EP2465334B1 - Protective nozzle cap, protective nozzle cap retainer, and arc plasma torch having said protective nozzle cap and/or said protective nozzle cap retainer - Google Patents

Description

The present invention relates to a nozzle cap for an arc plasma torch. The arc plasma torch can serve both for dry cutting and underwater cutting of various metal workpieces.

In plasma cutting, an arc (pilot arc) is first ignited between a cathode (electrode) and anode (nozzle) and then transferred directly to a workpiece to make a cut.

Said arc generates a plasma, which is a thermally highly heated, electrically conductive gas (plasma gas), which consists of positive and negative ions, electrons and excited and neutral atoms and molecules. As plasma gas, gases such as argon, hydrogen, nitrogen, oxygen or air are used. These gases are ionized and dissociated by the energy of the arc. The resulting plasma jet is used to cut the workpiece.

A modern arc plasma burner roughly consists of basic components, such as torch body, electrode (cathode), nozzle, one or more caps, such as nozzle cap and Nozzle protection cap surrounding the nozzle and connections used to supply the arc plasma torch with power, gases and / or liquids.

Nozzle covers are used to protect a nozzle from the heat and spewing molten metal of the workpiece during the cutting process.

The nozzle may consist of one or more components. In direct water-cooled arc plasma torches, the nozzle is held by a nozzle cap. Cooling water flows between the nozzle and the nozzle cap. A secondary gas then flows between the nozzle cap and nozzle protection cap. This serves to create a defined atmosphere, to constrict the plasma jet and to protect against splashing during piercing.

In gas-cooled arc plasma torches and indirect water-cooled arc plasma torches, the nozzle cap can be omitted. Then the secondary gas flows between the nozzle and nozzle protection cap.

The electrode and the nozzle are arranged in a certain spatial relationship to one another and delimit a space, the plasma chamber, in which this plasma jet is generated. The plasma jet can in its parameters, such as. As diameter, temperature, energy density and flow rate of the plasma gas, are strongly influenced by the design of the nozzle and electrode.

For the different plasma gases, the electrodes and nozzles are made of different materials and in different shapes.

Nozzles are usually made of copper and water cooled directly or indirectly. Depending on the cutting task and electrical power of the arc plasma burner nozzles are used, which have different inner contours and openings with different diameters and thus provide the optimum cutting results.

For example, the DE 10 2004 049 445 A1 shows an arc plasma torch with a water cooled electrode and nozzle and a gas cooled nozzle cap. For this purpose, the secondary gas is fed through a nozzle protection cup holder inside a Schraubverbindungsbereich between the Düsenschutzkappenhalter and a nozzle protection cap by a secondary gas channel formed between the nozzle cap and a nozzle cap a plasma jet.

The EP 0 573 653 B1 relates to an arc plasma torch with water-cooled electrode and nozzle and water-cooled nozzle cap. Just like the arc plasma burner according to the DE 10 2004 049 445 A1 For example, a secondary gas is supplied inside a nozzle guard holder inside a screw joint portion between the nozzle guard holder and a nozzle guard past a plasma jet. Just like the one from the DE 10 2004 049 445 A1 known arc plasma torch, the known arc plasma torch for certain applications on an insufficient cooling of the nozzle cap on.

In addition, the known arc plasma torch is configured to form an annular cooling water chamber within the base end portion of the nozzle guard. The cooling water flowing here cools the nozzle protection cap. This construction has the added disadvantage that upon unscrewing the nozzle cap, the cooling water exits the cooling chamber and drips or runs on the outer surface of the nozzle cap and the inner surface of the nozzle cap. As a result, coolant residues occur in the secondary gas space formed by the nozzle cap and the nozzle protection cap, which on the one hand impairs the quality of cut and reliability, on the other hand leads to loss of coolant.

The invention is therefore based on the object to improve the cooling of the nozzle cap of an arc plasma burner.

According to the invention this object is achieved by a nozzle cap for an arc plasma torch, comprising a front end portion and a rear end portion with a threaded portion on its inner surface for screwing to a burner body of an arc plasma torch, characterized in that at least one groove passes through the threaded portion on the inner surface and the at least a groove or at least one of the grooves crosses the threaded portion obliquely to the longitudinal axis of the nozzle cap or helically.

Furthermore, this object is achieved by a nozzle cap holder for an arc plasma torch, comprising a portion having a threaded portion on its outer surface for screwing to a nozzle cap of an arc plasma torch, wherein at least one groove passes through the threaded portion on its outer surface, characterized in that the at least one groove or at least one of the grooves traverses the threaded portion obliquely to the longitudinal axis of the Düsenschutzkappenhalters or at least one groove or at least one of the grooves traverses the threaded portion helically.

