Vacuum-keeping multistage vacuum-generating and vacuum-destructing valve

A vacuum-keeping multistage vacuum-generating and vacuum-destructing valve, comprising:

• a main body, which comprises an introduction port to which a pressure fluid is connected, a vacuum port adapted to connect to a suction mechanism, a discharge port through which the pressure fluid supplied through the introduction port is discharged to outside, and a vacuum-generating valve that when opened allows a negative pressure to be generated through the pressure fluid being supplied through the introduction port, wherein a vacuum-destructing valve is operable in combination with a flow conducting passage formed in the main body and connected to the vacuum port to allow the pressure fluid supplied through the introduction port to partly flow through the vacuum-destructing valve, and a vacuum-destructing two-port two-position valve is arranged in the flow conducting passage to increase flow rate of the pressure fluid passing therethrough to make a response of the vacuum port more sensitive in switching to a vacuum-destructing state;
• a reversal preventing valve is arranged between the vacuum port and the discharge port, which, when the vacuum port is in a condition of generating suction through vacuum, is closed when the vacuum-generating valve is closed, to allow the vacuum port to be full of negative pressure maintaining a vacuum-keeping state.