Abstract:
The invention relates to a wiper blade for a windscreen wiper, comprising a wiper strip on which at least one support rail ( 312, 314 ) is disposed, wherein said support rail has a spring element ( 412, 415 ) provided with a plastic sheath ( 313, 315 ), and further comprising a base connection device ( 160 ), which includes plastic and is welded to plastic sheath ( 313, 315 ), wherein a flat weld seam ( 419, 421 ) is formed between the base connection device ( 160 ) and the at least one support rail ( 312, 314 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a wiper blade for a windscreen wiper, having a wiper strip, on which at least one loadbearing rail is arranged which has a spring element which is provided with a plastic covering, and having a base connection device which has plastic and is welded to the plastic covering. 
         [0002]    U.S. Pat. No. 7,523,522 B2 describes a wiper blade of this type having a base connection device which has a plate-shaped carrier part with holding claws which are formed integrally thereon. The holding claws engage round associated loadbearing rails of the wiper blade at least in sections. Four cylindrical depressions are formed in the plate-shaped carrier part, into which cylindrical depressions cylindrical welding tools, what are known as rod-shaped sonotrodes, can be introduced in order to weld the base connection device to the loadbearing rails by means of ultrasonic welding. Said rod-shaped sonotrodes make punctiform welding of the loadbearing rails to the holding claws and the underside of the plate-shaped carrier part in the region of the cylindrical depressions possible. 
         [0003]    A disadvantage of said prior art is that the welding takes place only at four predefined welded points and is therefore problematic in the event of the occurrence of shear forces in a direction along the loadbearing rails. Moreover, the punctiform shape of a weld of this type prevents optimum transmission of the forces of a corresponding wiper arm to a wiper strip which is assigned to the wiper blade and therefore to the wiper lip of said wiper strip. In particular, this shape of the weld has a negative influence on the bearing force distribution of the wiper lip on an associated pane, which bearing force distribution is decisive for a desired wiping result. 
       SUMMARY OF THE INVENTION 
       [0004]    It is therefore an object of the invention to provide a novel wiper blade for a windscreen wiper, in which wiper blade an improved bearing force distribution for a wiper lip which is assigned to the wiper blade on a pane can be achieved. 
         [0005]    This problem is solved by a wiper blade for a windscreen wiper, having a wiper strip, on which at least one loadbearing rail is arranged which has a spring element which is provided with a plastic covering, and having a base connection device which has plastic and is welded to the plastic covering. A flat welded seam is formed between the base connection device and the at least one loadbearing rail. 
         [0006]    The invention therefore makes it possible to provide a wiper blade which makes an improved force transmission from an associated wiper arm to the wiper strip or a wiper lip which is assigned to the wiper blade possible, with a comparatively low spread of pull-off forces. 
         [0007]    According to one embodiment, the flat welded seam extends in a substantially tape-like manner over a longitudinal extent which is assigned to the base connection device. 
         [0008]    Stable welding of the base connection device to the loadbearing rail can therefore be achieved, in order to obtain an improved bearing force distribution. 
         [0009]    The at least one loadbearing rail is preferably formed in a tape-like manner with broad sides and narrow sides. The flat welded seam is preferably formed on one of the broad sides. 
         [0010]    Comparatively large-area welding of the base connection device to the loadbearing rail can therefore be achieved. 
         [0011]    According to one embodiment, the base connection device has a basic body, on which lateral holding members are provided which engage in a claw-like manner at least in sections around the at least one loadbearing rail. 
         [0012]    The invention therefore makes it possible to provide a simple and stable base connection device. 
         [0013]    The flat welded seam is formed between a broad side, facing away from the basic body, of the at least one loadbearing rail and a connecting section, facing the loadbearing rail, of the lateral holding member. 
         [0014]    Secure and reliable fastening of the base connection device to the loadbearing rail can therefore be achieved. 
         [0015]    According to one embodiment, the basic body has at least one through-passage opening which is formed for making it possible to guide a welding tool through the basic body as far as the at least one loadbearing rail during welding of the base connection device to the plastic covering of the at least one loadbearing-rail. 
