Note: Descriptions are shown in the official language in which they were submitted.
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Lamp
The invention relates to a lamp in accordance with the preamble
of claim 1.
I. Prior art
Such a lamp is disclosed, for example, in the patent
specification EP 1 006 551 Bl. This document describes a
halogen incandescent lamp, in particular a vehicle headlamp,
with a metal/plastic base, which is provided with an aperture
in order to be able to weld the power supply wires, which
protrude out of the lamp vessel, to in each case one metallic
contact lug arranged in the base by means of a laser.
II. Description of the invention
The object of the invention is to provide a lamp of the generic
type with an improved welded joint between the power supply
line and the electrical contact element.
This object is achieved according to the invention by the
features of claim 1. Particularly advantageous embodiments of
the invention are described in the dependent claims.
The lamp according to the invention has a lamp base, a lamp
vessel anchored therein and at least one luminous means
surrounded by the lamp vessel as well as at least two power
supply wires, which protrude out of the lamp vessel, are used
for supplying voltage to the at least one luminous means and
are each connected
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to an electrical contact element arranged on the lamp base, at
least one aperture being provided in the lamp base for welding
the at least one power supply wire to the corresponding
electrical contact element, which is designed in such a way
that a laser beam with an angle of incidence of zero degrees
can be focused onto the surface of the weld point through the
at least one aperture. This means that the at least one
aperture is designed in such a way that the laser beam for
carrying out the welding operation impinges perpendicularly on
the surface of the weld point. As a result, the quality of the
welded joint between the power supply wire and the contact lug
is improved. In particular, the strength of the welded joint is
increased by approximately 30 percent. It has been shown that,
in the welding operation illustrated in figure 4 in accordance
with the abovecited prior art, the laser beam impinges on the
surface of the weld point at an angle of incidence of
approximately 22.3 degrees and as a result some of the laser
energy is absorbed by the power supply wire and therefore can
no longer be used for the welding operation. Given an angle of
incidence of the laser beam of zero degrees on the surface of
the weld point, as is illustrated schematically in figure 3 for
the lamp according to the invention (the angle of incidence is
measured against the surface normal of the surface), this
disadvantage does not occur or only occurs to a lesser extent.
Preferably, a correspondingly shaped aperture is provided for
each pair of contact lug and
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power supply wire to be welded in order to be able to keep the
size of the apertures in the base as small as possible.
In accordance with the preferred exemplary embodiment, the at
least one aperture is arranged at the same height as the weld
point.
Preferably, the contact elements are in the form of contact
lugs, which each have a groove, into which a bent-back end of
the corresponding power supply wire is threaded. This makes it
possible to join the parts to be welded together in a simple
manner.
The weld point is preferably a web which delimits the groove of
the contact lug since this can be fused in a simple manner by
means of the laser in order to produce the welded joint between
the contact lug and the power supply wire.
III. Description of the preferred exemplary embodiment
The invention will be explained in more detail below with
reference to a preferred exemplary embodiment. In the drawing:
figure 1 shows a schematic illustration of the preferred
exemplary embodiment of the lamp according to
the invention with a reflector, in a partially
sectioned view,
figure 2 shows a cross section through part of the lamp
base of the lamp depicted in figure 1,
figure 3 shows a plan view of an arrangement for
laser-welding the contact lugs and the bent-back
end of the respective power supply line which is
arranged in the groove of the contact lugs
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corresponding to the lamp according to the
invention, and
figure 4 shows a plan view of an arrangement for
laser-welding the contact lugs and the bent-back
end of the respective power supply line arranged
in the groove of the contact lugs corresponding
to the lamp in accordance with the prior art.
