The present invention refers to an arrangement in a centri¬ cleaner for cleaning a pulp suspension e.g. a furnish from heavy as well as light contaminate particles e.g. plastic particles in providing the furnish to rotate in said centri- cleaner when it is injected tangentially, whereby heavy con¬ taminate particles are forced outwards to the outer wall of the centricleaner for rejecting through reject outlets pro¬ vided in said centricleaner and light contaminate particles are accummulated in the centre of the centricleaner, where- from they are removed through outlets provided in its end sections, said centricleaner comprises an upper and a lower cleaning chamber, in which the suspension which shall be cleaned, is fed through an inlet located in the upper part of the external wall of the lower cleaning chamber, the lower cleaning chamber has in its lower section a lower reject outlet for bigger, heavy contaminate particles and said upper cleaning chamber has in its upper section one centrally placed outlet for light contaminate particles as well as at least one outlet for accept i.e. cleaned suspen- sion located in the external wall.

Previously known centricleaners coirprising two cleaning chambers function in such a way that a suspension which shall be cleaned is injected tangentially into the middle part of the centricleaner through an inlet, whereby the sus- pension become rotating in a movement directed downwards in the lower cleaning chamber. Heavy contamine particles then are urged outwards towards the conically formed outer wall of this cleaning chamber and down towards a lower outlet i.e. the reject outlet. The opening of this outlet deter- mines how much of the suspension which shall be rejected and how much which has to be turned back and continue into the upper cleaning chamber, into which the suspension flows without larger energy losses and in which it has to go through centrifugal acceleration forces. An air core, con- centrated with light contaminate particles is built up in the centre of this cleaning chamber and said air core is not

disturbed by different streams which is the case in the lower cleaning chamber, where stream short circuits occur. Light particles now are drained from this upper cleaning chamber by aid of a conduit located in the centre of the outlet and the cleaned suspension is removed at the same time through a neighboring, tangentially arranged side- conduit. Thanks to absense of stream short circuits in the upper cleaning cliamber the cleaning efficiency will be very high.

However, it has shown be difficult to remain this high cleaning efficiency when different types of suspensions as well as suspensions having different consistency shall be cleaned. Due to the fact that there are no obstacles for the suspension to flow from the lower cleaning chamberto the upper one it is required substantially only some more energy than what is the case in a centricleaner having one cleaning chamber. It means that the cleaning operation of heavy par¬ ticles and the cleaning operation of light particles is possible to achieve at the same time with an amount of energy which is slightly higher than the energy demand which is necessary for a centricleaner having one cleaning chamber in order to separate only heavy or only light contaminate particles during one and the same separating operation. In a centricleaner comprising two cleaning chambers it must be a higher pressure than what is the case in a centricleaner having one cleaning chamber for cleaning of suspensions either from heavy or light contamine particles. This higher pressure has to be maintained because of there is a higher counter pressure to overcome in a centricleaner having two cleaning chambers than what the case is with a centricleaner having only one cleaning chamber. The higher pressure causes that the amount of reject in the lower cleaning chamber then become increased and to keep the amount of reject equal all the time as when using of only one cleaning chamber, it is necessary to decrease the reject opening at a higher pressure. The effect of this will be an increased risk that the reject opening will be plugged by bigger, heavy contamine particles with operation disturbances as a

consequence to clean the reject opening.

The object of the present invention is to provide a centri¬ cleaner, by which a high cleaning efficiency can be main¬ tained during cleaing of different types of suspensions as well as suspensions having different consistency. The characterizing features of the present invention are stated in the following claims. Due to that each cleaning chamber includes cylindrically formed sections in the middle part of the centricleaner and said sections are telescopically displaceable in each other in order to increasing or decreasing the inner pressure of the centricleaner, an optimal cleaning result always can be achieved independing of the type of suspension or suspensions having different consistency, since the relative location of the cleaning chambers has a great importance for the cleaning efficiency. In preventing plugging of the lower reject opening when the pressure is increased, e.g. in altering of the relative position of the cleaning chambers, the reject opening com¬ prises at least one nozzle, replaceable located in a dis- placeable holder, said nozzle can be automatically replaced by a new unplugged and clean nozzle or by a nozzle having a larger or smaller opeing.

