Abstract:
A mattress for institutional use provides upper and lower surfaces offering different levels of firmness through the use of gradiated firmness in multiple polymer foam layers.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional application 61/707,540 filed Sep. 28, 2012 and hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to mattresses providing pressure redistributing surfaces for medical or other use and in particular to a mattress providing for two different mattress firmnesses. 
     Mattresses intended for hospitals or long-term care may provide for a pressure redistribution layer intended to help reduce regions of pressure that may lead to pressure ulcers. One method of providing a pressure redistribution layer employs multiple layers of polyurethane or similar foam with the top layer that may be die cut or convoluted. Mattresses providing a pressure redistribution layer suitable for medical or institutional use will henceforth be termed “medical mattresses”. Such mattresses are generally intended to be used with articulating hospital or long-term care beds that allow the mattress to be flexed by a bed mechanism to elevate or lower a head, foot, or middle section. 
     Long-term care or hospital residents (henceforth patients) usually cannot choose the firmness of their mattress. While some facilities may purchase medical mattresses with different firmnesses, this approach is burdensome and expensive and does not allow for patient choice. To address this problem, mattresses may be constructed of two layers of polymer foam, for example, a top layer of softer foam and a bottom layer of firmer foam. By flipping the mattress, a different layer is presented at the upper surface of the mattress. Such mattresses may not provide for effective pressure redistribution necessary for reducing pressure points such as may cause localized blood circulation loss and ulceration. 
     SUMMARY OF THE INVENTION 
     The present invention provides a medical mattress that may be flipped to expose one of two different surfaces presenting different firmnesses. Improved pressure redistribution is obtained by multiple foam layers providing a more gradual transition in firmness. In some embodiments, a nonslip surface may be re-positionably attached on the lower surface depending on the mattress orientation to better hold the mattress in position during bed articulation. In some embodiments, peripheral foam walls (bolsters) may be re-positionably attached on the upper surface depending on the mattress orientation to help reduce the risk of patient falls from the mattress. In some embodiments, one end of the mattress may have opposed heel slopes to help reduce heel pressure regardless of mattress orientation. While developed for medical use, the mattress clearly has utility in other settings including schools, homes and vehicles, and the invention is not limited to a particular market. 
     In one embodiment, the present invention provides a mattress having a mattress body with opposed first and second supporting surfaces each sized to receive and support a supine individual when the surface is upwardly facing and horizontal. The mattress body includes at least three polymer foam layers having different firmnesses and extending along substantial portions of the mattress length. A firmness of the polymer foam layers is selected to present a lesser firmness to a supported individual lying on the first supporting surface than to the supported individual lying on the second supporting surface. A cover fits around the mattress body to retain the mattress body therein. 
     It is thus a feature of at least one embodiment of the invention to provide a single mattress that can offer different levels of firmness for different individuals and yet which provides for sufficient pressure redistribution to minimize pressure points for bedridden patients. By employing a gradiated structure of multiple foam layers, a trade-off between reducing point pressure and increasing broad area support can be managed. 
     A first polymer foam layer adjacent to the first supporting surface may have a lesser indentation force deflection (IFD) than the polymer foam layer adjacent to the second supporting surface. A third polymer foam layer positioned between the first and second polymer foam layers may have an IFD greater than the IFD of the first polymer foam layer and the second polymer foam layer. 
     It is thus a feature of at least one embodiment of the invention to provide a firm center core layer improving broad area support to both the soft and firm face while still allowing different firmnesses on the different faces. 
     The mattress may include a fourth polymer foam layer positioned between the first and third polymer foam layers having a greater IFD than the first polymer foam layer and a lesser IFD than the third polymer foam layer. 
     It is thus a feature of at least one embodiment of the invention to provide a graduated change in firmness of the foam layers to better accommodate the competing desires of different firmnesses and isolation of the different firmnesses on the single mattress. 
