JPH02305609A - Microwave drier - Google Patents

Abstract

PURPOSE:To control wear of an interposing matter, by a method wherein a ceramic body is fixed on the surface of the interposing matter comprised of material of a low dielectric loss interposed between a metallic agitating device agitating a matter to be dried and a wall surface of a drying chamber. CONSTITUTION:A microwave is fed within a drying chamber 3 from a magnetron 12 through a waveguide 13 and a bottom wall part is provided with a metallic agitating body 15 agitating a matter 5 to be dried. The agitating body 15 possesses a metallic boss 15a, the tip of a metallic driving shaft 14a arriving at the inside of the drying chamber 3 from a motor 14 which is outside of the drying chamber 3 is joined to a recessed part 15c of the upper part of the inside of the said boss through fitting into the recessed part 15c and the matter 5 to be dried is agitated by the agitating body 15. A washer 3e of Teflon whose dielectric loss is low is interposed between a metallic boss 15a and a bottom wall of the drying chamber 3. A ring 3f comprised of ceramics of a rigid material is fixed to the circumference of the washer 3e so that the same is not worn through hitting of the matter 5 to be dried entering away between the agitating body 15 and the bottom wall of the drying chamber 3 against the same.

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. 1-47803 discloses a microwave drying apparatus for drying the material to be dried using microwaves by applying microwaves to a drying chamber into which the material to be dried is completely supplied. 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 dried evenly.

If the stirring means is made of metal, microwave discharge will occur between it and the wall of the drying chamber, which is also made of metal, resulting in deterioration of the quality of the material to be dried.

Therefore, it is considered that an inclusion made of a low dielectric loss material is interposed between the stirring means and the wall surface of the drying chamber. However, in this case, due to the presence of such inclusions, the stirring means and the wall surface of the drying chamber are separated to a certain extent, and the generation of microwave discharge between them is suppressed, but a new problem arises.
Since the above-mentioned inclusions are exposed to frequent contact with the material to be dried, the inclusions are undesirably worn out.
If the material to be dried is hard and contains glass, such abrasion becomes noticeable.

(c) Problems to be Solved by the Invention The present invention has a structure in which an inclusion made of a low dielectric loss material is interposed between the stirring means and the wall surface of the drying chamber to prevent microwave discharge from occurring between the two. In addition, the purpose is to suppress undesirable wear of the inclusions.

(d) Means for Solving the Problems The microwave drying apparatus of the present invention includes a 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, a metallic stirring means arranged in the drying chamber for stirring the material to be dried, and a low induction i1 interposed between the stirring means and the wall surface of the drying chamber. It consists of an inclusion made of a lossy material and a ceramic body fixed to the surface of the inclusion.

(e) Operation The inclusion that is interposed between the agitation means and the wall surface of the drying chamber to prevent generation of microwave discharge is hard to wear out because a hard ceramic body is fixed to the surface of the inclusion.

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

The main part of the drying apparatus (1) is provided with a cylindrical drying chamber (3) having an upper lid (2) that can be opened and closed.

A supply pipe (4) is connected to the upper left part of the drying chamber, and the tip of the supply pipe is connected to the granular or powdery material to be dried (5).
) into the storage tank (6) that stores the water. Examples of the material to be dried (5) include resin pellets, rice, and powdered pharmaceutical products. Resin pellets are molded after being melted, but if the resin pellets are dried prior to melt molding, subsequent molding will be better.In this example, the material to be dried (5) was Resin pellets are selected. Further, a suction hopper (7) is connected to the center of the upper lid (2) of the drying chamber (3). A filter wire mesh (8a) and a filter paper (8) having a mesh smaller than the material diameter of the material to be dried (5) are arranged in the hopper, and a poppet valve (9) is located above the filter paper. )
is provided. At the top of the poppet valve (9), the suction hopper (7) is equipped with a suction vibrator (1).
A suction blower (11) is connected via the air conditioner 0). In this case, if the blower (11) is driven with the poppet valve (9) open, the suction action of the blower (11) will affect the suction vibrator (10), the suction hopper (7), and the drying chamber (3). ) to the supply pipe (4), and the material to be dried (5) in the storage tank (6) passes through the supply pipe (4) to the drying chamber (3). The material to be dried (5) is placed in the drying room (3)
When this happens, it falls and accumulates inside the drying chamber due to its own weight.

In the drying chamber (3), microwaves are supplied from the magnetron (12) to the inside through the waveguide (13), and as shown in detail in FIGS. 2 and 3, microwaves are supplied to the bottom of the drying chamber (3).
A metal stirring body (15) is provided as a stirring means for stirring the material to be dried (5). The stirring body (15) has a metal boss (15g) (to which a ceramic boss (15b) is added), and an upper recess (15c) in the boss is provided with a part outside the drying chamber (3). The tip (14b) of a metal transmission means, that is, a drive shaft (14a) that reaches from the motor (14) to the inside of the drying chamber (3) is internally connected, thereby transmitting the stirring driving force of the remoter (14). is transmitted to the stirring body (15) via the drive shaft (14a), and the material to be dried (5) is stirred by the stirring body (15). In the metal boss (15a), there is a space below the joint between the upper recess (15c) and the tip (14b) of the drive shaft (14a) to prevent microwaves from entering the joint. A blocking means, that is, a microwave choke space (15d) is formed to surround the drive shaft (14m), so that the boss (15a) of the metallic stirring body 15) and the drive shaft (14a) ) come into contact with each other through bonding, microwave discharge does not occur because microwaves do not reach there, and the material to be dried (5) is prevented from being altered by microwave discharge.

A microwave choke space (3a) is also formed on the ag1 outer surface of the drying chamber (3) so as to surround the drive shaft (14a), and is connected to the drive shaft through hole (3b) in the bottom wall of the drying chamber (3). Microwaves are prevented from leaking to the outside. The structure of the choke space (3a) also functions as a bearing for the drive shaft (14a). In addition, the metal boss (15
A sleeve (3C) made of Teflon or the like with low dielectric loss is provided between the lower end of a) and the drive shaft (14a) to prevent microwave discharge from occurring due to contact between the two. , the drive shaft through hole in the bottom wall of the drying chamber (3) (
A sleeve (3d) made of Teflon or the like having low dielectric loss is also provided between the drive shaft (14g) and the drive shaft (14g) for the same purpose.

Furthermore, a washer (3e) made of Teflon or the like having a small dielectric loss is interposed between the metal boss (14g) and the bottom wall of the drying chamber (3) for the same purpose. In this case, the washer (3e) is made of a hard material so that the material to be dried (5) that has entered between the agitator (15) and the bottom wall of the drying chamber (3) does not hit and wear out. Ring made of ceramics
3f) are fixed around the periphery. The upper end of the ring (3f) is larger than the upper end of the washer (3e) as shown in Fig. 4! It is located on the lower side of the tower to prevent the ring (3f) from coming into contact with the boss (15a). However, such dimensions! is such that the material to be dried (5) does not enter there. The agitator (15) and washer (3a) are removable, making it easy to clean the interior of the drying chamber (3) by opening the top cover (2).

Next, a level sensor (1) is installed on the side wall of the drying chamber (3).
6) and a temperature sensor (17) such as a thermistor are arranged. 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). .

In addition, a compressor (19) is connected to the left bottom of the drying chamber (3) via an intake valve (18), and the drying chamber (3)
An exhaust valve (20) is provided on the top cover (2). The drive of these humplets (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 the water vapor generated during drying is transferred to the compressor. Exhaust valve (20) with air from <19>
) and is discharged to the outside.

Furthermore, a discharge valve (21) is provided at the bottom right of the drying chamber (3), and the discharge valve discharges the dried material (
5) It is opened when discharging. The material to be dried (5) discharged upon opening of the discharge valve (21) falls through the discharge pipe (22) and accumulates in the preliminary chamber (23) below. A heat insulating heater (24) is arranged on the lower inclined wall of the preliminary chamber, and a rotating body (25) is arranged in the preliminary chamber (23).
) is provided. Such a level sensor (26) normally rotates a rotary body (25) and places a small predetermined amount of the material to be dried (5) in the preliminary chamber (23).
) has accumulated and the rotating body (25) is trying to rotate, but the material to be dried (5) acts as a negative bridge and the rotating body (25) cannot be rotated satisfactorily, a predetermined signal is output. Then, it is detected that a predetermined amount of the dried material (5) is accumulated.

The lower part of the preliminary chamber (23) is connected to a conveying pipe (28) to another suction hopper (27) located higher than the preliminary chamber (23).
) are connected through. Similar to the suction hopper (7), the suction hopper (27) also has a filter wire mesh (29a) having a mesh smaller than the material diameter of the material to be dried (5).
) and a filter paper (29) are arranged, and a poppet valve (30) is provided above the filter paper. And, in the upper part 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, the poppet valve (30) is opened and the blower (11
), the suction action of the blower (11) extends to the conveying pipe (28) via the suction pipe (31) and the suction hopper (27), and the drying material ( 5) passes through the conveying pipe (28) and reaches the suction hopper (27). The material to be dried (5) is transported to 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) ( 35) are located. The above on-off valve (3
3>, when the suction action works and the dried material (5) falls into the suction hopper (27), the dried material (5) accumulates in the suction hopper (27), while the opening/closing valve (
33> is opened, the dried material (5) accumulated in this way falls downward and reaches the next processing section, where the dried material (5), that is, the resin pellets, is melted. molded.

Fig. 5 shows the circuit of the microwave drying device, in which 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 of the drying device main body (1) and temperature information from the temperature sensor (17). , the above various level sensors (16
)(26)(34)<35) Based on the information etc.
The above magnetron (12), motor (14), intake valve (18), exhaust valve (20), compressor (19), discharge valve (21), heat retention heater (24) (32), suction blower (11), Bopect valve (9) (30), on-off valve (33
) to drive and control.

FIG. 6 shows a flowchart of the operation program stored in the microcomputer (36), and the operation of the microwave drying apparatus will be explained below with reference to the same chart.

After the IT power is turned on, the process goes through the S1 step and then goes through the normal S2, S3, and so on.
Steps 5-3a, 84, and S5 are executed cyclically.

In step S1, an initial setting operation is performed. That is, the entire writable area in the microcomputer (36) is cleared, and the magnetron (12),
Motor (14>, compressor (19), insulation heater (
24) (32), the suction blower (11) is placed in a stopped state, and the intake valve (18), exhaust valve (20), discharge valve (21), poppet valve (9), (30), on-off valve ( 3
3) are each placed in an open state. In step S2, operation information from the operation section (37) is input, and in step 83, it is determined by the lower limit level sensor (35) whether or not the material to be dried (5) is left in the suction hopper (27). At step 53, it is determined whether or not a predetermined amount of the material to be dried (5) is accumulated in the preliminary chamber (23) based on the detection by the level sensor (26). In step S4, it is checked whether a start flag is set in the computer (36), and in step S5, 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. Ru.

Therefore, when melt-molding the object to be dried (5), which is a resin pellet, in advance of drying the object to be dried (5) so that the molding can be done well, first, the operation part (37) is Then, set the desired drying time and drying temperature within the range of 20 to 60 minutes and 70 to 170°C by key operation, respectively.
Then, turn on the continuous switch (38). These operation information can be inputted in step S2. After this, the operation section (37
), the information to decline is similarly input in step 82, an affirmative judgment is made in step S5, the start flag is set in step S6, and each of the above-mentioned heat retention is set in step S7. Heater (24) (3
2) drive control is started. That is, the above preliminary room (23
) and the suction hopper (27) so that the drying temperature is approximately maintained at the set drying temperature.
32) is intermittently driven at a desired ratio, so the preliminary chamber (23) is driven intermittently at a desired ratio.
) and the inside of the suction hopper (27) are kept at the above temperature.

Next, steps S8, S9, and SlO can be executed in sequence. In step S8, it is checked whether the slow speed flag in the computer (36) is set (in this case, it is checked that it is not set), and in step S9, the material to be dried (5) is supplied to the drying chamber (3). Action is performed.

That is, the poppet valve (9) is opened and the suction blower (11) is opened.
) is fully driven, and the storage tank (
The material to be dried (5) is supplied from 6) into the drying chamber (3),
In addition, the motor (14) is fully driven, 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. In step S10, the level sensor (16) detects the drying material (5).
) reaches the position of this sensor (16) and the drying chamber (
3) It is determined whether or not a predetermined number of items to be dried (5) have accumulated in the chamber (in this case, it is determined that a predetermined number of items have not accumulated).

After that, S2, S3, S3a, 84, Sll, S8~S
Each step of IO is executed circularly. At this time, in the Sit step, it is checked whether the supply end flag in the computer 36 is set. When a predetermined number of items to be dried (5) accumulates in the drying chamber (3) and this is determined in the SlO step, step S12.813 is then executed. In step S12, the operation of supplying the material to be dried (5) to the drying chamber (3) executed in step S9 is completed.

In step S13, the supply end flag is set.

After that, S2, S3, S3a, S4.811, S14~
Each step of 917 is executed cyclically. At this time, S14
In step 315, a check is made to see if the drying end flag in the computer (36) is set, and in step 315, a drying operation is executed. In m, the magnetron (12) is intermittently driven depending on whether the temperature of the material to be dried (5) detected by the temperature sensor (17) has reached the set drying temperature, and the material to be dried (5) is dried. The temperature is maintained to perform microwave drying, and the motor (14) is driven again to rotate the agitation body (15) to agitate the material to be dried (5) so that it is evenly dried. (19) and the intake valve (18) and exhaust valve (20) are 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 S16, it is determined whether or not the elapsed drying time has reached the set drying time, and in step S17, it is checked whether or not the conveyance flag is set, as in step S8.

Therefore, when the elapsed drying time reaches the set drying time, 9
After 16 steps, 31g, step S19 is executed. In step 818, the drying operation performed in step S15 and the measurement of elapsed drying time are terminated, and the measured time is reset.

In step S19, the drying end flag is set.

And S17, S2, S3, S3a, S4, S11,
After passing through SL4 step, S20, S21, S22, S
23. Each step of S24 is executed sequentially. S20
In this step, it is checked whether the discharge flag in the computer (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 to be dried (5) has already accumulated in the preliminary chamber (23). In step S22, if a heat-retaining operation (described later) is being performed in the drying chamber (3), this is terminated and the discharge flag is set. In step S23, the material to be dried (5) is placed in the preliminary chamber (23) in step S21.
Because the predetermined amount of water is not accumulated, the drying room (3) is moved from the drying room (3) to the preliminary room (
This is executed when the dried material to be dried (5) is allowed to be newly discharged to step 23), and in this step 323, the dried material to be dried (5> is discharged from the drying chamber 3). An operation of discharging to the preliminary chamber (23) is performed. That is, the discharge valve (21) is opened and the motor (14) is opened.
) is subsequently driven to rotate the agitator (15), and as the agitator (15) rotates, the material to be dried (5) near the agitator (15) is pushed to the surroundings. , dried material (5)
is discharged from the discharge valve (21) via 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) has been kept warm since step S7. ) absorbs moisture again.
This prevents Furthermore, in step S23, the elapsed time of such discharge is started to be counted. In step S24, a predetermined elapsed elapsed elapsed time (elapsed elapsed time) is set.
This is a predetermined amount of material to be dried (5) stored in the drying chamber (3).
) is reached, which is sufficient time to eject all of the liquid.

After that, S2, S3, S3a, S4, Sll, S14,
When each step of S20.823 and S24.817 is executed in circulation, and 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 from 53m to 825m are executed in the circulation. , S26, 927, and S28 are sequentially executed. 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 warmed preliminary chamber (23) to the suction hopper (27).

That is, the poppet valve (30) is opened and the suction blower (1) is opened.
1) is driven, and the material to be dried (5) is transported from the preliminary chamber (23) to the suction hopper (27) by the suction action of the blower (11). The material to be dried (5) transported in this way is
Since the suction hopper (27) has been kept warm since step S7, there is no natural cooling and the material to be dried (
5) is prevented from absorbing moisture again. In step 828, it is determined whether or not the dried material (5) has accumulated in the suction hopper (27) up to the position of the senna based on the detection by the upper limit level sensor (34) (in this case, it is determined that no). ).

After that, S4, Stt, 814, S20. S23, S
Steps 24, S17, S27, and S2g are executed in circulation, and during this time, the discharge operation to the preliminary chamber (23) and the conveyance operation to the suction hopper (27) are processed in parallel, and the
The material to be dried (5) discharged to 3) is immediately transferred to the suction hopper
27).

