Projectile weaving

Projectile weaving

• 1.
  Projectile Weaving Projectile weavingmachine was invented in 1924 and introduced in the market in 1953. The main feature of this machine is weft insertion system. A bullet like shuttle 90 mm long and weighting about 40 gm, technically named as gripper projectile is used here to insert the weft thread into the warp threads which gets motion by a metal torsion rod. It is established especially in the field of machines with high reed width. In the projectile loom, the weft thread is gripped by jaws, fitted in a projectile which is then propelled through the shed. This filling insertion system produces good fabric quality with high economical efficiency and low energy consumption. The unique principle of projectile filling insertion allows the insertion of practically any types of yarn: cotton, wool, mono and multi filament yarns, polypropylene and even hard fibers like jute, flax fibers yarn. This is because all yarns, fine or coarse are securely gripped and inserted by the projectile, resulting in a wide variety of fabrics from simple staple yarn fabrics to superior fashion cloth and from wide heavy industrial fabrics to complex jacquard cloths. Sulzer projectile weaving machine differs from a conventional automatic loom mainly in two respects.  The method of insertion of weft into the warp shed.  The method of moving the reed and the projectile track. Weft insertion system has a great influence on physical properties of fabric: Crimp, thickness, tensile strength, elongation at break crease recovery etc. Main Features of Projectile Loom: 1. The picking and projectile receiving units are separated from the moving sley. The sley carries the reed & gripper guides. 2. The gripper projectile made of fine steel, 90 mm long 14mm wide and 6 mm thickness weight is 40 g. It carries the weft thread into the warp shed. 3. The weft is drawn directly from a large stationary cross wound package. There is no weft winding. 4. The gripper projectile is picked across the warp shed at a very high speed ,the picking energy being derived from the energy stored in a metal torsion bar which is twisted at predetermined amount of released to give the projectile a high rate of acceleration . 5. Picking always takes place from one side, but several projectiles are employed and all of them return to the picking side by a conveyor chain located underneath the warp shed. 6. During its flight through the shed the projectile runs in a rake likes steel guides, so that the warp threads are touched neither by the projectile nor weft thread.
• 2.
  7. Every pickis cut off at the picking side near the selvedge after weft insertion, leaving a length about 15 mm from the edge. 8. The ends of weft thread projecting on both sides of the cloth are tucked into the next shed by means of special tucking device and woven in with next pick, thus providing firm selvedges. 9. The reed & projectile guides are stationary during pick insertion. 10.A sley dwell of 25 degree at back center enables the projectile to travel through the warp shed without being unnecessary reciprocated by the sley. 11.Whenever the reed width is reduced for weaving a small width cloth from the standard reed width, the projectile receiving unit is moved inward on the telescope shaft, to the new selvedge position, and so the projectile travel distance is reduced. 12.Smaller shed opening because of the smaller size projectile. This might result in lower warp breakage rate. 13.Weft insertion rate up to 900-1500 m/min is possible depending up to the width of the weaving machine. 14.The color changing mechanism is less complicated. 15.In case of weft breakage the take up beam & heald frames can be driven in reverse by a pick finding mechanism. 16.There is facility of inserting two picks in the same shed without the use of dobby. Advantages of Projectile Loom as a Modern Loom: 1. Two or three cloths can be woven simultaneously. It causes of saving energy, space and more economical. 2. Fabric of large width is possible to weave (up to 540 cm). 3. The lower warp breakage rate in a projectile weaving machine may be due to:  Smaller warp shed  Reed with higher ratio of air to wire (70:30)  Beat up line being nearer to the centre of the reed between the two baulks. 4. Smaller warp shed will reduce the warp threads tension to some extent. However care should be taken to maintain uniform tension to ensure that the warp shed is of same depth from one end to another. Otherwise a few slack warp threads at the top shed will result in stitching and end cut of the projectile. 5. Since the projectile is passing through guides there is no reed to projectile or projectile to yarn contact. 6. With the introduction of four/six colors weaving machine all the mechanical problems of the conventional pick & pick multicolored loom are eliminated. 7. Projectile is fully controlled in the shed where the shuttle is not fully controlled. 8. Compared to the insertion systems of rapier and air-jet weaving machines, filling insertion by means of projectiles features the least energy requirement. The masses to be moved for insertion by projectiles are substantially smaller than those required
• 3.
