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 for manufacturing such a plug technical field

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

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

[0003] When a worker installs plugs on a construction site, particularly to delimit areas of the site, it can happen that during insertion, one of these plugs touches a live electrical cable and thus causes the worker to be electrocuted. To guarantee the safety of workers installing 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 requires the provision of an insulating sleeve to form a handle, enabling the worker to hold the plug during insertion. By holding the plug with this insulating sleeve, the worker will be at least partially insulated from the metal plug body.

[0005] While this solution offers protection to the worker against relatively high voltages, with the electrical insulation mentioned being 1000 Volts, it is not suitable for all situations. Indeed, with the undergrounding of low-voltage lines and especially medium-voltage lines (between 15 and 30 kV), the voltages in the electrical cables far exceed the 1000 Volts for which document FR 2 992 990 B1 indicates it offers protection. Description 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] For this purpose the invention relates to a plug intended to be driven into the ground comprising a metallic body and a sleeve made of an electrically insulating material and surrounding a first end of the metallic body, the plug being characterized in that the metallic 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 steel of the plug body, the body of The plug exhibits a higher electrical resistance than a conventional plug body, such as that used in FR 2 992 990 B1. Consequently, for an identical sleeve, it provides greater protection than the plug described in FR 2 992 990 Bl. A worker handling a plug according to the invention is exposed to a reduced risk of electrocution compared to that encountered with the plug in FR 2 992 990 Bl, since the electrical insulation offered is superior. It should be noted that, within the scope of the present invention, it is possible to obtain, according to the procedure described later in this document, a dry insulation voltage of 25,000 V.

[0009] The insulating material can 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 offer high electrical insulation and thus allow optimized protection for workers who have to handle 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 conferred by the plug against the risks of electrocution is particularly optimized.

[0014] The first end of the body may have a surface structure, 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 part of the first end of the body.

[0015] Such a surface structure 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 should be noted, in particular, that such a structure, when combined with a sleeve made by vulcanizing rubber onto the plug body, allows for a particularly strong hold of the sleeve on the plug body. Thus, with such a configuration, the risk of the sleeve slipping along the plug body is 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 can extend in a substantially longitudinal direction and have a central portion in this substantially longitudinal direction delimited by a structuring of an external surface of the sleeve, this surface structuring preferentially taking the form of two circumferential ribs.

[0018] Such ribs allow the worker having to hold the plug during its insertion 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 area of ​​an extremity part of the first end.

[0020] Such an extra thickness makes it possible to offer protection against impalement, in case of a fall near the plug and for the hands of the worker during the striking of the plug for its penetration into the ground.

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

[0022] The invention further relates to a method for manufacturing a plug intended to be embedded in the ground, comprising the following steps: - supply of a metal body for the plug, - supply of a sleeve made of an electrically insulating material and surrounding the body on one end of said body. During the supply stage, the metallic body comprises a steel having a carbon content of less than or equal to 0.1% by mass, preferably 0.07% by mass, or even 0.06% by mass.

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

[0024] During the sleeve supply stage, the insulating material being a natural or synthetic rubber, a sub-stage of molding and vulcanizing 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 upon reading the description of exemplary embodiments, given purely by way of illustration and in no way limiting, with reference to the accompanying 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 shown in [Fig.1].

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

[0029] [Fig.3B] illustrates a side view of the plug body shown 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 shown on a uniform scale, in order to make the figures more legible.

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

[0033] Detailed description of particular embodiments

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

[0035] It should be noted that while the stake 1 according to the present embodiment is a paver stake, it may be of another type, such as a lantern stake, without departing from the scope of the invention. It should also be noted that by embedding the stake in the ground, it is understood that a portion of the stake is embedded in the ground so that it has a fixed position relative to the worksite and can mark this position or serve as a support for a tape delimiting an area of ​​the worksite. This is generally achieved by embedding a portion representing 10 to 30 cm of the total length of the stake 1.

