Abstract:
A fastening device for a line, in particular for an electric cable ( 12 ) in a motor vehicle, is proposed, the fastening device having a bush ( 10 ) which can be locked in a holder ( 18 ), at least partially surrounds the line, is made of elastically deformable material and is fastened releaseably in a cutout ( 16 ) of the holder ( 18 ) by means of a contour ( 14 ). According to the invention, the surface of a bush ( 10 ), which is injection-moulded from plastic, is of segmented design in order to obtain easier deformability of the bush when fitting it into an associated holder ( 18 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2006 042 663.0 filed on Sep. 12, 2006. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a fastening device for a line, in particular for an electric cable in a motor vehicle. 
     DE 43 41 384 C2 describes a feedthrough for lines, which includes elastic grommets which are lockable in place in a carrier and accommodate the line in a sealed manner. The elastic grommets may be slid via their base regions in a fitted manner into recesses which are connected to the edge of the carrier. The recesses for the grommets are radial in design and have a width which corresponds to the diameter of the grommet. A ring which encloses the carrier on the edge is also provided in order to lock the grommets in place in the recesses. The ring secures the grommets in the inserted position. The entire system has a complex design, and inserting the cables with the grommets is time-consuming. 
     SUMMARY OF THE INVENTION 
     In contrast, the device according to the present invention having the features of the independent claim has the advantage that the fastening device is greatly simplified in terms of design and installation. The force required to insert the line with the grommet enclosing it may be kept low, since the segmented surface of the grommet contour is relatively easily deformable even when plastic is used to manufacture the grommet. 
     It is particularly advantageous when the contour of the grommet is designed in the shape of a groove with an irregularly shaped groove base. A grommet of this type may be inserted with minimal force in a suitably sized recess of a holder which is preferably manufactured from a flat sheet-metal or plastic part. The manufacturing costs for this fastening device and the time required for installation are much lower than they are for known systems. 
     It has proven particularly advantageous when the grommet contour is designed in the shape of a groove with tooth-like raised areas on the groove base. Expediently, the raised areas on the groove base are of equal height, so that the line with the grommet need not be oriented in a certain installation position when it is inserted into a recess in the holder. Individual raised areas on the base of the groove are substantially easier to deform than is a smooth, cylindrical groove base, thereby greatly simplifying the insertion of the grommet. 
     It has also proven expedient for connecting segments to extend between the raised areas of the contour, which are narrower in design than the raised areas themselves. In this manner it is possible to reduce or completely prevent the play remaining between the grommet and the inner edge of the recesses in the holder without increasing the installation force. This applies in particular when each of the connecting segments has the same height as the adjacent raised areas. 
     To prevent axial play between the line grommet and the holder, it is also expedient for the groove-shaped contour of the grommet to include at least one irregularly-shaped side wall. In this manner, easily deformable regions are created on the sides of the contour; these regions also reduce or eliminate the axial play of the grommet in the recess of the holder in which the grommet is situated, without increasing the installation force. 
     A particularly advantageous embodiment of the fastening device according to the present invention is obtained when the grommet is manufactured using an easily deformable plastic and is applied to the line—in particular to an electric cable in a motor vehicle—via injection using a plastic injection molding process, the grommet being preferably composed of polyurethane (PUR), in particular a polyether-based polyurethane. Although a material of this type has a greater Shore hardness than do rubber materials, given the proposed design of the contour of the grommet, the installation force may be limited to acceptably low values with minimal play, thereby making it possible to utilize the cost advantages of a design of this type as compared with a grommet which is subsequently slid onto the line, without making assembly more difficult and without reducing the accurate fit between the grommet and the assigned holder. The PUR material used for the plastic coating which is applied via injection molding preferably has a Shore hardness of 50 A to 100 A, in particular 60 A to 80 A. Its elasticity is therefore not substantially greater than that of rubber materials and, due to the manner in which it is processed, costs and assembly effort may be greatly reduced. 
     Further advantageous embodiments of the present invention are presented in the dependent claims and are described in greater detail in the description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       An embodiment of the present invention is presented in the drawing and is described in greater detail in the description below. 
         FIG. 1  is a perspective illustration of a fastening grommet to be installed on a line, 
         FIG. 2  is a longitudinal sectional view through a grommet according to  FIG. 1 , which has been applied via injection molding to line, 
         FIG. 3  is a cross-sectional view through the grommet along line III-III in  FIG. 2 , and 
         FIG. 4  is a schematicized, perspective depiction of a holder of a fastening device according to the present invention as shown in  FIGS. 1 through 3 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a grommet  10  of a fastening device for a line, in particular for an electric cable  12  in a motor vehicle, which is composed of plastic and is applied directly to the cable using a plastic injection molding process. A particularly suitable plastic material for grommet  10  is polyurethane, preferably polyether-based polyurethane, with a Shore hardness of 60 A to 80 A. A grommet  10  of this type which has been applied via injection molding bonds at the surface with the insulation of cable  12  when it is applied via injection molding, and is thereby situated in a fixed and non-slidable manner in a position on cable  12  which is specified for the particular fastening application. For special applications, grommet  10  may also be produced via injection molding separately from the line or the cable, e.g. using an elastomeric plastic, and it may be subsequently slid onto the cable. 
