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US2480843A - Locking plug and jack - Google Patents

Locking plug and jack Download PDF


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US2480843A US547748A US2480843A US 2480843 A US2480843 A US 2480843A US 547748 A US547748 A US 547748A US 2480843 A US2480843 A US 2480843A
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Alvin C Follmer
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Alvin C Follmer
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    • H01R24/00Two-part coupling devices, or either of their cooperating parts, characterised by their overall structure
    • H01R24/58Contacts spaced along longitudinal axis of engagement
    • H01R2103/00Two poles


Sept. 6, 1949. A. c. FOLLMER LOQKING PLU G AND JACK 2 Sheets-Sheet 1 Filed Jan. 30', 1948 'l l n Sept. 6, 1949.

A. C. FOL LMER LOCKING PLUG AND JACK Filed Jan. 30, 1948 2 Sheets-Sheet 2 gn'ucnror Patented Sept. 6, 1949 UNITED STATES PATENT OFFICE 6 Claims. (o1. 173-332) (Granted under the act of March 3, 1883, as

"amended April 30, 1928; 370' O. G. 757) The invention described in the specification and claims may be 'manufa'cturedand used by or for the Government for governmental purposes, without the payment'to'me of any royalty thereon.

The invention relates to connectors for electrical conductors, and particularly to those of the plug-and-jack type, and it is particularly well suited to the production of telephone switchboard jacks and plugs and other receptacle and plug connections, especially in situations where rough usage, vibration, and shock may be expected. 'It' is especially an aim to present a plug and jack wherein the plug will be locked in the jack when inserted by the ordinary practice of insert; ing a plug longitudinally into a socket, but which may also be unlocked and withdrawn by the usual motion heretofore involved in grasping and withdrawing the ordinary plugs, without special manipulations otherwise.

It issought to present such a connector which will be useful in ceiling outlets of armored vehicles, and elsewhere, as well as at wall and floor outlets and portable apparatus, where head phones or other electrical units havetheir leads connected by inserted plugs.

The weight of cord and plug will often cause the dropping of a plug from'its' receptacle, especially where the latter is defective; and in floor and wall outlets where gravity is less apt to cause disconnection, a plug will often be withdrawn by swinging of the extension cord conductor, or-by a person brushing thereagainst.

It is a highly important object to embody a plug and socket construction which will be de pendably certain to release when the plug itself is purposely grasped and pulled with moderate efiort, and at the same time to present an article readily adaptable to manufacture at low cost in a rugged form which will be free in large degree from liability of derangement incident to varied uses to be expected, especially in military operations and in portable installations.

It is an advantage of the invention that it makes possible the embodiment of a plug ofextremely small size suitable for use in small tele-' phone exchanges, and generally in telephone 'or telegraph outlets, in which the improved jack element may be substituted for a'conventionaljack with standard mounting.

' It is a further purpose to enable the attach-' and the product will correspond closely as to manipulation, and space requirements to prior equipment.

' It is an advantage that the device will ordinarily, in its safest form, not permit withdrawal cf the plug bypumng on the cord leading thereto, but is adapte'd'topermit such use in case of need therefor. It is important that the plug shall utilize the prior practice of'th'e' insulated tip contact at its extremity, and a side contact sleeve as its stem portion so that noc'ompl'exity in circuit hook-ups shall'be'introduc'e'd.

Amon other objects of the invention it is sought 'to present' a plug which may be readily attached 'to lead 'cords'by the ordinary servicem'an, lineman, or erection electrician, without liability of confusion'due to complications in the invention; the parts of'which'may'be'readily re placed at the job, -without requiring s ecial tools ornrietl'iods;

Additional objects, advantages and features of inventionre'side in 'thecons'truction, arrangement and combination "of parts involved in the embodiment of theinventionas will appear from the following "description and accompanying 'drawin'gs, wherein Figure l is a vertical section of an exchange panel or the like with my plug'installed, the inner end of the plug being in elevation'and the outer end. portionp'a'rtly in section;

Figure 2' is a horizontal diametrical section through the plug cnthe line 33 of Figure 1,

' Figure 3 is a similar view with the lock released;

Figure 4 is a plan'of 'th'e'blank for the lock contact;

Figure 5 is a plan of the lever dog;

Figure 6 is a cross section on the line 6-6 of Fig. 1; i 1 Figure 7 is a fragmentary section of the handle of theplug showing a modified use;

There is illustrated conventionally a portion of a switchboard panel'lm'which in the present instance is assumed to be of conducting material to serve 'as'a ground, although'other mountings for jacks including insulating materials may be employed as required.

