| 摘要 |
This invention relates to an improvement upon the film winding and rewinding apparatus forming the subject matter of my copending application Ser. No. 666,187 filed Oct. 29, 1984, by a replacement of its former manually-shifted electrochemical reversing system for changing from a so-called "A-wind" to a "B-wind" with an electromagnetic one employing a pair of electromagnetic clutches on parallel counterrotating output shafts operatively linked together with a belt and pulley power transfer mechanism which cooperates with the clutches to impose a drag upon the supply reel regardless of which direction it is being turned by the power supplied to the take-up reel. The invention also encompasses an electromechanical circuit in which an idler spool responsive to the tension in the film passing between the supply and take-up reels actuates a potentiometer which, in turn, lessens the drag on the supply reel as the tension increases. The invention further encompasses a control circuit in which two or more different combinations of resistances can be switched to vary the drag on the supply reel to adjust for different reel sizes.
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