Abstract:
A fastening element for fastening lining parts has a fastening section for attachment of a lining part thereto, and a locking section adapted to lock with a carrier for the fastening element. The locking section includes at least one locking tab. The locking tab has a release tab provided thereon for engagement by a tool for shifting the locking lab to a release position.

Description:
The invention relates to a fastening element for fastening lining pants, a carrier for a fastening element, and to a tool for removing a fastening element. 
     BACKGROUND OF THE INVENTION 
     The fastening element serves in particular to attach a lining part, for example a door lining, to a carrier which in turn is fitted to a vehicle-fixed component, such as, e.g., a vehicle body part. 
     Some lining parts require to be removable. To this end, use may be made of snap-in fastening elements which are released from the carrier as soon as a holding force, specified by design, is exceeded. The advantage of such fastening elements is that they allow the lining part to be removed with little effort. The drawback resides in that they provide only a comparatively small holding force which may possibly be exceeded unintentionally in operation, which then results in the lining part being inadvertently detached from the carrier. 
     Also already disclosed in the prior art are fastening elements which can not readily be pulled off from their carrier, but require additional steps when it is intended to release the fastening elements from the carrier. 
     DE 198 54 293 A1, for example, discloses a trim strip fastening for motor vehicles, having a fastening clip which can be inserted into an opening of a metal sheet or the like by means of a base part and can be located there by an expanding pin that can be driven into a central borehole of the fastening clip. The fastening clip includes a supporting plate and, spaced therefrom, a head piece around which the trim strip at least partly engages. The head pace is provided with a cut-out protruding as far as to the expanding pin, and the expanding pin has a slot-like recess disposed thereon, so that a removal of the expanding pin contrary to the insertion direction is allowed by means of an auxiliary tool. 
     However, use of an expanding pin is awkward and increases the number of parts to be assembled. 
     It is the object of the present invention to further develop a fastening element for fastening lining parts, a carrier for a fastening element, and a tool for removing a fastening element of the kind initially mentioned in an advantageous manner, in particular to the effect that a fastening element for fastening lining parts is structured more simply than was the case so far. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In order to solve this object, the invention provides a fastening element for fastening lining parts has a fastening section for attachment of a lining part thereto, and a locking section adapted to lock with a carrier for the fastening element. The locking section includes at least one looking tab. The locking tab has a release tab provided thereon for engagement by a tool for shifting the looking tab to a release position. The invention is based on the basic idea of suitably actively deforming the fastening element by means of the tool when it is intended to release the fastening element from the carrier. This allows the fastening element to be configured such that it basically, i.e. without the tool being operated, reliably locks on the carrier and, in doing so, provides a high holding force. The locking connection used here between the fastening element and the carrier need not be designed to the effect that the fastening element becomes automatically released from the carrier in case of a high release force, for example by suitable slopes on the fastening element or on the carrier. In fact, the connection between the carrier and the fastening element can be made to be self-retaining, for example by means of an undercut. When it is intended to release the fastening element, it is suitably deformed by means of the tool, so that it becomes released from the carrier. This ensures that the fastening element can be released from the carrier with little force when required. 
     The holding force that can be attained may be comparatively high. For example, the holding force can be greater than 300 N. 
     The force required for the locking or insertion of the fastening element may be comparatively low and amount to, e.g., about one seventh to about one tenth of the holding force. For example, the insertion force that needs to be applied for the fastening element to be locked may amount to less than about 40 N. 
     The release force, i.e. the force that needs to be applied in order that the mounted fastening element is released, may be lower than the insertion force, for example, and may more particularly amount to only about one third to about half of the insertion force. The release force may amount to about 20 N, for example. 
     The fastening element may be an injection molded part. This results in low manufacturing costs. 
     More particularly, the fastening element may be formed in one piece. This obviates assembly costs for assembling the fastening element from a plurality of individual parts. 
     The fastening element may, for example, be made of a thermoplastic material such as polypropylene or polyamide. 
     The carrier may be a carrier as will be described further below, which can be fastened to a vehicle body part, for example. 
     The fastening element may more particularly be connected to a lining part by means of a separate intermediate piece. 
     In addition, provision may be made that the release tab is arranged on the end of the locking tab facing the fastening section. This results in the advantage that a tool for removal of the fastening element can be introduced and applied close to the carrier for the fastening element and therefore so as to be well accessible from outside. 
