AU710750B3 - Method of manufacturing electrical connector - Google Patents

Description

AUSTRALIA

PATENTS ACT 1990

ORIGINAL

COMPLETE SPECIFICATION PETTY PATENT Invention Title: METHOD OF MANUFACTURING ELECTRICAL CONNECTOR Name of Applicant: UTILUX PTY LIMITED The following statement is a full description of this invention, including the best method of performing it known to me/us: -2- Method of Manufacturing Electrical Connector The present invention relates to a method of forming an electrical connector, and particularly, but not exclusively, to a method of manufacturing a plug-pin connector, such as the type used in domestic electrical plugs. The invention particularly rates to a method of manufacturing an electrical connector which includes an insulating layer for protecting from electric shock.

Plug-pin connectors are well known. They commonly consist of a forwardly extending portion, in use extending from the face of a plug housing and comprising a substantially flat blade element or a cylindrical plug-pin element adapted for mechanical and electrical interengagement with a suitable receptacle plug-socket receptacle). They also comprise a rearwardly extending portion, in use mounted within the plug and being arranged to be connected to an electrical conductor. The rearwardly extending portion usually comprises a part which is crimpable to an exposed conductive wire and also may comprise a further section or portion crimpable around the wire insulation. A plurality of such connectors (usually three) are employed in most domestic plugs. During manufacture, the plurality of plug-pins are mounted through slots or holes in a partition which is to form one face of the plug, being held in predetermined orientation with respect to each other in the partition. Wire conductors are inserted into the rearwardly extending portions, which are crimped thereto and then the wires and the rearwardly extending portions are potted in an insulating material.

Plugs manufactured in this way are safe because it is not possible for anybody to access and rewire the plug. An alternative procedure is to crimp the wires to the plugpins first, and subsequently insert the plug-pins into the partition and pot.

One problem with electrical connectors such as J:\Speci\300 399\300 349\33015.doc 3 domestic plugs is that, in some circumstances, a plug may be slightly removed from a socket or tilted so that portions of the plug-pins are exposed while the ends of the forwardly extending portions are still in electrical contact with the socket. This is dangerous, as a small child can slip their fingers between the plug socket face and the plug face and touch the conductors, which are still live. Metal or otherwise conductive implements may also fall down in between the plug face and socket face and become live themselves, and lead to the possibility of accidental electrocution.

This problem has been addressed in some countries by the manufacture of plug-pins having a part of the forwardly extending portion insulated. The insulated part preferably extends along a sufficient length of the forwardly extending portion of the plug-pin that, if a plug mounting the plug-pins is partially removed from a plug socket, the actual conductive part of the forwardly extending portion will not be exposed until it is no longer in electrical contact with the socket. Only the insulated part will be exposed while electrical contact is maintained. This reduces the chances of accidental electric shock.

The applicant's own prior petty patent application number AU40006/97 discloses an improved plug pin and method of manufacturing an improved plug pin. The plug pin includes a first forwardly extending conductive element including a first portion with first, larger, external dimensions, and a second portion having second external dimensions which are smaller than the first external dimensions. The second portion is covered with an insulating layer or member. This improved plug pin is manufactured, preferably, by folding a flat blank of material. The disclosure of patent application number AU40006/97 is incorporated herein by reference.

The plug pin of application 40006/97 is a development J:\Speci\300 399\300 349\33015.doc 4 of the applicant's earlier granted Australian petty patent number 659988, which discloses an electrical connector including a forwardly extending blade element portion which is substantially hollow. The disclosure of petty patent number AU659988 is also incorporated herein by reference.

A further problem which needs to be addressed in the formation of electrical connectors such as plug pins which have a portion of a forwardly extending element insulated, is how to conveniently fit the insulation to the portion which is to receive it. This portion will usually be of reduced dimensions relative to the rest of the forwardly extending element of the electrical conductor. In the prior art, a number of approaches have been taken to mount the insulating material, and all raise problems.

