YARN TRAVERSE APPARATUS

Abstract: Apparatus for winding a yarn on a bobbin, comprising setting means for setting a limit value (ϑ H or ϑ L ) of a leash angle, a traverse stroke (S) of a package (3) wound on the bobbin (2), a width (w) of the yarn, and a ribbon occurrence region (Y); means (28) for detecting the number of rotations of the bobbin; means (17) for detecting a winding speed of the yarn; means (13) for calculating a diameter of the package (3) in accordance with the number of rotations of the bobbin (2) and the winding speed of the yarn; means for calculating a winding ratio in accordance with the number of turns (T₀) of the yarn over two traverse strokes and with the number of turns (T 1(N) ) of the yarn over one pitch (P) corresponding to the limit value of the leash, and varying the winding ratio in steps so that the winding ratio is moved outside the ribbon occurrence region (Y) when the package (3) reaches a predetermined value within a predetermined region of the leash angle; means (13) for calculating the number of traverse strokes in accordance with the number of rotations of the bobbin and the winding ratio corresponding to the package diameter; and a traverse mechanism (12) for traversing the yarn in accordance with an output of the traverse operation means.

Description: The present invention relates in general to a yarn traverse apparatus for winding a continuous yarn or thread on the bobbin, and in particular to an improved yarn traverse apparatus which can prevent an occurrence of a so-called ribboning during the yarn winding operation. The US-A-4 049 211 discloses a winding apparatus winding a continuous yarn on a bobbin with a constant winding ratio. A speed control of a first drive controlling the rotation of the friction drive drum adjusts the speed of the first drive in accordance with the calculated rotational speed of the friction drive drum, in order to obtain a desired winding ratio. The bobbin holder and the yarn traversing means are separately driven by individual motors. The apparatus allows winding of a precision wound package or a random wound package. An electronic control unit calculates a desired value signal for the speed of the drive drum as a function of the yarn speed and compares this value to the actual value in order to obtain a correction signal for the drive of the drive drum. A similar calculation is made for controlling the speed of the yarn traversing means. In winding a continuous yarn or thread at high speed on a bobbin and forming a yarn package on the bobbin, the yarn Is generally wound with a constant leash angle of the yarn during the yarn winding operation. In this case, when a ratio of the number of rotations of the bobbin to the number of yarn traversing strokes (hereinafter referred to as a "winding ratio") is an integral number, the yarn to be wound tends to be wound on a turn of the yarn previously wound on the bobbin, thereby making the outer circumferential surface of the yarn package uneven and forming circumferential rib portions on the yarn package (called "ribboning"). Such a ribboning phenomenon may cause the outer circumferential layer of the yarn package to slide toward the center of a vibration during the yarn winding operation. If the vibration is caused by the ribboning phenomenon, the yarn tends to be unwound from the layer of the circumferential rib portion formed previous to the rib portions being now formed. In order to avoid these disadvantages, a step type yarn traverse device has been proposed in Japanese patent publication No. 57-33264. In this device, the aforementioned winding ratio is varied in steps to prevent the occurrence of ribbonning during the yarn winding operation. The conventional yarn traverse device of the step type, however, still has the following disadvantages: (I) It is recently desired that a various kinds of brands of different deniers be produced with a short cycle. In this instance, the winding ratio is required to be varied depending upon different widths of different yarns. It is, however, difficult to vary the winding ratio depending upon the different widths. (II) In the case that, in one yarn take-up device, it is required to vary a yarn traversing stroke depending upon a various kinds of brands in response to the requirement of FMS (Flexible Manufacturing System), it is difficult to vary the yarn traversing stroke. For example, it is the case that, in one yarn take-up device, a winding of four cops (i.e., four yarn packages and a stroke of 170) and a winding of eight cops (i.e., a stroke of 70) are put into practice. (III) Since an actual diameter of the package actually wound on the bobbin differs from a package diameter calculated from the number of rotations of the bobbin due to the contact pressure applied between the package and the friction roller held in rolling engagement with the package and due to the rib portions at the axial opposite ends of the package, there are the fluctuations of winding ratio. Furthermore, since the number