The present invention pertains to a system for facilitating an order change in the dry end conversion of a corrugated paperboard web. In particular, the invention relates to a method and apparatus for accomplishing an order change using a minimum slit head configuration slitter.
In a corrugator dry end, where a corrugated paperboard web is longitudinally scored and slit into multiple parallel output webs (or “outs”), the outs are directed through one or more downstream cut-off knives which cut the output webs into selected sheet lengths. When two cut-off knives are used, they are vertically separated and each is capable of cutting the full corrugator width web. A web selector positioned downstream of the slitter/scorer, divides the outs into two groups, one of which is directed to the upper cut-off knife and the other to the lower cut-off knife. Order changes must be effected while the upstream corrugator wet end continues to produce and deliver the continuous web to the slitter/scorer. An order change will typically result in a change in widths of the output webs; requiring redirection of at least a central portion of the web from one knife level to the other and possibly changes in edge trim widths as well.
The prior art has developed two basic order change systems for corrugator dry ends utilizing double level cut-off knives. One system is known as a gapless or plunge style order change system. In this system, there are two slitter/scorer stations immediately adjacent one another in the direction of web movement and through both of which the web travels. At order change, one slitter/scorer, operating on the currently running order, will lift out of operative engagement with the web, and the other slitter/scorer which is set to the new order alignment plunges down into operative engagement with the web. The result is a small order change region of corrugated web with overlapping slits and scores for both the running and the new orders.
The second basic order change system is known as a gap style system. In this system, there is normally a single slitter/scorer station 121 as shown in
The two station gapless slitter of
In principle, it would be possible to implement a gapless order change with a single slit axis machine 124, as shown in
An approach to use of a single axis slitter to accomplish a gapless order change of
An object of the invention is to achieve the continuous slitting and scoring of the corrugated web in a gapless order change with a slitter/scorer that has the fewest slit heads possible consistent with the specification for the maximum number of “outs” required.
A further objective of the invention is to minimize the length of waste material generated during the order change by accomplishing the change over from one job to the next as quickly as possible.
Another objective of a particularly advantageous embodiment of this invention is to provide a trim slit change-over method that will significantly improve order change-over reliability.
Yet another objective of the invention is to reduce the head support structure of the slitter scorer that will minimize the overall cost of the slitter/scorer.
It is also an objective of the invention to provide a slitting method that will require a small number of head positioning robots so as to reduce the overall cost and complexity of the slitter and to achieve a high reliability.
These and other objectives and advantages, which will be clear to those skilled in the art from reading the description that follows, are achieved with a slitter/scorer device that has slit heads mounted on both sides of a single support structure that allows heads from either side to be run in any combination. This allows some slit heads to be located and engaged in the web for a current running order while leaving space available for location of unused slit heads for an upcoming order.
Prior art slitter/scorers have used two in-line series of rotary scoring tools and two in-line series of rotary slitting tools to make it possible to process one job on one series of slitting and scoring tools while the other series of slitting and scoring tools is positioned by robots for the processing of the next job. For a six-out slitter/scorer, there are a minimum of five internal slit heads required on one job. The prior art slitter/scorers utilize five internal slit heads on each slitter series.
The single axis slitter 10 of the present invention has dedicated trim slitting tools 13, 13a on each side and each end of the single slit axis, in addition to the internal slit heads 11, 11a. There will be a set of externally mounted trim chutes 14 as shown in
This problem is solved by the present invention by a concept that always allows trim to be taken by the downstream dedicated trim slitting tool 13 of the
Another aspect of the current invention involves the use of asymmetric trim to allow use of an otherwise dedicated upstream mounted trim slit tool 13a for internal web slitting. This occurs when going into or out of a five- or six-out order to maximize the number of slit heads available for the changeover. This method of order change involves leaving the dedicated trim slit tool 13 engaged in its currently running position at order changeover, as shown in
Another aspect of the present invention is the use of asymmetric trim and graceful degradation of the order change process from a gapless change to a gap-style change when making an order change from or to a five- or six-out. This allows the pre-set of unused slitting tools to be available during the running of the old order and then a positioning of the robot on one currently running tool 11, 11a, or 13a closely located in a cross corrugator position to the required position for the new order. At order change, a gap is pulled and the robot quickly positions the slit head 11, 11a, or 13a in the gap as the tailing out order clears the slitter. Alternately, the order change region as described in US Patent Application Publication No. US2006/0090617 and shown in
Another aspect of the current invention is the use of a rules-based order scheduling module to accommodate the specific limitations of the single axis plunge slitter that has a complement of six internal slit heads. In the normal scheduling of a corrugator, the scheduling software assumes that capability exists for solutions involving numbers of outs of successive orders in any combination up to the maximum possible. The solutions also assume the use of symmetric trim by the slitter setup controls and so only provides web width and out widths to derive a trim combination solution. The goal of this scheduling software is to pick order solutions that minimize the overall average trim widths in a wet end paper setup. There is a problem with this type of scheduling system when used on a corrugator with a slitter/scorer of the configuration of the present invention. The problem is that, in the absence of any rules to the contrary, the schedule solutions may well involve orders with number of outs on successive orders that exceed the capability of the slitter scorer. An objective of the slitter/scorer of the present invention is to reduce the overall cost of the machine by reducing the slit head complement. This reduced slit head machine cannot perform order changes on six-out to six-out or five-out back-to-back orders. The solution to this problem is to include a software module that will take the dry end setup solutions provided by the scheduling system and to reconfigure the sequence in which these orders are scheduled for the express purpose of eliminating six-out to six-out or five-out back-to-back orders. A second aspect of the solution is the selection of orders to precede or follow six-out or five-out orders with either two-out or three-out orders; or with three-out or four-out orders with trim width solutions that are wide enough to run asymmetric trim on the five-or six-out running order as well as the order following the five-out or six-out order. Failing any of the foregoing solutions, the software module will signal that a gap-style or extended order change zone gapless order is to be run, will select a running order head to be positioned by the robot in the gap or order change zone and schedule an asymmetric trim solution. The function, then, of the software module is to custom tailor the scheduling solutions to the specific capability of the slitter of the present invention. Since six-outs and five-outs are normally not common in the industry, this software module will succeed in all but the most unusual situation. Of course, if no successful solution in terms of dry end order sequence can be found using the rules-based software modules, then feedback is provided to the scheduling system indicating that different paper combinations will be required to run the orders.
It would be consistent with the present invention to add more internal slit heads to the slitter/scorer if a specific plant felt that there were good reasons why larger number of six-out and five-out orders would be scheduled. By adding two internal slit heads to each side of the single slit axis, it would be possible to schedule without constraint, six-out and five-out orders back-to-back, without asymmetric trim in the plunge order change mode of operation. The machine would then take on the characteristic of current technology two-axis solutions as epitomized by the
In
This application relates to and claims priority from U.S. Provisional Patent Application Ser. No. 61/105,456, filed Oct. 15, 2008.
Number | Date | Country | |
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61105456 | Oct 2008 | US |
Number | Date | Country | |
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Parent | 12579868 | Oct 2009 | US |
Child | 13585593 | US |