It is conventional to form plug pins by cutting a blank from raw conductive material and folding the blank to form the plug pin. Applicant's earlier Australian petty patent application number 57394/98, discloses a method of forming an insulated plug pin, which includes the step of applying a layer of insulating material to a strip of conductive raw material prior to blanking and folding, the insulated material being applied in the area which will subsequently form the insulated portion of the completed plug pin. The disclosure of petty patent application 57394/98 is also incorporated herein by reference.

The folding steps of folding the blank to form the plug pin are conventionally carried out using formers which contact the surfaces of the blank and which are pushed together to fold the blank, during a series of folding steps using different formers. It has been found that, where the insulating material is applied before a folding, using conventional folding steps and formers, the insulating material can be damaged or even delaminated from the surface of the blank. This is undesirable as it can lead to the insulating layer being removed or partially J:\speci\300 399\300 349\33015.doc 5 removed from the plug pin, which can lead to accidental electric shock.

With the conventional method of formation of plug pins, the former used is usually substantially rectilinear, usually comprising a hammer and anvil pairing for each folding step, and results in substantial surface to surface shearing contact between the former(s) and the conductive blank during the folding of the blank. The substantial surface to surface shearing contact creates friction between the blank and the former(s) as the blank is being folded. Where an insulating layer is provided on one or more surfaces of the conductive blank, this friction may cause the insulating layer to be damaged or to rub away from the surface of the conductive blank. This is because of the rubbing or frictional action caused by the surface to surface shearing contact during folding, such that contacting surfaces of the former(s) and the conductive blank slide with respect to each other.

The present invention provides a method of manufacturing an electrical connector comprising a forwardly extending conductive element having an insulating layer on at least a portion thereof, from a blank of conductive material being provided with a layer of insulating material thereon to provide the insulating layer of the forwardly extending element when it has been formed, the method comprising the steps of folding the flat blank by a plurality of folding steps utilising a former, the folding steps and former being adapted so as to limit shearing contact between the former and the layer of insulating material.

By the term "shearing contact" we mean a contact which tends to apply friction in a direction coincident with the surface of the blank so as to tend to apply a force along the surface of the blank. This shearing contact could also be considered as a "sliding" contact between surfaces of J:\Speci\300 399\300 349\33015.doc 6the former and the blank.

The shearing contact between the insulating layer and the formers in each forming step is preferably limited by arranging the forming steps and formers so that, for each step, action on the insulating layer is by way of compression on to the conductive blank as opposed to applying a shear force between the insulating layer and former. The formers and forming steps are preferably adapted to minimise any shearing force.

This is preferably achieved by arranging the formers and forming steps so there is relatively little sliding movement between the contacting surfaces of the former and insulating layer/conductive blank during each forming step.

The only surface to surface movement is preferably a relative rolling motion of the respective surfaces.

Preferably, the shape of the formers and the folding steps are arranged so that for at least a plurality of the folding steps, the portions of the formers applying force to a section of the blank to fold that section of the blank apply the force through a relatively small surface area.

Preferably, the former may comprise one or more ridges arranged so that the only contact with the portion of the blank being folded is by way of the relatively small surface area ridge.

Features and advantages 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 from above and one side of an electrical connector which may be formed in accordance with an embodiment of the present invention; Figure 2 is a plan view of the connector of figure 1; Figure 3 is a side view from one side of the connector of figure 1; Figure 4 is an underneath view of the connector of J:\Speci\300 399\300 349\33015.doc 7 figure 1; Figure 5 is a rear view of the connector of figure 1; Figure 6 is a front view of the connector of figure 1; Figure 7 is a section on line B-B of figure 2; Figure 8 is a section on line A-A of figure 2; Figure 9 is a plan view of a flat blank for forming the electrical connector of figure 1; Figure 10 is a plan view of a plurality of the flat blanks of figure 9 shown attached to a former strip; Figure 11 is a schematic diagram illustrating a step in a conventional process for forming the connector from the blank; Figure 12 is a diagram illustrating the process in accordance with an embodiment of the present invention, for forming the connector from the blank; and Figure 13 is a diagram illustrating further steps in the process of this embodiment of the present invention.

