Injection nozzle and method for injection molding

Abstract

A valve stem is mounted in a nozzle body, with the valve stem moving from an open position retracted from the injection orifice permitting the flow of resin to the mold cavity, to a closed position blocking the injection orifice and preventing the flow of resin to the mold cavity, and to an advanced position within the gate nub area to assist in the ejection of a molded part and clear the gate nub area.

What is claimed is:  
     
       1. An injection nozzle for injection molding resin from a source of molten resin to a mold cavity, which comprises: 
       a mold cavity;  
       an injection nozzle having a nozzle body and a nozzle tip and having an internal flow channel therein communicating with an injection orifice which in turn communicates with said mold cavity for transportation of molten resin to the mold cavity;  
       a valve gate nub area between the mold cavity and injection orifice;  
       a valve stem mounted in the injection nozzle; and  
       means to move the valve stem between an open position retracted from the injection orifice permitting the flow of resin to the mold cavity, a fully closed position blocking the injection orifice and preventing flow of resin to the mold cavity, and an advanced position past the fully closed position and within the valve gate nub area to assist in ejection of a molded part and to clear the valve gate nub area.  
     
     
       2. An injection nozzle according to  claim 1 , wherein the valve gate nub area includes a passageway between the mold cavity and the injection orifice with an annular wall, wherein in the advanced position the valve stem is moved adjacent said annular wall to substantially fill the passageway. 
     
     
       3. An injection nozzle according to  claim 2 , wherein said valve stem has a continuous forward wall which extends completely across said passageway in the advanced position and a continuous annular wall extending therefrom which extends completely within the annular wall of said passageway in the advanced position. 
     
     
       4. An injection nozzle according to  claim 1 , including at least one piston connected to said valve stem operative to move said valve stem between the open, closed and advanced positions. 
     
     
       5. An injection nozzle according to  claim 4 , including two of said pistons connected to said valve stem operative to move the value stem between the open, closed and advanced positions. 
     
     
       6. An injection nozzle according to  claim 1 , wherein said internal flow channel is connected to a hot runner channel. 
     
     
       7. An injection nozzle according to  claim 6 , including at least three air inlets operative to move said pistons. 
     
     
       8. A method for injection molding, which comprises: 
       providing an injection nozzle having a nozzle body and a nozzle tip and having an internal flow channel therein communicating with an injection orifice which in turn communicates with a mold cavity;  
       transporting molten resin from said internal flow channel to said mold cavity;  
       positioning a valve gate nub area between the mold cavity and injection orifice;  
       mounting the valve stem between an open position retracted from the injection orifice permitting the flow of resin to the mold cavity, a fully closed position blocking the injection orifice and preventing flow of resin to the mold cavity, and an advanced position past the fully closed position within the valve gate nub area to assist in ejection of a molded part and to clear the valve gate nub area.  
     
     
       9. A method according to  claim 8 , including providing a passageway with an annular wall in the valve gate nub area between the mold cavity and injection orifice, and moving the valve stem in the advanced position adjacent said annular wall to substantially fill the passageway. 
     
     
       10. A method according to  claim 8 , including moving the valve stem with at least one piston between the open, closed and advanced positions. 
     
     
       11. A method according to  claim 10 , including moving the valve stem with two of said pistons between the open, closed and advanced positions. 
     
     
       12. A method according to  claim 8 , including connecting said internal flow channel to a hot runner channel. 
     
     
       13. A method according to  claim 11 , including moving said pistons by pressurized air supplied by at least three channels. 
     
     
       14. A valve gate assembly for injection molding, in use, resin into a mold cavity, the valve gate assembly comprising: 
       
         an injection nozzle having a nozzle body and a nozzle tip and having an internal flow channel therein communicating with an injection orifice which in turn communicates with said mold cavity for the transfer, in use, of resin to the mold cavity;  
       
       
         a valve gate area between the mold cavity and injection orifice;  
       
       
         a valve stem operatively positioned in the injection nozzle; and  
       
         means to move the valve stem between  ( i )  an open position retracted from the injection orifice permitting the flow of resin to the mold cavity,  ( ii )  a fully closed position blocking the injection orifice and preventing flow of resin to the mold cavity, and  ( iii )  an advanced position past the fully closed position and within the valve gate area to clear the valve gate area.   
     
