Reinforced fastening point

Abstract: The invention relates to a reinforced fastening point (3) for a plastics-material casing (2). In order to provide a reinforcement for a fastening point (2) which is simple to assemble and which is held automatically in the opening (6) in the casing (3) without further fastening means, it is proposed according to the invention to provide a cylindrical opening (6) at the fastening point on the casing. The reinforcement part corresponding thereto is constructed as a frustum (8) in that region which in the assembled state comes to rest in the region of the cylindrical opening (6). The smaller external diameter of this frustum (8) is smaller than or equal to the internal diameter of the cylindrical opening (6). The larger external diameter of the frustum, on the other hand, has an excess dimension with respect to the internal diameter of the cylindrical opening. In this case, the said excess dimension is selected to be such that it can be neutralized by resilient deformation of the reinforcement part.

Description: The invention relates to a reinforced fastening point for a plastics-material casing. In the case of plastics-material casings the problem arises of designing the fastening points in such a way that the forces which occur here are reliably introduced into the plastics-material casing. In particular, it is necessary to prevent the plastics-material casing from tearing or the like in the region of the fastening points. In this connexion it is generally known to design the fastening point in such a way that it is possible to use a fastening member with the introduction of force over a wide area, for example a screw with a washer. This solution, however, can only be used where reinforcement is required exclusively in the direction of the fastening force, but not at right angles thereto. Furthermore, it is generally known to reinforce fastening points on plastics-material casings in such a way that a reinforcement part adapted to the contour of the aperture in the casing is used in the region of the fastening point. It is also possible to absorb forces at right angles to the fastening direction by means of a reinforcement part of this type. In addition, it is possible to design the reinforcement part in such a way that the fastening forces too are partially absorbed by the reinforcement part, so that the fastening forces acting upon the plastics-material casing are restricted to a maximum and so damage to the plastics-material casing by excessive fastening forces is prevented in a reliable manner. Reinforcement parts of this type require additional steps during assembly. If the reinforcement part has to be fitted in the course of assembly, as well as the additional assembly step it is additionally necessary to supply the reinforcement parts. If the reinforcement parts are to be pre-assembled in the plastics-material casing, additional fastening devices are necessary for the reinforcement parts. The object of the invention is to provide a reinforcement for a fastening point which is simple to assemble and which is held automatically in the opening in the casing without further fastening means. To this end, it is proposed according to the invention to provide a cylindrical opening at the fastening point on the casing. The reinforcement part corresponding thereto is made from a resiliently deformable sheet metal and is constructed as a frustum in that region which in the assembled state comes to rest in the region of the cylindrical opening. The smaller external diameter of this frustum is smaller than or equal to the internal diameter of the cylindrical opening. The larger external diameter of the frustum, on the other hand, has an excess dimension with respect to the internal diameter of the cylindrical opening. In this case, the said excess dimension is selected to be such that it can be neutralized by resilient deformation of the reinforcement part. The reinforcement part is now advantageously held in the cylindrical opening by the forces which occur during the resilient deformation. In this case, it should be noted in particular that the reinforcement part need not be put in its final position during pre-assembly, but has only to be inserted so far that it is held in such a way as to prevent its loss. The final position is then set automatically during assembly by tightening the fastening member. Advantageous further embodiments of the invention are set out in the Sub-Claims. In this way, it is proposed to increase the force, by which the reinforcement part is held in the cylindrical opening, by providing a burr on the outside of the sheet-metal edge present at the largest diameter of the frustum. When the reinforcement part moves contrary to the direction of insertion this burr digs into the plastics-material casing and thus holds the reinforcement part securely in the cylindrical opening. A burr of this type can be produced in a particularly simple manner in that the reinforcement part is produced by deep drawing a stamped sheet-metal disc. The burrs necessarily occurring in this manufacturing process can thus be utilized in a profitable manner. The burr can be formed in such a way by a suitable choice of parameters during the manufacturing process (for example of the cutting gap during the stamping) that it achieves the greatest possible effect. The invention is described in greater detail below with reference to the embodiment illustrated in the Figures, in which Fig. 1 shows a fastening point of a plastics-material casing with a reinforcement inlay, and Fig. 2 shows the detail X of Fig. 1. Fig. 1 shows a sheet-metal inlay 1 used as a reinforcement part, the sheet-metal inlay 1 being shown in the non-assembled, i.e. relaxed, state in the left-hand half of Fig. 1 and in the assembled, i.e. pre-stressed, state in the right-hand half of Fig. 1. A plastics-material casing 2 illustrated in the right-hand half of Fig. 1 has a fastening point 3 which is formed as a cone 4 on the outside and as a stepped cylinder 5 on the inside. The upper step of the cylinder 5 is formed as a cylindrical opening 6, the diameter of which is larger than the diameter of a second cylindrical opening 7 adjoining it. The second cylindrical opening 7 is used for the passage of a fastening member (not shown). The lower region of the sheet-metal inlay 1 has an outer contour corresponding to the cylindrical opening 7. In the upper region, on the other hand, it is formed as a frustum 8, as indicated in the left-hand half of Fig. 1. The frustum 8 opens out towards the top, i.e. the lower end as viewed in a direction of insertion E corresponds in the external diameter thereof to the internal diameter of the cylindrical opening 6, whereas the upper diameter is larger. As a result, at the upper diameter D2 , an excess dimension is formed as compared with the cylindrical opening 6; in the fitted state, i.e. when the frustum 8 is inserted into the cylindrical opening 6, the said excess dimension is neutralized by resilient deformation of the sheet-metal inlay 1 in the region of the frustum 8. This resilient deformation results in a restoring force of the sheet-metal inlay 1 radially to the cylindrical opening 6, so that the upper edge of the sheet-metal inlay 1 in the region of the larger diameter D2 is pressed against the inner wall of the cylindrical opening 6. As shown in greater detail in Fig. 2, the said upper edge 9 is provided on the outside with a burr 10. This burr 10 is pressed by the restoring force against the inner wall of the cylindrical opening 6 and as a result digs into the cylindrical opening 6, when the reinforcement inlay 1 is moved contrary to the direction of insertion E . In this way, as soon as the sheet-metal inlay 1 is inserted so far into the opening 4 that the upper edge 9 rests against the inner wall of the cylindrical opening 6, the said sheet-metal inlay 1 can no longer be removed. In order to pre-assemble the sheet-metal inlay 1 in the plastics-material casing 2 in such a way as to prevent its loss, it is sufficient to insert the sheet-metal inlay until the upper edge 9 of the sheet-metal inlay 1 penetrates into the cylindrical opening 6. During the subsequent assembly, for example when tightening a screw, the sheet-metal inlay 1 is then pulled further into the cylindrical opening 6, until it finally comes to rest against the base thereof. In addition, it is provided in the embodiment that the axial length of the lower part of the sheet-metal inlay 1 is slightly smaller than the corresponding extension of the second cylindrical opening 7. This structural step ensures that the casing 2 comes to rest with pre-stressing against a surface 11, but this pre-stressing force cannot reach any impermissibly high figures since, as the fastening force is increased, the casing 2 in the region of the fastening point 3 can only be upset until the lower edge 12 of the sheet-metal inlay 1 comes to rest against the surface 11. When the fastening force is further increased, the additional force component on the fastening force is introduced into the surface 11 directly from the sheet-metal inlay 1. The burr 10 illustrated is produced by a sheet-metal disc first being stamped out of a sheet-metal panel during the production of the sheet-metal inlay 1. Depending upon the tool parameters during the stamping, and in particular the width of the gap in the stamping tool, a burr is formed on an outer edge of the sheet-metal disc. The outer edge of the sheet-metal disc will subsequently correspond to the upper edge 9 of the sheet-metal inlay 1. During the further production process, the lower region 7 of the sheet-metal inlay 1 is then drawn out of the sheet-metal disc by deep-drawing. Finally, the frustum 8 of the sheet-metal inlay 1 is produced, likewise by deep-drawing. During the further deep drawing, care should be taken that the sheet-metal disc is inserted into the deep-drawing tool in such a way that the burr 10 produced will subsequently come to be on the outside. The said burr 10 is further reinforced by the tensile forces acting on the outer periphery of the frustum 8. Alternatively, it is possible of course for the sheet-metal inlay 1 to be designed in such a way that the external diameter of the frustum 8 at the lower end thereof as viewed in a direction of insertion E is smaller than the internal diameter of the cylindrical opening 6. The construction of the lower region of the sheet-metal inlay 1 is likewise immaterial to the invention; it is possible, without adversely affecting the functioning, for this region to be omitted anywhere at the fastening point 3 where it is not necessary to limit the fastening force or where stresses are not to be expected at right angles to the direction of insertion E , which corresponds to the direction of the fastening force.

