To provide a device and method meeting the need for an efficient variable speed gap regulating mechanism at a low cost.

A stone crushing system or conical stone crusher 8 includes a bowl 46 screwed to a main frame 12. The bowl 46 is regulatable at plural speeds with respect to the main frame 12 by effectively utilizing the gap regulating mechanism 2 including a variable displacement hydraulic motor 9. More preferably the set of the two variable displacement hydraulic motor devices may be effectively activated in order to advance the bowl 46 with respect to the frame 12 by setting of a higher speed of lower torque and setting of the lower speed of the higher torque.