Patent Document

TECHNICAL FIELD 
       [0001]    The subject matter described herein relates to a cover for enhanced in-plane moisture transport. One example application for the cover is on a hospital bed where it may be used in conjunction with a microclimate control topper or as a stand alone mattress cover to help transport moisture away from a region underneath an occupant of the bed thus achieving better control of moisture on the occupant&#39;s skin. 
       BACKGROUND 
       [0002]    Long term occupants of beds, such as patients confined to a hospital bed, are at risk of skin breakdown. Such risks are exacerbated by excessive moisture on the occupant&#39;s skin. Frequently the source of the moisture is the occupant&#39;s own perspiration. One known way to control moisture in contact with the occupant&#39;s skin is to place a microclimate control (MCC) topper between the mattress and the occupant. A typical MCC topper comprises a vapor permeable top side and a bottom side. The sides define an interior cavity having an air inlet and an air outlet. The interior cavity serves as a flowpath for ambient or conditioned air. In operation, a blower propels a stream of air through the flowpath. Occupant perspiration, specifically the gaseous phase of the perspiration, enters the flowpath through the vapor permeable top side. The ambient or conditioned air flowing through the flowpath carries the moisture away. The flowpath thus serves as a moisture sink for moisture in contact with the occupant&#39;s skin. 
         [0003]    Although MCC toppers are effective, their effectiveness is limited by the fact that the source moisture is mostly present in a confined area immediately underneath the occupant. Only those portions of the air stream directly under the moist area are effective at removing the moisture. As a result some of the moisture removal capacity of the topper is unused. 
       SUMMARY 
       [0004]    One embodiment of an occupant support includes an intermediate layer defining at least part of a fluid flowpath and having a vapor permeable occupant side. The occupant support also includes a wicking layer atop the intermediate layer. The wicking layer comprises a first region having a first moisture wick rate and a second region having a second moisture wick rate that exceeds the first moisture wick rate. A moisture management cover described herein is cooperable with an occupant support article having an occupant support side so that the occupant support side and an opposing portion of the cover define a fluid flowpath. The cover has discrete higher and lower wick rate regions. A related method for transporting moisture away from a target region of area A of an occupant support comprises distributing the moisture over an area beyond area A and exposing the distributed moisture to a fluid stream capable of receiving the moisture. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The foregoing and other features of the various embodiments of the moisture transport cover described herein will become more apparent from the following detailed description and the accompanying drawings in which: 
           [0006]      FIG. 1  is a simplified side elevation view of a hospital bed showing a bed frame, a mattress, an intermediate layer in the form of a microclimate control (MCC) topper, and a moisture transport cover, which is also referred to as a wicking layer, in the form of a substantially flat sheet removably secured to the topper by a zipper. 
           [0007]      FIG. 2  is a plan view of the bed of  FIG. 1  showing that the wicking layer has a higher wick rate central region and a lower wick rate perimetrical region. 
           [0008]      FIG. 3  is a simplified perspective view of the bed of  FIGS. 1-2 . 
           [0009]      FIG. 4  is a perspective view of a wicking layer in the form of a fitted sheet. 
           [0010]      FIG. 5  is a view showing the wicking layer nonremovably secured to a topper. 
           [0011]      FIG. 6  is a view in which the wicking layer comprises a wicking material bonded to the topper by a vapor permeable adhesive. 
           [0012]      FIG. 7  is a view in which the wicking layer is a vapor permeable coating applied to a topper. 
           [0013]      FIG. 8  is a view in which the wicking layer is integrated into the topper. 
           [0014]      FIG. 9  is a perspective view showing an embodiment in which an air mattress comprising multiple bladders plays the role of the intermediate layer. 
           [0015]      FIGS. 10-11  are perspective views each showing moisture management covers in isolation, i.e. not in the context of a bed. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Referring to  FIGS. 1-3 , an occupant support such as a hospital bed  20  extends longitudinally from a head end H to a foot end F and laterally from a right side R (seen in the plane of  FIG. 1 ) to a left side L. The bed includes a frame  22 , a mattress  24  supported on the frame, and an intermediate layer  26  in the form of a microclimate control topper  30  resting on the mattress. The topper is referred to as an intermediate layer  26  because of its position between frame  22  and occupant  32 . 
