Adjustable valve pin assembly

Abstract

The valve pin adjustment system is provided for use in valve gated injection molding applications which enables adjustments to the positioning of the valve pin without necessitating removal of the clamping plates and valve assembly components, including valve pins. A piston associated with the valve pin includes a cylindrical body having first and second co-axially aligned internally threaded bores of respective first and second diameters. Preferably, the threads formed in the first and second bores are of the opposite hand. First and second externally-threaded cylindrical valve pin positioning members are respectively received in the first and second bores. Each of the positioning members includes a head portion and a tip portion. The tip of the second positioning member is in contact with the head of the first positioning member to lock the first positioning member in place, and the tip of the first positioning member is in contact with a head portion on the valve pin to locate the valve pin.

1. A valve gated injection molding apparatus comprising:
 a nozzle having a melt passage therethrough extending to a gate;  
 a valve pin having an elongated shaft with a front end terminating in a tip and a rear end terminating in an enlarged head;  
 a piston adapted to capture the head of the valve pin, the elongated shaft of the valve pin extending through the piston into the melt passage to the gate, the piston comprising a body having first and second internally-threaded bores of respective first and second diameters; and  
 first and second externally-threaded valve pin positioning members adapted to be received in the first and second bores in the body of the piston, the first positioning member engaging the head of the valve pin and the second positioning member contacting the first positioning member to lock the first positioning member in place.  
 
     
     
       2. The valve gated injection molding apparatus of  claim 1  wherein the first and second bores in the body of the piston are oppositely threaded. 
     
     
       3. The valve gated injection molding apparatus of  claim 1  wherein each of the first and second positioning members has a head and a tip, the head being configured with a surface adapted to be engaged by a torque-applying tool, the tip of the first positioning member adapted to contact the valve pin, and the tip of the second positioning member being adapted to engage the head of the first positioning member. 
     
     
       4. The valve gated injection molding apparatus of  claim 3  wherein the heads of the first and second positioning members are recessed and the tip of the second positioning member is sized to be received in the recess in the head of the first positioning member. 
     
     
       5. The valve gated injection molding apparatus of  claim 1  wherein the piston has at least one slot formed therein adapted to be engaged by a tool so as to prevent rotation of the piston. 
     
     
       6. A valve gated injection molding apparatus comprising:
 at least one nozzle having a melt passageway therethrough extending to a gate;  
 a manifold to deliver melt to the nozzle;  
 first and second clamp plates to enclose the manifold and maintain the nozzle in contact therewith;  
 a cylinder positioned between the first clamp plate and the manifold in alignment with the nozzle;  
 a valve pin having an elongated shaft with a front end terminating in a tip and a rear end terminating in an enlarged head;  
 a piston adapted to be received in the cylinder for capturing the head of the valve pin, the elongated shaft of the valve pin extending through the piston into the melt passage to the gate, the piston comprising a cylindrical body having first and second internally-threaded bores of respected first and second diameters;  
 first and second externally-threaded valve pin positioning members adapted to be received in the first and second bores in the body of the piston, the first positioning member engaging the head of the valve pin and the second positioning member contacting the first positioning member to lock the first positioning member in place.  
 
     
     
       7. The valve gated injection molding apparatus of  claim 6  wherein the first clamp plate includes a well through which access to the internally-threaded bores in the body of the piston is obtained, each of the well and the body of the piston having at least one slot, the slots being alignable upon rotation of the piston so as to receive a tool to prevent rotation of the piston with respect to the first clamp plate and to apply torque to the positioning members. 
     
     
       8. A valve gated injection molding apparatus comprising:
   a nozzle having a melt passage therethrough extending to a gate;        a valve pin having an elongated shaft with a front end terminating in a tip and a rear end terminating in an enlarged head;        a piston adapted to capture the head of the valve pin, the elongated shaft of the valve pin extending through the piston into the melt passage to the gate, the piston comprising a body having at least one internally - threaded bore; and        first and second externally - threaded valve pin positioning members, at least one of said valve pin positioning members being threadedly received in the at least one internally - threaded bore in the body of the piston, the first positioning member engaging the head of the valve pin and the second positioning member contacting the first positioning member to lock the first positioning member in place.     
     
     
       9. The valve gated injection molding apparatus of  claim 8  wherein each of the first and second positioning members has a head and a tip, each said head being configured with a surface adapted to be engaged by a torque- applying tool, the tip of the first positioning member adapted to contact the head of said valve pin, and the tip of the second positioning member being adapted to engage the head of the first positioning member.   
     
