GB2046641A

GB2046641A - A Method of Forming an Electrical Connection Member and a Connection Member Formed by Such Method

Info

Publication number: GB2046641A
Application number: GB8003546A
Authority: GB
Original assignee: Legrand SA
Current assignee: Legrand SA
Priority date: 1979-02-09
Filing date: 1980-02-01
Publication date: 1980-11-19
Also published as: IT8067195A0; ZA80636B; BE881442A; ES8105523A1; ES488418A0; AU5534380A; GB2046641B; FR2448796A1; IT1128038B; DE3004333A1; AU534644B2; JPS55108190A; CH635212A5; FR2448796B1

Abstract

A method of forming an electrical connection member (10) having the general form of a jointless sleeve with an integral tongue (15) projecting from one end and a screwthreaded hole (12) in an opposite wall portion (11) comprising stamping or pressing a flat metal blank to form a middle part thereof to a cup-shaped configuration, removing the bottom of the cup-shaped configuration, trimming the remaining flat part of the starting blank so as to retain thereon the desired tongue (15), piercing the hole (12) in the resulting sleeve, opposite the tongue portion (15), and tapping the hole (12). <IMAGE>

Description

SPECIFICATION g Method of Forming an Electrical Connection Member and a Connection Member Formed by Such Method The invention relates to electrical connection members of the kind which can be used, for example, as terminals on junction blocks.

Such a connection member may have the form of a sleeve of quadrangular configuration, in which sleeve a conductor which is to be connected can be engaged, and a clamping screw engaged in a screwthreaded hole in the wall of the sleeve for clamping the conductor either directly or, in most cases, by way of a pressure bar member.

The invention is concerned more particularly with a connection member which in addition has, projecting outwardly, from one end of the sleeve at a side thereof opposite to that having the screwthreaded aperture therein, a projecting tongue which extends substantially perpendicular to the axis of the sleeve which it forms.

The purpose of such a projecting tongue is to prevent an error in use of the connection member and particularly when setting a conductor to be connected in place, which error could result in the conductor being engaged beneath the connection member instead of within the connection member.

Clamp members provided with such a tongue have usually been made hitherto from a strip or band of metal which was suitably cut to size and folded, the metal band being so folded that its two end limb portions overlapped to form together the sides of a sleeve of quadrangular section, the screwthreaded aperture to receive the clamping screw generally being formed'in the overlapping end limb portions.

In such a connection member the quadrangular section sleeve is discontinuous and this gives rise to various disadvantages. In particular, during production, there is a very high rate of wear of screw taps used for screwthreading the aperture and in operation, there is a tendency for the sleeve to open, and unequal distribution, in the various limb portions of the sleeve, of the clamping force to which the member is to be subjected.

It is known moreover for connection members for connection terminals to be produced by cutting-off lengths from a tubular member. The sleeves of connection members which are produced in this way are continuous, which is advantageous since a sleeve of this kind does not, in itself, suffer from any tendency to come open, and the clamping force can be carried within the sleeve, in a symmetrical manner, which is also advantageous.

However, by virtue of the manner in which this connection member, in the form of a continuous sleeve, is produced, it has hithertq not been possible for such a connection member conveniently to include an outwardly projecting tongue of any kind, unless the connection member is subjected to a machining operation such as to cut away the sleeve to form a tongue in the appropriate side of the sleeve, which side of the sleeve must however be made of sufficient thickness for this purpose, which makes this operation expensive.

The invention is primarily directed to an economic method of manufacturing a connection member in the form of a continuous sleeve provided with an outwardly projecting tongue and to a connection member formed by such a method.

According to the invention, there is provided a method of forming an electrical connection member having the general form of a jointless sleeve with an integral tongue projecting from one end substantially perpendicular to the axis of the sleeve and with a screwthreaded hole in the wall of the sleeve at a position diametrically opposite the portion of the wall of the sleeve from which the tongue projects, the method comprising pressing or stamping a flat metal blank to form a middle part thereof to a cup-shaped configuration with the outline of the sleeve to be produced and with a part of the blank remaining flat to form said tongue, removing a portion forming the bottom of the cup-shaped configuration, punching an aperture in the sleeve in a side thereof, opposite to the side from which the tongue projects, and forming a screwthread in the wall of said aperture.

The method may include, subsequent to said pressing or stamping, trimming the remaining flat part of the blank to form the tongue to the desired shape and size.

An electrical connection formed by the method of the invention comprises a jointless metal sleeve, an integral tongue portion projecting from one end of the sleeve, substantially perpendicular to the axis of the sleeve and a screwthreaded aperture in the wall of the sleeve at position diametrically opposite the portion of the wall of the sleeve from which the tongue portion projects.

The invention is diagrammatically illustrated by way of example in the accompanying drawing, in which:- Figure 1 is an elevation of an electrical connection member formed by the method according to the invention Figure 2 is a sectional view taken on line Il-Il of Figure 1; Figure 3 is a sectional view taken on line Ill-Ill of Figure 1; Figures 4A, 4B, 4C, 4D and 4E illustrate various phases of the method according to the invention for producing a connection member; and Figure 5 is a view on a smaller scale, similar to that of Figure 1, showing use of a connection member according to the invention as a connection terminal.

