A textile machine with an improved device for detecting defects in winding yarn and relative method for detecting defects in winding yarn

Abstract

Textile machine (4) with improved device for detecting defects of the yarn (12) being wound comprising a spool (8) on which a yarn (12) is unwound and rewound on a reel (16), a reel (16) on which to wind said yarn (12) unwound from said spool (8), a head supporting a yarn guide cylinder (24), rotating about a rotation axis (X-X), said yarn guide cylinder (24) having a plurality of slots (28) which receive and guide the yarn (12) unwound from the spool (8), said slots (28) defining a speed profile (32) of the yarn (12) housed therein, said yarn (12) translating, parallel to said rotation axis (X-X), from a first transverse end or tip (36) of said yarn guide cylinder (24) to a second transverse end or tail (40) of said yarn guide cylinder (24) and vice versa in an alternating manner according to a crossing movement, before being wound onto the reel (16), a clearer (44), arranged between the spool (8) and the yarn guide cylinder (24) so as to analyse the yarn (12) unwound from the spool (8) and not yet wound on the reel (16), to identify possible defects thereof, in a given time interval, the yarn (12) crossing the clearer (44) along a straight direction according to a running speed, at least one position sensor (48) which identifies at least one transverse position (Y) of the yarn (12) with respect to the yarn guide cylinder (24), along said crossing movement, a processing and control unit (52) operatively connected to the clearer (44), to said yarn guide cylinder (24) and to said at least one position sensor (48), and provided with said speed profile (32) of the yarn (12), as a function of the transverse position (Y) of the yarn (12) with respect to the yarn guide cylinder (24), so as to be able to calculate the running speed of the yarn (12) at the clearer (44). The processing and control unit (52) being programmed so as to receive from the at least one position sensor (48) the transverse position (Y) of the yarn (12), calculate the running speed of the yarn (12) upstream of the yarn guide cylinder (24) and send it to the clearer (44) so as to calculate the length of the yarn (12) crossing the clearer (44) in said given time interval.

Description

FIELD OF APPLICATION

[0001] The present invention relates to a textile machine with an improved device for detecting defects in winding yarn and relative method for detecting defects in winding yarn.STATE OF THE ART

[0002] In the state of the art, textile machines, such as winding machines, are provided with clearers, i.e., devices for detecting defects in the yarn wound in a spool. To date, the clearers identify the defects in real time in the yarn which is unwound from the spool and passes in the clearer sensor (which can be optical, capacitive or a camera) and whose length is related to the winding speed communicated by the textile machine head. In fact, the length of the yarn defect is calculated by multiplying the yarn speed by the time in which the defect was seen, i.e., detected, by the clearer sensor. As is well known, yarn defects are classified into classes, e.g., by length and diameter, and can be recognised (and thus accepted or rejected) as a function of the use of the yarn, as per the settings settable on the control unit of the textile machine.

[0003] The clearer samples the signal generated by the yarn passing therethrough at a constant frequency and then transforms the length of the 'virtual' defect into a real one, as a function of the speed parameter described above.

[0004] Unfortunately, the speed which is used to determine the defect length is not the actual speed of the yarn, but only an average value thereof, as there are no sensors which measure the yarn speed in real time. The actual speed varies due to many factors, first and foremost the shape and depth of the slots of the rotating yarn guide cylinder, which imparts the rotating movement to the reel and distributes the yarn on the reel itself. This means that the actual yarn speed changes along the crossing (tail / tip / tail) and especially depending on the type of yarn guide cylinder installed on the textile machine head.

[0005] In more detail, in textile machines, such as the winding machine, the grooved yarn guide cylinder has the task of distributing the yarn on the reel in the desired manner and, typically, uniformly. Uniform distribution means that the density of the yarn turns must be as constant as possible along the reel, so as to ensure an easier unravelling but also so as to allow a uniform colouring of the yarn when the reel is soaked in a dye. The grooves present on the yarn guide cylinder force the yarn to move transversally on the basis of a precise geometrical shape which ensures the desired distribution. The yarn guide cylinder then forces the yarn to move in a 'zig-zagging' pattern between the opposite axial ends of the reel. In particular, the yarn has a fixed point at the outlet of the clearing, which acts as a 'pivot', and a movable point which follows the slots of the cylinder, on the cylinder itself.

[0006] Each yarn guide cylinder has its own speed configuration, which repeats cyclically each time it completes its passage from tail to tip and again tail. This movement is referred to in jargon as crossing.

[0007] Such a speed profile is given by the configuration of the yarn guide cylinder slots (number of helixes, cylinder gauge and diameter, angle of inclination of the helix, which can be at constant or variable pitch, depth and opening of the helixes) but also by the diameter of the reel being formed, which in turn varies over time. The yarn speed profile can thus be expressed as a function of the type of cylinder, the winding speed and the diameter of the reel being formed.

[0008] The solutions of the prior art, e.g., described in EP307644B1, involve determining the instantaneous yarn speed by calculating the peripheral speed with correction factors based on the reel diameter, yarn position and taking the related speed into account. However, these are estimated values and highly variable during crossing.

[0009] Indicatively, for the reasons stated above, the actual speed of the yarn can vary within a range of + / -20% in its cycle, whereby the solutions of the prior art imply an error in the evaluation of the length of the defect which is + / - 20%, said error being directly related to the difference between the actual speed and the set speed.

[0010] Obviously, an error of 20% can lead to reporting false defects, or the failure to detect them, during the winding step of the spool.

[0011] The need is therefore felt to resolve the defects and limitations related to the solutions of the prior art.

[0012] Such a need is met by a textile machine according to claim 1 and by a method for detecting defects in yarn according to claim 10.DESCRIPTION OF THE DRAWINGS

[0013] Further features and advantages of the present invention will be more clearly comprehensible from the description given below of preferred and non-limiting embodiments thereof, in which: figure 1 shows a front perspective view of a textile machine according to a possible embodiment of the present invention; figure 2 shows a front perspective view of a detail of the textile machine of figure 1; figure 3 shows schematic views of yarn speed profiles as a function of different yarn guide cylinders.

[0014] The elements or parts of elements common to the embodiments described below will be indicated using the same reference numerals.DETAILED DESCRIPTION

[0015] With reference to the aforesaid figures, the number 4 globally indicates an overall schematic view of a textile machine according to the present invention.

[0016] It should be noted that the term yarn or single yarn or continuous yarn refers to a single filament or continuous filament (for example in the case of silk, artificial or synthetic fibres), while the term yarn refers to a group of fibrils of varying lengths which are paralleled and joined together by twisting. Hereinafter, one or the other term will be used indifferently, it being understood that the applications of the present invention are not limited to one or the other type.

[0017] The textile machine 4, such as a winding machine, comprises a spool 8 on which a yarn 12 is wound to be unwound and rewound on a reel 16, in a known manner.

[0018] The textile machine 4 further comprises a head 20 supporting a yarn guide cylinder 24, rotating about a rotation axis X-X, said yarn guide cylinder having a plurality of slots 28 which receive and guide the yarn 12 unwound from the spool 8.

[0019] In accordance with a possible embodiment, the yarn guide cylinder 24 is configured so as to impart a rotational movement to the reel 16 on which is wound the yarn 16 exiting from the yarn guide cylinder 24.

[0020] In particular, said slots 28 define a speed profile 32 of the yarn 12 housed therein. In particular, the speed profile of the yarn 12 due to the shape and type of slots 28 of the yarn guide cylinder 24 can be uniquely identified and is repeated cyclically at each crossing.

[0021] The yarn 12 then translates, parallel to said rotation axis X-X, from a first transverse end or tip 36 of the yarn guide cylinder 24 to a second transverse end or tail 40 of the yarn guide cylinder 24 and vice versa in an alternating manner according to a crossing movement, before being wound on the reel 16.

[0022] The textile machine 4 further comprises a clearer 44, arranged between the spool 8 and the yarn guide cylinder 24 so as to analyze the yarn 12 unwound from the spool 8 and not yet wound on the reel 16, in order to identify any defects thereof, in a given time interval. In particular, the yarn 12 crosses the clearer 44 along a straight direction S-S according to a running speed.

[0023] The textile machine 4 further comprises at least one position sensor 48 which identifies at least one transverse position Y of the yarn 12 with respect to the yarn guide cylinder 24 along said crossing movement. The position sensor 48 can, for example, be of the optical or capacitive type; it is also possible to provide vision systems such as cameras or CCD-type sensors as position sensors 48.

[0024] The textile machine further comprises a processing and control unit 52 operatively connected to the clearer 44, to said yarn guide cylinder 24 and to said at least one position sensor 48. Furthermore, the processing and control unit 52 is equipped with all the speed profiles 32 of the yarn 12, per cylinder type and per working condition, as a function of the position of the yarn 12 with respect to the yarn guide cylinder 24, so that the running speed of the yarn 12 at the clearer 44 can be accurately calculated.

[0025] The processing and control unit 52 is programmed so as to receive from the at least one position sensor 48 the transverse position Y of the yarn 12, calculate the running speed of the yarn 12 and send it to the clearer 44 so as to calculate the correct length of the defect, when detected.

[0026] In accordance with a possible embodiment, said at least one position sensor 48 comprises a piezoelectric type sensor whose signal, suitably analyzed, allows to identify the passage of the yarn 12 at the first transverse end or tip 36 of the yarn guide cylinder 24 and / or the second transverse end or tail 40 of the yarn guide cylinder 24.

[0027] Preferably, said position sensor 48 is arranged between the clearer 44 and the yarn guide cylinder 24.

[0028] In accordance with a possible embodiment, two position sensors 48 of the yarn 12 are provided at the first transverse end or tip 36 of the yarn guide cylinder 24 and at the second transverse end or tail 40 of the yarn guide cylinder 24, respectively, so as to detect the passage of the yarn 12 at each of said transverse ends 36, 40.

[0029] In accordance with a possible embodiment, two position sensors 48 of the yarn 12 are provided, interposed between the clearer 44 and the yarn guide cylinder 24, near said slots 28 of the yarn guide cylinder 24.

[0030] In accordance with a possible embodiment, said at least one position sensor 48 is a continuous type sensor configured so as to continuously monitor the transverse position Y of the yarn 12 between the first transverse end or tip 36 of the yarn guide cylinder 24 and the second transverse end or tail 40 of the yarn guide cylinder 24, and to associate therewith the running speed of the yarn 12 upstream of the yarn guide cylinder 24, at each transverse position Y of the yarn 12 with respect to the yarn guide cylinder 24.

[0031] In accordance with a possible embodiment, such a continuous type sensor is a camera or a CCD array.

[0032] In accordance with a possible embodiment, the textile machine 4 comprises a diameter sensor 56 of the reel 16 during the formation of the latter, said diameter sensor 56 of the reel 16 being operatively connected to said processing and control unit 52 programmed so as to calculate the running speed of the yarn 12 upstream of the yarn guide cylinder 24 also as a function of the diameter of the reel 16 being formed.

[0033] The speed profile 32 of the yarn 12 is thus given by the configuration of the slots 28 of the yarn guide cylinder 24 (number of helixes, cylinder gauge and diameter, angle of inclination of the helix, which can be constant or variable pitch, depth and opening of the helixes) and the diameter of the reel 16 being formed, which in turn varies over time. The speed profile 32 can thus be expressed as a function of the type of yarn guide cylinder 24, the winding speed and the diameter of the reel 16 being formed.

[0034] The first two variables (type of yarn guide cylinder and winding speed) are fixed and known, while the third, i.e., the diameter of the reel being formed, obviously varies over time during winding, and is information which is obtained from the sensors located on the winding machine, more in particular on the winding arm. In fact, as the diameter of the reel 16 being formed increases, the rotational speed decreases.

[0035] The function which generates the instantaneous winding speed, i.e., the running speed of the yarn 12, therefore requires the speed profile 32 of yarn guide cylinder 24 and the position of the yarn 12 on the yarn guide cylinder 24, i.e., its position along the crossing. This information, as seen, can be obtained continuously with systems which identify the transverse position of the yarn 12 at each instant and translate it into instantaneous speed with an algorithm, such as a camera, suitably positioned CCD array, etc.

[0036] It can also be obtained virtually by knowing the moment of passage of the yarn 12 in a given position along the crossing, e.g., the tail, extracting the subsequent position values virtually as the instantaneous cylinder speed is known as well as the geometric configuration of the yarn guide cylinder 24 (number of round trips).

[0037] By increasing the number of controlled passage points - e.g., tip tail and centreline of the cylinder - it is possible to increase the accuracy of the running speed estimation of the yarn 12.

[0038] Thereby, the winding head is capable of giving much more precise information to the clearer 44 on the working speed, thus giving the possibility of greatly improving the defect detection accuracy.

[0039] The precise knowledge of the winding speed also makes it possible to more accurately calculate the quantity of yarn processed, i.e., the square footage of the reel, which today only refers to the theoretical winding speed by applying empirical parameters to adjust the final square footage value, being in fact a purely indicative value.

[0040] In subsequent processing, the variability of the square footage between reel and reel generates waste which must be subsequently recovered, but which is in fact a cost for the customer. An improved square footage calculation thus ensures a reduction in processing costs.

[0041] As can be appreciated from the description, the present invention makes it possible to overcome the drawbacks mentioned in the prior art.

[0042] In particular, the present invention, with respect to the solutions of the prior art which, as seen, imply an error in the defect length assessment of + / - 20% (related directly to the difference between the actual speed and the set speed), allows to provide the clearer with an extremely precise value of the yarn unravelling speed and thus the clearer can assess the length of the yarn defects passing therethrough it in real time and with great accuracy.

[0043] In particular, it is possible to associate the speed profile with each type of yarn guide cylinder used and, thanks to the use of one or more sensors which recognise the transverse position of the yarn, it is possible to estimate the running speed with extreme accuracy: thereby, a 'predictive' speed value can be passed to the clearer which will be very close to the actual speed value, thus substantially improving the measurement accuracy of the defect detected by the clearer itself.

[0044] Thanks to this precise evaluation, the clearer can effectively detect yarn defects and avoid possible false positives and false negatives.

[0045] Thereby, the clearer does not perform unnecessary winding stops in order to eliminate false defects and, at the same time, is always capable of detecting real defects in the yarn, imposing winding stops only when really necessary.

[0046] Furthermore, thanks to the knowledge of the actual unravelling speed of the yarn, it is also possible to obtain extremely precise information on the square footage of the reel being formed, so as to have batches of reels with predefined lengths which are extremely uniform with each other.

[0047] A person skilled in the art may make numerous modifications and variations to the solutions described above so as to satisfy contingent and specific requirements.

[0048] The scope of protection of the invention is defined by the following claims.List of references

[0049] 4: textile machine 8: spool 12: yarn 16: reel 20: head 24: yarn guide cylinder 28: slots 32: speed profile 36: first transverse end or tip 40: second transverse end or tail 44: clearer 48: pressure sensor 52: processing and control unit 56 diameter sensor of the reel 16 X-X: rotation axis of the yarn guide cylinder 24 S-S: straight direction of the yarn 12 Y: transverse position of the yarn 12

Examples

Embodiment Construction

[0015]With reference to the aforesaid figures, the number 4 globally indicates an overall schematic view of a textile machine according to the present invention.

[0016]It should be noted that the term yarn or single yarn or continuous yarn refers to a single filament or continuous filament (for example in the case of silk, artificial or synthetic fibres), while the term yarn refers to a group of fibrils of varying lengths which are paralleled and joined together by twisting. Hereinafter, one or the other term will be used indifferently, it being understood that the applications of the present invention are not limited to one or the other type.

[0017]The textile machine 4, such as a winding machine, comprises a spool 8 on which a yarn 12 is wound to be unwound and rewound on a reel 16, in a known manner.

[0018]The textile machine 4 further comprises a head 20 supporting a yarn guide cylinder 24, rotating about a rotation axis X-X, said yarn guide cylinder having a plurality of slots 28 ...

FIELD OF APPLICATION

[0001] The present invention relates to a textile machine with an improved device for detecting defects in winding yarn and relative method for detecting defects in winding yarn.STATE OF THE ART

[0002] In the state of the art, textile machines, such as winding machines, are provided with clearers, i.e., devices for detecting defects in the yarn wound in a spool. To date, the clearers identify the defects in real time in the yarn which is unwound from the spool and passes in the clearer sensor (which can be optical, capacitive or a camera) and whose length is related to the winding speed communicated by the textile machine head. In fact, the length of the yarn defect is calculated by multiplying the yarn speed by the time in which the defect was seen, i.e., detected, by the clearer sensor. As is well known, yarn defects are classified into classes, e.g., by length and diameter, and can be recognised (and thus accepted or rejected) as a function of the use of the yarn, as per the settings settable on the control unit of the textile machine.

[0003] The clearer samples the signal generated by the yarn passing therethrough at a constant frequency and then transforms the length of the 'virtual' defect into a real one, as a function of the speed parameter described above.

[0004] Unfortunately, the speed which is used to determine the defect length is not the actual speed of the yarn, but only an average value thereof, as there are no sensors which measure the yarn speed in real time. The actual speed varies due to many factors, first and foremost the shape and depth of the slots of the rotating yarn guide cylinder, which imparts the rotating movement to the reel and distributes the yarn on the reel itself. This means that the actual yarn speed changes along the crossing (tail / tip / tail) and especially depending on the type of yarn guide cylinder installed on the textile machine head.

[0005] In more detail, in textile machines, such as the winding machine, the grooved yarn guide cylinder has the task of distributing the yarn on the reel in the desired manner and, typically, uniformly. Uniform distribution means that the density of the yarn turns must be as constant as possible along the reel, so as to ensure an easier unravelling but also so as to allow a uniform colouring of the yarn when the reel is soaked in a dye. The grooves present on the yarn guide cylinder force the yarn to move transversally on the basis of a precise geometrical shape which ensures the desired distribution. The yarn guide cylinder then forces the yarn to move in a 'zig-zagging' pattern between the opposite axial ends of the reel. In particular, the yarn has a fixed point at the outlet of the clearing, which acts as a 'pivot', and a movable point which follows the slots of the cylinder, on the cylinder itself.

[0006] Each yarn guide cylinder has its own speed configuration, which repeats cyclically each time it completes its passage from tail to tip and again tail. This movement is referred to in jargon as crossing.

[0007] Such a speed profile is given by the configuration of the yarn guide cylinder slots (number of helixes, cylinder gauge and diameter, angle of inclination of the helix, which can be at constant or variable pitch, depth and opening of the helixes) but also by the diameter of the reel being formed, which in turn varies over time. The yarn speed profile can thus be expressed as a function of the type of cylinder, the winding speed and the diameter of the reel being formed.

[0008] The solutions of the prior art, e.g., described in EP307644B1, involve determining the instantaneous yarn speed by calculating the peripheral speed with correction factors based on the reel diameter, yarn position and taking the related speed into account. However, these are estimated values and highly variable during crossing.

[0009] Indicatively, for the reasons stated above, the actual speed of the yarn can vary within a range of + / -20% in its cycle, whereby the solutions of the prior art imply an error in the evaluation of the length of the defect which is + / - 20%, said error being directly related to the difference between the actual speed and the set speed.

[0010] Obviously, an error of 20% can lead to reporting false defects, or the failure to detect them, during the winding step of the spool.

[0011] The need is therefore felt to resolve the defects and limitations related to the solutions of the prior art.

[0012] Such a need is met by a textile machine according to claim 1 and by a method for detecting defects in yarn according to claim 10.DESCRIPTION OF THE DRAWINGS

[0013] Further features and advantages of the present invention will be more clearly comprehensible from the description given below of preferred and non-limiting embodiments thereof, in which: figure 1 shows a front perspective view of a textile machine according to a possible embodiment of the present invention; figure 2 shows a front perspective view of a detail of the textile machine of figure 1; figure 3 shows schematic views of yarn speed profiles as a function of different yarn guide cylinders.

[0014] The elements or parts of elements common to the embodiments described below will be indicated using the same reference numerals.DETAILED DESCRIPTION

[0015] With reference to the aforesaid figures, the number 4 globally indicates an overall schematic view of a textile machine according to the present invention.

[0016] It should be noted that the term yarn or single yarn or continuous yarn refers to a single filament or continuous filament (for example in the case of silk, artificial or synthetic fibres), while the term yarn refers to a group of fibrils of varying lengths which are paralleled and joined together by twisting. Hereinafter, one or the other term will be used indifferently, it being understood that the applications of the present invention are not limited to one or the other type.

[0017] The textile machine 4, such as a winding machine, comprises a spool 8 on which a yarn 12 is wound to be unwound and rewound on a reel 16, in a known manner.

[0018] The textile machine 4 further comprises a head 20 supporting a yarn guide cylinder 24, rotating about a rotation axis X-X, said yarn guide cylinder having a plurality of slots 28 which receive and guide the yarn 12 unwound from the spool 8.

[0019] In accordance with a possible embodiment, the yarn guide cylinder 24 is configured so as to impart a rotational movement to the reel 16 on which is wound the yarn 16 exiting from the yarn guide cylinder 24.

[0020] In particular, said slots 28 define a speed profile 32 of the yarn 12 housed therein. In particular, the speed profile of the yarn 12 due to the shape and type of slots 28 of the yarn guide cylinder 24 can be uniquely identified and is repeated cyclically at each crossing.

[0021] The yarn 12 then translates, parallel to said rotation axis X-X, from a first transverse end or tip 36 of the yarn guide cylinder 24 to a second transverse end or tail 40 of the yarn guide cylinder 24 and vice versa in an alternating manner according to a crossing movement, before being wound on the reel 16.

[0022] The textile machine 4 further comprises a clearer 44, arranged between the spool 8 and the yarn guide cylinder 24 so as to analyze the yarn 12 unwound from the spool 8 and not yet wound on the reel 16, in order to identify any defects thereof, in a given time interval. In particular, the yarn 12 crosses the clearer 44 along a straight direction S-S according to a running speed.

[0023] The textile machine 4 further comprises at least one position sensor 48 which identifies at least one transverse position Y of the yarn 12 with respect to the yarn guide cylinder 24 along said crossing movement. The position sensor 48 can, for example, be of the optical or capacitive type; it is also possible to provide vision systems such as cameras or CCD-type sensors as position sensors 48.

[0024] The textile machine further comprises a processing and control unit 52 operatively connected to the clearer 44, to said yarn guide cylinder 24 and to said at least one position sensor 48. Furthermore, the processing and control unit 52 is equipped with all the speed profiles 32 of the yarn 12, per cylinder type and per working condition, as a function of the position of the yarn 12 with respect to the yarn guide cylinder 24, so that the running speed of the yarn 12 at the clearer 44 can be accurately calculated.

[0025] The processing and control unit 52 is programmed so as to receive from the at least one position sensor 48 the transverse position Y of the yarn 12, calculate the running speed of the yarn 12 and send it to the clearer 44 so as to calculate the correct length of the defect, when detected.

[0026] In accordance with a possible embodiment, said at least one position sensor 48 comprises a piezoelectric type sensor whose signal, suitably analyzed, allows to identify the passage of the yarn 12 at the first transverse end or tip 36 of the yarn guide cylinder 24 and / or the second transverse end or tail 40 of the yarn guide cylinder 24.

[0027] Preferably, said position sensor 48 is arranged between the clearer 44 and the yarn guide cylinder 24.

[0028] In accordance with a possible embodiment, two position sensors 48 of the yarn 12 are provided at the first transverse end or tip 36 of the yarn guide cylinder 24 and at the second transverse end or tail 40 of the yarn guide cylinder 24, respectively, so as to detect the passage of the yarn 12 at each of said transverse ends 36, 40.

[0029] In accordance with a possible embodiment, two position sensors 48 of the yarn 12 are provided, interposed between the clearer 44 and the yarn guide cylinder 24, near said slots 28 of the yarn guide cylinder 24.

[0030] In accordance with a possible embodiment, said at least one position sensor 48 is a continuous type sensor configured so as to continuously monitor the transverse position Y of the yarn 12 between the first transverse end or tip 36 of the yarn guide cylinder 24 and the second transverse end or tail 40 of the yarn guide cylinder 24, and to associate therewith the running speed of the yarn 12 upstream of the yarn guide cylinder 24, at each transverse position Y of the yarn 12 with respect to the yarn guide cylinder 24.

[0031] In accordance with a possible embodiment, such a continuous type sensor is a camera or a CCD array.

[0032] In accordance with a possible embodiment, the textile machine 4 comprises a diameter sensor 56 of the reel 16 during the formation of the latter, said diameter sensor 56 of the reel 16 being operatively connected to said processing and control unit 52 programmed so as to calculate the running speed of the yarn 12 upstream of the yarn guide cylinder 24 also as a function of the diameter of the reel 16 being formed.

[0033] The speed profile 32 of the yarn 12 is thus given by the configuration of the slots 28 of the yarn guide cylinder 24 (number of helixes, cylinder gauge and diameter, angle of inclination of the helix, which can be constant or variable pitch, depth and opening of the helixes) and the diameter of the reel 16 being formed, which in turn varies over time. The speed profile 32 can thus be expressed as a function of the type of yarn guide cylinder 24, the winding speed and the diameter of the reel 16 being formed.

[0034] The first two variables (type of yarn guide cylinder and winding speed) are fixed and known, while the third, i.e., the diameter of the reel being formed, obviously varies over time during winding, and is information which is obtained from the sensors located on the winding machine, more in particular on the winding arm. In fact, as the diameter of the reel 16 being formed increases, the rotational speed decreases.

[0035] The function which generates the instantaneous winding speed, i.e., the running speed of the yarn 12, therefore requires the speed profile 32 of yarn guide cylinder 24 and the position of the yarn 12 on the yarn guide cylinder 24, i.e., its position along the crossing. This information, as seen, can be obtained continuously with systems which identify the transverse position of the yarn 12 at each instant and translate it into instantaneous speed with an algorithm, such as a camera, suitably positioned CCD array, etc.

[0036] It can also be obtained virtually by knowing the moment of passage of the yarn 12 in a given position along the crossing, e.g., the tail, extracting the subsequent position values virtually as the instantaneous cylinder speed is known as well as the geometric configuration of the yarn guide cylinder 24 (number of round trips).

[0037] By increasing the number of controlled passage points - e.g., tip tail and centreline of the cylinder - it is possible to increase the accuracy of the running speed estimation of the yarn 12.

[0038] Thereby, the winding head is capable of giving much more precise information to the clearer 44 on the working speed, thus giving the possibility of greatly improving the defect detection accuracy.

[0039] The precise knowledge of the winding speed also makes it possible to more accurately calculate the quantity of yarn processed, i.e., the square footage of the reel, which today only refers to the theoretical winding speed by applying empirical parameters to adjust the final square footage value, being in fact a purely indicative value.

[0040] In subsequent processing, the variability of the square footage between reel and reel generates waste which must be subsequently recovered, but which is in fact a cost for the customer. An improved square footage calculation thus ensures a reduction in processing costs.

[0041] As can be appreciated from the description, the present invention makes it possible to overcome the drawbacks mentioned in the prior art.

[0042] In particular, the present invention, with respect to the solutions of the prior art which, as seen, imply an error in the defect length assessment of + / - 20% (related directly to the difference between the actual speed and the set speed), allows to provide the clearer with an extremely precise value of the yarn unravelling speed and thus the clearer can assess the length of the yarn defects passing therethrough it in real time and with great accuracy.

[0043] In particular, it is possible to associate the speed profile with each type of yarn guide cylinder used and, thanks to the use of one or more sensors which recognise the transverse position of the yarn, it is possible to estimate the running speed with extreme accuracy: thereby, a 'predictive' speed value can be passed to the clearer which will be very close to the actual speed value, thus substantially improving the measurement accuracy of the defect detected by the clearer itself.

[0044] Thanks to this precise evaluation, the clearer can effectively detect yarn defects and avoid possible false positives and false negatives.

[0045] Thereby, the clearer does not perform unnecessary winding stops in order to eliminate false defects and, at the same time, is always capable of detecting real defects in the yarn, imposing winding stops only when really necessary.

[0046] Furthermore, thanks to the knowledge of the actual unravelling speed of the yarn, it is also possible to obtain extremely precise information on the square footage of the reel being formed, so as to have batches of reels with predefined lengths which are extremely uniform with each other.

[0047] A person skilled in the art may make numerous modifications and variations to the solutions described above so as to satisfy contingent and specific requirements.

[0048] The scope of protection of the invention is defined by the following claims.List of references

[0049] 4: textile machine 8: spool 12: yarn 16: reel 20: head 24: yarn guide cylinder 28: slots 32: speed profile 36: first transverse end or tip 40: second transverse end or tail 44: clearer 48: pressure sensor 52: processing and control unit 56 diameter sensor of the reel 16 X-X: rotation axis of the yarn guide cylinder 24 S-S: straight direction of the yarn 12 Y: transverse position of the yarn 12

Examples

Embodiment Construction

[0015]With reference to the aforesaid figures, the number 4 globally indicates an overall schematic view of a textile machine according to the present invention.

[0016]It should be noted that the term yarn or single yarn or continuous yarn refers to a single filament or continuous filament (for example in the case of silk, artificial or synthetic fibres), while the term yarn refers to a group of fibrils of varying lengths which are paralleled and joined together by twisting. Hereinafter, one or the other term will be used indifferently, it being understood that the applications of the present invention are not limited to one or the other type.

[0017]The textile machine 4, such as a winding machine, comprises a spool 8 on which a yarn 12 is wound to be unwound and rewound on a reel 16, in a known manner.

[0018]The textile machine 4 further comprises a head 20 supporting a yarn guide cylinder 24, rotating about a rotation axis X-X, said yarn guide cylinder having a plurality of slots 28 ...

Claims

1. Textile machine (4) with improved device for detecting defects of the yarn (12) being wound comprising - a spool (8) on which a yarn (12) is unwound and rewound on a reel (16), - a reel (16) on which to wind said yarn (12) unwound from said spool (8), - a head supporting a yarn guide cylinder (24), rotating about a rotation axis (X-X), said yarn guide cylinder (24) having a plurality of slots (28) which receive and guide the yarn (12) unwound from the spool (8), said slots (28) defining a speed profile (32) of the yarn (12) housed therein, said yarn (12) translating, parallel to said rotation axis (X-X), from a first transverse end or tip (36) of said yarn guide cylinder (24) to a second transverse end or tail (40) of said yarn guide cylinder (24) and vice versa in an alternating manner according to a crossing movement, before being wound onto the reel (16), - a clearer (44), arranged between the spool (8) and the yarn guide cylinder (24) so as to analyse the yarn (12) unwound from the spool (8) and not yet wound on the reel (16), to identify possible defects thereof, in a given time interval, the yarn (12) crossing the clearer (44) along a straight direction according to a running speed, - at least one position sensor (48) which identifies at least one transverse position (Y) of the yarn (12) with respect to the yarn guide cylinder (24), along said crossing movement, - a processing and control unit (52) operatively connected to the clearer (44), to said yarn guide cylinder (24) and to said at least one position sensor (48), and provided with said speed profile (32) of the yarn (12), as a function of the transverse position (Y) of the yarn (12) with respect to the yarn guide cylinder (24), so as to be able to calculate the running speed of the yarn (12) at the clearer (44), - the processing and control unit (52) being programmed so as to receive from the at least one position sensor (48) the transverse position (Y) of the yarn (12), calculate the running speed of the yarn (12) upstream of the yarn guide cylinder (24) and send it to the clearer (44) so as to calculate the length of the yarn (12) crossing the clearer (44) in said given time interval.

2. Textile machine (4) according to claim 1, wherein said at least one position sensor (48) comprises a piezoelectric type sensor of the textile machine which identifies the passage of the yarn (12) at the first transverse end or tip (36) of the yarn guide cylinder (24) and / or the second transverse end or tail (40) of the yarn guide cylinder (24).

3. Textile machine (4) according to claim 2, wherein said piezoelectric type sensor is arranged between the clearer (44) and the yarn guide cylinder (24).

4. Textile machine (4) according to claim 1, 2 or 3, wherein two position sensors (48) of the yarn (12) are provided, respectively at the first transverse end or tip (36) of the yarn guide cylinder (24) and at the second transverse end or tail (40) of the yarn guide cylinder (24), so as to detect the passage of the yarn (12) at each of said transverse ends (36,40).

5. Textile machine (4) according to claim 1, 2 or 3, wherein two position sensors (48) of the yarn (12) are provided, interposed between the clearer (44) and the yarn guide cylinder (24), near the slots (28) of the yarn guide cylinder (24).

6. Textile machine (4) according to any one of claims 1 to 5, wherein said at least one position sensor (48) is a continuous type sensor configured so as to continuously monitor the transverse position (Y) of the yarn (12), comprised between the first transverse end or tip (36) of the yarn guide cylinder (24) and the second transverse end or tail (40) of the yarn guide cylinder (24), and to associate therewith the running speed of the yarn (12) upstream of the yarn guide cylinder (24), at each transverse position (Y) of the yarn (12) with respect to the yarn guide cylinder (24).

7. Textile machine (4) according to claim 6, wherein said continuous type sensor is a camera and / or CCD array.

8. Textile machine (4) according to any one of claims 1 to 7, comprising a diameter sensor (56) of the reel (16) during the formation of the latter, said diameter sensor (56) being operatively connected to said processing and control unit (52) programmed so as to calculate the running speed of the yarn (12) upstream of the yarn guide cylinder (24) also as a function of the diameter of the reel (16) being formed.

9. Textile machine (4) according to any one of claims 1 to 7, wherein the yarn guide cylinder (24) is configured so as to impart a rotational movement to the reel (16) on which the yarn (12) exiting the yarn guide cylinder (24) is wound.

10. Textile machine (4) according to any one of claims 1 to 9, wherin said textile machine (4) is a winding machine.

11. Method for detecting defects of yarn (12) being wound comprising the steps of: - providing a spool (8) on which is wound a yarn (12) to be unwound and rewound on a reel (16), - providing a reel (16) on which to wind said yarn (12) unwound from said spool (8), - providing a head supporting a yarn guide cylinder (24), rotating about a rotation axis (X-X), said yarn guide cylinder (24) having a plurality of slots (28) which receive and guide the yarn (12) unwound from the spool (16), said slots (28) defining a speed profile (32) of the yarn (12) housed therein, said yarn (12) translating, parallel to said rotation axis (X-X), from a first transverse end or tip (36) of said yarn guide cylinder (24) to a second transverse end or tail (40) of said yarn guide cylinder (24) and vice versa in an alternating manner according to a crossing movement, before being wound onto the reel (16), - providing for a clearer (44), arranged between the spool (16) and the yarn guide cylinder (24) so as to analyse the yarn (12) unwound from the spool (8) and not yet wound on the reel (16), to identify possible defects therein, in a given time interval, the yarn (12) crossing the clearer (44) along a straight direction according to a running speed, - providing at least one position sensor (48) which identifies the transverse position (Y) of the yarn (12) with respect to the yarn guide cylinder (24), along said crossing movement, - calculating the running speed of the yarn (12) at the clearer (44) by means of the position of the yarn (12) provided by said position sensor (48) and said speed profile (32) of the yarn (12), - sending said running speed of the yarn (12) to the clearer (44) so as to calculate the length of the yarn (12) crossing the clearer (44) in said given time interval.

12. Method for detecting defects of yarn being wound according to claim 11, comprising the step of continuously monitoring the transverse position (Y) of the yarn (12), between the first transverse end or tip (36) of the yarn guide cylinder (24) and the second transverse end or tail (40) of the yarn guide cylinder (24), and associating the running speed of the yarn (12) upstream of the yarn guide cylinder (24), at each transverse position (Y) of the yarn (12) with respect to the yarn guide cylinder (24).

13. Method for detecting defects of yarn being wound according to claim 11 or 12, comprising the step of continuously monitoring the diameter of the reel (16) being formed and using such a diameter to estimate the running speed of the yarn (12) upstream of the yarn guide cylinder (24).

14. Method for detecting defects of yarn being wound according to claim 11, 12 or 13, comprising the step of obtaining the exact length of unravelled yarn and thus the precise square footage of the reel being formed, so as to have batches of reels with predefined lengths which are uniform with each other.

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