Method of fabricating an arc tube for an arc discharge lamp

Abstract

This invention provides an improved method of fabricating an arc tube, particularly a miniaturized arc tube having precise geometry and requiring exact electrode alignment. The improved method divides the press sealing operation into two distinct steps. In the first or preforming step, the ends of the arc tube are heated and preformed such that the ends have a substantially elliptical cross section; in the second or pressing step, the preformed ends are heated and pressed together to form completed press seals. During each step, the viscosity of the pliable glass remains low so that internal shearing forces are substantially reduced from those experienced in the prior art methods. As a result of the low viscosity during the pressing step, electrode misalignment, tearing of molybdenum foils, and deformation of the midsection of the arc tube are virtually eliminated. An electrode and a starting probe may be inserted with ease into a preformed end because of its flattened cross section. In the absence of the preforming step, a tubular blank having a larger internal diameter might be required thereby necessitating a more bulky arc tube and greater glass consumption.

Dependencies are inferred from the claim text.