SINGLE OR MULTI-PART INSULATING COMPONENT FOR A PLASMA TORCH, PARTICULARLY A PLASMA CUTTING TORCH, AND ASSEMBLIES AND PLASMA TORCHES HAVING THE SAME

Abstract

The invention relates to a single or multipart insulating component for a plasma torch, particularly a plasma cutting torch, for electrical insulation between at least two electrically conductive components of the plasma torch, characterized in that the insulating component consists of an electrically non-conductive and easily thermally conductive material, or at least one part thereof consists of an electrically non-conductive and easily thermally conductive material. The invention further relates to assemblies and plasma torches having the same and to a method for processing, plasma cutting and plasma welding.

Claims

1. A plasma gas conveying part configured to be arranged between an electrode and a nozzle of a plasma torch, the plasma gas conveying part including: a first part, a second part, and a third part; and an inner face adjacent a cavity located in the plasma gas conveying part; wherein at least a portion of the first part and at least a portion of the second part are arranged concentrically to one another; wherein the first part is arranged between the second part and the third part; wherein the third part has the same thermal and electrical properties as the second part; wherein at least a portion of the first part and at least a portion of the third part are arranged concentrically to one another; and wherein at least a portion of the second part and at least a portion of the third part are arranged concentrically to one another.

2. The plasma gas conveying part as claimed in claim 1, characterized in that the first part has at least one surface being aligned with or projecting beyond an immediately adjacent surface of the second part.

3. The plasma gas conveying part of claim 1, wherein: the first part comprises an electrically nonconductive material having a thermal conductivity of at least 40 W/(m*K); and the second part comprises an electrically conductive material having a thermal conductivity of at least 40 W/(m*K).

4. The plasma gas conveying part of claim 3, wherein the electrical conductivity of the first part has an electrical resistivity of 0.1 *cm or less.

5. The plasma gas conveying part as claimed in claim 3, characterized in that the first part has a thermal conductivity of at least 60 W/(m*K).

6. The plasma gas conveying part as claimed in claim 3, characterized in that the first part has an electrical resistivity of at least 10.sup.6 *cm.

7. The plasma gas conveying part as claimed in claim 3, characterized in that the first part is a ceramic or plastics material.

8. The plasma gas conveying part of claim 1, wherein: the first part comprises an electrically nonconductive material having a thermal conductivity of at least 40 W/(m*K); and the second part comprises an electrically nonconductive and thermally nonconductive material.

9. The plasma gas conveying part as claimed in claim 8, characterized in that the second part has a thermal conductivity of at most 1 W/(m*K).

10. The plasma gas conveying part as claimed in claim 1, characterized in that the first part and the second part are connected together in one or a combination of two or more of a form-fitting, a force-fitting or cohesive manner, by adhesive bonding or by a thermal method.

11. The plasma gas conveying part as claimed in claim 1, further comprising at least one opening and/or at least one cutout and/or at least one groove.

13. The plasma gas conveying part as claimed in claim 1, wherein the plasma torch additionally includes a nozzle cap, a nozzle protective cap, and a nozzle protective cap holder.

14. The plasma gas conveying part as claimed in claim 13, wherein the plasma gas conveying part is in direct contact with at least one of the electrode, the nozzle, the nozzle cap, the nozzle protective cap, or the nozzle protective cap holder.

15. The plasma gas conveying part as claimed in claim 1, characterized in that the first part has at least one surface in direct contact with a surface of a component of the plasma torch having an electrical resistivity of at most 0.01 *cm.

16. The plasma gas conveying part as claimed in claim 1, characterized in that the plasma gas conveying part has at least one surface which is in direct contact with a cooling medium during operation.

17. A method for machining a workpiece with a thermal plasma or for plasma cutting or for plasma welding, characterized in that the plasma gas conveying part as claimed in claim 1 is included in a plasma torch used in the machining.

18. The method as claimed in claim 17, characterized in that a laser beam of a laser is coupled into the plasma torch in addition to a plasma jet.

19. The plasma gas conveying part of claim 1, further comprising: an outer contact face in touching contact with an inner contact face of the nozzle; and the inner contact face of the plasma gas conveying part is in touching contact with an outer contact face of the electrode.

20. The plasma gas conveying part of claim 19, wherein: the outer face of the plasma gas conveying part comprises a cylindrical surface; and the inner face of the plasma gas conveying part comprises a cylindrical surface.

21. A plasma gas conveying part configured to be arranged between a nozzle and a nozzle protective cap of a plasma torch, the plasma gas conveying part including: a primary plasma gas conveying part; and a secondary plasma gas conveying part separate from the primary plasma gas conveying part, the secondary plasma gas conveying part comprising: a first part, a second part, and a third part; and an inner face adjacent a cavity located in the secondary plasma gas conveying part; wherein at least a portion of the first part and at least a portion of the second part are arranged concentrically to one another; wherein the first part is arranged between the second part and the third part; wherein the third part has the same thermal and electrical properties as the second part; wherein at least a portion of the first part and at least a portion of the third part are arranged concentrically to one another; and wherein at least a portion of the second part and at least a portion of the third part are arranged concentrically to one another.

22. The plasma gas conveying part of claim 21, wherein: the plasma torch additionally includes a nozzle cap positioned between the nozzle and the nozzle protective cap; and the secondary plasma gas conveying part is arranged between the nozzle cap and the nozzle protective cap.

23. The plasma gas conveying part of claim 21, wherein: the first part comprises an electrically nonconductive material having a thermal conductivity of at least 40 W/(m*K); and the second part comprises an electrically conductive material having a thermal conductivity of at least 40 W/(m*K).

24. The plasma gas conveying part of claim 21, wherein: the first part comprises an electrically nonconductive material having a thermal conductivity of at least 40 W/(m*K); and the second part comprises an electrically nonconductive and thermally nonconductive material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further features and advantages of the invention can be gathered from the appended claims and the following description, in which a number of exemplary embodiments are described by way of the schematic drawings, in which:

[0054] FIG. 1 shows a side view in partial longitudinal section of a plasma torch according to a first particular embodiment of the invention;

[0055] FIG. 2 shows a side view in partial longitudinal section of a plasma torch according to a second particular embodiment of the invention;

[0056] FIG. 3 shows a side view in partial longitudinal section of a plasma torch according to a third particular embodiment of the invention;

[0057] FIG. 4 shows a side view in partial longitudinal section of a plasma torch according to a fourth particular embodiment of the invention;

[0058] FIG. 5 shows a side view in partial longitudinal section of a plasma torch according to a fifth particular embodiment of the invention;

[0059] FIG. 6 shows a side view in partial longitudinal section of a plasma torch according to a sixth particular embodiment of the invention;

[0060] FIG. 7 shows a side view in partial longitudinal section of a plasma torch according to a seventh particular embodiment of the invention;

[0061] FIG. 8 shows a side view in partial longitudinal section of a plasma torch according to an eighth particular embodiment of the invention;

[0062] FIG. 9 shows a side view in partial longitudinal section of a plasma torch according to a ninth particular embodiment of the invention;

[0063] FIGS. 10a and 10b show a view in longitudinal section and a partially sectional side view of an insulating part according to one particular embodiment of the invention;

[0064] FIGS. 11 a and 11 b show a view in longitudinal section and a partially sectional side view of an insulating part according to a further particular embodiment of the invention;

[0065] FIGS. 12a and 12b show a view in longitudinal section and a partially sectional side view of an insulating part according to a further particular embodiment of the invention;

[0066] FIGS. 13a and 13b show a view in longitudinal section and a partially sectional side view of an insulating part according to a further particular embodiment of the invention;

[0067] FIGS. 14a and 14b show a view in longitudinal section and a partially sectional side view of an insulating part according to a further particular embodiment of the invention;

[0068] FIGS. 14c and 14d show views as in FIGS. 14a and 14b, but wherein a part has been omitted;

[0069] FIGS. 15a and 15b show a plan view in partial section and a side view in partial section, respectively, of an insulating part which is or can be used, for example, in the plasma torch in FIGS. 6 to 9;

[0070] FIGS. 16a and 16b show a plan view in partial section and a side view in partial section, respectively, of an insulating part which is or can be used, for example, in the plasma torch in FIGS. 6 to 9;

[0071] FIGS. 17a and 17b show a plan view in partial section and a side view in partial section, respectively, of an insulating part which is or can be used, for example, in the plasma torch in FIGS. 6 to 9;

[0072] FIGS. 18a to 18d show a plan view in partial section and sectional side views of an insulating part according to a further particular embodiment of the present invention;

[0073] FIGS. 19a to 19d show sectional views of an arrangement made up of a nozzle and of an insulating part according to one particular embodiment of the invention;

[0074] FIGS. 20a to 20d show sectional views of an arrangement made up of a nozzle cap and of an insulating part according to one particular embodiment of the present invention;

[0075] FIGS. 21a to 21d show sectional views of an arrangement made up of a nozzle protective cap and of an insulating part according to one particular embodiment of the present invention;

[0076] FIGS. 22a and 22b show views in partial section of an arrangement made up of an electrode and of an insulating part according to one particular embodiment of the present invention; and

[0077] FIG. 23 shows a side view in partial longitudinal section of an arrangement made up of an electrode and of an insulating part according to one particular embodiment of the present invention.

