DEVICE FOR CONVEYING AND DOSING LOOSE MATERIAL

Description

field of technology

[0001] The invention relates to a device for conveying and metering bulk material, comprising a first conveying roller driven about a first axis of rotation and a second conveying roller driven in the opposite direction about a second axis of rotation, which are arranged side by side within a housing in an axially parallel position while maintaining a conveying and metering gap, wherein both conveying rollers have conveying elements over their circumference that draw the material supplied to the device via a material inlet into the conveying and metering gap and convey it as a continuous flow of material in the direction of flow to a material discharge. State of the art

[0002] The industrial production process, from raw material to finished product, often comprises several processing stations that are sequentially processed until the desired product properties are achieved. For example, consider the processing of fibrous feedstock, particularly lignocellulosic materials such as wood chips, annual plants, straw, bagasse, and the like. These materials undergo a series of processing stages, including pre-shredding, washing, dewatering, pre-steaming, cooking, fiberizing, drying, and separation. The fibers obtained can be used for pulp production in paper manufacturing or as wood fibers in the production of wood fiber products and wood-based materials, such as MDF. A similar process applies to free-flowing plastics like film shreds or granules, which, after washing, pre-shredding, and cleaning, are fed into an agglomerator, for instance.Using suitable conveying and dosing devices, the feed material is provided in the necessary quantity per unit of time at the individual processing stations.

[0003] Suitable conveying and metering devices include, for example, twin-roller conveyors, in which the two axially parallel conveying rollers rotate in opposite directions and draw the feed material into the gap between the rollers. The conveying capacity can be adjusted by regulating the speed of the conveying rollers. Such devices generally allow for conveying and metering the feed material with sufficient accuracy. However, problems arise with compact feed material or material prone to bridging, which is only insufficiently drawn into the roller gap by the conveying rollers. Feed material with an almost free-flowing consistency, which unintentionally flows through the roller gap without the intervention of the conveying rollers, can also prove problematic. In these cases, controlled metering of the feed material solely by adjusting the speed of the conveying rollers is no longer possible.

[0004] Furthermore, DE 260 220 C discloses a device for emptying the suction chambers of vacuum conveyors, the discharge device of which is designed as a capsule gear train. The two gears of the capsule gear train draw the conveyed material out of the suction chamber while simultaneously preventing atmospheric air from entering the suction chamber. To increase the sealing of the suction chamber, a sealing surface can be brought into contact with the gears from below. Summary of the invention

[0005] Against this background, the invention is based on the objective of providing a device for conveying and dosing bulk material, with which controlled conveying and precise dosing of material of various types and qualities is possible.

[0006] This problem is solved by a device having the features of claim 1.

[0007] Advantageous embodiments are described in the dependent claims.

[0008] The basic idea of ​​the invention is to be able to control the flow of material through a device according to the invention at any time by means of suitable design measures. According to the invention, this control is not limited to the operating state of conveying and metering, but also includes a standstill of the device, in which the material flow is to cease simultaneously with the stopping of the conveying rollers.

[0009] The invention achieves this through the interaction, according to the invention, of the conveying elements of the conveying rollers and the flow resistance element in the conveying and metering gap, wherein the conveying elements actively draw the feed material from the material inlet into the conveying and metering gap between the conveying rollers. There, the conveying rollers with their roller shell, together with the flow resistance element, form spatially defined areas in which the feed material is accelerated by the conveying elements through the conveying and metering gap, depending on the rotational speed of the conveying rollers.

[0010] This initially leads to the advantage of a uniform material flow through a device according to the invention, even with compact feed material or material prone to bridging, since the conveying elements first loosen the feed material at the feed point before it is subsequently gripped and conveyed to the conveying and metering gap. In this way, a sufficient quantity of feed material is prepared at the feed point to ensure that the conveying and metering gap can be supplied with a constant quantity per unit of time. As a result, extremely precise metering of the feed material within narrow limits can be achieved by controlling the speed of the drive of the conveying rollers.

[0011] Simultaneously, when the machine is stopped, the conveyor rollers and the flow resistance element form a barrier in the conveying and metering gap, preventing the flow of the feed material through the device. The feed material located upstream of the conveying and metering gap is thus retained in the feed inlet until the device is restarted.

