High-power electrical discharge tool with plastic wire

Abstract

A high-power electrical discharge tool having a pair of electrodes including an anode and a cathode, the free ends of each of which are disposed opposite one another, and wherein the tool being configured to apply a voltage between the anode and the cathode to produce an electrical discharge, the tool having a wire consisting of plastic material connecting the free end of the anode to the free end of the cathode.

Description

TITLE: HIGH-POWER ELECTRICAL DISCHARGE TOOL WITH PLASTIC WIRETECHNICAL FIELD

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

[0002] Nowadays, a high-power electrical discharge tool is used to stimulate or clean a downhole, or for electrohydraulic forming of metal parts. For this purpose, the tool is first immersed in a liquid before an electrical discharge is triggered, causing a shock wave to propagate through 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 a pair of electrodes comprising an anode and a cathode, the free ends of each of which are arranged opposite each other. The tool is configured to enable a voltage to be applied between said anode and cathode to produce the electrical discharge.

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

[0005] To remedy these drawbacks at least in part, a known solution is to use a metal wire extending between the anode and cathode. The use of such a wire facilitates the triggering of the discharge, while allowing the energy to be fully restored and the preheating time to be reduced.

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

[0007] Documents US3603127, US3750441, RU44183, SU636569 and SU247530 disclose a discharge tool comprising a roller on which the metallic 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. Firstly, the wire is a consumable that has to be renewed after each shot or when the roll is empty, which can be timeconsuming and complex. Then, the unwinding of the wire can cause a misalignment of thewire between the anode and the cathode and therefore a decrease in the efficiency of the wire at the discharge, which can lead to energy losses. Moreover, the wire roll occupies a significant volume inside the tool, which increases its dimensions. In addition, the vapor generated during electrical discharge can alter the conductivity of the medium between the anode and cathode, which decreases the resistance of the wire and thus its efficiency. Finally, portions of the wire wound on the roller may weld together as a result of the heat generated, which can block the unwinding of the wire.

[0009] The document US3603127 proposes the use of a wire made of textile fibers sheathed with metal powder to reduce the risk of breakage, but this solution does not solve the other problems mentioned above, particularly as the metal powder melts during discharge, reducing the efficiency of the wire and increasing energy losses, and the wire remains a consumable to be changed.

[0010] So there's a need for a simple, effective solution to at least partially overcome these drawbacks.[Summary of the invention]

[0011] To this end, the invention has first of all the object of 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 disposed facing each other, 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, i.e. consisting of a plastic material (and therefore metal-free), 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 electrical discharge, while avoiding dissipation losses. Its plastic (non-metallic) composition, a priori counter-intuitive, prevents the wire from breaking with each shot, thus avoiding the need to replace it after each shot. The plastic material does not vaporize when fired and resists the shock waves generated by electrical discharges.

[0013] Preferably, the wire consists of a single strand, making it efficient, simple to manufacture and inexpensive.

[0014] Alternatively, the wire comprises several strands, e.g. braided, to increase its strength.

[0015] Preferably, the wire is made of nylon, which offers high resistance to the shockwave generated by the electrical discharge. Alternatively, the wire can be made of any other plastic material, such as polyethylene, polytetrafluoroethylene, etc.

[0016] Advantageously, the diameter of the wire is between 0.5 and 1.3 mm. Such a diameter makes the wire thick enough to withstand the shock wave, and thin enough to limit the heat loss related to the surface of contact of the wire with the anode and 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, with the wire extending between the pointed end of the anode and the center of the flat face.

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

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

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

[0021] Advantageously, the wire can be secured to the anode, particularly at its tip, using an adhesive such as tape or glue.

[0022] Advantageously, at least one end of the wire is secured to at least one damping element, such as a spring, to absorb more easily part of the energy generated by the discharge and prevent the wire from breaking.

[0023] In a particularly advantageous embodiment, the wire enters a channel formed in the cathode and emerges from a side face of the cathode to be secured to the cathode by means of a spring.[Description of the drawings]

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

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

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

[0027] Figure 1 illustrates the front part of an example of a high-power electrical discharge tool 1 according to the invention.

