Abstract:
A system and method for decurling a sheet medium including a first penetrating roller and a second elastomeric roller mounted substantially parallel. A pressure-sensitive electrically conductive material has properties that vary with its state of compression. An actuator is operative for moving the first penetrating roller and the second elastomeric roller in a direction towards each other, to penetrate the body of the second elastomeric roller with the body of the first penetrating roller. The pressure-sensitive electrically conductive material is subject to pressure by the penetration of the first penetrating roller into the second elastomeric roller. A pair of electrical terminals applies an electrical charge across the pressure-sensitive electrically conductive material. In further embodiments, an electrical property is substantially continuously measured and the depth of penetration is substantially continuously controlled based upon closed-loop feedback of the substantially continuously measuring.

Description:
BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates document creation. More specifically, the present disclosure is directed to a system and method for actively detecting the depth of penetration of a decurling roller 
     2. Brief Discussion of Related Art 
     In a printer, substrate media, e.g., paper, vellum, etc., is often turned over rollers or drums, etc., for example to change direction of media transport in handling and/or to effect printing processes. Occasionally and to varying degrees, the media retains the shape of the bend, which is referred to as “curl”. Curl is often detrimental to further handling and processes, and is undesirable in the finished document. 
     To address the problem of curl, U.S. Pat. No. 6,282,403 to Spencer, et al. (“Spencer”), hereby incorporated by reference, discloses a Decurler Roll Setup. The solution embodied in Spencer, e.g., is to pass the media over a decurling roller that has a radius in the opposite direction of the curl, to reverse the curl and result in a flatter media. For example, it is known from Spencer to use a pinch roller in conjunction with an opposing elastomeric roller, with the pinch roller penetrating the elastomeric roller and the media passing between the two rollers (Spencer, FIG. 2B). Accordingly, the elastomeric roller presses the media (sheet “S”) over the pinch roller. Furthermore, in such an embodiment, the pinch roller has substantially smaller radius, as compared with both the radius of the curl exhibited in the media, and the opposing elastomeric roller. 
     In a decurling technique and apparatus as just disclosed by Spencer, the amount by which the media is to be decurled is variable, and is dependent upon the depth of penetration of the pinch roller into the elastomeric roller. Accordingly, the relative position of the two rollers must be controlled to a high degree of precision and accuracy. Accurately determining the relative position of the pinch and elastomeric decurling rollers in Spencer requires a relatively lengthy homing process (Spencer,  FIG. 7 ), which slows cycle time and is a significant source of customer dissatisfaction. 
     Further, the process only infers the positions of the rollers by calculation. In order to calculate the position accurately, extremely tight tolerances in the mechanism are required, which increases build costs. 
     Lastly, one common and cost-effective method of locating the rollers is by use of a cam driven by a step motor. However, the failure to hold position of the cam under load is another source of error in decurling operation. Spencer does not provide real-time feedback of the relative positions between the pinch roller and the elastomeric roller. Therefore, an inadvertent shift of position by the step-motor driven locating system cannot be detected. 
     SUMMARY 
     In order to overcome these and other drawbacks in the present art, provided according to the present disclosure is a system for decurling a sheet medium including a first penetrating roller mounted for rotation around a first longitudinal axis and a second elastomeric roller mounted for rotation around a second longitudinal axis, the first and second longitudinal axes being substantially parallel with one another. The second elastomeric roller comprises a pressure-sensitive electrically conductive material which has electrically conductive properties that vary with its state of compression. An actuator is operative for moving one of the first penetrating roller and the second elastomeric roller in a direction transverse to the respective second or first longitudinal axis of the other, and to penetrate the body of the second elastomeric roller with the body of the first penetrating roller. The pressure-sensitive electrically conductive material is configured such that it is subject to pressure by the penetration of the first penetrating roller into the second elastomeric roller. A pair of electrical terminals is configured and operative to apply an electrical charge across the pressure-sensitive electrically conductive material. 
