GB2065993A

GB2065993A - Electrical connector

Info

Publication number: GB2065993A
Application number: GB8038448A
Authority: GB
Original assignee: PA Management Consultants Ltd
Current assignee: PA Management Consultants Ltd
Priority date: 1979-12-04
Filing date: 1980-12-01
Publication date: 1981-07-01

Abstract

An electrical connector having interengaging male and female parts, wherein one part, especially but not exclusively the female part, comprises a sleeve (26) having a slotted region (30) between two solid annular end regions. The slots are preferably of a helical form. For a female part, the slotted region has a reduced diameter compared with that of the solid annular end regions; the converse for a male part. The invention also concerns several methods of production, including the machining of a metal rod sleeve or sleeve blank resulting in an intermediate product of uniform diameter end to end, and the working of this sleeve to produce differential diameters. The latter step preferably consists in twisting the intermediate sleeve end to end about its axis, whereby initially formed straight slots are transformed into helical slots in the final product. <IMAGE>

Description

SPECIFICATION Improvements in and relating to electrical connectors Field of Invention This invention concerns electrical connectors and, in particular, an improved connector for high current applications.

Background to the Invention Electrical connectors normally comprise a male and a female member with the male member being a tight push-fit in the female member so as to make good electrical connection between the two parts of the connector. This requires close tolerance machining. However, by employing a push-fit it is possible simply to pull the male member from the female member to allow the connection to be broken.

For low current applications the female member is typically a sleeve of resilient metal which may or may not be surrounded by a bounding resilient sleeve further to improve the resilience of the member, whilst the male member is simply a metal pin. Alternatively the female member may be a cav;ty in a solid member and the male member may be rendered resilient by being formed from two or more segments of resiliently sprung apart material for engaging the inside of tne cavity in the solid member.

For higher current applications such arrangements are quite unsuitable and considerable overheating can result. In order to improve such connectors for high current work, it is known to form both the male and female members from solid material and to machine out the interior cylindrical cavity of the female member so as to provide an annular recess into which resilient fingers can be fitted or into which a flattened spring of metal can be slotted, the male member being cylindrical of slightly smaller diameter than the female cavity, so as to allow the male pin member to be easily inserted therein.The insert let into the wall of the cavity of the female member represents a restriction and reduction of the internal diameter of the female member which has to be expanded by the male pin as the latter is introduced thereinto and it is this engagement between the pin and the inserted spring member which provides the good electrical connection between the two members.

Since the metal fingers or flattened spring extend completely around the inserted male pin there are many points of contact between the two parts of the connector so that electrical ~ resistance is reduced and high currents can be accommodated.

The main problem with such designs is the high cost of manufacture. Furthermore, it is found that overheating can still result in the event that the internal spring insert has insufficiently high mass, or becomes dirty or corroded and local high resistance points occur causing local heating within the female member.

It is therefore an object of the present invention to provide an improved electrical connector and especially an improved female or male part for such connector which does not suffer from the aforementioned disadvantages.

The invention According to the invention, there is provided an electrical connector having male and female parts adapted to interengage one within the other, wherein one part comprises an electrically conductive sleeve formed with parallel slots extending between two solid annular regions at the respective ends of the sleeve, one of which constitutes the leading end of the part for respective entry of or entry into the other connector part and the other of which constitutes the rear end through which electrical connection to a terminal lead can be made, the slotted region of the sleeve having a diameter respectively less than or greater than the solid annular end regions for tight engagementwith a respectively slightly oversized or slightly undersized other connector part. Prefereably, the slots are generally of helical form.

Each segment or rib between the helical slots can be considered to be a torsional spring citing oppositely to a second similar torsiona! spring which itself operates in the opposite direction to the first spring.

According to one further feature, a female socket member of a two part electrical connector according to the invention is produced from a sleeve of conductive material such as metal by forming parallel slots around the sleeve, which slots extend between two solid annular regions, one of which defines the entrance to the sleeve for a male connector member, and the other of which constitutes the internal end of the sleeve to which electrical terminal connection can be made, and resilience is imparted to the slotted wall of the sleeve by a permanent rotational twist along the length of the sleeve which twist not only causes the slots between the ribs to become at least partially closed up but also causes the ribs to deform radially inwardly to reduce the internal cross-sectional area of the sleeve over at least part of the slotted section of the sleeve.

A female connector part constructed in accordance with this method possesses a natural resistance which will cause the ribs to grip a male pin member inserted thereinto and provide good electrical connection therewith.

The permanent rotational twist imparted to the sleeve member will not only cause deformation of the ribs in a generally radially inward direction but also causes each rib to twist slightly over its length and thereby present at least over a portion of its length a cutting edge profile when viewed from within the sleeve so that the device possesses a self-cleaning action in relation to the inserted male pin member.

