Cooling pipes, electrode holders and electrode for an arc plasma torch

Abstract

An electrode holder for an arc plasma torch includes an elongate holder body. The holder body includes a holder end for receiving an electrode and a hollow interior. An internal thread is positioned in the hollow interior for screwing in a rear end of said cooling tube. A cylindrical inner surface adjoins the internal thread for centering the cooling tube relative to the electrode holder.

Claims

1. An electrode holder for an arc plasma torch, comprising: an elongate holder body, said holder body having a holder end for receiving an electrode and a hollow interior; an electrode holder internal thread positioned in said hollow interior for screwing in a rear end of a cooling tube; and an electrode holder cylindrical inner surface for centering said cooling tube relative to said electrode holder by contacting an opposing cylindrical outer surface centering portion of the cooling tube, said electrode holder cylindrical inner surface adjoining said electrode holder internal thread and having an internal diameter that is larger than the internal diameter of said electrode holder internal thread.

2. The electrode holder of claim 1 wherein a stop face is provided for axially fixing said cooling tube in said electrode holder.

3. An arrangement of a cooling tube and electrode holder for an arc plasma torch comprising: said cooling tube having an elongate tube body having a rear end which can be releasably connected to said electrode holder, a coolant duct extending therethrough, a cooling tube external thread for releasably connecting said rear end to said electrode holder, and a cooling tube cylindrical outer surface for centering said cooling tube relative to said electrode holder, said cooling tube cylindrical outer surface adjoining said external thread and having an external diameter that is at least the same size or larger than the maximum external diameter of said cooling tube external thread; and said electrode holder having an elongate holder body, said holder body having a holder end for receiving an electrode and a hollow interior, an electrode holder internal thread positioned in said hollow interior for screwing in said rear end of said cooling tube, and an electrode holder cylindrical inner surface for centering said cooling tube relative to said electrode holder by contacting said cooling tube cylindrical outer surface, said cylindrical inner surface adjoining said electrode holder internal thread and having an internal diameter that is larger than the internal diameter of said electrode holder internal thread.

4. The arrangement of claim 3 wherein an annular gap is positioned at a front end between said cooling tube and said electrode holder.

5. The arrangement of claim 3 wherein said cooling tube cylindrical outer surface and said electrode holder cylindrical inner surface have narrow tolerances relative to one another.

6. An electrode for an arc plasma torch, comprising: a hollow elongate electrode body, said electrode body having an open end for arranging the front end of a cooling tube therein and a closed end; said open end having an electrode external thread for screwing together with an internal thread of an electrode holder; and an electrode cylindrical outer surface for centering said electrode relative to said electrode holder by contacting an opposing cylindrical inner surface centering portion of an electrode holder, said electrode cylindrical outer surface adjoining said electrode external thread towards said closed end and having an external diameter that is at least the same size or larger than the maximum external diameter of said electrode external thread.

7. The electrode of claim 6 wherein a stop face is provided for axially fixing said electrode in said electrode holder.

8. The electrode of claim 6 wherein said cylindrical outer surface has a peripheral groove.

9. The electrode of claim 6 further comprising: said electrode cylindrical outer surface has a peripheral groove; and an O-ring is disposed in said groove for sealing purposes.

10. An electrode holder for an arc plasma torch, comprising: an elongate holder body, said holder body having a holder end, provided with an electrode holder internal thread, for receiving an electrode, and a hollow interior; and an electrode holder cylindrical inner surface for centering the electrode relative to said electrode holder by contacting an opposing cylindrical outer surface centering portion of the electrode, said electrode holder cylindrical inner surface adjoining said electrode holder internal thread and having an internal diameter that is larger than the internal diameter of said electrode holder internal thread.

11. The electrode holder of claim 10 wherein a stop face is provided for axially fixing said electrode in said electrode holder.

