EP1089833B1 - Method for stripping and sanitizing a container inner surface and implementing device - Google Patents

Description

The present invention relates to a pickling process and sanitizing the internal surface of a container, for example made of wood, made of metal, concrete or any other material, in particular a wooden barrel having a surface layer of an organic matter deposit and / or mineral, in particular a deposit of tannin resulting from the breeding of a wine on tap, as well as a device for its implementation.

We will be more particularly interested in the rest of the description in wooden barrels, but it should be understood that the invention is in no way limited to it and can be applied to any type of container, whatever its material.

During the aging period of barrel wines, we admit generally that wood transfers various substances to wine, such as furans, lactones, aldehydes, phenol acids, phenols and ketones. The barrel puts the wine in a balance oxidant and acts as a kind of micro-doser of oxygen, which allows a first oxidoreductive aging of the wine. We consider generally that a new barrel transfers to wine from tannoid substances while an old barrel transfers wood decomposition substances. One year barrel, that is to say a barrel having already been used for the aging of a wine during a year, generally gives a pure wood taste to the wine, while a six-year-old barrels generally give a taste of rancio.

For the aging of certain wines, we also use wooden barrels whose interior has been burned on the surface, to transfer other substances, such as phenol compounds, furanic and color aldehydes.

Most often, a barrel can be used to raise up to four wines, for a period of 4 to 6 years. After this period, the barrel does not can no longer be used as a breeding tool, because the wine has penetrated about 5 to 10 mm in the thickness of the barrel which has a thickness approximately 22 to 27 mm, this penetration of the wine causing a clogging of wood pores by tannin deposits and by transformations of wood compounds, such as compounds phenolic, tartaric acid, etc., which prevents transfers substances between wood and wine, which transfers are essential for wine aging. These old barrels could still serve as storage containers, but this is generally not the case, because microbial accidents can occur during storage between the wine and the deposits covering the internal surface of the barrel.

For aging barrels, the quality of the wood used is very important and in French vineyards, we generally use wood from oaks around 150 to 300 years old, which therefore have a very long renewal in the face of very strong recent demand acceleration.

To reduce the cost of barrels and save heritage national limited in oaks, we have already proposed to carry out a renovation of the barrel.

One solution is to perform a mechanical pickling, using from a planer or a sander, from inside the barrel, then to possibly burn, to find the characters organoleptics characteristic of new barrels. However, this solution is long and expensive to implement and does not allow to sanitize the barrel against microbial infections. In addition, a such mechanical pickling results in the removal of a significant thickness from the barrel, several millimeters, which limits the number of renovations possible.

Another solution is to perform chemical maintenance of the barrel, but this solution is very heavy to implement and expensive.

In addition, current renovation processes are yielding results rather disappointing for the quality of the wines, because too intense pickling leads to a "plank" taste by refurbishing the raw wood, then that too light stripping has no effect. In addition, during the renovation from the barrel, it is difficult to reproduce the traditional burning initial, because when the barrel is burnt too much, it develops strange characters.

GB-A-2,316,528 describes a device in accordance with the preamble of claim 15. This device known involves an ultraviolet laser.

The object of the invention is to propose a pickling process and sanitizing the internal surface of a container, which is both simple to implement and which allows a number of renovations very high.

The invention is based on the principle of a laser renovation which ensures precise, selective and temperature-controlled pickling, performing a photoablation of biological stains, for example fungi, mold, polychlorophenol compounds and chloro-anisoles, and / or mineral stains that have settled on the inner surface of the container. Biological defilements having physical characteristics different from those of the constituent material the container, the rise in heat during the absorption of light produced by the laser will be faster on the deposition of organic matter and / or mineral only on the container, which eliminates the biological and / or mineral soils without causing transfer energy in depth of the material constituting the barrel.

To this end, the invention relates to a pickling process and for sanitizing the internal surface of a wooden, metal, concrete or other material, having a surface layer of a deposit organic and / or mineral matter, including a tannin deposit resulting from the aging of a wine in barrels, characterized in that it consists of applying pulsed radiation to the surface to be treated produced by an intense optical source, each pulse having a sufficiently short duration and an energy density per unit area to be treated high enough to cause the sublimation of said surface layer, the surface of the container thus exposed being sanitized by the heat given off by the radiation. Thanks to the invention, the layer of organic and / or mineral material is sublimated, which generates a gaseous plasma in the form of fumes, which avoids the disadvantages associated with the use of a solution aqueous.

