Connection system

Abstract

Connection system (1) for the detachable fastening of a housing (28, 30), comprising a retaining foot (2) attached externally to a base (32) of the housing (28, 30) and a receptacle (4) arranged in a surface (6), wherein the retaining foot (2) is rotationally symmetrical and a fastening hole (12) is arranged in the axis of symmetry of the retaining foot (2), wherein the retaining foot (2) comprises a guide piece (8) and a connecting piece (10) arranged between the guide piece (8) and the base (32), wherein the cross-sectional area of ​​the connecting piece (10) is smaller than the cross-sectional area of ​​the guide piece (8), wherein the receptacle (4) has a hole section (14) and a groove section (16), wherein the hole section (14) is configured such that the retaining foot (2) can be inserted perpendicular to the surface, and the groove section (16) is configured such thatthat the retaining foot (2) can be moved into the groove section (16) after being inserted into the hole section (14) by sliding it parallel to the surface (6), wherein the cross-section of the groove section (16) has an upper part (20) and a lower part (18), the extent of the lower part (18) being larger than that of the guide element (8) of the retaining foot (2) moved into the groove section (16), characterized in that the connecting piece (10) of the retaining foot (2) and the upper part (20) of the groove section (16) of the receptacle (4) are designed with an interference fit, and the connecting piece (10) has a torus-shaped cavity (24) between an inner wall enclosing the mounting hole (12) and an outer wall (26) facing a first inner wall of the upper part (20) of the groove section (16).

