|Title of Invention||
"AN INSTRUMENT FOR MEASURING TORSIONAL PROPERTIES OF FIBRES AND YARNS"
|Abstract||The present invention relates to a novel instrument and process for measuring the torsional properties of fibres or yarns. More specifically the invention relates to an instrument and process for measuring the torsional properties of spun yarn.|
|Full Text||Field of the Invention
The present invention relates to an instrument for measuring the torsional properties of fibres or yarns and a process thereof. More specifically the invention relates to an apparatus and method for measuring the torsional properties of spun yarn.
Many fabric properties depend in part on torsional response of the yarn in the fabric and yarn torsional response depends on the state of torsion of the individual filament of the yarn. The torsional properties of fibres influence that of yarn and yarn in turn affects snarling, unwinding, knitability during processing and spirality, shape factor, dimension of loops in knitted products and drape, crease recovery, crepe effect, etc. in woven fabrics. The magnitude, yarn torque and the recovery from these stresses, influence such effects as the distribution of twist in single yarn and the balance of twist in ply yarns.
Many laboratory instruments have been developed from time to time for the measurement of torque. These can be divided into two categories. (1) torsion - pendulum type (ii) torsion balance type
The simple pendulum method is based on an oscillating pendulum suspended by the fibre. In the compound pendulum an inertia disk is mounted between the torsion wire and the specimen. The torsional rigidity of fibres measured in an aqueous medium has been determined by Goodings using a double torsion pendulum technique. The torsion pendulum is rapid but is severely linked in that the rigidity is measured for only small strains imposed for a short period of time. Moreover the torsion-pendulum methods are not suitable for investigation of the torsional behaviour of twisted yarns owing to the untwisting tendency of the lower end of yarn.
In an idealized torsion balance, the specimen is mounted between a twisting head at its lower end and a torsion wire of known properties at its upper end. A pointer, or other indicating device, is positioned between the specimen and the torsion-wire. As the specimen is twisted, the torsion-wire head is rotated manually so as to maintain the pointer freely in a constant position; alternatively, the head may be fixed and the torque measured by the rotation of the indicating device.
In order to measure the torque, Peirce employed a magnet, suspended from the specimen thread, in a known magnetic field. An optical-lever method has been widely used by various workers. In order to obtain the torque-twist curve for a single wool fibre immersed in water, Mitchell and Feughelman used a photographic film to record the movement of a mirror in the optical-lever system. Postle et al. used a lamp-and-scale arrangement to measure the torque in a newly twisted worsted yarn; in this case, the twisting mechanism consisted of a motor-driven twisting head, which replaced the bottom jaw of an Istron Tensile Tester, so that the torque and tensile stress in the yarn could be measured simultaneously. Skelton used a circular scale to measure the angular rotation of the mirror. Armstrong and Mitchell employed the principle of a light-sensitive potentiometer to facilitate accurate measurement of torque in single wool fibres.
An instrument capable of determining the torsional properties of small diameter filament during loading and unloading was used at Fabric Research Laboratories in Massachusetts for theoritical analysis for the torsional recovery of filament and single yarn.
Another apparatus was developed by Department of Textile Industries, Leads, England on the principle that the torque is balanced by a hank against the torque of torsion wire, the latter being twisted so as to maintain zero twist in the hank. The apparatus was relevant for textured yarn. U.S. Patent No. 2,154,631 describes an apparatus for measuring potential torque of a twisted yarn employed in making crepe fabrics when the yarn is subjected to a torque releasing medium the yarn to be tested is increased in the liquid in this apparatus.
U.S. Patent No. 3,965,737 describes a method and device for indicating the amount of torque in a yarn wherein an elongated horizontal bar assembly has supported thereon a movable cantilevered arm member and a stationary cantilevered arm member having yarn clamps for receiving and clamping the yarn thereto whereby the movable arm member is moved towards said stationary arm member and the point at which the yarn held there between twists together into a loop is noted to indicated the torque therein.
US Patent No. 5144988 described an instrument for measuring the tension of yarns-particularly weft yarns which wind or unwind forming a balloon - avoiding further deviations thereof, which makes use of a viable impedance, for example a differential capacitor or a variable inductor, comprising a movable component and at least one fixed component as part of an electric measuring circuit./ All the components of the instrument have a centered symmetry and a passage through their center for the yarn whose tension has to be measured, with a yarn guiding and deviating eyelet positioned in correspondence of the closing vertex of the "ballon" and fixed to the movable component of the variable impedance. The variable voltage detected on one of the components of the impedance, as a function of the tension of the yarn sliding through the eyelet, is measured by a measuring device connected to the movable component. A weft yarn feeder for looms, having at its outlet an instrument with centered symmetry as described
hereabove, positioned on the main axis of the weft feeder so as to measure the tension of the unwinding yarn being fed to the loom is also disclosed.
CN 901323 describes an instrument comprising a needle which rests on the yarn and is otherwise supported by a low friction bearing permitting the needle to turn freely in a horizontal plane. If the needle is counter balanced, the yarn and the plane in which the needle turns need not be horizontal. As the yarn moves longitudinally and is rotated to produce twist or false twist, the needle assumes an angular disposition indicative of the amounts of twist being placed in the yarn.
An instrument capable of determining the torsional properties of fibres or yarn is not commercially available. Even at laboratory scale no such instrument has been made for spun yarn. Therefore there always existed a need for an instrument for measuring the torsional properties of the fibres or yarn. In particular a need existed for instrument for measuring the torsion properties of spun yarn.
The object of the present invention is therefore a novel instrument for measuring the torsional properties of fibres, yarns, tapes or twines etc.
Another object of the present invention is to determine the degree of torque in yarn.
Still another object of the present invention is to determine the torsional rigidity of the yarn.
Still another object of the present invention is to determine the torsional recovery of the yarn.
Yet another object of the present invention is to evolve a novel process for measuring the torsional properties of spun yarn.
In accordance with the invention these and other objects are attained by twisting the sample yarn at predetermined number of times and measuring the time lag between the torsion wire and the test sample in the instrument having a microprocessor controlled stepper motor to introduce required twist in required direction at required speed in the sample, axially balanced jaws for holding test sample and torsion wire, a torsion wire for measuring the torque, an encoder for measuring the twist inserted in the test sample, a solenoid for maintaining required tension and a user friendly microprocessing system for recording and processing of data.
Accordingly the present invention relating to an instrument for measuring the torsional properties of fibres and yarns comprises:
at least three metal plates placed horizontally parallel to each other and perpendicular to 3 supporting rods, while the top metal plate is mounted with a microprocessor controlled stepper motor and the base plate having a solenoid to slide up and down freely restricting the rotation
means for rotating the said stepper motor in clockwise or anticlock wise direction or in oscillation/hysteresis mode or in step wise rotation with pause at intervals at any predetermined speed for a specified amount of rotation or period
at least two pairs of axially balanced jaws wherein the first pair engages the torsion wire, and the second pair engages the test specimen/fibre/yarn sample
means for adjusting gauge length of the torsion wire and the test specimen
a digital encoder threaded on a shaft connected to the lower jaw of the first pair of jaws at one end and to a photo diode for reading the number of rotation of the test sample.
means for maintaining constant tension in the test sample
means for converting the signals received from encoder to digital form
means for controlling and maintaining the desired enviromental conditions around the testing zone.
Also the present invention relates to a process for measuring the torsional properties of fibres and yarns by the instrument as claimed in claim 1 comprising the steps of:
securing a length of the test sample
inserting the test sample by securing lower point of the second pair of jaws
adjusting the gauge length of the said test sample
clamping the test sample between the movable support and the stationary support
aligning all the elements of the instrument along the axis
rotating all the elements of the instrument except those attached to the bottom end by means of the stepper motor causing the test sample therebetween to twist into a loop
converting the signals from encoder assembly into total angular displacement of the encoder disc and recording the data in computer with proper interfacing
converting the signals from the load cell into suitable digital signals which are processed by computer and then fed back for controlling the power flowing into solenoid
providing the required tension to the test sample
determining the amount of torque by noting the amount of resistive force and the torque factor.
resetting the parameters
A more complete appreciation of the invention and the attendant advantages thereof will be more clearly understood by reference to the accompanying drawings, which are for illustrative purposes, hence the same should not be construed to restrict the scope of the invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 is a schematic diagram of the apparatus/insrument. Fig. 2(A) is the details of the components of the jaw. Fig. 2(B) is the cross section of the jaw. DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The schematic diagram of the instrument is given in fig. 1. The instrument is supported by circular plates and 3 vertical rods. All plates are perfectly horizontal and perpendicular to rods supporting them. At the center of each plate a hole is drilled to accommodate various components. At the base the instrument is provided with screws to adjust leveling.
The power supply system and microprocessor control cards are accommodated at convenient place inside the instrument.
At the center of metal plate, P2 a stepper motor (M) is mounted. This motor (M) is a bi-directional stepper motor with microprocessor and software control to operate it as per various choices such as number of rotations or fraction of rotation or their combination to the accuracy of 0.9°. Speed of rotation from quasistatic to 100 rpm. The motor can rotate in clock wise or anticlock wise or even in oscillation mode or in step wise rotation with pause at certain intervals, at any selected speed for specified amount of rotation of period. All these parameters are selected and controlled by the combination of electronic hardware (^p) and computer software by means of cards which convert the signals from the computer into suitable commands for operational control.
The piston of stepper motor carries an adapter (AD1) for adjusting gauge length of torsion element and a jaw (J1), which has been designed to be user friendly as well as axially balanced. At the center of this jaw (J1) a torsion element (TW) is inserted. Another jaw (J2) of similar design is hanged at bottom end of torsion element (TW). The torsion element (TW) is interchangeable and standard in quality but the torsion element made of different materials can be used in the instrument. The other end of jaw (J2) is threaded to a small shaft (SH). These jaws are dynamically, axially balanced of special design. All the components are circular in shape and axially balanced. The gripping of clamps is loaded by suitable spring in the jaws. The clamp has markings to mount samples at its
center. The length of torsion element can also be changed by changing the adapter (AD).
A digital encoder (EN) has been threaded on shaft (SH) and the photo diode, which reads the rotation of encoder, is fixed on a metal ring (MR) which is further fixed to the metal plate (P3). The digital encoder (EN) is error free in its reading, unlike light beams or photo potentiometers. The encoder cards are provided for converting the signals from encoder assembly into total angular displacement of the encoder disc. The data can be recorded in computer with proper interfacing and certain deviation in axial position would not affect reading of rotation. Shaft (SH) passes through the hole at the center of plate P3, as well as that of metal ring (MR). The metal ring (MR) has 3 radially cut holes and carry round but pointed screws to restrict the shaft (SH) in the event of any jerky motion. A "Z" shaped lever (LZ) supports the base of jaw (J2) while loading or unloading of test specimen.
The bottom end of shaft (SH) carries an adapter (AD2) which is used to adjust gauge length of test specimen. To the other end of adapter (AD2) the jaw (J3) is threaded. The simple adapters of various lengths with provision to lock at different depths into shaft (SH) of the instrument help in choosing any length between 5 to 100 mm. The jaw (J3) will hold the top end of test specimen while testing.
The axes of the stepper motor (M), jaws (J1 to J3), torsion element (TW), adapters (AD1 & AD2), shaft (SH), encoder (EN) as also test sample are aligned along the same vertical line. They are free to rotate co-axially in any direction depending on the rotation of motor.
On the base plate (P4) a solenoid (SL) is fixed at its center. The hollow coils of solenoid are covered by a lid at top into which a core (CR) has been inserted. The core can slide up and down freely but can not rotate.
At the top end of core (CR) a load cell (LC) is fixed on a circular ring and also the jaw (J4) for holding bottom end of test specimen. Three elements form a single unit and they can slide vertically but cannot rotate. The locking of the bottom jaw (J4) of test sample is a specialty of the instrument. The jaw is always free to slide vertically but can not rotate. This feature makes the instrument adaptable for spun yarn and for measuring residual twist in twisted yarns. This aspect is very crucial for spun yarns otherwise when the jaw is freely hanging, it would start untwisting the yarn due to residual torque in the yarn. At the same time the jaw can be subjected to the required tension.
The test specimen, fibre or yarn sample (S) is clamped by jaws (J3) and (J4) after the gauge length has been adjusted suitably.
Once the test sample is mounted all elements along the axial direction PT, LC, J4, S J3, AD2, SH, EN J2 & TW will be freely hanging but vertical to base plate. They are aligned along the axis of the instrument. When stepper motor (M) rotates all these elements except those attached to bottom end of test specimen is stationary and top end rotates in proportion and direction to that of stepper motor.
The power supply (PS) system supplies currents to various components in required voltage.
The functions of load cell and solenoid is synchronized and these two components along with stepper motor are interfaced with computer for operation, control, recording of data and its processing to represent result in numeric as
well as graphical form. The signals from them and feed back for control of tension is executed by tailor made microprocessor along with software program. For this software is prepared in C++ language. The solenoid and load cell used are uniquely adapted to the instrument. The load cell always measures the tension applied on the test specimen. The load cell card is provided for conversion of signals from the load cell into suitable digital signals which are processed by computer and then fed back for controlling the power flowing into solenoid which would affect the tension in the test sample and hence the output from the load cell. The solenoid applies required tension. The design of solenoid is such that tension to the tune of few mN to as high as 100 cN or more is made possible. During testing the insertion of twist or de-twist changes length of sample, which in turn causes change in tension. The load cell measures this change in tension and the same is corrected by change in voltage to solenoid by microprocessors. Thus, the entire testing can be conducted virtually under the constant tension.
The entire instrument is covered by acrylic sheets with doors at necessary positions. This cover is necessary to avoid the influence of surrounding air on the rotation and torque value of sample. It may also be used to maintain certain ambient/desired conditions in which the sample may be maintained and tested. By changing humidity or temperature inside the area between plates P2 and P4 the material can be tested under such conditions. All electronic components are suitably protected for such exposures.
While testing any sample the torsion element (TW) is selected according to material to be tested. The gauge length of wire can be adjusted by changing the adapter (AD1), if necessary. Similarly, the gauge length of test specimen (S) is also adjusted by chaning adapter (AD2), if necessary. Insert the test sample by securing (J2) under the Z lock. Release the lock after mounting the sample.
Before commencing the test the instrument is to be initialised or reset. To commence the testing select the testing parameters from user friendly software. One has to just enter parameters like direction of rotation, number of rotation, speed (optional), tension, file name, sample particulars and sample number. Then stepper motor (SM) starts rotating.
The rotation of stepper motor (SM) is transferred to all connected elements down the line. Hence, torsion element (TW), encoder (EN) and test sample (S) would also rotate. However, the bottom jaw (J4) of sample is stationary and only upper end of sample follows the rotation. This introduces twist in sample.
The test sample has resistance to torsional deformation (twist) and due to this the upper end of sample resists the twisting. This resistive force is transferred to torsion element (TW) and forces bottom end of this element to lag behind the stepper motor. The magnitude of this lag depends on resistive force of test sample and the torque factor of torsion element. This torsion element being a standard one, its torque factor is known or can be found out by using torsion pendulum.
The stepper motor rotates at certain speed and bottom end of torsion wire turns behind with certain lag. Thus, the rotation of bottom end has to be recorded and the digital encoder records this with the help of photodiodes. These readings are transferred to computer at pre-selected or standard intervals. This recording continues as long as motor rotates or say the encoder rotates.
During testing, depending on test sample and amount of twist the test specimen may contract or stretch. This may lead to changes in the tension in the sample. To maintain the constant tension the load cell and solenoid is used. .
While setting initial tension of sample, the voltage supply to solenoid is automatically adjusted in accordance with the tension value selected. During testing any change in length of specimen causes change in the position of the core in solenoid. This changes the tension on specimen. This needs correction. The load cell senses this change in tension and sends signal to microprocessors. They in turn change the supply voltage to solenoid and tension is re-adjuested. This correction can be set to the accuracy of ±1 cN. This correction is continuous and automatic.
The motor being bi-directional, the rotation can be clockwise, anticlock wise, or in hysteresis/oscillating mode, depending on testing requirement.
The signals received from encoder are converted into digital form by using standard ADC card and necessary microprocessors. The data is in the form of number of rotation to the accuracy of 0.72°. The lag in rotation between stepper motor and that of encoder is recorded. The torque of torsion element is known.
The torque in testing element is calculated by using the standard formula, Torque of test specimen = T = 2.7π (Φ-θ) K in Nm.
Φ = Rotation of stepper motor, K = toque balance factor of torsion element, θ = Rotation of encoder.
These data recorded at selected intervals are processed to tabulate in the form of torque value or torsional rigidity value and stored in a file. Rest of the torsional properties can be calculated by using standard formulae available in literature. The above formula is also used for the display of graph or hysteresis curve on the monitor of the computer. For the quick understanding of behavior of test
specimen the data is further processed and displayed on monitor in the graphical form. The plot too can be stored in a file.
The door of the instrument is kept closed while testing a sample.
The instrument is useful to all those who are concerned with torsional properties of fibres, yarns, tapes, twines, etc. The spinners of spun yarns require to know residual torque to understand the twist setting or conditioning or snarling tendency of yarn. The fabric manufacturers can assess yarn performance for functional properties like drape, crepe or crease recovery. The weaver or yarn consumer needs to know unwinding behavior or rolling tendency or yarn during process.
The greatest beneficiary can be knitter who can assess knitability of yarn or quality of his product with respect to loop dimensions, loop shape and spirality. The texturing processor can assess the quality of yarn by testing residual torque, one of the important factors of quality checking of yarn, after texturing.
In case of plied yarn balance of twist is an important factor for better functioning of yarn.
The characterization of fibres to understand its response to dynamic twisting is concern of all spinners because the torsional rigidity of fibres influences migration of fibres.
Though the potential for utility/application is quite vast and high the nonavailability of commercial instrument and lack of awareness for the importance of torsional properties had restricted the use of such instruments. The research work carried out in the recent past has been contributing to
creation of the awareness leading to the design of the current instrument in which a very high degree of flexibility has been built in for all types of end users.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
1. An instrument for measuring the torsional properties of fibres and yarns comprising:
at three or more metal plates placed horizontally parallel to each other and perpendicular to 3 supporting rods, while the top metal plate (P2) is mounted with a microprocessor controlled stepper motor (M) and the base plate having a solenoid (SL) to slide up and down freely restricting the rotation;
means for rotating the said stepper motor in clockwise or anticlock wise direction or in oscillation/hysteresis mode or in step wise rotation with pause at intervals at any predetermined speed for a specified amount of rotation or period;
at least two or more pairs of axially balanced jaws (J1-J4) wherein the first pair (J1.J2) engages the torsion wire (TW), and the second pair engages the test specimen/fibre/yarn sample(s);
means as herein described for adjusting gauge length of the torsion wire and the test specimen;
a digital encoder (EN) threaded on a shaft connected to the lower jaw (J2) of the first pair of jaws at one end and to a photo diode for reading the number of rotations o the test sample;
means as herein described for maintaining constant tension in the test sample;
means as herein described for converting the signals received from encoder to digital form; and
means for controlling and maintaining the desired environmental conditions around the testing zone.
2. An instrument for measuring the torsional properties of fibers and
yarns as claimed in claim 1, wherein the said means for maintaining constant
tension in the test sample are load cell (LC) and solenoid (SL).
3. An instrument for measuring the torsional properties of fibers and
yarns as claimed in claim 1, wherein the said means for rotating the said
stepper motor is combination of conventional electronic hardware and
4. An instrument for measuring the torsional properties of fibres and
yarns as claimed in claim 1, wherein the said means for controlling and
maintaining the desired environmental conditions around the testing zone is
an outer cover.
5. An instrument for measuring the torsional properties of fibres and
yarns as claimed in claim 1, wherein the said means for maintaining the
constant tension is a load cell (LC) connected to a microprocessor which in
turn changes the supply voltage to solenoid (SL) thus adjusting the tension of
the test sample.
6. An instrument for measuring the torsional properties of fibres and
yarns as claimed in claim 1, wherein the said means for adjusting gauge
length of the torsion wire (TW) and the test specimen (5) are adapters
7. A process for measuring the torsional properties of fibres and yarns by
the instrument as claimed in claim 1 comprising the step of:
securing a length of the test sample;
inserting the test sample by securing lower point of the second pair of jaws; adjusting the gauge length of the said test sample'
clamping the test sample between the movable support and the stationary support;
aligning all the elements of the instrument along the axis;
rotating all the elements of the instrument except those attached to the bottom end by means of the stepper motor causing the test sample therebetween to twist into a loop;
converting the signals from encoder assembly into total angular displacement of the encoder disc and recording the data in computer with proper interfacing;
converting the signals from the load cell into suitable digital signals which are processed by computer and then fed back for controlling the power flowing into solenoid;
providing the required tension to the test sample;
determining the amount of torque by nothing the amount of resistive force and the torque factor; and
resetting the parameters.
8. A process for measuring the torsional properties of fibres and yarns by
the instrument as claimed in claim 7, wherein the signals from computer are
sent to stepper motor by stepper motor card.
9. A process for measuring the torsional properties of fibres and yearns
by the instrument as claimed in claim 7, wherein the signals from the load
cell into suitable digital signals are converted by load cell card.
10. A process for measuring the torsional properties of fibres and yarns by
the instrument as claimed in claim 7, wherein the signals from encoder
assembly are converted by encoder cards.
11. An instrument for measuring the torque, substantially as herein before
described with reference to the accompanying drawings.
12. A process for measuring the torque by the instrument, substantially as
herein before described with reference to the accompanying drawings.
|Indian Patent Application Number||769/DEL/2002|
|PG Journal Number||50/2007|
|Date of Filing||24-Jul-2002|
|Name of Patentee||INDIAN INSTITUTE OF TECHNOLOGY|
|Applicant Address||HAUZ KHAS, NEW DELHI-110016, INDIA.|
|PCT International Classification Number||G01L 5/06|
|PCT International Application Number||N/A|
|PCT International Filing date|