EP0678263A1 - Pneumatic mattress - Google Patents

Abstract

The pneumatic mattress, has two principal walls (2,3) connected along their periphery to form a closed sealed chamber (6). Their is a valve for introducing compressed air into the chamber. The internal faces (2a,3a) opposite the principal walls are joined by several elastic connecting tension wires (7). The inflation pressure is chosen so as to separate the walls by a sufficient distance (1) to place the wires in tension. The tension wires can be stretched by at least 100% and preferably greater than 300% before rupture. When the mattress is inflated the tension wires are orthogonal to the principal walls. In their unstretched state the wires may be all of the same or different length. The density of the wires is equal to at least one wire per cm<2> and less than or equal to 20 wires per cm<2> of the wall. <IMAGE>

Description

The invention relates to an air mattress of the kind which has two main walls connected along their periphery to form a closed sealed chamber, and at least one valve for the introduction of a gas under pressure, in particular of compressed air. , in said room.

To simplify, the term "mattress" will mainly be used in the description and the claims, but this term should be understood in a broad sense as encompassing any device of the mattress, cushion, box spring, etc. type. intended to be placed between a support and a load to be supported or lifted. In particular, the airbags used to lift loads, like jacks, also belong to the field of the invention.

We know that the main property required of such a device of the mattress, cushion or box spring type, is to have a certain deformability under load in order to distribute the stresses existing between the load (person or object) and the mattress, according to an area contact greater than that which would be obtained if said load was placed on a rigid support. In addition, it is advantageous that these stresses are distributed in a more continuous and more uniform manner thanks to the deformation of the mattress.

The deformability of the mattress is obtained by the choice of the constituent material, deformable in compression and / or in shear with a greater or lesser reversibility.

Air mattresses are a family of devices whose behavior is fairly close to reversibility. They are very useful for storage and transport, both because they are foldable and compact when deflated, and because they are relatively light. However, their stress distribution performance is limited by their very structure. The air mattresses known to date have indeed several drawbacks.

First of all, to obtain after inflation a general shape adapted to the desired use, it is necessary to provide a structure of juxtaposed elements such as joined flanges, structure which impedes good continuity of the distribution of surface stresses. We have also proposed, in patent US-A-2 753 573, an inflatable mattress, the walls of which are connected by transverse wires which, when the mattress is inflated, are substantially orthogonal to the mean plane of said walls: this avoids, that upon inflation the mattress does not take a shape unfit for its use.

Secondly, the very mechanism of deformation under load limits the performance of stress distribution. Indeed, the depression of a surface element of the inflatable mattress leads, on the one hand, to transmit the inflation pressure to the supported body over the extent of the depressed area, and on the other hand, to create an effect of membrane due to the normal component of the tension of the wall deformed by localized depression. The calculation shows that this membrane effect is weak when there is no significant local depression causing a high angular deformation of the wall compared to its rest position. As a result, as a first approximation, the air mattress leads, on the contact surface with the supported body, to a uniform pressure equal to the inflation pressure. There is no way to act on this distribution.

A third drawback also results from the mechanism described above: when a surface element has started to sink, the only factor which can increase the resistance depending on the sink is the membrane effect, if one admits that the internal pressure of the mattress remains constant which is practically the case when the deformation is localized and therefore only causes a slight variation in the overall volume. The practical consequence is that this type of mattress cannot accept both, under good conditions, either a distributed load, such as a lying person, or a more localized load such as a seated person. Indeed, the comfort of a lying person requires a relatively low pressure in the mattress, pressure which will be insufficient to resist the action of a seated person; such a localized charge will lead to the complete insertion of the mattress under the loaded area and the coming into contact of the opposite walls.

In other words, a conventional air mattress does not make it possible to offer, under the effect of a load, a sufficiently progressive, that is to say a reaction starting from a zero value at the start of the deformation, and increasing with it.

A second family of mattresses is known, the behavior of which is also fairly close to reversibility and which makes it possible to obtain an increasing reaction with the deformation. These are mattresses made of a deformable material such as a pile of fibers, or juxtaposition of springs, combination of flexible blades, cellular rubber, etc.

However, the mattresses of this second family have a much larger size and self-weight than a conventional air mattress, which is an obstacle for storage during periods of non-use and for transport. Furthermore, it is not possible to slide them in a flattened state under a load in order to lift it, as is possible with a deflated air mattress.

