Vibrating screen machine

Abstract

To provide a vibration sieve machine capable of easily increasing an undersize powder recovery amount.SOLUTION: In a vibration sieve machine 1, classification object powder dropped on a net tool 40 is sieved by vibrating a sieve frame body 7 with the net tool 40 incorporated therein. The vibration sieve machine comprises a vibrator 30 that is arranged on both sides of the sieve frame body 7 so as to be able to apply vibration to the powder. The vibrator 30 includes a double pole motor 31 and an eccentric weight 32.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vibrating sieve machine that vibrates a sieve frame with a mesh element installed therein to sieve powder to be classified that has been dropped onto the mesh element. [Background technology]

[0002] One known example of this type of vibrating sieve is a direct-type vibrating sieve in which vibrators (vibration motors) are disposed on both sides of the sieve frame (see, for example, Patent Document 1). This direct-type vibrating sieve is configured to perform sieving by applying vibrations to the powder on the mesh via the sieve frame through the operation of the vibrator, and has the advantage of being able to keep the height of the machine low.

[0003] Here, sieving refers to the operation 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).

[0004] In the vibrating sieve machine of Patent Document 1, the vibrator is configured to include 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, thereby crushing and dispersing the agglomerated powder, thereby increasing the amount of powder that can be recovered as undersieve material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 082644 Summary of the Invention [Problem to be solved by the invention]

[0006] In the vibrating sieve machine of Patent Document 1, the mesh device vibrates together with the sieve frame. Due to the structure of the mesh device, the amplitude of the mesh device is relatively larger in the central portion than in the portions near the periphery. Therefore, the classification efficiency is generally low in the portions near the periphery of the mesh device, but increases toward the central portion. Therefore, in order to increase the amount of powder recovered that falls through the sieve, it is important to sieve the powder using the central portion of the mesh device and its vicinity.

[0007] However, even if the powder to be classified is dropped into the center of the mesh device, depending on the conditions of the object to be classified, such as the particle size, density, and cohesive force of the powder, the magnitude of the amplitude of the sieve frame may have an excessive effect, i.e., 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, and the amount of powder recovered under the sieve may not be increased as desired.

[0008] Therefore, by increasing the rotation speed of the four-pole motor, the vibration frequency of the sieve frame body, which is proportional to the motor rotation speed, can be increased, thereby effectively reducing the amplitude of the sieve frame body, which is inversely proportional to the square of the vibration frequency of the sieve frame body.If the amplitude of the sieve frame body is reduced, the action of expelling powder from the center of the net device toward the outer periphery can be suppressed, so the amount of powder that remains in the center of the net device and its vicinity for a long time can be increased, and it is thought that this can increase the amount of powder recovered.

[0009] However, since the motor rotation speed is inversely proportional to the number of poles, it is structurally difficult to increase the rotation speed of a four-pole motor, which has a relatively large number of poles. Therefore, the vibrating sieve machine of Patent Document 1 cannot increase the amount of powder that falls through the sieve as desired.

[0010] The present invention has been made in view of the above-mentioned problems, and has an object to provide a vibrating sieve machine that can easily increase the amount of powder that falls under the sieve and is recovered. [Means for solving the problem]

[0011] 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.

[0012] In this vibrating sieve machine, a vibrator having a two-pole motor and an eccentric weight is activated to vibrate the powder on the mesh element through the mesh element from both sides of the mesh element. A two-pole motor has the smallest number of poles, making it structurally easy to increase its rotation speed. Therefore, by increasing the rotation speed of the two-pole motor and increasing the vibration frequency of the mesh element, which is proportional to the rotation speed of the two-pole motor, the amplitude of the vibration of the mesh element, which is inversely proportional to the square of the vibration frequency of the mesh element, can be effectively reduced. Reducing the amplitude of the vibration of the mesh element suppresses the tendency for powder to be ejected from the center of the mesh element toward the outer periphery, thereby increasing the amount of powder remaining in and around the center of the mesh element. This makes it easy to increase the amount of powder recovered that falls below the mesh element.

[0013] 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.

