METHOD AND APPARATUS FOR PRODUCING INDIVIDUAL ROLLS OF PACKING MATERIAL BACKGROUND OF THE INVENTION Field Of The Invention The present invention relates in general to the methods and apparatus to manually or automatically expand a slit paper type of packaging material and to apparatus for forming the expanded slit paper into spiral cylinders of cushioning materials to be used in packaging. Brief Description of the Drawings The objects and advantages of the instant invention will be apparent when the specifica- tion is read in conjunction with the drawings, wherein: FIGURE 1 is an end view of a representation of the spiral cylinder of the instant inven- tion; FIGURE 2 is a partial end view of the expanded paper forming the spiral cylinder; FIGURE 3 is a side elevation of an alternate apparatus for spiraling expanded sheet material into cylinders for use as void fill material; FIGURE 4 is a top view to the expansion machine of the instant invention; FIGURE 5 is a side view of the expansion machine of FIGURE 4; FIGURE 6 is a side view of the dual paper positioning in conjunction with the expansion machine of FIGURE 4; FIGURE 7 is a schematic side view of a feed roll housed within a container; FIGURE 8 is front elevational view of the container of Figure 7; FIGURE 9 is a side view of another embodiment of a delivery system, showing a feed roll, restraining rolls, and a tear bar; FIGURE 10 is a side view of a further embodiment of a delivery system, and FIGURE 11 is a fragmentary illustration of tensioning mechanism for a restraining roll; FIGURE 12 is a side view of an additional embodiment of a delivery system; FIGURE 13 is a schematic illustration of a two roll delivery system;
FIGURE 14 A-F are schematic illustrations of an alternate embodiments of a two roll delivery system; FIGURE 15 is a fragmented illustration of a two roll delivery system using guide wheels; FIGURE 16 is a fragmented illustration of an alternate two roll delivery system using fila- ment wrap; FIGURE 17 is an alternate emobodiment of Figure 16; FIGURE 18 is a schematic illustration of a slitting system; FIGURE 19 is a top view of the knives of Figure 18. Detail Descripiton of the Invention The instant disclosure relates to the method and equipment for the expansion of an expan- dable material, preferably slit, recycled paper, as a packing material and to the use of the ex- panded material as a void fill in packaging. The paper, once expanded creates semi-rigid peaks or lands. These peaks are similar to a spring in that once force is applied and removed, they return to their original positioning, provid- ing the elastic limit is not exceeded. The elastic force created by the resistance of the paper fibers slows the acceleration of the force. The work performed by movement of the semi-rigid peaks as a force is applied by an article, is the elastic potential energy of the expanded material. The yield point is the point beyond stress when a large increase in strain occurs with almost no increase in stress. The use of expanded paper in widths of 1/2 inch increments from 1/2 inch to 6 inches and unrolled, unexpanded paper lengths varying from 3 to 24 inches was tested as a void fill. The material was found to retract to some degree if not bound at the ends or wrapped around an ar- tide, making optimum expansion difficult to achieve. The slit pattern can be varied with op- timum results being obtained with patterns which form hexagonal cells. With the identical paper, load bearing capacity is dramatically increased with the hexagonal pattern, as compared with a diamond cell yielding slit pattern. By winding the paper in the form of a cylinder, the tension on the expanded paper can be maintained without the use of adhesives or the like, since the cells
"interlock", thus preventing unwinding of the completed cylinders. The sheet material decreases in width during the expansion step and the dimensions of the cylinder are in terms of final dimen- sion of the finished cylinder. Cylinders less than 1 inch in length having a tendency to unravel, due to insufficient interlocking of cells, with the problem increasing with decreasing length. Cylinders under 1 inch in diameter offer insufficient cushioning effect for general applications. In terms of the correlation between unexpanded flat sheet material and finished cylinders, one square foot of sheet material will produce about two and three quarter finished cylinders, as one 2x2 cylinder equals .376 square feet of sheet material. Obviously, the tighter the cylinder is wound, the greater the amount of sheet material required to form a cylinder. Thus, the aforenoted correlation between sheet material square feet and cylinder diameter and length, is a measure of how tightly the cylinder is wound. Although the tighter the cylinder, the firmer the cushion effect which is achieved, winding the cylinder too tightly will have the effect of remov- ing air from the cylinders and lessening their cushioning qualities. Hence, winding forces on the slit paper material and the quantity of slit paper material used to produce a cylinder are critical. Thus, the cylinders can be customized to meet specific system requirements. Expanded paper cylinders were attached to hand-made cardboard cores and wound around the cores. Cylinders ranging in size from about 1X1 inch to 6X6 inches were tested. All sizes worked, with the 2X2 size being most effective. The solid core presented a rigid surface and lacked cushioning for side impact. Coreless cylinders were formed using hand powered winders. The coreless cylinders were better at absorbing impact at the sides and edges of the cylinders, than the rigid core centered cylinders. However, the number of square feet of sheet material required to produce a cubic foot of coreless cylinders was higher than optimally desired, from a cost standpoint. On the other hand, the coreless cylinders provided highly effective cushioning characteristics. Using a small hand winder, cylinders were produced with a hollow core and characterized by a 40 square feet of unexpanded sheet material to 1 cubic foot of cylinder. The hollow core cylinders provided excellent impact and vibration protection. The hollow center spiral wound ex-
