  account for their relative positions along the slope of the sides  18  of the PLA  14 . The differing standouts provide a cushion insert  13 , when folded or otherwise inserted into the PLA  14 , having a substantially planar surface, or a stepped substantially planar surface, that contacts the user. 
     The cushion insert  13  further includes a front region  42  and a rear region  44 . The front region  42  includes first row cells  46 , second row cells  48 , and corner cells  50 . Similar to the side regions  34  and  36  described above, the first row cells  46  are shown having a shorter standout, relative to the base  26 , than the second row cells  48 . The difference in standouts, likewise, accommodates the relative positions of the cells against the sloping sides  18 , when assembled on the PLA  14 . The first row cells  46  are shown as smaller sized cells positioned closer to the perimeter of the cushion insert  13  than the second row cells  48 , though such is not required. The first and second row cells  46  and  48  are angled relative to the base portion  26 , similar to the cells of the side regions  34  and  36  described above, though such an angular orientation is not required. The first and second row cells  46  and  48  may also be angled at a steeper or shallower angle than the angle of the cells of the side regions  34  and  36  in order to accommodate a difference in the front angle versus the side angles of the sloping sides  18  of the PLA  14 . The corner cells  50  are similarly angled relative to the base portion  26  to lean or otherwise be oriented toward the perimeter of the cushion insert  13 . The corner cells  50  may be angled toward both the perimeter of the front region and the perimeter of the side regions  34  and  36 , in a compound angle orientation, though such a compound angle is not required. The rear region  44  is illustrated having one row of similarly shaped cells  52 , though being shaped as such is not required. The rear region cells  52  are also angled toward the perimeter of the cushion insert  13  such that when positioned in the PLA  14  the cells  52  form a substantially planar orientation. 
     There is further included on the cushion insert  13  a plurality of center region cells  54 . As shown in  FIG. 9 , the uppermost portions of the center region cells  54  may form a substantially planar surface  54   a  that is above a substantially planar surface  54   b  of the remaining cells  32 . Alternatively, the center region cells  54  may be below the remaining cells  32  if so desired. The center region cells  54  are positioned substantially perpendicular to the base  26  such that their orientation relative to the bottom  16  of the PLA  14  is also substantially perpendicular. However, when the bottom  16  of the PLA  14  is shaped other than generally flat, the center region cells  54  may be oriented at an angle to the base  26 . The angular orientation may be such that the center region cells  54  are substantially perpendicular to the associated portion of the bottom surface  16 . The center region cells  54  are typically sized to isolate and support the boney prominences of the user relative to the seat bottom  4  of the wheelchair  2 . The center region cells  54  may also support a majority of the weight of the user, though such is not required. Typically, the cells  32  may form a generally parallel orientation relative to adjacent cells when the cushion insert  13  is inserted in the PLA  14 , though such is not required. 
     Referring now to  FIGS. 7-10 , the cushion insert  13  is shown in a folded or contained condition ready to be positioned in the PLA  14  of the foam base  12 . The first and second side regions  34  and  36  are moved toward the center region cells  54  of the cushion insert  13  such that the second row cells  38   c  and  40   c  are positioned proximate to, or alternatively located against, the center region cells  54 . The first row cells  38   a ,  38   b ,  40   a , and  40   b  are positioned proximate to or against the second row cells  38   c  and  40   c . Likewise, the front region  42  and the rear region  44  are moved toward the center of the cushion insert  13 . The first and second notches  28  and  30  are shown with the edges drawn together such that the side regions may be positioned against the center region without significant distortion. The resulting shape of the base  26  of the cushion insert  13  is generally complimentary to the shape of the PLA  14 . 
     Referring now to  FIGS. 9 and 10 , when the cushion insert  13  is folded and positioned within the PLA  14 , the center region cells  54  form an elevated, substantially planar surface and the cells of the front rear and side regions form another substantially planar surface. The center region cells  54  insulate the boney prominences of the user from contact with the seat bottom  4  by increasing the surface area to support the user. The increased surface area supplied by the cushion insert  13  prevents the user&#39;s ischial tuberosities  22  and trochanters  20  from contacting the seat bottom  4  in a highly stressed manner. The center region cells  54  may also support a majority of the user&#39;s weight as applied by the ischial tuberosities  22 . 
     When the user&#39;s weight is applied to the PLA cushion assembly  10 , the center region cells  54  are compressed and also may deflect outwardly. The outward component of deflection of the center region cells  54  may be resisted by the cells of the first and second side regions  34  and  36  and the front and rear regions  42  and  44 . By virtue of the sloping angle of the sides  18  of the PLA  14  and the complimentary angle of the cells  38   a - c ,  40   a - c ,  46 ,  48 ,  50 , and  52 , the cells resist the outward component of deflection of the center region cells  54 . The trochanters  20  may be supported by the cells  38   a - c  and  40   a - c  in a combination of shear and compression by virtue of the slope angle of the sides  18  of the PLA  14 . 
