Powder/granular material feeding device

A provided powder/granular material feeding device fully satisfies the function of sufficiently preventing bridges and ratholes and the function of favorably stabilizing the filling rate of an outlet portion. Moreover, the powder/granular material feeding device does not require consumable items such as a flexible chute or leave a large amount of powder/granular material in a specific region inside a chute. The powder/granular material feeding device includes: a hopper 1 that receives powder/granular material; an outlet portion 2 that discharges powder/granular material; a chute 3 that guides, into the outlet portion 2, powder/granular material dropped from the hopper 1; and a stirring part 4 that rotates stirring members 4b about a shaft 4a protruding so as to tilt diagonally upward from the lower part of the interior of the chute 3.

FIELD OF THE INVENTION

The present invention relates to powder/granular material feeding devices, and particularly relates to a powder/granular material feeding device suitable for quantitative feeding of powder/granular material.

BACKGROUND OF THE INVENTION

Powder/granular material feeding devices, also called feeders, have been widely known as devices for quantitative feeding of powder/granular material. As illustrated inFIGS. 20 and 21, such a powder/granular material feeding device includes a hopper51that receives powder/granular material, an outlet portion52having screws52afor discharging powder/granular material, a chute53that guides, into the outlet portion52, powder/granular material dropped from the hopper51, and a stirring device54that is also called an agitator for agitating powder/granular material in the chute53and the hopper51. The powder/granular material feeding device for quantitative feeding of powder/granular material includes, in addition to these constituent elements (the hopper51, the outlet portion52, the chute53, and the stirring device54), a metering unit55on which these constituent elements are loaded, and a control unit (not shown) that controls the outlet portion52so as to keep constant the weight of discharged powder/granular material (the amount of discharged powder/granular material) per hour or the weight of powder/granular material in each discharge.

Various kinds of powder/granular material feeding devices are available. The hopper51inFIGS. 20 and 21is a cylinder that is vertically extended with a constant shape in cross section. A hopper82inFIGS. 22,23A, and23B is shaped like a rectangular prism. A hopper61inFIG. 24has a curved shape, e.g., a conical or pyramidal shape expanding upward in cross section. As simply illustrated inFIG. 24, the curved hopper61expands upward in cross section and can be advantageously reduced in height with a sufficient capacity. However, the hopper61with a curved wall surface decreases in cross-sectional area toward the bottom of the hopper61, causing bridging, that is, partially or entirely remaining powder/granular material with high adhesion and compressibility or a rathole that is a central hole of a material. These phenomena are effectively avoided by adopting a cylindrical hopper or hanging, as illustrated inFIG. 24, a vertical agitator (stirring part)62downward into the hopper61from the top surface of the hopper61. A hopper agitator including such a vertical agitator is disclosed in, for example, Japanese Patent Laid-Open No. 9-216688.

Unfortunately, the provision of the vertical agitator62requires a space for lifting the agitator62during cleaning of the hopper61(the hopper61is always cleaned each time a powder/granular material type is changed). Furthermore, a top surface61aof the hopper61needs to be lifted with an additional weight of the agitator62and an electric motor63for driving the agitator, reducing workability of cleaning and so on. For this reason, the agitator in general is not so popular among users.

The chute provided under the hopper contains the stirring device that is a mechanism for agitating powder/granular material in the hopper on the chute to prevent bridges in the hopper. A typical stirring device is, as illustrated inFIGS. 20 and 21, a horizontal agitator that has a stirring part (agitator)54bfor vertically agitating powder/granular material with respect to a shaft54aprotruding from the side of the chute53. Furthermore, as illustrated inFIG. 25, a table-type powder/granular material feeding device is available that rotates powder/granular material in a circumferential direction by means of a stirring part72that is called a vertical agitator. The stirring part72rotates about a shaft71dprotruding upward from a bottom71aof a chute71. Moreover, as illustrated inFIGS. 22,23A, and23B, a powder/granular material feeding device of flexible chute type is available in which a chute81disposed under the hopper82is made of flexible resin and is deformed from the outside so as to move an internal material.

The stirring device (stirring part) also supplies powder/granular material into an outlet portion provided under the stirring device and stabilizes the powder/granular material with a high filling rate in the outlet portion. The stable filling rate in the outlet portion remarkably contributes to more stable discharging capability and higher feeding accuracy (small variations).

