in the following description , various embodiments of the present invention will be described . for purposes of explanation , specific configurations and details are set forth in order to provide a thorough understanding of the embodiments . however , it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details . furthermore , well - known features may be omitted or simplified in order not to obscure the embodiment being described . cushions in accordance with current embodiments use single - density closed cell foam , such as eva foam . eva is a polymer that approaches elastomeric materials in softness and flexibility , yet can be processed like other thermoplastics . the material has good clarity and gloss , barrier properties , low - temperature toughness , stress - crack resistance , hot - melt adhesive water proof properties , and resistance to uv radiation . eva has little or no odor and is competitive with rubber and vinyl products in many electrical applications . although eva foam is one type of closed cell foam that can be used , other closed cell foams can be used for cushions in accordance with embodiments herein . this type of foam is similar to the type of foam used to make “ flip - flop ” sandals and similar products . the foam has several advantages over standard polyurethane and memory foams in that it is lightweight , very durable and completely waterproof ( the waterproof feature is very important for wheelchair cushions ). the reason that this type of foam has not been used for wheelchair cushions is that it is not very resilient . unlike polyurethane foams that are designed to have a lot of elasticity , the foams in cushions of current embodiments only allow a very small amount of immersion . this low level of immersion produces a response to load that is the opposite of the common foam and fluid wheelchair cushions . the lack of resiliency would not matter much if the present foam was used to produce cushions that are molded to the exact shape of the user , but the lack of compressibility does not work well with a more generic cushion configuration that requires a lot of immersion . however , a pre - contoured wheelchair cushion produced in the traditional manner but using closed cell foam instead of a polyurethane foam will not allow sufficient immersion to pass the medicare required testing for coding as a wheelchair cushion . thus , in order to use single density closed - cell foam to achieve the pressure redistribution characteristics found in more traditional cushions , the design of the present cushion is dramatically different . instead of relying on the elastic properties of the foam materials to allow immersion , the cushion itself changes shape and conforms to the load and contour of the individual user . to achieve the redistribution of pressure found in other cushion designs , applicants herein designed a cushion so that it responds to the applied load of the user by actually changing shape . to clarify , the standard polyurethane foam cushion changes shape only through compression . the closed cell cushion material in accordance with current embodiments is shaped so that it not only allows compression , but the cushion is shaped to provide a dynamic response in which it bends and flexes before receiving a full load , and thus the structure of the molded foam allows the cushion to “ bend ” around the applied load . whereas pre - contoured top surfaces of other commercial wheelchair cushions may rely on both their pre - contour and compressibility to achieve their pressure distribution , such cushions are not using pre - contouring , compression , and bending to achieve a dynamic redistribution of pressure away from the areas of high pressure to areas of lower pressure as in current embodiments which incorporate a pre - contoured top surface not unlike other commercial wheelchair cushions . in addition to pressure redistribution , the dynamic bending and shaping of the cushion to a user is further beneficial for its effect on lateral stability of the pelvis . because the substantial compressibility of other foam cushions responds to load by compressing to allow immersion , such cushions do not resist pelvic retrusion due to slouching . in contrast , since a cushion of present embodiments bends into a new shape under load and has minimal compressibility , it will provide resistance to pelvic retrusion , thereby helping maintain the spine in its natural curvature , which may prevent significant back pain from an uncorrected prolonged pelvic retrusion and straightened spine . referring now to the drawings , in which like reference numerals represent like parts throughout the several views , fig2 shows a top perspective view and fig3 shows a bottom perspective view of a cushion 200 in accordance with various embodiments . the cushion 200 has a top sitting face 201 which contacts the user &# 39 ; s body and conforms to it when the user sits on the cushion , a bottom supporting face 301 which contacts the support surface 150 at various points , and a cushion body 202 which connects the top sitting face 201 and the bottom supporting face 301 . the points which contact the support surface 150 when a user sits on the cushion 200 will depend upon the weight and body shape contour of the user . as best seen in fig2 , in some embodiments , the top sitting face 201 has a pre - countoured configuration which includes contoured areas formed so that the cushion , without load , is already contoured to meet the general anatomical shape of a person when in the seated position . for example , the cushion 200 can have a contoured depression or pelvic well 220 shaped for receiving the its 101 of a user . while the shape of this well shown in fig2 is elliptical , the well 220 can be any other shape , including , but not limited to , both shapes that are