JP7748703B2 - vibrating sieve machine - Google Patents

Description

The present invention relates to a vibrating sieve machine that sifts powder to be classified that has been dropped onto the mesh by vibrating a sieve frame with the mesh installed.

One known example of this type of vibrating sieve is a direct-type vibrating sieve, in which vibrators (vibration motors) are mounted on both sides of the sieve frame (see, for example, Patent Document 1). This direct-type vibrating sieve is configured to sieve by vibrating the powder on the mesh via the sieve frame when the vibrator is activated, which has the advantage of allowing the height of the machine to be kept low.

Here, sieving refers to the process of separating powder dropped onto a mesh into powder that passes through the mesh (under the sieve) and powder that does not pass through the mesh (over the sieve).

In the vibrating sieve machine of Patent Document 1, the vibrator is configured with a four-pole motor (induction motor) and an eccentric weight. According to the vibrating sieve machine of Patent Document 1, the vibration of the sieve frame caused by the operation of the vibrator causes powder on the mesh to bounce up and then collide with the mesh, crushing and dispersing the agglomerated powder, thereby increasing the amount of powder that can be recovered as undersieve material.

International Publication No. 2019/082644

In the vibrating sieve machine of Patent Document 1, the mesh device vibrates along with the sieve frame. Due to the structure of the mesh device, the amplitude of the mesh device is relatively larger in the center than in the areas closer to the periphery. For this reason, the classification efficiency is generally low in the areas closer to the periphery of the mesh device, but increases toward the center. Therefore, in order to increase the amount of powder recovered that falls through the sieve, it is important to sift the powder using the center of the mesh device and its vicinity.

However, even if the powder to be classified is dropped into the center of the mesh device, depending on the conditions of the powder to be classified, such as the particle size, density, and cohesive strength of the powder, the amplitude of the sieve frame may have an excessive effect. In other words, the effect of expelling the powder from the center of the mesh device to the outer periphery may become too strong, causing the powder to flow from the center to the outer periphery of the mesh device shortly after being dropped, preventing the desired increase in the amount of powder recovered through the sieve.

Therefore, by increasing the rotation speed of the four-pole motor, the vibration frequency of the sieve frame, which is proportional to the motor rotation speed, can be increased, which effectively reduces the amplitude of the sieve frame, which is inversely proportional to the square of the vibration frequency of the sieve frame. Reducing the amplitude of the sieve frame suppresses the action of expelling powder from the center of the mesh device toward the outer periphery, which increases the amount of powder that remains in and around the center of the mesh device for a long time, which is thought to increase the amount of powder recovered.

However, the motor rotation speed is inversely proportional to the number of poles. For this reason, it is structurally difficult to increase the rotation speed of a four-pole motor, which has a relatively large number of poles. As a result, the vibrating sieve machine described in Patent Document 1 is unable to achieve the desired increase in the amount of powder recovered below the sieve.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a vibrating sieve machine that can easily increase the amount of powder recovered below the sieve.

The characteristic configuration of the vibrating sieve machine according to the present invention for solving the above problems is as follows:
A vibrating sieve machine that sieves powder to be classified that is dropped onto a sieve frame in a state where a sieve device is incorporated, by vibrating the sieve frame,
vibrators are provided on both sides of the sieve frame so as to be able to impart vibrations to the powder,
The vibrator has a two-pole motor and an eccentric weight.

With this type of vibrating sieve machine, the operation of a vibrator having a two-pole motor and an eccentric weight applies vibrations to the powder on the sieve frame from both sides of the sieve frame, thereby sieving it. A two-pole motor has the smallest number of poles, and its structure makes it easy to increase its rotation speed. Therefore, by increasing the rotation speed of the two-pole motor and increasing the vibration frequency of the sieve frame, which is proportional to the rotation speed of the two-pole motor, it is possible to effectively reduce the amplitude of the sieve frame, which is inversely proportional to the square of the vibration frequency of the sieve frame. Reducing the amplitude of the sieve frame suppresses the effect of expelling powder from the center of the sieve toward the outer periphery, thereby increasing the amount of powder that remains in and around the center of the sieve. This makes it easy to increase the amount of powder recovered that falls through the sieve.

In the vibrating sieve machine according to the present invention,
a mode switching means for switching between a sieving mode for sieving the powder and a discharge mode for discharging the powder;
a motor control means for controlling the two-pole motor;
Furthermore,
When the sieving mode is selected, the motor control means controls the two-pole motor to rotate at a rotation speed suitable for sieving the powder.
When the discharge mode is switched to, it is preferable to control the two-pole motor so that it rotates at a rotation speed suitable for discharging the powder.

