WO2011162607A1

WO2011162607A1 - Printing system and printer unloading device

Info

Publication number: WO2011162607A1
Application number: PCT/NL2011/050453
Authority: WO
Inventors: Peter Ivan Sygall; Bart Hoogers
Original assignee: Book Factory Systems B.V.
Priority date: 2010-06-22
Filing date: 2011-06-22
Publication date: 2011-12-29
Also published as: NL2004941C2

Abstract

Paper sheets are transferred from a printer to a stack of paper sheets on a sheet collector (4). Each paper sheet (S) in shot from the printer into a wedge shaped space (W) formed between a lower surface of one or more transport belts and the stack (P). The transport belt runs at an inclination to the horizontal, towards a narrow side of the wedge shape space. The sheets are caught in the wedge shaped space (W) onto the lower surface of the transport belt, when the sheets are successively output from the printer. Each sheet is fed from the wedge shaped space between the stack and a roller on the stack. The roller being mounted together with the transport belts on a vertically movable transport arm. As a result, feeding of the sheet between the stack and a roller causes the transport belt to be raised.

Description

Title: Printing system and printer unloading device. Field of the invention

The invention relates to a printing system and an unloading and stacking device for unloading and stacking paper sheets from a printer.

Background

Known printing systems use paper transport belts to feed printed sheets to a collector tray. Accurately stacked sheets are needed when the stack of sheets is subsequently be cut and/or bound into a book. In the known printing systems the transport belts located above the sheets may extend horizontally to a position over the collector tray to transport each sheet until the sheet accurately abuts against a stop at the end of the paper collector and on top of a stack of unloaded sheets in the collector tray.

The transport mechanism with horizontal belts has the

disadvantage that the transport belts remain in contact with the most recently transported sheet, even when its motion has been stopped, the belts slipping over this sheet. This may result in damage to the sheets. It may also

contribute to inaccurate positioning of the paper on the stack and thus in imperfections in the regularity of the stack of paper sheets. When the stack has a considerable height, for example when it is intended for binding into a book of more than one centimetre thickness, this may result into reduced quality of the end product.

An alternative stacking mechanism ejects sheets in flight into a collector tray, so that each sheet, or at least a major part of each sheet flies unsupported into the collector tray, until its edge is stopped by a stop wall. However, this creates the risk that a sheet will bounce back from the stop wall, which results in irregular stacking. Also air underneath the sheet may give rise to fluttering that results in irregular stacking.

Moreover, when the height at which sheets are ejected from the printer is fixed, their initial height relative to the top of the stack of sheets in the collector tray may vary. This can be compensated for by lowering the bottom of the stack as the stack grows. This gives rise to problems when separate stacks of sheets must be formed for successive books. The easiest way to form separate stacks is to interrupt the supply of sheets when the stack for use in one book is complete, and before a next stack for a next book is formed. Without such an interruption, damage or inaccurate stacking may result. However, interruption of the flow of sheets increases production time and it may cause problems elsewhere in the supply line. If an uninterrupted flow of sheets is used, the height compensation may mean that a plurality of height lowering mechanisms must be provided, which complicates the system. It would be desirable that only one such mechanism suffices for collecting sheets from the same printer. But even a single height lowering mechanisms may have to face excessive demands, if it has to be able to respond fast enough to handle sheets that are ejected at high speed by the printer. Summary

Among others, it is an object of the invention to provide a printer paper unloading device which enables a more reliable building of stacks of paper sheets.

A printer paper unloading device according to claim 1 is provided.

Herein sheets fed from a printer are caught in a wedge shaped space between a growing stack of sheets and an inclined lower surface of an endless transport belt or a plurality of parallel endless transport belts. In an embodiment the endless transport belt or plurality of parallel endless transport belts runs around a pair of rollers, the inclined surface extending between the rollers. The inclined surface makes it possible to catch sheets over a range of heights.