Typically the sleeve is formed from brass, such as machined out brass rod, and in one embodiment, half-hard brass is used which is machined and softened to allow the sleeve to be twisted upon the application of an appropriate torsional twist which not only imparts the required rotational twist as between one end'and the other of the sleeve but also work-hardens the material back to an appropriate hardness level.

The number and size of the slots are related to the size of the sleeve which in turn is related to the size of the male pin member and this is in turn related to a certain extent to the current carrying capacity desired of the connector.

One side effect of forming slots in the wall of the sleeve is to increase the surface area of the sleeve so that in the event that any heating does occur due to local corrosion or dirt etc., the rise in temperature is less than would be the case if a solid sleeve member were employed, due to the increased surface area for heat dispersal offered by the sleeve.

With regular insertion and withdrawal of the male pin member, the material from which the slotted sleeve is formed may become worn and the grip on the male pin member can be reduced.

This may result in an increase in contact resistance and local heating. The process is cumulative since heating will result in a reduction in the hardness of the material forming the sleeve and this in turn will reduce the resilient grip of the sleeve on the inserted member.

In order to compensate for this, means is preferably provided by which a torsional twist can be imparted to the sleeve member to compensate for wear and tear or a lack of resilience due to a reduction in the hardness of the material due to heating. The means may comprise hexagonal nut profiles formed at opposite ends of the slotted twisted region of the sleeve. Alternatively parallel flats may be formed at opposite ends of the slotted and twisted sections of the sleeve to allow a spanner or similar tool to be fitted thereto at each end and the two spanners twisted.

In a still further arrangement, one or more but not all of the slots are extended through the solid annular regions at opposite ends of the slotted section of the sleeve to a depth sufficient to allow a C-clamp to be fitted around the end with one or more tongues provided internally of the clamp inserted into one or more of the slots in the solid annular regions so that by twisting that end relative to the other (typically by inserting a second similar clamp into the other end) so a torque can be applied across the slotted and twisted region of the sleeve so as to further increase the twist and thereby deform the ribs more than before and thereby reduce the cross sectional area of the sleeve not only to compensate for wear but also to re-work-harden the material forming the ribs and sleeve generally and in part the original resilience to the member which may have been lost or reduced due to heating.

According to another feature of the invention a female socket sleeve may be formed from a metal stamping in which a series of parallel equally spaced slots are formed during the stamping operation. By wrapping the stamping around a mandrel and either brazing the adjoining edges or providing bounding bands or rings at least at the ends of the wrapped around stamping, so a sleeve can be formed which corresponds to the subassembly formed by machining the brass bar previously referred to.

As with the sleeve formed from brass sleeving or machined out rod, permanent rotational twist can then be imparted to the stamping so formed so as to produce the required resilience and cause the slots between the ribs to become at least partially closed up and the ribs deform radially inwardly to reduce the internal cross-sectional area of the sleeve over at least part of the slotted section of the sleeve.

Manufacture in accordance with this second method obviates the need for machinging and furthermore allows standard section, flat stampings to be formed as manufactured subassemblies for stock which can then be called up as required and cut to length prior to being wrapped around a mandrel to form a sleeve.

Where the working of the metal alters the hardness or temper of the material, suitable annealing steps can be introduced into the process so as to re-temper the material during or at the end of the manufacturing procedure.

According to a third feature of the invention the female socket sleeve may be formed in any of the aforementioned ways but without twisting, the slotted region of the sleeve simply being shrunk down using a sizing mandrel to determine the required internal dimensions of the sleeve. The slots may be stamped at an angle relative to the sleeve blank when the intial step of the second method is employed, so that the slots remain of helical form in the finished sleeve.

Such a form of construction does not possess all of the advantages associated with the twisted forms of construction but is simpler to produce and if required can always be twisted at a later stage using suitable tools to compensate for wear.

Moreover, the third method is useful for production of a male connector part in accordance with the invention. By working of the slotted and/or end regions of the sleeve on a sizing mandrel, the slotted region can be given a greater diameter than the solid annular end regions, so that this slotted region of the male part will be slightly compressed when the male part is inserted into a slightly undersized conductive rigid cavity in a female part, thereby to ensure good electrical contact.

