Electrically insulated plug and method for manufacturing such a plug

Abstract

The invention relates to a ground plug (1) comprising a metallic body (10) and a sleeve (15) made of electrically insulating material and surrounding a first end (11) of the metallic body. The metallic body (10) comprises steel having a carbon content of 0.1% or less by mass, preferably 0.07% or even 0.06% by mass. The invention also relates to a method for manufacturing such a plug (1). (See Figure 2 for abbreviations.)

Description

Title of the invention: Electrically insulated plug and method of manufacturing such a plug Technical field

[0001] The invention relates to the field of pins intended to be driven into the ground and more particularly paver pins and lantern holders.

[0002] The invention thus relates more specifically to an electrically insulated plug and a method of manufacturing such a plug. State of the prior art

[0003] When a worker installs plugs on a construction site, in particular to delimit areas of this construction site, it may happen that during its insertion one of these plugs touches a live electrical cable and therefore causes the electrocution of the worker. In order to guarantee the safety of the workers involved in the installation of these plugs, it is therefore important to provide electrical insulation for the plug.

[0004] In order to limit these risks of electrocution, it is known from the document FR 2 992 990 B1 to provide a sleeve of insulating material in order to form a handle to allow the worker to hold the plug while it is being inserted. In this way, by holding the plug by this sleeve of insulating material, the worker will be at least partly insulated from the metal plug body.

[0005] While this solution offers protection to the worker for relatively high voltages, the electrical insulation mentioned being 1000 Volts, it is not suitable for all situations. Indeed, with the burial of low voltage lines and especially that of medium voltages (between 15 and 30 KV), the voltages in the electric cables greatly exceed the voltage of 1000 Volts for which document FR 2 992 990 B1 indicates that it offers protection. Statement of the invention

[0006] The invention aims to remedy the above drawback and thus aims to provide electrical insulation superior to that proposed by the prior art and in particular by document FR 2 992 990 Bl.

[0007] To this end, the invention relates to a plug intended to be driven into the ground comprising a metal body and a sleeve made of an electrically insulating material and surrounding a first end of the metal body, the plug being characterized in that the metal body comprises a steel whose carbon content is less than or equal to 0.1% by mass, preferably 0.07% by mass, or even 0.06% by mass.

[0008] With such a reduced carbon content of the plug body steel, the plug body plug has a higher electrical resistance than a conventional plug body, such as that implemented in FR 2 992 990 B1. This results, for an identical sleeve, in a protection superior to that offered by the plug described in document FR 2 992 990 Bl. A worker handling a plug according to the invention presents a reduced risk of electrocution compared to that incurred with the plug of document FR 2 992 990 Bl, since the electrical insulation offered is superior. It will be noted that within the framework of the present invention, it is possible to obtain, according to the protocol indicated in the remainder of this document, a dry insulation voltage of 25,000V.

[0009] The insulating material may be a natural or synthetic rubber preferably vulcanized on the first end of the metal body.

[0010] The insulating material may be a synthetic rubber of the EPDM type.

[0011] Such insulating materials provide high electrical insulation and thus allow optimized protection for workers handling the plug.

[0012] The sleeve may have a thickness greater than or equal to 3 mm, and preferably greater than or equal to 4 mm.

[0013] With such a thickness, the protection provided by the plug against the risk of electrocution is particularly optimized.

[0014] The first end of the body may have a surface structuring, preferably in the form of at least one groove extending over at least a portion of the circumference of the body or at least one groove extending longitudinally along at least a portion of the first end of the body.

[0015] Such a surface structuring makes it possible to provide good support for the sleeve, particularly in the case where the sleeve is molded onto the plug body.

[0016] It will be noted, in particular, that such a structuring, when combined with a sleeve made by vulcanizing a rubber on the plug body, allows a particularly strong hold of the sleeve on the plug body. Thus, with such a configuration, the risks of the sleeve sliding along the plug body are limited, or even eliminated, which could be detrimental to the worker safety functions provided by the plug according to the present invention.

[0017] The sleeve may extend in a substantially longitudinal direction and have a central portion in this substantially longitudinal direction delimited by a structuring of an outer surface of the sleeve, this surface structuring preferably taking the form of two circumferential ribs.

