Patent Abstract:
A window shade arrangement for motor vehicles that includes plastic injection molded guide rails designed such that they may be formed with injection tools that do not require moveable cores for forming guide grooves therein. In one embodiment, the guide rail includes an outer part ( 41 ) formed with a guide groove and a support part ( 42 ) made from less deformable material than the outer part for preventing widening of and deforming of the guide groove during usage. In another embodiment, the first and second molded parts are interconnectable to define the guide groove.

Full Description:
BACKGROUND OF THE INVENTION 
     DE 100 57 759 A1 describes a rear window shade for motor vehicles. This rear window shade comprises a winding shaft that is rotatably supported underneath a rear window shelf, wherein one edge of the strip-shaped shade is fixed the winding shaft. The strip-shaped shade is cut into an approximately trapezoidal shape with its other end distant to the winding shaft fixed to a draw-out rod Movement of the draw-out rod is laterally guided in two guide rails that are either bonded to the inner side of the rear window or hidden in the car body behind the lining of a C-column. Elastically bendable thrust elements for moving the draw-out rod are guided in the guide rails in a buckle-proof fashion. 
     The guide rails consist of an extruded aluminum profile with a continuous undercut groove. The groove is composed of a section with a circular cross section and a section with a rectangular cross section, wherein the section with a rectangular cross section is narrower than the diameter of the circle. The rectangular section forms a slot that opens the guide groove in the outward direction. 
     Sliding or guiding elements move in the guide rails the sliding or guiding elements have a head, the cross section of which is adapted to the circular section of the guide rail profile. This head has the shape of a ball or a short cylindrical section, with dimensions such that it cannot become jammed in the curved sections of the guide rails. A diameter of a neck of the sliding or guiding elements is chosen such that it fits through the slot of the guide groove without getting stuck. 
     The head of the guiding element usually is an injection-molded plastic part. Long-term usage has revealed that the combination of the plastic part and an aluminum rail is not rattle-free under all conditions. The friction between the plastic guide elements and the aluminum guide rail is not suited for optimal relative movement. In addition, certain difficulties can occur when integrating the guide rail into the inside lining. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved guide rail arrangement for motor vehicle window shades that eliminates the foregoing disadvantages of the prior art. 
     According to one embodiment of the invention, the guide rail arrangement is composed of two parts. One part forms an outer part that is manufactured from an elastically deformable material. The other part serves as a support and is made of a less deformable material in order to ensure that the outer part containing an undercut groove is always stabilized and the slot width of the guide groove does not changed over time. 
     The significant advantage of this arrangement can be seen, among other things, in that injection-molding tools with a drawable core are not required for manufacturing various designs of the outer part. Since the material of the outer part can be elastically deformed, the injection-molded part can simply be removed from the core that produces the undercut groove during the injection-molding process. This significantly reduces the costs of the manufacturing method. It is possible, in particular, to integrate the outer part into a section of the inside lining of the motor vehicle. The support part itself does not contain undercut grooves so that its manufacture does not require injection-molding tools with movable cores. 
     The outer part may have a narrow, oblong shape that essentially follows the progression of the guide groove. The connecting means between the support part and the outer part may consist of snap-in means. These snap-in means comprise, for example, a hook that is in the form of an undercut tab. Complimentary connecting means are provided on the support part. It also is possible to utilize an undercut web in this case. An undercut web represents a simple solution on the support part because it can be manufactured, for example, in the form of an extruded profile that is subsequently bent into the desired shape. 
     The material of the outer part preferably is selected from a group of thermoplastics. This makes it possible to achieve the desired resilience, wherein the support part counteracts a possible deformation over time. For this purpose, the support part, which may be manufactured from a light metal, contains a region that laterally supports, at least sectionally, the guide groove on flanks in the installed condition. In the simplest design, the support part contains a groove that is U-shaped and has parallel flanks. 
     In another embodiment, the guide rail arrangement consists of a first part and a second part, both of which are molded. In this case, the joint between the two interconnected parts extends in the longitudinal direction of the guide groove. Due to this design, neither part needs to have undercuts. The undercut guide groove for the window shade is formed after the two parts are joined together. 
     Since neither part contains undercuts, it also is possible to make one of the two parts integrally with a section of the inside lining, for example, of the C-column. In other words, this part of the guide rail arrangement is injection-molded integrally with the plate-shaped part of the lateral lining. 
