Abstract:
There are disclosed embodiments of a decurler system for tag webs used for example in printers and stackers to automatically remove curl from tag webs to promote further tag handling and better tag appearance. The decurler system may determine the current diameter of a stock roll and gradually adjust parameters such as resistance and back bend so as to compensate for increased set in tag webs as the diameter of the stock roll decreases. In an embodiment, the decurler system may include different sets of parameters for different stock roll diameters depending on the material used for the tag webs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   U.S. patent application Ser. No. 10/779,990 filed Feb. 17, 2004, Publication No. US 2005/0189796A1 is incorporated herein by reference in its entirety. 
   Another U.S. patent application entitled “UNWIND FOR PRINTER” , wherein the named inventor is and Donald J. Ward, Ser. No. 11/409,804, filed Apr. 24, 2006, has a disclosure the entirety of which is incorporated herein by reference, and that application discloses features of the printer and its unwind not disclosed either in application Ser. No. 10/779,990 or in the present application. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to methods and apparatus for decurling tags and webs in devices such as printers with stacker. 
   2. Description of Related Art 
   Printable webs can be comprised of various materials such as uncoated tag stock, coated tag stock, fabric, pressure sensitive label stock, and the like. These materials are typically wound into a supply roll. Such web materials differ as to the amount of memory or set they have from having been wound into a supply roll. For example, it has been found that the memory of certain uncoated tag stock is substantial and is greater than the memory of coated tag stock. On the other hand, the memory of a fabric web is very small. In addition, the amount of curl in a web increases as the distance between the outside of the supply roll and the center of the supply roll decrease. Thus, for materials in which the memory is substantial, the web does not decurl sufficiently as the web passes through a utilization device such as a printer to result in flat tags. Flat tags can be easier to stack in a stacker than curled tags, flat tags can be easier to handle and apply to garments than curled tags, and flat tags have a better appearance. Curled tags present an unsightly appearance. As used herein, the expression “tag web” includes “label webs” and “tags” include “labels”. 
   BRIEF SUMMARY OF THE INVENTION 
   The following represents a simplified summary of some embodiments of the invention in order to provide a basic understanding of various aspects of the invention. This summary is not an extensive overview of the invention nor is it intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some embodiments of the invention in simplified form as a prelude to the more detailed description that is presented thereafter. 
   Aspects of the invention relate to decurling methods and apparatus to decurling tag webs that require decurling so that resultant tags are essentially flat to assist in further handling such as printing and/or stacking and to provide tags of enhanced appearance. Methods for decurling tag webs may include increasing tension on tag webs as they are fed from a supply roll. Methods for decurling may alternatively or additionally include modifying the path of the tag web so as to increase the back bend of the tag webs as they are fed from a supply roll. Systems for decurling may include a motor-driven unwind that can resist the feed of tag webs. Systems for decurling may alternatively or additionally include a movable guide that can be adjusted so as to increase the back bend of the tag webs as the they are fed from a supply roll. 
   Other features and benefits will be evident from the following detailed description and reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example and not limited in the accompanying Figures in which like reference numerals indicate similar elements and in which: 
       FIG. 1  is an elevational view of a printer for printing on tag webs; 
       FIG. 2  is an enlarged elevational view of portions of the printer and a stacker for stacking tags; 
       FIG. 3  is an exploded fragmentary perspective view of one embodiment of a decurler for a tag web also shown in  FIG. 1 ; 
       FIG. 4  is an assembled fragmentary perspective view of the portion of the decurler shown in  FIG. 3 ; 
       FIG. 5  is an elevational view of a fragmentary portion of the printer with an alternative embodiment of a decurler; 
       FIG. 6  is an exploded perspective view of the alternative embodiment of a decurler shown in  FIG. 5 ; 
       FIG. 7  is an enlarged elevational view of the stacker shown in  FIG. 2  with tags that have not been decurled; 
       FIG. 8  is a simplified block diagram of the control for the decurler system; 
       FIG. 9  is a flow chart of the decurler system&#39;s software control; and 
       FIGS. 10 and 11  are charts showing amperages applied to the unwind motor for webs of different materials. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Disclosed are embodiments of methods that comprise providing a tag web wound into a supply roll, the tag web having a curl from having been-wound into a supply roll, the amount of curl in the tag web increasing as the distance between the outside of the supply roll and the center of the supply roll decreases, and performing either one or both of the following steps: increasing the tension in the tag web as the tag web is fed from the supply roll, and modifying the path of the tag web to increase the back bend or reverse bend in the tag web as the tag web is fed from the supply roll. The result is the production of flatter tags. Also disclosed is apparatus for performing the disclosed methods. 