of yarn traversing strokes is calculated by detecting the number of rotations of the bobbin and multiplying the detected value by the winding ratio, there is a delay of time in the calculation. Because of the delay of time, even if a winding ratio is set which does not cause the occurrence of ribboning, the ribboning will occur if the winding ratio is set in the vicinity of an integral number. The aforementioned disadvantages all degrade quality of the yarn wound on the bobbin. It is, accordingly, an important object of the present invention to provide an improved yarn traverse apparatus which is capable of enhancing quality of the yarn wound on the bobbin and which eliminates the aforementioned disadvantage attendant with the prior art. The object of the present invention is achieved by varying the winding ratio in steps so that an occurrence of ribboning and the like is avoided. A yarn traverse apparatus according to the invention comprises a bobbin on which a yarn is wound forming a yarn package; means for rotating said bobbin; setting means for setting upper and lower limit values of a crossing angle of said yarn, a traverse stroke of said yarn wound on said bobbin, a width of said yarn wound on said bobbin, and a ribbon occurrence region; bobbin rotational number detecting means for detecting the number of rotations of said bobbin on which said package is wound; winding-speed detecting means for detecting a winding speed of said yarn; package-diameter operation means for calculating a diameter of said package in accordance with said number of rotations of said bobbin detected by said bobbin rotational number detecting means and said winding speed of said yarn detected by said winding-speed detecting means; winding-ratio operation means for calculating a winding ratio in accordance with the number of turns of said yarn when a distance of two traverse strokes is divided by said yarn width and the number of turns of said yarn when one pitch corresponding to said upper limit value of said crossing angle is divided by said yarn width; traverse operation means for calculating the number of traverse strokes in accordance with said number of rotations of said bobbin and said winding ratio corresponding to said package diameter; and a traverse mechanism for traversing said yarn alternately in opposite directions parallel to an axis of rotation of said bobbin in accordance with an output of said traverse operation means so that said yarn is wound throughout said traverse stroke of said package; said winding-ratio operation means varying said winding ratio in steps so that said winding ratio is moved outside said ribbon occurrence region when said package diameter reaches a predetermined value between said upper and lower limit values of said crossing angle. The features and advantages of a yarn traverse apparatus according to the present invention will be more clearly understood from the following description in which Fig. 1 is a block diagram showing the fundamental concept of the present invention; Fig. 2 is a diagrammatic view of one embodiment of the yarn traverse apparatus according to the present invention; Fig. 3 is a block diagram of a program for calculating the winding ratio of the embodiment shown in Fig. 2; FIG. 4 is a schematic view of a bobbin on which a yarn is wound through a yarn traverse stroke with an upper limit value of a leash angle; FIG. 5 is a block diagram of a program for calculating the number of the yarn traverse strokes of the embodiment shown in FIG. 2; FIG. 6 shows the relationship between the winding ratio and a ribbon occurrence region with the leash angel in degree taken on the abscissa and with a package diameter in mm taken on the ordinate; FIG. 7 shows the relationship between the winding ratio and the ribbon occurrence region in the case that the width between the upper and lower limit values of the leash angle is relatively small; FIG. 8 is a block diagram of a program for calculating the winding ratio of another embodiment of the yarn traverse apparatus according to the present invention; and FIG. 9 shows the relationship between the winding ratio and the ribbon occurrence region according to the embodiment shown in FIG. 8. Referring now to FIG. 2 of the drawings, a cylindrical bobbin, designated by reference numeral 2, is rotatably supported on a bobbin spindle 1. The bobbin 2 is adapted to have a continuous yarn or thread wound thereon into a suitable form of yarn package 3. In parallel with the bobbin 2 is provided a friction roller 4 which is carried on a roller shaft 4a and which is rotatable on the shaft 4a. During the yarn winding operation, the yarn package 3 on the bobbin 2 is held in rolling contact with the friction roller 4. The yarn to be wound on the bobbin 2 is fed through a yarn traversing cam 5 adapted to move the yarn alternately in opposite directions parallel with the center axis of the bobbin 2 so that the yarn is distributed uniformally throughout the length of the yarn package 3. The spindle 1 