# Patent

## Title
Topper with preferential fluid flow distribution

## Abstract

A bed comprises a mattress and a topper resting atop the mattress and extending in longitudinal and lateral directions. The topper has a fluid flowpath having an inlet and an outlet. The flowpath exhibits a nonuniform resistance to fluid flow in at least one of the longitudinal and lateral directions. The bed also includes a blower connected to the inlet for supplying air to the flowpath. The resistance may be a monotonically varying resistance to fluid flow in at least one of the longitudinal and lateral directions and configured to preferentially drive fluid flow through the topper so that a larger proportion of the fluid flowing through the topper flows under a target region and a relatively smaller portion bypasses the target region.

## Background
TECHNICAL FIELD
The subject matter described herein relates to mattress toppers of the kind used in connection with beds, in particular a microclimate control topper having features for preferentially distributing fluid flowing through the topper to locations where fluid flow is expected to be of most benefit to an occupant of the bed.
BACKGROUND
Microclimate control toppers are typically used in conjunction with the mattresses of beds found in hospitals, nursing homes, other health care facilities, or in home care settings. The topper rests atop the mattress and is secured thereto by, for example, straps, snaps or zippers. A fluid flowpath having an inlet and an outlet extends through the interior of the topper. A pump or similar device supplies a stream of air to the topper so that the air flows into the flowpath by way of the inlet, flows through the flowpath, and exhausts from the flowpath by way of the outlet. The airstream establishes a microclimate in the vicinity of the occupant's skin. Specifically, the airstream helps cool the occupant's skin thereby reducing its nutrient requirements at a time when it is compressed by the occupant's weight and therefore likely to be poorly perfused. The airstream also helps reduce humidity in the vicinity of the occupant's skin thus combatting the tendency of the skin to become moist and soft and therefore susceptible to breakdown.
The need for microclimate control is not uniformly distributed over the occupant's skin. For example skin temperature on the occupant's torso can be considerably higher than skin temperature on the occupant's arms and legs. In addition, nonuniform distribution of sweat glands causes perspiration to accumulate on the skin of the occupant's back and pelvic region. Moreover, many modern beds are profile adjustable. When the bed profile is adjusted the occupant's tissue is exposed to shear which distorts the vasculature and further degrades perfusion. This exacerbates the need for microclimate control.
SUMMARY
The subject matter described herein includes a bed comprising a mattress and a topper resting atop the mattress and extending in longitudinal and lateral directions. The topper has a fluid flowpath having an inlet and an outlet. The flowpath exhibits a nonuniform resistance to fluid flow in at least one of the longitudinal and lateral directions. The bed also includes a blower connected to the inlet for supplying air to the flowpath. The resistance may be a monotonically varying resistance to fluid flow in at least one of the longitudinal and lateral directions and configured to preferentially drive fluid flow through the topper so that a larger proportion of the fluid flowing through the topper flows under a target region and a relatively smaller portion bypasses the target region. The subject matter described herein also includes a topper for a bed, the topper extending in longitudinal and lateral directions and including a fluid flowpath having an inlet and an outlet. The flowpath exhibits a nonuniform resistance to fluid flow in at least one of the longitudinal and lateral directions.



BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other features of the variants of the topper described herein will become more apparent from the following detailed description and the accompanying drawings in which:
FIGS. 1-4 are simplified perspective, plan, side elevation and end elevation views of a mattress and a conventional topper having a fluid flowpath extending therethrough.
FIGS. 5-8 are end elevation views of variants of a topper as described herein, each exhibiting a spatially nonuniform resistance to fluid flow through the topper as a result of a spatially nonuniform distribution of the properties of a filler material.
FIG. 9 is a plan view showing a fluid flow pattern representative of the fluid flow pattern attributable to the spatially varying resistance characteristics of the toppers of FIGS. 5-8.
FIGS. 10A and 10B are plan views showing a topper as described herein exhibiting a spatially nonuniform fluid flow resistance as the result of pores or tubules in a filler material which are locally oriented to encourage an airstream to flow in a desired direction and impede it from flowing in other directions.
FIG. 11 is a plan view similar to that of FIG. 9 showing a fluid flow pattern attributable to longitudinally nonuniform fluid flow resistance rather than the laterally nonuniform resistance of FIGS. 5-8.
FIGS. 12-14 are views similar to those of FIGS. 6-8 in which partitions divide the flowpath into channels.
FIG. 15 is a plan view showing a fluid flow pattern representative of the fluid flow pattern attributable to the spatially varying resistance characteristics of the toppers of FIGS. 12-14.
FIGS. 16-17 are end elevation views showing an alternate topper construction comprising an insert and a cover or ticking.



