Patent Application
20220169469
The invention relates to a sheet stacker, a printer comprising such a sheet stacker, and a method for stacking sheets.
Sheet stackers, specifically those used for medium-to-large volume printers, may comprise a sheet flipping device, which reverses the orientation of the sheet during the stacking process. Such sheets stackers are known e.g. from EP 2776352 A1. It is further known that when flipping more rigid sheets, a transport belt may be positioned adjacent the flipping device to force the rigid sheets into the desired flipping motion, for example from US2011309566 AA, U.S. Pat. No. 5,261,655 A, U.S. Pat. No. 5,026,036 A, or U.S. Pat. No. 5,145,167 A. It was found that such configurations were not able to more reliably and stack relatively very flexible sheets, such as (long) paper sheets with low grammage or thin foils. It was found that sheets could collapse upon themselves during flipping, resulting in an undesired fold in the sheet and a disturbed sheet stack. It is further known to support the sheets during flipping by means of an air vortex, as described in e.g. EP 3148908 A1.
It is an object of the invention to provide more reliable sheet stacking, specifically one that supports a wider media range including longer and/or more flexible sheets.
In accordance with the present invention, a sheet stacker according to claim 1, a printer according to claim 14, and a method according to claim 15 are provided. The sheet stacker according to the present invention comprises:
As the sheet is engaged by the sheet flipping device the holding device holds a portion of the sheet engaged by flipping device, preventing the sheet from collapsing upon itself under the influence of gravity. The holding device is configured to move the held portion of the sheet to allow the sheet sufficient freedom of movement to execute its flipping motion. Thereby sheets regardless of their flexibility are reliably flipped and stacked. The object of the present invention has been achieved.
More specific optional features of the invention are indicated in the dependent claims.
In an embodiment, the holding device is arranged for engaging an outer surface of the sheet. The outer surface herein is the radially outward facing side of the sheet during its flipping motion. This is preferably the bottom side of the sheet after it has been flipped.
In an embodiment, the sheet supply path is moveable with respect to both the holding device and the sheet flipping device. The sheet supply path has a sheet releasing end or exit, where a sheets leave the sheet supply path, for example as defined by a pinch or and end of a conveyor belt. The exit is moveable by means of an actuator, such that the exit can be positioned either adjacent the sheet flipping device in the first position or adjacent the holding device in the second position. In another embodiment, the holding device is moveable with respect to the sheet flipping device and the sheet supply path. In the first position, the holding device is moved out of the a trajectory of a sheet from the sheet supply path into the sheet flipping device, while in the second position the holding device is positioned along, in, or at said trajectory sufficiently close to the sheet to adhere a trailing portion to the holding device.
In an embodiment, the sheet flipping device comprises a flipping wheel provided with at least one slot for receiving the sheet. The flipping wheel is rotatable, such that the sheet with its leading edge engaged in the slot is flipped around the rotation axis of the flipping wheel. The flipping wheel may be provided with one or more slots, which may be positioned in a receiving position in time with the arrival of a sheet. This results in a highly productive system. It will be appreciated that such a flipping wheel is described in detail in EP 2776352 A1, the description of which is herein incorporated by reference.
In an embodiment, the holding device comprises a holding surface to which the portion of the sheet is adhered during flipping, the holding surface being moveable in the first direction. The holding surface is able to carry the engaged portion of the sheet in the first direction to complete the flipping motion of the sheet by the sheet flipping device. The holding surface moves the held portion of the sheet away from the flipping wheel, such that the trailing portion of the sheet unrolls in said direction, until the trailing portion is released.
In an embodiment, the holding device comprises an endless conveyor belt. The conveyor belt comprises means for holding the portion of the sheet against it, such as suction holes for applying an underpressure or an electrostatically charged surface. The endless belt loops cyclically around its support making it well suited for processing large volumes of consecutive sheets.
