IE54984B1

IE54984B1 - A non-rewirable electrical plug and a method of moulding therefor

Info

Publication number: IE54984B1
Application number: IE292883A
Authority: IE
Original assignee: Irish Driver Harris Company Li
Priority date: 1983-12-13
Filing date: 1983-12-13
Publication date: 1990-04-11
Also published as: GB2152301B; GB2152301A; GB8431088D0; IE832928L

Description

54984 -Z- The invention relates to a non-rewirable electrical plug and a method of moulding therefor.

In one known method of moulding a non-rewirable plug the body of the plug is either moulded in one or two layers around the 5 contacts of the pins to which corresponding conductors have been previously attached.

The principal disadvantage of this method is that stray strands of conductor wire may migrate to the surface of the plug body during the first moulding operation. This presents 10 a serious safety hazard to the plug user.

In another known method of moulding a non-rewirable plug the pins are inserted in corresponding holes in a pre-formed base insert either before or after the electrical connections are made between the contact pi ns and conductors .

The principal.disadvantage of the use of pre-moulded insert is that a complex construction of base insert is required. Such inserts generally include various ramps and shoulders for holding the pins and conductors in position. In addition, the ^ requirement of shoulders or protrubences on the pins to retain ZO them in position in the holes in the pre-formed base insert -3- 54984 leads to a complex and hence costly construction of pin with various changes in cross-section.

This invention is directed towards providing an improved method of moulding an electric non-rewirable plug which will 5 overcome the problems with the presently known methods. The invention is also directed towards providing an improved construction of non-rewirable plug.

According to one aspect of the invention there is provided a method of moulding non-rewirable electrical plug having 10 at least a pair of pre-formed plug pins comprising the steps of sequentially: mounting a portion of each pin in a predetermined position in a mating recess in a mould; moulding insulating material around a portion of each pin 15 to form a base member mounting the pins; electrically connecting each pin to a corresponding current carrying conductor of an electric cable to form a connection; and moulding a body of insulating material around a portion of the 20 base member to enclose the connections and conductor cable and to form an outer body of the plug.

In a preferred embodiment of the invention the body of insulating material is formed by:- moulding a first layer of insulating material around the oortion 25 of the base member to substantially enclose the connections to form a sub-assembly, and -4- -4- 54984 moulding a second layer of insulating material around the first layer.

Preferably the method includes the step of, after moulding of the first layer of insulating material and before 5 moulding of the second layer, checking the sub-assembly to ensure that no stray strands of conductor have risen to the outer face of the first layer.

In a preferred embodiment of the invention the base member is moulded from a dimensionally stable and electrically 10 resistant thermoplastics material such as glass filled polyester.

In a preferred embodiment of the invention the body may be of any suitable thermoplastic or thermosetting material preferably of a plastisised polyvinyl chloride material.

In another aspect the invention provides a non-rewirable electrical plug comprising a base member mounting at least a pair of plug pins to each of which a corresponding current carrying conductor of an electric cable is electrically connected to form a connection, and a body of 20 insulating material moulded around a portion of the base member, the base member being moulded around a portion of each pin before the conductors are electrically connected to the pins, and at least one pin being formed with a pin keying means for inter-engagement with the base member on 25 moulding of the base member around the portion of the pin.

In one embodiment of this aspect of the invention the pin keying means comprises an undercut groove formed intermediate -5- 54984 the ends of the pin.

Usually the groove extends transversely around at least the portion of the pin.

Alternatively the pin keying means comprises a hole 5 extending through the pin intermediate the ends thereof.

As a further alternative the pin is knurled intermediate its ends to provide the pin keying means.

As a still further alternative the pin is formed with a flange extending transversely around at least portion of the 10 pin to provide the pin keying means.

In a further embodiment of this aspect of the invention the body of insulating material comprises a first layer of insulating material moulded around the portion of the base member to substantially enclose the connections and a second 15 layer of insulating material moulded around the first layer.

In a further embodiment of this aspect of the invention layer keying means are provided between the base member and at least one said layer of insulating material.

In another embodiment of this aspect of the invention indicating 20 means are provided for indicating the presence of the first layer of insulating material after the second layer has been moulded on.

The indicating means may comprise an indicating lug formed -6- 549 8 4 integrally with the first layer and projecting to the outer surface of the second layer.

The indicating lug may comnrise keying means between the base member and the first layer.

Usually the second layer of insulating material extends Over the portion of the base member to provide at least a portion of the keying means.

The base member may be moulded from a dimensionally stable and electrically resistant thermoplastics material such 10 as glass filled polyester.