DETAILED DESCRIPTION

[0078] FIG. 1 shows a liquid-cooled plasma cutting torch 1 according to one particular embodiment of the present invention. It comprises an electrode 2, an insulating part, configured as a plasma-gas conveying part 3, for conveying plasma gas PG, and a nozzle 4. The electrode 2 consists of an electrode holder 2.1 and an emission insert 2.2. The electrode holder 2.2 consists of a material with good electrical conductivity and good thermal conductivity, in this case of a metal, for example copper, silver, aluminum or an alloy in which at least one of these metals is contained. The emission insert 2.2 is produced from a material which has a high melting point (>2000 C.). In this case, when non-oxidizing plasma gases (for example argon, hydrogen, nitrogen, helium and mixtures thereof) are used, tungsten is suitable for example, and when oxidizing gases (for example oxygen, air, mixtures thereof, nitrogen/oxygen mixture) are used, hafnium or zirconium are suitable for example. The emission insert 2.2 is introduced into the electrode holder 2.1. The electrode 2 is illustrated here as a flat electrode in which the emission insert 2.2 does not project beyond the surface of the front end of the electrode holder 2.1.

[0079] The electrode 2 projects into the hollow interior space 4.2 of the nozzle 4. The nozzle is screwed by way of a thread 4.20 into a nozzle holder 6 with an internal thread 6.20. Arranged between the nozzle 4 and the electrode 2 is the plasma-gas conveying part 3. Located in the plasma-gas conveying part 3 are bores, openings, grooves and/or cutouts (not illustrated) through which the plasma gas PG flows. By way of a corresponding arrangement, for example with a radial offset and/or an inclination of radially arranged bores with respect to the center line M, the plasma gas PG can be set in rotation. This serves to stabilize the arc and the plasma jet.

[0080] The arc burns between the emission insert 2.2 and a workpiece (not illustrated) and is constricted by a nozzle bore 4.1. The arc itself is already at a high temperature, which is increased even more by its constriction. In this case, temperatures of up to 30 000 K are indicated. For this reason, the electrode 2 and the nozzle 4 are cooled by a cooling medium. A liquid, in the simplest case water, a gas, in the simplest case air, or a mixture thereof, in the simplest case an air/water mixture, which is referred to as an aerosol, can be used as the cooling medium. Liquid cooling is the most effective. Located in an interior space 2.10 of the electrode 2 is a cooling pipe 10 through which the coolant is fed back to the coolant return line WR2 from the coolant feed line WV2, through the coolant space 10.10 toward the electrode 2, into the vicinity of the emission insert 2.2, and through the space which is formed by the outer face of the cooling pipe 10 in the inner face of the electrode 2.

[0081] In this example, the nozzle 4 is cooled indirectly via the nozzle holder 6, to which the coolant is conveyed through a coolant space 6.10 (WV1) and away from which the coolant is conveyed again via a coolant space 6.11 (WR1). The coolant usually flows with a volumetric flow of 1 to 10 l/min. The nozzle 4 and the nozzle holder 6 consist of a metal. As a result of the mechanical contact formed with the aid of the external thread 4.20 of the nozzle 4 and the internal thread 6.20 of the nozzle holder 6, the heat arising in the nozzle 4 is guided into the nozzle holder 6 and dissipated by the flowing cooling medium (WV1, WR1).

[0082] The insulating part configured as a plasma-gas conveying part 3 is formed in one part in this example and consists of an electrically nonconductive material with good thermal conductivity. As a result of such an insulating part being used, electrical insulation is achieved between the electrode 2 and the nozzle 4. This is necessary for operation of the plasma cutting torch 1, specifically the high-voltage striking and the operation of a pilot arc burning between the electrode 2 and the nozzle 4. At the same time, heat is conducted between the electrode 2 and the nozzle 4 from the hotter to the colder component via the insulating part with good thermal conductivity that is configured as a plasma-gas conveying part 3. Additional heat exchange thus occurs via the insulating part. The plasma-gas conveying part 3 is in touching contact with the electrode 2 and the nozzle 4 via contact faces.

[0083] In this exemplary embodiment, a contact face 2.3 is for example a cylindrical outer face of the electrode 2 and a contact face 3.5 is a cylindrical inner face of the plasma-gas conveying part 3. A contact face 3.6 is a cylindrical outer face of the plasma-gas conveying part 3 and a contact face 4.3 is a cylindrical inner face of the nozzle 4. Preferably, a clearance fit with a small clearance, for example H7/h6 according to DIN EN ISO 286, between the cylindrical inner and outer faces is used here in order to realize both the plugging into one another and also good contact and thus low thermal resistance and thus good heat transfer. The heat transfer can be improved by applying thermally conductive paste to these contact faces. (Observation: even if a thermally conductive paste is used, this is still intended to be covered by the expression direct contact.) A fit with a larger clearance, for example H7/g6, can then be used. Furthermore, the nozzle 4 and the plasma-gas conveying part 3 each have a contact face 4.5 and 3.7, here, these being annular faces and in touching contact with one another, here. This is a force-fitting connection between the annular faces, which is realized by screwing the nozzle 4 into the nozzle holder 6.

[0084] On account of the good thermal conductivity, high temperature differences between the nozzle 4 and the electrode 2 can be avoided and mechanical tensions in the plasma cutting torch 1 that are caused thereby can be reduced.

[0085] A ceramic material for example is used here as the electrically nonconductive material with good thermal conductivity. Aluminum nitrite, which, according to DIN 60672, has very good thermal conductivity (about 180 W/(m*K)) and high electrical resistivity (about 10.sup.12 *cm), is particularly suitable.

[0086] FIG. 2 shows a cylindrical plasma cutting torch 1 in which the electrode 2 is cooled directly by coolant. The indirect cooling, shown in FIG. 2, of the nozzle 4 via the nozzle holder 6 is not provided. The nozzle 4 is cooled by heat conduction via an insulating part, configured as a plasma-gas conveying part 3, toward the electrode 2 cooled directly by coolant. As a result of such an insulating part being used, electrical insulation between the electrode 2 and the nozzle 4 is achieved. This is necessary for operation of the plasma cutting torch 1, specifically the high-voltage striking and the operation of the pilot arc burning between the electrode 2 and the nozzle 4. At the same time, heat is conducted between the electrode 2 and the nozzle 4 from the hotter to the colder component via the insulating part with good thermal conductivity that is configured as a plasma-gas conveying part 3. Additional heat exchange thus occurs between the electrode 2 and the nozzle 4 via the plasma-gas conveying part 3. The plasma-gas conveying part 3 is in touching contact with the electrode and the nozzle 4 via contact faces.

[0087] In this exemplary embodiment, a contact face 2.3 is for example a cylindrical outer face of the electrode 2 and a contact face 3.5 is a cylindrical inner face of the plasma-gas conveying part 3. A contact face 3.6 is a cylindrical outer face of the plasma gas conveying part 3 and a contact face 4.3 is a cylindrical inner face of the nozzle 4. Preferably, a clearance fit with a small clearance, for example H7/h6 according to DIN EN ISO 286, between the cylindrical inner and outer faces is used here in order to realize both the plugging into one another and also good contact and thus low thermal resistance and thus good heat transfer. The heat transfer can be improved by applying thermally conductive paste to these contact faces. A fit with a larger clearance, for example H7/g6, can then be used. Furthermore, the nozzle 4 and the plasma-gas conveying part 3 each have a contact face 4.5 and 3.7, respectively, here, these being annular faces and in touching contact with one another, here. This is a force-fitting connection between the annular faces, which is realized by screwing the nozzle 4 into the nozzle holder 6.

[0088] The omission of the indirect cooling for the nozzle 4 results in a considerable simplification of the structure of the plasma cutting torch 1, since the coolant spaces in the nozzle holder 6, which are otherwise necessary in order to convey the coolant to its area of action and away again, are dispensed with. The electrode is cooled as in FIG. 1.

[0089] FIG. 3 shows a plasma cutting torch 1 in which a nozzle 4 is cooled indirectly via a nozzle holder 6, to which the coolant is conveyed through a coolant space 6.10 (WV1) and away from which the coolant is conveyed again via a coolant space 6.11 (WR1). The direct cooling, shown in FIGS. 1 and 2, of the electrode 2 is not provided. The thermal conduction from the electrode 2 to the nozzle 4 takes place via an insulating part, configured as a plasma-gas conveying part 3, with respect to the indirectly coolant-cooled nozzle 4. In this respect, the statements made with regard to FIGS. 1 and 2 apply.

