Patent Publication Number: US-2016222552-A1

Title: Systems and methods for electrostatically individualizing and aligning fibers

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/109,996 entitled “Systems and Methods for Electrostatically Individualizing and Aligning Fibers,” filed Jan. 30, 2015, which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Fiber length measurement is a longstanding problem in textile and para-textile materials characterization. It is a particularly challenging task in applications using natural fibers, such as cotton. Among all measured characteristics of cotton and most other fibrous materials, length has typically been considered the most crucial. The market value and end-use of the fiber along with the processes adopted for its transformation are largely determined by its length properties. Unfortunately, reliably characterizing the length distribution in a bulk fiber sample is rather challenging, and existing solutions present multiple biases and shortcomings. One major challenge stems from the intrinsic variability of single fiber lengths, which is typically determined by complex interactions involving genetic, environmental, and processing factors. As a result, obtaining a representative sample from a bulk fiber lot can be troublesome. 
     Currently, there are two major approaches for addressing this problem. One approach is fiber bundle sampling, and the other approach is single fiber measurement. Fiber bundle sampling includes clamping a bundle, or “beard,” of parallel fibers by using a set of combs and brushes. The beard is scanned for length measurement, or to determine the “fibrogram.” Due to the sample clamping, the shortest fibers are not scanned, which leads to a bias of the length distribution toward the long fibers. In a single fiber measurement approach, fibers are individualized using an aeromechanical opener or separator and individually conveyed through a set of optical sensors that generate electrical signals proportional to the fiber length. One major shortcoming of current methods using the single fiber measurement approach is that in the process of measuring fibers, breakage typically occurs at the mechanical opening, which biases the measured length distribution toward the shorter fibers. 
     Accordingly, systems and methods are needed for individualizing fibers and measuring the individual fibers without breaking the fibers or biasing the measurements. 
     SUMMARY 
     Various implementations include systems and methods of using electrostatic forces to separate samples into individual fibers with minimal to no breakage and align the individual fibers with minimal handling. These systems and methods allow for testing, such as measuring the length, of individual fibers without the biases caused by breakage or bundling that are present in prior art systems and methods. These systems and methods may also be useful in applications requiring fiber alignment with minimal material handling. 
     For example, various implementations include a pair of nip rollers and a collector that are spaced apart from each other to define an air gap therebetween. The nip rollers are grounded or negatively charged, for example, and the collector is positively charged to create an electrostatic field in the air gap. The electrostatic field separates the fibers, elongates the fibers end to end, and urges the fibers toward the collector. In other implementations, the nip rollers may be positively charged and the collector grounded or negatively charged to create the electrostatic field in the air gap. In certain implementations, the system may also include a power supply (e.g., a high voltage DC power supply) for creating a voltage difference between the nip rollers and collector. 
     In certain implementations, the collector is a collection roller that has an axis of rotation that is parallel to the first and second axes of rotation, and the direction of rotation of the collection roller is the same as the direction of rotation of the second nip roller, which is disposed below the first nip roller. The collector may also include a plate or other suitable collection device, according to other implementations. 
     In addition, the system may also include an imaging system that has a field of view that includes at least a portion of the air gap between the exit side of the nip rollers and the collector. The imaging system receives image signals of each fiber passing through the air gap, and the image signals may be used to measure a length and/or diameter of each fiber or to inspect each fiber. The imaging system may further include one or more digital cameras and one or more light sources, for example. 
     The system may also include a suction device, such as a vacuum collection device, that is disposed adjacent an exit side of the collector. The suction device urges each fiber passing over or through the collector from an entry side of the collector to the exit side of the collector to enter the suction device for collection after one or more images of each fiber is received. 
     Furthermore, the system may also include additional pairs of nip rollers disposed upstream of the first and second nip rollers that receive a beard of fibers and feed the fibers toward the entry side of the first and second nip rollers. 
     Various implementations further include a method of separating and aligning fibers. The method includes: (1) rotating a pair of nip rollers, an exit side of the nip rollers being spaced apart from an entry side of a collector to define an air gap therebetween; (2) creating an electrostatic field in the air gap; and (3) feeding a beard of fibers between the nip rollers. The electrostatic field separates the fibers, elongates the fibers end to end between the exit side of the nip rollers and the entry side of the collector, and urges the fibers toward the collector. A width of the air gap from the exit side of the nip rollers to the entry side of the collector is larger than a maximum length of any fiber within the beard of fibers. 
