WO2004008587A1

WO2004008587A1 - Improved plug assembly and plug pin

Info

Publication number: WO2004008587A1
Application number: PCT/GB2003/003068
Authority: WO
Inventors: Philip Kenneth Timbrell; Tarlochan Ghataora; Michael Mackenzie Instance; Walter Leonard Riede; Henry Quoc Nghia Thai; Peter Sibary
Original assignee: Tyco Electronics Pty. Ltd; Tyco Electronics Uk Ltd
Priority date: 2002-07-17
Filing date: 2003-07-15
Publication date: 2004-01-22

Abstract

A plug pin having (i) a forward conductive portion (3); (ii) an intermediate conductive portion (7) which in use receives an insulating sleeve (4), which may be integral with the plug bridge or may be free-standing; and (iii) a rearward connecting portion (9) which is small enough to pass through the sleeve before an electrical conductor is connected to the said connecting portion. Also provides a plug assembly incorporating at least one such pin, together with the said sleeve, a plug bridge (30), and connecting means (8), preferably a separately-formed crimp bucket, for connecting a conductor (20, 21, 28) to the rearward connecting portion of the pin. Reduces the cost of insulating the pins and facilitates plug assembly.

Description

IMPROVED PLUG ASSEMBLY AND PLUG PIN

The present invention relates generally to electrical connectors, and particularly, but not exclusively, to plug pins and an electrical plug housing mounting the plug pins. The invention also relates to a method of manufacturing electrical plugs. Electrical plugs are well known. Modern plugs usually comprise a plug pin bridge, which may form part or all of the face of the plug housing and which includes slots or holes for receiving and firmly mounting plug pins, and a rear portion which essentially consists of potting material which is injection moulded to form an appropriate plug housing shape. A plurality of plug pins, usually two or three, are mounted in the housing of most domestic electrical plugs.

Each plug pin commonly consists of a forwardly extending portion, in use extending from the face of the plug housing and comprising a substantially flat blade element or rectangular, square, or round cylindrical pin element arranged for mechanical and electrical engagement with a suitable receptacle (plug-socket receptacle). The plug pin also usually comprises a rearwardly extending portion, in use mounted within the plug housing and being arranged to be connected to an electrical conductor. The rearwardly extending portion usually comprises a crimp portion, commonly known as a "crimp bucket", which is supplied open to receive an electrical conductor and is crimpable to fasten the conductor to the pin.

During manufacture, the plurality of plug pins are mounted through slots or holes in a plug pin bridge and the electrical conductors are inserted into the rearwardly extending crimp portions which are thereafter crimped to the conductors. The conductor and the rearwardly extending portions are then potted in an insulating material. Automated manufacturing processes are usually applied, in which the conductor wires are automatically inserted into the rearwardly extending pin portions and a crimping machine automatically crimps the rearwardly extending portions to the wires. The plug pins are inserted through the plug pin bridge and the housing is formed by injection moulding potting material. The plug pins are usually inserted through the slots in the plug bridge from the rear of the plug bridge and the conductor wires may be crimped into the rearwardly extending pin crimp buckets either before or after the plug pins have been inserted through the plug pin bridge. For crimping after insertion, the crimp buckets either have to be aligned so that the crimping action can be carried out from one direction, or the crimping tool has to be realigned each time a crimp bucket of one of the plug pins is crimped. This results in a relatively expensive assembly process for the plug. It is known to insulate part of the forwardly extending portion of the plug pin. In domestic plugs, in some circumstances, a plug may be slightly removed from a socket or tilted so that parts of the plug pins are exposed while the ends of the forwardly extending portions are still in electrical connection with the power supply. This is dangerous and can result in electric shock. A small child may slip their fingers between the plug socket face and the plug housing face and touch the conductors, which are still live (although standards attempt to dictate the dimensions of the plug pins and socket com ectors in order to prevent this, prevention is not certain). Metal or otherwise conductive implements may fall in between the plug housing face and socket face and become live themselves. The provision of insulation about a part of the forwardly extending portion, usually the part which extends immediately from the plug housing face, up to part way along the forwardly extending portion, reduces the danger of accidental electric shock in this manner. With presently available insulated plug pins, the insulation is applied during manufacture of the plug pin, for example by moulding of plastics insulating material or by winding plastics tape around the part of the plug pin to be insulated, thus increasing the cost of the plug pins, and consequently the cost of the plug when the insulated plug pin is used to manufacture the plug assembly in the conventional fashion.

