Field of the invention

The present invention concerns a fixing device with tolerance compensation, usable in particular for fixing a structure to a box-section support.

Description of the relevant art

The invention was developed to provide improved fixing devices for the automobile industry. In particular, the invention was developed to resolve the problem of fixing components to box-section supports. A typical example is that of fixing the crosspiece supporting the dashboard to the two lateral uprights of the vehicle. The uprights have a box shape including an outer wall and an inner wall welded to each other. The crosspiece is fixed by means of bolts to the lateral uprights. These bolts are inserted through aligned holes provided in the outer wall and the inner wall of the upright, starting from the outside. Tightening the bolts is carried out to a preset torque by means of automatic drivers. Manufacturing tolerances mean that during tightening of the bolts there is a risk of deformation of the sheet-metal walls of the uprights.

To obviate this disadvantage in the known art, use is made of spacers which must be fixed inside the uprights. Solutions have also been proposed which specify a metal washer fixed onto the shank of the bolt at a certain distance from the head and a washer of malleable material located adjacent to the head of the bolt.

All the known solutions are however unsatisfactory for various reasons, among them the necessity of providing spacing elements to be fixed inside the box-section supports or providing fixing elements dedicated to the specific application.

Object and summary of the invention

The present invention sets itself the task of providing a fixing device which resolves the problems of the known art .

According to the present invention, this object is achieved by a fixing device having the characteristics forming the subject of claim 1.

Brief description of the drawings

The present invention will now be described in detail with reference to the annexed drawings, provided purely by way of non-limiting example, in which:

- figure 1 is a schematic view of a vehicle,

- figure 2 is an exploded perspective view of the part indicated by the arrow II in figure 1 illustrating a fixing device according to the present invention,

- figure 3 is a perspective view of the fixing device according to the invention,

- figure 4 is an axial section of the fixing device of figure 3, and

- figures 5 and 6 are axial sections illustrating the sequence of fitting the fixing device according to the invention .

Description of preferred embodiments

With reference to figure 1, no. 10 schematically indicates the load-bearing structure of a motor vehicle, comprising two lateral uprights 12 between which is fixed a crosspiece 14 intended to support the dashboard of the vehicle .

Figure 2 illustrates the fixing of the crosspiece 14 to one of the uprights 12 by means of fixing devices 16 according to the present invention. Although what is illustrated, by way of example, is the use of fixing devices 16 for fixing the crosspiece 14 to the uprights 12, it is intended that fixing devices 16 according to the invention can be used for any other type of fixing. Fixing devices 16 according to the invention are particularly suitable for fixing a generic component to a box-section support .

In the example illustrated in figure 2, the upright 12 has a box-section structure including an outer wall 18 and an inner wall 20. The walls 18, 20, both of pressed sheet metal, are fixed to each other by welding. The outer wall is provided with at least one hole 22 and the inner wall is provided with at least one hole 24. The axes of the holes 22, 24 are aligned with each other on an axis Y. The crosspiece 14 is provided with two plate ends 26 which are used for fixing the crosspiece 14 to the uprights 12. At least one threaded nut 28 is fixed to each plate 26.

Figures 3 and 4 illustrate a fixing device according to the present invention. The fixing device 16 comprises a bolt 30 having a head 32 and a shank 34. The shank 34 has a threaded portion 36 having an outside diameter Dl . A clutch 38, preferably made of plastic, is fixed onto a portion of the shank 34 adjacent to the head 32. The clutch 38 may be driven by force or may be co-molded onto the shank 34. In any event, the clutch 38 is fixed with respect to the bolt 30, without the possibility of rotating around the axis of the bolt. The clutch 38 has an outer surface 40 with a diameter D2 greater than the diameter Dl of the first threaded portion 36.

