Bed mattress with variable characteristics of carrying capacity throughout its length

Abstract: Bed mattress, of the type consisting essentially of a stratified expanded-foam panel formed by the arrangement, on top of one another, of at least three layers with different load-bearing and/or air-permeability characteristics. The main layer, which is situated in the middle of the other two layers and is basically assigned the load-bearing function, has a thickness variable along the length of the mattress. Said middle load-bearing layer has high load-bearing characteristics, with small-size closed cells, and its thickness varies from a minimum of about 50 mm, in the region of the neck zone of the sleeping person, to a maximum of about 130 mm, in the region of the trunk and respectively the pelvis of the sleeping person.

Description: The present invention relates to a bed mattress in which it has been attempted to provide conditions for resting and supporting of the body which, from the functional point of view of the anatomy, are considered essential for ensuring maximum comfort for the body structure of a person, taking into account its widely varying constitution and characteristics. On the market nowadays there are essentially two types of mattresses: one formed by a fairly complex composite structure, consisting partly of resilient elements of the metal spring type and partly of various types of padding and covering or lining fabrics, and the other being formed by a simple plastic-foam panel of suitable thickness. In the first case, the composite-structure mattress may be made in accordance with different criteria, in order to satisfy the various requirements for a more or less rigid response to the weight of the body lying on the mattress and/or more generally with regard to environmental comfort (structure which on one side is cooler for the summer and on the other side warmer for the winter). The mattresses of this type, which even today can only be manufactured on a mainly craftsman's level, as is known, are very costly. In the second case, the mattress consisting of a plastic-foam panel, which can be manufactured with a much higher degree of automation and therefore industrially on a large scale, for this reason has a much lower cost, although its comfort characteristics are relatively limited. Attempts have already been made, in fact, to improve these characteristics by manufacturing stratified panels, using plastic-foam layers of varying porosity, but with limited success. US-A-3,885,258 describes a mattress of this second type in which it has been attempted to improve the comfort for the person lying on the mattress, by forming the latter as a multiple-layer panel with a flat upper and lower surface, in which, however, the middle layer, which possesses a greater elastic resistance, has an undulating configuration - but uniform thickness - the undulations being located directly opposite the undulations of the human body lying on the mattress. In this patent it is stated that the aim of the undulations located opposite those of the human body is to ensure that the mattress offers a greater resistance in the region of those parts of the body which have a greater weight. However, this aim is not achieved to the degree which would be desirable because it has been established that in practice this resistance depends, in these materials, solely on their thickness. In the case of the mattress according to US-A-3,885,258, the resistance of the middle layer is therefore uniform, despite the fact that its profile is undulating, owing to the fact that its thickness is uniform. An effect of varied resistance is therefore produced mainly by the bottom layer, which in fact has a variable thickness; however, this effect is at least partly offset by that of the upper layer - which has variable thicknesses contrary to those of the bottom layer - in particular in the case where these two layers are made of the same material. Document WO84.02260 also relates to a mattress with variable firmness characteristics, i.e. it is made by two external layers of foamed material, having different firmness, applied onto opposite sides of a central layer formed by a series of stiff plates, the one being hinged onto the other. The hinges are made so as to allow the plates to oscillate relative to each other in only one direction: i.e. when the mattress lies onto a plan in a first position (fig. 3), it is perfectly horizontal and substantially firm, while when it is laid upside down (fig. 5) relative to the first position, it flexes significantly under the weight of the sleeping person. However, not even this arrangement is apt to provide sufficient comfort for the human body, either. The object of the present invention is therefore that of providing a mattress of the same type as that according to US-A-3,885,258, i.e. which is made by means of the arrangement, on top of one another, of layers of plastic foam, but which however is able to satisfy in an optimum manner the comfort requirements of the human body which, with regard to what stated in the introduction, differ greatly from one individual to another. This object is achieved by means of the characteristic features mentioned in Claim 1. A further object of the invention is to provide a mattress which offers improved comfort characteristics in relation to the season, i.e. summer or winter, in which it is used. This object is achieved by means of the characteristic features mentioned in Claims 3 and 5. Further characteristic features and advantages of the mattress according to the invention will emerge, however, more clearly from the detailed description which follows of an embodiment thereof, provided purely by way of example and illustrated in the accompanying drawings, in which: Fig. 1 is a longitudinally sectioned view of the mattress according to the invention, with the body of an individual lying on it in the supine position, in the configuration for summer use; Fig. 2 is a view, also longitudinally sectioned, through the same mattress, in the configuration for winter use; and Fig. 3 shows, on a much larger scale, a portion of the mattress according to the invention. As can be easily understood from the drawing, the mattress according to the invention consists of a composite panel formed by three plastic-foam layers arranged on top of one another, the middle layer 1 performing the main load-bearing function, the upper layer 2 (with reference to Figure 1) performing the function of a cool summer support surface and the layer 3 (bottom layer with reference to Fig. 1) performing