CA1038458A - Microwave paint dryer - Google Patents
Microwave paint dryerInfo
- Publication number
- CA1038458A CA1038458A CA247,367A CA247367A CA1038458A CA 1038458 A CA1038458 A CA 1038458A CA 247367 A CA247367 A CA 247367A CA 1038458 A CA1038458 A CA 1038458A
- Authority
- CA
- Canada
- Prior art keywords
- drying
- path
- heating
- along
- heated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/78—Arrangements for continuous movement of material
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B3/00—Drying solid materials or objects by processes involving the application of heat
- F26B3/32—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action
- F26B3/34—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects
- F26B3/343—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects in combination with convection
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2206/00—Aspects relating to heating by electric, magnetic, or electromagnetic fields covered by group H05B6/00
- H05B2206/04—Heating using microwaves
- H05B2206/046—Microwave drying of wood, ink, food, ceramic, sintering of ceramic, clothes, hair
Landscapes
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Microbiology (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Biotechnology (AREA)
- Molecular Biology (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Drying Of Solid Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method of and apparatus for the continuous or batch drying of a material, e.g. a painted surface or a glued laminate, uses microwave energy for heating and a cooling air flow for re-moving moisture from the material. The air, thus heated, is re-directed to the material at a preheating position to preheat the material prior to the heating of the material by the microwave energy.
A method of and apparatus for the continuous or batch drying of a material, e.g. a painted surface or a glued laminate, uses microwave energy for heating and a cooling air flow for re-moving moisture from the material. The air, thus heated, is re-directed to the material at a preheating position to preheat the material prior to the heating of the material by the microwave energy.
Description
~038458 The present invention relates to methods of and apparatus for drying a material using microwave energy.
With a view to improving industrial drying processes, considerable research into methods of drying has been carried out.
Such research has revealed that water is contained in a material as free water within the material or on the surface, and as bound water. Free water is easier to remove, but the removal of bound water presents greater difficulty and may result in changes in the physical characteristics of the material.
v When the material is dryed, water is initially evaporated from the surface of the material independently of the characteristics of the material and at a rate dependent on the heat energy absorbed and the air flow condi-tions at the surface of the material. After this, water is removed by capil-lary action, and greater energy is required for removing the moisture.
It has previously been proposed to use microwave energy for drying since the absorbed microwave energy creates a temperature gradient which accelerates moisture migration towards the surface of the material, where the moisture evaporates.
It i9 an object of the present invention to provide an improved drying apparatus, and an improved method of drying a material, which employ microwave energy in conjunction with an air flow directed against the surface of the material for removing moisture therefrom.
It is a further object of the present invention to provide an ;~
improved drying apparatus and method for the continuous drying of a material utilizing microwave energy in conjunction with an air flow in which energy loss is reduced by recycling air heated by contact with the material being dried to effect preheating of the up path material before the material is heated by the microwave energy.
~, -~,~
~38458 ~ ccording to the present invention, there is provided drying apparatus comprising a microwave generator; a guide means for directing a material to be dried along a predetermined path; a heating area on said path wherein said material is heated by microwave energy; means for guiding micro-wave energy from said microwave generator to said heating area, to thereby heat the material; means for directing a flow of dry cooling air onto the heated material to dry said material, whereby the cooling air becomes heated;
and means for redirecting the heated air to the material at a preheating area up path of said heating area to preheat the material prior to the heating of the material by the microwave energy.
The material may be fed through the apparatus in batches or con-tinuously, for example, on a conveyor.
The flow of dry cooling air onto the heated material has the -effect of removing moisture from the material, and also of absorbing the heat energy produced in the material by the microwave energy. This heat energy is then carried in the air flow to the incoming material for preheating the ~ -latter.
The removal of the heat energy from the heated material by the air flow is a cooling process which does not harm the material and in fact assists in preparing the material for transportation or further processing since the material is brought back to the desirable room temperature.
Preferably, the microwave energy and the air flow are employed simultaneously for drying the material by both heating and moisture removal.
For a given material to be dried, the designer of the apparatus can determine the amount of microwave energy and the air flow required to achieve the desired drying effect. To obtain optimum efficiency, he must also determine whether both the microwave energy and the air flow are to be applied simultaneously and uniformly with respect to the space coordinates of a heating chamber and with respect to time.
