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(11) | EP 0 173 995 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Bridgeless tungsten halogen lamp |
| (57) A single-ended, tungsten halogen lamp having a tubular hard glass envelope containing
an inert gas and a halogen, preferably bromine, therein. An improved bridgeless support
structure is provided in which a wire support is attached to one end of a pair of
filament coils. The wire support extends in two directions from the point of attachment
and includes two extension portions which are each secured in the press-sealed base
portion of the envelope to provide a fixed filament support with improved shock resistant
capabilities and with reduced possibility of contamination due to elimination of the
bridge element. A method of making the lamp is also described. |
TECHNICAL FIELD
[0001] The present invention relates in general to incandescent lamps of the tungsten halogen type and more particularly to an improvement in the filament support structure of such lamps.
BACKGROUND
[0002] In conventional tungsten halogen lamps, the parameters of the mount assembly are the limiting factor dictating the lamp dimensions which in turn control the performance characteristics of the lamp. Such characteristics include coil temperature, wattage and light distribution.
[0003] One example of a mounting structure for use in conventional tungsten halogen lamps is described in Oetken et al.. U.S. Patent 4.415.833. A more sophisticated mounting structure is shown in U.S. Patent 4,450.381 to Kendrick et al. Typically. such lamps employ an insulative bridge (quartz or glass) usually located below the filament structure in which the lamp filament leads are embedded. The bridge secures the filament leads thereby supporting the filaments. In addition, the bridge serves to define the mount dimensions.
[0004] Most lamps of this variety are of "single-ended" construction, in that only one end of the lamp is press-sealed about the lead-in filament wires and additional structure, if any (e.g.. molybdenum foil elements). The remaining, opposed end is typically sealed using a known tipping operation.
[0005] Various bridge structures are shown in the following patents:
U.S. 3.629.642 (Demas)
U.S. 3.736.456 (Middlehoek et al)
U.S. 3.764.845 (DeFraeye)
U.S. 3.780.333 (Flynn)
[0006] The bridge understandably adds to the cost of the lamp structure, in addition to being a potential source of contamination. The added cost results from the labor and material required to produce the bridge assembly and effect location of the filament structure therein. The contamination is attributed to moisture or other impurities entrapped in the bridge which is driven out under the high temperatures encountered during lamp operation.
DISCLOSURE OF THE INVENTION
[0007] In accordance with the invention, the lamp filament structure is improved by eliminating the typical glass or quartz bridge. In place thereof, a wire support is provided which is attached to one end of the filament coil(s). The wire support extends in two directions from the point of attachment. Each extension has sufficient length and flexibility to extend beyond the internal dimensions of the lamp envelope. Therefore, when initially assembled in such envelope, the supports extensions must be compressed and the lamp envelope slid over the compressed wire support attached to the filament, or vice versa.
[0008] Once assembled in the lamp envelope, the lamp filament support structure maintains its assembled position within the envelope through friction between the interior wall of the envelope and the compressed wire. The lower portion of the lamp envelope is then press-sealed such that the ends of the wire support extensions, as well as the filament support leads. are embedded (e.g.. simultaneously, using known pressing equipment) in the pressed portion of the lamp envelope. This results in a fixed filament support and an improved shock-resistant lamp structure with lessened possibility for contamination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009]
FIG. 1 is a front elevation view, partly in section, of a tungsten halogen lamp according to a preferred embodiment of the present invention;
FIG. 2 is a partial sectional view of the embodiment of FIG. 1. on a slightly enlarged scaled, in a partially disassembled state showing the procedure for inserting the support structure into the lamp envelope:
FIG. 3 is a front elevation view, partly in section, of a tungsten halogen lamp according to an alternate embodiment of the invention;
FIG. 4 is a front elevation view, partly in section, of a further embodiment of the invention:
FIG. 5 is a front elevation view, partly in section, of a tungsten halogen lamp according to yet another embodiment of the invention; and
FIG. 5A is a sectional view as taken along the lines A-A in FIG. 5 which for simplicity only shows the curved portions of the filament support wire.
BEST MODE FOR CARRYING OUT THE INVENTION
[0010] 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 in connection with the above described drawings.
[0011] Before discussing the details of the improved filament support structure of this invention, a discussion follows of the main lamp components. In this regard, like reference characters have been used to identify like parts. Thus, all embodiments of the lamp 10 comprise a hermetically sealed. light-transmitting envelope 12 of generally tubular (cylindrical) shape with a conventional (press-sealed) base portion 14. A pair of molybdenum foil seals 16 disposed within the base serve to interconnect the input leads 18 to the filament body. A high melting point material, such as quartz. is typically used for envelope 12, although other hard glasses may also be employed. The hermetically sealed envelope 12 is usually filled with an inert gas, such as argon, nitrogen. krypton, or a mixture thereof, and a halogen additive such as iodine or bromine. In accordance with the present invention, the lamp envelope is preferably of the bromine fill type. The bromine fill may be provided in the form of a given mixture of hydrogen bromide.
[0012] Any one of a number of different types of filament bodies may be incorporated into the lamp. One basic type of filament body is described in connection with the invention.
[0013] FIG. 1 shows a tungsten filament 24 which is referred to in the art as a CC2V (coiled coil) filament including two individual tungsten filament coils 26 and 28. These coils 26 and 28 are secured to respective leads (legs) 27 and 29. respectively.
