US2993192A

US2993192A - Electric lamp base

Info

Publication number: US2993192A
Application number: US827567A
Authority: US
Inventors: Robert W Mouat
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1959-07-16
Filing date: 1959-07-16
Publication date: 1961-07-18
Anticipated expiration: 1978-07-18

Description

July 18, 1961 R'w. MOUAT 2,993,192

ELECTRIC LAMP-BASE Filed July 16. 1959 7 lnverw tow:

Robev t W. Mcua-"t, b5 0% Hi5 A tfo neg.

ttes

York

Filed July 16, 1959, Ser. No. 827,567 2 Claims. (Cl. 339-146) The present invention relates to electric lamp bases of the type comprising a metal shell contact, a center contact in the form of a metal eyelet and a molded insulator in the form of a web uniting the shell and the center contact at one end of the base.

Bases of this type have been used commercially for more than fifty years for incandescent lamps and are disclosed and claimed in U.S. Patent 774,404 to Alfred Swan, patented November 8, 1904, and assigned to the assignee of the present application.

Cup-shaped bases having cylindrical shells provided with screw threads and formed with a dome at one end of the shell to which end the center contact is united by the molded insulator are also disclosed and claimed in the aforesaid patent and are in extensive use at present for incandescent lamps of the usual household sizes and wattages. Such bases are open at one end to receive the neck of the lamp bulb.

The bases are secured to the vitreous bulb of the lamp by basing cement bonding the shell to the neck of the bulb. The bulb neck is constricted and generally cylindrical extension of the spherical part of the bulb and the outer sealed end thereof of reduced diameter is enclosed by the base in the completed lamp. In the manufacture of the lamp, the base shell is lined with basing cement in the form of a ring applied close enough to the rim or edge of the open end of the base shell to engage the bulb neck and the base shell when the base is properly positioned on the bulb with the sealed end of the neck of the bulb enclosed by the base and the rim or edge of the open end of the base seated against a shoulder formed in the neck of the bulb at the sealed outer end of the neck.

In the present commercial form of such bases for lamps of common household sizes, such as 60 and 100 Watt lamps, the screw threads in the cylindrical wall of the shell extend from the dome toward the opposite open end of the shell but terminate short of the rim at the open end of the shell. The cylindrical wall of the shell between the rim and the threaded portion is straight sided and constitutes the skirt of the shell. The rim is flared outwardly to seat against the shoulder on the cylindrical neck of the bulb. The rim seats on this bulb part when the base is properly mounted on the lamp bulb.

In the manufacture of the lamp bases and of the lamps provided with such bases by mass production methods, bulk handling, that is, packing in a loosely commingled haphazard arrangement, of the base shells, the eyelet contacts, as well as the completed bases is highly desirable for reducing the cost of packing and handling such lamp components during the manufacture of the based lamps. Bulk handling of the completed bases after the cement has been applied thereto and before the cement-lined bases have been mounted on the lamp bulb has not been practiced until recently and even at the present time is not entirely satisfactory.

For many years the cement-lined bases were placed by hand on trays on which they were separated from each other for transportation from the machine which lined with soft cement the shells of the completed bases to the machine which mounted the cement-lined bases on the lamp bulbs. This manual handling of the individual cement-lined bases was made necessary by the location atent O Y with the cement lining of another base.

ice

of the cement on the base. As described in the U.S. Patent 1,306,643 to Swan, patented June 10, 1919, and assigned to the assignee of this application, the cement was disposed by the patented machine in the form of an annular layer or ring on the inner edge or skirt portion of the base shell. Attempts to bulk handle bases lined with cement in this manner resulted in smearing of the cement on the bases due to one base coming into contact The parts of such bases most likely to be smeared with cement when bulk handled are the exposed parts of the center contact, the insulator and the domed part of the shell contact as these parts of one base would enter the cement-lined opening of another base and thus be smeared with the soft cement.

More recently, the bases have been deep-filled with the soft cement by the apparatus disclosed and claimed in the Us. Patent 2,798,455, Beck, patented July 9, 1957, and assigned to the assignee of this application. This deepfilling of the bases has made possible bulk handling of the bases after being lined with the soft cement. In such deep-filled bases the ring of basing cement is located a substantial distance inwardly from the rim or edge of the base shell at the open end of the base to leave the skirt of the shell free from cement. However, the depth at which the ring of cement may be applied within the shell is limited because the cement must completely fill the cross section of the annular space between the bulb neck and the base shell for a substantial distance longitudinally of these lamp parts to firmly bond the base and the bulb together.

It has been found that at the depth required for obtaining a bond of the requisite strength between the base and the bulb the ring of basing cement is close enough to the rim or edge of the base shell that the exposed parts of the center contact of one base may be smeared with cement from another base when the bases are bulk handled. This happens with sufiicient frequency to add appreciably to the cost of manufacture of the lamps due to the necessity for inspection of all the bases prior to mounting them on the lamp bulb, or all the based lamps if such bases are not inspected before being mounted on the lamp bulb, to detect and discard or repair those with smeared center contacts. Basing cement on the center contacts interferes with the soldering of the lead wire to the contact in the manufacture of the lamp. Lamps having center contacts on their bases smeared with basing cement are not commercially acceptable because the cement is not only unsi-ghtly but, due to its electrical insulating properties, also may act to prevent effective electrical engagement between the center contact of the base and the corresponding contact of a socket in which the lamp is mounted.

