A cage structure for goods transport

Abstract

 A cage structure comprises a base (2) suitable for supporting goods (31), and a pair of sides (5) which are opposite one another, the sides (5) being movable between a folded configuration in which the sides (5) are folded on the base (2) and an open configuration in which a space for receiving goods (31) is defined between the sides (5) and the base (2), the sides (5) having respective free ends (11) which are delimited by end surfaces (12) which, in the open configuration, define a rest plane (P) for receiving a pallet (20) to be positioned on the cage structure (1).

Description

[0001] The invention relates to a cage structure suitable for supporting and containing goods while the goods are transported, particularly internally of load compartments of lorries or other transporting vehicles, or internally of a container.

[0002] In order to transport goods of various types internally of a load compartment of a vehicle, it is known to arrange the goods in loading units, each of which is obtained by resting a certain number of products to be transported on a rest surface defined by a bench or pallet. The pallet, after having been loaded with the goods, is positioned internally of the load compartment of the vehicle, for example by means of a lift truck, and is thus transported towards the desired destination. In some cases, different products are loaded onto a same pallet; the products will be sorted later, so as to be delivered to different consignees. The thus-obtained loading units cannot be superposed on one another during the transport, as each loading unit has an irregular upper surface defined by the final layer of products loaded on the pallet, which are usually arranged at different levels from one another.

[0003] Since it is impossible to superpose two loading units of the above-described type on one another, the operators try to load the greatest possible number of products on a single pallet, such as to maximise the height of each loading unit. However, the operators cannot manually position the products above a certain height. Therefore, the loading units obtained by manually arranging a plurality of different products on a pallet have usually a maximum height of about 1.80 metres. In many lorries, however, the load compartment is 2.40 metres high. As a consequence, the loading units of the above-described type leave a significant volume unused in an upper region of the load compartment of the vehicles. Furthermore, it is not possible to stack additional goods on some types of products loaded on pallets, for example in order to prevent the products in question from getting damaged or breaking. When easily-damageable products of the above-described type have to be transported, it becomes even more difficult to fully exploit the space internally of the vehicle load compartment.

[0004] An object of the invention is to improve the goods transport, particularly internally of load compartments of vehicles or internally of containers.

[0005] A further object is to exploit and fill in the best possible way the space internally of the vehicle load compartments in which goods are transported, or internally of the containers, such as to reduce the number of journeys required for transporting a predetermined quantity of products and consequently to reduce transport costs.

[0006] According to the invention, a cage structure is provided comprising a base suitable for supporting goods, characterised in that the cage structure further comprises a pair of opposite sides, the sides being movable between a folded configuration in which the sides are folded on the base and an open configuration in which between the sides and the base a space is defined to receive goods, the sides having respective free ends delimited by end surfaces which, in the open configuration, define a rest plane for receiving a pallet to be positioned on the cage structure.

[0007] Owing to the invention, it is possible to improve operations of goods transport, particularly internally of load compartments of vehicles or internally of containers. The goods can be rested on the base of the cage structure arranged in the open configuration, the cage structure being positioned on a pallet. Thereafter, a further pallet can be arranged on the cage structure, the further pallet being supported by the free ends of the sides and being suitable for receiving if necessary a further cage structure loaded with other goods.

[0008] The cage structure, in the open configuration, thus provides a rest plane which enables several pallets to be stacked one on another, independently of the shape and sizes of the goods loaded on the cage structure. By stacking several pallets one on another, the available space internally of the transport compartments of vehicles or internally of containers can be filled optimally.

[0009] When the goods have reached their destination, the cage structure can be arranged in the folded configuration such as to reduce the volume thereof during the return journey, in a case in which the cage structure is not to be loaded with further goods.

[0010] In an embodiment, the end surfaces are provided with anti-slip means for preventing the pallet arranged above the cage structure from slipping on the rest plane.

[0011] The anti-slip means enable a pallet to be stacked on the cage structure in a particular safe way, even where the load compartment of the container in which the cage structure is to be transported is subject to oscillation during the transport.

[0012] The anti-slip means can comprise a plurality of protrusions projecting upwards from the end surfaces. These protrusions are suitable for penetrating into wood, a material frequently used for manufacturing pallets, in order to obstruct movements of the pallet arranged on the cage structure.

