Abstract:
The invention relates to a method for producing a wiper blades and to a wiper blade for wiping panes, in particular motor vehicle panes, comprising a support element ( 12 ) for receiving a wiper strip ( 14 ), to which a connecting device ( 20 ) is attached, which has a wiper blade-side part ( 15 ) having claw-like shoulders ( 50 ) surrounding the support element ( 12 ) at least in some regions. According to the invention, the wiper blade-side part ( 15 ) is pushed onto the support element with an only slightly larger inner width ( 44 ) than the thickness of the support element ( 12 ) and positioned, and is heat-treated after positioning.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    In the case of wiper blades having a supporting element and a connection device, which is secured on the supporting element by means of a part on the wiper blade side, which has claw-type shoulders which engage around the supporting element, 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 are 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 secured on the supporting element. 
         [0002]    EP 0914269 B1 has disclosed the practice of securing the connection device on the supporting element by means of a welded joint. For this purpose, the connecting element on the wiper blade side, which is made of either metal or plastic, is applied to or to pushed onto the supporting element and connected 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 torque and vibration levels 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 the wiper blade more expensive, which is precisely what needs to be avoided in the case of mass-produced goods. 
       SUMMARY OF THE INVENTION 
       [0003]    The method according to the invention for producing a wiper blade has the advantage that the wiper blade can be produced very economically. In general, the supporting element consists of drawn or rolled rails, which can be obtained within tight tolerances at no extra cost, while the part on the wiper blade side is a folded sheet-metal part or is injection molded. In this case too, the required tolerances can be achieved without problems. By virtue of the fact that heat treatment takes place after the assembly of the parts, however, it is not necessary to maintain very tight tolerances. The heat treatment ensures that the elements of the supporting element and of the part on the wiper blade side rest snugly against one another and produce at least a nonpositive joint. By means of appropriate surface characteristics and/or choice of material, it is also possible to ensure that the parts interlock or even bond adhesively to one another. 
         [0004]    The heat treatment preferably acts on claw-type shoulders of the part on the wiper blade side, the shape and/or extent of which varies in such a way that they rest snugly against the supporting element. 
         [0005]    If the heat treatment is applied to the supporting element, in particular to the lower side of the supporting element, the heat acts from the inside and therefore directly in the area of contact between the supporting element and the part on the wiper blade side and thus improves the joint. 
         [0006]    Introducing the heat is particularly simple if it is directed at the locations to be heated in the form of blown hot air. 
         [0007]    If it is necessary to introduce the heat as far as possible without any other influencing factors, the heat treatment can take place in the form of heat radiation. However, it is also possible, for example, to heat the supporting element inductively insofar as it is made of a metal and, in this way, to direct the heat selectively from the inside outward in a defined area. 
         [0008]    If the heat treatment takes place by means of a hot plate, this can merely be held at a distance from the parts to be heated or, as an alternative, can enter into direct contact. In the latter case, it is possible to exert a shaping effect on the elements of the supporting element and/or of that part of the connection device which is on the wiper blade side and to improve the joint. 
         [0009]    The heat treatment can take place very gently by means of a heating bath, through which at least the parts to be heated are drawn. 
         [0010]    If as uniform as possible heating of the entire supporting element is to take place, the supporting element can be placed in a heating furnace. 
         [0011]    Following the heat treatment, the heated parts are preferably subject to shaping, in particular being pressed onto one another. This reduces the gaps and results in a nonpositive and/or positive connection. Cooling of the heated parts may take place while they come into contact, and therefore a stepping shaping process is achieved. 
         [0012]    The connection between the supporting element and that part of the connection device which is on the wiper blade side can be improved if a substance which hardens and/or swells and/or bonds adhesively during the heat treatment is introduced into the region between said parts. This substance can then embed itself in the smallest cracks and considerably improve the joint. 
         [0013]    The application of that part of the connection device which is on the wiper blade side to the supporting element, in particular before the heat treatment, can be achieved in a particularly simple manner if the supporting element comprises or has two spaced spring rails, which are placed against one another before the part on the wiper blade side is pushed on and are adjusted to the specific spacing after the positioning of the part on the wiper blade side, that is to say, in particular, are pushed apart. 
         [0014]    A wiper blade according to the invention for wiping windows, has the advantage that it can be produced in a very simple manner because the connection between the supporting element and that part of the connection device which is on the wiper blade side is significantly improved by a heat treatment in this region. This is particularly important because there are considerable torques between the supporting element and that part of the connection device which is on the wiper blade side during wiping operation, especially when the window is dry or when there is snow on the window. Moreover, these torques are not constant but alternate in a regular manner. 
