Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION ST-9720
TITLE OF THE INVENTION
SINGLE TERMINAL TYPE DISCHARGE LAMP
BACKGROUND OF THE INVENTION
5 1. Field of the Invention
The present invention relates to a discharge lamp,
and more particularly to a discharge lamp of a single
terminal type at one end of which a base is provided for
purposes of using it as a light source for a head lamp of an
automobile or a light source for an LED projector.
2. Background Art
One example of a prior single terminal type
discharge lamp is disclosed in, for example, Japanese Patent
Application Laid-Open No. Hei.8-64114. In this prior
discharge lamp, a burner is once attached to a self-core
adjustment type holder member with a spherical outer surface,
and then the holder member is inserted into a tubular socket.
Thereafter the holder member and the socket are welded in a
condition that the depth and the direction of the holder
member are adjusted.
However there are some problems for the
above-described discharge lamp. First, the manufacturing
costs of the discharge lamp increase, because the necessity
of two members, the holder member and the socket, as the base
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makes the construction of the lamp complicated and the
necessity of two attachment steps consisting of the
attachment between the burner and the holder member and the
attachment between the holder member and the socket increases
the number of total manufacturing steps.
Second, a dielectric strength of the discharge lamp
against a high voltage required on turning on the discharge
lamp is insufficient, because the distance between lead wires
respectively connected to two electrodes of the discharge
lamp is too small in the socket due to the necessity of two
connecting spaces in the socket for attaching the burner to
the holder member and attaching the holder member to the
socket.
Third, a mechanical strength between the holder
member and the socket of the discharge lamp is also
insufficient, because the welding area of the holder member
and the socket is small due to a linear contact between the
holder member with a spherical outer surface and the socket.
Thus the holder member would separate from the socket due to
vibrations or impacts on driving an automobile.
SUM~aRY OF THE INVENTION
It is an object of the present invention to provide
a single terminal type discharge lamp which can be
manufactured with low costs and has a sufficient dielectric
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strength against a high voltage and a sufficient mechanical
strength between the holder member and the socket.
In order to achieve the foregoing object and
others, the present invention provides a single terminal type
discharge lamp comprising: a burner comprising a discharge
tube and a covering tube; a thermoplastic socket attached to
one end of the burner; a tubular holder, to which the burner
is fitted, provided in the socket along a predetermined
direction in which the burner is to be aligned; and a tubular
metal holder spring which is mounted to the holder for
radially depressing the holder toward the burner with
deflecting force; wherein the burner is adhered to the socket
due to the melt of the holder caused by the heat of the
holder spring owing to radio-frequency heating which is
performed when the one end of the burner is fitted to the
holder such that the burner attains a predetermined position.
Other features and advantages of the present
invention will be apparent from the following description
taken in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially exploded perspective view of
a single terminal type discharge lamp of an embodiment
according to the present invention.
FIG. 2 is a sectional view taken along the line A-A
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of FIG. 1.
FIG. 3 is a perspective view of the principal part
of a single terminal type discharge lamp of an another
embodiment according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. l and 2, reference numeral 1 is
a single terminal type discharge lamp of one embodiment
according to the present invention. The single terminal type
discharge lamp 1 is constructed such that a socket 3 made of
a thermoplastic resin is attached by welding to one end of a
burner 2 comprising a discharge tube 2a and a covering tube
2b, as well as the prior discharge lamp described above.
In the present invention, the holder 4 made of a
thermoplastic resin is formed at the inside of the socket 3
and integrated with the socket 3 in one piece. The holder 4
with a tubular shape is provided on the base 3a of the socket
3 along a predetermined direction in which the burner 2 is to
be aligned such that the outer surface of the burner 2 faces
the inner surface of the holder 4 when the burner 2 is fitted
to the holder 4.
A tubular holder spring 5 having a deflecting force
toward a direction for reducing the diameter thereof made of
a metal member comprising a predetermined amount of, e.g.,
wolfram as a resistance component with elasticity of an
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appropriate value such as steel alloy products or spring
products is mounted to the holder 4 to cover the outer
surface of the holder 4. The deflecting force of the holder
spring 5 must not be so large, but it should be sufficient
for reducing the diameter of the holder 4 in welding
described later.
Reference numeral 7 in the figures is a lead wire
provided on both ends of the burner 2. Reference numeral 8
designates a ceramic plate for protecting the socket 3 from
the heat of the burner 2 generated when it is turned on, and
so on. Reference numeral 9 designates a ceramic tube for
insulating the lead wire 7 on the opposite side of the socket
3.
When the burner 2 is attached to the socket 3
formed as described above, one end of the burner 2 is
inserted into the holder 4. In this case, since the holder 4
is provided in the socket 3 along the predetermined direction
in which the burner is to be aligned, the central axis of the
burner 2 is positioned at a designed position in the socket
3.
