Roll firmness measuring system and process

<u>Background of the Invention</u>

0001In the manufacture of paper products, such as tissue products, a wide variety of product characteristics must be given attention in order to provide a final product with the appropriate blend of attributes suitable for the product's intended purposes. Improving the softness of tissues is a continuing objective in tissue manufacture, especially for premium products. Softness is a perceived property of tissues comprising many factors including thickness, smoothness and fuzziness.

0002Many tissue products and other paper webs are typically formed into large supply rolls after being manufactured. After the supply rolls are formed, the rolls are rewound into smaller sized rolls, which are generally more useful for commercial purposes. For example, in conventional systems, a core is often placed onto a mandrel that is capable of spinning so that the spinning of the mandrel in conjunction with the core can effectuate winding of the paper thereon.

0003<patcit id="pcit0001" dnum="US5150850A"><text>US 5,150,850</text></patcit>, <patcit id="pcit0002" dnum="US6494399B"><text>US 6,494,399</text></patcit>, <patcit id="pcit0003" dnum="GB2162872A"><text>GB 2162872</text></patcit>, <patcit id="pcit0004" dnum="US200310116296A"><text>US 200310116296</text></patcit> and <patcit id="pcit0005" dnum="US6036137A"><text>US 6,036,137</text></patcit> disclose prior art methods for winding webs of material. In particular, <patcit id="pcit0006" dnum="GB2162872A"><text>GB 2162872</text></patcit> discloses a process for winding a web of material, the process and the associated apparatus having the features of the preambles of claims 1 and 10 respectively. In contrast, <patcit id="pcit0007" dnum="US5061230A"><text>US 5,061,230</text></patcit> discloses a method of folding a web into a stack.

0004When tissue products, however, are formed into a rolled product during winding and converting, the inner layers of the rolled product may tend to lose a noticeable amount of bulk due to the compressive forces that are exerted on the base web. Lowering bulk can reduce the perceived quality of the product. As such, a need currently exists for a process and system that controls the winding process in order to control bulk reduction,

0005Another problem experienced in the formation of wound products is in producing multiple rolls of material that all have a diameter and roll firmness within desired limits. Ideally, the rolled products should have a substantially uniform diameter and roll firmness so that there are no consumer noticed differences between the rolls. Further, consumers desire rolled products, especially rolled tissue products, to have a roll firmness within a desired range such that the rolls do not feel too hard or too "mushy".

0006The ability to form rolled products having a substantially uniform diameter and roll firmness also provide various other benefits during production of the product. For instance, controlling roll firmness can, in some applications, increase throughput efficiency. Further, uniform products can be easier to package, eliminating or reducing packaging delays that may occur if the rolls were formed with irregular properties.

0007In the past, one method of measuring roll firmness was to use a Kershaw roll firmness tester as described, for instance, in <patcit id="pcit0008" dnum="US6077590A"><text>U.S. Patent No. 6,077,590</text></patcit> to Archer, et al.. The Kershaw roll firmness tester is designed to measure the roll firmness of selected individual cut rolls offline. Unfortunately, once measurements are taken, it is sometimes difficult to use the data for modifying process conditions in order to improve the quality of products produced, due to the delay involved in obtaining the measurement.

0008As such, a need currently exists for a roll firmness device that is capable of measuring the roll firmness of a roll of material shortly after the roll is formed. A need also exists for a system that can automatically make process adjustments based upon online roll firmness measurements.

DEFINITIONS

0009A <u>tissue product</u> as described in this invention is meant to include paper products made from base webs such as bath tissues, facial tissues, paper towels, industrial wipers, foodservice wipers, napkins, medical pads, and other similar products.

0010<u>The Kershaw Test</u> is a test used for determining roll firmness. The Kershaw Test is described in detail in <patcit id="pcit0009" dnum="US6077590A"><text>U.S. Patent No. 6,077,590</text></patcit> to <u>Archer, et al.</u><figref idref="f0004">Figure 5</figref> illustrates the apparatus used for determining Kershaw roll firmness. The apparatus is available from Kershaw Instrumentation, Inc., Swedesboro, New Jersey, and is known as a Model RDT- 2002 Roll Density Tester. Shown is a towel or bath tissue roll 200 being measured, which is supported on a spindle 202. When the test begins a traverse table 204 begins to move toward the roll. Mounted to the traverse table is a sensing probe 206. The motion of the traverse table causes the sensing probe to make contact with the towel or bath tissue roll, The instant the sensing probe contacts the roll, the force exerted on the load cell will exceed the low set point of 6 grams and the displacement display will be zeroed and begin indicating the penetration of the probe. When the force exerted on the sensing probe exceeds a set point, the value is recorded. After the value is recorded, the traverse table will stop and return to the starting position. The displacement display indicates the displacement/penetration in millimeters. The tester may record this reading. Next the tester will rotate the tissue or towel roll 90 degrees on the spindle and repeat the test. The roll firmness value is the average of the two readings. The test needs to be performed in a controlled environment of 73.4 ± 1.8 degrees F. and 50 ± 2% relative humidity. The rolls to be tested need to be introduced to this environment at least 4 hours before testing.

