PLASMA ARC TORCH CONSUMABLE HOLDER

Abstract

A consumables holder assembly for a plasma arc torch having a torch head, the consumables holder assembly comprising a main body, a shielding cup which engages to the main body, a connection means which engages the main body to the torch head and consumable components including an electrode, a nozzle, a plasma gas distributor, a shielding gas distributor which are all positioned inside the shielding cup, wherein that the consumable holder assembly can be detached from the torch head together with the consumable components and the shielding cup as one unit, wherein the connection means comprises a mechanical attachment mechanism which is engageable with the torch head.

Claims

1-15. (canceled)

16. A consumables holder assembly for a plasma arc torch having a torch head, the consumables holder assembly comprising, a main body, a shielding cup which engages to the main body a connection means which engages the main body to the torch head consumable components including an electrode, a nozzle, a plasma gas distributor, a shielding gas distributor which are all positioned inside the shielding cup wherein the consumable holder assembly can be detached from the torch head together with the consumable components and the shielding cup as one unit, wherein the connection means comprises a mechanical attachment mechanism which engages the connection means to the torch head and wherein a compression member, for example a spring, is provided between the connection means and the main body which allows the connection means to keep moving proximally via the mechanical attachment mechanism, when the electrode engages the torch head and the rest parts of the consumables holder assembly stay axially in place.

17. The consumables holder assembly according to claim 16, wherein the mechanical attachment mechanism is a bayonet mount which comprises at least two pins in the connection means and two corresponding grooves on the torch head side to lock the pins.

18. The consumables holder assembly according to claim 16, wherein the mechanical attachment mechanism comprises a locking tab feature mating with a locking feature on the torch head which provides a predetermined axial distance for engagement of the compression member.

19. The consumables holder assembly according to claim 16, wherein the force for engagement of the compression member is between 20 N and 500 N, preferably between 50 N and 150 N.

20. The consumables holder assembly according to claim 16, wherein at least two main body pins are provided at the distal end of the main body which corresponds to recesses of the nozzle to engage the main body to the nozzle.

21. The consumables holder assembly according to claim 16, wherein the main body is made of metallic and insulative material, preferably brass and polyether ether ketone.

22. The consumables holder assembly according to claim 21, wherein the metallic material is positioned at the proximal end of the main body from 10% to 30% of the axial length of the main body and the rest of the main body is made of insulative material.

23. The consumables holder assembly according to claim 16, wherein the nozzle comprises two focus gas passageways which lead a focus gas out of the nozzle through at least two focus holes, wherein the two focus holes are situated in the nozzle perpendicular to the welding direction.

24. The consumables holder assembly according to claim 16, wherein the main body has a middle section comprising at least two circumferential grooves having the same axis in the main body, wherein a first groove comprises a first radial passageway and a second groove (19) comprises a second radial passageway which extend through the main body and allow a fluid communication between the exterior and the interior of the main body, wherein a axial passageway is provided between the at least two grooves which allows an axial fluid communication from the first groove to the second groove.

25. The consumables holder assembly according to the claim 24, wherein the first radial passageway and the second radial passageway are aligned axially and the axial passageway is positioned in the opposite of both radial passageways.

26. The consumables holder assembly according to claim 16, wherein the main body comprises multiple axial passageways for passing a shielding gas from the interior to the exterior of the main body.

27. The consumables holder assembly according to claim 16, wherein an external visual feature is provided on the consumable holder assembly and the main torch showing the alignment of the consumable holder assembly to the torch head, preferably showing the location of the focus holes and indicating proper assembly.

28. The consumables holder assembly according to claim 16, wherein the consumables holder assembly comprises a rotational lock, wherein the rotational lock is axially translatable with the compression member, wherein the rotational lock comprises at least one locking pin in the connection means which prevents a rotational movement between the connection means and the main body by inserting them in grooves of the main body.

29. The consumables holder assembly according to claim 16, further comprising orientation means providing angular localization between the consumable holder assembly and the main torch.