panded paper provided a greater degree of soft cushioning than was provided by the tightly wound coreless cylinders of expanded paper. The cylinder of expanded paper with a hollow core center provided an excellent compromise between excessive use of raw material in the tightly wound cores and lack of side impact protection and added expense associated with the production of expanded paper cylinders with a rigid core. To form the cylinder of the instant disclosure the slit paper is expanded and rolled into a cylindrical spiral, having a predetermined diameter and length based on end use. As disclosed, as the paper is expanded, it forms raised cells which, when rolled, interlock with cells in adjacent layers as the paper spirals outward. The interlocking of the cells eliminates the need to secure the cylinders, thereby making them immediately ready for use. The spiral cylinder 40 of Figure 1 is a conceptual illustration of an end view, showing the concept of the interlocking cells raised from the land, however for clarity, rectangles are used to depict the cells formed by the row spacing 44 and the slit spacing 42. Detailed description and illustration of the expanded and unexpanded paper are disclosed in PCT/US/93/02369 published 30 September 1993. In Figure 2, a portion of the spiral cylinder 10 is illustrated which more accurately depicts the formation of the cells. The actual cells cannot be seen in the side view of Figure 2, however the material forming the cells is depicted. The row spacing 38a and 38b and the slit spacing 36 are warped, thereby forming the peaks and valleys which interlock with one another. The self-locked cylinder provides maximum protection of an article by absorbing the energy created by the impact. The absorbency is achieved by placing the layers in a position to force interaction between the cells. The positioning of the paper in a spiral prevents the paper from turning back on itself or twisting, which lessens the cushioning effect from the cell interac- tion. The spiral configuration is not only the most economical and easy to produce, it is struc- turally the most effective. The force applied to the cylindrical elastic body compresses in toward the center, with each interior layer creating an elastic force to return to its original position. The interaction of the cells additionally distributes the impact force through the entire cylinder, thereby providing increased protection of edge or corners of the object being shipped. This is un-
like the commonly used styrofoam peanuts which act independently. With the styrofoam peanuts, if the corner of an item receives the main force of impact, the peanuts separate, thereby allowing the item to slide within the box. The interlocking of the cells of the cylinders not only interlocks each individual cylinder but locks the cylinders to one another, preventing slippage of the item within the box. The spiral cylinder 10 can be varied in size dependent upon the intended use. The preferable size is approximately 2 inches in length and 1 1/2 - 2 inches in diameter. The hollow core cylinders provide good packaging protection from all angles of impact and utilize the square footage within the core most efficiently. Desired results are obtained with paper weight of 70 pound per 3000 square feet of recycled Kraft, 100% post consumer recycled paper and 3.2 inches by 16 inches (52 square inches of unexpanded slit paper) produces one hollow core cylinder. One hundred twenty cylinders, representing 40 square feet of unexpanded paper, filled one cubic foot volume as opposed to 210 tightly wound coreless cylinders being required to fill the same volume. Cylinders with a rigid cardboard core required 110 cylinders to fill one cubic foot. One cubic foot of unexpanded 70 lb. slit paper produces 37.2 cubic feet for void filling purposes when utiliz- ing the hollow core method. Figure 3 is a side elevation of an apparatus for spiraling expanded sheet material into cylinders for use as void fill material. In the embodiment of Figure 3, expanded sheet material 800 is fed between the upper moving belt 802 and the lower moving belt 804. The upper moving belt 802 is driven and carried by the upper belt drive roll 806 in the counter clockwise direction, as indicated by directional arrow 801. The lower belt drive roll 808 carries and powers the lower moving belt 804 in the clock wise direction, as indicated by directional arrow 803. The upper belt 803 is tensioned between the drive roll 806 and the cooperative roll 805. The tension plate 810 is biased against the belt 802 by the tension springs 814. Similarly, the lower belt 804 is tensioned between the drive roll 808 and the cooperative roll 809. The tension plate 812 is biased against the belt 804 by the tension springs 816.
