FR2760814A1 - EXTENDED TUBULAR PRODUCT, ESPECIALLY OF THE TYPE OF INSTALLATION DUCT - Google Patents

Abstract

The invention concerns an elongated tubular product with the same cross section along its whole length, comprising a solid tube (1) made of at least a plastic material, both sufficiently flexible to be wound and unwound, and sufficiently rigid to resist a centripetal or centrifugal radial force, said solid tube comprising, on the inside and/or on the outside, a surface coating (3) whose free surface constitutes a friction surface and comprising a plastic matrix in which is distributed a lubricant. The invention is characterised in that, with synergistic effect, the particles (4) of a solid lubricant are distributed in the plastic matrix, at least partly flush at the free surface of the surface coating, and a liquid lubricant, compatible with the plastic matrix, is dispersed in the surface coating, practically without wetting the free surface of the latter.

Description

 The present invention relates to an elongated tubular product, generally having the same section along its entire longitudinal direction, and comprising a solid tube, consisting of at least one plastic, both flexible enough to be itself wound and unrolled, and rigid enough to withstand itself a centripetal or centrifugal radial force.

 By the preceding generic definition, the present invention intends to group under the same concept, for example both an installation conduit, of at least one cable or a pipe, then contained in said installation conduit, that a sheath of protection of at least one cable, for example electrical.

 Furthermore, by the expressions "cable" or "pipe", the present invention intends to cover any conduit generally ensuring the transfer or the transport of a flow, whether it is a fluid (water or gas by example), energy (electricity for example), or information or signals (video transmission by optical cable for example), or data in the form of electrical, analog, digital signals, etc.

 To introduce and define the present invention, reference will now be made, by way of example, to the installation conduits.

 In order to limit the civil engineering works, and in particular the number of drawing chambers, it is known to lubricate the friction surface, corresponding to the interior surface of the solid tube forming the installation conduit. This makes it possible to increase the length of tube that can be installed.

 This lubrication cannot be permanent, and the sliding effect disappears over time, either because of the aging of the lubricating agent used, or again due to the extraction and then the pulling, or the combination of several operations. (for example push-carry) carried out with new cables in the same installation conduit, during its operation.

 The subject of the present invention is, in general, an elongated tubular product, allowing permanent dry lubrication of the friction surface, whether internal in the case of an installation duct, or external in the case of '' a cable protection sheath.

 According to the present invention, in general, the solid tube comprises at least one surface layer, the free surface of which constitutes the dry friction surface, and which comprises a plastic matrix in which particles of a solid lubricant are distributed, flush with the at least partly at the level of this free surface.

 Thanks to the invention, whatever the wear of the surface layer defined above, particles of the solid lubricant are exposed at the level of the dry friction surface, thus guaranteeing a permanent and effective sliding, with respect to any surface. opposite coming into sliding contact with the solid tube, for example the outer surface of a cable protection sheath in the case of an installation conduit.

 Preferably, but not exclusively, a lubricant of a liquid nature, compatible with the plastic matrix, is essentially diffused in this same surface layer at least, practically without wetting the free surface of this surface layer. In this case, as shown in the experimental protocol described below, there is a synergistic lubricating action between the solid lubricant on the one hand, and the liquid lubricant on the other hand, all other things being equal.

The present invention also has the following secondary characteristics
the solid lubricant has a lamellar structure, and is for example graphite, or also has a polymer structure with long, straight, oriented chains, and is for example a polytetrafluoroethylene,
the particles of the solid lubricant are micro-beads having a diameter at most equal to 20 ssm, and preferably between 1 and 15 ssm,
- The liquid lubricant is preferably but not exclusively a silicone; it has a viscosity at most equal to 1000 centistokes, at ambient temperature, and for example between 10 and 1000 centistokes,
- the dry lubricant constitutes a charge,
- The surface layer is discontinuous following the periphery of the solid tube, and corresponds for example to longitudinal ribs or grooves; but this same surface layer can be continuous, following the periphery of the solid tube.