In an embodiment, the conveyor belt is provided with suction holes for applying an underpressure to the portion of the sheet, such that the portion is held against the belt. The underpressure may be applied via a suction box positioned adjacent the belt with openings facing the flipping volume through which the sheets travels during its flipping motion. The suction box is provided with or connected to a suction source, such as a pump or fan.
In an embodiment, the flipping device defines a flipping volume through which the sheet travels during flipping, and wherein conveyor belt is positioned over the flipping device and over the flipping volume. The holding device is positionable sufficiently adjacent the sheet flipping device, such that it is able to draw against it a sheet which is engaged by the sheet flipping device. To support the portion of the sheet during its flipping motion, the holding device extends over the flipping volume, preferably over the majority of or the entire flipping volume.
In an embodiment, the holding device is positioned over the sheet flipping device and extends away from the sheet flipping device in a direction parallel to a sheet stacking surface for receiving the flipped sheets. The sheet flipping device is configured to form a sheet stack on the sheet stacking surface. The flipping volume is contained between the holding device and the sheet stacking surface. The sheet stacking surface may be height adjustable to compensate for a growing sheet stack. The sheet stacking surface preferably extends in the first direction. The holding surface is preferably configured to move in said first direction. In a further embodiment, the holding device and the flipping device, specifically the flipping axis, are moveable with respect to one another. The height of the flipping volume may be determined by setting a predetermined distance between the sheet stacking surface and the flipping axis. The holding device or the flipping device may be made to be height adjustable. The sheet stacking surface is preferably height adjustable to maintain the top level of the sheet stack constant with regard to the flipping axis.
In an embodiment, the sheet stacker further comprises a controller configured to control the sheet stacker, such that:
In the first state the leading portion, specifically the leading edge of the sheet, passes into the slot of the sheet flipping device without interference by the holding device. The holding device may be positionable out of the path of the incoming sheet, at least with respect to the sheet flipping device. The holding forces exerted by the holding device thus do not affect the sheet's entry into the slot of the flipping wheel. In a second state the holding device is positionable or positioned with respect to the flipping wheel, such that the sheet is affected by the holding forces exerted by the holding device. In consequence, a portion of the sheet following the leading portion is drawn against the holding device and held there. The held portion is moved in the first direction as the sheet is flipped, preferably by moving the holding surface engaging the sheet in the first direction.
In an embodiment, the sheet stacker further comprises a sheet supply path for supplying sheet to the sheet flipping device, wherein the holding device is positioned adjacent the sheet supply path. In another embodiment, the sheet supply path is moveable with respect to the holding device between a first position wherein a portion of the sheet may pass into the sheet flipping device without being adhered against the holding device and a second position wherein the holding device is able to draw a portion of the sheet against it. An actuator may be provided for moving the sheet supply path and the holding device with respect to another. In the first corresponding to the first state the exit of the sheet supply path is preferably near the flipping wheel and remote from the holding device, while in the second position corresponding to the second state the exit is positioned sufficiently near the holding device to allow the holding device to draw the sheet against it. In the second state the exit may be at a greater distance from the flipping wheel as in the first state. This prevents the holding device from affecting delivery of the sheets from the sheet supply path into the slots of the flipping wheel.
In an embodiment, the flipping wheel has a receiving position for receiving a sheet from a sheet supply path and a trigger position different from the receiving position, wherein the controller is configured to switch the sheet stacker from the first to the second state, when the flipping wheel reaches the trigger position. The trigger position may be determined by a suitable sensor, such as an encoder for determining the orientation of the flipping wheel or an optical or touch sensor, which sensor detects the sheet reaching a certain position, such as the leading edge of the sheet contacting a stop element which ejects the sheet from its slot. When the controller determines that the sheet has reached the trigger position, the sheet supply path and the holding device are brought into proximity with each other, such that a portion of the sheet is drawn against the holding device. Before the arrival of a subsequent sheet, the controller returns the sheet stacker to the first state, preferably by controlling the actuator to increase the distance between the holding device and the sheet supply path.
