US2734177A - gilbert - Google Patents

Description

Feb. 7, 1956 c. E. GILBERT &

ELECTRIC CONNECTOR APPARATUS 2 Sheets-Sheet l Filed Oct. l6, 1951 I TU/QJUOT.- C'arCeSE GLer p HOTJI 25,

Feb. 7, 1956 c. E. GILBERT ELECTRIC CONNECTOR APPARATUS 2 Sheets-Sheet 2 Filed Oct. 16, 1951 F .TO.

United tates Parent ELECTRIC CONNECTOR APPARATUS Charles E. Gilbert, New York, N. Y.; Margaret Doris Gilbert, Norman Coates, and The Chase National Bank of the City of New York, executors of said Charles E. Gilbert, deceased Application October 16, 1951, Serial No. 251,523

8 Claims. (Cl. 339-97) The present invention relates to improvements in electrc plug constructions and assemblies of electric plugs with conductor cords.

In the manufacture of conductor cord and plug assemblies for use with electric appliances, lamps or the like, it is an important consideration to provide for simple fabrication of the various parts of the plug and simple assembly of the plug with the conductor cord. In the past various methods of assembly of the necessary contact blades in the plug body and of making contact between the contact blades and the conductor cord have been suggested and used. Many of these methods, however, are commercially impracticable because of the multiplicity of steps required.

According to the present invention an especially simple Construction of plug body and contact blades is provided, which permits assembly with -a conductor cord with a minimum of difiiculty and cost. In particular, according to one form of the invention the plug body and contact blades are formed to permit assembly with a conductor cord without requiring any stripping or baring of the conductors of the cord. Not only does this facilitate assembly by reducing the number of steps required, but it also has the very important efiect of minimizingtthe possibility of accidental short circuits or stray contacts, since the conductors of the cord are not exposed either inside the plug body or outside the plug body. However, in some circumstances it may be desirable to provide increased contact between the cord conductors and the contact blades, which can be obtained by stripping the ends of the conductor cord for extended area contact with the contact blades. In such case the plug of the present invention is so arranged that all portions of the bared conductor are completely contained within the plug body leaving no possibility of accidental undesired electrical contact.

These and other objects and advantages of the present invention will become apparent from consideration of the following detailed description of preferred embodiments of the invention, taken in conjunction with the appended drawings, in which,

Figure 1 shows a longitudinal cross-sectional view of the plug and cord assembly according to one aspect of the present invention;

Figure 2 shows a longitudinal cross-sectional view of the plug body of Figure 1;

Figure 3 shows an end view of the plug body of Figures 1 and 2, from the cord entrance end;

Figure 4 shows the other end view of the plug body,

Figure 5 is a transverse longitudinal cross-sectional view of the plug body of Figures 1-4;

Figure 6 is a perpective view of a contact blade member for the plug assembly of Figure l;

Figures 7 and 8 are similar perspective views of modified forms of contact'blade;

Figure 9 is a longitudinal cross-sectional view of a modified plug and cord assembly;

F ice Figure 10 is a longitudinal cross-sectional view of the plug body of Figure 9;

Figure 11 is a longitudinal cross-sectional view taken transverse to Figure 10;

Fgures 12 and 13 are respective end views of the plug body of Figures 9 and 10;

Figure 14 is a perspective view of the contact blade member of Figure 9; and

Figure 15 is a similar perspective View of a modified form of contact blade.

Referring to Figures 1-6, there is shown a conductor cord 21 which may, for example, be a twin-conductor rubber-covered cord of conventional type. The cord 21 passes through an opening 22 in the plug body 23 and is therein assembled with a pair of identical contact blades 24 in the manner to be described.

As shown more clearly in Figures 2-5 the plug body 23 has a substantially rectangular or oval opening 22 extending therethrough and adapted to accommodate the cord 21. The plug body 23 is made to have a substantially rectangular cross-section with a pair of flat side walls 25, 26 and slightly curved end walls 27, 28. The body is tapered slightly from the narrower end shown in Figure 4 to the larger end shown in Figure 3, the conductor cord 21 extending into the larger end and the contact blades 24 projecting from the smaller end.

