Transporting sheets

Abstract

 A sheet conveying device in which sheets are conveyed to a first sheet conveyor (13) by a second sheet conveyor (10). A suction device (14) deflects a trailing portion of a sheet as it reaches the first sheet conveyor (13), slowing the sheet down. A gas blast device (30) deflects a leading portion of a second sheet in the opposite direction, so that an overlap is formed between the leading edge of the second sheet and the trailing edge of the first sheet. A control body (20) moves to control the suction and gas blast device (14, 30). Sheets can be deflected from a first path of travel to a second path of travel using a roller (66) and beak (67).

Description

[0001] The present invention relates to the transporting of sheets from location to another. It is particularly, but not exclusively, concerned with transporting sheets of paper from e.g. a printing apparatus to a location where the printed sheets are to be collected. The present invention is also applicable eg. to transporting sheets of plastics or metal foils.

[0002] It is well known for a printing apparatus to print a multiplicity of sheets rapidly and successively, and for those sheets then to be carried by a suitable conveyor arrangement to a location in which the sheets are to be stacked or otherwise collated. Such printing apparatuses are generally arranged to print the sheets as rapidly as possible, so the transportation arrangements must be efficient. It is also known, e.g. from EP-A-0246081, for the printing apparatus to print on a web of material, and then for the web subsequently to be cut into sheets. Again, the transportation of those sheets needs to be efficient to match the speed of printing. Although many attempts have been made to improve the speed of printing, such attempts are of little value if the sheets cannot subsequently be transported satisfactorily.

[0003] For a printing apparatus which prints on successive sheets, similar issues arise in transporting the sheets to the printing apparatus.

[0004] In transporting sheets, there are several areas where problems arise. As will immediately be seen, if a sheet is resting on a suitable conveyor, which is merely to move the sheet from one location to another, then the efficiency of sheet transport is determined by the efficiency of the conveyor. Normally, such a simple arrangement does not cause difficulties. However, the transporting of sheets often involves more complex movements of the sheets, and these movements introduce more technical difficulties. In particular, two different areas of difficulty can be identified:

1. If sheets are being transported consecutively, it is often necessary partially or completely to overlap successive sheets. This requires one sheet to have its speed changed relative to a subsequent or preceding sheet, so that there will need to be relative movement of the sheets. It is also necessary to prevent the edges of the sheets colliding with each other during the overlapping.

2. In many situations, it is necessary for the path of some of the sheets to be changed, relative to the path of others of the sheets. This needs some diversion arrangement, and the diversion arrangement must operate quickly, without damaging the sheets.

[0005] It should be noted that, in paper handling systems, the conveyors used to transport the sheets are usually known as tapes, and this terminology will used subsequently. However, it should be noted that the present invention is not limited to the transportation of paper sheets.

[0006] The present invention has several aspects, which address the various different problems of sheet transportation that were identified earlier. The first aspect of the invention is concerned with overlapping one sheet with another. To generate such an overlap, it is known to pass the sheets from a tape travelling at one speed, to a tape travelling at a slower speed. In such arrangements, it is desirable that the movement of a sheet passing to the slower tape is retarded to allow the leading edge of the subsequent sheet to pass over the proceeding sheet to generate an appropriate overlap. To retard a sheet in this way, it is known to pass the sheet over a suction device which, by applying a vacuum or reduced pressure to the sheet, grips the sheets sufficiently to retard its movement, generally without halting that movement completely. The timing of the application of the reduced pressure by such a suction device must then be accurately synchronised with the movement of the sheets, and to achieve this it is known to provide a moveable plate which moves so as to obstruct or open one or more orifices in the suction device below the sheet. By controlling the position of that plate in a suitably timed way, it can be ensured that the suction is applied to each sheet, to allow the leading edge of each subsequent sheet to pass over that trailing edge. It is preferable that the suction is applied adjacent the trailing edge of each sheet, as this has the advantage that the suction device holds down the trailing edge of the leading sheet, thereby reducing the risk of the leading edge of the trailing sheet striking the trailing edge of the leading sheet.

