EP0523224B1 - Device for strippping a coating - Google Patents

Abstract

A heat stripper for removing a coating such as paint, varnish or adhesive from a substrate to which it adheres is characterized in that it comprises a steam generator (3), means (27, 28) for superheating the steam produced by the steam generating means (3), and means (7) for spraying the superheated steam onto the coating.

Description

The present invention relates to a technical stripper intended for the stripping of surfaces covered with a coating such as, for example, a paint, a varnish or an adhesive.

Several methods and apparatuses allowing the stripping of such coatings are currently known.

Among these, a commonly used process is chemical pickling. There are thus on the market strippers intended to be spread on a surface to be stripped, for example using a brush. Such strippers chemically attack the coating, which can then be gradually removed by scraping, for example using a metal spatula. This pickling process generally gives good results, but it is often necessary to repeat a large number of times the operations of depositing pickling product and then scraping. In addition, the application of these products is often unpleasant, even dangerous, especially for the skin and the eyes of the user, because they are relatively toxic, and can give off harmful vapors, not only during their application, but also several days after this, due to their ease of penetration into pickled substrates. Finally, these products tend to soak pickled supports, in particular porous supports such as wood, and abundant rinsing is generally necessary to restore a reusable support surface.

Another known pickling process is thermal pickling which is carried out using heaters, either with pulsed hot air, the temperature of which is typically between 200 ° C. and 550 ° C., or with an open flame. , at a temperature generally around 750 ° C. The principle of pickling according to this process consists in separating the coating from its support by indiscriminately playing on the various transformations undergone by the coating when it is brought to high temperatures, such as cracking, blistering, softening or combustion. The coating thus cracked, softened or charred, is then scraped off. Combustion takes place as soon as the jet of hot air or the flame brings the coating to a temperature at least equal to that of its point of combustion, which is frequent because the temperatures of the points of combustion of most of the current coatings are lower at temperatures reached by heat guns.

This type of thermal pickling has its own limits in its effectiveness. Indeed, by burning easily coating, these devices also tend to burn, at the same time, the support thereof, or at least to darken it superficially, or even in depth, since the combustion temperature of many supports, including that of wood , is often below the combustion temperature of the coating. It is therefore difficult to restore the support with a quality allowing it to be left as is.

This type of thermal pickling also has the drawbacks of often generating strong, particularly unpleasant odors, both for the user and those around him, and for emitting a significant noise which can prove tiring during long stripping sessions.

Finally, the use of open flame strippers poses safety problems when they are used in premises in which volatile flammable products are stored, which is frequently the case on construction sites.

Also known from patents EP-A-0 323 328 and EP-A-0 159 134 are steam generators intended for use in devices for taking off wall coverings in which water vapor is produced in an enclosure containing a temperature close to 100 ° C. and then projected onto the surface of the covering to be peeled off. Such devices, due to the low temperature of the steam used, do not allow effective stripping of paints or varnishes.

It has also been proposed, in patent FR-A-2 621 259, again with the aim of ensuring takeoff of wall coverings, to use a steam generator in which the water vapor is produced in an enclosure rising in pressure, so that the temperature of the water vapor produced is of the order of 120 ° C.

The steam generator member located inside a reservoir body has a steam outlet duct, a steam circuit cut-off valve being provided in the steam circuit duct.

The object of the present invention is to propose an apparatus intended in particular to strip all types of surfaces covered with a coating adhering by itself to a support, such as for example a paint, a varnish or an adhesive, effectively, fast, without emission of toxic vapors, without noise, and without damaging the coating support which provides a blank support and immediately ready for further processing.

The present invention thus relates to a heat gun intended for the removal of a coating, such as a paint, a varnish or an adhesive, adhering by itself to a support, comprising a steam generator, characterized in that it includes means for overheating the steam produced by the steam generator and means for projecting superheated steam onto the covering, the projection means being in free communication with the steam generator.

The Applicant has demonstrated, by tests, that most of the paints, varnishes and adhesives detach from their support when they are subjected to a jet of water vapor, at a temperature between 100 ° C. and 450 °. C, without burning the coating or the support.

