WO2018122351A1

WO2018122351A1 - Mobile contact device for an electrode of a plasma torch and tool for fixing said device

Info

Publication number: WO2018122351A1
Application number: PCT/EP2017/084773
Authority: WO
Inventors: Giorgio Bassi
Original assignee: Tec. Mo. S.R.L.
Priority date: 2016-12-29
Filing date: 2017-12-28
Publication date: 2018-07-05
Also published as: IT201600132405A1; EP3563644A1

Abstract

A mobile contact device for an electrode (E) of a plasma torch (T) comprises a seating (S) for said device (1) and a chamber (C) assigned to slidingly house an electrode (E) electrically powered by the device (1) and movable between a rest condition (R), in which it (E) matches with an end of a hollow of a nozzle (U) of the torch (T), and an operating condition (O), in which it (E) is spaced from said end. Said device (1) comprises a tubular body means (3) having a side wall (5) and an inner cavity (7) longitudinally crossing said tubular body means (3) from a first end to a second end of the tubular body means (3) itself. The first end is provided with a connection (9) for the removable connection to the seating (S) of the body means (3) which is electrically connected to electrical power supply means of the torch (T). Said device further comprises a contact means (11) movable in said inner cavity (7) and having a contact end (13) protruding, at least in the rest condition (R), from the second end of the body means (3) through a respective end opening (15) of said inner cavity (7). The inner cavity (7) further contains a resilient means (17) compressed between a shoulder means (19) of the contact means (11) and an abutment means (21). At least in the rest condition (R), the contact end (13) of the contact means (11) contacts a corresponding contact end of the electrode (E) electrically connecting it (E) to electric power supply means of the torch (T) through said body means (3) and/or resilient means (17) and/or abutment means (21). The inner cavity (7) is fed through a duct of said seating (S) with a fluid flowed into the torch (T) by respective feeding means of said fluid. The side wall (5) is located between the connection (9) and the second end of the body means (3) and it has a set of second pass-through channels (29) each flowing, on one side, to the outside of the device (1) and, on the other side, into the inner cavity (7) of the body means (3).

Description

MOBILE CONTACT DEVICE FOR AN ELECTRODE OF A PLASMA TORCH AND TOOL FOR FIXING SAID DEVICE

DESCRIPTION TECHNICAL FIELD

The present invention relates to the field of plasma torches and it relates to a mobile contact device for an electrode of a plasma torch, for example of the contact trigger type or of the pneumatic trigger type, and to similar equipment. The present invention further relates to a tool specifically assigned to install said plasma torch device and to disassemble it.

BACKGROUND ART There are known plasma torches in which the triggering of the electric arc and of the plasma jet occurs through the detachment of the electrode from the torch nozzle when the earlier is switched on. Such detachment occurs through the axial translation of the electrode and of all torch parts integral therewith. A drawback of these known plasma torches is that the need to allow the translation of many electrical and pneumatic torch parts places design constraints and causes an increase in costs.

Another drawback of said known plasma torches derives from the fact that the replacement of the electrode, which is a consumable part subject to wear, may require the replacement of other torch parts that are integral with the electrode.

DISCLOSURE OF INVENTION An object of the present invention is to provide a mobile contact device for an electrode of a plasma torch, that is suitable for the production of torches that are simple, reliable and inexpensive also with respect to the use and the maintenance. Another object is to provide a device that allows the easy, rapid, inexpensive replacement of the electrode alone. A further object is to provide a device that may be easily disassembled and replaced even by means of a simple hand tool.

Another object is to provide a device that is provided with canalizations for excellent cooling and that allows optimal cooling of the electrode.

A further object is to provide a device that may replace electrodes of known torches together with one of its own electrodes.

Another object is to provide a tool for fixing said device to a plasma torch, and for disassembling it.

