JPH0432688A - Microwave drier - Google Patents

Abstract

PURPOSE:To stir up material to be dried thoroughly by separating a metallic stirring means from a bottom wall of a drying chamber by a distance long enough not to cause microwave discharge between the means and the bottom wall of the drying chamber to perform agitation between the both with a rod body comprising a low dielectric loss material. CONSTITUTION:The inside of a drying chamber 3 is fed with a microwave through a waveguide 13 from a magnetron 12. A stirring means for stirring up material 5 to be stirred up, namely, a metallic stirring body 15 is provided on a bottom wall thereof. The stirring body 15 thus obtained is fixed on a transmission shaft 15a piercing the bottom wall 3a of the drying chamber 3. The stirring body 15 is separated by a specified distance from the bottom wall 3a of the drying chamber 3a so that a microwave discharge is checked between the stirring body 15 and the bottom wall 3a of the drying chamber to eliminate the denaturalizing of the material 5 to be dried. Even if building up between the stirring body 15 and the bottom wall 3a of the drying chamber, the material 5 to be dried is stirred up with a rod body 15f made of a low dielectric loss material, namely, ceramics as fixed on a transmission shaft 15a and positioned between the stirring body 15 and the bottom wall 3a of the drying chamber.

Description

[Detailed description of the invention] (b) Industrial application field The present invention relates to a microwave drying device.

(b) Prior art Japanese Patent Application No. 2-2230 discloses a microwave drying device that applies microwaves to a metal drying chamber into which the material to be dried is supplied to microwave-dry the material to be dried. There is. The apparatus is provided with a stirring means for stirring the material to be dried in the drying chamber so that the material to be dried is evenly dried. The stirring means is connected to a transmission shaft inserted from outside the drying chamber into the drying chamber, and the stirring means is driven by stirring force transmitted from the transmission shaft.

Here, if the stirring means is made of metal to ensure high strength, there is a risk that microwave discharge will occur between the stirring means and the bottom wall of the drying chamber, resulting in deterioration of the material to be dried. .

Regarding this, it is conceivable to separate the stirring means from the bottom wall of the drying chamber by a distance that does not generate microwave discharge, but in this case, it is possible to stir the material to be dried that accumulates between the stirring means and the bottom wall of the drying chamber. become unable to do so.

(c) Problems to be Solved by the Invention The present invention provides a microwave drying device that is configured to stir the material to be dried using a metallic stirring means, and is capable of suppressing microwave discharge and thoroughly stirring the material to be dried. This is what I am trying to do.

(d) Means for Solving the Problems The microwave drying apparatus of the present invention includes a metal drying chamber into which a granular or powdery material to be dried is supplied, and a device for microwave-drying the material to be dried in the drying chamber. microwave supply means for supplying microwaves and the drying chamber bottom wall, the microwave supply means being arranged in the drying chamber and spaced apart from the drying chamber bottom wall by a distance that does not cause microwave discharge between the drying chamber bottom wall and stirring the drying object. a transmission shaft that penetrates the bottom wall of the drying chamber and transmits the stirring force to the stirring means; the transmission shaft is made of a low dielectric loss material and is fixed to the transmission shaft, and is fixed to the transmission shaft and connects the stirring means and the bottom of the drying chamber. It consists of a rod located between the wall and the wall.

(E) Function The metallic stirring means is spaced from the bottom wall of the drying chamber by a distance that does not cause microwave discharge between the metal stirring means and the bottom wall of the drying chamber, and the material to be dried does not change in quality.

In addition, in this case, although the material to be dried accumulates between the stirring means and the bottom wall of the drying chamber, the material to be dried is fixed to the transmission shaft and is made of a low dielectric loss material located between the stirring means and the bottom wall of the drying chamber. The material to be dried is thoroughly stirred with a rod made of.

(F) Embodiment FIG. 1 shows the structure of a microwave drying apparatus according to an embodiment of the present invention, which consists of a drying apparatus main body 1 and peripheral mechanisms thereof.

