Automatic gas control for a plasma arc torch

Abstract

A method and apparatus for controlling a gas supply to a plasma arc torch uses a proportional control solenoid valve positioned adjacent the torch to manipulate the gas flow to the torch, thereby extending electrode life during arc transfer and shutdown. Swirl ring design can be simplified and gas supply and distribution systems become less complicated. The invention also allows manipulation of shield gas flow to reduce divot formation when making interior cuts. The system can be controlled with a digital signal processor utilizing a feedback loop from a sensor.

Description

RELATED APPLICATIONS [0001] This application is a continuation-in-part of U.S. Ser. No. 11 / 045,012, filed on Jan. 27, 2005, the contents of which are incorporated herein by reference. This application claims benefit of and priority to U.S. Ser. No. 11 / 045,012.FIELD OF THE INVENTION [0002] The invention relates generally to plasma arc cutting torches, and more particularly to control systems and methods for controlling gas supplies to such torches to enhance their operation. BACKGROUND OF THE INVENTION [0003] Plasma arc cutting torches have a wide variety of uses, such as the cutting of aluminum sheet metal, thick plates of steel or stainless steel, or thin sheets of galvanized metal. As illustrated in FIG. 1, a plasma torch 10 includes a torch body 12, an electrode 14 and a nozzle 16 mounted within the body. The nozzle has a central exit orifice 18 and can be surrounded by a shield 22. An exit port 24 of the shield is generally aligned with the exit orifice 18 of the nozzle. A power...

AI Technical Summary

Benefits of technology

[0017] The programmable control valve can be directly coupled to the torch body of the torch, e.g., such that there is no hose length between the valve and the torch. In some embodiments, at least a portion of the programmable control valve is disposed within the torch. The method can also the step of increasing a ramp down time of the flowing first gas to prolong a life of the electrode. This ramp down time can be increased based on, e.g., an increased cut duration of the torch or a higher operating current level of the torch. In some embodiments the...

Problems solved by technology

During operation of the torch, certain consumable parts become worn and have to be replaced.

Unfortunately, there are drawbacks associated with these different approaches.

Such tedious empirical determinations were performed for different torches, systems, consumable sets, and cutting conditions.

These control difficulties are exacerbated by the rapid system dynamics, which can all take place within a time span of about 300 milliseconds or less.

The determination of the proper hose length and current ramp down characteristics to achieve an acceptable termination gas ...

Images