Document EP1599075A2 discloses a device having the features of the preamble of claim 1. BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention are highlighted hereafter, with specific reference to the accompanying drawings, in which: - Figure 1 shows an exploded partial section view of a torch equipped with the mobile contact device for an electrode of a plasma torch subject-matter of the invention, in which some parts have been removed;

Figures 2 and 3 show respectively in a side view and in an enlarged view of the mobile contact device of Figure 1 for the device of Figure 2;

- Figures 4 and 5 show an axial section view of some parts of the torch of Figure 1 , including the device and the relative seating respectively in the rest condition, i.e., prior to the triggering of the plasma jet, and in the operating condition; Figures 6 and 7 show respectively axonometric views of the sections of Figures 4 and 5;

Figures 8 and 9 show respectively enlarged side view and axial sectioned view of the device in the rest condition;

- Figures 10 and 11 show respectively enlarged side view and axial sectioned view of the device in the operating condition;

Figures 12 and 13 show enlarged and axonometric views of the device in the rest condition respectively complete and partially sectioned by an axial plane;

Figures 14 and 15 show show enlarged and axonometric views of the device in the operation condition respectively complete and partially sectioned by an axial plane;

Figures 16 and 17 show axonometric views from respective points of view of a tool for mounting the device into the respective seating of the torch and for dismounting it.

BEST MODE TO CARRY OUT THE INVENTION

Referring to Figures 1-15, numeral 1 indicates the mobile contact device subject-matter of the present invention, for ensuring the supply of electrical power to a slidable electrode E of a plasma torch T with contact trigger, for example, of the pneumatic type. Said the torch T is equipped with means for supplying electrical power to its active components (where the electrical power is fed by an external power supply) and is fed with air, gas, water, etc. by means for supplying fluids.

The plasma torch T comprises a seating S, for example with a threaded connection, for said device 1, and a chamber C, which is preferably tubular and removable, assigned to slidingly house the electrode E supplied with electrical power by the device 1 and movable between a rest condition R, in which it matches with an end, or a shoulder, of a cavity of a nozzle U of the torch T, and an operating condition O in which it is spaced from said end.

In an operating condition of the torch and of the device 1, the latter 1, the seating S, the chamber C, the electrode E and the nozzle U are coaxial with one another. The device 1 comprises a tubular-shaped body means 3, for example made of copper or bronze alloy. The body means 3 has a side wall 5 in the form of a rotation solid or of an axially symmetric solid, and an inner cavity 7 longitudinally passing through it 3, from one first end to a second end of said body means 3.

The first end of the body means 3 is provided with a removable connection to the seating S, where such connection and seating may have a bayonet coupling, a snap-fit coupling or preferably, and as shown in the accompanying Figures, a threaded coupling, i.e., a male/female screw coupling. Said body means 3 is electrically connected with means of the torch T, for supplying electrical power.

The device further comprises a contact means 11 movable in said inner cavity 7 and having a contact end 13 projecting, at least in the rest condition R, from the second end of the body means 3 through a corresponding end opening 15 of said inner cavity 7.

Such inner cavity 7 further comprises a resilient means 17, preferably consisting of a helicoidal spring of the compression type, for example made of phosphor bronze or of another conductive, elastic and thermally resistant material. Such helicoidal spring is compressed between a shoulder means 19 of the contact means 11 and an abutment means 21 of the body, or fixed thereto.

In the absence of any major opposite forces, i.e., in the rest condition R, the elastic force of the helicoidal spring resilient means 17 is strong enough to keep the contact end 13 of the contact means 11 projecting from the second end of the body means 3.

Vice versa, in the operating condition O, the electrode E transmits an overwhelming force, and the contact means 11 becomes retracted within the profile of the body means. The contact means 1 1 comprises a cylindrical shaft having a diameter slightly smaller than that of the end opening 15 of the second end of the body means 3, and an annular enlarged portion, for example in the form of a circular ring, forming the shoulder means 19 and having a maximum diameter slightly smaller than that of the portion of the inner cavity 7 adjacent to said second end of the body means 3. The distance between the projecting contact end 13 of the shaft of the contact means 11 and the respective shoulder means 19 is equal to or slightly greater than the stroke of the electrode E between the rest condition R and the operating condition O.

In the rest condition R, the contact end 13 of the contact means 11 contacts a corresponding electrical connection end of the electrode E (opposed to the active end of the electrode usually provided with a hafnium insert, or the like), thus electrically connecting the electrode with the means for supplying electrical power of the torch T when the torch T is switched on, whereby such means for supplying electrical power to the torch T are activated at the same time as the means for supplying fluids (air, gas, water, etc.) to the torch T. A very short time after its switching on, the electrode translates in the direction of the device and stops when it matches and becomes in contact with the body means 3 of the device 1 itself, thus reaching the operating condition O in which the plasma jet is activated.