<u>Summary of the Invention</u>

0011The present invention is generally directed to the production of spirally wound products, such as tissue products, that have consumer desired roll bulk and firmness values. The present invention is also directed to a system for producing rolls of material and to online roll firmness measuring devices.

0012The roll firmness measuring device of the system of the present invention, for instance, in one embodiment applies a contact element against a roll of material that penetrates the roll a fixed distance. The amount of force exerted against the contact element by the roll of material is then recorded. In another embodiment, however, the roll firmness measuring device applies a constant force to a roll of material and the distance a contact element penetrates the roll is recorded.

0013For example, in the first embodiment, the system of the present invention includes a contact element positioned a predetermined distance from a support surface. The predetermined distance is such that the contact element contacts a roll of material when the roll of material is being supported by the support surface. A force measuring device is used to measure the amount of force exerted against the contact element when a roll of material is placed in between the contact element and the support surface. From the diameter of the roll, the distance between the contact element and the support surface and the amount of force exerted against the contact element by the roll of material, the firmness of a roll can be determined. In one embodiment, for instance, a correlation factor can be used to determine the Kershaw roll firmness.

0014In one embodiment, the force measuring device can be, for instance, a load cell. A controller, such as a microprocessor, can be placed in communication with the force sensing device for automatically calculating the firmness of a roll.

0015In calculating the firmness of a roll using the above system, the diameter of the roll of material is measured. In one embodiment, for example, the system can include a diameter measuring device for measuring the diameter of the roll in conjunction with taking a roll firmness measurement. For instance, the diameter measuring device can comprise a laser spaced from a light sensor. The laser-may emit a curtain of light that is intercepted by a roll of material for measuring the diameter of the roll based upon the amount of light sensed by the light sensor. The diameter measuring device sends information to the controller for use in calculating the firmness of a roll.

0016In the above embodiment, the contact element is maintained in a fixed position and the amount of force exerted on the contact element when a roll of material is placed on the support surface is measured. In an alternative embodiment of the present invention, however, the-contact element can apply a predetermined amount of force against the roll of material and be movable away from the support surface when a force is exerted on the contact element that is greater than the predetermined amount of force that the contact element exerts on the roll of material. The contact element can apply a predetermined amount of force against the roll of material by, for instance, carrying a predetermined amount of weight.

0017In this embodiment, a displacement measuring device measures the displacement of the contact element from an engagement position to a final position when a roll of material is placed in between the contact element and the support surface. From this information, the firmness of the roll can be calculated.

0018The displacement measuring device may be, for instance, a potentiometer. A controller, in this embodiment, can also be used to automatically calculate the firmness of a roll by receiving information from the diameter sensing device and the displacement measuring device.

0019Because the system of the present invention is capable of measuring the firmness of a roll of material online or at least close in time to the production of the roll, various open loop or closed loop controls may be added to the system for ensuring that the rolls of material being produced have uniform and desired properties.

0020For example, in one embodiment, the system of the present invention includes a caliper control device for controlling the caliper of a web of material. A log winding device receives the web of material from the caliper control device and winds the web of material into a roll. In one embodiment, the log winding device can comprise a winding cam and can be programmed to wind the web of material into a roll under determined tension.

0021A roll firmness device determines a roll firmness value for selected rolls of material wound by the log winding device. A controller, such as a microprocessor, is in communication with the roll firmness device and the caliper control device. The controller can control the caliper control device in order to selectively increase or decrease the caliper of a web of material based upon the roll firmness value determined from the roll firmness device. For example, the controller can be configured to cause the caliper control device to decrease the caliper of a moving web if the roll firmness value of a previously formed roll is outside a preset limit indicating that the roll is firmer than desired. In a likewise manner, the controller can also be configured to cause the caliper control device to increase the caliper of a moving web if the roll firmness value of a previously formed roll is outside a preset limit indicating that the roll is less firm than desired.

0022Through the system and process of the present invention, rolls of material having desired characteristics may be repeatedly produced. The process of the present invention is set forth in claim 1. The system of the present invention is set forth in claim 10.

0023Other objects and features of the present invention are discussed in greater detail below.

