Oven frame, in particular shaft oven frame, for charging an oven system with material to be heat treated

Abstract

Oven frame (1) for charging an oven system with a material to be heat treated, comprising at least one load-bearing vertical beam and at least one horizontal beam (3a, 3b) arranged on the vertical beam with a support cross formed by support arms (11a, 11b), characterized in that one vertical beam is designed as a central beam (2) and / or at least two vertical beams are designed as edge beams, the horizontal beam (3a, 3b) has a centrally arranged central opening (4a, 4b) for receiving the central beam (2) and the horizontal beam (3a, 3b) has sleeves (14a, 14b) with edge openings (5a, 5b) arranged at the free ends of the support arms (11a, 11b) for receiving the at least two edge beams through which the edge beams extend.

Description

The invention relates to a furnace frame, in particular a shaft furnace frame, for charging a furnace system with a heat-treated material, comprising a load-bearing vertical support and a horizontal support arranged on the vertical support with a support cross formed by support arms. Furnace racks, in particular shaft furnace racks of the type mentioned above, which are structurally adapted to the shaft furnaces intended for hot treatment, are used to hold components, such as gear parts, which are to be subjected to hot treatment. The horizontal beams are connected to the vertical beam and provide a support surface for the material to be heat-treated. The furnace frame, equipped with components and consisting of at least one vertical beam and one horizontal beam which provides a support surface for the material, can then be moved as a whole into the furnace system intended for heat treatment by a lifting unit attached to the vertical beam, and subsequently removed from the furnace system. If the furnace frame is designed as a shaft furnace frame, the vertical beam typically has a connection point for suspended transport of the shaft furnace frame, allowing the frame to be moved, lifted, and lowered, for example, using a suitable crane. Due to continuous use, the furnace racks themselves are subject to considerable mechanical and thermal stresses, which lead to significant wear on the horizontal beams over time, potentially resulting in irreparable damage. Furthermore, the typically central placement of the vertical beam often results in an insufficient surface area on the horizontal beam to accommodate larger items requiring heat treatment. It is generally known that several horizontal beams can be arranged one above the other, and their spacing allows for a larger number of items to be heat-treated on a single frame. However, even in this case, a central vertical beam presents an obstacle, particularly preventing the placement of large items to be heat-treated on the horizontal beam. From DE 698 10 662 T2 and DE 10 2014 205 426 A1, generic loading racks for holding workpieces during a heat treatment or coating process are known. The invention is based on the objective of providing a furnace rack, in particular a shaft furnace rack, which offers the possibility of accommodating even large components. The invention solves the problem by means of an oven rack with the features of claim 1. Advantageous further developments of the invention are specified in the dependent claims. A characteristic feature of the oven frame according to the invention is that a vertical support is designed as a central support and / or at least two vertical supports are designed as edge supports, and the horizontal support has a centrally arranged central opening for receiving the central support and sleeves with edge openings arranged at the free ends of the support arms for receiving the at least two edge supports, through which the edge supports extend. The central opening is typically an opening that penetrates the horizontal beam in the middle and is designed to receive the vertical beam, which also serves as the central beam. In its assembled state, the horizontal beam is slid onto the vertical beam up to a receiving section of the vertical beam. This receiving section is adapted to the central opening in such a way that the horizontal beam is fixed to the vertical beam in the longitudinal direction within the area of ​​the receiving section. In addition to the central opening, the horizontal beam also has, according to the invention, at least two edge openings around its circumference, which are provided for receiving vertical beams designed as edge beams. The edge beams also typically have a receiving section at one end, to which the horizontal beam is axially fixed as the base beam. The edge beams extend through the edge openings of the horizontal beam. The edge openings are preferably arranged on the outer circumference of the horizontal beam, so that a free area is formed in the area between the edge beams, which is not interrupted by a central beam. The number of edge openings for receiving the edge beams and their arrangement on the horizontal beam, e.g.,The design of the horizontal beam, whether detachable or integral, is generally freely selectable, with four or more edge openings preferably being evenly distributed around the circumference of the horizontal beam. The inventive design of the furnace frame with a horizontal support, which can be combined with