Abstract:
The invention starts from a wiper blade ( 20 ) of a windshield wiper with a wiper strip support ( 22 ) and wiper strip ( 24 ), which feature end caps ( 28 ) on their ends, whose inner cross-sectional profile is adapted to the cross-sectional profile of the wiper strip support ( 22 ). It is proposed that a guide rib ( 42, 48, 50 ) running transverse to the longitudinal direction ( 58 ) of the wiper blade ( 20 ) and having a guide surface ( 44, 54 ) be formed laterally on at least one of the end caps ( 28 ).

Description:
BACKGROUND OF THE INVENTION 
   Known windshield wipers have a wiper arm constructed of a fastening part and an articulated part, which is connected to the fastening part in an articulated manner and has a wiper rod. Connected to the free end of the wiper rod in an articulated manner is a wiper blade constructed of a wiper strip and a wiper strip support, as a rule a supporting bracket system with a center bracket and, if necessary, subordinate brackets, e.g., an intermediate bracket and/or claw brackets, which hold the wiper strip. The brackets are also connected to the subordinate brackets in an articulated manner so that the wiper strip can adapt to the curvature of the vehicle window during the rotating movement. These types of windshield wipers are known from DE 37 44 237 A1, for example. The joints between the brackets are formed as a rule by plastic parts, which simultaneously cover the front side of the profile of the higher-order bracket. 
   In addition, a wiper strip support in the form of a supporting element made of an elastic high-strength plastic for a wiper strip is known from DE 197 38 232 A1, which has a curvature in an unloaded state that is designed so that uniform application force is produced when the wiper strip is applied completely to the vehicle window during operation of the wiper blade. In addition, similar wiper blades with a supporting element are known in which pre-bent spring rails are laterally inserted into a plastic profile. Caps made of plastic are mounted on the front sides as a conclusion of the profile. Both a supporting bracket system as well as a supporting element in the sense described above shall be understood in the following as a wiper strip support. 
   Wiper blades frequently tend to vibrate during the wiping process. During the rotating movement, the speed with which the wiper blade glides over the windshield continuously increases from the inner radius towards the outer radius. The frictional forces acting transverse to the longitudinal direction of the wiper blade, which are a function of the gliding speed, decrease with increasing glide speed so that a torque is produced around the vertical axis of the wiper blade, which changes its direction in the reverse positions. This changing torque stresses the bearing position between the wiper arm and the wiper blade. Above all with relatively long wiper blades, the guidance on the joint between the wiper blade and the wiper arm is not sufficiently stable to inhibit vibrations. The wiper blade is incited to vibrate since a wiper blade is a slim, elastic component and because of great speed differences in the frictional conditions between the drive-side inner area and the outer area of the wiper blade as well as due to the stick-slip effects. This leads, particularly on the inner circle of the wiper blade where especially low friction speeds are predominant, to undesired lateral movements, which starting at a certain size can lead to the wiper blade impacting the wiper arm and causing clattering noises. This is particularly critical if the vehicle windows are dry, dirty, icy, or not moist enough or there is snow on the vehicle window. Because the wiper blade can briefly lose contact with the vehicle window in this case, the wiped image is also unsatisfactory. The more bracket parts the wiper blade has, the sooner it tends to rattle. In addition, light wiper blades with low spring rigidity are less favorable than others. 
   In addition, a device to guide the wiper blade, which has a first and a second part, is known from DE 197 31 683 A1. It is arranged in the area of the coupling location of the claw bracket and permanently connected to the articulated part of the wiper arm, e.g., via adhesion, welding, soldering, clipping, clamping, etc. The first part of the device has guide cheeks, which grip around the articulated location of the claw bracket and guide laterally with respect to the wiper arm. The second part also has guide cheeks, between which the first part is guided in a telescoping manner so that its guide cheeks can be held briefly and a collision with the vehicle window need not be feared even when the vehicle window has strong curvatures. The first part is appropriately connected with the device so that it is secure from loss, for example, via a flexible element. 
   The device can be manufactured and composed of individual sheet metal parts, but it is preferably a plastic injection molded part made of a suitable plastic. In any case, additional components are required to guide the wiper blade, whereby increased expenditures for fabrication and assembly, and additional material costs are incurred. Air gaps are provided as a rule between the guide surfaces of the device in order to prevent the joint between the wiper blade and the wiper arm from jamming due to wiper-arm geometry that is influenced by tolerances such as right angles on the wiper rod. Clattering noise can also occur in this case, because, though the lateral vibrations are highly diminished, they are not avoided completely. 
