Aluminum Electrical Connection

Abstract

This invention relates to a connector for electrical conductors and more particularly to a connector made from aluminum and adapted to receive aluminum conductors therein. The connector includes an elongated groove wherein the inwardly facing edges of the sidewalls defining the grooves provide a scrapping action against the conductor to break up the oxide film or insulation thereon and further wherein the sidewalls are elastically flexed outwardly by the tamping of the conductor into the groove so as to maintain a continual pressure on the conductor and thereby counter creep induce by temperature change and the like.

Description

BACKGROUND OF THE INVENTION

The connection of an electrical conductor to a connector by tamping the conductor into a groove in the connector is taught in U.S. Pat. No. 3,038,958 issued to R.C. Swengel, the disclosure of which is incorporated herein by reference.

As pointed out in Swengel, good results are obtained if the wire is of soft copper and the connector is of brass or steel. Recently, increased attention is being given to the use of aluminum conductors, particularly in industrial construction, mobile homes, modular housing and the like. A problem with the use of aluminum conductors, however, is that of terminating them to achieve superior electrical and mechanical junctures. It was found that the aluminum conductor would break in the area immediately adjacent to the end of the connector after very little bending due to the abrupt transition from the configuration of the wire in the groove to the round shape.

Accordingly, it is an object of this invention to provide a grooved aluminum connector adapted to receive aluminum conductor therein so that from 70 to 100 percent of the conductor is tamped within the groove and further that there is a gradual transition zone between the connection and the non-deformed conductor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the aluminum connector made in accordance with the invention and the aluminum conductor to be connected thereto;

FIGS. 2 and 3 illustrate the connection between the connector and conductor shown in FIG. 1; FIG. 3 being a cross-section taken along lines 3--3 of FIG. 2;

FIGS. 4a and 4b show the tool members used in connecting the conductor to the connector shown in FIGS. 1-3;

FIGS. 5-7 illustrate various uses and shapes of the connector shown in FIG. 1; and

FIGS. 8-14 illustrate different embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, a wire 10 with its insulation 12 stripped back away from aluminum conductor 14 is ready for connection to aluminum connector 16 which is shown directly below the conductor.

Connector 16 includes at its front end 18 a conventional ring tongue 20. It is to be understood that the front end is not part of this invention and will not be further described.

The back end 24 of connector 16 includes a conductor-receiving groove or channel 26 which is defined by sidewalls 28 and floor 30.

As seen in FIG. 1, sidewalls 28 are positioned from about 70.degree. to 80.degree. relative to floor 30 with the preferred angle being about 75.degree.. This structure provides a generally trapezoidal shape to channel 26 as can be seen in FIG. 3. The radius of the intersection of sidewall 28 and floor 30, designated in FIG. 3 by R.sub.1, is preferably rounded. The edges 32 between the inner surface 28a of sidewalls 28 and top surface 34 are preferably sharp so that as the conductor is pressed into channel 26, the oxide film or insulation thereon can be scraped away to provide a better electrical contact between the conductor 14 and connector 16.

Because of edges 32 being preferably sharp, some of the conductors 14 will be peeled back as the conductor is pressed into channel 26. This peeled material forms a crown 36 which amount should be kept as small as possible. However, in order to insure that channel 26 is filled completely with conductor 14, the cross-sectional area of channel 26 is made to be slightly less than the cross-sectional area of conductor 14. Thus, for a conductor having a diameter d, the cross-sectional A of channel 26 is:

A = .20 d.sup.2

Theoretically, the above formula would result in all but 20 percent of conductor 14 being received into channel 26. As a practical matter, as the conductor is tamped into the conductor, sidewalls 28 are elastically deformed laterally with the result that the channel will accommodate up to another 10 percent of the conductor.

The importance of having at least 80 percent of the aluminum conductor within channel 26 is that there must be as much interfacial contact between the conductor and connector as possible. Obviously, the more interfacial contact therebetween, the higher the conductivity and less susceptability to attack by corrosion. Experiments have shown, however, that there are primary contact areas without which suitable conductivity is not achieved. These primary contact areas are on the upper sides of the sidewalls 28 in the vicinity of edges 32 and adjacent thereto. Such areas are designated generally at 37 in FIG. 3. A secondary contact area exists on the floor 30 of channel 26.

