FR2469960A1 - METHOD FOR CONTINUOUSLY REALIZING THE COATING OF THE EXTERNAL SURFACE OF A PROFILE, DEVICE FOR ITS IMPLEMENTATION AND PROFILE OBTAINED - Google Patents

Abstract

1. A device for obtaining the coating on a continuous basis of the external surface of a section (2) with a substantially constant cross section, in particular a closed one such as a pipe, by means of a liquid product, comprising means (3) for causing the section to advance along a longitudinal feeding motion through a coating tank (9) comprising an inlet opening provided with a leak proof seal (14) and an outlet opening provided with a semi-leak proof seal (18) capable of being traversed by the section, characterized in that the semi-leak proof seal (18) is, on the internal side of the coating tank, entirely immersed in the liquid product and that it is formed by a hollow tubing (19) of an expanding material and filled by a fluid under with a density close to that of the said liquid product.

Description

The present invention relates to a method for continuously producing the

  coating the outer surface of a substantially constant profile profile, particularly closed such as a tube, to

using a liquid product.

  Numerous methods are known for coating the outer surface of a profile. According to the physical properties

  the product to be applied, and in particular its viscosity

  temperature and pressure, it is sometimes possible to apply it without transformation from its initial conditioning state. This is the case, for example, of polyethylene strips wound helically around tubes, epoxy powder applied by electrostatic powdering, or else

  spray applied paint.

  In other cases it is necessary to transform the product to be applied to bring it to a suitable physical state, for example by raising the temperature and possibly the pressure. It is

  the case for example in the extrusion of ducts or strips.

  However, there are products for which

  existing methods are not satisfactory.

  These are first and foremost products that can not be degraded without risk, raise the temperature to such a level that they have a viscosity suitable for the spraying is possible and have sufficient finesse to

get a regular surface.

  For other products, extrusion is a solution

  uneconomical or imperfect technically.

  This is the case, for example, with certain copolytic adhesives

  lymers for tube coatings. It is known to apply

  extrusion but this solution is related to

  The high oil content of the extruded product does not allow it to penetrate deeply into the cavities of the rough surface of the steel as a less viscous product could do. Therefore, the contact area between

  adhesive and steel is less important and the thickness required

  to obtain the desired adhesion must be increased.

  The present invention aims to overcome these disadvantages by providing a method for the application of products for which the extrusion is not practicable or uneconomical because of the energy consumption or the nature of the product

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  and for which spraying is not possible because it would be necessary to obtain a regular surface to raise

  their temperature to a level that they would be degraded.

  For this purpose, the subject of the present invention is a method for continuously producing the coating of the outer surface of a profile of substantially constant profile, in particular a closed profile such as a tube, with the aid of a liquid product characterized by the that the profile is scrolled in a longitudinal advance movement, which is coated by forming at a point of the profile path a ring of liquid product in contact with the surface to be coated and passed the profile downstream of

  this point through a semi-waterproof joint.

  This longitudinal advance movement may optionally in some cases be completed with a rotational movement, such as when it is desired to coat tubes of large diameter. In a first embodiment, said ring of liquid product is formed by flowing by gravity

  transversely to the profile a film of liquid product.

  Nevertheless, in a preferred embodiment of the invention, said ring of liquid product is formed by passing through the profile a coating tank containing the liquid product, the profile entering the coating tray through a

  seal and exiting through said semi-seal.

  Advantageously, the flow rate of the liquid product in the coating tank is adjusted according to the desired thickness of the coating. Indeed, as the speed of travel of the profile and the length of its periphery are known, it is understood that the

  flow rate of liquid material determines the thickness of the coating.

  - It is also preferably adjusted the pressure exerted by the semi-seal at the periphery of the profile in function

the flow of liquid material.

  In some cases, it may be necessary to heat the

  liquid material contained in the coating tank.

