US2913697A - Electric lamp base - Google Patents

Description

NOV. 17,1959 I w, c s ETAL- 2,913,697

ELECTRIC LAMP BASE Filed June 19, 1956 INVENTOM 6: M CflPL/S d 2,913,697 t ELECTRIC BASE 1 George W. Caplis, Preakuess, and HarryFr Fox, J11,

, Macopin, N.J., assignors to Westinghouse Electric Cor,-

poration, Vania 5 Application June 19, 1956,SerialN0. 592,425 j 5 Claims. (c 339-146 East Pittsburgh, Pa., a corporation of Pennsyl- This invention relates to electric .lampbasesand, more particularly, to bases for incandescent lamps requiring a plurality of contacts on the'end surface ofthe base, such as three-light lamps orthe like. v

As presently manufactured, electric lamp bases consist generally of a cylindrical metal shell formed with laterally extending threads or positioning pins and an end aperture or bottom piercing having a filling of insulating material therein. Electrical connection with the lamp lead-in conductors and filament is effected by embedding metal eyelets in the filling or insulator cap and soldering or other- Wise joining the exterior end portions of thelconductors to the eyelets to form protruding contact surfaces. In the screw-type bases customarily. employed on singlefilament incandescent lamps for general, householduse, only one centrally-disposed eyelet is employed inasmuch as one of the conductors is connected .to the base shell to form a so-called side-contact. such as the three-light lamp, on the other hand, require at least two contacting surfaces'on the insulator cap in addition to the side-contact in order to permit separate or multiple operation of the filaments. This requirement is usually met by providing a center-contact-in. the form of a ring which is mounted on the insulator. cap 'in coaxial alignment with a centrally-disposed eyelet or end contact.

Hereto-fore, the insulator cap was formed 'as an. integral part of the base by heating the insulating ma'terial,:.us'ually glass, to plasticityand molding it into thebottompiercing of the base shell in an operation known as glassingf This method of fabrication has proven objectionableinasmuch astheintense heat liberated by the glass oxidized themetal-parts and necessitated a cleaning 'or bright dip operation which was both troublesome and costly but essential in view of the soldering difficultiesiand unsightly appearance which would otherwise result. Furthermore, and more significantly, any reduction in the thickness of theshell beyond a certain limit in an effort to conserve base material would precipitate a defect known as a melt whereby the concentration of heat in thedome of the shell during the glassing operation would become sufficient to melt the light gauge metal or defo'rmit in such a manner that the insulation dimensions are decre'ased thus rendering the base unfit for user The adoption of aluminumas the standard base material inplace of brass occasioned by thehighwost and critical listingof the latter has increased the disadvantages of conventional type base structuresand fabricating methods inasmuch as aluminumdoes not lend itselfto highspeed lari1p-making machines now employed in the industry. 7

Aluminum also has a lower'melting point than brass which property tends to promote the formation of melts during the glassing operation. In order to overcome this problem and improve the automatic feeding of the metal base parts into a molding device, three-light lamp bases employing thermosetting plastic material in place of glass and an elongated center-contact plate [with straight sides and curved ends instead of the circular contact ring previously used haverecently been developed Multiple-filament lamp's,