The invention will now be described more in detail below with reference to the accompanying drawings wherein

Fig. 1 shows a preferred embodiment of the centricleaner according to the invention in a schematic side view partly in section and in which the lower part is illustrated to the left,

Fig. 2 shows a schematically view in a larger scale of the reject outlet of the lower cleaning chainber in a sectional elevation,

Fig. 3 shows a side view of the reject outlet in a sectional elevation illustrated in Fig.2 and

Fig. 4 shows a partially enlarged view of the middle part of the centricleaner partly in section.

As can be seen from Fig. 1 the centricleaner according a preferred embodiment of the present invention comprises of an upper cleaning chamber 1 and a lower cleaning chamber 2. The suspension which shall be cleaned is tangentially in¬ jected through an inlet 4 provided in the upper part of the outer wall 3 of the lower cleaning chamber 2. In the lower part of the lower cleaner 2 there is a lower reject outlet 5 for bigger, heavy contaminate particles. The upper cleaning chamber 1 is in its upper section provided with a centrally located outlet 6 for light contaminate particles as well as at least one outlet 8 for accept, i.e. a cleaned suspension, said outlet is located in the outer wall 7 of said chamber 1. The opposed, from each other turned end sections 10,11 of the two cleaning chambers 1,2, have a conical formation. The middle section 9 of the centricleaner, see also Fig.4, which is formed of the end sections 12,13 of the two cleaning chambers 1,2, said end sections are turned towards each other and telescopically cooperable with each other, has a cylindrical configuration, in the embodiment illustrated the upper cleaning chamber 1 is displaceable into the lower cleaning chamber 2 by means that the outer diameter of latter is somewhat larger than the one of the former. The difference between the outer diameters of the two cleaning chambers is so great that one of them is displaceable into the other at the same time as there is room for a sealing device 14 comprising 0-rings 15 in providing of the dis¬ placement mentioned above while maintaining of a proper sealing between the two cleaning chambers 1,2. This tele- copically displacement, which can be performed by aid of a handle 21, has a great importance for the cleaning effi¬ ciency, since it has been revealed that different types of suspensions and also suspensions having different consis- tency, receive different cleaning results during different positions of the cleaning chambers of the centricleaner re¬ lative each other.

In order to stop plugging of the lower reject outlet 5 of the cleaning chamber 2, which can occur when it has to be a greater pressure iathis chamber to overcome that resistance existing in centricleaner having two cleaning chambers 1,2, and to maintain the same amount of reject in spite of an in¬ creased pressure, the reject outlet 5 has been provided with at least one replaceable nozzle 17 provided in a displace¬ able holder 16. In the eπtbodiment illustrated in Fig. 2 and 3 the holder 16 is formed as a box displaceable in a guiding house 18. The nozzles 17 are easy to replace in that they have a conically formed flange 19, which is fixable in a position in a conically formed seat 20 in the holder 16 and which is cooperating with said flange. When plugging occurs of the nozzle 17 situated in the reject outlet 5, the holder 16 is pushed away to either side, which is illustrated in Fig.2, and can now be cleaned e.g. by aid of compressed air beside the reject outlet 5. When the centricleaner is work¬ ing during optimal conditions, a nozzle 17 having an optimal opening is placed in the rejectoutlet 5. Standingby is at the same time anozzle 17 having a greater opening which can be push¬ ed in if a nozzle in the reject outlet 5 has been plugged.

The cleaning outside the centricleaner canbe performed at de¬ termined intervals by aid of compressed air. The movable part in the form of the holder 16 can be designed in any suitable way e.g. as a rotating element in the form of a wheel or plate.