US2209933A - Wire connector - Google Patents

Description

July 30, 1940.

J. ROGOFF WIRE CONNECTOR Filed Sept; 13, 1939 J21 i0 0)} /xka lmqg /m ATTORNEY.

Patented July so, 1940 UNITED, STATES PATENT. OFFICE Burndy Engineering New York 6 Claims.

The usual form of this device consists of a tube with tapered open ends. In each tapered end is a set of two or more wedges, the backs of the wedges resting on the inner tapered surface of the tube and the inner faces of the wedges conformed to fit the wire to be inserted. Usually the inner faces of the wedges are serrated to increase the friction or grip between the wire and the wedges. Between the two sets of wedges a spring is usually placed to keep the sets of wedges pressed outwardly into the tapered ends of the tube.

When a wire is inserted into a set of wedges, the friction between the wire and the serrated surfaces of the wedges is greater than that'between the smooth backs of the wedges and the inner tapered surface of the tube. The result is that when tension is exerted on the wire the wedges will move with the wire farther into the tapered portion of the tube. This travel causes the wedges to press more tightly on the wire and grip the wire even more securely. This action is progressive and as the tension on the wire increases, the grip on the wire will also increase, with the result that the connector will actually hold the wire until the full breaking strength of the wire is reached.

The operation of wire connectors of the type described herein is satisfactory as long as the friction or grip between the wedges and the wire is greater than that between the backsof the wedges and the tapered inner face of the tube. However, dirt between the wedges and tube and other causes can upset this relationship as ex-' plained, in my co-pending application, Serial Number 264,653, filed March 25, 1939. A method of minimizing the effect of dirt, etc., on the operation of the connector'is explained therein.

By far the most serious source of trouble with this type of wire connector is caused by twisting of the wire in the connector, especially when the wire is under relatively low tension. Twisting of the wire with relation to the contact surfaces of the Wedges has the efiect of wearing the tops of the serrations or teeth smooth. In so doing, the serrations are made ineffective for 00. km, a corporation of Application September 13, 1939, Serial No. 294,725

direction that the wire tends to unscrew? itself from the connector. With the conventional design of wire connector, it has been found that from two to seven turns of the wire are sufficient to twist the wire free and even with special designs made to minimize this efiect the wilrte can be twisted free with very little more effo That the ability of a wire connector to grip the wire, even though the wire twists, is important, 10 is readily apparent when the construction practices of the utility line crews which use these connectors are studied. In new construction it is the practice of the line crew to unwind the coiled wire and lay it on the ground from one 15 pole to the next on which the line is to be ultimately supported.

Splices between the end of one coil of wire and the beginning of the next are made by wire connectors as described herein. One end of the 20 wire is supported on the insulators on top of one pole and the portion of wire adjacent the next -pole is lifted over the cross-arm. The wire is then "sagged or pulled taut with the proper amount of sag in the span.

Very often the wire when uncoiled is not completely untwisted and some of the turns of the original coil remain present. As the wire is pulled taut it tends to straighten and untwist. If a wire connector is in the portion being pulled tight this untwisting action would tend to cause the wire to rotate in the wedges and possibly unscrew itself, thus causing failure of the joint.

Sometimes these wire connectors are installed 35 in lines where the tension is relatively small. In such lines, because of swaying and vibrating due to wind and other causes, there may be a momentary release and resumption of the tension.

At such times the wire often has a tendency to 40 twist or rotate in the wedges with consequent damage to the serrations on the wedges.

Very often, in installing wire connectors, linemen have a tendency to turn or twist the connectors on the wire in order to set the con- 45 nector properly. This process results in damage to the serrated surfaces and may cause th connector to become defective. 1

The principal object of my invention is to prevent'any twisting of the wire in relation to the 5 wedges.

Another object of my invention is to accomplish the foregoing without the addition of extra parts, thus obtaining my principal object at no extra cost.

Still another object of my invention is to set up a force resisting the rotational force which will be proportional to the rotational force, that is, the harder the force that is used to twist in relation to the wedges the greater the resisting force preventing such twisting.