The present invention improves on the known manufacture of plugs with insulated pins and accordingly, in a first aspect, provides a plug pin having (i) a forward conductive portion; (ii) an intermediate conductive portion which in use receives a separately -formed insulating sleeve, the intermediate portion of the pin preferably being smaller than the forward conductive portion and the sleeve when fitted onto the intermediate portion preferably substantially matching the cross-sectional outer size and shape of the forward portion; and (iii) a rearward connecting portion which is small enough to pass through the sleeve before an electrical conductor is connected to the said connecting portion.

This invention also provides, according to a second aspect, a plug assembly incorporating at least one pin of the above first aspect, together with the said sleeve, a plug bridge, and separate connecting means, preferably a separately-formed two-ended crimp connector, for connecting a conductor to the rearward connecting portion of the pin. In preferred forms of this invention, the said insulating sleeve may be conveniently formed as a forward extension from the plug face, for example as an integrally-moulded extension of the plug bridge, or alternatively as a separately moulded or extruded free-standing sleeve.

The invention thus has the great advantage of enabling- inexpensive separately- formed pin-insulating sleeves to be applied to the plug pins. By ingeniously eliminating the known integral pin crimp bucket and by making the rearward connecting portion of the pin relatively small (preferably without even a small crimp bucket), and preferably relatively flat for plugs having flat-blade pins, the invention allows the rearward connecting portion of the pin to be passed through the sleeve in order to position the sleeve on, and so insulate, the intermediate pin portion. The use of a separate connecting means to connect the conductor to the rearwardly-extending portion of the plug pin may advantageously enable connection to be carried out without special alignment of the rearwardly-extending portions of the plug pins or realignment of the connecting (e.g. crimping) tool during the connecting operation. Furthermore, the pins according to the present invention may be inserted into the plug bridge from the front, contrary to the inevitable rear insertion of the previously known pins.

In accordance with a first variant, the present invention provides a plug assembly, comprising a plug housing having a plug housing face from which extends a forwardly extending portion of at least one plug pin, the plug housing face including an insulating extension sleeve portion extending from the plug housing face and extending about at least a part of the at least one plug pin, whereby to provide insulation. for the part of the at least one plug pin.

In this variant, plug pin insulation is provided by the insulating extension portion of the plug pin housing face. It is not necessary, therefore, to separately insulate the plug pin during manufacture of the plug pin. This advantageously results in a decrease in the manufacturing cost of the plug pin. The plug housing face is preferably of plastics and may be injection moulded. The forward-extending insulating ' sleeve portion, therefore, may be provided relatively cheaply, so reducing the cost of manufacture of the plug. The plug housing face preferably comprises a plug bridge. On assembly, the plug housing may be formed about the plug bridge by injection moulding of appropriate insulating plastics material.

The rearwardly-extending connecting portion of the plug pin preferably includes a landing portion of smaller dimension than the adjacent conductive intermediate portion of the pin, and attachment of a conductor (eg. conductive wire) to the plug pin is preferably by way of affixing the conductor to the landing. This is preferably done utilising a separate holding member which can be placed about the conductor and landing and fixed thereto, preferably by a crimping action. The holding member may include a conductive sleeve. It is believed that it has not previously been known to use such a separate holding member to connect a conductor to the rearwardly extending portion of a plug pin. Preferably, the landing portion is substantially flat. The landing portion preferably includes projections at an end thereof, for example forming a "T" shape, to assist with retaining the holding member in place on the landing portion. It is a standard requirement of many countries that the dimensions of the portion of the plug pin extending forwardly from the plug housing face be substantially uniform. That is, the forwardly extending portion of the plug pin should have the same width and breadth along its length as it extends from the plug housing face. This enables it to engage physically and conductively in a stable manner with a plug pin socket of similar dimension for receiving the plug pin. With insulated plug pins, it is required that the insulated part and the non- insulated part should together form a plug pin forwardly extending portion of substantially uniform cross-sectional dimensions. This requires the part of the plug pin which is to receive insulation to be of narrower dimensions than the uninsulated part of the plug pin, so that when the insulation is added, the forwardly extending portion including the insulated part and the uninsulated part is of even dimensions. In the present invention, therefore, the forwardly- extending portion of the plug pin preferably includes a first part having first dimensions and a second part of narrower dimensions arranged to receive the insulating extension portion extending from the plug housing face.

