WO2009136849A1

WO2009136849A1 - Coaxial feeder with threads having a top

Info

Publication number: WO2009136849A1
Application number: PCT/SE2009/050476
Authority: WO
Inventors: Hans-Olof Backlund; Göran BYSTRÖM; Johan FÄLLMAN
Original assignee: Metso Paper Oy
Current assignee: Valmet Technologies Oy
Priority date: 2008-05-08
Filing date: 2009-04-30
Publication date: 2009-11-12
Anticipated expiration: 2010-11-08
Also published as: WO2009136849A9; SE532411C2; SE0801030L

Abstract

The invention relates to a refiner for refining of material such as wood chips or the like, which comprises: a first and a second opposed and with respect to each other rotatable rotors (11, 12), which are provided with refining elements (15, 16) and which between themselves define a refiner gap with a refining zone (17) for processing of the material, wherein the first rotor (11) comprises openings (19) having an inlet side and an outlet side (19a, 19b) intended to let the material through, and wherein the outlet side is adjacent to the feeding zone (18) of the refiner gap; a feeding chamber (22) to which the material is arranged to be fed, and which is adjacent to the inlet side of the openings (19) of the rotor; a coaxial feeder (23) having a screw body (24) and helix shaped threads (25), which coaxial feeder (23) is arranged inside the feeding chamber (22) in order to rotate together with the first rotor (11) and to carry the material towards the openings (19) of the rotor. The threads (25) of the coaxial feeder (23) comprise an essentially straight part (25a) that extends essentially perpendicular from the screw body (24) and that in operation is intended to carry the material in the longitudinal direction towards the refiner gap, wherein the straight part (25a) passes into a top (25b) that is intended to limit the motion of the material radially.

Description

Coaxial feeder with threads having a top .

TECHNICAL FIELD

The present invention relates to a refiner for refining of fibre material containing lignocellulose by means of opposed, with respect to each other rotating rotors, which are provided with refining elements, which between themselves define a refiner gap with a refining zone for processing of the material. In that connection, the material is brought to a feeding zone arranged radially inwardly of the refining zone. The invention also relates to a coaxial feeder (a feed ring) to be used in the device.

The invention relates to the preparation of different types of mechanical pulps, such as refiner mechanical pulp (RMP), thermomechanical pulp (TMP), chemimechanical pulp (CMP), and chemithermomechanical pulp (CTMP). The starting material may be wood chips or more or less processed pulp.

BACKGROUND AND PRIOR ART

It is previously known to utilise feed screws to feed fibre material into refiners or beating apparatuses. In the patent document SE 516 965, a device is described, in which fibre material is fed into a space between two refining elements; one of which is arranged on a fixed refining means and the other one is arranged on a rotor that is rotatable and opposite of the fixed refining means, and a feeding device is arranged on the rotor in order to rotate together with the same, and the material to be beaten is introduced to the feeding device by means of a feed screw through the centre of the fixed refining means.

However, the invention relates to feeding to a refiner, in which both of the opposed rotors are rotating, and the feeding of material must be effected by a rotor in order to reach the space between them. Thereby, partly different problems arise. In an arrangement such as the inventive one, there is a problem even to feed enough material to the space. Often, a coaxial feeder is arranged for this purpose. The coaxial feeder may be compared to a short and quickly rotating feed screw. The coaxial feeder is suitably arranged on the same shaft as one of the rotors in order to rotate together with it.

A problem related to known coaxial feeders is that the wood chips, due to the centrifugal force, partly are carried radially outwardly, perpendicular to the desired direction of transport, and thus a considerable part of the wood chips to be transported instead tend to stick between the coaxial feeder and the surrounding tubular wall. This results in a heavy rotation of the coaxial feeder and additionally, more material is gradually built up, such that it may be necessary to open up the space around the coaxial feeder at regular intervals for cleaning and maintenance.

SUMMARY OF THE INVENTION

The present invention is directed towards solving the problems that are mentioned above and that exist in the prior art.

According to a first aspect of the invention, this is solved by means of a refiner for refining of material such as wood chips or the like, which refiner comprises: a first and a second opposed and with respect to each other rotatable rotors, which are provided with refining elements, and which between themselves define a refiner gap with a refining zone for processing of the material, the first rotor comprising openings having an inlet side and an outlet side intended for letting material through, and the outlet side being adjacent to a feeding zone in the refiner gap; a feed chamber to which the material is arranged to be fed, and which is adjacent to the inlet side of the openings of the rotor; a coaxial feeder having a screw body and helix shaped threads, which coaxial feeder is arranged inside the feed chamber to rotate together with the first rotor and to feed the material to the openings of the rotor. The threads of the coaxial feeder comprise an essentially straight part which extends essentially perpendicular out from the screw body and which, in operation, is intended to carry the material in the longitudinal direction towards the refiner gap, which straight part passes into a top that is intended to limit the motions of the material radially. According to a second aspect, the invention also relates to a corresponding coaxial feeder.

With the coaxial feeder and the refiner according to the invention, the feeding into the space between the rotors is considerably improved. At the same time, the need for maintenance and cleaning is reduced since the material around the coaxial feeder is considerably less prone to plugging thanks to the inventive design.

SHORT DESCRIPTION OF THE DRAWINGS

The invention, together with further objects and advantages thereof, is best understood with reference to the enclosed description and the attached drawings, of which:

Fig. 1 shows a refiner according to an embodiment of the invention;

Fig. 2 shows a front view of a coaxial feeder according to an embodiment of the invention;

Fig. 3 shows a perspective view of the coaxial feeder of figure 2;

Fig. 4 shows a side view of the coaxial feeder of figure 2;

Fig. 5 shows a front view of a rotor partly in cross-section;

Fig. 6 shows a front view of a rotor having a coaxial feeder according to an embodiment of the invention mounted thereon; and

Fig. 7 shows a perspective view of the rotor and the coaxial feeder of figure 6.

DETAILED DESCRIPTION

In the drawings, similar or corresponding details are indicated by the same reference signs. The refiner or beating apparatus shown in fig 1 comprises a housing 10 in which is arranged a first rotor 11 and a second opposed rotor 12, each of which is attached to a separate rotating shaft 13 and 14, respectively. The rotors 11, 12 are each provided with a refining element 15 and 16, respectively, which between themselves define a refining zone 17 in a refiner gap between the refining elements. The refiner gap also comprises a feeding zone 18 radially inwardly, to which the material is intended to be fed. The first rotor 11 is provided with a central feeding opening 19 for the material to be processed. The housing 10 is also provided with an outlet 21 to carry away the material that has passed through the refiner gap and thereby has been processed to pulp.

A feed screw 20 is arranged to carry the material to a feeding chamber 22 in connection with the feeding opening 19. In the feeding chamber, a coaxial feeder 23 ("ring feeder") is arranged, which coaxial feeder is preferably arranged on the same shaft 13 as the first rotor 11.

Anyhow, it is favourable that the coaxial feeder 23 rotates together with said rotor 11. When the rotor is rotating, the material that is fed into the feeding chamber 22 is carried towards and through the feeding opening 19 of the first rotor 11 and for this to be efficiently performed; the rotor 11 and the coaxial feeder 23 should be fixed with respect to each other.

In figures 2-4, the coaxial feeder 23 is shown in detail. The coaxial feeder 23 is provided with a screw body 24 and at least one helix shaped wing or thread 25. The threads are arranged to carry the material into and through the openings 19 of the first rotor 11. For this purpose, the threads 25 comprise an essentially straight part 25a that extends essentially perpendicular from the screw body 24 and that in operation is intended to carry the material in the longitudinal direction of the axis towards the refiner gap. The straight part 25a passes into a top 25b that is intended to limit the motion of the material radially. The straight part 25a and the top 25b are thus interconnected, preferably by a smooth transition. The top 25b tapers outwardly from the essentially straight part 25a of the threads and forms a tip 25c in the forward direction with respect to the intended direction of rotation R of the coaxial feeder 23.

The top 25b of the threads thus have an underside that is intended to limit the motion of the material radially and that is essentially parallel to the axis L of the coaxial feeder 23. Preferably, the underside is slightly slanted upwardly from the essentially straight part 25a, whereby the tip 25c of the top may cut through the incoming material and carry it on towards the space between the rotors, via the openings 19 of the first rotor 11. As is also evident from especially figures 4 and 7, the coaxial feeder is designed such that the top 25b does not extend all the way into the rotor 11. This design is advantageous since it reduces the risk of plugging at the respective inlets of the openings 19. The gap that is formed between the thread 25 and the rotor 11 is also advantageous since the inlets of the openings 19 thereby may be made larger than the extension of the coaxial feeder. That this is the case in the embodiment shown, is most clearly seen in figure 6.

In the embodiment shown, the coaxial feeder 23 is provided with four threads 25, which are all designed equally, i.e. having an essentially straight part 25a with which a top 25b is connected. It is understood by a person skilled in the art that the number of threads may be varied from one and upwards in order to match different conditions of operation.

