Technical field

[0001] The present invention generally relates to a feeding apparatus for cellulosic material, in which a screw is feeding the material towards an anvil whereby a pressure tight material plug is built up.

Background art

[0002] In treatment of cellulosic material, such as refining in a grinding apparatus, steam is formed, which is separated from the material, retaining its high pressure, to be utilized separately in the process. However, discharge of the material separated from the steam is done at a lower pressure, such as atmospheric pressure. In order to prevent the steam from leaving with the material and to maintain the high pressure of the steam, the material must be fed out through sluice means of any kind. Another way to seal the steam separating portion from the discharge of the material is to allow the material at the discharge to form a pulp plug, which seals the outlet so that the steam will not be entrained in the material when discharged.

[0003] In known outlet means of the latter type, the material is provided to fall down into a screw, which is, in one end, provided with drive means and in the opposite end feeds the material towards a throttling opening so that the material plug builds up. Since the driving is provided on the pressure side, the drive means must be sealed by means of pack boxes or the like, which wear out and require maintenance and possibly replacing. The plug is also formed in the end of the relatively long screw, which is opposite to the drive means, wherefore the higher load on this end of the screw makes the screw unstable. This also limits the possibilities to control the forming of the plug depending on the loading conditions. [0004] This object is met in SE514960, belonging to the inventor. However, the technique needs some further refinements to meet the demands of the market.

Summary of invention

[0005] Such a feeding apparatus for cellulosic material has been invented and comprises a screw feeding the material towards an anvil whereby a pressure tight material plug is formed and whereby the screw comprises a peripheral part having an around said part, in the housing of the apparatus, arranged throttle means.

[0006] With this solution a feeding apparatus for cellulosic material can be accomplished which is robust and can handle high pressures and at the same time can be adjusted to provide the material plug with a desired compactness. Fewer parts need to be used, having lower tolerance demands as well.

[0007] In a preferred embodiment the throttle means comprises an inner and an outer ring shaped means with a plurality of openings, whereby the outer ring shaped means is rotatably displaceable in order to adjust the size of the openings in the throttle means. This embodiment discloses a simple way of controlling the size of the openings through which the material plug is fed and thereby easily controlling the counter pressure when creating the material plug, both in the building phase and during the continuous building of a material plug. Smaller added openings provide a larger counter pressure which builds up the material plug and increases its compactness. On the other hand, larger added openings provide a smaller counter pressure and a less compact material plug.

[0008] It is important to find a balance between easiness to feed and compactness so that pressurized steam is prevented from leaking out and at the same time the risk of a stop due to a too compact plug is minimized. In this way the difficultly regulated parallel displaceable pipe in prior art SE514960 is avoided. This pipe is difficult to parallel displace without risking an oblique pull and pinching. It also requires several maneuverability bars that need to be maneuvered at the same time.

[0009] Preferably is the inner ring shaped means attached to the housing and the outer ring shaped means is rotatably displaceable in order to adjust the size of the openings in the throttle means. The numbers of openings in the inner and outer ring shaped means are preferably the same.

[0010] In order to assure high quality of the function, a chosen displacement position is preferably maintained between the inner and outer ring shaped means until next displacement position is chosen.

[001 1] One possible way of accomplish an adjustable rotational displacement of the outer ring to a chosen displacement position is to arrange a gear rim section, for example at the outer ring shaped means, whereby the gear rim section is interacting with a rotating gear wheel. This gear wheel is preferably carried in the housing, for example with an shaft ejecting from the housing for a simple maneuvering of the gear wheel which in turn interacts with the gear rim section, whereby this together with the outer ring shaped means is rotated. It is also possible to use a worm gear so that the shaft of the gear wheel extends in a direction radially out from the outer ring shaped means.

[0012] Preferably is the shaft of the screw carried in an, outside the housing, arranged bearing housing, which is arranged at the feeding end of the screw.

Brief description of drawings

[0013] The invention is now described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 discloses a side view partly in a cut through the inventive feeding device. Fig. 2α, b discloses an outer and an inner ring shaped means in a completely open position and in a partially throttled position.

Fig 3 discloses an adjustment means for the outer ring shaped means.

