FR2803371A1 - DEVICE FOR REMOVABLE PLACEMENT INSIDE HEATED ENCLOSURES - Google Patents

Abstract

The device is intended to be removably placed inside heating enclosures such as ovens and ovens, of the type comprising walls and a bottom to protect the walls and the bottom of the enclosure itself. in that it comprises three integral panels (1, 2 and 3) delimited by parallel fold lines, and to be arranged in a triptych thus presenting a central panel called "bottom" (1) and two side panels (2 and 3) having two end free edges to be vertical when the device is in place in a heating chamber, which device is preformed in aluminum foil to have intermediate bands (16 and 17) which join the panels ( 1 and 2, 1 and 3) in pairs, which are integral with them and which are provided with at least two longitudinal corrugations (18) constituting an extensible bellows, while the free end edges, to be vertical , each have a reinforcement stiffening (30-31).

Description

Device to be removably placed inside

  There are already known disposable devices for protecting the inner walls of ovens, so that the projections due to the cooking of juice and grease are deposited not on the walls of the oven itself but on the disposable device. Thus, the patent document FR 2 728 657 describes a box formed of four walls

  integral with each other and unfolded in volume from a folded position flat.

  This box has no means of adjusting its external dimensions to the interior dimensions of the oven, essentially for two reasons: * the three walls intended to be vertical are integral with a lower portion to be horizontal, * the two vertical walls which are face are united to the single central wall by

  junction flaps provided with an adhesive.

  Thus, the dimensions of the box volume are fixed once and for all and therefore are not adjustable, because of its general design, based on principles

immutable geometry.

  In addition, this document provides for the box in "folding material" which should be interpreted as meaning that it is light sheets that it is necessary to

  "consolidate by means of a stiffening frame".

  The patent document GB 1 158 792 relates to a removable and folding box, intended to be placed inside a furnace after setting volume, it being adapted to the standard dimensions of the furnaces. It describes a way to enlarge the volume of the box along its diagonals, that is to say both in width and height, with flaps folded on themselves and can be deployed so that the walls of the box are closer to those of the oven. This arrangement is necessary here because the box is maintained in part by its own rigidity and partly thanks to the existing grids of the original oven which must be inserted into the box, which implies that if the walls of the box are removed from the oven walls, they will be torn or severely deformed during the installation of grids whose stiffness and strength

  are much greater than the resistance of thin sheets.

  But no means can adjust the depth of the box, dimension measured between the inner edges surrounding the front door and the rear wall of the oven, because the problem solved by this patent is that the veneer walls of the box against those of the walls of the oven (because of the use of the grids as means of maintaining the box) and not that of the integral protection of the walls of the oven against projections. Also note that the tight folds of the flaps give each of them a relative

  rigidity presented as contributing to the good behavior of the box.

  The present invention deviates from these known prior solutions and allows for a lightweight device, presented for sale flat, easy to put in volume and ensuring a

  complete protection of the walls of a heating chamber of the household oven type, that is to say

  adjustable to different dimensions of furnaces and ensuring the complete recovery of

vertical walls of the oven.

  To this end, the invention relates to a device intended to be removably placed inside heated enclosures such as ovens and ovens, of the type

  including walls and a bottom to protect the walls and the bottom of the enclosure itself

  same, characterized in that it comprises on the one hand three integral panels delimited by parallel fold lines, and to be arranged in triptych thus presenting a central panel called "bottom" and two side panels having two free edges d end to be vertical when the device is in place in a heating chamber, and secondly an independent sheet substantially rectangular, flat, stiffened by peripheral edges and by stiffening ribs, intended to be placed in line with the space determined by the triptych panels, which device is preformed in aluminum foil to present intermediate strips which join the panels in pairs, which are integral with them and which are provided with at least two longitudinal corrugations constituting an expandable bellows, while the free end edges, to be vertical,

  each have a stiffening reinforcement.