With this configuration of the vibrating sieve machine, when switched to sieving mode, the two-pole motor is controlled by the motor control means to rotate at a rotation speed suitable for sieving the powder. This allows for efficient sieving and ensures an increased amount of powder recovered below the sieve. When switched to discharge mode, the two-pole motor is controlled by the motor control means to rotate at a rotation speed suitable for discharging the powder. This allows for the powder remaining on the sieve to be quickly discharged, allowing for a smooth transition to the next sieving operation and improving productivity.

In the vibrating sieve machine according to the present invention,
The rotation speed suitable for sieving the powder is 2000 rpm or more and less than 4000 rpm,
The rotation speed suitable for discharging the powder is preferably 4000 rpm or more.

With this type of vibrating sieve, the rotation speed suitable for sieving powder is set to between 2000 rpm and 4000 rpm. This rotation speed range ensures that the powder remains in and around the center of the mesh device, where classification efficiency is high, for a sufficient amount of time, reliably increasing the amount of powder that can be recovered as undersieve. On the other hand, the rotation speed suitable for discharging powder is set to 4000 rpm or higher. At 4000 rpm or higher, the vertical vibration component acting on the powder is further suppressed, allowing the horizontal vibration component to act relatively dominantly on the powder, allowing the powder to quickly flow from the center of the mesh device to the outer periphery, and allowing residual powder on the sieve to be quickly discharged.

In the vibrating sieve machine according to the present invention,
It is preferable that the vibrator applies vibration to the sieve frame so that the amplitude of the vibration is 1.7 to 4.0 mm.

With this type of vibrating sieve machine, the amplitude of the sieve frame is set to 1.7 to 4.0 mm by the vibrator, which prevents the powder from being ejected from the center of the mesh toward the periphery, allowing the powder on the mesh to bounce up appropriately and then collide with the mesh. This ensures sufficient retention time for the powder in and around the center of the mesh, where classification efficiency is high, and effectively crushes and disperses the powder.

In the vibrating sieve machine according to the present invention,
The eccentric weight preferably includes a fixed weight and an adjustable weight whose position relative to the fixed weight is adjustable.

With a vibrating sieve machine of this configuration, the centrifugal force can be adjusted by adjusting the relative position of the adjustment weight to the fixed weight, allowing for precise centrifugal force settings and achieving optimal vibration conditions.

FIG. 1 shows a vibrating sieve according to an embodiment of the present invention, where (a) is a plan view and (b) is a front view. 2A and 2B show a vibrating sieve according to one embodiment of the present invention, in which (a) is a view seen from the arrow A in FIG. 1B, and (b) is an enlarged cross-sectional view taken along line BB in FIG. 1B. FIG. 3 is a front view of the eccentric weight of the vibrator as seen from the axial direction of the two-pole motor. FIG. 4 shows a mesh device used in a vibrating sieve machine according to one embodiment of the present invention, where (a) is a plan view showing a portion of the sieving mesh broken away, (b) is an enlarged view of part C in (a), and (c) is a view seen from the arrow D in (b). FIG. 5 is a block diagram showing a schematic configuration of a motor control system. 6A to 6C show the sieving operation according to the first embodiment, where (a) is a diagram showing the initial stage of sieving, (b) is a diagram showing the middle stage of sieving, and (c) is a diagram showing the final stage of sieving. 7A, 7B, and 7C show the sieving operation according to the second embodiment, in which (a) is a diagram showing the initial stage of sieving, (b) is a diagram showing the middle stage of sieving, and (c) is a diagram showing the final stage of sieving. 8A, 8B, and 8C show the sieving operation according to the third embodiment, in which (a) is a diagram showing the initial stage of sieving, (b) is a diagram showing the middle stage of sieving, and (c) is a diagram showing the final stage of sieving. 9A to 9C show the sieving operation according to Comparative Example 1, where (a) is a diagram showing the initial stage of sieving, (b) is a diagram showing the middle stage of sieving, and (c) is a diagram showing the final stage of sieving. FIG. 10 shows the sieving operation according to Comparative Example 2, where (a) is a diagram showing the initial stage of sieving, (b) is a diagram showing the middle stage of sieving, and (c) is a diagram showing the final stage of sieving. FIG. 11 shows the sieving operation according to Comparative Example 3, where (a) is a diagram showing the initial stage of sieving, (b) is a diagram showing the middle stage of sieving, and (c) is a diagram showing the final stage of sieving.

The present invention will now be described with reference to the drawings. However, the present invention is not intended to be limited to the embodiments described below or the configurations shown in the drawings.

