Plasma electrode for a plasma arc torch with replaceable electrode tip

Abstract

Plasma electrode (1) for a plasma arc torch consisting of an electrode body, at least one electrode core (4) disposed on the electrode tip, wherein the plasma electrode (1) is constructed in at least two parts and consists of the electrode tip (2) and an electrode part (3), and out of the electrode tip (2) and a electrode part (3) consists, and that the electrode tip (2) is held replaceably on the electrode part (3).

Claims

1. A plasma electrode for a plasma arc torch, consisting of an electrode body, the electrode body comprising: an electrode tip comprising: a front electrode tip having a first end having an electrode core arranged along a central longitudinal axis, and a second end having a connector, and a separate rear electrode tip having a first end and a second end, a tubular electrode part comprising a fastening flange and a screw thread or plug-type connection disposed at the send of the rear electrode tip to removably connect the rear electrode tip to an electrode holder, and a connector arranged on the second end of the rear electrode tip and between the front electrode tip and the separate rear electrode tip to releasably connect to the connector of the second end of the front electrode tip.

2. The plasma electrode according to claim 1, wherein the connector on the second end of the rear electrode tip and the connector on the second end of the front electrode tip is a sealed screw connection or plug-type connection or screw/plug-type connection.

3. The plasma electrode according to claim 2, wherein the sealed screw connection or plug-type connection or screw/plug-type connection is self-centering.

4. The plasma electrode according to claim 1, wherein the ratio of lengths between the front replaceable electrode tip and the rear electrode tip is in the range between 1:6 and 1:1.

5. The plasma electrode according to claim 1, wherein the material of the front electrode tip and of the electrode tip is identical.

6. The plasma electrode according to claim 1, wherein the material of the front electrode tip and of the rear electrode tip is not identical.

7. The plasma electrode according to claim 1, wherein the plasma electrode is a hollow cylindrical metal body, wherein a cooling tube is disposed in an interior of the hollow cylindrical metal body.

8. The plasma electrode according to claim 1, wherein at least the front electrode tip is made of a solid material.

9. The plasma electrode according to claim 1, wherein the threaded connector on the second end of the rear electrode tip and the threaded connector on the second end of the front electrode tip is constructed as a sealed flange connection with a union nut for fastening and securing the flange connection.

10. A plasma electrode for a plasma arc torch, consisting of an electrode body, the electrode body comprising: a front electrode tip having a first end configured to receive an electrode core, and a second end having a connector, and a rear electrode part having a first end and a second end, the first end of the rear electrode part comprising a fastening flange and a screw thread or plug-type connection configured to removably connect the rear electrode part to an electrode holder, the second end of the rear electrode part having a connector configured to releasably connect to the connector of the second end of the front electrode tip, wherein the threaded connector on the second end of the rear electrode part and the threaded connector on the second end of the front electrode tip is constructed as a sealed flange connection with a union nut for fastening and securing the flange connection.

Description

(1) In the drawings:

(2) FIG. 1 shows a section through a first embodiment of a two-part plasma electrode in the disassembled state,

(3) FIG. 2 shows a detail section through the screw connection according to FIG. 1,

(4) FIG. 3 shows a section through the plasma electrode according to FIG. 1 in the assembled state,

(5) FIG. 4 shows the screw connection according to FIG. 2 in the assembled state,

(6) FIG. 5 shows a section through a second embodiment of a two-part plasma electrode,

(7) FIG. 6 shows a section through the sealed screw connection,

(8) FIG. 7 shows the plasma electrode according to FIG. 5 in the disassembled state,

(9) FIG. 8 shows a detail of the threaded screw connection according to FIG. 7,

(10) FIG. 9 shows a third preferred embodiment of a plasma electrode in the disassembled state,

(11) FIG. 10 shows a detail of the threaded screw connection according to FIG. 9 in the disassembled state,

(12) FIG. 11 shows the plasma electrode according to FIG. 9 in the assembled state,

(13) FIG. 12 shows the threaded screw connection according to FIG. 10 in the screwed-in state,

(14) FIG. 13 shows a plasma arc torch according to the prior art according to DE000069937323T2,

(15) FIG. 14 shows a plasma arc torch according to the prior art according to EP 1 765 046 B1.

(16) The plasma electrode 1 shown in FIG. 1 is made up of two parts and consists of the front replaceable electrode tip 2 and a rear electrode part 3 which is centred by a radially outer fastening flange 7 on the inner face of a fastening body (electrode holder) not shown in greater detail and moreover can be screwed with a thread 8 into such a fastening body.

(17) Instead of a screw fastening by means of the thread 8 the entire plasma electrode 1 can also be inserted and sealed in a fastening body not shown in greater detail. A cooling tube 6 which engages with its front end in a receiving space 5 in the region of the electrode tip 2 is disposed centrally in the interior 10 of the plasma electrode 1.

(18) An electrode core 4 made of a highly emissive material such as for example a hafnium or zirconium material is introduced into a bore in the electrode tip 2.

(19) The cooling of the plasma electrode takes place in such a way that a stream of cooling medium is introduced into the interior 10 of the cooling tube 6, is redirected in the region of the receiving space 5 in the electrode tip 2 and is then returned again by means of the radially outer internal bore 9.

(20) It is important that the two parts (electrode tip 2 and electrode part 3) are releasably connected to one another. In the embodiment shown in FIG. 2 the connection region 11 of the releasable connection consists of a screw thread. In this case the electrode tip 2 has on a vertical flange an external thread which engages in an associated internal thread on a flange likewise formed on the electrode part 3. In this way a screw thread 12 is formed.