  According to other features of this device: the central panel has a height less than that of the side panels; each panel has a free upper edge provided with an extension folded flat against the face of the panel which is said to be "visible" when the device is put in place in an enclosure, as opposed to that which is invisible, vis-à-vis the wall of the enclosure, so that in this situation, the extension is accessible to the user, said extension being able to be straightened to increase the height of the panel; each extension has a stiffening edge; the lower edge of each panel has a stiffening edge; at least some of the stiffening flanges are each formed by a rolled fold of the aluminum foil; > the side panels each have horizontal undulations; horizontal corrugations form several groups which are separated by smooth spaces and which each extend over a height substantially covering the different possible levels of slideways existing on the side walls of heating chambers of several known standards; the side panels have on their visible faces facing one another when the device is placed in a chamber, two horizontal grooves each located on one of the panels, at the same level, near the edge lower panels; openings facilitating the gripping of the device are provided near the free end edges of the side panels; the openings are formed in the stiffening reinforcements; > stiffening reinforcements consist of inserts; > the inserts constituting stiffening reinforcements are attached to the side panels by means of welds; the device having side panels comprising smooth spaces, the inserts constituting stiffening reinforcements are welded to said side panels on the smooth spaces; the flat sheet has at least two straight, parallel paralleling lines and in the vicinity of at least two of its opposite edges, contributing to its stiffening and facilitating the straightening of at least one edge of the sheet to adapt the sheet to the width and / or depth of the enclosure; the stiffening ribs of the independent sheet are in relief on one side of said sheet and recessed on the other, this face being intended to constitute the upper face of the sheet when the latter is placed horizontally in a chamber, to the plumb with the space determined by the triptych panels, either below their lower edges or at an intermediate level between their upper edges and their lower edges; > the dimension of the independent sheet considered perpendicular to the depth of an enclosure, is greater than the distance between the two side panels of the triptych when it is deployed; the independent sheet has openings in the vicinity of two of its opposite edges.

  The invention will be better understood from the detailed description below, made in

  reference to the appended drawing. Of course, the description and the drawing are only given

  as an indicative and non-limiting example.

  Figure 1 is a schematic perspective view of three solidarity panels

  according to the invention, constituting a triptych.

  Figure 2 is a partial schematic view of the upper part of a panel.

  FIG. 3 is a partial schematic view illustrating the formation of a flange of

  stiffening by a rolled fold of the aluminum foil constituting the panels.

  FIG. 4 is a partial schematic view showing an intermediate band provided with

  of corrugations and likely to be lengthened by flattening of the undulations.

  FIG. 5 is a partial schematic view showing the panels in place in a

  furnace of reduced dimensions, the undulations of the intermediate band being intact.

  FIG. 6 is a partial schematic view showing the panels in place in an oven of larger dimensions than those of FIG. 5, the corrugations of the

  intermediate band being flattened and the band itself in extension.

  FIG. 7 is a diagrammatic cross-sectional view of an oven in which the device according to the invention is located, namely the three triptych panels and the horizontal independent sheet, the latter being placed on a standard plate, positioned at a

  intermediate level between the upper and lower edges of the triptych panels.

  FIG. 8 is a partial schematic view showing a vertical stiffener and its

  solder attachment to a side panel.

  FIG. 9 is a schematic perspective view of a planar independent sheet

according to the invention.

  Figure 10 is a partial schematic view showing the layout of the sheet

  independent when positioned under the lower edges of the panels.

  Fig. 11 is a partial schematic view showing the arrangement of the independent sheet when positioned at an intermediate level between the edges

  upper and lower panels.

  Referring to the drawing, we see that a device according to the invention comprises three panels 1, 2 and 3 integral and hinged together, cut from the sheet

  of quality aluminum called "food".

  The panels 1, 2 and 3 are presented flat, folded over each other, and are intended to be deployed in triptych to be placed in a heating chamber, that

  is designated in the following description by the more usual word "oven"

  but which can also be an oven, a flat heater, etc. The central panel 1 is called "bottom panel" because it must be placed against the wall of the oven located opposite the access door. The panels 2 and 3 hinged on either side of the panel 1 are side panels that must be placed against the walls

right and left of the oven.

  It is observed that the central panel 1 has a height h less than the height H of the side panels, which makes it possible to introduce the triptych into the oven very easily, with the minimum risk of hanging the heating resistors or gas burners

  At the top of the oven (Figure 7).

  It should be noted that the expression "against the walls" must be taken in the broadest sense of the term, firstly because of the great flexibility of the panels made of aluminum foil a few tenths of a millimeter thick, and on the other hand, considering that it is irrelevant that the panels are actually against the walls

  oven and somewhat distant (also irregularly) of these walls.

  The important thing is that the panels are interposed between the walls of the oven and its central space, where there are placed foods to cook, defrost or heat, because we try to intercept the projections and messy vapors which, as well , must be deposited

  not on the walls of the oven but on the panels of the triptych which is removable and disposable.

  The deployed triptych has dimensions corresponding to the interior of the household ovens

  the most frequently encountered on the market, of small size.

  However, furnaces of various capacities are commonly available, the interior volume of which is greater or lesser because of a greater width, a greater height, a greater depth or two or three of

these dimensions.

  As the object of the invention is to protect the oven walls against soiling, it is

  important that the triptych covers the entire surface of these walls.

  Therefore, to be able to increase the height of the panels and to better adjust to that of the walls, each of the three panels 1, 2 and 3 has an extension respectively 4, 5 and 6 which is folded flat against the panel which carries it when the

  panels are folded over each other for sale and presentation.

  When placing the triptych in the oven, the extensions 4, 5 and 6 are left in their folding position. After setting up, the user verifies at a glance whether the panels are high enough or not. In the first case, the extensions 4, 5 and 6 remain in the state. If, on the contrary, the panels are lower than the walls, the user rectifies the extensions 4, 5 and 6, as evoked by the arrow F1 in FIG. 2, along a pre-folding line respectively 7, 8 and 9, it being understood that this recovery can be total, in which case the extension is in the alignment of the panel, or partial. Maintaining the desired orientation and position is easy thanks to the flexibility of the aluminum foil, its malleability and its non-elasticity. So she stays in the position where she was put in pressing her a little

  in the corner formed by the side wall of the oven and its upper horizontal wall.

  In order for the user to access extensions 4, 5 and 6 after the triptych has been placed in the oven, these extensions must be folded against the face of the panels that are called "visible" as opposed to the other side, which is in

  vis-à-vis the corresponding wall of the oven and therefore inaccessible and invisible.

  Because of the thinness of the panels and so that the handling of the triptych during its deployment and its placement in the oven do not risk deforming, tearing or perforating the aluminum foil, it is good to provide for means of stiffening, which facilitates the handling during the unfolding, the establishment in a

oven and removal of the triptych.

  Already the pre-folding lines 7, 8 and 9 alone contribute to stiffen the panels parallel to their plane but, in addition, it is expected that the free edge of the extensions, 6 and 7 instead of being straight has a rim rolled respectively 10, 11 and 12, which has the advantage not only of increasing the stiffness of the corresponding panel, but in addition to providing protection against the danger of injury because a free edge of a

aluminum foil is cutting.

  For the same reasons of stiffening and protection, the lower edge of the panels 1,

  2 and 3 carries a rolled rim respectively 13, 14 and 15, (Figure 3).

  In order to allow the adaptation of the triptych not only at different heights but also at the different widths and depths of current furnaces on the market, the panels 1 and 2 on the one hand, 1 and 3 on the other hand are joined by an intermediate band respectively 16 and 17 having a plurality of longitudinal corrugations 18, as

can be seen in Figure 4.

  In FIG. 4, it can be seen that the intermediate strip 16 has an inclined upper edge, because the upper edge of the panel 1 (which is in fact formed by the pre-folding line 7) is out of alignment with the upper edges of the side panels (which are actually trained by the

  pre-folding lines 8 and 9) because of the difference in heights h and H (Figure 1).

  When the triptych is new, the corrugations 11 are well marked and the side panels 2 and 3 are as close as possible to the central panel 1. In FIG. 5, there is shown the case where the triptych corresponds substantially to the inside dimensions of the furnace, so that the undulations 18 remain what they are, unless they are a little more

  tight to shorten the perimeter of the three panels 1, 2 and 3 deployed in triptych.

  In Figure 6, there is shown the case where the oven is deeper and wider, so that the user had to move the side panels from one another and even pull a little on the side panels pushing the central panel 1 to the bottom, in short to place the panels of the triptych closer to the walls of the oven. This is possible thanks to the undulations 18 which flatten out and allow the extension of the intermediate strips 16

  and 17, behaving like two bellows.

  The furnaces have horizontal rails on their side walls, at several levels, to allow the introduction and removal of cooking accessories such as a plate, a grill, a broiler pan, a hollow dish, etc., as is

well known in itself.

  Depending on the furnace, these side rails are recessed or raised and are located at non-standard levels. However, the triptych must be able to adapt to all the models, so that the side panels 2 and 3 have horizontal corrugations constituting, like the corrugations 18 of the intermediate strips 16 and 17, reserves of length, allowing a transverse deformation of panels, both towards

  outside for recessed slides, only inwards for raised slides.

  FIGS. 1 and 8 show that the corrugations of the two lateral panels 2 and 3 are arranged in groups 20 for the panel 2 and 21 for the panel 3, situated in pairs at the same level, in the zone where the known furnace barriers, zone delimited in height between the highest and the lowest level of ovens

currents.

  Thus, during the establishment of the triptych, it is possible to very easily shape the side panels 2 and 3 to the desired height so that the corrugations deform and marry the hollow or the relief of the slide on which the user wishes place a cooking accessory. The aluminum foil constituting the panels 2 and 3 being very thin, it does not interfere with the setting up or the removal of the accessory and it protects very

well the wall of the oven.

  The corrugation groups 20 and 21 define between them smooth zones 22 and 23 and constitute stiffening ribs, giving the panels 2 and 3 a very good

  rigidity, guarantee of easy handling.

  In the lower part of the panels 2 and 3, there is a groove respectively 24 and 25 whose concavity is on the visible face of the panels and the convexity on the invisible face. The height of this groove 24-25 is set to allow to engage a cooking accessory, regardless of any slide. By unfolding the triptych and bringing the two side panels 2 and 3 together on either side of a cooking accessory such as a plate B, the two panels are held tight against the plate B

  rigid, which allows a very easy set up of the whole in an oven.

  As mentioned above, the sharp edges of an aluminum foil are sharp and, in addition, give no mechanical strength. It has been seen that to avoid sharp edges while stiffening panel edges, a rolled edge is provided. It is understood that it would be the same for the two free end edges of the panels 2 and 3 and one would think that a rolled edge would be satisfactory but, in fact, these free edges which are vertical when the triptych is in a kiln are particularly vulnerable and vulnerable, so provision is made for reinforcements

special stiffening.

  Here, we chose the solution which consists in bringing back aluminum foil elements whose thickness may be slightly greater than that of the sheet in which are

formed the panels 1, 2 and 3.

  These elements 30 and 31 are bent at right angles to present a portion 32-33 parallel to the plane of the corresponding panel 2-3 and a front portion 34-35 perpendicular, the

  fold line constituting a longitudinal stiffening rib.

  To easily remove the triptych out of the oven after use, it is advantageous to provide gripping means offering the user a grip by which he can

easily exert traction.