     Furthermore, provision may be made that the locking tab extends toward the fastening section, starting from an end of the locking section facing away from the fastening section. This results in the advantage that the locking tab is formed so as to be comparatively long and therefore flexible. This influences and advantageously increases the holding force. At the same time, the flexibility has the effect of allowing the fastening element to be locked and released applying low forces. 
     The fastening section may have two locking tabs arranged thereon which are symmetrically opposite each other. This allows a uniform distribution of force and also a uniform application of the holding force by the fastening element. In addition, this also facilitates the locking and release of the fastening element. 
     The locking tabs may be structured substantially identically. 
     Provision may further be made that at least one pretensioning element is provided which urges the fastening element away from the carrier when the fastening element has locked in place there. A pretensioning element of this type allows the fastening element to be braced in the carrier and vibrations to be thereby reduced or even entirely avoided. Any generation of noise, which is perceived to be unpleasant can be suppressed in this way. 
     Provision may be made for a plurality of pretensioning elements, in particular two pretensioning elements. The pretensioning elements may be arranged symmetrically. 
     More particularly, provision may be made that the pretensioning elements are designed so as to be wing-like, cushion-like or web-like. 
     The present invention further relates to a carrier for a fastening element. According thereto, a carrier for a fastening element includes a guide for a tool which is adapted to engage the release tab of the fastening element such that the locking tab is shifted to a release position. This results in the advantage that the tool for releasing the fastening element is automatically correctly positioned and guided, so that the fastening element can be released simply and reliably. This is an advantage in particular because the tool has to be applied “blindly” in most cases since the fastening element is usually arranged so as not to be visible. In addition, the guide ensures that the insertion force acts in the “right” direction, that is, in the direction necessary for releasing the fastening element. For this reason, only a small force is required for release, more particularly only a release force of about 20 N. 
     Furthermore, an insertion slope for the tool may be advantageously provided. This facilitates insertion and correct application of the tool. 
     Provision may further be made that the guide is in the form of a rectangular guide channel. This automatically results in guide faces which are opposite each other in pairs and allow the tool to be guided with little effort. In addition, a rectangular guide channel is simple to form. 
     Moreover, the present invention relates to a fool for removing a fastening element. According thereto, a tool for removing a fastening element is made from a flat material and has two release slopes opposite each other. This results in a small height of the tool, which leads to an overall flat design of the assembly according to the invention. The release slopes are advantageously arranged here such that when the tool is inserted, they will automatically move into engagement with the release tabs of the fastening element and press them together such that the fastening element is released from its locked condition. The fastening element can then be simply removed from the carrying member. 
     The base body of the tool may be elongated and have a rectangular cross-section. Such a cross-section may be obtained with little effort either by punching the tool from sheet metal or by injection molding of the tool. Here, the cross-section of the tool is adjusted to the guide channel of the carrying member for the fastening element such that the tool can be readily inserted but, at the same time, is reliably guided such that the release slopes engage the release tabs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention will be apparent from the description below and from the accompanying drawings, to which reference is made and in which: 
         FIG. 1  shows a perspective view of a fastening element according to an exemplary embodiment of the invention; 
         FIG. 2  shows a further perspective view of the fastening element of  FIG. 1 ; 
         FIG. 3  shows a side view of the fastening element of  FIGS. 1 and 2 ; 
         FIG. 4  shows a further side view of the fastening element of  FIGS. 1 and 2 : 
         FIG. 5  shows a top view of the fastening element of  FIGS. 1 and 2 ; 
         FIG. 6  shows a perspective view of a carrier according to an embodiment of the invention, the carrier being provided for cooperation with the fastening element of  FIGS. 1 to 5 ; 
         FIG. 7  shows a perspective top view of a receiving element for the fastening element according to  FIGS. 1 to 5 ; 
         FIG. 8  shows a perspective view of a tool according to an embodiment of the invention, the fool being provided for cooperation with a fastening element according to the invention; 
         FIG. 9  shows the release slopes of the tool of  FIG. 8  in an enlarged top view; 
         FIG. 10  shows the release slopes of the tool of  FIG. 8  in a still further enlarged side view; and 
         FIG. 11  shows a perspective view of the fastening element mounted in the carrier with a tool engaging it. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 to 5  show a fastening element  10  as an exemplary embodiment of the invention. 