The lower belt 804 rotates opposite the upper belt, thereby driving the forming cylinder 820 in the direction indicated by directional arrows 819. The upper belt 802 is rotated at seven times the speed of the lower belt 804, thereby causing the leading edge 824 of the expanded sheet 800 to drag and curl under. As the sheet progresses in the direction of arrow 819, the curling ef- feet is continued forming partly formed cylinder 820. The curling or spiraling effect continues until a fully formed cylinder 822 is produced and delivered to a receiving region, not shown. Figures 4 and 5 illustrate the expansion machine 700 which rapidly produces optimum ex- pansion of the slit paper 750. The paper is fed from a storage roll, not shown, to the upper and lower drive rollers 706 and 708, where it is placed between the rollers 706 and 708. The paper storage roll can be placed at any point along a 100° arch from the drive rollers 706 and 708, using the point directly perpendicular from the drive rollers 706 and 708 as the 0° point. Both the upper drive roller 706 and the lower drive roller 708 are covered with a friction material, such as shrink tubular material made of a heat shrinkable polymer, as for example polyvinyl chloride. Alterna- tively, a rubber spray or painted coating can be used. Additionally vinyl tape covered rollers and rubber rollers can be used. Abrasive coatings tended to produce some scratching of the paper and formation of dust due to the action of the abrasive material on the paper. There is no theoretical upper limit to the amount of friction caused by the roller fiction covering, except that damage to the paper must be avoided. Therefore, the use of a coarse material is to be avoided. The tension between the drive rollers and the expansion rollers must be sufficient to open, or expand the slit paper, but not sufficient to tear the paper. Typically, with a 30 pound paper, 2.5 oz. of force per linear inch, can be applied and with 70 pound paper, 5 oz. of force can be ap- plied. The expansion should be sufficient to not only expand the paper, but also to crack some of the fibers, thereby decreasing the tendency of the paper to return to its unexpanded form. With the aforenoted 70 pound paper, it required a .011 hp motor to deliver paper at a rate of 300 inches per minute, expanded one linear inch.
Utilizing a 20 by 36 inch sheet of the aforenoted unexpanded 70 pound paper, with one end secured in a rigid fixture across its entire width, the paper was suspended vertically and a force was applied to expand the paper. A force of about 50 ounces, that is, 2.5 oz. per inch, in- itiated the expansion of the paper and 3 oz. per linear inch opened all of the paper cells. 5 oz. per linear inch opened all cells fully and yielded cell wall fiber tearing which aids cell walls to remain open after the expanded paper is released in the open position. A force of 7.5 oz. expanded the paper and tore it after 10 seconds of continued stress. 10 oz. per linear inch opened the cells and immediately tore the paper. The use of about 5 oz. was thus shown to provide the optimum results. The lower drive roller 708 is driven by the motor 726 through the rotation of the motor gear 716 and drive gear 714. The rotation created by the motor 726 is transmitted along motor shaft 724 to the motor gear 716 where it drives the drive belt 718, which in turn rotates the drive gear 714. The motor gear 720, also connected to the motor shaft 724, drives the expansion belt 722, which in turn rotates the expansion gear 710. Due to the spacing of the motor gear 716 and the motor gear 720 along the motor shaft 724, an expansion shaft 712 is generally provided be- tween the expansion gear 710 and the upper expansion roller 702 and lower expansion roller 704. The drive gear 714 is provided with 20 teeth as compared to the expansion gear 710 which has 14 teeth. The difference in the number of teeth changes the rotation speed of the upper expansion roller 702 and lower expansion roller 704 as compared to the upper drive roller 706 and lower drive roller 708, allowing the motor shaft 724 to rotate at a single speed. The differential can be obtained by a number of methods known in the prior art and the foregoing is not intended to limit the scope of the invention. The speed differential between the upper and lower expansion rollers 702 and 704 and the upper and lower drive rollers 706 and 708 is critical as it provides the expansion of the slit paper 750. The slit paper 750 is being removed from the expansion machine 700 faster than it is entering, thereby forcing the slit paper 750 to expand. The speed differential between the expansion rollers 702 and 704 and the drive rollers 706 and 708 must be calculated to provide the required amount of expansion based on the weight of paper and end use. In the gear
assembly as illustrated in Figures 4 and 5, the expansion gear 710 and drive gear 714 can be changed to provide a increase or decrease in the speed differential. Other methods of changing the speed differential can be obtained and are known in the prior art. The spacing of the expansion rollers a distance of about 6 inches from the drive rollers produced some binding in the middle of the paper, apparently due to the contraction of the paper which coincides with the expansion of the paper in thickness and length. A space between the ex- pansion and drive rollers of about 11.25 inches worked well for 19.5 inch rolled paper. With 3 inch wide paper, a minimum of 4 inches of separation between the roller sets. The distance be- tween the drive rollers and the expansion rollers varies proportionally with the width of the unex- paπded paper. The expansion device can be used to produce expanded product for use directly as a wrap- ping material. The automated roll dispenser provides for immediate use of the expanded paper minimizing space requirements while yielding maximum packaging usage by allowing the user to pull tightly