Extrusion molding equipment for multi-layer parison

Extrusion molding equipment for molding a multi-layer parison having an outer resin layer and an inner resin layer, said extrusion molding equipment comprising:

• operational position detecting means for detecting an operational position of an accumulator to extrude said inner resin material and providing a position signal;
• pressure detecting means for detecting a pressure of said inner resin material in an inner resin conduit and providing a position signal;
• extrusion amount control means for controlling an extrusion amount of said inner resin by the use of said position signal detected by said operational position detecting means and said pressure signal detected by said pressure detecting means;
• said extrusion amount control means including memory means for converting said position signal to a regular pressure value and for memorizing said regular pressure value representative of pressure of said inner resin material in a normal operational condition, and correction means for producing a corrected pressure signal based on a comparison of said pressure signal and said regular pressure value;
• said extrusion amount control means controlling said accumulator according to said corrected pressure signal so that a substantial portion of said inner resin material is maintained to be equal to said regular pressure value.