The invention relates to a fastening clip for fastening a component on a carrier, in particular for fastening a door or wall molding on a bodywork part of a motor vehicle.

Such fastening clips are commonly constructed from a plurality of elements, a latching element being provided, which can engage behind an opening of the carrier with the aid of latching arms in order to fix the fastening clip, and a spreading element being provided, which can be adjusted relative to the latching element between a preassembly position and a fastening position and can lock the latching arms. It is also known to provide a seal which seals the opening in the carrier part and prevents, in particular, penetration of dirt and water, through the opening, into the interior of the carrier.

It is an object of the invention to create a fastening clip which provides for good sealing over a long period of time, in particular while being straightforward to produce and having modular adaptability.

This object is achieved according to the invention by the features of claim 1. The fastening clip for fastening a component on a carrier has a latching element, which can be locked in an opening of the carrier by means of at least two latching arms, and a spreading element, which can be adjusted relative to the latching element between a preassembly position, in which the latching arms are located in a preassembly position, and a fastening position, in which the latching arms are spread such that the latching element is latched on the carrier. The latching element is provided with a seal. The latching element has a carrier plate, on which the seal is positioned, wherein the latching element supports the seal in the axial direction over a radius which corresponds essentially to the radius of a main abutment region, by way of which the seal butts against the carrier. The main abutment region corresponds to that portion of the seal which is the first thing to come into contact with the carrier when the fastening clip is inserted into the opening. This region of the seal is essentially identical to that region of the seal which, in the fastening position, experiences the greatest level of contact-pressure force and is therefore mainly responsible for the sealing action of the seal in relation to the opening in the carrier.

The carrier plate supports the seal in the fastening position, that is to say it exerts an axial force in the direction of the carrier, to be precise at the location at which the sealing action predominantly takes effect. This means that the sealing action can be maintained to a high level over a long period of time, in particular over the entire service life of the fastening clip.

According to the invention, rather than being molded on the latching element, the seal is a prefabricated component which is separate from the latching element and the carrier plate and is positioned on the carrier plate. This configuration allows the fastening clip to be used in a modular manner. For example, it is possible for different seals for different use purposes, for example made of different materials or with different dimensions, to be mounted on an otherwise identical latching element. This also makes it possible to use, for the seal and the carrier plate, materials which for example cannot be processed together in two-component injection molding.

The modular construction of the fastening clip also means that, for different use purposes, for example for mounting on different types of vehicle, identical latching elements and seals can possibly be used for all customers, while it is only the spreading element which needs to be varied in a customer- specific manner in each case. Since a dedicated tool is necessary for producing each of the individual, separately produced components of the fastening clip, that is to say the latching element, the seal and the spreading element, it is thus possible to reduce the tool costs. It is possible for latching elements and seals, as described above, to be prefabricated with different dimensions, e.g. diameters and thicknesses, and from different materials and then to be combined with the respective customer-specific spreading element to form the finished fastening clip.

It is also thus possible, possibly prior to the mounting operation, for a seal or a spreading element to be straightforwardly changed over, should this be necessary.

The seal preferably butts against the carrier with essentially the same contact- pressure force over the entire circumference described by the radius. For this purpose, the carrier plate is advantageously designed such that it is continuous along the circumference denoted by said radius.

In order to define the main abutment region more precisely, and in order to be able to generate a uniform contact-pressure force, the main abutment region of the seal may be provided with a bead, which is directed toward the carrier and can form the essential contact between the seal and earner. It is, of course, also possible for other regions of the seal to rest on the carrier in the fastening position, but encircling contact of the main abutment region is normally enough to achieve a sufficient sealing action.

In order to be able to provide an assisting contact-pressure force over a long period of time, the carrier plate is preferably of frustoconical shape. The opening angle is directed toward the carrier, and therefore in particular an outer circumferential periphery of the carrier plate pushes in the axial direction on the seal, wherein the outer circumferential periphery of the carrier plate can butt against the seal on the opposite side of the bead of the main abutment region. As seen in the axial direction, the outer circumferential periphery of the carrier plate and the main abutment region of the seal here are located one above the other.

The opening angle of the truncated cone of the carrier plate increases preferably during the transition from the preassembly position to the fastening position, as a result of which the prestressing force to which the seal is subjected is increased. However, upon transition into the fastening position, the shape of the carrier plate should be altered only to the extent that the carrier plate retains a certain level of elasticity so that, even over the long term and even if the elasticity of the seal should possibly decrease, the seal can be subjected to a sufficient prestressing force in order to maintain sufficient sealing.