The outlet portion is a screw-type outlet (double screws or a single screw) using the screws52aand a screw84illustrated inFIGS. 21 to 23B. The outlet portion may be vibration type, belt type, disk type, and so on. However, the screw type is the most suitable for powder/granular materials having various properties, e.g., adhesion and discharge. The single screw84(seeFIGS. 22,23A, and23B) is preferably used for a less adhesive material, whereas the double screws52a(seeFIG. 21) capable of self-cleaning is preferably used for a highly adhesive material. The double screws capable of offsetting screw pulsations are frequently used for high feeding accuracy.

Hence, the stirring part of the stirring device disposed in the chute has the function of feeding a material to the screw acting as the outlet portion under the hopper as well as the function of preventing bridges in the hopper disposed on the chute. The stirring part is a mechanism that plays a key role in the powder/granular material feeding device and is quite important in determining the performance and character of the powder/granular material feeding device.

The conventionally used powder/granular material feeding devices of the respective types and the advantages and disadvantages thereof will be specifically described below.

FIGS. 20,21, and26illustrate the powder/granular material feeding devices, each having the horizontal stirring part called a horizontal agitator. The two types of powder/granular material feeding devices have the dome-shaped chute53inFIGS. 20 and 21and a square chute91inFIG. 26. The rectangular-prism chute91inFIG. 26can be produced by boiler making (also called a welded structure). A screw92awith a flat driving side and a flat discharging side allows the opening of the chute91to have a relatively simple sealing structure that advantageously facilitates sealing. Moreover, the rectangular-prism chute91and a screw casing92bthat accommodates the screws (outlet portion)92aare linearly in contact with each other, forming a long area of feeding to the screws92a. Thus, the powder/granular material feeding device including the rectangular-prism chute91can feed a material that is hard to come into the screws92a, for example, a film material.

However, a powder/granular material feeding device90disadvantageously requires welding over the corners of the chute91, is likely to deposit or leave a material on the corners of the chute91, and increases a screw length as compared with the dome-shaped chute53(seeFIG. 21), forming a dual support structure. Moreover, a hopper (not shown) disposed on the rectangular-prism chute91is inevitably shaped like a rectangular prism, so that the chute91and the hopper need to be joined with clamps at several points. Disadvantageously, the attachment and detachment of the hopper requires considerable effort and time as compared with the dome-shaped chute. Reference numeral93inFIG. 26denotes the stirring part of the horizontal agitator.

The powder/granular material feeding device with the dome-shaped chute53inFIGS. 20 and 21has no corners on the chute53, which reduces powder/granular material deposition and residue and facilitates cleaning. The cylindrical hopper51that hardly allows powder/granular material deposition is attached on the upper part of the chute53, and a clamp band56can be used on a joining area between the chute53and the hopper51. Advantageously, the hopper51can be attached and detached with less effort and time.

However, the dome-shaped chute53provided in the powder/granular material feeding device disadvantageously needs to be manufactured with a mold, for example, by drawing or a lost-wax process, so that the dome-shaped chute53and a screw casing52bthat accommodates the screws52aare joined with a slightly complicated configuration. Furthermore, the stirring part (agitator)54bapproaches closest to the screws52aonly at a center point. A space is formed between an agitation range and the screws52a, and powder/granular material is fed to the screws52awith a shorter feeding area as compared with the rectangular-prism chute, so that the powder/granular material is less supplied to the screws52athan in the rectangular-prism chute.

The powder/granular material feeding device having the horizontal agitator vertically agitates powder/granular material by means of the stirring part54bor93, vertically moving the powder/granular material regardless of whether the chute is a rectangular prism or a dome. Thus, in the case where the amount of discharged powder/granular material is controlled during measurement, the weight is likely to fluctuate. Particularly, the powder/granular material feeding device is seriously affected by fluctuations in weight during an operation with a low flow rate and thus a control state may be disturbed by the powder/granular material feeding device, disadvantageously leading to lower feeding accuracy.

FIG. 25is a perspective view illustrating the table-type powder/granular material feeding device. In such a powder/granular material feeding device, the bottom71aof the chute71is shaped like a round table. As has been discussed, powder/granular material is agitated in the circumferential direction by the stirring part72that is called a vertical agitator. The stirring part72rotates about the shaft71dthat protrudes upward from the bottom71aof the chute71. Reference numeral71binFIG. 25denotes a chute outlet for feeding powder/granular material to an outlet portion from the chute71. In such a so called table-type powder/granular material feeding device, the bottom71aof the chute71can have a relatively large size, allowing a hopper (not shown) to have a large base area. Since the stirring part72including the vertical agitator can be provided, bridges can be effectively prevented. A joining area between the chute71and the hopper is inevitably circular, allowing the use of a clamp band similar to the clamp band56inFIG. 21.

