Apparatus for intermittently actuating heating tools in packing machines

Abstract

A heated sealing tool is actuated intermittently for fixed intervals of time to engage thermoplastic envelopes of successive cigarette packs which are supported by an indexible turret. In order to ensure that the intervals of engagement between the tool and successive envelopes are not altered when the speed of the prime mover of the packing machine is changed, the tool is mounted on one arm of a two-armed lever the other arm of which carries roller followers for two discrete coaxial cams which jointly actuate the tool through the medium of the lever. Each of the cams is driven at a speed which is proportional to the speed of the prime mover; however, one of the cams is angularly adjustable relative to the other cam by a gear motor or a bevel gear transmission in response to signals which denote changes in the speed of the prime mover so that the duration of intervals of engagement remains unchanged. If the cams have lobes which serve to hold the tool out of engagement with the envelopes, that portion of each revolution of the cams during which the lobes engage the respective followers is shortened if the speed of the prime mover is increased and vice versa. The cams can be driven in the same direction or in opposite directions.