Patent Application
20180273334
The invention relates to sheet stacking devices and methods, useful for the formation of stacks of sheets, such as, but not limited to, corrugated board sheets. In particular, the invention concerns so-called up-stackers, i.e. sheet stacking devices wherein stacks are formed on a stacking surface which remains at a substantially fixed height, while a sheet conveyor arrangement, which delivers the sheets to be stacked has a sheet discharge end which is gradually lifted to accommodate a growing sheet stack.
In the paper industry, corrugated board sheets are manufactured starting from a continuous web-like corrugated board material, which is slit longitudinally and divided into strips. Each strip is further divided transversely to generate a plurality of sheets of desired length. Sheets thus obtained are delivered to a so-called stacker or stacking apparatus, which forms stacks or bundles of sheets. The stacks are subsequently delivered to the final user, for example for the manufacturing of corrugated board boxes or the like. Small bundles can be combined into larger stacks before shipping.
Fast advancing sheets must be carefully piled up to form stacks of regular shape. Known stacking apparatuses usually comprise a sheet conveyor arrangement which receives a substantially continuous flow of sheets which are shingled and delivered onto a stacking surface in a stacking bay.
In some cases, each stack is formed by staggered bundles, each bundle containing a predetermined number of sheets. TW-M423688U, US2014/0353119 and US2009/0169351 disclose sheet stackers configured and controlled for forming stacks of mutually staggered bundles of corrugated board sheets. In order to mutually stagger neighboring bundles of the stack, said stack is formed on a horizontally movable stacker platform. The reciprocating staggering motion is in a direction substantially parallel to the feed direction of the corrugated board sheets. The stacker platform comprises a conveyor belt, forming a stacking surface. The conveyor belt has a horizontal conveying motion, orthogonal to the reciprocating staggering motion of the stacker platform. The conveyor belt is used to evacuate the formed stack from the stacking bay according to an evacuation direction which is substantially orthogonal to the direction of arrival of the corrugated board sheets in the stacking bay. Each bundle of a stack is formed against a single stop plate or a dual stop plate, which are arranged in two positions which are staggered along the direction of arrival of the corrugated board sheets. Staggering of neighboring bundles is obtained by means of a reciprocating motion of the stacker platform in a horizontal direction. Moving the entire stacker platform is difficult and requires strong actuators and a particularly sturdy structure.
CN204057396U and CN203255778U disclose further embodiments of stackers designed and configured for producing stacks of sheets, each formed by a plurality of staggered bundles. Staggering is obtained by using two mutually spaced apart stop plates. The distance between the stop plates is equal to the staggering of neighboring bundles. In addition to moving the stop plates, the sheet discharge end of the sheet conveyor must also be reciprocatingly moved back and forth in a direction parallel to the feed direction, to achieve correct staggering of adjacent bundles.
These known methods and devices for the formation of staggered bundles of corrugated board sheets are expensive and cumbersome. There is still a need for improvements in stacking devices and methods capable of forming stacks of mutually staggered bundles.
According to embodiments disclosed herein, a sheet stacker is provided, which comprises: a sheet conveyor arrangement, configured for feeding a plurality of sheets and having a sheet discharge end; and a stacking bay, wherein sheets delivered by the sheet conveyor arrangement are formed into stacks. The stacking bay comprises a stack conveyor movable in a conveyor direction parallel to a sheet feeding direction, according to which the sheets are fed from the sheet discharge end onto the stack conveyor. The sheet conveyor arrangement is configured and controlled such that the sheet discharge end thereof is gradually lifted during sheet stacking, in order to accommodate a growing stack of sheets being formed on the stack conveyor. Thus, the sheet stacker operates as a so-called up-stacker.
Moreover, in order to orderly arrange the sheets of each stack, a stop plate is positioned in the stacking bay above the stack conveyor and in front of the sheet discharge end of the sheet conveyor arrangement. The stop plate is provided to form an abutment, against which the sheets delivered by the sheet conveyor arrangement onto the stack conveyor are caused to abut and to be stopped. The stop plate is further configured and controlled to be gradually lifted from the stack conveyor as the sheet stack grows. Moreover, the stop plate is configured to be withdrawn upon completion of the stack, to allow removal of the stack in an evacuation direction substantially parallel to the conveyor direction, away from the sheet discharge end of the sheet conveyor arrangement.
Withdrawing the stop plate to allow removal of the stack of just formed sheets means that the stop plate is removed from the path, along which the just formed stack shall be moved during evacuation thereof. Clearing off the stop plate from the stack evacuation path can be obtained e.g. by causing the stop plate to perform an over-travel in the lifting direction, e.g. such that the stop plate moves further upwards at a distance from the stack conveyor, which is greater than the height (vertical dimension) of the stack to be evacuated. Alternatively or in combination with a vertical over-travel, the stop plate can be caused to withdraw from the stack evacuation path by pivoting around an axis, for instance around a horizontal axis.