[0014] According to the vibrating sieve machine of this configuration, when switched to sieving mode, the two-pole motor is controlled by the motor control means so as to rotate at a rotation speed suitable for sieving the powder. This allows for sieving with high classification efficiency and ensures an increase in the amount of powder recovered below the sieve. When switched to discharging mode, the two-pole motor is controlled by the motor control means so as 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.

[0015] 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.

[0016] With the vibrating sieve machine of this configuration, the rotation speed suitable for sieving powder is set to between 2000 rpm and 4000 rpm, and within this rotation speed range, the powder can be retained for a sufficient amount of time in the center of the mesh device, where classification efficiency is high, and the amount of powder that can be recovered as undersieve can be reliably increased. On the other hand, the rotation speed suitable for discharging powder is set to 4000 rpm or higher, and at 4000 rpm or higher, the vertical vibration component acting on the powder is further suppressed, and the horizontal vibration component acts relatively dominantly on the powder, allowing the powder to quickly flow from the center of the mesh device to the outer periphery, and the remaining powder on the sieve can be quickly discharged.

[0017] In the vibrating sieve machine according to the present invention, The vibrator preferably applies vibration to the sieve frame with an amplitude of 1.7 to 4.0 mm.

[0018] 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, so that the powder on the mesh device can be moderately bounced up and then collided with the mesh while suppressing the action of flicking the powder from the center of the mesh device to the outer periphery, thereby ensuring sufficient retention time of the powder in and around the center of the mesh device, where classification efficiency is excellent, and effectively crushing and dispersing the powder.

[0019] 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.

[0020] According to the vibrating sieve machine of this configuration, the centrifugal force can be adjusted by adjusting the relative position of the adjustment weight with respect to the fixed weight, which allows for precise centrifugal force setting and allows for optimal vibration conditions to be obtained. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 shows a vibrating sieve according to one embodiment of the present invention, where (a) is a plan view and (b) is a front view. [Figure 2] FIG. 2 shows a vibrating sieve according to one embodiment of the present invention, where (a) is a view taken along the arrow A in FIG. 1(b) and (b) is an enlarged cross-sectional view taken along the line BB in FIG. 1(b). [Figure 3] FIG. 3 is a front view of the eccentric weight of the vibrator as seen from the axial direction of the two-pole motor. [Figure 4] 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). [Figure 5] FIG. 5 is a block diagram showing a schematic configuration of a motor control system. [Figure 6] FIG. 6 shows the state of 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. [Figure 7]FIG. 7 shows the state of the sieving operation according to the second 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. [Figure 8] FIG. 8 shows the state of the sieving operation according to the third 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. [Figure 9] FIG. 9 shows the state of 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. [Figure 10] FIG. 10 shows the state of 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. [Figure 11] FIG. 11 shows the state of 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. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be described below 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.

[0023] <Outline of the vibrating sieve machine> Fig. 1 shows 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. 1(a) and 1(b), the vibrating sieve 1 is a direct-type that allows the height of the machine to be kept 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 is equipped with a vibrating plate 3 disposed above a stand 2.

[0024] The vibration plate 3 is made of a plate-like member of a required thickness and octagonal ring shape in plan view, with a mounting hole in the center for mounting a sieve container 6 (described later). A plurality of (12 in this example) compression coil springs (elastic supports) 4 are installed in a predetermined arrangement along the circumferential direction of the vibration plate 3 between the vibration plate 3 and the stand 2, and these compression coil springs 4 support the vibration plate 3 so that it can vibrate freely.

[0025] 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-shaped plate material to fit the shape of the outer periphery of the vibrating plate 3, and is fixed to the vibrating plate 3 so as to protrude vertically downward from the lower plate surface of the vibrating plate 3 around substantially the entire periphery. This makes it possible to improve the rigidity of the vibrating plate 3 while suppressing an increase in the weight of the vibrating plate 3. Therefore, even if a high-output vibrator 30 (described later) is employed, it is possible to prevent the vibrating plate 3 from bending or twisting, which makes it possible to employ a high-output vibrator 30 and improve classification performance.

