Injection nozzle with multi-piece tip portion

Abstract

A hot runner nozzle assembly includes a nozzle heater, a hot runner nozzle, a nozzle tip, a nozzle tip seal surrounding the nozzle tip and a connecting element positioned to removably couple the tip seal to the nozzle tip and to create a first contact seal between the nozzle tip and the tip seal and a second annular contact seal between the tip seal and a mold component. The nozzle tip is made or shaped via a sintering process from a metal matrix composite (MMC) material having a first coefficient of thermal expansion. The tip seal is made or shaped from a ceramic based powder material, having a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion. In operation this hot runner nozzle assembly provides an improved heat profile and a reduced leakage at the tip area under a wider operating processing window.

1 . A hot runner nozzle comprising:
 a hot runner nozzle body having a nozzle melt channel therethrough and having a nozzle body head portion;   a nozzle heater coupled to the hot runner nozzle body;   a nozzle tip having an outer surface and an nozzle tip melt channel, wherein the nozzle tip is made from a sintered metal matrix composite (MMC) powder material, the nozzle tip having a first coefficient of thermal conductivity and a first coefficient of thermal expansion at an operating temperature window between about 100 degrees C. and about 400 degrees C. provided by the nozzle heater, and wherein the nozzle tip is removably coupled to the hot runner nozzle;   a tip seal surrounding the nozzle tip and having an inner surface and an outer surface and is made from a sintered ceramic-based powder material, the tip seal having a second coefficient of thermal conductivity lower than the first coefficient of thermal conductivity and a second coefficient of thermal expansion that is at least equal lower than the first coefficient of thermal expansion at an operating temperature window between about 100 degrees C. and about 400 degrees C. provided by the heater, and wherein the tip seal is removably coupled to the nozzle tip, wherein the tip seal is configured to form a seal with a mold component having a mold gate that adjacent the nozzle tip; and   a seal and connector element made as a unitary component, where the seal and connector element contacting both the nozzle tip and the tip seal, and wherein the unitary seal and connector element is positioned onto the nozzle tip and removably couples the tip seal to the nozzle tip, and controls a first seal between the nozzle tip and the tip seal.   
     
     
         2 . A hot runner nozzle according to  claim 1 , wherein the seal and connector element is threadedly connected to the nozzle tip. 
     
     
         3 . A hot runner nozzle according to  claim 1 , wherein the nozzle tip is threadedly connected to the nozzle body. 
     
     
         4 . A hot runner nozzle according to  claim 1 , wherein the metal matrix composite (MMC) powder material is a carbide that includes tungsten in a proportion exceeding 50%. 
     
     
         5 . A hot runner nozzle according to  claim 1 , wherein the metal matrix composite (MMC) powder material has a coefficient of thermal expansion at 20-1000 C in the range of 4.00-6.00 (×10 −6  K −1 ). 
     
     
         6 . A hot runner nozzle according to  claim 1 , wherein the metal matrix composite (MMC) powder material has a coefficient of thermal conductivity at 20 C in the range of (50-90) W m −1  K −1 . 
     
     
         7 . A hot runner nozzle according to  claim 1 , wherein the tip seal is made of a ceramic powder including zirconium oxide in a proportion in excess of 50%. 
     
     
         8 . A hot runner nozzle according to  claim 1 , wherein the tip seal is made of a ceramic powder having a coefficient of thermal conductivity in the range of (12-15) W/m·° K. 
     
     
         9 . A hot runner nozzle according to  claim 1 , wherein the tip seal is made of a ceramic powder having a coefficient of thermal expansion in the range of (2.5-7) ×10 −6 /° C. 
     
     
         10 . A hot runner nozzle according to  claim 1 , wherein the seal and connector element drives an annular surface on the tip seal against an annular surface on the nozzle tip with a selected force to generate the first seal therebetween. 
     
     
         11 . A hot runner nozzle according to  claim 1 , wherein the tip seal controls a seal between a radially inner surface of the tip seal and a radially outer surface of the nozzle tip.