| 摘要 |
In a document transport apparatus for feeding document sheets over a copier platen with a reversible direction of motion document feeding belt with a normal-force pressure system for applying pressure to an area of the back of the lower belt flight, mounted to engage and be moved by the belt, which pressure is automatically substantially greater for one direction of motion of the belt than the other, the improvement comprising apparatus for applying a preset maximum gravitational force with the pressure system actuated solely by engagement and movement of the pressure system by the lower belt flight in one direction, and further apparatus for counteracting that gravitational force automatically in response to the reversal of direction of the belt flight to greatly reduce the applied pressure in the reversed direction of motion of the belt flight, wherein a disclosed pressure system is an integral arm/roller unit with a variable axis of rotation about a fixed pivot by means of a limited slot connection therewith and a cooperative rotational stop, providing free vertical but restricted rotational movement of the pressure system in one direction of belt movement, and vertical retention but free rotational movement in the other direction of belt movement.
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