FIELD OF THE INVENTION
[0001] The present disclosure and related inventions are in the general field of engineered
foams for use as a layer in foam mattress constructions.
BACKGROUND OF THE INVENTION
[0002] Solid foams, included closed cell and open cell (reticulated) structures, provide
lightweight cellular engineering materials for weight bearing and distribution (pressure
distribution) and energy absorption. In general, open-cell-structured foams have pores
that are interconnected in a network. The interstitial spaces of open-cell foams can
be filled with gas, liquid or solid material. The density of foam is determined in
part by both the amount of structural material which forms the cells, such as polyurethane,
polyethylene or latex, and the volume or size of the cells.
[0003] Closed-cell foams generally do not have interconnected pores, generally have relatively
higher compressive strength due to the closed cell bubble structures, and are relatively
more dense. The closed-cell structure foams have higher dimensional stability, low
moisture absorption coefficients, and higher strength compared to open-cell-structured
foams. The closed cells can be filled with gases to provide improved insulation, or
with other materials to alter the physical properties of the foam. All types of foam
have been widely used as core material in sandwich structure composite materials.
[0004] A special class of closed-cell foams is known as syntactic foam, which contains hollow
particles embedded in a matrix material. The spheres can be made from several materials,
including glass, ceramic, and polymers. The advantage of syntactic foams is that they
have a very high strength-to-weight ratio, making them ideal materials for many applications,
including deep-sea and space applications. One particular syntactic foam uses shape
memory polymer which enables the foam to take on the characteristics of shape memory
resins and composite materials with hysteresis properties which enable it to be reshaped
repeatedly when heated above a certain temperature and cooled.
[0005] Shape memory foams have been increasingly used in bedding products such as mattresses
and pillows. A significant performance issue and problem with visco-elastic and latex
foam mattresses is the concentration of heat which accumulates during use as a result
of the high density and low thermal conductivity of the foam material.
[0006] Many different variations of solid foams, open and closed cell, have been made in
with different types of fillers have been made. Foams have been which contain gel
material, for example as described in
U.S. Patent No. 4,232,129, and polyurethane gel foams are disclosed in international application
WO 88/01878 (low viscosity liquid) as an additive. International application
WO 2009/070801 discloses gel infused foam formed by surface application of a gel precursor to a
piece of foam.
[0007] Gels are defined as a substantially dilute cross-linked systems which exhibit little
or no flow when in a steady-state. By weight, gels are mostly liquid, yet they behave
like solids due to a three-dimensional cross-linked network within the liquid. Crosslinks
within the fluid create the gelatin structure. Gels are a dispersion of molecules
of a liquid within a solid in which the solid is the continuous phase and the liquid
is the discontinuous phase. Gels consist of a solid three-dimensional network that
spans the volume of a liquid medium and increases surface tension. The network structure
may result from physical bonds (physical gels) or chemical bonds (chemical gels),
as well as crystallites or other junctions that remain intact within the fluid. Different
mediums can be used as an extender including water (hydrogels), oil, and air (aerogel).
Gels are mostly fluid in composition by weight and volume and exhibit densities similar
to those of their constituent liquids.
[0008] Gels, including polyurethane gels provide even pressure distribution and reduced
pressure concentration by deformation in multiple dimensions in response to loads.
Gels have measurable hardness and elastic properties, which can be engineered and
selected for particular applications and uses. Test method ISO 3386-1 provides for
calculation of a compression stress/strain value for gel and a resultant hardness
value. A gel sample (5cm x 5cm x 2.5cm) is compressed to 70%, with hardness measure
as the stress applied (kPa) at 40% compression. Polyurethane gels are known to be
resistant to hardening over time, have limited expandability and are resistant to
degradation.
[0009] In addition to gel as an additive to foam for enhanced mechanical (e.g. shock absorption)
properties, phase change material (PCM) has been combined with foam to enhance or
improve thermal transfer and temperature regulation properties. PCMs are materials
with a high heat of fusion which melt and solidify at particular temperature or temperature
range depending upon the type and purity of the material, and are capable of storing
and releasing large amounts of energy in the phase transition. Heat is absorbed or
released when the material changes from solid to liquid and vice versa. Latent heat
storage can be achieved through solid-solid, solid-liquid, solid-gas and liquid-gas
phase change. However, the only phase change used for PCMs is the solid-liquid change.