[0013] In an embodiment, the base comprises a central portion, which can be flat, and two raised peripheral portions, each side being connected to a respective raised peripheral portion.

[0014] In the folded configuration, the sides can be arranged above the central portion and contained internally of the volume defined by the raised peripheral portions.

[0015] Thus, the space occupied by the cage structure in the folded configuration can be significantly reduced, which enables transport in the load compartment of a vehicle or a container of a large number of empty cages and relative pallets.

[0016] In particular, in the folded configuration the cage structure can have a volume substantially equal to the volume of an empty pallet.

[0017] This makes pallets and cage structures particularly easy to transport together.

[0018] The invention can be better understood and carried out with reference to the attached drawings, which illustrate a non-limiting example thereof, in which:

Figure 1 is a side view of a cage structure for receiving goods, in an open configuration;

Figure 2 is a front view of the cage structure of Figure 1;

Figure 3 is a plan view of the cage structure of Figure 1;

Figure 4 is a perspective view of the cage structure of Figure 1;

Figure 5 is a perspective view which shows the cage structure of Figure 1, while the cage structure is folded on itself;

Figure 6 is a perspective view of the cage structure of Figure 1, in a folded configuration;

Figure 7 is a front view showing two cage structures, loaded with goods to be transported, arranged one above another;

Figure 8 is a front view showing two cage structures, in the folded configuration, arranged one above another;

Figure 9 is a schematic front view of a pallet suitable for supporting the cage structure of Figure 1.

[0019] Figures 1 to 4 show a cage structure 1 suitable for containing goods, particularly while the goods are transported internally of a load compartment of a vehicle or internally of a container.

[0020] The cage structure 1 is suitable for being supported by a pallet 20, of the type shown in Figure 9. The pallet 20 is of known type and can comprise a central beam 21 interposed between two peripheral beams 22. The central beam 21 and the peripheral beams 22 enable the pallet 20 to be rested on a flat surface.

[0021] At least two transversal planks 23 are arranged on the central beam 21 and the peripheral beams 22. On the transversal planks 23, a plurality of longitudinal planks 24 are superposed, the longitudinal planks 24 defining a support plane for supporting objects.

[0022] The cage structure 1 comprises a base 2 for supporting the goods and a pair of sides 5, opposite one another and connected to the base 2.

[0023] The base 2 can comprise a central portion 3, which can be flat, and two raised peripheral portions 4, arranged at two opposite ends of the central portion 3. The central portion 3 can be formed by a plurality of support bars, for example arranged parallel to one another. In the illustrated example, as shown in Figure 3, the central portion 3 comprises two support bars 6 that are parallel to one another. The raised peripheral portions 4 can each comprise a rectangular frame which projects from the central portion 3 in an upwards direction, for example perpendicular to the central portion 3.

[0024] The sides 5 are connected to the base 2 in such a way as to be reclinable with respect to the base 2. In particular, connecting means are interposed between the sides 5 and the base 2, the connecting means enabling the sides 5 to be moved between a folded configuration and an open configuration. In the folded configuration, the sides 5 are folded on the base 2, while in the open configuration the sides 5 project from the base 2 in such a way that between the sides 5 and the base 2 a space is defined in which the goods to be transported can be received. In the illustrated example, in the open configuration the sides 5 are arranged substantially perpendicular to the central portion 3 of the base 2, i.e. they are vertical.

[0025] The open configuration of the cage structure 1 is shown in Figures 1 to 4, while the folded configuration is shown in Figure 6.

[0026] In the illustrated embodiment, each side 5 is connected to the base 2 at a respective raised peripheral portion 4.

[0027] As shown in Figures 1 and 4, the connecting means which connect the sides 5 to the base 2 can comprise, for each side 5, at least one connecting pin 7 that is fixed relative to the side 5. The connecting means further comprise a slot 8 obtained in each raised peripheral portion 4, the connecting pin 7 being movable internally of the corresponding slot 8. Each slot 8 can extend along a vertical direction, such that the respective connecting pin 7 can be vertically displaced.

[0028] Each side 5 can be provided with a pair of connecting pins 7, arranged in a symmetrical position with respect to a vertical axis of symmetry Z of the side 5, visible in Figure 2.

[0029] The connecting means ensure that each side 5 can be rotated with respect to the base 2 about the corresponding connecting pin 7 and, simultaneously, enable each side 5 to translate vertically, even if only by a limited quantity, with respect to the base 2.

