Powder feeding device

Abstract

The present invention provides a powder supply device that reduces variations in the amount of powder supplied, stabilizes quantification, and shortens the powder supply time. [Solution] A powder supply device comprising a stirring means 3 having a screw section 4 with large and small diameters arranged in parallel, and a blade section whose lower end is at a height near the upper end of the blades of the screw section, and a measuring means capable of determining the amount of powder being stored and supplied by the difference in the measured amount, wherein the upper end height of the blades 7a of the large diameter screw 7 and the upper end height of the blades 8a of the small diameter screw 8 that constitute the screw section are at the same height, and a small gap 11 is provided in the vertical direction between the upper ends of the two blades and the lower ends of the blades of the stirring means, and a predetermined amount of powder to be supplied in advance and the amount of remaining powder to be discharged from the input of measuring information to the measuring means, and controls the start, stop and speed of operation of the large diameter screw and the small diameter screw according to the amount.

Description

Technical Field

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[0003]

[0001] The present invention relates to a powder supply device that can stably supply a predetermined amount of powder quickly and in a short time without causing a powder bridging phenomenon.

Background Art

[0002] Patent Document 1 discloses a powder supply device including a hopper into which powder or granules are charged, a discharge section that discharges the powder or granules by means of a screw, a chute that guides the powder or granules descending from the hopper to the discharge section, and a stirring section in which a stirring member rotates within the chute. The chute is provided with an inclined surface that is inclined with its inner surface facing obliquely upward. The stirring member is arranged to rotate about an axial center portion that protrudes in a state inclined obliquely upward from the inclined surface of the chute. The chute is provided with a connection opening that follows the discharge section along the tangential direction of rotation of the stirring member passing through the bottom of the chute, and the screw that discharges the powder or granules at the discharge section is arranged to extend along the connection opening.

[0003] Patent Document 2 discloses a powder bridging prevention device that is arranged in a powder conveyance path surrounded by a casing and prevents bridging occurring in a powder raw material that passes through the powder conveyance path and is supplied from a path outlet. The device includes a core disposed in a direction intersecting the conveyance direction of the powder raw material in the powder conveyance path, a rotating member that is rotationally driven around the core, and a rotational drive device that rotationally drives the core and the rotating member. The core is arranged to substantially cover the path outlet in the conveyance direction of the powder conveyance path.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

[0005] The invention described in Patent Document 1 is a structure in which powder or granular material is discharged using two screws of the same diameter, and in a chute where the inner diameter of the hopper narrows downwards, the formation of bridging of the powder or granular material can be suppressed by a stirring member, Increasing the diameters of the two screws significantly shortens the supply time for the powder, but increases the variability in the amount of powder supplied, making quantification difficult. On the other hand, decreasing the diameters of the two screws reduces the variability in the amount of powder supplied, making quantification possible, but increases the supply time. Furthermore, since it appears that one screw motor is rotating both screws, there is a problem of large variation in the amount discharged relative to the predetermined amount.

[0006] The invention described in Patent Document 2 is a technology for supplying powder with a single screw without generating bridges. However, while increasing the screw diameter shortens the supply time, it increases the variation in the amount of powder supplied, making quantification difficult. On the other hand, decreasing the screw diameter reduces the variation in the amount of powder supplied, making quantification possible, but it results in a longer powder supply time.

[0007] This invention was conceived in view of these problems, and aims to provide a powder supply device that can discharge a predetermined amount of powder stably while minimizing variations in the amount of powder supplied, without causing bridging of the powder, and can also shorten the powder discharge time. [Means for solving the problem]

[0008] The powder supply device according to claim 1 comprises a hopper for storing powder, a screw section disposed below the hopper and having a parallel arrangement of large and small diameter screws for horizontally supplying the powder by rotation, a stirring means installed above the screw section and having a screw-immediate blade section whose lower end is at a height near the upper end of the tip trajectory circle formed by the tip of the blades of the screw section when it rotates, a weighing means for continuously weighing the total weight of the component containing the discharged powder downstream from the discharge port of the screw section, or the total weight of the component containing the powder upstream from the discharge port of the screw section, and a control unit, wherein the screw section comprises a large diameter screw The clew and the small-diameter screw are arranged such that the upper end height of the tip trajectory circle formed by the tip of the blade of the large-diameter screw during rotation is the same as the upper end height of the tip trajectory circle formed by the tip of the blade of the small-diameter screw during rotation, and a small vertical gap is provided between the upper end height of the blade and the lower end height of the blade portion of the stirring means immediately adjacent to the screw. The control unit calculates the amount of powder to be discharged based on a predetermined supply amount of the powder and the input of metering information from the metering means, and controls the start / stop operation and rotation speed of the large-diameter screw and the small-diameter screw independently according to the amount of powder to be discharged.