     Connecting means are provided on both parts in order to position the two parts relative to one another. The connecting means also may extend over the entire length of both parts. For example, one of the connecting means may consist of a web that cooperates with another connecting means in the form of a groove. The web may contain pins that engage into additional openings in the groove in order to effect proper positioning in the longitudinal direction of the guide groove. 
     In order to achieve a favorable force gradient that does not exert a disadvantageous bursting effect upon the two parts when the guide element of the window shade moves through the guide groove, it is advantageous if the web extends at an acute angle relative to a plane that is defined by the slot and extends through the slot. 
     In addition to the two interconnected parts, a support part of a less deformable material may be provided, wherein this support part is attached to the two interconnected parts. The support part serves to prevent the molded plastic parts from distorting. Such a distortion may be caused by aging or age-related shrinkage. The support parts stabilize the groove and ensure that the slot of the guide groove maintains a constant width over its entire length. 
     The two parts may at least sectionally be integrally connected to one another. Such an integral connection can be produced by means of laser welding, ultrasonic welding, bonding or other connecting techniques. 
     Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially open perspective of a motor vehicle showing an inner side of a rear window having a window shade according to the invention; 
         FIG. 2  is an enlarged depiction of the window shade of the motor vehicle shown in  FIG. 1 ; 
         FIG. 3  is an enlarged section of a window shade guide rail arrangement according to the invention, taken transversely to a longitudinal direction of a guide groove thereof; 
         FIG. 4  is a section of an alternative embodiment of guide rail arrangement in accordance with the invention; 
         FIG. 5  is a transverse section of the guide rail shown in  FIG. 4 , taken at a different elevation; and 
         FIG. 6  is a transverse section of an embodiment of a guide rail arrangement according to the invention similar to that shown in  FIG. 4 , but inserted into the groove of a lateral lining. 
     
    
    
     While the invention is susceptible of various modifications and alternative constructions, certain illustrated embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now more particularly to  FIG. 1  of the drawings, there is shown the inside of a passenger car having a rear window shade in accordance with the invention The passenger car includes a body section  1  that includes a roof  2 , from which a B-column  3  laterally extends downward to a floor group, not shown. The roof  2  transforms into a rear window  4  on its rear edge. The rear window  4  laterally ends on a C-column  5  that is spaced apart from the B-column  3 . The C-column  5  carries the inside lining  6 . 
     As will be understood by persons skilled in the art, between the B-column  3  and the C-column  5 , a right rear door  7  is conventionally hinged to the B-column  3 . A rear bench  8  consisting of a seat  9  and a back rest  11  is arranged at the height of the right rear door  7 . The rear seat  9  lies on a base surface  12  that forms part of the floor group, wherein a certain leg room  13  is created in this floor group in front of the rear seat  9 . 
     A rear window shade  14  is mounted on the inner side of the rear window  4 . The window shade  14  is a strip-shaped shade mounted for movement between lateral guide rails  16 , being depicted in  FIG. 1  in a partially extended position. The guide rails  16  begins at a rear window shelf  17  arranged behind the back rest  11  and extend adjacent to the lateral window edge. The strip-shaped shade  15  extends out of a continuous slot  18  arranged in the rear window shelf  17 . 
     The window shade  14 , the basic design of which is shown in  FIG. 2 , has a winding shaft  19  rotatably supported underneath the rear window shelf  17 , with one edge of the strip-shaped shade  15  being fixed to this winding shaft. The winding shaft  19  is prestressed in the wind-up direction of the strip-shaped shade  15  on the winding shaft  19  with the aid of an appropriate spring drive  21 . The spring drive  21  in this case is a coil spring, one end of which is rigidly anchored on the car body and the other end of which is fixed in the winding shaft  19 . 
     The strip-shaped shade  15  has an approximately trapezoidal shape and is formed with a tubular loop  22  on an end opposite the winding shaft  19 . A draw-out profile or hoop extends through the tubular loop  22  and telescopically supports guide pieces  23 ,  24  in its interior. The guide pieces  23 ,  24  contain a neck part  25  of smaller diameter than an adjacent guide element  26  that has the shape of a short cylindrical section. The guide pieces  26  move in the guide rails  16  arranged adjacent opposite lateral edges of the rear window  4 . 
     Each guide rail  16 , as depicted in  FIGS. 3 and 4 , has a guide groove  27  that opens in the direction of the strip-shaped shade  15  in a guide slot  28 . The lower end of each guide rail  16  is connected to a guide tube  29 ,  30 , in which two bendable thrust elements  31 ,  32  are guided in a buckle-proof fashion. The bendable thrust elements  31 ,  32  comprise so-called Suflex shafts. They include a cylindrical core that is surrounded by a helically extending rib, which defines a flexible toothed rack with peripheral gearing. 
     The guide tubes  29  and  30  connect the guide rails  16  to a gear motor  33 . The gear motor  33  comprises a permanently excited D.C. motor  34  which is part of a drive  35  having an output shaft  36  onto which a cylindrical gear  37  in the form of a toothed wheel is fixed. The toothed wheel  37  positively meshes with both thrust elements  31 ,  32 . These thrust elements  31 ,  32  tangentially extend past the cylindrical gear  37  on diametrically opposite sides and are guided in corresponding bores  38 ,  39  for this purpose. 
     When the drive motor  33  is actuated, the thrust elements  31 ,  32  are selectively extended or retracted, with the guide pieces  23 ,  24  following the movement of the thrust elements  31 ,  32 . These guide pieces are held against the free ends of the thrust elements  31 ,  32  in the guide grooves  27  with the aid of a spring  21 . 
     The guide rails  16 , as depicted in  FIG. 3 , include an outer part  41  and a support part  42 . The outer part  41  consists of a thermoplastic material and integrally transforms into the inside lining  6  of the C-column  5 . The outer part  41  defines the undercut guide groove  27  that opens outwardly through the slot  28 . The guide groove  27  basically consists of a circular section  43  and a rectangular section  44 . The diameter of the circular section  43  is adapted to the diameter of the guide pieces  26 . 
     The outer part  41  has an outer or visual side  45  that extends approximately parallel to a rear side  46  thereof. The outer side  45  is divided into a section  45   a  and a section  45   b  by the slot  28 . 
     In addition to the slot  28 , the outer part  41  forms a wall section  47  that protrudes from the rear side  46  and transforms into a wall region  48  on its a free end. This wall region  48  extends along a segment of a circle and is followed by a straight wall section  49  that lies parallel to the wall section  47  and ends in the wall section  45   b . Accordingly, the structure on the rear side  46  in this case is free of undercuts, i.e., the two wall sections  47 ,  49  are limited by two parallel side walls on the outer side. 
     A first hook-shaped tab  51  extends adjacent to the wall section  47 , namely parallel to the longitudinal direction of the slot  48 . This first hook-shaped tab forms a groove  52  on the inner corner together with the wall section  47 . A second hook-shaped tab  53  is arranged in the form of a mirror image of the first hook-shaped tab and is situated adjacent to the outer side of the wall section  49 . This second hook-shaped tab forms a groove  54  together with the outer side of the wall section  49 . 
     The dimensions of both hook-shaped tabs  51 ,  53  are chosen such that the outer part  41  can be easily removed from the complementary mold cavity of the injection mold after an injection-molding process is completed, namely by utilizing the elasticity of the hook-shaped tabs  51  and  53 . Hence, complicated tools with moving cores are not required for producing the undercuts. 
     In addition, the wall thickness in the region of the wall section  48  surrounding the cylindrical region  43  has a cross-sectional profile chosen, in relation to the width of the slot  28 , such that the finished injection-molded outer part  41  can be removed from the mold core for producing the cross section  43  and the cross section  44 , namely in a direction perpendicular to the plane formed by the outer side  45   a  or  45   b , respectively. During the removal from the injection-molding tool, the outer part  41  is widened in the region of the guide groove until the corresponding part of the mold core is able to slide through the slot  28 . The outer part  41  subsequently springs back into the originally desired shape due to its inherent elasticity. 
