GB2242320A

GB2242320A - Improvements relating to electrical connectors

Info

Publication number: GB2242320A
Application number: GB9101875A
Authority: GB
Inventors: Frank Vause
Original assignee: Electrocomponents PLC
Current assignee: Electrocomponents PLC
Priority date: 1990-01-29
Filing date: 1991-01-29
Publication date: 1991-09-25
Anticipated expiration: 2011-01-29
Also published as: GB2242320B; GB9101875D0; GB9001980D0

Abstract

A terminal for connecting an electrical connector to an electrical conductor comprises a receptacle 16 and a leaf spring 15. The receptacle is arranged to receive an end portion of the conductor and the leaf spring 15 is adapted to fit into the receptacle 8 to trap the conductor end portion thereof. The leaf spring is retained in the receptacle by being a compressive fit and is strongly resistive to tension put on the conductor so as to tend to pull the conductor out of the receptacle. The arrangement provides an effective and reliable alternative to screw terminals and is suitable for both manual and automatic assembly in 3-pin plug. The plug includes a fuse holder 6 pivoted by a flap 26 to the plug base and cover. The holder and cover are interlocked to preclude cover removal unless the holder is pivoted to a disengaged position. <IMAGE>

Description

MPROVEXESTS RELATING TO ELDUTRICAL CONNECTORS This invention concerns improvements relating to electrical connectors and more particularly concerns an improved means for coupling an electrical conductor to a terminal. The invention will be described hereinafter with particular reference to multi-pin electrical plugs, especially three-pin mains electrical plugs, but it is to be well understood that the invention has wider application.

The time honoured means of coupling electrical conductors to the pins of a mains plug is the screw terminal and whilst this is effective and reliable, nonetheless it comes in for criticism as being fiddly and user-unfriendly and furthermore it is not at all well suited to automatic assembly. Numerous alternative proposals have been made, but few indeed of these have ever seen commercial production. The search thus has continued for an easy and convenient means of terminating an electrical conductor which is suitable both for manual use and for automatic assembly.

According to the present invention, a terminal for an electrical connector comprises a receptacle formed of a good electrical conductor and a leaf spring adapted to be fitted into said receptacle, the arrangement being such that with a bared electrical conductor end portion received in said receptacle the insertion of said leaf spring causes the conductor end portion to be held in the receptacle in contact with an interior surface thereof under spring loading.

In accordance with an exemplary embodiment of the invention which will be described in detail hereinafter, the receptacle comprises a generally rectangular box-shaped brass pressing having an open top face and an open front end wall, the open top face enabling the bared conductor end to be laid into the receptacle and the open front end wall enabling the leaf spring to be inserted, the rear end wall of the receptacle (opposite to the open front end wall) being partially cut away to accommodate the conductor leading away from the terminal, and the opposed side walls having cut-outs adapted to co-operate with the leaf spring, when it is inserted, to retain the leaf spring under compression within the receptacle.The leaf spring is at least U-shaped so as to lodge between the opposed side walls of the receptacle, preferably is looped back onto itself to develop greater spring force, and desirably has a portion adapted to co-operate with one of the side walls of the receptacle to effect a crimping action on the conductor end portion received therebetween.

The assembly of a bared conductor end portion to a terminal formed in accordance with the present invention is a simple matter which can be effected either manually or automatically and, particularly where the leaf spring is arranged to crimp the conductor against a receptacle side wall, the terminal can provide substantial resistance against any likelihood of the conductor end pulling out of the receptacle. Indeed, the arrangement of the leaf spring can advantageously be such that any pull on the conductor tends to tighten the spring and increase the spring pressure upon the conductor end.

The invention will best be appreciated from consideration of the following detailed description of an exemplary three-pin mains plug embodying the invention, such plug being illustrated in the accompanying drawings wherein: Fig. 1 shows a top plan view of the aforesaid mains plug with a cover portion removed to show the internal construction; Fig. 2 is a sectional view taken on the line A...A in Fig. 1; Fig. 3 is an end elevation view from the direction of the line B...B in Fig. 1; Fig. 4 is a sectional view taken on the line C..C in Fig. 1; Fig. 5 is a sectional view taken on the line D...D in Fig. 1; Fig. 6 is a sectional view taken on the line E...E in Fig. 1; Fig. 7 is a bottom plan view of the plug; and Figs. 8A, B, C and D are enlarged views of the receptacle and leaf spring; Figs. 9A, B and C are enlarged views of an alternative receptacle and leaf spring; and Figs. 10A, B, C and D are enlarged views representing stages in the assembly of the alternative receptacle and leaf spring.