In an embodiment, the holding device extends between a sheet supply path and a bypass path such that a sheet may be transported by the holding device from the sheet supply path to the bypass path without engagement with the sheet flipping device. The sheet flipping device may be bypassed by allowing the entire sheet to be engaged by the holding device. The leading portion of the sheet is for example transported from the sheet supply path onto the holding device with the sheet stacker in the second state at the arrival of said sheet. The leading edge and with it the rest of the sheet travels along the holding the device towards the bypass path, where it is released from the holding device. This allows the sheet stacker to direct specific sheets to an output location different than the sheet flipping device, for example a finisher configured for stapling, coating, book binding, etc. This further allows the sheet stacker to handle large sheets with dimensions exceeding its stacking capacity.
The present invention further relates to a printer comprising a sheet stacker according to the present invention. The printer is preferably a sheet printer, very preferably an inkjet sheet printer.
The present invention further relates to a method for stacking sheets comprising the step of a sheet flipping device flipping a sheet, the step of a holding device engaging a portion of the sheet and said holding device transporting the held portion away from a flipping axis of the sheet flipping device, and the step of the holding device releasing the portion of the sheet during the final part of the flipping motion of the sheet. A sheet supply path is moved with respect to the holding device for supplying sheet to the sheet flipping device between a first position wherein a portion of the sheet may pass into the sheet flipping device without being adhered against the holding device and a second position wherein the holding device is able to draw a portion of the sheet against it. Preferably, the sheet supply path is moved with respect to the holding device into the first position, followed by, while in the first position, passing a portion of the sheet may from the sheet supply path into the sheet flipping device without being adhered against the holding device. In another embodiment, the method further comprises the steps of moving the sheet supply path with respect to the holding device into the second position, and, while in the second position, the holding device drawing a portion of the sheet against it.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
The present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals have been used to identify the same or similar elements throughout the several views.
In
The sheet supply path 10 comprises one or more transport devices, such as motorized transport pinches 11, 12 to drive the sheet S into the slot 4. The sheet supply path 10 preferably extends upstream towards a printer. Sheet guides 14 formed as plates or fingers 14 may be provided along the sheet supply path 10 to guide the sheet S. When receiving the sheet S, the flipping wheel 3 may be stationary in the receiving position or be in rotational movement out of the initial receiving position. In the latter case the circumferential speed of the slot 4 is relatively lower that the transport speed of the sheet S on the sheet supply path 10, such that the sheet S is inserted into the slot 4. The controller (not shown) may be configured to drive the transport pinch 11 with a greater speed as compared to the circumferential speed that the controller sets for the flipping wheel 3.
It will be appreciated that the sheet S may in another embodiment be brought into contact with the holding device 20 by an outward folding motion of the sheet S, which is achieved by setting circumferential velocity of the flipping wheel lower than the transport sheet of the transport device 11, 12 on the sheet supply path 10. The transport device 11, 12 and guide element 14 may be suitably configured and positioned to allow for the outward radial motion of the sheet S.
The holding device 20 in
Since in
Although specific embodiments of the invention are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations exist. It should be appreciated that the exemplary embodiment or exemplary embodiments are examples only and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.
It will also be appreciated that in this document the terms “comprise”, “comprising”, “include”, “including”, “contain”, “containing”, “have”, “having”, and any variations thereof, are intended to be understood in an inclusive (i.e. non-exclusive) sense, such that the process, method, device, apparatus or system described herein is not limited to those features or parts or elements or steps recited but may include other elements, features, parts or steps not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms “a” and “an” used herein are intended to be understood as meaning one or more unless explicitly stated otherwise. Moreover, the terms “first”, “second”, “third”, etc. are used merely as labels, and are not intended to impose numerical requirements on or to establish a certain ranking of importance of their objects.
The present invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20210386.7 | Nov 2020 | EP | regional |