DETAILED DESCRIPTION
FIGS. 1-4 show a conventional topper 20 resting atop a mattress 24. The topper extends longitudinally from a head end 26 to a foot end 28 and spans laterally from a left side 32 to a right side 34. A longitudinally extending centerline 40 and centerplane 42 and a spanwise centerplane 44 are shown for reference. The topper has an upper or occupant side surface 46 and a lower or mattress side surface 48. A target region 50 on upper surface 46 is a region corresponding to a portion of an occupant's body judged to be especially needful of local climate control. The illustrated target region corresponds approximately to the torso of a representative patient lying face up (supine) and centered on the topper. A fluid flowpath 60 having an inlet 62 and an outlet 64 spans laterally across the topper from its left side 32 to its right side 34 and extends longitudinally through the topper. In the illustrated topper inlet 62 is a local inlet port at the foot end of the topper and outlet 64 is a wide vent opening at the head end of the topper. Other inlet and outlet designs may be used.
In the illustrated topper a filler material 70 occupies the flowpath but does not prohibit fluid, particularly air, from flowing through the topper from inlet 62 to outlet 64. Alternatively, the filler material may be absent. A blower 72 or similar device is connected to the inlet by a hose 74 having a blower end 76 and a topper end 78 so that the blower can impel a stream 88 of air to flow through the flowpath. The illustrated topper has no provisions for preferentially directing airstream 88 or any portion thereof to the target region.
FIG. 5 shows a topper 38 whose flowpath exhibits a purposefully nonuniform resistance to fluid flow, specifically to airflow, in the lateral direction. The nonuniformity arises from a filler material 70 which airstream 88 can flow through from inlet 66 to outlet 64 but whose height H varies laterally. Height H is relatively large at centerplane 42, diminishes with increasing distance from the centerplane and then increases with further increase in distance from the centerplane. Resistance to fluid flow and height H are related monotonically, i.e. as height increases, flow resistance decreases and vice versa. Accordingly, although the dominant direction of fluid flow is the longitudinal direction, a greater proportion of airstream 88 flows under the target region than is the case in the conventional topper of FIGS. 1-4. This is evident by comparing the flow pattern of FIG. 9 to that of FIG. 2.
FIG. 6 shows another topper whose flowpath exhibits a purposefully nonuniform airflow resistance in the lateral direction. The nonuniformity arises from a filler material 70 such as a mesh or batting which airstream 88 can flow through from inlet 62 to outlet 64 but whose density varies laterally as signified by the density of the horizontal dashes used to represent the material. The material density is relatively low at centerplane 42 and increases with increasing distance from the centerplane. Resistance to fluid flow and density are related monotonically, i.e. as density increases, flow resistance increases and vice versa. Accordingly, although the dominant direction of fluid flow is the longitudinal direction, a greater proportion of airstream 88 flows under the target region than is the case in the conventional topper of FIGS. 1-4. This is evident by comparing the flow pattern of FIG. 9 to that of FIG. 2.
FIG. 7 shows another topper whose flowpath exhibits a purposefully nonuniform airflow resistance in the lateral direction. The nonuniformity arises from a porous filler material 70 which airstream 88 can flow through from inlet 62 to outlet 64 but whose pore density (pore count per unit area) varies laterally. The pore density is relatively high near centerplane 42, and diminishes with increasing distance from the centerplane. Resistance to fluid flow is related monotonically to pore density, i.e. as pore density decreases, flow resistance increases and vice versa. Accordingly, although the dominant direction of fluid flow is the longitudinal direction, a greater proportion of airstream 88 flows under the target region than is the case in the conventional topper of FIGS. 1-4. This is evident by comparing the flow pattern of FIG. 9 to that of FIG. 2.
FIG. 8 shows another topper whose flowpath exhibits a purposefully nonuniform airflow resistance in the lateral direction. The nonuniformity arises from a porous filler material 70 which airstream 88 can flow through from inlet 62 to outlet 64, whose pore density is constant in the lateral direction, but whose pore size varies laterally. Pore size is relatively large near centerplane 42, and diminishes with increasing distance from the centerplane. Resistance to fluid flow is related monotonically to pore size, i.e. as pore size decreases, flow resistance increases and vice versa. Accordingly, although the dominant direction of fluid flow is the longitudinal direction, a greater proportion of airstream 88 flows under the target region than is the case in the conventional topper of FIGS. 1-4. This is evident by comparing the flow pattern of FIG. 9 to that of FIG. 2.
