EP3491896A1

EP3491896A1 - Plasma torch

Info

Publication number: EP3491896A1
Application number: EP17754286.7A
Authority: EP
Inventors: Volker Krink; Timo Grundke; Frank Laurisch; René Nogowski
Original assignee: Kjellberg Stiftung
Current assignee: Kjellberg Stiftung
Priority date: 2016-08-01
Filing date: 2017-07-27
Publication date: 2019-06-05
Also published as: KR102542211B1; RU2019102129A; RU2019102129A3; CN109804716B; RU2745109C9; BR112019001771A2; CA3032712A1; US20210329771A1; DE102016214146A1; WO2018024601A1; CN109804716A; KR20190035839A; RU2745109C2

Abstract

The invention relates to a plasma torch, in particular a plasma cutting torch, wherein at least one feeder is used for conducting a secondary medium through a plasma torch housing to an opening in a protective nozzle cap and/or additional openings in a protective nozzle cap. Directly inside the plasma torch housing, at least one valve for opening and closing the feeder is provided in the at least one feeder.

Description

plasma torch

The invention relates to a plasma torch, in particular a plasma cutting torch.

Plasma is a thermally highly heated electrically conductive gas, which consists of positive and negative ions, electrons and excited and neutral atoms and molecules. The plasma gas used is a variety of gases, for example the monatomic argon and / or the diatomic gases hydrogen, nitrogen, oxygen or air. These gases ionize and dissociate through the energy of an arc. The narrowed by a nozzle arc is then referred to as plasma jet. The plasma jet can be greatly influenced in its parameters by the design of the nozzle and electrode. These parameters of the plasma jet are, for example, the beam diameter, the temperature, the energy density and the flow velocity of the gas. In plasma cutting, the plasma is usually constricted by means of a nozzle, which may be gas or water cooled. As a result, energy densities up to 2x10 ⁶ W / cm ² can be achieved. Temperatures of up to 30,000 ° C occur in the plasma jet, which, in combination with the high flow velocity of the gas, result in very high cutting speeds on materials.

Plasma torches usually consist of a plasma torch head and a plasma torch shaft. In the plasma burner head, an electrode and a nozzle are attached. Between them flows the plasma gas, which exits through the nozzle bore. Most often, the plasma gas is passed through a gas guide that is mounted between the electrode and the nozzle and can be rotated.

Modern plasma torches also have a secondary fluid supply, either a gas or a liquid. The nozzle is then surrounded by a nozzle cap. The nozzle is fixed in particular in the case of liquid-cooled plasma torches by a nozzle cap, as described, for example, in DE 10 2004 049 445 A1. Between the nozzle cap and the nozzle then flows the cooling medium. The secondary medium then flows between the nozzle or the nozzle cap and the nozzle protection cap and emerges from the bore of the nozzle protection cap. It influences the plasma jet formed by the arc and the plasma gas. It can be set in rotation by a gas guide which is arranged between nozzle or nozzle cap and nozzle cap.

The nozzle protection cap protects the nozzle and the nozzle cap from the heat or the ejected molten metal of the workpiece, in particular when piercing the plasma jet into the material of the workpiece to be cut. In addition, it creates a defined atmosphere around the plasma jet during cutting.

For example, nitrogen is often used as a secondary gas to prevent alloyed steels plasma cutting from contacting and oxidizing the oxygen in the ambient air with the hot cut edges. In addition, nitrogen causes the surface tension of the surface Melt reduced and thus better driven out of the kerf. There are beard-free cuts.

Even with the use of oxygen as plasma gas for the cutting of structural steels can be described by different compositions of the secondary gas, as described in DE 10 2006 018 858 AI, z. B. different nitrogen and oxygen levels, different effects in terms of cut quality can be achieved. It is also known to change the composition of the secondary gas between the individual cutting operations in order to first cut small holes and then large contours. The switching takes place in the period in which is not cut. Arrangements are also known in which valves, preferably electromagnetically operated valves, switch or regulate the secondary medium. These are located at a coupling unit between the gas hoses of the plasma torch and the supply hoses for gas supply. Disadvantages of the prior art are:

No fast switching on and off of the secondary medium is possible

It is not possible to quickly switch from one to another secondary medium

- It can not quickly respond to changes, e.g. during cutting, grooving, puncturing, during cutting, when passing over the kerf or at the end of the cut by switching the secondary medium.

There is no quick change between two cutting operations possible

The cause for this are lines between valves and the plasma torch. This is particularly critical if it is necessary to switch between different secondary media, for example an oxidizing (oxygen, air) and a non-oxidizing gas or gas mixture. Also critical is switching between a liquid (eg water, emulsion, oil,

Aerosol) and a gas, as when using a common feeder, eg a hose, the gas must first rinse all the remaining liquid in it. This can take several 100 ms.

The attachment of valves on plasma torch shaft is unfavorable for mounting in the guide system, especially for swivel units, this is disturbing.

It is therefore an object of the invention to provide opportunities for improved conditions when switching off, switching or changes in a controlled or regulated operation of a plasma torch in the supply of secondary medium.

In the plasma torch according to the invention, in particular plasma cutting torch is guided by at least one supply at least one secondary medium through a housing of the plasma torch up to a Düsenschutzkappenöffnung and / or other openings that are present in a nozzle cap. In the at least one supply, at least one valve for opening and closing the supply is provided directly inside the housing of the plasma torch.

Advantageously, the feed can be divided into at least two parallel feeds through which secondary medium flows in the direction of the nozzle protective cap opening and / or further openings and within the housing then at least two valves for opening and closing the respective split feed are present, which can each be activated individually , so that there is the possibility that one of the valves alone can open the supply of the secondary medium, secondary medium can flow simultaneously through both split feeders or a switchover can take place from one to the other split supply line.

It is possible to use in at least one of the split feeds a diaphragm, a throttle or the free cross-section of the respective supply to the free cross section with respect to the other split feed changing element, so that different flow resistances in the split feeds for a secondary medium and different flow velocities and Pressures of the secondary medium can be reached.