The present invention further provides a plug pin, comprising a forwardly-extending portion for electrical and mechanical engagement with a corresponding plug pin socket, and a rearwardly-extending portion including a landing to which a conductor may be connected. The landing is not a crimp bucket. The landing is preferably of a shape which enables it to receive a conductor thereon for conductive contact. The landing preferably forms a substantially flat surface. In accordance with another aspect, the present invention provides a plug pin bridge including means for mounting at least one plug pin, and an insulating extension portion extending from the plug bridge and being arranged to extend about a part of the at least one plug pin when present in use, thereby to provide insulation for at least the said part of the plug pin. In accordance with a further aspect, the present invention provides a method of manufacturing a plug assembly, comprising a plug bridge having a means for receiving a plug pin and from which extends an insulating extension portion, and a plug pin having a forwardly extending portion, the forwardly extending portion including a part for receiving the insulating extension portion, and a rearwardly extending portion including a landing portion for receiving a conductor, comprising the steps of inserting the plug pin via the landing portion from the front of the plug bridge. Preferably, the method comprises the further step of attaching a conductor to the flat landing utilising a separate holding member to hold the conductor to the flat landing.

Features and advantages of the extension-sleeve aspects of the present invention will become apparent from the following description of an embodiment thereof, by way of example only, with reference to the accompanying drawings, in which;

Figure 1 is a perspective view of a plug assembly in accordance with an embodiment of the present invention, showing a part of the plug housing in ghost outline;

Figure 2 is an exploded perspective view of the plug assembly of figure 1; Figure 3 is a further exploded view of the plug assembly of figure 1; and Figure 4 is a further exploded view of the plug assembly of figure 1. In the figures, a plug pin assembly in accordance with an embodiment of the present invention is depicted. The plug assembly is generally designated by reference numeral 1. It comprises a housing, generally designated by reference numeral 2, and including plug housing face, in this embodiment being in the form of a plug bridge 3 which in this example comprises a generally disc like injection moulded plastics insulating part. The rest of the housing 2 is in fact in the form of a injection moulded cover 34 which is injection moulded onto the plug bridge 3 and other internal components (see later) to "pot" the components.

The plug bridge 3 mounts plug pins 4, 5, 6. These plug pins, in this embodiment, form live, neutral, and earth, respectively for a domestic electrical supply system. Each of the plug pins 4, 5 and 6 includes a forwardly extending portion 7, 8, 9 respectively which is arranged to engage with a corresponding socket portion providing the connection to the electricity supply.

The plug bridge 3 includes first 10 and second 11 insulating extension portions extending therefrom. The insulating portions 10 and 11 extend about a part 14, 15 respectively of the plug pins 4 and 5, so as to provide insulation for the parts 14 and 15.

In more detail, each of the forwardly extending portions 7 and 8 of the live 4 and neutral 5 plug pins comprise a first part 12, 13, having first dimensions (and positioned substantially adjacent the plug bridge 3), and a second part 14, 15 (positioned remote from the plug bridge 3) having second dimensions smaller than the first dimensions of the first parts 12 and 13. The second parts 14 and 15 are of appropriate dimensions to receive the insulating extension portions 10 and 11 thereabout, such that the resultants dimensions of the forwardly extending parts 7 and 8 of the plug pins 4 and 5 are essentially uniform along their length, to comply with the appropriate standards for the uniform dimensionality requirement for plug pins. Note that no insulating extension portion is required for the earth plug pin 6.

The plug bridge 3 includes a first slot 16 for receiving the earth pin 6. Second 17 slots and third 18 slots are also provided in the plug housing 3 for receiving the plug pins 4 and 5. The insulating extension portions 10 and 11 are formed as extensions of slots 17 and

18 respectively. Boxes 19, 20, 21 forming the slots provide stable mounting means for the plug pins 4, 5, 6.

Each plug pin 4, 5, 6 also includes a rearwardly extending portion 22, 23, 24. Each rearwardly extending portion 22, 23, 24 includes a substantially flat landing 25, 26, 27. When the plug is assembled, each flat landing 25, 26, 27 has a respective conductor 28, 29, 30, mounted to it. The conductors 28, 29, 30 are held to the flat landing 24, 26, 27 by holding means

31, 32, 33, respectively. The holding means 31, 32, 33 are in the form of crimpable sleeves which can be placed about the landings 25, 26, 27 and conductors 28, 29, 30 and crimped thereto. A suitable known type of holding means is the type used in the Auto Splice™ style arrangmement. These are known for splicing monolead devices such as resistors and diodes to conductors.

The plug bridge and plug pin assembly, with conductors attached to the plug pins, is then potted in injection moulding insulating material 34 to complete the plug housing 2.

The insulating extension portions 10 and 11 extend about the parts 14 and 15 of the plug pins 4 and 5 and reduce the possibility of electric shock by accident by either a conductive element or a person coming into contact with plug pins 4 and 5 when they are partially removed from electrical sockets but are still in conductive contact with an electrical power supply. The plug bridge 3 may be of plastics insulating material and is conveniently manufactured using plastics injection moulding.

