FR2878551A1 - CARRIER ELEMENT RESISTANT TO HIGH LOADS AND METHOD OF MAKING SAME - Google Patents

Abstract

The invention relates to a supporting element, such as a telephone or electric pole, intended to be anchored in the ground and designed to withstand a predetermined maximum deflection and not to exceed a predetermined maximum stress, characterized in that it has a composite structure with an elongated central part (10, 20, 30) made of a resistant material and the height of which corresponds substantially to that of the supporting element, as well as an outer casing (11, 21, 31) constituting a covering for said central part, this coating comprising at least one thermoplastic polymer.

Description

2878551 1

  The present invention relates to a load-bearing member resistant to heavy loads, in particular a telephone or electrical pole.

  In general, a telephone or electrical pole is designed to respect a maximum deflection under a given load and also, not to exceed the maximum permissible stress for the constituent material, in all parts of the pole.

  Thus, there are known wooden poles, the realization of which is relatively economical and which offer good resistance, to the extent that appropriate diameters are used.

  These posts, however, have many disadvantages.

  First, they require, to ensure their behavior over time, a heart treatment using particularly toxic products, such as arsenic.

  Therefore, the destruction of these poles can be operated only under very strict conditions.

  Moreover, these posts are necessarily of a large diameter, of the order of 200 mm, and are therefore particularly visible, once implanted in the environment.

  Finally, the aging of this type of post is random and requires a regular replacement plan. This entails relatively significant costs, because they include not only the cost of the new poles, but also that of the rehabilitation of the supported lines.

  Telephone or electrical poles 25 made of galvanized steel are also known.

  A post of this type is made from a sheet of steel cut, folded, rolled and welded with a generally frustoconical shape and a cross section often polygonal.

  It is of a higher cost, for equivalent mechanical strength, than a post made of wood.

  2878551 2 This is not only due to the manufacturing steps, and in particular to the galvanizing treatment of the sheets, but also to the finishing steps necessary, in particular for the good behavior of the post in time.

  In addition, the galvanic treatment required for these poles is polluting.

  Finally, these posts integrate poorly into the landscape in which they are located.

  Poles obtained by a filament winding pultrusion process from thermosetting resins and glass fibers are also known.

  These posts are of a high cost compared to wooden poles or steel. Indeed, given the required strength, the section of these posts must be important, which requires much more material.

  In addition, these posts pose recycling problems since they are made from non-recyclable resins.

  Finally, we know poles made of concrete which is a very economical material.

  However, concrete is a material with low mechanical strength. These posts therefore have dimensions much larger than those of steel poles, which leads to very heavy structures, expensive and which fit very poorly in the landscape.

  The present invention aims to overcome these disadvantages by providing a carrier element whose realization is very economical and is recyclable and easily integrated into a landscape, while having the required mechanical strength.

  Thus, the invention relates to a carrier element, such as a telephone or electrical pole, intended to be anchored in the ground and designed to withstand a predetermined maximum deflection and not to exceed a predetermined maximum stress, characterized in that it has a composite structure with an elongated central part, made of a resistant material whose height corresponds substantially to that of the carrier element, and an outer casing constituting a coating for said central portion, this coating comprising minus a thermoplastic polymer.

  Thus, that the central part is made of wood or metal, especially steel, it does not require any treatment, since the outer casing provides protection of the carrier element and thus guarantees its service life.

  In addition, this outer envelope avoids any pollution problem, both during the manufacture of the post and during its recycling, since the post is then made entirely of recyclable materials.

  This carrier element is intended to be anchored in the ground and has an invisible portion once installed. For aesthetic reasons, at least on the portion of the carrier element intended to be visible, the coating of the central portion may consist of at least one thermoplastic polymer and fillers, in a proportion of between 20 and 80% and preferably between 30 and 60%.

  Preferably, the coating of the central portion is constituted, over the entire height of the carrier element, by a mixture of at least one thermoplastic polymer and fillers, in a proportion of between 20 and 80% and preferably between 30 and 60%.

  Advantageously, these fillers are natural vegetable fillers, such as natural fibers or sawdust or natural mineral fillers.