12. An arrangement of an electrode and an electrode holder for an arc plasma torch comprising: said electrode having a hollow elongate electrode body, said electrode body having an open end for arranging a front end of a cooling tube therein and a closed end, said open end having an electrode external thread for screwing together with an electrode holder internal thread, an electrode cylindrical outer surface for centering said electrode relative to said electrode holder, said electrode cylindrical outer surface positioned adjoining said electrode external thread towards said closed end and having an external diameter that is at least the same size or larger than the maximum external diameter of said electrode external thread; said electrode holder having an elongate holder body, said holder body having a holder end, for receiving said electrode, and a hollow interior, electrode holder cylindrical inner surface for centering said electrode relative to said electrode holder by contacting the opposing said electrode cylindrical outer surface, said electrode holder cylindrical inner surface adjoining said electrode holder internal thread and having an internal diameter that is larger than the internal diameter of said electrode holder internal thread; and said electrode being screwed together with said electrode holder by means of said external thread and said internal thread.

13. The arrangement of claim 12 wherein said electrode cylindrical outer surface and said electrode holder cylindrical inner surface have narrow tolerances relative to one another.

14. An arc plasma torch comprising: a cooling tube, an electrode holder, and an electrode; said cooling tube having an axial length and a wall extending along at least a portion of said axial length, said cooling tube also having an elongate tube body, said tube body having a front end for positioning said tube body within an open end of said electrode and a coolant duct extending therethrough, said front end having a bead-like thickening of said wall of said cooling tube pointing inwards, outwards, or both; said electrode holder having an elongate holder body, said holder body having a holder end for receiving said electrode and a hollow interior, said electrode holder also having an electrode holder internal thread positioned in said hollow interior for screwing in a rear end of said cooling tube, said electrode holder further having an electrode holder cylindrical inner surface for centering said cooling tube relative to said electrode holder, said electrode holder cylindrical inner surface adjoining said electrode holder internal thread and having an internal diameter that is larger than the internal diameter of said electrode holder internal thread; and said electrode having a hollow elongate electrode body, said electrode body having an open end for arranging said front end of said cooling tube therein and a closed end, said open end having an electrode external thread for screwing together with said electrode holder internal thread, said electrode also having an electrode cylindrical outer surface for centering said electrode relative to said electrode holder by contacting the opposing said electrode holder cylindrical inner surface, said electrode cylindrical outer surface adjoining said electrode external thread towards said closed end and having an external diameter that is at least the same size or larger than the maximum external diameter of said electrode external thread.

15. An arc plasma arc torch comprising: a cooling tube, an electrode holder, and an electrode; said cooling tube having an elongate tube body, said tube body having a rear end which can be releasably connected to said electrode holder, and a coolant duct extending therethrough, said cooling tube having a cooling tube external thread for releasably connecting said rear end to said electrode holder, said cooling tube also having a cooling tube cylindrical outer surface for centering said cooling tube relative to said electrode holder, said cooling tube cylindrical outer surface adjoining said cooling tube external thread and having an external diameter that is at least the same size or larger than the maximum external diameter of said cooling tube external thread; said electrode holder having an elongate holder body, said holder body having a holder end for receiving said electrode and a hollow interior, an electrode holder internal thread positioned in said hollow interior for screwing in a rear end of said cooling tube, said electrode holder having an electrode holder cylindrical inner surface for centering said cooling tube relative to said electrode holder by contacting the opposing said cooling tube cylindrical outer surface, said electrode holder cylindrical inner surface adjoining said electrode holder internal thread and having an internal diameter that is larger than the internal diameter of said electrode holder internal thread; and said electrode having a hollow elongate electrode body, said electrode body having an open end for arranging a front end of said cooling tube therein and a closed end, said open end having an electrode external thread for screwing together with said electrode holder internal thread, an electrode cylindrical outer surface for centering said electrode relative to said electrode holder by contacting the opposing said electrode holder cylindrical inner surface, said electrode cylindrical outer surface adjoining said electrode external thread towards said closed end and having an external diameter that is at least the same size or larger than the maximum external diameter of said electrode external thread.

