Abstract:
A modifiable pressure distribution pad assembly for a wheelchair comprises a bottom pad of resilient foam material of high density and at least one upper pad of resilient foam material of intermediate density having at least one cutout defining an opening therethrough. Filler foam material of low density is frictionally mounted as an insert in at least one of the openings of the one of upper pads and removable therefrom. A cover encloses the pads, the cover permitting removal of the upper pads and associated filler material therefrom so that filler foam material in one opening can be separated from the upper pads and replaced in the one opening by filler foam material of a different density prior to return of the upper pads and associated filler foam material to the cover. A kit for preparing a modifiable assembly includes in addition, for at least one of the openings, a plurality of inserts of filler foam material adapted to be removably mounted in the opening, the inserts being of filler foam material having different low densities from each other.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to seat pads and more particularly to an improved pressure distribution pad for wheelchairs. 
     Conventional seat pads are often made from a generally solid material such as foam rubber or an equivalent plastic foam material. Less solid pads have incorporated a gel material or similar semi-viscous substance, Still less solid pads have included liquid filling the entire pad or disposed in individual compartments thereof. While these pads provide more comfort than a flat hard surface to a person seated thereon, there still does not result a desired type of support in that the reaction of the pad is uniform over the entire surface and the seated individual tends to shift or roll from side to side or from forward to rearward positions. Thus there is a certain degree of &#34;instability.&#34; 
     To overcome this problem, it has been proposed to provide pads which are contoured and which are made of compositions which have a &#34;memory.&#34; In both instances, it is usually required that the seated individual remain in the same position all the time in order to realize the best pressure distribution. In other words, the pressure points must remain within the contoured areas if the pad is to be effective. 
     Hall, U.S. Pat. No. 3,987,507, describes a pad assembly of resilient foam material having interior cutout portions at locations corresponding to those locations at which maximum pressures are typically exerted by a person seated on the pad-assembly. These cutout portions are filled with a foam material of lesser density than the remainder of the pad assembly. Unlike those pads utilizing liquids, semi-viscous gel materials or simple foam-rubber or plastic foam, the design of this resilient foam pad is such that there is no tendency to develop shear forces or for a patient to &#34;roll&#34; on the pad. Thus the design is such that the patient is not only &#34;stable&#34;, but the patient is not confined to one position as would occur with a contoured cushion or one of the type incorporating a memory pad. 
     However the Hall pad assembly has not proven to be entirely satisfactory in use. First, the density of the filler foam material placed in the interior cutout portions at the factory may not be the most suitable for use in those particular positions for particular patients. Second, even when the filler foam material placed in the interior cutout portions was of the most suitable density for a particular patient at the original time of usage of the assembly, as the patient&#39;s body undergoes changes over time that particular density at a later date may no longer be the most suitable. For example, the patient&#39;s weight may vary radically, bedsores or other skin irritations may appear or disappear, the amount of time that the patient will spend on the pad daily may vary, etc. Thus the need remains for a pad assembly of resilient foam material which can be manufactured so as to provide an initial customized level of support within the interior cutout portions and which can easily be modified as required over time, without return to the factory, so as to provide a different level of support within one or more of the interior cutout portions. 
     Accordingly, it is an object of the present invention to provide a pressure distribution pad assembly in which the density of the filler foam material in the interior cutout portions may easily be varied initially after receipt from the factory to meet the particular needs of the individual user. 
     Another object is to provide such an assembly in which the density of the filler foam material in the interior cutout portions may easily be varied over time, without return to the factory, in order to meet the changing requirements of the individual user. 
     A further object is to provide a kit from which such assemblies can be easily constructed and modified outside of the factory. 
     It is also an object to provide a pressure distribution pad which, by varying the foam density in different sections, helps control posture. 
     SUMMARY OF THE INVENTION 
     It has now been found that the above and related objects of the present invention are obtained in a modifiable pressure distribution pad assembly for a wheelchair comprising a bottom pad, at least one upper pad and a cover enclosing both of the pads. The upper pad is supported by the bottom pad and has at least one cutout defining an opening therethrough. Filler foam material is frictionally mounted as an insert in at least one of the openings of one of the upper pads and is removable therefrom. The cover permits removal of the upper pad and associated filler foam material therefrom so that the filler foam material in one opening can be separated from the upper pad and replaced in that opening by filler foam material of a different density prior to return of the upper pad and associated filler foam material to the cover. The bottom or anti-bottoming-out pad is formed of a resilient foam material of high density; the upper pad, of a resilient foam material of an intermediate density less than the high density. The filler foam materials used as inserts have low densities less than the intermediate density. 
