US3897124A

US3897124A - Lamp base assembly

Info

Publication number: US3897124A
Application number: US415628A
Authority: US
Inventors: Gasper Pagnotta; William G Moffatt
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1973-11-14
Filing date: 1973-11-14
Publication date: 1975-07-29
Anticipated expiration: 1992-07-29
Also published as: JPS5080249A

Abstract

An electrically conductive ferrule has two major opposed surfaces substantially parallel to each other. A raised boss projects from one major surface and a raised rim projects from the same major surface further than the boss and encircles the raised boss. The boss has walls defining an aperture extending entirely through the boss perpendicular to the major surfaces. Preferably, the boss has a re-entrant section for aiding the process of welding an electrical lead thereto. A portion of the surface of the electrically conductive member is shaped to substantially conform to at least a portion of the raised rim to provide a good physical and electrically conductive relationship therewith.

Description

United States Patent [1 1 Pagnotta et al.

[451 July 29, 1975 LAMP BASE ASSEMBLY [73] Assignee: General Electric Company,

Schenectady, NY.

[22] Filed: Nov. 14, 1973 [21] Appl. No.: 415,628

[52] U.S. Cl. 339/145 T; 339/275 R [51] Int. Cl H0lr 11/06 [58] Field of Search 339/144 R, 144 T, 145 R,

339/145 D, 145 T, 275 R; 313/220, 493

3/1969 Hudson, .lr 339/144 R X 3,434,097 3,502,933 3/1970 Leimonths 339/144 T X 3,629,640 12/1971 Audesse 339/145 T X Primary Examiner.loseph l-l. McGlynn Assistant ExaminerHoward N. Goldberg Attorney, Agent, or Firm--Donald M. Winegar; Joseph T. Cohen; Jerome C. Squillaro 5 7] ABSTRACT An electrically conductive ferrule has two major opposed surfaces substantially parallel to each other. A raised boss projects from one major surface and a raised rim projects from the same major surface further than the boss and encircles the raised boss. The boss has walls defining an aperture extending entirely through the boss perpendicular to the major surfaces. Preferably, the boss has a re-entrant section for aiding the process of welding an electrical lead thereto. A portion of the surface of the electrically conductive member is shaped to substantially conform to at least a portion of the raised rim toprovide a good physical and electrically conductive relationship therewith.

16 Claims, 6 Drawing Figures PATENTEB JUL 2 91975 SHEET LAMP BASE ASSEMBLY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to welded lamp base assemblies and, in particular, to the configuration of the ferrule comprising the lamp base assembly and a welding fixture for welding an electrical lead to the ferrule.

2. Description of the Prior Art Electric wires are usually joined to a ferrule of a lamp base assembly by solder means. The solder means produces one or more solder beads which form one or more electrical contacts of the lamp for a lighting fixture. Solder defects consistently cause production problems which must be constantly monitored. Uneven height of the solder beads cause unreliable operation of the lamp when the lamp is inserted into a light socket. Lamp failures also occur because of the lack of a good wire lead to the base connection. Additionally, the solder may bridge between adjacent leads and short out the lamp. During operation of the lamp, the solder can creep under pressure and may break the electrical contact between the lead and the ferrule to which it is connected.

D. S. Gustin in his U.S. Pat. No. 1,965,231, teaches a solderless connection of an electrical lead to an electrically conductive ferrule. The solderless connection is achieved by crimping a portion of the ferrule to the lead. However, this type of joining operation produces electrical connections of questionable reliability and varying contact resistances between the components so joined.

W. W. Watrous, Jr., in his U.S. Pat. No. 2,325,817, teaches the joining of an electrical lead to an electrically conductive ferrule by welding. However, the configuration of the ferrule and the welding method practiced is not conductive for mass producing lamp base assemblies for todays market requirements.

It is therefore an object of this invention to provide a new and improved electrically conductive ferrule for use in a lamp base assembly.

Another object of this invention is to provide a new and improved electrically conductive ferrule having a raised boss wherein an interior surface defines an aperture extending entirely through the boss along the vertical axis thereof and having a re-entrant portion for the welding of an electrical lead thereto.

