FIELD OF THE INVENTION Generally the present invention relates to sleep systems, preferably mattresses. In particular, the invention concerns so called hybrid mattress constructions that combine two or more support systems, usually foam layers along with an innerspring arrangement. BACKGROUND

A proper mattress can maintain the spine in optimal alignment thus improving sleep quality and alleviating back or neck related pain. Various sleep systems exist, which serve a purpose of relieving a pressure load from the backbone and surrounding musculature induced by a vertical posture typically maintained by humans during day. In some instances this purpose can be achieved by providing sleep systems with variable zonal stiffness to provide skeletal support for each area of the body.

So called hybrid type mattresses or mattress cores that combine a coil support system with foam materials have proved advantageous in regulating pressure distribution across the sleeping surface. Thus EP2062128 discloses a mattress, in which foam springs of varying firmness and/or metal coil springs are mixed within the head-, back- and leg regions. However, provision of individual springs of a first firmness within regions constructed of springs of a second firmness is inefficient in terms of creating an adequate pressure point relief system for spine and related musculature.

In EP2194814 a mattress core is disclosed comprising a frame divided into a number of mounting spaces by division walls composed of elastic foam, wherein each mounting space encompasses a cushion element comprising a plurality of pocketed coil springs. Individual cushion elements and/or inner division walls have varying elasticity as compared to that of the outer frame wall. In a mattress assembly disclosed in EP 1603434 variable zonal stiffness is attained, in turn, by provision of pocketed springs with two different heights, wherein some strings are shorter than the others and a foam filler is disposed above and/or below the shorter pocket springs.

However, in terms of the structure and a number of elements involved, the above mentioned multipart sleep systems are rather complex and thereby expensive in terms of materials and/or manufacturing that imposes relatively high costs on consumers. It is therefore desirable to develop a cost-effective sleep system product that would meet customer needs for a comfortable mattress at a fair price.

SUMMARY OF THE INVENTION

An objective of the present invention is to at least alleviate drawbacks of the related art. The objective is achieved by various embodiments of a mattress assembly provided according to what is defined in the independent claim 1. In preferred embodiment the mattress assembly comprises a core layer composed of a first foam material and comprising at least two rectangular-shaped cavities formed by vertical blind-cuts to a predetermined depth across the width of the core layer, each said cavity configured to receive a plurality of pocket spring units arranged into an at least one array, wherein the core layer encompasses at least five regions transversely adjacent to each other such, that the regions, which comprise the cavities occupied by the pocket spring units, alternate along the length of the core layer with the regions formed by the first foam material, wherein the pocket spring unit comprising regions are distinct from the first foam material-based regions in terms of at least firmness and resilience. In some embodiments, the pocket spring unit comprising regions correspond to at least shoulder and hip regions of the human body.

In some embodiments, the pocket spring unit comprising regions are configured to provide softer support to a user of the mattress assembly, as compared to the regions formed by the first foam material. In some further embodiments resilience rate in the regions formed by the first foam material exceeds resilience rate in the pocket spring unit comprising regions. The regions occupied by the pocket spring units and the regions formed by the first foam material preferably constitute a localized pressure point relief system within the core layer and the mattress assembly.

In preferred embodiment, each pocket spring unit comprises a coil spring individually packed into a fabric envelope. In some embodiments, the pocket spring units are 25 - 45 mm high, preferably 30 - 40 mm high. In some embodiments, the mattress assembly comprises, within each cavity, two overlaying arrays of the pocket spring units. In some embodiments, density of the first foam material is within a range of is within a range of 25 - 40 kilograms per cubic meter.

In preferred embodiment, the mattress assembly further comprises a plurality of vertical slots arranged into parallel rows at the bottom of each cavity, each individual slot being a vertical blind-cut extending from the bottom of the cavity to a predetermined depth in the core layer across the width of said core layer.

In preferred embodiment, the mattress assembly further comprises a surface layer composed of a second foam material and disposed on the top of the core layer such, that at least one array of the pocket spring units within each cavity adjoins said surface layer. Said second foam material is preferably an open-cell high-resilience foam configured to dissipate body heat and having density at least 40 kilograms per cubic meter. In some embodiments, the first foam material and/or the second foam material are polyurethane foams.

In still further embodiments, the mattress assembly further comprises an encasement. The expression "a number of refers in present disclosure to any positive integer starting from one (1), e.g. to one, two, or three. The expression "a plurality of refers to any positive integer starting from two (2), e.g. to two, three, or four.