     Preferably, the openings and the inserts are configured and dimensioned for frictional retention of the inserts in the openings. The inserts and openings are typically rectangular, preferably square, in configuration but may be of any configuration. 
     In a preferred embodiment, the assembly additionally includes a substantially inflexible foundation or anti-hammocking panel disposed beneath the bottom pad, the cover enclosing both the panel and the pads. Typically, the filler has manually operable closure means such as a slide fastener. 
     Another embodiment of the present invention comprises a kit for preparing an individualized and modifiable pressure distribution pad assembly for a wheelchair. The kit includes the aforementioned pad assembly elements (i.e., the bottom pad, at least one upper pad having at least one cutout defining an opening therethrough, and the cover adapted to enclose the pads) and, for each of at least one of the openings of the upper pad, a plurality of inserts of filler foam material adapted to be removably mounted in the opening. The inserts are formed of filler foam material having different low densities from each other. 
     Thus, the kit embodiment of the present invention not only enables the patient to initially construct a pad assembly wherein the openings of the upper pad are filled with the most appropriate filler foam material for that particular patient, but furthermore enables the patient at any given time in the future to easily replace the filler foam material in one or more of the openings with a filler foam material of a different density so as to modify the pad assembly to take into consideration the patient&#39;s changed physical circumstances. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The above brief description as well as further objects and features of the present invention will be more fully understood by reference to the following detailed description of the presently preferred, albeit illustrative, embodiment of the present invention when taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is an isometric view of a wheelchair on which rests a modifiable pressure distribution pad assembly of the present invention; 
     FIG. 2 is an exploded isometric view of the pad assembly showing the various pads and panel being removed from the cover and with cutout portions being indicated in phantom-line; 
     FIG. 3 is an isometric view of the upper pad with an insert being removed from each opening therein; 
     FIG. 4 is an isometric view of the upper pad with one of four inserts of differing low densities being inserted in each of the openings therein; 
     FIG. 5 is an exploded isometric view of the pad assembly showing the various pads, panel and associated inserts being returned to the cover; 
     FIG. 6 is a fragmentary rear elevation view showing a pair of buttocks (in phantom-line) seated on the pad assembly mounted in the wheelchair, with portions of the pad assembly being illustrated in section; and 
     FIG. 7 is a fragmentary rear elevation view, similar to FIG. 6, but showing a variant of the pad assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings and in particular to FIG. 1 thereof, therein illustrated is a pressure distribution pad assembly, generally designated by the reference numeral 10, constructed in accordance with the present invention and resting on the flexible seat 12 of a conventional collapsible wheelchair generally designated 14. The wheelchair 14 includes the normal tubular framework 16, including a spaced pair of horizontal tubular members 18 which support the fabric of seat 12. 
     Referring now to FIG. 2, therein illustrated is a cover, generally designated by the numeral 20, from which a variety of pads and a panel are being removed, as shown by the arrow 22. The cover 20 is typically rectangular or square in order to snugly fit within the seating area of the wheelchair as defined by the horizontal tubular members 18 and the width of the flexible seat 12. The proper orientation of the pad assembly is indicated by an arrow 24 disposed adjacent the front margin of the upper surface of the cover. If desired, other means may be used to indicate the appropriate orientation of the pad assembly 10; for example, the rear of the pad assembly (including the cover and the various pad and panel elements disposed within the cover) may be slightly bowed convexly to the rear. The cover defines an aperture 25 on the front thereof of sufficient size to enable removal from the cover of the various pads and panel and is provided with manually operable closure means 26 for the aperture 25, such as a zipper or Velcro fasteners. While the aperture 25 and closure means 26 are shown as disposed on the front surface of the cover 20, clearly they could be disposed on other surfaces such as the rear or side of the cover instead. The cover is preferably made from a material which is anti-bacterial, flame-retardant, anti-static, self-deodorizing, stain-resistant, fluid-proof, non-allergenic and long-lasting. 
