Hybrid injection actuator for an injection molding machine

1. An extruder unit ( 22 ) for an injection molding system ( 20 ), comprising

a barrel ( 28 ) containing a screw ( 30 );

a piston housing ( 40 ), connected to and in communication with the barrel ( 28 ), the piston housing ( 40 ) defining a piston chamber ( 42 );

a piston ( 48 ), slidably located within the piston chamber ( 42 ), and movable between a retracted position and an extended position; the piston ( 48 ) further being adapted to rotatably mount the screw ( 30 );

a motor assembly ( 36 ), mounted to the piston housing ( 40 ) and operable to rotate the screw ( 30 ); and

a hybrid injection actuator ( 38 ), the hybrid injection actuator ( 38 ) including:

a drive unit ( 50 ), the drive unit ( 50 ) being one of electrically driven and hydraulically driven and being operable to move the piston ( 48 ) between the retracted position and the extended position;

a gas pressure unit ( 93 ), coupled to the piston chamber ( 42 ) via a gas conduit ( 96 ), the gas pressure unit ( 93 ) being operable to provide a boosting force to the piston ( 48 ) to urge the piston ( 48 ) towards the extended position; and

a lock valve ( 98 ) located between the gas pressure unit ( 93 ) and the piston chamber ( 42 ), the lock valve ( 98 ) being movable between an open position and a closed position to provide a selective communication between the gas pressure unit ( 93 ) and the piston chamber ( 42 ).

2. The extruder unit ( 22 ) of claim 1 , wherein the gas pressure unit ( 93 ) is operable to store a gas at a first pressure, the gas pressure unit ( 93 ) being in the selective communication with the piston chamber ( 42 ); and when opened, the gas pressure unit ( 93 ) is operable to release the gas stored at the first pressure to apply the boosting force to the piston ( 48 ), thereby urging the piston ( 48 ) towards the extended position.

3. The extruder unit ( 22 ) of claim 1 , wherein the gas pressure unit ( 93 ) comprises:

at least one pressure bottle ( 94 ), the at least one pressure bottle ( 94 ) being adapted to store a gas at a first pressure;

the gas conduit ( 96 ), connecting the at least one pressure bottle ( 94 ) and the piston chamber ( 42 ); and

the lock valve ( 98 ) on the at least one pressure bottle ( 94 ), the lock valve ( 98 ) being movable between the open position and the closed position to provide the selective communication between the at least one pressure bottle ( 94 ) and the piston chamber ( 42 ).

4. The extruder unit ( 22 ) of claim 1 , wherein the gas pressure unit ( 93 ) comprises

at least one pressure bottle ( 94 ), the at least one pressure bottle ( 94 ) being adapted to store a gas at a first pressure;

the gas conduit ( 96 ), connecting the at least one pressure bottle ( 94 ) and the piston chamber ( 42 );

the lock valve ( 98 ) on the at least one pressure bottle ( 94 ), the lock valve ( 98 ) being movable between the open position and the closed position to provide the selective communication between the at least one pressure bottle ( 94 ) and the piston chamber ( 42 ); and

moving the piston ( 48 ) from the extended position to the retracted position within the piston chamber ( 42 ) recharges the at least one pressure bottle ( 94 ) to the first pressure with the lock valve ( 98 ) in the open position.

5. The extruder unit ( 22 ) of claim 1 , wherein the gas pressure unit ( 93 ) comprises

at least one pressure bottle ( 94 ), the at least one pressure bottle ( 94 ) being adapted to store a gas at a first pressure;

at least one recharge bottle ( 102 ), the at least one recharge bottle ( 102 ) being adapted to store the gas at a second pressure, the second pressure being higher than the first pressure;

the gas conduit ( 96 ), connecting the at least one pressure bottle ( 94 ), and the piston chamber ( 42 );

the lock valve ( 98 ) on the at least one pressure bottle ( 94 ), the lock valve ( 98 ) being movable between the open position and the closed position to provide the selective communication between the at least one pressure bottle ( 94 ) and the piston chamber ( 42 ); and

a recharge valve on the at least one recharge bottle ( 102 ), the recharge valve being movable between the open position and the closed position; and

wherein moving the recharge valve to the open position while the lock valve ( 98 ) is in the closed position restores a current pressure of the gas in the at least one pressure bottle ( 94 ) to the first pressure.

6. The extruder unit ( 22 ) of claim 5 , wherein the recharge valve is an analog valve ( 104 ) operable to move to a position located between the open position and the closed position.

7. The extruder unit ( 22 ) of claim 5 , wherein the gas pressure unit ( 93 ) further comprises a pump ( 106 ) for moving nitrogen from one of the at least one pressure bottle ( 94 ) and the at least one recharge bottle ( 102 ) to the other of the at least one pressure bottle ( 94 ) and the at least one recharge bottle ( 102 ).

8. The extruder unit ( 22 ) of claim 2 , wherein the gas stored in the gas pressure unit ( 93 ) is a nitrogen gas.

9. The extruder unit ( 22 ) of claim 5 , further comprising a pressure transducer ( 100 ) located within the piston housing ( 40 ), the pressure transducer ( 100 ) being operable to control the recharge valve based upon pressure readings within the piston chamber ( 42 ).

10. The extruder unit ( 22 ) of claim 5 , wherein the at least one recharge bottle ( 102 ) can be one of refilled and replaced without interrupting operation of the injection molding system ( 20 ).

11. The extruder unit ( 22 ) of claim 1 , wherein the drive unit ( 50 ) includes

at least one pinion ( 54 ) rotatably mounted within the piston housing ( 40 ), and operable to be at least one of electrically driven and hydraulically driven;

at least one rack portion ( 52 ) being defined by the piston ( 48 ) and intermeshing with the at least one pinion ( 54 ); and wherein

driving the at least one pinion ( 54 ) moves the piston ( 48 ) towards one of the extended position and the retracted position.

12. The extruder unit ( 22 D) of claim 1 , wherein the drive unit ( 50 ) includes:

at least one ball screw ( 30 ) assembly mounted within the piston housing ( 40 ), and operable to be one of electrically driven and hydraulically driven;

at least one threaded shaft ( 128 ), mounted to the piston ( 48 ), and intermeshing with the at least one ball screw ( 30 ) assembly; and wherein

driving the at least one ball screw ( 30 ) assembly moves the piston ( 48 ) towards one of the extended position and the retracted position.

13. The extruder unit ( 22 C) of claim 1 , wherein the motor assembly ( 36 ) includes:

a motor ( 122 ), mounted to the piston housing ( 40 );

a gearbox ( 86 ), operably connected to the motor ( 122 ); and

a drive shaft ( 88 ), operably connected to the gearbox ( 86 ) and extending through the piston housing ( 40 ) and into a rod chamber ( 58 ) defined by the piston ( 48 );

a screw adaptor ( 64 ), rotatably mounted within the piston ( 48 ), the screw adaptor ( 64 ) being adapted to fixedly mount the screw ( 30 ), and

the screw adaptor ( 64 ) further being slidably located within and rotatable by the drive shaft ( 88 ).

14. The extruder unit ( 22 C) of claim 1 , wherein the motor assembly ( 36 ) includes:

a motor ( 122 ), mounted to the piston housing ( 40 );

a gearbox ( 86 ), operably connected to the motor ( 122 ); and

a drive shaft ( 88 ), operably connected to the gearbox ( 86 ) and extending through the piston housing ( 40 ) and into a rod chamber ( 58 ) defined by the piston ( 48 );

a screw adaptor ( 64 ), rotatably mounted within the piston ( 48 ), the screw adaptor ( 64 ) being adapted to fixedly mount the screw ( 30 ), and further being slidably located within and rotatable by the drive shaft ( 88 ); and wherein

one of the drive shaft ( 88 ) and the screw adaptor ( 64 ) defines at least one spline groove ( 92 ) and the other of the drive shaft ( 88 ) and the screw adaptor ( 64 ) defines at least one spline, the at least one spline groove ( 92 ) and the at least one spline being intermeshed so that rotation of the drive shaft ( 88 ) rotates the screw adaptor ( 64 ).

