Abstract:
A wiper blade is proposed which is used to clean windows, especially of motor vehicles. The wiper blade is displaceable transversely to its length, preferably about a pendulum axis, and can be pressed with an elongated, rubber-elastic wiper strip ( 46 ) against the window ( 54 ) to be wiped; the wiper strip is disposed on the lower band face ( 49 ), oriented toward the window, of a bandlike-elongated, spring-elastic support element ( 42 ). Chattering that occurs during wiping operation and causes an unsatisfactory outcome of wiping as well as considerable noise, is avoided if the region of the upper band face ( 43 ), remote from the window, of the support element ( 42 ), the wiper blade is provided with a mass body, which is disposed movably, at least in the displacement direction ( 74 ) of the wiper blade.

Description:
BACKGROUND OF THE INVENTION 
   In certain types of wiper blades, the support element is meant to assure the most uniform possible distribution, over the entire field swept by the wiper blade, of the wiper blade contact pressure, originating in the wiper arm, against the window. By means of a suitable curvature of the unstressed support element—that is, when the wiper blade is not resting on the window—the ends of the wiper strip, which in wiper blade operation presses completely against the window, are stressed toward the window by the then-tensed support element, even if the radii of curvature of spherically curved vehicle windows change at every position of the wiper blade. The curvature of the wiper blade must accordingly be somewhat greater than that in the swept field, at the most pronounced measured curvature of the window to be wiped. The support element thus replaces the known, complicated support bracket construction with two spring rails disposed in the wiper strip and serving to reinforce the rubber-elastic wiper strip transversely (German Published, Nonexamined Patent Application DE-OS 15 05 257). 
   In wiper systems with a wiper blade that is guided over the window transversely to its length, a problem can arise which will now be explained in conjunction with  FIG. 1  of the drawing: In the wiping motion that takes place in pendulum-type wiper system  10  (double arrow  12  between pendulum turning points  14 ), a wiper blade  18  pivotably connected to a driven wiper arm  16  cleans a wiping field  20  shaped like an annular segment, and the wiper arm  16  supported on one end swings like a pendulum, together with the wiper blade  18 , about an axis  22 . The wiper blade  18  is pivotably connected to the free end of the wiper arm  16  in such a way that the wiper blade can swing about an axis  24  oriented approximately parallel to the window and can adapt to the course of the window surface, which because of its shaping differs from the plane in which the wiper arm swings. The wiping field boundary is defined by the two pendulum turning points  14  and the wiper radii  26  and  28 , of which the outer, longer radius  28  is defined by the end  30  of the wiper blade  18  remote from the pendulum axis, while the inner, shorter radius  26  is defined by the end  32  of the wiper blade  18  near the pendulum axis. A peculiarity of such wiper systems is considered to be that the speed at which the wiper blade  18  sweeps over the window increases from the inner radius  26  to the outer radius  28 . Thus the forces of friction decrease steadily from the shorter radius  26  to the longer radius  28 , as a function of the speed. The result is a moment acting on the known wiper blade that loads the wiper blade, or seeks to rotate it, about a vertical axis  34  perpendicular to the window. The alternating stress (double arrow  36 ) resulting as a function of the constantly changing pendulum direction (double arrow  12 ) acts on the support point between the wiper arm  16  and the wiper blade  18 , which must therefore be designed as sufficiently stable. Vibrations caused by the moment in the wiper arm and in the wiper blade—which causes the wiper blade to exert a so-called “stick-slip” effect on the window—also worsen the outcome of wiping. 
   To overcome this deficiency, in a known wiper blade (German Published, Nonexamined Patent Application DE-OS 21 22 678), which for the sake of the most uniform possible distribution of the force originating in the wiper arm for pressing the wiper strip against the window is nevertheless provided with a multi-member support bracket frame, on whose end remote from the drive shaft, or from the wiper arm hub that can be connected to that shaft, of the support frame main bracket a leaf spring is disposed, which is fixed by its one end to the main bracket. On the other, free end of the leaf spring, which spring can be deflected in the direction of displacement of the wiper blade, a small lead plate is mounted on each side of the spring leaf. If during the wiping work the wiper blade begins to chatter—which essentially leads to vibration in the plane of motion of the wiper blade—then the leaf spring is also induced to vibrate. Because of the inertia of the small lead plates—given a suitable adaptation of the leaf spring in terms of its length and thickness and of the adapted magnitude of the weight of the small lead plates—the vibrations of the leaf spring are in the opposite direction, with a time lag, from the vibrations originating in the wiper blade and cancel the latter out. 
