Technical Field

This document relates to a distributor for distributing an airflow mixed with materials in an agricultural implement.

The distributor can be used in particular when distributing an airflow mixed with material from a primary duct to a plurality of secondary ducts.

Background

Agricultural implements for distributing material in powder form or granular form to the ground on which the agricultural implement is travelling are known and may be in the form of seed drills and machinery for spreading fertilizer and/or pesticides.

Some machines use air-assisted material feeding which means that the material is fed from a container to a primary duct, in which an airflow is provided. The material is taken up by the airflow and is led via a distributor to a plurality of secondary ducts that lead to a respective material outlet, such as furrow openers, fertilizer openers, etc.

The primary ducts may be in the form of rigid tubes and/or somewhat flexible hoses with a relatively large diameter, such as 6-15 cm. The secondary ducts may be in the form of hoses with a smaller diameter, e.g. 2-5 cm, the flexibility of which permits the frame sections and tools to move in relation to each other, e.g. in order to permit movements during driving and folding of the machine.

In addition, it is desirable to provide agricultural implements that can carry out several operations simultaneously, for example, sowing different crops and/or feeding fertilizer and/or pesticides, or, in order to be able to control different sections of the agricultural implement individually, it is sometimes desirable to provide two or more primary ducts, and distributors associated with the respective primary duct and a set of secondary ducts leading from there.

Furthermore, it is desirable to provide even larger agricultural implements, which makes greater demands on the agricultural implement to be foldable for transport on public roads.

It will be appreciated that, with an increase in size and/or increased number of functions of the agricultural implement, several distributors may need to be arranged on the agricultural implement. For example, two to eight distributors may be needed depending on the size of the agricultural implement.

In addition, the amount of tubes is greater, as is the length of the tubes. Known distributors are based on the principle that a substantially horizontal primary duct transitions into a vertical riser tube leading on to a centre of a distributor head. The secondary ducts lead on from the

circumference of the distributor head. In order for such distributors to function well, a certain length of the riser duct is needed to compensate for the tendency of the material to be distributed asymmetrically in the riser tube after its direction of movement is re-directed by the bend leading from the primary duct to the riser tube.

However, the height of the riser tube can cause issues, since it may limit the possibility of folding the frame sections of the agricultural implement. This is especially true when it is desirable to locate distributors on, or within the range of movement for, foldable frame sections of the agricultural implement.

WO2013055288A1 shows a solution to this problem.

It is, however, desirable to provide a less complex solution which still permits maintained, or improved, distribution of the material between the secondary ducts. Summary

One object of this document is thus to provide a distributor that is more space-efficient, and that preferably has maintained distribution of the material between the secondary ducts.

The invention is defined by the accompanying independent claims.

Embodiments are set forth in the dependent claims, in the description that follows and in the accompanying drawings.

According to a first aspect, a distributor for distribution of a material- carrying air stream from a primary duct to a plurality of secondary ducts is provided, comprising a distributor input, which is connectable to the primary duct, a distributor base, which is connected to the distributor input and which transitions to a riser space, and a distributor head which has an inlet from the riser space, and a plurality of distributor outlets which are connectable to the secondary ducts. The distributor has a distributor input connected to a manifold for division of the material-carrying air stream into at least two flow manifolds, the flow manifolds connect to the riser space so that the flow directions into the riser space differ by at least 5 degrees, preferably at least 10 degrees or at least 30 degrees.

The riser space can be substantially vertical and have a generally cylindrical form.

By providing a pair of substantially counter-directed inlets to the riser space the distribution of the incoming material into the riser space is improved. Since the distribution is improved at the inlet, a shorter riser tube can be used without impairing the distribution, and by those means, a more compact distributor is provided.

The flow manifolds can connect to the riser space so that the flow directions into the riser space are counter-directed to each other by +/- 90 degrees, preferably by +/- 45 degrees, +/- 30 degrees or +/- 10 degrees.

The flow manifolds can be located in the same plane.