Description

The invention relates to a connection system for the detachable fastening of a housing, comprising a retaining foot attached externally to a base of the housing and a receptacle arranged in a surface, wherein the retaining foot comprises a guide element and a connecting element arranged between the guide element and the base, wherein the cross-sectional dimension of the connecting element is smaller than the dimension of the guide element, wherein the receptacle has a hole section and a groove section, wherein the hole section is configured such that the retaining foot can be inserted perpendicular to the surface, and the groove section is configured such that, after insertion into the hole section, the retaining foot can be moved into the groove section by sliding it parallel to the surface, wherein the cross-section of the groove section has an upper part and a lower part.where the extension of the lower part is greater than that of the guide piece of the retaining foot shifted into the groove section. It further relates to a housing with such a connection system. The principle of the connection system described above is known to those skilled in the art, for example, from so-called T-slot connections, such as those found in US 2021 / 0 018 029 A1 or DE 10 2009 054 422 B3. A retaining element, essentially T-shaped in cross-section, is inserted into a groove so that it is positively locked both transversely to the insertion direction and perpendicular to the surface into which the groove is cut. For insertion, the groove is either open laterally, extending over the entire component, or—as described above—a hole section adjoins the groove section of the retaining element, having a larger opening than the groove itself, allowing the retaining element to be inserted first and then laterally inserted into the groove. Corresponding connection systems are frequently used to attach electronic devices in vehicles that need to be regularly installed and removed. One example is data loggers, which are installed in test vehicles and connected to the vehicle's electronics to record and store data from the vehicle's bus system during test drives. A connection system, as described earlier, is often used for this purpose. Four mounting feet are located on the bottom of the data logger housing. Correspondingly, a corresponding number of the aforementioned type of mounting brackets are arranged in the same configuration on a mounting plate permanently installed in the trunk. The brackets are generally identical and oriented in the same direction. The housing can be placed onto the mounting plate so that the mounting feet are inserted into the holes in the brackets. The entire housing is then slid sideways so that all the mounting feet slide into the respective slots in the brackets. However, this has the disadvantage that manufacturing tolerances can lead to connections that are either too loose or too tight. This means the connection might be so loose that the housing doesn't stay in the adjusted position, or it might be so tight that easy adjustment is no longer possible. In the worst case, the connection system is unusable. It is therefore an object of the invention to provide a connection system of the type mentioned above which, on the one hand, ensures a secure fit of the housing and, on the other hand, allows for easy assembly and disassembly. This problem is solved according to the invention by a connection system according to appended claim 1. Advantageous embodiments are the subject of the dependent claims. The invention is based on the premise that a secure connection should be achieved through a frictional fit of the retaining foot in the groove, since other connection methods are difficult to implement due to the poor accessibility of the connection system during installation. Furthermore, additional fasteners such as screws should be avoided to facilitate easy assembly and disassembly. Therefore, an interference fit of the retaining foot in the groove section should be provided, so that the retaining foot is held in place by the resulting static friction within the groove section. In this case, an interference fit means that the nominal dimension of the retaining foot in the connecting piece is a few percent larger than the width of the upper part of the groove section. Less than 10%, ideally between 3% and 7%, has proven optimal. However, to prevent an overly tight connection, the friction-generating interface between the mounting foot and the groove section should be designed with a spring action. This is achieved by incorporating a cavity behind a wall of the mounting foot's connecting piece; that is, the mounting foot is not a solid component, but rather has a wall with a limited thickness. This allows the wall to spring back when slid into the groove section, ensuring the desired positive fit. Furthermore, the retaining foot is rotationally symmetrical. This design offers numerous advantages: First, it simplifies the manufacturing of the retaining foot. Second, no orientation needs to be considered during installation, as the cross-section of the retaining foot is identical in every rotational orientation. The retaining foot can therefore be inserted into the groove in any orientation. In addition, the cavity behind the wall of the retaining foot's connecting piece is also toroidal, ensuring a spring action in any direction. In a rotationally symmetrical design, the mounting base has a mounting hole located on its axis of symmetry. A screw, for example, can be inserted through this mounting hole to secure the mounting base to the housing base. A countersunk screw is advantageously used for this purpose. To accommodate the screw head, the mounting hole is preferably tapered towards the guide element. Particularly good spring action is achieved by ensuring that the thickness of the respective wall is less than 20%, preferably less than 10%, of the cross-sectional dimension of the connector. This makes the wall especially flexible and able to generate sufficient force to hold the retaining foot in the groove. Optimal results are achieved with a thickness of approximately 5%, i.e., between 3% and 7% of the connector's dimension. Furthermore, the guide element of the support foot is advantageously designed as a guide plate arranged parallel to the base of the housing at a distance from it. This reduces the height of the connection system and enables the housing to stand stably on the support feet, even if these are not positioned in a receptacle. The groove section of the receiver is advantageously designed as a T-shaped groove in cross-section. This also allows for a comparatively simple manufacturing process. In the rotationally symmetrical design of the retaining foot, the hole section of the receptacle is advantageously designed as a cylindrical hole whose height essentially corresponds to the height of the retaining foot and whose diameter essentially corresponds to the diameter of the guide piece. However, the retaining foot and hole should be designed for a clearance fit so that the retaining foot can be easily inserted into and removed from the hole. The hole transitions into the groove section on one side. Advantageously, the support base is made of plastic. Polyoxymethylene plastic is particularly suitable for this purpose. Such plastics are relatively stiff and exhibit good dimensional stability. They are therefore especially suitable for manufacturing a support base as described above. Manufacturing can be carried out, for example, by injection molding or milling. In a rotationally symmetrical design, the support base can also be rotated. An enclosure advantageously comprises a described connection system, as well as a enclosure base and a enclosure cover arranged parallel to the enclosure base, wherein a number of retaining feet of the connection system are arranged on the outside of the enclosure base, and