US2721986A - Self-insulated electrical connector - Google Patents

Description

Oct. 25, 1955 c, BADEAU 2,721,986

SELF-INSULATED ELECTRICAL CONNECTOR Filed March 12, 1952 FIG! FIG.2 FIG.3

FIG.4

S 3 9 2 IO FIG/O IN VEN TOR. W 3 I2 9 W 2 CARROLL A. BADEAU Z JSM ATTORNEY United States Patent SELF-INSULATED ELECTRICAL CONNECTOR Carroll A. Badeau, Westfield, N. 3., assignor to The Thomas & Betts Co., Elizabeth, N. J., a corporation of New Jersey Application March 12, 1952, Serial No. 276,077

2 Claims. (Cl. 339--217) An invention is disclosed herein which relates to connectors and more particularly to a self-insulated electrical connector improved in respect to simplicity of construction and increased utility in its insulated characteristics.

Electrical connectors in general, and especially those of the terminal species, are frequently used in wiring installations where they are crowded together in close relation on a wiring panel or other electrical apparatus. When so mounted, it is necessary that all metallic outer surfaces of the adjacent connectors be insulation-covered or jacketed to prevent short circuits in the event one connector touches another in the course of service involving wear and tear on the wired installation.

It is, of course, possible and frequent practice for a wiring mechanic to cover and insulate electrical connectors by makeshift means, such as the use of tape or jacketing sleeves when making the installation. However, it is preferred that such connectors be self or pre-insulated by the manufacturer in order to avoid uncertainties and possible oversight in careless and time-consuming efforts when insulating the parts either during or after completing a multiple-connector installation in cramped or crowded wiring quarters.

The present state and condition of the art reveals a variety of self-insulated connectors, but there exists a need for more pronounced simplicity in a fool-proof connector having positive self-insulating characteristics, one which can be installed (mechanically and electrically joined) on a conductor without need for the wiring mechanic to insulate them as a part of his work. Such need is pronounced in respect to conventional solderless pressure connectors which are bonded onto conductor wires or cables with a compression tool which automatically joins a conductor end with an electrical connector at a single stroke of the tool by cold-flowing the two metals together into a permanent electrically connected homogeneous joint of low resistance.

Such is the problem which the invention seeks to solve, the purpose being to provide the trade with better and more positive self-insulated solderless connectors, which may be installed in the same fashion as heretofore practiced, and not requiring a separate operation in covering them when making a wired circuit installation.

This specification with its claimed subject matter and accompanying drawings explains the invention preferred and embodied at this time for an understanding of the problems sought to be solved. Since the teachings herein may suggest structural changes to others who wish to avail themselves of the benefits of the invention, it is pointed out that subsequent modifications hereof may well be the same in spirit and principle as this disclosure.

An electrical connector of the terminal species is chosen for the purpose of illustrating the invention. in fact, a conventional solderless terminal (for making stud, binding post, and other like types of connections) poses one of the more pronounced needs in the trade, sets a useful environment for this improvement, and is shown "ice 2 in the drawings as constituting one of the elements of this new structural combination. Other types of conventional connectors, such as T-taps, etc., also may be improved by adopting the invention to them.

The first seven views illustrate one of the simplest types of known one-piece electrical terminals, the utility of which is enhanced by this invention. Thus, Figs. l7 show the first form of the invention, the structural organization of which is characterized by concentric relation of the parts constituting this self-insulated connector.

Fig. 1 shows a longitudinal section of an insulation sleeve having a jacket at one end for covering a connector, with a socket at its other end for receiving an electrical conductor, and a dividing annular flange within its mid portion.

Fig. 2 is an end elevation on the line 2 (the inner end) showing the annular flange formed within the sleeve and concentric with the sleeve axis.

Fig. 3 shows a side elevation of the aforementioned conventional one-piece terminal on which the insulating sleeve is adapted to be permanently mounted; and Fig. 4 shows a top view of the new selfinsulated connector in its finished form.

Fig. 5 shows a typical piece of a stranded-wire insulation-covered electrical conductor. its extremity is prepared in the usual way, by deinsulating and baring the wires clean, and thus adapting it to fit into the left-hand end of the self-insulated terminal of the previous view.

Fig. 6 shows the prepared end of the conductor wire pushed into final position within the sleeve socket of the self-insulated terminal; and Fig. 7 shows the terminal permanently joined onto the conductor end by one form of tool compression to make a solderless connection.