The main body 1 of the drying apparatus is provided with a metallic cylindrical drying chamber 3 having an upper lid 2 which can be opened and closed as a main part. A supply pipe 4 is connected to the upper left part of the drying chamber, and the tip of the supply pipe reaches into a storage tank 6 in which granular or powdery material 5 to be dried is stored. The storage tank is located below the drying chamber 3. Examples of the material to be dried 5 include glass-containing resin pellets, rice, and pharmaceutical powder. Resin pellets are molded after being melted, and if the resin pellets are dried prior to such melt molding, subsequent molding will be better. In this example, glass-containing resin pellets are the material to be dried.

A suction hopper 7 is connected to the center of the upper lid 2 of the drying chamber 3 via an integrally molded microwave shielding pipe 7a. The suction hopper 7 consists of a suction hopper main body 7b and a hopper top N7c that is detachably disposed on the main body. A filter wire mesh 8a and a filter paper 8 are removably arranged so as to be sandwiched between the suction hopper main body 7b and the upper hopper fi7c. These filter wire mesh 8
a and the filter paper 8 have a mensch smaller than the material diameter of the material to be dried 5, and the filter paper 8 has a filter wire mesh 8.
The mesh is smaller than a.

A poppet valve 9 is provided in the upper lid 7C of the hopper 7 above the filter wire mesh 8a and the filter paper 8. Then, in the upper part of the poppet valve 9,
A suction blower 11 is connected to the suction head puff through an intake pipe]0. In this case, if the suction blower 11 is driven with the poppet valve 9 being driven open,
The suction action of the suction blower 11 extends to the suction pipe 10, the bow hopper 7, and the microwave shielding pipe 4, and the material to be dried 5 in the storage tank 6 is suctioned and passes through the supply pipe 4 to the drying chamber 3. . When the material to be dried 5 reaches the drying chamber 3, it falls and accumulates inside the drying chamber due to its own weight.

Here, some of the objects 5 to be dried do not fall into the drying chamber 3 and are then sucked into the hopper 7, but from this point on, the objects 5 to be dried are passed through the filter wire mesh 8a and the filter paper. 8, and thus prevents the material 5 to be dried from being undesirably sucked toward the suction blower 11.

In the drying chamber 3, there is a magnetron 12 inside.
Microwaves are supplied from the dryer via a waveguide 13, and as shown in detail in FIGS. 2 and 3, a stirring means, that is, a metal stirring body 15 for stirring the material to be dried 5 is provided on the bottom wall. ing. The stirring body] 5 is fixed to a transmission shaft 15a passing through the bottom wall 3a of the drying chamber 3. The transmission shaft 15a is a needle-shaped shaft that smoothly rotates a linear ball bearing hook 15c and the bearing, which is located inside a metal housing 1.5b fixed to the bottom wall 3a of the drying chamber outside the drying chamber 3. It is rotatably supported by a roller bearing 15d. A pin 1 is provided at the lower end of the transmission shaft 15a.
5e is fixed. The lower end of the transmission shaft 15a is loosely fitted from above into a drive body 4a which is directly connected to the fixed motor 14, and the bin 15e is loosely fitted into a long hole 14b formed on the side of the drive body 14a. ing. In such a configuration, the agitating body 15 rotates when the agitating force from the motor 14 is transmitted via the transmission shaft 15a, and thus the material to be dried 5 is agitated.

Therefore, the stirring body 15 is spaced apart from the drying chamber bottom wall 3a by a predetermined distance P, and the generation of microwave discharge between the stirring body 15 and the drying chamber bottom wall 3a is suppressed, and the material to be dried is 5
does not change.

In addition, in this case, although the material to be dried 5 accumulates between the agitator 15 and the bottom wall 3a of the drying chamber, the material to be dried is fixed to the transmission shaft 15a and remains between the agitator 5 and the bottom wall 3a of the drying chamber. A rod 15f'' made of a low dielectric loss material, ie, ceramics, located at
C is stirred, and the material to be dried 5 is thoroughly stirred.

Here, the amount of the material to be dried that accumulates between the agitator 15 and the bottom wall 3a of the drying chamber is small, and the rod 15. f does not need to be made of a high-strength metallic material, and is made of ceramics as described above. Furthermore, the gap between the rod 15f and the bottom wall 3a of the drying chamber and the gap between the rod 15f and the stirring body 15 are extremely small, and it is difficult for the material to be dried 5 to get caught in these gaps. is prevented.