during the wrapping process by stopping or braking when needed. At the end of wrap- ping, prior to tearing, the foot pedal is released and the automated expander brakes for final pull- ing and tearing. This leaves the process of maximum stretch intact for greatest packaging protec- tion. An electronic unit can be employed to deliver measured quantities of expanded paper. Breaking at the end of the delivery provides for the user to tear the desired length of paper from the roll of paper. Alternatively, a cutting blade can be used to severe the delivered quantity of paper from the remainder of the roll. The upper expansion roller 702 and the lower expansion roller 704 are covered with a material which provides the affect of fingers. The covering must grip the unopened slit paper 750, without ripping the paper, and pull it open through use of the differential speed between the expansion rollers 702 and 704 and the driver rollers 706 and 708. The use of soft rubber covered rollers works to produce even expansion over the width of the paper. However, deformation of the paper can be experienced, in the form of crushed cells. That is, at the point of contact with the pair of expansion rollers, the expanded cells can be crushed by the rollers. The use of open
cell and light foam can work to provide the required expansion. However, low density, open cell foam have a life span which is shorter than optimally desired. When soft bristled brushes of the type employed in photocopy machine, were used, some difficulty was experienced in starting the expansion process. Harder bristled brushes cause some trouble in releasing the paper. Optimum results were obtained with medium stiff bristles cut to approximately 1/8 inch in length. Bristles can be made of metal wire, such as carbon steel, stainless steel, brass, bronze and a variety of bristle dimensions are commercially available. The preferred material is a nylon hook fiber of the type found in hook and loop fasteners of the type sold under the trademark VELCRO. The use of a set of rollers faced with hook ended fibers provided the required expansion without distortion of the expanded paper or deterioration of the rollers. Unlike, relatively firm foam covered rollers, the hook fibers did not crush the ex- panded cells as they passed between the expansion rollers. It should be understood that the role of the expansion rollers is critical in that they must be able to grip and pull the paper so as to impart a speed of travel to the paper which is greater than the speed of the paper when it passes through the drive rollers. This requirement is in conflict with the need to permit the expanded paper to pass between the rollers without the expanded cells being crushed. An alternate embodiment to the expansion device of Figures 4 and 5 is illustrated in Figure 6. The mulli roll expander 600 operates on the same basis as the expansion device 700. The ex- pander 600 is provided with a paper support unit 630 which is provided with at least one retaining area 638 to receive the paper roll 634. The retaining area 638, as illustrated herein, is a notched portion which receives a bar 636 which is placed through the core of the paper roll 634. The ex- pander 600, as illustrated, holds two rolls of paper 632 and 634 in retaining areas 638 and 640, however additional rolls can be added. The paper 642 from roll 632 is fed into the bottom roller set 620 and the paper 644 from roll 634 is fed into the top roller set 610. The top roller set 610 and bottom roller set 620 are each designed as described in Figures 4 and 5.
One embodiment of a manual expander system 1110 is shown in Figure 7, wherein the roll 1120 is retained within a container 1118. The sheet material 1112 is expanded by drawing the sheet material 1112 directly from the supply roll 1120 at a rate which is greater than the rota- tional speed of the supply roll 1120. The control of the rate of supply of sheet material 1112 from the supply roll 1120 can be achieved by limiting the rotational speed of the supply roll 1120 directly, as for example, through the use of a friction bearing on the axle 1114. This is not, however, the optimum method, as the friction bearing, or other method used to provide tension, must be frequently altered to coincide with decrease in the supply roll 1120 sizing or addition of a new supply roll 1120. The supply roll 1120 and the associated elements can conveniently be supported by a frame 1116, which can be in the form of a pair of X members. The ends of the legs of the frame 1116 can be in contact with the side walls, or positioned in the corners, of the container 1118. The con- tainer 1118 is provided with a cut line 1115. The cut line 1115 is preferably provided with a ser- rated, metal portion to easily tear the paper at the desired length. The container 1118 can be a cor- rugated cardboard box or lightweight wood. Each of the embodiments of Figures 9, 12 and 13 can be employed within the container 1118. Preferably, the manual expander system 1110 is provided with rollers to expand the sheet material 1112. In the embodiment of Figure 9, expansion is achieved by passing the sheet material between a guide roller 1124 and a secondary roller 1126. A pawl (not shown) engages the teeth of the wheel 1134, preventing counter-clockwise rotation. Any other convenient rotation direction limiting mechanism can be used. The guide roller 1124 is prevented from freely turning by means of a friction bearing, such as illustrated in Figure 11. The sheet material 1112 is held firmly against the guide roller 1124 by the secondary roller 1126, as shown in Figure 10. By holding the sheet material 1112 against the guide roller 1124, the secondary roller 1126 controls, or restricts, the speed of movement of the sheet material 1112 through the drag of the guide roller 1124. Where the speed of rotation of the supply roll 1120 is controlled, such as in Figure 7, the guide roller 1124 can be free rolling.