wherein receptacles of the connection system are provided in the outside of the enclosure cover, aligned with the retaining feet. This allows for the stacking of several identical enclosures, since each enclosure cover simultaneously provides receptacles for the arrangement of another enclosure with corresponding retaining feet. The advantages achieved with the invention consist particularly in the fact that the arrangement of a cavity behind the wall of a retaining foot, which is to be inserted into a groove of a receptacle, creates a flexibility in the wall that generates a restoring force when inserted into the groove and thus a frictional connection, ensuring a secure hold of the retaining foot in the receptacle. The described design compensates for manufacturing tolerances and, with a corresponding alignment of receptacles and retaining feet on the lid or base of a housing, ensures stackability. An embodiment of the invention is explained in more detail with reference to the drawings. These show: Fig. 1 a connection system with a retaining foot in a receptacle that is embedded in a surface, Fig. 2 a view of the retaining foot from below, Fig. 3 a section of the retaining foot in the groove section of the receptacle, Fig. 4 a top view of the connection system with the retaining foot in a hole section of the receptacle, Fig. 5 a top view of the connection system with the retaining foot in a groove section of the receptacle, Fig. 6 a view of the housing cover of two housings connected by the connection system, and Fig. 7 a view of the housing base of two housings connected by the connection system. Identical parts are marked with the same reference symbols in all drawings. The connection system 1 is first explained with reference to Figs. 1, 2, 3, 4 to 5. The connection system comprises a retaining foot 2 and a receptacle 4. In Fig. 1, the receptacle 4, which is embedded in a surface 6, is shown transparently. The retaining foot 2 is a rotationally symmetrical component. It is machined from round material made of polyoxymethylene plastic. It comprises a flat cylindrical, i.e., disc-shaped, guide piece 8 and a connecting piece 10, also flat cylindrical in its outer shape, which connects to the guide piece 8 in the axial direction and has a smaller diameter than the guide piece 8. A mounting hole 12 is machined into the axis of the retaining foot. This hole is cylindrical in the connecting piece 10 but widens conically in the guide piece 8, so that the head of a countersunk screw (not shown) can be accommodated, with which the retaining foot 2 can be fastened. The receptacle 4 is formed as a cavity in the body, which will be described later and is bounded by the surface 6. The receptacle 4 comprises a hole section 14 and a groove section 16. The hole section 14 is designed as a circular cylindrical hole, the height of which corresponds essentially to the axial height of the retaining foot 2, and the diameter of which corresponds essentially to the diameter of the guide piece 8. The dimensions are designed for a clearance fit, so that the retaining foot 2 can be easily inserted into and removed from the hole section 14 in a direction perpendicular to the surface 6. A groove section 16 adjoins the hole section 14. The cross-section of the groove section 16 essentially corresponds to the outer cross-section of the retaining foot 2 shown in Fig. 3, and is therefore essentially T-shaped. Corresponding to the guide piece 8 and the connecting piece 10, the groove section 16 thus has a lower part 18 and an upper part 20. The cross-sectional width of the lower part 18 corresponds to the diameter of the hole in the hole section 14. The guide piece 8 can therefore slide easily in the groove section 16 due to the clearance fit. The retaining foot 2 can be inserted from the position it is in, as shown in Fig. 1 and Fig. 4, into the groove section 16 by sliding it in the plane of the surface 6. Both the upper part 20 and the lower part 18 of the groove section 16 are semicircularly closed on the side facing away from the hole section 14, so that a stop 22 is formed for the retaining foot 2, which limits the sliding movement of the retaining foot 2. To compensate for manufacturing tolerances and ensure both the adjustability and sufficient retention of the retaining foot 2 in the groove section 16, the connecting piece 10 and the upper part 20 of the groove section 16 are designed with an interference fit. In the exemplary embodiment, the diameter of the connecting piece is approximately 9.3 mm. The width of the upper part 20 of the groove section 16, on the other hand, is only 8.8 mm to 9.0 mm (depending on manufacturing tolerances). This is particularly evident in Fig. 3, which clearly shows the greater width of the connecting piece 10. Fig. 3 is intended to illustrate the size relationships but does not represent a realistic depiction of the retaining foot 2 in the groove section 16: In reality, the connecting piece 10 will deform elastically so that it fits into the groove section 16. This deformation is not shown in Fig. 3. To facilitate this deformation, the connecting piece 10 is further provided internally with a torus-shaped cavity 24. This cavity extends over the entire height of the connecting piece 10. In the exemplary embodiment, its radial extent covers approximately one-quarter of the radius of the connecting piece 10. The remaining thickness of the outer wall 26 in the exemplary embodiment is approximately 5% of the total diameter of the connecting piece 10, or 10% of its radius. This allows the wall 26 to yield resiliently to the inner wall of the upper part 20 when inserted into the groove section 16. This enables the retaining foot 2 to be moved into the groove section 16 and back out of it into the hole section 14 by applying appropriate force, while still maintaining a secure, friction-fit connection. The described connection system 1 allows housings 28, 30, particularly for electronic devices intended for detachable mounting in vehicles, to be fastened, as shown in Figures 6 and 7. In Figures 6 and 7, a first housing 28 is stacked beneath a second housing 30 using the connection system. The housings 28, 30 have identical base areas but different heights. Both housings 28, 30 have four rectangularly arranged support feet 2 on their underside, which are screwed into the base 32 on the outside. Recesses 4 are provided in the covers 34 of the housings, aligned with the support feet 2. The recesses 4 are oriented in the same direction and arranged such that, when the respective support foot 2 is inserted, as shown in Figure 5, the bases of the housings 28, 30 lie exactly on top of each other. This arrangement of the connection system 1 allows several housings 28, 30 to be stacked on top of each other, as well as to be attached to a mounting plate permanently installed in a vehicle using corresponding receptacles 4. The covers 34 of the housings 28, 30 also incorporate further receptacles 4; in the exemplary embodiment, a total of twelve receptacles 4 are arranged in a rectangular pattern with different side lengths, so that smaller housings (not shown) can also be stacked on top of each other, their retaining feet 2 then being arranged according to a rectangle of receptacles 4 with shorter sides. In an alternative embodiment, not shown in detail, the retaining foot 2 could also have a constant diameter across the connecting piece 10 and the guide piece 8. Due to the elastic deformability of the connecting piece 10, a certain degree of retention in the vertical direction would still be present in the groove section 16 when compressed, since the guide piece 8 does not deform sufficiently. Reference symbol list 1 Connection system 2 Mounting foot 4 Receptacle 6 Surface 8 Guide piece 10 Connector 12 Mounting hole 14 Hole section 16 Groove section 18 Lower part 20 Upper part 22 Stop 24 Cavity 26 Wall 28 Housing 30 Housing 32 Base 34 Cover