16. An arc plasma torch comprising: a cooling tube, an electrode holder, and an electrode; said cooling tube having an axial length and a wall extending along at least a portion of said axial length, said cooling tube also having an elongate tube body, said tube body having a front end for positioning said tube body within an open end of said electrode, and a coolant duct extending therethrough; said front end having a bead-like thickening of said wall pointing inwards, outwards, or both; said electrode holder having an elongate holder body, said holder body having a holder end, provided with an electrode holder internal thread, for receiving an electrode, and a hollow interior, said electrode holder also having an electrode holder cylindrical inner surface for centering said electrode relative to said electrode holder, said electrode holder cylindrical inner surface adjoining said internal thread and having an internal diameter that is larger than the internal diameter of said electrode holder internal thread; and said electrode having a hollow elongate electrode body, said open end of said electrode positioned to arrange said front end of said cooling tube therein, said electrode also having a closed end, said open end having an electrode external thread for screwing together with said electrode holder internal thread, said electrode having an electrode cylindrical outer surface for centering said electrode relative to said electrode holder by contacting the opposing said electrode holder cylindrical inner surface, said electrode cylindrical outer surface adjoining said electrode external thread towards said closed end and having an external diameter that is at least the same size or larger than the maximum external diameter of said electrode external thread.

17. An arc plasma torch comprising: a cooling tube, an electrode holder, and an electrode; said cooling tube having an elongate tube body, said tube body having a rear end which can be releasably connected to said electrode holder, and a coolant duct extending therethrough, said cooling tube having a cooling tube external thread for releasably connecting said rear end to said electrode holder, said cooling tube also having a cooling tube cylindrical outer surface for centering said cooling tube relative to said electrode holder, said cylindrical outer surface adjoining said external thread; said electrode holder having an elongate holder body, said holder body having a holder end, provided with an electrode holder internal thread, for receiving said electrode, and a hollow interior, said electrode holder also having an electrode holder cylindrical inner surface for centering said electrode relative to said electrode holder, said electrode holder cylindrical inner surface adjoining said electrode holder internal thread and having an internal diameter that is larger than the internal diameter of said electrode holder internal thread; and said electrode having a hollow elongate electrode body, said electrode body having an open end for arranging the front end of a cooling tube therein and a closed end, said open end having an electrode external thread for screwing together with said electrode holder internal thread of said electrode holder, said electrode also having electrode cylindrical outer surface for centering said electrode relative to said electrode holder by contacting the opposing said electrode holder cylindrical inner surface, said electrode cylindrical outer surface adjoining said electrode external thread towards said closed end and having an external diameter that is at least the same size or larger than the maximum external diameter of said electrode external thread.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention will become clear from the enclosed claims the following description, in which several embodiments are illustrated in detail with reference to the schematic drawings, wherein:

(2) FIG. 1 shows a longitudinal sectional view through a plasma torch head in accordance with a first particular embodiment of the invention;

(3) FIG. 2 shows an individual view of a cooling tube of the plasma torch head shown in FIG. 1, seen from above (left) and in a longitudinal sectional view (right);

(4) FIG. 3 shows details of the connection between the electrode and the electrode holder in a longitudinal sectional view of the plasma torch head shown in FIG. 1;

(5) FIG. 4 shows details of the electrode holder shown in FIG. 3, partially in a longitudinal section;

(6) FIG. 5 shows details of the connection between the electrode holder and the cooling tube of the plasma torch head shown in FIG. 1;

(7) FIG. 6 shows details of the electrode holder shown in FIG. 5, partially in a longitudinal sectional view;

(8) FIG. 7 shows a detail (section A-A) of the connection between the electrode holder and the cooling tube of the plasma torch head shown in FIG. 1;

(9) FIG. 8 shows an individual illustration of the electrode of the plasma torch head shown in FIG. 1, in a longitudinal sectional view;

(10) FIG. 9 shows a longitudinal sectional view through a plasma torch head in accordance with a particular contemplated embodiment of the present invention;

(11) FIG. 10 shows an individual view of a cooling tube of the plasma torch head shown in FIG. 9, seen from above (left) and in a longitudinal sectional view (right);

(12) FIG. 11 shows details of the connection between the electrode holder and the cooling tube of the plasma torch head shown in FIG. 9;

(13) FIG. 12 shows a longitudinal sectional view through a plasma torch head in accordance with a contemplated particular embodiment of the present invention;

