High power plastic wire electric shock tool

Abstract

The invention relates to a high-power electrical discharge tool (1), said tool (1) comprising a pair of electrodes comprising an anode (30) and a cathode (40) the free ends (30B, 40B) of each of which are arranged opposite each other, said tool (1) being configured to apply a voltage between said anode (30) and said cathode (40) in order to produce an electrical discharge, said tool (1) comprising a wire (35) made of plastic material connecting the free end (30B) of the anode (30) to the free end (40B) of the cathode (40). Figure for abstract: Figure 1

Description

Title of invention: Plastic wire high-power electric discharge tool Technical field

[0001] The present invention relates to the field of high-power electronics and more particularly concerns a high-power electrical discharge device in a liquid. Prior art

[0002] Nowadays, it is known to use a high-power electric discharge tool to stimulate or clean a downhole well or to carry out electrohydraulic forming of metal parts. For this purpose, the tool is first immersed in a liquid before causing an electric discharge resulting in a shock wave propagating in the liquid to reach the walls of the well to be stimulated or cleaned or the metal part to be formed.

[0003] Such a tool comprises, in a known manner, a pair of electrodes comprising an anode and a cathode, the free ends of each of which are arranged opposite one another. The tool is configured to allow the application of a voltage between said anode and said cathode in order to produce the electrical discharge.

[0004] During a discharge into a liquid, a significant amount of energy, of the order of 30%, is dissipated during the initial phase of preheating the liquid. In addition, the preheating time of the tool before discharge can be relatively long.

[0005] In order to remedy at least in part these drawbacks, a known solution consists of using a metal wire extending between the anode and the cathode. The use of such a wire promotes the triggering of the discharge while allowing the restitution of all the energy and the reduction of the preheating time.

[0006] However, since the energy level of the discharge is particularly high, the discharge causes the vaporization of the metal which generates the shock wave. The wire must therefore be changed regularly, in practice after each discharge, which presents a significant drawback.

[0007] Documents US3603127, US3750441, RU44183, SU636569 and SU247530 disclose a discharge tool comprising a roller on which the metal wire is wound and which can be unwound after each discharge to extend between the anode and the cathode.

[0008] However, such a solution has several drawbacks. First of all, the wire is a consumable that must be renewed after each shot or when the roll is empty, which can be long, complex and time-consuming. Then, unwinding the wire can cause misalignment of the wire between the anode and the cathode and therefore a reduction in the efficiency of the wire during discharge, which can lead to energy losses. Furthermore, the roll of wire occupies a significant volume inside the tool, which increases its dimensions. In addition, the steam generated during the electrical discharge can modify the conductivity of the medium between the anode and the cathode, which reduces the resistance of the wire and therefore its efficiency. Finally, portions of the wire wound on the roll can weld together following shots due to the heat released, which can block the unwinding of the wire.

[0009] Document US3603127 proposes using a thread made from textile fibers coated with a metal powder to reduce the risk of breakage, but this solution does not solve the other problems mentioned above, given in particular that the metal powder melts during discharge, which reduces the efficiency of the thread and increases energy losses, and that the thread remains a consumable to be changed.

[0010] There is therefore a need for a simple and effective solution to at least partially remedy these drawbacks. Statement of the invention

[0011] To this end, the invention firstly relates to a high-power electrical discharge tool, said tool comprising a pair of electrodes comprising an anode and a cathode, the free ends of each of which are arranged opposite one another, said tool being configured to apply a voltage between said anode and said cathode in order to produce an electrical discharge, said tool being remarkable in that it comprises a wire made of a plastic material connecting the free end of the anode to the free end of the cathode.

[0012] The wire, in physical contact with the anode, promotes breakdown during the electrical discharge while avoiding losses by dissipation. Its composition in plastic material (non-metallic), a priori counter-intuitive in view of the prior art, prevents the wire from breaking with each shot, which avoids having to replace it after each shot. The plastic material does not vaporize during shots and resists the shock waves generated by the electrical discharges.

[0013] Preferably, the yarn is made of a single strand, which makes it efficient, simple to manufacture and inexpensive.

