GB2077052A

GB2077052A - Multi-pin electrical plugs

Info

Publication number: GB2077052A
Application number: GB8113164A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-04-30
Filing date: 1981-04-29
Publication date: 1981-12-09
Also published as: GB2077052B

Abstract

A multi-pin electrical plug, which may be of the non-rewirable or rewirable type, comprises a base 1 from which the pins 3, 4 and 5 project and a cover 19 mounted on the base. The cover 19 and the base 1 may be provided with interengaging guide means, such as ribs 23 on the cover which are received in respective recesses 13 in the base, by means of which the cover can be slid in a direction substantially perpendicular to the axes of the pins 3-5 into said position of securement on the base. Snap-action interlocking means, such as notches 24 in the ribs 23 and cooperating projections (not shown) in the recesses 13, automatically lock the cover 19 to the base 1 when the cover is moved into its position of securement on the base. In alternative arrangements the cover may be mounted over that side of the base from which the pins project. <IMAGE>

Description

SPECIFICATION Multi-pin electrical plugs This invention relates to a multi-pin electrical plug which may be of the rewirable or nonrewirable kind.

In my published British Patent Applidation No. 2042285A there is described and claimed a multi-pin electrical plug of the rewirable kind, comprising a base from one surface of which the pins project and a cover removably mounted on a second surface of the base opposite to said one surface, which is characterised in that the cover and base are provided with interengaging means by means of which the cover can be slid in a direction substantially perpendicular to the axes of said pins into a position of securement on the base, and in that the cover and the base are provided with a movable locking means which, at least when the plug is inserted into a corresponding electrical socket with the cover in said position of securement on the base, automatically locks the cover to the base.

In one embodiment of the pug described in Application No. 2042285A, said locking means is in the form of a plunger slidably mounted in a bore passing through the base of the plug, the axis of the bore being substantially parallel to the axes of the pins of the plug. This plunger is urged by resilient means into a position in which a first end of the plunger projects from said one surface of the base, and the opposite end of the plugner is flush with, or slightly below said second surface of the base. The cover then has a second bore which, when the cover is in said position of securement on the base, is aligned with the bore in the base so that it can receive said opposite end of the plunger when said first end of the plunger is pushed into the base by the action of inserting the plug into said electrical socket.

Whilst such a plunger provides an efficient locking means for the cover of the plug, the need to provide the plunger and its resilient means represents a complication in manufacture and adds to the expense of assembling the plug.

One aim of the present invention is to provide a multi-pin electrical plug of the rewirable kind which has a less complicated locking means than the plug described in Application No. 2042285A.

Non-rewirable multi-pin electrical plugs are known, in which the separate conductors of a multi-conductor cable are permanently secured to the pins of the plug, and a plug body is moulded around the pins, so that connections of the conductors to the pins cannot be tampered with. The manufacture of such plugs involves mounting the pins in a base portion of the plug, connecting the cable conductors to the pins and then moulding a non-removable cover portion over the connections to the pins using a moulding machine.

The need to install such moulding machines represents a considerable expense to appliance manufacturers who wish to market appliances with non-rewirable plugs connected thereto. Another aim of the present invention is to provide a multi-pin electrical plug of the non-rewirable kind which can be assembled easily by an appliance manufacturer without the need for complicated and expensive plant.

According to the invention, a multi-pin electrical plug comprising a base from which the pins project and a cover mounted on the base, is characterised in that the cover and base are provided with snap-action interlocking means which, when the cover is moved into a position of securement on the base, automatically locks the cover to the base.

In a first embodiment of the plug in accordance with the invention, said pins project from a first surface of the base and said cover is mounted on a second surface of the base opposite to said first surface. In this first embodiment, the cover and the base may be provided with inter-engaging guide means by means of which the cover can be slid in a direction substantially perpendicular to the axes of the pins into said position of securement on the base.

In a modified version of this first embodiment, the cover may be mounted on said first surface of the base, but it is then necessary to provide slots in the cover to enable the cover to be slid past the pins when the cover is slid into its position of securement on the base guided by said interengaging guide means.