   The disclosed embodiments can use a motor-driven unwind to supply the tag web under tension and a feed roll to feed the tag web. The motor for the unwind produces a back-electromotive force (back-EMF), which is useable to increase electrical energy to the motor and/or to move a movable guide to increase a reverse bend in the tag web. Thus, the unwind and the movable guide roll cooperate to provide a decurling system usable in conjunction with utilization devices such as printers and/or stackers. 
   In controlling the decurling, assessment or monitoring of the amount of curl at any place in the web in the supply roll is made preferably continuously during the operation of the utilization device such as the printer. A preferred method and apparatus is to sense or measure the back-EMF of the unwind motor because the back-EMF is representative of the amount of curl in the web at the place where the web is paid out of the supply roll. An alternative is to assess or monitor the speed of rotation of the supply roll by a suitable encoder. This can be accomplished by sensing or monitoring the speed of rotation of the supply roll directly or by a shaft encoder on the unwind or on the unwind motor shaft which is also representative of the amount of curl at the place the web is paid out of the supply roll. Yet another way is to sense the radius of the supply roll by a mechanical or optical sensor. 
   Before discussing additional details of embodiments of the present invention, reference may be had to application Ser. No. 10/779,990, for certain details of construction. It should noted that the references character used in the present application to designate components are used in a similar manner in the Ser. No. 10/799,990 application. 
   Referring now to  FIG. 1 , a printer  50  is used to print on webs W which can be comprised of various materials, such as coated tag webs, uncoated tag webs, fabric label webs and pressure sensitive label webs. The printer  50  includes a stacker  51  which is shown in  FIG. 2  for clarity of illustration. As depicted, the printer  50  includes an unwind or unwind mechanism  52  which mounts a web supply roll R. The unwind mechanism  52  includes a D.C. electric motor  211  that rotates a hub  181  through gearing G. A core C of the supply roll R is mounted on the hub  181 . The unwind  52  applies a tensioning force to the web W by attempting to rotate the roll counterclockwise, that is, opposite to the direction of arrow A in  FIG. 1 . However, the force exerted on the web W to feed the web W through the printer  50  overcomes the force exerted by the unwind  52  to enable the web W to be fed through the printer  50 . 
   The printer  50  includes print head assemblies  53  and  55  with respective print heads  53 ′ and  55 ′. Platen rolls  54  and  56  can cooperate with respective print heads  53 ′ and  55 ′ to print on lower and upper sides of the web W. Unlike in the printer of application Ser. No. 10/779,990, both platen rolls  54  and  56  are idler rolls. It should be noted that the dispositions of the print head assemblies  53  and  55 , the platen rolls  54  and  56  and the web path is slightly different in  FIG. 1  than in application Ser. No. 10/779,990. A feed mechanism  58  includes a driven feed roll  90  best shown in application Ser. No. 10/779,990. The feed roll  90  feeds the web W to a cutter  59 . The cutter  59  cuts the web W into predetermined length sheets such as tags or labels. In the case of tags T, they are fed into the stacker  51  by its stacker feed mechanism  60 . The stacker  51  is attached to a frame plate  70  of the frame of the printer  50 . 
   The printer  50  is illustrated to be a thermal transfer printer although the invention is applicable to other types of printers such as electrographic, ink jet, laser printers, stackers and other devices. The printer  50  includes microprocessor controlled ink ribbon systems  62  and  63 , each which may be controlled as disclosed in U.S. Pat. No. 5,820,277. The systems  62  and  63  bring ink ribbons I to between the print head  53 ′ and the platen roll  54  and the print head  55 ′ and platen roll  56 , respectively. 
   The web W has been wound into the supply roll R and the amount of curl in the tag web increases as the distance between the outside of the supply roll and center of the supply roll decreases. Due to the memory of the tag web, certain web materials take a substantial set, that is, they retain a substantial amount of their curl after having been fed out or paid out of the supply roll. It can be seen that the amount of curl in the outer wrap OR is substantially less than the curl in the inner wrap IR. 
