TECHNICAL FIELD

The invention concerns a device relating to a feeder tube, i.e. a conveyor intended for bulk product, in particular a feed-out device, which comprises a cylindrical drum or tube in which there are accommodated inlet openings distributed along the length of the tube, a screw conveyor disposed coaxially with the tube within the tube, means for rotating the tube about its axis, means for rotating the screw conveyor relative to the tube, means for displacing the feeder tube in the lateral direction.

PRIOR ART

Feeder tubes of the above-stated type are previously known and commonly used. Examples of such feeder tubes are described in SE 7611862-9, which describes a first generation non reversible feeder tubes. A second generation with reversible feeder tubes are known from W09526310 and WO02090223. Feeder tubes can be used as conveyors for a host of different bulk products (bulk material) such as wood chips, coal, paper pulp, peat, sand, cement, ashes, grain, pellets, etcetera. In order to facilitate the movements of the goods in the silo or equivalent in which the bulk product is stored and stimulate its feed-in through feed-in openings, activators, i.e. projections on the tube, are located at the back edge of the inlet openings. By back edge is herein meant the rear edge of the inlet opening viewed in the direction of rotation. A general problem with feeder tubes of this kind is spillage of bulk, at one end of the feeder tube. i.e. at the end side opposite it ^' s outlet end or feeding side. This end side of the feeder tube protrudes out from the silo through a longitudinal opening in the silo side wall and rests upon a movable supporting wagon. A traversing kind of feeder tube is configured to move back and forth by the wagons and along the longitudinal opening during conveying operation. The wagon upon which the feeder rests is arranged to move along a side like space positioned next to the longitudinal opening outside of the silo. A heretofore unsolved problem is that bulk material that exits through the longitudinal opening in the silo wall and pile up in the side like space in front of the feeder tube as it moves in a lateral direction. In W09526310 there is suggested a solution to this using fixed outer threads. At the portion of the tube which is protruding out from the silo there is no head load from bulk product and therefore the feeding into the feeder tube will be less efficient than along the rest of the feeder tube inside the silo where it is subject to gravitational pressure. It may be difficult to collect all the material from the side space into the feeder and as a consequence, a pile of bulk products may accumulate in front of the moving feeder tube, that will eventually spill over and out of the side. Accordingly it leads to undesired spillage.

SUMMARY OF THE INVENTION

It is an object of the invention to improve on the situation described above, e.g. to minimize spillage, which is achieved by means of a feeder tube arranged in accordance with the appended claims.

Thanks to the invention an improved feeding of bulk material may be achieved also at the outer end of the feeder tube (i.e. the end portion of the feeder opposite the outlet portion) despite lack of pressure from bulk material at this part of the feeder. Substantial savings may be achieved thanks to minimized spillage and also an improved

environment is obtained. Bulk material with certain flow characteristics like pellets has not earlier been possible to handle with previous feeder design but thanks to the invention it is possible to control flow as well as reclaim.

Further aspects will be evident from the following.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description of some preferred embodiments, reference will be made to the appended drawings, in which:

Fig. 1 schematically shows a feeder tube disposed in a silo for bulk product,

Fig. 2 schematically shows a side view of a feeder tube according to an embodiment of the invention, in operation,

Fig. 3 shows a front view, i.e. 90 degrees compared to Fig. 2, of a feeder tube

according to the invention,

Fig. 4 shows a cross-sectional view of a portion of the feeder tube of Fig. 3,

Fig. 5 shows a feeder tube according to a further embodiment of the invention, Fig 6 shows the same view as Fig 3, with the feeder tube 90 degrees further rotated, Fig 7 shows a perspective view of a feeder tube according to the a further embodiment of the invention,

Fig 8 shows a front view of a further embodiment of the invention,

Fig 9 shows the conveyer screw of feeder tube according to Fig 8, and

Fig 10 schematically shows a side view of a modified feeder tube according to the

