BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention pertains to modular mattresses having interlocking layers which are preferably interchangeable and which do not detach from each other if compressed and shipped.

2. Description of the Related Art

[0002] Mattresses employed for sleeping have evolved greatly over the years. From straw- filled ticks which are used centuries ago, modern mattresses are technologically complex, the complexity often being proportional to cost. Many mattresses are a combination of a top mattress intended to provide comfort to the sleeper, and a bottom support structure upon which top mattress rests. However, changes and improvements of mattresses have resulted in other physical embodiments. What is generally necessary is a support layer which is firm enough to accept the weight of a “comfort layer” and one or more “sleepers”, or “occupants”, without exceptional deformation. Thus, modem mattresses may not be of typical two part construction as they were in previous times.

[0003] The “top mattress” has, in previous times, consisted of inner springs which were either connected together by wire or cord or inner springs which were separately housed in individual containers. On the top of these inner springs is located a relatively thick layer of material which isolates the feeling of the springs from the sleeper. This thick layer, in previous times, and even today, may be formed of thick cotton or polyester batting or other material. At least as early as the 1980s, it was proposed to replace the entire top mattress with a foam slab. These foam slabs were made, for example, from latex foam or from polyurethane foam. Combinations of the structures have also been used, for example innersprings combined with a polyurethane or latex foam layer on top of the inner springs, and a thick fiber batting below and/or above the foam layer. Foam mattresses met with only limited commercial success, in part due to their weight, and in part due to the expense of shipping. The use of latex foams or polyurethane foams of lower density was helpful with regard to defraying shipping costs, but did not alleviate other actual or perceived disadvantages.

[0004] More recently, it has become common to provide foam mattresses which are compressed after their manufacture into a relatively small size which can fit within a cardboard shipping container. Upon receipt by the customer, the rolled up and compressed mattress is taken out of the box, unrolled, and allowed to expand to its design thickness. This type of mattress has achieved significant commercial success.

[0005] Foam mattresses do have some significant drawbacks which require addressing. In order to provide comfort, the foam must be a flexible foam, but to provide significant support, also must be relatively rigid, with a relatively high indentation force. However, such a foam is not particularly comfortable for many individuals, and thus such mattresses are often provided with a separate foam layer or a layer of other bedding material on top of the “support foam” in order to provide sufficient comfort for the sleeper. Such a layer may be called a “comfort layer”.

[0006] Foam mattresses, in particular mattresses composed of closed-cell foam, may also exhibit relatively low heat conduction. Thus, over a period of time, the inability to conduct heat away from the sleeper may raise the temperature to an uncomfortable level. These problems have been addressed by contouring the upper surface of the foam layer such that air channels are provided, through the introduction of gel infusions or gel “swirls” during production of the foam, or by the addition of metallic infusions or phase change infusions.

[0007] German published application DE 4025977 Al discusses prior art foam mattresses having two different mattress components, each having different material properties, which are adhesively bonded to each other. However the published application also indicates that the adhesive employed to bond the layers together is relatively stiff, and thus hinders elasticity and “punctual resilience” of the mattress. The German application purports to solve this problem through the use of two foam layers, one of which has T-shaped grooves which expand towards the center of the core and run transverse to the surface of the mattress, the other layer having T-shaped transverse extensions which are of smaller dimensions than the T-shaped grooves of the mattress core. These two layers are then assembled by forcing the T-shaped extensions into the T-shaped grooves. A stated advantage of this construction is the open space provided within the T-shaped grooves below the inserted T-shaped extensions, which can allow airflow to remove heat. However, such a construction is not commercially acceptable today, since both the manufacture of the two foam layers as well as the assembly of such layers is difficult, severely increasing manufacturing costs. Furthermore, it has been found that such a construction is not suitable for the manufacture of mattresses which can be shipped in a compressed state, as discussed below, and is also not suitable in terms of use over time. A similar mattress with similar problems is disclosed in Czech Patent CZ 14034 Ul.