Referring to the drawings, an electrical connector which may be formed by a process in accordance with an embodiment of the present invention, is generally designated by reference numeral i. The connector comprises a forwardly extending conductive element 2 which, in this embodiment, is a substantially flat blade element. The blade element 2 includes a first portion 3 having first external width W and breadth B dimensions (figures 3 and 4) The blade element also comprises a second portion 4, having second external width dimensions W2 and breadth dimensions B2 (figure The second external dimensions are smaller than the first external dimensions (it will be appreciated that Figure 8 is merely a larger scale drawing than Figs 3 and 4) In operation, the second portion 4 is covered with an insulating layer 5. In this preferred embodiment the insulating layer is a polyester layer, aramid layer, or J:\Speci\300 399\300 349\33015.doc 8 similar material.

The electrical connector also includes a rearwardly extending element 6. The rearwardly extending element 6 includes a crimp body 7 which is arranged to be crimped to a conductive connector, such as a wire.

In operation, the rearwardly extending element 6 is mounted within a plug housing (not shown, but would be clearly understood and well known to a person skilled in the art). The rearwardly extending element 6 may be potted in the plug housing after the crimp body is crimped to the electrical conductor in the plug. The forwardly extending element 2 extends outwardly of the plug housing to contact with an appropriate socket for the supply of power to an appliance, for example. The face of the plug from which the portion 3 extends, in operation abuts against the insulating layer 5 or extends slightly over it.

In operation of the plug, the portion 3 makes electrical contact with the power socket. Should the plug be pulled slightly outwardly away from the socket, the insulating layer 5 will ensure that no one can electrocute themselves. Preferably, the lengths of the portion 3 and portion 4 is such that when the plug is pulled out to an extent where the conductive portion 3 is exposed, the conductive portion 3 is no longer in electrical contact with the power supply socket.

The dimensions of the insulating layer 5 are such that when the insulating layer 5 is mounted about the second portion 2, external dimensions of the mounted insulating body 5 are less than or equal to the dimensions W and B of portion 3. The dimensions W and B are determined to comply with the standards required for the dimensions of pin plugs to fit into the appropriate sockets. When the plug-pin is complete, therefore, with the insulating layer 5, the forwardly extending portion 4 or at least the portion of it which is intended to extend into a socket receptacle will J:\Speci\300 399\300 349\33015.doc 9 comply with all the dimensional requirements. As long as the outer dimensions of the insulating layer 5 do not exceed the dimensions W and B the insulating layer will not interfere with the fit into the receptacle.

The embodiment shown in the drawings is formed from an blank of conductive material. The blank is formed from a plate or strip of raw conductive material copper, brass) by stamping/cutting to the appropriate shape and dimensions. The blank is then folded to form the final plug-pin.

To ensure that the portion 3 is of the correct dimension B, it is formed as a hollow portion 3. Parts 8, 9 of the conductive blank are folded over towards each other to form a top blade wall 8, 9 and further parts and 11 are folded to form a spacer wall 10, (not shown) which spaces the top wall 8,9 away from the opposite bottom wall 12 of the portion 3. This construction is the same as that used in the applicants earlier patent discussed above (Petty Patent No.659988).

The second portion is formed in a similar way, (as this is most clearly illustrated in Figure A top wall 31 is formed by folding over parts 30, 31 of the conductive blank and a spacer wall is formed by further parts 32 and 33, which operate to space the top wall 30, 31 away from the bottom wall 12. It can also be seen that sides 35, 36 of the spacer walls 32, 33, proximate the ends of the portions 32, 33, face each other. Portions 38, 39 of the insulating material are trapped between these sides 36 and this facilitates retention of the insulating layer 5 on the portion 4.