[0007] However, it has been found that the action of the suction device is not, in itself, sufficient to prevent the edges of the sheet striking each other. It is therefore known to provide a device for lifting the leading edge of the trailing sheet, to ensure that it passes over the leading sheet. Mechanical diversion arrangements are known for this, and it is also known to provide a blast of air or other gas which lifts the leading edge of the trailing sheet.

[0008] Of course, where such a gas blast is provided, it is important that the gas blast is synchronised with the application of suction to the leading sheet. Therefore, the first aspect of the present invention proposes that the application of suction to the leading sheet and the application of a gas blast to the trailing sheet are both synchronised by the movement of a single body acting on both the suction system and the gas blast system. Normally, the suction will be applied adjacently trailing edge of the leading sheet and the gas blast will be applied adjacent to the leading edge of the trailing sheet.

[0009] Preferably, a movable plate is used to form the movable body. That plate may be similar to that used to apply or release the suction, by blocking or opening one or more suction orifices, and at the same time block or open one or more gas blast orifices.

[0010] The currently preferred synchronisation arrangement using such a single moving body is to arrange for the gas blast to be applied just as the suction ceases. This timing has the advantage that the gas blast then overrides any residual suction effect. In the known suction arrangements, there may be some residual suction even after the suction orifices have been closed, and this may retard the leading sheet more than is desired. If the gas blast occurs just as the suction is intended to have ceased, then the gas blast will swamp any residual suction effects, so that the leading sheet will be released at the correct time.

[0011] The use of a movable body, such as a movable plate, to control the timing of both the application of suction and the application of the gas blast has the further advantage that the suction orifices and the gas blast orifices may be close together, with a spacing of eg. 25mm there between. This has the advantage that the gas blast can be applied as close as possible to the leading edge of the trailing sheet without affecting the gripping of the leading sheet by the suction effect.

[0012] As has previously been mentioned, it is known to provide a moveable body, usually in the form of a moveable plate, which obstructs or opens one or more suction orifices in the suction device, so that a suction force is applied to the sheet above the suction device when the suction orifices are not blocked by the plate. In such an arrangement, it is known to use a motor to drive the moveable body (the moveable plate) with a reciprocating motion, by a suitable rotary to linear conversion arrangement. In the known arrangements, the suction orifices thus are gradually opened, remain fully open only for a very short period and then are gradually closed.

[0013] Such a mechanism may be employed to move the movable body of the first aspect of the present invention. However, alternatively, a servo motor may be used to drive the plate, rather than a conventional motor. The servo motor is a low inertia motor which enables the plate to be moved at speeds which vary in dependence on the position of the plate, to allow the time profile of the opening of the suction orifices to be controlled.

[0014] The orifices may therefore be opened rapidly, held open for a relatively long period, and then closed rapidly, ensuring a more satisfactory gripping of the sheet by the suction device. In such an arrangement, the ratio of the times when the vacuum orifices are fully open to the times when they are partially open is at least 40%, more preferably 60%, whereas in known systems the ratio is less than 20%.

[0015] The second aspect of the present invention is concerned with selectively allowing sheets to pass on to one of two paths, by providing a diverting apparatus at the junction of the two paths, which diverting apparatus causes a sheet which arrives at the diverting apparatus to pass either to the first or the second path, as is desired.

[0016] One conventional way of achieving this is for the diverting apparatus to have a moveable beak (also sometimes referred to as a wing). The cross-section of the beak, perpendicular to the plane of the sheet, is generally in the form of an isosceles triangle, with the apex pointing in the opposite direction to the movement of the sheets. The beak is moveable so that its apex may be positioned on one side or the other of the path of the sheet. With the apex on one side, the sheet either passes the beak without contacting it, or possibly collides with one side of the beak, to cause the sheet to move along a first path. When the beak is moved to the other side of the paper path, the leading edge of the sheet collides with the other side of the beak and is thus diverted to a second path.

[0017] However, such conventional arrangements have the disadvantage that the leading edge of a sheet may be damaged when it collides with the beak. This problem increases as the angle the sheets makes with the side of the beak with which it collides increases. Thus, if a sheet moving along one path does not collide with the beak at all, a relatively large movement of the beak will be needed to divert the sheet to a second path, thereby increasing the angle of collision and so increasing the risk of damage. If, on the other hand, a sheet collides with either one of the two sides of the beak depending on which path it is to follow, the problem of damage to any single sheet is reduced, but there is then no path where the risk of damage is eliminated.