     In certain implementations, the method also includes capturing image signals of the separated and elongated fibers in the air gap with an imaging device that has a field of view that comprises at least a portion of the air gap. In addition, the method may also include identifying a length and/or a diameter of each separated fiber using the image signals. 
     Other systems, methods, features, and/or advantages will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The components in the drawings are not necessarily to scale relative to each other and like reference numerals designate corresponding parts throughout the several views: 
         FIG. 1  is a side view of a system for individualizing and aligning fibers according to one implementation. 
         FIG. 2  is a schematic diagram showing various components of the system of  FIG. 1   
         FIG. 3  is a flow chart illustrating various steps of a method of individualizing and aligning fibers, according to one implementation. 
         FIG. 4  is a top perspective view of a system for individualizing and aligning fibers according to another implementation. 
         FIG. 5  is a top perspective view of the housing shown in  FIG. 4 . 
         FIG. 6  is a top perspective view of a system for individualizing and aligning fibers according to another implementation. 
     
    
    
     DETAILED DESCRIPTION 
     Various implementations include systems and methods of using electrostatic forces to separate samples into individual fibers with minimal to no breakage and align the individual fibers with minimal handling. These systems and methods allow for testing, such as measuring the length, of individual fibers without the biases caused by breakage or bundling that are present in prior art systems and methods. These systems and methods may also be useful in applications requiring fiber alignment with minimal material handling. 
     In particular,  FIG. 1  shows a system  10  for using electrostatic forces to individualize and align fibers. The system  10  includes a pair of nip rollers  12   a,    12   b,  a collection roller  14 , a power supply  17 , an imaging system  16 , and a suction device  18 . The nip rollers  12   a,    12   b  include an upper nip roller  12   a  having a first axis of rotation and a first direction of rotation and a lower nip roller  12   b  having a second axis of rotation and a second direction of rotation that is opposite the first direction. The first and second axes of rotation are parallel and vertically aligned. The collection roller  14  is spaced apart from an exit side  15  of the nip rollers  12   a,    12   b,  and the exit side  15  of the nip rollers  12   a,    12   b  and the collection roller  14  define an air gap  13  therebetween. The axis of rotation of the collection roller  14  is parallel to the first and second axes of rotation of the nip rollers  12   a,    12   b  and lies within a horizontal plane extending between the first and second nip rollers. The horizontal plane in the implementation shown in  FIG. 1  is orthogonal to a plane that is tangential to the nip rollers  12   a,    12   b  on the exit side  15 . The direction of rotation of the collection roller  14  is the same as the direction of rotation of the lower nip roller  12   b  so as to move the fibers out of the air gap  13  and toward the suction device  18 . In other implementations (not shown), the axis of rotation of the collection roller  14  may be disposed above or below the horizontal plane extending between the first and second nip rollers  12   a,    12   b  and orthogonal to the plane that is tangential to the nip rollers  12   a,    12   b  on the exit side  15 . 
     Furthermore, the system  10  may also include additional pairs of nip rollers  16   a,    16   b,    19   a,    19   b  disposed upstream of the upper  12   a  and lower nip rollers  12   b.  The nip rollers  16   a,    16   b,    19   a,    19   b  receive a beard of fibers B and feed the fibers toward the entry side  11  of the upper  12   a  and lower nip rollers  12   b.  In other implementations, more or less than three pairs of nip rollers may be used in the apparatus. Implementations having more than one pair of nip rollers may provide better fiber individualization than implementations having only one pair of nip rollers. 
     The nip rollers  12   a,    12   b,    16   a,    16   b,    19   a,    19   b  are physically coupled to one or more support rails that support the axis of rotation of each of the nip rollers  12   a,    12   b,    16   a,    16   b,    19   a,    19   b.  For example, in the implementation shown in  FIG. 4 , first ends of the nip rollers are physically coupled to a first rail  202 , and second ends of the nip rollers are physically coupled to a second rail  204 . In other implementations, all of the nip rollers  12   a,    12   b,    16   a,    16   b,    19   a,    19   b  may be physically coupled to one rail (not shown). And, in another implementation (not shown), upper nip rollers  12   a,    16   a,  and  19   a  may be physically coupled to a first pair of rails, and lower nip rollers  12   b,    16   b,    19   b  may be physically coupled to a second pair of rails. 
