Electric cable for an electric or electronic detonator

Abstract

The invention relates to an electric cable (10) for an electric or electronic detonator, comprising at least one electrical conductor (11, 12). The electric cable (10) is coated with a thermoplastic polyester resin (13). Also disclosed is the use of said cable, in particular for connecting an electronic or electric module of an electronic or electric detonator used in mines or quarries.

Description

[0001] Electric or electronic detonator electrical cable

[0002] TECHNICAL FIELD OF THE INVENTION

[0003]

[0001] The present invention relates to an electric cable for an electric or electronic detonator.

[0004]

[0002] It also relates to an electric or electronic detonator comprising such an electric cable.

[0005] STATE OF THE ART

[0006]

[0003] Electric or electronic detonators are commonly used in civilian applications, such as in mines and quarries.

[0007]

[0004] Electrical cables for wired electric or electronic detonators are designed for environments where they are subjected to intense mechanical stress. Their integrity is crucial because they are essential for communication with electric or electronic detonators and the reliability of firing.

[0008]

[0005] Typically, an electrical cable for an electrical or electronic detonator comprises one or two electrical conductors intended for unidirectional or bidirectional data exchanges, for programming and / or firing the electrical or electronic detonator.

[0009]

[0006] Electrical cables can be damaged, for example cut or abraded, by the walls of blast holes, which can damage the insulating coating of the electrical cables and expose the electrical conductors, resulting in current leaks.

[0007] In mining and quarrying applications, collapses cause additional mechanical stresses on electrical cables, which can affect their operation.

[0010]

[0008] In order to have electrical cables resistant to the mechanical stresses encountered, it is known to use as electrical insulation, around the electrical conductors, a coating of Polyethylene (PE) and Polypropylene (PP).

[0011]

[0009] Advanced solutions also consist of using a double-layer protective coating: an inner layer, in contact with the electrical conductors, made of polypropylene (PP) and an outer layer of polyvinyl chloride (PVC), offering better performance in extreme conditions.

[0012]

[0010] However, such a two-layer coating, although efficient, is three times heavier (around 19 kg / km of electric cable) than a single-layer coating. Electric cables are thus heavier and more expensive to manufacture and transport than electric cables with a single-layer insulating coating. DISCLOSURE OF THE INVENTION

[0013]

[0011] The present invention aims to remedy all or part of the drawbacks of the state of the art cited above.

[0014]

[0012] To this end, the invention relates to an electrical cable for an electrical or electronic detonator, comprising at least one electrical conductor.

[0015]

[0013] According to the invention, the electric cable is coated with a thermoplastic polyester resin.

[0016]

[0014] The Applicant has found that this polyester material provides advantageous mechanical characteristics and good resistance to external aggressions when using the electric or electronic detonator.

[0017]

[0015] The polyester thus provides sufficient protection for the electric cable throughout the duration of use of the electric or electronic detonator, from its manufacture, transport, installation on site and firing operation.

[0018]

[0016] Advantageously, the thermoplastic polyester resin is an extrudable resin.

[0019]

[0017] The coating of an insulator around the electrical conductor(s) of the electrical cable can thus be carried out by extrusion.

[0020]

[0018] The electric cable can thus be coated with an insulating layer by simply passing it through an extrusion die, in which the molten polyester covers the electrical conductor(s).

[0021]

[0019] In practice, said at least one electrical conductor is embedded in the thermoplastic polyester resin.

[0022]

[0020] In a preferred embodiment, the electrical cable comprises a single layer of thermoplastic polyester resin.

[0023]

[0021] For example, the single layer of polyester thermoplastic resin has a thickness greater than 0.40 mm around said at least one electrical conductor.

[0024]

[0022] In a preferred embodiment, the electrical cable comprises two electrical conductors embedded in the thermoplastic polyester resin.

[0025]

[0023] Advantageously, the thermoplastic polyester resin is bio-sourced at least 40% by weight of material, and preferably at least 50% by weight of material.

[0026]

[0024] For example, the thermoplastic polyester resin comprises a bio-sourced carbon according to the standard ASTM D 6866: 2012-01.

[0027]

[0025] In an advantageous embodiment, the thermoplastic polyester resin is biodegradable.

