System for controlling the closing speed of valve gated nozzles

Patent metadata

Field	Value
Publication number	US-9776349-B2
Application number	US-201414762515-A
Country	US
Kind code	B2
Filing date	Jan 28, 2014
Priority date	Jan 30, 2013
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

Systems and methods for controlling the closing speed of valve gated nozzles are disclosed. In one embodiment, a hot runner have a valve gated nozzle including a valve stem movable between an open position and a closed position is provided. The valve stem is moved at a first speed for a first portion of valve stem closure and a second speed for a second end portion of the valve stem closure.

First claim

What is claimed is:

1. A method for molding a plastic part out of a polymer melt, the method comprising:
providing a valve gated nozzle including a valve stem movable between an open position and a closed position;
moving the valve stem towards the closed position at a first speed for a first portion between the open position and the closed position; and
moving the valve stem towards the closed position at a second speed less than a threshold speed for at least a final 2 mm between the open position and the closed position, wherein the threshold speed is a speed at which the valve stem is moved such that a deformation rate of the polymer melt due to movement of the valve stem is less than or approximately equal to a relaxation rate of the polymer melt.

2. The method of claim 1 , further comprising maintaining a substantially constant pressure of the polymer melt during movement of the valve stem for at least the final 2 mm between the open position and the closed position.

3. The method of claim 1 , wherein the second speed is less than approximately 5 mm/s.

4. The method of claim 1 , wherein the second speed is less than approximately 2 mm/s.

5. The method of claim 1 , wherein moving the valve stem at the second speed further comprises moving the valve stem at the second speed for at least a final 3 mm between the open position and the closed position.

6. The method of claim 1 , wherein moving the valve stem at the second speed further comprises moving the valve stem at the second speed for less than a final 10 mm between the open position and the closed position.

7. The method of claim 1 further comprising actuating a plurality of valve stems with a plurality of actuators to move the plurality of valve stems between the open position and the closed position.

8. The method of claim 1 further comprising actuating a plurality of valve stems with a plate actuator to move the plurality of valve stems between the open position and the closed position.

9. A method for molding a plastic part out of a polymer melt, the method comprising:
providing a valve gated nozzle including a valve stem movable between an open position and a closed position;
moving the valve stem towards the closed position at a first speed for a first portion between the open position and the closed position; and
moving the valve stem towards the closed position at a second speed less than the first speed for a second portion between the open position and the closed position, wherein the second speed is less than a threshold speed, and wherein the second portion is between a final 10% and 70% of a distance between the open position and the closed position, wherein the threshold speed is a speed at which the valve stem is moved such that a deformation rate of the polymer melt due to movement of the valve stem is less than or approximately equal to a relaxation rate of the polymer melt.

10. The method of claim 9 , wherein the second speed is less than approximately 5 mm/s.

11. The method of claim 9 , wherein the second speed is less than approximately 2 mm/s.

12. The method of claim 9 , wherein the first speed is between approximately 5 mm/s and 100 mm/s.

13. The method of claim 9 , wherein the second portion is between a final 20% and 50% of the distance between the open position and the closed position.

14. The method of claim 9 , maintaining a substantially constant pressure of the polymer melt during movement of the valve stem to the closed position.

15. The method of claim 9 further comprising actuating a plurality of valve stems with a plurality of actuators to move the plurality of valve stems between the open position and the closed position.

16. The method of claim 9 further comprising actuating a plurality of valve stems with an actuation plate to move the plurality of valve stems between the open position and the closed position.

17. A method for molding a plastic part out of a polymer melt, the method comprising:
providing a valve gated nozzle including a valve stem movable between an open position and a closed position, wherein a stroke length of the valve stem is less than approximately 3 mm; and
moving the valve stem towards the closed position at a speed less than a threshold speed, wherein the threshold speed is a speed at which the valve stem is moved such that a deformation rate of the polymer melt due to movement of the valve stem is less than or approximately equal to a relaxation rate of the polymer melt.

18. The method of claim 17 , wherein the threshold speed is less than approximately 5 mm/s.

19. The method of claim 17 , wherein the threshold speed is less than approximately 2 mm/s.

20. The method of claim 17 , wherein the stroke length is less than approximately 2 mm.

Assignees

• Husky Injection Molding Systems Ltd

Inventors

• Plumpton James Osborne
• Overfield Sarah Kathleen
• Bouti Abdeslam

Classifications

• B29C45/231 Primary

  Needle valve systems therefor · CPC title

• B29K2023/12

  PP, i.e. polypropylene · CPC title

• B29C2945/76598

  linear movement · CPC title

• B29C45/2806 Primary

  consisting of needle valve systems (B29C45/2896 takes precedence) · CPC title

• B29C2945/76943

  compare with thresholds · CPC title