conventional soldering thereby necessitating the"applicanon-6f special solder and flux material infanbperation deficiency has prompted manyattempts 'to eliminate soldered connections by mechanically'joiningfthe 'lead-in conductors to the base eyelets or shell-all of which were "cru 1 westd tedta l andgmarketed. Base structures of this type, while decreasing the dangerof melts and obviating the need for a ,bright dip operation, do not completely overcome all the disadvantages enumerated above since soldered, .or similar type connections arestill required, as eviden'ced bythe use of'a brass eyelet and contact plate to facilitate the soldering operation. 1 .In addition, the plastic is 'molded and integrally joined with the base shell in .accordance with the priorart practice so that the basing cement customarily employed to secure the base to the lamp envelope must be deposited within the base in a separate operation, known in the art as the base. prefilling operation, before the base is placed over the sealed end of the lamp. This sequence of operations not only increases the cost and complexity of the lamp assembly operation as a whole but also requires the use of additional equipment to handle and store the prefilled bases since prolonged exposure of the cement to the atmosphere will cause it to harden thereby deleteriously affecting its binding qualities or, if completelycaked, rendering it and the base totally unfit for use. It has also been found that center-contact plates of such elongated configuration have not been entirely satisfactory due to the fact that positive'electrical contact is not always effected wtih the semi-circular mating ringssometimes employed as thebottom terminal element in threelight lamp sockets. It is accordingly the general object of the present invention to overcome and avoid the foregoing and other difficulties andobjections to the prior art by providing a base structure foran electric lamp which may be conveniently and economically fabricated and assembled by high-speed manufacturing techniques. I a

A more specific object of the invention is to provide a sectional lamp base the parts of Which-can be fabricated separately and subsequently mechanically locked together during the final lamp assembly operation to form a' unitary base structure. it 1 Another object of the invention is to provide a multiplecontact lamp base which will obviate the need "for soldered or similar type connections and a separate base 'prefilling operation. i Still another objectof the invention is to provide an improved screw-type base for a three-light lamp which can-be assembled and mechanically connectedto-one of the lamp lead-in conductors in one simple operation and which will insure positive electrical contact with the socket elements regardless of their configuration.

-The aforesaid objects of the invention, and other ob- :jects which will-become obvious to those skilled in the art as the description proceeds, are achieved by forming the base in two separatespecially-shaped sections which can be snapped into interlocking non-rotatable engagement in such a manner that one of the lead-in conductors is permanently clamped therebetween thus not only facilitating the fabrication of the lamp but automatically effecting the most troublesomeof its base connections. Moreover, the contactor portion of the base is so coritoured that positive electrical connection with the socket terminal element is assured at all times and an exceedingly rugged structure obtained with a minimum amount of material.

A better understanding of the invention may be obtained byreferring -'to the accompanying drawing, in which like numerals of reference indicate similar parts throughout the several views, wherein:

Fig. l is a perspective view of a three light lamp incorporating the base construction of this invention;

Fig. 2 is an enlarged end view of the lamp shown in Fig. l and illustrates the functional configuration of the end cap and shell piercing;

Fig. 3 is a cross-sectional view through the basal end portion of the lamp along the line III--III of Fig. 2, in the direction of the arrows, illustrating the preferred embodiment of the invention and the manner in which the insulator cap, lead-in conductors and shell are mechanically coupled together to form a unitary base structure;

Fig. 4 is an exploded'perspective view of one phase in the fabrication of a three-light lamp in accordance with the preferred embodiment of the invention and illustrates the relationship and disposition of the various base parts just before they-are assembled;

Fig. 5 is'a side view, partly in section, of the basal end portion of a three-light lamp similar to that shown in Fig. 3 but illustrates an alternative embodiment of the invention wherein an eyelet and soldered connections are provided;

Fig. 6 is a view corresponding to that shown in Fig. 2 but illustrates another embodiment of the invention.

Although the principles of this invention are broadly applicable to other types of electric lamps and bases, the invention. is particularly adapted for use in conjunction withmogul screw-type bases for three-light lamps and hence has been so illustrated and will be so described.

Referring now to the drawing in detail, a three-light lamp is shown in Fig. l which incorporates the base construction of this invention. 'As is well known, lamps of this type generally consist of a sealed envelope 10 of vitreous material and'a mogul screw-type base which is cemented or otherwise secured to the tubular neck portion of the envelope. A re-entrant stem (not shown) is fused to the constricted end portion of the envelope 10 and the envelope walls immediately adjacent thereto compressed inwardly while plastic to form a molded seal 11 (see Figs. 3 and 5), as is customary in the art. Three lead-in conductors 12 project into the envelope 10 from a stem press 18 through which they are hermetically sealed and support a pair of filaments 14, 16 ofdilferent wattage ratings. One of the lead-in conductors 12 is connected to both filaments 14, 16 to provide acom'rnon path which permits selective operation 'of the filaments 14, 16 with a minimum number of lead-in conductors and base contacts.

