WO2021136563A1 - Plasma arc torch assembly with contact start - Google Patents

Plasma arc torch assembly with contact start Download PDF

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Publication number
WO2021136563A1
WO2021136563A1 PCT/CZ2020/050099 CZ2020050099W WO2021136563A1 WO 2021136563 A1 WO2021136563 A1 WO 2021136563A1 CZ 2020050099 W CZ2020050099 W CZ 2020050099W WO 2021136563 A1 WO2021136563 A1 WO 2021136563A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrode
cathode
nozzle
torch assembly
electrical contact
Prior art date
Application number
PCT/CZ2020/050099
Other languages
French (fr)
Inventor
Roman Chumchal
Original Assignee
B&Bartoni, spol. s r.o.
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 B&Bartoni, spol. s r.o. filed Critical B&Bartoni, spol. s r.o.
Publication of WO2021136563A1 publication Critical patent/WO2021136563A1/en

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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
    • H05H1/3421—Transferred arc or pilot arc mode
    • 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
    • H05H1/28—Cooling arrangements
    • 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
    • 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
    • H05H1/3489—Means for contact starting
    • 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
    • H05H1/42—Plasma torches using an arc with provisions for introducing materials into the plasma, e.g. powder, liquid
    • 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
    • H05H1/48—Generating plasma using an arc

Definitions

  • the invention relates to the design of a plasma arc torch with contact start (touch ignition). Specifically, the body of the torch and its replacement parts, enabling the contact start of the pilot arc.
  • Plasma arc torches with contact start are manufactured and used for manual and machine cutting, grooving and marking of metal materials.
  • the plasma arc torches with contact start are also called plasma arc torches with touch ignition.
  • These torch assemblies have a rotating cylindrical shape, through the middle of which a longitudinal axis passes in the axial direction.
  • the basic parts of the torch assembly are the torch body, electrode, nozzle, swirl ring, nozzle holder and protective shield.
  • the basic parts of the plasma torch body are cathode, insulator and anode.
  • the torch assembly includes a flexible member that is part of the torch body or consumable replacement parts of the torch assembly.
  • the consumable replacement parts are electrode, nozzle, swirl ring, nozzle holder and protective shield.
  • Plasma torches with contact start are designed so that after their assembly the electrode and nozzle are in physical and electrical contact.
  • a plasma chamber is formed between the electrode, the swirl ring and the nozzle. After switching on, the electric current is fed to the electrode and the nozzle, and the plasma gas flows into the plasma chamber.
  • the gas pressure in the plasma chamber causes the electrode and nozzle to move away in the longitudinal axis. Due to the short circuit between the electrode and the nozzle, a pilot plasma arc is created after their separation. The pilot arc ionizes the flowing plasma gas. The ionized plasma gas flows through an opening in the nozzle towards the material to be cut. An electrically conductive connection is formed between the electrode and the material to be cut through the ionized gas. A transferred plasma arc is created between the electrode and the material to be cut, a positive pole is connected to the material to be cut, and then the pilot plasma arc between the electrode and the nozzle is terminated.
  • Existing contact start plasma torches are designed so that the pressurized plasma gas supplied to the plasma chamber breaks the electrical contact between the electrode and the nozzle. Either the plasma gas pressure moves the moving nozzle away from the stationary electrode or the moving electrode away from the stationary nozzle. Another possibility is that the nozzle and the electrode are stationary, and another part of the plasma torch moves, which breaks the direct electrical contact between the electrode and the nozzle. This function is enabled by the flexible electrically conductive part in the plasma torch.
  • the flexible member is usually a steel compression spring. When the nozzle moves, the flexible member is between the nozzle and the nozzle holder. When the electrode moves, the flexible member is usually between the electrode and the cathode.
  • the flexible member can be located in another part of the plasma torch, and allows the electrode to move away from the nozzle, or only to break the direct electrical contact between the electrode and the nozzle.
  • the state of the art is described in U.S. Patents nos. 4791268, US 6 969 819, US 7 435 925, US 8035 055, US 8 089 025, US 8 115 136, US 8541 712, CZ 304595 and EP 3563 644.
  • an electrically conductive flexible member is always present in the torch assembly.
  • the mechanical properties of the flexible member allow the electrical contact between the electrode and the nozzle to be broken.
  • the electrical properties of the flexible member allow the pilot arc to pass through it.
  • the flexible member is loaded with at least a portion of the current passing through the pilot arc. Frequent starting of the pilot arc damages the flexible member. It may even melt. This cannot be solved by increasing the cross-section of the flexible member, because its compressive strength increases so much that the plasma gas pressure cannot over-press it.
  • the present invention relates to a contact start plasma arc torch assembly.
  • This torch assembly consists of at least the following parts: an electrode that contains an emissive insert; a nozzle that contains an opening for the passage of plasma gas; a swirl ring that contains a plasma gas passage; a nozzle holder that is designed to secure the nozzle, swirl ring and electrode into the torch assembly; a protective shield adapted to be attached to the nozzle holder; a cathode, which is connected to the first pole of the electrical circuit forming the pilot arc; an anode, which is connected to the second pole of the electrical circuit forming the pilot arc; an insulator, which is between the cathode and the anode, and electrically insulates them; an electrical contact through which the entire current of the pilot arc passes; two permanent magnets, or one permanent magnet and a magnetic member which pushes the electrode and the nozzle together, and at the same time allows them to move away from each other.
  • the electrode is movably arranged between a first position in which the electrode is in electrical contact with the nozzle and a second position in which the electrode is spaced from the nozzle.
  • the plasma arc torch assembly is formed so that after assembly the electrode and nozzle are in electrical contact, wherein the plasma arc torch assembly is designed to allow electrical contact between the electrode and the nozzle to be broken by plasma gas supplied to the plasma chamber under pressure.
  • the electrode is movable relative to the cathode, wherein the cathode and the electrode are in electrical contact with each other in all mutual positions.
  • the contact start plasma arc torch assembly of the present invention newly includes two permanent magnets compared to the prior art. These permanent magnets are oriented towards each other by the same magnetic poles. By this, they repel each other. Their repulsive force is used to press the electrode against the nozzle. Just as the force of a compression spring is used in the prior art. Electric permanent magnets press the electrode against the nozzle, and at the same time allow the electrode to move away from the nozzle by the force of the plasma gas in the plasma chamber acting on the surface of the electrode.
  • the advantage of the magnetic force between permanent magnets is that it is non-contact. No mechanical component is damaged, as in the case with the compression spring.