FIG. 10 shows another topper whose flowpath exhibits a purposefully nonuniform airflow resistance in the lateral direction. The nonuniformity arises from a filler material 70 having flow directing features such as tubules 86 (illustrated) fibers or high aspect ratio (high length/diameter ratio) pores having a length sufficient to influence the direction of fluid flow and which are oriented to encourage the airstream to flow in a desired direction and impede it from flowing in other directions.
Combinations of varying height, material density, pore density, pore size, pore or tubule or fiber orientation and other properties affecting resistance to fluid flow can be used to achieve the above described spatial variation in airflow resistance.
In the foregoing examples the dominant direction of airflow is the longitudinal direction, although it will be appreciated that because of the laterally varying resistance to airflow (i.e. resistance variation perpendicular to the the dominant direction of fluid flow) the fluid streamlines also have a lateral directional component to preferentially drive a relatively larger proportion of the airstream to flow under the target region and a relatively smaller portion to bypass the target region. Alternatively, as seen in FIG. 11, the dominant direction of airflow can be the lateral direction with the fluid streamlines having a more modest longitudinal directional component for preferentially driving a relatively larger proportion of the airstream to flow under the target region and a relatively smaller portion to bypass the target region. In general the resistance varies spatially in a direction substantially perpendicular to a dominant fluid flow direction through the flowpath.
Because the target region is a region corresponding to the torso of an occupant approximately laterally centered on the topper, the flowpaths of the toppers of FIGS. 5-11 exhibit a resistance gradient across the target region such that airflow resistance is lower at relatively more inboard locations and higher at relatively more outboard locations. That is, resistance is relatively lower near centerplane 42 or 44 and increases with proximity to the sides 32, 34 or the head and foot ends 26, 28.
FIGS. 12-14 and 15 illustrate toppers similar to those of FIGS. 6-8 but with longitudinally extending, laterally distributed partitions 92 joined to upper and lower topper surfaces 46, 48. The partitions divide flowpath 60 into longitudinally extending, laterally distributed parallel flow passages each occupied by a filler material. The four dividers in each illustration divide the flowpath into an inboard passage 94, a pair of intermediate passages 96 flanking the inboard passage, and a pair of outboard passages 98 each laterally between an intermediate passage and either the left or right side of the topper. The filler material is selected to impart a relatively low fluid flow resistance to the inboard passage, an intermediate fluid flow resistance to the intermediate passages and a relatively high fluid flow resistance to the outboard passages. These flow resistances are achieved with low, medium and high material density (FIG. 12) high, medium and low pore density (FIG. 13) and large, medium and small pore size (FIG. 14). Thus, airflow resistance differs from passage to passage but in a given passage is constant in the direction in which the passages are distributed, i.e. in the lateral direction. Alternatively a laterally nonuniform flow resistance can be established across each passage if desired. In addition although the illustrated passages are co-flowing passages (fluid flows from the foot end toward the head end in all passages) counter flowing passages can be employed. For example passages 94 and 98 could receive from inlets at their respective foot ends while passages 96 could receive air from an inlet at their head ends. In all cases each passage would have an outlet at its opposite end for exhausting the air.
As already noted in connection with the nonpartitioned embodiments of FIGS. 5-10 the dominant direction of fluid flow can be lateral rather than longitudinal. Similarly, the partitions of the partitioned embodiments of FIGS. 12-14 can be oriented so that they extend laterally and are distributed longitudinally with the result that the dominant direction of fluid flow is lateral rather than longitudinal. In general the passages extend in one direction (longitudinal or lateral) and are spatially distributed in the other direction (lateral or longitudinal) and the flow resistance differs from passage to passage but is constant in any given passage in the direction of passage distribution. Alternatively a nonuniform flow resistance can be established across each passage in the direction of passage distribution if desired.
FIGS. 16-17 shows a possible variation on the construction of the topper. The toppers of FIGS. 16-17 each comprise an insert 110 which exhibits the nonuniform resistance and a cover or ticking 112 that covers the insert. In FIG. 16 the ticking encloses the insert by circumscribing it. In FIG. 17 the ticking covers the insert but does not enclose it as in FIG. 16.
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.

