Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority under 35 USC §119 to German Patent Application No. 10 2011 104 994.4 filed Jun. 22, 2011, the entire disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD OF THE INVENTION 
     The invention concerns a steering wheel for a motor vehicle with a steering wheel base body and a jacket that comprises at least one strip surrounding the steering wheel base body on the outer circumference. A first free end of the at least one strip is held in position securely in a groove formed in the steering wheel base body. In addition, the invention concerns a process for producing such a steering wheel. 
     DESCRIPTION OF THE RELATED ART 
     DE 10 2007 028 201 A1 describes a leather-jacketed steering wheel. Two strips of leather are sewn together at a first end. In order to achieve an especially good positioning ability of the two leather strips on the steering wheel rim, the sewn-together ends of the two leather strips are clamped in a groove that is formed along the steering wheel rim in its circumferential direction extending around the hub of the steering wheel. After placing the sewn-together ends into the groove, the leather strips are then placed on the surface of the steering wheel rim on its outer circumference. Then, the free ends of the two leather strips are connected by means of a seam. 
     Also, it is known from prior art to provide only one leather strip for enclosing the steering wheel rim, with the width of the strip corresponding essentially to 2πr, and r being the radius of a cross-sectional surface of the steering wheel rim. The length of the leather strip corresponds to the length of the steering wheel rim in the direction that extends around the hub of the steering wheel. On its two ends, this leather strip receives a pre-stitched seam. When the leather strip is then placed around the steering wheel rim, its facing edges form a butt joint. The stitches of the pre-stitched seam are then connected with each other. The connecting seam to be used for this, for example an Indianapolis seam, is produced by hand because a sewing machine cannot be used when the leather strip is arranged on the steering wheel rim. Even with steering wheel jackets where the steering wheel rim does not have a pure torus shape and where, as a consequence, the strip has a complex basic form, it is usually necessary to sew together the two free ends of the strip on the steering wheel manually. 
     This hand sewing of the jacket of a steering wheel is very labor intensive and therefore very costly. 
     SUMMARY OF THE INVENTION 
     This invention therefore addresses the problem of creating a steering wheel and a process as described above that lends itself to a much less costly production. 
     Advantageous embodiments with practical developments of the invention are given in the related claims. 
     With the motor vehicle steering wheel according to the invention, a steering wheel base body and a jacket are provided, with the jacket comprising at least one leather strip surrounding the steering wheel base body on its outer circumference. A first free end of the at least one strip is held in position securely in a groove formed in the steering wheel base body. A second free end of the at least one strip is also held in position securely in a groove formed in the steering wheel base body. This means that, after the placement of the jacket on the steering wheel base body, none of the ends of the strip need to be sewn together by hand; rather, the insertion of the ends into the at least one groove ensures the fixed position of the jacket on the steering wheel base body. 
     The at least one strip of the jacket is placed on the steering wheel base body so that it surrounds said body on its outer circumference and is held in position on the steering wheel base body by the clamping of its ends in the at least one groove. Since this eliminates the step of sewing together the jacket on the steering wheel, the production of the steering wheel is an especially low-cost operation. 
     In an advantageous embodiment of the invention, the jacket comprises a single strip, and the two free ends of the strip are held in one and the same groove. Such an attachment of the jacket to the steering wheel base body is distinguished by especially low cost. A (decorative) seam that is necessary for steering wheel jackets known from prior art is thereby completely eliminated. 
     A cosmetically especially attractive design of the steering wheel can be achieved when, according to another advantageous embodiment of the invention, the jacket comprises at least one first strip and at least one second strip. Here, the first free ends of the two strips are held in a first groove and the second free ends of the two strips are held in a second groove. Here, too, the jacket is fixed in position on the steering wheel base body by the insertion of the free ends in the associated groove, without manual sewing operations having to be performed on the steering wheel. In alternative embodiments, even more than two strips may be provided whose ends are fixed in associated grooves extending around the steering wheel rim in the circumferential direction of the steering wheel rim around the hub of the steering wheel. 