  • the contact between the fixed part of the torch assembly connected to the first pole of the electrical circuit forming the pilot arc and the movable part of the torch assembly which further conducts electric current towards the emissive insert in the electrode provides electrical contact between the two parts.
  • the electrical contact can be formed as a flexible metal element interposed between the fixed and movable parts through which the pilot arc passes and conducts all the current of the pilot arc.
  • the electrical contact conducts current of the pilot arc as long as it is turned on.
  • Fig. 1 shows a longitudinal section of the contact start plasma arc torch assembly according to the first embodiment of the invention in the position of contact between the electrode and the nozzle.
  • Fig. 2 shows a longitudinal section of the contact start plasma arc torch assembly according to the first embodiment of the invention in the position when the electrode and the nozzle are away from each other.
  • Fig. 3 shows a longitudinal detailed section of the contact start plasma arc torch assembly according to the first embodiment of the invention in the position of contact between the electrode and the nozzle.
  • Fig. 4 shows a longitudinal detailed section of the contact start plasma arc torch assembly according to the first embodiment of the invention in the position when the electrode and the nozzle are away from each other,
  • Fig. 5 shows a longitudinal detailed section of the cathode, a moving part of the cathode and the electrical contact according to the first embodiment of the invention
  • Fig. 6 shows a longitudinal section of the contact start plasma arc torch assembly according to the second embodiment of the invention in the position of contact between the electrode and the nozzle..
  • Fig. 7 shows a longitudinal section of the contact start plasma arc torch assembly according to the third embodiment of the invention in the position of contact between the electrode and the nozzle. Examples of embodiments
  • Fig. 1 generally shows a longitudinal section of the contact start torch assembly 1 according to the first embodiment of the invention in the position of contact 101 between an electrode 16 and a nozzle 18.
  • the electrode 16 and the nozzle 18 are in electrical contact with each other.
  • the torch assembly 1 consists, inter alia, of an anode 10, an insulator 11, a cathode 12, an electrical contact 13, a contact element 14, two permanent magnets 15, an electrode 16, a swirl ring 17, a nozzle 18, a nozzle holder 19 and a protective shield 20.
  • the torch assembly 1 and its individual parts have a substantially rotating cylindrical shape, through which a longitudinal axis 100 passes in the middle.
  • the torch assembly 1 is designed so that the cathode 12 connects to the first pole of the electrical circuit forming the pilot arc, and to the first pole of the electrical circuit forming the plasma arc. Furthermore, plasma gas is introduced into the cathode 12 and flows through the passages in the torch assembly 1 into a plasma chamber 108.
  • the cathode 12 is made of copper alloy CuZn40Pb2.
  • a permanent magnet 15 is pressed into the cathode 12.
  • the insulator 11 is pressed on top of the cathode 12 and electrically insulates the cathode 12 from the anode 10.
  • the insulator 11 is made of an electrically insulating material.
  • the anode 10 is pressed onto the insulator 11 and connects to the second pole of the electrical circuit forming the pilot arc.
  • the anode 10 is shaped to mount the nozzle holder 19.
  • the anode 10 is made of copper alloy CuZn40Pb2.
  • the anode 10, the insulator 11 and the cathode 12 with the permanent magnet 15 do not wear out during use of the torch assembly 1, so they are not replacement parts of the torch assembly 1.
  • the other parts of the torch assembly 1 wear out during use. Worn parts are replaced with new ones.
  • the replacement part of the torch assembly 1 is the electrical contact 13, which is inserted into a hole in the lower part of the cathode 12.
  • the electrical contact 13 is made of a copper alloy, and is galvanically plated with a layer of gold.
  • the second permanent magnet 15 is pressed onto the contact element 14, which is a part of the torch assembly 1.
  • the second permanent magnet 15 is pressed onto the contact element 14 so that the two permanent magnets face each other by the same magnetic pole.
  • the permanent magnets 15 repel each other in the space 102 and push the contact element 14 away from the cathode 12.
  • the neodymium magnets which repel each other in the space 102 with a force of 8 to 10 N.
  • the contact element 14 is fixed in the cathode 12 and the electrical contact 13 so that it is movable in the longitudinal axis 100 but the repulsive force of the permanent magnets 15 acting on it will not release it from the cathode 12.
  • the electrode 16 is made of copper
  • the emissive insert 109 is made of hafnium.
  • the contact element 14 pushes the electrode 16 down towards the nozzle 18, which it touches in the point 101 of direct contact.
  • the swirl ring 17 abuts the lower part of the cathode 12 and comprises at least one passage 103 for the supply of plasma gas to the plasma chamber 108.
  • the plasma chamber 108 is an inner confined space between the surface of the electrode 16, the nozzle 18 and the swirl ring 17.
  • the nozzle 18 abuts the lower part of the swirl ring 17 and has an opening 106 in the axis 100 for the passage of plasma gas towards the material to be cut.
  • the nozzle holder 19 is slid onto the nozzle 18, and fixes the electrode 16, nozzle 18 and the swirl ring 17 firmly in the torch assembly by me an of a detachable connection to the anode 10.
  • the electrode 16, the nozzle 18 and the swirl ring 17 are secured in the torch assembly 1 by means of the nozzle holder 19.
  • the protective shield 20 is fastened to the nozzle holder 19 in its lower part by means of a detachable connection. The protective shield 20 protects the nozzle 18 from damage from sprayed molten material.
  • Fig. 2 generally shows a longitudinal section of the contact start torch assembly 1 according to the first embodiment of the invention in the position where the electrode 16 is axially moved away from the nozzle 18 by the pressure of gas in the plasma chamber 108, in the longitudinal axis 100.
  • the electrode 16 in the lower part comprises the emissive insert 109.
  • the electrode 16 together with the contact element 14 is pressed against the cathode 12.
  • the connection 104 of surfaces through which the electric current from the cathode 12 passes to the contact element 14 takes place. From the contact element 14, the electric current passes to the electrode 16.
  • the plasma arc passes from the electrode 16 through the opening 106 in the nozzle 18 to the material to be cut.
  • the torch assembly 1 in Fig. 2 consists of the same parts as in Fig.
  • FIG. 3 shows a detail of a longitudinal section of parts of the contact start torch assembly 1 according to the first embodiment of the invention in the position where the contact element 14 is pushed away from the cathode 12 due to the mutual repulsive force of the permanent magnets 15 in the space 102.
  • the contact element 14 is connected to the cathode 12 by the electrical contact 13 in such a way that the pilot arc passes from the cathode 12 by means of the electrical contact 13 to the contact element 14 without interruptions.
