The present invention relates to a refining apparatus of disc-type, consisting of a disc rotatable by a shaft and a stationary disc as well as sets of refiner elements provided between them. Within the cellulose technology, apparatuses of the above-mentioned description are frequently found, where the material intended for refining is supplied through an opening in the stationary disc and is refined between the set of stationary and the set of rotary refiner elements.

Here, the amount and intensity of the refining work may be said to be controlled by the rotational speed and diameter of the rotary disc, as well as the decided distance between the sets of refiner elements, the so-called disc gap. Since a standard-sized refining apparatus of today may have a disc diameter of 1700 mm and generate 15 MW, a resulting refining force, i.e., the axial tie force needed to sustain a given disc gap, corresponding to 80 kN or more may be required. The size of the disc gap may, dependent on the process, starting material and desired fibre quality, vary between about 0,2 and 1,0 mm. Irrespective of the nominal size of the disc gap, it is, however, of utmost importance for the refining result that the same is constant, in spite of fast variations in the flow of refining material. hi the latest years, the trend within this field of cellulose technology has been toward finer paper qualities, which means more refining work, which in turn has required larger disc diameters, greater rotational speed but above all smaller disc gaps. Then, this has elucidated another important area, the parallelism between the sets of refiner elements, i.e. the deviation of the disc gap around the periphery of the disc.

Previously, a deviation of 0,05 mm has frequently been accepted as a rule of thumb, but with a decreasing nominal disc gap, down to 0,2 to 0,3 mm, this has become increasingly difficult to accept. Furthermore, the larger diameters have made it more difficult to adjust the machine by such a precision. This adjustment has, moreover, to be carried out with the machine not running in a cool state. The thermal expansion during operation naturally involves additional deviations, since the trend also is toward higher process pressures and thereby temperatures. Simultaneously, greater demands have also been made on the stiffness of the machine, i.e., the size of the disc gap must not vary too much with the refining force.

The object of the present invention is to provide a refining apparatus, which has the set of refiner elements of the stationary disc self-adjusting parallelism-wise in relation to the set of refiner elements of the rotatable disc without the axial stiffness of the machine being

impaired appreciably. According to the features of the invention, this is attained by, between the stationary disc and the refiner elements thereof, there being arranged one or more axially deformable chambers, containing a preferably constant volume of incompressible hydraulic medium. It should be noted that the chamber or chambers do not necessarily need to be physically positioned between said stationary disc and refiner elements. They may, e.g., act by means of piston rods to the external cylinders on the other the side of the stationary disc.

The deformable chambers allow the set of refiner elements of the stationary disc to move angularly but, owing to the constant volume of hydraulic medium of the chamber, not axially.

Fig. 1 shows a refining apparatus of a previously known model. The rotatable shaft 1 is mounted in the bearings 1', 1 " as well as fixedly connected to the disc 2. The stationary disc 3 has an opening 3' for the supply of refinable material. The refiner elements 4, 5 are connected to the rotatable disc and the stationary disc, respectively, and arranged at a given distance, disc gap Hl, H2, to each other. Hl and H2 intend to indicate deviation of parallelism between the two sets of refiner elements.

Fig. 2 shows the essential parts of a refining apparatus according to the invention. The rotary disc 2 including the refiner elements 4 thereof is of a known type, while the stationary disc 3 has been equipped with a refiner element holder 7a and 7b, respectively, intended for the refiner elements 5, which holder contains the axially deformable chamber 6a and 6b, respectively. Above the centre line in the figure, a chamber 6a is shown that extends from the inner periphery of the refiner element holder 7a to the outer periphery thereof. Below the centre line, a variant is shown where the holder 7b is fixedly clamped to the stationary disc at the inner periphery thereof and has the deformable chamber 6b at the outer periphery thereof.

By adapting the amount of hydraulic medium in the chambers, the latter embodiment also allows, if required, to adjust the radial parallelism of the set of stationary refiner elements in relation to the set of rotary refiner elements.

In both these embodiments, the annular chamber 6 is filled with a constant amount of hydraulic medium, which can move within the chamber to allow the set of refiner elements 5 to be moveable angularly in order to adjust itself in parallel to the set of refiner elements 4 of the rotatable disc. Simultaneously, the incompressibility of the hydraulic medium prevents the set of refiner elements 5 from moving in a purely axial direction and thereby impairing the axial stiffness of the machine.

Fig. 3 shows a way to construct the deformable chamber 6c. An annular piston 8c is sealed using, e.g., 0-rings 8c ¹ against the surrounding refiner element holder 7c, which serves as a cylinder.

Fig. 4 shows a variant where the chamber 6d is entirely integrally integrated in the holder 7d. Sufficient deformation for the purpose is then carried directly by the holder material, like a membrane, 7d'.

Fig. 5 shows the annular chamber formed as a number of separate, circular chambers 6e connected by the ducts 6e'. This method allows flow throttles to be provided between the chambers in order to counteract possible vibrations, e.g., upon uneven supply. Fig. 6 shows an embodiment where the refiner element holder is fixedly clamped at the inner periphery thereof and the deformable chambers provided as external cylinders 6f on the other side of the stationary disc 3, as seen from the refiner elements 5 thereof, arranged to actuate the refiner element holder 7i by means of piston rods 8.