In order to size the opening of channel 26; i.e., the width between edges 32, so as to achieve the aforementioned peeling, the following formula may be used:

W = .80 d

where W is the width and d is the conductor diameter.

The thickness of sidewalls 28 may be kept thin; however, a minimum thickness is required so that as conductor 14 is being tamped in, the aforementioned deformation does not exceed the yield strength of the aluminum. Experimental data suggests that the optimal sidewall thickness be one-half d for conductors larger than 10 AWG and one-third d for conductors equal to or smaller than 10 AWG.

FIG. 2 illustrates connection 35 made between conductor 14 and connector 16. The pressing or tamping of conductor 14 into channel 26 is achieved by means of a suitable tool member 40 seen in FIG. 4.

FIG. 2 illustrates the important transition zone 38 which occurs between the deformed or tamped portion of conductor 14, hereinafter designated at 14a, and the non-deformed portion hereinafter designated at 14b. The transitional zone 38 comprises the top transition 38a and the lower transition 38b which is on connector 16. Both are formed as a result of the rounding or bevelling of dies 44 which can be seen in FIG. 4a and to which references will be made below. It has been found that with a sharp demarcation; i.e., no transitional zone, excessive stresses in a terminated conductor are present at that point and that breakage thereat occurs under mild bending tests. A gradual transition zone on the other hand eliminates the internal stresses and the flexibility of the connection is greatly enhanced; i.e., wire 10 may be moved relative to the connection a substantial number of times before breakage occurs at the juncture.

In the finished connection which is seen in cross-section in FIG. 3, conductor 14 contained in channel 26 is retained therein by the inwardly pinching action of the stressed sidewalls 28; i.e., the sidewalls are continually being urged against the conductor 14. An important advantage of this, which is well known to those skilled in the art, is that should the conductor undergo metallic creep during the life of the connection, the sidewalls 28 follow the wire by moving relatively towards each other. In this manner an intimate contact is constantly maintained.

FIG. 3 also shows how conductor 14 is extruded into all parts of channel 26 so as to completely fill the channel and thereby decrease or eliminate the likelihood of corrosion therein.

FIG. 4a illustrates the two piece tool member 40 with a connector 16 placed inbetween anvil member 42 and nest member 44. Both the anvil and nest members have on their connector-engaging surfaces 46-48 respectively, gently-sloping ends 50-52. As FIG. 4b shows, sloping end 50 on anvil 42 provides top transition 38a. The width of anvil 42 is no wider than the distance between edges 32 and preferably is slightly smaller. As the anvil is pressed down, most of its force is directed against the floor of connector 16 through conductor 14. Sloping end 52 in conjunction with surface 48 on nest 44 provides lower transition 38b onto connector 16 by bending back end 24 downwardly away from conductor 14. The amount of separation is slight, only enough to allow some freedom of movement of conductor 14 relative to the connector.

The versatility of the present invention can be seen in the variety of uses described hereinafter. As will be apparent, all the fundamental advantages are common to all embodiments.

Referring now to FIG. 5, an embodiment is shown which permits a splicing together of two separate conductors 14. The connector 60 may be cut to length to fit whatever space is available, such shortening having no detrimental effects on the mechanical connection. However, for good electrical connections, the length of channel 26 which receives conductor 14 should preferably be not less than about three or more wire diameters.

FIG. 6 shows a commoning bar 62 having double channels 26. As shown, bar 62 can accommodate a number of connections 64.

FIG. 7 illustrates a barrel shaped connector 66 having four channels 26. This style of connector illustrates the versatility of the present invention. Of course, connector 66 will accommodate any number of channels 26.

FIGS. 8, 9 and 10 show an embodiment of connector 16, herein designated as 16a, wherein floor 30 contains an insulation-piercing projection 68. Wire 10 is pressed into channel 26 without stripping back insulation 12. As the wire is pressed in, edges 32 cut into insulation 12 and the two free ends, 70-72, of the insulation are peeled over top surfaces 34 and down the outside of sidewalls 28 by die member 44. The conductor 14 enters channel 26 with projection 68 piercing insulation 12. The remnants 74 of the pierced insulation are loosely pressed down into grooves 75 defined by projection 68 and sidewalls 28. By lying loosely in grooves 75, remnants 74 may expand with any temperature increases without placing pressure against the connection. Insulation 12 on top of the connection (FIGS. 9 and 10) exhibits a depressed area 76 from contact with anvil 42 which as noted above has a width preferably less than the top opening to channel 26.

FIG. 11 illustrates a connection 80 wherein a solid conductor 14 has been tamped on top of a multi-stranded conductor 82. To accommodate multi-stranded conductor 82 the channel, herein designated as 26a, is modified to a circular shape up to the upper portions, designated as 84, where the sides assume the generally trapezoidal shape of channel 26 seen in FIG. 3; i.e., they are positioned from about 70.degree. to 80.degree. relative to the horizontal. The height of upper portion 84, designated by the small letter h in FIG. 11, is sized so that about 85 percent of the conductor 14 will be accommodated within channel 26a.

Another modification of connector 16b is the presence of exterior grooves 86. The grooves permit connector 16b to be held by corresponding splines (not shown) in the tool member (not shown). This is required as the operator must insert multi-stranded conductor 82 into channel 26a from one or the other end.

FIG. 12 illustrates a connector 90 wherein a conductor 14 is connected to a flat foil conductor 92 in channel 26b in connector 16c. To accommodate the foil conductor, a modification is made to the connector; i.e., one sidewall 28 extends upwardly at 90.degree. relative to the floor of the channel. It is against this sidewall, designated 28a in FIG. 12, that foil conductor 92 is positioned. FIG. 12 also shows where conductor 14 has been tamped completely within the confines fines of channel 26b as defined by the sidewalls; i.e., there is no crown 36. Illustrated in FIG. 13 is a connector 16 as described in FIG. 1-3 receiving a smaller conductor 14. As in FIG. 12, conductor 14 has been completely tamped into connector 16.

FIGS. 14a and b illustrate a connection between connector 16 and a multi-stranded conductor 94. FIG. 14a shows the positioning of conductor 94 within channel 26 prior to being tamped therein by anvil 42. FIG. 14b illustrates the completed connection.

In summary the present invention discloses a novel means of terminating or connecting aluminum conductors to aluminum connectors. For example, of the novel features, the transitional zone is one which enhances the use of the present invention in unstable environments; i.e., where such connections are subject to frequent vibrations and movements.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as some modifications will be obvious to those skilled in the art.

Claims

What is claimed is:

1. An electrical connection between an aluminum terminal and an aluminum conductor, said connection comprising:

a. an elongated terminal member having an open, axially extending channel therein wherein the sidewalls defining said channel converge inwardly from about 70.degree. to 80.degree. relative to the floor of said channel; and further the cross-sectional area of said channel being about 80 percent of the cross-sectional area of said conductor;

b. a length of said conductor being deformably pressed into said channel and occupying the cross-section thereof; and

c. a transition zone adapted to eliminate internal stress in said conductor adjacent to said terminal including an upper transition consisting of gradual change from the deformed length of said conductor in said channel to the non-deformed conductor extending up to said terminal and

a lower transition consisting of the end of said terminal being bent away from said conductor.

2. An electrical connection between an aluminum terminal, an aluminum conductor and a flat foil conductor comprising:

a. an elongated terminal member having an open, axially extending channel therein wherein a first sidewall defining said channel extends upwardly to a greater height above the floor of said channel than a second sidewall;

b. a portion of said flat foil conductor being positioned in said channel and extending along said first sidewall;

c. a length of said aluminum conductor being deformably pressed into said channel whereby said flat foil conductor is pressed against said first sidewall; and

d. a transitional zone adapted to eliminate internal stresses in said aluminum conductor adjacent to said terminal, said zone including

an upper transition consisting of a gradual change from the deformed length of said aluminum conductor in said channel to the non-deformed conductor extending away from said terminal, and a lower transition consisting of the end of said terminal being bent away from said aluminum conductor.