Patent Publication Number: US-6901617-B2

Title: Multi-layer cushion and cover

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority provisional application Ser. No. 60/378,236 filed May 6, 2002 and to provisional application Ser. No. 60/417,338, filed Oct. 9, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to orthopedic cushions in general, and more specifically to orthopedic wheelchair or other chair or seat cushions. 
     A well-recognized problem for individuals who are forced to spend extended time seated in wheelchairs or other chairs or seats is the risk of incurring tissue damage, and ultimately the development of decubitus ulcers, at those points on the body that are subject to constant pressure. Decubitus ulcers expose an individual to the risks of infection and irreversible tissue damage, and in any case are difficult to treat. For wheelchair-bound persons, such ulcers typically develop over the bony prominences exposed to pressure while the person is seated, such as the ischia (bony prominences of the buttocks) and the trochanter. Another problem for such individuals is a lack of stability accompanied by a sense of physical insecurity while seated in a wheelchair, and particularly while being moved about in a wheelchair. 
     There are known to the art, wheelchair cushions that attempt to address these problems by reducing pressure on restricted areas of tissue over bony prominences and redistributing pressure more uniformly over a larger surface area of the buttocks and back of the thighs. Such cushions may include cushions having shaped foam bases and with a cushioning layer on the base. However, a continuing problem for the cushion user is a sense of discomfort, particularly in the trochanter region, due to a transition between the cushioning layer and the base. The transition typically feels like a bump or ridge beneath the upper thighs and, while it does not usually cause tissue damage, is a constant source of discomfort and annoyance to the user. A need therefore exists for a wheelchair or other seat or chair cushion that adequately relieves pressure on pressure points in the regions of the ischia and trochanter, provides the user a sense of stability and security, while at the same time reduces or eliminates the discomfort and annoyance associated with the transition between components of the base. 
     BRIEF SUMMARY OF THE INVENTION 
     In an exemplary embodiment, a multi-layer cushion includes a shaped orthotic base, which may be foam or other acceptable material, on which is disposed a cushion layer of interconnected air cells in an array projecting upwardly from the base, wherein the air cells are not uniform in size and shape across the entire array but instead are modified in size and shape along edges of the air cell layer that are adjacent to upwardly projecting portions of the foam base, so that the tops of the air cells are approximately equal in height to the tops of the upwardly projecting portions of the foam. The modified array with air cells of varying size and shape in certain regions adjacent to upwardly projecting portions of the foam reduce the discomfort and annoyance associated with the user&#39;s sensation of what would otherwise be an abrupt, uncomfortable transition between the air cells and the foam base. The cushion includes a cover with a lower compartment for the foam base and an upper compartment for the air cell layer. The cover functions to keep the air cell layer properly in place on the foam layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the multi-layer cushion of the present invention enclosed in a cover; 
         FIG. 2  is an exploded view of the cushion; 
         FIG. 3  is a side elevational view of the disassembled cushion and cover, the cover shown in cross section; 
         FIG. 4  is a rear perspective view of the assembled cushion with the filler tube cover open; 
         FIG. 5  is a perspective view of the layer of air cells; 
         FIG. 6  is a side elevational view of the air cell layer; 
         FIG. 7  is a front perspective view of a foam base of the multi-layer cushion with a pommel on the front bolster of the foam base; 
         FIG. 8  is a rear elevational view of the foam base; 
         FIG. 9  is a side elevational view of the air cell layer positioned directly on the foam base; and 
         FIG. 10  is rear elevation view of the air cell layer positioned directly on the foam base showing the relationship of the layers in the assembled cushion. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     One preferred embodiment of the cushion and cover assembled and ready for placement on a support surface is indicated generally by reference number  10  in FIG.  1 . As can be seen, the preferred embodiment of cushion  10  has a generally rectangular configuration having a front edge  12 , a side edge  14  and opposed side edge  16  and a rear edge  18  with truncated corners  20  and  22  between the rear edge  18  and the two side edges  14  and  16 , respectively. The truncated corners facilitate positioning of cushion  10  on a support surface (not shown), such as a seat of a wheelchair or conventional chair, as will be understood. Cushion  10 , when assembled, has a seating surface to accommodate the buttocks of a user, indicated generally by reference numeral  24 . It will be appreciated that the cushion of the present invention can have other configurations dictated by the environment in which it is employed, without departing from the scope of the invention 
       FIG. 2  illustrates the arrangement of the major components of cushion  10 . The cushion comprises a supportive orthotic base  26 , an air cell layer  28  on top of the base and a compartmentalized cover  30 , which maintains air cell layer  28  and base  26  in proper position an alignment when assembled, as well as performing the typical functions one skilled in the art associates with a cover. 