30. A method of welding using a plasma arc torch with a consumables holder assembly according to claim 16.

Description

[0039] The present invention will be further discussed with the detailed description and the accompanying drawings.

[0040] FIG. 1: A longitudinal section view of a plasma arc torch comprising a torch head and a consumables holder assembly.

[0041] FIG. 2: A longitudinal section view of the consumables holder assembly comprising consumable components.

[0042] FIG. 3: A plane view of the nozzle comprising focus holes

[0043] FIG. 4: A perspective view of the main body

[0044] FIG. 5: A longitudinal section view of the main body

[0045] FIG. 6: A longitudinal section view of a plasma arc torch after the torch head is engaged with the consumables holder assembly.

[0046] FIG. 1 shows a plasma arc torch which has a torch main body 1 and a consumables holder assembly 3. The torch main body is connected to a power supply and comprises an anode element which is in electrical communication with the positive side of a power supply, and a cathode body that is electrical communication with the negative side of the power supply. The cathode body is insulated from the anode body by an insulative component.

[0047] A torch head 2 is provided at the distal end of the torch main body 1 and is further adjoined with a coolant supply tube, a plasma gas supply tube and a shielding gas supply tube. The plasma gas and shielding gas are supplied from the proximal end of the plasma arc torch via the torch head to the consumables holder assembly at the distal end and released to the atmosphere to benefit the welding process, while the coolant is supplied also from the proximal end to the consumables holder assembly and then return back to the proximal end of the plasma arc torch during operation.

[0048] The torch main body 1 is engaged with the consumables holder assembly 3 by connection means which ensures an accurate alignment of the supply passageways of the fluid in both torch main body 1 and the consumables holder assembly 3. The consumables holder assembly 3 holds all the consumable components in its housing which needs to be replaced regularly. By such a construction in accordance with the present invention all the consumable components can be attached to or detached from the torch head as one unit. This unit, which is the consumables holder assembly 3, provides a quick and reliable replacement of the consumable components which ensures an accurate alignment of the torch and a good repeatability of the welding outcome.

[0049] In addition, the referred proximal end and distal end are indicated as A and B respectively in FIG. 1.

[0050] FIG. 2 shows the consumables holder assembly in detail. The assembly 3 comprises a main body 4, a shielding cup 5, an electrode 6, a nozzle 7, a plasma gas distributor (PGD)8, a shielding gas distributor (SGD)9 and a bayonet mount 12.

[0051] The main body 4 is a cylinder-like shaped component which holds the electrode 6, PGD 8, nozzle 7 within its housing and can be connected and disconnected with the torch head. The main body 4 comprises coolant passageways allowing coolant to flow through, and it comprises also shielding gas passageways allowing shielding gas to flow through the main body 4. By “flow through” it means that the coolant or the shielding gas flows from interior to exterior of the main body 4 or vice versa. The main body 4 comprises however no passageway through which the plasma gas flows. Furthermore, there is no electrical power or signals are passed through the main body 4. The main body 4 is made of metallic and plastic material, preferably made of brass and polyether ether ketone.

[0052] After the electrode 6 is engaged to the torch head, the electrode 6 carries negative potential and operates as a cathode, whereas the nozzle 7 carries positive potential and operates as an anode. The electrode 6 is stick shaped without hollow space inside and is made of tungsten. There is an arc chamber 10 formed between the electrode 6 and the nozzle 7 in which a pilot arc is generated by ionization of the plasma gas.

[0053] The plasma gas is flowed into the arc chamber 10 through the PGD 8 which surrounds the electrode 6. The PGD 8 has multiple circumferential plasma gas holes 12 about its axis through which the plasma gas flows radially inwards into the arc chamber 10. The PGD 8 is assembled with the electrode 6 by sitting on a seat of the electrode 11 which encloses the electrode 6 on its proximal end.