Referring to Figures 1, 2, and 3, a connection member 10 according to the invention is in the general form of a continuous sleeve of overall quadrangular section, and therefore has four integral wall portions namely an upper wall portion 11 which in its central region has a screwthreaded aperture 12 therein, two side wall portions 1 3 and a lower wall portion 14 which is diametrically opposite the screwthreaded aperture 12. A tongue 1 5 integral with lower wall portion 14 projects outwardly substantially perpendicular to the axis A of the sleeve from one end of the lower wall portion.

In the embodiment illustrated, the side wall portions 1 3 are of a thickness El which is less than the thickness E2 of the upper wall portion 11; in addition, in this embodiment, the thickness E2 of the lower wall portion 14 is equal to thickness of the upper wail portion 11, and the thickness E3 of the tongue 1 5 is less than the thickness E2.

In the embodiment illustrated, the inner face of the upper wall portion 11 in which the screwthreaded aperture 12 is formed is provided with a longitudinally extending, that is to say extending parallel to the axis A, groove 17. The groove 1 7 is of a generally V-shaped section, with a rounded bottom.

Finally, in the embodiment illustrated, the inner face of the lower wall portion 14 has longitudinally extending ribs or ridges 1 8 thereon.

To produce the connection member 10, the starting material used is a flat metal blank 20 (see Figure 4A) which is of a thickness at least equal to the thickness of the thickest wall portion to be produced in the sleeve to be formed.

In order to simplify Figures 4A to 4E, the changes in thicknesses to which the blank 20 is subjected during the operation of shaping the blank have not been shown.

In a first step, see Figure 48, a cup-shaped configuration 21 having the outline of the sleeve to be produced is pressed or stamped in the blank 20; the outline of the configuration 21 is therefore quadrangular in the embodiment illustrated.

It will be appreciated that, in this stamping or pressing operation, the blank 20 is simultaneously subjected to drawing or stretching, and therefore, to produce the wall portions of different thicknesses in the sleeve formed by the process, the degree of drawing which is thus applied to the blank 20 is not the same for the whole of the wall of the cup-shaped configuration 21 which is formed in the blank 20.

In accordance with procedures which are known to the man skilled in the art, it is sufficient for the tools used for such a pressing or stamping operation to be provided in consequence of such considerations, in particular in relation to the annular distance between on the one hand the punch member and on the other hand the cooperating die, which form the main components of the tool assemblies required.

It is also in the pressing or stamping phase that the groove 1 7 is formed axially in the central region of the inner face of the part of the cupshaped configuration produced, being the part in which the screwthreaded hole 12 is subsequently to be formed, and it is equally in the stamping or pressing phase that the ridges or ribs 1 8 are formed in the part of the cup-shaped configuration opposite to the part in which the screwthreaded hole 1 2 is to be formed.

It is for this reason that the above-described connection member 10 has the ribs or ridges 18, extending longitudinally of the sleeve thereof. Finally, in the stamping or pressing phase, it is possible if desired for the starting blank to be subjected, around the cup-shaped configuration 21 formed, to a sufficient striking action for the thickness thereof to be reduced to the thickness required for the tongue 1 5 to be produced.

In a second step, see Figure 4C, the bottom of the cup-shaped configuration 21 is removed, for example by punching, which thus forms a sleeve 22.

If desired and as indicated in Figure 4D, the remaining flat portion of the starting blamk 20 is trimmed so as to leave the tongue 1 5 of the required shape and size.

Finally, as shown in Figure 4E, the hole 12 is produced, for example by punching, in the sleeve 22 which has been previously produced, at a position opposite to the tongue portion 15, and the hole 12 is tapped to form a screwthread therein.

Although such an operation of forming and tapping the hole can be carried out in any one of the above-described phases, after the cup-shaped configuration 21 has been formed, the hole forming and tapping operation is preferably the last operation to be carried out, as described above, in order to avoid any subsequent deformation of the screwthreaded hole.

It will be appreciated that these various operations can be carried out in series on the same machine which for this purpose is provided with a plurality of tools to be used in succession.

Due to the continuous nature of the sleeve 22, the connection member 10 formed thereby need not require any hardening treatment, after the forming operations.

The connection member need only be subjected to a surface treatment such as to increase the corrosion resistance thereof, by using per se known methods which need not therefore be described in detail herein.

However, the surface treatment is advantageously simplified by virtue of the previous lack of any hardening treatment, there being no degassing operation to carry out, whereas a degassing operation is usually necessary if hardening treatment has previously been carried out.

In addition, the rate of resilient elongation of the material of the connection member is advantageously still that of the starting metal blank from which the connection member was formed.

The material used is in practice a relatively malleable metal in order to permit the stamping or pressing operation and the drawing of flattening or rolling operation, and its rate of elastic elongation can therefore be advantageously relatively high.

This means that the connection member can have, in itself a not inconsiderable resilient reserve.

