| 摘要 |
PROBLEM TO BE SOLVED: To provide an evacuating device for a vacuum heat treating device capable of obtaining heat-treated articles of good quality with little dispersion by maintaining the interior of a furnace body to a predetermined pressure even when the fluctuation width of atmospheric gas flow exhausted from the furnace body is large like a multi-chamber type vacuum heat treating device. SOLUTION: The evacuating device for the vacuum heat treating device performs control of pressure in the furnace body by controlling the rotating speed of a vacuum pump (a mechanical booster pump 7) connected to the furnace body 2 through an exhaust line 3. The exhaust line 3 is provided with a branch part 11 wherein a plurality of branch lines 12a, 12b, 12c with different passage resistance comprising on-off valves A, B, C are arranged in parallel, and a changeover control means (a control device 10) is provided for performing opening/closing control of the on-off valves A, B, C to select one branch line as an exhaust flow passage and changing the exhaust flow passage over to the branch line on the high resistance side when the rotating speed of the vacuum pump reaches a lower limit value, while changing the exhaust flow passage over to the branch line on the low resistance side when the rotating speed reaches an upper limit value. COPYRIGHT: (C)2008,JPO&INPIT
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