Sheet Handling Apparatus The invention relates to a sheet handling apparatus having a sheet input section, a sheet processing section, a sheet output section, a conveying mechanism adapted to convey sheets from the input section through the processing section to the output section, and a controller for the conveying mechanism. An example of a sheet handling apparatus of this type is a stand-alone scanner in which the processing section includes a scanning head for scanning an image that is present on the sheet. A printer may be mentioned as another example.

An alternative type of sheet handling apparatus has a combined input and output section, and the conveying mechanism is adapted to convey the sheets from the input section to the processing section and, after processing, back from the processing section to the combined input and output section. This has the advantage that the operator may collect the processed sheets from the same side of the machine from which he has fed the sheets into the machine. On the other hand, this type has the drawback that the throughput is slightly reduced because the time needed for rewinding the processed sheet back to the input and output section delays the time at which the next sheet can be fed in.

It is an object of the invention to provide a sheet handling apparatus in which sheets, in particular sheets of different formats, can be handled reliably and efficiently.

According to the invention, the controller is adapted to be switched between a feed through mode in which the sheets are output by being fed through from the processing section to the output section, and a rewind mode in which the sheets are output by being fed in reverse direction from the processing section back to the input section.

In this apparatus, sheets which have a relatively small format may be handled in the rewind mode, which is most convenient for the operator. On the other hand, when processing a large format sheet, in particular a sheet which has a large dimension in the transport direction, it would be time-consuming to rewind the sheet to the input section. In this case, the apparatus may be switched to the feed through mode, so that the processed large format sheets will be output by feeding them forward to the output section in the same direction in which the sheets are fed in. As a consequence, a plurality of large format sheets may be fed through in close succession, so that a high throughput may be obtained.

The invention is particularly advantageous for apparatus that are designed for handling sheets with formats that vary in a large range, e. g. from AO to A4. Then, the output section which will be needed only for large format sheets does not have to be designed for handling small format sheets, which permits a low-cost design. The small format sheets which will be rewound towards the input section can readily be taken out by the operator, so that the input section is not required to be capable of reliably guiding and collecting the small format sheets. More specific optional features of the invention are indicated in the dependent claims.

In a particularly preferred embodiment, the controller has a format information processing section capable of automatically selecting the mode of operation of the conveying mechanism dependent upon the format of the sheets. Preferably, the apparatus further has a sensor system capable of detecting the format of the sheets that are being fed or have been fed into the processing section, so that the detection of the sheet format and the selection of the mode of operation may be automated. In case of a scanner, the sensor system for the format detection may be formed by or incorporated in the scanning head.

Embodiment examples of the invention will now be described in conjunction with the drawings, wherein:

Fig. 1 is a schematic side elevational view of a sheet handling apparatus according to the invention;

Fig. 2 shows the sheet handling apparatus of Fig. 1 in a top plan view;

Fig. 3 is a top plan view analogous to Fig. 2 but illustrates the handling of small format sheets; Fig. 4 is flow diagram of a decision process that is performed in a controller of the sheet handling apparatus; and Fig. 5 is a side elevational view of a sheet handling apparatus according to a different embodiment.

As an example of a sheet handling apparatus, Fig. 1 shows a scanner 10 adapted to electronically scan images that are carried on sheets 12, 14. The scanner 10 has a base part 16, and a bridge part 18 between which a sheet transport path 20 is formed through which the sheets 12, 14 may be fed through from an input section 22 via a processing section 24 to an output section 26.

The input section 22 is formed by a slanting part of the top surface of the base part 16 on one side of the bridge part 18 and by a number of projecting curved guide bars 28 for the sheet 12. The processing section 24 includes a scanning head 30 that is, accommodated in the bridge part 18 and extends over the entire width of the apparatus so as to scan the sheets on their entire width when they are passed through. The output section 26 is formed by a cage that is designed to collect the sheets 14. As in the example shown, the cage-like output section is formed by one or more bent wires which define guide rails 32 for limiting the cage in a lateral direction and at its free end, as well as a support part 34 for guiding and supporting the sheet 14 in the vicinity of its width- wise centre. Both the base part 16 and the bridge part 18 accommodate parts of a conveying mechanism 36 which, in the example shown, has two pairs of motor-driven conveying rollers 38.

