Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Electric lamp having an outer bulb
Technical field
The invention relates to an electric lamp having an outer bulb
and having an inner vessel, in particular a discharge vessel,
arranged therein, the inner vessel being elongate and having
two ends, the ends having seals , and the outer bulb only
partially surrounding the inner vessel. Of concern here are, in
particular, discharge lamps such as metal halide lamps, or else
halogen incandescent lamps.
Background Art
US-A 20040253897 has disclosed an electric lamp having an outer
bulb, in the case of which the outer bulb only partially
surrounds the inner vessel made from glass. The outer bulb is
itself produced from glass and is fixed to the seals of the
inner vessel. This partially covering outer bulb could in this
case be fixed using an established technique by means of glass
shaping and subsequent glass-to-glass fusing. However, it has
been shown that these steps overall have relatively stringent
requirements in terms of machine capacity and energy.
Disclosure of the Invention
One object of the present invention is to provide an electric
lamp having an outer bulb and having an inner vessel, in
particular a discharge vessel, arranged therein, the inner
vessel being elongate and having two ends, the ends having
seals , and the outer bulb only partially surrounding the inner
vessel , which lamp makes simple and cost-effective production
possible.
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This object is achieved by the following features:
the outer bulb is an open tube made from glass and having two
ends, at least one end being sealed by an essentially planar
sheet-metal part made from resilient sheet metal, the sheet-
s metal part being fixed on the associated seal.
Particularly advantageous refinements are described in the
dependent claims.
The electric lamp according to the invention has an outer bulb
and an inner vessel, usually a discharge vessel, which is
arranged therein and is sealed in a vacuum-tight manner.
However, the electric lamp according to the invention may also
be a halogen incandescent lamp having an outer bulb.
The novel connection between the inner vessel and the outer
bulb makes possible a purely mechanical mounting system, which
is based on sheet-metal clips. This considerably reduces the
machining complexity and also no longer requires any heating
energy. The novel concept is particularly suitable in cases in
which a specific atmosphere is not required in the outer bulb,
for example a vacuum or a pure nitrogen atmosphere.
One particularly preferred embodiment, in which the advantages
of the novel concept are particularly prevalent, is an
arrangement in which the outer bulb is sealed by sheet-metal
parts at both mutually opposing ends of the inner vessel.
Typical applications are metal halide lamps and halogen
incandescent lamps.
Of particular concern is an electric lamp having an outer bulb
and having an inner vessel, in particular a discharge vessel,
arranged therein, the inner vessel being elongate and having
two ends, the ends acting as seals, and the outer bulb being an
open tube made from glass and having two ends, at least one end
being sealed by an essentially planar sheet-metal part made
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from resilient sheet metal, the sheet-metal part being fixed on
the associated seal. The inner vessel can in this case either
be made from glass, usually quartz glass or hard glass, or from
ceramic.
The sheet-metal part is preferably of annular design, the outer
diameter of the ring approximately corresponding to the outer
diameter of the open tube.
In order to hold the sheet-metal part on the tube, lugs, which
are bent back through approximately 90° and bear on the inside
against the tube in a clamping manner, are preferably
distributed over the circumference of the outer diameter of the
sheet-metal part. Another way of holding the sheet-metal part
on the tube is a circumferential bent-back cover rim, which is
fixed to the tube, for example, by means of an adhesive
compound.
The outer bulb is centralized in a simple manner when the seal
has a circular cross section in the form of a cylinder.
In particular, the sheet-metal part has a central opening which
is matched to the cross section of the seal. The seal is
usually in the form of a fuse seal having a circular-
cylindrical cross section. The seal may, however, also be a
pinch seal, whose cross section is essentially rectangular.
A particularly simple way of stopping and holding the sheet-
metal part securely on the seal is achieved by the seal being
cylindrical with a given diameter and opening out over one edge
into an extension part which is in the form of an open tube
having a relatively large diameter, the diameter of the central
opening of the sheet-metal part being matched to that of the
seal.
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The outer bulb is fixed in a clamping manner by the lugs of the
sheet-metal part not being straight but being bent out in the
manner of a roof.
The sheet-metal part is matched to the seal by a zone, which
surrounds the central opening, of the sheet-metal part being
bent out slightly from the plane of the sheet-metal part.
This is preferably achieved by the zone being divided into a
plurality of tabs by means of radial slots, said tabs being
capable of individually being bent up slightly.
The two seals are preferably designed such that the tube can be
open on both sides and can be sealed at both ends by identical
sheet-metal parts. However, it is not impossible for one end of
the tube to be fixed to the seal in a conventional manner as in
the prior art.
In the case in which a specific atmosphere is desired in the
outer bulb, the outer bulb can be kept air-tight or vacuum-
tight by a suitable sealing means, such as a sealing ring,
being introduced in the contact region between the sheet-metal
part and the end of the open tube.
In one preferred embodiment, the inner vessel is sealed at two
mutually opposing ends with identical seals, the outer bulb
being fixed to identical seals of the inner vessel at both ends
by means of a sheet-metal part.
At least some of the sheet-metal part can, in particular, be
coated by an oxidic layer, in particular titanium oxide, in
order to prevent photo ionization being produced by means of UV
radiation. Furthermore, the oxidic layer improves thermal
insulation.