[0030] The cage structure 1 further comprises blocking means arranged for blocking each side 5 with respect to the base 2 in the open configuration. The blocking means can be associated to the raised peripheral portions 4 of the base 2. In particular, the blocking means can comprise at least one blocking pin 9, shown in Figures 1 and 4, arranged for engaging in a seating 10 obtained in the corresponding raised peripheral portion 4. The blocking pin 9 is fixed relative to the corresponding side 5. The seating 10 is superiorly open, such that the blocking pin 9 can disengage from the seating 10 when the side 5 is raised upwards with respect to the base 2.

[0031] Each side 5 can be provided with a pair of blocking pins 9, arranged in symmetrical positions with respect to the axis of symmetry Z.

[0032] Each side 5 comprises a first end which is connected to the base 2 and a second end, or free end 11, which superiorly delimits the side 5 in the open configuration. Each free end 11 is delimited by an end surface 12, which can be substantially flat. In the open configuration, the end surfaces 12 are substantially horizontal and are arranged at a same level, such as to identify a rest plane P, shown in a broken line in Figure 1, on which a pallet 20 can be rested, as will be more fully explained herein below.

[0033] As shown in Figures 3 and 4, each end surface 12 can be provided with anti-slip means 13 for preventing the pallet 20 arranged on the cage structure 1 from slipping with respect to the rest plane P.

[0034] The anti-slip means 13 can comprise a plurality of protrusions which, in the open configuration, project upwards from the end surfaces 12 such as to penetrate into the material, usually wood, with which the pallets are manufactured. Thus the protrusions oppose the movements of the pallet 20 arranged on the cage structure 1.

[0035] For example, the anti-slip means 13 can comprise respective plates 19, welded to the end surfaces 12, each plate having a plurality of holes. The holes, which can for example be circular, have edges which project upwards. These holes can be obtained very simply by punching.

[0036] Naturally it is possible to use anti-slip means 13 having a different conformation.

[0037] As shown in Figure 3, the anti-slip means 13 can be provided in two peripheral regions 14 of each end surface 12, such as to interact with the peripheral beams 22 of the pallet 20.

[0038] In addition to the peripheral regions 14, or alternatively thereto, the anti-slip means 13 can be arranged in a central region 15 of each end surface 12, the central region 15 being interposed between the peripheral regions 14. In this case, the anti-slip means 13 are suitable for interacting with the central beam 21 of the pallet 20.

[0039] Each end surface 12 can be provided, in the respective central region 15, with two protruding elements 16 suitable for preventing lateral displacements of the central beam 21 of the pallet 20 rested on the end surface 12. The protruding elements 16 can each be shaped as a prism having a triangular cross section, though other geometrical shapes are possible. As shown in figure 2, the protruding elements 16 are separated by a distance D1 which is slightly greater than, or equal to, the width L of the central beam 21 of the pallet. When the pallet is rested on the cage structure 1, the central beam 21 is positioned between the protruding elements 16 which prevent or at least obstruct lateral displacement of the pallet with respect to the cage structure 1, i.e. they prevent the pallet from slipping along the end surfaces 12 transversally to the axis of symmetry Z.

[0040] In the example shown in Figure 3, the anti-slip means 13 arranged in the central region 15 are interposed between the protruding elements 16 of each side 5.

[0041] The cage structure 1 further comprises at least one bar 25 arranged for connecting the two sides 5 to each other in the open configuration.

[0042] In an embodiment, the bar 25 is hinged to a side 5, such as to be movable between a rest configuration in which the bar 25 is substantially parallel to the side 5 to which the bar 25 is hinged and a working configuration in which the bar 25 connects the two sides 5 to one another. To this end, the bar 25 can be rotatable about a hinge pin 26 arranged along a hinge axis A, shown in Figure 1, the hinge pin 26 projecting downwards from a lower surface of the free end 11. In this way, the bar 25 can rotate about the hinge axis A, which in the open configuration of the cage structure 1 is arranged vertically. This enables the bar 25 to be manually displaced between the working configuration and the rest configuration.

[0043] The bars 25 are hinged to an upper portion of the corresponding side 5, i.e. they are hinged to the respective side 5 near the free end 11.