     In a preferred embodiment, base  26  is a foam base, shown in  FIGS. 2 and 7  through  10 , has a front edge  32 , a first side edge  34  a second side edge  36 , a rear edge  38 , top seating area  40  and a generally flat bottom surface  42 . Base  26  is contoured and is dimensioned to accommodate a range of buttocks sizes. Bolsters placed along the front and side edges generally form the contour of base  26 . Front bolster  44  is positioned along the front of the base. Bolster  44  is substantially wedge-shaped and has a relatively greater thickness towards the front edge and includes a sloping support surface  46  that is angled toward a substantially flat mid-portion support surface  48  of the base. 
     Bolster  44  includes a facing edge  49  that is angled downwardly toward the front edge of the base. Bolster  44  with its angled support surface  46  provides raised but gently sloping support beneath the thighs while the lower plateau in the portion of the cushion that bears the greatest weight, i.e. surface  48 , to accommodate the human buttocks shape. The angled facing edge  49  provides a more comfortable surface for the user&#39;s thighs and, with cells of the inflatable cushion  28 , forms a transition zone to enhance comfort. There is a pommel  50  on the front bolster to fit between the user&#39;s thighs and separate and angle the legs in a comfortable position and to stabilize the user&#39;s pelvis. 
     A first lateral bolster  51  is positioned along edge  34  and a second lateral bolster  52  is positioned atop and along edge  36 . The lateral bolsters positioned along the side edges provide support at the sides of the cushion to conform to the shape of the human buttocks and provide lateral stability. Lateral bolsters  51  and  52  are mirror images. Each is substantially wedge-shaped and has an interior support surface  54  that slopes downwardly and inwardly toward support surface  48 . Each lateral bolster extends nearly the entire length of the side as shown in  FIG. 9 , and form lateral support for the thighs and provide proper thigh loading characteristics without placing too much pressure on the thighs. 
     In an exemplary embodiment, base  26  is formed from urethane foam. Sections of the base can be formed from foam of varying firmness. For example, the main section of the foam base, including support area  48 , has relatively firmer foam in the mid portion and the lateral bolsters and relatively softer foam beneath the thighs. The base can be molded or formed from one piece of material or the various sections, for example the bolsters, can be formed separately and attached, glued or bonded together to form base  26 . Although preferably formed from foam material, base  26  can be formed or molded from other materials, depending upon the support characteristics desired, such as gel, molded plastic, fiberglass or even wood, without departing from the scope of the invention. 
     The rear edge of base  26  in the illustrated embodiment has truncated corners  55 ,  56 , shaped to fit into the curve of a wheelchair backrest, as explained above in reference to FIG.  1 . The dimensions of the foam cushion are adapted to accommodate a variety of human body sizes, and the foam contours are adaptable to fit a large proportion of users of a particular cushion size. 
     The cushion includes a shock-absorbing layer, which, in a preferred embodiment is an air cell layer  28 . Air cell layer  28  is comprised of an inflatable air cell cushion having flexible base  57  with individual air-filled cells  58  in an array. Generally, the cells  58  are parallel to each other and arranged on the base  56  in an array comprised of transverse and longitudinal rows of cells. The air cells  58  are fabricated from a resiliently flexible inflatable material such as neoprene, plastic or the like. The air cell layer  28  can be formed by conventional dip molding or vacuum molding. 
     It will be noted that, regardless of the configuration of the cell, each individual cell  58  is a four-finned collapsible or foldable cell. The foldable aspect of the cell is important in that it allows the cells to be spaced far enough apart to facilitate molding and to provide a reasonable amount surface area between the cells to permit solid bonding of top of the cushion to the bottom layer. The foldable four-fin design allows the cells to expand when inflated until they touch forming a continuous support surface. 