[0054] The electrode 6 and the surrounding PGD 8 are engaged to the nozzle 7 by dropping them into the central recess of the nozzle 7. The central recess has a shoulder 16 which has a diameter smaller than it of the PGD 8 but bigger than it of the electrode 6 which holds the PGD 8 sitting on the shoulder and render the electrode 6 go through to form the arc chamber 10. By having these components constituted as such, the anodic nozzle 7 is electrically isolated from the cathodic electrode 6 by the PGD 8. The nozzle 7 further comprises a central exit orifice 15 by which the arc is constricted. In operation, when the torch is moved to a position close to the workpiece to be treated, the pilot arc jumps from the torch nozzle 7 to the workpiece through the orifice 15 which constricts the arc to form a plasma arc between the electrode 6 and the workpiece. Accordingly, the workpiece serves as the anode and the plasma arc torch is operated in a transferred arc mode.

[0055] Furthermore, the nozzle 7 comprises two focus gas passageways 22 which extends axially to the distal end of the torch to lead a focus gas from the proximal end to outside of the torch via two focus gas holes 23 as shown in FIG. 3. The focus gas is used for injection on two sides of the arc. It influences the shape of the arc and changes it from a circular/symmetric arc to oval shape by cooling the fringes of the arc. In so doing, the focus gas also decreases the arc pressure. These two focus holes 23 are positioned perpendicular to the welding direction in operation which helps to further shape the arc in a desirable way. In addition, it is preferably to have visual signs on the outside of the torch indicating the orientation of the focus holes so that the operator can easily recognize the position of the arc torch. By doing so, it is not necessary for the operator to check the downside of the nozzle 7 every time to determine the correct operation direction of the arc torch

[0056] The SGD 9 is cup-shaped and made of insulative and metallic material, preferably PEEK and brass. The SGD 9 comprises a shoulder at its distal end which holds the nozzle 6 in a drop-in way when they are assembled. Furthermore, the SGD 9 comprises passageways for shielding gas to flow through it. After the shielding gas goes through the SGD 9, it flows into a shielding gas passageway 14 which is formed between the shielding cup 5 and the SGD 9, and then flows out of the torch to provide a shielding atmosphere surrounding the plasma arc which is generated through the exit orifice 15 in the middle.

[0057] The shielding cup 5 is the outermost cup which holds all the other consumable components within its internal space. It is engaged on the proximal portion of the main body 4 by a thread means.

[0058] Preferably, the connection means comprises two pins which lock grooves provided at the torch main body 1 to form a bayonet mount to engages the whole consumables holder assembly 3 to the torch main body 1. The bayonet mount ensures a high concentric alignment between the consumable holder assembly 3 and the torch main body 1 which prevents any undesirable rotation therebetween, so that all the supplies for coolant, plasma gas, focus gas and shielding gas in the torch main body 1 and the consumables holder assembly 3 can be accurately aligned to each other to allow fluid connection from the proximal end to the distal end of the arc torch.

[0059] Preferably, there is a visual feature (not shown) on the connection means 12 and the outside of the torch head 2 which indicates the orientation of the focus holes 23 at the nozzle 7. When the consumables holder assembly 3 is engaged with the torch head 2 correctly, the visual feature on the connection means 12 and the torch head 2 matches together and shows the direction of the focus holes 23 so that the operator does not have to look down at the focus hole 23 in nozzle 7 to determine the orientation of the arc torch in respect of the travelling direction of welding which makes the replacement of the consumables holder assembly 3 easier and more efficient.

[0060] FIG. 4 and FIG. 5 show the main body 4 in a perspective view and a longitudinal view respectively. The main body 3 has a middle section 17 which comprises multiple circumferential grooves (18, 19) having the same axis in the main body 4. The middle section 17 comprises a first groove 18 having a first radial passageway 20 and a second groove 19 having a second radial passageway 21. These two radial passageways extend both radially through the main body 4 which allow a fluid communication between the exterior and the interior of the main body 4. The both radial passageways 20 and 21 are aligned axially.