Advantageously, each pulse has a duration of between 10 and 200 ns and an energy density of between approximately 6.5 and 9 J / cm ² . Preferably, each pulse has a duration of approximately 100 ns and an energy density of approximately 8 J / cm ² .

A long pulse duration, for example of the order ms or µs, would transfer energy into the material constituting the container and a low speed of ejection of sublimated soiling, while organic deposits must be removed and / or minerals over a small thickness, quickly and without consuming too much energy. With a pulse duration of around 100 ns, we obtains a very high peak power for the beam, which causes a high ejection speed of the organic material and / or sublimed mineral and low heat diffusion in the material constituting the container.

According to another characteristic, the method consists in applying on each surface unit from 2 to 20 pulses, preferably between 4 and 10 pulses, depending on the type of material of the container to be treated, the state of the surface to be treated and the thickness of the organic and / or mineral deposit.

According to yet another characteristic, the radiation is determined to cause a quasi-adiabatic sublimation of the layer of organic and / or mineral matter on the surface to be treated. We can foresee, in particular, that 80% of the heat produced by the radiation is absorbed by the surface layer during the sublimation, the remaining 20% being dissipated in the thickness of the material constituting the container.

Preferably, each pulse causes sublimation approximately 20 µm thick on the surface to be treated.

Advantageously, the method consists in evacuating the plasma gaseous produced during sublimation, by aspiration or blowing of a inert gas or air.

According to another characteristic, the intense optical source is a laser source, for example a CO ₂ laser source at atmospheric pressure and with transverse excitation.

According to another aspect of the invention, for a wooden container, the process consists, simultaneously or after the step of pickling and sanitizing, to be applied to the surface to be treated second intense optical radiation, said second radiation being applied continuously or almost continuously for a period of time sufficiently long and with an energy density per unit area to be treated high enough to cause burning of the wood area. Advantageously, this second radiation is applied by a laser source with defocused beam or by beam scanning.

Preferably, the second radiation has a power density of between 100 and 200 W / cm ² for an application time of the order of 0.05 to 0.2 seconds. In this case, the second radiation preferably has an energy density per unit area to be treated of the order of 20 J / cm ² .

Although the energy density received by wood, in the case of burning or browning, greater than that for pickling, the total energy is transferred during the burn over a long period, which allows the heat to diffuse in the wood and to carbonize it in surface, while, in the case of pickling, energy is applied to a very short duration, causing an instant sublimation of the organic layer.

In another variant, the second radiation is applied by an infrared or ultraviolet lamp, for example a lamp having a power of 70 W for a duration of application of several minutes, at a distance of a few centimeters between the source of radiation and the surface to be treated.

The invention also relates to a device for the implementation the above process, according to claim 15.

Advantageously, the robot is able to rotate said head optical at an angle of about 120 ° relative to the axis of the container.

According to another characteristic, the robot is able to train in relative rotation about the axis of the container the optical head relative to the container.

According to yet another characteristic, the robot is able to drive in axial translation, either the container or the optical head, which can in this case be connected to a telescopic waveguide or extensible.

Preferably, the optical head is located at a distance from the surface to be treated on the order of a few tens of centimeters.

According to another aspect of the invention, the device comprises a camera for viewing the surface treatment, said camera being connected to a display screen and to the central control unit for visually control the surface treatment in real time.

According to another characteristic, the optical head is arranged to penetrate inside the container, for example by the bung of a barrel in wood, or through a hole specially arranged in one of the flanges of bottom of the barrel, or by one of the bottoms of the barrel whose flange was took of.

Advantageously, the device comprises a pipe suction or blowing fumes generated by pickling.

The purpose of evacuating the gaseous plasma is, on the one hand, to avoid any recontamination of the treated and surrounding surface, on the other hand, any interference with the optical beam and with the possible camera of visualization.

According to another characteristic, the device comprises a second intense optical source to produce the second radiation for burning a wooden container.

To better understand the object of the invention, we will describe now, by way of purely illustrative examples and not limiting, several embodiments shown in the drawing Annex.

