DE69107479T2 - LOCALLY WEAKENED SPOOL CORES FOR WINDING PAPER PRODUCTS. - Google Patents

Description

This invention relates to a core for core-wound products, in particular to a core which has been flattened or compressed to minimize its void space, and especially to a flattened core having a means for restoring the core to its original state.

BACKGROUND OF THE INVENTION

Core wound paper products, such as toilet tissue and paper towels, are well known in the art and are extremely useful consumer products. Such products include a core around which layers of the paper product are wound. The core can be, and often is, mounted on a spindle for convenient temporary storage of the paper product and for removing the paper product from the core and for balancing the roll in question. The spindle is mounted through the center of the core and thus requires that the core be open so that the spindle can pass through it without encountering excessive friction or causing later difficulty in dispensing the desired paper product.

A preferred core shape is a cylinder with a geometrically round cross-section so that the core (and the paper product wound thereon) rotates freely about the axis of the spindle and the paper product is easily removed from the roll. An improvement for rolls of core-wound paper products is to compress the core in a direction normal to the axis of the core to reduce the void space in the core. This arrangement provides convenient storage, handling and transport of core-wound paper products due to the fact that the products can be stored and transported more economically and at higher densities.

Various attempts have been made in the art to capitalize on the advantages of paper products wound around a compressed core. For example, U.S. Patent 4,762,61 issued to Watanabe et al. on August 9, 1988 and U.S. Patent 4,909,388 issued to Watanabe on March 20, 1990 disclose rolls of paper products wound to one-half to one-fifth of the original diameter of the product. The cores of these products are taught to be provided with a slight elasticity to allow the cores to return to the original cylindrical shape from the flattened shapes achieved under compression. It is generally desired by these patents that the flattened rolls be easily returned to their original shape.

US patent 1,005,787 issued to Sibley in October 1911 discloses a flattened toilet tissue packet wound around a hollow core made of flexible and axially fluted paper stock. The fluted core holds the stock and gives rise to an oscillatory motion when the paper is removed from the roll. UK patent specification 709,363 to Samson published on 19 May 1954 discloses a paper web or flexible sheet material wound around a core which is diametrically flattened and is said to readily resume its tubular shape when the roll is removed from the package. The core consists of spirally wound strips of cardboard sheet material and is flexible. Flexibility is said to allow the core to be flattened without ripping and to later return to its cylindrical shape after flattening.

U.S. Patent 4,886,167 issued to Dearwester on December 12, 1989 discloses single-sided compressed toilet tissue with flattened cores having the features set forth in the preamble of claim 1, with little to no void space between the diametrically opposed surfaces of the flattened core cross-section. The Dearwester patent is incorporated herein by reference for the purpose of showing particularly preferred compact, compressed rolls of toilet tissue and paper towels.

The foregoing teachings suffer from the disadvantage that after re-rounding, diametrically opposed folds often appear across the core and prevent the desired cylindrical shape from being obtained. These folds often cause the core to be poorly seated on a spindle and thereby result in a disadvantage to the user at any time such a core is placed thereon, used while seated, or removed from a spindle. Furthermore, the non-round The cross-section of such a core can prevent easy removal of the paper product from the rest of the roll, which creates a further inconvenience for the user every time a sheet or larger section of the paper product is desired. Likewise, a core with a non-round cross-section is generally noisier during dispensing.

One attempt to eliminate the problems associated with core flattening is to prevent such flattening, as disclosed in U.S. Patent 2,659,543 issued to Guyer on November 17, 1953, which patent suggests a way to maintain the original core shape. This patent teaches a core for tape products having at least one axially aligned groove, or slot, arranged along the outside of the core at uniform intervals around its circumference. When material is tightly wound onto the core, the grooves collapse somewhat, providing relief of the compressive hoop stress induced by the tight wrapping of the tape around the core. However, this teaching suffers from the disadvantage that the round cross-section of the core is maintained and the previously mentioned advantages of a flattened core are lost.