Initially, the solid-liquid PCMs behave like sensible heat storage (SHS) materials;
i.e. temperature increases as heat is absorbed. Unlike conventional SHS, however,
when PCMs reach the temperature at which the phase change occurs, heat is absorbed
at an almost constant temperature. Heat absorption continues without a significant
rise in temperature until all the material is transformed to the liquid phase. When
the ambient temperature around a liquid material falls, the PCM solidifies, releasing
its stored latent heat. A large number of PCMs are available in any required temperature
range from -5 up to 190 °C. Within the human comfort range of 20° to 30°C, some PCMs
are very effective, and can store 5 to 14 times more heat per unit volume than conventional
storage materials such as water, masonry or rock.
[0010] PCMs have been applied to fabrics and to thin foam layers as a surface coating for
temperature control, particularly for heat retention and storage properties, as disclosed
for example in
U.S. Patent Nos. 5,290,904 and
5,955,188. The PCM is provided in microsphere encapsulation and mixed with a polymer binder
for adhesion to a substrate.
U.S. Patent No. 5,677,048 discloses coating of skived foam with PCM in a polymer binder dispersion for penetration
of fabric-backed foam.
U.S. Patent No. 6,699,266, discloses use of PCMs with melting temperatures in a range of 18 to 32 degrees Centigrade,
held in a liquid suspension in a support pad to absorb body heat with no appreciable
increase in temperature of the pad. Heat conducted into the support pad from a body
is absorbed by the phase change material, i.e. absorbed as latent heat in the solid-to-liquid
transition of the phase change material.
U.S. Patent No. 5,366,801 discloses a coating of PCM capsules as a textile finish.
U.S. Patent No. 5,637,389 discloses foam with embedded PCM microcapsules. And U.S. patent application
US2004/0234726 discloses polyurethane gel combined with emulsified or finely dispersed phase change
material in the gel.
[0011] Prior art document
US 2009/0142551 A1 discloses an engineered foam for use as a layer in a foam mattress construction according
to the preamble of independent claim 1.
[0012] It is an object underlying the present invention to provide an engineered foam for
use as a layer in a foam mattress construction having improved thermal management
capabilities.
SUMMARY OF THE INVENTION
[0013] The object underlying the present invention is achieved by an engineered foam for
the use as a layer in a foam mattress construction according to independent claim
1. Preferred embodiments are defined in the dependent claims.
[0014] The present invention is of foam mattress constructions made and engineered foams
which contain additives for improved mechanical and thermal properties. In accordance
with one aspect of the disclosure and inventions, there is provided engineered foam
for use as a layer in a foam mattress construction having multiple layers including
a top layer of foam and at least one additional layer of foam, and a coating of phase
change material applied to a top surface of the top layer of foam. Surface application
of phase change material to a top surface of a top layer of foam of a foam mattress
provides more efficient transfer of heat away from a body on the mattress and reduced
heat accumulation at the body-mattress interface. The surface applied phase change
material is micro-encapsulated phase change material in combination with a binder,
and applied to a substantial area of a top surface of a top layer of foam of a mattress.
The surface application of phase change material can be used on any of the foam types
used in mattress construction and aftermarket foam pads, and with foam additives such
as gel or other material in the foam structure. The engineered foams can also be used
in innerspring and pocketed spring mattresses, and as separate foam cushions or layers
outside of mattress upholstery.
In preferred embodiments of the foam mattress constructions, the upper or uppermost
layers of a one-sided mattress are typically made of various types of visco-elastic
or "memory" foam. In each of the preferred embodiments of the foam mattress constructions,
at least one of the upper layers and preferably a top foam layer includes a temperature
control additive. In addition, at least one of the upper layers has a gel material
in the foam, i.e. integrated into the cellular structure of the foam. As further described,
the temperature control additive is preferably in the form of a phase change material,
for example as packaged or contained in micro-capsules or microspheres and applied
to or otherwise integrated with the foam material, but is preferably located substantially
at a surface of the foam and not within the foam structure. In a preferred foam mattress
construction, in addition to the coated top layer, there is at least on intermediate
layer and preferably two intermediate layers and even more preferably two or more
intermediate layers which underlie the top layer. The intermediate layers may be of
the same type of foam or a different type of foam as top layer, and with or without
any gel additive. The intermediate layer or layers may be of the same or greater thickness
than top layer, and when there are two or more intermediate layers the respective
thicknesses may be the same of different.
