Field of the invention

The invention relates to a device for controlling warp threads for the production of leno fabrics on a textile machine comprising a reed equipped with gliders separated from each other by slots intended to guide pairs of waφ threads, one of which belongs to a system of stationary waψ threads, and the other, to a system of rotating waφ threads. In the direction of the warp thread movement during the weaving process, a system of needles fitted with eyes for guiding the system of stationary warp threads, reversibly moveable, is arranged in front of the reed and coupled with a mechanism adapted to impart to it said reversible movement in front of which vertically adjustable heddle frames are situated. A first heddle frame has oblique slots for the passage of the rotating waφ threads, the other one, a straight slot passing through the whole width of the warp for the passage of the waφ thread system.

Background of the invention

Fabrics with leno weave show specific properties resulting from the different construction of the crossing point, the crossing proper and, consequently, the thread interlacing being achieved by the mutual turning of two warp threads around each other thereby eliminating the need to interlace the weft with said warp threads. In each weaving cycle, its position is each time over one and the same, and under the other, of the waφ thread systems, said waφ threads bringing about the interlacing effect not by mutually alternating the upper and the lower position but by their mutual turning around each other _.

Thus, the waφ threads are divided into two groups, i.e., into the stationary and the rotating ones. Special mechanisms are required to generate their mutual movement normal to their axis.

The known embodiments of such devices contain special leno heddles and return motion half-heddles.

Another embodiment makes use of shaft frames equipped with needles instead of with heddles. Here, the shaft frames, in addition to their shed forming motion, carry out a mutual reversible motion parallel with the direction of the shed insertion.

Another known method of leno weave creation is described in the patent CZ No., 280463 relating to a device for binding the fabric edge on weaving machines. Its advantage over the preceding ones consists in the method of generating the required motion of the rotating waφ threads by means of an oblique slot provided in the shaft frame carrying out the standard shed motion so that, unlike the preceding embodiment, the shaft frame need not move in two directions and, consequently, the arising dynamic forces are substantially reduced, and the mechanism is simplified. In comparison with the embodiment using special heddles, this embodiment contains no further components such as half-heddles for mediating the positive contact with the warp threads and whose motion shows discontinuous changes during the heddle frame alternations that by their impacts have adverse effects on the operation frequence of the weaving machine. However, the drawback of the mechanism described in the patent CZ 280643 consists in that it permits to produce the leno weave only with a limited number of waφ threads on the fabric edge, and not a complete leno fabric.

Another drawback of the described embodiment consists in that it fails to ensure the same tension in each of the two warp thread systems, and consequently, in the uneven proportionate elongation during the weaving process. For this reason, waφ threads to be interlaced in this way must be supplied from special accessory warp thread bobbins, each of them equipped with an independently adjustable brake.

Disclosure of the invention

The above drawbacks of the state of art have been eliminated by the device for

controlling warp threads according to this invention whose principle consists in that at least one guide member of the stationary waφ thread system situated over the heddle frames in parallel with them is coupled with the system of needles fitted with eyes and that at least two compensation rollers of the rotary warp thread system are mounted on a third heddle frame.

The device permits to keep equal traction forces both in the system of stationary waφ threads and in the system of rotating waφ threads and to eliminate the differences of their proportionate elongation in the area extending from the beat-up point to the whip roll during the weaving cycle and weaving process on a weaving machine.

Preferably, the- compensation rollers of the rotating waφ thread system, mounted on the third heddle frame, are arranged adjustably with respect to this third heddle frame, thus permitting to form and adjust the required angle of contact of the rotating strand of the waφ threads for producing the frictional resistance whose values are then continuously identical with the resistance of the waφ threads in the stationary strand.

Also preferably, the compensation rollers of the rotating warp thread system are mounted on a swinging shaft, adapted reversingly to swing on the third heddle frame (and coupled with the drive mechanism). This permits easily and continuously to change the angle of contact of the rotating warp thread system on the compensation rollers and by means of this, to modify the frictional force acting on the warp threads of the rotating waφ thread system.

Preferably, the guide member of the stationary waφ thread system is made as a longitudinal bar parallel with the heddle frames.

To obtain the optimum function of the mechanism, the guide member is preferably mounted on the connecting rods of the mechanism used to bring about the reversible motion of the system of needles fitted with eyes.

The advantage of this embodiment consists in the fact that the needle stroke governing the motion of the stationary waφ thread system passing over the guide member is approximately the same as the stroke of the oblique guide slots governing the motion of the

rotating waφ thread system. Each waφ thread belonging to the stationary warp thread system passes through the needle's eye carrying out a substantially rectilinear reversible motion during the shed formation. After the warp thread system has left the needle, these waφ threads pass via the guide member situated on the connecting rod of the drive mechanism. The trajectory of the guiding of this system has been chosen so as to ensure that the total length of the waφ thread belonging to the stationary waφ remains constant in the whole section between the beat-up point and the whip roll during the weaving cycle Having passed through the oblique guide slots provided in the heddle frame, the waφ threads belonging to the rotating waφ thread system pass through a compensation loop consisting of a pair of compensation rollers situated preferably as near as possible the heddle frame equipped with oblique slots

The equal tension of the two waφ strands in the area of the fabric formation ensures equal weaving ability and fabric quality Moreover, the elimination of the difference in the proportionate elongation through the section from the harness to the whip roll permits to make use of only one warp beam and only one whip roll.