         [0016]    The invention therefore makes precise energy transfer possible in the region of the through-passage opening for melt generation, and therefore makes defined and controlled melt generation possible in this region. 
         [0017]    The at least one loadbearing rail is preferably welded to the base connection device by ultrasonic welding. 
         [0018]    The loadbearing rail can therefore be welded to the base connection device comparatively quickly and reliably. 
         [0019]    An adapter unit which has plastic is preferably welded to the base connection device in order to articulate the wiper strip on a wiper arm. The adapter unit is preferably configured for connection to a connection member which is assigned to the wiper arm. 
         [0020]    The wiper strip can therefore be connected to the wiper arm in a simple way. 
         [0021]    The adapter unit preferably has at least one projection which engages into the at least one through-passage opening. 
         [0022]    A stable connection can therefore be achieved between the adapter unit and the base connection device, the loadbearing rail being held down in a simple way during operation of the wiper blade. 
         [0023]    The problem which is mentioned at the outset is also solved by a base connection device for a wiper blade, which base connection device has plastic and can be welded to a plastic covering of a loadbearing rail of the wiper blade. The base connection device has a basic body, on which lateral holding members are provided which in each case have at least one energy direction transmitter and are configured for engaging in a claw-like manner at least in sections around the loadbearing rail in such a way that the energy direction transmitters face a broad side of the loadbearing rail. The basic body has at least one through-passage opening which is formed for making it possible to guide a welding tool through the basic body as far as the loadbearing rail during welding of the base connection device to the plastic covering of the loadbearing rail in order to produce a flat welded seam by melting the energy direction transmitters. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The invention is explained in greater detail in the following description using exemplary embodiments which are shown in the drawings, in which: 
           [0025]      FIG. 1  shows a side view of a wiper blade having a wiper strip, to which a base connection device is fastened by means of ultrasonic welding, according to one embodiment, 
           [0026]      FIG. 2  shows a partially sectioned front view of the base connection device of  FIG. 1 , in the direction of the arrow II of  FIG. 1 , 
           [0027]      FIG. 3  shows a perspective view of the base connection device of  FIG. 2 , when welded to associated loadbearing rails, and 
           [0028]      FIG. 4  shows a partially sectioned view of the base connection device of  FIG. 3  which is welded to the loadbearing rails, with the adapter unit of  FIG. 1 , in the direction of the arrow IV of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIG. 1  shows a wiper blade  100  having a wiper strip  112  which has a wiper lip  129  which is connected to a rear strip  124  via a tilting web  127 . A spoiler  125  is provided on the rear strip  124 . A base connection device  160  is provided on the wiper strip  112 , to which base connection device  160  an adapter unit  150  is fastened in order to connect a connection member  190  which is assigned to a wiper arm  118 . In  FIG. 1 , the connection member  190  which is also called a holding spring is connected by way of example via a joint pin  169  to the adapter unit  150  which is also called a functional adapter. With the aid of the wiper arm  118 , the wiper blade  100  can be guided for wiping purposes over a pane  122 , for example a motor vehicle pane, which is shown in a dash-dotted manner. 
         [0030]    It is noted, however, that the design of the wiper blade  100  with base connection device  160  and adapter unit  150  for connection of the connection member  190  is of merely exemplary character and is not to be understood as a restriction of the invention. Rather, alternative designs are also possible which likewise fall under the scope of the present invention; for example, the base connection device  160  and the adapter unit  150  can be configured in one piece or the adapter unit  150  and the connection member  190  can be configured in one piece. Moreover, the spoiler  125  is also optional, with the result that the present invention can also be used in wiper blades without a spoiler. 
         [0031]    According to one embodiment, the wiper blade  100  is configured in the flat bar design, that is to say the wiper strip  112  has lateral longitudinal grooves, in which two loadbearing rails ( 312 ,  314  in  FIG. 3 ), preferably spring bars, are arranged, as will be described below by way of example with respect to  FIG. 3 . Here, the loadbearing rails ( 312 ,  314  in  FIG. 3 ) can be connected to one another at their axial ends, for example via suitable end caps. As an alternative to this, the wiper strip  112  can be configured as a hollow profile with an approximately central longitudinal channel, in which a single loadbearing rail is arranged. Wiper blades of this type and their designs are sufficiently well known to a person skilled in the art, with the result that a detailed description is omitted here for the purpose of conciseness of the description. 