- . ~. . .
103B4Sl~
For batch processlng, the mlcrowave energy may be gradually reduced, and the air flow may be increased so that the material is heated efficiently at ehe initial stage of the dry-lng process, and its moisture ls then removed efficiently by the slr flow during the latter stage of the drying process.
In the case of a continuously operating apparatus, in which the material iq carried on a conveyor through a heating chamber, the apparatus may be designed so that the microwave energy varies, and more particularly decreases, in the direction of ad~ance of the material through the heating chamberO
In this connection9 it should be understood that as the material travels along a heating path through the heating chamber and is sub~ected to the drying effect of the microwave energy, the material undergoes a change in dielectric constant9 due to moisture migration and removal, and is therefore less capable of absorbing microwave power as it travels along the heating chamber.
To take this effect into account, the apparatus may be deslgned so that the rate of drying of the material is reduced along the length of the drying path. This may be effected, for example, by maintaining the cross-sectional dimensions of the heating chamber constant, and by arranging the microwave energy and cool air flow so that the rate of drying of the material is reduced as the material travels along the heating path through the heating chamber. Alternatively, the cross-sectional di-mensions of the chamber may be varied along the length of the chamber to produce a similar effect, e.g. by providing a micro-wave energy profile which decreases along the length of the heating chamber.
Also, it is desirable eo ensure, insofar as possible, that the drying is uniform across the width of the drying path.
In practice, some non-uniformity of drying transversely ; ~
... .
of the drying path can be expected, unless special measures are taken, due to the fact that, regardless whether mode stirrers are used or not, the electric field distribution across the drying path will not be uniform. The consequential non-uniform drying - -might result in visible hot spots in the material, which cannot be tolerated in the drying or redrying of expensive paintings or painted surfaces ~e.g. painted cloth, paper or aluminum used for wall decorations).
To counteract such non-uniform drying across the heat- -ing path, the drying effect may be varied transversely of the heating path by either modifying the microwave energy profile and/or the air flow, or by modifying the transverse dimensions of the heating chamber, to provide an appropriately non-uniform -drying effect across the drying path.
As mentioned above, the present invention may be employ-ed for drying painted surfaces, in which case the substrate, i.e.
the material directly beneath the paint, is not restricted to any specific material, but may for example be paper, glass, metal, wood or cloth.
In addition, the present invention may be employed, for example, for drying glue between the plies of plywood.
The invention will be more readily understood from the following description of an experiment and of a preferred embodi-ment of the invention given, by way of example, with reference to the accompanying diagrammatic drawings, in which:-Figure 1 shows an experimental apparatus for applyingmicrowave energy to a sample to be dried; and Figure 2 shows a longitudinal cross-section view through a continuous drying a~ aratus.
... . . .
' lQ384~8 .
The apparatus illustrated in Figure 1 comprises a microwave generator 10 for supplying microwave energy through a rectangular wave guide ~ operating in the TElo mode at a frequency of 2.45 GHZ through a test sample 12 to a non-reflect-ing load 13, the direction of the electric field being indicated by arrow E.
The sample 12 is supported in a cylindrical glass tube 15, which has a wall thickness which is sufficiently thin to allow the microwave power to pass through the cylindrical , glass tube 15 from the.microwave generator 10 to the sample 12 and on to a non-reflecting load 13.
The sample 12 is disposed between upper and lower walls 16 and 17, which are perforated to allow the flow of air past the sample 12, as described in greater detail hereinafter.
- m e sample 12, which for convenience is a block of chalk, is supported at the top of a pin 19, which passes through the lower wall 17 and extends to a balance 20 for measuring the combined weight of the chalk sample 12 and the pin 19.
Opposite ends of the cylindrical glass tube 15 are connected to respective rubber hoses 22 and 23. The rubber hose 23 is an outlet or exhaust hose, and the rubber hose 22 is an air inlet hose extending to a second cylindrical glass tube 23.
A further chalk sample 24 is supported by a pin 25 . extending to a balance 26 between perforated upper and lower walls 28 and 29 in a manner similar to the arrangement of the first-mentioned chalk sample 12.
An air blower 30 is connected by a rubber hose 31 to the end of the glass tube 23 opposite from the rubber hose 22.
