Valve magnet

Details Valve magnet Valve magnet

2001-03-23

2004-06-22

Donovan, Lincoln (Department: 2832)

Valves and valve actuation

Electrically actuated valve

C251S129150, C335S256000

Reexamination Certificate

active

06752372

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a valve solenoid comprising a coil and a an iron circuit, which are arranged in a housing which can be employed in areas endangered by explosion.
Such valve solenoids have long been known and are evident, for example, from the German utility model 90 03 343 or from the U.S. Pat. No. 5,138,292.
Widely varying types of ignition protection are known. Types of ignition protection in accordance with IEC or EN (EN 50014 ff.) are: “pressure-resistant encapsulation (EExd)”, “enhanced safety (EExe)”, “over-pressure encapsulation (EExp)”, “intrinsic (EExi)”, “oil immersion (EExo)”, “sand filling (EExq)” and “cast encapsulation (EExm)”.
Designs for explosionproof solenoids are also known in which it is not only the “pure” ignition protection types mentioned above which are used but also combinations of these ignition protection types, such as the ignition protection types “cast encapsulation” combined with “enhanced safety” or “pressure-resistant encapsulation” combined with “increased safety” .
SUMMARY OF THE INVENTION
The object of the invention is to provide an explosionproof valve solenoid that can easily be manufactured at low cost while satisfying the ignition protection type “pressure-resistant encapsulation” in the region where external cables are connected.
This object is achieved according to the invention, in a valve solenoid of the type described above, in that the coil and the iron circuit are embedded in a casting compound introduced into a housing part, which casting compound prevents an explosive atmosphere reaching live parts and is simultaneously used for fixing purposes and electrical insulation (cast encapsulation). Connecting elements of the coil are arranged in a housing part which withstands internal pressure in the case of an explosion and prevents transmission of the explosion to the environment (pressure-resistant encapsulation).
The major advantage of dividing the housing into two housing parts, one of which satisfies the “cast encapsulation” ignition protection type and the other the “pressure-resistant encapsulation” ignition protection type is that the coil and the iron circuit, in particular the solenoid enclosure sleeve, are not part of the pressure-resistant area. This housing part does not therefore require complicated fitting procedures, which are necessary in the case of pressure-resistant encapsulations because of the fact that the gaps must not allow ignition penetration. The physical size of the solenoid can, in addition, be reduced by the avoidance of such gaps, which must have a specified minimum length.
In addition to its ease of manufacture, such valve solenoids also have the advantage that cast encapsulated coils and iron circuits or solenoid enclosure sleeves are available as standard parts with the result that stockholdings are reduced. Nevertheless, the external cables can be connected in a pressure-resistant, encapsulated area arranged in the second housing part.
Further advantages and features of the invention are the subject matter of the following description and of the drawing representation of an embodiment of the invention.


REFERENCES:
patent: 4412196 (1983-10-01), Teichert
patent: 6374814 (2002-04-01), Cook et al.
patent: 6392520 (2002-05-01), Hofmann et al.
patent: 29 26 549 (1981-01-01), None
patent: 298 672 (1993-10-01), None

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