Stack formed from connected groups of interfolded sheets

Abstract: A stack of interfolded sheets is formed from a plurality of groups of interfolded sheets. Adjacent groups are secured or bonded together so that the bottom sheet of each group pulls the top sheet of the next group. In one embodiment of the invention, the strength of the bond is such that when the bottom sheet of a group is withdrawn through an opening in a package for the stack, the bond releases the top sheet of the next group after the top sheet is partially withdrawn through the opening. In another embodiment of the invention, the strength of the bond is such that the top sheet remains secured to the bottom sheet and is completely withdrawn through the opening. The sheets can be secured by an adhesive bond or by a non-adhesive bond.

Description: Background This invention relates to interfolded sheets of wipes or similar material. More particularly, the invention relates to a stack of interfolded sheets which is formed from connected groups of interfolded sheets. Paper products such as sheets of tissues and towels are conventionally folded and superposed to form a stack which may be stored in a container or dispenser. It is desirable to interfold or interleave the sheets of the stack so that removing the top sheet from the container causes the next sheet to "pop up" or move into position for removal. The folded sheets can be either wet or dry. Stacks of interfolded sheets are conventionally formed by slitting a wide web into a plurality of narrow webs which are fed to a folder which interfolds the webs. If the stack contains, for example, 100 individual sheets, then 100 separate narrow webs are fed to the folder. The interfolded webs are cut into a plurality of separate consumer-sized stacks, and each stack is packaged in a separate container. Folding machines which interfold a large number, for example, 50 to 100, individual webs are relatively complex and expensive. More economical folding machines are available for interfolding a lesser number of webs, for example, 5 to 10. The interfolded webs are cut into a plurality of groups of interfolded webs, and each group of interfolded webs is called a clip. The number or count of interfolded webs in clips which can be produced by the more economical machines is relatively small. Commercial packages of interfolded wipes or tissues commonly have counts of 40 to 100 or more. If the economical, low count folding machine is used to form such a package by combining a number of clips, the bottom sheet of each clip will not be interfolded with the top sheet of the next clip. The package will therefore not have a continuous dispensing feature since the top sheet of each clip will have to be manually withdrawn from the package. As a result, the economical, low count machines are generally not used to provide interfolded webs. U. S. Patent No. 5,520,308 describes a tissue package which is produced without any interfolding apparatus. The tissues are not interfolded, and adjacent tissues are releasably attached by, for example, adhesive. DE OS 43 36 933 discloses adhesively attaching sheets that are substantially shorter than the other sheets in the stack. Two sheets which are adhesively attached are about one-half the length of the other sheets so that the adhesively attached sheets form a combined sheet which has substantially the same length as the other sheets. European Patent Application 0 955 260 also discloses a stack in which all of the sheets do not have substantially the same length. The sheets of each group which are attached to sheets of adjacent groups are longer than the other sheets. U. S. Patent No. 5,033,620 describes a method of attaching the ends of two paper towel stacks in a towel dispenser in order to replenish the supply of paper towels. The top stack is attached to the bottom stack only when the bottom stack is close to being exhausted. Thus, the bottom stack is a partial stack when the top stack is placed in the dispenser and attached to the bottom stack. Summary of the Invention The invention permits an economical, low count folding machine to be used for producing high count interfolded sheets by connecting clips of interfolded sheets. In one embodiment of the invention the clips are adhesively connected. The bottom sheet of each clip is adhesively bonded to the top sheet of the next clip so that, as the bottom sheet of one clip is withdrawn from the package, the top sheet of the next clip is partially withdrawn. The clips can also be connected by non-adhesive means. For example, the sheets can include polypropylene staple fibers which provide a mechanical bond. In one form of the invention, the strength of the adhesive or non-adhesive bond is adequate to withdraw a portion of the top sheet through the dispenser opening of the package but weak enough to break before the top sheet is completely withdrawn from the package. Description of the Drawing The invention will be explained in conjunction with an illustrative embodiment shown in the accompanying drawing, in which -- Figure 1 illustrates a pair of clips of interfolded sheets and adhesive