[0044] The side 5 to which the bar 25 is hinged can comprise retaining means for maintaining the bar 25 stationary in the rest configuration. The retaining means can comprise a hook 33, illustrated in Figure 4, which projects downwards from the free end 11.

[0045] The side 5 opposite to the side to which the bar 25 is hinged can, instead, comprise fastening means for blocking the bar 25 in the working configuration. The fastening means can comprise a peg 27, shown in Figure 1, fixed to the side 5 that is opposite the side to which the bar 25 is hinged. In the open configuration of the cage structure 1, the peg 27 is in a substantially vertical position. The fastening means further comprise an opening obtained in an end region of the bar 25, suitable for engaging with the peg 27.

[0046] The bar 25 can be made of two parts, in which case the bar 25 comprises a first part 28 hinged to the side 5, for example by the hinge pin 26, and a second part 29 connected rotatably to the first part 28. The opening which engages with the peg 27 is obtained at a free end of the second part 29. The first part 28 can be connected to the second part 29 at a hinge point 30, shown in Figure 1, such as to be rotatable about a horizontal axis as indicated by the arrow F. Thus, the second part 29 can be moved between an extended position in which the first part 28 and the second part 29 are arranged one following the other substantially along a straight line, and a retracted position in which the first part 28 and the second part 29 are superposed on one another, i.e. folded one on the other. A stiffening element 32 can be provided near the hinge point 30 in order to stabilise the connection between the first part 28 and the second part 29. The stiffening element 32 can comprise, for example, an upturned-U-shaped element fixed to the first part 28, defining a recess in which the second part 29 can be received.

[0047] In the illustrated example, the cage structure 1 comprises a pair of bars 25, the first of which is hinged to a side 5, while the second bar is hinged to the opposite side.

[0048] In the rest configuration, the bars 25 are substantially contained within the volume of the sides 5 and form no nuisance for the operators loading or unloading the products from the cage structure 1.

[0049] The sides 5 and the base 2 are so dimensioned that, when the sides 5 are arranged in the folded configuration, they are substantially contained internally of the space defined by the central portion 3 and the raised peripheral portions 4 of the base 2. In other words, as shown in Figure 6, in the folded configuration the sides 5 are arranged above the central portion 3 and internally of the volume defined by the raised peripheral portions 4. Consequently, in the folded configuration the cage structure 1 has very small dimensions and thus occupies a limited space. For example, the raised peripheral portions 4 can have a height H, shown in Figure 6, which is substantially equal to the height H1 of a pallet 20. For example, the height H of each raised peripheral portion 4 can be less than 15 centimetres.

[0050] The plan dimensions of the cage structure 1 can also, in the folded configuration, be less than or the same as the plan dimensions of a pallet. In this way, in the folded configuration, the cage structure 1 has a volume which is not greater than that of a pallet.

[0051] Figure 5 shows some movements that have to be made in order for the cage structure 1 to be moved into the folded configuration thereof. In the left part of Figure 5 the second part 29 of a bar 25 is shown, the second part 29 being rotated about the hinge point 30 to bring the bar 25 into the retracted position, as shown by the arrow F. The left side of Figure 5 also shows how the first part 28 can be rotated about the hinge axis A in order to be folded on the corresponding side 5 and to be brought into the rest configuration. This is indicated by the arrow F1.

[0052] In the right side of Figure 5 a side 5 is shown, the bar 25 of which has already been arranged in the rest configuration, while the side 5 is rotated downwards in order to be brought into the folded configuration as shown by the arrow F2.

[0053] A shown in Figure 2, each raised peripheral portion 4 is delimited by an upper surface 17 which, in the folded configuration, superiorly delimits the cage structure 1. Two protruding members 18 project from the upper surface 17, which protruding members 18 each have, for example, the shape of a prism with a triangular cross section. The protruding members 18 are arranged at a distance D2 from one another, the distance D2 being slightly greater than, or equal to, the width L of the central beam 21 of a pallet 20. When a pallet 20 is arranged on the cage structure 1 in the folded configuration, the central beam 21 of the pallet 20 is rested on the upper surface 17 between the protruding members 18. In this way, the protruding members 18 limit the lateral displacements of the central beam 21. The distance D2 between the protruding members 18 can be equal to the distance D1 between the protruding elements 17 associated to the end surface 12 of the sides 5.

