The present invention relates to the production of corrugated board and more particularly to a novel method for loading and threading-up paper rolls on the corrugator to facilitate the running of very short wet end orders.
Single wall corrugated board is comprised of three layers of paper including a top liner, a fluted medium and a bottom liner. The strength of the corrugated board is defined by an edge crush test (ECT) that is closely correlated with the strength of these papers. Paper strengths are commonly measured using a short span compression test (STFI). The corrugated board ECT can be estimated using a relationship that is a linear combination of the STFI's of the papers and the take up factor of the fluted medium. The STFI of the papers is primarily determined by the fiber content measured in pounds per thousand square feet or grams per square meter. The paper grades used in the formation of the corrugated board, as a consequence, determine the strength of the box produced.
Corrugated boxes manufactured using single wall board are frequently used to ship products by air, truck or rail. Freight carriers imposed packaging rules in exchange for accepting liability for the integrity of the contents of the goods transported. These rules were codified by the National Motor Freight Carriers Item 222 and the National Railroad Freight Committee Rule 41. These rules determined packaging material specifications that varied depending upon the gross weight of the package and the box dimensions. The specifications dictated box liner and medium combined basis weights. In 1990, trade associations for the corrugated industry sponsored proposals to eliminate Item 222 and Rule 41 and allow use of ECT instead of traditional paper basis weights as the primary specification for box design. These changes, when approved, gave the corrugated producers considerable more flexibility in the design of corrugated boxes that took the end users performance requirements into consideration.
In response to this change, the paper manufacturers developed a variety of liners and mediums with enhanced STFI to further expand the options for paper grades available to the corrugated producers. Since fiber content represents approximately 80% of the cost of producing a box, there was strong focus on use of specific paper combinations to just match customer ECT requirements. The end result of this development was a significant increase in the number of paper changes on the wet end of the corrugator. Along with the concurrent trend of just-in-time manufacturing, this has resulted in as many as 80 paper changes or more per shift on some sheet feeder corrugators.
Minimum length of a wet end order is normally determined by the time that it takes to change a paper roll and prepare it for a splice. This cycle begins when a paper butt roll is spliced out. The butt roll is removed from the corrugated and then a new paper roll powered on a track and trolley system beneath the corrugator. The paper must then be prepared for a splice. Papers are normally changed at the top liner, medium and bottom linear roll stand positions. These tasks can be conducted in parallel with adequate crew on the corrugator. Nonetheless, with four minute paper roll changeover and splice preparation and corrugator speed slowed to 500 FPM, the minimum order length on the wet end of the corrugator is 2000 lineal feet. Certain customers for sheet feeder corrugators would like orders shorter than 500 lineal feet.
One way of achieving short orders is to avoid width and paper grade change by either taking extra wide trim to avoid width change or to upgrade the basis weight of the papers run to avoid a paper grade changes. Both of these options create substantial fiber loss since the customer will not accept an upcharge for wasted trim or heavier grade papers used.
U.S. Pat. No. 6,575,217 discloses a technique for quick paper change that involves the addition of single sided roll stands that allow up to four rolls to be chucked up on the corrugator that are operationally related to one splicer. This idea allows the process of splice preparation and roll change to occur in an overlapped fashion to reduce wet end order change cycle times. The technique requires substantial space in-line in the corrugator to accommodate the extra roll stands. For existing corrugators, this would require very signification relocation of equipment and, in the vast majority of cases, is impractical because of building constraints and cost.
As a consequence, there is a need in the corrugated industry for a means of facilitating short orders on the wet end of the corrugator.
The method of the present invention involves use of tandem splicer/roll stands that allow paper rolls associated with two sequential next-up paper changes to be loaded and prepared for splice while running paper from rolls currently chucked upon on adjacent primary splicer/roll stands. A typical order change made using the method of the present invention would involve paper change at the top liner, medium and bottom liner positions. The chuck-up of these future wet end paper rolls in parallel with the current running of a longer order allow two future order changes to be made with simple splice initiation.
To accomplish this, the papers from the rolls chucked-up on the tandem splicer/roll stands are threaded through the tandem splicers, down around auxiliary splice preparation platforms and then through the splicer carriages available on the upstream end of the primary splicers where the papers are prepared for splice. After splice preparation is complete, the auxiliary splicing platforms can be either manually removed or raised to a higher running level position allowing yet future wet end paper rolls to be run beneath the corrugator and chucked-up on the upstream ends of the primary splicer/roll stands. This done, the corrugator has three future order paper types loaded onto the roll stands in anticipation of wet end order changes.