 Preferably, it is the solid tube which is constituted by the single plastic matrix, in which, on the one hand, particles of the dry lubricant are distributed, partially flush with at least one free surface, interior or exterior, and constituting a dry friction surface, and on the other hand a liquid lubricant is diffused, practically without wetting, neither the outer surface nor the inner surface of this same matrix.

 According to this preferred solution, whether or not the plastic material has a liquid lubricant in the diffused state, the dry lubricant constitutes a filler, the weight proportion of which is at least equal to 5% of the plastic matrix, in particular between 5% and weight and 20% by weight of this same matrix.

 Still according to this same preferred solution, when the matrix comprises, in the diffused state, a liquid lubricant, which constitutes a sort of additive, its proportion is at least equal to 0.02% by weight of the plastic matrix, and in particular between 0.02% by weight and 0.08% by weight of this same matrix.

In this case, by way of example, the proportion of dry lubricant / liquid lubricant is at least equal to 5% and is in particular between 5% and 20%.

The present invention is now described with reference to the accompanying drawing, in which
FIG. 1 schematically represents, in axial section, an installation duct according to the invention,
FIG. 2 shows in axial section a cable protection sheath according to the invention,
FIG. 3 represents in cross section an installation sheath according to the invention, but according to another embodiment of the latter,
In accordance with FIG. 1, an installation duct is constituted by a solid or rigid tube 1, made of charged plastic material (for example high density polyethylene), both sufficiently flexible to be itself wound and unwound, and sufficiently rigid to withstand itself a centripetal or centrifugal radial force. This solid tube has a dry friction surface, corresponding to its interior surface.

 In accordance with the present invention, in the solid tube 1, a surface layer 3 at least is formed, the free surface of which constitutes the dry friction surface (internal surface 2). This surface layer comprises a plastic matrix, corresponding to that of the solid tube, in which particles 4 (micro-balls) of a solid lubricant are distributed, partly flush with the free surface 2.

 According to another embodiment of an installation duct according to the invention, represented in FIG. 3, the latter comprises three concentric layers 6, 7 and 8, optionally constituted by respectively different plastics, one exterior 7, the other inner 6, in which the surface layer 3 is integrated, and the other median or intermediate 8. The surface layer 3 is discontinuous, following the periphery of the solid tube 1, and includes, for example, ribs 9 or adjacent, longitudinal.

 But of course, this same surface layer 3 can be continuous, following the periphery of the solid tube 1.

 As shown in FIG. 4, the surface layer 3 is obtained by spraying or diffusing inside the tube 1, after extrusion but in the visco-elastic phase, the solid lubricant, in particulate form, optionally mixed with the liquid lubricant.

 In this way, the solid lubricant and possibly the liquid lubricant are incorporated into the plastic matrix of the tube, at least on the surface.

 As a variant, it is possible to mix the solid lubricant, in powder form, with the granules of the plastic material constituting the solid tube, before extrusion, then to hot extrude the mixture thus obtained. In this case, the solid tube obtained is formed by the only plastic matrix in which the particles of the dry lubricant are distributed, which are partially flush with at least the free surface, interior or exterior, thus constituting a friction surface. dried up.

EXAMPLE
A high density polyethylene (HDPE) tube, (commercial reference DAPLEN 4610 from the French Company
PCD), having an inner diameter of 27 mm and a thickness of 3 mm, is extruded on a CMF6O machine from
CINCINATTI company.

 At the outlet of the extrusion head, a suspension of a polytetrafluoroethylene (PTFE) powder (commercial reference UNILUB T3 of the Company UNIFLON) having an average particle size of 16 pm, in a silicone oil (commercial reference 47V100 of the Company PENNWHITE) having a viscosity of 120 censtistokes, is projected in divided form inside the extruded tube, while it is still viscoelastic. PTFE powder represents 20% by weight (PTFE) relative to the oil.