Another object of this invention is to provide a new and improved ferrule having a raised boss and a raised rim external to, and encompassing the raised boss to aid in joining a wire lead to the boss and to protect the resulting weld nugget produced when the wire lead is welded to the boss.

A further object of this invention is to provide a welding fixture adaptable for use with the raised rim of the new and improved electrically conductive ferrule to join an electrical lead to the raised boss thereof and suitable for mass production of lamp base assemblies.

Other objects will, in part, be obvious and will, in part, appear hereinafter.

SUMMARY OF THE INVENTION In accordance with the teachings of this invention, there is provided an electrically conductive ferrule having two major opposed surfaces substantially parallel to each other. A raised boss extends from one of the two major surfaces. A raised rim extends from the same major surface as, and encircles the raised boss. The raised boss has an interior wall defining an aperture extending entirely through the ferrule and the boss wherein the apertures cross-sectional configuration is that of an hourglass. Preferably, the raised rim extends further from the major surface than the raised boss. A welding fixture is provided to aid in joining an electrical lead to the raised boss of the novel ferrule by thermal energy means. The welding fixture comprises an electrically non-conductive wall member having a melting point in excess of that temperature required to join the lead to the boss. An inner surface defines an enclosed area which comprises in part the chamber for the joining operation. A passage is provided in the wall member for exhausting gases employed and/or produced in the joining operation. Electrically conductive means are affixed to one end surface of the wall member. A portion of the surface of the electrically conductive means is shaped to substantially conform to at least a portion of the raised rim to provide both a good physical and electrical conductive relationship with each other.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view, partly in cross-section, of a lamp base assembly, embodying the ferrule of this invention prior to the joining of the components.

FIG. 2 is an elevation view, partly in cross-section, of the lamp base assembly shown in FIG. 1 after joining of the components.

FIG. 3 is an elevation view, partly in cross-section, of a welding fixture suitable for use in producing the lamp base assembly of FIG. 2.

FIG. 4 is an elevation view, partly in cross-section, of a lamp base assembly, prior to joining the components together, wherein the ferrule is an alternate embodiment of the ferrule of FIG. 1.

FIG. 5 is an elevation view, partly in cross-section, of a lamp base assembly, prior to joining the components together, wherein the ferrule is another alternate embodiment of the ferrule of FIG. 1.

DESCRIPTION OF THE INVENTION Referring now to FIG. 1, there is shown an assembly 10 suitable for use in a lamp base assembly. The assembly 10 comprises an electrically conductive ferrule 12 and a body 14 of electrical insulation material affixed thereto. Preferably, the body 14 is molded in situ to the ferrule 12 to provide a substantially void-free bond with the ferrule 12.

The ferrule 12 comprises a suitable electrically conductive material such, for example as copper, copper alloys, aluminum, aluminum alloys, nickel, nickel alloys and the like. The ferrule 12 comprises a raised boss 16 having an aperture extending therethrough. The raised boss 16 is formed by such suitable manufacturing means as embossing and piercing. A raised rim portion 20 projects from the same surface 18 as the boss 16 and encircles the same. The boss 16 is preferably located a sufficient distance below the rim 20 so that a weld nugget 32 (FIG.2) is formed as a result of a metallurgical joining process it will not interfere with the function of the raised rim 20. The raised rim 20 is the electrical contact between the wire from the filament of a light bulb and the electrical contact in a lamp socket into which the bulb is inserted. The inner edge 24 of the surface 22 defines an aperture through which an electrical lead 26 is inserted and then welded to the associated boss 16 by suitable thermal energy joining means such, for example, as laser welding, electron beam welding, plasma welding and tungsten inert gas welding.

The welding of an electrical lead 26 to the boss 16 is preferably performed in such a manner that sufficient heat is applied to the lead 26 in a minimum amount of time whereby a sufficient amount of the lead 26 is melted and fused to the ferrule 12 with as little melting of the boss 16 as possible. The end result is as shown in FIG. 2 wherein a substantially porous free electrically conductive metal nugget 32 fuses the lead 26 to the boss 16 of the ferrule 12.