The endless transport belt or belts is or are mounted on a movable arm together with a roller that rests on the stack on a narrow side of the wedge. After catching the edge of a sheet on the endless transport belt or belts, the belt or belts guides or guide the sheet toward the roller and between the roller and the stack, until the sheet stops against a stop wall of the sheet collector. When the sheet enters under the roller it raises the roller and as a result the roller raises the transport arm, lifting the belt or belts of the stack. Thus the disturbing and/or damaging effect of contact between the stack and the belt is removed. Furthermore the device is able to handle a range of sheet thicknesses and a range sheet and stack heights without requiring immediate lowering of the collector.

In an embodiment the roller is provided with a one way rotation mechanism that keeps the sheets from moving back from the end wall stop. Thus, the risk of irregularity of the stack is reduced.

In an embodiment transport arm is provided with a spring or other means that substantially compensates a force of gravity due to the total weight of the transport arm at the location of the second roller. This ensures that a small force exerted by the sheet suffices to lift the arm. In an embodiment the transport arm may be suspended on a pivot joint, for example, at its end away from the roller, to allow for lifting by rotation around the pivot joint. This provides for a simple construction.

In an embodiment a control loop may be provided to regulate the height of the floor of the paper collector, so that the position of a top of a stack of sheets is kept constant. Thus, the movements of the transport arm may be kept small when the loop is active, no more than necessary for fast and fine movements to keep the transport belt or belts from the stack. The height control loop may comprise a sensor measuring the height of the stack, for use in controlling the height. The printer unloading device is used on a printer system that also comprises a printer. The printer may be configured to shoots sheets into the wedge shaped space at a predetermined speed, so that the sheet or at least its edge is unsupported when it enters the wedge shaped space. In an

embodiment, the belt or belts of the unloading device are made to run at a lower speed than the speed with which the sheets are fed from the printer. As a result the belt or belts help to decelerate the sheet, reducing the risk of bounce back. After the stack is formed, the stack may be transferred to a conveyor line for transport to further processing stations, where the sheets may be cut into book blocks and bound into books for example.

Brief description of the drawing

These and other objects and advantageous aspects will become apparent from a description of an embodiment, using following figures:

Figure 1 shows a schematic side view on a printer paper unloading device, and

Figure 2 shows on enlarged scale part of the printer paper unloading device.

Figure 3 shows the printer paper unloading device at a further processing stage.

Detailed description of an exemplary embodiment The printer paper unloading device 1 shown in fig.l is coupled with a printer 2, part of which is shown schematically. The printer paper unloading device 1 will be referred to as an Automatic Printer Unloader (APU) . The printer 2 and the printer paper unloading device 1 may be part of a production system for producing books as disclosed in the NL patent application

No. 2004352 of applicant, filed on March 5, 2010. In the illustrated embodiment, sheets printed by the printer 2, are received from the output side 3 of the printer 2 and fed one by one by a paper feeder of the printer (not shown) in a substantially horizontal direction at a first unloading speed in a direction indicated by the arrow A towards the printer paper unloading device 1, were the sheets are collected and stacked vertically in a stack in a paper collector 4.

The printer paper unloading device 1 comprises a collector 4, a support fork (not shown in figure 1), a transport arm 6, a chassis part 7, a first, second and third roller 8, 9, 10, mounted on transport arm 6, a plurality of paper transport belts 5, a motor 11 and a spring 12. Belts 5 extend

substantially parallel to each other, realized as endless belts running between first roller 8 and third roller 10. Third roller 10 is located downstream the paper transport direction relative to first roller 8. Motor 11 is coupled to first roller 8. Belts 5 are mechanically driven by motor 11 via first roller 8.

Motor 11 may be mounted on arm 6. Motor 11 is arranged to drive belts 5 at a speed B that is the same or lower than the unloading speed A, with the lower surface of belts 5 moving in the direction towards third roller 10, i.e. towards the narrow side of the wedge.

