WO2013081527A1

WO2013081527A1 - Stand for refining apparatus

Info

Publication number: WO2013081527A1
Application number: PCT/SE2012/051252
Authority: WO
Inventors: Stefan MELLANDER; Jonas Lundberg
Original assignee: Metso Paper Sweden Ab
Priority date: 2011-11-30
Filing date: 2012-11-14
Publication date: 2013-06-06
Also published as: SE1151140A1; EP2785912A4; EP2785912A1; CN103998681B; SE536186C2; CN103998681A

Abstract

A stand for a refining apparatus which minimizes the problem of non-alignment of the refining gaps disclosed. The stand comprises a support beam structure adapted to transfer axial forces from the bearing unit, during operation of the refining apparatus, essentially from a longitudinal midsection of the intermediate member at the rear end (7) of the stand essentially horizontally towards the front end (6) of the stand and thereby distributes the axial forces in an optimal manner through the stand.

Description

STAND FOR REFINING APPARATUS

The present invention relates in general to a stand for a refining

apparatus. More specifically, it relates to a stand which minimizes the risk of obtaining a non-parallel refining gap during the refining process of a disc refiner as a result of the axial forces on the refining discs.

BACKGROUND

Refining apparatuses, such as disc refiners, are used for refining, i.e. converting lignocellulosic wood chips or the like into separated fibers. Disc refiners usually comprise two opposite refining discs rotatable in relation to each other. In many instances, one of the refining disc is rotatable, a so called rotor, around an axis, whereas the other refining disc is non-rotatable, a so called stator. However, in some refining apparatuses both refining discs are rotatably arranged. The refining discs are generally provided with exchangeable refining segments, arranged on the surface of the refining disc facing the opposite refining disc, i.e. the refining surfaces of the refining apparatus. The refining segments generally comprise bars and intermediate grooves arranged in specific patterns depending on the desired fiber quality. Grinding occurs between the two refining surfaces which are kept at a certain distance from each other, whereby a space, a so called refining gap, is provided between the refining surfaces. The material to be ground is generally supplied to the refining gap through an opening in one of the refining discs close to the center axis thereof. During grinding, the material which is ground is moved essentially radially relative to the refining discs.

The refining discs are arranged on a stand or frame. A rotatably arranged refining disc, i.e. a rotor, is connected to the stand by a bearing mounted to the stand, through which bearing an axle or shaft of the refining disc is arranged. A non-rotating refining disc, i.e. a stator, may be mounted to the stand by for example a plurality of pins, bolts or the like.

During operation, it is important that the refining surfaces of the apparatus are properly aligned and that the refining discs do not tend to tilt or deform such that the refining gap is not essentially parallel over the refining surfaces. The alignment between the refining surfaces is correct when the width of the refining gap is kept constant for every diameter for a complete revolution, the deflection of the stator itself in a horizontal plane being disregarded. If the refining surfaces would for example come in contact with each other, there is a risk of breakdown or at least wear of the refining surfaces which leads to a substantially shortened operation time of the apparatus before the refining segments have to be changed. Furthermore, the degree of alignment between the refining surfaces is important for the resulting quality of the ground material. When the degree of alignment between the refining surfaces is reduced, the quality of the ground material is deteriorated. Thus, a control of the refining gap and the alignment between the refining surfaces is of great importance.

During operation, the refining discs are subjected to a great axial force.

This axial force may cause the refining discs to somewhat tilt or tip relative to each other. More specifically, the axial force often causes the refining gap to be larger at the top and smaller at the lower part of the gap.

The problem has been previously addressed for example by various devices for aligning the refining discs, such as disclosed in WO 2007/139504 A1 , WO 2007/139505 A1 and WO 2007/09471 1 A1 .

It has now been found that the design of the stand of the refining apparatus to some extent contributes to the problem of non-alignment of the refining discs because the non-rotating disc tend not to move parallel to rotor a result of the mounting of the stator to the stand and how the forces are distributed in the stand. Therefore, there is a need for a new design of the stand.