In this first embodiment, and the modified version thereof, said snap-action interlocking means may comprise cooperating elements arranged in confronting surfaces of said interengaging guide means. For example, if the interengaging guide means comprises a rib on the cover (or base) which has sliding engagement with a groove in the base (or cover), then said snap-action interlocking means may comprises a projection on the rib (or in the groove) which snaps into a notch in the groove (or in the rib) as the cover is moved into its position of securement on the base.

In a second embodiment of the plug in accordance with the invention, said pins again project from a first surface of the base and the cover is mounted on a second surface of the base opposite to said first surface, but the cover is moved into its position of securement on the base in a direction substantially parallel to the axes of the pins. For example, the base may be in the form of an open-topped box with the pins projecting outwardly from the bottom of the box, and the cover is in the form of a lid for the box and has snap-action interlocking engagement in the open top of the base.

In a modified version of this second embod iment of the plug, the cover may be mounted on said first surface of the base, but it is then necessary to provide holes in the cover to enable the cover to be slid over the pins into its position of securement on the base.

In each of the embodiments mentioned above, the cover may be arranged so that it can be removed from the base by release of the interlocking means (in which case the plug would be a rewirable plug) or so that it cannot be removed from the base without consequent permanent damage to the cover and/or the base (in which case the plug would be a nonrewirable plug).

The invention will now be described, by way of example, with reference to the accompanying drawings, in which Figures 1 and 2 are perspective views of the cover and base, respectively, of one embodiment of a non-rewirable 3-pin, 1 3 amp fused plug in accordance with the invention, Figure 3 is an underside plan of the plug of Figs. 1 and 2 with the cover assembled on the base, but with part of the cover broken away to reveal details of the underlying base, Figures 4 and 5 are sectional views, taken on the lines IV-IV and V-V, respectively, of Fig. 3, Figures 6 and 7 are views similar to Figs. 4 and 5, respectively, of a modified embodiment of the plug of Figs. 1 to 5, this modified embodiment being a rewirable plug, Figures 8 and 9 are views similar to Figs. 1 and 2, respectively, of a second embodiment of a non-rewirable 3-pin, 1 3 amp fused plug in accordance with the invention, Figure 10 is a sectional view, taken on the line X-X of Fig. 8, of the assembled plug of Figs. 8 and 9, and Figure ii is a view, similar to Fig. 10, of a third embodiment of a non-rewirable 3-pin, 1 3 amp fused plug in accordance with the invention.

Referring to Figs. 1 to 5, the plug shown comprises a base, generally designated by the reference numerai 1, moulded from electrically-insulating plastics material and having a flat surface 2 from which the live, neutral and earth pins 3, 4 and 5, respectively, project.

There is an aperture 6 in the base 1 to obtain access to a removable fuse (not shown) housed in the base 1. The base also has a recess 7 for the reception of a cable grip (not shown). This cable grip may be of the kind described in my published British Patent Application No. 2039426A. The base 1 is also provided with means (not shown) for connecting the conductors of a cable (not shown) to the pins 3, 4 and 5. For example, the connection of the conductors to the pins 3, 4 and 5 may be arranged in the manner described in my British Patent Specification No.

1,559,789 or in the aforesaid published Applications Nos. 2042285A and 2039426A.

The base 1 has two spaced-apart, parallel side walls 8, disposed at right-angles to the surface 2, which extend from the end 9 of the base up to two spaced-apart wings 10 at the end 11 of the base where the recess 7 is situated. Each of the wings 10 has a wall disposed at right-angles to a respective one of the side walls 8.

A recess 1 3 is formed along each of the two corners of the base 1 defined by the surface 2 and the side walls 8, each recess 1 3 having a bottom surface 1 4 disposed parallel to the surface -2 and a side surface 1 5 disposed at right-angles to the surfaces 2 and 14. A straight groove 1 6 is formed in each of the bottom surfaces 1 4 at the foot of the respective side surface 15, the two grooves 1 6 being parallel to one another. The grooves 16 extend from the end 9 of the base up to the walls 1 2. Close to the wall 12, each groove projection 1 7 moulded integrally with its bottom surface 1 8 (see Fig. 4).

