EP0570875A2 - Process to determine a characteristic value for the operation of a loom and loom for the execution of this process - Google Patents

Abstract

In a loom, the tension in the weft thread (27) is measured, during the weaving operation, while it is being wound onto a drum (17) of a prewinding appliance (16), in order to obtain a characteristic value for the control of the weft insertion or the like. <IMAGE>

Description

The invention relates to a method for determining a parameter for the operation of a weaving machine, the means for inserting weft threads contain at least one prewinding device which has a winding device driven by a drive motor with a drum receiving the weft thread to be inserted in turns, and a weaving machine for performing the Procedure.

Weaving machines are known in which a weft thread supplied by means of a thread delivery system is inserted into a shed by means of a main nozzle and auxiliary nozzles. The thread delivery system contains a thread spool, a prewinder and one or more thread brakes. The values essential for the insertion of the weft thread, such as, for example, the pressure of the air, the time and the duration of the air supply at the main nozzle and the auxiliary nozzles, the time of the release of the weft thread on the prewinder and the time and duration of the action of the thread brake or Thread brakes are adjusted so that the weft reaches the opposite side of the shed within a certain time during the entry cycle.

It is known (FR 25 67 926 A1) to adapt these settings to the operating conditions during the weaving process, for which purpose the tension in the weft is measured at the end of the entry.

This measurement has the disadvantage that only adjustments to the settings for the subsequent firing process are possible, and that there is no clear connection between this measured voltage and the setting of the elements involved in the entry.

The invention has for its object to determine a parameter that can be evaluated for settings for the following weft entry or weft entries.

This object is achieved in that the tension in the weft thread is determined during winding on the drum of the prewinder.

The invention is based on the knowledge that the tension with which the weft thread is wound on the drum of the prewinding device is of essential importance for the quality of the weft thread insertion. Based on this value, which is determined before the actual weft entry, it is possible to adjust the settings for the subsequent weft entry immediately.

The tension in the weft thread during winding can be measured by means of a mechanical tension sensor. In a further embodiment of the invention it is provided that the tension in the weft thread is determined from measurements on the drive motor of the winding device of the prewinder. This results in a contactless determination of the tension in the weft thread, so that the weft threads are protected.

In one embodiment of the invention it is provided that the tension in the weft thread is determined by evaluating the measurements on the drive motor and taking into account the motor characteristics of the drive motor and by a control of predetermined target values. This determination of the tension in the weft takes into account the internal friction of the drive motor Not. This is generally not a problem, since it can be assumed that this internal friction is essentially constant and always the same.

In a further embodiment of the invention it is provided that characteristic values for the running behavior of the drive motor are measured and stored without a weft thread, and that characteristic values for the running behavior of the drive motor measured during winding of the weft thread are compared with the stored characteristic values in order to determine the tension in the weft thread. In this embodiment, the components of the internal friction of the drive motor of the winding device and / or components due to accelerations and decelerations on the thread tension are eliminated. In an expedient further refinement, it is provided that the measurement of the characteristic values for the running behavior of the drive motor without a weft thread is repeated one or more times during the operation of the weaving machine, after which these measured characteristic values are stored instead of the previously stored characteristic values. This ensures that changes in the internal friction of the drive motor of the winding device are taken into account, for example, by wear or temperature or the like. can change.

In a further embodiment of the invention it is provided that a thread brake with controllable braking action is connected upstream of the prewinding device, the braking action of which is controlled as a function of the tension determined in the weft thread. It is thus possible to set the tension with which the weft thread is wound onto the drum of the prewinding device, for example, to an approximately constant value.

In a further embodiment of the invention, to carry out the method in a weaving machine, it is provided that means are available which determine the tension in the weft thread during winding onto the drum of the prewinder.

Fig. 1

zeigt schematisch die Mittel zum Zuliefern eines Schußfadens und die Mittel zum Eintragen eines Schußfadens in ein Webfach einer Luftdüsen-Webmaschine,

Fig. 2

eine Motorcharakteristik für einen als Antrieb für einen Wickelarm eines Vorspulgerätes vorgesehenen Asynchronmotor und

Fig. 3

die Motorcharakteristik für einen als Gleichstrommotor ausgebildeten Antriebsmotor für den Wickelarm eines Vorspulgerätes.

Further features and advantages of the invention result from the following description of the embodiments shown in the drawing.