[0028] The tool 1 comprises a metal body 10 serving as reinforcement 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 free ends 30B, 40B of each are arranged opposite each other.

[0030] The tool 1 is configured to enable a voltage to be applied between said anode 30 and said cathode 40 to produce an electrical discharge. The voltage can be supplied by one or more capacitors, built into the tool 1 or external to the tool 1, connected to the pair of electrodes 30, 40 by a pair of electric cables (not shown in the figures for clarity).

[0031] The anode 30 is mounted in an electrically insulating tubular support 50, which in turn is 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, pointed end 30B facing the cathode 40, projecting from a free end 50A of the support 50 arranged in the internal space 10 A.

[0032] The cathode 40 takes the form of a solid metal cylinder, one end 40 A of which is secured to the head 12 of the tool 1 via a second fixing element 56, and the other end 40B is free and takes 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, to enable 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, i.e., a plastic material, preferably nylon, which connects the free end 30B of the anode 30 to the free end 40B of thecathode 40. The wire 35 is preferably made up 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 shown in Figures 1 and 2, one end 35A of the wire 35 is blocked between the body 10 and the fixing element 50, while the other end 35B of the wire 35 is secured to a spring 60 through the cathode 40.

[0036] The wire 35 extends between the anode 30 and the support 50 of the anode 30 to the free end 30B of the anode, 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 cathode 40.

[0038] The wire 35 enters 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, where the wire 35 passes through the cathode 40.

[0039] In the first embodiment shown in Fig. 1, the wire 35 protrudes from the external side face 40C of the cathode 40 and is secured by its end 35B to the spring 60, which in turn is secured to the second fixing element 56.

[0040] In the second embodiment shown in Fig. 2, the wire 35 protrudes from the other end 40A of the cathode 40 and is secured to the spring 60, which in turn is secured to an inner face 12A of the head 12 of the tool 1.

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

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

[0043] As another alternative, the end 35B of the wire 35 could be secured directly to the flat-faced free end 40B of the cathode 40, either directly or via a spring.

[0044] During 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 the liquid medium between the electrodes 30, 40 to preheat,followed by breakdown, triggering electrical discharge when the pressure and temperature breakdown conditions are met.

[0045] The wire 35 connecting the electrodes 30, 40 facilitates the creation of the arc compared with a wireless version of the tool 1, while avoiding the need to change it after each shot. Its composition in a non-conductive plastic material makes it resistant to voltage and electrical discharge, particularly shock waves. The wire 35 allows the tool 1 to extend its operating range in terms of pressure and temperature. The use of a spring 60 to secure the wire 35 also maintains the tension of the wire 35, ensures that the wire 35 is held in position and improves the resistance of the wire 35 to the shock wave by better absorbing the energy.

Claims

CLAIMS1. 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 disposed facing each other, said tool being configured to apply a voltage between said anode and said cathode in order to produce an electrical discharge, said tool being characterized in that it comprises a wire consisting of a plastic material connecting the free end of the anode to the free end of the cathode.

2. The tool according to claim 1, wherein the wire consists of a single strand.

3. The tool according to claim 1, wherein the wire comprises several strands.

4. The tool according to the preceding claim, wherein the strands are braided.

5. The tool according to any one of the preceding claims, wherein the wire is made of nylon.

6. The tool according to any one of the preceding claims, wherein the diameter of the wire is between 0.5 and 1.3 mm.

7. The tool according to any one of the preceding claims, wherein 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.

8. The tool according to the preceding claim, wherein the wire is secured to the flat face of the cathode.

9. The tool according to claim 7, wherein the wire enters a channel formed in the cathode and emerges at an external side face of the cathode to be secured, preferably, to said external side face , or emerges at the opposite end of the cathode .

10. The tool according to the preceding claim, wherein at least one of the ends of the wire is secured to at least one spring .

Images