Electrode for a plasma arc torch

• US 5,464,962 A
• Filed: 07/29/1994
• Issued: 11/07/1995
• Est. Priority Date: 05/20/1992
• Status: Expired due to Term

• Current Assignee: Hypertherm Incorporated
• Original Assignee: Hypertherm Incorporated
• Inventors: Luo, Lifeng, Couch, Richard W. Jr.
• Primary Examiner(s): Paschall, Mark H.
• Application Number:
  US08/283,070
• Time in Patent Office: 466 Days
• Field of Search: 219/119, 219/121.52, 219/121.47, 219/121.39, 219/121.44, 219/121.49, 219/74, 219/75, 219/121.48
• US Class Current: 219/121.52
• CPC Class Codes: H05H 1/34 Details, e.g. electrodes, nozzles
• CPC Class Codes: H05H 1/3442 Cathodes with inserted tip
• CPC Class Codes: H05H 1/3452 Supplementary electrodes between cathode and anode, e.g. cascade

Abstract

An insert securely disposed in a bottom end of an electrode has an exposed emission surface shaped to define a recess in the insert, wherein the recess is initially dimensioned as a function of the operating current level of the torch, the diameter of the insert, and the plasma gas flow pattern in the torch. The electrode has an elongated body formed of a high thermal conductivity material such as copper, and a bore disposed in the bottom end of the body along a central axis. The insert is formed of a high thermionic emissivity material, such as hafnium, and securely disposed in the bore with the emission surface exposed. The emission surface may be initially shaped by removing a predetermined amount of the high thermionic emissivity material from the insert to define a generally concave recess, a generally cylindrical recess or other shapes. When used in a torch, the electrode provides for reduced deposition of the high thermionic emissivity material on the nozzle, thereby reducing nozzle wear in the torch.

Claims

1. An electrode for a plasma arc cutting torch, the electrode comprising:

an elongated electrode body formed of a high thermal conductivity material and having a bore disposed in a bottom end of the electrode body along a central axis through the electrode body;

an insert including a high thermionic emissivity material and disposed in the bore such that an emission surface of the insert is exposed;

wherein the emission surface is shaped to define a predetermined recess in the insert for reducing deposition of the high thermionic emissivity material on the nozzle during operation of the torch.

2. The electrode of claim 1 wherein the emission surface is shaped to define a generally concave recess.

3. The electrode of claim 1 wherein the emission surface is shaped to define a generally cylindrical recess.

5. The electrode of claim 1 wherein emission surface is shaped to define a recess dimensioned to approximate an arc preferred shape.

6. The electrode of claim 1 wherein the insert comprises hafnium.

7. The electrode of claim 1 wherein the electrode body comprises copper.

4. The electrode of claim 4 wherein the generally cylindrical recess includes a concave portion.

8. An electrode for a plasma arc cutting torch having a torch body and a nozzle, the electrode comprising:

an elongated electrode body formed of a high thermal conductivity material and having a bore disposed in a bottom end of the electrode body along a central axis through the electrode body;

a generally cylindrical insert formed of a high thermionic emissivity material and securely disposed in the bore such that an emission surface located along an end face of the insert is exposable to plasma gas in the torch body;

wherein the emission surface is shaped to define a predetermined recess in the insert to reduce deposition of the high thermionic emissivity material on the nozzle during operation of the torch.

9. The electrode of claim 9 wherein the emission surface defines a generally concave recess.

10. The electrode of claim 9 wherein the emission surface defines a recess including a generally cylindrical portion.

11. A method of manufacturing an electrode for a plasma arc cutting torch, comprising the steps of:

forming an electrode body from a high thermal conductivity material and a bore in a bottom end of the electrode body along a central axis through the electrode body;

forming an insert from a high thermionic emissivity material, the insert being positionable in the bore to expose an emission surface of the insert; and

removing a predetermined amount of the high thermionic emissivity material from the insert such that the emission surface defines a recess in the insert for reducing deposition of the high thermionic emissivity material on the nozzle during operation of the torch.

12. The method of claim 11 further comprising the step of positioning the insert in the bore to expose the emission surface.

13. The method of claim 11 further comprising performing the positioning step prior to performing the removing step.

14. The method of claim 12 further wherein the emission surface defines a generally concave recess.

15. The electrode of claim 12 wherein the emission surface define a generally cylindrical recess.

16. The electrode of claim 12 wherein the removing step further comprises removing a predetermined amount of the high thermionic emissivity material from the insert with a lathe or a ball end mill.

17. The electrode of claim 16 wherein the generally cylindrical recess includes a concave portion.

19. The method of claim 12 further wherein the emission surface defines a generally concave or cylindrical recess.

20. The method of claim 12 further wherein the emission surface defines a recess dimensioned to approximate an arc preferred shape.

18. A method of manufacturing an electrode for a plasma arc cutting torch, comprising the steps of:

forming an electrode body from a high thermal conductivity material and a bore in a bottom end of the electrode body along a central axis through the electrode body;

forming a generally cylindrical insert from a high thermionic emissivity material;

positioning the insert in the bore such that an emission surface located along an end face of the insert is exposed; and

removing a predetermined amount of the high thermionic emissivity material from the insert such that the emission surface defines a recess in the insert for reducing deposition of the high thermionic emissivity material on the nozzle during operation of the torch.