     
       15. The valve gate assembly according to  claim 14 , wherein the valve gate area includes a passageway between the mold cavity and the injection orifice, wherein in the advanced position the valve stem is moved to substantially fill the passageway. 
     
     
       16. The valve gate assembly according to  claim 15 , wherein said valve stem has a forward wall which extends across said passageway in the advanced position and a continuous annular wall extending therefrom which extends completely within said passageway in the advanced position. 
     
     
       17. The valve gate assembly according to  claim 14 , including at least one piston, connected to said valve stem, operative to move said valve stem between the open, closed and advanced positions. 
     
     
       18. The valve gate assembly according to  claim 15 , including at least one piston, connected to said valve stem, operative to move said valve stem between the open, closed and advanced positions. 
     
     
       19. The valve gate assembly according to  claim 16 , including at least one piston, connected to said valve stem, operative to move said valve stem between the open, closed and advanced positions. 
     
     
       20. The valve gate assembly according to  claim 17 , including at least three air inlets operative to move said at least one piston. 
     
     
       21. The valve gate assembly according to  claim 14 , wherein said internal flow channel is in communication with a hot runner channel. 
     
     
       22. The valve gate assembly according to  claim 14 , wherein said injection orifice is configured sealingly to receive said valve stem to substantially stop the flow of resin to the mold cavity. 
     
     
       23. A valve gate assembly containing a nozzle body and a nozzle tip, the nozzle body having an internal channel terminating at the nozzle tip, the valve gate assembly further including a valve stem located within the internal channel and a valve stem actuator coupled to the valve stem to control a position of the valve stem relative to the nozzle tip, the valve gate assembly comprising: 
         the valve stem actuator being configured to cause extension of the valve stem between  ( i )  an open position,  ( ii )  a fully closed position, and  ( ii )  an advanced position beyond the fully closed position, the advanced position being sufficiently beyond the nozzle tip to cause the valve stem to clear away debris accumulated in front of the valve stem.   
     
     
       24. A method of operating a valve gate assembly associated with an injection mold, the valve gate assembly containing a nozzle body and a nozzle tip, the nozzle body having an internal channel terminating at the nozzle tip, the valve gate assembly further including a valve stem located within the internal channel and a valve stem actuator coupled to the valve stem to control a position of the valve stem relative to the nozzle tip, the method including the steps of: 
       
         operating the valve stem actuator to move the valve from an open position to a fully closed position; and  
       
       
         operating the valve stem actuator to move the valve stem beyond the fully closed position and beyond the nozzle tip such that the valve stem acts to clear away debris accumulated in front of the valve stem. 
       
     
     
       25. A method of clearing plastic debris from the vicinity of a gate orifice of a gate pad, the method comprising: 
       
         moving the valve stem from an open position to a fully closed position; and  
       
       
         forcing the valve stem beyond the fully closed position to extend through the gate orifice, to clear debris from the vicinity of the gate orifice. 
       
     
     
       26. An injection molding apparatus for injection molding from a source of molten material to a mold cavity, said nozzle comprising: 
       
         a mold cavity;  
       
       
         an injection nozzle having a nozzle body and a nozzle tip and having an internal flow channel therein communicating with an injection orifice which in turn communicates with said mold cavity for the transfer of molten material to the mold cavity;  
       
       
         a valve gate area between the mold cavity and the injection orifice;  
       
       
         a valve stem operatively positioned in the injection nozzle; and  
       
         structure to move the valve stem between  ( i )  an open position retracted from the injection orifice permitting the flow of material to the mold cavity,  ( ii )  a fully closed position blocking the injection orifice and preventing flow of material to the mold cavity, and  ( iii )  an advanced position past the fully closed position and within the valve gate area to clear the valve gate area.   
     
     
       27. Apparatus according to  claim 26 , wherein the valve gate area includes a passageway between the mold cavity and the injection orifice, wherein in the advanced position the valve stem is moved to substantially fill the passageway. 
     
     
       28. Apparatus according to  claim 27 , wherein said valve stem has a continuous forward wall which extends completely across said passageway in the advanced position and a continuous annular wall extending therefrom which extends completely within said passageway in the advanced position. 
     
     
       29. Apparatus according to  claim 26 , including at least one piston connected to said valve stem operative to move said valve stem between the open, closed, and advanced positions. 
     
     
       30. Apparatus according to  claim 29 , including two of said pistons connected to said valve stem operative to move the value stem between the open, closed and advanced positions. 
     