<u>Brief Description of the Drawings</u>

0024A full and enabling disclosure of the present invention, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures in which: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Figure 1</figref> is a perspective view of one embodiment of a system for producing rolls of material in accordance with the present invention;</li><li><figref idref="f0002">Figure 2</figref> is a perspective view of one embodiment of a roll firmness device made in accordance with the present invention;</li><li><figref idref="f0002">Figure 3</figref> is a perspective view of another embodiment of a roll firmness device made in accordance with the present invention;</li><li><figref idref="f0003">Figure 4</figref> is a perspective view of still another embodiment of a roll firmness device made in accordance with the present invention; and</li><li><figref idref="f0004">Figure 5</figref> is a perspective view of a prior art Kershaw roll firmness measurement device.</li></ul>

0025Repeated use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

<u>Detailed Description of the Invention</u>

0026It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary construction.

0027In general, the present invention is directed to a process and system for producing layered sheet products. The layered sheet products may include wound products of for instance, facial tissues, bath tissues, paper towels, wet wipes, industrial wipers, and the like. For instance, the present invention is particularly well suited to the construction of spirally-wound tissue products, such as paper towels and bath tissues. Through the process and system of the present invention, layered products having substantially uniform and desired characteristics may be produced. For example, through the system of the present invention, spirally-wound products may be formed that have a diameter and a roll firmness within desired parameters. The capability of producing roll products having uniform characteristics provides various advantages. For instance, by producing products with uniform properties, process throughput efficiency is increased.

0028More particularly, the present invention is directed to a system including a firmness measurement device that is capable of measuring the firmness, such as the roll firmness, of a multi-layered product either online or shortly after the product is formed. In the past, roll firmness was generally measured offline on selected rolled products at a relatively slow pace. Consequently, the roll firmness measurements were not available until many further products had already been produced. Further, if the roll firmness values were outside of desired limits, relating the data to winder or raw material conditions was very difficult due to the delay between the winding process and the point at which the roll firmness measurement was taken.

0029By providing an online roll firmness measurement device, however, roll firmness measurements may be provided immediately after the product is formed allowing for operators to make quick adjustments to the equipment used to form the rolls of product in order to produce uniform products having desired characteristics. In fact, the online roll firmness measurement device of the present invention may be electrically coupled to various pieces of equipment in a closed loop or open loop fashion for making almost instantaneous changes and adjustments in the winding process.

0030It should be understood, however, that even though the system of the present invention is well suited to producing online roll firmness measurements, the roll firmness device of the present invention need not be placed online. In fact, the system of the present invention may provide various benefits and advantages when used offline as well.

0031Referring to <figref idref="f0002">Figure 2</figref>, one embodiment of a roll firmness device generally <b>10</b> made in accordance with the present invention is illustrated. As shown, a roll of material <b>12</b> that may have just been formed is forwarded on a support surface to the roll firmness device <b>10</b>. In this embodiment, the support surface is a moving conveyor <b>14</b>. It should be understood, however, that in an alternative embodiment, the support surface may be stationary and the roll firmness device <b>10</b> may move into contact with the roll of material. Further, instead of a conveyor, the support surface may comprise a mandrel on which the roll is held.

0032The roll firmness device <b>10</b> is shown in conjunction with a diameter measuring device <b>16</b> that measures the diameter of the roll of material. In this embodiment, the diameter measuring device <b>16</b> includes a pair of focused light sources or lasers <b>18</b> and a corresponding pair of light sensors <b>20</b> positioned opposite the lasers <b>18</b>. The lasers <b>18</b> emit a curtain of light that is sensed by the light sensors <b>20</b>. The curtain of light can, for instance, have a width of approximately one inch such as from about 0.8 inches to about 1.2 inches. Further, the curtain of light from each laser is emitted at a particular height with reference to the conveyor <b>14</b>. When using two lasers as shown in <figref idref="f0002">Figure 2</figref>, the lasers may be positioned at different heights in a stepwise manner.

0033The laser beam that is emitted by the lasers <b>18</b> may be non-penetrating beams. Non-penetrating laser beams may be provided, for example, by a gas laser, a solid-state laser, a liquid laser, a chemical laser, a semiconductor laser, and the like.

0034As shown, when the roll of material <b>12</b> is moved on the conveyor <b>14</b> adjacent to the diameter measuring device <b>16</b>, the roll of material intersects the curtains of light being emitted by the lasers <b>18</b>. Light sensors <b>20</b> measure the difference in light intensity caused by the intersection of the light curtains. This information can then be used to determine the diameter of the roll <b>12</b>. By way of example, the laser beam or beams may have a height of about 24mm (about 1 inch). Therefore, the diameter of the roll of material is incrementally measurable based on the light sensors 20 receiving from between about 0 to 24 millimeters of the 24 millimeter laser beam. More specifically, a portion of the 24 millimeter laser beam is blocked by the roll of material or log while another portion of the beam is received by the light sensors and converted to the diameter.

