GB2077049A

GB2077049A - Electric plug

Info

Publication number: GB2077049A
Application number: GB8018137A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-06-03
Filing date: 1980-06-03
Publication date: 1981-12-09
Also published as: GB2077049B

Abstract

An electric plug of the kind disclosed in Specification No. 1,559,789, comprises an electrically- insulating contact-carrying base 1, metallic contact pins 2, 3, 4 carried by and extending from the base 1, metallic, conductor-piercing members 17, 18, 19 connected to the pins 2, 3, 4, respectively, pairs of conductor-locating jaws 10a, 10b, 11a, 11b and 12a, 12bfor the reception of insulated conductors 7, 8 and 9, respectively, which are to be electric-connected to the pins 2, 3 and 4, respectively, and jaw-receiving members 20, 21 and 22 associated with the piercing members 17, 18 and 19, respectively, for guiding the pairs of jaws onto the piercing members and arranged to urge the jaws of a pair together to locate the respective insulated conductor as it is pierced by the piercing member. The jaw-receiving members 20, 21 and 22, which in the case of Figure 1 are simply recesses in the base 1, are made at least partly of metallic material. Thus, in the embodiment of the invention shown in Fig. 3, one side of the jaw-receiving member 20 is defined by a metallic member 28. As shown, the metallic member 28 may be formed integrally with the contact pin 2 and with the conductor-piercing members 17a, 17b. <IMAGE>

Description

SPECIFICATION Electric plug This invention relates to an electric plug, in particular but not exclusively, to a 3-pin, 1 3 amp fused plug of the rewirable or nonrewirable kind.

In my British Patent Specification No.

1,559,789 there is described and claimed an electric plug which comprises an electricallyinsulating contact-carrying portion having three recesses in its surface and, mounted in each recess, an electrically-conductive metallic piercing member extending generally in the direction of, but spaced from, a pair of. opposed sides of the recess, each piercing member being electrically connected to a different one of three metallic contact pins carried by, and extending from, said contact-carrying portion, and a respective conductor-locating means associated with each recess and comprising a pair of cooperating jaws movable relative to each other and having mutually confronting surfaces configured to receive between them and locate an insulated electrical conductor when urged towards one another, at least one end of each pair of jaws being configured to enter its associated recess and to allow entry of the piercing member of that recess between the jaws and piercing of an insulated conductor located by the jaws when said one end of the pair of jaws is advanced into the associated recess, the outer surfaces of each pair of jaws and said opposed surfaces of its associated recess being configured to produce a camming action such that advancing said jaws into said recess urges said jaws towards each other to locate the conductor at least during piercing of the conductor by said piercing member.

In the electric plug of Specification No.

1,559,789 it will be appreciated that each pair of conductor-locating jaws is inserted into a respective recess formed in the electricallyinsulating contact-carrying portion of the plug in order to effect piercing of the conductor located by the pair of jaws. I have now found that in some cases there are advantages to be gained, in particular as regards economy in manufacture of the plug, if the means for urging the jaws of a pair together is made at least partly of metallic material.

According to the present invention, in an electric plug of the kind comprising an electrically-insulating contact-carrying portion, at least one metallic contact pin carried by and extending from said contact-carrying portion, a metallic, conductor-piercing member electrically connected to said pin, a pair of conductor-locating jaws for the reception of an insulated conductor which is to be electrically connected to said pin, and a jaw-receiving member associated with said piercing member for guiding the pair of jaws onto the piercing member and arranged to urge the two jaws together to locate the conductor as it is pierced by the piercing member, said jaw-receiving member is made at least partly of metallic material.

In one embodiment of the plug in accordance with the invention, said piercing member may be separate from the jaw-receiving member. In this case the jaw-receiving member may take the form of, for example, a metallic cradle with two spaced-apart limbs connected at one end by a web, the piercing member being arranged to pass through the web without making electrical contact therewith. The limbs of such a cradle may be given a certain degree of resilience so that when, in use of the plug, a pair of conductorlocating jaws is inserted between the limbs of the cradle, the limbs exert a compressive force on the jaws and so enable an adequate contact pressure to be maintained between the piercing member and the conductive portion of the conductor held by the jaws.Alternatively, the jaw-receiving member may be formed simply by a pair of spaced-apart metallic plates supported in said contact-carrying portion, for example in a recess in the contactcarrying portion. These plates may be of a resilient nature, again with the object of maintaining the contact pressure between the piercing member and the conductive portion of a conductor located by a pair of jaws inserted between the two metallic plates.

In another embodiment of the plug in accordance with the invention, said jaw-receiving member is joined, or formed integrally with, the metallic part or parts of the jawreceiving member. Said piercing member may be connected indirectly (for example via a fuse) or directly to said pin. In the latter case it is convenient for the said pin to be formed integrally both with said piercing member and with the metallic part or parts of said jawreceiving member. This provides a particularly convenient design when said pin is fabricated from sheet metal to provide a hollow- pin.