Still another object of my invention is to prevent unscrewing of a wire inserted in the wire connector.

A further object of my invention is to obtain a type of serrated contact surface on the wedges which will not reduce the wire strength so that when tension is exerted on the wire, the wire will break at its full rated strength at a point outside the wire connector.

I accomplish my objects, and obtain my new results as will be evident from the device illustrated in the accompanying drawing and particularly pointed out in the specification and claims that follow.

Fig. 1 shows a longitudinal view of the wire connector with the tube sectioned along its Iongitudinal center line and with one set of wedges shown sectioned.

Fig. 2 is a cross-sectional view taken along line 2-2 in Fig. 1.

Fig. 3 is an enlarged cross-sectional view taken along line 8--3 when the wedges are in the inmost position.

Fig. 4 is an enlarged view of a section of Fig. 3.

Fig. 5 is an enlarged cross-sectional view of my invention in the intermediate position.

Fig. 8 is an enlarged cross-sectional view of my invention in the outward position.

Figure 1 shows the general construction of my wire connector. It consists of a tube It tapered at each end it and with three wedges i2, i3 and 14 located in each tapered end ii. Each set of wedges is held together by a sheet metal spider 15 which prevents longitudinal relative motion but permits radial motion and limited relative circumferential motion. A spring I6 is located between the two sets of wedges to hold them in the tapered portions ii of the tube Iii. Figure 2 shows how the spider l5 holds the three wedges together and at the same time applies a positive initial grip on the wire ll as described in my copending application, Serial Number 264,653.

Figure 3 shows the essential details of my invention. This is a cross-section of the wire connector taken along the line 3-3, in the tapered portion H of the tube it. It is takenwhen the wedges i2, i3 and M, are in the position which they will assume when relatively little tension is exerted on the wire ll. Under such circumstances the wedges will locate themselves towards the innermost portion of the tapered end of the tube.- When in this position the wedges are made ,so that for any given cross-section the radius a of curvature of the backs is less than the radius b of inner surface of the tube at that point.

The result is that the wedges will rest on the tapered surface along the lines of tangency of the arcs of the wedge backs resting on the inner surface of the tube. Each wedge back will rest along a single line of tangency c.

The surfaces of the wedges which touch the wire are made each with a single row of pointed discontinuous serrations l8 which are located just below the line of tangency when the wedges are at rest or when a straight pull is exerted on the wire. Under conditions of straight pull on the wire H the forces on the wedge (taken in the cross section shown) are a thrust against the line of serrations and a reaction along the line of tangency.

When the wire is rotated there is a frictional force, originally small; set up along the line of serrations which operates in a direction tangent to the wire contact between the serrations and the wire circumference and opposite to the direction of rotation. The reaction to this force is located along the line of tangency between wedge and tapered inner surface of the tube. These two forces form a couple which have a tendency to roll the wedge. Such rolling will take place about the point d of the serrations 3 as a center and the line of tangency c between wedge and tapered inner surface of the tube will shift (see Fig. 4), to a point designated as e. The position of the rolled wedge I2, is shown in dot-dash.

Inasmuch as the distance I between the pointed serrations and the original line of tangency (when only a straight pull is exerted) is a smaller distance than that between the pointed serrations and any other line of tangency, say g, the pointed serrations are forced to bite into the wire. This action is progressive and the harder the twist on the wire the deeper the bite of the serrations into the wire. This action will finally progress to a point where the grip preventing rotation is so secure that it is impossible to twist the wire in the connector at all.

It should be noted that any single cross section of the wedges necessarily has a definite radius of curvature for the backs of the Wedges. As the wedges advance in the tapered end of the tube, the relative radii of curvatureof any single cross section of the wedge backs and the circumference of the inner surface of the tapered tube at that cross section changes.

