WO2000020265A1

WO2000020265A1 - Wiper blade and stem with enhanced mechanical properties, and method for obtaining same

Info

Publication number: WO2000020265A1
Application number: PCT/FR1999/002279
Authority: WO
Inventors: Catherine Evo
Original assignee: Valeo Systemes D'essuyage Service Propriete Industrielle
Priority date: 1998-10-05
Filing date: 1999-09-24
Publication date: 2000-04-13
Also published as: FR2784069B1; FR2784069A1

Abstract

The invention aims at distributing uniformly the pressure so as to provide optimised homogeneous rigidity and resistance, for the heel and the hinge of the blade respectively. More particularly, the invention concerns a wiper stem (10) made of elastically deformable material, for example elastomer, and comprises a heel part (12) for being mounted on a wiper-holder, a scraping lip portion (16) for wiping in co-operation with the surface of a window pane to be wiped, and a hinge part (14) between the heel and lip portions. In the stem material, reinforcing fibres (18) provided with adhesive properties are incorporated with homogeneous fibre ratios in the hinge and the heel, the fibre ratio in the heel being not less than the fibre ratio in the hinge.

Description

Wiper blade and blade with improved mechanical properties, and method for obtaining such a blade

The invention relates to the field of wiping, and more particularly the wiper blades of a motor vehicle and the blades of these brushes.

The wiper blade, obtained by extrusion or by molding, is made of an elastically deformable material. The molding can be carried out from rubber blanks, by vulcanization or pre-vulcanization. The extruded or molded blade has three parts, successively succeeding along the median axis of the section of transverse symmetry of the blade:

- a heel part, for mounting the blade on a frame with spreaders and stirrups, the frame and the blade constituting the broom;

- a connecting part, forming a hinge of articulation between the two other parts; - And a lip part, generally in the shape of an arrow, to perform the wiping function by scraping in cooperation with the surface of the window to be wiped.

An exemplary embodiment of such a blade is described in patent FR-A-2 253 649 (or 94 01 057).

The problem is to be able to have a blade of which each part can perform different functions requiring different qualities, even antagonistic: rigidity of the heel part to allow its mounting on an articulated support structure of the broom, resistance of the part of connection to tensile / compression forces and alternating bending while remaining flexible, flexibility of the lip part for effective wiping. The blade is generally made of an elastic material, a synthetic elastomer or a natural rubber. In order to obtain rigidity or mechanical strength, it is known to provide longitudinal reinforcing vertebrae in the heel part and in the connecting part. The vertebrae are made in the form of reinforcing plates, inserted into housings during extrusion, or inserts embedded in the body of material. The shape and location of these vertebrae are adapted to obtain the desired properties without excessively affecting the flexibility and elasticity of the blade.

However, the addition of the vertebrae increases the deformation of the blade at the level of its support, in particular around the retaining claws. In addition, this type of solution reduces the life of the blade which wears out, deforms, and risks becoming tear, especially at the hinge, faster than a blade without a vertebra.

In order to overcome these drawbacks, and in particular in order to improve the compressive strength and the creep resistance to reduce the residual deformation of the blade, the invention aims to distribute the bearing pressures uniformly in order to obtain stiffening and homogeneous resistance optimized, respectively for the heel and the hinge. To do this, it is proposed to incorporate fibers into the material of these parts.

More specifically, the invention relates to a wiper blade, in particular for a motor vehicle, comprising a blade of elastically deformable material having a heel portion for mounting on a wiper support, a scraping lip portion to ensure wiping in cooperation with the surface of a window to be wiped, and a hinge part between the heel and lip parts, in the material of which reinforcing fibers made adherent are incorporated with homogeneous fiber rates in the hinge and in the heel, the rate of fibers in the heel being greater than or equal to the rate of fibers in the hinge.

The fiber levels are homogeneous in the sense that the fibers are distributed homogeneously in the heel and the hinge of the blade, without being limited to constant values, that is to say covering, for example, uniformly variable values.

The fibers can be fillers of polymers produced by the textile industry, chosen from the group of aramids, polyesters and polyamides. The fibers can also be made of glass filaments. The fiber content is advantageously between 2 and 10 parts per 100 parts by weight in the hinge, and between 10 and 20 parts per 100 parts in the heel.

The fibers are made adherent or "adhered" by chemical pretreatment to facilitate their adhesion to the elastic material, so as not to cause delamination between the fibers and the elastic material. They are pretreated for example by treatment of the RFL (“Resorcinol Formaldehyde Latex”) type or by coating with a polymer. In this case, the dispersion in the material and therefore homogenization are favored.

According to two forms of implementation, the textile fibers are cut or pulped.

