OF CHEMICAL PRODUCTS

[001] The present invention relates to an apparatus and a method for providing a tunnel under controlled atmosphere for the photopolymerization/drying of photopolymerizable/dryable chemical products (paints) through the emission of radiations having a pre-defmed wavelength. In particular, the invention relates to a tunnel for the photopolymerization/drying of painted panels made of sundry materials (wood, fibrocement, glass, plastics, etc.) capable of conferring a matt (opaque) finishing to mainly flat panels, as well as to panels having a significant thickness. Moreover, the tunnel allows to confer said matt finish to mainly flat panels, on five of their six sides.

[002] In the art, mainly flat panels mean panels having a surface much bigger than the others, e.g. panels provided with a width of 400-600 mm and a length up to 1200 mm, while their thickness ranges up to 40 mm.

[003] Panels having a significant thickness means panels provided with a thickness ranging 40 to 80 mm, a width of 50-1000 mm and a length up to 2000 mm and beyond.

[004] Raised or shaped panels are panels wherein at least one of the main sides is not planar, but there are provided some reliefs, e.g. in the shape of a rhombus, lozenge or ellipse. Such raised panels are well-known in the art and are used to produce furniture doors (mainly kitchens) and doors.

[005] The surface finish of furniture belongs to two main families:

- Glossy finish, wherein the surface reflects light; in the most extreme cases the glossy finish is reflecting and a mirroring effect occurs;

- Matt finish, wherein the surface does not reflect light; usually such finish is due to the presence of a plurality of microdepressions on the surface of the painted panel, which capture light preventing its reflection like in a mirror. [006] The degree of opacity of finish is usually evaluated with a numeric index ranging 1-100, wherein the panels with glossy finish score around 100, while the panels with matt finish score around 2-5. In the art, a matt finish can have a score up to 30-40, while the finishes having an index of 50-60 are indicated as semi-glossy.

[007] In the art, industrial methods for obtaining such matt finish are known. One of the documents disclosing such a method is e.g. EP219898 IB 1 of IOT Innovative Oberflachentechnologien GMBH. Such document discloses a method wherein a panel coated with monomers and/or oligomers of acrylate and methacrylate undergoes a treatment with a xenon and/or argon excimer emitter and a mercury medium pressure emitter, under an inert gas. Nonetheless, the method of said patent does not allow to obtain a matt finish of raised panels also on their lateral edges, but only on one or both main panel surfaces (in the second case, in successive steps).

[008] It is known that the excimer treatment for being successful must occur in an inert atmosphere, i.e. an oxygen-free atmosphere. The content of oxygen in the natural earth atmosphere is around 21%.

[009] Typically, when working in an oxygen-free atmosphere is necessary, oxygen is replaced with nitrogen (N ₂ ), which is a harmless gas, widely used in industry.

[0010] Other kinds of producing methods under oxygen-free inert atmosphere are known, wherein carbon dioxide (C0 ₂ ) is employed.

[0011] In still other producing methods, argon (Ar) is used. It is worth noting that, differently from N ₂ and C0 ₂ , argon is a gas heavier than atmospheric air, and it tends to become stratified at the bottom.

[0012] In the art, panels to be painted and subsequently dried/fmished are conveyed through closed belt conveyors inside a tunnel containing an inert atmosphere. Typically, two rollers actuate the closed belt; usually one of them is motorized while the other is an idle roller. In lateral view, the closed belt assumes an oval shape, with its two long sides parallel to each other. Panels are carried by the upper outward section (advancement plane, substantially coinciding with the upper outward section), while the lower section is the return section.

[0013] Aim of the present invention is providing a tunnel under controlled atmosphere (oxygen free), inside which a device emits radiations of a pre-defmed wavelength for the polymerization/drying of coated panels.

[0014] This object is achieved by an apparatus and a method having the features of the independent claims. Advantageous embodiments and refinements are specified in claims dependent thereon.

