EP0959738B1

EP0959738B1 - Bed base

Info

Publication number: EP0959738B1
Application number: EP97925363A
Authority: EP
Inventors: Börje THULESKÄR
Original assignee: Jansson Ulf
Current assignee: Jansson Ulf
Priority date: 1996-05-29
Filing date: 1997-05-28
Publication date: 2003-11-12
Anticipated expiration: 2017-05-28
Also published as: SE9602050D0; SE9602050L; AU3052097A; DE69726187D1; EP0959738A1; WO1997045041A1

Abstract

Bed base comprising a core (1) consisting of a large number of spring units (2), each of which comprises a spring coil (3) enveloped by a textile cover (4), which textile covers are connected to each other and thus hold the springs in an upright position. A layer (6) of a stiff elastic material is arranged to support the spring core (1) in such a manner that when a spring (3) is depressed, its end will cause a certain depression in the stiff elastic material. Since the material has the property of springing back with a certain delay, the compression of the spring is smaller than in case of a compression which in its entirety corresponds to the depression of the surface of the bed base, so that the counter-force of the spring during prolonged pressure thus becomes smaller.

Description

TECHNICAL FIELD:

The present invention relates to a bed base comprising a spring core consisting of a large number of individually compressible spring units in the form of spring coils, connected by means of elements, such as textile covers, which are joined together, arranged to hold the spring coils in upright standing positions, extending between a support for the core and an upper padding on that side which forms the upper surface of the bed base, with said support arranged as a layer of compressible counter-springing material, the layer which forms the support, against which the spring units rest with one of their ends, consisting of an elastic material which has the property of slowly resuming its initial dimension subsequent to compression, so that the individual depression of each spring unit from the upper surface causes the opposite end of the spring unit, which rests against the support layer, to be pressed into the layer compressing the same, which, since the spring unit is allowed to assume a greater length, causes a correspondingly much lower counter-pressure at the upper surface, without this reduced spring pressure being counterbalanced by an increasing counter-springing force in the resilient support layer, since it, while the pressure is present, without instantaneous counter-springing maintains its depressed condition due to its visco-elastic properties.

BACKGROUND OF THE INVENTION:

There is a desire for bed bases to be individually spring resilient. This means that protruding body parts should be able to sink into the bottom, so that point pressure does not occur, at the same time as the bed base provides good support for the other parts. In order to achieve this, it is necessary that, on the one hand, the weighing down of the base due to pressure from protruding parts and the weight load does not spread to surrounding parts, with the result that these do not provide proper support - in the worst case causing a so-called "hammock effect" which causes a harmful load for the back - and, on the other hand, that compression does not cause too strong counteracting spring-forces, so that the counter-forces will not cause a noticeable point load on those protruding parts which weigh down the base.
Attempts have been made to obtain individual spring resilience and to avoid said negative effect by letting an upper padding rest on coiled springs or the like which can flex downwards separately. Although the hammock effect can be avoided in this manner, there is however a certain spread out deflection since the upper padding spreads the weight load to an area surrounding the smaller area which is weighed down by, for example, a hip joint if a person is resting on his side. In this way, the small of the back is poorly supported. This effect is even more accentuated and harmful when lying on one's back. The springs furthermore have a relatively high spring constant, and thus provide a high counter-pressure when being compressed.
These disadvantages become more accentuated as the area which the upwards facing surface of each spring occupies on the bed surface grows. For this reason, attempts have been made to manufacture spring cores consisting of a very large amount of coils of small diameter. In so doing, there is however the difficulty of getting the rod-shaped bodies which the springs form to stay in an upright position. As can be seen from, for example, patent document DE 4435234 (Hoffmann) a fixing of the springs in an upright position has been obtained by housing them separately, in pockets shaped by the joining together of pieces of fabric. Such bed bottoms are commonly called pocket spring mattresses.
However, the joining together of the pockets to each other in longitudinal and latitudinal rows, which provides the desired fixation of the springs in an upright position, partially counteracts the purpose of obtaining as individual resilience as possible. Due to said joint, the compression of a spring will, to a certain extent, bring with it the surrounding springs, due to the pockets being interconnected. This causes not only the undesired spreading of the compression, but also a higher spring resistance, since a certain number of springs will always be pressed together, even if the load is a point load. According to patent document US 3 633 228 (Zysman) attempts have been made to solve this problem by surrounding the formation of the feathers with a moulded compressible foam material, which is shaped as a plurality of tube shapes which each house a spring. These tube shapes are only connected at the middle of the latitudinal extension of the springs, so that the upper and lower part of each spring is completely unattached when compressed, at the same time as the foam body is sufficiently stiff to keep the springs in an upright position by means of said mid-connection between the tube shapes. This should, in the case of a point load, cause less spreading of the compression than the first mentioned kind of pocket spring mattress, but to a certain extent the problem of a considerable counteracting force remains, which might cause discomfort due to heavy point load at protruding body parts, especially when lying for a long period of time in the same position. The embodiment which is proposed in said patent document also causes a high manufacturing cost, due to the surrounding of a large amount of coils with the specially shaped moulded foam body.
Another kind of bed base is a thick mattress of foam rubber or foam plastic. These, however, also exhibit a spread compression with said consequences. In, for example, WO 81/02384 (Kennaway et al) and US 3 512 190 (Buff) it has been suggested to divide the foam mattress into a large amount of cube-shaped bodies which are separated from each other. In this way, the spreading of the compression is reduced; each body can be compressed individually without bringing with it adjacent parts, particularly if the covering sheet, which is practically always used, does not contribute too much to a spreading of the compression. However, the counter-force is more difficult to overcome. A compromise has to be made; either a relatively stiff material is used, thus causing a large point counter-pressure at protruding body parts, or a soft material is chosen, thus causing reduced counter-pressure, but also causing a risk of a spread compression in any case. In the case of very soft materials, the weight of the body itself can cause a certain hammock effect.
A further attempt to improve the foam mattress has been to use stiff elastic materials. These cause a delayed counter-springing, and a reduced point load is thus obtained. On the other hand, this material has other disadvantages, such as the body being pressed down into the material, thus reducing the ventilation. The material is also very expensive.
Whether one is lying on one's side or one's back, the small of the back is the problematic area. This is the location of the most protruding body parts, and the hip joint is furthermore an area which is relatively sensitive to pressure, as is moreover the shoulder. The body, furthermore, has the majority of its weight at the small of the back. This causes large compression effects. At the same time, in order to prevent stress on the spine, a good support at the waist and the small of the back respectively is necessary. There are thus two immediately adjacent body areas of which one, the small of the back, "the hip joint/bottom" requires a resilient surface and the other, the waist area, requires good support. Furthermore, this effect must be obtained at an arbitrary point within the mid-section of the bed base; the effect must within certain limits also be obtained regardless of the length and position of the person in the bed.
The European Patent document EP 0 052 389 A discloses a spring core made of a plurality of spring units, supported by means of support layer being a counter-spring material. However, the support layer can be damaged in case of particularly high point loads.

