Patent Publication Number: US-2015078876-A1

Title: Pack alignment apparatus and methods using linear motor

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This patent application claims the benefit of U.S. Provisional Patent Application No. 61/879,236, filed Sep. 18, 2013, the entire teachings and disclosure of which are incorporated herein by reference thereto. 
    
    
     FIELD OF THE INVENTION 
     This invention generally relates to systems for forming wrapped stacks of sheet-like product, and particularly to an alignment apparatus for aligning stacks of sheet-like product prior to being wrapped into packs. 
     BACKGROUND OF THE INVENTION 
     Many sheet-like products such as, for example, napkins, facial tissues or paper towels are stacked and then wrapped for shipment. Many wrapping arrangements for wrapping the stacks process the stacks in a single-file orientation. 
     The wrapping process and wrapping arrangements do not tolerate large variations in the spacing between stacks or variations in the shape/squareness of the stacks. As such, it is desirable to feed stacks to the wrapping arrangement at a constant interval with the stacks in a desired position along the path along which the stacks are fed to the stacking arrangement. Also, it is desired for the stacks to have all of the sheets properly aligned such that the sides of the stacks are generally planar. 
     As the speed of production of the stacks of sheet-like product increases it becomes more and more difficult to maintain the squareness of the stacks as well as the accuracy of the stacks along the stack travel path. 
     Further, many stacks are formed from cutting the stack (also referred to as a clip) from a larger log of stacks of sheet-like product, typically longer. These logs will typically pass through and be cut by a cutting arrangement which is typically a log saw. These logs are often produced and supplied to the log saw at varying intervals which causes further variation in the spacing and positional accuracy of the stream of stacks supplied to the wrapping arrangement. 
     Embodiments of the present invention relate to improvements in the current state of the art. 
     BRIEF SUMMARY OF THE INVENTION 
     A new and improved system for forming wrapped stacks of sheet-like product is provided. Methods of aligning sheets within a stack of sheet-like product are also provided. 
     In one particular embodiment, a method of aligning a stack of a plurality of vertically stacked sheet-like products as the stack travels along a travel path as the stack travels through a stack aligner as the stack travels along the travel path is provided. The stack has a downstream leading end, an upstream trailing end, a pair of sides extending between the leading end and the trailing end, a top and a bottom. 
     The method includes feeding the stack to the stack aligner, pressing the stack between a first paddle of the stack aligner that is downstream from the stack and a second paddle of the stack aligner that is upstream from the stack so as to substantially align all of the sheet-like product such that the leading end and trailing end of the stack are substantially parallel to one another and orthogonal to the travel path. 
     In one method, the method further includes the step of pushing the stack out of the stack aligner using the second paddle. 
     In one method, the method further includes squeezing the stack in a transverse direction that is perpendicular to the travel path so as to substantially align substantially all of the sheet-like product such that the sides of the stack are substantially parallel to one another and orthogonal to the leading and trailing ends. 
     In one embodiment, the step of squeezing the stack in a transverse direction is performed by passing the stack between a pair of transversely offset side guides that extend substantially parallel to one another and parallel to the travel path. Typically, the stack is pushed between the side guides by the second paddle. 
     In one embodiment, the method includes independently controlling the position of the first and second paddles along the travel path. After aligned, a method includes dispensing the stacks from the stack aligner. 
     In one embodiment, the stacks are fed to the stack aligner at a first speed along the travel path and are dispensed from the stack aligner at a second speed along the travel path. The second speed may be slower or faster than the first speed depending on the operating parameters of the system. 
     In one embodiment, a further method of aligning stacks of a stream of stacks as the stacks travel through a stack aligner as the stacks travel along a travel path is provided. Each stack has a plurality of stacked sheet-like products. Each stack generally has a downstream leading end, an upstream trailing end, a pair of sides extending between the leading end and the trailing end, a top and a bottom. 
     The method includes feeding the stream of stacks to the stack aligner with a gap formed between adjacent stacks; inserting a paddle of the stack aligner into each gap between adjacent stacks, such that each stack has a paddle upstream of the stack and a paddle downstream from the stack as the stacks travel through the stack aligner. The method also includes pressing each stack between the paddle upstream of the stack and the paddle downstream of the stack so as to substantially align all of the sheet-like product such that the leading end and trailing end of the stack are substantially parallel to one another and orthogonal to the travel path. 
     In one embodiment, the method also includes changing the spacing between the paddle upstream of the stack and the paddle downstream of the stack such that the paddle downstream of the stack no longer contacts the stack and the stack is pushed by the paddle upstream of the stack. This operation occurs after the step of squeezing. This can be done by increasing the speed of the downstream paddle or reducing the speed of the upstream paddle. This decision can be decided on the overall number of stacks accumulated within the stack aligner. 
     In one embodiment, the method further includes squeezing each stack in a transverse direction that is perpendicular to the travel path so as to substantially align all of the sheet-like product of a given stack such that the sides of a given stack are substantially parallel to one another and orthogonal to the leading and trailing ends of the stack. 
