SLUICE FOR DISCHARGING BULK MATERIAL

Abstract: A sluice (2) for discharging bulk material, in particular fibres, from a cyclone device comprises a circumferential wall (4) in the form of a curved bendable band, which defines a generally cylindrical chamber (10) with an inlet (38) for receiving bulk material from the cyclone device and an outlet (14) for discharging bulk material substantially tangentially from the cylindrical chamber. A sluice wheel (16) is rotatable in the chamber about a vertical axis (12) extending through the centre of the sluice wheel for sluicing the bulk material in batches from the inlet through the chamber to the outlet. The inlet (38) is situated centrally above the sluice wheel for supplying bulk material substantially axially to the sluice wheel.

Description: Sluice for discharging bulk material The present invention relates to a sluice for discharging bulk material from a cyclone device, comprising a circumferential wall defining a generally cylindrical chamber with an inlet for receiving bulk material from the cyclone device, an outlet for discharging bulk material from the chamber, and a sluice wheel, which is ro atable in the chamber for sluicing bulk material in batches from the inlet through the chamber to the outlet. Such a sluice maintains a counter pressure in the apex end of the cyclone device, through which the bulk material passes, so that the cyclone device works in the desired manner. In conventional sluices of this kind the sluice wheel rotates about a horizontal axis, wherein the inlet is situated on the top side of the circumferential wall for supplying the bulk material from the cyclone device radially to the sluice wheel and the outlet is situated on the underside of the circumferential wall for discharging the bulk material radially from the sluice wheel. The sluice wheel comprises radial sluice walls defining a number of cells evenly distributed around the horizontal axis of the sluice wheel. The radially outer ends of the sluice walls are provided with rubber seals sealing against the inner side of the circumferential wall, except when the sluice walls passes the inlet and the outlet during rotation of the sluice wheel. A problem of such a conventional sluice is that bulk material with low density, such as fibres, poorly fills the cells of the sluice wheel, which reduces the capacity of the sluice. The rotational speed of the sluice wheel is limited to a relatively low value, since otherwise the influence of the centrifugal force on the bulk material in the cells of the sluice wheel will be great such that the bulk material simply is prevented from passing through the inlet of the sluice into the bypassing cells. For this reason the capacity of the sluice can not be increased by increasing the rotational speed of the sluice wheel. The solution to this capacity problem in connection with sluicing of bulk material with low density has been to install over-dimensioned, space demanding sluices, which are operated with low rpm. Another problem of the conventional sluice is that long transition portions are required between the apex end of the cyclone device and the inlet of the sluice to prevent the vortex of the cyclone device from disturbing the filling of the cells of the sluice wheel with bulk material. For applications in which bulk material of fibres are dried in cyclone devices, such transitions portions may need to be up to seven metres long, as seen vertically. A further problem of the conventional sluice is that the air leakage from the cyclone device through the sluice to the surroundings increases unsatisfactorily rapidly over time, because of the fact that the rubber sealings of the sluice walls age relatively rapidly. In addition, the rubber seals are worn out relatively rapidly because of the fact that material is jammed between the rubber seals and the circumferential wall when the rubber seals again seal against the circumferential wall after having passed the inlet during rotation of the sluice wheel . The object of the present invention is to provide a sluice that eliminates the above mentioned problems of conventional sluices. This object is obtained by a sluice of the kind initially described, which is characterised in that the sluice wheel is rotatable about a vertical axis extending through the centre of the sluice wheel, that the inlet is situated centrally above the sluice wheel for supplying bulk material substantially axially to the sluice wheel, and that the inlet extends substantially tangentially to the cylindrical chamber. By the fact that the bulk material is axially received by the sluice wheel the influence by the centrifugal force on the bulk material will give the favourable consequence that the bulk material will be packed radially outwardly in the sluice wheel, which gives the sluice according to the invention a good capacity. In addition, the vortex of the cyclone device can be allowed to extend through the inlet all the way into the sluice wheel without disturbing the filling of the sluice with bulk material, which has the consequence that the length of the transition portion between the cyclone device and the sluice can be made relatively short. For instance, the transition portion needs only be about four metres in length when sluicing bulk material in the form of fibres, which compared to a corresponding transition portion in a conventional sluice means a reduction in length of about 40%. Since the sluice walls of the sluice wheel always abut with their radially outer seals against the inner side of the circumferential wall at the area of inlet, the risk of the bulk material jamming between said seals and the circumferential wall is significantly reduced. Preferably the sluice wheel comprises a plurality of at least substantially radial sluice walls, which are distributed spaced from one another along the circumference of the sluice wheel and which with their radial outer ends abut sealingly against the circumferential wall except at the outlet. The radial inner ends of the sluice walls are suitably situated at a predetermined distance from the centre of the sluice wheel, so that a central free space communicating with the inlet is formed in the sluice wheel. In accordance with a simple design of the sluice wheel it comprises a lower circular gable wall and an upper annular circular gable wall, wherein the sluice walls extend axially between and are connected to the lower and upper gable walls. The lower gable wall may suitably be connected to a drive motor. To achieve a good air sealing between said central space and the outlet the sluice according to the invention comprises a stationary part-cylindrical wall extending in said central space coaxially with the sluice wheel and abutting sealingly against the upper and lower gable walls, wherein the part-cylindrical wall