(14) FIG. 13 shows an individual view of a cooling tube of the plasma torch head shown in FIG. 12, seen from above (left) and in a longitudinal sectional view (right);

(15) FIG. 14 shows details of the connection between the electrode holder and the cooling tube of the plasma torch head shown in FIG. 12;

(16) FIG. 15 shows a longitudinal sectional view through a plasma torch head in accordance with a contemplated particular embodiment of the present invention;

(17) FIG. 16 shows an individual view of a cooling tube of the plasma torch head shown in FIG. 15, seen from above (left) and in a longitudinal sectional view (right); and

(18) FIG. 17 shows details of the connection between the electrode holder and the cooling tube of the plasma torch head shown in FIG. 15.

DETAILED DESCRIPTION

(19) FIG. 1 shows a first particular embodiment of a plasma torch head 1 according to the present invention; The plasma torch head has an electrode 7, an electrode holder 6, a cooling tube 10, a nozzle 4, a nozzle cap 2, and a gas line 3. The nozzle 4 is fixed in place by the nozzle cap 2 and a nozzle holder 5. The electrode holder 6 has a holder body 6.12, holder end 6.13, hollow interior 6.14, and receives the electrode 7 and the cool tube 10 via a thread in each case, namely the internal thread 6.4 and the internal thread 6.1. The gas line 3 is located between the electrode 7 and the nozzle 4 and causes a plasma gas PG to rotate. In addition, the plasma torch head 1 has a secondary gas protection cap 9, which in this embodiment is screwed onto a nozzle protection cap holder 8. A secondary gas SG, which protects the nozzle 4, especially the nozzle tip, flows between the secondary gas protection cap 9 and the nozzle cap 2.

(20) The cooling tube 10 (see also FIG. 2) is attached to the rear part of the electrode holder 6, and the electrode 7 is attached to the front part of the electrode holder 6. The cooling tube 10 has an elongate tube body 10.13 having a front end 10.17 and rear end 10.14, as well as a coolant duct 10.15. The cooling tube 10 projects beyond a region 7.5 of the electrode 7 extending inwardly, i.e. away from the nozzle tip and closed end 7.13 and toward an open end 7.12 (see also FIGS. 3 and 8). In that region, the internal diameter D10.8 over the length L10.8 of the cooling tube 10 is smaller than the internal diameter D10.9 of the internal portion 10.9 of the cooling tube 10 facing backwards, and the external diameter D10.10 over the length L10.10 of the cooling tube 10 is larger than the external diameter D10.11 of the external portion 10.11 of the cooling tube 10 facing backwards. This thus gives rise to a bead-like thickening 10.18 of the wall 10.19 of the cooling tube, facing inwards and outwards. This ensures that the flow cross-section available to the coolant is only constricted in the front internal portion 10.8 and front external portion 10.10, in which a high flow velocity of a coolant is required for good heat dispersal, and the greatest possible flow cross-section is available in the rear region in order to keep the pressure drops in the rear internal portion 10.9 and rear external portion 10.11 as tow as possible. A coolant first flows in the flow path through WV1 (water supply line 1) into the interior of the cooling tube 10 and encounters the inwardly extending region 7.5 of the electrode 7, before flowing back via the flow path WR1 (water return line 1) in the space between the cooling tube 10 and the electrode 7 and electrode holder 6.

(21) The plasma jet (not shown) has its point of attack on the outer surface of an electrode insert 7.8. That is where the most heat arises, which has to be dissipated in order to ensure a tong service life of the electrode 7. The heat is conducted via the electrode 7 made from copper or silver to the coolant in the interior of the electrode.

(22) In the region in which the cooling tube 10 project beyond the inwardly extending region 7.5 of the electrode 7, the gap between the opposing surfaces of the front internal portion 10.8 of the cooling tube and the electrode region 7.5 of the electrode 7 and of the front external portion 10.10 and the inner surface 7.10 of the electrode is very small. It is in the region of 0.1 to 0.5 mm.

(23) In addition, coolant flows in the space between the nozzle 4 and the nozzle cap 2 via a flow path WV2 (water supply line 2) and WR2 (water return line 2).