both a central vertical support and with central supports arranged at the edges to form a furnace frame, makes it possible to optimally adapt the furnace frame to the material intended for heat treatment. In particular, the use of the edge opening allows for a support surface that is not interrupted by a central support, so that even large-area materials can be fed into the furnace frame for heat treatment. A key feature of both the central and edge openings is their design: the horizontal beam forming the base support is fixed to a receiving section of the central beam, or the edge beams are fixed in the longitudinal direction of the vertical beam. Typically, the receiving section is located near the end of the vertical beam, so that in the assembled position, the horizontal beam is preferably flush with the end of the vertical beam, allowing the furnace frame to be placed on the base support. Furthermore, the forces exerted on the horizontal beam by the components being heat-treated are reliably transferred to the vertical beam. The orientation of the horizontal and vertical beams relative to each other is such that, in the operating position, the vertical beam extends essentially vertically and the horizontal beam horizontally. By arranging the horizontal beam on a receiving section of the central beam and / or edge beam, a variable furnace frame is formed that can be transported by a lifting device attached to the vertical beam. With respect to the operating position, the furnace frame according to the invention can, for example, be lifted and transported by a lifting device attached to the lower end of the vertical beam or by a crane device attached to the upper end of the vertical beam. The design of the receiving sections of the central beam or edge beam, as well as the design of the corresponding edge openings or central opening, is generally freely selectable. However, according to a particularly advantageous embodiment of the invention, the central beam has a receiving section with projections, and the central opening has recesses adapted to the projections. According to this embodiment of the invention, reliable force transmission from the horizontal beam to the central beam is ensured via the projections and recesses. The projections extending from a circumferential surface of the central beam in the area of ​​the receiving section, which engage with corresponding recesses in the central opening, ensure not only good load transmission from the horizontal beam to the central beam but also reliable positional stability. In principle, the number of projections and corresponding recesses is freely selectable. However, a particularly advantageous embodiment provides for the vertical support to have several projections in the area of ​​the receiving section, which are preferably arranged symmetrically around the circumferential surface of the central support. The use of multiple projections enables good load distribution and also allows the projections to be made smaller while increasing their load-bearing capacity. Furthermore, the connection of the central support and the central opening via projections and recesses creates a torsion-resistant connection between the vertical and horizontal supports, which allows for precise positioning of the material to be heat-treated during the heat treatment process, as rotation of the horizontal supports relative to the vertical support is prevented.When using at least two edge supports, an anti-rotation device is unnecessary, as this is already achieved by the outer edge supports. Therefore, the receiving section only needs to be designed to secure its axial position, although projections can be incorporated as an additional measure if the edge openings are appropriately designed. To increase the loading capacity of the furnace rack, a further embodiment of the invention provides that a further horizontal support is arranged in the longitudinal axis direction of the vertical support at a distance from the horizontal support forming the base support, wherein at least one coaxially arranged spacer sleeve is arranged on the vertical support in the area between the horizontal supports, spacing the horizontal supports apart. The use of spacers allows for the arrangement of multiple horizontal beams one above the other, with each of these – relative to the operating position – positioned above the first horizontal beam, which forms the base beam. The spacing of further horizontal beams is achieved by spacers arranged coaxially to the vertical beam, i.e., coaxially to the central beam or coaxially to the edge beams. The spacer sleeve rests against the spaced horizontal beam with its circumferential end faces, and in the case of multiple spacers, these spacers abut each other in the area between the horizontal beams. The spacing of the horizontal beams can thus be easily adjusted by using multiple spacers, with the spacers reliably transmitting the force to the vertical beam(s).By using different and / or multiple spacer sleeves, the oven stand can be adapted to the respective application in a particularly simple way. The design of the spacer sleeves is generally freely selectable. In their simplest design, the spacer sleeves are shaped like a tube with flat end faces. However, according to a particularly advantageous embodiment of the invention, the