Patent Publication Number: US-10765228-B2

Title: Body support cushion having multiple layers of phase change material

Description:
CLAIM TO PRIORITY 
     This continuation patent application claims priority to and benefit of, under 35 U.S.C. § 120, U.S. patent application Ser. No. 14/417,702, filed Jun. 17, 2015 and titled “Body Support Cushion Having Multiple Layers Of Phase Change Material”, which is a national stage entry of PCT Application No. PCT/US2012/048669, filed on Jul. 27, 2012, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to body support cushions such as those found in mattresses, pillows, office chairs, household furniture, ear seating, theater seating; and the like. 
     As is generally the case with all body support cushions, but particularly so with mattresses consisting of “memory foam” or other body conforming material, the effectiveness of the cushion in providing body support is partly a function of how well the memory foam responds to the contour of the user resting on the cushion. Body support cushions made from temperature-sensitive viscoelastic material, such as TEMPUR® material that is commercially available from Tempur-Pedic International Inc., for example, are able change shape based in part upon the temperature of the supported body part. This conformance of the cushion to the body, in effect, causes more of the body to be in contact with the body support cushion. Thus, as the cushion cradles the supported body part, more of the body part that is supported by the cushion. Since more of the body is in contact with the cushion, rather than being pushed above it, less of the body that is exposed to ambient air around the cushion. As a consequence, many users find memory foam mattresses and other memory foam cushions to “sleep hot” and, ultimately, choose other types of cushions notwithstanding the supportive benefits often associated with memory foam and similar types of body conforming cushions. 
     In an effort to attract users with concerns of “sleeping hot” in a memory foam mattress, many mattress manufactures have incorporated, so-called “cooler” technologies into their products. For example, many mattresses now come with covers containing latent heat storage units, such as phase change material (PCM), that provide a cool, albeit brief, dermal sensation. One such phase change material is OUTLAST®, which is commercially available from Outlast Technologies, Boulder, Colo. While the use of such PCM does provide: some cooling, it is short-lived because in relatively short order the PCM will absorb heat from the supported body part and hold that heat until the supported body part is withdrawn. 
     Another approach to providing a. “cooler” mattress has been in the inclusion of gel or similar material into the construction of the bed. Gel, similar to PCM, has some latent heat properties that provide a momentary dermal sensation of coolness. However, gel-like PCM, can only absorb so much heat before the gel becomes saturated and thus is no longer cool to touch. Further, once the gel is heated, it will hold that heat until the heat source, i.e., body, is removed. 
     Additional efforts to provide a “cooler” memory foam cushion have included the use of cooling blankets, such as the ChiliPacp&#39;M mattress pad from Chili Technology, Mooresville, N.C. Not only to do such blankets add to the overall cost of the cushion, but they can negatively impact the feel of the cushion as well. Moreover, such blankets require a pump to circulate coolant, e.g., water, and thus incorporate electromechanical devices that can fail and render the after-market blanket inoperable. 
     Based at least in part upon the limitations of existing cooling technologies and the demand from some consumers for a cooler memory foam body support cushion, new body support cushions are welcome additions to the art. 
     SUMMARY OF THE INVENTION 
     The present invention is generally directed to a multi-layer foam cushion enclosed within an outer cover. Portions of the outer cover and the foam cushion comprise PCM to provide an extended cool dermal sensation to a user resting on the cushion. In some alternate embodiments of the invention, the Multi-layer foam cushion has one or more layers of viscoelastic polyurethane foam and one or more layers of high resilience (HR) foam. In yet other embodiments of the invention, one or more layers of the multi-layer construction may include reticulated viscoelastic foam. 
     Other objects, features, aspects, and advantages of the invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a sleep system having a body support cushion according on an embodiment of the invention. 
         FIG. 2  is a section view of the body support cushion taken along line  2 - 2  of  FIG. 1 . 
         FIG. 2A  is a section view of the body support cushion taken along line A-A, of  FIG. 2 . 
         FIG. 3  is an isometric view of a body support cushion according to another embodiment of the invention. 
         FIG. 4  is a section view of the body support cushion taken along line  4 - 4  of  FIG. 3 . 
         FIG. 4A  is a section view of the body support cushion of  FIG. 4  taken along line A-A of  FIG. 4 . 
