FR2798187A1 - ELECTROMAGNETIC IRRADIATION DEVICE HAVING COOLING MEANS - Google Patents

Abstract

The invention concerns an irradiating device (1) comprising an electromagnetic radiation source having a radiation emitter (32) and two lateral reflectors (34). A fin (58) shaped like a projecting rib extends on the side of the rear surface (56) of each reflector (34) forming both a cooling surface and means for increasing the inertial moment of the profile of said reflector. A hook-shaped rim is provided at each end of the fin (58) allowing through pins (55) for fixing the reflectors (34) to positioning flanges (44). A winding cavity (17) carries the cooling fluid emerging on the side of the space exposed through one or several discharge outlets (80) capable of directing the fluid towards the median part of the exposed space. The invention is useful for drying all coatings on paper, cardboard, plastic and metal supports.

Description

TECHNICAL FIELD OF THE INVENTION The invention relates to an electromagnetic irradiation device comprising a source of electromagnetic radiation and cooling means.

Apparatus with visible and / or ultraviolet and / or infrared radiation is known for applications such as the drying of paints, varnishes, inks, baking of powders such as epoxy, Rilsan (registered trademark), etc., and such sterilization of solid products in webs, fluids of a foodstuff, syrup, water, etc. and, more especially for the polymerization of inks and / or varnishes, radical and / or cationic and / or adhesive and / or any other change in state generated mainly by radiation, in the field of graphic arts and for the treatment of continuous coatings or sheets of supports such as paper, cardboard, cotton or other synthetic products, plastic, PVC, PVB metal strips aluminum or steel or other metals, or any other products used in printing, fiduciary papers, stationery, cardboard, plastics, bagging, packaging, textile, automobiles, the manufacture of woods, electronics, credit cards, CDs, etc.

 STATE OF THE ART Documents WO98 / 01700 and WO99 / 36939 describe an electromagnetic radiation source comprising radiating means consisting of a radiation emitter and two lateral reflectors situated at a distance from the emitter on either side of the emitter. -this. Each reflector has a reflective front face facing the transmitter and a rear face. The emitter and the reflectors are arranged to direct the radiation to an exhibition space. The two reflectors are separated from each other by a slot and cooling means of the reflectors allow the passage of a cooling fluid side of the rear reflective side on the one hand, and through the slot on the side from the front side of the reflectors on the other hand. The reflectors consist of concave metal sheets whose face is reflective. form two portions of the same ellipse, the slot occupying the top of the ellipse. The emitting tube is located parallel to the slot, and its axis placed at the focus of the ellipse closest to the slot. The thermal energy released by the radiation source simultaneously with the photochemical energy tends to desiccate the product subjected to radiation. If the example of an application to the printing press is used, the source can very well irradiate areas of the paper on which the product to be polymerized has not been printed, in which case the substrate (for example paper) being exposed, air and heat are the cause of a localized drop in humidity, which will modify the structural behavior of the substrate. This constraint limits the power of the device in certain applications. Moreover, the thermal stresses on the device itself are considerable. Thermal deformations of the various elements, such as the risk of devitrification of the transmitter shell, must be taken into account during the design. <B> It </ B> is particularly difficult to design a housing that can contain the elements of the device in a small space while providing ventilation in a satisfactory manner. OBJECT OF THE INVENTION An object of the invention is to allow sufficient cooling of the preceding type of radiating device, in a confined space confined in a housing. Another objective is to allow ventilation and, where appropriate, sufficient cooling of the space subjected to radiation without decreasing the photon energy released. Another objective is to increase the power of the radiation source, in a given volume, to subject it radiation source itself and / or the object subjected radiation to a too considerable heating, by simple means. According to the invention, these objectives are achieved by means of an irradiation device comprising a source of electromagnetic radiation comprising a radiation emitter, at least two lateral reflectors located at a distance from the emitter on either side thereof, and each having a reflective front face facing the transmitter and a back face, the emitter and the reflectors being arranged to direct the radiation to the exposure space having a middle portion, the two reflectors being separated one from the other. on the other by a slot, # cooling means reflectors for the passage of a cooling fluid on the side of the rear face of the reflectors on the one hand, and through the slot on the side of the front side of the reflectors on the other hand, device comprises a carrier structure comprising a housing for the radiation source, the housing having walls c shaped so that they constitute with the rear face of each reflector a cavity constituting a path for the cooling fluid opening on the side of the exposure space by one or more orifices of expulsion able to direct the fluid towards the middle part of the exhibition space. The middle part of the exhibition space is the one that is subjected to the highest temperatures. Thanks to the invention, it is swept by the cooling fluid opening through both the expulsion orifices and the slot, which contributes to its cooling.