Particularly advantageously, at least two feeds for two different secondary media can be guided through the housing of the plasma torch up to a nozzle protection cap opening and / or further openings which are present in the nozzle protection cap and at least one each in the feeds for a respective secondary medium within the housing Valve for opening and closing the respective feeder is present.

The feeds should be designed so that the merging of the split feeders for a secondary medium or the merging of the feeds for different secondary media within the housing of the plasma torch, within the plasma head, in a space formed with the nozzle or nozzle cap and the nozzle cap, the supply flow of the secondary media streams from the split feeds and / or before, during or after passing through a gas guide of the plasma torch takes place. Accordingly, the confluence should occur within the housing, or plasma head.

At least two ports or two sets of ports carrying the respective secondary media (s) should be present on the gas guide. With these openings, a targeted influence on the emerging from the openings secondary media can be achieved. These openings can be different sized and geometrically designed free

Cross sections and / or be aligned in different axial directions. Openings of different groups can be arranged radially offset from each other. The number of openings in the individual groups can be chosen differently.

The arranged within the housing valves can be operated electrically, pneumatically or hydraulically and particularly preferably be designed as an axial valve.

The valves arranged in the housing should have a maximum outside diameter or a maximum mean surface diagonal of 15 mm not more than 11 mm and / or a maximum length of 50 mm, preferably not more than 40 mm, more preferably not more than 30 mm and / or the maximum outer diameter of the housing should be 52 mm and / or the maximum outer diameter of the valves should be a maximum of J4, preferably a maximum Have 1/5 of the outer diameter or a maximum average surface diagonal of the housing and / or require a maximum electrical power consumption of 10 W, preferably 3 W, particularly preferably 2 W for their operation.

In one or more electrically operable valve (s), the respective secondary medium or the plasma gas should flow through the winding of a coil (S) in order to achieve a cooling effect.

Advantageously, it can be designed as a quick-change burner with a plasma burner shaft that can be separated from a plasma burner head. This can be achieved quickly and easily to different machining tasks.

The nozzle guard should have at least one opening through which at least a portion of one of the secondary media flows, in addition to the nozzle guard opening or a retainer of the nozzle guard. In the case of several existing openings, one secondary medium in each case can exit through one or more selected openings in the direction of the workpiece surface. However, it is also possible, as already mentioned, to let a secondary medium flow out through a group of openings and another medium to be discharged through openings which are assigned to another group. There may also be at least one opening through which a secondary medium mixture formed from two different secondary media can escape.

It can be used gaseous and / or liquid secondary media. These may be two different gases, for example selected from oxygen, nitrogen and a noble gas, two different liquids, for example selected from water, an emulsion, oil and an aerosol or a gaseous and a liquid secondary medium. But there is also the possibility of two secondary medium mixtures used, which are each formed with the same gases and / or liquids and thereby differ only the proportions of the secondary media forming the respective mixture. This can be, for example, a different proportion of oxygen contained in the secondary media mixture.

The valve (s) disposed in a secondary fluid supply should be opened when at least a portion of the electrical cutting current flows through the workpiece, such that secondary medium from the plasma torch flows through the workpiece Can flow towards the workpiece surface. During a period in which a pilot arc is formed, the valve (s) should be kept closed. This can be achieved with a controller, which is preferably connected to a database.

During the piercing of the plasma jet into the material of the workpiece, a liquid or a liquid-gas mixture may be used as a secondary medium and a gas or gas mixture may be used as a secondary medium for cutting.

The valve (s) disposed in a secondary fluid supply should be opened at the earliest at the time such that secondary fluid flows from the nozzle cap bore at which the workpiece is at least about 1 when piercing a workpiece / 3, better half and best of all has been completely punctured.

At least one valve, which is arranged in a feed for secondary medium, should be able to be switched off during the start of cutting, between two cutting sections, when passing over a kerf F or at the cutting end. There is the possibility of switching two valves, which are arranged in two different feeds for secondary medium, during or during these processing tasks. That that a previously open valve closed and a hitherto closed valve can be opened.

At a start for cutting with a plasma jet, a piercing or cutting done.

When cutting a contour, it is possible to change the parameters of the secondary medium (as described above) and to change at least one other parameter of the plasma cutting process. This can be, for example, an adaptation of the electrical parameters, an adjustment of the feed rate, the volume flow, the distance of the plasma torch to the workpiece surface and / or the composition of the plasma gas. For this purpose, all parameters can be stored in a database and used so that an automatic operation with a control of the plasma torch is possible. In addition to the parameters mentioned, the parameters for the respective machining of a workpiece can also be present in the database and used.

The invention will be explained by way of example below. The individual features shown in the figures and explained therefor can be combined independently of the respective example or the respective figure.

Showing:

1 shows in schematic form a sectional view through an example of a plasma torch according to the invention with a secondary medium supply with a valve and a plasma gas supply;

2 shows in schematic form a sectional view through an example of a plasma torch according to the invention with a secondary medium supply with two valves and a plasma gas supply;

Figure 3 in schematic form a sectional view through another

Example of a plasma torch according to the invention with a secondary medium supply with two valves and a plasma gas supply; FIG. 4 is a schematic sectional view through a further example of a plasma torch according to the invention with a secondary medium feed with two valves and a plasma gas feed;

Figure 5a u. b a guide for secondary media; in schematic form a sectional view through an example of a plasma torch according to the invention with two Sekundärmediumzuführungen with two valves and a plasma gas supply; in schematic form a sectional view through a further example of a plasma torch according to the invention with two secondary media supplies with two valves and a plasma gas supply; in schematic form a sectional view through another example of a plasma torch according to the invention with two Sekundärmediumzuführungen with two valves and a plasma gas supply; in schematic form a sectional view through an example of a plasma torch according to the invention with two Sekundärmediumzuführungen with two valves and a plasma gas supply with a valve and a vent valve; in schematic form a sectional view through an example of a plasma torch according to the invention with two Sekundärmediumzuführungen with two valves and two plasma gas supplies with two valves and a vent valve;

Figure 11 is a sectional view of a usable in the invention

axial valve; Figure 12 way for the arrangement of valves within the housing of a plasma torch and

Figure 13 shows another possibility for the arrangement of valves within the housing of a plasma torch.

