EP0213689A2 - Circuit d'interruption d'une torche à plasma - Google Patents

Circuit d'interruption d'une torche à plasma Download PDF

Info

Publication number
EP0213689A2
EP0213689A2 EP86303754A EP86303754A EP0213689A2 EP 0213689 A2 EP0213689 A2 EP 0213689A2 EP 86303754 A EP86303754 A EP 86303754A EP 86303754 A EP86303754 A EP 86303754A EP 0213689 A2 EP0213689 A2 EP 0213689A2
Authority
EP
European Patent Office
Prior art keywords
power supply
circuit
signal
torch
voltage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP86303754A
Other languages
German (de)
English (en)
Other versions
EP0213689A3 (fr
Inventor
Wayman Leon Mollett
Richard A. Spaulding
Raymond G. Wilkins
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Victor Equipment Co
Original Assignee
Thermal Dynamics Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thermal Dynamics Corp filed Critical Thermal Dynamics Corp
Publication of EP0213689A2 publication Critical patent/EP0213689A2/fr
Publication of EP0213689A3 publication Critical patent/EP0213689A3/fr
Withdrawn legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H05H1/36—Circuit arrangements

Definitions

  • This invention relates to a plasma torch shutdown circuit as set forth in the introductory part of claim 1.
  • Plasma torches also known as electric arc torches, are commonly used for cutting, welding and spray bonding of workpieces and operate by directing a plasma consisting of ionized gas particles toward a workpiece.
  • Typical plasma torches are illustrated in US Patents 4,324,971, 4,170,727 and 3,813,510, assigned to our.
  • a gas to be ionized is supplied to the front end of the torch in front of an electrode.
  • a d.c. potential is applied between the electrode and the workpiece by a power supply that usually includes a dropping transformer and bridge rectifier. Gas ionized by this voltage exits an opening of a tip surrounding the electrode and appears as a flame which extends externally from the tip.
  • the arc jumps from the electrode to the workpiece and applies heat sufficient to cut, weld or bond the workpiece, as desired.
  • the torch can operate either in a stand-off mode or in a drag mode.
  • the torch tip In the stand-off mode, the torch tip is maintained a short distance above the workpiece; say 6 mm.
  • an arc is undesirably formed within the torch itself between the electrode and the sur­rounding tip and then from the tip to the workpiece. This condition is called double arcing.
  • an arc is undesirably formed within the torch itself between the electrode and the tip or any other metallic part of the internal torch body which is electrically connected to the tip. The electricity completes its path by flowing from the tip to the workpiece because the tip is touching the workpiece. The existence of the internal arc is usually not readily apparent to the torch user. If permitted to continue for a time, internal damage to the torch occurs.
  • One technique suggested for dealing with this problem is to sense an increased voltage of the torch tip resulting from the internal arcing, and turn off the power supply in response to an increase of that voltage over some threshold. This technique is satisfactory for detecting internal arcing during the stand-off mode, but is rendered inoperative during the drag mode because there is no voltage to detect on the top when the tip is in electrical contact with the workpiece which is grounded.
  • the present invention is defined in the characterising part of claim 1.
  • the undesired internal arcing of the plasma torch causes the voltage level between the internal torch electrode and the workpiece to drop to a fraction of its normal operating voltage.
  • the undesired arcing is thus detected by this voltage drop and the power supply disconnected.
  • these safety circuits are disabled for a short time after such initial turn-on in order to allow the operating voltage of the system to rise to its normal level before the automatic power shut-off feature is enabled.
  • a plasma torch head 11 of a standard design is schematically illustrated adjacent a workpiece 13 upon which the torch is operating.
  • a case 15 of the torch has a tip element 17 attached at one end.
  • An electrode 19 is held within the case 15 and tip 17.
  • the tip 17 has an opening 21 at one end.
  • a source 23 of plasma gas under pressure is connected with the interior of the torch 11 by a conduit 25. The plasma gas flows through the conduit 25, around the electrode 19 and then out of the opening 21.
  • Conductors 27 and 29 carry the direct current power supply to the torch head and workpiece.
  • the negative voltage lead 27 is attached to the electrode 19, and the ground potential lead 29 is connected to the workpiece 13.
  • an arc is formed between an end of the electrode 19 adjacent the tip opening 21 and the workpiece 13 through the flowing gas, thereby providing the heat for performing the desired cutting or welding operation on the workpiece 13.
  • the power supply lines 27 and 29 of the example system of Figure 1 are connected to an output of a bridge rectifier whose input is connected to secondary windings of a drooping transformer 33.
  • Primary windings of the transformer 33 are connected through lines 35 and 37 to single pole switches 39 and 41, respectively, and then to the a.c. power line source.
  • the ON/OFF switches 39 and 41 are preferably operated together as contacts of a solenoid 43 in response to an electrical signal in a line 45.
  • the desired condition of operation is, as is well known, for the arc to extend from the lower end of the electrode 19, through the orifice 21 and against the workpiece 13. It is not unusual, however, for the arc to extend instead between the electrode 19 and an inner surface of the tip 17. If this is permitted to continue very long, the electrode, tip and/or other internal parts are severely burned or melted due to excessive heat generated. This renders the torch unusable until re­paired. Heretofore, such a condition has been detected primarily by a visual indication of the torch operator, but by the time it is noticed, excessive damage has already been done.
  • the conditions that cause this undesirable internal arcing are many.