     Generally air cell layer  28  is dip molded from neoprene, as explained above. On the other hand, the cushions can be vacuum molded from a plastic material with the cells closer together than when dip molding and while avoiding thinning. Vacuum molding of plastic materials is simpler and less expensive than dip molding of neoprene. The cell geometry allows cells of any configuration to be vacuum molded, making individual seat cushions of differing cell configurations commercially feasible. The cell designs allow for pre-contoured seating surface that can be achieved by using different sizes and heights of cells. 
     The volume of air within the air cells  58  is adjustable and the cells are interconnected through flexible base  57  so that air flows from cell to cell. The cells are inflated by means of an inflation tube  60 , which is in fluid communication with one of the interconnected cells  58 . Tube  60  includes a manually operated open and close valve  62 . When the air is introduced through tube  60  is flows from cell to cell so that the pressure in the cells is equalized. The air cells exert a generally uniform force on the buttocks and legs of a user. On the other hand, the cells of the array can be divided into individual inflation zones, each zone inflated to a desired pressure. 
     When the cushion is in use by a seated user, the air-filled cells deform under the weight load to equalize forces and conform closely to the shape of the user&#39;s body, thereby reducing the deformation of skin tissue. The shape of the air cells, for example a modified cruciform shape as shown in the figures, is selected to deform without any resistance other than the volume of air within. The height of the cells is adaptable to accommodate the differences in body contours. 
     In the illustrated embodiment, the air cells are not uniform in size and shape across the entire array, but instead are in some portions of the cushion tapered or reduced in height so that the tops of the air cells when disposed on the foam base are approximately equal in height to adjacent, upwardly projecting cells or portions of the foam base, such as the front bolster, as shown in FIG.  10 . This arrangement of rows of cells of varied sizes can be seen in  FIGS. 5 and 6 , the air cells to meet the profile of an adjacent portion of foam. 
     For example, in one embodiment the first row  64  of air cells in the array, positioned along the front edge of the foam base, is reduced in height relative to the remaining cells in the array. This provides that the transition between the front row of air cells  64  and the front edge of the foam base is barely perceived by the user, and the front edge of the foam base adjacent to the modified air cells comes into contact with the user. More specifically, in the illustrated embodiment, the air cells  58  of the first row of air cells  64  that are disposed along the front edge of the foam base, beneath the thighs, have a reduced height and a wedged shape, as at  65 . The air cells of such a geometry provide a smooth transition from the air cell layer to the downwardly angled facing edge  49  of the base foam structure to provide added comfort beneath the thighs, reducing or eliminating the user&#39;s sense of a bump or ridge. 
     A second row  66  of cells  58  of reduced height positioned adjacent the first row  64  forms a transition area between the front bolster and first row of cells and the next three rows of cells,  68 ,  70 ,  72 . Referring to  FIG. 5 , the three rows  68 ,  70 , and  72  are comprised of cells that form the main ischial support area of the cushion. The main ischial support area is designed to be positioned under the ischial area of a user seated on cushion  10  to relieve pressure on the ischial area and reduce the risk of tissue break down and pressure sores. The end cells  74 ,  76 ,  78  of the respective three rows  68 ,  70  and  72  are of a lesser vertical height than the other cells in the rows. 
     Air cell layer  28  includes a pair of rear cells  80 ,  82  along the rear edge of the air cell layer. Cells  80  and  82  are generally elongated rectangles and can be greater in vertical height than the other cells of the array. These larger cells form a rear bolster when the air cell layer is positioned on the base. 
     The modified air cells more closely match the profile of the adjacent portions of the foam base, thus reducing the feel of the transition between the air cell layer and the foam base. Further, the array of air cells can include a gradual successive change in the height or profile of each successive row of air cells, to more gradually change the profile of the cushion. As shown in  FIG. 10 , the shorter end cells  74 ,  76  and  78  are positioned along the length of the side bolsters. The rear cells  80  and  82 , when positioned on the support area  48  of the base, assume the same approximate height as the side bolsters  51  and  52 . The shorter end cells and rear cells form a contiguous surface with the air cell layer is positioned on the base when the air cell layer is positioned on the base. That is, as can be seen in  FIG. 9 , the cells comprising the array of cells assume generally the same vertical height when the air cell layer is positioned on the base. 