The rearwardly extending element is of the form disclosed in applicants earlier Petty Patent No. 678541.

The rearwardly extending element 6 is in this case formed as in Petty Patent No. 678541, from a flat blank rolled to the shape shown to provide a conical entry 21 to J:\Speci\300 399\300 349\33015.doc 10 facilitate assembly.

Figure 9 shows a blank of material cut to the appropriate shape to form the pin of Figures 1 through 7 by folding and rolling. Like reference numerals are used for portions of the blank which are used to form the elements -with the same reference numerals in figures 1 through 7.

Figure 10 shows a plurality of the flat blanks 1 attached to a former strip 23. The plurality of flat blanks will usually have been cut from a single sheet of raw conductive material, leaving the flat blanks 1 and the former strip 23.

Before folding the blank portion of insulating material 50 which is subsequently to form the insulating layer 5, insulating material is mounted to the portion of the blank which is to form portion 4. In Figure 9, the insulating material 50 is shown in outline so that that blank can be perceived underneath it. When the blank is folded, therefore, the insulating material 50 will be folded with it to form the layer 5. In addition, the portions 38, 39 of the insulating material will be trapped between the parts 35, 36 of the spacer walls 32, 33 of the portion 4.

In a preferred process, insulating material 50 may be mounted to the sheet of raw conductive material before the blanks are formed by stamping/cutting. Preferably the insulating material is a polyester or aramid layer which is preferably adhered to the conductive material by using a low temperature curing adhesive. The adhesive can be heated by induction heating through the conductive material. In a preferred embodiment, the raw conductive material is stamped to form a step which is to divide the first portion and the second portion of reduced dimensions.

The insulating material is preferably applied after this step forming process.

The portion 40 of the connector, closest to the J:\Speci\300 399\300 349\33015.doc I I_ _I 11 rearwardly extending element, is of the same dimensions W and B as the first portion 3. Having this further portion the same width as the first portion 3 facilitates assembly into a plug bridge or face. A plug bridge or face has a slot for receiving each forwardly extending blade element.

This slot is usually dimensioned to receive a standard connector. The portion closest to the rearwardly extending portion will usually seat in this slot and therefore it is of advantage if it is of the same dimensions W and B as the standard connector (and the first portion). Preferably then, this further portion 40 is formed in a similar manner to the first portion 3, having the same dimensions W and B as the first portion. Preferably, it also has a spacer wall spacing opposed blade walls, as with the first portion 3.

Figure 11 illustrates one step in a conventional formation process for forming an electrical connector, such as the electrical connector of figures 1 through 8, from a blank, such as the blank of figure 9. The step illustrated in figures 1la, b and c is the first step in folding to form the forwardly extending portion, blade element 2. In the figure 11 diagram, the blank is shown viewing from the front end of the blank (reference numeral 50 in figure 9) and the carrier strip 23 is not shown in order to improve the clarity of the diagram.

The formation step illustrated in figure 11 is carried out by employing a former comprising a hammer portion 51 and an anvil portion 52, which are brought together as indicated by arrow A (see figure lla). The top surface 53 of the hammer 51 strikes the central area 54 of the forwardly extending portion 2 of the blank and forces this central area 54 into a recess 55 of the anvil 52, which recess is substantially the same cross-sectional shape as the hammer 51 (see figure 1lb). As the hammer 51 pushes into the recess 55, the sides 56 and 57 of the blank J:\Speci\300 399\300 349\33015.doc 12 adjacent the central area 54 are forced upwards and towards the sides of the hammer 51 as indicated. Finally (figure llc), a rectilinear cross sectional shape is formed which has a central area 54 of width corresponding to the width of the blade element and to upstanding portions 56 and 57 which are to be folded in further forming steps to form the final blade element. The hammer 51 and anvil 52 are moved away from each other as indicated by arrow B in figure llc.