extends past the outlet as seen in the circumferential direction of the sluice wheel. Suitably the radially inner end of each sluice wall abuts sealingly against the part-cylindrical wall when the latter is passed by the sluice wall during rotation of the sluice wheel, while the radially outer end of each sluice wall abuts sealingly against the circumferential wall except when the sluice wall passes the outlet during the rotation of the sluice wheel. The part-cylindrical wall has such an extension in the circumferential direction of the sluice wheel that at least one sluice wall seals between the circumferential wall and the part -cylindrical wall on each side of the outlet, as seen in circumferential direction, independent of the turning position of the sluice wheel. The circumferential wall may comprise a curved bendable band with one end fixed against movement in the longitudinal direction of the band and with one opposite end which is moveable in the longitudinal direction of the band for adjustment of the radial extension of the band. As a result, when required the band can be adjusted concurrently with the wear of the radial outer ends or seals of the sluice walls. Said opposite ends of the band is advantageously connected to a pre-stretched draw spring or air cylinder for automatic adjustment of the radial extension of the band, so that a satisfactory sealing between the band and the radially outer ends of the sluice walls are achieved during operation. Alternatively, a circumferential wall may of course be stationary and the radially outer ends of the sluice wall may be provided with conventional sealing rubber lips. The invention is described in more detail in the following with reference to the accompanying drawing, in which figure 1 shows an exploded view of a sluice according to the invention by way of example, and figure 2 shows a view, somewhat enlarged, obliquely from above of the sluice according to figure 1 in an assembled state. Figure 1 shows a sluice 2 according to the present invention for discharging bulk material from a cyclone device (not shown) . The sluice 2 comprises a circumferential wall in the form of a bendable steel band 4, which has two free ends 6 and 8 and which defines a generally cylindrical chamber 10 with a vertical centre axis 12. The two free ends 6 and 8 of the steel band 4 are situated spaced from each other and define an outlet 14 extending substantially tangentially to the cylindrical chamber 10. A sluice wheel 16 is situated in the chamber 10 and is rotatable about the vertical axis 12 on bearings not shown. The sluice wheel 16 comprises a lower circular gable wall 18, which is connectable to a drive motor not shown, an upper annular circular gable wall 20, and twelve radial sluice walls 22 extending axially between and connected to the lower gable wall 18 and the upper gable wall 20. The sluice walls 22 are evenly distributed spaced from one another along the circumference of the sluice wheel 16 and abut with their radially outer ends 24 against the steel band 4, possibly via rubber seals, except at the outlet 14. The radially inner ends 26 of the sluice walls 22 are situated at a predetermined distance from the centre of the sluice wheel 16, so that a central free space 28 is formed in the sluice wheel 16. A stationary part-cylindrical wall 30 extends in the central free space 28 in the sluice wheel 16 coaxially thereto and abut sealingly against the annular upper gable wall 20 and the lower gable wall 18, possibly via rubber seals not shown. The radially inner end 26 of each sluice wall 22 abut sealingly against the part-cylindrical wall 30, possibly via a rubber seal, when the wall 30 is passed by the sluice wall 22 during rotation of the sluice wheel 16. As seen in the circumferential direction of the sluice wheel 16 the wall 30 extends past the outlet 14, so that a discharge passage 32, through which the sluice walls 16 move towards the outlet 14, and a return passage 34, through which the sluice walls 16 move from the outlet 14, is formed between the steel band 4 and the wall 30. The wall 30 has such a long extension in the circumferential direction of the sluice wheel 16 that at least one sluice wall 22 is in the discharge passage 32 and the return passage 34, respectively, independent of the turning position of the sluice wheel 16, A circular sealing flange 36 is coaxially attached to the upper end of the part-cylindrical wall 30 and defines an inlet 38 for the bulk material. For the sake of clarity the sealing flange 36 has been omitted in figure 2. One end 8 of the steel band 4 is fixed against movement in the longitudinal direction of the steel band 4, while the other end 6 is connected to a pre-stretched draw spring 40, as schematically shown in figure 2. The draw spring 40 provides automatic adjustment of the radial extension of the steel band 4, so that a satisfactory sealing between the steel band 4 and the outer ends 24 of the sluice walls 22 is achieved for a long operation of the sluice 2. The function of the sluice 2 according to the invention is described in the following in connection with discharging bulk material in the form of fibres from a cyclone device, which constitutes an important application of the sluice according to the invention. The sluice 2 is connected to a cyclone device for drying fibres (a cyclone device of this kind can have a dimension in height of more than 20 metres) , so that the lower narrow part of the conical separation chamber of the cyclone device communicates with the inlet 38 of the sluice 2 via a relatively short transition portion of about four metres. The fibres are blown into the separation chamber of the cyclone device, so that a vortex of the mixture of air and fibres is generated therein. The vortex extends through the transition portion axially down into the central free space 28 of the sluice wheel via the inlet 38. In the space 28 the now dried fibres are thrown radially outwardly and are packed together in the open cells that are defined by six of the sluice walls 22, which are in fibre- receiving positions in the chamber 10. The drive motor not shown rotates the sluice wheel 16 counter clockwise in the same rotational direction as the vortex of the cyclone device, as indicated by an arrow in figure 2, so that the fibres are transported by the sluice walls 22 through the discharge passage 32 to the outlet 14. The sluice wheel 16 is rotated fast such that fibres that from the discharge passage 32 enter the outlet 14 directed tangentially to the chamber 10 are thrown by the centrifugal force from the cells between the sluice walls 22 out of the outlet 14. The sluice walls 22 that define emptied cells in the outlet 14 return through the return passage 34 to said fibres receiving positions in the chamber 10, whereafter the above described course is repeated.

