PURPOSE: To accurately and simply readjust the gap between mating roller to a proper value at an installation site.

CONSTITUTION: Rocking arms 2 are rotatably supported with rollers 1, a frame 5 is provided with contact sections 5b on the back face side, and they can be rocked around a fulcrum shaft 3. A setting shaft 6 is supported movably in the axial direction on the back face side of the frame 5, and it is provided with step sections 6a corresponding to the contact sections 5b. A pressing plate 4 is pressed and inserted between the rocking arms 2 and the frame 5. A lever 7 can be rotated around a shaft 7d, and it is constituted of a connection section 7a, a transmission section 7b, and a switching section 7c. An actuator 8 is operated at the time of gap adjustment, the setting shaft 6 is moved in the right direction via the switching section 7c of the lever 7, the outer periphery is faced to the contact sections 5b, the pressing plate 4 is inserted between opposite faces of the rocking arms 2 and the frame 5 as a wedge via the transmission section 7b and a spring 9 to fix both of them, then the operation is returned to form a gap between the contact sections 5b and the step sections 7a for use.