(24) As is also illustrated in FIGS. 5 and 6, the cooling tube 10 is screwed to the electrode holder 6 via the external thread 10.1 and the internal thread 6.1. An annular gap 11 is positioned between the cooling tube 10 and electrode holder 6. The cooling tube 10 and the electrode holder 6 are centred relative to one another by means of the cylindrical outer surface 10.3 of the cooling tube 10 and the cylindrical inner surface 6.3 of the electrode holder 6. These have narrow tolerances relative to one another in order to achieve good centring. In this context, the tolerance of the cylindrical outer surface 10.3 can be the nominal size of the external diameter D10.3 from 0 to −0.01 mm and the tolerance of the cylindrical inner surface 6.3 can be the nominal size of the internal diameter D6.3 from 0 to +0.01 mm. The internal thread 6.1 of the electrode holder 6 and the external thread 10.1 of the cooling tube 10 have sufficient play relative to one another so that the cooling tube 10 can easily be screwed into the electrode holder 6. It is only just before tightening that the centring occurs by means of the cylindrical inner surface 6.3 and cylindrical outer surface 10.3, which have narrow tolerances and face each other in the screwed-in state.

(25) The external diameter D10.3 of the cylindrical outer surface 10.3 of the cooling tube 10 is at least the same size as or larger than the external diameter D10.1 of the external thread 10.1. The internal diameter D6.3 of the cylindrical inner surface 6.3 of the electrode holder 6 is larger than the minimum internal diameter D6.1 of the internal thread 6.1, where D6.1=(D6.1−D6.1i)/2.

(26) The centring described above ensures the parallel alignment of the cooling tube 10 to the axis M of the plasma torch head 1, a uniform annular gap between the cooling tube 10 and the electrode region 7.5 and thus a uniform distribution of the coolant flow in the electrode interior, especially in the region of the front portion 10.8 of the cooling tube 20 and of the inwardly extending electrode region 7.5. When screwed in tightly, the stop faces 10.2 and 6.2 rest on one another. This causes the cooling tube 10 to be fixed axially in the electrode holder 6.

(27) As is also illustrated in FIGS. 3 and 4, the electrode 7 is screwed to the electrode holder 6 by means of the external thread 7.4 and the internal thread 6.4. The electrode 7 and the electrode holder 6 are centred relative to one another by means of the cylindrical outer surface 7.6 of the electrode 7 and the cylindrical inner surface 6.6 of the electrode holder 6. The outer surfaces have narrow tolerances relative to one another in order to achieve good centring. In this context, the tolerance of the cylindrical outer surface can be the nominal size of the external diameter D7.6 from 0 to −0.01 mm and the tolerance of the cylindrical inner surface 6.3 can be the nominal size of the internal diameter D6.6 from 0 to +0.01 mm. The internal thread 6.4 of the electrode holder 6 and the external thread 7.4 of the electrode 7 have sufficient play relative to one another, so that the electrode 7 can easily be screwed into the electrode holder 6. It is only just before tightening that the centring occurs by means of the cylindrical surfaces 6.6 and cylindrical outer surface 7.6, which have narrow tolerances and face each other in the screwed-in state.

(28) The external diameter D7.6 of the cylindrical outer surface 7.6 of the electrode 7 is at least the same size as or larger than the maximum external diameter D7.4 of the external thread 7.4 (see FIG. 8). The internal diameter D6.6 of the cylindrical inner surface 6.6 of the electrode holder 6 is larger than the internal diameter D6.4 of the internal thread 6.4, where D6.4=(D6.4a−D6.4i)/2.

(29) The centring described above is necessary for the parallel alignment of the electrode 6 to the axis M of the plasma torch head 1, which in turn ensures a uniform distribution of the coolant flow in the electrode interior, especially in the region of the front internal portion 10.8 of the cooling tube 10 and of the inwardly extending region 7.5 of the electrode 7. The purpose of centring the electrode 7 relative to the electrode holder 6 is to secure the centricity relative to the other components of the plasma torch head, especially the nozzle 4. The latter serves to form a uniform plasma jet, which is partly determined by the positioning of the electrode insert 7.8 of the electrode 7 relative to the nozzle bore 4.1 of the nozzle 4. In addition, the cylindrical outer surface 7.6 has a groove 7.3 with an O-ring 7.2 disposed in it for sealing purposes. When screwed in tightly, the stop faces 7.7 and 6.7 rest on one another. This causes the electrode 7 to be fixed axially in the electrode holder 6.