     In one embodiment, the step of squeezing each stack in a transverse direction is performed by passing the stacks between a pair of transversely offset side guides that extend generally parallel to one another and parallel to the travel path. 
     In one embodiment, the stack is pushed between the side guides by the second paddle. 
     In one embodiment, the method includes independently controlling the position of the first and second paddles along the travel path. 
     In one embodiment, the method is configured for accumulating stacks and the method includes increasing a number of accumulated stacks within the stack aligner. 
     In one embodiment, increasing a number of accumulated stacks within the stack aligner includes: feeding the stream of stacks to the stack aligner with a gap formed between adjacent stacks at an average feed rate but with an inconsistent gap width between adjacent stacks; and dispensing the stacks at an outlet end of the stack aligner at an average dispensing rate with a substantially equal spacing between adjacent stacks, the supply rate being greater than the dispensing rate. 
     In one embodiment, the step of feeding the stream of stacks to the stack aligner with a gap formed between adjacent stacks includes feeding the stream of stacks to the stack aligner at an average feed rate with inconsistent gap widths between sets of adjacent stacks; and further includes dispensing the stacks at an outlet end of the stack aligner at an average dispensing rate with substantially consistent gap widths between adjacent stacks. 
     In one embodiment, the average feed rate is substantially equal to the average dispensing rate. 
     In one embodiment, the average feed rate is less than the average dispensing rate such that a number of stacks within the stack aligner decreases. In one embodiment, the average feed rate is greater than the average dispensing rate such that a number of stacks within the stack aligner increases. Additionally, the system may switch between accumulating stacks and reducing the number within the stack aligner. 
     In one embodiment, each paddle travels in a substantially orthogonal direction relative to the travel path as the paddle is inserted into a corresponding gap between adjacent stacks. In one embodiment, the method includes retracting each paddle from the corresponding gap between each adjacent stack and wherein each paddle travels in a substantially orthogonal direction relative to the travel path as the paddle is retraced from the corresponding gap between adjacent stacks. 
     In another embodiment, a method of transporting stacks of a stream of stacks from a log saw where the stacks are formed from a plurality of longer logs to a wrapper for wrapping the stacks is provided. Each stack including a plurality of stacked sheet-like products, each stack generally having a downstream leading end, an upstream trailing end, a pair of sides extending between the leading end and the trailing end, a top and a bottom. 
     The method includes feeding the stacks to a stack aligner as the stacks travel along a stack travel path at a stack aligner inlet; dispensing the stacks from the stack aligner at a stack aligner outlet; sensing a position of each stack prior to feeding the stack to the stack aligner; calculating a motion profile to insert a paddle of the stack aligner after each stack. 
     In one embodiment, the method further includes receiving the stacks at an inlet end of the stack aligner at an average supply rate but with unequal spacing between adjacent stacks; and dispensing the stacks at an outlet end of the stack aligner at an average dispensing rate with a substantially equal spacing between adjacent stacks. 
     In one embodiment, the average supply rate is substantially equal to the average dispensing rate. 
     In one embodiment, the method includes independently controlling the motion of each of the paddles. 
     A stack aligner for aligning stacks of a stream of stacks as the stacks travel along a stack travel path is provided. Adjacent ones of the stacks are longitudinally spaced apart along the travel path forming a gap therebetween. Each stack includes a plurality of stacked sheet-like products. Each stack generally has a downstream leading end, an upstream trailing end, and a pair of sides extending between the leading end and the trailing end. 
     The stack aligner includes a plurality of paddles, a guide arrangement and a control arrangement. The paddles are configured for being inserted into the gap between adjacent stacks. The guide arrangement guides the paddles along a paddle travel path. The paddle travel path having a portion thereof that is coincident with a portion of the stack travel path. The control arrangement is configured to independently control the motion of the paddles along the paddle travel path. As such, the paddles can control the speed of the stacks through the coincident portion of the travel paths at different speeds. This allows for improved positional accuracy of the stacks as well as improving the squareness of the stacks. 
     In one embodiment, the control arrangement is configured to control the motion of the of the plurality of paddles such that when adjacent paddles have been inserted into corresponding gaps the control arrangement reduces the spacing between adjacent paddles such that the paddles press the stack positioned therebetween between the paddle upstream of the stack and the paddle downstream of the stack so as to substantially align all of the sheet-like product such that the leading end and trailing end of the stack are substantially parallel to one another and orthogonal to the travel path. 
     In one embodiment, the stack aligner includes a pair of side guides transversely offset from one another and that generally extend longitudinally along the stack travel path. The side guides may be transversely spaced apart a distance equal to a width of the stacks from side to side, slightly greater than the width of the stacks or slightly less than the width of the stacks. 
     In one embodiment, the side guides remain in a substantially fixed position while the stacks pass therebetween. 
     In one embodiment, the guide arrangement includes a carriage track that defines a closed guide path; a first cam track and a second cam track. Each paddle is pivotally attached to a guide carriage that is guided by the carriage track along the closed guide path. Each paddle is operably coupled to first and second cam followers. The first cam follower and the first cam track are configured to rotate the paddle relative to the carriage track and the closed guide path at least 60 degrees, preferably at least 75 degrees, more preferably at least 80 degrees and even more preferably at least 85 degrees and desirably about 90 degrees. The second cam follower and the second cam track are configured to rotate the paddle relative to the carriage track and the closed guide path at least 60 degrees, preferably at least 75 degrees, more preferably at least 80 degrees and even more preferably at least 85 degrees and desirably about 90 degrees. 