     
       10. The valve gated injection molding apparatus of  claim 9  wherein the head of the first positioning member is recessed and the tip of the second positioning member is sized to be received in the recess in the head of the first positioning member. 
     
     
       11. The valve gated injection molding apparatus of  claim 1  wherein the piston has at least one slot formed therein adapted to be engaged by a tool so as to prevent rotation of the piston. 
     
     
       12. A valve gated injection molding apparatus comprising:
   at least one nozzle having a melt passageway therethrough extending to a gate;        a manifold to deliver melt to the nozzle;        first and second clamp plates to enclose the manifold and maintain the nozzle in contact therewith;        a cylinder positioned between the first clamp plate and the manifold in alignment with the nozzle;        a valve pin having an elongated shaft with a front end terminating in a tip and a rear end terminating in an enlarged head;        a piston received in the cylinder for capturing the head of the valve pin, the elongated shaft of the valve pin extending through the piston and manifold and into the melt passage to the gate, the piston comprising a cylindrical body having at least one internally threaded bore;        first and second externally - threaded valve pin positioning members, at least one of said valve positioning members being threadedly received in said at least one internally - threaded bore in the body of the piston, the first positioning member engaging the head of the valve pin and the second positioning member contacting the first positioning member to lock the first positioning member in place.     
     
     
       13. The valve gated injection molding apparatus of  claim 12  wherein the first clamp plate includes a well through which access to the at least one internally- threaded bore in the body of the piston is obtained, each of the well and the body of the piston having at least one slot, said slots being alignable upon rotation of the piston so as to receive a tool to prevent rotation of the piston with respect to the first clamp plate the application of torque to the positioning members.   
     
     
       14. The valve gated injection molding apparatus of  claim 12  wherein the first clamp plate includes a well through which access to the at least one internally- threaded bore in the body of the piston is obtained.   
     
     
       15. The valve gated injection molding apparatus of  claim 12  wherein the body of the piston has a upper end which includes a radial slot that is adapted to receive a tool to prevent rotation of the piston during the application of torque to the positioning members. 
     
     
       16. A valve gated injection molding apparatus comprising:
   a nozzle having a melt passage therethrough extending to a gate;        a valve pin having an elongated shaft with a front end termination in a tip which is adapted to selectively shut off the flow of melt into the gate and a rear end terminating in an enlarged head;        a cylinder in an overlying relation to said nozzle;        a piston in said cylinder mounted for reciprocal movement therein, said piston including a cylindrical wall defining a generally cup - shaped chamber which includes at least one internally threaded bore and a bottom end wall through which the valve pin shaft extends;        first and second axially aligned externally threaded valve pin positioning members contained within said chamber together with the enlarged head of said valve pin which is captured in the space between an end face of said first valve pin positioning member and the bottom end wall of said chamber, said valve pin head being sized so that it has an axial length between a top face and a bottom collar thereof which is less than the axial distance between said end face of said first valve pin positioning member and the bottom end wall of said chamber,        whereby when said piston is actuated to move said valve pin to shut off the flow of melt into the gate, the end face of said first valve pin positioning member will be in contact with the top end face of said valve pin head and an open space will be present between the bottom collar of said valve pin head and the end wall of said chamber and, correspondingly, when said piston is actuated to move said valve pin to permit the flow of melt into said gate, said bottom collar of said valve pin head will be in contact with the end wall of said chamber to provide an open space between the top end face of said valve pin head and the end face of said first valve pin positioning member.     
     
     
       17. The valve gated injection molding apparatus of  claim 16  wherein said generally cup- shaped cylindrical chamber includes a second threaded bore in overlying axially aligned relation to said at least one internally threaded bore.   
     
     
       18. The valve gated injection molding apparatus of  claim 17  wherein said second threaded bore has a larger diameter than said at least one internally threaded bore. 
     
     
       19. The valve gated injection molding apparatus of  claim 18  wherein said second threaded bore is oppositely threaded with respect to the threads of said at least one internally threaded bore. 
     
     
       20. The valve gated injection molding apparatus of  claim 16  wherein first and second clamp plates enclose said manifold and maintain the nozzle in contact therewith and said first clamp plate includes a well through which access to said generally cup- shaped chamber is obtained.