     The different polymer foam layers extending along at least a portion of the first and second supporting surface may exclude a foot portion adapted to support feet of a supine individual. A foot region polymer foam element may extend along the mattress length in the foot portion having firmness no more than the least firmness of the different polymer foam layers outside of the foot portion. 
     It is thus a feature of at least one embodiment of the invention to provide improved foot comfort by eliminating heel pressure points in a reversible mattress. 
     The foot region polymer foam layer may have a uniform firmness. 
     It is thus a feature of at least one embodiment of the invention to simplify the construction of the foot region of the mattress. 
     The foot region may provide a reduced mattress thickness tapering inward to an end of the mattress. 
     It is thus a feature of at least one embodiment of the invention to further reduce pressure on the heel or foot by depressing the relative surface height of the mattress in the heel region. 
     The mattress may include a second cover outside the first cover wherein the second cover includes indicia indicating relative firmness of the first and second opposed surfaces. 
     It is thus a feature of at least one embodiment of the invention to guide users in orienting the mattress correctly for desired firmness. 
     The inner cover may include indicia indicating relative firmness of the first and second opposed surfaces. 
     It is thus a feature of at least one embodiment of the invention to allow the outer cover to be removed and reinstalled correctly. 
     The first and second opposed surfaces may be substantially planar without a convoluted surface. 
     It is thus a feature of at least one embodiment of the invention to provide firmness variations that do not rely on complex surface treatment. 
     The mattress may include a bottom cover adjustable to be positioned over at least a portion of the bottom of the mattress when the mattress is in either of two orientations with the opposed first or second supporting surface uppermost, the bottom cover including outwardly exposed anti-slip material. 
     It is thus a feature of at least one embodiment of the invention to provide a reversible mattress that nevertheless offers slip resistance. 
     The bottom cover may be permanently attached to a cover fully surrounding the mattress at one edge of the bottom cover and releasably attachable to the cover fully surrounding the mattress at an opposed edge of the bottom cover. 
     It is thus a feature of at least one embodiment of the invention to provide a simple method of changing the surface of slip resistance depending on the orientation of the mattress with reduced risk of loss or omission of the slip resistant surfaces. 
     The bottom cover may be releasably attachable to a mattress cover with hook and loop fasteners. 
     It is thus a feature of at least one embodiment of the invention to provide an attachment method consistent with commercial laundering of the cover material. 
     The mattress may include a top cover adjustable to be positioned over at least a portion of the top of the mattress body when the mattress body is in either of two orientations with the opposed first or second supporting surface uppermost, the top cover providing upwardly extending bolsters positionable at opposed left and right edges of the mattress body. 
     It is thus a feature of at least one embodiment of the invention to provide a reversible mattress that offers bolsters on its upper surface. 
     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified perspective view of an articulating hospital bed suitable for hospital or institutional use; 
         FIG. 2  is a perspective view in partial cutaway of one embodiment of the mattress of the present invention with the soft surface facing upward showing an internal layer configuration and a fragmentary perspective view of the same mattress rotated with the firm surface facing upward; 
         FIG. 3  is a fragmentary cross-section taken along lines  3 - 3  of  FIG. 2  showing multiple internal foam layers and outer covering materials of the present invention in one embodiment; 
         FIG. 4  is an exploded perspective view of the mattress of  FIG. 2  and a repositionable bottom cover providing a nonskid surface when attached to the mattress; 
         FIG. 5  is a figure similar to  FIG. 4  showing an alternative embodiment where the nonskid surfaces are placed on straps fixedly attached to one side of the mattress to be folded over or underneath the mattress depending on mattress orientation to expose a nonskid surface; 
         FIG. 6  is a cross-section similar to  FIG. 3  showing opposed heel slope surfaces that may be provided by the present invention: and 
         FIG. 7  is a cross-section taken along line  7 - 7  of  FIG. 3  showing a repositionable top cover providing for left and right mattress bolsters. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a hospital bed  10  or the like may provide for an articulating carriage  12  for supporting a mattress  14  thereupon. The articulating carriage  12  may provide, for example, multiple hinging sections  16  including a head section  16   a , center section  16   b , and foot section  16   c , that may be angled to flex the mattress  14  to conform with the sections  16 , for example, to raise the head of the mattress  14  or lower the foot of the mattress  14 . For this purpose, the mattress  14  may flex to follow motion of the sections  16 . 