     In one embodiment, the guide arrangement includes a carriage track that defines a closed guide path and a cam track arrangement. Each paddle is pivotally attached to a guide carriage that is guided by the carriage track along the closed guide path for motion in a single direction. Each paddle is operably attached to a cam follower arrangement. The cam track arrangement and cam follower arrangement are configured to rotate the paddle relative to the carriage track and the closed guide path while inserting the paddle between adjacent stacks. The cam track arrangement and cam follower arrangement are configured to rotate the paddle relative to the carriage track and the closed guide path while removing the paddle from between adjacent stacks. 
     In a more particular embodiment, the cam track arrangement and cam follower arrangement are configured to rotate the paddle relative to the carriage track and the closed guide path approximately 90 degrees in a first angular direction while inserting the paddle between adjacent stacks; and the cam track arrangement and cam follower arrangement are configured to rotate the paddle relative to the carriage track and the closed guide path in the approximately 90 degrees while removing the paddle from between adjacent stacks. 
     In one embodiment, the cam track arrangement and cam follower arrangement are configured to rotate the paddle relative to the carriage track and the closed guide path such that the paddle remains substantially orthogonal to the stack travel path as the paddle is inserted into the gap; and the cam track arrangement and cam follower arrangement are configured to rotate the paddle relative to the carriage track and the closed guide path such that the paddle remains substantially orthogonal to the stack travel path as the paddle is removed from the gap. 
     In one embodiment, the first and second cam tracks are transversely offset from one another in a direction perpendicular to the stack travel path. 
     In one embodiment, the first cam follower and the first cam track are configured to maintain upstream and downstream contact surfaces of the paddle in a substantially orthogonal orientation relative to the stack travel path as the paddles are transitioned into and enters a gap between adjacent stacks; and the second cam follower and the second cam track are configured to maintain the upstream and downstream contact surfaces of the paddle in a substantially orthogonal orientation relative to the stack travel path as the paddles are transitioned out of and exits a gap between adjacent stacks. 
     In one embodiment, the first and second cam followers and first and second cam tracks are configured to maintain the upstream and downstream contact surfaces orthogonal to the stack travel path substantially the entire time that the paddle travel path is coincident with the stack travel path. 
     In one embodiment, the control arrangement is configured to control the motion of the of the plurality of paddles such that after adjacent paddles have pressed a stack positioned therebetween, the longitudinal spacing along the paddle travel path, as well as the stack travel path, between the adjacent paddles is increased so that only the trailing end of the stack is contacted the paddle upstream from the corresponding stack. 
     In one embodiment, the control arrangement is configured to independently control the motion of the paddles such that the positional tolerance of each stack along the stack travel path after the stack is no longer controlled by a paddle of the stack aligner is less than +/−0.25 inches. 
     In one embodiment, the motion of the paddles is not mechanically tied to one another such that each paddle can be independently accelerated along the paddle travel path. 
     In one embodiment, the stack aligner includes an in feed conveyor, an out feed conveyor and a low friction surface. The low friction surface is interposed between the in feed conveyor and the out feed conveyor. 
     Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a simplified schematic illustration of a pack forming system; 
         FIG. 2  is a simplified illustration of a stack of sheet-like product that is formed and wrapped in the pack forming system of  FIG. 1 ; 
         FIG. 3  is a partial illustration of an embodiment of a stack aligner of the system of  FIG. 1 ; 
         FIG. 4  is a simplified schematic illustration of the stack aligner of  FIG. 3  in operation; 
         FIGS. 5 and 6  illustrate a slightly modified embodiment of the stack aligner of  FIGS. 3 and 4  illustrating the stack aligner in a maximum accumulation state ( FIG. 5 ) and a minimum accumulation state ( FIG. 6 ); 
         FIG. 7  is a simplified control algorithm for controlling the stack aligner; and 
         FIGS. 8-11  are more detailed control schematics for the control algorithm of  FIG. 7 . 
     
    
    
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a schematic illustration of a pack forming system  100  according to an embodiment of the present invention. The pack forming system  100  is configured to form and then wrap stacks of sheet-like product such as napkins or facial tissue to form packs of sheet-like product. Typically, the pack forming system  100  will receive a web of material and convert the web of material into the packs of sheet-like product. 
     The illustrated pack forming system  100  includes a folding arrangement  102  that receives a continuous web of material and cuts the web into individual sheets and stacks the sheets to form logs  104 . The sheets within the logs  104  may be folded any number of times. Further, adjacent sheets in the logs may be interfolded or merely in a stacked configuration and not interfolded. Preferably, adjacent sheets are vertically stacked. However, embodiments of the invention are not so limited and in some embodiments, the sheets may be vertically oriented such that the sheets rest on edges thereof and are stacked horizontally. 