[0028]

[0026] The biodegradability of the insulating coating of electric cables is a notable advantage in the field of pyrotechnics, the electric cable being a consumable. After the firing of the wired electric or electronic detonators, the electric cables remain in the field. The use of a biodegradable polyester thermoplastic resin makes it possible to limit environmental pollution after firing.

[0029]

[0027] Preferably, the thermoplastic polyester resin is compostable.

[0030]

[0028] Advantageously, the thermoplastic polyester resin used is industrially compostable according to standard NF EN 13432:2000.

[0031]

[0029] Production waste can also be recycled in production.

[0032]

[0030] According to a second aspect, the present invention relates to an electric or electronic detonator, comprising a housing housing at least one electric or electronic module and a sealing cap closing said housing.

[0033]

[0031] According to the invention, the electric or electronic detonator comprises an electric cable as described previously, connected to said at least one electric or electronic module.

[0034]

[0032] The electric or electronic detonator has characteristics and advantages similar to those described previously in relation to the electric cable according to the invention.

[0035]

[0033] In practice, the sealing cap is formed, preferably by overmolding, around the electric cable.

[0036]

[0034] Preferably, in order to ensure good sealing against water and / or chemical emulsions, as well as reliable holding of the electric cable in place, the housing is crimped onto the sealing cap.

[0037] BRIEF DESCRIPTION OF THE FIGURES

[0038]

[0035] Other features and advantages of the invention will emerge from the non-limiting description which follows.

[0039]

[0036] In the attached drawings, given by way of non-limiting example: [Fig. 1] is a cross-sectional view of the electric cable according to one embodiment of the invention; and [Fig. 2] is a schematic view illustrating an electronic detonator according to one embodiment of the invention.

[0040] DETAILED DESCRIPTION OF THE INVENTION

[0041]

[0037] We will first describe with reference to FIG. 1 an electric cable according to one embodiment of the invention.

[0042]

[0038] This electrical cable is intended to equip an electrical or electronic detonator known from the state of the art. An electronic detonator of the type of that of the present invention is for example described in document FR 3 031 867.

[0039] Such an electrical cable comprises one or more electrical conductors.

[0043]

[0040] As illustrated in FIG. 1, the electrical cable 10 comprises in this embodiment two electrical conductors 11, 12.

[0044]

[0041] The electrical conductors 11, 12 are typically formed respectively from a copper or copper-plated steel wire chosen for its electrically conductive properties.

[0045]

[0042] Other materials such as galvanized steel or copper-plated iron could be used to form these electrical conductors 11, 12.

[0046]

[0043] These electrical conductors 11, 12 have a circular section, with a diameter between 0.3 and 0.6 mm, and preferably equal to 0.5 mm.

[0047]

[0044] The length of the electrical conductors 11, 12 depends on the intended application and can typically be between 4m and 100m.

[0048]

[0045] In practice, the electric cable 10 may be in the form of a skein, with a length of between 4 and 10 m, or in the form of a coil, with a length of between 6 and 10 m.

[0049]

[0046] The electric cable 10 here comprising the two electric conductors 11, 12 is coated with a thermoplastic polyester resin 13.

[0050]

[0047] The thermoplastic polyester resin 13 thus forms a protective layer around the two electrical conductors 11, 12 so that the cross-section of the electrical cable 10 has an oblong shape.

[0051]

[0048] By way of non-limiting example, the width L of the electric cable 10 in its cross-section is equal to 2.80 mm, and between 2.65 and 2.95 mm depending on the manufacturing tolerances.

[0052]

[0049] Similarly, by way of non-limiting example, the height H of the electric cable 10 in its cross-section is equal to 1.50 mm, and between 1.45 and 1.55 mm depending on the manufacturing tolerances.

[0053]

[0050] The two electrical conductors 11, 12 are embedded in the thermoplastic polyester resin 13.

[0054]

[0051] The center distance e between the two electrical conductors 11, 12 is between 1.2 and 1.4 mm, and has a nominal value of 1.3 mm.

[0055]

[0052] Of course, these values ​​are illustrative of an embodiment and are given with the usual tolerance margins for this type of manufacturing.

[0056]

[0053] The electrical cable 10 comprises a single layer of thermoplastic polyester resin 13.

[0057]

[0054] The single layer of polyester thermoplastic resin 13 has a thickness greater than 0.40 mm around each of the two electrical conductors 11, 13.