invention. DESCRIPTION OF PREFERRED EMBODFMENTS

With reference to Fig. 1 there is shown a reversible feeder tube having a known basic construction, comprising a cylindrical reversible tube 1 and a screw conveyor 2 disposed coaxially within the tube. Further, there are one or more motors (not shown) for rotating the tube 1 about its axis and for rotating the screw conveyor 2 relative to the tube and so-called "traversing gear" (not shown) for moving the entire feeder tube in the lateral direction through bulk material within a compartment such as a silo, (as is known per se). This lateral displacement is effected directly at right-angles to the axis of the feeder tube 1, within a silo 3 for bulk product (not shown) adjacent the bottom 30 of the silo 3, feeding bulk in a direction away from a tail end 1 A into an output space 6. That which has hitherto been described belongs to the prior art and does not therefore constitute any part of the new invention. The outer end 1 A of the feeder tube 1, 2 protrudes through a lower opening 31 in the silo and rests upon a support wagon 5 which can move in a lateral direction in a side space 4. A vertical plate 32 protrudes at the outer edge of the silo bottom 30, to a height H below the centre of the tube 1. The feeder tube 1,2 continuously feeds out material into the output space 6. During extraction operation the bulk near the feeder tube will get stirred and set into motion leading to that some product will inevitably fall into and enter the side space 4 and accumulate, in front of the moving tube, eventually creating spillage. According to the invention measures are taken to avoid or at least minimize such spillage. In Fig. 2 there is shown a schematic side view of the outer part of the feeder tube 1, 2 according to the invention. As shown the outer tube 1 rotates in a direction C such that its lower surface will move in the same direction B as the movement of the whole feeder tube 1, 2, and with a higher speed than the travel speed B of the whole tube 1. This will to a height that may surpass the height H of the vertical plate 32, leading to undesired spillage into the side space 4. Create a pile of bulk material 8 building up in front of the feeder tube 1, 2. In order to improve feeding of bulk material 8 into the feeder tube 1,2 also within the side space 4 the feeder tube is arranged with one or several feeding device 7. Fig. 3 is showing that the feeding device 7 may be positioned adjacent the outer tail end 1 A of the feeder tube and in this embodiment symmetrically arranged in a relation to an inlet opening 10. A symmetrical arrangement is not required but feeding device 7 may be positioned at any angle along circumference of outer tube 1. The feeding device 7 comprises a triangularly shaped base part 70 and radially outwards on top of that 70 there is a curved plate 74 that may extend further than the triangular body 70. The outer edge 74A of the plate 74 is positioned substantially in line with the outer wall 73 of the triangular body 70. The inner edge 74B may substantially be in line with an apex 78 of the triangular body 70, such that the curved plate 74 forms a lid on the top of the triangular body 70, i.e. closing off the space therein. The length L of the plate 74 is substantially longer than the outer wall 73 of the triangular body. The measures of the inlet 10 is preferably such that it's width W is smaller than the length L of the plate member 74 and preferably also somewhat smaller than the length 1 of the outer wall 73 of the triangular body 70. The length X of the inlet 10 in the side space 4 is substantially larger than the length x see also Figs. 4 and 5 of the inlets 11 along the other part of the feeder tube 1. Also the width W is larger than the width w of the other inlets 11, such that the open area A of the inlet 10 within the side space 4 is at least 20% larger, more preferred at least 50% larger and more preferred more than 70% larger, than the area a of the other inlets 11. To use holes 10 of this size has shown to be possible within the side space 4, thanks to the low pressure exerted by the bulk material at this location. The axial extension b of the plate 74 is preferably about the same as the axial extension of the body 70 of the feeding device 7, and will preferably be in the range of 20-60% of tube diameter. It should be understood that the plate 74 need not be rectangular, but that various deviations from a rectangular design may be used to fulfill its function.

It is evident that also other shapes than triangular may be used for the body 70, to obtain the desired function, e.g. concave/plough shaped surfaces 71, 72, convex surfaces, etcetera.

In Fig. 4 there is shown a side view of a portion of a feeder tube 1 showing the feeding device 7 from the side. It is shown that the triangular body 70 has a substantial height h creating feeding sides 71,72, that thanks to its inclination a will assist in pushing bulk material 8 first axially and finally into the inlet opening 10. The plate 74 will also assist in pushing the bulk material 8 into the inlet opening 10, by withholding it 8 during rotation of the tube 1. In a preferred embodiment the height h of the feeding device 7 is about 10-30 % of the diameter of the tube 1, and the inclination a between 10-40°, corresponding to the actual angle a if straight surfaces 71, 72 and some average tangent if curved surfaces 71, 72. Furthermore the height h is preferably chosen such that the outer surface of the plate 74 will move very close to the bottom 30 (e.g. 1-30 mm above the bottom 30) to thereby further improve the feeding efficiency. Further, it is shown in Fig. 4 that there preferably is arranged a tapered end 74C at each end of the plate 74 to minimize penetration resistance and to improve feeding inwards radially.

In Fig. 5 there is shown a cross-sectional side view of a portion near the outer end 1 A of a feeder tube 1, 2 according to the invention, which is, arranged with a feeding device 7 as explained in connection with Figs. 3 and 4. The feeder tube 1, 2 comprises a conventional screw shaft 20 on to which there is arranged a helical blade 21, in a conventional manner. Furthermore the feeder tube 1, 2 according to the invention preferably is arranged with a second helical blade 22 positioned adjacent the outer end in connection with the larger inlet opening 10, positioned in the side space 4. As is shown the additional helical blade 22 has the same inclination as the first helical blade 21 and is interposed in between the traditional helical blade 21, such that the distance between adjacent blade parts 21, 22 within the side space 4 is half the distance (if positioned exactly in between, but it is evident that other also non-symmetrical positions will also provide the same basic function) compared to the distance between two adjacent blade parts of the traditional blade 21. The extra blade 22 will assist to increase feeding efficiency within the space 4. It is evident that more than one blade 22 may be used if appropriate/desired. Moreover the second helical blade 22 protrudes more radially outwards than the traditional blade 21, such that the outer edge 22A is positioned close to the inner surface of the tube 1. In connection with the more frequent inlets 11, a relatively large distance between the inner surface of the tube 1 and the edge 21 A of the first helical blade 21 is preferred, e.g. about 40-60 mm, whereas for the for the edge 22A of the second blade 22 a shorter distance improves the efficiency, and therefore preferably may be at least 50% less. In a preferred embodiment that distance is between 1 to 10 mm.