Description of Drawings The invention will now bedescribed by way of example with reference to the accompanying drawings in which: Figure 1 is a side view of one embodiment of the invention in which a female member is constructed in accordance with the first aspect of the invention described herein, Figure 2 is an end view of the female member of Figure 1 as viewed by the male member, Figure 3 is a cross-sectional view through the female member shown in Figure 1, Figure 4 is an end view of the female member similar to Figure 2 showing a C-clamp in position for rotating and twisting one end of the member relative to the other to work-harden the ribs extending between the two ends and to impart a further twist thereto to compensate for wear, Figure 5 is a perspective view of a metal stamping having punched slots and keyed ends, Figure 6 is another perspective view showing the stamping rolled to form a tube, Figure 7 is a further perspective view showing the tubular stamping after being twisted around a sizing mandrel, and Figures 8 and 9 are a perspective view and cross-section through another form of sleeve, which is not twisted.

Figures 7 to 9 of the drawings refer to an alternative arrangement in which the sleeve is formed from flat stock as by punching.

One embodiment of the invention is illustrated in Figures 1 to 4. Here a female socket sleeve which grips a male connector part in the form of a pin is a sleeve of material such as brass which is initially machined along a plurality of equally spaced parallel axial lines so that whilst annular rings of material are left at opposite ends (see Figure 2) as designated by reference numeral 22 at one end and 24 at the other end, the walls of the sleeve in between these two solid rings 22 and 24 are cut away to form parallel slots.The two ends of the sleeve are then relatively twisted about the axis of the sleeve so as to twist the parallel slots into the generally helical array as shown in Figure 1, the twisting action serving to deform the slotted region of the sleeve in a radially inward manner so as to reduce the cross-section of the interior of the sleeve albeit only over the central section thereof but by an amount sufficient to grip a male pin member 12 to be inserted therein.

The sleeve of Figures 1 and 3 is generally designated 26 and is conveniently formed by machining from solid rod, the interior of the sleeve being drilled out or otherwise removed as at 28 in Figure 3.

Referring to Figure 1 , the slots are shown in the twisted condition and are generally designated by reference numeral 30 and by extending some of the slots into the solid annular regions 22 and 24, so a key can be provided for a C-clamp or the like.

Figure 4 of the drawings illustrates a C-clamp 32 having a single tooth 34 which is adapted to engage in one of the slots 30 where it extends into the solid annular end 22 or 24. It will be appreciated that additional teeth (not shown) may be provided to give an additional key between the C-clamp and the member 26 but in practice it is found that a single tooth is normally all that is required. The C-clamp includes a handle by which it can be twisted so as to impart a turning moment about the axis of the member 26.

A similar C-clamp located at the opposite end of the member 26 and with opposite hand allows a twist to be imparted between the opposite ends of the member 26.

The slots 30 which are initially formed parallel to the axis of the untwisted member 26 are most conveniently formed by a plunge saw. By choosing a saw of appropriate diameter relative to the axial length of the member 26 between the solid annular ends 24 and 22, so each saw cut can be arranged to remove all the material required between the solid annular regions 22 and 24 to form slots and also to form partial slots in the ends 22 and 24 required to allow a C-clamp such as shown in Figure 4 to be secured thereto.

In one embodiment the member 26 is formed from brass rod 14 mm diameter. A concentric hole 9 mm diameter is drilled in the stock and using a 2T" x 1 mm saw twelve or more equally spaced saw cuts are made parallel to the axis of the brass sleeve after which the sleeve is cut square across its open end at the ends of the saw cuts nearer the open end. The closed end of the bar and the remainder of the bar beyond the closed end is finished as required to provide the necessary termination points and electrical connection points for the connector.

Figure 5 shows a preferred form of stamping produced by punching from sheet material such as sheet steel or sheet brass. The stamping is identified by reference numeral 36 and includes a plurality of parallel slots 38 and cut-away regions at the opposite ends of the stamping at 40 and 42 to provide keying between the two ends of the stamping when it is twisted around to form a tube.

The advanatage of this form of construction is that the stampings can be preformed and stocked more readily than tubular members and can simply be called up as required and twisted around a sizing mandrel to form a tube as shown in Figure 6. Here the partly formed sleeve is denoted by reference numeral 44 and it will be noted that the cut-away regions 40 and 42 receive the tabs 44 and 46 and maintain correct axial alignment of the two abutting edges of the twisted stamping.

In order to provide all the advantages previously described with reference to the sleeve machined from the solid rod described hitherto, the ends of the sleeve 44 are gripped by appropriate tooling and the sleeve is twisted around a sizing mandrel to form the final assembly shown in Figure 7 and identified by reference numeral 48. The twist imparted to the sleeve is clearly seen by the distortion of the slots 38 and now designated by reference numeral 50 and due to the twisting, as previously described, the slotted region of the tube shrinks in diameter at least internally so as to provide a good tight fit around a male pin (not shown) which is to be inserted into the sleeve to make electical contact therewith.

It is to be noted that, with the method of fabrication shown in Figures 5 to 7, the material itself can provide a degree of resilience which is not present in a sleeve machined from solid material.

