US 2749384 A
Description (OCR text may contain errors)
im@ 5 95@ W. J. SCQTT PLASTIC CONNECTORS Filed NOV. 26, 1954 United States Patent O PLASTIC CONNECTORS William J. Scott, Sycamore, Ill., assignor to Ideal Industries, Inc., Sycamore, Ill., a corporation of Delaware Application November 26, 1954, Serial No. 471,217
2 Claims. (Cl. 174-87) This is a continuation in part of my application Serial No. 343,141, tiled March 18, 1953.
My invention resides in the iield of connectors for electrical wires, cables, leads, conductors and the like, and is an improvement on prior devices for joining two or more electric wires or conductors in an eicient insulated connection. More specifically, my invention is a new and improved electrical connector of the screw on Variety, which is composed of a cap or shell with an internally threaded bore adapted to be turned down over the ends of two or more electric wires or conductors which have been stripped of their insulation and initially grouped together, the cap or shell thus vcovering the stripped ends of the conductors so as to insulate the same, as well as forming a tight, strong etlicient electrical connection between the wires.
Another object of my invention is a new and improved connector for two or more electric conductors that provides a strong as well as ehicient electrical connection.
Another object of my invention is a new and improved electrical connector of the screw on variety which is easy to manufacture, inexpensive to produce and very eiiicient in use.
Another object of my invention is a new and improved connector of the screw on type which, when screwed or turned down over the stripped ends of the conductors, will not abrade or cut them due to the action of the threaded portion of the connector thereon.
Another object of my invention is a new and improved all plastic connector which does not require any metal inserts or fastening means so that the connector can be manufactured and produced in nal form, in a plastic casting or molding machine.
Other objects will appear from time to time in the ensuing specication and drawings.
Figure 1 is a side view, taken in section, showing my new and improved connector cap or shell with its internal threaded bore;
Figure 2 is a sectional View taken along line 2-2 in Figure 1; and
`Figure 3 is an enlarged View in section of the threads formed in the bore of the cap.
ln Figure 1 my connector 10 is shown generally in the shape of a frustum of a cone with an internal tapered bore 12. Throughout a substantial portion of the length of the connectors outer surface a plurality of grooves 14 may be provided, the vertical walls 16 on each side of the grooves being co-extensive with the axis of the connectors center line so that the sides of all the grooves, if extended, would pass through the center line of the connector.
The bore 12 of the connector is divided into three portions, namely, an inner portion 18, an intermediate portion 19, and an outer portion 20. It should be noted that the angle of divergence of the inner portion 18 is substantially less than the angle of divergence of the outer portion 20 and the outer portion is used primarily to 2,749,384 Patented June 5, 1956 ICC guide the wires or conductors properly to the interior of the connector and secondarily, to serve as an additional holding means. The intermediate position has the greatest angle of divergence. The conical walls of the outer portion 20 may be threaded at 22, as shown in Figure 1, so as to firmly engage the insulation surrounding the inserted conductors and prevent the wires from easily being withdrawn from the bore of the connector.
The inner portion 18 of the bore is threaded in a manner so that a tight, eicient joint and connection is formed. The threads 22 in the outer portion 20 do not have any particular shape of dimensions and can be made in any well known, conventional fashion.
The connector I have shown in the drawings is specifically made of a plastic material. It should be noted that the connector does not have any type of crimpable ferrule, coil spring insert or other wire holding means. When the twisted bare wires are inserted into the bore of a connector, the plastic threads 24 on the inner portion of the bore are harder than the annealed or semi-annealed wires of the conductors. Thus, as the connector is twisted or turned over the wires or conductors, the wires are forced to the interior of the bore and the threads 24 form partial threads or grooves on the exposed surfaces of the conductors. The plastic threads 24 directly engage the wires and will not cut or abrade the surfaces of the wires, rather they will smoothly indent and slowly work-harden the surface of the wires. As the connector is smoothly twisted over the wires, the partial threads formed in the conductors become increasingly hardened until the wires workharden sufliciently to prevent further thread formation. At this stage the twisted stripped ends of the wires will substantially cease their inward movement in the hre portion 18 and will begin to rotate with the bore, which serves to further coil the insulated portion of the conductors outside of the connector. This results in a very tightly wound connection between the wires, and the twisting action will cease when the operator can no longer rotate the connector 10.