[0058]

[0055] This thickness of thermoplastic polyester resin is measured between the conductor and the outer surface of the electrical cable 10.

[0056] This thickness of at least 0.40 mm makes it possible to provide mechanical and electrical protection around the two electrical conductors 11, 12, and in particular sufficient resistance to abrasion.

[0059]

[0057] The thermoplastic polyester resin used is preferably extrudable.

[0060]

[0058] The thermoplastic polyester resin has a melting temperature of the order of 115°C and is extruded at 150°C at an extrusion die.

[0061]

[0059] The conductive wires 11, 12 are continuously introduced into the extrusion die and coated during their passage with the thermoplastic polyester resin. The latter is melted and flows around the electrical conductors 11, 12 to form, after cooling, an electrical cable 10 as described previously.

[0062]

[0060] The thickness of the layer of thermoplastic polyester resin 13 results from a compromise between the desired mechanical resistance properties and the weight of the electric cable.

[0063]

[0061] The mechanical resistance properties for an electric cable 10 intended to equip an electric detonator for use in mines and quarries are mainly resistance to cutting and abrasion, as well as resistance to traction and cracking.

[0064]

[0062] The Applicant compared the mechanical properties obtained for an electric cable 10 as described previously and those usually obtained for an electric cable called a two-layer cable.

[0065]

[0063] Such a two-layer cable is formed from the same copper-clad steel electrical conductors as those described above. They are coated with a double layer formed of an inner PP layer and a protective PVC oversheath.

[0066]

[0064] Abrasion resistance (test according to standard EN 13763-4)

[0067]

[0065] The test implemented according to standard EN 13763-4 consists of measuring the time

[0068] (in seconds) before reaching the electrical conductors by attacking the electrical cable and its insulating coating with an abrasive metal rotor. This measures the time required before reaching the exposed conductors.

[0069]

[0066] The measured time is greater than 200s both for the electrical cable 10 described previously and for a two-layer cable.

[0070]

[0067] The electrical cable 10 described above makes it possible to provide abrasion resistance of the same type as that provided by a two-layer cable, while limiting the weight of the electrical cable.

[0071]

[0068] Thus, while a two-layer cable typically has a linear weight of the order of 19 kg / km, the electrical cable described above has a linear weight of the order of 7.3 kg / km.

[0069] Cutting resistance (test according to standard EN13763-5)

[0072]

[0070] The test implemented according to standard EN 13763-5 consists of measuring the maximum force necessary to be exerted on the electric cable to obtain its cut.

[0073]

[0071] The cut-off value of the two-layer cable is on average 9.5 daN (between 9 and 10 daN).

[0074]

[0072] The cut-off value of the electric cable 10 is further improved and on average 15.6 daN (between 15 and 16 daN).

[0075]

[0073] The electrical cable 10 described above thus provides very good resistance to cutting when used in mines and quarries, and resists natural aggressions (stones, rocks, pebbles, etc.). This property is important in this type of application with the risks of cutting when installing the electronic detonators connected to these electrical cables.

[0076]

[0074] Preferably, the thermoplastic polyester resin 13 is bio-sourced at least 40% by weight of material, and preferably at least 50% by weight of material.

[0077]

[0075] According to the ASTM D 6866:2012-01 standard, the rate of biosourced carbons in the composition of the thermoplastic polyester resin can be substantially equal to 50%.

[0078]

[0076] The thermoplastic polyester resin is also preferably biodegradable.

[0079]

[0077] Since the electric cable is a consumable in the application, the biodegradability of its polyester thermoplastic resin coating allows the electric cable to naturally degrade over time in a mining environment. Thus, only the metallic electrical conductors remain after the complete disappearance of the polyester thermoplastic resin.

[0080]

[0078] Thanks to the biodegradability of the thermoplastic polyester resin, the electrical cable described above is well suited to single-use uses such as mining or quarrying applications, in which the electrical cable is a consumable, intended to remain in nature after use or sorted during the recovery of rubble.

[0081]

[0079] Preferably, the thermoplastic polyester resin is compostable, according to standard NF EN 13432:2000. Thus, production waste can be recycled in production.

[0082]

[0080] An example of the use of such an electric cable 10 to equip an electronic detonator will be described with reference to FIG. 2.

