US 3622947 A
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United States Patent  lnventor Robert M. Griffin C/O Sylvania Electric Products, Salem, Mass. 01970 ] Appl. No. 68,856  Filed Sept. 2, 1970  Patented Nov. 23, 1971  LAMP BASE EXTENSION 3 Claims, 3 Drawing Figs.
 U.S. Cl 339/146, 3 13/318  Int. Cl ll0lr 13/30  Field ofSearch 339/112, 146, 145, 179, 182; 313/318  References Cited UNITED STATES PATENTS 2,091,233 8/1937 Zobel 339/146X Primary Examiner-Richard E. Moore AttorneysNorman .l. OMalley and Joseph C. Ryan ABSTRACT: A lamp base extension for halogen-type lamps where the base to filament length is increased without enlarging the size of the lamp envelope, The extended base comprises a preformed ceramic bridge spaced between an extension skirt and a screw base. The ceramic bridge is formed with reduced end portions and spaced slots about its periphery. The metal base and extension skirt are fitted over each reduced end of the bridge and the edges of the skirt and base are criniped into the slots of the bridge. This forms an extended base that provides an increased light center length for the lamp without enlarging the lamp envelope or the utilization of an expensive glass insulation bridge.
PATENTED uuv 2 3 \sn 22 FIG.2
ROBERT M. GRiFFlN INVENTOR BY/ 1 (i & ATTORNEY LAMP lBASE EXTENSION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to an extension for a lamp from that of a normal light center to one that can be utilized in large fixtures. The light center length of a lamp is determined by the distance from the center of the filament to the bottom edge of the base. In most larger refiectorized fixtures the center of the filament should be at the proper focal point of the reflector, that is, where the optimum lumen efficiency of the lamp is realized. In recent years more efficient halogen-type lamps have been utilized. In this type of lamp a regenerative cycle is established producing a longer lasting and a more efficient lamp. The temperatures of the lamp wall and its distance from the filament are two critical factors for proper operation of the regenerative cycle. Therefore, larger spherical lamp envelopes would be prohibitive, mainly because of the relative distance of the wall of the lamp to the filament. With demand for larger fixtures, increased filament to base length adapters for standard lamps have become a necessity.
DESCRIPTION OF PRIOR ART Lamps requiring increased light center lengths have been made involving expensive molten glass operations to form the insulation between the standard metal base and the metal extension skirt. Briefly, the shell or metal base and the metal skirt are coaxial, with the bottom of the skirt adjacent to the open end of the shell but spaced axially from the skirt. During fabrication the skirt and shell are mechanically held in this way while a molten flow of glass is applied to the interior of the shell and skirt so that the glass completely covers the inside of the shell and also fills the space between the edges of the shell and skirt. The glass also flows to the bottom end of the base shell and forms a hemispherical insulator where a fiat brass cap is then anchored and thus insulated from the base.
On lamps of low production the setting up of this type of glass operation became very expensive.
SUMMARY OF THE INVENTION This invention relates to an improved base where the light center length of a lamp can be increased so that it can be used with larger reflectors without increasing the size of the lamp envelope or requiring expensive glass insulating operation. The size of the envelope is critical to the regenerative cycle of the newer halogen-type lamps. A minimum distance must be maintained between the filament and the bulb wall to produce the desired temperature for the regenerative cycle to function. In high wattage studio lamps the tubular-shape envelope is extensively used because the wall to filament distance is constant along the length of the filament. Therefore, in designing a particular filament for a desired wattage, the distance between the filament and the bulb wall is one of the critical factors. With our preformed ceramic bridge that requires no glass operation, low production volume lamps can be inexpensively fabricated.
In our invention, a metal extension skirt is attached to a lamp screw adapter fixed to the bottom of the lamp. The skirt is then fitted over one end of a ceramic bridge while a standard screw base is fitted over the other end of the bridge. Prior to the fitting of the screw base to the bridge the lead wires of the lamp are directed and soldered to the screw base. With the skirt and screw base positioned on the bridges, the edges of the skirt and screw base are crimped into slots located on the periphery of the bridge. The crimping operation completes the forming of the base of the lamp.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of the completed lamp and base.
FIG. 2 is an exploded view of the base components of the lamp.
FIG. 3 is an enlarged cross-sectional view of the base.
DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I of the drawing, the complete lamp structure is shown. The main components are an elongated tubularshaped envelope 10, having a conventional vertical filament structure 12 sealed within the envelope and a base assembly 14 fixed to its lower end. In FIG. 2 each component is clearly shown in an exploded view. The base assembly 14 comprises a standard screw base 16 and a ceramic bridge 18 positioned between the base 16 and an extension skirt 20. The skirt is provided with a formed screw impression 22 so that it can be fitted to a metal screw adapter 24 fixed to the lower end of the envelope 10. The ceramic bridge 18 has a central orifice l9 and two reduced steps 30 separated by a central portion 34 that is equal in diameter to that of the skirt 20 over the base 16. With this arrangement the base can be fitted over one of the steps 30 and the skirt 20 is fitted over the other step. The central portion 34, being of larger diameter than the steps 30, forms a ridge that insulates the base from the skirt. As viewed in FIG. 2, a series of slots 36 are positioned about the periphery of the bridge 18. Each alternate slot terminates just short of the length of the bridge providing a stop in both directions.
As viewed in FIG. 1, the extended base is shown in a fully assembled position. The skirt 20 is first fitted to one of the reduced steps 30 of the bridge 18 and then screwed onto the screw adapter 24 that is fixed on the lamp envelope 10.
The lead wires 38 are directed through the orifice 19 of the bridge 18, one of the lead wires being directed back into one of the slots 36 and the other lead wire being directed to a central contact button 40 of screw base 16. The base 16 is fitted over the other reduced end of the ceramic bridge 18. As can be seen in FIG. 3, the lead wire that is directed back into one of the slots 36 is in contact with the edge of the screw base 16. The distal end of each of the lead wires 38 are then soldered in place providing electrical continuity for the filament structure 12.
The final phase of the assembly of the base is accomplished by a staking or deforming operation where the edges of the skirt 20 and the base 16 are alternately deformed into the slots 36. As mentioned above, the edges of the skirt and the base are deformed into the slots that are aligned to the stop part of the slot. This will lock the skirt 20 and the base 16 permanently to the bridge 18.
This particular base fabrication allows low production volume lamps to be produced without the expensive cost of setting up glass-forming machinery that was usually used in forming the bridging between the skirt and the base.
1. A base assembly for a lamp having an hermetically sealed lamp envelope with a screw adapter fitted to an end thereof, a filament structure including a filament disposed in said lamp envelope and a pair of lead-in wires extending from said lamp envelope, said base assembly comprising: a preformed ceramic bridge, said bridge having reduced end portions, a central orifice and spaced slots about its periphery; a metal screw base having a contact button insulated from its main body portion; a metal extension skirt provided with the screw impressions at one end; said metal extension skirt is fitted over one of the reduced portions of said bridge and its edges are deformed into the slots of said bridge, the other end of said skirt is fitted to said screw adapter of said envelope; said lead-in wires of said envelope extend through the said orifice of said bridge; said metal screw base is fitted over the other reduced end of said ceramic bridge, wherein the ends of said lead-in wires are directed to their conductive points on said base, the edges of said base are deformed into said slots of said bridge thereby forming an extended length between the center of the said filament structure and the bottom of said screw base.
2. The base assembly according to claim 1 wherein said ceramic bridge is provided with a raised portion that separates and insulates said skirt from said base.
3. The base assembly according to claim 1 wherein said lead-in wires of said lamp are directed through the orifice of said ceramic bridge to said base.