An electronic controller 40 controls the scanning head 30 and the conveying mechanism 36 and also processes the image information received from the scanning head 30.

Of course, the scanning head 30 is not only capable of reading the image information carried on the sheets 12, 14 but also to detect the leading and the trailing edges as well as the lateral edges of the sheets. This information is processed in a format information processing section 42 of the controller 40 so as to automatically determine the format, i. e., the length in transport direction and the width in lateral direction, of the sheet that is being conveyed past the scanning head.

In the example shown in Figs. 1 and 2, the sheets 12, 14 have a relatively large format, e. g. AO. The bent wires forming the output section 26 are configured such that the large format sheet 14 can reliably be guided and supported in the cage. The format information processing section 42 of the controller 40 has detected the format of the sheet 14 and has, in particular, measured the length of the sheet when the trailing edge thereof has passed the scanning head 30. Based on this information, the controller 40 has controlled the conveying mechanism 36 such that the conveying rollers 38 continue to rotate in the same direction, so that the sheet 14 is output by being fed through to the output section 26.

For comparison, Fig. 3 illustrates a case where a sheet 12a with a relatively small format, e. g. A4, is fed in at the input section 22. It can be seen here that, in comparison to the format of the sheet 12a, the cage forming the output section 26 has voids that are so large that the sheet 12a would most likely drop out if one attempted to collect the sheet 12a in the output section. However, in this case the controller 40 has detected that the sheet 12a has only a small format and therefore controls the conveying mechanism 36 such that, once the trailing edge of the sheet has passed the scanning head, the direction of rotation of the conveying rollers 38 is reversed, so that the sheet 12a is rewound towards the input section 22, as has been indicated by arrows in Fig. 3.

The sheet 12a can readily be taken out by the operator who has fed in this sheet. Since the length of the sheet 12a is relatively small, the time that is needed for rewinding and returning the sheet to the input section 22 is negligible and does not significantly reduce the throughput of the apparatus.

And as is further shown in Figs. 2 and 3, the bridge part 18 of the scanner has a control panel 44 permitting the operator to input settings and instructions, including settings for the mode of operation of the conveying mechanism 36. In a preferred embodiment, the operator may select between a fed through mode in which all sheets, regardless of their size, are always output towards the output section 26, a rewind mode, where all sheets are always output by being returned to the input section 22, and an automatic mode in which the mode of operation is decided upon automatically, depending upon the detected format of the sheets.

When the automatic mode has been selected, the controller 40 performs an algorithm that has been illustrated in Fig. 4. In a step S1 , the sheet is drawn in from the input section 22. Then, when the trailing edge of the sheet has just passed the scanning head 30, the controller 40 reads the format of the sheet, especially the length of the sheet in transport direction, in step S2. Then, in step S3, it is decided whether or not, the format (length) of the sheet is larger than a certain threshold value max_rewind. For example, this threshold value may be set to about 30 mm, corresponding to the length of an A4- sheet supplied in portrait orientation and the length of an A3-sheet supplied in landscape orientation. When it is decided that the format is larger than max_rewind, the sheet is fed forward to the output section 26 in step S4. Otherwise, it is rewound to the input section 22 in step S5.

The invention is not limited to sheet handling apparatus with the physical configuration shown in Figs. 1 to 3. For example, as is shown in Fig. 5, the sheet transport path 20 may be curved, so that the input section 22 and the output section 26 may be disposed on the same side of the base part 16. Nevertheless, although the sheets are always delivered on the same side, there is a distinction between the mode in which the sheets are fed through the transport path 20 into the output section 26 and the mode of operation in which they are returned to the input section 22.

If the sheet handling apparatus is a scanner, the scanning head 30 may be disposed on either side of the transport path 20. In the example shown in Fig. 5, it is disposed on the bottom side, so that the sheets have to be supplied face-down.