[0015] All the apparatuses according to the present invention share a special configuration of the tunnel inside which panels are conveyed. Said tunnel comprises a plurality of chambers placed in series; inside each chamber, the lumen of said tunnel is variable; the radiation treatment occurs in a point of said tunnel; inside said tunnel a desired gas being supplied (N ₂ , C0 ₂ , Ar), which allows to control the quantity of oxygen present in the atmosphere under which said treatment occurs.

[0016] According to the first embodiment of the present invention, the inert tunnel inside which the panels to be treated are conveyed is provided with a linear path, which lies on the same plane.

[0017] According to further embodiments of the present invention, the inert tunnel inside which the panels to be treated are conveyed is provided with a path extending on a plurality of different levels, the irradiation treatment of panels occurring in a tract of the inert tunnel which is placed at a level from ground different from that of inlet and outlet openings of said tunnel. This allows to obtain a still better removal of oxygen molecules deriving from the atmosphere outside the tunnel. The path of the upper outward section of the tunnel, substantially following a polygonal curve (broken line), can be obtained in two ways:

- Through at least one adjustable roller, preferably two adjustable rollers, which allow/s to modify the path, i.e. the orientation with respect to the horizontal plane and/or the position with respect to the horizontal plane at least of the upper outward section of the belt conveyor (second and third embodiment);

- Using three distinct belt conveyors, placed in series one adjacent to the other, the first of which forms a ramp with respect to the inlet opening, the second of which, in correspondence with the radiation point, is parallel to ground i.e. horizontal, and the third of which forms a ramp toward the outlet opening (fourth embodiment).

[0018] In the case of gaseous nitrogen or carbon dioxide, the second tract of the belt conveyor, parallel to ground, is placed at a higher level with respect to ground than the inlet and outlet openings of panels, while the first tract of the belt conveyor is tilted so as to form an ascending ramp, and the third tract of the belt conveyor is tilted so as to form a declining ramp.

[0019] In the case of argon, due to its atomic weight leading to its stratification on the ground, the path of the belt conveyor is specular, providing a polygonal curve that from the inlet opening descends to the irradiation point, is parallel to ground near the irradiation point, and climbs back toward the outlet openings of panels.

[0020] A first advantage of the present invention is the possibility of obtaining the inertization of the atmosphere contained in a not height-adjustable tunnel, optimizing the quantity of desired gas, with an important saving in the quantity of supplied desired gas in order to obtain a suitably inert or anyway oxygen-free atmosphere. Experimental test showed that competitors use about 280 m ³ /h of desired gas in order to inertize a tunnel having a transversal section of 20x1400 mm, while using the tunnel according to the present invention having a transversal section of 30x1400 mm, 150 m ³ /h of desired gas were used.

[0021] A second advantage of the present invention consists in the fact that closing barriers at the entry and exit of said tunnel are not necessary: therefore, the treatment of panels can occur in passing, in a continuous way, allowing working speeds that would be otherwise impossible.

[0022] A third advantage is given by the possibility of treating panels of any shape, even raised panels, on five of their six sides, i.e. on their main side opposed to the side supported by the belt conveyor and all their lateral edges in just one working step, without the need to reprocess the same panel in order to obtain a matt finish on each side.

[0023] A fourth advantage consists in the flexibility of the apparatus according to the present invention, allowing to treat both mainly flat panels and panels provided with a significant thickness.

[0024] Further advantages and properties of the present invention are disclosed in the following description, in which exemplary embodiments of the present invention are explained in detail on the basis of the drawings: Figure 1 Example of a raised panel, in an axonometric view;

Figure 2 Longitudinal section of the overall apparatus according to a first embodiment of the present invention;

Figure 3 Detail of Figure 2, wherein the conveyance of the panels is shown;

Figure 4 Detail of Figure 2, wherein the circulation of inert gas is shown;

Figure 5 Detail of a gas-supplying bar, in an axonometric view.

Figure 6 Longitudinal section of the overall apparatus according to a second embodiment of the present invention;

Figure 7 Detail of the longitudinal section of the apparatus, at the outlet opening;

Figure 8 Longitudinal section of the overall apparatus according to a third embodiment of the present invention;

Figure 9 Longitudinal section of the overall apparatus according to a fourth embodiment of the present invention.

