Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Patent
1994-02-14
1995-05-23
Nimmo, Morris H.
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
174 74R, 174 84C, 174 94R, 174DIG8, 439730, 439874, 439882, 439936, H01R 422
Patent
active
054183316
DESCRIPTION:
BRIEF SUMMARY
This invention relates to electrical connectors and especially to electrical terminals for forming a connection between one or more electrical wires and a further, fixed, electrical terminal for example a screw terminal.
A number of terminals for wires have been proposed in which a shank of the terminal is crimped about the end of a wire after stripping the wire of insulation. One such terminal, for example, is described in our international patent application No. WO90/00819. In addition, it has been proposed to manufacture terminals in which the shank is connected to the wire by means of solder for example using a solder ring located within a dimensionally heat-recoverable sleeve.
These terminals suffer from the disadvantage that they have relatively little tolerance to the size of wire to be terminated, with the result that one must employ a large number (usually at least four) different sizes of terminals for each range of wires or cables to be terminated, especially in the case of crimp terminals. While terminals employing a solder connection are usually quite satisfactory as concerns electrical continuity they often do not exhibit sufficient resistance to tensile strain. Furthermore, such terminals are often not easily employable with solid conductor wires.
According to the present invention, there is provided an electrical terminal for connection to one or more electrical wires, which comprises a terminal portion having a lug portion and a hollow shank, a jacket of polymeric insulation that extends over the shank, and a tapering hollow connection piece that has an internal and an external screw thread, the connection piece being arranged partly within the end of the shank and being capable of receiving one or more electrical wires so that the wire or wires can be secured within the connection piece and the connection piece can be secured within the shank by twisting the terminal about the wire or wires.
Thus, by means of the present invention it is possible to terminate one or more than one wires at a single terminal where the wire gauges vary significantly, and produce a termination with relatively low electrical resistance and high tensile strength.
The connecting element may, if desired, by formed from a solid block of metal that has been tapped both internally and externally with a screw thread. However it is preferred, both in terms of ease of manufacture and effectiveness in use, to employ a metal wire that has been wound into a tapering helix, preferably a frusto-conical helix. Such a form of connection piece has the advantage that it will be locked in position in the end of the terminal shank as the wire or wires are screwed into it in a similar manner to a nut mounted within a bolt. The wire may be formed with a circular cross-section, although it is preferred for the wire to have a relatively sharp ridge along its length, eg. formed by cold drawing or cold rolling, which, when the wire has been coiled, is directed toward the interior of the coil in order to form the screw thread. In particular it is advantageous for the wire to be formed with a polygonal, and especially a square or diamond-shaped, cross-section. The wire may be formed from any appropriate metal or metal alloy, but preferably is formed from copper, and especially from copper having substantially the same purity as that conventionally employed for electrical conductors.
The insulating jacket is preferably at least partially dimensionally recoverable and especially dimensionally heat-recoverable, that is to say, it has a dimensional configuration that may be made to change when subjected to heat treatment.
Usually these articles recover, on heating, towards an original shape from which they have previously been deformed but the term "heat-recoverable", as used herein, also includes an article which, on heating, adopts a new configuration, even if it has not been previously deformed.
In their most common form, such articles comprise a heat-shrinkable sleeve made from a polymeric material exhibiting the property of elastic or pl
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Burkard Herbert G.
Nimmo Morris H.
Novack Sheri M.
Raychem SA
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