         [0017]    The microclimate control topper  30  has a vapor permeable top or occupant side  36 , whose longitudinal and lateral dimensions are D 1 , D 2 , a bottom side  38 , and an air permeable spacer  40  between the sides. The occupant and bottom sides  36 ,  38  define a fluid flowpath  42  extending longitudinally substantially the length L of the topper. The topper has an inlet  46  and an outlet  48 . A blower, not shown, propels a stream of air  50  through the flowpath. In operation, the occupant&#39;s perspiration, after having transitioned to the gaseous phase, passes through the vapor permeable occupant side  36  and enters the air stream  50 . The air stream carries the moisture away through outlet  48 . In the embodiment of  FIGS. 1-3  topper sides  36 ,  38  of the topper or intermediate layer define the flowpath from inlet  46  to outlet  48 . In another embodiment described below, the intermediate layer only partly defines the flowpath. 
         [0018]    The occupant support also includes a moisture management cover or wicking layer  52 , atop the intermediate layer. At least part of the wicking layer is made of a material exhibiting a high in-plane moisture transport rate, referred to herein as a wick rate. Examples of materials having high wick rates include polypropylene, Meryl Skinlife®, SORBTEK™, and Poro-Tex expanded PTFE (ePTFE). The wicking layer of  FIGS. 1-3  is in the form of a substantially flat sheet having longitudinal and lateral dimensions D 3 , D 4  approximately equal to the longitudinal and lateral dimensions D 1 , D 2  respectively of occupant side  36  of the topper. Although the wicking layer can be a stand-alone moisture management cover, the illustrated wicking layer is attached to the intermediate layer, i.e. to topper  30 , by a zipper  58 , a strip of VELCRO® or other connection that allows the wicking layer to be separated or removed from the topper without causing damage to or destruction of the wicking layer, the topper or the connection therebetween. 
         [0019]    The illustrated wicking layer comprises a first region  62  having a first moisture wick rate W 1  and a second region  64  having a second moisture wick rate W 2  that exceeds the first moisture wick rate. In one embodiment the longitudinal borders of region  64  are laterally extending border  91  located approximately at the occupant&#39;s scapula and border  92  located at about mid-thigh. In another embodiment the borders are border  93  at about midway along the occupant&#39;s back and  94  at about the occupant&#39;s buttocks. First region  62  is a perimetrical region that laterally and longitudinally bounds second region  64 . The second region extends laterally beyond the approximate outline  66  of a supine occupant of the bed. The high wick rate of second region  64  spatially distributes the occupant&#39;s perspiration more readily than would be the case if the wick rate were lower. In particular the high wick rate of region  64  spreads the perspiration beyond the outline  66  of the occupant. More moisture is therefore exposed to air stream  50  resulting in better use of the moisture removal capacity of the topper and an attendant increase in moisture removal from the occupant&#39;s skin. Nevertheless, it is also contemplated that a high wick rate that does not extend laterally beyond the occupant could be beneficial. 
         [0020]    The wicking layer illustrated in  FIGS. 1-3  is in the form of a flat sheet whose dimensions D 3 , D 4  are only slightly larger than topper dimensions D 1 , D 2  so that zipper  58  will not interfere with occupant comfort. The sheet could be made larger so that a considerably larger portion of it drapes over the edge of the topper, or smaller so that it does not completely cover occupant side  36  of the topper. Moreover, forms other than flat are not precluded. For example  FIG. 4  shows the wicking layer in the form of a fitted sheet having elastic corners  70  and/or an elastic edge  72  so that the wicking layer fits snugly on topper  30 . 
         [0021]    Wick rate W 2  may be spatially nonuniform, i.e. the wick rate need not be constant in any given direction. In addition the wick rate, even if constant in any given direction, need not be the same in one given direction as in another given direction. For example it is envisioned that wick rate W 2  could have a value W 2   LONG  in the longitudinal direction and a different, higher value W 2   LAT  in the lateral direction, with at least W 2   LAT  being greater than first wick rate W 1 . Because most occupants are taller than they are wide, the higher wick rate in the lateral direction can quickly transport moisture beyond the left and right edges  74 ,  76  of the occupant outline  66  where that moisture will be exposed to the drying effects of ambient air in addition to being acted on by the internal air stream  50 . The higher lateral wicking rate is therefore believed to be more efficacious than a higher longitudinal wicking rate. 