The cover of the plug, generally designated by the reference numeral 19, is moulded from electrically-insulating plastics material and comprises a top 20 with two spaced-apart, depending side walls 21 formed integrally with the top 20. At its end remote from the top 20, each wall 21 has an inwardly-directed flange 22, the inner edge of which has an upwardly-projecting rib 23 disposed in spaced parallel relationship with the wall 21. The spacing apart of the two ribs 23 is the same as the spacing apart of the two grooves 1 6 in the base 1. A notch 24 is formed in the upper surface of each of the ribs 23, each notch 24 being spaced from the end 25 of its rib 23 by a distance equal to the spacing, in the base 1, of each projection 1 7 from the wall 1 2.

After connection of a three-core cable (not shown) to the connection means in the base 1, the cover 1 9 is slid onto the base 1 with the ribs 23 of the cover engaged in respective ones of the grooves 1 6 in the base, the ends 25 of the ribs 23 being first entered into the grooves 1 6 at the end 9 of the base. As the ends 25 of the ribs 23 reach the walls 1 2 of the base, the projections 1 7 snap into the notches 24 to lock the cover to the base, this being allowed by flexing of the walls 21 and 22. It is then impossible to remove the cover from the base without permanently damaging one or both of these parts. In this connection the wings 10, by closing the ends of the grooves 16, prevent insertion of a tool into the grooves 1 6 in an endeavour to force the projections 1 7 from the notches 24.

Various modifications can be made to the plug shown in Figs. 1 to 5. For example, more than one projection 1 7 may be provided on the bottom 1 8 or each groove 16, there being a corresponding number of notches 24 in each of the ribs 23. Again, the projection or projections 1 7 need only be provided in one of the grooves 1 6.

In order to prevent the insertion of a tool between the flanges 22 and the base 1 at the end 9 of the base, in an attempt to prise the cover off the base, the cover 1 9 may have an end wall 26, shown in chain lines in Figs. 1 and 4, which covers the ends of the grooves 1 6 when the cover is locked to the base.

It will be appreciated that the above described plug offers advantages to an appliance manufacturer wishing to sell appliances fitted with non-rewirable electrical plugs. The base and cover of the plug can be bought from a plug manufacturer and assembled by the appliance manufacturer without any specialised equipment, such as a machine for moulding a cover on the base.

Referring to Figs. 6 and 7, the plug shown is of generally the same construction as the plug of Figs. 1 to 5, and the same reference numerals with the addition of a prime have been used in Figs. 6 and 7 to designate items in common with those of the plug of Figs. 1 to 5. In this embodiment of the plug, the side walls 21' of the cover 19' have flanges 22' at their ends remote from the top 20' of the cover. However, these flanges 22' do not have ribs at their free ends like the ribs 23 of the plug of Figs. 1 to 5. The recesses 13' of the base 1' do not have grooves, like the grooves 1 6 of the plug of Figs. 1 to 5, in their bottom surfaces 14'.

A projection 17' is moulded integrally on the side surface 15' of one of the recesses 13', and when the cover 19' is slid onto the base 1', the projection 17' snaps into a notch 24' formed in the free end surface of the corresponding flange 22' to lock the cover to the base. In order to remove the cover 19' from the base 1', the side wall 21' of the cover which carries the notch 24' has to be prised outwardly to release the projection 17' from the notch 24'. To facilitate this prising operation, a recess 27 may be formed in the .flange 22' in which the notch 24' is formed, to enable a screw-driver or other tool to be inserted between the free end surface of the flange 22' and the side surface 15' of the recess 13'. If desired, more than one notch 24' may be provided in the flange 22' for engagement by an equal number of projections 17' on the surface 15'.Again, in this embodiment of the plug, the cover may be provided with an end wall similar to the end wall 26 in Fig. 1.

Of course, one or more projections 17' may be formed on each of the side surfaces 15', with a corresponding notch 24' in the free end surface of each of the flanges 22'. This, however, makes more difficult the operation of removing the cover 19', since both side walls 21' have to be prised away from the side walls 8' of the base.