Thus a discharge chamber 2c of the burner 2 can be
placed at a predetermined position by adjusting the inserting
depth of the burner 2 in the holder 4 on the basis of a
flange 3b of the socket 3. On adjusting the inserting depth,
the burner 2 can freely slide in the holder 4, because the
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holder spring does not have a deflecting force enough to
deform the shape of the holder 4, but enough to reduce the
diameter of the holder 4.
After the discharge chamber 2c is placed at the
predetermined position by such procedures, the socket 3 is
subject to radio-frequency heating while the discharge
chamber 2c is maintained at the position. Then the holder
spring 5 is heated by dielectric heating. A part of the
holder 4 directly contacting the holder spring 5 is also
heated due to thermal conduction from the holder spring 5.
The holder 4 made of the thermoplastic resin is
softened and melted by the heating, and thus the diameter of
the holder 4 is reduced by the deflecting force of the holder
spring 5, thereby depressing the burner 2, allowing the
burner 2 to be welded to the holder 4. After the
radio-frequency heating is stopped at an appropriate timing,
the holder 4 which is once softened and melted is again
hardened, which in turn allows the burner 2 and the holder 4
to be fixed by welding.
Next, effects of the single terminal type discharge
lamp 1 of the present embodiment are described.
First, since the discharge lamp 1 has a
construction such that the holder 4 is provided on the base
of the socket 3, it is possible to form the socket 3 and the
holder 4 as an integrated body with the use of a mold or the
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like. Therefore, it is not necessary to provide the holder 4
as another parts, which in turn reducing the number of parts
of the discharge lamp 1. It is also possible to reduce
manufacturing steps, because a step for attaching the burner
2 to the holder 4 includes a step for attaching the burner 2
to the socket 3.
Second, only one connecting part for attaching the
burner 2 to the socket 3 is required in the socket 3, thereby
reducing spaces for connections in the socket 3.
Accordingly, it is possible to provide a large distance
between lead wires respectively connected to two electrodes
of the discharge lamp 1 in the socket, which in turn provides
a sufficient dielectric strength against a high voltage on
turning on the discharge lamp with the discharge lamp.
Third, it is possible to obtain a sufficient
mechanical strength between the burner 2 and the holder 4 or
the socket 3 such that they are not separated even if, for
example, vibrations or impacts are applied on driving an
automobile, because the burner 2 is welded to the holder 4 or
the socket 3 at a large area having a tubular shape.
Another embodiment of the present invention is
shown in FIG. 3. While the burner 2 is fitted to or inserted
into the holder such that the outer surface of the burner 2
faces the inner surface of the holder 4 in the foregoing
embodiment, in the present embodiment, the holder 4 is fitted
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to or inserted into the burner 2 such that the outer surface
of the holder 4 faces the inner surface of the burner 2.
In this case, a holder spring 6 has a deflecting
force in a direction for increasing the diameter thereof or
in a direction toward the burner 2. The holder spring 6 is
mounted on the inner surface of the holder 4. Thus the
holder 4 is welded to the burner 2 by radio-frequency heating
while the diameter of the holder 4 increases due to the
deflecting force of the holder spring 6.
As described above, according to a single terminal
type discharge lamp of the present invention comprising: a
burner comprising a discharge tube and a covering tube; a
thermoplastic socket attached to one end of the burner; a
tubular holder, to which the burner is fitted, provided in
the socket along a predetermined direction in which the
burner is to be aligned; and a tubular metal holder spring
which is mounted to the holder for radially depressing the
holder toward the burner with deflecting force; wherein the
burner is adhered to the socket due to the melt of the holder
caused by the heat of the holder spring owing to
radio-frequency heating which is performed when the one end
of the burner is fitted to the holder such that the burner
attains a predetermined position, first, it is possible to
reduce the number of parts of the discharge lamp and also the
number of manufacturing steps, only one welding part being
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required in the present invention although two welding parts
being required in the prior art, thereby providing an
excellent effect for reducing costs of such a single terminal
type discharge lamp.
Second, only one connecting part for attaching the
burner to the socket is required in the socket, thereby
reducing spaces for connections in the socket. Accordingly,
it is possible to provide a large distance between lead wires
respectively connected to two electrodes of the discharge
lamp in the socket, which in turn provides a sufficient
dielectric strength against a high voltage on turning on the
discharge lamp with the discharge lamp, thereby providing an
excellent effect for increasing properties of the discharge
lamp.
Third, it is possible to obtain a sufficient
mechanical strength between the burner and the holder or the
socket such that they are not separated even if, for example,
vibrations or impacts are applied on driving an automobile,
because the burner is welded to the holder or the socket at a
large area having a tubular shape, thereby providing an
excellent effect for increasing reliability of the discharge
lamp.
While there has been described what are at present
considered to be preferred embodiments of the invention, it
will be understood that various modifications may be made
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thereto, and it is intended that the appended claims cover
all such modifications as fall within the true spirit and
scope of the invention.
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