[0025] Figure 1 shows an axonometric view of an example of a raised furniture door. A panel 10 is provided with two main sides, the upper side 1 and its opposed side that is not visible in the Figure; a head edge 2, a tail edge 5 and two longitudinal edges 3 and 4. The raising is clearly visible in the Figure on the main side 1. In the present description, overall the head edge 2, the tail edge 5 and the two longitudinal right 3 and left edge 4 are grouped in the term lateral edges. Coating five out of six sides of the panel 10 means coating the main side 1 and the lateral edges 2, 3, 4, 5.

[0026] It is worth mentioning that all the embodiments according to the present invention share the internal structure of the chambers, which is explained in detail in the description of Figures 3-5.

[0027] The present invention is provided with four embodiments:

- First embodiment 100, shown in Figure 2: the tunnel according to the present invention is provided with a linear path, lying on the same plane;

- Second embodiment 600, shown in Figure 6: the tunnel according to the present invention is provided with a polygonal path, lying on three different planes; this embodiment is provided with just two end rollers, but the ramping of the conveying belt can be adjusted through two intermediate adjustable rollers; the tunnel is housed inside a unique carpentry assembly;

- Third embodiment 800, shown in Figure 8; the tunnel according to the present invention is provided with a polygonal path, lying on three different planes; this embodiment is provided with three distinct conveying belts, each provided with its motorized roller and idle roller; said conveying belts can be adjusted individually; the tunnel is housed inside a unique carpentry assembly;

- Fourth embodiment 900, shown in Figure 9; the tunnel according to the present invention is provided with a polygonal path, lying on three different planes; this embodiment is provided with three distinct conveying belts, each provided with its motorized roller and idle roller; said conveying belts can be adjusted individually; the tunnel is housed inside three distinct carpentry assemblies.

[0028] Figure 2 shows a longitudinal section of an apparatus 100 according to the present invention. The bold arrow indicates the conveying direction of panels. The entry of panels 10 into said apparatus 100 is indicated by an arrow 28, while the exit of panels 10 from said apparatus 100 is indicated by an arrow 29.

[0029] Said apparatus 100 comprises a belt conveyor 20, actuated by two rollers; a motorized roller 21, placed at the exit 29 of the apparatus 100, while an idle roller 22 is placed at the entry 28 of the apparatus 100. Said belt conveyor is provided with an upper outward section 23 and a lower return section 24. The panels 10 to be treated are conveyed on the upper outward section 23, supported on their main side (not visible in

Figure 1) opposed to the side 1 by said upper outward section 23. Panels are conveyed inside a tunnel 26 supplied with inert atmosphere.

[0030] Figure 3, which is a detail of the same longitudinal section of Figure 2, shows a tunnel 26 subdivided into a plurality of chambers 30 (visible in the Figure as the space comprised between two vertical dotted lines), placed in series. In other words, said tunnel 26 is provided with a plurality of identical chambers 30, which follow one another from the entry 28 to the exit 29 of the tunnel 26.

[0031] Each chamber 30 is the basic module of the apparatus 100 and of all the embodiments according to the present invention, which can be repeated any number of times in order to vary the overall length of the apparatuses 100, 600, 800, 900. From the outside of the apparatus 100, a chamber 30 corresponds to a housing 25 insulating the tunnel 26 from the outside environment. Indicatively, said housings 25 are 500 mm long. Obviously, the overall length of the apparatus 100, 600, 800, 900 is determined when the production line is designed; said apparatus 100, 600, 800, 900 is produced with a length that cannot be modified after the production line installation. Said housings 25 are connected to each other separating in an impermeable way the outside environment under earth natural atmosphere from the inside environment of tunnel 26 under controlled atmosphere. Thanks to this separation, inside said tunnel 26 a controlled atmosphere can be obtained with any desired gas, i.e. an inert atmosphere obtained through e.g. gaseous nitrogen or carbon dioxide or argon.

[0032] Each chamber 30 is provided with a non-homogeneous section in its longitudinal direction; instead, sections have a variable height in different points of the chamber due to the presence of flaps 27. The farther from the inlet opening 28 of the tunnel 26, progressively the more oxygen-free said chambers 30 are.

