US2951109A - Wire-connector - Google Patents

Description

Aug- 30, 1960 E, w. BOLLMEIER ET AL 2,951,109

WIRE-CONNECTOR Filed May 18, 1956 Vokaty, New Canada Township, Ramsey County, Minn.,lassignors to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Dela- Ware Filed May 1S, 1956, Ser. No. 585,757

5 Claims. (Cl. 174-84) This invention relates to the connecting of insulated conductors by a simplified procedure and employing novel connector devices permitting the formation of permanent electrical connections in a rapid simplified manner and without any necessity of first removing the insulating cover of the conductor.

The invention is particularly significant in the installation of telephone equipment employing small copper Wires insulated with coverings of treated paper or plastic film materials. The connection is made rapidly, without tools or applicators other than conventional pliers or side-cutters, and without requiring either the preliminary removal of insulation or the subsequent soldering of the connection. Effective electrical contact is provided; and such contact is permanently maintained even under repeated mechanical stress and vibration.

The invention provides novel connector devices which may be made in a wide variety of specific shapes and for a great number of specitic applications, but which in all cases employ novel principles and provide novel structure as will now be more fully pointed out in terms of specific but non-limitative examples.

In the drawings:

Figure 1 is a plan View, and Figure 2 a corresponding elevation of a spring connector made in accordance with the principles of the invention and designed for interconnecting a plurality of insulated conductors;

Figures 3-6 are plan views of spring connectors'employing the same principles but designed primarily for connecting single conductors to various types of electrical outlets; and

Figures 7 and 8 are cross-section and end views respectively of a compound-helix multiple-conductor connector.

The connector of Figures 1 and 2 consists essentially of a series of close-wound cylindrical spring wire helices 10a, 10b, 10c and 10d. Each helix is connected to the adjacent helix or helices by an extension of the spring wire of which the device is formed. The longitudinal axes of the several helices are in the same plane and parallel to, but somewhat removed from each other. The wire tip 111 at the end of the device will be seen to extend from an end coil of the helix lila in a tangential plane and at an angle with the plane of the terminal coil, i.e. at an increased pitch angle. Generally the same configuration is found with respect to the wire extension and the terminal coil at each end of each of the helices. There is provided a wedge-shaped throat or opening between the wire extension and the corresponding segment of the end coil. This opening provides for the insertion of a segment of an insulated wire conductor 12 between the extended tip and the end coil. The conductor may then be slid along the convolutions of the helix and into the position illustrated at helix tlc of Figure 1. During this sliding action, the high unit pressure provided by the strong close-wound coils of the helix, and the frictional force exerted on the insulated tice conductor by the sliding action, disrupt and displace the insulating coating of the coated wire at the area of contact, and permit the establishment of etective electrical Contact between the conductor and the spring wire of the helix. As illustrated in Figure 1 in connection with helix 10c, the end portion of the wire 12 may then be anchored around the spring wire extension between helices 19C and 10d; or, alternatively, this portion of the wire may simply be snipped oif and removed.

It will be apparent that each of the helices of the device of Figures 1 and 2 is open at both ends, so that insulated conductors may be inserted from either side of the connector. The specic angle a between the axis of the individual helix and the longitudinal axis of thc composite connector device, as shown in Figure 1, is of no particular significance so long as the ends of the individual helices are out of line with adjacent helices for effective accessibility. Figure l represents a structure with approximately the minimum angle for easy access to each helix where the helices are close together as illustrated. The angle may be increased to a full degrees if desired. Some variation in angle for individual helices may also be tolerated; but since'unitorm angles are easily and most conveniently provided by automatic coil Winding machinery, the structure illustrated is easily producible and is preferred.

Any number of helices may be combined together in structures such as are illustrated in Figures l and 2; and hence any desired number of conductors may be connected with such devices. in telephone communication cables it is frequently necessary to connect together three wires. Connectors such as shown in Figures 1 and 2 and having a much larger number of individual helices are conveniently separated into groups of lesser numbers of helices by twisting or bending the spring wire at points 16, the wire being lightly but effectively scored at such points for the purpose. Thus there is provided a substantially continuous source of springconnector assemblies having any desired number of connector units per assembly.