At least one of the flow manifolds can have a second manifold for division of the existing material-carrying air stream in the flow manifold into at least two subsidiary flow manifolds for further feeding to the riser space, so that the flow directions of the subsidiary flow manifolds into the riser space differ by at least 5 degrees, preferably at least 10 degrees or at least 30 degrees. For example, the flow directions of the subsidiary flow manifolds into the riser space can be counter-directed to each other or have an angle of about 90 degrees to each other.

The subsidiary flow manifolds can be located in the same plane.

The subsidiary flow manifolds can be located in the same plane as the flow manifolds.

Alternatively, the subsidiary flow manifolds can be on a separate plane from the flow manifolds.

At least one of the manifolds can divide the manifold incoming flow into at least two parts, the flow directions of which are 70-90 degrees, preferably 80-85 degrees to the flow direction of the incoming flow.

The first manifold to the flow manifolds as well as the second manifold to the subsidiary flow manifolds can be designed as described above.

At least one of the manifolds can have a stop surface to which the incoming flow is directed and which is preferably convex in at least one plane.

The riser space can have a conical bottom surface, wherein the flow directions into the riser space are at least partly directed towards the conical bottom surface.

"Conical surface" means surfaces that are conical in a strictly geometrical sense, but also surfaces that are frustoconical, or in any other way in the manner of a truncated cone. Preferably, the conical surface has a cylindrical base. The conical bottom surface can have a height corresponding to 20-100% of the height of an inlet to the riser space, preferably 40-60%.

The riser space can have walls that are parallel to a riser flow, which have differences in level, such as grooves, projections or cavities.

The inlet from the riser space can be centrally positioned in the distributor head, and the outlets to the secondary ducts are circumferentially positioned in the distributor head.

A substantially ring-shaped distributor chamber can be formed between the inlet and the outlet. The inlet from the riser space can be directed towards a conical stop surface.

Preferably, this stop surface is circular-conical. A centre axis of this circular cone can be aligned with a centre axis of the riser space.

The conical stop surface can have a height corresponding to 20-100% of the height of a distributor chamber formed in the distributor head, preferably 40-60%.

The distributor input can be configured to provide a flow direction which is horizontal by +/- 30 degrees, preferably +/- 10 degrees or +/- 1 degree.

In the distributor described above, the manifold ducts can have a substantially horizontal extension.

Furthermore, the distributor can comprise a rod, which extends along a flow direction in the riser space, preferably along a geometrical centre axis of the riser space. The rod can preferably extend along the full height of the riser space.

According to a second aspect, an agricultural implement for feeding granular or powdered material to the ground on which the agricultural implement is travelling is provided, comprising a material container, a feeder for feeding the material from the material container to a primary duct, a plurality of material outlets, and a distributor, as described above, wherein the distributor input is connected to the primary duct, and wherein the distributor outlets are connected via secondary ducts to a respective material outlet.

The distributor can be arranged on a main frame of the agricultural implement.

Alternatively, or as a complement, the distributor can be arranged on a rotatable frame portion relative to a main frame of the agricultural implement, such as a side frame portion, a front frame portion or a rear frame portion.

The distributor can further comprise a pre-distributor, which has a pre- distributor inlet and a plurality of pre-distributor outlets for forming said manifold, and wherein each of the pre-distributor outlets is connected to a respective distributor base inlet via a respective pre-distributor duct. The pre-distributor outlets can be arranged as a matrix comprising at least two rows and two columns of pre-distributor outlets.

The pre-distributor outlets can be connected to the distributor base inlets so that a pair of pre-distributor outlets that is located in the same column connects to respective distributor base inlets so that they provide the flow directions into the distributor base that are substantially counter-directed to each other.

The pre-distributor outlets can be connected to the distributor base inlets so that, viewed along a circumference of the distributor base, every other distributor base inlet connects to a pre-distributor outlet in a first of the rows and every other distributor base inlet connects to a pre-distributor outlet in a second of the rows.