0035Converting the passed-through or received laser beam portion to the diameter is accomplished by the laser assembly which sends, for instance, a 20 milliamp signal to a controller when no portion of the laser beam is being blocked. In other words, the 20mA signal is produced if the entire 24mm laser beam is received by the light sensors. Similarly, the laser assembly is configured to send a nominal signal, such as a 4mA signal to a controller when the laser beam is entirely blocked by the roll of material. Thus, a 4mA equates to no light being received by the light sensors. In general, the laser beam is adjusted to have a particular height such that half of the beam is blocked when a roll of material at a target diameter is placed on the conveyor. When further rolls of material are placed on the conveyor, the diameter of the roll is determined from the amount of light that is blocked by the roll.

0036It should be noted that a 4 to 20 milliamp signal, which corresponds to 0 to 24 mm, is by way of example only. For instance, a laser assembly can be provided which uses any suitable milliamp range. Numerous other signal ranges are contemplated to accommodate various lasers from different manufacturers and/or to accommodate specific user requirements.

0037The diameter measuring device as described above is also disclosed in <patcit id="pcit0010" dnum="US172799A" dnum-type="L"><text>U.S. Patent Application Serial No. 10/172,799</text></patcit> filed on June 14, 2002 to Sartain et al.

0038It should be understood, however, that any suitable diameter measuring device may be used in the system of the present invention. For example, in other embodiments, the diameter measuring device may reflect light off of the top of the roll to measure the diameter of the roll. Optionally, a wheel or roller may make contact with the roll of material for measuring the diameter.

0039As shown in <figref idref="f0002">Figure <b>2</b></figref>, downstream of the diameter measuring device <b>16</b> is a contact element <b>22</b> that contacts the roll of material <b>12</b>. As shown, contact element <b>22</b> is a wheel or a roller. In other embodiments, however, a stationery shoe may be used that has a low friction surface. The contact element <b>22</b> is maintained a particular distance from the support surface or conveyor <b>14</b>. This distance may be adjusted manually using a brake device <b>24</b>. It should be understood, however, that any suitable mechanism may be used in order to adjust the position of the contact element.

0040As the roll of material <b>12</b> passes under the contact element <b>22</b>, the roll <b>12</b> exerts a force against the contact element <b>22</b>. The amount of force placed against the contact element is measured by a force measuring device <b>26</b>, such as a load cell. The load cell may be, for instance, in one embodiment a strain gauge. As also shown in <figref idref="f0002">Figure <b>2</b></figref>, the contact element also displaces into the roll of material <b>12</b> as the roll passes below the contact element. The distance the contact element <b>22</b> is displaced into the roll of material <b>12</b> depends on the diameter of the roll of material and the height of the contact element.

0041From the diameter of the roll of material <b>12</b>, the distance between the contact element <b>22</b> and the conveyor <b>14</b>, and from the amount of force measured by the load cell <b>26</b>, a roll firmness value may be calculated.

0042In one embodiment, it may be desirable to create a callibration correlation for the roll firmness device prior to use in a process. For example, empirical data may be accumulated and the data can be used to solve the following equation: <maths id="math0001"><math display="block"><mfrac><mn mathvariant="normal">1</mn><mi mathvariant="italic">Load</mi></mfrac><mo mathvariant="italic">+</mo><mfrac><mn mathvariant="normal">1</mn><mi mathvariant="italic">Displacement</mi></mfrac><mo mathvariant="italic">+</mo><mi mathvariant="italic">constant</mi><mo mathvariant="italic">=</mo><mi mathvariant="italic">Roll Firmness</mi><mn mathvariant="italic">.</mn></math><img file="EP1530044B1_D0001.tif" /></maths> The above empirical equation can then be plotted for forming a curve. This curve may then be used to evaluate any roll firmness value that is later obtained.

0043If desired, the roll firmness made by the roll firmness device may be correlated into a Kershaw roll firmness value. For example, the Kershaw roll firmness may be calculated in units of distance such as millimeters.

0044For many products, particularly tissue products, the rolls of materials should have a Kershaw roll firmness within a consumer desired range. In general, the Kershaw roll firmness of a tissue product, for instance, may be between about 6 mm to about 10 mm, and particularly between about 6 mm and about 8 mm.

0045Through the roll firmness device <b>10</b> as shown in <figref idref="f0002">Figure 2</figref>, roll firmness values may be calculated shortly after the roll of material <b>12</b> is formed, allowing for quick or immediate adjustments to be made during the winding process for maintaining the rolls of material within desired ranges.

