This invention relates to an apparatus for the refining of fiber material. The apparatus, a so-called disk refiner, comprises two opposed refining disks, at least one of which is rotary and supported on a rotary shaft. In a disk refiner of said type, the shaft is mounted in a stand via a bearing housing comprising at least two bearings, one of which is an axial/radial bearing for carrying axial forces from the refiner disk as well as prevailing radial forces, and one is an axial/radial bearing intended primarily to carry radial forces.

A disk refiner equipped with such a bearing type is disclosed in "S'E— S 3-45892. The bearing is relatively complicated, because it comprises a bearing housing for the bearings which is axially movable in the refiner stand. The bearing housing there must be extensive in length and include several slide surfaces to be fitted into the stand. The bearings, furthermore, must be axially prestressed in such a way, that at least one bearing must carry radial load and simultaneously must be axially movable in the bearing housing. This compromise renders a complicated and more expensive structure and deteriorates its funct¬ ional efficiency.

The present invention offers a solution of the aforesaid problems. Due to the bearing housing being fixed in the stand, and the bearings rigidly mounted each in its axially movable bearing seat, and pre¬ stressing members arranged between the bearing seats, a simple and operationally reliable structure is obtained. The characterizing features of the invention are apparent from the attached claims.

The invention is described in greater detail in the following, with reference to the accompanying drawings showing different embodiments of the invention.

Figs. 1 and, respectively, 2 are cross-sections of embodiments com¬ prising two and, respectively, three bearings.

Figs. 3 and 4- are cross-sections of a detail in Fig. 2 of different designs.

Both embodiments consist of a refiner with a stand 1 and a refiner housing 2, in which two opposed refining disks 3,-4 are located. At these embodiments, a first refining disk 3 is rotary, and a second one is stationary. The rotary refining disk 3 is supported on a rotary shaft 5, which is mounted in the stand 1 via a bearing housing 6 and driven by a motor (not shown) .

The ref_i-ning disks 3,4- are provided on their surfaces facing toward each other with refi-ning elements 7,8, which between themselves define a refining gap. The stationary refining disk 4. has a central inlet opening 9, through which the material is fed in which is to be refined during its passage outward through the refining gap.

During the refining operation, a very high pressure is generated in the refining gap, which pressure yields an axial force which has to be carried by the bearing of the shaft. This force can amount to several tens of tons and, therefore, puts very high requirements on the bearing design.

The rotary shaft 5 also is movable so as to allow adjustment of the refining gap between the refining elements 7,8 on the refining disks 3,4.

According to the embodiment shown in Fig. 1 , the shaft 5 is supported by two bearings 11,12. The first bearing 11 is an axial/radial bearing intended to car axial forces from the first refining disk 3- This bearing 11 also shall carry prevailing radial forces, for example the dead weight of the shaft and refining disk. The second bearing 12 is an axial/radial bearing intended primarily to carry radial forces, for example counter forces to the radial forces on the first bearing.

The bearing housing 6 is mounted rigidly in the stand 1. The two bearings 11,12 are attached with their inner ring on the shaft 5

and with their outer ring are fixed in a first and, respectively, second bearing seat 21,22. These bearing seats are axially movable by means of slip fit, but not rotary in the bearing housing 6. In the stationary bearing housing 6, a plurality of first prestressing members 25 are arranged between the two bearing seats 21,22. Each prestressing member 25 preferably is designed as a spring-loaded piston/cylinder unit, the object of which is to keep apart the bearing seats 21 ,22 so as to prevent play.

The axial movement of the bearing seats 21 ,22 is controlled by a first and, respectively, second ring piston 4-1 ,4-2, which are rigidly connected to the .bearing housing 6 and thereby co-operate with a first and, respectively, second annular hydraulic cylinder 31 ,32 in the first and, respectively, second bearing seat 21,22. The first ring piston/ring_cylinder unit 4-1.31 is intended to move the first bearing seat 21 so as to reduce the refining gap. This implies, that the axial orces generated in the refining gap are to be taken up via the first ring piston/ring cylinder unit 4.1 _. 31. The second ring piston/ring cylinder unit 4-2,32 is intended to act in the opposite direction and, thus, is utilized when the refining disks are to be pulled apart.

A first and, respectively, second conduit 51,52 for hydraulic medium are arranged for operating the two ring piston/ring cylinder units 4-1,-42, 31,32. Said conduits extend through the stand 1 via the bearing housing 6 and respective ring piston -41 , 2 to respective ring cylinder 31,32.

Owing to this design, the two bearing seats 21 ,22 with associated bearings 11,12 can rapidly and sa ely be operated as one unit by means of the hydraulic medium in the two conduits 51,52. Simultane¬ ously, the axial forces from the first refining disk 3 are trans¬ ferred through the bearing 11 and bearing seat 21 to the stationary bearing housing 6.