[0018] Therefore, such diversion arrangements involving a moveable beak are normally only used to reject a faulty sheet. If the sheet is not to be rejected, it passes the beak without colliding with it at all. To reject a sheet, the beak is then moved so that an edge of the faulty sheet strikes the beak, and is thus diverted. Since the sheet has already been determined as faulty, damage to the sheet due to its collision with the beak is then irrelevant. This means that such arrangements are unsuitable for diversion of sheets between one path and another where it is desired that sheets on either path are to be used.

[0019] In order to avoid this problem, it has been proposed to replace the beak with a moveable roller which is moveable into and out of the paper path. When the roller is clear of the paper path, a sheet moves along a first direction. If the sheet is moved into the paper path, the sheet strikes the roller and is diverted. Since the angle the leading edge of the sheet makes with the roller will be small, the risk of damage is reduced. This risk can be reduced further by bringing the moveable roller into contact with a fixed roller over which the sheet is passing, thereby creasing a "nip" which grips the sheet as it passes along the second path.

[0020] It may also be desirable for the sheets to be led to the diversion apparatus between two generally parallel tapes. After the diversion apparatus, one tape leads to the first path and the other leads to the second path. In this arrangement, both tapes then pass through the nip between the movable roller and the fixed roller. Thus, in such arrangements, the sheet does not make contact with the movable roller, but instead the path of the tapes is deformed by the movable roller to divert the sheet.

[0021] However, in the known arrangements involving a movable roller, there must be a significant movement of the roller if they are to work successfully, and the time taken for the roller to move is thus significant. Such arrangements are therefore not satisfactory for arrangements in which the sheets are moving rapidly.

[0022] The second aspect of the present invention therefore proposes an arrangement in which there is both a moveable roller and a moveable beak, with the movement of the roller and the beak being synchronised. In one position of the roller and beak, a sheet does not collide with either of them. In a second position, a sheet contacts the roller or the position of a tape in contact with the sheet is altered and path of the sheet is diverted by a small amount. The sheet then strikes a side of the beak, to divert the sheet further onto the other path.

[0023] Since the roller only needs to divert the sheet by a small amount, the amount of movement of the roller needed is small, as compared with known roller systems. However, even that small degree of movement achieved by the roller reduces the angle the leading edge of the sheet makes with the side of the beak with which it collides, thereby reducing the risk of damage. This makes this aspect of the invention suitable for use in arrangements where sheets are to be used on both paths that they follow, or to provide a reject arrangement which operates more rapidly than conventional reject arrangements.

[0024] Embodiments of the present invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 shows a first embodiment to the present invention, being a device for causing overlapping of successive sheets;

Fig. 2 shows a modification of part of the apparatus of Fig. 1;

Fig. 3 shows a modification of another part of the apparatus of Fig. 1;

Figs. 4a and 4b are graphs showing alternative movement patterns of the arrangement of Fig. 1, illustrating the change in position P of a part of the arrangement of Fig. 1 with time T; and

Fig. 5 shows another embodiment of the present invention, for causing diversion of sheets along one of two paths;

[0025] A first embodiment will now be described with reference to Figs. 1, 2, 3, 4a and 4b. This first embodiment incorporates the first aspect of the present invention described previously. It is concerned with achieving overlap of successive sheets.

[0026] Referring first to Fig. 1, a first tape 10 transports sheets of e.g. paper with a linear speed V from e.g. a paper reel or printing apparatus. The tape 10 terminates at a roller 11 and there is then a gap to a roller 12 of a second tape 13. That second tape 13 transports the sheets at a slower speed than the first tape 10, e.g. ½ V. Positioned between the rollers 11 and 12 is a suction device 14, which acts to grip the trailing part of a sheet which has passed from the tape 10 to the tape 13. That gripping does not need completely to prevent movement of the sheet, but should retard its movement sufficiently to allow a leading edge of a subsequent sheet from the tape 10, which is moving at speed V, to pass over the trailing edge of the sheet that is gripped until a suitable overlap is achieved. This gripping holds down the trailing edge of the sheet to prevent that edge interfering with the leading edge of the subsequent sheet. Once a suitable overlap is achieved, the suction is released and the tape 13 then carries the leading sheet away from the suction device 14 at speed ½ V.

