Abstract: A door and hinge mechanism particularly adapted for use in a conical hopper where the door may be on the down side of the hopper. The hinge pin connecting the fixed hinge element with the movable hinge element is placed under tension by springs such as Belville washers so that the hinge pin is not freely rotatably in the fixed hinged element. The movable hinge element includes a cam member which rotates about an off-set axis until the cam surface engages the hinge pin to prohibit further free rotation of the movable hinge. A force must then be applied to the door supplementing gravity to rotate the movable hinge element and hinge pin relative to the fixed hinge element to thereby open the door.