Patent Publication Number: US-2002000526-A1

Title: Yarn sensor

Description:
[0001] This application claims benefit of priority from Provisional Application No. 60/081,669, filed Apr. 14, 1998. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] In the production of yarns, yarn cohesion is obtained by, for example, twisting, or by intermingling or interlacing the individual filaments in jet nozzles. Interlacing is a particularly economical measure. However, it does not produce completely uniform yarn cohesion over the entire length of the yarn, but, rather, leads to the formation of individual, more or less regularly spaced apart, intermingled sections where the filaments are closely entangled together, and looser, bulkier, sections of low yarn cohesion. This structure on the one hand confers a particular textile overall appearance on the yarns, but on the other also affects their further processibility.  
       [0003] The prerequisite for any non-damaging and problem-free further processing of interlaced yarns is that the interlaced sections are sufficiently close together. Missing interlaced sections have an adverse, and in certain circumstances, even catastrophic, effect on fabric quality and loom. It is therefore of particular importance to monitor the uniformity of the interlacing continuously.  
       [0004] Various yarn properties have been measured on-line in the past. Of particular interest is a sensor previously developed which measures the interlace in a yarn. Such a sensor is shown at  10  in FIG. 1. Sensor  10  comprises a housing  12  in which electronics are contained, and which has front and back faces. The back face is mounted to a spinning machine. On the front face is mounted a front face assembly  14  which holds a top and a bottom grooved ceramic pin  22 ,  26 , respectively. There is an opposing face plate  16  on which are attached additional grooved ceramic pins  21 ,  25 , positioned so that the grooves on these pins are aligned with those mounted directly on the front face of housing  12 . A hinge assembly  18  allows an opposing face plate  16  to swing both toward and away from front face assembly  14 . Alignment of the grooved ceramic pins is assisted by a clasp assembly  29 ,  40 . Moving yarns  24  are held in place when opposing face plate  16  is swung against front face assembly  14 , and clasp assembly  29 ,  40  is engaged.  
       [0005] Between grooved ceramic pins  21 ,  25  of opposing face plate  16  are radiation sources  36  used to transmit radiation to the yarn through transparent quartz window  34 . There is one radiation source for each moving yarn. The radiation passes through moving yarns  24  and through slit/window assembly  42  in the front face, where it enters detectors in housing  12  used to measure the presence or absence of the desired yarn parameter. For instance, if it is desired to measure interlace, this parameter is measured by evaluating the amount of light transmitted from a radiation source through the yarn to a sensing element using electric wires. Data from the sensor are transmitted to a control system and processed and summarized appropriately for evaluation. A drawback to this system, because it used electric wires, necessitated using two separate cable ends.  
       [0006] Moreover, with this system, the yarn was held mechanically between two opposing plates with grooved ceramic pins attached thereto. Alignment of the moving yarn was critical, and difficult to achieve. Also, the moving yarns were prone to break as they passed between the pins. Additionally, because the sensor had these two opposing plates, the cables in which the electric wires used to deliver radiation and carry signals back to the detector were constantly being flexed as the spinning machine was being strung up, thus subjecting the wires to premature failure.  
       [0007] Moreover, this prior art sensor had a transparent quartz window which served only to protect the light sources. Dirt and other contaminants collected regularly on the surface of this quartz window, thus reducing the level of transmitted radiation seen by the moving threadline.  
       [0008] On-line monitoring of interlace is known in the industry. See Hinchliffe, “ Second Generation On - Line Monitoring: The Next Step in Automation ”, IFJ, Oct, 1997, pp. 56 and 57. Also, optical sensors are known. See Japanese Kokai No. Hei 2(1990)-33342 also discloses an optical sensor. Japanese Patent Applications Publication Kokai 64-61531 and 64-61532 both disclose a method of evaluating the entanglement intensity of entangled yarn. However, both of these publications stress that the yarn must pass in a no-contact mode with the analyzing device. U.S. Pat. No. 5,140,852 to Bonigk et al. discloses a process and apparatus for measuring the degree of filament intermingling of a multifilament yarn. This process and apparatus require a sensor which examines the yarn without contact. U.S. Pat. No. 4,990,793 to Bonigk et al. also discloses a process and apparatus for measuring the degree of intermingling of a multifilament yarn, where there is contact between the yarn and a yarn transport support.  
       [0009] In light of the drawbacks of the prior art, it would be advantageous to have an on-line sensor for monitoring interlace, as well as other parameters, which sensor also wipes the wear surface clean.  
       SUMMARY OF THE INVENTION  
       [0010] In accordance with the present invention, there is provided a method and an apparatus for monitoring a particular yarn parameter, such as interlace.  
       [0011] The method of this invention comprises the steps of transmitting a radiation from a source to a wear surface which is transparent to the radiation, contacting the wear surface with a moving yarn to be monitored so that the yarn continuously wipes the wear surface, reflecting the radiation from the yarn to a detector, and processing the reflected radiation to monitor a desired yarn parameter.  
       [0012] The sensor of this invention comprises a radiation source for transmitting radiation, a radiation transparent wear surface for receiving a moving yarn at which radiation is directed from the radiation source and from which radiation is reflected, and a detector for receiving the reflected radiation. The sensor of the present invention may also include a mounting plate for attaching the detector to a spinning machine, a plurality of brackets mounted on the mounting plate, each bracket holding a first guide pin for guiding a moving yarn, and a hinge assembly mounted to the mounting plate for holding a second guide pin wherein the second guide pin swings toward the moving yarn to keep the moving yarn in contact with the wear surface. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013]FIG. 1 is an elevational schematic view of a sensor of the prior art.  
     [0014]FIG. 2 is an elevational schematic view of the sensor of the present invention.  
     [0015]FIG. 3 is a partial cross-sectional view of the sensor shown in FIG. 1, taken across lines  3 - 3  of FIG. 2.  
     [0016]FIG. 4 is a plan view of the source/detector unit and the sensor of this invention.  
     [0017]FIG. 5 is a schematic view of an alternative wear surface useful with the present invention.  
     [0018]FIGS. 6A and 6B are schematic representations of differential radiation reflectances in use of this invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0019] In accordance with the present invention, there is provided a sensor for monitoring a yarn parameter. A first embodiment of the sensor of the present invention is illustrated in FIGS.  2 - 4 . The sensor is shown generally at  50  in FIGS. 2 and 4. The sensor includes a wear surface  66  as shown in FIGS. 2 and 3. The yarn, or thread line, illustrated at  64  in FIGS. 2 and 3, continuously contacts wear surface  66 . In the embodiment of FIGS.  2 - 4 , the wear surface has a half-rod shape and covers a series of sensor ports. Preferably, the wear surface is a sapphire rod.  
     [0020] The sensor includes a radiation source  90  as shown in FIG. 4, for transmitting radiation and a detector  92  as shown in FIG. 4. Both radiation source  90  and detector  92  are housed in a source/detector unit  94 . As also shown in FIG. 4, a bifurcated cable  76  is connected to sensor  50 . The bifurcated cable splits into two fiber optic bundles,  76   a  and  76   b,  which are connected to the source/detector unit. Radiation is sent through fiber optic bundle  76   a  to the wear surface, and is reflected from the wear surface and returns through fiber optic bundle  76   b.  The source/detector unit of the present invention may be disposed either at a spinning machine, or, as shown in FIG. 4, remote from the wear surface, for example, up to 20 feet away. Moreover, with the embodiment of the present invention which is shown in FIG. 4, radiation source  90  and detector  92  are located on the same side of moving yarn  64 .  
     [0021] Wear surface  66  is transparent to the radiation. By “transparent” is meant that the radiation is not absorbed by the wear surface material, but rather the radiation is transmitted through to the yarn surface as it passes over the wear surface. Thus, the radiation may be reflected and subsequently fed to a radiation collection system, e.g., a computer. The difference between the transmitted and reflected radiation is calculated. This difference can be used to calculate pertinent parameters, such as degree of interlace, and reported as desired.  
     [0022] In the case of inspection of moving yarns for degree of interlace, the filaments of highly interlaced yarns will be bound together and the filaments of yarns without interlace will be spread out or splayed. This principle is illustrated in FIGS. 6A and 6B. FIG. 6A shows that, as a non-interlaced portion of a moving yarn  64  passes over the transparent wear surface  66 , the filaments are spread out and cover a relatively large surface area  69 . The reflected radiation is thus relatively large. By contrast, as shown in FIG. 6B, when an interlaced portion of moving yarn  64  passes over the transparent wear surface  66 , it is in the form of a tighter bundle, taking up less surface area, and thus capable of reflecting relatively less radiation  71 .  
     [0023] Interlaced portions of yarn are known as nodes. The reflectance data are processed in terms of the frequency of nodal (less) reflectance over time. The interlace nodes per unit yarn length are then determined, once the yarn speed (distance per unit time) is entered into the computer or other data analysis device. An optimum range of interlace (nodes/meter, for example) is established for a yarn product, and the interlacing process can be controlled to yield a finished product within that range.  
     [0024] The sensor of the present invention may also include a mounting plate  52  for attaching the sensor to a spinning machine. The mounting plate includes a plurality of holes  67  which are drilled through plate  52 . The holes are adapted to receive radiation transmitting cable  76 , which is bifurcated as shown in FIG. 4, for transmitting radiation to and from the wear surface. Each hole is surrounded by an “O” ring  68 . One hole is provided for each moving yarn to be measured.  
     [0025] The sensor of the present invention also includes a plurality of brackets  58  as shown in FIG. 2. The brackets are mounted on the front side of the mounting plate. Each pair of brackets  58  holds the ends of a grooved guide pin  62 , which guides a respective moving yarn. As shown in FIG. 3, other brackets  60  are provided on the mounting plate between the pairs of brackets  58  and hold the ends of wear surface  66 .  
     [0026] The sensor of the present invention also includes a hinge assembly mounted to the front of the mounting plate for holding a second pin. Such a hinge assembly is shown at  56  in FIG. 2, and holds a second pin  70 . This pin  70 , which is preferably ceramic, swings toward the moving yarns to keep the moving yarns in contact with the wear surface. Each moving yarn  64  is held against wear surface  66  by routine operating tension, and each yarn is guided by a groove  65  in grooved guide pins  62  and by a second pin  70 , which is held against the moving yarns by tension provided by hinge assembly  56 . In this way, the moving yarns continuously wipe wear surface  66  clean.  
     [0027] Alternate shapes for the wear surface are within the scope of the present invention. For instance, FIG. 5 shows another embodiment of the wear surface, especially suitable for single thread line position monitoring. This single position unit has a saddle-shaped transparent wear surface  66 ′ attached to the single end of bifurcated cable  76 ′ that, as described above, leads to and from the source/detector unit  94 .  
     [0028] Moreover, other yarn parameters can be monitored by use of this invention as well. The amount of finish on a yarn can be determined in like manner by careful selection of the wavelength of the radiation and the type of detector chosen for the specific wavelength(s) of interest. Generally, for water-based finishes, the radiation and detector are selected to permit measurement of the amount of water on the yarn. Alternatively, by utilizing a spectrophotometer as the detector, the wavelengths of light reflected from a colored yarn can be measured and quantified. This permits on-line color measurement of a moving yarn.  
     [0029] Interlace is generally imparted to a moving yarn by means of an interlace jet, which forces air or other gas through the filaments in the yarn and entangles them to form a node. Generally the air pressure at the interlace jets needed to form tight nodes is dependent on the yarn count, which is determined by parameters such as the denier per filament, the total denier of the yarn, the cross-sectional shape of the filaments, and the like. The number of nodes per meter can be controlled by controlling the interlace jet air pressure. Generally, the higher the pressure, the greater the number of nodes per meter (npm), as shown in the Examples below. Typically the degree of interlacing has been measured off-line by a destructive method by inserting a pin into the yarn to be tested and noting the incidence of entanglement by the nodes.  
     [0030] Several experiments were performed to compare the inventive sensor and method with the off-line sensor and method, especially as the number of nodes per meter relates to differences in the interlace jet air pressure. By comparing repeated measurements of a standard yarn with yarn of known interlace degree by both methods, a factor was determined which could be used to convert directly the measurement of this invention to the same scale as the previously-used off-line measurement.  
     EXAMPLE 1  
     Comparison of On-line Interlace Measurement with Off-line Measurement  
     [0031] The interlace of a 3.38 denier-per-filament (dpf) yarn sample was measured by both off-line and on-line measurements. Eight yarn samples spun on the same day were measured by the off-line measurement, and an average of 20.0 npm was obtained using the off-line method described above. Using the sensor of this invention, the same yarn count was measured on-line (4 positions on the same spinning machine), with the average interlace measured to be 23.4 npm. This then yielded a factor 1.2 (23.4/20). The sensor of this invention used in this example was fitted with an optic fiber cable of thick cladded glass. The electro/optical components of the sensor included an infrared LED identified as Optek OP 290 A and a silicon phototransistor identified as Optek OP 5731 . The wear surface was a half-rod of sapphire supplied by Imetra, Inc.  
     EXAMPLE 2  
     Variation in Interlace Jet Air Pressure and Resulting Measured Interlace  
     [0032] Two different interlace jets were tested on the same spinning machine position using the sensor of this invention. Testing included varying the air pressure and monitoring the subsequent interlace that resulted. Good agreement was noted between the results for the two different jets.  
                                                      Test Jet #1   Test Jet #2                                             pos press   NPM   APV   pos press   NPM                       65 (std)   24   300   65   21           50   22   280   50   19           40   20   260   40   17           30   18   240   30   15           20   10   200   20    9           10    8   276   10    7            0    7   290    0    6                      
 
     EXAMPLE 3  
     Measurement of Water on Yarn  
     [0033] A sensor of this invention was used to determine the amount of water based finish on moving yarns. The components of the sensor system were the same as that described above except that the particular cable used in this sensor is made from high transmission glass, available from the Cuda Products Company. The amount of finish present on the yarn can be calculated from the data obtained, since the concentration of the finish in water is known.  
     [0034] In use of this sensor for water/finish detection, the yarn is illuminated with a white light (broad spectrum) and the reflected light response, in the 1.4 um range, where water absorbs the light, is monitored, thus detecting the level of moisture (water) on the yarn. The radiation source was a Gilway lamp part #4115-2 a.  The detector was a Hamamatsu GaInAs detector part #G3476-05 mated with an optical band pass filter from OFC Corporation part #N01445. The optical band pass filter had a pass band response centered at 1445 nm with a +/− 56 nm bandwidth.  
     [0035] The sensor was tested using textile yarn from a production area in an “off-line” mode. A yarn transport carried the yarn from a bobbin over the sapphire wear surface. The voltage output from the detector was monitored for moist moving yarn. Yarn with increased moisture caused an increased voltage output.