[0009] The powder supply device according to claim 2 is characterized in that, in claim 1, the control unit operates the large-diameter screw and the small-diameter screw at a predetermined rotational speed when the remaining amount to be discharged is large, stops only the large-diameter screw at a predetermined timing when the remaining amount to be discharged exceeds half of the predetermined supply amount set in advance, and further reduces the rotational speed of the small-diameter screw at a predetermined timing when the remaining amount to be discharged approaches the predetermined supply amount set in advance, thereby controlling the rotational speed in stages according to the remaining amount to be discharged.

[0010] The powder supply device according to claim 3 is characterized in that, in claim 1 or 2, the hopper comprises a cylindrical portion and a substantially inverted frustoconical portion connected to the lower end of the cylindrical portion, and the stirring means comprises an inclined blade portion that can rotate along the inner circumferential surface of the substantially inverted frustoconical portion, a cylindrical portion with external teeth whose upper end is connected to the lower end of the inclined blade portion and connected to a rotational driving means, and a substantially vertical screw-immediate blade portion whose upper end is connected to the lower end of the cylindrical portion with external teeth and whose lower end is at a height near the upper end of the tip trajectory circle formed by the tip of the blade of the screw portion when it rotates. [Effects of the Invention]

[0011] The powder supply device described in claims 1 to 3 has the effect of reducing variations in the amount of powder supplied, enabling quantitative and stable supply, and shortening the powder supply time. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view illustrating the powder supply device of the present invention. [Figure 2] This is a front view explanatory diagram showing a transparent section illustrating the interior of the vertical cross-section at approximately the center in the front-to-back direction of the powder supply device (part of the hopper, related to the stirring means) of the present invention. [Figure 3] This is a front view explanatory diagram of the longitudinal cross-section of the stirring mechanism. [Figure 4] This is a perspective view illustrating the stirring mechanism. [Figure 5] This is a plan view diagram illustrating the horizontal cross-section of two screws of different diameters in the screw section. [Figure 6] This is a schematic diagram showing the inside of the powder supply device of the present invention, viewed from the right side. [Figure 7] This is an explanatory diagram showing the right side view of the longitudinal cross-section of two screws of different diameters in the screw section. [Figure 8] This is a schematic diagram showing the internal structure of the powder supply device of the present invention in a front view. [Figure 9] This is an enlarged view of section A in Figure 8. [Figure 10] This is a schematic diagram illustrating the powder supply device of the present invention in plan view. [Modes for carrying out the invention]

[0013] The powder supply device 1 of the present invention is a device that can quickly discharge a predetermined amount of powder without causing a bridging phenomenon in the powder.

[0014] The powder in this invention will now be described. The powder is an aggregate of solid particles, and is a concept that includes aggregates of granular materials such as pellets, crushed materials, or granules, and aggregates of powder having a shape smaller than that of granular materials. Furthermore, powder obtained by mixing the granular materials and the powder is also included in the powder of this invention.

[0015] As shown in FIGS. 1 to 10, the powder supply device 1 of the present invention includes a hopper 2 for storing powder, a screw section 4 disposed below the hopper 2 and having large and small diameter screw groups 7 and 8 arranged in parallel for feeding the powder horizontally by rotation, a stirring means 3 installed above the screw section 4 and having a screw near blade part 3c with the lower end at a height near the upper end of the tip locus circle formed by the leading ends of the blades 7a and 8a of the screw section 4 during rotation, a weighing means 5 for continuously weighing the total weight of the component part downstream of the discharge port of the screw section 4 where the discharged powder exists, or the total weight of the component part upstream of the discharge port of the screw section 4 where the powder exists, and a control unit 6. The large diameter screw 7 and the small diameter screw 8 constituting the screw section 4 are arranged such that the upper end height 10 of the tip locus circle formed by the leading end of the blade 7a of the large diameter screw 7 during rotation is the same as the upper end height 10 of the tip locus circle formed by the leading end of the blade 8a of the small diameter screw 8 during rotation, and a small gap 11 is provided in the vertical direction between the upper end height 10 of the blades 7a and 8a and the lower end height of the screw near blade part 3c of the stirring means 3. The control unit 6 calculates the remaining amount of the powder to be discharged based on the preset predetermined supply amount of the powder and the input of the weighing information from the weighing means 5, and independently controls the start / stop of the operation and the rotation speed of the large diameter screw 7 and the small diameter screw 8 according to the remaining amount to be discharged.

