Rice Lake Okidata 320-390-420 Turbo - Service Guide - Manual (Page 42)

(7) Paper clamp mechanism (See Figure 2-14.)
When setting the change lever to the BOTTOM , TOP or REAR position, the operation of the front release
gear arm changes according to the position of the release cam. At the same time, the position of the cam
relative to the front release gear arm changes, opening or closing the pressure roller.