[0008] In the manufacture of foam mattresses, it is been customary to fabricate the entire mattress from a single type of foam material. Thus, the foam physical properties such as indentation, resilience, and the like, are uniform across the entire surface of the mattress or mattress component. However, in some cases, it would be desirable to provide mattresses which have different physical characteristics on each side of the mattress. It is virtually impossible to fabricate such a mattress as an integral article, for example by molding.

SUMMARY OF THE INVENTION

[0009] The present invention is directed to a compressible modular mattress comprising at least one foam topmost “comfort layer” and at least one “support layer” which are reversibly attached to each other and/or to further intermediate layers of the mattress by a series of complementary stable extensions and grooves. The assembled mattress is capable of being compressed and shipped without significant damage.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0010] FIGURE 1 depicts one embodiment of a modular mattress with a comfort layer reversibly attached to a support layer, shown in perspective.

[0011] FIGURES 2 and 3 depict embodiments of interlocking mattress components as described in DE 4025977 Al. [0012] FIGURE 4 illustrates one embodiment of an interlocking mattress of the present invention, having an intermediate foam layer, with all layers reversibly attached to adjoining layers by stable complementary sets of extensions and grooves..

[0013] FIGURE 5 illustrates another embodiment of an interlocking mattress of the present invention, having an intermediate foam layer bonded to an innerspring component and reversibly attached to a comfort layer.

[0014] FIGURE 6 illustrates one asymmetric pattern of grooves for a mattress of the present invention.

[0015] FIGURES 7A-7E illustrate further embodiments of extension/groove shapes which may be used to attach mattress layers or siderails to other mattress components.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The mattresses of the present invention comprise modular mattresses which encompass, in general, a plurality of resilient, flexible layers. The topmost layer may be termed a “comfort layer” and may be interchangeable with other comfort layers with different physical properties, e.g. indentation, resilience, hardness, density, and the like. The comfort layer may be a conventional polyurethane or latex foam, or a so-called memory foam, and may be the same on both sides of the mattress surface, or may be different, thus being able to accommodate sleepers with different weights, sizes, or preferences. The mattress may contain spring-like elements such as box springs in addition to or in place of a so-called “support layer”.

[0017] To be commercially acceptable, a multiple layer construction of the mattress must be easily manufactured and easily assembled. It is further desirable that the uppermost comfort layer be capable of being separately provided to the end-user who can then replace the original comfort layer with a new one having different properties. This will allow the end-user to tailor the load bearing, resilience and other physical properties of the upper “comfort layer” to suit his or her personal preferences. Economical manufacture and ease of assembly cannot be achieved by the invention disclosed in German published application DE 4025977, as the two foam layers having T-shaped grooves or extensions disclosed therein are difficult to manufacture, and their assembly is exceptionally difficult. Moreover, upon compression for shipping, the two layers come apart again in numerous places and often exhibit tears in the foam materials, which is clearly commercially unacceptable. Moreover, the structure disclosed in the German published application fails the so-called “Rollator” fatigue test, which mimics the expected behavior during use by the customer.

[0018] The interlocking mattresses of German patent DE 4025977 Al are illustrated in Figures 2 and 3. As can be seen from Figure 2, two mattress cores 1 and 2 are positioned adjacent one another, the underlying mattress core or “support foam” 2 having T-shaped grooves 4 which extend transversely across the core and extend inwardly in a vertical direction towards the center of the core. Thus, the wider portion of these grooves is delimited towards the adjoining surface 3 by narrower, laterally protruding material webs 5 and 6. Extending away from the upper core 1, are T-shaped extensions 7. When the two cores are assembled by inserting the T-shaped extensions 7 into the T-shaped grooves 4, an airspace 8 between the two cores’ T-shaped extensions and T- shaped grooves remains. According to DE 4025977, this airspace allegedly allows for airflow to conduct heat away from a sleeper. A similar construction is shown in figure 3, where the T-shaped extensions occupy a significant amount of the volume of the T-shaped grooves, but still leave an airspace 8. However, as will be described later, such constructions are difficult to manufacture, very difficult to assemble, exhibit tears and separations upon use, and cannot be shipped in a compressed state without significant damage.

