Abstract: A thin-walled ceramic tube having a high light transmission and high dimens precision, which has been can be used as an envelope for a high pressure lamp, is produced by an extruding process in which a stiff plastic body for extruding is prepared, said body is extruded and the extruded tube is fired, said process being characterized in that the stiff plastic body consists essentially of ceramic raw material, a thermosetting organic substance and water and the extruded tube is hardened by heating immediately after extruded and pressured air is flawed into an inside portion of the extruded tube.

Abstract: The disclosed ceramic arc tube of metal vapor discharge lamps has an arc discharge portion with electrode-holding end portions integrally formed at opposite ends thereof. The outside diameter of the arc discharge portion is larger than that of the electrode-holding end portions. The ceramic arc tube is made by placing a tubular green body in a fusiform cavity of a die, inflating the middle portion of the green body more than end portions thereof, and firing the thus shaped green body.

Abstract: A ceramic green arc tube for a metal vapor discharge lamp wherein an outer diameter of the arc discharging portion is larger than that of the end portions holding the discharging electrodes is produced by preparing a stiff plastic body consisting mainly of a ceramic material or which main component is alumina, and a binder of which main component is thermal geltinizing organic substance; forming the prepared body into a straight tubular body by means of an extruder; placing the tubular body into an inner cavity of molding die having the above described ceramic arc tube shape wherein the molding die has been previously heated; closing one end portion of the tubular body; applying a compressed fluid from another opened end portion of the tubular body into the inside of said tubular body to inflate the central portion of tubular body until contacting to the inner cavity surface of the molding die,; hardening and drying the inflated body with the heat of previously heated molding die; and ejecting the dried body

Abstract: The disclosed ceramic arc tube of metal vapor discharge lamps has an arc discharge portion with electrode-holding end portions integrally formed at opposite ends thereof. The outside diameter of the arc discharge portion is larger than that of the electrode-holding end portions. The ceramic arc tube is made by placing a tubular green body in a fusiform cavity of a die, inflating the middle portion of the green body more than end portions thereof, and firing the thus shaped green body.