  Natural fibers or sawdust reinforce the thermoplastic polymer and provide a color close to the color of the wood, which color can be varied both by the type of polymer used and also by the type of filler. such as the nature of the wood, the nature of the mineral filler and the percentage of filler in the coating, or the use of natural pigments.

  The presence of these charges makes it possible to reduce the cost of the outer envelope and also to obtain an appropriate external appearance for a better visual integration into the environment.

  Moreover, the presence of these charges does not change the recyclability of the carrier element according to the invention.

  The carrier element according to the invention may thus have an outer shell whose composition is different on the portion of the carrier element intended to be anchored in the ground and on the other part of the carrier element which remains visible after anchoring. of the carrier element in the ground.

  The thermoplastic polymer (s) used in the composition of the outer casing of this carrier element are in particular chosen from polyvinyl chloride, polyethylene, polyethylene copolymers or even polypropylene.

  Advantageously, the central part of the carrier element consists of two steel profiles fixed to each other, the section of the central portion being hollow.

  Thanks to this particular structure, it is possible to design supporting elements which are of a lower cost than conventional posts, because of the use of a smaller amount of material, or which have a smaller cross-section than a conventional pole, while resisting the constraints imposed on this type of carrier element.

  The central portion may, for example, have a rectangular section, octagonal or substantially oval.

  The invention also relates to a method of producing a carrier element, and in particular a pole as described above.

  This process consists in extruding, on an elongated central part, a layer of at least one thermoplastic polymer, so as to produce an outer envelope of the central part.

  On at least a portion of the carrier member, the extruded layer is preferably composed of a mixture of at least one thermoplastic polymer and fillers, said fillers being present in the mixture in a proportion of between 20 and 80 % and, preferably, between 30 and 60%.

  Advantageously, these fillers are natural vegetable fillers such as natural fibers or sawdust or mineral fillers, so as not to change the recyclability of the carrier element.

  Advantageously, the fibers of vegetable origin are flax or hemp fibers. As mineral fillers, it is possible to use chalk, dolomite or alumina hydrate.

  These fillers are even less expensive than the thermoplastic polymers used in the composition of the mixture, which reinforces the economic nature of the carrier element according to the invention.

  Moreover, the use of natural pigments associated with natural plant fillers allows a coloration in the mass of the outer shell which gives the carrier element the appearance of wood.

  On the contrary, conventional treatments of steel columns, by paint application, never completely erase the defects of the steel.

  Advantageously, the thickness of the extruded layer is of the order of a few millimeters and preferably between 2 and 4 mm. t

  The method according to the invention can be implemented with a central portion of any kind, for example wood or steel. An important feature of the process according to the invention is that it does not require any prior treatment of this central part, in particular a core treatment for a central part made of wood or a galvanizing or finishing treatment for a central part of steel.

  In all cases, the material constituting the central portion can be crude, which solves the pollution problems caused by these treatments themselves during the manufacture of poles, as well as by the recycling of poles.

  Preferably, when the method according to the invention is implemented with a central part of steel, it is used as a punch and heated during the extrusion of the outer casing, to increase the adhesion of this casing. on the central part.

  Preferably, the method according to the invention consists in producing the central part of steel, from at least two sections which are fixed to each other.

  These profiles are obtained by folding or curving raw steel strips.

  Advantageously, the central part is made from two generally U-shaped sections. In this case, the method consists of placing these two sections with their concave faces facing each other and to interleave the two sections with one another. other, so that they overlap at least in part.

  The two profiles are fixed at their overlapping portions.

  Advantageously, the method according to the invention consists in producing a carrier element in several operations carried out continuously from raw material in raw form.

  Thus, the central part of the carrier element will be made directly from steel sheet strips that can be delivered in great length in the form of a roll. These strips are unwound and then formed into sections, which are then assembled and fixed together.

  A layer of at least one thermoplastic polymer is then extruded on the central portion. The product obtained is finally cooled and cut to the desired length.

  In a particular embodiment of the preceding method, the extruded layer comprises charges on at least a portion of the carrier element.

