Injection Mold With Fail Safe Pressure Mechanism

• US 20140127338A1
• Filed: 11/08/2012
• Published: 05/08/2014
• Est. Priority Date: 11/08/2012
• Status: Active Grant

• Current Assignee: Imflux Inc. (The Procter & Gamble Company)
• Original Assignee: The Procter & Gamble Company
• Inventors: Altonen, Gene Michael, NEUFARTH, Ralph Edwin, BREIDENBACH, Vincent Sean, PRATEL, Dennis James, DAVIS, Walter Thomas III
• Granted Patent: US 9,604,398 B2
• Time in Patent Office: Days
• US Class Current: 425/146
• CPC Class Codes: B29C 2045/1796 Moulds carrying mould related information or codes, e.g. bar codes, counters
• CPC Class Codes: B29C 2045/2722 Nozzles or runner channels provided with a pressure sensor
• CPC Class Codes: B29C 2945/7621 nozzle
• CPC Class Codes: B29C 2945/76498 Pressure
• CPC Class Codes: B29C 2945/76598 linear movement
• CPC Class Codes: B29C 2945/76665 screw
• CPC Class Codes: B29C 2945/76765 Moulding material
• CPC Class Codes: B29C 2945/76859 Injection
• CPC Class Codes: B29C 2945/76923 in case of emergency
• CPC Class Codes: B29C 33/0011 thin-walled moulds
• CPC Class Codes: B29C 45/1781 Aligning injection nozzles with the mould sprue bush
• CPC Class Codes: B29C 45/234 Valves opened by the pressure of the moulding material B29C45/231 takes precedence
• CPC Class Codes: B29C 45/7653 mould clamping forces
• CPC Class Codes: B29C 45/768 Detecting defective moulding conditions B29C45/84 takes precedence
• CPC Class Codes: B29C 45/77 of velocity or pressure of moulding material
• CPC Class Codes: B29C 45/84 Safety devices B29C45/7626 takes precedence

Abstract

A low pressure injection mold includes a failsafe pressure mechanism that prevents the low pressure injection mold from being subjected to excessive injection pressures or excessive clamping tonnage that could damage the low pressure injection mold.

Claims

1. An injection molding apparatus comprising:

a mold having a mold cavity;

a melt holder for pressurizing molten thermoplastic or thermoset prior to injection into the mold cavity;

a sensor in communication with the melt holder for sensing a characteristic of the molten plastic; and

a controller communicatively connected to the sensor, the controller receiving a signal from the sensor, the signal being indicative of a melt pressure of the molten thermoplastic or thermoset entering the mold cavity, the controller further being communicatively connected with an injection cylinder in the melt holder, the injection cylinder applying a force to the molten thermoplastic or thermoset to advance the molten thermoplastic or thermoset from the melt holder into the mold cavity,

wherein a failsafe device is communicatively connected with the injection cylinder or the controller to limit the injection pressure below a maximum design pressure for the mold by one of

stopping the injection cylinder,

slowing the injection cylinder,

diverting excess pressure of the molten thermoplastic or thermoset before the molten thermoplastic or thermoset enters the mold cavity, and

preventing installation of the mold into an injection molding apparatus that is capable of providing molten thermoplastic or thermoset at pressures in excess of a maximum design pressure for the mold.

2. The injection molding apparatus of claim 1, wherein the failsafe device may only be overridden by an intentional action from an operator.

3. The injection molding apparatus of claim 1, wherein the maximum melt pressure limit is input into the controller through an input device operatively connected to the controller.

4. The injection molding apparatus of claim 1, further comprising an electronic media connected to the mold, the electronic media storing the maximum melt pressure limit and the controller being communicatively connected to the electronic media to receive the maximum melt pressure limit from the electronic media.

5. The injection molding apparatus of claim 4, wherein the electronic media is one of an RFID chip and a microchip.

6. The injection molding apparatus of claim 5, wherein the one of the RFID chip and the microchip is permanently attached to the mold.

7. The injection molding apparatus of claim 1, wherein the controller activates an alarm when the signal from the sensor indicates that the melt pressure exceeds the maximum design pressure for the mold.

8. The injection molding apparatus of claim 7, wherein the alarm is one of visual, aural, tactile, and an electronic message.

9. The injection molding apparatus of claim 1, wherein the maximum design pressure for the mold is less than 68.95 MPa (10,000 psi).

10. The injection molding apparatus of claim 1, wherein the mold includes at least one mold part having an average thermal conductivity of more than 51.9 W/m °

C. (30 BTU/HR FT °

F.) and the at least one mold part has at least one of

a milling machining index of greater than 100%,

a drilling machining index of greater than 100%, and

a wire EDM machining index of greater than 100%.

11. The injection molding apparatus of claim 1, wherein the mold cavity is formed from a material having a surface hardness less than 30 Rc and the mold having an average thermal conductivity of more than 51.9 W/m °

C. (30 BTU/HR FT °

F.).

12. The injection molding apparatus of claim 1, wherein the mold has at least one of a thin-walled mold cavity, at least four mold cavities, and a guided ejection system.

13. The injection molding apparatus of claim 1, wherein the sensor is in fluid communication with the melt holder.

14. An injection molding apparatus comprising:

a mold having a mold cavity;

a melt holder for pressurizing molten plastic prior to injection into the mold cavity;

a pressure limiting device in fluid communication with the melt holder for limiting a melt pressure of the molten plastic to a value less than a maximum melt pressure limit associated with the mold,

wherein the mold has a Rc of less than 30 and one or more of,

an L/T of greater than 100, and

a guided ejection system.

15. The injection molding apparatus of claim 14, wherein the mold has one or more of,

at least four mold cavities;

and

a thermal conductivity of more than 51.9 W/m °

C. (30 BTU/HR FT °

F.).