[0012] The flow resistance element is preferably designed such that the material flow is not only slowed down but also advantageously divided and directed. To this end, the flow resistance element has two guide surfaces extending along its entire length, the longitudinal edges of which, facing away from the material flow, form a common longitudinal edge that divides the material flow into two partial flows. Preferably, this longitudinal edge lies above the plane defined by the two axes of rotation, thus ensuring the earliest possible division and promoting a uniform distribution of the material flow.

[0013] In an advantageous further development of this embodiment, the two guide surfaces of the flow resistance element diverge in the direction of the material flow and follow the circumference of the conveying rollers at a radial distance. This ensures intensive contact between the conveying elements and the feed material. Preferably, the guide surfaces have a concave cross-section to form a flow channel in the area of ​​interaction with the conveying rollers. Depending on the relative position of the flow resistance element with respect to the conveying rollers, this channel widens, narrows, or remains essentially constant in the flow direction.

[0014] According to a preferred embodiment of the invention, the position of the flow resistance element in the conveying and metering gap is adjustable, preferably its vertical position relative to the conveying rollers, in order to change the distance between the guide surfaces and the conveying rollers and thus the flow resistance exerted on the feed material. In a simple embodiment, this is achieved by attaching the flow resistance element to the device with fasteners engaging in elongated holes. Alternative adjustment devices consist, for example, of spindle drives or adjusting wedges with opposing wedge surfaces, which are actuated by means of actuators, so that adjustment of the flow resistance element is also possible during conveying and metering operation.

[0015] In a further embodiment of the invention, the flow resistance element is flexibly mounted on the device such that it can deflect in the direction of flow of the feed material when subjected to an extraordinary load exerted by the material flow. This flexible mounting can be elastic, meaning that the flow resistance element springs back to its original position after the extraordinary load ceases. In this way, a self-regulating effect occurs, whereby the flow resistance element yields when flow resistance increases, thereby reducing the flow resistance exerted on the material flow. Alternatively, the flexible mounting can also be achieved by permanently deforming the mounting of the flow resistance element.Under exceptional stress on the flow resistance element, for example due to foreign matter in the feed material, bearing components break or deform, allowing the flow resistance element to deflect in the direction of flow. This prevents major damage to the device. The invention also includes embodiments in which an elastic mounting of the flow resistance element is combined with a permanently deformable mounting.

[0016] In an advantageous embodiment of the invention, the conveying elements consist of rod-shaped conveying tines projecting radially from the roller shell and / or conveying strips extending axially along the roller shell, which exert a conveying effect on the feed material during the rotation of the conveying rollers. If the conveying rollers have both conveying strips and conveying tines, the conveying tines preferably form a radial projection beyond the conveying strips in order to effect the aforementioned loosening of the feed material and to enhance the conveying effect.

[0017] According to a further embodiment of the invention, the roller shell of the conveying rollers, which is effective for conveying and metering, consists of a circumferentially alternating sequence of conveying elements arranged along generatrices at uniform circumferential intervals, and conveying plates arranged between them. The conveying plates can be formed directly by circumferential sections of the base bodies of the conveying rollers, or by separate plates that lie on the base bodies of the conveying rollers or are arranged at a radial distance from them. The circumferential sections of the conveying rollers formed in this way, in conjunction with the flow resistance element, create temporary, spatially limited receiving areas in which the feed material is guided in a controlled manner through the conveying and metering gap. The advantage of this embodiment lies in the possibility of extremely precise metering.

[0018] Without limiting itself to this, the invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings, whereby further features and advantages of the invention become apparent. Where possible, identical reference numerals are used for identical or functionally equivalent features of different embodiments. Brief description of the drawings

[0019] It shows Fig. 1 shows an oblique view of a device according to the invention, Fig. 2 shows a cross-section through the in Fig. 1 The device shown in the xz plane, Fig. 3 an oblique view of a conveyor roller according to the invention on a larger scale, Fig. 4 an oblique view of a flow resistance element according to the invention on a larger scale, Fig. 5 a view of a partial section of the in Fig. 3 the conveyor roller shown, Fig. 6 a detailed view of the in Fig. 2The area marked VI, Fig. 7 shows a cross-section through a second embodiment of a device according to the invention with a flexible bearing of the flow resistance element, and Fig. 8 shows a cross-section through a third embodiment of a device according to the invention with an adjustment device for adjusting the height of the flow resistance element. Description of the embodiments