<General configuration of vibrating sieve machine>
1A and 1B show a vibrating sieve 1 according to one embodiment of the present invention, with (a) being a plan view and (b) being a front view. As shown in Figs. 1A and 1B, the vibrating sieve 1 is a direct-type vibrating sieve that can keep the height of the machine low, and has the function of classifying various powders such as pharmaceuticals, food products, minerals, metals, and resin raw materials by vibration. This vibrating sieve 1 includes a vibrating plate 3 disposed above a base 2.

The vibration plate 3 is an octagonal ring-shaped plate of the required thickness in plan view, with a central mounting hole for attaching the sieve container 6 (described below). A number of (12 in this example) compression coil springs (elastic supports) 4 are installed in a predetermined arrangement around the circumference of the vibration plate 3 between the vibration plate 3 and the base 2, and these compression coil springs 4 support the vibration plate 3 so that it can vibrate freely.

A reinforcing plate 5 is provided along the outer periphery of the vibrating plate 3. This reinforcing plate 5 is formed by bending a strip of plate material to fit the shape of the outer periphery of the vibrating plate 3, and is fixed so that it protrudes vertically downward from the lower plate surface of the vibrating plate 3 around almost the entire circumference of the vibrating plate 3. This improves the rigidity of the vibrating plate 3 while minimizing the weight of the vibrating plate 3. Therefore, even if a high-output vibrator 30 (described below) is used, it is possible to prevent the vibrating plate 3 from bending or twisting, which makes it possible to use a high-output vibrator 30 and improves classification performance.

A sieve container 6 is attached to the mounting holes in the vibration plate 3. The sieve container 6 is primarily composed of a sieve frame 7 with openings at the top and bottom, through which the powder to be classified is introduced, and a lid 8 that is removably attached to the upper opening of the sieve frame 7. An inlet 8a for the powder to be classified is formed in the center of the lid 8.

<Sieve frame>
2A and 2B show a vibrating sieve machine 1 according to an embodiment of the present invention, in which (a) is a view taken along the arrow A in FIG. 1B, and (b) is an enlarged cross-sectional view taken along the line B-B in FIG. 1B. As shown in FIGS. 2A and 2B, the sieve frame body 7 is configured by combining an upper divided sieve frame 7a and a lower divided sieve frame 7b which can be separated into upper and lower parts.

As shown in Figure 2(b), the upper divided sieve frame 7a is composed of a cylindrical upper divided sieve frame body 10 that is open at the top and bottom, a flange portion 11 that extends radially outward from the lower end of the upper divided sieve frame body 10 around the entire periphery, and a tapered flange portion 12 that extends outward and slopes upward from the upper end of the upper divided sieve frame body 10 around the entire periphery. A ring-shaped gasket 13 is attached to the flange portion 11 of this upper divided sieve frame 7a around the entire periphery.

As shown in Figure 2(a), a discharge duct 14 is attached to one side of the upper divided sieve frame 7a in the front-to-rear direction (the left side in Figure 2(a)) so as to protrude from the cylindrical wall surface of the upper divided sieve frame main body 10. This discharge duct 14 serves to discharge to the outside any residual powder (residual powder on the sieve) remaining on the mesh 40 (described below) during the classification process.

As shown in Figures 1(a) and (b), the upper divided sieve frame 7a (upper divided sieve frame main body 10) has a discharge port 10a that corresponds to the discharge duct 14. Furthermore, a guide member 70 is disposed inside the upper divided sieve frame main body 10, near the outer periphery of the mesh element 40 (described below), to guide the powder to be classified, which flows clockwise on the mesh element 40, to the discharge port 10a during the classification process operation (described below).

As shown in Figure 2(b), the lower divided sieve frame 7b is composed of a lower divided sieve frame main body 20 and a flange portion 21 that extends radially outward from the upper end of the lower divided sieve frame main body 20 around the entire periphery to correspond to the flange portion 11 on the upper divided sieve frame 7a. A ring-shaped gasket 22 is attached around the entire periphery of the flange portion 21 of this lower divided sieve frame 7b.

The lower divided sieve frame body 20 has a cylindrical portion 25 that is open at the top and bottom. As shown in Figure 2(a), a funnel-shaped chute portion 26 that tapers downward is integrally connected to the lower side of this cylindrical portion 25. Also integrally connected to the lower side of this chute portion 26 is a discharge opening portion 27 that allows the powder in the chute portion 26 to fall and be discharged downward.

<Vibrator>
As shown in Figures 1(a) and (b), a beam member 28 is integrally arranged on the lower divided sieve frame 7b so as to penetrate in the left-right direction, and a motor mounting plate 29 is fixed to each end of this beam member 28, and a vibrator 30 is fixedly attached to each motor mounting plate 29.