Additional tests carried out by the applicant consisted in examining the behavior of several coatings and supports, when they are subjected to a jet of hot air and to a jet of hot steam moving at a speed of approximately 2 to 5 centimeters / second, as a stripping tool would do. The stripping, in particular of different types of glycerophthalic paint, vinyl paint, polyurethane varnish, was thus tested comparatively. In general, the treatment under a jet of steam without combustion takes place more quickly than under a jet of hot air, and this for temperature differences of at most a few tens of degrees. The separation of sub-layers has proved relatively easy under a jet of superheated steam, and often impossible under a jet of hot air without partial combustion of the support, in particular when the latter has raised parts.

The Applicant has thus established that the steam used in the process and the stripper according to the invention derives its effectiveness from two essential effects. A first effect consists in causing a rapid warming of the coating by the implementation of two thermal transfer phenomena, namely a first thermal transfer phenomenon consisting of a condensation of part of the vapor projected on the coating, which yields over there last its latent vaporization energy, such a phenomenon persisting as long as the coating has not reached the vaporization temperature of water, (that is to say around 100 ° C.) and a second phenomenon of thermal transfer, constituted by the convection of the vapor on the coating, the projected vapor yielding part of its heat energy to the coating. Under these conditions, the strippers according to the invention therefore provide, at an equal temperature for heating the coating, a higher heat flux than the thermal strippers of the prior art. Thus, when the latter provide, for a gram of air at 400 ° C., an amount of heat of approximately 380 joules, a scraper according to the invention provides an amount of heat of 2240 joules. By this double thermal transfer, the coating temperature is quickly brought to 100 ° C, then beyond, depending on the temperature of the sprayed steam. This results in a significant transformation of the coating, generally the greater the higher the temperature of the vapor. This transformation is sufficient so that the coating can then be easily removed by scraping. Thus, for the same temperature of the heat flow, the stripper according to the invention proves to be much more efficient than the thermal strippers of the prior art.

The stripper according to the invention also makes it possible, consequently, for a quantity of heat supplied equal to that of a thermal stripper, to deliver a heat flux whose temperature is much lower than that delivered by the latter. Such a possibility is particularly advantageous when the support on which the coating is to be stripped is sensitive to temperature.

A second effect consists in delaying the combustion phenomena due to the local presence of water vapor and condensed water on the coating. This effect, which is added to the possibility of pickling at lower temperatures, with an equal heat flow, make the scraper according to the invention an apparatus particularly suitable for stripping coatings covering temperature-sensitive supports.

In other words, the use of superheated steam makes it possible to carry out a pickling benefiting from the advantages of thermal pickling and not having the drawbacks thereof.

Preferably, the steam is superheated, prior to being sprayed, at a temperature of the order of 200 ° C to 450 ° C. Indeed, many coatings, such as glycerophthalic paints, lacquers or most varnishes, can only be effectively treated with steam at fairly high temperatures. Only a few coatings, such as water-based paints, are effectively steam treated at around 100 ° C.

According to the invention, the steam is projected onto the surface to be stripped using projection means, designed so as to provide a relatively concentrated jet of steam well oriented towards the surface to be stripped. This concentrated steam jet allows an efficient heat transfer, and allows a rapid treatment of the coating which can then, in a second phase, be scraped and removed.

The Applicant has observed that the treatment thus obtained of certain coatings tends to gradually fade when they are no longer subjected to a jet of steam. It is therefore preferable to scrape off the coating treated with steam immediately after spraying it. This is why the device according to the invention comprises scraping means, consisting for example of a metal blade or a metal brush, which are preferably arranged near the outlet port of the superheated steam. These scraping means can be integral with the stripper, so that, in a single movement of translation of the latter against the surface to be stripped and therefore in a single step, the coating is successively treated with superheated steam and then scraped off.

According to the invention, steam can be produced by any type of steam generator and, in a particularly advantageous manner, by steam generators of the type with porous body, such as those described in French patents FR-A-2,341,340 and FR-A-2 420 731. These generators have, in fact, the advantage of being quick to vaporize and also function in all positions. They include in particular a porous element impregnated, at least partially, with the water to be vaporized, and means for heating the water contained therein. These heating means may consist, for example in a known manner, of electrodes between which an electric current is passed, these electrodes being arranged in contact with the porous element or inserted therein, and / or of a or several electrical resistances, in contact with or inserted into the porous element.

