Open/close mechanism of upper frame for use in image forming apparatus

摘要

This invention relates to an image forming apparatus constructed such that an upper frame is openably mounted on a main base frame and a pivotal movement transmitter (gear) is rotatably mounted on the upper frame about an axis of a rotation of the upper frame, i.e., in association with the rotation of the upper frame. The gear has a cam portion. One end of a lever comes into contact with part of the cam portion of the gear, while the opposite end of the lever comes into contact with a coil spring. Further, a distance from the pivotal axis of the gear to the contact position of the lever with the cam portion decreases in accordance with a proceeding of the closing operation. Accordingly, as the lever (cam follower) follows the cam portion in accordance with the closing operation of the upper frame, a compression force to compress the coil spring increases. Thereby, a brake force applied to the upper frame on the way of closing also increases.