[0020] The Figs. 1 and 2Figure 1 shows an overview of the structure of a device 1 according to the invention. The device 1 has a housing 4 formed by transverse walls 2 and longitudinal walls 3, which has an upper opening 5 and, opposite it, a lower opening 6. A chute, feed shaft, funnel, or the like can be connected to the upper opening 5 to form a material inlet. The lower opening 6 serves as a material outlet, through which the feed material can be fed, for example, to a screw conveyor or belt conveyor, or directly to a processing machine such as a mill or the like. The direction of flow of the feed material in the device 1 is indicated by arrows 34.

[0021] The housing 4 encloses a conveying and metering chamber 7, in which a first conveying roller 9, driven about a first axis of rotation 8, is arranged, and a second conveying roller 11, driven in the opposite direction about a second axis of rotation 10, is arranged in a position parallel to the axis. The drive shafts 12 of the conveying rollers 9 and 11 are held in rotary bearings on the transverse walls 2 and each is coupled to a speed-controlled drive. For clarity, the rotary bearings and drives are shown in the Figs. 1 and 2 not shown. The opposing directions of rotation of the two conveyor rollers 9, 11 are symbolized by the two arrows 13, 14.

[0022] Especially from Fig. 2The relative arrangement of the two conveying rollers 9, 11 to each other is evident. It can be seen that the first axis of rotation 8 and the second axis of rotation 10 span a horizontal plane 15 in which the first conveying roller 9 and the second conveying roller 11 are positioned opposite each other along their entire axial length at a clear distance, maintaining a conveying and metering gap 16.

[0023] In the conveying and metering gap 16, a beam-shaped flow resistance element 17 extends parallel to the axes of rotation 8, 10 and cantilevered between the transverse walls 2, which is held in the conveying and metering gap 16 in a height-adjustable manner perpendicular to the plane 15 by means of an adjustment device.

[0024] The inventive design of the flow resistance element 17 results primarily from a combination of the Fig. 4 and 6, which show that the opposite ends of the flow resistance element 17 are each provided with an axially perpendicularly aligned head plate 18 with fastening holes 35.

[0025] For height-adjustable mounting of the flow resistance element 17, the mounting holes 35 align with vertically extending elongated holes 31 in the transverse walls 2 ( Fig. 1 The flow resistance element 17 can be fixed to the housing 4 in the predetermined height position relative to the plane 15 by means of fastening screws extending through the elongated holes 31 and fastening bores 35.

[0026] In the area between the end plates 18, the flow resistance element 17 has a constant cross-section, formed by a hollow or solid profile with a first guide surface 19 facing the first conveyor roller 9 and a second guide surface 20 facing the second conveyor roller 11. The upper longitudinal edges of the two guide surfaces 19, 20 form a common longitudinal edge 21, which lies above the plane 15 and points centrally between the two conveyor rollers 9, 11, opposite to the flow direction 34, towards the upper opening 5. The opposing lower longitudinal edges 22, however, also run parallel to each other at a distance below the plane 15. This results in the two guide surfaces 19, 20 diverging from the upper longitudinal edge 21 to the lower longitudinal edges 22, so that the flow resistance element 17 has a wedge-shaped cross-section.Without limiting ourselves to this, in the present embodiment the course of the guide surfaces 19, 20 essentially follows a circular path around the axes of rotation 8, 10 (. Fig. 6 ).

[0027] The constructive design of the conveyor rollers 9, 11 is shown in particular by the Fig. 2 , 3 , 5 and 6Accordingly, the conveying rollers 9, 11 have a solid or hollow cylindrical base body 23 with a circular cross-section in the present embodiment, although equilateral polygonal cross-sections, such as a hexagon or octagon, are equally suitable. Radially directed conveying tines 26 extend from the cylindrical surface 24 of the base body 23 along generatrix 25 at uniform circumferential or angular intervals, for example, 30°, 45°, or 60°. The conveying tines 26 of a common generatrix 25 maintain a mutual axial distance b. For example, the axial distance b can be 40 mm or less. The conveying tines 26 of two circumferentially adjacent generatrix 25 can be arranged with an axial offset from each other or lie on common circumferential lines. The conveying tines 26 are, for example, formed from bars of wear-resistant material and are screwed or welded to the base body 23.The free ends of the conveying tines 26 can be blunt, edged, or pointed.