As an additional means of locking the cover 1 9' to the base 1', the aperture 6' for the fuse (not shown) may be formed partly in one of the flanges 22', as shown in Fig. 6, so that the fuse has to be removed from the plug before the cover can be slid off. A similar positioning of the fuse may be adopted in the embodiment of the plug shown in Figs. 1 to 5.

Of course, the plugs shown in Figs. 1 to 7 may be modified by arranging the notch 24 (or 24') in the groove 1 6 (or the surface 15') of the base and the projection 1 7 (or 17') on the cover. With this arrangement of the notches and projections, it is a simple matter to design the base of the plug as shown in Figs. 1 to 5 (but with a notch in the bottom of each groove instead of a projection 1 7) and a further notch in at least one of the side surfaces 1 5 of the recesses 1 3. Such a base could then receive either a cover of the kind shown in Fig. 1 (with projections on the ribs 23 instead of the notches 24) in order to provide a non-rewirable plug, or a cover of the kind shown in Figs. 6 and 7 (with a projection on the flange 22' instead of the notch 24') in order to provide a rewirable plug.

Referring to Figs. 8 to 10, the plug shown is of generally the same construction as the plug of Figs. 1 to 5, and the same reference numerals with the addition of the suffix "a" have been used in Figs. 8 to 10 to designate items in common with those of the plug of Figs. 1 to 5. In this embodiment of the plug, the base 1 a has a respective wing 30 projecting from each of its sides 8a adjacent the end 9a of the base, so that a recess 31 is formed at each side of the base between the wings 1 0a and 30 at that side. The base 1 a has recesses 1 3a of the same shape as the recesses 1 3 of the plug of Figs. 1 to 5, but these recesses only extend from the wing 10a to the wing 30 on each side of the base.

Furthermore, the recesses 1 3a do not have projections, like the projections 1 7 of the plug of Figs. 1 to 5, in the grooves 1 6a of their bottom surfaces 14 a.

The cover 1 9a of the plug has a top 20a and spaced-apart side walls 21 a. Each side wall 21 a has an inwardly-directed flange 22a with an upwardly-projecting rib 23a, like the cover 1 9 of the plug of Figs. 1 to 5. However, the ribs 23a are not provided with notches 24 as in the plug of Figs. 1 to 5, and each of the side walls 21 a is shorter, between its ends 32 and 33, than the side walls 21 of the plug of Figs. 1 to 5. The length of each of the side walls 21 a between its ends 32 and 33 is slightly less than the length of the recesses 31 in the base 1 a.

In all other respects the plug of Figs. 8 to 10 is the same as the plug of Figs. 1 to 5.

After connection of a three-core cable (not shown) to the connection means in the base 1 a, the cover 1 9a is slid onto the base lain a direction parallel to the axes of the pins 3a, 4a and 5a, with the side walls 21 a of the cover received in the recesses 31 of the base.

The cover 1 9a is made of a flexible plastics material, for example nylon, so that the side walls 21 a can spring apart (as indicated in chain lines in Fig. 10) as the cover is slid onto the base. When the cover has been fully slid onto the base, the flanges 22a can be pressed inwardly into the recesses 1 ga and the ribs 23a then snap into the grooves 16a of the recesses 13a, as shown in Fig. 10.

It is then impossible to remove the cover from the base without permanently damaging one or both of these parts.

Referring to Fig. 11 the plug shown has a base 41 in the fonn of an open-topped box moulded from electrically-insulating plastics material. This box has side walls 42 and a bottom 43 from which the pins of the plug project. In Fig. 11, only one of these pins, namely the earth pin designated by the numeral 44, can be seen. As in the case of the previously described plugs, the base 41 has an aperture 45 in the bottom 43 to obtain access to a removable fuse (not shown) housed in the base 41. It also has a recess (not shown), similar to the recess 7 of the plug of Figs. 1 to 5, for the reception of a cable grip, for example of the kind described in the aforesaid Application No. 2039426A.

The base 41 is also provided with means (not shown) for connecting the conductors (not shown) of a cable to the pins of the plug, which connection means may be of the kind disclosed in the aforesaid Specification No.

1,559,789 or in the aforesaid Applications Nos. 2042285A and 2039426A.