Referring again to FIG. 1, as little as possible of the boss 16 is melted during the joining process since as more of the boss 16 is melted, the greater the distance becomes between the lower surface 28 of the ferrule in the boss area and the external surface 30 of the lead 26. This occurrence tends for increasing the possibility that molten metal will fall through the widening gap and result in a faulty mechanical and/or electricaljoint. In addition, as more of the boss 16 is melted during the joining operation, the greater the possibility becomes that the material of the body 14 may be thermally decomposed. Decomposition of the material comprising the body 14 releases gaseous components which may become entrapped in the metal nugget 32 (FIG. 2) resulting in a porous joint and an unreliable electrical connection between the lead 26 and the ferrule 12. Frequently, the material of the body 14 which is decomposed during the joining process is present as flash material resulting from the molding in situ of the body 14 to the ferrule 12. The raised rim has an additional advantage of aiding the metal joining process, particularly, that process embodying tungsten inert gas weld- Referring now to FIG. 3, there is shown a welding fixture 50 suitable for use in a metal joining process embodying tungsten inert gas welding equipment and the like to join the lead 26 to the ferrule 12. The welding fixture comprises wall member 52 having an electrical ground and chill member 54 affixed to one end thereof. The

interior walls

56 and 58 of the

respective members

52 and 54 define a chamber within which the joining of the end of the wire 26 to the ferrule 12 is accomplished.

The wall member 52 comprises a material which is electrically non-conductive and has the ability to withstand the temperature range required for joining the lead 26 to the ferrule 12. In addition, the material of the wall member 52 must be compatible with the materials employed in the joining process and the gaseous products resulting therefrom. Suitable materials from which the wall member 52 may be fabricated are any suitable ceramic dielectric materials of compositions well known to those skilled in the art. Interior wall surface 60 defines an aperture which extends entirely through the wall member 52 to provide a means for exhausting the gases resulting from the metal joining process as well as the gas employed in providing a controlled atmosphere for the process.

The electrical ground and chill member 54 is electrically conductive and is made of a suitable material such, for example as copper, copper alloys, and the like. The electrical ground and chill member 54 has a surface area 62 which substantially conforms with at least a portion of the surface area 64 of the raised rim 20 of the ferrule 12. It is essential that the

surfaces

62 and 64 be substantially contiguous with each other in order to provide a good physical and electrical conduction relationship between the electrical ground and chill member 54 and the ferrule 12. The function of the electrical ground and chill member 54 is to prevent welding current from flowing through the lead 26 and the filament connected thereto. The mass of the member 54 is provided to act as a chill for the weld product. An electrically conductive metal strap 66 is affixed to the electrical ground and chill 54 by a suitable fastener means 68 such, for example, as a screw. The strap provides a means for electrically connecting the member 54 and the ferrule 12 into the electrical circuit necessary for the metal joining process.

The welding fixture 50 is configured to enable the positioning of an electrode 70, of either the consumable or nonconsumable type, to within a given distance from the end of the lead 26 which is sufficient to initiate the metal joining process when power is applied to the electrode 70. When the electrode 70 is consumable, the material comprising the electrode 70 must be compatible with that of the lead 26 and the ferrule 12 and produce a weld nugget 32 (FIG.2) (FIG. 2) iselectrically conductive. Preferably, a nonconsumable electrode is employed and the tungsten inert gas welding process is practiced to produce the weld nugget 32.

The configuration of the ferrule 12 and the welding fixture 50 enables one to repetitively achieve an excellent electrically conductive weld nugget 32. The raised rim portion 20 surrounds the weld nugget produced joining the lead 26 to the ferrule 12 as required by the lamp base design. Additionally, the manufacture of a lamp base assembly having the configuration of this invention is ideally suited for modern mass production techniques practiced for manufacturing very small electric lamps.

FIG. 4 is illustrative of a lamp base assembly comprising a ferrule 112 which is a modification of the ferrule 12 of FIG. 1, 2 and 3. All items denoted by the same reference numerals as shown in FIGS. 1, 2 and 3 denote the same item of the figures and comprise the same materials, and function in the same manner, as described heretofore. The ferrule 1 12 comprises a boss 116 which is formed by a suitable manufacturing technique such, for example, as by embossing and piercing.