[0083]

[0081] Of course, this example of application is not limiting, and the electric cable 10 could also equip an electric detonator.

[0084]

[0082] As clearly illustrated in Figure 2, the electronic detonator 30 comprises a housing formed here from a metal case 31 containing an explosive compound 32.

[0083] In this embodiment, the metal case 31 has a tubular shape having a closed end 33 and an open end 34. The metal case 31 may be cylindrical or frustoconical. The metal case 31 is for example made of aluminum or copper.

[0085]

[0084] The explosive compound 32 is conventionally a primary explosive, for example compacted powder, placed inside the metal case 31 at the closed end 33.

[0086]

[0085] An electronic module 20 formed of a printed circuit is inserted inside the metal case 31 forming the housing of the electronic detonator 30.

[0087]

[0086] The printed circuit is intended to support various electronic components for the usual operation of an electronic detonator and will not be described in further detail here.

[0088]

[0087] The electronic module 20 is associated with an electronically controlled primer 25 allowing the ignition of the primary explosive formed from the explosive compound 32.

[0089]

[0088] An electrical cable 10 as described with reference to FIG. 1 is connected to the electronic module 20. Thus, the electrical power supply of the electronic module 20 is provided by the electrical cable 10 and the two electrical conductors 11, 12 which make it possible to electrically power the printed circuit and to connect the electronic module to an external control device (not shown). The electrical conductive wires 11, 12 are electrically connected to the printed circuit of the electronic module 20.

[0090]

[0089] The housing formed from the metal case 31 is further closed on the side of the open end 34 by a sealing plug 38. In practice, the sealing plug 38 is formed, preferably by overmolding, around the electric cable 10. The overmolding of the sealing plug 38 can be carried out by injection of a plastic material compatible with the material of the cable.

[0091]

[0090] The sealing cap 38 can thus be made of plastic and overmolded onto the electric cable 10 to ensure perfect sealing and reliable holding in place of the electric cable 10 and the connection to the electronic module 20.

[0092]

[0091] The metal case 31 is itself crimped onto the sealing cap 38 in order to ensure perfect sealing of the electronic detonator 30.

[0093]

[0092] Such an electric cable thus makes it possible to reduce plastic consumption in production, while retaining mechanical properties identical to, or even superior to, those obtained by two-layer cables.

[0094]

[0093] Of course, the examples of embodiment given above are in no way limiting, in particular with regard to the examples of dimensions or materials.

Claims

Claims 1. Electrical cable for an electrical or electronic detonator, comprising at least one electrical conductor (11, 12), characterized in that said electrical cable (10) is coated with a thermoplastic polyester resin (13).

2. Electric cable according to claim 1, characterized in that the thermoplastic polyester resin (13) is an extrudable resin.

3. Electric cable according to one of claims 1 or 2, characterized in that said at least one electrical conductor (11, 12) is embedded in the thermoplastic polyester resin (13).

4. Electric cable according to one of claims 1 to 3, characterized in that it comprises a single layer of thermoplastic polyester resin (13).

5. Electric cable according to claim 4, characterized in that the single layer of polyester thermoplastic resin (13) has a thickness greater than 0.40 mm around said at least one electrical conductor (11, 12).

6. Electric cable according to one of claims 1 to 5, characterized in that the electric cable (10) comprises two electrical conductors (11, 12) embedded in the thermoplastic polyester resin (13).

7. Electric cable according to one of claims 1 to 6, characterized in that the thermoplastic polyester resin (13) is bio-sourced at least 40% by weight of material, and preferably at least 50% by weight of material.

8. Electric cable according to one of claims 1 to 7, characterized in that the thermoplastic polyester resin (13) is biodegradable.

9. Electric cable according to claim 8, characterized in that the thermoplastic polyester resin (13) is compostable.

10. Electric or electronic detonator, comprising a housing (31) housing at least one electric or electronic module (20) and a sealing plug (38) closing said housing (31), characterized in that it comprises an electric cable (10) according to one of claims 1 to 9, connected to said at least one electric or electronic module (20).

11. Electric or electronic detonator according to claim 10, characterized in that the sealing cap (38) is formed, preferably by overmolding, around said electric cable (10).

12. Electric or electronic detonator according to claim 11, characterized in that the housing (31) is crimped onto the sealing cap (38).

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