Chassis part 7 is coupled with printer 2. Transport arm 6 has first and second end portions 6b, 6c on mutually opposite sides of transport arm 6. Transport arm 6 is connected on chassis part 7 via a pivot 6a near a first end portion 6b. Arm 6 is movable by pivoting around the axis of pivot 6a, allowing up and down movement of second end portion 6c of arm 6, relative to the floor 4a of collector 4. Transport arm 6 is provided with a weight compensating device for compensating the total weight of the arm at the location of the second roller 9. In the illustrated embodiment, said weight compensating device comprise at least one spring 12, compensating with its spring force the weight of the transport arm 6 such that during operation a small force from a paper sheet positioned under the second roller 8 enables an upward pivoting of the transport arm 6. Other examples of embodiments of the weight compensating device may comprise a spring between transport arm 6 and a position below transport arm 6, a combination of springs, springs attached to different positions on the transport arm 6, other resilient elements such as elastic material, an air spring (comprising a cylinder and a piston) and/or an electronic force control circuit comprising an electrically driven actuator, and/or choosing the pivot point 6a, so that transport arm 6 is substantially balanced. The orientation of arm 6 determines an angle between belts 5 and the horizontal. This angle has a non-zero nominal value, so that the lower surface of belts 5 is progressively lower along the transport direction A. In the figures an exaggerated angle is shown. A nominal angle between three and fifteen degrees may be used for example. In an embodiment, the nominal angle between belts 5 and the horizontal is six degrees.

Collector 4 has a floor 4a with an end portion 4b, a stop wall 4c and a guiding wall 4d. Floor 4a may comprise a transport belt or belts (not shown) for lateral transport of a stack of sheets. Stop wall 4c and guiding wall 4d extend in parallel and are located on mutually opposite sides of floor 4a.

Furthermore, the printer paper unloading devices comprises a paper height sensor (not shown), a further motor 13, a spindle 14 and a further arm 15. Guiding wall 4d is located adjacent the output side 3 of printer 2. Stop wall 4c is located remote from the output side 3 of printer 2. The floor 4a of collector 4 is movable downwardly relative to the walls 4c and 4d and the rollers 8, 9 and 10. Further motor 13 is coupled to spindle 14 and via this spindle 14 with an arm 15 connected with the floor 4a. The paper height sensor (not shown) is coupled to further motor 13 to control movement of floor 4a with further motor 13 via spindle 14 and arm 15.

In operation each printed paper sheet S enters the printer paper unloading device 1 in the direction of the paper collector 4 and the stack P, from the output side 3 of the printer 2 with a speed A. In an embodiment, the sheet is passed unsupported, in flight or at least partly unsupported. Printer 2 may comprise a pair of facing rollers for example, between which the sheet is transported and launched into the wedge shaped space between at one side the first roller 8, the second roller 9 and the belts 5 and at the other side the stack P. When the sheet S is fed into the wedge shaped space, at least its edge that extends into the wedge shaped space is unsupported.

Belts 5, capture the edge of sheet S and the part of sheet S adjacent the edge when the sheet fed into the wedge shaped space. The inclination of the lower surface of belts between first and third roller 8, 10 ensures that the edge is captured independent of height variations due to height variations of sheet S, or curling of sheet S. When sheet S contacts belts 5, belts 5 move the sheet S with at most a speed B, being the same or preferably lower than the speed A. When the speed is lower, belts 5 help to slow down the sheet S, so that subsequent risk of bounce is reduced. Belts 5 guide sheet S to second roller 9. Belts 5 and gravity force the sheet S onto the stack P and move it under second roller 9 where it proceeds at least by inertia until the edged of the sheet S has reached the stop wall 4c and is positioned on the stack P with high accuracy.

When the sheet S reaches second roller 9, the sheet S exerts a lifting force on the second roller 9, resulting into a slight pivoting motion of arm 6 and thus into a small elevation of the roller 9 and the belts 5. Preferably, the gravity force of the roller 9 on the sheet S is partly or entirely compensated by spring 12 or other means for compensating the total weight of the arm 6. This compensation makes it possible that also relatively light sheets with a small moment of inertia can lift the arm 6 with second roller 9.

In an embodiment the weight compensating device is set to leave a small downward force on said roller, for example a force in a range of 0.01 to 2 Newton for a roller of 0.5 m. long, and more preferably in a range of 0.05 to 2 Newton. With a longer or shorter roller, this range will vary in proportion to the length. This helps to keep the stack in place.