Brief description of the drawings

Fig. 1 shows the structure of the leno weave in a fabπc produced on a weaving machine equipped with the device for controlling warp threads according to the invention, whose example of embodiment is shown in perspective view in Fig. 2.

Specific description

The device for controlling warp threads shown in Fig. 1 is a part of a weaving machine having a well-known reed I with a pick channel 2 of a weft 2J. fixed to a not represented batten. In front of the reed I in the direction of the warp thread motion, a system of needles 3 fitted with eyes 4 and fixed to a fixing member 5 fixed in turn to at least two reversibly

moveable connecting rods 6 is arranged. Situated reversibly moveable in vertical direction in front of the system of said needles 3 is a first heddle frame H ⁾ fitted with a row of oblique slots 12, a second heddle frame H fitted with a rectilinear slot 13, and a third heddle frame 14 fitted with a pair of compensation rollers 15 seated reversibly moveable with respect to the shaft frame of the third heddle frame 14, for instance fixed to a swinging shaft 16 coupled with a not represented drive. A whip roll 12 is mounted in front of the heddle frames 10, ϋ, 14 in the direction of the waφ thread motion. The designation of the heddle frames as "first", "second", and "third" relates to the heddle frames actively participating in the formation of the leno weave according to the invention. In case of need, the weaving machine can comprise further well-kown heddle frames situated in front, between, or behind, the heddle frames 10, H, 14.

The connecting rods 6 are mounted for instance on a two-balance beam drive mechanism 7 with a drive pin 8, as is the case in the shown example of embodiment. On the side turned away from the drive mechanism 7, each connecting rod 6 is fitted with a holder 9 having fixed thereto a guide member 20 of a system of stationary warp threads 19 consisting in the shown example of embodiment of a bar. This guide member 20 is arranged in parallel with the heddle frames 10, H, 14 and over the heddle frames 10, l_l.

The waφ threads are drawn-off from a not represented waφ beam via the whip roll 1.7. From the whip roll onward, they are distributed into a system of rotating waφ hreads 18 and a system of stationary warp threads 19. The system of rotating waφ threads 18 is led from the whip roll 17 into the pair of the compensation rollers 15 that bend through the rotating waφ threads 18 and thus produce the contact angle required for creating areas of frictional resistance. Preferably, the compensation rollers 15 are situated so as to obtain as small as possible distance between the axis of the first roller and the second heddle frame H _. The mutual position of the compensation rollers 15 can be either fixed or adjustable. Depending on the program required, the required value of the frictional resistance forces acting on the system of the rotating warp threads 8 can be adjusted. Also, the compensation rollers 15 can change their actual position with respect to a not represented weaving plane in

accordance with the required program, for instance by changing the angular position of the swinging shaft 16 on which they are fixed as shown in Fig. 1.

From the pair of the compensation rollers 15 on, the system of the rotating waφ threads 18 is led into the rectilinear slot 13 of the second heddle frame H and from there, each rotating warp thread 18 of the system is led into its respective oblique slot 12 of the first heddle frame .10 and then between the respective gliders of the reed 1. The system of the stationary waφ threads 19 is led from the whip roll 17 upwards over the heddle frames 10, H, 14 and via the guide member 20. Each stationary waφ thread 19 is then led (separately) into the eye 4 of the respective needle 3 and further on, like the rotating waφ threads 18, separately between the respective gliders of the reed |. Thus, each slot between the gliders of the reed 1 receives one rotating waφ thread 18 and one stationary waφ thread 19 of the respective systems.

During the movement of the system of needles 3 downward accompanied by the simultaneous movement of the first and second heddle frames Jj), 1_1 upward, the system of stationary waφ threads 19 and the system of the rotating waφ threads 18 produce in a well-known not represented manner the shed for the insertion of a not represented weft.

The needles 3 are situated at all times in the axis of the respective oblique slot 11 of the first heddle frame 10. The side of the needle 3 the respective rotating waφ thread 18 will turn around, is determined by its position in the oblique slot 12 of the first heddle frame 10, and the displacing of the rotating warp thread 18 in said oblique slot 2 is carried out by the force exerted by the edges of the rectilinear slot 13 of the second heddle frame ϋ. The action of the upper or lower edge of the rectilinear slot 3 on the rotating waφ thread 18 is due to the difference in amount, or in speed, of the stroke of the first heddle frame 10 and the second heddle frame ! .

If the velocity of the second heddle frame H is superior to that of the first heddle frame 10, the edges of the rectilinear slot 13 will push the rotating warp thread 18 of the system out of the upper position in the oblique slot 12 of the first heddle frame 10, and vice

versa.

In this way, the rotating waφ threads 18 are being moved with respect to the stationary waφ threads 19 and subsequently interlaced with the weft 2J. in the form of the leno weave, as shown in Fig. 2.

The trajectory of the motion of the guide member 20 is chosen so as ensure that the total length of the system of the stationary waφ threads 9 led via the guide member 20 remains constant throughout the weaving cycle in the section from the beat-up point to the whip roll 1/7.

In this way, undesirable changes in the tension of the stationary waφ threads \9_ in the course of the weaving process are eliminated.