[0061] Moreover, there is an essentially axial groove 24 provided between the first groove 18 and the second groove 19 which allows a fluid communication from the first groove to the second groove, especially from the first radial passageway 20 to the second radial passageway 21. The axial groove 24 is positioned in the opposite of the both radial passageways which enable an efficient cooling of the both grooves (18, 19). In operation, the coolant, e.g. water, flows from the interior of the main body towards the first groove 18 via the first radial passageway 20 and then flows to the second groove 19 via the essentially axial groove 24 and then flows again in the interior of the main body 4 via the second radial passageway 21 in the second groove 19.

[0062] Furthermore, the middle section 17 comprises multiple axial passageways at its circumference (not shown) for passing the shielding gas axially from the interior to the exterior of the main body 4 and then through the shielding gas passageway 14 to exit the arc torch. There is no passageway in the main body 4 to pass plasma gas and the electrical power or signals are also not passed through the main body 4. Moreover, the main body 4 comprises two main body pins (29) sitting opposite to each other which correspond to the recesses in the nozzle (7) to engage it to the nozzle (7) to prevent rotational movement between the nozzle (7) and the main body (4).

[0063] The main body 4 is made of metallic and plastic material. It is shown in the FIG. 3 that the lower part 25 is made of brass and the upper part 26 is made of PEEK. The lower part accounts preferably for 10% to 30% of the axial length of the main body 4. By having the two different material distributed like so, the main body 4 can resistant the intense heat coming from the arc chamber 10 and maintain a lightweight at the same time in a more cost-effective way.

[0064] FIG. 6 shows a longitudinal sectional view of the arc torch after the engagement of the torch main body 1 and the consumables holder assembly 3. The consumables holder assembly 3 comprises a rotational lock which is axially translatable with a spring 27 as compression member. The rotational lock comprises multiple locking pins (28) in the connection means (12) which corresponds to grooves in the main body. When the connection means (12) engages to the main body (4), the pins (28) lock in the grooves and thus prevent a rotation movement therebetween. It provides a set force ensuring repeatable contact of the electrode to the torch.

[0065] When the assembled consumable holder assembly 3 is attached to the torch main body 1, the electrode 6 engages the cathode of the torch main body 1 and initiate the contact. As the consumable holder assembly 3 is engaged with the torch main body 1, the inner component comprising main body 4, electrode 6, PGD 8, nozzle 7, shielding cup, SGD stay axially in place, which the connection means keeps moving up through the bayonet mount of the connection means 12 engaging the spring 27 activating a force on the electrode 6. Through the proper design the axial movement compresses the spring 27 through a pre-determined distance which results a pre-defined force on the contact area between the electrode 6 and torch head 2. It ensures the correct contact for both electrical connection and thermal heat transfer from the electrode 6 to the torch main body 1.

[0066] The engagement of the consumables holder assembly 3 and the torch main body 1 allows all the fluid communication of the coolant, plasma gas, shielding gas, focus gas to flow from the proximal end to the distal end of the torch.

REFERENCES LIST FOR THE FIGS

[0067] 1. torch main body [0068] 2. torch head [0069] 3. consumables holder assembly [0070] 4. main body [0071] 5. shielding cup [0072] 6. electrode [0073] 7. nozzle [0074] 8. plasma gas distributor [0075] 9. shielding gas distributor [0076] 10. arc chamber [0077] 11. seat [0078] 12. connection means [0079] 13. plasma gas passage [0080] 14. shielding gas passage [0081] 15. orifice [0082] 16. shoulder [0083] 17. middle section [0084] 18. first groove [0085] 19. second groove [0086] 20. first radial passageway [0087] 21. second radial passageway [0088] 22. focus gas passageway [0089] 23. focus hole [0090] 24. axial groove [0091] 25. metal part [0092] 26. plastic part [0093] 27. compression member [0094] 28. locking pin [0095] 29. main body pin