EP0670384A1 - Thread loss detection in dummy shuttle looms - Google Patents

Abstract

In a projectile weaving machine the weft thread (14) is caught in movable yarn clamps (32,34) and severed. The free end is then tucked into the selvedge and the clamps are opened. To detect misses the presence of the weft thread (14) between the clamp body (50) and the spring loaded jaw (54) is sensed directly by evaluating an electrical signal produced by the direct contact of the clamp jaws (52,56) for a pre-determined time interval.

Description

The invention relates to a method and an apparatus for the detection of thread losers in the weft and catch mechanism of a projectile weaving machine, in which a tensioned weft thread is taken over and clamped by edge thread clamps which can be pivoted on a movable rod, separated from a pair of scissors in the weft mechanism with a free end free thread ends are inserted into the fabric edges with selvage needles and the edge thread clamps are opened. The invention further relates to an application of the method.

In the case of a projectile weaving machine, for example from Sulzer Rüti, a rapier projectile enters the weft thread into a shed. The energy required to fire the projectile is stored by turning a torsion bar. After releasing a lock, the torsion bar snaps back into its original position and accelerates the projectile smoothly using a lever. During its flight through the shed, the projectile slides through a rake-shaped guide. A transport device arranged under the shed brings the projectile braked in the catching mechanism back into the firing position in the shooting mechanism.

A projectile weaving machine can process all kinds of thread-like yarns, for example spun yarns made of natural, chemical and mixed fibers, endless yarns made of cellulose and synthetic materials, smooth and textured, fancy yarns and threads as well as glass fiber yarns, but also narrow ribbons and metal threads. In the following, all these and other forms of training are summarized with the term thread, especially weft thread.

Fig. 1 shows the known entry principle on a partial indicated projectile weaving machine 10 by Sulzer Rüti. All parts which are not essential for the description of the present invention and are known to the person skilled in the art are omitted for the sake of simplicity.

A weft thread 14 is unwound from a thread bobbin 12 and is held in the weft mechanism 16 (not shown in more detail). A swiveling retraction lever 18 with deflection rollers, not shown, forms a thread triangle 20. The weft thread 14 first passes through a thread brake 22, then a probe 24, which controls whether the thread is pulled and is therefore also called thread guide.

On the right side of the projectile weaving machine 10 there is the catch mechanism 26 which, among other things, brakes the projectile 28, which is shown in a greatly enlarged manner, and leads it back to the weft mechanism 16. The projectile 28, which is brought to a standstill and pushed back by a projectile catching brake, not shown, with a projectile clip 30 for the weft thread 14 has a distance a of about 15 to 20 mm from the edge thread clamp 32 of the catching mechanism 26. Arranged in the weft mechanism 16 is a mirror-image-shaped edge thread clamp 34, likewise on a displaceable, not visible linkage, which travels about 30 to 40 mm back and forth in the direction perpendicular to the plane of the drawing per work cycle.

The distance b of the edge thread clamps 32, 34 from the reed 36 is very small, it is approximately 1 mm. The reed 36 penetrated by the warp threads 38 places the weft threads 14 on the fabric 40, depending on the program after one to five shots.

The edge thread clamps 32, 34 have the task of taking over and holding the weft thread 14 after the projectile 28 has been braked and positioned until the free thread ends, which in practice are approximately 15 mm long, pass through the selvage needles 42, 44 into the fabric edges 46, 48 which last procedural step is also referred to as depraved. To after pushing back the braked projectile 28, the weft thread 14 is no longer stretched for the time being, it is tensed by a retraction phase. If an edge thread clamp 32 loses the weft thread 14, it springs back and cannot be inserted into the fabric edge 46 by the selvage needle 42. There is a particular risk of thread loosening with thin weft threads. This thread loser results in a reduction in the quality of the fabric.

• Beim in Fig. 1 dargestellten Eintragprinzip an Projektilwebmaschinen ist ein Tastkopf 24, der Fadenlaufwächter, in jede Schussfadenzuführung eingebaut. Mit dieser Ueberwachung kann jedoch lediglich festgestellt werden, dass das Projektil 28 den Schussfaden 14 in die Endposition gebracht hat, ein Nichterfassen oder Verlieren des Schussfadens durch die Randfadenklemme 32 wird nicht angezeigt.
• In der DE,A1 4010106 wird ein Preller-Wächter beschrieben, welcher der Detektion von Fadenverlierern dient, die infolge mangelhaft gebremster Projektile auftreten. Auch diese Preller-Wächter können das Nichterfassen oder Verlieren des Schussfadens durch die Randfadenklemme nicht erfassen.

