Fastener for connecting and spacing parts

Fastener (1) includes a head (2) and a body (3). The head (2) has a transverse stop (5) able to bear on the first piece (23). The body (3) has a first spacer (10) and a second spacer (11), coaxial and disposed in line with each other in an axial direction. The first spacer (10), adjacent to the head (2), has a diameter greater than that of the second spacer (11) which extends starting from the first spacer (10), on the opposite side from the head (2). Each of the spacers (10, 11) has at least one lug (13; 18).

FIELD OF THE INVENTION

The invention relates to the field of the fastening and positioning of mechanical parts.

It concerns more particularly a fastener comprising spacers adapted for the assembly of two parts each comprising a through-hole.

BACKGROUND OF THE INVENTION

In numerous fields, in particular the automotive field, it is necessary to have available fasteners capable of connecting two parts together while ensuring the double function of relative fixing as well as spacing.

Mechanical parts of all types, such as mechanical links, axles or rods thus need to be connected to the frame or structure of the system to which they belong, while being held away from that frame or structure.

Furthermore, such fasteners must be designed to promote rapid assembly, often performed blind, within mechanical structures with difficult access.

Devices of the prior art are already capable of fulfilling these functions. For example, a simple screw/nut system provided with a spacer, or a rivet tightened after spacing apart of the parts, or again certain types of resin.

Although these known devices ensure the fixing and spacing of the parts, they have high mechanical complexity making them difficult to implement on an automated production line. Their assembly requires different operations (the spacing apart and fixing being ensured by different parts) and their withdrawal, when possible, is also complex.

SUMMARY OF THE INVENTION

The object of the invention is to provide a simple fastener ensuring the functions described above and being easy to mount, in order to be suitable for automation and/or for implementation in conditions where access is difficult.

To that end the invention relates to a fastener comprising a head and a body, intended for connecting a first piece and a second piece, each comprising a through-hole with a predetermined contour, the first and second pieces having respectively a first and second predetermined thickness, characterized in that the head comprises a transverse stop able to bear on the first piece, and in that the body comprises a first spacer and a second spacer, coaxial and disposed in line with each other in an axial direction, the first spacer, adjacent to the head, having a diameter greater than that of the second spacer which extends starting from the first spacer, on the opposite side from the head, each of the spaces comprising at least one lug, the lugs on the first spacer being separated from the head by a distance corresponding substantially to the said first thickness and the lugs on the second spacer being separated from the first spacer by a distance corresponding substantially to the said second thickness, the lugs on the first spacer being aligned with the lugs on the second spacer.

Such a fastener is adapted to be easily mounted, in a single operation. The principle of lugs fixed on the spacers permits the locking of the fastener onto the first part and onto the second part, simultaneously, by a simple rotation of the body.

The withdrawal of the fastener is not only possible but as simple as the mounting of which the operations are repeated in the opposite order.

These operations are limited to the insertion of the fastener then to its rotation for example through a quarter turn.

According to one embodiment, the fastener is made in a single piece.

The structure of the fastener makes such one-piece manufacture possible, for example by molding, which is simpler and thus the cost is advantageous.

According to a preferred feature of the invention, the join between the first spacer and the second spacer forms a shoulder defining a transverse abutment surface.

This transverse abutment surface plays the same role for the second part as the transverse stop bearing on the first part.

Each of the parts is thus held on one of its faces by a surface or a transverse stop, and on the other of its faces by the lugs respectively arranged on the first and second spacers.

Additional functions may furthermore be provided in accordance with the features of the fastener described.

Thus, the second spacer may comprise, at its join with the first spacer, a frangible region of lesser thickness.

When forces in opposite directions are applied to the parts, with the fastener in place, the shear or tension stress produced will result in the rupture of that frangible region.

The force threshold to reach to cause the rupture is determined by the dimensions of the frangible region and by the properties of the material used in manufacture.

Furthermore, for improved bearing on the first part, the transverse stop on the head may be a projecting collar on the periphery of the head.

Other preferred features of the invention relate to this collar. It may be elastically deformable in the axial direction so as to ensure take-up of axial play.

Stable fastening is thus obtained, even after rotation of the fastener.

Similarly, the collar may comprise two cut-outs leaving an axially movable locking tooth.

This locking tooth inserts into a cavity provided on the first part. This cavity is positioned such that the locking tooth comes opposite to it after rotation of the fastener.

The width of the said locking tooth may be substantially equal to the width of the lugs of the first. This makes it possible to lock the tooth directly onto a part of the through hole of the first part.

According to another preferred feature of the invention, the second spacer comprises a chamfer at its end that is opposite from the head.

