Note: Descriptions are shown in the official language in which they were submitted.
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Description
Method and apparatus for producing a lamp
Technical field
The invention relates to a method for producing a lamp,
preferably an incandescent lamp pinched at one end, having a
lamp bulb, into which a luminous means and supply leads are
inserted through a feed opening, the lamp bulb being sealed by
pinching the region of the feed opening. In addition, the
invention relates to an apparatus for carryinJ out such a
method, and a lamp produced using such a method.
Background art
Such a method known, for example, from DE 196 23 499 A1 is
used, for example, to produce halogen incandescent lamps.
However, in principle, this method can also be used to produce
lamps of another design, for example, discharge lamps. In the
case of the known method, a bulb tube is firstly provided at an
end face with a rounded dome at which an axially projecting
pump tube fitting is constructed. Furthermore, the bulb tube is
reshaped in a mold by blowing in inert gas to form a lamp bulb
through whose open feed device a frame is inserted for which at
least one filament and the supply leads are constructed.
Furthermore, the pump tube fitting is partially severed such
that a pump tube can be attached to the open tube that results.
The feed opening for the frame is then sealed in a gas-tight
fashion by a pinch, and the inner space enclosed by the lamp
bulb is evacuated via the pump tube and filled ~~:ith a filling
gas containing halogens. In a concluding work coeration, the
pump tube is then melted off such that the lamp bulb is sealed
and the two supply leads project from the pinch.
A similar method is also described in US patent 4,756,701, in
which, however, the configuration of the contour in the region
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of the dome cannot be so exactly executed as is the case in the
prior art in accordance with DE 196 23 499 Al.
It is disadvantageous in the case of these solutions that an
axial projection, the so-called pumping tip, always remains in
the region of the dome owing to the melted-of f pump tube, and
can lead to shadows and interfering structures in the case of
frontal illumination. It is disadvantageous, furthermore, that
these known methods are relatively complicated, since the pump
tube firstly has to be attached and severed again in a
subsequent work step, and the remaining pumping tip must be
sealed.
Disclosure of the invention
It is an object of the present invention to provide a method
and an apparatus for carrying out this method and a lamp in the
case of which the disadvantages described above are eliminated.
This object is achieved by a method for producing a lamp,
having a lamp bulb, into which a luminous means and supply
leads are inserted through a feed opening, the lamp bulb being
sealed by pinching the region of the feed opening, wherein the
filling of the lamp bulb is performed through the feed opening
before the pinching.
Particularly advantageous refinements are to be found in the
dependent claims.
According to the invention, the filling of a lamp bulb is not -
as in the prior art - performed via a specifically attached
pump tube, but via the feed opening that is prese:~:t in any case
and through which a luminous means has been fed into the lamp
bulb. As a result of this solution, a dome of she lamp bulb
that is remote from this feed opening can be designed with a
smooth surface without a pumping tip, and so it -s possible to
significantly improve the end-face illuminatio:~: by contrast
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with conventional solutions. In comparison tc the generic
methods, the production of the lamps is also simplified, since
the separated work steps for constructing and se-:ering/welding
the pump tube can be eliminated.
It is preferred to carry out the filling and tr_~ pinching in
the region of the feed opening in a space sealed -n a gas-tight
fashion, preferably in a pressure vessel in which both a holder
for the lamp bulb, the luminous means and also the pinching
device are arranged.
The filling can be performed by flooding the pressure vessel
with the filling gas or via a suitable gas filling apparatus.
The method can be further simplified when the 1-.~ating of the
region of the lamp bulb that is to be pinched is performed by
high-energy radiation, for example laser radiation. The laser
itself can be arranged outside the space/pressure vessel, it
being possible for the laser beam to enter the vessel interior
via one or more laser windows.
It can be advantageous, depending on the lamp tc be produced,
to allow the laser beam to enter from two sides or one side,
there being a need in the last-named case, at least, to rotate
the lamp in order to heat the pinch region on bot:-: sides, while
in the first-named case diametrically arranged surfaces are
heated simultaneously.
The quality of the pinch seal can be substant,~ally improved
when a laser spot is deflected by means of a scanner in order
to produce a predetermined beam profile that males the pinch
region to be directionally heated. This beam profile is set,
for example, such that the intensity rises gradua-1y toward the
feed opening, that is to say toward the lower ed~:e of the lamp
bulb, in order to avoid radiation losses in this ragio~~:. In the
case when the lamp bulb is held via lamp pincers or the like,
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it is preferred to raise the intensity of radiation toward
these lamp pincers, as well, in order to mini~:.ize radiation
losses via the pinchers, such that continuous and uniform
heating of the pinch region is ensured.
For halogen incandescent lamps, the lamp body is usually formed
from silica glass - in order to minimize formation of Si02
(that is to say formation of SiO~ vapor), and the laser power
can be reduced as a function of the irradiatio~: period. The
SiO~ vapor or quartz vapor produced during heating is
preferably evacuated, for example, by means of an evacuation
tube that is directed onto that region of the lamp vessel which
is to be heated.