[0090] This results in a considerable simplification of the structure of the plasma torch 1 and of the electrode 2, since the cooling pipe 10 and the coolant spaces 2.10 and 10.10, shown in FIGS. 1 and 2, which are otherwise necessary in order to convey the cooling liquid to its area of action (WV2) and away again (WR2), are dispensed with.

[0091] The plasma cutting torch 1 illustrated in FIG. 4 differs from the plasma cutting torch illustrated in FIG. 1 in that the nozzle 4 is cooled directly by a coolant. To this end, the nozzle 4 is fixed by a nozzle cap 5. An internal thread 5.20 of the nozzle cap 5 is screwed together with an external thread 6.21 of a nozzle holder 6. The outer face of the nozzle 4 and a part of the nozzle holder 6 and also the inner face of the nozzle cap 5 form a coolant space 4.10 through which the coolant, which flows to its area of action (WV1) and back again (WR1) through coolant spaces 6.10 and 6.11 in the nozzle holder 6.

[0092] Arranged between the nozzle 4 and an electrode 2 is an insulating part configured as a plasma-gas conveying part 3. Thus, the same advantages are achieved as were explained in connection with FIG. 1. The heat is transferred between the electrode 2 and the nozzle 4 from the hotter to the colder component via the insulating part with good thermal conductivity that is configured as a plasma-gas conveying part 3. The plasma-gas conveying part 3 is in touching contact with the electrode 2 and the nozzle 4. Thus, mechanical tensions in the plasma cutting torch 1 that are brought about by large temperature differences can be reduced.

[0093] One advantage compared with the plasma cutting torch shown in FIG. 1 is that the directly coolant-cooled nozzle 4 is cooled better than the indirectly cooled nozzle. Since the coolant in this arrangement flows right into the vicinity of the nozzle tip and of a nozzle bore 4.1, where the greatest heating of the nozzle takes place, the cooling effect is particularly great. The coolant space is sealed by O-rings between the nozzle cap 5 and the nozzle 4, between the nozzle cap 5 and the nozzle holder 6 and between the nozzle 4 and the nozzle holder 6.

[0094] The nozzle cap 5, too, is cooled by the coolant which flows through the coolant space 4.10, which is formed by the outer face of the nozzle 4 and the inner face of the nozzle cap 5. The nozzle cap 5 is heated primarily by the radiation of the arc or of the plasma jet and of the heated workpiece.

[0095] However, the structure of the plasma cutting torch 1 is more complicated, since a nozzle cap 5 is additionally required. A liquid, in the simplest case water, is preferably used as the coolant, here.

[0096] FIG. 5 shows a plasma cutting torch 1 which is similar to the plasma cutting torch in FIG. 1 but in which a nozzle protective cap 8 is additionally arranged outside the nozzle 4. Bores 4.1 in the nozzle 4 and 8.1 in the nozzle protective cap 8 are located on a center line M. The inner faces of the nozzle protective cap 8 and of a nozzle protective cap holder 9 form, with the outer faces of the nozzle 4 and of the nozzle holder 6, spaces 8.10 and 9.10 through which a secondary gas SG flows. This secondary gas passes out of the bore in the nozzle protective cap 8.1 and encloses the plasma jet (not illustrated) and ensures a defined atmosphere around the latter. In addition, the secondary gas SG protects the nozzle 4 and the nozzle protective cap 8 from arcs which can form between them and the workpiece. These are referred to as double arcs and can result in damage to the nozzle 4. In particular when piercing the workpiece, the nozzle 4 and the nozzle protective cap 8 are highly stressed by hot molten material splashing up. The secondary gas SG, the volumetric flow of which can be increased during piercing compared with the value during cutting, keeps the material splashing up away from the nozzle 4 and the nozzle protective cap 8 and thus protects them from damage.

[0097] For cooling the electrode 2 and the nozzle 4, the statements made with respect to the plasma cutting torch 1 according to FIG. 1 apply. In principle, direct cooling of only the electrode 2as shown in FIG. 2and indirect cooling of only the nozzle 4as shown in FIG. 3are also possible in a plasma cutting torch 1 with secondary gas. The statements made with respect thereto also apply.

[0098] In the case of the plasma cutting torch 1 shown in FIG. 5, in addition to the electrode 2 and the nozzle 4, the nozzle protective cap 8 also has to be cooled. The nozzle protective cap 8 is heated in particular by the radiation of the arc or of the plasma jet and of the heated workpiece. In particular when piercing the workpiece, the nozzle protective cap 8 is highly thermally stressed and heated by red-hot material splashing up and has to be cooled. Therefore, materials with good thermal conductivity and good electrical conductivity, generally metals, for example silver, copper, aluminum, tin, zinc, iron, alloyed steel or a metal alloy (for example brass) in which these metals are contained individually or in a total amount of at least 50%, are used therefor.

[0099] The secondary gas SG first of all flows through the plasma cutting torch 1, before it passes through a first space 9.10 which is formed by the inner faces of the nozzle protective cap holder 9 and of the nozzle protective cap 8 and the outer faces of the nozzle holder 6 and of the nozzle 4. The first space 9.10 is also bounded by an insulating part, configured as a secondary-gas conveying part 7, which is located between the nozzle 4 and the nozzle protective cap 8. The secondary-gas conveying part 7 can be formed in a multipart manner.

[0100] Located in the secondary-gas conveying part 7 are bores 7.1. However, these can also be openings, grooves or cutouts through which the secondary gas SG flows. By way of a corresponding arrangement of the bores 7.1, for example arranged radially with a radial offset and/or an inclination with respect to the center line M, the secondary gas can be set in rotation. This serves to stabilize the arc or the plasma jet.

[0101] After it has passed through the secondary-gas conveying part 7, the secondary gas flows into an interior space 8.10 which is formed by the inner face of the nozzle protective cap 8 and the outer face of the nozzle 4, and then passes out of the bore 8.1 in the nozzle protective cap 8. With the arc or plasma jet burning, the secondary gas strikes the latter and can influence it.

[0102] The nozzle protective cap 8 is usually cooled only by the secondary gas SG. Gas cooling has the drawback that it is not effective for achieving acceptable cooling or dissipation of heat and the required gas volumetric flow is very high for this purpose. Gas volumetric flows of 5000 to 11 000 l/h are often necessary here. At the same time, the volumetric flow of the secondary gas has to be selected such that the best cutting results are achieved. Excessive volumetric flows, which are required for cooling, however, often impair the cutting result.

[0103] In addition, the high gas consumption brought about by the high volumetric flows is uneconomical. This applies particularly when gases other than air, for example argon, nitrogen, hydrogen, oxygen or helium, are used.

[0104] These drawbacks are remedied by the use of the insulating part configured as the secondary-gas conveying part 7. By using such an insulating part, electrical insulation is achieved between the nozzle protective cap 8 and the nozzle 4. In combination with the secondary gas SG, the electrical insulation protects the nozzle 4 and the nozzle protective cap 8 from arcs which can form between them and the workpiece. These are referred to as double arcs and can result in damage to the nozzle 4 or the nozzle protective cap 8.

[0105] At the same time, heat is transferred between the nozzle protective cap 8 and the nozzle 4 from the hotter to the colder component, in this case from the nozzle protective cap 8 to the nozzle 4, via the insulating part with good thermal conductivity that is configured as a secondary-gas conveying part 7. The secondary-gas conveying part 7 is in touching contact with the nozzle protective cap 8 and the nozzle 4. In this exemplary embodiment, this takes place via annular faces 8.2 of the nozzle protective cap 8 and 7.4 of the secondary-gas conveying part 7 and the annular faces 7.5 of the secondary-gas conveying part 7 and 4.4 of the nozzle 4. These are force-fitting connections, wherein the nozzle protective cap 8 with the aid of the nozzle protective cap holder 9 which is screwed by way of an internal thread 9.20 to an external thread 11.20 of a receptacle 11. Thus, this is pressed upwardly against the secondary-gas conveying part 7 and this is pressed against the nozzle 4.

[0106] In this way, the heat is conducted from the nozzle protective cap 8 to the nozzle 4 and thus cooled. The nozzle 4 for its part is indirectly cooled, as explained in the description of FIG. 1.

[0107] FIG. 6 shows the structure of the plasma cutting torch 1 as in FIG. 4, but in which a nozzle protective cap 8 is additionally arranged outside the nozzle cap 5.