  • FIG. 3 shows a detail of the torch assembly 1 shown in Fig.l. It shows the cathode 12, the electrical contact 13, the contact element 14 and the permanent magnet 15 fixed in the cathode 12 and the permanent magnet 15 mounted on the contact element 14. All of the parts shown have a substantially rotating cylindrical shape through which the longitudinal axis 100 passes in the middle.
  • Fig. 4 shows a detail of a longitudinal section of parts of the contact start torch assembly 1 according to the first embodiment of the invention in the position where the contact element 14 is pushed to the cathode 12 by the pressure of gas in the plasma chamber 108.
  • the connection 104 of surfaces through which the electric current from the cathode 12 passes to the contact element 14 takes place.
  • Fig. 4 shows a detail of the torch assembly 1 shown in Fig.2. It shows the cathode 12, the electrical contact 13, the contact element 14 and the permanent magnet 15 fixed in the cathode 12 and the permanent magnet 15 mounted on the contact element 14. All of the parts shown have a substantially rotating cylindrical shape through which the longitudinal axis 100 passes in the middle.
  • Fig. 5 shows a detail of a longitudinal section of the cathode 12, the electrical contact 13, the contact element 14, the permanent magnet 15 fixed in the cathode 12 and the permanent magnet 15 mounted on the contact element 14
  • the individual parts shown have a substantially rotating cylindrical shape, through which the longitudinal axis 100 passes in the middle.
  • the electrical contact 13 and the contact element 14 are shown separately before the electrical contact 13 is inserted into an inner shape 107 in the cathode 12. Subsequently, the contact element 14 is inserted into the inner shape 107 so that the electrical contact 13 abuts the contact surface 105.
  • Fig. 5 shows the same cathode 12 electrical contact 13, contact element 14, the permanent magnet 15 fixed in the cathode 12 and the permanent magnet 15 mounted on the contact element 14 as shown in Figs. 1, 2, 3 and 4.
  • Fig. 6 generally shows a longitudinal section of the contact start torch assembly 2_ according to the second embodiment of the invention in the position of contact 101 between the electrode 16 and the nozzle 18.
  • the electrode 16 and the nozzle 18 are in electrical contact with each other.
  • the torch assembly 2_ consists, inter alia, of the anode 10, insulator 11, cathode 12 electrical contact 13, contact element 14, two permanent magnets 15, electrode 16, swirl ring 17, nozzle 18, nozzle holder 19 and the protective shield 20.
  • the torch assembly 2_ and its individual parts have a substantially rotating cylindrical shape through which the longitudinal axis 100 passes in the middle.
  • the torch assembly 2_ is designed in such a way that the cathode 12 is connected to the first pole of the electrical circuit forming the pilot arc, and to the first pole of the electrical circuit forming the plasma arc. Furthermore, plasma gas is introduced into the cathode 12 and flows through the passages in the torch assembly 2_into the plasma chamber 108.
  • the cathode 12 is made of copper alloy CuZn40Pb2.
  • the contact element 14 abuts the cathode 12 in the lower part.
  • the insulator 11 is pressed on top of the cathode 12 and electrically insulates the cathode 12 from the anode 10.
  • the insulator 11 is made of an electrically insulating material.
  • the anode 10 connected to the second pole of the electrical circuit forming the pilot arc is pressed onto the insulator 11.
  • the anode 10 is shaped to mount the nozzle holder 19.
  • the anode 10 is made of copper alloy CuZn40Pb2.
  • the anode 10, insulator 11 and cathode 12 do not wear out during use of the torch assembly 2, so they are not replacement parts of the torch assembly 2.
  • the other parts of the torch assembly 2 wear out during use. Worn parts are replaced with new ones.
  • the replacement part of the torch assembly 2 is the electrical contact 13, which is inserted into a hole in the upper part of the electrode 16.
  • the electrical contact 13 is made of a copper alloy, and is galvanically plated with a layer of gold.
  • the permanent magnet 15 is pressed onto the upper part of the electrode 16.
  • the contact element 14, which is made of an aluminum alloy, is inserted into the upper part of the electrode 16 and the electrical contact 13.
  • the second permanent magnet 15, which is a part of the torch assembly 2 is pressed onto the contact element 14.
  • the second permanent magnet 15 is pressed onto the contact element 14 so that the two permanent magnets face each other by the same magnetic pole.
  • the permanent magnets 15 repel each other in the space 102 and push the contact element 14 away from the electrode 16.
  • the neodymium magnets which repel each other in the space 102 with a force of 8 to 10 N. From the cathode 12 the pilot arc passes over the mutual contact surfaces to the contact element 14.
  • the contact element 14 is connected to the electrode 16 by the electrical contact 13 in such a way that the pilot arc passes from the contact element 14 by means of the electrical contact 13 to the electrode 16 without interruptions.
  • the contact element 14 is fixed in the electrode 16 and the electrical contact 13 so as to be movable in the longitudinal axis 100, but the repulsive force of the permanent magnets 15 acting on it does not release it from the electrode 16.
  • the upper face of the contact element 14 rests freely on the lower face of the cathode 12.
  • the electrode 16 in the lower part comprises the emissive insert 109.
  • the electrode 16 is made of copper, the emissive insert 109 is made of hafnium.
  • the electrode 16 is pushed down by the mutual repulsive force of permanent magnets 15 towards the nozzle 18, which it touches in the point 101 of direct contact.
  • the swirl ring 17 abuts the lower part of the cathode 12 and comprises at least one passage 103 for the supply of plasma gas to the plasma chamber 108.
  • the plasma chamber 108 is an inner confined space between the surface of the electrode 16, the nozzle 18 and the swirl ring 17.
  • the nozzle 18 abuts the lower part of the swirl ring 17 and has an opening 106 in the axis 100 for the passage of plasma gas towards the material to be cut.
  • the nozzle holder 19 is slid onto the nozzle 18, and fixes the electrode 16, nozzle 18 and the swirl ring 17 firmly in the torch assembly 2 by means of a detachable connection to the anode 10.
  • the electrode 16, nozzle 18 and the swirl ring 17 are fixed in the torch assembly 2 by means of the nozzle holder 19.
  • the protective shield 20 is fastened to the nozzle holder 19 in its lower part by means of a detachable connection. The protective shield 20 protects the nozzle 18 from damage from sprayed molten material.
  • Fig. 7 generally shows a longitudinal section of the contact start torch assembly 3 according to the third embodiment of the invention in the position of contact 101 between the electrode 16 and the nozzle 18.
  • the electrode 16 and the nozzle 18 are in electrical contact with each other.