  In this case, a differential heating is preferably carried out between the inlet seal and the remainder of the coating tank. For example, it may be advantageous for copolymer adhesives for the inlet seal to be heated to a higher temperature than the remainder of the tank so that the viscosity is lower in this part where the product is deposited in the cavities. the surface of the profile so that it penetrates more deeply. The temperature in the inlet seal depends on the residence time of the product in the inlet seal at this temperature

  so that the product is not degraded and therefore depends on the thickness

  the final profile to be applied to the profiles and the speed of

scrolling.

  Preferably, the outer surface of the profile is heated prior to coating at a temperature close to

from that of the liquid product.

  In this case the heating is preferably carried out by

radiation.

  This heating mode makes it possible to raise the

  surface temperature of the profile while maintaining a

  the highest possible difference between this temperature and

average temperature of the profile.

  The surface temperature rise of the profile is intended to allow as close as possible to the temperature of the product so that the viscosity of the product is maintained during contact with the surface of the profile as close as possible to what it was before contact so that the

  product penetrates well inside the cavities of the surface.

  Another advantage of this elevation of surface temperature is that it carries the air present in the cavities of the surface of the profile at the highest possible temperature so that during cooling following the path of the profile in the coating tray , the decrease in volume of this air is the largest possible and thus contributes to a better

  penetration of the product into the cavities.

  The temperature difference between the surface temperature of the profile and its mean temperature is intended to allow surface cooling as soon as the product is

  come into contact with the surface of the profile.

  Indeed, it results on the one hand that the air trapped in the cavities is reduced in volume by cooling and

  that the product thus penetrates more into the cavities

so the contact surface.

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  On the other hand, at the exit of the coating tank, the cooling

  deformation of the coating on the profile produced by the heat transfer to the profile whose average temperature is lower, thus makes it possible to have the highest local viscosity possible so that the product flows as little as possible by gravity

  around the profile so as not to disturb the regularity of thick-

  sor. It is also for this purpose that the profile is preferably cooled immediately after passing through the

semi-waterproof seal.

  In the case where the profiles are tubes, they are connected end to end by inner sleeves and are covered

  the junction between these tubes using an adhesive tape.

  The tubes can thus be coated continuously because the adhesive tapes ensure the continuity of the outer surface. The present invention also relates to a device

  for the implementation of the method described above.

  According to the invention this device is characterized in that it comprises means for scrolling the profile in a longitudinal advance movement, coating means for forming a ring of liquid product in contact with the surface to be coated and a semi-tight seal likely to be

crossed by the profile.

  In a preferred embodiment, this device comprises a coating pan having an inlet for the profile provided with a seal and an outlet port at the

  periphery of which is adapted said semi-seal.

  The tank can be completely closed except

  the arrival duct of the product from which it follows that the

is isolated from the outside air.

  This arrival can for example be done from below, the

  product being brought to the coating tank by a volum

  such as a gear pump whose flow is conveniently

  independent of the pressure to the discharge.

  This volumetric apparatus is preferably equipped with a

  variable speed and adjustable motor.

  In an advantageous embodiment, the seal comprises a cylinder whose section is such that the

  distance between its inner surface and the profile is sensi-

  constant around the entire circumference, the watertightness being ensured by the speed of the running of the profile taking into account the

viscosity of the liquid product.

  This distance is a function of the tolerance on the dimensions of the profile to always allow its passage in the

seal.

  The length of the seal is a function of the viscosity of the product under the temperature conditions considered, the minimum speed of travel of the profile and the maximum possible pressure in the coating tank. These provisions make it possible to ensure that the product does not rise against the direction of the running of the profiles further than the end of the joint

  to escape through the opening left free.

  Advantageously, the semi-seal is formed of a hollow coil of extensible material and filled with a fluid under pressure. Advantageously, this fluid has a density close to

that of the liquid product.

  In this case, the inside of the bead can be put into communication in one of its parts with a pressure device

  adjustable. The density of the liquid being close to that of the

  the pressure distribution obtained by the bead on the profile reproduces that which exists inside the container, which possibly compensates for the casting of the product on the profile

  after leaving the bin, between the bin and an applicator

  cation of any other coating or between the outlet of the tank and the solidification of the product or its drying in the case of a paint. It can thus be ensured that the quantity of product injected into the coating tank is evacuated to the surface of the profile and that the distribution of the product around the periphery of the profile is regular, for example at the time of extrusion of the next coating or at the moment of drying. This provides a means to ensure a constant and adjustable coating thickness

over the entire surface of the profile.