It is assumed above that the matrix described above has two rows and two or more columns. However, it will be appreciated that the same

arrangement can be used if such a matrix is transposed to having two columns and two or more rows.

A distributor space located in the distributor base can have a bottom surface having at least two substantially radially extending valleys, which are divided by a substantially radially extending ridge.

According to a third aspect, a method for distribution of an airflow mixed with material from a primary duct to a plurality of secondary ducts is provided, comprising dividing the incoming airflow mixed with material into at least two manifold flows, feeding said manifold flows to a riser space, so that the manifold flows flow into the riser space with flow directions that differ by at least 5 degrees, preferably at least 10 degrees or at least 30 degrees, from each other, for forming a riser flow, leading the riser flow substantially vertically upward to a distributor head, and in the distributor head, distributing the riser flow between a plurality of secondary ducts.

The method can be used for feeding granular or powdered material to the ground on which an agricultural implement is travelling.

The flow directions into the riser space can be counter-directed to each other by +/- 30 degrees. The manifold flows can run in substantially the same plane.

The manifold flows can provide flow directions into the riser space, which are 90 +/-45 degrees, preferably 90 +/- 30 degrees or 90 +/- 15 degrees, to the flow direction of the incoming airflow mixed with material.

Brief description of the drawings

Fig 1 schematically illustrates an agricultural combination comprising a tractor vehicle 1 and an agricultural implement 2.

Figs 2a-2c illustrate a distributor according to a first embodiment.

Figs 3a-3c illustrate a distributor according to a second embodiment.

Figs 4a-4d illustrate a distributor according to a third embodiment.

Figs 5a-5f illustrate a distributor according to a fourth embodiment.

Detailed description

Fig 1 shows an agricultural combination comprising a tractor vehicle 1 and an agricultural implement 2 which can be a seed drill.

The agricultural implement comprises a frame 21 and a container 22 for material to be distributed to the ground on which the agricultural implement is travelling. A feeder 23 is located below the container 22 for feeding the material from the container 22. A fan 24 generates an airflow in the primary duct 25. The feeder 23 feeds material from the container 22 to the primary duct 25, the airflow in the primary duct 25 carrying the material to a distributor 26. A plurality of secondary ducts 27 run from the distributor 26 with which secondary ducts respective material outlets 28, here illustrated as furrow openers, are connected.

It will be appreciated that the agricultural implement can comprise several frame sections that can be moveable in relation to each other, several material containers 22 and/or several feeders 23, several primary ducts 25, several distributors 26 and several sets of secondary ducts 27 and the material outlets 28 connected thereto.

Figs 2a-2c show a distributor 26 according to a first embodiment. The distributor comprises a primary duct connection 261 forming an inlet 261 1 to a distributor base 262, a riser tube 263 which together with the distributor base 262 form a riser space 2631 and a distributor head 264 with a plurality of outlets 2643 to the secondary ducts 27.

The embodiment shown is intended for a primary duct with a circular cross section. The inlet 261 1 is designed to provide a transition from the primary duct circular cross section to a substantially rectangular cross section.

The distributor base can have an inlet portion 2621 , a manifold 2622, a pair of manifold ducts 2623a, 2623b, which connects the manifold 2622 with a pair of inlets 2624a, 2624b to a lower part 2625 of the riser space. The riser space lower part 2625 can have a bottom surface 2626, which can be planar, but preferably tapering upward, such as conical or semi-spherical.

The manifold 2622 can be designed so that in the inlet portion 2621 the incoming flow strikes a stop surface 26221 . The stop surface can be planar, prismatic or, as shown, convex. From the manifold 2622, the manifold ducts 2623a, 2623b can deflect in different directions in a respective direction which can be about 5-90 degrees, preferably about 30-85 degrees or 60-85 degrees, to the flow direction of the incoming flow (in the primary duct).

Then the manifold ducts can deflect again, so that a total change of direction after the first manifold is about 120-210 degrees, preferably about 150-190 degrees before it reaches the lower part 2625 of the riser space.

