Process for evacuation and filling of glass tube for illuminated signs

摘要

The process involves evacuating the glass tube (10) and then filling it with an inert gas. The inside of the glass tube is coated with an emissive powder to produces light as an electrical discharge passes through the tube. The tube is ignited and the internal pressure and/or the electric current are regulated. The ignition of the tube is detected by the resulting sharp increase in current. The pumping is continued till the temperature at a point in the tube reaches a set value. The tube is then filled with the inert gas. The pumping and filling is controlled by solenoid valves (20) which direct gas flow. The monitoring of temperature and operation of the solenoid valves is controlled by an automatic controller(31).