applied to the bottom sheet of the top clip and to the top sheet of the bottom clip for adhesively connecting the two clips; Figures 2-3 illustrate portions of a pair of adhesively connected clips which use other types of interfolds; Figure 4 is a diagrammatic illustration of a pair of clips in which the upper and lower sheets include laterally extending flaps for adhesively connecting the clips; Figures 5(a) through 5(h) illustrate various types of folds which can be used to form clips of interfolded sheets; Figures 6-10 illustrate representative adhesive patterns which can be used for adhesively connecting the clips; Figure 11 is a perspective view of a pair of clips which are connected by matching, intermittent glue patterns on the top and bottom of the clips; Figure 12 is a plan view of a clip of moistened sheets, the top sheet having a dry strip to which patterned adhesive is applied; Figure 13 illustrates a stack of adhesively connected clips of interfolded sheets in a dispensing package; Figures 14-16 are enlarged fragmentary cross sectional illustrations of sheets which are bonded by interlacing fibers. Description of Specific Embodiments Referring to Figure 1, a pair of clips or small groups 10 and 11 of interfolded sheets 12 are superposed to form a stack. The height of each clip is indicated by the dimension H. It will be understood that a complete stack will include as many clips as are needed to provide the desired count. The sheets 12 in Figure 1 are provided with a conventional Z fold. Each Z folded sheet includes a center panel 13 and top and bottom panels 14 and 15. The sheets of each clip are interfolded by interleaving the top and bottom panels of adjacent sheets. The overlapping portions of the sheets form a fold lap having a width dimension W in the center of the clip. In the embodiment illustrated in Figure 1, each of the clips includes four individual sheets 12. However, the counts of the clips can vary depending upon the equipment which is used to form the clips and other considerations. Low cost economical folding machines typically produce clips having counts ranging from 4 to 12. A layer of adhesive 17 is applied to the bottom panel 15 of the bottom sheet of the clip 10. A layer of adhesive 18 is applied to the top panel 14 of the top sheet of the clip 11. The width of the adhesive layers 17 and 18 corresponds to the width W of the fold lap. However, the pattern, location, and registration of the adhesive may vary. The adhesive 17 and 18 adhesively connects the two clips 10 and 11. If more clips are used to form the complete stack, then the additional clips are adhesively connected in a similar manner. Figures 7-11 illustrate representative patterns which can be used to form the adhesive layers 17 and 18. The specific patterns illustrated are formed by hotmelt spray guns available from Nordson Corporation of Norcross, Georgia. Other adhesive patterns can also be used. Figure 7 illustrates a swirl pattern 19 which is currently preferred. The swirl pattern is formed by a series of loops 20, and the distance d between adjacent loops and the width w of the loops can be adjusted to vary the strength of the adhesive bond. Figure 8 illustrates a spray pattern 21 which provides an non-continuous layer of adhesive over a width w, which may be the same as, or narrower than the width of the clip. Figure 9 illustrates a film pattern 22 which provides a continuous layer of adhesive over a width w. The length of the continuous layer of adhesive extends parallel to the long dimension of the clip. Figure 10 illustrates a continuous line 23 of adhesive which is applied in the middle of the clip and parallel to the long side edges 24 of the clip. Figure 11 illustrates intermittent dots 25 of adhesive which are aligned in a direction which is parallel to the long side edges 26 of the clip. All of the adhesive patterns can be applied to either wet or dry sheets and may be applied to both or only one of a pair of adjacent clips. Wet or moistened sheets are commonly used as wipes for cleaning, for example, skin. Figure 2 illustrates portions of a pair of clips 28 and 29 which are formed by Z folded sheets 30 and V folded sheets 31. Each Z folded sheet includes a center panel 32 and top and bottom panels 33 and 34. Each V folded sheet includes top and bottom panels 35 and 36. The sheets of each clip are interfolded to form fold laps having a width W along the right and left edges of the stack. Figure 2 shows only a portion of each clip, and the complete clip includes more interfolded Z and V sheets. A layer of adhesive 37 is applied to the bottom panel 34 of the bottom sheet of the clip 28 and a layer of adhesive 38 is applied to the top panel 35 of the top sheet of the clip 29. The clips are thereby adhesively connected. Figure 3 illustrates a pair of clips 40 and 41 of Z folded sheets 42. The bottom panel of the bottom sheet of each clip is folded to form a starter flap or tab 43 to which a layer of adhesive 44 is applied. The top panel of the top sheet of the next clip is similarly folded to form a starter flap or tab 45 to which a layer of adhesive 46 is