Patent ID: 7240401
Filing Date: 2007-07-10
Classification: E05D,E05Y,G03G,Y10T

Abstract:
1. A hinge mechanism supporting a platen cover for holding an original document at a fixed position on a platen glass of an image forming apparatus, said hinge mechanism comprising: a hinge unit supporting the platen cover in such a manner that the platen cover is pivotable between an open position and a closed position, the hinge unit including an elastic member biasing the platen cover in its opening direction; and a hinge holder accommodating said hinge unit including said elastic member, said hinge holder being fitted in a hole formed in a rear end portion of a housing of the apparatus, wherein the hinge unit is accommodated in the portion of said hinge holder that is fitted in the hole, the platen cover is integrated with an automatic document feeder for feeding original documents to the platen glass automatically, said hinge unit is provided with a hinge torque keeping mechanism which causes said elastic member to produce a specific amount of hinge torque to bias the platen cover in its opening direction even when the platen cover is closed, said hinge unit includes a cam mounted on a shaft for pivotably supporting the platen cover, and a cover portion for covering said elastic member, the cover portion being slidably mounted in the hinge holder, wherein the cover portion has a point contact portion for point contact with said cam, and a center of a circular arc of a point of the cam in contact with the point contact portion is off from a line that passes the point contact portion and is parallel to a direction whereby the cover portion is slid, within a range of a diameter of the shaft perpendicular to the line.