[0001] This invention relates to electrical connectors, especially but not exclusively for
joining the bared ends of insulated wires, and to a method of connecting electrical
conductors.
[0002] In 'Research Disclosure' April 1990, page 348, there is disclosed an electric wire
whose conducting medium consists of a conductive polymer - textile composite, one
example being a rope whose fibres have individually been coated with polypyrrole,
a conductive polymer, the rope insulated with a plastics sheath.
[0003] The purpose of the present invention is to provide some means of connecting mechanically
and electrically such non-metallic electric wires; conventional techniques employing
soldering or crimping are of course inappropriate.
[0004] Accordingly, the invention in one aspect provides an electrical connector for joining
two or more electrical conductors, comprising a heat-shrinkable sleeve coated on at
least part of its inner surface with a conductive polymer. In use, the sleeve is heat-shrunk
over the bare conductors to grip them frictionally and to create an electrical joint.
[0005] In another aspect, the invention provides a method of connecting electrical conductors
comprising placing a heat-shrinkable sleeve, coated on at least part of its inner
surface with a conductive polymer, over the conductors, and heat-shrinking the sleeve
onto the conductors to create an electrical path therebetween which includes the conductive
polymer.
[0006] The connection is most conveniently made between two electric wires; in the case
of insulated wires, the ends are preferably bared and the sleeve should be long enough
to cover the bared ends. There may be a lengthwise gap between the conductor ends;
alternatively, the ends may be butted up against each other.
[0007] However, a connector of appropriate shape, cylindrical or irregular, could be provided
for connecting any number of electric wires, or electric conductors of other configuration
such as strips. It is not essential for the sleeve to be cylindrical.
[0008] The sleeve is preferably of electrically-insulating heat-shrinkable polymer, so that
the resulting electrical connection is insulated.
[0009] The invention is particularly useful for connecting textile-composite wires of the
type described above, because an even pressure is applied around their periphery at
the join, giving a good frictional grip and a strong electrical connection without
crushing or interfering with the surface of the wire.
[0010] According to a third aspect, therefore, the invention provides an electrical joint
comprising two non-metallic wires interconnected electrically and mechanically by
a connector comprising a heat-shrunk sleeve coated on at least part of its inner surface
with a conductive polymer.
[0011] The connectors may be made by extruding thermoplastics tubing, expanding the tubing
within a rigid cylindrical chamber by fluid pressure and cooling it so that it becomes
heat-shrinkable, coating its inner surface with a conductive polymer, and cutting
the tubing to size. The surface may be coated with conductive polymer, such as polypyrrole
or polyaniline, from appropriate solvents by spraying, or else by building up a coating
of the polymer from a reacting solution of the appropriate monomer, e.g. pyrrole,
with an oxidising agent, e.g. ferric chloride. Such a process is described, in relation
to coating textiles, in Gregory, R.V., Kimbrell, W.C and Kuhn, N.H., "Conductive Textiles",
Paper presented at the International Conference on Science and Technology of Synthetic
Metals, June 26th-July 2nd 1988, Santa Fe, New Mexico, and in our copending Patent
Application mentioned above.
1. An electrical connector for joining two or more electrical conductors, comprising
a heat-shrinkable sleeve coated on at least part of its inner surface with a conductive
polymer.
2. A method of connecting electrical conductors comprising placing a heat-shrinkable
sleeve, coated on at least part of its inner surface with a conductive polymer, over
the conductors, and heat-shrinking the sleeve onto the conductors to create an electrical
path therebetween which includes the conductive polymer.
3. A connector according to Claim 1, in which the sleeve is of electrically-insulating
heat-shrinkable polymer.
4. An electrical joint comprising two non-metallic wires interconnected electrically
and mechanically by a connector comprising a heat-shrunk sleeve coated on at least
part of its inner surface with a conductive polymer.
5. A connector according to Claim 2 and substantially as described herein.
6. A method of connecting electrical conductors, substantially as described herein.