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A method for producing a lamp having an outer bulb follows the
following steps, namely that an open tube is pushed centrally
over an inner vessel, and then a sheet-metal part is placed
onto the open end of the tube, the lugs being bent back through
approximately 90°, and the central opening being selected to be
slightly smaller than the cross section of the associated seal,
with the result that, when it is placed on the seal, the
central opening is enlarged to the diameter of the seal by the
individual tabs of the surrounding zone being bent out slightly
from the plane of the sheet-metal part.
Brief description of the drawings
The invention will be explained in more detail below with
reference to a plurality of exemplary embodiments. In the
drawings:
figure 1 shows a perspective side view of a metal halide
lamp;
figure 2 shows various views of one exemplary embodiment
of a sheet-metal part;
figures 3 to 5 show various views of further exemplary
embodiments of a sheet-metal part; and
figure 6 shows a side view of a further exemplary
embodiment of a halogen incandescent lamp.
Best mode for carrying out the invention
Figure 1 shows the perspective view of a metal halide lamp 1
sealed at two ends. The discharge vessel 2 which is in the form
of a barrel body and is made from quartz glass (or else A1203
ceramic) encloses two electrodes 3 (only one is visible) in
addition to a metal halide filling. A coating 11 is applied at
the level of the electrodes 3. The bulb ends are sealed off by
means of fuse seals 4, in which foils 5 are embedded. These
foils 5 are connected to outer power supply lines 6. The outer
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power supply line 6 is guided in a tubular sleeve 7 and ends at
a base part (not illustrated). The central part of the
discharge vessel is surrounded by an outer bulb 12.
The outer bulb 12 comprises a tube 13 which is open at both
ends, is made, for example, from hard glass and has a
considerably larger diameter than the discharge vessel 2. A
sheet-metal part 14 in the form of a disk-shaped circular ring
is fixed to each of the ends of said tube 13. The outer
diameter of the sheet-metal part 14 approximately corresponds
to the diameter of the open tube 13. Bent-back lugs 15, which
guide the tube 13, are distributed over the circumference.
The sheet-metal part 14 also has a central opening 19, as shown
in figure 2, which is matched to the cross section of the
associated seal 4.
In order to reliably achieve this aim, a zone 20, which is bent
out slightly from the plane of the sheet-metal part, adjoins
the central opening. For this purpose, the zone 20 is divided
into five tabs 21, which are separated from one another by
radially extending slots 22.
In the still uninstalled state, these tabs 21 are initially
almost in the same plane as the rest of the sheet-metal part,
but, in contrast, are bent back through approximately 5°. If
the sheet-metal part 14 is pushed onto the sleeve 7, the tabs
open out and in the process increase the size of the central
opening, in which case they surround it closely. The diameter
of the seal 4 is slightly smaller than that of the sleeve 7,
with the result that the tabs are anchored on the edge 23 there
between if they slide over the sleeve 7 finally onto the seal
4.
In the still uninstalled state, the lugs 15 are likewise
initially in the plane of the sheet-metal part 14, since
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initially they are stamped out, cf. figure 2a. The stamped
sheet-metal part is only then preprocessed by the lugs being
bent back through approximately 90° and the base of the zone
being perforated, if appropriate. Only then is the sheet-metal
part pushed onto the seal. See in this regard the schematic
sectional illustration shown in figure 2b and the perspective
illustration shown in figure 2c, in each case in the bent-back
state.
Figure 3 shows one exemplary embodiment of a sheet-metal part
25 having a continuously circumferential rim 26 made from
spring steel. This rim 26 can be fixed to the open end of the
tube 13 by means of adhesive, as a result of which an air-tight
seal is made possible there. However, it is generally
sufficient if the two sheet-metal parts merely fix the outer
bulb between them, in which case they themselves are stopped at
the edge of the seal. Another possibility for the outer bulb
being kept air-tight is for a sealing ring 40 to be introduced
in the contact region between the sheet-metal part and the end
of the open tube 13, cf. figure 3b.
Figure 4 shows a sheet-metal part 27 having a rectangular
opening 28. This sheet-metal part 27 is especially suitable for
discharge vessels having a pinch seal as the seal.
Figure 5 shows an exemplary embodiment of a sheet-metal part 30
having lugs 31, which are bent back out slightly in the form of
a roof. This embodiment also fixes the outer bulb 13 in a
clamping manner such that rattling noises are reliably
suppressed.
Finally, figure 6 shows a halogen incandescent lamp 35, in the
case of which one end 36 of the outer bulb is fixed in a manner
known per se to the seal 4 of the inner vessel by means of
being integrally formed on a bead 37. The other open end 38 of
the outer bulb is fixed to a sheet-metal part 14, as described.
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In this case, the central part 12 of the outer bulb has a
larger diameter than the ends 36 and 38. The open tube 7 behind
the fuse seal 4 has a markedly larger diameter than said fuse
seal 4, as a result of which the sheet-metal part 14 is stopped
reliably at the edge there between. Although such an edge is
not absolutely necessary if the spring force of the sheet-metal
part is selected to be sufficiently high, it does considerably
improve the stopping effect.