     The second elastomeric roller may optionally comprise an electrically conductive layer surrounding the pressure-sensitive electrically conductive material of the second elastomeric roller. At least one electrical terminal of the pair is held in contact with an outer surface of the elastomeric roller. In certain embodiments of the present disclosure, one electrical terminal is electrically connected with the first penetrating roller, and the second electrical terminal is electrically connected with the second elastomeric roller. The pair of electrical terminals may optionally be collectively arranged to apply the electrical charge axially or radially though the second elastomeric roller. 
     In certain embodiments of the present disclosure, the first penetrating roller has a hardness greater than the second elastomeric roller. In certain embodiments of the present disclosure, the first penetrating roller has a diameter smaller than the second elastomeric roller. 
     The actuator according to the present disclosure may comprise one or more cams configured and operative to act on a corresponding number of followers positioned on the respective first penetrating roller or second elastomeric roller. A motor may be configured and operative to rotate the one or more cams, the motor selected from the group comprising an electric step motor, an electric servo motor, and a fluid-powered motor. 
     Also provided according to the present disclosure is a method for decurling a sheet media includes feeding a sheet media between a first penetrating roller and a second elastomeric roller. The second elastomeric roller comprising a pressure-sensitive electrically conductive material which has electrically conductive properties that vary with its state of compression, wherein the body of the first penetrating roller penetrates the body of the second elastomeric roller. The pressure-sensitive electrically conductive material of the second elastomeric roller is configured such that it is subjected to pressure by the penetration of the first penetrating roller into the second elastomeric roller. An electrical property of the pressure-sensitive electrically conductive material is measured; and the depth of penetration of the first penetrating first roller into the second elastomeric roller is set based upon the measured electrical property. 
     In further embodiments of the presently disclosed method, an electrical property of the pressure-sensitive electrically conductive material is substantially continuously measured and the depth of penetration is substantially continuously controlled based upon closed-loop feedback of the substantially continuously measuring. Optionally, wear in the second elastomeric roller may be measured based upon the relative positions of the first penetrating roller and the second elastomeric roller. 
     In further embodiments of the presently disclosed method, setting the depth of penetration of the first penetrating first roller into the second elastomeric roller comprises operating an actuator operative for moving one of the first penetrating roller and the second elastomeric roller in a direction transverse to the respective second or first longitudinal axis of the other. The actuator may comprise one or more cams configured and operative to act on a corresponding number of followers positioned on the first penetrating roller or second elastomeric roller. A motor, selected from the group comprising an electric step motor, an electric servo motor, and a fluid-powered motor, may be configured and operative to rotate the one or more cams. 
     The presently disclosed method may optionally include applying an electrical charge across the pressure-sensitive electrically conductive material, for example in one of a radial or axial direction. The property measured may comprise the current or voltage of the applied electrical charge. 
     These and other purposes, goals and advantages of the present application will become apparent from the following detailed description of example embodiments read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings in which: 
         FIG. 1  illustrates a front elevation view of a decurler system according to an embodiment of the present disclosure, having a penetrating roll and a decurling roll disengaged from one another; 
         FIG. 2  illustrates an end elevation view of the decurler system depicted in  FIG. 1 ; 
         FIG. 3  illustrates a front elevation view of a decurler system according to an embodiment of the present disclosure, having a penetrating roll and a decurling roll engaged with one another; 
         FIG. 4  illustrates an end elevation view of the decurler system depicted in  FIG. 3 ; and 
         FIG. 5  illustrate an axial cross-section taken along line  5 - 5  of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Introduction 
     As used herein, a “printer” refers to any device, machine, apparatus, and the like, for forming images on substrate media using ink, toner, and the like. A “printer” can encompass any apparatus, such as a copier, bookmaking machine, facsimile machine, multi-function machine, etc., which performs a print outputting function for any purpose. Where a monochrome printer is described, it will be appreciated that the disclosure can encompass a printing system that uses more than one color (e.g., red, blue, green, black, cyan, magenta, yellow, clear, etc.) ink or toner to form a multiple-color image on a substrate media. 