To measure the temperature of the sample 12, leads 32 ., . . ~ , : , - . .
-: . ,, : , . - . ~ . , 103845~
connected to a shielded thermocouple (not shown) are attached :
to the middle of the sample 12. ; .
The operation of the above-described apparatus, which is intended for experimental purposes, is as follows:
In a first experiment, the chalk sample 12 was weighed, '~
and then wetted and weighed again before being inserted into the position shown in the'cylindrical glass tube 15. After such insertion, the'sample lZ was subjected to drying by micro-wave energy from the microwave generator 10 for a period of . -:
360 seconds, after whi`ch'i`t was again weighed.
The'res'ults of this experiment are as shown in the following table: . ~ .
Blackboard Chalk Sample - :
length = 1 11/16"
diameter = 0.4" ~ ~
ml ='2.40 gm .' m2 = 4.31 gm m3 = 2-58 gm .
Exposure Time in Seconds Pl 2 ~P 3 4 0 400340 60 2 58 ':
' 325255 70 15 55 i50' 140 70 69 40 30 240 90 30 60 38 22 :
270 . 85 25 60 38 22 . 360 70 141 56 40 16 .
.. -', ' :' :' ' -; ' '. ', ': :
ml = initial weight m2 = wet weight m3 = final weight after 360 seconds of the exposure time Pl = power in watts delivered by generator P2 = power in watts reflected back to the generator ~P = Pl - P2 = power incident on load P3 = power transmitted past sample load P4 - QP - P3 = power actually absorbed by sample load As will be evident from the right-hand end of this Table, it is clear that the microwave power P4 absorbed by the /~
sample ~ is decreased with time, which indicates that the J~
ability of the sample ~ to absorb microwave power is only appreciable at the begining of the dryi~ng process.
During this first experiment, the air blower 30 was de-energized, and therefore no thermal energy was recovered from sample 24 to aid in the drying of the sample 12, nor was any air used to carry out transport thermal energy from the sample 24 to the sample 12.
In a second experiment, the-sample 24 was firstly heated, and the blower 30 was energized, and in a third experiment, in order to distinguish between the effect of the air flow on sample 12 when the sample 24 w.as not heated, the sample 24 was replaced by a similar, unheated sample of identical dlmensions to the samples 12 and 24. In this way, it was possible to ascertain the effect of heat transfer from the sample 24 to the sample 12, and it was found that this efect caused the sample 12 to dry more quickly. ::
It was found that the final weight (2.58 gm) of the .`
sample subjected to the recycled air in the second experiment :
was obtained in 110 seconds, instead of 360 seconds without ;
.
., ~, . 103845&~ ", recycled air, and in the third experiment the final weight of the sample subjected to the recycled air (i.e. 2.58 gm) was attained in 135 seconds, instead of 110 seconds in the second experiment and 360 seconds in the first experiment.
The dif~erence of 25 seconds was attributed to the heat from the heatea sample recycled through the air discharged ~ -by the blower.
The apparatus illustrated in Figure 2 comprises a conveyor belt 110 supported by rollers 111 and 112.
The conveyor belt 110 extends along a heating path ~
through a heating chamber defined by a housing 114. ~ -A microwave generator 115 is connected by waveguide 116 and 117 to a microwave outlet 119 disposed above the heating path within the interior of the housing 114.
A first air pump 120 is connected by an air inlet passage 121 to the interior of the housing 114 at the outlet end of the latter, i.e. at the end of the latter through which the conveyor belt 110 leaves the heating chamber when the conveyor j belt 110 advances in the direction indicated by arrow 122.
At the opposite end of the housing 114, there is pro-vided an air outlet passage 123 communicating with the lnterior of the housing 114 and extending to a second air pump 124.
The outlet of the air pump 124 communicates through an air passage 125 with an air discharge hood 126.
The air discharge hood 126 is disposed above the con-veyor belt 110 at a preheating position which is disposed before the housing 114 in the direction of advance of the conveyor belt 110 .
In operation of the above-described apparatus, material to be dried, e.g. a painted substrate or newly glued plywood, is , .~
- 8 - ~
- . ~ .
.. . ..
. 1Q3~45B
carried on the conveyor belt 110 through the preheating position beneath the air discharge hood 126 and then through the interior of the housing 114 and beneath the microwave outlet 119.