In cut form, the fibers have an average length and a diameter adapted to the dimensions and to the nature of the elastic material used, in order to obtain a reinforcement optimized in quality and duration. In an exemplary embodiment, the cut fibers have an average length of the order of 1 to a few millimeters, preferably from 1 to 3 mm.

The pulp is in the form of fiber agglomerates, obtained from fibers from continuous filaments, according to a three-dimensional network.

According to particular embodiments:

- the fibers are predispersed in a polymeric binder before being incorporated;

- a pre-pasta pulp has optimized isotropic mechanical properties, without any difficulty in dispersing appearing in the mixture based on elastic material;

- The fiber material is combined with vertebrae of dimension substantially reduced compared to that of known vertebrae.

The blade according to the present invention has improved resistance to chemical agents, in particular to windshield washer fluid, as well as excellent resistance to temperature and to aging.

The invention also relates to a process for obtaining a wiper blade according to the above teaching, in which the fibers can advantageously be pre-dispersed or precut. According to a first mode, called "open mixer", the fibers are incorporated in a mixer after plasticization of the masterbatch of the elastic material, the incorporation of the fibers being carried out gradually, before the incorporation of the vulcanization system.

According to another embodiment, known as an “internal mixer”, the elastomeric polymer, half of the fillers of the mixture and half of the fibers are kneaded in the mixer for a given time, then the rest of the fibers and fillers are introduced and kneaded at the same time, before the introduction and kneading of the other finishing ingredients.

Other characteristics and advantages of the invention will appear on reading the detailed description of exemplary embodiments which follows, accompanied by the appended figures which represent respectively:

- Figure 1, a cross-sectional view of a wiper blade according to a first embodiment according to the invention; and

- Figure 2, a view similar to that of Figure 1 illustrating a second embodiment according to the invention. In Figure 1, the cross-sectional view shows a wiper blade, or squeegee 10 for a wiper blade (not shown) of a motor vehicle.

The blade 10 has a heel part 12, a connecting part 14 and a scraping part 16. The heel 12, which extends longitudinally, is designed to be received in a series of claws (not shown) of a support for blade with articulated structure, belonging to a wiper blade. The heel 12 is solid with respect to the other parts of the blade.

The elastomeric material, used to form the blade 10 in this embodiment, is reinforced in the heel by aramid fibers cut 18, uniformly dispersed in the material and incorporated into the elastomeric material during extrusion according to a process described below. By weight, the percentage of fibers relative to the material thus loaded represents approximately 15%.

In the illustrated embodiments, the scraping part 16 has, in cross section, an arrow-shaped lip whose tip 20 cooperates with the window to be wiped. The scraping part 16 is connected to the heel 12 by the central connecting strip 14, which is extruded at the same time as the heel and the scraping part 16.

The connecting strip 14 extends longitudinally in the median plane P-P of the cross section of the blade. According to the invention, the elastomeric material of the connecting strip 14 is reinforced by aramid fibers, uniformly dispersed in the material and incorporated into it during extrusion according to a process described below. By weight, the percentage of fibers relative to the material thus loaded represents approximately 6% in the strip. The incorporation of the fibers does not stop clearly at the junction of the strip 14 with the lip 16, but advantageously extends around this junction in order to reinforce it effectively.

In the first embodiment illustrated in FIG. 1, the aramid fibers 18 are cut and have an average length of the order of 1 mm. In the second embodiment illustrated in Figure 2, the fibers are in pulp, in the form of agglomerates 19, obtained by grinding aramid fibers, to form a three-dimensional network. These pulp fibers are known under the trade name TWARON ^® ^® Rhenogran or if they are predispersed in a polymeric binder. Whether the fibers are cut or ground, they are pretreated before extrusion so that they can adhere intimately to the elastomeric material or rubber during extrusion. This treatment is a chemical treatment of the type

"RFL". Coating of the fibers with a dispersive polymer can also be carried out.

The incorporation of pretreated fibers, and possibly pre-dispersed, into the elastomeric material is carried out during kneading in an open mixer. According to this process, the fibers are incorporated into the open mixer after plasticization of the masterbatch, under known speed and temperature conditions, the incorporation of the fibers being carried out gradually, before incorporation of the vulcanization system. The flow of fibers, made directive according to known techniques, makes it possible to directly and selectively load the heel and the binding strip until the concentration levels respectively targeted are reached, ie approximately 15 and 6% in the preceding examples. The mixture thus loaded is taken out at the end of extrusion.

As a variant, the incorporation is carried out in an internal mixer, of the Banbury type. The temperature of the mixer being from 30 to 50 ° C and the speed from 70 to 80 rpm. During a period of 30 seconds, a first kneading relates to the polymer, half of fillers and half of pretreated fibers. At the end of this operation, the second half-charge of fibers and the rest of the charges are incorporated and kneaded for a period equal to that of the first kneading. The other finishing ingredients, plasticizer and carbon black, are incorporated for a final kneading which lasts, in the embodiment, three times the time interval covering the first two kneading. Whether in an open or internal mixer, coextrusion with the base material of the lip is finally carried out to obtain the lip blade without fibers.