  • the torch assembly3 consists, inter alia, of the anode 10, insulator 11, cathode 12 electrical contact 13, two permanent magnets 15, electrode 16, swirl ring 17, nozzle 18, nozzle holder 19 and the protective shield 20.
  • the torch assembly 3 and its individual parts have a substantially rotating cylindrical shape, through which the longitudinal axis 100 passes in the middle.
  • the torch assembly 3 is designed such that the cathode 12 connects to the first pole of the electrical circuit forming the pilot arc, and to the first pole of the electrical circuit forming the plasma arc.
  • the plasma gas is introduced into the cathode 12 and flows through the passages in the torch assembly 3 into the plasma chamber 108.
  • the plasma chamber 108 is an inner confined space between the surface of the electrode 16, the nozzle 18 and the swirl ring 17.
  • the cathode 12 is made of copper alloy CuZn40Pb2.
  • a permanent magnet 15 is pressed into the cathode 12.
  • the insulator 11 is pressed on top of the cathode 12 and electrically insulates the cathode 12 from the anode 10.
  • the insulator 11 is made of an electrically insulating material.
  • the anode 10 connected to the second pole of the electrical circuit forming the pilot arc is pressed onto the insulator 11.
  • the anode 10 is shaped to mount the nozzle holder 19.
  • the anode 10 is made of copper alloy CuZn40Pb2.
  • the anode 10, the insulator 11 and the cathode 12 with the permanent magnet 15 do not wear out during use of the torch assembly 3, so they are not replacement parts of the torch assembly 3.
  • the other parts of the torch assembly 3 wear out during use. Worn parts are replaced with new ones.
  • the replacement part of the torch assembly 3 is the electrical contact 13, which is mounted on the protrusion 110 in the lower part of the cathode 12.
  • the electrical contact 13 that is mounted on the protrusion 110 is made of a copper alloy.
  • the electrical contact 13 is galvanically plated with a layer of gold to improve its electrical properties and extend its service life.
  • the electrode 16 is slid onto the protrusion 110 and the electrical contact 13.
  • the second permanent magnet 15, which is a part of the torch assembly 3, is pressed on the electrode 16.
  • the second permanent magnet 15 is pressed on the upper part of the electrode 16 so that the two permanent magnets face each other by the same magnetic pole.
  • the permanent magnets 15 in the space 102 repel, and push the electrode 16 away from the cathode 12.
  • the neodymium magnets which repel each other in the space 102 with a force of 8 to 10 N.
  • the electrode 16 is slid onto the protrusion 110 of the cathode 12 and the electrical contact 13 so as to be movable in the longitudinal axis 100.
  • the electrode 16 in the lower part comprises the emissive insert 109.
  • the electrode 16 is made of copper, the emissive insert 109 is made of hafnium.
  • the electrode 16 is pushed down by the mutual repulsive force of permanent magnets 15 in the space 102 towards the nozzle 18, which it touches in the point 101 of direct contact.
  • the swirl ring 17 abuts the lower part of the cathode 12 and comprises at least one passage 103 for the supply of plasma gas to the plasma chamber 108.
  • the nozzle 18 abuts the lower part of the swirl ring 17 and has an opening 106 in the axis 100 for the passage of plasma gas towards the material to be cut.
  • the nozzle holder 19 is slid onto the nozzle 18, and fixes the electrode 16, nozzle 18 and the swirl ring 17 firmly in the torch assembly 3 by means of a detachable connection to the anode 10.
  • the electrode 16, the nozzle 18 and the swirl ring 17 are fixed in the torch assembly 3 by means of the nozzle holder 19.
  • the protective shield 20 is fastened to the nozzle holder 19 in its lower part by means of a detachable connection. The protective shield 20 protects the nozzle 18 from damage from sprayed molten material.
  • the torch assembly design according to the fourth embodiment of the invention which also comprises two permanent magnets 15, is possible.
  • the permanent magnets 15 are turned towards each other by the opposite polarity, and are attracted to each other.
  • the design of the torch assembly is changed. This torch is designed so that an attractive magnetic force between the permanent magnets 15 is used to push the electrode 16 against the nozzle 18.
  • the torch assembly according to the fifth embodiment of the invention which comprises only one permanent magnet L5.
  • the second permanent magnet JL5 is replaced by a metal magnetic portion, and the design of the torch assembly is changed.
  • This torch is designed so that an attractive magnetic force between the permanent magnet 15 and the metal magnetic portion is used to push the electrode 16 against the nozzle 18.
  • protective shield 100 longitudinal axis 101 point of direct contact (of the electrode and nozzle) 102 space 103 passage (for plasma gas in the swirl ring) 104 connection of surfaces 105 contact surface 106 opening (in plasma nozzle) 107 inner shape 108 plasma chamber 109 emissive insertllO protrusion

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Plasma Technology (AREA)

Abstract

The plasma arc torch assembly (1) of the invention comprises an anode (10), an insulator (11), a cathode (12), an electrode (16), a swirl ring (17), a nozzle (18), a nozzle holder (19) and a protective shield (20), the electrode (16) being movably arranged between a first position in which the electrode (16) is in electrical contact with the nozzle (18) and a second position in which the electrode (16) is spaced from the nozzle (18). The electrode (16) is movable relative to the cathode (12), wherein the cathode (12) and the electrode (16) are in electrical contact with each other in all mutual positions; the cathode (12) and the electrode (16) being provided with permanent magnets (15), wherein the permanent magnet (15) of the cathode (12) and the permanent magnet (15) of the electrode (16) face each other by coincident poles to create a magnetic field pushing the electrode (16) against the nozzle (18).

Description

A plasma arc torch assembly with contact start
Field of the Invention
The invention relates to the design of a plasma arc torch with contact start (touch ignition). Specifically, the body of the torch and its replacement parts, enabling the contact start of the pilot arc.
State of the Art
Plasma arc torches with contact start are manufactured and used for manual and machine cutting, grooving and marking of metal materials. The plasma arc torches with contact start are also called plasma arc torches with touch ignition. These torch assemblies have a rotating cylindrical shape, through the middle of which a longitudinal axis passes in the axial direction. The basic parts of the torch assembly are the torch body, electrode, nozzle, swirl ring, nozzle holder and protective shield. The basic parts of the plasma torch body are cathode, insulator and anode. Further, the torch assembly includes a flexible member that is part of the torch body or consumable replacement parts of the torch assembly. The consumable replacement parts are electrode, nozzle, swirl ring, nozzle holder and protective shield.
