GB2081140A

GB2081140A - Making Contact Elements for Electrical Plugs and Sockets

Info

Publication number: GB2081140A
Application number: GB8121606A
Authority: GB
Original assignee: BRETER SpA
Current assignee: BRETER SpA
Priority date: 1980-08-05
Filing date: 1981-07-14
Publication date: 1982-02-17
Also published as: AR226373A1; DE3128483A1; IT8024008A0; ES271620Y; IT1132327B; BR8104993A; ES271620U; FR2488454A1

Abstract

A process for the manufacture of contact elements for electrical sockets and plugs of the kind including a box- type body formed from insulating material in which a plurality of housings suitable to contain a plurality of contact pins or sockets are defined is as follows. The contact elements, especially the pins, are obtained by cutting pieces having all the same length from a starting drawn bar of a predetermined section, by carrying out a plate-shaped end flattening on each piece, this fattening lying substantially in the same axis of the piece and in providing said end flattening with a transverse central hole suitable to allow the passage of an operating screw, this screw being designed to be screwed in a clamping plate parallelly facing said end flattening in order to anchor the wire. The plate-shaped flattenings of the contact elements are accommodated in prismatic cavities of the body, together with the corresponding clamping plates and operating screws. <IMAGE>

Description

SPECIFICATION Process for the Manufacture of Contact Elements of Electrical Sockets and Plugs in General and Product Obtained by the Same Process This invention relates to a process for the manufacture of contact elements of electrical sockets and plugs, of the kind including a boxtype body formed from insulating material in which a plurality of housings suitable to contain a plurality of contact pins are defined and a boxtype body of insulating material too, in which housing suitable to contain an equal number of contact bushes are defined.

The invention also relates to contact elements obtained by the same process, these contact elements particularly concerning sockets and plugs of industrial type, though they can also be utilized in ordinary sockets and plugs for domestic use.

The contact elements (pins and bushes) now used in electrical sockets and plugs are normally provided with an axial hole at one end of which the head of a wire to be connected is introduced.

One or more clamping screws secure the wire to the pin or bush concerned, these screws passing through corresponding threaded holes provided radially on the circular wall defining said axial hole. However, this kind of contact elements requires a rather complicated and expensive machining.

So, in order to obtain a pin of the known type it is necessary to carry out a first lathe machining suitable to obtain, from a starting bar, a cylindrical rod having an end portion of a bigger diameter, in this latter portion being successively machined an axial hole for the introduction of the wire and a radially threaded hole or holes for the clamping screws.

Furthermore, though the wire clamping system provided for in pins and bushes of the known art is satisfactory as to its quick installation, it has some drawbacks in relation to the tightening of the screws.

In fact, when the screws are tightened they tend to wedge themselves in the wire, so that they break some metal filaments generally forming the wire. In this way the wire cross section is locally reduced and therefore the electrical resistance is varied, giving rise to unavoidable increases in intensity of current which may produce dangerous effects. It is also to be noted that whenever a socket or plug has to be replaced, before carrying out the connection the user is obliged to accomplish a series of operations such as to cut off the length of damaged wire, to take away a part of the insulting sheath and to twist the portion of naked wire.It is also necessary to remember that a subsequent untightening of the screw in order to introduce the wire may cause the compiete coming out of the same screw which may even be lost thereby allowing the rotation of the pin or of the bush in the body, the re-introduction becoming therefore more difficult. In any case these operations involve a considerable loss of time during the installation.

In order to avoid the end portion of the wire being damaged, it is possible to utilize ordinary wire terminals; however this gives rise to an increase in manufacturing costs while the time necessary to carry out the connections becomes even longer.

The problem of the present invention is to achieve a simple and rational process to manufacture contact elements for electrical sockets and plugs so as to obtain a considerable reduction in the manufacturing costs and to accomplish a wire connecting system in which during the clamping operations there is no deterioration of the wires.

The problem is solved by the process according to the present invention for the manufacture of contact elements for electrical sockets and plugs in general, of the kind comprising a box-type body formed from insulating material in which a plurality of housing suitable to contain a plurality of contact pins are defined and a box-type body of insulating material too, in which housing suitable to contain an equal number of contact bushes are defined, this process consisting in cutting rectilinear pieces having all the same length from a starting drawn bar of electrically conductive material and of a predetermined cross section; in carrying out a plate-shaped end flattening on each piece, this flattening lying substantially in the same axis of the piece and having a portion projecting laterally on both sides with respect to the remaining parts of the same piece; and in providing said end flattening with a transversal central hole suitable to allow the passage of an operating screw, this screw being designed to be screwed in a clamping plate parallelly facing said end flattening in order to anchor the wire.