The object of the invention is, above all, to provide an air mattress which, while retaining the advantages of conventional air mattresses for storage and transport, makes it possible to offer a progressive reaction as a function of the deformation. The invention also aims to allow control of the stress distribution and contact performance greater than that obtained with conventional mattresses.

The subject of the invention is an air mattress comprising two main walls connected along their periphery to constitute a sealed closed chamber, and at least one valve for the introduction of a pressurized gas, in particular of compressed air, into said chamber, the internal faces opposite the main walls being connected by a plurality of connection means suitable for working in traction, characterized in that the connection means are elastic with significant elongation under tension, the inflation pressure being chosen to separate the walls a sufficient distance to make the elastic connection means work in tension, said distance being greater than the length of said connection means in the non-tensioned state.

The elastic connections allow, on the one hand the control of the geometry of the mattress without using partitions and, on the other hand, create an elastic reaction of the mattress when it is subjected to an external pressure.

Advantageously, the elastic connecting means are elastic threads; the elastic connecting means have an elongation before rupture at least equal to 100% and preferably greater than 300%. Preferably, the arrangement is such that when the mattress is inflated, the elastic connection means are substantially orthogonal to the main walls.

According to a first possibility, the elastic connecting means have the same length, in the non-stretched state.

As a variant, the elastic means have different lengths in the non-stretched state, so as to create different reactions depending on the zones of the mattress.

The surface density of the elastic connection means is at least equal to one connection means per cm² of wall and less than or equal to 20 connection means per cm² of wall; an average surface density corresponds to an average distance between the connecting means of approximately 5 mm.

The presence of these stretched elastic means helps to balance, at rest, the pressure exerted on the walls. As soon as a load is applied to an area of the wall, the localized deformation causes a reduction in the tension of the connecting means and an increasing reaction of the mattress.

Advantageously, the mattress is produced using a double-walled textile consisting of two textile plies made airtight, the warp and weft yarns of each ply being standard or high tenacity yarns having elongations at relatively low break, while the elastic means of connection between the two plies are elastic threads having an elongation before break greater than 100%.

The invention also relates to a method of manufacturing a mattress as defined above in which the connecting means are transverse elastic threads, this process being characterized by the fact that said transverse threads are put in place at " tight wire ".

The invention consists, apart from the arrangements set out above, of a certain number of other arrangements of which it will be more Explicitly question below about an exemplary embodiment described with reference to the accompanying drawing, but which is in no way limiting.

Figure 1 of this drawing is a perspective diagram, with parts broken away, of an air mattress according to the invention, in the deflated state.

Figure 2 shows, also in perspective, the mattress according to the invention in the inflated state, with parts torn off.

Figure 3 is a longitudinal section of a mattress made with a double-walled textile.

Figure 4 is a sectional diagram of an area of the inflated mattress, at rest.

Figure 5 finally shows, similarly to Figure 4, the area of the inflated mattress, subjected to a load.

Referring to Figure 2, we can see, in the inflated state, an air mattress 1 having two main walls respectively upper and lower 2, 3 connected along their periphery by a side wall 4. These walls 2, 3 and 4 are made of flexible flexible material, so that when the mattress 1 is deflated, as illustrated in FIG. 1, the walls 2 and 3 can come to bear against each other, the side wall 4 being folded, the thus flattened together which can itself be folded or rolled for easy storage. At least one inflation valve 5 is provided for the introduction of a pressurized gas, in particular air, into the sealed closed chamber 6 delimited by the walls 2, 3 and 4.

The facing internal faces 2 a , 3 a of the main walls 2, 3 are connected by a plurality of elastic connecting wires 7 with significant elongation under tension. The elastic threads 7 have an elongation before breaking at least equal to 100% and preferably greater than 300%. The inflation pressure of the mattress 1 is chosen so as to separate the walls 2, 3 by a distance 1 sufficient to make the elastic threads 7 work in traction. In other words, the distance 1 is greater than the length, in the untensioned state, of the wires 7.

When the mattress 1 is deflated and flattened, the wires 7 fold back and do not hinder the coming of the wall 2 against the wall 3.

When the mattress is inflated, as illustrated in FIG. 2, the wires 7 are preferably substantially orthogonal to the main walls 2, 3.

The surface density of the wires 7, on the faces 2 a , 3 a is at least equal to 1 wire per square centimeter of wall 2 or 3. This density is preferably less than or equal to 20 wires per square centimeter of wall. Advantageously, the average distance e between the connecting wires 7 is around 5 mm.

