System and a method for irradiating an object

Abstract

A system and a method for irradiating an object and potentially for controlling the irradiation or other conditions relating to an effect of the irradiation. A sensor is translated along a longitudinal direction of the radiation emitter and in a space between the radiation emitter and the objects irradiated to arrive at information relating to a parameter relating to the effect of the irradiation, such as the radiation, and derived in the space between the radiation emitter and the objects irradiated. Calibrating the sensor readings and adjusting the radiating emitter output, thereby controlling the irradiation.

Claims

1. An irradiating system comprising: an elongate radiating element having a longitudinal axis and being configured to output radiation from multiple positions thereof and in a first direction away from the longitudinal axis, a transporting element configured to transport one or more objects in a second direction past the radiating element to have the object(s) irradiated by the radiation, a sensor configured to sense a parameter, the sensor comprising a collecting element, a translator configured to translate the collecting element along the longitudinal axis and at a position between the radiating element and the transporting element.

2. An irradiating system according to claim 1, wherein the translator is configured to translate the collecting element to a position outside of a space between the radiating element and the transporting element.

3. An irradiating system according to claim 1, further comprising a cleansing element configured to cleanse an outer surface of the collecting element.

4. An irradiating system according to claim 1, wherein the sensor is configured to determine a representation of an intensity of radiation emitted as a function of position along the longitudinal direction.

5. An irradiating system according to claim 1, wherein: the radiating element comprises: a plurality of radiation emitters positioned sequentially along the longitudinal direction and a power supply individually supplying power to each radiation emitter, the sensor is configured to: as the parameter, sense the intensity output from the emitters identify a first emitter outputting insufficient intensity and output first information relating to one or more emitters adjacent to the first emitter as well as second information relating to an intensity increase desired from the adjacent emitter(s).

6. An irradiating system according to claim 1, wherein the sensor is configured to determine, as the parameter, one or more of the group consisting of: a lowest sensed radiation intensity, a highest sensed intensity, a difference between a highest and a lowest sensed intensity.

7. An irradiating system according to claim 1, wherein the collecting element is an elongate element configured to guide radiation received thereby toward a sensing element configured to sense the radiation and output a corresponding signal.

8. An irradiating system according to claim 1, wherein the collecting element is a rod transparent to radiation output of the radiating element.

9. An irradiating system according to claim 1, further comprising an additional sensor configured to be translated along the longitudinal direction and which is configured to receive radiation from the objects and output a parameter relating to the objects.

10. A method of operating the system according to claim 1, the method comprising: the transporting element transporting elements in the second direction, the radiating element emitting the radiation in the first direction, the translator translating the collecting element while the collecting element collects radiation or gas and feeds at least a portion thereof to a sensing element of the sensor, the sensor sensing a parameter of the radiation or gas.

11. A method according to claim 10, wherein the translating step comprises translating the collecting element to a position outside of a space between the radiating element and the transporting element.

12. A method according to claim 11, further comprising the step of cleansing an outer surface of the collecting element.

13. A method according to claim 10, wherein the sensing step comprises determining a representation of an intensity of radiation emitted as a function of position along the longitudinal direction.

14. A method according to claim 10, wherein: the radiating element comprises: a plurality of radiation emitters positioned sequentially along the longitudinal direction and a power supply individually supplying power to each radiation emitter, the sensing step comprises: sensing, as the parameter, an intensity output from the emitters identifying a first emitter outputting insufficient intensity and outputting first information relating to one or more emitters adjacent to the first emitter as well as second information relating to an intensity increase desired from the adjacent emitter(s).

15. A method according to claim 10, wherein the sensing step comprises determining, as the parameter, one or more of the group consisting of: a lowest sensed radiation intensity, a highest sensed intensity, a difference between a highest and a lowest sensed intensity.

Description

(1) In the following, preferred embodiments of the invention will be described with reference to the drawing, wherein:

(2) FIG. 1 illustrates a system according to the invention seen from the front,

(3) FIG. 2 illustrates the system of FIG. 1 seen from the side,

(4) FIG. 3 illustrates an output type of the sensor element and

(5) FIG. 4 illustrates a sensor comprising multiple elongate radiation receivers/guides.