symmetrical ( such as circles , triangles , squares , and other common polygons ) and shapes that are not symmetrical ( e . g . with a left side of the shape larger or otherwise shaped differently from a right side , a front part of the shape larger or otherwise shaped differently from a back side , or any other non - matching combination of parts ). the cushion can also have outer or lateral thigh ridges 221 for aligning and supporting the thighs of a user from a lateral position . these outer thigh ridges 221 also can be shaped alike or shaped differently . the cushion can also have one or more inner or medial thigh ridges 222 at the front of the cushion for aligning and supporting the thighs of a user from a medial position . these inner thigh ridges 222 also can be shaped alike or shaped differently . the cushion can also have one or more buttocks or lateral hip ridges 223 at the back of the cushion for aligning and supporting the buttocks and / or lateral hip portions of a user in a seated position . these buttocks ridges 223 also can be shaped alike or shaped differently . as may be appreciated in fig1 b and 5 , such general contours can also provide additional support to a user &# 39 ; s body to supplement the resistance to pelvic retrusion provided by the dynamic bending and shaping response of cushion 200 , thereby assisting in orienting the spine 110 toward its natural curvature . in various embodiments , the dynamic bending and shaping response to load of cushion 200 is accomplished by special configuration of ventilation holes such as port 210 and spacing members such as pillar 211 . standard port and pillar technology is described in u . s . pat . no . 7 , 695 , 069 , entitled “ seat cushion ”, and incorporated herein by reference . as part of the special configuration , support pillars on the cushion 200 are of different heights on supporting face 301 ( e . g ., in the embodiment shown in fig4 , pillars 411 and 412 are each taller than each of pillars 413 - 417 ). the supporting face 301 includes a bottom 302 of the body 202 which is generally flat , with these pillars attached to this flat bottom 302 . thus , in an unloaded state of cushion 200 , not all pillars contact the support surface 150 on which the cushion 200 is placed ( e . g ., in the embodiment shown in fig4 , each of pillars 413 - 417 have a nonzero height — h 413 - h 417 , respectively — of the distance between the bottom of the pillar and the support surface 150 , while pillars 411 and 412 have h 411 = h 412 = 0 because each is touching the support surface 150 ). however , in embodiments , as the cushion 200 receives a load , the cushion 200 bends so that some of the shorter pillars are moved closer to the support surface 150 ( e . g . in the embodiment shown in fig5 , pillars 413 - 416 are moved such that each of h ′ 413 - h ′ 416 is less than each of h 413 - h 417 , repectively ). among those pillars , some may be pressed down into contact with the surface 150 ( e . g ., in the embodiment shown in fig5 , for pillar 415 h ′ 412 = 0 ). it is also possible that other pillars will not move relative to supporting surface 150 at all ( e . g ., in the embodiment shown in fig5 , for pillar 417 , h ′ 417 = h 417 ). thus the cushion 200 bends and flexes under the particular load and contour of the user &# 39 ; s body to provide an additional contouring of the cushion over prior art cushions , which helps to distribute the load more appropriately to high pressure areas on the user &# 39 ; s body . as may be appreciated from fig5 , the amount of bending and the determination of which pillars will actually contact the support surface when a user is supported by cushion 200 will both depend on the specific weight and body contour specifics of the user as well as the configuration of pillar height of the particular embodiment . thus , the height selected for pillars on the supporting face 301 may be varied individually or as part of a larger pattern in order to create different embodiments of cushion 200 for different users or groups of users . for example , in embodiments such as that shown in fig4 , the pillars on the cushion are very short underneath the pelvic well 220 and gradually become longer as the cushion contours travel out toward an area for supporting the trochanteric shelf 104 of a user and forward toward the front of the cushion 200 . as described earlier , the ischial area 101 is first to contact the cushion . a pattern may also vary height in a lateral direction , as best seen in the embodiment of fig4 , wherein short pillar 417 may be seen in front of medium pillar 418 and tall pillar 418 . as may be best seen in fig3 , in embodiments , the cushion 200 can also have troughs 30 on the supporting face 301 to make the cushion 200 bend and flex more easily . in many embodiments , the troughs 310 are rounded and run between the pillars to provide areas of strain relief by decreasing surface tension on the supporting face 301 of cushion 200 , thereby lowering the force needed to cause the cushion 200 to bend and flex in response to load and decreasing the need for the supporting face 301 to stretch in those areas . the troughs 310 can be arranged in a column and row pattern . the cushion 200 can have troughs 310 between all or only some of the rows , and the troughs 310 may extend from one edge of cushion 200 to the other , or may only be positioned in selected locations . in some embodiments , the troughs 310 only run between the shortened pillars on the supporting face 301 of the cushion 200 . the troughs can also be positioned only in locations of maximum surface tension , or can extend over the entirety of the cushion , or any subset thereof . for example , as shown in the embodiment of fig3 , the supporting face 301 of the cushion 200 has rounded troughs 310 in a column and row pattern only