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's skin.
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's skin. Frequently the source of the moisture is the occupant's own perspiration. One known way to control moisture in contact with the occupant'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's skin.
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.
US Patent Application Publication No. 2007/0261548 discloses a MCC topper in which the vapor permeable top side has a first region with a first permeability and a second region having a second permeability, wherein the second permeability is greater than the first permeability so that vapor transfers through the vapor permeable top side at a higher rate in the second region.
The invention is defined by the claims.
The invention will now be further described by way of example with reference to the accompanying drawings, in which:
- 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.
- 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.
- FIG. 3 is a simplified perspective view of the bed of FIGS. 1-2.
- FIG. 4 is a perspective view of a wicking layer in the form of a fitted sheet.
- FIG. 5 is a view showing the wicking layer nonremovably secured to a topper.
- FIG. 6 is a view in which the wicking layer comprises a wicking material bonded to the topper by a vapor permeable adhesive.
- FIG. 7 is a view in which the wicking layer is a vapor permeable coating applied to a topper.
- FIG. 8 is a view in which the wicking layer is integrated into the topper.
- FIG. 9 is a perspective view showing an embodiment in which an air mattress comprising multiple bladders plays the role of the intermediate layer.
- FIGS. 10-11 are perspective views each showing moisture management covers in isolation, i.e. not in the context of a bed.
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.
The microclimate control topper 30 has a vapor permeable top or occupant side 36, whose longitudinal and lateral dimensions are D1, D2, 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'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.
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 D3, D4 approximately equal to the longitudinal and lateral dimensions D1, D2 respectively of occupant side 36 of the topper. Although the wicking layer can form part of 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.
The illustrated wicking layer comprises a first region 62 having a first moisture wick rate W1 and a second region 64 having a second moisture wick rate W2 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's scapula and border 92 located at about mid-thigh. In another embodiment the borders are border 93 at about midway along the occupant's back and 94 at about the occupant'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'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's skin. Nevertheless, it is also contemplated that a high wick rate that does not extend laterally beyond the occupant could be beneficial.
The wicking layer illustrated in FIGS. 1-3 is in the form of a flat sheet whose dimensions D3, D4 are only slightly larger than topper dimensions D1, D2 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.
Wick rate W2 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. The wick rate W2 has a value W2LONG in the longitudinal direction and a different, higher value W2LAT in the lateral direction, with at least W2LAT being greater than first wick rate W1. 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.
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'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. In one embodiment (not shown), the overlays 106, 108 form the top wall of the topper 52.
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 W1.
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.
FIGS. 10-11 shows 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 W2 and W1 respectively where W2 is greater than W1 (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.
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.
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.
The terms "moisture management cover" and "wicking layer" are used somewhat interchangeably herein but as will be appreciated, at least one embodiment is disclosed where a moisture management cover includes a wicking layer and where there is a wicking layer but not a stand alone moisture management cover.
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.