A cord-receiving channel 22 is formed centrally within the body 23 by means of a pair of internal walls 29 having generally cylindrical exterior surfaces which join and merge into the interior surfaces of the side walls 25 and 26. The channel 22 is then formed within these walls 29 and is provided with beveled edges as shown at 31 to prevent contact between the cord 21 and any sharp edges.

Extended transversely of the plug body 23 intermediate the ends thereof are a pair of partitions 33, 34 which divide the plug body 23 into two separate portions, except for the channel 22 running therethrough. The lower portion of the plug body as viewed in Figures 1 and 2 is the contact-blade-receiving portion. For the purpose of accommodating the contact blades, two opposed pairs of grooves 35 and 36, are formed adjacent the end wall 27 to take one contact blade, and two more pairs of grooves 37, 38 are forrned adjacent the other end wall 28 for the other contact blade. These grooves are separated from the interier surfaces 39 and 40 of these end walls 27 and 28 by sufficient distances to accommodate the individual insulated conductors of the cord.

As will be seen, each of the grooves 35, 36, 37 and 38 is of a width substantially equal to the thckness of one leg of the contact blade 24 to be inserted therein, Each of these blades 24 is adapted to be fabricated from strips or rolls of conductive sheet material by successive punching, stamping, shearing and bending, and, as is shown in Figure 6, has a pair of parallel contiguous legs 42 and 43 integrally joined at one end as at 44. Each of the legs 42, 43 is formed with stifienjng ribs 45, 46 stamped therein to add rigidity without increasing its weight or size substantially. At one end the legs 42 and 43 are provided with registering apertures 47 which serve in cooperation with mating projections on the plug receptacle contacts to act as detents for preventng inadvertent withdrawal of the plug. Each of the legs 42, 43 is provided with a pair of aligned shoulders 48 intermediate the ends thereof. As will be shown these shoulders are adapted to abut the bottom surface of the plug body 23 after assembly. The upper portions or free ends of the legs 42, 43 are accordingly of reduced width With respect to the lower or outer portions of these legs, this width being substantially equal to the separation between each pair of grooves 35, 36, 37, 33 of the plug body 23. These reduced portions are provided with protruding serrations 49, which are cut from the body of the leg, and

are bent ontward therefrom to form projecting teeth, as shown. These teeth 49 are adapted 'to permit ready insertion of the contact blades 24 into the plug body 23 with the edges of the legs 42, 43 siiding into the respective grooves 35,36, 37,2 8, but the projectingateeth thereafter prevent withdrawal of the contact bladeasince `upon attempted.withdrawal these teeth dig into the wallsof the grooves and resist withdrawal.

The .ends of the-lega 42., 43 areprovided with pairso points 51 and 52 respectively. As shown in Figure 6, points SZeXtend beyond points 51 and are coplanar with the leg 43, whereas points 51 protrnde at an angle with respectto the leg42, asseen most clearly in Fignre l, Upon assembly, these points Sii and 52, pierce the insulation of the cord conductors to make electrical contact between eachcondnctor anda respective contact blade. Preferably these points areplaced in pairsas shown, so as to assure that one or the other or both of the points of any one leg will make proper electrical contact with its cord conductor. However, where desired, a single point or alarger plnrality of points may also be used.

ln assembly, the cord 21 is passed through the opening 22 from the larger end of the plug body. The two conductors, while still insulated, are separated and each is caused to extend over an end wall 27 or 2 of the plug body 23 at the bottom end thereoiby a predetermined small amount. Then the two contact blades 24 are inserted in their respective grooves 35, 2-6, 3-7, 38. so doing, thepoints 52 and 51 en age the insulated cord, pierce the insulation to make electrical contact with the condnctor within it, and simultaneonsiy force` the ends the conductor cord back into the plug body until the contact blades are firmly seated in their grooves with its points adjacent the partitions 33, ?i t and the shonlders 4-3 engaging the rim of the grooves. The bent points 51 serve to assist in more readily inserting the contact blades 24 by helping retain the conductor cord end against the side wall 27 or 28 of the body. At the same time it provides further electrical contact in addition to the contact provided by the points %2. Also, both points 51 and 52 serve to retain the cord conduetor against any outward pull.

