WEFT YARN MEASURING METHOD FOR A PICKING DEVICE

Abstract: A weft yarn measuring method for controlling the picking device (1) of a fluid jet loom to pick a weft yarn (2) of a predetermined length in each picking cycle. In releasing loops of the weft yarn (2) wound on the storage drum (6) of the pickig device (1), the retaining pin (7) of the picking device (1) is controlled so that only one of the loops of the weft yarn (2) is unwound at each reciprocation of the retaining pin (7), and the reciprocation of the retaining pin (7) is repeated a plurality of times to unwind accurately a plurality of loops of the weft yarn (2) corresponding to a predetermined length of the weft yarn (2) necessary for one picking cycle.

Description: The present invention relates to a weft yarn measuring method for a picking device for a fluid jet loom which enables the accurate measurement of a weft yarn of a necessary length. A drum type weft yarn measuring and storing device measures a weft yarn of a necessary length by winding the weft yarn on a stationary storage drum with a rotary yarn guide while a retaining pin retains the weft yarn on the storage drum. At a picking phase, the retaining pin is retracted from the circumference of the storage drum to release the weft yarn wound on the storage drum, and then the weft yarn is picked into a shed by a jet of fluid jetted by a picking nozzle. In measuring the weft yarn, the length of yarn unwound on the storage drum is determined by the number of loops of the weft yarn on the storage drum. Japanese Patent Laid-open Publication No. 57-29640 (DE-A-31 23 760) discloses an invention for unwinding the weft yarn of a length necessary for one picking cycle, in which the number of loops of the weft yarn unwound from a storage drum is counted by a photoelectric sensor disposed near the circumference of the storage drum. It is possible that such a photoelectric counting means fail to detect the quick passage of a thin weft yarn across a counting position and that the photoelectric counting means fails to count the number of loops accurately because fly and dust are liable to deposit on the light receiving surface of the photoelectric counting means. On the other hand, a device disclosed in Japanese Utility Model Laid-open Publication No. 61-164288 releases a plurality of loops of a weft yarn necessary for one picking cycle from a storage drum by controlling the duration of retraction of a retaining pin. This device, however, is unable to release the predetermined plurality of loops of the weft yarn accurately, because the running mode of the picked weft yarn with respect to a time axis is variable due to variation in the physical properties of the weft yarn and variation in the pressure of the picking fluid. That is, although the retaining pin is retracted for a predetermined time, the running speed of the picked weft yarn is caused to vary by the variation of the physical properties of the weft yarn and the variation of the pressure of the picking fluid and, consequently, the number of loops of the weft yarn unwound in the predetermined time during which the retaining pin is held at the retracted position varies. The greater the number of loops of the weft yarn necessary for one picking cycle, the greater is error in the measurement. Accordingly, it is an object of the present invention to provide a weft yarn measuring method by which an accurate number of loops of a weft yarn can be unwound from a storage drum in feeding the weft yarn for picking operation. To achieve the object of the invention, the present invention provides a weft yarn measuring method with the features of claim 1 A single loop of the weft yarn wound on a storage drum is unwound every time a retaining pin is retracted instead of unwinding a plurality of loops of the weft yarn every time the retaining pin is retracted, and the retraction and advancement of the retaining pin is repeated several times for one picking cycle to unwind a necessary length of the weft yarn accurately from the storage drum for each picking cycle. Thus, the loops of the weft yarn are unwound from the storage drum one at a time and, consequently, the loops of the weft yarn ar retained by the retaining pin before the loops of the weft yarn are affected by the large variation of the running characteristics of the picked weft yarn. Thus, the predetermined number of loops of the weft yarn are unwound accurately. According to the present invention, a predetermined number of loops of the weft yarn are unwound by repeating the retraction and advancement of