0046In the embodiment illustrated in <figref idref="f0002">Figure 2</figref>, the contact element <b>22</b> may be maintained at a particular height as rolls of material are carried along the conveyor <b>14</b>. Alternatively, the contact element <b>22</b> may move between an engagement position where the contact element <b>22</b> contacts the roll of material and a disengagement position in which the contact element does not contact the roll of material. For example, in one embodiment, when the roll of material <b>12</b> is sensed by the diameter measuring device <b>16</b>, an actuator may be activated causing the contact element <b>22</b> to move from a disengagement position to an engagement position for taking a measurement. The actuator can be, for instance, a pneumatic or hydraulic cylinder, a roller screw, or a linear motor. The contact element <b>22</b> may move along a linear pathway or may pivot into place. By moving between an engagement position and a disengagement position, the contact element only contacts the roll of material <b>12</b> when a roll firmness measurement is desired.

0047The roll firmness device <b>10</b> may take roll firmness measurements at a single location on the roll of material <b>12</b> or along the entire length of the roll. By taking multiple roll firmness readings along the length of the roll of material, variations of firmness values within the roll itself may be discovered, which may indicate that the rolls of material are not being wound properly. This data may ultimately be used to improve product consistency and uniformity.

0048To prevent the contact element <b>22</b> from causing damage to the roll of material <b>12</b> or to prevent the roll firmness device from being damaged, in one embodiment, the roll firmness device <b>10</b> can include a safety release device that releases the contact element from an engagement position when a force exerted against the contact element exceeds a preset limit. When the safety release device is activated, an alarm, such as an audible or visible alarm may also be set off in order to alert an operator.

0049In the embodiment illustrated in <figref idref="f0002">Figure 2</figref>, the contact element <b>22</b> is placed in a fixed position and a force measuring device <b>26</b> measures the amount of force exerted against the contact element when the roll of material is passed below the contact element. Referring to <figref idref="f0002">Figure 3</figref>, an alternative embodiment of a roll firmness device generally <b>110</b> is shown. In this embodiment, a contact element <b>122</b> applies a fixed amount of force to a roll of material <b>112</b>. The contact element <b>122</b> is also movable. The amount of movement or displacement of the contact element <b>122</b> is then measured in order to calculate the roll firmness.

0050More particularly, as shown in <figref idref="f0002">Figure 3</figref>, the roll firmness device <b>110</b> includes a diameter measuring device <b>116</b> similar to the embodiment illustrated in <figref idref="f0002">Figure 2</figref>. A roll of material 112 is conveyed on a conveyor 114 into contact with the contact element <b>122</b>. The contact element <b>122</b> is initially placed a predetermined distance from the conveyor <b>114</b> that is controlled by a brake <b>124</b>.

0051In this embodiment, the contact element <b>122</b> is associated with a first weight <b>128</b> and a second weight <b>130</b>. The weights <b>128</b> and <b>130</b> are selected such that the contact element applies a predetermined amount of force onto the roll of material <b>112</b>.

0052As shown, the contact element <b>122</b> may pivot about a pivot point <b>132</b>. When the roll of material <b>112</b> is positioned below the contact element <b>122</b>, the roll of material causes the contact element to pivot a distance away from the conveyor <b>114</b>. This distance is then measured by a displacement measuring device <b>134</b>.

0053The displacement measuring device <b>134</b> may be any suitable instrument capable of measuring the displacement of the contact element <b>122</b>. In one embodiment, for instance, the displacement measuring device <b>134</b> may be a potentiometer. Alternatively, a laser may be used to directly measure how much the contact element <b>122</b> has displaced into the roll of material <b>112</b>.

0054By knowing the diameter of the roll of material <b>112</b>, the amount of force applied to the roll of material by the contact element <b>122</b>, and by knowing the amount the contact element displaces when a roll of material is positioned below the contact element, one can calculate a roll firmness value for the roll of material. Similar to the embodiment illustrated in <figref idref="f0002">Figure 2</figref>, this roll firmness value may be correlated to a Kershaw roll firmness value.

0055Thus, in the embodiment illustrated in <figref idref="f0002">Figure 3</figref>, a constant force is applied to the roll of material and the displacement of the contact element is measured. The amount of force exerted onto the roll of material <b>112</b> by the contact element may be varied as desired. For example, more or less weight may be applied to the contact element. In an alternative embodiment, the contact element may be in operative association with a pneumatic or hydraulic cylinder that applies the predetermined amount of force to the roll of material.

0056In the embodiment shown in <figref idref="f0002">Figure 3</figref>, the contact element <b>122</b> pivots between an engagement position and a final resting position when the roll of material <b>112</b> is positioned below the contact element. In an alternative embodiment, however, as shown in <figref idref="f0003">Figure 4</figref>, the contact element <b>122</b> may be positioned on a linear track <b>136</b> that allows the contact element <b>122</b> to move up and down. In this embodiment, the contact element <b>122</b> is placed in association with a weight <b>128</b>.

0057Similar to the description of the embodiment illustrated in <figref idref="f0002">Figure 2</figref>, the contact element <b>122</b> in <figref idref="f0002">Figures 3</figref> and <figref idref="f0003">4</figref> may also be connected to an actuator that moves the contact element from an engagement position to a disengagement position. As described above, in this manner, the roll of material <b>112</b> is only contacted by the contact element <b>122</b> when a measurement is desired.