Plasma torches with contact start are designed so that after their assembly the electrode and nozzle are in physical and electrical contact. A plasma chamber is formed between the electrode, the swirl ring and the nozzle. After switching on, the electric current is fed to the electrode and the nozzle, and the plasma gas flows into the plasma chamber.
The gas pressure in the plasma chamber causes the electrode and nozzle to move away in the longitudinal axis. Due to the short circuit between the electrode and the nozzle, a pilot plasma arc is created after their separation. The pilot arc ionizes the flowing plasma gas. The ionized plasma gas flows through an opening in the nozzle towards the material to be cut. An electrically conductive connection is formed between the electrode and the material to be cut through the ionized gas. A transferred plasma arc is created between the electrode and the material to be cut, a positive pole is connected to the material to be cut, and then the pilot plasma arc between the electrode and the nozzle is terminated.
Existing contact start plasma torches are designed so that the pressurized plasma gas supplied to the plasma chamber breaks the electrical contact between the electrode and the nozzle. Either the plasma gas pressure moves the moving nozzle away from the stationary electrode or the moving electrode away from the stationary nozzle. Another possibility is that the nozzle and the electrode are stationary, and another part of the plasma torch moves, which breaks the direct electrical contact between the electrode and the nozzle. This function is enabled by the flexible electrically conductive part in the plasma torch. The flexible member is usually a steel compression spring. When the nozzle moves, the flexible member is between the nozzle and the nozzle holder. When the electrode moves, the flexible member is usually between the electrode and the cathode. Furthermore, the flexible member can be located in another part of the plasma torch, and allows the electrode to move away from the nozzle, or only to break the direct electrical contact between the electrode and the nozzle. The state of the art is described in U.S. Patents nos. 4791268, US 6 969 819, US 7 435 925, US 8035 055, US 8 089 025, US 8 115 136, US 8541 712, CZ 304595 and EP 3563 644. In all prior art plasma arc torch designs, an electrically conductive flexible member is always present in the torch assembly. The mechanical properties of the flexible member allow the electrical contact between the electrode and the nozzle to be broken. The electrical properties of the flexible member allow the pilot arc to pass through it. The flexible member is loaded with at least a portion of the current passing through the pilot arc. Frequent starting of the pilot arc damages the flexible member. It may even melt. This cannot be solved by increasing the cross-section of the flexible member, because its compressive strength increases so much that the plasma gas pressure cannot over-press it.
This problem is partly solved, for example, by the design of plasma arc torch with contact start according to U.S. Patents Nos. 8035 055 and 8 115 136, where the flexible member is part of the electrode. The electrode is a consumable replacement part of the torch assembly. With the new electrode, a new flexible member is used in the torch assembly. The disadvantage of this design is that it increases the cost of the electrode.
Summary of the Invention
Thus, there is a need for a contact start plasma arc torch assembly without a flexible electrically conductive member. The design, which optimizes the operation of the torch assembly without premature failure, will be simple for the torch body as well as for all replacement parts of the torch assembly. The present invention relates to a contact start plasma arc torch assembly. This torch assembly consists of at least the following parts: an electrode that contains an emissive insert; a nozzle that contains an opening for the passage of plasma gas; a swirl ring that contains a plasma gas passage; a nozzle holder that is designed to secure the nozzle, swirl ring and electrode into the torch assembly; a protective shield adapted to be attached to the nozzle holder; a cathode, which is connected to the first pole of the electrical circuit forming the pilot arc; an anode, which is connected to the second pole of the electrical circuit forming the pilot arc; an insulator, which is between the cathode and the anode, and electrically insulates them; an electrical contact through which the entire current of the pilot arc passes; two permanent magnets, or one permanent magnet and a magnetic member which pushes the electrode and the nozzle together, and at the same time allows them to move away from each other.
The electrode is movably arranged between a first position in which the electrode is in electrical contact with the nozzle and a second position in which the electrode is spaced from the nozzle.
Thus, the plasma arc torch assembly is formed so that after assembly the electrode and nozzle are in electrical contact, wherein the plasma arc torch assembly is designed to allow electrical contact between the electrode and the nozzle to be broken by plasma gas supplied to the plasma chamber under pressure. According to the invention, the electrode is movable relative to the cathode, wherein the cathode and the electrode are in electrical contact with each other in all mutual positions.
The contact start plasma arc torch assembly of the present invention newly includes two permanent magnets compared to the prior art. These permanent magnets are oriented towards each other by the same magnetic poles. By this, they repel each other. Their repulsive force is used to press the electrode against the nozzle. Just as the force of a compression spring is used in the prior art. Electric permanent magnets press the electrode against the nozzle, and at the same time allow the electrode to move away from the nozzle by the force of the plasma gas in the plasma chamber acting on the surface of the electrode. The advantage of the magnetic force between permanent magnets is that it is non-contact. No mechanical component is damaged, as in the case with the compression spring.
The contact between the fixed part of the torch assembly connected to the first pole of the electrical circuit forming the pilot arc and the movable part of the torch assembly which further conducts electric current towards the emissive insert in the electrode, according to a preferred embodiment of the invention provides electrical contact between the two parts. The electrical contact can be formed as a flexible metal element interposed between the fixed and movable parts through which the pilot arc passes and conducts all the current of the pilot arc. The electrical contact conducts current of the pilot arc as long as it is turned on.
This design of the plasma arc torch with contact start allows the operation of the torch assembly without premature failure, is simple for the torch body, as well as for all replacement parts of the torch assembly. Brief description of the Drawings
The design of the contact start plasma arc torch assembly according to the invention is shown in more detail in the drawings
Fig. 1 shows a longitudinal section of the contact start plasma arc torch assembly according to the first embodiment of the invention in the position of contact between the electrode and the nozzle.
Fig. 2 shows a longitudinal section of the contact start plasma arc torch assembly according to the first embodiment of the invention in the position when the electrode and the nozzle are away from each other.
Fig. 3 shows a longitudinal detailed section of the contact start plasma arc torch assembly according to the first embodiment of the invention in the position of contact between the electrode and the nozzle.
Fig. 4 shows a longitudinal detailed section of the contact start plasma arc torch assembly according to the first embodiment of the invention in the position when the electrode and the nozzle are away from each other,
Fig. 5 shows a longitudinal detailed section of the cathode, a moving part of the cathode and the electrical contact according to the first embodiment of the invention,
Fig. 6 shows a longitudinal section of the contact start plasma arc torch assembly according to the second embodiment of the invention in the position of contact between the electrode and the nozzle..
Fig. 7 shows a longitudinal section of the contact start plasma arc torch assembly according to the third embodiment of the invention in the position of contact between the electrode and the nozzle. Examples of embodiments
The present invention will now be described in more detail by way of examples of embodiments with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The invention may be embodied in other different methods and is not limited to the embodiments set forth herein.