central support spacer sleeve, which can be arranged on the central support, is designed as a spacer sleeve suitable at both ends for a rotationally secure connection with the central opening; or the central support spacer sleeve is designed as an intermediate sleeve suitable at both ends for a rotationally secure connection with a spacer sleeve; or the central support spacer sleeve is designed as an adapter sleeve, which is designed at one end for a rotationally secure connection with a spacer sleeve and at the other end for a rotationally secure connection with the central opening. According to this embodiment of the invention, the central beam spacer sleeve can have three different configurations. In its configuration as a spacer sleeve, it is designed at both ends for a rotationally secure connection with the central opening. In the case of a configuration with a recess, the spacer sleeve can, for example, have end faces with projections that engage with the recesses, which makes it possible to transfer the rotational protection of the base beam to a horizontal beam arranged above the base beam via the spacer sleeve. As an intermediate sleeve, the central beam spacer sleeve has a configuration that enables a rotationally secure connection at both ends with the previously described spacer sleeve. The intermediate sleeve is thus suitable for being arranged between two spacer sleeves in order to connect them to each other in a rotationally secure manner. In the case of a spacer sleeve with projections arranged on both end faces, the intermediate sleeve can, for example, be provided with recesses on both end faces that correspond to the projections. According to a further development of the invention, the design of the intermediate sleeve with recesses also allows for the arrangement of releasable locking cams in the recesses, which then fulfill the function of projections. The intermediate sleeve with recesses can thus be easily transformed into a spacer or adapter sleeve, whereby the locking cams can, for example, be arranged in the recesses via a dovetail-like connection. The use of locking cams thus increases the variability of the intermediate sleeve with recesses arranged on one or both end faces. In a further embodiment, the central support spacer sleeve is designed as an adapter sleeve, with one end configured for a rotationally secure connection to a spacer sleeve and the other end for a rotationally secure connection to the central opening. According to this embodiment of the invention, a rotationally secure connection between the superimposed horizontal supports can be easily established by using a spacer sleeve and one or more adapter sleeves. If a spacer sleeve with projecting cams on both sides is used, the adapter sleeve can, for example, be provided with one or more projections on one side and recesses shaped accordingly on the other, in order to establish a rotationally secure connection between the sleeves and the horizontal supports connected to the sleeves. Overall, the various design options for the central support spacer sleeve allow the oven frame to be individually adapted to specific needs. For example, a kit consisting of several different sleeves and, if necessary, locking cams, enables the oven frame to be precisely tailored to its intended use, with the sleeves providing reliable protection against rotation. The spacer sleeves for spacing the horizontal beams in the case of the use of edge beams can be designed as simple cylindrical bodies with flat end faces, since the use of at least two edge beams which are connected to the horizontal beams already provides protection against rotation; the sleeves arranged on the edge beams can therefore be designed solely for the horizontal spacing of the horizontal beams. The design of the central opening, e.g., the arrangement of the recess, is generally freely selectable. However, according to a particularly advantageous embodiment of the invention, the recesses of the central openings are arranged at intervals of 60° on the inside of the central opening, the sleeve has two diametrically opposed projections at both ends that are adapted to the recesses, and the adapter sleeve has two diametrically opposed recesses at one end and recesses at other ends that are distributed around the circumference at intervals of 60° or 90°. This design of the central opening, the spacer sleeve, and the adapter sleeve allows the stacked horizontal beams to be fixed in 30° increments relative to each other. This enables optimal alignment of the horizontal beams, which can, for example, be equipped with different sections for holding the heat-treated material. This ensures a consistent heat distribution of the heat-treated material through optimal alignment of the horizontal beams. The design of the horizontal beam, which is generally intended to accommodate support grids that can be arranged on the horizontal beams, is fundamentally freely selectable. However, according to the invention, the horizontal beam has at least two support arms, preferably at least three, and particularly preferably six, each of which has an opening at its free end. According to this embodiment of the invention, the horizontal beam has support arms radiating from the central opening in a star-like pattern, on which the support grids can be arranged, with edge openings