circulation of the cooling fluid between the rear face of reflectors and the carrier structure allows increased heat exchange, and in particular limits the heating of the carrier structure. The cooling fluid may be room air or a neutral gas, such as nitrogen, for products to be inerted. Alternatively, it may also be air with a high relative humidity rate, favoring the drop in temperature by the use of the latent heat of vaporization, or of the cold air temperature below 20 ° C. or below 0 ° C. C, or demineralised liquid water at room temperature. Advantageously, the reflectors are provided, on the side of their rear face, with one or more cooling fins, such that the exchange surface formed by the posterior face of the reflectors is significantly larger than the reflecting surface constituted by the anterior face. reflectors. The housing comprises walls shaped in such a way that the cavity that they form with the posterior face of each reflector is a sinuous cavity. The fins and complementary conformation of the carrier structure increase the exchange surfaces of both the reflector side and the supporting structure side, resulting in a greater cooling capacity. According to one embodiment, the sinuous cavity has a substantially constant thickness.

Advantageously, the carrier structure comprises a cooling fluid distribution pipe arranged parallel to the slot. The device has less than one channel connecting each sinuous cavity to the pipe. The pipe is separated from the cavity by an intermediate wall comprising one or more communication orifices constituting a fluid path connecting the sinuous cavity to the pipe. The section of the orifices of expulsion is substantially lower than the section of the or orifices of communication. Advantageously, intermediate wall comprises at least one orifice connecting the pipe to the slot. This orifice may also be one of the previous communication orifices. According to one embodiment, the rear face of the reflector comprises at least one abutment bearing on a complementary abutment formed in the structure, the resultant of the forces due to the pressure exerted by the fluid on the posterior surface of the reflector tending to increase the force exerted by the stop on the complementary stop. The device thus allows good distribution of mechanical and thermal stresses between the reflectors and the carrier structure. Preferably, the device comprises motorized means imposing a forced circulation of the fluid in the pipe. These motorized means may be integrated into the carrier structure or separated therefrom by a fluid supply line. Advantageously, the device comprises a nebulizer projecting into the fluid a liquid in fine droplets. The nebulizer is preferably placed between the motorized means and the fluid distribution line. The nebulized liquid vaporizes, firstly in contact with the emitter tube bypassing flowing towards the anterior face, and secondly through the cavity formed between the reflectors and the carrier structure, thereby absorbing a considerable heat corresponding to its own latent heat of vaporization, and contributing to the cooling of the transmitter and walls. Advantageously, the vaporized liquid is water, which makes it possible to control the moisture content in the exposure space and to prevent drying of objects subjected to radiation. The source of electromagnetic radiation is a unitary unit assembly mounted to slide and supported along two orthogonal axes in the aeraulic carrier structure by means of sliding surfaces on supports, and slides sliding on bosses. BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and characteristics of the invention will emerge from the following description of various embodiments of the invention, given by way of non-limiting example and represented in the accompanying drawings, in which: FIG. represents a cross section of a device according to the invention; FIG. 2 represents an exploded and cutaway perspective of the device of FIG. 1; FIG. 3 represents a side view of the device of FIG. 1; FIG. 4 represents a section of the part of the device shown in FIG. 2; # 5 shows a detail of an alternative embodiment of the invention. DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIGS. 1 to 4, a radiating device 10 comprises a supporting structure 12 constituted by an aluminum or steel profile approximately in the shape of A, having an intermediate wall 14 delimiting a