applied. The flaps 43 and 45 are aligned with the center line CL of the stack which is formed by the clips so that the adhesive bond is at or near the center line. In Figures 1-3 a full width sheet of one clip is adhesively bonded to a full width sheet of the next clip. The adhesive bond is relatively weak. The adhesive bond is strong enough to partially withdraw the top sheet of the second clip through the dispenser opening, but the adhesive bond breaks before the top sheet is completely withdrawn from the package. Breaking the adhesive bond provides two separate full width sheets. Figure 4 diagrammatically illustrates a pair of clips 56 and 57 which are formed from conventional interfolded sheets. However, the top and bottom panels 58 and 59 of each clip extend laterally beyond one of the side edges of the clip to form flaps 60 and 61. Adhesive layers 62 and 63 are applied to the flaps for adhesively connecting adjacent clips. Figure 5 illustrates some of the various folds which can be used_with the invention: Figure 5(a) J fold Figure 5(b) C fold Figure 5(c) Z fold Figure 5(d) V fold Figure 5(e) C fold with wings Figure 5(f) modified V fold Figure 5(g) V-Z fold Figure 5(h) Z interfold Figure 11 illustrates a pair clips 65 an 66. Each of the clips is rectangular and has long side edges 67 and short side edges 68. Discrete adhesive patterns 69 are applied to the bottom panel of the top clip, and matching or registered adhesive patterns 70 are applied to the top panel of the bottom clip. it is also possible to apply adhesive to only one of the clips. The clips will be adhesively connected when they are pressed together. Figure 12 illustrates the top panel 72 of a clip which is formed from interfolded wet or moistened sheets. The top panel 72 includes a wetted area 73 and a dry strip 74 which is not wetted or moistened and which extends parallel to the long side edges 75 of the clip. Patterned adhesive 76 is applied to the panel in the dry strip. The facing panel of the next clip may also have a dry strip to which adhesive is applied. Figure 13 illustrates a package 78 which comprises a stack 79 of a plurality of adhesively connected clips 80 which are contained in a dispensing container 81. The container 81 includes a plurality of sidewalls 82, and one of the sidewalls is provided with a dispenser opening 83. When the first sheet of the top clip 80 is withdrawn through the dispenser opening 83, the overlapping portion of the next sheet of the interfolded sheets is withdrawn through the dispenser opening. The bottom sheet of each clip is adhesively connected to the top sheet of the next lower clip by adhesive 84. If the top and bottom sheets of adjacent clips are full width sheets, the adhesive bond between those sheets is relatively weak so that when the bottom sheet of a clip is withdrawn through the opening, the adhesive connection will pull the top sheet of the next clip partially through the dispenser opening. The adhesive bond will break before the top sheet of the next clip can be fully withdrawn through the opening. The shape of the dispenser opening can vary depending upon the geometry of the interfold and/or the location and volume of the adhesive. The opening needs to provide enough friction or resistance to separate the sheets if the sheets are full width sheets. In the preferred embodiments of the invention the bottom sheet of one clip is secured to the top sheet of the next clip by adhesive. However, other types of bonding could be used, for example, ultrasonic bonding, mechanical bonding such as crimping, and the like. One particular type of non-adhesive bonding can be provided by including polypropylene staple fibers in the sheets which are to be bonded. The fibers are engineered to have a geometry that mechanically bonds the two sheets together, for example, by interlocking the fibers of adjacent sheets. Figures 14-16 diagramatically illustrate various types of interlocking fibers for bonding two sheets together. In Figure 14 upper and lower sheets 127 and 128 each include relatively straight fibers 129 which extend from the surface of the sheet. The projecting fibers are the result of the normal manufacturing process for the sheets. For example, some paper products are provided with a rough or textured surface to provide, e.g., better wickingor moisture absorption. Figures 14-16 show the fibers at only the ends of the sheet for clarity of illustration, but the fibers are present across the entire surface of the sheet. The sheets 127 and 128 are pressed together to cause the fibers to interlock. The sheets are thereby attached by friction between the fibers or by a mechanical locking/bonding mechanism similar to the attachment that is provided by hook and loop fasteners sold under the trademark Velcro. Figure 15 illustrates sheets 130 and 131 which include curly fibers 132 which are interlocked or mechanically bonded. Figure 16 illustrates sheets 133 and 134 which include interlocked hooked fibers. If the bonded sheets are full width sheets, the bond is relatively weak so that the bond breaks before the lower sheet is completely withdrawn from the package.