[0054] When a cage structure 1 is required for goods transport, the cage structure 1 is positioned on a first pallet 20, as shown in Figure 7. The support bars 6 of the base 2 have such dimensions, and are located at such a distance, as to engage in the recesses defined between two longitudinal planks 24 of the pallet 20. This enables the cage structure 1 to be positioned stably on the pallet 20, as the longitudinal planks 24 between which the support bars 6 are interposed prevent the cage structure 1 from moving transversally with respect to the longitudinal planks 24.

[0055] To improve the stability of the cage structure 1 positioned on the pallet 20, a rough finishing or a plurality of protruding elements can be provided on a lower surface of the base 2, which protruding elements can penetrate into the material, especially wood, which forms the pallet 20.

[0056] The sides 5 are blocked in the open configuration owing to the blocking means.

[0057] The bars 25 are instead arranged in the rest configuration in order to enable the operators to easily load the goods on the cage structure 1. To this end, the second part 29 of each bar 25 has been folded on the corresponding first part 28 such as to reach the retracted position. The bar 25 arranged in the retracted position has been rotated about the hinge pin 26 such as to be positioned parallel to the corresponding side 5. The bar 25 has finally been anchored to the side 5 of the retaining means.

[0058] As the bars 25 are anchored to the corresponding sides 5, the space defined between the two sides 5 is completely open and easily accessible to the operators. Thus, the operators do not encounter obstacles while they are loading one or more products 31 onto the cage structure 1.

[0059] When the cage structure 1 has been loaded with the products 31, the operator can disengage the bars 25 from the retaining means and rotate each bar 25 about the respective hinge pin 26, such that each bar 25 is substantially perpendicular to the side 5. At this point, the operator can rotate the second part 29 with respect to the first part 28 about the hinge point 30, thereby bringing the corresponding bar 25 into the extended position. The bar 25 can now be connected to the opposite side 5 owing to the fastening means. In this way, the bars 25 give a greater stiffness to the cage structure 1.

[0060] Thus a loading unit is obtained, the loading unit comprising a pallet 20 on which a cage structure 1 loaded with products 31 is rested.

[0061] It is now possible to rest a further loading unit on the rest plane P defined by the end surfaces 12 of the sides 5, the further loading unit comprising a further pallet 20' supporting a further cage structure 1' on which further products 31' have been loaded.

[0062] In particular, the further pallet 20' resting on the rest plane P is positioned stably on the underlying cage structure 1 owing to the anti-slip means 13, which obstruct the movements of the peripheral beams 22 and the central beam 21, and owing to the protruding elements 16, which keep the central beam 21 still.

[0063] The cage structure 1 thus enables stacking several loading units on one another, independently of the dimensions and shapes of the goods that each pallet supports. Furthermore, as the cage structure 1 supports the weight of the goods loaded on the further pallet 20' arranged on the cage structure 1, there are no risks of damaging the products 31 of the loading unit arranged lower. The weight of the further products 31' arranged higher does not bear down on the products 31 of the lower loading unit.

[0064] In an embodiment, each loading unit can have, in the open configuration, a height of about 1.2 metres, such that two loading units can be superposed in the load compartment of a transport vehicle, such as to exploit the whole height of the load compartment, normally 2.4 metres high. This can be obtained, for example, by using a cage structure 1 having a height of about 1050 mm, in combination with a pallet having a height which is 150 mm or slightly less.

[0065] To unload the products 31 from a cage structure 1, the bar 25 associated to a side 5 is disengaged from the fastening means which connect it to the opposite side 5 and the second part 29 is folded on the first part 28 by rotating the second part 29 about the hinge point 30. Then, the folded bar 25 is rotated about the hinge pin 26 in order to be arranged in the rest configuration and is thus anchored to the side 5 by the retaining means. The operator can now freely accede to the space defined between the sides 5 in order to unload the products 31. When the cage structures 1 have been unloaded and the empty cage structures 1 are to be transported into the starting place therefor, the operator positions the sides 5 in the folded configuration. To this end, each side 5 is raised with respect to the base 2 such that the blocking pin 9 disengages from the seating 10. At the same time, the connecting pin 7 slides upwards internally of the slot 8. After the blocking pin 9 disengages from the seating 10, the side 5 can be rotated towards the inside of the base 2 such that the side 5 is positioned almost horizontally, in a plane that is approximately parallel, or slightly inclined with respect to the central portion 3. The same operations are then repeated with reference to the opposite side 5.

