The invention relates to a wiper blade for cleaning windshields of motor vehicles.
The wiper strips which are a part of the wiper blade which serves to remove water drops from the windshield of a motor vehicle, for example, and which are attached to the wiper blades of a wiper blade device that move back and forth in front of the windshield, are customarily produced, in that a previously compounded and vulcanized initial rubber material, therefore an un-vulcanized synthetic caoutchouc, is shaped in a metal mold and vulcanized. Subsequently the surface of the thus obtained rubber wiper strip is post-treated in order to reduce the friction resistance on the windshield to be wiped in accordance with the requirements, or to improve the slidability of the rubberized wiper strip on the windshield to be wiped. At a temperature t of 23.degree..+-.5.degree. C. and a relative humidity of 50.+-.3%, the desired coefficient of friction A may not exceed the value of 2.0. This post-treatment of the surface consists for example of a hardening of the surface of the rubberized wiper strip by chlorination or of a coating, in order to achieve a surface layer of the wiper strip which contains a fine, lubricating powder, for example powder-like molybdenum sulfide. Even though the chlorination reduces the friction resistance and improves the slidability, the necessary durability for wear and tear is still missing. The application of a lubricating surface layer containing powder presents the disadvantage in that it is scraped off after the wiper strip has been in use for a short period of time, thus lacking the necessary durability.
Incidentally, it should be considered that the improvement of the sliding properties of the wiper strips because of the reduced friction coefficient between the wiper strip and the glass surface of the windshield presents difficulties in that they do not tilt in the tilting bar when the wiper blade reverses directions during the operation of the wiper blade device which is normally embodied as pendular wiping device, so that the wiper strip is not dragged but pushed. A flawless, noiseless operation of the wiper blade device is thus ruled out.
To overcome this problem, in connection with a known wiper blade (DE 34 40 677 A1) of the species in question, the areas of the wiper strip which come into contact with the windshield during the wiper blade operation were made of a lubricating synthetic rubber, for example urethane rubber, styrene butadiene rubber, fluoro rubber, chlorinated sulfonized rubber or a mixture of these materials. However, such wiper strips are not, or are only insufficiently halogenizable, so that the desired coefficient of friction can hardly be reached.