Abstract:
The invention relates to a production method and to a wiper blade for wiping panes, in particular motor vehicle panes, comprising a retaining element ( 12 ) for receiving a wiper strip ( 14 ), said retaining element having two spring rails ( 28, 30 ) which are separated from each other by a gap ( 32 ) and to which a connecting device ( 20 ) is fixed. The connecting device has a wiper blade-side part ( 15 ) with claw-like receiving portions ( 34, 36 ) that engage around the retaining element ( 12 ) at least in some regions. Each of the receiving portions ( 34, 36 ) has an internal width ( 42 ) that expands in the direction of the gap ( 32 ).

Description:
BACKGROUND OF THE INVENTION 
     In the case of wiper blades for wiping windows, in particular motor vehicle windows, comprising a supporting element for receiving a wiper strip which supporting element has two spring rails which are separated from one another via a gap and to which a connection device is fastened, which connection device has a wiper blade-side part with claw-like receptacles which engage around the supporting element at least in certain regions, the supporting element is supposed to ensure as uniform as possible distribution of the wiper blade contact pressure emanating from the wiper arm against the window over the entire wiping area wiped by the wiper blade. By means of an appropriate curvature of the supporting element when under no load—i.e. when the wiper blade is not resting against the window—the ends of the wiper strip, which is laid fully on the window during the operation of the wiper blade, are subjected to a load in the direction of the window by the supporting element, which is then stressed, even though the radii of curvature of spherically curved vehicle windows differ at each wiper blade position. The curvature of the wiper blade must therefore be somewhat greater than the greatest curvature measured in the wiping area at the window to be wiped. A connection device, by means of which the connection with the wiper arm is established, is fastened to the supporting element. 
     EP 0914269 B1 has disclosed the practice of fastening the connection device to the supporting element by means of a welded joint. For this purpose, the wiper blade-side connection element, which is made of either metal or plastic, is applied to or pushed onto the supporting element and connects it materially to the supporting element by means of a resistance weld in the case of a metal connecting element or by means of an ultrasonic weld in the case of a plastic connecting element. In everyday use, this welded joint is exposed to extreme conditions and must withstand high torques and vibrations in different weather conditions. Especially in the case of wiper blades which are produced in large numbers, a welded joint makes high quality demands on process management and thus makes a wiper blade more expensive, which is precisely what needs to be avoided in the case of mass-produced goods. 
     SUMMARY OF THE INVENTION 
     The wiper blade according to the invention has the advantage that simple assembly is made possible by expanding the inner widths in the direction of the gap. The spring rails can be connected reliably and cost-effectively to the wiper blade-side parts of the connection device. 
     By means of a bevel on one side or a spherical profile at least on one side of the inner widths, the spring rails are automatically centered when inserted into the inner widths. Moreover, the wiper blade-side part can be produced as an injection molding without problem. 
     If the bevel or the spherical profile is arranged on a concave side of the spring rails, whereas the inner surfaces of the inner widths arranged on the convex side of the spring rails are aligned with one another, it is ensured that, after assembly and during later use of the wiper blade, the pressing force exerted by the wiper arm on the connection device can be transmitted flat onto the spring rails. As a result, torques which load the connection can be avoided. 
     A secure and fixed clamping connection results when the size of the inner widths in the groove bases opposite the gap are the same size or somewhat smaller than the thickness of the spring rails. It is ensured in this way that the spring rails are firmly clamped in the inner widths. 
     The connection device can be simply pushed onto the spring rails when the receptacles are provided with run-on bevels. 
     A very simple and reliable method in which welded joints are effectively avoided is provided by the method according to the invention for producing a wiper blade whereby the spring rails are inserted individually or together into the receptacles and, after reaching the predetermined longitudinal position of the wiper blade-side part of the connection device, the spring rails are pressed into the groove bases of the inner widths to create the gap. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawing: 
         FIG. 1  shows a wiper blade according to the invention in perspective representation with a wiper arm indicated in chain-dotted lines and a windshield surface indicated in chain-dotted lines, 
         FIG. 2  shows a view according to II-II in  FIG. 1 , 
         FIG. 3  shows a schematic representation of the view shown in  FIG. 2  with just one spring rail, 
         FIG. 4  shows a schematic view in the direction of view IV in  FIG. 1  with just one end cap, and 
         FIGS. 5 to 8  show exemplary embodiments of wiper blade-side parts of the connection device with a different design of the inner widths. 
     