     Referring now to  FIG. 2 , the mattress  14 , when unarticulated, may present a generally planar cushion having opposed broad surfaces presenting a soft face  18   a  on one side and a firm face  18   b  on an obverse side separated by a mattress thickness, for example, of five to eight inches. Each of the faces  18  extends along the mattress length  20  from a head end  22  to a foot end  24 , for example, any of 76, 80, and 84 inches, and extends along the mattress width  26  between left and right sides, for example, of any of 35, 39 and 42 inches. It will be appreciated that a variety of other dimensions may also be provided. The mattress  14  is generally sized to support a supine adult along its length (the mattress length extending from head end  22  to foot end  24 ) on either of the soft face  18   a  or firm face  18   b  when that face is horizontal and uppermost. 
     The soft face  18   a  may be labeled with a firmness designator  30  such as the word “soft” or other similar phrase or symbol as well as manufacturer information  31  visible when the soft face  18   a  is positioned on top. Conversely the firm face  18   b  may be labeled with a firmness designator  30  such as the word “firm” or other similar phrase or symbol together with manufacturer information  31  visible when the firm face  18   b  is positioned on top. An indication of the head of the mattress  14  may be provided, for example, in the orientation of the firmness designators  30  being positioned to be read while facing the head of the mattress  14  or other designator (not shown). These firmness designators  30  may be applied directly to the outer faces of the elastomeric foam described below. 
     Referring now to  FIG. 3 , the mattress  14  may be constructed from multiple parallel laminated layers  32  and  34  each of an elastomeric foam material such as polyurethane foam. The foam layers  32  will generally have a width substantially equal to the width of the mattress  14  and a thickness being a fraction of the thickness of the mattress  14  so that the number of layers  32  times their thickness equals the thickness of the mattress  14 . The width may be reduced slightly when side bolsters  76  are used as described below. 
     All but the outermost, softest of foam layers  32   a  will have a length slightly shorter than the length of the mattress  14  to extend from a head end  22  of the mattress  14  to a point just short of the foot end  24  of the mattress  14  where a patient&#39;s heels would rest. This length will generally be at least three quarters of the length of the mattress. The outermost, softest foam layer  32   a  may, in contrast, extend the full length of the mattress  14 . 
     Foam layer  34  will have a width generally equal to the width of the mattress  14  and a total thickness comparable to the thicknesses of the layers  32  minus the softest, outermost foam layer  32   a . The length of foam layer  34  will be such as to make up the difference between the length of the inner foam layers  32  and the length of the mattress  14  and so that layer  34  is positioned primarily beneath the heel of the patient when the patient is resting on the mattress  14 . 
     In one embodiment, as shown in  FIGS. 3 and 4 , layers  32   a - 32   d  will be provided assembled together by adhesive into a unitary mattress core. Specifically layer  32   a  may be positioned proximate to the soft face  18   a  and layer  32   d  may be positioned proximate to the firm face  18   b . Layer  32   a  may then have its inner broad surface attached to a first broad surface of layer  32   b  with the second broad surface of layer  32   b  attached to a first broad surface of layer  32   c , and with the second broad surface of layer  32   c  attached to the inner broad surface of layer  32   d.    
     Generally the layers  32  will each have a different firmness, for example, as designated by an indentation force deflection number (IFD), for example, as measured by ASTM D3574 for a uniform volume of material (e.g., a 15″ by 15″ by 4″ foam slab). Preferably, layer  32   a  is softer (lower IFD number) than layer  32   d  and layer  32   b  will be softer than layer  32   c . Layer  32   b , on the other hand, will be harder than layer  32   a , and layer  32   c  will be harder than layer  32   d . Accordingly, a relatively firm middle layer, for example including layers  32   b  and  32   c , which is normally used on the bottom of medical mattresses, is placed in the center of the mattress  14 . Positioning the firm layer in the middle of mattress  14  allows both top and bottom sides of the mattress  14  to provide improved weight capacity and pressure redistribution when used on either face  18   a  or face  18   b.    
     The layers  34  under the patient&#39;s heel will desirably each provide low IFD values so as to reduce point pressures on the patient&#39;s heel. This layer may be of uniform IFD value, for example, comparable to layer  32   a.    
     Layer  34  may be attached in a butt joint to the layers  32  by adhesive. 
     One possible selection of foam values for each layer is provided in the following table: 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE I 
               