As the material passes beneath the microwave outlet 119, it is subjected to heating by microwave energy supplied from the microwave generator 115.
The material is then subjected to an air flow, supplied by the pump 120 through the air flow passage 121, and this air flow removes moisture from the heated material.
Simultaneously, this air flow becomes heated by the heat producted in the material by the microwave energy.
The heated air flow is then pumped from the housing 114 by the second air pump 124, and is discharged onto the incoming material at the preheating position beneath the air discharged hood 126.
Consequently, the heat carried by the cooling air stream from the heated material within the housing 114 is em-ployed to preheat the material before the latter is subjected to microwave heating.
'' '.: : ~
~ ' . ' ' :, ,. .
.' ' ~ .
~ ~
- _ g _ ~ ' :
~, " ' .
With a view to improving industrial drying processes, considerable research into methods of drying has been carried out.
Such research has revealed that water is contained in a material as free water within the material or on the surface, and as bound water. Free water is easier to remove, but the removal of bound water presents greater difficulty and may result in changes in the physical characteristics of the material.
v When the material is dryed, water is initially evaporated from the surface of the material independently of the characteristics of the material and at a rate dependent on the heat energy absorbed and the air flow condi-tions at the surface of the material. After this, water is removed by capil-lary action, and greater energy is required for removing the moisture.
It has previously been proposed to use microwave energy for drying since the absorbed microwave energy creates a temperature gradient which accelerates moisture migration towards the surface of the material, where the moisture evaporates.
It i9 an object of the present invention to provide an improved drying apparatus, and an improved method of drying a material, which employ microwave energy in conjunction with an air flow directed against the surface of the material for removing moisture therefrom.
It is a further object of the present invention to provide an ;~
improved drying apparatus and method for the continuous drying of a material utilizing microwave energy in conjunction with an air flow in which energy loss is reduced by recycling air heated by contact with the material being dried to effect preheating of the up path material before the material is heated by the microwave energy.
~, -~,~
~38458 ~ ccording to the present invention, there is provided drying apparatus comprising a microwave generator; a guide means for directing a material to be dried along a predetermined path; a heating area on said path wherein said material is heated by microwave energy; means for guiding micro-wave energy from said microwave generator to said heating area, to thereby heat the material; means for directing a flow of dry cooling air onto the heated material to dry said material, whereby the cooling air becomes heated;
and means for redirecting the heated air to the material at a preheating area up path of said heating area to preheat the material prior to the heating of the material by the microwave energy.
The material may be fed through the apparatus in batches or con-tinuously, for example, on a conveyor.
The flow of dry cooling air onto the heated material has the -effect of removing moisture from the material, and also of absorbing the heat energy produced in the material by the microwave energy. This heat energy is then carried in the air flow to the incoming material for preheating the ~ -latter.
The removal of the heat energy from the heated material by the air flow is a cooling process which does not harm the material and in fact assists in preparing the material for transportation or further processing since the material is brought back to the desirable room temperature.
Preferably, the microwave energy and the air flow are employed simultaneously for drying the material by both heating and moisture removal.
For a given material to be dried, the designer of the apparatus can determine the amount of microwave energy and the air flow required to achieve the desired drying effect. To obtain optimum efficiency, he must also determine whether both the microwave energy and the air flow are to be applied simultaneously and uniformly with respect to the space coordinates of a heating chamber and with respect to time.
- . ~. . .
103B4Sl~
For batch processlng, the mlcrowave energy may be gradually reduced, and the air flow may be increased so that the material is heated efficiently at ehe initial stage of the dry-lng process, and its moisture ls then removed efficiently by the slr flow during the latter stage of the drying process.
In the case of a continuously operating apparatus, in which the material iq carried on a conveyor through a heating chamber, the apparatus may be designed so that the microwave energy varies, and more particularly decreases, in the direction of ad~ance of the material through the heating chamberO
In this connection9 it should be understood that as the material travels along a heating path through the heating chamber and is sub~ected to the drying effect of the microwave energy, the material undergoes a change in dielectric constant9 due to moisture migration and removal, and is therefore less capable of absorbing microwave power as it travels along the heating chamber.