Thus, a completed stack can be moved away from the sheet conveyor arrangement and, once the stack has been cleared-off the sheet discharge end of the sheet conveyor arrangement, the sheet discharge end can be moved downwards towards the stack conveyor, in order to start formation of a subsequent stack.
According to some embodiments, the sheet stacker is configured and controlled to form stacks of staggered bundles. The bundles are staggered in the conveyor direction. Staggering can be obtained by means of a reciprocating movement of the stack conveyor. The staggering back-and-forth motion of the stack conveyor can be substantially parallel to the evacuation direction.
According to some embodiments, the staggering pitch can be constant. According to other embodiments, the staggering pitch can be adjusted depending upon one or more production parameters of the sheets, for instance depending upon the length of the sheets in the conveyor direction and/or upon the sheet stiffness. In order to facilitate the formation of staggered bundles, the stop plate can have a reciprocating vertical movement and horizontal movement, which are synchronized with the reciprocating staggering motion of the stack according to the stack conveyor direction.
Staggering of the bundles can thus be obtained acting upon the stack conveyor, while a horizontal movement of the sheet conveyor arrangement is not required.
In embodiments disclosed herein, therefore, the stack conveyor is configured and controlled to perform a combined action, namely: to perform a reciprocating staggering motion to form staggered bundles of sheets, and to further perform an evacuation motion, to remove a completed stack from the stacking bay.
Thus, according to embodiments disclosed herein, an evacuation motion of the completed stack is performed in a direction parallel to the reciprocating staggering motion, preferably in a direction concordant with the direction according to which the sheets are delivered onto the stack conveyor.
According to some embodiments, if stacks of staggered bundles are formed, for a smoother operation, the sheet discharge end of the sheet conveyor arrangement can be combined with an actuator, which controls a lifting and lowering movement of the sheet discharge end, which movement is synchronized with the reciprocating staggering motion of the stack conveyor.
The stack conveyor can comprise a single conveyor member, e.g. an endless conveyor member. In other embodiments, the stack conveyor can comprise a first stack conveyor member and a second stack conveyor member, which are sequentially arranged one after the other in the evacuation direction. The first stack conveyor member and the second stack conveyor member can be arranged and controlled such that a stack is formed on the first stack conveyor member and, upon formation thereof, the completed stack is moved by the first stack conveyor member to the second stack conveyor member and sequentially by the second stack conveyor member outside the stacking bay. Once the formed stack has been cleared-off the first stack conveyor member, formation of a new stack can start on the first conveyor member, while the previous stack continues moving in the evacuation direction along the second stack conveyor member. The production rate of the stacking device can thus be improved.
The sheet discharge end can be combined with a bundle retaining device, which is configured and arranged for retaining the top-most bundle of the stack when the stack conveyor performs the staggering motion in a direction away from the sheet discharge end. Undesired displacements of the top-most sheet of a bundle upon starting formation of a subsequent, staggered bundle, are thus reduced or eliminated. The bundle retaining device can comprise at least one resilient sheet braking member, arranged under the sheet discharge end, between the sheet discharge end and the stack being formed on the stack conveyor.
According to a further aspect, the invention also concerns a method of forming sheet stacks on a stacking surface, comprising the following steps:
The method can further comprise the steps of dividing the stack in mutually superposed and staggered bundles of sheets by reciprocatingly moving the stack conveyor according to a back-and-forth, i.e. reciprocating staggering motion, in a direction parallel to the evacuation direction.
The method can further comprise the step of lifting the sheet discharge end from the top of the stack under formation on the stack conveyor when the stack under formation is moved by the stack conveyor towards the sheet discharge end during the back-and-forth staggering motion of the stack conveyor.
When the stack conveyor comprises a first stack conveyor member and a second stack conveyor member sequentially arranged along the direction of motion of the stack conveyor; the method can be such that:
Other features and advantages of the invention will be better appreciated from the following detailed description of exemplary embodiments.
A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
The following detailed description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Additionally, the drawings are not necessarily drawn to scale. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.
Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase “in one embodiment” or “in an embodiment” or “in some embodiments” in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
Referring now to
The sheet conveyor arrangement 3 has a sheet inlet side 15 and a sheet discharge end 17. Sheets, e.g. corrugated board sheets coming from a slitter-scorer or other upstream section (not shown) of the manufacturing line, enter the sheet conveyor arrangement 3 at the sheet inlet side 15 and are advanced according to a feeding direction F towards the sheet discharge end 17, where the sheets are discharged in the stacking bay 5 to form stacks S of sheets C as will be described later on.