However, the piercing member and at least part of the jaw-receiving member may be formed integrally with a solid pin.

Whilst an electric plug in accordance with the invention may have a single contact pin or two contact pins, the main interest of the invention lies if the field of 3-pin plugs, which may be either of the rewirable or non-rewirable kind.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 is an exploded perspective view of the base and conductor-locating jaws of a known 3-pin, 1 3 amp fused electric plug, Figure 2 is a perspective view of the pins and fuse of the plug shown partly in Fig. 1, and Figures 3 to 11 are views showing features of various embodiments of electric plugs in accordance with the present invention.

Fig. 1 shows part of a 1 3 amp, 3-pin electric plug of the kind shown in Figs. 3 and 4 of Specification No. 1,559,789 but adapted to receive conductor-locating jaws of the general kind shown in Figs. 7 and 8a-8c of that Specification. The plug illustrated comprises a base 1 moulded from electricallyinsulating material and carrying neutral, live and earth pins 2, 3 and 4, respectively, which are shown in more detail in Fig. 2.

The numeral 5 designates a 3-core insulated electric cable with outer insulation 6 removed from one end thereof to reveal insulated neutral, live and earth wires 7, 8 and 9, respectively. The insulated wires 7, 8 and 9 are received between pairs of jaws 1 0a, 1 Ob, 11 a, 11 b and 12a, 1 2b, respectively, the wires being inserted into conductor-locating slots 13, 14 and 15, respectively, defined by recesses of substantially semicircular crosssection provided in confronting portions of the jaws 10a, 10b, 11a, 11band 12a, 12b, respectively. The jaws of each pair are hinged together at their lower ends (as viewed in Fig.

1), there being two apertures 10c, 11 C, 12c through the hinged ends of the respective pairs of jaws.

Metallic insulation-piercing means, generally designated by the reference numerals 17, 18 and 19, are located in recesses 20, 21 and 22, respectively, provided in the upper portion of the base 1. Each of these insula- tion-piercing means comprises a pair of coplanar blades 17a, 17b, 18a, 18b and 19a, 19b, respectively (see Fig. 2). The piercing means 1 7 and 1 9 are electrically and physically connected to the pins 2 and 4, respectively. The piercing means 18 is formed from a metallic strip which is bent, at its end remote from the blades 18a, 1 8b, into the shape of a clip 23. Another metallic strip 24, bent into the shape of a clip 25, is electrically and physically connected to the pin 3.The clips 23 and 25 receive a fuse 26 to complete an electrical circuit from the pin 3 to the blades 18a, 18b.

Electrical contact between the pins 2, 3 and 4 and the insulated wires 7, 8 and 9, respectively, is made by pressing the pairs of jaws 1Oa, 10b, 11a, ill and 12a, 12b into the recesses 20, 21 and 22, respectively, so that the blades 17a, 176, 18a, 18b and 19a, 19b pass through the apertures 10c, 11 C and 12c, respectively, and enter between and are guided by their respective pairs of jaws 1 Oa, lOb, 11 a, 1 1 6 and 12a, 12b.As the pairs of jaws are pressed into the recesses in this way, the pairs of blades 17a, 17b, 18a, 18band 19a, 1 9b pierce the insulation of the wires 7, 8 and 9, respectively, as indicated for the wire 8 in Fig. 2, and make electrical contact with the conducting parts of these wires.

When the wires 7, 8 and 9 have been pierced in this way, a cover (not shown) is secured over the base 1.

An electric plug of the same general kind as that shown in Figs. 1 and 2 is illustrated and described in page 7 of the "Electrical Review" Vol. 204 No. 1 2 dated 23rd March 1978,but in that version of the plug the recesses 20, 21 and 22 are differently positioned in the base 1.

In these known electric plugs, the pairs of jaws 10a, 10b, 11a, riband 12a, 12bare pressed into recesses 20, 21 and 22 defined entirely by walls of electrically-insulating material from which the base 1 is moulded. The present invention is concerned with modified forms of electric plugs, of the same general character as the above described known plugs, in which the or each pair of conductorlocating jaws is pressed into a jaw-receiving member defined at least in part by metallic material.

Figure 3 is a perspective view of the pin 2 and part of the base 1 of a first modified embodiment of the plug of Figs. 1 and 2 and constituting a plug in accordance with the invention. In Fig. 3, the pin 2 is of folded sheet metal construction and has the conductor-piercing blades 17a, 17b formed integrally with a bent strip 27 forming part of the sheet metal from which the pin 2 is formed. The strip 27 is shaped to position the blades 1 7a, 1 7b in the recess 20, a portion 28 of the strip being applied against a side wall of the recess 20. In this embodiment of the plug, it will be appreciated that when the pair of jaws 1 Oa, lOb (Fig. 1) is inserted into the recess 20, the jaws will be ureged together between the wall 29 of the recess and the strip portion 28.

