EP0817547A1 - Plasmabrennerkopf - Google Patents

Plasmabrennerkopf Download PDF

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Publication number
EP0817547A1
EP0817547A1 EP97401417A EP97401417A EP0817547A1 EP 0817547 A1 EP0817547 A1 EP 0817547A1 EP 97401417 A EP97401417 A EP 97401417A EP 97401417 A EP97401417 A EP 97401417A EP 0817547 A1 EP0817547 A1 EP 0817547A1
Authority
EP
European Patent Office
Prior art keywords
electrode
nozzle
axial
torch head
plasma torch
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Withdrawn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
EP97401417A
Other languages
English (en)
French (fr)
Inventor
Michel Delzenne
André Borne
Christophe Bertez
Régis Augeraud
Eric Salassa
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.)
Lincoln Electric Company France SA
Original Assignee
La Soudure Autogene Francaise
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 La Soudure Autogene Francaise filed Critical La Soudure Autogene Francaise
Publication of EP0817547A1 publication Critical patent/EP0817547A1/de
Withdrawn legal-status Critical Current

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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
    • 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
    • H05H1/3442—Cathodes with inserted tip
    • 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
    • H05H1/3478—Geometrical details
    • 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
    • H05H1/3489—Means for contact starting

Definitions

  • the present invention relates to a torch head with plasma, of the type comprising an axial electrode and a cup-shaped peripheral nozzle with bottom has an axial pipe for ejecting the plasma jet and whose side wall surrounds the electrode, the electrode and the nozzle being axially displaceable one by relation to the other with a view to putting them in contact temporary following a contact surface to initiate a electric arc, called pilot arc, between the electrode and the nozzle.
  • a torch head with plasma of the type comprising an axial electrode and a cup-shaped peripheral nozzle with bottom has an axial pipe for ejecting the plasma jet and whose side wall surrounds the electrode, the electrode and the nozzle being axially displaceable one by relation to the other with a view to putting them in contact temporary following a contact surface to initiate a electric arc, called pilot arc, between the electrode and the nozzle.
  • Such torch heads are used in plasma torches for welding, cutting, heat treatment or thermal spraying.
  • an electric arc is established at through the axial ejection duct between the electrode and the metal piece worked.
  • the electrode and this part are connected to the terminals of an electric generator.
  • the nozzle and the electrode are temporarily connected to the terminals of a electric generator, so that a pilot arc takes birth directly between these two elements.
  • the arc pilot is then transferred to the workpiece under the effect of the plasma flow. After the transfer of the arc, the nozzle is no longer supplied by the generator, the power being applied to the workpiece.
  • the nozzle is not not powered.
  • the pilot arc is initiated by support of the conductive nozzle on the workpiece and contact of the electrode with the nozzle.
  • a short-circuit is then established between the workpiece and the electrode through the nozzle, so that an arc arises between the nozzle and the electrode during their spacing.
  • the electrode has a flat end surface and the nozzle also has a flat bottom.
  • bringing the electrode into contact with the nozzle is carried out along most of the surface flat end of the electrode.
  • the document FR-A-2,650,470 describes, for example, a electrode whose planar end face has a axial counterbore ensuring withdrawal of an insert emissive centrally positioned.
  • This configuration particular solution to the problems related to the deformation of the surface of the insert during the operation.
  • a large flat annular surface dimension remains at the end of the electrode around the counterbore. Contact with the flat bottom of the nozzle takes place over the entire extent of this surface annular.
  • the arc is very unstable and moves from erratically over the entire flat surface of the bottom of the nozzle and in particular near the entrance to the axial ejection duct. This same phenomenon of random displacement of the root of the arc is also found on the surface of the electrode located opposite.
  • Arc movement causes erosion electric, local mergers and displacements of melting residue on the outer walls of the electrode and the internal walls of the nozzle. These phenomena quickly lead to a change in the condition of surfaces channeling the plasma gas. In particular, under the effect of the plasma gas flow, the residues of fusion converge towards the entry of the ejection duct, modifying its geometry. Geometric modifications surfaces cause disturbances in the flow of the plasma jet, thereby reducing the quality of the work done.
  • the object of the invention is to remedy the drawbacks mentioned above and in particular to propose a plasma torch head undergoing little degradation of its internal surfaces during the ignition phase and of which the lifespan is extended, with conservation of working qualities.
