FR2716788A1 - Air 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.

Description

AIR MATTRESS

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

compressed, in said chamber.

  To simplify, we will mainly use the term "mattress"

  in the description and the claims but this term must be understood

  in a broad sense as encompassing any device such as a mattress, cushion, box spring, etc. 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, belong

  also within the scope 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

  more or less great 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, in order to obtain, after inflation, a general shape adapted to the desired use, it is necessary to provide a structure made of juxtaposed elements such as contiguous flanges, a structure which prevents

  good continuity of the distribution of surface stresses.

  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 by o10 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 load 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 reaction, that is to say a reaction starting from a zero value at the

  beginning 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 an air mattress

1o deflated.

  The invention aims, above all, to provide an air mattress which, while retaining the advantages of conventional air mattresses for storage and transport, allows

  to offer a progressive reaction according to the deformation.

  The invention also aims to allow control of the performance of stress distribution and contact greater than that obtained with

classic mattresses.

  According to the invention, an air mattress of the kind defined above, is characterized in that the internal faces opposite the main walls are connected by a plurality of elastic connecting wires, with significant elongation under tension, the inflation pressure being chosen to spread the walls a sufficient distance

  to work the elastic connecting son in tension.

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

external pressure.

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

orthogonal to the main walls.

  According to a first possibility, the elastic connecting wires have

  same length, not stretched.

  As a variant, the elastic threads have different lengths in the untensioned state, so as to create different reactions depending on the

mattress areas.

  An average surface density corresponds to an average distance between the bonding wires of approximately 5 mm. The presence of these stretched elastic threads 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 wires and a reaction of the

i0 mattress which increases.

  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 relatively weak at break, while the elastic connecting threads between the two plies are

  elastic threads having an elongation before breaking greater than 100%.

  The invention also relates to a method of manufacturing a mattress as defined above, this method being characterized

  by the fact that the transverse threads are put in place with "stretched thread".

  The invention consists, apart from the arrangements set out above

  above, in a number of other provisions which will be more explicitly discussed below in connection with an exemplary embodiment described with reference to the attached 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

  the invention in the inflated state, with parts torn off.

  FIG. 3 is a longitudinal section of a mattress produced at

  using a double-walled textile.

  Figure 4 is a sectional diagram of an area of the mattress

swollen, at rest.

  Figure 5 finally shows, similarly to Figure 4, the area of the

  inflated mattress, under 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 10 for the introduction of a pressurized gas, in particular air, into the

  sealed chamber 6 closed delimited by walls 2, 3 and 4.

  The facing internal faces 2a, 3a 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 I 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 up 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 walls

main 2, 3.

  The surface density of the wires 7, on the faces 2a, 3a 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 approximately 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 wall.

support 2 or 3.

  It is advantageous to produce the mattress of the invention using a double-walled textile 2, 3 (see Figure 3) consisting of two sheets

  textiles 9, 10 linked together by a plurality of elastic threads 7.

  The two textile layers 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 flat structures, for example for the manufacture of inflatable boats, the connecting threads between the two plies are standard or high tenacity textile threads having 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, by

  example greater than 300% and up to 400% or 500%.

  Such elastic threads 7 are known in the industry.

  clothing to make elastic clothing.

  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 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 0.2.102 N / tex (0.2 gf / tex). A modulus of 10-2 N / tex (or lgf / tex) means that a 1 tex thread 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 threads 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, independently 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 10.102 Pa (1Ogf / cm2). 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 capacity

  elongation of the connecting wires 7.

  The behavior under the action of an external load will be

  now described with reference to Figures 4 and 5.

  FIG. 4 illustrates a fraction of the mattress 1 inflated under pressure P, the lower wall 3 of which rests on a rigid bearing 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 tensioned, located in zone 3 0 S. We therefore have the relation PS = T. If a localized load C is applied in zone S, as shown diagrammatically in FIG. 5, wall 2 tends to sink distance AI such that the resulting tension of the elastic wires 7 concerned becomes T - C. At equilibrium under load C, the elastic wires 7, in the zone concerned, will have decreased on average by a length AI such that

C = f (A).

  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 movement of the wall. The force C necessary to move the wall 2 is therefore gradually increasing as the decrease

  the thickness of the mattress, that is to say the length 1 - AI of the wires 7.

  An elastic reaction of the system is therefore obtained, 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 threads 7 and the inflation pressure which puts these

  connecting wires in prestressed condition.

  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 in

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%, assuming 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 (as an 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, although

  superior to most solutions currently known.

  The invention finally has another advantage, which is to be able to vary the behavior characteristics of the mattress by making

vary the inflation pressure.

  A change in pressure has several effects.

  Firstly, it modifies the external load threshold beyond which the connection wires are completely relaxed, that is to say at

  from which the elastic reaction no longer increases with deformation.

  Then, the membrane effect is greater when the pressure is higher, the wall tension being proportional to the pressure and the

  height of the mattress, itself a function of 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 module as a function

deformation.

Claims (10)

  1. Air mattress comprising two main walls (2, 3) connected along their periphery to constitute 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, characterized in that the internal faces (2a, 3a) facing the main walls are connected by a plurality of elastic connecting wires (7) suitable for working in traction, with significant elongation under tension, the inflation pressure being chosen to separate the walls by a sufficient distance (1) to work the elastic threads (7) of voltage connection.   2. Mattress according to claim 1, characterized in that the elastic connecting son (7) have an elongation at break at less than 100%.   3. Mattress according to claim 2, characterized in that the elastic connecting son (7) have an elongation at break greater than 300%.   4. Mattress according to one of the preceding claims,   characterized in that when the mattress is inflated, the elastic connecting threads (7) are substantially orthogonal to the walls main (2, 3).   5. Mattress according to one of the preceding claims,   characterized in that the elastic connecting threads (7) have the same length, unstretched.   6. Mattress according to one of claims 1 to 4, characterized by the   the fact that the elastic connecting wires (7) have different lengths, the unstressed state.   7. Mattress according to one of the preceding claims,   characterized in that the surface density of the elastic connecting threads (7) is at least equal to one thread per cm2 of wall and less than or equal to 20 wires per cm2 of wall.   8. Mattress according to claim 7, characterized in that the   average distance between the connecting wires is approximately 5 mm.   9. Mattress according to any one of claims   above, characterized in that it is produced using a double-walled textile made up of two textile plies (9, 10) connected to each other by a plurality of elastic threads (7), the two textile plies ( 9,) 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 or high tenacity textile threads having relatively low elongations at break, while the elastic connecting threads (7) between the two plies have an elongation at the rupture greater than 100%.   10. A method of manufacturing a mattress according to any one   of the preceding claims, characterized in that the weaving is   o10 made with stretched elastic threads (7).