the function of a warm winter support surface. More particularly, the load-bearing layer 1 does not have a uniform thickness - as is usually the case in plastic-foam panel mattresses of the known type - but a variable thickness, which takes account of the different weight-loads of the various parts of the human body. In fact, considering the functional anatomical characteristics of a body in conditions where there is no active control of the body parts, as occurs in the sleeping state, it is necessary to remember that the mattress must be capable of supporting each part of the body through an optimum distribution of the load. In particular it necessary to avoid the situation where the complete muscular relaxation occurring in the sleeping state is accompanied by the adoption of an abnormal posture. To state the problem more clearly, it is necessary to avoid - in the main positions assumed spontaneously by the sleeping person, i.e. the supine, lateral and prone positions - that the various parts of the body are able to assume involuntarily postures capable of causing contractions or aches. The condition to be satisfied is therefore that the mattress should have varied "load-bearing" characteristics from one point to another, such that the mattress is able to flex in a varied manner under the pressure of the weight of the various regions of the body, but so as to provide an optimum response according to the load per unit of surface area. It must obviously be taken into account that this "pressure" is fairly different depending on the shape and mass characteristics of the various regions of the body. It must also be remembered, finally, that indispensable features in a modern mattress are those offering, depending on the seasons, either favourable retention of the body heat or, on the contrary, more rapid disposal of the accumulated heat and, in particular, any sweat caused by the high external temperatures. In order to satisfy the various requirements mentioned above the mattress according to the invention has the following characteristic features: 1) First of all, as already mentioned, the basic structure of the mattress is formed by the arrangement, on top of one another, of three layers, each possessing different mechanical and heat-dispersion characteristics, and in particular: 1.1) The "load-bearing" layer 1, which forms the element arranged between two superficial layers, has the function of supporting, with minimum yielding, the body weight. Its main feature is that it has characteristics of high resistance to compression, or a high load-bearing capacity, and that it has a thickness which varies along the length of the entire mattress, i.e. from the section where the head is supported to the section which supports the bottom ends of the legs.The thickness is varied precisely so as to offer the ideal support conditions according to the various body regions.The information necessary for defining the various thicknesses of the layer in the different zones of the mattress is provided below. Numerical data is also provided, purely by way of example, this data referring to a mattress with an overall thickness of about 200 mm, in which the load-bearing layer 1 consists of closed-cell foam with high load-bearing characteristics. a) In the region of the neck and the head it is recommended to have a thickness which is fairly large, but decreasing so as to ensure a supporting action capable of avoiding undesirable deviations and excessive overloading of the cervical section of the vertebral column. For example, the thickness of the layer 1 gradually increases - from the head end towards the end where the feet are situated - from 60 mm to 110 mm for the head support zone, while it suddenly drops to 50 mm in the neck zone; b) in the region of the trunk there is a fairly large thickness for supporting, without significant yielding, the high weight of this section of the body. For example, the thickness may be 130 mm here with a zone joining the thin zone of the neck which reaches a maximum value in the shoulder zone; c) in the region of the waist there is a slight reduction in the thickness. For example the thickness may be reduced down to 85 mm; d) in the region of the pelvis the thickness of the "load-bearing" layer is increased, precisely in order to support correctly this part of the body, which has a fairly high weight per unit of area. In this zone the thickness may be for example increased again to the same value as the trunk zone, i.e. up to 130 mm; e) from the base of the thighs as far as the feet the "load-bearing" layer is gradually but progressively reduced, for example, from 120 to 60 mm, progressively decreasing over the entire length of the legs. For reasons associated essentially with constructional simplification and a reduction in the waste material, this layer of variable thickness is preferably formed with a perfectly flat surface on one side, while on the opposite side the surface is undulating, as shown in the drawings. It is obvious, however, that this layer may also be formed with two opposite undulating surfaces, provided that the basic feature of the thickness varying from one point to another is maintained. 1.2) The layer 2 - which, when the mattress is used in the summer position (position illustrated in Figure 1), is situated on the upper side so as to perform, as said, the function of a cool summer support surface - is a layer of preferably uniform thickness. According to the present invention, its essential functional feature is that it is made of foamed material which has large open cells, but is nevertheless capable of withstanding the weight of the body without collapsing, i.e. while maintaining its permeability with regard to the circulation of air. For example, the layer 2 may consist of a layer which has a medium load-bearing capacity, but which is fairly rigid, with relatively large open cells - for example with a diameter even of a few mm (4 to 8 cells per linear cm) - having a thickness for example of 30 to 50 mm.In this way this layer may perform correctly the function which has been assigned to it, consisting in disposal of the heat given off by the parts of the body resting on the mattress owing to the effect, on the one hand, of simple ventilation of the open cells and, on the other hand, through removal of the sweat by means of capillarity along the walls of the cells.The collapse-resistant open-cell foamed material in fact allows the formation of a layer which is highly permeable to air, so that the air which circulates freely inside the intercommunicating channels of the open cells allows an extremely favourable disposal of heat and sweat.The purpose of this layer is therefore to prevent "airtight" adhesion between body and mattress.In order to perform this function, it is preferable if this layer 2 is applied onto the flat surface of the load-bearing layer, while the layer 3 will be applied onto the opposite undulating surface, as explained hereinbelow. 