The terms "first" and "second" are used herein to distinguish an element from other element and not to denote any particular order or importance if not otherwise explicitly indicated.

The utility of the present invention arises from a variety of reasons depending on each particular embodiment thereof. On the whole, the mattress assembly disclosed hereby provides to a sleeper continuous support, distributes the body weight and alleviates stress on the spine.

In the hybrid structure presented hereby the pocket spring unit comprising regions allow the heaviest body areas, such as shoulders and hips, to immerse into the mattress, thus providing relief from contact pressure, whereas the foam-based regions resiliently support the lighter body areas, such as head, torso, legs and feet. Such combination results in maintaining spine in optimal alignment by avoiding local pressure points on the human body. The aforementioned features are generally independent of sleep posture.

As shoulders and hips are the heaviest parts of the body, compression of these areas on a firm surface during longer periods of time (such as sleeping), will often force muscle soreness, pain, spasm and cramping. The mattress assembly disclosed hereby helps to avoid these problems.

The mattress assembly according to the present invention is generally designed to suit the majority of body shapes and weights. Still, in some embodiments the mattress assembly comprises additional means to provide improved support for heavier individuals.

In addition to the aforesaid, the mattress assembly is configured, as the sleeper moves, to ventilate and cool itself by allowing increased air circulation permitted by its carefully designed structure. The mattress assembly can be maintained dry and clean for lengthier periods of time; thereupon visits to the dry-cleaners can be diminished, as well as associated costs, while lifetime of the mattress can be generally extended. Different embodiments of the present invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a prospective view and Fig. IB is a side view of a mattress assembly according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS Detailed embodiments of the present invention are disclosed herein with the reference to accompanying drawings. The same reference numerals are used throughout the drawings to refer to same members as follows:

10 - a mattress assembly;

11 - a core layer;

12 - a first foam material;

13 A, 13B - cavities / posture chambers;

14 A, 14B - pocket spring units; 15 A, 15B - compression slots;

21 - a surface layer / a second foam material.

Fig. 1A illustrates at 10 a concept underlying various embodiments of a mattress assembly in accordance with the present invention. In one preferred embodiment the mattress assembly 10 is an elongated rectangular member suitable for a standard, non- adjustable bed. In terms of dimensions the mattress assembly 10 is advantageously configured to accommodate an at least one adult person. Dimensions (width x length) of the mattress assembly 10 can further vary according to any standard size grading, such as single bed size (90 cm ^χ 190-200 cm), double bed size or larger (e.g. 120-180 cm x 200-245 cm). The mattress assembly 10 may be also configured to accommodate a child. Depth of the mattress assembly 10 may vary within a range of 25-40 cm.

In one preferred embodiment the mattress assembly 10 comprises a core layer (a base layer) 11 composed of a first foam material 12 and a surface layer (a comfort layer) 21 composed of a second foam material. Depth of the core layer 11 may vary within a range of 20-30 cm, whereas depth of the surface layer 21 may vary within a range of 5- 10 cm. In some embodiments the first foam material and/or the second foam material are flexible polyurethane (PU) foams. Polyurethanes are complex polymers that result from chemical reactions of two main components, polyol(s) and isocyanate(s) with water.

The first foam material 12 is preferably configured as a polyurethane foam having density within a range of 25 - 40 kilograms per cubic meter (kg/m ³ ). In some exemplary configuration the first foam material is selected from polyurethane Combustion Modified Ether (CME) range foams, and has density of 30 kg/m ³ and hardness of 105 Newton (N). An average air flow rating for the first foam material with above identified parameters constitutes 80 liter per minute (1/min).

In some alternative embodiments, the first foam material 12 may be composed of viscoelastic foams (so called memory foams) of similar density. The core layer 11 may have either open- or closed-cell structure. Foam cells, both open and closed, are bubbles of the foam material expanded with air. In open-cell foams these bubbles burst, thereupon interconnected structures are created allowing for air escape when pressure is applied. Escaping from the compressed open cells air is spread to adjoining cells, thereby open-cell type foams better conform to body contours. In the closed-cell foams the cells remain unbroken; thereby air is trapped in the cells and squeezed upon compression.