This chamfer forms a frusto-conical portion on the end of the second spacer. As the fastener according to the invention is adapted to be inserted in two coaxial holes, this frusto-conical portion facilitates the entry of the fastener into its housing.

Similarly the lugs of the second spacer may comprise beveled portions adapted to facilitate the entry of the fastener into its housing or adapted to facilitate the operation of locking by rotation of the fastener.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The fastener1appearing in isolation inFIGS. 1 to 4comprises a head2and body3as its main parts.

The head2is adapted for the manipulation of the fastener1and comprises a transverse disc4of which the periphery is provided with a projecting collar5.

Means for manipulation are also provided on the head2, here comprising a tongue6for gripping, since the fastener1is adapted in the present embodiment, for being manipulated by hand.

With reference toFIG. 3, the tongue6for this purpose has faces that converge towards each other so as to be able to be grasped optimally between the thumb and index finger of the user.

The collar5is formed by a frusto-conical wall delimiting a circle of smaller diameter and a circle of larger diameter, the circle of smaller diameter being attached to the edge of the transverse disc4and the circle of larger diameter being positioned around the body3.

As can be seen inFIGS. 2 and 3, the collar5thus forms a frusto-conical surface flaring from the disc4towards the body3.

The collar5is moreover constituted by an elastic material enabling it to be deformed when a force is applied to it tending to bring the circle of larger diameter into the plane of the transverse disc4.

FIGS. 1 and 4show furthermore that the collar5comprises two cut-outs7delimiting a locking tooth8.

The locking tooth8is thus movable in the axial direction, that is to say in the general direction in which the fastener1extends, independently of the rest of the collar5.

Tooth8further comprises a projection9(FIG. 3), in the direction of the body, adapted to ensure the locking of the fastener in the manner set out hereinafter.

The body3of the fastener1comprises a first spacer10attached to the head2so as to be coaxial with the transverse disc4of the head2. A second spacer11is also provided on the body3, this spacer11being coaxially attached to the first spacer10on the opposite side from the head2.

The transverse disc4of the head2, the first spacer10and the second spacer11are all three coaxially disposed, their common axis defining the general direction in which the fastener1extends.

The first spacer10has the form of a cylinder which comprises recesses12as well as two lugs13projecting from the contour of the cylinder.

The recesses12are formed, according to the present embodiment, in the first spacer10for reasons of economy of material on molding as well as for improvement in the weight of the finished part.

Other recesses may be provided in the same manner provided that the initial cylinder keeps a circular section.

The lugs13project from the contours of the cylinder in a substantially parallelepiped form. Nevertheless, the faces of the lug13that are remote from the cylinder are rounded such that the lugs13are contained within the collar5of the head2when the fastener1is viewed from below (FIG. 4).

With reference toFIG. 2, the height of the lugs13substantially corresponds to two-thirds of the height of the spacer10to which they correspond and are disposed flush with the end that is on the opposite side from the head2of the first spacer10. A space14is provided in this manner between the lugs13and the head2(the space here having a height of approximately one-third of the height of the first spacer10) or more specifically between the lugs13and the collar5of the head2.

The height of the space14is dimensioned depending on the thickness of one of the parts to assemble as set out later.

The second spacer11is formed from a solid cylinder nevertheless comprising a chamfer15at its end that is opposite from the head2.

The diameter of this cylinder is less than the diameter of the cylinder forming the first spacer10so as to create a shoulder, that is to say that when the fastener1is viewed from the side (FIGS. 2 and 3), the first spacer10has a transverse abutment surface16extending beyond the projection of the contour of the second spacer11on the end that is opposite from the head2of the first spacer10.

This abutment surface16may thus bear on a part when the second spacer has been inserted in an aperture made in said part (the diameter of this aperture being greater than that of the second spacer11but less than that of the first spacer10).

The second spacer11is attached to the first spacer10by a cylindrical region17having a diameter less than that of the cylinder forming the second spacer11.

This region of lesser thickness17is destined to form a frangible region adapted to break above a predetermined shear force, it being possible for the shear force to be created by a relative displacement of the two fastened parts, when fastener1is in place.

To hold fastener1in place on those two fastened parts, the second spacer11is provided with two diametrically opposed lugs18projecting transversely of the spacer11, at its end that is on the opposite side from the first spacer10.

The lugs18are thus attached to the second spacer11adjacent the chamfer15.

As for the first spacer10, a space is thus provided between the lugs18of the second spacer11and the lugs13of the first spacer10, this space corresponding to the thickness of one of the parts to assemble.