The preferred exemplary embodiment of the invention is a
single-filament halogen incandescent lamp, which is provided
for use in a motor vehicle headlamp. This lamp has a vitreous,
substantially cylindrical lamp bulb 10 with a pinch-seal foot
10a, which is sealed in a gas-tight manner. The dome 10b of the
lamp bulb 10 is provided with a light-absorbent coating. An
incandescent filament 11, which is aligned parallel with
respect to the lamp bulb axis and is electrically conductively
connected to two power supply wires 12, 13, which are passed
out of the pinch-seal foot 10a and are made from a molybdenum
wire, is used as the light source. The pinch-seal foot 10a of
the lamp bulb 10 is fixed in a metallic holder, which comprises
the bowl-like holder part 14a, the intermediate ring 14e and
the annular support sleeve 14b. In addition to the metallic
holder 14a, 14b, the lamp base also has a plastic base part 15,
which is provided with the electrical terminals 16, 17 of the
lamp and in which the annular metallic support sleeve 14b is
anchored. The support sleeve 14b has three reference tabs 14c
lying in one plane and a contact-pressure spring 14d for
fitting the lamp in the reflector 20 of a motor vehicle
headlamp. Sealing of the reflector 20 takes
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place by means of a silicone sealing ring 19, which bears
against the outer wall of the reflector 20 and against the
plastic base part 15. The design of the lamp in accordance with
the preferred exemplary embodiment and its use in a headlamp is
illustrated schematically in figure 1.
The electrical terminals 16, 17 of the lamp comprise two
metallic contact lugs 16, 17, which are each welded (not
depicted in figure 1) to one of the power supply wires 12, 13.
The contact lugs 16, 17 are manufactured from sheet steel and
are injection-molded in the plastic base part 15 of the lamp
base. Said contact lugs 16, 17 each comprise an L-shaped steel
sheet. In each case one limb 16a, 17a of the L-shaped contact
lugs 16, 17 is in the form of a plug-type contact, while the
other limb 16b, 17b is equipped with a groove 16c, 17c, into
which in each case the bent-back end 12a, 13a of a power supply
wire 12, 13 is threaded. Those regions of the contact lugs 16,
17 which are normally hidden in the cross section in figure 2
are illustrated by dashed lines in figure 2. The angle region
of the L-shaped contact lugs 16, 17 is injection-molded tightly
in the plastic base part 15 and is therefore not normally
visible. The grooves 16c, 17c are each laterally delimited by
two webs 16d, 16e and 17d, 17e, respectively, of different
lengths. The two webs 16d, 16e and 17d, 17e each have, on their
edge facing the grooves 16c, 17c, a bevel 16f, 17f, which
bevels are used to thread the power supply wire 12, 13 into the
groove 16c, 17c. The shorter web 16e, 17e has a smaller width
than the longer web 16d, 17d. The welded joint between the
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power supply wires 12, 13 and the contact lugs 16, 17 is
produced by means of heating the material of the shorter webs
16e, 17e for a short period of time to above their melting
point by means of a laser. Once the melt has solidified, the
bent-back end 12a, 13a of the power supply wire 12, 13 is
connected to the shorter web 16e, 17e. The L limbs 16b, 17b
which have been welded to the power supply wires 12, 13 extend
as far as into the interior space formed by the support sleeve
14b anchored in the plastic base part 15. The support sleeve
14b is provided with two apertures 18 at the level of the webs
16e, 17e, which apertures are used for the laser welding of the
power supply wires 12 and/or 13 to the short webs 16e, 17e of
the corresponding contact lug 16 and/or 17 after the lamp base
has been fitted. The two apertures 18 in the support sleeve 14b
are located next to one another, at the same height as the
welded joint between the contact lug 16 and the power supply
wire 12 or at the same height as the welded joint between the
contact lug 17 and the power supply wire 13. Each of the
apertures 18 is designed in such a way that the laser beam 19
can be focused at an angle of incidence of zero degrees onto
the surface of the corresponding weld point, i.e. onto the
surface of the narrow side of the web 16e or 17e, so as to form
the abovementioned welded joints. In other words, the laser
beam 19 impinges, as is illustrated schematically in figure 3,
perpendicularly on the surface of the narrow side of the web
16e or 17e during the welding process.
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The invention is not restricted to the exemplary embodiment
explained in more detail above. For example, in the case of two
luminous means with three power supply wires and three contact
lugs, the lamp base can also have three apertures. However, it
is also possible for only one single, correspondingly larger
aperture to be provided instead of a plurality of apertures in
order to perform all of the laser welding operations of the
contact lugs and power supply wires through this aperture.