Figures 8 and 9 illustrate a further embodiment of the invention in which no twist is applied to the sleeve during or after manufacture. The perspective view in Figure 8 shows the final form of the sleeve 58 which is initially constructed either by machining analogously to the method steps described with reference to Figures 1 and 2 or by forming from a flat stamping as described with reference to Figures 5 and 6. The slotted region of the sleeve so formed is then shrunk down onto a sizing mandrel (not shown) and distorted radially so as lo form a region of reduced diameter 52 for better gripping of a pin member inserted thereinto than would otherwise be the case.Figure 9, which is a cross-section through the sleeve of Figure 8 on the line AA, shows how the reduced diameter section 52 provides a region for gripping a pin (not shown) between the entrance 54 and the closed end 56 of the female socket sleeve. In a modification of this embodiment and method, the slots are stamped at an angle to the axis of the sleeve blank of Figure 5, so as to be of helical form when the blank is wrapped around a sizing mandrel and worked to produce the socket sleeve of Figures 8 and 9.

It will be apparent without further illustration that the construction of Figures 8 and 9, in particular, is suited to production of a male connector part in the form of a resilient sleevs serving as a pin for insertion in a slightly undersized female connector part. After a slotted sleeve of uniform diameter from end to end~has been produced, the solid annular end regions are subjected to reduction working, resulting in a final pin member having a slotted region of greater diameter than the solid annular leading end and solid annular rear end which provides for connection of an electrical terminal lead to said pin.

Claims

1. An electrical connector having male and female parts adapted to interengage one within the other, wherein one part comprises an electrically conductive sleeve formed with parallel slots extending between two solid annular regions at the respective ends of the sleeve, one of which constitutes the leading end of the part for respective entry of or entry into the other connector part and the other of which constitutes the rear end through which electrical connection to a terminal lead can be made, the slotted region of the sleeve having a diameter respectively less than or greater than the solid annular end regions for tight engagement with a respectively slightly oversized or slightly undersized other connector part.

2. An electrical connector according to claim 1, wherein the slots are generally of helical form.

3. An electrical connector according to claim 1 or claim 2, wherein one or more but not all the slots are extended into the solid annular end region or regions at one or both ends of the sleeve.

4. An electrical connector according to claim 1 or claim 2 or claim 3, having an operative head formed externally at the solid annular end region of the sleeve.

5. An electrical connector according to any of claims 1 to 4, wherein the one part is the female part of the connector adapted to receive a male pin member inserted therein.

6. An electrical connector according to any of claims 1 to 5, produced by cutting slots in a cylindrically complete metal sleeve.

7. An electrical connector according to claim 6, wherein the said cylindrically complete sleeve is produced by machining out the interior of an initially solid metal rod.

8. An electrical connector according to any of claims 1 to 5, produced by stamping slots in sheet metal, the slotted blank being formed into a sleeve around a sizing mandrel.

9. An electrical connector according to claim 8, wherein the formed blank is brazed, welded or soldered at adjoining edges or bound at the ends with wrapping bands or wrapping rings.

10. A method according to any of claims 6 to 9, for producing a connector according to claim 5 when appendant to claim 2, wherein the slots are formed parallel to the axis of the sleeve or sleeve blank, and the slotted sleeve. is twisted along its length to deform the slots into a reduced width helical form accompanied by a radially inward deformation of the metal ribs between the slots which reduces the diameter of the slotted region of the sleeve.

11. A method according to claim 10, wherein the slotted sleeve is formed of partially hardened metal and the twisting of the sleeve is imparted in a manner to effect word-hardening of the material.

12. A method according to claim 10 or claim 11 when appendant to claim 3, wherein twisting of the slotted sleeve, or further twisting thereof to compensate for wear, is effected by applying a tongued C-clamp to at least one end of the sleeve with the tongue or tongues engaged in an extended slot or slots.

13. A method according to claim 10 or claim 11 when appendant to claim 4, wherein twisting of the slotted sleeve, or further twisting thereof to5 compensate for wear, is effected by applying a spanner or like tool to the operative head at least at one end of the sleeve.

14. A method according to any of claims 6 to 13, including one or more annealing steps carried out on the slotted sleeve during or subsequent to formation thereof.

1 5. A method according to any of claims 6 to 9, wherein the slotted region and/or the solid annular end regions are worked over a sizing mandrel to produce the lesser or greater diameter of the slotted region compared to the end regions.

1 6. An electrical connector substantially as hereinbefore described with reference to the accompanying drawings.

17. A method of producing the male or female part of a two part electrical connector substantially as hereinbefore described with reference to the accompanying drawings.