The second foam material is preferably a high-resilience (HR) polyurethane foam configured to dissipate body heat and having density at least 40 kg/m ³ . The second foam material is preferably highly breathable open-cell type foam, which allows for greater airflow. High-resilience PU foams provide better support to more pressing parts of the sleeper's body and prevent them from sinking through a generally soft comfort (surface) layer. In some exemplary configuration the second foam material is high-resilience PU foam with density of 50 kg/m ³ and hardness of 70 N. Being open-cell foam with high porosity, said second foam material is about 30 times more breathable than high-grade memory foams. An average air flow rating for the second foam material featuring above identified characteristics is 110 1 min. In foams resilience is typically measured by dropping a standardized steel ball from a predetermined height onto a foam sample and measuring how high the ball rebounds. The resilience value is calculated as a rebound height attained by the ball expressed as a percentage of the original drop height. In high-resilience foams the resilience value constitutes >60%, whereas in conventional resilience foams the resilience value is about 40%.

In some preferred embodiment the core layer 11 comprises at least two rectangular- shaped cavities 13A, 13B formed in the first foam material 12. Each of these cavities is formed by cutting a rectangular-shaped area out of the first foam material 12 to a predetermined depth (z axis) across the width (y axis) of the core layer 11. In some embodiments (Figs. 1A, IB) the cavities 13A, 13B constitute through-cuts across the entire width (y axis) of the core layer 11, thus being devoid of side walls lengthwise (along the x axis), accordingly. Nevertheless, configuration with cavities 13 A, 13B formed by cutting a rectangular-shaped four-sided aperture in the first foam material 12 is not excluded. Cutting can be implemented by means of a Computer Numerical Control (CNC) router machine or any other suitable equipment.

Each said cavity 13 A, 13B is configured to receive a plurality of pocket spring units 14A, 14B arranged into an at least one array advantageously comprising a number of parallel and/or adjacent spring rows or -strings. The pocket spring units within each array may be interconnected. Dimensions of the cavities 13 A, 13B are adjusted accordingly. In some exemplary embodiment depth of each cavity may vary within a range of 4 - 15 cm. In some embodiments each cavity 13 A, 13B incorporates two overlaying arrays of pocket spring units (14A, 14B). Such an arrangement is shown on Figs. 1A and IB, wherein the pocket spring unit arrays are disposed on the top of one another.

In some embodiments all pocket spring units 14A, 14B are identical. In some other embodiments the number, dimensions (including size, shape, coil thickness and number of turns) and arrangement of the pocket spring units 14A, 14B can be adjusted within each array in the cavity 13 A, 13B. It is preferred that the pocket spring units 14A, 14B comprise a coil spring, such as a standard metal- or steel wire spring, individually packed into a fabric envelope to form a pad. Coil springs made of plastics and/or composites, such as fiber reinforced polymer composites, for example, can be utilized. Production of such individually packed coil springs preferably involves ultrasonic welding methods and equipment. The pockets may be interconnected by sewing, gluing or welding, for example.

In some preferred embodiment so called micro-coils (also referred to as mini-coils) are utilized to produce the pocket spring units 14A, 14B. Micro-coils (mini-coils) are smaller than standard spring coils. With micro-coils included, height of each individual pocket spring unit is within a range of 25 - 45 mm, preferably 30 - 40 mm (compressed and packed); and diameter thereof may range within 10 - 60 mm. Such spring may comprise 4-12 turns. Because each individually packed coil responds independently, the array formed by a plurality of the pocket spring units 14A, 14B better conforms to body contours, helping to relieve pressure and dampen motion transfer. Moreover, provision of individually packed spring units of mini- or micro-size enables improved coverage.

In some exemplary configuration the pocket spring units 14 A, 14B have been utilized that comprise coil springs 38 mm high and 30 mm in diameter. Said pocket spring units comprised 5 -turn coil springs made of 1.7 mm diameter medium carbon steel wire, wherein each coil spring has been individually enclosed in an ultrasonically welded non-woven fabric envelope to form a pad.

The reference is further made to Fig. IB that shows division of the mattress assembly

10 into at least five adjacent regions across the width of the core layer 11, said regions indicated by roman numerals i, ii, iii, iv and v. In preferred embodiment the core layer

11 encompasses adjacent regions i, ii, iii, iv, and v, wherein the regions ii and iv comprise the cavities 13 A, 13B occupied by the pocket spring units 14A, 14B and the regions i, iii and v are formed by the first foam material. Division concept is advantageously applied to the entire depth of the core layer 11 ; therefore, said regions ii and iv preferably include the layer of the first foam material 12 underlaying said cavities 13 A, 13B. The regions ii and iv, comprising said cavities 13 A, 13B with the pocket spring units 14A, 14B transversely alternate, along the length of the core layer 11, with the regions i, iii and v formed by the first foam material 12.