     
    
    
     Before the various embodiments of the present invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that phraseology and terminology used herein with reference to device or element orientation (such as, for example, terms like “front”, “back”, “up”, “down”, “top”, “bottom”, and the like) are only used to simplify description of the present invention, and do not alone indicate or imply that the device or element referred to must have a particular orientation. In addition, terms such as “first”, “second”, and “third” are used herein and in the appended claims for purposes of description and are not intended to indicate or imply relative importance or significance. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and variations thereof herein are used broadly and encompass direct and indirect connections and couplings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings. 
     DETAILED DESCRIPTION 
     The present invention will be described with respect to a body support cushion in the form of a mattress for use with a sleep system but it should be understood that the invention can be embodied in other types of support cushions, including but not limited to, pillows and seat cushions. 
     Turning, now to  FIG. 1 , sleep system  6  is generally comprised of a foundation  8  and a mattress  10 . The foundation  8  and the mattress  10  are supported in a raised position by a frame (not shown) as known in the art. The foundation  8  is of known construction and thus will be not be described in greater detail herein; however, it should be noted that the mattress  10  could be used with other types of mattress supports, such as box springs or tables. 
     With additional reference to  FIG. 2 , mattress  10  according to an embodiment of the present&#39; invention generally consists of three discrete, yet integrated components: a comfort foam system  12 , a support foam system  14 , and an outer cover system  16 . The comfort foam system  12  includes a top comfort layer  18  comprising open-celled non-reticulated viscoelastic foam (sometimes referred to as “memory foam” or “low resilience foam”) and a bottom comfort layer  20  comprising open-celled reticulated viscoelastic foam. The top comfort layer  18  and the bottom comfort layer are secured to another by adhesive or cohesive bonding material  22 . In a similar manner, the bottom comfort layer  20  is secured to the support foam system  14  using a suitable bonding material  22 . In one embodiment, the bonding material used to bond the two comfort layers together is the same that is used to bond the comfort foam system  12  to the support foam system  14 , but the invention is not so limited. Also, other types of bonding devices may be used to secure the foam layers together. For example, the top and bottom layers  18 ,  20  can be bonded together by tape, hook and loop fastener material, conventional fasteners, stitches extending at least partially through the top and bottom layers  18 ,  20 , or in any other suitable manner. 
     In one embodiment of the invention, the top comfort layer  18  is made of non-reticulated viscoelastic foam and the bottom comfort layer  20  is made of reticulated viscoelastic foam. In other embodiments, both of the aforementioned layers are made of reticulated viscoelastic foam. In yet other embodiments, both layers are made of non-reticulated viscoelastic foam. It is also contemplated that the top comfort layer  18  could be formed of reticulated viscoelastic foam. It is also contemplated that one or more of the comfort layers may be comprised of non-viscoelastic material. 
     Each of the top and bottom, layers  18 ,  20  can be substantially flat bodies having substantially planar top and bottom surfaces  24 ,  26 ,  28 , and.  30  as shown in  FIG. 2 . However, in other embodiments, one or more of the top and bottom surfaces  24 ,  26 ,  28 ,  30  of either or both top and bottom layers  18 ,  20  can be non-planar, including without limitation surfaces having ribs, bumps, and other protrusions of any shape and size, surfaces having grooves, dimples, and other apertures that extend partially or fully through the respective layer  18 ,  20 , and the like. Also, depending at least in part upon the application of the mattress  10  (i.e., the product defined by the mattress  10  or in which the mattress  10  is employed), either or both of the top and bottom layers  18 ,  20  can have shapes that are not flat. By way of example only, either or both layers  18 ,  20  can be generally wedge-shaped, can have a concave or convex cross-sectional shape, can have a combination of convex and concave shapes, can have a stepped, faceted, or other shape, can have a complex or irregular shape, and/or can have any other shape desired. 
     As illustrated in  FIGS. 1 and 2 , in one embodiment, the top comfort layer  18  provides a relatively soft and comfortable surface for a user&#39;s body or body portion (hereinafter referred to as “body”). Coupled with the slow recovery characteristic of the viscoelastic foam, the top comfort layer  18  can also conform to a user&#39;s body, thereby distributing the force applied by the user&#39;s body upon the top comfort layer  18 . In some embodiments, the top comfort layer  18  has a hardness of at least about 30 N and no greater than about 175 N for desirable softness and body-conforming qualities. In other embodiments, a top comfort layer  18  having a hardness of at least about 40 N and no greater than about 160 N is utilized for this purpose. In still other embodiments, a top comfort layer  18  having a hardness of at least about 40 N and no greater than about 75 N is utilized. In one preferred embodiment, the top comfort layer  18  has a hardness of 48 N. Unless otherwise specified, the hardness of a material referred to herein is measured by exerting pressure from a plate against a sample of the material having length and width dimensions of 40 cm each (defining a surface area of the sample of material), and a thickness of 5 cm to a compression of 40% of an original thickness of the material at approximately room temperature (e.g., 21-23 Degrees Celsius), wherein the 40% compression is held for a set period of time, following the International Organization of Standardization (ISO) 2439 hardness measuring standard. 
