CHAIN TENSIONING APPARATUS FOR A PACKAGING MACHINE

摘要

A tensioning system for an endless chain (25) comprising a snail cam (52) mounted on a second shaft (51) parallel to a sprocket shaft (31) which supports a sprocket (27) and chain (25), a follower (46) running against the snail cam (52) and mounted on a mechanism supporting the sprocket shaft, a ratchet device (55) which selectively limits the rotational direction of the second shaft (51) so that the radius of the snail cam at the follower increases with rotation, a means (61) 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.