The problem with this process is illustrated clearly in figure llb. As the hammer 51 is brought down onto the anvil 52, outer surfaces of X, Y of the portions 56 and 57 of the blank abut the corners U and Z of the recess 55 of the anvil 52. These outer surfaces X, Y continue rubbing against these corners U and Z and also against the sides of the recess 55 as the hammer 51 moves further into the recess, creating a significant amount of shearing friction on the surfaces X and Y. Where an insulating layer 50 is applied, as in the blank shown in figures 9 and 10 forming the electrical connector of figures 1 to 8, it has been discovered that this shearing friction, caused by the conventional forming process, can deleteriously affect the insulating layer 50, can cause an enormous amount of rubbing and stretching on the film which can lead to imperfections in the insulating layer or even delamination and removal, of the insulating layer from the conductive surface.

Figures 12 and 13 illustrate stages in a process of forming a forwardly extending element of an electrical conductor in accordance with an embodiment of the present invention. The element illustrated being formed is the blade element of the plug-pin connector illustrated in figures 1 to 8, but it will be appreciated that the process of the present invention may be applied to other electrical connectors and is not limited to the electrical connector illustrated in figures 1 to 8.

J:\Speci\300 399\300 349\33015.doc 13 In figures 12 and 13 (and in figures 11) the blank is shown as a flat sheet, but it will be appreciated, that to form the connector of figures 1 through 8, the flat blank is first of all stamped to form a recess therein which receives the insulating layer. This recess is not illustrated in figures 11, 12 and 13 for clarity.

Figures 12a through i illustrate the five stages in the folding process for formation of the forwardly extending blade element together with respective hammer and anvil former arrangements which are used to carry out the folding steps.

Figures 13a through f illustrate in more detail each of the stages and in particular where the various hammer and anvil arrangements contact the blank and where they apply a folding force.

As with the conventional process, the process in accordance with this embodiment of the invention commences with a blank of material such as the blank illustrated in figure 9 for forming the forwardly extending element 2 of the plug pin of figures 1 to 8. In this process, the forwardly extending part of the blank includes a covering of insulating material 50 as illustrated in figure 9. As with figure 11, the forwardly extending portion 2 of the blank is viewed from the front, and the carrier strip 23 is not shown for purposes of clarity. It will be appreciated that, as is conventional, the folding process will take place while the blank is still attached to the carrier strip 23. It will also be appreciated that the formers are in fact three dimensional objects and not two dimensional.

The face of each former which contacts the blank to carry out the folding step will extend at least the full length of the blank.

In a first stage, (figures 13a and 12b) hammer 61 and anvil 62 are brought together on the blank to form the blank into a substantially shape as seen from the front J:\Speci\300 399\300 349\33015.doc 14 (figure 12c). As can be seen from figures 12b and 13a, the hammer 61 and anvil 62 are of substantially different form than the hammer 51 and anvil 52 used in the conventional forming process. The arrangement 61 and 62 in fact comprises complimentary projections 63, 64, 65 and recesses 66, 67, 68. Projection 63 on hammer 61 fits within the recess 68 on anvil 62 and, likewise, the projections 64, on anvil 62 fit within recesses 66, 67 in hammer 61. The projection 63, 64, 65 essentially form "ridges" the tops 69, 70 and 71 of which contact the flat blank (figure 13a) As the hammer 61 and anvil 62 are brought together, the force is mainly applied by the tops of the ridges 69, and 71 and it is only these relatively small surface areas which apply force to fold the blank. Further, the force is compressive and there is little or no shearing frictional force on the blank. Any limited shearing force that exists is in the form of a rolling motion, as portions of the blank roll with respect to the ridges 69, 70 and 71. There is no significant sliding and rubbing force, as with the conventional process.