16. The injection molding apparatus of claim 14, wherein the pressure limiting device is a pressure relief mechanism.

17. The injection molding apparatus of claim 16, wherein the pressure relief mechanism is located between a cylinder of the melt holder and a gate of the mold cavity.

18. The injection molding apparatus of claim 16, wherein the pressure limiting device is one of a rupture disk, a pressure relief valve, and a pressure regulating valve.

19. The injection molding apparatus of claim 18, wherein the pressure relief mechanism is a pressure relief valve includes a spherically-shaped nose disposed in a barrel of the melt holder and an annular skirt operatively connected to the spherically-shaped nose.

20. The injection molding apparatus of claim 19, wherein the annular skirt includes a pressure sensitive feature.

21. The injection molding apparatus of claim 20, wherein the pressure sensitive feature is one of a rupture disk and a pressure channel.

22. The injection molding apparatus of claim 21, wherein the pressure channel includes one of a calibrated depth feature and a tortuous path.

23. The injection molding apparatus of claim 19, wherein the pressure relief valve directs excess molten plastic material back to a barrel of the melt holder to relieve excess melt pressure.

24. The injection molding apparatus of claim 15, wherein the pressure limiting device is a pressure blocking device fluidly connected with the molten plastic between the melt holder and the mold cavity.

25. The injection molding apparatus of claim 24, wherein the pressure blocking device is operatively connected to the mold.

26. The injection molding apparatus of claim 24, wherein the pressure blocking device includes an actuation arm pivotably connected to the mold and a blocking arm pivotably connected to the mold.

27. The injection molding apparatus of claim 26, wherein the pressure blocking device further includes a spring that biases actuation arm.

28. The injection molding apparatus of claim 24, wherein the pressure blocking device includes a body having a hollow flow path and a blocking section.

29. The injection molding apparatus of claim 28, wherein the pressure blocking device is disposed in a flow path for the molten plastic, the flow path including a well.

30. The injection molding apparatus of claim 29, further including a spring disposed in the well.

31. The injection molding apparatus of claim 29, further including a proximity sensor disposed in the well.

32. A mold for an injection molding apparatus, the mold comprising:

a first mold part and a second mold part, the first and second mold parts defining a mold cavity therebetween;

a guide pin attached to the first mold part; and

a hard stop insert disposed on the second mold part.

33. The mold of claim 32, wherein a thickness of the hard stop insert and a length of the guide pin determine a minimum distance between the first and second mold parts.

34. The mold of claim 32, wherein the guide pin and the hard stop insert are capable of withstanding more than 10 times a maximum rated pressure of the first and second mold parts.

35. The mold of claim 32, further comprising a bushing attached to the second mold part, wherein the hard stop insert is disposed within the bushing.

36. A mold for an injection molding apparatus, the mold comprising:

a first mold part and a second mold part, the first and second mold parts defining a mold cavity therebetween;

a guide pin attached to the first mold part;

a bushing attached to the second mold part;

an interlock device disposed in the bushing, the interlock device including a piston and a lock.

37. The mold of claim 36, wherein the piston is biased by a biasing mechanism.

38. The mold of claim 36, further comprising a plurality of locking teeth disposed on the lock and a corresponding set of locking teeth disposed on the guide pin.

39. The mold of claim 38, wherein at least one of the locking teeth on the lock is angled.

40. The mold of claim 39, wherein at least one of the locking teeth on the guide pin is angled.

41. The mold of claim 36, wherein the interlock device is a hydraulic interlock device including a hydraulic circuit that actuates the lock.

42. A spring loaded nozzle-bushing connection for an injection molding machine, the spring loaded nozzle-busing connection comprising:

a fluid inlet;

a fluid outlet; and

a spring loaded valve, the spring loaded valve having an auxiliary fluid outlet, the spring loaded valve venting fluid through the auxiliary fluid outlet when fluid pressure in the spring loaded valve exceeds a predetermined limit

43. The spring loaded nozzle-bushing connection of claim 42, wherein the spring loaded valve includes a valve plug and a valve seat, the valve plug and the valve seat cooperating to control fluid flow through the spring loaded valve.

44. The spring loaded nozzle-bushing connection of claim 43, wherein the spring loaded valve includes a valve stem connected to the valve plug and to a plate, the plate controlling movement of the valve stem and the valve plug.

45. The spring loaded nozzle-bushing connection of claim 44, further comprising a spring that biases the plate towards the valve seat.

46. The spring loaded nozzle-busing connection of claim 45, further comprising an adjustment mechanism for the spring.

47. The spring loaded nozzle-bushing connection of claim 42, wherein the spring loaded valve includes a hollow valve pin.

48. The spring loaded nozzle-bushing connection of claim 47, further comprising a spring that biases the hollow valve pin towards the fluid outlet.

49. A fail safe device for a low pressure injection mold, the fail safe device comprising:

a sprue bushing for a low pressure injection mold, the sprue bushing including a male mating surface for mating with a nozzle of an injection molding machine.

50. The fail safe device of claim 49, wherein the male mating surface is spherically convex.

51. The fail safe device of claim 49, further comprising a nozzle of an injection molding machine, the nozzle including a female mating surface.

52. The fail safe device of claim 51, wherein the female mating surface is spherically concave.

53. The fail safe device of claim 49, wherein the sprue bushing is operatively connected to a low pressure injection mold, the low pressure injection mold having a Rc of less than 30.

54. The fail safe device of claim 53, wherein the low pressure injection mold includes at least one of,

a thin-walled mold cavity (e.g., L/T >

100),

at least four mold cavities, and

a guided ejection system.

55. The fail safe device of claim 53, wherein the low pressure injection mold has an average thermal conductivity of more than 51.9 W/m °

C. (30 BTU/HR FT °

F.).