The base 20 consists of a threaded shell 22 of cylindrical configuration which may be formed from any'suitable metal, preferably aluminum, and an insulator cap 24 of moldable electrically non-conductive material,

preferably a thermosetting plastic such as wood-filled phenol-formaldehyde marketed by the Durez Plastic and Chemicals, Inc., North Tonawanda, N.Y. under the trade name Durez. The envelope 1-0 is evacuated and preferably filled with an inert gas prior to sealing, as is common in the art. Electrical connection with the filaments 14, 16- is effected by joining the exterior portions of the lead-in conductors 1-2 to the-base shell 22 to efiect'a sidecontact and to the end-contact 34 and center-contact 28, respectively, carried by the insulator cap 24.

The essence of this invention resides in the base construction and in'the manner in which the base is assembled and connected to the lamp lead-in conductors and 'these are hereinafter more fully described.

As seen in Fig. 4, the base20 consists of twoseparate in the usual manner.

The bottom of the shell 22 is provided with a centrallydisposed square-shaped piercing or end aperture 23 leaving four laterally-extending end panels 21 which are substantially equal in area and arcuate in form. The insulator cap 24 is also square-shaped but is slightly larger than the end aperture 23 and carries four upstanding shoulders 25 which parallel and extend along a substantial portion of each side of the cap 24. In order to provide a snap-fit between the insulator cap 24 and shell 22, the shoulders 25 are desirably formed with outwardly projecting lip portions 29 which extend beyond the periphery of the aperture 23 and curve inwardly to provide a recess for the edge portions of the panels 21 and impart the necessary degree of resiliency to the shoulders 25. The shoulders 25 may be stepped back from the edges of the cap 24 to form a flange 31 against which the panels 21 will firmly seat when the cap 24 is inserted and snapped into place within the shell 22 (see Figs. 3 and 4).

As shown in Figs. '1, 2 and 4, the insulator cap 24 is formed with an outwardly projecting platform 26, which is square-shaped and angularly displaced with respect to the cap 24, and a centrally-disposed annular embossment -32 having an aperture therethrough. Superimposed over the square-shaped platform 26 is a ce'ntrally-apertured metal plate 28 of the same configuration which plate is fastened to the platform by means of eyelets 27 having inwardly disposed burrs or projections that are embedded in the cap 24 during the fabrication thereof. One of the eyelets 27 is kept free of plastic to provide an aperture for receiving one of the lead-in conductors 12 during the final basing operation. The square-shaped platform 26 and coinciding metal plate 28 mounted thereon provide a center-contact of such configuration and size that a multiplicity of angular surfaces are provided thereby insuring positive electrical connection with the corresponding matingmember of a three-light lamp socket regardless of its shape. In order to conserve plastic material the int'erior surface of the insulator cap 24 may be shaped to correspond to its exterior configuration thereby providing a member of substantially the same wall thickness (see Figs. 3, 4 and 5). This construction also serves to promote uniform curing of the plastic during fabrication of the cap 24. The shell 22 and insulator cap 24 with itsrnetal contact plate 28 as heretofore described may be conveniently formed by well-known stamping and molding techniques.

In assembling the base 20, the shell 22 is first placed over the molded seal 11 of the lamp and a filling of basing cement 13 is deposited through the aperture 23 into the pocket formed by the upper rim of the shell 22 and the seal shoulder and cured through the application of heat With the lead-in conductors 12 arranged substantially as shown in Fig. 4, the insulator cap 24 is then threaded over the conductors 12 and forcibly inserted into the end aperture 23. The lip portions 29 cooperate with the end panels 21 to laterally displace the shoulders 25 which, by virtue of their resiliency,

*spring back in a snap-type action to their original position after the edges of the panels 21 have been forced over the lip portions 29 thereby locking the members together and firmly seating the panels 21 against the flange 31, as illustrated in Figs. 3 and 4. By virtue of the close fit between the shoulders 25, flange 31 and end panels 21, the laterally projecting conductor 12 is forced into intimate contact with the shell 22 thereby automatically effecting the side-contact. It will beobvious from the configuration of and cooperation between the aforementioned members that the conductor 12 is securely wedged or clamped between the cap 24 and shell 22 and locked in that position to provide a built-in electrical connection, so tospeak, which is not only permanent but automatically. and economically effected. The protruding ..portion of theconductor12 is desirably severed substantially flush with the edge of the platform 26 in order to "the prior art practice;

eliminate a possible source of trouble or injury to the user and to present amuch neater finished appearance.

To facilitate complete automatic assembly of the base 20, fasteners in the form of nails 30, 34 may beemployed to mechanically engage and clamp the remaining lead-in conductors 12 to the insulator cap 24. The nails30, 34 are desirably fabricated from a metal which is easily deformed, such as lead, and shaped to provide a rounded head portion and a shank portion havinghelical flutes or other protuberances projecting therefrom. Fastening members of this type may be conveniently formed during the basing operation by automatic devices well known in the art for upsetting the end portion of a soft metal wire to form the rounded head, fluting the shank portion, and then tapering and terminating the wire to form nails of the proper configuration and dimensions.

The nails 30, 34 are aligned with and forcibly driven by a suitable mechanism not shown) into the apertures provided in the square-shaped platform 26 and annular embossment 32, respectively, whereupon the lead-in conductors 12 disposed in said aperturesand the plastic material of the cap 24 deform the flutes thereby clamping the parts together and firmly anchoring the nails 30, 34 within the cap 24 with their head portions protruding, as shown in Fig. 3. The head of. the nail 34 serves as the endcontact whereas the nail 30 effects electrical connection with the square-shaped plate 28 to complete the centercontact. The portions of the lead-in conductors 12 that project beyond the periphery of the nail heads are severed as in the case of the side-contact to complete the assembly of the base and fabrication of the lamp. Inasmuch as mechanical means are utilized to effect the electrical connection of the center-contact, the plate 28 may be fabricated from aluminum instead of brass normally employed in prior art bases to facilitate soldering thereby achieving a more pleasing appearance and, more significantly, reducing thewcostof the base. 1

As illustrated in Fig.2, it is-preferable to displace the square-shaped platform 26 and coinciding contact plate 28 through an angle of approximately 45 from parallel relation with the sides of the insulator cap 24 so that the corners of the plate 28 substantially bisect the sides of the cap 24 and abutting end panels 21. .In this manner a cross-ribbed configuration is obtained which strengthens the base structure and permits a substantially uniform' wall thickness to be maintained thereby conservingplastic material and eifectin'g a substantial cost saving.

. In Fig. there is illustrated an alternative embodiment formable nail in a manner similar to that disclosed above in connection with the preferred embodiment of the invention, or an eyelet may be centrally mounted on the cap and a soldered connection made in the usual manner;

It willalso be obvious that configurations other than square-shapes may be employed in forming the end aperture, insulator cap, and any platforms embossed thereonthe only limitations being that the aperture and cap be noncircular to prevent the cap from rotating within the shell should the parts become loose and that the platform extend laterally in more than two directions to provide contact surfaces of such shape and area that positive electrical connection withthe socket elements is assured at all times. Regular multilateral or polyhedral configurations, such as squares or equilateral triangles, are preferred inasmuch as they provide the necessary degree of functionality without unduly complicating the structure or fabrication of the base thereby fully exploiting the novel and useful features of the invention.

ofthe invention wherein an eyelet 35 is partly embedded h inthe annular embossment 32 during the fabrication of the insulator cap In this form of the invention the lead-in conductors 12 are severed flush with the plate 28 and eyelet 35, w hich in this case are preferably made of brass, and are electrically joined thereto by fusing a quantity of conductive material, such as solder, around the conductors and adjacent portions of the plate and eyelet to form rounded protuberances 36, 38 in accordance with lAnother' square-shaped platform and plate combination may be provided and angularly displaced in accord- 'a1'tce"with 'ftheprinciples'of this invention, as shown; in

Fig. 6', to fori'rfa"multiple-contact base having'acentrally-disposed end-contact 34, an intermediate-contact 40,

and a center-contact 28. Additional platforms and plates may be. included and successively displaced each from the other if desired. It will be obvious to those skilled in the art that the invention may also be applied to the fabrication of single-filament lamps requiring only one contacting surface on the insulator cap by merely eliminating the square-shaped platforms (and the annular embossment if desired) to provide a medium-screw type base having a square-shaped insulator cap which snaps into the shell and mechanically effects the side-contact in the same manner as heretofore described. The end-contact may be effected mechanically through the use of a de- It will be recognized from the foregoing that the objects of the invention have been achieved by providing a sectional lamp base consisting of two parts which cooperate in a most simple and efficacious manner to form a unitary base structure and effect electrical connection with the base shell thereby simplifying the fabrication and assembly of the base and the associated basing operations. Moreover, the angular configuration of the shell piercing, insulator cap, and center-contact provides a functional design which prevents rotation between the shell and cap should these members become loose through use or unequal heating during the basing operation and drastically reduces the quantity of. waste material produced in fabricating the metal contact plates. The use of deformable members as combination fastening and contact elements in combination with the two-piece base of this invention reduces the final assembly of the lamp and base and the electrical connection of the lead-in conductors with the shell and cap to a series of simple easily controlled operations which can be readily incorporated into the high-speed lamp-making machines presently employed in the industry.

Although the best known mode of carrying out the present invention has been shown and described in accordance with the patent statutes, it will be understood that otherlmodifications may be made without departing from thespirit and scope of the appended claims.

We claim:

1.' An electric lamp comprising an envelope having a ments having recessed outward surfaces which are sprung over and snapped into engagement with the end edges of ;said end panels thereby to firmlyclamp said insulator "cap'againstsaid panels, the outer surface of said insulator cap being conformed to provide a non-circular platform of substantially the same configuration as but smaller dimension than said cap and the aperture in said shell, said platform being angularly displaced with respect to the sides of said insulator cap and edges of said end panels and having a metal contact plate of substantially the same contour mounted thereon and connected to one of said lead-in conductors.

2. An electric lamp comprising an envelope having a sealed end portion from which lead-in conductorsextend, a base attached to the sealed end portion of said envelope, said base comprising a metal shell partly closed at its outer end by a plurality of end panels conformed to 7 definea'polyhedral-shaped aperture thereat, an insulator cap of substantially'the same configuration asbut slightly larger than said aperture attached to said end panels and depending outwardly from said shell, a plurality of upstanding shoulder portions integral with and projecting from the'inward surface of said insulator cap, said shoulder portions having recessed outer surfaces which are sprung over and snapped into engagement with the end edges of said end panels thereby to firmly clamp said insulator cap against "said end panels, the outer surface of said insulator cap being conformed to provide a platform of substantially the same configuration as but slightly smaller dimension than said insulator cap and the aperture in said shell, said platform being displaced withrespect to the edges of said insulator cap and end panels through an angle such that the corners of said platform are disposed approximately at the midpoints of'the aforesaid cap and end panel edges, a metal contact plate mounted on said platform,'said contact plate being of substantially the same configuration as said platform and electrically connected to one of said lead-in conductors, and another of said lead-in conductors being interposed'between the edge of one of said end panels and said insulator cap and thereby firmly clamped in positiveelectrical contact with said shell.

3. A three-light electric lamp comprising an envelope having a sealed end portion from which at least three lead-in conductors extend, a base attached to the sealed end portion of said envelope, said base comprising a threaded metal shell partly closed at its outer end by four arcuate-shaped and conjoined end panels the inward edges whereof are substantially straight and define a square-shaped aperture through the bottom of said shell, and an insulator cap of substantiallythe sameconfiguration as but larger than said aperture, fourupstandin'g shoulders integral with and projecting from the inward surface of said insulator cap, .said shoulders being disposed along but stepped back from the sides of said cap and having theirbuter surfaces contoured to provide a protruding lip and a recess which are seated behind and accommodate, respectively, the edges of said end panels thereby firmly clamping said insulator cap to said shell,

the outer surface of said insulator cap being conformed tolpro'vide a square-shaped platform of smaller dimension than said cap and a centrally-located annular embossment, said square-shaped platform being displaced with respect to the sides of said insulator cap and edges of said end panels through an angle such that the corners thereof are disposed in substantially bisecting relation with the aforesaid sides and edges, an apertured squareshaped contact plate mounted on said platform in coinciding relation therewith, one of said lead-in conductors being connected to said contact plate by a fastening member, another of said lead-in conductors being interposed between the edge of one of said end panels and said insulator cap and thereby firmly clamped in positiv'eel'ectrical contact with said shell, and the other of said lead-in conductors being connected to a second fastening member carried by said annular embossment, said -fastening members comprising nail-like elements anchored in 'saidhplatform and annularembossment and having rounded head portions which protrude beyond sa'id contact plateand embossment and serve-as end and center-contacts respectively for the-lamp.

4. A'bisection'al base for an electric lamp comprising a metal shell partly closed at one end by a plurality of end panels the edges whereof define a non-circular aperture, and an insulator cap of substantially the same configuration as but slightly larger than said aperture, a plurality of upstanding elements integral with and disposed along'but inwardly of the sides of said cap, said elements having portions adapted to be resiliently snapped behind and into engagement with the end edges of said end panels, a platform of substantially the same configuration as but smaller than said insulator cap and aperture integral with and depending outwardly from the outer surface of said insulator cap, said platform being angularly displaced with respect to the edges of said insulator cap and end panels, and a contact plate of substantially the same configuration as said platform-mounted in coinciding relationship thereon.

5. A bisectional base for a three-light electric lan p comprising a cylindrical metal shell partly closed at'its outer end by four arcuate and conjoined end panels each having straight edge portions which define a squareshaped aperture-through the bottom of said shell, and an'insulator cap of substantially the same configuration as but slightly'larger than said aperture, an upstanding shoulder integral with and disposed along the sides of said insulator cap at the upper surface thereof, each said shoulder being disposed inwardly from the adjacent side of said cap and outwardly conformed to provide a protruding lip and a recess which, in conjunction with the corresponding parts of the other shoulders, are adapted to resiliently seat behind and snugly receive respectively the edges of said end panels to effect a snap interlock therewith and permanently clamp'said shell and insulator cap in operative relation, a square-shaped platform projecting from and smaller than the outer surface'of-said insulator cap and displaced through an angle of approximately 45 with respect to the sides of said cap and edges of said end panels so that the corners of said platform are disposed approximately at the midpoints of the aforesaid sides and edges, a centrally-disposed annular embossment projecting outwardly from said platform, an apertured contact plate of substantially the same configuration as said platform mounted in coinciding relationship thereon, and nail-like fastening members of deformable electrically-conductive material adapted to ,be inserted into apertures provided in said platform and plate assembly and said annular embossment and permanently anchored in the material of said insulator cap.

References Cited in the file of this patent -UNITED STATES PATENTS

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