Fig. 1

shows schematically the means for supplying a weft and the means for inserting a weft into a shed of an air jet loom,

Fig. 2

a motor characteristic for an asynchronous motor provided as a drive for a winding arm of a pre-winding device and

Fig. 3

the motor characteristic for a drive motor designed as a DC motor for the winding arm of a prewinding device.

The weaving machine (1) shown only partially in FIG. 1 has a thread delivery system (2) for a weft thread and an insertion system (3) for this weft thread. The entry system (3) contains a main blowing nozzle (5) and auxiliary blowing nozzles (6) mounted on a sley (4), as well as valves (7) for supplying compressed air from a supply system (8) with a certain pressure of the main blowing nozzle (5) and the auxiliary blowing nozzles (6) feed. The entry system (3) also contains a thread detector (9) in order to detect the inserted weft thread on the side opposite the main blowing nozzle (5), as well as a reed (10).

The thread delivery system (2) contains a thread spool system (11) with a thread spool (12) attached to a holder, a thread guide (13) arranged after the thread spool (12), a thread detector (14) and a thread brake (15) that is electrically controlled in terms of its braking action ), which is arranged in front of a prewinder (16). The thread delivery system (2) also includes the prewinder (16), which contains a winding drum (17), on which the weft thread is wound into turns (28) by means of a winding arm (19) driven by a drive motor (18) becomes. The pre-winding device (16) also contains a locking pin (20) to release the weft thread to the entry system (3), and one or more detectors (21) to detect existing weft thread on the winding drum (17). The pre-winding device (16) also contains a winding detector (22) which detects the passing of the winding arm (19). A winding detector (23) is also provided in order to detect the windings (28) drawn off the winding drum (17). A thread guide (24) and an electrically controlled weft thread brake (25) are arranged after the winding drum. The weaving machine (1) has a control unit (26) which controls the weft insertion.

In order to insert a weft thread (27) into a compartment formed by the weaving machine (1), the control unit (26) removes the locking pin (20) from the winding drum (17) at a suitable time. The valves (7) of the main blowing nozzle (5) and / or the auxiliary blowing nozzles (6) are then activated for a suitable period of time. After the supply of a certain number of turns (28) to the entry system (3), which are detected by the winding detector (23), the control unit (26) activates the weft brake (25) in order to brake the weft (27). The locking pin (20) is then moved again to the winding drum (17) in order to lock the weft thread (27). The success of the insertion of the weft thread (27) is monitored by the thread detector (9).

In order to be able to feed turns (28) to the entry system (3), an endless weft thread (27) is removed from the yarn spool (12) by means of the winding arm (19), which is driven by the drive motor (18), and turned into turns (28 ) placed on the winding drum (17). The number of rotations of the drive motor (18) for the winding arm (19) is controlled by the control unit (26) in such a way that the winding arm (19) places on the winding drum (17) an average of as many turns per time period, depending on the number of signals of the winding detector (22) is determined how turns (28) were fed to the entry system (3), which had been determined from the number of signals from the winding detector (23).

According to the present invention, the tension is determined with which the weft thread (27) is placed on the winding drum (17) of the prewinder. It is possible to measure this thread tension by means of a mechanical tension sensor arranged between the thread brake (15) and the winding arm (19) - or better between the winding arm (19) and the winding drum (17). However, the tension in the weft thread is preferably carried out by means of measurements on the drive motor (18) of the winding arm (19), while windings (28) are placed on the winding drum (17).

In a first embodiment, the tension in the weft thread (27) is determined via the speed difference of the drive motor (18), i.e. via the speed difference between the speed specified by the control unit (26) and the actual speed of the drive motor (18). This speed difference is a measure of the torque that the drive motor (18) applies to lay the windings (28). This torque is in turn characteristic of the tension in the weft thread (27) with which this weft thread (27) is placed on the winding drum (17) of the prewinding device (16).

2 shows an example of a motor characteristic of a drive motor (18) designed as an asynchronous motor. The curve (29) represents the torque (t) theoretically delivered by this drive motor (18) as a function of the speed (N) of this drive motor (18). The speed (N0) is the synchronous speed at which the drive motor (18 ) is controlled by the control unit (26). If the frequency of the current supplied to the drive motor (18) is 50 Hz, the synchronous speed is 3000 rpm. By measuring the number of signals from the winding detector (22) per unit of time, the speed (N1) at which the drive motor (18) actually operates turns, be determined. Taking into account the speed difference between the speed (N0) and the speed (N1) and the associated motor characteristics, the torque (T1) that the drive motor (18) applies can be determined. The tension with which the weft thread (27) is placed on the winding drum (17) is a function of the torque (T1) which the drive motor (18) delivers. The tension in the thread approximately corresponds to the quotient of the torque (T1) and the radius of the winding arm (19) about its axis of rotation.