Then, when the elapsed discharge time reaches a predetermined discharge time, all of the material to be dried (5) is discharged from the drying chamber (3) to the preliminary chamber (23>), and then S29.830.
Each step of 831 is executed sequentially.

In step S29, the ejection operation executed in step S23 and the elapsed elapsed time measurement are completed, and the elapsed time is reset. In step S30, all of the above-mentioned supply end flag, drying end flag, and discharge flag are reset. In step S31, the operation section (37)
It is determined whether the continuous switch (38) is turned on or not.

In this case, the continuous switch (38) is in the on state, and after passing through step S17, S4, Sit, S8.
Steps 27 and 328 are executed cyclically. and,
The material to be dried (5) in the preliminary chamber (23) is transported,
When the material to be dried (5) accumulates in the suction hopper (27) up to the position of the upper limit level sensor (34), steps 828 to 83
2. Step S33 is executed. In step S32, the conveyance operation that was completed in step 827 is stopped, and in step 333, the conveyance flag is reset.

The material to be dried (5) accumulated in the suction hopper (27) in this way is subjected to jIF melt molding in the next processing section. This is executed when an external command signal P for instructing melt molding is given to the computer 36 when the material to be dried (5) has accumulated up to the position (34). That is, at this time, the computer (36) operates the on-off valve (33).
is opened, and the material to be dried (5) is discharged from the suction hopper (27) to the next processing section. The opening/closing valve (33) is closed again when all of the material to be dried (5) in the suction hopper (27) is discharged. Then, the above-mentioned released material to be dried (5
) is melt-molded in the next processing section, and in this case, the resin pellets, that is, the material to be dried (5), 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 carrying out the melt-forming is slow, the operations from the drying material supply operation to the conveyance operation are repeated, so that the suction hopper (27) and the preparatory chamber (23 ) remains to be dried (5). Therefore, when the drying material (5) is accumulated in the preliminary chamber (23) and the drying material (5) is about to be discharged from the drying chamber (3), this is determined in step 821. In other words, it is determined that more than a predetermined amount of the material to be dried (5) has accumulated in the preliminary chamber (23) and that the material to be dried (5) is not allowed to be newly discharged from the drying chamber (3) to the preliminary chamber (23). be done. Then, the dried material (5) is left in the drying chamber (3) even after drying. If the material to be dried is simply left to stand, the material to be dried (5) will naturally cool down and absorb moisture again even after being dried, but in the embodiment of the present invention, step 834 is executed at this time to prevent this. That is, such S3
In step 4, the same control as the drying operation in step S15 is performed, and the object to be dried (5) is kept warm at the set drying temperature using microwaves, so that the object to be dried (5) is kept in the drying chamber (3).
) prevents it from absorbing moisture again.

The series of operations described above is ended by turning off the continuous switch (38). That is, when step S31 is executed during such off-time, step 835 is executed next,
The start flag is reset and the respective heat-retaining heaters (24) and (32) are stopped. Then S2
, S3, S3a, and S4.95 steps are executed cyclically.

(G) Effects of the Invention According to the present invention, an inclusion made of a low dielectric loss material is interposed between the stirring means and the wall surface of the drying chamber to prevent microwave discharge from occurring between the two. Since the hard ceramic body is fixed to the surface of the inclusion, it is possible to prevent the inclusion from being undesirably abraded due to contact with the material to be dried.

Furthermore, if the inclusion is made of Teflon as in this embodiment, smooth driving (@-movement) of the stirring means can be promoted because Teflon has low frictional resistance.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a sectional view, FIGS. 2 and 3 are sectional views and exploded sectional views showing details around the stirring body, respectively, 4150 is a sectional view of the washer, and 4150 is a sectional view of the washer. FIG. 5 is a circuit diagram, and FIG. 6 is a flowchart of the operating program of the microcomputer. (3)...Drying room, (12)...Magnetron,
(15)... Stirring body, (14a)... Drive shaft, (1
5d)...Microwave titan space, (3g)...
・Wash ~, (3f)...Ring.

Claims (1)

[Claims] (1) A drying chamber to 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; and a microwave supply means disposed within the drying chamber. a metallic stirring means for stirring the dried material;
A microwave drying device comprising: an inclusion made of a low dielectric loss material interposed between the stirring means and the wall surface of the drying chamber; and a ceramic body fixed to the surface of the inclusion.