[0026] A sieve container 6 is attached to the mounting holes of the vibration plate 3. The sieve container 6 is mainly composed of a sieve frame 7 with openings at the top and bottom, through which powder to be classified is introduced, and a lid 8 that is detachably 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.

[0027] <Sieve frame> Fig. 2 shows a vibrating sieve machine 1 according to one embodiment of the present invention, where (a) is a view taken along the arrow A in Fig. 1(b) and (b) is an enlarged cross section taken along the line BB in Fig. 1(b). As shown in Fig. 2(a) and (b), the sieve frame body 7 is composed of an upper divided sieve frame 7a and a lower divided sieve frame 7b which can be separated into upper and lower parts.

[0028] 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 projects radially outward over the entire circumferential area from the lower end of the upper divided sieve frame body 10, and a tapered flange portion 12 that projects outward and inclines upward over the entire circumferential area from the upper end of the upper divided sieve frame body 10. An annular gasket 13 is attached to the flange portion 11 of the upper divided sieve frame 7a over the entire periphery.

[0029] As shown in Figure 2(a), a discharge duct 14 is attached to one side (the left side in Figure 2(a)) of the upper divided sieve frame 7a in the front-to-rear direction 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 the residual powder (residual powder on the sieve) remaining on the mesh 40 (described later) during the classification process.

[0030] 1(a) and 1(b), the upper divided sieve frame 7a (upper divided sieve frame main body 10) is provided with a discharge port 10a corresponding to the discharge duct 14. Furthermore, inside the upper divided sieve frame main body 10, a guide member 70 is provided in the vicinity of the outer periphery of the later-described mesh member 40 to guide the powder to be classified, which flows clockwise on the mesh member 40, to the discharge port 10a during the classification process operation described below.

[0031] 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 projects radially outward over the entire circumferential area from the upper end of the lower divided sieve frame main body 20 to correspond to the flange portion 11 of the upper divided sieve frame 7a. An annular gasket 22 is attached to the flange portion 21 of the lower divided sieve frame 7b over the entire periphery.

[0032] The lower divided sieve frame body 20 has a cylindrical portion 25 which is open at the top and bottom, and as shown in FIG. 2(a), a funnel-shaped chute portion 26 tapering downward is integrally connected to the lower side of this cylindrical portion 25, and a discharge opening portion 27 which drops and discharges the powder in the chute portion 26 downward is also integrally connected to the lower side of this chute portion 26.

[0033] <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.

[0034] As shown in FIG. 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, and is configured to generate vibrations by rotating the eccentric weights 32 when the two-pole motor 31 is operated.

[0035] In the 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°, and in this example, the left and right vibrators 30 are arranged at an angle of θ = 60°. Regarding the left and right vibrators 30, the one vibrator 30 and the other vibrator 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 arranged symmetrically with respect to the vertical axis on the vertical plane that passes through the intersection of these axes S. In this way, it is possible to secure the necessary horizontal vibration component while maximizing the vertical vibration component, and the powder on the screen device 40 (described later) is thrown up by the vibration wave and hits the screens 43 and 44 (described later), thereby breaking down and dispersing the agglomerates of powder particles, thereby further improving the classification ability.

[0036] Fig. 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 Fig. 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 as viewed from the axial direction of the rotating shaft 31a, and have an insertion hole 33 formed in a central corner portion 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 adjusting weight 32b, a bolt 36 is screwed in a direction intersecting the extending direction of the slit 35 so as to be tightened. In both the fixed weight 32a and the adjustable weight 32b, by tightening the bolt 36, the insertion hole 33 is reduced 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.

[0037] 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 a 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 continuously adjusted, allowing for precise centrifugal force settings and achieving an 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.

[0038] As shown in Figure 2(b), a lid gasket 51 that seals the gap between the outer peripheral edge of the lid body 8 and the tapered flange portion 12 of the upper divided sieve frame 7a is inserted and supported by a ring plate 52. A fastening band 53 with a V-shaped cross section that can sandwich the outer peripheral edge of the lid body 8 and the tapered flange portion 12 of the upper divided sieve frame 7a is wrapped around the butt joint between the lid body 8 and the upper divided sieve frame 7a, and the lid body 8 and the upper divided sieve frame 7a can be fastened together by fastening with this fastening band 53, while the lid body 8 can be removed from the upper divided sieve frame 7a by releasing the fastening of this fastening band 53.