     The top comfort layer  18  can also have a density providing a relatively high degree of material durability. The density of the foam in the top comfort layer  18  can also impact other characteristics of the foam, such as the manner in which the top comfort layer  18  responds to pressure, and the feel of the foam. In some embodiments, the top comfort layer  18  has a density of no less than about 25 kg/m 3  and no greater than about 150 kg/m 3 . In Other embodiments, a top comfort layer  18  having a density of at least about 40 kg/m 3  and no greater than about 125 kg/m 3  is utilized. In still other embodiments, a top comfort layer  18  having a density of at least about 60 kg/m 3  and no greater than about 115 kg/m 3  is utilized. In one preferred embodiment, the top comfort layer  18  has a density of 60 kg/m 3 . 
     The viscoelastic foam of the top comfort layer  18  can be selected for responsiveness to any range of temperatures. However, in some embodiments, a temperature responsiveness in a range of a user&#39;s body temperatures (or in a range of temperatures to which the mattress  10  is exposed by contact or proximity to a user&#39;s body resting thereon) can provide significant advantages. For example, a viscoelastic foam selected for the top comfort layer  18  can be responsive to temperature changes above at least about 0° C. In some embodiments, the viscoelastic foam selected for the top comfort layer  18  can be responsive to temperature changes within a range of at least about 10° C. In other embodiments, the viscoelastic foam selected for the top comfort layer  18  can be responsive to temperature changes within a range of at least about 15° C. 
     As used herein and in the appended claims, a material is considered “responsive” to temperature changes if the material exhibits a change in hardness of at least 1.0% measured by ISO Standard 3386 through the range of temperatures between 10 and 30 degrees Celsius. 
     The bottom comfort layer  20  is similar to the top comfort layer  18  in that is made of viscoelastic material. However, in a preferred embodiment, the bottom comfort layer  20 , unlike the top comfort layer  18 , is made of reticulated viscoelastic polyurethane foam. That is, while top comfort layer  18  and the bottom comfort layer  20  each comprise a cellular structure of flexible viscoelastic polyurethane foam in which the walls of the individual cells are substantially intact, the bottom comfort layer  20  comprises reticulated viscoelastic foam. As described in U.S. Ser. No. 11/265,410 (published as U.S. Publ. No. 2006/0288491), which is assigned to the Assignee of this application and which the disclosure thereof is incorporated herein in its entirety, the cells of reticulated foams are essentially skeletal structures in which many (if not substantially all) of the cell walls separating one cell from another do not exist. In other words, the cells are defined by a plurality of supports or “windows” and by no cell walls, substantially no cell walls, or by a substantially reduced number of cell walls. Such a cellular foam structure is sometimes referred to as “reticulated” foam. In some embodiments, a foam is considered “reticulated” if at least 50% of the walls defining the cells of the foam do not exist (i.e., have been removed or were never allowed to form. during the manufacturing process of the foam). 
     Also, in some embodiments it is desirable that the bottom comfort layer  20  of reticulated viscoelastic foam be capable of providing some degree of support that is substantially independent of temperatures experienced by the top comfort layer  18  when supporting a user&#39;s body (i.e., independent of a user&#39;s body heat). Therefore, it is contemplated that the bottom comfort layer  20  can comprise reticulated viscoelastic foam that is responsive to temperature changes within a range of between about 10° C. and about 35° C. In some embodiments, the bottom comfort layer  20  can comprise reticulated viscoelastic foam that is responsive to temperature changes within a range of between about 15° C. and about 30° C. In still other embodiments, the bottom comfort layer  20  comprising reticulated viscoelastic foam that is responsive to temperature changes within a range of between about 15° C. and about 25° C. can be used. It is also contemplated that the comfort layer  20  could be reticulated non-viscoelastic foam, such as reticulated high resiliency foam. 
     By virtue of the skeletal cellular structure of the bottom comfort layer  20 , heat in the top comfort layer  18  can be transferred away from the top comfort layer  18 , thereby helping to keep a relatively low temperature in the top comfort layer  18 . Also, the reticulated viscoelastic foam of the bottom comfort layer  20  can enable significantly higher airflow into, out of, and through the bottom comfort layer  20 —a characteristic of the bottom comfort layer  20  that can also help to keep a relatively low temperature in the top comfort layer  18 . Additionally, since the bottom comfort layer  20  contains viscoelastic material, the bottom comfort layer  20  of the comfort system  12  also provides the performance benefits often associated with viscoelastic foam; namely, the distribution of force applied thereto. 
     Like the top comfort layer  18 , the bottom comfort layer  20  can have a density providing a relatively high degree of material durability. Also, the density of the foam in the bottom comfort layer  20  can also impact other characteristics of the foam, such as the manner in which the bottom comfort layer  20  responds to pressure, and the feel of the foam. In. some embodiments, the bottom comfort layer  2 ) has a density of no less than about 20 kg/m 3  and no greater than about 130 kg/m 3 . In other embodiments, a bottom comfort layer  20  having a density of at least about 25 kg/m 5  and no greater than about 150 kg/m 3  is utilized. In still other embodiments, a bottom comfort layer  20  having a density of at least about 30 kg/m 3  and no greater than about 150 kg/m 3  is utilized. In a preferred embodiment, the bottom comfort layer  20  has a density of 85 kg/m 3 . 
     Also, in some embodiments, the bottom comfort layer  20  has a hardness or at least about 50 N and no greater than about 150 N. in other embodiments, a bottom comfort layer  20  having a hardness of at least about 40 N and no greater than about 100 N is utilized. In still other embodiments, a bottom comfort layer  20  having a hardness of at least about 40 N and no greater than about 80 N is utilized. In a preferred embodiment, the bottom comfort layer  20  has a hardness of 60 N. 
     In one embodiment, the mattress  10  can have a bottom comfort layer  20  that is at least as thick as the top comfort layer  18 , e.g., 5 cm. However, it is contemplated that the layers  18 ,  20  could have different thickness. For instance, the top comfort layer  18  could have a thickness that is less than or greater than the thickness of the bottom comfort layer  20 . In one embodiment, the top comfort layer  18  has a thickness of S cm and the bottom comfort layer  20  has a thickness of 0.5 cm. 
     In the illustrated embodiment, the support system  14  also includes two foam layers: a top support layer  32  and a bottom support layer  34 . Each of the top and bottom support layers  32 ,  34  can be substantially flat bodies having substantially planar top and bottom surfaces or, as shown in  FIG. 2 , convoluted top surfaces  36 ,  40  and planar bottom surface  38 ,  42 . In addition to. the illustrated convolutions, other non-planar shapes are contemplated, including without limitation, surfaces having ribs, bumps, and other protrusions of any shape and size, surfaces having grooves, dimples, and other apertures that extend partially or fully through the respective layer  32 ,  34 , and the like. Also, by way of example only, either or both layers  32 ,  34  can be generally wedge-shaped, can have a concave or convex cross-sectional shape, can have a combination of convex and concave shapes, can have a stepped, faceted, or other shape, can have a complex or irregular shape, and/or can have any other shape desired. 
     The support layers  32 ,  34  are preferably made of high resiliency (HR) polyurethane foam and provide support for the support comfort system  12 . Alternately, the support layers  32 ,  34  are made of conventional foam. Preferably the support layers  32 ,  34  have a minimum ball rebound of  50 . The support layers  32 ,  34  can independently have a reticulated or non-reticulated cellular structure. It is also contemplated that the support layers may be made from other types of foams. In one embodiment, the support layers  32 ,  34  each have a hardness of at least about 100 N and no greater than about 300 N for desirable support. In other embodiments, support layers  32 ,  34  each having a hardness of at least about 125 N and no greater than about 200 N is utilized for this purpose. In still other embodiments, support layers  32 ,  34  each having a hardness of at least about 150 N and no greater than about 175 N is utilized. In a preferred embodiment, each support layer  32 ,  34  has a hardness of 150 N. Unless otherwise specified, the hardness of a material referred to herein is measured by exerting pressure from a plate against a sample of the material having length and width dimensions of 40 cm each (defining a surface area of the sample of material), and a thickness of 5 cm to a compression of 40% of an original thickness of the material at approximately room temperature (e.g., 21-23 Degrees Celsius), wherein the 40% compression is held for a set period of time, following the International Organization of Standardization (ISO) 2439 hardness measuring standard. 