of the bobbin 2 is connected through a drive shaft 6 to an induction motor 7 so that the bobbin 2 is driven for rotation about the spindle 1. The induction motor 7 is connected with an invertor 8 and rotates with the frequency corresponding to the output of the invertor 8. Thus, the bobbin 2 rotates with the frequency corresponding to the output of the invertor 8. The yarn traversing cam 5 is connected through a drive shaft 9 to an induction motor 10 so that it is driven for rotation about the drive shaft 9. The induction motor 10 is connected with an invertor 11 and rotates with the frequency corresponding to the output of the invertor 11. Thus, the yarn traversing cam 5 rotates with the frequency corresponding to the output of the invertor 11. The aforementioned yarn traversing cam 5, drive shaft 9, induction motor 10 and invertor 11 as a whole constitute a traverse mechanism indicated generally by reference numeral 12. The output of each of the invertors 8 and 11 is controlled by command signals from a controller 13 to which signals from first and second electromagnetic pick-ups 14 and 15 are inputted. The first electromagnetic pick-up 14 is disposed adjacent a gear 16 fixed on the shaft 4a of the friction roller 4 and detects the number of rotations of the gear 16. As a result, the number of rotations Nc of the friction roller 4 is detected indirectly from the number of rotations of the gear 16. The first electromagnetic pick-up 14 and the gear 16 of the friction roller 4 as a whole constitute winding-speed detecting means for detecting a winding speed of the yarn, which is designated generally by reference numeral 17. The second electromagnetic pick-up 15 is disposed adjacent a gear 18 fixed on the drive shaft 9 of the yarn traversing cam 5 and detects the number of rotations of the gear 18. As a result, the number of rotations Nt of the yarn traversing cam 5 is detected indirectly from the number of rotations of the gear 18. The second electromagnetic pick-up 15 and the gear 18 of the yarn traversing cam 5 as a whole constitute cam rotational number detecting means for detecting the number of rotations of the yarn traversing cam 5, which is designated generally by reference numeral 19. A third electromagnetic pick-up 27 is disposed adjacent a gear 26 fixed on the drive shaft 6 of the bobbin 2 and detects the number of rotations Nb of the bobbin 2. The third electromagnetic pick-up 27 and the gear 26 of the drive shaft 6 as a whole constitute bobbin rotational number detecting means for detecting the number of rotations of the bobbin 2, which is designated generally by reference numeral 28. To the controller 13 is inputted a signal from a setting device or means 20 which is adapted to set an upper limit value ϑ H of a leash angle (FIG. 4) of the yarn, a traverse stroke S of the package to be wound, a width w of the yarn to be wound, and a ribbon occurrence region Y. These values may be set manually by an operator of a winding machine or automatically by the setting device 20 itself on the basis of information from the controller 13. The controller 13 has a package-diameter operation means, a winding-ratio operation means and a traverse operation means, and comprises a central processing unit 21 labelled as "CPU", a read-only memory 22 labelled as "ROM", a random access memory 23 labelled as "RAM" and an input-output port 24 labelled as "I/O". The CPU 21 has received therein external datum which are necessary in accordance with programs read on the ROM 22, and processes values necessary for the yarn traversing control, giving and receiving datum between the CPU 21 and the RAM 23. The processed values are transferred from the CPU 21 to the I/O port 24. The I/O 24 receives signals from the electromagnetic pick-ups 14, 15 and 27 and a signal from the setting device 20 and delivers command signals to the invertors 8 and 11 and an indicative signal S H to an indicator 25. The ROM 22 has stored therein programs and datum in the CPU 21. The RAM 23 temporary memorizes external information and datum to be used in operation. The indicator 25 indicates information necessary for the winding control on the basis of the indicative signal S H delivered from the controller 13. FIGS. 3 and 5 are respectively block diagrams showing a program for the yarn traversing control. The yarn traversing control program according to the present invention consists or a winding-ratio arithmetic operation program indicated by "JOB-1" in FIG. 3 and a traverse number arithmetic operation program indicated by "JOB-2" in FIG. 5. The winding-ratio program JOB-1 and the traverse number program JOB-2 are processed in the recited order. In FIG. 3, the winding-ratio program JOB-1 commences by an input commencement operation to the setting device 20. At a step P₁ in the program JOB-1, necessary information, that is, a yarn winding speed V₁, a yarn traverse stroke S, a yarn width w, an upper limit value ϑ H of the crossing angle, and a ribbon occurrence region Y (FIG. 6) are first set. At