Thus in the innermost position the radius of curvature a of the wedge backs is less than the radius b of the inner circumference of the tapered tube, as shown in Fig. 3. As the wedges advance into the taper an intermediate position is reached where the two radii of curvature h and 7', respectively, are identical. This position is shown in Fig. 5. As the wedges advance still further the radius of curvature of the wedge backs k will actually become greater than the radius 1 of the inner circumference of the tapered tube. This position is shown in Fig. 6.

Of course, by making the radius of curvature of the wedge backs sufliciently smaller than that of the inner circumference of the tapered tube in the innermost position it will remain smaller than that of the inner circumference of the tapered tube even in the furthest outward position. In such event the gripping action resisting twist will remain operative in all positions of the wedges in the tapered tube end. However, this may not always be most desirable as will be hereafter disclosed.

As previously explained, most twisting occurs when the tension exerted on the wire is relative-,

ly small. When the tension is small the wedges are in the innermost portion of the taperedtube end. It is, therefore, important that my invention be operative in this position. However, when sufiicient tension is exerted on the wire to pull the wedges forward into the'positions shown in Figures 5 and 6, it is very unlikely that twisting of the wire will take place. Even if such twisting does occur, the serrations have bitten sufli ciently into the wire because of the straight pull, to grip the wire as it is turnedand thus prevent relative motion of the wire on the serration of the wedges. It is, therefore, necessary for the It is desirable that my invention function pref erably on relatively small tensions. When the wedges each contact the inner circumference of the tapered tube end only along one line of tangency, the constricting forces on the wire are transmitted from each wedge to the tube along this single line contact. Naturally, such line contact has a tendency to distort the tube end from its circular shape.

At low tensions,,the force is not suflicien'tly great to cause distortion of the tube end even with only one line of contact for each wedge.

However, as the tension increases, the distorting force increases and it is desirable that more of the wedge surface come in contact with the inner surface of the tapered tube end. Therefore, in order to eliminate distortion of the tube end. it is desirable that the wedges gradually progress to the positions shown in Figures and 6 as the tension increases. In these posi-; tions there are at least two lines of contact for each wedge on the inner circumference of the tapered tube end and, therefore, the tendency to distort the tube is minimized. I

In order to hold the wire securely on a straight forward "pull it is necessary that the serrations have sufllcient cross-sectional area in the plane tangent to the wire, at the point where the serrations bite into the wire. Inasmuch as the wedges are made of material of greater hardness and strength than the wire, it is more than sufllcient for the total cross-sectional area (in the planes tangent to the wire at the points where the serrations bite into the wire) of the serrations be equal to the transverse cross-section of the wire in order to hold the full breaking strength of the wire.

A second condition necessary for the serrations to hold the full breaking .strength of the wire is that the total of the projected areas behind the portion of the serrations which bite into the wire be at leastv equal to the transverse cross-sectional area of the wire. If these two conditions are met it is not necessary for additional serrations to be provided.

As a matter of fact, it is detrimental to have more than enough serrations than are necessary to hold the full breaking strength of the wire. At low tensions, the "biting pressure" tending to force the serrations into the wire is divided over the total number of serrations and if there are many, the unit pressure on each serration is small. The result is that the initial bite" may not be sufficient to grip the wire properly and the wire may slip in the jaws. A small number of pointed serrations will present the maximum unit pressure on each serration and thereby present a firm grip on the wire even at low tensions.

Having determined the minimum number of' serrations necessary for any particular wire size,-

the arrangement of the serrations must be determined. Ignoring the effect of twist, I have found that even on a straight pull a single line of serrations for each wedge is most eflicient. The pointed serrations may be distributed in several rows for each wedge, in which case for any given number of serrations, the wedge will be relatively short. If the serrations are distributed in a single row the wedge will be relatively long. The longerwedge will naturally have a greater bearing surface against the tubular envelope and will be less likely to distort the envelope. The

arrangement of pointed serrations in a single longitudinal row for each wedge also means that the serrations bite into the wire for a minimum proportion of the circumference at any single cross-section. This means that the strength of the wire itself is reduced by a minimum amo nt .and'therefore-thabreakingmtrengthuofsfliemwwe V,

will remain equal or very nearly equal to its full breaking strength.

