Injection molding nozzle

Abstract

In an injection molding nozzle with a nozzle head including at least one discharge opening and a closure element for closing the discharge opening movably supported in the nozzle head for closing the discharge in order to control the supply of melt material to a communication opening in an injection mold, the closure element is operable by a drive mechanism provided with a short stroke actuating means for displacing the closure element in a direction opposite to the closing direction of the closure element by a predetermined short distance so as to automatically retract the closure element by the predetermined short distance when it is no longer biased by the actuating means in the closing direction.

1 . An injection molding nozzle with a nozzle head ( 11 ) including at least one discharge opening ( 1 ), a positively controlled closure element ( 2 ) movably supported in the nozzle head ( 11 ) for closing a communication opening in an injection mold ( 4 ), and short stroke actuating means for displacing the closure element ( 2 ) in a direction opposite to the closing movement direction ( 6 ) thereof by a predetermined short stroke distance.  
   
   
       2 . An injection molding nozzle according to  claim 1 , wherein the short stroke distance is 0.05 to 1 mm.  
   
   
       3 . An injection molding nozzle according to  claim 1 , wherein the short stroke distance is about 0.3 mm.  
   
   
       4 . An injection molding nozzle according to  claim 1 , wherein the nozzle head ( 11 ) is connected to a drive ( 7 ) for operating the closure element ( 2 ), said drive ( 7 ) including said short stroke actuating means in the form of a return element ( 5 ) having an operating position and a rest position to which the return element ( 5 ) returns when the drive ( 7 ) is in-activated.  
   
   
       5 . An injection molding nozzle according to  claim 4 , wherein the return element ( 5 ) is a plate spring.  
   
   
       6 . An injection molding nozzle according to  claim 1 , wherein the nozzle head ( 11 ) includes at least two discharge openings ( 1 ) oriented in opposite directions and having closure element ( 2 ) operable by a control means ( 8 ).  
   
   
       7 . An injection molding nozzle according to  claim 1 , wherein the closure elements ( 2 ) are positively controlled via a slide guide structure ( 9 ).  
   
   
       8 . An injection molding nozzle according to  claim 4 , wherein the closure elements ( 2 ) are closure needles which extend through the discharge openings ( 1 ) and are provided at their ends ( 2   b ) opposite the discharge openings ( 1 ) with a T-shaped engagement structure, and the drive means ( 7 ) includes a control rod ( 8 ) having a wedge-shaped end disposed in the nozzle head ( 11 ) and being provided with a T-shaped groove ( 9 ) in which the T-shaped engagement structures of the closure elements ( 2 ) are received for actuating the closure elements ( 2 ) by axial movement of the control rod ( 8 ).  
   
   
       9 . An injection molding nozzle according to  claim 8 , wherein the closure elements ( 2 ) are provided at their ends with cylindrical sections ( 2   a ) extending into the discharge openings ( 1 ) for closing the discharge openings ( 1 ).