By this process, the contact elements, above all the contact pins, can be achieved in a very simple and cheap way, without carrying out any turning or other machining, except for the final turning in order to obtain the chamfering of the end of the pins opposite to the flattened portion.

The process cited above allows to obtain a rational structure of sockets and plugs of the kind specified, this structure being characterized in that in each pin and bush, the end portion suitable to be connected to the corresponding wires is plate-shaped and provided with a hole suitable to allow the passage of un operating screw to be screwed down in a clamping plate parallelly facing the same plate-shaped end portion, for anchoring said wires to said pin and bush.

Advantageously and according to a further feature of the invention, each of said box-type bodies has a cover fitted into it in a removable manner.

The advantages resulting from sockets and plugs obtained according to this invention reside essentially in their facility of use which allows to carry out the connection of the wires with the corresponding pins or bushes very quickly, without breaking or damaging the metal filaments forming the wires. In fact, as the naked end of the wire is no more in contact with the screw thread but it is introduced and clamped between the plate-shaped portion of the pin or of the bush and the corresponding clamping plate in an offset position with respect to the axis of the pin or of the bush, it is possible to apply even considerable clamping forces without damaging the structure of the wire.Consequently, when either the socket or the plug have to be replaced, it is no more necessary to cut the end portion of the wire and repeat the above mentioned operations as this portion can still be validly utilized.

A further important advantage of the invention resides in the extreme facility of construction both of the pins or of the bushes and of the covers to be fitted into, which allows to achieve finished products having a lower number of pieces and cheaper prices if compared with the traditional sockets and plugs.

Further features and advantages of the invention will appear more evident from the detail description of a preferred embodiment of a structure of sockets and plugs given hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a piece of a drawn bar suitable to obtain a pin by the process of the present invention; Figures 2 and 3 are two side views turned through 900 with respect to each other of a pin during the intermediate working stage thereof; Figure 4 is a side view of a finished pin; Figure 5 is a cross-sectional side view of a plug according to the invention; Figure 6 is a cross-section along the chain dotted line VI--VI of Figure 5; Figure 7 is a cross sectional side view of a socket according to the invention;; Figure 8 is a perspective view to an enlarged scale of a pin and of the corresponding clamping means thereof; Figure 9 is a side in part sectional view of a bush to an enlarged scale; Figure 10 is a top view of a bush at the end of the shearing operation and before its 1 800 bending; Figure 11 is a diagrammatic perspective view of an exaxple showing the assembling between a cover and a socket-body or a plug-body.

Referring particularly to Figures 5 and 6 of the drawings, it has been indicated at 1, as a whole, an electrical plug composed of a box-type body 2 laterally closed by a cover 3 which will be more ciearly described later. The mutual assembling of the box-type body 2 and the cover 3 defines a plurality of hollow housings 4 having substantially rectangular sections and axes lying in the same transverse plane and a further hollow housing 5, having a rectangular section too, the axis of which is parallel to and spaced in a predetermined manner from the plane containing the axes of the hollow housings 4.

The sidesurface of the box-type body 2 opposed to the cover 3 has a plurality of projections 1 5 in the shape of a truncated cone, each one of these projections 15 being centrally provided with a through hole 6 of circular section communicating with the corresponding hollow housing 4. A further through hole 7, the circular section of which has a larger diameter than the holes 6 and which communicates with the hollow s housing 5 is providedat the lower part of the body 2.

Referring particularly to Figure 8, it has been indicated at 8 as a whole, a metal pin substantially consisting of a cylindrical member 9 terminating in a rectangular plate-shaped end 10 lying in the same axis than the pin in the middle of which a hole 11 is provided. At 12 it has been indicated a ground metal pin (Figure 1) the structure of which is identical to the pin 8; it consists of a cylindrical member 13 the transverse and longitudinal sizes of which are greater than the corresponding cylindrical members 9, and of a plate-shaped end 14 having the same size than the pins 8.

The plate-shaped ends 10 and 14 of the pins 8 and 12 are located in the hollow housings 4 and 5 respectively, while the portions of the cylindrical members which are in close proximity to said plate-shaped ends are engaged in the through holes 6 and 7 of the box-type body 2 respectively.

The pins 8 and 12 are obtained from a drawn bar made of electrically conductive material, e.g.

brass, having the same cross section than the pins must have at the end of the different machinings.

In Figures 1 to 4 are shown all the different working steps of a pin 8, the same process being also carried out for the grand pin 12.

