GB2234404A

GB2234404A - Electrical connection device

Info

Publication number: GB2234404A
Application number: GB9013839A
Authority: GB
Inventors: Bernard Julius Sarna
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-06-23
Filing date: 1990-06-21
Publication date: 1991-01-30
Also published as: GB8914401D0; GB9013839D0

Abstract

The bared end of a wire (12) may be clamped outer a contact (3) by releasably mounting an insert (7) in a contact-containing recess (2). The insert has a bore for the wire. A plug body (1) is wired using three inserts (7) to attach the three cores of a cable (10). The insert may be screw or bayonet mounted. A back-shroud (20) containing a cable clamp may be attached to the body (1) releasably (as shown) or via a hinge (fig. 10, not shown). <IMAGE>

Description

ELECTRICAL CONNECTION DEVICE The present invention relates to an electrical connection device, and in particular, though not exclusively, to an electrical plug for connecting the cable of an electrical appliance to the mains supply at a power point.

Conventional electrical plugs comprise a moulded plastics or rubber body and a cap which is secured to the body by a screw. Three terminal pins project from the body of the plug, the ends of the terminal pins inside the plug body being provided with holes into which the bared ends of the wires from the cable of an electrical appliance are inserted. The bared ends of the wires are secured in contact with the terminal pins by tightening small screws. The cable is clamped inside the point of entry to the plug by a plastics strip which is forced against the cable by tightening further small screws.

Feeding the wires into the small holes in the terminal pins, ensuring that the filaments of different wires are not in contact, and manipulating the small screws to clamp the wires in position, cause significant problems to many people. In addition, since the terminal pins are arranged in a triangular configuration, the wires of the cable must be either cut to different lengths or folded in the spaces between the terminal pins to ensure that the wires lie sufficiently flat against the plug body to allow the cap to be secured in position. Tightening the screws of the cable clamp presents an additional problem to those who have difficulty handling a small screwdriver.

If any of the screws in the plug are not tightened sufficiently, there is a possibility of wires working loose within the plug body. Even if the plug is correctly assembled in the first instance, screws may work loose over a period of time allowing wires to stray from their correct locations within the plug.

It is an object of the present invention to provide an alternative electrical plug which is both safe and simple to assemble.

According to the present invention there is provided an electrical plug for connecting the cable of an electrical appliance to the mains supply at a power point, which plug comprises: a body from which the terminal pins of the plug project, the body having a plurality of recesses therein, each recess giving access to an electrical contact arranged to provide an electrical connection with an associated terminal pin; an insert associated with each said recess in the body, each insert having a longitudinal bore therein for passage of a wire of the cable, the insert being adapted for reception in the recess in such a manner that the bared end of the wire contacts the electrical contact, and securing means for releasably securing the inserts in the recesses.

Where the plug is a three-pin plug, the terminal pins corresponding to the live, neutral and earth wires respectively, there will be three said recesses in the body of the plug, each associated with a different terminal pin.

To connect the wires of the cable to the terminal pins, it is necessary simply to feed each wire through the longitudinal bore in an insert until the bared end of the wire protrudes from the end of the bore, and then insert the insert into the appropriate recess in the main body of the plug. The recesses, and preferably also the inserts, may be colour coded in correspondence with the live, neutral and earth wires of the cable to facilitate connection of the wires to the correct terminals. Once the inserts are fully inserted in the appropriate recesses, the bared ends of the wires will contact the electrical contacts at the end of each recess. The wires are then electrically connected to the terminals deep within the plug body, there being no danger of accidental contact of the wires.

It is preferred that the inserts and recesses are shaped for the bared ends of the wires to be folded back over the ends of the inserts in use. In this case, each electrical contact may comprise a metal cup for accommodating the bared end of a wire in use.

The securing means are provided to ensure that the inserts are held safely in place in the associated recesses in use. The securing means may comprise cooperating fastening means on each insert and recess.