Description of embodiments

[0014] The device comprises a connection piece or inlet 10 which, by a flange 12, is connected in a pressure tight manner to the outlet of a steam separator, for example of the same type as disclosed in Swedish patent 9101342-5, so that the material in the form of a pulp is feed to the inlet 10 when the steam generated during refining has been separated in the steam separator in order to under pressure be guided to different applications in the process. In order to prevent a decreased or loss of steam pressure, the pulp must be pressure sealed during feeding. Hence the pulp is falling into a, under the inlet 10 existing, sealed housing 14 in which a transport screw 16 with flights 18 arranged on an shaft 20 is carried.

[0015] The shaft 20 has a conically increasing diameter towards the feeding end of the screw 16, i.e. in the feeding direction of the by the screw transported material in order to guide the material towards to inner periphery of the housing. At the feeding end a shaft 20 is attached to a peripheral section, for example a rotor 22, which may have a conically increasing diameter in said feeding direction. Surrounding this rotor 22 is one in the housing arranged throttle means 32 with at least one radially arranged opening 28. On the rotor 22 there is arranged at least one rotor wing 24 adapted to grid and to assist the feeding of the material radially through the openings 28.

[0016] The throttling means 32 comprises an inner ring shaped means 50 attached to the housing 14 comprising a number of openings 28' and an outer ring shaped means 52 comprising a number of openings 28". The inner openings 28' and the outer openings 28" form aggregated radial openings 28. Preferably, the number of inner openings 28' corresponds to the number of outer openings 28". In a preferred embodiment of the ring shaped means 50 and 52 the inner openings 28' are formed with essentially radial walls, while the outer openings 28" have at least one diagonal wall so that the opening area of the openings radially increases in a direction outwards in the ring shaped means 52. The outer ring 52 can clockwise be turned from an entirely opened mode, see figure 2a, into a partially throttled mode, see figure 2b, or a completely closed mode. The part of the outer ring 52 that partially closes the openings 28 operates as a cutting edge, and the diagonal wall improves the output of the material radially from the partially closed opening 28.

[0017] The outer ring shaped means 52 is rotatably displaceable around the inner ring shaped means 50. In that way an adjustable counter pressure is created against the output of the material in the openings 28, which builds up a material plug 40 in front of the rotor 22. The material plug 40 seals the inner part of the housing 14 from the outside the rotor existing room 34. On the outside of the rotor 22, in view of the feeding direction, there are wings 24 attached which are arranged to grind the ring shaped material plug, build up in a plug build up zone in the end of the screw, and feed the material further out through the radial openings 28 so that the material is falling down into the bottom of the room 34. This bottom is opened downwards and provided with a sleeve coupling 36 arranged to be coupled to any means arranged to further transport of the material. At a distance from and opposite the feeding opening 28 the room 34 is limited by a sealing wall 38, which sealingly surrounds an extension 44 of the shaft 20 and which shaft extension 44 is journalled in the bearing housing 42 and is arranged to be attached to a driving motor (not disclosed) for the screw 16. [0018] The disclosed apparatus operates in the following way: The from the steam separator (not disclosed) to the inlet 12 coming mass falls down into and feeds by the screw 1 ό towards the outlet of the housing 14, that is to the left in figure 1 , and will by the conically increasing shaft 20 be forced out towards the inner periphery of the housing 14 so that a material plug 40 is build up before the material outlet restricted by the on the shaft 20 arranged rotor in cooperation with the throttling means 32. In order to control the feeding of the material plug 40 and thereby maintain the pressure sealing function of the plug 40, the size of the feeding openings 28 is according to the invention adjusted by a gear of any kind. Preferably, a gear rim section 46 interacting with a gear wheel 48 is arranged by the outer ring shaped means 52. The gear wheel 48 can be carried on a shaft ejecting out through the housing 14 for a simple maneuvering and adjustment of the displacement position of the outer ring shaped means 52. Of course, it is also possible to use a worm gear if the shaft of the gear wheel is requested to be in another direction. After that the mass is falling down into the lower part of the housing 34 and is feed out through the output 36 to further treatment.

[0019] As evident from disclosed embodiment the shaft 20 of the screw 16 is, via a shaft extension, joumalled in the bearing housing 42 on a side of the housing 14 of the screw 16 where atmospheric pressure is present. In that way no pressure sealed packing boxes are required in the bearing housing, which simplifies and reduces the costs for maintenance and operation of the apparatus. By arranging the bearing 42 of the screw nearest the end of the screw 16 where the material plug 40 is build up, instability of the screw 16 is to a great extent prevented so that a better precision is obtained when adjusting the size of the feeding opening.