Even in the case of a granular material, e.g., a pellet that does not need agitation, the simple stirring part (agitator)72is necessary to prevent quite a large amount of the material from remaining on the bottom71ashaped like a flat table. Also in the case of a powder material, the material is deposited and left in a gap between the stirring part72and the surface of the bottom71aand on the blade of the stirring part72. A screw75disposed directly under the bottom (table surface)71ais laterally shifted so as to avoid a driving shaft that rotates the stirring part72, limiting an area of feeding to the screw75. Moreover, the stirring part72only passes above the screw, reducing the capability of filling to the screw75.

The screw75can be centered by providing another room under the bottom (table surface)71a. Moreover, the provision of a stirring part (horizontal agitator)73around the screw75can improve the capability of filling to the screw75, though a large amount of powder/granular material is left under the screw75.

FIGS. 22,23A, and23B are a perspective view and side cross-sectional views of a powder/granular material feeding device80that includes the hopper82shaped like a square cylinder (that is, a rectangular prism) on the flexible chute81. The side of the chute is deformed by a paddle83from the outside of the flexible chute81to move internal powder/granular material, thereby preventing bridges. In the case of the rectangular-prism hopper82, powder/granular material having medium flowability, e.g., calcium carbonate or talc is highly unlikely to cause bridges. The rectangular-prism hopper82can be more easily manufactured than a conical or pyramidal hopper in terms of the manufacturing cost, leading to lower manufacturing cost. Furthermore, the flexible chute type has a lower resistance than in the rotations of a stirring part acting as a rotating object in powder/granular material. Thus, the capacity of a motor for driving the stirring part can be reduced, achieving a clear cost advantage. Since the resistance is low, the flexible chute81can have a larger size, so that the hopper82can advantageously have a large capacity with relative ease.

In the powder/granular material feeding device80including the flexible chute81, however, the flexible chute81is a consumable item that is an elastic body made of resin or the like. Thus, the flexible chute81needs replacing every several years (e.g., two years), requiring running cost for each replacement of the flexible chute81. Since the paddle83desirably comes into contact with a flat surface, the flexible chute81and the hopper82have squares, which may lead to deposition of a material on the corners of the hopper82so as to cause bridges. In other words, the capability of preventing bridges is slightly lower than in the case where the hopper82has a circle. Moreover, agitation by the paddle83does not generate a force pressing a material to the screw84, so that the material is dropped and inserted to the screw84only by its own weight. Thus, the capability of filling a material to the screw84is lower than in internal agitation. Since the flexible chute81is vibrated by swinging of the paddle83, the weight is likely to fluctuate. In the case where the amount of discharged powder/granular material is controlled during measurement, the feeding accuracy may decrease.

DISCLOSURE OF THE INVENTION

As has been discussed, the conventional powder/granular material feeding devices of any types have advantages and disadvantages. Any of the powder/granular material feeding devices does not fully satisfy the function of sufficiently preventing bridges and ratholes, the function of fully stabilizing the filling rate of the outlet portion with a sufficient area of feeding to the screw, and the function of suppressing the amount of remaining powder/granular material. Some of the powder/granular material feeding devices regularly require consumable items such as the flexible chute81or leave a large amount of powder/granular material in a specific area inside the chute.

The present invention has been devised to solve the problems. An object of the present invention is to provide a powder/granular material feeding device that fully satisfies the functions of sufficiently preventing bridges and ratholes and fully stabilizing the filling rate of an outlet portion without requiring consumable items such as a flexible chute or leaving a large amount of powder/granular material in a specific area inside the chute.

In order to solve the problems, a powder/granular material feeding device according to the present invention includes: a hopper that receives powder/granular material; an outlet portion that discharges powder/granular material; a chute that guides, into the outlet portion, powder/granular material dropped from the hopper; and a stirring part that rotates a stirring member about a shaft protruding so as to tilt diagonally upward from the lower part of the interior of the chute.