Figure 14 shows another possibility for the arrangement of valves within the housing of a plasma torch.

Figure 15a u. b a sectional contour with large and small sections (contours)

Figure 16a u. b is a sectional contour with vertical and chamfer cut and

17 shows a plasma torch with its positioning to the workpiece

FIG. 1 shows a plasma torch 1 with a plasma burner head 2 with a nozzle 21, an electrode 22, a nozzle protection cap 25, a supply 34 for a plasma gas PG1, a secondary medium feed SGI 61 and a plasma burner shaft 3 having a housing 30. In the invention, including in all other examples, which fall under the invention, the plasma torch shaft 3 may be integrally formed and formed only with a correspondingly configured housing 30, where all the necessary components can be present and formed.

The feed 61 may be outside the housing 30 a gas hose, which is connected to a supply of secondary medium SGI with a coupling unit 5. The gas hose is followed by another part of the supply 61 and the valve 63, which are arranged inside the housing 30. The feeder 34 may be outside the housing 30 a gas hose, which is connected for a supply of plasma gas PGl with a coupling unit 5. In the coupling unit 5, a solenoid valve 51 for opening and closing the feeder 34 is arranged. The gas hose is followed by a further part of the feed 34, which is formed inside the housing 30.

The electrode 22 and the nozzle 21 are spaced apart by the gas guide 23 so that a space 24 is formed within the nozzle 21. The feed 34 of the plasma gas PG1 is connected to the space 24. the.

The nozzle 21 has a nozzle bore 210 which, depending on the electrical cutting current, may vary in diameter from 0.5 mm for 20 A to 7 mm for 800 A. The gas guide 23 also has openings or bores (not shown) through which the plasma gas PG1 flows. These can also be designed in different size or diameter and even number. The nozzle 21 and the nozzle guard 25 are spaced apart so that the spaces 26 and 28 are formed within the nozzle guard 25. The space 26 is located in the flow direction of the secondary medium SGI in front of the guide 27, the space 28 is located between the guide 27 and the Düsenschutzkappenöffnung 250. With the help of the gas guide 27, the flow of the secondary medium SGI, for example, a gas, gas mixture, a Liquid or a gas-liquid mixture are symmetrized and / or rotated. There is also the possibility that no guide 27 is used, if e.g. no rotation of the

Secondary medium SGI is desired. The nozzle 21 may also be replaced by a nozzle cap or the like. be fixed (not shown). Then, the nozzle cap and the nozzle cap form the spaces 26 and 28.

The secondary gas SGI is thus passed via the supply 61 and arranged in the plasma torch valve 63 into the space 26, symmetrized by the guide 27 and set in rotation. The secondary gas SGI then flows into the space 28 then exits the nozzle guard opening 250. There is also the possibility that in the nozzle cap 25 or a holder for the nozzle cap 25 one or more further holes 250a are located, through which the secondary medium SGI flows.

The valve 63 is designed as an axial valve in a small design. For example, it has an outer diameter D of 11 mm and a length L of 40 mm. It requires a low electrical power for operation, here for example about 2 W to reduce the heating in the housing 30.

Upon ignition of the arc and during cutting, the plasma gas PG1 flows through the open valve 51 and the supply 34 into the housing 30 and from there into the space 24 between the electrode 22 and the nozzle 21 and ultimately flows through the nozzle bore 210 and the Düsenschutzkappenöff - 250 out. After cutting, the valve 51 is closed again and the supply 34 of the plasma gas PG1 is drained.

The secondary medium, in this example a gas (secondary gas SGI), can be switched through the valve 63 at the same time as the valve 51 of the plasma gas PG1. Due to the inventive arrangement of the valve 63 in the plasma burner shaft 3 and close to the plasma burner head 2, the secondary medium SGI can be switched on and off at other times.

In plasma cutting, first the pilot arc with low electric current, for example 10 A to 30 A, which burns between the electrode 22 and the nozzle 21, is ignited. When the plasma jet 6 generated by the pilot arc touches the workpiece W to be cut, the arc is transferred from the nozzle 21 to the workpiece W. The control of the plasma cutting system detects this sensory and increases the electrical current to the required value, depending on the workpiece thickness in the processing area to 30

A to 600 A.

During the time the pilot arc burns, the secondary medium SGI is not needed yet. It even disturbs and shortens the plasma jet 6 emerging from the nozzle 21, since it flows sideways. Therefore, the plasma torch 1 must be positioned closer to the workpiece W with its nozzle guard opening 250 and / or openings 250a. This in turn leads to jeopardy of the nozzle cap 25 and the nozzle 21 by hot high-pressure molten material. Remedy here creates the connection of the secondary medium SGI only at the time at which at least a portion of the electrical cutting current flows over the workpiece W and the arc is at least partially transferred to the workpiece W. Thus, on the one hand, the nozzle guard opening 250 of the plasma torch 1 can be positioned far enough away from the upper surface of the workpiece for piercing, and the arc still transitions. On the other hand, by an arrangement according to the invention, which ensures the fast, only a little time-delayed feeding and flowing after switching on the valve 63 of the secondary medium SGI, the nozzle cap 25 and the nozzle 21 are protected from high-injection molten hot material of the workpiece W to be machined. This is especially important for thick parts to be cut with thicknesses of approx. 20 mm. With thinner workpieces W, on the other hand, it is often even better if the secondary medium SGI does not flow through the nozzle protection cap opening 250 until the workpiece W has been partially or completely pierced by the plasma jet 6. If during a part of the time of piercing or the total time of piercing - which is the time required to completely pierce the workpiece W - the secondary gas does not flow, smaller piercing holes can be achieved. This results in less slag deposits on the workpiece surface that can interfere with the cutting process.