US 3,762,660 discloses a stand which is said to solve the problem of deformation of the stand during operation as a result of the axial forces subjected to the refining discs. The stand comprises trestles for the support of bearing devices for the shafts of the discs. The trestles are connected to each other by a plurality of beams arranged both above and below the horizontal plane of the shafts of the discs thereby preventing the obliqueness of the discs in relation to each other. Furthermore, the stand includes ducts for circulation of a heat-transfer fluid through the stand and means for keeping the fluid at constant temperature in order to avoid deformation of the stand during operation. The proposed design of the stand is however disadvantageous because it is fairly space consuming and requires the presence of a circulating heat-transfer fluid.

Another example of a stand for a refining apparatus is disclosed in US 3, 166,260. The stand comprises inter alia plates welded together. SUMMARY

The object of the present invention is to minimize the problems associated with the axial forces applied to a stator during operation of a refining apparatus for disintegrating and refining lignocellulose-containing material. More specifically, the object of the invention is to minimize the risk of non-alignment between the refining surfaces, i.e. of the refining gap, during operation as a result of the axial forces. The alignment between the refining surfaces is correct when the width of the refining gap is kept constant for every diameter for a complete revolution, the deflection of the stator itself in a horizontal plane being disregarded.

The object is achieved by the stand in accordance with independent claim 1 and the refining apparatus in accordance with claim 16. Preferred embodiments are defined by the dependent claims.

The stand has a front end and an opposing rear end and comprises a first and a second side member, which side members in turn each comprise a leg section and an arm section. The arm section is adapted for mounting of a stator, i.e. a non-rotating refining disc, thereto at the front end of the stand, preferably at an end surface of the arm section.

The stand further comprises a first intermediate member having a first end connected to the first side member and a second end connected to the second side member. The first intermediate member comprises means adapted for mounting a bearing unit thereto in which bearing unit a shaft of a rotor, i.e. a shaft of a rotating refining disc, is to be arranged. The stand may suitably also comprise a second intermediate member extending between the side members. The second intermediate member is arranged essentially in a vertical plane, preferably perpendicular to the horizontal axis of the shaft of the rotor.

The stand further comprises a support beam structure adapted to transfer axial forces from the bearing unit, during operation of the refining apparatus, essentially from a longitudinal midsection of the intermediate member at the rear end of the stand, preferably essentially horizontally, towards the front end of the stand. This ensures that the axial forces are distributed in the stand in a suitable manner. Thereby, it is possible to keep the desired alignment of the refining surfaces during operation of the refining apparatus. In accordance with one embodiment of the invention, the support beam structure comprises a first support member extending from a region in the vicinity of the means adapted for mounting a bearing unit of the first intermediate member at the rear end of the stand (preferably essentially from a longitudinal midsection of the first intermediate member) to the first side member. Moreover, the first support member has a longitudinal extension which is longer than the distance along the first intermediate member, in the direction of the longitudinal extension of the first intermediate member, between the connection point of the first support member to the intermediate member and the first side member. The support beam structure further comprises a second support member extending from a region in the vicinity of the means adapted for mounting a bearing unit of the first

intermediate member at the rear end of the stand (preferably essentially from a longitudinal midsection of the first intermediate member) to said second side member. Like the first support member, the second support member has a longitudinal extension which is longer than the distance along the first intermediate member, in the direction of the longitudinal extension of the first intermediate member, between its connection point to the intermediate member and the side member. Thus, the first and second support members preferably extend from essentially a mid rear section of the stand towards the sides in a frontward direction of the stand. The longitudinal extension of the support members may be essentially straight or being bent or arc-shaped.

In accordance with one preferred embodiment, the first and second support members together form a first support beam. The first support beam extends between said first and second side members and is arranged such that its cross sectional center of gravity is located in a first horizontal plane arranged at a distance from the horizontal axis of the shaft of the rotor. The first horizontal plane is preferably located between the ground surface and the horizontal axis of the shaft of the rotor. The first support beam is arc-shaped in said first horizontal plane such that it is concave towards the front of the stand. The arrangement of the first support beam further ensures that the axial forces are distributed through the stand in an optimal manner such that their negative influence on the alignment of the refining gap is minimized. The fact that it is arc-shaped is advantageous because it has a beneficial effect on the transfer of the forces through the stand. In accordance with one embodiment, the stand further comprises a second support beam. The second support beam has its longitudinal extension essentially in a vertical plane along the horizontal axis of the shaft of the rotor. Moreover, the second support beam is essentially straight in its longitudinal extension. The second support beam may preferably, be connected to the first support beam at a longitudinal midsection of the first support beam. The second support beam provides rigidity to the stand where the bearings are mounted.