0058Since the roll firmness device of the system of the present invention is capable of online roll firmness measurements, the roll firmness device is well suited to being integrated into a winding process. Once integrated into a winding process, roll firmness measurements may be taken as desired and the information obtained from the roll firmness device may be used to control various equipment in the process in order to produce rolls of material having substantially uniform and desirable characteristics.

0059For example, one embodiment of a system for forming rolled products is illustrated in <figref idref="f0001">Figure 1</figref>. Although the system in <figref idref="f0001">Figure 1</figref> may form rolls of any type of material, the system is particularly well suited for forming paper rolls, such as rolls of bath tissue or paper towels. Such products are typically formed from pulp fibers, have a bulk of at least 2 cc/g, and may have a basis weight of from about 6 gsm to about 120 gsm, such as from about 10 gsm to about 80 gsm.

0060As shown in <figref idref="f0001">Figure 1</figref>, in this embodiment, a web of material <b>40</b> is first fed through a caliper control device <b>42</b>. The caliper control device <b>42</b> may be, for instance, a calendering device containing a top roller <b>44</b> spaced from a bottom roller <b>46</b>. The rollers <b>44</b> and <b>46</b> form a nip through which the web of material <b>40</b> is fed. By applying pressure to the web, the thickness or caliper of the web may be reduced.

0061When using a calendering device, the calendering device may be a gap calendering device or a contact calendering device. Further, the rollers <b>44</b> and <b>46</b> may be steel rollers, rubber-coated rollers, or mixtures thereof.

0062In addition to a calendering device, any suitable caliper control device may be used in accordance with present invention. For example, in an alternative embodiment, an embossing device may be used in order to control the caliper of the web. In still another alternative embodiment, the caliper may be controlled by adjusting tension in the web as the web is wound. For example, tension in the web can be increased or decreased using a dancer roll, which are well known in the art.

0063From the caliper control device <b>42</b>, the web of material <b>40</b> is fed to a log winding device. In general, any suitable long winding device may be used in accordance with the present invention. For instance, the winding device may be a surface winding device, a center winding device, a coreless winding device, and the like.

0064In the embodiment shown in <figref idref="f0001">Fig. 1</figref>, the log winding device is incorporated into a turret assembly generally <b>48</b>. As shown, the turret assembly <b>48</b> includes a turret <b>50</b> attached to various mandrels. Turret <b>50</b> can generally be indexed into a variety of positions during the winding process. For instance, the indexing can occur by rotating the turret 50 about its longitudinal axis. The rotation of the turret can be accomplished by any variety of methods known in the art.

0065In the embodiment illustrated in <figref idref="f0001">Figure 1</figref>, six mandrels <b>1, 2, 3, 4, 5</b> and <b>6</b> are rotatably affixed to the turret <b>50</b>. Although the turret assembly <b>48</b> is depicted as including six mandrels, it should be understood that only one mandrel or any number of mandrels greater than one can be affixed to the turret <b>50</b>. In other embodiments, it should be understood that a turret assembly is not needed. For instance, in an alternative embodiment, a surface winder may be used.

0066The winding process is generally initiated by placing a core 7 onto the mandrel 3 according to any method known in the art. The position of mandrel 3 as shown in <figref idref="f0001">Figure 1</figref> may be described as the "core loading position" of the turret <b>50</b>. Once the core <b>7</b> is placed onto the mandrel <b>3</b>, the turret <b>50</b> can then be indexed into an "adhesive application position", which is the position occupied by mandrel <b>4</b> in the embodiment shown. In this position, any suitable adhesive (not shown) can be applied to the core 7 by any method known in the art.

0067Once an adhesive is applied to the core <b>7</b>, the turret <b>50</b> is once again rotated moving the core into a "prespin position", which is the position occupied by mandrel <b>5</b>. At the "prespin position", the mandrel can be rotated to ensure that the mandrel achieves a certain rotational speed before the web of material <b>40</b> is wound on the core <b>7</b>. In one embodiment, as shown in <figref idref="f0001">Figure 1</figref>, the mandrel <b>5</b> can be "prespun" in a counter-clockwise direction.

0068Once initially rotated at the "prespin position", the mandrel can then be indexed by the turret <b>50</b> into a "winding position", which is the position occupied by mandrel <b>6</b>. The rotational speed of the mandrel imparted at the "prespin position" is generally greater than the feed speed of the web of material <b>40</b> such that, as the rotating mandrel is indexed into the "winding position", the web of material <b>40</b> can wind around the mandrel. In particular, a leading edge of the web of material <b>40</b> contacts the adhesive on the core <b>7</b> which secures the web of material to the core as winding continues.

