Method using manifold system having flow control

Abstract

An injection molding apparatus is provided in which the rate of material flow during the injection cycle is controlled. According to one preferred embodiment, a method is provided for use in an injection molding apparatus including a hot runner assembly comprising a manifold and at least first and second injection nozzles, the hot runner assembly to direct material injected into said manifold through said at least first and second injection nozzles through a corresponding at least first and second gates to one or more mold cavities. The method includes the steps of injecting material into the manifold, controlling, in the hot runner away from the first gate, a first rate at which material is injected through the first gate, and controlling, in the hot runner away from the second gate, a second rate at which material is injected through the second gate, independently from the first rate.

What is claimed is:  
     
         1 . In an injection molding apparatus including a hot runner assembly comprising a manifold and at least first and second injection nozzles, the hot runner assembly to direct material injected into said manifold through said at least first and second injection nozzles through a corresponding at least first and second gates to one or more mold cavities, a method comprising the steps of: 
 (A) injecting material into the manifold;    (B) controlling, in the hot runner away from the first gate, a first rate at which material is injected through the first gate; and    (C) controlling, in the hot runner away from the second gate, a second rate at which material is injected through the second gate, independently from the first rate.    
     
     
         2 . The method of  claim 1 , wherein the first and second rates are controlled in the manifold.  
     
     
         3 . The method of  claim 1 , wherein the first and second rates are controlled in the first and second nozzles, respectively.  
     
     
         4 . The method of  claim 3 , wherein the first and second rates are controlled at a rearward end of each of the first and second nozzles, respectively.  
     
     
         5 . The method of  claim 1 , wherein controlling the first rate is based on a first sensed condition related to the rate of material flow through the first gate, and controlling the second rate is based on a second sensed condition related to the rate of material flow through the second gate.  
     
     
         6 . The method of  claim 5 , wherein controlling the first rate is based only on the first sensed condition, and controlling the second rate is based only on the second sensed condition.  
     
     
         7 . The method of  claim 5 , wherein the sensed condition is pressure.  
     
     
         8 . The method of  claim 1 , wherein step (B) includes altering a size of a first pathway in the hot runner through which the material flows to control the first rate, and step (C) includes altering a size of a second pathway in the hot runner through which the material flows to control the second rate.  
     
     
         9 . The method of  claim 8 , wherein the first and second pathways are in the manifold.  
     
     
         10 . The method of  claim 5 , wherein the first rate is controlled based on a result of a comparison of the first sensed condition to a first target value of the first sensed condition, and the second rate is controlled based on a result of a comparison of the second sensed condition to a second target value of the second sensed condition.  
     
     
         11 . The method of  claim 10 , further comprising controlling the first and second rates so that the first and second sensed conditions track the first and second target values throughout an injection cycle.  
     
     
         12 . The method of  claim 1 , wherein the first rate differs from the second rate during at least of portion of an injection cycle.  
     
     
         13 . The method of  claim 10 , wherein the first and second target values differ from one another.  
     
     
         14 . The method of  claim 10 , wherein the first and second sensed conditions are material pressure.  
     
     
         15 . The method of  claim 8 , wherein the first and second pathways are in a rearward end of the first and second nozzles.  
     
     
         16 . The method of  claim 10 , wherein the first and second target values are the same.  
     
     
         17 . The method of  claim 5 , wherein the first and second sensed conditions are sensed in the hot runner.  
     
     
         18 . The method of  claim 17 , wherein the first and second sensed conditions are sensed in the first and second injection nozzles, respectively.  
     
     
         19 . The method of  claim 17 , wherein the first and second sensed conditions are sensed in the manifold.  
     
     
         20 . In an injection molding apparatus including a hot runner to direct material injected into the hot runner and through a gate and into one or more mold cavities, a method comprising the steps of: 
 (A) injecting material into the hot runner assembly;    (B) sensing, in the hot runner, a sensed condition related to a rate at which material is injected through the gate; and    (C) controlling the rate based on said sensed condition.    
     
     
         21 . The method of  claim 20 , wherein the rate is controlled in the hot runner.  
     
     
         22 . The method of  claim 20 , wherein the sensed condition is a first sensed condition, the rate is a first rate, the gate is a first gate and the method further includes: 
 (D) sensing, in the hot runner, a second sensed condition related to a second rate at which material is injected through a second gate and into said one or more mold cavities; and    (E) controlling the second rate based on said second sensed condition.    
     
     
         23 . The method of  claim 22 , wherein the first rate is controlled independently from the second rate.  
     
     
         24 . The method of  claim 23 , wherein the first and second rates are controlled in the hot runner.  
     
     
         25 . The method of  claim 20 , wherein the rate is controlled as a result of a comparison of the sensed condition to a target value of the sensed condition.  
     
     
         26 . The method of  claim 22 , wherein the first rate is controlled based on a comparison of the first sensed condition to a first target value of the first sensed condition, and the second rate is controlled based on a comparison of the second sensed condition to a second target value of the second sensed condition.  
     
     
         27 . The method of  claim 26 , wherein the first and second rates are controlled in the hot runner.  
     
     
         28 . The method of  claim 27 , wherein step (C) includes altering a size of a first pathway in the hot runner through which the material flows to control the first rate, and step (E) includes altering a size of a second pathway in the hot runner through which the material flows to control the second rate.  
     
     
         29 . The method of  claim 26 , further comprising controlling the first and second rates so that the first and second sensed conditions track the first and second target values throughout an injection cycle.  
     
     
         30 . The method of  claim 22 , further comprising independently adjusting the first and second rates throughout an injection cycle based on the first and second sensed conditions, respectively.  
     
     
         31 . The method of  claim 5 , further comprising independently adjusting the first and second rates throughout an injection cycle based on the first and second sensed conditions, respectively.