Rapid detection of a thread loser is therefore essential so that the resulting tissue defects are not only noticed during the follow-up inspection. The control takes place according to the known prior art, for example as follows:

• In the entry principle shown in Fig. 1 on projectile looms, a probe 24, the thread guide, is installed in each weft feed. With this monitoring, however, it can only be ascertained that the projectile 28 has brought the weft thread 14 into the end position, a failure to detect or lose the weft thread by the edge thread clamp 32 is not indicated.
• DE, A1 4010106 describes a bouncer guard which is used to detect thread losers which occur as a result of poorly braked projectiles. These bouncer guards also cannot detect the failure to detect or lose the weft thread through the edge thread clamp.

The inventor has set himself the task of creating a method and a device of the type mentioned at the outset with which the non-detection or the loss of the weft thread by the edge thread clamps can be systematically and quickly reliably and reliably detected by automatic detection and the necessary follow-up actions triggered.

With regard to the method, the object is achieved according to the invention in that a direct check is carried out to determine whether the weft thread lies between the clamp body and the tensionable clamp foot of the edge thread clamps, by a direct contact of the contact surfaces of the clamp body with the contact surfaces of the clamp foot during a fixed time interval electrical signal is generated and evaluated. Further developing and special embodiments of the method according to the invention are the subject of dependent patent claims.

No electrical signal can be generated if there is such a thin thread on the contact surfaces between the terminal body and the terminal foot. The electrical signal is generated in a manner known per se, but with means arranged on the edge thread clamp, e.g. electrostatic, piezoelectric, electro-optical or inductive. Of course, in the case of a metal thread which electrically short-circuits the terminal body and the terminal foot, electrostatic and measurement methods based on electrical contacts are not taken into account.

When a signal is generated by the piezoelectric effect, mechanical pressure is exerted on polar crystals. A thread lying on the contact surfaces between the terminal body and the terminal foot dampens the shocks when it is closed in such a way that a greatly reduced electrical signal is generated compared to the terminal body and terminal foot hitting one another directly.

According to another variant, photocells on the clamp body and on the shaft for the clamp foot can be used to check whether the contact surfaces of the clamp body and the clamp foot are closed at a distance corresponding to the thread thickness or directly, without an intermediate thread.

According to a further variant, it is inductively checked whether the shaft for the terminal foot is immersed so deeply in a coil that this corresponds to a direct contact between the terminal body and the terminal foot, which is indicated when an electrical signal is triggered.

Since the signals generated are generally relatively weak, they are expediently amplified in the area of the edge thread clamp and passed on to a processor.

The edge thread clamps move back and forth at a high frequency of about 30 to 40 mm in one work cycle. The signal is therefore transmitted not only by cable, but also optically, especially in the infrared range, or inductively.

Strong and numerous sources of interference occur in a working weaving machine, which have a disruptive effect on the method according to the invention. For this reason, the electrical signals are only generated and evaluated during a defined time interval. The time interval, also called the time window, is triggered by a precisely defined movement sequence of the projectile weaving machine or by a flight trigger, which detects the projectile flying by.

A minimum threshold value, which must be exceeded for evaluation, is preferably established for the electrical signal. This threshold value is, for example, 50% of the measurement signal determined. All underlying electrical signals are filtered out as interference signals. For example, according to the piezoelectric method, an electrical signal is produced even with the thread lying between the clamp body and the clamp foot, which, however, due to the damped impact, does not reach the threshold value and is filtered out.

With regard to the device, the object is achieved according to the invention in that a residual thread monitor is arranged in or on the edge thread clamps.

The remaining thread monitor is connected to the evaluation circuit, for example a microprocessor, via electrical connection cables, also to an inductive or optical intermediate stage with converters known per se.

The remaining thread monitor is expediently installed in a recess in the terminal body, depending on the measuring method used, preferably adjacent to the contact surface to the terminal foot. In the piezoelectric method, for example, shocks can be absorbed practically undamped.

The residual thread monitor can also be applied to the clamp body with a clamping bracket or another holding device or fixed to it with a housing or carrier. Because of the narrow space in the area of the edge thread clamps, the remaining thread monitor is preferably attached to the narrow side of the clamp body, as already mentioned by clamping or flanging, but also by inserting it.

The edge thread monitor is preferably a shock sensor, in particular with a piezo oxide, a potentiometric measuring cell, an electrical micro-contact between the contact surfaces of the terminal body and the terminal foot, a pair of photocells or an inductive displacement sensor, all elements known per se.

The method according to the invention is used for switching off a projectile weaving machine and / or signaling a weft error when the weft thread is missed or lost due to the edge thread clamp. This ensures for the first time that it can be determined with certainty whether the edge thread clamp has missed or lost the weft thread. Weaving errors that have so far often remained undetected or discovered too late can thus be immediately detected and eliminated.

- Fig. 2

eine Ansicht einer Randfadenklemme mit zwei Varianten eines eingebauten Randfadenwächters,

- Fig. 3

eine Variante gemäss Fig. 2, mit einem nachgerüsteten Randfadenwächter, und

- Fig. 4

einen Horizontalschnitt durch einen Randfadenwächter gemäss Fig. 3.

The invention is explained in more detail with reference to exemplary embodiments shown in the drawing, which are also the subject of dependent claims. They show schematically:

- Fig. 2

a view of an edge thread clamp with two variants of a built-in edge thread monitor,

- Fig. 3

a variant of FIG. 2, with a retrofitted edge thread monitor, and

- Fig. 4

3 shows a horizontal section through an edge thread monitor according to FIG. 3.

The edge thread clamp 32, 34 shown in FIGS. 2 and 3 has an essentially C-shaped clamp body 50 with a contact surface 52 in the direction of a clamp foot 54 with a corresponding contact surface 56.

Two spring bolts 58, 60 are guided in the clamp body 50. The longer spring bolt 58 is rigidly connected to the clamp foot 54. The force of the spring 62 guided by the spring pin 58 can be adjusted with an adjustable bracket 64 with a locking screw 66.

The shorter spring pin 60 is freely guided through the opening of a driver 68. An auxiliary spring 70 guided by the shorter spring bolt 60 strikes the catch 68 with its locking ring 72.

A front opening roller 74 fastened to the machine frame lies on the two spring bolts 58, 60, presses them down and opens the contact surfaces 52, 56 for taking over the weft thread 14. In the embodiments according to FIGS the edge thread clamps 32, 34 arranged on a rod (not visible) have initially been moved in the direction of arrow 76. First, the shorter spring pin 60, then the longer spring pin 58 for the clamp foot 54 has been pressed down. In the end position, the axis A of the front opening roller 74 lies vertically above the longer spring bolt 58, the clamp foot 54 is opened to the maximum and the weft thread 14 shifts in the direction of the longer spring bolt 58. Then the edge thread clamps 32, 34 move back in the direction of the arrow 78 . Because this movement takes place very quickly, the weft thread 14 is suddenly clamped, cut off by scissors (not shown), and the edge thread clamps 32, 34 are displaced approximately 30 to 40 mm in the direction of arrow 78. Arranged in this area is a rear opening roller (not shown) which is adjustably fastened to the machine frame and which in turn presses the spring bolts 58, 60 downward and releases the weft thread 14 previously folded over into a fabric edge (46, 48 in FIG. 1). With the adjustable rear opening roller mentioned, the time during which the weft thread 14 is to be clamped can be adjusted by shifting.

In the embodiment according to FIG. 2, the clamp body 50 has an inserted hard metal plate 80 in the area of the contact surface 52. This ensures a wear-resistant contact surface 52. In a recessed groove of the clamp body 50, a shock sensor 82 with electrical conductors, not shown, is inserted against the hard metal plate 80. When the edge thread clamps 32, 34 are moved away in the direction of the arrow 78, the contact surfaces 52, 56 hit the weft thread 14, the shock sensor 82 generates a small signal which is filtered out. If the weft thread 14 is missing in the case of a thread loser, the contact surfaces 52, 56 hit each other so hard that the shock sensor 82 generates a signal lying above the response threshold.