Thus a flow direction at the inlet of the manifold ducts to the riser space can be about 90 +/- 45 degrees, preferably 90 +/- 30 degrees or 90 +/- 15 degrees, to the primary duct direction of flow, viewed in projection on a horizontal plane.

The inlet portion 2621 and the ducts 2623a, 2623b can have a substantially rectangular or square cross section. The height of the inlet portion and the ducts can be substantially constant. Thus the distributor base can be designed so that the flow, before it reaches the lower part 2625 of the riser space, only deflects in one plane. The inlets to the riser space can be designed so that the directions of flow at the inlets deviate from each other by at least 5 degrees, preferably by at least 30 degrees or by at least 90 degrees. In the embodiment shown in Figs 2a-2c, the directions of flow are counter-directed, i.e. they deviate from each other by 180 degrees. In variants of this embodiment, the deviation can be about 150-210 degrees.

The conical bottom surface of the riser space can have a height amounting to about 20-100% of the height of the inlets 2624a, 2624b to the riser space, preferably 40-60%.

The riser tube 263 can be formed as a tube, the lower end of which is fixed to, or made in one piece with, the distributor base 262. The upper end of the riser tube 263 is fixed to the distributor head 264.

The distributor head 264 can be formed in any desired manner and a manner known per se. In the embodiment shown, the distributor head comprises a cylindrical distributor space 2641 with a height of less than 50% of the radius of the space, preferably less than 30% of the radius. The riser tube 263 exits at the centre 2642 of the distributor space, and the outlets 2643 of the secondary ducts 27 emanate from the peripheral surface of the space. One or more outlets can be individually controllable using actuators 2644, which enables marking a track by shutting down the feeding to one or more secondary ducts.

The distributor space can have a centrally positioned stop surface portion 2645, which can have a radial extent of sufficient size to serve as a stop surface for the incoming airflow mixed with materials coming from the riser tube. The stop surface portion can be planar, but preferably tapering downward, such as conical or semi-spherical. The height of a downwardly tapering stop surface portion 2645 can be about 30-60% of the height of the distributor space 2641 .

Figs 3a-3c show a distributor 26' according to a second embodiment. Principally, this second embodiment differs from the first embodiment in Figs 2a-2c by not only providing two manifold ducts but four manifold ducts, and thus four inlets to the riser space. Furthermore, the riser space is provided with a longitudinal centre rod, and the riser tube is provided with a corrugated jacket surface. The distributor head 264 is identical to the one shown in Figs 2a-2c.

With reference to Fig 3b, the distributor base 262' will be described in more detail.

The distributor base can have an inlet portion 2621 , a first manifold 2622, a pair of first manifold ducts 2623a, 2623b, which connects the manifold 2622 to respective second manifolds.

The first manifold duct 2623a exits at a second manifold, which comprises a stop surface 26221 a, which can be convex, the first manifold duct being divided into first subsidiary manifold ducts 2623aa, 2623ab, which in turn exit at a respective inlet 2624aa, 2624ab to the riser space 2625.

In the same way, the second manifold duct 2623b exits at a second manifold, which comprises a stop surface 26221 b, which can be convex, the second manifold duct 2623b being divided into second subsidiary manifold ducts 2623ba, 2623bb, which in turn exit at a respective inlet 2624ba, 2624bb to the riser space 2625.

The surfaces 26221 a, 26221 b can also have another form than convex, such as planar or prismatic.

The manifold 2622 can be designed so that in the inlet portion 2621 the incoming flow strikes a stop surface 26221 , which can be planar, convex or prismatic, as described above. From the manifold 2622, the first manifold ducts 2623a, 2623b can lead in a direction which can be about 70-90 degrees, preferably about 80-85 degrees to the flow direction of the incoming flow in the primary duct. The ducts 2623a, 2623b can deflect, so that the flow therein changes direction about 150-210 degrees, preferably 170-190 degrees before it reaches the manifolds to the subsidiary manifold ducts 2623aa, 2623ab; 2623ba, 2623bb.