         [0032]    The wiper strip  112  with the base connection device  160  provided on it is preferably of joint-free configuration, the base connection device  160  preferably being premounted on the wiper strip  112 . According to one embodiment, the base connection device  160  is welded to the loadbearing rails ( 312 ,  314  in  FIG. 3 ) by way of a suitable welding operation, for example an ultrasonic welding operation, and the adapter unit  150  is welded to the base connection device  160 , as will be described below with respect to  FIGS. 3 and 4 . To this end, the base connection device  160  and the adapter unit  150  have plastic and can be configured as plastic parts, for example by means of plastic injection molding. 
         [0033]    In  FIG. 1 , the wiper blade  100  has not yet been placed completely onto the pane  122 ; only its axial wiper blade ends  121 ,  123  bear against the pane  122 , whereas the wiper strip  112  is still spaced apart from the pane  122  in the wiper blade center  126 , that is to say approximately in the region of the adapter unit  150 . If a provided pressing force is exerted on the connection member  190  and therefore the adapter unit  150  via the wiper arm  118 , the wiper strip  112  comes to bear against the pane  122 , a uniform contact pressure being achieved over the entire wiper blade length, even if the pane curvature changes during the course of the wiping movement. Here, a bearing force distribution of the wiper strip  112  and of the wiper lip  129  on the pane  122  is achieved, which bearing force distribution is dependent on a shape which is introduced into an associated welded seam ( 419 ,  421  in  FIG. 4 ) during the welding of the base connection device  160  to the loadbearing rails ( 312 ,  314  in  FIG. 3 ), as will be described below with respect to  FIG. 4 . 
         [0034]      FIG. 2  shows a partially sectioned front view of the base connection device  160  of  FIG. 1  according to one embodiment. It has, by way of example, a basic body  290 , on which lateral holding members  220 ,  240  are provided, for example are integrally molded. 
         [0035]    By way of example, two elongate through-passage openings  222 ,  242  are formed in the basic body  290 . By way of illustration, three optional, elongate energy direction transmitters  282 ,  284 ,  286  are provided on an upper side  250  of the basic body  290 , which energy direction transmitters  282 ,  284 ,  286  are used during welding of the of the base connection device  160  to the adapter unit  150  of  FIG. 1 , as will be described below with respect to  FIG. 4 . 
         [0036]    By way of illustration, the lateral holding member  220  extends in an L-shaped manner starting from the basic body  290 , and forms a groove  229  with the latter. According to one embodiment, the lateral holding member  220  has a lateral wall section  225  and a lower connecting section  226 , on the upper side  227  of which, which faces the basic body  290 , an elongate energy direction transmitter  224  is provided. 
         [0037]    Relative to the holding member  220 , the lateral holding member  240  extends in an approximately horizontally mirrored L-shaped manner starting from the basic body  290 , and forms a groove  249  with the latter. According to one embodiment, the lateral holding member  240  has a lateral wall section  245  and a lower connecting section  246 , on the upper side  247  of which, which faces the basic body  290 , an elongate energy direction transmitter  244  is provided. 
         [0038]    According to one embodiment, the base connection device  160  is produced by means of plastic injection molding, as has been described above with respect to  FIG. 1 . Here, the energy direction transmitters  224 ,  244  can be formed by a core puller which reaches through the through-passage openings  222  and  242  or suitable contours of a corresponding injection molding die with the specification of a desired shape which cannot be produced in this way starting from the lateral wall sections  225 ,  245  of the holding members  220  and  240 , for example in the shape of a pyramid. 