     As used herein, “substrate media” refers to a tangible medium, such as paper (e.g., a sheet of paper, a long web of paper, a ream of paper, etc.), transparencies, parchment, film, fabric, plastic, paperboard up to between about 26 and 29 point (i.e., about 0.026-0.029 in. thickness) or other substrates on which an image can be printed or disposed. 
     Description 
     Referring now to  FIGS. 1 &amp; 2 , illustrated is an active decurler adjustment system, generally  10 , according to an embodiment of the present disclosure, in front and side elevations views, respectively. A penetrating roll  12  is mounted on an axle  14 , for example a prismatic spline, and is rotatable with the axle  14  around a longitudinal axis. The axle  14  is driven by a motor or the like (not shown). An opposing elastomeric roller  16  is mounted on an axle  18 , which may also be a prismatic spline, and is likewise rotatable with the axle  18  around a longitudinal axis. Elastomeric roller  16  and axle  18  are further optionally driven by a motor or the like (not shown) instead of or in addition to a rotational force driving the axle  14  of the penetrating roll  12 . 
     The axle  18  is mounted to translate in a direction transverse to the axis of the penetrating roll  12 , in this case vertically, to bring the elastomeric roll  16  into engagement with the penetrating roll  12 . In one embodiment, one or more cams  20   a ,  20   b  are mounted on an axle  22 , for example a prismatic spline, and rotate with the axle  22 . The axle  22  is in turn driven by a actuator  24 , in this example a stepper motor, to position and hold the cams  20   a ,  20   b , which act on the axle  18  through cam followers  26   a ,  26   b , formed thereon, which are in this case embodied as collars on the axle  18 . Alternately or additionally, the motor may comprise a servo motor, or a hybrid motor, or a fluid-powered motor. It will also be appreciated that optionally the cams may be moved linearly rather than or in addition to rotationally. Within the range of motion of the elastomeric roll  16 , and space  28  may be formed to admit a substrate media, for example a cut sheet of paper. The space  28  may be closed to the penetrating roller  12  penetrates the body of the elastomeric roller  16 , as illustrated, for example, in  FIGS. 3-5 , described further below. 
     It will be appreciated by those skilled in the art and in light of the instant disclosure that the penetrating roll  12  may be moved into or out of engagement with the elastomeric roll  16  rather than, or in addition to, the motion of the elastomeric roll  16  as previously described. The apparatus effecting the motion of the penetrating roll  12  may be similar to that described above with respect to the elastomeric roll  16 , or either or both may be substituted by those known in the art without departing from the scope of the present disclosure. 
     Referring now to  FIGS. 3 and 4 , illustrated is the active decurler adjustment system  10 , showing the penetrating roll  12  engaged with the elastomeric roll  16 . As illustrated in  FIGS. 3 &amp; 4 , the actuator  24  rotates axle  22  and therewith cams  20   a ,  20   b , which act on followers  26   a ,  26   b , respectively. Axle  18  and elastomeric roller  16  is thereby moved towards axle  14  and penetrating roll  12 . 
     According to the present embodiment, the elastomeric roll  16  has electric properties which vary with its state of compression. A pressure-sensitive and electrically conductive roller is disclosed, for example, in U.S. Pat. No. 5,458,324 to Nakamura, et al. (“Nakamura &#39;324”) or U.S. Pat. No. 5,499,807, also to Nakamura, et al. (“Nakamura &#39;807”), the complete disclosures of which are hereby incorporated by reference for all purposes. Generally speaking, the electrical characteristics of the pressure-sensitive roller vary according to its state of compression. In one embodiment, a voltage is applied to the axle  14 , for example at a terminal  30 , in which case the axle  14  would comprise an electrically conductive material. A current would be generated in the axle  14 , pass through the penetrating roll  12 , also electrically conductive, into the elastomeric roll  16 . This arrangement presumes an area of electrical conductivity between the penetrating roll  12  and the elastomeric roll  16 , for example in an area of contact between the two outside the borders of the sheet media passing between them for decurling, or else through the sheet media depending upon its electrical properties of conductivity or resistivity. 