     In addition, in some implementations, the rail(s) includes an electrically conductive material, such as aluminum, such that the nip rollers are electrically coupled to each other through the rails and/or through contact with each other. The collection roller  14  is mounted separately from the nip rollers  12   a,    12   b,    16   a,    16   b,    19   a,    19   b  with sufficient electrical insulation to prevent electrostatic discharge between the nip rollers  12   a,    12   b,    16   a,    16   b,    19   a,    19   b  and the collection roller  14 . 
     The power supply  17  is in electrical communication with at least one of the nip rollers  12   a,    12   b,  such as the lower nip roller  12   b,  and the collection roller  14 . The power supply  17  creates a positive electrical charge on the collection roller  14  and a negative electrical charge on the lower nip roller  12   b.  The voltage difference between the nip rollers  12   a,    12   b  and the collection roller  14  creates an electrostatic field in the air gap  13 . As the fibers F pass through the nip rollers  12   a,    12   b,  the electrostatic field causes the fibers F to separate from each other in the air gap  13 , elongate end to end between the exit side  15  of the nip rollers  12   a,    12   b  and an entry side  21  of the collection roller  14 , and move toward the positively charged collection roller  14 . The power supply  17  may be, for example, a DC high voltage power supply, according to certain implementations. 
     In some implementations, the power supply  17  may be electrically coupled to the support rail(s) physically coupled to the nip rollers  12   a,    12   b,    16   a,    16   b,    19   a,    19   b  and/or to one or more of nip rollers  12   a,    12   b,    16   a,    16   b,    19   a,    19   b.  In addition, in other implementations, one or more of the nip rollers and/or rails may be grounded (instead of negatively charged). And, in other implementations, the collector may be grounded or negatively charged, and the nip rollers and/or rails may be positively charged. In one such implementation, the motor and control board are insulated and protected from being influenced by the positive charge. 
     Furthermore, as shown in  FIG. 2 , a motor  25  is provided to drive rotation of one or more of the nip rollers  12   a,    12   b,    16   a,    16   b,    19   a,    19   b.  The speed of rotation may be controlled by a computer processing unit  22 , which is described below. 
     The width of the air gap  13  is selected such that it is greater than the maximum expected length of a fiber F to be passed through the system  10 . This allows the fiber F to be elongated, or extended, to its full length and oriented end to end between the exit side  15  of the nip rollers  12   a,    12   b  and the entry side  21  of the collection roller  14 . In addition, the size of the air gap  13  may be based on the minimum length that allows a fiber F to travel through the air gap  13  and be captured by the imaging system  16  and that allows for proper installation of the imaging system  16  and light source  24 , according to some implementations. For example, in certain implementations, the air gap  13  may be between about 90 and about 100 millimeters. 
     The imaging system  16  has a field of view that includes at least a portion of the air gap  13  between the nip rollers  12   a,    12   b  and the collection roller  14 . The imaging system  16  receives image signals of each fiber F passing through the air gap  13 , and these image signals may be used to measure a length or diameter of or inspect each fiber F. The imaging system  16  may include one or more digital cameras, according to certain implementations. In other implementations, the imaging system  16  may include one or more line scan cameras or optical sensor arrays. In addition, the system  10  may include one or more light sources  24  to illuminate at least a portion of the field of view of the imaging system  16 , according to certain implementations. Light sources  24  may include one or more light emitting diodes (LEDs) or other suitable light source. 
     The suction device  18  is disposed adjacent an exit side  23  of the collection roller  14 . The suction device  18  urges fibers F passing over the collection roller  14  from the entry side  21  of the collection roller  14  to the exit side  23  to enter the suction device  18  for collection after one or more images of each fiber F is collected. According to certain implementations, the suction device  18  may include a vacuum collection device. For example, the vacuum collection device may include a Venturi suction device. 
       FIG. 1  illustrates three fibers F being urged through the system  10 . The full length of fiber F M  is within the air gap  13  and is being imaged by the imaging system  16 . The fiber F P  adjacent the collection roller  14  is the fiber that just passed through the air gap  13  and is being (or is about to be) collected by the suction device  18 . The fiber F N  adjacent the nip rollers  12   a,    12   b  is the fiber that is next to enter the air gap  13 . Occasionally, two or more fibers F advance through the air gap  13  simultaneously, but these fibers F are separated, or spaced apart from each other, by the electrostatic field, which allows the imaging system  16  to capture image signals for each fiber F. 
