WO1998054525A1

WO1998054525A1 - Device for exposing a substrate to uv rays and method for using this device

Info

Publication number: WO1998054525A1
Application number: PCT/CH1998/000186
Authority: WO
Inventors: Bernhard Max Glaus
Original assignee: Bernhard Max Glaus
Priority date: 1997-05-26
Filing date: 1998-05-07
Publication date: 1998-12-03
Also published as: EP0985121A1; EP0985121B1; DE59805621D1; ATE224523T1

Abstract

The invention relates to a device comprising a UV lamp (2) which is accommodated in a housing (3) in such a way that UV rays emerge directly or indirectly from an exit (4), and strike a substrate (1) which is to be exposed to the rays. The lamp is air-cooled in a closed circuit, whereby the air enters the housing through an air inlet (6) and leaves the housing again through an air outlet (7). The exit (4) is sealed with a glass plate transparent to UV, so that neither cooling air nor ozone can exit directly from the housing. This also protects the lamp and the reflector surrounding the lamp from being dirtied by the suctioned cooling air.

Description

Device for irradiating a substrate by means of UV rays and method for operating the device

The invention relates to a device for irradiating a substrate by means of UV rays according to the preamble of claim 1. Such devices are used, for example, in printing technology for drying lacquers, inks, etc. by polymerization. Treatments using UV rays are also used, for example, in food technology for preservation purposes, etc.

A problem with UV radiation sources is that in addition to UV radiation, a very high proportion of heat-intensive infrared radiation is emitted. On the one hand, this requires permanent cooling of the radiation source and, on the other hand, measures must be taken so that the mostly heat-sensitive substrate cannot be damaged. To cool the UV radiation source, it was therefore already known to direct an air stream through the housing, which was sealed off with a quartz glass plate.

For example, US-A-5,094,010 shows a UV lamp of the same type, the housing of which is additionally equipped with water cooling. The reflector of the UV lamp is firmly integrated in a relatively solid lamp head. This UV lamp is for drying large workpieces such as Boat hull made of glass fiber reinforced plastic is not intended and suitable for irradiating substrates that pass the radiation source at high speed. It is not possible to quickly shut down or turn away the radiation source.

DE U 93 12 809.6 describes a UV radiation device which is used for highly productive production lines, both is intended for example for the production of compact discs. The outlet opening is covered with a quartz glass pane, but the housing is not hermetically sealed from the surroundings. Ambient air is drawn in via an exhaust device via side ventilation openings and slots. This has the disadvantage that dirt and dust particles can also get into the housing. The reflector of the UV lamp is divided into two movable reflector halves that can be moved together to overlap each other to shield the radiation. Despite the air cooling, the reflector halves are exposed to very high temperatures when closed and the heat rays are also reflected back onto the lamp.

A major disadvantage of open airflow cooling is that the cooling air drawn in contaminants such as Carries dust or fine paint particles. These contaminants hit the surface of the UV lamp or the reflector, where they are burned in due to the high temperature and form a film of dirt over time. This reduces the efficiency of the radiation source.

On the other hand, the known devices with a closed cooling air system cannot work in different operating positions and the very sensitive reflectors are only exposed to the cooling air flow on one side.

It is therefore an object of the invention to provide a device of the type mentioned at the outset in which the UV lamp can be cooled by means of cooling gas without the risk of contamination. Cooling should also be possible with a movable housing or with a movable lamp, in such a way that not only the UV lamp itself, but also the reflector is sufficiently cooled. This object is achieved according to the invention with a device which has the features in the claim 1 has.

Closing the exit side with a UV-radiation-permeable glass plate, in particular with a quartz glass plate, makes it possible to conduct a closed cooling air circuit within the lamp housing. For this purpose, the housing is provided with at least one cooling gas inlet and at least one cooling gas outlet each, in such a way that the UV lamp can be acted upon by the gas flow between the inlet and outlet. Cooling at full power is therefore possible in any operating position without the environment being affected by a current. No more ozone can escape from the lamp. This means that there is no longer any risk that the surface of the substrate will be directly exposed to air containing ozone, which in certain cases can delay the drying desired with the UV rays.

Despite this closed cooling circuit, either the entire housing or the UV lamp in the housing can be moved between a working position and a stand-by position. The reflector is freely mounted in the housing in such a way that cooling gas flows around it in every operating position.

