US2857580A - Communications cords and methods of making them - Google Patents

Description

Oct. 21, 1958 B. A. RAETSCH COMMUNICATIONS CORDS AND METHODS OF MAKING THEM Filed May 7, 1953' FIG! 5 .58 64 $6 72 ii; i g I l o I FIG 2 ATTORNEV 2 Sheets-Sheet 1 Oct. 21, 1958 B. A. RAETSCH 2,857,580

COMMUNICATIONS CORDS AND METHODS OF MAKING THEM Filed May 7, 1953 I 2 Sheets-Sheet 2 FIG. '8

FIG. .9

HQ 7 INVENTOR B. A. RAETSCH A ATTORNEY 2,857,580 Patented Oct. 21,. 1958 United States Patent Ofiice COlVlNIUNICATIONS CORDS AND METHODS OF MAKING THEM Application May 7, 1953, Serial No. 353,479

'3 Claims. (Cl. 339-483) This invention relates to communications cords and methods of manufacturing such cords, and more particularly to cords having plugs thereon used to make connections in telephone switchboards, and the like, and methods of manufacturing such cords.

The connection plugs on switchboard cords used in telephone exchanges must be ruggedly constructed to withstand being rapidly and repeatedly inserted into the jacks in the switchboards by telephone operators. In making connections the plugs are subjected to wear, stress and strain, which tend to make it necessary to replace them periodically. In manufacturing such plugs for the telephone industry, it has been necessary to employ considerable manual labor to assemble the many small parts of which the plugs are constructed. Consequently, a need has existed to simplify the construction and the method of manufacturing cords provided with such plugs.

An object of this invention is to provide new and improved communications cords and methods of making such cords.

:.Another object of this invention is to provide new and improvedvcords having telephone plugs thereon, and the like, and methods of making such cords.

-A cord illustrating certain features of the invention may include a conductive tube mounted concentrically and in spaced relationship on a conductive center pin and within a conductive tubular shank of a plug body,

a mass of plastic material molded in situ for separating the pin, the tube and the shank, said mass having sockets formed at one end thereof, into which a plurality of conductors at one end of a length of cordage are inserted to make electrical contacts with the pin, the tube and the shank,v and a plastic shell molded around the conductors at the end of the cordage and around the adjacent portions of the cordage and of the shank.

A method illustrating certain features of the invention may include. the steps of assembling a conductive tube on a conductive center pin and within a conductive tubular shankof a plug body, molding plastic between the center pin, the tube and the shank, then electrically connecting the center pin, the tube and the shank to a plurality of insulated conductors at one end of a cord, and molding a plastic shell around the conductors at the end of the cord and around the adjacent, portions of the cord and of the shank.

A complete understanding ofthe invention may be obtained from the following detailed description of cords embodying the invention and methods of making such cords, when considered in conjunction with the appended drawings, in which:

Fig. 1 is a fragmentary elevation of a completed communications cord embodying the invention;

Fig. 2 is a side elevation of apparatus suitable for performing one step in a method of manufacturing the cord illustrated in Fig. 1;

Fig. 3 is an enlarged, vertical section of aportion of the apparatus shown in Fig. 2;

Fig. 4 is a fragmentary, vertical section taken along line 4+4 of Fig. 3 ask would appear ,ifthe apparatus in Fig. 3 were unsectioned; V

Fig. 5 is an enlarged perspective view of a portion of the apparatus shown in Fig. 3 as it would appear if the apparatus in Fig. 3 were unsectioned;

Fig. 6 is an enlarged perspective view of a portion of a plug at an intermediate stage of its manufacture;

Fig. 7 is a longitudinal section of the plug portion illustrated in Fig. 6; i

Fig. 8 is a vertical section of apparatus suitable for erforming another step in the method of manufacturing the cord illustrated'in Fig. 1; and

Fig. 9 is an enlarged view, partially in section, of a portion of the plug in another stage of its manu facture.