the retaining pin for each picking cycle, and the weft yarn wound on the storage drum is retained with the retaining pin before the weft yarn wound on the storage drum is affected by the large variation of the running characteristics and variation in the physical properties of the picked weft yarn. Therefore, the method of the present invention reduces error in the measurement of the weft yarn more effectively than the conventional method by which a plurality of loops of the weft yarn is unwound from the storage drum in one cycle of retraction and advancement of the retaining pin. The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings. Fig. 1 is a block diagram of a picking device for carrying out a weft yarn measuring method in a first embodiment according to the present invention; Fig. 2 is a block diagram of a controller incorporated into the picking device of Fig. 1; Fig. 3 is a time chart of assistance in explainig the operation of the picking device of Fig. 1; Fig. 4 is a block diagram of a controller incorporated into a picking device for carrying out a weft yarn measuring method in a second embodiment according to the present invention; Fig. 5 is a time chart of assistance in explaining the operation of the picking device for carrying out the weft yarn measuring method in the second embodiment according to the present invention; and Fig. 6 is a block diagram of a controller incorporated into a picking device for carrying out a weft yarn measuring method in a third embodiment according to the present invention. Referring to Fig. 1 showing a picking device 1 for carrying out a weft yarn measuring method in a first embodiment according to the present invention, a weft yarn 2 unwound from a yarn package 3 is wound by the rotary motion of a rotary yarn guide 5 on a stationary storage drum 6 while the free end of the weft yarn 2 is held on the circumference of the storage drum 6 with a retaining pin 7. The retaining pin 7 is operated for advancement and retraction by an operating unit 8. The operating unit 8 is controlled by a first controller 9 during the highspeed operation of the loom and is controlled by a second controller 10 on the basis of a weft yarn measuring method of the present invention during the low-speed operation of the loom. The operating unit 8 retracts the retaining pin 7 from the circumference of the storage drum 6 in synchronism with picking operation to release the loops of the weft yarn 2 from the circumference of the storage drum 6, a picking nozzle 11 jets a fluid to pick the weft yarn 2 into a shed 12, and then a plurality of subnozzles 13 assist the picked weft yarn 2 in running through the shed 12. The picking nozzle 11 and the subnozzles 13 are connected to fluid sources 14 and 15 storing pressurized fluid through piping 16 and control valves 17 and 18, respectively. The control valves 17 and 18 are controlled by a picking controller 19 in synchronism with the operation of the loom. While the loom is operated at a low speed for gaiting the loom or in correcting mispicks, the second controller 10 controls the operating unit 8 in accordance with the weft yarn measuring method of the present invention to release a plurality of loops of the weft yarn from the storage drum 6 at a time so that the weft yarn 2 of a length necessary for one picking cycle is picked. That is, upon the reception of a weft yarn release command from the main controller of the loom, the second controller 10 executes one control routine to make the operating unit 8 retract the retaining pin 7 from the circumference of the storage drum 6 to release the weft yarn 2 from the storage drum 6 and to make the operating unit 8 advance the retaining pin 7 to the circumference of the storage drum 6 before a time necessary for releasing one loop of the weft yarn 2 elapses after the retraction of the retaining pin 7 so that only one loop of the weft yarn 2 is unwound from the storage drum 6. On the other hand, the picking controller 19 controls the control valves 17 and 18 to jet the fluid continuously from the picking nozzle 11 and the subnozzles 13 at a pressure lower than the normal pressure for the normal picking operation to insert the weft yarn 2 of a length corresponding to one loop on the storage drum 6 in the shed 12. Thus, the weft yarn 2 of a length corresponding to one loop on the storage drum 6 is inserted at each reciprocation of the retaining pin 7. Suppose that the length of the weft yarn 2 necessary for one picking cycle corresponds to four loops. Then, the second controller 10 repeats the control routine