         [0015]    To ensure that the heat treatment works effectively, the clear width between the supporting element and that part of the connection device which is on the wiper blade side, the tolerance range should be from 0 mm to 0.5 mm, preferably from 0 mm to 0.2 mm, but at least from 0 mm to 0.05 mm. 
         [0016]    The dimensional stability of the arrangement can be maintained in a simple manner if the spaced spring rails are covered at the ends thereof by end caps, wherein at least one end cap has a spacer. 
         [0017]    Simple assembly is obtained if the connection device has run-on bevels in the region of the shoulders, thus ensuring that the spring rails can be threaded in in a simple manner in this region. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    In the drawing: 
           [0019]      FIG. 1  shows a wiper blade according to the invention in perspective representation with a wiper arm indicated in chain-dotted lines and a windscreen surface indicated in chain-dotted lines, 
           [0020]      FIG. 2  shows a view according to II-II in  FIG. 1 , 
           [0021]      FIG. 3  shows a schematic representation of the view shown in  FIG. 2  with just one spring rail, 
           [0022]      FIG. 4  shows a schematic view in direction of view IV in  FIG. 1  with just one end cap, 
           [0023]      FIG. 5  shows a schematic view, corresponding to  FIG. 2 , of an illustrative embodiment having a warm air blower, 
           [0024]      FIG. 6  corresponds to  FIG. 5  with a radiant heat source, 
           [0025]      FIG. 7  corresponds to  FIG. 5  with an induction heating unit, 
           [0026]      FIG. 8  corresponds to  FIG. 5  with a heating surface, 
           [0027]      FIG. 9  corresponds to  FIG. 5  in a heating furnace, and 
           [0028]      FIG. 10  shows a schematic representation from the side of a wiper blade according to the invention in a heating bath. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    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 secured 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 that part  15  of a connection device which is on the wiper blade side, 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 backwards and forwards in the direction of a double arrow  18  in  FIG. 1 , is loaded in the direction of arrow  24  toward the window to be wiped—e.g. toward the windscreen of a motor vehicle—the surface of which is indicated in  FIG. 1  by a chain-dotted line  22 . Since 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 also ensuring uniform distribution of the contact pressure (arrow  24 ). 
         [0030]    The particular embodiment of the wiper blade according to the invention will be explained in greater detail below. 
         [0031]    In  FIG. 2 , it can be seen that the supporting element  12  is constructed from two mutually separate spring strips  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 strips  28  and  30  are received. The receptacles  34  and  36  surround each of the spring strips  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. There is a small gap  41  between the spring strips  28 ,  30  and the respective receptacles  34 ,  36 . 
         [0032]    In  FIG. 3 , the connection device  15  is illustrated schematically, wherein the corresponding spring strip  28  is depicted in receptacle  34 , while spring strip  30  is not in the corresponding receptacle  36 , allowing the clear width  42  to be seen. It can be seen that receptacles  34  and  36  fit around spring strips  28  and  30 , and further details of the existing tolerances will be given later. In the region above spring strips  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  14  comes to rest when the wiper blade  10  is assembled. 
         [0033]    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 spring strips  28  and  30 , the gap  32  and receptacles  34  and  36  of the connection device  15 . It can be seen that, in this embodiment of the wiper strip  10 , spring strips  28  and  30  are completely separated from one another and are only held together by the connection device  15  or by means of the end caps  38 , of which only one is depicted at one end in  FIG. 4 . At least one of the end caps  38  has a spacer  39 , which holds spring strips  28 ,  30  at the spacing of the gap  32  in the assembled state. 
         [0034]    In the method according to the invention, that part  15  of the connection device  20  which is on the wiper blade side is then pushed onto the supporting element  12 , for which purpose the part  15  on the wiper blade side has a clear width  42  in the region of receptacles  34 ,  36  which is the same as or slightly greater than the thickness of spring strips  28 ,  30 . For this purpose, the clear width is approximately 0 mm to at least 0.05 mm greater than the thickness of spring strips  28 ,  30 . Assembly is simpler if the permitted tolerance range is in a range of from 0 mm to 0.2 mm, although in that case increased demands have to be made on the heat treatment. Very simple assembly can be accomplished if the tolerance range is between 0 mm and 0.5 mm, in which case it can be assumed that additional measures will be necessary to reduce the gap after the heat treatment. In the case of small gaps  41 , in particular, mounting of the part  15  on the wiper blade side on spring strips  28 ,  30  must be performed in such a way that spring strips  28 ,  30  are held next to one another in the clear widths, with the gap  32  being reduced, the part  15  on the wiper blade side is pushed on, and only then are spring strips  28 ,  30  adjusted to the spacing  32  and thus pushed into the receptacles. Of course, this method can also be advantageous in the case of different tolerances. 
