Electric lamp and discharge devices – With gas or vapor – Envelope with particular structure
Utility Patent
1998-05-21
2001-01-02
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Envelope with particular structure
C313S570000, C313S025000, C313S573000
Utility Patent
active
06169367
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a high pressure discharge lamp and more particularly to a composition and a method of producing a high pressure discharge lamp for an automobile headlight or fog light.
2. Discussion of the Related Art
FIG. 4
illustrates a horizontal cross sectional view of a conventional automobile high pressure discharge lamp
40
used in an automobile headlight. The automotive high pressure discharge lamp
40
includes a bulb
41
including a center portion
41
a
, a discharge chamber
45
filled with a rare gas and a metal halide, and sealed portions
41
c
and sealed ends
41
b
are positioned around the center portion
41
a
. The sealed ends
41
b
each include molybdenum foils
43
, lead wires
44
, and a pair of electrodes
42
projecting a predetermined distance into the discharge chamber
45
.
A conventional method of forming the discharge chamber includes providing a silica glass pipe (not shown) for forming the bulb
41
, heating and softening the center portion
41
a
, blowing air into the silica glass pipe and expanding the center portion
41
a
until it obtains a substantially barrel-shaped form. In an actual application, an outer bulb and a socket are also added, although these steps are not illustrated herein.
FIG. 6
illustrates a conventional automobile headlight
60
including a high pressure discharge lamp
40
, a reflector
61
, a lens
62
, and a shade
63
.
FIG. 5
depicts a light distribution pattern H
j
of the conventional high pressure discharge lamp
40
. An X-axis in
FIGS. 5 and 6
correspond to the X-axis in FIG.
4
. The X-axis passes through the center of an electrical arc A (shown in FIG.
4
), formed between the electrodes
42
, and crosses horizontal Z-axis of the automotive high pressure discharge lamp
40
at substantially a right angle. Light is emitted from the conventional automotive high pressure discharge lamp
40
symmetrically, i.e, forward and backward, through an angle range of approximately 45° with respect to the X-axis.
The conventional automotive high pressure discharge lamp
40
experiences several problems, the most severe of which is that the light distribution pattern Hj is inappropriate for use as an automobile headlight. As shown in
FIG. 6
, the reflector
61
of the automobile headlight
60
typically has a small longitudinal length and a small depth dimension. The light that is directed forward, through a large angle range of approximately 20°-45° with respect to the X-axis, is often glare light, since the light has not been reflected by the reflector
61
but passes directly through the lens
62
. The function of shade
63
is to restrict the light directed forward of the X-axis at angles ranging between 20°-45°. The shade
63
substantially decreases efficiency of the automobile headlight
60
to such an extent that the emitted light from the high pressure discharge lamp
40
is approximately 25% of the total light emitted from the electrical arc A. As shown in
FIG. 4
, the difference of curvature between the bulb center portion
41
a
and the sealed ends
41
b
substantially changes at the sealed portions
41
c
. Therefore, when the automobile headlight
40
is turned on, spot-shaped glare light is emitted from the sealed portion
41
c
such that the automobile headlight
60
looks as if it has two or more light sources.
SUMMARY OF THE INVENTION
The present invention is directed to an automotive high pressure discharge lamp that substantially obviates one or more of the problems due to the limitations and disadvantages of the related art.
An object of the present invention is to provide a high pressure discharge lamp having an improved light distribution pattern.
Another object of the present invention is to provide a high pressure discharge lamp having increased efficiency.
A further object of the present invention is to provide a method of fabricating a high pressure discharge lamp with the above improved properties.
Additional features and advantages of the present invention will be set forth in the description which follows, and will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure and process particularly pointed out in the written description as well as in the appended claims.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, in accordance with a first aspect of the high pressure discharge lamp for an automobile there is provided a lamp bulb for an automotive high pressure discharge lamp includes a pair of opposing electrodes that projects a predetermined distance into a discharge chamber, molybdenum foils, lead wires, and a bulb, the lamp bulb including a discharge chamber filled with a metal halide and a rare gas, the discharge chamber including a concave surface curving inwardly with respect to a Z-axis of the automotive high pressure discharge lamp, a discharge chamber portion surrounding the discharge chamber, including a convex surface curving outwardly with respect to the Z-axis of the high pressure discharge lamp, tapered portions tapering towards the discharge chamber, sealed ends in which are located the molybdenum foils, the electrodes, and the lead wires, and sealed portions substantially free from substantial curvature change, the sealed portions being located between the discharge chamber and the sealed ends.
In accordance with a second aspect of the high pressure discharge lamp, a method for producing a high pressure discharge lamp includes a pair of opposing electrodes a portion of which is projected to a predetermined distance into a discharge chamber, molybdenum foils, lead wires, tapered portions, sealed ends, wherein the discharge chamber has a concave surface curving inwardly relative to a Z-axis of the high pressure discharge chamber, and a discharge chamber portion that has a convex surface curving outward relative to a horizontal axis of the high pressure discharge lamp, the method for producing the high pressure discharge lamp includes the steps of disposing an electrode, a molybdenum foil, and a lead wire within a silica glass pipe, sealing the electrode, the molybdenum foil, and the lead wire within the silica glass pipe, heating and melting the silica glass pipe about its center portion, disposing a curvature pattern adjacent to an outer surface of the silica glass pipe corresponding to the convex surface, rotating the silica glass pipe in contact with the pattern to form the convex surface, and applying a first pressure to the silica glass pipe externally maintaining the shape of the outer surface of the pipe such that the inner surface of the pipe at a softened center portion deforms inwardly along a Z-axis of the automotive high pressure discharge lamp to form the concave surface, while air is introduced into the silica glass pipe at a second pressure.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 3250941 (1966-05-01), Wilson et al.
patent: 3870919 (1975-03-01), Hellman et al.
patent: 5471110 (1995-11-01), Van Der Leeuw et al.
patent: 5528104 (1996-06-01), Kim et al.
patent: 5866982 (1999-02-01), Scott et al.
patent: 5923127 (1999-07-01), Keijser et al.
patent: 4-32497 (1992-05-01), None
Muto Masaaki
Omori Shinya
Morgan & Lewis & Bockius, LLP
Patel Nimeshkumar D.
Stanley Electric Co. Ltd.
Williams Joseph
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