SUMMARY OF THE INVENTION

The above problems are eliminated by means of the bed base according to the present invention which is characterized in that in order to support the layer of stiff, elastic material, there is arranged an additional spring core and a rigid frame to support it, so that punctures against the frame in case of particularly high point loads are prevented.

BRIEF DESCRIPTION OF THE DRAWINGS:

In the following, an embodiment and certain variants are described with reference to the appended drawings. These show:

Fig. 1: a schematic longitudinal cross-section of the bed base according to the invention;
Fig. 2: shows a top view of a corner of the bed base with an upper padding removed, so that the pocket spring-core can be seen;
Fig. 3: shows a detailed cross-section of two springs with their pockets which are part of the core;
Fig. 4: shows a longitudinal cross-section corresponding to the cross-section of Fig. 1 but on a larger scale and in more detail, and limited only to an end portion of the bed base; and
Fig. 5: shows a layer of the bed base in a top view and on the same scale as Fig. 1.

PREFERRED EMBODIMENT:

Fig. 1 shows, in a longitudinal cross-section, the principle of the spring system of the bed base according to the invention. The following main layers are shown schematically:
A pocket spring core 1 consisting of a large amount of spring coil units 2, which according to Fig. 3 consist of a spring coil 3 enveloped by a textile cover 4, which textile covers over the entire core 1 are joined to each other along a limited part 5, which preferably is placed centrally relative to the longitudinal extension of the spring coil units. It is important that the portions 5 are not too long, since they will cause an increased compression of surrounding coils if they are very long.
The spring core 1 rests on a layer 6 of a stiff elastic material, also called visco-elastic. This material is a plastic foam with the property of delayed counter-springing during compression, thus reducing the counter-spring force of the material during compression. However, when the load is removed, the material resumes its original shape, which thus occurs with a delay. A suitable thickness of the layer 6 is 3-6 cm.
The layer 6 in turn rests on a supporting backing 7, which at least partially consists of a stiff material which can be supported by a rigid base by means of, for example, legs or a bed frame.
Fig. 2 shows a corner of the bed base with the spring coil units 2 and their spring coils 3 and textile covers 4 shown opened in a top view, from which the connections 5 between the coil units 2 can be seen. At the corner itself, an upper padding is shown, which to a large extent has been removed, which padding is not shown in Fig. 1, but will be described more closely in the following.
While Fig. 1 only schematically shows the three main layers of the bed base, Fig. 4 shows these in more detail, together with additional layers which are commonly used. Fig. 4 is a longitudinal cross-section on a larger scale than Fig. 1 of a limited part of an edge portion of the bed base. From the figure, it can be seen that the spring core 1 has said upper padding, here given the reference numeral 10, which suitably consists of a rubber foam or plastic foam layer of a relatively low hardness (density), and suitably of a thickness of 2-3 cm. This layer is fixed by a textile cover 11 with an upper portion 12 and side portions 13, which extend along the sides of the base and are fixed to the rigid structure of the supporting backing at 14 in Fig. 4. Between the spring core 1 and the upper padding 10, there is placed a layer 15 of a somewhat stiff cloth, for example fibre cloth (non-woven), which prevents the ends of the coils from working their way into the foam material of the upper padding 10. In the same way, a somewhat stiff cloth 16 is placed between the spring core 1 and the stiff elastic material 6. This layer 16, and possible also the layer 15, which thus consists of a somewhat stiff material which provides support for the coils against the foam layer can, as shown in Fig. 5, be slit. In this way, separate portions of the cloth material can be compressed and be compressed locally, and thus not spread the compression of one or a group of coils to the surrounding areas. The slitting thus provides a more individual compression, but still supports the ends of the coils. This possibility of individual compression is particularly important between the spring core and the underlying layer 6, while at the upper layers 10 and 15 it is important that the resting surface becomes smooth and not "lumpy". The stiff layers 15 or 16, or one of them, can be glued to the coil ends. In this way, these are better fixed in an upright position, and the connections 5 can be made more limited.
