Abstract:
A supporting element having a rigidity which may be adjustably controlled includes a cover (29) and a filler (30). The filler includes a flexible laminated structure having a plurality of layers (31, 32, 33; 32a, 32b; 34) which are mounted to be moveable relative to one another under the effect of a non-uniform distribution of force compressing the filler in the absence of a controlled pressure. The cover (29) is coupled to a vacuum source and is adapted to receive a controlled pressure to make the supporting element more or less rigid. When the cover (29) has a predetermined inner pressure, the relative displacement of the respective layers is prevented thereby giving the layers a predetermined rigidity. The layers may have a device for immobilizing the layers distributed on either side of at least one compressible layers (32, 32a, 32b).

Description:
The invention relates to controlled-rigidity supporting elements comprising a cover which is subject to a control pressure. 
     The invention applies, by way of non-limiting examples, to pieces of furniture such as individual seats, bench seats or sofas. 
     The invention relates more particularly to a supporting element which can be adapted to the shape of any user whatsoever in order to obtain retention and support in an anatomically correct position which gives rise to no phenomenon of fatigue and causes no deformation of the spine which is likely to cause lordosis or kyphosis. 
     BACKGROUND OF THE INVENTION 
     The publication FR-A 2,096,133 describes a seat in which the squab is equipped with a cushion containing a resiliently compressible porous mass connected to a reduced-pressure source. This source adjusts the thickness of the cushion until its rigidity is sufficient to resist the compression caused by the load communicated by the user of the seat. It has been found, however, that such a design of the squab is poorly suited to the requirements of lateral retention of the trunk and of sacrolumbar lordosis during the changes in posture of the user of the seat. 
     The publication EP-A 0,113,613 describes a seat including a partitioned PVC cover containing a layer of particles such as polystyrene balls. This cover is connected by means of a pipe to a vacuum pump. Once suction has been established, the walls of the cover compress the polystyrene balls without any substantial variation in volume, creating a coherence between the balls which hardens the layer in the position required by the sitting position of the user of the seat. 
     The bursting of the balls following external vibrations and friction communicated to the cover results in a total loss of effectiveness of the lining element. Furthermore, it proves difficult to distribute the balls satisfactorily when the cover is situated in a non-horizontal plane. 
     The publication EP-A-267,640 describes a cover for surgical use which is capable of preserving a shape by the vacuum effect and in which balls are held in place by adhesive bonding on layers of non-woven fabric or in a plastic network produced by injection-molding. 
     The publication DE-GM 7,617,960 furthermore discloses a backrest consisting of pneumatic sleeves. Pumps, each equipped with an outlet valve, make it possible to adjust individually the internal pressure of each sleeve and to adapt the backrest to the requirements of the user. It is difficult to modify the support effect while the vehicle is moving, in particular for the driver, and it is possible only if the operating member has been designed in order to be used with just one hand. 
     SUMMARY OF THE INVENTION 
     The subject of the invention is a controlled-rigidity supporting element comprising an outer cover and an inner filler which is improved with the aim of avoiding the disadvantages which were noted with ball fillers. 
     According to the invention, the filler consists of a flexible laminated structure, the various strata of which are mounted with relative displacement under the effect of a non-uniform distribution of the force compressing the filler in the absence of any control pressure, and the cover of which is subjected to a variation in pressure in order to eliminate any relative displacement between the various strata, giving them the necessary rigidity. 
     The supporting element constructed in this way fulfils the function of rigidification and finds its place, for example, in the manufacture of coverings associated with adjustment devices with inflatable air pockets. 
     It will be able, in particular, to have a substantially more reduced constant thickness, irrespective of the position of use, and to be obtained easily using automated cutting-out methods. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention will emerge upon reading the description of illustrative embodiments of the supporting element and of an example of the manufacture of a seat which makes use of the supporting element, with reference to the attached drawing, in which: 
     FIG. 1 shows in perspective the frame of the seat with a set of rests mounted on the squab, 
     FIG. 2 is a sectional view of the supporting element consisting of a sealed outer cover surrounding an inner laminated filler of superposed sheets, 
     FIG. 3 is a perspective view of the supporting element consisting of a sealed outer cover surrounding a laminated inner filler with the incorporation of one or more compressible strata, and of grids permitting an embedding effect, 
     FIG. 4 is a sectional view of an alternative embodiment of the supporting element employing mechanical means for immobilization by a locking effect, 
     FIG. 5 shows the alternative embodiment in FIG. 4 after a vacuum has been applied to the cover, 
     FIG. 6 refers to an alternative embodiment of the supporting element as shown in FIG. 4, 
     FIGS. 7a, 7b-8a, 8b describe alternative embodiments of the supporting element, in which the mechanical means for immobilization connect together the outer strata directly through the central stratum or strata, 
     FIG. 9 describes another alternative embodiment of the supporting element, in which the sealed cover is situated inside the supporting element. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a backrest zone 3 arranged on the frame of the squab 1 of a motor vehicle seat covered with a padding 2. 
