US2444997A

US2444997A - Method of making electric contact plugs

Info

Publication number: US2444997A
Application number: US659022A
Authority: US
Inventors: Lovesey Horace
Original assignee: Telephone Manufacturing Co Ltd
Current assignee: Telephone Manufacturing Co Ltd
Priority date: 1945-04-13
Filing date: 1946-04-02
Publication date: 1948-07-13
Anticipated expiration: 1965-07-13

Description

July 13,1948. H LOVESEY METHOD OF MAKING ELECTRIC CONTACT PLUGS Filed April 2. 1946 'ing ring Patented July 13, 1948 METHOD OF -MAKING ELECTRIC I I CONTACT PLUGS Horace Lovesey,

London, "England, assignor to Telephone Manu'facturing 'Company Limited,

London, England Application April 2,1946,?Serial N 0.659.022 In Grcat'Britain April .13, .1945

Thepresent invention relates to contact plugsand the like comprising two or more elongated elements assembled coaxially one within the other, the said elements being separated by insulating material.

The present invention has for its object the provision of improvements in a device such as a contact plug or the like and in the manufacture thereof, and, according tothe invention,-an inner element thereof has a separating and locatof insulating material'initially moulded on it of such size that it can be located within the tubular bore of the next larger element, and, when the elements are then held into their proper relationship, the remaining insulating material is injected.

The invention is particularly applicable to telephone jack plugs of the tip, ring and sleeve type consisting of an inner rod mounted coaxially within an inner sleeve which in turn is mounted coaxially within an outer sleeve. The inner rod at its forward end projects beyond the forward end of the inner sleeve and has an annular contact on its projecting end. The inner sleeve at its forward end projects beyond the forward end of the outer sleeve. Ihe three elements are separated by insulating material and the ring on the forward end of the inner rod forms the tip contact; the projecting end of the inner sleeve forms the ring contact and the outer sleeve forms the sleeve contact.

In making a plug of this kind it is convenient to insert the insulating material by injection of a thermoplastic or thermo-setting insulation, but this may result in faulty plugs, due to the conducting elements being displaced. While jigs may be employed during the injection to reduce the displacement it is still diflicult to ensure that the elements, especially the central rod and the inner sleeve are correctly aligned and insulated. With the present invention this defect can be substantially eliminated.

In the accompanying drawing is shown by way of example stages in the assembly of a telephone jack plug of the tip, ring and sleeve type. In this drawing Figure 1 is an elevation of the inner element;

Figure 2 is a section of the inner element located within the first sleeve;

Figure 3 is a section of both the elements of Figure 2 located within the outer sleeve before the insulating material is inserted; and

Figure 4 shows the plug with insulating material inserted, and with the contacts shaped to standard profile.

'tral'ro'd I is located In this embodiment of the invention 'the'cenwithin the inner sleeve 2, which in turni's arranged.- within the outer sleeve 3. .The rod I'is stamped or otherwise formed at its one end with longitudinal .grooves 4 in'two parts, with an ungrooved portion 5 between .them of slightly reduced diameter. "At its other end the rod is formed with an off-set portion 6 with a threaded hole "I therein.

After the rod I has been shaped as described, a small insulating'locator ring 8 is moulded on to the rod,'the external diameter of the ring being equal'to'the internaldiameter of the innersleeve 2. To assist in securing this ring uponthe rod a small nick may be made at 9.

The rod I after the ring 8 is moulded thereon,

is positioned within the inner sleeve 2 and a Washer I0 of hard insulating material is placed over that end of the rod which projects through the sleeve. A brass or other suitable collar II is then forced on to the grooves 4 and deformed by crimping at I2 to grip in the portion 5 of the rod between the grooves, thus securely holding the collar on the shaft. The ring 8 will fit closely within the sleeve 2, and to assist in securing this fit the ring may be moulded in a two-part mould, when the "flash formed at the junction of the two parts will provide two high spots which will give a good frictional fit in the sleeve.

The inner sleeve 2 is cut away at I3 in the usual manner to give access to the rear end of the rod I, and is .provided with a threaded hole I4 at its rear end. The sleeve also has a stepped portion I5 at its forward end which eventually provides the ring contact of the plug, and the end face I6 of this stepped portion is serrated or otherwise roughened. The outer end of the bore of the sleeve 2 may be tapered as shown at IT.

The rod I and inner sleeve 2 as assembled are next inserted in the outer sleeve 3. As is usual,

I sleeve 3 is cut away as at I8, to give access to the ends of sleeve 2 and rod I. The parts are then mounted in a moulding die, pins, or preferably screws, being inserted in holes 1 and I4 in the members I and 2. In addition the sleeve 3 and the forward end of sleeve 2 are located in the die; the stepped portion l5 on the sleeve 2 enables this to be done accurately.

When the parts are correctly positioned insulating material I9 is injected into the mould, and allowed to harden; it will be apparent that if this process involves heat, as is usually the case, the material of the ring must be such as not to soften at the temperatures involved. In this moulding the parts of the plug are firmly held and the obstruction caused by the locating ring 8" i will be negligible. The high spots caused by the moulding flash will leave a small gap for material to pass through; if this is found to be insufficient the locator ring may be formed; with a groove or grooves or may be otherwise shaped to facilitate the flow of the material past the ring.

The plug is completed by cleaning and shaping 7 the tip and ring portions to a standard profile,

as shown in Figure 4, and an outer insulating What I claim and desire to secure by Letters Patent is:

Method of manufacturing a contact plug of the type comprising a central rod terminating in a tip contact, an inner conductive sleeve surrounding said rod and terminating in a contact ring, and an outer conductive sleeve surrounding said inner sleeve and constituting a contact sleeve, said method including the steps of molding a short cylindrical insulator onto said rod of a diameter substantially equal to the inner diameter of said inner sleeve to provide a close friction fit therebetween, sliding said inner sleeve in place on said rod over said insulator to provide a sub-assembly of said rod and inner sleeve, positioning said sub-assembly and outer sleeve in place inside a mold, and injecting insulating case 20 is slipped over the sleeve 3 in the usual" manner. 7

In this description of one embodiment of the invention reference has been made to the use of one ring 8 of insulating material for holding the parts in position prior to moulding, but it will be understood that more than one ring may be used if necessary. With the arrangement shown and described, however, we have found that the one ring 8 is sufficient to ensure that the number of reject plugs due to misalignment or short circuits between adjacent members isaminimum. It is desirable to use the minimum number of rings, as the obstruction to the injected moulded material is then minimized.

plastic-material into the mold to fill the annular voids between said rod and inner sleeve and between said inner and outer sleeves.

I HORACE LOVESEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Brunetti Apr. 16, 1940