BACKGROUND OF THE INVENTION

The present invention relates to an arrangement for feeding a weft yarn along several yarn paths to a jet loom, according to the preamble of the independent claim.

DESCRIPTION OF THE PRIOR ART

Arrangements for feeding weft yarn typically comprise a creel with several cone holders or cone holder pairs for carrying weft yarn cones. The weft yarn is unwound from the cone and directed through a yarn brake unit to a weft yarn storage unit, from where it is inserted into a jet loom.

Yarn sensors for measuring at least one intrinsic yarn parameter are used in looms in order to monitor or measure the weft thread to be inserted. Examples are provided by the following specifications: WO-2012/068697 A2, WO-2012/068698 A2, and

WO-2013/010278 Al .

An "intrinsic" yarn characteristic is understood to be such a yarn characteristic which is given by the build-up or the structure o the yarn itself. Examples of intrinsic yarn characteristics are the mass per length unit, diameter, density, surface structure, hairiness, material composition, presence o foreign matter, etc. In contrast, an extrinsic

characteristic would be such a yarn characteristic which depends on the external influences or reference systems. Examples of extrinsic yarn characteristics are a yarn velocity or acceleration relative to a certain reference system, a position of a yarn tip in a certain reference system, or a mechanical yarn tension dependent on an external tensile force.

Creels with sensors for extrinsic yarn characteristics are known from the prior art.

JP-2006- 1933 13 A discloses a creel with a thread-break sensor for each cone holder supporting a cone. The sensors are connected to a central processing unit monitoring thread break of the entire creel. DE-43 ^" 12 ^* 823 Al also discloses a creel with a thread-break sensor. EP-1 '245 ^* 705 A2 discloses a method to optimize the yarn take-off speed from a creel. For this purpose, the creel is equipped with a yarn balloon sensor registering the size of the yam balloons. GB-1 '516'356 A discloses a speed sensor arranged between the creel and the loom. JP-2004- 156187 A discloses a length-measurement sensor for determining the length of the yam unwound from the creel.

The yam sensors for measuring intrinsic yam parameters can be used to control a jet loom, in order to optimize the energy and fluid consumption of the jet loom, as disclosed in WO-2012/068698 A2. A jet loom contains a plurality of relay nozzles arranged along a fluid feed conduit. A weft yam is introduced into the fluid feed conduit. The relay nozzles are actuated so as to eject time-staggered fluid pulses which produce a fluid flow in the fluid feed conduit. The weft yam is conveyed by the fluid flow through the fluid feed conduit. As proposed in WO-2012/068698 A2, at least two different individual, intrinsic characteristics of a weft-yarn section to be introduced into the fluid feed conduit are determined via the yarn sensors. These sensors are arranged on a separate stand between a creel and the weft yam storage unit of a jet loom. The relay nozzles are actuated based on the previously determined at least two different individual, intrinsic characteristics of the respectively conveyed weft-yam section.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an arrangement for feeding a weft yam along several yam paths to a jet loom, with which the energy and fluid consumption of the jet loom is reduced and the productivity of the jet loom is increased.

These and other objects are achieved by the arrangement in accordance with the invention, as defined in the independent claim. Advantageous embodiments are disclosed in the dependent claims.

An arrangement for feeding weft yam along several yam paths to a jet loom, according to the invention, comprises a weft creel having several cone holders and several yam brake units, wherein at least one of the several cone holders and at least one of the several yarn brake units are assigned to each yarn path. The arrangement further comprises a yarn sensor unit configured for determining at least one intrinsic characteristic of a weft yarn and for being connected to a control unit for controlling a fluid feed of the jet loom. A plurality of yarn sensor units is provided. At least one of the plurality of yarn sensor units is assigned to each of the yarn paths, and each of the plurality of yarn sensor units is mounted stationarily on the weft creel.

In some embodiments, each of the plurality of yarn sensor units is configured to measure at least one intrinsic characteristic of the weft yarn chosen from the following group: yarn mass per length unit, yarn diameter, yarn density, yarn-surface structure, yarn hairiness, yarn material.

Each of the plurality o yarn sensor units may comprise at least one yarn sensor, preferably two yarn sensors, for measuring at least one, preferably two, intrinsic characteristic of the weft yarn.

In some embodiments, the at least one yarn sensor unit is arranged downstream of the at least one yarn brake unit, preferably within 3 to 10 centimeters. With such a close positioning of the two units the amplitude of possible oscillations of the weft yarn can be reduced leading to increased measurement precision.

In some embodiments, a yarn outlet of the yarn brake unit and a yarn inlet of the at least one yarn sensor unit are offset such that the yarn path from the yarn brake unit to the yarn sensor unit is diverted from a straight line and the yarn runs over an edge of the inlet. Oscillations of the weft yarn out of the ideal yarn path through the sensor (sensor path), which originate from unwinding the yarn, may be further reduced, leading to increased measurement precision.

In some embodiments, the fluid feed control unit of the jet loom is arranged on the creel and is connected to the plurality of yarn sensor units. In some embodiments, the arrangement further comprises at least one weft yarn storage unit, from which the weft yarn is inscrtable into the jet loom, wherein each yarn path is provided with one weft yarn storage unit arranged downstream of the yarn sensor unit. A yarn guide may be arranged between the at least one yarn sensor unit and the at least one weft yarn storage unit, in order to more precisely define the yarn path between an outlet of the sensor unit and the waft yarn storage unit. Also, the yarn guide may be placed close the outlet of the sensor unit and may be offset to define a diversion of the yarn path from a straight line, leading to a smoother passage of the yarn through the sensor unit. The at least one yarn sensor unit can be designed as a yarn- clearer measuring head. Such yarn-clearer measuring heads are well known from the prior art. They are usually mounted on spinning or winding machines for monitoring the yarn quality.

Preferably a pair of cone holders is assigned to each yarn path.

The invention also relates to an apparatus for controlling a jet loom, which jet loom contains a plurality of relay nozzles arranged along a fluid feed conduit. The apparatus comprises a fluid feed control unit for actuating the relay nozzles so as to eject time- staggered fluid pulses which generate a fluid flow in the fluid feed conduit, by means of which a weft yarn is conveyable through the fluid feed conduit. Upstream with respect to the fluid feed conduit an arrangement for feeding weft yarn along at least one yarn path to a jet loom as described above is provided. The arrangement has a plurality of yarn sensor units for determining at least one intrinsic characteristic of the weft yarn. The fluid feed control unit is configured to actuate the relay nozzles based on the previously determined at least one intrinsic characteristic of the respectively conveyed weft yarn section.

The invention also relates to a jet loom, preferably an air-jet loom or a water-jet loom, with an apparatus for controlling the jet loom as described above. The invention thus proposes an arrangement including yarn sensor units measuring at least one intrinsic characteristic of a weft yarn section. Depending on the number of cone holders or cone holder pairs on a weft creel several weft yarn paths are defined. Each f the several weft yarn paths is provided with at least one yarn sensor unit stationarily mounted on the creel. With the fixed position of the yarn sensor unit with regard to the cone and the subsequent yam brake unit each individual yarn path through the sensor is defined more precisely. Also, the sensor may be placed more closely to the yarn brake unit. Oscillations of the weft yarn from the ideal yarn path are reduced and the flow of the yarn through the sensor unit gets smoother, which increases the measurement precision of the sensor unit. Experiments have shown that even a small increase of measurement precision results in better controlling of the jet loom, which leads to a considerable decrease of energy and fluid consumption. As the conveyance of the weft yam by the fluid flow through the fluid feed conduit depends on several intrinsic yam parameters, more precise measurement of these intrinsic yam characteristics thus allowed a better adaptation of the jet-loom control to the individual characteristics of the weft-yam section to be inserted.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will be explained below with reference to the drawings.

Figure 1 schematically shows an arrangement in accordance with the invention;

Figure 2 shows a perspective view of an arrangement in accordance with the invention; Figure 3 shows a perspective view of the arrangement of Figure 2 including a yarn

storage unit; and

Figure 4 shows a detail view the arrangement of Figure 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 1 schematically shows an arrangement for feeding weft yam 10 along a weft yarn path to a jet loom (not shown). The arrangement mainly comprises a creel 1 having several cone holders 21, 21 ', 21 ". Each cone holder 21 , 21 ^" , 2 Γ ^* can hold a cone 20 of weft yam 10. The weft yarn 10 from each cone 20 follows an individual yam path within the arrangement. The creel 1 further comprises several yarn brake units 30, 30 ^' , 30", wherein one yarn brake unit is provided to each yarn path downstream of the cone holder 21 , 21 ", 21 ". Each yam path is further provided with one yam sensor unit 40, 40', 40 ^" arranged downstream of the yarn brake unit 30, 30', 30" and also stationarily mounted onto the creel 1. The creel 1 shown has four of these setups with cone holder, yarn brake unit and yarn sensor unit, wherein each setup defines a yarn path. The yarn sensor unit may be a yarn sensor unit with two yarn sensors to measure two different intrinsic characteristics of a weft yarn section, such as yarn mass per length unit, yarn diameter, yarn density, yarn- surface structure, yarn hairiness, yarn material.

Figure 2 shows a perspective view of an embodiment of the schematic arrangement of Figure 1. Instead of one cone holder 21 for each yarn path the arrangement of Figure 2 is provided with a cone holder pair 21.1 , 21.2 for faster changing of empty cones. The yarn sensor units 40, 40 ^" , 40" are mounted directly downstream of and as close as possible to the yarn brake units 30, 30 ^" , 30 ^{" "} in order to minimize possible oscillations of the weft yarn out of the ideal yarn path. The yarn sensor units 40, 40 ^" , 40 ^{" "} may be mounted on a hollow pole, in which the cables of the sensors may be guided to a cover 2 of the creel 1 accommodating electronics and control units for the sensors. These are further connectable to a fluid feed control unit of the jet loom.

Figure 3 shows a perspective view of the arrangement of Fig. 2 including a yarn storage unit 50, 50 ^" for each yarn path. The yarn storage units 50, 50' are mounted on a separate yarn storage unit stand 51 placed downstream of the creel 1 and upstream of the jet loom. From the yarn storage unit 50, 50 ^" the weft yarn is inserted into the jet loom. A yarn guide 52, 52 ^" is provided to each yarn path via a yarn guide arm 53. The yarn guide 52, 52 ^* may be placed close to an outlet of the yarn sensor unit 40, 40 ^" and may define a diversion of the yarn path from the straight line through the sensor unit, leading to a smoother passage the yarn through the sensor unit 40, 40 ^' .

Figure 4 shows a detail view of a yarn brake unit 30 and a yarn sensor unit 40 of the arrangement of Figure 2. The yarn brake unit 30 may be a standard yarn brake with blades having an outlet orifice 31. The outlet 3 1 of the yarn brake unit and the inlet 41 of the yarn sensor unit 40 are arranged within a few centimeters, preferably 3 to 10 centimeters, and slightly offset such that the weft yarn is diverted from a straight path. Oscillations of the weft yarn originating from unwinding the yarn from the cone, although already reduced by the yarn brake unit, are further reduced such that the weft yarn follows a smooth straight line through the sensor path 43. In that way, measurement precision is considerably increased.

It is understood that the present invention is not limited to the embodiments as discussed above. The person skilled in the art will be able to derive further variants with knowledge of the invention which also belong to the subject matter of the present invention.

LIST OF REFERENCE NUMERALS

1 Weft creel

2 Cover with control units

10 Weft yarn

20, 20', ... Cone

-1. _^ 2* 1 Cone holder

21.1, 21.1 ', .

21.2, 21.2', . Cone holder pair

30, 30', ... Yarn brake unit

31 Outlet of yarn brake unit

40, 40', ... Yarn sensors unit

41 Inlet of yarn sensor unit

42 Outlet of yarn sensor unit

43 Sensor path

50, 50', ... Weft yam storage unit

51 Weft yam storage unit holder

52, 52', ... Yam guide

53 Yam guide arm