         [0039]    By way of illustration,  FIG. 3  shows the base connection device  160  of  FIG. 2 , when welded to exemplary loadbearing rails  312 ,  314  of the wiper blade  100  of  FIG. 1 , and clarifies the elongate through-passage openings  222 ,  242  of  FIG. 2  which can extend almost completely over a longitudinal extent  399  of the base connection device  160 . In the context of the present invention, this means that the through-passage openings  222 ,  242  can have a length  398  which is preferably as great as possible relative to the longitudinal extent  399 , but does not compromise the functionality of the base connection device  160 . 
         [0040]    According to one embodiment, the base connection device  160  is arranged on the wiper strip  112  in such a way that its holding members  220 ,  240  engage in a claw-like manner at least in sections around the loadbearing rails  312  and  314  which are provided with plastic coverings  313 ,  315 , with the result that the energy direction transmitters ( 224  and  244  in  FIG. 2 ) which are provided on the holding members  220 ,  240  in each case face a broad side ( 463 ,  473  in  FIG. 4 ), facing away from the basic body  290 , of the loadbearing rail  312  and  314 . Here, by way of example, the loadbearing rail  312  is arranged in the groove  229  and the loadbearing rail  314  is arranged in the groove  249  of the base connection device  160 . 
         [0041]    Moreover, as has been described with respect to  FIG. 1 , the loadbearing rails  312 ,  314  are arranged in associated lateral longitudinal grooves of the wiper strip  112  of  FIG. 1 , which longitudinal grooves are formed, for example, on the rear strip  124  of said wiper strip  112 . The rear strip  124  is shown in  FIG. 3  only diagrammatically for the purpose of clarity and conciseness, whereas an illustration of the remaining wiper strip components has been dispensed with in order to simply the drawing. 
         [0042]    In order to weld the base connection device  160  to the plastic covering  313 ,  315  of the loadbearing rails  312  and  314 , elongate welding tools  293 ,  295  are introduced, by way of example, into the elongate through-passage openings  222  and  242  in the direction of an arrow  299 . Here, the welding tools  293 ,  295  are preferably guided through the basic body  290  as far as the loadbearing rails  312 ,  314  in order to produce a flat welded seam ( 419 ,  421  in  FIG. 4 ) by melting the energy direction transmitters ( 224 ,  244  of  FIG. 2 ). 
         [0043]    According to one embodiment, the base connection device  160  is welded to the loadbearing rails  312 ,  314  or their plastic coverings  313  and  315  by ultrasonic welding. Here, what are known as blade sonotrodes with curved and rounded or straight and flattened base faces are used as welding tools  293 ,  295 . 
         [0044]      FIG. 4  shows a partially sectioned view of the base connection device  160  of  FIG. 2  which is welded to the loadbearing rails  312 ,  314  of  FIG. 3  of the wiper strip  112  of  FIG. 1 . It is noted, however, that, for the purpose of simplification and clarity of the drawing, a complete depiction of the wiper strip  112  has been dispensed with and merely its rear strip  124  is indicated diagrammatically in sections. 
         [0045]    According to one embodiment, the loadbearing rails  312 ,  314  in each case have a spring element  412  and  415  which is provided with the plastic covering  313  and  315 . The spring elements  412 ,  415  are, for example, spring bars which are formed from flat or round wire and are configured, for example, from hardened steel, titanium or aluminum. As an alternative, the spring elements  412 ,  415  can be configured from plastic. 
         [0046]    The loadbearing rail  312  which is arranged in the groove  229  of the base connection device  160  is preferably of tape-like configuration and, by way of illustration, has an upper broad side  461 , a lower broad side  463 , a left-hand narrow side  464  and a right-hand narrow side  462 . In an analogous manner to this, the loadbearing rail  314  which is arranged in the groove  249  and is likewise preferably of tape-like configuration has, by way of illustration, an upper broad side  471 , a lower broad side  473 , a left-hand narrow side  474  and a right-hand narrow side  472 . 