In accordance with yet an embodiment, the stand further comprises a third support beam extending between said first and second side members. The third support beam preferably has its cross sectional center of gravity located in the same horizontal plane as the first support beam. Just like the first support beam, the third support beam is arc-shaped in the horizontal plane such that it is concave towards the front of the stand. A connection point of the first support beam to the first side member is preferably immediately adjacent a connection point of the third support beam to the first side member. Preferably, the arc-shape of the third support beam has a larger radius than the radius of the arc-shape of the first support beam.

In accordance with yet another embodiment, the stand also comprises a fourth support beam arranged between said first and second side members. The fourth support beam is arc-shaped in a horizontal plane such that it is convex in the direction towards the front of the stand. Moreover, the cross sectional center of gravity of said fourth support beam is preferably arranged in a second horizontal plane, said second horizontal plane arranged at a distance from the horizontal plan in which the cross sectional center of gravity of the first support beam is arranged. The fourth support beam is suitably connected with the third support beam essentially in the middle of the longitudinal extension of the first support beam.

In accordance with yet another embodiment, the arm section of the side members comprises an end surface adapted for mounting of the stator thereto and is provided with a recess arranged in a lower portion of the arm section in the vicinity of said end surface. Moreover, the arm section preferably comprises a lip at the bottom part of the arm section closest to the stator. The lip is delimited by the end surface of the arm section adapted for mounting of the stator, a bottom lip surface preferably extending essentially horizontally, and a tangent surface of the recess. The recess is suitably rounded and has a radius arranged essentially in a vertical plane. The recess allows a certain flexibility of the stator in the lower portion thereof and thereby counteracts a force pushing the lower portion of the stator towards the rotor which would cause a non-parallel refining gap.

In accordance with yet another embodiment, the first intermediate member has a front end surface at the front part of the stand, said front end surface being divided into a first front end surface section and a second front end surface section on its respective side of said means adapted for mounting a bearing unit thereto. The second front end section is closest to a connection point of the first

intermediate member to the side member and is suitably bent such that it has a radius in the horizontal plane of the horizontal surface of the first intermediate member. Preferably, the second front end surface section is essentially straight.

BREIF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates a perspective view of a refining apparatus comprising a stand in accordance with the invention.

Figure 2 illustrates a rear perspective view of a stand of a refining apparatus in accordance with the invention.

Figure 3a illustrates a bottom perspective view of a stand in accordance with one embodiment of the invention.

Figure 3b illustrates a bottom plan view of the stand according to figure 3a. Figure 4 illustrates a side perspective view of a stand in accordance with another embodiment of the present invention.

Figure 5 illustrates a top plan view of a stand in accordance with yet another embodiment of the present invention.

Figure 6 illustrates a bottom perspective view of a stand in accordance with an alternative embodiment of the invention.

DETAILED DESCPRIPTION

The invention will be described in further detail below with reference to the accompanying drawings. The invention is not limited to the specific embodiments described below and shown in the figures, but may be varied within the scope of the claims. Moreover, it should be noted that the drawings are not necessarily drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention.

In the present disclosure, the term "stator" is considered to mean the non- rotating refining disc and encompasses the refining segments of the stator, the segment holder, as well as the stator plate, unless otherwise explicitly disclosed. The term "rotor" is considered to mean the rotating refining disc of the refining apparatus.