In an advantageous form of implementation of the invention, which makes the scraper portable and autonomous, the steam generator is housed near the other elements (handle, temperature raising device, means for spraying steam and means scraping), in mechanical continuity.

In another embodiment of the invention, the steam generator is separated from the other elements constituting the scraper, and can for example be integrated into a sled on casters, such as those with which certain floor cleaning devices are fitted. In the latter case, the appliance is supplied with steam, for example, by means of a pipe, preferably flexible, connecting the steam generator to the stripper.

The superheating of the steam can be obtained, in a simple and known manner, by the simple passage of the latter, after its emission by the steam generator, over a heated resistor placed in a tube. Since the surface temperature of such a resistance is conventionally around 600 ° C., the vapor can be easily brought to such a temperature, as long as its passage through the tube lasts long enough. Intermediate temperatures can also be easily obtained, for example by modifying the electric power supplied to said resistor, or even by modifying the time of passage of the vapor along the latter.

In a particularly advantageous embodiment of the invention, the scraper comprises means for adjusting the flow rate and the temperature of the sprayed steam. It is thus possible to optimize the operating parameters of the stripper as a function of the coating to be stripped and of its support.

In another form of implementation of the invention, the vapor projection means of the stripper are located within a confinement chamber, open only towards the face applied against the surface to be stripped. This confinement chamber makes it possible to prevent the vapor from rapidly dissipating its heat in the surrounding air, and allows it to reach the surface to be stripped with a temperature close to that at which it was emitted, and therefore to optimize thermal effects on the coating.

One of the edges of said confinement chamber can itself constitute a scraping blade. In this case, the steam is sprayed by pressing the confinement chamber, which contains the steam outlet orifice, onto the coating to be stripped, then the coating treated by translation is scraped off on the surface to be stripped from said chamber, the scraping edge allowing the coating to be removed immediately after its treatment with steam. The pickling efficiency is then optimal, since the treated coating does not have time to cool, and the pickling operation is thus particularly effective.

The scraping means can also consist for example of a metal blade, or for example of a metal brush. In the case of a wire brush, this can be placed, by example, near the vapor projection means, so as to brush the surface to be stripped immediately after the vapor projection, by simply moving the device. The vapor projection means can also, for example, be housed above or in said brush, the vapor being thus released by the brush itself. This brush can be actuated in rotation, for example by a motor, in order to obtain a scraping of greater efficiency and with less physical effort.

Advantageously, the scraper according to the invention can be provided, on its upper part, with a location on which one can exert pressure with one hand, so as to help scraping. It may also include means for cleaning the scraping means, so as to rid them of coating residues which could accumulate as the pickling takes place. For example, when the scraping means consist of a metal blade, a second blade of the same width, or cleaning blade, can slide to the end of the scraping blade, thereby peeling off the residues accumulated on the scraping blade. The actuation of such a cleaning blade can be manual, or this blade can be moved by a spring or any other mechanical means, which makes it slide automatically along the scraping blade, when the latter is no longer applied to a area.

• La figure 1 est une vue en coupe verticale et longitudinale d'un mode de mise en oeuvre du décapeur suivant l'invention.
• La figure 2 est une vue en coupe longitudinale suivant la ligne II-II de la figure 1 du décapeur représenté sur celle-ci.
• La figure 3 est un schéma représentant le circuit d'alimentation électrique du décapeur suivant l'invention.
• La figure 4 est une vue en perspective et coupe transversale de l'enceinte principale montrant le générateur de vapeur mis en oeuvre dans le décapeur suivant l'invention.
• La figure 5 est une vue en perspective du dispositif utilisé pour réaliser la surchauffe de la vapeur produite par le générateur de vapeur.
• La figure 6 est une vue de dessous en perspective du dispositif de projection de vapeur représenté sur la figure 1.
• La figure 6' est une vue en perspective d'une variante de mise en oeuvre du dispositif de projection de vapeur.
• La figure 7 est une vue en perspective de la résistance de chauffage utilisée dans le générateur de vapeur représenté sur les figures 1 et 4.
• La figure 8 est une vue en perspective et coupe transversale de l'enceinte principale montrant une variante de mise en oeuvre du générateur de vapeur.
• La figure 9 est une vue en coupe verticale et longitudinale d'une variante d'un dispositif de projection de vapeur.
• Les figures 10 et 11 sont des vues en perspective de deux variantes de mise en oeuvre d'un dispositif de grattage accouplé au générateur de vapeur.
• La figure 12 est une vue en perspective d'un dispositif permettant d'assurer le nettoyage des moyens de grattage mis en oeuvre dans le décapeur suivant l'invention.
• La figure 13 est une vue en perspective d'une variante d'un dispositif permettant d'assurer le nettoyage des moyens de grattage.
• La figure 14 est une vue en perspective d'une variante de mise en oeuvre d'un décapeur suivant l'invention.