In a modified version of the pin 2 of Fig. 3, the gap between the strip portion 28 and the pin 2 is reduced to zero. In this case, the pin 2 is mounted closely adjacent to the recess 20.

Fig. 4 is a perspective view of a modified form of the clip 23 of the plug of Figs. 1 and 2. In this embodiment, the conductor-piercing blades 18 a, 1 8b are formed integrally with a bent metallic strip 30 which is secured to, or formed integrally with, the fuse clip 31. The strip 30 has a portion 32 which is applied against a side wall of the recess 21 (Fig. 1) so that, when the pair of jaws 11 a, 11 b is inserted into the recess, the jaws will be urged together between one wall of the recess and the metallic strip portion 32.

It will, of course, be understood that, to accommodate the pin and fuse clip shown in Figs. 3 and 4, it may be necessary to position the recesses 20-22 in the base 1 in a different way from that shown in Fig. 1.

Fig. 5 is a perspective view of the pin 2 and part of the base 1 of a second modified embodiment of the plug of Figs. 1 and 2 and constituting a plug in accordance with the invention. In Fig. 5, the pin 2 is again of folded sheet metal construction and has the conductor-piercing blades 17a, 17b formed integrally with the side 33 of the pin. The upper end of this pin is received in the recess 20 with the side 34 of the pin bearing against one side wall of the recess. So that the arrangement can be readily understood from the drawing, the base 1, with its recess 20, is shown in phantom outline in Fig. 5.

When the pair of jaws 1 0a, 1 Ob (Fig. 1) is inserted into the recess 20 in the base 1 of Fig. 5, it will be understood that one of the jaws will enter the hollow interior of the pin 2 and that the two jaws will be urged together between the side 34 of the pin and the opposite side wall of the recess 20.

Fig. 6 is a perspective view, on a reduced scale, of a modified version of the pin of Fig.

5, in which the conductor-piercing blades 1 7a, 1 7b are formed integrally with a portion 35 of the side 33 of the pin, the portion 35 being bent at right angles to the longitudinal axis of the pin. In this case the upper part of the pin 2 is received in a recess similar to the recess 20 of Fig. 5, and when the pair of jaws 1 ova, lOb (Fig. 1) is inserted into the recess the two jaws are urged together by engagement between the edges 36, 37 of the pin, on the one hand, and the opposite side wall of the recess.

Fig. 7 is a perspective view of the pin 2 of a third modified embodiment of the plug of Figs. 1 and 2 and constituing another plug in accordance with the invention, and Fig. 8 is a sectional view of part of the base 1 of this third embodiment showing the pin 2 therein.

In the embodiment of Figs. 7 and 8, the pin 2 is again of folded sheet metal construction and at its upper end one side of the pin has a rectangular extension 38 disposed parallel to the longitudinal axis of the pin. The opposite side of the pin has an extension 39 which is bent over at right angles to the pin axis, the two conductor-piercing blades 1 7a and 1 7b being bent upwardly from this extension 39.

The upper end of the pin 2 is received in the recess 20 of the base 1, as shown in Fig. 8.

When the jaws 1 0a, 1 Ob (Fig. 1) are entered into the recess 20, the two jaws are urged together between the extension 38 and the side wall 40 of the recess.

In the embodiments so far described, the conductor-locating jaws are urged together by engagement between a metallic member, on the one hand, and a wall of a recess formed in the electrically-insulating base 1. Fig. 9 is a perspective view of the upper end of the pin 2 of another modified embodiment of the plug of Figs. 1 and 2, and constituting another plug in accordance with the invention, in which the jaw-receiving member is made entirely of metallic material and is provided by the pin 2 itself. In Fig. 9 the pin 2 is again of folded sheet metal construction and the conductor-piercing blades 1 7a, 1 7b are formed integrally with the sides 41 and 42, respectively, of the pin. When the jaws 1 Oa, 1 Ob (Fig. 1) are inserted into the upper end of the pin 2, the two jaws are urged together between the sides 41 and 42 of the pin.A slot 43 is formed in the side 44 of the pin to allow passage of the conductor 7 (Fig. 1) into the hollow interior of the pin when the jaws are pressed into its upper end.

