Dosing apparatus for powder, granule or flake materials

Abstract

A dosing apparatus (1) for powder, granule or flake materials includes a tank (2) configured to contain a material to be dosed, wherein the tank (2) communicates with a first dosing device (8) and with a second dosing device (9), in which the first dosing device (8) and the second dosing device (9) communicate with a dispensing element (30) by which said material can be dispensed into a container; the tank (2) is provided with a flat bottom (5) in which a first opening (6) is made, through which the material to be dosed is fed to the first dosing device (8), and a second opening (7) is made through which the material to be dosed is fed to the second dosing device (9), wherein inside the tank (2) a stirring element (24) is arranged, which can rotate around a respective axis of rotation (25) substantially perpendicular to the bottom (5) of the tank (2), said stirring element (24) being provided with one or more stirring arms (42), wherein at least one of the stirring arms (42) can be internally hollow and be provided with a plurality of openings (44) facing the bottom (5) of the tank (2), by which a flow of compressed gas can be sent to the first opening (6) and the second opening (7).

Description

DOSING APPARATUS FOR POWDER, GRANULE OR FLAKE MATERIALSBACKGROUND OF THE INVENTION

[0001] The present invention relates to a dosing apparatus for powder, granule or flake material.

[0002] In particular, the invention relates to a dosing apparatus for dispensing with great precision dosed quantities of dry loose products, in powder, granule, flake, chip or pellet state.PRIOR ART

[0003] Dosers are known from the prior art that comprise a containing chamber that is fed, for example by a hopper, with the material to be dosed.

[0004] In the lower part of the containing chamber, a feed screw dosing device is arranged, which can comprise a single feed screw or also a double feed screw, with a substantially horizontal axis of rotation, each of which is driven by a respective motor.

[0005] Inside the containing chamber, a homogenizing device is also arranged that mixes the material to be dosed and maintains the material aerated.

[0006] The homogenizing device comprises a plurality of vanes fixed to a shaft that can rotate around a substantially horizontal axis of rotation.

[0007] The object of the homogenizing device is to prevent, as far as possible, the risk that material accumulates above the dosing device, compromising correct operation of the dosing apparatus.

[0008] However, as the entire mass of the material contained inside the containing chamber rests on the feed screw, or on the feed screws of the dosing device, it is substantially inevitable that material accumulates in the transit zone between the containing chamber and the dosing device, which compromises product feeding capacity and thus the dosing precision of the dosing apparatus.

[0009] One object of the present invention is to eliminate the risk of material accumulating in the transit zone between the containing chamber containing the material to be dosed and the dosing device, thus ensuring constant dosing precision of the dosing device.

[0010] Another object of the present invention is to ensure constant feeding to the dosing device so as to improve the dosing precision of the dosing apparatus and extend both the continuous and batch dosing range.SUMMARY OF THE INVENTIONThe objects of the invention are achieved by a dosing apparatus for powder, granule, flake, chip and pellet materials, comprising a tank, opened above, configured to contain a material to be dosed, wherein the tank communicates with a first dosing device and with a second dosing device, wherein the first dosing device and the second dosing device communicate with a dispensing element by which said material can be dispensed into a container, characterized in that the tank is provided with a flat bottom in which a first opening is made, through which the material to be dosed is fed to the first dosing device, and a second opening is made, through which the material to be dosed is fed to the second dosing device, wherein inside the tank a stirring element is arranged, which can rotate around a respective axis of rotation substantially perpendicular to the bottom of the tank, said stirring element being provided with one or more stirring arms, one of which can be internally hollow and be provided with a plurality of openings facing the bottom of the tank, by which a jet of compressed air can be sent to the first opening and to the second opening.Owing to the invention, it is possible to avoid with certainty the formation of accumulations, or bridges, of material on the openings through which the material to be dosed moves from the tank that contains the material to the dispensing devices because accumulations, or bridges, of material that start to form at the aforesaid openings can be immediately eliminated.The invention further permits very high dosing precision.The double feed screw further enables the dosing range to be extended.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further features and advantages of the invention will be clear from the following description of an embodiment of the invention that is provided purely by way of non-limiting example, with reference to the attached drawings, in which: figure l is a perspective top view of a dosing apparatus according to the invention; figure 2 is a perspective bottom view of the doser of figure 1; figure 3 is a raised view of the dosing apparatus of figure 1; figure 4 is a plan view of the dosing apparatus of figure 1; figure 5 is a section of the dosing apparatus according to the invention, along the line V-V in figure 3;figure 6 is a section of the dosing apparatus according to the invention, along the line VI- VI in figure 4; figure 7 is a section of the dosing apparatus according to the invention, along the line VII- VII in figure 4; figure 8 is an enlarged detail of figure 5; figure 9 is an enlarged detail of figure 7.DETAILED DESCRIPTION OF THE INVENTION

[0012] With reference to the figures, a dosing apparatus 1 for dosing powder, granule, flake, chip and pellet materials, according to the invention includes a tank 2, for example in the form of a hopper open above intended to contain the material to be dosed.