[0108] Bores 4.1 in the nozzle 4 and 8.1 in the nozzle protective cap 8 are located on a center line M. The inner faces of the nozzle protective cap 8 and of the nozzle protective cap holder 9 form, with the outer faces of the nozzle cap 5 and of the nozzle 4, spaces 8.10 and 9.10, respectively, through which a secondary gas SG can flow. This secondary gas passes out of the bore 8.1 in the nozzle protective cap 8, encloses the plasma jet (not illustrated) and ensures a defined atmosphere around the latter. In addition, the secondary gas SG protects the nozzle 4, the nozzle cap 5 and the nozzle protective cap 8 from arcs which can form between them and the workpiece (not shown). These are referred to as double arcs and can result in damage to the nozzle 4, the nozzle cap 5 and the nozzle protective cap 8. In particular when piercing a workpiece, the nozzle 4, the nozzle cap 5 and the nozzle protective cap 8 are highly stressed by hot material splashing up. The secondary gas SG, the volumetric flow of which can be increased during piercing compared with the value during cutting, keeps the material splashing up away from the nozzle 4, the nozzle cap 5 and the nozzle protective cap 8 and thus protects them from damage.

[0109] For cooling the electrode 2, the nozzle 4 and the nozzle cap 5, the statements made in the description of FIG. 4 apply.

[0110] The nozzle protective cap 8 is heated in particular by the radiation of the arc or of the plasma jet and of the heated workpiece. In particular when piercing the workpiece, the nozzle protective cap 8 is highly thermally stressed and heated by red-hot material splashing up and has to be cooled. Therefore, materials with good thermal conductivity and good electrical conductivity, generally metals, for example copper, aluminum, tin, zinc, iron or alloys in which at least one of these metals is contained, are used therefor.

[0111] The secondary gas SG first of all flows through the plasma torch 1, before it passes through a space 9.10 which is formed by the inner faces of the nozzle protective cap holder 9 and of the nozzle protective cap 8 and the outer faces of a nozzle holder 6 and of the nozzle cap 5. The space 9.10 is also bounded by an insulating part, configured as a secondary-gas conveying part 7 for the secondary gas SG, which is located between the nozzle cap 5 and the nozzle protective cap 8.

[0112] Located in the secondary-gas conveying part 7 are bores 7.1. However, these can also be openings, grooves or cutouts through which the secondary gas SG flows. By way of a corresponding arrangement thereof, for example bores 7.1 with a radial offset and/or bores 7.1 arranged radially with an inclination with respect to the center line M, the secondary gas SG can be set in rotation. This serves to stabilize the arc or the plasma jet.

[0113] After it has passed through the secondary-gas conveying part 7, the secondary gas SG flows into the space (interior space) 8.10 which is formed by the inner face of the nozzle protective cap 8 and the outer face of the nozzle cap 5 and of the nozzle 4, and then passes out of the bore 8.1 in the nozzle protective cap 8. With the arc or plasma jet burning, the secondary gas SG strikes the latter and can influence it.

[0114] The nozzle protective cap 8 is usually cooled only by the secondary gas SG. Gas cooling has the drawback that it is not effective for achieving acceptable cooling or dissipation of heat and the required gas volumetric flow is very high for this purpose. Gas volumetric flows of 5000 to 11 000 l/h are often necessary here. At the same time, the volumetric flow of the secondary gas has to be selected such that the best cutting results are achieved. Excessive volumetric flows, which are required for cooling, however, often impair the cutting result. In addition, the high gas consumption brought about by high volumetric flows is uneconomical. This applies particularly when gases other than air, for example argon, nitrogen, hydrogen, oxygen or helium, are used. These drawbacks are remedied by the use of the insulating part configured as the secondary-gas conveying part 7. By using such an insulating part, electrical insulation is achieved between the nozzle protective cap 8 and the nozzle cap 5 and thus also the nozzle 4. In combination with the secondary gas SG, the electrical insulation protects the nozzle 4, the nozzle cap 5 and the nozzle protective cap 8 from arcs which can form between them and a workpiece (not shown). These are referred to as double arcs and can result in damage to the nozzle, nozzle cap and nozzle protective cap.

[0115] At the same time, heat is transferred between the nozzle protective cap 8 and the nozzle cap 5 from the hotter to the colder component, in this case from the nozzle protective cap 8 to the nozzle cap 5, via the insulating part with good thermal conductivity that is configured as a secondary-gas conveying part 7. The secondary-gas conveying part 7 is in touching contact with the nozzle protective cap 8 and the nozzle cap 5. In this exemplary embodiment, this takes place via annular faces 8.2 of the nozzle protective cap 8 and 7.4 of the secondary-gas conveying part 7 and the annular faces 7.5 of the secondary-gas conveying part 7 and 5.3 of the nozzle cap 5. In this example, these are force-fitting connections, wherein the nozzle protective cap 8 is screwed by way of an internal thread 9.20 to an external thread 11.20 of a receptacle 11 with the aid of the nozzle protective cap holder 9. Thus, this is pressed upwardly against the secondary-gas conveying part 7 for the secondary gas SG and this is pressed against the nozzle cap 5. In this way, the heat is conducted from the nozzle protective cap 8 to the nozzle cap 5 and thus cooled. The nozzle cap 5 for its part is cooled as explained in the description of FIG. 4.

[0116] FIG. 7 shows a plasma cutting torch 1 for which the statements made with respect to the embodiment according to FIG. 6 apply. In addition, the nozzle protective cap holder 9 is screwed by way of its internal thread 9.20 to an external thread 11.20 of the receptacle 11, which is designed as an insulating part. The receptacle 11 consists of an electrically nonconductive material with good thermal conductivity. Thus, heat is transferred to the receptacle 11 from the nozzle protective cap holder 9, which can receive said heat for example from the nozzle protective cap 8, from a hot workpiece or from the arc radiation, via the internal thread 9.20 and the external thread 11.20. The receptacle 11 has coolant passages 11.10 and 11.11 for the coolant feed line (WV1) and coolant return line (WR1), which are embodied here as bores. The coolant flows through the latter and in this way cools the receptacle 11. Thus, the cooling of the nozzle protective cap holder 9 is further improved. The heat is transferred from the nozzle protective cap 8, via the contact face 8.3 thereof, configured as an annular face, to a contact face 9.1, likewise configured as an annular face, on the nozzle protective cap holder 9. The contact faces 8.3 and 9.1 touch one another in a force-fitting manner in this example, wherein the nozzle protective cap 8 is screwed by way of the internal thread 9.20 to the external thread 11.20 of the receptacle 11 with the aid of the nozzle protective cap holder 9. Thus, this is pressed upward against the secondary-gas conveying part 7 and the nozzle protective cap holder 9 is pressed against the nozzle protective cap 8. In the present example, the receptacle 11 is produced from ceramic. Aluminum nitride, which has very good thermal conductivity (about 180 W/(m*K)) and high electrical resistivity (about 10.sup.12 *cm) is particularly suitable.

[0117] Coolant is simultaneously conveyed to the nozzle 4 and nozzle cap 5 through coolant spaces 6.10 and 6.11 in the nozzle holder 6 and cools said nozzle 4 and nozzle cap 5.

[0118] FIG. 8 shows an embodiment of a plasma torch 1 which is similar to the one in FIG. 7. Thus, the statements made with respect to the embodiment according to FIGS. 6 and 7 also apply in principle. However, it contains a different embodiment of the insulating part embodied as a receptacle 11 for the nozzle protective cap holder 9. The receptacle 11 consists of two parts in this example, wherein an outer part 11.1 consists of an electrically nonconductive material with good thermal conductivity and an inner part 11.2 consists of a material with good electrical conductivity and good thermal conductivity.

[0119] The nozzle protective cap holder 9 is screwed by way of its internal thread 9.20 to the external thread 11.20 of the part 11.1 of the receptacle 11.

[0120] The electrically nonconductive material with good thermal conductivity is produced from ceramic, for example aluminum nitride, which has very good thermal conductivity (about 180 W/(m*K)) and high electrical resistivity, about 10.sup.12 *cm. The material with good electrical conductivity and good thermal conductivity is in this case a metal, for example copper, aluminum, tin, zinc, alloyed steel or alloys (for example brass) in which at least one of these metals is contained.

[0121] Generally, it is advantageous for the material with good electrical conductivity and good thermal conductivity to have a thermal conductivity of at least 40 W/(m*K) and electrical resistivity of at most 0.01 *cm. In particular, provision can be made here for the material with good electrical conductivity and good thermal conductivity to have a thermal conductivity of at least 60 W/(m*K), better still at least 90 W/(m*K) and preferably 120 W/(m*K). Even more preferably, the material with good electrical conductivity and good thermal conductivity has a thermal conductivity of at least 150 W/(m*K), better still at least 200 W/(m*K) and preferably at least 300 W/(m*K). Alternatively or in addition, provision can be made for the material with good electrical conductivity and good thermal conductivity to be a metal, for example silver, copper, aluminum, tin, zinc, iron, alloyed steel or a metal alloy (for example brass) in which these metals are contained individually or in a total amount of at least 50%.