(30) A further improvement in the radial centring of the cooling tube 10 relative to the electrode holder 6 is obtained by means of a group of projections 10.6 and a group of projections 10.7, which are located on the outer surface of the cooling tube 10. The projections fix the distance from the inner surface of the electrode holder 6. In this embodiment, there are three projections 10.6 and 10.7 per group distributed offset by 120° on the periphery of the outer surface of the coolling tube and also with an offset L10a in the longitudinal direction of the cooling tube 1 relative to one another (see FIGS. 2 and 7). The projections 10.6 are arranged in this case offset by 60° relative to the projections 10.7. This offsetting improves the radial centring. At the same time, the projections 10.7 can be used as a counterpart for a tool (not shown) for screwing the cooling tube 10 in and out. The projections 10.6 and 10.7 have a rectangular cross-section when seen from the front region 10.8. This means that only the corners of the rectangular cross-sections rest on the cylindrical inner surface 6.11 of the electrode holder 6. In this way, a high degree of centricity is achieved, while at the same time preserving ease of assembly.

(31) FIG. 9 shows a further particular embodiment of a plasma torch head 1 in accordance with the invention, which differs from the embodiment shown in FIGS. 1 to 8 in the design of the front internal portion 10.8 of the cooling tube 10 (see also FIG. 10). The length L10.8 of the internal portion 10.8 is shorter, as a result of which the flow cross-section is increased considerably only in the front-most region. The lengths of the front internal portion 10.8 and the front external portion 10.10. are identical here. In addition, in the region in which the electrode holder 6 and the cooling tube 10 are screwed together, there is a groove 10.4 in the cylindrical outer surface 10.3 of the cooling tube 10, with an O-ring 10.5 disposed in the groove for seating purposes (see also FIG. 11).

(32) FIG. 12 shows a further particular embodiment of a plasma torch head of the invention, which differs from the two embodiments shown in FIGS. 1 to 11 in the design of the front internal portion 10.8 of the cooling tube 10 (see also FIG. 13). The length L10.8 of the internal portion 10.8 is shorter than in FIG. 1, and the length L10.10 of the front external portion 10.10 is greater than in FIG. 9. As a result, the flow resistance of the overall arrangement is reduced, since narrow gaps are only found in the front-most part between the cooling tube and the electrode.

(33) The centring between the cooling tube 10 and the electrode holder 6 is likewise achieved by means of a cylindrical inner surface 6.3 and a cylindrical outer surface 10.3. These are, however, arranged differently from what is shown in FIGS. 1 and 9. As a result of this arrangement, the cylindrical centring surfaces are enlarged. This further improves the centring and is achieved by changing the order “thread—centring surface—stop face” to “thread—stop face—centring surface”. A further advantage is that the size of the unit is not increased. If the order were retained, the stop face would have to have a different diameter from the centring surface.

(34) FIG. 15 shows a further special embodiment of the plasma torch head of the invention. It differs from the embodiment of FIG. 1 in the design of the front internal portion 10.8 of the cooling tube 10 (see also FIG. 16). The lengths of the front internal portion 10.8 and the front external portion 10.10. are identical here. In their length, these portions correspond to the region 7.5 of the electrode 7.

(35) Centring between the cooling tube 10 and the electrode holder 6 is achieved as in FIG. 12. In addition, in the region in which the electrode holder 6 and the cooling tube 10 are screwed together, there is a groove 10.4 in the cylindrical outer surface 10.3 of the cooling tube 10, with an O-ring 10.5 disposed in the groove for sealing purposes, That is illustrated in FIG. 17.

(36) The features of the invention disclosed in the present description, in the drawings and in the claims can be essential to implementing the invention in its various embodiments both individually and in any combinations. It is contemplated that several modifications can be made to the embodiments described herein within the spirit and scope of the invention without departing from the anticipated scope of the claims.