[0027] As illustrated in Fig. 1, in order to provide that suction effect, an upper plate 15 of the suction device 14 has an orifice 16 therein, which is aligned with an outlet 17 of a vacuum system 18. The vacuum system 18 may be conventional and is therefore not described in detail. Between the upper surface 19 of the vacuum system 18 and the plate 15, is a moveable plate 20 with an opening 21 therein. In the position shown in Fig. 1, the opening 21 is not aligned with the orifice 16 and the outlet 17, so that no suction is applied to the trailing part of a sheet 22 over the suction device 14. If, however, the plate 20 is moved so that the opening 21 is aligned with the orifice 16 and the opening 17, suction is applied to the sheet 22 in the direction of arrow A.

[0028] Thus, as can be seen, suction is only applied to the sheet 22 when the opening 21 in the moveable plate 20 is aligned with the orifice 16 and the outlet 17. This enables the vacuum device 18 to generate a constant vacuum, as this is easier to achieve than arrangements in which intermittent vacuums are created.

[0029] The suction device 14 also contains a gas blast device 30, such as a source of pressurised air with an outlet 31 aligned with another orifice 32 in the plate 15 of the suction device 14. The moveable plate 20 has another opening 33 which, when aligned with the orifice 32 and the opening 31, causes a gas blast to be expelled in the direction of arrow B. That gas blast lifts the leading edge of a sheet 34 passing from the tape 10 over the suction device 14. That lifting of the leading edge of the sheet 34 prevents it colliding with the trailing edge of the sheet 22, as overlap occurs.

[0030] In operation, a sheet passes from the tape 10 over the suction device 14 on to the second tape 13. The sheet is then permitted to move at or less than the speed of the second tape 13, and is gripped by the suction device 14. This gripping is achieved by aligning the opening 21 and the moveable plate 20 with the orifice 16 and the outlet 17, thereby generating a suction force on the sheet. In practice, this suction force is not normally great enough completely to arrest the movement of the sheet, but instead slows it by a suitable amount.

[0031] This slowing of the sheet allows a subsequent sheet to begin to pass from the tape 10 over the suction device 14. At this time, the moveable plate 20 is moved so that the opening 21 is no longer aligned with the orifice 16 and the outlet 17, so that the suction force is no longer applied to the leading sheet. At the same time, the opening 33 in the moveable plate 20 becomes aligned with the gas blast outlet 31 and the orifice 32, generating a gas blast which lifts the leading edge of the subsequent sheet to allow it to pass over the preceding sheet. The preceding sheet begins to move away from the suction device 14 as it is transported by the tape 13, but since the tape 13 is moving at a slower speed than the tape 10, the leading edge of the subsequent sheet then passes over the trailing edge of the leading sheet, to generate an appropriate overlap.

[0032] Once that overlap has been achieved, the moveable plate 20 is again moved to block the gas blast, and to generate the suction, which now acts on the subsequent sheet. This process is then repeated for successive sheets.

[0033] As can be seen, the use of a single moveable plate 20 to control both the suction and the gas blast ensures accurate timing of the two operations.

[0034] Fig. 1 also shows that there may be a gripping roller 35 acting on the sheet 22, being transported by the tape 13. That gripping roller 35 needs to be positioned sufficiently far from the roller 12 that it only grips a sheet after the sheet has been released from the suction device. It can also be seen from Fig. 1 that the upper surface of the tape 13 is slightly lower than the upper surface of the tape 10. This assists in the overlap operation. Moreover, the leading and trailing corners of the suction device 14 may be provided with rollers 36, 37 to prevent damage to sheets which strike those parts of the suction device 14.