Referring to the drawings, and with particular attention to Fig. 1, the mains plug illustrated is of the 13 amp type commonly employed in the UK in domestic situations and comprises a moulded plastics base 1, a cover 2 adapted to make a sliding fit onto the base, live and neutral terminal pins 3 and 4 respectively each with an insulating sleeve moulded integrally with the base, an earth pin 5, a fuse holder 6, and a cable clamp 7. For a non-rewirable plug, the cover and base could be provided with cooperating detents such as to prevent the cover from being removed once it has been assembled with the base, and for a rewirable plug the cover can advantageously be arranged not to be removable from the base until the fuse holder has been opened.Since the fuse holder cannot be opened until the plug is removed from a socket outlet, the possibility of removing the cover whilst the plug is plugged into a live socket outlet is thereby precluded.

As is shown most clearly in Fig. 1, conductor receptacles 8, 9 and 10 respectively are provided in the base 1 of the plug in electrical contact with the terminal pins 3, 4 and 5, the electrical contact in the case of the live pin being by way of a fuse 11 in the fuse holder 6. As shown in Figs. 1 and 4, the upper end of the live pin 3 extends through the plug base 1 and is staked into electrical contact with a first metal fuse holder part 12. A second metal fuse holder part 13 is integrally formed with the conductor receptacle 8. The upper end of the neutral pin 4 is similarly staked to a conductive strap 14 formed integrally with the conductor receptacle 9, and the upper end of the earth pin 5 is staked to the bottom of the conductor receptacle 10.

Each conductor receptacle 8, 9 and 10 is generally box-shaped but with an open upper face and an open front end wall, the terms "upper" and "front" in this context referring to the disposition of the plug as shown in Fig. 1. The construction of the receptacles can best be seen from Fig. 1 and from the enlarged showings of Figs. 8A, B, C and D wherein Fig.

8A is a top plan view of one of the receptacles, Fig.

8B is an end elevation view, Fig. 8C is a top plan view of a leaf spring 15 before insertion into a receptacle and Fig. 8D shows the leaf spring inserted into the receptacle. As can be seen, the rear wall 16 of each receptacle is partially cut away to admit to the receptacle the conductor end that is to be terminated. The left-hand side wall 17 of the receptacle has a rectangular cut-out 18 adapted to receive part of the leaf spring 15 when it is inserted (see Fig. 8D) and the right-hand side wall 19 has a cut-out 20 for engaging an end portion 21 of the leaf spring 15 and a released part 22 for co-operation with a convoluted part 23 of the leaf spring for crimping the bared end of a conductor lodged therebetween. As will be appreciated, the leaf spring 15 is adapted to be a firm push-fit into the open end of the receptacle, not solely with translation of the spring but also with a degree of anti-clockwise rotation, so that the end portion 21 of the spring engages in the cut-out 20 of the receptacle, the bowed portion 24 of the spring engages in the cut-out 18, and the "corner" part 25 of the spring moves in an arc towards the rear right-hand corner of the receptacle. With the bared end of a multi-stranded electrical conductor laid into the receptacle through the cut-away rear wall thereof, the insertion of the leaf spring 15 will cause the conductor end to be trapped between the spring and the rear and right-hand walls of the receptacle and to be crimped between the convoluted portion 23 of the spring and the complementary formation 22 on the receptacle.By this means, a good electrical contact is made between the conductor and the receptacle with the spring force, particularly in the area where the conductor end is crimped, strongly resisting any tension put on the conductor such as to tend to pull it out of the receptacle.

As previously mentioned herein, the leaf spring 15 may be looped back upon itself, namely the end portion 26 of the spring may be extended (for example substantially as shown by the broken lines in Fig. 8C) so as to buttress the opposite side of the spring. As will be appreciated by those possessed of the appropriate skills, the shape of the leaf spring 15 and the shape of the accommodating receptacles are susceptible to modification and variation without departure from the present invention.

The fuse holder 6 comprises a moulded plastics body adapted to be snap-fitted into a recess in the base 1 of the plug and formed with fuse support structures best seen in Fig. 6. The fuse holder shown in the drawings has a flexible tail portion 26 best seen in Fig. 6 which engages slidingly within a recess 27 defined between the plug base 1 and the cover 2 and enables the fuse holder to be opened from the plug base for the purpose of enabling the fuse to be replaced. As previously mentioned, when the fuse holder is closed into the base, the plug cover cannot be removed, the closed fuse holder blocking the inter-engaging sliding surfaces of the cover and base.

As can be seen from Fig. 1, the three receptacles 8, 9 and 10 are conveniently in line across the plug body and each has a clear and well defined access route through the plug body for its respective conductor. By virtue of these and other features, particularly the design of the receptacles and of their leaf springs, the plug can readily be assembled to a three-conductor mains cable either as an industrial operation or in the home.