         [0022]    In  FIGS. 1-4  second region  64  is rectangular which, as used herein, includes the special case of a square, and the wicking layer is removably attached to the intermediate layer (topper  30 ).  FIG. 6A  shows a nonrectangular second region  64 , specifically a substantially circular region. The illustrated nonrectangular region could also be shaped and dimensioned so that distance D from the edge of occupant outline  66  to the edge of second region  64  were approximately constant, or varied depending on typical perspiration rates at different portions of the occupant&#39;s body.  FIGS. 5-8  show alternative architectures. In  FIGS. 5A-5B  the alternative architecture is one in which wicking layer  52  is nonremovably attached to the topper, for example by a stitched seam  80 . In such an arrangement at least the stitching would be destroyed or damaged by the act of separating the wicking layer from the topper. In  FIGS. 6A-6B  the alternative architecture is one in which the wicking layer  52  comprises higher and lower wick rate materials  84 ,  86  bonded to intermediate layer  30  by a vapor permeable adhesive  88 . Alternatively the bond could be effected by spot bonding with a non-vapor permeable adhesive. Higher wick rate region  64  corresponds to the higher wick rate material  84 ; lower wick rate region  62  corresponds to the lower wick rate material  86 . In  FIGS. 7A-7B , the alternative architecture is one in which wicking layer  52  is a vapor permeable higher wick rate coating  100  and a vapor permeable lower wick rate coating  102  applied to the topper. Higher wick rate region  64  corresponds to the higher wick rate coating  100 ; lower wick rate region  62  corresponds to the lower wick rate coating  102 . In  FIGS. 8A-8B  the alternative architecture is one in which wicking layer  52  comprises higher and lower wick rate overlays  106 ,  108  integrated into the topper. Higher wick rate region  64  corresponds to the higher wick rate overlay  106 ; lower wick rate region  62  corresponds to the lower wick rate overlay  108 . 
         [0023]    In the variants of  FIGS. 6-8 , the lower wick rate material  86  ( FIG. 6 ), lower wick rate coating  102  ( FIG. 7 ) and lower wick rate overlay  108  ( FIG. 8 ) could be dispensed with, in which case the portion of occupant side  36  of topper  30  outboard of region  64  could serve as the low wick rate region having a wick rate W 1 . 
         [0024]      FIG. 9  shows an embodiment in which an air mattress  120  comprising multiple bladders  122  plays the role of intermediate layer  26 . Collectively, the bladders define a mattress occupant side  136  and a bottom side  138 . Air discharge apertures  126  penetrate through the occupant side of the mattress. A blower, not shown, supplies pressurized air to inflate the bladders. The moisture management cover or wicking layer  52  rests atop the air mattress. In this embodiment, intermediate layer  26 , as represented by air mattress  120 , only partly defines fluid flowpath  42  for airstream  50 , and is analogous to the bottom side  38  of the topper in the embodiments of  FIGS. 1-3 . The wicking layer itself cooperates with the occupant side of the mattress to define flowpath  42  and is therefore analogous to the occupant side  36  of the topper in the embodiments of  FIGS. 1-3 . Collectively, apertures  126  serve as an inlet analogous to inlet  26  of  FIGS. 1-3 . Air discharges from the flowpath at the edges of the wicking layer. In operation the high wick rate wicking layer causes moisture to spread out over a relatively large area so that it can be more readily carried away by airstream  50 . If the wicking layer is connected to the intermediate layer by an airtight seam, other avenues for air discharge can be provided. 
         [0025]      FIGS. 10-11  shows the wicking layer or moisture management cover  52  in isolation, i.e. without the contextual framework of a hospital bed. The cover is nevertheless capable of being placed atop a companion article such as air mattress  120  of  FIG. 9  or mattress  24  augmented by MCC topper  30  of  FIGS. 1-3 . The moisture management cover has discrete higher and lower wick rate regions  64 ,  62  with wick rates of W 2  and W 1  respectively where W 2  is greater than W 1  ( FIG. 11 ). The moisture management cover can take the form of, for example, a flat sheet (as depicted in  FIG. 10 ) or a fitted sheet (as depicted in  FIG. 11 ). The illustrated cover of  FIG. 10  includes an attachment element or elements, such as zipper  58  so that the moisture management cover can be removably joined to the occupant support article by way of a cooperating attachment element on the occupant support article. Alternatively the moisture management cover could be nonremovably secured to the occupant support article by, for example, continuous or spot stitching. In yet another alternative the cover is devoid of a closure element and is merely placed atop the occupant support article without being secured thereto. As already described previously the high and low wick rate regions of  FIGS. 10-11  can be bonded onto a substrate, can be a coating applied to a substrate or can be integral with the cover. The wick rate can be spatially nonuniform. 
         [0026]    Although the embodiments disclosed herein have a first region with a lower wick rate and a second region with a higher wick rate, more than two regions each having individual, customized wick rates can be used. 
         [0027]    The terms “wicking” and its variants, as used herein to describe the moisture management cover, are intended to convey the notion of moisture transport in the plane of the cover and are not to be interpreted as limited to any particular physical mechanism of moisture transport. 
         [0028]    Although this disclosure refers to specific embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the subject matter set forth in the accompanying claims.

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