In an embodiment second roller 9 is provided with one way rotation mechanism, which allows forward rotation corresponding to entry of the sheet underneath second roller 9, as indicated by the arrow C in fig.2, and blocks backward rotation. Bearing-like devices with such one way rotation

mechanisms are commercially available. Such a bearing may be used to mount second roller 9 on arm 6. A fine toothed wheel and a ratchet mechanism may be used for example, or a freewheel clutch or an electronic blocking circuit driving a motor coupled to second roller 9 to exert a countertorque when second roller experiences a backward torque. The one way rotation mechanism prevents the sheet from bouncing back from stop wall 4c, or at least minimized bounce. However, the one way rotation mechanism may not be needed if only a limited range of sheet types is used that does not suffer from significant bounce back, for example relatively rough and heavy sheets. Rotation of second roller 9 may be entirely driven by sheet S, so that no rotating force is executed when the roller and the sheet in contact with the roller is at rest.

As will be appreciated, the wedge shaped space, formed between the top of the stack of sheets and the inclined lower surface of belts 5 allows sheets to be caught when they leave printer 2. Unpredictable bending of the sheets can be handled. Preferably, the speed of belts 5 is slower than the speed at which the sheets are fed from printer 2. This allows the sheets to be slowed down. Belts 5 guide the edge of the sheet to second roller 9, until its edge reaches stop wall 4c. At the same time second roller 9 lifts belts 5 above the sheet, so that no lasting slipping contact arises between the sheet and belts 5.

The process of transporting sheets, catching and accurately positioning the respective sheets on the stack P due to the working of the roller 9 is repeated for successive sheets. Thus, the height of the stack P of sheets of paper will steadily grow. When the stack rests on floor 4a, the sensor constantly measures the height of the top of the paper stack P and switches the motor 13 the floor 4a and moves the paper stack P in small steps downwardly in the direction of the arrow D in fig.2, so that the measured height of the top of the stack is regulated to maintain a substantially constant target height when the stack grows by adding sheets of paper. This enables a very accurate height positioning of each upper sheet S with respect to the remaining non-movable parts of the printer paper unloading device 1, a positioning within a height tolerance of only a few millimetres.

When the height of the top of the stack is at the target value, arm 6 is directed so that belts 5 run at a nominal angle relative to the horizontal. In an embodiment an angle of six degrees is used. When belts 5 run at such an angle, first roller 8 has a higher position that third roller 10. The lower surface of second roller 9 is located lower than the lowest point of belts 5. Thus, once the sheet lifts arm 6 with second roller 9, belt 5 is raised above the surface of the sheet S.

At the end of the process of forming a stack, this results into a well defined stack, facilitating next processing steps of the production of a book, such as cutting and binding.

Figure 3 illustrates the use of a support fork 30 in side view. The printer paper unloading device 1 comprises a support fork 30 and a fork driver 32. Fork 30 has a plurality of teeth that extend in a horizontal plane (only one visible in the side view). Wall 4c may have openings to allow the teeth of fork 30 to pass through it. Fork driver 32 is configured to move fork 30 in a horizontal direction between a passive position (partly shown by dashed lines) and an active position at a location underneath arm 6. As seen in the side view this active position overlaps with a position that may be taken up by floor 4a of collector 4. Floor 4a has slots (not shown) corresponding to the teeth of support fork 30, allowing floor 4a to be moved vertically through the teeth of support fork 30 in its active position.

In operation, when a stack of sheets for a book has been completed, and before the first sheet of a next book is produced, floor 4a is moved down and support fork 30 is moved from its passive position to its active position. Thus, the first and following sheets of the next book will be stacked on support fork 30, which acts as a temporary platform for the stack, using the same procedure as described for floor 4a. At the same time the stack on floor 4a may be transferred to a further device for the next processing step in the production of a book. Floor 4a may comprise a transport belt or belts for lateral transport of the stack to realize this transfer. The stack of printed sheets may be transferred to a conveyor line of the books manufacturing system for example. Once floor 4a has become empty, it is moved vertically back into position underneath arm 6, through the teeth of support fork 30, so that support of the growing stack of the next book is taken over from support fork 30. Support fork is then moved back into its passive position.