## Claims

1. A topper for a bed, the topper extending in longitudinal and lateral directions and including a fluid flowpath having an inlet and an outlet, the flowpath being occupied by a filler through which fluid can flow and wherein the filler has a varying material density which results in the flowpath exhibiting a nonuniform monotonically varying resistance to fluid flow in the lateral direction, wherein the material density is relatively low at a centerplane of the topper and increases with increasing distance from the centerplane such that a greater proportion of fluid flows under a center region of the topper than a proportion which flows under relatively more outboard regions.

2. The topper of claim 1 in which the resistance varies spatially in a direction substantially perpendicular to a dominant fluid flow direction through the flowpath.

3. The topper of claim 1 in which the flowpath includes fluid flow passages distributed across the lateral direction.

4. The topper of claim 3 in which the resistance differs from passage to passage and is constant in a given passage.

5. A bed comprising:
a mattress;
a topper resting atop the mattress, the topper extending in longitudinal and lateral directions and including a fluid flowpath having an inlet and an outlet, the flowpath being occupied by a filler through which fluid can flow and wherein the filler has a varying material density which results in the flowpath exhibiting a nonuniform monotonically varying resistance to fluid flow in the lateral direction;
wherein the material density is relatively low at a centerplane of the topper and increases with increasing distance from the centerplane such that a greater proportion of fluid flows under a center region of the topper than a proportion which flows under relatively more outboard regions; and
a blower connected to the inlet for supplying air to the flowpath.

6. The bed of claim 5 in which the resistance varies spatially in a direction substantially perpendicular to a dominant fluid flow direction through the flowpath.

7. The bed of claim 5 in which the flowpath includes fluid flow passages distributed across the lateral direction.

8. The bed of claim 7 in which the resistance differs from passage to passage and is constant in a given passage.

9. A bed comprising:
a mattress;
a topper configured to rest atop the mattress, the topper extending in longitudinal and lateral directions and including a fluid flowpath having an inlet and an outlet, the flowpath being occupied by a filler through which fluid can flow and wherein the filler has a varying material density which results in the flowpath exhibiting a nonuniform, monotonically varying resistance to fluid flow in the lateral direction, wherein the material density is relatively low at a centerplane of the topper and increases with increasing distance from the centerplane such that the resistance is configured to preferentially drive fluid flow through the topper so that a larger proportion of the fluid flowing through the topper flows under a center region of the topper and a relatively smaller portion bypasses the center region; and
a blower connected to the inlet for supplying air to the flowpath.

10. The bed of claim 9 in which the resistance varies spatially in a direction substantially perpendicular to a dominant fluid flow direction through the flowpath.

11. The bed of claim 9 in which the flowpath includes fluid flow passages distributed across the lateral direction.

12. The bed of claim 11 in which the resistance differs from passage to passage and is constant in a given passage.