The inlet portion 2621 , the first manifold ducts 2623a, 2623b and the subsidiary manifold ducts 2623aa, 2623ab; 2623ba, 2623bb can have a substantially rectangular or square cross section. The height of the inlet portion and the ducts can be substantially constant. Thus the distributor base can be designed so that the flow, before it reaches the lower part 2625 of the riser space, only deflects in one plane.

The subsidiary manifold ducts 2623aa, 2623ab; 2623ba, 2623bb can deflect from the incoming flow of the manifold ducts 2623a, 2623b to a direction which can be about 60-90 degrees, preferably about 5-90 degrees, preferably 30-90 degrees, 60-90 degrees or 70-80 degrees to the flow direction of the incoming flow from the manifold ducts 2623a, 2623b.

At the inlets 2624aa, 2624ab; 2624ba, 2624bb of the subsidiary manifold ducts to the riser space 2625, the direction of the respective flow can be about 30-80 degrees relative to the flow directions at the inlets of the subsidiary manifold ducts 2623aa, 2623ab; 2623ba, 2623bb.

If the inlets, as shown in the figures, are formed symmetrically around a vertically oriented plane through the riser space, inlets that are mirrored in pairs can have flow directions in relation to each other which differ by 90 degrees +/- 30 degrees, preferably +/- 10 degrees or +/- 1 degree. Such counter-directed inlets can be aligned, or laterally displaced in relation to each other.

Furthermore, the flow directions at the inlets can be, but do not have to be, parallel to the radii of the riser space.

As will be seen in Fig 3c, the riser tube 263' can have circumferentially running grooves. Alternatively, the tube can have inward protrusions and/or cavities, all with the purpose of spreading bouncing material to the walls to provide the most even distribution possible of the material in the riser space.

In this embodiment, the riser tube 263' can have a height

corresponding to about 3-6 x the height of the subsidiary ducts at the inlet to the riser space.

Furthermore, a central rod 2627, or a tube, can extend upward from the bottom surface 2626 of the riser space. This rod can extend all the way to the corresponding downward facing stop surface 2645 of the distributor head.

Figs 4a-4d show a distributor 26" according to a third embodiment. The embodiment in Figs 4a-4d differs from the one shown in Figs 2a-2c and Figs 3a-3c by the distributor base 263" having two levels: one inlet level, in which a first division to first manifold flows is provided, and one outlet level, which, in the example shown, is vertical below the inlet level, in which a division of the respective manifold flow into subsidiary manifold flows and feeding of the subsidiary flows to the riser space is provided.

Figs 4a-4d show a distributor 26" according to a third embodiment.

This third embodiment differs from the second embodiment in Figs 3a-3c by two manifold ducts and the four subsidiary manifold ducts being arranged in different planes.

The inlet 261 , 261 1 and riser space 2625 are designed in a

corresponding manner to Figs 2a-2c, and the distributor head 264 is identical to the embodiments shown in Figs 2a-2c and Figs 3a-3c.

With reference to Figs 4a-4d, the distributor base has two parts, comprising an upper part 262a, which is connected to the inlet 261 , 261 1 , and which has the first manifold 2622 and the stop surface 26221 and which provides the division into two manifold ducts 2623a, 2323b in the same way as shown in Figs 2a-2c and Figs 3a-3c.

Fig 4b shows an embodiment of the upper part 262a of the distributor base. Instead of a direct connection to the riser space or to other manifolds, the manifold ducts 2623a, 2623b connect to the respective shaft 2628a, 2628b, which connect the upper part 262a of the distributor base to the lower part 262b of the distributor base, as shown in Fig 4b.

The flow in each manifold duct will, as will be seen in Fig 4b, strike respective upper shaft stop surfaces 2629a, 2629b, which can be of any shape, such as planar, prismatic, convex, concave. However, in the example shown, they are concave.