0069The rotational speed of the mandrel 6 at the "winding position" is controlled by any suitable log winding device, such as a winding cam <b>52</b>. In one embodiment, for instance, the winding cam <b>52</b> may vary the rotational speed of the mandrel <b>6</b> as the size of the roll increases in order to maintain the web of material <b>40</b> under constant tension.

0070After the web of material <b>40</b> is wound onto the core <b>7</b> at the mandrel <b>6</b>, the mandrel may then be indexed by the turret <b>50</b> into a "tail seal and removal position", which is the position occupied by mandrel <b>1</b> in the embodiment illustrated in <figref idref="f0001">Figure 1</figref>. At the "tail seal and removal position", the end portion of the paper web <b>40</b> can be sealed to the roll of material using any suitable sealing device. The sealing device may be configured, for instance, to apply glue or some other adhesive to the end of the web of material such that the tail can be sealed to the roll.

0071Once the end of the web of material has been sealed, the finished roll <b>12</b> may then be removed onto the conveyor <b>14</b> as described in <figref idref="f0002">Figure 2</figref>. As described above, the conveyor <b>14</b> transports the roll of material <b>12</b> into contact with the roll firmness device <b>10</b>. The roll firmness device <b>10</b> takes one or more roll firmness measurements. The roll of material <b>12</b>, if desired, may then be cut into smaller lengths as shown in <figref idref="f0001">Figure 1</figref> and packaged for consumer use.

0072As shown in <figref idref="f0001">Figure 1</figref>, the system of the present invention further includes a controller <b>54</b>, such as a microprocessor. The controller <b>54</b> is placed in communication with a caliper control device <b>42</b>, the winding device <b>52</b>, the diameter measuring device <b>16</b>, and the load cell <b>26</b>. The controller is configured to calculate a roll firmness value for the roll of material <b>12</b> and, based on this information, to then control the caliper control device <b>42</b> and/or the winding cam <b>52</b> should the diameter of the roll of material <b>12</b> or the measured firmness of the roll be outside preset limits. Specifically, the controller <b>54</b> can be configured to make adjustments in the thickness of the sheet of material <b>40</b> and/or in the amount of tension that is placed upon the web of material during winding. Through the system, the diameter of the rolls of material produced and/or the firmness of the rolls of material produced may be controlled within preset limits such that every roll produced has substantially uniform and desirable characteristics.

0073For example, in one embodiment, the winding device <b>52</b> may be preprogrammed to wind the web of material into a roll according to a particular winding profile. Once the rolls are formed, roll firmness measurements may be made using the roll firmness device <b>10</b>. A roll firmness value may be calculated by the controller <b>54</b>. Based upon the calculated roll firmness values, the controller <b>54</b> can then be configured to control the caliper control device for selectively increasing or decreasing the caliper of the web of material <b>40</b>. For example, the controller can be configured to cause the caliper control device to decrease the caliper of the moving web if the roll firmness measurements are outside a preset limit indicating that the roll is firmer than desired. Similarly, the controller can also be configured to cause the caliper control device to increase the caliper of the moving web <b>40</b> if the roll firmness measurements are outside a preset limit indicating that the roll is less firm than desired.

0074The above process may also be used to maintain the diameter of the rolls of material within preset limits. Through the roll firmness device of the present invention, diameter and firmness adjustments may be made instantaneously instead of being checked periodically as is done currently.

0075In one alternative embodiment, as shown in <figref idref="f0001">Figure 1</figref>, the system of the present invention can further include at least one caliper sensor. For example, the system can include a first caliper sensor <b>62</b> positioned after the calendering device <b>42</b> and an optional second caliper sensor <b>60</b> positioned before the calendering device <b>42</b>. The caliper sensors <b>62</b> and <b>60</b> may be used to measure the sheet caliper and to modify the calendering load to produce a constant caliper. The caliper sensors may also be used to correct for changing incoming raw materials or other transient process conditions. In general, any suitable caliper-sensing device known in the art may be used. The caliper sensor <b>62</b> and <b>60</b>, for instance, may determine the caliper of a web mechanically and/or electronically.

0076When using two caliper sensors as shown in <figref idref="f0001">Figure 1</figref>, the downstream caliper sensor <b>62</b> may be used to correct caliper in a feedback manner, while the upstream caliper sensor <b>60</b> may be used in a feed-forward control. The combination of the readings obtained from the caliper sensors <b>60</b> and <b>62</b> may allow for the correction of short-term variation in the system. The roll firmness device <b>10</b> may then modify the caliper set point to maintain the required firmness as described above.