For example, such fastening means may comprise a screw-thread on the exterior surface of each insert, which screw-thread cooperates with a corresponding screw-thread provided on each recess. As a further example, the cooperating fastening means may comprise a bayonet fastening on each insert and recess.

The plug may include a cover for preventing or inhibiting access to the inserts in use.

To assist insertion of the inserts into the associated recesses, it is preferred that each insert has a head portion which may be gripped to manipulate the insert, and that, when an insert is fully inserted in the recess, the head portion protrudes out of the end of the recess. In this case, the securing means may comprise a portion or portions of the cover arranged to engage the head portions of the inserts in use, thereby preventing or inhibiting withdrawal of the inserts from the recesses. Such securing means on the cover may be provided in addition to the cooperating fastening means on each insert and recess as an additional safeguard against the inserts working loose when the plug is assembled.

As an example, each insert may be provided with an enlarged, knurled head portion, and the cover may be provided with one or more bars, extending across theinterior of the cover, which press against the knurled head portions of the inserts when the plug is assembled. As an alternative, and in particular where each insert is inserted into a recess by rotation thereof to engage cooperating fastening means on the insert and recess, the head portion of each insert may comprise a substantially planar flange, and the securing means may comprise a portion or portions of the cover arranged to rest against the side faces of the flanges of the inserts when the plug is assembled, thereby preventing rotation of the inserts and release of the cooperating fastening means.

When the inserts are fully inserted in the recesses, the bared end of each wire of the cable may be clamped between the electrical contact at the end of each recess and the insert to prevent or inhibit the wires being accidentally pulled out of the inserts in use. However, as an alternative, or as an additional safeguard, the head portion of each insert may have a lateral slot therein which extends through to the bore of the insert, and the securing means on the cover may comprise a flange which is arranged to be received in the slots in the head portions of the inserts, thereby clamping the wires of the cable against the bores of the inserts in use.

It is preferred that the recesses in the body of the plug are arranged in a lateral array so that the wires need not be cut to different lengths when the plug is assembled.

The plug may include clamping means for clamping the cable of the electrical appliance adjacent the point of entry of the cable to the plug. For example, the body of the plug and the cover may include cooperating clamping means for clamping the cable in position relative to the plug in use. Alternatively, for example, a spring clip may be provided on the body of the plug for gripping the cable in use.

The cover may be completely detachable from the main body of the plug. However, in a preferred embodiment, the cover is hinged to the main body of the plug. In either case, means may be provided to releasably secure the cover relative to the body of the plug in use. For example, lugs may be provided on the body or cover for engagement with corresponding recesses on the other of the body and cover to provide a "snap fit" fastening between the cover and body when the plug is assembled. Alternatively, or as an additional safeguard, a screw may be provided for fastening the cover to the body of the plug.

A fuse will be housed in the plug body and incorporated in the circuit between the "live" terminal pin and the electrical contact at the end of the corresponding recess. The fuse may be accessed via a further cover provided on the body of the plug.

In the assembled plug, all wires are well insulated and secured in position. All fastenings may be designed so that no tools are necessary for assembling the plug.

In accordance with a further aspect of the invention there is provided an electrical connection device comprising a body having a recess therein, the recess giving access to an electrical contact; an insert adapted for reception in the recess in the body, the insert having a longitudinal bore therein for passage of a wire; and seccuring means for releasably securing the insert in the recess, wherein the insert and recess are shaped for the bared end of the wire to be folded back over the end of the insert in use, thereby connecting the wire to the electrical contact.

The invention extends to a method of connecting a wire to an electrical connection device, which method comprises: threading the wire through a longitudinal bore in an insert of the connection device, folding the bared end of the wire back over the end of the insert, inserting the insert into a recess in the connection device in such a manner that the bared end of the wire contacts an electrical contact in the recess, and releasably securing the insert in the recess.

Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a body of a first embodiment of an electrical plug in accordance with the invention; Figure 2 is a perspective view of a cover for the body of the electrical plug of Figure 1; Figure 3 is a perspective view of an electrical plug comprising the body and cover of Figures 1 and 2 assembled for use; Figure 4 is a side view of an insert for the electrical plug of Figures 1 to 3; Figure 5 is a schematic plan view, partially cut away, of the body of Figure 1; Figure 6 is an enlarged view of a portion of Figure 5; Figure 7 is a schematic plan view, partially cut away, of the cover of Figure 2; Figure 8 is an end view of the cover of Figures 2 and 7;; Figure 9 is a schematic side view, partially cut away, of the cover of Figures 2, 7 and 8; Figure 10 is a schematic perspective view of a second embodiment of an electrical plug in accordance with the invention; Figure 11 is a schematic side view of a third embodiment of an electrical plug in accordance with the invention; Figure 12 is a perspective view of an insert of the electrical plug of Figure 11; Figure 13 is a schematic perspective view of a portion of the electrical plug of Figure 11; Figure 14 shows an alternative form of cooperating fastening means for an electrical plug in accordance with the invention; Figure 15 is an end view of the insert of Figure 14, and Figure 16 is a schematic view of an alternative head portion of an insert.

Figures 1 and 3 show a body 1 of an electrical plug in accordance with a first embodiment of the invention. The body 1 has three elongate recesses 2 therein, arranged in a lateral array, each of which recesses terminates in an electrical contact in the form of a metal cup 3. Each metal cup 3 is connected via a connecting wire 4 to an associated terminal pin 5 of the plug. A fuse 6 is connected in the circuit to the "live" terminal pin. The body 1 has two lugs 28, one on each side thereof, the function of which will be described hereinafter.

Three elongate inserts 7 are provided, one for reception in each of the elongate recesses 2 in the body 1. Each insert 7 has a longitudinal bore 8 therein for passage of a wire 9 of a cable 10 of an electrical appliance. Each insert 7 terminates in a metal nipple 12 over which the bared end of a wire 9 is bent back in use as shown in Figure 4.

Cooperating fastening means are provided on each insert 7 and recess 2 for releasably securing the inserts in the recesses. The cooperating fastening means comprises a screw-thread 13 on the exterior surface of each insert 7 and a corresponding screw-thread 14 on each recess 2.

Each insert 7 has an enlarged, knurled head portion 15 which may be gripped to enable the insert 7 to be screwed into a recess 2. When each insert 7 is fully inserted into a recess 2, the bared end of a wire 9 folded back over the metal nipple 12 of the insert is pressed against the metal cup 3 at the end of the recess as shown in Figure 6. The metal cups 3 are of larger diameter than the metal nipples 12 on the inserts 7 to accommodate the bared ends of the wires 9.

Figures 2, 7, 8 and 9 show a cover 20 for preventing or inhibiting access to the recesses 2 and inserts 7 in use. The cover 20 has a cable tube 21 for passage of the cable 10 of an electrical appliance. A screw 18 is provided on the side of the cable tube 21 for clamping the cable in position. Securing means are provided on the cover 20 and comprise two parallel bars 24 extending across the interior of the cover 20 between the sides thereof. The function of the bars 24 will be described hereinafter. A recess 27 is provided on the interior of each side of the cover 20 for receipt of the lugs 28 on the body 1 in use.

A screw 25 is provided through the cover 20 for fastening the cover 20 to the body 1 of the plug. The screw 25 is received in a threaded aperture 26 in the body 1 when the plug is assembled as shown in Figure 3.

Figure 10 shows a second embodiment of an electrical plug in accordance with the invention. The plug comprises a body 30 and a cover 31 which is hinged to the body 30. - The internal structure of the body 30 is equivalent to that of the body 1 of Figures 1 and 5, the body 30 having three screw-threaded recesses 33 for reception of three elongate inserts 7 (not shown in Figure 10) as previously described.