An intermediate portion of the side wall 5 of the body means 3 comprised between the connection 9 and the second end of the body means 3 is enlarged, i.e., consists of a projection 27 in the form of a toothed wheel or of a finned wall that is preferably annular- shaped, as shown in the accompanying Figures, and/or of a cylindrical wall.

The projection 27 is provided with a set of first pass-through channels 25 leading to the opposite longitudinal ends of such projection 27 and assigned to be passed through by a fluid flow supplied by respective means for supplying such fluid to the torch T. Preferably, such first pass-through channels 25 are parallel to the longitudinal axes of the device 1 and of the torch T.

Through a duct of said seating S, the inner cavity 7 is fed with a fluid supplied to the torch T by respective means for supplying such fluid. The side wall 5, comprised between the connection 9 and the second end of the body means 3, has a set of second pass-through channels 29 each of them leading to the outside of the device 1, on the one side, and to the inner cavity 7 of the body means 3, on the other side 3. The second pass-through channels 29 pass through the projection 27 of the body means 3 and are inclined with respect to the longitudinal axes of the device 1 and of the torch T with an interposed angle ranging between 70° and 20°, preferably between 30° and 45°.

The external mouth of each of said second pass-through channels 29 is on the lateral face of the projection 27 of the body means 3, whereas the corresponding internal mouth, i.e., the mouth in the inner cavity 7, is closer to the first end of the body means 3 than the external mouth; preferably said internal mouth of each of said second pass-through channels 29 is located between the first end of the body means 3 and the abutment means 21. As a result of this arrangement, the second pass-through channels 29 are divergent in the direction from the first to the second end of the body means 3.

The first 25 and second 29 pass-through channels are separated, i.e., they are not in mutual and direct flow communication; furthermore, such first 25 and second 29 pass-through channels are mutually interposed and angularly spaced in a regular manner.

The abutment means 21 consists of an annular or disc-shaped partition that is pierced or preferably solid, and is fixed into the inner cavity 7 of the body means 3 between the mouths of the second pass-through channels 29 into the inner cavity 7 and the second end of the body means 3. The second end of the body means 3 consists of a terminal element 31 having an approximately annular shape and provided with the end opening 15 at the centre, whereby it 31 is fixed to, or integral with, the side wall 5 of the body means 3. The internal face of the terminal element 31 matches with the shoulder means 19 of the contact means 11 in the rest condition R. In the operating condition O, the external face of the terminal element 31 matches with said electrical connection end, i.e., contact end, of the electrode E and electrically connects it, through the body means 3, to the means for supplying electrical power to the torch T.

The external faces of the terminal end 31 and of the contact end, i.e., of the electrical connection end, of the electrode E are complementary, preferably flat, mutually parallel and perpendicular to the longitudinal axes of the torch and of the device. Alternatively, the surfaces of the terminal element 31 and of the electrode E, which are in mutual contact in the operating condition, may be conical and frusto-conical in shape, dome-shaped, etc., and convex and concave, respectively, or vice versa.

A simple alternative device, whose understanding requires no specific drawings, provides that the end of the first contact means 11 opposed to the respective contact end 13 is slidingly housed in a corresponding concave or pass-through seating obtained at the centre of the abutment means 21 to ensure a fluid translation of the contact means 11 in the transition from the rest stage R to the operating stage O, and vice versa.

The operation of the device 1 provides that starting from the time when the electrode is switched on (which occurs in the rest condition) and for a very short time, the electrode is supplied by the contact means 11 of the device 1, and that in the immediately subsequent operating condition O the electrode is supplied by the body 3 through the terminal element 31. Notably, the arrangement of the first 25 and second 29 pass-through channels guarantees the optimal cooling of the device 1 and of the helicoid spring resilient means 17.

The tool shown in Figures 16 and 17, for fitting the device 1 described above, is assigned to the fitting and disassembling of the device 1 itself into and from its own seating S in the plasma torch T. Such tool 101 comprises a rigid or ratchet shaft having, at one end, a handle or knob, and having, at the other end, a cylindrical head 103 whose diameter is equal to or slightly smaller than the maximum diameter of the device 1. The free end of the head 103 comprises a plurality of parallel pin means 105 mutually spaced and dimensioned such that they may be inserted in corresponding first pass-through channels 25 of the device 1. Preferably, the central portion of the free end of the head 103, surrounded by the pin means 105, may be provided with an optional cavity 107 for housing the terminal element 31 of the body means 3 during the operation of the device, whereby the latter will be fitted and disassembled by axial rotation according to the thread of the connection 9.