"Setthroughan'aperture in this panel there is a jack, socket, or receptacle l l representing an individual'telephone outlet or other electrical circuit outlet. This receptacle consists in this instance of a metal bushing 12, externally threaded to'one extremity inserted through the'panel, and having an integral flange l3 at its forward or outer extremity against the front of the 'panel. If found'more' convenient inassembly and servicing, however, the threaded end may be extended toward the front. A look nut I4 is engaged on the bushing against the rear side of the panel and against this nut there is set an insulating washer l5, a ring terminal 16, a second insulating washer 15, a lock washer, and an assembly nut l1, clamping the last-named 'parts'against the lock nut 14.

The ring terminal I6 is stamped from spring laid snugly against the flat 29 of the assembly block 28. The lug is apertured to receive assembly 's'crews3l by'which it isfastened to the assembly block, locking the latter firmly against longitudinal or rotative relative movement in the case sheet metal, and consists of a simple annular -'10 21. One of the binding screws 30 is also engaged blank from opposite sides of which integral contact and lock spring arms l8 are extended radially with uniform width in this particular" instance. Intermediately of the basesoii the arms on the in this lug; attaching the lead-in 32 which completes the circuit to the case 21.

The block'28 stops within the forward limit of sliding movement of the handle 26 on the case outer edge of the ring a short tongue i flf is ex- 1 :5 2'il as'rn'ay' b'seen in Figure 1, and is bored contended therefrom suitable for the soldering-of a lead wire thereto; it is inclinedgawayfrom the panel for convenient access." .Thei'arr'ns' [8 are curved inwardly at their bases on a short radius, and extended thence as convergentrectilinear arms symmetrically arranged in relation to the axis of the jack andnearly or quite contacting at their outer parts in their normal free forzn. Thelengtl -of thesearms in their rectilinear parts 11s,.. u th t co reree t anemia an which may approximate sixty degrees,'a lthough it mayvaryin either direction to a considerable I exte w o e i e a afis t ne h immtion of the: device;. 'Ifhe smaller the angle the --easier nay my plug be inserted, as will appear. Near their extremities, the arms l8are bent out- .ward atright angles, to form short shoulders 2U, and again bent in the s ame direction as the re ti r parts, u st n ie r at i an the ho der .2 t prm stq sri w l w l engage the head of a tip contact as will-be later .shown, to prevent closing of the arms toward each other farther than necessary in locking function. The structure thus describedconstitutes the complete jack or receptacle. The parts and 2! on each arm IB-may be called clasp members, since they will clasp the head at theend of an inserted plug conductor, as will appear. The plug of this invention in the instant embodiment, comprises two main parts relatively movable longitudinally, one on the other, the-one being an outer tubular two-piece sleeve or handle including a knob, of insulatingmaterial, while the other part, therewithin, is a composite member comprising a-cylindricaltubular case 2'! of conducting material (its external diameter being such that it may fit slidably in the bushing I2 and serve as a conductor-thereto for one'side of a circuit), and a release or unlocking plunger of insulating 'materiaL'to be described. 1 H

The case 21 extends for nearly the whole length of the plug and has fixed in its outer end por- -tion (which may be considered its rear part) an assembly block 28 of insulating material, the forward part of which is fitted snugly in the case, and the major rear portion of which, excepting theextremity; is semicircular in section, presenta ing a fiat part 29, affording a space at one side of the block within the plug to accommodate binding and assembly screws-"30" and 31; By a number of the latter'the block is secured in the case 21,-and circuit wire leads 32 from a cord 33 are'fastened by the'screws 30. The extreme end portion of the block is formed with a split semiannulus 34 concentric with the block 28 and serving as a protective bushing for the lead-in wires. The gap 35 in this semi-annulus allows rapid placing of the lead-in-wires in the device without inserting them through the end of the block 28.