As the sheet material 1112 is pulled manually from the supply roll 1120 it is expanded as it passes between the guide roller 1124 and secondary roller 1126. When the desired length of material has been withdrawn it is torn from the remainder of the sheet material 1112. The tearing action is greatly facilitated by drawing the expanded sheet against a tear bar 1132. The tear bar 1132 can be a threaded rod or other rough surfaced member, such as the jagged member 1115, il- lustrated in Figure 8. The expanded sheet material has an irregular surface which engages the sur- face of the tear bar 1132, and provides for the controlled tearing of the sheet material. The manual expander system 1110 can be mounted on a table or floor, or suspended from an overhead support, for downward dispensing of expanded paper, as illustrated in Figure 9. The supply roll 1120, or rolls, can be offset from the final direction travel of the paper within a 300° arc, with the axle 1114 of the supply roll 1120 parallel to the axis of the guide roller 1124 and secondary roller 1126. The sheet material 1112 can be provided by multiple rolls, or a multi-ply roll, with the limitation being the strength of the operator to draw paper against the required ten- sion resistance. In the embodiment of Figure 10, the manual expander system is configured as for a floor or table set up. The sheet material 1112 leaves the supply roll 1120 and is fed between the secon- dary roller 1126 and the guide roller 1124. The sheet material 1112 passes along to the retaining bar 1140 where it is dispensed, expanded, until a sufficient length is achieved. The spring loaded retaining bar 1140 prevents the paper 1112 from pulling toward the guide and secondary rollers 1124 and 1126 due any clockwise motion of the supply roll 1120. Preferably, the guide roller 1124 is friction tensioned by means of the mechanism of Figure 11. A friction plate 1152 is mounted adjacent the guide roller 1124 and attached to the wall 1156. The guide roller 1124 is mounted on a shaft 1150 which is passed through the friction plate 1152 and the wall 1156 of the carrier for the manual expander system 1110. At least the end of the shaft 1150 is threaded to receive a wing nut 1158. The shaft 1150 passes through the wall 1156 and receives a spring 1154, which is secured onto the shaft 1150 with the wing nut 1158. The spring 1154 must have a diameter less than that of the wing nut 1158 to maintain the spring 1154
in place. The wing nut 1158, when tightened, applies a selected amount of pressure to the spring 1154, thereby pulling the roller 1124 against the friction pad 1152. The pressure can be easily regulated to maintain the desire amount of turning resistance. The force applied to the paper must be within a relatively controlled range. The use of too much force will tear the paper rather than produce controlled expansion, and too little pressure will unwind the paper without expan- sion. The preferable expansion force is in the range from about 3 oz. to about 7.5 oz. and preferably about 5 oz. per linear inch of paper width. Tensioning can also be provided by pressing together a pair of rollers through which the paper travel, thereby tying the rate of movement of the paper to the rotational speed of the guide rolls, and restricting the rotational rate of the rolls. Tensioning can also be regulated by varying the positions of a pair of guide rolls relative to the travel of the paper. As the position of at least one guide roll is moved such that the paper contacts an increasing degree of the perimeter of the guide rolls, the tension is increased. The paper acts to force apart the two guide rolls 1124, and 1126 of Figure 9. In the embodiment of Figure 10, the guide rolls displace the direction of travel of the paper to a greater extent than in the position illustrated in Figure 9, thereby providing an higher degree of tension on the paper. Additionally, surface tension can be applied by a band with a weight or spring. The friction device can be a friction clutch, pneumatic, magnetic or hydraulic tension mechanism. The magnetic tensioning mechanism is sold as a magnetic particle tensioning brake. The exact form of the tensioning mechanism is not critical, and any commer- daily available mechanism can be used. The portion of expanded paper between the supply roll 1120 and the cut end tends to retract once it has been released from the tension of being pulled. The retraction of the leading edge of the paper can be restricted by a roller 1160 as shown in Figure 12, or the aforenoted spring loaded retaining bar 1140, of Figure 10. The springs enable the paper to force the gripping fingers aside during expansion but pull the gripping fingers into tighter engagement with the paper if the paper is pulled in the reverse direction. The retraction prevention mechanism has its paper contacting surface covered with a surface for gripping the expanded paper. The covering
must grip the unopened slit paper when moving in the retract direction, without ripping the paper, when the user is pulling it off of the feed roller. The material used to grip the paper can be angled to provide the unidirectional travel of the paper, as compared to being on a spring loaded mechanism which can give way during the paper expansion step. The gripping mechanism can be a plurality of monofilament polymer strands mounted in an inclined position relative to the travel line of the paper. The incline permits the paper to slid past the gripping mechanism in one direc- tion, but results in the engagement of the strands and the cells during travel in the reverse direc- tion. The sheet material 1112 must not be deformed, through the crushing of cells, while the ex- panded paper is passing through the retraction prevention mechanism. At the point of contact with the pair of retraction prevention rollers, either the spring loaded bar or the single retraction prevention roller, the expanded cells can be crushed by the retraction mechanism. The use of open cell and light foam can work to provide the required expansion. As noted heretofore, the preferred material is a nylon hook fiber which does not crush the expanded cells as they passed under the retraction mechanism 1140. The barb of the hook is oriented in the leading position such that the barbs engage the slits in sheet material during the retraction of said paper, but permit the sheet material to slid past during the unwind/expansion step. In the modification of Figure 15, the bar 1140 is spring biased toward the sheet such that unwinding movement causes the bar to move away from the paper. Conversely, a tendency of the paper to rewind or retract, pulls the bar toward the paper. Thus, the hooks dig into the slits during rewinding, but freely permit the paper to move in the unwind direction. Figure 12 illustrates a mechanism in which the retraction prevention is provided by a guide roll 1160 and bracing roll 1161 positioned on either side of the paper 1112. The guide roll 1160 is provided with the same type of hook filaments, bristles, or the like, as provided for bar 1140 to prevent crushing the paper. Reverse travel is prevented through the use of any convenient means for limiting the guide roll 1160 to a single direction rotation. Conveniently, a ratchet mechanism
such as wheel 134, illustrated in Figure 9 can be used. The bracing roll 1162 maintains the paper 1112 against the guide roll 1160 and can be either free rolling or provided with reverse travel means. In another embodiment, the amount of paper which is delivered for expansion can be in- creased by using multiple layers of paper. The only change in the system is the use of a plurality of feed rolls to supply slit paper to the system. Alternatively, the sheet material 1112 can be in the form of multi-layers of the slit expanded sheet material on a single roll. Thus, the requirement for the simultaneous feeding of multilayers can be achieved through the use of a multi-ply, single roll or a plurality of feed rolls. Each method has its advantages. The multi-roll allows the choice of using single ply rather than multi-ply. The use of multiple rolls does, however, take more space than the multi-ply, single roll system. As shown in Figure 13, a first roll 1170 can be positioned above a second roll 1172. Paper is feed simultaneously between two guides rolls, 1124 and 1126 which serve as a tensioning mechanism, as previously described. The output 1178 is two layers of expanded sheet material. When the filling material is wrapped around an article, it is in the form of a plurality of layers of interlocked expanded sheets due to the land areas of adjacent sheets of the layers of sheets nesting and interlocking with each other. Contraction of the expanded sheets is thus prevented or at least restricted. The length of the slit and the ratio of the land intervals between slit affects the dimensions of the polygons which are formed during the expansion step. The higher the ratio of slit length to interval length the greater is the maximum angle which can be formed between the plane of the sheet and the planes of the land areas. The greater the uniformity of the shape and size of the formed polygonal shaped open areas and the angle to which the land areas incline relative to the flat sheet, the greater is the degree to which interlocking of land areas can be achieved. Interlock- ing of land areas, that is, the nesting of layers of sheets, reduces the effective thickness of the sheets. However, the net effect is still a dramatic increase in effective sheet thickness. For ex- ample, .008 inch thick paper having a slit pattern of a 1/2" slit, 3/16" slit spacing, and 1/8" row
spacing, produces a 1/4" by 3/16" land which can expand to under about one quarter of an inch thickness and will have a net effective thickness for two layers, when nested, of about .375 inches. It is noted that the land width is double the width of the legs. The net effect is a useful thickness expansion of roughly at least 20 times the unexpanded thickness of the paper. The nesting of adjacent layers can occur to an excessive extent, as for example, where ab- solute uniformity of expansion exists in adjacent layers, and the adjacent layers merge or com- mingle with each other to a second layer adds to the combined thickness of two sheets only to the extent of the unexpanded thickness of the second sheet rather than the expanded thickness of the second sheet. Stated another way, where merging takes place rather than limited nesting, the cumulative effect of the addition of successive layers of sheets is based on a thickness increase relative to the unexpanded thickness of each successive sheet. The desired net effect is a nesting where the land of one layer drops into the cell of the adjacent layer only to the extent necessary to provide interlocking, that is, preclude relative motion of the layers. The overall object is to prevent slippage between adjacent layers,' while maximizing the cumulative thickness of the layered material. Thus, on the one hand, the adjacent layers should interlock while on the other hand the adjacent layers should not interlock in order to maximize the thickness of the expanded, multilayercd product. The balance between interlocking and maximizing thickness can be achieved by offsetting the adjacent layers or offsetting the slit pattern and reversing the direction of offset on layer rela- tive to the adjacent layer. The offsetting of the slit pattern can be relative to a multi-ply, single roll, in which adjacent plies are offset, as well as to a multi-ply configuration formed from two rolls of single ply material, as described above. The parallel rows of individual slits preferably form an angle with the longitudinal axis (the opposing edges of the sheet) in the range from about 89.5 to 87 degrees. This produces the aforementioned offset. By alternating the adjacent rows the net offset between the parallel rows of slits of adjacent layers forms an angle in the range from about 1° to about 6°. That is, the line of slits of adjacent plies cross each other at an angle in the range from about 1° to about 6°. As
