Earlier we learned about the formation of Terrys fabrics, so we use the washcloth, golf towels, salon towels major production out of it by any way! Next we come to find out!
The production of terry fabrics is a complex process and is only possible on specially equipped weaving machines. Terry weaving machines are constructed so as to impart a loop
to warp yarns via weft yarns which are beaten up at a beating-up station to form a fabric. Two warps are processed simultaneously, the ground warp, with tightly tensioned ends and the pile warp, with lightly tensioned ends. In general, the reed has two beat-up positions which do not impose alternative movements to the warp, fabric and various components of the weaving machine. Special weaving methods enable loops to be performed with the lightly tensioned warp ends on the fabric surface. Those methods are divided into two mains methods as follows:
1. Reed control mechanism
2. Fabric control mechanism.
to warp yarns via weft yarns which are beaten up at a beating-up station to form a fabric. Two warps are processed simultaneously, the ground warp, with tightly tensioned ends and the pile warp, with lightly tensioned ends. In general, the reed has two beat-up positions which do not impose alternative movements to the warp, fabric and various components of the weaving machine. Special weaving methods enable loops to be performed with the lightly tensioned warp ends on the fabric surface. Those methods are divided into two mains methods as follows:
1. Reed control mechanism
2. Fabric control mechanism.
1. Weaving machine equipped with the reed control mechanism
Reed control mechanism must be used to vary the stroke of the reed to effect partial beat-up of certain picks of weft and full beat up of other picks of weft. Reciprocating motion is applied to a lay beam on which the reed is mounted by a crank arm whose motion is driven by a rotatable driving element. The rotatable driving element is coupled to the crank arm through a mechanical linkage which includes a pneumatic or hydraulic cylinder. The pneumatic or hydraulic cylinder serves to shift the arc of the reed so as to effect partial beat up of certain picks of weft and full beat up of other picks of weft.
Reed control mechanism must be used to vary the stroke of the reed to effect partial beat-up of certain picks of weft and full beat up of other picks of weft. Reciprocating motion is applied to a lay beam on which the reed is mounted by a crank arm whose motion is driven by a rotatable driving element. The rotatable driving element is coupled to the crank arm through a mechanical linkage which includes a pneumatic or hydraulic cylinder. The pneumatic or hydraulic cylinder serves to shift the arc of the reed so as to effect partial beat up of certain picks of weft and full beat up of other picks of weft.
Figures 1A and b illustrate a reed control mechanism generally indicated by numeral 1. The reed control mechanism 1 serves to control the reciprocating motion of the reed 2 which is mounted on a lay beam 3. Although not indicated in the figures, the reed 2 and the lay beam 3 extend substantially across the width of the loom. Reciprocating motion is imparted to the reed 2 and the lay beam 3 by a reciprocating motion imparting means here shown as a crank arm 4 which reciprocates about a lay shaft 5. Generally, crank arm 4 is located near the center of the lay beam 3 and the reed 2. The reciprocating movement of the crank arm 4 is driven by a driving element or crank 6 which as shown preferably rotates in the clockwise sense about a shaft crank 7 that is mounted on the loom and extends parallel to lay beam 3 and lay shaft 5. The crank 6 is connected to crank arm 4 through a mechanical linkage 8 which includes a pair of spaced apart longitudinal links 9 and 10 and an interposed adjustable member here shown to be a pneumatic piston-cylinder 11 for controlling the spacing between the longitudinal links 9, 10 and thus the length of the mechanical linkage 8. Of course, the adjustable member may be a hydraulic piston-cylinder instead of pneumatic piston-cylinder 11 or any other such member, such as, for example, an electromagnetically controlled piston-cylinder.
Longitudinal element 9 which is fastened to the piston-rod 12 of the cylinder 11 is pivotally connected to the crank 6 by axle 14. Similarly, longitudinal element 10, which is fastened to the base end 13 of the cylinder 11, is pivotally connected to the crank arm 4 by axle 15. A pressure medium, here shown as compressed air is connected to the cylinder 11 near the base 13. In the Figures, this connection is shown in a schematic manner only, the actual structure being well within the skill of the ordinary worker. The flow of the compressed air from diagrammatically illustrated standard pressure vessel 16 is controlled by diagrammatically illustrated standard timing circuit 18. When the pressure medium stored in vessel 16 enters the cylinder 11, near the base 13 through diagrammatically illustrated inlet 19, the piston-rod 12 is forced outward from the cylinder thereby extending the effective length of mechanical linkage 8.
