Gas-Cooled Plasma Arc Cutting Torch

• US 20080217305A1
• Filed: 02/15/2008
• Published: 09/11/2008
• Est. Priority Date: 02/16/2007
• Status: Active Grant

• Current Assignee: Hypertherm Incorporated
• Original Assignee: Hypertherm Incorporated
• Inventors: Sanders, Nicholas A.
• Granted Patent: US 8,089,025 B2
• Time in Patent Office: Days
• US Class Current: 219/121.49
• CPC Class Codes: H05H 1/28 Cooling arrangements
• CPC Class Codes: H05H 1/34 Details, e.g. electrodes, nozzles
• CPC Class Codes: H05H 1/3478 Geometrical details
• CPC Class Codes: H05H 1/3489 Means for contact starting

Abstract

A method and apparatus for a gas-cooled plasma arc torch. Components of the torch can include an electrode, nozzle and a shield, each of which can be gas-cooled. The nozzle can be disposed relative to the electrode and can include a generally hollow conductive body and a cooling gas flow channel defined by at least one fin disposed about an exterior surface of the body, the body providing a thermal conductive path that transfers heat between the nozzle to the cooling gas flow channel during operation of the torch. The shield can be disposed relative to the nozzle and can include a generally hollow conductive body and a cooling gas flow channel defined by at least one fin disposed about an exterior surface of the body, the body providing a thermal conductive path that transfers heat between the shield to the cooling gas flow channel during operation of the torch.

Claims

1. A nozzle for a plasma arc cutting torch having a substantially hollow body capable of receiving an electrode, the nozzle comprising:

a body;

an orifice disposed at an end of the body; and

a cooling gas flow channel defined by at least one fin disposed about an exterior surface of the body, the body providing a thermal conductive path that transfers heat between the body and the cooling gas flow channel during operation of the torch.

2. The nozzle of claim 1 wherein the body of the nozzle comprises a flange that includes at least one port, the port configured to pass at least a portion of a cooling gas flow between the flange and the cooling gas flow channel during operation of the torch.

3. The nozzle of claim 1 wherein the cooling gas flow channel comprises a spiral groove disposed on an external surface of the body of the nozzle.

4. The nozzle of claim 1 wherein the cooling gas flow channel is supplied by more than one gas source.

5. The nozzle of claim 1 wherein the cooling gas flow channel comprises a width, a height and a length dimensioned to establish sufficient heat transfer from the nozzle to a cooling gas flow channel during operation of the torch.

6. The nozzle of claim 1 wherein the body is substantially cylindrical.

29. A method for extending the life of a plasma arc cutting torch comprising:

providing a torch body which includes a plasma gas flow path for directing a plasma gas through a swirl ring to a plasma chamber in which a plasma arc is formed;

providing the nozzle of claim 1 mounted relative to an electrode at a distal end of the torch body to define the plasma chamber; and

operating the plasma arc cutting torch at an amperage level of at least about 100 Amps.

7. A shield for a plasma arc cutting torch capable of protecting a nozzle, the shield comprising:

a body;

an orifice disposed at an end of the body; and

a cooling gas flow channel defined by at least one fin disposed about an exterior surface of the body, the body providing a thermal conductive path that transfers heat between the body and the cooling gas flow channel during operation of the torch.

8. The shield of claim 7 wherein a height of the shield is at least half of the diameter of the body.

9. The shield of claim 7 wherein the cooling gas flow channel comprises a spiral groove disposed on an external surface of the body.

10. The shield of claim 7 further comprising a flange that includes at least one port, the port configured to pass at least a portion of a cooling gas flow passing between the flange and the cooling gas flow channel during operation of the torch.

11. The shield of claim 7 wherein the cooling gas flow channel can be supplied by more than one gas source.

12. The shield of claim 7 wherein the cooling gas flow channel comprises a width, a height, and a length dimensioned to establish sufficient heat transfer from the shield to a cooling gas flow channel during operation of the torch.

13. The shield of claim 7 further comprising:

a central longitudinal axis;

an interior surface of the shield defining in part a shield gas flow passage; and

a bleed port off-set from a central longitudinal axis of the shield that creates an exit flow counter to a swirling motion of the shield gas flow, thereby dampening the swirling motion of the shield gas flow exiting the exit orifice of the shield.