Referring to Fig. 1, there is shown one end of a communications cord having a plug designed generally by the numeral 10 attached to a length of flexible, braided cordage 12. The right hand end of the plug-10 is provided in the usual manner with a ball contact 14, which completes an electrical circuit when this end of the plug is inserted into a jack on a telephone switchboard (not shown). Surrounding the plug 10 near the ball contact 14 is a ring contact 16 which completes another circuit when the plug is inserted into the jack. A little further away from the ball contact 14, the plug 10 is provided with-a cylindrical metallic shank 18 which makes a third connection with the jack for electrical circuits involving three conductors. The diameter of the shank 18 is somewhat larger than that of the ring contact 16, which in turn has a slightly larger diameter than the ball contact 14. The ball contact 14, the ring contact 16 and the metallic shank 18 are all composed of brass.

A collar 20, known in the trade as a dead collar, is located between the ball contact 14 and the ring contact 16.

tact 14 and the ring contact 16. The collar 20 functions as a bearing surface as well as a guide when the plug 10 is being inserted into the jack on a switchboard.

Since this operation subjects the collar 20 to consider-' When the component parts of the plug 10 are first as-' sembled, they do not yet have the contours illustrated in Fig. 1. These contours are imparted to the plug in a profiling machine, in which portions of an incomplete plug are machined away to attain the final shape and dimensions of the plug. Before the profiling operation,

the incomplete plug may have the appearance illustrated in Fig. 7, in which a generally cylindrical, brass tip 26 threadedly engages an end of a steel center pin 28, which extends axially through a brass tube 30 and protrudes beyond both ends thereof. An enlarged end 32 of the tube 30 is separated from the tip 26 by an insulating washer 34, a bronze ring 36, and another insulating washer 38, in the order given. The tube 30 is mounted concentrically within the cylindrical shank 18 with the enlarged,

end 32 thereof located beyond one end of the shank.

From a comparison of the incomplete plug shown in Fig. 7 with the finished plug shown in Fig. 1, it is seen that the tip 26 is eventually profiled to form the ball contact 14, theenlarged end 32 of the tube 30 is me- The collar 20 approaches the size of the shank 18 in diameter, being larger than the ball con' chined away to :form the-ring contact 16, the bronze ring I 36 .is profiled .toproducethe .dead collar .20, and the outer peripheries of the washers 34 and 38 are machined to become the annular washers 24 and 22, respectively. luv-addition; anjannul'ar, hard rubber. bushing-40 onv the incomplete. plug profiled to become a P'bushing 1.142 separating the contact ring 16 ifromthe cylindrical shank 18 onithe-finis'hedplug. Y i i The length of flexible cordage 12-contains a plurality of individually insulatedconductors-43, 44 and 45, which respectively are electrically connected to the ball contact'14,;the-ring'contact l 6iand; the cylindrical shank '18 when :-.the;plug-, 1 isattached to ;.the end of the cordage. These connections are made through the-center pin 28, the tube30 and the IiH1'0f: th.ShaDk =18, respectively. The'conduotors43,;44iand:45:areafirst,.exposed at the adjacent end of the.:-.cord, andthenwthe ends of the conductorsare rencir'cledvby 'solderless terminals 46-46. Each-"of the-terminals 416-46 provided with a :prong 48 (Fig. 9) which, when the terminal is wrapped around the; endof the conductor, penetrates-the insulation and makes electrical =contact'with tinsel conductors, of which atconductor 47 is shown, forming :the cores of the insulated conductors. Each g'of :the solderless terminals 46-46 is .also :provided Wifll' fi flat ;tang'50,,- which, protrudes beyond one end of the &terminal :in -alignment with the longitudinal axis thereof. 7

The tanks 50-50 ofithesolderless termina1sJl6-46 are pushed into a plurality=of sockets (:Figs. 6 and 9), of which-three;designated 51, 52 and '53. are provided,.-to make :electrical contacts with the shank 18 the center pin 28, and 'the tube 30. 1 Although ;these sOQcketsare not much higher than thei'thickness of the tangs 50-50, it is advisable to bend the -tangsinto .asomewhat sinuous shape,;as shown :in Fig. '9 in-1order-to=make them contact snugly against opposite :walls of .the sockets, which walls are: not identical in composition. .-In -each case,;=one of the walls is composed. :of :a molded gplastic and :the other wall is metallic. For example, in the case :ofw-the socket 5'1-:=showrr;in:Fig. "9., the :inner periphery of the metallic shank 18 forms'one Wallof athissocket, and-the'opposite wall is formed' by a' molded .plastic spacer 54. 1 Thus, only one'wall'of each socket :is electrically conductive.

Jslihe spacer 54 :is tubular ,in shape,-and it extends between the shank 18 and'the tube'30 up to the bushing 40. Aplastic :spaceri55, similar in construction to the spacer 54, extends between :the center pin 28 .and the tube 30. The spacers 54fand 55ware both integral with a block 56 of :molded plastic, :which surrounds a portion of the centerzpin 28 projecting beyond one end-of the tube 30. It .may be said :that the-spacers 54 and '55 project from one end of a single .mass of :plastic material molded in situ, and ztheablock 56 projects from the other end of this mass. Thus, theyblock-56 is a continuation of the spacer 55 beyond thejtube 30 aswell as a continuation of-asegment .ofgthe spacer 54:on one side of .thewcenter pin The :spacer .54 contains :theisockets 51 and- 53, with the socket 51rlocated on :the 01111611 periphery thereof next to the metallic shank-18 and the "socket; 53 located near .the innerperiphery thereof adjacentto the tube 30. The third :socket .52 is formed 'in the block 5.6 and :is adjacent tolthe centerpin 28. These three sockets are spaced 120 apartrabout-the'axis of the center,;pin .23., and they are --all situatedonthe-same end of theplug l0.

Thesocketsj51, 52 andv 53, the spacers theiblock 56 are all formed simultaneously by injecting molten plastic between' the center pin 28, the tube.30.and the shank. 18. This operation is performed in a two-part mold designated generally by the numeral, 57 (Figs. 2 and3.).. One-part of .themold 571s agenerally rectangular membeLSShaVing'a sprue hol'e 60 formed in one side thereof for Zthevadmission'of moltenplastic into an interior .mold cavity 62. .The. other part;of the mold'57 is divided into two hinged sections 64-64, which, are

54 land .55, and

generally frustoconical in shape when these sections are .closed about the lug 1.0.

One end of the plug 10 in its incompletely assembled condition is inserted into the mold cavity 62, and the other end of the plug fits into the interior of the sections 1 to. :the fact that this end of .the plug 10 .has .an irregular v shape at this stage'of its manufacture, the mold sections 64-64 are hinged together to enable them to be closed snugly thereabout, while the other end of the plug can"v be merely slid into the member 58.

A holder 66 is provided with a generally frustoconical recess 68, which matches the shape of the mold sections 64-64 when they are closed. The holder 66 is designed to receive the mold sections 64-64 when they 'are closed about an incomplete plug 10, and to allow the 'center'pin 28 to protrude into 'an aperture 70 formed in the-centerof the recess 68 in the holder 66. I

When the mold-57 is loaded with the plug 10, the holder 66 rests against a vertical abutment 72 provided at one end of a mold support 74. The other end-of the mold support 74 -is provided with a vertical post 76 carrying a'pivoted cam'78 at the .upper end thereof. The cam 78 -is arranged to engage and shove a pivoted-plate-80Mv against the adjacent end of the rectangular mold 58,

which action in turn thrusts the rest ;of mold57 and tli ef-n V holder 66 against the abutment'72. In "doing so,= both parts of the mold 57 are forced tightly against theop posite ends of the incomplete plug '10. A pairo'f re-' tainers, of which a retainer 82 is shown, are secured to thesupport 74 on opposite sides of the rectangularmetna ber 58, in order to align this part of the mold 57 with the rest-of the mold.

Thesockets 51, 52 and 53' are -formed by =suitahly I shaped prongs 84, 85 and 86, respectively (Figs. 4 and.

5), which project fromadjacentends of a pair ofcylinders 88and-89. As shown in Figs. 3 and 5, the'cylin'ders'; 88 and 89 are placed in end to end abutment when they are positioned in the mold cavity 62 0f the rectangular.

V mold member 58. A pair-of locating pins 90-90 (Fig.

2) secure the cylinders 88 and in their proper position in the mold cavity 62. The'cylinder-88 carries the prong- 85, and the cylinder 89 carries the-prongs-84 and "86. The cylinders 88 and 89 are centrally apertured so that i the center pin 28 may protrude through 'themand project into an'aperture 91-formed in the mold cavity 62.

As s'hown-in Fig. 4, the prongs 84,85 and 86 are-spaced 120 apart about the axis of the-center pin :28. The

prong '85 fits snuglyagainst oneside of the center pin '28, i

and it is properly dished out for such purpose. The

prong 86 fits snugly against the rim of the tube 30, and this prong is similarly dished out to obtain a snug "fit-x The prong 84 is positioned against the inside of the rim 7 of the shank 18, and it is suitably curved on its outer side to conform to 'the'curvature of the shank 18.

When molten plastic is forced into the spruehole-60 (Fig. 3) in the mold-57, it fills the space between-thetube 30 and the shank 18-upto the bushing-40to' form1 the spacer 54. ,The space between the center pin 28 and v the tube 30 becomes filled up :to'a small annularshoulder:

92 located on the center pin 28, thereby forming the a spacer '55 :(Figs. 7 and 9). The annular shoulder 92 is:

engaged by the mold sections "64-64 to -prevent the center pin from-moving longitudinally in'the aperture 70,- .1

and to seal the molten plastic within this end :of the mold member 57.

The injected plastic also fills a plurality of helical. grooves 94-94 formed on an intermediate portion of 2 the centerpin 28, thereby forming corresponding threads on the inner periphery of the spacer 55, which bond the 7 center pin 28 to the 'spacer 55 in'the completed plug 10.

The washer 34 and the bronze ring 36 are also bonded to this body of molded plastic.

After the injection molding operation has been performed in the mold 57, the washer 38 and the brass tip 26 are placed on the center pin 28 and the resulting partially molded portion of the plug then has the appearance illustrated in Figs. 6 and 7. The partially completed portion of the plug 10 is then placed in a profiling machine of known type to produce the ball contact 14 and the ring contact 16, in the manner previously described.

The next step in the manufacture of the plug 10 involves the formation of a cylindrical shell 98 of plastic molded around adjacent ends of the plug 10 and the cordage 12. This operation is performed in a mold 100 (Fig. 8) having a sprue hole 102 which leads to a mold cavity 104 in the interior of the mold 100. Before the plug is placed in this mold, the tangs 5050 are inserted into the sockets 51, 52 and 53 as shown in Figs. 8 and 9.

The plug 10 is provided with an annular shoulder 106 located on the cylindrical shank 18 near the midpoint thereof. The shoulder 106 functions as a stop when the right hand end of the plug 10, as viewed in Fig. l, is

inserted into the jack on a telephone switchboard. The

molded shell 98 covers the the end of the cordage 12, of the shank 18 up to the joint between the plug 10 and as well as the adjacent portion shoulder 106. In addition, the cordage 12 is encased by the shell 98 for a distance approximately equal to the amount of the shank 18 of the plug 10 that is covered by molded plastic. The exposed portions of the conductors 43, 44 and 45, as well as the metallic bands 46-46 are completely enveloped by the molded shell 98. The shell 98 becomes an integral portion of the main body of the plug 10, and also functions as a hand grip for operators at the telephone switchboard. The end of the cordage 12 is embedded firmly in the molded shell 98, and there is no tendency for the plug 10 to become detached therefrom.