In particular, the boss 116 has a configuration which is substantially perpendicular to the general planar orientation of the ferrule 112. The boss 116 projects above the surface 18 of the ferrule 112 a distance less than the distance that the raised rim 20 projects above the surface 118. This enables one to form a weld nugget which lies at a lower level than the raised rim 20 so as not to interfere with the electrical functioning thereof. The inner wall surface 118 of the boss 116 defines an aperture through which a lead 26 is disposed to be bonded by a suitable thermal energy process to the boss 116. Such suitable thermal energy process means includes laser welding, plasma welding, electron beam welding, metal inert gas welding, and tungsten inert gas welding. The welding fixture of FIG. 3 is preferred when the process practiced is tungsten inert gas welding.

The preferred configuration of the boss 116 enables one to join the lead 26 to the boss 116 to produce a sound electrically conductive weld nugget, as shown in FIG. 2. As the metal joining process proceeds, both the lead 26 and the boss 116 become progressly molten but, unlike the occurrence with boss 116, FIG. 1, the gap between the surface 30 of the lead 26 and the surface 1 18 of the boss 1 16 remains substantially constant. The possibility of molten metal falling through the gap and producing an undesirable weld is substantially reduced. Excellent electrically conductive weld nuggets are consistently achieved with this ferrule 112 configuration which is readily adaptable for mass production manufacturing practices.

Referring now to FIG. 5, there is shown a lamp base assembly 210 comprising a ferrule 212 which is another modification of the ferrule 12 of FIG. 1. All items denoted by the same reference numerals as those of FIGS. 1, 2, 3 and 4 are the same items, and comprise the same materials, and function in the same manner, as previously described. The ferrule 212 comprises a boss 216 which is formed by a suitable manufacturing technique such, for example, as by embossing and piercing.

Each boss 216 comprises a re-entrant member 214 having an inner wall surface 218 defining an aperture extending entirely through the boss 216. The configuration of the re-entrant member 214 is such that with increasing distance from the surface 18 the crosssectional area of the aperture extending through the boss 214 becomes increasingly larger. The appearance of a cross-sectional view of the aperture extending through the boss 216 is that of an hourglass or of two truncated cones joined together at their upper end surfaces.

The lead 26 to be joined to the ferrule 212 is disposed within the aperture and extends slightly above the end surface 222 of the boss 216 as well as the rim portion 20. The configuration of the re-entrant member 214 of the boss 216 is such that the surface area 224 of inner surface 218 is closest to the surface 30 of the lead 26 and the remaining surface area of the inner surface 218 flares away from the lead 26. Therefore, with increasing distance along the surface 218 from the area 224, the distance between the inner surface 218 of the boss 216 and surface 30 of the lead 26 becomes increasingly greater. This desirable configuration for the re-entrant member 214 enables one to produce a more reliable electrically conductive weld nugget 32 (FIG. 2) then by utilizing any of the previously described

ferrules

12 or 112 and metal joining processes. The welding fixture of FIG. 3 may be employed with the tungsten inert gas welding process to join the lead 26 to the ferrule 212. As the welding process proceeds and more and more of the boss 216 and the lead 26 becomes molten to form the nugget 32, with or without additional additive metal depending upon the welding process employed, the gap or distance between the surface 218 of the re-entrant member 214 and the surface 30 of the lead 26 decreases until surface area 224 is reached. The decreasing distances of the gap prevents the molten metal from being lost through the gap, which is a more possible oc' currence in the previous boss designs. Thereafter the gap increases and the amount of molten boss material increases. However, the weld nugget 32 is formed at or before the surface area 224 is reached. This ferrule configuration is readily adaptable with use of the welding fixture 50 for mass production purposes.

Wall surface 230 defines an aperture in the body 14 of electrically insulative material. Preferably, the joint 232 at which the surface 230 contacts the surface 28 of the ferrule 212 should be consistent with molding practices, as far as is possible removed from the point 234 where the inner surface 218 of the boss 216 becomes integral with the surface 28 of the ferrule 212..

This enables one to allow some flash material from the body 14 to be present from an improper fit of a core pin during the molding process but still minimize the probability of the material melting and outgassing during the welding operation and causing a porous weld nugget 32 to be produced.

