Classifications

• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
  • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
  • E04C5/08—Members specially adapted to be used in prestressed constructions
  • E04C5/10—Ducts

Definitions

• the present invention relates to a cable sheath, in particular a prestressing sheath or a shroud sheath, its manufacturing process and the machine for implementing said process.
• Prestressing ducts which are intended to be embedded in concrete structures and to receive the prestressing cables of these structures, must meet several requirements:
• these plastic sheaths generally have, as protruding relief, grooves on their outer surface. These corrugations do not make it possible to fix sheath fittings by screwing.
• threaded portions are generally provided at the ends of the sheaths, these threaded portions generally being produced by molding.
• this implementation prevents the sizing on site of these sheaths to any desired length.
• special sleeves are provided, in the form of half-shells which are assembled after the installation of the sheaths. This implementation also causes an increase in manufacturing costs.
• plastic sleeves Another disadvantage of plastic sleeves is that it is difficult to find a plastic material which simultaneously fulfills all the above-mentioned requirements.
• the present invention aims to provide a cable sheath meeting the above requirements by eliminating the aforementioned drawbacks.
• the present invention therefore aims to provide an improved cable sheath which is waterproof and resistant, which has a minimum wall thickness, which has low friction inside, and which can effect the transfer of the prestressing forces to the concrete. .
• the present invention aims to provide an improved cable sheath which has a structure such that the above requirements are each optimally fulfilled.
• the present invention also aims to provide such an improved cable sheath, the manufacture of which is simple, rapid and economical.
• the present invention also aims to provide such an improved cable sheath which can be manufactured in situ at any desired length.
• the present invention also aims to provide such an improved cable sheath made essentially of plastic.
• the present invention therefore relates to a cable sheath comprising a multi-layer structure comprising at least two continuous superimposed layers of plastic material, each consisting of a strip arranged in a helix and the lateral edges of which are respectively joined with tight junctions.
• This multi-layer structure has many advantages. Thus, it is possible to easily vary the thickness of the wall of the sheath by modifying the number of layers, these may each have very small thicknesses, which largely eliminates the winding difficulties due to memory. shape of plastics. On the other hand, it is possible to incorporate layers of different materials, each layer having particular properties.
• the multi-layer structure can comprise more than two plastic layers.
• the invention provides a cable sheath made entirely of plastic.
• said at least two plastic layers are welded to each other at at least one point, advantageously along a line, for example by thermal welding. This characteristic makes it possible to make irreversible connections between the layers and guarantees repeatability and homogeneity of the sheath.
• the cable sheath has on its outer surface at least one continuous helical thread.
• the presence of the helical thread or continuous spiral makes it possible to fix duct fittings by simple screwing.
• the fact that the thread extends continuously over the entire sheath makes it possible to cut the latter to any desired length.
• the rigidity of the sheath can be modified.
• an insert such as a metal wire, is arranged in the multi-layer structure of the sheath, in particular in at least one longitudinal rib of at least one strip.
• This insert can act to reinforce the rigidity of the sheath or possibly be a heating insert.
• a particularly suitable use of the sheath according to the invention is the use as a prestressing sheath.
• the sheath according to the invention can also be used as a shroud sheath.
• the advantageous presence of a continuous spiral net on the outer surface of the sheath has in this case aerodynamic advantages with respect to the wind as well as rainwater which can flow more easily by being channeled, and the multilayer structure makes it possible to produce an outer layer having any practical or aesthetic characteristic desired.
• the present invention further relates to a method of manufacturing a cable sheath, comprising the following steps:
• the method comprises the step of welding at least one point said at least two superimposed layers of plastic.
• this welding is carried out thermally along a continuous helical line, which provides improved sealing of the sheath.
• the method comprises, before the step of assembling, of forming at least one longitudinal rib in each strip.
• the invention further relates to a machine for implementing the method comprising at least two reels for receiving strip rolls to supply said at least two strips, and an assembly device for assembling the strips in a helical manner so their respective lateral edges are joined.
• the assembly device comprises a fixed cylindrical mandrel, which may comprise at least one continuous spiral thread on its outer surface, on which a respective longitudinal rib of each strip formed is wound helically. beforehand by means of a corresponding rib forming module, the winding being advantageously carried out by means of driving rollers and / or pressers.
• the assembly device comprises two rotary cylindrical mandrels, around which the strips are wound in a helix, the assembly formed by said two rotary mandrels being itself rotary.
• the winding is also advantageously carried out by means of driving rollers and / or pressers.
• This variant makes it possible to produce ducts of oblong cross section.
• FIG. 1 is a schematic view in longitudinal section of the wall of a sheath with a multi-layer structure according to the invention
• FIG. 2 represents a part of the assembly device according to the invention and schematically illustrates the manner in which the sheath with a multi-layer structure according to the invention is assembled
• FIG. 3 is a schematic view of a machine for implementing the method of manufacturing a sheath with a multi-layer structure according to the invention, said machine incorporating a first variant of the assembly device
• Figure 4 is a view similar to Figure 3, the machine incorporating a second variant of the assembly device.
• the sheath 1 comprises a multi-layer structure which can for example comprise three superimposed layers 10a, 10b, 10c.
• the number of layers 10 which is at least two is not limited and the embodiment of the sheath comprising three layers as shown in the figures only represents an advantageous embodiment.
• the three-layer structure is advantageous when the sheath is used as a prestressing sheath because, to obtain the minimum wall thickness required, that is to say approximately 2 millimeters before the cables are tensioned, it is possible to in this case use layers of material having a standard thickness of about 0.7 millimeter.
• the thickness of the wall may be less or more, and the number of layers may therefore be different.
• the sheath with a multi-layer structure comprises at least one layer of plastic material.
• said sheath comprises at least two layers of superimposed plastic material, which makes it possible to bind them intimately together as will be explained later on in the description of the process for manufacturing the sheath.
• sheath with a multi-layer structure comprising three layers 10a, 10b, 10c made of plastic, but it is clear that the sheath may comprise a layer made of a other material, such as fiberglass or metal, for example.
• a particularly advantageous characteristic of the sheath with a multi-layer structure of the present invention lies in the possibility of choosing each layer in a particular material having particular intrinsic characteristics, so that each layer of the multi-layer structure fills a special function.
• the layer 10a located inside the sheath can be made of a material which has a low friction during the tensioning of the prestressing cables, for example Teflon or graphite high density polyethylene (HDPE).
• the second layer 10b that is to say the one which is directly superimposed on said first inner layer 10a, can for example be made of a material having a relatively high rigidity.
• the outer layer 10c can be made of a material having characteristics of good resistance to ultraviolet rays.
• This multi-layer structure also allows the cable sheath according to the invention to be suitable for other uses than that of prestressing sheath.
• a sheath can be used as a shroud sheath.
• the characteristics required for the inner 10a and outer 10c layers of the sheath are not necessarily the same as those of a prestressing sheath, it is then possible to choose different materials for the layers constituting said sheath.
• the outer layer 10c can for example be made of a colored material to meet aesthetic requirements, said colored material also having good resistance to ultraviolet rays to guarantee good hold. in colour.
• each layer 10 of the sheath is continuous, that is to say that each layer of the sheath forms a closed sleeve 10, the multi-layer structure therefore being a superposition of several of these individual sleeves 10a , 10b, 10c.
• each layer 10 of the sheath is formed from a strip or strip of material 11, which is assembled in such a way that its lateral edges 12, 13 are contiguously adjacent to form said sleeve.
• said lateral edges 12a, 13a; 12b, 13b; 12c, 13c of each strip l ia, l lb, 1 le of plastic material, which are contiguously adjacent after their assembly, are thermally welded together to form a layer of sheath of homogeneous and waterproof plastic.
• these zones of thermal welding 17 of the lateral edges of each plastic strip are offset from one layer to the other axially along the sheath 1. This additionally ensures perfect sealing of the multi-layer structure of the sheath, these zones 17 of relatively weak sealing of the different layers of sheath not being located opposite one another.
