Parsion stabilizing method and system therefor for blow-molding machine

A parison stabilizing system for use in a hollow formation molding machine which is formed such that after a parison extruded out of a cross head has been introduced into a metal mold, an amount of air is supplied thereto by way of an air passage formed within the cross head to cause the parison to expand, said parison stabilizing system comprising:

• an exhaust pipe connected with the air passage and having an exhaust valve;
• a pre-blow pipe connected between the exhaust valve and the air passage and is further connected to an air source through a pre-blow valve;
• and
• a forced exhaust pipe, with one end thereof being connected on the downstream side of the exhaust valve of the exhaust pipe and the other end thereof being connected to the air source, and having a forced exhaust valve,
• wherein a negative pressure is formed within the air passage by first closing the exhaust valve and the forced exhaust valve, opening the pre-blow valve to perform a pre-blowing treatment in the parison, followed by opening the exhaust valve and the forced exhaust valve, and closing the pre-blow valve, so as to cause the air to move to the forced exhaust pipe.