Electricity: circuit makers and breakers – Electric switch details – Cases and bases
Patent
1996-02-26
1997-12-23
Walczak, David J.
Electricity: circuit makers and breakers
Electric switch details
Cases and bases
200303, H01H 904
Patent
active
056998996
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an electromechanical component, in particular a relay, having a casing which is formed from a base and a cap, the base, which is composed of plastic, having apertures in which connecting elements are anchored and sealed by insertion.
Various methods are already used in order to seal an electromechanical component, for example a relay according to German reference DE 34 28 595 C2, in a plastic casing against moisture and other environmental influences, in order on the one hand to bond or to weld the cap to the base in the edge region and, on the other hand, to seal the bushings of the connecting elements using a potting compound. These conventional methods are, however, relatively complex and uneconomic.
German reference DE 26 17 633 A1 discloses an arrangement for an electromechanical component of the type mentioned initially, in the case of which the openings in the base of the component are provided with sealing lips which are molded onto the base and are intended to be closely joined to the connecting pins. However, since these sealing lips are formed from the same material as the base, success of the sealing is doubtful. This is because either the base material is soft, so that the base cannot give the contact elements sufficient robustness in the interior of the casing, or the plastic is dimensionally stable, which in turn has the disadvantage that the sealing lips formed from the same material are not closely joined to the connecting elements in a soft enough manner to produce reliable sealing. In addition, such sealing lips intrinsically on their own produce only a more or less linear seal which, particularly in the case of connecting elements having a rectangular cross section, for example flat plugs, do not allow reliable sealing.
On the other hand, sealing lips in the edge gap between the base body and the cap have already been proposed in German reference DE-OS 23 20 617; however, this relates only to a preliminary seal which is intended to prevent the potting compound, which is to be inserted later, from running into the casing.
DE 33 19 329 A1 discloses a relay having a washproof base plate in which potting compound is inserted in the intermediate space between the slots of the base plate and the inserted connecting pins. This is associated with the disadvantage mentioned initially, that the additional potting compound must be distributed, and subsequently cured, using complex operations.
Finally, DE 25 56 610 B2 discloses a base body, which is composed of insulating material, for relays which can be hermetically sealed, a base body composed of thermosetting plastic having a jacket of thermoplastic material extrusion coated onto it. The connecting elements are in this case actually embedded in the thermosetting plastic base body, which, just on its own, requires a complex production process. In this case, an additional operation, by means of which the parts are intended to be bonded or welded, is proposed for sealing between the thermoplastic jacket and the cap.
SUMMARY OF THE INVENTION
The aim of the present invention is to design a component of the type mentioned initially, such that a seal of the casing gaps and bushings, particularly to the connecting elements which are secured by insertion, is achieved in a very simple and economic manner.
This aim is achieved according to the invention in that the base, which is composed of a dimensionally stable plastic, is coated, at least in the wall regions of the apertures, with a layer of a thermoplastic elastomer, and in that the connecting elements have a cross section, which is larger than the remaining width of the respective aperture, in such a manner that said connecting elements are anchored in a sealed manner by the insertion, with a press fit.
Thus, in the case of the invention, two plastic materials having different properties are used at least for the base body or base which supports the connecting parts. The plastic having the higher strength, for example a mineral-reinforced or g
REFERENCES:
patent: 3323199 (1967-06-01), Prival
patent: 4622739 (1986-11-01), Pejouhy et al.
patent: 4780578 (1988-10-01), Heskel
patent: 4975545 (1990-12-01), Ching et al.
Siemens Aktiengesellschaft
Walczak David J.
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