Among the plastics which may be used in the manufacture of cords embodying the invention are thermoplastics, such as nylon, polystyrene, polyethylene, and polymerized methyl methacrylate. Of these thermoplastics, nylon is preferred. In view of the brittle nature of pure polystyrene, it may be advisable to incorporate plasticizers or to employ copolymers of styrene with other synthetic resins. In the case of nylon, the high molecular weight copolymers derived from hexamethylenediamine and adipic acid are particularly useful. These thermoplastics exhibit toughness, impact resistance, light weight, ease of molding, good insulating properties, and dimensional stability over a wide range of temperatures, which properties make them outstandingly valuable in the manufacture of telephone cords. They are readily available in the form of molding powders in the commercial chemical market, and in this form they may be injected into molds in accordance with established procedures. Specific details of these procedures are readily obtainable from suppliers of such molding powders.

As a matter of convenience, the invention has been illustrated and described with reference to the specific construction of a cord designed for making connections in a three-conductor system. However, the principles of the invention are equally applicable in the construction of cords for two-conductor systems, as well as cords designed for systems employing more than three conductors. Furthermore, the construction of other component parts of the cord may be varied without departing from the spirit and scope of the invention.

What is claimed is:

1. The method of making electrical connection plugs and attaching them to an end of a cord having a plurality of insulated conductors therein, which comprises mount;

6 ing a conductive tube on a conductive center pin and within a conductive tube shank of a plug body in concentric spaced relationship thereby partially assembling a plug body, placing the subassembly within a mold having a plurality of arcuate shaped projections having a common radial center and being spaced from the radial center varying distances, said mold having a configuration designed to form in the interior of the plug body a mass of plastic material having a plurality of spaced arcuate sockets formed by said arcuate projections and adjacent to the shank, the tube and the center pin and having a common radial center with the radial center of said projections, the shank, the tube and the center pin, injecting plastic material into the mold to form said mass and said sockets, placing metallic terminals at the end of said cord, inserting the terminals into the arcuate sockets in frictional engagement with said shank, said tube and said center pin, respectively, to make individual electrical connections therewith, and molding plastic into a shell encasing the conductors at the end of the cord and the adjacent portions of the cord and of the plug body.

2. A connection cord including a length of Cordage having a plurality of individually insulated conductors therein, one end of said length of cordage being attached to a telephone plug including at least one conductive tube mounted concentrically in spaced relationship over a conductive center pin having a contact ball formed at one end thereof, the improvement which comprises a mass of molded plastic in situ individually insulating the center pin and each conductive tube and holding them in concentric spaced relationship, said mass of molded plastic having an arcuate-shaped socket adjacent to the center pin and each conductive tube, radial center and'being spaced from the radial center at varying distances, and'a plurality of metal terminals at the end of said cord positioned individually in the arcuate-shaped sockets in frictional engagement and electrical contact with the center pin and each of said tubes.

3. A connection cord including a length of cordage having a plurality of individually insulated conductors therein, one end of said length of cordage being attached to a telephone plug including at least one conductive tube mounted concentrically in spaced relationship over a conductive center pin having a contact ball formed at one end thereof, the improvement which comprises a mass of molded plastic in situ individually insulating the center pin and each conductive tube and holding them in concentric spaced relationship, said mass of molded plastic having an arcuate-shaped socket adjacent to the center pin and each conductive tube, the sockets having a common radial center and being spaced from the radial center at varying distances, a plurality of metal terminals at the end of said cord positioned individually in the arcuate-shaped sockets in frictional engagement and electrical contact with the center pin and each conductive tube, and a shell of molded plastic enveloping the terminals, the conductors at the end of the length of cordage, and the adjacent portions of the cord and of the body of the telephone plug.

References Cited in the file of this patent UNITED STATES PATENTS 2,399,836 Taylor May '7, 1946 2,444,997 Lovesey July 13, 1948 r 2,632,788 Ustin Mar. 24, 1953 2,657,369 Ziemianin Oct. 27, 1953 FOREIGN PATENTS 745,017 France Jan. 31, 1933 the sockets having a common

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