[0018] Such ribs allow the worker who has to hold the plug while inserting it to easily identify the area by which he must hold the plug in order to limit the risks of electrocution when inserting the plug.

[0019] The sleeve may have an excess thickness, such as a flare, on a proximal circumferential zone of an extreme portion of the first end.

[0020] Such extra thickness provides anti-impalement protection in the event of a fall near the plug and for the worker's hands when striking the plug to drive it into the ground.

[0021] The plug can be a paver plug or a lantern plug.

[0022] The invention further relates to a method of manufacturing a plug intended to be sunk into the ground comprising the following steps: - provision of a metal body of the plug, - providing a sleeve made of an electrically insulating material and surrounding the body on a first end of said body. During the providing step, the metal body comprises a steel whose carbon content is less than or equal to 0.1% by mass, preferably 0.07% by mass, or even 0.06% by mass.

[0023] Such a method allows the manufacture of a plug according to the invention and therefore to benefit from the advantages associated therewith.

[0024] During the step of providing the sleeve, the insulating material being a natural or synthetic rubber, a sub-step of molding and vulcanization of a prepolymer / latex on the body of the plug may be provided. Brief description of the drawings

[0025] The present invention will be better understood on reading the description of exemplary embodiments, given purely for informational purposes and in no way limiting, with reference to the appended drawings in which:

[0026] [Fig-1] illustrates a front view of a plug according to the invention,

[0027] [Fig.2] illustrates a longitudinal sectional view of the figure illustrated in [Fig.l].

[0028] [Fig.3A] illustrates a front view of a plug body of the plug illustrated in Figures 1 and 2.

[0029] [Fig.3B] illustrates a side view of the plug body illustrated in Figures 1 to 3A.

[0030] Identical, similar or equivalent parts of the different figures bear the same numerical references so as to facilitate the transition from one figure to another.

[0031] The different parts represented in the figures are not necessarily on a uniform scale, in order to make the figures more readable.

[0032] The different possibilities (variants and embodiments) must be understood as not being mutually exclusive and can be combined with each other.

[0033] Detailed description of particular embodiments

[0034] [Fig.l] illustrates a paver plug 1 according to the invention intended to be driven into the ground and which has the particularity, in accordance with the invention, of being electrically insulated.

[0035] It will be noted that if the plug 1 according to the present embodiment is a paver plug, it can be of another type, such as a lantern holder plug, without departing from the scope of the invention. It will also be noted that by driving the plug into the ground, it is understood to mean driving a part of the plug into the ground so that the latter is a fixed location with respect to the construction site and can mark this location or serve as a support for a ribbon delimiting an area of ​​the construction site. This is generally obtained by a recess of a part representing 10 to 30 cm of the total length of the plug 1.

[0036] As shown in Figures 1 and 2, the plug 1 according to the invention comprises: - a body 10 of plug 1 having a first end 11 and a second end 12, - a sleeve 15 comprising an electrically insulating material and surrounding the first end 11 of the body 10.

[0037] The plug body 1 is in the form of a metal rod tapered at its second end. The plug body more specifically comprises a steel. According to a feature of the invention, this steel has a carbon content less than or equal to 0.1% by mass, preferably 0.07% by mass, or even 0.06% by mass. It will be noted that according to an exemplary embodiment of the invention, the carbon content of the steel is less than or equal to 0.053% by mass.

[0038] Of course, if according to one possibility of the invention, the body 10 is made of steel having such a carbon content, other conformations are conceivable without departing from the scope of the invention, in particular with a body 10 having distinct carbon contents between the first and second ends.

[0039] In the context of the present embodiment, in accordance with the dimensions expected for a paver plug, the body 10 may have a length of 1 m and a diameter of 14 mm.

[0040] The first end 11 of the body 10 is preferably shaped to allow good support of the sleeve 15.

[0041] As shown in Figures 3A and 3B, the first end may include a surface patterning. Such a surface patterning may include one or more grooves extending over at least a portion of the circumference of the body.