     The backrest zone 3 is extended on the left and the right by two side rest zones 4, 5. An adjustment system 10, worked via operating members such as a manipulator unit 11, rests, on the one hand, on the rigid frame 12 which defines the loading surface of the squab and which is fixed, in a known manner, between the side posts 13 of the frame of the squab and, on the other hand, on supports 14, 15 for the additional padding cushions respectively carried by the side posts 13. The adjustment system 10 is covered by a covering 28 of fibers agglomerated by an appropriate binder, in order to give the seat the desired permeability and ventilation and to ensure better distribution of the pressures of the trunk on the squab. The adjustment system 10 and the covering of fibers are covered by the padding 2 and consequently constitute the assembly of backrest 3 and side rests 4, 5. 
     The adjustment system here consists of two superposed supporting elements 16, 17, the size of which can be modified by varying their internal pressure. To this end, each of the elements 16, 17 consists of a hollow member, the walls of which are impermeable to gas. The unit 16 which rests on the frame 12 has a shape which is predetermined by the assembly of three compartmentalized inflatable cushions 18, 19, 20, the general configuration of which corresponds with the various rest zones 3, 4, 5 and which are joined together so as to define three capacities which can be inflated separately or simultaneously under the action of inflation pulses communicated by the manipulator unit. 
     The element 17 as shown in FIG. 2 consists of an outer cover 29 connected via the manipulator to a vacuum source forming part of a pneumatic control device, an illustrative embodiment of which has been described in the publication EP-A 0,113,613. 
     A filler 30 is contained in the cover 29 and consists of an assembly of pliable and flexible sheets 31 constituting a layer which can be deformed under the effect of a non-uniform distribution of the compressive force. By way of example, the substance constituting the sheets can be paper, textile, plastic or metal which are capable of relative displacements under the effect of a deformation and the physical properties (texture--thickness--coefficients of friction) of which are adapted to the qualities of rigidity required for the element 17 when the cover 29 is in communication with the vacuum source. In this case, the rigidity is obtained by immobilizing the sheets under pressure by friction forces or following an embedding or locking effect. 
     To this end, the sheets 31 can have different properties and exhibit a surface with buttons or spikes which can be engaged in recesses or meshes of a grid. The sheets can also have perforations, be cut away or possess rigidification elements (plates, rings etc.) in order to facilitate the application of a reduced pressure to the cover, to increase the rigidity of the filler, to improve the cohesion between the sheets or to avoid the formation of wrinkles. 
     In what follows, identical elements or members forming part of the composition of the various fillers 30 will be designated by the same reference numerals. 
     The element in FIG. 3 consequently comprises a filler 30 consisting of at least one stratum formed in a block 32 of compressible foam rubber arranged between two grids 33 in order to obtain penetration of the block 32 into the meshes of the grid when the cover 29 is connected to the vacuum source. The thickness of the block 32 is determined as a function of the desired rigidity. 
     A mechanical link is consequently made between the strata 32, 33 following the application of a reduced pressure to the cover 29. 
     The elements shown in FIGS. 4 and 5 comprises a filler similar to that in FIG. 3, in which the central stratum consists of a grid such as 33 arranged between two blocks 32a and 32b which are themselves in contact with two grids 34. Each of the grids 34 carries spikes 35 positioned perpendicularly to the blocks 32a, 32b and pointing through the said blocks towards the central grid 33. 
     When the element is subjected to a compressive force which imparts a curvature to it, the grids 34 and the blocks 32a, 32b are displaced relative to the grid 33. 