Splicing of a roll mounted on the tandem splicer/roll stand with use of a splicer carriage of the primary splicer/roll stand involves intermodal splicing. Intermodal splicing uses the splicer carriage functions of stop bar, cutoff knife and splice sealing rolls on the primary splicer/roll stand and the paper roll accelerating functions of the capstan roll, dancer system and brake control on the tandem splicer/roll stand. The intermodal splicing idea is the key concept of the present invention that allows a roll chucked on the tandem splicer to be spliced into a roll located on the primary splicer. Once this is done, then a further wet end paper can be spliced onto the tail of the next order at order change using the normal splice cycle of the tandem splicer.
Normally, minimum length of a wet end order is determined by the cycle time associated with splicing and changing out a butt roll and then loading and chucking-up a new roll and preparing this roll for splice. However, with the tandem splicer/roll stand concept of the present invention using intermodal splicing, the minimum length of the first and second orders ahead can be cut in half because these two orders are ready to run with simple push of a splice activate button. The time available to change out the roll on the downstream end of the primary splicer/roll stand that will become the third order ahead is equal to the duration of running two wet end orders instead of one. The fourth order ahead would become the roll chucked-up on the upstream end of the primary splicer. Since this roll must only be prepared for a splice during the running of the third order ahead, this third order ahead can also be a short order.
The tandem splicer/roll stand of the present invention requires that two splicer/roll stand pairs be available on each side of a single facer as well as at the bottom liner position. Most corrugators have at least two single facers to allow the manufacture of double wall board. A typical corrugator will run with one single facer making single wall board more than 85% of the time. For various reasons, the upstream single facer is normally the most used. With the advent of single facers with quick cassette change, it is possible to rim nearly all single face board on the most upstream single facer. Using the most upstream single facer allows the top liner splicer/roll stand on the downstream single facer to be used as the tandem splicer/roll stand for short order set-up on the medium side of the upstream single facer. Similarly, the medium splicer/roll stand on the downstream single facer can become the tandem splicer/roll stand for the double backer or bottom liner position. This means that only one additional splicer/roll stand must be added at the most upstream end of the typical corrugator to run short wet end orders with the tandem splicing concept of the present invention. There is space at the end of most corrugators to install another splicer/roll stand that would become the tandem splicer/roll stand for the top liner paper on the upstream single facer. Of course, on a new corrugator, tandem splicer/roll stands could be factored into the design to alleviate some of the considerations noted.
Features and advantages of the tandem splicer/roll stand concept with intermodal splicing will become apparent from the following description of the preferred embodiment considered along with the accompanying drawings.
Primary and essential elements of the wet end of a corrugator are shown in
A dual position roll stand 110 is located on the upstream side of single facer 35 for the top liner paper 41 and another dual position roll stand 100 is located on the downstream side of single facer 35 for the medium paper web 42. The medium paper 42 is unwound from one end of the dual position roll stand 100 through web splicer 40 and into single facer 35. The single facer normally has associated with it a means of heating and preconditioning the medium paper 42 with a steam shower 45 to soften the fibers so that the medium can be fluted between corrugating rolls 36. As the fluted medium web 42 exits the labyrinth 37 between the corrugating rolls 36, it is retained in a fluted fashion on one of the corrugating rolls 36 using either a vacuum or a pressure technique. A glue roll 39 contained within single facer 35 is located in close proximity to the corrugating rolls 36 and applies an adhesive to the medium flute tips. At this point, the glued flute tips of the medium 42 are pressed against the top liner 41 using a pressure roll 38 where a green bond is quickly formed creating the single face web 43. The top liner 41 enters the single facer 35 from the upstream side. The top liner is normally heated on a preheater 46 located between the top liner splicer 50 and the single facer 35. As the glued medium flute tips are pressed against the top liner 41, the latent heat in the liner continues to cure the bond as it transits down the wet end of the corrugator 150.
A second single facer 55 on the corrugator wet end 150 allows flutes of a different profile to be run. As such, the
Because of space constraints, many corrugators are located against one side of a factory wall as shown in
The time to remove a butt roll from beneath the corrugator, reposition a new roll and prepare it for splice along with the corrugator speed are the variables that determine the minimum length of a wet end order. The present invention seeks to eliminate the roll change time completely for two orders ahead by using a tandem splicer.
The short order change technique of the present invention will be described for one set of tandem splicer/roll stands 60, 120 and primary splicer/roll stands 50, 110, the technique being identical for all paper positions. The process begins as shown in
The short order sequence begins, as shown in
While the invention has been described with reference to a preferred embodiment, those skilled in the art will appreciate that certain substitutions, alterations and omissions may be made without departing from the spirit thereof. Accordingly, the foregoing description is meant to be exemplary only and should not be deemed limitative on the scope of the invention set forth with the following claims.
This application relates to and claims priority from U.S. Provisional Application Ser. No. 61/392,207 filed on Oct. 12, 2010.
Number | Date | Country | |
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61392207 | Oct 2010 | US |