Claims

Mobile contact device for an electrode (E) of a plasma torch (T) comprising a seating (S) for said device (1) and a chamber (C) assigned to slidingly house an electrode (E) electrically powered by the device (1) and movable between a rest condition (R), in which it (E) matches with an end of a hollow of a nozzle (U) of the torch (T), and an operating condition (O) in which it (E) is spaced from said end; said device (1) comprises a tubular body means (3) having a side wall (5) and an inner cavity (7) longitudinally crossing said tubular body means (3) from a first end to a second end of the tubular body means (3) itself, where the first end is provided with a connection (9) for the removable connection to the seating (S) of the body means (3) which is electrically connected to electrical power supply means of the torch (T); said device further comprises a contact means (11) movable in said inner cavity (7) and having a contact end (13) protruding, at least in the rest condition (R), from the second end of the body means (3) through a respective end opening (15) of said inner cavity (7), the latter (7) further contains a resilient means (17) compressed between a shoulder means (19) of the contact means (11) and an abutment means (21); at least in the rest condition (R), the contact end (13) of the contact means (11) contacts a corresponding contact end of the electrode (E) electrically connecting it (E) to electric power supply means of the torch (T) through said body means (3) and/or resilient means (17) and/or abutment means (21) ; said device (1) being characterized in that the inner cavity (7) is fed through a duct of said seating (S) with a fluid flowed into the torch (T) by respective feeding means of said fluid and in that the side wall (5) located between the connection (9) and the second end of the body means (3) has a set of second pass- through channels (29) each flowing, on one side, to the outside of the device (1) and, on the other side, into the inner cavity (7) of the body means (3).

Device according to claim 1 characterized in that at least a portion of the side wall (5) between the connection (9) and the second end of the body means (3) has a set of first pass-through channels (25) where said portion consists of at least a projection (27), preferably annular or cylindrical wall shaped or cogwheel or finned wall shaped, of the body means (3) and said first pass-through channels (25) flow at least at the ends of said projection (27) and they (25) are assigned to be passed through by a flow of a fluid feed by respective means for supplying the fluid to the torch (T) where preferably said first pass-through channels (25) are parallel to a longitudinal axes of the device (1) and of the torch (T).

3) Device according to claim 1 characterized in that the second pass-through channels (29) pass through the projection (27) of the body means (3) and they are inclined in respect to the longitudinal axes of the device (1) and of the torch (T) of an interposed angle ranging from 70° to 20°; the external mouth of each of said second pass-through channels (29) is located onto the external side face of the projection (27) of the body means (3); the opposite mouth of each of said second pass-through channels (29) flows into the inner cavity (7) and is located between the first end of the body means (3) and the abutment means (21).

4) Device according to claim 3 characterized in that the pass-through channels first (25) and second (29) are not in mutual and direct flow communication and they are mutually interposed and angularly spaced in a regular manner.

5) Device according to claim 1 characterized in that the abutment means (21) consists of an annular or disc-shaped partition that is solid or pierced and fixed into the inner cavity (7) of the body means (3) between the inner openings of the second pass- through channels (29) inside the inner cavity (7) and the second end of the body means (3) and in that the resilient means (17) comprises one helicoid spring.

6) Device according to any of the preceding claims characterized in that the second end of the body means (3) consists of a terminal element (31) approximately annular shaped and centrally having the end opening (15), said terminal element (31) being fixed to, or integral with, the side wall (5) of the body means (3) where the internal face of the terminal element (31) matches with the shoulder means (19) of the contact means (11) in the rest condition (R).

7) Device according to claim 6 characterized in that, in the operating condition (O), the external face of the terminal element (31) matches with said contact end of the electrode (E) electrically linking the latter (E) with electric feeding means of the torch (T) through the body means (3) where the external face of the terminal element (31) and the face of the contact end of the electrode (E) are mutually complementary, preferably flat and parallel.

Tool (101) for installing into and dismounting from the torch the device according to the preceding claims characterized in that it (101) comprises a head (103) whose diameter in equal to or slightly smaller than the maximum diameter of the device (1) and in that it comprises a plurality of pin means (105) insertable into respective first pass-through channels (25) of the device (1), where preferably the central portion of the head (103) surrounded by the pin means (105) can be provided with an optional cavity (107) for housing the terminal element (31) of the body means (3).