Claims: CLAIMS 1. A sluice (2) for discharging bulk material from a cyclone device, comprising a circumferential wall (4) defining a generally cylindrical chamber (10) with an inlet (38) for receiving bulk material from the cyclone device, an outlet (14) for discharging bulk material from the chamber, and a sluice wheel (16) , which is rotatable in the chamber for sluicing the bulk material in batches from the inlet through the chamber to the outlet, characterised in that the sluice wheel (16) is rotatable about a vertical axis (12) extending through the centre of the sluice wheel, that the inlet (38) is located centrally above the sluice wheel for supplying bulk material substantially axially to the sluice wheel and that the outlet (14) extends substantially tangentially to the cylindrical chamber (10) . 2. A sluice according to claim 1, characterised in that the sluice wheel (16) comprises a plurality of at least sub- stantially radial sluice walls (22) , which are distributed spaced from one another along the circumference of the sluice wheel and which with their radially outer ends (24) abut sealingly against the circumferential wall (4) except at the outlet (14) , and that the radially inner ends (26) of the sluice walls are situated at a predetermined distance from the centre of sluice wheel, so that a central free space (28) communicating with the inlet (38) is formed in the sluice wheel . 3. A sluice according to claim 2, characterised in that the sluice wheel (16) comprises a lower circular gable wall (18) and an upper annular circular gable wall (20) , the sluice walls (22) extending axially between and being connected to the lower (18) and upper (20) gable walls. 4. A sluice according to claim 3, characterised by a stationary part-cylindrical wall (30) , which extends in said central space (28) coaxially with the sluice wheel (16) and which abuts sealingly against the upper and lower gable walls (20,18), the part-cylindrical wall extending past the outlet (14) as seen in the circumferential direction of the sluice wheel . 5. A sluice according to claim 4, characterised in that the radially outer end (24) of each sluice wall (22) abuts sealingly against the circumferential wall (4) except when the sluice wall passes the outlet (14) during rotation of the sluice wheel (16) . 6. A sluice according to claim 5, characterised in that the circumferential wall comprises a curved bendable band (4) with an end (8) which is fixed against movement in the longitudinal direction of the band and with an opposite end (6) which is moveable in the longitudinal direction of the band for adjustment of the radial extension of the band. 7. A sluice according to claim 6, characterised in that said opposite end (6) of the band (4) is connected to a pre- stretched draw spring (40) for automatic adjustment of the radial extension of the band, so that a satisfactory sealing between the band and the radially outer ends (24) of the sluice walls (22) is achieved during operation. 8. A sluice according to any of claims 4-7, characterised in that the radially inner end (26) of each sluice wall (22) abuts sealingly against the part cylindrical wall (30) when the latter is passed by the sluice wall during rotation of the sluice wheel (16) . 9. A sluice according to claim 8, characterised in that the part-cylindrical wall (30) has an extension in the circumferential direction of the sluice wheel (16) such that at least one sluice wall (22) seals between the circumferential wall (4) and the part-cylindrical wall at each side of the outlet (14) , as seen in the circumferential direction, independent of the turning position of the sluice wheel .

Inventors: GUSTAVSSON LENNART, GUSTAVSSON, LENNART
Applicants: GUSTAVSSON LENNART, VALMET FIBERTECH AB, GUSTAVSSON, LENNART
Application year: 2000
Main classification: B65G53
IPC codes: B65G53