provided at the ends of the support arms for receiving the edge supports. This embodiment of the invention enables a simple and cost-effective design of the horizontal beams with edge openings arranged at their free ends. Furthermore, the arrangement of the edge opening at the ends of the support arms ensures good force transmission between the horizontal beams arranged one above the other. According to the invention, sleeves are arranged at the free ends of the support arms, which have edge openings for receiving the edge supports. According to the invention, the support arms form a cross-shaped support structure and enable the application-specific arrangement of support grids that can be arranged between the support arms. The support grids, which, for example, have a grid-like support structure, allow for good drainage of liquids, e.g.,Oils can be used after heat treatment to adjust the microstructure of the components to be heat-treated. Furthermore, the use of support grids can reduce the dead weight of the horizontal beams. According to a particularly advantageous embodiment of the invention, the support arms are symmetrically aligned, thus ensuring uniform force transmission. When horizontal beams are used to support load-bearing grids, the support arms can, in principle, be designed in any way to accommodate the grids. However, a particularly advantageous embodiment provides that the support arms have circumferentially projecting cams designed to receive load-bearing grids between the support arms. This embodiment of the invention enables a simple and reliable arrangement of the support grids on the support arms, whereby the cams projecting circumferentially from the support arms can engage, for example, with recesses arranged on the support grids. The cam-recess connection ensures a high degree of positional stability of the support grids on the support arms, while simultaneously allowing for easy replacement of the support grids if desired. As an alternative to the configuration of the horizontal beams with detachable support grids, a further development of the invention provides that the support grids are formed integrally with the horizontal beam. This embodiment of the invention makes it possible to use the entire surface area created by the horizontal beam and the area between the horizontal beams to form a homogeneous support structure. Furthermore, a continuous surface provides a consistent load distribution, and the load transfer at connection points between the support grid and the support arm can be eliminated. As already explained above, the design of the support grates and / or the horizontal beam formed integrally with the support grates is fundamentally freely selectable and can be designed according to the load and application of the furnace frame. However, according to a further embodiment of the invention, the support grates and / or the horizontal beam formed integrally with the support grates have a honeycomb structure and / or a branched, radial design. When using a honeycomb structure, the cells can be designed with identical side lengths, regularly spaced to form a load-bearing grid. Alternatively, the honeycomb structure can be designed in a "bionic" style, where the cells have different side lengths and / or the sides of a cell form different angles. The design of the load-bearing grids or the entire horizontal beam with such a honeycomb structure is characterized by high load-bearing capacity despite low weight. An alternative design for the support grids, or for the entire horizontal support surface formed by the support grids and horizontal beams, involves the use of a branched, radial design. Starting from the central opening, two intermediate webs branch off radially from a wide base web, each of which in turn has two further branched end webs. The free ends of the end webs can then be connected to each other around their circumference via intermediate webs, with additional intermediate webs in the radial direction providing extra support for the individual webs. This design is also characterized by its low weight and high load-bearing capacity. According to a further embodiment of the invention, the spacer sleeve for coupling two horizontal beams is designed such that the horizontal beams abut each other in the arrangement achieved via the spacer sleeve. According to this embodiment of the invention, two horizontal beams are coupled to each other in a rotationally fixed manner via the spacer sleeve. Furthermore, the load-bearing capacity of the receiving surface is also increased by the fact that the horizontal beams abut each other in the vertical direction, since the bending stiffness of the horizontal beams is increased overall by the coupling of the horizontal beams to each other caused by the spacer sleeve. An embodiment of the invention is explained below with reference to the drawings. In the drawings, Fig. 1 shows a perspective view of a shaft furnace frame with a central beam and horizontal beams arranged thereon; Fig. 2 shows a perspective view of the uppermost horizontal beam of Fig. 1; Fig. 3 shows a perspective view of the middle horizontal beam of Fig. 1; Fig. 4 shows a perspective view of the lowest horizontal beam, which is formed integrally with support grids; Fig. 5 shows a perspective view of the middle horizontal beam with a support