Figure 1 illustrates a refining apparatus 1 for disintegrating and refining lignocelluloses-containing material in accordance with the present invention. The refining apparatus 1 comprises a refining housing 2 in which a rotating disc, a so called rotor, is located. The rotor is arranged on a shaft (not shown) placed in a shaft package 5 and driven by a motor unit (not shown). The shaft is arranged in bearings mounted to a stand 4. The stand 4 comprises a first side member 9a, which in turn comprises a leg section 10a, a foot 1 1 a at the lower end of the leg section 10a and an arm section 12a at the upper end of the leg section 10a. The leg section with its foot 1 1 a is adapted to stand on a ground surface. A plate 3 of a non-rotating disc, a so called stator, is mounted to the stand 4 at an end surface 13a, 13b of the arm section 12a, 12b, for example by means of a first set of bolts (not shown). The stator plate 3 is generally also mounted to the refining housing 2 by means of for example a second set of bolts (not shown). The refining segments of the stator and the corresponding segment holder are located inside the refining housing 2. To the center of the rear surface of the stator plate is connected means for introducing material to be ground. Said means have been omitted in the figure in order to more clearly show the other details.

The front part of the stand 6 is closest to where the stator is mounted, whereas the rear part 7 of the stand is the furthest from where the stator is mounted as shown in figure 1 .

The stand 4 is shown in more detail in figure 2. As clearly shown in the figure, the stand 4 comprises a first and a second side member 9a, 9b, arranged at opposite sides of the stand. The side members 9a, 9b are arranged essentially vertically relative to the ground surface on which the stand rests on, they may however also be slightly tilted versus a vertical plane if desired. The side members each comprise a leg section 10a, 10b and an arm section 12a, 12b. The arm section has an end surface 13a, 13b arranged essentially vertically and preferably being slightly bent in the vertical plane, the end surface 13a, 13b being adapted for mounting of a stator plate thereto.

The stand 4 further comprises a first intermediate member 14 having a first end connected to the first side member 9a and a second end connected to the second side member 9b, thus extending between the side members. The first intermediate member 14 comprises means adapted for mounting of a bearing unit 8 thereto, which bearing unit in turn is adapted to receive the shaft of the rotor (not shown). The first intermediate member 14 is arranged essentially in a horizontal plane parallel to the horizontal axis 26 (shown in figure 5) of the shaft of the rotor. The horizontal plane of the first intermediate member is located below the horizontal axis of the shaft of the rotor.

It should be noted, that even though the figure shows an embodiment wherein the bearing unit is somewhat lowered compared to the horizontal plane of the first intermediate member, it is also plausible that the bearing unit for example is mounted on top of the surface of the first intermediate member.

Furthermore, the stand may also comprise a second intermediate member 15 having a first end connected to the first side member 9a and a second end connected to the second side member 9b, thus extending between the side members. The second member 15 is arranged essentially in a vertical plane and located in the vicinity of the side portion of the leg section 10 which is the furthest from the refining discs, i.e. at the rear part 7 of the stand. The second intermediate member may be a plate like member, but is may also be in the form of a beam or the like.

Figure 2 further shows one example of a horizontal plane as illustrated by the arrows h_x and h_y, in this case the horizontal plane of the upper surface of the first intermediate member 14. Furthermore, one example of a vertical plane is illustrated by the arrows v_x and v_y in this case the vertical plane in which the second intermediate member 15 is arranged.

Figure 3a shows a perspective view of one embodiment of the stand 4 seen essentially from the underside thereof and figure 3b illustrates a bottom plan view, i.e. a plan view seen from the underside thereof, of the stand shown in figure 3a. A first support beam 16 is arranged between the first and second side member 9a, 9b, preferably between the leg sections 10a, 10b of the side members. The respective ends of the support beam in its longitudinal extension are connected to the respective side members. The first support beam 16 is arc-shaped along its longitudinal extension and in a first horizontal plane arranged at a distance from the horizontal axis of the shaft of the rotor. More specifically, the center of gravity of any cross section of the support beam in its longitudinal extension is located in said first horizontal plane. Preferably, said first horizontal plane is located between the horizontal axis of the rotor and the ground surface on which the stand is placed. Thus, the cross sectional center of gravity of the first support beam is also arranged in a horizontal plane below the first intermediate member 14.

