EP3403798A1

EP3403798A1 - Mobile structure and procedure for the prefabrication of desirably prestressed concrete bars

Info

Publication number: EP3403798A1
Application number: EP18020206.1A
Authority: EP
Inventors: Mihaly Török
Original assignee: Dvb Delmagyarorszagi Vasbetonipari Kft
Current assignee: Dvb Delmagyarorszagi Vasbetonipari Kft
Priority date: 2017-05-15
Filing date: 2018-05-14
Publication date: 2018-11-21
Anticipated expiration: 2038-05-14
Also published as: HUE056993T2; EP3403798B1; HUP1700206A1

Abstract

The subject of the invention is a mobile structure for desirably prefabricated reinforced concrete bars, which is composed of: two end elements (1); at least one intermediate element (3a, 3b, 3c); a collision element (4a, 4b) assisting the connection of an end element (1) and an intermediate element (3a, 3b, 3c) or two intermediate elements (3a, 3b, 3c); and stressing elements (2) attached to the end elements (1), in the intermediate element (3a, 3b, 3c) and the end elements (1), a groove is inserted (8), with the grooves (8) being arranged adjacent to each other, thus forming a contiguous and interconnected channel. It is characterized in that the placement of an adjustable shutter element (5) in the grooves (8) placed adjacently, the stressing element (2) contains stressing plates (6), and a rut (7) is formed at the height of the stressing plates (6) in the end element (1). The subject of the invention also includes the procedure for the application of the structure.