Preferably however, the number of threads is between 2 and 8. It is further understood by the skilled person that the number of threads, and their placement, should correspond to the openings 19 of the first rotor, such that the material that has been carried forward by the respective thread 25 arrives at an opening 19 and thereby may be carried further towards the space between the rotors 11 and 12.

This is best illustrated in the figures 5-7. In figure 5, the rotor 11 is shown separately, where the openings 19 are shown partly in cross-section, such that the inlet as well as the double outlets 19a and 19b are visible. From figure 5, it is also evident that the rotor 11 is provided with four feeding openings 19, each of which having one inlet and two outlets 19a and 19b. The foremost reason for each opening 19 to have two outlets is that the feeding of material to the refining zone shall be efficient regardless of in which direction the rotor 11 is rotating. Thus, the material will be carried through one set of openings when the rotor rotates in a first direction and through the other set of openings when the rotor rotates in the other direction. Once a coaxial feeder has been installed at the rotor, the direction of rotation for the arrangement, which the rotor 11 and the coaxial feeder 23 form together, will however be limited, since the coaxial feeder 23 is designed to rotate in a certain direction R and thereby to carry the material in a certain direction. Due to the manner that the coaxial feeder is mounted in figures 6 and 7, the material will, thanks to the centrifugal force, follow the thread direction of the coaxial feeder 23 and will thereby preferably be carried towards the outlet 19b.

From figures 6-7 it is also evident that the coaxial feeder 23 in the embodiment shown is screwed onto the rotor 11 by means of screws 26. The screws 26 are screwed into screw holes 27 in the rotor, which holes are shown in figure 5. The coaxial feeder 23 is placed such that the openings 19 will form a natural continuation for the material that has been fed by the respective threads 25.

The invention has been described hereinabove by reference to an exemplifying embodiment. To a person skilled in the art it is however obvious that the invention may be designed in a large number of ways without departing from the inventive thought or its scope, which is only limited by the enclosed claims.

Claims

1. A refiner for refining of material such as wood chips or the like, which refiner comprises; a first and a second opposed and with respect to each other rotatable rotors (11,12), which are provided with refining elements (15,16) and which between themselves define a refiner gap with a refining zone (17) for processing of the material, the first rotor (11) comprising openings (19) having an inlet side and an outlet side (19a, 19b) intended to let material through, and the outlet side being adjacent to a feeding zone (18) in the refiner gap; a feeding chamber (22) to which the material is arranged to be fed, and which is adjacent to the inlet side of the openings (19) of the rotor; a coaxial feeder (23) having a screw body (24) and helix shaped threads (25), which coaxial feeder (23) is arranged inside the feeding chamber (22) to rotate together with the first rotor (11) and to carry the material to the openings (19) of the rotor; characterised in that the threads (25) of the coaxial feeder (23) comprise an essentially straight part (25a) which extends essentially perpendicular out from the screw body (24) and which, in operation, is intended to carry the material in the longitudinal direction towards the refiner gap, the straight part (25a) passing into a top (25b) that is intended to limit the motion of the material radially.

2. The refiner according to claim 1, characterised in that the top (25b) of the threads (25) has an underside that is intended to limit the motion of the material radially, which underside is essentially parallel to the axis (L) of the coaxial feeder (23).

3. The refiner according to claim 3, characterised in that the underside is slightly slanted upwardly from the essentially straight part (25a), and terminates in a tip (25c).

4. The refiner according to any of the previous claims, characterised in that the top (25b) of the thread terminates a little before the thread (25) reaches the outer wall of the rotor (11), such that a certain space is present between the top and said wall.

5. A coaxial feeder (23) for feeding of material such as wood chips or the like to a refiner having a first and a second opposed and with respect to each other rotatable rotors (11,12), which are provided with refining elements (15,16) and which between themselves define a refiner gap with a refining zone (17) for processing of the material, the first rotor (11) comprising openings (19) having an inlet side and an outlet side (19a, 19b) intended to let material through, and the outlet side being adjacent to a feeding zone (18) in the refiner gap; which coaxial feeder (23) has a screw body (24) and helix shaped threads (25), and which coaxial feeder (23) is intended to be arranged inside the feeding chamber (22) and to be mounted on the same shaft as a rotatable rotor in order to rotate together with it, the rotor being provided with openings that coincide with the threads of the feed screw, characterised in that the threads (25) of the coaxial feeder (23) comprise an essentially straight part (25a) which extends essentially perpendicular out from the screw body (24) and which, in operation, is intended to carry the material in the longitudinal direction towards the refiner gap, the straight part (25a) passing into a top (25b) that is intended to limit the motion of the material radially.