[0033] Figure 4 shows a detail of a chamber 30 composing said tunnel 26. Each chamber 30 comprises:

- A first portion 31 of said tunnel 26 provided with a height slightly larger than the panel to be treated;

- A second portion 32 of said tunnel 26 provided with a height greater than the first portion 31;

- A third portion 33 of said tunnel 26 provided with a height smaller than that of the second portion 32, preferably with the same height of the first portion 31.

[0034] The difference in height of a chamber 30 is due to the presence or absence of flaps 27. In the second portion 32 wherein said flap 27 is absent, there is provided a bar 34 supplying a desired gas, preferably two bars 34, 34’ supplying the desired gas.

[0035] Said bars 34, 34’ supplying the desired gas inside the chamber 30 are placed perpendicularly to the direction of advancement of panels 10, so that the distance between a pair of bars 34, 34’ and the successive pair is kept at a constant pace of 500 mm. In this way, a homogeneous distribution of the desired gas is obtained in each point of the tunnel 26.

[0036] Figure 5 shows a detail of a gas-supplying bar, rotated of 180° with respect to its position inside said apparatus 100. Each gas-supplying bar 34, 34’ is provided with a square section and a length equal to the width of the belt conveyor 30. Said bars 34, 34’ supply the desired gas in a laminar way, through two calibrated slits 51, 52 placed on two adjacent sides of said bar. In use, the first slit 51 is always facing the panel 10 to be treated, while the second slit 52 is placed at 90° with respect to the first slit 51.

[0037] In the preferred embodiment, in each chamber 30 there are provided two gas- supplying bars 34, 34’. The second slit 52 of first bar 34 faces the entry 28 of said tunnel 26, while the second slit 52 of the second bar 34’ faces the exit 29 of said tunnel 26. In other words, the second two slits 52 of the bars 34 and 34’ supply gas in opposite directions.

[0038] All the first bars 34 are connected through a first circuit, while all the second bars 34’ are connected through a second circuit; the first and the second circuit are independent from each other, allowing to adjust the intensity and the direction of gas flow inside each chamber 30, and therefore inside said tunnel 26.

[0039] In an embodiment, the first supplying bars 34 can supply a first desired gas, while the second supplying bars 34’ can supply a second, different desired gas, realizing in use a mixture of two different gases. As the two circuits connecting said bars are independent, providing mixtures of two desired gases in different, variable proportions is possible.

[0040] In Figure 4, the small arrows inside the tunnel 26 represent the path of the desired gas supplied inside a chamber 30.

[0041] As can be observed in Figure 3, the height of the tunnel 26 is slightly greater than the thickness of the panel 10 to be treated: e.g., if the panel has a thickness of 20 mm, the tunnel 26 has a height of 30 mm. When panels 10 are conveyed, this small difference in height generates a perturbation in the distribution of the desired gas, with an increase in its pressure and dynamic movement on all the exposed surfaces (1, 2, 3, 4, 5) of the conveyed panel.

[0042] When the conveyed panels 10 occlude a considerable portion of the transversal section of the tunnel 26, the pressure of the desired gas per surface unit increases, and the panels behave like the blades of a pump, favouring the expulsion of oxygen, reducing the consumption of desired gas and obtaining a self-cleaning tunnel 26.

[0043] The more the tunnel 26 is occluded by conveyed panels, the more efficient is the system, which consumes a lower quantity of desired gas per unit of time than when the same tunnel 26 is emptier. The advantage in terms of gas consumption is appreciable when at least 50% of the transversal section of the tunnel 26 is occluded by the transversal section of the conveyed panel 10. The conveyed panels are of variable width, and when their transversal section is lower than the 40% of the transversal section of the tunnel 26, they are placed two by two, if their width allows.

[0044] The efficiency of the system is linked to the efficiency of the production line, meaning the productivity in square meters per unit of time.