The fixing device 16 comprises a first spacing element 42 and a second spacing element 44. The spacing elements 42, 44 have a tubular shape and are arranged coaxially with the bolt 30. The first spacing element 42 has a cylindrical tubular body 46 with an inside diameter equal to the diameter D2 of the external surface of the clutch 38. The first spacing element 42 has a radial external flange 48 situated at the end of the tubular body 46, facing towards the head 32. At the opposite end to the flange 48 the tubular body 46 has a threaded portion 50 with an external thread .

The second spacing element 44 has a tubular body 52 with a threaded portion 54 with an internal thread, which engages the external threaded portion 50 of the first spacing element 42. The radial flange 48 of the first spacing element 42 has an outside diameter greater than the outside diameter of the second spacing element 44. The threaded portions 50, 54 have threads with a direction matching that of the threaded portion 36 of the bolt 30. The pitch of the threads 50, 54 is coarser than the pitch of the thread 36. The second spacing element 44 has a front stop surface 56 opposite to the head 32 of the bolt 30. The frontal surface 56 has a hole 58 through which the distal end of the bolt 30 extends with ample radial play.

With reference to figures 5 and 6, the operation of the fixing device 16 according to the invention will now be described .

The fixing device 16 is inserted into the aligned holes 22, 24 of the upright 12 from the outside towards the inside. The hole 22 in the outer wall 18 has a diameter greater than the outside diameter of the second spacing element 44. The diameter of the hole 22 is less than the outside diameter of the radial flange 48. The hole 24 in the inner wall 22 has a diameter greater than the diameter Dl and less than the outside diameter of the second spacing element 44. In the initial configuration the length L of the two spacers 42, 44 is greater than the distance between the holes 22, 24. The clutch 38 engages the inner surface of the first spacing element 42 with slight radial interference and is inserted axially into the inside of the first spacing element 42 to a depth not less than 10 mm. Axial and rotational movement is possible with friction between the clutch 38 and the first spacing element 42.

The fixing device 16 is inserted into the upright 12 as illustrated in figure 5, and is positioned with the front wall 56 in contact with the inner wall 20. The distal end of the bolt 30 projects from the inner wall 20 of the upright 12 and is aligned with the nut 28 on the fixing plate 26. In this condition the bolt 30 is rotated, usually by means of an automatic driver calibrated with a preset tightening torque. The clutch 38 rotates integrally with the bolt 30. The frictional contact between the clutch 38 and the first spacing element 42 drags the first spacing element 42 round. The rotation of the first spacing element 42 screws the threaded portion 50 of the first spacing element 42 into the threaded portion 54 of the second spacing element 44. As a result, the second spacing element 42 moves axially in the direction of axis Y towards the inside of the upright 12. The axial movement of the first spacing element 42 ceases when the radial flange 48 comes into contact with the outer surface 18 of the upright 12. At this point, as the bolt 30 continues to rotate, the clutch 38 slips against the inside of the first spacing element 42. As the bolt 30 is screwed in, it engages the threaded nut 28 and moves towards the inside of the upright 12. The clutch 38 moves axially towards the inside of the first spacing element 42. The axial movement of the bolt 30 continues until the preset torque is reached. In this condition the device has reached the configuration illustrated in figure 6. In the final condition of assembly the spacers 42, 44 are in contact respectively with the outer wall 18 and with the inner wall 20 of the box-section upright 12. When assembly is completed the effective length of the spacers is equal to L ' . The value L' adapts automatically to the dimension in direction Y of the upright 12. Any variations in width of the upright 12 due to construction tolerances are automatically compensated for by the fixing device 12. The pack formed by the two spacers 42, 44 therefore guarantees the correct clearance between the two walls 18, 20 of the box section and prevents the tightening torque of the bolt from deforming the sheet metal walls 18, 20.

Thanks to the present invention it is possible to use standardized fixing devices for various models and dimensions of uprights. The device according to the invention furthermore increases the solidity of the assembly and ensures greater rigidity of the vehicle body/dashboard in case of side impact.

Naturally, while the principle of the invention remains unaffected, the construction details and embodiments can vary widely with respect to what has been described and illustrated, without for this reason departing from the scope of the present invention, as defined in the claims which follow.