     The support layers  32 ,  34  can also have a density providing a relatively high degree of material durability. The density of the foam in the support layers  32 ,  34  can also impact other characteristics of the foam, such as the manner in which the support layers  32 ,  34  responds to loading. In some embodiments, the support layers  32 ,  34  each has a density of no less than about 15 kg/m 3  and no tauter than about 150 kg/m 3 . In other embodiments, a support layers  32 ,  34  each having a density of at least about 25 kg/m 3  and no greater than about 125 kg/m 3  is utilized. In still other embodiments, support layers  32 ,  34  each having a density of at least about 25 kg/m 3  and no greater than about 115 kg/m 3  is utilized. In one preferred embodiment, each support layer  32 ,  34  has a density of 25 kg/m 3 . It is understood that the support layers  32 ,  34  may have different densities and. hardness values from one another. In one embodiment, the support layers are comprised of polyurethane foam similar to that described in International Patent Application PCT/US2012/022893. 
     In one embodiment, the mattress  10  can have a bottom support layer  34  that is at least as thick as the top support layer  32 , e.g., 10.75 cm. However, it is contemplated that the layers  18 ,  20  could have different thickness. For instance, the top support layer  32  could have a thickness that is less than or greater than the thickness of the bottom support layer  34 . In one embodiment, the top support layer  32  has a thickness of 8 cm and the bottom support layer  34  has a thickness of 10.75 cm. It will be appreciated that these thickness values are merely illustrative and that the mattress could be constructed to have layer thicknesses different from those provided above. Alternately, the support layers  32 ,  34  could be combined into a single layer. 
     Referring again to  FIGS. 1 and 2 , the outer cover system  16  comprises an outer cover  44  that encloses, or at least partially encloses, the comfort and support systems  12 ,  14 , respectively. The outer cover  44  is made of fabric and, in a preferred embodiment, a combination of polyester, cotton natural yarn, and spandex. It is contemplated that other types of fabric or ticking could be used at is also contemplated that a quilted outer cover could be used. The outer cover  44  has an outer surface  46  and an inner surface  48  that are spaced from one another by at least one layer of fabric or ticking  50  that extends across the upper surface of the mattress  10  and down the sidewalls  10 ′ of the mattress  10 . The outer cover  44  fits snuggly around the mattress  10 , which holds the outer cover  44  in place. Alternately, the outer cover  44  can extend completely around the mattress  10  with ends thereof being connectable, such as by a zipper, to allow removability of the outer cover  44 , such as for washing. As known in the art, a fire sock  52  envelopes the comfort and support layers and, as such, the outer cover  44  fits around the fire sock  52  as well. 
     To provide a cool dermal sensation, the outer cover  44  is impregnated with phase change material (PCM). In a preferred embodiment, PCM is in the form of a layer of microspheres  54  that are doped onto the outer surface  46 , inner surface  48 , and ticking  50  of the outer cover  44  using one of a number known application techniques. For example, the PCM could be applied using a screening process. Alternately, the outer cover  44  could be passed through a PCM bath. Regardless of application technique, it is contemplated that the portion of the outer cover  44  that extends across the upper surface of the mattress  10  is substantially saturated with PCM to, in effect, form a PCM layer  56  that is coextensive with the fabric layer  50 . Alternately, the PCM could be applied to the outer surface  46  of the outer cover  44  to form a PCM layer (not shown) atop the outer surface  46 . In one preferred embodiment, the PCM is THERMIC™ microcapsules commercially available from Devan Chemicals of Belgium. In other embodiment, the PCM is OUTLAST® microcapsules, which is commercially available from Outlast Technologies. 
     With additional reference to  FIG. 2A , in addition to PCM in the outer cover  44 , mattress  10  also includes microspheres  54  of PCM forming a PCM layer  60  in the top comfort layer  18 . The PCM microspheres  54  are preferably spray-applied to the upper surface of the top comfort layer  18  to form a PCM layer  60  having a thickness of between 500 μm and 4.0 mm, and preferably approximately 2.0 mm. 
     The material used to form the PCM layer  60  is similar to that applied to the outer cover  44 , but it is contemplated that different types of phase change material could be used to form the respective PCM layers. Preferably, the thickness of the PCM layer  60  in the mattress is greater, or more dense, than the PCM layer  56  in the outer cover  44 . That is, it is preferred that the heat capacity of the PCM layer  60  will be greater than the heat capacity of PCM layer  56 . 