Even when cutting on one edge, it makes sense not to let the secondary medium SGI flow and to keep the valve 63 closed, because here too the pilot arc already passes over the workpiece W at a greater distance and cuts it more securely.

When cutting itself, the secondary medium SGI is again needed to improve the quality of cut by its influence. This should be done immediately after piercing or cutting in order to achieve a good cut quality from the beginning of the cutting. Cutting quality includes perpendicularity and inclination tolerance, roughness and beard attachment, as well as groove after-run (DIN EN ISO 9013).

A non-flowing secondary medium SGI can also have a positive effect when crossing over kerfs F or when cutting corners or curves. The oscillation or pulsation of the plasma jet 6 can be reduced.

In Figure 2, a similar arrangement as shown in Figure 1, but are in the feed medium 61 SGI in the housing 30 of the

Plasma torch 1 two parallel valves 63 and 64. The supply 61 of the secondary medium SGI is thus divided into the feeds 61a with the valve 64 and 61b with the valve 63. Thus, it is possible to switch on and off the flow of the secondary medium SGI at the points in time in the description of FIG. 1, but additionally also to rapidly change the volume flow in a simple manner. Here is an example For this purpose, in the supply 61a, a shutter 65 is installed, which reduces the volume flow compared to the feed 61b, which can be achieved by the correspondingly smaller free cross section through which the secondary medium SGI can flow. The feeds 61a and 61b of the partial gas streams of secondary medium SGla and SGlb of the secondary gas SGI are here combined again in the plasma burner shaft 3. Thus, only one feed 61 to the plasma burner head 2 for the secondary medium SGI needs to be provided. In particular, for a plasma torch 1 with quick-change head this is advantageous.

A reduction of the secondary medium flow has a positive effect at the same points in time as are the sections without flowing secondary medium SGI described in the example according to FIG.

In addition to the rapid switching on and off of the flow of the secondary medium SGI additional possibility of setting different sizes of flow rates, the plasma cutting process in particular to the

Transition operations, such as grooving, cutting, passing over a joint F, cutting a corner or rounding be further improved.

Furthermore, in contrast to the example of Figure 1, the nozzle 21 is fixed here by a nozzle cap 29. This allows a cooling medium, for example cooling water, to flow in the space between the nozzle 21 and the nozzle cap 22 (not shown).

FIG. 3 shows, by way of example, a similar arrangement to FIG. 2, but the feeds 61a and 61b of the secondary media SGla and SGlb are merged to form the secondary medium SGI only in the plasma burner head 2. In this example, the merge takes place in the flow direction of the secondary medium SGI further ahead of the guide 27 of the secondary medium.

FIG. 4 likewise shows an arrangement in which the feeds 61a and 61b of the secondary medium SGI are first brought together in the plasma burner head 2. In this example, the merging takes place from the nozzle cap 25 and the nozzle cap 29 in the flow direction of the secondary medium SGI to the gas guide 27 of the secondary medium. The gas guide 27 has two groups of openings, one group for the secondary medium SGla and the other group for the secondary medium SGlb.

Advantageously, the openings differ in their design, di- dimensioning and / or alignment of their center axes (dash-dot lines), here for example in offset from the radial. The openings 271 and 272 of the groups can be arranged offset in different planes and in the planes in each case. This is also shown in FIG. 5. Thus, the secondary medium SGI can be split into two differently rotating

Secondary medium streams SGla and SGlb and SGI and SG2 are divided, which ultimately flow around the plasma jet 6.

Thus, when inserting into the material of the workpiece W, little or no rotation of a flowing secondary medium SGI makes sense, whereas for cutting, a larger rotation is advantageous. Due to the larger offset g from the radial, the rotation of the exiting secondary medium flow is increased. In addition, the possibility of influencing the quality of cut during cutting by switching or jointly switching on the flows of the secondary media SGla and SGlb results. In this case, long straight sections with large rotation of the outflowing secondary medium SGI and high feed rate and small sections with less rotation of the outflowing secondary medium SGI and smaller feed rate are cut. A long section usually starts at a length at least twice the thickness of the workpiece W to be cut, but is at least 10 mm in length. With greater rotation, ie greater angular velocity of the flow of the secondary medium SGI can be cut faster, with less rotation must be cut slower. However, a lower feed rate is for cutting small sections, for. B. small radii, for example, be less than twice the thickness of the workpiece W, saw teeth, quadrilateral contours whose edge length is also less than twice the thickness of the workpiece W in the respective processing area, advantageous. Due to the lower feed speed, the guide system guides the plasma burner 1 more accurately even when the direction of movement changes. In addition, the plasma jet 6 does not run after, the groove trailing is reduced, which has a positive effect on corners on inner contours (Figure 17) and inner corners. For long sections, this does not matter, here can be cut with great rotation of the flow of the secondary medium SGI with greater feed rate. FIGS. 5a and b show, by way of example, a guide 27 for the secondary medium, here by way of example gas, which is designated here as secondary gas SG1, SG2, SGla and SGlb.

The group of holes 271 are for the secondary medium SGI or SGla, the holes for the group 272 for the secondary medium SG2 or SGlb. The holes of a group are arranged in one plane. The group of holes 271 has, for example, an offset to the radial of 3 mm and the group of holes 272 no offset to the radial. When this guide 27 is installed in the plasma torch 1 of FIG. 4, the flow of the secondary medium SGla supplied through the supply 61a and the group of bores 271 has a larger rotation at a higher angular velocity than the flow of the secondary medium SGlb through the supply 61b and the group of bores 272 is supplied.

There are also other openings than holes 271 and 272, such as. As grooves, squares, semicircular or angular shapes possible. Likewise, the openings may have different sized free cross sections through which secondary medium can escape.

