Apparatus and method for refining pulp stock

A method of refining pulp stock, comprising the steps of:

• introducing pulp material to be ground in a grinding process into a grinding space between a first rotatable grinding means carried by a shaft and being axially displaceable by a main servo motor, and a second non-rotatable grinding means, said main servo motor being actuated by pressurized fluid for adjusting and controlling the grinding space and for producing a grinding pressure between the first and second grinding means and for preventing axial displacement of the first rotatable grinding means relative to the second non-rotatable grinding means in response to fluctuating axial grinding forces, said second non-rotatable grinding means comprising a plurality of concentrically arranged annular grinding members at least one of which being axially adjustable by setting means;
• and
• absorbing at least some of the fluctuating axial forces generated from the grinding process that are projected on said setting means by using the pressure of a pressurized fluid of said main servo motor to provide a counter pressure on the second non-rotatable grinding means to reduce the axial forces on said setting means.