(19)
(11)EP 3 543 633 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
24.02.2021 Bulletin 2021/08

(21)Application number: 19163899.8

(22)Date of filing:  23.12.2009
(51)Int. Cl.: 
F26B 3/34  (2006.01)
F26B 3/28  (2006.01)
F26B 5/02  (2006.01)
B41F 23/04  (2006.01)
F26B 7/00  (2006.01)
F26B 21/00  (2006.01)

(54)

ULTRASONIC DRYING APPARATUS AND METHOD

ULTRASCHALLTROCKNUNGSAPPARAT UND -VERFAHREN

PROCÉDÉ ET DISPOSITIF DE SÉCHAGE À ULTRASONS


(84)Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR

(30)Priority: 09.02.2009 US 367803

(43)Date of publication of application:
25.09.2019 Bulletin 2019/39

(62)Application number of the earlier application in accordance with Art. 76 EPC:
09839835.7 / 2394121

(73)Proprietor: Heat Technologies, Inc.
Atlanta, GA 30356 (US)

(72)Inventor:
  • PLAVNIK, Zinovy, Z.
    Atlanta, GA Georgia 30350 (US)

(74)Representative: Eisenführ Speiser 
Patentanwälte Rechtsanwälte PartGmbB Am Kaffee-Quartier 3
28217 Bremen
28217 Bremen (DE)


(56)References cited: : 
WO-A1-2006/042559
JP-A- 2000 258 055
JP-A- H0 626 764
US-A1- 2003 184 630
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    TECHNICAL FIELD



    [0001] The present invention relates generally to heating and drying technologies and, in particular, to heating and drying assisted with ultrasound.

    BACKGROUND OF THE INVENTION



    [0002] It is well known that the majority of energy intensive processes are driven by the rates of the heat and mass transfer. Specific details of a particular application, such as the chemistry of a substrate to be dried (e.g., a factor in label printing, sheet-fed and continuous printing, converting, packaging, mass mailing), the temperature of a material being applied, the needed residence time for a coating to dry, and water or solvent evaporation rates, are necessary for a drying and heating process to work properly. These factors dictate the size of the drying equipment.

    [0003] It is also well known that the main thing that prevents an increase in heating and drying rates is the boundary layer that is formed around the subject or material to be heated or dried. In modern heating and drying practice there are several methods to disrupt the boundary layer. The most common method is to add hot convection air to other heating methods, such as, for example, radiant heating.

    [0004] With convective heat, high-velocity impinging jets of hot air are directed onto the material and, consequently, onto the boundary layer to agitate the boundary layer. Similarly, impinging hot-air jets are used in infrared-light heating. Applying a convective airflow or infrared light typically increases the heat transfer rate by about 10-25%. Thus, these approaches have provided some improvement in heat-transfer rates, but further improvements are needed.

    [0005] There are also known efforts of using pulse combustion to establish pulsating heat jets and apply them onto a material in order to reduce the boundary layer. With pulse combustion jets, flame generates sound in the audible frequency range. The use of pulse combustion jets typically increases the heat transfer rate by about 200-500% (when making a comparison with the same steady-state velocities, Reynolds numbers, and temperatures). Thus, this approach has provided significant improvement in heat-transfer rates, but the pulse combustion equipment is large/space- consuming and costly to purchase and operate. Additionally, a variety of industries require more compact equipment, and combustion gases sometimes are not allowed in the process due to its chemical nature (food, paints, coatings, printing, concerns of explosives, building codes, needs for additional natural gas lines, its maintenance, etc.).

    [0006] Accordingly, it can be seen that a need exists for improved drying technologies that produce significantly increased heat-transfer rates but that are cost- efficient to make and use and preferably have a smaller footprint and require less material. It is to the provision of solutions meeting this and other needs that the present invention is primarily directed. JP H06 26764 A discloses a hot air drier having a nozzle for generating an ultrasonic pressure wave. WO 2006/042559 A1 discloses a method and device for drying a flow of biomass particles.

    SUMMARY OF THE INVENTION



    [0007] The present invention provides a method of drying a material according to claim 1 and a drying apparatus according to claim 6, the drying apparatus including a delivery air enclosure, through which forced air is directed toward the material, and at least one ultrasonic transducer. The ultrasonic transducer is arranged and operated to generate acoustic oscillations that effectively break down the boundary layer to increase the heat transfer rate. In particular, the acoustic outlet of the ultrasonic transducer is positioned a spaced distance from the material such that the acoustic oscillations are in the range of about 120 dB to about 190 dB at the interface surface of the material. Preferably, the acoustic oscillations are in the range of about 160 dB to about 185 dB at the interface surface of the material.

    [0008] In another aspect which is not part of the present invention, the ultrasonic transducers are positioned a spaced distance from the material to be dried of about (λ)(n/4), where λ is the wavelength of the ultrasonic oscillations and "n" is plus or minus 0.5 of an odd integer (0.5 to 1.5, 2.5 to 3.5, 4.5 to 5.5, etc.). Preferably, the ultrasonic transducers are positioned relative to the material to be dried the spaced distance of about (λ)(n/4), where "n" is an odd integer (1, 3, 5, 7, etc.). In this way, the amplitude of the acoustic oscillations is at about maximum at the interface surface of the material to more-effectively agitate the boundary layer.

    [0009] In a first example embodiment of the invention, the apparatus includes a return air enclosure for drawing moist air away from the material, with the delivery enclosure positioned within the delivery enclosure so that the warm moist return air in the return enclosure helps reduce heat loss by the air in the delivery enclosure. The ultrasonic transducer is of a pneumatic type that is positioned within an air outlet of the delivery enclosure so that all or at least a portion of the forced air is directed through the pneumatic ultrasonic transducer.

    [0010] In a second example which is not part of the present invention, the apparatus is included in a printing system that additionally includes other components known to those skilled in the art. In this embodiment, the apparatus includes two delivery enclosures, one return enclosure, and two ultrasonic transducers. In addition to the apparatus, the printing system includes an air-mover (e.g., a fan, blower, or compressor) and a heater that cooperate to deliver heated steady-state air to the apparatus.

    [0011] In a third example which is not part of the present invention, the apparatus is included in a printing system that additionally includes other components known to those skilled in the art. In this embodiment, the apparatus includes five delivery enclosures each having at least one ultrasonic transducer. In addition to the apparatus, the printing system includes an air-mover and control valving that can be controlled to operate all or only selected ones of the ultrasonic transducer for localizing the drying, depending on the particular job at hand.

    [0012] In fourth and fifth example which are not part of the present invention, the apparatus each include a return enclosure with a plurality of return air inlets and three delivery enclosures within the return enclosure. In these embodiments, one delivery enclosure is dedicated for delivering steady-state air and the other two have ultrasonic transducers for delivering the acoustic oscillations to the material. In the fourth example which is not part of the present invention the two acoustic delivery enclosures are positioned immediately before and after (relative to the moving material) the dedicated air delivery enclosure. And in the fifth example which is not part of the present invention the two acoustic delivery enclosures are positioned at the front and rear ends (relative to the moving material) of the return enclosure, that is, at the very beginning and end of the drying zone.

    [0013] In a sixth example which is not part of the present invention, the apparatus includes a return enclosure, a delivery enclosure, and an ultrasonic transducer. However, the delivery enclosure is not positioned within the return enclosure; instead, these enclosures are arranged in a side-by-side configuration. In addition, an electric heater is mounted to the delivery enclosure for applying heat directly to the material.

    [0014] In a seventh example which is not part of the present invention, the apparatus includes a delivery enclosure, an ultrasonic transducer, and a heater. The heater may be bi-directional for heating the air inside the delivery enclosure (convective heat) and directly heating the material (radiant heat).

