GB2034768A

GB2034768A - A Method and Apparatus for Taking off Weft Yarn in a Weaving Loom

Info

Publication number: GB2034768A
Application number: GB7937361A
Authority: GB
Original assignee: Adolph Saurer AG
Current assignee: Saurer AG
Priority date: 1978-11-24
Filing date: 1979-10-29
Publication date: 1980-06-11
Also published as: IT7969195A0; FR2442286A1; JPS5576139A; AT363394B; BR7907582A; ATA883078A; DE2936197A1; BE880047A

Abstract

A yarn supply mechanism for a rapier loom comprises two continuously rotating rollers 17, 17' which are cam-operated to move together to supply weft 5 during a first phase of their operation and are then moved apart, during a second phase, in which the rapier takes and inserts the weft. A temporary suction storage tube 7, guides 29, 30, tensioner, presenter 12 and shears 13 are provided. The cam 24 moving the roller 17, 17' is adjustable. <IMAGE>

Description

SPECIFICATION A Method and Apparatus for Taking Off Weft Yarn in a Weaving Loom The invention relates to a method of taking off weft yarn from a supply package arranged outside the shed on a weaving loom in which the individual weft threads are inserted by means of a weft picking device, such as a picking needle.

When weaving on such looms it is not possible for the weft picking device to take off the weft yarn directly from the supply package (cop) because the great variations in the speed of the weft picking device with considerable acceleration and deceleration lead to disturbances, for example to thread breakages, loop formation, or slipping of entire windings of thread from the supply. The weft thread is therefore taken off and inserted in two separate operations using differing apparatuses.

Two basic systems of taking off the weft thread are known and have the common feature that, between the means of taking off the weft yarn from the supply and transferring it to the weft picking device, is provided a temporary store for at least one length of weft thread, including its ends which are inserted into the next shed to form firm seivedges, and including excess thread to correct irregularities in the picking operation, this thread usually being unavoidable and having to be severed after the beating-up operation.

With one system, the weft thread is taken off continuously at an approximately constant speed which is somewhat higher than the average picking speed, that is to say the ratio of the cloth width to the duration of a picking cycle, and is temporarily stored on a drum or in a container, the storage drum also being able to take off the thread (German Patents Nos. 1 535 639 and 1 958 299 and Swiss Patent No. 454 762). In this case, the weft lengths are determined only after the pick, by severing, on the one hand, the excess thread at the tip and, on the pother hand, othe following weft yarn to be inserted in the next operation.

With this system, the take-off speed has to be monitored and regulated to ensure that the temporary store is provided at all times with an adequate, but not excessive, number of weft lengths. Regulation is expensive.

With the other system, the weft yarn is taken off intermittently in the intervals between the transfer of the weft thread, inserted in the shed by the weft picking device, and the following operation. The temporary store, which can also act as a take-off apparatus, has a mechanism for measuring the length of the weft threads and only takes off one weft thread length at a time. The length-measuring mechanism is expensive. In addition, the excess length of the weft threads has to be calculated generously, as they have to be severed after the beating-up operation both at the tip and at the end of each individual, already measured weft (German Patent No. 1 535 288).

The present invention simplifies the preparation of the weft thread by dispensing with both the speed regulator and the lengthmeasuring mechanism; each complete weft thread is taken off by a take-off apparatus in a first phase and is taken off by the actual weft thread picking device in a second phase in which the weft thread pick slows down toward the end of the pick.

With the method according to the invention, only the thread length needed for one pick is taken off the supply package at any time, and automatic regulation is effected without additional apparatus in that the weft picking device takes the thread directly off the supply package at an earlier or later moment, depending on whether the take-off apparatus has taken off and supplied too little or too much thread respectively.

The actual apportionment of the taken-off thread to the apparatus and to the weft picking device can be selected within wide limits, and the take-off speeds and operating time of the apparatus can be adapted to each other as desired on the basis of this apportionment. For the sake of continuity, however, the take-off operation is transferred from the apparatus to the picking device and vice-versa with a minimum of delay, preferably at about 450, based on the rotation of the main shaft of the loom, before completion of the picking operation. The thread length taken off the apparatus obviously has to be stored, and a simple, known pneumatic thread tension device of the type described, for example, in Swiss Patent No. 601 538 is suitable for this purpose.