Fig 4c shows an embodiment of the lower part 262b of the distributor base. From the respective shaft 2628a, 2628b, a pair of subsidiary manifold ducts 2623aa, 2623ab; 2623ba, 2623bb leads to inlets 2624aa, 2624ab; 2624ba, 2624bb in the lower part of the riser space 2625. Thus the flow, after striking the upper shaft stop surfaces, will change direction about 90 degrees (can be 90 +/-45 degrees or +/- 30 degrees) from the horizontal plane, stream downward inside the shaft and next strike a lower shaft stop surface 2630a, 2630b, to then be guided to the respective subsidiary manifold duct.

The subsidiary manifold ducts in the embodiment shown in Figs 4a-4d can, be curved to provide a change in the flow direction between the shaft 2628a, 2628b and the inlet 2624aa, 2624ab; 2624ba, 2624bb to the riser space 2625 which amounts to 45-150 degrees.

If the inlets are formed symmetrically around a vertical plane through the centre of the riser space 2625, opposite inlets that are mirrored in pairs can have counter-directed flow directions in relation to each other which differ by 90 degrees +/- 30 degrees, preferably +/- 10 degrees or +/- 1 degree. Such counter-directed inlets can be aligned, or laterally displaced in relation to each other.

Furthermore, the flow directions at the inlets can be, but do not have to be, parallel to the radii of the riser space.

By way of the embodiment in Figs 4a-4d, the air-mixed material flow will not only be subject to direction-changing in one plane, but also in a plane- cutting direction (here vertical).

It will be appreciated that the riser tube 263 in Figs 2a-2b and Figs 4a- 4d can instead be formed as the riser tube 263' in Figs 3a-3c.

The distributors 26, 26', 26" as described herein can be used in agricultural implements to distribute seed, fertilizer and/or pesticides in granular form or in powder form.

By way of the low design of the distributor, it can be located on a main frame, such as shown in Fig 1 , and thus replace existing distributors.

Alternatively, the distributor can be located on a side frame portion, which is foldable or rotatable in relation to a main frame. Thus, routing of feed lines to the material outlet of the side frame is facilitated, as it is sufficient that the primary duct can follow the relative movement between the side frame portion and the main frame.

As a second alternative, the distributor can be located on foldable or rotatable front portions or rear portions, relative to a main frame, of an agricultural implement. It will be appreciated that the drawings show basic diagrams, and that the different ducts can preferably be provided in the form of injection-moulded ducts or duct parts of polymer material. Abrasion plates can possibly be fitted on such portions that are subjected to the greatest wear, e.g. stop surfaces or duct bends.

The exact design of the walls and the cross section of the ducts is of lesser importance. It is important that the ducts are designed so that incoming flow is divided into subsidiary flows that change direction, preferably, a number of times.

With the embodiments according to Figs 2a-2c and Figs 4a-4d, a larger base plate, i.e. a "footprint", than is required is provided. This protects the motors 2644. It can be desirable to also provide a larger footprint in an embodiment according to Figs 2a-2c, to protect the motors.

Figs 5a-5b show perspective views of a distributor according to a fourth embodiment. Here, the distributor comprises a pre-distributor 31 , a distributor base 32, a riser tube 263 and a distributor head 264. The riser tube 263 and the distributor head 264 can be structured in the same way as previously described.

The pre-distributor 31 comprises a casing 310, a pre-distributor inlet 31 1 and a plurality of pre-distributor outlets 312a-312f.

In the example shown, which assumes that the incoming primary duct 25 has a circular cross section, the pre-distributor inlet 31 1 is circular, in order to connect to the primary duct 25. Naturally, if the primary duct has a different shape, the pre-distributor inlet 31 1 will be provided with a corresponding shape.

The casing forms a transition from the cross section of the pre- distributor inlet 31 1 to the pre-distributor outlets 312a-312f.