   SUMMARY OF THE INVENTION 
   According to the invention, a guide rib running transverse to the longitudinal direction of the wiper blade and having a guide surface is formed laterally on at least one of the end caps. An additional component is not required to guide the wiper blade since the guide rib, which represents a part of a device to guide the wiper blade, forms one component with the end cap. The manufacturing expense and assembly expense are advantageously reduced as a result. The end cap can be guided with the guide rib directly or with the use of a guide bracket in the profile of the wiper arm, into which the end of the wiper blade pointing to the windshield wiper drive dips. As a rule, it is only necessary for one of the two end caps of the wiper blade to feature a guide rib. However, in order to avoid assembly errors, it is expedient to place the same end cap with a guide rib on both ends. 
   The guide bracket is preferably a plastic part and is inserted into the articulated part, for example, clipped in. As a result, it can also be mounted simply and with low expense. In addition, it can also improve the gliding properties between the end cap and the wiper arm and make a more favorable guidance profile possible than the inner profile of the wiper arm. Another advantage of the wiper blade guidance is that it is covered by the wiper arm to a large extent, does not require any additional installation space, and also makes a compact design of the windshield wiper possible in the wiper arm and wiper blade area. A compact windshield wiper produces less wind noise and possesses a better design. 
   The guide bracket features an outer profile adapted to the inner dimensions of the articulated part. It is supported on the inner contour of the articulated part. In order to lengthen the guide surfaces, a portion of the guide bracket can project beyond a side wall, which, in the area of the dipping end cap, serves as a bearing surface for the guide surface of the guide rib. Because of the inserted guide bracket, the articulated part is only lengthened in one area required for wiper blade guidance and otherwise remains unchanged. Analogous to the guide bracket, the shape of the guide rib is also adapted to the profile of the articulated part. If the articulated part has a U-shaped cross-sectional profile, for example, the allocated end cap can have formed-on guide ribs on both sides, whose guide surfaces run approximately rectangular to the base surface of the end caps and are guided onto the side walls of the U-profile with a slight amount of play. Because of the two-sided arrangement, the wiper blade can be guided in both wiping directions. 
   In one embodiment of the invention, the end cap features a guide rib formed on one side with angle of inclination to the base surface of the end cap, which is slightly less than 90°. This end cap shall be assigned to a wiper arm with a roof-like cross-sectional profile, whereby the guide rib is guided onto a side wall whose inclination is adapted to the shape of the guide rib. If the end cap dips into the wiper arm, the guide rib is positioned on the side wall of the wiper arm or the guide bracket, whereby the wiper blade is slightly pre-stressed transverse to its longitudinal direction. Because of the pre-stress there is advantageous contact between the guide rib and the guide bracket in every case since manufacturing tolerances and wear of the individual components are balanced out. In addition, the end cap also does not lose contact with the wiper arm because of the pre-stress even if the guide rib lies in the wiping direction in front of the wiper blade during a wiping movement. However, the guide rib is expediently arranged in such a way that, in the wiping direction that requires the greatest propelling force, it lies in the wiping direction behind the wiper blade. 
   The wiper blade is guided on the critical inner circle of the wiper field so that vibrations are avoided and the profile of the articulated part of the wiper arm can be used as a bearing surface. In addition, the joint between the wiper arm and wiper blade is relieved since the torque around the vertical axis of the wiper blade is supported on a wide basis because of the lateral guidance on the inner circle. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional advantages are yielded from the following description of the drawings. Exemplary embodiments of the invention are depicted in the drawings. The drawings, the description, and the claims contain numerous features in combination. The expert will also observe individual features expediently and combine them into additional, meaningful combinations. 
     The drawings show: 
       FIG. 1  A schematic side view of a wiper arm with a wiper blade that is connected in an articulated manner. 
       FIG. 2  A section corresponding to Line II-II in  FIG. 1 . 
       FIG. 3  A variation of  FIG. 2 . 
       FIG. 4  A perspective partial view of  FIG. 3  in a modified relative position between an articulated part and a wiper blade. 
