Electrical connectors – Contact comprising cutter – Insulation cutter
Patent
1994-06-03
1996-06-04
Pirlot, David L.
Electrical connectors
Contact comprising cutter
Insulation cutter
439404, H01R 424
Patent
active
055227333
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to electrical connectors and in particular to insulation displacement contacts which are commonly mounted in connecting blocks for connecting insulated wires either to contacts on a wiring block or to a second set of wires. The Invention also relates to connecting blocks for housing insulation displacement contacts.
Insulation displacement contacts are of particular applicability to the voice and data communications industry. There have been many proposals for insulation displacement contacts (IDC) in the past. However. all prior proposals suffer from one or more of number of disadvantages as will be described.
The basic function of a connector block is to house a number of insulation displacement contacts, normally 4 or 8. The individual contacts provide at one end a pair of contacts for attachment either to a wiring block or to individual wires and at the other end a pair of contacts for receiving an insulated wire. The contacts are disposed in a manner which ensures that the insulation around the wire is stripped away or displaced as the wire is fed between the contacts. Commonly, this has been achieved by a cantilevered split beam where the two beam halves are displaced by a distance less than the width of the insulation of the wire with which the connector is to be used. The open ends of the beams are usually shaped so that the wire can be guided between the beam halves or tynes and a slot or opening is provided to retain the wire, with its insulation displaced, in contact with the connector and to give the tynes a degree of flexibility.
U.S. Pat. No. 4,964,812 (Siemon) discloses an IDC which comprises two opposed cantilevered beams each of which comprises a pair of tynes and each of which extends from a central portion. Each tyne pair is separated by an elongate opening along a part of its length and is formed from an original cantilevered beam by shearing along a shear axis which forms the cutting surface for cutting the insulation on a wire. The shear axis is conveniently the longitudinal axis of the cantilevered beam. This shearing produces a closed gap between the tynes of a beam. However, a secondary closing action is necessary to achieve a satisfactorily small gap between the tynes. This is achieved by a coining operation performed on the outside edges at the base of the tynes and decreased coin surfaces pre-load the beam elements whilst maintaining clean contact surfaces and raising the contact force to a level where it is sufficient to penetrate the insulation on small wires.
The need for a secondary operation to close the slot to the required dimension is undesirable and arises from an attempt to overcome problems with beam stiffness by increasing contact thickness.
The performance of a split beam contact is determined by the stiffness of the beam, which is itself proportional to the cube of the contact width in the direction of flexing. The requirement for contact stiffness is in direct conflict with the requirement that the IDCs have the smallest possible pitch so as to minimise installation space and connector block width.
The solution proposed in U.S. Pat. No. 4,964,812 requires the secondary closing operation because the beam stiffness problem has been overcome by increasing contact thickness rather than width. The result is an IDC which is difficult to manufacture.
A similar approach has been taken by A T & T in their 110 series connectors, for example the 110C-4. The displacement contacts for the connectors are described in a number of U.S. patents, for example U.S. Pat. No. 3,611,264 (Ellis), U.S. Pat. No. 3,798,587 (Ellis) and U.S. Pat. No. 4,118,095 (Berglund).
The contacts described in all these documents suffer from the same problems as the Siemon patent due to the attempt to solve beam stiffness problems by increasing contact thickness.
It has been proposed to overcome the requirements of a stiff beam and a narrow contact by producing a wide beam and rotating it in the connecting block by an angle of 45.degree. to the central b
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International Search Report.
Ivey David E.
Jones Keith H.
White Rowland S.
MOD-TAP W Corp.
Pirlot David L.
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