An embodiment of the present invention will be described below, by way of non-limiting example, with reference to the appended drawing in which:

• Figure 1 is a vertical and longitudinal sectional view of an embodiment of the stripper according to the invention.
• Figure 2 is a longitudinal sectional view along line II-II of Figure 1 of the scraper shown thereon.
• FIG. 3 is a diagram representing the electrical supply circuit of the stripper according to the invention.
• Figure 4 is a perspective view and cross section of the main enclosure showing the steam generator used in the stripper according to the invention.
• Figure 5 is a perspective view of the device used to overheat the steam produced by the steam generator.
• FIG. 6 is a bottom perspective view of the vapor spraying device shown in FIG. 1.
• Figure 6 'is a perspective view of an alternative embodiment of the vapor spraying device.
• Figure 7 is a perspective view of the heating resistor used in the steam generator shown in Figures 1 and 4.
• Figure 8 is a perspective view and cross section of the main enclosure showing an alternative embodiment of the steam generator.
• Figure 9 is a vertical and longitudinal sectional view of a variant of a vapor spraying device.
• Figures 10 and 11 are perspective views of two alternative embodiments of a scraping device coupled to the steam generator.
• Figure 12 is a perspective view of a device for cleaning the scraping means used in the scraper according to the invention.
• Figure 13 is a perspective view of a variant of a device for cleaning the scraping means.
• Figure 14 is a perspective view of an alternative embodiment of a stripper according to the invention.

In FIGS. 1 to 3, the scraper according to the invention essentially consists of a main enclosure 1 inside which is placed a steam generator 3, a secondary enclosure 5 containing a device for overheating the steam produced by the steam generator 3, a steam projection device 7, gripping and control means 10, and an electrical circuit 11.

The main enclosure 1 consists of a parallelepipedal housing with a longitudinal axis xx 'made of a plastic material such as polypropylene. The main enclosure 1 comprises, on its upper face, a vertical tube 12 made of polypropylene, intended for filling with water the main enclosure 1, which is welded to the enclosure 1 and which opens out inside the latter. , this tube being provided with a removable closure plug 13.

The steam generator 3 takes place in the main enclosure 1 and is made up of a resistor 15, of cartridge type, that is to say made up of a tubular stainless steel element inside which is housed a electrical resistance proper, with a power of about 600 Watts, this tube being provided, at each of its ends, with a fixing plate 17. These fixing plates 17 are fixed on the opposite side walls of the enclosure main 1, in the center thereof, by any suitable means not shown in the drawing, such as screwing. The rear end of the resistor 15 is provided with a bimetallic strip 19, in thermal contact with the resistor 15, this bimetallic strip 19 being such that in the rest position, its contacts are in the closed position (FIG. 3), said contacts moving to the open position as soon as the temperature exceeds a given threshold of 120 ° C. A porous body 20, consisting for example of rock fibers, with a density of approximately 75 kg / m3, comprising a binder so as to promote its mechanical strength and its impregnation, is placed inside the main enclosure 1 around of the resistor 15, in a slightly compressed state, so as to give it an apparent density, that is to say once compressed, of approximately 110 kg / m ³ , a free space 18 being provided between the surface upper porous body 20 and the upper internal face of the main enclosure 1. Other porous bodies such as quartz wool, cotton wool or silica and alumina complexes, such as that marketed under the brand " Durablanket ", can also be used.