A particularly high degree of efficiency can be achieved if the cooling gas inlet is connected to a pressure fan and if the cooling gas outlet is connected to a suction fan. In this way, large amounts of cooling gas can be guided through the lamp housing with a specific flow. Harmful ozone is extracted. Alternatively, it is of course also conceivable that only the cooling gas inlet is connected to a pressure fan or that only the cooling gas outlet is connected to a suction fan.

This enables particularly efficient cooling that a temperature sensor is arranged in the housing and that control means for controlling the amount of air flowing through the housing are arranged on the pressure fan and / or on the suction fan and are operatively connected to the temperature sensor. The amount of cooling gas can thus be controlled via the temperature sensor. This can be achieved, for example, by the control means having a motor-controlled flap for changing the flow cross section. As a result, the fan drive motor always works at full capacity, so that maximum cooling capacity can be used without delay. Alternatively, the control means can also have a frequency control for the drive motor of the pressure fan and / or the suction fan.

It is particularly advantageous if the cooling gas outlet or an outlet line connected to it is provided with an ozone filter. This prevents contamination of the environment with artificially generated ozone. The air cleaned in this way can be released into the room at a suitable location for heating purposes, since it can have temperatures of up to 80 ° Celsius. It is also conceivable to feed the heated exhaust air into a heat exchanger for the recovery of the heat given off.

In certain cases it is also expedient if the cooling gas inlet or an inlet line connected to it is provided with an air filter. The cooling gas entering the housing is thus cleaned of dust and contamination of the UV lamp is prevented.

The UV lamp in the housing is preferably surrounded by a reflector which is provided with at least one opening for the passage of the air flow. This can advantageously be a longitudinal slot lying on the plane of symmetry of the reflector and running parallel to the UV lamp. As a result, at least part of the amount of cooling gas can be directed directly onto the UV lamp.

A reflector with or without an opening can also be designed to be permeable to heat radiation. As a result, the reflector only reflects the UV rays, while a large part of the heat-intensive IR radiation penetrates the reflector. Such a design of the reflector can be specifically taken into account when guiding the cooling gas within the housing. The reflector particularly advantageously consists of a glass ceramic provided with a mirror layer (e.g. ROBAX® registered trademark). Glass-ceramic materials have a very high permeability to heat rays and are also used for this purpose in electric stovetops. A mirror layer can be applied by known coating techniques, so that UV rays are nevertheless reflected.

To compensate for the relative movement of the housing between the working position and the stand-by position, the supply line and the discharge line are at least partially configured as flexible lines or as telescopic tubes. In this way, the housing forms an autonomous module that can be supplied with a cooling gas flow in a closed system, regardless of its operating position. The housing is advantageously mounted to be linearly displaceable between the working position and the stand-by position. Alternatively, however, it could also be rotatably or pivotably mounted.

In addition to the housing, an absorber for absorbing the heat and UV rays is advantageously arranged in the stand-by position. The absorber can be connected to a suction device for additional cooling.

In the event of a temporary stoppage of the substrate run the housing is automatically moved into the stand-by position so that the substrate is not exposed to excessively long exposure to radiation, which in extreme cases could lead to self-ignition. The UV rays are absorbed by the absorber so that the operating personnel are not at risk.

The maximum possible extension position of the housing for reaching the working position can be adjustable in such a way that the UV lamp irradiates only one section of the substrate, while the remaining section is directed at the absorber and irradiates it. The adjustable extension position has the advantage that the irradiation section can be adapted to the size of the workpiece that is passing through. In this way, means of transport or the like which would heat up need not be irradiated unnecessarily. The housing can be moved linearly particularly advantageously if it is suspended from at least one guide rail and if it can be moved between the working position and the standby position with a pneumatic cylinder. Other drive means such as Linear motors etc. would of course also be conceivable.

The housing is advantageously divided into a first flow chamber in which the UV lamp is arranged and a second flow chamber, the cooling gas inlet being arranged on the first flow chamber and the cooling gas outlet being arranged on the second flow chamber. The two flow chambers are connected to one another via a slot running parallel to the UV lamp or via a series of openings.

The quartz glass plate has a different coefficient of thermal expansion than the steel housing. It is therefore advantageously stored in a dilatation bearing on the housing.

The invention also relates to a method for operating the device mentioned above. This method is characterized by the features in claims 15, 16 and 17. Feeding the cooling gas at a pressure of at least 1 kilopascal causes intensive cooling of all parts within the housing. The working pressure on the pressure fan can be 2 to 3 kilopascals. The pressure difference compared to the housing results from the transmission lines. Depending on the size of the housing, the cooling gas throughput can be up to approx. 400 mV hour. The temperature of the cooling gas fed in can correspond to the ambient temperature, but should not exceed approx. 25 to 30 ° Celsius. In certain cases, it would be conceivable to reduce the temperature of the cooling gas fed in with a cooling unit. The temperature of the exhaust air at the outlet can be 45 to 80 ° Celsius, so that heat recovery makes sense in certain cases.

In certain circumstances it may be advantageous to always maintain a pressure below the atmospheric pressure in the housing. This ensures that no air containing ozone can escape from the housing.

The problem of ozone formation due to the interaction of UV rays and atmospheric oxygen could, however, also be completely eliminated by using nitrogen as the cooling gas. It has also surprisingly been found that the polymerization process proceeds better in a nitrogen atmosphere and it would therefore be conceivable to irradiate the substrate in a nitrogen atmosphere and at the same time to pass the gas as cooling gas through the housing.

Embodiments of the invention are shown in the drawings and are described in more detail below. Show it:

1 shows the side view of a linearly displaceable loading radiation head with the features of the invention,

FIG. 2 shows a cross section through a lamp housing with reflector,

FIG. 3 shows the schematic representation of a cooling air control,

FIG. 4 shows a cross section through a lamp housing with a pivotable UV lamp,

FIG. 5 shows a cross section through a lamp housing for direct and indirect irradiation of the substrate,

FIG. 6 shows a side view of a linearly displaceable radiation head analogous to FIG. 1, but with further structural details,

FIG. 7 shows a top view of the radiation head according to FIG. 6,

8 shows an end view on the radiation head according to FIG. 6 on a somewhat enlarged scale, and

9 shows a dilatation bearing for the quartz glass plate.

In all of the exemplary embodiments described below, ambient air is used as the cooling gas. For the sake of simplicity, the term "air" is therefore always used instead of "cooling gas".

FIG. 1 shows a highly schematized UV lamp 2, which is arranged in a housing 3. Through an exit side 4 on the housing, the UV rays strike a substrate 1, which is guided, for example, on a conveyor belt under the housing. The outlet side 4 on the housing 3 is closed with a UV radiation-permeable quartz glass plate 5. Except for an air inlet 6 and an air outlet 7, the housing 3 is thus largely hermetically sealed. The air inlet 6 is connected to a pressure fan 8, which draws in ambient air and feeds it into the housing 3 at a relatively high pressure. The air outlet 7 is connected to a suction fan 9 which sucks air out of the housing and in turn releases it to the environment via an ozone filter 12. The feed line 10 and the discharge line 11 are preferably designed as flexible lines. Air inlet 6 and air outlet 7 are arranged on the housing such that the UV lamp 2 is in the main flow area. Of course, additional baffles, baffles and the like can be arranged in the housing in order to improve the flow effect. The housing 3 is fastened on a slide, not shown here, on a linear guide 14 and can be moved in the direction of arrow a. With the output of the fans 8, 9 unchanged, the housing can thus be shifted to the right in the illustration from the illustrated working position until the UV lamp 2 lies over the absorber 13. In this stand-by position, the throughput of the substrates 1 can be temporarily stopped. In this way, switching off the UV lamp 2 can be avoided.

A cross section through the housing 3, the outlet side 4 of which is closed with a quartz glass plate 5, is likewise shown in highly schematic form. The UV lamp 2 is surrounded by a reflector 15 which has a gap 16 above the UV lamp 2. Through this gap, cooling air from the air inlet 6 can strike the UV lamp 2 directly. Part of the cooling air sweeps along the back of the reflector 15 and also cools it. The air outlet 7 is arranged on the long side, but, like the air inlet, could also be on an end side. Self-evident In each embodiment, several air inlets or air outlets could also be arranged on the housing.

The reflector 15 is designed by means of a surface coating in such a way that only the UV rays 21 are reflected, while heat-intensive IR rays 22 penetrate the reflector directly. This measure also serves to keep harmful heat rays away from the substrate.

FIG. 3 schematically shows a lamp housing 3 with a UV lamp 2 arranged therein. A temperature sensor 19 is also fitted in the housing, with the aid of which the internal temperature can be monitored continuously. The temperature sensor 19 is operatively connected to an actuator 20 with which flap valves 18, 18 'in the feed line 10 or in the discharge line 11 can be actuated. The drive motors 17, 17 'of the Druckventilatorε 8 and the suction fan 9 always work at full power and the control of the air volume takes place only via the flap valves. Alternatively, the drive motors 17, 17 'could also be provided with a frequency control which receives control pulses from the temperature sensor 19.

FIG. 4 shows a lamp housing 3 in which the UV lamp 2 arranged therein, together with its reflector 15, can be pivoted through 90 °. In the working position shown, the UV rays exit through the quartz glass plate 5 on the exit side 4. In the standby position of the reflector shown at 15 ', the rays strike a protective plate 23.

Of course, alternative working positions or stand-by positions would also be conceivable, in which the UV rays are deflected onto the substrate or away from the substrate via a partially transparent mirror. Such embodiments are described, for example, in CH-A-660 489. The part- transparent mirror can be fixed or pivoted in the housing.

FIG. 5 shows a UV lamp in which two different operating positions are possible. A plurality of air inlets 6, 6 ′, 6 ″ and a plurality of air outlets 7, 7 ′ are arranged in the housing 3 with the outlet side 4 closed by a quartz glass plate 5. The UV lamp 2 is provided with a reflector 15 which can be rotated into three different positions. A partially transparent mirror 24 is arranged next to the UV lamp, via which UV rays 21 can be directed onto the substrate 1 in a first operating position, while the heat-intensive IR rays 22 penetrate the mirror and are absorbed on the absorber 13. In a second operating position, the reflector 15 can be pivoted through 90 ° in such a way that the radiation falls directly through the glass plate 5 onto a substrate 1. This direct radiation contains the entire radiation spectrum, including the IR rays, which may be desirable in certain cases. In the stand-by position, the reflector 15 is turned upward so that the rays fall onto the mudguard 23. On such a multifunctional radiation head, air cooling in the closed housing is particularly advantageous because the mechanically movable parts and in particular also the sensitive mirror 24 are protected by the quartz glass plate 5. The cooling air can be directed inside the housing to where it is needed, e.g. also on the absorber 13.

Of course, additional cooling measures can also be provided on the housing without thereby departing from the subject matter of the invention. So it would be e.g. conceivable that cooling channels are additionally provided for the passage of a cooling liquid.

FIGS. 6 to 8 show an irradiation head which if linearly displaceable in the direction of arrow a. The shift takes place on a frame 25, which can be part of an irradiation device. For this purpose, roller bearings 26 are arranged on the frame, which engage in two U-shaped guide rails 27 on the top of the housing 3. A pneumatic cylinder 28 is attached between the two guide rails, the piston rod of which is connected to the frame at a piston attachment 37. The pneumatic cylinder is supplied via pneumatic lines, not shown here. The fully extended position is shown in FIG. 6, so that the UV lamp 2 emits down over its entire length onto the substrate.

Using limiting means not shown here, such as plug-in stop bolts or the like, the maximum possible extension position can be limited. Such a limitation has the effect, for example, that the end face of the radiation head extends only up to the vertical plane 36. In this position, the UV lamp 2 emits radiation downward only over part of its length. The remaining section of the lamp partially overlaps the absorber 13, which is arranged firmly under the housing 3. The absorber 13 consists of grill-like lamellae and can heat up to red heat when intensely irradiated. In the withdrawn standby position, the UV lamp 2 irradiates the absorber over its entire length.

In the present case, a cylindrical bottle cap 35 is shown as the substrate, which is attached to the end of a mandrel 34. When the UV lamp 2 is completely extended, a part of the mandrel 34 would obviously also be irradiated and thus heated. Since the mandrel 34 is not cooled, this could damage the closure cap 35. On the other hand, when extending to the extended position 36, practically only the locking cap 35 irradiated.

The housing 3 is divided into a first flow chamber 29 and a second flow chamber 30. Separation plates 31, which leave a longitudinal slot 32 open in the middle, serve as the subdivision. This longitudinal slot runs over the longitudinal slot 16 which the two reflector halves form. The cooling air enters the first flow chamber 29 via the supply line 10, flows around the UV lamp 2 and its reflector 15 and then passes in the direction of arrow b into the second flow chamber 30, which also leaves it again via the discharge line 11 at the end. The lines 10 and 11 are designed as flexible hose lines. This also applies to the absorber suction line 33, via which ambient air is extracted through the absorber grill for cooling purposes. The electrical lines which lead to the UV lamp 2 or to the temperature sensor 19 are likewise combined in a flexible hose 40.

FIG. 9 shows a dilatation bearing 38 for holding the quartz glass plate 5. This is attached to the housing 3 by means of a holder 39 such that it can expand in the direction of the arrow c. The bracket 39 must not clamp the quartz glass plate. Rather, it has proven to be advantageous that the quartz glass plate rests freely with sufficient play in the holder 39 (dash-dotted position). If a negative pressure is maintained in the housing in relation to the atmosphere, the quartz glass plate is sucked in and presses tightly against the housing opening (hatched position). However, the use of high-temperature resistant sliding seals would also be conceivable.

Claims

claims

1. Device for irradiating a substrate (1) by means of UV rays, with a UV lamp (2) which is arranged in a housing (3) in such a way that UV rays directly or indirectly on an exit side (4) from the Exit the housing, the outlet side being closed with a UV-radiation-permeable glass plate (5), and with means for cooling the UV lamp by means of a cooling gas stream, the housing (3) each having at least one cooling gas inlet (6) connected to a supply line (10) ) and at least one cooling gas outlet (7) connected to a discharge line (11) so that cooling gas can be passed through the housing, characterized in that the entire housing (3) or the UV lamp in the housing between a working position in which the UV rays hit the substrate and a stand-by position, in which the UV rays are directed away from the substrate, is movable, and that the UV lamp (2) has a reflector (15) which is in the walk The cooling gas flows around the housing (3) in the working position and in the standby position.

2. Device according to claim 1, characterized in that the supply line (10) with a pressure fan (8) and / or that the discharge line (11) with a suction fan (9) is connected, that in the housing (3) a temperature sensor (19 ) and that control means for controlling the amount of air flowing through the housing are arranged on the pressure fan (8) and / or on the suction fan (9) and are operatively connected to the temperature sensor.

3. Device according to claim 2, characterized in that the control means a motor-controlled flap (18, 18 ') for changing the flow cross section exhibit.

4. The device according to claim 2, characterized in that the control means have a frequency control for the drive motor (17, 17 ') of the pressure fan and / or the suction fan.

5. Device according to one of claims 1 to 4, characterized in that the reflector (15) has a lying on its plane of symmetry and parallel to the UV lamp longitudinal slot (16) for passing the cooling gas stream.

6. Device according to one of claims 1 to 5, characterized in that the reflector (15) is designed to be permeable to heat radiation.

7. The device according to claim 6, characterized in that the reflector (15) consists of a glass ceramic provided with a mirror layer.

8. Device according to one of claims 1 to 7, characterized in that the housing is mounted linearly displaceable between the working position and the stand-by position.

9. The device according to claim 8, characterized in that the feed line (10) and the discharge line (11) are designed to compensate for the relative position of the housing between the two working positions at least in sections as flexible lines or as telescopic tubes.

10. The device according to claim 8 or 9, characterized in that in addition to the housing, an absorber (13) for absorbing the heat and UV rays in the stand-by Position is arranged, and that a suction device is arranged on the absorber for additional cooling.

11. The device according to claim 10, characterized in that the maximum possible extension position of the housing (3) for reaching the working position is adjustable such that the UV lamp (2) irradiates only one section of the substrate, while the remaining section the absorber irradiated.

12. Device according to one of claims 8 to 11, characterized in that the housing (3) is suspended on at least one guide rail (27) and can be displaced with a pneumatic cylinder (28) between the working position and the stand-by position.

13. Device according to one of claims 1 to 12, characterized in that the housing (3) in a first flow chamber (29), in which the UV lamp (2) is arranged, and in a second flow chamber (30) is divided , and that the cooling gas inlet (6) is arranged on the first flow chamber (29) and the cooling gas outlet (7) on the second flow chamber (30), the two flow chambers via a slot (32) running parallel to the UV lamp (2) or are connected to one another via a series of openings.

14. Device according to one of claims 1 to 13, characterized in that the quartz glass plate (5) is mounted in a dilatation bearing (38) on the housing such that temperature-related expansions in your plane can be compensated.

15. The method, in particular for operating the device according to one of claims 1 to 14, characterized in that cooling gas with a pressure of at least one kilopase. cal is fed into the housing (3) via the cooling gas inlet (6).

16. The method, in particular for operating the device according to one of claims 1 to 15, characterized in that a pressure below atmospheric pressure is maintained in the housing.

17. The method, in particular for operating the device according to one of claims 1 to 15, characterized in that nitrogen is used as the cooling gas.