Thanks to the multiplicity of transverse elastic threads 7, the air mattress does not need to have a structure of juxtaposed elements such as contiguous tubes, used for conventional mattresses. The mattress of the invention therefore makes it possible to ensure good continuity of the distribution of the stresses on the surface of the support wall 2 or 3.

It is advantageous to produce the mattress of the invention using a double-walled textile 2, 3 (see FIG. 3) consisting of two textile plies 9, 10 linked together by a plurality of elastic threads 7. The two textile sheets 9, 10 are made airtight by coating and / or bonding and / or any other sealing means. Double-walled textiles are known and described, for example, in an article "USE OF THREE-DIMENSIONAL MATERIALS" by J.C. Malézieux published in the journal TUT (Textiles for technical use, 4th quarter 1991, n ° 2, pages 25 to 27). However, in these known double-walled textiles, possibly used for inflatable planar structures, for example for the manufacture of inflatable boats, the connecting threads between the two plies are standard or high tenacity textile threads having low elongations before breaking, generally between 8 and 20% and leading to very low elongations in service given the inflation pressures generally used and which are not taken into account in practice. In other words, in the double-walled textiles of the prior art, the connecting threads between the two plies are not elastic threads within the meaning of the invention.

According to the invention, the connecting son 7 between the plies 9, 10 are made of elastic son with great elongation before breaking, for example greater than 300% and which can reach 400% or 500%.

Such elastic threads 7 are known in the clothing industry for producing elastic garments.

The plies 9 and 10 are produced with threads 11 of warp and 12 of conventional weft, standard or high tenacity. These warp and weft threads are chosen according to the weaving criteria and the sealing ability. Take for example standard polyester flat yarn of 1,100 decitex with ten warp threads per centimeter and 10 weft threads per centimeter.

The connecting wires 7 are on the other hand elastic wires, for example of 600 dtex with an average modulus, between 0 and 200% elongation, of 0.2.10⁻² N / tex (0.2 gf / tex). A module of 10⁻² N / tex (or 1gf / tex) means that a wire of 1 tex subjected to a force of 10⁻² N will undergo an elongation of 100%. The density of the connecting wires is 10 per square centimeter.

Weaving is carried out under stretched yarn 7. The distance between the plies 9 and 10, with the wires 7 stretched, is chosen for example equal to 300 mm.

When the mattress is inflated to a pressure of 100.10² Pa (100 gf / cm²) the thickness of the mattress, that is to say the distance between the plies 9 and 10, is approximately 180 mm. A pressure exerted on the mattress will produce, regardless of the membrane effect, a depression of 8 mm for each pressure increment of 10.10² Pa (10 gf / cm²), up to the pressure of 100.10² Pa (100 gf / cm²).

With the same characteristics, but by bringing the number of elastic connecting threads to 16 per square centimeter, there will be a depression of approximately 5 mm per pressure increment of 10 × 10 2 Pa (10 gf / cm 2).

This value of 5 mm can be increased by choosing a longer length of connecting wires for the same inflation pressure.

The inflatable mattress structure according to the invention, after sealing the walls 2, 3 and 4, has a thickness which is highly variable as a function of the inflation pressure, due to the elongation capacity of the connecting wires 7.

The behavior under the action of an external load will now be described with reference to FIGS. 4 and 5.

FIG. 4 illustrates a fraction of the mattress 1 inflated under a pressure P, the lower wall 3 of which rests on a rigid support surface 13. The upper wall 2 is not subjected to any load and has substantially a flat shape parallel to the wall 3. If we consider an area S of the wall 2, this area is in equilibrium under the action of the thrust PS exerted by the gas under pressure contained in the mattress, and under the reverse action T exerted by the wires 7 tense, located in zone S. We therefore have the relation PS = T.

If a localized load C is applied in the zone S, as shown diagrammatically in FIG. 5, the wall 2 tends to sink a distance Δ 1 such that the resulting tension of the elastic threads 7 concerned becomes T - C.

At equilibrium under load C, the elastic threads 7, in the zone concerned, will have decreased on average by a length Δ 1 such that C = f (Δ1).

f is the relation existing between the length of the elastic threads 7 and their tension. In particular, the variation of the tension of an elastic thread 7 can be proportional to its elongation, in the manner of a spring.