What is required, therefore, is a core which can be flattened as taught in the prior art, but which can be more conveniently and accurately re-rounded after the compressive forces applied to the paper product have been removed.

Accordingly, it is the object of this invention to provide a core having a means for flattening and re-rounding the core in a manner which is more convenient for the user and which will accurately and repeatedly cause the core to more readily assume its original shape.

BRIEF SUMMARY OF THE INVENTION

The present invention comprises a flattened core around which a core-wound paper product is wound to comprise a roll of the paper product. The flattened core has an inner periphery, an outer periphery and two oppositely disposed ends defining a longitudinal axis. The flattened core is capable of approximating a circular cross-section after re-rounding. The The core further comprises at least one axially directed means for weakening the resistance of the core to applied compressive forces. The weakening means is located on at least one of the inner periphery and the outer periphery or may intersect both the inner periphery and the outer periphery by passing through the entire thickness of the core.

In one embodiment, the weakening means comprises a plurality of axially aligned continuous score lines. In a second embodiment, the weakening means comprises a plurality of axially aligned perforations. In a third embodiment, the weakening means comprises a plurality of axially aligned holes. The score lines, perforations or holes may either be blind so that only one periphery of the core is affected by the weakening means or may pass through the entire thickness of the core to cut both the inner periphery and the outer periphery of the core.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims which particularly point out and distinguish the present invention, it is believed that the same will be better understood from the following description taken in conjunction with the accompanying drawings in which like parts have been designated by the same reference numerals, and in which:

Figure 1 is a perspective view of a flattened core and paper product according to the invention;

Figure 2 is a perspective view of a core according to the invention prior to flattening and having a plurality of different types of axially aligned score lines arranged around the inner periphery and outer periphery of the core;

Figure 3 is a schematic plan view of a core according to the invention after it has been expanded and with five circumferentially spaced axially offset holes;

Figure 4 is a schematic plan view of a core according to the invention after it has been spread out, and with five circumferentially spaced holes offset inward from each end;

Figure 5 is a schematic plan view of a core according to the invention after it has been expanded and having five rows of equally sized cuts and connecting webs extending inwardly from each end of the core for approximately one inch;

Figure 6 is a schematic plan view of a core according to the invention after it has been expanded and with five rows of equally sized cuts and ridges penetrating only about one-half the thickness of the core;

Figure 7 is a schematic plan view of a core according to the invention after it has been spread out and with five rows of perforations with cuts of one third of the length of the webs;

Figure 8 is a schematic plan view of a core according to the invention after it has been spread out and with five rows of cuts ending before intersecting each end of the core;

Figure 9 is a schematic plan view of a core according to the invention after it has been expanded and with five rows of cuts and ridges larger than those of either of Figures 6 or 7;

Figure 10 is a schematic plan view of a core according to the invention after it has been expanded and with five rows of equally sized cuts and webs smaller than those of the preceding figures; and

Figure 11 is a schematic plan view of a core according to the invention after it has been expanded and having five rows of alternately spaced cuts and lands, the cuts being three times as large as the lands.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated in Figure 1 and used herein, a "core" refers to a hollow tubular member around which another component is wound in a spiral for later dispensing and removal. As used herein, a "paper product" refers to a cellulosic base product wound on the core 20 and typically in the form of paper-wrapped quantities, ie one or more sheets, at a time, are removed for use and eventual disposal. A used paper product 24, once removed from the core 20, is not returned. As used herein, a "roll" refers to the aggregation of a "core" and a "paper product" wound thereon. The roll 28 may further include a wrapper 32 to maintain the configuration illustrated by Figure 1.

A core 20 according to the invention can be advantageously used for toilet tissue or paper towels. The core 20 is generally cylindrical prior to compression and flattening, having an axial length defined by two oppositely disposed ends. The ends of the core 20 are circular in cross-section prior to flattening. The line connecting the centers of these circles is the "longitudinal axis" of the core 20. As used herein, "axial" refers to the longitudinal axis.