Deep filling of the bases as described above has practically eliminated the smearing with cement of the dome and the insulator on the bases when bulk handled but has not completely eliminated the smearing of the center contacts of bulk handled cement-lined bases.

The principal object of the present invention is to provide a base of the above type which may be lined with cement at a depth effective for establishing a strong bond between the base and the lamp bulb and which completely eliminates the smearing of any part of bases lined with soft basing cement and bulk handled prior to being mounted on a lamp bulb. Further objects and advantages of the invention will appear from the accompanying drawing, the following detailed description of a species of base embodying the invention and from the appended claims.

The invention attains its objects by forming, as by rolling, in the skirt or edge portion of the base shell an inwardly extending, outwardly opening circumferential groove located between the flared out rim of the shell and the threaded part of the shell wall. The inward side of the groove protrudes into the space defined by the skirt and serves as a stop to limit the distance the center contact bearing end of one base can enter the open end of another base in any relative positions of the bases and particularly when the bases are canted with respect to each other. The inward side of the groove also serves as a dam or boundary for the basing cement which lines the inner surface of the shell on the side of the groove away from the rim or edge of the shell. The inward side of the groove extends radially inward from the cylindrical wall of the shell a greater distance than the ocment bordering the groove and thus holds the center contact of one base out of the cement of another base in any canted relative positions of bulk handled bases to keep the center contacts of all of such bases free from cement and thus to eliminate the need for inspection of the cement-lined bases after bulk handling.

In the drawing:

FIG. 1 is a fragmentary side view partly in section of the bulb neck portion of an electric incandescent lamp provided with a cup-shaped base embodying the invention, and

FIG. 2 is an enlarged, side elevational view of bases of the type shown in FIG. 1, one of said bases being shown in full and the other being shown partly in section.

Referring to the drawing, the incandescent lamp shown in FIG. 1 comprises a bulb 1 having a filament (not shown) sealed therein and a basal attached to the neck 3 of the bulb by basing cement 4. The exhaust tip of the lamp is shown at 3'. The base consists of a threaded metal shell 5 of aluminum, a molded insulator 6 of glass and a bottom brass contact 7 which is in the form of the usual eyelet united with the shell '5 by the molded insulator. The shell 5 has a re-entrant flange 8 at the domed end thereof which acts as a collar on the insulator and holds the insulator therein as disclosed and claimed in the co-pending application Serial No. 692,214, filed October 24, 1957, Rudler et al. which application is assigned to the assignee of the present application.

One end of the lamp filament is connected to the base shell by the inlead wire 9 which is bent back over the end of the bulb neck and soldered or welded as shown at 10 to the outer edge portion of the shell 5. The other end of the lamp filament is connected to the inlead wire 11 which extends through the funnel-shaped opening in the insulator 6 and is secured by a drop of solder 12 to the eyelet contact 7, as shown in FIG. 1.

In accordance with the present invention the skirt 13 of the base shell 5 between the rim 14 and the screw threads rolled into the cylindrical Wall of the shell 5 is provided with an inwardly extending, outwardly opening circumferential groove 15. As shown in FIG. 2 when the bases 2 are bul k handled, the groove 15 prevents the end contact of one base from engaging the ring 4 of basing cement of another base in any relative positions of the bases including the position shown in FIG. 2. The relative positions of the bases shown in FIG. 2 is that which would result in the cement 4 smearing the exposed surface of the eyelet contact 7 except for the provision of the circumferential groove 15. In other relative positions assumed by the bases when bulk handled, the cement 14 is recessed within the base a sufficient distance to prevent smearing of any part of one base with cement from another base.

The basing cement is applied in the form of a ring 4 to the inner surface of the shell of each base on the side of the groove away from the rim 14 of the base shell 5. The apparatus disclosed and claimed in the abovementioned U.S. Patent 2,798,455 may be used for applying the basing cement to the base shell in this location on the shell.

' one base with cement from another base.

As presently manufactured, screw threaded aluminum bases for incandescent lamps of 60 and watt sizes for operation on power sources of commercial voltages are approximately fifteen-sixteenths of an inch in overall length and have an outside diameter of 1.050 to 1.075 inches at the flared-out rim 14 of the base shell. The outside diameter of the shell at the skirt 13 is approximately one inch and the eyelet contact 7 has a diameter of approximately seven-sixteenths of an inch. The depth of the base from the part of maximum diameter of the dome to the outer surface of the eyelet contact 7 is approximately five-eights of an inch and the dome has a radius of curvature of approximately five-thirty-seconds of an inch and a depth of approximately three-sixteenths of an inch. 1

The thread is rolled in the cylindrical wall of the shell at seven turns to the inch. The diameter of the thread is 1.029 to 1.037 inches at its crest and 0.965 to 0.971 of an inch at its root and, in section, is in the form of reversed arcs each having a radius of 0.047 of an inch with no taper, The thread terminates at the domedshaped end of the shell and extends axially of the shell to within about one-eighth of an inch of the rim 14.

The objects of this invention are attained with bases of this structurewhen the circumferential groove 15, formed by rolling, for example, has a width of approximately 0.050 of an inch, measured as shown at A in FIG. 2, is located approximately 0.100 of an inch inward from the rim 14 of the shell, measured as shown at B in this figure, and has a depth such that the inner diameter of the shell at the groove is approximately 0.965 of an inch. The inner diameter of the shell at the cylindrical skirt portion 13 bordering the sides of the groove is approxiamtely 0.990 of an inch so that the groove, in effect, constitutes a ledge projecting or protruding inward from the cylindrical surface of the skirt portion 13 of the shell 5 and serves to prevent the eyelet contact 7 of one base coming into engagement with and being smeared by the cement 4 of another base when the bases are bulk handled.

The basing cement is applied as shown in FIG. 2 so as to border on the side of the groove 15 away from the rim 14 ofthe shell and is in the form of a slightly flattened ring with the part thereof bordering the groove 15 spaced approximately 0.150 of an inch from the rim 14. When the basing cement is cured by heating after the cement lined base is placed on the neck of the lamp bulb it swells while being cured and fills the annular space between the base shell and the part of the neck enclosed by the shell, including the space surrounded by the grooved skirt portion of the base shell, as shown in FIG. 1.

As pointed out above, bases of the above structure may be bulk handled after the basing cement has been applied thereto and before the base is cemented to the cylindrical neck 3 of the lamp bulb 1 without smearing Further, the strength of the bond between the bulb neck 3 and the base 2 cemented thereto is sufficient for commercial acceptance of the based lamp. The torque strength of the bond is, of course, enhanced by the increased area and the irregular surface of the shell 5 at the grooved skirt portion, the groove 15 being embedded in the cement 4 after the cement has been cured and when the base 2 is properly mountedon the lamp bulb neck 3 with the rim 14 seated against the shoulder 16 on the bulb neck 3 as shown in FIG. 1.

A further advantage secured by providing a groove 15 in the skirt 13 of the base shell as described above, is

obtained when the base shells are bulk handled before the insulator 6 and the eyelet contact 7 is united therewith and when the completed bases are bulk handled. At each of these steps in the manufacture of the base difficulty has been encountered heretofore in the bulk handled shells or bases sticking together. This has necessitated manual separation of such base shells in order to feed such shells to base making machines by automatic means, during the dipping of the completed bases for brightening purposes, while feeding the completed bases to the cement applying machine and while feeding the cement lined bases to the lamp basing machine. The groove 15 also strengthens the base shells to better withstand such bulk handling.

Thus, the present invention has eliminated completely individual manual handling and made practical the bulk handling of the base shells and the completed bases at any stage of the manufacture of a lamp having such bases cemented thereto with consequent substantial savings in the manufacturing cost of lamps equipped with bases of the kind described above while completely eliminating smearing of the bases and increasing the strength of the bond between base and the lamp bulb.

While the invention has been described in connection with bases of a particular size having aluminum base shells, it will be understood that the above description is for the purpose of giving an example of the invention and that the invention is useful in connection with different sizes of screw-threaded bases of similar shape with shell contacts made of brass or aluminum and with insulators of other shapes and material, such as thermo-setting organic plastic material.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A cup-shaped base for attachment by basing cement to the cylindrical neck of a lamp bulb comprising a generally cylindrical screw threaded shell contact domeshaped at one end and having a cylindrical skirt at the opposite end thereof, a center eyelet contact and a molded web of electrically insulating material uniting said shell contact and said eyelet contact at the domed end of said shell contact with the eyelet contact exposed at the end of the base, said shell contact having a flared rim for seating the base on a bulb neck and an inwardly extending outwardly opening circumferential groove in the skirt of the shell and a ring of basing cement on the inner surface of the shell contact on the side of the groove away from the flared rim and bordering the groove, the said groove extending radially inward of the shell a sufiicient distance to protect the basing cement from casual contacts with the eyelet contacts of similar bases when bulk handled.

i2. A cup-shaped base for attachment by basing cement to the cylindrical neck of a lamp bulb comprising a generally cylindrical screw threaded shell contact domeshaped at one end and having a cylindrical skirt at the opposite end thereof, a center eyelet contact and a molded web of electrically insulating material uniting said shell contact and said eyelet contact at the domed end of said shell contact with the eyelet contact exposed at the end of the base, said shell contact having a flared rim for seating the base on a bulb neck, said skirt having a circumferential protrusion extending into the space defined thereby and a ring of basing cement on the inner surface of the shell contact on the side of the protrusion away from the flared rim, the circumferential protrusion extending into the space defined by the shell a suflicient distance to protect the basing cement from casual contacts with the eyelet contacts of similar bases when bulk handled.

References Cited in the file of this patent UNITED STATES PATENTS 430,437 Rockwell June 17, 1890 2,733,419 Beck Jan. 371, 1956 2,798,455 Beck July 9, 1957