| 摘要 |
PURPOSE:To make it possible to operate unit pumps, independent from each other, to obtain different capacities, in a two stage vacuum pump in which two unit pumps are connected, by disposing, in a connecting pipe for the vacuum pump, a valve for opening and closing the connecting pipe and by forming, also in the pipe, sub-suction port and sub-discharge port. CONSTITUTION:A vacuum pump 11 is composed of two unit pumps 12, 13 which are operated independent from each other and which are disposed in a casing 14 and are driven by only one motor 15. Further, one 12 of the unit pumps 12, 13 is provided therein with a main intake port 16 while the other one 13 is formed therein with a main discharge port 17, and both unit pumps 12, 13 are connected together in a series and in two stages by means of a connecting pipe 18 in the intermediate section of which a valve 20 for opening and closing the pipe is disposed. Further, a check valve 23 and a normally closed valve 24 are disposed in a sub-discharge port 21 formed upstream of the valve 20, and a normally closed valve 25 is disposed in a sub-suction port 22 formed downstream of the valve 20. |