To take this effect into account, the apparatus may be deslgned so that the rate of drying of the material is reduced along the length of the drying path. This may be effected, for example, by maintaining the cross-sectional dimensions of the heating chamber constant, and by arranging the microwave energy and cool air flow so that the rate of drying of the material is reduced as the material travels along the heating path through the heating chamber. Alternatively, the cross-sectional di-mensions of the chamber may be varied along the length of the chamber to produce a similar effect, e.g. by providing a micro-wave energy profile which decreases along the length of the heating chamber.
Also, it is desirable eo ensure, insofar as possible, that the drying is uniform across the width of the drying path.
In practice, some non-uniformity of drying transversely ; ~
... .
of the drying path can be expected, unless special measures are taken, due to the fact that, regardless whether mode stirrers are used or not, the electric field distribution across the drying path will not be uniform. The consequential non-uniform drying - -might result in visible hot spots in the material, which cannot be tolerated in the drying or redrying of expensive paintings or painted surfaces ~e.g. painted cloth, paper or aluminum used for wall decorations).
To counteract such non-uniform drying across the heat- -ing path, the drying effect may be varied transversely of the heating path by either modifying the microwave energy profile and/or the air flow, or by modifying the transverse dimensions of the heating chamber, to provide an appropriately non-uniform -drying effect across the drying path.
As mentioned above, the present invention may be employ-ed for drying painted surfaces, in which case the substrate, i.e.
the material directly beneath the paint, is not restricted to any specific material, but may for example be paper, glass, metal, wood or cloth.
In addition, the present invention may be employed, for example, for drying glue between the plies of plywood.
The invention will be more readily understood from the following description of an experiment and of a preferred embodi-ment of the invention given, by way of example, with reference to the accompanying diagrammatic drawings, in which:-Figure 1 shows an experimental apparatus for applyingmicrowave energy to a sample to be dried; and Figure 2 shows a longitudinal cross-section view through a continuous drying a~ aratus.
... . . .
' lQ384~8 .
The apparatus illustrated in Figure 1 comprises a microwave generator 10 for supplying microwave energy through a rectangular wave guide ~ operating in the TElo mode at a frequency of 2.45 GHZ through a test sample 12 to a non-reflect-ing load 13, the direction of the electric field being indicated by arrow E.
The sample 12 is supported in a cylindrical glass tube 15, which has a wall thickness which is sufficiently thin to allow the microwave power to pass through the cylindrical , glass tube 15 from the.microwave generator 10 to the sample 12 and on to a non-reflecting load 13.
The sample 12 is disposed between upper and lower walls 16 and 17, which are perforated to allow the flow of air past the sample 12, as described in greater detail hereinafter.
- m e sample 12, which for convenience is a block of chalk, is supported at the top of a pin 19, which passes through the lower wall 17 and extends to a balance 20 for measuring the combined weight of the chalk sample 12 and the pin 19.
Opposite ends of the cylindrical glass tube 15 are connected to respective rubber hoses 22 and 23. The rubber hose 23 is an outlet or exhaust hose, and the rubber hose 22 is an air inlet hose extending to a second cylindrical glass tube 23.
A further chalk sample 24 is supported by a pin 25 . extending to a balance 26 between perforated upper and lower walls 28 and 29 in a manner similar to the arrangement of the first-mentioned chalk sample 12.
An air blower 30 is connected by a rubber hose 31 to the end of the glass tube 23 opposite from the rubber hose 22.
To measure the temperature of the sample 12, leads 32 ., . . ~ , : , - . .
-: . ,, : , . - . ~ . , 103845~
connected to a shielded thermocouple (not shown) are attached :
to the middle of the sample 12. ; .
The operation of the above-described apparatus, which is intended for experimental purposes, is as follows:
In a first experiment, the chalk sample 12 was weighed, '~
and then wetted and weighed again before being inserted into the position shown in the'cylindrical glass tube 15. After such insertion, the'sample lZ was subjected to drying by micro-wave energy from the microwave generator 10 for a period of . -:
360 seconds, after whi`ch'i`t was again weighed.
The'res'ults of this experiment are as shown in the following table: . ~ .
Blackboard Chalk Sample - :
length = 1 11/16"
diameter = 0.4" ~ ~
ml ='2.40 gm .' m2 = 4.31 gm m3 = 2-58 gm .