     In some embodiments, the length of the logs may be in excess of 8 feet. 
     The logs  104  are transported downstream to a cutting mechanism. The cutting mechanism is in the form of a log saw  106 . The log saw  106  cuts the logs  104  into individual stacks  108  (a stack  108  may also be referred to as a “clip”). A typical log  106  may be cut into 5 to 15 separate stacks  108 . However larger logs or smaller stacks may result in more stacks per log. 
     Adjacent stacks  108  downstream from the log saw  106  are typically spaced apart along a stack travel path  112  forming gaps  110  therebetween. 
     The stream of stacks  108  travel along the stack travel path  112  downstream from the cutting mechanism to a pack aligner  114 . The stack aligner  114  is configured to square up or otherwise straighten the sheets within the pack as well as to provide consistent spacing between the stacks  108  and proper positional location of the stacks  108  along the stack travel path in preparation for wrapping. 
     After passing the pack aligner  14 , the stacks  118  travel along the stack travel path  112  to a wrapping arrangement  116 . In a preferred embodiment the wrapping arrangement  116  is a progressive wrapper. Typically, the stacks  108  are wrapped in a clear plastic material. However, other wrapping arrangements could be incorporated that are not progressive wrappers or that utilize other materials such as other plastic or paper materials. The wrapped stacks form individual packs  118 . The packs  118  will travel downstream where they can be further packaged for shipment. 
     Other folding arrangements  102  are contemplated. For instance, rather than forming logs of sheets that need to be cut into individual clips or stacks, the folding arrangement could directly form individual stacks of sheet-like product such that a cutting mechanism is not required between the folding arrangement and the stack aligner. In such an embodiment, a plurality of lanes of stacks may be formed. Because the stacks  108  must pass through the wrapping arrangement  116  in single file, a stack merger (not shown) may be interposed between the folding arrangement and the stack aligner  114  if only a single wrapping arrangement  116  is provided in the system. 
     It is desired to supply the stream of stacks  108  to the wrapping arrangement  116  with a position tolerance less than +/−0.05 inches. The position tolerance for various mechanisms upstream from the pack aligner can range from +/−0.25 inches to in excess of +/−1 inch depending on the type of sheet-like product or the upstream processes used to produce the single file stream of stacks  108 . This positional tolerance can provide significant problems with the wrapping process. The stack aligner  114  can rectify this low tolerance to improve the operation of the wrapping arrangement  116  and provide tolerance of less than +/−0.25. 
     For reference,  FIG. 2  illustrates a simplified representative stack  108 . The stack has a plurality of sheets  124 . The sheets  124  may have one or more panels. If a plurality of panels are provided the panels would be connected to one another by a fold, as is generally well known. The sheets  124  are stacked generally vertically on top of one another. Vertically on top of one another shall include having adjacent ones of the sheets  104  interfolded with one another. 
     The stack  108  generally includes a downstream leading end  126  that is generally parallel to an upstream trailing end  128 . A pair of opposed sides  130 ,  132  extend generally parallel to one another and between leading and trailing ends  126 ,  128 . A top side  134  extends generally parallel to a bottom side  136 . The top and bottom sides  134 ,  136  extend generally perpendicular to the opposed sides  130 ,  132  as well as generally perpendicular to the leading and trailing ends  126 ,  128 . All of the ends/sides  126 ,  128 ,  130 ,  132 ,  134 ,  136  are desirably rectangular and planar. 
     With additional reference to  FIG. 1 , when the stacks  108  travel along the stack travel path  112  upstream of the stack aligner  114 , the leading and trailing ends  126 ,  128  are generally orthogonal to the stack travel path  112  and the opposed sides  130 ,  132  and top and bottom sides  134 ,  136  are generally parallel to the stack travel path  112 . 
     Due to the process upstream from the stack aligner  114  that form and align the stacks in a single file line for wrapping, the stacks  108  can be less square than desirable. For instance, individual sheets  124  could be rotated relative to the stack such as about a vertical axis  140  that is perpendicular to the panels of the sheets  124 . This will give the stack a twisted configuration. Additionally, sheets  124  could be shifted forward or backward along the sheet travel path  112  such as illustrated by arrow  142  such that some the leading and trailing ends  126 ,  128  of the stack are not orthogonal relative to the stack travel path. Additionally, the sheets  124  can be laterally shifted in a direction perpendicular to the sheet travel path such as illustrated by arrow  144  such that the opposed sides  130 ,  132  are not perpendicular to the top and bottom sides  134 ,  136 . The stack aligner  114  can also rectify these deficiencies and square-up the sheets  124  within a stack  108 . 
       FIG. 3  is a partial illustration of the stack aligner  114 . The stack aligner  114  is used to both square-up the sheets in a given pack as well as improve the positional tolerances of the stream of stacks prior to the stacks  108  reaching the wrapping arrangement  116 . 