The next three views show a second form of construction, in which the principle of the invention is adapted to a simple known type of two-piece electrical connector of the terminal species and which is characterized by eccentric relation of the parts.

Fig. 8 shows a lengthwise section of the insulating sleeve, modified in respect to Fig. 1, and adapted to the known type of two-piece terminal shown in Fig. 10. It is of interest to compare the two sleeves of Figs. 1 and 8.

Fig. 9 is an end elevation on the line 9 (the outer end) showing the annular flange formed within the sleeve and eccentric to the sleeve axis, this a feature which adapts the invention to the two-piece terminal next illustrated.

Fig. 10 is a longitudinal section of the self-insulated connector (second form of the invention) assembled on the electrical conductor (Fig. 5), complete in form to match andcompare with Fig. 6, and which is adapted to be permanently joined (solderless pressure connection) with the conductor in the same fashion as in Fig. 7.

The scope and principle of the invention is believed to be more appreciated by presenting two examples of the connector.

Figs. 1-7

Insulating sleeves of cylindrical form and open at both ends are made, in either of the illustrated examples (Figs. 1, 2 and 8, 9), of molded semi-hard plastic material, nylon being satisfactory for the purpose of this invention. Such semi-hard molded nylon plastic, or other like tough material, is sufficiently soft to deform and yield under pressure (when making solderless pressure electrical connections) and yet is hard enough in its resistant toughness to maintain its set after being deformed or indented by a tool used for the purpose of installing the connectors of an electrical conductor.

The insulator, in the form of a sleeve with a smooth interior surface, has a jacket portion 2 at its inner end shQulder-end S of a conductor Wire W (Fig.

for receiving and covering the tubular body or barrel of a connector (Fig. 3) and a socket portion 3 at its outer end for receiving and covering a cut-off insulation The insulating sleeve 2, 3 also includes an integrally molded inner annular flange means 4 which is concentric with the axis of the sleeve and which also is semi-hard and tough. The flange 4 may be molded somewhat closer to the outer end of the sleeve, thereby making the wirereceiving socket 3 shorter than the connector-receiving jacket 2.

An electrical connector is shown in Fig. 3 typical of one-piece terminals having a metallic tubular body or wire-receiving barrel 6 with an integral tongue 7 extending from one side and one end of the terminal body. The tongue 7 is for screw-fastening or bolting the fitting permanently to a binding post or other terminal. Or a contact blade of known type may take the place of the tongue 7 in wiring installations where quick plugin disconnect fittings are used with outlet receptacles.

It is observed that the outside diameter of the termineral barrel 6 is dimension formed to make a close and sliding pressure or drive fit with the smooth inside surface of the insulating jacket 2. Thus, the sleeve jacket is pressed upon the terminal barrel with a tight fit, the outer end edge or perimeter of the barrel being jammed or seated against the inner concentric flange 4 to abut it and complete the connector. The telescopic pressure fit of these two parts holds them together in ordinary handling, in the course of manufacture, packaging, sorting, etc., so that the trade receives the connectors as a completed fitting, self-insulated, and ready for use.

For service, the ready for use and self-insulated connector (Fig. 4) is installed on the electrical conductor wire W (Figs. 6 and 7) by first trimming the insulationcovering and preparing the squared-off shoulder-end S in the usual manner (Fig. 5) near the extremity of the wire strands. The prepared wire-end S is then pushed through the socket portion 3 of the insulating sleeve, through the flange 4 and into the barrel 6 of the terminal, until the insulation-covering shoulder-end S of the conductor seats against the flange 4.

The chamfer at the bottom of the socket 3, adjacent the flange 4, aids in pushing or guiding the wire end through the flange, by piloting the strands toward the open end of the terminal barrel 6. Likewise, the chamfer constricts the peripheral edge of the insulation shoulder-end S at the flange 4 and tightens the joint between the socket 3 and conductor Wire W.

Thus, it is seen that the insulating flange means 4 is disposed between and is interlocked by and between the shoulder-end S of the wire W and the outer end edge of the terminal barrel 6. In this simple and effective way, the insulation sleeve 2, 3 is keyed permanently upon the conductor and upon the terminal in such manner that the sleeve no longer depends upon its pressure tight fit with the terminal barrel for holding the parts together.

