LEAD-IN DEVICE FOR LEAK GAS IN VACUUM EXHAUST SYSTEM

PURPOSE:To make fine adjustment for a leak gas flow rate ever so easy as well as to complete a leak in a short time without making minute duct inside a vacuum chamber flying up, by installing a buffer tank in position between the vacuum chamber and a leak gas source and also installing a leak valve in front and the rear of the tank. CONSTITUTION:At the time of leading gas out of a leak gas source 4 into a vacuum chamber 1 made into the vacuous air by a vacuum pump 2, first of all, while a valve 8 and a leak valve 9 both are closed, a leak valve 10 is opened and gas is once lead into a buffer tank 3. Next, when a fact that a pressure differential between the buffer tank 3 and the vacuum chamber 1 comes to the setting value is detected by vacuum gauges 6 and 7, the leak valve 10 is closed by a control circuit 11 and on the other hand, the leak valve 9 is opened whereby the gas is led into the vacuum chamber 1 via a filter 5. In succession, at that point that the said pressure differential becomes less than the setting value, it is regarded as completion of leading-in the gas into the vacuum chamber 1 from the buffer tank 3, and so the leak valve 9 is closed while the leak valve 10 is opened instead.