[0045] It is apparent that when designing the apparatus 100, 600, 800, 900 the designer chooses the dimensions (height and width) of the tunnel 26 so as to obtain a tunnel 26, and particularly the first and third portions of the chamber 30, having dimensions as near as possible to the transversal section of the panels to be treated. Such dimensions can range 80 x 80 mm of a profile to 2200 x 2 mm of composite material sheets.

[0046] Downstream the midpoint of the tunnel 26, towards the exit 29, a treatment lamp 40 is placed, emitting radiations having a pre-defmed wavelength for treating panels 10, treatment that must be performed in an atmosphere different from the earth natural atmosphere, e.g. in an inert, oxygen-free atmosphere .

[0047] In a preferred embodiment of the present invention, the treatment lamp 40 is an excimer lamp allowing to perform a matting treatment of panels 10 in an inert atmosphere, wherein the desired gas is gaseous nitrogen. Again, in the same preferred embodiment, the wavelength emitted by the excimer lamps ranges 165 to 200 nm, preferably 172 nm.

[0048] In a second preferred embodiment, the treatment lamp 40 is a UV lamp emitting a wavelength ranging 365 to 420 nm for drying panels 10.

[0049] With a lamp 40 as long as the width of the belt conveyor 20, planar or raised panels can be treated on five sides, i.e. the main side 1 and the lateral edges 2, 3, 4, 5.

[0050] Figure 6 shows a longitudinal section of an apparatus 600 according to a second embodiment of the present invention. The bold arrow indicates the conveying direction of panels. The inlet opening of panels 10 into said apparatus 600 is indicated by an arrow 28, while the outlet opening of panels 10 from said apparatus 100 is indicated by an arrow 29. [0051] Said apparatus 600 comprises a belt conveyor 20, actuated by two rollers; a motorized roller 21, placed at the exit 29 of the apparatus 100, and an idle roller 22 placed at the entry 28 of the apparatus 100. Said belt conveyor is provided with an upper outward section 23 and a lower return section 24. The panels 10 to be treated are conveyed on the upper outward section 23, supported on their main side (not visible in Figure 1) opposed to the side 1 by said upper outward section 23. Panels are conveyed inside a tunnel 26 supplied with inert atmosphere.

[0052] Moreover, Figure 6 shows that said tunnel 26 is subdivided into a plurality of chambers 30 (a chamber is visible in the Figure as the space comprised between two vertical dotted lines), placed in series. In other words, said tunnel 26 is provided with a plurality of identical chambers 30, which follow one another from the inlet opening 28 to the outlet opening 29 of the tunnel 26. For a detailed description of the functioning of the chambers, see above the description of Figures 2-5.

[0053] Figure 7 shows an enlarged detail of the outlet opening of said tunnel 26.

[0054] The outlet opening 29 is provided with a bulkhead 60’ that can be raised or lowered just enough to allow the exit of a panel 10 from the tunnel 26. At the inlet opening 28 there is provided a corresponding bulkhead 60, visible in Figure 6; this bulkhead too, is raised just enough to allow the entry of a panel 10 into said tunnel 26. Said bulkheads 60, 60’ are manually adjusted by a human operator at the beginning of a processing cycle wherein panels 10 provided with a homogeneous thickness, different from the preceding batch, are worked. In an alternative embodiment, the adjustment of bulkheads 60, 60’ can be automated.

[0055] In particular, the upper outward section 23 of the belt conveyor 20 raises the panels 10 to a height from ground higher than the lower point of bulkheads 60, 60’, that is higher than the horizontal dotted line 69, visible in Figure 6. Said line 69 is the hydrostatic head over which the atmosphere is always more controlled thanks to the supply of the desired gas.

[0056] The tangent touching the top of the two motorized roller 21 and idle roller 22, parallel to ground, defines the height of a basic plane. The height of the conveying plane, corresponding to the upper outward section 23 of the belt conveyor, can be modified acting on different devices, as will be better explained in the following. This has the aim of reducing the dimensions of the tunnel 26 inside which panels 10 are conveyed, in order to reduce the consumption of desired gas.