When toilet tissue 20 is wound on the core, the resulting toilet tissue roll 28 typically has a diameter of about 10.2 cm to about 12.7 cm (4.00 to 5.00 in) and a length of about 11.4 cm (4.50 in) between the ends. When a core 20 embodying the present invention is used for paper towels, the paper towel roll 28 typically has a diameter of about 10.2 to about 15.2 cm (4.00 to 6.0 in) and a length of about 27.9 cm (11.0 in) for the embodiments described herein.

The typical core 20 may be made from two plies of paper with any suitable combination of bleached kraft, wood pulp, hardwood, softwood and recycled fibers. The core 20 should have uniform strength with no weakening points. Preferably, the core 20 is not calendered so that it is relatively stiff and retains adhesive deposited thereon. The core 20 should have a burst strength, measured in accordance with ASTM Test Method D2529, of at least 60, and preferably at least 70. The core 20 may have a thickness of about 0.5 mm (0.020 in). The core 20 should be free of objectionable odor and impurities or contaminants that could cause irritation to the skin.

The core 20 may be made of paper with a basis weight of approximately 0.16 kg per square meter (0.032 pounds per square foot) and a hoop strength of at least 6.79 kg per centimetre (38 pounds per inch), and preferably at least 8.93 kg per centimetre (50 pounds per inch), measured in accordance with Tappi Standard T818 0M--87.

The core 20 according to the invention is provided with at least one means 36 for selectively weakening the resistance of the core 20 to compressive forces, and in particular diametrically applied compressive forces. The diametrically applied compressive forces can occur at any point along, or across, the entire axis of the core 20.

As used herein, "diametrically applied compressive forces" refers to opposing compressive forces applied at any diameter of any cross-section of the core 20. It is to be understood, of course, that compressive forces may be applied along a chord of the cross-section and need not be coincident in diameter. However, the principles associated with such an application are substantially similar to those of diametrically applied compressive forces and will not be further distinguished or repeated.

Upon application of the compressive forces, the core 20 will collapse to the flattened state of Figure 1. The cross-section of the flattened core 20 of Figure 1 has a major axis a-a, a minor axis i-i orthogonal thereto. The major axis a-a and the minor axis i-i of the cross-section are transverse and orthogonal to the longitudinal axis of the core 20. The major axis a-a is in line with the longest dimension of the cross-section of the paper product 24 when flattened, and the minor axis i-i is the perpendicular cutting line therethrough.

It has been found that at least one circumferentially disposed means 36 for weakening the resistance of the core 20 to applied compressive forces is required. Preferably, but not necessarily, each means 36 for weakening the resistance of the core 20 to applied compressive forces is equally spaced from the adjacent means 36 for weakening the resistance of the core 20 to applied compressive forces at the circumference so that the cross-section of the core 20 after re-rounding approaches a circle rather than an irregular polygon.

The azimuth orientation of the major axis a-a and the minor axis i-i of the flattened core 20 can be predetermined by the circumferential arrangement and spacing of the means 36 for weakening the resistance of the core to applied compressive forces. If the core 20 is provided with two diametrically opposed means 36 for weakening the resistance of the core to applied compressive forces and if the diameter along which the compressive forces are applied is approximately 90° with respect to the two means 36 for weakening the resistance of the core 20 to applied compressive forces, the core 20 will generally flatten at the two means 36 for weakening the resistance of the core 20 to applied compressive forces.

The resulting flattened core 20 will have a major axis a-a with two vertices, one located at each end of the major axis a-a and corresponding to the means 36 for weakening the resistance of the core 20 to applied compressive forces. Accordingly, preferably an even number of means 36 for weakening the resistance of the core 20 to applied compressive forces are provided, such that each means 36 for weakening the resistance of the core 20 to applied compressive forces is located diametrically opposite the other means 36 for weakening the resistance of the core 20 to applied compressive forces.