[0019] In the present invention, the extensions and grooves of the support layer, comfort layer, and optional intermediate layers represent extensions and grooves of a stable shape, preferably a dovetail shape or trapezoidal shape, an L-shape, a bulbous shape, or a wave pattern shape, and the corresponding grooves and extensions of the layer to which the respective layer will be joined have a complementary shape, as shown in Figure 1. It has been surprisingly and unexpectedly discovered that mattress cores having such stable connections are more easily manufactured than the T-shaped connections disclosed in DE 4025977 Al, are easy to assemble, are capable of surviving compression for shipment, and exhibit excellent performance in the Rollator fatigue test. They may thus be described as “stable” shapes. It is highly preferable that these shapes, when “nested” into their complementary groove or extension, leave very little airspace in the “join”, preferably no airspace, and in any case, such a small airspace that the mattress components will not come apart during compression and shipment. The depth and height of the respective complementary grooves and extensions are substantially the same. Thus, upon nesting, a mating surface is provided between adjoining layers. Since the nesting grooves and extensions are similarly sized, a large contact area is provided in each pair of nesting extensions and grooves, which assists in preventing detachment.

[0020] Thus, by the term “stable” with respect to the shapes of the extensions and grooves, is meant that the cores of the mattress are able to be assembled easily by one person, do not exhibit significant tearing and/or separation upon use, as determined by the Rollator fatigue test, and are compressible for shipment in a compressed state without substantial tearing or separation. By “substantially no” and like terms which are related to stability of the mattress against separation is meant that only very small portions of the respective layers are separated, and these can be easily put back in place with minimal effort. The term “stable” does not include T-shaped extensions and corresponding larger grooves, as these do not meet any of the above requirements. Preferred stable shapes are so-called “dovetail” or “trapezoidal” shapes as shown in Fig. 7A, and combinations of these. “L-shape, “bulbous,” and “wave” shapes as illustrated in Figures 7B to 7D have also proven suitable. With regard to the preferred shapes, modifications such as radiusing of otherwise straight sides, rounding of corners to eliminate acute angles, and the like are all possible so long as the shapes are easily manufactured, assembled, compressed for shipment and shipped in a compressed state, and resist separation and tearing upon use. These characteristics can easily be determined for any given shape. The complementary grooves and extensions may also be described as “interlocking” with respect to the mattress proper, as the enclosed portion of the extensions will have a larger width than the width of the grooves at the surface of the respective mattress component. This larger width of the distal portions of the extensions as compared to the entry width of the grooves into which the extensions are inserted resist the pulling apart of the respective components, as also do the large contact area between the sides of the extensions and grooves. These attributes cannot be obtained when the grooves are larger than the extensions. In such case, significant adjoining surface area is lost, allowing for ease of detachment. [0021] The cores below the comfort layer may be manufactured out of any suitable resilient material. Preferably, the cores are manufactured from latex foam or polyurethane foam. With respect to the lower core, which may be termed the “support core” or “support layer”, this core may also be made of other resilient materials, for example expanded polyolefin foam or other materials which would not be particularly suitable for a comfort layer. Examples are porous materials made of randomly overlapping melt-bonded polyolefin, polyester, or composite polyolefin/polyester or other polymer filaments. One example of such a base material is Indura© spring material, available from Indratech, Troy, Michigan, United States of America. This material may be machined to provide a required extension or groove, and then assembled with a comfort layer or intermediate layer to form an intermediate product to which a comfort layer will be attached, or a final product having a comfort layer or a combination of comfort and intermediate layers. A support layer of expanded polyolefin foam or a non-foam material, with or without mating extensions and grooves can also be bonded to an intermediate foam layer. Expanded polyolefin foam may also be utilized in substitution or in addition to an innerspring layer. Bonding of these layers may be accomplished using standard adhesives, by stitching, melt bonding, or combinations of these. The intermediate layer may have extensions from its top surface or grooves in its top surface to receive corresponding mating grooves of a comfort layer or another intermediate layer. Because the adhesive, if used, is substantially distant from the comfort layer, any stiffness or resistance to indentation which might have been provided by the adhesive layer will not be felt by the sleeper. Multiple intermediate layers may be used if desired.