The arrangement according to FIG. 6 has the features of the example according to FIG. 1, but has, in addition to the feed 61 for the secondary medium SGI, a feed 62 for a second secondary medium SG2. The feeders 61, 62 may be outside the housing 30 hoses, which are connected to a supply line of the secondary media SGI, SG2 with a coupling unit 5. Each of the hoses is followed by another part of the feeders 61, 62 and in each case the valves 63, 64, which are arranged inside the housing 30.

The feeds 61 and 62 of the secondary media SGI and SG2 are here combined again in the plasma burner shaft 3. Thus, only one feed 66 to the plasma burner head 2 needs to be provided for the secondary media SGI and SG2. For a plasma torch 1 with quick-change head this is particularly advantageous.

As a result of this arrangement, in addition to the rapid switching on and off as well as the rapid change of the volume flow of the secondary medium flows, the composition of the emerging secondary medium can also be effected by switching or simultaneously switching on the valves 63, 64. So For example, in a work piece W of mild steel, small contours or small portions are cut with a secondary medium mixture containing a higher proportion of oxygen with respect to a content of nitrogen; C0 ₂ , air or argon as in large sections. The information given in the explanation in FIG. 4 applies here. By way of example, such contours are also shown in FIGS. 15a and 15b. The oxygen content is then over 40 vol .-%. K3 is a small section and sections Kl and K5 are larger sections.

Likewise, it is advantageous if when plunging into mild steel with oxygen as the sole secondary medium is inserted, because it makes the melt is less viscous and puncturing faster vonstattengeht. When cutting itself, too high an oxygen content can again lead to the formation of irregularities on the cutting edge or surface. Again, a quick switch is advantageous.

Another application is the use of a liquid, for example

Water, as one of the secondary media used. Thus, it is advantageous for water to flow into the structural steel as secondary medium SGI. This prevents or reduces the high-splash hot metal splashes and thus protects the plasma torch 1 and also the environment. After piercing through the workpiece W, the water is turned off and it flows a gas or gas mixture as the secondary medium SG2. The process can also be used for high-alloy steel and non-ferrous metals.

Furthermore, the secondary medium or secondary medium mixture in the transition from vertical sheath to bevel cutting in terms of

Parameters such as flow velocity, flow rate, rotation and composition are changed. When chamfering the plasma torch 1 (central axis) is not perpendicular to the workpiece surface as in perpendicular cutting, but is inclined to form a cutting edge with a certain angle. This is for further processing, usually a subsequent welding advantage. Since the effective thickness of the workpiece W to be cut changes (increases) during the transition from vertical to bevel cutting, modified parameters for a higher quality of cut then make sense. The same applies in principle to the transition from chamfering to vertical cutting (reduction)

It is also advantageous if the change of parameters in sections takes place, which were not on the cutting contour after cutting out the workpiece W, so for example at the beginning of cutting, driving around corners, at the end of the cut, driving over a kerf or other parts of the "waste piece".

FIG. 7 shows, by way of example, a similar arrangement to FIG. 6, but the feeders 61 and 62 of the secondary media SGI and SG2 are first brought together in the plasma burner head 2. In this example, the merge takes place in the flow direction of the secondary media SGI, SG2 before the guide 27 for the secondary media.

FIG. 8 likewise shows an arrangement in which the feeds 61 and 62 of the secondary media SGI, SG2 are first brought together in the plasma burner head 2. FIG. 8 has all the advantages of the example according to FIG.

Further advantages will be described below. In this example, the merging of the secondary media SGI and SG2 before the nozzle cap 25 and nozzle cap 29 takes place in the flow direction of the secondary media SGI, SG2 and after the guide 27 for the secondary media. The guide 27 has two groups of openings, one group for the secondary medium SGI and the other group for the secondary medium SG2.

Advantageously, the openings 271 and 272 differ in their design, here for example offset from the radial. This is also shown in FIG. 5a. Thus, the secondary medium SGI a different rotating secondary fluid flow than the secondary medium SG2, which ultimately flow around the plasma jet 6, form.

Thus, little or no rotation of the secondary media SGI, SG2 is useful when plunging into the workpiece material, but when cutting a larger rotation with a higher angular velocity is desirable. The larger offset from the radial increases the rotation. In addition, there is the possibility of influencing the quality of cut during a cut by switching or jointly switching on the flows of the secondary media SGI and SG2. Long straight sections of high rotation and high speed and small sections of lesser rotation and lower speed are cut. A long section usually begins at a length which is at least twice the thickness of the workpiece W to be cut in the respective machining process. range, but at least 10 mm in length. With greater rotation of secondary fluid / media flow can be cut faster, with less rotation must be cut slower. However, a lower feed rate is for cutting small sections, for. B. small radii, for example, be less than twice the thickness of the workpiece W in the respective processing area, for example, sawtooth contours, quadrilateral contours whose edge length is also less than twice the workpiece thickness in the respective processing area, advantageous. Due to the lower forward thrust speed, the guide system guides the plasma torch 1 more accurately even when the direction of movement of the feed movement is changed. In addition, the plasma jet 6 does not run after, the groove trailing is reduced, which has a positive effect on corners on inner contours and inner corners. In long sections, this does not matter, here can be quickly cut with large rotation of the flow of / the secondary medium / media.

In this arrangement, the exiting secondary medium or

Secondary medium mixture with respect to the parameters such as flow rate, flow rate, rotation of the flow and composition can be changed.

FIG. 9 additionally shows in the supply 34 of the plasma gas PG1 a valve 31 in the housing 30 of the plasma burner shaft 3, which switches the plasma gas PG1 on and off. The valve 33 serves to vent the cavity 11, which is necessary in particular at the end of the cut in order to ensure a rapid outflow of the plasma gas PG1.

FIG. 10 shows, in addition to FIG. 9, the supply 35 of a further plasma gas PG2, which is supplied via a gas hose 35 and a valve 31 analogous to plasma gas PG1. This can be done by switching and switching the valves 31 and 32, a change of the plasma gases PG1 or PG2 depending on the process state. The valve 33 also serves to vent the cavity 11.