1.3) The layer 3 - which is located on the upper side when winter use thereof is envisaged (i.e. with the mattress overturned with respect to the summer position illustrated in Figure 1), so as to perform the function of a warm enveloping support surface capable of retaining heat - is composed of a foamed material with a load-bearing capacity which is markedly less than that used for the middle layer. Its essential functional feature is that it is mainly composed of closed cells and that it is fairly soft hence with a low load-bearing capacity - so as to provide a somewhat enveloping contact with the body. This enveloping contact, obtained with a surface of the mattress composed of closed cells, allows excellent retention of the body heat, as is desirable precisely during the cold season.By way of example, the layer 3 may have closed cells with a small diameter and good elasticity. This layer 3 - in view of the fact that the finished mattress must in any case be in the form of a panel with flat surfaces - has in turn a variable thickness, since it interfaces with and follows, in close contact, the surface of the load-bearing layer 1 on the side where the undulations due to the variation in thickness are present. The minimum thickness will in any case at least be equivalent to the summer thickness, i.e. 50 mm. On the other hand, in view of its low load-bearing capacity, this layer contributes only marginally to the overall load-bearing capacity of the multiple-layer mattress, which is therefore mainly guaranteed by the middle layer 1. 2) Particular care must be taken to choose lining fabrics capable of enhancing and not diminishing the characteristics determined by the choice of the different layers which make up the mattress. 2.1) The fabric lining which covers the "summer surface", i.e. the open-cell layer, must also be characterized by extreme permeability. In this fabric, in fact, preference must be given to the use of fabric with wide meshes capable of assisting and supplementing the passage of the air which is sought after by means of the use of the open-cell foamed layer. 2.2) The lining fabric which covers the "winter surface" of the mattress does not pose, on the other hand, particular problems because, being intended to cover a closed-cell foamed material, it does not have particular permeability requirements so that, when choosing it, more importance may be attached stylistic features and those associated with pleasantness of feel. 2.3) As regards the wide band of lining fabric which surrounds the perimetral edge of the mattress, there are no particular requirements in this innovative mattress. It is merely necessary to pay particular attention to the stitching with the lining fabric which covers the "summer" side of the mattress, because the high-permeability and wide-mesh material from which it is made could create certain problems during joining with fabrics made of different material. It is understood, however, that the invention is certainly not limited to the particular thicknesses indicated and structure of the materials mentioned above, which form only non-limiting examples of scope of the invention itself, but that numerous variations are possible, all of which within the grasp of a person skilled in the art, without thereby departing from the scope of the invention. It must in fact be remembered that the variations in the thicknesses may be modified in percentage terms, for example on the basis of the nature, in particular the load-bearing capacity, of the material used to form the three layers which make up the mattress and/or on the basis of the intended use of the mattress, i.e. for persons of short, medium or high stature.

Claims: Bed mattress, of the type consisting essentially of a stratified expanded-foam panel formed by the arrangement, on top of one another, of at least three layers with different load-bearing characteristics, characterized in that : the main layer, situated in the middle of the other two layers, has a thickness variable along the length of the mattress and is made from a material with a high load-bearing capacity; the other two external - lower and upper - layers, each of which has a respective flat external surface and an internal surface which follows the profile of the main middle layer, are made from a soft material with a low load-bearing capacity; one (2) of the two said external layers is formed by a soft foamed material, with open cells with a high air permeability; the other (3) of the two said external layers is formed by a soft foamed material, with closed cells; the overall load-bearing effect of the mattress being essentially determined by said middle layer. Mattress according to Claim 1, characterized in that said middle load-bearing layer has, on one side, a surface which is entirely flat and, on the opposite side, an undulating surface which results in said variable thickness. Mattress according to Claim 1 or 2, characterized in that said external layer formed by an open-cell foamed material has "summer" characteristics, and is applied onto a flat surface of the middle load-bearing layer. Mattress according to Claims 1 or 2, characterized in that said external layer formed by a soft, yielding, closed-cell foamed material, has "winter" characteristics, and is applied onto an undulating surface of the middle load-bearing layer, having in turn an undulating surface matching and closely adhering to the undulating surface of the load-bearing layer. Mattress according to Claim 1, characterized in that said middle load-bearing layer (1) has high load-bearing characteristics with small-size closed cells. Mattress according to Claims 1 or 5, characterized in that the thickness of said middle load-bearing layer (1) varies from a minimum value, in the region of the neck zone of the sleeping person, to a maximum value, in the region of the trunk and respectively the pelvis of the sleeping person. Mattress according to Claim 6, characterized in that said minimum thickness is about 50 mm and said maximum thickness is about 130 mm.

Inventors: DAL MONTE ANTONIO, DAL MONTE, ANTONIO
Applicants: ORSA S R L, ORSA S.R.L.
Application year: 1998
Main classification: A47C27
IPC codes: A47C27