30. A method for extending the life of a plasma arc cutting torch comprising:

providing a torch body which includes a plasma gas flow path for directing a plasma gas to a plasma chamber in which a plasma arc is formed;

providing a nozzle mounted relative to an electrode at a distal end of the torch body to define the plasma chamber;

providing the shield of claim 7 in a spaced relationship to a nozzle at a distal end of the torch body; and

operating the plasma arc cutting torch at an amperage level of at least about 100 Amps.

14. An electrode for a plasma arc cutting torch comprising:

an elongate electrode body;

a high thermionic emissivity material disposed at a distal end of the electrode body;

an internal electrical contact surface at a proximal end of the electrode body, the internal electrical contact surface sized to receive a circumscribing radial spring element;

an external gas cooled surface including a cooling gas flow channel defined by a fin, the external gas cooled surface disposed opposite the internal electrical contact surface; and

a wall thickness between the internal electrical contact surface and the gas cooled surface sized to transfer sufficient heat to the cooling gas flow channel during operation of the torch.

15. The electrode of claim 14 wherein the internal electrical contact surface is sized to center the circumscribing radial spring element.

16. The electrode of claim 14 wherein the internal electrical contact surface comprises a feature to retain the circumscribing radial spring element within a bore that is at least partially defined by the internal electrical contact surface.

17. The electrode of claim 14 wherein a ratio of a diameter of the internal electrical contact surface to a length of the internal electrical contact surface is less than about ⅔

.

18. The electrode of claim 14 wherein the internal electrical contact surface has a length that is not more than about three times a diameter of the internal electrical contact surface.

19. The electrode of claim 14 wherein the cooling gas flow channel comprises a spiral groove disposed on an external surface of the electrode.

20. The electrode of claim 14 wherein the cooling gas flow channel can be supplied by more than one gas source.

21. The electrode of claim 14 wherein the cooling gas flow channel comprises a width, a height and a length dimensioned to establish a pressure drop that results in sufficient heat transfer from the electrode to a cooling gas flow channel during operation of the torch.

22. The electrode of claim 14 wherein the internal electrical contact surface is conductively cooled by a cooling gas flow.

23. The electrode of claim 14 wherein the internal electrical contact surface reacts against the circumscribing radial spring element when installed in the torch.

24. The electrode of claim 23 wherein the circumscribing radial spring element is attached to the torch by a diametric interference fit.

25. The electrode of claim 23 wherein the cooling gas flow channel is dimensioned to provide an amount of pressure drop sufficient to overcome a longitudinal frictional resistance between the internal electrical contact surface and the circumscribing radial spring element.

26. The electrode of claim 14 wherein the internal electrical contact surface includes the circumscribing radial spring element that, when installed in the torch, reacts against an electrical contact surface of the torch.

27. The electrode of claim 26 wherein the cooling gas flow channel is dimensioned to provide an amount of pressure drop sufficient to overcome a longitudinal frictional resistance between the electrical contact surface of the torch and the circumscribing radial spring element.

28. The electrode of claim 26 wherein the circumscribing radial spring element is attached to the internal electrical contact surface by a diametric interference fit.

31. A plasma arc torch comprising:

a torch body including a plasma gas flow path for directing a plasma gas to a plasma chamber in which a plasma arc is formed; and

an electrode disposed relative to a first end of the torch body, the electrode including an electric contact means and cooling means to transfer heat from the electrode during operation of the torch

32. The plasma arc torch of claim 31 further comprising a nozzle disposed relative to the electrode at a second end of the torch body to define the plasma chamber, the nozzle including cooling means to transfer heat from the nozzle during operation of the torch.

33. The plasma arc torch of claim 32 further comprising a shield disposed relative to the nozzle at the second end of the torch body, the shield including cooling means to transfer heat from the nozzle during operation of the torch.

34. A plasma arc torch system comprising:

a torch body including a plasma gas flow path for directing a plasma gas to a plasma chamber in which a plasma arc is formed;

an electrode disposed relative to a proximal end of the torch body;

a nozzle disposed relative to the electrode at a distal end of the torch body to define the plasma chamber, the nozzle comprising;

a generally hollow conductive body; and

a cooling gas flow channel defined by at least one fin disposed about an exterior surface of the body, the body providing a thermal conductive path that transfers heat between the nozzle to the cooling gas flow channel during operation of the torch; and

a shield disposed relative to the nozzle at the distal end of the torch body, the shield comprising;

a generally hollow conductive body; and

a cooling gas flow channel defined by at least one fin disposed about an exterior surface of the body, the body providing a thermal conductive path that transfers heat between the shield to the cooling gas flow channel during operation of the torch.