| 摘要 |
PURPOSE:To maintain always the explosive gas in a vacuum furnace in a non- explosive state by detecting the pressure and oxygen ratio of the explosive gas and emitting a danger signal and adjusting the pressure and oxygen ratio when the danger of explosion is judged. CONSTITUTION:When the pressure in a vacuum furnace 1 rises to the neiborhood of an upper limit pressure, a control means 7 outputs a danger signal P1 to a vacuum pump 8 and a solenoid valve 10 by the signal from a pressure sensor 3 to open the valve 10, thereby sucking the gaseous atmosphere in the furnace 1 and restoring the initial pressure in the furnace. When the pressure drops to the neiborhood of a lower limit pressure, the control means outputs a danger signal P2 to a solenoid valve 11 to supply an inert gas from a storage device 9, thereby restoring the initial pressure in the furnace 1. When the oxygen ratio in the furnace from an O2 sensor 4 indicates an abnormal increase, the means 7 outputs a danger signal O to the valve 11 to introduce an inert gas from the device 9 into the furnace and to expel the gas in the furnace to the external atmosphere through the discharge path (d), thereby decreasing the oxygen ratio.
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