Securing means are provided in the form of a flange 34 which extends across the interior of the cover 31 between the sides thereof. Three cut-away edges 35 are provided along the free edge of the flange 34, which edges 35 engage the head portions 15 of the inserts 7 in the recesses 33 when the cover 31 is closed, ie pivoted so as to enclose the recesses and inserts.

Cooperating clamping means are provided in the form of the raised channels 36 and 37 on the body 30 and cover 31 respectively for clamping the cable of an electrical appliance in position in use.

A tab 38 is provided on the cover 31 and has a hole 39 therein which registers with a threaded recess 40 in the body 30 of the plug when the cover 31 is closed. A screw (not shown) may be passed through the hole 39 in the tab 38 and screwed into the recess 40 to secure the cover 31 relative to the body 30 in use.

Figure 12 is a perspective view of an alternative form of insert 45 for use in the embodiment of the electrical plug shown in Figures 11 and 13. The insert 45 has a longitudinal bore 46 therein and terminates in metal nipple 47. The head portion of the insert comprises a planar flange 48 which projects from a cylindrical portion 49 of the insert 45. A peripheral slot 50 is provided on the cylindrical portion 49 of the insert 48. The slot 50 extends through approximately 90e around a circumference of the portion 49, one end of the slot 50 extending longitudinally to the edge of the portion 49 nearest the metal nipple 47.

The electrical plug of Figure 11 comprises a body 55 and a cover 56 which is hinged to the body 55. The body 55 has three elongate recesses 57 therein, arranged in a lateral array, each of which recesses terminates in an electrical contact in the form of a metal cup (not shown). The shape of each recess 57 corresponds generally to that of the insert 45. Each recess 57 has a locating pin 58 projecting downwardly from the upper surface thereof for reception in the peripheral slot 50 of an insert 45 when the insert 45 is inserted in the recess 57. The peripheral slots 50 and locating pins 58 thus provide a bayonet fastening for each insert and recess. When the inserts 45 are fastened into the recesses 57, the flanges 48 on the head portions of the inserts are horizontal relative to the plug body 55.

The body 55 of the electrical plug carries a spring clip 60 which holds the cable of an electrical appliance in the assembled plug. The interior of the cover 56 of the plug has a flange 61 projecting outwardly therefrom which flange bears against the cable in the spring clip 60 when the cover is closed.

The spring clip 60 and flange 61 thus constitute cooperating a clamping means for clamping the cable of an electrical appliance in position relative to the plug in use.

Securing means are provided on the cover 56 in the form of the additional flange 62 which extends across the interior of the cover 56 between the sides thereof.

The flange 62 engages the flanges 48 on the inserts 45 when the cover is closed.

Means (not shown) are provided for securing the cover 56 in the closed position relative to the body 55. Such means may take the form of the tab 38 and threaded recess 40 described with reference to Figure 10.

Figures 14 and 15 show an alternative form of cooperating fastening means for fastening an insert in a recess of an electrical plug in accordance with the invention. An elongate insert 65 is generally similar to the insert 45 except that the head portion of the insert 65 comprises a flat disc 66 having a slot 67 extending therethrough. A rectangular hook 68 projects outwardly from the upper surface of each recess 75 in the body of the plug, which hook 68 extends through the slot 67 in the insert 65 to provide a bayonet fastening when the insert is received in a recess 75 of the plug body. The fastening means 67, 68 may be utilised in the electrical plug of Figure 11 instead of the fastening means 50, 58 previously described.

Figure 16 is schematic representation of a portion of a modified form of insert 73. The head portion of the insert 73 comprises a generally planar flange 70 having a lateral slot 71 extending through to the bore 72 of the insert. The insert 70 is otherwise identical to the insert 45 or the insert 65 previously described.

When such inserts 73 are utilised in the electrical plug of Figure 11, the flange 62 on the cover 56 is received in the slots 71 when the cover is closed, thereby clamping the wire passing through. the bore 72 of the insert against the bore 72.

The electrical plugs described above are wired as follows.