Figure 11 shows the greatly simplified construction of an axial solenoid valve, as can be used in the invention in the feeds for secondary media and plasma gas. Inside his body is the coil S with the

Windings flowing through the plasma gas from input E to output A. can be arranged. Inside, the mechanism for opening and closing is arranged. The body of the solenoid valve has a length L and an outer diameter D. The solenoid valve shown here has a length L of 25 mm and a diameter of 10mm.

Figure 12 shows a possible space-saving arrangement of the valves 31, 63 and 64. They are arranged in the housing 30 so that they are arranged in a plane perpendicular to the center line M at an angle al, of 120 °. The deviation from this angle should not exceed ± 30 °. As a result, the arrangement is space-saving and can be arranged in the housing 30 or plasma torch shaft 3. The distances between the central longitudinal axes LI, L2 and L3 between the valves 31, 32, 33 are each <20mm. Of the valves 31, 32 and 33, at least one valve with its inlet E is opposite to the other valves, i. aligned to their outputs A. The oppositely directed valve is the valve 33 in the example shown

Cavity 11.

Figure 13 shows an arrangement with four valves 31, 33, 63 and 64. They are arranged in the interior of the housing 30 so that they are arranged in a plane perpendicular to the center line M at angles al, a2, a3, a4 of 90 ° , The

Deviation from these angles should not exceed ± 30 °. As a result, the arrangement is space-saving and can be arranged in the housing 30 or plasma torch shaft 3. The distances of the central longitudinal axes LI, L2, L3 and L4 of the valves 31, 33, 63 and 64 are <20 mm. Of these valves 31 and 33, at least one valve is opposite its inlet E to the other valves, i. aligned to their outputs A.

Figure 14 shows an arrangement with four valves 31, 33, 63 and 64 and another valve 32. They are arranged in the interior of the housing 30 so that they in a plane perpendicular to the center line M at angles al, a2, a3, a4 , a5 are arranged by 72 °. The deviation from these angles should not exceed ± 15 °. As a result, the arrangement is space-saving and can be arranged in the housing 30 or plasma torch shaft 3. The distances between the middle longitudinal axes LI, L2, L3, L4 and L5 between the valves are <20 mm. Of these valves 31 to 33 is at least one valve with his Input E opposite to the other valves, ie aligned to the outputs A.

FIG. 15 a shows a schematic contour guidance of a plasma torch for cutting a contour from a workpiece W as viewed from above onto the workpiece and FIG. 15 b shows the resulting workpiece in a perspective view. Here a workpiece with two long sections, contour Kl, K5 and several short sections, contour K3, is to be cut. Section K0 is the beginning of cutting, it is there pierced into the workpiece. The sections contours K2 and K4 are due to cutting technology to achieve a sharp corner and are located in the so-called "waste part", they are not part of the cut workpiece.

The following possibilities exist during grooving: a. At the time of pilot arc operation, the secondary medium is not yet needed. It even disturbs and shortens the jet of plasma 6 emerging from the nozzle 21 even as it flows sideways. Therefore, the plasma torch 1 must be positioned with its nozzle guard opening 250 at a smaller distance from the workpiece surface (Figure 17, distance d). This in turn leads to endangerment of the nozzle cap 25 and the nozzle 21 by hot high-rate molten material. Remedy here creates the connection of the secondary medium only at the time at which at least a portion of the electrical cutting current flows over the workpiece and the arc is at least partially transferred to the workpiece. Thus, on the one hand, the nozzle protection cap opening 250 of the plasma torch 1 can be positioned for piercing at a greater distance d from the workpiece surface, and the arc nevertheless sets over.

By flowing the secondary medium SGI with a larger flow rate, the nozzle cap 25 and the nozzle 21 are protected from high-injection molten hot material of the workpiece to be machined. This is particularly important for thick workpieces to be cut starting from approx. 20 mm in the respective machining area. For example, a plasma torch 1 according to FIGS. 1 to 10 can be used for this purpose.

For thinner workpiece thicknesses, it is better if the secondary medium only flows through the nozzle guard opening 250 when the workpiece is partially or completely pierced. If, during one part, the time of piercing or the total time of piercing - which is the time required to completely pierce the workpiece - secondary medium does not flow, smaller piercing holes will be reached. This results in less slag deposits on the workpiece surface that can interfere with the cutting process. Secondary medium should flow from the nozzle protection cap opening 250 at the earliest at the time at which the workpiece has been punctured at least 1/3, better half, and preferably completely when piercing a workpiece.

For example, a plasma torch according to FIGS. 1 to 10 can be used for this purpose.

Furthermore, small or no rotation of the secondary medium SGI, SGla, SGlb, SG2 is often useful when piercing the workpiece, whereas a larger rotation at a larger angular velocity is useful when cutting.

For example, a plasma torch 1 according to FIGS. 4 and 8 can be used for this purpose. Due to the greater offset of the openings 271 and 272 from the radial in the gas guide 27 for the secondary media, the secondary media SGla and SGlb (FIG. 4) and SGI and SG2 (FIG. 8) rotate to different degrees.

The change of the rotation of the secondary medium or the secondary media should be carried out at the earliest at the time from the nozzle guard opening 250 at which the workpiece has been pierced at least 1/3, better half and best completely completely when piercing a workpiece.

Likewise, it may be advantageous for piercing into structural steel, when water flows as a secondary medium SGI. This prevents or reduces graces the high-splash hot metal splashes and thus protects the plasma torch 1 and the environment. After piercing through the workpiece, the water is switched off and it flows a gas or gas mixture as a secondary medium SG2.

The change from water to gas as a secondary medium should be made at the earliest at the time from the Düsenschutzkappenöffnung 250 at which the workpiece has been pierced at least to 1/3, better half and best completely completely when piercing a workpiece.

The process can also be used for high-alloy steel and non-ferrous metals.

For example, a plasma torch 1 according to FIGS. 6 and 10 can be used for this purpose.

