US2811706A - Electrical split-t connector - Google Patents

Description

Oct. 29, 1957 c, LOGAN 2,811,706

ELECTRICAL SPLIT-T CONNECTOR Filed May 2, 1955 INVENTOR Maw-us G. lioqom/ ATTORNEY 1 2,811,706 ELECTRICAL SPLIT-T CONNECTOR Maurus C. Logan, Elizabeth, N. J., assignor to The Thomas & Betts (10., Elizabeth, N. J., a corporation of New Jersey Appiication May 2, 1955, Serial No. 505,129 2 Claims. ((31. 339276) This invention relates to improvements in solderless connectors and is entitled Electrical Split-T Connector. It is characterized by high compression of its mechanical grip exerted on an electrical conductor, by its reduced resistance to current flow through its joints (area of pressure contact) with the conductor, and also by the simplicity and convenience of its installation and use.

In explaining the novel principle of this connector and distinguishing it from the prior art, mention is first made of that particular class of known solderless electrical connectors (the indenter type) which, to install them in service position, requires a first operation by a workman employing a compression tool that cold-flows the connector and the conductor (usually a stranded wire) into a homogeneous joint to thereby first wire the connector. Then a second operation is required for attaching or mounting the wired connector to and on another electrical component, such as a binding post in a meter pan, or on a wiring panel, or other terminal, thus requiring two separate and independent steps or operations.

The foregoing known class of electrical connectors and others (whether solderless or not) also have the further disadvantage of oxide quickly forming on the cleaned and scraped bare end of the conductor before it can be inserted in the connector and thus before the permanent joint can be established. Accordingly, the oxide film becomes a part of the joint, compressed into two metals (conductor and connector), is in the path of the current flow, and may increase the resistance of the electrical connector.

In contrast to the foregoing, the new connector herein requires only a single step operation to install on an electrical conductor and also to mount it in service position. Not only this advantage of the two-in-one step installationbut this new connector also has a built-in deoxidizing means for automatically scraping away the oxide film and penetrating to the virgin metal of the conductor during and as a part of making the installation comprising two simultaneously established connections.

Accordingly, the new principles herein, together with novel structural features, and the new mode of deoxidizing pressure coaction of the connector with its conductor, when simultaneously making the two electrical connections, taken all together, is believed to possess functional advantages and to supply a need in the solderless electrical connector field not met by prior art connectors.

It is noted, therefore, that a main purpose of this invention is to produce an electrical connector which makes a clean (deoxided) connection with an electrical conductor (a wire) and simultaneously connects with another electrical component or terminal, both steps being performed in one and the same operation (thereby eliminating one of the conventional steps heretofore mentioned) and which possesses a resultant strong mechanical grip of increased contact compression and thus forming a joint of low resistance to current flow therethrough.

The drawing;

This specification and its claimed subject matter, with the accompanying drawings, describe the invention as preferred and embodied at this time for understanding .the problems sought to be solved. Since the teachings herein may suggest changes to others who wish to avail themselves of the benefits of the invention, it will be appreciated that subsequent modifications hereof may well rates Patent 2,811,706 Patented Oct. 29, 1957 2 be equivalent in form and hence the same in spirit and principle as this disclosure.

The original patent drawings herein are made from a production specimen connector and are enlarged to approximately twice the size thereof. Consequently, the original drawings may be referred to for an understanding of the size relationship between the parts or portions of the device.

Fig. 1 is a top view looking down on the connector which is T-shaped, has a wire-receiving sleeve or ferrule, and an integral bolting-tongue means (extending at an angle therefrom) adapted to compress the sleeve on the wire when the tongue is clamped in a binding post.

Fig. 2 is a view looking into the outer end of the bolting-tongue means and showing it divided or formed of two one-half semi-circular portions on a diameter comparable to that of its integral wire-receiving sleeve. Deoxidizing longitudinal serrations (splines) in the sleeve are observed through the tongue and lengthwise slit of the sleeve.

Fig. 3 is looking into either end of the sleeve and at the side of its bolting-tongue means. The splines clearly appear at the open end of the sleeve.