The stiff elastic layer 6 rests on a backing layer 7, as indicated in connection with the description of Fig. 1. According to Fig. 5, this consists of a frame 20 of a rigid material such as wood, and a stiff spring core 21 in this frame, on which the stiff elastic layer 6 rests with an intermediate stiff cloth 22, which should be perforated in order to allow ventilation of the foam material. The spring core 21 can be simpler than the spring core 1, and can have a small amount of larger spring coils, or can consist of, for example, horizontal zigzag springs. Its object is mainly to prevent punctures in case of high point loads, caused by, for example, rapid sitting down on the bed base. The spring force in the spring core 21 should for this reason be large and still afford an elastic resistance, even at the highest possible point load. The spring core 21, in turn, rests on a bottom 23, here shown as a ribbed bottom, which together with the frame 20 is the totally rigid supporting portion of the bed base.
An important principle of the bed base according to the invention is that, in case of constant and usually not particularly spread out loads, the material of the stiff elastic layer 6 is pressed down due to the pressure from the compressed springs, so that their compression does not entirely need to correspond to the depression of the upper side of the bed base which is required in order to achieve comfort. Reduced compression also brings about a reduced spring force, and the object of the invention, to reduce the counter-springing force in areas of larger depression, has been achieved. When the depressing force has ceased or been reduced, the stiff elastic material resumes its initial thickness with a certain delay, so that a lasting deformation of the upper surface of the bed base is not caused.
This particular softness and adjustment to the spring force afforded by this principle, permits the upper padding formed by the upper layer, the foam layer 10 and the cloth layer 15, to be made very flexible and allows very local depressions. Suitably, the top layer is an elastic cloth, for example jersey fabric, and the foam layer 10 is relatively soft and the cloth layer 15 is not too hard, and can possibly also be slit. Due to this flexible construction, depressions can be kept local without the forming of any larger craters in case of point loads. The cover, in turn, in its slit shape permits individual depression of the spring ends. The cloth pockets 4 around the spring coils 3 have said limited connections 5 with each other, which also contributes to this, since the depression of one coil is only to a small extent transferred to adjacent coils. This is obtained, according to the suggestion, by the cloth pockets being connected only at their mid-portions. Alternatively, however, the initially mentioned principle of letting the spring coils be connected by being surrounded by moulded covers of a foam material can of course be used, however with the consequence of a higher cost of manufacturing. If, however, such a spring core is utilized, the described basic principle of coils supported by a stiff elastic material will still be utilized.

Claims

A bed base comprising a spring core (1) consisting of a large number of individually compressible spring units (2) in the form of spring coils (3), connected by means of elements, such as textile covers (4), which are joined together, arranged to hold the spring coils in upright standing positions, extending between a support for the core and an upper padding (10,11) on that side which forms the upper surface of the bed base, with said support arranged as a layer (6) of compressible counter-springing material, the layer (6) which forms the support, against which the spring units (2) rest with one of their ends, consisting of an elastic material which has the property of slowly resuming its initial dimension subsequent to compression, so that the individual depression of each spring unit (2) from the upper surface (10, 11) causes the opposite end of the spring unit, which rests against the support layer (6), to be pressed into the layer compressing the same, which, since the spring unit is allowed to assume a greater length, causes a correspondingly much lower counter-pressure at the upper surface, without this reduced spring pressure being counterbalanced by an increasing counter-springing force in the resilient support layer (6), since it, while the pressure is present, without instantaneous counter-springing maintains its depressed condition due to its visco-elastic properties, characterized in that in order to support the layer of stiff, elastic material (6), there is arranged an additional spring core (21) and a rigid frame (20,23) to support it, so that punctures against the frame in case of particularly high point loads are prevented.
Bed base according to claim 1,
characterized in that between the spring core (1) and the layer of the visco-elastic material (6) there is arranged a layer (16) of a relatively stiff cloth material which is slit in order to permit individual depression in said layer (6) of the ends of the spring units (2) of the spring core (1).
Bed base according to claim 1 or 2,
characterized in that said upper padding (10,11) on the upper side of the spring core (1) and constituting the upper surface of the bed base, is made so as to be flexible and with a low spreading of local depressions by the choice of resilient, deformable materials, such as, for the outer surface, an elastic cloth (12) over a layer (10) of foam material resting on the spring core (1) via a flexible, soft material.