The plug pins 4, 5, 6 are preferably formed of conductive metal, such as brass or copper, and stamped and folded from a flat blank of metal. In plug pins 4 and 5, the parts 14 and 15 and rearwardly extending portions 22 and 23 are formed by stamping and the parts 12 and 13 are formed by folding over from stamped material to meet at line 34, 35. The forwardly extending portion 9 of plug pin 6 is formed by folding from stamped material to meet at line 36, and the rearwardly extending portion 27 is formed by stamping. The rearwardly extending portions 22, 23, 24 are formed with a "T" shape 40, 41, 42. The "T" bar assist in retaining the holding members 31, 32, 33 in place. Conductors 28, 29, 30 extend from a cable 43 which may be connected to an electrical device (not shown) requiring power. The steps in plug assembly are as follows (in no particular order).

Plug pins 4 and 5 are inserted from the front of the plug brigge 3 into the insulating extension portions 10 and 11 in the direction of arrows 45, 46 (figure 2) into slot 17 and 18 formed in boxes 20 and 21. The earth pin 6 is inserted from the rearward side of the plug housing face 3 into slot 16 formed in box 19. The plug pin 6 has a projection 47 on its rearwardly extending portion 24 which prevents it from being pulled through the slots 16.

Rearwardly extending portions 22, 23, 24 of plug pins 4 and 5 include notches 50, 51, 52, 53 in the sides thereof. Boxes 20 and 21 include projecting portions 54, 55, 56, 57 which are arranged to slot into the notches 52, 53, 50, 51 (as best shown in figure 3) and prevent the plug pins 4 and 5 from being pulled back through the slots 17 and 18. Conductors 28, 29, 30 are then mounted to the landings 25, 26, 27 and fixed thereto by the holding means 31, 32, 33 which are crimped by an appropriate crimping tool. The assembly is then potted in injection moulding 34.

The plug of the above described embodiment includes three plug pins, two of which are insulated. It will be appreciated that embodiments may exist with more or less pins. For example, an earth pin in some cases may be dispensed with. Further, it will be appreciated that the orientations of the plug pins may be different in different embodiments.

The above-described embodiment is a domestic electrical plug. The invention may be applied in electrical plugs and electrical connectors which are not domestic eg. industrial plugs. In the above-described embodiment, the plug is of the form comprising a plug bridge which mounts the components and injection moulded potting material which is subsequently added to insulate the components and form the plug body. This is but one form of plug assembly and it will be appreciated that the present invention could be applied in other forms of plug assembly. For the example, the UK form of plug often consists of a plug body formed as a pair of halves, one half providing the plug housing face. The rearwardly-extending portion of the plug pin in the above described embodiment has a flat landing for attaching the conductor. The landing is to be of sufficiently small dimensions to be able to be inserted via the insulating extension sleeve portion 10. The landing preferably provides a flat surface for receiving the conductor, but the surface need not be flat and could be, for example, slightly curved.

Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

In accordance with a further variant, the present invention provides a plug pin assembly, comprising a plug pin including a forwardly-extending conductive portion for mechanical and electrical engagement with a plug-socket receptacle, an insulating member mounted about an insulating receiving portion of the forwardly extending portion, and a conductor-securing member for securing a conductor to the plug pin, the conductor-securing member being provided as a separate item which is secured to the plug pin after mounting of the insulating member thereon, preferably after incorporation of the plug pin assembly into a plug assembly.

Preferably, the insulating member is formed as a unitary body, preferably of injection-moulded plastics material, which has the advantage that it can be simply mounted to the plug pin without it being necessary to wind insulating tape about the plug pin or separately mould insulating material to the plug pin. Manufacture of the plug pin assembly is therefore preferably simplified. The insulating member is preferably in the form of a unitary sleeve which, during assembly of the plug, can be slid onto a relatively small dimension portion of the plug pin (the insulating-receiving portion). Preferably, the relatively small dimension insulating-receiving portion is formed behind a larger dimension forwardly-extending conductive portion of the plug pin and the insulating member in the form of a unitary sleeve is preferably slid onto the insulating receiving portion from a rearwardly extending end of the plug pin. The separate conductor-securing member, which is subsequently attached to the plug pin, conveniently acts as a "stop" to secure the insulating sleeve in place. This further simplifies the manufacture of the plug pin assembly. The rearwardly-extending portion of the plug pin preferably includes a substantially flat receiving element for receiving the conductor-securing member, the latter preferably including a crimp member arranged to be affixed to the receiving element. The conductor- securing member also includes means for securing a conductor, the means preferably being a crimp bucket. The conductor-securing member preferably includes an attachment means for attaching the crimp member to the plug pin. The attachment means may be crimped, ultrasonically welded or attached in some other way to the receiving element of the plug pin. Preferably, the attachment means is a further crimp bucket which can be crimped to the receiving element. When assembling this form of plug pin assembly into a plug, the plug pin assembly may conveniently be inserted through slots or holes in a plug pin bridge from the rear of the plug pin bridge using conventional procedures. Preferably, the insulating member is formed with a stop to prevent the plug pin assembly from being inserted too far through the plug pin bridge. The stop is preferably formed as part of the unitary insulating sleeve.