    [0015] In eighth, ninth, and tenth example which are not part of the present invention, the apparatus include a delivery enclosure with a plurality of air outlets and a plurality of electric ultrasonic transducers. In the eighth example which is not part of the present invention the air outlets and electric ultrasonic transducers are positioned in an alternating, repeating arrangement. The ninth example which is not part of the present invention includes an electric heater within the delivery enclosure. And the tenth example which is not part of the present invention includes waveguides housing the ultrasonic transducers for focusing/enhancing and directing the acoustic oscillations toward the material.

    [0016] In an eleventh example which is not part of the present invention, the apparatus includes a delivery enclosure with a plurality of air outlets and a plurality of electric ultrasonic transducers. In addition, the apparatus includes infrared-light-emitting heaters.

    [0017] In a twelfth example which is not part of the present invention, the apparatus is a stand-alone device including a delivery enclosure with a plurality of air outlets and housing a plurality of electric ultrasonic transducers, a plurality of infrared-light-emitting heaters, and an air mover.

    [0018] In a thirteenth example which is not part of the present invention, the apparatus includes a delivery enclosure with a plurality of air outlets, a plurality of electric ultrasonic transducers, and a plurality of infrared-light-emitting heaters. In this embodiment, steady-state air is not forced by an air mover through the delivery enclosure, but instead the infrared heater by itself generates the heat and the airflow.

    [0019] In a fourteenth example which is not part of the present invention, the apparatus includes a plurality of ultrasonic transducers mounted on a panel, with no steady-state air forced by an air mover through an enclosure. Instead, the apparatus includes at least one UV heater for generating the heat and the airflow.

    [0020] In fifteenth and sixteenth example which are not part of the present invention, the apparatus each include a delivery enclosure with an air outlet for delivering forced air to the material, and at least one ultrasonic transducer for delivering acoustic oscillations to the material. The ultrasonic transducers are mounted within the delivery enclosure to set up a field of acoustic oscillations through which the forced air passes before reaching the material to be dried, and they are not oriented to direct the acoustic oscillations toward the air outlet. In the fifteenth example which is not part of the present invention three rows of ultrasonic transducers are mounted to an inner wall of the delivery enclosure to set up a field of acoustic oscillations throughout the delivery enclosure. And in the sixteenth example which is not part of the present invention the ultrasonic transducer is mounted immediately adjacent the air outlet. In addition, wing elements can be mounted to the electric ultrasonic transducers to enhance the acoustic oscillations for more effective disruption of the boundary layer.

    [0021] In addition, a method which is not part of the present invention provides a method of calibrating drying apparatus such as those described above. The method includes the steps of calculating the spaced distance using the formula (λ)(n/4); positioning the ultrasonic transducer outlet and the material at the spaced distance from each other; positioning a sound input device immediately adjacent the interface surface of the material; connecting the sound input device to a signal conditioner; measuring the pressure of the acoustic oscillations at the interface surface of the material using the sound input device and the signal conditioner; converting the measured pressure to decibels; and repositioning the ultrasonic transducer relative to the material and repeating the measuring and converting steps until the decibel level at the interface surface of the material is in the range of about 120 dB to about 190 dB, or more preferably in the range of about 160 dB to about 185 dB. In the formula (λ)(n/4), "λ" is the wavelength of the ultrasonic oscillations and "n" is in the range of plus or minus 0.5 of an odd integer so that the acoustic oscillations at the interface surface of the material are within about a 90-degree range centered at about maximum amplitude. Preferably, "n" is an odd integer so that the acoustic oscillations at the interface surface of the material are at about maximum amplitude.

    [0022] The specific techniques and structures employed by the invention to improve over the drawbacks of the prior devices and accomplish the advantages described herein will become apparent from the following detailed description of the example embodiments of the invention and the appended drawings and claims.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0023] 

    FIG. 1 is a longitudinal cross-sectional view of a drying apparatus according to a first example embodiment of the present invention, showing an air delivery enclosure, an ultrasonic transducer, and an air return enclosure in use drying a material.

    FIG. 2 is a cross-sectional view of the drying apparatus taken at line 2-2 of FIG. 1.

    FIG. 3 is a perspective view of the air delivery enclosure of FIG. 1.

    FIG. 4 is a partially exploded perspective view of the ultrasonic transducer of FIG. 1.

    FIG. 5 is a side view of the air delivery enclosure of FIG. 1, showing the distance between the outlet from ultrasonically charged air that comes out of the enclosure with ultrasonic transducer and the material being dried.

    FIG. 6 is a side view of a converting or printing system including a drying apparatus according to a second example which is not part of the present invention.

    FIG. 7 is a plan view of a system including a converting or printing apparatus according to a third example which is not part of the present invention.

    FIG. 8 is a longitudinal cross-sectional view of a drying apparatus according to a fourth example which is not part of the present invention, showing two acoustic delivery enclosures and an interposed dedicated standard or steady state air delivery enclosure.

    FIG. 9 is a longitudinal cross-sectional view of a drying apparatus according to a fifth example which is not part of the present invention, showing a dedicated air delivery enclosure and two acoustic delivery enclosures at the beginning and end of the drying zone.

    FIG. 10 is a longitudinal cross-sectional view of a drying apparatus according to a sixth example which is not part of the present invention, showing an air delivery enclosure and a return enclosure arranged in a side-by-side configuration.

    FIG. 11 is a longitudinal cross-sectional view of a drying apparatus according to a seventh example which is not part of the present invention, showing an air delivery enclosure and an ultrasonic transducer without a return enclosure.

    FIG. 11A is a detail view of a heater element of the apparatus of FIG. 11.

    FIG. 12 is a front view of a drying apparatus according to an eighth example which is not part of the present invention, showing an air delivery enclosure and electric-operated ultrasonic transducers.

    FIG. 13 is a side view of the drying apparatus of FIG. 12.

    FIG. 14 is a side cross-sectional view of a drying apparatus according to a ninth example which is not part of the present invention, showing an air delivery enclosure with an electric-operated heater.

    FIG. 15 is a side cross-sectional view of a drying apparatus according to a tenth example which is not part of the present invention, showing an air delivery enclosure with waveguides for the ultrasonic transducers.

    FIG. 16 is a front view of a drying apparatus according to an eleventh example which is not part of the present invention, including infrared heaters and air-moving fans.

    FIG. 17 is a cross-sectional view of the drying apparatus taken at line 17-17 of FIG. 16.

    FIG. 18 is a side cross-sectional view of a drying apparatus according to a twelfth example which is not part of the present invention, including infrared heaters and an air-moving fan.

    FIG. 19 is a cross-sectional view of the drying apparatus taken at line 19-19 of FIG. 18.

    FIG. 20 is a front view of a drying apparatus according to a thirteenth example which is not part of the present invention, including infrared heaters without an air-moving fan.

    FIG. 21 is a side view of the drying apparatus of FIG. 20.

    FIG. 22 is a front view of a drying apparatus according to a fourteenth example which is not part of the present invention, including ultraviolet heaters.

    FIG. 23 is a side cross-sectional view of a drying apparatus according to a fifteenth example which is not part of the present invention.

    FIG. 24 is a side cross-sectional view of a drying apparatus according to a sixteenth example which is not part of the present invention.

    FIG. 25 is a side detail view of a wing mounted to an ultrasonic transducer of the drying apparatus of FIG. 24.


    DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS



    [0024] The present invention provides a method of drying according to claim 1 and an apparatus for drying according to claim 6 that include the use of ultrasound to more effectively break down the boundary layer and thereby increase the heat and/or mass transfer rate. Examples are described herein in general configurations for illustration purposes. The examples also provide specific configurations for use in specific applications such as but not limited to printing, residential and commercial cooking appliances, food processing equipment, textiles, carpets, converting industries, fabric dyeing, and so on. In particular, the invention can be configured for flexographic and gravure printing of wallpaper, gift-wrap paper, corrugated containers, folding cartons, paper sacks, plastic bags, milk and beverage cartons, candy and food wrappers, disposable cups, labels, adhesive tapes, envelopes, newspapers, magazines, greeting cards, and advertising pieces. The invention can be adapted for these and many other batch and continuous heating and drying processes.