     It also proved to be advantageous if the free ends of the two strips held in a common groove were equipped with at least one mechanically sewn decorative seam. This decorative seam can be produced with a sewing machine prior to the insertion of the two ends into the groove so that a decorative seam will then be present on the steering wheel, as is the case with a decorative seam produced manually. After the mechanical sewing of the decorative seam, the free ends of the two strips carrying the decorative seam are then inserted into the common groove. This insertion of the free ends into the groove attaches the jacket to the steering wheel base body. In this way, various and complex decorative patterns can be provided on the jacket without having to produce them manually. 
     In addition, or as an alternative, the free ends of the two strips held in a common groove may be connected with at least one braid arranged in the common groove. Such a decorative braid, i.e. a strip folded once, will produce a cosmetically very attractive appearance of the steering wheel if it is implemented in a different color. The connection of the free ends of the two strips with the braid can be accomplished by means of mechanical sewing, i.e. before the jacket is attached to the base body of the steering wheel. 
     In order to improve the hold of the ends of the at least one strip in the associated groove, an adhesive may be provided. This adhesive may be arranged in the groove at least sectionally. 
     If, additionally or alternatively, adhesive is applied at least to sections of the steering wheel base body and/or to the inside of the jacket, the result is an especially secure attachment of the jacket to the steering wheel base body. 
     Lighting elements such as LEDs, luminous strips, etc. may be integrated in the groove and may be used for a decorative illumination of the surroundings of the steering wheel. 
     In the process according to the invention for producing a steering wheel for a motor vehicle, a steering wheel base body is equipped with a jacket that comprises at least one strip surrounding the steering wheel base body on its outer circumference. A first free end of the at least one strip is fixed in a groove that is formed in the steering wheel base body. A second free end of the at least one strip is also fixed in a groove that is formed in the steering wheel base body. Such an arrangement of the jacket on the steering wheel base body is an especially low-cost feature because sewing of the strip by hand is not required. 
     The advantages and preferred embodiments described above for the steering wheel according to the invention also apply to the process according to the invention for the production of a steering wheel. 
     The characteristics and combinations of characteristics referred to above in the description, as well as the characteristics and combinations of characteristics referred to below in the description of the figures and/or shown by themselves in the figures can be used not only in the specific combination referred to but also in other combinations or by themselves, without going beyond the scope of the invention. 
     Additional advantages, characteristics, and details of the invention follow from the claims, the description of preferred embodiments below, as well as from the figures in which identical or functionally equivalent elements are identified by identical reference symbols. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective, schematic section view of a steering wheel rim of a steering wheel where the free ends of two leather strips are held in associated grooves that are formed in the base body of a steering wheel rim extending in the circumferential direction of the steering wheel rim around the hub of the steering wheel; 
         FIG. 2  shows the two leather strips whose first free ends are sewn to a decorative braid, prior to the arrangement of the two ends in one of the two grooves provided in the base body of the steering wheel rim; 
         FIG. 3  shows the two ends of the leather strips connected with the decorative braid that form a seam that can be inserted into the groove; 
         FIG. 4  shows a top view of the two leather strips each of which has—in addition to the decorative braid—a decorative seam at their end intended for insertion into the groove; 
         FIG. 5  shows a greatly simplified cutting of a single leather strip for jacketing a steering wheel rim whose base body comprises only one groove extending in the circumferential direction of the steering wheel rim around the hub of the steering wheel; 
         FIG. 6  shows a top view of the two leather strips in combination with LED lights. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a schematic and simplified view of a steering wheel rim  10  of a steering wheel for a motor vehicle. The steering wheel rim  10  comprises a bearing structure  12  made of metal, for example an aluminum alloy, that is enclosed by a synthetic material, specifically a foam material  14 . The base body of the steering wheel rim formed in this way has a radius r. 
     On its outer circumference, the base body is surrounded by a leather jacket  16  that comprises a first leather strip  18  and a second leather strip  20  in the embodiment shown in  FIG. 1 . A first free end  22  of the first leather strip  18  and a first free end  24  of the second leather strip  20  are sewn to a decorative braid  26 . These two free ends  22 ,  24  and the decorative braid  26  are held in a groove  28  that is formed in the foam material  14  of the base body of the steering wheel rim  10 . The groove  28  extends in a circumferential direction of the steering wheel rim  10  around a hub (not shown) of the steering wheel, with this circumferential direction identified by the double arrow  30  in  FIG. 1 . 
