Short arc discharge lamp
AssigneeUshio Denki Kabushiki Kaisha
InventorTomoki Watanabe
Life of this patent
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Abstract
A cathode for a discharge lamp in which an electron emitting section containing an easily electron emitting material at its end is provided that has simplified yet non-breakable structure and can reduce the manufacturing cost. A short arc discharge lamp includes an arc tube in which a cathode and an anode face each other and a xenon gas is enclosed. The cathode has an electron emitting section made from tungsten to which thorium is added as an easily electron emitting substance. The cathode also has an electrode body section made from tungsten to which no thorium is added. The electrode body section has a recess at a front end side. The electron emitting section has a circular truncated conical shape, a rear end side of the electron emitting section is received in the recess, and a front end side portion protrudes from the recess.
Claims11
A short arc discharge lamp comprising:
- an arc tube configured to enclose a light emitting gas;
- a cathode disposed in the arc tube;
- and
- an anode disposed in the arc tube such that the anode and the cathode face each other in the arc tube,
- the cathode comprising an electron emitting section made from tungsten to which thorium is added, and an electrode body section made from tungsten to which thorium is not added,
- the electrode body section being provided with a recess portion at a front end side of the electrode body section, and
- the electron emitting section having a circular truncated conical shape, a rear end side of the electron emitting section being received in the recess portion and a front end side of the electron emitting section protruding from the recess portion, wherein
- the electrode body section is provided with an annular flat surface portion at an opening surface of the recess portion, and
- a step is formed by the annular flat surface portion and the electron emitting section;
- wherein a percentage of a width of the annular flat surface portion to a diameter of a cylindrical lateral surface portion of the electron emitting section is set to 16% or more.
A short arc discharge lamp comprising:
- an arc tube configured to enclose a light emitting gas;
- a cathode disposed in the arc tube;
- and
- an anode disposed in the arc tube such that the anode and the cathode face each other in the arc tube,
- the cathode comprising an electron emitting section made from tungsten to which thorium is added, and an electrode body section made from tungsten to which thorium is not added,
- the electrode body section being provided with a recess portion at a front end side of the electrode body section, and
- the electron emitting section having a circular truncated conical shape, a rear end side of the electron emitting section being received in the recess portion and a front end side of the electron emitting section protruding from the recess portion, and
- the material of the electron emitting section having a theoretical density of tungsten filling percentage of 90% of more, wherein
- the electrode body section is provided with an annular flat surface portion at an opening surface of the recess portion, and
- a step is formed by the annular flat surface portion and the electron emitting section,
- wherein a percentage of a width of the annular flat surface portion to a diameter of a cylindrical lateral surface portion of the electron emitting section is set to 16% or more.
Dependencies are inferred from the claim text.