The distributor base 32 comprises a distributor base casing 320, a plurality of distributor base inlets 321 a-321 f, a distributor base space 324, which connects to a riser duct 263 defining a riser space, which in turn, connects to the distributor head 264. As suggested by the broken lines in Fig 5d, each of the pre-distributor outlets 312a-312f is connected to a respective distributor base inlet of the distributor base inlets 321 a-321 f. This connection can be provided by a respective pre-distributor duct (not shown), which can each be designed as a flexible hose or a rigid tube, and which are not shown in any of the figures. Alternatively, the pre-distributor ducts can be provided in the form of manifolds, where two or more, e.g. all, pre-distributor ducts can be integrated, for example, designed in one piece or permanently attached to each other, in order to form one manifold module.

Each of the pre-distributor ducts can have a respective length, where a length of one of the shortest ducts is at least 50% of a length of one of the longest ducts, preferably at least 75%, at least 90% or at least 99%.

The pre-distributor outlets 312a-312f can be arranged as a matrix comprising at least two rows and at least two columns, where each row or column comprises at least two pre-distributor outlets. Specifically, each column can comprise exactly two pre-distributor outlets, and each row can comprise 2-5, preferably 2-3 pre-distributor outlets.

A pair of adjacent columns can be displaced in relation to each other so that the space between the columns is reduced.

In the same way, a pair of adjacent rows can be displaced in relation to each other.

In the example shown, the upper row comprises three pre-distributor outlets with the reference designations 312a, 312c, 312e and the lower row comprises three pre-distributor outlets with the reference designations 312b, 312d, 312f. In the same way, the first column comprises two pre-distributor outlets with the reference designations 312a, 312b, the second column comprises two pre-distributor outlets with the reference designations 312c, 312d, and the third column comprises two pre-distributor outlets with the reference designations 312e, 312f.

Since the pre-distributor outlets 312a-312f are arranged as a matrix, the downstream end of the casing 310 can have a rectangular (as shown) or a square cross section (when the number of rows and columns is the same as the pre-distributor outlets). Thus, each of the pre-distributor outlets 312a- 312f can have an upstream end that connects to the matrix and preferably has a rectangular or a square (as shown) cross section, so that air-tight connections can be provided between the pre-distributor outlets 312a-312f, and a downstream end, the cross section of which is designed to connect to a duct for further coupling to the distributor base 32. In the example shown, these downstream ends of each pre-distributor outlet 312a-312f are circular.

The distributor inlets 321 a-321 f can be arranged so that a pair of pre- distributor outlets 312a, 312b; 312c, 312d; 312e, 312f that is located in the same column or in the same row, via the distributor ducts (not shown), connects to the distributor base 32 with the flow directions substantially counter-directed in relation to each other. For example, the flow directions can be counter-directed +/- 90 degrees, preferably +/- 45 degrees, +/- 30 degrees, +/- 10 degrees or +/- 5 degrees.

The distributor base inlets 321 a-321 f can also be arranged such that, viewed along the circumference of the distributor base, every other distributor base inlet comes from the upper row in the matrix and every other distributor base inlet comes from the lower row in the matrix.

In addition, if the distributor base inlets 321 a-321 f are arranged so that opposite pairs of the distributor base inlets connect to different rows in the matrix, a good distribution in particular is provided.

The distributor base space 324 can be designed as a substantially cylindrical space.

Alternatively, the distributor base space 324, as shown in Fig 5f, can be designed with a distributor space, the base of which having a plurality of radially extending ridges 327a-327f and valleys 326a-326f, where each valley 326a-326f coincides with a respective distributor base inlet 321 a-321 f and where adjacent valleys are divided by one of the ridges 327a-327f. The ridges 327a-327f can extend a radial distance corresponding to about 20-80%, preferably 30-70% of a radius from the centre of the distributor space to an inner vertical wall of the casing 320 of the distributor base. At the central part of the distributor space 324, a conical portion 2626, corresponding to a part as described with reference to Figs 2a-4d, can exist. At the centre of the distributor space 324, a rod 2627 can extend upward along the riser space to, or practically through, the distributor head 264.