[0013] The tank 2 is fixed to a support element 3, which is in turn fixed to a base 4 of the dosing apparatus 1. The base 4 can comprise a plate 36, provided with a plurality of pins 37, which constitute a hooking system, by which the base 4 can be hooked by a robot arm to move the dosing apparatus 1.

[0014] The tank 2 is provided with a flat bottom 5, in which a first opening 6 is made, through which the material to be dosed is fed to a first dosing device 8, and a second opening 7 is made through which the material to be dosed is fed to a second dosing device 9. On the perimeter of the first opening 6 and of the second opening 7, a plurality of holes or nozzles can be provided by means of which a compressed gas can be injected to fluidify the material to be dosed and prevent the formation of bridges of material that could obstruct, even only partially, the openings 6 and 7, compromising dosing precision.

[0015] The first dosing device 8 and the second dosing device 9 are fixed to the support element 3.

[0016] Inside the tank 2, a stirring element 24 is arranged, which can rotate around a respective axis of rotation 25 substantially perpendicular to the bottom 5 of the tank 2.

[0017] The stirring element 24 is used to mix the material contained in the tank 2, so as to fluidify the material and prevent material bridges being formed that could obstruct, even only partially, the first opening 6 and / or the second opening 7, compromising dosing precision.

[0018] The stirring element 24 is rotated by a respective motor 26 connected to a respective shaft 27 of the stirring element 24 by a respective reduction gear, or worm reduction gear

[0019] The stirring element 24 is provided with a plurality of stirring arms 42, for example three, which extend radially from a hub 43 fixed to the respective shaft 27.

[0020] The stirring arms 42 are arranged preferably at a constant angular pitch around the hub 43 and extend on a plane substantially parallel to the bottom 5 of the tank 2.

[0021] At least one of the stirring arms 42 can be hollow and be provided with a plurality of openings 44 facing the bottom 5 of the tank 2. The hollow stirring arm 42 can be connected to a compressed air source so as to send, through the aforesaid openings 44, a flow of compressed air to the first opening 6 and / or the second opening 7, to break up possible bridges of material that start to form on the first opening 6 or on the second opening 7. In this manner, it is possible to prevent with certainty the formation of the aforesaid bridges, which might form despite the continuous action of mixing the material to be dosed, which is performed by the stirring arms 42.

[0022] The hub 43 can be provided with a gas supply system, which has a dual function: supplying the hollow stirring arm 42 and supplying a dust seal system placed therein. This dust seal system prevents dust entering inside the rotation shaft and water infiltrations during washing operations.

[0023] The respective shaft 27 of the stirring element is associated with an inductive sensor 35, or with an encoder, or a similar system, which is used to detect the angular position of the respective shaft 27 of the stirring element 24, so as to command the dispensing of compressed air when the hollow stirring arm 42 is at the first opening 6, or at the second opening 7.

[0024] The first dosing device 8 is a feed screw dosing device, which comprises a first cylindrical casing 10, with a first inner diameter D 1 , inside which a first screw 11 is arranged, which is rotated around a first axis of rotation 12 by a first motor 13, for example a brushless motor, connected to a first shaft 14 of the first screw 11, for example by a first reduction gear 15.

[0025] The first inner diameter DI corresponds to the outer diameter of the first screw 11, less the clearance necessary to enable the first screw 11 to rotate inside the first cylindrical casing 10.

[0026] The rotation speed of the first motor 13 is adjustable, for example, between 0 and 3000 rpm, or between 0 and 6000 rpm, or between 0 and 12000 rpm.

[0027] The reduction ratio of the first reduction gear 15 can be advantageously set at 1 / 10, or have any other value.