     The fastening element  10  includes a fastening section  12  and a locking section  14 . The fastening section  12  is provided for connection with a component to be fastened. To this end, a receiving element may be provided, which may be formed in one piece with the component or in the form of a separate part fitted to the component. The locking section  14  is provided for locking with a carrier to be discussed further below, so that the component to be fastened is then attached to the carrier. The carrier may also be configured as a separate part or may be integrated in some other part. 
     The fastening section  12  includes a cylindrical section  16  and a substantially rectangular platform  18  which is integrally formed with the cylindrical section  16 . In cooperation with a suitably designed receiving element the rectangular basic shape of the platform ensures that the fastening element  10  can be inserted into the receiving element only in the correct orientation. To this end, the dimensions of the receiving element are adjusted to the smaller width of the platform; when rotated through 90 degrees, that is, by its larger width, the platform can not be inserted into the receiving element. 
     As is apparent from  FIG. 2 , the platform  18  has an opening  20  in its center. The end of the cylindrical section  16  facing the platform  18  protrudes into the opening  20  and is connected with the platform  18  via a plurality of spring bars  22 . 
     The spring bars  22  have a spiral shape, as is well visible in  FIG. 5 . 
     The spring bars  22  are hinged to a substantially triangular end section  17  of the cylindrical section  16 . The spring bars here extend along the outer surfaces of the end section over a large part of their length, so that in the case of large deflections, they are held in contact and supported there. This prevents an excessive deflection of the end section and, hence, an excessive deformation of and load on the spring bars. 
     The locking section  14  includes a middle web  15  and a pair of locking tabs  24  which are symmetrically opposite each other. The structure of the two locking tabs  24  is identical. 
     The locking tabs  24  extend toward the fastening section  12 , starting from an end of the looking section  14  facing away from the fastening section  12 . 
     The locking tabs  24  each have a release tab  26  provided thereon which is arranged on the end of the looking tab  24  facing the fastening section  12 . 
     Opposite the free ends of the release tabs  26 , a flange  28  is provided on the end of the cylindrical section  16  facing away from the platform  18 . The flange  28  has a pair of pretensioning elements  30  arranged thereon, again symmetrically with each other. 
     The pretensioning elements  30  project from the flange  28  at an acute angle toward the looking section  14  and, in this exemplary embodiment, have a wing-like configuration. 
     The tip of the middle web  15  of the locking section  14  facing away from the platform  18  and the side of the platform  18  facing the locking section  14  have a distance of 21.4 mm from each other. 
     The platform  18  has a thickness of 2.2 mm. As is apparent from the top view of the platform  18  in  FIG. 5 , the platform  18  has a rectangular basic shape with a length of 28.4 mm and a width of 25.6 mm. 
     The cylindrical section  16  has a diameter of 4.9 mm. 
     The locking tabs  24  each have an elastically deformable spring section  32  by which they are resiliently linked to the middle web  15 . The spring section  32  is adjoined by a thickening reinforcement section  34  which terminates in the locking tooth  36 . 
     The reinforcement section  34  is then adjoined by the release tab  26 . The release tab  26  is arranged on the side of the reinforcement section  34  facing the middle web  15  and, in the non-loaded condition of the fastening element  10 , extends parallel to the middle web  15 . 
     The release tabs  28  each have a length of 5.7 mm. The two inner sides of the release tabs  26  facing the middle web  15  have a distance of 9.2 mm from each other. 
     Rounded tool engagement surfaces  27  are formed on the side of the release tab  26  facing away from the middle web  15 . The tool engagement surfaces  27  define a circle having a diameter of 11.8 mm. 
     The looking tooth  36  has a tooth face  38  and a tooth back  39 . The tips of the looking teeth  36  have a distance of 15.1 mm from each other. 
     The tooth back  39  is formed by the side of the reinforcement section  34  facing away from the middle web  15 . 
     The transition between the spring section  32  and the middle web  15  is made with a radius of 0.95 mm on the inside, that is, in the region where the spring section  32  transitions into the reinforcement section  34 . 
     The pretensioning elements  30  project from the flange  28  toward the locking section  14  at an angle of 54 degrees. The tips of the pretensioning elements  30  have a distance of 10.5 mm from the side of the platform  18  facing the locking section  14 . The two tips of the pretensioning elements  30  have a distance of 21.8 mm from each other. 
     It is apparent from the side view according to  FIG. 4  that the middle web  15  has an arrow-shaped design. The base body of the middle web  15  has a width of 11.8 mm. 