The secondary enclosure 5 is arranged on the front part of the main enclosure 1, and consists of a cylindrical metal casing, for example made of copper, of vertical longitudinal axis yy '. This enclosure 5 is fixed, by any suitable means not shown in the drawing, to the main enclosure 1, and is connected, at its upper part, with the tube 12, by a collecting tube 21. A cylindrical mandrel 25 made of refractory ceramic , pierced in the direction longitudinal yy 'of seven cylindrical channels 27 opening at the upper and lower parts of the mandrel, is placed in the secondary enclosure 5. A wire, for example of kanthal, of resistivity of around 25 ohms per meter, wound on itself, is arranged in each of the seven channels 27, so as to form an electrical resistance 28. The ends K, L of each of these electrical resistors 28 are connected, as shown in the diagram in FIG. 3, and as explained below. after.

The vapor projection device 7 consists of a first metal tube 29 which is fitted, at one of its ends, at the base of the secondary enclosure 5, in a socket 30 integral with the latter, thus establishing communication with the interior of the secondary enclosure 5. The tube 29 is secured, at its opposite end, to a tube 31 which is perpendicular to it, which is closed at each of its ends, and which comprises, on its entire length and at its lower part, a series of holes 33 arranged in staggered rows (Figures 1 and 6).

The gripping and control means 10 consist of a handle 39 comprising, at its lower part, an actuation button 40 of a switch 41 intended to ensure, at the request of the user, the closing of the electrical circuit of the stripper, as will be explained below. The means of gripping and control 10 are extended, at their opposite part, by a casing element 43 fixed on the upper face of the main enclosure 1 and intended to contain the electric circuit 11 of the stripper.

This electrical circuit 11, shown in FIG. 3, essentially comprises three branches supplied by the terminals A and B of the electrical network, via the control switch 41.

The first CD bypass is made up of a warning lamp 45 signaling, when it is on, when the stripper is switched on.

The second derivation EF comprises, in series, the bimetallic strip 19, the contacts of which are closed in the normal position of use and at the terminals I and J of which is arranged a control lamp 46, the heating resistor 15, of terminals J and M, and a power diode 48 at the terminals M and F of which is disposed a switch 50. The bimetallic strip 19 is in thermal relation with the resistor 15, so as to detect an abnormal heating thereof, which may result for example from a lack of water around this resistor 15. During normal operation of the scraper, and when the switch 50 is closed, the current flows through the bimetallic strip 19, the resistor 15 and the switch 50. Under these conditions, the terminals I and J of the indicator lamp 46 are at the same potential, and the latter is off. When, as a result of a lack of water, for example, the temperature of the resistor 15 reaches a limit threshold, the contacts of the bimetallic strip 19 open, thereby interrupting the current supply to the resistor 15. The terminals I and J of the indicator lamp 46 are therefore no longer at the same potential, and this lamp lights up, thus indicating to the user a failure of the stripper. When it is desired to reduce the electric power supplied to the resistor 15, the switch 50 is opened, so that the current passes through the power diode 48 which, ensuring the rectification of alternation in two of the alternating supply current, reduces the power supplied to about half of its nominal power.

The third GH branch is substantially identical to the previous one and is intended to ensure the temperature rise of the steam produced by the resistor 15 which is admitted into the secondary enclosure 5 by the collecting tube 21. This derivation comprises, in series, a bimetallic strip 52, the contacts of which are closed in the normal position of use, the seven resistors 28 mounted in parallel between the terminals K, L and which are intended to ensure the rise in temperature of the vapor, a power diode 54 aux terminals L and H of which is disposed a switch 56. As previously the bimetallic strip 52 is in thermal relation with the resistors 28, so that, following a abnormal rise in temperature thereof, its contacts open and cut the current supply to the resistors 28. As before, the power supplied to the resistors 28 which ensure the superheating of the steam, can be reduced by about half by opening of the switch 56.

Under these conditions, the operation of the scraper is established as follows. Before using it, the user fills the porous body 20 contained in the main enclosure 1 with water, by introducing it through the tube 12, until the water level is flush with the upper part of the porous body 20. The heating resistor 15 is such that, after closing the switch 41, the steam flow reaches its nominal speed after about one minute and the steam enters the collecting tube 21 in the upper part of the secondary enclosure 5, heats up by crossing the channels 27, in contact with the resistors 28, to arrive at the base of the secondary enclosure 5 and exit under pressure by the tube 29 and be sent to the surface to be stripped by the steam projection device 7. Half the steam flow can be obtained by opening the switch 50. Pickling is carried out by lifting the coating treated with steam using scraping means consisting for example of a spatula .

