The present invention relates to a conveying device in the form of a twin shuttle unit for use as an interface between a stacking system which produce stacks of newspapers and a strapping system which wraps and straps those stacks in a post press system of a newspaper printing works.

In one existing stacking system, produced by Ferag AG Foerder-und Verarbeitungssysteme of CH-8340 Hinwil, Switzerland, loose unwrapped stacks of newspapers are presented alternately at twin cell outputs of the stacking system. These loose stacks must then be conveyed to the machines of the strapping system. An existing bundle merging unit (Ferag Type PZF) conveys the loose stacks alternately from each output of the stacking system to the input of a transfer unit to an underwrapper which is the first machine of the strapping system, comprises two curved belt caterpillar conveyers which converge at the input. These curved conveyers have proved unsatisfactory in practice. The technical problems are outlined below.

Firstly, the belt caterpillar conveyers drive the stacks from below. The stacks consist of folded newspapers stacked one on top of another. In many cases the newspapers have been stuffed with various inserts such as magazines and advertising material. This results in the newspapers varying in thickness over their width and tends to increase the instability of the stack. Driving such a stack from below produces shear forces on the stack causing shingling during transport along the conveyer. This means that the structure of the stack is unacceptably degraded for input to the underwrapper of the strapping system.

Secondly, the unstable stacks caused by inserts in the newspaper are prone to being thrown off the conveyer

altogether during their passage along the curved path.

These technical problems have existed for some time and there is a long felt want for a satisfactory conveying device to act- as a shuttle unit between the twin outputs of a stacking system and the single input of a strapping system.

The present invention seeks to solve these technical problems by providing a conveying device or shuttle unit as defined in any of the appended claims.

The advantage of a shuttle unit in accordance with the invention is that 'buckets' support the stack throughout its transport between the two systems preventing both shingling and the stack being thrown out of the system altogether as Previously occurred. In this way the inherent instability of the stack caused by the inserts is controlled.

Other advantageous features of the invention are defined in the claims.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:-

Figure 1 is a plan view of a shuttle unit in accordance with one embodiment of the invention showing the shuttle unit interposed between the twin cell outputs of a stacking system and an input to a strapping system;

Figure 2 is an elevation at the line A-A in Figure 1; and

Figure 3 is an elevation at the line B-B in Figure 1.

A shuttle unit 2 is shown interposed between a twin cell output from a FERAG stacking system 4 and a transfer unit 6

providing the input to the strapping system 8 which comprises a duplex underwrapper 10 and a strapping machine 12.

Each of the twin outputs 14 from the strapping system is equipped with a pusher unit 16. The ram of the pusher unit 16 moves from the position shown in solid lines in Figure 3 to the position 16" shown in chain lines in that figure to move a stack of newspapers out of the system. In the arrangement illustrated the stacks are fed into the shuttle unit 2 over a short stretch of driven conveyer 18. The pusher units 16 and conveyer 18 at the two outputs operate alternately so that when one pusher unit is extended to output a stack of newspapers, the other is retracted and ready to receive a fresh stack for output.

The shuttle unit 2 comprises two outer stations 20, 22 each aligned with a respective one of the twin outputs 14 from the stacking system 4. The shuttle unit also has an intermediate station 24 which is aligned with the input passage of the transfer unit 6 of the strapping system. Two buckets 26, 28 are provided. Each bucket 26, 28 comprises a generally U-shaped member sized to receive a stack of newspapers supported on the base of the U with the sides of the stack, transverse to its direction of movement through the strapping system, supported by the side walls of the U-shaped bucket. Retaining lips 30 are provided at the ends of the side walls remote from the stacking system output 14. As shown in Figure 1 these lips are operated by three hydraulic cylinders 32 and pivoted link members 34 which connect the lips to the rod of the piston so that the lips of the shuttle unit are closed at the outer stations 20, 22 but are opened when the bucket is. moved to the intermediate station 24 so that a stack can be pushed out of the bucket onto the conveyer belt of the transfer unit 6 which feeds the stack into the underwrapper 10 of the strapping system 8. The lips 30 preferably extend along the full height of the edge of the side walls of the

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bucket to retain the stack securely in position within the bucket until the stack is to be moved out of the shuttle unit 2. This prevents any shingling occurring.

The lips could also be spring-loaded and held in the closed position by means of engagement with a wall of the shuttle unit at the outer stations only.

A pusher unit 36 with ram 38 is provided in order to push a stack from a bucket at the intermediate station 24 onto the conveyer belt of transfer unit 6 at the input of the strapping system 8.

The buckets 26, 28 are moved laterally between the stations by pneumatic or mechanical means. Any known type of reciprocating drive can be used for this purpose.. The hydraulic system illustrated in which each bucket is mounted on a trolley driven along a track by means of a respective hydraulic cylinder is one example of a suitable drive. The control for the drive must be such that a bucket is at a receiving outer station 20,22 when a stack is ready to be fed out from the aligned output of the stacking system. At this time the other bucket will be at the intermediate station as shown in Figure 2. An electronic control circuit may be utilised to ensure the required synchronism of this drive with the drivers of the -stacking and, if necessary, strapping systems. A suitable input signal for the electronic control circuit can be taken from the ram of the pusher unit 16 of the associated stacking system output. The signal which causes the ram to retract after feeding a stack into the bucket can also be used to actuate the lateral drive for transferring that bucket sideways to the intermediate station 24. An appropriate delay after that actuating signal an actuating signal may be provided to the ram 38 which pushes the stack out of the intermediate station 24 onto the belt of the transfer unit. Once that step is completed the drive for the

bucket must move it laterally towards its outer station to allow the bucket from the other station to move into position. It is within the skill of those familiar with electronic timing control circuits to achieve the required synchronisation between the drives to the two buckets and the ram pusher unit 36 using the control signals generated from the stacking system and any appropriate circuit may be employed. Alternatively the required synchronism could be achieved by mechanical means.

While on the belt of the transfer unit 6, the stack is also supported and driven by means of vertical feed rollers 40 on either side of the stack. These provide additional guidance to the stack on its path into and through the strapping system, which is of otherwise conventional design-. The system illustrated diagrammatically here is based on the strapping system manufactured by Pakseal Industries Limited of Cordwallis Industrial Estate, Maidenhead, Berks SL6 7DB.