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.
1. A tungsten halogen lamp comprising:
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.
2. The lamp of Claim 1 wherein a portion of said lamp envelope is pressed at one end
thereof to form a base for fixedly retaining both said filament wires and said extensions
of said filament support wire therein.
3. The lamp of Claim 2 wherein said lamp envelope includes a tubulated dome portion,
said loop extending within said dome portion.
4. The lamp of Claim 2 further including a pair of foil seals, each of said foil seals
connecting individual external filament leads to a respective one of said tungsten
filaments.
5. The lamp of Claim 2 wherein said filament support wire includes a portion extending
into a recess in said lamp envelope.
6. The lamp of Claim 2 wherein said filament support wire includes a pair of arcuate
portions shaped to conform to the inner periphery of said lamp envelope, said arcuate
portions each engaging an internal surface of the walls of said envelope.
7. A method of making a tungsten halogen lamp having a glass envelope and a filament
member therein, said method comprising:
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.
8. The method according to Claim 7 further including providing a dome portion within
said opposing end portion of said glass tubing and thereafter positioning at least
part of said loop of said filament support structure within said dome portion during
said insertion of said filament member and said filament support structure.
9. The method according to Claim 7 wherein said sealing of said open end of said glass
tubing is accomplished using a press-sealing operation.
10. The method according to Claim 7 wherein said sealing of said opposing end portion
of said glass tubing is accomplished using a tipping operation.