It is very important that the threads 24 in the inner portion of the bore do not cut the wires as they are being rotatably inserted into the interior of the connector and for this purpose I mold my entire connector from a plastic. I have found that an alpha-cellulose filled, melamineformaldehyde, thermosetting molding compound is very satisfactory for these purposes. However, various other compounds have also proven successful. For example, I have also found that an alpha-cellulose filled, urea formaldehyde, thermosetting molding compound also will generally satisfy the various characteristics of the desired material. The general name for these types is amino which designates both urea and melamine.
In general, the plastic material used should have a hardness greater than the hardness of the metal conductors. I have found that a plastic material with a hardness of at least Rockwell E- approximately or greater, should be used. Another factor of the plastic material is its tensile strength and the plastic material of my connector has a minimum tensile strength of 5,000 pounds per square inch.
The type of plastic materials set forth above is thermosetting and they have suiiicient hardness so that they will properly groove or thread the surfaces of the wires and will work-harden the metal surfaces during the twisting action. In addition, they have sufficiently high strength and heat resistant properties to withstand the various temperature and stress conditions to which such connectors are subjected. Of course, if a thermoplastic material can be produced with these properties, my connector could be made out of it.
When a connector is made from plastic the form of the thread in the inner portion of the bore takes on an :ddet' -ortanee due to the type of connection h l on that is necessary in addition to the workh which the threads produce on the surface of ln Figare 3 l have shown an enlarged secthreads 154 and it will be noted that the are rounded so as to present a smooth workt to the wires. in eixect, the threaded :e with sides disposed at 9G- acquire a deep t surface for the wrres. area that is engaged on the 2S on the threads is not too cfered te the user who is turnr over tire wires is not too great for satis wed between adiacent turns of the coil so that the metal of tl e conductors that fio-ws in and t r 23 during the work-hardening process vrent roem for adequate penetration into rather than cut or abraded. The crowns roove tne wires and have found that the radius R of these crowns should be .G05 inch or less. that a connector with crowns having nch work exceptionally well.
rthile i have shown and described the preferred form of my inve tion, it should be understood that numerous ations and modifications can be made within e scope and spirit without departing therefrom, and l wish tha; my invention be unrestricted except as by the appended claims.
The use, operation and function of my invention are as follows:
The invention is in the field of connectors and is a screw on cap type cap connector. Prior to this invention. 'rrrectors of this type were composed of generally an inst 'ng cop or shell with a metal securing member. f r e: pic. the coil spring is a cylindrical ferrule insert or cr tl e bore of t're cap d 4 rial. Tt is, of course, old to make a connector of this type out oi porcelain or -glass, however, the threads will. cut the copA er wires and for this reason my connector, in addition to being more inexpensive, will also provide a stronger joint.
claim: fm insulating molded all plastic cap for covering connecting by compression the stripped ends of a l of insulated electrical conductors or the like. `mprising a shell oi rigid sulatiry material forrnefl .asrv metal working surface, the well rounded crown t ad being spaced a sufcient distance from its nt crowns, the elongated threaded section having relative to and many times greater than the crown e er, and the thread depth of the threaded section ed from the conductors by the pressure of rotating a emitted to the conductors through the well rotin tins, the material of the cap including tre "rr-,l wire engaging surface being an amino thermo plastic.
he ruotare of claim l in which the sides of the tr reads leading up to the well rounded crowns are ilat and smooth, and are disposed at an acute angle relative to the plane of the crowns, the root of the threads between adjacent sides being dat in cross section and generally conical in overall appearance about the bore oi the shell as an axis.
References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Article A Review of Plastic Materials, by H. L. Brouse, pub. in Proc. l. R. E., December 1945, pages S25-829 incl.