It is also advantageous if when piercing in mild steel with oxygen or a higher oxygen content at a

Secondary medium mixture is inserted, because then the melt is thinner and the piercing is faster. When cutting itself, too high an oxygen content can again lead to the formation of irregularities on the cutting edge or surface. Also, for the cutting of high-alloy steel, alumiminium and other metals, a change of the secondary medium between the piercing and the cutting may be advantageous. The change of outflowing secondary medium should be made at the earliest at the time from the Düsenschutzkappenöffnung 250 at which the workpiece has been at least 1/3, better half and best completely pierced when inserting into a workpiece.

It may be of particular advantage if the secondary medium and the rotation of the flow of the secondary medium are changed during insertion into the workpiece. Here it comes to those in the points c. and e. described effects. As plasma torch 1, by way of example, the one shown in FIG. 8 can be used. In principle, it may be advantageous to change the secondary medium (s) to one or more parameters, such as flow rate, volumetric flow, flow and composition rotation during the plunge phase, as compared to other operating conditions.

After piercing, the cutting movement is made with the selected secondary medium. After piercing the workpiece contour K0, the long section Kl is cut, after which the section K2 is to be moved around the corner. A sharp-edged corner is obtained when the plasma cutting torch 1 is guided as in corner section contour K2. Here, as shown in Fig. 15, the plasma cutting torch 1 leaves the contour of the part to be cut, and is passed over the "waste part" to return to the contour of the part to be cut, which is also called the "corner swept". After section contour K2, a section contour K3 follows with an exemplary sequence of small sections with advancing axis direction changes. During the time in which the plasma torch 1 is guided over the "waste part" in the section contour K2, at least one change took place on the outflowing secondary medium.

The following possibilities exist when crossing the "waste part" to contour K2:

a. It is advantageous to influence the quality of cut during cutting by varying the rotation of the secondary medium / media flow. Long straight sections with high rotation and high speed and small sections with less rotation and smaller feed speed are cut. A long section usually begins at a length which is at least twice the workpiece thickness in the respective machining area of the workpiece to be cut, but at least a length of 10 mm. With greater rotation of the flow of the secondary medium (s), it is possible to cut at a higher feed rate, with less rotation, it must be with a smaller forward speed. However, a lower feed rate is for cutting small sections, for. Small ones Radii that are, for example, smaller than twice the workpiece thickness in the respective processing area, sawtooth contours, quadrilateral contours whose edge length is also less than twice the workpiece thickness, advantageous. Due to the lower feed speed, the guide system leads the plasma torch 1 more accurately even when the direction of movement changes. In addition, the plasma jet 6 does not run after, the groove trailing is reduced, which has a positive effect on corners on inner contours and inner corners. For long sections, this does not matter, here can be cut with large rotation of the flow of / the secondary medium / media at a higher feed rate.

For example, a plasma torch 1 according to FIGS. 4 and 8 can be used for this purpose.

It is also advantageous during the cutting to make a change in the volume flow and / or the composition of the secondary medium. Thus, a workpiece made of mild steel, small contours or small sections with a

Secondary medium mixture cut, which has a higher proportion of oxygen than in large sections. The oxygen content is then over 40 vol.%.

For example, a plasma torch 1 according to FIGS. 6 to 10 can be used for this purpose.

It is of particular advantage if the points a. and b. combined possibilities.

For example, a plasma torch according to the figures 8 can be used.

In this arrangement, the secondary medium or

In principle, it may be advantageous to use the secondary medium or secondary medium mixture with one or more parameters, such as, for example, flow velocity, volume flow, rotation the flow and composition during cutting and particularly advantageous when driving over the "waste part" to change.

If the change in one of the described parameters occurs in the region of the waste part, ie not at a cutting edge of the workpiece to be cut, no transition or difference in the quality of the cut is visible on the cut edge of this workpiece.

But it is also possible to make a change of parameters on a portion of the resulting cut edge of the workpiece. For this purpose, but at least one other parameters of the plasma cutting process, feed rate, distance plasma torch - workpiece surface (nozzle protection cap - workpiece surface), electrical cutting current and / or electrical cutting voltage, but must be changed in addition to the secondary medium.

But it is also possible to realize one of the described changes of the secondary medium when driving over a kerf F.

Section K10 Cut ends cutting. Again, parameters of the effluent secondary medium or secondary medium mixture can be changed again.

After one of the described changes of at least one parameter of the secondary medium or of the secondary media, the contour K3 with the small sections is cut with the parameter (s) most suitable therefor.

The change to the parameters on the section with long contour K5 takes place in area K4 on the "waste part" analogous to the change in the section contour K2.

Figures 16a and 16b also show a cut component. Again, as described in Figures 15a and 15b, the form of the change of the outflowing secondary medium in the sections K2 and K4 between the sections Kl and K3 and K5. The parameters of the effluent secondary medium for the section are changed from section K21 because in section K3 a bevel with an angle, for example se 45 ° is cut. This is also described in the last paragraph to FIG.

FIG. 17 shows, by way of example, a plasma burner 1 with its positioning relative to the workpiece with the distance d between nozzle protection cap 25 and workpiece W.

LIST OF REFERENCE NUMBERS

1 plasma torch

2 plasma burner head

3 plasma torch shaft

5 coupling unit

6 plasma jet (pilot or cutting arc)

1 1 cavity

21 nozzle

22 electrode

23 gas routing

24 space (between electrode - nozzle)

25 nozzle protection cap

26 space (nozzle - nozzle protection cap)