In an alternative embodiment shown in FIG. 8 the steam generator 3 essentially consists of three electrodes 59 extending longitudinally inside the main enclosure 1, along the axis xx ′ thereof, namely a central electrode connected to the 'one of the terminals J of the second lead EF and two electrodes arranged on the opposite lateral internal walls of the main enclosure 1 and which are connected to the other terminal M of the second lead EF. As before, the main enclosure 1 is filled with a porous body, compressed in the enclosure so as to have a density of 110 kg / m2.

As shown in FIG. 6 ', the vapor projection device can, in a particularly simple embodiment, consist of a steam supply tube 29', bent at 90 °, one end of which is connected to the secondary enclosure 5 and the other end is flattened so as to constitute a slot-shaped surface 32 ensuring a concentration of the projected vapor.

It is possible, as shown in FIG. 9, to have on the vapor projection device 7, a chamber for confining the emitted vapor. This chamber essentially consists of a parallelepipedic box 60 open at its lower part, into which opens a steam supply tube 29 'connected to the secondary enclosure 5. In use, the underside of the housing 60 is applied to the coating to be stripped so that the steam released by the vapor spraying device 7 escapes exclusively on the surface to be stripped. This confinement chamber thus makes it possible to concentrate the flow of vapor brought to the surface to be scoured and to limit the heat losses undergone by the vapor so that the temperature of the latter, when it arrives on the coating, is close to its temperature at the outlet of the secondary enclosure 5.

Of course, the stripper according to the invention can be equipped with other different vapor projection devices 7, which are fixed on the secondary enclosure 5 by means of tubes 29 'of the same section as the tube 29 and which are fit like him in the holding sleeve 30.

It is advantageously possible to combine the vapor projection devices 7 with scraping devices 9, which makes it possible to scrape the coating immediately after its treatment with steam, which provides optimum efficiency of the stripper.

Thus, as shown in FIG. 10, a combined vapor spraying and scraping device consists of a steam supply tube 29 ′ opening into a transverse housing 61 consisting of a vertical transverse wall 62 on which is fixed the tube 29 ', an upper wall 64, two side walls 66, and a front wall 68 inclined vertically from top to bottom and from front to back and projecting under the wall 62 of so as to constitute a scraper.

In order to improve the rigidity of the vapor projection / scraping device, the housing 61 can be fixed, by means not shown in the drawing, to the main enclosure 1 and / or secondary 5 of the stripper.

It is also possible, as shown in FIG. 11, to use a vapor projection / scraping device comprising a tube 29 ′, one end of which is connected to the secondary enclosure 5 and the other end to the center of a brush. metallic 70.

In addition, to ensure optimum scraping force, the scraper may be provided, on its upper front part, as shown in FIG. 1, with a gripping element 72 that the operator will use to maintain the scraper and exercise on it the pressure force necessary to obtain the desired degree of pickling / scraping.

Interestingly, the device may include means for cleaning the scraping device 9 making it possible to rid the latter of the coating residues which stick to it during the stripping.

Such cleaning means can be consist, as shown in Figure 12, of a metal frame 76, slidably mounted along a scraping blade 77 by means of two rails 78. This frame 76, when moved downwards, by pressing manually on its upper part, removes, by pushing them away, the coating residues accumulated on the scraping blade 77. The metal frame 76 is held in the high position by means of a bending spring 80 fixed, by one of its ends, to the frame 76 and bearing, by a curved part, on the upper edge of the scraping blade 77. In another embodiment, the frame can be at rest in the low position, lower than the scraping blade 77 , and to be held there also by means of springs, this frame being automatically placed in the higher retracted position, when the scraping blade 77 is pressed against the surface to be stripped, by compression of said spring. An automatic cleaning of the scraping blade 77 is thus obtained during stripping, each time the stripper is raised.

In another embodiment shown in FIG. 13, the means for cleaning the scraping means 9 consist of a small blade 86 pivotally mounted around an axis 87 perpendicular to the scraping blade 77, and sweeping the surface thereof like a car wiper, the blade 86 being kept in the lateral position during pickling.

