The present invention is directed to a ceramic discharge vessel for a high-intensity discharge lamp, and more particularly to a single-ended discharge vessel with electrodes that diverge from each other so that a discharge arc is confined to tips of the electrodes.
One of the problems with this side-by-side arrangement of electrodes is that an arc discharge between the electrodes can walk down the electrodes toward the wall of the discharge vessel and damage the ceramic. To discourage this, the electrodes are angled apart so that they diverge from each other thereby making the tips of the electrodes the closest two points between the electrodes inside the discharge vessel. The electrodes 16 in
The amount of divergence of electrodes 16 from each other can be confined to a relatively small angular range (up to about 12°) in discharge vessels in which the distal ends of capillaries 14 do not project beyond an edge of body 12, as illustrated by the dashed lines E in
Further, it would be desirable to offer an attractive alternative arrangement of the capillaries to create an additional option for reducing the overall size of the discharge vessel.
An object of the present invention is to provide a novel ceramic discharge vessel for a lamp in which the electrodes diverge from each other.
A further object of the present invention is to provide a novel ceramic discharge vessel with a hollow body, and two capillaries having respective electrodes therein, where portions of the electrodes inside the body are spaced from each other and have longitudinal axes that are not coplanar.
A yet further object of the present invention is to provide a novel ceramic discharge vessel with a body and two hollow capillaries, wherein a longitudinal axis of one capillary and a point where the second capillary is attached to the body define a plane, and wherein a longitudinal axis of the second capillary intersects this plane only at the point.
These and other objects and advantages of the invention will be apparent to those of skill in the art of the present invention after consideration of the following drawings and description of preferred embodiments.
With reference now to
Preferably, the electrodes are comprised of multiple metal and/or cermet sections. In particular, it is desirable to have a feedthrough section comprised of niobium because of its favorable coefficient of thermal expansion with regard to the commonly used polycrystalline alumina ceramic. The feedthrough section is sealed hermetically to its respective capillary with a frit material, e.g., Al2O3—SiO2—Dy2O3. The portion of the electrode protruding into the body of the discharge vessel is preferably comprised of a tungsten shaft with a tungsten coil attached to its end to serve as the electrode tip and point of arc attachment. For ceramic metal halide lamps, the discharge vessel is filled with a mixture of metal halide salts and may include mercury. For example, a typical metal halide fill material may comprise mercury plus some combination of Nal, Cal2, Dyl3, Hol3, Tml3, and TlI. The discharge vessel will also contain a buffer gas, e.g., 30 to 300 torr Xe or Ar.
An understanding of the arrangement of capillaries 24 in discharge vessel 20 may be enhanced by again referring to
This may be more clearly seen in
When one considers the geometry of the discharge vessel 20 of
The capillaries 24 and their respective electrodes 26 diverge from each other so as to avoid the problem of the arc discharge walking down the electrodes and damaging the ceramic of the body. The divergence is achieved regardless of whether the capillaries and electrodes are given a further inclination. With reference again to
The discharge vessel of the present invention may be made using conventional methods, such as the one described in U.S. Pat. No. 6,620,272, which is incorporated by reference. This patent describes a method for assembling a ceramic body in which two ceramic halves are joined together. The surfaces to be joined are heated to cause localized melting and then brought together and joined at a seam by alternately compressing and stretching the seam. The body parts are held in place with retractable pins.
Other devices may not use this technique and for such devices an alternative approach may be used. The body may be provided in two parts that are to be joined, such as along line A in
The fixture 50 is held in the clamp at a projection 56 that extends from a rear of the fixture. The projection 56 may be polygonal and held in correspondingly configured clamp to set the angle θ1 (
While embodiments of the present invention have been described in the foregoing specification and drawings, it is to be understood that the present invention is defined by the following claims when read in light of the specification and drawings.
Number | Name | Date | Kind |
---|---|---|---|
3900237 | Marcucci | Aug 1975 | A |
4056751 | Gungle et al. | Nov 1977 | A |
4482842 | Fujimura et al. | Nov 1984 | A |
4498027 | Karlotski et al. | Feb 1985 | A |
4724361 | Wada et al. | Feb 1988 | A |
4912364 | Hollo et al. | Mar 1990 | A |
5539271 | Sulcs et al. | Jul 1996 | A |
5936351 | Lang | Aug 1999 | A |
6620272 | Zaslasky et al. | Sep 2003 | B2 |
20030116892 | Horibe | Jun 2003 | A1 |
Number | Date | Country |
---|---|---|
3713371 | Nov 1987 | DE |
0438060 | Jul 1991 | EP |
0877412 | Nov 1998 | EP |
1 111 654 | Jun 2001 | EP |
2191337 | Dec 1987 | GB |
2000628 | Sep 1993 | RU |
Number | Date | Country | |
---|---|---|---|
20050212433 A1 | Sep 2005 | US |