Fig. 4 is similar to Fig. 3, except the splines are omitted and the two tongue portions have been slightly spread apart (an optional feature) to facilitate inserting the bare end of a wire into the sleeve.

Fig. 5 is a top view of the connector installed (mounted) in a typical terminal, such as a binding post on a wiring panel, and gripping the wire, which completes a circuit through the connector and the binding post.

Fig. 6 shows a section on the line 6, further illustrating the typical screw-actuated binding-post terminal (Fig. 5) and how this new connector is adapted and acts to simultaneously perform its two functions, i. e., establish its electrical mechanical-pressure connection with its wire and also with its binding post, by virtue of a single screw-tightening operation, thus effecting both functions by one manual operation of a wiring mechanic.

The illustrated example of the invention consists of a conductor or wire-receiving sleeve 2, in the form of a ferrule, made of copper or other electrically conductive material. The sleeve 2 is provided with a straight slit 5 extending longitudinally from end to end thereof. The slit 3 may extend in a straight line direction, thus along one side of the sleeve, and cuts through both of its ends. Lengthwise serrations (splines 4) are formed in the sleeve 2 from end to end thereof. It is seen that the slit 3 renders the sleeve radially resilient for closing on an electrical conductor (wire W, Figs. 5 and 6) with a gripping compresslon.

The longitudinal side of the sleeve 2, which is opposite its lengthwise slit 3 and also parallel thereto, may be regarded as an approximate line of flexure for permitting the edges (defining the slit 3) to approach or close toward each other for reducing the sleeve diameter and thereby exerting a wrap-around mechanical grip and powerful squeeze of the sleeve 2 upon the bare end of the wire W, by the means next described.

A bolting-tongue means 5 consists of a pair of parallel legs or tangs, having their inner ends integral with the sleeve, and extending at an angle therefrom, a angle being suitable. The connector is generally T-shaped, is sometimes referred to as a flag type terminal, and is well adapted to connections made at right angles to the axis of the wire W. The two tongue portions 5 are similar, stand parallel and outwardly, one on each side of and adjacent the lengthwise slot 3. Each portion'of the bolting tongue is semi-circular (arched) in cross section for strength, thus reinforced against bending, when transmitting leverage for compressively reducing the diameter of the sleeve 2.

The bare end of an insulated wire W is forced into the sleeve 2 (preferably splined longitudinally from end to end at 4), While the connector stands open, as in the first fou'r views. The bolting tongue 5 is then inserted in the transverse aperture 8 of a suitable binding post, on a wiring panel or in a meter pan P, and the clamping screw 9 is tightened down. The tongues 5 close toward each other, producing a powerful wrap-around compression of the wire-receiving sleeve 2 against the conductor W.

The sleeve actively reduces in diameter, by flexure along its rear side opposite the slot 2, and the latter continues to close under the leverage exerted by the tongue pair 5. This action causes the splines 4 to penetrate the oxide film (ever present on electrical conductors) and reach the virgin metal of the copper or aluminum wire strands. An eifective low resistance connection is the result (simultaneously made) on the wire W and the binding post (Fig. 6), through which the current passes to a service wire which may be on the other side of the wiring panel P.

The connector is preferably made of copper alloy having spring resilience. The semi-circular (arched) 'form of the two leverage bolting tongues 5 provide a rigid (non-yielding) joint, where their inner ends are integrated part way around the sleeve 2 symmetrically on each side of the slit 3. The inherent'resiliency of the two tongues 5 apply a follow-up compression force on the sleeve and subject the latter to further reduction in diameter and a tightening on the wire W as the latter gives during use.

Accordingly, it is found that the splines 4 penetrate the wire uniformly around itsdiameter, with'a characteristic compression which endures after installation. This action is derived from the semi-circular bolting tongues 5, spring loaded by the clamping screw 9. By reason thereof, the splines continually seek depth-connection Withintht: conductorgand seal out atmospheric contact,

thus resisting deterioration of the joint during long use.

Tests demonstrate that the select shapeand form of this connector (arched tongues 5 acting on the split sleeve 2) possess good response to thermal variations.