     The support part  42  is provided because the structure alone could, under certain circumstances, be excessively resilient for reliably guiding the guide elements  26  and preventing their release from the guide groove  27 . The support part  42  in this case is rigidly arranged on an inner side of a car body section  55 . The illustrated support part  42  consists of a mounting plate  56  with two projecting limbs  57 ,  58 . The limbs  57 ,  58  define an interior suitable for accommodating the rear side of the outer part  41  in the region of the guide groove  27  without play. This U-shaped opening is composed, in particular, of an arc-shaped portion that receives and is adjoined by the wall section  48 , as well as two parallel surfaces that receive and are adjoined by the outer sides of the wall sections  47 ,  49 . The free ends of both limbs  57  and  58  are provided with flat hook-shaped tabs  59 ,  61  that are complementary to the hook-shaped tabs  51 ,  53 . 
     The support part  42  consists of a relatively rigid and inelastic material that is able to generate a sufficient resistance to forces acting in the widening direction of the slot  28  during the operation of the window shade. The support part  42  consists, for example, of an extruded aluminum profile that can be subsequently bent, if so required, in accordance with the desired configuration. 
     In the installed condition, the two free limbs  57 ,  58  enter into and interlockingly engage the grooves  52 ,  54 . This simultaneously results in an anchoring of the inside lining  6  in the region of the guide rail  16 . 
     According to the invention, it is possible to manufacture a plastic guide rail  16 , which may be of considerable length, wherein no movable core is required in the injection-molding tool. Otherwise the mold would be extremely difficult and expensive to manufacture, namely because it is very difficult to hold a movable core in proper position over a length of approximately 50 cm of the circular part  43  of the guide groove  27 , which has a diameter of approximately 8 mm. The design of the guide rail  16  in accordance with the invention eliminates the necessity for such a movable core because the core can be rigidly fixed on a web that molds the slot  28 . 
     Another advantage of the invention can be seen in the fact that the color in the visible regions of the guide rail  16  can be made to correspond exactly to the color of the inside lining  6 . This eliminates the customary measures for concealing a shiny aluminum rail. 
     The thermoplastic material also has superior sliding properties for the guide member  26 . If the guide rail consisted of an aluminum profile, it would be necessary to manufacture the guide member  26  from plastic or to provide the guide member with a plastic coating in order to achieve suitable sliding properties. The invention eliminates these requirements. 
     Due to its resilience, the plastic surface of the guide rail has a much lower tendency to generate rattling noises than a hard metal surface. Only the support part  42  consists of metal. The rigid support part  42  ensures that the guide groove  27  maintains its shape over an extended period of time. 
     Another embodiment of a plastic guide rail  16  is shown in  FIGS. 4 and 5 . In this embodiment, structural elements that are identical or equivalent to those described above with reference to  FIG. 3  are identified by the same reference symbols and not described in detail anew. The guide rail  16  in this case has a guide groove  27  configured similar to the above-described shape, i.e., it is composed of a circular section and a rectangular section that corresponds to the slot  28 . 
     The guide rail  16  in this instance, as depicted in  FIG. 4 , consists of two parts, wherein a first part  63  is integrally connected to the section  45   a  and another part  64  is integrally connected to the section  45   b . The visual side section  45   a  forms part of a flange  65  that extends as far as the slot  28  and transforms into a wall section  66  at this location. The wall section  66   a  ends on a surface  67  that extends at an angle of approximately 30–60 degrees referred to the visual side  45   a.    
     The flange  65  and the wall section  66  form an approximately rectangular profiled rail that, in turn, forms a section of the wall that corresponds to the section  43  with a circular cross section, as well as a wall section that limits the section  44  with a rectangular cross section on the outer side of the wall section or limb  66  that extends away from the inner corner, as shown in  FIG. 4 . The wall  67  ends approximately at the height of a plane that corresponds to the upper limiting wall of the slot  28 . Beginning at this location, the wall or the limb  66  transforms into a narrow web  68  that protrudes, as shown in  FIG. 4 , over a plane defined by the center of the circular section  43  and the center of the slot  28 . Considering the circular section  43  as a clock, the point of transition between the wall  67  and the web  68  that has a smooth outer surface that lies between 10 o&#39;clock and 11 o&#39;clock. 
     The other part  64  of the guide rail  16  forms an integral component of the inside lining  6  and has, in principle, a shape that is about complementary to that of the part  63 . The visual side section  45   b  is adjoined by a limb  69  that lies parallel to the limb  66 . The side of the limb  69  facing the limb  66  has an outside contour that supplements the outside contour of the limb  66  such that the complete guide groove  67  is formed. 