Exposure Time in Seconds Pl 2 ~P 3 4 0 400340 60 2 58 ':
' 325255 70 15 55 i50' 140 70 69 40 30 240 90 30 60 38 22 :
270 . 85 25 60 38 22 . 360 70 141 56 40 16 .
.. -', ' :' :' ' -; ' '. ', ': :
ml = initial weight m2 = wet weight m3 = final weight after 360 seconds of the exposure time Pl = power in watts delivered by generator P2 = power in watts reflected back to the generator ~P = Pl - P2 = power incident on load P3 = power transmitted past sample load P4 - QP - P3 = power actually absorbed by sample load As will be evident from the right-hand end of this Table, it is clear that the microwave power P4 absorbed by the /~
sample ~ is decreased with time, which indicates that the J~
ability of the sample ~ to absorb microwave power is only appreciable at the begining of the dryi~ng process.
During this first experiment, the air blower 30 was de-energized, and therefore no thermal energy was recovered from sample 24 to aid in the drying of the sample 12, nor was any air used to carry out transport thermal energy from the sample 24 to the sample 12.
In a second experiment, the-sample 24 was firstly heated, and the blower 30 was energized, and in a third experiment, in order to distinguish between the effect of the air flow on sample 12 when the sample 24 w.as not heated, the sample 24 was replaced by a similar, unheated sample of identical dlmensions to the samples 12 and 24. In this way, it was possible to ascertain the effect of heat transfer from the sample 24 to the sample 12, and it was found that this efect caused the sample 12 to dry more quickly. ::
It was found that the final weight (2.58 gm) of the .`
sample subjected to the recycled air in the second experiment :
was obtained in 110 seconds, instead of 360 seconds without ;
.
., ~, . 103845&~ ", recycled air, and in the third experiment the final weight of the sample subjected to the recycled air (i.e. 2.58 gm) was attained in 135 seconds, instead of 110 seconds in the second experiment and 360 seconds in the first experiment.
The dif~erence of 25 seconds was attributed to the heat from the heatea sample recycled through the air discharged ~ -by the blower.
The apparatus illustrated in Figure 2 comprises a conveyor belt 110 supported by rollers 111 and 112.
The conveyor belt 110 extends along a heating path ~
through a heating chamber defined by a housing 114. ~ -A microwave generator 115 is connected by waveguide 116 and 117 to a microwave outlet 119 disposed above the heating path within the interior of the housing 114.
A first air pump 120 is connected by an air inlet passage 121 to the interior of the housing 114 at the outlet end of the latter, i.e. at the end of the latter through which the conveyor belt 110 leaves the heating chamber when the conveyor j belt 110 advances in the direction indicated by arrow 122.
At the opposite end of the housing 114, there is pro-vided an air outlet passage 123 communicating with the lnterior of the housing 114 and extending to a second air pump 124.
The outlet of the air pump 124 communicates through an air passage 125 with an air discharge hood 126.
The air discharge hood 126 is disposed above the con-veyor belt 110 at a preheating position which is disposed before the housing 114 in the direction of advance of the conveyor belt 110 .
In operation of the above-described apparatus, material to be dried, e.g. a painted substrate or newly glued plywood, is , .~
- 8 - ~
- . ~ .
.. . ..
. 1Q3~45B
carried on the conveyor belt 110 through the preheating position beneath the air discharge hood 126 and then through the interior of the housing 114 and beneath the microwave outlet 119.
As the material passes beneath the microwave outlet 119, it is subjected to heating by microwave energy supplied from the microwave generator 115.
The material is then subjected to an air flow, supplied by the pump 120 through the air flow passage 121, and this air flow removes moisture from the heated material.
Simultaneously, this air flow becomes heated by the heat producted in the material by the microwave energy.
The heated air flow is then pumped from the housing 114 by the second air pump 124, and is discharged onto the incoming material at the preheating position beneath the air discharged hood 126.
Consequently, the heat carried by the cooling air stream from the heated material within the housing 114 is em-ployed to preheat the material before the latter is subjected to microwave heating.
'' '.: : ~
~ ' . ' ' :, ,. .
.' ' ~ .
~ ~
- _ g _ ~ ' :
~, " ' .