     When the cover 29 is connected to the vacuum source, the spikes 35 of the grids 34 embed themselves in the meshes of the grid 33 and improve the abovementioned mechanical link by connecting together the two grids 34 by a locking effect. In the process, the blocks 32a, 32b, the thickness of which is slightly greater than the effective length of the spikes 35, are compressed and the spikes 35 embed themselves in the grid 33. On the other hand, when the cover 29 is in communication with atmospheric pressure, the blocks 32a, 32b resume their initial state and the spikes 35 are automatically disconnected from the grid 33 by an unlocking effect. In the event of a change in curvature of the filler 30, the spikes 35 embed themselves in other meshes of the grid 33. The reversibility of the locking and the unlocking enables the shape of the supporting element to be modified as desired. 
     According to the illustrative embodiment shown in FIG. 6, the central stratum is formed by two sets of spikes 35 mounted opposite each other and integrally joined to two grids 34. It will, however, be possible in certain configurations of the element to use only one grid such as 34 to which the spikes 35 are integrally joined and point in two opposite directions normal to the grid towards outer grids 33, respectively traversing two compressible blocks 32a, 32b. 
     The abovementioned assembly is protected by outer strata 37 in order to protect the cover 29 from possible perforations. 
     In FIGS. 7a, 7b, the spikes 35 are replaced by bars 38 linking the outer grids 33 through the compressible central block 32. 
     The bars 38 can have a cylindrical body of larger diameter which is designed to preserve a substantially constant spacing between the grids 33, as indicated in FIG. 7b, while studs 38a situated at the end of the said bars are engaged in the meshes of the grids 33. 
     In FIG. 8a, the bars 38 have a central enlargement 38b and extend through an assembly of two compressible blocks 32a, 32b. In FIG. 8b, the bars 38 are integrally joined to a central stratum or grid 34. The purpose of these devices is to achieve the correct centering of the bars in the laminated layer. 
     In FIG. 9, the sealed cover 29 constituting the central stratum is inside the supporting element. The outer walls of the cover 29 (act on e.g., impact) spikes 35 integrally joined to grids 34 and extending through compressible blocks 32a, 32b. The cover 29 contains a compressible pliable body 39 such as a cellular foam. The cover 29 is connected to a vacuum or pressure source in order to obtain a displacement of the spikes perpendicularly to the outer walls of the cover towards two outer grids 33. 
     The outer strata respectively consisting of a protective wall 37, by an upholstery cover 40 and by the outer grids 33 remain at atmospheric pressure. 
     The grids 33, the walls 37 and the upholstery 40 are held in position by a spacing device 50 in order to maintain the spacing of the grids 33, while giving pliability to the supporting element assembly when the spikes 35 are not engaged positively in the meshes of the grids 33. 
     The operating mode of the supporting element depends on the initial spacing of the grids 34, 33 and on the length of the spikes 35. 
     In the case where the spikes 35 are not engaged in the grids 33 in the normal position, when the cover 29 is at atmospheric pressure, when the cover 29 is under a pressure greater than atmospheric pressure, the body 39 expands, the spikes 35 embed themselves in the grids 33 and the supporting element is rigidified. 
     Let us assume that the spikes 35 are engaged in the grids 33 in the normal position, when the cover 29 is at atmospheric pressure. 
     When the cover 29 is connected to a vacuum source, the body 39 contracts, the spikes 35 are released from the grids 33 and the supporting element is pliable again. In this case, the grids 33 and 34 are displaced parallel to each other when the supporting element is assuming its shape. 
     Re-establishment of atmospheric pressure enables the cover 29 to assume its normal size again, and the spikes 35 to engage in other meshes of the grids 33 in order to rigidify the supporting element in its new shape. 
     In this embodiment of the supporting element, the shape of the latter is maintained at atmospheric pressure, and the vacuum source is actuated only for the period necessary for the modifications of shape. 
     Without going beyond the scope of the invention, it is clear that the application of a sealed inner cover is equally appropriate in the example described with reference to FIGS. 3, 7a, 7b, 8a, 8b. In the latter case, the bars 38 will extend through the cover, the locally welded walls of which enable the creation of eyelets for the passage of the bars such as 38. Reciprocally, and by way of non-limiting example, the bars such as 38 can equally well replace the spikes 35 used in the illustrative embodiment in FIG. 9. 
     It is also understood that the supporting element can equally well be applied to the manufacture of mattresses, casts and splints which can be used in the medical field, and to the manufacture of molds or industrial packings.