(6) In FIG. 1, a standard radiating system 10 is seen having an elongate radiation emitting element 12, such as a UV lamp comprising one or more elongate emitters which may be UV LEDs or more old-fashioned emitters. The emitters may be formed as individual blocks 121 of emitters which are assembled to a desired length.

(7) Objects 14 to be irradiated are transported below the element 12 on a carrier band 16. The irradiation may be to cause a coating or ink to cure, to sterilize the objects or e.g. to modify a surface of the objects 14 or the like. The radiation impinging on the objects may be used for generating any desired effect in or on the objects. A coating on or of the objects may be affected, such as cured, or the surface may be sterilized or otherwise modified. Surface characteristics of the objects, such as gloss, surface tension or the like may also be affected by the radiation. Polymers may be cross-bound by the radiation if desired. Thus, all known radiation induced reactions may be controlled using the present set-up.

(8) The objects 14 are transported at a velocity ensuring, under normal circumstances, sufficient curing/sterilization/treatment of the objects 14, but this often requires that the intensity of the radiation 18 is within a desired interval or above a lower limit.

(9) Radiation emitters may fade over time or become inoperable. Some emitters have a built-in sensor providing an output of the intensity output of this particular emitter.

(10) However, the emitters may also be covered by dirt or debris, reducing the overall intensity output in the direction toward the objects. A built-in sensor would not sense this.

(11) In the present embodiment, a sensor 20 is provided which is translatable along a guide 201 along the longitudinal length of the emitter 12 while having (see also FIG. 2) an elongate radiation receiver or guide 203 extending below the emitter 12, the receiver/guide 203 collecting radiation from below the emitter 12 and feeding it to a sensor element 202.

(12) In this manner, the actual radiation intensity output may be determined along the length of the emitter. From an output of the sensor element, information may be derived as to the state of the emitter 12 and/or the quality of the curing/treatment/sterilization taking place.

(13) The guide 203 may simply be a transparent rod collecting whatever radiation is impingent. The rod may have across its cross section a variation in refractive index in order to better guide radiation. Alternatively, the outer edges of the rod may be surrounded by e.g. air generating the desired index difference.

(14) In other embodiments, the guide may comprise e.g. a mirror or other reflector for directing radiation from a predetermined direction, such as an upward direction, toward the sensor element. Then, no refractive index change may be required to guide the radiation to the sensor element.

(15) The output may be a simple graph as seen in FIG. 3 illustrating an output of the sensor 202 as the receiver/collector 203 is translated along the length of the receiver. This output may be representative of an intensity of the radiation at the individual positions along the longitudinal direction.

(16) From the output, a number of types of information may be derived. Firstly, the intensity itself may be estimated at different positions. This intensity may directly relate to the quality of the curing of the coatings/inks on the elements, the surface modification or the sterilization of objects. As the intensity may vary along the length of the emitter, so may the quality of the curing/modification/sterilization. A desired intensity interval may be set for optimal curing. If the intensity at a position along the longitudinal axis falls outside of the interval, an un-optimal curing (or other treatment) may be obtained. Thus, non-cured objects may be obtained, or objects may be obtained which have received too much radiation. Too much radiation may heat the object too much and thus damage it.

(17) The output may itself be used for a quantitative determination and thus for e.g. controlling the speed of the belt, such as from a maximum or minimum value of the output. Alternatively, the mere variation of the output of the sensor may be used to give a general idea of the state of the system but other sensors may be used to sense the actual intensities output.

(18) Clearly, the intensity or dose of radiation received may also depend on the velocity of transport of the objects 14 by the belt 16. Thus, if a too high intensity is generally experienced by the sensor, the velocity of the belt 16 may be increased. However, if parts of the emitter output too low intensity, that would then bring parts of the elements or parts of the emitter outside of the desired range.

(19) From the output of the sensor, different quantifications or parameters may be obtained depending on the situation. In some situations, it is merely desired that the lowest intensity is known. Then, the output may be analyzed to determine the lowest value (indicated in FIG. 3). In other situations, the highest intensity is of interest and in yet other situations, the difference between the highest and lowest intensities may be of interest.

