The invention discloses an air blowing device for an injection blow molding machine, comprising a support base, a mandrel and a core rod coaxially sleeved, a small piston is fixedly connected to one end of the core rod located at the support base, a spring return mechanism is also arranged between the core rod and the support base, an air blowing pre-vent valve and an air blowing valve far away from and close to the mandrel head are respectively arranged on the support base on both sides of the stroke of the small piston, the small piston comprises a large section and a small section, the small section is fixedly connected to the end of the core rod, the large section is fixedly connected to the small section, an annular boss is arranged on the inner wall surface of the support base at the outer periphery of the small section, the inner wall surface of the annular boss is in sliding sealing fit with the outer peripheral surface of the small section, the end surface of the annular boss is in stop fit with the end surface of the large section, the large section has a large end surface, the small section has a small end surface, the area of the large end surface is larger than that of the small end surface, let the area of the large end surface be S1, the area of the small end surface be S2, the restoring force of the spring return mechanism be F, the air blowing pre-vent pressure be P1, the air pressure in the bottle cavity be P3, S2 ≤ F/P3.

Country Code: CN

Application Number: CN201910193563.X