       FIG. 2  illustrates a schematic diagram of the system  10  according to one implementation. As shown, the system  10  further includes computer processing unit  22  for receiving the image signals from the imaging system  16  and processing the image signals. The computer processing unit  22  may include at least one memory and at least one processor, according to certain implementations. For example, the memory of the computer processing unit  22  may be configured for storing a set of instructions to be executed by the processor that allow the processor to identify a length, a diameter, and/or other characteristics of each fiber F based on the received image signals. The memory of the computer processing unit  22  may also be configured for storing image signals or portions thereof. 
     In certain implementations, the computer processing unit  22  may also be configured for controlling the speed of rotation of one or more motors  25  driving the rotation of one or more of the nip rollers  12   a,    12   b,    16   a,    16   b,    19   a,    19   b  and the collection roller  14 , the suction power of the suction device  14 , the voltage difference between the nip roller  12   a,    12   b  and the collection roller  14 , and/or the light intensity of the light source  24 . For example, the processing unit  22  may be configured to adjust these parameters based on the image signals received from the imaging device  16 . For example, if the image signals indicate that the fibers F are not passing through the air gap  13  individually or aligned as expected, the computer processing unit  22  may adjust the voltage and/or speed of the rollers  12   a,    12   b,    16   a,    16   b,    19   a,    16   b,    14  and/or the suction power of the suction device  18 . In other implementations (not shown), one or more additional computer processing units may be provided to perform one or more of these functions. 
       FIG. 3  illustrates a method  100  of separating and aligning fibers according to one implementation. The method  100  begins as step  101  with rotating the pair of nip rollers, such as nip rollers  12   a,    12   b.  Step  103  includes creating an electrostatic field in the air gap. For example, this step may include applying a positive electrical charge to the collector and grounding or applying a negative electrical charge to at least one nip roller. Alternatively, this may include grounding or applying a negative electrical charge to the collector and applying a positive electrical charge to at least one nip roller. The voltage difference between the nip rollers and the collector creates an electrostatic field in the air gap. Steps  101  and  103  may be performed simultaneously or in sequence. Then, in step  105 , a beard of fibers is fed between the nip rollers. The electrostatic field separates the fibers, elongates the fibers end to end between the exit side of the nip rollers and the entry side of the collector, and urges the fibers toward the collector. Furthermore, a width of the air gap from the exit side of the nip rollers to the entry side of the collector is larger than a maximum length of any fiber within the beard of fibers. Next, at step  107 , image signals of each separated and aligned fiber in the air gap are captured with an imaging device that has a field of view that includes at least a portion of the air gap. Then, at step  109 , a length or diameter of each separated fiber is identified using the image signals. 
       FIG. 4  illustrates a system  200  for separating and aligning fibers according to another implementation. The system  200  includes elements similar to those described in relation to  FIG. 1  except as noted. In particular, the system  200  includes a fringe roller  210  disposed immediately adjacent the exit side  15  of nip rollers  12   a,    12   b.  The fringe roller  210  has an axis of rotation that is parallel to the axes of rotation of nip rollers  12   a,    12   b  and rotates in the same direction as the lower nip roller  12   b.  At least a portion of the fringe roller  210  includes a combing surface  211  that is configured for gently urging the fibers F exiting the nip rollers  12   a,    12   b  into the air gap  13 . Thus in certain implementations, the spacing between the exit side  15  of the nip rollers  12   a,    12   b  and the fringe roller  210  is sufficiently small to allow the combing surface  211  to contact the fibers as they exit the nip rollers  12   a,    12   b.    
     A second motor (not shown) is configured for driving rotation of the fringe roller  210 , and the processing unit  22  is configured for controlling the rotation of the second motor. To process a fiber F through the system  200 , the processing unit  22  instructs motor  25  to rotate the nip rollers  12   a,    12   b  until a leading end of fiber F exits the nip rollers  12   a,    12   b  at a length sufficient to be controlled by the fringe roller  210 . For example, this length may include the leading end being in contact with a surface of the fringe roller  210  or in contact a certain amount of the surface of the fringe roller  210 . The processing unit  22  then stops rotation of nip rollers  12   a,    12   b  and directs the second motor to rotate the fringe roller  210  a half revolution to capture the leading end of fiber F and another half revolution to present the leading end of fiber F into the air gap  13 . The cycle repeats after image signals for the fiber F have been received by the imaging device  16 . In some implementations, motor  25  may control the rotation of fringe roller  210  (not shown). In addition, in some implementations, motor  25  and/or the second motor may be controlled by another processing unit (not shown). 