With this configuration, the stirring member rotates about the shaft protruding so as to tilt diagonally upward from the lower part of the interior of the chute. Thus, powder/granular material is agitated diagonally, that is, in various directions such as a vertical direction and a circumferential direction by the stirring member of the stirring part. This configuration sufficiently agitates powder/granular material in the chute and the hopper, thereby preventing the occurrence of bridges and ratholes. Moreover, the track of rotation of the stirring part can be located along the outlet portion, thereby fully stabilizing the filling rate of powder/granular material to the outlet portion. Furthermore, in the case of weight measurement of powder/granular material being discharged, the stirring member rotating about the inclined shaft of the stirring part can reduce vertical motions of agitated powder/granular material and suppress fluctuations in weight as compared with a horizontal agitator including a stirring part that rotates in the vertical direction. The outlet portion preferably contains a screw.

Furthermore, according to the powder/granular material feeding device of the present invention, the shaft of the stirring part protrudes to the center of the interior of the chute in plan view. This configuration can sufficiently agitate powder/granular material over the entire interior of the chute.

Moreover, according to the powder/granular material feeding device of the present invention the chute preferably includes an inclined plane with an inner surface inclined diagonally upward, and the shaft is preferably protruded from the inclined plane. Hence, the chute and the stirring part can be disposed with a relatively simple configuration. Since the shaft of the stirring part is protruded perpendicularly to the inclined plane, the seal structure of the inclined plane of the chute and the shaft can be constructed with relative ease, minimizing an increase in manufacturing cost.

Preferably, the inclined plane of the chute is circular. With this configuration, powder/granular material can be sufficiently agitated and hardly remains near a joining area between the inclined plane and the side wall of the chute. Moreover, the hopper is oval and has a constant cross-sectional shape in the vertical direction, that is, an oval cylinder, thereby minimizing the occurrence of bridges in the hopper without the need for a vertical agitator.

Furthermore, according to the powder/granular material feeding device of the present invention, the outlet portion includes a screw casing having an internal space, the internal space of the screw casing and the bottom space of the chute are linearly connected to each other, and the stirring member provided in the stirring part passes directly above the connected part of the spaces. With this configuration, the bottom of the chute and the screw casing are linearly connected, thereby increasing the dimensions of a feed opening to the screw. Moreover, the stirring member passes directly above the overall feed opening to the screw while pressing powder/granular material. This configuration improves filling of powder/granular material into the screw casing, stably keeping a high filling rate.

The powder/granular material feeding device according to the present invention further includes a driving force transmission mechanism that transmits the driving force of a motor to a screw provided in the outlet portion and the stirring part, wherein the outlet portion and the stirring part are driven through the driving force transmission mechanism. This configuration can reduce the number of motors as compared with the case where motors are used respectively for the screw and the stirring part, achieving lower manufacturing cost.

Furthermore, according to the powder/granular material feeding device of the present invention, the chute includes an inclined plane with an inner surface inclined diagonally upward, a conical wall extended from the outer periphery of the inclined plane, and a side wall that connects the conical wall and the hopper to guide powder/granular material in the hopper to the conical wall of the chute.

In this case, the side wall of the chute may be oval in plan view and may have a constant cross-sectional shape in the vertical direction. With this configuration, the side wall of the chute can have a relatively simple shape.

The side wall of the chute may have a cross-sectional shape expanding in the lower part of the chute relative to the upper part. With this configuration, powder/granular material introduced from the hopper into the chute is hardly compressed, so that a pressure on the side wall of the chute decreases and powder/granular material deposited on the side wall is likely to fall off the side wall by its own weight. This can reliably prevent bridges caused by powder/granular material deposition on the side wall of the chute.

In this case, the side wall of the chute may have a circular upper end in plan view, and the hopper may be circular and have a constant cross-sectional shape in the vertical direction. With this configuration, the hopper can be circular. The hopper can be more easily formed than an oval hopper. Furthermore, the hopper and the chute can be easily connected with a simple structure while the hopper can be connected to other members with a simple structure.

According to the present invention, the stirring member of the stirring part rotates about the shaft protruding so as to incline diagonally upward from the lower part of the interior of the chute, thereby preventing the occurrence of bridges and ratholes. Furthermore, the filling rate of powder/granular material to the outlet portion can be sufficiently stabilized. Even in the case where powder/granular material is discharged during weight measurement, fluctuations in weight can be suppressed, achieving high feeding accuracy. Since the need for consumable items such as a flexible chute can be eliminated, only small maintenance cost is necessary. Moreover, the shaft protruding diagonally upward allows the stirring member, e.g., a stirring blade for agitation in the bottom of the chute to be sufficiently supported on the base of the shaft.