The invention is not limited to the embodiments described and shown. It is for example possible to provide a decreasing fiber concentration along the connecting hinge, between a value close to that of the heel and a value close to zero at the scraping lip. The lip can also be reinforced with fibers with a low concentration rate, for example from one to a few parts / phr. A pre-pasta pulp has optimized isotropic mechanical properties, without any difficulty in dispersing appearing in the mixture based on elastic material.

It is also possible to combine the fiber material with vertebrae of dimensions considerably reduced compared to those of the vertebrae adapted to this type of application.

Furthermore, the hinge may comprise one or two pairs of lateral wings, which extend on either side of the hinge, and possibly integrated into the scraping part, reference 21 in FIGS. 1 and 2, to ensure protecting the blade from the brush holder claws and isolating the scraping lip from the rest of the brush. These wings, as well as the lip itself, can also be loaded with fibers in accordance with the invention at a rate substantially lower than that of the connecting hinge.

In addition, in order to smooth out any appearance defects which would result from the extrusion of the rubber mixture filled with fibers, a person skilled in the art can increase the number of parts of plasticizer. Furthermore, by reducing the level of carbon black compared to that usually practiced in this type of technique, the initial mixture is well suited to the extrusion of fibers in accordance with the teaching of the present invention.

Claims

1. Wiper blade, in particular for a motor vehicle, comprising a blade of elastically deformable material, and comprising a heel portion (12) for mounting on a wiper support, a lip portion (16) for scraping to ensure wiping in cooperation with the surface of a window to be wiped, and a hinge part (14) between the heel and lip parts, characterized in that the blade comprises reinforcing fibers (18,19) adhered and incorporated in the material with homogeneous fiber rates in the hinge (14) and in the heel (12), the fiber rate in the heel being greater than or equal to the fiber rate in the hinge.

2. A wiper blade for a broom according to claim 1, characterized in that the fibers are chosen from textile fibers from the group comprising aramids, polyesters, polyamides, and glass filaments.

3. Wiper blade according to claim 2, characterized in that the textile fibers are pasted by coating, in order to promote the dispersion of the fibers in the material.

4. Wiper blade according to one of claims 2 and 3, characterized in that the textile fibers are used in cut form (18) with an average length of substantially between 1 and 3 mm.

5. Wiper blade according to any one of claims 2 to 4, characterized in that the textile fibers are used in the form of pulp (19) formed by an agglomerate of fibers obtained by grinding continuous filaments to form a three-dimensional network.

6. Wiper blade according to any one of claims 2 to 5, characterized in that the fiber content is between 2 and 10 parts / phr in the hinge, and between 10 and 20 parts per 100 parts in the heel.

7. Wiper blade according to any one of claims 2 to 6, characterized in that the hinge comprises at least one pair of lateral wings, which extends on either side, these wings also being loaded with fibers at a rate equal to or less than that of the connecting hinge.

8. Method for obtaining a wiper blade according to any one of the preceding claims, characterized in that it consists in using an open mixer in which the fibers pretreated to be adhesive are incorporated after plasticization of the mixture master, the incorporation of the fibers being done so progressive before incorporation of the vulcanization system, the fibers being brought in directional flow to load the heel and the connecting hinge until reaching the respectively targeted concentration rates, a final coextrusion being effected with the material of the lip to constitute the blade .

9. A method of obtaining a wiper blade according to any one of claims 1 to 8, characterized in that it consists in kneading for a given time, in a mixer at an initial temperature of 30 to 50 ° C, the load of elastic polymer with a first half of fillers and half of fibers pretreated to be adhesive, then to carry out a second kneading with the other half-load of fibers and the rest of the fillers for an equivalent duration, then to introduce the other finishing ingredients and to knead the whole, a final coextrusion being operated to constitute a lip blade.

10. A method of obtaining by extrusion of a wiper blade according to one of claims 8 and 9, characterized in that the pretreatment of the fibers is chemical obtained by a method of RFL type.

11. A method of obtaining by extrusion of a wiper blade according to claim 9, characterized in that the speed of rotation of the mixer is of the order of 70 to 80 rpm and in that the final kneading lasts about three times the duration of the first two mixes.

12. Method for obtaining by extrusion of a wiper blade according to one of claims 8 and 9, characterized in that the pretreatment of the fibers is mechanical obtained by coating with a polymer having dispersive properties .

13. Method of obtaining according to one of claims 8 and 9, characterized in that the fiber concentration decreases along the connecting hinge, between a value close to that of the heel and a value close to zero at the scraping lip.