With reference to FIG. 6, there is shown a portion of apparatus 310 for the assembling of lamps embodying the lamp base assemblies of this invention. The apparatus 310 includes suitable means 312, such, for example, as an inclined track which preferentially orients a lamp assembly 314 therein. Small lamps most usually embody a pair of protrusions 315, or other locating devices, for assembling and locking the lamp assembly 314 in a light socket. The protrusions 315 provide suitable means for the proper orientation of the lamp assembly 314 for welding. The lamp assembly 314 comprises any of the lamp base assemblies 10, or 210, and the leads 26 which are to be welding to the associated boss of the respective ferrules. A gating means 316 associated with the track 312 for inserting a lamp assembly 314 into one of a plurality of fixtures 318 mounted on a rotating plate 320. The fixtures retain the preferred orientation of the lamp assembly 314. The plate 320 rotates in the direction of the arrow 322 to index the plurality of fixtures 318 properly at the various operation stations A, B, C and D of the apparatus 310. When a fixture 318 is properly indexed at station A, suitable means such, for example, as a microswitch (now shown) operates the gating means 314 to insert a lamp assembly 314 into a cavity of the fixture 318. The lamp assembly 314 is oriented in the fixture 318 by the protrusions 315 or other locating devices to properly align the

ferrules

324 and 326 for the metal joining operation.

The plate 320 is rotated to move the fixture 318 and the lamp assembly 314 inserted therein to station B, for a welding operation. Welding apparatus 328 including laser beam or electron beam welding equipment suitable for providing two electron beams for simultaneously welding the leads 26 to their

respective ferrules

324 and 326. A single source of the electron or laser beam may be employed and means (not shown) provided in the apparatus 328 to divide the beam into two parts to perform the simultaneous welding operation. Laser beam welding is preferred as no vacuum means is required as in the case with electron beam welding. The apparatus 328 is operable only when the fixture 318 is properly indexed at station B. Next, the plate rotates the fixture 318 and lamp assembly 314 therein to station C where it is indexed properly. At station C electrical test apparatus 330 automatically checks the electrical continuity of the lamp assembly 314 via probes 332 and 334 which contact the respective weld nuggets formed at station B.

Upon completion of the electrical checks, the plate 320 is rotated to move the fixture 318 and lamp base assembly 314 contained therein to station D. An ejector 336 controlled by a programmer 338 connected to, and responsive to signals generated by, the electrical test apparatus 330 removes the completed lamp assembly 314 from the fixture 318. In accordance to the signals generated by the electrical test apparatus 330, the

ejector 336 places the lamp assembly 314 with acceptable or rejected lamp assemblies.

We claim:

1. An electrically conductive ferrule comprising:

a. an electrically conductive material;

b. two major opposed surfaces substantially parallel to each other;

c. a raised boss having a wall member extending from one of the two major surfaces, the wall member having a re-entrant portion located remote from the one major surface and an interior wall surface defining an aperture extending entirely through the ferrule and the boss;

d. a raised rim encircling the raised boss and extending from the one major surface,

e. an electrical lead disposed in the aperture and extending upwardly through the raised boss, and

f. a substantially sound electrically conductive weld nugget joining together the electrical lead and the re-entrant portion of the ferrule, the material of the weld nugget consisting essentially of material of the raised boss and material of the electrical lead.

2. The electrically conductive ferrule of claim 1 wherein the raised boss and the raised rim are integral with the ferrule.

3. The electrically conductive ferrule of claim 2 wherein the raised rim extends to a height above the one major surface of the ferrule greater than that of the raised boss.

4. The electrically conductive ferrule of claim 1 wherein the material comprising the ferrule is one selected from the group consisting of copper, copper alloys, aluminum, aluminum alloys, nickel and nickel alloys.

5. The electrically conductive ferrule of claim 4 wherein the material of the ferrule is a copper alloy.

6. The electrically conductive ferrule of claim 1 including a body of electrically non-conductive material affixed in situ to the other major surface of the electrically conductive ferrule, the body having walls defining an aperture extending entirely through the body, the aperture being aligned with the aperture of the raised boss and having a vertical axis coinciding with the vertical axis of the aperture of the raised boss.

7. The electrically conductive ferrule of claim 6 wherein the end of the walls of the electrically nonconductive material contacting the ferrule and defining the aperture of the body are spaced apart more distant from each other than the distance that the wall surfaces of the raised boss are spaced apart from each other.