  • the invention relates to a head of plasma torch comprising an axial electrode and a cup-shaped peripheral nozzle with bottom has an axial duct for ejecting the plasma jet and whose side wall surrounds the electrode, the electrode and the nozzle being axially displaceable one by relation to the other with a view to putting them in contact temporary following a contact surface to initiate a electric arc between the electrode and the nozzle, characterized in that the bottom of the nozzle has a first axial peripheral projection.
  • the plasma torch head shown in the Figures 1 and 2 is intended, for example, for cutting metal parts. It has a general form of X-X axis revolution. It mounts on a body of suitable plasma torch, for example by snap-fastening in this body.
  • This head essentially comprises an electrode 10 of axis X-X and a peripheral nozzle 12, both adapted to be associated with generators of appropriate electrical potential.
  • the electrode and the nozzle are rigidly connected by a cover (not shown) forming a plasma gas diffuser.
  • the electrode 10 is mounted movable axially by with respect to the nozzle 12 by any appropriate means, between an arc striking position in contact with the nozzle and a working position axially spaced from the nozzle. These positions are shown respectively in Figures 1 and 2.
  • the electrode 10 is made of a suitable metal and has a general form of revolution. It includes internal conduits 14 intended for the circulation of a coolant.
  • An emissive insert 16 on the face flat, in hafnium for example, is arranged axially at the end of the electrode 10. It is flush with the center of the end face 18 thereof.
  • the electrode has further on its end face 18 a projection convex axial device 20 forming a rim continuous device surrounding a flat surface 18A at center of which the insert is flush 16.
  • the projection peripheral 20 is formed by a toroidal bead coming of material and disposed at the outer periphery of the electrode.
  • the nozzle 12 has a general shape of an axle cup X-X. It has a flat bottom 22 crossed by a axial duct 24 for ejecting the plasma gas.
  • the bottom 22 is extended by a side wall 26 surrounding the electrode 10 and delimiting therewith a space 28 substantially annular circulation of plasma gas to conduit 24.
  • the electrode 10 is in contact with the nozzle 12 along the crest 20A of the projection periphery 20.
  • the contact surface 23 established between the ridge 20A and the bottom 22 is moved away from the entry of the axial ejection duct, so that the surface 22A surrounding the entrance to this conduit is free of all contact with the electrode.
  • the conduit entrance is defined as the line of rupture existing between the axial ejection duct and the nozzle bottom. If such a breaking line does not exist not and that the diameter of the conduit varies continuously in its connection area with the bottom, the entrance to the duct is defined as the place where the diameter of the duct is 1.5 times the minimum diameter of the drove.
  • the electrode 10 is in the position of working, away from the nozzle 12.
  • the arc electric arises between a crown 22B of small width containing the circular contact line and the crest 20A of the projection 20.
  • the crown 22B is symbolized by a thick line in this figure.
  • the nozzle 12 is identical to that of the mode of previous achievement.
  • the end face 18 of the electrode further comprises an axial cup 30 bordered by the peripheral projection 20.
  • the surface 32 delimiting the bowl 30 is frustoconical and connects tangentially the crest of the peripheral projection 20 to the periphery of the plan insert 16.
  • the peripheral projection 20 is toroidal with a inner radius noted R.
  • the frustoconical surface 32 is tangentially connects to the torus delimiting the projection 20.
  • the electrode 10 is analogous to the electrode shown in Figures 3 to 5.
  • the nozzle 12 has a bottom provided a first axial peripheral projection 40, again called axial bending 40, at the top of which opens the axial ejection duct 24.
  • the profile of the bending 40 corresponds substantially to the profile of the axial bowl 30 formed on the surface end of the electrode.
  • the surface 42 of the bending 40 is substantially frustoconical.
  • This surface 42 defines with a plane perpendicular to the X-X axis of the torch an angle a substantially equal to 10 ° ( Figure 8).
  • the surface 32 of the axial bowl 30 defines with this same plane perpendicular to the axis X-X an angle ⁇ substantially equal to 12 °. So the slope of the surface of the bowl axial taken in relation to the transverse plane of the torch is slightly greater than the slope of the surface of the bending taken in relation to this same plane.
  • frustoconical surface 42 is connected tangentially to the inner surface of the wall side of the nozzle.
  • the gas undergoes plasmagenicity between the frustoconical surfaces substantially parallel 32 and 42, rolling ensuring stabilization of the root of the electric arc on insert 16, during steady state operation of the torch.
  • the electric arc being established between the points closest to the electrode and the nozzle, the roots of the emerging electric arc are maintained on the crown 22A of the nozzle and on the crest 20A of the projection. So, as long as the electric arc is not blown by the plasma gas, it is kept in a defined area of small area.