The assembly also preferably includes an anti-back out tang which, once the plug pin has been inserted through the bridge, prevents the plug pin from being pushed out of the bridge in the reverse direction. The anti-back out tang is preferably formed as part of the insulating member. In accordance with a further aspect, the present invention provides a method of assembling a plug pin assembly including a plug pin having a forwardly-extending conducting portion and an insulating member formed as a unitary body, the unitary body being formed as a sleeve with a passageway therethrough, and the plug pin including a rearwardly-extending insulation-receiving portion of suitable dimensions to pass through the passageway, comprising the step of inserting the insulating-receiving portion of the pin through the said passageway in the insulating member.

Preferably, a conductor-securing member is mounted to a rearwardly extending portion of the plug pin, in order to retain the insulating member on the plug pin.

The forwardly-extending conducting portion of the pin is preferably of larger dimensions than the insulating-receiving portion, and the. rearwardly-extending portion of the plug pin is passed through the sleeve, not the forwardly-extending portion.

This form of plug pin assembly according to the present invention can advantageously be utilised in the manufacture of plug assemblies utilising conventional techniques, and conventional plug bridges. In one embodiment, a plurality of plug pins carrying the free-standing insulating sleeves in accordance with the present invention have conductors attached to their conductor-securing portions and then are inserted through a plug bridge from the rear thereof until they are secured in the plug bridge. A plug housing is then injection moulded over the plug bridge, connector and conductor assembly as is conventional.

In accordance with a further aspect, the present invention provides an insulating member for a plug pin assembly, the insulating member being formed as a unitary sleeve having a passageway therethrough capable of receiving a portion of a plug pin in order to mount the insulating member on the plug pin. Preferably, the insulating member is formed with a stop to prevent a plug pin carrying the sleeve from being inserted too far through a plug pin bridge. Preferably, the insulating member is formed with an anti-back out tang.

In accordance with a further aspect, the present invention provides the aforesaid plug pin and insulating sleeve together with a conductor-securing member for a plug pin assembly, the conductor-securing member including a first portion arranged to be attached to the plug pin and a second portion arranged to secure an electrical conductor to be electrically connected to the plug pin. Features and advantages of this variant of the present invention will become apparent from the following description of an embodiment thereof, by way of example only, with reference to the accompanying drawings, in which;

Figure 5 is an exploded view of a plug pin assembly in accordance with an embodiment of the present invention;

Figure 6 is a perspective view of a plurality of assembled plug pins in accordance with the Figure 5 embodiment, shown in proximity to electrical conductors to be connected to the plug pins;

Figure 7 shows the plurality of plug pin assemblies of Figure 6 connected to the electrical conductors and in proximity to a plug pin bridge through which they are to be inserted, and

Figure 8 is a perspective view of a plug assembly incorporating plug pin assemblies in accordance with Figure 5, with the plug housing being shown in ghost outlined.

Referring to Figure 5, a plug pin assembly is illustrated, generally designated by reference numeral 1. The assembly includes a plug pin 2, which includes a forwardly extending portion 3 which is arranged for electrical and mechanical engagement with a corresponding socket receptacle (not shown).

The plug pin assembly 1 also includes an insulating member 4, in this embodiment being formed as a unitary body. In this embodiment, the insulating member 4 is formed as a sleeve, having walls 5 defining a passageway 6 therethrough. The plug pin 3 includes an insulating receiving portion 7, which in this embodiment is formed as a continuation of the forwardly extending portion 3, the continuation being of narrower dimensions than the forwardly extending conductive portion. The passageway 6 in the insulating member 4 is arranged to receive the insulating receiving portion 7 of the plug pin 2 to form the plug pin assembly. Reference numerals 10 and 11 in Figure 6 illustrate assembled plug pin assemblies with respective insulating members 4 shown seated on the insulation-receiving portions of the plug pins 2. In this embodiment the plug pins are stamped and folded from blanks to form blade-like elements. In this embodiment, the plug pin assembly also includes a conductor-securing member 8 in the form of a crimp member 8. The crimp member 8 is arranged to be attached to a crimp receiving element 9 of the plug pin 2. The crimp receiving element 9 of the plug pin 2 is arranged to pass through the passageway 6 in the sleeve 4 and project out from the passageway 6 when the insulating member 4 is seated correctly on the plug pin 2. On assembly, the receiving element 9 is passed into and through the passageway 6 so that the insulating member is slid onto the insulating receiving portion 1 from the rearward end of the plug pin 2.