[0066] The sides 5 thus fill the space defined between the central portion 3 and the raised peripheral portions 4 and do not project upwards with respect to the raised peripheral portions 4. The cage structure 1, in the folded position, thus occupies a very small space.

[0067] As shown in Figure 8, the further pallet 20' can be arranged on the cage structure 1 positioned in the folded configuration and arranged on the respective pallet 20, the further pallet 20' in turn supporting the further cage structure 1', also in the folded configuration. In this way many pallets and folded cage structures can be stacked on top of one another, up to filling all the space available internally of the load compartment of the vehicle or internally of the container.

[0068] The stack of pallets and cage structures thus obtained is very stable, as each pallet rests on the upper surface 17 of the raised peripheral portions 4 of the underlying cage structure 1 and is maintained in the correct position by the protruding members 18.

Claims

1. A cage structure comprising a base (2) suitable for supporting goods (31), characterised in that the cage structure (1) further comprises a pair of sides (5) which are opposite one another, the sides (5) being movable between a folded configuration in which the sides (5) are folded on the base (2) and an open configuration in which a space for receiving goods (31) is defined between the sides (5) and the base (2), the sides (5) having respective free ends (11) which are delimited by end surfaces (12) which, in the open configuration, define a rest plane (P) for receiving a pallet (20) to be positioned on the cage structure (1).

2. A cage structure according to claim 1, wherein the end surfaces (12) are provided with anti-slip means (13) for preventing the pallet (20) arranged on the cage structure (1) from sliding with respect to the rest plane (P).

3. A cage structure according to claim 2, wherein the anti-slip means (13) are positioned in two peripheral regions (14) of each end surface (12), such as to interact with two peripheral beams (22) of the pallet (20).

4. A cage structure according to any preceding claim, wherein each end surface (12) has a central region (15) from which two protruding elements (16) project, the protruding elements (16) being suitable for opposing lateral displacements of a central beam (21) of the pallet (20).

5. A cage structure according to claim 4, as appended to claim 2 or 3, wherein the anti-slip means (13) are arranged in said central region (15) in a position interposed between the protruding elements (16) .

6. A cage structure according to any preceding claim, wherein the base (2) comprises a central portion (3) and two raised peripheral portions (4), each side (5) being connected to a respective raised peripheral portion (4).

7. A cage structure according to claim 6, wherein, in the folded configuration, the sides (5) are arranged on the central portion (3) and internally of a volume defined by the raised peripheral portions (4).

8. A cage structure according to claim 6 or 7, wherein each raised peripheral portion (4) is delimited by an upper surface (17) from which two protruding members (18) project, the protruding members (18) being suitable for opposing lateral displacements of a central beam (21) of a pallet (20) arranged on the cage structure (1) in the folded configuration thereof.

9. A cage structure according to any one of claims 6 to 8, and further comprising blocking means (9, 10) that can be activated in the open configuration for blocking each side (5) on a corresponding raised peripheral portion (4).

10. A cage structure according to claim 9, wherein the blocking means (9, 10) comprise at least one blocking pin (9) fixed to a side (5) and arranged such as to engage in a seating (10) obtained in the corresponding raised peripheral portion (4).

11. A cage structure according to any preceding claim, and further comprising at least one bar (25) arranged for connecting the sides (5) to one another in the open configuration.

12. A cage structure according to claim 11, wherein said at least one bar (25) is hinged to a side (5) such as to be movable between a rest configuration in which said at least one bar (25) is substantially parallel to said side (5) and a working configuration in which said at least one bar (25) connects the two sides (5) to one another.

13. A cage structure according to claim 12, wherein the side (5) to which said at least one bar (25) is hinged comprises retaining means (33) for maintaining said at least one bar (25) stationary in the rest position thereof, and the side (5) opposite to the side to which said at least one bar (25) is hinged comprises fastening means for blocking said at least one bar (25) in the working configuration.

14. A cage structure according to any one of claims 11 to 13, wherein said at least one bar (25) comprises a first part (28) which is hinged to a side (5) and a second part (29) which is hinged to the first part (28).

15. A cage structure according to any one of claims 11 to 14, wherein a pair of bars (25) are provided, each bar (25) being hinged to a respective side (5) in order to connect the side (5) to the opposite side (5).

Drawing