'By this is meant that the capacity to store its spring loading (under the initiallyapplied binding post pressure) permits the connector to give (yield) when the conduc- -tor'expands and thereafter causes it'to re-exert (force back) its wrap-around compression when the conductor contracts dueto thermal changes or'shrinks due to'service aging. This "feature makes for'auniformly constant "pressure 'on the wire joint, thereby avoiding variations in resistance and in current flow, otherwise caused by changing thermal conditions and also long service.

The foregoing valued characteristic of this new connector derives from its select shape and form and enhances wire joint endurance. To explain'the point, it is seen that 'thecross sectional bow (arch) of the two tongues '5 isa structural form qualifying them to take and store tension from the pressure of the binding post. Likewise, it'is seen that the two arches have a linear tongue cantilever span from the binding post to the wrap-around sleeve and thus increasethestored tension.

In action, the tension (spring loading) of the arch and span go and come, i. e., yield and force back proportionally with the expansion and contraction of the conductor. This quality is an asserted point of novelty and has been referred to as connectorbreathing in so'meof the research work on this invention. his a new function in the art which maintains the wire andsleevejoint (always the-critical point in'electrical wiring) in its originally-installed condition over aprotracted perio'd of service. i

The endurance of the sleeve-and-wire joint is further aided by this point: it is found that the axial serrations (splines 4) being lengthwise, are a feature which minimizes crushing and pinching the wires, especially the outer strands of flexible stranded conductors. The sleeve 2 is free of inward pressure concentrated at a limited area, by virtueof which the life of the joint is prolonged, since it is free of pinching and crushing, as in the case of indent-compression connectors heretofore mentioned in distinguishing from the prior art. Linear and circumferential compression of the sleeve on the outer strands make for evenly distributed pressure over the entire working contact area of the connector. 7

This disclosure explains the principles of the invention and the best mode contemplated in applying them, so as to distinguish the invention from others; and there is particularly pointed out and distinctly claimed the part, improvement or combination which constitutes this discovery as understood by a comparison thereof with the prior art.

What is claimed is:

1. An electrical connector, consisting of a sleeve, formed of resilient metal, open at both ends, with a slit extending throughout its length, cutting through both open ends, thereby rendering the resilient sleeve radially flexible, by whichit may contract and expand its diameter; and elongated bolting-tongue means, consisting of two separate parallel spaced tongues, which are semicircular in cross section throughout their lengths, and

are arched away from each other throughout their said lengths; the inner "arched end, of each parallel arched tongue, being formed integrally with the sleeve, at a point between the-open ends thereof, one arched inner end on one side of'the slit, and the other arched inner end on-the-other side of the slit, with each inner arched end adjacent the slit, thus in symmetrical relation therewith, and extending at an angle away from said sleeve;

Whereby'clamping' pressure exerted 'on the bolting-tongue means, at a point spaced from the sleeve, acts to force the two separate parallel spaced tongues toward each other, thereby reducing the slit, and contracting the sleeve on an electrical conductor therein, with a wrap-around compression exerted on the conductor, thereby applying uniform contact pressure against it from end to end of the sleeve; and whereby said clamping pressure also acts to spring load the two arched tongues, from the point of clamping pressure to the sleeve; by which the two tensioned tongues resiliently give to the expanding conductor and the sleeve, thus preventing the sleeve from pinching the expanding conductor; and also resiliently forcing back to contract the sleeve as the conductor contracts, thus to prevent the sleeve from loosening on the-conductor; the two actions of which maintain a constant and uniform contact pressure, between the sleeve and conductor, during thermal variations.

2. An electrical connector, as described in claim 1, but additionally consisting of serrations formed within the sleeve, lengthwise from one open end of the-sleeve to its other open end, the lengthwise serrations forming parallel splines, which penetrate oxide formed on the conductor; thereby establishing a linear and circumferential depth-contacting grip on the conductor, the compression of which is uniformly distributed throughout the innerworking contact surface of the sleeve, thus free of pinching and crushing'action on the conductor.

References Cited in the tile of this patent UNITED STATES PATENTS 1,647,762 Wiseman Nov. 1,4927

-l,9l 6,7Z8 Hill g July 4, 1933 2,136,814 Flynn NOV. 15, 1933 2,464,565 Evans Mar. 15, 1949 FOREIGN PATENTS 990,091 France May 30, 1951

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