  • the level of electrical erosion being linked to the surface swept by the electric arc, circumscribing the arc to an area reduced limits surface degradation.
  • the arc being kept away from the entry of the axial duct ejection, any fusion residues produced do not cannot reach this one, thus guaranteeing the geometric preservation of the duct. We can see that with such an arrangement, the lifetime of the torch head at plasma is elongated.
  • the electric arc takes birth in a localized area of small extent and distant from the inlet of the axial ejection duct 24, thus preserving the torch head.
  • the embodiment shown in Figures 9 to 11 is similar to that of FIGS. 6 to 8.
  • the electrode 10 however, further comprises at least three grooves 50; in this case, four grooves 50 are shown. These grooves extend radially and cross the crest of the projection 20 thus cutting the contact line 23 which is then discontinuous. As shown in the figure 11, the grooves 50 are distributed along a equiangular arrangement. They cross the surface frustoconical 32 of the bowl as well as the peripheral projection 20.
  • the grooves 50 may be slightly offset parallel to the radial grooves shown in Figure 11. So as shown in FIG. 13, grooves 50A are offset in the clockwise, so one of the edges of the grooves extends tangentially to the insert emissive 16. So the plasma gas flowing through of these creates at the outlet a vortex flowing in the direction of arrow F1. The gas circulating in space annular 28 forms a vortex circulating in the direction of arrow F2, identical to the direction of arrow F1. So, the root of the electric arc is stabilized by the effect swirling plasma gas streams with senses identical rotation.
  • the grooves 50B are offset parallel to the radial grooves 50 of Figure 11 counterclockwise of a watch, so that the vortex created at the outlet of grooves 50B rotates in the direction of arrow F3 opposite in the sense of circulation of the plasma gas in space annular 28 and indicated by arrow F2.
  • the root of the arc is then stabilized by the two vortex flows traveling counter-rotating.
  • the end of the electrode 10 has a convex frustoconical surface 60 and has in its center the flat face insert 16.
  • the diameter of the electrode is thus gradually decreasing from the diameter of its lateral surface cylindrical up to the outside diameter of the insert 16.
  • the bottom of the nozzle 12 also has a bowl 62 centered on the X-X axis, hereinafter designated by the sleeve term 62.
  • the axial evacuation duct 24 opens into the center of this sleeve 62.
  • the surface 64 of the sleeve 62 is substantially tapered.
  • the slope of the surface 64 taken relative to to a transverse plane of the torch is greater than the slope of the surface 60 taken with respect to this same plane.
  • the diameter of the sleeve 62 is greater than the outside diameter of electrode 10. So, as shown in Figure 15, the electrode 10 enters contact with the nozzle on the surface of the sleeve 62 at the periphery of it along a line of contact circular 66.
  • the electrode 10 is applied to the surface 64 along the line connecting the frustoconical surface 66 to the cylindrical lateral surface of the electrode.
  • the electric arc arises on the outskirts of the electrode 10 and the nozzle sleeve 12 on an area of small extent.
  • the entry of the axial duct ejection is preserved from arc attacks electric, the arc being kept away from the conduit.
  • the bottom of the nozzle 12 is delimited by an axial sleeve 70 formed of two successive frustoconical surfaces 70A, 70B of conicities different.
  • the electrode 10 has a planar end face 72 whose outside diameter is less than the diameter of the sleeve 70.
  • the insert 16 is flush with the center of this area.
  • Grooves 74 are formed radially on the end surface of the electrode.
  • the end of the electrode has a slightly 76 lateral surface tapered. The grooves 74 open, on the one hand, onto the side wall 76 of the electrode and, on the other hand, on the end face thereof on the outside of the insert 16.
  • the contact between the electrode 10 and the nozzle 12 is established between the crest electrode device and the inner surface of the sleeve 70 in the vicinity of the periphery of the surface 70B.
  • the plasma gas flows through grooves 74, allowing thus the birth of the electric arc in a medium rich in plasma gas.
  • the electrode surfaces and of the nozzle are preserved by maintaining the location of the roots of the nascent electric arc and by the presence of grooves allowing circulation permanent plasma gas.
  • the torch heads in Figures 15-18, as those of Figures 6 to 14, have, on the bottom of nozzle, of a first axial peripheral projection 40, of so the circulation of the plasma gas stream flowing between the electrode 10 and the nozzle is carried out optimally, i.e. substantially without turbulence.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Geometry (AREA)
  • Plasma Technology (AREA)
  • Arc Welding In General (AREA)
EP97401417A 1996-06-24 1997-06-19 Plasmabrennerkopf Withdrawn EP0817547A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9607816 1996-06-24
FR9607816A FR2750286B1 (fr) 1996-06-24 1996-06-24 Tete de torche a plasma

