DEVICE FOR SECONDARY CLOSURE OF AN UNDERGROUND CHAMBER

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of access chambers for underground infrastructure. More specifically, it relates to underground chambers providing access to networks such as telecommunications networks or distribution networks (water, electricity, gas, etc.). It particularly concerns means of closing and securing such chambers. STATE OF THE ART

[0002] Communication networks, as well as water, electricity, and gas distribution systems, are often buried underground. Access chambers are installed at various points within these underground infrastructures to allow for inspections, connections, and / or maintenance work on these networks.

[0003] These access chambers are closed when not in use to access the corresponding underground infrastructure. This closure is achieved by means of a cover, also called a manhole cover, which forms the main closing device.

[0004] Such a lid can be metallic, for example cast iron or steel, but it can also be made of plastic, for example composite. The lid protects the contents of the chamber and allows passage over it for people and / or vehicles.

[0005] The cover forming the main closing device of a chamber can have various configurations. It is generally positioned in a frame that is sealed in the ground.

[0006] The cover can be removed from the frame or tilted to allow access to the chamber below the frame and the network it contains.

[0007] However, when the main locking device is removed or tilted to allow access to the chamber—in other words, when the chamber is open—certain problems can arise. For example, there is a risk of an operator falling while the chamber is open but the operator is not working inside it, or during the chamber opening process. Furthermore, improper handling can cause the cover or a tool to fall into the chamber, particularly during the opening, which can damage the underground infrastructure within the chamber.

[0008] To address these issues, a known solution is to install a secondary closure device beneath the primary one. This second device is usually in the form of a grille. While this grille does not offer the same sealing capacity or resistance as the primary lid, it does prevent a person or object (for example, from the lid itself) from falling into the chamber.

[0009] As is known, this grid can be held in position in two alternative ways.

[0010] In one configuration, the grid can be inserted into supports that are fixed to opposite walls of the chamber, towards the top of these walls. This can then be referred to as a grid with pegged or "spun" supports.

[0011] According to a second configuration, the grid is placed on supports welded to the frame of the access chamber.

[0012] To access the chamber, and depending on the type of grille, the grille can be removed or opened by pivoting (this is called a hinged grille). The latter solution is preferable, as a removable grille could itself fall into the chamber.

[0013] Thus, whether the grid supports are fixed to the frame or to the chamber, advantageously, these supports and the grid can be configured to allow on the one hand the grid to pivot and on the other hand the grid to be locked, for example with a padlock.

[0014] The grid is typically articulated by aligning holes formed in the supports and the grid itself, and inserting a transverse axis through them. Alternatively, an axis can be rigidly attached to the grid and inserted into a hinge formed by the support.

[0015] Document FR3062860 thus discloses an example of a fall arrest grid, as described above, with a bolted axle.

[0016] Another example of a grille as described above is known from document FR2792662A1. The grille described in this document is further configured so that it can be opened by pivoting 180° relative to the frame of the chamber it equips.

[0017] Nevertheless, secondary sealing solutions for access chambers to underground infrastructure can still be improved. One particular challenge is that installing such grates requires precise positioning of the grate supports, while the chambers are often manufactured with significant dimensional tolerances. This is especially true when the supports are fixed, or bolted, to the chamber walls. It is also true when the supports are connected to the frame, as any significant manufacturing precision translates into higher costs. In general, the cost of achieving the function of the secondary grate, whether the cost of the supports or the cost associated with the required tight tolerances, can be reduced. DESCRIPTION OF THE INVENTION

[0018] The present invention aims to remedy all or part of the drawbacks of the prior art mentioned above.

[0019] To this end, the invention relates to a secondary closure device for an underground chamber, intended to be installed in said underground chamber under a main closure device, in order to block, when said secondary closure device is in a closed position, at least partially the access to a bottom of said underground chamber, the secondary closure device comprising a grid having a transverse axis of circular section, and supports adapted to support the grid in said underground chamber in said closed position.