[0042] According to this possibility, at least one groove can extend over at least a portion of the circumference of the body 10. It can thus be seen in FIGS. 3A and 3B that such circumferential grooves can extend over a portion of the circumference, for example between 30 and 70% of the perimeter of the body 10, or even between 40 and 60% or even 44 and 48% of this same perimeter. Similarly, as shown in [Fig. 3A], when such circumferential grooves extend over a portion of the circumference, it is conceivable that such grooves extend alternately, along the first end 11 on distinct circumference portions. As shown in [Fig.3A], these distinct portions may be a first lateral side of the first end 11 and a second lateral side of the first end 11 opposite the first lateral side of the first end 11.

[0043] Such circumferential grooves may be arranged along the first end in a staggered manner.

[0044] Similarly and as illustrated in [Fig.3B], at least one groove may extend longitudinally along at least a portion of the first end 11 of the body 10, for example this portion may represent a majority portion, here greater than 70%, or even 80% or even 90% of the length of the first end 11. It may be noted that in the present embodiment, the first end comprises two grooves extending longitudinally opposite one another. Of course, such longitudinal grooves may extend over different lengths of the first end without departing from the scope of the invention.

[0045] It may also be noted, as shown in [Fig. 2], that the first end 11 may comprise a portion of reduced diameter for also good support of the sleeve 15. It will be noted that in the context of the present embodiment the first end 11 of the body 10, which is the part of the body 10 surrounded by the sleeve, extends over a length of the body comprised between 15 and 30% of the length of the body 10, or even between 20 and 25% and may, for example, represent 21% of the length of the body 10.

[0046] The sleeve 15 extends longitudinally along the body 10, surrounding the first end 11 of the body 10. The sleeve 15 may have a substantially tubular shape, the internal surface of which matches that of the external surface of the first end 11.

[0047] The sleeve 15 comprises an electrically insulating material. This insulating material may be a natural or synthetic rubber. According to a preferred possibility of the invention, the insulating material is a synthetic rubber of the EPDM type. It is recalled, in accordance with the understanding of those skilled in the art, that EPDM is the acronym for “ethylene-propylene-diene monomer” and that a synthetic rubber of the EPDM type is an amorphous terpolymer obtained by copolymerizing in ethylene and propylene, with a level of non-conjugated diene.

[0048] The sleeve 15 has a thickness greater than or equal to 3 mm, and preferably greater than or equal to 4 mm. This thickness may be, for example, equal to 4 mm. Thus, in the context of the present embodiment, the sleeve 15 may have, over its major part, an external diameter greater than 20 mm, being, for example, equal to 22 mm.

[0049] As shown in [Fig.2], in order to allow the plug 1 to be struck on a part of the body 10, an end part 111 of the first end 11 may not be re covered by the sleeve 15 or be covered with a portion of reduced thickness of the sleeve 15.

[0050] The end portion 111 extending beyond the sleeve 15 or covered with a thin portion of sleeve 15, the sleeve may have an excess thickness, such as a flare 17, on a zone proximal to said end portion 111. It will be noted that in the context of the present embodiment, the flare 17 has an external diameter greater than 40 mm, or even 45 mm and may, for example, be equal to 46.3 mm.

[0051] Such an extra thickness, or tip, thus provides protection for the hand of the worker holding the plug 1 by the sleeve 15 while striking the plug with a tool, such as a sledgehammer, to drive it into the ground. This same extra thickness also acts as an anti-impalement device so as to limit the risks of injury, in particular by impalement, for a worker falling in the direct vicinity of the plug 1.

[0052] In order to provide a good grip for the worker having to handle the plug, the sleeve 15 has a central portion 16 in this substantially longitudinal direction delimited by a structuring of an outer surface of the sleeve. This central portion 16 of the sleeve 15 acts as a handle for the plug 1 in order to allow it to be grasped during its handling and in particular its insertion. As shown in Figures 1 and 2, the structuring of the outer surface of the sleeve 15 can take the form of two circumferential ribs 161, 162.

[0053] It will be noted that such a central portion 16 allows the worker to know that by holding the plug by the sleeve 15 on the central portion 16 delimited by the circumferential ribs 161, 162, he is protected against electrocution in the event that the second end 12 of the body 10 touches a live cable when the plug 1 is driven into the ground. Insulation test

[0054] In order to demonstrate the advantage provided by the present invention, two paver plugs 1 according to the invention were subjected to electrical insulation tests at alternating voltages of 20 kV and 25 kV.

[0055] In the context of these tests, the paver sheets 1 comply with the present embodiment, namely: - a body 10 of plug 1 made of steel with a carbon content of less than 0.053% by mass, the body 10 having a first end of 21 cm, - a sleeve comprising an insulating material made of EPDM rubber 4 mm thick, extending along the first end and having a central portion 16 with a length of approximately 10 cm and lateral portions 18A, 18B extending on either side of the central portion over a length of approximately 5 cm.

[0056] In order to carry out these tests, the central portion 16 of each plug 1 was coated with an aluminum foil in order to form a first electrical contact representing the worker's hand. This first electrical contact was maintained at ground. The alternating voltage was applied by the second end 12 of the body 10 in order to represent the contact of the plug 1 with a medium voltage cable. The environmental conditions during these tests were 20.7°C with a relative humidity level of 68.9%.

[0057] These tests were therefore carried out twice by applying to the second end 12 the alternating voltage of frequency 50 Hz and a voltage of 20 KV for 60s. During this period of time, a leakage current of less than 2 mA was measured and no perforation of the sleeve or flashover was observed. This result was confirmed during these same tests for an alternating voltage of frequency 50 Hz and a voltage of 25 KV for 60s.

[0058] These results are summarized in the following table:

[0059] [Tab. 1] Data sheet Applied voltage (kV) Duration (s) Leakage current (mA) Results 1 20 60 1.00 Satisfactory 2 20 60 1.02 Satisfactory 1 25 60 1.29 Satisfactory 2 25 60 1.32 Satisfactory

[0060] It can thus be seen that in relatively humid conditions (relative humidity level of 68.2%), the plugs 1 according to the invention offer good protection for medium voltages (in particular up to 25 kV).

[0061] In order to confirm the protection offered by the plugs 1 according to the invention in the event of bad weather, similar tests were also carried out on plugs which had been previously immersed for 24 hours. These tests made it possible to obtain substantially identical results for alternating voltages of 20 kV.

Claims

Claims

1. Plug (1) intended to be driven into the ground comprising a metal body (10) and a sleeve (15) comprising an electrically insulating material and surrounding a first end (11) of the metal body, the plug (1) being characterized in that the metal body (10) comprises a steel whose carbon content is less than or equal to 0.1% by mass, preferably 0.07% by mass, or even 0.06% by mass.

2. Plug (1) according to claim 1, in which the insulating material is a natural or synthetic rubber preferably vulcanized on the first end (11) of the metal body.

3. Sheet (1) according to claim 2, wherein the insulating material is a synthetic rubber of the EPDM type.

4. Sheet (1) according to any one of claims 1 to 3 in which the sleeve has a thickness greater than or equal to 3 mm, and preferably greater than or equal to 4 mm.

5. Plug (1) according to any one of claims 1 to 4, wherein the first end (11) of the body (10) has a surface structuring, preferably in the form of at least one groove extending over at least a portion of the circumference of the body or at least one groove extending longitudinally along at least a portion of the first end (11) of the body (10).

6. Plug (1) according to any one of claims 1 to 5, in which the sleeve (15) extends in a substantially longitudinal direction and has a central portion (16) in this substantially longitudinal direction delimited by a structuring of an external surface of the sleeve, this surface structuring preferably taking the form of two circumferential ribs (161, 162).

7. Plug (1) according to any one of claims 1 to 6, in which the sleeve (15) has an excess thickness, such as a flare, on a circumferential zone (17) proximal to an end portion (111) of the first end (11).

8. A plug (1) according to any one of claims 1 to 6, wherein the plug is a paver plug or a lantern plug.

9. Method of manufacturing a plug (1) intended to be driven into the ground comprising the following steps: - providing a metal body (10) of the plug (1), - providing a sleeve (15) made of an insulating material electrical and surrounding the body (10) on a first end (11) of said body (10), The manufacturing method being characterized in that during the supply step, the metal body (10) comprises a steel whose carbon content is less than or equal to 0.1% by mass, preferably 0.07% by mass, or even 0.06% by mass.

10. A method of manufacturing a plug according to claim 9, wherein during the step of providing the sleeve (15), the insulating material being a natural or synthetic rubber, a sub-step of molding and vulcanizing a prepolymer / latex on the body (10) of the plug (1) is provided.

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