[0039] <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.

[0040] 2(b), the meshing device 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 formed by bending a rectangular pipe material having a square annular cross section into a circular shape. In this way, the meshing device 40 can be made lighter while easily ensuring strength so that it will not be crushed to the point of being unusable even when clamped between the divided sieve frames 7a, 7b.

[0041] When the mesh frame 42 is clamped between the split sieve frames 7a, 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, 42b are clamped between the flange portions 11, 21 of the split sieve frames 7a, 7b via gaskets 13, 22. In this way, the mesh frame 42 is disposed completely outside the divided sieve frame bodies 10, 20, and the reinforcing mesh 43 and the sieving mesh 44, which essentially function to sieve the powder to be classified, are disposed throughout the entire frame of the upper and lower divided sieve frame bodies 10, 20. This maximizes the effective area of ​​the reinforcing mesh 43 and the sieving mesh 44, which function to sieve the powder, and enables more efficient sieving of the powder to be classified. In addition, the gaskets 13, 22 can reliably prevent the powder to be classified from leaking between the divided sieve frames 7a, 7b and the mesh fixture 40.

[0042] 4 shows a mesh device 40 used in a vibrating sieve machine 1 according to one embodiment of the present invention, with (a) being a plan view showing a portion of a 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 Fig. 4(a), the reinforcing mesh 43 is stretched so as to cover the opening of the mesh device frame 42, and is fixed to the upper edge of the inner cylindrical portion 42d by a fixing means such as seam welding while stretched across the opening of the mesh device frame 42. The reinforcing mesh 43 is made of, for example, stainless steel and has a relatively coarse mesh.

[0043] The sieving net 44 is placed over the netting device main body 41 so as to cover the reinforcing net 43 and hang from above the reinforcing net 43 onto the outer circumferential surface of the netting device frame 42. The sieving net 44 is made of a sheet-like material, such as nylon (stainless steel is also acceptable) with a finer mesh than the reinforcing net 43. The sieving net 44 is tightly bound and fixed to the netting device main body 41 by tightening fastening bands 45 that are wrapped around the outer circumferential surface of the netting device frame 42 (outer cylindrical portion 42c) so as to sandwich the sieving net 44, while the sieving net 44 is detachably 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.

[0044] 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 process of the powder, so that simply by replacing the sieving mesh 44, mesh replacement can be easily performed to restore the functionality of the mesh 40.

[0045] As shown in FIGS. 4(b) and 4(c), the tightening band 45 is made up of a band member 46 and a band diameter adjustment mechanism 47.

[0046] The band member 46 is bent into a ring shape so that it can be wrapped around the outer peripheral surface of the mesh frame 42 (outer cylindrical portion 42c) so as to sandwich the sieving mesh 44 between itself and the outer peripheral surface of the mesh frame 42, and is made of a metal material such as stainless steel.

[0047] 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 a plurality of worm grooves 50, and has the function of adjusting the size of the band diameter of the band member 46. Here, the housing 48 is attached to one end of the band member 46. The spindle 49 has a shaft portion that is rotatably supported in the housing 48, and worm teeth (not shown) disposed inside the housing 48 are formed on the outer periphery of the shaft portion. The plurality of 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.

[0048] 2(a) and 2(b), a plurality of hanging brackets 60 are provided at a predetermined pitch in the circumferential direction on the outer peripheral surface of the upper divided sieve frame 7a. The hanging brackets 60 each have a pair of hanging portions 60b on either side of a receiving opening 60a that opens radially outward of the upper divided sieve frame 7a.

[0049] On the upper surface of the vibration plate 3, swing bolts 61 are installed which can swing freely between a lying position where the swing bolts 61 are laid on the vibration plate 3 side and an upright position where the swing bolts 61 are erected so as to span between the vibration plate 3 and the hanging bracket 60. The upper and lower divided sieve frames 7a and 7b are fastened together by tightening nuts 62 which are threaded onto the swing bolts 61 in the upright position and seated on the hanging bracket 60.