However, after re-rounding, the core 20 will not approximate its original cylindrical shape due to the fact that the two vertices will maintain the cross-section of the core 20 in a fairly double-convex shape. Additional circumferentially located means 36 for weakening the resistance of the core 20 to applied compressive forces are required to provide additional vertices. After re-rounding, the core 20 will assume a polygonal cross-section corresponding in number of sides to the number of vertices, each vertex corresponding to a particular individual means 36 for weakening the resistance of the core 20 to applied compressive forces.

As previously stated, at least one and even a plurality of two means 36 for weakening the resistance of the core 20 to applied compressive forces is inadequate due to the fact that after attempted re-rounding, a double convex shape is obtained. If four means 36 are provided for weakening the resistance of the core 20 to applied compressive forces, the core 20 will re-round to a generally square cross-section and have a hollow hexahedral shape. After attempted re-rounding, such a core 20 suffers from excessive wobble and noise at the spindle and is thus generally not preferred.

A core 20 having six means 36 for weakening the resistance of the core 20 to applied compressive forces, each circumferentially equally spaced from adjacent means 36 for weakening the resistance of the core to applied compressive forces (at increments of about 600 or a multiple thereof) works well. Two means 36 for weakening the resistance of the core 20 to applied compressive forces occur at each end of the major axis a-a of the core 20 when it is flattened. Two means 36 for weakening the resistance of the core 20 to applied compressive forces are arranged on each side of the flattened core 20, spanning the minor axis i-i and superimposed with the two means 36 for weakening the resistance of the core 20 to applied compressive forces on the other side of the flattened core 20. This core 20 is rerounded to a hexagonal cross-section and exhibits less wobble and noise during dispensing.

A core 20 having eight, ten or twelve equally spaced means 36 for weakening the resistance of the core 20 to applied compressive forces is undesirable due to the natural tendency of the core 20 to re-form to a four-sided shaped cross-section. Also, this structure requires two re-rounding steps, which further represents a disadvantage to the user.

As illustrated in Figure 2, a particularly preferred means 36 for weakening the resistance of the core 20 to applied compressive forces is a continuous axially directed score line. The score line is preferably parallel to the axis of the core 20, but may, if desired, predictably wrap around the core 20 in a helical shape. A means 36 for weakening the resistance of the core 20 to applied compressive forces is referred to as "axially aligned" if a line drawn through the attenuation means 36 forms an angle of less than ± 45º with the longitudinal axis of the core 20.

The score lines may be located either on the inner or outer periphery of the core 20. It will be apparent that if a plurality of score lines are provided, the plurality may be divided between the inner periphery and the outer periphery of the core 20.

As used herein, "score lines" include compression lines and preferably lines defined by material removed from the core 20. The score lines may be made by a scorer or by a rotating die and preferably penetrate from about 25% to about 100% of the thickness of the core 20. The score lines preferably extend between and to both ends of the core 20.

If desired, the means 36 for weakening the resistance of the core 20 to applied compressive forces, such as a score line, may be continuous, discontinuous or intermittent and may resemble individual holes or perforations. The individual holes or perforations may, but need not, extend to each end of the core 20 and may be axially offset from the ends of the core 20.

For example, referring again to Figures 3 through 10, eight non-limiting examples are provided illustrating various means 36 for weakening the resistance of the core to applied compressive forces. A sample of each example is tabulated in Table 1 to provide an easier comparison of the effect of the parameters listed in Table 1 on attempted re-rounding.

Each row in Table 1 represents a sample made from commercially available Charmin brand toilet tissue manufactured and sold by The Procter & Gamble Company of Cincinnati, Ohio. The cores 20, which were provided with the designated agent 36 for weakening the resistance of the core 20 to applied compressive forces, were removed from the roll 28 of paper product 24 and reinserted into the center of the paper product 24 to complete the roll 28. Each roll 28 of paper product 24 was then compressed diametrically along the minor axis i-i with a force of about 36 kilograms (80 pounds).

