NL2004941C2

NL2004941C2 - Printing system and printer unloading device.

Info

Publication number: NL2004941C2
Application number: NL2004941A
Authority: NL
Inventors: Peter Ivan Sygall; Bart Hoogers
Original assignee: Book Factory Systems B V
Priority date: 2010-06-22
Filing date: 2010-06-22
Publication date: 2011-12-27
Also published as: WO2011162607A1

Description

P91502NL00

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.

5

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 10 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.

15 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 20 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 25 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, 2 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 5 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.

10 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 15 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.

20 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.

25 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 30 endless transport belt or plurality of parallel endless transport belts runs 3 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.

5 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 10 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 15 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 20 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 25 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 30 in controlling the height.

4

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 5 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 10 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 15 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.

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

Detailed description of an exemplary embodiment 25 The printer paper unloading device 1 shown in fig.1 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 nr, 30 2004352 of applicant, filed on March 5, 2010. In the illustrated embodiment, 5 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 5 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 10 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 15 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.

20 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 25 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 30 compensating device may comprise a spring between transport arm 6 and a 6 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, 5 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 10 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 15 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 20 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.

25 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 30 transported and launched into the wedge shaped space between at one side the 7 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 5 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.

10 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.

15 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 20 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 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 25 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 30 second roller experiences a backward torque. The one way rotation mechanism 8 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.

5 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.

10 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 15 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 20 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.

25 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 9 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, 5 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 10 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 15 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, 20 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 25 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 30 is then moved back into its passive position.

10

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 5 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 10 advantageous way in printing systems of different kind.

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 15 from the scope of the invention as expressed in the appended claims.

Claims

A printer paper unloading device for collecting printed sheets of paper from a printer, comprising - a sheet collector (4) provided with a collector floor (4a) and a sheet stop wall (4c); 5. an endless belt transport mechanism provided with an endless belt (5) with a lower surface extending above the collector floor (4c), characterized in that the discharge device is provided with - a transport arm (6), wherein at least one portion of the endless belt conveyor mechanism comprising the endless belt mounted on the transport arm (6) with the bottom surface at an angle to the horizontal, so that a wedge-shaped space is formed between the bottom surface of the belt and the collector floor (4a) wherein the wedge-shaped space narrows in a sheet transport direction and wherein the transport arm is suspended such that one end of the transport arm can be moved vertically on the narrowest side of the wedge-shaped space 15, - a roller (7) arranged on the transport arm (6) downstream of the endless belt (5) and prior to the sheet stop wall (4c) in the sheet transport direction, the roller (9) being mounted so high on the transport arm that when resting on an upper sheet on said sheet collector, the roller (9) lifts the transport arm (6) to a height at which a lowest point of the endless belt is lifted from the upper sheet.

2. A printer paper unloading device according to 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 insertion of the sheets under the roller (9) and rotation in blocks the opposite direction.

A printer paper unloading device according to claim 1 or 2, characterized in that said transport arm (6) is provided with means (12) for at least substantially compensating for gravity due to the total weight of the transport arm at the location of the roller (8) .

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

A printer paper unloading device according to any one of the preceding claims, characterized in that said roller (9) is connected to a first end (6a) of the transport arm (6) to said transport arm (6) and that said transport arm (6) is rotatable suspended from a second end (6b) of the transport arm (6) opposite the first end (6a).

A printer paper unloading device according to any one of the preceding claims, wherein the endless belt transport mechanism is provided with a pair of further rollers (8, 10) connected to the transport arm (6), the endless belt (5) between the further rollers are running, the lower surface extending between the further rollers, and - a motor which is coupled to at least one of the further rollers (8, 10) to rotate at least one of the further (8, 10) rollers.

A printer paper unloading device according to any one of the preceding claims, characterized in that the collector floor (4a) is movable vertically relative to said roller (9), wherein the printer paper unloading device is provided with a height control loop adapted to position a top of a stack of sheets on said collector floor (4a) to a set value.

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

9. A printer paper unloading device according to claim 7 or 8, wherein the collector floor (4a) is provided with a further conveyor belt for lateral transport of the stack of sheets, wherein the printer paper unloading device comprises means for receiving sheets on a temporary floor at a fixed height while the further conveyor belts transport the stack of sheets sideways.

A printer system provided with the printer paper unloading device according to any of the preceding claims and a printer arranged to feed printed sheets to the wedge-shaped space, characterized in that the endless belt transport mechanism is arranged to realize a transport speed of the endless belt which is lower is then a feed rate (A) of the 10 sheets applied by the printer when the sheets are fed to the printer paper unloader.

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

A method of transferring sheets of paper from a printer to a stack of sheets of paper on a sheet collector (4), which method comprises - transporting each sheet of paper (4) toward the stack (P) using 20 of a running conveyor belt (5) which is at least partly above the stack (P); characterized in that a bottom surface of the conveyor runs at an angle to the horizontal, a wedge-shaped space being formed between the bottom surface of the conveyor and the stack (P), the bottom surface conveying to a narrowest side of the wedge-shaped space, the method comprises - catching each sheet in the wedge-shaped space (W) against the bottom surface of the conveyor belt when the sheets are successively ejected from the printer; - feeding each sheet between the stack and a roller from the wedge-shaped space, the roller being mounted together with the conveyor belt on a vertically movable conveyor arm, whereby the introduction of the sheet between the stack and the roller causes the conveyor belt to be lifted.

A method according to claim 12, wherein the conveyor runs at a lower speed than a speed at which the sheets are fed into the wedge-shaped space, the sheets being decoded by contact with the conveyor.

14. Method according to claim 12 or 13, comprising detecting a position of a top of the stack (P) and controlling vertical movement of a floor of the paper collector (4) depending on the detected position around the position at a set height to keep.

15. Method as claimed in claim 14, comprising - initializing the formation of the stack on a platform at a fixed height, wherein movement of the transport arm compensates for an increasing height of the stack as a result of feeding a plurality of sheets while the stack is formed on the platform and then - move the vertically movable floor (4a) to take over support from the platform stack.