[0050] FIG. 5 is a block diagram showing a schematic configuration of a motor control system. As shown in FIG. 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 (a three-phase AC induction motor) by freely changing the frequency of a power supply 83 for the two-pole motor 31. The operation / setting / display device 82 is a touch-panel operation / setting device, for example, a liquid crystal display device 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, in addition to operation buttons (not shown) for performing the various operations, 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.

[0051] For example, in the vibrator 30, a two-pole motor with a rated rotational speed of 3375 rpm is used, 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 by the inverter device 81 to 40 Hz, 45 Hz, 50 Hz, 55 Hz, 60 Hz, 65 Hz, and 70 Hz. In this case, 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.

[0052] [Table 1]

[0053] <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)).

[0054] Next, if necessary, the inlet 8a is covered with a lid (not shown), and then the sieving selection button 85 (see FIG. 5) is pressed. This switches to a sieving mode in which powder is sieved. When switched to the sieving mode, the inverter device 81 (see FIG. 5) serving as a motor control means controls the two-pole motor 31 so that it rotates 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.

[0055] If the rotation speed is set in the range of 2000 rpm or more but less than 4000 rpm, the powder can be retained for a sufficient time in and around the center of the mesh device 40, where classification efficiency is high, and the amount of powder recovered as undersieve can be reliably increased. If the rotation speed is less than 2000 rpm, the amplitude of the sieve frame 7 becomes too large, and the action of expelling the powder from the center of the mesh device 40 to the outer periphery becomes too strong, causing the powder to flow from the center to the outer 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 more, the vertical vibration component acting on the powder is further suppressed, and the horizontal vibration component acts relatively dominantly on the powder, causing the powder to flow from the center to the outer periphery of the mesh device 40, making it impossible to increase the amount of powder recovered as undersieve.

[0056] The amplitude of the vibration 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.

[0057] 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 bounced 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, thereby ensuring sufficient retention time of the powder in and around the center of the mesh device 40, where classification efficiency is excellent, and effectively crushing and dispersing the powder. If the amplitude of the sieve frame 7 is less than 1.7 mm, the amount of powder bounced 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.

[0058] The two-pole motor 31 is a motor with the smallest number of poles, and structurally, it is 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. If the amplitude of the sieve frame 7 is reduced, the action of the sieve frame 7 to expel powder from the center of the mesh device 40 toward the outer periphery is suppressed.

[0059] In the sieving mode, the amount of powder remaining 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, 44, thereby breaking down and dispersing the agglomerates of powder particles. In this way, sieving is performed with high classification efficiency, and the amount of powder that falls under the sieve can be reliably increased. 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.

[0060] When discharging the residual powder (above the sieve) remaining on the sieving mesh 44, the discharge selection button 86 (see FIG. 5) is pressed. This switches to a discharge mode for discharging the powder. When switched to the discharge mode, the inverter device 81 (see FIG. 5) serving as a motor control means controls the two-pole motor 31 to rotate at a rotation speed suitable for discharging the powder. Here, the rotation speed suitable for discharging the powder is preferably 4000 rpm or higher. If the rotation speed is 4000 rpm or higher, the vertical vibration component acting on the powder is further suppressed, and the horizontal vibration component acts relatively dominantly on the powder. This allows the powder to flow quickly from the center of the mesh device 40 to the outer periphery, allowing the residual powder on the sieve to be quickly discharged.

[0061] In the discharge mode, the residual powder (on the sieve) remaining on the sieving screen 44 flows from the center of the mesh device 40 to 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 guiding action of the guide member 70 (see FIG. 1(a)) to the discharge port 10a, and is discharged from the discharge port 10a 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. [Example]

[0062] Specific examples of the vibrating sieve machine 1 of the present invention will be described below, but the present invention is not limited to the following examples.

[0063] (Examples 1 to 3) In the vibrator 30, a two-pole motor 31 with a rated rotation speed of 3375 rpm was used, and the vibration force was set to 90% of the maximum vibration force by adjusting the centrifugal force using the adjustment weight 32b. The frequency (power supply frequency) of the power supply 83 supplied to the two-pole motor 31 was changed to 50 Hz, 55 Hz, and 60 Hz using the inverter device 81 to sift the powder.