The embodiment according to Fig. 2 agrees in principle with Fig. 1. A distinguishing feature is that the shaft 5 is supported on three bearings 11,12,13- The first bearing 11 is an axial/radial bearing intended to carry part of the axial forces from the first refining disk 3- As in the case of the first embodiment, the bearing 11 shall carry also prevailing radial forces. The second bearing 12 is an axial/radial bearing intended primarily to carry:-radial ^" forces. The third bearing 13 is located between the two firstmentioned bearings and arranged to carry only axial forces. The bearing 13, however, preferably is an axial/radial bearing.

The third bearing 13 is attached with its inner ring on the shaft 5 and with its outer ring secured in a third bearing seat 23. This third bearing seat 23 is axially movable with a certain play in the bear¬ ing housing 6. According to this embodiment, a plurality of second and, respectively, third prestressing members 26,27 are located between the first and third bearing seat 21 ,23 and, respectively, between the second and third bearing seat 22,23. The prestressing members preferably are designed as spring-loaded piston/cylinder units and capable to keep the bearing seats 21 ,22,23 apart from each in order to avoid play. The collective force from the third prestressing members 27 shall exceed the collective force from the second pre¬ stressing members 26.

The third bearing seat 23 is formed with a third annular hydraulic cylinder 33, which co-operates with a third ring piston 4-3 rigidly connected with the bearing housing 6. The third ring piston/ring cylinder 43,33 is moved by means of a hydraulic medium via a third supply conduit 53- The third ring piston/ring cylinder unit 43,33 further is arranged to co-operate with the first ring piston/ring cylinder unit 41 ,31 in order to take up axial forces from the first refining disk 3.

The distribution of the axial forces from the first and third bear¬ ing 11,13 is dr ^■ armined by the ratio between the areas in the first and third ring cylinder 31 ,33 by maintaining the same pressure in the respective conduit 51,53- The load distribution then is directly proportional to the area ratio. The third bearing 13 does not carry any radial forces, because the bearing seat 23 is located with play in the bearing housing 6. As the first bearing 11 carries also radial forces, it may be suitable to design the third ring cylinder 33 with a slightly greater area than the first ring cylinder 31 , so that the axial load on the third bearing is slightly greater.

It is, of course, possible to arrange additional bearings between the first and second bearing 11,12. These additional bearings with associated bearing seats then, like the third bearing, shall carry only axial forces, which are distributed in proportion to the area of the respective ring piston/ring cylinder unit. Prestressing members between the bearing seats are arranged as described above.

The bearing detail according to Fig. 2 shown in Fig. 3 comprises the two bearing seats 22,23 and one prestressing member 27- According to this embodiment, the prestressing members 27 are formed with a piston/piston rod 61 , the rear end 62 of which abuts the bearing seat 22, and its forward end is axially movable in a cjcLinder 63. Between theTear end 62 of the piston rod and the cylinder 63, a prestressed spring package 64 is located which tends to press apart the piston/piston rod 61 and cylinder 63, and therewith also the bearing seats 22 and 23, so that play in the bearings 12,13 is avoided. The remaining prestressing members 25,26 are designed and operate correspondingly. This operational function is essential when the first refining disk 3 is moved axially towards the second refin¬ ing disk 4 for adjusting the refining gap before the production is started, because the pressure in the ring cylinders 31 ,33 then is very low.

At the start of the production, the pressure in the ring cylinders 31 ,33 increases in order to counteract the axial forces generated in the refining gap as described above. The prestressing members 25,26,27 in this phase deliver only a minor force to the second (rear) bearing 12. It is, therefore, possible to arrange a relief of at least some of the prestressing members 25,26,27 in each group. ___n Fig. 4 is shown how such a relief can be provided. Fig. 4 shows the same detail of the bearing as in Fig. 3, but the prestressing member 27 is designed differently. A piston rod 65 abuts the bearing seat 22 with its rear end 66. The forward end of the piston rod is formed with a piston 67, which is axially movable in a cylinder 68. Be¬ tween the rear end 66 of the piston rod and the cylinder 68, a pre¬ stressed spring package 64 is located. The cylinder 68 communicates via a channel 69 with the space in the ring cylinder 33 in front of the ring piston 43. At increasing pressure in the ring cylinder 33, the pressure in the cylinder 68 increases simultaneously and thereby counteracts the force of the spring package 64. The remaining pre¬ stressing members 25,26, of course, can be designed in a correspond¬ ing manner, thereby avoiding unnecessary axial load on the bearings during operation. As regards the embodiment according to Fig. 2, the collective force from the prestressing members 27 all the time shall exceed the collective force from the prestressing members 26.

The invention, of course, is not restricted to the embodiments shown, but can be varied within the scope of the invention idea.