(21) For automatic centring of this screw thread it is provided that conical surfaces 13, 14 which are opposite to and aligned with one another are disposed on associated flanges of the electrode tip 2 and of the electrode part 3 and that furthermore a preferably circumferential annular flange 15 on the electrode part 3 engages in an associated annular groove 16 and is centred there.

(22) Automatic centring of the screw connection takes place by the engagement of the annular flange 15 and the annular groove 16 in conjunction with the obliquely directed conical surfaces 13, 14.

(23) In addition, in the case of complete stabilisation of the screw connection (see FIG. 4) the horizontal projections 17, 18 rest in a sealing manner on one another. Additional sealing means such as for example a sealing ring 19 can be disposed in this region.

(24) FIG. 3 shows the assembled structure of the plasma electrode shown in the disassembled state in FIG. 1, where it can be seen that the front replaceable electrode tip 2 has a relatively short length 24 which is shorter by a multiple than, by comparison, the non-replaceable electrode part 3 with a substantially greater length 25.

(25) The ratios of these two lengths 24, 25 may vary in the range between 1:1 and 1:6.

(26) In all embodiments it is important that the electrode tip 2 is fastened so as to be easily releasable on the electrode part 3 on the electrode side and is therefore easily replaceable if it is worn. It is kept short in order to keep the material consumption low during replacement.

(27) FIGS. 5 to 8 show the kinematic reversal of a screw thread illustrated by 12 in FIGS. 1 to 4. It can be seen there that the screw thread 12 consists of an internal thread which is disposed on the inner face of the electrode tip 2 and which can be screwed into an associated radially outwardly directed external thread on the electrode part 3.

(28) The threaded screw connection is sealed in a liquid-tight manner by a sealing ring 19.

(29) A further sealing ring 19 can be disposed in the region of the projections 17, 18 facing one another.

(30) FIGS. 7 and 8 show another embodiment of the screw connection, and moreover show that in the region of the electrode tip 2 a key surface 20 can be provided for the engagement of a suitable tool by which the electrode tip 2 can be unscrewed from the electrode part 3.

(31) Here too an external thread which co-operates with an internal thread in the interior of the electrode part 3 is disposed on the rear face of the electrode tip 2, and the entire threaded screw connection is sealed in a liquid-tight manner by a sealing ring 19 which is inserted in an associated annular groove 23 on the vertical flange of the electrode tip 2.

(32) Thus the external thread 21 on the electrode tip 2 co-operates with the internal thread 22 on the electrode part 3 as a screw thread 1.

(33) FIGS. 9 to 12 show as a further embodiment a plasma electrode in which the sealing ring 19 is formed in the region of an outwardly open annular groove 23 on the foot of the vertical flange in the electrode part 3.

(34) Here the electrode tip 2 has an internal thread 22 which with the associated external thread 21 produces the sealed screw connection in the region of the connecting part 11.

(35) In FIGS. 11 and 12 the threaded screw connections shown in FIGS. 9 to 10 are shown in the screwed-in state.

(36) FIG. 13 shows the prior art according to DE000069937323T2 and FIG. 2 of this document shows an electrode 16 which can be screwed into a holder, is constructed in one piece and in the event of wear must be replaced as an entire part. For this purpose the electrode 16 is screwed with an upper screw thread 19 into a holder.

(37) By comparison with this prior art the invention consists of constructing the known electrode 16 in two parts, constructing the front tip as an easily replaceable electrode tip 2 and the rear part of the electrode 16 as an electrode part of the electrode body of the plasma electrode.

(38) According to the invention the sub-division would take place at the level of the lowermost edge of the electrode 16 illustrated in FIG. 2 of this document. Thus the lower region of the electrode adjoining the hexagon is designed according to the invention to be replaceable and forms a replaceable electrode tip which is held releasably there. This is characterised by the broken line a. Another possibility resides in the separation of the two electrode parts according to the upper line b.

(39) Thus in the event of wear of the electrode 16 the front tip region of the electrode (characterised by the lines a or b) which is located in the immediate vicinity of the core 29 must be replaced, and therefore the rear part of the plasma electrode 16 no longer has to be replaced.

(40) FIG. 14 (prior art according to EP 1 765 046 B1) shows a replaceable one-part electrode 2 of considerable length, which corresponds in principle to the embodiment of the electrode according to the invention. The features which are identical are the upper screw-in thread and two annular grooves, in each of which an O ring is inlaid, in order to be able to screw the electrode into an electrode holder in a sealed manner.

(41) The invention provides that the electrode shown in FIG. 14 is divided on the lowermost tip—approximately at the level of the reference numeral 3—and there forms the replaceable electrode tip. The electrode tip thus formed only has to be constructed with such a length that the fastening surfaces to be disposed there and the electrode core can be arranged.

KEY TO DRAWINGS

(42) 1 plasma electrode 2 electrode tip 3 electrode part 4 electrode core 5 receiving space 6 cooling tube 7 fastening flange 8 thread 9 internal bore 10 interior 11 connecting part 12 screw thread 13 conical surfaces 14 conical surfaces 15 annular flange 16 annular groove 17 projection 18 projection 19 sealing ring 20 key surface 21 external thread 22 internal thread 23 annular groove (for 19) 24 length (of 2) 25 length (of 3)