Next, it may be pointed out that it is the usual practice to fasten electrical connectors, terminals and the like, of the type herein improved, on electrical conductors by compressing an indentation 8 into the barrel 6 and thus into the wire strands W. A tool-compressed area 8 (dotted lines, Fig. 7) is one form of solderless pressure connection applied either by a hand or a power operated tool which cold-flows the area 8 of the metallic terminal barrel 6 into the wire strands W, thereby making a homogeneous joint of low electrical resistance and substantial strength against pull-out of the Wire.

The solderless pressure-joint at 8, heretofore used on non-insulated connectors, is also adapted to this new self-insulated connector. The tough semi-hard plastic sleeve, at its jacket end 2, deforms and also cold-flows under the compression of the indenting tool, follows the tool into the metallic barrel 6 indented area, and main tains its set contour when the compression tool is removed. In this Way, the insulating sleeve cold-molds and bonds onto the connector barrel.

Figs. 8, 9 and 10 The last three views show a second example of the invention and follow the principle described in the foregoing, diflering only in respect to an insulating sleeve modified in form to receive an electrical connector (also of conventional terminal type) having a tubular body and a bolting tongue which are first made as two separate parts (Fig. 10) and then fabricated into a single assembly.

In these three views, the same reference numbers as heretofore noted are again used for identification where the parts or portions thereof are of substantial similarity to those already described. Further part numbers 9, 10, l1 and 12 point out the characteristics of this second example of self-insulated connector.

It is seen (Fig. 8, etc.) that the tough semi-hard molded plastic sleeve 2, 3 is provided with an integrally molded inner annular flange means 9, and that said flange is eccentric to the axis of the sleeve. This eccentricity of the flange 9 makes its Wall and that of the insulating socket 3 noticeably thicker on one side than on the other and is for the purpose of receiving the conventional two-part terminal shown in the last view.

Regarding the two-piece electrical terminal, it is seen to comprise a tubular body or barrel 10 but with a separate tongue 11. These two parts are sweated together as an integral assembly of popularly known form, being a fabricated type of terminal in many instances preferred over the first one (Fig. 3). This two-piece terminal 10, 11 is characterized by a double-wall thickness on one side (the tongue side) of its barrel. The double thickness (tongue lamination 11) extends around a portion of the inner circumference of the barrel 10 and from end to end thereof.

It is seen that the molded insulating sleeve, with its off-center or eccentric flange means 9, makes a neat covering fit with the two-piece terminal when assembled as in Fig. 10. The thick side of the insulating flange 9, and of the wire-receiving socket 3, is aligned with the doublewall thickness of the two-part terminal 10, 11. In other words, it may be said that the off-center flange 9 accommodates the off-center axis of the two-piece terminal 10, 11 and makes correction for lack of symmetry.

To compensate for the non-symmetrical form, an outside taper finish 12 extends around the circumference and relieves the thicker side of the wall of the conductorreceiving socket 3. The exterior taper 12 imparts circumferential or rim symmetry and uniformity of thickness at the end edge (the perimeter) of the. socket 3. Accordingly, both open ends of the insulating sleeve may have their perimeters molded uniformly in thickness by reason of the outwardly reducing taper 12 provided at the eccentric socket-end portion.

The ready-made self-insulated two-piece terminal 10, 11 is installed on the shouldered wire-end S in the same fashion as heretofore described for Fig. 7, at the solderless connection 8; and both forms of keying flanges 4 and 9 perform their new functions equally well. The toolindented joint 8 is merely one means of making a permanent electrical connection, it being understood that either assembly (Fig. 6 or 10) is adapted to other types of joint means to complete the new combination of conductor and self-insulated connector.

General explanation of both examples It is seen that the two forms of insulating sleeves per se provide simple, fool-proof, and permanent self-insulating connectors of either the one-piece or two-piece terminal type. And they also contribute novelty in a new combination of the conductor W and its insulation shoulder-end S with said sleeves. Accordingly, the insulating flange means 4 and 9, with related sleeve portions, aid the art in these three respects.

The annular insulating flange means 4 and 9 are of first importance in the manufacture of these connectors. In the assembly operation, the flange acts as a stop for the outer end of the terminal barrel 6 or 10. In other words, the insulating jacket 2 and connector barrel are press fitted together, the two members sliding one into the other until the flange and the terminal stop each other, thereby insuring factory-designed fit.

