Positive feed picking device for a fluid jet loom

Abstract: A positive feed picking device (1) for a fluid jet loom comprises a yarn measuring and storing device (4), a main picking nozzle (9), a positive feed mechanism (12) comprising a drive roller (17) and a motor (16) for driving the drive roller (17), and disposed between the yarn measuring and storing device (4) and the main picking nozzle (9) to feed a weft yarn (2) positively to the main picking nozzdle (9) during a picking period, a sensor (13) disposed on a yarn path along which the weft yarn (2) travels to detect the delivery of a predetermined length of the weft yarn (2) from the yarn measuring and storing device (4), a motor controller (15) for controlling the operating speed of the motor (16) of the positive feed mechanism, and a controller (14) for controlling the positive feed mechanism (12). The controller (14) starts the positive feed mechanism at the start of a picking period. The motor controller (15) controls the motor (16) so that the rotating speed of the motor (16) varies according to a predetermined speed control characteristic.

Description: The present invention relates to a picking device for a fluid jet loom and, more particularly, to a positive feed picking device provided with a positive feed mechanism for positively feeding a weft yarn for picking. The main picking nozzle of a fluid jet loom needs to pick a weft yarn against a resistance against pulling out the weft yarn from a yarn measuring and storing device. US-A-4 932 442 discloses a positive feed picking device for a fluid jet loom according to the preamble of claim 1. However, the control of the positive feed mechanism is insufficient with respect to preventing a yarn breakage. Accordingly, it is an object of the present invention to enable yarn feeding operation at a high efficiency without entailing yarn breakage by accurately synchronizing the operation of a positive feed mechanism and the picking operation of a loom. Another object of the present invention is to further improve the efficiency of positive yarn feed operation by synchronizing the yarn feed operation of a positive feed mechanism and the weaving operation of a loom. To achieve the objects, the said controller stops the operation of the positive feed mechanism upon the reception of a detection signal provided by the sensor upon the detection of delivery of the predetermined length of the weft yarn from the yarn measuring and storing device; and in that a motor controller controls the operating speed of a motor for driving a drive roller of the positive feed mechanism so that the operating speed of the motor varies with the angular position of the main shaft of the fluid jet loom according to a speed control characteristic during the operation of the positive feed mechanism. Advantageously said speed control characteristic is represented by an upward convex curve on a rectangular coordinate system in which speed is measured upward on the vertical axis and the angular position of the main shaft of the loom is measured to the right on the horizontal axis. According to the invention yarn breakage is prevented and the rotation transmission efficiency of the rollers is enhanced. Fig. 1 is a block diagram of a positive feed picking device for a fluid jet loom; Fig. 2 is graphs of assistance in explaining the operating characteristics of the positive feed picking device of Fig. 1; and Fig. 3 is a fragmentary schematic view of a modification of a positive feed mechanism included in the positive feed picking device of Fig. 1. Referring to Fig. 1 showing the general constructin of a positive feed picking device 1 for a fluid jet loom, in a preferred embodiment according to the present invention, a weft yarn 2 unwound from a yarn package 3 is measured by, for example, a yarn measuring and storing device 4 of a fixed drum type and a predetermind length of the weft yarn 2 for one picking cycle, for example, a length corresponding to four coils on the yarn storage drum 6 of the yarn measuring and storing device 4, is stored on the yarn storage drum 6. In storing the weft yarn 2 on the yarn storage drum 6, the weft yarn 2 is held on the yarn storage drum 6 with a holding pin 7 and a rotary yarn guide 5 revolves around the yarn storage drum 6 to wind the weft yarn 2 around the yarn storage drum 6 in a predetermined number of coils. At the start of the picking period, the holding pin 7 is retracted by a pin operating device 8 to allow the weft yarn 2 stored on the yarn storage drum 6 to be unwound from