0077In one particular embodiment, the caliper sensors <b>62</b> and <b>60</b> may be used to form a control loop for maintaining a constant caliper. The roll firmness device <b>10</b> in conjunction with the controller <b>54</b> may then be used to change the caliper set point so that the rolls being produced fall within a target firmness value. In essence, in this embodiment, the system includes two control loops, namely a fast inner loop to control caliper and a slower outer loop to control the resulting firmness. In this embodiment, controller <b>54</b> may be used alone or in conjunction with further controllers. For example, a separate controller may be used for the caliper control loop.

0078In another embodiment of the present invention, the caliper control device <b>42</b> may be fixed at a particular position and the controller <b>54</b> may be used to make adjustments to the winding device <b>52</b> in response to diameter and roll firmness measurements received from the roll firmness device <b>10</b>.

0079In still another embodiment of the present invention, the controller <b>54</b> can be configured to control the caliper control device <b>42</b> and the winding device <b>52</b> simultaneously based upon measurements received from the roll firmness device <b>10</b>.

0080Through the system of the present invention, as described above, rolls of material can be produced having uniform and desired firmness values and diameters. Various other advantages are also possible through the present invention, however. For instance, the system of the present invention can also be used to control the caliper of the web of material <b>40</b> that is presented to the winding device. By controlling the caliper of the web, the amount of tension placed on the web during winding and the roll firmness characteristics of the rolls, the sheet width within the finished rolls is also controlled. If the sheet width within the rolls were irregular, for example, when cut, the material layers contained in the rolls may have a tendency to shift. Further, irregular sheet width within the rolls can also lead to misalignments of a design that has been printed onto the material.

0081For instance, in some embodiments, designs are printed upon the web of material <b>40</b>. By producing rolls that have uniform firmness and diameter values, print registration on a cut roll may be improved. In the past, print patterns had a tendency to fall out of alignment when the rolls of material were cut after being wound due to sheet width irregularities. Through the process of the present invention, this problem may be minimized.

0082In the embodiments shown in the drawings, a conveyor <b>14</b> is used to move the rolls of material into contact with the roll firmness measuring device. In other embodiments, however, it should be understood that the roll firmness measuring device may be placed at different locations in the system. For example, in one embodiment, the roll firmness device may be placed adjacent to the mandrel <b>2</b>. In this embodiment, roll firmness measurements may be taken prior to unloading the roll of material from the mandrel.

0083In still another embodiment, the roll firmness device of the system of the present invention may be used at other manufacturing locations. For example, the roll firmness device of the present invention is particularly well suited for use during consumer packaging of the rolled products. The roll firmness device may be used online as the products are being packaged or may be set up offline in order to selectively test certain rolls prior to packaging. In this embodiment, for example, the roll firmness device may be used to determine whether a roll has a particular diameter and/or roll firmness suitable for packaging. If the roll does not fall within preset limits, the roll may be discarded or recycled. Further, should one or more rolls fall outside preset limits, a controller may be used to automatically make adjustments to the process line, such as to the packaging equipment, in order to provide corrective feedback.

0084Irregular rolls may interfere with the packaging of the products, especially when multiple rolls are being packaged in the same container. An irregular sized roll may, for instance, cause the packaging to tear or cause the packaging equipment to malfunction. By using the roll firmness device of the present invention to remove rolls without desired characteristics, packaging delays may be minimized.

0085The present invention may be better understood with reference to the following example.

<u>Example</u>

0086In this example, a system for measuring the firmness of a roll of material was constructed similar to the apparatus illustrated in <figref idref="f0002">Figure 2</figref>. Rolls of SCOTT® paper towels produced by the Kimberly-Clark Corporation were measured using the apparatus in order to develop a calibration correlation for the roll firmness device as described above. Over 70 rolls were measured using the device. The empirical data was plotted in order to solve for the following equation:<maths id="math0002"><math display="block"><mfrac><mn>1</mn><mi mathvariant="italic">Load</mi></mfrac><mo>+</mo><mfrac><mn>1</mn><mi mathvariant="italic">Displacement</mi></mfrac><mo>+</mo><mi mathvariant="italic">constant</mi><mo>=</mo><mi mathvariant="italic">Roll Firmness</mi><mn>.</mn></math><img file="EP1530044B1_D0002.tif" /></maths>

0087The following result was obtained:<maths id="math0003"><math display="block"><mi mathvariant="italic">Roll Firmness</mi><mo>=</mo><mfrac><mn>3463.97</mn><mi mathvariant="italic">Load Average</mi></mfrac><mo>-</mo><mfrac><mn>35.636</mn><mi mathvariant="italic">Displacement Average</mi></mfrac><mo>+</mo><mn>6.55078</mn></math><img file="EP1530044B1_D0003.tif" /></maths>

0088From the above equation, roll firmness values may be established for rolls of material tested by the apparatus. Further, it is believed that the above equation will provide roll firmness data for other types of commercial products tested on the apparatus in addition to the SCOTT® paper towels.

0089These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.