   SUMMARY OF THE INVENTION 
   To counteract chattering of the wiper blade of this generic type, it is embodied in accordance with the definitive features of the present invention. As a result, the structural height of the support element, which is low because of the support element can be kept low. The length of the wiper blade also remains limited to the minimum amount necessary for wiping. 
   If the mass body is embodied in striplike fashion and extends longitudinally of the support element, then depending on the applicable criteria it can be provided with a suitable length, which is at maximum approximately equivalent to the length of the wiper blade. In this way it is possible to adapt the available mass to requirements, without requiring greater space for the wiper blade. 
   In a refinement of the invention, the support element has two spring rails, spaced apart from one another and extending parallel to one another and disposed in the same plane, and the wiper strip, over at least a part of its length, extends with an extension through a gap between the two spring rails. At least one mass body can be disposed in a simple way on the extension. 
   For many applications, in which the demand for a spoiler must be considered, the mass body is advantageously embodied as a spoiler. 
   To vary the center of gravity of the mass body relative to the support element and thus to vary its vibration frequency, it can be expedient if the mass body has an at least approximately triangular cross section, or if the mass body, viewed in cross section, is provided with a thickened portion on its free end remote from the extension. 
   In a refinement of the concept of the invention, the spoiler comprises a different material from the wiper strip that is fabricated jointly with it and solidly connected to it. This makes it possible to choose a material that is especially suitable both for the wiper strip and for meeting the demands made of the wiper strip, while the desire for a mass body or the spoiler can be respected in a particular way. 
   In applications with especially stringent demands made of the wiper blade and its spoiler, a multiple-material composite of these elements can be achieved by providing that the wiper strip has a base body, which on a side remote from the window changes over via the extension to the spoiler and furthermore, a striplike wiper lip that can be placed against the window and that is made from a different material jointly with the base body and is joined thereto via a rib strip is disposed on the side of the base body toward the window. 
   A further feature of the invention provides that a spoiler embodied as an elongated hollow body is formed onto the extension, and located in the cavity of the spoiler is the mass body that is joined to the extension and is movable in the displacement direction of the wiper blade. 
   In such embodiments of the wiper blade, it has proved especially advantageous if viewed in cross section, the extension of the wiper strip changes over, at the upper band side of the support element, into a bandlike base strip, with which the wiper strip is connected via an articulated strip formed by longitudinal grooves that are laterally open at the edges. The support element thus includes two spring bands, located in the same plane extending approximately parallel to the window, which rest in grooves assigned to them that are bounded at the top by the base strip. The spacing between the inner edges, oriented toward one another, of the spring bands makes it possible for the wiper strip to pass through support element. The articulated strip makes the requisite mobility of the mass body in the displacement direction of the wiper blade possible, and its dimensioning is oriented to the requirements in terms of the requisite vibration frequency of the mass body. 
   If, viewed in cross section, the extension of the wiper strip changes over, at the upper band side of the support element, into a bandlike base strip, with which the hollow body, comprising a different material but fabricated jointly with the wiper strip, is solidly connected via an articulated strip formed by longitudinal grooves that are laterally open at the edges, then for the choice of material for the hollow body, it is possible to a material that is especially advantageous for it, yet is unsuited to meeting the demands made of the wiper strip. 
   Further advantages for the wiper blade of the invention can be attained if the mass body comprises a different material from the wiper strip, the latter being fabricated jointly with it and solidly joined to it. 