[0016] The hopper 2 will be described. As shown in FIG. 1, the hopper 2 includes an upper cylindrical portion 2a and a substantially inverted frustum-shaped portion 2b connected to the lower end of the cylindrical portion 2a. The peripheral edge of the lower end of the cylindrical portion 2a and the peripheral edge of the upper end of the substantially inverted frustum-shaped portion 2b are connected with the same size, and powder (not shown) is stored inside.

[0017] The screw part 4 will be described. As shown in FIGS. 5 to 7, the screw part 4 is disposed below the hopper 2 and has a function of feeding the powder in the horizontal direction by rotation and discharging the powder from the discharge port. Screw groups 7 and 8 with large and small diameters are arranged in parallel. The screw part 4 has the large-diameter screw 7 and the small-diameter screw 8 arranged in parallel in the longitudinal direction. The large-diameter screw 7 includes blades 7a for conveying powder, a rotating shaft 7b to which the roots of the blades 7a are fixed, and a cylindrical body 7c forming the flow path of the powder. The small-diameter screw 8 includes blades 8a for conveying powder, a rotating shaft 8b to which the roots of the blades 8a are fixed, and a cylindrical body 8c forming the flow path of the powder.

[0018] In addition, in the screw part 4, when the powder is of a size that is not likely to scatter, it has a screw part structural form A in which it is directly accommodated in a storage container (not shown) from the discharge port of the cylindrical body 7c of the large-diameter screw 7 and the discharge port of the cylindrical body 8c of the small-diameter screw 8. Or, when the powder is of a size that is likely to scatter, there is a screw part structural form B that also includes a receiving hopper 40 and a surrounding cover (not shown) that surrounds the periphery between the cylindrical bodies 7c and 8c and the storage container. That is, in the present invention, the meaning of the range up to the discharge port of the screw part 4 is that it includes the constituent members until immediately before the powder is accommodated in the storage container. Therefore, it means that not only up to the discharge ports of the cylindrical bodies 7c and 8c, but also the constituent members until immediately before the powder is accommodated in the storage container are included.

[0019] The aforementioned screw groups 7 and 8 of different diameters may also consist of two screws, such as the large-diameter screw 7 and the small-diameter screw 8, as shown in Figure 5. However, the purpose of the screw groups 7 and 8 of different diameters in the present invention is to provide the large-diameter screw 7 for the purpose of quickly feeding and discharging the powder, and the small-diameter screw 8 for the purpose of accurately discharging a predetermined amount with minimal variation. Therefore, the screw groups 7 and 8 of different diameters may include, for example, a combination of two screws with a relatively large diameter and two screws with a relatively small diameter, as well as a combination of one screw with a relatively large diameter and two screws with a relatively small diameter. In other words, the screw groups 7 and 8 of different diameters may consist of any number of screws, as long as they are a combination of screws with a relatively large diameter that can feed out a large amount of powder and screws with a relatively small diameter that can feed out only a very small amount of powder.

[0020] The screw section 4 then sends the powder through the cylindrical bodies 7c and 8c and causes it to flow down into the receiving hopper 40, thereby storing a predetermined amount of the powder in the storage container. Furthermore, a surrounding cover (not shown) is provided between the receiving hopper 40 and the storage container to prevent the powder from leaking out and to ensure that it is stored in the storage container.

[0021] The sizes of the large-diameter screw 7 and the small-diameter screw 8 can be such that, for example, there is a difference in size of approximately 3:1 between the tip trajectory circle formed by the tip of the blade 7a during rotation and the tip trajectory circle formed by the tip of the blade 8a during rotation. Any difference in size, such as approximately 2:1 or approximately 4:1, is also acceptable.

[0022] Furthermore, as shown in Figure 2, the large-diameter screw 7 and the small-diameter screw 8 that constitute the screw section 4 are arranged such that the upper end height 10 of the tip trajectory circle formed by the tip of the blade 7a of the large-diameter screw 7 during rotation is the same as the upper end height 10 of the tip trajectory circle formed by the tip of the blade 8a of the small-diameter screw 8 during rotation. This makes it easy to prevent closure by bridging of the powder near the top of the screw section 4 using the same stirring means 3.