Furthermore, the chute includes the inclined plane that is directed diagonally upward, and the shaft protruded from the inclined plane. Thus, the chute and the stirring part can be disposed with a relatively simple configuration. Moreover, the seal structure of the inclined plane of the chute and the shaft can be constructed with relative ease, suppressing the manufacturing cost.

Since the inclined plane of the chute is circular, powder/granular material can be sufficiently agitated and hardly remains near the joining area between the inclined plane and the side wall of the chute. Moreover, the oval hopper has a constant cross-sectional shape in the vertical direction, thereby minimizing the occurrence of bridges in the hopper without the need for a vertical agitator.

Furthermore, the internal space of the screw casing provided in the outlet portion and the bottom space of the chute are linearly connected to each other, and the stirring member provided in the stirring part passes directly above the connected part. This configuration improves filling of powder/granular material into the screw casing, stably keeping a high filling rate. Consequently, the stability of discharge and the feeding accuracy can be improved.

The side wall of the chute has a cross-sectional shape expanding in the lower part of the chute relative to the upper part. This configuration can satisfactorily prevent powder/granular material deposition on the side wall of the chute, thereby reliably preventing the occurrence of bridges. Therefore, powder/granular material can be stably discharged from the powder/granular material feeding device, improving the feeding accuracy and reliability of the powder/granular material feeding device.

In this case, the upper end of the side wall of the chute may be circular in plan view and the circular hopper may have a constant cross-sectional shape in the vertical direction. With this configuration, the hopper can be circular and thus can be more easily formed than an oval hopper. Furthermore, the hopper and the chute can be easily connected with a simple structure while the hopper can be connected to other members with a simple structure, thereby reducing the manufacturing cost.

DESCRIPTION OF THE EMBODIMENTS

A powder/granular material feeding device according to embodiments of the present invention will be described below with reference to the accompanying drawings. These embodiments are merely exemplary and thus the present invention is not always limited to these embodiments. In the following explanation, a direction along which powder/granular material is fed in an outlet portion will be referred to as a forward direction.

As illustrated inFIGS. 1 to 5, a powder/granular material feeding device according to a first embodiment of the present invention includes a hopper1that receives powder/granular material, an outlet portion2that discharges powder/granular material, a chute3that guides, to the outlet portion2, powder/granular material dropped from the hopper1, a stirring part4that rotates stirring members4babout a shaft4aprotruding so as to incline diagonally upward from the lower part of the interior of the chute3, a metering unit5loaded with these constituent elements, and a control unit (not shown). Moreover, the top surface of the hopper1is covered with a lid, which is not illustrated. The lid is optionally connected to a powder/granular material feed pipe and so on.

The hopper1and the upper part of the chute3(a side wall3cof the chute3) are oval in plan view and have a constant cross-sectional shape in a vertical direction, that is, like an oval cylinder. Particularly, on the rear side of the chute3, an inclined plane3ais formed with an inner surface inclined diagonally upward (that is, the inner surface inclined in the forward direction). The stirring part4rotates the stirring members4b, which include stirring blades, about the shaft4a. In the present embodiment, the shaft4aof the stirring part4is extended perpendicularly to the inclined plane3afrom the inclined plane3aand protrudes to the center of the interior of the chute3in plan view.

The inclined plane3aof the chute3has a round shape. In the present embodiment, the stirring members4bof the stirring part4are respectively extended from two points: the proximal end and the leading end of the shaft4ain the radial direction of the inclined plane3a. Moreover, the ends of the stirring members4bare radially extended so as to incline along a conical wall3band the side wall3cof the chute3. In the present embodiment, the two stirring members4bof the stirring part4are extended perpendicularly to each other in a direction perpendicular to the shaft4aat angles differing from each other by 90 degrees each. The present invention is not limited to this configuration.