Finally, this object is also achieved by an arc plasma torch, comprising: a torch body and a nozzle cap screwed thereto in a Schraubverbindungsbereich according to one of claims 1 to 3 wherein the burner body and / or the nozzle protection cap is / are designed so that at least one channel formed between them is that traverses the Schraubverbindungsbereich.

In the nozzle protection cap can be provided that the threaded portion is designed for screwing to the burner body via a Düsenschutzkappenhalter.

Conveniently, the nozzle cap is designed in two parts. For example, this allows the only worn part to be replaced.

According to a particular embodiment of the arc plasma torch, the nozzle cap is screwed in said Schraubverbindungsbereich via a nozzle protector cap holder, in particular according to claim 4 with the burner body.

Preferably, the at least one channel or at least one of the channels is formed from a groove in the burner body or nozzle protection cap holder and / or a groove in the nozzle protection cap.

In particular, it can be provided that the channel is a secondary medium channel. For example, the secondary medium may be a liquid such as water and oil, a gas, or, for example, water vapor.

In particular, it can be provided that the secondary medium channel is a secondary gas channel.

Finally, a secondary medium inlet channel may be provided in the burner body, in particular in the nozzle protection cup holder, which communicates with the at least one secondary medium channel or at least one of the secondary medium channels.

The arc plasma torch may be both an arc plasma torch water- and gas-cooled with respect to the electrode and nozzle. The nozzle cap may be water or gas cooled.

The invention is based on the surprising finding that, when used with, for example, a secondary gas, better cooling of the nozzle protection cap is achieved by guiding the secondary gas through the screw connection region. At the same time, the symmetry and thus the homogeneity of the secondary gas in the entire area are improved, which is shown in better cutting results. Sometimes even a secondary gas guide part can be omitted. In addition, the reliability is improved. When using the invention with a secondary gas its advantages, such as constriction of the plasma jet, protection of the nozzle against high-injection metal at Piercing, creation of a defined atmosphere around the plasma jet and active participation of the secondary gas in the plasma process, continue to be used while ensuring the stability of the plasma jet.

Figur 1

eine Längsschnittansicht eines Lichtbogenplasmabrenners gemäß einer ersten besonderen Ausführungsform der Erfindung;

Figur 2

eine Schnittansicht entlang der Linie A-A von Figur 1;

Figur 3

eine Längsschnittansicht einer Düsenschutzkappe eines Lichtbogenplasmabrenners;

Figur 4

eine Längsschnittansicht eines Lichtbogenplasmabrenners gemäß einer zweiten besonderen Ausführungsform der Erfindung;

Figur 5

eine Längsschnittansicht des oberen Teils einer Düsenschutzkappe eines Lichtbogenplasmabrenners;

Figur 6

ein Beispiel einer Nut;

Figur 7

eine Ausführungsform einer Nut;

Figur 8

eine weitere Ausführungsform einer Nut;

Figur 9

eine Längsschnittansicht und eine Detailansicht von einem Lichtbogenplasmabrenner gemäß einer dritten besonderen Ausführungsform der Erfindung; und

Figur 10

eine Längsschnittansicht von einer Düsenschutzkappe des Lichtbogenplasmabrenners von Figur 9.

Further features and advantages of the invention will become apparent from the claims and the following description in which several embodiments are explained in detail with reference to the schematic drawings. Showing:

FIG. 1

a longitudinal sectional view of an arc plasma burner according to a first particular embodiment of the invention;

FIG. 2

a sectional view taken along the line AA of FIG. 1 ;

FIG. 3

a longitudinal sectional view of a nozzle cap of an arc plasma torch;

FIG. 4

a longitudinal sectional view of an arc plasma burner according to a second particular embodiment of the invention;

FIG. 5

a longitudinal sectional view of the upper part of a nozzle cap of an arc plasma torch;

FIG. 6

an example of a groove;

FIG. 7

an embodiment of a groove;

FIG. 8

another embodiment of a groove;

FIG. 9

a longitudinal sectional view and a detailed view of an arc plasma burner according to a third particular embodiment of the invention; and

FIG. 10

a longitudinal sectional view of a nozzle cap of the arc plasma burner of FIG. 9 ,

FIG. 1 shows an arc plasma torch according to a particular embodiment of the invention. The arc plasma burner 1 has a burner body 2, which comprises a nozzle guard holder 2.1, a nozzle holder 2.2, an insulating piece 2.3 and an electrode holder 2.4. In the burner body 2, an electrode 3 and a nozzle 4 are arranged coaxially with the longitudinal axis L of the burner body and at a spatial distance, thereby forming a plasma chamber 6 through which a plasma gas PG flows, which is supplied via a plasma gas channel 6a. A nozzle cap 5 is arranged coaxially to the longitudinal axis L of the plasma torch 1 and holds the nozzle 4. Between the nozzle 4 and a nozzle cap 5 is a space 11, flows through the cooling water. The cooling water is supplied via a water feed WV and flows through a water return WR. A nozzle cap 7, which is integrally formed here and consists of a rear portion 7a and a front portion 7b with an outlet opening 7c, is arranged coaxially to the longitudinal axis L of the plasma torch 1 and encloses the nozzle cap 5 and the nozzle 4. It is over a threaded portion with an internal thread 7.2 with an external thread 2.1.2 of the cap holder 2.1 connected to selbigem. The nozzle cap 7 is preferably made of a good heat conducting material, such as copper, brass or aluminum.