  In some cases, the device according to the invention

  comprises means for heating the coating tank.

  In the latter case, it advantageously comprises a

  radiation furnace upstream of the coating means.

  Preferably it also includes cooling means

  downstream of the coating means.

  The present invention also relates to a profile characterized in that it comprises a coating produced by

the process described above.

  Other features and advantages of the invention

  will appear in the following description given as an example

  non-limiting ple of one of its embodiments.

In the attached schematic drawings:

  FIG. 1 is a perspective view of a device

  for the implementation of the process according to the invention,

  FIG. 2 is an axial section of the device

  putting the coating of a tube and, - Figure 3 is a section of the bead forming the joint

  semi-waterproof outlet of the coating tray.

  The installation shown in FIG. 1 comprises a storage grid 1 for sections of tubes 2 to be coated. Downstream of this storage grid is a double drive track 3 capable of pushing the tube sections

one behind the others.

  Following the drive tracks 3 is disposed an electric heating furnace with radiation 4 capable

  to be crossed by the tubes and a device 5 according to the invention.

  vention making it possible to cover the sections of

tubes 2.

  The installation comprises downstream of the device 5 a

  annular extrusion head 6 and a cooling device

  7 at the outlet of which the sections of tubes 2 are dried on

a drying rack 8.

  Figure 2 shows in more detail the device 5.

  This device comprises a coating tank 9 forming a container supplied with liquid product through a pipe 10. The pipe 10 comprises a double envelope so that a space It ensures the circulation of a thermal fluid

  to heat the liquid product passing through the pipe 10.

  The fluid flowing in the space 11 then ensures the heating of the tank 9 by circulating in a space 12 formed between the two envelopes of the tank 9. The space 12 is connected to a pipe of -7-

  output 13 for the evacuation of the thermal fluid.

  The coating tank 9 has an inlet port provided with

  a seal formed by a cylinder 14 with a double envelope, the space

  this between the two envelopes being capable of being fed with thermal fluid through a pipe 16 and another pipe 17 being provided for the evacuation of this thermal fluid. In the case shown in the drawing, where the

  are circular tubes, tray 9 is itself

  even a cylinder whose section is such that the distance between its inner envelope and the tube 2 is constant all the way around. This distance is sufficient for the circulation of the product in the coating tank 9 does not create any loss of

significant load.

  For its part, the diameter of the cylinder 14 of the seal of

  trea is such that given the speed of travel of the tube 2, the liquid product contained in the enclosure 9 can not go up between the inner surface of the inlet seal and the surface

outside the tube 2.

  The coating tank 9 also comprises an outlet orifice at the periphery of which an outlet gasket is provided.

semi-waterproof 18.

  The seal 18 is formed of an expandable strand 19 contained in an envelope 20 (Figure 3). The inside of the flange 19 contains a liquid and is placed in communication with an expansion tank 21 which is itself connected to a source of pressure

  Variable and adjustable compressed air.

  The coil 19 has at its inner periphery a lip 22 (FIG. 3) which, depending on the pressure in the vase

  21, exerts on the outer surface of the tube 2 a pressure

adjustable voltage.

  A set of nozzles 23 fed with compressed air allows

  Moreover, to cool the tubes 2 at the exit of the tank of

duction 9.

  This installation works as follows.

  The sections of tubes 2 are first assembled to each other as and when they advance with the help of

inner sleeves 24.

  The tubes thus assembled are pushed by the provisions

  3 and adhesive tape is available for the ex-

  The interior of the junctions between tubes in order to obtain a smooth surface.

  The tubes which then pass through the furnace 4 are heated

  mainly in their outer zone.

  The tube 2 then passes through the device 5 inside which it is coated with the liquid product contained in the tank.

coating 9.