As shown in Figure 2(a), the vibrator 30 has a two-pole motor 31, which is a two-pole induction motor, and eccentric weights 32 attached to both ends of the rotating shaft (rotor shaft) 31a of the two-pole motor 31. The vibrator 30 is configured to generate vibrations by rotating the eccentric weights 32 when the two-pole motor 31 is operated.

In each vibrator 30, the angle θ that the axis S of its rotation shaft 31a makes with respect to the horizontal plane H is set in the range of 55° to 65°; in this example, the vibrators are tilted at θ = 60°. The left and right vibrators 30 are arranged so that they are in opposite phases to each other; that is, when viewed from one side in the left-right direction, the axis S of one vibrator 30 and the axis S of the other vibrator 30 projected onto a vertical plane perpendicular to the left-right direction are symmetrical with respect to the vertical axis on the vertical plane that passes through the intersection of these axes S. This ensures the necessary horizontal vibration component while maximizing the vertical vibration component. The vibration causes the powder on the mesh device 40 (described below) to bounce up and collide with the meshes 43 and 44 (described below), thereby breaking down and dispersing the powder particle agglomerates, further improving classification performance.

Figure 3 is a front view of the eccentric weight 32 of the vibrator 30 as viewed from the axial direction of the two-pole motor 31. As shown in Figure 3, the eccentric weight 32 includes a fixed weight 32a and an adjustable weight 32b. Both the fixed weight 32a and the adjustable weight 32b are formed in a fan shape when viewed from the axial direction of the rotating shaft 31a, and have an insertion hole 33 formed in the central corner so that the rotating shaft 31a can be inserted therethrough, and a slit 35 extending from the insertion hole 33 toward the arc portion 34 at the circumferential end. In both the fixed weight 32a and the adjustable weight 32b, a bolt 36 is threadedly engaged so as to be tightened in a direction intersecting the extension direction of the slit 35. In both the fixed weight 32a and the adjustable weight 32b, tightening the bolt 36 causes the insertion hole 33 to contract in diameter, and the inner surface of the insertion hole 33 tightly clamps the outer surface of the rotating shaft 31a, thereby fixing it to the rotating shaft 31a.

When setting the vibration force of the vibrator 30, the centrifugal force is adjusted by adjusting the relative position of the adjustment weight 32b with respect to the fixed weight 32a. Specifically, the bolt 36 attached to the adjustment weight 32b is loosened, and the indicator 37 of the adjustment weight 32b is rotated to match the scale on the scale plate (not shown) attached to the end face of the rotating shaft 31a according to the required vibration force. The bolt 36 is then tightened to secure the adjustment weight 32b to the rotating shaft 31a. The relative position of the adjustment weight 32b with respect to the fixed weight 32a can be adjusted continuously, allowing for precise centrifugal force settings and achieving the optimal vibration state. The fixed weight 32a remains essentially fixed by tightening the bolt 36 attached to the fixed weight 32a. Therefore, when setting the centrifugal force, the relative position of the adjustment weight 32b around the rotating shaft 31a with respect to the fixed weight 32a is adjusted.

As shown in Figure 2(b), a lid gasket 51 is supported by a ring plate 52 and inserted between the outer peripheral edge of the lid body 8 and the tapered flange portion 12 of the upper divided sieve frame 7a to seal the gap between them. A fastening band 53 with a V-shaped cross section is wrapped around the butt joint between the lid body 8 and the upper divided sieve frame 7a, allowing it to sandwich the outer peripheral edge of the lid body 8 and the tapered flange portion 12 of the upper divided sieve frame 7a. The lid body 8 and the upper divided sieve frame 7a can be fastened together by tightening the fastening band 53, while the lid body 8 can be removed from the upper divided sieve frame 7a by releasing the fastening band 53.

<Net equipment>
As shown in Figure 2 (b), a mesh device 40 is incorporated between the upper divided sieve frame 7a and the lower divided sieve frame 7b in the sieve frame body 7. The mesh device 40 is mainly composed of a mesh device frame 42 and a reinforcing mesh 43 that constitute a mesh device body 41, a sieving mesh 44, and a tightening band 45.

As shown in the partially enlarged view of Figure 2(b), the mesh frame 42 has an upper annular plate surface portion 42a, a lower annular plate surface portion 42b, an outer cylindrical portion 42c, and an inner cylindrical portion 42d, and is made by bending a rectangular pipe material with a square cross section into a circular shape. This makes it possible to reduce the weight of the mesh 40 while easily ensuring that it is strong enough to withstand being crushed to the point of being unusable even when clamped between the divided sieve frames 7a and 7b.