Claims: A stack of interfolded sheets comprising a plurality of groups (10, 11, 28, 29) of interfolded sheets (12, 30, 31) which includes a top group and a bottom group and at least one intermediate group, each of the groups of interfolded sheets having a top panel (14, 35) and a bottom panel (15, 34), characterized by each of the sheets having substantially the same width and means (17, 18, 37, 38) for releasably attaching the bottom panel of each group above the bottom group to the top panel of the next lower group. The stack of claim 1 in which the stack includes a pair of sides, the attaching means being located between the sides in about the middle of the stack. The stack of claim 1 in which the stack includes a pair of sides, the attaching means being located adjacent one of the sides. The stack of claim 1 in which the attaching means comprises adhesive. The stack of claim 1 in which the attaching means comprises adhesive in the shape of a swirl pattern. The stack of claim 1 in which the attaching means comprises adhesive applied to both said bottom panel and said top panel. The stack of claim 1 in which the attaching means comprises adhesive formed by matching adhesive patterns on both said bottom panel and said top panel. The stack of claim 1 in which the stack has long side edges and short side edges and the attaching means extends continuously in a direction which is parallel to the long side edges. The stack of claim 1 in which the stack has long side edges and short side edges and the attaching means extends intermittently in a direction which is parallel to the long side edges. The stack of claim 1 in which the sheets are moistened. The stack of claim 1 in which the sheets are dry. The stack of claim 1 in which the sheets are wet and each of said bottom panel and said top panel includes a dry portion (14), the attaching means comprising adhesive applied to said dry portions. The stack of claim 1 in which the stack has a center and each of said bottom panel and said top panel is folded to form a starter tab (43, 45) which is substantially aligned with the center of the stack, the attaching means comprising adhesive applied to the starter tabs. The stack of claim 1 in which the attaching means comprises a mechanical bond. The stack of claim 1 in which the attaching means comprises interlocking fibers (129, 132, 135) in said top and bottom panels. A package of interfolded sheets comprising: a container (81) having a plurality of sidewalls (82), one of the sidewalls having an opening (83), a stack as described in claim 1, said attaching means permitting the bottom panel to pull the top panel out of the opening but releasing the top panel before the sheet which provides the top panel is pulled through the opening.

Inventors: CRAIG GRANTLAND A, HEATH PETER A, HERTEL JAMES E, HUEMPFNER THOMAS D, JOHNSON GARY E, LUEBKE WAYNE W, WUNDERLICH JOHN H, CRAIG, GRANTLAND A., HEATH, PETER A., HERTEL, JAMES E., HUEMPFNER, THOMAS D., JOHNSON, GARY E., LUEBKE, WAYNE W., WUNDERLICH, JOHN H.
Applicants: PAPER CONVERTING MACHINE CO, PAPER CONVERTING MACHINE COMPANY
Application year: 2000
Main classification: B65H45
IPC codes: B65H45, A47K10