Apparatus and method for multiple cavity injection molding

Abstract

A runner system and runner component particularly adapted for use in multiple cavity injection molding systems is disclosed. The runner system and runner component utilize particular structural features and geometrical configurations that have been found to result in superior molding practices and molded components in multiple cavity injection molding systems. A corresponding multiple cavity injection molding system utilizing the noted runner system is described. And, a related method for promoting uniform filling of multiple mold cavities is also disclosed.

We claim:  
     
         1 . A multiple cavity injection molding system comprising: 
 a feed source providing flowable polymeric material at conditions suitable for producing molded products therefrom;    a plurality of mold cavities adapted to receive flowable polymeric material from said feed source and produce molded products therefrom;    a primary sprue extending from said feed source; and    a runner system extending between and providing fluid communication between said primary sprue and said plurality of mold cavities, said runner system having a feed inlet in communication with said primary sprue and a plurality of discharge ports in communication with said plurality of mold cavities, said runner system having a symmetrical configuration with respect to said primary sprue and including at least two turbulence inducing components selected from the group consisting of turbulence inducing runners, turbulence inducing steps, and turbulence inducing angles, such that upon performing an injection molding operation, the shear rate of polymeric material exiting said runner system is at least 50% of the shear rate of said polymeric material entering said runner system at said feed inlet.    
     
     
         2 . The injection molding system of  claim 1  wherein said runner system has a mirror image configuration.  
     
     
         3 . The injection molding system of  claim 1  wherein said shear rate of said polymeric material exiting said runner system is at least 60% of the shear rate of said polymeric material entering said runner system.  
     
     
         4 . The injection molding system of  claim 1  wherein said shear rate of said polymeric material exiting said runner system is at least 70% of the shear rate of said polymeric material entering said runner system.  
     
     
         5 . A runner system adapted for multiple cavity injection molding, said runner system comprising: 
 a primary runner having a first end, a second end opposite from said first end, and defining a feed opening about midway between said first end and said second end;    a first secondary runner disposed proximate to said first end of said primary runner, said first secondary runner having a first end, a second end, and defining an entrance opening about midway between said first end and said second end, said entrance opening providing communication between said first end of said primary runner and said first secondary runner;    a second secondary runner disposed proximate to said second end of said primary runner, said second secondary runner having a first end, a second end, and defining an entrance opening about midway between said first end and said second end, said entrance opening providing communication between said second end of said primary runner and said second secondary runner;    a plurality of tertiary turbulence inducing runners, each of said tertiary turbulence inducing runners disposed at a corresponding end of said first and second secondary runners, each said tertiary turbulence inducing runner comprising a first exit port, a second exit port opposite from said first exit port, and an inlet opening defined about midway between said first and second exit ports, said inlet opening providing communication between a respective tertiary turbulence inducing runner and a corresponding secondary runner;    wherein upon introducing a flowable material into said feed opening of said primary runner under conditions suitable for injection molding, said material in said tertiary turbulence inducing runners is in a pseudo-turbulent state.    
     
     
         6 . The runner system of  claim 5  wherein said runner system has a balanced configuration with respect to said feed opening of said primary runner.  
     
     
         7 . The runner system of  claim 6  wherein said runner system has symmetrical configuration with respect to said feed opening of said primary runner.  
     
     
         8 . The runner system of  claim 7  wherein said runner system has a mirror image configuration with respect to said feed opening of said primary runner.  
     
     
         9 . A turbulence inducing runner adapted for incorporation in a runner system for a multiple cavity injection molding system, said turbulence inducing runner comprising: 
 a primary runner having a first end, a second end opposite from said first end, a feed entrance defined midway between said first end and said second end, a first turbulence inducing angle disposed between said feed entrance and said first end, and a second turbulence inducing angle disposed between said feed entrance and said second end;    a first secondary runner disposed at and in communication with, said first end of said primary runner, said first secondary runner having a first end, and a second end opposite from said first end, and an opening defined at a midpoint between said first and second ends of said first secondary runner, said opening providing communication between said first secondary runner and said primary runner;    a second secondary runner disposed at and in communication with, said second end of said primary runner, said second secondary runner having a first end, and a second end opposite from said first end, and an opening defined at a midpoint between said first and second ends of said second secondary runner, said opening providing communication between said second secondary runner and said primary runner; and    a plurality of turbulence inducing steps, each disposed at and in communication with, a respective end of said first and second secondary runners;    wherein said primary runner and said first and second secondary runners extend within a common plane, and said plurality of turbulence inducing steps extend within a plane different than said common plane.    
     
     
         10 . The turbulence inducing runner of  claim 9  wherein said runner exhibits a balanced configuration with respect to said feed entrance of said primary runner.  
     
     
         11 . The turbulence inducing runner of  claim 10  wherein said runner exhibits a symmetrical configuration.  
     
     
         12 . The turbulence inducing runner of  claim 11  wherein said runner exhibits a mirror image configuration.  
     
     
         13 . The turbulence inducing runner of  claim 9  wherein the configuration of said runner is such that upon administering a flowable polymeric material to said feed entrance of said primary runner at a pressure suitable for displacing said material through said runner and exiting through said plurality of turbulence inducing steps, said material exhibits pseudo-turbulence flow at said steps.  
     
     
         14 . A method for promoting uniform filling of a plurality of mold cavities in an injection molding system, said injection molding system comprising (i) a feed source for providing flowable polymeric material, (ii) a plurality of mold cavities adapted for receiving flowable polymeric material and producing molded articles therefrom, and (iii) a plurality of runners for transferring said polymeric material from said feed source to said plurality of mold cavities, said method comprising: 
 providing said plurality of runners;    providing at least two turbulence inducing components selected from the group consisting of turbulence inducing angles, turbulence inducing steps, and turbulence inducing runners;    incorporating said at least two turbulence inducing components with said plurality of runners; and    configuring said plurality of runners and said at least two turbulence inducing components to thereby form a turbulence inducing runner system having a balanced configuration and upon performing an injection molding operation, maintaining a shear rate within said polymeric material entering said plurality of mold cavities that is at least about 40% the shear rate of said polymeric material exiting said feed source.    
     
     
         15 . The method of  claim 14  wherein said runner system maintains a shear rate within said polymeric material entering said plurality of mold cavities that is at least about 50% the shear rate of said polymeric material exiting said feed source.  
     
     
         16 . The method of  claim 14  wherein said runner system maintains a shear rate within said polymeric material entering said plurality of mold cavities that is at least about 60% the shear rate of said polymeric material exiting said feed source.  
     
     
         17 . The method of  claim 14  wherein said runner system maintains a shear rate within said polymeric material entering said plurality of mold cavities that is at least about 70% the shear rate of said polymeric material exiting said feed source.