The conical wall3bof the chute3is conically extended forward, laterally, and upward from the inclined plane3a. The ends of the stirring members4bof the stirring part4are rotated along the inner surface of the conical wall3bof the chute3. The proximal ends of the stirring members4bof the stirring part4are rotated along the inner surface of the inclined plane3aof the chute3. The lower end of the side wall3cof the chute3is connected along the outer edge of the conical wall3bof the chute3. The side wall3cof the chute3is oval in plan view and is vertically extended upward while keeping the shape of the lower end. The hopper1is identical in shape to the side wall3cof the chute3in plan view and is extended upward. The upper end of the chute3and the lower end of the hopper1can be joined to each other with a clamp band7, which is not illustrated. Moreover, a gasket8is disposed between the upper end of the chute3and the lower end of the hopper1.

The outlet portion2is substantially cylindrical in longitudinal section or has a spectacle shape that is laterally extended. An outlet pipe2aand a screw casing2e, which are longitudinally extended, contain a single rotatable screw2bor double rotatable screws2b(the single screw2binFIGS. 1 to 6). A longitudinally extended part of the conical wall3bof the chute3and the upper edge of the screw casing2eare linearly connected and opened. The screw casing2eis filled with powder/granular material from the opening (also called a feed opening). The end of the outlet pipe2ais connected to an exit pipe2cthat has an opening at the bottom. Powder/granular material delivered into the exit pipe2cin the screw2bis discharged downward (outside) from the exit pipe2c.

In the present embodiment, a motor6is provided diagonally at the rear of the chute3and a worm gear6ais provided on the end of the drive shaft of the motor6. The shaft4aof the stirring part4is protruded diagonally downward from the outer surface of the inclined plane3aof the chute3. A stirring part gear4cis attached to the end of a part protruding downward. Furthermore, the rear end of the shaft of the screw2bis protruded from the rear end of the screw casing2e. An outlet gear2dis attached to the protruded part of the screw2b. The stirring part gear4cand the outlet gear2dare engaged with the worm gear6aattached to the end of the drive shaft of the motor6. Thus, the motor6is driven to rotate the stirring members4bof the stirring part4and the screw2bof the outlet portion2through the stirring part gear4c, the outlet gear2d, and so on. In other words, in the present embodiment, the worm gear6aattached to the motor6and the stirring part gear4cand the outlet gear2dthat are engaged with the worm gear6aconstitute a driving force transmission mechanism that transmits the driving force of the motor6to the screw2band the stirring members4bof the stirring part4. The screw2bof the outlet portion2and the stirring part4are driven through the driving force transmission mechanism.

The constituent elements, specifically, the hopper1, the chute3, the stirring part4, and the outlet portion2are placed on the metering unit5. The total weight of the constituent elements and powder/granular material is measured by the metering unit5. The control unit (not shown) controls the rotation speed of the screw2bso as to keep constant the weight of discharged powder/granular material (the amount of discharged powder/granular material) per hour or the weight of powder/granular material in each discharge.

In this configuration, the motor6is driven to rotate the stirring members4bof the stirring part4, thereby agitating powder/granular material in the chute3and the lower part of the interior of the hopper1. The powder/granular material is then introduced into the screw casing2efrom the lower part of the chute3, is passed through the outlet pipe2aby the screw2b, and is discharged out of the exit pipe2c.

In this case, the stirring members4bof the stirring part4rotate about the shaft4a. The shaft4aprotrudes so as to incline diagonally upward from the lower part of the interior of the chute3, achieving the advantages of a so-called horizontal agitator type and a table type.

Since the shaft4aof the stirring part4is disposed in an inclined position, powder/granular material can be sufficiently agitated by the stirring members4bin various directions including the vertical direction and a circumferential direction. Moreover, the hopper1has a constant cross-sectional shape, that is, a cylindrical shape in the vertical direction. Hence, the occurrence of bridges and ratholes in the chute3and the hopper1can be quite satisfactorily prevented. Thus, in the case of calcium carbonate or talc powder/granular material with medium flowability as well as pellet or glass fiber powder/granular material with high flowability, bridges and ratholes can be prevented. Moreover, bridges and ratholes can be satisfactorily prevented for materials including titanium oxide that is likely to increase in adhesion and compressibility with low flowability. Furthermore, this configuration can eliminate the need for a vertical agitator and so on, thereby effectively preventing bridges and so on while suppressing an increase in manufacturing cost with high cleaning performance. This configuration can be reliably applied to most kinds of powder/granular material.