[0028] Each conveying roller 9, 11 also has a roller shell 27 arranged coaxially to the axis of rotation 8, 10, which is effective for conveying and metering the feed material and which - as in the present embodiment - surrounds the base body 23 at a radial distance, but can also be in contact with the outer surface 24 of the base body 23 in whole or in part or be formed directly by the outer surface 24 of the base body 23.

[0029] The roller shell 27, with respect to the roller cross-section, is composed alternately of conveying strips 28 and conveying bases 29, each extending over the entire axial length of a conveying roller 9, 11. The conveying strips 28 extend between or along the conveying tines 26 of a shell line 25, to which they are rigidly attached. With their radially inner longitudinal edges, the conveying bars 28 are firmly connected to the longitudinal edges of the conveying plates 29, so that a contour closed over the circumference of the roller shell 27 is formed, with an alternating sequence of conveying bars 28 with conveying tines 26 and conveying plates 29. In this way, each pair of adjacent conveying bars 28 with an intermediate conveying plate 29 forms axially parallel, trough-shaped receptacles in cross-section and open towards the flow resistance element 17, which, in conjunction with the conveying tines 26, draw the feed material into the conveying and metering gap 16.

[0030] The relative position of the conveying bars 28 to the conveying tines 26 is chosen such that the conveying tines 26 with their free ends each form a radial projection c over the radially outer longitudinal edge 30 of the conveying bars 28 ( Fig. 5 For example, the radial height of the conveyor bars 28 can be between 3 mm and 30 mm and / or the projection c can be in a range between 10 mm and 30 mm.

[0031] The axial ends of the conveyor rollers 9, 11 are each formed by a ring disk 36, which sits coaxially with its inner circumference on the shaft section 12 there and to whose outer circumferential area the roller shell 27 connects.

[0032] Fig. 6Figure 1 shows the detailed design of the device 1 in the area of ​​the conveying and metering gap 16. The facing sections of the first conveying roller 9 and the second conveying roller 11 are visible, each with a base body 23, conveying tines 26, conveying strips 28 and a conveying base 29. During the rotation of the conveying rollers 9 and 11, the ends of the conveying tines 26 describe a circular path, which is indicated by reference numeral 32.

[0033] Parallel to the axis between the two conveyor rollers 9, 11 runs the wedge-shaped flow resistance element 17, the upper longitudinal edge 21 of which lies above the plane 15 and whose guide surfaces 19, 20 extend into the area below the plane 15 at a constant radial distance r to the flow circles 32. For example, the distance r is a maximum of 10 mm and preferably lies in a range between 1 mm and 5 mm.

[0034] The dimensions of the flow resistance element 17 perpendicular to the plane 15 are such that, in every position of the conveyor rollers 9, 11, at least one conveyor bar 28 with conveyor tines 26 is radially opposite the first guide surface 19 or the second guide surface 20. Fig. 6An operating condition is shown in which two circumferentially adjacent conveyor bars 28 with conveying tines 26 are simultaneously radially opposite the guide surfaces 19, 20 and thus, during the rotation of the conveying rollers 9, 11, form temporary chambers 33 in which the feed material is guided in a controlled manner through the conveying and metering gap 16. In this case, the circumferential distance between two adjacent conveyor bars 28 is smaller than the dimension of the guide surfaces 19, 20 between the upper longitudinal edge 21 and the lower longitudinal edges 22. The feed material is metered by appropriately adjusting the rotational speed of the conveying rollers 9, 11. When the device 1 is stationary, the flow resistance element 17 and the radially opposite conveyor bars 28 with conveying tines 26 form a flow obstruction that prevents unwanted material passage through the conveying and metering gap 16.