     The stack aligner  114  includes a plurality of paddles  150  that push the stacks  108  through the stack aligner  114 . Each paddle  150  is pivotally attached to a guide carriage  152  which is carried and guided by a carriage track  154 . The carriage track  154  defines a closed guide path along which the guide carriages  152  are guided. The carriage track  154  and guide carriages  152  are preferably configured such that the guide carriages  152  are independently controllable along the guide path defined by the carriage track  154  such that each guide carriage  152  can be accelerated independently of the rest of the guide carriages  12  mounted to the carriage track  154 . In one embodiment, the carriage track  154  and guide carriages  152  form a linear synchronous motor such as provided by Jacobs Automation Inc of Erlanger, Kentucky. 
     The guide track  154  and a pair of cam tracks  156 ,  158  form a guide arrangement that guides the motion of the paddles  150  through a paddle travel path as the guide carriages  152  travel along the guide path of the carriage track  154 . 
     The pair of cam tracks  156 ,  158  are laterally spaced apart in a direction perpendicular to the stack travel path  112  such that the cam tracks are on opposite sides of the carriage track  154  as well as opposite sides of the paddles  150  and guide carriages  152 . The paddles  150  are fixedly attached to corresponding cam followers  157 ,  159  that cooperate with cam track  156  and cam track  158 , respectively, for rotating the paddles  150  about rotational axis  161 . 
     The guide arrangement is configured such that the paddles  150  are inserted into the gaps  110  (see  FIG. 1 ) between adjacent stacks  108  in a substantially orthogonal direction relative to the stack travel path  112 . Front (i.e. downstream) and rear (i.e. upstream) surfaces  160 ,  162  of the paddles  150 , which are substantially planar surfaces, remain substantially orthogonal to the stack travel path  112  as the paddles  150  are inserted into gaps  110 . Preferably, the paddles  150  remain substantially vertically upright while moving in the vertical downward direction illustrated by arrow  164  as the paddles  150  are inserted in to gap  110  between adjacent stacks  108 . 
     This motion of the paddles  150  is controlled by cam track  156  and corresponding cam follower  157 . This causes the paddle to rotate relative to the carriage track  154  and the guide carriage  152  approximately 90 degrees about rotational axis  161  in a first direction during the insertion process while a paddle  150  is being inserted into gap  110 . This motion transitions the paddle  150  from the orientation illustrated by paddle  150 ′ to the orientation illustrated by paddle  150 ″. However, prior to this motion, cam track  156  causes the paddles  150  to rotate in a second, opposite, direction about rotational axis  161  of approximately 90 degrees. This initial motion transitions the paddle  150  from the orientation illustrated by paddle  150 ′″ to the orientation illustrated by paddle  150 ′. 
     Additionally, the guide arrangement is configured such that the paddles  150  are retracted from the gaps  110  (see  FIG. 1 ) between adjacent stacks  108  in a substantially orthogonal direction relative to the stack travel path  112 . Front and rear surfaces  160 ,  162  of the paddles  150  remain substantially orthogonal to the stack travel path  112  as the paddles  150  are retracted from gaps  110 . Preferably, the paddles  150  remain substantially vertically upright while moving in the vertical upward direction illustrated by arrow  166  as the paddles  150  are retracted from gap  110  between adjacent stacks  108 . 
     This motion of the paddles  150  is controlled by cam track  158  and corresponding cam follower  159 . This causes the paddle to rotate relative to the carriage track  154  and the guide carriage  152  approximately 90 degrees about rotational axis  161  in a the first direction during the retraction process while the paddle is being retracted from gap  110 . After this initial motion in the first direction, cam track  158  causes the paddles  150  to rotate in the second direction about rotational axis  161  of approximately 90 degrees. 
     As such, the first cam track  156  is configured to cause the paddles  150  to undergo rotation in both the first and second directions about rotational axis  161  while the paddles  150  are under control of the first cam track  156 . Similarly, the second cam track  158  is configured to cause the paddles  150  to undergo rotation in both the first and second directions about rotational axis  161  while the paddles  150  are under control of the second cam track  156 . The first cam track  156  first causes rotation of paddles  150  about axis  161  in the second direction and then in the first direction. The second cam track  156  first causes rotation of paddles  150  about axis  161  in the first direction and then in the second direction. 
     The cam tracks  156 ,  158  have overlapping regions  167  where the paddles  150  transition from being controlled by one of the cam tracks  156 ,  158  to being controlled by the other one of the cam tracks  158 ,  156 . In the illustrated embodiment, the overlapping regions  167  exist adjacent a linear section, e.g. straight section, of the guide track  154  travel path where the paddle  150  extends orthogonally relative to the guide track  154 . 
     As the paddle  150  travels around the guide track  154 , the cam tracks  156 ,  158  will cause the paddle  150  to rotate relative to guide carriage  152  typically approximately +/−90 degrees from the perpendicular orientation depending on the particular location around the guide track  154 . 
     Typically, the stacks  108  will be fed to the stack aligner by an in feed conveyor  170  and transferred to a low friction table  172  or other non-moving sliding surface/table upon which the stacks  108  can easily slide. The stacks  108  are pushed along the stack travel path  112  through the stack aligner  114  by the paddles  150  while the stacks  108  rest and slide on the low friction table  172 . The paddles  150  will push the stacks  108  out of the stack aligner  114  onto an out feed conveyor  174  which transport the stacks downstream to the wrapping arrangement  116 . The in feed and out feed conveyors  170 ,  174  are preferably compression conveyors that each have a top and bottom conveyor that vertically compresses the stacks  108  therebetween as the stacks travel along the stack travel path  112  into and out of the stack aligner  114 . 