The torque (T1) is applied not only to place the weft thread (27) on the winding drum (17), but also to overcome the internal friction of the drive motor (18). The torque required to overcome the internal friction can be determined experimentally, for example, by driving the drive motor (18) in succession at different frequencies if there is no weft thread (27) in the winding arm (19). An example of the torque required to overcome the internal friction as a function of the speed (N) of the drive motor (18) is shown in FIG. 2 with the curve (30). This torque required for the internal friction depends on the wear and the temperature of the bearings of the drive motor. For this reason, it is advisable to regularly redefine the curve (30). This curve (30) can be determined, for example, whenever there is a break in the weft thread (27) in the region of the winding arm (19). Such a weft break can be determined by the thread detector (14) so that its signal can be used to cause the control unit (26) to determine the torque of the drive motor (18) required to overcome the internal friction. This newly determined torque is then stored in the control unit instead of the previously measured torque of the internal friction and used for the next comparisons to determine the tension in the weft thread (27). The difference between the torque (T1) that the drive motor (18) applies and the torque (T2) for overcoming the internal friction is then the torque which is applied to place the weft thread (27) on the winding drum (17). The tension in the weft thread (27) with which it is placed on the winding drum (17) is then the quotient of the torque (T1-T2) and the radius of the winding arm (19) about its axis of rotation.

The determination of the tension in the weft thread (27) can be further refined if the torques for the acceleration or deceleration of the drive motor (18) are taken into account. Since a torque is required for the acceleration of the drive motor (18) and a torque is also released during the deceleration of the drive motor (18), this torque must additionally be subtracted from the torque difference (T1-T2) or added to this in order to do exactly that Determine torque that is applied to place the weft (27) on the winding drum. The torque for accelerations or decelerations can be determined analogously to the torque for the internal friction of the drive motor if there is no weft thread in the winding arm (19). For this purpose, the winding arm (19) can be accelerated or decelerated differently at each speed.

Since the torque for overcoming the internal friction and for accelerating and decelerating high-speed pre-winding devices (16) is usually significantly smaller than the torque for placing the weft thread (27) on the winding drum, it can also be assumed with a simplified evaluation that this Torque for placing the weft thread (27) on the winding drum corresponds approximately to a certain percentage of the total torque (T1).

The curve (31) in FIG. 3 shows the current consumption (i) of a drive motor (18), designed as a direct current motor, of the winding arm (19) against the rotational speed (N). The recorded one Current is a measure of the torque. By measuring the absorbed current, a speed difference of the drive motor (18) to a speed specified by the control unit (26) can be measured. At the speed (N0) the speed difference = 0. The current has a value (I0) which corresponds to the current which is required to apply the torque to overcome the internal friction of the drive motor (18). The speed difference of the drive motor (18) can be determined from the difference between the measured current (I1) and the stored value of the current (I0). As mentioned above, the torque (t1) of the drive motor (18) can also be determined from this. The current (I0) can also be determined repeatedly in order to calculate the influence of the wear and the temperature of the bearings on the internal friction of the drive motor (18).

From the above it is clear that in principle any type of electric motor is suitable as a drive motor (18) for the winding arm (19). It is then also used to determine the tension in the weft thread (27), in which the applied torque is determined by using a feedback system, according to which the applied torque from the speed difference between the speed specified by the control unit and the measured, actual speed of the drive motor (18) is determined.

In a modified embodiment, it is not the winding detector (22) that is used to determine the speed of the drive motor (18), but a tachometer that is connected directly to the drive shaft (32) of the drive motor (18). Such a tachometer allows the speed to be determined on the basis of a so-called step response of the drive motor (18). The step response is the reaction time that the drive motor (18) needs to reach a suddenly specified, increased speed. From this reaction time, the torque that the drive motor (18) applies can be determined using known forms from electromechanics.

Since the tension with which the weft thread (27) is placed on the winding drum (17) is both a function of the diameter of the bobbin (12) and the speed at which the weft thread (27) is placed on the winding drum (17) and since this changes during the weaving process, it is possible, by determining the tension in the weft thread (27) during winding onto the drum (17), the settings of the times and the duration of the actuations of the elements of the insertion system ( 3) optimally before inserting a weft thread.