    [0025] Referring now to the drawing figures, FIGS. 1 - 5 show a drying apparatus 10 according to a first example embodiment of the present invention. The drying apparatus 10 includes an air-delivery enclosure 12, an air-return enclosure 14, and at least one ultrasonic transducer 16. The ultrasonic transducer 16 delivers acoustic oscillations 18 (i.e., pulsating acoustic pressure waves) coupled with heated or ambient air 22 onto the boundary layer of a material 20 to be dried while the delivery enclosure 12 delivers a heated airflow 22 onto the material, and the return enclosure 14 draws moist air 24 away from the material. The air-delivery enclosure 12 has an air inlet 26 and at least one air outlet 28, and the air-return enclosure 14 has at least one air inlet 30 and an air outlet 32. In typical commercial embodiments, the delivery and return enclosures 12 and 18 are made of metal (e.g., sheet metal), though other materials can be used.

    [0026] The material 20 to be dried can be any of a wide range of materials, depending on the application. For example, in printing applications the material to be dried is ink on paper, cardboard, plastic, fabric, etc., and for food processing equipment the material is food. Thus, the material 20 can be any substance or object for which heating and drying is desired.

    [0027] In the depicted embodiment, the material 20 is conveyed beneath the apparatus 10 by a conventional conveyor system 34. In alternative embodiments, the material 20 is conveyed into operational engagement with the apparatus 10 by another device and/or the apparatus is moved relative to the material.

    [0028] A steady-state forced airflow 21 is delivered to the delivery enclosure 12 under positive pressure by an air-moving device 50 that is connected to the air inlet 26 by an air conduit 52 (see FIG. 5). And the return airflow 24 is drawn away from material 20 under the influence of an air-moving device that is connected to the return enclosure air outlet 30 by an air conduit. As such, the delivery enclosure 12 is a positive-pressure plenum and the return enclosure 14 is a negative-pressure plenum. The air-moving devices 50 may be provided by conventional fans, blowers, or compressors, and the air conduits 52 may be provided by conventional metal piping. In alternative embodiments, the air-moving devices are integrally provided as parts of the apparatus 10, for example, with the delivery air-mover positioned inside the delivery enclosure 12 and the return air-mover positioned inside the return enclosure 14.

    [0029] In typical commercial embodiments, the steady-state inlet airflow 21 is pre-heated by a heat source 54 that is positioned near the apparatus 10 and connected to the delivery enclosure inlet 26 (see FIG. 5). In some alternative embodiments, a heat source is included in the delivery enclosure 12, in addition to or instead of the pre-heater. And in alternative embodiments for applications in which no or relatively little heat is required for the needed drying, the airflow 21 is not heated before being delivered onto the material 20. In such embodiments, the frictional forces from operating the pneumatic ultrasonic transducers 16 can generate temperatures of for example about 150 F, which in some applications is sufficient that a pre-heater is not needed. And in some embodiments without heating, the apparatus 10 may be provided without the return enclosure 14.

    [0030] The delivery enclosure 12, the return enclosure 14, and the ultrasonic transducer 16 of the depicted embodiment are arranged for enhanced thermal insulation of the heated delivery airflow 21. In particular, the delivery enclosure 12 is positioned inside the return enclosure 14 so that the warm moist return air 24 in the return enclosure helps reduce heat loss by the heated air 21 in the delivery enclosure. The ultrasonic transducer 16 is positioned in the delivery enclosure air outlet 28 and extends through the return enclosure 14. In alternative embodiments in which the heater is positioned within the delivery enclosure, only the portion of the delivery enclosure carrying heated air is positioned within the return enclosure. In other alternative embodiments, the delivery enclosure and the return enclosure are positioned in a side-by-side arrangement with the delivery enclosure positioned ahead of the return enclosure relative to the moving material. And in yet other alternative embodiments, the apparatus includes a plurality of the delivery enclosures, return enclosures, and ultrasonic transducers arranged concentrically, side-by-side, or otherwise.

    [0031] The ultrasonic transducer 16 of the depicted embodiment is an elongated pneumatic ultrasonic transducer, the air outlet 28 of the delivery enclosure 14 is slot-shaped, and the transducer is positioned in the air outlet so that all of the steady-state airflow 21 is forced through the transducer. In this way, the heated airflow 22 and the acoustic oscillations 18 are delivered together onto the material 20. In alternate embodiments, the size and shape of the ultrasonic transducer 16 and the delivery enclosure air outlet 28 are selected so that some of the heated airflow 21 is not routed through the ultrasonic transducer but instead is routed around it and through the same or another air outlet. In other alternative embodiments, the apparatus 10 includes a plurality of the pneumatic ultrasonic transducers 16 (elongated or not) and the delivery enclosure 14 includes a plurality of the air outlets 28 (slot-shaped or not) for the transducers.

    [0032] The ultrasonic transducer 16 depicted in FIGS. 3 and 4 includes two walls 36 and two end caps 38 that hold the walls in place spaced apart from each other to form an air passage 40. The walls 36 each have an inner surface 42 with two grooves 44 in them that extend the entire length of the wall, with the grooves of one wall oppositely facing the grooves of the other wall. When the steady-state airflow 21 is forced through the passage 40, the grooves 44 induce the acoustic oscillations 18 in the airflow 22 that exits the transducer 16. The depicted transducer 16 is designed to be operable to cost-efficiently produce certain desired decibel levels, as described below.

    [0033] The ultrasonic transducer 16 is operable to produce fixed frequency ultrasonic acoustic oscillations in the sound pressure range of about 120 dB to about 190 dB at the interface surface of the material 20 being treated. Preferably, the ultrasonic transducer 16 is designed for producing acoustic oscillations in the sound pressure range of about 130 dB to about 185 dB at the interface surface of the material 20 being treated, more preferably about 160 dB to about 185dB, and most preferably about 170 dB to about 180 dB. These are the decibel levels at the interface surface of the material 20, not necessarily the output decibel level range of the ultrasonic transducer 16. In typical commercial embodiments, the ultrasonic transducer 16 is selected to generate up to about 170 to about 190 dBs, though higher or lower dB transducers could be used. Ultrasonic transducers that are operable to produce these decibel levels are not known to be commercially available and are not known to be used in commercially available heating and drying equipment.

    [0034] Sound (ultrasound is part of it) dissipates with the second power to the distance, so the closer the ultrasonic transducer is positioned to the material, the lower in the dB range the dB level generated by the transducer can be. Many applications, by the nature of the process, require a transducer-to-material distance of from about 10 mm to about 100 mm. The longer the distance, the higher the dB level that must be generated by the ultrasonic transducer in order to obtain the needed dB level at the interface surface of the material. In addition, dB levels above the high end of the dB range could be used in some applications, but generally the larger transducers that would be needed are not as cost-effective and the sound level would be so high that humans could not safely or at least comfortably be present in the work area.

    [0035] As shown in FIG. 5, the ultrasonic transducer 16 is positioned with its outlet 46 (where the ultrasound is emitted from) spaced from the interface surface of the material 20 to be dried by a distance D. The distance D is about (λ)(n/4), where "λ" is the wavelength of the ultrasonic oscillations 18 and "n" is preferably an odd integer (1, 3, 5, 7, etc.). In this way, when the ultrasonic oscillations 18 reach the interface surface of the material 20, they are at about maximum amplitude A, which maximizes the disruption of the boundary layer and results in increased water/solvent evaporation rates. For relatively lower frequency oscillations, the distance D is preferably such that "n" is either 1 or 3, and most preferably such that "n" is 1, so that the distance D is minimized. For relatively higher frequency oscillations, "n" can be a larger odd integer. In alternative embodiments that produce workable results, the distance D is such that "n" is in the range of plus (+) or minus (-) .5 of an odd integer (0.5 to 1.5, 2.5 to 3.5, 4.5 to 5.5, 6.5 to 7.5, etc.). In other words, the oscillations are in the ranges of 45 to 135 degrees, 225 to 315 degrees, etc. In other alternative embodiments that produce workable results, the distance D is such that "n" is in the range of plus (+) or minus (-) .25 of an odd integer (i.e., 0.75 to 1.25, 2.75 to 3.25, 4.75 to 5.25, 6.75 to 7.25, etc.). In other words, the oscillations are in the ranges of 67.5 to 157.5 degrees, 247.5 to 337.5 degrees, etc. In this way, when the ultrasonic oscillations 18 reach the interface surface of the material 20, even though they are not at maximum amplitude A, they are still close enough to it (and within the workable and/or preferred decibel ranges) for acceptable boundary layer disruption.

    [0036] In order for the ultrasonic transducer 16 to be spaced from the material 20 in this way, the apparatus 10 can be provided with a register surface fixing the distance D. For example, the register surface can be provided by a flat sheet and the material 20 can be conveyed across it on a conveyor belt driven by drive rollers before and after the sheet. Or the register surface can be provided by one or more rollers that support the material directly, by a conveyor belt supporting the material 20, or by another surface know to those skilled in the art. In any event, the register surface is spaced the distance D from the ultrasonic transducer 16 (or positioned slightly more than the distance D from the ultrasonic transducer to account for the thickness of the material 20 and the conveyor belt). Embodiments without a register surface are typically used when the material is web-based, otherwise self-supporting, or tensioned by conventional tensioning mechanisms.

    [0037] In addition, the apparatus can be provided with an adjustment mechanism for adjusting the distance between the ultrasonic transducer 16 and the material 20. The adjustment mechanism may be provided by conventional devices such rack and pinion gearing, screw gearing or the like. The adjustment mechanism may be designed to move the air-delivery enclosure 12, air-return enclosure 14, and ultrasonic transducer 16 assembly closer to the material, to move the material closer to the ultrasonic transducer, or both.

    [0038] In order to consistently produce the precise decibel levels at the interface surface of the material 20, a method which is not part of the present invention of manufacturing and/or installing the apparatus 10 is provided. The method includes calibrating the apparatus 10 for the desired decibel levels. First, the distance D is calculated based on the frequency of the selected ultrasonic transducer 16. For example, an ultrasonic transducer 16 with an operating frequency of 33,000 Hz has a wavelength of about .33 inches at a fixed temperature, so acceptable distances D include (.33)(3/4) equals .25 inches and (.33)(5/4) equals .41 inches, based on the formula D equals (λ)(n/4). Similarly, an ultrasonic transducer 16 with an operating frequency of 33kHz has a wavelength of about .41 inches, so acceptable distances D include (.41)(3/4) equals .31 inches and (.41)(5/4) equals .51 inches.

    [0039] Then the ultrasonic transducer 16 is positioned at the calculated distance D from the material 20 (or from the conveyor belt that will carry the material, or from the register surface). Next, a sound input device (e.g., a microphone) is placed at the material 20 (or at the conveyor belt that will carry the material, or at the register surface, or at the distance D from the ultrasonic transducer 16). The sound input device is connected to a signal conditioner. The sound input device and the signal conditioner are used to measure the air pressure wave (i.e., the acoustic oscillations 18) in psig and convert that to decibels (dB). For example, at a temperature of 120 F and a flow rate of 35 ft/sec, a sound wave measured at 5 psig converts to 185 dB. Suitable microphones and signal conditioners are commercially available from Endevco Corporation (San Juan Capistrano, California) and from Bruel & Kjer (Switzerland).

    [0040] Once this baseline decibel level has been determined, the apparatus 10 can be adjusted for maximum effectiveness. For example, the adjustment mechanism can be adjusted to alter the preset distance D to see if the decibel level increases or decreases at the altered distance. If it decreases, then the preset distance D was accurate to produce the maximum amplitude A, and this distance is used. But if it increases, then the altered distance D is used as the new baseline and the distance is adjusted again. This fine-tuning process is repeated until the maximum amplitude A within the design ranged is found.

    [0041] In addition, because the depicted embodiment includes a pneumatic-type ultrasonic transducer 16, it is operable to produce the desired decibel levels by adjusting the flow-rate of the steady-state inlet airflow 21. So if the baseline decibel level is not in the desired range, then the inlet airflow 21 rate can be adjusted (e.g., by increasing the speed of the fan or blower) until the decibel level is in the desired range. Exactly the same procedure can be applied to electrically powered ultrasonic transducers. Similar adjustments can be made with a signal amplifier, when electrically based ultrasonic transducers are used.

    [0042] Table 1 shows test data demonstrating the resulting increased effectiveness of the apparatus 10. The test data in Table 1 was generated using the apparatus 10 of FIGS. 1-5, and the data are the averages from sixty tests. In this specification the conversion between feet and meter is 1 feet equals 0.3048 m. The conversion between inch and meter is 1 inch equals 0.0254 m. The temperature T in Kelvin (K) is equal to the temperature T in degrees Fahrenheit (°F) plus 459.67, times 5/9. The conversion water column and Pascal is 1 mm H2O column equals 9.80665 Pa.
    Table 1
    Distance (inches)Δ Pressure (in. H2O columnTemp. (F)Speed (ft/min)Water Removal (grams)Factor of Improvement
    at 169 dBat 175 dB
    0.6 4.3 160 30 8.16 13.88 1.7
    0.6 4.3 160 60 3.99 11.58 2.9
    0.6 4.3 160 90 3.19 7.02 2.2


    [0043] The "Distance" is the distance D between the ultrasonic transducer 16 and the material 20, in inches. The "Δ Pressure" is the differential pressure drop in the air supply line in both experiments, measured in inches of water column, representing that the same amount of air was delivered through the acoustic dryer and non-acoustic dryer at the same temperature. The differential pressure of air corresponds to the amount of air supplied from the regenerative blower, it was the same in both cases, so the only difference between two series of experiments was ultrasound. Measurement of differential pressure in the air supply line is the most accurate and inexpensive method of measuring the quantity of air delivered by the blower. The "Temp." is the temperature of the inlet steady-state air 21. The "Speed" is the speed of the conveyer (i.e., the speed of the material 20 passing under the ultrasonic transducer 16). The "Water Removal" is the amount of water removed by the apparatus 10, first when operated at an airflow rate so that the ultrasonic transducer 16 produces acoustic oscillations 18 at the interface surface of the material 20 of 169 dB and then of 175 dB. As can be seen, a noted improvement is provided by operating the apparatus 10 so that it produces 175 dB acoustic oscillations at the interface surface of the material 20 instead of 169 dB.

    [0044] FIG. 6 shows an apparatus 110 according to a second example which is not part of the present invention, with the apparatus included in a printing system 148 that additionally includes other components known to those skilled in the art. In this example, the apparatus 110 includes two delivery enclosures 112, one return enclosure 114 with one exhaust outlet 130, and two ultrasonic transducers 116. In addition to the apparatus 110, the printing system 148 includes an air-moving device 150 (e.g., a fan, blower, or compressor), air conduits 152, and a heater 154, which cooperate to deliver heated steady-state air to the apparatus. A heater bypass conduit 156 is provided for print jobs in which no preheating is needed. The system 148 also includes a printing block 158 for applying ink (or paint, dye, etc.) to articles (e.g., labels, packaging) thereby forming the material 120 to be dried, and a conveyor system 134 for delivering the material to the apparatus 110 to dry the ink on the articles. In typical commercial examples, the conveyor system 134 is designed to operate at speeds of about 150-1,000 ft/min.

    [0045] FIG. 7 shows an array of apparatus 210 according to a third example which is not part of the present invention, with the apparatus included in a printing system 248 that additionally includes other components known to the skilled in the art. In this embodiment, the apparatus 210 includes five delivery enclosures 212 each having at least one ultrasonic transducer 216. In addition to the apparatus 210, the printing system 248 includes an air-moving device (not shown), air conduits 252 connecting the apparatus to the air-mover, and control valving 260. The printing system 148 also includes a conveyor system 234 for conveying the material 220 past the apparatus 210. The valving 260 can be controlled to operate all or only selected ones of the apparatus 210 for localizing the drying, depending on the particular job at hand. For example, in some print jobs only a portion of the material 220 is to be dried (e.g., when ink is not applied to the entire surface of a container or label), and in some print jobs the material may be of a smaller the typical size, so some of the valves 260 can be turned off to shut down the apparatus 210 not needed for the job.

    [0046] FIG. 8 shows an apparatus 310 according to a fourth example which is not part of the present invention. In this example, the apparatus 310 is similar to that of the first embodiment, in that it includes a return enclosure 314 with a plurality of return air inlets 332 and an air outlet 330, and at least one delivery enclosure within the return enclosure. However, in this example, the apparatus 310 includes three delivery enclosures, with one dedicated air delivery enclosure 312a having an air outlet 328a and with two acoustic delivery enclosures 312b each having at least one air outlet 328a and at least one ultrasonic transducer 316. The dedicated air delivery enclosure 312a delivers steady-state air 322 through the air outlet 328a and toward the material. And the acoustic delivery enclosures 312b deliver acoustic oscillations 318 through the air outlets 328b and toward the material. The acoustic delivery enclosures 312b are positioned immediately before and after (relative to the moving material) the dedicated air delivery enclosure 312a.

    [0047] FIG. 9 shows an apparatus 410 according to a fifth example which is not part of the present invention. In this example, the apparatus 410 is similar to that of the fourth embodiment, in that it includes a return enclosure 414, a dedicated air delivery enclosure 412a, and two acoustic delivery enclosures 412b each having at least one ultrasonic transducer 416. In this example, however, the two acoustic delivery enclosures 412b are positioned on the front and rear ends (relative to the moving material) of the return enclosure 414, that is, at the very beginning and end of the drying zone.

    [0048] FIG. 10 shows an apparatus 510 according to a sixth example which is not part of the present invention. In this example the apparatus 510 is similar to that of the first embodiment, in that it includes a return enclosure 514 with at least one return air inlet 532 and an air outlet 530, a delivery enclosure 512 with at least one air outlet 528, and at least one ultrasonic transducer 516 positioned within the delivery enclosure air outlet. In this example, however, the delivery enclosure 512 is not positioned within the return enclosure 514; instead, these enclosures are arranged in a side-by-side configuration. In addition, the ultrasonic transducer 516 includes a directional outlet conduit 517 extending from it for directing the acoustic oscillations more precisely.

    [0049] Furthermore, an electric heater 554 is embedded in or mounted to the delivery enclosure 512 for applying heat directly to the material instead of (or in addition to) pre-heating the air to be delivered to the material. So the function of the air forced through the ultrasonic transducer 516 is only being a carrier for the ultrasound. The electric heater 554 can be mounted to the outside bottom surface of the delivery enclosure 512 or it can be mounted within the enclosure to the inside bottom surface (provided that the bottom wall of the enclosure has a sufficiently high thermal conductivity). The heater 554 can be of a conventional electric type or another type known to those skilled in the art.

    [0050] FIG. 11 shows an apparatus 610 according to a seventh example which is not part of the present invention. In this example the apparatus 610 is similar to that of the sixth example, in that it includes a delivery enclosure 612 housing at least one ultrasonic transducer 616 and at least one heater 654. In this example however, the apparatus 610 does not include a return enclosure for removing moist air. This example is suitable for applications in which there is less moisture to be removed from the material.

    [0051] In addition, the heater 654 of this example includes an inner heater element 654a and an outer heater element 654b mounted to the inside and outside surfaces of the bottom wall of the delivery enclosure 612 (see FIG. 11A). The inner and outer heater elements 654a and 654b can be provided by thermal conductive plates (e.g., of aluminum) with embedded resistance heaters. Also, the delivery enclosure 612 includes air outlets 628 for delivering steady-state air to the material separately from the acoustic oscillations delivered by the ultrasonic transducer 616. These air outlets 628 in the delivery enclosure 612 extend through both of the heater elements 654a and 654b. This example of the heater provides bi-directional heating to the air inside the delivery enclosure 612 (convective heat) and directly to the material (radiant heat). In alternative examples one of the heater elements can be provided in place of the bottom wall of the delivery enclosure, thereby doubling as a plenum wall and a heater.

    [0052] FIGS. 12 and 13 show an apparatus 710 according to an eighth example which is not part of the present invention. In this example, the apparatus 710 is similar to that of the seventh example, in that it includes a delivery enclosure 712 with an air inlet 726 and a plurality of air outlets 728 defined in the delivery enclosure and with a plurality of ultrasonic transducers 716 mounted to the delivery enclosure. Steady-state air 721 is forced through the air inlet 726, into the enclosure 712, and out of the air outlets 728 toward the material 720, and the ultrasonic transducers 716 deliver acoustic oscillations 718 toward the material 720 onto the boundary layer.

    [0053] In this example, however, the ultrasonic transducers 716 are provided by electric-operated ultrasonic transducers. Such ultrasonic transducers are commercially available (with customizations for the desired decibel levels described herein) for example from Dukane Corporation (St. Charles, Illinois). The electric ultrasonic transducers 716 can be mounted to the exterior surface of the bottom wall 711 of the delivery enclosure 712 or positioned within openings in the bottom wall.

    [0054] In addition, the ultrasonic transducers 716 and the air outlets 728 are arranged in an array on the delivery enclosure 712, preferably in a repeating alternating arrangement and also preferably in a staggered arrangement with a shift to avoid dead spots (e.g., with a 30-degree shift). The ultrasonic transducers 716 and the air outlets 728 may be circular, though they can be provided in other shapes such as rectangular, oval, or other regular or irregular shapes. In addition, the ultrasonic transducers 716 may have a diameter of about 2 inches, and the air outlets 728 may have a diameter of about 0.4 to 0.8 inches, though these can be provided in other larger or smaller sizes. Furthermore, the ultrasonic transducers 716 may be spaced apart at about 1 to 50 diameters, though larger or smaller spacings can be used. The number of ultrasonic transducers 716 and air outlets 728 are selected to provide the drying desired for a given application, and in typical commercial embodiments are provided in about equal numbers anywhere in the range of about 1 to about 100, depending on the physical properties of an individual transducer, that is, its physical size, the area of coverage, etc.

    [0055] FIG. 14 shows an apparatus 810 according to a ninth example which is not part of the present invention. In this example the apparatus 810 is similar to that of the eighth example in that it includes a delivery enclosure 812 with a plurality of air outlets 828 and with a plurality of ultrasonic transducers 816. In this example, however, a heater 854 is mounted within the delivery enclosure 812 to heat the air before it is delivered to the material. The heater 854 in this example can be of a similar type as that provided in the examples of FIGS. 10 and 11, or it can be of another known electrical or other type of heater.

    [0056] FIG. 15 shows an apparatus 910 according to a tenth example which is not part of the present invention. In this example, the apparatus 910 is similar to that of the eighth example in that it includes a delivery enclosure 912 with a plurality of air outlets 928 and with a plurality of ultrasonic transducers 916. In this example however, the ultrasonic transducers 916 are mounted within waveguides 919 that are positioned within the delivery enclosure 912 for focusing/enhancing and directing the acoustic oscillations toward the material. The waveguides 919 are preferably provided by conduits that have outlets 917 through the front wall of the delivery enclosure 912 (closest to the material to be dried) and that extend all the way through (or at least a substantial portion of the way through) the delivery enclosure. And the transducers 916 are preferably positioned adjacent the back wall (opposite the material to be dried) of the delivery enclosure 912. The waveguide conduits 919 are preferably tubular with a cross-sectional shape (e.g., circular) that conforms to that of the ultrasonic transducers 916. The ultrasonic transducers 916 can be mounted to the inside back surface of the delivery enclosure 912 or they can be installed into openings in the delivery enclosure (such that they form that portion of the enclosure wall). This compact example is particularly useful in applications in which there is little space for the apparatus.

    [0057] FIGS. 16 and 17 show an apparatus 1010 according to an eleventh example which is not part of the present invention. In this example, the apparatus 1010 is similar to that of the eighth example, in that it includes a delivery enclosure 1012 with a bottom wall 1011 having plurality of air outlets 1028, and a plurality of ultrasonic transducers 1016 mounted to the enclosure. In this example, however, the apparatus 1010 additionally includes at least one infrared-light-emitting heater 1054. The depicted example, for example, includes three infrared heaters 1054. The infrared heater 1054 can be of a conventional type, for example, a nichrome wire or carbon-silica bar type. The infrared heater 1054 can be mounted in front of the delivery enclosure 1012 (between the delivery enclosure and the material to be dried, as depicted), within the delivery enclosure, or even behind it. In addition, the apparatus includes at least one air-mover 1050, for example, the two fans depicted, mounted to the rear of the delivery enclosure 1012. In addition to better convecting the heat from the infrared heaters 1054 toward the material, the air-mover 1050 helps cool the delivery enclosure 1012 (conventional infrared heaters generate relatively high temperatures). This example may be particularly useful in applications in which infrared heating is desired but the top/rear wall of the delivery enclosure 1012 may not exceed a certain temperature (e.g., 175 F drying of porous synthetic materials, such as filter fabrics or technical textiles).

    [0058] FIGS. 18 and 19 show an apparatus 1110 according to a twelfth example which is not part of the present invention. In this example, the apparatus 1110 is similar to that of the eleventh example, in that it includes a delivery enclosure 1112 with a plurality of air outlets 1128 in its bottom wall 1111, a plurality of ultrasonic transducers 1116 mounted within it, at least one infrared heater 1154 mounted within it, and at least one air-mover 1150 mounted within it. This stand-alone example may be particularly useful in the same applications as for the example of FIGS. 16 and 17, except that this example provides a more vertical configuration which saves footprint space for a more compact design. Such applications may include printing of mini-packaging, mailing labels, and other items for which short residence time and equipment compactness are desired.

    [0059] FIGS. 20 and 21 show an apparatus 1210 according to a thirteenth example which is not part of the present invention. In this example the apparatus 1210 is similar to that of the eleventh example in that it includes a plurality of ultrasonic transducers 1216 for generating ultrasound and at least one infrared heater 1254 for generating heat. In this example, however, steady-state air is not forced by an air mover through an enclosure with air outlets, and instead the infrared heater 1254 by itself generates the heated airflow. Because there is no delivery enclosure, the ultrasonic transducers 1216 are mounted to another element such as the depicted reflector panel 1213. This example may be particularly useful in the applications for which relatively little heating is required and conserving space is a priority.

    [0060] FIG. 22 shows an apparatus 1310 according to a fourteenth example which is not part of the present invention. In this example the apparatus 1310 is similar to that of the thirteenth example, in that it includes a plurality of ultrasonic transducers 1316 mounted on a panel 1313, with no steady-state air forced by an air mover through an enclosure with air outlets. Instead, the apparatus 1310 includes at least one UV emitter 1354 for generating the heated airflow. The depicted example for example, includes three UV emitters 1354. The UV heater 1354 can be of a conventional type known to those skilled in the art. This example may be particularly useful in the applications for which relatively little heating is required, for example, drying specialty UV varnishes and UV water-based coatings.

    [0061] FIG. 23 shows an apparatus 1410 according to a fifteenth example which is not part of the present invention. In this example the apparatus 1410 is similar to that of the eighth example, in that it includes a delivery enclosure 1412 with at least one air inlet 1426 and at least one air outlet 1428 for delivering forced air to the material, and at least one ultrasonic transducer 1416 for delivering acoustic oscillations to the material. In the particular example shown, the apparatus 1410 includes an array of electric-operated ultrasonic transducers 1416. In this example, however, the ultrasonic transducers 1416 are mounted within the delivery enclosure 1412 to set up a field of acoustic oscillations through which the forced air passes before reaching the material to be dried. In the depicted example, for example, the ultrasonic transducers 1416 are mounted to an inner wall of the delivery enclosure 1412 and are not oriented to direct the acoustic oscillations toward the air outlet 1428.

    [0062] FIG. 24 shows an apparatus 1510 according to a sixteenth example which is not part of the present invention. In this example, the apparatus 1510 is similar to that of the fifteenth example, in that it includes a delivery enclosure 1512 with at least one air inlet 1526 and at least one air outlet 1528, and at least one electric-operated ultrasonic transducer 1516 mounted within the delivery enclosure for setting up a field of acoustic oscillations through which forced air passes before reaching the material to be dried. In this example, however, the ultrasonic transducer 1516 is mounted immediately adjacent the air outlet 1528 and is not oriented to direct the acoustic oscillations toward the air outlet.

    [0063] FIG. 25 shows a wing element 1564 that can be mounted to the electric-operated ultrasonic transducer 1516 of the example of FIG. 25. The wing 1564 may be disk-shaped (e.g., for used with disk-shaped electric-operated ultrasonic transducers 1516), or it may be provided by a plurality of radially extending arms by another structure with at least one member extending away from the transducer. The wing 1564 may be made of a material such as steel, titanium, or another metal. With the wing 1564 mounted to the electric ultrasonic transducer 1516, when the transducer is operated it induces vibrations in the wing, which vibrations enhance the acoustic oscillations for more effective disruption of the boundary layer. Thus, the wings 1564 function as mechanical amplifiers, working in resonance with the electric ultrasonic transducers 1516 to increase the amplitude of the ultrasonic pressure wave. The wing 1564 can be included in any of the example embodiments, and alternative embodiments thereof, that include electric-operated ultrasonic transducers.


    Claims

    1. A method of drying a material (20), the method comprising:

    positioning an ultrasonic transducer (16) a spaced distance from an interface surface of the material;

    forcing air through a delivery air enclosure (12) of the ultrasonic transducer, the ultrasonic transducer including a first inner surface; a second inner surface, the second inner surface facing the first inner surface, the first inner surface and the second inner surface defining an air passage through the ultrasonic transducer; a first groove defined in the first inner surface, the first groove including a first flat portion, the first flat portion angled at 90 degrees with respect to an innermost portion of the first inner surface and extending away from the innermost portion of the first inner surface; and a second groove defined in the second inner surface, the second groove including a second flat portion, the second flat portion angled at 90 degrees with respect to an innermost portion of the second inner surface and extending away from the innermost portion of the second inner surface;

    inducing acoustic oscillations through the ultrasonic transducer; and

    directing the acoustic oscillations and air towards the material.


     
    2. The method of claim 1, wherein inducing acoustic oscillations with the ultrasonic transducer includes inducting acoustic oscillations with the first groove and the second groove of the ultrasonic transducer.
     
    3. The method of claim 1, wherein the first groove includes an angled portion, the angled portion facing at least partially in the direction of an airflow path, or wherein the first groove has a triangular cross-section.
     
    4. The method of claim 1, wherein the material and an ultrasonic transducer outlet are positioned relative to each other such that the spaced distance is (λ)(n/4), wherein " λ" is a wavelength of the acoustic oscillations and "n" is in a range of plus or minus 0.5 of an odd integer so that the acoustic oscillations at the interface surface of the material are within a 90-degree range centered at maximum amplitude, "n" being equal to an odd integer.
     
    5. The method of claim 1, wherein an end cap bridges the first wall and the second wall to define the air passage therebetween.
     
    6. An apparatus (10) for drying a material (20), the apparatus comprising:

    a delivery air enclosure (12) with an air inlet and an air outlet through which forced air is directed toward the material; and

    an ultrasonic transducer (16) connected to the air outlet of the delivery air enclosure, the ultrasonic transducer including:

    a first inner surface;

    a second inner surface, the second inner surface facing the first inner surface, the first inner surface and the second inner surface defining an air passage through the ultrasonic transducer;

    a first groove defined in the first inner surface, the first groove including a first flat portion, the first flat portion angled at 90 degrees with respect to an innermost portion of the first inner surface and extending away from the innermost portion of the first inner surface; and

    a second groove defined in the second inner surface, the second groove including a second flat portion, the second flat portion angled at 90 degrees with respect to an innermost portion of the second inner surface and extending away from the innermost portion of the second inner surface.


     
    7. The apparatus (10) of claim 6, wherein the ultrasonic transducer includes
    a third groove defined in the first inner surface, the third groove including a third flat portion; and
    a fourth groove defined in the second inner surface, the fourth groove including a fourth flat portion.
     
    8. The apparatus (10) of claim 6, wherein the second flat portion is parallel to the first flat portion, or wherein the second flat portion is coplanar with the first flat portion, or wherein the first flat portion and the second flat portion face in an opposite direction to an airflow path through the ultrasonic transducer.
     
    9. The apparatus (10) of claim 6, wherein the first groove and the second groove each have a triangular cross-section.
     
    10. The apparatus (10) of claim 6, wherein the first inner surface and the second inner surface define a transducer outlet from which acoustic oscillations generated by the ultrasonic transducer are directed toward the material and, optionally, wherein the transducer outlet is positioned a spaced distance from an interface surface of the material such that the amplitude of the
    acoustic oscillations at the interface surface of the material is in the range of about 120 dB to about 190 dB.
     
    11. The apparatus (10) of claim 6, wherein the first groove includes an angled portion.
     
    12. The apparatus (10) of claim 11, wherein the angled portion intersects the first flat portion at an angle of less than ninety degrees, or wherein the angled portion faces at least partially in the direction of an airflow path.
     
    13. The apparatus (10) of claim 10, further comprising a register surface for supporting the material a spaced distance from the transducer outlet.
     
    14. The apparatus (10) of claim 6, wherein a spaced distance from an outlet of the ultrasonic transducer to the material is (λ)(n/4), wherein "λ" is a wavelength of acoustic oscillations generated by the ultrasonic transducer and "n" is in a range of plus or minus 0.5 of an odd integer so that the acoustic oscillations at an interface surface of the material are within a 90-degree range centered at about maximum amplitude.
     
    15. The apparatus (10) of claim 6, further comprising a heater positioned within or operably connected to the delivery air enclosure for heating the forced air.
     


    Ansprüche

    1. Ein Verfahren zum Trocknen eines Materials (20), wobei das Verfahren umfasst:

    Positionieren eines Ultraschallwandlers (16) in einem räumlichen Abstand von einer Grenzoberfläche des Materials;

    Treiben von Luft durch ein Luftversorgungsgehäuse (12) des Ultraschallwandlers, wobei der Ultraschallwandler eine erste innere Oberfläche aufweist; eine zweite innere Oberfläche, wobei die zweite innere Oberfläche der ersten inneren Oberfläche zugewandt ist, wobei die erste innere Oberfläche und die zweite innere Oberfläche einen Luftkanal durch den Ultraschallwandler definieren; eine erste Nut, die in der ersten inneren Oberfläche definiert ist, wobei die erste Nut einen ersten flachen Teil aufweist, wobei der erste flache Teil um 90 Grad in Bezug auf einen innersten Teil der ersten inneren Oberfläche abgewinkelt ist und sich von dem innersten Teil der ersten inneren Oberfläche weg erstreckt; und eine zweite Nut, die in der zweiten inneren Oberfläche definiert ist, wobei die zweite Nut einen zweiten flachen Teil aufweist, wobei der zweite flache Teil um 90 Grad in Bezug auf einen innersten Teil der zweiten inneren Oberfläche abgewinkelt ist und sich von dem innersten Teil der zweiten inneren Oberfläche weg erstreckt;

    Induzieren von akustischen Oszillationen durch den Ultraschallwandler; und

    Ausrichten der akustischen Oszillationen und der Luft auf das Material.


     
    2. Das Verfahren nach Anspruch 1, wobei das Induzieren von akustischen Oszillationen mit dem Ultraschallwandler das Induzieren von akustischen Oszillationen mit der ersten Nut und der zweiten Nut des Ultraschallwandlers umfasst.
     
    3. Das Verfahren nach Anspruch 1, wobei die erste Nut einen abgewinkelten Teil aufweist, wobei der abgewinkelte Teil zumindest teilweise in die Richtung eines Luftströmungspfades zugewandt ist, oder wobei die erste Nut einen dreieckigen Querschnitt aufweist.
     
    4. Das Verfahren nach Anspruch 1, wobei das Material und ein Ultraschallwandlerauslass relativ zueinander so positioniert sind, so dass der räumliche Abstand (λ)(n/4) ist, wobei "λ" eine Wellenlänge der akustischen Oszillationen ist und "n" ist in einem Bereich von plus oder minus 0,5 einer ungeraden ganzen Zahl, so dass die akustischen Oszillationen an der Grenzoberfläche des Materials innerhalb eines 90-Grad-Bereichs zentriert bei maximaler Amplitude vorliegen, wobei "n" gleich einer ungeraden ganzen Zahl ist.
     
    5. Das Verfahren nach Anspruch 1, wobei eine Endkappe die erste Wand und die zweite Wand überbrückt, um den Luftkanal dazwischen zu definieren.
     
    6. Eine Vorrichtung (10) zum Trocknen eines Materials (20), wobei die Vorrichtung umfasst:

    ein Luftversorgungsgehäuse (12) mit einem Lufteinlass und einem Luftauslass, durch das getriebene Luft auf das Material gerichtet wird; und

    einen Ultraschallwandler (16), der mit dem Luftauslass des Luftversorgungsgehäuses verbunden ist, wobei der Ultraschallwandler Folgendes umfasst:

    eine erste innere Oberfläche;

    eine zweite innere Oberfläche, wobei die zweite innere Oberfläche der ersten inneren Oberfläche zugewandt ist, wobei die erste innere Oberfläche und die zweite innere Oberfläche einen Luftkanal durch den Ultraschallwandler definieren;

    eine erste Nut, die in der ersten inneren Oberfläche definiert ist, wobei die erste Nut einen ersten flachen Teil aufweist, wobei der erste flache Teil um 90 Grad in Bezug auf einen innersten Teil der ersten inneren Oberfläche abgewinkelt ist und sich von dem innersten Teil der ersten inneren Oberfläche weg erstreckt; und

    eine zweite Nut, die in der zweiten inneren Oberfläche definiert ist, wobei die zweite Nut einen zweiten flachen Teil aufweist, wobei der zweite flache Teil um 90 Grad in Bezug auf einen innersten Teil der zweiten inneren Oberfläche abgewinkelt ist und sich von dem innersten Teil der zweiten inneren Oberfläche weg erstreckt.


     
    7. Die Vorrichtung (10) nach Anspruch 6, wobei der Ultraschallwandler eine dritte Nut aufweist, die in der ersten inneren Oberfläche definiert ist, wobei die dritte Nut einen dritten flachen Teil aufweist; und
    eine vierte Nut, die in der zweiten inneren Oberfläche definiert ist, wobei die vierte Nut einen vierten flachen Teil aufweist.
     
    8. Die Vorrichtung (10) nach Anspruch 6, wobei der zweite flache Teil parallel zu dem ersten flachen Teil ist, oder wobei der zweite flache Teil komplanar mit dem ersten flachen Teil ist, oder wobei der erste flache Teil und der zweite flache Teil in einer entgegengesetzten Richtung zu einem Luftströmungspfad durch den Ultraschallwandler ausgerichtet sind.
     
    9. Die Vorrichtung (10) nach Anspruch 6, wobei die erste Nut und die zweite Nut jeweils einen dreieckigen Querschnitt aufweisen.
     