three more times so that the weft yarn 2 of a length corresponding to four loops on the storage drum 6 is released accurately from the storage drum 6 for one picking cycle. Thus, according to the present invention, one loop of the weft yarn 2 is unwound from the storage drum 6 at each reciprocation of the retaining pin 7 and the reciprocation of the retaining pin 7 is repeated by necessary times. Accordingly, the measurement of the necessary length of the weft yarn 2 released from the storage drum 6 is affected scarcely by variation in the physical properties of the weft yarn 2 and variation in the picking conditions, so that accurate measurement of the necessary length of the weft yarn is achieved. First Embodiment (Figs. 2 and 3) In the first embodiment, the second controller 10 repeats the control routine continuously in response to one weft yarn release command. Referring to Fig. 2, when a release signal A of HIGH is applied to an input terminal 20, a one-shot multivibrator 21 generates a pulse at a leading edge, sets a down counter 26, and starts a timer 23 througth an OR circuit 22. Then, the timer 23 generates a timer output signal B of HIGH for a time t₁ as shown in Fig. 3. A NOT circuit 24 converts the timer output signal B is converted into a driving signal G of LOW, an amplifier 25 amplifies the driving signal G, and then the amplified driving signal G is applied to the operating unit 8 to make the operating unit 8 retract the retaining pin 7. A timer 27 provided after the timer 23 generates a timer output signal C of HIGH for a time t₂ after the timer output signal B has fallen to decrement the count of the down counter 26 by one. Thus, the retaining pin 7 is retracted for the time t₁ and then the retaining pin 7 is held at the retaining position for the time t₂ to unwind one loop of the weft yarn 2 from the storage drum 6 while the retaining pin 7 is retracted. A setting unit 28 for setting the length of the weft yarn necessary for one picking cycle is set beforehand for the number of loops corresponding to the necessary length of the weft yarn 2. A counter output signal D remains HIGH until the count of the down counter 26 reaches zero. An AND circuit 29 generates an output signal of HIGH when the counter output signal D of HIGH, and the output signal of HIGH of a NOT circuit 30 which receives the timer output signal C are applied thereto. Therefore, the AND circuit 29 generates an output signal of HIGH to start the timer 23 again when the timer output signal C becomes LOW. Thus, four cycles of the weft yarn releasing operation is executed successively to release four loops of the weft yarn 2 from the storage drum 6. The time t₂ is determined so that one loop of the weft yarn 2 is released completely in a time t₁ + t₂. While the output signal D of the down counter 26 is HIGH, an OR circuit 32 applies a jet start signal F of HIGH to the picking controller 19 to make the picking nozzle 11 and the subnozzles 13 jet the fluid continuously. A timer output signal E of HIGH is generated countinuously for a time t₃ after the counter output signal D has changed LOW, and hence the picking nozzle 11 and the subnozzles 13 continue jetting the fluid for the time t₃. Thus, upon the reception of the weft yarn release signal A of HIGH, the second controller 10 reciprocates the retaining pin 7 by a number off reciprocations corresponding to the number of loops corresponding to the length of the weft yarn 2 necessary for one picking cycle, the loops of the weft yarn 2 is unwound intermittently one at a time from the storage drum 6. Second Embodiment (Figs. 4 and 5) The first embodiment determines timing of the next weft yarn releasing operation by the timer 27, while the second embodiment determines timing of the next weft yarn releasing operation by detecting a shock of engagement of the retaining pin 7 with the weft yarn 2 after one loop of the weft yarn 2 has been released. In the second embodiment, a flip-flop 33 is provided instead of the timer 27 between the timer 23 and the down counter 26 as shown in Fig. 4. A strain gauge 34 attached to the retaining pin 7 is connected through a shaping circuit 35 to the reset input terminal of the flip-flop 33. The timer 23 generates a timer output signal B of HIGH for a time t₁ after the weft yarn release signal A of HIGH has been applied to the second controller 10 as shown in Fig. 5 to set the flip-flop 33, so that the flip-flop 33 generates a flip-flop output signal J of HIGH. When the retraced retaining pin 7 is advanced, and engages the weft yarn 2 being unwound, an