under the pelvic well 220 of the cushion 200 . as best shown in fig2 , cushion 200 may also include a plurality of nubs 212 spread out across the sitting face 201 . these nubs 212 can provide a desirable additional tactile characteristic to cushion 200 and are thought to stimulate nerve activity and improved blood circulation in the portion of a person &# 39 ; s body placed in contact with them . additionally , the nubs 212 may be included to improve performance of a cushion cover ( not shown ). for example , if a cushion cover is placed over a cushion 200 , when a user is not pressing the fabric of the cover into the cushion seating face 201 by sitting on it , the nubs may provide sufficient separation between the cushion cover and the cushion 200 so as to provide airflow there between to allow more rapid cooling or drying of the cover due to increased airflow and convection . any suitable method of manufacturing or fabricating the cushion 200 can be used . for example , in some embodiments , the cushion 200 may be formed in two general sections , a top section and a bottom section , where the top section is a perforated core which is molded onto the lower section made up of pillars with different heights . in some embodiments , the cushion 200 is injection molded as one piece , including the pillars 211 . in addition , if desired , voids can be added to selective sections of the cushion 200 to aid in molding , the reduce the amount of mold material used , and / or to provide selective flexibility of the cushion . furthermore , the cushion 200 can be adapted for a variety of uses . while many embodiments herein describe the cushion adapted for use in a wheelchair to prevent pressure sores , the cushion 200 can be used in any situation where a person will be sitting or in any situation where a person may support even a portion of their weight or a body part relative to a support surface . examples include , but are not limited to , use of the cushion with office chairs , home furniture , stool , automobiles , trains , airplanes , boats , tractors , motorcycles , bicycles , unicycles , tricycles , recreational vehicles , dune buggies , jet skis , stadium seats , spacecraft , hovercraft , ski lifts , roller coaster , glider , luge , bobsled , recliners , gurneys , beds , yoga mats , pet crate liners , gardening knee mats , or any other kind of cycle , vehicle , seat , or furniture . other variations are within the spirit of the present invention . thus , while the invention is susceptible to various modifications and alternative constructions , certain illustrated embodiments thereof are shown in the drawings and have been described above in detail . it should be understood , however , that there is no intention to limit the invention to the specific form or forms disclosed , but on the contrary , the intention is to cover all modifications , alternative constructions , and equivalents falling within the spirit and scope of the invention , as defined in the appended claims . the use of the terms “ a ” and “ an ” and “ the ” and similar referents in the context of describing the invention ( especially in the context of the following claims ) are to be construed to cover both the singular and the plural , unless otherwise indicated herein or clearly contradicted by context . the terms “ comprising ,” “ having ,” “ including ,” and “ containing ” are to be construed as open - ended terms ( i . e ., meaning “ including , but not limited to ,”) unless otherwise noted . the term “ connected ” is to be construed as partly or wholly contained within , attached to , or joined together , even if there is something intervening . recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range , unless otherwise indicated herein , and each separate value is incorporated into the specification as if it were individually recited herein . all methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context . the use of any and all examples , or exemplary language ( e . g ., “ such as ”) provided herein , is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed . no language in the specification should be construed as indicating any non - claimed element as essential to the practice of the invention . preferred embodiments of this invention are described herein , including the best mode known to the inventors for carrying out the invention . variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description . the inventors expect skilled artisans to employ such variations as appropriate , and the inventors intend for the invention to be practiced otherwise than as specifically described herein . accordingly , this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law . moreover , any combination of the above - described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context . all references , including publications , patent applications , and patents , cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein .
a cushion for supporting a user relative to a support surface is provided . the cushion has material with sufficient flexibility to deform under a weight of the user and sufficient resilience to return to its original state when the weight is removed . a supporting face contacts the support surface and is characterized by a plurality of points . the supporting face is contoured such that , when the cushion is in an unloaded configuration , a first subset of the plurality of points contact the support surface and a second subset of the plurality of points do not contact the support surface . when a user then sits on the cushion so that it is in a loaded configuration , at least some of the points in the second subset are displaced under the user &# 39 ; s weight and contact the support surface . the cushion thus both bends and compresses to distribute the weight of the user .