Packets of cigarettes are normally fed from a cellophaning machine to a cartoning machine using a single pocket feed conveyor, which feeds the packets directly from the cellophaning machine to the cartoning machine in a single orderly succession, and constitutes both an output conveyor of the cellophaning machine and an input conveyor of the cartoning machine. This solution, on the one hand, has the obvious advantage of maintaining the timing of the two machines and, on the other, has the obvious drawback of allowing no compensation for any gaps, i.e. empty pockets, along the feed conveyor, and so preventing the formation of incomplete groups on the cartoning machine.
To compensate for gaps, it has been proposed to keep the output conveyor of the cellophaning machine and the input conveyor of the cartoning machine separate, and to interpose an interoperational (preferably FIFO) store between the two. The store is fed by the output conveyor of the cellophaning machine with a first orderly succession of packets of cigarettes in time with the cellophaning machine; the packets are brought together inside the store to form queues, are withdrawn from the queues in the store by the input conveyor of the cartoning machine, and are again arranged into a second succession in time with the cartoning machine. Any gaps along the output conveyor of the cellophaning machine are thus compensated for, but the two machines no longer operate in time with each other. Moreover, at relatively high production speeds, withdrawal of the packets from the queues in the store is not easy, and may result in damage to the packets.
Patent Application EP1721844A1 proposes a unit for feeding packets of cigarettes from a cellophaning machine to a cartoning machine. A first output pocket conveyor of the cellophaning machine and a second input pocket conveyor of the cartoning machine move continuously in respective opposite first and second directions, and are connected by a pocket transfer wheel interposed between the first and second conveyor. The pocket transfer conveyor rotates about an axis of rotation crosswise to the first and second conveyor; or translates, together with the second conveyor, crosswise to the axis of rotation to compensate one or more gaps on the first conveyor; or translates, together with the first conveyor, crosswise to the axis of rotation to form a succession of gaps, in time with the cartoning machine, on the second conveyor.
The feed unit described in Patent Application EP1721844A1, however, has several drawbacks, by failing to allow for optimum location of the heat-shrink devices necessary to obtain high-quality plastic overwrappings of the packets, and by failing to effectively handle sharp deceleration (or stoppage) of the cartoning machine, on account of the greater inertia of the cellophaning machine, which prevents the cellophaning machine from decelerating or stopping as fast as the cartoning machine. As a result, in the event of sharp deceleration (o stoppage) of the cartoning machine, a number of packets are invariably fed onto the output conveyor of the cellophaning machine, and, not being feedable to the cartoning machine, must be rejected.
Patent Application EP2007114457 proposes a unit for feeding packets of cigarettes to a cartoning machine which forms groups of packets. An orderly succession of packets is fed in a first direction by a first conveyor; the packets are transferred from the first conveyor to a second conveyor by a first transfer device, and an orderly succession of packets is fed in a second direction by the second conveyor; the packets are transferred from the second conveyor to a third conveyor by a second transfer device, and an orderly succession of packets is fed by the third conveyor in a third direction parallel to the second direction. When a gap is detected along the first transfer device, the second conveyor is stopped and, simultaneously, the second transfer device is moved in the second direction towards the first transfer device.
The feed unit described in Patent Application EP2007114457, however, has several drawbacks: it is fairly complicated mechanically, does not allow easy access to all the areas through which the packets travel, and is not always successful in handling sharp deceleration (or stoppage) of the cartoning machine.
Patent Application DE2618905A1 describes a unit for transferring single cigarettes between two conveyors, and for compensating for any difference in speed between the conveyors. A first output pocket conveyor and a second input pocket conveyor move continuously in respective parallel opposite first and second directions, and are connected by a pocket transfer drum interposed between the first and second conveyor and rotating about an axis of rotation crosswise to the first and second conveyor to transfer cigarettes between the two conveyors. In the event of a difference in speed between the two conveyors, the transfer drum translates in the first or second direction, together with one of the two conveyors.
Patent Application DE1124584A1 describes a unit for transferring products between two belt conveyors moving at different speeds, and for compensating for the difference in speed between the two conveyors. A first belt conveyor and a second belt conveyor move continuously in respective parallel opposite first and second directions, and are connected by a third belt conveyor interposed between the first and second conveyor, and which translates back and forth in the first direction or second direction.