The invention will be more clearly understood from the following description thereof given by way of example only with reference to the accompanying drawings in which:- Fig. 1 is a perspective view of a first sub-assembly comp 15 rising a base member,mounting plug pins, forming part of a non-rewirable plug according to the invention, Fig. 2 is a top plan View of the sub-assembly of Fig. 1, Fig. 3 is a cross-sectional view in the direction of 20 the arrows ΤΓΤ-ΤΤΤ in Fig. 2, Fig. 4 is a perspective view of an electric cable with terminals and fuse clips attached, Fig. 5 is a perspective view of a second sub-assembly comprising the first sub-assembly of Figs. 1 to 3 with the cable, terminals and fuse clips of Fig. 4 connected to the pins, Fig. 6 is a top plan view of the sub-assembly of Fig. 5, Fig. 7 is a cross-sectional view in the direction of the arrows Vli-VII in Fig. 6, Fig. 8 is an underneath plan view of a third sub-assembly comprising the sub-assembly of Figs. 5 to 7 with a first layer of insulating material moulded-on, Fig. 9 is a cross-sectional view in the direction of the arrows I5t - _IX in Fig. 8, Fig. 10 is a cross-sectional view in the direction of the arrows in Fig. 8, Fig. 11 is a perspective view of an electric plug according to the invention, Fig. 12 is another perspective view of the plug of Fig. Π in a different position, -8- -8- 54984 Fig. 13 is a further perspective view of the plug of Figs. 11 and 12 in a different position, Fig. 14 is an exploded perspective view of the plug of Fig. 12, Fig. 15 is an underneath plan view of the plug of Figs. 11 to 13, and Fig. 16 is a cross-sectional view in the direction of the arrows XVI -XVIin Fig. 15.

Referring to the drawings there are illustrated various parts of sub-assemblies used in forming a non-rewirable electrical plug in accordance with the invention. The finished plug is illustrated particularly in Figs. 11 to 16 and is indicated generally by the reference numeral 1. The plug 1 comprises a base member 2 mounting at least a pair and in this case three plug pins namely a live pin 3, a neutral pin 4 and an earth pin 5. A corresponding current carrying conductor respectively indicated by reference numerals 7,8 and 9 of an electric cable 10 is electrically connected to the pins 3,4,5 to form a connection. A body of insulating material which in this case comprises a first inner layer 15 and a second outer layer 16 is moulded around the connections and portion of the base member to form the body of the plug.

The plug is moulded by first mounting a portion of each pin -9- -9- 5 4 9 8 4 3,4,5 in a predetermined position in a mating recess in a mould and then moulding insulating material around portion of the pins 3,4,5 to form the base member 2. The base member 2 with the pins mounted therein forms a first sub-assembly which is illustrated in Figs.l to 3. Each pin 3,4,5 is then electrically attached to its corresponding current carrying conductor 7,8,9 of a cable 10 to form a connection. A second sub-assembly which comprises the first sub-assembly with the pins electrically connected to its corresponding current carrying conductor is illustrated in Figs. 5 to 7. The first layer of insulating material is then moulded around portion of the base member 2 to enclose the conductor connections forming a third sub-assembly as illustrated in Figs. 8 to 10. A second layer 16 of insulating material is moulded around the first layer 15, the cable 10 and portion of the base member 2 to form the outer body of the plug 1.

Referring particularly to Figs. 1 to 3 pin keyingmeans are provided on each pin 3,4,5 for interengagement with the base member 2. In this case the pin keying means comprises a transverse groove 25 extending around portion of each pin 3,4,5 and into which the material of the base member 2 flows on moulding to retain the pins in position.

It will be noted that the side edges of each of the pins 3,4,5 are radiussed to reduce stress concentration particularly in the area of the keying grooves 25. The head of each pin is hollowed out at 60 to facilitate rivetting on of the ring -10- -10- 54984 terminals or fuse clips as required.

The base member 2 is of a relatively simple construction and is formed with four flared keying holes 30 for engagement with the insulating material of the first layer 15 as 5 illustrated in Figs. 5 to 7. A recess 31 is also provided for reception of fuse clips 20, 21 in which is mounted a conventional fuse 32 which is retained in a fuse carrier 35.

In the particular arrangement illustrated in Fig. 14 the fuse carrier 35 is fully removable from the recess 31 10 however it will be appreciated that the fuse carrier may also be of the captive type, for example the carrier may be slidably, hingedly or in any convenient manner mounted on the base member 2 to facilitate replacement of the fuse 32 without detaching the carrier 35 from the base member 15 2. A ramp 35 provides access for a screwdriver or similar tool for removal of the carrier 35 and fuse 32 from the clips 20, 21. Grooves 37 guide the conductors 7,8 and 9 of the cable to their appropriate locations. Portion of the fuse clips 20, 21 are inserted into the recess 31 through appropriately shaped 20 channels 38. A keying ledge 35 off-set from the back base 2 is provided for interengagement with the second layer 16 of encapsulation as will be apparent particularly from Fig. 7.