The stacking bay 5 can comprise a stack conveyor 19. The stack conveyor 19 can be placed in a fixed vertical position, e.g. adjacent a ground level G. The stack conveyor 9 can be comprised of motor-driven rollers, which can be arranged in sequence according to a conveyor direction f19. In other embodiments, the stack conveyor 19 can be comprised of continuous flexible members, e.g. flexible belts or chains. In some embodiments, the stack conveyor 19 comprises a first stack conveyor member 19A and a second stack conveyor member 19B. The first and second stack conveyor members 19A, 19B can be arranged in sequence in the conveyor direction f19. In the exemplary embodiment shown in the drawings, the first stack conveyor member 19A is arranged upstream from the second stack conveyor member 19B in the conveyor direction f19. The first stack conveyor member 19A can be comprised of a plurality of motor-driven roller, or a plurality of co-extensive endless belts or chains, as shown by way of example in the drawings. The second stack conveyor member 19B can be comprised of a plurality of motor-driven rollers, or a plurality of co-extensive endless belts or chains, as again shown in the drawings by way of example. The first and second stack conveyor members 19A, 19B can be controlled one independent of the other. Independently controlled, as used herein may be understood in the sense that the first and second stack conveyor members 19A, 19B can move a stack of sheets placed thereon according to movements which are independent for the two conveyor members. For example, a stack of sheets can be moved from the first stack conveyor member 19A on the second stack conveyor member 19B, and once the stack is on the second conveyor member 19B the first conveyor member 19A can be stopped.
Independently driven motors can e.g. be used to drive the first stack conveyor member 19A and the second stack conveyor member 19B.
In some embodiments, and for the purposes which will be described later on, the stack conveyor 19 can be controlled to move back-and-forth, i.e. with a reciprocating motion, in the conveyor direction f19. In some embodiments, at least one of the stack conveyor members 19A, 19B, preferably the first, i.e. the most upstream stack conveyor member 19A can be controllable with a back-and-forth motion in the conveyor direction f19, while according to some embodiments the second, i.e. the most downstream stack conveyor member 19B can be controlled to move constantly in only one way, rather than reciprocatingly.
In some operating conditions the two stack conveyor members 19A, 19B can be controlled to operate as a single conveyor, for instance when sheets C are processed, which have a dimension in the sheet feeding direction F which is longer than the length of stack conveyor member 19A.
The stack conveyor 19 can be configured to download stacks S on an evacuation conveyor schematically shown at 20. The evacuation conveyor can move the stacks according to a direction parallel to the conveyor direction f19, or according to a direction transverse to the conveyor direction f19, e.g. orthogonal thereto.
The sheets C are fed to the stacking bay 5 according to a sheet feeding direction. Reference F indicates the sheet feeding direction when the sheets C are fed on a stack S under formation on the stack conveyor 19. The direction F is substantially parallel to the stack conveyor direction f19.
It shall be understood that the actual feeding direction F of the sheets upon leaving the sheet conveyor arrangement 3 can be inclined to some extent with respect to the horizontal direction, such that the sheet feeding direction F can have an upwardly or downwardly oriented speed component when the sheets first enter the stacking bay 5. However, the sheets enter the stacking bay 5 according to a direction F which lays in a vertical plane parallel to
The sheet conveyor arrangement 3 is configured such that the sheet discharge end 17 thereof is vertically movable in an upwards and downwards direction, as shown by arrow f17. In
Along the cross member 13 a carriage 31 can be slidingly mounted. The carriage 31 can move along the cross member 13 according to double arrow f31 under the control of a motor 35, e.g. through a rack-and-pinion transmission system, a belt 36 (as schematically shown e.g. in
Referring now to
The vertical motion according to double arrow f17 of the sheet discharge end 17 can be controlled by a linear actuator, such as a cylinder-piston actuator, by an electric motor 51 or the like.
The operation of the sheet stacker 1 described so far will now be described with reference to the sequence of
During stacking, the stop plate 37 is located at a distance from the sheet discharge end 17 of the sheet conveyor arrangement 3, which is determined by the dimension of the corrugated board sheets C in the direction F. In this way, each corrugated board sheet C delivered into the stacking bay 5 will advance until reaching the stop plate 37, and all the sheets C will thus abut against the stop plate 37 and be aligned with their most advanced edges (leading edges) abutting against the stop plate 37.
The height (vertical dimension) of the stack S increases (
According to embodiments disclosed herein, also the stop plate 37 is gradually moved upwards and distanced from the stack conveyor 19, according to arrow f37 while the vertical dimension of the stack S increases. For instance the stop plate 37 can be supported by a slide 38, which can be moved along vertically extending guides 40. The guides 40 may be mounted on vertical beams 42, which may in turn project downwardly from the carriage 31. A motor 42 can be provided to move the slide 38 upwards and downwards as disclosed herein.
