GB2286297A

GB2286297A - Electrical connectors

Info

Publication number: GB2286297A
Application number: GB9501319A
Authority: GB
Inventors: Salvatore Pulire; Rowland Spencer White
Original assignee: Mod Tap W Corp
Current assignee: Molex Premise Networks Inc
Priority date: 1994-01-24
Filing date: 1995-01-24
Publication date: 1995-08-09
Also published as: GB9501319D0

Abstract

In a connector, e.g. for telecommunications, the conductor channels 17 (Fig. 12) are open at the ends adjacent the contacts, facilitating cable termination. In a second aspect (Fig. 10) the contacts are arranged in a second aspect the contacts are arranged such that the capacitance between adjacent contacts is reduced, whilst that between alternate contacts is increased, e.g. by providing staggered holes 6, 6a in adjacent contacts. A third aspect (Fig. 7) relates to the reduction of cross talk between conductors within the body of an electrical connector. To this end a conductor pair, e.g. comprising wires 7 and 8, is arranged such that the relative spacing of the wires 7 and 8 is less than the distance from an adjacent wire 6. <IMAGE>

Description

REDUCED CROSS TALK CONNECTOR This invention relates to the termination of wires to electrical connectors. The invention also relates to the reduction of cross-talk between wires or contacts which are in close proximity with one another in such connectors.

An example of an existing data communications connector is the RJ type connector, the specification of which is defined in International standard IEC 603-7 of the International Electrochemical Commission. This connector has eight parallel contacts which terminate eight wires, which are substantially parallel and equidistant for a portion of their length within the connector. Connectors of this type generally comprise a simple plastic moulding having a series of parallel channels to guide the wire conductors into cavities, where they can be connected, by piercing the wire insulation, to relatively large flat contacts. The contacts comprise flat conductors which are adjacent and parallel to one another.

The termination of a cable to this type of connector is established by removing a section of outer cable sheath, which houses the eight wires, from the end of the cable; the length of insulated wire exposed, by removal of the outer sheath, is predetermined so that the wires are the correct length for the guiding channels. The exposed wires are arranged in the correct sequence; and the cable is inserted from the rear of the connector so that each wire is guided along a channel to a respective contact.

When correctly positioned, the wires will abut the closed ends of the channels and part of the outer sheath will protrude into the rear of the connector where it is clamped by a cable clamp.

In connectors of this type it is essential that the wires are of the correct length so that the above arrangement may be satisfied.

High speed data transmission is prone to interference problems which it is desirable to control. One of the most serious forms of interference is cross talk, which may be defined as the voltage generated in a wire or contact due to interference from a wire or contact in close proximity. The induced signal will have some inductive and capacitive components and will, therefore, vary with frequency. Cross talk is a particular problem at higher frequencies and an especiallzr difficult problem to control as the induced cross talk signal is a true data signal and is recognised, accepted and processed as such by the associated data processing equipment.

It is known that cross talk may be reduced in cabling systems by twisting together pairs of wires used for a single circuit. This has two benefits. A first benefit is that electrostatic and electromagnetic fields through which the cabling passes, which may include fields produced by neighbouring data wires, affect both wires of the pair equally. The nett effect being that the interference is reduced or cancelled. A second benefit is that since the current flow in one wire of the pair is in an opposite sense to the other, the fields produced by each wire are also in opposite senses, and so interfere destructively. The nett effect is that the resultant field produced by the pair is reduced or cancelled. The pair will, therefore, produce less interference in other neighbouring wires. Our copending applications GB 9225573.6 and GB 9226481.1 describe ways in which this technique may be applied to an electrical connector.

We have appreciated that connectors, for which the length of exposed wires must be carefully arranged prior to termination, are prone to connection problems.

Accordingly there is provided an electrical connector comprising a body and a plurality of contacts for connection to electrical conductors, the body having a plurality of channels extending along the length of the body for receiving the conductors, characterized in that the channels are open at both ends whereby conductors lying in the channels can extend beyond the ends of the body.

This has the advantage of obviating one of the constraints on the length of the wires to be connected. The cable is inserted at the rear of the connector so that individual wires locate within the guide channels. The cable is inserted until proper location of the outer sheath with the cable clamp is established. If the wires protrude from the front of the connector the excess may be trimmed.

We have appreciated that connectors in which the contacts are substantially parallel and planar, and connectors in which the wires connected to the contacts are substantially parallel for a portion of their length, are particularly prone to cross talk interference. Since there are standard arrangements of contacts within existing connectors, we have also appreciated that any new connectors should retain compatibility with existing designs, and that this places constraints upon the ways in which new connectors may be arranged. The invention therefore aims to reduce cross talk whilst maintaining compatability with existing designs.