Description

The subject of the present invention is a mobile structure for the prefabrication of desirably prestressed concrete bars. The subject of the invention also includes the procedure for the application of the structure.
As per the current state of technical development, the following solutions are known in the field of manufacturing prestressed concrete beams. Long-stretch stressing technology, short-stretch stressing technology, pattern stressing technology, mobile stretch technology.
When using a long-bench stretching technology, reinforced concrete elements are manufactured in a large production hall. During its application, two large shafts are made from concrete and reinforced steel at a distance of 60-100 m. Steel lamellas are placed in the shafts and the lashes are stretched between the lamellae, due to the fact that during this production type the counterweight is provided by the weight of the shafts' concrete contained in them. This technology requires high investment costs as well as a long production hall with a minimum of 100 m in longitude, comes with a high productivity, and the size of the stressed parts can be varied.
The principle of short-stretch stressing technology resembles the long-stretch manufacturing regarding the fact that a concrete frame composed of rectangular concrete beams is used during the manufacturing process - the pinnacle is stretched between the two ends of this frame. Stressing is made possible by the fact that the concrete beams can withstand the tension generated during the stressing procedure due to their size. In this case, the frame itself can be disassembled, assembled and transported, however, its disassembling and assembling is a time-consuming process (takes up to 20 days to complete). The frame is fixed to the ground, while a concrete bed shall be manufactured underneath of it at the construction site.
For the pattern-stretching technology, prefabricated and pre-sized steel patterns are used to manufacture the stressed components. The advantage of this technology is that the position of the pattern can be changed, meaning that it does not require its placement in a production hall, since it is also possible to manufacture the stressed elements at the construction site. In this case, an individual pattern is designed for each size or diameter, so that the variability of the patterns is limited.
Under the mobile stretching technology, the stressing is performed by using a steel structure, while the stretch is fixed to the ground by numerous glued blades.
The U.S. patent No. US4040775 A provides a description for a structure which enables the on-site production of prestressed concrete blocks. The multitude of wires, which are fixed by their ends, may be placed geometrically as per needed. By using a lever, the structure can be placed in a position that stresses the wires, followed by the concrete being poured on top of such stressed wires. The U.S. disclosure description No. US4149306 A presents a structure which is used for the on-site manufacturing of prestressed concrete beams. This structure consists of prefabricated elongated concrete modules that serve as molding tools for the pertinent beams. Bore holes run down along all modules. The modules can be aligned, disassembled after their use and reused again. Its advantage is that it can be easily transported and can be used to produce a beam of any given length.
The international patent No. WO2010007192 A1 describes a system consisting of modules. These modules can be used to produce stressed concrete elements. Each module functions as a mold, completed by stressing and fixing wires. The length of the elements to be manufactured can be modified, as the alignment of more modules is required to manufacture a longer element. The disadvantage of the solution is that the diameter of the beam to be manufactured is not optional.
The U.S. disclosure description No. US2003113395 A1 presents a method, as well as a device related thereto, by the use of which prestressed reinforced concrete railway beams may be manufactured. The pertinent device has portable parts. No permanent building is needed for the manufacturing of the beams, their production is possible in a temporary tent or even out in the open when suitable weather conditions are present. No special groundwork is required for the unit.
The British disclosure description No. GB1377189 A elaborates on a formwork by the use of which prestressed concrete elements may be manufactured. The tension forces are absorbed by the formwork, making it is easy to transport even along with the stressing cables, whether being already filled up by concrete or left empty.
The Chinese patent No. CN102277920 A presents a hollow reinforced concrete floor design and its manufacturing process. The floor consists of prefabricated and on-site manufactured concrete elements that create an overall stressed reinforced concrete structure. A lightweight, low manufacturing costs, high performance construction is produced.
The U.S. disclosure description No. US4629408 A elaborates on a transportable structure which allows the on-site manufacturing of reinforced concrete beams. The structure consists of reverse T-shaped concrete elements, each of more than 20 feet (about 6 meters) in longitude, along which sequential bore holes are running down. This allows the elements to be aligned and a stressing cable may be passed through them. One of its advantages is that this design allows the manufacturing of multiple beams at the same time.
The U.S. Patent No. 5766648 A presents a stressing frame structure by the use of which the manufacturing of railway fastening beams made of stressed concrete is possible. The advantage of the frame is that it can be dismantled, allowing for it to be easily transported.
The solutions presented possess many disadvantages. The disadvantage of the long-stretch stressing technology is that it cannot be used outside the production hall (lack of mobility), and the installing of shafts made of concrete and steel is necessary (to provide counterweight). A further disadvantage is that it requires a minimum of 2 x 15-ton bridge cranes, elevating the technology investment demand rate to a high level.