   With reference to the embodiment of  FIGS. 1 through 4 , there is provided a decurling system generally indicated at  10 . The decurler system  10  is shown in  FIG. 3  to include a decurler  10 D having an electric motor  11  to drive a gear or pinion  12  rotatably mounted in a block  13 . The block  13  is bolted to the frame plate  70 . The block  13  has a T-slot  14  which slidably receives a rack or gear  15 . The rack  15  has gear teeth  16  that are coupled by meshing with teeth  17  of the pinion  12 . The block  15  mounts a shaft  18 . The shaft  18  is secured to the rack  15  by a screw  19 . The shaft  18  extends through a slot  20  in the frame plate  70  and rotatably mounts a guide in the form of a roll  21 . Rotation of the pinion  12  by the motor  11  causes the rack  15  and the roll  21  to translate in a straight line to change the position of the roll  21 . 
   The guide  21  and the web W are shown in solid line positions in  FIG. 1 , wherein the outer wrap OR of the web W of a substantially full roll R passes partially around or about the movable guide  21 . From there, the web W passes through a bend  22  partially around or about a preferably fixed guide  23 . 
   In that the web W is bent in a direction opposite to the curl, the modestly curled web is straightened. From there the web W passes partially around a preferably fixed guide  24 . From there the web W passes to print heads  53 ′ and  55 ′ in succession, then to the feed mechanism  58  and to the cutter  59 . When a stacker  51  is provided, the stacker feed mechanism  60  feeds the cut tag T into a stack S in the stacker  51 . It is the portion of the web path between the movable guide  21  and the fixed guide  23  that is modifiable by moving the guide  21 . The guide  21  is also shown in a different position by phantom line PL. In the phantom line portion of the guide  21 , the reverse bend  22  in the W has greatly increased. Accordingly, as the curl in the web increases upon depletion of the roll R, the decurling action increases because the guide  21  is moved toward the phantom line position progressively to cause the web to undergo greater and greater bending in a direction opposite to the curl in the web W. 
   In the embodiment of  FIGS. 5 and 6 , which is the same as the embodiment of  FIGS. 1 through 4  except as otherwise shown and described, decurler  10 D′ of the system  10  includes a guide  25  which takes the form of a curved plate or partial circular cylinder controlled as best shown in  FIG. 6 . A bracket  26  is secured to the rear face of the frame plate  70 . Bearings  27  and  28  mounted in the bracket  26  and the frame plate  70 , respectively, rotatably mount a shaft  29 . The shaft  29  is secured to an arm  29  and to a compound gear. The gear  30  includes a small gear (not shown in  FIG. 6 ). The small gear of the compound gear  30  meshes with a compound gear  31  which includes a pinion  31 ′ is directly driven by a D.C. motor  33 . The guide positioning motor  33  is mounted to the bracket  26 . The arm  29  includes a tubular portion  34  through which the shaft  29  extends and a tubular portion  35  which receives and is secured to a shaft  36 . The shaft  36  extends through an arcuate slot  37  in the frame plate  70 . The guide  25  preferably has a smooth low-friction outer surface that contacts the web W. 
   When the motor  33  is energized it can cause the movable guide  25  to move between the phantom line position shown by phantom lines PL′ and the solid line position shown in  FIG. 5 . The web paid out of the roll R in the phantom line position is shown at W′. From there the web indicated: at W′ passes partially around the guide  25  and from there through a bend  22  partially about the fixed guide  23 . As the roll is depleted the motor  33  moves the guide progressively toward the solid line position at which the reverse bend  22  is the greatest. Thus, in the phantom line position, the position for the guide  25  causes the web to undergo the least bending as the web passes about the guide  23 , whereas in the solid line position, the position of the guide  25  causes the web to undergo the greatest reverse bending. In all positions of the guide  25 , the web is bent in a direction opposite to the curl, as in the embodiment of  FIGS. 1 through 4 . 
     FIG. 7  illustrates how poorly certain curled tags T′ would stack in the stacker  51 , a situation the decurler system  10  avoids. 
   The use of a small diameter core for the supply roll can be beneficial because more web can be loaded onto a small diameter core. The amount of curl in the web can be problematic with some web materials when the diameter of the core is small. By way of example, not limitation, a small diameter core can have a three inch (7.62 cm) diameter. A more usual size core has a four inch (10.16 cm) diameter. Thus, the web within a radius of one and one-half inches (3.81 cm) and two inches (5.08 cm) has considerably more curl than the web at greater radii. The method and apparatus of the invention are useful with supply rolls of various sizes including those with small diameter cores. 