     The current flowing from is directed through a pickup  32 , which is electrically connected with a neutral voltage  38 . The pickup  32  may include a roller  34  and a spring  36  to bias the roller  34  against the elastomeric roll  16 , in order to maintain contact with the roller and thus an electrical circuit from the terminal  30  to the pickup  32 . The current induced by the voltage can be sensed, and changes in the current that result with changes to the state of compression of the elastomeric roll  16  can be detected. Changes in this flow of current can be calibrated to represent the corresponding depth of penetration of the penetrating roll  12  into the elastomeric roll  16 . 
     Alternately, a voltage may be applied axially across the elastomeric roll  16 , i.e., from one axial end thereof to the other, for example by a duplicate follower  32  placed at the opposite axial end. The resulting current induced through the elastomeric roll will show variation with the state of compression of the elastomeric roll  16 . In that case, it may be beneficial to avoid any short circuit or parallel path, for example through the axle  18 . Alternately, a sensing voltage may be applied radially across the elastomeric roll  16 , for example between a follower  32  and the axle  18 . Moreover, follower  32  may be replaced or supplemented by a brush or the like. 
       FIG. 5  illustrates a detailed view of the penetrating roll  12  engaged with the elastomeric roll  16 . The depth of penetration of the penetrating roll  12  into the elastomeric roll  16  is indicated at dimension lines  40 . In  FIG. 5 , the elastomeric roll  16  is shown in one optional configuration having an electrically-conductive pressure-sensitive outer cylinder  42  surrounds an inner core  44 , radially inward from the outer cylinder  42 . Both are mounted together on and rotate with the axle  18 . The elastomeric roller  16  may further optionally include an outer conductive layer  46  to evenly distribute an applied electrical current or voltage across its surface. The electrical properties of the outer cylinder  42  are modeled schematically as a plurality of resistors, R 1 , R 2 , R 3 , R 4 , R 5 . The properties of the electrically-conductive pressure-sensitive material comprised in the outer cylinder  42  are such that the change in compression alters the resistivity of the material. This change in resistivity is measurable by detecting the change in voltage drop across the electrically-conductive pressure-sensitive material exhibited in a test current, as the electrically-conductive pressure-sensitive material is subjected to varying degrees of compression. 
     The system and methods according to the present disclosure have several advantages. Among these, the depth of penetration of the penetrating roll  12  into the elastomeric roll  16  may be directly measured, not merely inferred. Therefore, the system is more accommodating of wider tolerances in manufacturing, and thus manufacturing costs are less. Because the depth of penetration of the penetrating roll  12  into the elastomeric roll  16  is directly measured, it can be monitored in real-time during a decurling operation and controlled in a closed-loop manner based upon the measurement feedback. Any error, for example imparted by inadvertent slippage of the actuator  24  driving the cam axle  22 , can be immediately detected and corrected. 
     The system according to applicant&#39;s instant disclosure is also substantially immune to the effects of wear in either roll  12  or  16 , but mostly elastomeric roll  16 . Because the depth of penetration is measured as electrical changes dependent upon the state of compression, to the extent that the elastomeric roll  16  diameter is reduced in service due to wear, the relative position of the rolls  12 ,  16  are simply adjusted until a necessary depth of penetration is achieved, which directly correlates with the decurl characteristics imparted to the media. Moreover, by sensing for changes to the electrical current applied across the elastomeric roll  16  during the positioning of the roll  16  by the actuator  24 , the presence and amount of any wear of the elastomeric roll  16  can be detected. 
     Because the interface of the penetrating roll  12  into the elastomeric roll  16  is directly detected through changes in the electrical properties of the elastomeric roll  16 , the manner of positioning a penetrating roll  12  and an elastomeric roll  16  according to the present disclosure further eliminates the need for a preliminary homing operation to infer its position. This, in turn, improves (by shortening) the initialization and start-up times of a printer implementing such a system. 
     It will be appreciated by those skilled in the art that certain alterations or modifications of the system and methods of the present disclosure, including their features and functions, or alternatives thereof, may be apparent. The same may be desirably combined into many other different systems or applications. The systems and methods disclosed are offered as merely exemplary of, and not liming on, the scope of the present disclosure. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.