The disadvantage of the short-stretch stressing technology is the time-consuming assembly process and the necessity to produce a concrete bed underneath it at the construction site. Medium-sized productivity and medium variability may be achieved at a medium investment demand rate. At the same time, it can be considered a downside that its application requires a minimum of 2 x 10-ton bridge cranes, while it can only produce elements of up to 24 m in longitude.
When applying the pattern-stretching technology, it should be noted that a pattern may only be applied to a diameter that is of the same size as the pattern, as its size is not variable. Therefore, it is a significant disadvantage to have the need for as many patterns of different sizes as many sizes of diameters they should be applied on. Although it is theoretically a mobile technology, it does come with variability and only allows to manufacture elements of up to 15 m of longitude.
Lastly, the disadvantage of using a mobile stretch technology is that it is necessary to build a concrete slab underneath it, to which the stretch is fixed by numerous glued blades, making its assembly a time-consuming process.
In conclusion, it should be noted that the additional technology used during the manufacturing of non-stressed elements is the on-site prefabrication. On-site prefabrication of stressed elements would incur high transportation costs when using the long-stretch technology, and regarding the short-stretch and pattern-stressing technology, the size of the elements to be manufactured is limited (e.g. no elements of more than 40 m in longitude can be manufactured this way). The construction of a traditional stressing plant requires an investment of billion-forint high costs, and the delivery of manufactured stressing elements to the construction sites would incur additional expenses.
The aim of the present invention is to address the disadvantages of the solutions avaliable today, as well as to present a structure along with its manufacturing method, which would allow the production of prestressed reinforced concrete elements of any size in longitude or diameter. The aim of the present invention is to guarantee its utility and easy-to-use nature during smaller investment projects as well, without the need of its fixation to the ground.
The inventive step is based on the recognition that an invention, which is more advantageous than the previous one, may be created by executing the procedure according to claim 1. Such recognition enables us to produce prefabricated reinforced concrete bar elements of any size in longitude or diameter.
According to our goal, the most general embodiment of the invention is described in claim 1. The most general form of application procedure is described in the independent claim 7. The various implementation forms are described in the dependent claims.
The solution is generally a mobile structure for the prefabrication of desirably prestressed reinforced concrete bars, which are produced two end elements; with at least one intermediate element; a collision element ensuring the alignment of an end element and an intermediate element or two intermediate elements; while also containing stressing elements attached to the end elements, a groove is embedded in the intermediate element and the end element, with their entirety being subsequently aligned adjacent to each other to form a contiguous and interconnected channel. It is a feature of the invention that an adjustable shutter element is placed in the adjacent grooves, the stressing element contains stressing plates, and a rut is created in the end element at the height of the stressing plates.
Various designs may be implemented when the shutter element has a horizontal rib, a vertical rib, a mobile unit and a rail; the mobile unit is connected to the rail, while the vertical rib is connected to the mobile unit; the horizontal rib and the vertical rib are interconnected in an unlockable design.
It may also be characteristic that the mobile unit comes with lower and upper fixing binding elements as well as a rolling unit.
Different designs may allow for the longitude of the end piece to be between 4-8 meters and its width between 1-3 meters, while the longitude of the intermediate element is between 4-8 meters and its width between 1-3 meters.
It may also be characteristic for the stressing element to contain 2 to 10 stressing plates. It may also be characteristic for the shutter element to have two pairs of interlocking parts and to be filled with mortar.
It is a feature of the general use of the invention that, according to the length of the beam to be manufactured, at least one newly assembled or disassembled intermediate element is placed between two newly assembled or disassembled end elements, having the intermediate element and the end element or the two intermediate elements closely adjoined by using collision elements, a new shutter element is produced according to the diameter of the bar element to be manufactured, the shutter element is placed in the adjacent grooves of the end element and the intermediate element, with pinnacles included in the shutter element, the pinnacles are led through the rut and fixed between the stressing plates, the shutter element is filled up with concrete and, after the concrete being dried and fixed, the shutter element is disassembled, and the procedure is repeated as needed.
It is also characteristic for the end elements and the intermediate element to be placed on the ground or on the floor without the need of their fixation.
It may also be characteristic to reuse the end elements and the intermediate element during the repetition of the procedure, while the shutter element shall be replaced before the procedure may be repeated.
It may also be characteristic that a rail is inserted into the groove during the manufacturing of the shutter element, while a mobile unit to be moved longitudinally along the rail is connected to the rail, followed by the mobile unit being fixed after positioning by using a fastening element.
The invention is presented in more detail using drawings relating to its implementation forms.
The attached drawings depict

Figure 1 is an axonometric figure of the structure, a
Figure 2 is an axonometric figure of a different design of the structure
Figure 3 is an axonometric figure of a certain type of the intermediate element,
Figure 4 is an axonometric figure of the end element,
Figure 5 is an axonometric figure of a different type of the intermediate element,
Figure 6 is an axonometric figure of a third type of the intermediate element,
Figure 7 is an axonometric figure of the stressing element, while
Figure 8 is an axonometric figure of the shutter element.

Figure 1 illustrates a design of the structure from a spatial view. The present invention contains two end elements 1, and an optional number of intermediate elements, which in our case is 3 pieces, are placed between the end elements 1. In the example shown in Figure 1, intermediate elements 3a are placed alongside the end elements 1, while the intermediate elements 3a are interposed with the intermediate elements 3b. The end elements 1 and the intermediate elements 3 are composed of reinforced concrete, measuring six meters in longitude and two to three meters in width. The end elements 1 and the intermediate elements 3 can be repeatedly reused and, thanks to their characteristic features, provide the counterweight themselves, meaning that it is not necessary to provide a concrete bed underneath them, or to fasten the structure to the ground, or to incinerate it in a shaft. They allow for the production of large (up to 40 m) stressed elements without the aforementioned requirements. In addition, the stressing element 2 can be observed on the figure. The stressing element 2 enables the invention to actually function as a stressing stretch, as well as it allows for the prefabrication of prestressed pillars and beams. The shutter elements 5 are placed in the grooves 8 of the end elements 1 and the intermediate elements 3. The shutter elements 5 can be adjusted according to the size of the bar to be manufactured. The bars to be manufactured may be of any measure in longitude and diameter, meaning that the shutter elements 5 may be produced according to the width, height and shape - may that be a rectangle, an I, a T or an inverted T - and the desired length of the desired diameter. In the example shown in Figure 1, the shutter elements 5 are adjusted to produce a rectangular bar section element. The diameter of the bar to be produced may generally range between 50 to 60, even up to 100 cm in width. The shutter elements 5 comes along with horizontal ribs 9, a mobile unit, a rail, a rolling unit and vertical ribs 10. The mobile unit moving along the rail, which is used to determine the diameter of the bar to be manufactured, can be fixed in place by the lower and upper fixing screws in the desired position. The vertical ribs 10 are, desirably, durable steel section which are C shaped in diameter, while the horizontal ribs 9 are typically made of wood, generally to be changed between the bar element production processes. The horizontal ribs 9 are securely fastened to the vertical ribs 10, for example by using a screw, a rivet or glue. Desirably, the pertinent mobile unit and the vertical ribs 10 are integrated into a single piece. The size of the shutter elements 5, as well as the width and longitude of the steel plate inside it can be modified, thus having a high level of variability. The stressing elements 2 are supplied by steel stressing plates 6 aligned over one another, measuring approximately 25 mm in thickness, with a gap between them of approximately 15mm. The stressing wires and pinnacles are stressed and fixed between the stressing plates 6 contained in the stressing elements 2. The stressing plates 6 are designed to withstand the stress forces (approximately 130 kN, i.e. the weight of fourteen cars per pinnacle) as long as it takes for the concrete to solidify. These stressing plates 6 direct the stress force onto the end element 1, which directs it further towards the other elements. The stressing elements 2 stay immobile because the stressing plates 6 are only subjected to a horizontal force while the full stress is distributed by the end element 1. Two elements are connected to each other by the use of 4-4 collision elements 4a, 4b, with the highly rigid mortar providing the distribution of full stress between them. After being used, the structure can be disassembled thanks to the presence of the mortar, and later re-assembled again measuring at a variable longitude. The collision element 4a, more precisely its outer receiving half (bolt) can be observed between the end element 1 and the 3a intermediate element. The collision element 4a is made of steel. In order for the end element 1 and the intermediate elements 3a, 3b, 3c to withstand forces arising during the stressing, reinforced concrete elements need to be prepared by special armoring techniques based on a unique armoring plan.
Similarly to Figure 1, Figure 2 shows an axonometric figure of a design variant. In this variation, the intermediate element 3a is placed next to the end element 1, while the two intermediate elements 3c are placed adjacent to it, and by this pattern, it is possible to manufacture a stressed bar element measuring of approx. 30 meters in longitude (as one element measures six meters in length). We have also depicted on the figure the shutter elements 5, the stressing elements 2, the stressing plates 6 and the collision element 4a, the roles and form of which are the same as described in the previous figure.
Figure 3 shows the intermediate element 3a in separately from a spatial view. The intermediate element 3a is made of reinforced concrete and measures approx. six meters in length. It can be placed adjacent to the end element 1 and any type of intermediate element, upon which case the other (nut) half of the collision element 4a is aligned with the collision element 4a. Should the alignment be inaccurate, the collision element 4a must be filled with shrink-free mortar. In the figure, a dashed line indicates the steel collision element's 4a solidification into the concrete. The grooves 8 of the intermediate element 3a creates an interconnected channel along with the grooves of the other intermediate elements and end elements which are aligned adjacent, in which the reinforced concrete bar element may be manufactured by using the adjustable shutter elements.
Figure 4 depicts the end element 1 separately from a spatial view. In the end element 1 there are ruts 7, through which the concrete steel may be passed. The end element 1 is supplied with four collision elements 4a, which assists with the attachment and positioning of the adjacent intermediate elements. It is also possible to produce a end element 1 containing four 4b collision elements. We can also recognize the grooves 8 of the end element 1 depicted on the chart.
Figure 5 depicts an intermediate element 3c with grooves 8 separately from a spatial view. The intermediate element 3c is provided with a collision element 4a and a collision element 4b placed adjacent on its sides, which assist with the alignment and positioning of any additional intermediate or end elements.
Figure 6 shows an intermediate element 3b with grooves 8 separately from a spatial view. The intermediate element 3b is provided with eight 4b collision elements, which assist with the alignment and positioning of any additional intermediate or end elements.