[0122] The use of two different materials has the advantage that, for the complicated part in which different formations are required, for example different bores, cutouts, grooves, openings etc., the material which can be machined more easily and more cost-effectively can be used. In this exemplary embodiment, this is a metal which can be machined more easily than ceramic. Both parts (11.1 and 11.2) are connected together in touching contact in a force-fitting manner by being pressed into one another, with the result that good heat transfer between the cylindrical contact faces 11.5 and 11.6 of the two parts 11.1 and 11.2 is achieved. The part 11.2 of the receptacle 11 has coolant passages 11.10 and 11.11 for the coolant feed line (WV1) and coolant return line (WR1), these being embodied here as bores. The coolant flows through the latter and in this way carries out its cooling action.

[0123] As can be gathered from FIG. 8 and the associated description, the present invention also relates to an insulating part for a plasma torch, in particular a plasma cutting torch, for electrical insulation between at least two electrically conductive components of the plasma torch, wherein said insulating part consists of at least two parts, wherein one of the parts consists of an electrically nonconductive material with good thermal conductivity and the other or one other of the parts consists of a material with good electrical conductivity and good thermal conductivity.

[0124] FIG. 9 shows a further embodiment of a plasma cutting torch 1 according to the present invention, which is similar in principle to the embodiment shown in FIG. 8. Thus, the statements made with respect to the embodiments according to FIGS. 6, 7 and 8 also apply. However, a different embodiment variant of the insulating part embodied as a receptacle 11 for the nozzle protective cap holder 9 is shown. The receptacle 11 consists of two parts, wherein in this case the outer part 11.1, in contrast to the embodiment shown in FIG. 8, consists of a material with good electrical conductivity and good thermal conductivity (for example metal) and the inner part 11.2 consists of an electrically nonconductive material with good thermal conductivity (for example ceramic).

[0125] The nozzle protective cap holder 9 is screwed by way of its internal thread 9.20 to the external thread 11.20 of the part 11.1 of the receptacle 11.

[0126] In this embodiment, the advantage is that the external thread can be introduced into the metal material, which is used for the part 11.1, and not the ceramic, which is harder to machine.

[0127] igures 10 to 13 show (further) different embodiments of an insulating part configured as a plasma-gas conveying part 3 for the plasma gas PG, it being possible to implement said embodiments in a plasma torch 1, as is shown in FIGS. 1 to 9, wherein each figure with the letter a shows a longitudinal section and each figure with the letter b shows a side view in partial section.

[0128] The plasma-gas conveying part 3 shown in FIGS. 10a and 10b is produced from an electrically nonconductive material with good thermal conductivity, for example ceramic in this case. Aluminum nitride, which has very good thermal conductivity (about 180 W/(m*K)) and high electrical resistivity (about 10.sup.12 *cm) is particularly suitable. The associated advantages when used in a plasma cutting torch 1, for example better cooling, reduction in mechanical tensions, simpler structure, have already been mentioned and explained above in the description of FIGS. 1 to 4.

[0129] Located in the plasma-gas conveying part 3 are radially arranged bores 3.1 which can be for example radially offset and/or radially inclined with respect to the center line M and cause a plasma gas PG to rotate in the plasma cutting torch. When the plasma-gas conveying part 3 has been fitted into the plasma cutting torch 1, its contact face 3.6 (cylindrical outer face here, for example) is in touching contact with the contact face 4.3 (cylindrical inner face here, for example) of the nozzle 4, its contact face 3.5 (cylindrical inner face here, for example) is in touching contact with the contact face 2.3 (cylindrical outer face here, for example) of the electrode 2, and its contact face 3.7 (annular face here, for example) is in touching contact with the contact face 4.5 (annular face here, for example) of the nozzle 4 (FIGS. 1 to 9). In the contact face 3.6, there are grooves 3.8. These guide the plasma gas PG to the bores 3.1 before it is conveyed by the latter into an interior space 4.2 in the nozzle 4, in which the electrode 2 is arranged.

[0130] FIGS. 11a and 11b show a plasma-gas conveying part 3 which consists of two parts. A first part 3.2 consists of an electrically nonconductive material with good thermal conductivity, while a second part 3.3 consists of a material with good electrical conductivity and good thermal conductivity.

[0131] For the part 3.2 of the plasma-gas conveying part 3, use is made here for example of ceramic, again for example aluminum nitride, which has very good thermal conductivity (about 180 W/(m*K)) and high electrical resistivity (10.sup.12 *cm). For the part 3.3 of the secondary-gas conveying part 3, use is made here of a metal, for example silver, copper, aluminum, tin, zinc, iron, alloyed steel or a metal alloy (for example brass) in which these metals are contained individually or in a total amount of at least 50%.

[0132] If for example copper is used for the part 3.3, the thermal conductivity of the plasma-gas conveying part 3 is greater than if it only consisted of an electrically nonconductive material with good thermal conductivity, for example aluminum nitride. Depending on its purity, copper has greater thermal conductivity (max. about 390 W/(m*K)) than aluminum nitride (about 180 W/(m*K)), which is currently considered to be one of the best thermally conducting materials which does not simultaneously have good electrical conductivity. In the meantime, there is also aluminum nitride with a thermal conductivity of 220 W/(m*K).

[0133] On account of the better thermal conductivity, this results in even better heat exchange between the nozzle 4 and the electrode 2 of the plasma cutting torch 1 according to FIGS. 1 to 9. In the simplest case, the parts 3.2 and 3.3 are connected together by the contact faces 3.21 and 3.31 being pushed one over the other.

[0134] The parts 3.2 and 3.3 can also be connected in a force-fitting manner by way of the pressed-together, opposing and touching contact faces 3.20 and 3.30, 3.21 and 3.31, and 3.22 and 3.32. The contact faces 3.20, 3.21 and 3.22 are contact faces of the part 3.2 and the contact faces 3.30, 3.31 and 3.32 are contact faces of the part 3.3. The cylindrically configured contact faces 3.31 (cylindrical outer face of the part 3.3) and 3.21 (cylindrical inner face of the part 3.2) form a force-fitting connection by being pressed into one another. In this case, an interference fit DIN EN ISO 286 (for example H7/n6; H7/m6) is used between the cylindrical inner and outer faces.

[0135] It is also possible to connect the two parts (3.2 and 3.3) together by way of a form fit, by soldering and/or by adhesive bonding and/or by way of a thermal method.

[0136] Since the mechanical machining of the ceramic material is usually more difficult than that of a metal, the machining complexity drops. Here, for example six bores 3.1 have been introduced into the metal part 3.3, said bores having a radial offset al and being distributed equidistantly at an angle al around the circumference of the plasma-gas duct. Very different formations, for example grooves, cutouts, bores etc., are also easier to produce when they are introduced into the metal.

[0137] FIGS. 12a and 12b show a plasma-gas conveying part 3 which consists of two parts, wherein a first part 3.2 consists of an electrically nonconductive material with good thermal conductivity, while a second part 3.3 consists of an electrically nonconductive and thermally nonconductive material.

[0138] For the part 3.2 of the plasma-gas conveying part 3, use is made here for example of ceramic, again for example aluminum nitride, which has very good thermal conductivity (about 180 W/(m*K)) and high electrical resistivity (10.sup.12 *cm). For the part 3.3 of the plasma-gas conveying part 3, use can be made for example of a plastics material, for example PEEK, PTFE (polytetrafluoroethylene), Torlon, polyimide-imide (PAI), polyimide (PI), which has high temperature stability (at least 200 C.) and high electrical resistivity (at least 10.sup.6, better still at least 10.sup.10 *cm).

[0139] In the simplest case, the parts 3.2 and 3.3 are connected together by the contact faces 3.21 and 3.31 being pushed one over the other. They can also be connected in a force-fitting manner by way of the pressed-together, opposing and touching contact faces 3.20 and 3.30, 3.21 and 3.31, and 3.22 and 3.32. The cylindrically configured contact faces 3.31 (cylindrical outer face of the part 3.3) and 3.21 (cylindrical inner face of the part 3.2) then form the force-fitting connection by being pressed into one another. In this case, an interference fit DIN EN ISO 286 (for example H7/n6; H7/m6) is used between the cylindrical inner and outer faces. It is also possible to connect the two parts (3.2 and 3.3) together by way of a form fit and/or by adhesive bonding.

[0140] Since the mechanical machining of the ceramic material is usually more difficult than that of a plastics material, the machining complexity drops. Here, for example six bores 3.1 have been introduced into the plastics part 3.3, said bores having a radial offset al and being distributed equidistantly at an angle 1 around the circumference of the gas duct. Very different formations, for example grooves, cutouts, bores etc., are also easier to produce when they are introduced into the plastics material. FIGS. 13a and 13b show a plasma-gas conveying part 3 as in FIG. 12, except that a further part 3.4, which consists of a material with the same properties as the part 3.3, belongs to the plasma-gas conveying part 3.

[0141] The parts 3.2 and 3.4 can be connected together in the same way as the parts 3.2 and 3.3, wherein the contact faces 3.23 and 3.43, 3.24 and 3.44, and 3.25 and 3.25 are connected.