In the embodiment of Figures 1 to 9, the cover 20 is first removed from the body 1 by loosening the screw 25. A cable 10 of electrical appliance is then fed through the cable tube 21 of the cover 20. In the embodiments of Figures 10 and 11, the screw securing the cover 31, 56 is removed from the hole 39 in the flange 38 and the cover 31, 56 is pivoted to allow access to the recesses and inserts.

Each wire 9 of the cable 10 is then threaded through the bore 8, 46, 72 of an insert 7, 45, 65, 73 and the bared end of the wire 9 folded back over the metal nipple 12, 47 at the end of the insert.

In the embodiments of Figures 1 to 10, the inserts 7 are then screwed into the appropriate recesses 2, 33.

In the embodiments of Figures 11 to 16, the flange 48, 70 of each insert is then orientated vertically relative to the body 55 of the plug, and the insert pushed to a recess 57, the pin 58 or hook 68 registering with the slot 50, 67 on the insert. Each insert 45, 65, 73, is then rotated so that the pin 58 or hook 68 passes along the arcuate portion of the slot 50, 67 until the flange 48, 70 on the insert is horizontal. The insert cannot then be withdrawn directly without first rotating the inserts so that the pin 58 or hook 68 moves out of the arcuate portion of the slot 50, 67.

In all embodiments, colour coding corresponding to that on the wires 9 may be provided on the recesses 2, 33, 57, and preferably also on the head portions of the inserts 7, 45, 65, to facilitate connection of the wires 9 to the correct terminal pins.

When the inserts 7, 45, 65 are fully inserted into the recesses 2, 33, 57, the bared ends of the wires 9 are accommodated by, and forced against, the metal cup 3 at the end of each recess. The wires are then electrically connected to the terminal pins of the plug.

In the embodiment of Figures 1 to 9, the cover 20 is then pushed back onto the body 1 so that the inserts 7 in the recesses 3 are fully enclosed, the lugs 28 on the body 1 being received in the recesses 27 on the cover 20 to provide a "snap fit" fastening. The screw 25 is then tightened, additionally securing the cover 20 to the body 1. Finally, the screw 18 is tightened to clamp the cable against the cable tube 21. Assembly is then complete.

In the embodiment of Figure 10, once the inserts 7 are fully inserted into the recesses 33, the cover 31 is pivoted into the closed position so that the cable 10 is clamped between the channels 36, 37 on the body 30 and cover 31 respectively. The cut-away edges 35 of the flange 34 then bear against the head portions 15 of the inserts 7 so inhibiting rotation of the inserts while the cover 31 is closed. The fastening screw (not shown) is then passed through the hole 39 in the tab 38 and screwed into the threaded recess 40 on the body 30.

Assembly is then complete.

In the embodiments of Figures 11 and 13r once the inserts are fully inserted in the recesses 57, the cable 10 is then pressed into the spring clip 60 and the cover 56 is pivoted into the closed position. The flange 61 on the cover 56 then clamps the cable 10 in position in the spring clip 60. In addition, the flange 62 on the cover 56 then engages the flanges 48, 70 of the inserts preventing rotation, and hence withdrawal, of the inserts. Where the inserts are provided with lateral slots 71 as shown in Figure 18, the flange 62 on the cover 56 is received in the lateral slots 71 and clamps the wires 9 against the bores 72 of the inserts, providing an additional safeguard against accidental withdrawal of the wires 9.

The cover 56 is then secured in the closed position by tightening the fastening screw as described with reference to Figure 10. Assembly is then complete.

An LED may be provided on the body 1, 30, 55 of the plug to indicate that the fuse is in tact. The fuse may be accessed through an additional cover (not shown) in the body 1, 30, 55.

It will be appreciated that, in a modification to the embodiment of Figures 11 to 13, instead of providing a pin 58 in each recess and a peripheral slot 50 on each insert 45, a pin could be provided on each insert for reception in a peripheral slot in the recess in use.

