Abstract:
Method and apparatus for preventing the curling of a composite material having a fluid permeable base and a fluid impermeable outer surface in a manufacturing operation wherein a continuous sheet of the composite material is moved in incremental amounts through a cutter-creaser apparatus to have carton blanks formed therein wherein the curling is prevented by forming a curtain of air under pressure to apply downwardly directed forces on the fluid impermeable surface during the incremental movement of the continuous sheet through the cutter-creaser apparatus and the forming of the carton blanks.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to the making of carton blanks from a continuous sheet of material and more specifically the making of carton blanks from a continuous sheet of a composite material which has a paperboard base and a plastic film outer surface. 
     BACKGROUND OF THE INVENTION 
     A conventional method for forming carton blanks is to feed a continuous sheet of a paperboard material into a cutter-creaser apparatus in which a portion of the continuous sheet is cut and creased to form one or more carton blanks. In one commercial method, the continuous sheet comprises a composite material, of the type described in U.S. Pat. No. 4,254,173, which is incorporated herein by reference, which has a paperboard base and a plastic film outer surface. When this composite material is fed into the cutter-creaser apparatus, the paperboard base faces the lower platen and the plastic film faces the upper die. Since the plastic film outer surface will not allow moisture to escape from the paperboard base through it, there is a tendency for the composite material to curl up particularly in the cross-machine direction. This tendency to curl is increased after the cutting and creasing operations not only in the cross-machine direction but also for the portions of the flaps of the individual cartons that have been cut away on at least three sides thereof. Because of this, there is a tendency for portions of the composite material that have been cut and creased to hang up or get caught in portions of the upper die as the continuous sheet is moved in an incremental moving operation to its next location. This results in damaged carton blanks or, when serious enough, the stopping of operations to correct the difficulty. This is particularly true for relatively small cartons wherein the repeat length of each carton is less than about 12.5 inches and less than 8.5 inches in the cross-machine direction. The large number of cuts required to form a plurality of carton blanks of this size results in less overall stability of the portion of the continuous sheet being formed into cartons. Also, cartons of this size are formed from lower caliper material, such as less than 0.020 of an inch, which also results in less stability. 
     While the invention is described in relation to the composite material of the &#39;173 patent, it includes other types of composite material having at least two layers, one of which is fluid containing and/or fluid permeable, such as moisture, and the other of which is a fluid impermeable layer such as a poly coated SBS (solid bleach sulfate) so as to have a fluid impermeable outer surface normally facing the upper die. 
     BRIEF DESCRIPTION OF THE INVENTION 
     This invention relates to the formation of carton blanks from a continuous sheet of a composite material having at least a fluid permeable base and a fluid impermeable outer surface and provides a curtain of air acting on at least a portion of the fluid impermeable outer surface particularly at about the same time it is being cut and creased and as it is being moved from the location between the upper die and the lower platen toward the stripper apparatus until it has been completely moved to a location clear from the actual cutting and creasing portions of the cutting-creasing apparatus. 
     In a preferred embodiment of the invention, a continuous sheet of the composite material of the type described in the U.S. Pat. No. &#39;173 is fed into a conventional cutting-creasing apparatus so that the paperboard base faces the lower platen thereof and the plastic film outer surface faces the upper die thereof. The upper die comprises a rectangularly shaped block of material having lower and upper surfaces and a plurality of side surfaces and is mounted at a fixed location. A plurality of orifices are formed in the rectangularly shaped block of material and have openings in the lower surface thereof. The upper die is mounted at a fixed location while the lower platen is mounted opposite to the upper die and for reciprocal linear movement toward or away from the upper die. The continuous sheet of the composite material is moved in a conventional manner through the cutting-creasing apparatus in uniform successive incremental amounts. When the next succeeding incremental amount of the continuous sheet of composite material has been positioned between the actual cutting-creasing portions, the lower platen is moved toward the upper die so that the incremental amount of the composite material is located therebetween and sufficient pressure is applied to cut and crease the incremental amount of the composite material. During the incremental movement of the continuous sheet and during the actual cutting and creasing operations, air under pressure flows through the orifices in the rectangularly shaped block of material and moves downwardly into contact with the plastic film outer surface of portions of the continuous sheet. The air for the orifices is provided by a plurality of conduits mounted in channels in the upper surface of the rectangularly shaped block of material having openings therein in fluid communication with the orifices in the rectangularly shaped block of material. The conduits are connected to a supply of air which feeds the air to the conduits at desired pressures. The air flowing through the orifices is in quantities and pressures sufficient to form a curtain of air pushing downwardly against the plastic film outer surface to limit up curling thereof. The curtain of air applies a sufficient amount of forces on the plastic film outer surface so as to minimize any upwardly directed movement of portions of the plastic film outer surface. A plurality of openings are also located over at least the leading segment of the next succeeding incremental amount of the continuous sheet so that a curtain of air is pushing downwardly on such leading segment. A portion of the curtain of air also acts on the trailing portion of the next preceding incremental amount of the continuous sheet of the composite material which has had carton blanks formed therein. The air flow through the openings in the lower surface is continuous so that the curtain of air is acting on the succeeding incremental amounts of the continuous sheet of the composite material as they are being moved into and out of the position between the actual cutting and creasing portions of the lower platen and the upper die and while the cutting and creasing operation is being performed. Therefore, the continuous sheet of the composite material is in contact with the lower platen as it moves through the cutting and creasing apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An illustrative and presently preferred embodiment of the invention is shown in the accompanying drawings in which: 