The crimp member includes a crimp portion 14 which is arranged to be crimped about the crimp receiving element 9 of the plug pin 2 (note that the conductor securing member may be attached to the receiving element 9 in other ways than crimping. For example it may be attached by ultrasonic welding, or any other way). This is best illustrated in Figure 6, where the crimp portions are shown crimped about the receiving element 9. The receiving element 9, in this embodiment includes projections 15, 16 which extend outwardly of a main body 17 of the receiving portion and act to retain the crimp portion 14 of the crimp member 8 in place. The crimp member 8 also includes a further crimp bucket 19 which is arranged to receive a conductor, such as a wire conductor 20, 21 (Figure 6) for crimp connection to the plug pin 2 (note that other ways of the securing the conductor to the conductor securing member may be applied, apart from crimping). The arrangement is therefore easily assembled. When assembled, the dimensions of the forwardly extending portions 3 of the plug pin 2 and the insulating member 4 are such as to provide uniform dimensions allowing for insertion into a conventional plug pin socket. An advantage of having a unitary insulating member is that it simplifies assembly of the plug pin assembly. In this embodiment, the insulating member 4 also includes a stop 22 which, on assembly into a plug prevents the assembly from being pushed entirely through the slot of a plug bridge, and an anti-back out tang 23 which, when the plug assembly 1 is mounted through a plug bridge, prevents it from being removed from the plug bridge in a reverse direction. It is advantageous that these components can be injection moulded, for example as part of the unitary body 4. In Figure 6, there are illustrated two fully assembled plug pin assemblies 10 and 11, and a conventional earth pin 25. The earth pin is made completely of conductive material and includes a forwardly extending conductive portion 25 arranged for electrical and mechanical engagement with an earth pin socket receptacle, and a standard bucket crimp 27 for receiving earth conductor 28. The earth plug pin 25 also includes a stop 29 and an anti- back out tang (not visible on these drawings). On assembly, live 20, neutral 21 and earth 28 conductors are crimped to plug pin assemblies 10 and 11 and earth pin 25, respectively.

Figure 7 illustrates the conductors, plug pin assemblies, and earth pin, when assembled, and a conventional plug pin bridge 30, which includes passageways 31, 32 and 33 for receiving the plug pin assemblies 10 and 11 and earth pin 25, respectively.

Assembly of the plug assembly is conventional. Plug pin assemblies 10, 11 and earth pin 25 are inserted through the plug bridge 30 from the rear, as usual. Referring to Figure 8, it can be seen that the plug pin assemblies 10 and 11 and earth pin assembly seat within insulating members 34, 35 and 36 respectively, projecting rearwardly from the plug bridge 32. The stops 22 formed on the insulating members 4 of the respective plug pin assemblies 10 and 11 are butt against an inner edge of insulating projections 34 and 35 preventing the plug pin assemblies 10 and 11 from being pushed any further through the plug bridge 30. Stop 29 on earth pin 25 has a similar function. The anti-back-out tangs 23 on insulating members 4 of the plug pin assemblies 10 and 11 are pushed through the bridge 30 and prevent plug pin assemblies 10 and 11 from being pushed back though the bridge 30 in the reverse direction. The plug pin assemblies 10 and 11 are secured within the plug bridge 30. A similar anti back out tang on earth pin 25 has a similar function. The arrangement is then potted in a plug pin housing 40 (shown in ghost outline), to complete the plug assembly. The plug bridge 30 is of plastics insulating material and is conveniently manufactured using plastics injection moulding. The housing 40 is also manufactured from injection moulding and includes potting material for potting the entire assembly. The plug pin 2 is preferably formed of conductive material, such as brass or copper, and stamped and folded from a flat blank of the metal. The crimp members 8 are also preferably formed by folding blanks of conductive metal, such as copper or brass. The insulating member 4 is preferably formed as an injection moulded plastics sleeve.

It will be appreciated that the plug pin assembly and plug assembly can be made of any suitable materials and are not limited to the materials discussed above.