[0057] When the devices working on the height of the outward section 23 are not active, the upper outward section of the belt conveyor 20 potentially can coincide with the basic plane, in its turn coinciding with the tangent touching the top actuating the belt conveyor. In this configuration, the tunnel 26 is provided with its maximal height, and its lower wall is parallel to ground for all its extension (not shown).

[0058] In the second embodiment 600, the height from ground of the second tract of conveying belt 20 parallel to ground can be adjusted with respect to said basic plane working on one, preferably two height-adjustable idle rollers 64, 65. This adjustment, too, is performed manually by a human operator at the beginning of a processing cycle of a new batch. In a further embodiment, such rollers can be automated.

[0059] By raising said height-adjustable 64, 65, three tracts 61, 62, 63 are formed, wherein the path of the upper outward path is higher than said basic plane. In fact, the upper outward section 23 is provided with a first upward tract 61, a second tract 62 parallel to ground placed under said treatment lamp 40, and a third downward tract 63.

[0060] The tract 62 parallel to ground must be higher than the basic plane of at least the thickness of the panel 10 to be treated, when nitrogen or carbon dioxide are used as desired gas, and lower than the basic plane when argon is used as desired gas.

[0061] Figure 8 shows a third embodiment 800, alternative to the embodiment 600 of Figure 6. In fact, in the second embodiment, the path of the upper outward section 23 is modified by the presence of said height-adjustable rollers 64, 65, allowing to raise said panels 10 towards the irradiation point with respect to inlet and outlet openings 28, 29.

[0062] On the other hand, in the third embodiment 800 there are provided three distinct adjacent belt conveyors 20’, 20”, 20’” placed in series, allowing to obtain the same path of the conveying broken line obtained with the height-adjustable rollers 64, 65.

[0063] The three belt conveyors 20’, 20”, 20’” can be provided inside a unique carpentry assembly forming the supporting frame of the apparatus 800; in this case the rollers 21”, 22” of the central belt conveyor must be adjusted according to the thickness of the panels 10 to be treated, adjusting accordingly the adjacent rollers 22’, 2 ” of the external belt conveyors in order to allow the passage of the panels 10 to be treated. [0064] Alternatively, there can be provided three distinct belt conveyors 20’, 20”, 20’”, each provided with its own carpentry assembly. In this case, the height adjustment of said belt conveyors is performed working on the adjusting feet typically available for this kind of conveyors.

[0065] Figure 9 shows a third embodiment 900, wherein said housings 25 and chambers 30 are provided with a path which is parallel, in lieu of to the tract 32 parallel to ground, to the ramping tracts 31 and 33 of the upper outward section 23. In this third embodiment, providing three distinct adjacent conveying apparatuses 1100, 1200, 1300 placed in series is preferable.

[0066] The conveying apparatus 1100 substantially corresponds to the first ramping portion 61 or 20’ of the upper outward section shown in Figures 6 or 8; the conveying apparatus 1200 substantially corresponds to the second, horizontal portion 62 or 20” of the upper outward section shown in Figures 6 or 8; the conveying apparatus 1300 substantially corresponds to the third ramping portion 63 or 20’” of the upper outward section shown in Figures 6 or 8. Evidently, connections impermeable to the external atmosphere must be provided among the apparatuses 1100, 1200, 1300, so as to hinder the entry of oxygen molecules in the connecting points.

[0067] Although not shown in the schematic representations of Figure 8 and 9, the structure of the tunnel 26 in the third 800 and in the fourth embodiment 900 of the portions 31, 32, 33 of the upper outward sections 23 is identical to the structure of the first embodiment 100 shown in Figure 2, i.e. each portion of the belt conveyor is made of a suitable number of chambers 30 provided with flaps 27, gas-supplying bars 34, 34’ and housings 25.

[0068] It is likewise apparent that, when using argon, the path of the tracts 61, 62, 63 is specular to what is shown in Figures 8 and 9, with the treatment portion 62 parallel to ground which is lower than the inlet and outlet opening 28 and 29 (not shown). When using argon as desired gas, only the third 800 and fourth embodiment 900 are possible, due to the impossibility of placing height adjustable rollers over the upper outward section 23, where they would hinder the advancement of panels 10.