In a typical connector designed for the interconnection of telephone cable conductors, the spring wire was a tin plated steel spring wire having a diameter of 0.931. Each helix had an outside diameter of 0.138 and consisted of four contiguous turns or coils. The wire extension connecting adjacent helices was approximately 17/16 long and was notched at approximately the center. Such a connector was found to provide effective connection to insulated copper wire of a size equivalent to No. 19-No. 26.

It is to be noted that the diameter of the spring-wire represents a substantial proportion of the diameter of the helix. In the specific example, the ratio of wirediameter to internal diameter of the helix is .G3i/.076, or 41%. Adequate strength and rigidity is ordinarilj,l provided with spring-wire having a diameter of approximately one-third to one-half the internal diameter of the cylindrical helix. In all cases, the size and strength of the spring wire is so selected as to cause displacement of insulation from insulated conductors which may be inserted within the helix.

For telephone communication work, where very low current ow is permitted, spring steel wire, particularly when plated with zinc, tin, nickel, silver or other metallic corrosion resistant finish has been found to be fully effective. Phosphor bronze, beryllium bronze, silicon bronze, and hard copper are useful where greater current carrying ability is required.

Figures 1 and 2 illustrate the connection of but a single insulated conductor at an individual helix. Two or more conductors may be connected within a single helix, in

which case a somewhat larger number of coils is usually preferred. Such a connection requires that the different conductors be individually positioned between different contiguous pairs of coils, and hence that some of the conductors must be advanced much farther than others along the helix.. Such a method of inserting the conductors is unduly time-consuming if the conductors are inserted from the same end, or, if both ends of the helix are used, difficulty in holding the connector is usually encountered. A preferred structure employs a compound helixy made of two or more interspaced spring wires, as shown in Figures 7 and 8. The connector 70, here illustrated, consists of two separate helices formed of spring wires 71 and 72 close-wound into a single unit, the two being sealed together at one end as indicated at 73. Longer helices may be similarly bonded centrally rather than terminally. The free end of each of these wires 71 and 72 projects from the open end ofthe helix, forming a wedge shaped throat opening into which an insulated conductor may be slidably advanced.

In use, two conductors are threaded axially through the compound helix 70. The end segment of one conductor is forced into the throat opening between the extended end of the spring-wire 71 and the outer coil of spring-wire 72, and the end segment of the other is similarly forced into the opposite throat opening. Slidably advancing each wire around a single turn of the helix produces a fully effective connection.

The connector of Figures 7 and 8, like that of Figures l and 2, is designed primarily for interconnecting a multiplicity of insulated conductors. On the other hand, the connector devices of Figures 3-6 are designed primarily for use in connecting one or more insulated conductors to a bolt, binding post, bus bar, or other electrical outlet. The connector 39 of Figure 3 is provided with an eyeshaped member 31 for mounting on a suitable bolt or binding post. Connector 40 of Figure 4 has a straight prong type terminal 41 for insertion into a suitable jack or eyelet. Connector 50 of Figure 5 is provided with a second helix member 51 terminating in a handle member 52, for connection to a post or pin S3. The helix 51 grips the post 53 tightly, but may easily be removed by application of torque to the handle 52, thereby expanding the helix. Figure 6 illustrates a connector 6ft terminating in an extended connector portion 61 indicated as being spirally fastened to ya bar connector or bus bar 62.

In each of the foregoing alternative examples, the spring connector member comprises a plurality of contiguous equal coils and at least one terminal extension providing a wedge-shaped throat opening betweeny the spring wire of the extension 'and the corresponding portion of the spring wire of the adjacent end coil. This wedge-shaped opening, as previously indicated, provides for the entry of a segment of the insulated connector between the contiguous tightly compact coils.

There has therefore been provided a new and useful spring connector device suitable for forming permanent electrical connections to insulated conductors without any necessity of rst removing any portion of the insulation. The high spring tension available inthe device not only provides for effective displacement of most types of insulation from the copper wire or other conductor, but 'also produces and maintains completely adequate electrical connection with such conductor. Long continued vibration, handling, or other types of mechanical stressdo'not destroy or weaken the electrical connection thus provided, but on the contrary serve to Hatten the conductor and thereby to increase thetotal area of contact between conductor and connector. Connections are easily `and quickly made by hand, without the use of applicators or other tools. A neat and compact connection is produced, which can be adequately and effectively protected and insulated either by wrapping with adhesive tape or in other ways.