The plug assembly described above includes three plug pins two of which are insulated plug pin assemblies in accordance with an embodiment of the present invention. It will be appreciated that the present invention may be implemented in plug assemblies with more or less connectors. For example, an earth pin in some cases may not be required. Further, it will be appreciated that the orientations of the plug pins may be different in different embodiments. Further, the plug assembly described above corresponds to a general type of plug assembly used in Australia. The present invention may be adapted to be incorporated with different types of plug assemblies (eg plug assemblies usually used in other countries) and the shape of the plug pin assembly may be varied according to standards required for various countries. The above described embodiment is domestic electrical plug. The invention may be applied in electrical plugs and electrical connectors which are not domestic eg industrial plugs.

Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. The preferred crimp connectors described above could be replaced by solder or screw connections or other wire-connecting arrangements designed so as to pass through the insulating sleeve according to the present invention. This insulating sleeve principle, which has been described above mainly in relation to thin blade-like plug pins and potted plug bodies as used in Australia, could be applied to the thicker heavy-duty type of plug pin used in re-enterable plugs in the United Kingdom, as hereinafter described by way of example with reference to Figures 9 to 12 of the accompanying drawings, wherein:

Fig.9 shows schematically in perspective a UK-type plug pin with moulded-on insulation and a screw connection for attaching a conductor thereto;

Fig.10 shows schematically in partial cross-section the pin of Fig.9 fitted into a re- enterable plug housing having a cap separably connected to the plug bridge;

Fig.11 shows a modified screw-connecting plug pin insertable through a sleeve according to the present invention; and

Fig.12 shows the pin and sleeve of Fig.11 fitted into a re-enterable plug housing similar to that of Fig.10. As shown in Figs. 9 and 10, a copper plug pin 50 of typical dimensions 4 mm thick,

6 mm wide, and 30 mm long has a forward conductive contact portion 52, a reduced portion 54 over which is moulded plastics insulation 56 matching the exterior dimensions of the contact portion 52, and an enlarged head portion 58, typically measuring 6 mm by 6 mm by 6 mm, having a bore 60 and screw 62 for receiving and securing the stripped end of a conductor 64 to be electrically connected to the pin in use. When the pin is inserted through an aperture in the plug bridge 66 from the rear of the plug bridge 66 in the forward direction of arrow A, the enlarged head portion 58 is seated within upstanding enclosure walls 68 formed integrally with the bridge 66 and engages with the inner surface of the bridge to limit the forward movement of the pin. The plug cap 70 is removably secured to the bridge by screw 72 engaging integral cap socket 74, the cap acting to secure the pin 50 against rearward movement. The cap can be removed to permit connection or disconnection of conductors to the pin. These plugs normally have two such partly-insulated pins, live and neutral respectively, and an uninsulated earth pin.

The expense of over-moulding the pin insulation onto the pin in these known plugs can be avoided as illustrated in Figures 11 and 12. Here the known insulated pin of Fig. 9 is replaced by a pin 80 and a separately-formed plastics insulating sleeve 90 according to the present invention. The pin 80 has a forward conductive contact portion 82 and reduced- thickness insulation-receiving portion 84 similar to those of the Fig.9 pin, but the head portion of the present pin containing bore 86 and screw 88 for connection of wire 64 is reduced in size to be capable of passing through the sleeve 90 in the direction of arrow B. In this example, the pin has a depression 85 in its insulation-receiving portion 84, and the sleeve has an inward-facing resilient tang 92 which snaps into the depression 85 to retain the sleeve in place on the pin as shown in Fig. 12. The pin and sleeve can then be inserted into the aperture in the plug bridge 66 from the front of the bridge in a rearward movement in the direction of arrow C. The sleeve also has an outward-facing resilient tang 94 which snaps into place against the inside surface of the bridge 66, when the pin is inserted as shown in Fig. 12, to retain the pin against forward withdrawal, while the plug cap 70 again releasably secures the pin against rearward movement, as described for Fig. 10.

Claims

1. A plug pin having (i) a forward conductive portion; (ii) an intermediate conductive portion which in use receives a separately-formed insulating sleeve; and (iii) a rearward connecting portion which is small enough to pass through the sleeve before an electrical conductor is connected to the said connecting portion.

2. A plug pin according to claim 1, wherein the intermediate portion of the pin is smaller than the forward conductive portion and the sleeve when fitted onto the intermediate portion substantially matches the cross-sectional outer size and shape of the forward portion.

3. A plug assembly incorporating at least one pin according to claim 1 or 2, together with the said sleeve, a plug bridge, and separate connecting means for connecting a conductor to the rearward connecting portion of the pin.

4. A plug assembly according to claim 3, wherein the separately-formed connecting means is a two-ended crimp device.

5. A plug pin or assembly according to any preceding claim, wherein the said insulating sleeve is formed as a forward extension from the plug face, for example as an integrally-moulded extension of the plug bridge.