• la figure 1 est un schéma synoptique fonctionnel du dispositif de l'invention adapté pour un essai sur un échantillon ;
• la figure 2 est un schéma simplifié partiel du dispositif de l'invention pour le décapage d'un fût ; et
• la figure 3 est une vue agrandie d'un détail de la figure 1, montrant une zone de décapage.

On this drawing :

• FIG. 1 is a functional block diagram of the device of the invention adapted for a test on a sample;
• Figure 2 is a partial simplified diagram of the device of the invention for pickling a barrel; and
• Figure 3 is an enlarged view of a detail of Figure 1 showing a pickling area.

In Figure 1, there is shown a laser source 1 which is intended to produce a laser beam 2 towards a lens convergent 3 which converges a beam 4 towards a stave 5 of a wooden barrel. The stave 5 is carried by a robot 6. A central unit 7 is connected by a robot control interface 8 to robot 6, and by a synchronization interface 9 with the source laser 1. The central control unit 7 is associated with a peripheral 10 consisting of a screen 11 and a keyboard 12. A camera 13 can also be connected to the central control unit 7, as indicated in dashed lines, to visualize the surface treatment of the stave 5. Although the installation illustrated in figure 1 is suitable for testing a sample 5, the general principle of the invention remains substantially the same.

In FIG. 2, we see a wooden barrel 14, swollen in the middle, and made up, in a known manner, of assembled and encircled staves, one of the bottoms of which is closed by a circular flange 16 and the other of which bottom is open towards the laser source 1. The barrel 14 rests by the convex external surface of its side wall 17 on rollers rotary 18 which are intended to be rotated about an axis parallel to the axis 15 of the barrel 14, by the aforementioned robot 6.

The aforementioned converging lens 3 is integrated in a head focusing optics 19 which is connected to the laser source 1 by a guide wave 20 which is provided here telescopic in the axial direction materialized by the double arrow L, but could alternatively be extensible. The waveguide 20 is substantially aligned with the axis 15 of the barrel 14. The optical head 19 is articulated relative to the guide of waves 20 on a horizontal axis 21 perpendicular to the axis 15 of the barrel. The optical head 19 is designed to pivot around this axis 21 at an angle  of approximately 120 °, so that the beam converges 4 coming out of the optical head 19 can pivot between a position (not shown) where said beam 4 is aligned with the axis 15 of the barrel, in direction of the bottom flange 16, and an inclined position of 30 ° by vertical, towards the open bottom of the barrel. So the optical head 19 can scan the entire internal surface of the barrel, except know the internal surface of the bottom flange 16 and the internal surface concave of the side walls 17 of the barrel.

The rotating rollers 18 make it possible to rotate the barrel 14 around its axis 15, as indicated by arrow 22. Of course, one could alternatively provide the axially rotary waveguide 20, instead of rotating the barrel 14.

We see in Figure 3 that the beam 2 from the optical source 1 is transformed into a converging beam 4 by the lens 3, to make converge this beam over a predetermined limited area of the internal wall of the stave 5, to sublimate a layer of deposit of organic matter 23. The fumes produced by the sublimation of the layer of organic material 23 can be vacuumed or blown out through a pipe 24 inserted in the barrel 14, preferably near the treatment area on a stave 5.

The smoke suction or blowing pipe 24 can be associated with the camera 13. The camera 13 is preferably provided with a autofocus lens, allowing to visualize the surface to be treated on the control screen 11, and therefore the operator to control, without risk, the quality of pickling and burning.

Thanks to the combined movements of the waveguide 20 in the axial direction of the barrel, of the axial rotation of the barrel 14 and of the limited angular pivoting of the optical head 19, the entire internal surface of the barrel.

Stripping step

During the stripping tests which were carried out, it was found that with a pulsed laser beam having an energy density of 2 J on a surface to be treated of 24 mm ² , namely an energy density of 8 J / cm ² which corresponds to a power density of 80 MW / cm ² , for a pulse duration of 100 ns, each pulse causes the removal of 20 µm of wood thickness, which is negligible compared to l thickness of a stave which is generally between 22 and 27 mm. Indeed, the deposition of organic matter is generally intimately linked to a surface layer of the internal surface of the wood, which causes, during pickling, the removal of organic matter and a layer of wood of corresponding thickness which is impregnated with said layer of organic material.

The laser source is preferably a CO ₂ laser at atmospheric pressure and transverse excitation (TEA), having a wavelength of 10.6 μm, with a beam exit section of 16 × 32 mm.

The focusing head will preferably have a large focal length relation to the distance between said head and the surface to be treated, in order to reduce the positioning accuracy of the head relative to the section beam interaction with the surface to be treated. The distance between the optical head 19 and the surface to be treated can vary between 30 and 50 cm.

To industrialize the process, several laser sources could be coupled in parallel, for example three sources, each having a pulse frequency of 200 Hz, to alternately deliver energy on the same optical path, which makes it possible to obtain a frequency of global pulses of 600 Hz, each pulse having for example an energy density of between 150 and 200 mJ / cm ² , the speed of movement of the laser beam relative to the surface to be treated being determined by the central processing unit control which includes a computer, so as to obtain an energy density of 8 J / cm ² on the surface to be treated.

Burning stage

• avec une source laser à CO₂ ayant une puissance de 3 kW et générant un faisceau défocalisé ayant une densité de puissance de 180 W/cm², la durée d'exposition nécessaire est supérieure à 50 ms ;
• avec une source laser à CO₂ ayant une puissance de 10 W et générant un faisceau à balayage ayant une densité de puissance de l'ordre de 10 W/cm², la distance entre la tête de focalisation et la surface à traiter étant de l'ordre de 60 cm, la durée d'exposition nécessaire est nettement plus longue, de l'ordre de 5 mn, pour obtenir le brûlage souhaité, mais dans ce cas, le brûlage affecte une profondeur de l'ordre du mm et la quantité d'énergie déposée est bien plus importante ;
• avec une lampe à infrarouge de 1 µm de longueur d'ondes, ayant une puissance de 80 W et un angle d'ouverture du faisceau de 28°, à une distance d'environ 3 cm de la surface à traiter, la durée d'exposition nécessaire est nettement plus longue de l'ordre de 9 mn.

For the burning of wood, three different solutions have been tried:

• with a CO ₂ laser source having a power of 3 kW and generating a defocused beam having a power density of 180 W / cm ² , the required exposure time is greater than 50 ms;
• with a CO ₂ laser source having a power of 10 W and generating a scanning beam having a power density of the order of 10 W / cm ² , the distance between the focusing head and the surface to be treated being l order of 60 cm, the exposure time required is much longer, of the order of 5 min, to obtain the desired burn, but in this case, the burn affects a depth of the order of mm and the quantity much more energy is deposited;
• with an infrared lamp of 1 µm wavelength, having a power of 80 W and a beam opening angle of 28 °, at a distance of approximately 3 cm from the surface to be treated, the duration of exposure required is significantly longer on the order of 9 min.

These three burning solutions are not illustrated in the drawing, but they could be mounted on the robot so as to couple the intense optical source for burning and laser source for stripping. One could also provide a single bi-beam optical source producing the radiation simultaneously or successively pulsed pickling and continuous burning radiation. These two radiation can be produced simultaneously because their interaction characteristics with the surface to be treated are clearly different, which avoids any interference.

For pickling, the number of pulses per unit area, the duration of each pulse and the energy density per unit of surface, can be determined according to the state of the surface, the quality of the wood and the thickness of the layer to be removed.

For burning, exposure time and power density of the intense optical source will be determined according to the degree of burn desired by the user.

Although the invention has been described in conjunction with several particular embodiments, it is obvious that it is not there in no way limited.