In
In a manner known per se, a gap is formed in the flow of sheets C traveling along the sheet conveyor arrangement 3, such that for a certain period of time as required to clear off the stack S, no further sheets C are delivered at the sheet discharge end 17 of the sheet conveyor arrangement 3. This time interval is sufficient to perform evacuation of the stack as described here below referring to
In order to remove the just formed stack S from the stacking bay 5, the stop plate 37 is cleared off the evacuation path, i.e. the path along which the stack S must be moved by the stack conveyor 19. In
Once the stop plate 37 has been cleared off the stack evacuation path, the stack S can start moving in an evacuation direction fE (
The same sheet stacker 1 described so far can be used to produce stacks S of staggered bundles B of sheets, as shown in
Each stack S is formed of a plurality of bundles B. Each bundle B contains a certain number of corrugated board sheets C. The number of sheets of each bundle B of a stack S can be constant. The bundles B are mutually staggered by a pitch P in the direction F, i.e. the sheet feeding direction on the stack conveyor 19, that is in turn parallel to the stack evacuation direction fE and to the conveyor direction f19. Staggering of mutually superposed bundles B is obtained by means of a back-and-forth, i.e. a reciprocating staggering motion of the stack conveyor 19 according to double arrow f19. The sheet discharge end 17 can move in a vertical direction, but does not require to move horizontally.
During stacking, the stop plate 37 is located at a distance from the sheet discharge end 17 of the sheet conveyor arrangement 3, which is determined by the dimension (length) of the corrugated board sheets C in the direction F. In this way, each corrugated board sheet C delivered into the stacking bay 5 will advance until reaching the stop plate 37, and all the sheets C will thus be aligned with their most advanced edges (leading edges) abutting against the stop plate 37.
In order to stagger the bundles B in the direction f19, once the desired number of corrugated board sheets C forming a bundle B has been piled up, the stack conveyor 19 moves by a pitch P towards the sheet conveyor arrangement 3 and away therefrom, alternatively. Starting from
In order to allow the trailing edges of the sheets (i.e. the most upstream edges of the cardboard sheets C with respect to the direction of feed F) of the last formed bundle B to move under the sheet discharge end 17, this latter is temporarily lifted when the stack S moves to the left. Bundle retention means (not shown) can be arranged at the sheet discharge end 17 of the sheet conveyor arrangement 3, to prevent undesired misplacement of the sheets C when the stack S is moved back-and-forth to form the staggered bundles B1, B2, B3, . . .
The stop plate 37 can remain stationary during formation of each bundle or may be gradually lifted, depending e.g. upon the height (vertical dimension) of each bundle B.
When the bundle B4 has been completed, the stack conveyor member 19A moves the stack back in the position of
Once the desired number of bundles B has been formed on the stack S, this latter is evacuated as described above, by moving the first stack conveyor member 19A and the second stack conveyor member 19B, until the stack has cleared off the first stack conveyor member 19A. The stop plate 37 is temporarily removed from the stack evacuation path.
Once the first stack has been removed from conveyor member 19A, this latter can accommodate the next stack and can be controlled to move back-and-forth, i.e. reciprocatingly, according to arrow f19 in order to stagger bundles B1, B2, B3 . . . of the next stack, while the previously formed stack S can be moved farther by the second stack conveyor member 19B towards the evacuation conveyor 20 or any other suitable removal means.
In some embodiments, the stack conveyor 19 may include a single section or stack conveyor member. In such case formation of a next stack cannot start until the previous stack S has been moved towards a pick-up position, wherefrom it can be picked up without further motion of the stack conveyor 19. This may require more time before formation of the next stack can start. Nevertheless, re-positioning of the stop plate 37 and of the sheet discharge end 17 can be made while the formed stack continues moving towards the pick-up area, e.g. the evacuation conveyor 20.
The above described sheet stacker structure can be used also to produce stacks of sheet bundles which are different one from the other, e.g. which can be formed of sheets having differing length in the sheet feeding direction F. A group of identical sheets can form a job. Different jobs, formed of sheets of different dimensions, can thus be placed one on top of the other in the same stack S. The reciprocating movement of the stack conveyor 19 in the conveyor direction f19 allows the various bundles to be centered one with respect to the other, such that when a shorter bundle and a longer bundle are placed in sequence, in the same stack S, the longer bundle (i.e. the bundle formed by sheets having a longer dimension in the sheet feeding direction F) projects from the bundle formed by sheets having a shorter dimension both upstream and downstream thereof. The reciprocating movement of the stack conveyor 19 thus allows sheets of different dimensions to be stacked in an optimal way. In preferred embodiments, the bundles of different jobs are stacked in a symmetrical way, such that each bundle is centered (in the sheet feeding direction) with respect to the adjacent bundles.
While the invention has been described in connection with what is presently considered to be the most practical and preferred examples, it is to be understood that the invention is not to be limited to the disclosed examples, but on the contrary, is intended to cove various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17162274.9 | Mar 2017 | EP | regional |
