Bidirectional web medium drive

摘要

A bidirectional web medium drive for moving a web of material such as a roll of microfilm between two reels consisting of a pair of reversible motors coupled through irreversible drives to corresponding spindles which receive and support each of the film reels. A torque controller is coupled to one of the motors for applying a constant output torque to that motor while a variable speed controller is coupled to the other motor for controlling the output speed of that motor. In one embodiment, a switch is provided so that when the switch is in a first position, the torque controller is connected to one of the motors to apply a constant torque to its spindle so that its associated reel becomes the take-up reel while the speed controller is connected to the other motor so that its reel becomes the supply reel and both motors rotate in the same direction. When the switch is thrown into a second position, the outputs of the torque controller and speed controller are interchanged with respect to the motors, and the polarity of the motors is reversed so that the film moves in the opposite direction and the function of the reels are interchanged. In another embodiment, the switch is eliminated so that the motors are directly connected to the controllers and the speed controller is converted to a torque controller while the torque controller is converted to a speed controller and the polarity applied to the inputs of the motors is reversed so that the supply and take-up functions can be reversed.