  for rapier insertion,and they are far more efficient than filling insertion with the aid of compressed air. Projectiles and its types with dimension: There are various projectile versions: Made of steel 9 cm long and 40 gm heavy with small cross section suitable for yarns of fine to medium count. Made of steel 9 cm long and 60 gm heavy with large cross section suitable for machines with high width reed or for bulky yarns i.e, when fancy yarns are used. Generally projectiles are made of steel or carbon composites with different variations. The popularity of carbon composite projectiles has been declining due to their poor fatigue performance compared to steel projectiles. D1 is the standard steel projectile for the vast majority of commercial yarns. D12 is the same as D1 with a larger yarn clamping surface to ensure more reliable gripping, even of delicate yarns. D2 has a big cross section and large clamping surface and is used for extremely coarse yarns. K3 is the synthetic (carbon composite) projectile which was intended to economically produce very delicate fabrics. Projectile Guide: Two types of projectile guides: aligned guide teeth and staggered guide teeth. Aligned guide teeth are used for applications such as bolting cloth, silk, fly screen, coated glass, rain proof fabric, voile, linings and tape yarns. Staggered teeth are Figure: Different types of projectiles
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  used for applicationssuch as multifilament yarns, monofilament yarns, staple yarns including terry, woolen yarns, hard fiber yarns and leno fabrics. During reed beat-up the guide teeth emerge below the shed and release the filling yarn through the upward facing opening. Projectile Jaws: 1. Smooth 2. With groove 3. Crisscross knurls 4. With friction coating and lateral guidance Figure: Projectile Guide
• 5.
  Picking/Filling insertion sequence(Insertion cycle of the projectile machine): A: Projectile 1 moves into the picking position. B: Projectile feeder 2 opens after projectile 1 has gripped the filling end presented to it. C: The projectile has drawn the yarn through the shed, while filling tensioner lever 3 and adjustable filling brake 4 act to minimize the strain placed on the yarn during picking. D: The projectile is braked by projectile brake 8 in the receiving unit and pushed back, while the filling tensioner lever and the filling brake hold the filling yarn lightly stretched. At the same time, the projectile feeder moves close to the selvage. E: Projectile feeder 2 takes over the filling yarn, while filling end grippers 5 hold it at both sides of the fabric.
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  F: The yarnis released by the projectile on the receiving side. Filling cutter 6 cuts the filling yarn. A conveyor takes expelled projectile 1 and carries it outside the shed back to the picking position. G: The reed has beaten up the pick. Tucking needles 7 tuck the filling tails into the next shed (tucked selvage). Filling tensioner lever 3 has taken up the length of yarn remaining when projectile feeder 2 returns. The next projectile 1 is brought into the picking position. Hints: 1-Projectile, 2- Projectile Feeder, 3-Weft Tensioner Lever, 4-Weft Brake, 5-Weft End Gripper, 6-Weft Cutter, 7-Tucking Needles, 8-Projectile Brake.
• 7.
  Figure: Weft insertionwith projectile Figure: Dwell during the filling insertion of different weaving machine for different width.
• 8.
  Torsion bar pickingmechanism: Working principle: A strain energy is developed by twisting the torsion bar and released suddenly to transfer the maximum possible strain-energy to the projectile before the projectile leaves the picker-shoe. Projection velocity of the weft carrier can be increased 1. By increasing the angle of twist. 2. By maintaining the same angle of twist on a larger diameter rod. Weft is withdrawn from the package through a tension device, weft tensionar, shuttle feeder, scissor, and weft end gripper. The picking arm released the projectile which is shown in the guide teeth at the mid-shed position. At the receiving side the weft end gripper is positioned to grip the weft after reception. Strain energy is developed in the bar and released in such a way as to transfer the maximum possible strain energy to the projectile before it separates from the picker shoe. The torsion bar (A) has its splined ends rigidly constrained in an adjustable housing with provision for adjusting the maximum angle of Hints: A=Torsion bar, B=Picking shaft, C=Picking lever, D=Picking shoe, E=Picking shaft lever, F=Toggle plate, G=Antifriction bowl, H=Link, I=Picking cam, J=Shaft, K=Bevel wheels, L=Oil brake, P=Projectile, R=Projectile guide. Figure: Torsion bar (Projectile) picking mechanism.