[0035] The in the Figs. 7 and 8The embodiments shown largely correspond to those described below. Figs. 1 to 6 described, so that, to avoid repetition, reference is made to what has been said there using identical reference marks.

[0036] In contrast, the flow resistance element 17 according to the embodiment according to Fig. 7 The device 1 is flexibly mounted in the flow direction 34. For this purpose, the device 1 has at least one spring element 37, which is arranged between the housing 4 and the flow resistance element 17. For example, a spring element 37 can be provided in the area of ​​each of the end plates 18, or the spring element 37 can extend over the entire axial length of the flow resistance element 17.

[0037] The spring element 37 comprises a lower part 38 with circumferential side walls, attached to the housing 4, and an upper part 39 with circumferential side walls, attached to the flow resistance element 17. The side walls of the lower part 38 and the upper part 39 face each other and enclose a cavity 40. The distance between the side walls of the lower part 38 and the upper part 39 is smaller than the distance between the side walls of the upper part 39 such that the lower part 38 and the upper part 39 can be inserted into one another in the flow direction 34, with their side walls overlapping.

[0038] The spring action of the spring element 37 is generated by one or more elastically deformable elements 41 extending between the lower part 38 and the upper part 39. An elastically deformable element 41 can, for example, consist of a coil spring, a gas spring, an elastically compressible material such as rubber, or the like.

[0039] Under the influence of a high load on the flow resistance element 17, caused by the flowing feed material or foreign matter contained therein, the flow resistance element 17 deflects downwards in the flow direction 34. The distance between the flow resistance element 17 and the conveyor rollers 9, 11 increases, and consequently, the flow resistance exerted on the material flow decreases. After the extraordinary load condition ends, the spring element 37 returns the flow resistance element 17 to its original position. The flow resistance element 17 can be guided, for example, along the elongated holes 31, into which guide pins on the flow resistance element 17 engage.

[0040] Instead of an elastically deformable spring element 37, the flexible bearing can also be formed by a unit that permanently deforms when a limit load is exceeded, so that the flow resistance element 17 no longer returns to its original position. For this purpose, the flexible bearing can be formed instead of the one described in Fig. 7 The elastic elements shown (41) may have plastically deformable elements or predetermined breaking points not shown.

[0041] subject of Fig. 8This embodiment is characterized by a targeted adjustability of the flow resistance element 17 in the conveying and metering gap 16 perpendicular to the plane 15, for example to adapt to the properties of the feed material and to optimize the metering and conveying function of the device 1. For this purpose, an adjustment device 42 is arranged between the housing 4 and the flow resistance element 17, for example in the form of a cylinder-piston unit, the cylinder 34 of which is attached to the housing 4 of the device 1 and the movable piston of which is articulated with piston rod 44 to an axis 45 that extends between the two end plates 18.Alternative adjustment devices 42 can have a spindle drive instead of the cylinder-piston unit or be formed by horizontally adjustable wedges whose opposing inclined wedge surfaces rest against each other, whereby the height of the flow resistance element 17 is adjusted by a relative movement of the wedges to each other. Here, too, the elongated holes 31 can guide the flow resistance element 17 during adjustment, cooperating with guide pins on the flow resistance element 17.

[0042] Although not explicitly shown in the drawings, the invention also encompasses embodiments in which the roller shell 27 is formed directly from the outer surface 24 of the roller base body 23, or embodiments in which the conveying elements are formed solely by conveying tines 26 or solely by conveying bars 28. Likewise, the invention includes combinations of features from different embodiments, even if these are not explicitly described. For example, a flexible mounting of the flow resistance element 17 can be combined with an adjustment device 42.

Claims

1. Device for conveying and metering free-flowing feed material, the device comprising a first conveyor roller (9) driven about a first rotation axis (8) and a second conveyor roller (11) driven in the opposite direction about a second rotation axis (10), which rollers are arranged next to one another within a housing (4) in an axially parallel position while maintaining a conveying and metering gap (16), both conveyor rollers (9, 11) having conveyor elements (26, 28) over the roller circumference thereof, which draw the feed material (34) supplied via a material inlet of the device (1) into the conveying and metering gap (16) and convey it as a continuous material flow in the flow direction (34) to a material output, characterized in that a flow resistance element (17) is arranged in the conveying and metering gap (16) between the first conveyor roller (9) and the second conveyor roller (11), which flow resistance element extends over the axial length of the two conveyor rollers (9, 11) and cooperates with the two conveyor rollers (9, 11)for conveying and metering the feed material (34), in each case a distance being maintained between the flow resistance element (17) and the first conveyor roller (9) and between the flow resistance element (17) and the second conveyor roller (11), and the feed material passing through the conveying and metering gap (16) between the flow resistance element (17) and the two conveyor rollers (9, 11).