The chute3and the outlet portion2, specifically, the bottom of the chute3and the screw casing2eare linearly connected (feed opening), thereby increasing the dimensions of the feed opening to the screw2b. Moreover, the stirring members4bpass directly above the overall feed opening to the screw2bwhile pressing powder/granular material. This configuration improves filling of powder/granular material into the screw casing2e, stably keeping a high filling rate. Consequently, the stability of discharge and the feeding accuracy can be improved.

Moreover, this configuration hardly moves stirred powder/granular material in the vertical direction as compared with the stirring part of a horizontal agitator. Thus, fluctuations in weight can be suppressed to obtain a stable weight. This stabilizes the control state of the powder/granular material feeding device that controls a weight being measured, achieving high feeding accuracy. Thus, the powder/granular material feeding device can be used for feeding a small amount of powder/granular material in an optimum condition.

The powder/granular material feeding device is similar to the table-type powder/granular material feeding device inFIG. 20in that the shaft is protruded from a surface near the bottom and rotor blades are provided to rotate about the shaft. However, the powder/granular material feeding device is different from the table-type powder/granular material feeding device in that the rotary stirring members4bcan scrape powder/granular material substantially over the inclined plane3aand the conical wall3bof the chute3. Since a space in the screw casing2eis directly connected to the conical wall3bof the chute3, only quite a small amount of powder/granular material is left on the inner surface of the conical wall3bof the chute3. Even in the case where powder/granular material is deposited on, for example, the stirring members4b, the stirring members4brotating in a tilted state facilitate falling of powder/granular material, thereby preventing powder/granular material from partially remaining on the stirring members4b.

The chute3including the inclined plane3a, the conical wall3b, and the side wall3cshaped like an oval cylinder can be manufactured by boiler making (also called a welded structure) without using molds. The chute3can be manufactured using molds. In this case, the manufacturing cost of the chute3can be reduced by high volume production.

As illustrated inFIG. 2, the rear of the lower part of the chute3is inclined as if the rear was cut in side view, thereby suppressing the length of the screw2b. Thus, the end of the screw2bdoes not always need to be supported. The manufacturing cost can be reduced by eliminating bearings. Moreover, the screw2bcan be reduced in diameter, allowing the powder/granular material feeding device to be optimally used for feeding a small amount of powder/granular material.

Some of the components of this configuration are similar to those of the table-type powder/granular material feeding device. As illustrated inFIG. 1, the screw2bcan be located at the center of the powder/granular material feeding device in front view. Hence, the inlet and the outlet for powder/granular material fed to the hopper1are located on the same straight line, allowing a user to easily create an installation plan of the powder/granular material feeding device with higher convenience.

Furthermore, the shaft4aprotrudes diagonally upward from the inclined plane3anear the bottom of the chute3, allowing the stirring members4bto be sufficiently supported and stably rotated on the base of the shaft4a. The shaft may be protruded from above to the bottom of the chute3such that the stirring blades are fixed on the end of the shaft. In this case, however, the stirring blades attached to the end of the shaft may vibrate the end of the shaft during rotations and cause unstable rotations of the stirring blades. In contrast, in the present embodiment, the stirring members4bfor agitation near the bottom of the chute3can be particularly sufficiently supported on the base of the shaft4a, so that the stirring members4bcan be stably rotated.

The shaft4aof the stirring part4is protruded perpendicularly to the inclined plane3a, thereby relatively easily constructing a seal structure of the inclined plane3aof the chute3and the shaft4aof the stirring part4. This configuration can reduce the manufacturing cost.

In the present embodiment, the inclined plane3aof the chute3is inclined at 45° with respect to a horizontal line or the conveyance line of the screw2bin side view, and the shaft4aprotrudes perpendicularly to the inclined plane3a. In this case, the stirring members4bcan sufficiently agitate powder/granular material in the vertical direction and particularly, in the circumferential direction. The inclination angle of the inclined plane3ais not limited to 45°. As illustrated inFIGS. 6 to 8, a shaft4amay be inclined at more than 45°, for example, 60° with respect to a horizontal line or may be inclined at less than 45°, for example, 30° (not shown) with respect to the horizontal line (a powder/granular material feeding device according to a second embodiment of the present invention).

In the above-described embodiment, the relatively large inclined plane3ais formed in the rear of the lower part of the chute3. The present invention is not limited to this configuration. As illustrated inFIG. 9, a shaft4amay protrude diagonally upward substantially from a corner in the rear of the lower part of a chute3such that stirring members4brotate about the shaft4aalong a conical wall3bof the chute (a powder/granular material feeding device according to a third embodiment of the present invention).