[0023] As shown in Figure 7, the rotating shafts 7b and 8b are each rotated by two rotational drive means 18 (18a, 18b) that are separately connected to them, and the two rotational drive means 18 (18a, 18b) are controlled to operate differently according to the instructions of the control unit 6. The control unit 6 can independently control the start and stop of rotational operation and the rotational speed of the large-diameter screw 7 and the small-diameter screw 8.

[0024] Next, the stirring means 3 will be described. The stirring means 3 can be configured in any form as long as it has the function of preventing the powder from bridging inside the hopper 2 and above the screw section 3. An example of the configuration of the stirring means 3 is shown in Figures 2 to 4, for example, and comprises an inclined blade section 3a that can rotate along the inner circumferential surface of the substantially inverted frustoconical section 2b, a cylindrical section 3b with external teeth 21 formed on its outer circumferential surface, the upper end of which is connected to the lower end of the inclined blade section 3a and connected to a rotational drive means 19, such as a motor, via a gear (not shown), and a substantially vertical screw-near blade section 3c, the upper end of which is connected to the lower end of the cylindrical section 3b with external teeth, and the lower end of which is at a height near the upper end height 10 of the tip trajectory circle formed by the leading edges of the blades 7a and 8a of the screw section 4 when they rotate.

[0025] The inclined blade portion 3a is a scraper-like wall-following blade that rotates along the inner surface of the substantially inverted truncated cone-shaped portion 2b while maintaining a clearance 12 from the inner surface, thereby scraping up the powder stored in the hopper 2 and preventing it from adhering to the inner surface and forming a bridge that blocks the lower end opening of the inclined blade portion 3a.

[0026] As shown in Figure 2, the external toothed cylindrical portion 3b has an upper end connected to the lower end of the inclined blade portion 3a and a lower end connected to the upper end of the screw-adjacent blade portion 3c, and has an external tooth 21 formed on the outer circumferential surface of the approximately central part in the vertical direction. As shown in Figure 7, the external tooth 21 is connected to the rotational drive means 19 via several gears, and when the rotational drive means 19 rotates in response to an instruction from the control unit 6, the external tooth 21 rotates, and the external toothed cylindrical portion 3b, the inclined blade portion 3a, and the screw-adjacent blade portion 3c, which are integrated with the external tooth, rotate together as a single unit.

[0027] The screw-immediate blade portion 3c has its upper end connected to the lower end of the externally toothed cylindrical portion 3b, and its lower end is positioned so as to be near the height of the upper end height 10 of the tip trajectory circle formed by the leading edges of the blades 7a and 8a of the screw portion 4 when they rotate, as shown in Figure 2, with a small gap 11 between the height of the lower end of the screw-immediate blade portion 3c and the height of the upper end height 10 of the tip trajectory circle formed by the leading edges of the blades 7a and 8a of the screw portion 4 when they rotate. The presence of only this small gap 11 prevents the powder from bridging directly above the screw portion 4.

[0028] The powder flows downward from the hopper 2 by gravity, descends through the toothed cylindrical section 3b by gravity, and reaches and is stored in a feeding guide section 15 surrounded by walls. This guide section prevents the descending powder from leaking laterally and ensures that all of it flows into the screw section 4. It is then necessary to prevent the powder stored in the feeding guide section 15 from forming a bridge and blocking the area above the screw section 4.

[0029] Therefore, the blade portion 3c immediately adjacent to the screw is a scraper-shaped blade that rotates with a small gap 11 between the upper end height 10 of the tip trajectory circle formed by the tip of the blade 7a of the large-diameter screw 7 during rotation and the upper end height 10 of the tip trajectory circle formed by the tip of the blade 8a of the small-diameter screw 8 during rotation, in order to prevent the powder from forming a bridge and blocking the area above the screw portion 4.

[0030] Next, the weighing means 5 will be described. The weighing means 5 has two weighing modes: weighing mode A, which continuously weighs the total weight of the components containing the discharged powder downstream from the discharge port of the screw section 4; and weighing mode B, which continuously weighs the total weight of the components containing the powder upstream from the discharge port of the screw section 4. In weighing mode B, the components to be weighed include the hopper 2, the stirring means 3, and the screw section 4, etc.

[0031] The weighing means 5 in weighing configuration A includes, for example, a load cell that continuously weighs the total weight of the components associated with the container in which the powder is contained. In weighing configuration A, the weight of the powder contained in the container can be accurately determined by subtracting the weight of the components associated with the container from the total weight.