A microwave choke space 15g is formed between the drying chamber bottom wall 3a and the housing 15b. The choke space surrounds the transmission shaft 15a.
5a, and the choke opening directly faces the transmission shaft 15a.

The choke space 15g prevents microwaves from leaking out of the drying chamber from the vicinity of the bottom wall 3a of the drying chamber through which the transmission shaft 15a passes.

A level sensor 16 and a temperature sensor 17 such as a thermistor are arranged on the side wall of the drying chamber 3. The level sensor 16 detects whether a predetermined amount of the material to be dried 5 has accumulated in the drying chamber 3, and the temperature sensor 17 detects the temperature of the material to be dried 5. Further, a compressor 19 is connected to the left bottom portion of the drying chamber 3 via an intake valve 18, and an exhaust valve 20 is provided on the upper lid 2 of the drying chamber 3. The driving of the compressor 19 and the opening of the intake valve 18 and exhaust valve 20 are performed when the material to be dried 5 is dried by microwaves, and water vapor generated during drying flows through the exhaust valve 20 together with air from the compressor 19. through which it is discharged to the outside.

Further, a discharge valve 21 is provided at the bottom right of the drying chamber 3, and the discharge valve is opened when the dried material 5 is discharged after drying. The dried material 5 discharged upon opening of the discharge valve 21 falls through the discharge pipe 22 into the preliminary chamber 23 below and accumulates therein. A heat insulating heater 24 is disposed on the lower inclined wall of the preliminary chamber, and a level sensor 26 having a rotating body 25 is provided in the preliminary chamber 23. Such a level sensor 26 normally rotates the rotating body 25, and even if a small predetermined amount of the dried material 5 accumulates in the preliminary chamber 23 and the rotating body 25 is attempted to be rotated, the dried material 5 does not become a load. When the rotating body 25 cannot be rotated satisfactorily, a predetermined signal is output to detect that a small predetermined amount of the material to be dried 5 has accumulated.

The lower part of the preliminary chamber 23 is connected to another suction hopper 27 located higher than the preliminary chamber 23 through a conveying pipe 28. Similar to the suction phone puff, a filter wire mesh 29a and a filter paper 29 having a mesh smaller than the material diameter of the material to be dried 5 are arranged in the p-reaction hopper 27, and a poppet is placed above the filter paper. valve 30
is provided. At the top of the poppet valve 30, the suction blower 11 is also connected to the suction hopper 27 via an intake pipe 31.

In this case, with the poppet valve 30 open, the blower 1
When the blower 1 is driven, the suction action of the blower 1 extends to the conveying pipe 28 via the air pipe 31 and the p-reverse hopper 27, and the material to be dried 5 accumulated in the preliminary chamber 23 flows through the conveying pipe 28. The suction hopper 27 is reached through the suction hopper 27. Material to be dried 5
When it reaches the suction hopper 27, it falls into the hopper due to its own weight.

In the suction hopper 27, a heat insulating heater 32 is arranged on the lower inclined wall, an on-off valve 33 is provided at the lower end, and upper and lower limit level sensors 34 are provided at the upper and lower ends.
．． 35 are arranged.

When the on-off valve 33 is closed, the suction action is activated and the dried material 5 falls into the suction hopper 27, and the dried material 5 accumulates in the suction hopper 27. On the other hand, when the on-off valve 33 is opened, the dried material 5 falls into the suction hopper 27. The dried material 5 thus accumulated falls downward and reaches the next processing section, where the dried material 5, that is, resin pellets, is melt-molded.

Figure 4 shows the circuit of the microwave drying device, and the main control section is a part number LC-65PG23 manufactured by Sanyo Electric Co., Ltd.
A microcomputer 36 is provided, and the computer receives operation information from the operation section 37 disposed on the front side of the drying apparatus main body 1, temperature information from the temperature sensor 17, and various level sensors 16.2G mentioned above. , 34.35
Based on the information etc. from
, discharge valve 21, heat retention heater 24.32, suction blower 11
, the poppet valves 9 and 30, and the on-off valve 33.

FIG. 5 shows a flowchart of the operation program installed in the microcomputer 36, and the operation of the microwave drying apparatus will be explained below with reference to the chart.