A secondary gas SG flows through a secondary gas inlet channel 2.1.3 and a hole 2.1.4 vertically into an annular space 9a, which passes through the outer surface 2.1.1 of Nozzle protection cap holder 2.1 and the inner surface 7.1 of the nozzle cap 7 is formed and distributed. To the rear, this space 9a is sealed with a round ring 2.5. The secondary gas SG then flows through the secondary gas channels 9b (see FIG. 2 ) in the threaded connection region formed by the internal thread 7.2 and the external thread 2.1.2 in a space 9c formed by the protective cap 7 and the nozzle cap 5. The space 9c tends to taper toward the tip of the plasma burner 1. The secondary gas SG passes through a secondary gas guide part 8 through the openings 8a before it passes from a space 9d to the plasma jet (not shown) and exits the outlet opening 7c of the protective cap 7.

Since, in contrast to the prior art, the secondary gas SG is introduced into the space 9 with respect to the tip of the plasma torch 1 behind the Schraubverbindungsbereich, improves the cooling of the nozzle cap 7. First, the secondary gas SG cools the inner surface of the nozzle cap 7 almost over the total length, on the other hand, in particular the Schraubverbindungsbereich is cooled with little effort by the secondary gas flow, which is particularly important because the nozzle guard holder 2.1 is made of plastic and is damaged in case of overheating. In the secondary gas channels 9b formed in the screw connection region or in the threaded region, the secondary gas SG flows faster than in the following space 9c, since the sum of the areas of the flow cross sections is smaller than the flow cross section of the space 9c. This high flow rate additionally improves the cooling effect. With appropriate dimensioning, the secondary gas can be set in rotation, thus increasing the flow velocity in the space 9c and improving the cooling.

FIG. 2 shows the section along the line AA of the arc plasma burner 1 from FIG. 1 , The thread 7.2 pass through three grooves, one of which is visible and denoted by reference numeral 7.3, which are distributed here at equal angles α 7 and thus symmetrically on the circumference. They form with the outer surface of the external thread 2.1.2 of the Düsenschutzkappenhalters the Sekundärkaskanäle 9b, through which the secondary gas SG flows to the tip of the Lichtbogenplasmäbrenners 1 out.

FIG. 3 shows a nozzle cap 7. This is designed in one piece and consists essentially of the cylindrical, open at the top, rear portion 7a and the conically tapered front portion 7b and the outlet opening 7c. In section 7a is the thread 7.2 (internal thread), in which the grooves 7.3 are introduced, of which only one is visible and through which flows in the assembled state, the secondary gas SG.

In the FIG. 4 The embodiment shown differs from that in FIG FIG. 1 embodiment shown essentially in that the nozzle protection cap 7 consists of two components 7.10 and 7.11, which are inserted into one another. In this embodiment, these are not with the sections 7a and 7b of FIG. 1 identical, but it can be quite. The heat conduction between the front component 7.11 and the rear component 7.10 takes place via an annular bearing surface between the two. The seal is made using a round ring (not marked).

FIG. 5 shows the rear part 7.10 of FIG. 4 consisting essentially of a cylindrical open-topped portion 7a and a portion of the tapered portion 7b. In section 7a is a thread 7.2 (internal thread), are introduced in the grooves 7.3 through which flows in the assembled state, the secondary gas SG.

The FIGS. 6 to 8 show different embodiments of the grooves 7.3 in the thread 7.2 of the rear portion 7a of the cap 7th

FIG. 6 shows, for example, a parallel to the longitudinal axis L of the arc plasma burner 1 lying groove 7.3 with the length t7 and the width b7.

In FIG. 7 the groove 7.3 is inclined at 45 ° to the longitudinal axis L. As a result, the secondary gas is set in rotation and flows at high speed through the space 9c which adjoins the tip of the arc plasma torch (see FIG FIG. 1 ). This improves the cooling of the nozzle protection cap 7.

In FIG. 8 the grooves 7.3 are formed cross-shaped, which leads to a particularly strong turbulence of the secondary gas SG and thus to improve the cooling of the protective cap 7.

