| 摘要 |
<p>First feeding means serve to deliver a first strip at a controlled velocity. Second feeding means serve to receive said first strip from said feeding means and to intermittently pull said first and second strips in contact with each other. Looping means serve to engage said first strip between said first and second feeding means and to urge said strip to form a loop. Sensing means serve to indicate the length of said loop. Control means serve to control the velocity at which said first strip is delivered by said first feeding means in response to said sensing means in inverse relation to the length of said loop. In preferred embodiments, the looping means comprise a looping roller arranged to engage said first strip between said first and second feeding means and to urge said first strip to form a loop, said sensing means comprise a lever carrying said looping roller and arranged to perform an angular movement in response to a change of the length of said loop and said control means comprise a tachometer generator for producing a tachometer output voltage representing the speed of said motor, a potentiometer mechanically coupled to said lever and serving to produce a potentiometer output voltage representing the position of said lever, a comparator for producing a comparator output voltage which represents the difference between said tachometer output voltage and said potentiometer output voltage, and a motor controller for controlling the speed of said motor in dependence on said comparator output voltage. The first feeding means include the motor.</p> |
