Chain tensioning apparatus for a packaging machine

摘要

A tensioning system for an endless chain comprising a snail cam mounted on a second shaft parallel to a sprocket shaft which supports a sprocket and chain, a follower running against the snail cam and mounted on a mechanism supporting the sprocket shaft, a ratchet device which selectively limits the rotational direction of the second shaft so that the radius of the snail cam at the follower increases with rotation, a means of applying a controlled rotational force to the second shaft to advance the ratchet device if chain tension is below a predetermined level, but not advance it if chain tension is above a predetermined level.