the yarn storage drum 6 and to be picked into a shed 11 formed by warp yarns 10 by a fluid jetted by a main picking nozzle 9. The positive feed picking device 1 comprises, as principal components, a positive feed mechanism 12, a sensor 13, a controller 14 and a motor controller 15. The positive feed mechanism 12 is disposed between the yarn measuring and storing device 4 and the main picking nozzle 9 and comprises a drive roller 17, a servomotor 16 for driving the drive roller 17, a movable driven roller 18 capable of being brought into contact with the driveroller 17, and a lever 19 supporting the driven roller 18. The lever 19 has one end pivotally supported on a shaft 20 at a fixed position and the other end supporting the driven roller 18. The lever 20 is turned on the shaft 20 by, for example, an electromagnetic actuator 21 between a position where the driven roller 18 is separted from the drive roller 17 and a position where the driven roller 18 is in contact with the drive roller 17 to feed the weft yarn 2. The sensor 13 may be disposed at a position between a position where the weft yarn 2 is unwound from the yarn storage drum 6 and a position immediately before an exit of the shed 11 on a yarn passage. In this embodiment, the sensor 13 is disposed close to the circumference of the yarn storage drum 6 and near the holding pin 7 to detect the number of coils of weft yarn unwound from the yarn storage drum 6. The controller 14 receives an angular position signal indicating an angular position of the main shaft 22 of the loom provided by a rotary encoder 23 and a length signal provided by the sensor 13, and controls the pin operating device 8, the electromagnetic actuator 21 and the motor controller 15. The motor controller 15 is provided with a programs and a table containing the surface speed of the drive roller 17 in relation with the angular position of the main shaft 22. The motor controller 15 provides a command signal on the basis of an angular position signal indicating an angular position of the main shaft 22 provided by the rotary encoder 23 to control the operating speed of the servomotor 16. While the loom is in operation, the yarn measuring and storing device 4 stores four coils of weft yarn 2 on the yarn storage drum 6 for each picking cycle. Referring to Fig. 2, with the main shaft 22 at an angular position for pcking, the controller 14 drives the pin operating device 8 to release the weft yarn 2 stored on the yarn storage drum 6 by retracting the holding pin 7. At the same time or after a predetermined lag, the controller 14 gives a command signal to the motor controller 15 and drives the electromagnetic actuator 21 so that the driven roller 18 is brought into contact with the drive roller 17 to nip the weft yarn 2 therebetween. The motor controller 15 gives a driving signal to drive the servomotor 16 so that the drive roller 17 is driven for rotation at a surface speed corresponding to the angular position of the main shaft 22 of the loom according to a speed control characteristic represented by an upward convex curve. According to the speed control characteristic, the surface speed of the drive roller 17 increases sharply with time after the picking period has been started, reaches a maximum in a time in which one or two coils of the weft yarn 2 is unwound from the yarn storage drum 6, and then decreases gradually with time. During the picking period, the main picking nozzle 9 jets out picking fluid to pick the weft yarn 2 into the shed 11. Thus, the drive roller 17 and the driven roller 18 rotate according to the speed control characteristic to pull out the weft yarn 2 positively from the yarn storage drum 6 and feed the same to the main picking nozzle 9. Accordingly, the main picking nozzle 9 is subjected scarcely to resistance in picking the weft yarn 2 into the shed 11 formed by the warp yarns 10. Upon the reception of a detection signal indicating the delivery of three coils of weft yarn 2 from the yarn storage drum 6 from the sensor 13, the controller 14 drives the electromagnetic actuator 21 so that the driven roller 18 is moved away from the drive roller 17 to stop the positive feed operation of the positive feed mechanism 12. The sensor 13 may be disposed at a position shown in Fig. 1 and time when three coils of weft yarn are unwound from the yarn storage drum 6 may be estimated by detecting time when two and a half coils of weft yarn 2 are unwound from the yarn storage drum 6 by the sensor 13. A picking terminating period start at the time when the sensor 