  • One cause is a reduced flow of plasma gas through the torch and out the opening 21. It is the swirling motion of plasma gas that provides a high resistance path between the electrode and the internal surface of the tip 17. But when the plasma gas source 23 does not provide enough gas, or there is a leak in the system, or the opening 21 is covered by a placement against the workpiece, or some other cause, such internal arcing will occur.
  • Another common cause of such internal arcing is the excessive wear of the lower end of the electrode 19 from extended periods of use. As the electrode end burns upward away from the opening 21, the arc finds a lower resistance path to the tip 17 than to the workpiece 13.
  • control circuits 51 are provided to turn off the power to the transformer 33 by actuating the solenoid 43 when such conditions are detected. Since the transformer 33 is wound to have a generally constant current output under varying load conditions, it has been found that the undesired internal arcing conditions cause the output voltage across lines 27 and 29 of such a power supply to decrease significantly from that voltage that exists under normal operating conditions without the undesired internal arcing. It is, therefore, this vol­tage drop that is sensed by the circuits 51 and which causes the power to be turned off at switches 39 and 41. This voltage is sensed by a line 53 connected to the negative rectifier output line 27, and by a connection to ground potential.
  • a manually operated switch 55 is Also connected to the control circuits 51, through a line 57, is a manually operated switch 55.
  • the pushbutton switch 55 is of a type currently used in plasma torches to cause the power supply to be turned off unless the operator is depressing the switch.
  • a plasma gas flow sensor 59 that is connected by a line 61 to the control circuits 51. As in current torches, the power supply is turned off in response to sensing little or no plasma gas flow into the torch.
  • a threshold circuit 65 receives the bridge rectifier 31 output voltage as an input and emits as an output, in a line 67, a binary signal representative of whether the rectifier output voltage is above or below a specified threshold.
  • a typical torch operating voltage is around 100 volts, and the threshold is set to be about 50 volts, or one-half of the normal operating voltage.
  • the voltage in the line 67 is denoted to have a value of a logical "1" when the rectifier output voltage is above the set threshold, and a level of a logical "0" when below that threshold.
  • the circuit 65 may be formed of any commonly available threshold device, such as a comparator circuit, inherent threshold operation of available logic elements, and the like.
  • Additional logic circuit elements of Figure 2 include an OR-gate 69 having the line 67 as one of two inputs, the other input being a line 71.
  • An output line 73 becomes one input of an AND-gate 75 whose output is a line 77.
  • the AND-gate 75 has a second input, a line 79.
  • the line 79 is an output of an AND-gate 83 which is shown to have four inputs, namely the line 57 from the operator controlled ON/OFF switch 55, the line 61 from the plasma gas flow sensor 59, and two other lines 85 that are often provided for detecting other conditions, such as excessive power supply temperature, open cabinet doors, and the like.
  • a normal con­dition from any of these sensors in the four input lines to the AND gate 83 is considered to be a logical "1" voltage level.
  • its output line 79 is a "1" which causes the driver circuit 81 to keep the power ON/OFF switch in its ON position.
  • This initial turn-on condition is detected when the operator pushes the power control button 55 ( Figure 1) which causes the output of the AND-­gate 83 ( Figure 2) in line 79 to rise from a logical "0" to a "1".
  • the circuit 87 in response to that change of voltage level in the line 79, generates a logical "1" in the voltage level in the line 71 to effectively disable the threshold circuit 65. This occurs since, during that short interval of time after power is first turned on to the system, the logical "1" in line 71 is forced through the line 73 to the AND-gate 75 regardless of whether the voltage level in the line 67 is a "0" or "1".
  • the reason for this timing circuit 87 is to force the control circuits to allow power to remain connected for a short time until the voltage level which is sensed by the threshold circuit 65 rises from zero to its normal operating voltage. If it does so rise during that interval, the return of the voltage level in the line 71 from a "1" to a "0" at the end of that short interval does not affect operation of the device. However, if there is a problem with internal arcing at the time that power is turned on to the system, it may turn off again at the end of that initial interval set by the timing circuit 87 since the voltage in the line 67 will be "0" instead of "1". But such a short period of arcing causes little damage.
  • the timing circuit 87 can be of any convenient design that utilizes a resistance-capacitance (RC) cir­cuit, as is well known.
  • the output of the threshold detecting circuit 65 (which is shown in Figure 3(B)) changes from a "0" to a "1" sometime later, at time t1, the time necessary for the power supply output to reach its normal level after first being turned on.
  • the signal in the line 71 keeps the control circuits from immediately shutting off the power supply again, at least until the time t2 when the signal output of the timing circuit 87 returns to its "0" level, as shown in Figure 3(A).
  • the interval between times t0 and t2 is usually a fraction of a second, as little as 0.1 second.
  • FIG. 3 Another change of condition is illustrated in Figure 3, occurring at time t3. It is assumed that the threshold circuit 65, at that instant, detects a low voltage, and its output thus drops from a "1" to a "0", as shown in Figure 3(B). This then causes the signal in line 77, as shown in Figure 3(D), to drop from a "1” to a "0", and the driving circuits 81 are caused to turn off the power supply through the solenoid switch.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Arc Welding Control (AREA)
EP86303754A 1985-09-04 1986-05-16 Circuit d'interruption d'une torche à plasma Withdrawn EP0213689A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US77260685A 1985-09-04 1985-09-04
US772606 1985-09-04