     In the region of the flange  28 , the middle web includes a shoulder  40  which has a height of 4.5 mm. The shoulder  40  has a diameter of 16 mm. 
       FIG. 6  shows a perspective top view of an exemplary embodiment, according to the invention, of a carrier  42  for the fastening element  10  as is shown in  FIGS. 1 to 6 . 
     The carrier  42  includes a guide  44  which is in the form of a rectangular guide channel  44 . 
     The guide channel  44  has an insertion slope  46  on its input side. 
     On the output side of the guide channel  44 , the carrier  42  includes a middle section  48  auf. Provided in the middle section  48  is a central, circular opening  50 . 
     Furthermore, the middle section  48  has three lateral sections  52 ,  54 ,  56  formed integrally therewith, which have fastening holes  58 . 
     The carrier  42  is formed in one piece here. 
     The carrier  42  may, for example, be a metal component or a plastic component or a composite fiber material component. 
       FIG. 7  shows a perspective top view of a receiving element  60  for the fastening element  10  according to  FIGS. 1 to 5 . 
     The receiving element  60  has a middle section  62  including an insertion channel  64  having an insertion slope  66  and a latching rib  68 . 
     The middle section  62  has two lateral wings  70  formed thereon which each have a pair of fastening holes  72 . 
       FIGS. 8 to 10  show a tool  74  for removing a fastening element  10 . 
     The tool  74  is made from a flat material and has two release slopes  76  opposite each other. 
     The release slopes  76  here are each formed on a respective end of two parallel pins  78  which are integrally formed with an end of the tool  74 . 
     The release slopes  76  and the internal surfaces of the pins  78  define an intermediate space  80  which narrows toward the tool  74 . 
     This intermediate space  80  has its largest width at the level of the tips of the release slopes  76  and reduces its width along the release slopes  76  toward the tool  74 . 
     The tool  74  includes a handle portion  82  at its end facing away from the release slopes  76 . 
     The middle portion  84  of the tool  74  has information or labels attached thereto, printed thereon or stamped therein, for example. 
     The release slopes  76  are arranged symmetrically and have an opening angle of 90 degrees. 
     The release slopes  76  are integrally formed with the end of the portion  84 , which here has a width of 24 mm. 
     As can be further seen from the detailed side view according to  FIG. 10  of the release slopes  76  of the tool  74 , the release slopes  76 , viewed in the side view, form a rounded tip  86 . 
     In this exemplary embodiment, the rounded tip  86  has a radius of 0.5 mm here. 
     The rounded tip  86  is arranged here at the level of one of the flat sides, in this case the upper side  88 . 
     In a side view, starting from the tip  86  a first lateral slope  90  runs at an angle of 55 degrees, which is then adjoined by a second lateral slope  92  running at an angle of 30 degrees toward the second flat side, in this case the underside  94 . 
     The function of the fastening element  10  can be described as follows: 
     The fastening element  10  is locked in the central circular opening  50  of the carrier  42  by means of the locking section  14 . 
     The insertion force therefor amounts to less than 40 N here, for example. 
     The design of the locking tabs  24  allows holding forces of more than 300 N. 
     The fastening section  12  along with the platform  18  is inserted into the receiving element  60 . 
     To this end, the platform  18  is pushed into the insertion channel  64 , which is facilitated by the insertion slope  66 . The latching rib  68  prevents the platform  18  from slipping out. The receiving element  60  is snap-fitted with a lining part by means of the fastening holes  72 , for example. 
     Any lateral offset between the carrier  42  and the receiving element  60  for the lining part can be compensated for by means of the spring bars  22 . 
       FIG. 11  shows a perspective top view of the fastening element  10  as mounted in the carrier  42 , but without the receiving element  60 . 
     To release the fastening element  10 , the tool  74  is pushed, with the release slopes  76  first, into the rectangular guide channel  44 , which is facilitated by the insertion slope  46  on the input side. A certain flexibility of the tool also facilitates its insertion. 
     The release slopes  76  are moved toward the release tabs  26  through the guide channel  44 . By applying the release slopes  76 , the release tabs  26  are pushed into the intermediate space  80  and thus toward the middle web  15  of the fastening element  10 . 
     This causes the locking tabs  24  to be released from their locked condition in the opening  50 , and the fastening element  10  can be removed. 
     According to this exemplary embodiment, releasing the locking mechanism only requires a release force of less than 20 N to be applied.