Publications (1)

Publication Number Publication Date
EP0817547A1 true EP0817547A1 (de) 1998-01-07

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ID=9493346

Family Applications (1)

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EP97401417A Withdrawn EP0817547A1 (de) 1996-06-24 1997-06-19 Plasmabrennerkopf

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EP (1) EP0817547A1 (de)
FR (1) FR2750286B1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2917314A1 (fr) * 2007-06-14 2008-12-19 Air Liquide Electrode pour torche a arc plasma a geometrie amelioree
IT201600081330A1 (it) * 2016-08-02 2018-02-02 Cebora Spa Torcia al plasma con accensione a contatto
WO2021102147A1 (en) * 2019-11-19 2021-05-27 Hypertherm, Inc. Consumable designs for a plasma arc torch

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3840459A1 (de) * 1988-11-14 1990-05-17 Merkle Wilhelm Schweissmasch Schneidbrenner
FR2650470A1 (de) * 1989-07-28 1991-02-01 Soudure Autogene Francaise
FR2669847A1 (fr) * 1990-11-29 1992-06-05 Trafimet Trafilerie Metalliche Chalumeau coupeur a plasma, dans lequel le declenchement de l'amorcage est realise a l'aide d'un contact.
EP0591018A1 (de) * 1992-10-02 1994-04-06 La Soudure Autogene Francaise Lichtbogenplasmabrenner und Verfahren zu seiner Anwendung

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4902871A (en) * 1987-01-30 1990-02-20 Hypertherm, Inc. Apparatus and process for cooling a plasma arc electrode
US4791268A (en) * 1987-01-30 1988-12-13 Hypertherm, Inc. Arc plasma torch and method using contact starting

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3840459A1 (de) * 1988-11-14 1990-05-17 Merkle Wilhelm Schweissmasch Schneidbrenner
FR2650470A1 (de) * 1989-07-28 1991-02-01 Soudure Autogene Francaise
FR2669847A1 (fr) * 1990-11-29 1992-06-05 Trafimet Trafilerie Metalliche Chalumeau coupeur a plasma, dans lequel le declenchement de l'amorcage est realise a l'aide d'un contact.
EP0591018A1 (de) * 1992-10-02 1994-04-06 La Soudure Autogene Francaise Lichtbogenplasmabrenner und Verfahren zu seiner Anwendung

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2917314A1 (fr) * 2007-06-14 2008-12-19 Air Liquide Electrode pour torche a arc plasma a geometrie amelioree
IT201600081330A1 (it) * 2016-08-02 2018-02-02 Cebora Spa Torcia al plasma con accensione a contatto
WO2021102147A1 (en) * 2019-11-19 2021-05-27 Hypertherm, Inc. Consumable designs for a plasma arc torch
US11420286B2 (en) 2019-11-19 2022-08-23 Hypertherm, Inc. Consumable designs for a plasma arc torch

Also Published As

Publication number Publication date
FR2750286A1 (fr) 1997-12-26
FR2750286B1 (fr) 1998-07-24

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