a step P₂, a lower limit value ϑ L of the crossing angle is calculated in accordance with the following equation (1): ϑ L = ϑ H - 0.1 (1). After a count value of the number of changes of the winding ratio (hereinafter referred to as a "change count value") is set up as N = 0 at a step P 2a , a diameter D N of the yarn package 3 is set up as D₀ at a step P₃. That is, the package diameter D₀ is a diameter of the unwound bobbin 2 when the change count value N is zero. The yarn traverse stroke S, yarn width w, upper limit value ϑ H of the crossing angle, and package diameter D N are shown in FIG. 4. At a step P₄, the number of turns T₀ of the yarn wound on the bobbin 2 over one layer (that is, the number of turns T₀ of the yarn when a distance of two traverse strokes 2S is divided by the width w of the yarn) is calculated in accordance with the following equation (2), and changed into an integral number by omitting fractions or raising to a unit or counting fractions of .5 and over as an integral number. T₀ = 2 S / w (2). Likewise, at a step P₅, the number of turns T 1(N) of the yarn over one pitch corresponding to the upper limit value ϑ H of the crossing angle (that is, the number of turns N 1N of the yarn when the one pitch is divided by the yarn width w of the yarn) is calculated in accordance with the following equation (3) and changed into an integral number by omitting fractions or raising to a unit or counting fractions of .5 and over as an integral number. T 1(N) = π D N tan ϑ H / w (3). In the equations (2) and (3), it is preferable that the yarn width w be one to 1.2 times the actual size of the yarn. Thereafter, at a step P₆, a temporary winding ratio M N is calculated in accordance with the following equation (4): M N = T₀ / T 1(N) (4). The temporary winding ratio M N means the state wherein the yarn of width w is wound through one layer with that the number of rotations N B of the bobbin 2 is T₀ and the number of traverses is two times T 1(N) . At a step P₇, the temporary winding ratio M N is compared with the ribbon occurrence region Y. It is noted that a so-called ribonning (the yarn to be wound is wound on a turn of the yarn previously wound on the bobbin and makes the outer circumferential surface of the yarn package uneven) occurs if the winding ratio is within the ribbon occurrence region Y. If the temporary winding ratio M N is not within the ribbon occurrence region Y, the T 1(N) and the T₀ are discriminated at a step P₈ whether they are prime numbers from each other or not. If the T 1(N) and the T₀ are not prime numbers from each other, a value of 1 is added to the T₀ or T 1(N) at a step P₉ and thereafter, the T₀ or T 1(N) are returned back to the step P₆. In this instance, for example, in the case of the T₀, the value of 1 is added to the T₀ as T₀ = T₀ + 1 . It is noted that the addition may be also processed in accordance with the following equation (5): If, on the other hand, the temporary winding ratio M N calculated at the step P₆ is within the ribbon occurrence region Y at the step P₇, it is replaced with an upper limit value R H of the ribbon occurrence region Y (M N = R H ) at a step P₁₀ so that the temporary winding ratio M N is not within the ribbon occurrence region Y. A new T₀ is calculated at a step P₁₀ by the aforementioned equation (4) wherein the temporary winding ratio M N is equal to the upper limit value R H of ribbon occurrence region Y. The new T₀ calculated at the step P₁₀ is changed into an integral number at a step P₁₁. Thereafter, the T₀ advances from the step P₁₁ to the step P₈. It is noted that, in the stead of the T₀, the T 1(N) may be also calculated at the step P₁₀ by the aforementioned equation (4) wherein the temporary winding ratio M N is equal to the upper limit value R H of ribbon occurrence region Y and changed into an integral number at the step P₁₁. Thus, the step P₆ through the step P₉ and the steps P₁₀ and P₁₁ are repeated so that the T₀ and the T 1(N) become prime numbers from each other and that the temporary winding ration M N is moved outside the ribbon occurrence region Y. When the T₀ and the T 1(N) become prime numbers from each other and the temporary winding ration M N is not within the ribbon occurrence region Y, the T₀ and the T 1(N) advance from the step P₈ to a step P₁₂. At the step P₁₂, the T₀ thus processed through the steps noted above is set up as a new T₀, and at a step P₁₃, a true winding ratio W N is calculated in accordance with the following equation (6): W N = T₀ / T 1(N) (6). It is noted that if, in the stead of the T₀, the T 1(N) is calculated at the step P₁₀ by the aforementioned equation (4), the T 1(N) may be also set up as a new T 1(N) . Thereafter, the package diameter D N is calculated at a step P₁₄ when the lower limit value of the crossing angle and the winding ratio are ϑ T and W N , respectively. The package diameter D N calculated at the step P₁₄ is compared at a step P₁₅ with the package diameter D N-1 calculated through the previous routine. If the package