Referring to Figs. 4 to 7 after the base member 2 has been moulded around the pins 3,4,5 the neutral and earth conductors 2-5 8,9 of the cable 10 are mechanically by rivetting attached through ring terminals 40 to the appropriate pins respectively 4,5. The live conductor 7 54984 -Ills mechanically attached to one fuse clip 20. The fuse clip 20 and the other clip 21 are then inserted in their appropriate recesses 31 to form a second base sub-assembly which is illustrated in Figs. 5 to 7. The cable 10 with ring terminals 40 and fuse clips 20, 21 is illustrated in Fig. 4. When the fuse is in place electrical connections between the live conductor 7 and the live pin 3 is made.

When the connections have been made and the fuse clips 20, 21 are loaded, the inner first layer of insulating material is moulded around the connections and portion of the base member 2 to encapsulate the connections and form a third sub-assembly. The third sub-assembly with the first layer 15 in place is illustrated in Figs. 8 to 10.

Insulation material for the first layer 15 is keyed to the base member 2 through the keying holes 30 as will be particularly apparent from Fig. 10. An indicating lug 45 projects proud of at least one of the keying holes 30 to a position flush with the back face of the base member 2 and may be clearly viewed when the second layer 16 of insulating material is moulded on. Thus a visual inspection of the finished plug reveals that the inner layer 15 has been included. To facilitate ease of inspection the material of the inner layer 15 may be of a different colour than that of the outer layer 16. A pair of keying holes 47 are formed over the fuse clips 20 for bonding the outer layer 16 to the inner layer 15.

Referring to Figs. 11 to 16 there is illustrated a finished -12- -12- 5 4984 plug including a second layer 16 of insulating material moulded over the first layer 15. The insulation material of this layer 16 engages in the keying holes 47 in the first layer 15 and behind the ledge 39 of the base member 2.

The insulation material also engages around the cable 10 to form a sleeve 50 having a number of cut-out grooves 51 to allow sufficient flexibility while preventing removal of the cable from the plug. Two sidewardly extending ribs 55 on each side of the outer body of the plug facilitate 10 finger gripping on insertion and withdrawal of the plug into and from a socket.

Referring particularly to Fig. 4 the fuse clip 20 to which the live conductor 17 of the cable 10 is attached is illustrated. The clip 20 comprises a fuse receiving portion 15 formed from a generally channel-shaped member 60 including a slightly arcuate portion 61 for reception of a conventional fuse 32 and a cap 62 spot welded to the channel-shaped member 60. It will be noted that the cap is wider than the channel in which the fuse 32 is received 20 and therefore acts as a seal or shut-off for the fuse clip recesses in the base member 2 to prevent flash particularly during moulding on of the first layer 15 of insulating material. The cap 62 includes a pair of upstanding lugs 63 (see Fia. 6) which are crimped to engage with the wires of 25 the live conductor 7.

The other fuse clip 21 is also illustrated in Fig. 4 and is -13- -13- 54984 similar to the clip 20, and like parts being assigned the same reference numerals. The fuse clip 21 is for rivetting to the live pin 3 and consequently the cap 62 is formed with an L-shaped extension 65 having a through hole 66 for 5 engagement over the head of the live pin 3 on rivetting on.

Referring particularly to Fig. 14 the fuse carrier 35 includes a generally rectangular shield 70 and a central collar 71 for accommodating the fuse. Viewing apertures 72 are provided in the shield 70.

The base member 2 is preferably of 30¾ glass filled thermoplastic polyester material. The first 15 and second 16 layers of encapsulation are usually of a plastisised polyvinyl chloride material however both the layers and base member may be of any suitable thermoplastic or thermo-setting 15 material.

One advantage of the method according to the invention is that because the base member is moulded around the pins it is of very simple construction. Consequently the tooling required is also a simple construction and the construction of pin is 20 considerably less complex than that required in previous methods of moulding such plugs.

It will be appreciated that in some cases instead of a first layer of insulating material moulded on or around the connections and base member a preformed cap or gaiter may be -14- -14- 5 4 9 8 4 provided.

It will also be appreciated that after moulding on of the first layer a suitable check may be made to ensure that no stray strands of conductor have migrated to the surface of 5 the layer. This check may be conducted either electrically or by visual inspection. However, it is envisaged that even if such strands were present these would be safely confined to the outer surface of the first layer which is covered by the outer layer or layers.

It will be appreciated that a dummy earth pin may be provided in the plug in some cases.

It will also be appreciated that as a safety feature the pins may be sleeved over portion of their length. For example when forming the base insert.

It will also be appreciated that any number of layers of insulation material may be employed.

It will be appreciated that in the case where the pin keying means is provided by a groove the groove may extend either partially or fully around the pin. The pin keying means may 20 also be provided by a flange extending transversely around at least portion of the pin. A hole or a number of blind or through holes may be provided in the pin intermediate the ends thereof to provide the keying means. As a further 54984 -15- alternative the pin may be knurled to provide the keying means.

It will also be appreciated that each of the fuse clips may be formed from a single piece of electrically 5 conductive material.

Claims

1. 6- 16- 54984

2. 1. A method of moulding a non-rewirable electrical plug having at least a pair of pre-formed plug pins comprising the steps of sequentially: 5 mounting a portion of each pin in a predetermined position in a mating recess in a mould; moulding insulating material around a portion of each pin to form a base member mounting the pins; electrically connecting each pin to a corresponding current 10 carrying conductor of an electric cable to form a connection; and moulding a body of insulating material around a portion of the base member to enclose the connections and conductor cable and to form an outer body of the plug. 15 2. A method as claimed in claim 1 in which the body of insulating material is formed by:- moulding a first layer of insulating material around the portion of the base member to substantially enclose the connections to form a sub-assembly, and 20 moulding a second layer of insulating material around the first layer.

3. A method as claimed in claim 2 which includes the step of, after moulding of the first layer of insulating material and before moulding of the second layer, checking the sub-assembly to ensure that no stray strands of conductor 25 -17- -17- 5 4 9 8 4 have risen to the outer face of the first layer.

4. A method as claimed in any of claims 1 to 3 in which the base member is moulded from a dimensionally stable and electrically resistant thermoplastics material. 5 5. A method as claimed in claim 4 in which the base member is moulded from a glass filled polyester material.

5. 6. A method as claimed in any preceding claim in which the body is of a thermoplastic or thermosetting material.

6. 7. A method as claimed in claim 6 in which the body is 10 of plastisised polyvinyl chloride material.

7. 8. A method substantially as hereinbefore described with reference to the accompanying drawings.

8. 9. A non-rewirable electrical plug comprising a base member mounting at least a pair of plug pins to each of 15 which a corresponding current carrying conductor of an electric cable is electrically connected to form a connection, and a body of insulating material moulded around a portion of the base member, the base member being moulded around a portion of each pin before the conductors 20 are electrically connected to the pins, and at least one pin being formed with a pin keying means for interengagement with the base member on moulding of the base member around the portion of the pin. 5 4 9 8 4 -Ιδιο. A plug as claimed in claim 9 in which the pin keying means comprises an undercut groove formed intermediate the ends of the pin.

9. 11. A plug as claimed in claim 10 in which the groove 5 extends transversely around at least the portion of the pin.

10. 12. A plug as claimed in claim 9 in which the pin keying means comprises a hole extending through the pin intermediate the ends thereof.

11. 13. A plug as claimed in claim 9 in which the pin is knurled 10 intermediate its ends to provide the pin keying means.

12. 14. A plug as claimed in claim 9 in which the pin is formed with a flange extending transversely around at least portion of the pin to provide the pin keying means.

13. 15. A plug as claimed in any of claims 9 to 14 in 15 which the body of insulating material comprises a first layer of insulating material moulded around the portion of the base member to substantially enclose the connections and a second layer of insulating material moulded around the first layer. 20 16. A plug as claimed in claim 15 in which layer keying means are provided between the base member and at least one said layer of insulating material. -19- -19- 54984

14. 17. A plug as claimed in claim 15 or claim 16 in which indicating means are provided for indicating the presence of the first layer of insulating material after the second layer has been moulded on. 5 18. A plug as claimed in claim 17 in which the indicating means comprises an indicating lug formed integrally with the first layer and projecting to the outer surface of the second layer.

15. 19. A plug as claimed in claim 18 in which the indicating 10 lug comprises keying means between the base member and the first layer.

16. 20. A plug as claimed in claim 19 in which the second layer of insulating material extends over the portion of the base member to provide at least a portion of the keying 15 means.

17. 21. A plug as claimed in any of claims 9 to 20 in which the base member is moulded from a dimensionally stable and electrically resistant thermoplastics material.

18. 22. A plug as claimed in claim 21 in which the base member 20 is moulded from a glass filled polyester material.

19. 23. A plug as claimed in any of claims 9 to 22 in which the body is of a thermoplastics or thermosetting material. 54984 -20-

20. 24. A plug as claimed in claim 23 in which the body is of a plastisised polyvinyl material.

21. 25. A plug substantially as hereinbefore described with reference to and as illustrated in the accompanying 5 drawings. Dated this 10th day of December 1984 CRUICKSHANK & CO. Agents for the Applicants,

22. 1, Holies Street, Dublin 2.