| 摘要 |
Web feeding apparatus includes a rotatable supply roll (10) on which a supply of sheet or ribbon to be dispensed may be placed, a brake (78) for applying variable braking force to said supply roll (10) to prevent overrunning of the sheet or ribbon from the roll due to inertial effects, a cam (60) for controlling the brake (78) to provide maximum braking force when the supply of sheet or ribbon on the roll (10) is a maximum and for reducing the braking force as the supply of sheet or ribbon on the roll (10) is reduced, cam operating mechanism (46, 52) driven by the rotation of the supply roll (10) to move the cam (60) incrementally for each revolution of the supply roll (10), and a reset mechanism (62) for resetting the cam (60) back to its initial position following each feeding operation. |
