Plasticizing apparatus for use in an injection molding machine

In a plasticizing apparatus for use in an injection molding machine, which apparatus comprises

• a plasticizing cylinder formed with at least part of a central discharge passage and with an inside peripheral surface, which defines a cylindrical plasticizing chamber having a conical forward portion merging into said discharge passage;
• a feed screw, which has forward and rear ends and is disposed in said plasticizing chamber and mounted to be rotatable and axially movable and rotatable to feed plasticizing plastic material from said rear end to said forward end;
• and
• a backflow-preventing valve, which is mounted on said feed screw at its forward end and defines in said plasticizing chamber a low-pressure space behind said valve and a high-pressure space, which is in front of said valve and adapted to receive and accumulate said plasticized plastic material fed by said feed screw;
• said feed screw being adapted to axially yield rearwardly to said plasticized plastic material accumulating in said high-pressure space and to assume a plurality of rear initial positions and operable to perform from any of said rear initial positions an axial discharge stroke for discharging said plasticized plastic material from said high-pressure space through said discharge passage;
• said backflow-preventing valve being arranged to seal said high-pressure and low-pressure spaces from each other throughout said discharge stroke;
• the improvement wherein
• said plasticizing cylinder comprises a cylinder head and a cylinder shank, which are detachably interconnected;
• said cylinder head encloses said high-pressure space throughout its axial length and also encloses said backflow-preventing valve in all said initial rear positions of said feed screw;
• said cylinder shank encloses said low-pressure space throughout its axial extent and also encloses said feed screw;
• said cylinder head and said cylinder shank have confronting end faces, which define a joint, which along a circular line adjoins said inside peripheral surface at said low-pressure space;
• both said confronting end faces have axially confronting finish-machined sealing surfaces;
• and
• clamping means are provided for axially forcing said sealing surfaces of said confronting end faces against each other;
• said clamping means comprises a sleeve overlapping said cylinder head and said cylinder shank and is secured to said cylinder shank and is formed with an annular series of tapped through bores, and
• clamp screws screwed through said tapped through bores and axially bearing on said sleeve and engaging said cylinder head at abutment surfaces formed on said cylinder head.