The rolled paper products 24 were then aged for a period of about four weeks at about 50% relative humidity and at 72º F. A minimum of a two week aging period is considered necessary to allow some memory or elasticity of the core 20 to be developed so that storage and shipping conditions are approximated and accurate data are obtained when the sample is later re-rounded. An aging period of less than about two weeks has been found to be inadequate since the results obtained do not approximate those seen in actual practice when the product is manufactured, stored, transported to the point of sale, sold, taken home by the consumer and finally placed on a spindle and used.

Each core 20 was made from the previously mentioned materials and is approximately 11.43 centimeters (4.5 in) long. The samples of Figures 3 through 10 were provided with six equally spaced means 36 for weakening the resistance of the core 20 to applied compressive forces, one cut to open the core 20 and five means 36 for weakening the resistance of the core 20 to applied compressive forces as described below.

The first column of Table 1 provides an illustration of the top view of the described means 36 for weakening the resistance of the core 20 to applied compressive forces. In the second column of Table 1, the five means 36 for weakening the resistance of the core 20 to applied compressive forces are described. However, for these specimens, the cores 20 had to be slit and opened as illustrated in the top views of Figures 3 through 10 to install the described weakening means 36 for a total of six means 36 for selectively weakening the resistance of the core 20 to applied compressive forces.

Whenever five described weakening means 36 with a continuous through-slit were used, the through-slit was again closed with adhesive tape and the core 20 was compressed so that after flattening the major axis aa crossed the taped slit and one of the described weakening means 36. In practice, the aforementioned through-slit would be replaced by a means 36 for weakening the resistance of the core 20 to applied compressive forces which is similar to the other five as described, so that all six means 36 for weakening the resistance of the core 20 to applied compressive forces are identical.

The percentage of perforated or cut surface area listed in the third column of Table 1 is the percentage of axial linear dimension effected by the means 36 for weakening the resistance of the core 20 to applied compressive forces. Each core 20 has a total linear dimension of about 68.8 centimeters (27.1 in) (6 lines x 4.5 in). The fourth column lists the long axis distribution of the weakening means 36, either from end to end and extending through the entire length of the core 20, centered and not intersecting the ends, or at the end and extending from both ends but not meeting in the middle.

The cresting effect of the weakening means 36 in the fifth column of Table 1 was rated as low ("L"), medium ("M"), or high ("H") based on subjective assessment when attempting to re-round the core 20 to its original cylindrical state. A specimen was rated as having low cresting effect if no distinguishable crests were observed after re-rounding. A specimen was rated as having medium cresting effect if a change in the direction of curvature was evident at one or more of the crests. A specimen was rated as having high cresting effect if the crests formed corners at the means 36 for weakening the resistance of the core 20 to applied compressive forces.

The specimen of Figure 3 was provided with five holes of approximately 6.4 millimeters (0.25 in) diameter. Each hole was axially offset from the adjacent circumferential hole by approximately one-fifth of the length of the core 20.

The specimen of Figure 4 was provided with ten circumferentially spaced holes approximately 6.5 millimeters (0.25 in) in diameter, five at each end of the core 20. Each of the five holes was in the same plane and offset inwardly from the end of the core 20 approximately 2.54 centimeters (1 in). The five holes at each end of the core 20 were axially aligned with the opposite five holes at the other end of the core 20.

The sample of Figure 5 was perforated from each end toward the center of the core 20 with alternating one-millimeter (0.04 in) cuts 36 and one-millimeter (0.04 in) lands. The perforations extended approximately 2.54 centimeters (1 in) inward from each end of the core 20.

The sample of Figure 6 was perforated with alternating one millimeter (0.04 in) cuts 36 and one millimeter (0.04 in) lands. The cuts 36 are made from the inside shell through one-half the thickness of the core 20. The percentage of effective surface area of Figure 6 was halved to account for the fact that the perforation only affects one-half the total thickness of the core 20.