Accordingly, a second aspect of the invention provides an electrical connector comprising a body housing three or more conductive contacts for connection to respective electrical conductors the contacts being parallel to a common plane and at least partially overlapping in a direction perpendicular to the common plane characterized in that the contacts are housed in the body such that the area of overlap of adjacent contacts is less than the area of overlap of the alternate contacts.

An embodiment of this aspect of the invention may achieve a reduction in the capacitance between adjacent contacts, whilst increasing the capacitance between alternate contacts. The reduction in capacitance between adjacent contacts is desirable to reduce cross talk, the increase in capacitance between alternate contacts is also desirable, as it will in some measure compensate for the residual influence between adjacent contacts.

A third aspect of the invention provides an assembly comprising at least three electrical conductors, and an electrical connector comprising a body having at least three conductive contacts each having a conductor conductively attached, characterised in that two of the conductors form a circuit pair and are arranged so that for a portion of their length along the connector the separation of the circuit pair from the at least one other conductor is greater than the separation of the conductors forming the circuit pair.

An assembly embodying this aspect of the invention has the advantage that conductors which are further apart are less influenced by each others electromagnetic and electrostatic fields. Conductors forming a circuit thus have reduced influence upon other conductors forming different circuits, and cross talk is reduced. Since conductors which form a complete circuit produce equal and opposite electrostatic and electromagnetic fields the nett effect is that interference is cancelled within the circuit. There is thus no detriment in having conductors which form a circuit close to one another.

In a preferred embodiment of this aspect of the invention the circuit pair of conductors is arranged so that the line between the perpendicular cross-sections of the conductors in a pair is substantially perpendicular to the plane of the upper surface of the connector body.

This arrangement has the added advantage that the distance between a first conductor of the pair and an adjacent conductor not forming a part of the pair is substantially equal to the distance between a second conductor of the pair and the adjacent conductor for a portion of their length. The fields produced at the adjacent conductor due to the first and second conductors of the pair will be substantially equal and opposite, for a portion of the conductor length, the nett effect being a reduction or cancellation of cross talk interference.

Preferred embodiments will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a prior art contact; Figure 2 shows the contact of Figure 1 positioned in the housing of a connector; Figure 3 shows a cross section of a prior art plug and including the contact of Figures 1 and 2; Figure 4 shows a perspective view of the prior art plug of figures 1 to 3; Figure 5 shows the plug of figure 4, but with the latch removed to show the arrangement of wires; Figure 6 shows a plug according to a first embodiment of the third aspect of the invention; Figure 7 shows a plug according to a second embodiment of the third aspect of the invention; Figure 8 shows a cross section of a plug according to a third embodiment of the third aspect of the invention; Figure 9 shows a contact embodying to a second aspect of the invention; Figure 10 shows the contact of Figure 9 positioned in the housing of the connector; and Figure 11 shows a plan view of a plurality of contacts of Figure 9 positioned within the housing.

Figure 12 shows a cross section of a plug according to a first aspect of the invention.

Figure 13 shows the plug of Figure 12, the excess wires having been trimmed.

A typical prior art male connector is shown in Figures 1 - 5. A typical contact is shown in Figure 1. The contact 2 comprises a flat blade-like contact having at one end a flat edge 9. When positioned within the connector body and the male connector is coupled with a female connector the flat edge establishes conductive contact with a respective contact in the female connector. At its opposite end the contact has two points 7 which, when the contact is positioned in the connector body, pierce the insulation of a wire and establish conductive contact with that wire. Between the two ends there is a waisted portion 10 which locates with protrusions 15 within the connector body (Figures 2 and 3), in order to hold the contact in position.

Figure 2 shows the contact of Figure 1 positioned within a receiving slot of the connector. Referring to Figure 2b) the slot comprises three portions: Upper and lower portions 11, 12 are wider than the contact thickness wherein the middle portion 13 is substantially the same thickness as the contact thickness so that the contact is snugly received therein. The upper portion 11 of the slot contains the portion of the contact having the flat edge 9 and has a depth d deeper than the length of this upper portion of the contact. The contact is, therefore, recessed within the slot. The middle portion of the slot 13 contains the waisted portion of the contact 10 (Figure 2a). The third portion of the slot contains the two points of the contact 7 and a section of the wire to be connected. As can be seen from Figures 3 to 5, the plug comprises the connector body 1, and a set of contacts which are received in parallel slots 11 as described. A latch 14 is provided on one side and retains the connector in place when connected to a female connector. A cable 8 comprises an outer sheath housing eight wires. Each wire is individually insulated. The cable enters the connector body at one end, a portion of the outer sheath having been removed so that the wires are exposed for a portion of the length of the connector body. Each wire is terminated to a contact at the second end of the connector body, in the manner described. The wires are gathered by the outer sheath at the first end of the body and are terminated so that the wire ends are equidistant and in a line at the second end. In between the first and second ends the wires lie substantially parallel, equidistant and in a common plane which is parallel to plane of the upper surface of the body 16.

