Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1999-09-28
2001-09-11
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Plain bearing
Reexamination Certificate
active
06287007
ABSTRACT:
PRIOR ART
Wiper systems with a number of windshield wipers for motor vehicles are directly or indirectly fastened to their wiper bearings by way of a mounting plate on the body of the vehicle. The mounting plate has a wiper drive mechanism with a wiper motor whose motor shaft drives cranks by way of a rod assembly and these cranks are connected to one end of a drive shaft for each windshield wiper. It is also possible that only one drive shaft of one windshield wiper is driven by the wiper motor while another windshield wiper is connected to the first windshield wiper by means of a four-hinge lever mechanism and has a bearing axle. The drive shaft or the bearing axle is supported in a wiper bearing. The explanations below with regard to a drive shaft naturally also apply to a bearing axle, which is intentionally not mentioned again for the sake of simplicity.
At least one radial bearing is provided in the bearing housing and axial bearings are provided on the end faces between the bearing housing and a part affixed to the drive shaft, e.g. stop rings or a stop ring and a crank plate of the crank. The drive shaft protrudes from the vehicle body and moves a windshield wiper attached to its free end over a windshield. The bearing gaps are sealed in relation to the outside in order to prevent damaging substances such as dirt, water, corrosive substances such as salt dissolved in water, and impurities in the air from getting into the bearing gaps and destroying the bearings.
To this end, known bearing housings have an open space on one or both end faces toward the drive shaft in which an 0-ring is disposed, which rests with an initial stress against the stop ring or the crank plate, the bearing housing, and the drive shaft. In bearing houses made of cast material with bearing bushes that are press-fitted into them and are as a rule made of sintered material, the bearing housing protrudes beyond the end faces of the bearing bushes, which produces the open space between the bearing bush, the stop ring or crank plate, and the bearing housing. The open space is formed onto bearing housings made of plastic. Seals of this kind increase the axial length of the bearing housing, protect only the radial bearing, and have a relatively high degree of friction.
ADVANTAGES OF THE INVENTION
According to the invention, the seal is disposed with a radial distance from the radial bearing, outside the axial bearing, and the bearing gaps of the axial and radial bearings are sealed in relation to the outside so that in comparison to the known embodiment with an O-ring, in addition to the radial bearings, the axial bearing is also protected against damaging substances. This is particularly advantageous in bearing houses made of plastic which are increasingly used due to their low cost and weight but are frequently less resistant to water and harmful substances than bearing housings made of cast material (zinc or aluminum). The plastic can prematurely age or become brittle, particularly in unprotected bearings that are placed under stress. A long service life is assured when there is a low degree of wear and low friction, since the favorable sliding properties are maintained. As a result, a low degree of bearing play can be maintained throughout the entire service life, which has a favorable effect on the vibrational behavior of the windshield wiper and therefore on the wiping quality. Furthermore, the sealing device according to the invention does not take up any additional room so that the space available can be used for a long bearing base of the radial bearing. In particular, high lateral forces can be absorbed with a low, specific material stress. Consequently, softer materials such as plastic can also be used while maintaining a long service life.
In one embodiment of the invention, the seal is non-rotatably connected to the bearing housing and rests with an axially acting sealing lip against the stop ring or the crank plate in the outer region which radially adjoins the axial bearing. Preferably, an axial lip seal is used as the seal. The lip seal can be sealed with a slight pressure, a small sliding friction surface, and therefore a small amount of sliding friction. The lip seal experiences a low degree of wear over continued operation, and a wiper drive mechanism only has to exert small freeing forces as a result of a low degree of static friction. In lieu of a lip seal, it is also possible to use a contact-free seal, for example a labyrinth seal, by means of which the sliding friction for the seal is completely eliminated.
The seal is suitably disposed in a recess of the bearing housing. In one embodiment of the invention, the bearing housing, which as a rule is comprised of cast iron, has bearing bushes press-fitted into it which are comprised for example of sintered material. On one or both end faces, the bearing bushes protrude beyond the bearing housing and in addition to radial bearings, simultaneously constitute bearing surfaces for axial bearings against a stop ring or crank plate of the drive shaft. As a result, a recess is formed between the bearing housing and the stop ring or crank plate and can favorably accommodate the seal. Furthermore, a radial bearing can be produced which has a large axial bearing base despite a short and therefore lightweight and space saving bearing housing. A favorable material used for the radial bearing is simultaneously used for the axial bearing, which can advantageously achieve a low friction in the axial bearing.
The proposal is also made to embody the bearing housing and the seal as a dual-component unit, i.e. of a rigid plastic part and a soft seal, for example a lip seal. The number of components is therefore reduced, as are the assembly costs.
In order to embody the externally visible part of the drive shaft and the bearing housing in a streamlined fashion and in particular to protect the bearing from direct splashing, it is known to dispose a protective cap on the drive shaft which encompasses the end of the bearing housing protruding outward from the vehicle body. In one embodiment of the invention, the protective cap is simultaneously used to produce a radial sealing surface for a radial seal, which seals the axial and radial bearings of the drive shaft. In the vicinity of the axial bearing, the recess for the seal is thus eliminated, which means that the bearing can be embodied as larger while taking up virtually the same radial space. The protective cap can preferably be embodied with the seal as a dual-component unit or as a one-piece component made of rubber-elastic material. The number of individual components and the assembly costs are consequently reduced. The protective cap is press-fitted onto the shaft and/or according to one embodiment according to the invention, is engaged in detent fashion with the shaft by way of an indentation in the shaft, by means of which the protective cap can be rapidly and exactly positioned when being mounted, is securely fixed in both axial directions after being mounted, and does not slip during use, which would lead to a functional failure of the seal.
The seal is preferably a lip seal, wherein other seal types are also possible by themselves or in addition, which can act axially and/or radially, for example contact-free labyrinth seals. In order to be able to easily mount the protective cap without damaging and/or folding the seal, the bearing housings have an insertion bevel in the mounting direction.
Another embodiment of the invention is comprised in fastening a rubber collar onto the bearing housing on the side of the crank plate. The rubber collar is preferably supported against the bearing housing in a first direction oriented away from the axial bearing and is supported against the crank plate or against a stop ring in a second axial direction and therefore seals the radial and axial bearing in relation to the outside.
REFERENCES:
patent: 4380860 (1983-04-01), Riester et al.
patent: 5809610 (1998-09-01), Eustache
Footland Lenard A.
Robert & Bosch GmbH
Striker Michael J.
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