     
       31. Apparatus according to  claim 26 , wherein said internal flow channel is in communication with a hot runner channel. 
     
     
       32. Apparatus according to  claim 29 , including at least three air inlets operative to move said pistons. 
     
     
       33. Apparatus according to  claim 26 , wherein said molded part is a short shot that has not completely filled said mold cavity. 
     
     
       34. An injection nozzle for injection molding from a source of molten material, said nozzle comprising: 
       
         an elongated nozzle housing having an internal flow channel therein, said internal flow channel in communication with the source of molten material for communication of the molten material to a mold cavity; and  
       
         a valve stem configured to  ( i )  open the flow channel,  ( ii )  fully close the flow channel, and  ( iii )  move beyond the fully close position to clear said mold cavity of debris.   
     
     
       35. The injection nozzle according to  claim 34 , further comprising a piston configured to move said valve stem. 
     
     
       36. The injection nozzle according to  claim 35 , wherein said piston is an air piston. 
     
     
       37. The injection nozzle according to  claim 34 , wherein said valve stem is disposed in said internal flow channel. 
     
     
       38. The injection nozzle according to  claim 37 , wherein said valve stem is disposed substantially coaxial to said internal flow channel. 
     
     
       39. The injection nozzle according to  claim 34 , further comprising a nozzle tip affixed to said nozzle housing adjacent the mold cavity. 
     
     
       40. The injection molding nozzle according to  claim 39 , wherein said nozzle tip comprises a central melt channel in fluid communication between said internal flow channel and the mold cavity. 
     
     
       41. The injection molding nozzle according to  claim 40 , wherein said nozzle tip further comprises an orifice in fluid communication between said central melt channel and the mold cavity. 
     
     
       42. The injection molding nozzle according to  claim 41 , wherein said orifice is configured to sealingly receive said valve stem when said valve stem is positioned to substantially stop the flow of the material to the mold cavity. 
     
     
       43. The injection molding nozzle according to  claim 39 , further comprising an insulator disposed between said nozzle tip and the mold cavity. 
     
     
       44. The injection molding nozzle according to  claim 43 , further comprising a first piston configured to limit the stroke of a second piston, said second piston affixed to said valve stem. 
     
     
       45. The injection molding nozzle according to  claim 44 , wherein said second piston is sealingly disposed in a cavity of said first piston and said first piston sealingly disposed in a piston cavity associated with a respective said injection molding nozzle. 
     
     
       46. The injection molding nozzle according to  claim 45 , wherein said first piston is moved to a first position to allow said second piston to move said valve stem between an open and fully closed position to start and stop the flow of molten material, and said first piston is further positioned to allow said second piston to move said valve stem to clear a gate orifice of substantially solidified material associated with a respective nozzle. 
     
     
       47. A method of clearing a gate orifice of an injection mold comprising the steps of: 
         providing a valve stem movable between  ( i )  a first position where molten material may flow through the gate orifice,  ( ii )  a second position to fully stop the flow of molten material through the gate orifice, and  ( iii )  a third position beyond the second position whereby said valve stem is placed completely through the gate orifice; and    
       
         placing said valve stem through said gate orifice to remove debris therefrom. 
       
     
     
       48. The method according to  claim 47 , wherein said solidified material comprises a short shot that did not completely fill a mold cavity associated with said gate orifice. 
     
     
       49. The method according to  claim 47 , further comprising the steps of: 
       
         placing at least one piston in communication with said valve stem to position said valve stem in a predetermined position relative to the gate orifice; and  
       
       
         applying energy to said at least one piston to extend said valve stem through said orifice to remove the solidified material from said gate orifice. 
       
     
     
       50. The method according to  claim 47 , wherein said solidified material comprises a short shot that failed to completely fill the mold cavity. 
     
     
       51. The method according to  claim 47 , wherein said solidified material is produced as a result of a short shot. 
     
     
       52. The method according to  claim 47 , wherein said solidified material comprises a PET preform. 
     
     
       53. The method according to  claim 47 , wherein said debris comprises solidified material that leaked around said valve stem when said valve stem was in a closed position. 
     