Fig. 1 generally shows a longitudinal section of the contact start torch assembly 1 according to the first embodiment of the invention in the position of contact 101 between an electrode 16 and a nozzle 18. The electrode 16 and the nozzle 18 are in electrical contact with each other. The torch assembly 1 consists, inter alia, of an anode 10, an insulator 11, a cathode 12, an electrical contact 13, a contact element 14, two permanent magnets 15, an electrode 16, a swirl ring 17, a nozzle 18, a nozzle holder 19 and a protective shield 20. The torch assembly 1 and its individual parts have a substantially rotating cylindrical shape, through which a longitudinal axis 100 passes in the middle. The torch assembly 1 is designed so that the cathode 12 connects to the first pole of the electrical circuit forming the pilot arc, and to the first pole of the electrical circuit forming the plasma arc. Furthermore, plasma gas is introduced into the cathode 12 and flows through the passages in the torch assembly 1 into a plasma chamber 108. The cathode 12 is made of copper alloy CuZn40Pb2. At the bottom, a permanent magnet 15 is pressed into the cathode 12. The insulator 11 is pressed on top of the cathode 12 and electrically insulates the cathode 12 from the anode 10. The insulator 11 is made of an electrically insulating material. The anode 10 is pressed onto the insulator 11 and connects to the second pole of the electrical circuit forming the pilot arc. In the lower part, the anode 10 is shaped to mount the nozzle holder 19. The anode 10 is made of copper alloy CuZn40Pb2. The anode 10, the insulator 11 and the cathode 12 with the permanent magnet 15 do not wear out during use of the torch assembly 1, so they are not replacement parts of the torch assembly 1. The other parts of the torch assembly 1 wear out during use. Worn parts are replaced with new ones. The replacement part of the torch assembly 1 is the electrical contact 13, which is inserted into a hole in the lower part of the cathode 12. The electrical contact 13 is made of a copper alloy, and is galvanically plated with a layer of gold. The contact element 14, which is made of the copper alloy CuZn20Pb2 and is galvanically plated with a layer of nickel, is inserted into the cathode 12 and the electrical contact 13. The second permanent magnet 15 is pressed onto the contact element 14, which is a part of the torch assembly 1. The second permanent magnet 15 is pressed onto the contact element 14 so that the two permanent magnets face each other by the same magnetic pole. As a result, the permanent magnets 15 repel each other in the space 102 and push the contact element 14 away from the cathode 12. In the torch assembly 1 we used the neodymium magnets which repel each other in the space 102 with a force of 8 to 10 N. The contact element 14 is fixed in the cathode 12 and the electrical contact 13 so that it is movable in the longitudinal axis 100 but the repulsive force of the permanent magnets 15 acting on it will not release it from the cathode 12. The electrode 16, which comprises the emissive insert 109 in the lower part, rests freely on the lower face of the contact element 14. The electrode 16 is made of copper, the emissive insert 109 is made of hafnium. The contact element 14 pushes the electrode 16 down towards the nozzle 18, which it touches in the point 101 of direct contact. The swirl ring 17 abuts the lower part of the cathode 12 and comprises at least one passage 103 for the supply of plasma gas to the plasma chamber 108. The plasma chamber 108 is an inner confined space between the surface of the electrode 16, the nozzle 18 and the swirl ring 17. The nozzle 18 abuts the lower part of the swirl ring 17 and has an opening 106 in the axis 100 for the passage of plasma gas towards the material to be cut. The nozzle holder 19 is slid onto the nozzle 18, and fixes the electrode 16, nozzle 18 and the swirl ring 17 firmly in the torch assembly by me an of a detachable connection to the anode 10. The electrode 16, the nozzle 18 and the swirl ring 17 are secured in the torch assembly 1 by means of the nozzle holder 19. The protective shield 20 is fastened to the nozzle holder 19 in its lower part by means of a detachable connection. The protective shield 20 protects the nozzle 18 from damage from sprayed molten material.
Fig. 2 generally shows a longitudinal section of the contact start torch assembly 1 according to the first embodiment of the invention in the position where the electrode 16 is axially moved away from the nozzle 18 by the pressure of gas in the plasma chamber 108, in the longitudinal axis 100. The electrode 16 in the lower part comprises the emissive insert 109. The electrode 16 together with the contact element 14 is pressed against the cathode 12. The connection 104 of surfaces through which the electric current from the cathode 12 passes to the contact element 14 takes place. From the contact element 14, the electric current passes to the electrode 16. The plasma arc passes from the electrode 16 through the opening 106 in the nozzle 18 to the material to be cut. The torch assembly 1 in Fig. 2 consists of the same parts as in Fig. 1; namely the anode 10, insulator 11, cathode 12, electrical contact 13, contact element 14, two permanent magnets 15, electrode 16, nozzle 18, nozzle holder 19, protective shield 20 and swirl ring 17, which comprises at least one passage 103 for supplying plasma gas to the plasma chamber 108. Fig. 3 shows a detail of a longitudinal section of parts of the contact start torch assembly 1 according to the first embodiment of the invention in the position where the contact element 14 is pushed away from the cathode 12 due to the mutual repulsive force of the permanent magnets 15 in the space 102. The contact element 14 is connected to the cathode 12 by the electrical contact 13 in such a way that the pilot arc passes from the cathode 12 by means of the electrical contact 13 to the contact element 14 without interruptions. Fig. 3 shows a detail of the torch assembly 1 shown in Fig.l. It shows the cathode 12, the electrical contact 13, the contact element 14 and the permanent magnet 15 fixed in the cathode 12 and the permanent magnet 15 mounted on the contact element 14. All of the parts shown have a substantially rotating cylindrical shape through which the longitudinal axis 100 passes in the middle.
Fig. 4 shows a detail of a longitudinal section of parts of the contact start torch assembly 1 according to the first embodiment of the invention in the position where the contact element 14 is pushed to the cathode 12 by the pressure of gas in the plasma chamber 108. The connection 104 of surfaces through which the electric current from the cathode 12 passes to the contact element 14 takes place. Fig. 4 shows a detail of the torch assembly 1 shown in Fig.2. It shows the cathode 12, the electrical contact 13, the contact element 14 and the permanent magnet 15 fixed in the cathode 12 and the permanent magnet 15 mounted on the contact element 14. All of the parts shown have a substantially rotating cylindrical shape through which the longitudinal axis 100 passes in the middle.