    10. Die Vorrichtung (10) nach Anspruch 6, wobei die erste innere Oberfläche und die zweite innere Oberfläche einen Wandlerauslass definieren, von dem aus vom Ultraschallwandler erzeugte akustische Oszillationen auf das Material gerichtet werden und, optional, der Wandlerauslass optional in einem räumlichen Abstand von einer Grenzoberfläche des Materials angeordnet ist, so dass die Amplitude der akustischen Oszillationen an der Grenzoberfläche des Materials im Bereich von etwa 120 dB bis etwa 190 dB liegt.
     
    11. Die Vorrichtung (10) nach Anspruch 6, wobei die erste Nut einen abgewinkelten Teil aufweist.
     
    12. Die Vorrichtung (10) nach Anspruch 11, wobei der abgewinkelte Teil den ersten flachen Teil in einem Winkel von weniger als neunzig Grad schneidet, oder wobei der abgewinkelte Teil zumindest teilweise in die Richtung eines Luftströmungspfades ausgerichtet ist.
     
    13. Die Vorrichtung (10) nach Anspruch 10 umfasst weiter eine Registeroberfläche zur Stützung des Materials in einem räumlichen Abstand von dem Wandlerauslass.
     
    14. Die Vorrichtung (10) nach Anspruch 6, wobei ein räumlicher Abstand von einem Auslass des Ultraschallwandlers zu dem Material (λ)(n/4) ist, wobei "λ" eine Wellenlänge der von dem Ultraschallwandler erzeugten akustischen Oszillationen ist und "n" in einem Bereich von plus oder minus 0,5 einer ungeraden ganzen Zahl liegt, so dass die akustischen Oszillationen an einer Grenzoberfläche des Materials innerhalb eines 90-Grad-Bereichs zentriert bei etwa maximaler Amplitude vorliegen.
     
    15. Die Vorrichtung (10) nach Anspruch 6 umfasst weiter ein Heizgerät, das innerhalb des Luftversorgungsgehäuses positioniert oder betriebsmäßig mit diesem verbunden ist, um die durchgetriebene Luft zu erwärmen.
     


    Revendications

    1. Procédé de séchage d'une matière (20), le procédé comprenant :

    le positionnement d'un transducteur ultrasonique (16) à une distance espacée d'une surface d'interface de la matière ;

    le passage forcé d'air à travers une enceinte de distribution d'air (12) du transducteur ultrasonique, le transducteur ultrasonique comportant une première surface interne ; une deuxième surface interne, la deuxième surface interne étant tournée vers la première surface interne, la première surface interne et la deuxième surface interne définissant un passage d'air à travers le transducteur ultrasonique ; une première gorge définie dans la première surface interne, la première gorge comportant une première portion plate, la première portion plate étant inclinée à 90 degrés par rapport à une portion la plus interne de la première surface interne et s'étendant en éloignement de la portion la plus interne de la première surface interne ; et une deuxième gorge définie dans la deuxième surface interne, la deuxième gorge comportant une deuxième portion plate, la deuxième portion plate étant inclinée à 90 degrés par rapport à une portion la plus interne de la deuxième surface interne et s'étendant en éloignement de la portion la plus interne de la deuxième surface interne ;

    l'induction d'oscillations acoustiques à travers le transducteur ultrasonique ; et

    l'orientation des oscillations acoustiques et d'air vers la matière.


     
    2. Procédé selon la revendication 1, dans lequel l'induction d'oscillations acoustiques avec le transducteur ultrasonique comporte l'induction d'oscillations acoustiques avec la première gorge et la deuxième gorge du transducteur ultrasonique.
     
    3. Procédé selon la revendication 1, dans lequel la première gorge comporte une portion inclinée, la portion inclinée faisait face au moins partiellement à la direction d'un trajet d'écoulement d'air, ou dans lequel la première gorge a une section transversale triangulaire.
     
    4. Procédé selon la revendication 1, dans lequel la matière et une sortie de transducteur ultrasonique sont positionnées l'une par rapport à l'autre de sorte que la distance espacée soit (λ) (n/4), dans lequel « λ » est une longueur d'onde des oscillations acoustiques et « n » est dans une plage de plus ou moins 0,5 d'un nombre entier impair pour que les oscillations acoustiques à la surface d'interface de la matière soient centrées dans une plage de 90 degrés à une amplitude maximale, « n » étant égal à un nombre entier impair.
     
    5. Procédé selon la revendication 1, dans lequel un embout forme un pont entre la première paroi et la deuxième paroi pour définir le passage d'air entre elles.
     
    6. Appareil (10) de séchage d'une matière (20), l'appareil comprenant :

    une enceinte de distribution d'air (12) avec une entrée d'air et une sortie d'air à travers laquelle de l'air forcé est orienté vers la matière ; et

    un transducteur ultrasonique (16) raccordé à la sortie d'air de l'enceinte de distribution d'air, le transducteur ultrasonique comportant :

    une première surface interne ;

    une deuxième surface interne, la deuxième surface interne étant tournée vers la première surface interne, la première surface interne et la deuxième surface interne définissant un passage d'air à travers le transducteur ultrasonique ;

    une première gorge définie dans la première surface interne, la première gorge comportant une première portion plate, la première portion plate étant inclinée à 90 degrés par rapport à une portion la plus interne de la première surface interne et s'étendant en éloignement de la portion la plus interne de la première surface interne ; et

    une deuxième gorge définie dans la deuxième surface interne, la deuxième gorge comportant une deuxième portion plate, la deuxième portion plate étant inclinée à 90 degrés par rapport à une portion la plus interne de la deuxième surface interne et s'étendant en éloignement de la portion la plus interne de la deuxième surface interne.


     
    7. Appareil (10) selon la revendication 6, dans lequel le transducteur ultrasonique comporte
    une troisième gorge définie dans la première surface interne, la troisième gorge comportant une troisième portion plate ; et
    une quatrième gorge définie dans la deuxième surface interne, la quatrième gorge comportant une quatrième portion plate.
     
    8. Appareil (10) selon la revendication 6, dans lequel la deuxième portion plate est parallèle à la première portion plate, ou dans lequel la deuxième portion plate est coplanaire avec la première portion plate, ou dans lequel la première portion plate et la deuxième portion plate sont tournées dans une direction opposée à un trajet d'écoulement d'air à travers le transducteur ultrasonique.
     
    9. Appareil (10) selon la revendication 6, dans lequel la première gorge et la deuxième gorge ont chacune une section transversale triangulaire.
     
    10. Appareil (10) selon la revendication 6, dans lequel la première surface interne et la deuxième surface interne définissent une sortie de transducteur depuis laquelle des oscillations acoustiques générées par le transducteur ultrasonique sont orientées vers la matière, et, facultativement, dans lequel la sortie de transducteur est positionnée à une distance espacée d'une surface d'interface de la matière de sorte que l'amplitude des oscillations acoustiques à la surface d'interface de la matière soit dans la plage d'environ 120 dB à environ 190 dB.
     
    11. Appareil (10) selon la revendication 6, dans lequel la première gorge comporte une portion inclinée.
     
    12. Appareil (10) selon la revendication 11, dans lequel la portion inclinée coupe la première portion plate à un angle inférieur à 90 degrés, ou dans lequel la portion inclinée fait face au moins partiellement à la direction d'un trajet d'écoulement d'air.
     
    13. Appareil (10) selon la revendication 10, comprenant en outre une surface de repérage pour supporter la matière à une distance espacée de la sortie de transducteur.
     
    14. Appareil (10) selon la revendication 6, dans lequel une distance espacée d'une sortie du transducteur ultrasonique à la matière est (λ) (n/4), dans lequel « λ » et une longueur d'onde d'oscillations acoustiques générées par le transducteur ultrasonique et « n » est dans une plage de plus ou moins 0,5 d'un nombre entier impair pour que les oscillations acoustiques à une surface d'interface de la matière soient centrées dans une plage de 90 degrés à environ une amplitude maximale.
     
    15. Appareil (10) selon la revendication 6, comprenant en outre un élément chauffant positionné au sein de l'enceinte de distribution d'air ou raccordé fonctionnellement à celle-ci, pour chauffer l'air forcé.
     




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    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description