Publications (2)

Publication Number Publication Date
EP0213689A2 true EP0213689A2 (fr) 1987-03-11
EP0213689A3 EP0213689A3 (fr) 1988-09-21

Family

ID=25095623

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86303754A Withdrawn EP0213689A3 (fr) 1985-09-04 1986-05-16 Circuit d'interruption d'une torche à plasma

Country Status (2)

Country Link
EP (1) EP0213689A3 (fr)
JP (1) JPS62267080A (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5717187A (en) * 1994-03-25 1998-02-10 Commonwealth Scientific And Industrial Research Organisation Plasma torch condition monitoring
US5756960A (en) * 1994-03-25 1998-05-26 Commonwealth Scientific And Industrial Research Organization Detecting non-symmetrical nozzle wear in a plasma arc torch
ES2115542A1 (es) * 1996-07-24 1998-06-16 Iberdrola Sa Fuente de alimentacion de antorchas de hornos de plasma.
WO1998056215A1 (fr) * 1997-06-06 1998-12-10 Hypertherm, Inc. Circuit de securite pour chalumeau a arc de plasma a demarrage par contact vers l'avant et a soufflage
US7807937B2 (en) * 2005-01-03 2010-10-05 Illinois Tool Works Inc. Method and system of conserving plasma torch consumable
US20140254054A1 (en) * 2009-02-17 2014-09-11 Albert Bulliard Power supply device for plasma processing
CN109709427A (zh) * 2018-12-30 2019-05-03 常州九圣焊割设备有限公司 等离子电弧喷枪中易耗件故障检测方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0688141B2 (ja) * 1988-03-24 1994-11-09 株式会社小松製作所 プラズマアーク切断におけるダブルアーク防止切断方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2151219A5 (en) * 1971-08-26 1973-04-13 Shapiro Ilya Plasma beam arc control - prevents voltage surges
JPS597480A (ja) * 1982-07-05 1984-01-14 Matsushita Electric Ind Co Ltd 自動ア−ク溶接機

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS53108048A (en) * 1977-03-04 1978-09-20 Hitachi Ltd Electron beam welding method
JPS6043831B2 (ja) * 1980-08-30 1985-09-30 株式会社三社電機製作所 プラズマア−ク用ト−チの損傷防止装置

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2151219A5 (en) * 1971-08-26 1973-04-13 Shapiro Ilya Plasma beam arc control - prevents voltage surges
JPS597480A (ja) * 1982-07-05 1984-01-14 Matsushita Electric Ind Co Ltd 自動ア−ク溶接機

