| 摘要 |
PURPOSE: To save an occupation space by a machine by providing a changeover valve which selectively communicates the suction side of an air pump with a negative pressure chamber and atmosphere, at the halfway of the suction pipe of the air pump where its suction side is connected with the negative pressure chamber and its discharge side is connected to an operation pressure chamber, and thereby commonly using the air pump as a negative pressure source and a compressed air source. CONSTITUTION: The suction side of an air pump 50 is connected to a negative pressure chamber 4 through a suction pipe 51, and its discharge side is connected to a pressure accumulating chamber 8 through a air duct 52. And its compressed air is supplied to an operating pressure chamber 5. A change-over valve 59 provided for a suction pipe 51 selectively communicates the suction side of the air pump 50 with the negative pressure chamber 5 and atmosphere, and communicates the air pump 50 with the negative pressure chamber 4 at the normal time. When the pressure of the pressure accumulating chamber 8 is lowered, the air pump 50 is operated by a controller 64 based on a pressure sensor 62, and compressed air is led to the pressure accumulating chamber 8. Besides, the pressure of the negative pressure chamber 4 which is lowered by applying the brake, allows the change-over valve 59 to be turned off by the controller 64 based on a pressure sensor 63, and the negative pressure chamber 4 is thereby decompressed from the suction side of the air pump 50. |