  Here, openings 36 and 37 are provided in the parts 32 and 33, which is particularly judicious because of the good rigidity and robustness of the elements.

reinforcements 30 and 31.

  As a result, the openings leave horizontal tabs 38 and 39 located at the smooth zones 22 for the panel 2 and 23 for the panel 3, whereby the elements 30 and 31 can be fixed to the panels 2 and 3 by the legs 38 and 39 at

means of welding 40.

  These welds 40 do not interfere with the deformability of the panels 2 and 3 by using their height reserve due to the corrugation groups 20 and 211when this reserve is necessary to allow the panels 2 and 3 to adapt locally to the slides

  of the oven, as can be seen in FIG.

  Referring now to FIGS. 9 to 11, there is shown a rectangular, substantially flat, independent sheet 51 which is usable with the triptych that comes

to be described.

  The sheet 51 is cut from an aluminum foil and the edges of its four sides, so as not to be sharp and to stiffen the sheet, have a rolled edge 52 for

  its short sides and 53 for its long sides.

  Two straight pre-folding lines 54 and 55 are at a small distance from the flanges 52 and parallel to them, by determining two lateral flaps 56 and 57. In practice, it is possible to provide at least two pre-fold lines near each edge, so that the user can easily straighten the flaps 56 and 57 clearly and without tearing more or less far from the corresponding edge, which means that after straightening the flaps 56 and 57 are more or less wide according to the pre-folding line

which has been used by the user.

  It is observed that there is a discontinuity 58 on the rolled edges 53 to the right of the flaps 56 and 57, that is to say that these rolled edges 53 are non-existent or are crushed flat after being formed, between the pre-folding lines 54-55 and the flanges 52, in order to

  facilitate the net adjustment of components 56 and 57.

  When there are several pre-fold lines, the discontinuity 58 of the rolled edges 53

  from flange 52 to the pre-pliage line furthest from this flange.

  With the example shown, the lateral flaps 56 and 57 are traversed by openings 59 and 60. The central portion of the sheet 51 must also be stiffened so that it can be

  easily manipulated and set up as described below.

  For this, the forming of the sheet 51 comprises not only the creation of the rolled flanges 52 and 53 but also the drawing of several lines which on one side of the sheet 51 constitute raised ribs 61 and on the opposite face of the grooves hollows 62 which also serve to collect any liquids that might flow

  accidentally when heating food.

  The sheet 51 is independent of the triptych and therefore constitutes an autonomous product that can be provided either with a triptych or separately, alone or in groups of

less two.

  hA It is intended to be placed in line with the space determined by the three panels 1, 2 and 3 deployed in triptych, that is to say either under their lower edge, or between them

panels 1, 2 and 3 themselves.

  The triptych is intended to protect the vertical walls of the oven and the sheet 51 is intended to protect its lower part. The dimensions of the sheet 51, like those of the triptych, are established according to those of the current furnaces but as it must be able to cooperate with the triptych, its dimensions must be coordinated with those of this triptych Indeed, the user may wish to use all the available height of the oven and arrange the food to be heated near its lower part, so that it is necessary to provide the possibility of placing the lower edges of the triptych above the sheet 51, as

  it is shown in Figure 10, the sheet 51 is then a simple tray.

  As already indicated above, the aluminum foil is easily deformable because of its flexibility, so that it can straighten a little side edges 1i5 behind the panels 2 and 3, as we have evoked in dashed lines in Figure 10, this

  possibility depending on the spacing of the panels 2 and 3 at their lower part.

  It is therefore possible to bring the lower part of the panels 2 and 3 a little closer and / or to straighten the lateral edges of the sheet 51 in order to avoid any dripping of the juice,

  drops and condensates under the sheet 51.

  It is thus advantageous to give the sheet 51 a width L measured between the lateral flanges 52 a little greater than the distance separating the panels 2 and 3 when these

  are parallel to each other and perpendicular to the central panel 1.