More particularly, in order to obtain the pins 8 (as well as the pins 12) it is necessary to prearrange a drawn bar having a suitable section and to cut the drawn bar into pieces 9 (Figure 1) of the same length. Afterwards, each piece is introdcued in a die (not shown) suitable to flatten one end of the same piece according to a plateshaped portion lying in the axis of the piece and projecting on both sides. Immediately afterwards, said plate-shaped portion is sheared so that its outline can take a rectangular shape, as indicated at 10 in Figures 2 and 3, a transverse central hole 11 being at the same time machined in said portion.

In order to finish the pin 8 it is necessary to carry out a chamfering 9a (Figure 4) at the end opposite to the flattened portion 10 described above. This chamfering can be carried out by means of a short lathe working.

It is to be noted that the plug 1 will be provided with a number of pins 8 depending on the type of polarity of the plug, while the provision of the ground pin 12 is not compulsory. More particularly, the plug can be bipolar or bipolar plus ground pin, of the three-pole kind or of the threepole kind plus ground pin and so on.

In each of the hollow housings 4 and 5 there is also located an operating screw 1 6 and a substantially rectangular clamping plate 17, provided with a plurality of surface grooves 18, parallel to one another, more evident in Figure 8, and with a threaded central hole 19. The screw 1 6 passes through the hole 11 of the pins 8 getting engaged into the threaded hole 1 9 of the clamping plate 17; it is the same in the case of the ground pin 12.

The precise arrangement of the through holes 6 and 7 and of the contiguous hollow housings 4 and 5 allow all the pins and the clamping means thereof to take a perfectly adjusted and anti rotating position, once they are introduced in their housings. Always referring to Figures 5 and 6 of the drawings, at 20 it has been indicated a plurality of wires covered with an insulating sheath but having a naked end 21 to allow the electric connection thereof with the corresponding pins 8 and 12.

According to a further feature of this invention the box-type body 2 is laterally closed by a cover 3 fitting thereinto by means of a pair of flexible tongues 22 (Figure 11) each one being provided with a central longitudinal slit 23 suitable to engage with a corresponding stop tooth 24 located on the outer surface of the box-type body 2.

It is to be noted thatthe closure engagement between the cover 3 and the box-type body 2 can be also obtained by a traditional screw system, in which case it should be provided at least a through hole in the cover and a threaded hole in the socket body to allow the introduction of the screw.

The cover 3 is also provided, in connection with the hollow housing 4, with a plurality of projections 25 suitable to be introduced in said hollow housings in order to prevent the pins 8 and 1 2 and the corresponding clamping means from moving axially. In each projection 25 and in each corresponding housing 5 holes 26 are also provided for the passage of the wire 20, the axes of which are offset with respect to those of the pins 8 and 12.

The electric connection is carried out by introducing the naked end 21 of the wire 20 between the plate-shaped ends 10 and 14 of the pins 8 and 12 and the clamping plates 17. A pair of shoulders 46 both located in the hollow housing 4 and in the hollow housing 5 hold the operating screw 1 6 axially fixed since the screw heads are trapped between the shoulders 46 and the piate-syaped portions 10 and 14 of the pins.

In this way each rotation of the screw 1 6 by means of an usual screwdriver causes the clamping plates 1 7 to move, these latter owing also to the presence of the grooves 18 allowing a steady connection between the wires and the pins. It is also to be noted that the length of the screws 1 6 must substantially correspond to the height of the housing 4 and 5; for this reason the screws cannot be lost since they cannot be completely unscrewed from the clamping plates 17, unless the cover 3 is taken away and the pins removed. In this way there is no loss of time during the assembling and disassembling operations.

Turning now to Figure 7, it is indicated at 27 an electrical socket substantially including a boxtype body 26 laterally closed by a cover 29 fitted into it, quite similar to the cover 3 of the plug 1.

By assembling the box-type body 28 to the cover 29 a plurality of hollow housings 30 having a rectangular section are defined, as well as a hollow housing 31 having a rectangular section too. The axes of the housings 30 lie in a plane which is parallel to and spaced, according to a predetermined distance, from the axis of the hollow housing 31. A plurality of longitudinal through holes 32 communicate with said housings 30, these holes being suitable to accommodate the cylindrical hollow portion 33 of a plurality of contact bushes 34 provided with a plate-shaped end portion 35; this portion 35, having a central hole 40, is located in the hollow housing 30.

Likewise, the hollow housings 31 communicates with a longitudinal through hole 1 6 having a greater diameter than the holes 32, suitable to accommodate the cylindrical hollow portion 37 of a bush 38 for the ground pin 12, whilst the plate-shaped end portion 39 is located in the hollow housing 31.