The above described arrangement allows establishing, within the mattress assembly 10, at least five separate zones with varying resilience and firmness to match body shape and to provide support and comfort selectively to each area of the body. While resilience is generally defined as an indicator of surface elasticity (or its "springiness"), firmness generally reflects the surface feel and immersion characteristics of the material.

The regions i, ii, iii, iv a v, as shown on Fig. IB, correspond to head (i), shoulder (ii), torso (iii), hips (iv), legs and feet (v). The regions ii and iv advantageously correspond to at least shoulder and hip regions of the human body.

In one preferred embodiment the regions ii and iv that encompass pocket spring units are distinct from the foam-based regions i, iii and v in terms of at least firmness and resilience. Thus, said regions ii and iv comprising the cavities 13 A, 13B occupied by the pocket spring units 14A, 14B are configured to provide softer support to a user of the mattress assembly, as compared to the regions i, iii and v formed by the first foam material 12. From the other hand resilience rate in the regions foam-based regions i, iii and v exceeds resilience rate in the pocket spring unit containing regions ii and iv.

In other words, the pocket spring units 14A, 14B give softer support to the heaviest body areas, such as shoulders and hips, allowing them to sink further into the mattress and providing pressure relief. The foam sections are, in turn, more resilient and support, by lifting, the lighter body areas, such as head, torso, legs and feet. The whole combination results in optimal spinal alignment and greater postural stability for the whole body together with pressure distribution that provide relief from contact pressure to the heavy areas of the body. The regions i, ii, iii, iv and v with varying firmness and resilience thus constitute a localized pressure point relief system within a core layer 11 and a mattress assembly 10.

The above described arrangement is designed to suit majority of body shapes and weights. In order to provide better support for heavier individuals the mattress assembly 10 further comprises a plurality of narrow vertical slots 15A, 15B (Figs. 1A, IB) formed in the core layer 11 at the bottom of each cavity 13 A, 13B. Said slots are hollow (thus comprising nothing but air). Each slot is preferably implemented as a vertical blind-cut extending from the bottom of the cavity 13 A, 13B to a predetermined depth in the core layer 11 across the width of said core layer as a narrow groove. These groove-like slots are arranged into parallel rows. The embodiment shown on Figs. 1A, IB comprises five slots 15A in the "shoulder" region ii and six slots 15B in the "hip" region iv. Alternatively the slots may be implemented as a plurality of individual substantially tubular apertures blind-cut in the bottom of each cavity 13 A, 13B and disposed substantially underneath each individual pocket spring unit 14 A, 14B in the array, accordingly. The slots 15 A, 15B provide improved support for heavier sleepers allowing them to sink further into the foam base (formed by the first foam material 12) after compressing the spring units 14 A, 14B therefore increasing pressure relief.

Additionally, the entire mattress structure as described above contributes to ventilating and cooling itself by allowing air circulation through the slots 15 A, 15B, the individually packed pocket spring units 14A, 14B, and the breathable surface layer 21, as the sleeper moves.

In preferred embodiments the above described surface layer 21 is further disposed on the top of the core layer 11 such, that at least one array of the pocket spring units 14A, 14B within each cavity 13 A, 13B adjoins said surface layer 21. It is preferred that the at least one array of the pocket spring units 14 A, 14B within the cavities 13 A, 13B directly contacts the surface layer 21. The surface layer 21 is composed of a second foam material, as disclosed hereinabove.

In some embodiments the mattress assembly 10 further comprises an encasement manufactured from any suitable material, such as fabric, for example. In some exemplary embodiment the encasement is produced from a knitted polyester fabric. Said encasement is preferably treated by anti-dust mite-, anti-allergen- and/or fire- resistance agents. The encasement may be detachable or it may be permanently attached to the mattress assembly 10.

EXAMPLE 1 : A mattress assembly 10 is provided with the following characteristics.

First foam material 12: PU Combustion Modified Ether range foam. Density 30 kg/m ³ , hardness 105N, average air flow rate 80 1/min. Second foam material / surface layer 21 : high-resilience, open-cell PU foam. Density 50 kg/m ³ , hardness 70N, average air flow rate 110 1/min.

Pocket spring units 14 A, 14B comprise coil springs individually enclosed in an ultrasonically welded non-woven fabric envelope to form a pad. Coil springs: height 38 mm, diameter 30 mm, 5 turns, medium carbon steel wire (1.7 mm diameter).

It is clear to a person skilled in the art that with the advancement of technology the basic ideas of the present invention are intended to cover various modifications and equivalent arrangements included in the spirit and the scope thereof. The invention and its embodiments are thus not limited to the examples described above; instead they may generally vary within the scope of the appended claims.