Wiper blade for a windshield wiper

In a wiper blade (100) for a windshield wiper, having a wiping strip (112) on which there is arranged at least one supporting rail (214) which has a spring element (215) provided with a plastic sheath (217), wherein the plastic sheath (217) is welded, at least in a predefined connecting region (180), to a base connecting device (160) which comprises thermoplastic material having a predefined melting point, the plastic sheath (217) comprises at least a first and a second thermoplastic material.

REFERENCE TO RELATED APPLICATIONS

This application is a 371 of PCT/EP2011/051700, filed Feb. 7, 2011, which claims the benefit of German Patent Application No. 10 2010 003 645.5, filed Apr. 6, 2010, each of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention concerns a wiper blade for a windshield wiper having a wiping strip on which there is arranged at least one supporting rail which has a spring element provided with a plastic sheath, wherein the plastic sheath is welded, at least in a predefined connecting region, to a base connecting device which comprises a thermoplastic material with a predefined melting point.

EP 1 359 073 B1 describes such a wiper blade with a wiping strip which on its long sides has opposing longitudinal grooves in which are arranged, spaced apart, longitudinal strips of a carrier element, wherein adjacent ends of the longitudinal strips are joined together by means of a connecting piece. Engagement elements of a connecting device are welded to the long sides of longitudinal strips facing away from each other such that they resist shear forces in a direction along the longitudinal strips. This connecting device and the engagement elements comprise a piece of a thermoplastic material and the longitudinal strips are provided with a sheath formed from this thermoplastic material.

The disadvantage with this prior art is that e.g. due to slipping of one of the longitudinal strips or both longitudinal strips relative to the wiping strip before a corresponding welding process, the engagement elements of the connecting device can be welded to the longitudinal strip or strips at an incorrect position.

SUMMARY OF THE INVENTION

One object of the invention is therefore to provide a new wiper blade for a windshield wiper, in which welding of an allocated base connection device in an incorrect position on the corresponding supporting rail of the wiper blade can be avoided.

This problem is solved by a wiper blade for a windshield wiper having a wiping strip on which there is arranged at least one supporting rail which has a spring element provided with a plastic sheath. The plastic sheath is welded, at least in a predefined connecting region, to a base connecting device which comprises a thermoplastic material with a predefined melting point. The plastic sheath comprises at least one first and one second thermoplastic material.

The invention thus allows the provision of a wiper blade with a supporting rail to which the base connecting device can be welded substantially exclusively in predefined positions in which e.g. the plastic sheath comprises the second thermoplastic material.

The problem cited initially is also solved by a wiper blade for a windshield wiper having a wiping strip on which there is arranged at least one supporting rail which has a spring element provided with a plastic sheath. The plastic sheath comprises a thermoplastic material with a predefined melting point and is welded, at least in a pre-specified connecting region, to a base connecting device. The base connecting device comprises at least one first and one second thermoplastic material.

The invention thus allows the provision of a simple and economic base connecting device which can be welded safely and reliably to the supporting rail of the wiper blade.

Preferably a first melting point is allocated to the first thermoplastic material and a second melting point which is lower than the first melting point is allocated to the second thermoplastic material.

Thus in a corresponding welding process in production of the wiper blade, on melting of the second thermoplastic material, melting of the first thermoplastic material can be safely and reliably prevented.

The second melting point and the predefined melting point preferably lie within a predefined temperature range which lies below the first melting point.

Thus in a simple manner the thermoplastic material with the predefined melting point and the second thermoplastic material can be melted and welded together in a corresponding welding process, wherein the melting of the first thermoplastic material is safely and reliably prevented.

The second melting point and the predefined melting point are preferably approximately the same.

Thus a precise and stable melting and welding of the thermoplastic material with the predefined melting point with the second thermoplastic material can be guaranteed.

According to one embodiment the first melting point is determined such that on melting of the thermoplastic material with the predefined melting point and the second thermoplastic material, a melting of the first thermoplastic material can be avoided.

Thus an undesirable welding of the thermoplastic material with the predefined melting point with the first thermoplastic material can be effectively prevented.

The thermoplastic material with the predefined melting point and the second thermoplastic material preferably have a substantially corresponding composition.

Thus a simple and economic design of the at least one supporting rail and the base connecting device can be achieved.