By controlling the thread brake (15) as a function of the measured tension in the weft thread (27) with a different braking effect, it is possible to keep the tension in the weft thread (27) largely constant during winding onto the winding drum (17), even if the diameter of the bobbin (12) and the winding speed of the weft thread (27) change. The force with which the thread brake (15) brakes the weft thread (27) becomes greater when the measured tension becomes smaller. This approximately constant tension in the weft leads to the advantage that the settings of the elements of the entry system have to be changed less frequently during the weaving process. In addition, this measure also allows the length of the inserted weft thread (27), which is measured on the winding drum (17) of the prewinder (16), to remain almost constant. This allows weaving with a limited length of waste.

When the braking action of the thread brake (15) is controlled, the instantaneously determined tension in the weft thread (27) placed on the winding drum (17) is used. For the control of the adjustable elements of the entry system (3), on the other hand, an average tension is evaluated with which the weft thread (27) has been placed on the winding drum (17).

The measurement of the tension in the weft thread (27) during winding onto the drum (17) of the pre-winding device (16) also allows, if weft thread types of the same type are woven with several weft thread delivery systems, the mixing ratio between the respective weft thread delivery systems to be entered and corresponding to one another adapt coming weft threads in such a way that the tension in the respective weft thread (27) is as low as possible. It is also possible to switch off a thread delivery system if the measured tension becomes too high. In addition, it is also possible to adapt the working speed of the weaving machine to the tension measured in the weft thread (27). In addition, the regular determination of the torque required for the internal friction of the drive motor (18) allows defects in the pre-winding device (16) to be recognized at an early stage. Likewise, the determination of the tension in the weft thread (27) while laying on the winding drum (17) of the pre-winding device (16) allows the control of the drive motor (18) of the pre-winding device (16) to be better controlled by the control unit (26).

The invention has been described in the foregoing with reference to a pre-winding device (16) with a driven winding arm (19) and a stationary winding drum (17). In an analogous manner, the invention can of course also be applied to pre-winding devices which have a stationary winding arm and a winding drum driven by a drive motor.

Claims (10)

Method for determining a parameter for the operation of a weaving machine (1), the means for inserting weft threads (27) contain at least one prewinder (16), which has a winding device driven by a drive motor (18) with a weft thread to be inserted into windings (28 ) receiving drum (17), characterized in that the tension in the weft thread (27) during winding on the drum (17) of the prewinder (16) is determined. Method according to claim 1, characterized in that the tension in the weft thread (27) is determined from measurements on the drive motor (18) of the winding device of the prewinding device (16). Method according to Claim 1 or 2, characterized in that the tension in the weft thread (27) is determined by evaluating the measurements on the drive motor (18) and taking into account the motor characteristics of the drive motor and setpoint values specified by a control unit (26). Method according to Claim 1 or 2, characterized in that characteristic values (N, I) for the running behavior of the drive motor (18) are measured and stored without a weft thread, and in that characteristic values (N, I) for measured during winding of the weft thread (27) the running behavior of the drive motor (18) for determining the tension in the weft is compared with the stored characteristic values. Method according to Claim 4, characterized in that the measurement of the characteristic values (N, I) for the running behavior of the drive motor (18) without a weft thread (27) is repeated one or more times during the operation of the weaving machine (1), after which the measured characteristic values with the previously stored characteristic values compared and / or stored instead of the previously stored characteristic values. Method according to one of Claims 1 to 5, characterized in that the thread winding device (16) is preceded by a thread brake (15) with a controllable braking action, the braking action of which is controlled as a function of the tension determined in the weft thread (27). Weaving machine (1) with means for inserting weft threads (27), which contain at least one prewinding device (16), which has a drive motor (18) controlled by a control unit (26) for a winding device with a weft thread (27) inserted into turns ( 28) receiving drum (17), characterized in that means are provided which determine the tension in the weft thread (27) during winding onto the drum (17) of the prewinder (16). Weaving machine according to claim 7, characterized in that means for detecting characteristic values (N, I) of the running behavior of the drive motor (18) of the winding device are provided, which are connected to an evaluation stage of a control unit (26). Weaving machine according to Claim 8, characterized in that the evaluation stage of the control unit (26) has a comparison stage for comparing characteristic values (I, N) determined and stored without weft thread (27) for the running behavior of the drive motor (18) with characteristic values measured during winding ( N, I) for the running behavior of the drive motor (18) contains. Loom according to one of claims 7 to 9, characterized in that the control unit (26) is connected to a thread brake (15) connected upstream of the prewinding device (16) with controllable braking action.

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