Claims: A reinforced fastening point for a plastics-material casing with an aperture (5) in the casing (2) for receiving a fastening member, a cylindrical opening (6) arranged at the entry to the aperture (5) substantially concentrically to the aperture, a reinforcement part (1) made of a resiliently deformable sheet metal provided with a region (8) corresponding to the cylindrical opening (6), wherein the said region (8) is constructed as a frustum, and the smaller external diameter of the frustum ( D1 ) is smaller than or equal to the internal diameter of the cylindrical opening (6), and the larger external diameter ( D2 ) of the frustum has an excess dimension with respect to the internal diameter of the cylindrical opening (6), wherein the excess dimension is selected to be such that it can be neutralized by resilient deformation of the reinforcement part (1). A reinforced fastening point according to Claim 1, characterized in that the outside of the sheet-metal edge (9) present at the largest diameter ( D2 ) of the frustum is provided with a burr (10). A reinforced fastening point according to Claim 1, characterized in that the reinforcement part (1) is produced as a sheet-metal part by stamping and subsequent deep drawing. A reinforced fastening point according to Claim 3, characterized in that during the production of the reinforcement part (1), a sheet-metal disc produced by stamping is inserted into a deep-drawing tool in such a way that a burr (10) present on the sheet-metal edge of the discwill subsequently come to be on the outside at the largest external diameter ( D2 ) of the frustum.

Inventors: BRAVO ERNESTO, HOEBEL PETER, BRAVO, ERNESTO, HOEBEL, PETER, Höbel, Peter
Applicants: PORSCHE AG, DR.ING. H.C. F. PORSCHE
Application year: 1997
Main classification: F16B43
IPC codes: F16B43, F16B9