The arc-shape of the first support beam is such that the support beam is concave seen in the direction toward the stator, i.e. towards the front part of the stand. Consequently, the support beam is convex in the rear direction of the stand.

The first support beam 16 may be connected to the second intermediate member 15 (if present) at a midsection of the longitudinal extension of the first support beam.

The first support beam 16 has its highest point of the arc-shape, i.e. the middle portion of its longitudinal extension, located at the rear part of the stand and in the vicinity of a rear part of the bearing unit. Thus, the axial forces are transmitted to the first support beam essentially at the highest point of the arc- shape and are transmitted through the support beam towards the front of the stand. Thus, the arc-shape of the first support beam ensures that that the axial forces to which the stator of the refining apparatus is subjected are more efficiently distributed in the stand compared to previously known stands. The design of the stand with the arc-shaped first support beam thus reduces the risk of the refining gap not being parallel during the refining process.

It should be noted that the arc-shape of the first support beam 16 may have a constant radius over the whole longitudinal extension of the first support beam between the side members of the stand as illustrated in the figures.

However, it is also plausible that the support beam is divided into a plurality of longitudinal portions, preferably wherein at least one of said longitudinal portions has an arc-shape with a first radius and an adjacent longitudinal portion has an arc-shape with a second radius different from said first radius. Even though it is preferred that the longitudinal portions are bent, it is also plausible that one or more are essentially straight without departing from the scope of the invention. For example, the longitudinal portions arranged at the respective ends connected to the side members may be essentially straight.

In accordance with a preferred embodiment, the stand 4 further comprises a second support beam 17 arranged essentially in a vertical plane along the horizontal axis of the shaft of the rotor and having a longitudinal extension parallel to said horizontal axis. The second support beam is essentially straight in its longitudinal extension. Moreover, the second support beam preferably has its cross sectional center of gravity located in the same horizontal plane as the cross sectional center of gravity of the first support beam 16. Moreover, the height of the second support beam, i.e. its vertical extension in the vertical plane, is preferably essentially the same as the height of the first support beam. Furthermore, the second support beam 17 is suitably connected to a longitudinal midsection of the first support beam 16. The second support beam may also be connected to a longitudinal midsection of a third support beam 18 (if present), which will be described in more detail below.

The purpose of the second support beam 17 is to give sufficient rigidity to the part of the stand where the bearings are mounted. This is because any type of deformation to that part of the stand is undesirable and the design of the stand should thus be as rigid as possible in the vicinity of the bearings.

The forces to which the stand is subjected during the refining process are generally very high. Therefore, it is in most instances preferable that the stand also comprises a third support beam 18 as illustrated in figures 3a and 3b. Like the first support beam 16, the third support beam 18 is also arc-shaped in a horizontal plane. It is also bent in the same direction as the first support beam, i.e. the third support beam is arc-shaped such that it is concave towards the front 6 of the stand.

The connection point 20a of the third support beam to the first side member 9a is preferably located in the close vicinity, or preferably even directly adjacent, to the connection point 21 a of the first support beam to the first side member, as is shown in figures 3a and 3b. Naturally, the same applies to the connection points 20b, 21 b of the first and third support beam to the second side member 9b as well. The arrangement of the connection points results in that the arc-shape of the third support beam has a greater radius in the horizontal plane than the radius of arc-shape of the first support beam.

As in the case of the first support beam 16, the arc-shape of the third support beam 18 may have a constant radius over the whole longitudinal extension between the side members. However, it is also plausible that the third support beam is divided into a plurality of longitudinal portions, wherein at least one of said longitudinal portions has an arc-shape with a first radius and an adjacent longitudinal portion has an arc-shape with a second radius different from said first radius. Even though it is preferred that the longitudinal portions are bent, it is also plausible that one or more are essentially straight without departing from the scope of the invention. For example, the longitudinal portions arranged at the respective ends connected to the side members may be essentially straight.

The third support beam 18 further ensures that the axial forces to which the non-rotating refining disc and the stand are subjected to during the refining process are distributed in the stand in an optimum manner. The design thereby minimizes the effect said forces has on the refining gap because it limits the possible non-parallel dislocation of the stator relative to the rotor.

As previously mentioned, the stand should be as rigid as possible in the vicinity of the bearing unit. This can be further improved in accordance with a preferred embodiment by a fourth support beam 19. The fourth support beam 19 extends between the first and second side members 9a, 9b and has its cross sectional center of gravity in a second horizontal plane which is arranged at a distance from the first horizontal plane in which the cross sectional center of gravity of the first support beam is located as well as at a distance from the horizontal axis of the shaft of the rotor. More specifically, the second horizontal plane is arranged between the horizontal axis of the shaft of the rotor and the first horizontal plane. Thus, the fourth support beam has a cross sectional center of gravity which is closer than the cross sectional center of gravity of the first support beam to the first intermediate member 14 and to the horizontal axis of the shaft of the rotor. The height, i.e. the extension in the vertical direction, of the fourth support beam is preferably smaller than the height of the first support beam, as can be seen from figure 3a. Like the first and third support beam, the fourth support beam 19 is arc- shaped in the horizontal plane. However, in contrast to the first and third support beams, the fourth support beam is arranged such that it is convex in the direction towards the front of the stand.

The fourth support beam 19 is preferably connected to the third support beam 18 essentially in the middle of the longitudinal extension of the third support beam. Moreover, the fourth support beam 19 preferably also connects with the first support beam at a distance from the middle of the longitudinal extension of the first support beam and at a distance from the respective longitudinal ends of the first support beam, i.e. at a distance from where the first support beam connects to the side members.

Even though the fourth support beam is described above as in one piece, it will be readily apparent to the skilled person that the fourth support beam may consist of a plurality of axial segments, suitably four, where each segment extends either between a side member and another support beam, or between two different support beams. In such a case, it is obvious that the different segments are connected to each other by means of the support beams located in between.

In accordance with one preferred embodiment of the stand according to the invention, the arm sections of the respective side members are designed to allow some flexibility of the arm section in the lower region of the end surface 13a, 13b where the stator plate is mounted. Thereby, the stator, and thus its refining surface, is allowed to tilt in relation to a vertical plane in order to obtain a position essentially parallel to the refining surface of the rotor. As previously described, the arm section 12a, 12b comprises a vertically arranged end surface 13a, 13b adapted for mounting of the stator thereto. The end surface may suitably be slightly bent or arc shaped in its vertical plane to allow a suitable fit with the outer shape of the stator and provide adequate support to the stator.

In order to allow the desired flexibility, the arm section may be provided with a recess 22a, 22b arranged in a lower portion of the arm section 12 and in the vicinity of the end surface 13 such that a lip 23 is formed at the bottom part of the arm section closest to the stator, i.e. at the front end of the stand. The lip 23 is delimited by the end surface 13a, 13b of the arm section a bottom lip surface 24 which preferably extends essentially horizontally, and a tangent surface 25 of the recess 22, as is shown in figure 4. Preferably, the recess is rounded and has a radius essentially in a vertical plane in order to allow a smooth flexibility during operation.

The arrangement of the recess 22a, 22b ensures that the neutral plane of the area moment of inertia of the stand coincide with the horizontal axis of the shaft of the rotor and thus that the stator is allowed to tilt in relation to a vertical plane in order to obtain a position essentially parallel to the refining surface of the rotor. Thus, the alignment of the refining discs will be essentially correct during operation of the refining apparatus. More specifically, the recess and the lip allows for the lower portion of the end surface and thus the lower portion of the stator plate (and thus the refining surface of the stator) to deflect in the forward direction which is the same direction as the upper portion of the stator generally tend to deflect. Thus, the recess allows a certain flexibility of the stator in the lower portion thereof and thereby counteracts a force pushing the lower portion of the stator towards the rotor.

In accordance with a preferred embodiment, the front connection point 29 of the leg section 10a, 10b and the arm section 12a, 12b, i.e. the connection point closest to the stator, is arranged at a distance from the lip 23. The front connection point 29 between the leg section and the arm section may suitably be arranged in the recess 22, as shown in figure 4.