Claims

Connection system (1) for the detachable fastening of a housing (28, 30), comprising a retaining foot (2) attached externally to a base (32) of the housing (28, 30) and a receptacle (4) arranged in a surface (6), wherein the retaining foot (2) is rotationally symmetrical and a fastening hole (12) is arranged in the axis of symmetry of the retaining foot (2), wherein the retaining foot (2) comprises a guide piece (8) and a connecting piece (10) arranged between the guide piece (8) and the base (32), wherein the cross-sectional area of ​​the connecting piece (10) is smaller than the cross-sectional area of ​​the guide piece (8), wherein the receptacle (4) has a hole section (14) and a groove section (16), wherein the hole section (14) is configured such that the retaining foot (2) can be inserted perpendicular to the surface, and the groove section (16) is configured such thatthat the retaining foot (2) can be moved into the groove section (16) after being inserted into the hole section (14) by sliding it parallel to the surface (6), wherein the cross-section of the groove section (16) has an upper part (20) and a lower part (18), the extent of the lower part (18) being larger than that of the guide element (8) of the retaining foot (2) moved into the groove section (16), characterized in that the connecting piece (10) of the retaining foot (2) and the upper part (20) of the groove section (16) of the receptacle (4) are designed with an interference fit, and the connecting piece (10) has a torus-shaped cavity (24) between an inner wall enclosing the mounting hole (12) and an outer wall (26) facing a first inner wall of the upper part (20) of the groove section (16). Connection system (1) according to the preceding claim, wherein the thickness of the respective wall (26) is less than 20%, preferably less than 10%, particularly preferably between 3% and 7% of the cross-sectional extent of the connecting piece (10). Connection system (1) according to one of the preceding claims, wherein the guide element (8) is designed as a guide plate arranged parallel to the ground at a distance from the ground. Connection system (1) according to one of the preceding claims, wherein the groove section (16) is designed as a T-shaped groove in cross-section. Connection system (1) according to one of the preceding claims, wherein the hole section (14) is designed as a cylindrical hole, the height of which corresponds substantially to the height of the retaining foot (2) and the diameter of which corresponds substantially to the diameter of the guide piece (8). Connection system (1) according to one of the preceding claims, wherein the retaining foot (2) is made of a plastic, particularly preferably a polyoxymethylene plastic. Housing (28, 30) with a connection system (1) according to one of the preceding claims, with a housing base (32) and a housing cover (34) arranged parallel to the housing base (32), wherein a number of retaining feet (2) of the connection system (1) are arranged on the outside of the housing base (32), and wherein receptacles (4) of the connection system (1) are provided in the outside of the housing cover (34) aligned with the retaining feet (2).

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