Rotation dependent frictional hinge mechanism

A foldable housing for an electronic device, comprising:

• a base unit having an attachment gear;
• and
• a cover unit having a hinge mechanism for rotatably coupling the cover unit to the base unit, the hinge mechanism including
• a cam member having a cam surface at a first end, an attachment post at a second end mating with the attachment gear and a radially extending flat surface at an intermediate position,
• a cam follower fixed to the cover unit and sized and adapted to mate with the cam surface, the cam follower bearing upon the cam surface and causing translational movement of the cam member in response to relative rotational motion between the cam member and the cam follower, and
• an o-ring sized and adapted to mate with the flat surface, the cam member compressing the o-ring against a side of the cover unit in response to the translational movement of the cam member toward the o-ring, compression of the o-ring producing frictional torque for resisting rotational movement of the cover unit relative to the cam member, thereby resisting rotational movement of the cover unit relative to the base unit.