Electricity: conductors and insulators – Boxes and housings – Hermetic sealed envelope type
Patent
1998-09-28
2000-10-31
Reichard, Dean A.
Electricity: conductors and insulators
Boxes and housings
Hermetic sealed envelope type
174 66, 220 38, 220241, H02G 308
Patent
active
061405787
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with a lid for a gear box of the type as set out in the preamble portion of claim 1.
Lids of this type are especially used with driving aggregates for windscreen wiper systems. The driving aggregate comprises an electromotor driving a worm gear. The gear is housed in a pot-shaped box to which the electromotor is laterally coupled. The worm gear is located within the box, with the driven shaft being externally guided through the bottom of the housing. The gear wheel is actuated by a worm, which is formed in the extension of the motor shaft.
The worm gear, on one side thereof facing the open side of the box, is provided with contact lines cooperating with contact lugs at the bottom side of the box lid. Contact lines and contact lugs form a so-called park position switch insuring that the windscreen wiper driven by the aggregate also after disconnection of the main switch be supplied with energy until the windscreen wipers have reached their parking position at the bottom edge of the windscreen.
The contact lugs, through printed conductors extending along the outer side of the lid, are supplied with power, with the printed conductors being embedded in a plastic layer injection-molded to the lid and, as a rule, having a cross-section in the form of a plug.
Normally, the said plastic layer has a dimension sufficient to cover or accommodate the printed conductors.
The side walls forming the edge of the plastic layer are at right angles on the outer face of the metallic lid of the gear box.
This arrangement has only little protection against corrosion. The different heat exchange coefficients of plastics and metal result in that at extreme temperature fluctuations to which the aggregate is exposed within the vehicle, the edge of the plastic layer separates from the lid thereby permitting the ingress of dirt and rain water. Moreover, the metallic lid must be extremely stable in order that tensions occurring within the plastic do not result in a deformation of the lid.
It is, therefore, the object of the invention to provide a lid adequately protected against corrosion, being of a sufficient stability and having a weight that is not excessively high.
This problem, in the practice of the invention, is solved in that the plastic layer so expands across the outer face of the base plate that the plastic layer overlaps the base plate in at least two marginal segments, with the bottom edge of the plastic layer, within the said segments, being flush with the bottom side of the base plate, and that the marginal segments overlapped by the plastic layer are apart from one another by at least 90 degrees, measured by the volume of the base plate.
To achieve an adequate stability of the combination of plastic layer and metallic base plate, the extension of the overlapped marginal segments should be at least 90 degrees, if not 180 or even 270 degrees.
As a consequence thereof, the individual sections in which an overlap of the base plate occurs, are passing over one into the other, forming a frame to embrace the metallic plate at least in part if not in full.
This frame-type construction, in addition, results in that the transition between plastic layer and metal plate occurs at the bottom side of the base plate covered by the bearing edge of the gear box.
To achieve a particularly intimate connection between the plastic layer and the metal base plate provision can be made to the effect that the same, at the bottom side thereof, includes recesses open at the edge engaged by the plastic layer, thereby seizing the edge at these points in U-shaped manner.
In order to avoid as far as possible the ingress of dirt and rain water, provision can be made to the effect that the layer of plastic material almost completely covers the outer side of the base plate.
In that case it is favorable to provide extended plastic faces also on the bottom side of the base plate to generate a certain counter-tension in order to prevent the base plate from deforming during cooling of the plastic layer after injection-mo
REFERENCES:
patent: 5243130 (1993-09-01), Kitagawa
patent: 5621189 (1997-04-01), Dodds
Ade Rolf
Csermak Martin
Scheele Hubert
Walther Bernd
ITT Manufacturing Enterprises Inc.
Lewis J. Gordon
Reichard Dean A.
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