Figures 12 and 13 show a plug according to a first aspect of the invention. Figure 12 shows a cross section of a plug having open ended channels 17 through which the wires to be connected may protrude prior to being cut.

To terminate a cable to the conductor of Figures 12 and 13, a section of the outer cable sheath 8 is removed exposing the eight insulated wires. The length of the exposed insulated wires is not crucial but they must, of course, extend at least as far as the contacts 2. The wires are then arranged in the correct sequence and the cable inserted from the rear of the connector.

The wires will lie in respective channels 17 in the connector body and any excess length will extend through the open ended channels 17 beyond the end of the conductor. The wires may then be trimmed to the correct length.

Figures 9 - 11 show a second aspect of the invention. Figure 9 shows a contact 2 in which a hole 6 has been made. Figure 10 shows the same contact positioned in the slot of the connector body. The hole position of an adjacent contact is shown by a dotted line 6a. Figure 11 shows a plan view of the arrangement of the holes in the contacts of the fourth embodiment. The shaded areas represent the positions of the holes. Alternate contacts have a hole in a first position, the second set of alternate contacts having a hole in a second position. Although the holes shown are circular, they may be any shape. The contacts may, alternatively, have a section removed rather than a hole. The contacts may also differ in shape so that alternate contacts are identical and adjacent contacts differ, or the shapes may differ in another arrangement.

The arrangements of this embodiment produce an increased capacitance between alternate contacts whilst reducing the capacitance between adjacent contacts. This reduction in capacitance between adjacent contacts reduces the cross talk effects, the increase between alternate contacts helps to counteract the remaining capacitance between adjacent contacts.

Figure 6 shows how the prior art connector is modified according to a first embodiment of the third aspect of the invention. The connector has a body 1 and contacts 3 as shown in Figures 1 to 5. A cable 8, comprising eight insulated wires, enters the connector body at a first end. Each wire is terminated to a respective contact at the second end of the connector, in the manner described. The eight wires, numbered 1 to 8, are conventionally arranged as follows. There are three pairs of wires: one and two, four and five, seven and eight. The wires which are paired form a complete circuit, as do wires three and six which are unpaired. The wires lie substantially in a common plane which is parallel to the plane of the upper body surface 16. At the first end of the body the wires are grouped together by the outer sheath and at the second end of the body the ends of the wires are equidistant along a line. To reduce cross talk, each wire of a pair is contiguous with the other wire of the pair for a portion of the length between first and second ends of the connector, and the wire pairs have increased separation from any other wire. By increasing the separation of wires carrying different data signals, the strength of electromagnetic and electrostatic fields at a wire, radiated by another wire carrying different data, are reduced. Wires carrying the same data signal are closer together (contiguous) and so are induced more by one another. Since the induced signal is in the same sense in both wires the nett effect is that interference between them is cancelled, and so there is no detriment in having wires of the same data circuit close together.

Figure 7 shows a perspective view of a second embodiment of the third aspect of the invention, comprising body l and contacts 2 as previously described. The arrangement of wires is similar to Figure 6. In this embodiment, however the wires forming pairs are arranged so that for a portion of the length of the wires the line between the cross sections of the two wires forming the pair is substantially perpendicular to the plane of the upper surface of the body 16. The distance between a first conductor of a pair and an adjacent conductor is substantially equal to the distance between a second conductor of the pair and said adjacent conductor for a portion of their lengths. The fields produced at said adjacent conductor by the first and second conductors of the pair will be substantially equal and opposite, for a portion of the conductor length, the nett effect being a reduction of cross talk interference.

Figure 8 shows a cross section of a third embodiment of the third aspect of the invention, comprising a body 1 and contacts 2 as previously described with reference to figures 6 and 7 and additionally having a printed circuit board 5. The printed circuit board (pcb) has eight electrically conductive tracks. At a first end each track is electrically connected to a respective wire 3. At a second end each track is electrically connected to a respective contact 2, so that electrical connection is established between each wire 3 and a respective contact 2.