After turning on the power, it goes through steps S2, S3, and S.
Steps 3a, S4, and S5 are executed cyclically. S1
In this step, an initial setting operation is performed. That is, all writable areas in the microcomputer 36 are cleared, and the Macnetron 12, motor]4,
The compressor 19, the heat insulating heater 24, 32, and the suction blower 11 are placed in a stopped state, and the intake valve 18,
The exhaust valve 20, the exhaust valve 21, the exhaust valve 9, 30, and the on-off valve 33 are each placed in a closed state. In step S2, operation information from the operating section 37 is input, in step S3, it is determined by the lower limit level sensor 35 whether or not the material to be dried 5 has accumulated in the suction hopper 27, and in step S3a, the level sensor 26 is inputted. Based on this detection, it is determined whether a predetermined amount of the material to be dried 5 is accumulated in the preparatory chamber 23 or not. In the S4 step, microcomputer 3
The presence or absence of the start flag in 6 is checked, and the process proceeds to step S5.
In step S2, it is determined whether or not the start key is currently being operated by the operation unit 37 based on the input information in step S2.

When melt-molding the dried material 5, which is a resin pellet, to dry the dried material 5 in advance so that such molding can be performed well, first, the operating unit 37 is used to melt and mold the dried material 5, which is a resin pellet.
The desired drying time and drying temperature are respectively set within the range of 10 minutes and within the range of 70 to 170° C. using the keys, and the continuous switch 38 is turned on. These operating information are input in step S2. After that, when the start key is operated on the operation unit 37, such information is similarly input in step 82, an affirmative judgment is made in step S5, a start flag is set in step S6, and the above-mentioned information is entered in step S7. Drive control of the heat retention heaters 24 and 32 is started. That is, the heat-retaining heaters 24 and 32 are intermittently driven at a desired ratio so that the interiors of the preliminary chamber 23 and suction hopper 27 are maintained approximately at the set drying temperatures, and therefore the interiors of the preliminary chamber 23 and suction hopper 27 are maintained at approximately the set drying temperature. It is kept warm at the above temperature.

Next, steps S8, S9, and S10 are sequentially executed. In step S8, the presence or absence of a cent in the transport flag in the microcomputer 36 is checked (in this case, it is checked that it is not set). In step S9, an operation of supplying the material to be dried 5 to the drying chamber 3 is executed. That is, the poppet valve 9 is opened, the suction blower 11 is driven, the material to be dried 5 is supplied from the storage tank 6 into the drying chamber 3 by the suction action of the suction blower 11, and the motor 4 is driven to supply the agitator. 15 rotates, and the upper surface of the material to be dried 5 supplied into the drying chamber 3 is aligned with a smooth horizontal surface. S1
At step 0, it is determined by the detection by the level sensor 16 whether a predetermined amount of the material to be dried 5 has accumulated in the drying chamber 3 (in this case, it is determined that the predetermined amount has not accumulated).

After that, S2, S3, S3a, S4, Sll, S8~S
Each step of ho is executed cyclically. At this time, in the Sll step, it is checked whether the supply end flag in the microcomputer 36 is set. When a predetermined amount of the material to be dried 5 has accumulated in the drying chamber 3 and this is determined in step 810, step S12.513 is then executed. S
At step 12, the operation of supplying the material to be dried 5 to the drying chamber 3, which was executed at step S9, is completed. In step S13, the supply end flag is set.

After that, S2, S3, S3a, S4.511, S14~
Each step of S17 is executed cyclically.

At this time, in step 514, the microcomputer 36
The presence or absence of the drying end flag of the target is checked, and 515
A drying operation is performed in the step. That is, the magnetron 12 is intermittently driven depending on whether or not the temperature of the object 5 to be dried detected by the temperature sensor 17 has reached the set drying temperature, and the object 5 to be dried is maintained at the drying temperature to perform medium microwave drying. Then, the motor 14 is driven again and the stirring body 1
5 is rotated so that the material to be dried 5 is agitated so as to be dried evenly, and the compressor 19 is driven and the intake valve 1 is
8. The exhaust valve 20 is opened and the water vapor generated from the material to be dried 5 is discharged to the outside. Furthermore, in step S15, along with this drying operation, measurement of the elapsed drying time is started.