[0028] At the first opening 6 of the bottom 5 of the tank 2, the first cylindrical casing 10 has a third opening 22, that, together with the first opening 6, places the inside of the tank 2 in communication with the inside of the first cylindrical casing 10 of the first feed screw dosing device 8.

[0029] The first screw 11 has a first pitch P0 in a first zone 35, that is at the third opening 22, and a second pitch Pl, in a second zone 36, which follows the first zone 35. The first pitch P0 can be less than the second pitch Pl, to facilitate breaking up of possible bridges of material that may form in the opening 22.

[0030] Also the second dosing device 9 is a feed screw dosing device that comprises a second cylindrical casing 16, with a second inner diameter D2, inside which a second screw 17 is arranged, with a third pitch P2 that is less than the second pitch Pl. The second screw 17 is rotated around a second axis of rotation 18 by a second motor 19, for example a brushless motor, connected to a second shaft 20 of the second screw 17, for example by a second reduction gear 21.

[0031] The second inner diameter D2 corresponds to the outer diameter of the second screw 17 less the clearance necessary to enable the second screw 17 to rotate inside the second cylindrical casing 16.

[0032] The rotation speed of the second motor 19 is adjustable, for example, between 1 and 3000 rpm.

[0033] The reduction ratio of the second reduction gear 21 can be advantageously set at 1 / 15, or have any other value.

[0034] At the second opening 7 of the bottom 5 of the tank 2, the second cylindrical casing 16 has a fourth opening 23, that, together with the second opening 7, places the inside of the tank 2 in communication with the inside of the second cylindrical casing 16 of the second feed screw dosing device 9.

[0035] A P1 / P2 ratio between the second pitch Pl and the third pitch P2 can be advantageously set between 3 and 5, in particular equal to 4, for example with Pl=80 mm and P2 =20 mm, whereas the first pitch P0 can be set at 50 mm.

[0036] A ratio D1 / D2 between the first diameter DI and the second diameter D2 can be advantageously set between 2.5 and 3.5, in particular equal to 3, for example with Dl= 84 mm and D2= 28 mm.

[0037] The first dosing device 8 is provided with a first discharge port 29, obtained at an end of the first cylindrical casing 10 and communicating with a chamber 31 of a dispensing element 30.

[0038] The second dosing device 9 is provided with a second discharge port 32, obtained at an end of the second cylindrical casing 16 and communicating with the chamber 31 of the dispensing element 30.

[0039] The chamber 31 communicates below with a dispensing frustoconical element 33, terminating in a dispensing opening 34, through which the material, discharged into the chamber 31 by the first dosing device 8 and by the second dispensing device, is dispensed into a floppy or stiff container, which is not shown.

[0040] The dispensing element 30 can be further provided with a powder recovery system, for recovering the powder that could exit the container in which the material is being dosed. This system extends along the perimeter of the frustoconical element 33.

[0041] The first discharge port 29 of the first dosing device 8 can be closed by a sliding first closing device 38, for example a plate, arranged inside the chamber 31, and movable, by a first operating cylinder 39, for example a pneumatic operating cylinder, between a first position, in which the first closing device 38 does not interact with the first discharge port 29, and a second position, in which the first closing device 38 occludes completely the first discharge port 29.

[0042] The second discharge port 32 of the second dosing device 9 can be closed by a sliding second closing device 40, for example a plate, arranged inside the chamber 31, and movable, by a second operating cylinder 41, for example a pneumatic operating cylinder, between a first position, in which the second closing device 40 does not interact with the second discharge port 32, and a second position in which the second closing device 40 occludes completely the second discharge port 32.

[0043] Using a first feed screw dosing device 8 and a second feed screw dosing device 9, with screws of different diameter and different pitch, in addition to the wide adjusting field of the rotation speed of the first motor 13 and of the second motor 19 permit great flexibility and great dosing precision, with respect to known prior-art dosing apparatuses.

[0044] The first dosing device 8 performs initial rough dosage of the material to be dosed, whereas the second doser 9 performs precision dosage of the material. For dosing very small or very large quantities of material, also just one of the two screws can be used.

[0045] The dosing precision that can be achieved by the dosing apparatus according to the invention is equal to 0.1g.

