Electrical connectors – Contact comprising cutter – Insulation cutter
Reexamination Certificate
2000-01-07
2001-03-27
Sircus, Brian (Department: 2839)
Electrical connectors
Contact comprising cutter
Insulation cutter
C439S404000, C439S405000
Reexamination Certificate
active
06206720
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an insulation displacement connector, and to an assembly or electrical plug which comprises the insulation displacement connector and is used for making an electrical connection to an electrical cable.
2. Introduction to the Invention
Elongate cables such as power cords, grounded power leads, or heating cables often must be electrically connected to another elongate cable or to a source of electrical power such as a wall outlet. An electrical plug is frequently used to make connection to a power source. Connection of the cable to the connector or the plug can require tedious and craft-sensitive assembly, as well as the use of special tools, in order to ensure that good electrical connection is achieved.
Elongate heating cables are one type of cable which often requires connection to a connector or a plug. Such heating cables are known for use in the freeze protection and temperature maintenance of pipes. Particularly useful elongate heating cables comprise (a) first and second elongate electrodes, (b) a plurality of resistive heating elements connected in parallel between said electrodes, e.g. a continuous strip of a conductive polymer in which the electrodes are embedded or which is wrapped around the electrodes, and (c) an insulating jacket, composed, for example of an insulating polymer, which surrounds the electrodes and heating elements. In addition, the heating cable often also comprises a metallic grounding layer, in the form of a braid or a tape, surrounding the insulating jacket, which serves to electrically ground the heating cable and provides abrasion resistance. The heating cable may be cut to the appropriate length for each application, and connection must then be made to the connector or plug.
Conventional connectors and electrical plugs for use with electrical cables such as heating cables often require that, prior to installation of the cable into the plug, the conductive polymer must be stripped from the electrodes. Such an electrical plug is disclosed in U.S. Pat. Nos. 5,002,501 (Tucker) and 5,004,432 (Tucker). Stripping the polymer can be difficult, may require special tools, and may not result in completely “clean” electrodes, thus making good electrical connection to the plug difficult. In addition, the time required to strip the polymer and assemble the plug can be relatively high. Other conventional plugs do not require that the cable be stripped prior to insertion into the plug. U.S. Pat. No. 5,252,081 (Hart) discloses a plug in which connection to the electrodes is made with conductive piercing means which penetrate the insulating jacket and the conductive polymer, thus contacting the electrodes. In order to make adequate contact, it is necessary that the piercing means, e.g. screws, be sufficiently tightened. In addition, it is important that the dimensional tolerance be precise to ensure that the screws directly contact the electrodes and maintain good electrical connection even after creep and/or aging of the polymer and electrodes. U.S. Pat. No. 5,718,600 (D'Amario et al) discloses another plug which does not require stripping of the polymer prior to insertion, but which uses a rotating cutting element located inside the plug housing to cut and remove polymer from the electrodes. Rotation of the cutting element also forces the electrodes into physical contact with electrical contacts. U.S. Pat. No. 5,756,972 (Vranicar et al) discloses a connector in which a cable is inserted into a housing and connection is made to a second cable. Insulation displacement connectors are used to make connection to the unstripped cables. The disclosure of each of these patents is incorporated herein by reference.
BRIEF SUMMARY OF THE INVENTION
Insulation displacement connectors are known for use in making electrical contact to the electrodes of electrical cables. An insulation displacement connector (IDC) can be of any configuration, but often has a fork shape, with two tines separated by a slot and connected at the base. Often the tines have sharp edges at their tips to penetrate the polymer surrounding the electrodes. However, one problem that can arise when an IDC of this type is used is that the polymer can build up at the base of the slot, interfering with making a dependable electrical connection. While some conventional IDCs have a relief cavity for extra material, they must be made from expensive alloys, e.g. beryllium-copper, which have sufficient elasticity to provide adequate spring force or hold strength. We have now found that it is possible to make an easy, reliable connection to an electrical cable, especially an electrical cable comprising stranded electrodes, by using an IDC which comprises a beveled groove at the bottom of the slot between the tines. The beveled groove provides a notch in the polymer surrounding the electrodes, which separates the polymer and leaves a clean surface for good electrical connection. There is no need for a relief cavity and thus less expensive materials, e.g. brass, can be used, while still achieving good contact. Such IDCs are useful in an assembly for making connection, as well as in a connector or an electrical plug. Thus, in a first aspect this invention provides an insulation displacement connector in the form of a fork which comprises
(1) a first tine comprising (a) a first beveled tip, and (b) a first section having a first length and a first width,
(2) a second tine comprising (a) a second beveled tip, and (b) a second section having a second length and a second width,
(3) a base connecting the first and second tines,
(4) a slot which (a) separates the first and second tines, and (b) has an open end between the first and second tips and a closed end at the base; and
(5) a beveled groove (a) comprising a cutting edge, and (b) extending from the closed end away from the first and second tips and along part of the base.
It is often useful to mount IDCs onto a fixture to make electrical connection easier. Thus, in a second aspect, the invention provides an assembly for making an electrical connection to an electrical cable which comprises a first elongate electrode and a second elongate electrode, said first and second electrodes surrounded by and separated from one another by a polymer, said assembly comprising
(A) an insulation displacement connector (IDC) module which comprises first and second piercing members, each of which comprises an insulation displacement connector according to the first aspect of the invention; and
(B) a wire guide module which
(1) contains a channel sized to contain the cable, and
(2) is capable of mating with the IDC module in a unique mated configuration so that when the cable is inserted into the channel and the IDC module and the wire guide module are mated, the first piercing member pierces the cable and makes electrical contact to the first electrode, and the second piercing member pierces the cable and makes electrical contact to the second electrode.
In a third aspect, this invention provides an electrical plug for connecting an electrical cable to an electrical power outlet, said electrical cable comprising a first elongate electrode and a second elongate electrode, said first and second electrodes surrounded by and separated from one another by a polymer, said plug comprising
(A) a housing which comprises
(1) a first housing member, and
(2) a second housing member, the first and second housing members being movable relative to each other between a demated configuration and a unique mated configuration which provides an opening for receiving the cable;
(B) an insulation displacement connector (IDC) module which comprises first and second piercing members, each of which comprises an insulation displacement connector according to the first aspect of the invention; and
(C) a wire guide module which
(1) fits within the first housing member,
(2) contains a channel sized to contain the cable, said channel aligned with the opening formed when the first and second housing members are mated, and
(3) is
Aromin Victor V.
Larkin Brian S.
Prasad Chandrika
Sircus Brian
Tyco Electronics Corporation
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