Dual motor web material transport system

A bidirectional ribbon transport apparatus for maintaining uniform speed and tension of a flexible ribbon wound on a pair of storage reels and transferred therebetween, comprising:

• first and second electric motors having first and second excitation windings, respectively, electrically connected in series such that one of said motors is torque determinative and the other of said motors is speed determinative;
• first and second storage reels rotatably mechanically coupled to said first and second electric motors, respectively;
• an excitation voltage source for supplying excitation voltages to said first and second excitation windings for exciting said first and second motors for rotation in the same direction;
• a voltage divider network for causing greater excitation voltage to be applied to the excitation windings of said first motor when said motor is torque determinative than is applied to said second motor;
• said switching means for simultaneously reversing the polarity and magnitude of the excitation voltages applied to said first and second motor, such that said torque determinative motor becomes speed determinative and said speed determinative motor becomes torque determinative.

A system for bidirectionally transporting web material between storage reels upon which said web material is wound such that the tension and velocity of transport of said web material between said storage reels is controllably varied between predetermined limits, comprising:

• first and second electric motors connected in series to each other and to a source of excitation voltage for rotation in the same direction;
• first and second storage reels rotatably coupled to said first and second motors, respectively;
• means for generating a control signal;
• switching means for alternately reversing the polarity of said excitation voltage in response to said control signal to reverse the direction of rotation of said motors;
• and
• means for reducing the excitation voltage applied to said first motor and increasing the excitation voltage applied to said second motor when said motors rotate in one direction and for increasing the excitation voltage applied to said first motor and reducing the excitation voltage applied to said second motor when said motors rotate in said reverse direction, such that the torque generated by said first and second motors and the speed of rotation of said first and second motors varies to compensate for changes in the radii of web material on said first and second reels by increasing the excitation voltage across the torque producing motor with increasing load and decreasing speed and maintaining the tension in said web material and the speed of transport thereof between said predetermined limits.