[0014] Alternatively, the wire comprises several strands, for example braided, to reinforce its resistance.

[0015] Preferably, the wire is made of nylon which offers high resistance to the shock wave generated by the electric discharge. Alternatively, the wire could be made of any other plastic material such as, for example, polyethylene, polytetrafluoroethylene, etc.

[0016] Advantageously, the diameter of the wire is between 0.5 and 1.3 mm. Such a diameter makes the wire sufficiently thick to withstand the shock wave and sufficiently thin to limit the thermal losses linked to the contact surface of the wire with the anode and the cathode.

[0017] According to one aspect of the invention, the free end of the anode has a pointed shape and the free end of the cathode has a flat face, the wire extending between the pointed end of the anode and the center of the flat face.

[0018] In one embodiment, the wire is attached to the flat face of the cathode.

[0019] In another embodiment, the wire enters a channel formed in the cathode and spring at a side face of the cathode to be fixed, preferably, to said external side face of the cathode.

[0020] In another embodiment, the wire enters a channel formed in the cathode and exits at the opposite end of the cathode.

[0021] Advantageously, the wire can be fixed to the anode, in particular at its tip, using an adhesive, for example of the adhesive tape or glue type.

[0022] Advantageously, at least one of the ends of the wire is fixed to at least one damping element such as, for example, a spring in order to more easily absorb part of the energy generated by the discharge and thus prevent the wire from breaking.

[0023] In a particularly advantageous embodiment, the wire enters a channel formed in the cathode and emerges on a side face of the cathode to be fixed to the cathode using a spring. Brief description of the drawings

[0024] Other characteristics and advantages of the invention will become apparent from reading the description which follows. This description is purely illustrative and should be read in conjunction with the appended drawings in which:

[0025] [Fig-1] [Fig. 1] is a partial sectional view of a first embodiment of the tool according to the invention.

[0026] [Fig.2] [Fig.2] is a partial sectional view of a second embodiment of the tool according to the invention. Description of the embodiments

[0027] [Fig.l] illustrates the front portion of an exemplary high-power electric discharge tool 1 according to the invention.

[0028] The tool 1 comprises a metal body 10 serving as an armature and comprising a head 12. The body 10 defines an internal space 10A in which a pair of electrodes 30, 40 is mounted and which is adapted to fill with a liquid when the tool 1 is immersed in said liquid, for example water.

[0029] The pair of electrodes 30, 40 comprises an anode 30 and a cathode 40 whose ex- free ends 30B, 40B of each are arranged opposite each other.

[0030] The tool 1 is configured to allow the application of a voltage between said anode 30 and said cathode 40 in order to produce an electrical discharge. The voltage can be provided by one or more capacitors, integrated in the tool 1 or external to the tool 1 by being connected to the pair of electrodes 30, 40 by a pair of electrical cables (not visible in the figures for the sake of clarity).

[0031] The anode 30 is mounted in an electrically insulating tubular support 50 itself mounted on the body 10 via a first fixing element 55. The anode 30 is in the form of a metal rod comprising an end 30A mounted inside the support 50 and a free end 30B, pointed and oriented towards the cathode 40, protruding from a free end 50A of the support 50 arranged in the internal space 10A.

[0032] The cathode 40 is in the form of a solid metal cylinder, one end 40A of which is fixed at the level of the head 12 of the tool 1 via a second fixing element 56 and the other end 40B is free and is in the form of a flat face.

[0033] The anode 30 and the cathode 40 are spaced apart by a predetermined distance d, for example between 3 and 100 mm, and preferably between 3 and 30 mm, in order to allow the creation of an electric arc during a current discharge at the voltage applied between the anode 30 and the cathode 40.

[0034] The tool 1 comprises a wire 35 made of a plastic material, preferably nylon, which connects the free end 30B of the anode 30 to the free end 40B of the cathode 40. The wire 35 is preferably made of a single strand but may comprise several braided strands. Preferably, the diameter of the wire 35 is between 0.5 and 1.3 mm.

[0035] In the embodiments illustrated in Figures 1 and 2, one end 35A of the wire 35 is locked between the body 10 and the fixing element 50 while the other end 35B of the wire 35 is fixed to a spring 60 through the cathode 40.