[0022] Preferably, the mattress consists of a support layer, optionally one or more intermediate layers, and a comfort layer. As discussed previously, the support layer is designed to provide a significant support function to the mattress. The support layer is thus generally constructed of a material which has a relatively high flexural modulus — in other words a relatively stiff yet still it’s flexible material. A preferred material is a semi-flexible polyurethane foam. The support layer may also be an innerspring component. Intermediate layers may be supplied as modules which occupy selected areas of the mattress. For example an intermediate layer may contain stiffer foam portions which extend transversely across the mattress to provide increased support in shoulder or hip areas. The sides of these portions of the intermediate layer may be straight and parallel to the sides of an adjoining portion of the intermediate layer or may be secured by interlocking extensions and grooves.

[0023] The intermediate layer, when present, may be used to isolate the comfort layer from the support layer or may be used to alter the overall compressibility or other physical properties of the mattress without significantly modifying the properties of the comfort layer. The intermediate layer will have stable extensions and/or grooves in its upper surface to mate with corresponding grooves and/or stable extensions of the comfort layer or a subsequent further intermediate layer. The intermediate layer may be made of an expanded polyolefin foam, other flexible materials such as those previously described, but is preferably made of a latex foam or polyurethane foam, most preferably a polyurethane foam. Each side of the mattress top surface may have different intermediate or comfort layers. The modular mattresses are thus highly tailorable to satisfy individual taste.

[0024] The comfort layer is preferably a latex foam or a polyurethane foam, with or without gel, metallic, or phase change infusions to promote heat dissipation, and may be contoured or channeled on its top surface to promote air flow. The foam materials may be conventional foam materials or may be so-called “memory foam” materials. A particular advantage of the present invention is that the comfort layer may be changed by the end user if the comfort layer provided originally is found, for example, to be too hard or too soft, or suffers damage due to accident or misuse. Additionally, the support layer, optional intermediate layer, comfort layers, and any other attachable components may be shipped separately or in various combinations. Preferably, however, the modular mattresses are compressed, rolled, up, boxed, and shipped. Such a modular mattress is illustrated in Figure 1, where support layer or support core 9 is attached to comfort foam layer 10 by extensions 11 nested into grooves 12 to comprises the mattress 15.

[0025] Those skilled in the art of resilient materials, in particular latex foams and polyurethane foams, can readily tailor the physical properties of the materials used in the respective layers to meet any reasonable requirements. For example, conventional, high resilience, and viscoelastic polyurethane foam comfort layers may be produced with a density of from 0.5 pounds per cubic foot to 10 pounds per cubic foot (8 kg/m ³ -160 kg/m ³ ), more preferably 1 pound per cubic foot to 7 pounds per cubic foot (16 kg/m ³ to 112 kg/m ³ ), and a 25% IFD of from 2 to 70 pounds (8.9 N to 311 N), more preferably 3 to 50 pounds (13.3 N to 222 N). Base or support layers may be produced, for example, from conventional foams with a density of from 1 to 6 pounds per cubic feet (16 kg/m ³ to 96 kg/m ³ ) and a 25% IFD of from 20 to 80 pounds (89 to 356 N). Examples of suitable foams may be found in numerous patents and publications, for example US patent 11,202,517 B2, and published application 2011/0252572 Al. Today, the majority of these foams will be blown through the use of non-chlorofluorocarbon blowing agents such as water (which generates carbon dioxide by reaction with isocyanate groups), or pentane or other volatile hydrocarbonoxy compounds. Use of water-blown foams is preferable.