  The invention will be better understood and other objects, advantages and features will appear more clearly from the description which follows and which is made with reference to the appended drawings, in which: FIG. 1 represents, in cross-section, a first example; embodiment of a carrier element according to the invention, with a rectangular section, FIG. 2 represents, in cross-section, a second exemplary embodiment of a carrier element according to the invention, of octagonal section, FIG. 3 also shows in cross-section a third embodiment of the carrier element according to the invention, of substantially oval section, and FIG. 4 schematically represents an exemplary implementation of the method according to the invention.

  Referring firstly to Figure 1, the carrier element 1 comprises a central portion 10 covered with an outer casing 11.

  This central portion is elongated and has a height corresponding substantially to that of the carrier element.

  The central portion 10 is made from two substantially identical steel sections 12 and 13 which have a U-shape.

  These two steel profiles have previously been obtained by folding two strips of crude steel.

  They were arranged so that their concave faces were facing each other and they were then nested one inside the other.

  Thus, the branches 121, 131, respectively 122, 132 of the two profiles 12, 13 are superimposed, the branches 121 and 132 being on the inner side of the central portion 10, while the branches 122 and 131 are located on the outer side of the central part 10.

  In the example illustrated in Figure 1, the central portion 10 has a rectangular cross section. This section is hollow and closed.

  Two sections 12 and 13 are connected to one another by fastening means which are preferably provided between the superimposed branches of the two sections.

  These fixing means 14 may consist of rivets, glue or welding.

  The method according to the invention makes it possible to optimize the dimensions of the sheet metal strips used, compared with conventional techniques.

  This will be illustrated by Table 1 which gives three examples of embodiment of a central portion from steel strips.

  Example 1 relates to a carrier element according to FIG.

  Example 2 relates to a conventional steel structure of rectangular section, made from a sheet of steel cut, folded, rolled and welded and used for an electric or telephone pole.

  Example 3 also relates to a conventional structure with a rectangular cross section, but made from steel strips whose thickness is optimized.

  In the table below, H represents the long side of the rectangular cross section and h its small side.

  The thickness of the sheet metal strip used is identified by e.

  Of course, in Example 1, the sheet thickness is doubled in the areas of the central portion in which the branches of the U are superimposed.

Table 1

  Example 1 Example 2 Example 3 H 116.6 mm 116.6 mm 146.8 mm h 77.7 mm 77.7 mm 97.9 mm e 2.0 mm 4.0 mm 2.0 mm quadratic moments 2.399E + 06 2.826E + 06 3.023E + 06 ly 9.362E + 05 1.495 + 06 1.625E + 06 Ix Strain Qmax 196 N / mm2 166 N / mm2 196 N / mm2 Surface of the steel in 1 056 mm2 1491 mm2 963 mm2 the section rectangular section perimeter of the section 389 mm 389 mm 489 mm Table 1 above shows that a conventional structure according to example 2, having dimensions identical to those of a carrier element according to the invention and in accordance with the Example 1 (and thus a perimeter of the same cross-sectional area, ie 389 mm), has a steel surface in the rectangular section which is approximately 41% greater than the corresponding area in Example 1 (1491 mm 2 for 1056 mm 2).

  Thus, the carrier element according to the invention, according to Example 1, makes it possible to save material compared to a conventional structure. This is due to the use of steel strips whose thickness is twice as low for Example 1 and does not compromise the strength of the carrier element.

  Indeed, in Example 1, the maximum stress remains within the limits imposed by the users, this limit being conventionally 240 N / mm 2.

  This Table 1 also shows that with a conventional structure, according to Example 3, in which the amount of steel is optimized, the latter is slightly less important than in Example 1, but the dimensions of the rectangular section are larger than those of the carrier element according to Example 1.

  Indeed, in a structure according to Example 3 made from 2 mm thick steel sheets, for a maximum stress of 196 N / mm 2, it is necessary to provide a larger rectangular section (H = 146, 8 mm for example 3 and 116.6 mm for example 1 and h = 97.9 mm for example 3 and 77.7 mm for example 1).