     A second free end  22  of the first leather strip  18  and a second free end of the second leather strip  20  are held in a second groove  36  that is arranged parallel to the first groove  28  in the base body of the steering wheel rim  10 . This second groove  36  is also formed in the foam material  14  of the base body of the steering wheel rim  10 . 
     During the production of the steering wheel, the two free ends  22 ,  24  of the two leather strips  18 ,  20  are first sewn to the decorative braid  26  (see  FIG. 2 ). This is done before the two free ends  22 ,  24  are inserted into the first groove  28 . The width of the two leather strips  18 ,  20  is selected so that it is easy to produce, by means of a sewing machine, a seam  38  that connects the leather strips  18 ,  20  with the decorative braid. 
     After that, the narrow leather strip  20  is cut to the intended width. A mark  40  in  FIG. 2  schematically indicates the place where the cutting is performed. Also, the wider leather strip  18  that surrounds the larger part of the base body of the steering wheel rim  10  is cut to the correct width, in such a way that the second free ends  32 ,  34  of the two leather strips  18 ,  20  can be inserted into the second groove  36 . The arrows  42  in  FIG. 2  illustrate the placement of the two leather strips  18 ,  20  that is performed in such a way that the first two free ends  22 ,  24  of the leather strips  18 ,  20  form a seam in conjunction with the decorative braid  26  (see  FIG. 3 ). 
     After the cutting, the narrow leather strip  20  and the wider leather strip  18  have the correct width for jacketing the base body of the steering wheel rim  10 . As can be seen from  FIG. 3 , the seam including the decorative braid  26  can then be inserted into the first groove  28  intended for this purpose. 
     Then, the two leather strips  18 ,  20  are placed around the base body of the steering wheel rim  10  in such a way that their free ends  32 ,  34  are located in the area of the second groove  36  (see  FIG. 1 ). The two free ends  32 ,  34  are then clamped in the second groove  36  into which adhesive has been placed. In this way, it is possible to attach the leather jacket  16  to the base body of the steering wheel rim  10  without having to produce a seam by hand on the steering wheel. 
     In the leather jacket  16  for the steering wheel rim  10  shown in  FIG. 4 , a decorative seam  44 ,  46  is provided in addition to the decorative braid  26  on the two leather strips  18 ,  20  in the area of their ends  22 ,  24  that are to be held in the groove  28 . These decorative seams  44 ,  46  are also produced mechanically prior to the attachment of the leather jacket  16  to the base body of the steering wheel rim  10 . It is also possible to produce just one or several decorative seams rather than the two decorative seams  44 ,  46  shown here by way of an example, and the decorative braid  26  may be eliminated. 
     In another leather jacket  16  shown in  FIG. 5 , only the first leather strip  18  is provided for jacketing the base body of the steering wheel rim  10 . Here, the length L corresponds to the outer circumference of the steering wheel rim  10  in the direction extending around the hub of the steering wheel, indicated in  FIG. 1  by the double arrow  30 . 
     Here, the width of the leather strip  18  is larger by the width of the two free ends  22 ,  32 —i.e. by 2Δ—than the circumference 2πr of the base body of the steering wheel rim  10 . This makes it possible to insert the free ends  22 ,  32  into the common groove  36  that is provided in the foam material  14  of the base body of the steering wheel rim  10 . By fixing the two free ends  22 ,  32  of the leather strip  18  that are clamped in the groove  36 , it is possible here, too, to eliminate the need for manual sewing of the leather strip  18  on the steering wheel. Since no decorative seam is provided in this embodiment, the groove  28  can be eliminated. 
     It is possible to apply an adhesive to the common groove  36  as well as to areas of the surface of the base body of the steering wheel rim  10  that face the leather jacket  16  in order to improve the attachment of the leather jacket  16  to the base body of the steering wheel rim  10 . 
     In the groove  36 , ambient lighting may be integrated, for example in the form of a luminous strip  47  (schematically shown in  FIG. 4 ) or in the form of one (or several side-by-side) LED lights  48  (schematically shown in  FIG. 6 ). This opens new possibilities for the illumination of the interior of a vehicle as well as—very generally—for the design of the interior that were not achievable before. 
     Although the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalents and modifications will occur to others skilled in the art upon the reading and understanding of the specification. The present invention includes all such equivalents and modifications, and is limited only by the scope of the following claims.

Technology Category: 7