     The unique design of the front transition rows of cells already has been discussed. It will be appreciated that the cell size and arrangement of cells in the inflatable cushions illustrated are one exemplary shown to work well in the instant invention. However, the various numbers of cells, sizes of cells and arrangements of cells in rows may be varied to suit the needs of a user. Any cushion layer design is intended to be encompassed by the scope of the invention. Furthermore, the multi-layer cushion can be constructed so that the upper deformable layer comprises a material other than an air cell cushion  28 . For example, the upper layer could be comprised of cells filled with elastomeric gel. The layer could be configured form a gelatinous cushioning media or gelatinous elastomer formed in a honeycomb arrangement or in columns or any other material of resilient, shock-absorbing deformable material that can be used to produce a deformable yet resilient layer that fits appropriately with the base and cooperates with the base to provide the desired smooth translational areas between the upper layer and the base. 
     An outer cover  30  fits over the air cell layer  28  and base  26  and holds the two layers in place relative to one another. One embodiment of a cover design is shown in  FIGS. 2 and 3 . The cover  30  is fabricated from any suitable fabric such as nylon or the like, rubber or rubberized material or foam, or a composite of different fabric or rubberized materials. Cover  26  has durable bottom panel  84  comprising a flexible, wear resistant, non-skid material such as vinyl. The cover includes a rear panel  86 , a first side panel  88  and opposite side panel  90  ( FIG. 1 ) and a top panel  92  and front panel  93 . In a preferred embodiment, the top panel section is constructed from an elastic fabric material that can stretch in multiple directions. The respective side panels are constructed from a polymer material, such as nylon or the like. The recited panels define an inner compartment  94 . 
     The inner compartment  94  is subdivided by a flexible cloth or polymer middle panel  96  that divides the cover into an upper compartment or pocket  98  and a lower compartment or pocket  100 . There is an inner zipper  102  comprised of opposed, interengaging toothed tracks  102 A,  102 B that attaches the edge of the middle panel  96  to the inside of the upper panel so as to close the upper compartment. A main outer zipper  103  comprised of opposed interengaging toothed tracks  103 A and  103 B extends from side panel to side panel and transects the rear panel. The main zipper  103 , when closed, functions to close the lower compartment  100  resulting in the two layers  26  and  28  being tightly secured inside the cover, each in its own compartment. 
     Any type of known securing means, such as zippers, hook-and-loop type fabric strips, hooks, snaps or the like can be used to close the cover and retain the air cell layer in its pocket and base in its pocket. This novel arrangement keeps the upper layer appropriately positioned on the base, and prevents the upper air cell cushion layer from being displaced during user movement or other movement of the cushion. 
     There is an opening  104  in one side panel covered by a flap  106 . The opening allows the air tube  60  to protrude out of the cover. The flap  106  and the side panel have opposed segments of hook and loop fastener  108 A,  108 B. 
     An opening or hole (not shown) in the middle panel  96  near opening  104  allows the air filling tube  60  to protrude out of compartment  98  and through the cover at opening  104 . Tube  60  can be pressed against the side panel and the flap  106  secured closed to keep the valve out of the way. The bottom panel  84  of the cover can have attachment means  110 , such as hook and loop fastener, to facilitate attachment of the cushion  10  to a wheelchair seat, vehicle seat, chair or other seating device. The bottom can include a strap that can be fastened upon itself by hook and loop fastener, such as Velcro® to secure the cushion to a seat. 
     The combination of the base layer with bolsters and upper layer of soft or resilient material such as an air cell cushion or gel type cushion provides a cushion that reduces and redistributes pressure from restricted pressure points in the ischial and trochanter regions, and provides the user with a sense of postural stability and security, while also reducing discomfort and annoyance due to the transition between air-filled cells and the foam base. Furthermore, the cover functions to provide an aesthetically pleasing seating surface, protect the cushion and base and, importantly, keep the upper layer in proper position on the base layer so to reap full advantage of the cell and bolster arrangement that eliminates uncomfortable transition areas and unwanted pressure to increase comfort and safety in use.