The connection systems and the clamping means between said bushes 34 and 38 and the corresponding electrical wires are quite similar to those in the plug 1 in this case too being provided clamping plates 1 7 in which the operating screws 1 6 are screwed.

It is to be noted (Figure 9) that the hollow cylindrical portions 33 and 37 of Thebushes 34 and 38 are provided with two or more longitudinal slits 42 suitable to allow the introduction of the corresponding pins of the plug 1.

Finally it has been indicated at 43 an elastic band situated in proximity of the free end of the cylindrical hollow portions 33 and 37 to assure an adequate contact pressure between the pins and the corresponding bushes, while a plurality of notches or transverse reliefs have been indicated at 44, these being located on the outer surface of the bushes to allow their precise positioning in the socket body. In the bushes too, as in the pins, the operating screws are trapped in the housing 30 and 31 so that they cannot be lost, the heads thereof being held by adequate shoulders so that by turning them the plates 1 7 are moved.

In order to obtain the above described bushes it is possible to follow the same process than for the pins, i.e. to prearrange a tubular drawn bar, to cut it into pieces of the same length and to submit each piece to a pressing and shearing operation in order to obtain the plate-shaped end portions provided with central holes.

According to another embodiment, each bush can be carried out by means of the pressing of two half-bushes which make up a single body being in correspondence with the end side 35a of the plate-shaped portions 35, as shown in Figure 10. In the plateshaped portions 35 are also provided corresponding holes 40 and afterwards the piece is bent through 1 800 along the line 35a to achieve the shape seen in Figure 9.

Obviously the invention herein described may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.

Claims

1. A process for the manufacture of contact elements for electrical sockets and plugs in general, of the kind comprising a box-type body formed from insulating material in which a plurality of housings suitable to contain a plurality of contact pins are defined and a box-type body of insulating material too, in which housings suitable to contain an equal number of contact bushes are defined, characterized in that it consists in cutting rectilinear pieces having all the same length from a starting drawn bars of electrically conductive material and of a predetermined cross section; in carrying out a plate-shaped end flattening on each piece, this flattening lyng substantially in the same axis of the piece and having a portion projecting laterally from both sides with respect to the remaining parts of the same piece; and in providing said end flattening with a transverse central hole suitable to allow the passage of an operating screw, this screw being designed to be screwed in a clamping plate parallelly facing said end flattening in order to anchor the wire.

2. A process according to claim 1, characterized in that said end flattening is obtained by pressing, the same flattening being then sheared according to a quadrangular shape.

3. A structure of sockets and plugs in general of the kind comprising a box-type body formed from insulating material in which a plurality of housings suitable to contain a plurality of contact pins are defined and a box-type body of insulating material too, in which housing suitable to contain an equal number of contact bushes are defined, at least a part of said contact elements being obtained by the process according to claim 1, characterized in that the end portion of each pin and bush suitable to be connected to the wires, is plate-shaped and is provided with a transverse hole allowing the passage of an operating screw designed to be screwed in a clamping plate parallelly facing the same plateshaped end portion, in order to anchor said wires to said pin and bush.

4. A structure according to claim 3, characterized in that said plate-shaped portion substantially lies in the axis of the corresponding; contact element (pin or bush) and has a quadrangular outline projecting laterally on both sides with respect to the remaining parts of the same contact element.

5. A structure according to claims 3 and 4, characterized in that said housings have a substantially prismatic cavity in which said plateshapedend portion of the corresponding contact element is accommodated together with the corresponding operating screw and clamping plate, said cavity being provided with a pair of shoulders suitable to engage with the operating screw head in order to hold said head between the same shoulders and said plate-shaped portion, thereby preventing axial displacements of the operating screw.

6. A structure according to claim 5, characterized in that the length of said screw is substantially equal to that of said prismatic cavity, in order to prevent the same screw from unscrewing from said clamping plate.

7. A structure according to any one of claims 3 to 6, characterized in that each of said box-type bodies is provided with a side closing cover fitted thereinto in a removable manner.

8. A structure according to claims 3 and 7, characterized in that said side cover is provided with a pair of tongues disposed perpendicularly with respect to the inner surface of the same cover, each of these tongues being provided with a longitudinal slit suitable to engage with a stop tooth located on the outer surface of the box-type body.

9. A structure according to claims 3 and 7, characterized in that the closing side cover of each box-type body is provided, for the introduction of the wire, with a hole the axis of which is offset with respect to the axis of the corresponding contact pin or bush.

10. A process and structure substantially as hereinbefore described with reference to the accompanying drawings.