According to one embodiment the supporting rail is welded to the base connecting device by ultrasound welding in the predefined connecting region.

Thus the supporting rail can be safely and reliably welded to the base connecting device.

On the base connecting device is preferably attached an adapter unit for hinging of the wiping strip on a wiper arm, which unit is formed to connect with a connecting element allocated to the wiper arm.

Thus the wiping strip can easily be connected with the wiper arm.

The problem cited initially is also solved by a supporting rail for a wiper blade which has a spring element provided with a plastic sheath. The plastic sheath comprises at least one first and one second thermoplastic material.

The problem cited initially is also solved by a base connecting device for a wiper blade which can be welded to a supporting rail of the wiper blade. The base connecting device comprises at least one first and one second thermoplastic material.

DETAILED DESCRIPTION

FIG. 1shows a wiper blade100with a wiping strip112which comprises a wiper lip129connected via a rocker web127with a back strip124. On the back strip124is provided a spoiler125. On the wiping strip112is provided a base connecting device160, to which is attached an adapter unit150for connection of a connecting element190allocated to a wiper arm118. The connecting element190inFIG. 1is connected to the adapter unit150as an example via a hinge bolt169. By means of the wiper arm118the wiper blade100can be guided to wipe over a windshield122shown in dotted lines e.g. a motor vehicle windshield.

It is however pointed out that the design of the wiper blade100with base connecting device160and adapter unit150for connection of the connecting element190has merely an exemplary character and should not be regarded as a restriction of the invention. Rather alternative embodiments are also possible which again lie within the scope of the present invention, e.g. the base connecting device160and the adapter unit150can be formed as one piece or the adapter unit150and the connecting element190can be formed as one piece.

According to one embodiment, the wiper blade100is formed in the manner of a flat bar, i.e. the wiping strip112has lateral longitudinal grooves (202,204inFIG. 2) in which are arranged two supporting rails (212,214inFIG. 2), preferably spring rails, as described for example below with reference toFIG. 2. Alternatively the wiping strip112can be formed as a hollow profile with an approximately central longitudinal channel (425inFIG. 4) in which is arranged a single supporting rail (414inFIG. 4), as described below as an example with reference toFIG. 4.

The wiping strip112with the base connecting device160provided thereon is formed preferably hinge-free, wherein the base connection device160is preferably pre-mounted on the wiping strip112. According to one embodiment the base connection device160is welded to the supporting rails (212,214inFIG. 2) by a suitable welding process, e.g. an ultrasound welding process, at least in a predefined connecting region180which is predefined for example by an axial extent of the base connecting device160, as described below with reference toFIG. 2.

InFIG. 1the wiper blade100is not placed completely against the windshield122; only its axial wiper blade ends121,123lie against the windshield122while the wiping strip112in the wiper blade center126, i.e. approximately in the region of the adapter unit150, is still spaced from the windshield122. If via the wiper arm118a specified contact force is applied to the connecting element190and hence the adapter unit150, the wiping strip112lies against the windshield122. Here an even contact pressure is achieved over the entire wiper blade length even if the screen curvature changes in the course of the wiping movement.

FIG. 2shows a section view of the wiper blade100with the wiping strip112and the adapter unit150ofFIG. 1in the direction of the arrows marked II inFIG. 1, according to one embodiment before a corresponding welding process. The adapter unit150has approximately an inverted U-shaped structure with wall segments250,251, on which are formed illustratively hook-like engaging teeth254and252via which the adapter unit150engages on the base connecting device160. It is however pointed out that the engagement of the adapter unit150on the base connecting device160has merely an exemplary character and does not serve as a restriction of the invention. Rather the adapter unit150can be attached to the base connecting device160in any arbitrary manner e.g. by welding or bonding.

The base connecting device160preferably comprises at least one thermoplastic material with a predefined melting point and illustratively has two lateral retaining elements220,240which at least in segments surround, in the manner of a claw, the allocated supporting rails212and214arranged approximately parallel to each other. The supporting rails212,214are arranged in longitudinal grooves202,204formed in the back strip124of the wiping strip112. The supporting rails212,214at their axial ends can thus be connected together e.g. via suitable end caps, as adequately known to the person skilled in the art.