[0020] The supports consist of a first hinged support that allows the grid to pivot around its transverse axis, so that the grid can be rotated to an open position that provides access to the underground chamber, and a second support. The first and second supports are positioned near opposite walls of the underground chamber, along a longitudinal direction.

[0021] The first support comprises two parallel wings perpendicular to the grid's transverse axis. Each wing has a slot with a complex trajectory, the width of which is slightly greater than the diameter of the axis. This allows the axis to slide within the slot from an entry point to a terminal portion, and enables the grid to rotate around the axis. The terminal portion is straight and allows for longitudinal translation of the transverse axis. The slot in each wing of the first support has a trajectory that is approximately C-shaped or S-shaped.

[0022] The configuration of the first support, which can be implemented very simply and economically, allows for easy, tool-free installation and removal of the grid. It also allows for some flexibility in the grid's longitudinal position. This enables the secondary closure to be used without complex adjustments, even when the manufacturing tolerances of the underground chamber or frame are relatively large (e.g., 10 mm, 20 mm, or even more). Furthermore, to adapt the device to larger chambers, or chambers whose dimensions exceed the maximum tolerance, shims can be easily added to adjust the position of the supports.

[0023] The second support may include at least one vertical tab, adapted to pass through a notch formed in the grid.

[0024] The notch can have a length greater than the width of the leg, allowing longitudinal movement of the grid.

[0025] At least one vertical leg of the second support may have a hole located above the grid, when the latter is in the closed position, so as to be able to fix on said vertical leg a locking device, for example a padlock.

[0026] The first support or the second support may be formed of two angle brackets, each angle bracket having a fixing flange intended to be fixed, for example pegged, to a wall of the underground chamber.

[0027] The secondary closure device may further include an installation template to determine the position of the drillings to be made on a wall of the underground chamber to fix the first or second support, the template being made of a plate, said plate having a first surface intended to be made in contact with an upper rim of the chamber, a second surface intended to be made in contact with said wall of the underground chamber to which the first or second support is to be fixed, and an edge intended to be made in contact with a side wall of the underground chamber which is perpendicular to said wall of the underground chamber to which the first or second support is to be fixed, the second surface of the template having openings whose position corresponds to the position of the drillings to be made.

[0028] The first support can be formed from a piece comprising a central plate and two wings parallel to each other and perpendicular to the central plate, said central plate having a folded end part adapted to be welded to a frame.

[0029] The second support may be formed from a piece comprising a central plate and two vertical legs, said central plate having a folded end part adapted to be welded to a frame.

[0030] The secondary closure device may further include a frame forming a seating surface for a primary closure device of an underground chamber, for example for a cover, in which the first support and the second support are welded to opposite edges of the frame.

[0031] The first support and / or the second support can be made solely by folding and cutting a flat sheet of metal. BRIEF DESCRIPTION OF THE FIGURES

[0032] Other advantages, purposes and particular features of the present invention will become apparent from the following non-limiting description of at least one particular embodiment of the devices and methods of the present invention, with reference to the accompanying drawings, in which: there figure 1 is a schematic view of an underground chamber with a secondary closure conforming to the state of the art; the figure 2 represents the supports used for the secondary closure of the figure 1 , in accordance with the state of the art; the figure 3 represents, according to a schematic three-dimensional view, an example of a support for a secondary closure of an underground chamber, according to an embodiment of the invention, the figure 4 is another view of one of the supports of the figure 3 ; there figure 5 is a detailed view of one side of a secondary underground chamber closure mounted on the supports of the figure 3; there figure 6 is a detailed view of the other side of a secondary underground chamber closure mounted on the supports of the figure 3 ; there figure 7 is a schematic three-dimensional view of an underground chamber with a secondary closure device including the supports of the figure 3 ; there figure 8 represents a template allowing the installation of the supports of the figure 3 ; there figure 9 represents a template similar to that of the Figure 10 , when used in an underground chamber; the Figure 10 represents an example of a support for the secondary closure of an underground chamber, according to a prior art embodiment in which the supports are linked to one side of the underground chamber frame; the figure 11represents an example of a support for the secondary closure of an underground chamber, according to a prior art embodiment in which the supports are linked to the other side of the underground chamber frame; the figure 12 represents an example of a support for the secondary closure of an underground chamber, according to an embodiment of the invention in which the supports are linked to one side of the frame of the underground chamber; the figure 13 represents an example of a support for the secondary closure of an underground chamber, according to an embodiment of the invention in which the supports are linked to the other side of the underground chamber frame; the figure 14 is a schematic three-dimensional view of a frame and a grid forming a secondary closure according to another embodiment of the invention; the figure 15represents a grid adapted to form a secondary closure of an underground chamber as illustrated in the figure 14 . DETAILED DESCRIPTION OF THE INVENTION