    
    
     DETAILED DESCRIPTION 
     A wiper blade  10  shown in  FIG. 1  has a supporting element  12  ( FIGS. 1 and 2 ), which is elongated in the manner of a band, which has spring elasticity and on the lower band side  13  of which, that facing the window, an elongated wiper strip  14  having rubber elasticity is fastened parallel to the longitudinal axis. Arranged on the upper band side  11 , that facing away from the window, of the supporting element  12 , which can also be referred to as a spring rail, in the central section of said supporting element, is the wiper blade-side part  15  of a connection device, by means of which the wiper blade  10  can be releasably connected in an articulated manner to a wiper arm  16  indicated in chain-dotted lines in  FIG. 1 . The wiper arm  16 , which is driven backward and forward in the direction of a double arrow  18  in  FIG. 1 , is loaded in the direction of an arrow  24  toward the window to be wiped—for example toward the windshield of a motor vehicle—the surface of which is indicated in  FIG. 1  by a chain-dotted line  22 . Since the line  22  is intended to represent the greatest curvature of the window surface, it is clearly apparent that the curvature of the wiper blade resting by the two ends thereof against the window is greater while under no load than the maximum window curvature ( FIG. 1 ). Under the contact pressure (arrow  24 ) the wiper blade  10  comes to rest over its entire length, by means of its wiping lip  26 , against the window surface  22 . At the same time, a stress builds up in the supporting element  12  which is made of metal and has spring elasticity, said stress ensuring proper contact between the wiper strip  14  or the wiping lip  26  and the window surface  22  over the entire length of said strip or lip and ensuring uniform distribution of the contact pressure (arrow  24 ). 
     The particular embodiment of the wiper blade according to the invention will be explained in greater detail below. 
     In  FIG. 2 , it can be seen that the supporting element  12  is constructed from two mutually separate spring rails  28  and  30 , which are spaced apart and form the basis of a gap  32 . In a lower region, the connection device  15  has two u-shaped receptacles  34  and  36 , in which the spring rails  28  and  30  are received. The receptacles  34  and  36  surround each of the spring rails  28  and  30  over a relatively large proportion of the cross section thereof, wherein that part of the connection device  15  which corresponds to the wiper arm  16  is arranged on the convex side  29  of the supporting element  12 , while the concave side  31  lies opposite said convex side. 
     In  FIG. 3 , the connection device  15  is illustrated schematically, wherein the corresponding spring rail  28  is depicted in the receptacle  34 , while the spring rail  30  is not in the corresponding receptacle  36 . It can be seen that the receptacles  34  and  36  fit around the spring rails  28  and  30 . In the region above the spring rails  28  and  30  and above the gap  32 , the connection device  15  has a recess  40 , in which a head part of a wiper strip comes to rest when the wiper blade  10  is assembled. 
     The wiper blade  10 , which is shown from below in  FIG. 4  and is depicted without the wiper strip  14  or wiper lip  26 , shows the spring rails  28  and  30 , the gap  32  and the receptacles  34  and  36  of the connection device  15 . It can be seen that, in this embodiment of the wiper blade  10 , the spring rails  28  and  30  are completely separated from one another and are only held together by the connection device  15  or by means of end caps  38 , of which only one is depicted at one end in  FIG. 4 . 
     In  FIG. 5 , a wiper blade-side part of a connection device  20  is illustrated analogously to  FIG. 3 . It can be seen that the receptacles  34 ,  36  have a bevel  44 . The bevels widen the inner widths  42  from a groove base  46  in the direction of the gap  32  between the spring rails  28 ,  30 . If the spring rails  28 ,  30  are inserted into the inner width  42 , they can thus slide along the bevel  44  up to the groove bases  46 . 
     In  FIG. 6 , the bevel  48  is arranged analogously to the bevel  44  of  FIG. 5 . However the bevel  48  is of spherical design. In the region of the groove base  46 , the spring rails  28 ,  30  are clamped over a relatively large region; nevertheless, the opening when pushing the spring rails  28 ,  30  into the inner width  42  allows simple centering. The same is made possible by the step-shaped bevel  50  shown in  FIG. 7 . 
     Common to the exemplary embodiments according to  FIGS. 5 to 7  is the fact that the sides of the wiper blade-side part  15  which rest on the upper side of the spring rails  28 ,  30 , that is to say the convex side of the curved spring rails  28 ,  30 , are aligned with one another. No bevel is thus arranged in this region. In this way, the wiper blade-side part  15  can transmit the pressing force applied by the spring arm  16  flat onto the spring rails  28 ,  30 . In the variant shown in  FIG. 8 , bevels in  52  are also arranged in this region. 
     It can be seen that the inner width  42  in the region of the groove bases  46  must approximately correspond to the thickness of the spring rails  28 ,  30  or is rather somewhat smaller. In this way, a clamping connection can be achieved. The bevels  44 ,  48 ,  50  form the basis of an opening angle between 1° and 15° or are 0.5 mm to 1.5 mm larger at their expanded side than in the region of the groove base  46 . 
     The wiper blade-side part  15  has, on its outer sides, run-on bevels  51  which make it possible for the wiper blade-side part to be pushed simply onto the spring rails  28 ,  30 . 
     In the method according to the invention for producing a wiper blade  10 , the spring rails  28 ,  30  are inserted together into the receptacles  34 ,  36  or the connection device is pushed onto the spring rails, wherein the spring rails  28 ,  30  bear against one another more or less without a gap. It is only when the longest position of the connection device  20  relative to the spring rails  28 ,  30  has been reached that the spring rails  28 ,  30  are completely inserted into the inner widths  42  of the receptacles  34 ,  36 , with the result that the gap  32  is formed. 
     If the inner widths  42  have at least one beveled side, this considerably simplifies the sliding operation. Run-on bevels  51  simplify the threading of the spring rails  28 ,  30  into the wiper blade-side part  15 .