According to one embodiment the supporting rails212,214each have a spring element219and215provided with a plastic sheath213and217. The spring element219,215can e.g. be formed of hardened steel, titanium, aluminum and/or plastic. The plastic sheath213,217preferably comprises at least one first and one second thermoplastic material, wherein the second thermoplastic material is provided at least in the predefined connecting region180and serves for welding of the plastic sheath213and217to the thermoplastic material of the base connecting device160, as described below and with reference toFIG. 3.

On the retaining elements220,240of the base connecting device160, for simplification and improvement of a corresponding welding process, energy directors224and244are formed. These are pressed, preferably sprung, by the retaining elements220,240against the supporting rails212and214in the direction of an arrow290.

To attach the base connection device160to the supporting rails212,214, energy is introduced into the predefined connecting region180e.g. by means of ultrasound, such that first the energy directors224and244melt and then the second thermoplastic material provided on the supporting rails212and214and the thermoplastic material of the base connecting device160. These then fuse together and weld the base connecting device160to the supporting rails212,214in the predefined connecting region180.

According to one embodiment the first thermoplastic material has a first melting point and the second thermoplastic material has a second melting point which is lower than the first melting point, wherein the second melting point and the predefined melting point of the thermoplastic material of the base connecting device160lie within a predefined temperature range which lies below, preferably substantially below, the first melting point. Preferably the second melting point and the predefined melting point are approximately the same. To simplify the description, the first melting point is referred to below as the “high” melting point while the second and the predefined melting points are referred to below as the “low” melting point.

The high melting point is preferably determined such that on melting of the thermoplastic material with the predefined low melting point and of the second thermoplastic material, melting of the first thermoplastic material is avoided. Preferably the thermoplastic material with the predefined low melting point and the second thermoplastic material are formed substantially correspondingly or at least have a similar or approximately the same composition.

It is however pointed out that the embodiment described inFIG. 2has merely an exemplary character and should not be regarded as a restriction of the invention. Many deviations and modifications are possible within the context of the present invention. For example the plastic sheath213,217of the supporting rails212,214can be formed from the thermoplastic material with the predefined low melting point, while the base connecting device160comprises the first and second thermoplastic materials described above, wherein the second thermoplastic material is preferably provided on a segment of the base connecting device160facing the connecting region180. In addition e.g. the energy directors224,244can be formed on the plastic sheath213,217of the supporting rails212and214instead of on the retaining elements220and240of the base connecting device160as shown inFIG. 2.

FIG. 3shows the supporting rail214with the spring rail215and the plastic sheath217ofFIG. 2which, according to one embodiment, is formed from a co-extrusion of the first and second thermoplastic material. The spring rail215illustratively has two opposing upper and lower wide sides302,304and two opposing left and right narrow sides303,305which are enclosed by the plastic sheath217.

According to one embodiment a first region340of the plastic sheath217which comprises approximately the upper wide side302, the left and right narrow sides303,305and at least segments of the lower wide side304, is sheathed by the first thermoplastic material with the high melting point. The second thermoplastic material with the low melting point is provided in a region350not sheathed by the first thermoplastic material on the lower wide side304, which in dimensions corresponds approximately to the predefined connecting region180.

It is however pointed out that the formation of the second thermoplastic material on the lower wide side304has merely exemplary character and should not be regarded as a restriction of the invention. Rather the second thermoplastic material can be provided at any arbitrary predefined point on the supporting rail214to which the base connecting device160ofFIG. 2is to be welded, e.g. at the narrow sides303and305and/or at the upper wide side302.

FIG. 4shows a wiping strip412according to an alternative embodiment which can also be used in the wiper blade100ofFIG. 1. The wiping strip412has a back strip424formed as a hollow profile with an approximately central longitudinal channel425in which is arranged a single supporting rail414.

The supporting rail414illustratively has a spring rail415provided with a plastic sheath417, which rail is made e.g. of hardened steel, titanium, aluminum and/or plastic. The plastic sheath417is formed for example similarly to the plastic sheath217ofFIG. 3and also comprises the regions340,350.

The wiping strip412illustratively has one or more recesses450on its back strip424. An allocated base connection device (e.g. base connecting device160ofFIG. 1) has suitable engagement elements (e.g. retaining elements220,240ofFIG. 2) which can surround the supporting rail414at least in segments through the recesses450in order, according to one embodiment, to allow a welding of the supporting rail414with the allocated base connecting device as described above with reference toFIG. 2.