For the purpose of providing a strain relief so-that any pnll on the` condnctor cord will not. be transmitted to the contact blade, points, eachof the partitions 33, 3 thas a downwardly extending projection 53 over which each cordconductor is bent with a reverse or &bend; in this Way any pnll on. the conductor cord is converted into a force tending to maintain the contact bladepeints iri-electrical ccntactwith the cord conductor, rather than attempting to sever such electrical contact.

Figures 7 and 8 show modifications of the form of contact blade which may be used where desired er eppropriate. in Figore 7 the points Sila are copianar with the leg 42; otherwise, Figure 7 is the same as Fignre 6. Figure 8 offers a further modification with respect to Figur-e 7 in that the leg 42:: is here made of a length equal to that of leg 43. lt Will be understood that while the form of contact blade as shown in Figure 6 is considered preferable, the other types of blade may optionaily be used where desired.

Fignres 944 illustrate a similar plug and cord arrangement adapted for use with asbestos covered cords, such as are used with appliances consuming suitable current, such as electric heaters, irons, broilers or the like. In this form of the invention, the central channel 22a is made of circular cross section to conform to the or ter shape of the conductor cord Zi::. Fnrthermore, the ends til, 62 of the condnctor cord are bared and are jammed between the body side walls 27, 28 and the contact blades 2411 so as to provide an extended surface of contact between the bared ends 61 and the blades 2441, as is desirable where large Currents occnr. Since the condncters are bared at their ends, the insulation piercng points 51 and 52 are no longer necessary, and the contact blades are of the form shown in Figure 14 being similar to those of Fgure 6 with the omission of the pointed ends 51, 52. I-Iowever, the leg 42 is still shorter than the leg 43 and, as shown in Figure 9, this assures good contact between the contact blades 2461 and the conductors at more than a single point. The plug body 230 is provided with similar grooves 35, 36, 37, 33'for receiving the pairs of legs of the contact blades. Space is provided between the outermost grooves 35 and 38 and the inncr surfaces of the side walls 27 and 28 to accommodate the barcd conductor ends 61. In order to further resist-pulling out of the conductor cord, the recess for each condnctor end, such as 61, is formed with a shoulder eSabout which the conductor is bent providing further resistance to pulling out. It Will be seen that strain relief ridges 53 are provided as in Figures 1 and 2.

Where desired the legs 42 and 43 of the contact blade of Figure 14 might be made of equal length as shown in Pigure 15.

For the purpose of'permitting easy manip iationcf the plug during insertion and extraction, the plng body side Walls are made tapered and a rim' '71 is formed. around the upper edge of the plug body in both forms of the invention especially at the side walls thereof to provide a finger grip for` withdrawing the plug from a receptacle.

It will readily be apparent that the fabrication and assembly of the plugs of the present invention are extremely simple. The plug bodiescanreadily be made-by molding from a therrnoplastic or therno-setting insulating material, such as Bakelite or thelike, and can be manufactured in large quantities by the use, of automaticmolding machines. cated in multiple stage stampjng machines, where the successive stages serve to punch, stamp, cntandbend the blades to the desired final configuration. Preferably the blades are manufactnred from continuons rolls otcondnctive material and are allowed to remain a continuous strip, each blade being joined to a succeeding blade by a narrow isthmus of material not cut away. The design of the plug is readily adapted to assembly of the plug with a conductor cord by automatic nachinery'by which plug bodies may be continuously fed to an Operating positionfrom a hopper. Two rclls of connected contact blades can supply the pair of contact blades at the proper position. After the conductor cord is inserted through the cord receiving channel; 22 or 2251, bya simple translational, motion the contact blades can besevered from their strips` or rolls and forced into position, This completes the entire assembly. In the case-of the nnstripped conductor cord, provision may bemade for` automatically separating the twoconductors while still insnlated, and