[0035] In the embodiment illustrated in Fig. 1, the moveable plate 20 moves generally parallel to the direction of movement of the sheets. In practice, such movement may not be easy to achieve, and therefore it is preferable for the moveable plate to move perpendicular to the direction of movement of the sheets. This enables the drive system to be positioned to one side of the apparatus. Of course, in such an arrangement, the position of the openings 21, 33 in the moveable plate 20 needs to be changed to enable suitable synchronisation of the suction effect and the gas blast effect. Such a modification to the first embodiment is illustrated in more detail in Fig. 2, which shows the moveable plate 20 connected via a connection rod 40 to a suitable drive 41 which causes the moveable plate 20 to oscillate laterally in the direction of arrow C. That direction is perpendicular to the movement of sheets carried by tape parts 10a, 10b which move the sheets in the direction of arrow D.

[0036] In Fig. 2, the upper plate 15 of the suction device 14 is omitted for the sake of clarity, so that the openings in the moveable plate 20 can be seen. As illustrated in Fig. 2, there are a first row of openings 42 which correspond to the openings 21 in Fig. 1, and a second row of openings 43 corresponding to the openings 33. Fig. 2 also illustrates, by dotted lines, outlets 44 of the vacuum device 18 and outlets 45 of the gas blast device 30. If the drive 41 moves the moveable plate 20 to the left in Fig. 2, the openings 43 will become aligned with the outlets 45, and a gas blast will occur. Similarly, if the plate 20 is moved to the right, the openings 42 will become aligned with the outlets 44, causing a suction effect.

[0037] Another modification of the embodiment of Fig. 1 is shown in Fig. 3. In this modification, the upper plate 15 of the suction device 14 is replaced by a tape 46 extending around rollers 36 and 37, and also around a drive roller (not shown). The tape 46 has openings 47 therein which act in the same way as orifices 21 and 32 in the plate 15. The advantage of using such a tape 46 is that the tape 46 can be driven in the direction of arrow G with its upper surface between the rollers 36 and 37 moving at the same speed as the tape 13. This has the advantage that the sheet 22 is then supported at a moving surface at each end. Of course, in such an arrangement, the spacing and position of the openings 47 in the tape 46 needs to be determined so that, at the times when the suction effect and the gas blast effect are needed, appropriate openings 47 will be aligned with the outlets 17, 31 of the suction device 18 and the gas blast device 30 respectively. This is relatively straight forward to do since the tape 46 is moving at the same speed as the sheet 22 and the tape 13.

[0038] Consider now the movement of the moveable plate 20. If it moves uniformly to the right in Fig. 2, the openings 42 will gradually become aligned with the outlets 44, and thus the suction effect will slowly increase, generally in the way shown in Fig. 4a. In that Figure, the upper dotted line 48 represents the position of the plate 20 for which the outlets 44 may be considered to be substantially unblocked, and the lower dotted line 49 represents the position of the plate 20 where they may be considered to be substantially blocked. There is thus a short period 50 when the outlets 44 are substantially unblocked, as compared with the total time 51 when the outlets 44 are not completely blocked.

[0039] It is preferable, however, that the drive 44 does not move the plate 20 in such a uniform way. Instead, it is preferable for the plate 20 to be moved so that there is a relatively long time in which the outlets 44 are substantially unblocked, and the time in which they are partially blocked is relatively short. The resulting movement of the plate 20 is shown in Fig. 4b, where the time 52 in which the outlets 44 are substantially unblocked is a very large proportion of the time 53 when they are not substantially completely blocked. In practice, the ratio of times 52 to 53 should be at least 40%, more preferably 60%. In this way a more accurate suction effect can be achieved. Such movement of the plate 20 can be achieved by using a servo motor in the drive means 41, and controlling that servo motor to achieve the desired movement.

[0040] It can be seen that a similar effect will also be applied to the gas blast, due to the relative movement of the openings 43 and the outlets 45.

[0041] Another embodiment of the present invention will now be described, with reference to Fig. 5. Fig. 5 illustrates a diversion apparatus for diverting a sheet to a selected one of two paper paths.

