GB2243033A - Electric connector - Google Patents

Abstract

A miniature electric connector, such as a cord-mounted data jack, comprises at least two plastics mouldings (2-4) which snap fit together. One (3) is insulating, and supports at least one contact. The second (2 or 4) is a screening part, and is metallised all over. The metallised part is spaced from the contact(s) when assembled. Preferably there are two metallised screening pants (2, 4) which snap fit with each other and trap the insulating part (3) between them. <IMAGE>

Description

ELECTRIC CONNECTOR This invention relates to electric connectors, and more particularly to connectors of small size. Extremely compact designs of connector, often based on a monolithic plastics moulding, have become commonplace in the connection of telecommunication apparatus, and are generally satisfactory for use with telephone speech circuits, but if they are to be used successfully for data transmission the need to provide for screening against interference becomes apparent.

The present invention provides connectors of comparable dimensions that are screened and suitable for use with screened or fully-shielded cords and thus suitable for data transmission applications, for example in Local Area Networks. The connectors in accordance with the invention may, inter alia, be cord-mounted plugs or sockets, panel-mounted sockets, wall mounted sockets or printed wiring board input/output data sockets. For simplicity, such connectors, whether male or female, will be referred to hereinafter as "data jacks".

Metal screening components of the small dimensions required for such data jacks are difficult to make and assemble with the necessary precision to ensure electrical continuity at their joints, and the small size and complexity of the plastics moulding makes the use of selective metallisation on its surface impracticable.

The connector in accordance with the invention comprises at least two plastics mouldings which snap-fit together; namely an insulating part which supports at least one electric contact and a screening part which is metallised over substantially its entire surface and which is spaced and thereby insulated from the said contact when the parts are assembled.

Preferably there are two screening parts which snap-fit with each other to trap and enclose (to the extent required) the insulating part witch a cord connected, or to be connected, to the said contact passing between them, so that there is no need to thread the cord through a screening part prior to terminating its conductors.

When the contact(s) is/are of the insulation-displacing kind, the connector preferably includes an additional (insulating) member which serves to press a cord conductor end into connecting engagement with the or each contact when the parts are assembled.

The use of a separate insulating part to mount the contacts avoids the need for selective metallising.

When the connector is a data jack, the number of contacts will usually be four, six, eight or ten. More generally, when there is more than one contact, the screening part(s) may contact, or be otherwise electrically connected to, one of the contacts (or if required more than one - but not all - of them).

In the case of a connector, such as a male data jack, having a flexible part for locking or other purposes, such part is preferably not metallised and should therefore be on a part that is not (one of) the screening part(s); it may be formed in one piece with the said insulating part, or it may be an additional part snap-fitting with one or more of the other parts or trapped between two or more of them.

When the connector is mounted on a cord having a metal screening braid underlying a plastics sheath, preferably the braid is terminated by a fitting comprising of ferrule dimensioned to push onto and engage a cut-back end of the said sheath and a ring concentrically surrounding the ferrule, an end portion of the said braid being turned back to lie radially between the said ferrule and the said ring and the said ring being compressed to grip the said end portion of the braid, and the ring is electrically and mechanically engaged by gripping it between two connector parts, at least one of which is a said screening part.

Preferably the said ferrule includes a first part which surrounds the sheath and a second part which overlies the part of the braid from which the sheath has been removed. Preferably the ferrule is stepped or tapered so that the second part surrounds the braid with only a small clearance; preferably also the ferrule is stepped or tapered externally e.g. it can be of uniform wall thickness; and the outside diameter of the ring is then preferably similar to that of the first part of the ferrule. The ring may by formed with at least one projecting lug.

The invention will be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 an exploded view showing five parts of a cord mounted data jack in accordance with the invention separated from one another in correct vertical alignment; Figures 2, 3 & 4 are plan views of three of these members; Figure 5 is an end view of another member; Figure 6 is a diagramatic sectional view of a cord end prepared for connection to the data jack; Figure 7 is a diagramatic end view of the cord termination of figure 6; and Figures 8 & 9 are sketches of earthing accessories for use with the termination of figures 6 and 7.

Refering first to figures 1 to 5, the jack (which is designed to North American, rather than British, practice) comprises five separate mouldings all formed in a plastics material having suitable small degree of flexibility; the components have been numbered from top to bottom for ease of reference to the drawing.