Consequently, in service, when a clamping screw 25 screwed into the screwthreaded hole 12 is tightened to clamp a conductor 26, with, usually an interposed pressure bar member 27, resilient elongation E of the side wall portions 13 of the sleeve occurs, as shown in diagrammatic form in broken lines in Figure 5.

The result of this resilient elongation is that, in the event of any play occurring between the clamping screw 25 and the conductor 26, for example due to the conductor 26 suffering from bruisirig or compacting, the connection member will of itself absorb such play, by virtue of its tendency to return resiliently to its initial configuration.

In practice, the groove 1 7 which is provided on the inside surface of the upper wall portion 11 is provided to prevent any unscrewing of the screw 25.

Indeed, by virtue of the reduction in thickness which it causes in the upper wall portion 11, the groove 1 7 thus forms, in relation to the upper wall portion 11, a line of weakness which, when the upper wall portion 11 is subjected to a loading under the forces applied by the clamping screw 25, causes the upper wall portion 11 to deform into a dihedron configuration with its concavity facing towards the lower wall portion 14, thus to lock the screw 25 in position by virtue of the screwthreaded hole 12 in which the screw is engaged suffering deformation resulting from the deformation of the upper wall portion 11.

Be that as it may, the symmetry as between the side wall portions 1 3 of the connection member advantageously results in optimum equilibrium in respect of the conditions under which the two side wall portions 1 3 work, under a loading.

The method of production described advantageously makes it possible for the thickness of the side wall portions 13 to be adapted to the optimum degree to the forces which are to be carried.

The same consideration also applied as regards the upper wall portion 11 and the lower wall portion 14.

Finally when the screwthreading of the hole 12 is effected by extruding or upsetting material, all the benefit of the cold-working effect due to such a tapping operation is advantageously preserved in the connection member because the method of production thereof makes it possible to omit any hardening treatment, as referred to hereinbefore.

As will be readily appreciated, the ribs or ridges 18 on the lower wall portion 14 of the connection member advantageously enhance the anchoring of the conductor 26 to the lower wall portion 14 of the connection member when in the clamping condition.

Experience has shown that, with longitudinally extending ribs or ridges 1 8 of this kind, with all other conditions being equal, the connection member enjoys better resistance to a pulling force accompanied by a rotational force applied to the conductor 26, than a connection member of the same kind which is provided with transverse ribs or ridges on its corresponding lower wall portion, in conventional manner.

It will be appreciated that the invention is not limited to the described and illustrated embodiment, many modifications being possible within the scope of the appended claims.

Claims

1. A method of forming an electrical connection member having the general form of a jointless sleeve with an integral tongue projecting from one end substantially perpendicular to the axis of the sleeve and with a screwthreaded hole in the wall of the sleeve at a position diametrically opposite the portion of the wall of the sleeve from which the tongue projects, the method comprising pressing or stamping a flat metal blank to form a middle part thereof to a cupshaped configuration with the outline of the sleeve to be produced and with a part of the blank remaining flat to form said tongue, removing a portion forming the bottom of the cup-shaped configuration, punching an aperture in the sleeve in a side thereof opposite to the side from which the tongue projects, and forming a screwthread in the wall of said aperture.

2. A method according to claim 1, including, subsequent to said pressing or stamping, trimming the remaining flat part of the blank to form the tongue to the desired shape and size.

3. A method according to claim 1 or claim 2, wherein when stamping or pressing the starting blank, drawing of the blank is effected at the same time, and wherein the degree of drawing thereby applied to the worked blank is not the same for the whole of the wall of the cup-shaped configuration formed in said blank.

4. A method according to any one of claims 1 to 3, including, when pressing or stamping the starting blank, forming a longitudinally extending groove in the inner face of the cup-shaped configuration, at said position at which the screwthreaded hole is subsequently formed.

5. A method according to any one of claims 1 to 4, including, when stamping or pressing the starting blank, forming longitudinally extending ribs or ridges on the inner face of the cup-shaped configuration opposite said position at which the screwthreaded hole is subsequently formed.

6. A method according to any one of claims 1 to 5, wherein, when stamping or pressing the starting blank, the blank is subjected to striking thereby to reduce the thickness thereof.

7. An electrical connection member produced by the method according to any one of claims 1 to 6, comprising a jointless metal sleeve, an integral tongue portion projecting from one end of the sleeve substantially perpendicular to the axis of the sleeve and a screwthreaded aperture in the wall of the sleeve at a position diametrically opposite the portion of the wall of the sleeve from which the tongue portion projects.

8. An electrical connection member according to claim 7, wherein the inner face of the wall of the sleeve has a longitudinally extending groove therein at said position at which the screwthreaded aperture is located.

9. An electrical connection member according to claim 7 or claim 8, wherein the inner face of said portion of the wall of the sleeve has a longitudinally extending ribs or ridges thereon.

10. A method of forming an electrical connection member as claimed in claim 1 and substantially as hereinbefore described.

11. An electrical connection member substantially as hereinbefore described and illustrated with reference to the accompanying drawings.