[0142] Since the mechanical machining of the ceramic material is usually more difficult than that of a plastics material, the machining complexity drops and very different formations, for example cutouts, bores etc., are also easier to produce when they are introduced into the plastics material.

[0143] FIGS. 14a to 14b show a further embodiment of a plasma-gas conveying part 3. FIGS. 14c and 14d show a part 3.3 of the plasma-gas conveying part 3. In this case, FIGS. 14a and 14c show a longitudinal section and FIGS. 14b and 14d show a side view in partial section.

[0144] A part 3.2 consists of an electrically nonconductive material with good thermal conductivity, while a part 3.3 consists of an electrically nonconductive and thermally nonconductive material.

[0145] Located in the part 3.3 of the plasma-gas conveying part 3 are radially arranged openings, in this case bores 3.1, which can be radially offset and/or radially inclined with respect to the center line M and through which a plasma gas PG flows when the plasma-gas conveying part 3 has been fitted in the plasma cutting torch 1 (see FIGS. 1 to 9).

[0146] The part 3.3 has further radially arranged bores 3.9 which are larger than the bores 3.1. Introduced into these bores are six parts 3.2 which are illustrated here for example as round pins. These are distributed equidistantly around the circumference at an angle, which results between midpoint lines M3.9, of 3=60.

[0147] When the plasma-gas conveying part 3 has been fitted in the plasma cutting torch 1 according to FIGS. 1 to 9, contact faces 3.61 (outer faces) of the parts 3.2 (round pins) are in touching contact with a contact face 4.3 (a cylindrical inner face here) of the nozzle 4 and contact faces 3.51 (inner faces) of the parts 3.2 (round pins) are in touching contact with the contact face 2.3 (a cylindrical outer face here) of the electrode 2.

[0148] The parts 3.2 have a diameter d3 and a length l3 which is at least as great as half the difference of the diameters d10 and d20 of the part 3.3. It is even better when the length l3 is slightly greater in order to obtain secure contact between the contact faces of the round pins 3.2 and the nozzle 4 and the electrode 2. It is also advantageous for the surface of the contact faces 3.61 and 3.51 not to be planar, but to be adapted to the cylindrical outer face (contact face 2.3) of the electrode 2 and to the cylindrical inner face (contact face 4.3) of the nozzle 4 such that a form fit is produced.

[0149] In the contact face 3.6, there are grooves 3.8. These guide the plasma gas PG to the bores 3.1 before it is conveyed by the latter into an interior space 4.2 in the nozzle 4, in which the electrode 2 is arranged.

[0150] Since the mechanical machining of the ceramic material is usually more difficult than that of a plastics material, the machining complexity drops and very different formations, for example grooves, cutouts, bores etc., are also easier to produce when they are introduced into the plastics material. Thus, in spite of the use of identical round pins, very different gas ducts can be produced in a cost-effective manner.

[0151] Furthermore, by changing the number or the diameter of the round pins 3.2, different thermal resistances or thermal conductivities of the plasma-gas conveying part 3 are achievable.

[0152] If the diameter and/or the number of round pins is/are reduced, the thermal resistance increases and the thermal conductivity drops.

[0153] Since very different thermal loads arise at the nozzle 4 and the electrode 2 depending on the power of 500 W to 200 kW to be implemented in the plasma torch or plasma cutting torch, it is advantageous to adapt the thermal resistance. Thus, for example the manufacturing costs are reduced when fewer bores have to be introduced and fewer round pins have to be used.

[0154] FIGS. 15 to 17 show (further) different embodiments of an insulating part configured as a secondary-gas conveying part 7 for a secondary gas SG, it being possible to implement said embodiments in a plasma cutting torch 1, as is shown in FIGS. 6 to 9, wherein each figure with the letter a shows a plan view in partial section and each figure with the letter b shows a side view in section.

[0155] FIGS. 15a and 15b show a secondary-gas conveying part 7 for a secondary gas SG, as can be used in a plasma cutting torch according to FIGS. 6 to 9.

[0156] The secondary-gas conveying part 7 shown in FIGS. 15a and 15b consists of an electrically nonconductive material with good thermal conductivity, for example ceramic in this case. Aluminum nitride, which has very good thermal conductivity (about 180 W/(m*K)) and high electrical resistivity (about 10.sup.12 *cm) is particularly suitable again here. As a result of the low thermal resistance and high thermal conductivity, large temperature differences can be avoided and mechanical tensions in the plasma cutting torch that are caused thereby can be reduced.

[0157] Located in the secondary-gas conveying part 7 are radially arranged bores 7.1 which can also be radial or radially offset and/or radially inclined with respect to the center line M and through which the secondary gas SG can flow or flows when the secondary-gas conveying part 7 has been fitted in the plasma cutting torch 1. In this example, 12 bores are radially offset by a dimension all and are distributed equidistantly around the circumference, wherein the angle which is enclosed by the midpoints of the bores is denoted all. However, there may also be openings, grooves or cutouts through which the secondary gas SG flows when the secondary-gas conveying part 7 has been fitted in the plasma cutting torch 1. The secondary-gas conveying part 7 has two annular contact faces 7.4 and 7.5.

[0158] By using this secondary-gas conveying part 7, electrical insulation is achieved between the nozzle protective cap 8 and the nozzle cap 5 and thus also the nozzle 4 of the plasma cutting torch 1 illustrated in FIGS. 6 to 9. In combination with the secondary gas, the electrical insulation protects the nozzle 4, the nozzle cap 5 and the nozzle protective cap 8 from arcs which can form between them and the workpiece (not shown). These are referred to as double arcs and can result in damage to the nozzle 4, the nozzle cap 5 and the nozzle protective cap 8.

[0159] At the same time, heat is transferred between the nozzle protective cap 8 and the nozzle cap 5 from the hotter to the colder component, in this case from the nozzle protective cap 8 to the nozzle cap 5, via the insulating part with good thermal conductivity that is configured as a secondary-gas conveying part 7. The secondary-gas conveying part 7 is in touching contact with the nozzle protective cap 8 and the nozzle cap 5. In this exemplary embodiment, this takes place via annular faces 8.2 of the nozzle protective cap 8 and 7.4 of the secondary-gas conveying part 7 and annular faces 7.5 of the secondary-gas conveying part 7 and 5.3 of the nozzle cap 5, which touch, as illustrated in FIGS. 6 to 9.

[0160] FIGS. 16a and 16b likewise show a secondary-gas conveying part 7 for a secondary gas SG, which consists of two parts. A first part 7.2 consists of an electrically nonconductive material with good thermal conductivity, while a second part 7.3 consists of a material with good electrical conductivity and good thermal conductivity.

[0161] For the part 7.2 of the secondary-gas conveying part 7, use is made here for example of ceramic, again for example aluminum nitride, which has very good thermal conductivity (about 180 W/(m*K)) and high electrical resistivity (about 10.sup.12 *cm). For the part 7.3 of the secondary-gas conveying part 7, use is made here of a metal, for example silver, copper, aluminum, tin, zinc, iron, alloyed steel or a metal alloy (for example brass) in which these metals are contained individually or in a total amount of at least 50%.

[0162] If for example copper is used for the part 7.3, the thermal conductivity of the secondary-gas conveying part 7 is greater than if it only consisted of electrically nonconductive material with good thermal conductivity, for example aluminum nitride. Depending on its purity, copper has greater thermal conductivity (max. about 390 W/(m*K)) than aluminum nitride (about 180 W/(m*K)), which is currently considered to be one of the best thermally conducting materials which does not simultaneously have good electrical conductivity. On account of the better conductivity, this results in even better heat exchange between the nozzle protective cap 8 and the nozzle cap 5 of the plasma cutting torch 1 according to FIGS. 6 to 9.

[0163] In the simplest case, the parts 7.2 and 7.3 are connected together by the contact faces 7.21 and 7.31 being pushed one over the other.

[0164] The parts 7.2 and 7.3 can also be connected in a force-fitting manner by way of the pressed-together, opposing and touching contact faces 7.20 and 7.30, 7.21 and 7.31, and 7.22 and 7.32. The contact faces 7.20, 7.21 and 7.22 are contact faces of the part 7.2 and the contact faces 7.30, 7.31 and 7.32 are contact faces of the part 7.3. The cylindrically configured contact faces 7.31 (cylindrical outer face of the part 7.3) and 7.21 (cylindrical inner face of the part 7.2) form a force-fitting connection by being pressed into one another. In this case, an interference fit DIN EN ISO 286 (for example H7/n6; H/m6) is used between the cylindrical inner and outer faces.

[0165] It is also possible to connect the two parts together by way of a form fit, by soldering and/or by adhesive bonding.

[0166] Since the mechanical machining of the ceramic material is usually more difficult than that of a metal, the machining complexity drops. Here, for example twelve bores 7.1 have been introduced into the metal part 7.3, said bores having a radial offset all and being distributed equidistantly at an angle 11 around the circumference of the gas duct. Very different formations, for example grooves, cutouts, bores etc., are also easier to produce when they are introduced into the metal.