FIG. 9 shows a further particular embodiment. The nozzle protection cap 7 here consists of two components, the rear component 7.10 and the front component 7.11. The secondary gas SG flows through a channel 2.1.3 and a bore 2.1.4 of a Sekundärgaseinlasskanal perpendicular in an annular space 9a, which is formed by an outer surface 2.1.1 of Düsenschutzkappenhalters 2.1 and an inner surface 7.1 of the nozzle cap 7, and spreads. To the rear, this space 9a is sealed with a round ring 2.5. The secondary gas SG then flows through a channel 9b in the screw connection region, which runs parallel to the threads, into the space 9c formed by the nozzle protection cap 7 and the nozzle cap 5. As a result, the rotation of the secondary gas flowing into the space 9c is increased again.

FIG. 10 shows a in the embodiment of FIG. 9 usable nozzle protection cap, which consists of a component.

The protective cap holder 2.1 can for the guidance of the secondary gas SG from the channel 2.1.3 instead of one also have several holes 2.1.4, which are distributed on the circumference of the cylindrical surface 2.1.1 and communicate with the channel 2.1.3. Furthermore, the bore (s) may be perpendicular or inclined to the surface of the nozzle guard holder 2.1. The nozzle cap 7 may consist of one or more components (7.10, 7.11). These components do not have to be with the sections 7a and 7b can be identical, but it can be. For example, the rear part 7.10 may have the portion 7a and part of the portion 7b (see FIG FIG. 4 ).

To the Figures 9 and 10 It should also be noted that in the embodiment shown therein, the external thread of the Düsenschutzkappenhalters 2.1 is stirred as zweigängiges thread with two parallel thread grooves and consequently also two parallel threaded ridges between the thread grooves. The internal thread of the nozzle cap 7 is constructed with the same thread pitch only catchy by the normally existing in a double-threaded thread second threaded ridge is not present, but forms a wider groove. Through the wide groove in conjunction with the external thread of the nozzle protection cap holder 2.1, the medium can flow.

In principle, three-thread or more threads can be used. However, then the slope is getting bigger, which makes screwing difficult.

Claims (10)

1. Protective nozzle cap (7) for an arc plasma torch (1), comprising
   a front end section and
   a rear end section with a threaded region on its internal surface (7.1) for screwing onto a torch body (2) of an arc plasma torch (1),
   characterized in that
   at least one groove (7.3) passes through the threaded region on the internal surface (7.1) and the at least one groove (7.3) or at least one of the grooves (7.3) passes through the threaded region at an angle to the longitudinal axis of the protective nozzle cap (7) or helically.
2. Protective nozzle cap (7) according to Claim 1, characterized in that the threaded region is designed to be screwed onto the torch body (2) via a protective nozzle cap retainer (2.1).
3. Protective nozzle cap (7) according to either of the preceding claims, characterized in that it is in two parts.
4. Protective nozzle cap retainer (2.1) for an arc plasma torch (1), comprising
   a section with a threaded region (2.1.2) on its external surface (2.1.1) for screwing into a protective nozzle cap (7) of an arc plasma torch, wherein at least one groove passes through the threaded region (2.1.2) on its external surface (2.1.1),
   characterized in that the at least one groove or at least one of the grooves passes through the threaded region (2.1.2) at an angle to the longitudinal axis of the protective nozzle cap retainer (2.1) or
   the at least one groove or at least one of the grooves passes through the threaded region (2.1.2) helically.
5. Arc plasma torch (1), comprising:

   a torch body (2) and, screwed thereto in a screw connection region, a protective nozzle cap (7) according to one of Claims 1 to 3, wherein the torch body (2) and/or the protective nozzle cap (7) is/are designed such that at least one channel is formed therebetween which passes through the screw connection region.
6. Arc plasma torch (1) according to Claim 5, characterized in that the protective nozzle cap (7) is screwed onto the torch body (2) in said screw connection region via a protective nozzle cap retainer (2.1), in particular according to Claim 4.
7. Arc plasma torch (1) according to Claim 5 or 6, characterized in that the at least one channel or at least one of the channels is formed from a groove (7.3) in the torch body (2) or protective nozzle cap retainer (2.1) and/or a groove (7.3) in the protective nozzle cap (7).
8. Arc plasma torch (1) according to one of Claims 5 to 7, characterized in that the channel is a secondary medium channel.
9. Arc plasma torch (1) according to Claim 8, characterized in that the secondary medium channel is a secondary gas channel.
10. Arc plasma torch (1) according to one of Claims 5 to 9, characterized in that a secondary medium inlet channel (2.1.3) is provided in the torch body (2), in particular in the protective nozzle cap retainer (2.1), which channel is connected to the at least one secondary medium channel or at least one of the secondary medium channels.

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