The seal preferably butts with elastic prestressing against the outer circumferential periphery of the carrier plate and engages around, in particular, the outer circumferential periphery. This allows the seal to be fixed straightforwardly and reliably on the carrier plate, wherein the prestressing, at the same time, allows more precise positioning of the main abutment region in relation to the carrier plate. The seal preferably has its surface area resting on that side of the carrier plate which is directed away from the carrier, and this helps to provide precise positioning.

The seal can extend over the outer circumferential periphery by means of a skirt, wherein the skirt has a width which is at least 10% of the maximum diameter of the seal. The skirt extends radially inward, and therefore the large width of the skirt creates a deep holder, in which the outer circumferential periphery of the carrier plate is retained such that it cannot be displaced. In the fastening position, when the fastening clip has been mounted on the carrier, the skirt can rest wholly or partially on the earner. The main sealing action, however, is always applied by the main abutment region of the seal, it being possible for said region to be arranged at the radially outer end of the skirt, and therefore in the vicinity of the radially outer circumference of the seal. Since the carrier plate is located in the holder formed by the skirt, it is also the case that the outer circumferential periphery of the carrier plate is in the vicinity of the outer circumference of the seal.

In the preassembly position, an inner circumferential periphery of the skirt may be spaced apart from the carrier plate. The remaining gap can be used for the purpose of simplifying automated positioning of the seal on the carrier plate.

On its inner circumferential periphery, the skirt is provided with a bead preferably on the side which is directed toward the carrier plate, said bead increasing for example the stability of the skirt.

In order to provide for complete sealing of the opening by the seal, the seal preferably has a through-opening, of which the inner circumferential periphery butts against the spreading element. It is thus possible to seal the transition to a spreading- element shank which projects through the opening. The inner circumferential periphery of the through-opening may be provided with a bead which, in particular in the fastening position, engages in a groove on the shank of the spreading element in order to enhance the sealing action.

Since the seal and the carrier plate are two separate components, it is readily possible for the seal and carrier plate to be produced from different materials. In an advantageous material pairing, the seal consists of a thermoplastic elastomer (TPE) and the carrier plate consists of polyoxymethylene (POM). The seal can thus be produced from a considerably more elastic and more flexible material, whereas, for the carrier plate, use can be made of a material which has a high level of long-term stability and, even after having been installed in a vehicle for a number of years, can still subject the seal to sufficient contact-pressure force. Other advantageous material pairings are at the discretion of the person skilled in the art.

The invention also relates to a method of mounting a seal on a carrier plate of a fastening clip as has been described above. The seal here is widened by a gripper and fitted over the carrier plate. The fastening clip can thus readily be produced in an automated manner, without the seal being subjected to excessive forces as it is being mounted quickly, and in a precisely positioned manner, on the carrier plate.

The invention will be described in more detail hereinbelow by way of an exemplary embodiment and with reference to the accompanying drawings, in which:

- figure 1 shows a schematic exploded illustration of a fastening clip according to the invention;

- figure 2 shows a schematic sectional view of the fastening clip according to the invention in the fastening position, mounted on a carrier;

- figure 3 shows a schematic exploded illustration of the latching element and of the seal of the fastening clip according to the invention;

- figure 4 shows a schematic sectional view through the seal of the fastening clip according to the invention; - figure 5 shows a schematic sectional view through the latching element with the seal of the fastening clip according to the invention mounted thereon; and

- figure 6 shows an enlarged detail from figure 5.

The figures show a fastening clip 10, which serves to fix a component 11 (not shown specifically here) on a carrier 12 (see figure 2). The component is, for example, a door molding, whereas the carrier 12 may be a bodywork part of a motor vehicle.

The fastening clip 10 here comprises a latching element 14, a spreading element 16, a seal 18, which is arranged on the latching element 14, and also a cap 19, which is fixed on an end point of the spreading element 16 once the fastening clip 10 has been produced.

The latching element 14 has two opposite latching arms 20, which can be spread apart from one another in the radial direction. An opening 22, through which a shank 24 of the spreading element 16 is pushed, is formed between the latching arms 20.

The fastening clip 10 can assume a preassembly position, in which the latching arms 20 are also located in a preassembly position, in which they have not yet been spread apart from one another and can be pushed through an opening 26 in the carrier 12. The fastening clip 10 can also assume a fastening position, in which the shank 24 of the spreading element 16 has been pushed onward between the latching arms 20, through the opening 26, and the latching arms 20 are spread apart such that they engage behind the periphery of the opening 26 in the carrier 12 and latch the fastening clip 10 on the carrier 12 (see figure 2). The component 11 which is to be fastened can be fixed at an upper end 28 of the spreading element 16.