Fig. 1: Reed control mechanism
A pressure medium, here shown as compressed air is also connected to the cylinder 11 near end 17. The flow of compressed air from diagrammatically illustrated standard pressure
vessel 16′ into the cylinder 11 through diagrammatically illustrated inlet 19′ is regulated by diagrammatically illustrated standard timing circuit 18′. When compressed air enters the
cylinder 11 near end 17, the piston rod 12 is forced inward, thereby shortening the effective length of the mechanical linkage 8.
vessel 16′ into the cylinder 11 through diagrammatically illustrated inlet 19′ is regulated by diagrammatically illustrated standard timing circuit 18′. When compressed air enters the
cylinder 11 near end 17, the piston rod 12 is forced inward, thereby shortening the effective length of the mechanical linkage 8.
As previously indicated, the reed control mechanism 1 is intended to enable the reed to perform a three pick terry cycle which involves partial beat up of the first two picks of weft
followed by full beat up of the third pick of weft. The workings of the inventive reed control mechanism 1 can be understood by considering its operation during a single three pick cycle which corresponds to three rotations of the crank 6, one for each pick. Operation of the reed control mechanism 1 during the first two picks is shown in Fig. 1A, and operation of the reed control mechanism 1 during the third pick is shown in Fig. 1B.
followed by full beat up of the third pick of weft. The workings of the inventive reed control mechanism 1 can be understood by considering its operation during a single three pick cycle which corresponds to three rotations of the crank 6, one for each pick. Operation of the reed control mechanism 1 during the first two picks is shown in Fig. 1A, and operation of the reed control mechanism 1 during the third pick is shown in Fig. 1B.
Starting from an arbitrary initial position of the reed 2 and associated reed control mechanism 1 which is shown in phantom in Fig. 1A, as the driver element 6 rotates in the clockwise direction about the shaft crank 7, the reed 2 is driven leftward in an arc. The leftward most position of the reed 2 is indicated by position A in Fig. 1A. At this time, the orientation of the associated reed control mechanism 1 is shown in Fig. 1A. As the reed moves leftward through the arc, it carries with it a pick of weft (not shown). As the crank 6 continues in its clockwise rotation returning reed 2 and associated reed control mechanism 1 to the initial position shown in Fig. 1B, the reed 2 moves rightward through its arc leaving the pick of weft behind at position A. Note that position A is separated from the fell of the fabric whose location is schematically illustrated by position B. Thus, there has occurred partial beat up of the first pick of weft. Upon a second rotation of the crank 6, another pick of weft is positioned near position A.
Illustratively, as shown in Fig. 1B, at the start of the third rotation of the crank 6, the piston rod 12 of the cylinder 11 starts to extend outward, thus lengthening the mechanical linkage 8 and causing the arc of the reed 2 to shift leftward in an arc. The leftwardmost position of the reed 2 is indicated by Fig. 1A. As the reed 2 moves leftward through its arc the third pick of weft as well as the first two picks of weft which were previously positioned at A are positioned at position B. Position B is the leftward most position of the reed 2 as it moves through its arc and generally corresponds to the fell of the fabric. When the reed 2 reaches position B, the corresponding orientation of the reed control mechanism 1 is shown by the drawing of Fig. 1C. When this position is reached, the piston rod 12 of the cylinder 11 is maximally extended. Hence, as will be recognized by those of ordinary skill, the height of the terry pile is determined by the difference in position of points A and B. Note that, during the second half of the third rotation of the crank 6, the piston rod of the pneumatic cylinder 11 is forced inward so that the mechanical linkage is shortened and partial beat up of the first pick of the next cycle is effected.
Mechanical linkage 8 also includes continuously adjustable nut 20 for adjusting the relative positions of points A and B to thereby adjust the pile height of the resulting terry fabric. The nut 20 is incorporated as part of the piston-rod 12 and serves as a means for regulating the length of the mechanical linkage 8 during partial beat up steps. Adjustment of the nut 20 results in a leftward or rightward shift of the arc of the reed but does not appreciably change the length of the arc of the reed. When it is desired that there be a relatively short pile height, the nut 20 should be positioned adjacent end 17 of the cylinder 11 during the partial beat up steps. When the nut 20 is so positioned, the movement of the piston rod 12 into the cylinder 11 is limited by the nut. Thus mechanical linkage 8 is relatively long and the corresponding arc of the reed 2 is shifted to the left, thereby giving rise to a relatively small distance between the partially beat up first two picks of the three pick terry cycle (point A) and the fell of the fabric (point B). On the other hand where a relatively large pile height is desired, the nut may be spaced apart from the end 17 of the cylinder 11 during the partial beat up steps in which case movement of the piston-rod 12 into the cylinder is limited only by the geometry of the cylinder. This serves to shift the arc of the reed 2 to the right and results in a relatively long distance between the partially beat up first two picks of the three pick terry cycle (point A) and the fell of the fabric (point B).
