Electrical connectors – Contact comprising cutter – Insulation cutter
Patent
1997-05-27
1998-11-17
Abrams, Neil
Electrical connectors
Contact comprising cutter
Insulation cutter
439395, H01R 424
Patent
active
058367829
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a connector for forming an electrical connection with wires, including those covered in insulation. Such connectors are commonly mounted in an array within a housing of insulating material. The present invention relates also to the design of connecting blocks for retaining the connector elements, and controlling their movements.
A number of proposals and orientations for such insulation displacement connectors (IDCs) are known. All these proposals suffer from one or more of the disadvantages as described below.
IDCs commonly comprise a cantilevered split beam, whose narrow, slotted portion is dimensioned to be smaller than the diameter of the smallest wire to be terminated therein. At the upper end of the slot, there commonly exists a tapered section of slot which acts as a guide for an incoming wire. On insertion of a wire, any insulation is intended to be cut by the sides of this tapered section of the slot. Commonly, the narrow portion of the slot cuts into the wire forming an airtight joint between the wire conductor and both of the IDC slot sides.
1. Flat IDC at approximately 90.degree. to the wire, movement of the two IDC forks forming the sides of the slot is restricted to one plane, tending to force the forks apart, widening the slot. However, it is noted that deflection is inversely proportional to the cube of the spring thickness. In this deflection mode, the thickness should be taken as the width of each IDC fork. The result is often an extremely stiff action with negligible widening of the slot when a wire is inserted.
Such an arrangement is necessarily limited in the range of wire diameters which may be conveniently terminated if all diameters of wire are cut to essentially the same depth by the stiff slot sides. Also, since the slot impinges onto the wire in two places which are opposite to one another, and the profile of copper wire cut out by each IDC fork is rectangular in section, serious weakening of the wire in the IDC region is likely to be encountered, with an increased risk of wire shearing.
2. Flat IDC at approximately 45.degree. to the wire.
When a copper wire is inserted into the slot of a flat IDC held at 45.degree. to the wire, movement of the two IDC forks forming the sides of the slot occurs in torsional mode, tending to force the forks apart and thus widening the slot.
It is noted that the force exerted on the wire by such IDC forks is directly proportional to the angle of displacement. Such an arrangement would therefore be suitable for terminating a wide range of wire diameters, since the slot dimension would change to correspond with the gauge of wire inserted.
This feature would depend for success on the presence of sharp edges on the IDC forks and it is noted that only one of the two corners of the IDC forks presented to the wire would have the sharp punching burr known to be beneficial for successful IDC connections. A risk of adverse consequences for contact reliability therefore exists.
When shapes such as those required for IDC slot formation are punched from sheet metal, invariably the side from which the metal is punched is left with a blunt, rounded corner. Also, the opposite side of the sheet is left sharp where the punching tool emerged through the slot. For IDC applications it is highly desirable to make use of these sharp edges in order to produce an IDC of reduced insertion force and high reliability.
When the connectors are mounted in an array the array usually consists of parallel pairs of forks. Consequently a capacitance exists between adjacent connectors in the array. This is known to cause problems, particularly at high operational frequencies of the order 100 MHz when capacitive effects are significant. 3. Bent IDC with each IDC fork at approximately 45.degree. to the wire, movement of the two IDC forks forming the sides of the slot would tend to occur, forcing the forks apart and thus widening the slot.
However, with this arrangement the two points of contact between the IDC forks and the wire are opposite one another,
REFERENCES:
patent: 4448472 (1984-05-01), Hardesty
patent: 5269700 (1993-12-01), Mitra
patent: 5447449 (1995-09-01), Kaneko
Hebenstreit Martin
Odley Richard Austin
Abrams Neil
Austin Taylor Communications Limited
Biggi Brian J.
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