15. The extruder unit ( 22 C) of claim 1 , wherein the motor assembly ( 36 ) includes:

a motor ( 122 ), mounted to the piston ( 48 );

a screw adaptor ( 64 ), rotatably mounted within the piston ( 48 ), and adapted to fixedly mount the screw ( 30 ); and

a drive belt ( 112 ), operably connected to the motor ( 122 ) and the screw adaptor ( 64 ), whereby engaging the motor ( 122 ) rotates the screw adaptor ( 64 ).

16. A method for operating an extruder unit ( 22 ) of an injection molding system ( 20 ) having a screw ( 30 ) rotatably mounted to a piston ( 48 ) movably located within a piston chamber ( 42 ) defined by a piston housing ( 40 ), comprising:

actuating the piston ( 48 ) located in the piston chamber ( 42 ) by engaging a drive unit ( 50 ) to translate the piston ( 48 ) to an extended position;

selectively connecting an external source of gas pressure to the piston chamber ( 42 ) by opening a lock valve ( 98 ) to provide a boosting force to the piston ( 48 ) while the screw ( 30 ) is being translated to the extended position by releasing a gas stored at a first pressure from the external source of gas pressure; and

retracting the screw ( 30 ) back to a retracted position using the drive unit ( 50 ); and

wherein retracting the screw ( 30 ) back to the retracted position within the piston chamber ( 42 ) recharges the external source of gas pressure back to the first pressure.

17. A hybrid injection actuator ( 38 ) for an extruder unit ( 22 ) of an injection molding system ( 20 ), comprising

a piston ( 48 ), slidably located within a piston chamber ( 42 ) on the extruder unit ( 22 ), and movable between a retracted position and an extended position; the piston ( 48 ) further being adapted to rotatably mount a screw ( 30 );

a drive unit ( 50 ) operable to move the piston ( 48 ) between the retracted position and the extended position;

a gas pressure unit ( 93 ), operable to provide a boosting force to the piston ( 48 ), thereby urging the piston ( 48 ) towards the extended position; and

a lock valve ( 98 ) located between the gas pressure unit ( 93 ) and the piston chamber ( 42 ), the lock valve ( 98 ) being movable between an open position and a closed position to provide a selective communication between the gas pressure unit ( 93 ) and the piston chamber ( 42 ).

18. The hybrid injection actuator ( 38 ) of claim 17 , wherein the gas pressure unit ( 93 ) is operable to store a gas at a first pressure, the gas pressure unit ( 93 ) being in selective communication with the piston chamber ( 42 ); and when opened, the gas pressure unit ( 93 ) is operable to release the gas stored at the first pressure to apply the boosting force to the piston ( 48 ), thereby urging the piston ( 48 ) towards the extended position.

19. The hybrid injection actuator ( 38 ) of claim 17 , wherein the gas pressure unit ( 93 ) comprises

at least one pressure bottle ( 94 ), the at least one pressure bottle ( 94 ) being adapted to store a gas at a first pressure;

at least one recharge bottle ( 102 ), the at least one recharge bottle ( 102 ) being adapted to store the gas at a second pressure, the second pressure being higher than the first pressure;

a gas conduit ( 96 ), connecting the at least one pressure bottle ( 94 ), and the piston chamber ( 42 );

the lock valve ( 98 ) on the at least one pressure bottle ( 94 ), the lock valve ( 98 ) being movable between the open position and the closed position to provide a selective communication between the at least one pressure bottle ( 94 ) and the piston chamber ( 42 ); and

a recharge valve on the at least one recharge bottle ( 102 ), the recharge valve being movable between an open position and the closed position; and

wherein moving the recharge valve to the open position while the lock valve ( 98 ) is in the closed position restores a current pressure of the gas in the at least one pressure bottle ( 94 ) to the first pressure.

20. The hybrid injection actuator ( 38 ) of claim 19 , wherein the gas pressure unit ( 93 ) further comprises a pump ( 106 ) for moving nitrogen from the at least one pressure bottle ( 94 ) to the at least one recharge bottle ( 102 ).