Claims

CLAIMS1. Dosing apparatus (1) for powder, granule, flake, chip or pellet materials, including a tank (2), configured to contain a material to be dosed, wherein the tank (2) communicates with a first dosing device (8) and with a second dosing device (9), wherein the first dosing device (8) and the second dosing device (9) communicate with a dispensing element (30) by which said material can be dispensed into a container, characterized in that the tank (2) is provided with a flat bottom (5) in which a first opening (6) is made, through which the material to be dosed is fed to the first dosing device (8), and a second opening (7) is made through which the material to be dosed is fed to the second dosing device (9), wherein inside the tank (2) a stirring element (24) is arranged, which can rotate around a respective axis of rotation (25) substantially perpendicular to the bottom (5) of the tank (2), said stirring element (24) being provided with a plurality of stirring arms (42), wherein at least one of the stirring arms (42) is internally hollow and is provided with a plurality of openings (44) facing the bottom (5) of the tank (2), by which a flow of compressed air can be sent to the first opening (6) and the second opening (7).

2. Dosing apparatus (1) according to claim 1, wherein the stirring element (24) is associated with a sensor element configured to detect an angular position of a respective shaft (27) of the stirring element (24), during the rotation of the latter around the respective axis of rotation (25).

3. Dosing apparatus (1) according to claim 2, wherein the stirring arms (42) extend radially from a hub (43) fixed to the respective shaft (27), in which the stirring arms extend on a plane substantially parallel to the bottom (5).

4. Dosing apparatus (1) according to claim 3, wherein the stirring arms (42) are arranged at a substantially constant angular pitch around the hub (43).

5. Dosing apparatus (1) according to one of the preceding claims, wherein the internally hollow at least one of the stirring arms (42) is configured to be connected to a source of compressed air.

6. Dosing apparatus (1) according to one of the preceding claims, wherein the first dosing device (8) is a feed screw dosing device that includes a first cylindrical casing (10)inside which a first screw (11) is arranged that is rotatable around a first axis of rotation (12) wherein the first cylindrical casing (10) is provided with a third opening (22), communicating with the first opening (6).

7. Dosing apparatus (1) according to claim 6, wherein the first screw (11) has a first pitch (P0) in a first zone (35), which is at the third opening (22), and a second pitch (Pl), in a second zone (36) that extends from the first zone (35) as far as a first discharge port (29) obtained at an end of the first cylindrical casing (10), wherein the first pitch (P0) is less than the second pitch (Pl).

8. Dosing apparatus (1) according to one of the preceding claims, wherein the second dosing device (9) is a feed screw dosing device that includes a second cylindrical casing (16) inside which a second screw (17) is arranged that is rotatable around a second axis of rotation (18), wherein the second cylindrical casing (16) is provided with a fourth opening (23), communicating with the second opening (7).

9. Dosing apparatus (1) according to claim 8, wherein the second screw (17) has a third pitch (P2) that is less than the second pitch (Pl) of the first screw (11).

10. Dosing apparatus (1) according to one of claims 6 to 9, wherein the first screw (11) is rotated by a first motor (13) by a first reduction gear (15), wherein a rotation speed of the first motor (13) is adjustable between 1 and 3000 rpm, wherein a reduction ratio of the first reduction gear (15) is equal to 1 / 10.

11. Dosing apparatus (1) according to one of claims 8 to 10, wherein the second screw (17) is rotated by a second motor (19) by a second reduction gear (21), wherein a rotation speed of the second motor (19) is adjustable between 1 and 3000 rpm, wherein a reduction ratio of the second reduction gear (21) is equal to 1 / 15.

12. Dosing apparatus (1) according to one of claims 7 to 11, wherein the first discharge port (29) of the first dosing device (8) and a second discharge port (32) of the second dosing device (9), obtained at one end of the second cylindrical casing (16), communicates with a chamber (31) of a dispensing element (30), wherein the chamber (31) communicates with a dispensing frustoconical element (33) terminating in a dispensing opening (34).

13. Dosing apparatus (1) according to claim 12, characterized in that it further includes a first closing device (38) configured to completely occlude the first discharge port (29) of the first dosing device (8) and a second closing device (40) configured to completely occlude the second discharge port (32) of the second dosing device (9).

14. Dosing apparatus (1) according to one of claims 8 to 13, wherein a ratio between a first inner diameter (DI) of the first cylindrical casing (10) and an inner diameter (D2) of the second cylindrical casing (16) is comprised between 2.5 and 3.5, in particular is equal to 3.

15. Dosing apparatus (1) according to one of claims 9 to 14, wherein a ratio between the second pitch (Pl) of the first screw (11) and a third pitch (P2) of the second screw 17 is comprised between 3 and 5, in particular is equal to 4.

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