Ends 72, 73 of the blank are finally contacted by the walls of the recesses 66 and 67 of the hammer 61 and are bent over, forming the precursors to the spacer walls 32 and 33 of the finally formed blade element.

Because there is only limited surface contact between the blank and the hammer and anvil 61, 62, and because any limited contact is only of a compressive or rolling nature rather than of a shearing nature, the insulating layer on the surface of the blank remains undamaged.

Subsequent stages in the process utilise similar principals. The formers are arranged so that only limited surface to surface contact occurs between the formers and the blank where a folding force is being applied. This limits the folding action to rolling or compression between the respective surfaces.

J:\Speci\300 399\300 349\33015.doc 15 The second step in the process (figures 12d and 13b) is to fold down portions 74, 75 of the blank which will eventually form the top wall 30, 31 of the blade element.

Projections 78, 79 on the hammer 76 contact the portions 74 and 75 and, in a rolling motion as the hammer 76 is brought together with the anvil 77, fold the portions 74, downwards to produce the shape shown in figures 12d and 13c. Again, shear force is minimised. At any one time the contact between the surfaces of the portions 74, 75 and the ridges 78 and 79 on the anvil 76 will only be a minimal contact where the force is being applied compressively.

In the next step (figures 12e and 13c) rectilinear formers, hammer 80 and anvil 81 having planar surfaces 82 and 83 respectively are applied to form the blank in terms of substantially rectangular shape with one open side (figures 12f and g and figure 13d). Again, the forces applied are compressive, as the planar surfaces 82 and 83 of the hammer 80 and anvil 81, respectively, contact ridges 84, 85 and 86 of the shape formed in the previous step.

The contact is therefore only limited in surface area until the rectilinear shape shown in figure 13d is formed, and is compressive and limited in shearing force.

In the next step (figures 13d and figure 12h) the portions 74 and 75 of the blank are forced towards each other by hammer 88 and anvil 89 arrangement. The anvil 89 has a shaped recess and contacts corners 90, 91 of the portions 74 and 75 to force them towards each other to produce the shape shown in figure 13e and figure 12h.

Again, because the areas 90 and 91 of the blank are the only areas which contact the anvil 89, (which provides the folding force) the force on the areas 90 and 91 is mainly in the nature of compression, with limited shear.

In the final step, a hammer 96 and anvil 95 are used to push the portions 74 and 75 towards the base portion 97 of the blank to form the final flat blade element as shown J:\Speci\300 399\300 349\33015.doc 16 in figure 13f and 12i. Again, the contact force is mainly compressive.

Note that the electrical connector formed by this process is not limited to the electrical connector shown in figures 1 to 8. Other electrical connectors could be formed by using a similar process which limits friction and -shearing forces with respect to the surface of the blank.

For example, a blade element could be formed without a spacer wall separating top and bottom blade walls, which would, instead abut each other.

Note also that in the connector of figures 1 to 8, the rearwardly extending portion 6 need not be of the form shown, but could be of any other form.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

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Claims (3)

1. A method of manufacturing an electrical connector comprising a forwardly extending conductive element having an insulating layer on at least a portion thereof, from a blank of conductive material being provided with a layer of insulating material thereon to provide the insulating layer of the forwardly extending element when it has been formed, the method comprising the steps of folding the flat blank by a plurality of folding steps utilising a former(s), the folding steps and former(s) being adapted so as to limit shearing contact between the former and the layer of insulating material.

2. A method in accordance with claim i, wherein the folding steps and former(s) are adapted so that for each forming step force on the insulating layer is predominantly by way of compression on to the layer as opposed to a shear force between the insulating layer and former(s)

3. A method in accordance with claim 2, the former(s) and forming steps being adapted so that there is relatively little sliding movement between the contacting surfaces of the former(s) and insulating layer during the forming steps. Dated this 26th day of July, 1999 UTILUX PTY LIMITED By their Patent Attorney GRIFFITH HACK S:\Speci\300 399\300 349\33015.doc