[0042] Sheets approach the diverting apparatus on a first tape 60 which passes around a roller 61. The two paths from the diverting apparatus are formed by tapes 62, 63 which pass round respective rollers 64, 65. The diverting apparatus then comprises a diverting roller 66, a beak 67, a supporting roller 68 and a linkage 69 interconnecting the diverting roller 66 and the beak 67. The linkage comprises a first bar 70 pivotable around a pivot point 71, with a stub bar 72 on the bar 70 supporting the diverting roller 66. A tie rod 73 then links the upper end of the bar 70 with a bar 74 fixed to the beak 67. If the bar 70 is pivoted anti-clockwise around the pivot point 71, the diverting roller 66 will move to the position 75 shown by dotted lines, and the beak 67 will move to the position 76 also shown by dotted lines. Stops 77, 78 may be provided adjacent the bar 70 to limit the movement thereof and so limit the movement of the diverting roller 66 and the beak 67.

[0043] In the position shown in solid lines in Fig. 5, a sheet 79 passes from the tape 60 so that its leading edge contacts the diverting roller 66. That diverting roller 66 causes the leading edge to be forced downwardly through the nip between the diverting roller 66 and the supporting roller 68. The leading edge then strikes a side of the beak 67 at a shallow angle, and is diverted downwardly further to pass to the tape 63. Since the angle of impact made by the leading edge of the sheet 79 with the diverting roller 66, and the angle made with the side 80 of the beak are very shallow, the risk of damage to the leading edge of the sheet 79 is very small.

[0044] If the bar 70 is pivoted anti-clockwise about the pivot point 71, to cause the diverting roller 66 and the beak 67 to move to the positions 75, 76 respectively, then a sheet from the tape 60 is not diverted by the diverting roller 67 and can then pass over the upper surface 81 of the beak 67 to the tape 62.

[0045] It can be seen from Fig.5 that the amount of movement of the diverting roller 66 and the beak 67 which is needed to change the path of the sheet 79 between the tapes 62 and 63 is very small. Thus, the system can switch rapidly between those two positions. The rod 70 may be moved e.g. by a suitable hydraulic, pneumatic or electric system controlled by contact of the bar 70 with the stops 77, 78. It has been found that a 50% increase in change-over speed can be achieved with this embodiment, as compared with known arrangements.

[0046] Various modifications to this embodiment are possible. For example, assuming all the tapes are moving at the same speed, it is possible for the sheet approaching the diverting apparatus to be held between upper and lower tapes. The upper tape then passes over the roller 61, between rollers 66 and 68, and over roller 64. With the diverting roller 66 and beak 67 in the position shown by solid lines in Fig. 5, that upper tape then passes between the nip between the roller 66 and 68, and is held clear of the sheet 79 by the upper surface 81 of the beak 67. When a sheet is not to be diverted, and the diverting roller 66 and beak 67 are in the positions 75 and 76 respectively, that upper tape then passes in a straight line from the roller 61 to the roller 64. A lower tape passes over the roller 61, 68 and 65 so guiding the sheet 79 when it is being diverted by the diverting roller 66 and the lower surface 80 of the beak 67.

[0047] It is possible to make the length of tie rod 73 adjustable. This has the advantage that it enables a position of the apex of the beak 67 to be adjusted, thereby emitting the position of the beak 67 when it is to divert sheet to be position accurately. Also, by making the distance between the pivot point 71 and the connection 82 between the tie rod 73 and the bar 70 adjustable, it is possible to adjust the ratio of movement of the diverting roller 66 and the beak 67 when they move between the position shown in solid lines in Fig. 5 and the position shown in dotted lines. These two adjustment possibilities enable accurate positioning of the diverting roller 66 and the beak 67.

Claims

1. A sheet conveying device comprising:

a first sheet conveyer for conveying sheets in a first direction in their plane;

a second sheet conveyer for successively conveying sheets in said first direction to the leading end of said first sheet conveyer;

a suction device for applying suction to a trailing portion of a first sheet conveyed to said leading end of said first sheet conveyer, thereby retarding the motion of the first sheet in the first direction and displacing the trailing portion of the first sheet in a lateral direction perpendicular to the plane of the first sheet;

a gas blast device for applying a gas blast to a leading portion of a second sheet trailing the first sheet, to displace the leading portion of the second sheet oppositely to the lateral direction; and

a control body, motion of said control body controlling said suction device and said gas blast device.

2. A sheet conveying device according to claim 1 in which at least a portion of said control body is located between the first sheet and said suction and gas blast devices.