grid arranged thereon; Fig. 6 shows a perspective view of a support grid arranged on the middle horizontal beam; Fig. 7 shows a perspective view of a support grid arranged on the upper horizontal beam; Fig. 8 shows a perspective view of a central beam spacer sleeve designed as a spacer sleeve; Fig.Fig. 9 a perspective view of a central support spacer sleeve designed as an adapter sleeve and Fig. 10 a perspective view of a vertical support designed as a central support with receiving section and lifting wedge. Figure 1 shows a perspective view of a furnace frame designed as a shaft furnace frame 1. The shaft furnace frame 1 has a vertical support beam designed as a central beam 2, which is formed by a central support rod. In this case, the central beam 2 serves to support a total of three horizontal beams 3a, 3b, 3c, which in turn serve to support components to be heat-treated (not shown here). For transporting the shaft furnace frame 1 using a lifting device (not shown), the central support 2 has a lifting wedge 8 at its upper end. This wedge extends through an opening 7 penetrating the central support 2 and is designed to accommodate a load-bearing device, such as a chain or a crane hook of a suitable crane. The shaft furnace frame 1, equipped with the components to be heat-treated, can thus be lifted over the lifting wedge 8 using the crane and transported into a shaft furnace (not shown) or, after heat treatment, removed from the furnace for further processing. (See Fig. 10) The upper and middle horizontal beams 3a, 3b each have a support cross formed by support arms 11a, 11b. The support arms 11a, 11b extend radially symmetrically from a central area 20. Sleeves 14a, 14b are arranged at the free ends of the support arms 11a, 11b, which have edge openings 5a, 5b for receiving edge beams (not shown). The edge beams can be used alternatively or additionally to the central beam 2 for the arrangement of the horizontal beams 3a, 3b, 3c, with the edge beams extending through the edge openings 5a, 5b, 5c. (See Fig. 2 and Fig. 3) In the area between the support arms 11a, 11b, support grids 19a, 19b are detachably arranged on the horizontal beams 3a, 3b. The support grids 19a, 19b rest on cams 18, which project circumferentially from the support arms 11a, 11b into the area between them. The support grids 19a, 19b have a honeycomb-shaped grid structure, with the support grids 19a arranged on the upper horizontal beam 3a having an irregular honeycomb structure, whereas the support grids 19b arranged on the horizontal beam 3b have a regular honeycomb structure. The regular honeycomb structure has essentially uniformly sized webs 26, whereas the webs 26 of the irregular honeycomb structure differ from one another (see Figs. 5-7). The horizontal beam 3a has support arms 11a, which are formed by longitudinal webs 12 arranged at intervals from one another and extending radially in pairs from the central area 20, the longitudinal webs 12 being connected to each other via transverse webs 13. The design of the support arms 11a makes it possible to use the transverse webs 13 to suspend a heat-treated item from the support arms 11a, thus eliminating the need for support grids 19a, 19b. In contrast, the support arms 11b of the horizontal beam 3b are formed by simple longitudinal webs extending radially from the central area 20 of the horizontal beam 3b. Cams 18 arranged on the longitudinal webs also serve to receive the support grids 19a, 19b. The horizontal beams 3a, 3b, 3c each have a central opening 4a, 4b, 4c for their coaxial arrangement on the central beam 2. The horizontal beams 3a, 3b, 3c are each supported on the circumferential surface of the central beam 2 via an inner surface of the central opening 4a, 4b, 4c. The central openings 4a, 4b, 4c also have recesses 10a, 10b, 10c extending on both sides, i.e., from their upper and lower surfaces, which are bounded in the longitudinal direction by a stop surface. The design of the central opening 4a, 4b, 4c allows each horizontal beam 3a, 3b, 3c to be arranged in its basic position on a correspondingly designed receiving section 6 of the central beam 2. In the basic position, where the recesses 10a, 10b, 10c engage in projections 9 on the receiving section 6, the horizontal beam 3a, 3b, 3c arranged there forms a base beam via which the loads acting axially on the horizontal beams 3a, 3b, 3c are transferred to the central beam 2. The receiving section 6, located at the lower end of the central beam 2, has cams 9 projecting from a surface, which are adapted to the shape of the recesses 10a, 10b, 10c. To position a horizontal beam 3a, 3b, 3c on the receiving section 6, the horizontal beam 4c is first placed with its central opening 4c onto the central beam 2 before the lifting wedge 8 is applied, and then moved along the central beam 2 in the sliding direction, i.e., from its upper end towards the receiving section 6, until the recesses 10c engage with the cams 9. The cams 9 and the recesses 10c, in their engagement position on the receiving section 6, form a form-fit connection acting in the longitudinal and circumferential directions of the central support. The symmetrical design of the central opening 4a, 4b, 4c allows the horizontal supports 3a, 3b, 3c to be arranged on both sides. In the embodiment shown in Fig. 1, a horizontal beam 3b is spaced apart