The lugs18of the second spacer11, of which one is visible from the side inFIG. 3, each comprise an upper surface19and a lower surface20, as well as beveled side walls21.

The characterization of these surfaces as upper, lower and side is made with reference to the fastener1in the position ofFIG. 3.

Moreover, consideringFIG. 2again, the lugs18of the second spacer11also comprise a bevel22on their end wall, that which is on the opposite side from the spacer11.

The fastener1which has just been described may be utilized in the manner indicated below.

The fastener1is adapted to rigidly assemble a first part23and a second part24, while maintaining a space between the two of them, in accordance with the assembly ofFIG. 7. The presence of a third part25close to the second part24does not participate in said assembly but, inFIGS. 6 to 8, makes it possible to simulate an environment in which the second part24is not accessible and in which that second part24is disposed virtually against another member (here the third part25), leaving little space for the lugs18of the second spacer11.

With reference toFIG. 5, the two parts23,24to be assembled each comprise a perforation26,27passing all the way through having the form of a circular hole associated with two diametrically opposed rectangular holes biting into the periphery of the circular hole.

This configuration of the perforations26,27makes it possible to introduce into each of them a spacer provided with lugs and to lock it by a quarter turn as explained further on.

The two perforations26,27have identical shape but are of different size: perforation26of the first part23is larger than perforation27of the second part24. The diameter of the circular hole of perforation26of the first part23corresponds to the diameter of the first spacer10of the fastener1, and the width of the rectangular diametrically opposed holes corresponds to the width of the lugs13of the first spacer10.

Similarly, the diameter of the circular hole of perforation27of the second part24corresponds to the diameter of the second spacer11of the fastener1and the width of the rectangular diametrically opposed holes corresponds to the width of the lugs18of the second spacer11.

Finally, the thickness of the first part23corresponds to the distance14separating the first spacer10from the head2and the thickness of the second part24corresponds to the distance between the first spacer (more specifically: the abutment surface16) and the upper surface19of the lugs18of the second spacer11. Since parts23,24have perforations26,27satisfying these conditions, it is possible to assemble and space them with the fastener1.

The two parts23,24are first of all put into position in accordance withFIGS. 5 and 6, that is to say such that the perforations26,27are coaxial and such that the two pairs of rectangular holes are in line with each other.

Fastener1is then inserted through the two perforations26,27, the lugs13,18being positioned face-to-face with the rectangular holes of the perforations26,27.

Note that the chamfer15and the bevels21,22of lugs18of the first spacer11are adapted to facilitate the insertion of the fastener1.

This insertion is made with one hand, holding the tongue6between the thumb and the index finger, and may consequently be performed blind.

Once the fastener1has been fully inserted through both parts23,24, the user must still exert a force to press the head1against the first part23, elastically deforming the collar5, and simultaneously rotate the fastener1by a quarter turn.

The bevels21of the lugs18of the second spacer11serve here to facilitate the start of this rotation, for example alleviating the fact that the fastener1may be insufficiently pressed against the first part23, this pressing being necessary in order for the lugs13,18to be freed from the rectangular holes of the two perforations26,27.

Once the quarter locking turn has been made, the fastener1is in place on the two parts23,24as represented inFIGS. 7 and 8.

FIG. 7shows the holding of the first part23between the lugs13,18and the holding of the second part between the collar5and the lugs13of the first spacer10. The elasticity of the collar5is taken advantage of to take up the plays of the assembly or to compensate for creep of the fastener1.

FIG. 8shows the locking tooth8of which the projection9becomes inserted in a cavity28arriving opposite that tooth8after the quarter locking turn has been made. This cavity28may be a cavity specially created for that purpose or else, as is the case here, cavity28may be one of the rectangular holes of the perforation26of the first part23.

The third part25, or any other member preventing access to one of the sides of the assembly, in no way interferes with the mounting operation described due to the insertion of the fastener from a single side and due to the fineness of the lugs18of the second spacer.

The frangible region17is thus positioned within the thickness of the second part24(seeFIGS. 7 and 8), flush with that part on the side of the abutment surface16of the first spacer10.

In this position, the rupture of this frangible region17leads to the separation of parts23,24but the maintenance of their spacing since the part of the fastener1formed of the head2and the first spacer10remains in place on the first part23.

The force necessary for the rupture of the frangible region17, in shear or in tension, may be calibrated to correspond to a stress limit induced by a relative movement between the two parts23,24. This is the case when such an assembly is adapted to remain integral under that stress limit and, on the contrary, be broken above it.

Depending on the desired value of this stress limit and on the material used to form the fastener1, the frangible region17may be dimensioned by calculation and/or empirically, through rupture tests.