2. Device according to claim 1, characterized in that the flow resistance element (17) is bar-shaped and has a first guide surface (19) facing the first conveyor roller (9) and a second guide surface (20) facing the second conveyor roller (11).

3. Device according to claim 2, characterized in that the first guide surface (19) and the second guide surface (20) each form a common longitudinal edge (21) with the first longitudinal edge thereof pointing against the flow direction (34).

4. Device according to claim 3, characterized in that the longitudinal edge (21) is arranged upstream of the plane (15) spanned by the first rotation axis (8) and the second rotation axis (10).

5. Device according to any of claims 2 to 4, characterized in that the first guide surface (19) and the second guide surface (20) diverge in the direction of the second longitudinal edges (22) thereof pointing in the flow direction (34).

6. Device according to any of claims 2 to 5, characterized in that the first guide surface (19) and the second guide surface (20) are concave in cross-section and the flight circles (32) of the conveyor elements (26, 28) of the first conveyor roller (9) and the second conveyor roller (11) having the first guide surface (19) and the second guide surface (20) maintain a radial distance r which remains constant in the direction of rotation (13, 14) or increases in the direction of rotation (13, 14) or decreases in the direction of rotation (13, 14).

7. Device according to any of claims 1 to 6, characterized in that the position of the flow resistance element (17) relative to the conveyor rollers (9, 11) can be adjusted in or against the flow direction (34) by means of an adjusting apparatus (42).

8. Device according to claim 7, characterized in that the adjusting apparatus (42) comprises elongate holes (31) and the flow resistance element (17) is fastened to the device (1) by means of fastening screws (35) extending through the elongate holes (31).

9. Device according to claim 7, characterized in that the adjusting apparatus (42) comprises a spindle drive or cylinder-piston unit (43, 44) which acts between the flow resistance element (17) and the device (1).

10. Device according to claim 7, characterized in that the adjusting apparatus (42) comprises adjusting wedges which are arranged between the flow resistance element (17) and the device (1) and have opposing wedge surfaces which are adjustable relative to one another.

11. Device according to any of claims 1 to 10, characterized in that the conveyor elements (26, 28) are arranged at a uniform circumferential distance along shell lines (25) of the first conveyor roller (9) and the second conveyor roller (11).

12. Device according to any of claims 1 to 11, characterized in that the conveyor elements are formed by conveyor strips (28) and / or conveyor tines (26) which extend radially from the shell surface (24, 27) of the conveyor rollers (9, 11).

13. Device according to any of claims 1 to 12, characterized in that the conveyor elements are formed by conveyor strips (28) and conveyor tines (26), the conveyor strips (28) being arranged between or along the conveyor tines (26) along a shell line (25).

14. Device according to either claim 12 or claim 13, characterized in that the conveyor tines (26) form a radial projection a relative to the conveyor strips (28).

15. Device according to any of claims 1 to 14, characterized in that the roller shell (27) effective for conveying and metering the feed material (34) has conveyor floors (29) in addition to the conveyor elements (26, 28), and the conveyor floors (29) each extend between conveyor elements (26, 28) which are adjacent in the circumferential direction of the roller.

16. Device according to any of claims 1 to 15, characterized in that the roller shell (27) effective for conveying and metering the feed material has a polygonal or circular cross-section.

17. Device according to either claim 15 or claim 16, characterized in that the first conveyor roller (9) and / or the second conveyor roller (11) have a cylindrical main body (23) and the conveyor floors (29) are arranged radially outside the main body (23).

18. Device according to any of claims 1 to 17, characterized in that the flow resistance element (17) is resiliently mounted in the flow direction (34).