In step 516, it is determined whether the elapsed drying time has reached the set drying time, and in step 517, it is checked whether the conveyance flag is set, as in step S8.

Therefore, when the elapsed drying time reaches the set drying time, S
After 16 steps, steps S18 and S19 are executed. In step S18, the drying operation executed in step S15 and the measurement of elapsed drying time are completed, and the measured time is reset. In step S19, the drying end flag is set.

And 517, S2, S3, S3a, S4.511.
After completing 514 steps, S2Q, 52], S22, S
Steps 23 and S24 are sequentially executed. In step S20, it is checked whether the discharge flag in the microcomputer 36 is set. In step S21, it is determined based on the detection by the level sensor 26 whether a predetermined amount of the material 5 to be dried has already accumulated in the preliminary chamber 23 or not.

In step S22, a heat retention operation is performed in the drying chamber 3 (described later).
When this is in progress, it is terminated and the discharge flag is set. Step S23 is executed when the dried material 5 is allowed to be newly discharged from the drying chamber 3 to the preliminary chamber 23 because the material 5 to be dried is not accumulated in the preliminary chamber 23 in step 521. , such S
In step 23, the operation of discharging the dried material 5 from the drying chamber 3 to the preliminary chamber 23 is executed. That is, when the discharge valve 21 is opened, the motor 4 is continuously driven to rotate the agitator 15, and as the agitator 15 rotates, the material to be dried 5 near the agitator 15 is The material to be dried 5 is pushed to the surroundings and is discharged from the discharge valve 21 through the discharge pipe 22 into the preliminary chamber 23 . The material to be dried 5 discharged in this way is not naturally cooled because the preliminary chamber 23 is kept warm from the step S7.
This prevents the material to be dried 5 from absorbing moisture again due to natural cooling. Furthermore, in step S23, the elapsed time of such discharge is started to be counted. In step S24,
Determine whether or not the elapsed discharge time has reached a predetermined discharge time (this is sufficient time to discharge all of the predetermined amount of material to be dried 5 stored in the drying chamber 3). be done.

After that, S2, S3, S3a, S4, Sll, 514,
S20. Each step of S23, S24, and S17 is executed in circulation, and when a small predetermined amount of the material to be dried 5 accumulates in the preparatory chamber 23 as a result of the above-mentioned discharge, steps S25, S26, and S27. Each step is executed sequentially. In step S25, a conveyance flag is set, and in step S26, if the drying material supply operation is being executed in step S9, the operation is stopped. In step S27, an operation is carried out to transport the dried material 5 from the preliminary chamber 23, which is kept warm, to the suction hopper 27. That is, poppet valve 3
0 is opened and the suction blower 11 is driven, and the suction action of the suction blower 11 causes the suction hopper 27 to be drawn from the preliminary chamber 23.
The material to be dried 5 is transported to. The dried material 5 transported in this manner is not naturally cooled because the suction hopper 27 has been kept warm since step S7, and the dried material 5 is prevented from absorbing moisture again. In step S28, it is determined by the detection by the upper limit level sensor 34 whether or not the dried material 5 has accumulated in the suction hopper 27 up to the position of the sensor (in this case, it is determined not to).

After that, S4, S11.514, S20, S23, S2
4.517 and S27.528 are executed in circulation, and during this period, the discharge operation to the preliminary chamber 23 and the suction hopper 27
The conveying operation to is performed in parallel, and the dried material 5 discharged to the preliminary chamber 23 is immediately conveyed to the suction hopper 27.

Then, when the elapsed discharge time reaches a predetermined discharge time (all the materials to be dried 5 are discharged from the drying chamber 3 to the preliminary chamber 23), steps S29, 530 and S31 are sequentially executed. Ru.

In step S29, the ejection operation executed in step S23 and the elapsed elapsed time measurement are completed, and the measured time is reset. At step 530, all of the above-mentioned supply end flag, drying end flag, and discharge flag are reset. In step S31, it is determined on the operating section 37 whether the continuous switch 38 is turned on.