   As already noted, for a prescribed distribution of the contact pressure of the wiper blade or the wiper arm, it is a basic prerequisite that the unstressed support element is curved in the longitudinal direction, with the connection device for the wiper arm located on the convex outer side of the support element and the wiper strip disposed on the concave inner side of the support element. 
   Other advantageous refinements and features of the invention are disclosed in the ensuing description of exemplary embodiments shown in the associated drawing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawing, 
       FIG. 1  is a basic illustration of a pendulum wiper system for windows of motor vehicles, with a wiper blade pivotably connected to the wiper arm and showing the field swept by the wiper blade; 
       FIG. 2  is a side view of a wiper blade of the invention; 
       FIG. 3  is a top view on the wiper blade of  FIG. 2 , with the wiper arm indicated by dot-dash lines; 
       FIG. 4  is an enlarged sectional view through the wiper blade of  FIG. 2 , taken along the line IV—IV; 
       FIG. 5  shows the arrangement of  FIG. 4 , with the terminal vibration positions of a mass body disposed on the wiper blade shown in dot-dash lines; 
       FIG. 6  shows a different design of the mass body located on the wiper blade; 
       FIG. 7  shows the arrangement of  FIG. 4 , with a further design of the mass body located on the wiper blade; 
       FIG. 8  shows the arrangement of  FIG. 4  with a wiper strip made of two materials; 
       FIG. 9  shows the arrangement of  FIG. 4  with a multiple-material wiper strip; 
       FIG. 10  shows the arrangement of  FIG. 4 , in which the mass body is accommodated in a spoiler provided with a cavity; 
       FIG. 11  shows the arrangement of  FIG. 10 , with the terminal vibration positions of the mass body of  FIG. 10  shown in dot-dash lines; 
       FIG. 12  shows the arrangement of  FIG. 10 , in which the spoiler is made of a different material from the wiper strip; and 
       FIG. 13  shows the arrangement of  FIG. 12 , in which the mass body is also made of a different material from the wiper strip. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A wiper blade  40 , shown in  FIGS. 2 and 3 , of a first embodiment of the invention has a bandlike-elongated, spring-elastic support element  42  with two spaced-apart, parallel spring rails  41  extending in the same plane. In the middle portion of the support element  42  ( FIG. 4 ), on the top side  43  remote from the window  54  to be wiped, a connection device  44  is disposed, with the aid of which the wiper blade  40  can be connected releasably to a wiper arm  48  ( FIGS. 2 and 3 ) driven in pendulum fashion about a pendulum axis  45  and guided on the body of a motor vehicle. An elongated, rubber-elastic wiper strip  46  is retained, longitudinally axially parallel, on the underside  49  of the support element  42 , oriented toward the window  54 . As a counterpart connection means, a pivot bolt  50  belonging to the connection device  44  of the wiper blade  40  is provided on the free end  47  of the wiper arm  48 ; it cooperates in the manner of a joint with a support point that is present in the connection device  44 . The wiper arm  48  and thus the wiper blade  40  as well are urged in the direction of the arrow  52  toward the window  43  to be wiped, whose surface to be wiped is represented in  FIG. 2  by the dot-dash line  54 . Since the dot-dash line  54  is meant to represent the greatest curvature of the window surface, it is quite clear that the longitudinal curvature of the still-unloaded wiper blade, resting with its ends on the window, is greater than the maximum window curvature. That is—unloaded—it has a concave course facing the window. On the convex outer top side  43  of the support element  42 , the connection device  44  is seated, while on the concave inner underside  49  of the support element  42 , the wiper strip  46  is disposed, with its wiper lip  56  that performs the wiping work. In response to the contact pressure (arrow  52 ), the wiper blade  40 , with its wiper lip  56 , presses over its entire length against the window surface  50  and changes over into a working position that approximates the extended position. In this process a tension builds up in the bandlike, spring-elastic support element  42 , and this tension provides for a proper contact between the wiper strip  46 , or its wiper lip  56 , over its entire length with the motor vehicle window  54  and thus assures a prescribed distribution of the contact pressure. 
