# US 8,541,710 B2 · Method and apparatus for automatic gas control for a plasma arc torch > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,541,710 B2 - Document ID: US8541710B2 - Status: Granted - Kind: B2 - Application number: 12/040,787 - Filed: 2008-02-29 - Published: 2008-07-17 - Granted: 2013-09-24 - Earliest claimed: 2005-01-27 - Assignees: Hypertherm, Inc. - Applicants: Aaron D. Brandt; Christopher S. Passage; Shane M. Selmer; Girish R. Kamath; Guy T. Best; Stephen M. Liebold; Jon W. Lindsay; Zheng Duan - Inventors: Aaron D. Brandt; Christopher S. Passage; Shane M. Selmer; Girish R. Kamath; Guy T. Best; Stephen M. Liebold; Jon W. Lindsay; Zheng Duan - Web page: https://patentgrep.com/patent/US8541710B2 ## CPC - H05H 1/36: Circuit arrangements (H05H1/38, H05H1/40 take precedence) - H05H 1/34: Details, e.g. electrodes, nozzles - B23K 10/00: Welding or cutting by means of a plasma - B23K 10/02: Plasma welding - H05H: PLASMA TECHNIQUE (apparatus or processes specially adapted for producing X-rays H05G2/00); PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS - B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM ## 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. ## Claims ### Claim 1 A method for control of a gas flow to a plasma arc torch for prolonging a life of an electrode or optimizing a duty cycle, the plasma arc torch including a plasma chamber defined by the electrode and a nozzle and disposed within a body of the plasma arc torch, the method comprising the steps of: providing a first fluid line for supplying a plasma gas to the plasma chamber; positioning in the first fluid line of the plasma arc torch a programmable control valve using a predetermined setpoint curve to control a flow of the plasma gas based on associating the flow with a duration of an operation of the electrode producing a plasma arc; and controlling the flow of the plasma gas to the plasma chamber during shutdown of the plasma arc torch, the controlling comprising: (i) increasing, by manipulating the programmable control valve via a digital signal processor, a ramp down time of the flow of the plasma gas to the plasma chamber for a longer duration electrode operation or (ii) decreasing, by manipulating the programmable control valve via the digital signal processor, the plasma gas ramp down time for a shorter duration electrode operation. ### Claim 2 (depends on 1) The method of claim 1 wherein the programmable control valve is directly coupled to the body of the plasma arc torch. ### Claim 3 (depends on 1) The method of claim 1 wherein the programmable control valve controls the flow of the plasma gas a plurality of times during a ramp cycle of the plasma gas. ### Claim 4 (depends on 1) The method of claim 1 wherein at least a portion of the plasma gas is vented to the atmosphere through a vent valve. ### Claim 5 (depends on 4) The method of claim 4 wherein the vent valve includes two or more on-off solenoid valves mounted in parallel. ### Claim 6 (depends on 4) The method of claim 4 wherein the vent valve includes a programmable control valve. ### Claim 7 (depends on 1) The method of claim 1 wherein the plasma gas comprises at least one of oxygen, nitrogen, hydrogen, methane, helium, or argon. ### Claim 8 A plasma arc torch for cutting a workpiece, the plasma arc torch having a plasma gas source to supply a plasma chamber, such that an electrical current passing between an electrode and a nozzle produces a plasma arc that exits the plasma arc torch through a nozzle exit orifice, the plasma arc torch comprising: a means for sensing a parameter in a first fluid line that supplies a plasma gas from the plasma gas source; and a means for controlling a flow of the plasma gas based on the sensed parameter using a programmable control valve disposed in the first fluid line of the plasma arc torch, the programmable control valve using a predetermined setpoint curve to prolong electrode life or to optimize a duty cycle based on associating the flow with a duration of an operation of the electrode producing the plasma arc by: (a) increasing the plasma gas ramp down time for a longer duration electrode operation or (b) decreasing the plasma gas ramp down time for a shorter duration electrode operation. ### Claim 9 (depends on 8) The plasma arc torch of claim 8 wherein the programmable control valve is directly coupled to the plasma arc torch. ### Claim 10 (depends on 8) The plasma arc torch of claim 8 further comprising a plasma gas vent valve that includes at least one of a programmable control valve or a plurality of on-off solenoid valves. ### Claim 11 A method for control of a plasma gas flow to a plasma arc torch for prolonging a life of an electrode or optimizing a duty cycle, the plasma arc torch including a plasma chamber defined by the electrode and a nozzle and disposed within a body of the plasma arc torch, the method comprising the steps of: providing a first fluid line for supplying a plasma gas to the plasma chamber; positioning in the first fluid line of the plasma arc torch a programmable control valve using a predetermined setpoint curve to control a flow of the plasma gas; and controlling the flow of the plasma gas to the plasma chamber during shutdown of the torch, the controlling comprising: (i) increasing, by manipulating the programmable control valve via a digital signal processor, a ramp down time of the flow of the plasma gas to the plasma chamber when the plasma arc torch has been operated for a duration of an operation of the electrode at a higher current level or (ii) decreasing, by manipulating the programmable control valve via the digital signal processor, the ramp down time of the flow ofthe plasma gas to the plasma chamber when the plasma arc torch has been operated for a duration of an operation of the electrode at a reduced current level. ### Claim 12 (depends on 11) The method of claim 11 wherein the programmable control valve is directly coupled to the body of the plasma arc torch. ### Claim 13 (depends on 11) The method of claim 11 wherein the programmable control valve controls the flow of the plasma gas a plurality of times during a ramp cycle of the plasma gas. ### Claim 14 (depends on 11) The method of claim 11 wherein at least a portion of the plasma gas is vented to the atmosphere through a vent valve. ### Claim 15 (depends on 14) The method of claim 14 wherein the vent valve includes two or more on-off solenoid valves mounted in parallel. ### Claim 16 (depends on 14) The method of claim 14 wherein the vent valve includes a programmable control valve. ### Claim 17 (depends on 11) The method of claim 11 wherein the plasma gas comprises at least one of oxygen, nitrogen, hydrogen, methane, helium, or argon. ### Claim 18 A plasma arc torch for cutting a workpiece, the plasma arc torch having a plasma gas source to supply a plasma chamber, such that an electrical current passing between an electrode and a nozzle produces a plasma arc that exits the plasma arc torch through a nozzle exit orifice, the plasma arc torch comprising: a means for sensing a parameter in a first fluid line that supplies a plasma gas from the plasma gas source; and a means for controlling a flow of the plasma gas based on the sensed parameter using a programmable control valve disposed in the first fluid line of the plasma torch, the programmable control valve using a predetermined setpoint curve to prolong electrode life or to optimize a duty cycle by: (a) increasing the first gas ramp down time when the plasma arc torch has been operated for a duration of an operation of the electrode at a higher current level, or (b) decreasing the first gas ramp down time when the plasma arc torch has been operated for a duration of an operation of the electrode at a reduced current level. ### Claim 19 (depends on 18) The plasma arc torch of claim 18 wherein the programmable control valve is directly coupled to the plasma arc torch. ### Claim 20 (depends on 18) The plasma arc torch of claim 18 further comprising a plasma gas vent valve that includes at least one of a programmable control valve or a plurality of on-off solenoid valves.