Fig. 10 is a perspective view of a modified version of the pin of Fig. 9. In this embodiment the pin 2 is again of folded sheet metal construction and a recess 45 is formed in the side 46 of the pin between its upper end 47 and a bent-in portion 48 of the side 46. The conductor-piercing blades 1 7a, 1 7b are formed integrally with the portion 48. When the jaws 1 0a, 1 Ob (Fig. 1) are inserted into the recess 45, the two jaws are urged together between the end 47 and the portion 48 of the pin. A slot 49 in the side 50 of the pin allows passage of the conductor 7 (Fig. 1) into the recess 45 as the jaws are pressed into the recess.A degree of resilience can be provided in the end 47 and the portion 48 so that, when the jaws 1 Oa, 1 orb are inserted into the recess 45, these parts 47 and 48 exert a compressive force on the jaws to maintain an adequate contact pressure between the blades 17a, 17b and the conductive portion of the conductor located by the jaws.

In the plugs described above with reference to Figs. 9 and 10, it will be appreciated that no recesses are provided in the base 1 (Fig. 1) for the reception of the pairs of conductorlocating jaws.

In the various embodiments described above with reference to Figs. 3 and 5 to 10 it will, of course, be appreciated that the pin 4 (Fig. 1) would be modified in the same way as the pin 2. It will also be appreciated that, although not illustrated in these Figures, the pins are retained in the contact-carrying portion of the plugs in conventional manner.

Although in the various embodiments described above the modified pins are all of sheet metal construction, it is possible to provide solid pins with upper ends fashioned in the various ways illustrated in Fig. 3 and 5 to 10.

In each of the embodiments described so far, the conductor-piercing blades 17a, 17b are formed integrally with the pins 2. Fig. 11 is a sectional view of part of the base 1 of a further modified embodiment of the plug of Figs. 1 and 2, and constituting a plug in accordance with the invention, in which there is no connection between the jaw-receiving member and the conductor-piercing blade of the plug. In Fig. 11, two metallic plates 51 are mounted at opposite sides of the recess 20 in the base 1. These plates, which form a jaw-receiving member of the plug, are resilient and are of curved shape with their convex surfaces facing one another. When the pair of jaws 1 0a, 1 Ob (Fig. 1) is inserted into the recess, the jaws are urged together by engagement with the plates 51, and the resilience of these plates maintains an adequate contact pressure between the piercing blade 1 7a and the conductive portion of the conductor 7 (Fig. 1) located between the jaws.

Claims

1. An electric plug comprising an electrically-insulating contact-carrying portion, at least one metallic contact pin carried by and extending from said contact-carrying portion, a metallic, conductor-piercing member electrically connected to said pin, a pair of conductor-locating jaws for the reception of an insulated conductor which is to be electrically connected to said pin, and a jaw-receiving member associated with said piercing member for guiding the pair of jaws onto the piercing member and arranged to urge the two jaws together to locate the conductor as it is pierced by the piercing member, said jaw-receiving member being made at least partly of metallic material.

2. An electric plug according to claim 1, in which said piercing member is separate from the jaw-receiving member.

3. An electric plug according to claim 2, in which said jaw-receiving member is in the form of a metallic cradle with two spacedapart limbs connected at one end by a web, the piercing member being arranged to pass through the web without making electrical contact therewith.

4. An electric plug according to claim 3, in which the limbs of said cradle are resilient so that when, in use of the plug, a pair of conductor-locating jaws is inserted between the limbs of the cradle, the limbs exert a compressive force on the jaws and so enable an adequate contact pressure to be maintained between the piercing member and the conductive portion of the conductor held by the jaws.

5. An electric plug according to claim 2, in which said jaw-receiving member is formed by a pair of spaced-apart metallic plates supported in said contact-carrying portion.

6. An electric plug according to claim 5, in which said plates are supported in a recess in said contact-carrying portion.

7. An electric plug according to claim 5 or 6, in which said plates are resilient so that when, in use of the plug, a pair of conductorlocating jaws is inserted between the plates, the plates exert a compressive force on the jaws and so enable an adequate contact pressure to be maintained between the piercing member and the conductive portion of the conductor held by the jaws.

8. An electric plug according to claim 1, in which said piercing member is joined to, or formed integrally with, the metallic part or parts of the jaw-receiving member.

9. An electric plug according to any of claims 1 to 8, in which said piercing member is connected directly to said pin.

10. An electric plug according to claim 9, when dependent on claim 8, in which said pin is formed integrally with both said piercing member and with the metallic part or parts of said jaw-receiving member.

11. An electric plug according to claim 10, in which said pin is fabricated from metallic sheet material to provide a hollow pin.

1 2. An electric plug according to claim 8, in which said piercing member is connected via a fuse to said pin.

1 3. An electric plug according to claim 14, in which said piercing member and said metallic part or parts of the jaw-receiving member are formed integrally with a fuse clip for the reception of one end of a cartridge fuse.

1 4. An electric plug constructed and arranged substantially as herein described with reference to, and as illustrated in, Figs. 1 and 2 as modified by any of Figs. 3, 4, 5, 6, 7 and 8, 9, 10 and 11, of the accompanying drawings.