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  twist and projectileinitial velocity. The other end of the torsion rod is splined into the picking lever (C) which carries the picking shoe (D) at its extremity. The projectile (P) is illustrated in the shuttle lifter with the projectile spring opener. The bevel wheel (K) rotates the picking cam shaft (J) which carries the picking cam (I). The picking shaft lever (E) is rigidly connected to the torsion bar and through a short linkage to the toggle plate (F) center at anti friction bowl (G).The action of the cam is for the small roller to bear against the toggle rotate it anti clockwise about anti friction bowl (G), thus withdrawing the picking shoe to its rearmost position. In this position the center of the toggle arrangement are in line and the torsion bar is twisted to its predetermined angle. The nose of the picking cam then bears against the roller carried between the toggle plates and moves the central pivot of the toggle system off line center, thus permitting the strain energy in the rod to be transmitted instantaneously to the projectile. The projectile separates from the shoe after 6.4 cm travel in 0.007 s as a velocity of about 24.4 m/s after being subjected to a maximum acceleration of about 6700 m/s2 at a point 1.5 cm inboard of the rest position. The residual energy in the picking system, some 62% of the whole is absorbed in the hydraulic buffer the body and plunger of which are shown at (L). Hints: 1-Picking shoe 2. Projectile 3. Projectile lifter 4. Tension flange 5. Knee joint 6. Roller lever 7. Oil brake 8. Cam 9. Torsion rod 10. Picking shaft 11. Picking lever 12. Roller Figure: Torsion bar (Projectile) picking mechanism.
• 10.
  Loading of thetorsion bar: a) Torsion bar 2 in rest, knee joint lever (4+5) in articulate position. b) Loading phase c) Torsion bar in tension and knee joint lever in stable position, before the launching control by roller 7.
• 11.
  Air supported fillinginsertion: Pre-acceleration of the filling with compressed air reduces the strain on the filling yarn. Two part, staggered guiding teeth reduce the strain on warp and filling. Therefore, even delicate yarns, such as those without twist or air-intermingled, can be used in the warp to make fabrics of good quality. With the air supported filling insertion, the peak values of the tensile stress, which the filling yarns are subjected to, are reduced to a degree that permits insertion of low tenacity yarns even at the highest speeds. Due to the support provided by the compressed air, the flow of the tensile load phase is markedly softer and the peak values of the tensile stress are reduced by approximately 50%. This allows weaving of fine yarns. Selvedge formation: The tucking unit or intermediate tucking unit of the projectile weaving machine forms clean tucked-in selvages. Because of the filling insertion system, the filling yarn is of exactly the right length and need not be shortened, as a result, there is no yarn wasted. The projectile weaving machine can also be fitted with units to make leno or sealed selvages. The yarn end is tucked in by the interaction of filling end gripper 1 and tucking needle 2. After filling insertion, the filling end grippers seize the pick on the left and right of the reed. After the 1- Weft end gripper 2- Tucking needle Figure: Selvage formation in projectile loom.
• 12.
  projectile gripper hasopened in the receiving unit and the filling yarn has been cut on the picking side, the sley moves towards reed beat-up. The filling end grippers with the clamped yarn ends move forward with it at the same time. While the next pick is inserted, the tucking needles pull the filling ends out of the filling end grippers and place them in the newly formed shed. In the case of very filling -intensive styles or when weaving with coarse filling yarn, a split selvage with half cross leno interlacing can be used. For synthetic fabrics, a selvage sealing device can be used for severing the selvage. Intermediate tuck-in units used between the fabric widths during multi-width weaving, form the tucked selvages at the cloth width dividing lanes.