BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a portion of a prior art outer shell;
FIG. 2 is a similar view of an embodiment of the invention'
FIG. 3 is a similar view of an alternate embodiment of the invention;
FIG. 4 is a planar view of a prior art lamp base after extended heating; and
FIG. 5 is a similar view of a lamp base according to an aspect of the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims taken in conjunction with the above-described drawings.
Referring now to the drawings with greater particularity, there is shown in FIG. 1 a prior art shell or subassembly 8 for a compact fluorescent lamp. The shell 8 comprised a cup-shaped body of a plastic material, such as 30% glass fiber filled, polybutylene terephthalate (30% GFF, PBT). A plurality of lamp receiving apertures 8a were formed in an upper surface 8b, and the interior may accept the electronic ballast components (not shown), mounted upon a flange 8d whose peripheral edge 8e was sealed to the inner surface 8f of the shell 8 opposite the upper surface 8b (see FIG. 4). The problem with such construction appears after some extended use of a lamp in a fixture when the jointure between the flange of the base and the inner surface of shell would separate or crack. This condition is shown in FIG. 4 where the separation is enumerated as 8c.
Referring now to FIGS. 2, 3 and 5, there is shown a subassembly 10 for a lamp base. The subassembly 10 comprises an outer housing 12 having a circumferential wall 14 and a top 16 closing one end 18 of said outer housing 12. At least one and preferably several lamp-receiving apertures 20 are formed in said top 16 and these openings have an edge 20a. An inner housing 22 is contiguous with the entire inside surface 24 of said outer housing 12, including the edges 20a. The outer housing 12 is a metallic material and the inner housing 22 comprises a plastic material. In a preferred embodiment of the invention the metallic material is aluminum and the plastic inner housing material is the before mentioned 30% GFF, PBT.
The plastic material of the inner housing 22 can be injection molded into outer housing 12 as shown in FIG. 2 or can be cemented or otherwise positioned with the outer housing 12 by the intermediary of a compound 23 having good heat transfer capabilities, such as, for example, Locktite 384, as is shown in FIG. 3.
FIGS. 4 and 5 are plan views of a prior art base and a base in accordance with an aspect of the invention after exposure to a high temperature (180° C.) for 2000 hours. While exaggerated here for illustration, the gap 8c that formed in the prior art structure is real and detrimental to the operation of the lamp and is a safety concern upon removal of the lamp from a live electrical socket.
The composite structure of the invention, i.e., the metal outer shell with the integral plastic lining showed no such effects, apparently because of the heat-sinking effect and structural rigidity of the metal shell. It has also been found that constructing the lamp base as described lowers the ignition voltage by up to 25 V. The metal outer shell also eliminates the emission of plastic material from the base, which would deposit on light reflective surfaces of the lighting fixture. The metal shell, therefore, improves lumen maintenance of the lighting system.
While there have been shown and described what are present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.
Patent Application
20070270030