     Grommet  10  according to  FIG. 1  encloses the cable entirely and, after installation, it detachably engages via its groove-shaped contour  14  in a recess  16  of a holder  18 , as shown in  FIG. 4  and which will be described in greater detail below. The surface of contour  14  of grommet  10  is segmented and bears against the smooth inner surface of recess  16  of holder  18 . 
     Grommet  10  includes, in the region of its locking in holder  18 , two flange-shaped ridges  20  and  22  which limit groove-shaped contour  14  and bear, after installation, against the surfaces of holder  18  on either sides of recess  16 . Groove base  24  has an irregular design with segments, including a plurality of tooth-like raises areas  26  of equal height. Connecting segments  28  extend between raised areas  26  on groove base  24 . Connecting segments  28  are narrower in design than are raised areas  26 , but they have the same height as raised areas  26 . An essentially homogeneous but easily deformable surface therefore results on groove base  24 , which requires only relatively minimal installation force to be inserted in recess  16  of holder  18  and, depending on the magnitude of the specified, permissible installation force, ensures a complete or at least largely play-free radial seat in holder  18 . 
     The design of the surface of groove-shaped contour  14  between ridges  20  and  22  is freely selectable within wide limits. In the embodiment, the wall formed by ridge  20  extends vertically relative to the cable axis, and the wall formed by ridge  22  extends slightly conically; both of the ridge edges are rounded to make them easier to press into recess  16 . One side wall of groove-shaped contour  14  is irregular in design with slight recesses  30 —which have a shape similar to that of groove base  24 —so that the deformation forces are also reduced on at least one side wall of the groove-shaped contour, thereby further reducing the installation forces required for insertion into recess  16 , while also ensuring a play-free seat of grommet  10  in recess  16  of holder  18 . 
     To increase the stiffness of the entire system composed of cable  12  and grommet  10  which has been applied via injection molding, a grid-shaped sleeve  32  which is designed as one piece with the remaining pieces of the grommet and which is also fixedly connected to cable  12  via injection molding abuts ridge  22 . Sleeve  32  counteracts a bending of cable  12  during assembly. The outer edge of ridge  22  slants downward, and its diameter decreases from the required height of groove-shaped contour  14  to the diameter of sleeve  32 , thereby resulting in an even distribution of installation forces on cable  12 . 
       FIGS. 2 and 3  show a longitudinal sectional view and a cross section through grommet  10 , cable  12  being shown diagrammatically only to illustrate the shape of grommet  10  which has been applied via injection molding.  FIG. 2  shows, in particular, the cylindrical shape of ridge  20  and the side wall of ridge  22  which slants slightly toward groove-shaped contour  14 , and the rounded outer edges of ridge  20  and  22 , which limit the groove-shaped contour toward the outside. 
     Raised areas  26  on groove base  24  are shown more clearly in  FIG. 3 . Section III-III in  FIG. 2  lies between connecting segments  28  and the inner wall of ridge  20 . In contrast to connecting segments  28 , tooth-shaped raised areas  26  are cut in the illustration in  FIG. 3  and are therefore shown shaded. Components that are the same are labelled with the same reference numerals in  FIGS. 1 through 3 . 
       FIG. 4  shows a greatly schematicized view of holder  18  for cable  12  with grommet  10  which is applied via injection molding. The shape of recess  16  and wall thickness d of holder  18  are of particular significance in this case. Diameter D of recess  16  in the receiving region of groove-shaped contour  14  should correspond approximately to the outer diameter at groove base  24 , and wall thickness d of holder  18  should correspond approximately to the inner width of groove-shaped contour  14 . These dimensions may be varied within certain limits in accordance with the permitted installation force applied when grommet  10  is inserted with cable  12  into recess  16 ; the installation force is determined by the shape of the individual elements of groove-shaped contour  14  and the elasticity of the plastic used for grommet  10 . Recess  16  is essentially composed of a circular receiving opening  34 , a constriction  36  which secures the locking of grommet  10  with cable  12  in receiving opening  34 , and an installation opening  38  which widens outwardly in a conical shape for grommet  10  with cable  12 . Holder  18  is usually punched from a piece of sheet metal, or it is composed of a plastic part, either one having suitable wall thickness d in accordance with the width of groove-shaped contour  14 . 
     Via the design—according to the present invention—of the fastening device it is made possible to replace known grommets which are made of rubber material, are manufactured as individual parts, and are slid onto the line with grommets which are applied via injection molding directly or are slid in place on the lines to be secured, the greater Shore hardness of the plastic material being compensated for by the design according to the present invention, thereby making it advantageously possible to utilize the greater stiffness, lower costs, and fixed seat of the grommet on the line.