[0032] Furthermore, the weighing means 5 of weighing configuration B, as shown in Figure 9, for example, has the function of suspending and supporting the powder, the hopper 2, the stirring means 3, the screw section 4, and the components connected thereto during storage and feeding, and weighing the total weight of the powder, the hopper 2, the stirring means 3, the screw section 4, and the components connected thereto, and as shown in Figure 10, there are load cells arranged in a total of four places on the frame 30, on the left, right, front, and rear. The load cells, which are the weighing means 5 of weighing configuration B, can be positioned in four places on the front, rear, left, and right to allow weighing in a stable position, but the number of load cells can be any number that allows the total weight to be weighed in a stable position.

[0033] Furthermore, if the receiving hopper 40 and the surrounding cover are installed between each discharge port of the screw group and the storage container, the receiving hopper 40 and the surrounding cover are also included in the weighing to measure the amount of powder not contained in the storage container. In the case of weighing method B, by subtracting the weight of the hopper 2, the stirring means 3, the screw section 4, and the components connected thereto, including the receiving hopper 40 and the surrounding cover, which are within the range up to the discharge port of the screw section 4, from the total weight, the weight of all the powder within the range up to the discharge port of the screw section 4 can be accurately determined.

[0034] As a result, after the powder is put into the hopper 2, as shown in Figure 1, the upper opening of the hopper 2 is covered with a lid to prevent the addition of more powder, and the screw section 4 rotates and the powder is discharged, the weight of the powder in the range up to the discharge port of the screw section 4, or the weight of the powder in the container, can be accurately and continuously measured. Once the required amount of powder is determined, the remaining amount of powder to be discharged can be accurately determined by a predetermined calculation by continuously measuring the readings of the measuring means 5.

[0035] Next, the control unit 6 will be described. The control unit 6 is connected by wiring to the measuring means 5, the rotational drive means 19 for rotating the stirring means 3, the rotational drive means 18a for rotating the rotation shaft 7b of the large-diameter screw 7, and the rotational drive means 18b for rotating the rotation shaft 8b of the small-diameter screw 8.

[0036] The control unit 6 calculates the remaining amount of powder to be supplied based on a predetermined supply amount of the powder and the input of metering information from the metering means 5, and controls the start and stop of rotational operation and the rotational speed of the large-diameter screw 7 and the small-diameter screw 8 independently according to the remaining amount to be supplied.

[0037] As an example of the control of the control unit 6, the control unit 6 operates the large-diameter screw 7 and the small-diameter screw 8 at a predetermined rotational speed when the remaining amount to be supplied is large, gradually reduces the rotational speed of the large-diameter screw 7 and the small-diameter screw 8 at a predetermined timing when the remaining amount to be supplied exceeds half of the predetermined supply amount, stops only the large-diameter screw 7 at a predetermined timing when the remaining amount to be supplied is less than the predetermined supply amount, further gradually controls the rotational speed of the small-diameter screw 8 to a lower speed at a predetermined timing when the remaining amount to be supplied approaches the predetermined supply amount, and stops the rotation of the small-diameter screw 8 the moment the remaining amount to be supplied reaches zero. This allows for the accurate discharge of a predetermined amount quickly and in a short amount of time.

[0038] As an example of the control of the control unit 6, for instance, the diameter of the cylindrical body 7c of the large-diameter screw 7 is set to approximately 90 mm, the diameter of the cylindrical body 8c of the small-diameter screw 8 is set to approximately 30 mm, and the predetermined amount of powder to be supplied is set to 100 g. In this control example, first, both the large-diameter screw 7 and the small-diameter screw 8 are rotated at 100 rpm, and the moment the remaining amount reaches 50 g, both the large-diameter screw 7 and the small-diameter screw 8 are slowed down to 50 rpm, and the moment the remaining amount reaches 10 g, the rotation of the large-diameter screw 7 is stopped and the rotation of the small-diameter screw 8 is slowed down even further to 10 rpm, and the moment the remaining amount reaches 0 g, the small-diameter screw 8 is stopped. This allows for the accurate discharge of the predetermined amount quickly and in a short amount of time.

[0039] Here, if the screw configuration consists only of a large-diameter screw, there is the advantage that the powder feeding time can be shortened, but there is a problem that the amount of powder fed and discharged varies greatly and does not match a predetermined amount. On the other hand, if the configuration consists only of a small-diameter screw, there is the advantage that the amount of powder fed and discharged is approximately the same as a predetermined amount, but there is a problem that the powder discharge time is long and productivity is significantly reduced.