In another embodiment of the stripper according to the invention, shown in FIG. 14, it consists of a stripper body 89 receiving, by a flexible pipe 91, steam produced by a steam generator exterior, not shown in the drawing. A device for superheating the steam, arranged in a secondary enclosure 5, of the type identical to that described above, is fixed to the front part of the body 89 of the stripper. Steam is admitted into the secondary enclosure 5 by a pipe 93 and leaves it by a steam supply tube 29 to end in a containment chamber 61 secured to the front part of the stripper, the front end part of which is provided with a scraping blade 95. Such an apparatus, since it does not contain a steam generator, can be of a reduced size and weight, giving it excellent maneuverability.

Claims (17)

1. Thermal stripper intended for the removal of a coating such as paint, varnish or glue, adhering by itself on a support, comprising a steam generator (3), characterized in that it comprises means (27, 28) for superheating the steam produced by the steam generator (3) and means (7, 60, 61, 70) for projecting superheated steam onto the coating, the projection means being in free communication with the steam generator.
2. Stripper according to Claim 1, characterized in that the means for superheating the steam are constituted by at least one tube (25) traversed by the steam coming from the steam generator (3), said tube being provided with an electric heating element (28).
3. Stripper according to Claim 2, characterized in that the means for superheating the steam are constituted by a cylindrical mandrel (25) made of refractory ceramics longitudinally traversed by a series of parallel canals (27) containing electric heating resistors (28), these canals (27) being traversed by the steam (3) coming from the steam generator and directed towards the exit of the stripper.
4. Stripper according to any one of the preceding Claims, characterized in that the steam generator is constituted by a porous body (20) in which is stored, in toto, the water to be vaporized, and by means (15, 59) for heating the water contained in said porous body (20).
5. Stripper according to Claim 4, characterized in that the means for heating the water contained in the porous body (20) are constituted by at least two electrodes (59) disposed in contact with the porous body (20), each of these electrodes (59) being connected to one of the terminals (J, M) of an electric current generator.
6. Stripper according to Claim 4, characterized in that the means for heating the water contained in the porous body (20) are constituted by at least one electric resistor (15) disposed in contact with the porous body (20).
7. Stripper according to any one of the preceding Claims, characterized in that the means (7) for projecting the superheated steam are constituted by a tube (29') connected, at one of its ends, to the steam-superheating means (27, 28), and of which the other end is flattened so as to constitute a slot-shaped outlet surface (32) ensuring concentration of the projected steam.
8. Stripper according to any one of Claims 1 to 6, characterized in that the means (7) for projecting the superheated steam are constituted by two tubes, namely a first tube (29) for admission of steam, of which one end is connected to the steam-superheating means (27, 28), and the other end opens out in a second tube (31), closed at each of its ends, and comprising, in the vicinity of its lower generatrix, a series of steam-outlet holes (33).
9. Stripper according to any one of the preceding Claims, characterized in that the steam projecting means (7) comprise a steam admission tube (29') of which one end is in communication with the steam-superheating means (27, 28), and the other end opens out in a containment chamber (60, 61) open over at least a part of its lower surface intended to come into contact, during stripping, with the coating to be stripped.
10. Stripper according to Claim 1, characterized in that it comprises scraping means (68, 77, 95) disposed near the exit of the steam emitted by the steam-projection means (7, 60, 61, 70).
11. Stripper according to Claim 10, characterized in that the scraping means are fast with the steam-projecting means (7).
12. Stripper according to either one of Claims 10 and 11, characterized in that the scraping means are constituted by a metal blade (68, 77, 95).
13. Stripper according to Claim 11, characterized in that the scraping means are constituted by a metal brush (70) at the centre of which opens out one of the ends of a steam-admission pipe (29') of which the other end is connected to the steam-superheating means (5).
14. Stripper according to any one of Claims 10 to 13, characterized in that it comprises gripping means (72) adapted to apply the scraping means in contact with the surface of the coating to be stripped.
15. Stripper according to any one of Claims 10 to 14, characterized in that the scraping means are provided with cleaning means (76, 86).
16. Stripper according to Claim 15, characterized in that the scraping means are constituted by a first blade (77), and the cleaning means of the scraping means are constituted by a second blade (76, 86) applied on the first and mounted mobile with respect thereto.
17. Stripper according to one of the preceding Claims, characterized in that the steam generator (3) is mechanically independent of the other elements constituting the stripper, the vapour produced by the steam generator (3) being conducted to the steam-superheating means (27, 28) of the stripper by means of a flexible pipe (91).

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