     In addition, the collector in system  200  shown in  FIG. 4  includes a stationary collection plate  214  and housing  216 , instead of the collection roller  14  shown in  FIG. 1 . The collection plate  214  includes an electrically conductive material, such as aluminum or stainless steel. The housing  216  is made of a non-conductive material, such as, for example, polycarbonate or acrylic.  FIG. 5  illustrates the housing  216  without the collector plate  214  disposed on it. The housing  216  includes an entry face  218  that faces the air gap  13  and the exit side  15  of the nip rollers  12   a,    12   b.  The entry face  218  defines a horizontal slot  219  that extends through the entry face  218 . The air gap  13  is in fluid communication with an interior of the housing  216  through this slot  219 . The collection plate  214  is embedded onto the entry face  218  above the slot  219  and attracts the fibers F passing through the air gap  13  toward the housing  216  and through slot  219 . This collector arrangement guides the fibers F within a consistent plane through the air gap  13 , minimizing image acquisition depth variation. The suction device  18  is disposed adjacent another face of the housing and is in fluid communication with the interior of the housing  216  to allow for evacuation of the fibers F after the imaging device  16  has captured image signals for the fibers F. In other implementations (not shown), the collection plate  214  may be embedded below the slot  219 . 
       FIG. 6  illustrates a system  300  for separating and aligning fibers according to another implementation. The system  300  includes elements similar to those described in relation to  FIGS. 1  and  4  above except as noted. In particular, the system  300  includes a set of nip rollers  314   a,    314   b  that are horizontally spaced apart from the exit side  15  of nip rollers  12   a,    12   b.  The nip rollers  314   a,    314   b  have axes of rotation that are parallel to the axes of rotation of nip rollers  12   a,    12   b.  Upper nip roller  314   a  rotates in the same direction as the upper nip roller  12   a,  and lower nip roller  314   b  rotates in the same direction as the lower nip roller  12   b.  The upper nip roller  314   a  is coupled to the upper nip roller  12   a  by an apron  301   a  that extends around portions of the rollers  314   a,    12   a  through which the fibers F are expected to pass. The lower nip rollers  12   b  and  314   b  are coupled by an apron  301   b.  The apron  301   a  and apron  301   b  gently urge the fibers F from nip rollers  12   a,    12   b  toward nip rollers  314   a,    314   b  and prevents slippage of the fibers F. The cots  303  and apron  301  may be formed of rubber or other suitable, non-conductive material for gently urging the fibers through the rollers  12   a,    12   b,    314   a,    314   b.  In addition, to further prevent slippage of the fibers passing through the nip rollers  12   c,    12   d  that are upstream of the nip rollers  12   a,    12   b,  each nip rollers  12   c,    12   d  may include a cot  303  around an outer diameter thereof. 
     In some implementations, motor  25  may control the rotation of nip rollers  314   a,    314   b,  and the nip rollers  12   a,    12   b  may be driven by the aprons  301   a,    301   b.    
     The air gap  13  is defined between an exit side  315  of nip rollers  314   a,    314   b  and collection plate  214 . In this system  300 , nip rollers  12   a,    12   b  are not charged, but at least one of the nip rollers  314   a,    314   b  are grounded or negatively charged, and the collection plate  214  is positively charged. As noted above in relation to  FIGS. 4 and 5 , the electrostatic field created in the air gap  13  urges the fibers F from the exit side  315  of the rollers  314   a,    314   b  toward the slot  219  in the collection plate  214 . 
     The above-described implementations create an electrostatic field within an air gap, and the electrostatic field separates, aligns, and allows for inspection and collection of fibers passing through the air gap. However, it should be understood that the systems and methods described above may be used with other types of materials other than fibers, such as dust particles and impurities. 
     Various modifications of the devices and methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain representative devices and method steps disclosed herein are specifically described, other combinations of the devices and method steps are intended to fall within the scope of the appended claims, even if not specifically recited. Thus, a combination of steps, elements, components, or constituents may be explicitly mentioned herein. However, other combinations of steps, elements, components, and constituents are included, even though not explicitly stated. The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms.