Method of fixating a shaft in its bearing casing in wiper instal

Details Method of fixating a shaft in its bearing casing in wiper instal Method of fixating a shaft in its bearing casing in wiper instal

1995-03-03

1997-06-03

Hannon, Thomas R.

Bearings

Rotary bearing

Plain bearing

152503, 1525031, 29898049, 264242, 384295, 384138, 384416, F16C 3302, B60S 134, B29C 3900

Patent

active

056347260

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a system of fixating a shaft in its bearing casing and more particularly relates to a system of fixing a shaft in its bearing casing wherein an annular gap is provided between the shaft and the bearing casing.


BACKGROUND OF THE INVENTION

From German Patent Application (DE) No. 40 28 892 A1 a drive mechanism has become known which in particular is used for windscreen wipers of automotive vehicles and which has a shaft projecting out of one front side of a bearing casing, with a cylindrical slide bearing being mounted to the bearing casing with a small spacing in respect of the latter's front side. Because of the slide bearing, an annular gap is confined between the bearing casing and the shaft. A bushing made of elastic plastic is provided for sealing the annular gap with regard to its surroundings. This bushing is fixed on the bearing casing and shuts the annular gap off from the slide bearing. On its end averted from the bearing casing, the bushing is provided with a radially inward projecting sealing flange engaging an annular groove of the shaft. Such a shaft bearing has the advantage of being extremely sturdy. However, the design and assembly of the shaft bearing is complicated and expensive and, as a rule, several components will be required to render the best support and sealing possible.
It is thus an object of this invention to provide a system for allowing the shaft to be easily supported in the bearing casing.
Regarding the method referred to at the beginning, this object is solved according to this invention in that, after insertion and alignment of the shaft in its bearing casing, the annular gap is at least sectionally filled by the injection of plastified plastic material or metal.
The present invention includes embodiments where the annular gap is filled by the injection of plastic material. However, it can also be filled by the injection of a copper, lead and/or tin alloy. Thus, in the inventive method, neither slide or roller bearings are inserted between the shaft and the bearing casing. All that is done there is to fill the annular space by injecting plastic material. After curing of the plastic material the same serves both as a bearing of the shaft and as a seal against the penetration of dirt and humidity from the surroundings into the bearing and/or against leakage of lubricant out of the bearing. This renders the advantage of not having to insert any additional components other than the plastic material into the annular gap in order to support and seal the shaft. Further, manufacture of such a type of shaft fixation is easily and quickly implemented. Admittedly, as a rule, the shaft is aligned, i.e. centered, after its insertion into the bearing casing. This operation, however, is not necessary by all means. Due to the injected plastic material it is also possible to fixate the shaft in offset or tilted positions in the bearing casing. A further advantage of the injection of plastic material into the annular gap is that the internal shape of the bearing casing may also feature a conical design. This is of special advantage in case of cast casings.
Further, there is no need for aftertreating the internal shape after the manufacture of the bearing casing, in particular so with regard to widening it to predetermined dimensions. In particular, no mechanical aftertreatment is required in case of bearing casings made from aluminum die-castings despite the considerable dimensional tolerances caused by the cooling of the bearing casings.
In order to maintain a defined play between the shaft and the cured plastic material the shaft is heated before filling the annular gap by injection, in particular up to a temperature of 200.degree. C..+-.30.degree. C. As, after the injection, curing of the plastic material will take place at a faster rate than cooling of the shaft, a defined play will be generated by the amount of shrinkage of the shaft, thereby an easy-motion rotatability of the shaft is guaranteed.
The plastic material is advantageously injec

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patent: 3846000 (1974-11-01), Kohler
patent: 4290181 (1981-09-01), Jackson
patent: 4660996 (1987-04-01), Marshall

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