When the mesh frame 42 is clamped between the split sieve frames 7a and 7b, the upper annular plate surface portion 42a faces the flange portion 11 of the upper split sieve frame 7a, and the lower annular plate surface portion 42b faces the flange portion 21 of the lower split sieve frame 7b, and these annular plate surface portions 42a and 42b are clamped between the flange portions 11 and 21 of the split sieve frames 7a and 7b via gaskets 13 and 22. In this way, the mesh frame 42 is positioned completely outside the sieve frame bodies 10, 20, and the reinforcing mesh 43 and sieving mesh 44, which actually function to sieve the powder to be classified, are positioned throughout the entire interior of the upper and lower sieve frame bodies 10, 20. This maximizes the effective area of the reinforcing mesh 43 and sieving mesh 44, which function to sieve the powder, allowing for more efficient sieving of the powder to be classified. Furthermore, the gaskets 13, 22 reliably prevent the powder to be classified from leaking between the sieve frames 7a, 7b and the mesh 40.

Figure 4 shows the mesh 40 used in the vibrating sieve machine 1 of one embodiment of the present invention, with (a) being a plan view showing a portion of the sieving screen 44 cut away, (b) being an enlarged view of part C in (a), and (c) being a view seen from the arrow D in (b). As shown in Figure 4(a), the reinforcing mesh 43 is stretched so as to cover the opening of the mesh frame 42, and while stretched across the opening of the mesh frame 42, it is fixed to the upper edge of the inner cylindrical portion 42d by a fixing means such as seam welding. The reinforcing mesh 43 is made of, for example, stainless steel and has a relatively coarse mesh.

The sieving net 44 is placed over the netting device main body 41, covering the reinforcing net 43 and draping over the reinforcing net 43 onto the outer periphery of the netting device frame 42. The sieving net 44 is a sheet-like material made of nylon (stainless steel is also acceptable) with a finer mesh than the reinforcing net 43. The sieving net 44 is tightly bound and secured to the netting device main body 41 by tightening the fastening bands 45 that are wrapped around the outer periphery of the netting device frame 42 (outer cylindrical portion 42c) so as to sandwich the sieving net 44. However, the sieving net 44 is removably attached to the netting device main body 41 so that it can be removed from the netting device main body 41 by loosening the fastening bands 45.

In this way, the reinforcing mesh 43 stretched across the mesh frame 42 functions as a reinforcing material supporting the sieving mesh 44 from below, and the sieving mesh 44, which is detachably attached to the mesh body 41 so as to cover the reinforcing mesh 43, functions as a mesh that substantially contributes to the classification of powder. Therefore, simply replacing the sieving mesh 44 can easily be used to restore the functionality of the mesh device 40.

As shown in Figures 4(b) and (c), the tightening band 45 is composed of a band member 46 and a band diameter adjustment mechanism 47.

The band member 46 is bent into a ring shape so that it can be wrapped around the outer surface of the mesh frame 42 (outer cylindrical portion 42c) and sandwiches the sieving mesh 44 between it and the outer surface of the mesh frame 42. The band member 46 is made of a metal material such as stainless steel.

The band diameter adjustment mechanism 47 is attached to the outer peripheral surface of the band member 46 and includes a housing 48, a spindle 49, and multiple worm grooves 50. Its function is to adjust the band diameter of the band member 46. The housing 48 is attached to one end of the band member 46. The spindle 49 has a shaft that is rotatably supported in the housing 48, and worm teeth (not shown) are formed on the outer periphery of the shaft. The multiple worm grooves 50 are formed on the other end of the band member 46 so as to mesh with the worm teeth of the spindle 49.

As shown in Figures 2(a) and (b), multiple hanging brackets 60 protrude from the outer peripheral surface of the upper divided sieve frame 7a at a predetermined pitch in the circumferential direction. These hanging brackets 60 have a pair of hanging portions 60b on both sides of an inlet 60a that opens radially outward of the upper divided sieve frame 7a.

Swing bolts 61 are installed on the upper surface of the vibration plate 3. They can swing between a prone position in which they are laid face down on the vibration plate 3 side and an upright position in which they are erected so as to span between the vibration plate 3 and the hanging bracket 60. When the swing bolts 61 are in the upright position, the upper and lower divided sieve frames 7a and 7b are fastened together by tightening nuts 62 that thread onto the swing bolts 61 and seat on the hanging bracket 60.