The elastic threads 7 will therefore exert a retaining force on the wall 2 all the more reduced as they shorten under the effect of the displacement of the wall. The force C necessary to move the wall 2 is therefore progressively increasing as the thickness of the mattress decreases, that is to say the length 1 - Δ 1 of the wires 7. elastic reaction of the system, similar to that obtained with a spring mattress, when it is subjected to an external compression force, due for example to a localized load. This elastic reaction results from the combined effect of the tensile elasticity of the elastic connecting wires 7 and the inflation pressure which puts these connecting wires in a prestressed state.

The air mattress 1 of the invention has an elastic behavior similar to that of a spring mattress, and therefore fundamentally different from that of a conventional air mattress which is not capable of opposing an increasing reaction as a function of the deformation .

The membrane effect described for the conventional air mattress in the event of localized action also exists for the mattress according to the invention. The calculation shows that it can represent a significant part of the load, for example 10 to 40%, in the hypothesis of a seated person.

In addition, the distribution of the forces exerted on the wall by the connecting wires is of very great continuity owing to the very high density of the connecting wires. In fact, depending on the wires chosen, a number of connecting wires is used from 1 to 20 per square centimeter; for a value of four connecting wires per cm² (for example), the average distance of the connecting wires is 5 mm. The mattress thus formed is therefore equivalent to a mattress with elastic springs which would have a spring every 5 mm in both directions, ie four springs per square centimeter. Such a mattress allows exceptional quality in the continuity of the distribution of contact stresses, far superior to most of the solutions currently known.

The invention finally has another advantage, which is to be able to vary the behavior characteristics of the mattress by varying the inflation pressure.

A change in pressure has several effects.

Firstly, it modifies the external load threshold beyond which the connecting wires are completely relaxed, that is to say from which the elastic reaction no longer increases with deformation. Then, the membrane effect is greater when the pressure is higher, the tension of the walls being proportional to the pressure and to the height of the mattress, itself a function of the pressure.

Thirdly, increasing or decreasing the pressure makes it possible to modify the reaction module (force required for a given elementary deformation) if the reaction of the connecting wires is not linear, that is to say if one uses wires or a combination of wires whose modulus is variable according to the elongation. We thus arrive at a mattress which can be more or less "hard" according to the desire of the user, simply by varying the inflation pressure.

Another possibility is to use connecting wires of different lengths, which makes it possible to obtain a decreasing modulus as a function of the deformation.

Claims (11)

Air mattress comprising two main walls (2, 3) connected along their periphery to form a sealed closed chamber (6), and at least one valve for the introduction of a pressurized gas, in particular of compressed air, into said chamber , the internal faces (2 a , 3 a ) facing the main walls being connected by a plurality of connection means (7) suitable for working in traction, characterized in that the connection means (7) are elastic with elongation high under tension, the inflation pressure being chosen to separate the walls by a sufficient distance (1) to make the elastic means (7) of tension connection work, the distance (1) being greater than the length of said means (7 ) in the untensioned state. Mattress according to claim 1, characterized in that the elastic connecting means (7) have an elongation at break at least equal to 100%. Mattress according to claim 2, characterized in that the elastic connecting means (7) have an elongation at break greater than 300%. Mattress according to one of the preceding claims, characterized in that when the mattress is inflated, the elastic connecting means (7) are substantially orthogonal to the main walls (2, 3). Mattress according to one of the preceding claims, characterized in that the elastic connecting means (7) have the same length, in the non-stretched state. Mattress according to one of claims 1 to 4, characterized in that the elastic connecting means (7) have different lengths, in the non-stretched state. Mattress according to one of the preceding claims, characterized in that the surface density of the elastic connecting means (7) is at least equal to one connecting means per cm² of wall and less than or equal to 20 connecting means per cm² of wall. Mattress according to claim 7, characterized in that the average distance between the connecting means is approximately 5 mm. Mattress according to one of claims 1 to 8, characterized in that the connecting means are elastic threads. Mattress according to claim 9, characterized in that it is produced using a double-walled textile consisting of two textile plies (9, 10) connected together by a plurality of elastic threads (7), the two textile plies (9, 10) being made airtight by coating and / or gluing or any other sealing means, the warp and weft threads (11, 12) of each ply being standard textile threads or high tenacity having relatively low elongations at break, while the elastic connecting son (7) between the two plies have an elongation at break greater than 100%. Method of manufacturing a mattress according to one of claims 9 or 10, characterized in that the weaving is carried out with the elastic threads (7) stretched.

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