     FIG. 1 is a bottom plan view of an upper die of the preferred embodiment of this invention; 
     FIG. 2 is a schematic illustration of a conventional process line for forming carton blanks; 
     FIG. 3 is a cross-sectional view of the upper die and lower platen of a conventional cutting-creasing apparatus; 
     FIG. 4 is an enlarged top plan view of a portion of FIG. 1; 
     FIG. 5 is a cross-sectional view taken on the line of 5--5 of FIG. 4; 
     FIG. 6 is a cross-sectional view taken on the line 6--6 of FIG. 4; 
     FIG. 7 is a top plan view of the plastic film outer surface of one of the carton blanks of this invention; 
     FIG. 8 is an enlarged bottom plan view of a portion of FIG. 1 illustrating the cutting and creasing rules for one carton blank and portions of next adjacent carton blanks and 
     FIG. 9 is a top plan view of FIG. 7. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The preferred embodiment of the invention is illustrated in FIGS. 1, 4 - 6, 8 and 9 and comprises an upper die 2 comprising a rectangularly shape block 4 of material. The rectangularly shaped block 4 may be formed in a conventional manner such as one Prior Art block illustrated in FIG. 3 which has a lower surface 6 and comprises five layers 8 of laminated die lumber and an upper platen 10 secured thereto by screws 12. A plurality of cutting rules 14 and creasing rules 16 are embedded in the rectangularly shaped block 4. A layer of a resilient material 18, such as rubber or rubberized cork, is secured to the lower surface 6 on each side of the cutting rules 14 and the creasing rules 16 and at other locations and functions to push the carton blank 20 off of the cutting rules 14 and creasing rules 16 after the carton blank 20 have been formed. One carton blank 20 is illustrated in FIG. 7 and the cutting rules 14 and the creasing rules 16 of FIG. 1 are positioned so as to form eighteen carton blanks 20. The numbers and positions of the carton blanks being formed can be varied as desired. In FIG. 3, there is also illustrated a conventional lower platen 22 having a spot sheet 24, a counter plate 26 and a creasing matrix 28. 
     In FIG. 2, there is a schematic illustration of a conventional process line 40 for forming carton blanks. The process line 40 comprises apparatus 42 for holding a roll of a composite material and have feed rolls 44 for incrementally feeding a continuous sheet 46 of the composite material to a cutter-creaser apparatus 48 which has a stationary upper die and a reciprocating lower platen which function to cut and crease successive incremental amounts of the continuous sheet into carton blanks. After the carton blanks have been cut and creased, they are pulled into a stripper apparatus 50 in a conventional manner. 
     The upper die 2 is illustrated in FIG. 1 wherein a plurality of cutting rules 14 and creasing rules 16 are embedded in the layers 8 while in FIGS. 4-6, there is illustrated one portion of the upper die 2 for forming a flap portion 54 of a carton blank 20. The cutting rule 14 is embedded in the layers 8 of the rectangularly shaped board 4. An incremental amount of the continuous sheet 44 comprising a paperboard base 56 and a plastic film outer surface 58 is adjacent to the layer of resilient material 18. A plurality of channels 60 are formed in the upper die 2 and extend downwardly from the upper surface 62. A plastic conduit 64 is positioned in each of the channels 60. The plastic conduits 64 are connected by fittings 66 and tubes 68 to a main supply conduit 70 all of which are positioned in channels similar to the channels 60. The main supply tube 70 is connected to a supply of air 72 under pressure of between about 30 to 60 psi and preferably about 40 psi for supplying air to the conduits 64. The conduits 64 are also illustrated as being interconnected by fittings 74 and conduits 76. However, if desired, the fittings 74 and conduits 76 could be omitted and the end of each conduit 64 could be sealed. As illustrated in FIG. 6, spaced apart openings 78 are formed in each conduit 64 and are aligned with spaced apart orifices 80, FIGS. 1 and 6, extending through layers 8 and opening through the lower surface 6. In construction, the orifices 80 are formed through the layers 8, the conduits 64 are positioned in the channels 60 and then the openings 78 are drilled in the conduits 64 using a drill bit passing through the orifices 80. The air under pressure exiting from the orifices 80 contacts the plastic film outer surface 58 and spreads out. There are sufficient number of orifices 80 so that the air issuing therefrom are in quantities and pressures sufficient to form a curtain of air applying forces over the entire surface of at least a major portion of the plastic film outer surface 58 under the rectangularly shaped block 4. At least one conduit 64 is in a channel 60 which is opposite to a leading segment 86 of the next succeeding incremental amount of the continuous sheet 44 and has a plurality of orifices 80 to direct air under pressure onto the plastic film outer surface 58 thereof. 
     In operation, the continuous sheet 44 is fed in incremental amounts under the upper die 2 so that one incremental amount thereof is beneath and spaced from the layer of resilient material 18 surrounding the cutting rules 14 and the creasing rules 16 with the plastic film outer surface 58 facing the layer of resilient material 18. Air under pressure of between about 30 and 60 psi and preferably about 30 psi is continuously being emitted from the orifices 80 each of which has a diameter of between about 0.020 and 0.040 of an inch and preferably about 0.03125 of an inch so that it is sufficient to form a curtain of air that moves downwardly onto the plastic film outer surface 58 to apply forces thereto during the movement of the continuous sheet 44 and when it is stopped under the upper die 2. The lower platen is moved upwardly and the carton blanks 20 are formed. The lower platen is moved downwardly and the formed carton blanks 20 are pushed off the upper die by the layer of resilient material 18. The curtain of air provides downwardly directed pressure forces on the plastic film outer surface 58 so as to prevent any substantial curling of that incremental amount of the continuous sheet or of any portions of the carton blank. Therefore, there is nothing to catch in any portion of the upper die as the continuous sheet is incrementally moved to place the next succeeding incremental amount of the continuous sheet between the upper die and the lower platen. After the carton blanks have been formed, they are pulled into the stripper apparatus 50 in a conventional manner. 
     While an illustrative and presently preferred embodiment of the invention has been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by the prior art.