After the conductor wire W is electrically connected (Fig. 7) to the terminal barrel 6 or 10, as by the compression joint 8, it follows that the insulating sleeve 2, 3 as a whole is irremovably self-locked in a keyed and covering position upon the electrical terminal and the wire-end S.

The socket end 3 of the sleeve importantly embraces the insulation-covering of the conductor W, prevents fraying thereof at the cut shoulder S, makes a neat and permanently finished joint, and constitutes a barrier which isolates against electrical potential flashover by increasing the insulation-covering on the conductor where it enters the terminal. The wire-receiving socket 3 also resists bending of the conductor at its terminal joint where a break due to rugged use may first occur.

The interlock of the insulating flange 4 or 9 so permanently secures either form of the sleeve (Fig. 1 or 8) onto the conductor and onto the electrical connector that there arises no likelihood of the plastic sleeve loosening and slipping out of position due to aging. The shouldered conductor-end S and flange 4 and 9 likewise so anchor the sleeve that it no longer depends either upon its pressure fit with the connector or its deformed indent 8 to hold it in position.

Another advantage noted is that in electrical wiring installations extending vertically, the shoulder-locked insulating sleeve cannot be vibrated or gravitated out of position during long and severe service. This and other known problems are believed to be solved.

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

What is claimed is:

1. In an insulator for an electrical connector, the latter having a metallic barrel adapted to receive the conventional insulation-shouldered bare-wire end of an electrical conductor, and wherein the insulator is of sleeve form, and also is cylindrical axially from end to end, is adapted to fit onto said metallic barrel, be indented thereinto by a compression tool, and which barrel in turn is simultaneously indented into said bare-wire end to make a permanent electrical connection therewith; and that improved means for permanently interlocking the insulating sleeve with and on said metallic barrel and with and on said insulation-shouldered bare-wire end of said conductor; wherein the sleeve is pre-molded of elastic semi-hard deformable plastic, is pre-set to a given-size conductor insulation, and to a tight slip-fit on said metallic barrel, with an annular plastic flange means integrally pre-molded and pre-set inside thereof, and transversely between its two end por tions; thereby providing an insulating socket at one end of the sleeve, and an insulating jacket at its other end; the flange means having an aperture premolded and pre-set to receive said bare-wire end of said given-size conductor, and the flange means also providing a stop against one side of which abuts the end-edge of said metallic barrel when it is slip-fitted into the jacket, and against the opposite side of which abuts said given-size insulation-shoulder when said bare-wire end is inserted into said metallic barrel, this opposite side of the annular flange means being pre-molded and pre-set with an annular chamfer, the bevel of which extends to the pre-molded aperture, to provide a piloting means adapted to guide said bare-wire end therethrough, and thus permit said given-size insulation-shoulder to seat against such opposite side of the flange means; whereby the sleeve is permanently interlocked on said metallic barrel and on said conductor by the flange means, which is keyed between the end-edge of said metallic barrel and said insulation-shoulder, thereby permanently anchoring the sleeve against displacement in the event the tight slip-fit should be initially loosened by said indenting operation of said compression tool or eventually become loosened due to aging in service.

2. An insulator for an electrical connector, as described in claim 1 except that said metallic barrel is thicker on one side than the other; and the annular flange means and its aperture are eccentric to the axis of the insulating sleeve, also eccentric to the axis of its socket and of its jacket, and likewise to said barrel; one side of the socket having a thicker wall than its other side, and the thick side thereof being disposed in alignment with the thick side of said metallic barrel; and an exterior taper finish pre-molded on the thick wall side of the socket, reducing the latter thickness outward, and its outer end having a rim-edge of uniform circumferential thickness.

References Cited in the file of this patent UNITED STATES PATENTS 1,376,844 Weber May 3, 1921 2,405,111 Carlson et al Aug. 6, 1946 2,410,321 Watts Oct. 29, 1946 2,554,813 Buchanan May 29, 1951 2,648,030 Kickhaefer Aug. 4, 1953 FOREIGN PATENTS 142,674 Great Britain May 13, 1920 494,015 Germany Mar. 17, 1930 OTHER REFERENCES AMP Catalog (received in Patent Oflice January 23, 1948), page 8 entitled on tab Plasti-Grip; page 6 entitled on tab Diamond-Grip.

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