[0033] This description is given as a non-limiting example of implementation. figure 1 This is a schematic view of an underground chamber with a secondary closure conforming to the prior art. The underground chamber 1 is in the form of a rectangular shaft formed in the ground. The underground chamber has walls 2, here made of concrete. The upper edge of the underground chamber 1 is reinforced by a frame 3. The frame 3 is generally metallic and forms a bearing surface 4 on which a cover can be placed to seal the underground chamber 1.

[0034] A secondary closure of the chamber is provided, in the form of a grid 5. The grid 5, in the closed position, extends horizontally under the frame, and therefore under the cover (not shown) which forms a primary closure device for the underground chamber 1.

[0035] The purpose of the grid 5 is to secure underground chamber 1, primarily during the opening of the cover (or other primary closing device), or when said cover is opened or removed. Indeed, when opening the chamber cover, which is generally heavy, there is a risk that the cover or a tool may fall into underground chamber 1. There is also a risk of falling into the underground chamber for the operator opening the cover.

[0036] The secondary closure device thus prevents the cover, a tool, or a person from falling to the bottom of the underground chamber 1. This avoids a risk of injury to the person concerned, and / or damage to the equipment contained in the underground chamber 1.

[0037] The grid 5, which is not subjected to such significant and repeated stresses (e.g., the passage of vehicles) as the primary closure, must nevertheless be securely fixed to the underground chamber 1.

[0038] To this end, supports 6 are, in the example shown here, securely fixed, preferably pegged, to opposite walls 2 of the underground chamber.

[0039] The chamber is arbitrarily oriented by considering that the walls where the supports 6 are fixed are longitudinally opposed, that is to say here along a longitudinal direction L. The longitudinal direction corresponds in the example shown to the largest side of the underground chamber, which is rectangular in this example.

[0040] The transverse direction T is defined as the horizontal direction perpendicular to the longitudinal direction L, and here it is parallel to the short side of the rectangular chamber.

[0041] The supports 6 thus comprise: a first support 7, allowing the extraction or articulation of the grid 5 (to bring it into the open position), and a second support 8.

[0042] Six different types of supports are known in the prior art. An example of a known, functionally advanced support is shown in the image. figure 2 .

[0043] There figure 2thus represents the first support 7 and the second support 8.

[0044] The first support 7 consists of two solid, rigid brackets. Each bracket has a first portion 9 with holes 10, each allowing the insertion of an anchor bolt. A second portion 11 of the bracket has a hook 12 which is attached, for example welded, to the first support.

[0045] The hook 12 allows a transverse axis 13 of the grid 5 to be locked in order to allow it to tilt.

[0046] The second support 8 also includes two solid, rigid brackets. A first portion 9 of each bracket has holes 10, each allowing the insertion of an anchor bolt. At least one of the two brackets of the second support 8 has a ring 14 fixed, for example welded, to its second portion 11. When the gate 5 is in the closed position, it rests on the second portion 11 of each of the brackets of the second support 8. The ring 14 then protrudes above an upper surface 15 of the gate. A padlock can be fitted into the ring 14 to lock the gate 5 in the closed position.