         [0047]    According to one embodiment, at least the elongate energy direction transmitter  224  ( FIG. 2 ) which is provided on the connecting section  226  of the lateral holding member  220  of the base connection device  160  is melted off during an ultrasonic welding operation which is carried out as described in  FIG. 3 , in such a way that the plastic covering  313  of the loadbearing rail  312  and the melted-off energy direction transmitter  224  ( FIG. 2 ) form a flat welded seam  419  which connects the lower broad side  463  of the loadbearing rail  312  to the connecting section  226 . The flat welded seam  419  preferably extends at least over the length  398  ( FIG. 3 ) of the through-passage opening  222 . In other words, the flat welded seam  419  preferably extends in a substantially tape-like manner over the longitudinal extent  399  ( FIG. 3 ) which is assigned to the base connection device  160 . 
         [0048]    In an analogous manner to this, the elongate energy direction transmitter  244  ( FIG. 2 ) which is provided on the connecting section  246  of the lateral holding member  240  of the base connection device  160  is preferably melted off in such a way that the plastic covering  315  of the loadbearing rail  314  and the melted-off energy direction transmitter  244  ( FIG. 2 ) form a flat welded seam  421  which connects the lower broad side  473  of the loadbearing rail  314  to the connecting section  246 . The flat welded seam  421  preferably extends at least over the length  398  ( FIG. 3 ) of the through-passage opening  242 . In other words, the flat welded seam  421  preferably extends in a substantially tape-like manner over the longitudinal extent  399  ( FIG. 3 ) which is assigned to the base connection device  160 . 
         [0049]    Here, a desired profile of the welded seams  419  and  421  and therefore of the loadbearing rails  312  and  314  in the region of the base connection device  160  can have been formed by a suitable design of the blade sonotrodes  293 ,  295  of  FIG. 3  or of its base faces. The desired profile can be, for example, of rounded and curved or flattened and straight configuration. 
         [0050]    According to one embodiment, the adapter unit  150  of  FIG. 1  can be welded to the base connection device  160  after welding of the base connection device  160  to the loadbearing rails  312 ,  314 . By way of example, the adapter unit  150  has two projections  422 ,  442  on its underside  459 , which projections  422 ,  442  are configured for centering the adapter unit  150  on the base connection device  160 . Said projections  422 ,  442  have external dimensions which correspond approximately to the internal dimensions of the through-passage openings  222  and  242 . The projections  422 ,  442  divide the underside  459  in  FIG. 4  into three sections  451 ,  453 ,  455 , on which energy direction transmitters can be formed. By way of illustration, optional energy direction transmitters  452 ,  454  are formed on the sections  451 ,  455 . Moreover, one or more energy direction transmitters  482 ,  492  can also be formed on the projections  422 ,  442 . 
         [0051]    In order to weld the adapter unit  150  to the base connection device  160 , the projections  422 ,  442  are introduced in the direction of arrows  420 ,  440  into the through-passage openings  222  and  242  and therefore engage into the latter. The energy direction transmitters  452 ,  455 ,  282 ,  284 ,  286  are then melted off in a suitable welding operation, for example an ultrasonic welding operation or an alternative plastic joining process, for example laser plastic welding, with the result that the adapter unit  150  and the base connection device  160  are connected to one another in the region of the sections  451 ,  453 ,  455 . Here, melted plastic can flow by way of capillary action into gaps which occur between the projections  422 ,  442  and the through-passage openings  222  and  242  and therefore improve the attachment of the adapter unit  150  to the base connection device  160 . Moreover, the projections  422 ,  442  are welded to the plastic coverings  313  and  315  by melting off of the energy direction transmitters  482 ,  492  with simultaneous melting of the plastic coverings  313 ,  315  of the loadbearing rails  312  and  314  in the region of the energy direction transmitters  482 ,  492 , with the result that positively locking and substantially complete embedding of the loadbearing rails  312 ,  314  in the grooves  229  and  249  is achieved. 
         [0052]    It is noted that the above-described use of the energy direction transmitters  452 ,  455 ,  282 ,  284 ,  286  and  224 ,  244  of  FIG. 2  is merely exemplary in character and is not to be understood as a restriction of the invention which can likewise be carried out without the use of energy direction transmitters of this type. For example, a suitable, melting additional material can be used in each case during the welding for melt production. However, the use of the energy direction transmitters is advantageous, in order to achieve improved melt production during the welding.