The base 41 is closed by a cover 46, moulded from a flexible plastics material, for example nylon, which is forced into the open top of the base against shoulders 47 formed on the side walls 42. Along its edges adjacent the side walls 42, the cover 46 has a projecting ribs 48 which snap into grooves 49 in the side walls 42 when the cover is pressed -down against the shoulders 47. It is then impossible to remove the cover 46 from the base 41 without permanently damaging one or both of these parts.

As in the case of the plug shown in Figs. 1 to 5, it will be appreciated that the plugs shown in Figs. 8 to 11 offer advantages to an appliance manufacturer wishing to sell appliances fitted with non-rewirable electrical plugs, since the base and cover of the plugs can be bought from a plug manufacturer and assembled by the appliance manufacturer without any specialised equipment.

In each of the embodiments described above with reference to the drawings, the cover of the plug overlies, or is engaged in, that side of the base remote from the side from which the contact pins project. In some forms of multi-pin plugs, for example the plug illustrated in Fig. 1 5 of the aforesaid Specification No. 1,559,789, it may be desirable to mount a cover over that side of the base from which the pins project, and such a plug may be provided with snap-action interlocking means between the cover and the base in one of the ways described above with reference to thXdrawings. It will, however, be appreciated that if the cover moves into its position of securement on the base in a WirvçtiQn perpendicular to the axes of the contact pins, then the cover must be provided with slots to accommodate the contact pins. Alternatively, if the cover moves into its position of securement on the base in a direction substantially parallel to the axes of the contact pins, then the cover must be provided with holes to accommodate the contact pins.

Claims

1. A multi-pin electrical plug comprising a base from which the pins project and a cover mounted on the base, characterised in that the cover and the base are provided with snap-action interlocking means which, when the cover is moved into a position of securement on the base, automatically locks the cover to the base.

2. A plug according to claim 1, in which said pins project from a first surface of the base and said cover is mounted on a second surface of the base opposite to said first surface.

3. A plug according to claim 2, in which the cover and the base are provided with interengaging guide means by which the cover can be slid in a direction substantially perpendicular to the axes of the pins into said position of securement on the base.

4. A plug according to claim 1, in which said pins project from a first surface of the base and the cover is mounted on said first surface.

5. A plug according to claim 4, in which the cover and the base are provided with interengaging guide means by which the cover can be slid in a direction substantially perpendicular to the axes of the pins into said position of securement on the base, the cover being provided with slots to enable the cover to be slid past the pins when the cover is slid into its position of securement on the base guided by said interengaging guide means.

6. A plug according to claim 3 or claim 5, in which said snap-action interlocking means comprises cooperating elements arranged in confronting surfaces of said interengaging guide means.

7. A plug according to claim 6, in which said interengaging guide means comprises a rib on the cover (or base) which has sliding engagement with a groove in the base (or cover).

8. A plug according to claim 7, in which said snap-action interlocking means comprises a projection on the rib (or in the groove) which snaps into a notch in the groove (or in the rib) as the cover is moved into its position of securement on the base.

9. A plug according to claim 2, in which said cover is moved into its position of securement on the base in a direction substantially parallel to the axes of the pins.

10. A plug according to claim 9, in which said base is in the form of an open-topped box with the pins projecting outwardly from the bottom of the box, and the cover is in the form of a lid for the box and has snap-action interlocking engagement in the open top of the base.

11. A plug according to claim 9, in which said cover comprises side walls which are guided by the base as the cover is moved into its position of securement on the base.

1 2. A plug according to claim 11, in which said snap-action interlocking means comprises cooperating ribs and grooves on said side walls and said base.

1 3. A plug according to claim 4, in which said cover is moved into its position of securement on the base in a direction substantially parallel to the axes of the pins, the cover being provided with holes to enable the cover to be moved over the pins when the cover is slid into its position of securement on the base.

14. A multi-pin electrical plug constructed and arranged substantially as herein described with reference to, and as illustrated in, Figs. 1 to 5, Figs. 6 and 7, Figs. 8 to 10 or Fig. 11 of the accompanying drawings.