2. Weaving machine equipped with the fabric control mechanism
Fabric control mechanism was developed by Sulzer and Dornier companies. Loop formation proceeds according to the principle of fabric control. That is, the reed moves in a conventional manner but the fabric or fabric is periodically moved away from beating-up station by a common movement of the breast beam and temple. Usually, two or three partial beating-ups are carried out after each complete beating-up for a subsequent looping of the pile warp
Fabric control mechanism on Sulzer weaving machine
Referring to Fig. 2, the terry weaving machine is of generally conventional structure. For example, the weaving machine has a ground warp beam 1 from which a plurality of ground
warps 2 extend via a deflecting beam 3 to a whip roll 4 as well as a pile warp beam 5 from which a plurality of pile warps 6 extend via a temple 7 and a resiliently mounted whip roll 10 which is secured to a lever pair 11.
warps 2 extend via a deflecting beam 3 to a whip roll 4 as well as a pile warp beam 5 from which a plurality of pile warps 6 extend via a temple 7 and a resiliently mounted whip roll 10 which is secured to a lever pair 11.
Fig. 2: Loop formation by using fabric control mechanism on Sulzer weaving machine
As indicated, the lever pair 11 is pivotally mounted about a pivot 12 and is biased by a spring 13 against the pile warps 6. In addition, the ground warps 2 and pile warps 6 are guided via warp yarn detectors 14 into a means for forming a shed. This means includes a plurality of heddles 15 which are able to shift the warps into a top shed position and/or a bottom shed position. In addition, a means is provided in the form of a reed 16 for beating up a weft yarn within the shed to a beating-up station to form a fabric or fabric. The machine has also a slide 17 comprised of a temple 8 having a needle roller 18 and a breast beam 19 over which the fabric is guided away from the beating up station. In addition, a needled stepping beam 20, a pressing beam 21, and a temple 9 are provided to guide the fabric onto a fabric beam 22.
As indicated, a means is provided for periodically reciprocating the temple 8 and breast beam 19 to effect a terry weave in the fabric. This means includes a pull link 23 which is connected to the breast beam 19, a pull hook or lever 24 and a cam follower lever 25 which connect the breast beam 19 to a terry cam 26. This cam 26 meshes with a worm drive 28 forming part of a warp beam drive 27. The worm drive 28 also meshes with a toothed annulus 29 of the warp beam 5. In addition, a drive motor 30 is provided for driving the warp beam drive 27. Referring to Fig. 2, a means in the form of a stationary deflecting mechanism 31 is disposed between the reed 16 and temple 8 for narrowing the shed on opposite sides, i.e., from the top and from the bottom, as viewed at least on one edge in order to maintain a tucked-in end of a weft yarn in the shed. During operation of the weaving machine, the terry cam 26 (Fig. 2) acts via the lever 25, hook 24 and link 23 to reciprocate the slide 17 in the direction indicated by the double arrow 33. The fabric 32 thus makes an operative movement (lift) H relative to the beating- up position of the reed
Fabric control mechanism on Dornier weaving machine
Pile formation by using this mechanism is based on the principle of a stable and precise shifting of the beat-up point. Using this principle the fabric is shifted towards the reed by
means of a positively controlled movement of the whip roll 6 and a terry bar together with the temples on the beat-up of the fast pick. The sturdy reed drive is free of play. It provides the necessary precision for the beat-up of the group of picks.
means of a positively controlled movement of the whip roll 6 and a terry bar together with the temples on the beat-up of the fast pick. The sturdy reed drive is free of play. It provides the necessary precision for the beat-up of the group of picks.
A compact, simplified whip roll system 6 with the warp stop motions arranged on two separate levels improves handling and has a decisive influence on reducing broken ends. Due to a drastic reduction in the number of mechanical components the amount of maintenance required is reduced. With the help of electronics the precision of measuring the Iength of pile yarn is improved. This leads to a better fabric quality due to constant pile height and fabric weight. The weaving process is so exact that precise mirrored patterns are possible and velour weavers experience minimal shearing waste. The tensions of the ground and pile warps 1 and 2 are detected by force sensors 3 and 9 and electronically regulated. In this way warp tension is kept uniform from full to the empty warp beam. To prevent starting marks or pulling back of the pile loops the pile warp tension can be reduced during machine standstill. Fig. 3 illustrates Dornier air-jet terry weaving machine
Fig. 3: Fabric control mechanism on Dornier air-jet weaving machine
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