     The stack aligner  114  further includes a pair of side guides  176  that laterally squeeze the stacks  108  as the stacks  108  pass along the stack travel path  112  through the stack aligner  114 . The side guides  176  help align the stacks  108  by constraining the sheets of the stacks in a direction that is generally perpendicular to the sheet travel path. The side guides  176  typically, at least initially, taper towards one another in a downstream direction. 
     To push the stacks  108  through the stack aligner, a portion of the paddle travel path, i.e. the path the paddles  150  travel as the guide carriages  152  travel around the carriage track  154 , is coincident with the stack travel path  112 . 
     The stack aligner  114  includes a controller  178  that controls the motion profile of the individual paddles  150  by controlling the motion profile of the guide carriages  152  along the carriage track  154 . More particularly, the controller  178  will typically control the speed and acceleration of the guide carriages  152  along the guide path defined by the carriage track  154 . The controller  178 , guide track  154  and guide carriages  152  are configured such that the motion profile of each of the guide carriages  152 , i.e. speed and acceleration thereof, can be independently controlled. 
     In operation, after paddles  150  are inserted both downstream of and upstream of a particular stack  108 , the controller  178  will control the paddles  150  such that the paddles  150  will reduce the distance therebetween and press on the leading and trailing ends  126 ,  128  of the stacks  108  to further facilitate squaring-up the stacks  108 . 
     The stacks  108  are discharged from the stack aligner  114  and dispensed onto the out feed conveyor  174 . Once the stacks  108  are fully under the control of the out feed convey  174 , the controller  178  will slow the motion of the paddles  150  along the stack travel path such that the paddle  150  no longer contacts or pushes the corresponding stack  108  and then the paddle  150  moves in the orthogonal direction out of the gap  110  between adjacent stacks in which the paddle  150  is positioned. 
     The operation of the stack aligner  114  will be described in more detail with additional reference to  FIG. 4 . The stacks  108  are moving from left to right and are moving along the stack travel path  112  as illustrated by arrow  180 . 
     Paddle  150 A is accelerating vertically downward between stacks  108 A and  108 B into gap  110 A and beginning to accelerate forward in a downstream direction relative to the stack travel path  112 . The paddle  150 A is substantially vertically oriented and substantially orthogonal to the stack travel path  112  so as to avoid contacting either of stacks  108 A,  108 B during the insertion process. Paddle  150 A is beginning to rotate angularly about axis  161 A relative to guide carriage  152 A in an angular clockwise direction as illustrated by arrow  200 A so as to maintain the vertical/orthogonal orientation relative to the stack travel path  112  during the insertion process. 
     Paddle  150 B has rotated relative to guide carriage  152 B about axis  161 B and is partially between stacks  108 B and  108 C and positioned within gap  110 B. It is ideally equally spaced from the leading end of stack  108 B and trailing end of stack  106 C during the insertion process. Paddle  150 B has a downstream component of motion that moves the paddle  150 B downstream relative to stack travel path  112  as well as a vertical/orthogonal component of motion that moves the paddle  150 B further into gap  110 B while rotating about axis  161 B to maintain the vertical/orthogonal orientation of the paddle  150 B to avoid premature contact with either of stacks  108 B,  108 C. 
     Paddle  150 B will travel at a faster speed along the stack travel path  112  until the downstream surface of paddle  150 B contacts the upstream end of stack  108 C, such as paddle  150 D relative to stack  108 E. 
     The position of stack  108 D is controlled by in feed conveyor  170  until the stack  108 D crosses junction  202  between in feed conveyor  170  and sliding table  172 , at which time the motion of stack  108 D will be provided by paddle  150 C as paddle  150 C presses against the upstream end of stack  108 D. Paddle  150 D and stack  108 E illustrate such an arrangement where the stack  108 E is being pushed along the stack travel path  112  by the paddle  150 D, rather than in feed conveyor  170 . 
     At this time, stack  108 E is illustrated as being axially squeezed and captivated between the downstream front surface of paddle  150 D and an upstream rear surface of paddle  150 E. This vertically squares the leading and trailing ends of stack  108 E. Stack  108 E will also pass through side guides  176  (not shown in  FIG. 4 ) to square up the opposed sides  130 ,  132  of the stack  108 E in a direction perpendicular to stack travel path  112  and perpendicular to the vertical direction, i.e. in a direction generally parallel to top and bottom sides  134 ,  136 . To square up the stack  108 E between paddles  150 D,  150 E, the distance between the adjacent surfaces of paddles  150 D,  150 E is reduced to a length along the stack travel path  112  that is slightly less than the relaxed length of stack  108 E. 