rear volume constituting a longitudinal pipe 16 of rectangular section and an anterior volume constituting a housing 18 approximately inverted U-shaped, open on one of its sides. One end of the pipe is provided with an air outlet 20 for a supply of cooling fluid. The intermediate wall 14 has orifices 22 of variable cross sections arranged on either side of a median plane 24 of supporting structure, these orifices 22 providing as many openings between the pipe 16 and the front housing 18 of the structure 12 The intermediate wall 14 is provided with two supports 26 placed on either side of the median plane 24 and projecting towards the inside of the anterior volume 18. The two lateral walls delimiting the anterior volume 18 of the structure comprise on their outer face each a longitudinal groove 28 of circular section, corresponding to a boss 30 formed inside the previous volume. The anterior volume 18 of the structure 12 is occupied by radiating means comprising a transmitter 32 located in the median plane of the structure and two lateral reflectors 34 located on either side of the transmitter 32 and at a distance thereof. , symmetrically with respect to the median plane. The transmitter is a Xenon or Krypton lamp or other gas having comparable properties, composed of a cylindrical tube 36 of transparent quartz, inside which is disposed a plasma cylinder emitting in the ultraviolet and / or in the visible and / or infrared. Each of the axial ends of the tube is provided with a ceramic tip 38 provided with an external electrical connector 40 connected to an electrode 42 inserted in the tube. At each longitudinal end of the anterior volume 18 of the carrier structure 12 is disposed a positioning flange 44, visible in FIGS. 4, and having lateral guides 46 slidably positioned on the two lateral bosses 30. Each flange has a notch 48 U whose opening is facing the intermediate wall, and whose reflective inner surface surrounds the tube portion in which the electrode extends. This notch has shoulder 47 visible in Figure 4 and a wider portion for positioning a perforated holding piece 49. This holding piece 49 can also be advantageously replaced by a Teflon piece or similar material with a thickness and a sufficient diameter to the housing of the O-ring of the ceramic end piece 38 having the same geometrical outline as the piece 44 thus ensuring a symmetry with respect to the axis 54. The intermediate wall 14 comprises, at the height of the connection between the tail the electrode and the ceramic tip, a wide opening 50. The flange is itself perforated by openings 41. Each of the reflectors 34 is constituted by a metal profile, in particular of aluminum or steel, having a concave front face 52 reflecting. Viewed in section in a plane perpendicular to the axis 54 of the cylindrical tube 36, the reflection surfaces 52 of the two reflectors 34 follow the envelope of the same ellipse whose focus would be located on the axis 54 of the cylindrical tube. Each of the reflectors 34 is provided, on the side of its rear face 56, a main fin 58 of large size, and asperities 60 of smaller dimensions. A bearing 62 contra the positioning of the reflector in the carrier structure 12 and abuts against the corresponding support 26 of the intermediate wall 14.

Two adjacent edges 64 of the two reflectors 34 delimit a longitudinal slot 66 parallel to the axis 54 of the tube 36. A gap is formed between the slot 66 and intermediate wall 14, which opens laterally the orifices 22.

The two flanges 44 receive the ends of the lateral reflectors so as to position them longitudinally in the anterior housing 18.

The intermediate wall 14 supports in its middle part a longitudinal reflective aluminum plate, held by two supports and facing the tube 36 through the slot 66.

Each end of the supporting structure 12 is further provided with an outer plug 72 and an inner plug 74, visible in FIGS. 2 and 4. The outer plug 72 closes the pipe 16. It is provided with four pawns 76 being inserted into circular grooves of the supporting structure. The inner plug 74 produces in rounded form the change of direction at 90 of the cooling fluid and, by construction, the electrical isolation sufficient to seal the electrical connection point of the lamp with its power cable. The plugs 72, 74 are made of plastic, so as to match the shapes of the profile by embedding, while strengthening the electrical insulation.

