Extrusion head for use in blow molding machine

Claim 1

In an extrusion head for use in blow molding machine having an extruder and supplied with resin wherein an outer periphery of a plunger is in contact with inner walls of a head body and an opening of a support plate, said head body and said support plate being located coaxial with the plunger, and inner periphery of the plunger being in contact with a core which is positioned coaxially with the plunger, said plunger being slidable in an axial direction, the improvement comprising: a feed port for supplying said resin from the extruder to the head body and being a horizontal hole formed in said support plate above the head body; a sealing block secured to said support plate and having a lower face abutting the upper part of said supply port, the supply port being extended to a lower face of said sealing block, said sealing block being fitted in a longitudinal groove formed axially on the outer periphery of the plunger thereby preventing the resin from remaining in the longitudinal groove in excess of a predetermined time interval when said plunger is slid vertically, said sealing block also preventing the resin from leaking when said plunger is slid vertically; an extended lower part of the longitudinal groove forming a flared portion widening in width in a circumferential direction of the plunger, a lower part of the flared portion being formed with a throttle which is annular in the circumferential direction of the plunger and shallower than the flared portion, an edge provided on the upper side of said flared portion for scraping off the material adhering to the inner peripheral surface of said head body during each extrusion of material; the side of the throttle portion toward a nozzle being at the lower end of the plunger; an accumulation chamber having a narrow annular flow path between the annular throttle portion and the head body, communicating with the flared portion; and the accumulation chamber being provided with an upper portion surrounded by said annular path and said lower end of the plunger, an outer periphery defined by the inner wall of the head body, an inner periphery defined by the outer wall of the core, and a lower portion extending to the nozzle.