     After stack  108 E is squared up by being squeezed between paddles  150 D,  150 E, paddle  150 E accelerates stack  108108 F to match the linear speed of out feed conveyor  174 . Not only does paddle  150 E many the linear speed of stack  108 F with the linear speed of out feed conveyor  174 , paddle  150 E properly linearly positions the stack  108 F along the stack travel path  112 . This acceleration separates paddle  150 E from the downstream leading end of stack  108 E such that stack  108 E is fully controlled only by paddle  150 D as stack  108 E travels along the stack travel path  112 . 
     Paddle  150 F has completed this acceleration and is pushing stack  108 G out feed conveyor  174  as the stack  108 G is illustrated as crossing junction  204  between sliding table  172  and out feed conveyor  174 . Stack  108 G enters out feed conveyor  174  at the same speed as the out feed conveyor  174  and at the desired linear position along stack travel path  112 . 
     Paddle  150 G has fully pushed stack  108 H on to out feed conveyor  174  and its speed component parallel to stack travel path  112  has reduced compared to out feed conveyor  174  such that a gap is formed between the trailing end of stack  108 H and the downstream front surface of paddle  150 G. Paddle  150 G is transitioning vertically/orthogonally out from between stacks  108 G and  108 H in a substantially orthogonal direction to, again, prevent undesirable contact between the paddle  150 G and adjacent stacks  108 G,  108 H as the paddle  150 G is being retracted. As the paddle  150 G is being retracted, the paddle  150 G rotates angularly about axis  161 G in the clockwise direction as represented by arrow  200 G. 
     The paddles  150  will rotate approximately 180 degrees around the corresponding rotational axis  161  in the clockwise direction (illustrated by arrows  200 A,  200 G) from the begging of the entry process (see e.g. paddle  150 A) to the end of the exiting process (e.g. slightly past the location of Paddle  150 G) where the paddle  150  has been removed from the gap  110  between adjacent stacks  108 . 
     Paddle  1501  has begun to rotate angularly about axis  1611  in an opposite angular direction, i.e. counter-clockwise as illustrated by arrow  206 . The paddles  150  will rotate approximately 180 degrees around the corresponding rotational axis  161  in the counterclockwise direction  206  after the paddle  150  has been removed from the gap  110  between adjacent stacks  108 . 
     The motion profile of each of the guide carriages  152 , and thus each of the attached paddles  150 , is independently controlled by controller  178 . Further, the position of each guide carriage  152  (and attached paddle  150 ) is continuously monitored. Because each guide carriage  152  is independently controlled and positionally monitored, the positional tolerances of the stacks  108  along the stack travel path  112  as the stacks  108  are dispensed on to out feed conveyor  174  is very tight. It is desired that the position of the stacks  108  is approximately +1-0.1 inch after the stacks  108  exit the stack aligner. More preferably the positional tolerance of the stacks  108  along the stack travel path  112  is approximately +/−0.05 inches. 
     This tight positional tolerance of the stacks  108  along the stack travel path  112  as the stacks  108  exit the stack aligner  114  and, consequently, enter the wrapping arrangement  116  significantly improves the operation and consistency of the wrapping process by wrapping arrangement  116 . 
     When the pack forming system  100  uses a folding arrangement  102  that forms longer logs  104 , such as illustrated in  FIG. 1 , the spacing between adjacent logs  104  upstream of the log saw  106  will typically include inconsistent gap lengths. For instance, individual logs  104  may have a spacing of between about 1 to 5 stack lengths and the gap spacing can vary from one gap to the next. These gaps may also be expressed in the number of “air cuts” that the log saw  106  will perform between adjacent logs  104  as no cuts will occur as the log saw  104  passes between the adjacent logs  104 . 
     However, the stack wrapping arrangement  116  cannot accommodate such random spacing. Without an intervening structure between the log saw  106  and wrapping arrangement  116 , the stacks  108  would arrive at the wrapping arrangement  116  in groups with varying spacing between adjacent groupings of stacks  108 . 
     The stack aligner  114  can be used to accumulate and control the stacks  108  in such a configuration such that the stacks arrive at the wrapping arrangement with equal spacing. As such, the stack aligner  114  may also be referred to as an accumulator or an aligner/accumulator. 
     In such a system where groups of stacks  108  are formed with larger spaces formed between groups of stacks  108 , i.e. the spacing due to the spacing between adjacent logs  104  upstream of the log saw  106 , it can be desirous to lengthen the linear section  210  (also referred to as “accumulation section  210 ”) of the stack aligner  114  (see  FIG. 5 ). By lengthening the linear section  210 , more stacks  108  may be accumulated within the stack aligner  114  to compensate for the larger gaps and inconsistencies of the upstream flow of stacks  108  that is being feed from the log saw  106  to the stack aligner  114 . 
       FIG. 5  illustrates a stack aligner similar to that of  FIG. 4 . However, the stack aligner  114  has been stretched parallel to the stack travel path  112  so as to allow more stacks  108  to be positioned within the stack aligner  114 .  FIG. 5  illustrates the stack aligner  114  at maximum capacity.  FIG. 6  illustrates the stack aligner  114  at significantly less than maximum capacity. 
     The stacks  108  enter and leave the stack aligner  114  in the same manner as discussed above and are squared up as discussed above. However, the amount of stacks  108  accumulated within the stack aligner  114  can fluctuate between that shown in  FIG. 5  (maximum accumulation) and that shown in  FIG. 6  depending on the consistency of the upstream supply of stacks  108 . 