Component 3 (figures 1 and 3) is the main insulating component upon which are mounted contacts 6 having portions (at the right hand end as drawn) for making contact with the mating connector and (at the left hand end) insulation piercing formations for contacting conductors of an electric cord. Depending on design preference, component 3 may be a monolithic moulding or it may be a composite made of two (or more) mouldings welded or snapped together. This component 3 is trapped between two main screening components, 1 and 4, both of which are metallised all over, including their inner and outer surfaces and their edge surfaces, and which snap fit together; spigots 7 and apertures 8 on components 4 and 3 respectively assist in precise location.The remaining members of the connector proper are an unmetallised, insulating "conductor stuffer" 2, which is first snap fitted inside component 1 as shown in dotted lines in figure 1, and which presses the cord conductor ends into effective engagement with the appropriate insulation-displacing contacts 6 when the parts are assembled, and eliminates any risk that a properly terminated cord conductor end might make electrical contact with the metallising on component 1, and a locking member 5 which is trapped between the insulating component 3 and the housing member 4, with a recess 9 providing precise location. This member 5 is unmetallised, not for any electrical reason but because repeated flexing in use might tend to cause unsightly flaking off of the metallisation.

Figures 6 and 7 show the way in which a wire braided cord is terminated for connection to the phone jack; the cable comprises (say) four insulated conductors 10 surrounded by wire braid 11 and enclosed in a plastics sheath 12. In preparation for termination, these parts are cut back to a appropriate distance in the usual way. A metal ferrule 13 is threaded over the cut-back cord end so that one of its ends is pushed onto the sheath 12 while its other end overlies the exposed part of the braid 11. The ferrule is a resilient push fit on the end of the sheath, and local detents 14 may if desired be provided to improve the grip and give a measure of security against tension. The ferrule is preferably of tapered or stepped internal diameter, to avoid leaving any substantial gap between it and the underlying part of the braid, and its external surface may be correspondingly stepped or tapered, for instance by making it of uniform wall thickness. The projecting end portion 15 of the braid 11 is next turned back to surround the end part of the ferrule 13, and an outer metal ring 16 is threaded over it and compressed with a crimping tool so that the braid is firmly gripped between the ring 16 and the ferrule 13. The ring 16 might be a simple circular one, but preferably it is formed with a pair of projecting lugs 17 (or at least one lug) since this provides a ready means of securing the cord end against tension and any tendency to rotation.Specifically, the lugs 17 may enter recesses 18 (figure 4) to provide the required location, and at the same time ensure adequate electrical contact between the cord braid and the metallising on components 1 and 4.

It will often be a requirement also to provide connection between the cord braid and one of the contacts 6, and this may be acheived using an auxillary component of the form shown in either figure 8 or figure 9. Figure 8 shows a one-piece metal clip having an end part 20 which is of suitable dimensions and resilience for gripping engagement either with one of the lugs 17 or with the main body of the ring 16 and a thin flexible projection 21 which can be bent by the installer to engage it with any selected one of the contacts 6. Two of these components can be used to provide earth connections on two of the conductors 6 if required. The alternative design in figure 9 is similar, except that the integral projecting finger 21 is replaced by a short length of insulated wire conductor 22, and is used in a substantially the same way.

Claims (13)

1. An electric connector comprising at least two plastics mouldings which snap fit together, namely an insulating part which supports at least one electric contact and a screening part which is metallised over substantially its entire surface and which is spaced and thereby insulated from the said contact when the parts are assembled.

2. A connector as claimed in claim 1 in which there are two screening parts which snap fit with each other to trap and enclose the insulating part with a cord connected, or to be connected, to the said contact passing between the two screening parts.

3. A connector as claimed in claim 2 in which the said contact is an insulation-displacing one and in which an additional member serves to press a cord conductor end into connecting engagement with the said contact when the parts are assembled.

4. A connector as claimed in any one of the preceding claims having a flexible part which is neither metallised nor part of the or any screening part.

5. An electric connector as claimed in any one of the preceding claims when mounted on a cord having a metal screening braid underlying a plastics sheath and terminated by a fitting comprising of ferrule dimensioned to push onto and engage a cut-back end of the said sheath and a ring concentrically surrounding the ferrule, an end portion of the said braid being turned back to lie radially between the said ferrule and the said ring and the said ring being compressed to grip the said end portion of the braid, the ring being electrically and mechanically engaged by gripping it between two connector parts, at least one of which is conductive.

6. A connector as claimed in claim 5 in which the said ferrule includes the first part which surrounds the sheath and a second part which overlies the part of the braid from which the sheath has been removed.

7. A connector as claimed in claim 6 in which the ferrule is stepped or tapered so that the second part surrounds the braid with only a small clearance.

8. A connector as claimed in claim 7 in which the ferrule is stepped or tapered externally and the outside diameter of the ring is similar to that of the first part of the ferrule.

9. A connector as claimed in claim 7 or claim 8 in which the ferrule is of uniform wall thickness.

10. A connector as claimed in any one of claims 5-9 in which the said ring is formed with at least one projecting lug.

11. An electric connector substantially as described with reference to figures 1 to 4 of the drawings.

12. A connector substantially as described with reference to figures 1 to 7 of the drawings.

13. A connector substantially as described with reference to all the accompanying drawings.