  But we must also be able to have the sheet 51 no longer under the edges of the triptych

but between panels 2 and 3.

  Then, after setting up the triptych in the oven, the flaps 56 and 57 are straightened, which fold easily along the pre-folding lines 54 and 55, as shown in FIG. 11, and then the sheet 51 is inserted between panels 2 and 3 until it abuts against the bottom panel 1, and the user takes care to fold down the flaps 56 and 57 to properly apply the flanges 52 against the panels 2 and 3, for the purpose to bring back to the center of the sheet 51 the liquids that could flow to

the surface of panels 2 and 3.

  A 2L In Figures 10 and 11, there is shown the sheet 51 without any support but in reality the sheet 51 is not self-supporting and as it is not a hollow tray but a simple tray, it can only be really effective if it is

  placed on a cooking accessory such as a plate or a grill.

  This is shown in Figure 7 where we see that it was laid on two rails facing the oven an accessory such as a grid C (there is provided here a plate B in the bottom of the oven), then the sheet 51 whose shutters 56 and 57 are applied against the panels 2 and 3. Finally, the foods (not visible in the drawing) are here placed in

a dish D placed on the sheet 51.

  It can be seen that the vapors, condensates and other projections resulting from the heating of food can not reach either the vertical walls or the lower horizontal wall of the oven. The openings 59 and 60 formed in the flaps 56 and 57 are intended to improve the free heat transfer, and especially the free path of the heating air in the case of a fan oven. In Figure 7 it is seen, in particular, that the provision of food at half height would have the effect of compartmentalize the oven in two unequally heated floors if a solid support was arranged across the oven, which would be the case of a plate or a sheet 51. That is why it is preferable to place a grid C at mid-height and not a plate, and to provide openings through the sheet 51 from one side to the other, without diminishing its rigidity or its sealing to

recovered liquids.

  The sheet 51 is not the equivalent of a broiler pan or a plate. On the other hand, since it is placed on a stable base, it serves as a support for food to be heated, either directly (pizzas, frozen foods, etc.), or indirectly when

  food is placed in a container (dish, tray, etc.).

  After removing the dish D and extinguishing the oven, the user crumples the sheet 51, removes it and throws it and then engages one or two fingers in openings 37 and extracts the soiled triptych, folds, wrinkles and eliminates it, which allows him to find an oven free of

  any stain, having no need to be cleaned.

  Naturally, this withdrawal is not systematic after each use because it depends on the degree of soiling of the triptych on the one hand and the sheet 51 on the other hand. The user can therefore, at choice, keep the triptych and / or the sheet in place for several uses or for one, just as it can replace the sheet 51 alone and keep the

  triptych, or replace the triptych and keep the sheet 51.

  The example which has been described above may of course give rise to variants, particularly in the realization of the stiffening ribs. The vertical reinforcements 30 and 31, in particular, may be made differently, in particular by folding the aluminum foil onto itself to increase its thickness.

  thickness and therefore its rigidity, which eliminates the welds 40.

  Similarly, the openings 37 may be replaced by any equivalent allowing

  facilitate extraction of the triptych out of the oven after use.

*** 4q

Claims (19)

  1. Device intended to be removably placed inside heated enclosures such as ovens and ovens, of the type comprising walls and a bottom to protect the walls and the bottom of the enclosure itself, characterized in that it comprises on the one hand three integral panels (1, 2 and 3) delimited by parallel fold lines, and to be arranged in triptych thus presenting a central panel said "bottom" (1) and two side panels (2 and 3) having two end free edges to be vertical when the device is in place in a heating chamber, and secondly a substantially rectangular, flat, independent sheet (51) stiffened by peripheral flanges (52 and 53) and by stiffening ribs (61-62), intended to be placed in line with the space determined by the panels (1, 2 and 3) in triptych, which device is preformed in the sheet of aluminum to present b andes intermediates (16 and 17) which bring together the panels (1 and 2, 1 and 3) in pairs, which are integral therewith and which are provided with at least two longitudinal corrugations (18) constituting an expandable bellows, while the free end edges, to be vertical,   each have a stiffening reinforcement (30-31).   2. Device according to claim 1, characterized in that the central panel (1) has a   height (h) less than that (H) of the side panels (2 and 3).   3. Device according to claim 1, characterized in that each panel (1-2-3) has a free upper edge provided with an extension (4-5-6) folded flat against the face of the panel which is called " visible "when the device is set up in an enclosure, as opposed to the one that is invisible, vis-à-vis the wall of the enclosure, so that in this situation, the extension (4-5-6) accessible to the user, said extension (4-5-6) being capable of being straightened in order to   to increase the height of the panel (1-2-3).   4. Device according to claim 3, characterized in that each extension (4-5-   6) has a stiffening edge (10-11-12).   5. Device according to claim 1, characterized in that the lower edge of each   panel has a stiffening edge (13-14-15).   6. Device according to any one of claims 1, 4 and 5, characterized in that   at least some of the stiffening flanges (10-11-12, 13-14-15) are each formed by a rolled fold of the aluminum foil. 7. Device according to claim 1, characterized in that the side panels (2 and   3) each have horizontal undulations.   8. Device according to claim 7, characterized in that the horizontal corrugations form several groups (20 and 21) which are separated by smooth spaces 22 and 23) and which each extend over a height substantially covering the different possible levels of slides -existing on the side walls of speakers   heating of several known standards.   9. Device according to claim 1, characterized in that the side panels (2 and 3) have on their visible faces facing each other when the device is placed in a chamber, two horizontal grooves ( 24 and 25) each located on one of the panels (2-3), at the same level, near the edge lower panels (2 and 3).   10. Device according to claim 1, characterized in that openings (37) facilitating the gripping of the device are provided in the vicinity of the free edges.   end of the side panels (2 and 3).   11. Device according to claim 10, characterized in that the openings (37) are   formed in stiffening reinforcements (30 and 31).   12. Device according to claim 1, characterized in that the stiffening reinforcements   are constituted by added elements (30 and 31).   13. Device according to claim 12, characterized in that the inserts (30 and 31) constituting stiffening reinforcements are attached to the side panels (2 and 3). by means of welds.   14. Device according to claim 13, whose side panels (2 and 3) comprise smooth spaces (22 and 23), characterized in that the elements constituting stiffening reinforcements (30 and 31) are welded to said   side panels (2 and 3) on the smooth spaces (229 and 23).   15. Device according to claim 1, characterized in that the plane sheet (51) has at least two straight pre-folding lines (54 and 55), parallel and in the vicinity of at least two of its opposite edges, contributing to its stiffening. and S facilitating the straightening of at least one edge of the sheet (51) to adapt the   sheet (51) at the width and / or depth of the enclosure.   16. Device according to claim 1, characterized in that the stiffening ribs of the independent sheet (51) are in relief (61) on one side of said sheet (51) and recessed (62) on the other, this face being intended to constitute the upper face of the sheet (51) when it is placed horizontally in an enclosure, to   perpendicular to the space determined by the panels (1, 2 and 3) in triptych, that is to say   below their lower edges (13, 14 15), or at an intermediate level between   their upper edges and their lower edges.   17. Device according to claim 1, characterized in that the dimension (L) of the independent sheet (51) considered perpendicular to the depth of an enclosure is greater than the distance between the two side panels (2 and 3).   the triptych when it is deployed.   18. Device according to claim 1, characterized in that the independent sheet (51)   has openings (59 and 60) in the vicinity of two of its opposite edges.   19. Device according to claim 1, characterized in that the peripheral rims (52 and 53) are separated by a discontinuity (58) in the vicinity of the corners of the sheet (51), or that some of the peripheral rims (53) have a end located below the corners of the sheet (51), or that said peripheral edges are flattened by localized crushing.