   Turning to  FIG. 8 , a schematic representation of an embodiment of a control system  800  for a decurler system. A controller  810 , which includes a micro processing unit (MPU)  815  and a memory module  820 , provides control signals to a motor driver  830  that controls an unwind motor  211 . A back-EMF sensor  850  is coupled to the unwind motor  211  and configured to detect back-EMF from the unwind motor  211  and provide feedback to the controller  810 . The controller  810  also provides control signals to a motor driver  835 , which controls a guide positioning motor  33 . In an embodiment, the controller  810  interacts with the detected back-EMF signal provided by the back-EMF sensor  850  according to executable instructions stored in the memory module  820 . 
   As can be appreciated, the memory module  820  may be one or more memories and may further comprise one or more types of memory, including but not limited to, flash memory, random-access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM). As the use and select of various type of memory is known in the art, no further discussion of the memory module  820  will be provided. 
   It should be noted that while depicted as two separate components, the motor driver may be a single component configured to control both the unwind motor  211  and the guide positioning motor  33 . Furthermore, the motor driver may be incorporated into the controller and may also be included in the motors themselves. However, as can be appreciated, some mechanism for converting the digital signals of the controller to analog control signals for the motor should be provided such as, for example, commercially available analog-to-digital converters. 
   It should be noted that an embodiment of the controller may comprise an amalgam of hardware and software. As can be appreciated, application specific integrated circuits (ASICs) without separate software may also be used to implement aspects of the present invention. 
     FIG. 9A  depicts a high-level process for using the control system  800 . First in step  901 , the stock unwind speed is determined. In an embodiment, the speed may be determined by a signal provided from the back-EMF sensor, which may measure voltage across the unused winding of a brushless DC motor. Thus, in an embodiment, the rotational velocity of the stock roll may be determined by measuring the resultant back-EMF generated by the unwind motor. As can be appreciated, numerous other methods of determining the rotational velocity of the stock roll are possible. In an embodiment without an unwind motor, for example, an optical sensor (not shown) could be configured to measure the rotational velocity of the stock roll. As the use of sensors to measure rotation velocity is well known in the art, no further discussion will be provided. 
   Next in step  903 , the diameter of the stock roll is determined. In an embodiment, this can be determined by comparing the rotational speed of the stock roll with the print speed. Alternatively, a sensor (not shown) may be used to determine the diameter of the stock roll. Such a sensor may physically measure the size or may provide information, such as the weight of the stock roll, that allows the diameter of the stock roll to be determined through some other calculation. 
   Next in step  905 , a check is made to determine the appropriate settings for parameters of the decurling system in view of the current diameter. As noted above, it can be useful to increase the amount of either tension or bend back or both as the diameter of the stock roll decreases so as to overcome the set of the tag web due to the decreased radius. As can be appreciated, the change in the parameters may be linear with the change in the radius of the bend in the tag web or it may be non-linear, depending on the material and the lower diameter limit of the stock roll. As can be appreciated, some materials may require more than a proportional increase in decurling efforts while other materials may respond equally well to a decurling effort that is capped at some upper limit of decurling effort. 
   Then in step  907 , the parameters of the decurling system are adjusted to account for the current stock roll diameter. In an embodiment, an increased current may be supplied to the unwind motor  211  ( FIG. 8 ) so as to increase the resistance to the feeding of the tag web stock. In an alternative embodiment, the position of the movable guide  21  ( FIG. 1 ) may be adjusted so as to provide additional back bend to the tag stock as it travels along the feed path. In another alternative embodiment, both the resistance provided by the unwind motor  211  and the bend back provided by the movable guide  21  may be adjusted. 
     FIG. 9B  provides a more detailed embodiment of the method generally disclosed in  FIG. 9A . As can be appreciated, the method in disclosed in  FIG. 9B  includes steps that are typically performed by a printer. However, this embodiment is merely representative and steps may be omitted or additional steps may be added as is appropriate. 