centrically to receive snugly through its forward part and partly across the flat 29 a center con- *ductorbar-or, stem 31 of a tip contact 38 fixed thereon and located a suiiicient distance forward- 20 ly ofthe case 2'! to pass between and slightly beyond the shoulders 20, but not beyond the stops 2lfofthe 'jack'when the"for-ward art of the handle 25 engages the bushing l2. The shoulder 20 then engages inwardly of andbehind therim of the tip contact. The latter is a circular mushroom-shaped head formed on orattached to the stem, the rear side 39 of the tip toward the right,Figure,"1I being'conical and its elements extended at an acute angle to a plane normal to the 30 stem and defined by a sharp-edged rim 40 on the tip formed by the junction of the rear and forward surfaces of the tip. The forward part 4| ofvthe tip has a .major conical base part; the conicalelements ofwhich are at a much greater 35. angle "to the planeof the rim than'th os e of the side. 39,.and converge forwardly. at an 'angIeLincreasing toward the axis of the tip, .sothat a 'rounded apex is formed thereon, substantially as shown. Other shapessuitable for the func- =1o tion of this part may be utilized.

The, rear end of the stem 31 extends across the hat 29 as before stated, and is flattened in this part,s0, as to. receive assembly screws}! engaged therethrough and in the block=28, to hold the stem in rigid relation with the block andlcase '21, and a binding. screw 30. is also provided on this flat, holding onelead wire 32 of the circuit connections to theplug.

Fitted slidably in the forward end portion of the case 21, there is a plunger 42, axially bored to'slide along the stem 31 and having an enlarged frusto-spherical concentric cam head 43, the base of which is planiform and engages the extremity of the case 21 when the plunger is at its rear 5 orretracted limit of movement nearly abutting the assembly block 28. The plunger is slidable i forwardly we position with its forward extremity very close to or at the" rear side of the tip 38, 'and'is of such radius that in its forwardmost 0 position, it is engaged with and holds the arms l8 ofthe ring terminal apart and clear of the rim 40 of the tip 38', permitting the plug to be freely withdrawn from the jack.