3. A sheet conveying device according to claim 1 in which the control body is movable between a first position in which said control body enables said suction device and disables said gas blast device, and a second position in which said control body enables said gas blast device and disables said suction device.

4. A sheet conveying device according to claim 3 in which said control body is a plate located between the first sheet and said suction and gas blast devices, said plate including one or more apertures, in said first position at least one of said one or more apertures being in register with said suction device, and in said second position at least one of said one or more apertures being in register with said gas blast device.

5. A sheet conveying device according to claim 4 in which said plate moves between said first position and said second position in a direction perpendicular to said first direction.

6. A sheet conveying device according to claim 4 further comprising a servo-motor for moving said plate and a controller controlling said servo-motor to control the time profile of the motion of said plate.

7. A sheet conveying device according to claim 6 in which said servo-motor moves said plate faster at a time when at least one of said one or more apertures is in register with said suction device or said gas blast device then at a time when at least one of said one or more apertures is partially in register with said suction device or said gas blast device.

8. A sheet conveying device according to claim 2 comprising an endless belt having a portion between the first sheet and said suction device and gas blast device, said endless belt including one or more apertures, and the sheet conveying device further comprising a motor for driving said endless belt, whereby when at least one of said one or more apertures is in register with said suction device, said suction device is enabled, and when at least one of said one or more apertures is in register said gas blast device, said gas blast device is enabled.

9. A sheet conveying device according to claim 8 in which said motor moves said portion of the endless belt in said first direction.

10. A method of controlling a sheet conveying device, the sheet conveying device comprising:

a first sheet conveyer for conveying sheets in a first direction in their plane;

a second sheet conveyer for successively conveying sheets in said first direction to the leading end of said first sheet conveyer;

the method comprising:

applying using a suction device suction to a trailing portion of a first sheet conveyed to said leading end of said first sheet conveyer, thereby retarding the motion of the first sheet in the first direction and displacing the trailing portion of the first sheet in a lateral direction perpendicular to the plane of the first sheet;

displacing a control body to disable said suction device;

applying using a gas blast device a gas blast to a leading portion of a second sheet trailing the first sheet, to displace the leading portion of the second sheet oppositely to the lateral direction; and

displacing said control body to disable said gas blast device.

11. A sheet conveying system having an inlet path, a first outlet path extending from the inner end of said first inlet path, and a second outlet path, comprising:

a deflection roller;

a deflection member located between said first and second outlet paths and having an apex directed towards said inlet path; and

a control mechanism for moving the deflection roller and the deflection member between a first arrangement in which said deflection roller and deflection member do not intercept the first inlet path, whereby a sheet travelling along said inlet path continues along said first outlet path, and a second arrangement in which said deflection roller intercepts said inlet path, whereby a sheet moving along said inlet path is deflected along a deflection path to intercept said deflection member and deflected by said deflection member into said second outlet path.

12. A sheet conveying system according to claim 11 further including:

a first drive tape on the side of the first outlet path opposite said deflection member and extending along said inlet path and said first outlet path;

a second drive tape on the side of said first outlet path opposite said deflection member and extending along said inlet path and said second outlet path; and

a motor or motors for driving said first and second drive tapes.

13. A diversion device for a sheet conveying system having an inlet path, a first outlet path extending from the inner end of said first inlet path, and a second outlet path, the diversion device comprising:

a deflection roller;

a deflection member located between said first and second outlet paths and having an apex directed towards said inlet path; and

a control mechanism for moving the deflection roller and the deflection member between a first arrangement in which said deflection roller and deflection member do not intercept the first inlet path, whereby a sheet travelling along said inlet path continues along said first outlet path, and a second arrangement in which said deflection roller intercepts said inlet path, whereby a sheet moving along said inlet path is deflected along a deflection path to intercept said deflection member and deflected by said deflection member into said second outlet path.

14. A diversion device according to claim 13 further comprising a support roller located on the other side of said input path from said deflection roller, in said second arrangement the deflection roller pressing sheets passing along said input path against said support roller.

15. A diversion device according to claim 13 further comprising a support arm, said support arm and said deflection member being connected by a link, said deflection roller being mounted on said support arm, whereby motion of the support arm moves both said deflection roller and said deflection member between said first and second arrangements.

Drawing