Elizabeth B Hackett

US Patent:

57603634, Jun 2, 1998

Filed:

Sep 3, 1996

Appl. No.:

8/707227

Inventors:

Elizabeth B. Hackett - Lebanon NH
Timothy M. Brewer - Lebanon NH
Zhipeng Lu - Hanover NH
Richard W. Couch - Hanover NH

Assignee:

Hypertherm, Inc. - Hanover NH

International Classification:

B23K 1000

US Classification:

21912144

Abstract:

A plasma arc torch apparatus and method for cutting or marking a workpiece includes a torch having an electrode and a nozzle coupled to a power supply, and a plasma gas source coupled to a fluid line for delivering plasma gas to the torch. A flow restriction member is disposed in the fluid line adjacent the torch and causes the pressure of the plasma gas in the torch to gradually increase during start up thus creating a stable plasma arc. A three-way valve is disposed in the fluid line downstream of the flow restriction member and has an inlet, a torch outlet, and a vent outlet. The inlet is in fluid communication with the torch outlet for delivering plasma gas to the torch when the valve is in the open position, and the torch outlet is in fluid communication with the vent outlet when the valve is in the vent position, for rapidly dissipating the gas in the plasma chamber of the torch to atmosphere after the arc has been extinguished. The rapid reduction of the gas pressure in the torch reduces the cycle time, enabling the torch to be restarted more quickly after completion of a prior cutting cycle.

US Patent:

57737886, Jun 30, 1998

Filed:

Sep 3, 1996

Appl. No.:

8/707247

Inventors:

Zhipeng Lu - Hanover NH
Elizabeth B. Hackett - Lebanon NH

Assignee:

Hypertherm, Inc. - Hanover NH

International Classification:

B23K 1000

US Classification:

21912159

Abstract:

A method of operating a plasma arc torch for marking a metallic workpiece spaced a stand-off distance from the torch utilizes a torch that includes a body, an electrode, and a nozzle mounted in the body so as to define a plasma chamber. The nozzle has a central passage and an exit orifice through which the transferred arc passes to the workpiece. The method also utilizes a plasma gas flow through the body to form a pilot arc in the plasma chamber and then to form a transferred arc between the electrode and the workpiece. The method includes forming the plasma gas flow with a selected mixture of hydrogen and an inert gas. The percentage of hydrogen in the selected mixture is between 0% and 35%. The percentage of inert gas in the selected mixture is between 100% and 65%. The inert gas may be argon.