On the vertical web of the clamp body 50 and on the longer spring bolt 58, a photocell 84 is arranged, which emits a signal when the contact surfaces 52, 56 lie on one another. Of course, in practice these photocells 84 are only arranged if the shock sensor 82 is missing.

3, a conventional edge thread clamp 32, 34 has been retrofitted with a shock sensor 86, which, with a pressure plate (94 in FIG. 4) resting on the clamp body 50, is held by a clamp 88. The shock sensor 86 corresponds functionally to the shock sensor 82, it reacts to the direct collision of the contact surfaces 52, 56 and generates an electrical signal.

The shock sensor 86 lies on the narrow side 92 of the clamp body 50, which is necessary in view of the limited space in the weft 16 and catch mechanism 26.

The edge thread clamps 32, 34 are held on the displaceable linkage via a pivot axis 90 and are positioned with a spring, also not shown.

A shock sensor 86, shown in FIG. 4 and held by a clamping bracket 88, is designed as a piezo oxide with two brass pressure plates 94, 96. The one pressure plate 94 lies on the outer narrow side 92 of the clamp body 50. The pressure plate 94, like the other pressure plate 96, is connected to an electrical conductor 98. The pressure-active plate 100 in between, in the present case a quartz plate made of hexagonal crystals, generates an electrical signal when the pressure is generated by vibration, which is led via the soldered brass plates 92, 96 to a microprocessor after any amplification. In the space between the plate 96 and an enveloping plastic tube 102, a filling compound 104 is arranged, which consists for example of solder, plastic or the material of the plates 94, 96, brass. The arrangement of this mass 104 is essential because it can generate stronger electrical signals.

In practice, the shock sensor 82 according to FIG. 2 contains only the two pressure plates 94, 96 and the pressure-active plate 100 according to FIG. 4. A filling compound 104 is not absolutely necessary here because the vibrations that occur when the adjacent contact surfaces 52, 56 strike one another practically are undamped.

Claims (10)

Method for the detection of thread losers in the weft (16) and catching mechanism (26) of a projectile weaving machine (10), in which a tensioned weft thread (14) is taken over and clamped by edge thread clamps (32, 34) pivotable on a movable rod, by a pair of scissors in the The free end of the weft mechanism (16) is separated, the free thread ends are inserted into the fabric edges (46,48) with selvage needles (42,44) and the edge thread clamps (32,34) are opened.
characterized in that
It is directly checked whether the weft thread (14) lies between the clamp body (50) and the tensionable clamp foot (54) of the edge thread clamps (32, 34) by directly contacting the contact surfaces (52, 56) of the clamp body during a fixed time interval (50) and the terminal foot (54) an electrical signal is generated and evaluated. A method according to claim 1, characterized in that the signal is generated electrostatically, piezoelectrically, electro-optically or inductively. Method according to Claim 1 or 2, characterized in that the time interval is triggered by a precisely defined movement sequence of the projectile weaving machine (10) or by a flight trigger which detects the projectile (28) flying past. Method according to one of claims 1 to 3, characterized in that interference signals are filtered out below a predetermined threshold value, which is preferably about 50% of the measurement signal. Device for performing the method according to one of claims 1 to 4,
characterized in that
a residual thread monitor (82, 84, 86) is arranged in or on the edge thread clamps (32, 34). Device according to claim 5, characterized in that the residual thread monitor (82, 84) is installed in a recess in the clamp body (50), preferably in a shock sensor (82) adjacent to the contact surface (52) to the clamp foot (54). Apparatus according to claim 5, characterized in that the residual thread monitor (86) is fastened to the clamp body (50) with a clamping bracket (88) or is fixed with a housing and / or a carrier. Apparatus according to claim 7, characterized in that the residual thread monitor (86) on the narrow side (92) of the clamp body (50) is clamped, inserted or flanged. Device according to one of Claims 5 to 8, characterized in that the residual thread monitor (86) is a shock sensor (82, 86), in particular with a piezo oxide, a potentiometric measuring cell, an electrical microcontact, photo cells (84) or an inductive displacement sensor. Use of the method according to one of claims 1 to 4 for switching off a projectile weaving machine (10) and / or for signaling a weft error when missing or losing the weft thread (14) by means of an edge thread clamp (32, 34).

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