Figure 5 illustrates a top plan view of the stand in accordance with yet a preferred embodiment. As can be seen from the figure, the upper horizontal surface of the first intermediate member 14 has a specific design in the part closest to the stator. Instead of the front end surface of the first intermediate member, i.e. the end surface which faces the stator, being arc shaped over essentially its entire extension between the first and second side member or essentially straight, it is divided into a first front end surface section 27 and a second front end surface section 28 on its respective side of the bearing unit 8. The first front end section is the section closes to the bearing unit and is preferably essentially straight. The second front end section is closest to the connection point of the first intermediate member to the side member and is bent such that it has a radius in the horizontal plane of the horizontal surface of the first intermediate member. The first and second front end surfaces can also be seen in figure 3b. Preferably, the rear end surface 30 of first intermediate member 14 is essentially straight and extends essentially perpendicular to a vertical plane along the horizontal axis 26 of the shaft of the rotor.

The specific design of the upper horizontal surface of the first intermediate member achieves the effect that the natural frequency of the refiner housing sideways is not too close to the frequency of the rotation speed during the refining process.

Figure 6 illustrates an alternative embodiment of the stand. In the figure, the first intermediate member comprising means adapted for mounting of the bearing thereto has been omitted but the horizontal axis 26 of the shaft of the rotor is shown. The stand according to the present embodiment differs from the one shown in figures 3a and 3b in that it only comprises one support beam, namely the first support beam 16. Said support beam is arc-shaped in a horizontal plane such that it is concave in the frontwards direction of the stand.

As previously stated, the invention is not limited to the embodiments shown in the figures. For example, the stand may not necessarily comprise a support beam being arc-shaped as long as it comprises a support beam structure adapted to transfer axial forces from the bearing unit, essentially from a

longitudinal midsection of the intermediate member at the rear end of the stand essentially horizontally towards the front end of the stand. In accordance with one embodiment, the support beam structure comprises a first support member extending essentially from a longitudinal midsection of the intermediate member at the rear end of the stand to said first side member, and a second support member extending essentially from a longitudinal midsection of the intermediate member at the rear end of the stand to said second side member. The first and second support members each have a longitudinal extension which is larger than half of the longitudinal extension of the first intermediate member. Thus, the first and second support members extend from essentially a mid rear section of the stand towards the sides in a frontward direction of the stand. The longitudinal extension of the support members may be essentially straight or being bent or arc-shaped. Such a support beam structure may for example comprise two support beams which are connected to the intermediate member essentially at a longitudinal midsection of the intermediate member at the rear end of the stand and each of said support beams connected to the respective side member of the stand in the vicinity of the front end of the stand, thus forming a support beam structure having a V-shape. However, it is preferable to have at least one arc-shaped support beam adapted to transfer the forces towards the front of the stand.

The stand according to the present invention is preferably cast in one monolithic structure. However, it is also possible to produce the stand by assembling the different parts thereof and weld them together.

It should also be noted that the cross sectional geometrical shape of the different support beams is not limiting to the invention. Furthermore, they may be solid or hollow depending for example on the magnitude of the forces they are designed to withstand.

Claims

1 . Stand (4) for a refining apparatus (1 ), the stand having a front end (6) and an opposing rear end (7), and comprising a first and a second side member (9a, 9b), each side member (9a, 9b) comprising a leg section (10a, 10b) and an arm section (12a, 12b), said arm section adapted for mounting of a stator (3) at a front end of the stand; a first intermediate member (14) having a first end connected to the first side member (9a) and a second end connected to the second side member (9b), the first intermediate member (14) comprising means adapted for mounting a bearing unit (8) thereto in which bearing unit a shaft of a rotor is to be arranged, said shaft having a horizontal axis (26),

ch a racte rized i n a support beam structure adapted to transfer axial forces from the bearing unit, during operation of the refining apparatus, essentially from a longitudinal midsection of the intermediate member at the rear end (7) of the stand towards the front end (6) of the stand.

2. Stand according to claim 1 , wherein said support beam structure comprises a first support member extending from a region in the vicinity of the means adapted for mounting a bearing unit of the first intermediate member at the rear end (7) of the stand, preferably essentially from a longitudinal midsection of the first intermediate member, to said first side member (9a), said first support member having a longitudinal extension which is longer than the distance along the first intermediate member, in the direction of the longitudinal extension of the first intermediate member, between the connection point of the first support member to the intermediate member and the first side member; a second support member extending from a region in the vicinity of the means adapted for mounting a bearing unit of the first intermediate member at the rear end (7) of the stand, preferably essentially from a longitudinal midsection of the first intermediate member, to said second side member (9a), said second support member having a longitudinal extension which is longer than the distance along the first intermediate member, in the direction of the longitudinal extension of the first intermediate member, between the connection point of the second support member to the intermediate member and the second side member.

3. Stand according to claim 2, wherein said first and second support members together form a first support beam (16) extending between said first and second side members (9a, 9b) and arranged such that its cross sectional center of gravity is located in a first horizontal plane arranged at a distance from said horizontal axis (26), said first support beam (16) being arc-shaped in said first horizontal plane such that it is concave towards the front part (6) of the stand.

4. Stand according to any of the preceding claims, wherein said arm section comprises an end surface (13a, 13b) arranged at the front end of the stand and adapted for mounting of the stator thereto, and wherein the arm section is provided with a recess (22) arranged in a lower portion of the arm section in the vicinity of said end surface (13a, 13b).

5. Stand according to claim 4, wherein the arm section comprises a lip (23a, 23b) at the bottom part of the arm section at the front end of the stand, said lip (23a,

23b) delimited by said end surface (13a, 13b) of the arm section adapted for mounting of the stator, a bottom lip surface (24), and a tangent surface (25) of the recess (22).

6. Stand according to any of claims 4 or 5, wherein the recess (22) is rounded and has a radius arranged essentially in a vertical plane.

7. Stand according to any of claims 2 to 6, wherein the support beam structure further comprises a second support beam (17), the second support beam having a longitudinal extension essentially in a vertical plane along said horizontal axis (26) of the shaft of the rotor, and wherein said second support beam is essentially straight in its longitudinal extension.

8. Stand according to claim 7, wherein that said second support beam (17) is connected to a longitudinal midsection of the first support beam 16.

9. Stand according to any of claims 3 to 8, wherein the support beam structure further comprises a third support beam (18) extending between said first and second side members (9a, 9b) such that its cross sectional center of gravity is located in a horizontal plane, preferably said first horizontal plane, said third support beam (18) being arc-shaped in said horizontal plane such that it is concave towards the front part of the stand.

10. Stand according to claim 9, wherein a connection point (21 a) of said first support beam to said first side member (9a) is immediately adjacent a connection point (20a) of said third support beam to said first side member (9a).

1 1 . Stand according to any of claims 3 to 10, wherein the support beam structure comprises a fourth support beam (19) extending between said first and second side members (9a, 9b), said support beam being arc-shaped in a horizontal plane such that it is convex towards the front part of the stand.

12. Stand according to claim 1 1 , wherein said fourth support beam (19) has a cross sectional center of gravity arranged in a second horizontal plane, said second horizontal plane arranged at a distance from said first horizontal plane.

13. Stand according to any of claims 1 1 or 12, wherein said fourth support beam (19) is connected with said third support beam essentially in the middle of the longitudinal extension of the third support beam.

14. Stand according to any of the preceding claims, wherein the first intermediate member (14) has an front end surface, said front end surface being divided into a first front end surface section (27) and a second front end surface section (28) on its respective side of said means adapted for mounting a bearing unit (8) thereto, wherein the second front end section is closest to a connection point of the first intermediate member to the side member (9) and is bent such that it has a radius in the horizontal plane of the horizontal surface of the first intermediate member.

15. Stand according to claim 14, wherein the second front end surface section (28) is essentially straight.

16. Refining apparatus for disintegrating and refining lignocellulose-containing material comprising a rotor and an opposite stator, the rotor and the stator each having a refining surface, a refining gap between said refining surfaces, the apparatus further comprising a stand in accordance with any of claims 1 to 15.