   The particular features of the wiper blade  40  of the invention will now be addressed in further detail. In a first embodiment ( FIGS. 4 and 5 ), the wiper blade  40  is provided with a striplike mass body  60 , which extends in the longitudinal direction of the support element  42 . The mass body  60  is disposed in the region of the upper band face  43 , remote from the window, of the support element  42 . In the exemplary embodiment, the support element  42  has two spaced-apart, parallel spring rails  41 , extending in the same plane, which rest in laterally peripherally open longitudinal grooves  62  of the wiper strip  46 . The wiper strip  46  has a base body  64  of substantially square cross section, with the wiper lip  56  located on its lower side, the side toward the window. The wiper lip  56  itself is connected to the base body  64  via a narrow tilting rib  66 . The base body  64  has the two longitudinal grooves  62 , laterally open on the periphery, for the spring rails  41  of the support element  42 . The wiper strip, or its base body  64 , extends with an extension  68  through the gap between the two spring rails  41 , and this gap changes over, at the upper band face  43  of the support element  42 , into a bandlike base strip  70 . On the top side, remote from the support element, of the base strip  70 , this strip changes over, because of the disposition of two laterally peripherally open longitudinal grooves, into a narrow articulated strip  72 , which likewise extends longitudinally of the wiper blade  18 . Thus the wiper strip  46  includes the base body  64 , with its extension  68  and the base strip  70 ; the tilting rib  66 ; the wiper lip  56  that performs the wiping work; the articulated strip  72 ; and the mass body  60 . The mass body  60  spaced apart from the base body  64 , or from its base strip  70 , on the articulated strip  72 , or else the mass body is integrally joined to the base body  64  via the articulated strip  72 . Since the articulated strip  72  thus likewise comprises a rubber-elastic material, the mass body  60  is disposed movably in the displacement direction of the wiper blade (double arrow  74 ), so that it can oscillate over a certain angle about the articulated strip  72 . This oscillating motion is represented in  FIG. 5  by a double arrow  76 . The mass body itself is represented in  FIG. 5  in its two terminal vibration positions by dot-dash lines. 
   Now if during wiper operation—in which the wiper blade  18  is displaced transversely to its length in the direction of the double arrow  74  ( FIG. 4 ) over the window  54 —and if for instance because of the aforementioned circumstances the sliding motion of the wiper blade changes into a chattering motion, then the mass body  60  is put into a vibrating motion (double arrow  76 ) that is chronologically opposite the chattering motion, so that the chattering vibrations are suppressed near their origin. This is true especially if the magnitude of the mass of the mass body  60  and the dimensioning of the articulated strip  72  are adapted to the criteria of the particular application of the wiper blade. Hence the chattering vibrations cannot be propagated via the wiper arm to the gear and to the drive motor of the wiper system, so that even these drive components of the wiper system are not induced to vibrate and thus cause noise. An especially advantageous feature of the invention is considered to be that the mass body  60  is embodied as a spoiler. To that end, on its long side that during wiper operation is oriented toward the primary air flow (arrow  78 ), the mass body has a hollow throat  80 , which counteracts the forces that seek to lift the wiper blade, especially at vehicle speeds. The length of the mass body embodied as a spoiler depends on the particular vehicle-specific conditions. It can be seen from  FIGS. 2 and 3  that the mass body  60  has two partial mass bodies  61 , which are disposed one on each side of the connection device  44 . 
   The location of the center of gravity of the mass body relative to the longitudinal axis of the center of gravity relative to the articulated strip  72  can also contribute substantially to an effective elimination of the chattering vibrations. Two examples of this are shown in  FIGS. 6 and 7 . Since the two exemplary embodiments differ from the exemplary embodiment already described, shown in  FIGS. 4 and 5 , only in terms of the cross-sectional shape, the reference numerals used for the above exemplary embodiment are used here as well—where necessary. In the compact cross-sectional shape of  FIG. 6 , the result is a center of gravity line of the mass body  160 , embodied as a spoiler, whose effective spacing  162  from the articulated strip  72  is relatively slight. 