[0047] These supports can nevertheless be improved: they are complex parts to manufacture (they require the assembly of the hooks 12 and the ring 14, in particular), they are laminated parts assembled by welding, which are relatively expensive, and they require high precision during assembly. In particular, if the longitudinal spacing between the supports is not correctly maintained and is too large, there is a risk that the grid 5 could be removed from the first support 7 despite the presence of a padlock in the ring 14. Conversely, if the spacing is too small, mounting the grid 5 may be impossible, or the grid may rest incorrectly on the support 6.

[0048] According to known embodiments, an accuracy of around 2 mm is required to ensure the correct positioning and proper functioning of the grid 5. However, such accuracy is rarely achieved with certainty with regard to the spacing between the opposite walls of an underground chamber, which requires adapting the position of the supports during their assembly, for example by means of shims.

[0049] There figure 3 illustrates 6A supports conforming to a first embodiment of the invention.

[0050] Just as in the known embodiment represented in the figure 2 , the 6A supports include a first 7A support and a second 8A support.

[0051] The first support 7A comprises two parts, namely two angle brackets 16. The two angle brackets 16 may be identical. Each angle bracket 16 has a fixing flange 17 intended to be fixed, for example by means of anchors, to a wall of the underground chamber. The fixing flange 17 may thus have holes 10, each allowing the insertion of an anchor bolt. In the example shown here, the holes 10 are oblong, allowing for some adjustment of the transverse position of the angle brackets 16. Each angle bracket 16 also has a flange 18, perpendicular to the fixing flange 17.

[0052] Wing 18 has a slot 19.

[0053] As can be seen in the figure 4The slot 19 has a substantially constant width l. This width l is such that it allows the passage, with minimal play, of the axis 13 of the grid 5, which has a diameter D. The slot 19 can have a complex trajectory, for example, essentially a curvilinear one. In the example shown here, the slot 19 has a trajectory that is substantially C-shaped. The slot 19 has a terminal portion 20, which is closed and straight. This terminal portion is substantially horizontal when the first support 7A is fixed in an underground chamber.

[0054] As depicted in the figure 5When the first support 7A is fixed to the wall 2 of the underground chamber 1 using dowels, the two angle brackets 16 are fixed so that their flanges 18 are parallel to each other and aligned. The axis 13 of the grid 5 is inserted into the slot 19 of each of the angle brackets 16 through its opening 21 (the beginning of the upper arm of the "C" formed by the slot). The axis 13 is then advanced through each slot 19 of the angle brackets until it is in the terminal portion 20 (formed by the lower arm of the "C"). The axis 13 can then no longer escape from the first support 7A from above. It nevertheless remains free to rotate, and its longitudinal position can also be adjusted to a certain extent. For example, the length of the terminal portion of the slot 19 can be on the order of 20 mm to 30 mm, allowing a corresponding adaptation of the longitudinal position of the axis 13.

[0055] On the figure 5The axis 13 is positioned near the closed end of the terminal portion 20, which corresponds to the position of the axis 13 when the grid 5 is tilted towards its open position. In particular, the "C"-shaped configuration of the slot 19 allows the axis 13 to be moved away from the wall 2 of the chamber, which improves the stability of the grid 5 in the open position.

[0056] It is also noteworthy that the grid 5, assuming it is free at its opposite longitudinal end, can be very easily removed from the first support 7A, by making the axis 13 follow the path of the slot 19 to its entrance 21.

[0057] Each of the two angle brackets 16 forming the first support 7A can be obtained by cutting and bending (in a single 90° fold) a metal plate. A steel plate (for example, stainless steel or galvanized steel) approximately 3 mm thick can be used for this purpose. Given the small dimensions of the angle brackets 16, a scrap piece of metal plate can generally be used to form each angle bracket 16.

[0058] Regarding the second support 8A of the embodiment of the figure 3It also comprises two parts, namely two angle brackets 16A. The two angle brackets 16A may be identical. Each angle bracket 16A has a fixing flange 17A intended to be fixed, for example by anchoring, to a wall of the underground chamber (opposite the wall where the first support 7A is fixed). The fixing flange 17A of each angle bracket may thus have holes 10, each allowing the insertion of an anchor bolt. In the example shown here, the holes 10 are oblong, allowing some adjustment of the transverse position of the angle brackets 16A.