The means for operating the plunger 42 comprises two or more lever dogs 44, which are set through transverse diametrically opposite slots 45 formed in the case 21 a short distance forwardly I of the assembly block 28, the inner ends of these dogs being set in a circumferential'channel 46 in the periphery of the plunger, and the outer ends of the dogs are in a channel 41 formed on the interior of the two-piece handle. This channel is formed in a metal ferrulesleeve 48,- interiorly threaded at its rear end and screwed on to a corresponding exteriorly threaded sleeve part snet of t does 9 Just ffieieii t'e eraii si n? wh sqni a surfas s extend d yersen ly of the knob 422 hases! in the tarsa iiess hds in form n ar as masheah s is t a at the bhanne 4-6 nd ea h shanne as is s. a a s a re annular g oov 99 Q I Q h h 21 s and s i h l wide than the i iieknsss h a $195 e w mile eih pi s ash ea h t a wh n a i n d th sash e her 11. a stamps p an mrma it the ax o the plus the r ia di ast b e n he b t ens li h re a th th eg s is be arran ed a r gh ngl s to th z j 9 th plu with ut binding betw e th handle and n er asse reen; I? s o sli h d h and here ara lel ani qrm sides e miiis the reminder o the ch ls 46 41. The s t 5 are s msi nt tent 1. udi a l 9 th Pl sh? allo t e does t lie ns medlo silidii n e e r s lln substantially a sh wn in F u e The lsn th oi the do s is film d .50 as o mpin e on op i acin sides I e pec v sleev s i case the hand e of th us s u d hems ed qnsitud na ly o th case 21 oppo i e th direction of incl nation or the dogs. n sh mqrement o the hand eas last rer edl a P e sure 9 the hand ooll a ai st the ends of the dogs, causes them to pivot in the slots as fulcrum s, and to operate as levers against the side of the groove in the plunger, and so move theplungerlongitudinally in the plug. Wh n the lus t p is Presented n he ack-h at the "bushing I2,itenter's 'n e y ther'ein'hnd may be moved longitudinally therethrough until-j th tip 38engage's 'the arms"-'|a.*" 1r it should happen that at this time the handle islat its outermost position on the case 2] 0i the plug "(the plunger being then" forward) opposition of an he andle the sk s will mm dia e releas the oc .ne pa s, and withdraw t e D u The 'liandle knot} 26 inturnedatits'onter ns-s i e 'e ran the e a era aafilossiil s te sa t e 1 1 pgi 'has a opening throu h which the cord 33 may freely sli'de,"s0 thatnorrnally'no nu l on 'the'c'ord'will tend to i ita s sn s s elease im lus- "However, in case of need, the space between the outer end of the 1310 1 and the assemblyblpck zzifinay be :sufii cient' 't permitknotting ofthe cord within the h andle; substantially as 'fshown in Figure 8, i whicn'case' a pull on the cord n s n eire esse ape ra ip' Q h'e a d s nd s nus and withdrawal of the lug. Thisiha'nner of use will be ben cial i time m casual wit d awa of the plug by gravity thenfo'rces less than that required operate the plunger, Will go e mit disconnection by a good pullon the cord. snsh th t n ei her po tion th r end pesi- It assures" it? and dependable connection in many'situat onswhere loose plug would represent a liability of'accident'or circuit interruption Wh e h im ahs'e o e ed b th s in arms I8 to f "ar'd o' protractile movement of the n er wi l so pas ex an t-Wa eF lpdenjt a'l fullon tw'ard movement of the handle 26, i a f 'm de ira l t in e a s r 50 b el wfill tner' rwagq end of the tubular part of the handle '25 and the dogs 94. 'In the instance illustrated a single 'protract'ile' helical wire spring egsurrounds the case 21 within the rear part of the ferrule ,Qwhioh islarger than the case to t e ext n if the t i hhf 'Sd. the thr aded end of'the handle knob; This spring tends to thrust the does rwar at th ir outer arts; wh w hold theha d o 'wsrd 'van Pre ent i s 1? a 'r' li a iqn o t lea t prevent its loose msiv mentiwhich is its pr c al Pur osethe arms l8 toprbgress' of'the plunger will tend flfl T'J U I QQYF Q FIiDd i1 Pa!- to press the plunger baclg, and continued manual P 99 2 Y 3' spec arm 9? in en i n which pressure will cause the handle to moveforvvard est emb dim n a 91 known to me, it

on the case 27 operating the dog levers so as to retract the plunger.

It is significant that upon withdrawal of the plug from the jack by simple conventional grasping and pulling of the plug, protraction operation of the plunger will be caused, its forward movement resulting from leverage of the dogs due to outward movement of the handle, and causing separation of the ends of the arms I8 until the shoulders 20 clear the rim 40 of the tip 38 and permit easy withdrawal of the latter. The engagement of these shoulders by the tip theretofore will prevent rearward movement of the tip and case 21, so that the described operation of the plunger by the handle is assured.

It will be seen from the foregoing that, due to the lightness of the handle 26, a moderate strength in the arms l8 will be sufiicient to prevent withdrawal of the plug under very severe shocks and high inertia forces due to movements of any structure in which the jack and plug are installed. The angle at which the shoulders 20 are set with respect to the axis of the plug, and the fact that the corresponding angle of the rear face 39 of the tip 38 is substantially the same, causes these parts to coact as a positive lock, preventing withdrawal of the plug as long as the arms are engaged with the tip, unless the arms themselves collapse. This safeguards the plug against accidental withdrawal even if a person or object should become entangled with the cord in ordinary movements. Yet a very moderate pull ture, arrangement and combination of parts, substitution of materials and equivalents, mechanical or otherwise, may be made without departing from the spirit of the invention set forth in the appended claims, wherein I claim:

1. An electrical coupling comprising a receptacle having a plug-receiving passage therein, inwardly convergent spring members at the inner end of the passage having a normal minimum spacing at their proximal parts, a plug having a head thereon transversely larger than said spacing and adapted to pass and receive the said proximal parts in looking engagement therebehind when the plug is inserted in the receptacle, a reciprocable cam member on the plug inwardly of said head movable toward and from the head and constructed to cam said spring members apart at the proximal limit of movement of the cam, a longitudinally slidable handle surround- 5 ing the outer part of the plug, and motion rethe same inwardly of the head to prevent withdrawal To f the plug, a eohtn'aiserufisrsli'dable aroundsaid conductor, to andirom a position closely adjacent said head, and;having a lateral cam part thereon arranged to engage and cam apart said plug locking parts iarther than the periphery of said'head when said head is advanced beyond the plug locking parts'and when said plunger is at the corresponding limitjof its slidable movement, a handlearound and longitudinally slidableonthe opposite end 'portion of theplug, lever devices of the first'order pivotally mounted in the plug on an axis transverse to the longitudinal dimension of the plug each having one end engag with the handle and the other end engagedwiththe plunger, whereby putwa-rd movement oi the handle will movethe cam into release engagement with said contacts.

, 3. The structur of claim 2 wherein saidpiug includes a tubular case, said plunger beingslidably fitted therein, said handle including a concentric tubular part slidably fitted exteriorly on the case in lapped relation with the plunger when the latter is retracted, said plunger havi g an external circumscribing groove therearound in its lapped part, said handle having an internal perimetral groove in its lapped part positioned to lie in a plane with the first groove when the handle and plunger are at intermediate positions, said case having at least one slot therethrough in said plane and a lever dog set loosely in said slot having end parts extended into respective said grooves, said grooves being shaped and having divergent sides positioned to allow inclination of the lever dog under relative reciprocation of handle and plunger. A

4. The structure of claim 3 wherein said axial conductor and plunger extend beyond the end of the case, said plunger having an annular cam thereon operable between the case andcsaidhead and of greater diameter than said head, and having a retracted position spaced inwardly from the head and clear of said spring contacts. 7

5. alocking electi'icalplug" and jack comprising areceptaclehaving opposed resilient clasp memterse plug notched'fcn the side insertable between said clasp members to receive'the latterfin the notch, an aii'a'llysflidable release member on the plug mos/stamens froma release position adjacent said notli' constructed to engaga'and separate the claspjnembers from en a ement in said notch when the release member is at said position, a handle slidable over the outer end portions of the'plug distant 'from the notched part, and amotion reversing connection between the handle and said release member.

6. The structure of claim 5 inwhich the motion reversing connection comprises a body sleeve, said release member being slidable therein, said han- "dle being withbut'andislidable along the sleeve, at least one slot formed in the sleeve, an internal recess formed in the handle movable across the slot in reciprocation of the handle and an external recess formed in the release member I movable past'the slot in movementof the release member from and to release position in relation to the clasp members, anda lever dog of elongated form set loosely in the slot with its end portions in respective said recesses for oscillation of the lever by reciprocation of the handle, and for reciprocatio'n of 'the release member by the inner end of the lever.


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

UNITEDv STATES PATENTS Number Name Date 2,423,250 Modrey July 1, 1947 FOREIGN PATENTS

US2480843A 1948-01-30 1948-01-30 Locking plug and jack Expired - Lifetime US2480843A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4828505A (en) * 1988-02-26 1989-05-09 Electrix, Inc. Electrical connection for track lighting
US5090921A (en) * 1990-03-22 1992-02-25 Lumiance B.V. Connecting means

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB243571A (en) * 1925-02-06 1925-12-03 Stanton Wilding Cole A new or improved electric terminal connection
US2423250A (en) * 1942-05-27 1947-07-01 Modrey Patents Corp Electrical plug and socket spring contact or connector

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB243571A (en) * 1925-02-06 1925-12-03 Stanton Wilding Cole A new or improved electric terminal connection
US2423250A (en) * 1942-05-27 1947-07-01 Modrey Patents Corp Electrical plug and socket spring contact or connector

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4828505A (en) * 1988-02-26 1989-05-09 Electrix, Inc. Electrical connection for track lighting
US5090921A (en) * 1990-03-22 1992-02-25 Lumiance B.V. Connecting means

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