[0167] FIGS. 17a and 17b likewise show a secondary-gas conveying part 7 for a secondary gas SG, which consists of two parts. In contrast to the embodiment according to FIG. 16, a first part 7.2 consists here of a material with good electrical conductivity and good thermal conductivity and a second part 7.3 consists of an electrically nonconductive material with good thermal conductivity. Otherwise, the same observations as made with regard to FIGS. 16a and 6b apply.

[0168] FIGS. 18a, 18b, 18c and 18d show a further embodiment of a secondary-gas conveying part 7 for a secondary gas SG, which can be used in a plasma cutting torch according to FIGS. 6 to 9.

[0169] FIG. 18a shows a plan view and FIGS. 18b and 18c show sectional side views of different embodiments thereof. FIG. 18d shows a part 7.3, consisting of electrically nonconductive and thermally nonconductive material, of the secondary-gas conveying part 7.

[0170] Located in the part 7.3 of the secondary-gas conveying part 7 are radially arranged bores 7.1 which can also be radial or radially offset and/or radially inclined with respect to the center line M and through which the secondary gas SG can flow when the secondary-gas conveying part 7 has been fitted in the plasma cutting torch 1. In this example, twelve bores are radially offset by a dimension all and are distributed equidistantly around the circumference, wherein the angle which is enclosed by the midpoints of the bores is denoted all (for example 30 here). However, there may also be openings, grooves or cutouts through which the secondary gas SG flows when the secondary-gas conveying part 7 has been fitted in the plasma cutting torch 1 (see in this regard for example FIGS. 6 to 9).

[0171] FIG. 18d shows that in this example the part 7.3 has twelve further axially arranged bores 7.9 which are larger than the bores or openings 7.1.

[0172] In FIGS. 18a and 18b, twelve parts 7.2, which are illustrated here for example as round pins, have been introduced into these bores 7.9. The round pins 7.2 consist of an electrically nonconductive material with good thermal conductivity, while the part 7.3 consists of an electrically nonconductive and thermally nonconductive material.

[0173] When the secondary-gas conveying part 7 has been fitted in the plasma cutting torch 1 according to FIGS. 6 to 9, contact faces 7.51 of the round pins 7.2 are in touching contact with a contact face 5.3 (annular face here, for example) of the nozzle cap 5 and contact faces 7.41 of the round pins 7.2 are in touching contact with a contact face 8.2 (annular face here, for example) of the nozzle protective cap (FIGS. 6 to 9).

[0174] The parts 7.2 have a diameter d7 and a length l7 which is at least as great as the width b of the part 7.3. It is even better when the length l7 is slightly greater in order to obtain secure contact between the contact faces of the round pins 7.2 and the nozzle cap 5 and the nozzle protective cap 8.

[0175] FIG. 18c shows another embodiment of the secondary-gas conveying part 7 for secondary gas. In this case, two parts 7.2 and 7.6 indicated as round pins for example have been introduced into each bore 7.9. The part 7.3 consists of an electrically nonconductive and thermally nonconductive material, the round pins 7.2 consist of an electrically nonconductive material with good thermal conductivity and the round pins 7.6 consist of a material with good electrical conductivity and good thermal conductivity.

[0176] When the secondary-gas conveying part 7 has been fitted in the plasma cutting torch 1 according to FIGS. 6 to 9, contact faces 7.51 of the round pins 7.2 are in touching contact with a contact face 5.3 (annular face here, for example) of the nozzle cap 5 and contact faces 7.41 of the round pins 7.6 are in touching contact with a contact face 8.2 (annular face here, for example) of the nozzle protective cap 8 (see also FIGS. 6 to 9). Both round pins 7.2 and 7.6 are connected by their contact faces 7.42 and 7.52 touching.

[0177] The parts 7.2 have a diameter d7 and a length l71. In this example, the parts 7.6 have the same diameter and a length l72, wherein the sum of the lengths 171 and 172 is at least as great as the width b of the part 7.3. It is even better when the sum of the lengths is slightly greater, for example greater than 0.1 mm, in order to obtain secure contact between the contact faces 7.51 of the round pins 7.2 and the nozzle cap 5 and the contact faces 7.41 of the round pins 7.6 and the nozzle protective cap 8.

[0178] As FIG. 18c and the associated description show, the present invention thus also relates in a generalized form to an insulating part for a plasma torch, in particular a plasma cutting torch, for electrical insulation between at least two electrically conductive components of the plasma torch, wherein the insulating part consists of at least three parts, wherein one of the parts consists of an electrically nonconductive material with good thermal conductivity, one other of the parts consists of an electrically nonconductive and thermally nonconductive material, and the further part or a further one of the parts consists of a material with good electrical conductivity and good thermal conductivity.

[0179] The secondary-gas conveying parts 7 shown in FIGS. 15 to 18 can also be used in a plasma cutting torch 1 according to FIG. 5. There, by using this secondary-gas conveying part 7, electrical insulation is achieved between the nozzle protective cap 8 and the nozzle 4. In combination with the secondary gas SG, the electrical insulation protects the nozzle 4 and the nozzle protective cap 8 from arcs which can form between them and a workpiece. These are referred to as double arcs and can result in damage to the nozzle 4 and the nozzle protective cap 8.

[0180] At the same time, heat is transferred between the nozzle protective cap 8 and the nozzle 4 from the hotter to the colder component, in this case from the nozzle protective cap 8 to the nozzle 4, via the insulating part with good thermal conductivity that is configured as a secondary-gas conveying part 7. The secondary-gas conveying part 7 is in touching contact with the nozzle protective cap 8 and the nozzle 4. For the exemplary embodiments of the secondary-gas conveying part 7 that are shown in FIGS. 15, 16 and 17, this takes place via the annular contact faces 8.2 of the nozzle protective cap 8 and the annular contact faces 7.4 of the secondary-gas conveying part 7 and the annular contact faces 7.5 of the secondary-gas conveying part 7 and the annular contact faces 4.4 of the nozzle 4, which, as illustrated in FIG. 5, touch.

[0181] In the exemplary embodiments of the secondary-gas conveying part 7 shown in FIGS. 18b and 18c, the heat transfer takes place via the annular contact face 8.2 of the nozzle protective cap 8 and the contact faces 7.41 of the round pins 7.2 or 7.6 of the secondary-gas conveying part 7 and 7.51 of the round pins 7.2 by touching the contact face 4.4 (the annular face for example, here) of the nozzle 4, as illustrated in FIG. 5.

[0182] FIGS. 19a to 19d show sectional illustrations of arrangements of a nozzle 4 and a secondary-gas conveying part 7 for a secondary gas SG according to particular embodiments of the invention in FIGS. 15 to 18. The statements given with respect to FIG. 5 and FIGS. 15 to 18 apply here.

[0183] In this case, FIG. 19a shows an arrangement with a secondary-gas conveying part 7 according to FIGS. 15a and 15b, FIG. 19b shows an arrangement with a secondary-gas conveying part according to FIGS. 16a and 16b, FIG. 19c shows an arrangement with a secondary-gas conveying part according to FIGS. 17a and 17b and FIG. 19d shows an arrangement with a secondary-gas conveying part according to FIG. 18a and FIG. 18b.

[0184] In these exemplary embodiments, the secondary-gas conveying part 7 can be connected to the nozzle 4 in the simplest case by one being pushed over the other. They can also be connected in a form-fitting and force-fitting manner or by adhesive bonding, however. When metal/metal and/or metal/ceramic is used at the connecting point, soldering is also possible as a connection.

[0185] FIGS. 20a to 20d show sectional illustrations of arrangements of a nozzle cap 5 and a secondary-gas conveying part 7 for a secondary gas SG according to FIGS. 15 to 18 according to particular embodiments of the invention. The statements given with respect to FIGS. 6 to 9 and FIGS. 15 to 18 apply here.

[0186] In this case, FIG. 20a shows an arrangement with a secondary-gas conveying part according to FIGS. 15a and 15b; FIG. 20b shows an arrangement with a secondary-gas conveying part according to FIGS. 16a and 16b; FIG. 20c shows an arrangement with a secondary-gas conveying part according to FIGS. 17a and 17b and FIG. 20d shows an arrangement with a secondary-gas conveying part according to FIGS. 18a to 18d.

[0187] In these exemplary embodiments, the secondary-gas conveying part 7 can be connected to the nozzle cap 5 in the simplest case by one being pushed over the other. They can also be connected in a form-fitting and force-fitting manner or by adhesive bonding, however. When metal/metal and/or metal/ceramic is used at the connecting point, soldering is also possible as a connection.

[0188] FIGS. 21a to 21d show sectional illustrations of arrangements of a nozzle protective cap 8 and a secondary-gas conveying part 7 for a secondary gas SG according to FIGS. 15 to 18. The statements given with respect to FIGS. 5 to 9 and FIGS. 15 to 18 apply here.