The platform formed by support fork 30 may remain at a fixed height. There is no need to adjust the height of support fork 30 when the stack grows, because only a small number of sheets will be stacked on it while floor 4a is away, for example only six sheets and this height variation can be handled by pivoting motion of arm 6.

In the book manufacturing system a plurality of printers 2 with printer unloading devices 1 and transfer devices in parallel may be used. The described printer paper unloading device, with its accurate building of a stack of paper sheets can be applied in combination with printers in an

advantageous way in printing systems of different kind.

Although an embodiment has been shown wherein a wedge shaped space between belts 5 and the stack of paper is used to stack the sheets, it should be appreciated that other means of stacking may be used. For example, in an alternative solution, belts 5 may be omitted. Instead a vertically movable surface or surfaces above the stack may be used. In an example a set of vertically movable pins is used, whose lower surfaces form the vertically movable surfaces. A drive mechanism is provided to drive this surface or these surfaces up and down (e.g. solenoids and magnets to drive pins). In this embodiment the vertically movable surface or surfaces are initially in a position that leaves a spacing between the stack and the surface of surfaces, the spacing allowing sheets to be fed from the printer. When a sheet has been fed, the vertically movable surface or surfaces are moved down to force the sheet on top of the stack. As another example, the second roller may be omitted. Instead a horizontally movable wall (solid or containing openings) may be provided to the side of the stack on the side of the printer, with a driving mechanism to drive horizontal movements of the wall. The top of this wall is located so low that the printer is able to feed sheets over the top of the wall. When a sheet has been fed and forced down on the stack, the wall is made to move in the direction of the stack, so that the sheet is moved into contact with stop wall 4c. The motion may be triggered for example by a signal form the printer that a sheet has been fed, or by a signal from sheet feeding detector (not shown), e.g. comprising a light sensor.

A printer paper unloading device for collecting printed sheets of paper from a printer may be provided that, comprises a sheet collector comprising a collector floor and a sheet stop wall, means for aligning the sheets on a stack in the sheet collector, the collector floor being vertically movable, the printer paper unloading device comprising a height control loop configured to regulate a position of a top of a stack of sheets on said collector floor to a set value, wherein the collector floor comprises a transport belt for lateral transport of the stack of sheets, the printer paper unloading device comprising means for receiving sheets on a temporary floor at a fixed height while the further transport belt laterally transports the stack of sheets. The means for aligning may be implemented with an endless belt transport mechanism comprising an endless belt with a lower surface extending above the collector floor, a transport arm, and a roller attached to the transport arm downstream from the endless belt to lift the transport belts that help define the wedge shape space. In another example the means for aligning may be implemented with or a movable wall of the sheet collector and a mechanism to move the wall.

The detailed drawings, specific example and particular formulations given, serve the purpose of illustration only. Furthermore, other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the exemplary embodiment without departing from the scope of the invention as expressed in the appended claims.

Claims

1. A printer paper unloading device (1) for collecting printed sheets of paper from a printer, comprising

- a sheet collector (4) comprising a collector floor (4a) and a sheet stop wall (4c);

- an endless belt transport mechanism comprising an endless belt (5) with a lower surface extending above the collector floor (4a), characterized in that the unloading device (1) comprises

- an transport arm (6), at least a part of the endless belt transport mechanism that comprises the endless belt being mounted on the transport arm (6) with the lower surface at an angle to the horizontal, so that a wedge shaped space is formed between the lower surface of the belt and the collector floor (4a), the wedge shaped space narrowing down in a sheet transport direction, the transport arm (6) being suspended so that an end of the transport arm (6) at the narrowest side of the wedge shaped space is vertically movable;

- a roller (9) attached to the transport arm (6) downstream from the endless belt (5) and preceding the sheet stop wall (4c) in the sheet transport direction, the roller (9) being attached to the transport arm (6) at a height so that the roller (9), when supported on an upper sheet on said sheet collector, lifts the transport arm (6) to a height where a lowest point of the endless belt is lifted off the upper sheet.