[0036] As shown in Figures 1 and 2, sheet 1 according to the invention comprises: - a body 10 of a 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. More specifically, the plug body comprises a steel. According to a particular feature of the invention, this steel has a carbon content of 0.1% by mass or less, preferably 0.07% by mass, or even 0.06% by mass. It should be noted that, according to one embodiment of the invention, the carbon content of the steel is 0.053% by mass or less.

[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 content between the first and second ends.

[0039] In the context of this embodiment, in accordance with the dimensions expected for a paver slab, 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 retention of the sleeve 15.

[0041] As shown in Figures 3A and 3B, the first end may include a surface structure. Such a surface structure 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 Figures 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 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 can 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 can be arranged along the first end in a staggered pattern.

[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, here greater than 70%, or even 80% or 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 in opposite directions. Of course, such longitudinal grooves may extend over different lengths of the first end without departing from the scope of the invention.

[0045] It can also be noted, as shown in [Fig.2], that the first end 11 can include a portion of reduced diameter for also good retention of the sleeve 15. It should 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 between 15 and 30% of the length of the body 10, or even between 20 and 25% and can, 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 whose internal surface 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 embodiment 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 ethylene and propylene, with a non-conjugated diene content.

[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, for example, be equal to 4 mm. Thus, in the context of the present embodiment, the sleeve 15 may have, over most of its length, an outside diameter greater than 20 mm, for example, being equal to 22 mm.

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

[0050] The extremity part 111 extending beyond the sleeve 15 or covered by a thin portion of sleeve 15, the sleeve may have an excess thickness, such as a flare 17, on an area proximal to said extremity part 111. It should 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 added thickness, or tip, thus provides protection for the hand of the worker holding the plug 1 by the sleeve 15 during the striking of the plug with a tool, such as a sledgehammer, to drive it into the ground. This same added thickness also acts as an anti-impalement device so as to limit the risk of injury, particularly impalement, for a worker falling in the immediate vicinity of the plug 1.

[0052] To provide a good grip for the worker handling the plug, the sleeve 15 has a central portion 16 along this substantially longitudinal direction, delimited by a structure on the outer surface of the sleeve. This central portion 16 of the sleeve 15 acts as a handle for the plug 1, allowing it to be gripped during handling and, in particular, insertion. As shown in Figures 1 and 2, the outer surface structure 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 1 paver plugs 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 paving slabs conform to 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 consisting of EPDM rubber with a thickness of 4 mm, extending along the first end and having a central portion 16 of 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] To perform these tests, the central portion 16 of each plug 1 was covered with aluminum foil to form a first electrical contact representing the worker's hand. This first electrical contact was grounded. Alternating voltage was applied through the second end 12 of the body 10 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 of 68.9%.

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

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

[0059] [Table 1] Voltage applied (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 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 case of inclement weather, similar tests were also carried out on plugs that had been previously immersed for 24 hours. These tests yielded substantially identical results for alternating voltages of 20 kV.

Claims

Demands

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

2. Sheet (1) according to claim 1, wherein 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 wherein the sleeve has a thickness greater than or equal to 3 mm, and preferably greater than or equal to 4 mm.

5. Sheet (1) according to any one of claims 1 to 4, wherein the first end (11) of the body (10) has a surface structure, 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. Sheet (1) according to any one of claims 1 to 5, wherein 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. Sheet (1) according to any one of claims 1 to 6, wherein the sleeve (15) has an overthickness, such as a flare, on a circumferential area (17) proximal to an extremal part (111) of the first end (11).

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

9. A method for manufacturing a plug (1) intended to be driven into the ground, comprising the following steps: - supplying a metallic body (10) of the plug (1), - supplying 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 process being characterized in that, during the supply stage, 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. Method of manufacturing a plug according to claim 9, wherein during the step of supplying the sleeve (15), the insulating material being a natural or synthetic rubber, a substep of molding and vulcanizing a prepolymer / latex on the body (10) of the plug (1) is provided.

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