[0026] The various layers of foam material may be produced by molding operations, in which case stable extensions and corresponding mating grooves may be molded directly into the product layer, or may be produced as slab foams which are then cut to an appropriate thickness. In the case of slab foams, the layer surface, stable extensions, and grooves will be cut by conventional cutting operations involving wire cutting or blade cutting, also known as “slicing”. Following the cutting operation, the waste is removed and discarded or recycled. Support materials such as polyolefin foams or Indura© spring material and melt-bonded filamentary material can also be prepared by wire or blade slicing, sometimes by use of a heated wire. Foam layers are preferably produced by cutting slab foam. The complementary extensions and grooves allow assembly in a reversible manner. Once assembled, the components may be parted, and reassembled. Prior to reassembly, one or more components may be substituted by one or more different components. Such reversible assembly does not prevent the application of an adhesive, rendering the final choice of components irreversible in whole or in part. However, the use of an adhesive to permanently bond components is not preferred.

[0027] A core layer surface having grooves or stable extensions and a further layer having corresponding stable extensions or grooves, may be termed a “mating surface”. The respective grooves and stable extensions of these mating surfaces may all have the same type of shape, e.g. dovetail or wave shape, or may have different types of shapes, for example dovetail shapes and bulbous shapes may be used together in different portions of the respective components, which is not preferred. In some cases, a stable type of shape may be used in conjunction with a shape which is not stable in and of itself, such as grooves and extensions having a square or rectangular crosssection, as long as the resulting assembly is “stable” as that term has been defined earlier herein. The stable extensions or grooves of the mating surfaces may also be of a single type, but may have different sizes. For example, dovetail-type grooves and extensions may be provided with different sizes, as shown in Figure 6.

[0028] Illustrative examples of stable extensions and grooves are shown in figures 7A through 7D. Figure 7A discloses trapezoidal grooves and extensions, in this case being fully symmetrical such that the respective grooves and extensions are of the same size and spacing, with no air gap between them when assembled, which is preferred. Unsymmetrical trapezoidal shapes may also be used. Figure 7B illustrates “L” shaped grooves and extensions. In this case, the grooves and extensions are symmetrical with respect to each other, so that “one cut” symmetry is achieved. Figure 7C illustrates “bulbous” extensions and grooves, while figure 7D illustrates “wave shape” extensions and grooves. As was the case with figure 7B, the extensions of figures 7C and 7D are able to be manufactured in a symmetrical fashion if desired. Figure 7E illustrates non-stable extensions and grooves which are not suitable for securing a comfort layer to an intermediate layer or a core or support layer, but might be used to secure a side rail to the side of the mattress.

[0029] Figure 4 illustrates a three piece modular mattress, with an intermediate layer 22 reversibly attached by stable complementary sets of extensions and grooves to both an upper foam comfort layer 10 and a lower foam or other material support layer or “core layer” 9.

[0030] Figure 5 illustrates a mattress 15 which consists of a comfort layer 10, an intermediate layer 23, and a support layer 24, which may, in this case, be an innerspring component. In Figure 5, the intermediate layer is adhesively bonded to the support layer. The glue line is not shown. This adhesive bonding does not significantly affect comfort, as it is remote from the comfort layer and shielded by the intermediate layer. The comfort layer and intermediate layer are secured to each other by interlocking stable extensions and grooves.

[0031] One of the advantages of the manufacture of the modular mattresses and mattress components of the present invention is that if grooves and stable extensions are selected such that they form the symmetrical repeating arrangement described above in reference to Fig. 7, one slicing operation is capable of forming two layers, each made of the same material, and each having the same arrangement of grooves or stable extensions. Such an arrangement is shown in figure 7A. The grooves and extensions have respective top and bottom surfaces and sidewalls which are substantially identical, such that a single cutting operation of a slab foam can provide two comfort layers, intermediate layers, or support layers, with only edge trimming being further necessary.

[0032] Layers which are asymmetric with respect to the type and/or size and/or spacing of the grooves and stable extensions may also be produced. Such “asymmetric layers” may be especially useful, for example, as the mating surfaces between an upper comfort layer and a core layer or intermediate layer, to alter the loadbearing or resilience characteristics of the layers over only a portion of the mattress, for example areas which would be expected to lie below a sleeper’s shoulders or hips. An example of interlocking layers which have an asymmetric arrangement of grooves and stable extensions, is shown in figure 6, where the support or core layer 9 and comfort layer 10 have interlocking dovetails 13 of one size, and interlocking dovetails 14 of another size, in this case distributed non-uniformly (asymmetrically) over the area of the mattress 15.