Referring to Figs. 9 and 10 of the drawings an alternative conductor receptacle 28 can instead be provided in the base 1 of the plug, in electrical contact with the terminal pins 3, 4 and 5 as previously described hereinabove. The construction of the conductor receptacle 28 can best be seen from the enlarged drawings in 9A, 9B and 9C wherein Fig. 9A is an end elevation view, Fig. 9B is top plan view and Fig. 9C is a side elevation view. As can be seen in Figs. 9A, B and C, the receptacle 28 is again generally box-shaped having an open front face. The upper face of the receptacle 28 is substantially open but includes retaining tabs 29a, 29b extending from side walls 30, 31.The receptacle 28 further comprises a rear wall 32 having a cutaway portion to admit a conductor end portion to be terminated therein and a bottom wall 33 by which receptacle 28 can be staked to a terminal either directly by riveting through an aperture 34 for example or via an integrally formed conductive strap (not shown). The receptacle 28 can be formed from a single pressing. An aperture 35 is defined toward the front of the bottom wall 33 for receiving an end portion 36 of a crimping leaf spring 37 as can be seen in Figs. lOA, lOB, lOC and lOD.

As can be seen from Figs. lOA to D, the leaf spring 37 is inserted into the receptacle via the open front face so that the end portion 36 enters the aperture 35 defined in the bottom wall 33. A conductor end portion 38 to be terminated is introduced through the cutaway portion in the rear wall 32 and the leaf spring is urged into the receptacle so that the bared multistrand wires of the conductor end portion 38 are trapped between the spring and the rear wall 32 and crimped between the convoluted portion of the spring and the bottom wall 33. The spring 37 is constructed to be a firm push fit into the receptacle. During insertion of the spring, rotation thereof tends to urge the conductor strands into the covered position for retention. As the end portion 36 moves away from the back face 32 the conductor strands become trapped between the spring and the bottom wall.

It will be noted that once the "corner" part 39 of the spring has been pushed beyond the retaining tabs 29a and b, as shown in Fig 10D, the spring is held firmly in place in the receptacle by the "corner" part 39 co-operating with the tabs. The spring 37 is held in compression in the receptacle between the tabs 29a and b and the rear wall 32. This retaining arrangement makes it extremely difficult to remove the spring 37 once it has been fully inserted into place in the receptacle and thus provides a substantially permanent electrical contact between the conductor and the receptacle which is strongly resistant to any force leading to pull the conductor out of the receptacle.

The hereinbefore described embodiment of the present invention is in all respects exemplary, and modifications and variations will occur to those possessed of the relevant skills without departure from the scope of the invention as defined by the appended claims.

Claims

CIAIS:

1. In or for an electrical connector, a terminal for attachment to an electrical conductor and comprising a receptacle for receiving an end portion of said conductor and a leaf spring adapted to be fitted into said receptacle so as to capture said conductor end portion therein.

2. A terminal as claimed in claim 1 wherein said receptacle is electrically conductive.

3. A terminal as claimed in claim 1 or 2 wherein said receptacle is generally in the shape of a rectangular box having an open face for insertion of the leaf spring into the box.

4. A terminal as claimed in claim 3 wherein the leaf spring is generally U-shaped or comprises a generally U-shaped portion whereby when inserted into the receptacle it is compressed between opposed side walls thereof.

5. A terminal as claimed in claim 4 wherein the leaf spring and said opposed side walls are formed so that the leaf spring engages positively therewith when it is inserted into the receptacle.

6. A terminal as claimed in claim 5 wherein said opposed side walls have cut-outs into which portions of the leaf spring are positively engaged when the leaf spring is inserted into the receptacle.

7. A terminal as claimed in any of claims 4, 5 and 6 wherein the leaf spring is looped onto itself by virtue of one of the limbs of its generally U-shaped being extended to buttress the other limb.

8. A terminal as claimed in claim 4, wherein the leaf spring is further arranged such that when inserted into the receptacle it is compressed between portions of adjacent walls of the receptacle.

9. A terminal as claimed in claim 8 wherein the leaf spring engaged positively with said portions when inserted into the receptacle.

10. A terminal as claimed in claims 8 or 9 wherein the portion of one adjacent wall is defined by retaining tabs extending from side walls of the receptacle.

11. A terminal as claimed in any of the preceding claims wherein the leaf spring and the receptacle have co-operating portions serving in use to crimp the end portion of the conductor therebetween.

12. A terminal as claimed in any of the preceding claims and formed as a portion of a pin of an electrical plug.

13. A terminal substantially as herein described with reference to Figs. 8A, B, C and D of the accompanying drawings.

14. An electrical connector incorporating one or more terminals as claimed in any of the preceding claims.

15. An electrical connector as claimed in claim 14 and comprising a three-pin mains electrical plug having live, neutral and earth pins each conductively attached to a said terminal.

16. A three-pin mains electrical plug substantially as herein described with reference to the accompanying drawings.

17. A fused electrical plug comprising a moulded plastics base and a moulded plastics cover adapted to be removably affixed to said base, said plug further including a fuse holder and the fuse holder being arranged to interlock with the attachment of the cover to the base such that the cover cannot be removed until such time as the fuse holder is opened so as to break the internal circuit within the plug.