The end of the structure opposite to the air outlet is provided with a multi-pin electrical outlet 78, shown in FIG. 5, for lamp supply voltages of less than 3000 volts. Beyond these values, that is to say up to 10,000 volts or more, electrical conductors pass through the ventilation duct which provides additional insulation security with respect to people.

The air outlet 20 is connected by a pipe 99 downstream of a fan 96, shown schematically in FIG. 3. Optionally, the device is further provided with a vaporizer 98 located at the suction inlet of the fan, which allows to discharge to the air outlet 20 and the conduit 16 of the air containing a mist of fine water droplets in suspension. According to one variant, the vaporizer 98 may be placed directly in the vicinity of the air outlet 20.

The mounting of the device is carried out as follows The longitudinal ends of the reflectors 34 are inserted into the flanges 44. Thus, the two end flanges 44, the two reflectors 34 and the transmitter 32 constitute a subset unitary and mechanically secured, which can be slidably inserted along the bosses 30 in the anterior volume 18 of the structure 12, bearings 62 slid on the supports 26. This subset is thus largely dissociated, from a point of view mechanical, electrical, thermal and aeraulic, of the supporting structure 12. A continuous space is formed between each lateral reflector 34 and the side wall facing carrier structure 12, this space opening on the front side by a slot 80 located between the edge front of each reflector and the corresponding edge of the wall of the supporting structure 12, and, on the posterior side, through the orifices ns the side wall. Once this subassembly inserted and positioned in the carrier structure 12, the pins that hold the reflectors 34 integral to the flange 44 protrude on the rear face of the latter with a length such that they abut on the inner face 73 inside cap 74 whose plastic material is sufficiently elastic to absorb the dilation of the reflectors.

The external grooves 28 of the supporting structure allow the device 10 to be introduced as a drawer in a machine element provided with complementary parallel runners. The compactness, maneuverability and unity of the assembly make it possible to consider in standard exchange the total replacement of the apparatus during maintenance or interventions, rather than repair or partial replacement of one of the components of the unit. 'apparatus.

In operation, the thermal and aeraulic behavior of the device is as follows. A cooling fluid is introduced into the pipe through the mouth 20. The orifices 22 have an increasing section from the end comprising the mouth 20 towards the opposite end, so as to compensate for the pressure loss along line 16 and to produce a substantially constant flow rate fluid flow along line 16. Part of the fluid flow passes through slot 66 to the radiation exposed space , where it participates in a heat exchange with the reflecting faces 52 of the reflectors and with the tube 36. Another part of the flow follows the sinuous path formed between the lateral walls of the structure 12 and the posterior faces 56 of the reflectors 34 and opening through the slots 80, which direct the outflow approximately to the median plane 24 of the irradiated space. This part of the fluid carries out a heat exchange with the posterior face 56 of the reflectors, important because of the fins 58 which contribute both to increase the exchange surface and to slow down the fluid. The asperities 60 also contribute to increase this heat exchange.

At the ends of the transmitter 32, the openings 50 and 41 allow fluid flow, and therefore cooling.

The reflective plate allows a reflection of the radiation that escapes from the slot 66. It also isolates the intermediate wall 14 from any contact with infrared radiation that could cause a localized temperature rise of the profile constituting the carrier structure 12, and to generate heterogeneous deformations of the elements.

The different thermal expansions of the reflectors 34 and of the structure 12 lead to a sliding flanges 44 relative to the bosses 30, and bearing surfaces 62 in support 26, the displacement of the ends of the radiating assembly being absorbed by the elasticity of the plugs interiors. The supports 26 oppose the overpressure generated by the fluid under pressure along the rear faces of the reflectors 34, and thus ensure the existence of a slot 66 of constant and homogeneous width between the adjacent edges 64 of the two reflectors 34, which whatever the airflow.

The expression of cooling employed hitherto is a deliberately generic expression. In fact, if the radiation transmitter comprises plasmas sensitive to thermal shocks, such as for example the ignition of the lamp, or a strong temperature gradient of the quartz envelope, which essentially concerns the plasmas formed by the Mercury, Gallium and / or Lead, Iron and / or Cobalt, and / or other metal iodides of the same nature, then the cooling of the emitter will be limited to the use of local ambient air or neutral gases, such as nitrogen, for products to be inerted.

