| 摘要 |
PURPOSE:To prevent excessive compression and improve reliability by blocking a discharge port with a piston when the pressure of a discharge chamber is higher than that of a compression chamber, while opening said discharge port into said discharge chamber via the through passage of a piston when the pressure of said compression chamber is higher than that of said discharge chamber. CONSTITUTION:When the captioned machine is started, the pressure in a compression chamber 9 rises, and is introduced from a gas pressure introducing port 33 into an operating chamber 36, and a piston 37 is moved leftward pushed by this pressure and stopped by a stop ring 38. In this condition, a ring groove 37a provided on the piston 37 is positioned in between a discharge port 34 and a discharge outlet 35, connecting the compression chamber 9 to a discharge chamber 1a. Accordingly, the gas of a compression-chamber 9 pressure which became higher than a discharge-chamber 1a pressure, is discharged into the discharge chamber 1a through the discharge port 34, the ring groove 37a, and the discharge outlet 35. Since the gap pressure introducing port 33 is formed into a small port, the pressure in the operating chamber 36 is considerably smaller than the width of variation of the compression-chamber 9 pressure to which the chamber 36 is connected, reaching a value close to the average of integration during rotation. Accordingly, the piston 37 is moved slowly without being affected by the compression-chamber 9 pressure, preventing excessive compression.
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