(20) Such parameters may be used for determining a state of the system, such as if the emitter 12 or a portion 121 thereof is to be replaced or if cleaning, compensation or alteration is required to bring the intensity within the desired regime again.

(21) In one situation, the emitter 12 comprises a number of smaller emitters, such as LEDs along the longitudinal direction. Thus, if one LED is defect or has a lower emission, neighbouring LEDs may be controlled to output more radiation to compensate for the lower emission from the less performing LED. This situation may be identified in the output of FIG. 3 as a dip in intensity. The faulting LED or position may be determined as may the neighbours which may then be operated to output a higher intensity. Once the compensating scheme is determined, the sensor may be operated again to ensure that the compensation takes place as desired.

(22) Alternatively or additionally, the lowest value, highest value, mean value or difference value may be used for alarming an operator to take action.

(23) Naturally, not just a single emitter may be provided at each position along the longitudinal direction. The emitter may comprise an array of emitters having rows along the longitudinal direction and columns perpendicular thereto (the array being parallel to the plane wherein the elements 14 are transported.

(24) Thus, if a column is identified from which the intensity is too low (or too high), the neighbouring columns may be operated to compensate.

(25) As described above, any intensity pattern or curve may be obtained along the longitudinal axis. A constant intensity is usually desired. Thus, the elongate radiating element or the emitters may be controlled to arrive at the desired intensity by e.g. increasing or lowering the intensity output at particular positions. This intensity may be that of a portion or emitter outputting the least intensity or a predetermined intensity where, if a portion or emitter is not able to output that intensity, neighbouring emitters or portions may have their intensity increased to arrive at the desired intensity.

(26) Instead of actually taking action on the basis of the representation of the information, the representation may simply be stored in order to document the operation of the system.

(27) In fact, the collector/guide may be able to determine the intensity also at different positions along its length, whereby the particular faulting LED in the column may be determined. Then, the other LEDs of the column may additionally or alternatively be used for compensating.

(28) The receiver/guide may be a single rod of a material transmissive to the wavelength(s) output by the emitter. Alternatively, the receiver/guide may comprise a number of individual guides, such as individual guides collecting radiation at different positions along the length of the element 203, so that not only can the complete intensity output from a position along the longitudinal direction of the emitter be determined but also the intensity profile perpendicular thereto (along the length as seen in FIG. 2).

(29) Naturally, after correction, the collector may be translated again and the information re-determined to ascertain that the correction was performed as desired.

(30) It may be possible that the guide 203 itself may also be contaminated. Thus, it may be desired that the guide, when not translated between the emitter and the band, is moved into a protective housing 204 which may be positioned outside of (along the longitudinal direction) the area between the belt and emitter so as to not block the radiation when not operating.

(31) Additionally or alternatively, the guide may be cleansed at regular intervals or after/before each use, such as by cleansing brushes, cleansing fluid or the like.

(32) In order to take into account any damage, dirt, aging or the like on or of the guide, the sensor may output information relating to a relative measurement.

(33) Thus, the guide may be translated from one end of the emitter to the other and back again and calibration measurements may be made before translating the guide and after. If a too large difference exists, the guide may need replacing.

(34) Also, any difference may be used for correcting the output of the sensor, such as the graph of FIG. 3.

(35) Alternatively, a calibration emitter may be provided (not illustrated) in the housing 204 so as to provide a measure of the state of the guide. The read-out of the sensor may thus be used for correcting the output of the sensor when the guide is translated. In that manner, the output of the sensor may be quantified to read-out fx the actual intensity output.

(36) Naturally, the sensor may be used for sensing other parameters than the intensity output, such as a wavelength output, wavelength interval or the like output, or a spectrum of the radiation output. Emitters may vary not only or not at all in intensity but in wavelength. A shift in wavelength may also give a variation in the curing/modification/sterilization performed.

(37) On one embodiment, the guide 203 may be used for sensing not parameters of the radiation 18 of the emitter but a parameter of the objects 14. The guide thus may be configured to receive radiation from the objects 14. Naturally, both radiation from the emitter 12 and the objects 14 may be desired sensed. This may be obtained using the same collector.