     On the opposite side of the slot  68 , the limb  69  protrudes upwardly over the slot  28  by a certain distance and is provided with a groove  71  that accommodates the web  68  in the mounted condition as shown. The web  68  and the groove  71  extend over the entire length of the guide rail  16 . 
     In order to hold the two parts  63  and  64  in the correct position in the longitudinal direction of the guide rail  16 , the web  68  carries tabs  72  that are spaced apart by distances of approximately 5 cm–10 centimeter, as shown in  FIG. 5 . In the installed condition the tabs  72  are inserted into rectangular openings  73  provided in the base of the groove  71 , namely in an extension thereof. 
     Ribs  74  may be provided on the tabs  72 , as shown in  FIG. 5 . These ribs make it possible to locally weld the respective wall of the opening  73  to the rib  74 . This can be effected by means of ultrasonic welding, namely by pressing corresponding sonotrodes at these locations, or alternatively, the parts may be welded to one another by means of laser welding. 
     If it is questionable whether or not the thermoplastic parts  63  and  64  can maintain their dimensional stability over an extended period of time, wherein the width of the gap  28  could conceivably change, an additional stabilizing element  75  can be used, as depicted in broken lines in  FIG. 5 . The illustrated stabilizing element  75  is shorter than the guide rail  16  and essentially has a U-shaped design. On its free ends, the stabilizing element  75  is provided with upwardly directed hook-shaped tabs  76 ,  77  that cooperate with hook-shaped tabs  51 ,  53  in a manner similar to that described above with reference to  FIG. 3 . Since the stabilizing element  75  adjoins the outer side of the limbs  66 ,  69  with the inner sides of its limbs, the slot  28  is prevented from widening, as well as from reducing its width. Several stabilizing elements  75  of this type may be provided and spaced apart from one another by a certain distance. 
     In the embodiments of  FIGS. 4 and 5 , respectively, the two parts  63 , and  64  also are practically free of undercuts. The hook-shaped tabs  51 ,  53 , if provided at all, have such small undercuts that the inherent elasticity of tabs  51 ,  53  would suffice for their removal from the injection-molding tool. This eliminates the need for a drawable core. Hence, the illustrated structure also makes it possible to injection-mold the guide rail from plastic by utilizing very cost-efficient injection-molding tools. 
     The guide rails  16  according to  FIGS. 3 and 4  are shown and described as forming, at least sectionally, part of the inside lining, for example, of the C-column. However, it will be understood that the guide rails  16  also could be made separately thereof and connected to snap-in elements of the lateral lining or the car body, such as by means complementary tabs or snap-in elements. The visual side section  45   b  then would end approximately at the location at which the arc-shaped progression begins in the structure. The tabs for interlocking the guide rail  16  would be arranged, for example, on the limb  69  in an extension of the slot  28  in the embodiment shown in  FIGS. 4 and 5 . 
       FIG. 6  shows an embodiment of the guide rail arrangement  16  that corresponds, in principle, to the embodiment shown in  FIGS. 4 and 5 . However, the guide rail arrangement  16  is inserted into a groove  78  provided in the lateral lining part  6 . Consequently, the lateral lining part  6  integrally extends beyond the groove  78 . 
     The groove  78  is laterally limited by two walls  79 ,  81 . The groove  78  has parallel flanks in this region. The two side walls  81 ,  79  are integrally connected to one another by a base  82 . As indicated above, the guide rail arrangement  16  corresponds to the guide rail arrangement  16  shown in  FIGS. 4 and 5  and is composed of the two parts  64  and  65 . They form short tab-like flanges  83 ,  84  on the outer side of the lateral lining part, wherein said flanges are sunk in a flush fashion into corresponding depressions  85 ,  86  of the lateral lining part  6 . 
     In order to positively hold the guide rail arrangement  16  in the groove  78 , flutings  87 ,  88  with a sawtooth-shaped profile are provided on the outer side of the limb  66  and on the outer side of the limb  69 , wherein said flutings are complementary to flutings on the inner side of the walls  81 ,  79 . 
     From the foregoing, it can be seen that the motor vehicle window shade of the present invention comprises guide rails that consist of plastic. The guide rails are designed, in particular, such that the injection-molding tools used form the guide rails need not contain movable cores in order to produce the guide groove. Hence, they are subject to much more economical manufacture.

Technology Classification (CPC): 1