2. A printer paper unloading device in accordance with claim 1, wherein said roller (9) is provided with a one way rotation mechanism that allows rotation of the roller (9) in a direction corresponding to feed in of sheets under the roller and blocks rotation in the opposite direction.

3. A printer paper unloading device in accordance with claim 1 or 2, characterized in that said transport arm (6) is provided with means (12) for at least substantially compensating a force of gravity due to the total weight of the transport arm at the location of the roller (9) .

4. A printer paper unloading device in accordance with claim 3, characterized in that said means for compensating the force of gravity comprise a weight compensating device (12) attached to the transport arm (6), set to exert a spring force that substantially compensates the force of gravity due to weight of the transport arm (6) .

5. A printer paper unloading device in accordance with any one of the preceding claims, characterized in that said roller (9) is attached to said transport arm (6) at a first end (6a) of the transport arm (6) and said transport arm (6) is pivotably suspended at second end (6b) of the transport arm (6), opposite said first end (6a).

6. A printer paper unloading device in accordance with any one of the preceding claims, wherein the endless belt transport mechanism comprises

- a pair of further rollers (8, 10) attached to the transport arm (6), the endless belt (5) running between further rollers (8, 10), the lower surface extending between the further rollers, and

- a motor coupled to at least one of the further rollers (8, 10) to rotate to at least one of the further rollers (8, 10).

7. A printer paper unloading device in accordance with in accordance with any one of the preceding claims, characterized in that the collector floor (4a) is vertically movable with respect to said roller, the printer paper unloading device comprising a height control loop configured to regulate a position of a top of a stack of sheets on said collector floor (4a) to a set value.

8. A printer paper unloading device in accordance with claim 7, characterized in that the height control loop comprises a height sensor configured to sense the position of the top of the stack of sheets (P).

9. A printer paper unloading device in accordance with claim 7 or 8, wherein the collector floor (4a) comprises a further transport belt for lateral transport of the stack of sheets, the printer paper unloading device comprising means for receiving sheets on a temporary floor at a fixed height while the further transport belt laterally transports the stack of sheets.

10. A printing system provided with the printer paper unloading device in accordance with any one of the preceding claims and a printer arranged to feed printed sheets into the wedge shaped space, characterized in that the endless belt transport mechanism is configured to realize a transport speed of the endless belt that is lower than an feeding speed (A) of the sheets applied by the printer when feeding the sheets to the printer paper unloading device.

11. A printer system according to claim 10, characterized in that the printer paper unloading device (1) is coupled with a transfer device for transferring the stacks of printed sheets (P) to a conveyor line.

12. A method of transferring paper sheets from a printer to a stack of paper sheets on a sheet collector (4), the method comprising

- transporting each paper sheet (S) in the direction of the stack (P) using a running transport belt (5) located at least partially above the stack (P) characterized in that a lower surface of the transport belt runs at an inclination to the horizontal, a wedge shaped space (W) being formed between the lower surface of the transport belt and the stack (P), the lower surface transporting towards a narrowest side of the wedge shape space, the method comprising - catching each sheet in the wedge shaped space (W) onto the lower surface of the transport belt, when the sheets are successively output from the printer;

- feeding each sheet between the stack and a roller on the stack from the wedge shaped space, the roller being mounted together with the transport belt on a vertically movable transport arm, whereby feeding of the sheet between the stack and a roller causes the transport belt to be raised.

13. A method in accordance with claim 12, wherein the transport belt runs at a lower speed than a speed at which the sheets are fed into the wedge shaped space, the sheets being decelerated by contact with the transport belt (5).

14. Method in accordance with claim 12 or 13, comprising sensing a position of the top of the stack (P) and controlling vertical movement of a floor (4a) of the paper collector (4) dependent on the sensed position to maintain the position at a set value.

15. Method in accordance with claim 14, comprising

- initiating formation of the stack on a platform at fixed height, movement of the transport arm compensating for an increasing height of the stack due to feeding of a plurality of sheets while the stack is formed on said platform, and subsequently

- moving in the vertically movable floor (4a) to take over support of the stack from the platform.