  The flow of liquid product brought by the channeling

  10 is adjusted according to the desired thickness of the

  coating and the pressure exerted by the semi-

  watertight 18 and itself adjusted according to this flow.

  The liquid product with which the tube 2 is coated

  in the device 5 may for example be a copolymer adhesive.

  At the outlet of the device 5, the tube 2 enters the extrusion head 6 o it is coated with an extruded synthetic material such as for example polyethylene, in a known manner

in itself.

  The tube 2 is then cooled in the device 7 o

  nozzles 25 fed by a conduit 26 provide a spray

water.

  The sections 2 are then separated and placed on the

drying rack 8.

  The invention therefore provides a continuous tube coating plant with products for which extrusion is not suitable and for which spraying is not possible given the temperature at which this is achieved.

spraying should take place.

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Claims (21)

  1. A method for continuously producing the coating of the outer surface of a profile of substantially constant profile,   particularly closed such as a tube, using a liquid product, -   characterized in that the profile is scrolled in a longitudinal advance movement, which is coated by forming at a point of the profile path a ring of liquid product in   contact with the surface to be coated and that the   spun, downstream of this point, through a semi-seal.   2. Method according to claim 1, characterized in that said ring of liquid product is formed by making it flow by gravity, transversely to the profile, a film of liquid product.   3. Method according to claim 1, characterized in that said liquid product ring is made by passing through the profile a coating tray containing the liquid product, the profile entering the coating tray through a   seal and exiting through said semi-seal.   4. Method according to claim 3, characterized in that it adjusts the flow of the liquid product in the tray   coating according to the desired thickness of the coating.   5. Method according to any one of claims 1   to 4, characterized in that the pressure exerted by the semi-sealing gasket at the periphery of the profile is adjusted according to the flow of the liquid product.   6. Method according to any one of claims 3   at 5, characterized in that the liquid product is heated contained in the coating tank.   7. Method according to claim 6, characterized in that one carries out a differential heating between the joint   waterproof inlet and the rest of the coating tank.   8. Process according to any one of claims 1   to 7, characterized in that the outer surface is heated   the profile before coating, at a temperature of   close to that of the liquid product.   9. Process according to claim 8, characterized by 11   that heating is achieved by radiation.   10. Process according to any one of the claims   at 9, characterized in that the profile is cooled -10- 2469960   immediately after passing through the semi-seal.   11. Method according to any one of claims 1   at 10, characterized in that said profiles are tubes that are connected end to end by inner sleeves and that the junction between these tubes is covered with an adhesive tape. 12. Device for implementing the method according to   any of claims 1 to 11, characterized by the   it comprises means for scrolling the profile in a longitudinal advance movement, coating means for forming a ring of liquid product in contact with the surface to be coated, and a semi-tight seal capable of being crossed by the profile.   13. Device according to claim 12, characterized in that it comprises a coating tank having an inlet for the profile, provided with a seal, and an outlet orifice on the periphery of which is adapted said semi-waterproof seal. 14. Device according to claim 13, characterized in that the seal comprises a cylinder whose section is such that the distance between its inner surface and the profile is substantially constant around the circumference, the sealing being provided by the speed scrolling   profile considering the viscosity of the liquid product.   15. Device according to any one of the claims   13 and 14, characterized in that the coating tank   is powered by a positive displacement pump.   16. Device according to any one of the claims   12 to 15, characterized in that the semi-seal is formed of a hollow coil of extensible material and filled with a fluid under pressure.   17. Device according to claim 16, characterized in that said fluid has a density close to that of the liquid product.   18. Device according to any one of the claims   13 to 17, characterized in that it comprises means to heat the coating tank.   19. Device according to any one of the claims   12 to 18, characterized by the fact that it comprises an oven with   radiation upstream of the coating means.   20. Device according to any one of the claims   12 to 19, characterized by the fact that it includes   cooling means downstream of the coating means.   21. Profile characterized in that it comprises a coating produced by the method according to any one of Claims 1 to 11.