[0069] The method according to the present invention comprises the following steps: a) Inserting a quantity of desired gas measured e.g. with the use of a flowmeter, sufficient to saturate the tunnel 26 with gas;

b) Feeding regularly the apparatuslOO or 600 or 800 or 900 with a plurality of panels 10 in series, which behave like pump blades;

c) According to the dimensions of the panels 10 feeding the tunnel, reducing the quantity of desired gas needed to saturate the tunnel 26 with gas.

[0070] According to an embodiment, the method provides for the steps to configure the tunnel or at least a part of it by adjusting at least one dimension of the passage for the panels at least at a certain point and/or for a certain section of the longitudinal extension of the said tunnel in such a way as to be closest to the corresponding dimension of the panels still allowing the panels to pass through the tunnel.

[0071] In an embodiment at least the inlet and/or the outlet opening and or a certain section of the tunnel between the said inlet and the said object are adjusted according to the above criteria relatively to their height in relation to the corresponding dimension of the panel. This effect is the more effective the more the cross section of the tunnel along a plane transversal to the direction of travel of the panels 10 at least in the chambers 30 is close to the cross section of the panels 10.

[0072] When passing through the tunnel, the panels exercises on the gas filling the tunnel a sort of pushing effect similarly to the vanes of a vane pump.

[0073] In relation to the above general method step, when using the apparatuses 600, 800, 900 according to second, third and fourth embodiment, upstream step a), when processing two subsequent batches of panels 10 provided with a different thickness, it is necessary to adjust both the slope of the ramps 61 and 63 by adjusting the height- adjustable rollers 64 and 65 in the second embodiment 600, or on the height of rollers 22’, 21”, 22”, 2G” in the third embodiment 800 and fourth embodiment 900, and the bulkheads 60 and 60’ in order to adjust both the overall height of the tunnel 26 and the inlet and outlet openings 28 and 29 to the thickness of the panel 10.

[0074] Determining experimentally the minimum quantity of desired gas needed to saturate the empty tunnel 26 at the departure stage for a given time (as described in point a), is possible. Determining experimentally the minimum quantity of desired gas needed to saturate the tunnel 26 while panels are conveyed according to their dimensions is also possible (as described in points b and c). In this way, the fundamental parameters of a working recipe, which is repeatable over time using simple time-delay relay, or programmable logics, installed on the electric control board of the apparatus according to this invention.

[0075] In an alternative embodiment, each chamber 30 can be adjusted independently from the others concerning the quantity, direction and kind of desired gas emitted inside the tunnel 26.

[0076] At the start of a new production batch of panels 10 having dimensions different from the preceding batch, the apparatus 100 or 600 or 800 or 900 according to the present invention supplies a quantity of desired gas for a pre-defmed time in order to perform a pre-cleaning step with empty tunnel 26. At the end of the pre-cleaning step, the working step can start, providing the conveyance of panels 10 of known dimensions. For the above-explained reasons, during the working step a lower quantity of desired gas is supplied with respect to the pre-cleaning step.

[0077] Preferably, before each working step a pre-cleaning step must be performed. The pre-cleaning step can evidently be provided with different durations, according to the quantity of desired gas supplied per unit of time.

1 main side

2 head edge

3 right longitudinal edge

4 left longitudinal edge

5 tail edge

10 panel

20 belt conveyor

21 motorized roller

22 idle roller

23 upper outward section

24 lower return section

25 housing

26 tunnel

27 flap

28 inlet opening

29 outlet opening

30 chamber

31 first portion

32 second portion

33 third portion

34 gas supplying bar 0 lamp

51 slit

52 slit

60 bulkhead

61 first tract of upper outward section

62 second tract of upper outward section

63 third tract of upper outward section

64 adjustable roller

65 adjustable roller

69 dotted line

100 apparatus, first embodiment

600 apparatus, second embodiment

800 apparatus, third embodiment

900 apparatus, fourth embodiment

1100 first apparatus of the fourth embodiment

1200 second apparatus of the fourth embodiment

1300 third apparatus of the fourth embodiment