[0040] In contrast to the case of having only a large-diameter screw or only a small-diameter screw, the powder supply device 1 of the present invention comprises the large-diameter screw 7 and the small-diameter screw 8 as constituent elements, and is arranged such that the upper end height 10 of the tip trajectory circle formed by the tip of the blade 7a of the large-diameter screw 7 during rotation and the upper end height 10 of the tip trajectory circle formed by the tip of the blade 8a of the small-diameter screw 8 during rotation are at the same height, and the upper end height 10 of the tip trajectory circle formed by the tip of the blade 7a of the large-diameter screw 7 during rotation and the blade 8a of the small-diameter screw 8 The stirring means 3 is rotated with a small gap 11 between the tip and the upper end height 10 of the tip trajectory circle formed when the tip rotates, preventing the formation of bridges in the powder. The control unit 6 calculates the remaining amount of powder to be supplied based on a predetermined supply amount of the powder and the input of metering information from the metering means 5. By controlling the start, stop, and speed of the operation of the large-diameter screw 7 and the small-diameter screw 8 according to the remaining amount to be supplied, the predetermined amount can be discharged quickly, in a short time, and accurately, which has the advantageous effect of providing a predetermined amount. [Explanation of Symbols]

[0041] 1 Powder feeding device 2 Hopper 2a Cylindrical part 2b Approximately inverted truncated cone shape 3 Stirring means 3a Inclined blade section 3b External toothed cylindrical section 3c Screw blade section closest to the screw 4. Screw section 5 Measuring means 6 Control Unit 7 Large diameter screw 7a Feather 7b Rotation axis 7c cylindrical body 8 Small diameter screws 8a Feather 8b Rotation axis 8c Cylindrical body 10 Upper edge height 11 Small gap 12 Clearance 15. Distribution Guide Department 18 Rotary drive means 19 Rotary drive means 21 External teeth 30 mounting bases 40 Receiving Hopper

Claims

1. A hopper for storing powder, A screw section is provided below the hopper, and a group of large and small diameter screws are arranged in parallel to feed the powder horizontally by rotation. A stirring means comprising a screw-adjacent blade section installed above the aforementioned screw section, with its lower end positioned at a height near the upper end of the tip trajectory circle formed by the tip of the blade of the aforementioned screw section during rotation, A weighing means for continuously weighing the total weight of the component containing the discharged powder downstream from the discharge port of the screw section, or the total weight of the component containing the powder upstream from the discharge port of the screw section, It comprises a control unit and, The large-diameter screw and the small-diameter screw constituting the screw section are arranged such that the upper end height of the tip trajectory circle formed by the tip of the blade of the large-diameter screw during rotation is the same as the upper end height of the tip trajectory circle formed by the tip of the blade of the small-diameter screw during rotation, and a small vertical gap is provided between the upper end height of the blade and the lower end height of the blade section of the stirring means immediately adjacent to the screw. A powder supply device characterized in that the control unit calculates the amount of powder to be discharged based on a predetermined supply amount of the powder and the input of metering information from the metering means, and independently controls the start / stop operation and rotation speed of the large-diameter screw and the small-diameter screw according to the amount of powder to be discharged.

2. The powder supply device according to claim 1, characterized in that the control unit operates the large-diameter screw and the small-diameter screw at a predetermined rotational speed when the remaining amount to be discharged is large, stops only the large-diameter screw at a predetermined timing when the remaining amount to be discharged exceeds half of the predetermined supply amount set in advance, and further reduces the rotational speed of the small-diameter screw at a predetermined timing when the remaining amount to be discharged approaches the predetermined supply amount set in advance, thereby controlling the rotational speed in stages according to the remaining amount to be discharged.

3. The hopper comprises a cylindrical portion and a substantially inverted truncated cone-shaped portion connected to the lower end of the cylindrical portion. The powder supply device according to claim 1 or 2, characterized in that the stirring means comprises an inclined blade section that can rotate along the inner circumferential surface of the substantially inverted truncated cone-shaped section, an externally toothed cylindrical section whose upper end is connected to the lower end of the inclined blade section and connected to a rotational driving means, and a substantially vertical screw-immediate blade section whose upper end is connected to the lower end of the externally toothed cylindrical section and whose lower end is at a height near the upper end of the tip trajectory circle formed by the tip of the blade of the screw section when it rotates.

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