Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
1999-06-29
2001-06-12
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C313S634000, C313S110000
Reexamination Certificate
active
06246167
ABSTRACT:
BACKGROUND OF THE INVENTION
When fluorescent lamps break, fragments of the glass tube and powders from the phosphor coating inside the lamp are scattered about. In places where food is processed or stored, and particularly in food-processing plants and lighted display cabinets in supermarkets where stocking clerks and customers handle food in proximity to the cabinet lamps, it is at least highly desirable, and is often required by government regulations, that the lamps be protected in a way that minimizes the possibility of the lamps being broken and if they do break the possibility of glass fragments and phosphor powders escaping and contaminating the food. Fluorescent lamps with protective assemblies are known and widely used for this purpose. Fluorescent lamps with protective assemblies are also desirable in industrial settings and in various places in residences, such as kitchen, shops and garages. Examples of such lamps are those described and shown in U.S. Pat. Nos. 3,453,470 (Hammer, Jul. 1, 1969); 3,602,759 (Evans, Aug. 31, 1971); 3,720,826 (Gilmore et al., Mar. 13, 1973); 3,808,495 (Win, Apr. 30, 1974); 4,048,537 (Blaisdell et al., 1977); 4,924,368 (Northrup et al., 1990); 5,173,637 (Sica, 1992); 5,536,998 (Sica, 1994); and 5,729,085 (Sica, 1998). The Sica patents are owned by the assignee of the present invention.
In most instances, the prior art protective assemblies for fluorescent lamps include special molded end fittings that fit onto the terminal caps of the lamp and hold a protective sleeve in place on the lamp. In some cases, the end fittings are intentionally designed so that they can be removed from the lamp, thus allowing the protective assembly to be reused as lamps burn out and are replaced. Removable protective assemblies do not fully ensure that glass fragments and phosphor powders are retained in case the lamp breaks, inasmuch as the removable end fitting can be dislodged from the lamp and the protective sleeve if the lamp breaks. Regardless of whether the end fittings are permanently attached to the lamp or are removable, they are relatively expensive and usually have to be designed for a specific lamp style to ensure a proper fit.
The protective assemblies of the Sica '637 and '998 patents referred to above consist of a protective tube extruded from a polycarbonate resin that is stabilized against ultraviolet radiation and a collar at each end that is shrink-fitted over the flange portion of the respective terminal cap and over an end portion of the protective sleeve. Each collar is bonded to both the terminal cap and the protective sleeve to ensure that the terminal caps, collars and protective sleeve remain intact should the glass tube of the lamp break. The protected lamp of the Sica '085 patent also has a protective tube extruded from a polycarbonate resin that is stabilized against ultraviolet radiation. Each end of the tube is formed by thermal and mechanical compression working to provide a necked down end portion. The necked down end portions are secured to the terminal caps of the fluorescent lamp by an adhesive, preferably by a double-faced contact adhesive tape. The lamps of the Sica patents provide excellent protection against breakage of the lamp, and if the lamp should break, the protective assembly provides an enclosure for the lamp glass tube and terminal caps that is secure against separation, thus preventing release and scattering of glass fragments and phosphor powders. The Sica lamps are relatively inexpensive to produce, inasmuch as they use simple tubular elements and commercially available adhesive tapes and are easily and quickly assembled.
WO 99/12186 (published Mar. 11, 1999, Sica) describes and shows curved fluorescent lamps, such as U-shaped lamps, that are protected by two-part sleeves, each part being injection-molded to a shape in plan that corresponds to the shape of the lamp and to a semi-cylindrical cross-section from a polycarbonate resin that is highly stabilized against ultraviolet radiation. Each part has a flange along each edge, and the flanges of the two parts mate and are joined by fusion bonding, chemical bonding or adhesive bonding. Each end of the protective sleeve is sealed and adhered to the terminal cap of the lamp by a shrink-fit collar and an adhesive (see Sica '637 and '998 patents referred to above) or by a thermally/mechanically formed necked down portion and an adhesive (see Sica '085 patent referred to above).
In order to fit over an entire lamp, the two parts of the protective sleeve of WO 99/12186 are of large size, thus requiring very expensive molds. Similarly, the very long lengths of the mating flanges make it difficult to join the flanges, regardless of the type of joints.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a U-shaped fluorescent lamp in which the glass tube or envelope of the fluorescent lamp component is protected from impacts and thus from being broken. Yet another object is to prevent scattering of glass fragments, phosphor powders, and mercury in the environment in the event that the glass tube of the fluorescent lamp is shattered or broken. Still another object is to minimize the size of injection-molded parts, thus reducing the costs of the molds, reducing the lengths of joints between molded parts, and facilitating joining the injection-molded parts.
The foregoing objects are attained, in accordance with the present invention, by a lamp assembly that includes a U-shaped fluorescent lamp having a U-shaped glass tube that includes a loop portion and a pair of straight leg portions integral with the loop portion and a terminal end cap joined to a free end of each leg portion. The lamp of the lamp assembly is of conventional construction and is widely available commercially. The lamp is enclosed in and protected by a protective assembly having a loop unit and a pair of leg units. The loop unit is composed of a pair of loop parts, each loop part being formed of a transparent or translucent non-frangible polymeric material and being semi-cylindrical in cross-section and shaped in plan to match the shape in plan of the loop portion of the glass tube of the lamp. The loop parts are coextensive and engage each other along mating edges and are joined to each other along the edges. Each leg unit is a straight tube of a transparent or translucent non-frangible polymeric material of cylindrical cross section and is joined at one end to one end of the loop unit and at the other end to the terminal end cap of the lamp.
The construction of the protective assembly from two molded loop parts and two straight parts allows the loop parts to be relatively small, which permits the use of a much smaller, lower cost mold to produce them. The smaller loop unit also facilitates joinder of the two parts, the lengths of the joints between the two parts being much less than those of a protective assembly made of two half parts that are joined to cover the entire lamp (see WO 99/12186 referred to above). A protected lamp according to the present invention is also attractive in appearance, the joints of the loop unit being relatively unobtrusive and the straight parts being free of joints along their lengths.
In a preferred embodiment, the edges of the loop parts are joined to each other by mechanical couplings, such as a Ad plurality of snap-fit couplings. Each coupling may consist of a lug on one loop part, the lug having a slot, and a hook on the other loop part, the hook being received through the slot and having a shoulder engaged in capturing relation with a portion of the lug adjacent the slot. Mechanical snap-fit couplings make assembly of the loop unit quick and easy—assembly can be done by hand, no tools being required.
Each straight tube is, to advantage, joined to the loop unit by a telescopic joint between an end portion of the loop unit that is cylindrical in cross section and an end portion of the straight tube. It is desirable for the end portion of the straight tube to telescopically receive the end portion of the loop u
Baker & Botts L.L.P.
Patel Nimeshkumar D.
Williams Joseph
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