     Typically, it is desired to have a minimum of at least two to four packs of accumulation within the stack aligner  114  at all times, i.e. as a minimum accumulation, so as to avoid starving the wrapping arrangement  116 . 
       FIG. 7  is a flow chart illustrating the control algorithm  300  for the portion of the system  100  that includes the log saw  106 , stack aligner  114 , and wrapping arrangement  116 . In some embodiments, the portion of the algorithm that utilizes inputs regarding the log saw  106  could be modified to incorporate information from an upstream stream of stacks supplied from a stack merger if a log saw  106  is not incorporated into a system (e.g. such as in a system for forming napkins). 
     The algorithm  300 , at block  302 , reads the orbit head position and speed of the log saw  106 , the position of a log  104  entering the saw, and calculates the positions of the stacks  108  leaving the log saw  106 . The number of stacks per log is entered as a product code. A sensor  220  (see  FIG. 1 ) checks the position of each stack along the stack travel path  112  shortly before entering the stack aligner  114 . These inputs along with the number of stacks  108  in the accumulation section  210  are used to control the speed of the wrapper. 
     As noted above, a paddle  150  is inserted behind each stack  108  entering the stack aligner  150 . The paddle  150  is inserted a distance upstream from each stack  108 . After being inserted into the gap  110 , the paddle  150  is moved into contact with the trailing upstream end of the stack. At this point, the preceding paddle  150  slows down to contact the leading downstream end of the stack  108  to square up the stack  108 . Alternatively, the trailing paddle  150  speeds up to push the leading end of the stack  108  against the back side of the preceding paddle to square up the stack  108 . These two paddle motions are used selectively depending on the stat of accumulation of stacks within the accumulation section  210  of the stack aligner. 
     The algorithm  300  includes a queue manager  304  that performs three functions. First, the queue manager  304  controls the wrapping arrangement  116  speed. Second, the queue manager  304  keeps track of the state of the accumulation of stacks  108  within the stack aligner  114 . Third, the queue manager  304  controls the motion of the stacks  108  within the stack aligner  114 . 
     The incoming stream of stacks is categorized as full, small gap, or large gap. A full incoming stack stream consists of stacks from one log. A small gap stack stream consists of a gap between consecutive logs where the logs  104  are supplied to the log saw with the minimum gaps between logs. A small gap is typically 2 to 4 log saw orbits (e.g. air cuts) between consecutive logs  104 . A large gap is a gap in the supply of logs  104 . 
     The accumulator state is the number of stacks  108  within the accumulation section  210 , the position of each stack  108 , and the velocity of each stack  108 . The position and velocity of each stack within the stack aligner  114  along the stack travel path  112  is inferred from the position and velocity of the paddles  150 . The electronics that control the motion of the guide carriages  152  measure the velocity and position of the guide carriages  152  and consequently the paddles  150 . When the accumulation section  210  is full, stacks  108  flow from entry to exit with minimum or no gap between stacks  108  within the stack aligner  114  (see e.g.  FIG. 5 ). When the accumulation section  210  is empty, each stack  108  enters the stack aligner  114 , is aligned, and then immediately and quickly moved to the exit and onto the out feed conveyor  174 . When the accumulation section  210  is partially filled to some extent between maximum and minimum accumulation, operation is controlled to an intermediate degree or degrees. For instance, the operation could be controlled as a ratio based on the accumulation state of the accumulation section  210 . 
     The queue manager controls the speed of the wrapping arrangement  116  according to the queue state and incoming stack stream. The table of  FIG. 10  summarizes the algorithm for controlling the speed of the wrapping arrangement  116 . The gap between adjacent logs  104 , as mentioned above, is normally not constant, therefore the speed of the wrapping arrangement  116  must vary to follow the flow of stacks  108 . 
     The stack discharge algorithm, with reference to  FIG. 11 , reads the speed and phase of the wrapper, along with the position of the next stack to be discharged from the accumulation section  210 , and calculates a motion profile to put that stack  108  onto the out feed conveyor  174  at correct speed and position along the stack travel path  112 . When the stack is fully on the out feed conveyor  174 , the corresponding paddle  150  slows to clear the trailing end of the stack  108  and moves up and away as discussed above. 
     The ability to independently control the guide carriages  152  and consequently paddles  150  allows for the ability to adjust the flow of the stacks out of the stack aligner  114  independent of the flow of stacks  108  into the stack aligner  114 , within the limits of the amount of stacks  108  that can be accumulated within the stack aligner  114 . This is a significant upgrade over the prior art that typically utilized a fixed paddle conveyor where if the speed of the wrapper had to be reduced the entire speed of the system had to be reduced to avoid jamming the system. Additionally, the present system eliminates or significantly reduces the stack entering variation into the wrapping arrangement  116 . Stack entering variation forces the wrapping arrangement  116  to stop and start. However, wrapping arrangements, and particularly progressive wrapping arrangements, do not readily handle stopping and starting operation. 
     All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.