Projectile Loom

Projectile Loom:

The projectile weaving machine made its appearance in the market at the beginning of the 50’s and is today still used in the whole world. Now a days it is modified to advanced electronic systems as well as of microprocessors for the supervision and the control of the various devices, this machine is characterized by a good productivity level (450 rpm and 1050 m/min of inserted weft) and by high equipped reliability. It is established especially in the field of machines with high reed width.

Fig: Projectile Loom.

General operation

In this weaving machine the weft insertion is carried out by small clamp projectiles (fig. 45), which number depends on the weaving width and which with their grippers take out the weft yarn from big cross-wound bobbins and insert it into the shed always in the same direction. The projectiles work in sequence that is they are launched in succession. They run therefore one after the other, describing in the space a continuous, endless route, as if they would be stuck on a conveyor belt.

The first projectile takes and holds in its back the weft in form of a tail; then, pushed by the release of the projectile thrower, it passes through the shed and deposits the weft inside the warp; subsequently the projectile falls and is collected by a device which, by passing under the array of the warp threads, takes it at reduced speed back to the starting point. Here the projectile goes up to take up a new weft; meanwhile the other projectiles have run after each other making the same operation.

Fig: Weft Insertion Device for projectile loom.

Features and Advantages of Projectile Weaving Machine:

      The picking and the projectile units are separated from the moving sley. The sley (Projectile track) carries the reed and griper guides.

      The gripper Projectile, made of fine steel 90mm long 14 mm wide and 6 mm thickness (3.5 in * 0.55in *0.14 in). It carries the weft thread in to the warp shed.

      The weft is drawn directly from a large, stationary cross wound package. There is no weft winding.

      The gripper Projectile is picked across the warp shed at very high speed, the picking energy being derived from the energy stored in the metal torsion bar which is twisted at predetermined amount and release to give the projectile at high rate of acceleration.

      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 wrap shed.

      During its flight through the shed the Projectile runs in a rack like steel guides, so that the wrap threads are touched neither by the projectile nor weft thread.

      Every pick is cut off at the picking side near the selvedge after weft insertions, leaving a length about 15mm from the edge. Similar length of weft also projects from the selvedge on the receiving side.

      The ends of weft thread projecting on both sides of the cloth are tucked into the next shed by means of a special tucking device and woven in with next pick, thus providing firm selvedges.

      The reed is not reciprocated as in a shuttle loom, but rocked about its axis by a pair of cams.

      The reed and projectile guides are stationary during pick insertion.

      The sley which carries the reed and projectile guides is moved forward and backward through a saddle carrying two follower bowls, which bear against the surface of two matched cams.

      A sley dwell of 255 at back centre enables the projectile to travel through the warp shed without being unnecessarily reciprocated by the            sley.

      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 telescopic shaft, to the new selvedge position, and so the projectile travel distance is reduced.

      Smaller shed opening because of the smaller size projectile. This might result in lower warp breakage rate.

      Weft insertion rate up to 900 to 1500 m/min. is possible depending up to the width of the weaving machine.

      The color changing mechanism is less complicated.

      There is facility of inserting two picks in the same shed without the use of a dobby.

      In case of weft breakage the take-up beam and heald frames can be driven in reverse by a pick finding mechanism.

      Two or three cloths can be woven simultaneously.

      It is possible to achieve weaving performances with breakage rates per square meter of cloth.50% of the number of breaks that would occur on a conventional loom.

      The lower warp breakage rate in a Projectile Weaving Machine may be due to

1.     Smaller warp shed

2.    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.