     Typically disposed within the cover 20 are, in sequence from bottom to top, a substantially inflexible anti-hammocking board or foundation panel 30, a bottom pad 32 of resilient foam material of high density, and at least one upper pad 34 of a resilient foam material of an intermediate density less than the high density. In the illustrated embodiment there are two upper pads 34, a bottom upper pad which for the sake of convenience we will refer to as the intermediate pad 36, and a top upper pad which we shall for convenience refer to as the top pad 38. As indicated, the top pad 38 rests on the intermediate pad 36 which in turn rests on the bottom pad 32, which is in turn supported by the foundation panel 30. 
     The inflexible foundation panel 30 acts as an anti-hammocking device and negates the tendency of all wheelchair seats (especially flexible wheelchair seats) to hammock or sink towards the center of the seat when used, thereby undesirably transferring some of the pressure from the buttocks and thighs of the patient to the hip bones. The foundation panel is typically a rigid panel preferably of tempered masonite reinforced with steel edging. 
     Much as the foundation panel 30 acts as an anti-hammocking device the bottom pad 32 acts as an anti-bottoming-out device. Except for the seats which contain fluid materials such as water, gel or air, most other seats &#34;bottom out&#34;--i.e., in use over time, the seat reaches a point where the various foams offer no resistance and the buttocks therefore rest upon a hard surface (such as the foundation panel 30). 
     Accordingly, the bottom pad 32 is formed of a very firm resilient foam material of high density so as to provide at least some cushioning effect, regardless of the weight placed on it. Bonded foams, especially those with a density of about 6 lbs/ft 3 , are particularly suited for this pad. 
     The intermediate pad 36 is formed of a resilient foam material of an intermediate density less than the high density of the bottom pad 32 and is provided with one or more cutout portions 40 extending therethrough, each of the two cutout portions 40 (shown in phantom-line) leaving an opening 41. As illustrated, for the sake of simplicity, one square opening 41 is provided for each cheek of the buttocks, in actual practice the number, position and size of the openings 41 will typically be determined by a doctor or rehabilitation specialist on the basis of the needs of the patient at the time that the pad assembly is ordered. The openings 41 are preferably square or at least rectangular, rather than circular, so as to provide corners for reasons which will become apparent later. Generally cutouts of 2 by 4, 3 by 4, or 4 by 4 inches are employed. 
     Like the intermediate pad 36, the top pad 38 is formed of a resilient foam material of intermediate density and is provided with one or more cutout portions 42 (two being shown in phantom-line) defining openings 43. While the openings 43 of this upper pad 38 will typically be aligned vertically with the openings 41 of the other upper pad 36, in particular instances other arrangements may be desirable. 
     Also provided with the cover 20, foundation panel 30, bottom pad 32 and at least one upper pad 34 are a plurality of inserts 44, as shown in FIG. 4. A plurality of the inserts 44 are preferably provided for each opening 41, 43 defined by a cutout portion 40, 42, with the inserts 44 being of similar peripheral outline so that each insert 44 may be firmly, but releasably, retained in the appropriate opening through frictional forces. The inserts 44 are formed of filler foam material having a low density less than the intermediate density, the several filler foam materials for a given opening having somewhat different low densities from each other. Both the openings and the inserts are configured and dimensioned for frictional retention of the inserts in the appropriate openings, this frictional retention being enhanced by the provision of corners in the rectangular and square configurations. 
     It will be appreciated that while at least one, and generally all, of the openings 41 in the intermediate pad 36 will be filled by appropriate inserts 44, the openings 43 in the top pad 38 may be either filled with inserts 44 or left vacant (as shown in FIG. 5); indeed, some of openings 43 may be filled and others left vacant. If desired, the insert receiving apertures 43 of the top pad 38 may be aligned vertically with the insert-receiving apertures 41 of the intermediate pad 36 so as to provide the combined effect of two inserts of differing densities or even a double thickness of an insert of a single density for a particular pressure point. 
     Once the appropriate inserts for the openings 40 have been selected, the various pads and panel 30, 32, 36 and 38 are put back in sequence and in vertical alignment and then, as shown in FIG. 5, replaced within the cover 20, as indicated by the arrow 48. The cover closure means 28 is then used to close the cover aperture 25, and the pad assembly is now ready for use. 