On the other hand, if the radiation emitter comprises plasmas practically insensitive to thermal shocks, such as those formed by xenon, krypton, by other associated ionizing gases of the same kind, then, in addition to the ambient air or the neutral gases, high relative humidity air can be used with the water vaporizer, preferably demineralized water, which promotes the temperature drop by the use of latent heat of vaporisation, or of the air at lower temperature. at 20 ° C. or below 0 ° C., or even demineralised water at ambient temperature, into which the radiating element is immersed, insofar as the electrical connection of the emitter is isolated from the liquid medium.

The vaporization of water through the slit 66 makes it possible to obtain a strong temperature gradient between the inner wall of the quartz tube 36 which is in contact with the plasma at about 5000 K to 7000 K, and the outer wall which can be in direct contact with water at 20 C without causing modification of the plasma neither in its spectrum, nor in the quantity of energy released in the wavelengths considered. The latent heat of the water in suspension in the cooling air at a predetermined temperature, in particular ambient temperature, which, when in contact with the quartz tube, the emitter, is then transformed into a vapor state by heat pump 2250 kJ / kg of water.

Moreover, it must be emphasized that the thermal energy released simultaneously with the photochemical energy tends to dry out the product subjected to radiation. an example is an application to the printing press, the source 10 can very well irradiate areas of the paper on which the product to be polymerized has not been printed, in which case the substrate (for example paper) is in the open, air and heat are the cause of a localized drop in humidity, which will modify the structural behavior of the substrate.

it is then possible to avoid drying by increasing the humidity rate cooling air that propels on the irradiated side of the product. It is then advantageous to direct the expelled air towards the median part of the zone subjected to the radiation. The air passing through the slot 66 is naturally directed in this region. The expulsion slots 80 formed between the lateral reflectors and the flanges of the side walls of the supporting structure 12 are shaped so as to direct towards the median plane 24 of the supporting structure 12 the air expelled from the sinuous path formed between the side walls. of the structure 12 and the rear face 56 of the reflectors.

Of course, various variations are possible without departing from the scope of the invention.

An embodiment variant is shown in FIG. 5. When the structure exceeds a certain length (for example 1 meter), the thrust exerted on the air coming out of the slot 66 and arriving on the cylindrical tube 36 can cause deformation of the tube 36 In order to avoid the inadvertent movement of the emission focal point, it is possible to have, at regular intervals, a loop 90 holding at one or more turns. This loop goes around the tube 36 passes through the edge 64 rounded reflectors 34 and in the thickness of those. where it is maintained by a glue plug 92 (high temperature type, ceramic type). The wire 94 of the loop 90 is of a very small diameter to show flexibility (1110 mm to about 10 pm). It is resistant to temperatures above 900 C. The wire can be chromium I molybdenum, better quartz fibers which are of the same nature as the tube of the lamp, transparent and with a low expansion rate.

The pipe constituting the rear volume of the carrier structure may be of rectangular section, as indicated in the embodiment, but also of any geometric shape, for example circular, ovoid, or square.

The supporting structure 12 may be made of any metallic or composite material having the desired mechanical and thermal resistance characteristics.

The pipe 16 can be separated from the carrying structure 12 and attached thereto, which makes it possible to constitute the pipe 16 in a material different from that of the structure 12. The carrying structure can thus have an H-shaped section. , with a housing for the radiating means, and a housing for a tubular pipe reported thermosetting plastic material. In such a configuration, it is useful to provide pipe-holding flanges which do not constitute excessive thermal bridges between the structure and the pipe.

The shape of the concave reflection surface constituted by the two reflectors 34 can be seen in a plane perpendicular to the axis of the tube, a parabola whose focus is the axis of the cylindrical tube. The tube 36 may be slightly offset from the focal point concave surface. The reflectors 34 may also take a shape approaching that of an ellipse or a parabola, for example a broken form consisting of arcs of circles and / or segments of straight lines.

elsewhere, for manufacturing reasons (surface treatments), the length of the reflectors 34 can not exceed a certain dimension. To obtain a structure 12 of large size (for example several meters), it is possible to have end-to-end sections of reflectors thus achieving a longitudinal surface of homogeneous reflection.

