| 摘要 |
A belt tensioning device for use in a copying machine. In front of and behind the place of application of the contact pressure of the first transfer step a floating roller (9,10) tensions the belt (1) with the formation of a loop. Each floating roller is suspended in the ends of the short arms (19a, 21a) of a pair of identical two-armed levers (19,21). The end of each long arm (19b, 21b) of one pair of levers is connected to the end of the corresponding long arm of the other pair of levers by a tension spring system (24). One pair of levers has a larger transmission ratio than the other, so that the floating rollers return into their old positions after the transfer stage. As a result of this construction the forces exerted on the floating rollers are sufficient to keep the belt tensioned, but are not so great as to cause impacts and vibrations in the belt when the floating rollers move from one position to the other. Difficulties which occur in practice with the known belt tensioning devices due to the cumulation of deviations in the forces caused by manufacturing tolerances of the various components are obviated. |