from the horizontal beam 3c, which forms the base beam, by means of spacer sleeves 15a, 15b. The spacer sleeves 15a, 15b are arranged between the facing surfaces of the horizontal beam 3c in its basic position and the horizontal beam 3b arranged above it, and bear against the horizontal beams 3b, 3c on opposite upper surfaces in the central area 20. A load acting on the horizontal beams 3b, 3c is thus transferred via the spacer sleeves 15a, 15b to the horizontal beam 3c in its basic position and from there via the receiving section 6 to the central beam 2. To prevent the two horizontal supports 3b, 3c from rotating relative to each other, the spacer sleeves 15a, 15b are designed as a spacer sleeve 15a and an adapter sleeve 15b. The spacer sleeve 15b is provided at both ends with two diametrically opposed projections 16 for a rotationally secure connection to the central opening 4a, 4b, 4c. These projections extend from the end faces and engage in the recess 10a, 10b, 10c. In a further embodiment, the spacer sleeve is also designed as an adapter sleeve 15b for adjusting the distance. This adapter sleeve 15b has recesses 17 arranged at 90° intervals around its circumference to securely receive the projections 16 of the adapter sleeve 15b or spacer sleeve 15a. The adapter sleeve 15b also has two diametrically opposed projections 16. (See Fig. 8 and Fig. 9) The depicted shaft furnace frame 1 has a horizontal support 3c formed in one piece, in which the support grids and the support arms are not separate components. The horizontal support 3c exhibits a kind of "bionic" design. Several main webs 21 extend radially from a central area 20. Two intermediate webs 22 branch off from each of the main webs 21, and from each of these, two end webs 23 branch off. In the area between the webs 22 and 23, these are connected by intermediate webs 24. At the edge of the horizontal support 3c, it has sleeves 14c for receiving edge supports (not shown), which extend through the edge opening 15c. Reference symbol list 1 Shaft furnace frame 2 Vertical beam / central beam 3a, 3b, 3c Horizontal beam 4a, 4b, 4c Central opening 5a, 5b, 5c Edge opening 6 Receiving section 7 Opening 8 Lifting wedge 9 Projection 10a, 10b, 10c Recess 11a, 11b Support arm 12 Longitudinal web 13 Transverse web 14a, 14b, 14c Sleeve 15a, 15b Spacer sleeve 16 Projection 17 Recess 18 Cam 19a, 19b Support grid 20 Central area 21 Base web 22 Intermediate web 23 End web 24 Intermediate web 26 Web

Claims

Oven frame (1) for charging an oven system with a heat-treated material, comprising at least one load-bearing vertical beam and at least one horizontal beam (3a, 3b) arranged on the vertical beam with a support cross formed by support arms (11a, 11b), characterized in that one vertical beam is designed as a central beam (2) and / or at least two vertical beams are designed as edge beams, the horizontal beam (3a, 3b) has a centrally arranged central opening (4a, 4b) for receiving the central beam (2) and the horizontal beam (3a, 3b) has sleeves (14a, 14b) with edge openings (5a, 5b) arranged at the free ends of the support arms (11a, 11b) for receiving the at least two edge beams through which the edge beams extend. Oven rack (1) according to claim 1, characterized in that the central support (2) has a receiving section (6) with projections (9) and the central opening (4a, 4b) has recesses (10a, 1ob) adapted to the projections (9). Oven frame (1) according to claim 1 or 2, characterized in that two horizontal supports (3a, 3b) are arranged at a distance from each other in the longitudinal axis direction of the central support (2), wherein at least one spacer sleeve (15a, 15b) is arranged coaxially on the central support (2) in the area between the horizontal supports (3a, 3b). Oven frame (1) according to claim 3, characterized in that the central support spacer sleeve (15a, 15b) which can be arranged on the central support (2) is designed as a spacer sleeve (15a) at both ends for a rotationally secure connection with the central openings (4a, 4b), as an intermediate sleeve at both ends for a rotationally secure connection with a spacer sleeve (15a) or as an adapter sleeve (15b) at one end for a rotationally secure connection with a spacer sleeve (15a) and at the other end for a rotationally secure connection with the central opening (4a, 4b). Oven frame (1) according to claim 4, characterized in that the recesses (10a, 10b) of the central openings (4a, 4b) are arranged at a distance of 60° on the inside of the central openings (4a, 4b), the spacer sleeve (15a) has two diametrically arranged projections (16) adapted to the recesses (10a, 10b) at both ends, and the adapter sleeve (15b) has two diametrically arranged recesses (17) at one end and at the other end distributed at a distance of 60° or 90° around the circumference. Oven frame (1) according to claim 5, characterized in that the support arms (3a, 3b) have circumferentially projecting cams (18) which are designed to receive support grids (19a, 19b) between the support arms (11a, 11b). Oven frame (1) according to one or more of claims 3 to 6, characterized in that the spacer sleeve (15a) for coupling two horizontal beams (3a, 3b) is designed such that the horizontal beams (3a, 3b) are abutted in the arrangement via the spacer sleeve (15a).

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