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Drying apparatus, comprising:
a microwave generator;
a guide means for directing a material to be dried along a predeter-mined path;
a heating area on said path wherein said material is heated by micro-wave energy;
means for guiding microwave energy from said microwave generator to said heating area, to thereby heat the material;
means for directing a flow of dry cooling air onto the heated material to dry said material, whereby the cooling air becomes heated; and means for redirecting the heated air to the material at a preheating area up path of said heating area to preheat the material prior to the heating of the material by the mircrowave energy.
a microwave generator;
a guide means for directing a material to be dried along a predeter-mined path;
a heating area on said path wherein said material is heated by micro-wave energy;
means for guiding microwave energy from said microwave generator to said heating area, to thereby heat the material;
means for directing a flow of dry cooling air onto the heated material to dry said material, whereby the cooling air becomes heated; and means for redirecting the heated air to the material at a preheating area up path of said heating area to preheat the material prior to the heating of the material by the mircrowave energy.
2. Drying apparatus as claimed in claim 1, which includes means for continuously feeding the material along said predetermined path.
3. A method of drying a material, comprising the steps of:
guiding the material to be dried along a predetermined path;
generating microwave energy;
guiding the microwave energy to the material at a heating area on said path to thereby heat the material;
directing a flow of dry cooling air onto the heated material to dry the material, whereby the air becomes heated; and redirecting the heated air to the material at a preheating area up path of said heating area to preheat the material prior to the heating of the material by the microwave energy.
guiding the material to be dried along a predetermined path;
generating microwave energy;
guiding the microwave energy to the material at a heating area on said path to thereby heat the material;
directing a flow of dry cooling air onto the heated material to dry the material, whereby the air becomes heated; and redirecting the heated air to the material at a preheating area up path of said heating area to preheat the material prior to the heating of the material by the microwave energy.
4. A method as claimed in claim 3, which includes reducing the power of the microwaves as a function of time to reduce the heating of the material thereby, and increasing drying of the material by the air flow, after initial heating of the material by the microwave energy.
5. A method as claimed in claim 3, which includes the steps of conveying the material along a predetermined drying path along which the material is subjected to drying by the microwave energy and the air flow, and reducing the rate of drying of the material along the length of the drying path.
6. A method as claimed in claim 5, in which the micro-wave energy to which the material is subjected decreases as the material advances along the drying path.
7. A method as claimed in claim 3, which includes the steps of conveying the material along a predetermined drying path along which the material is subjected to drying by the microwave energy and the air flow, and varying the rate of drying of the material transversely of the drying path.
8. A method as claimed in claim 7, which includes conveying the material through a drying chamber whose dimensions vary transversely of the drying path to vary the microwave power across the material.
9. A method as claimed in claim 7, which includes varying the air discharge across the width of the drying path.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA247,367A CA1038458A (en) | 1976-03-08 | 1976-03-08 | Microwave paint dryer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA247,367A CA1038458A (en) | 1976-03-08 | 1976-03-08 | Microwave paint dryer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1038458A true CA1038458A (en) | 1978-09-12 |
Family
ID=4105407
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA247,367A Expired CA1038458A (en) | 1976-03-08 | 1976-03-08 | Microwave paint dryer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1038458A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2463904A1 (en) * | 1979-08-21 | 1981-02-27 | Ceraver | Drying of objects, esp. ceramics, without distortion - where object is directly heated and exposed to air or gas stream which is at lower temp than object |
| WO1993017882A1 (en) * | 1992-03-06 | 1993-09-16 | Haakansson Goeran | Method of removal of paint etcetera from a timber element and equipment for practising the method |
| WO2007062180A1 (en) * | 2005-11-23 | 2007-05-31 | The Sherwin-Williams Company | System and method to control energy input to a material |
-
1976
- 1976-03-08 CA CA247,367A patent/CA1038458A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2463904A1 (en) * | 1979-08-21 | 1981-02-27 | Ceraver | Drying of objects, esp. ceramics, without distortion - where object is directly heated and exposed to air or gas stream which is at lower temp than object |
| WO1993017882A1 (en) * | 1992-03-06 | 1993-09-16 | Haakansson Goeran | Method of removal of paint etcetera from a timber element and equipment for practising the method |
| WO2007062180A1 (en) * | 2005-11-23 | 2007-05-31 | The Sherwin-Williams Company | System and method to control energy input to a material |
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