Patent ID: 8186380

Claim:
A decompression apparatus comprising: a vacuum chamber and an exhaust mechanism which decompresses the vacuum chamber and comprising: a main exhaust passage one end of which is connected to the vacuum chamber and the other end of which is connected to a vacuum pump; a first valve provided in the main exhaust passage; a slow exhaust passage one end of which is connected to the vacuum chamber directly or via the main exhaust passage and the other end of which is connected to the vacuum pump directly or via the main exhaust passage; a cylindrical inorganic porous body provided in the slow exhaust passage so that a first gap is formed between the inorganic porous body and an inner surface of the slow exhaust passage; and a second valve provided in the slow exhaust passage wherein, the inorganic porous body is non-bottomed cylindrical shape having opening at both ends, a hollow metallic vent passage having a vent hole on circumferential wall thereof is provided inside the inorganic porous body so that a second gap is formed between an inside surface of the inorganic porous body and an outer circumferential surface of the metallic vent passage, one end portion of the metallic vent passage is closed by a closing member which is threadedly engaged with the one end portion of the metallic vent passage, one end of the inorganic porous body is pressed and closed by the closing member via a first soft gasket, the other end portion of the metallic vent passage penetrates through a metallic attachment ring in air-tight manner and the other end of the inorganic porous body is pressed by the metallic attachment ring via a second soft gasket.