Electrical connectors – With insulation other than conductor sheath – Plural-contact coupling part
Reexamination Certificate
2000-05-22
2001-10-30
Paumen, Gary (Department: 2833)
Electrical connectors
With insulation other than conductor sheath
Plural-contact coupling part
Reexamination Certificate
active
06309256
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electric plug capable of preventing a tracking of a main body of the plug made of a synthetic resin material.
As shown in
FIG. 7
, an electric plug or electric power supply plug
1
comprises a pair of electrically conductive blades
3
,
3
respectively electrically connected to the tip ends of electrical wires of a cord or cable
2
, a plug body
4
formed by extrusion-molding process of a synthetic resin material so as to allow the front portions of the parallel-blades
3
,
3
to become exposed, and a bellows
5
, and generally the plug body
4
and the bellows
5
are integrally formed by a thermoplastic polyvinyl chloride resin material (PVC).
However, since the electric plug made of PVC is considered to lack the resistance against tracking (the formation of a carbonized electrically conductive path due to a short-circuiting through dust or water-drops and an electric breakdown resulting therefrom), it is said to be unsuitable for use with strict specifications (for example, the 250V and 20A condition).
One of proposals for eliminating such problem is disclosed in the specification of the Japanese Utility Model No. 3021727. The attachment plug disclosed in this specification is of the type having a structure such that it has a plurality of terminals (corresponding to the parallel-electrically conductive blades) extending from the front face portion of the plug main body and that a thermosetting resin portion having a suitable thickness, which is hardly carbonized, is formed on the entire front face of the plug main body and a concave portion for increasing the creeping distance along an outer surface of the front face portion between the opposing surfaces of the terminals is formed.
Apart from the attachment plug disclosed in the above-described specification, there is another proposal disclosed in the Japanese Patent Laid-Open Publication No. H8-236189 such that a space filling means is provided at the root portions of a pair of electrically connecting terminals (electrically conductive blades) that extend from the plug main body so as to increase the above-described creeping distance between the terminals. According to this structure, about a half of each of the electrically connecting terminals (blades) is practically covered with a resin material.
However, the above-described prior art electric power supply plugs have the disadvantage that since the main body of each of the electric plugs is made up of the thermosetting resin portion and the soft synthetic resin portion, the manufacturing process becomes complicated and both of the resin portions lack the integrality thereof. Further, the structure in which about one half of each of the plug bodies is covered with a synthetic resin material has a serious problem in productivity with respect to its yield because the plug blades are required to be processed within the range prescribed by the industrial standard.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made to eliminate the above-described disadvantages of the prior art.
In order to solve the above-described disadvantages, the present invention basically makes use of a technical conception such that a plug main body which supports parallel-electrically conductive blades (terminals) is formed with a synthetic resin material with the formation of a groove between the blades on the side of the front face portion thereof.
The employment of such technical conception makes it possible to increase the creeping distance of the outer surface of the front face portion of the plug body between the blades and to remove dust and water-drops outside so that the anti-tracking characteristic of the plug body is improved thereby making it possible to improve an electric power supply plug made of a vinyl chloride resin material only.
More concretely, an object of the present invention is to provide an electric plug comprising a plug body provided with a pair of electrically conductive blades respectively electrically connected to bare electrical wires of an electrical cable at the tip end of the cable and covered with a synthetic resin material in such a manner that the front portions of the pair of blades are kept projecting from the front face portion of the plug body and characterized in that a groove is formed on the front face portion of the plug body so as make it open to the front face portion and both planar portions of the plug body and the plug body is made of a single material.
Further, another object of the present invention is to provide an electric plug comprising a plug body provided with a pair of electrically conductive blades respectively electrically connected to bare electrical wires of an electrical cable at the tip end of the cable and covered with a synthetic resin material in such a manner that the front portions of the pair of plug blades are kept projecting from the front face portion of the body and characterized in that a groove and a hole are formed in the front face portion of the plug body at a position between the pair of plug blades with the groove being kept open outside through the hole and both planar portions of the plug body and the plug body is made of a single material.
REFERENCES:
patent: 2193294 (1940-03-01), Osenberg
patent: 2457789 (1948-12-01), Von Scheven
patent: 3781913 (1973-12-01), Liburdi
patent: 3848957 (1974-11-01), Brush
patent: 4080036 (1978-03-01), Hagel
patent: 4346419 (1982-08-01), Janniello
patent: 3021727 (1995-12-01), None
patent: 8-236189 (1996-09-01), None
Hosono Takeshi
Yokota Minoru
Gilman Alexander
Kawasaki Electric Wire Co., Ltd.
Parkhurst & Wendel L.L.P.
Paumen Gary
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