diameter D N is equal to or less than the package diameter D N-1 , a new lower limit value ϑ L of the crossing angle is set up by the following equation (7): ϑ L = ϑ L - 0.1 (7). The new lower limit value ϑ L of the crossing angle returns back to the step P 2a . As a result, the difference between the upper and lower limit values ϑ H and ϑ L of the crossing angle gradually increases by 0.1 degrees. If, on the other hand, the package diameter D N is more than the package diameter D N-1 , it advances from the step P₁₅ to a step P₁₇. At the step P₁₇, the winding ratio W N-1 corresponding to the package diameter D N-1 is memorized in the random access memory (RAM) 23 of the aforementioned controller 13. At a step P₁₈, the package diameter D N is compared with the maximum diameter D H of a machine specification value. If the package diameter D N is equal to and less than the diameter D H , the change count value N is increased at a step P 18a as N = N + 1 . The change count value N increased by one returns back to the step P₃. Thereafter, the aforementioned steps are repeated. If, on the other hand, the package diameter D N is more than the D H , that is, if the diameter of the yarn package 3 exceeds the specification value of the machine, the calculation of the winding ratio W is completed, so that the winding-ration operation program JOB-1 ends. The traverse number operation program JOB-2 shown in FIG. 5 is then processed. The traverse number operation program JOB-2 commences at a step P₂₁ thereof by an actuation switch of the yarn take-up device. When the operation of the yarn take-up device commences, the number of rotations N B of the bobbin 2 is sampled in consecutive order with predetermined cycles at a step 22. At a step 23, a varying diameter D P of the package 3 is calculated with the number of rotations N B sampled at the step 22 and the yarn winding speed V in accordance with the following equation (8): D P = V / (π N B ) (8). The diameter D P of the package 3 calculated at the step 23 is compared with the maximum diameter D HP of a machine specification value at a step 24. If the diameter D P of the package 3 is more than the maximum diameter D HP , it is determined that it is impossible to wind, and therefore the now processing routine ends. If, on the other hand, the diameter D P of the package 3 is equal to and less than the maximum diameter D HP , it is determined that it is possible to wind, and the diameter D P of the package 3 is compared at a step P₂₅ with the diameter D N calculated in the program JOB-1 shown in FIG. 3. When the diameter D P is equal to the diameter D N , a winding ratio W corresponding to the diameter D P of the package 3 is looked up at a step P₂₆ and advances to a step P₂₇. When, on the other hand, the diameter D P is not equal to the diameter D N , the step P₂₅ advances directly to the step P₂₇ without through the step P₂₆. At the step P₂₇, a standard value B of the number of traverses is calculated in accordance with the following equation (9): B = N B / W N (9). The standard value B calculated at the step P₂₇ is compared at a step 28 with sampled values of the number of rotations N T of the yarn traversing cam 5, and the frequency of the invertor 11 supplying power to the motor 10 is controlled in accordance with the magnitude of the deviation between the standard value B and the number of rotations N T by a so-called PID control. Thereafter, the step 28 returns back to the step 22. Thus, the aforementioned steps are repeated until the diameter D P of the package 3 is more than the maximum diameter D HP . In this instance, the yarn is traversed alternately in opposite directions along the length of the package 3 on the bobbin 2 so that the winding ratio is the winding ratio W N determined in the program JOB-1 during the yarn winding operation. As a result, the occurrence of the ribbonning is prevented, and therefore the yarn wound according to the present invention is enhanced in quality. The reason why the yarn is suitably traversed is that the winding ratio such that the occurrence of the ribbonning is prevented is determined in advance in the program JOB-1 before the operation of the yarn take-up machine commences. The determination of such winding ratio will hereinafter be described in detail in conjunction with FIG. 6. As stated above, the yarn winding speed V₁, yarn traverse stroke S, yarn width w, upper limit value ϑ H of the crossing angle, and ribbon occurrence region Y are first inputted at the step P₁ of the program JOB-1. The lower limit value ϑ L of the crossing angle is then calculated in accordance with the upper limit value ϑ H of the crossing angle inputted at the step P₁ and the aforementioned equation (1). The change count value N is set up as N = 0, so that the diameter D N of the unwound bobbin 2 is set up as D₀ at the step P₃. It is noted that the diameter D₀ of the unwound bobbin 2 may be inputted in advance at the step P₁. At the step P₄, the number of turns T₀ of the yarn wound on the unwound bobbin 2 over one layer (that is, the number of turns T₀ of the yarn when a distance of two traverse strokes 2S is divided by the width w of the yarn) is calculated by the aforementioned equation (2) and changed into an integral number. Likewise, at the step P₅, the number of turns T 1(0) of the yarn over one pitch (when the diameter D N is equal to D₀ and the upper limit value of the crossing angle is ϑ H ) is calculated by the aforementioned equation (3) wherein the change count value N equals to zero, and changed into an integral number. Thereafter, according to the number of turns T₀ and the number of turns T 1(0) , the temporary winding ratio M₀ is calculated by the aforementioned equation (4) wherein the change count value N equals to zero. That is, a winding ratio of a point a indicated in FIG. 6 is obtained. The temporary winding ratio M₀ of the point a is compared with the ribbon occurrence region Y. In this embodiment, since the point a is outside the ribbon occurrence region Y, the T 1(0) and the T₀ are discriminated whether they are prime numbers from each other or not. In this embodiment, since the T 1(0) and the T₀ are not prime numbers from each other, a value of 1 is added to the T₀. When the T₀ and the T 1(0) become prime numbers from each other and the temporary winding ration M₀ is not within the ribbon occurrence region Y, the true winding ratio W₀ is calculated in accordance with the aforementioned equation (6) wherein the change count value N equals to zero. The winding ratio W₀ thus obtained corresponds to a point b indicated in FIG. 6. Accordingly, a point m of FIG. 6 is a starting point of the winding ratio of the unwound bobbin. Thereafter, the yarn package diameter D₁ is calculated when the lower limit value of the crossing angle and the winding ratio are ϑ L and W₀, respectively. That is, the diameter of a point c of FIG. 6 is obtained. The yarn package diameter D₁ is compared with the unwound bobbin diameter D₀ previously calculated. Since the diameter D₁ is more than the diameter D₀, the winding ratio W₀ corresponding to the diameter D₀ is memorized. As a result, the yarn is wound between the diameters D₀ and D₁ with the winding ratio W₀ indicated by line m-c which is not within the bobbin occurrence region Y. In this instance, since the diameter D₀ is less than the maximum diameter D H of the machine specification value, the program JOB-1 is repeated. That is, the change count value N is increased as N = N + 1 so that the number of turns T 1(1) of the yarn over one pitch (when the diameter D N is equal to the yarn package diameter D₁ and the upper limit value of the crossing angle is ϑ H ) is first calculated by the aforementioned equation (3), and the temporary winding ratio M₁ is calculated this time by the aforementioned equation (4). The winding ratio M₁ corresponds to a point d indicated in FIG. 6. Since the point d is within the ribbon occurrence region Y, the temporary winding ratio M₁ is replaced with an upper limit value R 2H of the ribbon occurrence region Y (M₁ = R 2H ). A new T₀ is calculated when the temporary winding ratio is the upper limit value R 2H of the ribbon occurrence region Y, and changed into an integral number. The temporary winding ratio R 2H corresponds to a point e indicated in FIG. 6. At the step P₈, the T 1(1) and the T₀ are discriminated whether they are prime numbers from each other or not. Since the T₀ and the T 1(1) are prime numbers from each other, the true winding ratio W₁ is calculated. The diameter D₂ is calculated from the winding ratio W₁ when the lower limit value of the crossing angle is ϑ L and the winding ratio is W₁. The diameter D₂ corresponds to a point f of FIG. 6. The diameter D₂ is compared with the diameter D₁ previously calculated. Since the diameter D₂ is more than the diameter D₁, the winding ratio W₁ corresponding to the diameter D₁ is memorized. The winding ratio W₁ starts from a point n of FIG. 6 when the diameter is D₁. The diameter D₁ is compared with the maximum diameter D H of the machine specification value. Since the diameter D₁ is still less than the maximum diameter D H of the machine specification value, the program JOB-1 is repeated. Likewise, the change count value N is increased to 2, and the number of turns T 1(2) is first calculated when the diameter of the package is D₂ and the upper limit value of the crossing angle is ϑ H , and the winding ratio M₂ is calculated this time. The winding ratio M₂ corresponds to a point g indicated in FIG. 6. The above noted processes are hereinafter repeated. As a result, as shown in FIG. 6, the winding ratio M₂ between the package diameters D₂ and D₃ is indicated by line g-h. The winding ratio M₃ between the package diameters D₃ and D₄ is indicated by line i-j. The winding ratio M₄ between the package diameters D₄ and D₅ is indicated by line k-o. The package diameter D₅ at the point o is compared with with the maximum diameter D H of the machine. In this embodiment, since the package diameter D₅ is more than the maximum diameter D H , the program JOB-1 ends. Thus, before the yarn traversing device is operated, the winding ratio which is capable of suitably avoiding the occurrence of the ribbonning is properly set up in advance in accordance with the various datum of yarn. Accordingly, the occurrence of the ribbonning can be effectively prevented when the yarn is traversed in opposite directions in accordance with the program JOB-2. FIG. 7 shows a characteristic of winding ratio when the difference between the upper and lower limit values ϑ H and ϑ L of the crossing angle is small. In FIG. 7, the winding ratio between points a ' and b ' is calculated as in the case of FIG. 6. At the point b ', the winding ratio M N of a point c ' is calculated. In this instance, since the winding ratio M N of the point c ' is within the ribbon occurrence region Y, it is set up as R 2H and the package diameter D N of a point e ' is calculated. With M N = R 2H , the package diameter D N is calculated again and as a result becomes equal to the diameter previously calculated. In this instance, the lower limit values ϑ L of the crossing angle is set up as ϑ L = ϑ L - 0.1 , the aforementioned processes are repeated until the point f is moved outside the ribbon occurrence region Y, so that the width between the upper and lower limit values ϑ H and ϑ L of the crossing angle become minimum. Although, in this embodiment, it has been determined at the step P₁₅ of the program JOB-1 whether the width between the upper and lower limit values ϑ H and ϑ L of the crossing angle is changed or not in accordance with the package diameter D N , it is noted that the change of the width may be also determined in accordance with the winding ratio W N at the step preceding to the step P₁₃. Furthermore, although the upper limit value ϑ H has been varied to change the width between the upper and lower limit values ϑ H and ϑ L of the crossing angle by the equation ϑ L = ϑ H - 0.1 , it is noted that the lower limit value ϑ L may be varied by an equation ϑ H = ϑ L - 0.1 . Furthermore, while the T₀ has been processed when the T₀ and T 1(N) are prime numbers from each other, it is noted that the T 1(N) may be processed. The effect of the present invention will hereinafter be compared with the aforementioned disadvantages (I), (II) and (III) attendant with the prior art. With respect to (I): A desired winding ratio is suitably selected depending upon the yarn width and the like. Accordingly, in the case that a various kinds of brands of different deniers are produced with a short cycle, the winding ratio can be easily varied depending upon different widths of different yarns. As a result, in the present invention, a loss resulting from the change of brands and a cost of production are extremely reduced. With respect to (II): In the case that, in one yarn take-up device, it is required to vary a yarn traversing stroke depending upon a various kinds of brands in response to the requirement of FMS (Flexible Manufacturing System), the yarn traversing stroke can be easily varied in accordance with present invention for the same reason noted above. With respect to (III): Since the number of rotations of the bobbin is detected without mechanically connecting the bobbin with the yarn traversing device and in accordance with this detected value the number of traverse strokes is calculated, the yarn traverse apparatus according to the present invention does not have the disadvantages that there are fluctuations of winding ratio due to the contact pressure applied between the package and the friction roller and due to the rib portions at the axial opposite ends of the package, and thus the yarn is enhanced in quality. In addition to the aforementioned effects, since the difference between the upper and lower limit values of the crossing angle is gradually increased by extremely small quantities (0.1 degrees), an unevenness on the lateral end faces of the package can be minimized which is caused by variation of strokes and the like resulting from variation of the crossing angle during the winding operation, thereby enhancing quality of the yarn and configuration of the package. While, in the aforementioned embodiment of the present invention, the width between the upper and lower limit values ϑ H and ϑ L of the crossing angle has been maintained constant from the beginning to the end of the winding operation, it is noted that the width of the crossing angle may also be controlled to be selected between 0.1 and 0.2 degrees if the winding ratio is not within the ribbon occurrence region and minimized only when the winding ratio is within the ribbon occurrence region. Such a variation of the width of the crossing angle will hereinafter be described as a second embodiment of the present invention in conjunction with FIGS. 8 and 9. In a program shown in FIG. 8, the step P₂ of the program shown in FIG. 3 is omitted and a new step P 4a is added therefor. At the step P 4a , the upper limit value ϑ H of the crossing angle is calculated in accordance with the following equation (10), and at a step P 16a , the upper limit value ϑ H of the crossing angle is calculated in accordance with the following equation (11): ϑ H = ϑ L + 0.2 (10), ϑ H = ϑ L + 0.1 (11). As a result, in the case that the winding ratio is within the ribbon occurrence region as shown in FIG. 9, the ratio of the upper and lower limit values ϑ H and ϑ L is raised to a unit with M N and R H for the first time, and the upper limit value ϑ H increases by 0.1 degrees because D N is equal to or less than D N-1 after the second time. Thereafter, the width between the upper and lower limit values ϑ H and ϑ L is varied and reduced to the minimum value so that the winding ratio is moved outside the ribbon occurrence region. It is noted that, in the case of the second embodiment, at a step P₁, the value of ϑ L is inputted in stead of the value of ϑ H . Also, in the calculation at the step P₄, the value of 0.2 in the equation (10) may be inputted as an input data at the step P₁. Furthermore, in the second embodiment, although the upper limit value ϑ H has been varied to change the width between the upper and lower limit values ϑ H and ϑ L of the crossing angle by the equations ϑ H = ϑ L + 0.2 and ϑ H = ϑ L + 0.1 , it is noted that the lower limit value ϑ L may be also varied by equations ϑ L = ϑ H + 0.2 and ϑ L = ϑ H + 0.1 . Furthermore, while the yarn winding speed has been detected in the calculation of the package diameter D N , it is noted that values set by the setting device may be also used. The present invention is applicable to both yarn take-up devices of the spindle drive type and the friction drive type. While, in the first and second embodiments, the induction motor has been used, it is noted that a synchronous motor, a DC motor and the like may be also used. From the foregoing description, it will be seen that an improved yarn traverse apparatus which is capable of enhancing quality of the yarn wound on the bobbin and which eliminates the aforementioned disadvantages attendant with the prior art is afforded by the present design.

Claims: A yarn traverse apparatus, comprising a bobbin (2) on which a yarn is wound forming a yarn package (3); means (7) for rotating said bobbin (2); setting means (20) for setting upper and lower limit values (ϑ H and ϑ L ) of a crossing angle of said yarn, a traverse stroke (S) of said yarn wound on said bobbin (2), a width (w) of said yarn wound on said bobbin, and a ribbon occurrence region (Y); bobbin rotational number detecting means (28) for detecting the number of rotations of said bobbin (2) on which said package (3) is wound; winding-speed detecting means (17) for detecting a winding speed of said yarn; package-diameter operation means (13) for calculating a diameter of said package (3) in accordance with said number of rotations of said bobbin (2) detected by said bobbin rotational number detecting means (28) and said winding speed of said yarn detected by said winding-speed detecting means (17); winding-ratio operation means (13) for calculating a winding ratio in accordance with the number of turns (T₀) of said yarn when a distance of two traverse strokes (2S) is divided by said yarn width (w) and the number (T 1(N) ) of turns of said yarn when one pitch corresponding to said upper limit value (ϑ H ) of said crossing angle is divided by said yarn width (w); traverse operation means (13) for calculating the number of traverse strokes in accordance with said number of rotations of said bobbin and said winding ratio corresponding to said package diameter; and a traverse mechanism (12) for traversing said yarn alternately in opposite directions parallel to an axis of rotation of said bobbin in accordance with an output of said traverse operation means so that said yarn is wound throughout said traverse stroke (S) of said package (3); said winding-ratio operation means varying said winding ratio in steps so that said winding ratio is moved outside said ribbon occurrence region when said package diameter reaches a predetermined value between said upper and lower limit values of said crossing angle. A yarn traverse apparatus as set forth in claim 1, in which said winding-ratio operation (13) has means for raising fractions of a winding ratio to a unit if the winding ratio is within said ribbon occurrence region (Y). A yarn traverse apparatus as set forth in claim 1, in which said setting means (20) has means for changing said upper and lower limit values (ϑ H and ϑ L ) of said crossing angle, and in which said winding-ratio operation means (13) has means which, if the winding ratio is within said ribbon occurrence region (Y), raises fractions of the winding ratio to a unit for the first time and varies the winding ratio in steps within a region of said upper and lower changed limit values (ϑ H and ϑ L ) of said crossing angle after the second time.

Inventors: SUGIOKA, TAKAMI
Applicants: TEIJIN SEIKI CO. LTD.
Application year: 1987
Main classification: B65H54
IPC codes: B65H54