In Fig. 6 there is shown the same kind of view as in Fig. 5 (without showing any cross- section having the inlet opening 10 rotated 90 degrees, showing that the second helical blade 22 preferably protrudes further from the center C of the tube 1, 2 than the second helical blade 21. Further it is shown that the feeding device 7 is positioned centrally i.e. symmetrically in relation to the inlet opening 10. The outer plate 74 is positioned a substantial distance L (e.g. 30 mm to 150mm) away from the outer surface of the tube 1. Furthermore it is shown that an extra feeding device 7 ^' may be arranged 90 degrees displaced away from the inlet opening 10, to further assist in moving bulk material away from the outer wall. Preferably also this free standing feeding device 70 is arranged with a lid 7', to hinder bulk accumulate therein, but also without a lid 74' the basic function is achieved, since the rear wall will hinder bulk from being pushed in the wrong direction. Fig 7 shows a further embodiment according to the invention where the feeding device 7 is in the form of an outer helical blade 700 positioned outside of the feeder tube 1, 2. The outer helical blade 700 is driven by an independent motor (not shown) to facilitate the same direction of rotation at all times, such that the pile of bulk material 8 in front of the feeder tube 1, 2 will always be pushed in a direction away from the wagon 5, towards the inlet opening 10 and eventually no pile 8 is created. In Fig. 7 it is also shown the motor 200 for driving the tube 1, 2. The motor for driving of the helical blade 700 is not shown.

In Figs. 8 and 9 there is shown a further embodiment according to the invention, to avoid spillage at one end of the feeder tube 1, 2. In this embodiment the conveyor screw 2 is arranged to feed the bulk material 8 out from the silo 3 in both directions, such that it feeds out in a left outlet space 6A a and right outlet space 6B. In Fig. 9 it is shown that the screw conveyer 2 of this embodiment has helical blades that from a midpoint 25 of the screw conveyer 2 moves the bulk material in opposite directions. Hence the helical blades 23, 24 on opposite sides of the midpoint 25 are symmetrically arranged on both sides outwardly from that midpoint 25, where also a support for screw shaft can be arranged as option to restrict shaft deflection. It is evident that the "mid point" 25 must not be positioned in the middle, but any position, also far from the middle may be chosen. It is foreseen that this latter embodiment, and possibly also specific details described above, may be the object for its own protection, e.g. by means of filing a divisional application.

In Fig. 10 there is shown a side view of a modification in accordance with the invention, wherein the arrangement except for the extra feeding device 7 also is arranged with an extra anti-spillage arrangement 9. A basic part of the anti-spillage arrangement 9 is stop disc 90 that is fixed to the outer end 1 A of the tube 1. The outer diameter D of the disc 90 is larger than the outer diameter of the tube 1, sufficiently so to extend further than the gap G and to cover the gap G between the tube 1 and the bottom 30 of the silo 3. The end of the tube 1 A is positioned substantially in line with the inner wall 40 of the side space 4, such that the stop disc 90 will extend down into the space 4 near the inner wall 40, thereby hindering bulk from falling down into the inner space, (how near the disc 90 shall preferably be positioned may vary depending on the size of the bulk material, i.e. the gap shall be sufficiently small not to allow (most of) bulk material to pass through). The disc 90 may be annular and have its inner diameter substantially matching the outer diameter of the tube 1. It may be fixed to the tube 1 or rotationally mounted thereto. If the latter concept is used the disc 90 may be rectangular and fixed to the frame 5 in a manner to provide the same function as mentioned above to hinder spillage. As also shown in Fig. 10 the above modification may preferably be used in a silo 3 wherein band conveyers 45, 65 are used on each side and wherein more preferred two feeder tubes (merely one shown) are used, one to feed out in each direction.

The invention is not limited to what is described above but may be varied within the scope of the claims, accordingly it is for example evident that more than one larger openings 10 may be used in order to optimize the flow capacity in the side space 4, and that also different combinations of the devices described above may be used to optimize in different situations. Further, the mentioning of reclaimer is to be construed in a broad sense, since as is evident for the skilled person the functionality is not dependent on the application, i.e. it may be used in different kind of installations, e.g. called feeder tube, extractor, etc.