Plasma arc torch and nozzle assembly

• US 4,311,897 A
• Filed: 07/18/1980
• Issued: 01/19/1982
• Est. Priority Date: 08/28/1979
• Status: Expired due to Term

• Current Assignee: Esab AB (Enovis Corp.)
• Original Assignee: Union Carbide Corporation (Dow, Inc.)
• Inventors: Yerushalmy, Yosef
• Primary Examiner(s): Tolin, Gerald P.
• Assistant Examiner(s): Paschall, Mark H.
• Application Number:
  US06/170,040
• Time in Patent Office: 550 Days
• Field of Search: 219/76.16, 219/121 PM, 219/121 PN, 219/121 PP, 219/121 PQ, 219/121 PR, 219/121 P, 219/121 PJ, 313/231.4, 313/231.5
• US Class Current: 219/121.5
• CPC Class Codes: H05H 1/28 Cooling arrangements
• CPC Class Codes: H05H 1/3423 Connecting means, e.g. electrical connecting means or fluid connections
• CPC Class Codes: H05H 1/3436 Hollow cathodes with internal coolant flow
• 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
• CPC Class Codes: H05H 1/3468 Vortex generators
• CPC Class Codes: H05H 1/3478 Geometrical details

Abstract

In combination, a plasma arc torch having an electrode structure adapted to be connected to a power supply for establishing a transferred plasma arc between the electrode structure and a workpiece and a nozzle assembly for constricting the plasma arc wherein the nozzle assembly comprises a first and second arc constricting passageway separated by a water chamber with the length of each passageway and the length of the water chamber being defined by a predetermined relationship to optimize the cutting speed and to minimize sensitivity to torch stand off.

Claims

1. In combination, a plasma torch having a nonconsumable electrode adapted to be connected in circuit with a power supply and workpiece for establishing a transferred plasma arc between the nonconsumable electrode and the workpiece through a nozzle assembly arranged beneath said electrode relative to said workpiece and means for passing a swirling flow of gas around said arc and through said nozzle assembly thereby forming a constricted plasma arc of high current density;

said nozzle assembly comprising;

a first arc constricting passageway having a longitudinal axis in alignment with the longitudinal axis of said nonconsumable electrode;

a second arc constricting passageway in coaxial alignment with said first arc constricting passageway, said second arc constricting passageway having an essentially constant diameter throughout its length;

a water chamber separating said first and second arc constricting passageways; and

means for introducing a jet of liquid into said water chamber for enveloping said swirling gas and arc within said second arc constricting passageway;

wherein said first and second arc constricting passageways are each of a predetermined length in a predetermined relationship to one another and to the length of the water chamber separating said passageways defined as follows;

space="preserve" listing-type="equation">L.sub.1 =K (L.sub.2 +Wg)

where K is a multiplying constant which must be greater than one and less than about four, and wherein

L₁ is equal to the length of said first arc constricting passageway;

L₂ is equal to the length of said second arc constricting passageway; and

Wg is equal to the length of said water chamber separating said first and second passageways.

2. The combination as defined in claim 1 wherein K is between 2 and 3.

3. The combination as defined in claim 2 wherein L₂ lies between 0.07-0.16 inches.

4. The combination as defined in claim 3 wherein L₁ lies between 0.16 to 0.36 inches.

5. The combination as defined in claim 4 wherein the diameter of said second passageway is between about 8 to about 20 percent larger than the diameter of said first arc constricting passageway.

6. The combination as defined in claim 5 wherein the diameter of said second passageway is about 12% greater than the diameter of the first arc constricting passageway.

7. The combination as defined in claim 6 wherein said means for introducing said liquid jet comprises a swirl ring having a plurality of orifices tangentially disposed around said water chamber to cause said liquid jet to form a swirling vortex.

8. The combination as defined in claim 5 wherein said first passageway has a chamfered end adjacent said electrode structure.

9. The combination as defined in claim 6 wherein said chamfered end forms a chamfered angle of about 45 degrees.