external force acts on the strain gauge 34, and then the strain gauge 34 generates an output signal to reset the flip-flop 33. Thus, loops of the weft yarn 2 corresponding to a length of the weft yarn 2 necessary for one picking cycle are unwound automatically. Third Embodiment (Fig. 6) In the third embodiment, the retaining pin 7 is retracted and advanced manually. An operator closes a weft yarn release switch 36 to provide the weft yarn release signal A. Then, a one-shot multivibrator 37 is actuated to retract the retaining pin for a time t determined by a timer 38, and thereby one loop of the weft yarn 2 is unwound surely from the storage drum 6. For picking operation during the gaiting of the loom, the loom is stopped in a picking phase where the shed is formed for picking operation and the control valves 17 and 18 are opened simultaneously to jet the fluid continuously from the picking nozzle 11 and the subnozzles 13. Then the operator pushes the push-button of the weft yarn release switch 36 by a frequency corresponding to the number of loops corresponding to the length of the weft yarn 2 necessary for one picking cycle to insert the weft yarn 2 in the shed. Then, the operator makes the main shaft of the loom rotate one full turn to form a new shed 12 for the next picking operation, and then repeats the same picking procedure. Modification Although the present invention has been described as applied to the measurement of the weft yarn while the loom is operating at a low operating speed, the present invention is applicable also to the measurement of the weft yarn in a transient operating state subsequent to the start of the loom and to that in the normal high-speed operation of the loom. Although the invention has been described in its preferred form with a certin degree of particularity, it is to be understood that many variations and changes are possible in the invention without departing from the scope thereof.

Claims: A weft yarn measuring method for a picking device (1) which winds a weft yarn (2) in loops around a stationary storage drum (6) by a rotary motion of a rotary yarn guide (5) while a part of the weft yarn (2) is held on the circumference of the storage drum (6) with a retaining pin (7), retracts the retaining pin (7) to release the loops of the weft yarn (2) from the storage drum (6), and picks the released weft yarn (2) into a shed (12) by a picking nozzle (11) by a means of a jet of fluid, characterized in that the retaining pin (7) after having been retracted from the circumference of the storage drum (6) to release the weft yarn (2) from the storage drum (6) is advanced to the circumference of the storage drum (6) before the necessary time for unwinding one loop of the weft yarn (2) from the storage drum (6) has elapsed in order to unwind only one loop of the weft yarn (2) from the storage drum (6), the weft yarn (2) releasing procedure being repeated a plurality of times to unwind loops of the weft yarn (2) corresponding to a length of the weft yarn (2) necessary for one picking cycle. A weft yarn measuring method according to Claim 1, wherein timing of retraction of the retaining pin (7) and timing of advancement of the retaining pin (7) are controlled by timer output signals (C, D). A weft yarn measuring method according to Claim 1 or 2, wherein the frequency of reciprocation for retraction and advancement of the retaining pin (7) is counted by a down counter (26), and the reciprocation of the retaining pin (7) is stopped when the counter output signal (D) is provided upon the arrival of the count of the down counter (26) at zero. A weft yarn measuring method according to Claim 1, wherein the completion of operation for unwinding one loop of the weft yarn (2) is detected by a signal generated upon the engagement of the retaining pin (7) with the weft yarn (2). A weft yarn measuring method according to Claim 1, wherein the second weft yarn releasing operation and the subsequent weft yarn releasing operation is started at a moment detected by the signal generated upon the engagement of the retaining pin (7) with the weft yarn (2). A weft yarn measuring method according to any one of Claims 1 through 5, wherein a command to start releasing the weft yarn (2) from the storage drum (6) is provided by either a weft yarn released command signal (A) provided by the main controller of the loom or the manual operation of a weft yarn releasing switch (36) by the operator.

Inventors: MAENAKA, KOYU
Applicants: TSUDAKOMA CORPORATION
Application year: 1988
Main classification: D03D47
IPC codes: D03D47