The specimen of Figure 7 was perforated with alternating two-millimeter (0.08 in) cuts 36 and six-millimeter (0.24 in) lands. The cuts 36 and lands extend the entire length of the core 20.

The specimen of Figure 8 was provided with double cuts 36 of approximately 2.54 centimeters (1.0 in) in length. The cuts 36 terminated axially approximately 1.27 centimeters (0.5 in) inward from each end.

The specimen of Figure 9 was perforated with alternating 9.6 millimeter (0.38 in) cuts 36 and 9.6 millimeter (0.38 in) lands. The perforations extend entirely from one end to the other end of the core 20.

The specimen of Figure 10 was perforated with alternating one-millimeter (0.04 in) cuts 36 and one-millimeter (0.04 in) lands. The perforations extend from one end to the other end of the core 20.

The specimen of Figure 11 was provided with alternating three-millimeter (0.12 in) cuts 36 and one-millimeter (0.04 in) lands. The perforations extend from one end to the other end of the core 20. TABLE I Fig. No. Description Percentage perforated or cut Axial dimension Axial distribution of attenuation agents Peak forming effect Axial offset holes Five holes at each end Inward cut across half the thickness of the core End-to-end web centered at the end

As can be seen from Table 1, when the specimens had less than about 20 * of the axial dimension affected by the means 36 for weakening the resistance of the core 20 to applied compressive forces, the peak-forming effect was judged to be low. When the percentage of perforated or cut zone affected by the means 36 for weakening the resistance of the core 20 to applied compressive forces approached 20% to 45%, the peak-forming effect was judged to be medium, compared to the other specimens. When the percentage of perforated or cut zone caused by the means 36 for weakening the resistance of the core 20 to applied compressive forces increased above 50%, the peak-forming effect was judged to be high. However, all specimens were placed on a spindle and then dispensed. All specimens were judged to be superior to a control specimen (with no means 36 for weakening the resistance of the core 20 to applied compressive forces) in both noise and smooth, uninterrupted dispensing.

Claims (10)

1. A flattened core (20) around which a paper product can be wound and having an inner surface, an outer surface and two oppositely disposed ends defining a longitudinal axis, said flattened core being capable of approaching a tubular cross-section, characterized in that the core comprises an axially directed means (36) for weakening the resistance of said core to radially applied compressive forces, said weakening means (36) being disposed on at least one of said inner surface and said outer surface of said flattened core (20) and locally reducing or perforating the cross-sectional thickness of the core. 2. A flattened core (20) according to claim 1, characterized in that said weakening means (36) comprises a plurality of axially aligned perforations on at least one of said inner surface and said outer surface of said flattened core. 3. A flattened core (20) according to claim 1, characterized in that said weakening means (36) comprises at least one axially aligned score line disposed along at least one of said inner surface and said outer surface of said flattened core. 4. A flattened core (20) according to claim 1, characterized in that said weakening means (36) comprises a plurality of holes, said holes being distributed in a plurality of axially aligned lines. 5. A flattened core (20) according to claim 3, characterized in that said at least one score line is substantially continuous and arranged along said outer surface of said flattened core (20). 6. A flattened core (20) according to claim 1, 2 or 3, characterized in that said weakening means (36) is oriented at an angle of 0º to 45º to said longitudinal axis. 7. A flattened core (20) according to claim 6, characterized in that said weakening means (36) is substantially parallel to said longitudinal axis. 8. A flattened core (20) according to claim 1, 2 or 3, characterized in that the weakening means (36) does not interrupt any end of said flattened core. 9. A flattened core (20) according to claim 3, characterized in that it comprises a plurality of axially aligned score lines (36) which are substantially circumferentially spaced about said longitudinal axis when said core (20) is rounded to a circular cross-section. 10. A flattened core (20) according to claim 9, characterized in that the said number of score lines is six.