The invention also provides a take-off apparatus for carrying out the method, which apparatus comprises two rollers rotatably mounted on either side of the weft thread, as well as a thread guide which is arranged upstream of the rollers in the thread take-off direction and makes unpressured contact with the weft thread, wherein at least one roller can be directed in two positions by the main shaft of the loom, for example by means of a cam arrangement, and at least one roller is driven at a constant speed in the thread take-off direction, the rollers in one position pressing against the weft thread and in the other position releasing the weft thread, i.e. at most making unpressured contact with the weft yarn.

Regulating and length-measuring mechanisms are superfluous in the take-off apparatus according to the invention, which is consequently very simple.

It also affords the advantage of allowing the thread to be taken off with care, since the transfer of the thread take-off operation from the picking device to the rollers is effected gently owing to the proximity of the thread surface and roller surface, maintained while the thread is taken off by the picking device, and the resultant reduction in the friction, which only increases gradually as the roller surfaces approach each other.

Finally, by taking off the thread by means of the picking device against the slight resistance exerted by the thread guide, it is possible to dispense with the subsequent tension device, normally needed on looms of the type mentioned at the outset, for the weft thread inserted into the shed by the picking device. This measure represents a further simplification.

The invention is described in more detail below by way of example with reference to the accompanying drawing, whose sole Figure is a schematic illustration of an embodiment of the take-off apparatus on a loom, which is only partly illustrated.

Reference numeral 1 designates the warp of a loom with warp edge threads 1'. Reference numeral 3 designates already woven fabric and reference numeral 4 designates a stationary weft thread supply in the form of a cop fixed outside the shed in a holder (not shown). A weft thread 5 is taken off the cop 4 by a take-off apparatus 6 and is guided to a pneumatic thread tension device 7, in which the weft thread forms a loop 9 owing to the action of the air flowing toward the suction opening 8, and is drawn into the shed by the picking device (not shown), the axis of whose path is indicated by the chain 'ine 11.In order to reach the tip of the weft thread 5 being inserted, which is to be gripped by the picking device, the connecting piece 5' (indicated in broken line) of the previously inserted weft thread, which has been beaten up toward the fabric 3, is brought by the thread tension device 7 from a feeder 1 2 into the path axis 11 of the picking device and then cut to length by a cutting device 13.

The take-off apparatus has two levers 14,14' which are rotatably mounted on respective axles 15,15' and which support respective rollers 17,17'. The rollers are rotatably mounted on rotational axles 1 6,1 6' respectively. One of the rollers 1 7 cooperates with a gear wheel 1 8 which meshes with a counter-wheel 1 9 which, in turn, cooperates with the main shaft 34 of the loom.

Two pivotally mounted laminae 21 ,2 1', which rest against each other virtually without pressure, serve as thread guide 20, the thread 5 being drawn between them.

Each lever 14,14' has a respective second lever arm 22,22'. The lever arm 22 has a rotatably mounted small roller 23 at its end. This small roller revolves on the periphery of a cam disc 24 cooperating with the main shaft 34 of the loom. The periphery of the cam disc 24 has a cam notch 32 extending over the angle 0. The cam disc can be in two parts in a manner known per se, each part being fixed on a hub so as to rotate independently so that the position and length (angle O) of the cam notch can be adjusted. A third lever arm 25 on the lever 14 is hinged to a third lever arm 27 on the lever 14' by means of a connecting rod 26 in order to make the movements of the levers 14,14' symmetrical to each other with respect to the strand of thread 5 located in the take-off apparatus.A compression spring 28 acting on the arm 22' of the lever 14' ensures that the small roller 23 makes contact with the periphery of the cam disc 24. An eyelet 29 on the take-off apparatus and another eyelet 30 on the thread tension device 7 are arranged approximately in the plane of symmetry of the take-off apparatus in order to protect the weft yarn.