[0059] Each angle bracket 16A forms a leg 22, which extends perpendicularly to the fixing wing 17A.

[0060] The leg 22 also extends vertically, so that it passes through a notch 23 formed in the grid 5 when the latter is supported on the second support 8A, as shown in the figure 6 .

[0061] The notch 23 preferably has an elongated shape in the longitudinal direction. The length w of the notch 23 is advantageously greater than the width e of the tab 22.

[0062] This offers some freedom in the longitudinal positioning of the 16A angle brackets forming the second 8A support, between the two extreme positions shown in the figure 6 offering a range of motion d.

[0063] At least one of the legs 22 of the second support 8A has a hole 24. When the grid 5 is in the closed position, resting on the second support 8A, the hole 24 is located above the grid 5, more precisely above the upper surface 15 of the grid 5.

[0064] Hole 24 allows a padlock or other suitable locking device to be passed through, in order to lock the gate 5 in its closed position.

[0065] There figure 7is a schematic three-dimensional view of an underground chamber 1 comprising a secondary closure device including the supports of the figure 3 .

[0066] Compared to the underground chamber of the figure 1 , the underground chamber 1 of the figure 7 It differs in the secondary closing device used. In particular, the first support 7A, comprising the two angle brackets 16 having a slot 19 into which the axis 13 of the grid 5 is inserted, is fixed to a first wall of a longitudinal end of the underground chamber 1.

[0067] The second support 8A, comprising two angle brackets 16A with tabs 22 allowing the locking of the grid 5, is fixed to the wall of the underground chamber 1 opposite longitudinally.

[0068] There figure 8represents a template allowing the correct positioning of the angle brackets forming the first support 7A and the second support 8A respectively in an underground chamber. This template 25 is formed from a plate such that it has a first surface 26 and a second perpendicular surface 27.

[0069] As shown in the figure 9 , the first surface 26 of template 25 is intended to be in contact with an upper edge of the underground chamber 1, in this case on the support surface 4 of the frame 3 of the chamber.

[0070] The first surface 27 may include a handle 28 which is foldable to facilitate handling of the template 25.

[0071] The second surface 27 is pressed against the wall 2 of the underground chamber 1 to which one of the first support 7A or second support 8A is to be fixed. An edge 29 of the template 25 is pressed against the wall of the chamber which is perpendicular to the wall of the chamber to which the first support 7A or the second support 8A is to be fixed.

[0072] The second surface 27 of the template has openings 30 whose position corresponds to the position of the holes to be drilled. In particular, as in the example shown in figures 8 And 9 , openings 30 having various shapes may be present in the second surface 27. The openings have the correct spacing between them in the transverse direction for the mounting of a suitable grid 5, and, two openings 30 of the same shape have the correct vertical spacing, corresponding to the vertical spacing of the orifices 10 of the supports.

[0073] The selection of the openings used to make the drillings in the wall 2 of the underground chamber 1 allows the installation depth of the grid 5 to be chosen in relation to the bearing surface 4 of the frame 3.

[0074] There Figure 10 represents an example of a support for the secondary closure of an underground chamber, in this case the first support 7B, according to a prior art embodiment in which the supports are linked to one side of the underground chamber frame. Figure 10 This illustrates the fact that the support for a secondary locking device can be directly linked to frame 3. This simplifies the installation of the secondary locking device, but, of course, this is only feasible for underground chambers that are designed from the outset to be equipped with such a secondary locking device. In the known embodiment of the Figure 10, the first support 7B has two tabs 31 welded to the frame 3. Each tab 31 has a perforated plate 32 allowing an axle 33 (for example in the form of a bolt) to be mounted for the articulation of a grid 5.

[0075] Regarding the second corresponding support 8B, represented at the figure 11 It also includes two tabs 31A, each forming a support to receive the grid 5. At least one of the two tabs 31 can be equipped with a ring 14A for locking the grid 5, for example with a padlock.

[0076] The support of Figures 10 And 11 is complex, requires many welded parts, and does not allow tool-free disassembly of the grid from frame 3.

[0077] Following the same principle as detailed above with reference to figures 3 to 7, it is proposed within the framework of the present invention of supports 6C, comprising a first support 7C represented in the figure 12 and a second support 8C represented at the figure 13 .

[0078] The first support 7C is formed of a piece comprising a central plate 34 and two wings 18A parallel to each other and perpendicular to the central plate 34.

[0079] The central plate 34 further comprises an end part 35 which is welded to the frame 3.

[0080] Each wing 18A has a slot 19A.

[0081] Slot 19A, just like the slot in the embodiment of the figures 3 to 7 , presents a substantially constant width such that it allows the passage, with little play, of the axis 13 of the grid 5.

[0082] Slot 19A, in the example shown here, has a trajectory that is essentially "S" shaped. Slot 19A has a terminal portion 20A, which is closed, straight, and essentially horizontal when frame 3 is in place on an underground chamber.

[0083] The grid's axis 13 can easily be inserted into slot 19A and positioned in section 20A, where it can no longer escape from the top of the first support 7C. The grid 5 can nevertheless be tilted around its axis 13 to an open position. The grid can be removed from the first support 7C without tools.

[0084] The second support 8C, represented at the figure 13The second support 8C has a general structure similar to that of the first support 7C. Thus, the second support 8C comprises a central plate 34A having an end portion 35A which is welded to the frame 3. The second support also comprises two tabs 22A, which extend perpendicularly to the central plate 34A. The tabs 22A also extend vertically, so that they pass through the notches 23 formed in the grid 5 when the latter is supported by the second support 8C.

[0085] Just as in the embodiment represented in figures 3 to 7 , the 22A legs advantageously have a width less than the length of the notches 23.

[0086] At least one of the legs 22A has a hole 24 located above the grid 5, more precisely above the upper surface 15 of the grid 5 when it is supported on the second support 8C.

[0087] Hole 24 allows a padlock or other suitable locking device to be passed through, in order to lock the gate 5 in its closed position.

[0088] Compared to the known embodiment represented in Figures 10 And 11 The first support (7C) and the second support (8C) can be made by folding and cutting a metal sheet, without any added parts. They also allow for very easy and tool-free installation and removal of the grid.

[0089] In addition, the frames include the support for the secondary closing grille according to the Figures 12 And 13 They are stackable for storage and transport, without requiring any interposed piece (wooden block or otherwise) between the frames. This is not the case with frames known in prior art, such as those of Figures 11 and 12because elements of the first support 7B and / or the second support 8B (in particular the perforated plates 32 or the rings 14A) would interfere.

[0090] All the embodiments described above assume that the support is installed on the most distant opposite walls of an underground chamber. However, whether the support is brought into the chamber or directly welded to the frame, it can be positioned on the closest opposite walls of the chamber. This is illustrated in the figure 14 , which shows a frame 3 with a secondary closure support. The support of the figure 14 may correspond to the one illustrated in Figures 12 And 13 Thus, by convention, the longitudinal direction L is considered to correspond, on the figure 14 , to the direction of the shorter side of frame 3. The transverse direction T is that of the longer side of frame 3.

[0091] There figure 15Figure 5 illustrates a grid that can thus be used to form a secondary closure device according to one embodiment of the invention. The grid 5 is characterized by having, on either side (along the longitudinal direction L), structures that each form a portion of axis 13 and a notch 23. The grid is therefore symmetrical and can be mounted in either direction. It should be noted that axis 13 is formed here of several coaxial portions.

[0092] It is therefore proposed within the framework of the present invention, a secondary closing device for an underground chamber allowing easy installation and removal of a grid, and tolerating significant dispersions in the dimensions of the underground chamber or frame, for example up to 20 mm to 30 mm.

[0093] The support for the secondary closing grille can also be obtained by simple folding and cutting of metal plates, and is therefore simple and cheap to obtain.

Claims

1. A secondary closure device for an underground chamber, to be installed in said underground chamber (1) under a primary closure device, in order to at least partly obstruct, when said secondary closure device is in a closed position, access to a bottom of said underground chamber (1), the secondary closure device comprising: - a grid (5) comprising a circular cross-section transverse pin (13), - supports (6A, 6C) adapted to support the grid (5) in said underground chamber (1) in said closed position, the supports (6A, 6C) comprising: - a first support (7A, 7C) forming a hinge and allowing pivoting of the grid (5) about the transverse pin (13), such that the grid (5) can be pivoted to an open position in which access to the underground chamber (1) is released, - a second support (8A, 8C), the first support (7A, 7C) and the second support (8A, 8C) being positioned proximate to opposite walls, according to a so-called longitudinal direction (L), of the underground chamber (1), characterised in that the first support (7A, 7C) comprises two wings (18, 18A) parallel to each other and perpendicular to the transverse pin (13) of the grid (5), each wing (18, 18A) comprising a slot (19, 19A) which has a substantially C-shaped trajectory or a substantially S-shaped trajectory, said slot (19, 19A) having a width (l) larger than the diameter (D) of the pin (13), thereby allowing sliding of the pin (13) in the slot from an inlet (21) up to an end portion (20, 20A) and allowing rotation of the grid about the pin (13), said end portion (20, 20A) being straight and allowing a longitudinal translation of the transverse pin (13).

2. The secondary closure device for an underground chamber according to claim 1, wherein the second support (8A, 8C) comprises at least one vertical tab (22, 22A), adapted to pass through a notch (23) formed in the grid (15).

3. The secondary closure device for an underground chamber according to claim 2, wherein the notch (23) has a length (w) greater than a width (e) of the tab (22, 22A), allowing longitudinal displacement of the grid (5).

4. The secondary closure device for an underground chamber according to claim 2 or 3, wherein the at least one vertical tab (22, 22A) of the second support (8A, 8C) comprises a hole (24) located above the grid (5), when the same is in the closed position, so as to be able to attach a locking device, for example a padlock, to said vertical tab (22, 22A).

5. The secondary closure device for an underground chamber according to one of the preceding claims, wherein the first support (7A, 7C) or the second support (8A, 8C) is formed by two angle pieces (16, 16A), each angle piece (16, 16A) comprising a fastening wing (17, 17A) intended to be fastened, for example pegged, to a wall (2) of the underground chamber (1).

6. The secondary closure device according to claim 5, further comprising an installation template (25) for determining the position of the holes to be made on a wall (2) of the underground chamber (1) to attach the first support (7A) or the second support (8A) thereto, the template being comprised of a plate, said plate comprising a first surface (26) to be brought into contact with an upper edge of the chamber, a second surface (27) to be brought into contact with said wall (2) of the underground chamber (1) to which the first support (7A) or the second support (8A) is to be attached, and an edge (29) to be brought into contact with a side wall of the underground chamber which is perpendicular to said wall (2) of the underground chamber (1) to which the first support (7A) or the second support (8A) is to be attached, the second surface (27) of the template (25) comprising openings (30) whose position corresponds to the position of the piercings to be made.

7. The secondary closure device for an underground chamber according to one of claims 1 to 4, wherein the first support (7C) is formed of a part comprising a central plate (34) and two wings (18A) parallel to each other and perpendicular to the central plate (34), said central plate (34) comprising a folded end section (35) adapted to be welded to a frame (3).

8. The secondary closure device for an underground chamber according to claim 7, wherein the second support (8C) is formed of a part comprising a central plate (34A) and two vertical lugs (22A), said central plate (34A) comprising a folded end section (35A) adapted to be welded to a frame (3).

9. The secondary closure device for an underground chamber according to claim 8, further comprising a frame (3) forming a seating surface (4) for a primary closure device of an underground chamber (1), for example for a lid, wherein the first support (7C) and the second support (8C) are welded to opposite edges of the frame (3).

10. The secondary closure device for an underground chamber (1) according to one of the preceding claims, wherein the first support (7A, 7C) and / or the second support (8A, 8C) is made only by bending and cutting a flat sheet.