     
       54. An injection molding system for the formation of a molded article comprising: 
       
         structure configured to provide a supply of molten material in communication with a melt channel in a manifold;  
       
       
         a manifold plate having a cavity formed therein for the receipt of a nozzle housing;  
       
       
         a central melt channel in said nozzle housing in fluid communication between said melt channel and a mold cavity; and  
       
       
         a valve element configured to start and stop the flow of molten material to the mold cavity, said valve element being movable between an open position, a fully closed position, and a position beyond the fully closed position to clear debris from a gate area. 
       
     
     
       55. The injection molding system of  claim 54 , further comprising a nozzle tip in fluid communication between said nozzle housing and the mold cavity. 
     
     
       56. The injection molding system of  claim 55 , wherein said nozzle tip comprises a gate orifice adjacent the mold cavity. 
     
     
       57. The injection molding system of  claim 56 , wherein said gate orifice is configured to sealingly receive said valve element to substantially stop the flow of molten material to the mold cavity. 
     
     
       58. The injection molding system of  claim 57 , wherein said valve element is an elongated cylindrical member that is configured to extend through said gate orifice a predetermined distance. 
     
     
       59. The injection molding system of  claim 58 , wherein said valve element extends coaxially in said central melt channel. 
     
     
       60. The injection molding system of  claim 54 , further comprising a valve bushing inserted into a cavity of said manifold, said valve bushing having a passageway in fluid communication between said melt channel and said central melt channel. 
     
     
       61. The injection molding system of  claim 60 , further comprising a piston configured to selectively position said valve element in relation to said gate orifice. 
     
     
       62. A method for injection molding, which comprises the steps of: 
       
         providing an injection nozzle having a nozzle body and a nozzle tip, said nozzle having an internal flow channel therein communicating with an injection orifice which in turn communicates with a mold cavity;  
       
       
         transporting molten material from said internal flow channel to said mold cavity;  
       
       
         providing a valve gate area between the mold cavity and injection orifice;  
       
         mounting the valve stem between  ( i )  an open position retracted from the injection orifice permitting the flow of material to the mold cavity,  ( ii )  a fully closed position blocking the injection orifice and preventing flow of resin to the mold cavity, and  ( iii )  an advanced position past the fully closed position within the valve gate area to clear the valve gate area.   
     
     
       63. A method according to  claim 62 , including providing a passageway with an annular wall in the valve gate area between the mold cavity and injection orifice, and moving the valve stem in the advanced position adjacent said annular wall to substantially fill the passageway. 
     
     
       64. A method according to  claim 62 , including moving the valve stem with at least one piston between the open, closed and advanced positions. 
     
     
       65. A method according to  claim 64 , including moving the valve stem with two of said pistons between the open, closed and advanced positions. 
     
     
       66. A method according to  claim 62 , including connecting said internal flow channel to a hot runner channel. 
     
     
       67. An injection nozzle for injection molding from a source of molten material, said nozzle comprising: 
       
         a nozzle housing means having an internal flow channel therein, said internal flow channel in communication with the source of molten material for communication of the molten material to a mold cavity;  
       
       
         a valve element means configured to move between an open position and a fully closed position to respectively start and stop the flow of the molten material to the mold cavity, said valve element means also being configured to move to a position beyond the fully closed position to clear at least a portion of said mold cavity of solidified material. 
       
     
     
       68. The injection nozzle according to  claim 67 , further comprising a piston means configured to move said valve element means. 
     
     
       69. The injection nozzle according to  claim 68 , wherein said piston means is an air piston. 
     
     
       70. The injection nozzle according to  claim 67 , wherein said valve element means is disposed in said internal flow channel. 
     
     
       71. The injection nozzle according to  claim 70 , wherein said valve element means is disposed substantially coaxial to said internal flow channel. 
     
     
       72. The injection nozzle according to  claim 71 , further comprising a nozzle tip means affixed to said nozzle housing means adjacent the mold cavity. 
     
     
       73. The injection molding nozzle according to  claim 72 , wherein said nozzle tip means comprises a central melt duct in fluid communication between said internal flow channel and the mold cavity. 
     
     
       74. The injection molding nozzle according to  claim 73 , wherein said nozzle tip means further comprises an orifice means in fluid communication between said central melt duct and the mold cavity. 
     
     
       75. The injection molding nozzle according to  claim 74 , wherein said orifice means is configured to sealingly receive said valve element means when said valve element means is positioned to substantially stop the flow of the material to the mold cavity. 
     
     
       76. The injection molding nozzle according to  claim 75 , further comprising an insulator means affixed between said nozzle tip means and the mold cavity.