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, vol. 8, no. 90 (M-292)[1527], 25th April 1984; & JP-A-59 007 480 (MATSUSHITA DENKI SANGYO K.K.) 14-01-1984 *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5717187A (en) * 1994-03-25 1998-02-10 Commonwealth Scientific And Industrial Research Organisation Plasma torch condition monitoring
US5756960A (en) * 1994-03-25 1998-05-26 Commonwealth Scientific And Industrial Research Organization Detecting non-symmetrical nozzle wear in a plasma arc torch
ES2115542A1 (es) * 1996-07-24 1998-06-16 Iberdrola Sa Fuente de alimentacion de antorchas de hornos de plasma.
WO1998056215A1 (fr) * 1997-06-06 1998-12-10 Hypertherm, Inc. Circuit de securite pour chalumeau a arc de plasma a demarrage par contact vers l'avant et a soufflage
US5900169A (en) * 1997-06-06 1999-05-04 Hypertherm, Inc. Safety circuit for a blow forward contact start plasma arc torch
US7807937B2 (en) * 2005-01-03 2010-10-05 Illinois Tool Works Inc. Method and system of conserving plasma torch consumable
US20140254054A1 (en) * 2009-02-17 2014-09-11 Albert Bulliard Power supply device for plasma processing
US9214801B2 (en) * 2009-02-17 2015-12-15 Solvix Gmbh Power supply device for plasma processing
US9997903B2 (en) 2009-02-17 2018-06-12 Solvix Gmbh Power supply device for plasma processing
CN109709427A (zh) * 2018-12-30 2019-05-03 常州九圣焊割设备有限公司 等离子电弧喷枪中易耗件故障检测方法
CN109709427B (zh) * 2018-12-30 2021-09-03 常州九圣焊割设备股份有限公司 等离子电弧喷枪中易耗件故障检测方法

Also Published As

Publication number Publication date
JPS62267080A (ja) 1987-11-19
EP0213689A3 (fr) 1988-09-21

Similar Documents

Publication Publication Date Title
CA2225942C (fr) Commande d'arc de plasma pilote
AU614449B2 (en) Plasma arc torch system interlock
EP0573771B1 (fr) Dispositif de surveillance de l'état d'un contact
KR950011708B1 (ko) 플라즈마 노즐을 보호하기 위한 시스템, 방법 및 회로
US6350960B1 (en) Parts-in-place safety reset circuit and method for contact start plasma-arc torch
US4814577A (en) Control circuit in plasma arc cutting and welding equipment designed for transferred arc operation
US5961855A (en) Low voltage electrical based parts-in-place (PIP) system for contact start torch
US4585921A (en) Torch operation interlock device
EP0213689A2 (fr) Circuit d'interruption d'une torche à plasma
US4663515A (en) Plasma-arc torch interlock with flow sensing
US6670572B2 (en) Solenoid control and safety circuit system and method
JP3458632B2 (ja) 溶接電圧検出方法およびアーク溶接機
JPS57168772A (en) Short circuit transfer arc welding machine
JPH07314150A (ja) 交流式抵抗溶接機におけるサイリスタ電圧検出装置
JP2850397B2 (ja) プラズマアーク加工装置
US4862095A (en) Wire electrode breakage detection method and apparatus
KR960001529Y1 (ko) 용접 제어장치
KR960004789B1 (ko) 저전압에서도 고감도의 용접이 가능한 전격방지기
KR100382125B1 (ko) 인버터 용접기에서의 입상용적이행 제어 방법 및 장치
JPS6159834B2 (fr)
KR890008327Y1 (ko) 교류 아크 용접기용 전격(電擊) 방지회로
JP3264741B2 (ja) フィラワイヤ供給ｔｉｇ溶接装置
KR200308216Y1 (ko) 교류아크용접기용 자동전격방지기
SU823027A1 (ru) Устройство дл ограничени напр жени ХОлОСТОгО ХОдА СВАРОчНОгО ТРАНСфОРМАТОРА
KR19980080346A (ko) 아크 전이 회로

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): DE FR GB IT

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): DE FR GB IT

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19890322

RIN1 Information on inventor provided before grant (corrected)

Inventor name: SPAULDING, RICHARD A.

Inventor name: MOLLETT, WAYMAN LEON

Inventor name: WILKINS, RAYMOND G.