FIELD OF THE INVENTION

[0001] The present invention relates to mattress assemblies, and more particularly to mattress assemblies for use in beds.

BACKGROUND OF THE INVENTION

[0002] Mattress assemblies are typically used in a bed to support a user's body or a portion thereof (e.g., head, shoulders, legs, etc.) while the user is at rest. Some mattress assemblies include multiple foam layers. Such mattress assemblies can be costly to manufacture and heavy. Conventional mattress assemblies can also differ in firmness and comfort feel by adjusting the number, thickness and composition of the constituent foa layers.

SUMMARY OF THE INVENTION

[ΘΘΘ3] The invention provides, in one aspect, a mattress assembly including a first layer of viscoelastic foam defining an upper surface, and a second layer of non-viscoelastic foam supporting the first layer. The mattress assembly also includes a pluralit of static spring elements positioned beneath the upper surface for enhancing a firmness of the combined first and second layers.

[0004] Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005} FIG. 1 is a perspective view of a mattress assembly in accordance with an embodiment of the invention.

[0006] FIG. 2 is a cross-sectional view of the mattress assembly of FIG. 1, taken along line 2— 2 in FIG. 1.

[0007] FIG. 3 is a cross-sectional view of the mattress assembly of FIG. 1 , taken along line 3— 3 in FIG. 1.

[0008] FIG. 4 is a cross-sectional view, similar to that of FIG. 2, of a mattress assembly in accordance with another embodiment of the invention. {0009] FIG. 5 is a cross- sectional view, similar to that of FIG. 3, of the mattress assembly of FIG. 4.

[0010] Before any embodiments of the 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 arrangement of components set forth in the following description or illustrated in the accompanying 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 the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

DETAILED DESCRIPTION f 0011] FIG. 1 illustrates a mattress assembly 1 for use in a bed. The mattress assembly I includes a first layer 4 of viscoelastic foam defining an upper surface 8 of the mattress assembly 1 and having a thickness T _t (FIG. 2). Viscoelastic foam is sometimes referred to as "memory foam" or "low resilience foam." Coupled with the slow recovery characteristic of the viscoelastic foam, the first layer 4 can at least partially conform to the user's body or body portion (hereinafter referred to as "body"), thereby distributing the force applied by the user's body upon the viscoelastic foam layer 4. The viscoelastic foam layer 4 can provide a relatively soft and comfortable surface for the user's body.

[001 ] The viscoelastic foam layer 4 has a hardness of at least about 20 N and no greater than about 80 N for desirable softness and body-conforming qualities. Alternatively, the viscoelastic foam layer 4 may have a hardness of at least about 30 N and no greater than about 70 N. In still other alternative embodiments, the viscoelastic foam layer 4 may have a hardness of at least about 40 N and no greater than about 60 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 to a compression of 40 percent of an original thickness of the material at approximately room temperature (e.g., 21 to 23 degrees Celsius). The 40 percent compression is held for a set period of time, following the international Organization of Standardization (ISO) 2439 hardness measuring standard,

[0013] With continued reference to FIG. 1, the viscoelastic foam layer 4 can also have a density providing a relatively high degree of material durability. The density of the viscoelastic foam layer 4 can impact other characteristics of the foam, such as the manner in which the viscoelastic foam layer 4 responds to pressure, and the feel of the viscoelastic foam layer 4. In the illustrated embodiment, the viscoelastic foam layer 4 has a density of no less than about 30 kg m ³ and no greater than about 150 kg/m ³ . Alternatively, the viscoelastic foam layer 4 may have a density of at least about 40 kg/m ³ and no greater than about 135 kg/m ³ . in still other alternative embodiments, the viscoelastic foam layer 4 may have a density of at least about 50 kg/m ³ and no greater than about 120 kg/m ³ .

[0014j Thfi viscoelastic foam layer 4 can be made from non-retieulated or reticulated viscoelastic foam. Reticulated viscoelastic foam has characteristics that are well suited for use in the mattress assembly, including the enhanced ability to permit fluid movement through the reticulated viscoelastic foam, thereby providing enhanced air and/or heat movement within, through, and away from the viscoelastic foam layer 4 of the mattress assembly 1 , Reticulated foam is a cellular foam structure in which the cells of the foam are essentially skeletal. In other words, the cells of the reticulated foam are each defined by multiple apertured windows surrounded by struts. The cell windows of the reticulated foam can be entirely gone (leaving only the cell struts) or substantially gone. For example, the foam may be considered "reticulated" if at least 50 percent of the windows of the cells are missing (i.e., windows having apertures therethrough, or windows that are completely missing and therefore leaving only the cell struts). Such structures can be created by destruction or other removal of cell window material, or preventing the complete formation of cell windows during the manufacturing process,

{00153 With reference to FIG. 1 , the mattress assembly 1 also includes a second layer

12 of non -viscoelastic foam supporting the viscoelastic foam layer 4. The non -viscoelastic foam layer 12 has a thickness T ₂ that is greater than the thickness T _¾ of the viscoelastic foam layer 4. Alternatively, the thickness T ₂ of the non-viscoelastic foam layer 12 may be the same or less than the thickness Ti of the viscoelastic foam layer 4. The non-viscoelastic foam layer 12 may be a latex foam or a high-resilience (HR) polyurethane foam. Such a latex foam has a hardness of at least about 30 N and no greater than about 130 N for a desirable overall mattress assembly firmness and "bounce." Alternatively, the latex foam may have a hardness of at least about 40 N and no greater than about 120 N, or at least about 50 N and no greater than about HO N. The latex foam has a density of no less than about 40 kg/m ³ and no greater than about 100 kg/m ³ . In still other alternative embodiments, the latex foam may have a density of at least about 50 kg m ³ and no greater than about 100 kg/m ³ , or at least about 60 kg/m ^J and no greater than about 100 kg/m ³ .

[0016] In embodiments of the mattress assembly 1 in which the non-viscoelastic foam layer 12 includes H polyurethane foam, such a foam can include an expanded polymer (e.g., expanded ethylene vinyl acetate, polypropylene, polystyrene, or polyethylene), and the like. The HR polyurethane foam has a hardness of at least about 80 N and no greater than about 200 N for a desirable overall cushion firmness and "bounce." Alternatively, the HR polyurethane foam may have a hardness of at least about 90 N and no greater than about 1 0 N, or at least about 100 N and no greater than about 180 N, The HR polyurethane foam has a density, which provides a reasonable degree of material durability to the non-viscoelastic foam layer 12, The HR polyurethane foam can also impact other characteristics of the non- viscoelastic foam layer 12, such as the manner in which the non-viscoelastic foam layer 12 responds to pressure. The HR polyurethane foam has a density of no less than about 10 kg/m ³ and no greater than about 80 kg/m ³ . in still other alternative embodiments, the HR polyurethane foam may have a density of no less than about 15 kg/m ³ and no greater than about 70 kg m ³ , or no less than about 20 kg m ³ and no greater than about 60 kg/m ³ .

[0017 J With reference to FIGS. 2 and 3, the mattress assembly 1 further includes multiple static spring elements 16 positioned beneath the upper surface 8 of the mattress assembly 1 for enhancing a firmness of the combined viscoelastic and non-viscoelastic foam layers 4, 12. Particularly, the spring elements 16 are embedded into the non-viscoelastic foam layer 12 using a molding process, and the viscoelastic foam layer 4 is attached to the upper surface 20 of the non-viscoelastic foam layer 12 (e.g., using adhesives, etc.). in the illustrated embodiment, the spring elements 16 are aligned with a thickness T ₃ of the mattress assembly 1 and are entirely encased within the non-viscoelastic foam layer 12 (FIG. 2), In other words, each spring element 16 is separated or isolated from adjacent spring elements 16 by the non-viscoelastic foam layer 12. Alternatively, the spring elements 16 may be partially encased within the non-viscoelastic foam layer 12 and covered by the viscoelastic foam layer 4 such that the spring elements 16 may be positioned between the viscoelastic and non- viscoelastic foam layers 4, 12.