It emerged that a laser power between 300 watts a:~:d 2500 watts,
and an irradiation period in the range from 2 seconds to
20 seconds suffice.
An important field of application of the method according to
the invention consists in the production of so-called reflector
lamps in which the lamp bulb is widened in the manner of a
reflector and provided with a reflection layer, since no
pumping tip that is inevitably produced in lamps produced using
conventional methods is constructed in the region of a dome
closing the reflector.
Brief description of the drawings
The aim below is to explain the invention in more detail with
the aid of exemplary embodiments and with reference to
drawings, in which:
figure 1 shows a front view of a halogen inca:,descent lamp
produced using the method according to the invention;
figure 2 shows a side view of the halogen inca:vdescent lamp
from figure l;
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figure 3 shows a bottom view of the halogen incandescent lamp
from figure l;
figure 4 shows a side view of a halogen reflector lamp produced
using the method according to the invention;
figure 5 shows a basic design of an apparatus according to the
invention for carrying out the method and
figure 6 shows a schematic of a lamp holder of the apparatus
from figure 5.
Best mode for carrying out the invention
The invention is explained below with the aid of low-volt
halogen incandescent lamps. As already mentioned at the
beginning, however, the application of the method according to
the invention and of the apparatus according to the invention
are not in any way restricted to such lamp types, but are
selected here only by way of example.
Figures 1 to 3 show an exemplary embodiment of a halogen
incandescent lamp that can be designed for low-volt operation
or system voltage, and which can be used in the living room or
as a built-in furniture luminaire.
The incandescent lamp 1 has a lamp bulb 2 that has
approximately the shape of a hollow cylinder in the raw state
(dashed in figure 2), an end section being formed by a
spherically curved dome 4. By contrast with conventional
halogen incandescent lamps, this dome is not provided with a
pumping tip 6, which is indicated by dashes in figure l, but is
of smoothly flat design such that the end-face e~.ission is not
impeded. The lamp bulb 2 is produced from silica glass or from
hard glass.
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Constructed at the lower end section, in figures 1 and 2, of
the lamp bulb 2 is a pinch seal 8 via which a frame 10 is held
in a gas-tight fashion in the lamp bulb 2. The frame 10 has a
filament 12 whose axis runs coaxially with the lamp axis
(vertically in figure 1). The filament wire forms two supply
leads 14, 16 that are connected to the molybdenum foils 18, 20
arranged in the pinch seal 8. These foils are connected, for
their part, to base pins 22, 24 which are situated outside the
pinch seal 8. The pinching is performed via shaping pinching
jaws such that in the side view in accordance with figure 2,
the cylindrical base body is pressed flat thus resulting in
accordance with figure 3 in a profile that is widened in the
shape of a trapezoid at its outer narrow sides 26, 28. The
profile, to be seen in figure 3, of the pinch 8 is determined
by the geometry of the shaping pinching jaws.
The inner space of the lamp bulb 2 is filled in the case of
halogen lamps with a filling gas that contains a fraction of a
halogen (30 to 3000 ppm). The halogen cycle set up when the
lamp is switched on is sufficiently well known, and so there is
no need for explanations in this regard.
A particular feature of the above-described incandescent lamp 1
consists in that the evacuation and filling with filling gas is
not - as is customary - performed via a pump tube applied to
the pumping tip 6, but through the feed opening 30, open in the
raw state (dashed in figure 2), of the lamp W_ilb 2 before
pinching - no pumping tip 6 is required and the dome 4 can
therefore be designed with high optical quality.
Figure 4 illustrates a variant of an incandescent lamp 1
designed as a halogen reflector lamp. The basic design of this
lamp is the same as in the above-described exemplary
embodiment, that is to say, a frame 10 is held in a lamp bulb
2, the lower end section of the lamp bulb 2 bei~:g sealed in a
gas-tight fashion via the pinch seal 8. In contrast to the
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above-described exemplary embodiment, the pinch seal 8 merges
into a neck 32 that then widens like a funnel to form a
reflector 34 that is closed by the dome 4, which is likewise of
spherical design but more strongly cambered. The funnel-shaped
peripheral walls of the reflector 34 are provided with a silver
coating 36 acting as reflection layer.
Both lamps (figures 1 to 3; figure 4) can additionally be
further provided with a special interference filter coating via
which heat is retroreflected onto the filament such that less
energy need be fed from outside in order to keep the filament
at operating temperature. This infrared coating (IRC) enables a
higher light yield and thus a saving of energy costs for
operating the lamp. If such a coating is applied, the lamp bulb
2 is constructed with an elliptical cross section.
As mentioned at the beginning, the pinch and thus the gas-tight
sealing of the lamp bulb 2 is performed downward in the prior
art after the outer contour of the lamp bulb 2 has been shaped
by means of shaping pinching jaws 35, via which the regions of
the lamp bulb 2 which adjoin the pinch seal 8 can also be
subsequently shaped. In the case of conventional solutions,
heating to deformation temperature is usually performed by
means of gas burners via which the region of the pinch seal 8
is heated.
