YARN TESTING METHOD AND APPARATUS

Abstract: A predetermined length of yarn (10) is fed from a holder (12) to extend between a pair of spaced clamps (17, 19; 18, 20) and one or both clamps are caused to move relative to the other progessively to tension the yarn. The yarn tension is measured during the tensioning process by causing the yarn to engage a sensor (23) which is displaced out of a linear path between the clamps (17, 19; 18, 20).

Description: This invention relates to a method of testing yarn and apparatus adapted for use in the method. The method of the invention will in particular be suitable for determining the suitability of yarns for weaving and knitting purposes. It is however envisaged that the method of the invention could find other applications and the term "yarn" herein includes any elongated fibre, strand, string, sliver or the like. The method of the invention envisages determining the tensile properties of a yarn and could also give a statistical indication of the number of weak points per unit length of yarn. According to the invention the method of testing a yarn is characterised in the steps of feeding a predetermined length of yarn from a holder so that it extends between a pair of spaced clamps clamping the length of yarn towards the ends thereof by means of the clamps, and causing one or both clamps to move relative to the other progressively to tension the yarn. Further according to the invention the method includes the step of measuring the yarn tension during the tensioning process. Still further according to the invention the method includes the step of measuring the enlongation of the length of yarn between the clamps during the tensioning process. In one embodiment of the invention the yarn will be tensioned until breakage thereof and in such an arrangement, the invention envisages that a measurement will be made of the elongation of the yarn until breakage occurs. Also according to the invention the tension in the yarn is measured by causing the yarn to engage a sensor which is displaced out of a linear path between the clamps. It is for example envisaged that the yarn should be caused to follow a generally half-wave pathway with the sensor disposed at the wave crest. The elongation of the yarn during the tensioning process is preferably measured by measuring the distance which the clamps move relative to one another. Still further according to the invention one or both clamps will be in the nature of a rotable disc or pulley having a belt draped over a portion of the periphery thereof, and the method includes the step of clamping the yarn between the disc and belt, by rotating the disc and feeding the yarn into the nip between the belt and disc. With such an arrangement the step of causing relative movement between the clamp can be carried out by continuing to rotate the disc once the yarn has been clamped, with the rotational axis of the disc being disposed transverse to the direction of the yarn. Still further according to the invention the method is characterised in feeding the yarn by means of a fluid stream. The method of the invention envisages that a length of yarn will be accumulated during the tensioning process preparatory to being fed to the clamp during the feeding cycle. With this arrangement continuous yarn feed is possible, with means being provided to take up slack in the yarn being prepared for feeding to the clamp in a controlled fashion while a preceding length is being tensioned. Also included within the scope of the invention is an apparatus adapted for use in the method, comprising a pair of spaced clamps, means for feeding a length of yarn into a position for clamping by the clamps, the arrangement being one wherein one or both clamps are movable relative to the other in order to tension a clamped length of yarn. Still further according to this aspect of the invention, a sensor is provided intermediate the clamps to measure the yarn tension during relative movement between the clamps. It is envisaged that such a sensor could be in the nature of a force transducer displaced out of a linear path between the clamps. For example the yarn could be guided to follow a U-shaped path between a first guide, the sensor, and a second guide. Also according to the invention one or both clamps comprise a disc or pulley with an endless belt engaging over a portion of the periphery thereof, so that the yarn fed into the nip between the disc and belt upon rotation of the former, will be clamped between the periphery of the disc and the belt. The invention envisages that the rotational axis of the disc will be disposed transverse to the direction of the yarn so that after clamping further rotation of the disc will act to tension the yarn. Also according to the invention the feed means comprise a fluid stream and pathway therefore, with the clamps and sensor being disposed within such pathway. Preferably the feed means will also include a continuous yarn feed device which is adapted to introduce a predetermined length of yarn into the feed pathway at the onset of each clamping and tensioning cycle. Such a feed device could for example comprise a pair of feed rollers rotating at a predetermined speed, with the feed pathway being adapted to be opened periodically to draw yarn from the feed rollers into the pathway. It is envisaged that prior to opening the pathway, a predetermined length of yarn will be accumulated as result of feed from the rollers, with an eccentric device being provided to take up slack in a controlled fashion when the pathway is closed. The invention provides that the eccentric will move from a position proximate to the feed rollers to a remote position to take up the slack. Still further according to the invention means are provided for measuring the elongation of the yarn during the tensioning process. The invention envisages that such means could comprise means for measuring the angular displacement of a disc clamp during the tensioning process until breakage of the yarn occurs. In order to more clearly illustrate the invention an embodiment thereof is described hereunder purely by way of example with reference to the accompanying drawings wherein: Fig. 1 is a schematic perspective view of an apparatus according to the invention; Fig. 2 is an exploded view of a portion of the apparatus of Fig. 1; Fig. 3 is a sectioned elevation of a force transducer of the apparatus of Fig. 1; Fig. 4 is an elevational view of the apparatus of Fig. 1; Fig. 5 is a plan view of the apparatus of Fig. 1; Fig. 6 is an enlarged view of a section on line VI-VI of Fig. 4; and Fig. 7 is an enlarged partially sectioned elevational view of a portion of the apparatus of Fig. 4. Referring to the drawings the apparatus in accordance with the invention for testing yarn 10 comprises a yarn pathway which starts with a spool 12 or other suitable reservoir for yarn, and which terminates in an outlet 16 which is coupled to a suction device, not shown. The yarn 10 is continually fed from the spool 12 by means of a pair of rollers 11 and during a feed cycle, a predeterminded length of yarn which has passed through the rollers 11, is sucked along the yarn pathway to be tested during a testing cycle which is described in more detail below. In order to prevent knotting of the yarn during the feed cycle, an eccentric device is provided to guide the yarn from a position remote from the feed rollers 11 towards a position which proximates the rollers 11 and thus serves to take up slack during the feed cycle. With reference to Figure 6 it will be noted that the eccentric comprises a plate 13 which has an eccentric aperture 13a therein which defines an inlet to the suction pathway 13b for the yarn. The yarn pathway 13b leads to a pair of spaced clamps in the form of pulleys 17 and 18 over which belts 19 and 20 respectively run. The belts 19 and 20 are of the endless variety and extend between the pulleys 17 and 18 and spaced idlers 21 and 22 respectively. During the testing cycles mentioned above, yarn is fed into the nip defined by the belts 19, 20 and the pulleys 17, 18, and thus clamped. During further rotation of the pulleys 17 and 18 in the direction shwon in Figure 1, the yarn is tensioned until breakage occurs. During the tensioning stage the tension in the yarn 10 is measured by a force transducer 23 which is located in the yarn pathway. In the zone of the force transducer 23, the yarn pathway follows a half-wave curve with the yarn passing around a roller 22 over the transducer 23 and back around a roller 24. During the tensioning process, the elongation in the yarn 10 will also be measured by means of a slotted pulse generator 40, Figure 4, 5, which is coupled in the drive train for the apparatus. By counting the number of pulses given by the generator 40 during the period when the force measured by the transducer 23 is greater than zero, the elongation of the yarn can be determined. The clamping and tensioning pulleys 17 and 18 are located in spaced housings 14 and 15, which define an outlet 14a and an inlet 15a respectively, the outlet 14a and inlet 15a being coupled in the pathway leading to and from force transducer zone, Fig. 1. Also rotatable within the housing 14 in conjunction with the pulley 17, is a disc 27 which defines an axial portion 27b which extends from the portion 13b of the yarn pathway described above. From the axial portion 27b the yarn pathway extends radially along a cut-­ out 27a in the disc 27 to beyond the periphery of a pulley 17. At the outer extremity of the cut-out 27a, the latter aligns with apertures 26a in a pair of plate elements 26 which flank the pulley 17 and rotate in conjunction therewith. A horse-shoe shaped disc 25 fits between the plates 26 and defines a cut-out 25a therein so that the plate 25 seals off the apertures 26a in all angular positions of the plates 26 except when the apertures 26a align with the cut-out 25a. Thus, during the period when the apertures 26a align with the cut-out 25a, the yarn pathway will be opened and yarn will be sucked therealong by means of the suction device. With reference to Figure 2 it will be noted that the cut-out 25a corresponds with a 180° portion of the pulley 17 which is not in engagement with the belt 19. The feeding and suction cycle thus commences when the pulley 17 and belt 19 release a length of yarn, and the cycle ceases, when the belt and pulley again clamp a length of yarn at the onset of a tensioning cycle. With this arrangement, suction at the outlet 16 will be continuous, with suitable seals such as that shown at 26b on the plates 26 being provided effectively to shut-off airflow during the tensioning cycle. As mentioned above the disc 27, pulley 17, plates 26, and eccentric plate 13, will also rotate in conjunction and for this purpose a common drive pulley 34, Figure 6, is provided. The drive train of the apparatus is shown more clearly in Figure 4 and Figure 5, and comprises a belt 30 driven by a suitable drive motor, not shown. The belt 30 drives a shaft 41 via a pulley 41a, with the shaft 41 driving the pulse generator 40, feedrollers 11, and a pulley 41b. The latter pulley in turn drives a pulley 32 which drives a belt 33 which in turn drives pulleys 34 for appropriate rotation of the clamping pulleys 17 and 18. The advantages of the arrangement of the invention will be apparant to persons skilled in the art. The apparatus provides a continuous yarn feed with extremely rapid threading and tensioning of the yarn to breakage. With the arrangement of the invention yarn can be tested at a rapid rate to provide an indication of the level and frequency of waek places in the yarn and therefore the expected weaving performance of the yarn. Doubtless variations of the invention exist without departing from the principles set out in the consistory clauses.

Claims: 1. A method of testing yarn, characterised in the steps of feeding a predetermined length of yarn (10) from a holder (12) so that it extends between a pair of spaced clamps (17, 19; 18, 20), clamping the length of yarn towards the ends thereof by means of the clamps (17, 19; 18, 20), and causing one or both clamps to move relative to the other progressively to tension the yarn. 2. The method according to claim 1, characterised in the step of measuring the yarn tension during the tensioning process. 3. The method according to claim 1 or 2, characterised in the step of measuring the elongation of the length of yarn (10) between the clamps (17, 19; 18, 20) during the tensioning process. 4. The method according to any one of claims 1 to 3, wherein the yarn (10) is tensionded until breakage thereof including the step of measuring the elongation of the length of yarn (10) until such breakage occurs. 5. The method according to claim 2, characterised in that the tension in the yarn is measured by causing the yarn to engage a sensor (23) which is displaced out of a linear path between the clamps (17, 19; 18, 20). 6. The method according to claim 5, characterised in that the yarn is caused to follow a generally half-wave pathway and the sensor (23) is disposed at the wave crest and is displaceable under tension of the yarn towards the wave base. 7. The method according to claim 3, characterised in that the elongation of the yarn during the tensioning process is measured by measuring the distance which the clamps (17, 19; 18, 20) move relative to one another. 8. The method according to any one of claims 1 to 7, wherein one or both clamps are in the form of a rotable disc (17, 18) each having a belt (19, 20) draped over a portion of the periphery thereof and the method is characterised in the steps clamping the yarn between the disc and the belt by rotating the disc and feeding the yarn (10) into the nip between the belt and disc. 9. The method according to claim 8, wherein the step of tensioning the yarn (10) comprises causing relative movement between the clamps, characterised in that such step is effected by rotating the disc (17, 18) once the yarn has been clamped, with the rotational axis of the disc being disposed tranverse to the direction of the yarn. 10. The method according to any one of claims 1 to 9, wherein the yarn is fed by means of a fluid stream. 11. The method according to any one of claims 1 to 10, characterised in that a length of yarn is accumulated during the step of tensioning a preceding length of yarn, preparatory to being fed to the clamps (17, 19; 18, 20) during the feeding step. 12. Apparatus adapted for use in the method claimed in any one of claims 1 to 11, characterised in a pair of spaced clamps (17, 19; 18, 20), means for feeding a length of yarn (10) into position for clamping by the clamps, the arrangement being one wherein one or both clamps are movable relative to the other in order to tension a clamped length of yarn (10). 13. Apparatus according to claim 12, characterised in the provision of a sensor (23) intermediate the clamps (17, 19; 18, 20) to measure yarn tension during relative movement between the clamps (17, 19; 18, 20). 14. Apparatus according to claim 13, wherein the sensor (23) is a force transducer which is displaced out of a linear path between the clamps. 15. Apparatus according to claim 14, wherein a pair of spaced guide formations (22, 24) is provided in the linear path between the clamps (17, 19; 18, 20), provided in the zone of the guide formations (22,24), the arrangement being one wherein yarn is guided to follow a U-shaped path between a first guide formation (22), the sensor (23) and a second guide formation (24). 16. Apparatus according to any of claims 11 to 15, wherein one or both clamps comprise a disc (17, 18) with an endless belt (19, 20) engaging over a portion of the periphery thereof, so that yarn fed into the nip between the disc (17, 18) and the belt (19, 20) upon rotation of the former, will be clamped onto the periphery of the disc (17, 18). 17. Apparatus according to claim 16, wherein the rotational axis of the disc (17, 18) is disposed transverse to the direction of the clamped yarn (10) so that after clamping, further rotation of the disc (17, 18) will act to tension to yarn. 18. Apparatus according to any one of claims 11 to 17, wherein the feed means comprise a fluid stream and pathway (13a, 13b, 27a, 27b, 27c, 14a, 15a) therefore, with the clamps and sensor being disposed within such pathway. 19. Apparatus according to any one of claims 11 to 18, wherein the feed means include a continuous yarn feed device (11, 12, 13) which is adapted to introduce a predetermined length of yarn into the feed pathway (27a, 27b, 27c) at the onset of each clamping and tensioning cycle. 20. Apparatus according to claim 19, wherein the feed means comprise a pair of feed rollers (11) rotating at a predetermined speed, with the feed pathway being adapted to be opened periodically to draw yarn from the feed rollers (11) into the pathway. 21. Apparatus according to claim 20, wherein an eccentric device (13) is provided to take up slack of yarn fed by the feed rollers (11) while the yarn pathway is closed. 22. Apparatus according to claim 21, wherein the eccentric device (13) is adapted to move from a position proximate to the feed rollers (11) to a remote position to take up the slack in the yarn. 23. Apparatus according to any one of claims 11 to 22, wherein means are provided for measuring the elongation of the yarn during the tensioning process, such means comprising means for measuring the relative displacement between the clamps (16, 18; 17, 19) during the tensioning process.

Inventors: CIZEK, JAROMIR
Applicants: ZELLWEGER USTER AG
Application year: 1987
Main classification: G01N3
IPC codes: D06H3, G01N3, G01N33