LIQUID COOLED SHIELD FOR IMPROVED PIERCING PERFORMANCE

• US 20090230097A1
• Filed: 03/12/2008
• Published: 09/17/2009
• Est. Priority Date: 03/12/2008
• Status: Active Grant

• Current Assignee: Hypertherm Incorporated
• Original Assignee: Hypertherm Incorporated
• Inventors: Liebold, Stephen M., Lindsay, Jon W.
• Granted Patent: US 8,212,173 B2
• Time in Patent Office: Days
• US Class Current: 219/121.490
• CPC Class Codes: H05H 1/28 Cooling arrangements
• CPC Class Codes: H05H 1/34 Details, e.g. electrodes, nozzles
• CPC Class Codes: H05H 1/3457 Nozzle protection devices

Abstract

A shield for a plasma arc torch that pierces and cuts a metallic workpiece producing a splattering of molten metal directed at the torch, the shield protecting consumable components of the plasma arc torch from the splattering molten metal. The shield can include a body, a first surface of the body configured to be contact-cooled by a gas flow, a second surface of the body configured to be contact-cooled by a liquid flow, and a seal assembly configured to be secured to the body and disposed relative to the second surface configured to retain the liquid flow contact-cooling the second surface.

Claims

1. A shield for a plasma arc torch that pierces and cuts a metallic workpiece producing a splattering of molten metal directed at the torch, the shield protecting consumable components of the plasma arc torch from the splattering molten metal, the shield comprising:

a body;

a first surface of the body configured to be contact-cooled by a gas flow;

a second surface of the body configured to be contact-cooled by a liquid flow; and

a seal assembly configured to be secured to the body and disposed relative to the second surface configured to retain the liquid flow contact-cooling the second surface.

2. The shield of claim 1 wherein the gas flow convectively cools the first surface.

3. The shield of claim 1 wherein the liquid flow convectively cools the second surface.

4. The shield of claim 1 wherein the seal assembly is in mechanical communication with a retaining cap.

5. The shield of claim 1 further comprising a region conductively cooled by at least one of the gas flow or the liquid flow.

6. The shield of claim 5 wherein the region conductively cooled comprises a temperature gradient across the region.

7. The shield of claim 1 wherein the shield further comprises a flange disposed proximally relative to a surface of the shield that is exposed to the molten metal, wherein at least a portion of the second surface is disposed on the flange.

8. The shield of claim 1 further comprising an orifice disposed at a distal end of the body and a third surface disposed relative to a distal end of the body and exposed to splattering molten metal, the second surface disposed proximally relative to the third surface.

9. The shield of claim 8, wherein the third surface is conductively cooled by the liquid flow.

10. The shield of claim 9, wherein the third surface is conductively cooled by the gas flow.

11. The shield of claim 1 wherein the shield is in communication with the plasma arc torch, the shield generally surrounding a nozzle of the plasma arc torch.

12. A method for reducing formation of slag on a shield secured to a plasma arc torch that pierces and cuts a metallic workpiece producing splattered molten metal directed at the torch, comprising:

contact-cooling a first surface of the shield by a gas flow;

contact-cooling a second surface of the shield by a liquid flow;

providing a seal assembly to retain the liquid flow, the seal assembly configured to retain the liquid in contact with the second surface relative to a retainer cap of the plasma arc torch; and

conductively cooling a third surface of the shield exposed to the splattered molten metal by providing a thermal conductive path formed at least in part of a thermally conductive material in thermal communication with the first surface and the second surface.

13. The method of claim 12 wherein the second surface is disposed relative to a first end of the shield and the third surface of the shield exposed to the splattered molten metal is disposed relative to a second end of the shield.

14. The method of claim 13 wherein the shield further comprises a flange disposed relative to the first end of the shield, at least a portion of the first surface and second surface disposed on the flange.

15. The method of claim 12 wherein contact-cooling the second surface by the liquid flow comprises providing for constant liquid flow around an outer surface of the shield.

16. A method for reducing formation of slag on a shield secured to a plasma arc torch that pierces and cuts a metallic workpiece producing splattered molten metal directed at the torch, comprising:

rapidly cooling the shield secured to the plasma arc torch with a cooling medium flow;

retaining the cooling medium flow in the plasma arc torch; and

repeatedly cooling the shield to prevent formation of slag on a surface of the shield exposed to the splattered molten metal.

17. The method of claim 16 wherein rapidly cooling comprises cooling the shield such that molten metal is cooled to prevent strengthening of the bond between the molten metal and the shield.

18. The method of claim 16 wherein rapidly cooling comprises cooling the shield so that the shield stays at substantially the same temperature during piercing as before piercing by extracting the heat from the molten metal in contact with the surface of the shield.

19. The method of claim 16 wherein rapidly cooling comprises contact-cooling a surface of the shield in thermal communication with the surface of the shield exposed to the splattered molten metal.

20. The method of claim 16 wherein the surface of the shield exposed to the splattered molten metal is conductively cooled.

21. The method of claim 16 wherein the shield is cooled to below ambient temperature.

22. The method of claim 21 wherein the shield is cooled to below about 60 degrees Fahrenheit.

23. A shield for a plasma arc torch that pierces and cuts a metallic workpiece producing a splattering of molten metal directed at the torch comprising:

a portion configured to be directly cooled by a flowing liquid; and

a first sealing mechanism and a second sealing mechanism disposed relative to the portion directly cooled by a flowing liquid, the first and second sealing mechanism configured to retain the flowing liquid directly cooling the portion of the shield relative to a retainer cap of the plasma arc torch.

24. The shield of claim 23 further comprising a portion configured to be directly cooled by a gas.

25. The shield of claim 23 further comprising a lip, wherein the portion configured to be directly cooled by the liquid is disposed on the lip.

26. The shield of claim 24 wherein the portion configured to be directly cooled by the liquid is disposed on an outer surface of the shield and the portion configured to be directly cooled by the gas is disposed on an inner surface of the shield.

27. The shield of claim 23 wherein the sealing mechanism is at least one of an o-ring, epoxy seal or hard metal contact seal.

28. A plasma arc torch system comprising:

a plasma arc torch;

a cooling device configured to provide a cooling medium; and

a shield disposed relative to the plasma arc torch, a first portion of the shield being exposed to splattering molten metal, the shield comprising;

a second portion directly cooled by the cooling medium flowing from the cooling device, the second portion in thermal communication with the first portion exposed to splattering molten metal; and

a sealing device configured to retain the cooling medium flowing from the cooling device, the sealing device configured to retain the cooling medium in contact with the second portion of the shield in the plasma arc torch.

29. The system of claim 28 wherein the cooling device is a chiller.

30. The system of claim 28 wherein the cooling medium repeatedly cools the second portion.