13 detects the two and a half unwound coils of weft yarn 2 and the weft yarn 2 is driven for picking only by the picking force of the main picking nozzle 9. Since the operating speed of the servomotor 16, namely, the surface speed of the drive roller 17, has sufficiently been reduced before the positive feed operation is stopped, the weft yarn 2 is not subjected to the sharp variation of yarn tension during the picking terminating period and hence the weft yarn 2 is not broken. At time when the positive feed operation of the positive feed mechanism is stopped or at time after the positive feed operation of the positive feed mechanism has been stopped, for example, time by which the three and a half coils of weft yarn 2 are unwound, the controller 14 drives the pin operating device 8 to bring the holding pin 7 into contact with the circumference of the yarn storage drum 6 to check the feed of the weft yarn 2. Accordingly, upon the completion of unwinding the four coils of weft yarn 2, the weft yarn 2 is held on the yarn storage drum 6 with the holding pin 7, and then the rotary yarn guide 5 is actuated to wind new coils of weft yarn 2 on the yarn storage drum 6 for the next picking cycle. According to the present invention, the positive feed mechanism controlled so as to start its operation at the start of a picking period and to stop its operation before the holding pin 7 holds the weft yarn. Accordingly, a predetermined length of weft yarn can accurately be fed by the yarn measuring and storing device, the frequency of yarn breakage by the roller's nipping or by cause of high tension is reduced, and the effiency of the yarn feed operation of the positive feed mechanism is enhanced. A positive feed picking device in accordance with the present invention may employ a sensor 13 for detecting the length of weft yarn inserted in the shed 11, disposed in the shed 11 as indicated by alternate long and two short dashes lines in Fig. 1. The positive feed mechanism 12 may be provided, instead of the drive roller 17 and the driven roller 18, with a drive roller 17 and a pressing member 24 for pressing the weft yarn 2 against the circumference of the drive roller 17, and the pressing member 24 may be operated directly by an electromagnetic actuator 21. The positive feed mechanism 12 may be provided with a drive roller and a driven roller kept continuously in contact with the drive roller, and with means for positively advancing the weft yarn to or positively retracting the weft yarn from the pair of rollers.

Claims: A positive feed picking device (1) for a fluid jet loom, comprising: a yarn measuring and storing device (4) for measuring and storing a weft yarn (2); a main picking nozzle (9) for picking the weft yarn; and a positive feed mechanism (12) disposed between the yarn measuring and storing device (4) and the main picking nozzle (9) to feed the weft yarn (2) positively to the main picking nozzle in a picking cycle; and a sensor (13) disposed at a position on a yarn path along which the weft yarn (2) delivered from the yarn measuring and storing device (4) travels to detect the delivery of a predetermined length of weft yarn (2) from the yarn measuring and storing device; a controller (14) that actuates the positive feed mechanism (12) upon the start of a picking period to feed the weft yarn (2) positively to the main picking nozzle (9) characterized in that the said controller stops the operation of the positive feed mechanism (12) upon the reception of a detection signal provided by the sensor (13) upon the detection of delivery of the predetermined length of the weft yarn (2) from the yarn measuring and storing device (4); and in that a motor controller (15) controls the operating speed of a motor (16) for driving a drive roller (17) of the positive feed mechanism (12) so that the operating speed of the motor (16) varies with the angular position of the main shaft of the fluid jet loom according to a speed control characteristic during the operation of the positive feed mechanism (12). A positive feed picking device for a fluid jet loom according to claim 1, wherein said speed control characteristic is represented by an upward convex curve on a rectangular coordinate system in which speed is measured upward on the vertical axis and the angular position of the main shaft of the loom is measured to the right on the horizontal axis.

Inventors: TAKEGAWA YUJIRO, TAKEGAWA, YUJIRO
Applicants: TSUDAKOMA IND CO LTD, TSUDAKOMA CORP.
Application year: 1991
Main classification: D03D47
IPC codes: D03D47