Metal working – Method of mechanical manufacture – Electrical device making
Patent
1995-12-04
1999-11-23
Young, Lee
Metal working
Method of mechanical manufacture
Electrical device making
29868, 29871, H01R 4300
Patent
active
059877456
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and associated devices for jointing a power cable for medium voltage, that is, preferably a power cable intended for use in the voltage interval from 12 kV to 36 kV.
BACKGROUND OF THE INVENTION
When jointing a cable, the conductors of two cable ends are joined together by means of a connector, the respective cores having first been freed from the surrounding insulation. The joint with the exposed connector must then be insulated. This insulation is usually carried out by means of a prefabricated jointing body of rubber. Known jointing bodies are usually designed with substantially cylindrical shells. The jointing body itself is provided with a continuous cylindrical hole, wherein the hole in a natural, non-elongated state, has an inside diameter somewhat smaller than the outside diameter of the insulation on the cable which is to be joined. This is necessary for the elastic jointing body, after the jointing operation, to embrace the insulation of the cable ends in order to obtain a tightly fitting joint.
When a jointing operation is to be carried out, the work is initiated by moving the jointing body to a position of rest over one of the cable cores. The cable ends are prepared, which means exposure of the conductors to be joined and removal of the insulation screens, and the conductors are joined together. The jointing is usually carried out with a ferrule, which by mechanical deformation brings the ferrule into contact with the conductors. Afterwards, the jointing body is brought to a centered position over the joint. The connector sometimes has a larger diameter than the cores and can therefore constitute an obstacle to positioning the jointing body right across the joint.
Moving a jointing body over the exterior of a cable without expanding the jointing body in advance is difficult and means that the jointing body can only be used on a cable with a well-defined outside diameter adapted to the size of the jointing body. The tolerance range for variation of outside diameters of cables, for which a certain jointing body can be used, becomes very limited because a very considerable force is required to move the jointing body along the cable. Certain known jointing bodies must be expanded in order for the jointing body to be moved into position, partly over one of the cable cores prior to the work with jointing of the conductors, partly to be able afterwards to center the jointing body over the joint.
It is known to expand the jointing body from the factory on an inner carrier in the form of a thin pipe, which may be built up of a plastic tape which is wound into a pipe, the jointing body thus covering the plastic pipe like a cover. The jointing body with its carrier pipe has then been given an inside diameter which is larger than both the outside diameter on the cable to be joined and any connectors in the joint, whereby the jointing body can easily be fitted on the cable according to the above. After returning the jointing body over the joint, the expanding plastic pipe is removed by making the end or ends of the plastic tape, from which the pipe is formed, accessible and withdrawable from the interior of the jointing body, the jointing body thus collapsing and surrounding the joint. The disadvantage of this arrangement is that the jointing body will be expanded for a long time and then there is a risk that the rubber settles and possibly loses its re-sealing power, or that the storage time of the jointing body becomes limited. A further disadvantage is that the amount of material required to manufacture the carrier is considerable.
Another known jointing body is made as a cylindrical tube of rubber surrounded by a cylindrical shell of shrinking hose, to which the rubber tube is applied, whereby the rubber tube is kept stretched. The jointing body is applied over the joint, as described above, whereupon the rubber body surrounds the joint when the shrinking hose is heated, at which time the expanding forces of the shrinking hose are eliminated,
REFERENCES:
patent: 2405399 (1946-08-01), Bugg et al.
patent: 2683924 (1954-07-01), Schryver
patent: 3010194 (1961-11-01), Fratzke
patent: 3119174 (1964-01-01), Wokeck
patent: 4391661 (1983-07-01), Izraeli
patent: 4416059 (1983-11-01), Humphrey et al.
patent: 4968857 (1990-11-01), McGrane
patent: 5016346 (1991-05-01), Gerst et al.
patent: 5315065 (1994-05-01), O'Donovan
Hoglund Mikael
Johansson Bert
Kabeldon AB
Rushing, Jr. Bobby
Young Lee
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