In the present case, the continuous switch 38 is in the on state, and after passing through the step S17, the steps S4, S11, S8, and S27 are performed.
, S28 are executed cyclically. Then, the material to be dried 5 in the preliminary chamber 23 is transported to the suction hopper 2.
When the dried material 5 accumulates up to the position of the upper limit level sensor 34 at step 7, steps 528 to 532 and step S33 are executed. In step S32, the conveyance operation executed in step S27 is stopped, and in step S33, the conveyance flag is reset.

Therefore, the dried material 5 accumulated in the suction hopper 27 in this way
is melt-molded in the next processing section;
This is executed when an external command signal P for instructing melt molding is given to the microcomputer 36 in a state where the material to be dried 5 has accumulated in the suction hopper 27 up to the position of the upper limit level sensor 34 . That is, at this time, the on-off valve 33 is opened by the microcomputer 36, and the dried material 5 is discharged from the suction hopper 27 to the next stage processing section. The opening/closing valve 33 is closed again when all of the dried material 5 in the suction hopper 27 is discharged. Then, the discharged material 5 to be dried is melt-molded in the next processing section, and in this case, the sugar beet pellets, that is, the material 5 to be dried, have been dried in advance, so that the molding can be performed well.

Here, if the processing capacity of the next-stage processing section for the melt-molding is slow, the process from supplying the dried material to the conveying operation is repeated, so that the suction chamber 27 and the preliminary chamber 23 are filled with the dried material. remains accumulated. Therefore, when the drying material 5 is accumulated in the preliminary chamber 23 and the drying material 5 is to be further discharged from the drying chamber 3, this is determined in step 521. 5 has accumulated in excess of a predetermined amount, and the OI5 to be dried is transferred from the drying chamber 3 to the preliminary chamber 23.
It is determined that the new discharge is not permitted. Then, the dried material 5 is left as it is in the drying chamber 3 even after drying. If the O15 to be dried is simply left to stand, the O15 to be dried will be naturally cooled and absorb moisture again even after being dried, but in this embodiment, in order to prevent this, S34 is
Step is executed. That is, in step S34, the same control as the drying operation in step S5 is performed, and the material to be dried 5 is kept warm at the set drying temperature by microwaves.
Therefore, the material to be dried 5 is prevented from absorbing moisture again in the drying chamber 3.

The series of operations described above is ended by turning off the continuous switch 38. That is, when step 831 is executed in such an off state, step S35 is executed next, the start flag is reset, and the drive of each of the heat retention heaters 24 and 32 is stopped. That @S2, S3,
Steps S3a, S4, and S5 are executed cyclically.

(G) Effects of the Invention According to the microwave drying apparatus of the present invention, in the configuration in which the material to be dried is stirred by the metallic stirring means, the metallic stirring means is separated from the bottom wall of the drying chamber, and the stirring means and the drying chamber are separated from each other. Since microwave discharge is prevented from occurring between the drying material and the bottom wall, deterioration of the quality of the material to be dried can be suppressed.

Furthermore, in this case, although the material to be dried accumulates between the stirring means and the bottom wall of the drying chamber, the material to be dried is fixed to the transmission shaft and is made of a low dielectric loss material located between the stirring means and the bottom wall of the drying chamber. Since it is stirred with a rod made of, it is possible to thoroughly stir the material to be dried.

[Brief explanation of the drawing]

The drawings relate to a microwave drying device according to an embodiment of the present invention.
The figure is a front sectional view, FIGS. 2 and 3 are a front sectional view and a side sectional view of essential parts, respectively, FIG. 4 is a circuit diagram, and FIG. 5 is a flowchart of an operating program of the microcomputer. 3... Drying room, 12... Magnetron, 15...
Stirring body, 15a...transmission shaft, 15f...rod.

Claims (1)

[Claims] (1) A metal drying chamber into which a granular or powdery material to be dried is supplied; a microwave supply means for supplying microwaves for microwave drying the material to be dried to the drying chamber; a metallic stirring means for stirring the material to be dried, spaced apart from the bottom wall of the drying chamber by a distance that does not cause microwave discharge between the stirring means and the bottom wall of the drying chamber; A microwave drying device comprising a transmission shaft that transmits stirring force to a stirring means, and a rod made of a low dielectric loss material, fixed to the transmission shaft and located between the stirring means and the bottom wall of the drying chamber. .