Fig. 5 shows a detail of a longitudinal section of the cathode 12, the electrical contact 13, the contact element 14, the permanent magnet 15 fixed in the cathode 12 and the permanent magnet 15 mounted on the contact element 14 The individual parts shown have a substantially rotating cylindrical shape, through which the longitudinal axis 100 passes in the middle. The electrical contact 13 and the contact element 14 are shown separately before the electrical contact 13 is inserted into an inner shape 107 in the cathode 12. Subsequently, the contact element 14 is inserted into the inner shape 107 so that the electrical contact 13 abuts the contact surface 105. Fig. 5 shows the same cathode 12 electrical contact 13, contact element 14, the permanent magnet 15 fixed in the cathode 12 and the permanent magnet 15 mounted on the contact element 14 as shown in Figs. 1, 2, 3 and 4.
Fig. 6 generally shows a longitudinal section of the contact start torch assembly 2_ according to the second embodiment of the invention in the position of contact 101 between the electrode 16 and the nozzle 18. The electrode 16 and the nozzle 18 are in electrical contact with each other. The torch assembly 2_consists, inter alia, of the anode 10, insulator 11, cathode 12 electrical contact 13, contact element 14, two permanent magnets 15, electrode 16, swirl ring 17, nozzle 18, nozzle holder 19 and the protective shield 20. The torch assembly 2_ and its individual parts have a substantially rotating cylindrical shape through which the longitudinal axis 100 passes in the middle. The torch assembly 2_ is designed in such a way that the cathode 12 is connected to the first pole of the electrical circuit forming the pilot arc, and to the first pole of the electrical circuit forming the plasma arc. Furthermore, plasma gas is introduced into the cathode 12 and flows through the passages in the torch assembly 2_into the plasma chamber 108. The cathode 12 is made of copper alloy CuZn40Pb2. The contact element 14 abuts the cathode 12 in the lower part. The insulator 11 is pressed on top of the cathode 12 and electrically insulates the cathode 12 from the anode 10. The insulator 11 is made of an electrically insulating material. The anode 10 connected to the second pole of the electrical circuit forming the pilot arc is pressed onto the insulator 11. In the lower part, the anode 10 is shaped to mount the nozzle holder 19. The anode 10 is made of copper alloy CuZn40Pb2. The anode 10, insulator 11 and cathode 12 do not wear out during use of the torch assembly 2, so they are not replacement parts of the torch assembly 2. The other parts of the torch assembly 2 wear out during use. Worn parts are replaced with new ones. The replacement part of the torch assembly 2 is the electrical contact 13, which is inserted into a hole in the upper part of the electrode 16. The electrical contact 13 is made of a copper alloy, and is galvanically plated with a layer of gold. The permanent magnet 15 is pressed onto the upper part of the electrode 16. The contact element 14, which is made of an aluminum alloy, is inserted into the upper part of the electrode 16 and the electrical contact 13. The second permanent magnet 15, which is a part of the torch assembly 2, is pressed onto the contact element 14. The second permanent magnet 15 is pressed onto the contact element 14 so that the two permanent magnets face each other by the same magnetic pole. As a result, the permanent magnets 15 repel each other in the space 102 and push the contact element 14 away from the electrode 16. In the torch assembly 2 we used the neodymium magnets which repel each other in the space 102 with a force of 8 to 10 N. From the cathode 12 the pilot arc passes over the mutual contact surfaces to the contact element 14. The contact element 14 is connected to the electrode 16 by the electrical contact 13 in such a way that the pilot arc passes from the contact element 14 by means of the electrical contact 13 to the electrode 16 without interruptions. The contact element 14 is fixed in the electrode 16 and the electrical contact 13 so as to be movable in the longitudinal axis 100, but the repulsive force of the permanent magnets 15 acting on it does not release it from the electrode 16. The upper face of the contact element 14 rests freely on the lower face of the cathode 12. The electrode 16 in the lower part comprises the emissive insert 109. The electrode 16 is made of copper, the emissive insert 109 is made of hafnium. The electrode 16 is pushed down by the mutual repulsive force of permanent magnets 15 towards the nozzle 18, which it touches in the point 101 of direct contact. The swirl ring 17 abuts the lower part of the cathode 12 and comprises at least one passage 103 for the supply of plasma gas to the plasma chamber 108. The plasma chamber 108 is an inner confined space between the surface of the electrode 16, the nozzle 18 and the swirl ring 17. The nozzle 18 abuts the lower part of the swirl ring 17 and has an opening 106 in the axis 100 for the passage of plasma gas towards the material to be cut. The nozzle holder 19 is slid onto the nozzle 18, and fixes the electrode 16, nozzle 18 and the swirl ring 17 firmly in the torch assembly 2 by means of a detachable connection to the anode 10. The electrode 16, nozzle 18 and the swirl ring 17 are fixed in the torch assembly 2 by means of the nozzle holder 19. The protective shield 20 is fastened to the nozzle holder 19 in its lower part by means of a detachable connection. The protective shield 20 protects the nozzle 18 from damage from sprayed molten material.