[0064] (Comparative Examples 1 to 3) The vibrator used a four-pole motor with a rated rotation speed of 1700 rpm, 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 frequency) supplied to the four-pole motor was changed to 50 Hz, 55 Hz, and 60 Hz using an inverter device to sift the powder.

[0065] 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 shown in Table 2 are the times required for a series of processes, including sieving and discharging the powder, in Examples 1 to 3 and Comparative Examples 1 to 3, when the motor rotation speed is kept constant at the rotation speed shown in Table 2. In Examples 1 to 3, sieving is performed for a predetermined time in the 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 the discharge mode (motor rotation speed: 4116 rpm) to quickly discharge the powder remaining on the sieve. This allows the amount of powder that falls below the sieve to be recovered to be increased, while shortening the time required for a series of processes, including sieving and discharging the powder.

[0066] [Table 2]

[0067] 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 stage, (b) is a diagram of the middle sieving stage, and (c) is a diagram of the final sieving stage.

[0068] 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, bounces up in small increments, and then collides with the mesh, whereby the agglomerated powder is crushed and dispersed, and separated into over-sieve and under-sieve powder. 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 outer periphery of the mesh device 40, and in this state it bounces up in small increments and is further separated into over-sieve and under-sieve powder. 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 bounced up in small increments in this state, and is further separated into over-sieved and under-sieved 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 bounced up in small increments in this state, and is further separated into over-sieved and under-sieved particles. In any of Examples 1 to 3, the residual powder remaining on the net device 40 ultimately flows from the center of the net 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 net device 40, is guided to the discharge outlet 10a by the guiding action of the guide member 70, and is discharged from the discharge outlet 10a to the outside via the discharge duct 14 (see Figure 1(a)).

[0069] In Examples 1 to 3, most of the sieving operation was performed using the center of the mesh device 40 and its vicinity, and the sieving operation was performed for a relatively long time (571 [sec], 350 [sec], 172 [sec]), so a sufficient amount of powder could be recovered as under-sieve.

[0070] Figures 9, 10, and 11 show the sieving operations for Comparative Example 1, Comparative Example 2, and Comparative Example 3, respectively, where (a) is a diagram of the initial sieving stage, (b) is a diagram of the middle sieving stage, and (c) is a diagram of the final sieving stage.

[0071] 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 charged toward the center of the mesh device 40, bounces up violently, and then collides with the mesh, whereby the agglomerated powder is broken down and dispersed, and separated into oversized and undersized powder. Even if the powder to be classified is dropped into the center of the mesh device 40, the effect of the amplitude of the sieve frame 7 is excessive, 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 moves from the initial stage to the middle stage, most of the powder on the oversized powder 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 outlet 10a, and is discharged from the discharge outlet 10a to the outside via the discharge duct 14 (see Figure 1(a)).

[0072] In Comparative Examples 1 to 3, sieving operations were hardly performed using the central part of the net device 40 or its vicinity, and sieving operations were mainly performed using the parts of the net device 40 closer to the periphery.Furthermore, the time for which the sieving operations were performed was relatively short (95 [sec], 103 [sec], 145 [sec]), so a sufficient amount of powder could not be recovered as under-sieve material. [Industrial Applicability]

[0073] 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. [Explanation of symbols]

[0074] 1 Vibrating sieve machine 7 Sieve frame 30 Vibrator 31 Two-pole motor 32 Eccentric weight 32a fixed weight 32b Adjustment Weight 40 Netting 81 Inverter device (motor control means) 85 Screening selection button (mode switching means) 86 Discharge selection button (mode switching means)

Claims

1. 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.

2. 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.

3. 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.

4. 4. The vibrating sieve machine according to claim 1, wherein the vibrator applies vibration to the sieve frame so that the amplitude of the vibration is 1.7 to 4.0 mm.

5. 5. The vibrating sieve machine according to claim 1, wherein the eccentric weight includes a fixed weight and an adjustable weight whose position relative to the fixed weight is adjustable.

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