     It should be understood that although the inserts and apertures shown are generally square or rectangular, the inserts and apertures can be of any shape and size prescribed for a particular patient or condition. For example, as shown by the phantom lines in FIG. 5, the cutout and insert 43 can be of a semicircular or other shape in a location on the cushion to relieve pressure in the area of the scrotum, rectum or spine. Initially, the top layer of the cushion can be used without the insert to provide maximum pressure reduction and, as the patient&#39;s condition improves, a lower density and subsequently the same density foam insert can be reinserted in the aperture to distribute the load of the patient over the largest area of the cushion. 
     Referring now to FIG. 2, if the patient is unsatisfied with the pad assembly thus produced, he has only to open the cover closure means 26 and remove through cover aperture 25 the panel and pads 30, 32, 36 and 38 along with any inserts 44 (not shown in FIG. 2) associated with the upper layers 36, 38. One or more of the inserts 44 may now be removed from one or more of the openings of the upper pads 34 (as shown in FIG. 3) and new inserts 44 of different densities inserted (as shown in FIG. 4) so as to create a modified pad assembly when the panel and pads along with any associated inserts 44 are replaced in the cover 20 (as shown in FIG. 5). Instead of simply trying different inserts 44 within the openings 41 of the intermediate pad 36, as specifically shown in FIGS. 3-5, one may try, alternatively or in addition thereto, various inserts 44 in the openings 43 of the upper pad 38. 
     Referring now to FIG. 6, therein illustrated is the effect of a patient (represented by buttocks 50) sitting on a pad assembly 10 of the type shown in FIG. 5. The openings 43 of the top pad 38 and the inserts 44 in the openings 41 of the intermediate layer 36 combine to provide a maximum of relief to the pressure points of the buttocks 50. 
     Referring now to FIG. 7, therein illustrated is a variant pad assembly similar to the pad assembly of FIG. 6 except that there is but a single upper pad 34--namely, pad 36. Instead of a top pad 38 defining at least one aperture 43 (either with or without inserts 44 therein), there is an imperforate pad 52, differing structurally therefrom in the absence of any openings 43 therein. The imperforate pad 52 is not used for gross pressure correction purposes and may be composed of either the same material as an upper pad 34 or an impact foam to provide slow contouring and high air circulation. An impact foam allows maximum air circulation, typically because of a largely open-cell structure, and is preferably a visco-elastic that contours slowly to form-fit to the body, in a manner similar to a gel or fluid. Suitable impact foams include Sunmate (a trademark of Dynamic Systems, Inc. of North Carolina for its visco-elastic material) and Puggie (a trademark of the same company for its orthopedic contouring foam). 
     A kit according to the present invention will include the items indicated in FIG. 5--namely a cover 20, a foundation panel 30, a bottom pad 32, at least one upper pad 34 and a plurality of inserts 44 for each of at least one of the openings in at least one of the upper pads. One or more imperforate pads 52 may also be included. 
     The various pads may be provided in different thicknesses, for example, 0.5 or 1 inch thicknesses, depending on the needs of the patient, the thickness of the inserts 44 being correspondingly selected. A pad assembly is generally at least 3 inches high, but less than 4 inches. 
     For those patients who require posture correction because of a tendency to lean to one side, forwards or backwards, a mini-pad (typically a half of a regular sized pad) may be placed immediately atop the bottom pad under the appropriate buttock and/or thigh to raise that area. Such a mini-pad is preferably formed of the same material as a bottom pad--namely, a high density foam, although other materials such as the intermediate density foam may also be used. The kit embodiment of the present invention generally includes at least one such mini-pad. 
     To summarize, the pressure distribution pad assembly of the present invention enables the density of the filler foam material in the pad openings to be easily varied either initially after receipt from the factory to meet the particular needs of the individual user or over time in order to meet the changing requirements of the individual user. The kit embodiment of the present invention enables such assemblies be easily constructed and modified by the user outside of the factory. 
     Now the preferred embodiments of the present invention have been shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art. Accordingly, the spirit and scope of the present invention is to be limited only by the appended claims, and not by the foregoing specification.