[0036] The wire 35 extends between the anode 30 and the anode support 50 to the free end 30B of the anode while being in mechanical contact with the tip of the anode 30.

[0037] The wire 35 then extends from the tip of the anode 30 to the flat-faced free end 40B of the cathode 40.

[0038] The wire 35 penetrates at the center of the flat face of the free end 40B of the cathode 40B into a through channel 42, formed in the cathode 40, the place where the wire 35 passes through the cathode 40.

[0039] In the first embodiment illustrated in [Fig. 1], the wire 35 springs at the external lateral face 40C of the cathode 40 and is fixed by its end 35B to the spring 60 which is itself fixed to the second fixing element 56.

[0040] In the second embodiment illustrated in [Fig.2], the wire 35 springs out at level of the other end 40A of the cathode 40 and is fixed to the spring 60 which is itself fixed on an internal face 12A of the head 12 of the tool 1.

[0041] As a variant of the first embodiment, the end 35B of the wire 35 could be fixed directly (i.e. without spring 60) to the external lateral face 40C or to the second fixing element 56 or to an internal surface of the body 10 of the tool 1.

[0042] As an alternative to the second embodiment, the end 35B of the wire 35 could be attached directly to the opposite end 40B of the cathode 40 or to an internal surface of the body 10 of the tool 1.

[0043] As a further variant, the end 35B of the wire 35 could be fixed directly to the free end 40B with a flat face of the cathode 40, directly or by means of a spring.

[0044] In operation of the tool 1, a voltage, preferably of several kilovolts, for example between 8 and 30 kV, is first applied between the anode 30 and the cathode 40. The application of this voltage causes preheating of the liquid medium between the electrodes 30, 40 then a breakdown causing the electrical discharge when the breakdown conditions in pressure and temperature are met.

[0045] The wire 35 connecting the electrodes 30, 40 facilitates the creation of the arc compared to a cordless version of the tool 1 while avoiding changing it after each shot. Its composition in non-conductive plastic material makes it resistant to voltage and electric discharge, in particular to the shock wave. The wire 35 makes it possible to increase the operating range of the tool 1 in pressure and temperature. The use of a spring 60 to fix the wire 35 also makes it possible to maintain the tension of the wire 35, to guarantee that the wire 35 is held in its position and to improve the resistance of the wire 35 to the shock wave by better absorbing the energy.

Claims

Claims

1. A high-power electrical discharge tool (1), said tool (1) comprising a pair of electrodes comprising an anode (30) and a cathode (40) the free ends (30B, 40B) of each of which are arranged opposite each other, said tool (1) being configured to apply a voltage between said anode (30) and said cathode (40) in order to produce an electrical discharge, said tool (1) being characterized in that it comprises a wire (35) made of plastic material connecting the free end (30B) of the anode (30) to the free end (40B) of the cathode (40).

2. Tool (1) according to claim 1, wherein the wire (35) consists of a single strand.

3. Tool (1) according to claim 1, wherein the wire (35) comprises several strands.

4. Tool (1) according to the preceding claim, in which the strands are braided.

5. Tool (1) according to any one of the preceding claims, wherein the wire (35) is made of nylon.

6. Tool (1) according to any one of the preceding claims, wherein the diameter of the wire (35) is between 0.5 and 1.3 mm.

7. Tool (1) according to any one of the preceding claims, wherein the free end (30B) of the anode (30) has a pointed shape and the free end (40B) of the cathode (40) has a flat face, the wire (35) extending between the pointed end of the anode (30) and the center of the flat face.

8. Tool (1) according to the preceding claim, in which the wire (35) is fixed on the flat face of the cathode (40).

9. Tool (1) according to claim 7, wherein the wire (35) enters a channel formed in the cathode (40) and emerges at an outer side face (40C) of the cathode (40) to be fixed, preferably, to said outer side face (40C), or emerges at the opposite end (40A) of the cathode (40).

10. Tool (1) according to the preceding claim, wherein at least one of the ends (35A, 35B) of the wire (35) is fixed to at least one spring (60).

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