100181 The spring elements 16 are arranged in an array having multiple rows and multiple columns (FIG. 3). The array can be in the form of a grid, in which the spring elements 1 are spaced across a portion or all of the vvidth and length of the mattress assembly 1. In such cases, consecutive spring elements 16 extending in width-wise and length-wise directions along the mattress assembly 1 can extend substantially parallel to the width and length of the mattress assembly 1. Alternatively, consecutive spring elements 16 may extend diagonally with respect to the width and length of the mattress assembly 1. In other words, each row may be offset or shifted relative to the preceding and/or following row. In still other alternative constructions, the spring elements 16 may be arranged randomly, in a single row, in a single column, or combinations thereof (0019] With continued reference to FIGS. 2 and 3, the spring elements 16 are made of a polymeric material, and more specifically, a thermoplastic material (e.g., TPEE, SBS, SEBS, TPV, etc.). The spring elements 16 are configured as coil springs having the same length. Alternatively, the spring elements 16 may be configured as leaf springs, for example, or any of a number of different types of springs. In still other alternative constructions, the spring elements 16 may include different lengths. For example, a first spring element 36 may have a different length than a second spring element 16 or a first group of spring elements 16 may have a different length than a second group of spring elements 16, and so forth. In the illustrated embodiment of the mattress assembly 1, the spring elements 16 have the same spring rates. Alternatively, the spring elements 16 may have different spring rates. For example, a first spring element 16 may have a different spring rate than a second spring element 16 or a first group of spring elements 16 may have a different spring rate than a second group of spring elements 16, and so forth.

[0020] The spring rate of the spring elements 16 can be a constant spring rate or a variable spring rate. Spring elements 16 including a constant spring rate often have the same or a constant spacing between coils of the spring element 16 as compared to a variable spring rate, in which the spacing between the coils is different or variable.

[0021] In some embodiments of the mattress assembly 1, the firmness of the combined viscoelastic and non-viscoelastic foam layers 4, 12 can be enhanced substantially uniformly across the width and length of the mattress assembly 1 . Alternatively, the firmness of the combined viscoelastic and non-viscoelastic foam layers 4, 12 can be enhanced non- uniformiy across the width and length of the mattress assembly 1. For example, the nonuniform firmness of the mattress assembly 1 may be tuned (e.g., by using different spring elements, different rate spring elements, a combination of constant and variable rate spring elements, etc.) in accordance with the locations or regions of the mattress assembly 1 normally associated with certain portions (e.g., head, shoulders, legs, etc.) of the user's body that require different support. In other words, the spring elements 16 may be selected to enhance the firmness of the combined viscoelastic and non-viscoelastic foam layers 4, 12 a greater amount in regions of the mattress assembly 1 associated with a reclined user's lower legs, posterior, and head/neck, for example.

[0022] With continued reference to FIGS. 2 and 3, the spring elements 16 have the same wire thickness, density, shape, and ring size. However, in alternative embodiments of the mattress assembly 1, the wire thickness, density, shape, ring size, or combinations thereof may be altered to more or less enhance the firmness of the combined viscoelastic and non- viscoelastic foam layers 4, 2.

[0023] When using the mattress assembly 1 , the user's body contacts the upper surface 8 of the mattress assembly 1. In turn, the spring elements 16 enhance the firmness of the combined viscoelastic and non-viscoelastic foam layers 4, 12 to provide comfort to the user. By replacing a portion of the non-viscoelastic foam layer 12 with the spring elements 16, the mattress assembly 1 has a lower cost and weight as compared to conventional mattress assemblies. Additionally, the mattress assembly 1 can be readily altered with respect to the comfort and feel provided to the user by altering the spring elements 16 to have a different spring rate, wire thickness, shape, and th like. In other words, the mattress assembly 1 can be manufactured in a cost-effective manner to provide users with different mattress assemblies 1 having different properties (e.g., firmness, comfort feel, etc.) by altering the spring elements 16 as compared to a conventional mattress assembly in which an entire layer or more would need be redesigned to provide a different mattress assembly to the user.

[0024] FIGS. 3 and 4 illustrate a second embodiment of the mattress assembly l a used in connection with beds. Like components are identified with like reference numerals with the letter "a," and will not be described again in detail. Rather than embedding the spring elements 16 into the non-viscoelastic foam layer 12 like that shown in FIGS. 2 and 3 and described above, the mattress assembly la includes spring elements 16a positioned within discrete cavities 24 within the non-viscoelastic foam layer 12a, The cavities 24 can be formed in the non-viscoelastic foam layer 12a by a drilling process or a cutting process, for example. The spring elements 16a are placed or positioned within the cavities 24, and the viscoelastic foam layer 4a is attached or fastened to the upper surface 20a of the non- viscoelastic foam layer 12a (e.g., using adhesives, etc.).

[0025] The mattress assembly l a is used in an identical fashion as the mattress assembly 1 shown in FIGS. 2 and 3.

[0026] Various features of the invention are set forth in the following claims.