27 Media Guide SG, SG2, SG1 a, SG2a

28 Room (nozzle - nozzle protection cap), towards the nozzle tip

29 nozzle cap

30 housing

31 valve PG1

32 valve PG2

33 valve venting

34 feeder PG1

35 feeder PG2

37 line

51 valve

61 feed SG1

61a feed SG1 a

61 b supply SG1 b

62 feeder SG2 63 Valve SG1, SG1 a

64 valve SG2, SG1 b

65 aperture

66 feeder

21 0 nozzle bore

250 nozzle protection cap opening

250a further drilling

271 holes in media guide 27 for secondary medium SG1, SG1 a

272 holes in media guide 27 for secondary medium SG2,

SG1 b

A output

D diameter

D Plasma torch distance - workpiece

E entrance

F Groove

g offset

K Contour of the cut workpiece

K0 cutting start, grooving

K1 section contour 1

K2 section between two sections

K3 section contour 3

K4 section between two sections

K5 section contour

K1 0 cutting end

L length

Center axis of the plasma torch

PG1 plasma gas 1

PG2 plasma gas 2

SG1 secondary medium 1 SG1a secondary medium 1a

SG1b secondary medium 1b

SG2 secondary medium 2

S coil

L1 -L4 Distances of the valves

V cutting direction, feed axis direction

W workpiece

W1 cut surface

W2 workpiece thickness

α1-α4 angle

Claims

claims

Plasma torch, in particular plasma torch, with a supply (34) for plasma gas (PG1), in which by at least one feed (61, 62) at least one secondary medium (SGI, SG2) through a housing (30) of the plasma torch (1) up to a Nozzle cover opening (250) and / or further openings (250a) which are present in a nozzle cover (25), and in the at least one feed (61, 62) directly within the housing (30) of the plasma torch ( 1) at least one valve (63, 64) for opening and closing the supply (61, 62) is present.

Plasma torch according to claim 1, characterized in that the one feed (61) in at least two parallel feeds (61a, 61b) through the secondary medium (SGI) in the direction Düsenschutzkap- penöffnung (250) and / or further openings (250a) flows divided and inside the housing (30) at least two valves (63, 64) for opening and closing the respective split feed (61a, 61b) are present, which are each individually activated.

Plasma torch according to claim 2, characterized in that in at least one of the divided feeds (61a, 61b) a diaphragm (65), a throttle or the free cross-section of the respective feed (61a) with respect to the free cross-section with respect to the other split feed ( 61b) changing element is present.

Plasma torch according to one of the preceding claims, characterized in that at least two feeds (61, 62) for two different secondary media (SGI, SG2) are guided through the housing (30) of the plasma torch (1) to a nozzle protection cap opening (250) and / or further openings (250a) which are present in the nozzle cover (25) are guided, and and at least one valve (63, 64) for opening and closing the respective supply (61, 62) is present in each of the feeders (61, 62) for a respective secondary medium (SGI, SG2) within the housing (30).

Plasma torch according to one of the preceding claims, characterized in that the merging of the split feeders (61a, 61b) for a secondary medium or the merging of the feeds (61, 62) for different secondary media (SGI, SG2) within the housing (30) of the plasma torch (1), within the plasma head, in a space formed with the nozzle or nozzle cap and the nozzle guard, and preferably the confluence of the secondary media streams from the split feeds (61a, 61b and / or 61, 62) before, during, and after passing a gas guide (27) of the plasma torch (1).

Plasma torch according to one of the preceding claims, characterized in that at least two openings (271, 272) or two groups of openings (271, 272) containing the respective secondary medium (s) (SGI , SG2) exist; in which

Preferably, the openings (271, 272) have different sized and geometrically shaped free cross sections and / or are aligned in different axial directions or openings (271, 272) of different groups are radially offset from each other and / or the number of openings (271, 272) is chosen differently in the individual groups.

Plasma torch according to one of the preceding claims, characterized in that at least one to a feed (34) connected cavity (11) within the housing (30) is present, at the opening at an opening opening and closing a valve (33), with an extraction of the at least one plasma gas from the at least one feed (34) for the plasma gas to the nozzle opening (210) in the open state of this valve (33) is reached, is present. Plasma torch according to one of the preceding claims, characterized in that within the housing (30) arranged valves (33, 63, 64) electrically, pneumatically or hydraulically actuated, preferably designed as an axial valve and

particularly preferably have a maximum outer diameter or a maximum average surface diagonal of a maximum of 15 mm, a maximum length of 50 mm and / or

the maximum outer diameter of the housing is 52 mm and / or the maximum outer diameter of the valves is at most J4, the outer diameter or a maximum mean surface diagonal of the housing (30) and / or the valves (33, 63, 64) have a maximum electrical power consumption of 10 W to their operation require; wherein preferably with electrically operable valve (s) (33, 63, 64), the respective secondary medium or the plasma gas flows through the winding of a coil (S).

Plasma torch according to one of the preceding claims, characterized in that the plasma torch (1) is designed as a quick-change burner with one of a plasma burner head (2) separable plasma torch shaft (3).

Plasma torch according to one of the preceding claims, characterized in that in addition to the Düsenschutzkappenöffnung (250) or a holder of the nozzle protection cap (25) at least one opening (250a) is provided, through which at least a portion of the secondary media (SGI, SG2) flows In the case of several existing openings (250a), one secondary medium (SGI or SG2) exits through one or more selected openings (s) (250a) in the direction of the workpiece surface.

Plasma torch according to one of the preceding Anspürche, characterized in that gaseous and / or liquid secondary media can be used.

Plasma torch according to one of the preceding claims, characterized in that the plasma torch (1) is connected to a control that is configured to open the valve (s) (63, 64) disposed in a secondary medium supply (SGI, SG2) (61, 62, 61a, 61b) are when at least part of the electric cutting current flows through the workpiece (W), so that secondary medium (SGI, SG2) can flow out of the plasma torch (1) towards the workpiece surface in this operating state and in a period in which a pilot arc is formed the valve (s) (63, 64) are / is kept closed and / or

the valve (s) (63, 64) disposed in a secondary medium supply line (SGI, SG2) (61, 62, 61a, 61b) are opened at the earliest at the time of the Piercing into a workpiece, the workpiece (W) has been pierced at least 1/3, preferably half and more preferably completely and / or at least one valve (63, 64), which is arranged in a supply for secondary medium (SGI, SG2) , is switched on and off during cutting start (K0), between two cutting sections (K2), when passing over a kerf (F) or at the cutting end (K10).