         [0035]    In order to facilitate the introduction of the part on the wiper blade side and spring rails  28 ,  30  into one another, receptacles  34 ,  36  have run-on bevels  51  in the region of the claw-type shoulders  50 . 
         [0036]    As soon as the supporting element  12  and the part  15  on the wiper blade side have adopted the correct position relative to one another, a heat treatment is begun, being directed either at the part  15  on the wiper blade side or at the supporting element  12  or even at both elements. As a result, there is a change in the clear width  42  such that it completely or at least largely closes the gap  41 . 
         [0037]      FIG. 5  illustrates how a hot air stream  48  is blown from below at receptacles  34  and  36  or directly at claw-type shoulders  50  by means of a hot air blower  46 . For this purpose, the hot air blower  46  has a directional device  52 , which is designed in a funnel shape in the illustrative embodiment. The hot air stream  48  is thereby directed simultaneously at both claw-type shoulders  50 , at the spring strips  28 ,  30  projecting in the gap  32 , and into the recess  40 . The entire region is thus heated uniformly. 
         [0038]    The length of the hot air blower  46  can be matched to the length of the part  15  on the wiper blade side, when viewed in the longitudinal direction of the wiper blade, or, alternatively, it can be kept smaller and moved in the longitudinal direction. 
         [0039]    In another illustrative embodiment, shown in  FIG. 6 , a radiant heater  54  is shown as a heat source, radiant heat  56  being directed from said heater at the lower region of the wiper blade  10 . In the illustrative embodiment, the radiant heat  56  is produced by two radiant heaters  58  of the kind used, for example, in “reflow furnaces” during soldering. Compared with the hot air stream  48 , the radiant heat  56  has the advantage that no swirling or turbulence and hence no forces on the wiper blade  10  arise. However, it can be disadvantageous that, overall, the heat acts only directly from below, whereas the hot air stream  48  can propagate right into the recess  40 . 
         [0040]    An illustrative embodiment shown in  FIG. 7  takes a different approach, in which the heat is produced in the metal spring strips  28 ,  30  of the supporting element  12  by means of an induction device  60 . For this purpose, the already assembled ensemble consisting of spring strips  28 ,  30  and the part  15  on the wiper blade side is moved through an induction loop  62 , or the induction loop  62  is guided over the ensemble while a high frequency alternating current is applied to the induction loop  62 , which is preferably designed as a coil. 
         [0041]      FIG. 8  once again illustrates the already assembled ensemble consisting of spring strips  28 ,  30  and the part  15  on the wiper blade side, under which a hot plate  64  is positioned. If a spacing is maintained between the plate  64  and the claw-type shoulders  50 , the heat is transferred by means of heat radiation, in a manner similar to that in the illustrative embodiment shown in  FIG. 6 . However, it is also possible to forcibly press the plate  64  onto the claw-type shoulders  50 , giving rise, in addition to the heating, to a shaping pressure which closes the gap  41  or the gaps  41 . 
         [0042]    In  FIG. 9 , the assembled ensemble consisting of spring strips  28 ,  30  and the part  15  on the wiper blade side is positioned in a heating furnace  66 , in which a defined atmosphere can prevail. In  FIG. 10 , the assembled ensemble consisting of spring strips  28 ,  30  and the part  15  on the wiper blade side is immersed in a heating bath  68 . 
         [0043]    Depending on the manner in which the heat is introduced and/or the manner in which spring strips  28 ,  30  and the part  15  on the wiper blade side are prepared, the gaps  41  may close spontaneously or may require closure by the expenditure of additional force. If this further step is necessary, then, in the simplest case, a plate heated to a greater or lesser extent can be pressed in on the part  15  on the wiper blade side, as can be seen in the example shown in  FIG. 8 . The plate can have a temperature which introduces additional heat, or a cooling process can be set in train even at this stage. By means of the cooling, a permanent change in shape is achieved. 
         [0044]    In all the methods according to the illustrative embodiments, it is possible to introduce an additional substance  70  into the clear width  42 , which hardens and/or swells and/or adhesively bonds spring strips  28 ,  30  to the part  15  on the wiper blade side during the heat treatment.