Fig. 7 generally shows a longitudinal section of the contact start torch assembly 3 according to the third embodiment of the invention in the position of contact 101 between the electrode 16 and the nozzle 18. The electrode 16 and the nozzle 18 are in electrical contact with each other. The torch assembly3 consists, inter alia, of the anode 10, insulator 11, cathode 12 electrical contact 13, two permanent magnets 15, electrode 16, swirl ring 17, nozzle 18, nozzle holder 19 and the protective shield 20. The torch assembly 3 and its individual parts have a substantially rotating cylindrical shape, through which the longitudinal axis 100 passes in the middle. The torch assembly 3 is designed such that the cathode 12 connects to the first pole of the electrical circuit forming the pilot arc, and to the first pole of the electrical circuit forming the plasma arc. Furthermore, the plasma gas is introduced into the cathode 12 and flows through the passages in the torch assembly 3 into the plasma chamber 108. The plasma chamber 108 is an inner confined space between the surface of the electrode 16, the nozzle 18 and the swirl ring 17. The cathode 12 is made of copper alloy CuZn40Pb2. At the bottom, a permanent magnet 15 is pressed into the cathode 12. Furthermore, there is a protrusion 110 on the lower part of the cathode 12. The insulator 11 is pressed on top of the cathode 12 and electrically insulates the cathode 12 from the anode 10. The insulator 11 is made of an electrically insulating material. The anode 10 connected to the second pole of the electrical circuit forming the pilot arc is pressed onto the insulator 11. In the lower part, the anode 10 is shaped to mount the nozzle holder 19. The anode 10 is made of copper alloy CuZn40Pb2. The anode 10, the insulator 11 and the cathode 12 with the permanent magnet 15 do not wear out during use of the torch assembly 3, so they are not replacement parts of the torch assembly 3. The other parts of the torch assembly 3 wear out during use. Worn parts are replaced with new ones. The replacement part of the torch assembly 3 is the electrical contact 13, which is mounted on the protrusion 110 in the lower part of the cathode 12. The electrical contact 13 that is mounted on the protrusion 110 is made of a copper alloy. The electrical contact 13 is galvanically plated with a layer of gold to improve its electrical properties and extend its service life. The electrode 16 is slid onto the protrusion 110 and the electrical contact 13. The second permanent magnet 15, which is a part of the torch assembly 3, is pressed on the electrode 16. The second permanent magnet 15 is pressed on the upper part of the electrode 16 so that the two permanent magnets face each other by the same magnetic pole. As a result, the permanent magnets 15 in the space 102 repel, and push the electrode 16 away from the cathode 12. In the torch assembly 3 we used the neodymium magnets which repel each other in the space 102 with a force of 8 to 10 N. The electrode 16 is slid onto the protrusion 110 of the cathode 12 and the electrical contact 13 so as to be movable in the longitudinal axis 100. The electrode 16 in the lower part comprises the emissive insert 109. The electrode 16 is made of copper, the emissive insert 109 is made of hafnium. The electrode 16 is pushed down by the mutual repulsive force of permanent magnets 15 in the space 102 towards the nozzle 18, which it touches in the point 101 of direct contact. The swirl ring 17 abuts the lower part of the cathode 12 and comprises at least one passage 103 for the supply of plasma gas to the plasma chamber 108. The nozzle 18 abuts the lower part of the swirl ring 17 and has an opening 106 in the axis 100 for the passage of plasma gas towards the material to be cut. The nozzle holder 19 is slid onto the nozzle 18, and fixes the electrode 16, nozzle 18 and the swirl ring 17 firmly in the torch assembly 3 by means of a detachable connection to the anode 10. The electrode 16, the nozzle 18 and the swirl ring 17 are fixed in the torch assembly 3 by means of the nozzle holder 19. The protective shield 20 is fastened to the nozzle holder 19 in its lower part by means of a detachable connection. The protective shield 20 protects the nozzle 18 from damage from sprayed molten material.
In general, the torch assembly design according to the fourth embodiment of the invention, which also comprises two permanent magnets 15, is possible. The permanent magnets 15 are turned towards each other by the opposite polarity, and are attracted to each other. The design of the torch assembly is changed. This torch is designed so that an attractive magnetic force between the permanent magnets 15 is used to push the electrode 16 against the nozzle 18.
Furthermore, it is generally possible to design the torch assembly according to the fifth embodiment of the invention, which comprises only one permanent magnet L5. The second permanent magnet JL5 is replaced by a metal magnetic portion, and the design of the torch assembly is changed. This torch is designed so that an attractive magnetic force between the permanent magnet 15 and the metal magnetic portion is used to push the electrode 16 against the nozzle 18.
Reference Signs List
1 torch assembly (according to the first embodiment of the invention)
2 torch assembly (according to the second embodiment of the invention)
3 torch assembly (according to the third embodiment of the invention) 10 anode
11 insulator
12 cathode
13 electrical contact 14 contact element
15 permanent magnet 16 electrode 17 swirl ring 18 nozzle
19 nozzle holder
20 protective shield 100 longitudinal axis 101 point of direct contact (of the electrode and nozzle) 102 space 103 passage (for plasma gas in the swirl ring) 104 connection of surfaces 105 contact surface 106 opening (in plasma nozzle) 107 inner shape 108 plasma chamber 109 emissive insertllO protrusion

Claims

Patent Claims
1. A plasma arc torch assembly (1) comprising an anode (10), an insulator (11), a cathode (12), an electrode (16), a swirl ring (17), a nozzle (18), a nozzle holder (19) and a protective shield (20), wherein the electrode (16) is movably arranged between a first position in which the electrode (16) is in electrical contact with the nozzle (18) and a second position in which the electrode (16) is spaced from the nozzle (18), characterized in that the electrode (16) is movable relative to the cathode (12), wherein the cathode (12) and the electrode (16) are in electrical contact with each other in all mutual positions, wherein the cathode (12) and the electrode (16) are equipped with permanent magnets (15), wherein the permanent magnet (15) of the cathode (12) and the permanent magnet (15) of the electrode (16) face each other by coincident poles to create a magnetic field pushing the electrode (16) against the nozzle (18).
2. The plasma arc torch assembly (1) according to claim 1, characterized in that the permanent magnet (15) is a neodymium, samarium-cobalt, AlNiCo or ferrite magnet.
3. The plasma arc torch assembly (1) according to claim 1 or 2, characterized in that the cathode (12) is partially inserted into the electrode (16) to make electrical contact between the cathode (12) and the electrode (16).
4. The plasma arc torch assembly (1) according to claim 1 or 2, characterized in that the electrode (16) is partially inserted into the cathode (12) to make electrical contact between the cathode (12) and the electrode (16).
5. The plasma arc torch assembly (1) according to claim 3 or 4, characterized in that a contact element (14) is located between the cathode (12) and the electrode (16).
6. The plasma arc torch assembly (1) according to claim 5, characterized in that the contact element (14) is provided with a permanent magnet (15), wherein the second permanent magnet (15) is on the cathode (12) or electrode (16), wherein to create a magnetic field pushing the electrode (16) against the nozzle (18), the permanent magnets (15) face each other with coincident poles.
7. The plasma arc torch assembly (1) according to claim 5 or 6, characterized in that the contact element (14) is coated with a layer of nickel or chromium.
8. The plasma arc torch assembly (1) according to any one of the preceding claims, characterized in that at the point of mutual electrical contact between the cathode (12) and the electrode (16) an electrical contact (13) is arranged, which is coated with a layer of silver, gold, platinum or palladium.
9. The plasma arc torch assembly (1) according to claims 1 to 7, characterized in that at the point of mutual electrical contact between the cathode (12) and the contact element (14), an electrical contact (13) is arranged which is coated with a layer of silver, gold, platinum or palladium.
10. The plasma arc torch assembly (1) according to claims 1 to 7, characterized in that at the point of mutual electrical contact between the electrode (16) and the contact element (14) an electrical contact (13) is arranged, which is coated with a layer of silver, gold, platinum or palladium.
PCT/CZ2020/050099 2019-12-30 2020-12-23 Plasma arc torch assembly with contact start WO2021136563A1 (en)

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