Patent ID: 6422856
Filing Date: 2002-07-23
Classification: B29C

Abstract:
A hot runner system for molding preforms, being arranged under a preform-molding injection mold having cavity gates, said hot runner system including:a plurality of nozzle members abutting said cavity gates of said injection mold, respectively; a cylindrical runner block having a gate formed on a lengthwise central portion of a side surface thereof, said runner block mounting therein said plurality of nozzle members such that said nozzle members protrude from respective upper portions of said runner block, said runner block having a hot runner extending through a core portion thereof to communicate between said gate and an interior of each of said plurality of nozzle members, said runner block having band heaters enclosing a periphery thereof; blocking members fitted into both end portions of said runner block, for blocking said hot runner; and support plates fitted to said runner block at both said end portions of said runner block; said hot runner system comprising a heater inserted into a core portion of each of said blocking members and a heater enclosing a periphery of said each of blocking members, for compensating for heat loss due to heat radiation and heat transfer to said support plates, to thereby keep temperature at said each of said end portions of said runner block in a predetermined range of temperature, wherein said each of blocking members is of an inside plug shape and formed by a lid body which is fitted into a concave portion formed in an end surface of said runner block, and a shaft portion which is fitted into a runner opening which is larger in diameter than said hot runner, and wherein said heaters for compensating for said heat loss comprise a cartridge heater embedded in said shaft portion and having a length from an external end surface of said lid body to a portion close to an end portion of said hot runner, and a heating plate tightly attached to said external end surface of said lid body together with a second band heater enclosing the same.