The number of reflectors is not necessarily limited to two. For example, three reflectors forming a quasi-continuous concave reflection surface may be provided with two longitudinal slots allowing air flow towards the space exposed to the radiation, or even four reflectors with three or more intermediate slots.

radiation emission method may be arbitrary. For example, the transmitter lamp may be either filled with a neon-type low-pressure gas, or provided with an axial filament aligned with the focal line and emitting in the infrared and / or the visible, replacing the plasma cylinder. . quartz tube can be replaced by a glass tube. The tube can not be rigorously cylindrical.

The mouth 20 for supplying the fluid line may be placed in one of the outer plugs, in the longitudinal axis of the support structure. It can also be arranged on a side face. It can still be positioned midway between the longitudinal ends of the pipe, which naturally imposes in this case a different distribution of the orifices.

Claims (1)

1. An irradiation device (10) comprising an electromagnetic radiation source comprising a radiation emitter (32), at least two reflectors (34) side remote from the transmitter (32) on either side of the one and each having a reflecting front face (52) facing the transmitter (32), and a rear face (56), the transmitter (32) and the reflectors (34) being arranged to direct the radiation to an exposure space having a middle portion, the two reflectors (34) being separated from each other by a slot (66), means for cooling the reflectors (34) allowing the passage of a fluid cooling the rear face side (56) of the reflectors on the one hand, and through slot (66) on the side of the front face (52) of the other reflectors characterized in that it comprises a carrier structure ( 12) having a housing (18) for the radiation source nt, said housing having walls shaped such that they constitute with the rear face of each reflector a cavity forming a path for the cooling fluid opening on the side of the exposure space by one or more orifices of expulsion ( 80) able to direct the fluid towards the middle part of the exhibition space. 2. irradiation device according to claim 1, characterized in that the reflectors (34) are provided on the side of their rear face (56), a fin (58) cooling, such that the exchange surface formed by the posterior face (56) of the reflectors is significantly greater than the reflective surface formed by the anterior face (52) of the reflectors, and in that the housing (18) has walls shaped in such a way that the cavity they constitute with the posterior face of each reflector is a sinuous cavity. 3. Irradiation device according to claim 2, characterized and that the sinuous cavity has a substantially constant thickness. 4. Irradiation device according to claim 2, characterized in that the carrier structure (12) comprises a distribution duct (16) cooling fluid disposed parallel to the slot (66), and that the device (10) comprises at least one path connecting each serpentine conduit (16). 5. Irradiation device according to claim 4, characterized and that the pipe (1 is separated from the cavity by an intermediate wall having or more communication ports (22) constituting a fluid path connecting the sinuous cavity to the pipe (16). 6. Irradiation device according to claim 5, characterized in that the section of the expulsion orifices (80) is substantially smaller than the section of the orifices of communication 7. The irradiation device according to claim 5, characterized and this intermediate wall (14) comprises at least one orifice (22) connecting the pipe to the slot (66) 8. The irradiation device according to claim 1, characterized and that the rear face (56) comprises at least one stop (62) bearing complementary stop (26) formed in the structure (12), the resultant forces due to the pressure exerted by the fluid on the rear face (56) of the reflector tending to increase the force e exerted by the stop (62) on the complementary stop (64). Irradiation device comprising a source according to the claim characterized in that it comprises motorized means (96) imposing a forced circulation of the fluid in the pipe. 0. Irradiation device according to claim 9, characterized in that comprises a nebulizer (98) projecting into the fluid a liquid in fine droplets. 1. Irradiation device according to claim 1, characterized in that the source of electromagnetic radiation constitutes a unitary unit assembly mounted to slide and supported along two orthogonal axes in the carrier structure (12) aeraulic by means of sliding surfaces (62). on supports (26), and slides (46) sliding on bosses (30).