In the above-described embodiment, the stirring members4bof the stirring part4are extended from two points: the base and end of the shaft4a. The present invention is not limited to this configuration. As illustrated inFIG. 9, the stirring members4bmay be extended to two sides from a point of the shaft4a. Alternatively, as illustrated inFIGS. 10 and 11, a shaft4amay be further protruded upward with stirring members4bprovided at three points (or at least three points). Moreover, in the above-described embodiment, the stirring members4bare extended in the radial direction. The present invention is not limited to this configuration. The stirring members4bprovided at any intervals in a circumferential direction may be extended in multiple directions (at least three directions, a powder/granular material feeding device according to a fourth embodiment of the present invention).

In the drawings of the above-described embodiments, the single screw2bis illustrated. As has been discussed, double screws2binFIG. 12may be optionally disposed instead.

In the above-described embodiment, the driving force transmission mechanism including the worm gear6a, the stirring part gear4c, and the outlet gear2dis provided to transmit the driving force of the single motor6to the screw2bof the outlet portion2and the stirring part4. The screw2bof the outlet portion2and the stirring part4are driven through the driving force transmission mechanism. This configuration only requires the single motor, advantageously reducing the manufacturing cost.

The present invention is not limited to this configuration. As illustrated inFIG. 13, a motor11for rotating a screw2bof an outlet portion2and a motor12for rotating a stirring part4may be separately provided (a powder/granular material feeding device according to a fifth embodiment of the present invention). In this case, the number of motors11and12leads to higher manufacturing cost. However, the screw2bof the outlet portion2and the stirring part4can be separately driven or controlled with different adjusted rotation speeds.

In these embodiments, the side wall3cof the chute3is oval in plan view and has a constant cross-sectional shape in the vertical direction. The present invention is not limited to this configuration.FIGS. 14 to 18illustrate a powder/granular material feeding device according to a sixth embodiment of the present invention. As illustrated in these drawings, a side wall3cof a chute3in the powder/granular material feeding device expands in the lower part of the chute in cross section relative to the upper part. As illustrated inFIG. 14and so on, in the powder/granular material feeding device, the left side wall3cand the right side wall3cof the chute3expand in the lower part of the chute in front view. As illustrated inFIG. 15, the side wall3con the front end and the side wall3con the rear end are formed like vertical straight lines in side view. The side walls3care seamlessly connected in circumferential and vertical directions. Moreover, in the present embodiment, the upper end of the side wall3cof the chute3is circular in plan view (perfect circle) and a hopper1is a cylinder (perfect circle) as large as the upper end of the side wall3cof the chute3. The hopper1has a constant cross-sectional shape in the vertical direction.

With this configuration, the side wall3cof the chute3expands in the lower part of the chute in cross section relative to the upper part. Thus, powder/granular material introduced from the hopper1into the chute3is hardly compressed, so that a pressure on the side wall3cof the chute3decreases and powder/granular material deposited on the side wall3cis likely to fall off the side wall3cby its own weight. This configuration can satisfactorily prevent powder/granular material deposition on the side wall3cof the chute3. Since the hopper1and the upper end of the chute3are circular in plan view, a degree of curving is kept constant but is not locally increased unlike in the case of an oval shape in plan view, thereby satisfactorily preventing powder/granular material deposition on the side wall3cof the chute3. This configuration can prevent the occurrence of bridges in the chute3with higher reliability, stabilize the weight of powder/granular material discharged from the powder/granular material feeding device, and stabilize the rate of filling into a screw2bof an outlet portion2provided under the chute3, thereby improving the accuracy of feeding and reliability of the powder/granular material feeding device.

In this configuration, the hopper1and the upper end of the chute3are circular in plan view. Thus, the hopper1can be more easily formed than the oval hopper1. Furthermore, the hopper1and the chute3can be connected to each other with a simple structure, and the hopper can be also connected to other members with a simple structure, thereby reducing the manufacturing cost.

In the present embodiment, the powder/granular material feeding device is a screw feeder including the screw2bprovided in the outlet portion2. The present invention is not limited to this configuration. As illustrated inFIG. 19, the outlet portion2may be a feeder device including a belt-type feeder13(a powder/granular material feeding device according to a seventh embodiment of the present invention). The present invention is also applicable to a powder/granular material feeding device including an outlet portion with an on-off valve.