shown in Figure 13, two feed rolls 1170 and 1172 can be provided. By having one roll unwind counterclockwise and the other clockwise, the aforenoted crossing of the lines of slits of adjacent rolls occurs, producing the desired blend between interlocking and maximizing of expanded thick- ness. The use of guide rolls to regulate the tensioning of the delivery system, is shown in Figures 14A through 14F. In Figure 14A, no tension is provided on the sheet 1180, passing between the guide rolls 1182 and 1184. The rotation of the two guide rolls relative to each other, as shown in Figure 14B, produces moderate tension which is increased with the rotation of the relative roll positions as shown in Figures 14C and 14D. As the path of the paper becomes more tortuous, as il- lustrated in Figure 14E and F, the tension increases. The expansion drive rollers can be adjusted to alter the space between the rollers. In this manner, a required balance can be attained between compression of the paper sheet between the rollers and minimization of the crushing of the cells of the expanded paper. Once the process has been started and the paper is expanded, the Velcro hooks can grab and pull the expanded cells with little need to apply a compression force. Prior to the expansion, that is, during the start up, the pressure on the paper must be maximized since the inclined surfaces of the expanded paper are not yet available. A variety of mechanism are available to adjust for the change in the thick- ness of the paper and the creation of inclined surfaces. In the embodiment of Figure 15, the dual expansion rollers 1502 and 1504 are illustrated. The dual expansion rollers 1502 and 1504 are provided with a pair of rigid gripping wheels 1506, 1510 and 1508, 1512, respectively. The rigid wheels 1506, 1510, 1508 and 1512 are somewhat greater in diameter than the expansion rollers 1502 and 1504 and serve to grip the paper and draw it through. In the case of paper which expands to a thickness of one quarter of an inch, the dif- ference between the diameter of rollers 1502 and 1504 and the wheels 1506, 1510 and 1508, 1512 must be greater than one quarter inch in order to avoid crushing the expanded paper. The use of small rigid wheels 1506, 1510 and 1508, 1512 to carry the paper limits the amount of expanded material which is contacted and therefore crushed. The wheels 1506, 1510, 1508 and 1512 can be
formed of rubber or any of the materials disclsoed for use with the expander rolls. The width of the wheels 1506, 1510 and 1508, 1512 is as small as feasible to limit the amount of expanded paper which is crushed. The wheels 1506, 1510 and 1508, 1512 leave an elongated path or region of crushed cells along the length of the paper. Preferably, the wheels are about one half inch wide. Wider wheels provide greater gripping power but crush a greater amount of expanded cells. The amount of material crushed is equal to the width of the wheels times the number of wheels. The number of wheels is not narrowly critical but, the use of too few wheels will produce uneven drawing of the sheet material. At least two wheels are required, but three wheels evenly spaced along the draw rollers produced more consistent and even drawing of the paper. Since the wheels must be in opposed pairs, too narrow a width produces a risk that the opposed wheels will be out of alignment and fail to provide a gripping force. The minimum width of the wheels is controlled by the ability to keep the wheels in proper gripping alignment. The maximum width of the wheels is limited by need to minimized crushing of the expanded material. In the instance of a 20 inch wide paper, the use of four half inch wheels, crushes 10 percent of the paper. The combined width of the rollers multiplied by the number of rollers, must be less than 20% of the width of the expanded paper, and preferably should be less than 10% of the expanded width. Most preferably, the combined width is no more than 5% of the expanded paper width. In the embodiment of Figures 16 and 17, the Velcro® type hook filament material 1606, 1608 and 1610, 1612, respectively, is spirally wound around the draw rollers 1602 and 1604, il- lustrating two of the possible patterns. Once expanded the hook filaments 1606 and 1608 have a great drawing power and is not necessary to have the entire roll covered. In fact, using less than full coverage can be advantageous. Where the hook filament material 1606 an 1608 is spirally wound around each draw roll, contact with the expanded material is continuous, but the expanded sheet material is compressed between opposed hook material intermittently and only over a limited region. In this manner the paper is compressed during the start up of the expansion cycle, and once expanded the paper is drawn primarily on one surface unopposed by material. Thus, crush- ing of expanded paper is minimized.
In the embodiment of Figure 16, the spiral of the hook filament material 1606 on the first roller 1602 is opposite from the spiral direction of the filament material 1608 on the second roller 1604. In this manner the hook filament material of the first draw roller 1602 is always opposed by the corresponding material of the second draw roller 1604. Preferably, as shown in Figure 17, the filament material spirals 1610 and 1612 are in the same direction. In this manner, the two spirals 1610 and 1612 are only in opposition, or contact, periodically. In this manner, the paper is compressed between opposing spirals, as required to start the expansion process. Once expanded contact between the spirals 1610 and 1612 and the expanded paper is predominantly one side unop- posed, thereby minimizing the problem of crushing of the expanded cells, while providing periodic high compression needed for the startup of the expansion cycle. If preferred, the draw rollers can be provided with a solenoid or a pair of solenoids, one at each end. The solenoid is provided with a timer which raises the top roller slightly once the expan- sion is achieved, so that maximum start up compression is available to initiate the expansion, but minimal compression occurs after the expansion has been achieved so as to avoid crushing of the expanded cells. This is possible, because of the interaction between the hooks and the inclines of the expanded material. The hooks grab the paper and it is not necessary to force the paper against the hooks by means of an opposing roller. Light contact between the hooks and the expanded material is sufficient to draw the sheet of expanded paper and maintain the expansion operation. Once the rotation of the rollers has ceased, the solenoid releases the top roller to come in contact with the bottom roller. The rotary die cutting of the expanded paper is preferably performed using a hardened steel die with tolerances of .001 of an inch. The anvil is a round, extremely hard cylinder. It has been found that the cutting of the plurality of slits results in a vibration of the rotary die cutter and a shortening of the life of the equipment, in particular, the die. The vibration problem can, however, be eliminated by offsetting the knives about 1.5° from the axis of the die. It appears that the vibration is due to the fact that the rows of knives are spaced 1/8 inch apart. Even though the cutting action is on a sheet of paper only .007 or .008 inch thick, the net effect is a