  This leads, for Example 3, to a perimeter of 489 mm and therefore to an increase in the perimeter of about 26%, compared to Example 1.

  However, the larger its perimeter, the more the structure is bulky and visible in the environment.

  As a result, the users favor structures whose perimeter is the weakest, while presenting the desired resistance.

  Table 1 shows that the method according to the invention leads to a central part of steel with a perimeter of cross section substantially identical to those of the least bulky conventional structures and a very large decrease in the amount of steel used.

  Referring again to Figure 1, after completion of the central portion 10 of steel, is carried out the extrusion of a layer of a mixture, which leads to the formation of an outer casing 11 on the central portion 10 .

  This extrusion step will be described in more detail with reference to FIG. 4.

  On at least a portion of the carrier member, this layer is preferably comprised of a blend of at least one thermoplastic polymer and natural fillers, such as wood fibers. This portion of the carrier element is that which is intended to remain, at least in part, visible after anchoring the element in the ground.

  This mixture can comprise between 20 and 80% of fillers and preferably 30 to 60% of fillers.

  The thickness of the extruded layer is, in the example illustrated in FIG. 1, 2 mm. Thus, in this example, the thickness of the outer casing 11 substantially corresponds to the thickness of the steel.

  Referring now to Figure 2 which illustrates a carrier member 2, having a central portion 20 covered with an outer casing 21.

  The central portion 20 is composed of two sections 22 and 23.

  The latter are obtained from steel strips which are folded so as to have five sides of substantially equal lengths which form five faces of an octagon. They still have a general U shape. In accordance with the method according to the invention, these two sections 22 and 23 are arranged facing each other, with their concave faces facing each other.

  The two profiles 22 and 23 are then nested one inside the other, so that their end branches 221, 231, 222, 232 respectively, are superimposed.

  As illustrated in FIG. 2, the end branch 221 of the profile 22 is on the outer side of the central part 20, while its other end branch 222 is on the inner side of the central part 20.

  Similarly, the branch 231 of the profile 23 which is superimposed with the branch 221 of the profile 22 is on the inner side of the central part, while the other end branch 232 of the profile 23 is on the outer side of the central portion 20 .

  Fixing means 34 of the two sections are provided between the superimposed sides 221, 231, respectively 222, 232.

  After completion of the central part 20 made of steel, a layer is extruded onto it in order to produce the outer casing 21, as described for the carrier element of FIG. 1.

  For the embodiment of the carrier element according to the invention, in accordance with FIG. 2, it will also be shown that the invention makes it possible to optimize both the quantity of steel used and the perimeter of the section of the central part of the carrier element.

  With reference to Table 2 below, Example 4 is a carrier element according to the invention and according to Figure 2, Example 5 is a conventional steel structure made from cut steel strips, folded, rolled and welded, with an octagonal cross section and Example 6 is a conventional steel structure, of octagonal cross section, and the thickness has been optimized.

  In the table below, D denotes the diameter of the octagonal section (ie the distance between two faces opposite the octagonal section), L denotes the length of one side of the octagonal section. and e is the thickness of the steel strip used to make each of the examples.

Table 2

  Example 4 Example 5 Example 6 D 125.1 mm 125.1 mm 152.3 mm L 51.8 mm 51.8 mm 63.1 mm e 2.0 mm 4.0 mm 2.0 mm quadratic moments 2.575E + 06 3.532E + 06 3.135E + 06 ly 1.785E + 06 3.532E + 06 3.135E + 06 Ix Stresses umax 196 N / mm2 143 N / mm2 196 N / mm2 Steel area in the 1036 mm2 1658 mm2 1010 mm2 section octagonal Perimeter of section 414 mm 414 mm 505 mm 2878551 13 Table 2 above shows that a conventional structure according to example 5 and having dimensions identical to those of a carrier element according to the invention and in accordance with FIG. Example 4 (i.e. a perimeter of the same 414 mm cross section), has a steel surface in the octagonal section that is about 60% greater than the corresponding area in Example 1 (1658 mm2 against 1036 mm 2).

  Thus, the carrier element according to the invention, according to Example 4, allows a material saving of about 37% compared to a conventional structure.

  This is due to the use of steel strips whose thickness is 2 mm for Example 4 and 4 mm in Example 5.

  In addition, the use of steel strips of thickness two times lower does not compromise the strength of the carrier element according to the invention.

  Indeed, the maximum stress of 196 N / mm2 remains within the limits imposed by the users (240N / mm2).

  Table 2 also shows that with a conventional structure, according to Example 6, in which the amount of steel is optimized, the latter is slightly less important than in Example 4, but the dimensions of the octagonal section of Example 6 are much larger than those of the carrier element according to Example 4.

  Indeed, in a structure according to Example 6 made from steel sheets of 2 mm thick, for a maximum stress of 196 N / mm 2, it is necessary to provide a larger octagonal section (D = 152, 3 mm for example 6 and 121.1 mm for example 4 and L = 63.1 mm for example 6 and 51.8 mm for example 4).

  This leads, for example 6, to a perimeter of 505 mm and therefore to an increase of the perimeter of approximately 22% compared with example 4.

  As previously stated, users are looking for low perimeter carriers to be less visible in the environment.

  Thus, Table 2 confirms that the method according to the invention makes it possible to obtain a central part of steel with a perimeter of cross-section substantially identical to that of the least bulky conventional structures, with a very significant decrease in the quantity of steel. .

  FIG. 3 illustrates yet another embodiment of a carrier element 3 according to the invention.

  The latter comprises a central portion 30, covered with an outer casing 31.

  In this example, the central portion 30 is made from two substantially identical steel profiles 32 and 33 which have a rounded U-shape.

  As in the previous examples, these two sections are obtained by folding two strips of crude steel.

  They were arranged so that their concave faces are facing each other and they were then nested one inside the other, so that the free ends of the profiles overlap partially.

  Thus, the end portions 321, 331, respectively 322, 332 are superimposed, the portions 321 and 332 being on the outer side of the central portion 30, while the portions 331 and 322 are located on the inner side of the central portion 30 .

  These two profiles 32 and 33 are fixed to each other by appropriate means 34. They are provided between the superimposed portions of the profiles, 321, 331, respectively 322, 332.

  An exemplary implementation of the method according to the invention will now be described with reference to FIG. 4.

  The process consists firstly of producing, from webs 41 and 42, packaged in the form of rolls, sections 43 and 44.

  As previously described with reference to FIGS. 1 to 3, these 5 sections have a generally U-shaped shape. The profiles 43 and 44 then pass to an assembly station 45, in which the sections arrive so that their concave faces are next to each other, the profiles then being nested one inside the other and fixed to one another.

  At the exit of the assembly station 45, is formed a central portion 46 whose section may be for example rectangular, octagonal or substantially oval.

  This central portion 46 then passes into an extrusion station 47.

  During extrusion, the coating comprising at least one thermoplastic polymer is deposited on the central portion 46 of steel. The latter is then advantageously used as a punch during extrusion. Thus, the central portion is heated before entering the extrusion station. This allows the flow of the melt around the central part and the increase of the adhesion of the coating on the central part.

  At the extrusion station 47, the process may consist of extruding the same mixture over the entire central part or alternatively providing different mixtures extruded successively.

  This is particularly the case if it is desired to obtain bearing elements whose portion intended to be anchored in the ground comprises an outer casing without load and whose portion intended to remain visible comprises an outer casing with loads.

  At the extrusion station, then alternately extruded a layer of a mixture without load and a layer of a mixture with charges. Suitable means are provided in the extrusion station.

  By way of illustration, the portion of the carrier element intended to be anchored in the ground corresponds approximately to H / 10 + 0.7m, H being the height of the carrier element in meters.

  At the outlet of the extrusion station 47, the composite element 48 is, after cooling, cut to the desired length by means of sawing 49. The carrier element or post 50 is thus obtained.

  Thus, advantageously, the method according to the invention makes it possible to obtain continuously, a carrier element of hybrid structure.

  However, the method according to the invention could also be implemented from steel core parts obtained previously or still from steel sections previously formed from strips of steel sheets.

  Finally, the method according to the invention makes it possible to insert, on or in the outer casing, various elements such as: advertising impressions, decorative elements or fluorescent materials to ensure signaling for example, or means capable of giving information or enabling connections with telecommunication or signaling means (electronic cards for example).

  The method may also include providing a particular surface condition at a predetermined location on the surface of the envelope, which will then receive advertising or information media.

  The reference signs inserted after the technical characteristics appearing in the claims are only intended to facilitate understanding of the latter and can not limit its scope.

Claims (2)

17 Claims   A carrier element, such as a telephone or electrical pole, intended to be anchored in the ground and designed to withstand a predetermined maximum deflection and not to exceed a predetermined maximum stress, characterized in that it has a composite structure with an elongate central portion (10, 20, 30) made of a resistant material and whose height corresponds substantially to that of the carrier element, and an outer casing (11, 21, 31) constituting a covering for said part central, this coating comprising at least one thermoplastic polymer.   2. Bearing element according to claim 1, characterized in that the coating of the central portion is formed, on at least a portion of the height of the central portion, of a mixture of at least one thermoplastic polymer and fillers in a proportion of between 20 and 80% and preferably between 30 and 60%.   3. Bearing element according to claim 2, characterized in that the fillers are natural vegetable fillers, such as natural fibers or sawdust, or mineral fillers.   4. Carrier element according to claims 1 to 3, characterized in that the thermoplastic polymer (s) used in the composition of the outer casing is (are) chosen from: polyvinyl chloride, polyethylene, polyethylene copolymers or polypropylene.   5. Supporting element according to one of claims 1 to 4, characterized in that the central portion is made of wood.   6. Supporting element according to one of claims 1 to 4, characterized in that the central portion (10, 20, 30) consists of two steel profiles (12, 13; 22, 23; 32, 33), fixed to each other, the section of the central part being hollow.   7. Bearing element according to one of claims 1 to 6, characterized in that it has a rectangular hollow section, octagonal or substantially oval.   8. A method of producing a carrier element according to one of claims 1 to 7, characterized in that it consists in extruding, on an elongated central portion (10, 20, 30), a layer of at least one thermoplastic polymer, so as to provide an outer shell (11, 21, 31) of the central portion.   9. Method according to claim 8, characterized in that the extruded layer is constituted, on at least a portion of the carrier element, a mixture of at least one thermoplastic polymer and fillers, said fillers being present in the mixture in a proportion of between 20 and 80% and preferably between 30 and 60%.   10. Process according to claim 9, characterized in that these fillers are natural vegetable fillers, such as natural fibers or sawdust, or mineral fillers.   11. Method according to one of claims 8 to 10, characterized in that the thickness of the extruded layer is of the order of a few millimeters and preferably between 2 and 4 mm.   12. Method according to one of claims 8 to 11, implemented with a central portion of steel, characterized in that it is used as a punch and heated to increase the adhesion of the coating obtained on said central portion.   13. Method according to one of claims 8 to 12, characterized in that it consists in producing the central part of steel and from at least two sections which are fixed to each other.   14. The method of claim 13, characterized in that the central portion is made from two sections (12, 13; 22, 23; 32 33) of generally U-shaped. 15. The method of claim 14, characterized in that it consists in placing the two generally U-shaped sections, with their concave faces facing each other and in interleaving the two sections one in the other, so that they overlap at least in part .   16. The method of claim 15, characterized in that the fixing is performed between the superimposed portions of the profiles.   17. Method according to one of claims 8 to 16, characterized in that it comprises several operations carried out continuously including the unwinding of strips (41, 42) of steel sheet, the forming of these strips of profiles (43 , 44), the mechanical assembly of the profiles and their attachment, so as to obtain an elongated central steel portion (46), the extrusion of said layer of at least one thermoplastic polymer, the cooling of the extruded material and finally the cutting the carrier member (50) obtained to the desired length.   18. The method of claim 17, characterized in that the extruded layer comprises charges on at least a portion of the carrier member.