Two of the tracks may form a circuit pair and are arranged so that for a portion of their length along the connector, the separation of the circuit pair from the at least one other track is greater than the separation of the tracks forming the circuit pair. This arrangement of tracks reflects the arrangement of wires of the first embodiment of the invention.

By arranging the tracks in this way, the capacitance between tracks forming the circuit pair is increased and compensates for the inherent capacitance of the connector assembly, and so reduces crosstalk.

The circuit pair may also be arranged so that the line between the perpendicular cross sections of the conductors in the pair is substantially perpendicular to the plane of the pcb. This arrangement of tracks reflects the arrangement of wires of the second embodiment. In order to achieve this arrangement a double-sided circuit board may be used, with tracks on each side of the board. The tracks forming the circuit pair are disposed on opposite sides of the board from one another. The capacitance between the tracks forming the circuit pair may be varied by variation of the track area. Increasing the area of the tracks forming a circuit pair results in an increase in the capacitance between them. This increase is advantageous in compensating for the inherent capacitance between other tracks in the connector assembly.

Use of a pcb in this embodiment has the advantage that the capacitance between the tracks may be controlled to achieve a precise effect. Additionally, in this embodiment the control of capacitance between more than two tracks is achieved.

The tracks may alternatively be in other arrangements in order to reduce cross talk effects within the connector. Such arrangments may vary the area, shape or configuration of the tracks in order to control the capacitance and reduce crosstalk.

Whilst this embodiment has been described with respect to an eight track pcb, the pcb may have another number of tracks.

Whilst the embodiments have been described with respect to an eight wire data connection plug, the invention may be applied to any assembly in which a number of wires or contacts are substantially parallel or to another type of electrical connector.

Claims

1. An electrical connector comprising a body and a plurality of contacts for connection to electrical conductors, the body having a plurality of channels extending along the length of the body for receiving the conductors, characterized in that the channels are open at both ends whereby conductors lying in the channels can extend beyond the ends of the body.

2. A method of connecting sheathed insulated wires to an electrical connector, the connector comprising a body housing a plurality of contacts, the body having a plurality of channels extending along the body which are open at both ends, the method comprising removing a section of the sheath to expose the insulated wires, arranging the wires in a desired wiring configuration with respect to each other, inserting each insulated wire into a respective channel at a first end thereof, the wires being guided along the channels to respective contacts, connecting each wire to a respective contact at a desired point along the wire, and removing excess wire extending beyond the second end of each channel.

3. An assembly comprising at least three electrical conductors (3), and an electrical connector comprising a body (1) having at least three conductive contacts (2) each having a conductor (3) conductively attached, characterised in that two of the conductors form a circuit pair and are arranged so that for a portion of their length along the connector the separation of the circuit pair from the at least one other conductor is greater than the separation of the conductors forming the circuit pair.

4. An assembly according to claim 3, wherein two or more of the conductors lie substantially in a common plane.

5. An assembly according to claim 4, wherein the pair of conductors is arranged so that the line between the perpendicular cross sections of the conductors in the pair is substantially perpendicular to the plane of the upper surface of the connector body (16).

6. An assembly according to claims 3 to 5, wherein one or more of the conductors comprise insulated electrical wire.

7. An assembly according to any of claims 3 to 6, comprising eight conductors, wherein six of the conductors are arranged as three of said circuit pairs, and each of the remaining conductors, which together form a complete circuit, is disposed separately adjacent at least one circuit pair.

8. An assembly according to claim 6 or 7, wherein the contacts are arranged so that they pierce the wire insulation of the conductors to establish electrical contact therebetween.

9. An assembly according to claims 3 to 5, or 7, wherein one or more of the conductors comprise printed circuit tracks.

10. An electrical connector comprising a body (1) housing three or more conductive contacts (2) for connection to respective electrical conductors the contacts being parallel to a common plane and at least partially overlapping in a direction perpendicular to the common plane characterized in that the contacts are housed in the body such that the area of overlap of adjacent contacts is less than the area of overlap of the alternate contacts -

11. A connector according to claim 10, wherein alternate contacts are identical in orientation and adjacent contacts differ in orientation.

12. A connector according to claim 10 or 11, wherein alternate contacts each have a hole in a first position and the one or more remaining contacts has a hole in a second position.

13. An assembly substantially as herein described with reference to Figures 6 to 8 of the accompanying drawings.

14. An electrical connector substantially as herein described with reference to Figures 9 to 11 of the accompanying drawings.

15. An electrical connector substantially as hereina described with reference to Figures 12 and 13 of the accompanying drawings.

16. A method of connecting sheathed insulated wires substantially as herein described with reference to Figures 12 and 13 of the accompanying drawings.