Process for producing double helical glass tube, light-emitting tube for fluorescent lamp, and fluorescent lamp

Abstract

A process for producing a double helical glass tube having a projecting part. A double helical glass tube with a projecting part produced by the process is less apt to break at the projecting part. The process comprises: a step in which a glass tube (23) formed into a double helical shape is made thicker in that part (32) in a central part (13) where a projecting part is to be formed than in the other parts of the glass tube; a step in which the part where a projecting part is to be formed is locally heated to soften it; and a step in which nitrogen gas (27) is blown into the glass tube through an end part of the glass tube to expand the part where a projecting part is to be formed and thereby form a projecting part (14). Since the part where a projecting part is to be formed has been made thick beforehand, that part can retain sufficient strength even after it expands and becomes thin in projection formation.

Description

technical field [0001] The invention relates to a manufacturing method of a double helical glass tube, a luminescent tube for a fluorescent lamp and a fluorescent lamp. Background technique [0002] With the advent of the energy-saving era, in the lighting field, bulb-type fluorescent lamps and compact fluorescent lamps are also popularized as energy-saving light sources instead of general light bulbs. [0003] Conventional bulb-type fluorescent lamps have been downsized by developing the same outer shape as general incandescent bulbs. Recently, an arc tube made of a double helical glass tube, which is particularly advantageous for this miniaturization, has been adopted. [0004] This luminous tube is formed by folding back a glass tube at an approximately central portion, and turning both side portions of the glass tube sandwiching the approximately central portion around a helical axis. A pair of electrode parts are sealed at both ends of the glass tube, and rare gases f...

AI Technical Summary

Problems solved by technology

[0011] However, when the inventors mass-produced bulb-type fluorescent lamps, the problem that the convex portion formed in the approximate center of the double-helical glass tube was easily broken in the manufacturing process of the mass-produced lamps occurred. A double-helical glass tube with protrusions formed by the above-mentioned conventional method is used

Images