[0015] These and other aspects of the disclosure and inventions are further described herein
with reference to the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
[0016]
FIG. 1 is a perspective view of an embodiment of a foam mattress of the present disclosure;
FIG. 2 is a partial cross-sectional view of an alternate embodiment of a foam mattress of
the present disclosure;
FIG. 3 is a partial cross-sectional view of an alternate embodiment of a foam mattress of
the present disclosure;
FIG. 4 is a partial cross-sectional view of an alternate embodiment of a foam mattress of
the present disclosure;
FIG. 5 is a partial cross-sectional view of an alternate embodiment of a foam mattress of
the present disclosure;
FIG. 6 is a partial cross-sectional view of an alternate embodiment of a foam mattress of
the present disclosure;
FIG. 7 is a partial cross-sectional view of an alternate embodiment of a foam mattress of
the present disclosure;
FIG. 8 is a partial cross-sectional view of an alternate embodiment of a foam mattress of
the present disclosure;
FIG. 9 is a partial cross-sectional view of an alternate embodiment of a foam mattress of
the present disclosure;
FIG. 10 is a perspective view of an alternate embodiment of a foam mattress construction
of the present disclosure;
FIG. 11 is a perspective view of an alternate embodiment of an innerspring mattress construction
of the present disclosure,
FIG. 12 is an exploded view of an alternate embodiment of a foam mattress construction of
the present disclosure.
DETAILED DESCRIPTION OF PREFERRED AND ALTERNATE EMBODIMENTS
[0017] Novel engineered foams and foam mattress constructions are disclosed which include
engineered foams as layers in foam mattresses. As used herein, the term "engineered
foam" refers to and means the various different types and configurations of described
foams and attendant properties, and the various described additives and treatments
and related methods of manufacturing and processing. Each of the various alternate
embodiments of the foam mattresses are constructed of multiple layers of foam of differing
types, configurations, dimensions, properties and additives or modifiers.
[0018] In preferred embodiments of the foam mattress constructions, the upper or uppermost
layers of a one-sided mattress (wherein top to bottom orientation of the layers remains
the same, with the uppermost layers being the first layers in contact with, proximate
to or initially compressed by a load such as a human body) are typically made of various
types of visco-elastic or "memory" foam with densities in an approximate range of
2.0-8.0 lbs/cu.ft., and an initial force deflection (IFD, 25% indentation) in an approximate
range of 10 to 20 lbs. As used herein, the terms "upper layer", "upper layers", "comfort
layers" and "top layer" and "topper" all refer to and mean the one or more layers
of a foam mattress construction which are located in an upper or uppermost region
of the mattress, proximate to or forming the support surface of the mattress, and
supported by one or more intermediate layers and a one or more base layers or core
layers, which generally has an aggregate thickness dimension greater than a thickness
dimension of the upper layers.
[0019] In each of the preferred embodiments of the foam mattress constructions, at least
one of the upper layers and preferably a top foam layer includes a temperature control
additive. In addition, at least one of the upper layers has a gel material in the
foam, i.e. integrated into the cellular structure of the foam. As further described,
the temperature control additive is preferably in the form of a phase change material,
for example as packaged or contained in micro-capsules or microspheres and applied
to or otherwise integrated with the foam material, but is preferably located substantially
at a surface of the foam and not within the foam structure. The phase change material
(PCM) may be of the paraffinic hydrocarbon type as listed in Table I, and preferably
contained or encapsulated within microspheres (also referred to as "micro-capsules"),
which may range in diameter from 1 to 100 microns. Polymeric microspheres containing
paraffinic wax or n-octadecane or n-eicosane are commercially available and are suitable
for combination with foam, either as an additive in any area or region of a particular
piece or layer of foam, or as a surface coating, for example when contained in a water
based acrylic-latex coating which can be applied to a foam surface by spraying or
roll coating to any desired thickness or density, such as for example in the range
of 50-100 g/m
2. The paraffinic wax can be selected or blended to have a desired melt temperature
or range. The polymer for the microspheres is selected for compatibility with the
foam material. For the described mattress applications and constructions, a preferred
PCM has a phase transition temperature range is 28-32 degrees C, such as are commercially
available from Outlast Technologies, Inc.
[0020] In a representative embodiment of a foam mattress constructed with engineered foams
including phase change material, a foam mattress
10 as shown in
FIG. 1 has an uppermost or top layer or top layer
100 (also referred to herein as "PCM coated layer" and "top layer of foam") which is
made of a visco-elastic foam with a density in an approximate range of 4.0 to 8.0
lbs./cu.ft. and an IFD (25% indentation) in an approximate range of 10 to 20 lbs.
In the preferred embodiments at least one side of the top layer
100 has a convoluted surface, i.e. non-planar which is oriented downward to face the
underlying layers of the mattress
10. However, the disclosure also includes top layers, and other layers which are planar
on both sides. On a top surface of the top layer
100, an area
101 is a prescribed area in which a PCM is applied by sprayed, rolled or other mode of
application as a relatively thin layer or coating, referred to generally herein as
"PCM coating". The area
101 is illustrated as somewhat less than the total surface area of the top layer
100, but can alternatively be equal to the total surface area of top layer
100. The PCM is in the described microcapsule encapsulation form, and in combination with
an adhesive or binding agent (or "binder") which adheres the PCM microcapsules to
the surface of top layer
100. The PCM microspheres are mixed with an acrylic binder that makes up 55% of the solids,
for example in a mixed liquid formulation which is sprayed onto the foam surface.
The foam with the applied PCM can then be passed under heaters to evaporate the liquid
carrier from the surface.
[0021] A preferred thickness of the applied PCM layer is on the order of approximately 50-100
mils or greater, and may be varied in accordance with the concentration of PCM microcapsules,
the type of PCM in the microcapsules, and the amount of heat absorption desired. It
is preferred that the PCM coating layer reside primarily and substantially at the
surface of top layer
100, although some penetration of the PCM into the top layer
100 is acceptable. This configuration maximizes the thermal transfer and heat sink efficiency
of the PCM with a body in contact with top layer
100. In a further alternate embodiment, the top layer
100 is substantially impregnated with PCM, either by application to one or both surfaces
of the layer
100, or integrated into the foam structure in the manufacturing process. These alternate
embodiments are more suitable for the foam mattress constructions in which the top
layer
100 has a relatively small thickness dimension, for example 2 inches or less, whereby
the PCM in the top layer
100 is present in sufficient quantity and held in close proximity to a body in contact
with the top layer
100 for efficient thermal transfer.
[0022] A further advantage of the topical layer, coating or surface application of PCM to
the top layer
100 of a foam mattress is that the PCM is present in an effective amount or concentration
without altering the support characteristics or feel of the foam. The top layer 100
retains all of its compression, resilience and support properties which are effectively
unaltered by the relatively thin layer or PCM. Furthermore there is no degradation
of the foam structure, and no surface tension is created which alters the firmness
or feel of the top layer
100. The area
101 of the PCM coating or layer is sufficient to be in thermal contact with one or more
bodies on the mattress
10 and to effectively absorb heat from the body or bodies, i.e. to undergo the phase
transition without an appreciable increase in the temperature at the surface of top
layer
100. The size, shape and thickness of area
101 of the foam top layer
100 can be varied for any desired thermal performance on any size or type of foam mattress,
or with any type of mattress (foam or innerspring or other non-foam core or components).
Multiple areas or zones of surface applied PCM may be formed on top layer
100. Applying PCM as a coating to an area or areas within the boundaries of top layer
100 results in concentration of PCM enhances the thermal transfer efficiency. Application
by template or controlled spray provides precise control and tolerances and is adaptable
to any size mattress. Preferably the PCM does not penetrate into the foam structure
no more than 1 to 2 mm.
[0023] A particular advantage of the surface application or coating of PCM on the top layer
of a foam mattress construction is the absorption of heat from one or more bodies
on the mattress and reduction in the increase of the surface temperature of the mattress.
With the PCM in the closest possible proximity to the body heat source, the transfer
of heat into the foam of the mattress is retarded. The foam of the mattress thus receives
and stores a lesser amount of heat. As the mattress cools, the stored heat is released
from the PCM more efficiently than heat from a non-PCM coated foam mattress. The PCM
surface coating
101 can be applied to any layer of a foam mattress of any configuration. For example,
in a foam mattress with a top layer with relatively thin thickness of for example
one inch, PCM may be applied to an underside of such layer and provide the described
thermal functions. Alternatively, both sides of one or more foam layers of a mattress
may be coated with PCM in the same or different patterns. Also, differing types of
PCM materials may be surface applied to the same or opposing sides of one or more
foam layers. Blends of different PCM materials may be surface applied, either in a
single application or as applied layers. A further advantage of surface application
of PCM over infusion, impregnation or knife-over-roller application is, in addition
to achieving the desired thermal effects, the application is faster than these other
methods and the distribution of PCM on the foam is more precise and uniform, and the
even distribution is not dependent upon or affected by the internal cellular structure
of the foam. PCM surface coating can be applied to any type of foam which is suitable
for use in a foam mattress, or to any foam layers of any type of mattress such as
innerspring or pocketed coil spring mattresses.
[0024] One or more layers of the foam mattress constructions of the present disclosure may
be comprised of foam material, such as visco-elastic foam including for example natural
or synthetic latex, polyurethane or polyethylene foams, and gel such as polyurethane
gels, preferably in particular form. In a preferred embodiment, the gel containing
foam layer of layers of a foam mattress construction is comprised of any of the disclosed
foam materials with discrete particles of gel interspersed and generally evenly distributed
throughout the foam structure or cellular network. The gel particles may range in
size from less than 1mm to greater than 5mm in diameter. Substantially even distribution
of gel particles throughout the foam structure produces a hybrid material in which
the physical properties of the foam and gel, including hardness, density, energy absorption
and thermal conductance are combined. To the extent that the mechanical properties
of the foam and gel differ, the combination of the two materials produces a hybrid
material with hybrid properties. For example, a visco-elastic foam with particular
density and hardness properties will correspondingly deform at a particular rate under
a load. The presence of a dispersed gel additive (the density of which is generally
greater than that of foam, e.g. in a range of 600 to 1100 kg/m
3), for example in particle form, in the same foam can alter the rate and degree of
deformation as well as the recovery rate (memory) when unloaded.
[0025] The thermal properties of gel are also employed when present as an additive in particulate
or other form in the foam, and in combination with PCM applied to a surface of the
foam. In general, gel has greater thermal conductivity than foam, and the thermal
conductivity can be altered by use of certain fillers. In the engineered foams and
foam mattress constructions of the present disclosure, the thermal conductivity of
the PCM coating applied to the top layer 100 can be selected, matched or balanced
with reference to the thermal conductivity of the foam and/or the thermal conductivity
of the gel in top layer
100 for the desired thermal management properties. In this aspect of the disclosure,
the thermal conductivity of the PCM corresponds to the thermal conductivity of the
foam of the foam layer to which the PCM is applied, and/or to the gel in the foam
layer to which the PCM is applied.
[0026] According to the invention, the thermal conductivity of the gel in the top layer
of foam is matched with the thermal conductivity of the foam of the top layer of foam
and the thermal conductivity of the phase change material.
[0027] In the various embodiments of the foam mattress constructions
10 shown in
FIGS. 2-9, additional foam layers are provided in combination with the top layer
100 with the PCM coating layer
101. Any of the various layers may be planar on one or both sides, or convoluted or otherwise
contoured on one or both sides. The layers of the foam mattresses are referenced in
groups as core layers
C1-Cn, intermediate layers
I1-In, top layer
100. Gel is depicted in particulate form at
G in
FIGS. 2-9. In a preferred foam mattress construction, in addition to the PCM coated top layer
100, there is at least on intermediate layer
I and preferably two intermediate layers and even more preferably two or more intermediate
layers which underlie the top layer
100. The intermediate layers may be of the same type of foam or a different type of foam
as top layer
100, and with or without any gel additive. The intermediate layer or layers
I may be of the same or greater thickness than top layer
100, and when there are two or more intermediate layers the respective thicknesses may
be the same of different, as illustrated.
[0028] A preferred core construction of layers
C1-C3 includes relatively thick layers
C1 and
C3, each having a planar side and a non-planar side such as convoluted, with the non-planar
sides in an opposing arrangement, and a medial core layer
C2 which is planar and of substantially less thickness. The relative thicknesses of
layers
C1 and
C3 may be the same of different as illustrated. Representative total thickness dimensions
for layers
C1 and
C3 range from approximately 2 to 6 inches with a density of approximately between 2
to 2.25 lb/ft
3, preferably 2.05 lb/ft
3. Representative thickness dimension for the medial core layer
C2 is in the approximate range of 0.5 to 2 inches. The core layers
C1 and
C3 can also be configured with full thickness dual planar edge regions, indicated at
105 (shown in
FIG. 1), which provide increased foam density and rigidity along the longitudinal edges of
the mattress. Alternatively, as shown in
FIG. 12, a planar insert
1051 can be provided at the edges, such as the longitudinal edges of layer
C3 to provide greater hardness or rigidity in that region, and a flush planar wall construction
of layers
C3 and
I1, alternatively, optionally, or additionally along the longitudinal edge of layer
C1, as shown in
FIGS. 1 and
11.
[0029] FIG. 11 illustrates an alternate embodiment of a mattress of the disclosure wherein layers
100 and
I1 are combined with an innerspring
200. The innerspring
200 or spring core may be any type of innerspring which has a plurality of springs, such
as coil springs or the like, which are arranged in a matrix and interconnected either
by wire or other material such as fabric, such as pocketed or encased coils.
[0030] Covering or upholstery for the different types of mattresses are illustrated in
FIGS. 1, 10 and
11, indicated at
U, enclosing the described foam constructions and other internal components such as
innerspring or pocketed coils. As shown in
FIG. 10, a PCM coated top layer
110 can be used external to the upholstery
U of a mattress, which supplied for example as an accessory or an aftermarket product
for use with a mattress. This provides the improved thermal properties and additional
support of top layer
110 in combination with any mattress.