chopping action and a resultant vibration. The skewing of the knives results in a continuous cut- ting action, since there is a simultaneous entry of a plurality of knives into the paper and withdrawing from the paper. The range is limited at one extreme by the necessity for the slits to be close to being perpendicular to the edges of the web, so that during the expansion step, the ex- pansion proceeds in a controlled manner. That is, the paper expanded without skewing in one direction. At the other extreme, the skewing of the knives must be sufficient to provide a con- tinuous cutting and prevent die vibration. Accordingly, the skewing of the knives, as illustrated in Figure 19, must be at least about 0.5 but less than 5 degrees. Optimally, the range is within 1.0 degrees and 1.75 degrees. When the paper is fed from two rolls to an expander, by reversing the angular offset of the rolls, the line of the cells formed from the slits, are offset by an angle which is double the offset produced by the skewing of the knives, rather than being parallel. This serves to optimize the nesting effect and maximize the cushioning effect. The extcndiblc sheet material can be a single layer of flexible paper material or multiple layers wound on (he same roll. Preferably, the multiplies plies are formed in-situ by using mul- tiple rolls of single layer sheet material which are combined in the guide roll path. The advantage of using, for example, two rolls of single layer sheet material is that where a small amount of material is required to wrap an object, a single roll can be used in the system. In applications where large amounts of void fill are required, two rolls can be unwound simultaneously, to produce a two-ply void fill material. Where a plurality of plies of sheet material are used, either through the preferred use of two rolls or by using a multi-ply roll, the parallel rows of individual slits preferably form an angle with the longitudinal axis (the opposing edges of the sheet) in the range from about 89.5 to 87 degrees. Consequently, the parallel rows of slits of adjacent layers form an angle in the range from about 1° to about 6° with each other. That is, the line of slits of adjacent plies cross each other at an angle in the range from about 1° to about 6°. Thus, the skewing of the knives not only improves the cutting operation but also optimizes the cushioning affect.
The rotary die cutting equipment includes a paper supply roll 8100 and web tension guide, indicated generally as 8102, as shown in Figure 18. The web guide controls tracking of paper from side to side, thereby facilitating high speed die cutting. The roller 8101 serves to decurl the rolled paper, prior to die cutting. The paper 8104 is fed between between nip rollers 8106, to the die cutting station indicated generally as 8108. The rotary die 8110, containing the knives 8111, shown in Figure 19, interacts with the hard anvil 8112 to produced the desired slit pattern. The rotary die is driven by a conventional power source, not shown, and can be belt driven or driven through gear teeth. The slit paper is then wound on a rewind roller 8114. Nip rollers can be used between the rotary die cutting and the rewind roller 8114. The web tension must be less than 4.5 oz. per inch of width. For paper webs less than 20 inches in width, the problem of maintaining the rewind tension within the necessary limits is par- ticularly severe. This problem is discussed in copending patent application, serial number, 119,472, filed Sept. 10, 1993. The regulation of the rewind tension can be achieved through the use of a variable tension sensor and control 8120. The variable tension sensor and control senses the amount of paper which has been rewound on the rewind roller 8114. Preferably, the speed of the paper web through the rotary die 8110 is essentially constant. As the amount of paper on the rewind roller 81 14 inc reases along with the diameter of the rewound web, the linear speed of the web increases. To maintain a constant tension, the rotational speed of the rewind roller 8114 must be decreased. A highly sensitive plasma magnetic clutch or a hydraulic clutch can be used to maintain the rewind tension within the required limits, relative to the width of the paper web. When the rewind tension exceeds the proper limit, the cells open, and the paper is wound in the form of open cells. If the rewind tension is too low, the paper web is traveling at an uneconomically slow rate. Further, at low tension the roll is not tight. A tightly wound roll provides the optimum amount of material relative to the diameter of the roll. An open cell roll represents one extreme, while a tightly wound roll represents the other extreme. A loosely wound unexpanded roll is preferable to a tightly wound expanded roll. In order to amortize the cost of the equipment over a
reasonable period of time, the paper through put must be maintained at the maximum possible speed. When the tension is unnecessarily low, the rewind mechanism becomes the bottle neck in the manufacturing operation. The use of a rewind turret mechanism such as disclosed in British patent 777,576 Published June 26, 1957, U.S. Patent No. 1,739,381 and 2,149,832, provides for a continuous operation, in that the system need not be stopped when the rewind roll has the desired footage of material, preferably about 30 pounds of paper per roll. It is to be understood that the filling material sheets of the present invention may be formed of any desirable and suitable dimensions depending upon the hollow spaces to be filled in packaging materials. While the description of the filling material sheet member of the present in- vention describes one example with respect to size and thickness, this is not intended to limit the scope of the invention. Where the slit pattern and paper characteristics have interacted to form a hexagonal cell, the slit paper has sufficient resistance to expansion, to permit the sheet material in roll form, to be rewound without expansion. This is not the case for slit pattern/material charac- teristic combinations which fail to produce the hexagonal pattern. Where the legs of the cells are insufficiently rigid to form the hexagonal shape, the cells are also excessively easy to open. In such cases, the sheets have to have the slit patterns cut on a flat press, for the sheets to be shipped unexpanded, since the conventional rewind rolling action would expand the slit sheets. Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the example chosen for the purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention.