Package with means for holding at least one item

Abstract

The present invention relates to a box (2) having a bottom (21) and means for holding at least one item on the bottom (21), the holding means comprising a plate (4), Plate (4) is a frame to which the return means (5) are connected; a central part connected to the frame by at least one flexible connection, The present invention relates to a package (1) characterized in that the central part comprises a plurality of plaques, which are connected on the one hand to the frame by flexible connections and on the other hand to at least one other plaque by a link.

Description

[Technical field]

[0001] The field of the invention is that of logistics.

[0002] More specifically, the present invention relates to a package or logistics packaging, i.e. a container, for transporting goods between two destinations by the package. [Background technology]

[0003] For the total safe and secure transportation of goods, packages such as cases or cardboard boxes are known.

[0004] Generally, the package comprises a box having a base and a periphery which together define an interior space in which the items to be shipped are contained.

[0005] The periphery may be movable relative to the bottom of the box. In this regard, it comprises several panels that may be lowered onto the bottom of the box or onto an extension of the bottom.

[0006] The package further comprises a lid movable relative to the box, the lid being capable of assuming, inter alia, a closed position in which the lid closes the interior space of the box.

[0007] To allow for protection of the transported items, some packages are provided with retention means that keep the transported items in place within the box.

[0008] Retention means are known which may take the form of foam panels integrated into the box and lid. The foam panels may be added to the box where appropriate, in other words the foam panels may be integrated into the box only if their presence is required.

[0009] More specifically, the foam panel is secured to the bottom of the box and, where appropriate, to its periphery and lid.

[0010] The item to be transported is then inserted into the interior space, comes into contact with the foam, and is prevented from moving by the base foam and the lid foam.

[0011] This type of retaining means has as its major drawback its thickness, in other words the total volume it occupies in the interior space of the box.

[0012] Specifically, the foam occupies a large portion of the interior space of the box, but has elastic properties such that it forms a retaining means that can deform to conform to the contours of the items being transported.

[0013] However, depending on the size of the item, several packages must be prepared.

[0014] For example, the same box cannot be used for bulky and small items: in the case of small items, if a box or package suitable for large items is used, the foam will not deform properly in contact with the small items, and therefore the small items may move around within the interior space of the box with the risk of being damaged.

[0015] Conversely, if a large item is inserted into the interior space of a box intended to accommodate a small item, the package may become unusable due to lack of sufficient space in the interior space, and therefore the lid cannot be successfully closed to completely fill the interior space of the box. This results in the item being effectively unprotected and visible to anyone transporting the package, which may lead to a risk of theft of the item.

[0016] As a result, shippers or packing professionals must have different sized packages depending on the size of the item being shipped.

[0017] Using another known technique, the retaining means takes the form of a plastic shroud into which the article to be transported is slid. The shroud is then deformed so that its walls contact the article to be transported and hold the article in place.

[0018] In the first type, the cover may be fixed to the bottom of the box and its deformation may be performed, for example, by heating the material, generally plastic, so as to shrink it and harden it in contact with the item.

[0019] The drawback of this solution lies in the fact that when deformation of the covering is performed by heating, not everyone can perform the deformation of the covering, since this technique requires the use of specific heating equipment.

[0020] Specifically, a heating means such as a heat gun must be used, which may require special training and only a professional can deform the covering.

[0021] Moreover, if the cover is secured to the bottom of the box, particularly if it is made of cardboard, this can be a serious drawback to the integrity of the box, as excessive heat can burn and destroy the cardboard.

[0022] In addition, it may become difficult or even impossible to insert the item to be transported into the enclosure.

[0023] This is particularly true when the article to be transported is to be inserted into the enclosure once the box has been molded, i.e. once the interior space has been defined, the periphery of the box presents a significant obstacle to the insertion of the article into the enclosure.

[0024] To alleviate this, it may be necessary to first insert the item into the cover, then shape the box, and finally deform the cover.

[0025] This can be tedious for a professional and requires significant processing time that may not be feasible for an individual, particularly one who is modifying the cover or forming the box.

[0026] Also, according to a second type, the cover may be fixed to a plate intended to be contained in a box. In this case, the object is inserted into the cover, and then the cover is deformed by folding the edges of the plate in order to fix and hold the object, and the two walls of the cover are stretched taut to confine the object. Once this is done, the folded plate may be inserted into the box and then a movable lid may be closed on the box.

[0027] This retention means also has some drawbacks.

[0028] Specifically, while inserting the object into the covering does not pose a problem, the deformation of the plate, especially the folding of its edges, requires difficult or even impractical handling if the object is bulky and the covering to be deformed resists significant deformation. The deformation of the covering is therefore time-consuming and may discourage specialists, who will therefore perform an incomplete deformation or even provide a larger package which will generate higher shipping costs for the end consumer.

[0029] Moreover, this requires simultaneous storage of the box, lid and holding means, which means an undesirable overall volume and therefore extra costs that are often passed on to the final customer.

[0030] It is also known that the addition of crumpled paper, air bubbles, cardboard spacers, or foam balls can secure the shipped item within the package and protect it during transport.

[0031] Alternative technologies have been developed that address the need to retain items within a package while providing a more convenient method of operation compared to known technologies.

[0032] This technique provides that a retaining means is fixed to the lid, the retaining means comprising an elastically deformable membrane that contacts and covers the item contained in the package and holds it against the bottom of the box.

[0033] Although such a solution is satisfactory, it can still be improved.

[0034] Specifically, flexible membranes subject the article to an applied tension that can damage the article, especially if the article is particularly fragile.

[0035] Moreover, some articles may have complex shapes for which the elastically deformable membrane cannot guarantee good retention, so that it may happen that only a part of the article is retained by the elastically deformable membrane, while another part remains free to move within the package and runs the risk of colliding with the box if the package is moved roughly.

[0036] Furthermore, if two items of different dimensions must be transported in the same package, it is necessary to hold them both within the package, which is only possible by means of a spacer or shim inserted between the two items, which requires adding weight within the package, in particular storing means that can form a spacer.

[0037] Additionally, once the package reaches its destination, the items are removed and the package can be reused, but the spacers are discarded as they are no longer needed, which has environmental impacts, especially if the spacers are not discarded into the recycling circuit or if their recycling is not possible. Summary of the Invention

[0038] The present invention aims inter alia to alleviate the drawbacks of the prior art.

[0039] More specifically, the present invention aims to provide a solution that allows the fastening of at least one article without causing damage to said article, by automatically adapting to the characteristics of the respective article, in particular with regard to the mechanical resistance forces related to the shape of the article.

[0040] It is also an object of the present invention to provide such a solution in a manner that is easy to implement for package senders.

[0041] Moreover, the present invention aims to provide such a solution which has a small volume when the package is stored between uses.

[0042] These objects, together with others which will become apparent hereinafter, are achieved thanks to the invention, which is directed to a package comprising a box having a base and means for holding at least one article on the base, the holding means comprising: a plate and return means tending to exert a displacement force on the plate in the direction of the base and holding said article or articles between the base and the plate, the plate a frame to which the return means are connected; a central part connected to the frame by at least one flexible connection, The central portion comprises a plurality of plaques, each plaque being connected on the one hand to the frame by a flexible connection and on the other hand to at least one other plaque by a link.

[0043] Such a plate can thus be deformed to conform as closely as possible to the shape of the respective item held on the bottom of the package.

[0044] Specifically, by using multiple plates connected to each other by joints and to a frame by flexible connections, the centers of the plates can be deformed to contact each item held on the bottom of the package.

[0045] According to an advantageous embodiment, each flexible connection takes the form of at least one elastically deformable groove.

[0046] The elastically deformable grooves allow the central portion to change its position relative to the frame and to deform so that it conforms as closely as possible to the contours of each item held on the bottom of the package.

[0047] Furthermore, the shape of the grooves can induce an initial deformation that allows the flexible connections to unfold, ensuring the mobility of each plate relative to the frame.

[0048] According to another advantageous aspect, at least one of the flexible connections comprises a plurality of adjacent grooves forming a series of alternating valleys and peaks.

[0049] The series of alternating valleys and peaks formed by the grooves creates a concertina style, easily deformable flexible connection.

[0050] Thus, each groove can elastically deform independently of the other grooves to adapt the position of the plaque connected thereto on the plate and ensure good retention of each article on the bottom of the package.

[0051] According to another advantageous embodiment, each connection takes the form of at least one elastically deformable groove.

[0052] The use of elastically deformable grooves allows the position of the central portion relative to the frame to be changed so that the central portion deforms as closely as possible to the contours of each item held on the bottom of the package.

[0053] Furthermore, the shape of the grooves can induce an initial deformation that allows the flexible connections to unfold, ensuring the mobility of each plate relative to the frame.

[0054] According to another advantageous aspect, at least one of the connections comprises a plurality of adjacent grooves forming a series of alternating valleys and peaks.

[0055] The series of alternating valleys and peaks formed by the grooves creates a concertina style, easily deformable flexible connection.

[0056] Thus, each groove can elastically deform independently of the other grooves to accommodate the position of the plaque connected thereto to the plate and ensure good retention of each article on the bottom of the package.

[0057] According to another advantageous aspect, the frame has a rectangular shape and the central part of the plate is - a central strip comprising two rectangular plaques connected by a central joint and extending between two opposing edges of the frame; - Four triangular plaques connected in pairs on either side of a central strip.

[0058] Such a structure in the center of the plate therefore ensures an arch-shaped deformation of the plate in order to hold one or more items on the bottom of the package.

[0059] Specifically, while using a substantially planar plaque, the central connector can deform to fold two rectangular plaques towards each other, and the triangular plaques can be oriented relative to each other to form a dome shape.

[0060] Thus, each item is held perfectly on the bottom of the package.

[0061] According to another advantageous aspect, the plate is symmetrical with respect to a plane of symmetry passing through the central joint.

[0062] This symmetry makes it possible to control deformation of the plate, in particular to deform it into a dome shape, when the plate is intended to conform to the shape of the item held on the bottom of the package.

[0063] In other words, the symmetry of the plate allows the article to be centred relative to the plate to ensure good retention thereof.

[0064] According to another advantageous embodiment, the central strip extends in a first plane and the triangular plaques extend in a second plane offset with respect to the first plane.

[0065] Thus, when the plate comes into contact with some object held on the bottom of the package, the offset between the first and second planes can ensure that the plate comes into contact with the object.

[0066] Moreover, if the article held on the bottom has a height difference, the height difference can be compensated for by the height difference between the first plane and the second plane.

[0067] Finally, if the item to be held is flat, e.g., a coin, magazine, or envelope, the height difference between the central strip and the triangular plaques can ensure that the item is well held, since at least one of the portions of the plate will be in contact with the item.

[0068] According to another advantageous embodiment, the plate is made of polypropylene.

[0069] The use of polypropylene provides good rigidity while still adequately holding each item on the base of the package without significantly increasing the weight of the package.

[0070] In other words, by using polypropylene, excellent retention of items on the bottom of the package can be obtained without making the package heavier, which would have an adverse effect on its ease of handling.

[0071] According to another advantageous aspect, the box comprises a peripheral edge extending from the bottom, the package further comprises a lid rotatably attached to the peripheral edge by a joining edge, the lid being capable of assuming a position for closing the box, the package further comprises, at its extremity opposite the joining edge, a post rotatably attached to the lid, the post having a free end intended to penetrate into the periphery of the bottom in the closing position of the lid, the plate being movable along the post and the return means being interposed between the free end of the post and the plate.

[0072] The presence of the post allows the plate to be placed as close to the bottom as possible when the lid is in the position to close the box.

[0073] Thus, especially if the frame is located near the bottom, the central portion may deform, tending to resume its original position and pressing each item flat against the bottom of the package.

[0074] Moreover, by placing return means between the free ends of the posts and the plate, the plate can be pulled towards the bottom of the package, which ensures that the deformation of the central part of the plate holds the article against the bottom of the package.

[0075] This construction therefore automatically holds the item flat against the bottom of the package.

[0076] Other characteristics and advantages of the present invention will appear more clearly on reading the following description of preferred embodiments of the invention, given as illustrative and non-limiting examples, and the accompanying drawings, in which: [Brief description of the drawings]

[0077] [Figure 1] FIG. 1 is a schematic diagram of a package according to the invention, the package being provided with means for holding an article on its base. [Diagram 2] FIG. 2 is a bottom perspective view of a plate of a retaining means of a package according to the present invention. [Diagram 3]FIG. 3 is a bottom view of the plate of the retaining means of the package according to the invention. [Figure 4] FIG. 4 is a detailed cross-sectional view along section IV-IV of FIG. 3, which includes a first enlarged detailed inset showing the flexible connection and a second enlarged detailed inset showing the coupling of the means of the plate of the retaining means of the package according to the invention. [Diagram 5] FIG. 5 is a detailed view of a longitudinal section along section VV of FIG. 3, showing the connection of the plates of the means for holding a package according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] Referring to FIG. 1, a package 1 according to the present invention is shown.

[0079] Package 1 is -Box 2 and a lid 3 intended to close the box 2, - means for retaining the article within the package.

[0080] The box 2 has a base 21 and a perimeter 22 extending from the base.

[0081] The periphery 22 and the base 21 together define a storage space within the box 2 .

[0082] The perimeter 22 comprises a number of panels 221 adjacent to one another to define a closed contour.

[0083] Each panel 221 is pivotally mounted to the bottom 21 of the box 2 .

[0084] Thus, each panel 221 can have a use position in which it extends substantially perpendicular to the base 21 and a storage position in which it extends substantially parallel to the base 21 .

[0085] As shown by FIG. 1, the lid 3 is rotatably mounted to one of the panels 221 of the peripheral portion 22 .

[0086] More specifically, the lid 3 is connected to one of the panels 221 by a joint edge 31 through which it is rotatably connected to said panel 221 .

[0087] Opposite the joining edge 31 the lid 3 has a tip 32 .

[0088] The lid is rotatable relative to the panel 221 to which it is attached, between a first position in which it is substantially perpendicular to the panel 221 to which it is attached, and a second position in which it is substantially parallel to said panel 221.

[0089] In its first position, the lid 3 prevents access to the interior storage space of the box 2. In other words, in its first position, the lid 3 closes the package 1.

[0090] Conversely, in its second position, the lid 3 leaves free access to the interior storage space of the box 2. In other words, in its second position, the lid 3 opens the package 1.

[0091] According to the embodiment shown in the figures, the lid 3 is part of a closure assembly incorporating a panel 221 to which it is attached.

[0092] Thus, in the first position of the lid 3, the panel 221 is in its use position and in the second position of the lid 3, the panel 221 is in its storage position.

[0093] The holding means is - Plate 4 and - return means 5 tending to exert a displacement force on the plate 4 in the direction of the bottom 21 of the box 2, as will be explained below.

[0094] As shown in FIG. 1, package 1 has at least one post 6 rotatably attached to lid 3 at its distal end 32 .

[0095] The post 6 has a free end 61 intended to penetrate into the periphery of the bottom 21 in the closed position of the lid 3, ie in the second position of the lid 3.

[0096] The return means 5 , for example in the form of an elastic cord, is placed between the free end of the post 6 and the plate 4 .

[0097] The plate 4 can therefore be moved rotationally relative to the post 6. Moreover, the plate 4 is translationally guided along the post 6 by special means.

[0098] As shown in FIG. 1, the package 1 comprises two posts 6 rotatably attached to the lid 3 and positioned at the top end 32 of the lid.

[0099] The two pillars 6 are positioned on either side of the plate 4 .

[0100] In order to further guide the plate in its translational movement relative to the post 6, the package 1 comprises means for guiding the plate 4 in its displacement on the panel 221 to which the lid 3 is rotatably mounted.

[0101] This means for guiding the plate 4 in its displacement comprises at least one slider 7 on which the panel 4 or at least part of the panel 4 is positioned, making it possible to guide the panel 4 translationally along the panel 221 fixed to the joint edge 31 of the lid 3.

[0102] Thus, the panel 4 is translationally movable along a displacement direction perpendicular to the bottom 21 of the box 2 , and can be moved away from the bottom 21 and drawn towards it using the return means 5 .

[0103] 2, 3, 4 and 5, the plate 4 will now be described.

[0104] Plate 4 is a frame 41 to which the return means 5 are connected; a central part 42 connected to the frame 41 via at least one flexible connection 43;

[0105] 2, the frame 41 has a substantially rectangular shape. At each of its corners, the frame 41 has at least one hole 410 for attaching the return means 5.

[0106] The central portion 42 includes a plurality of plaques 44 .

[0107] Each plaque 44 is connected on the one hand to the frame 41 by a flexible connection 43 and on the other hand to at least one other plaque 44 by a link 45 .

[0108] Thus, the central portion 42 of the plate 4 may deform to accommodate each item held within the package 1, as will be explained below.

[0109] Referring to FIG. 2 and FIG. 3, the central portion 42 of the plate 4 is a central strip comprising two rectangular plaques 441 connected by a central link 451; - four triangular plaques 442 connected in pairs on either side of a central strip;

[0110] The use of rectangular plaques 441 and triangular plaques 442 allows the plate 4 to be deformed into a dome shape that tends to return each held item to the center of the plate 4 .

[0111] More specifically, triangular plaque 442 has the shape of a right-angled triangle.

[0112] The triangular plaques 442 are arranged in pairs so that together they form a rectangle.

[0113] Thus, on each side of the central strip, triangular plaques 442 are positioned to form a rectangle that extends the entire length of the central strip.

[0114] In other words, the triangular plaques 442 are gathered in groups of four on both sides of the central strip, and are arranged such that two triangular plaques 442 are connected to each other by their hypotenuses via connectors 45. Furthermore, in this structure, two triangular plaques 442 are connected to each other via connectors 45 at their shortest lengths.

[0115] As shown by FIGS. 2 and 3, the flexible connection 43 is discontinuous around the central portion 42 .

[0116] In particular, the flexible connection portion 43 has a number of cutouts 431 at each junction with the coupling portion 45 .

[0117] Similarly, each link 45 has an opening 452 where it meets another link 45 .

[0118] The openings 452 and the cutouts 431 on the one hand facilitate the manufacture of the plate 4, but also facilitate the deformation of the central portion 42, as described below, without risking tearing due to stress concentrations in the flexible connections 43 or the connecting portions 45.

[0119] With reference to FIG. 3, the plate 4 is symmetrical about a plane of symmetry P passing through the central connecting portion 451 .

[0120] Thus, as shown in FIG. 3, the central portion 42 of the plate 4 has a rectangular plaque 441 on either side of the plane of symmetry P, and two triangular plaques 442 on either side of the rectangular plaque 441 .

[0121] With reference to the detailed view of FIG. 4, the central strip formed by the two rectangular plaques 441 extends in a first plane P1, while the triangular plaque 442 extends in a second plane P2 offset with respect to the first plane P1.

[0122] According to the embodiment illustrated by FIG. 4, the rectangular plaques 441 of the central strip are intended to be closer to the bottom 21 of the package 1 than the triangular plaques 442 .

[0123] This misalignment is evident when panel 4 is not subjected to deformation, ie when it does not interact with at least one article held within package 1 .

[0124] As an illustrative, non-limiting example, the plate 4 is made of polypropylene.

[0125] Advantageously, the plate 4 is transparent.

[0126] With reference to FIG. 4, each flexible connection 43 takes the form of at least one elastically deformable groove.

[0127] As shown by the lower detail inset of FIG. 4, at least one of the flexible connections 43 includes a plurality of adjacent grooves that form a series of alternating valleys 46 and peaks 47 .

[0128] More specifically, the flexible connection 43 has, successively from the frame 41 toward the central portion 42 , a first valley 46 , a first peak 47 , a second valley 46 , a second peak 47 , and finally a third valley 47 .

[0129] In other words, the flexible connection 43 comprises two steps.

[0130] This series of alternating valleys 46 and peaks 47 allows the plaque 44 to deform independently relative to the frame 41 .

[0131] Like the flexible connections 43, each link 45 takes the form of at least one elastically deformable groove.

[0132] Referring to FIG. 5, the connector 45 located between the two triangular plaques 442 and extending along the plane of symmetry P is a simple connector.

[0133] In other words, a simple connection is formed with only one groove.

[0134] Referring to the upper detail inset shown in FIG. 4, at least one of the interlocking portions 45 includes a plurality of adjacent grooves that form a series of alternating valleys 46 and peaks 47 .

[0135] Referring to the upper detail inset of FIG. 4, the link 45 shown has, from the frame 41 towards the central portion 42, a first valley 46, a peak 47 and finally a second valley 46.

[0136] In other words, the link 45 comprises only one step.

[0137] According to the embodiment shown in FIG. 3, each rectangular plaque 441 carries a capture means 48 .

[0138] This catch means 48 is intended to interact with each of the articles held in the package 1 to prevent them from slipping relative to the plate 4 .

[0139] The capture means 48 consists, for example, of a piece of material attached to a rectangular plaque 441 .

[0140] The capture function of the capture means 48 can be achieved by using a material with a roughness that provides the desired capture, or by using a friction-reducing material that has a friction-reducing function to hold the article, or by using a material with a repositionable adhesive coating.

[0141] In use, the package 1 according to the invention allows one or more items to be held against the bottom 21 of the box 2 via the plate 4 of the holding means.

[0142] To transport goods in total safety, the user places the goods to be transported on the bottom 21 of the box 2 and then places the lid 3 in its closed position (ie its first position).

[0143] The plate 4 connected to the post 6 then rises towards the lid 3 while being pulled away from the bottom 21 of the box 2 by the presence of the items held within the box 2 .

[0144] The return means 5 then tend to exert a displacement force on the plate 4 in the direction of the bottom 21 , retaining the respective article between the bottom 21 of the box 2 and the plate 4 .

[0145] This force displacing the plate 4 towards the bottom 21 causes the central portion 42 of the plate 4 to deform so as to conform as closely as possible to the shape of each item held within the box 2 .

[0146] This deformation of the central portion 42 is obtained in particular by using the links 45 and the respective flexible connections 43 .

[0147] Thus, the plaques 44 are oriented independently of one another according to the shape of the article or articles to be held, thereby enabling the plate 4, and in particular its central portion 42, to fit the article or articles to be held and press these articles tightly against the bottom 21 of the box 2.

[0148] Thus, the package 1 just described provides effective retention of each item during their transportation within the package 1, thereby ensuring that they remain intact.

[0149] Furthermore, by using a material such as polypropylene, it is easy to manufacture the plate 4 which securely holds the article against the bottom 21 of the box 2 without making the package 1 significantly heavier.

Claims

1. A box (2) having a bottom (21) and means for holding at least one item on said bottom (21), said holding means comprising: A plate (4); return means (5) tending to exert a displacement force on said plate (4) in the direction of said bottom (21) and holding said article between said bottom (21) and said plate (4); The plate (4) is a frame (41) to which the return means (5) is connected; a central portion (42) connected to said frame (41) by at least one flexible connection (43); The package (1), characterized in that the central part (42) comprises a plurality of plaques (44), each plaque (44) being connected on the one hand to the frame (41) by the flexible connection part (43) and on the other hand to at least one other plaque by a connecting part (45).

2. 2. A package (1) according to claim 1, characterised in that each flexible connection (43) takes the form of at least one elastically deformable groove.

3. 2. The package (1) according to claim 1, characterized in that at least one of said flexible connections (43) comprises a plurality of adjacent grooves forming an alternating sequence of valleys (46) and peaks (47).

4. 2. A package (1) according to claim 1, characterised in that each connection (45) is in the form of at least one elastically deformable groove.

5. 5. A package (1) according to claim 4, characterized in that at least one of said connecting portions (45) comprises a plurality of adjacent grooves forming a series of alternating valleys (46) and peaks (47).

6. The frame (41) has a rectangular shape, and the central part (42) of the plate (4) is a central strip extending between two opposite edges of said frame (41) and including two rectangular plaques (441) connected by a central connector (451); 2. A package (1) according to claim 1, characterised in that it comprises four triangular plaques (442) connected in pairs on either side of said central strip.

7. 7. The package (1) according to claim 6, characterized in that the plates (4) are symmetrical with respect to a plane of symmetry (P) passing through the central connection (451).

8. 8. The package (1) according to claim 6 or 7, characterized in that the central strip extends in a first plane (P1) and the triangular plaques (442) extend in a second plane (P2) offset with respect to the first plane (P1).

9. A package (1) according to claim 1, characterized in that the plate (4) is made of polypropylene.

10. The box (2) has a peripheral edge (22) extending from the bottom (21); The package (1) further comprises a lid (3) rotatably attached to the peripheral edge (22) by a joining edge (31), the lid (3) being capable of assuming a box-closing position, the package (1) further comprising a post (6) rotatably attached to the lid (3) at an end (32) opposite the joining edge (31), said post (6) having a free end (61) intended to penetrate into the periphery of said bottom (21) in said closed position of said lid (3); 2. The package (1) according to claim 1, characterized in that the plate (4) is movable along the column (6) and the return means (5) is located between the free end (61) of the column (6) and the plate (4).

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