     The cells  32  may be fabricated from a resiliently flexible inflatable material such as neoprene, plastic or the like. The cells  32  may be formed by conventional dip molding or vacuum molding. The volume of fluid within the cells  32  may be adjustable and the cells  32  may be interconnected through the base portion  26  so that fluid may flow from cell to cell. Additionally, when interconnected, the cells  32  may be in communication with valves (not shown) to alter or otherwise regulate fluid flow therebetween. The cells  32  may be inflated by means of an inflation tube (not shown), which may be in fluid communication with one of the interconnected cells. The tube may include a valve that is operable to open and close. When fluid, such as air, is introduced through the tube, the air may flow from cell to cell so that the pressure in the cells  32  is equalized. The cells  32  may exert a substantially uniform force on the buttocks and legs of a user. On the other hand, the cells  32  of the cushion insert  13  may be divided into individual inflation zones, such as the first and second side regions  34  and  36 , the front and rear regions  42  and  44  and the center region cells  54 , where each zone may be inflated to a desired pressure. 
     When the cushion insert  13  is in use by a seated user, the cells  32  may deform under load to equalize forces and conform closely to the shape of the user&#39;s buttocks, thereby spreading the load and reducing the deformation of skin tissue. The shape of the cells  32  may be selected to deform without substantial resistance other than that provided by compressing the volume of fluid within the cells  32 . The height and orientation of the cells accommodates the shape and contour of the PLA  14 , to conform to the sloped walls  18  and radii corners of the PLA  14 . The cells  32  may have side walls that are generally straight, as illustrated, or the cells may have convoluted side walls to control the deflections of the cells  32  when the user&#39;s weight is applied to the PLA cushion assembly  10 . 
     Referring now to  FIGS. 11-14 , an embodiment of a PLA cushion assembly  110  is illustrated having a contoured foam base  112  including a pelvic loading area (PLA)  114  and a cushion insert  113 . The contoured foam base  112  may include a leg support area  124  that may have depressions forming a pair of spaced-apart leg contours  125 , though such is not required. The cushion insert  113  includes a base  126  that is molded or otherwise formed in a pre-contoured shape including a plurality of cells  132 . Where possible, similar reference numbers will be used to describe similar features and elements to those described in the embodiment above. The shape of the pre-contoured base  126  of the cushion insert  113  is molded to fit into the PLA  114  of a foam base  112 . The pre-contoured cushion insert  113  may be used in the same way and have a similar effect as the cushion insert  13  described above. The pre-contoured cushion insert  113  may include similar regions corresponding to relative positions of the foam base  114  as the cushion insert  13  described above. For example, side regions  134  and  136  and front and rear regions  142  and  144  may form a continuous perimeter about a section formed by a plurality of center region cells  154 . 
     The first side region  134  may include first and second row cells  138   a  and  138   c , which are illustrated having the same size and shape, though such is not required. The first and second row cells  138   a  and  138   c  are angled relative to the base  126  such that the cells  138   a  and  138   c  are generally parallel to adjacent cells  132 . The first side region  134  may also include corner cells  138   b  that are also angled relative to the base  126  and may further include compound angles as described above. The corner cells  138   b  are illustrated as two cells that are smaller in size that the first and second row cells, though such is not required. Similarly, the second side region  136  also includes first and second row cells  140   a  and  140   c  and corner cells  140   b . These cells may be similarly angled, though pointing in an opposite direction, to the cells of the first side region. The cells of the first and second side regions  134  and  136  are angled relative to the base in order to maintain a generally parallel relative orientation. 
     The cushion inert  113  further includes a front region  142  and a rear region  144 . The front region  142  is illustrated having first row cells  146  and second row cells  148 , though any number of cells and any relative orientation may be provided. The first row cells  146  are illustrated as being smaller than the second row cells  148 , though the cells  146  and  148  may be any desired relative size or the same size. The smaller cells  146  are designed and sized to support the lower weight requirements of the front pelvic region of the user. The rear region  144  is shown having a single row of rear cells  152 , though any number, size and orientation of cells may be provided. The rear region cells  152  are configured to support the user&#39;s coccyx or tail bone region. Alternatively, the cells  132  may have any desired relative size, shape, and dispersion pattern across the cushion insert  113 . 
     Referring now to  FIGS. 3 and 4 , there is illustrated a prior art air cushion indicated generally at  200 . The prior art air cushion  200  includes a plurality of air filled cells  210  positioned across a base  212 . The base  212  is formed in a generally flat configuration with the cells  210  arranged generally perpendicular thereto. The cells  210  are illustrated having the same size and shape. When folded or otherwise positioned in a pelvic loading area of a foam base, the base  212  and the cells are distorted such that some cells are no longer oriented in a generally parallel relationship relative to the remaining cells. 
     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.