In Figure 7, the tail part of the end element 1 is depicted, alongside with the stressing element 2 and the stressing plates 6 positioned inside thereof. In the end element 1 there are ruts 7, through which the concrete steel may be passed. The stressing element 2 contains steel stressing plates 6, arranged over one another, measuring approx. 25 mm in thickness. The amount of stressing plates 6 is desirably between 2-10 pc, with 3 pc being present in the example as shown. Between the stressing plates 6, gaps of 15 mm are created, in which the pinnacles are being stressed and fixed in place. The stressing plates 6 withstand the stress forces for as long as in takes for the concrete to solidify.
In Figure 8, some parts of the shutter elements 5 can be seen zoomed in, in an axonometric view. The bottom rail 12 is - typically, just as shown in this example, where it forms an I shape in diameter - positioned horizontally along the channel of the structure. The rail 12 is perpendicular to the bar element to be manufactured. Along this rail 12, the mobile unit 11 can be moved longitudinally, thereby adjusting the width of the diameter of the reinforced concrete block to be manufactured. After adjusting the desired position, the mobile unit can be fixed by the lower and upper fixing screws. The mobile unit 11 has a design adapted to the rail 12, by which the rail 12 provides a suitable platform to the mobile unit 11's movements. The mobile unit 11 is provided with a rolling unit 13, which is similar to 2-4 or even 6-8 rollers or wheels to facilitate its steady movement. The mobile unit 11 is provided with a vertical rib 10, though this connection may also be created by an unlockable attachment. The vertical rib 10 is preferably steel section with a C shape in diameter, to which horizontal ribs can be adjoined by fastening elements, bolts, nails, or glued or plastered thereto. The mobile unit 11 allows to create concrete elements of several different sizes and shapes (rectangular, T, I or inverted T in diameter) by using the same end elements, intermediate elements and collision elements within the dimensions of the groove.
During the application of the invention, the intermediate elements 3a, 3b, 3c and the end elements 1 are manufactured first. It is not necessary to make/obtain a separate pattern for each of the required sizes or diameters, because the exact shutter element dimension of the reinforced concrete bar to be manufactured is determined by the shutter elements 5, which are completely exhausted by the end of the manufacturing process. When assembling the structure, the respective intermediate elements 3a, 3b, 3c and the end elements 1 are placed adjacent to each other, e.g. placed on the ground or the floor, and positioned exactly adjacent to each other by the collision elements 4a, 4b. The collision elements 4a, 4b are filled with mortar, no other fixation is required. Following that, the mobile unit 11 of the shutter elements 5 is adjusted along the rail 12 in accordance with the desired width of the bar to be manufactured, and fastened by screws at the desired position. The horizontal ribs 9 and vertical ribs 10 of the shutter elements 5 are also aligned according to the desired diameter. It is then placed into the intermediate elements 3a, 3b, 3c and the end element 1. After that, we fasten the pinnacles and the cables. During the prestressing process, these pinnacles are being stressed by the stressing elements 2 and the stressing plates 6. When manufacturing a beam, the pinnacles are placed in the lower, stretched section of the beam. Their ends are exited through the ruts 7 of the end elements 1 in between the stressing plates 6, and then fixed. Concreting works are carried out following the placement and stressing of the pinnacles. After the concrete has solidified, the pinnacles are cut off, causing the force in the pinnacles to act directly on the completed reinforced concrete element directed from the stressing plates 6 of the stressing elements 2, and therefore, the lower edge of the reinforced concrete element is compressed, causing the beam to bend, and to be straightened out only under the effect of stress. The end elements 1 and the intermediate elements 3a, 3b, 3c may be repeatedly used for the manufacturing of various reinforced concrete bars. Upon this case, the stressing construction may always be assembled in a different order. The shutter element 5 should preferably be replaced before each use, since it is usually exhausted after a single bar element is manufactured.
The presented invention has many advantages. One of the advantages is that it allows for mobile prefabrication at construction sites. Another advantage of the present invention is that it enables to produce any elements of variable and modifiable size by using the adjustable size pattern inserted into the reinforced concrete frame. An important economic advantage is that the use of the invention does not require a new production hall to be created - which would incur the investment demand for billions of dollars -, furthermore, it may be utilized in a production hall not equipped with a crane or out in the open as well. For the aforementioned reasons, the production of stressed elements can be carried out directly at a construction site as well. The advantage of the structure is that the counterweight function required for the production of stressed elements is provided by the prefabricated reinforced concrete elements of the structure, meaning that the structure does not require a ground fixing (e.g. it can be utilized on a gravel bed or concrete slabs, without the need for a prefabricated concrete flooring). Frames of optional lengths may be assembled from the reinforced concrete and steel frame patterns, with the possibility of disassembling the elements later as it is not necessary to fix them to each other, and later be rebuilt as well. The present invention reduces the manufacturing costs of concrete elements, especially when several different configurations of concrete elements are required to be produced at a single site within a well-defined size range. Due to the adjustable shutter elements, concrete and reinforced concrete beams and elements of sizes variable within a broad range may be produced even by using only a single concrete groove. It is also a positive feature that the weight of the structure allows for road transport to be an option. By applying the present solution, the production of longer elements measuring up to 200 meters in longitude on site is made possible, for which there was no option up until now. It is beneficial that the intermediate and end elements can be reused on an almost unlimited number of occasions. To sum things up, we can conclude that the present idea envisions a mobile- and modular stressing stretch, which comes with a low investment cost and a freely variable system, under which beams of any given measure in longitude may be manufactured.
The field of application of the invention extends to construction sites and production halls, where prefabrication of stressed elements may be required.
In addition to the above examples, the invention can be implemented in other forms and with other manufacturing processes within the scope of protection.

