In a spinning operation it is necessary to replace full bobbins or sleeves or cores on which roving has been wound with empty sleeves or cores that can be reintroduced into the spinning machine or fly frame for winding roving thereon. The full bobbins are transported away for further treatment which invariably separates the roving from the sleeves that are then returned for reuse. This operation takes place in a highly automated high-speed environment and is invariably carried out by an automatic machine.
Japanese patent documents 58-41919, 60-181330, and 62-62933 describe conveyors that move two parallel rows of staggered full bobbins, each comprising a sleeve carrying a mass of wound yarn or roving, to a transfer location where a complex two-arm unloader removes the full bobbins two at a time and passes them on to another machine, for instance a spinning machine. The arms can also pick up empty sleeves and fit them to the empty hangers of the conveyor so that they can be fed back to the respective machines, for instance roving machines, for winding of a mass of yarn or roving on them. Such a bobbin changer is a fairly complex piece of equipment that operates in a complex manner. It is expensive to build and maintain.
European 0,306,450 of Kogiso describes a conveyor for roving bobbins in a spinning plant which switches full bobbins traveling in two rows past a transfer location with two rows of empty spools passing on the other side of the transfer location. Since each incoming row is associated with a respective outgoing row, the exchange is fairly simple.
Furthermore German 4,313,024 of Kroll describes a bobbin changer that receives full bobbins in two parallel rows and that hands them off to another conveyor. This device is extremely complex, having holders that pivot on arms mounted on a beam pivotal itself about an axis between the input and output rows.