8. The electrically conductive ferrule of claim 6 wherein the material of the ferrule is a copper alloy.

9. An electrically conductive ferrule comprising:

a. an electrically conductive material;

b. two major opposed surfaces substantially parallel to each other;

c. a raised boss having a wall member extending from one of the two major surfaces;

(1. a re-entrant member disposed on, and integral with, the raised boss;

e. an interior wall surface defining an aperture extending entirely through the raised boss and the reentrant member;

f. the diameter of the aperture located in that portion of the re-entrant member furthest from the raised boss increasing in length with increasing distance from the raised boss, and

g. a raised rim member encircling, and extending further from the major surface than, the raised boss and the re-entrant member.

10. The electrically conductive ferrule of claim 9 and further including:

h. an electrically conductive lead disposed in the aperture and extending upwardly through the raised boss and re-entrant member, and

i. a substantially sound electrically conductive weld nugget joining together the electrical lead and the re-entrant member of the ferrule, the material of the weld nugget consisting essentially of material of the raised boss and material of the electrical lead.

11. The electrically conductive ferrule of claim 10 wherein the raised boss and the raised rim are integral with the ferrule.

12. The electrically conductive ferrule of claim 10 wherein the material comprising the ferrule is one selected from the group consisting of copper, copper alloys, aluminum, aluminum alloys, nickel and nickel alloys.

13. The electrically conductive ferrule of claim 12 wherein the material of the ferrule is a copper alloy.

14. The electrically conductive ferrule of claim 10 including a body of electrically non-conductive material affixed in situ to the other major surface of the electrically conductive ferrule, the body having walls defining an aperture extending entirely through the body, the aperture being aligned with the aperture of the raised boss and having a vertical axis coinciding with the vertical axis of the aperture of the raised boss.

15. The electrically conductive ferrule of claim 14 wherein the end of the walls of the electrically nonconductive material contacting the ferrule and defining the aperture of the body are spaced apart more distant from each other than the distance that the wall surfaces of the raised boss are spaced apart from each other.

16. The electrically conductive ferrule of claim 14 wherein the material of the ferrule is a copper alloy.

Claims

1. An electrically conductive ferrule comprising: a. an electrically conductive material; b. two major opposed surfaces substantially parallel to each other; c. a raised boss having a wall member extending from one of the two major surfaces, the wall member having a re-entrant portion located remote from the one major surface and an interior wall surface defining an aperture extending entirely through the ferrule and the boss; d. a raised rim encircling the raised boss and extending from the one major surface, e. an electrical lead disposed in the aperture and extending upwardly through the raised boss, and f. a substantially sound electrically conductive weld nugget joining together the electrical lead and the re-entrant portion of the ferrule, the material of the weld nugget consisting essentially of material of the raised boss and material of the electrical lead.

7. The electrically conductive ferrule of claim 6 wherein the end of the walls of the electrically non-conductive material contacting the ferrule and defining the aperture of the body are spaced apart more distant from each other than the distance that the wall surfaces of the raised boss are spaced apart from each other.

9. An electrically conductive ferrule comprising: a. an electrically conductive material; b. two major opposed surfaces substantially parallel to each other; c. a raised boss having a wall member extending from one of the two major surfaces; d. a re-entrant member disposed on, and integral with, the raised boss; e. an interior wall surface defining an aperture extending entirely through the raised boss and the re-entrant member; f. the diameter of the aperture located in that portion of the re-entrant member furthest from the raised boss increasing in length with increasing distance from the raised boss, and g. a raised rim member encircling, and extending further from the major surface than, the raised boss and the re-entrant member.

10. The electrically conductive ferrule of claim 9 and further including: h. an electrically conductive lead disposed in the aperture and extending upwardly through the raised boss and re-entrant member, and i. a substantially sound electrically conductive weld nugget joining together the electrical lead and the re-entrant member of the ferrule, the material of the weld nugget consisting essentially of material of the raised boss and material of the electrical lead.

15. The electrically conductive ferrule of claim 14 wherein the end of the walls of the electrically non-conductive material contacting the ferrule and defining the aperture of the body are spaced apart more distant from each other than the distance that the wall surfaces of the raised boss are spaced apart from each other.