 The coefficient of friction between the internal surface of such a tube, compared to a HDPE sheath (same commercial reference as above) is 0.075.

All other things being equal,
PTFE and silicone oil act in synergistic action to reduce the coefficient of friction, because
- the coefficient of friction obtained, without treatment of the internal surface of the tube is 0.19,
- the coefficient of friction obtained, with projection of the silicone oil alone is 0.102.

Claims (17)

 1) Elongated tubular product, having the same section along its entire longitudinal direction, comprising a solid tube (1) consisting of at least one plastic material, both sufficiently flexible to be itself wound and unwound, and sufficiently rigid to withstand itself even at a centripetal or centrifugal radial force, said solid tube comprising a surface (2) of internal or external friction, lubricated,  characterized in that the solid tube (1) comprises at least one surface layer (3), the free surface of which constitutes the dry friction surface, and comprising a plastic matrix in which particles (4) of a solid lubricant are distributed , flush at least partially at the level of said free surface (2).  2) Tubular product according to claim 1, characterized in that the solid lubricant has a lamellar structure, and is for example graphite, or has a polymer structure with long straight and oriented chains, and is for example a polytetrafluoroethylene.  3) Tubular product according to claim 1, characterized in that a liquid lubricant compatible with the plastic matrix is essentially dispersed in the surface layer (3) at least, practically without wetting the free surface (2) of the surface layer.  4) Tubular product according to claim 3, characterized in that the liquid lubricant is a silicone.  5) Tubular product according to claim 1, characterized in that the liquid lubricant has a viscosity at most equal to 1000 centistokes, at room temperature, and for example between 10 and 1000 centistokes.  6) Tubular product according to claim 1, characterized in that the particles (4) of the solid lubricant are microbeads having a diameter at most equal to 20 µm, and preferably between 1 and 15 µm.  7) Tubular product according to claim 1, characterized in that the solid tube (1) consists of the single plastic matrix, in which are distributed particles (4) of the dry lubricant, partially flush with at least one free surface (2), interior or exterior, constituting a dry friction surface.  8) Tubular product according to claim 7, characterized in that the dry lubricant constitutes a filler, the proportion of which is at least equal to 5% by weight, and between 5 and 20% by weight of said matrix.  9) Tubular product according to claims 3 and 7, characterized in that the liquid lubricant is essentially in the liquid state and essentially in the diffused state in the plastic, practically without wetting or the outer surface , nor the interior surface of said matrix.  10) Tubular product according to claim 9, characterized in that the liquid lubricant constitutes an additive, the proportion of which is at least equal to 0.02% by weight of the plastic matrix, and in particular between 0.02% and 0, 08% by weight of said matrix.  11) Tubular product according to claim 10, characterized in that the proportion of dry lubricant / liquid lubricant is at least equal to 5%, and is between 5% and 20%.  12) Tubular product according to claim 1, characterized in that the solid tube (1) is an installation conduit (Figure 1), and the inner surface of the latter is the dry friction surface (2).  13) Tubular product according to claim 1, characterized in that the solid tube (1) is a protective sheath of a cable (Figure 2), and the outer surface of this sheath is the dry friction surface (2) .  14) Tubular product according to claim 12, characterized in that it comprises at least one cable (5) or a pipe contained in the installation duct.  15) Tubular product according to claim 12, characterized in that the installation duct (1) comprises at least two layers (6, 7), in particular concentric, optionally constituted by respectively different plastics, one (7) exterior, and the other (6) interior in which said surface layer (3) is integrated.  16) Tubular product according to claim 1, characterized in that the surface layer (3) is discontinuous, following the periphery of the solid tube, and corresponds for example to ribs (9) or longitudinal grooves.  17) Tubular product according to claim 1, characterized in that the surface layer (3) is continuous, following the periphery of the solid tube.