     The two PCM layers  56 ,  60  provide the dermal sensation of cool as well as the ability to absorb heat over an extended exposure period. As a result, as the thinner outer cover PCM layer  56  becomes saturated, i.e., heated, the latent heat characteristics of the PCM layer  60  in the top comfort layer  18  will effectively be a heat sink and thus absorb heat from the now-heated outer cover  44 . This translates to an extended period by which PCM absorbs heat from the user as the .user rests upon the mattress  10 , and ultimately provides a longer cooler sleeping surface, which is believed to be desirable for those that “sleep hot”, For example, in one embodiment, the amount of PCM in the outer cover provides approximately 15-30 seconds of cool dermal feel whereas the amount of PCM in the top comfort layer provides cool dermal feel for up to 120 minutes. Moreover, should the ambient temperature drop below the melting point of the phase change material, the latent heat stored in the PCM will be released and thus provide some heating back to the consumer during the night. 
       FIGS. 3 and 4  illustrate another embodiment of a body support according to the present invention. This embodiment employs much of the same structure and has many of the same properties as the embodiments of the body support described above in connection with  FIGS. 1 and 2 . Accordingly, the following description focuses primarily upon the structure and features that are different than the embodiments described above in connection with  FIGS. 1 and 2 . Reference should be made to the description above in connection with  FIGS. 1 and 2  for additional information regarding the structure and features, and possible alternatives to the structure and features of the body support illustrated in  FIGS. 3 and 4  and described below. Structure and features of the embodiment shown in  FIGS. 3 and 4  that correspond to structure and features of the embodiment of  FIGS. 1 and 2  are designated hereinafter in the 100 series of reference numbers. 
     Like the embodiment illustrated in  FIGS. 1 and 2 , the mattress  100  illustrated in  FIGS. 3 and 4  has a comfort layer system  102 , a support layer system  104 , and an outer cover system  106 . In the illustrated embodiment, the only differences between the mattress  100  of  FIGS. 3 and 4  and mattress  10  of  FIGS. 1 and 2  can be found in the composition of the comfort layer system  102 . As such, description of  FIGS. 3 and 4  will be limited to that of the comfort layer system  102 . Notwithstanding these similarities between mattress  100  and mattress  10 , it is understood that mattress  100  could be constructed with a different, support system and outer cover than those described with respect to mattress  10 . 
     The comfort layer system  102  is comprised of two comfort layers  118  and  120  that are secured together using adhesive or similar bonding agent that effectively forms a bonding layer  22 . The upper comfort layer  118  is formed from non-reticulated viscoelastic foam and the bottom comfort layer  120  is formed from reticulated viscoelastic foam. In a preferred embodiment, the upper comfort layer  118  has a thickness between 1-5 cm and more preferably 3 cm. The bottom comfort layer  120  has a thickness between 5-12 cm and more preferably 7 cm. The top comfort layer  118  has a density between 25 kgirn3 and 150 kg/m 3 , and more preferably a density of 100 kg/m. The lower comfort layer  120  has a density between 25 kg/m 3  and 150 kg/m 3  and more preferably a density of 75 kg/m 3 . The upper comfort layer  118  has a hardness between 40 N and 150 N and preferably a hardness of 55 N. The bottom comfort layer . 120  has a hardness between 30 N and 150 N and preferably a hardness of 55 N. With additional reference to  FIG. 4A , the upper comfort layer  118  includes microspheres  54  of PCM that effectively form a PCM layer  60  that together with PCM in the outer cover provides multiple bands or layers of PCM in the mattress  100 . 
     In the foregoing description, the application of PCM to a layer of polyurethane foam has been described but it should be understand that the body support cushions described herein may have different or other types of layers, such as latex or spacer fabric, to which PCM may be applied. For example, a body support cushion may be constructed with a spacer fabric between the outer cover and the top foam layer and the PCM could be applied to the spacer fabric. 
     Additionally, in preferred embodiments of the invention, the amount of PCM that is applied to the cover and/or foam layer is substantially consistent across the surface thereof. However, it is contemplated that intentional uneven applications of the PCM could be used to efficiently deposit the PCM based on believed sleeping preferences. For instance, the amount of PCM in the cover and/or foam layer upon which a sleeper&#39;s torso would rest may exceed that found in those sections upon which a sleeper&#39;s feet are expected to rest. Similarly, less PCM could be used along the periphery of the cover and/or foam layer in expectation that most sleepers do not rest on the edge of the mattress. Furthermore, it is contemplated that a mattress having two sleeping surfaces, e.g., a left side and a right side, such as that conventionally found in queen and king sized mattresses, the amount of PCM in the cover and/or foam could be selected to provide different cooling capacities for the respective sleeping surfaces. 
     The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.