The recesses 2, 33, 59 may be provided in a terminal block of the body 1, 30, 55 which terminal block is removable from the remainder of the body to facilitate assembly. In this case, pins connected to the metal cups 3 at the end of each recess would project from the terminal block, and plug into corresponding holes in the remainder of the body to connect the terminal block thereto.

It will be appreciated that many other variations and modifications may be made to the specific embodiments described above without departing from the scope of the invention as defined in the following claims.

Claims

1. An electrical plug for connecting the cable of an electrical appliance to the mains supply at a power point, which plug comprises: a body from which the terminal pins of the plug project, the body having a plurality of recesses therein, each recess giving access to an electrical contact arranged to provide an electrical connection with an associated terminal pin; an insert associated with each recess in the body, each insert having a longitudinal bore therein for passage of a wire of the cable, the insert being adapted for reception in the recess in such a manner that the bared end of the wire contacts the electrical contact, and securing means for releasably securing the inserts in the recesses.

2. An electrical plug as claimed in Claim 1, wherein the inserts and recesses are shaped for the bared ends of the wires to be folded back over the ends of the inserts in use.

3. An electrical plug as claimed in Claim 2, wherein each recess includes an enlarged internal region to accommodate the bared end of the wire in use when folded back over the end of the insert.

4. An electrical plug as claimed in Claim 3, wherein each electrical contact comprises a metal cup for accommodating the bared end of the wire in use when folded back over the end of the insert.

5. An electrical plug as claimed in any preceding claim wherein the securing means comprises cooperating fastening means on each insert and recess.

6. An electrical plug as claimed in Claim 5 wherein the cooperating fastening means on each insert and recess comprises a bayonet fastening.

7. An electrical plug as claimed in any preceding claim including'a cover for preventing or inhibiting access to the inserts in use.

8. An electrical plug as claimed in Claim 7 wherein each insert has a head portion which protrudes out of the recess in use, and the securing means comprises a portion or portions of the cover arranged to engage the head portions of the inserts in use, thereby preventing or inhibiting withdrawal of the inserts from the recesses.

9. An electrical plug as claimed in Claim 8 wherein the head portion of each insert has a lateral slot therein extending through to the bore of the insert, and the securing means comprises a flange on the cover, which flange is arranged to be received in the slots in the head portions of inserts in use, thereby clamping the wires of the cable against the bores of the inserts.

10. An electrical plug as claimed in any one of Claims 7 to 9 wherein the body and the cover include cooperating clamping means for clamping the cable of an electrical appliance in position relative to the plug.

11. An electrical plug as claimed in any one of Claims 7 to 10 wherein the cover is hinged to the body of the plug.

12. An electrical plug as claimed in any preceding claim wherein the said recesses in the body of the plug are arranged in a lateral array.

13. An electrical plug, as claimed in any one of the preceding claims, when assembled with the bared ends of the wires to be connected in the plug folded back over the ends of the inserts and the inserts releasably secured in the recesses in such a manner that the bared ends of the wires contact the electrical contacts.

14. An electrical plug substantially as hereinbefore described with reference to the accompanying drawings.

15. An electrical connection device comprising: a body having a recess therein, the recess giving access to an electrical contact; an insert adapted for reception in the recess in the body, the insert having a longitudinal bore therein for passage of a wire; and securing means for releasably securing the insert in the recess, wherein the insert and recess are shaped for the bared end of the wire to be folded back over the end of the insert in use, thereby connecting the wire to the electrical contact.

16. An electrical connection device substantially as hereinbefore described with reference to the accompanying drawings.

17. A method of connecting a wire to an electrical connection device, which method comprises: threading the wire through a longitudinal bore in an insert of the connection device, folding the bared end of the wire back over the end of the insert, inserting the insert into a recess in the connection device in such a manner that the bared end of the wire contacts an electrical contact in the recess, and releasably securing the insert in the recess.

18. A method of connecting a wire to an electrical connection device substantially as hereinbefore described with reference to the accompanying drawings.