Method and apparatus for automatically supplying a molding material

A method of automatically supplying a molding material to a molding machine, comprising the steps of:

• (a) introducing natural resin pellets fed from a natural resin pellet feeder to a vertical pipe structure having an upper end via a chute connected to said upper end of said pipe structure, said pipe structure having a lower end connected to a supply port of the molding machine and having a wall downwardly flared or vertical, so that cross-sectional areas are substantially equal in a vertical direction or greater at a lower part than at an upper part;
• (b) introducing, simultaneously with said natural resin pellets, masterbatch pellets fed from a masterbatch feeder to said pipe structure via said chute;
• (c) permitting said natural resin pellets and said masterbatch pellets introduced from the respective feeders to fall continuously until reaching a feed build-up thereof formed in said pipe structure;
• (d) supplying said natural resin pellets and said masterbatch pellets of said feed build-up, as a molding material, to the molding machine, wherein said pellets in said feed build-up move downward in said pipe structure along said vertical or downwardly flared wall;
• and
• (e) controlling the level of said feed build-up between an upper part and a lower part of said pipe structure by discontinuing steps (a)-(c) when the level of said feed build-up reaches a predetermined upper-limit level, and starting steps (a)-(c) when the level of said feed build-up reaches a predetermined lower-limit level.

An apparatus for automatically supplying a molding material to a molding machine, comprising:

• a vertical pipe structure having an upper end and a lower end, through which natural resin pellets and masterbatch pellets will pass downwardly, said lower end being adapted to be connected to the molding machine, said pipe structure having a wall downwardly flared or vertical, so that cross-sectional areas are substantially equal in a vertical direction or greater at a lower part than at an upper part, wherein said natural resin pellets and said masterbatch pellets introduced from the respective feeders will fall continuously until reaching a feed build-up thereof formed in said pipe structure;
• an upper-limit level meter provided at an upper part of said pipe structure for detecting the level of the feed build-up in said pipe structure when reaching a predetermined upper-limit level;
• a lower-limit level meter provided at a lower part of said pipe structure for detecting the level of the feed build-up in said pipe structure when reaching a predetermined lower-limit level;
• a chute for guiding natural resin pellets and masterbatch pellets to said pipe structure, said chute being connected to said upper end of said pipe structure;
• a natural resin feeder for supplying natural resin pellets to said chute;
• a masterbatch feeder for supplying masterbatch pellets to said chute;
• and
• a supply control mechanism for controlling the level of the feed build-up between said predetermined upper-limit level and said predetermined lower-limit level by inactivating said natural resin feeder and said masterbatch feeder when the level of the feed build-up reaches said predetermined upper-limit level, and by activating said natural resin feeder and said masterbatch feeder when the level of the feed build-up reaches said predetermined lower-limit level.