[0189] In this case, figure FIG. 21a shows an arrangement with a secondary-gas conveying part according to FIGS. 15a and 15b; FIG. 21b shows an arrangement with a secondary-gas conveying part according to FIGS. 16a and 16b; FIG. 21c shows an arrangement with a secondary-gas conveying part according to FIGS. 17a and 17b and FIG. 21d shows an arrangement with a secondary-gas conveying part according to figures FIGS. 18a to 18d.

[0190] In these exemplary embodiments, the secondary-gas conveying part 7 can be connected to the nozzle protective cap 8 in the simplest case by one being pushed over the other. They can also be connected in a form-fitting and force-fitting manner or by adhesive bonding, however. When metal/metal and/or metal/ceramic is used at the connecting point, soldering is also possible as a connection.

[0191] FIGS. 22a and 22b show arrangements of an electrode 2 and a plasma-gas conveying part 3 for a plasma gas PG according to FIGS. 11 to 13 according to particular embodiments of the invention.

[0192] In this case, FIG. 22a shows an arrangement with a plasma-gas conveying part according to FIG. 11 a and FIG. 11b, and FIG. 22b shows an arrangement with a plasma-gas conveying part according to FIG. 13a and FIG. 13b.

[0193] In this exemplary embodiment, a contact face 2.3 is for example a cylindrical outer face of the electrode 2 and a contact face 3.5 is a cylindrical inner face of the plasma-gas conveying part 3. Preferably, a clearance fit with a small clearance, for example H7/h6 according to DIN EN ISO 286, between the cylindrical inner and outer faces is used here in order to realize both the plugging into one another and also good contact and thus low thermal resistance and thus good heat transfer. The heat transfer can be improved by applying thermally conductive paste to these contact faces. A fit with a larger clearance, for example H7/g6, can then be used.

[0194] It is also possible to use an interference fit between the plasma-gas conveying part 3 and the electrode 2. This improves heat transfer, of course. However, it has the consequence that the electrode 2 and plasma-gas conveying part 3 can only be replaced together in the plasma cutting torch 1.

[0195] FIG. 23 shows an arrangement of an electrode 2 and a plasma-gas conveying part 3 for a plasma gas PG according to one particular embodiment of the present invention.

[0196] In this arrangement, contact faces 3.51 of the round pins 3.2 of the plasma-gas conveying part 3 are in touching contact with a contact face 2.3 (cylindrical outer face for example, here) of the electrode 2 (see also FIGS. 1 to 9).

[0197] The parts 3.2 have a diameter d3 and a length l3 which is at least as great as half the difference of the diameters d10 and d20 of the part 3.3. It is even better when the length l3 is slightly greater in order to obtain secure contact between the contact faces of the round pins 3.2 and the nozzle 4 and the electrode 2. It is also advantageous for the surface of the contact faces 3.61 and 3.51 not to be planar, but to be adapted to the cylindrical outer face (contact face 2.3) of the electrode 2 and to the cylindrical inner face (contact face 4.3) of the nozzle such that a form fit is produced. The arrangements made up of wearing parts and the insulating part or the gas-conveying part are listed only by way of example. Other combinations, for example nozzle and gas-conveying part, are also possible, of course.

[0198] Where reference was made to cooling liquid or the like in the above description, a cooling medium is quite generally intended to be meant thereby.

[0199] Arrangements and complete plasma torches, inter alia, are described in the above description. It goes without saying for a person skilled in the art that the invention can also consist of subcombinations and individual parts, for example components or wearing parts. Therefore, protection is also explicitly claimed therefor.

[0200] Finally, a few definitions which are intended to apply to the entire description above:

[0201] Good electrical conductivity is intended to mean that the electrical resistivity is at most 0.01 *cm.

[0202] Electrically nonconductive is intended to mean that the resistivity is at least 10.sup.6 *cm, better still at least 10.sup.10 *cm and/or that the dielectric strength is at least 7 kV/mm, better still at least 10 kV/mm.

[0203] Good thermal conductivity is intended to mean that the thermal conductivity is at least 40 W/(m*K), better still at least 60 W/(m*K), even better still at least 90 W/(m*K).

[0204] Good thermal conductivity is intended to mean that the thermal conductivity is at least 120 W/(m*K), better still at least 150 W/(m*K), even better still at least 180 W/(m*K).

[0205] Finally, good thermal conductivity particularly for metals is understood to mean that the thermal conductivity is at least 200 W/(m*K), better still at least 300 W/(m*K).

[0206] The features of the invention that are disclosed in the above description, in the drawing and in the claims can be essential both individually and in any desired combinations in order to realize the invention in its various embodiments.

LIST OF REFERENCE SIGNS

[0207] 1 Plasma cutting torch

[0208] 2 Electrode

[0209] 2.1 Electrode holder

[0210] 2.2 Emission insert

[0211] 2.3 Contact face

[0212] 2.10 Coolant space

[0213] 3 Plasma-gas conveying part

[0214] 3.1 Bore

[0215] 3.2 Part

[0216] 3.3 Part

[0217] 3.4 Part

[0218] 3.5 Contact face

[0219] 3.6 Contact face

[0220] 3.7 Contact face

[0221] 3.8 Groove

[0222] 3.9 Bore

[0223] 3.20 Contact face

[0224] 3.21 Contact face

[0225] 3.22 Contact face

[0226] 3.23 Contact face

[0227] 3.24 Contact face

[0228] 3.25 Contact face

[0229] 3.30 Contact face

[0230] 3.31 Contact face

[0231] 3.32 Contact face

[0232] 3.43 Contact face

[0233] 3.44 Contact face

[0234] 3.45 Contact face

[0235] 3.51 Contact face

[0236] 3.61 Contact face

[0237] 4 Nozzle

[0238] 4.1 Nozzle bore

[0239] 4.2 Interior space

[0240] 4.3 Contact face

[0241] 4.4 Contact face

[0242] 4.5 Contact face

[0243] 4.10 Coolant space

[0244] 4.20 External thread

[0245] 5 Nozzle cap

[0246] 5.1 Nozzle cap bore

[0247] 5.3 Contact face

[0248] 5.20 Internal thread

[0249] 6 Nozzle holder

[0250] 6.10 Coolant space

[0251] 6.11 Coolant space

[0252] 6.20 Internal thread

[0253] 6.21 External thread

[0254] 7 Secondary-gas conveying part

[0255] 7.1 Bore

[0256] 7.2 Part

[0257] 7.3 Part

[0258] 7.4 Contact face

[0259] 7.5 Contact face

[0260] 7.6 Part

[0261] 7.9 Bores

[0262] 7.20 Contact face

[0263] 7.21 Contact face

[0264] 7.22 Contact face

[0265] 7.30 Contact face

[0266] 7.31 Contact face

[0267] 7.32 Contact face

[0268] 7.41 Contact face

[0269] 7.42 Contact face

[0270] 7.51 Contact face

[0271] 7.52 Contact face

[0272] 8 Nozzle protective cap

[0273] 8.1 Nozzle protective cap bore

[0274] 8.2 Contact face

[0275] 8.3 Contact face

[0276] 8.10 Interior space

[0277] 8.11 Interior space

[0278] 9 Nozzle protective cap holder

[0279] 9.1 Contact face

[0280] 9.10 Interior space

[0281] 9.20 Internal thread

[0282] 10 Cooling pipe

[0283] 10.1 Coolant space

[0284] 11 Receptacle

[0285] 11.1 Part

[0286] 11.2 Part

[0287] 11.5 Contact face

[0288] 11.6 Contact face

[0289] 11.10 Coolant passage

[0290] 11.11 Coolant passage

[0291] 11.20 External thread

[0292] PG Plasma gas

[0293] SG Secondary gas

[0294] WR1 Coolant return line 1

[0295] WR2 Coolant return line 2

[0296] WV1 Coolant feed line 1

[0297] WV2 Coolant feed line 2

[0298] a1 Radial offset

[0299] a11 Radial offset

[0300] b Width

[0301] d3 Diameter

[0302] d7 Diameter

[0303] d10 Outside diameter

[0304] d11 Inside diameter

[0305] d15 Diameter

[0306] d20 Inside diameter

[0307] d21 Outside diameter

[0308] d25 Diameter

[0309] d30 Inside diameter

[0310] d31 Outside diameter

[0311] d60 Outside diameter

[0312] l3 Length

[0313] l31 Length

[0314] l32 Length

[0315] l7 Length

[0316] l71 Length

[0317] l72 Length

[0318] l73 Length

[0319] l2 Length

[0320] M Center line

[0321] M3.1 Center line

[0322] M3.2 Center line

[0323] M3.9 Center line

[0324] M7.1 Center line

[0325] M3.6 Center line

[0326] 1 Angle

[0327] 3 Angle

[0328] 7 Angle

[0329] 11 Angle