   In step  910 , power is turned on. Next in step  915  the guide is moved to its home position. It should be noted that the roller referred to in step  915  may also be referred to as the guide  21  or the guide  25 . In step  920  a check is made to see if the printer is printing. If it is not, in step  925  a check is made to see if the guide is the home position. If the guide is not in the home position, in step  930  the guide is moved to the home position. Steps  920  and  925  are repeated until the printer begins to print. As can be appreciated, this check may take place at some predetermined frequency that is determined to be sufficiently often so as to avoid undesirable delays between the initiation of printing and the adjustment of the decurling parameters. 
   Once it is determined that the printer is printing, in step  935  the unwind speed of the stock roller is determined by reading the unwind motor back-EMF. The speed may be determined in rpm&#39;s or some other unit of measurement such as radium per second (which is a simply rpm&#39;s multiplied by (π/30)). Next in step  940 , the stock roll diameter is determined by comparing the unwind speed of the stock roll with the print speed. As is known, the arc length s=θr where θ is in radians. As the print speed may be determine in units of distance per second, the radius may be approximated as r=v/ω. Therefore, as v (the printer speed) is known and ω, the angular speed is known because of the determination in step  935 , r can be determined. Of course this will only provide an approximate answer because r is not constant; however such a method should be sufficiently accurate for the diameter determination of step  940 . 
   Next in step  945 , the appropriate table is selected depending on the material that is being used. Examples of tables are provided in  FIGS. 10 and 11 . As can be appreciated from tables  10  and  11 , both a guide displacement value and a current value may be provided. It should be noted that these values can vary depending on the size of the guide and the efficiency of the unwind motor and the type of material. Consequently, the provided values are for illustrative purposes. It should be noted that in an embodiment, the type of material can be entered or selected by a user. In an alternative embodiment, the stock roll may include an indicium or some type of indicator that can be read by the printer so that the type of material is known. For example, a radio frequency identification (RFID) transponder in the stock roll could be used to provide the type of material. 
   It should also be noted that while both a current value and a guide position are provided, in an embodiment where only one or the other is adjustable it is expected that the parameter that is not adjustable will not be provided. For example, if the position of the movable guide automatically adjusts as the diameter of the stock roll decreases (perhaps due to an interaction with a guide that maintains contact with the surface of the stock roll), then only the current of the unwind motor may be adjusted. Alternatively, if the current of the unwind motor is left fixed so as to simplify the controls, then only the position of the guide motor may be adjusted. While either of these approaches may be less flexible, for situations where there is less of a variation in the type of tag web they may provide desirable results at a reduced cost. 
   Next, in step  950 , the current radius is used to determine the desired current and (guide position. It should be noted that additional values may be provided for more fine-grained control. Alternatively, the radius of the stock roll may be rounded off to the depicted level of precision. 
   In step  955 , the current is adjusted per the value provided in the table. Next in step  960 , a check is made to determine whether the guide is in the correct position. As can be appreciated, a stepper motor may be used so as allow the controller  810  ( FIG. 8 ) to track the position of the movable guide (by counting the number of steps). In an alternative embodiment, Hall-effect sensors could be used to track the rotations of the motor and thus be used to determine the current position of the guide based on a known initial position. Alternatively, the translation of the movable guide may be resisted by a biasing element that stores potential energy (such as a spring). Assuming a linear relationship, the equation F=kx may be used, where F is the force, k is the spring constant (which will be known) and x is the displacement in length. By measuring the force, the displacement x can be ascertained (and thus the position of the roller determined). As can be appreciated, however, numerous other known methods of determining the location of the movable guide and the associated roller may be used. 
   If the guide is in the correct position, the check in step  920  is repeated. However, if the guide is not in the correct position, in step  965  the guide is moved to the correct position and then the check in step  920  is repeated. 
   As can be appreciated, additional methods of initiating the steps  935  through  960  are possible. In an embodiment, the controller  810  ( FIG. 8 ) may keep track of whether the printer is printing and rather then a looped check as depicted, box  920  may simply wait for a signal that the indicates the printer is printing without checking. Furthermore, if a variable current is not supplied to an unwind motor then steps  950  and  955  may be omitted. Other variations in the method depicted will occur to a person of ordinary skill in the art. 
   The present invention has been described in terms of preferred and exemplary embodiments thereof. Numerous other embodiments, modifications and variations within the scope and spirit of the appended claims will occur to persons of ordinary skill in the art from a review of this disclosure.