Figure 5 shows an apparatus with which the method according to
the invention can be carried out, in which case the lamp bulb 2
is filled from below via the feed opening 30, and the lamp bulb
2 is heated by means of laser radiation.
In accordance with figure 5, the apparatus has a pressure
chamber 38 in which one or more of the incandescent lamps 1
that are to be filled and pinched are arranged. T:~ese are held
via a device that is illustrated in more detail i.~. figure 6.
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The pressure chamber 38 can be filled with inert gas by means
of an inert gas line 40, or evacuated. Furthermore, dipping
into the pressure chamber 38 is a filling gas tube 42 that dips
into the feed opening 30 that is illustated in figure 2 and is
connected to a filling gas line 44.
As an alternative to the tube, it is also possible - as
indicated by dashes - for the entire pressure chamber to be
flushed via the filling gas line 44 such that it is possible to
dispense with the tube 42.
A laser 46 is used to heat the pinch region, a CO= laser with a
wavelength of 10.6 um being employed in the illustrated
exemplary embodiment - it also being possible, of course, for
other laser types to be used.
The laser beam emitted by the laser 46 is directed onto the
pinch region of the lamp bulb 2 through a laser window 54 of
the pressure chamber 38 via a suitable focusing optical system
comprising, for example, a prism 48, a parabolic mirror 50 and
a swivelable scanner mirror 52. In the exemplary embodiment
illustrated in figure 5, the laser beam enters the pressure
chamber 38 on one side such that in each case it is also only
one side of the lamp bulb 2 that is heated. Such a focusing
optical system presupposes that the incandescent lamp 1 is held
rotatably in the pressure chamber 38 such that the pinch region
can be heated uniformly on both sides. It is possible to
dispense with this rotatable bearing of the incandescent lamp 1
when the laser beam is split via the prism 48 into two
component beams that then enter the pressure chamber 1 from
left and right via two laser windows 54 - that is to say the
beam path illustrated in figure 5 is then reflected about the
vertical axis. However, it can also be advantageous with this
variant to rotate the incandescent lamp 1 during heating.
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The drive of the scanner mirror 52 is controlled in such a way
that the laser spot sweeps a predetermined area a, it being
possible by controlling the scanner drive to set a
predetermined beam profile via which the heating is controlled
as a function of distance. This may be explained with the aid
of figure 6.
Figure 6 shows the incandescent lamp 1 in the clamped state,
the area swept by the laser beam being indicated by dashes.
The non-deformed lamp bulb 2 (see figure 2) is held by a bulb
rod 54 that can rotate about the vertical axis. The frame 8
introduced into the lamp bulb 2 through the feed opening 30 is
held in its predetermined position relative to the lamp bulb 2
by a frameholder 58, which is likewise supported rotatably.
Extending through the frameholder is the tube 42 through which
the filling gas can be pressed into the interior of the lamp
bulb 2.
Depending on the setup of the method (filling gas being fed via
the tube 42 or by flushing the pressure chamber 38), the
filling gas is set to a slight overpressure that can be bet~,reen
190 and 300 mbar depending on lamp volume.
After or during the filling of the lamp bulb, the laser 46 is
fired, and the bulb rod 56 as well as the frameholder 58 rotate
synchronously at a rotational speed of between 1~0 to 600 rpm.
The scanner mirror drive is controlled in this case such that a
beam profile as indicated on the right in figure ~ is set. That
is to say, the intensity profile rises slightly in the region
of the bulb rod 56 in order to compensate radiation losses via
the lower edge of the bulb. The intensity profile also rises
toward the lower edge, that is to say, toward the feed ope:,ing
30, in order to compensate the radiation losses v~n this region
- the result of which is to achieve a very uniform heating of
the sections to be pinched. The irradiation period and the
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laser power are set in this case such that the Si0= development
(that is to say, the evaporation of Si02 or the formation of
quartz vapor) is minimized. Experiments showed that an
irradiation period can lie in the range of between 2 to
20 seconds given a laser power of between 300 and 2500 watts.
The laser power can be reduced in stages during the irradiation
period in order to minimize further the SiO~ development. It
was possible in principle to establish that the SiO~ formation
can be reduced in conjunction with falling laser power and, at
the same time, a somewhat longer irradiation period.
After the pinch region has been heated, the shaping pinching
jaws 60, 62 (dashed and dotted in figure 6) are closed and the
pinch illustrated in figures 1 to 3, or another geometry, is
formed.
In order to remove the Si0-~ vapor produced during heating, it
is also possible to provide a further evacuation in the
pressure chamber 38 with the aid of an evacution tube. The
evacuation tube is directed toward the region to be heated, for
example, the pinch, in order to evacuate the quartz vapor
produced during heating.
There are disclosed a method and an apparatus for producing a
lamp, and also a lamp produced using this method, in the case
of which a lamp bulb closed at one end is filled through a feed
opening for a luminous means. It is thereby possible to design
a dome of the lamp bulb to be smooth without a pumping tip.