placing them in the proper positionrelative to the; contact blade receiving grooves immediately prior to insertien of the grooves, so that all phases of the assembly operation, except possibly the insertion of thecOnduct r-Cord into-its channel 22 or 22a, can be performedautomatically. In the case of thestripped conductor form shown in Figure 9, the conductors of the cord can be readily stripped by an automatic stripper before insertion into the cord-receivingcharnel, whereuponthe machine would separate the conductors, position them properly 'relative to the blade-receiving grooves just priorto inserting the blades into grooves to jam thebared conductor ends` into position making contact.

Accordinglyby the present invention aplugand cord assembly has been provided. whichisextremely easy to fabricate in large quantities by automatic machinery and which can be assembled speedily and nearly .automatically, the' assembly operation se'ving simultaneously to place the contact blades in position and to make contact with-therespective conductors ofjthe cord.

It will be understood that many, apparently Widely varying modifications of the present, invention will be readily apparent to those skilled in the art, without, departing from the spirit` of" the 'present nyention. Accordingly,

The contact blades can he easily fabrithe above description is to be considered as illustrative only and is not to be taken in a limiting sense, the inven tion being defined solely by the appended claims.

What is claimed is:

l. An electric plug and cord combination comprsing a hollow plug body having side walls and end walls, a pair of identical contact blades therein, and a two-conductor cord having its two condnctors respectively in electrical contact with said blades, said body being formed of rigid insulating material, and having two hollow sections, one of said sections having means defining a cord-receving bore extendng centrally therethrough and the other of said sections having blade receiving means, said two sections being separated by a pair of transverse partitions connecting said bore-definng means with the walls of said body, said blade receiving means comprising means defining two pairs of blade-receving grooves in the side walls of said body on each side of said bore and extending substantially parallel therewith, the pair of said grooves Closer to the body end walls being spaced therefrom by a distance adapted to receive one conductor of said cord; each of said contact blades being formed of a folded planar strip of conductve material forming two parallel planar legs, each leg being adapted to engage a respective pair of said grooves and having sharp tongues cut and bent outwardly from the plane thereof and engaging the side walls of said grooves for preventing withdrawal of said blade from said grooves after insertion thereof said conductor cord extending into said cord-receiving bore and having its two conductors spread, with each conductor positioned between a body end wall and the adjacent leg of its respective contact blade.

2. A combinaton as in claim 1, wherein each of said contact blade legs terminates in pointed insulation-piercing prongs adapted to make contact with its conductor through the insnlation thereof.

3. A combinaton as in claim 2, wherein said legs are of different length, and the prongs on the leg remote from its adjacent body side wall are bent toward its side wall.

4. A contact blade for an electn'c plug comprising a folded flat stn'p of conductive material formng two parallel substantially contiguous legs, each leg having a plurality of short transverse cuts at each edge thereof, with the material bordering said cuts on one side thereof bent outwardly of the planes of said legs.

5. A blade as in claim 4, wherein said legs terminate in pointed insulation-percing prongs. I

6. A blade as in claim 5 wherein the prongs of only one of said legs are bent outwardly from the plane thereof.

7. A blade as in claim 6 wherein said bent-prong leg is shorter than the other leg.

8. A blade as in claim 4, wherein said legs are of unequal length.

References Cited in the file of this'patent UNITED STATES PATENTS 2,260,365 Charnoy Oct. 28, 1941 2,422,393 Bryant June 17, 1947 2,495,623 Benander Jan. 24, 1950 2,521,298 Ludwig Sept. 5, 1950 2,593,743 Galvao Apr. 22, 1952

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