[0033] According to the present invention, it is also eminently feasible to produce mattresses which have significantly different properties on each half of the top surface, as mentioned previously. This is particularly desirable when two sleepers are of significantly different size and/or weight, or have different expectations with regard to indentation, resilience, or other properties of the foam materials. The difference in properties may be established through the use of different materials for the comfort layer in each half of the mattress, may be established through the use of different materials in respective halves of an intermediate layer, may be established through the use of different materials in respective halves of a base/core layer, or by a combination of these methods.

[0034] The invention will now be described by the following examples, which should be construed as illustrative, and not as limiting examples. The foams used in each example, whether an inventive example or comparative example, are the same, and are polyurethane slab foams. The foams of the core layer have a density of approximately 1.75 lb/ft ³ (28 kg/m ³ ), a 25% IFD of approximately 36 lbs (160 N), and a resilience of approximately 45%. The foams of the comfort layer have a density of approximately 2.50 lb/ft ³ (40 kg/m ³ ), a 25% IFD of approximately 15 lbs (67 N), and a resilience of approximately 10%. The respective layers were achieved by slicing the foam slabs to an appropriate thickness, and slicing to form extensions and grooves as described below.

[0035] The Rollator test is an ASTM durability test where a 240-lb hexagonal roller is rolled back and forth across the width of a mattress for 100,000 cycles. In this application, the mattresses were rollated per ASTM F1566-14, Test 7 (Durability Test) and then visually assessed for any signs of damage - i.e. foam tearing and layer dislodging.

[0036] Comparative Examples 1 and 2

[0037] Polyurethane foam cores and their respective comfort layers were prepared having grooves and extensions corresponding to those of figures 1 and 2 (prior art), which also correspond to figures 1 and 2 of German patent application DE 4025977 Al. Following slicing the contoured pieces from the foam slab, removing the trim material (de-webbing) after contour cutting proved to be extremely difficult. It proved impossible to assemble the comfort layer onto the core layer without the use of multiple persons and a pole. Even under these conditions, assembly took approximately 10 minutes for each mattress and both mattresses had multiple centrally-located sections where complete joining could not be achieved. No customer could be expected to disassemble/assemble a mattress using either of these designs.

[0038] The mattresses of comparative examples one and two were compressed in the manner commonly used for compressed bed packaging. After unpacking the mattress, the mattresses corresponding to both figures 1 and 2 had significant connection issues after being unwrapped. The mattresses were also fatigue tested employing the Rollator test. Each mattress sustained noticeable wear/damage. In particular, the comfort layer of figure 1 sustained several large tears 4-8 inches in length and as deep as 1 inch, whereas the design of figure 2 sustained smaller tears, and several sections of the core became warped during the fatiguing process.

[0039] Example 3 [0040] A mattress was produced using the same polyurethane foam core material and comfort layer material as was used in the comparative examples. However, the grooves in the lower mattress (core) component were dovetail (trapezoidal) in shape, and the corresponding respective extensions of the comfort layer were complementarily shaped such that mating surfaces were formed which enabled assembly of the comfort layer onto the core layer. De-webbing was straightforward and not particularly difficult for both the core layer and the comfort layer. Two persons were able to assemble the mattress, without the use of a pole, in less than two minutes. Under similar conditions, a single person was able to put mattress together in about five minutes. The assembled mattress contained no “un-joined” sections.

[0041] The assembled mattress was packaged in the same manner as was used for comparative examples 1 and 2. Upon unpacking and unwrapping, no issues of any kind were observed. The mattress was then subjected to fatigue testing using the Rollator test. The mattress sustained minimal wear and only a few small tears were observed. The mattress remained in its assembled state. The extensions meet the subject invention’s designation as “stable”.

[0042] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0043] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.