The latching element 14 comprises a carrier plate 30, from which the latching arms 20 project in the axial direction A. The carrier plate 30 is of frustoconical shape, wherein the truncated cone opens in the direction of the latching arms 20 and, in the mounted state, in the direction of the carrier 12. The carrier plate 30 is closed all the way round and has a free outer, encircling circumferential periphery 32.

The seal 18 has an upper cover portion 34 with a central opening 36, through which the shank 24 of the spreading element 16 projects. The inner circumferential periphery 38 of the opening 36 is designed in the form of a bead 40. In the fastening position, the bead 40 engages in a groove 42 in the shank 24 of the spreading element 16.

The radially outer periphery of the cover portion 34 has provided on it a circumferentially encircling peripheral portion 44, which extends essentially in the axial direction A and merges into a radially inwardly running skirt 46. The skirt 46 terminates at a radially inner circumferential periphery 48, on which is formed a bead 50 which is directed toward the interior of the seal 18 and, in the mounted state, toward the carrier plate 30.

The skirt 46, in this example, has a width b in the radial direction which is at least 10%, in particular approximately 10 to 20%, of the overall diameter d of the seal 18.

In the preassembly position, the inner circumferential periphery 48 of the skirt 46, including the bead 50, is spaced apart by a certain gap 51 from an underside of the carrier plate 30, the underside being directed toward the latching arms 20. In this embodiment, the fastening clip 10 is assembled in an automated manner. A gripper (not illustrated) uses a plurality of arms to grip in the interspace between the skirt 46 and the cover portion 34 and expands the seal 18 in the radial direction, the seal 18 being widened as a result. In this state, the seal 18 is fitted over the carrier plate 30 of the latching element 14, wherein the carrier plate 30 ends up located between the skirt 46 and the cover portion 34. The gripper is then drawn back. To conclude, the spreading element 16 is pushed through the opening 36 of the seal 18, and the opening 22 between the latching arms 20, into a preassembly position, in which the latching arms 20 have not yet been spread apart from one another. Finally, the cap 19 is fitted onto the free end point of the spreading element 16.

For mounting on the carrier 12, the fastening clip 10 is pushed, in the first instance in this preassembly position, through the opening 26 and then the spreading element 16 is pushed onward in the axial direction A, relative to the latching element 14, into the carrier part 12, the spreading element spreading apart the latching arms 20 until the fastening clip 10 has reached its fastening position and is fixed on the carrier 12.

In the preassembly position, the outer circumferential periphery 32 of the carrier plate 30 is located in a holder 52 formed at the transition between the skirt 46 and the peripheral portion 44 of the seal 18.

In terms of its shape, the region 54 of the cover portion 34, said region adjoining the peripheral portion 44, follows the truncated cone of the carrier plate 30, and its surface area therefore butts against an outer side 56 of the carrier plate 30. The outer circumferential periphery 32 of the carrier plate 30 is therefore enclosed by the seal 18. As seen in the axial direction A, a bead 58 is located beneath the circumferential periphery 32 of the carrier plate 30, on that side of the skirt 46 which is directed toward the carrier 12, and defines a main abutment region 60 of the seal 18. The main abutment region 60 comes into contact with the carrier 12 for the first time when the fastening clip 10 is pushed into the opening 26. Moreover here the highest contact-pressure force takes effect here on a sustained basis, and the main abutment region 60 provides for the main sealing action in relation to the opening 26 in the carrier 12.

The bead 58 is located in the radially outer portion of the seal 18 and can adjoin the peripheral portion 44 directly in the radically inward direction.

The surface-area abutment of the region 54 of the seal 18 against the earner plate 30 and the fixed seating of the outer circumferential periphery 32 of the carrier plate 30 in the holder 52 mean that the bead 58 is largely fixed in position in relation to the outer circumferential periphery 32.

Upon transition from the mounting position into the fastening position, there is no significant change in the relative position between the bead 58 and the outer circumferential periphery 32, even if the carrier plate 30 is pushed apart to a certain extent, so that the opening angle of the truncated cone increases. This deformation generates prestressing, to which the skirt 46 and in particular the bead 58 of the seal 18 are subjected, said prestressing subjecting the main abutment region 60 of the seal 18 to a uniform contact-pressure force which acts over a long period of time.

It is also the case in the fastening position that the outer circumferential periphery 32 of the carrier plate 30 and the bead 58 of the skirt 46 of the seal 18 are located at least essentially one above the other in the axial direction A. The carrier plate 30 therefore supports the seal 18 over a radius ri which corresponds essentially to a radius r ₂ on which the bead 58, and therefore the main abutment region 60, is located.

In this example, the seal 18 is produced from a thermoplastic elastomer (TPE), while the latching element 14, and in particular the carrier plate 30, consists of polyoxymethylene (POM).