(38) Alternatively, as is illustrated in FIG. 4, another radiation collector or guide 205 may be provided which may be configured to receive radiation from the objects 14. The guides 203 and 205 may be configured to receive radiation from different directions (one from a downward direction and the other from above) or may be configured to guide radiation of different wavelengths. Alternatively, the sensor element 202 may be configured to filter, from the received radiation, the radiation desired for the intensity output and the parameter of the objects 14. The guide 205 may be of the general types described above.

(39) One parameter of interest of the objects 14 is gloss. The gloss of the objects may be affected by the intensity of the radiation impinging on the objects. Variation in the irradiation may result in a variation in gloss. Gloss is often measured as relative reflection of radiation/light (UV or visible) at a defined angle.

(40) Radiation reflected from a particular angle may be determined by a collector or detector aimed in a predetermined angle toward the objects or the transporting element. Such aiming may be obtained using e.g. a lens, an aperture or the like.

(41) The radiation thus detected may be generated by the elongate radiating element, if the direction is selected so that radiation emitted by the radiating element may be reflected under the desired angle and toward the collector/detector.

(42) Alternatively, a separate light/radiation source may be positioned so as to emit radiation or light on to the objects under the desired angle and so that the reflected radiation/light impinges on the collector/detector. In this situation, the separate light/radiation source may be translated along with the collector/detector, such as if also attached to the translator.

(43) When a separate light/radiation source is used, a wavelength may be used which is not output from the elongate radiating element. This facilitates separation, if required, of the radiation from the elongate radiation source and the separate light/radiation source.

(44) A wide range of parameters may be determined from the objects based on radiation emitted/reflected/scattered therefrom or thereby. One parameter of interest of the objects 14 is the degree of hardening/curing. One advantage of radiation hardening/curing is that the hardened objects may be immediately stacked or touched, but this requires that the hardening is sufficient. Hardening may be determined or quantified from the number of residual double bonds in the object/coating/paint/surface. The fewer residual doublebonds, the higher the degree of curing.

(45) Double bonds may be quantified in a number of manners, one being based on the infrared absorption spectrum of the surface/coating/ink. From this spectrum, such as using Fourier transformation, an estimate of the degree of curing may be obtained.

(46) For this determination, radiation from the elongate radiating element may be used, or again a separate radiation emitter may be provided for launching radiation on to the objects. The absorption may be determined or estimated from radiation reflected by the objects.

(47) Also, fluorescence may be used for determining the degree of curing. See e.g. “Characterization of Photocurable Coatings Using Fluorescence Probes”, Song et al, Naval contract N00014-93-1-0772.

(48) Naturally, also other parameters of the objects may be determined from radiation output thereof, such as a surface temperature of the object or of the lamp.

(49) Another feature would be colour or colour differences and/or surface imperfections of the objects. Surface imperfections and colour differences may stem from imperfect coating thereof and/or knots in underlying wood. Colour differences may be caused by imperfect coating or imperfect treatment, such as curing.

(50) In another embodiment, the irradiation is desired performed in a particular atmosphere, typically an oxygen free or oxygen depleted atmosphere. Thus, a particular gas, often Nitrogen, is fed to the space between the radiating element and the objects. This gas may be fed into this space at a number of locations along the longitudinal direction.

(51) In this situation, the collector and sensor may be configured to determine a gas parameter, such as a partial pressure or temperature, to arrive at a representation of this parameter long the longitudinal directions.

(52) The gas may be oxygen, the gas input (nitrogen) or a gas emitted by the objects during irradiation, for example.

(53) This representation may be compared to minimum and/or maximum values. This representation may be used for varying the gas introduction at positions at which the gas pressure determined is not desirable. Alternatively, the representation may be used for varying the irradiation or transport if desired.

(54) The gas may be fed to a space between the radiating element and the objects/transporting element especially if a shroud or the like is provided sealing this space from the surroundings (while allowing the objects to enter/exit this space). The gas may be fed to this space via one or more openings into this space, where flow controllers preferably are provided for individually controlling the flow into each of these openings so that a variation (along the length) of a gas pressure for example may be compensated for by varying the gas pressure at an identified opening.