It should be clearly understood that the serrations discussed herein are pointed or substantially pointed. serrations which are linear-+- either circumferentially or longitudinally-have the disadvantage of greater biting area than pointed serrations, and therefore require more pressure. In addition, circumferential serrations have a tendency to nick the wire circumferentially and to reduce its breaking strength. Longitudinal serrations have fewer projected areas behind the serrations in the wire to hold the wire against longitudinal pull.

The use of the term substantially pointed as used in the specification and the claims, in-

.cludes serrations or teeth which are discontinuous longitudinally, and are pointed in any crosssection taken transversely to the longitudinal axis as a wedge having a single row of such serrations could utilize the inventions concept.

From. the foregoing, it ,can be readily seen that I have obtained a novel construction of jaws, serrations. and envelope that solves a problem of considerable difficulty in the electrical connector field.

I have provided a connector that is capable of engaging a wire at low tensions, and will 'ef-' fectively prevent loosening the same either by a forward or rotational pull. Furthermore, I have changed hitherto acceptable designs, by providing only a single row of pointed or knife edges, discontinuous to enable a proper bearing of teeth against the conductor.

The device provided accomplishes the objects of. my invention without any additional parts,

extra cost, or loss of ultimate gripping strength.

I have thus described my invention, but I desire it understood that it is not confined to the particular forms or uses shown and described. the same being merely illustrative, and that the invention may be carried out in other ways without departing from the spirit of my invention, and, therefore, I claim broadlythe right to employ all equivalent instrumentalities coming within the scope of the appended claims, and by means of which, objects of my invention are attained and new results accomplished, as it is obviousthat the particular embodiments herein shown and described are only some of the many that can be employed to attain these objects and accomplish these results.

What I claim and desire to secure by Letters Patent, is as follows:

1. A wire connector comprising a tube, having a tapered open end; wedges for gripping the wire inserted in the tapered end, at least one of said wedges having a single longitudinal row of substantially pointed serrations the back of the wedge having the single row of substantially pointed serrations, being curved and adapted to rock on the inner surface of the tube about a line, as an axis, which passes through the points of the serrations on the front of the wedge.

2. A wire connector comprising a tubehaving less than the radius of the inner surface of the '*--tapered tube when the wire is in place in the connector.

3. A wire connector comprising a tube having 5 a tapered open end, wedges for gripping the wire inserted in the tapered end, at least one of said wedges having a back with a radius of curvature less than the radius of the inner surface of the tapered tube end at any single cross section when 10 the wedges are in the furthest innermost position assumed when the wire is inserted into the connector and before tension is exerted on the wire.

4. A wire connector comprising a tube having 15 a tapered open end, wedges for gripping the wire inserted in the tapered end, at least one of said wedges having a backso formed that the contact between the wedge and the inner surface of the tube will be along a single line of tangency 20 when the wire is in place in the connector.

5. A wire connector comprising a tube with a tapered open end; wedges for gripping the wire inserted in the tapered end, at least one of said wedges having a single longitudinal row of substantially pointed serrations, and a back so formed that the contact between the wedge and the inner surface of the tube will be along a single line of tangency when the wire is in place in the connector, and with the distance between 5 the points of the line of substantially pointed 'serrations and the line of tangency less than the distance between the points of the line of substantially pointed serrations and any other longitudinal line along the back of the wedge, when 10 only a straight pull is exerted on the wire.

,6. A wire connector comprising a tube with a tapered open end; wedges for gripping the wire inserted in the tapered end, at least one of said wedges having a single longitudinal row of sub- 15 stantially pointed serrations, and a back having a radius of curvature less than the radius or the inner wall of the tube in contact therewith when substantially no tension is exerted on the wire, and having a radius not less than the radius of to the wall in contact therewith when a substantial amount of tension is exerted on the wire.

JULIAN ROGOFF.

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