Patent ID: 8157557

Claim:
A rotary die head for a film blowing machine for use with starch-based biodegradable material, comprising a core mould and an outer body, wherein the core mould and the outer body are disposed concentrically and together form a material annular gap flow channel; the core mould comprises a spiral core mould ( 22 ) sleeved on a center pivot ( 15 ) via a supporting bearing ( 28 ) and a rotary core mould ( 20 ) fixed on a top end of the center pivot ( 15 ) via a locknut ( 16 ), and an inner coniform surface of a top end of the spiral core mould ( 22 ) is jointed and cooperates with an outer coniform surface of a bottom end of the rotary core mould ( 20 ); the outer body comprises an inner die casing ( 21 ) sleeved on the spiral core mould ( 22 ), an outer die casing ( 19 ) in transition fit with the inner die casing ( 21 ), and a mouth die casing ( 23 ) surrounding the rotary core mould ( 20 ); an upper end of the inner die casing ( 21 ) is fixed with a lower end of the mouth die casing ( 23 ) via a fixing element; an outer circulation cooling water channel ( 12 ) is formed between an outer wall of the inner die casing ( 21 ) and an inner wall of the outer die casing ( 19 ); inner walls of the inner die casing ( 21 ) and the mouth die casing ( 23 ) and outer walls of the spiral core mould ( 22 ) and the rotary core mould ( 20 ) form a material flow and molding channel comprising in sequence from bottom to top a herringbone feed-in slot ( 10 ), a spiral conveying slot ( 11 ), an annular gap buffer zone ( 29 ), a tapering cone passage ( 30 ), an annular loosing cavity ( 8 ), and a final molding gap ( 31 ); and the core mould and the outer body are mounted on a die base ( 17 ) fixed on a connection plate ( 3 ); a lower end of the center pivot ( 15 ) passes the connection plate ( 3 ) and connects with a big gear ( 5 ); a motor ( 2 ) is disposed on the connection plate ( 3 ) and an output end of the motor ( 2 ) is connected with a small gear ( 4 ); the small gear ( 4 ) and the big gear ( 5 ) are engaged with each other so as to drive the center pivot ( 15 ) and the rotary core mould ( 20 ) at the top end thereof to rotate around the spiral core mould ( 22 ).