[0014] In the embodiment shown in FIG. 1. a filament support structure comprises a wire 20 attached to the filament coils 26 and 28 at the intersection 30 between the two coils. As shown, the filaments are held by forming a loop 32 on wire 20 with the intersecting portion 30 passing therethrough. The base of the loop thus holds the filaments at intersection 30. Wire 20 is formed of ductile material compatible with normal environment encountered in halogen lamp operation. Suitable materials include tungsten and molybdenum.
[0015] The wire support structure 20 extends in two directions by wire extensions 40 and 42 outwardly from loop portion 32. The termination of each extension 40 and 42 is, as illustrated. embedded within the pressed portion 14 of lamp envelope 12 along with the foil seals 16 and input leads 18 during the conventional press sealing operation.
[0016] FIG. 2 shows a preferred method of assembling the support structure (shown generally at 60) into an open end of a length of glass tubing which eventually forms the lamp envelope 12 prior to exhausting and sealing thereof. As seen in FIG. 2. the extensions 40 and 42 of wire support 20, when not in compression, extend beyond (and are thus spaced farther apart than) the inner periphery of the envelope. Accordingly, to insert the support structure 60 within the envelope, the extensions must be compressed in the direction shown (by the arrows) as the envelope is slid over the support structure 60. The resultant friction between the wire extensions 40 and 42 and the internal surfaces of the envelope walls enables the support structure to maintain a proper position such that the filaments 26 and 24 are suitably located for optimum lamp illumination. The aforedescribed insertion occurs to the extent that both the filament support structure and filament are located a predetermined distance within the glass tubing. By predetermined is meant a distance such that the subsequent press-sealing of the tubing's open end will include encapsulation (containment) of the extreme ends of extensions 40 and 42 therein, in addition to the ends of the leads 27 and 29. Understandably, this four-point retention at this location assures positive securement of the filament in the desired position. The final step in this process involves tipping the opposing (upper in FIG. 2) end of the tubing using a tipping operation well known in the art.
[0017] Variations of the securing loop 32 shown in FIG. 1 are envisioned in accordance with the invention, with FIGS. 3-5 showing various embodiments of such loops. Each of these alternative embodiments comprises a lamp support structure 60 within a lamp envelope 12 having a pressed base portion 14 and having a pair of molybdenum foil seals 16 respectively affixed to filament leads 27 and 29, which in turn form part of or are connected to filament coils 26 and 28, respectively. In addition, both filament coils are interconnected by the described intersection portion 30.
[0018] Referring to FIG. 3, support wire 20' is similar to support wire 20 of FIG. 1 in that the filament is held or supported by the base of the loop 32'. However, the loop 32' in this embodiment is rotated 180° upwardly (towards the tubulated end of the lamp envelope) to allow the loop to extend into and thus be securedly retained within the tubulated dome portion 70 of the lamp envelope 12. This extension provides an additional point of filament support and therefore added shock or vibration resistance. Dome portion 70 is formed as a result of the aforementioned, known tipping procedure.
[0019] FIG. 4 shows an oval shaped loop structure with a lower portion 32" which holds the filaments at the intersection 30 but includes an upper portion 33 shaped to fit into tubulated device 33 for additional shock resistance. This embodiment thus combines both the advantageous features of the embodiments of FIGS. 1 and 2.
[0020] In FIGS. 5 and 5A, the loop 32 is substantially the same as that shown in FIGS. 1 and 2. However, the portions (80) of wire 20 adjacent the loop are formed into substantially semicircular (arcuate) shapes which each conform (and engage) to the inner peripheral surface of the lamp envelope (as shown more clearly in FIG. 5A). This enables more lamp envelope internal wall surface to be used for filament positioning and retention for shock resistance.
[0021] Comparative tests between the bridgeless mount construction shown in the embodiment of FIG. 1 with respect to prior art quartz bridge mount assemblies were conducted. The results showed that the quartz bridge lamp samples operated an average of about 808 hours before failing, whereas the bridgeless lamps operated for more than about 850 hours with no failures. In addition, many of the quartz bridge lamps exhibited excessive crystal growth, thereby indicating contamination. It is believed that this contamination was caused by the quartz bridge used in the lamp construction. On the other hand, the bridgeless samples, which were processed along with the bridged samples, indicated no such contamination.
[0022] Having described a limited number of embodiments of the present invention, it should now be apparent to those skilled in the art that numerous other embodiments are contemplated as falling within the scope of this invention. Accordingly, this invention should not be limited except as required by the scope of the following claims.
an hermetically-sealed, light transmitting envelope:
an inert fill and halogen disposed within said envelope: filament means including a pair of tungsten filaments interconnected together at one end thereof;
filament wires extending from the opposed, remaining ends of said filaments: and
a filament support wire forming a loop at the interconnection of said filaments to provide support for said filament means, said wire having extensions from said loop which are compressed within said lamp envelope to hold said filament support wire in a fixed position within the lamp to thereby locate and support said filament means within said envelope.
providing a length of substantially cylindrical glass tubing having at least one open end;
providing a filament member including at least one coiled tungsten filament and an extending lead wire secured to or forming part of one of the end portions of said coiled tungsten filament:
positioning a filament support structure including a wire member having at least one loop therein on said filament member, said wire member further including a pair of extension portions which extend from said loop in substantially opposing directions such that portions thereof are spaced apart a greater distance than the internal diameter of said substantially cylindrical tubing;
inserting said filament member and said filament support structure a predetermined distance within said open end of said glass tubing to cause said extension portions of said support structure to compress and frictionally engage the internal surfaces of said tubing member:
providing a seal within said open end of said glass tubing. said seal including part of said lead wire and part of each of said extension portions of said filament support structure therein; and
providing a seal within the opposing end portion of said glass tubing to thereby define said glass envelope.