               
                   
                   
               
               
                   
                   
                   
                 IFD for standard 
                 Thickness 
               
               
                   
                 Section 
                 Layer 
                 test sample 
                 (inches) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 All 
                 32a 
                 7 
                 1.5 
               
               
                   
                 Head and torso 
                 32b 
                 13 
                 1.5 
               
               
                   
                   
                 32c 
                 75 
                 1.0 
               
               
                   
                   
                 32d 
                 20 
                 2.5 
               
               
                   
                 Heels 
                 34  
                 7 
                 6.5 total 
               
               
                   
                   
               
             
          
         
       
     
     Referring still to  FIG. 3 , the layers  32  and  34  when assembled may be covered by Nomex® or another fire resistant material  40  to provide a burn resistant “sock” which in turn may be covered by a stretchable fabric cover  42  possibly including waterproof qualities. This latter fabric cover  42  may provide for a zipper to allow it to be removed, cleaned, and then re-installed and includes the manufacturer information  31  and firmness designator  30 , described above, printed or embroidered on the outer surface. The cover  42  may, for example, be made of Stafford CPU 150 fabric, commercially available from Stafford Textiles Limited of Toronto, Canada, a stretchable fabric that reduces “hammocking” allowing better pressure redistribution. 
     Referring now to  FIG. 4 , in one embodiment, cover  42  at the portions extending over the sides of the mattress  14  may support hook and loop fastener strips  44  (for example Velcro®) running generally horizontally along the vertically extending left and right edges and head and foot edges of the mattress  14  as stitched thereto. A bottom cover  46  having generally a central rectangular panel equal in area to the area of the soft face  18   a  or firm face  18   b  may have left and right extending flaps and headward and footward extending flaps  54  supporting mating hook and loop strips  55 . In this way, the bottom cover  46  may be attached to either cover the firm face  18   b  when the soft face  18   a  is facing upward to be used by the patient, or to cover the soft face  18   a  when the farm face  18   b  is facing upward to be used by the patient, as held in place by inter-engagement of the strips  55  and  44 . In either configuration of the bottom cover  46 , an outwardly exposed surface of the panel  50  may provide for patches of slip resistant material  56  such as a rubber that will frictionally engage the sections  16  of the bed  10  (shown in  FIG. 1 ) to hold the mattress  14  in place during articulation of the bed  10 . 
     Referring now to  FIG. 5 , in an alternative embodiment, cover  42  may be attached to one vertical edge (a right edge as shown) of each of two rightwardly extending fabric strips  60  seamed at one edge to the cover  42  and having a length to be folded over or under the mattress  14  as indicated by arrows  62 . When so folded, the fabric strips  60  may releasably attach to an opposite edge of the cover  42  by means of hook and loop fasteners  64  on the strips  60  and corresponding hook and loop fasteners  66  on imposed vertical edges of the cover  42 . Both sides of the strips  60  may be coated with a nonskid material  68  such as rubber or the like so that some nonskid material  68  is exposed in either orientation. 
     Referring now to  FIG. 6 , the layers  32   a  and  34  beneath the patient&#39;s heel  70  may be tapered to provide a downward slope  72  toward a foot end  24  of the mattress  14  on the upper surface of the mattress  14  and an upward slope  74  mirroring that of downward slope of  72  on the under surface of the mattress  14  so that in either orientation pressure on the patient&#39;s heel against the mattress  14  is reduced in favor of pressure against a larger surface of the patient&#39;s calf. 
     Referring now to  FIG. 7 , in one embodiment, the left and right edges of the foam layers  32  (and  34 ) may optionally abut side bolsters  76  constructed of a high IFD foam, for example, having a value of  60 . The side bolsters  76  extend the full height and length of the mattress  14  and have a thickness of approximately 2 to 3 inches to provide stiff elements at the side of the mattress  14  that tend to cradle the patient away from the edges of the mattress  14 . The side bolsters  76  may be attached to the other foam layers and positioned inside of the fabric covering of the mattress  14 . 
     An upper cover  80  may be constructed to be similar to the bottom cover  46  and to provide for left and right and foot and head tabs  82  extending away from a center panel  84 . Each of the tabs  82  may include a hook and loop strip  86  attaching to a corresponding hook and loop strip  88  on the vertical walls of the cover  42  to retain the panel  84  against an upper surface of the mattress  14 . Positioned on the left and right edge of the panel  84  near the left and right edge of the mattress  14  may be upwardly extending foam bolsters  90  that assist in retaining the patient centered in the panel  84 . The bolsters  90  may include a central foam element, for example, having a high IFD of  75  and may extend upward by approximately 5 inches. The bolsters  90  may be held against the upper surface of the panel  84  by a fabric covering  92  attached by stitching to the remainder of the cover  80 . In this way the bolsters  90  may be placed on either the soft face  18   a  or the firm face  18   b  according to how the mattress  14  is oriented. 
     In either orientation of the mattress  14 , having the soft face  18   a  upward or the firm face  18   b  upward, the mattress  14  may receive a patient to provide a pressure redistributing surface suitable for sleeping and moderating high-pressure points which may lead to pressure ulcers or the like. The selection of the firmness of the exposed face of the mattress may be made according to a desire to control the concentration of pressure on the surface of the user&#39;s body and/or to provide for support of the patient in the particular posture, for example, to alleviate back pain or the like. In addition, the firmness of the exposed face of the mattress may be selected to control the temperature of the interface between the patient&#39;s skin and the mattress, with a firmer mattress, which is less enveloping, providing a cooler interface. 
     In this regard, it will be appreciated that not only will different users prefer different firmnesses in the mattress, but that a single individual may wish to vary the firmness of the mattress at different times. A single mattress offering two degrees of firmness provides a substantial cost savings in both situations. 
     It will be appreciated that other polymer foams may be used in lieu of polyurethane foam including for example latex foams and so-called “memory foam”. 
     Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. 
     When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. All of the publications described herein, including patents and non-patent publications are hereby incorporated herein by reference in their entireties.