Figure 5 is a block diagram showing the schematic configuration of the motor control system. As shown in Figure 5, the vibrating sieve mill 1 of this embodiment includes a control panel 80 for controlling the two-pole motor 31 of the vibrator 30. The control panel 80 is primarily composed of an inverter device 81 and an operation/setting/display device 82. The inverter device 81 controls the rotation speed of the two-pole motor 31 (three-phase AC induction motor) by freely changing the frequency of the power supply 83. The operation/setting/display device 82 is a touch-panel operation/setting device, for example, an LCD display with a touch screen attached. By pressing display buttons on the display screen, various operations such as starting and stopping operation, setting operating parameters, and displaying operation results can be performed. In this embodiment, the operation/setting/display device 82 includes operation buttons (not shown) for performing the various operations described above, as well as a sieving selection button 85 and a discharge selection button 86 as mode switching means for switching between a sieving mode for sieving powder and a discharge mode for discharging powder.

For example, if the vibrator 30 uses a two-pole motor with a rated rotational speed of 3,375 rpm, the vibration force is set to 90% of the maximum vibration force by centrifugal force adjustment using the adjustment weight 32b, and the frequency (power supply frequency) of the power supply 83 supplied to the two-pole motor 31 is changed to 40 Hz, 45 Hz, 50 Hz, 55 Hz, 60 Hz, 65 Hz, or 70 Hz using the inverter device 81, the vibration frequency of the sieve frame 7, which is proportional to the rotational speed of the two-pole motor 31, and the amplitude of the sieve frame 7, which is inversely proportional to the square of the vibration frequency of the sieve frame 7, can be changed as shown in Table 1. Thus, in this example, the power supply frequency can be considered to be approximately the vibration frequency of the sieve frame 7. In this example, the rotation speed suitable for sieving powder is 2388 to 3888 rpm, which corresponds to the sieving mode, while the rotation speed suitable for discharging powder is 4116 rpm, which corresponds to the discharge mode.

<Classification process>
In the vibrating sieve 1 configured as described above, the classification process in which the powder to be classified is classified by sieving is performed as follows: In the vibrating sieve 1 shown in Fig. 2(a), the powder to be classified is introduced through an inlet 8a provided in the center of the lid 8, aiming at the center of the mesh 40 (see Fig. 2(b)).

Next, if necessary, the inlet 8a is covered with a lid (not shown), and the sieving selection button 85 (see Figure 5) is pressed. This switches to sieving mode, which sieves powder. When switched to sieving mode, the inverter device 81 (see Figure 5) serving as motor control means controls the two-pole motor 31 to rotate at a rotation speed suitable for sieving powder. Here, the rotation speed suitable for sieving powder is preferably 2000 rpm or more and less than 4000 rpm, more preferably 2700 to 3800 rpm, and even more preferably 3000 to 3600 rpm.

If the rotation speed is set between 2000 rpm and 4000 rpm, sufficient time can be ensured for the powder to remain in and around the center of the mesh device 40, where classification efficiency is high, thereby reliably increasing the amount of powder recovered as undersieve. If the rotation speed is less than 2000 rpm, the amplitude of the sieve frame 7 becomes too large, causing the powder to be expelled from the center of the mesh device 40 toward the periphery too strongly, resulting in the powder flowing from the center to the periphery of the mesh device 40 shortly after the powder is dropped, making it impossible to increase the amount of powder recovered as undersieve. On the other hand, if the rotation speed is 4000 rpm or higher, the vertical vibration component acting on the powder is further suppressed, causing the horizontal vibration component to act relatively dominantly on the powder, causing the powder to flow from the center of the mesh device 40 toward the periphery, making it impossible to increase the amount of powder recovered as undersieve.

The amplitude of the sieve frame 7 imparted by the vibrator 30 is preferably 1.7 to 4.0 mm, more preferably 1.9 to 2.8 mm, and even more preferably 2.0 to 2.5 mm.

If the amplitude of the sieve frame 7 is set to 1.7 to 4.0 mm, the powder on the mesh device 40 can be moderately kicked up and then collided with the mesh while suppressing the effect of flicking the powder from the center of the mesh device 40 toward the outer periphery. This ensures sufficient retention time of the powder in and around the center of the mesh device 40, where classification efficiency is excellent, and the powder can be effectively crushed and dispersed. If the amplitude of the sieve frame 7 is less than 1.7 mm, the amount of powder kicked up on the mesh device 40 is insufficient, resulting in reduced classification efficiency. If the amplitude of the sieve frame 7 exceeds 4.0 mm, the effect of flicking the powder from the center of the mesh device 40 toward the outer periphery becomes too strong, shortening the time the powder remains in and around the center of the mesh device 40, and reducing classification efficiency.

The two-pole motor 31 is a motor with the smallest number of poles, and its structure makes it easy to increase the rotation speed. Therefore, by increasing the rotation speed of the two-pole motor 31 and increasing the vibration frequency of the sieve frame 7, which is proportional to the rotation speed of the two-pole motor 31, it is possible to effectively reduce the amplitude of the sieve frame 7, which is inversely proportional to the square of the vibration frequency of the sieve frame 7. Reducing the amplitude of the sieve frame 7 reduces the effect of expelling powder from the center of the mesh device 40 toward the outer periphery.

