Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
2000-03-14
2001-09-11
Beck, Shrive (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S488000, C427S492000, C427S491000, C427S509000, C427S533000, C427S554000, C427S562000, C427S569000, C427S596000, C427S255280, C427S255600, C427S248100, C427S322000, C427S402000, C204S192120, C204S192160
Reexamination Certificate
active
06287642
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention related to a coating process for a rubber wiper and, more particularly, to a coating process for a rubber wiper made of elastomer material, in which a wear-resistant protective coating is formed on the rubber wiper by a chemical and/or physical vapor deposition method from a vaporous coating material generated and activated thermally, by plasma and/or by laser.
2. Prior Art
Known windshield wipers possess a wiper arm incorporating a fastening device secured to a drive shaft, a hinged portion connected therewith by way of a toggle joint, and a wiper rod rigidly secured to the hinged structure. In addition, the windshield wiper possesses a wiper blade, featuring a bearing yoke assembly and a rubber wiper supported by it. The wiper blade is hinged on the wiper arm, whereby a hook-shaped extremity of the wiper rod projects between the two side cheeks of the bearing yoke, embracing a hinged bolt. The articulation constructed in this fashion guides the wiper blade with its rubber wiper over the windshield of the motor vehicle, whereby the hinged portion and the bearing yoke make it possible for the rubber wiper to adapt to the curvature of the windshield. The requisite contact pressure of the rubber wiper upon the windshield of the vehicle is achieved by at least one tension spring, which braces the fastening device and the hinged structure together with the wiper rod by way of the toggle joint.
The rubber wiper consists of an elastomer, for example a natural or synthetic rubber. It has a head cleat connected via a rocker flange with a wiper lip butting against the windshield to be wiped. By way of the rocker flange, the wiper lip is able to shift in inverse direction at the turnabout point of its wiper travel, so as to retain at all times a proper angle to the windshield. When the wiper is activated, the rubber wiper glides over the windshield of the vehicle with its wiper lip, whereby the friction between the lip and the windshield causes the former to abrade. Beyond that, the rubber wiper is subject to environmental factors such as temperature changes, UV radiation, seawater, exhaust gases etc., which may cause premature aging of the materials and enhanced wear.
In principle, wear can be reduced by improved gliding properties, reduced friction and/or harder rubber wipers. German patent DE 26 23 216 describes rubber wipers initially halogenated with chlorine or bromine in a chemical wet hardening process and subsequently treated with a moderate to strongly alkaline solution at temperatures up to 100° C.
After producing the rubber wiper, for example by extrusion, it features a proper, smooth surface. The chemical wet hardening process affects the rubber wiper in its entirety, so that its material properties change, even where that is not required or is very undesirable. Beyond that, its microstructure and macrostructure are altered, for example by chlorine and heat. As a rule, the rubber turns coarser and more brittle, impairing its contact with the windshield and its wiping efficacy. In addition, there is a danger that small or larger particles may break out of the rubber wiper in wiping the windshield. Moreover, for proper cleansing quality, the wiper lip should quickly and easily flip over in reversing its travel direction, without significant resistance. Yet, with harder and more brittle material, its resistance is increased, impeding or at least retarding the reversal process, and there is a tendency for the wiper blade to rattle.
Belgian patent BE 84 8 964 A describes a coating process apt to improve the gliding properties after a hardening process. Accordingly, the rubber wiper receives at least in the area of the lip, by a chemical wet process, a coating which is softer than the base material and is therefore not particularly resistant to wear.
SUMMARY OF THE INVENTION
Coating processes wherein the coating materials are mixed or utilized in a vaporous state, then conveyed to the surface of the object to be coated, and deposited thereon may be basically classified as PVD (Physical Vapor Deposition) and CVD (Chemical Vapor Deposition) processes.
Such coating processes are especially known in coating silicon wafers for integrated semiconductor circuits (cf. D. Widmann; H. Mader; H. Friedrich. 2nd ed. Springer 1996, p. 13-34). CVD processes, also referred to as gas phase deposition processes, are triggered by chemical reactions, in the sense that the applied coating materials turn into a coating in a chemical reaction on the coated surface. Conversely, PVD processes are primarily triggered by physical factors, such as for example cathodic sputtering, although there is no clearcut dividing line between these processes.
The advantage of these processes consists in the possibility of creating many different, particularly thin, compact and highly cross-linked coatings. Thin layers, though hard, may be made flexible and resistant to break-up as the rubber wiper is deformed. The compact surface is preserved, lending it high chemical resistance, in that no aggressive agents, such as seawater, exhaust gases etc. will penetrate between the coating and the rubber wiper to attack it and peel off the coating.
Beyond that, thin coatings require less coating materials. There is little waste and the need to keep coating materials in stock is limited. Because of the limited quantity of materials, the coating equipment may be readily sealed off tight towards the outside. There is no need for chemically aggressive solvents and the coatings require no time-consuming drying and hardening cycles. The production processes are friendly to the environment, economical and well suited to large -scale production.
Beyond that, a special advantage of these processes lies in the fact that while the wiper is being coated, the process parameters may be simply varied, and the properties of the coating may be altered within a thin layer so as to match specific requirements. Within the inner structure of the rubber wiper, it is possible to achieve in one single process an elastic and soft coating system adapted to the properties of the rubber wiper, with a hard, wear-resistant outer coating.
In the transition from a soft to a thin and hard coating within an altogether thin coating system, the latter is on the whole elastic, with no more than limited effect on the elasticity of the rubber wiper, with which it is securely bonded. The coating system will not peel off when the rubber wiper is deformed, and it is chemically resistant.
Particularly advantageous is a smooth transition from elastic/soft to the wear resistant/hard region. In one embodiment of the invention, it is proposed that the process parameters be varied, as for example the blending ratios of process gases, the electric or thermal input, the distance between the source of the material and the rubber wiper, flow parameters, etc., so as to achieve an infinitely variable gradient layer, that is, a layer whose stock parameters and properties follow from inside out, perpendicular to the rubber wiper and consistent with the chemical and morphologic gradients, possessing at all times constant properties along one plane in the longitudinal direction of the rubber wiper. Nevertheless, under different boundary conditions in the production process, it may be more advantageous to alter process parameters gradually in order to produce a multi-ply layer, in other words, several overlapping thin layers deviating slightly in the properties of the stock.
The gradient layer or multi-ply coating may at the same time form the outer hard and wear-resistant top coating. It is also possible to apply the wear-resistant hard coating in a separate deposition stage. One proposed embodiment of the invention envisages an additional final application of a dry lubricant and/or hydrophobic coating. Good results have been achieved with coatings having a water wetting contact angle between 60 and 150 degrees, preferably over 90 degrees.
In one preferred embodiment, it is also possible to deposit only one ho
Forget Jeanne
Leutsch Wolfgang
Rauschnabel Johannes
Voigt Johannes
Barr Michael
Beck Shrive
Robert & Bosch GmbH
Striker Michael J.
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