       FIG. 5  An enlarged perspective depiction of an end cap in accordance with  FIG. 4 . 
       FIG. 6  Another variation in accordance with  FIG. 2 . 
   

   DETAILED DESCRIPTION 
   A wiper arm  10  constructed of an articulated part  12  and a wiper rod  14  is connected to a wiper blade  20  via a joint  18  and a connecting piece  16  ( FIG. 1 ). The wiper blade  20  has an elastic, non-articulated wiper strip support  22 , which is embodied as a spoiler and bears a wiper strip  24 . The joint  18  between the wiper rod  14  and the wiper blade  20 , and the elasticity of the wiper strip support  22  make it possible for the wiper strip  24  to be able to adapt to the curvature of a windshield  26  during the wiping movement. In doing so, the wiper blade  20  moves in a plane vertical to the windshield  26  relative to the wiper arm  10 , whereby the relative stroke movement on the end of the wiper blade  20  is especially great. 
   A wiper blade guide is provided for lateral guidance of the wiper blade  20  on the end facing the wiper arm  10 . It is composed of an end cap  28  with laterally formed-on guide ribs  48 , which run transverse to the longitudinal direction  58  of the wiper blade  20 , and of the articulated part  12  with an inserted guide bracket  36 , which serves as a bearing surface for the guide ribs  48 . The end cap  28  made of plastic encircles the wiper strip support  22  and a portion of the wiper strip  24  together with two spring rails  40  made of spring steel, which are inserted into lateral longitudinal grooves of the profile ( FIG. 2 ). It forms a covering for the wiper blade  20  in the end area and simultaneously fastens the spring rails  40  axially and together with the connecting piece  16 . The guide ribs  48  are formed onto the end cap during manufacturing. They have lateral guide surfaces  44 , which run vertical to a base surface  56  of the end cap  28  and in an assembled state in the profile of the wiper arm  10 , e.g., when using a guide bracket  36 , are guided on the two side walls  34  of the articulated part  12 . In the embodiment according to  FIG. 2 , the articulated part  12  has a U-shaped cross-sectional profile. The guide bracket  36  is also a plastic part. It lines the inner contour of the articulated part  12  in the area of the end cap  28  and is supported on the side walls  34  and on the covering wall  30 . 
   In one embodiment of the invention, guide ribs  42  or  50  with guide surfaces  44  or  54  are formed on only one side part  32  of the end cap  28  ( FIG. 3  through  FIG. 6 ). In addition, the guide surfaces  44  feature an angle of inclination a to the base surface  56 , which is slightly less than 90° and is adapted to the inclination of the side wall  34  of the articulated part  12 . This end cap  28  shall be assigned to a wiper arm  10  whose articulated part  12  features a roof-like cross-sectional profile having side walls  34  of different inclinations. The inclination of the guide surfaces  44  is adapted to the steeper side wall  34  and the guide ribs  42  are adjacent to this side wall  34  in an assembled position. In the wiper arm&#39;s  10  parking position, the flatter side wall  34  points downward and acts as a spoiler during the wiping operation. 
   So that the guide surfaces  44  are long enough to also have constant contact with the bearing surface on the side wall  34  of the articulated part  12  even in the case of greater stroke movements, in the embodiment in accordance with  FIG. 3  through  FIG. 5 , the guide ribs  42  project beyond the outer profile of the end cap  28  on one of the sides facing away from the base surface  56  by an area  46 . Moreover, the bearing surface on the articulated part  12  is lengthened by the guide bracket  36 , which projects beyond the side wall  34  by a part  38 . A possible extreme position between the articulated part  12  and the wiper blade  20  is depicted in  FIG. 4 . 
   According to the invention, the guide bracket  36  is inserted into the articulated part  12 , for example, clipped in, clamped or glued. As a result, the articulated part  12  is changed in a simple manner and only in the area of the dipping end cap  28 , and otherwise corresponds to the standard design. As a result, a wiper arm  10  can also be subsequently equipped with this type of wiper blade guidance. 
   According to another embodiment ( FIG. 6 ), the guide bracket  36  is composed of a metallic material and the guide ribs  50  are shortened as compared with the height of the end cap  28 . This end cap  28  is adjacent with the guide surfaces  54  in one area and its upper part is adjacent with the guide bracket  36  in another area. A flute  52  forms the transition between the areas.