6. A plug pin or assembly according to any of claims 1 to 4, wherein the said insulating sleeve is formed as a separately moulded or extruded free-standing sleeve.

7 . A plug assembly according to claim 3 or 4, comprising a plug housing having a plug housing face from which_' extends a forwardly extending portion of at least one plug pin, the plug housing face including an insulating extension portion extending from the plug housing face and extending about at least a part of the at least one plug pin, whereby to provide insulation for the part of the at least one plug pin.

8 . A plug assembly in accordance with claim 7, wherein the at least one plug pin further includes a rearwardly extending portion including a landing portion.

9 . A plug assembly in accordance with claim 8, a conductor being fixed to the landing portion by a holding member separate from the landing portion.

10 . A plug assembly in accordance with claim 9, the landing portion including projections forming a "T" shape, the projections assisting with retention of the holding member in place on the landing portion.

11. A plug pin according to claim 1 or 2, comprising a forwardly extending portion for electrical and mechanical engagement with a corresponding plug pin socket, and a rearwardly extending portion, including a landing to which a conductor may be connected.

12. A plug pin in accordance with claim 11, the plug pin including a part of the forwardly extending portion having first dimensions, and another part of the forwardly extending portion having second, smaller dimensions, for receipt of insulation thereabout.

13. A plug pin in accordance with claim 11 or claim 12, the flat landing having a projection for assisting in retaining a holding member for holding a conductor to the flat landing.

14. A plug pin bridge including means for mounting at least one plug pin, and an insulating extension portion extending from the plug bridge and being arranged to extend in use about a part of the at least one plug pin, whereby to provide insulation for at least the part of the one plug pin.

15. A method of manufacturing a plug assembly, comprising a plug housing face having a means for receiving a plug pin and from which extends an insulating extension portion, and a plug pin having a forwardly extending portion, the forwardly extending portion including a part for receiving the insulating extension portion, and a rearwardly extending portion including a landing portion for receiving a conductor, comprising the steps of inserting the plug pin via the landing portion from the front of the plug housing face.

16. A method in accordance with claim 15, comprising a further step of attaching a conductor to the landing utilising a separate holding member to hold the conductor to the flat landing.

17 . A plug pin assembly according to claim 1 or 2, comprising a plug pin connector including a forwardly extending conductive portion for mechanical and electrical engagement with a plug-socket receptacle, an insulating member mounted about an insulating receiving portion of the forwardly extending portion, and a conductor securing member for securing a conductor to the plug pin assembly, the conductor securing member being provided as a separate item which is secured to the plug pin assembly on assembly of the plug pin assembly.

18 . A plug pin assembly in accordance with claim 17, wherein the insulating member is formed as a unitary sleeve, having a passageway therethrough, on assembly the passageway being arranged to received the insulation-receiving portion.

19 . A plug pin assembly in accordance with claim 18, the plug pin connector including a receiving element arranged to pass through the passageway and extend out of the passageway when the insulating member is mounted about the insulating receiving portion.

20 . A plug pin assembly in accordance with claim 19, including a crimp member arranged to be affixed to the receiving element and including a crimp bucket for receiving an electrical conductor to be connected to the plug pin assembly.

21 . A plug pin assembly in accordance with any one of the preceding claims, the insulating member including a stop to prevent the plug assembly from being inserted too far through a plug pin bridge.

22 . A plug pin assembly in accordance with any one of the preceding claims, the insulating member including a anti-backout tang.

23 . A plug pin assembly in accordance with any one of the preceding claims, the insulating member being formed by injection mounting.

24 . A method of assembling a plug pin assembly including a plug pin connector having a forwardly extending conducting portion and an insulating member formed as a unitary body, the unitary body being formed as a sleeve with a passageway therethrough, and the plug pin connector including an insulating receiving portion of suitable dimensions to pass through the passageway, comprising the steps of inserting the insulating receiving portion through the passageway from a rearward extending of the plug pin connector.

25 . An insulating member for a plug pin assembly, the insulating member being formed as a unitary sleeve the unitary sleeve having a passageway therethrough which is arranged to receive a portion of a plug pin connector in order to mount the insulating member to the plug pin connector.

26. A plug pin and insulating sleeve together with a conductor-securing member for a plug pin assembly, the conductor-securing member including a first portion arranged to be attached to the plug pin and a second portion arranged to secure an electrical conductor to be electrically connected to the plug pin.

27. A plug pin or assembly according to any preceding claim, wherein the comiecting portion of the plug pin includes a bore and screw for securing an electrical conductor thereto.