Claims

Mobile structure for desirably prefabricated reinforced concrete bars, comprising two end elements (1), at least one intermediate element (3a, 3b, 3c), a collision element (4a, 4b) assisting the connection of an end element (1) and an intermediate element (3a, 3b, 3c) or two intermediate elements (3a, 3b, 3c), and stressing elements (2) attached to the end elements (1); in the intermediate element (3a, 3b, 3c) and the end elements (1) a groove is inserted (8); with the grooves (8) being arranged adjacent to each other, thus forming a contiguous and interconnected channel, characterized by the placement of an adjustable shutter element (5) in the grooves (8) placed adjacently, the stressing element (2) contains stressing plates (6), and a rut (7) is formed at the height of the stressing plates (6) in the end element (1).
The structure according to claim 1, characterized in that the shutter element (5) includes a horizontal rib (9), a vertical rib (10), a mobile unit (11) and a rail (12); the mobile unit (11) is connected to the rail (12); while the vertical rib (10) is connected to the mobile unit (11); the horizontal rib (9) and the vertical rib (10) are connected by an unlockable design.
The structure according to claim 1 or 2, characterized in that the mobile unit (11) includes lower and upper fastening elements for its fixation, as well as a rolling element (13).
The structure according to any of claims 1 to 3, characterized in that the end element (1) measures between 4-8 meters in length and 1-3 meters in width, while the intermediate element (3a, 3b, 3c) measures between 4-8 meters in length and 1-3 meters in width.
The structure according to any of claims 1 to 4, characterized in that the stressing element (2) includes 2 to 10 stressing plates (6).
The structure according to any of claims 1-5, characterized in that the collision element (4a, 4b) comprises two interlocking parts and is filled with mortar.
The procedure for the application of the structure according to claim 1, characterized by at least one newly assembled or disassembled intermediate element (3a, 3b, 3c), which is inserted between two newly assembled or disassembled end elements (1), according to the desired longitudinal measurement of the beam to be manufactured, the intermediate element (3a, 3b, 3c) and the end element (1) or two intermediate elements (3a, 3b, 3c) are positioned closely adjacent by using the collision elements (4a, 4b), a new shutter element (5) is manufactured according to the diameter of the bar element to be manufactured, the shutter element (5) is placed in the grooves (8) of the end elements (1) and the intermediate elements (3a, 3b, 3c) aligned adjacent to each other, pinnacles are inserted into the shutter element (5), the pinnacles are led through the rut (7) and fastened in between the stressing plates (6), the shutter element (5) is filled with concrete, and, following the drying and solidification of the concrete, the pinnacles are cut, and the shutter element (5) is disassembled, and the procedure is repeated as needed.
The procedure according to claim 7, characterized in that the end elements (1) and the intermediate elements (3a, 3b, 3c) are placed on the ground or on the floor without the need for their fixation.
The procedure according to claim 7 or 8, characterized in that the end elements (1) and the intermediate elements (3a, 3b, 3c) are reused during the repetition of the process, while the shutter element (5) is replaced before repeating the procedure.
The procedure according to any of claims 7 to 9, characterized in that during the manufacturing of the shutter element (5), a rail (12) is inserted into the groove (8), a mobile unit (11) capable of longitudinal movement along the rail (12) is connected to the rail (12), and the mobile unit (11) is fixed in place following its positioning by using a fastening element.