The apparatus operates in the following manner. On completion of a picking operation, the small roller 23 leaves the cam notch 32 and begins revolving on the cylindrical part of the outer contour of the cam disc 24, so that the levers 14, 14' are pivoted into their end position, in which the rollers 17,17' press against the weft thread 5, as illustrated in solid lines in the Figure.

In this process, the roller 1 7 rotates at a constant speed in the direction of the arrow 31 and entrains the roller 17' so that it rotates in the opposite direction. The weft thread is taken off the supply package owing to the friction with the roller surface and is supplied to the thread tension device, forming a loop.

A slight frictional resistance is produced in the thread guide owing to the contact between the thread and the laminae 21,21', and this produces sufficient tension in the thread to calm the travel of the thread. While the rollers 1 7,17' continue taking off the thread, the weft picking device returns to its starting position, and the slay beats the inserted thread, which is brought into the path of the weft picking device by the feeder 12 and severed by the cutting device 13. A new picking operation then begins, during which the speed of the picking device soon exceeds the circumferential speed of the rollers 17,17' and, consequently, the thread tension device 7 is not supplied with sufficient weft thread. The loop retracts.Suitable choice of the supply speed and duration allow the loop to retract completely almost completely at a moment when the supply speed and the speed of the picking device, which is decreasing after having exceeded the maximum speed toward the middle of the picking operation, coincide. In this process, the cam disc can be adjusted in such a way that the small roller travels into the cam notch 32 at this moment, so the rollers 17,17' move apart under the influence of the spring 28 and virtually cease exerting a frictional force on the weft thread S. The take-off operation is now transferred directly and smoothly to the picking device. In this process, the weft thread remains under the influence of the thread tension device 7 or, if there is no loop in it, under the influence of the guide 20, under a detectable, though slight tension until the end of the picking operation, after which the picking device delivers the weft thread to a known type of take-over device.

The smooth transfer of the take-off operation from the rollers 17,17' to the picking device is not absolutely essential, but is an advantageous feature of the take-off apparatus.

It should also be noted that the abovedescribed method and apparatus can also be adopted in looms in which the weft thread is inserted by means of two picking devices which penetrate the shed from either side and transfer the weft thread from one to the other in the middle of the shed. An electromagnetic arrangement which could also be controlled by the main shaft could be used instead of the cam arrangement 23,24.

Claims

1. A method of taking off weft yarn from a supply package arranged outside the shed on a weaving loom in which the individual weft threads are inserted by means of a weft picking device, each compiete weft thread being taken off by a take-off apparatus in a first phase and by the weft thread picking device in a second phase in which the weft thread pick slows down toward the end of the pick.

2. A method as claimed in claim 1, in which the take-off apparatus takes the weft thread from the supply at a constant speed in the first phase.

3. A method as claimed in claim 2, in which the transfer of the take-off operation from the take-off apparatus to the weft picking device is effected at a moment when the speed of the weft picking device corresponds to the take-off speed of the take-off apparatus.

4. A method as claimed in claim 3, in which the said transfer takes place before completion of the pick, when the main shaft of the loom is at an angular position of about 45 .

5. A weft yarn take-off apparatus in combination with a loom having a weft picking device, the take-off apparatus comprising two rollers rotatably mounted on either side of the weft thread, a thread guide which is arranged upstream of the rollers in the thread take-off direction and makes unpressured contact with the weft thread, wherein at least one roller can be selectively located in two positions by the main shaft of the loom, and means for driving at least one roller at a constant speed in the thread-takeoff direction, the rollers pressing against the weft thread in one of the two positions and releasing the weft thread in the other position.

6. A take-off apparatus as claimed in claim 5, in which the positions are selected by the main shaft via a cam arrangement.

7. A take-off apparatus as claimed in claim 6, in which the cam arrangement has a cam disc whose cam surface has an adjustable cam notch on its periphery and cooperates with a cam follower which locates the roller(s) in the said position via a lever system.

8. A method of taking off weft yarn from a supply package substantially as described with reference to the accompanying drawings.

9. A weft yarn take-off apparatus, substantially as described with reference to, and as shown in, the accompanying drawings.