In sieving mode, the amount of powder that remains in and around the center of the mesh device 40 increases, and the powder is bounced up by the vertical vibration component at and around the center of the mesh device 40 and then collides with the meshes 43 and 44, breaking down and dispersing the agglomerates of powder particles. In this way, sieving is performed with high classification efficiency, ensuring an increase in the amount of powder that falls below the sieve. The powder that passes through the sieving mesh 44 during this classification process (under the sieve) is discharged to the outside from the discharge outlet 27 of the lower divided sieve frame 7b.

To discharge the residual powder (above the sieve) remaining on the sieving mesh 44, press the discharge selection button 86 (see Figure 5). This switches to discharge mode, which discharges the powder. When switched to discharge mode, the inverter device 81 (see Figure 5), which serves as a motor control means, controls the two-pole motor 31 to rotate at a rotation speed suitable for discharging the powder. Here, a rotation speed suitable for discharging the powder is preferably 4000 rpm or higher. At 4000 rpm or higher, the vertical vibration component acting on the powder is further suppressed, allowing the horizontal vibration component to act relatively dominantly on the powder, allowing the powder to flow quickly from the center of the mesh device 40 to the outer periphery, and allowing the residual powder on the sieve to be quickly discharged.

In discharge mode, the residual powder (on the sieve) remaining on the sieving screen 44 flows from the center of the mesh device 40 toward the outer periphery due to the horizontal vibration component, and while flowing clockwise near the outer periphery of the mesh device 40, it is guided by the guide member 70 (see Figure 1(a)) to the discharge outlet 10a, from which it is discharged to the outside via the discharge duct 14. In this way, the residual powder on the sieve can be quickly discharged, allowing for a smooth transition to the next sieving operation and improving productivity.

Specific examples of the vibrating sieve machine 1 of the present invention are described below. However, the present invention is not limited to the following examples.

(Examples 1 to 3)
In the vibrator 30, a two-pole motor 31 having a rated rotation speed of 3375 rpm was used, and the vibration force was set to 90% of the maximum vibration force by centrifugal force adjustment using the adjustment weight 32b. The frequency (power supply frequency) of the power supply 83 supplied to the two-pole motor 31 was changed by the inverter device 81 to 50 Hz, 55 Hz, and 60 Hz to sieve the powder.

(Comparative Examples 1 to 3)
In the vibrator, a four-pole motor with a rated rotation speed of 1700 rpm was used, and the vibration force was set to 80% of the maximum vibration force by adjusting the centrifugal force with an adjustment weight. The frequency of the power supply (power supply frequency) supplied to the four-pole motor was changed to 50 Hz, 55 Hz, and 60 Hz by an inverter device, and the powder was sieved.

Table 2 shows the measured amplitude and frequency of the sieve frame 7, as well as the time required for sieving and discharging the powder in Examples 1 to 3 and Comparative Examples 1 to 3. The required times in Table 2 are the times required for the series of processes of sieving and discharging the powder in Examples 1 to 3 and Comparative Examples 1 to 3 when the motor rotation speed is maintained constant at the speed shown in Table 2. In Examples 1 to 3, sieving is performed for a predetermined time in sieving mode (motor rotation speed: 2994 rpm, 3294 rpm, 3588 rpm) to sufficiently recover the powder that falls below the sieve, and then the mode is switched to discharge mode (motor rotation speed: 4116 rpm) to quickly discharge the powder remaining on the sieve. This increases the amount of powder that falls below the sieve and shortens the time required for the series of processes of sieving and discharging the powder.

Figures 6, 7, and 8 show the sieving operations of Examples 1, 2, and 3, respectively, where (a) is a diagram of the initial sieving state, (b) is a diagram of the middle sieving state, and (c) is a diagram of the final sieving state.