   Conversely, the effective spacing  262  from the articulated strip  72  in the embodiment, also in the form of a spoiler, of  FIG. 7  is relatively great. This is due to the fact that in the exemplary embodiment of  FIG. 7 , the mass body  260 , viewed in cross section, is provided with an enlargement  264  on its free end remote from the extension  68 . 
   In a departure from the exemplary embodiments described above, in which the wiper strip  46  has three striplike regions integrally joined to one another—that is, the base body  64 , wiper lip  56 , and mass body strip  60 ,  160  and  260 —in the embodiment of  FIG. 8  the mass body strip  360  of the wind strip  346  is made of a different material from the base body strip  364  with its wiper lip  56 . The connecting seam between the base body strip  364  and the mass body strip  360  is identified in  FIG. 8  by reference numeral  362 . In this embodiment as well, the mass body strip  360  is embodied as a spoiler. Because of this particular design, it is possible to optimize the choice of materials in such a way that the mass body strip  360 , for instance, is stiffer than the base body strip  364  with its wiper lip  56 . 
   In the embodiment of  FIG. 9  as well, the mass body strip  460  embodied as a spoiler is made from a different material from the base body strip  464 . The connecting seam is identified there by reference numeral  462 . Furthermore, the wiper lip  456  is likewise of a different material from the base body strip  464 . The connecting seam between the base body strip  464  and the wiper lip  456  is identified in  FIG. 9  by reference numeral  463 . Along with the advantage, already mentioned, of the stiffening of the mass body strip  460  relative to the base body strip  464 , for instance, it is also possible in this embodiment for the wiper lip strip  456  to be further optimized in terms of the choice of material, with a view to the results of wiping sought. 
   A common feature of the embodiments of  FIGS. 10 ,  11  and  FIGS. 12 and 13  is that a spoiler embodied as an elongated hollow body is formed onto the extension  68 , or onto the base strip  70  adjoining the extension of the wiper strip, or of the base body  64 , in the cavity of which hollow body, the mass body is located—protected against the oncoming flow of air—the mass body being joined to the extension or to the base strip and being movable in the displacement direction of the wiper blade. From  FIG. 10  it can be seen that the spoiler  500  embodied as a hollow body surrounds the striplike mass body  560  with spacing. The spoiler has two legs  502 ,  503 , diverging from an apex line  501 , and the ends of the legs change over, near the support element  42 , to the base strip  570 . In  FIG. 11 , the two terminal positions of the vibrating motion of the mass body  560  are indicated by dot-dash lines. In dimensioning the mass body, or the spoiler  500  embodied as a hollow body, care must be taken to assure that the mass body strip  560  is not restricted in terms of its freedom of motion by the legs  502 ,  503  of the spoiler  500 . If the mass body strip were to strike the inner walls of the legs, the result would be further uncontrollable vibrations in the wiper blade. 
   In the embodiment of  FIG. 12 , the spoiler  600  is made from a different material from the wiper strip, with its base body strip  64 , wiper lip strip  56 , and mass body strip  560 . The resultant connecting seams are identified in  FIG. 12  by reference numeral  605 . 
   The embodiment of  FIG. 13  is substantially equivalent to that of  FIG. 12 ; once again, the spoiler  700  is of a different material from the base body strip  64  with its wiper lip strip  56 . However, in the embodiment of  FIG. 13 , the mass body strip  760  is formed of a different material from the base body strip  64  and/or from the spoiler  700 . The resultant connecting seam is identified in  FIG. 13  by reference numeral  707 . 
   It is a common feature of all the embodiments proposed here for the invention that they can be produced by the economical extrusion process. For the embodiments of  FIGS. 8 and 12 , so-called dual-substance extrusion is attractive, while for the embodiment of  FIGS. 9 and 13 , so-called multiple-substance extrusion is advantageous. 
   Another substantial common feature of all the described embodiments of the invention is considered to be that in the region of the upper band face  43 , remote from the window, of the support element  42 , the wiper blade  40  is provided with a mass body  60 ,  160 ,  260 ,  360 ,  460 ,  560 ,  660 , or  760 , which is disposed movably at least in the displacement direction (double arrow  74 ) of the wiper blade.