Claims (20)

1. Process for stripping and sterilizing the internal surface of a wooden container (14), having a surface layer (23) of a coating of organic and/or mineral material, especially a coating of tannin resulting from the maturation of a wine in a cask, characterized in that it consists in applying, over the surface to be treated, pulsed radiation (4) produced by an intense infrared optical source (1), each pulse having a duration which is short enough and an energy density per unit area to be treated which is high enough to cause the sublimation of the said surface layer, the surface of the wood thus stripped being sterilized by the heat released by the radiation.
2. Process according to Claim 1, characterized in that each pulse has a duration of between 10 and 200 ns and an energy density of between about 6.5 and 9 J/cm².
3. Process according to Claim 2, characterized in that each pulse has a duration of about 100 ns and an energy density of about 8 J/cm².
4. Process according to one of Claims 1 to 3, characterized in that it consists in applying, over each unit area, from 2 to 20 pulses, preferably between 4 and 10 pulses, depending on the type container to be treated, the state of the surface to be treated and the thickness of the organic and/or mineral coating.
5. Process according to one of Claims 1 to 4, characterized in that the radiation is determined so as to cause a quasi-adiabatic sublimation of the layer of organic and/or mineral material on the surface to be treated.
6. Process according to Claim 5, characterized in that 80% of the heat produced by the radiation (4) is absorbed by the surface layer (23) during the sublimation, the remaining 20% being dissipated within the thickness of the wood.
7. Process according to one of Claims 1 to 6, characterized in that each pulse causes the sublimation of about 20 µm thickness of material on the surface to be treated.
8. Process according to one of Claims 1 to 7, characterized in that it consists in evacuating the gaseous plasma produced during the sublimation, by sucking it up or blowing it out using an inert gas or air.
9. Process according to one of Claims 1 to 8, characterized in that the intense optical source is a laser source, for example a CO₂ laser source at atmospheric pressure and with transverse excitation.
10. Process according to one of Claims 1 to 9, characterized in that it consists, simultaneously with or subsequent to the step of stripping and sterilizing, in applying over the surface to be treated of the wooden container a second intense optical radiation, the said second radiation being applied continuously or quasi-continuously for a duration which is long enough and with an energy density per unit area to be treated which is high enough to cause scorching of the wood on the surface.
11. Process according to Claim 10, characterized in that the second radiation is applied by a laser source with an out-of-focus beam or by beam scanning.
12. Process according to Claim 10 or 11, characterized in that the second radiation has a power density of between 100 and 200 W/cm² for a duration of application of about 0.05 to 0.2 seconds.
13. Process according to one of Claims 10 to 12, characterized in that the second radiation has an energy density per unit area to be treated of about 20 J/cm².
14. Process according to Claim 10, characterized in that the second radiation is applied by an infrared or ultraviolet lamp.
15. Device for implementing the process according to one of the preceding claims, comprising

    an intense optical source (1) capable of producing pulsed radiation (2);

    a waveguide (20) connected to the optical output of the source;

    an optical focusing head (19) connected to the output of the waveguide, in order to define the cross section of interaction with the surface to be treated and thus the energy density to deposit per unit area;

    a robot (6) for the relative movement between the optical head and the internal surface of the container to be treated, characterized in that the said source is an intense infrared optical source, each pulse of which has a duration of between 10 and 200 ns and an energy density of between 6.5 and 9 J/cm² for the stripping and the sterilization of the internal surface of a wooden container (14) and in that it comprises a central control unit (7) in order to control and synthesize, on the one hand, the source parameters such as the number of pulses to be applied per unit area, the impulse frequency and the radiation power of the source, and on the other hand, the movements to be carried out by the robot in order to treat the entire internal surface of the container.
16. Device according to Claim 15, characterized in that the robot (6) is capable of making the said optical head (19) pivot through an angle () of about 120° with respect to the axis (15) of the container (14), of driving the optical head (19) in relative rotation about the axis (15) of the container (14) with respect to the container, and in driving the container in relative axial translation with respect to the optical head.
17. Device according to one of Claims 15 and 16, characterized in that it comprises a camera (13) for displaying the surface treatment, the said camera being connected to a display screen (11) and to the central control unit (7) in order to control the surface treatment visually and in real time.
18. Device according to one of Claims 15 to 17, characterized in that the optical head (19) is arranged so as to penetrate inside the container (14), for example by the bunghole of a cask made of wood, or by a hole specially made in one of the heading pieces (16) of the cask or else by one of the ends of the cask from which the heading piece has been removed.
19. Device according to one of Claims 15 to 18, characterized in that it comprises a pipe (24) for sucking up or blowing out smoke generated by the stripping.
20. Device according to one of Claims 15 to 19, characterized in that it comprises a second intense optical source for producing the second radiation for scorching a container made of wood.

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