What is claimed is as follows:

1. A spring-wire connector suitable for forming a permanent electrical connection between insulated conductors as herein described and consisting essentially of a series of close-wound cylindrical spring-wire helices whose longitudinal `axes are parallel and spaced apart, the springwire having sufficient strength to cause displacement of insulation from an insulated conductor, and contact between the spring-wire and the conductor, on slidably forcing the insulated conductor along the contacting springwire surfaces; each helix being displaced from adjacent helices to an extent permitting free access to the open interior of the helix from either end thereof; adjacent helices being connected together by an extension of the spring-wire from an end coil in a tangential plane and at an angle with the plane of the coil just suflicient to enable the insulated conductor to be easily slid between the extension and the end coil; the spring-wire extension being lightly notched between adjacent helices to permit separation by bending.

2. A spring-wire connector suitable for forming a permanent electrical connection between insulated conductors as herein described and consisting essentially of a series of close-wound spring-wire helices, the spring-wire having suliicient strength to cause displacement of insulation from an insulated conductor `and Contact between the spring-wire and the conductor on slidably forcing the insulated conductor along the contacting spring-wire surfaces, the helices being open-ended and sufliciently separated from each other to permit free access to the open interiors thereof, and the spring-wire forming each of said helices being extended from an end coil of the helix at an increased pitch angle and forming a wedge-shaped Y throat opening between the extension and the end coil enabling an insulated conductor passing axially through the helix to be easily slid between the extension and the end coil.

3. A spring-wire connector suitable for forming a permanent electrical connection between insulated conductors as herein described and consisting essentiall-y of a close-wound compound *helix of at least two springwires forming alternate coils of said helix, the springwires havingv sufficient strength to cause displacement of insulation from an insulated conductor and contact between the spring-wire and the conductor on slidably forcing the insulated conductor along the contacting spring-wire surfaces, the spring-wires each being extended at a common end of the helix at an increased lpitch angle and forming a wedge-shaped throat opening between the extended wire and the corresponding segment of the adjacent close-wound end coil, enabling insulated conductors passing axially through the helix each to be easily separately slid between an extended springwire and its adjacent coil.

4. In combination, a spring-wire connector and an insulated wire conductor in electrical connection therewith, said connector comprising a close-wound contiguous-coil cylindrical helix having an internal diameter sutiicient to allow easy entry of said i-nsul-ated wire and formed of spring-wire having a diameter of about onethird to about one-half of said internal diameter, said spring-wire being extended from at least one end coil of said helix at an increased pitch angle and forming a wedge-shaped throat opening between the extension and the end coil of a size suiiicient to enable said insulated wire to be easily slid between the extension and the end coil, said insulated wire conductor lying partly within said helix and emerging from within said helix between twol adjoining turns or coils thereof, the insulation on said wire conductor being displaced and the conductor being in electrical connection with said two turns at the area of emergence of said conductor from said helix.

5. In combination, a spring-wire connector and an insulated wire conductor in electrical connection therewith; said connector comprising a close-wound contignous-coil cylindrical spring-wire helix, the spring-wire having suiiicient strength to cause displacement of insulation from an insulated conductor, and Contact between the spring-wire and the conductor, on slidably forcing the insulated conductor between adjoining coils, the spring-wire being extended from at least one end coil of the helix' at an increased pitch angle and forming a wedge-shaped throat opening between the extension and the end coil, and at least one extension terminating in mounting means for mounting said connector to an electrical outlet; and said insulated wire conductor axially entering said helix at an open end thereof and emerging from said helix between two adjoining coils thereof, the insulation on said conductor being displaced and the conductor being in electrical connection with said two coils at the area of emergence.

UNITED STATES PATENTS Thompson May 12, 1885 Wooldridge `et al. Jan. 9, 1906 Read Apr. 28, 1908 Forrester lan. 11, 1927 Wood Apr. 5, 1949 Dubilier Apr. 21, 1951 Blomstrand Oct. 20, 1953 Ripley Apr. 1, 1958 FOREIGN PATENTS Great Britain Nov. 17, 1921

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