In Examples 1 to 3, as shown in Figures 6(a), 7(a), and 8(a), the powder to be classified (indicated by the symbol "K" in the figures) is introduced toward the center of the mesh device 40. It bounces up in small increments and then collides with the mesh, causing the agglomerated powder to be broken down and dispersed, separating it into over-sieve and under-sieve particles. In the middle stage of sieving, as shown in Figures 6(b), 7(b), and 8(b), most of the over-sieve powder remains in or near the center of the mesh device 40, with a portion spreading toward the periphery of the mesh device 40. In this state, it bounces up in small increments and is further separated into over-sieve and under-sieve particles. In Examples 1 and 2, as shown in Figures 6(c) and 7(c), even at the end of sieving, most of the powder on the sieve remains in and around the center of the mesh device 40, and is then bounced up in small increments to be further separated into over-sieve and under-sieve particles. In Example 3, as shown in Figure 8(c), at the end of sieving, less powder remains in the center of the mesh device 40, but the powder on the sieve remains near the center of the mesh device 40, and is then bounced up in small increments to be further separated into over-sieve and under-sieve particles. In all of Examples 1 to 3, the residual powder remaining on the mesh device 40 ultimately flows from the center of the mesh device 40 to the outer periphery due to the horizontal vibration component of the vibrator 30, and while flowing clockwise near the outer periphery of the mesh device 40, it is guided by the guiding action of the guide member 70 to the discharge port 10a, and is then discharged from the discharge port 10a to the outside via the discharge duct 14 (see Figure 1(a)).

In Examples 1 to 3, most of the sieving operation was performed using the center of the mesh device 40 or its vicinity, and the sieving operation was performed for a relatively long time (571 seconds, 350 seconds, 172 seconds), so a sufficient amount of powder was recovered as undersieve material.

Figures 9, 10, and 11 show the sieving operations for Comparative Examples 1, 2, and 3, respectively, where (a) is a diagram of the initial sieving state, (b) is a diagram of the middle sieving state, and (c) is a diagram of the final sieving state.

In Comparative Examples 1 to 3, as shown in Figures 9(a), 10(a), and 11(a), the powder to be classified (indicated by the symbol "K" in the figures) is introduced toward the center of the mesh device 40, bounces up violently, and then collides with the mesh, causing the agglomerated powder to break down and disperse, separating it into oversized and undersized particles. Even if the powder to be classified is introduced into the center of the mesh device 40, the large amplitude of the sieve frame 7 has an excessive effect, i.e., the effect of ejecting the powder from the center of the mesh device 40 toward the outer periphery becomes too strong, and as the sieving process transitions from the initial to intermediate stages, most of the powder on the sieve flows from the center of the mesh device 40 toward the outer periphery, as shown in Figures 9(b), 10(b), and 11(b). The powder on the sieve is kicked up near the outer periphery of the mesh device 40, but soon after, as shown in Figures 9(c), 10(c), and 11(c), it flows clockwise near the outer periphery of the mesh device 40 and is guided by the guiding action of the guide member 70 to the discharge port 10a, from which it is discharged to the outside via the discharge duct 14 (see Figure 1(a)).

In Comparative Examples 1 to 3, sieving operations using the central portion of the mesh device 40 and its vicinity were hardly performed, and sieving operations were mainly performed using the portion of the mesh device 40 closer to the periphery. Furthermore, the sieving operations were performed for a relatively short period of time (95 seconds, 103 seconds, 145 seconds), so it was not possible to recover a sufficient amount of powder that would pass through the sieve.

The vibrating sieve of the present invention can be suitably used for classifying various powders, such as pharmaceuticals, food products, minerals, metals, and resin raw materials.

REFERENCE SIGNS LIST 1 vibrating sieve machine 7 sieve frame 30 vibrator 31 two-pole motor 32 eccentric weight 32a fixed weight 32b adjusting weight 40 meshing tool 81 inverter device (motor control means)
85 Screening selection button (mode switching means)
86 Discharge selection button (mode switching means)

Claims (5)

A vibrating sieve machine that sieves powder to be classified that is dropped onto a sieve frame in a state where a sieve device is incorporated, by vibrating the sieve frame,
vibrators are provided on both sides of the sieve frame so as to be able to impart vibrations to the powder,
The vibrator has a two-pole motor and an eccentric weight , thereby suppressing the action of expelling the powder from the center of the mesh device toward the outer periphery . a mode switching means for switching between a sieving mode for sieving the powder and a discharge mode for discharging the powder;
a motor control means for controlling the two-pole motor;
Furthermore,
When the sieving mode is selected, the motor control means controls the two-pole motor to rotate at a rotation speed suitable for sieving the powder.
2. The vibrating sieve according to claim 1, wherein when switched to the discharge mode, the two-pole motor is controlled so as to rotate at a rotation speed suitable for discharging the powder. The rotation speed suitable for sieving the powder is 2000 rpm or more and less than 4000 rpm,
3. The vibrating sieve according to claim 2, wherein the rotational speed suitable for discharging the powder is 4000 rpm or more. A vibrating sieve machine according to any one of claims 1 to 3, wherein the vibrator applies vibrations to the sieve frame so that the amplitude of the vibrations is 1.7 to 4.0 mm. A vibrating sieve machine according to any one of claims 1 to 4, wherein the eccentric weight includes a fixed weight and an adjustable weight whose position relative to the fixed weight is adjustable.