• the sheath 1 has on its outer surface at least one continuous helical or spiral thread 15.
• This spiral thread 15 acts in particular to fulfill the above-mentioned requirement for transfer of forces to concrete, after hardening cement grout.
• this continuous spiral thread 15 outside the sheath is formed by one or more longitudinal ribs 14a, 14b, 14c formed in each strip l ia, llb, the ie constituting said multi-layer structure.
• Said longitudinal ribs 14a, 14b, 14c of the different strips are preferably equidistant so as to be superposed on each other during the assembly of said sheath.
• each strip 1a, 1lb are preferably equidistant so as to be superposed on each other during the assembly of said sheath.
• the sheath 1 therefore has on its outer surface three continuous helical threads 15. This characteristic is particularly advantageous when the sheath has a circular cross section, because it allows the fitting of sheath fittings by simple screwing on said threads. spirals 15, at the ends of the sheath 1.
• the width of the different strips l ia, l lb, l ie forming the multi-layer structure as well as the number and / or the distance between the longitudinal ribs 14a, 14b, 14c formed in each of said strips l ia, l lb, l ie can be variable, which advantageously makes it possible to modulate the rigidity of said sheath 1.
• an insert 19 is arranged in the multi-layer structure of the sheath.
• This insert 19, which may for example be a metal wire, can serve to further strengthen the rigidity of said sheath, but it can also act as a heating insert by passing an electric current through it.
• said insert 19 acts to heat the sheath in the event of an extremely low temperature, thus making it possible to inject the cement slurry even in cold weather.
• This insert or metal wire is advantageously disposed in one or more of said longitudinal ribs 14a, 14b, 14c of one or more of said strips 11a, 11b, 1e. In this case, it extends over the entire length of the sheath in a spiral manner.
• the sheath according to the invention can have a circular cross section, but it can also have a different cross section and in particular oblong, as visible in FIG. 4. This implementation ensures, in certain applications, a better distribution of prestressing forces, especially in thin structures.
• the invention also relates to the method of manufacturing a sheath with a multi-layer structure as described above.
• This method essentially comprises assembling in a spiral by superimposing said strips by means of an assembly device 20. The assembly is carried out so that the respective lateral edges of each strip are joined to form continuous sheath layers .
• at least one of said strips l ia, l lb, l ie is made of plastic and according to a preferred aspect of the manufacturing process, at least two of said strips l ia, l lb, l ie are made of plastic to form at least two superimposed layers of plastic in the multi-layer structure of the sheath.
• Each strip l ia, l l b, 1 le is fed from a roll or a reel
• rib forming in which at least one longitudinal rib 14a, 14b, 14c is respectively formed in said strip l ia, l lb, 1 le.
• modules 40 are adapted to form ribs 14a, 14b, 14c which are identical in the different strips constituting the multi-layer structure and advantageously include heating means making it possible to deform the material to form said ribs l ia, llb, linked in each strip respective.
• Said strips 11a, 11b, 1 constituting the multilayer structure are then assembled, preferably simultaneously as visible in FIGS. 3 and 4, by means of an assembly device 20. This assembly is preferably carried out by winding in spiral each of said strips so that their longitudinal ribs 1a, 1lb, 1 are superimposed. Said strips thus form the different layers 10a, 10b, 10c of the multi-layer structure of the sheath.
• said assembly device 20 comprises a fixed cylindrical mandrel 21 which in this example comprises at least one continuous helical or spiral thread 22 on its outer surface.
• the assembly device 20 is suitable for assembling a sheath with a multi-layer structure having a substantially circular cross section.
• the mandrel 21 comprises a continuous spiral thread 22 for each longitudinal rib 14a, 14b, 14c of the different strips l ia, l lb, Uc.
• the strips each have three longitudinal ribs as well as the mandrel.
• each of said longitudinal ribs 14a, 14b, 14c of each of said strips comes to engage on a respective spiral thread 22 of the mandrel 21, during assembly.
• This assembly is advantageously done by helically winding said strips around said mandrel 21. As visible in FIG. 3, this winding is preferably carried out by means of driving rollers 25 which are advantageously arranged in an inclined manner to follow said continuous spiral threads 22 of mandrel 21 and which are rotated by a suitable device 26.
• These rollers 25 act in particular to guide the strips so that their longitudinal ribs 14a, 14b, 14c engage on said spiral threads 22 of the mandrel 21.
• Each strip l ia, llb, l ie therefore wraps around said mandrel 21 to form a layer 10a, 10b, 10c of the multi-layer structure of the sheath 1, this winding being carried out in such a way that the lateral edges 12a, 13a; 12b, 13b; 12c, 13c of each strip 1a, llb, lie are adjacent to each other in a contiguous manner after winding around said mandrel 21.
• Figure 2 in which we also see that the winding of three strips 1 la, l lb, l ie is produced in such a way that these overlap with their lateral edges offset axially.
• the method advantageously provides for having a heating module 30 for each strip of plastic material, intended in particular to heat its lateral edges 12a, 13a; 12b, 13b; 12c, 13c.
• a heating module 30 for each strip of plastic material, intended in particular to heat its lateral edges 12a, 13a; 12b, 13b; 12c, 13c.
• the adjacent heated edges of each plastic strip are thermally welded together by means of said drive rollers 25 which, in this case, also act as pressure rollers. This characteristic makes it possible to obtain with each plastic strip a tight and homogeneous plastic layer.
• each of said heating modules 30 is further intended to locally heat so-called melting zones 18 in each strip so that, during winding, said respective heated zones 18 of two strips, which overlap during said winding , are pressed against each other by means of said pressure rollers 25, so that said superimposed layers formed by said two strips are intimately linked in these melting zones 18.
• melting zones 18 in each strip so that, during winding, said respective heated zones 18 of two strips, which overlap during said winding , are pressed against each other by means of said pressure rollers 25, so that said superimposed layers formed by said two strips are intimately linked in these melting zones 18.
• the spiral ribs no longer serve to ensure the transfer of the forces to the concrete. We can then dispense with it. Note, however, that these ribs participate in obtaining good rigidity of the sheath.
• Figure 4 is shown a second variant of the assembly device 20 described above.
• the assembly device 20 does not include a fixed mandrel, but two rotary cylindrical mandrels 23a, 23b which may each include one or more continuous spiral threads (not shown) on their outer surface.
• the assembly formed by said two rotary mandrels 23a and 23b is itself rotary around an axis.
• the strips are wound around said two mandrels 23a, 23b to form a sheath with a multi-layer structure having an oblong cross section.
• the sheath with a multi-layer structure advantageously passes through a cooling module 60 in order to freeze the shape of said sheath 1. Since the heating modules 30 only act locally, that is to say on the lateral edges and in particular melting zones of each strip, this cooling is not essential and in any case does not need to be particularly important. Then, the sheath with a multi-layer structure preferably passes through a cutting module 70 in which said sheath is cut to any desired length.
• the manufacturing process described above therefore has very significant advantages which are:
• the sheath obtained has a multi-layer structure, which implies the advantages mentioned above, namely in particular that according to the desired characteristics, the number of layers and / or the material of the strips constituting the layers can be modified very simply.
• the machine for implementing this process is simple and space-saving and therefore allows manufacturing on site, that is to say on site, of the sheath with a multilayer structure of the invention.
• the sheath obtained with this process may include one or more continuous spiral threads on its outer surface which allows sheath connections to be made by simply screwing in suitable sleeves, whatever the desired length of the sheath.
• the cutting module makes it possible to cut the sheath obtained to any desired length.
• the fact that this process can be implemented on site possibly makes it possible to produce ducts of great length, which is impossible when the ducts have to be transported from the factory to the site.
• the machine for implementing the process for manufacturing the sheath according to the invention also makes it possible to carry out said sites on site. connection sleeves which are screwed onto the ends of said sheaths to connect the latter.

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• Engineering & Computer Science (AREA)
• Architecture (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Laminated Bodies (AREA)
• Insulated Conductors (AREA)
• Manufacturing Of Electric Cables (AREA)
• Rigid Pipes And Flexible Pipes (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Citations (7)

• 1995
  • 1995-06-19 FR FR9507290A patent/FR2735511B1/fr not_active Expired - Fee Related
• 1996
  • 1996-06-13 WO PCT/FR1996/000905 patent/WO1997000361A1/fr not_active Application Discontinuation
  • 1996-06-13 EP EP96922920A patent/EP0833994A1/fr not_active Withdrawn
  • 1996-06-13 CA CA002225166A patent/CA2225166A1/en not_active Abandoned
  • 1996-06-13 AU AU63617/96A patent/AU709765B2/en not_active Ceased
  • 1996-06-13 JP JP9502719A patent/JPH11508005A/ja active Pending
• 1997
  • 1997-12-16 NO NO975904A patent/NO975904L/no not_active Application Discontinuation

Patent Citations (7)

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