Rapier Weaving Machine: Features, Types and Weft Insertion

What is Rapier Weaving Machine?

Rapier weaving machines use a rigid or flexible element called rapier to insert the weft yarn in the warp shed. Insertion of weft by rapier is a mechanically modern and refined version of the primitive method of fabric production in which the weft was secured in a slot of a stick. The rapier head picks up the weft yarn from one side and carries it to the other side of the weaving machine. The rapier returns empty to pick the weft yarn for the next pick, which completes one cycle. The rapiers per­form reciprocating motions. Rapier weaving machines are reliable and flexible. A wide range of fabrics can be woven, from lightweight to heavyweight. Rapier weav­ing machines can weave cotton, wool, silk and synthetic fibres, such as polyester, amongst others.

Application range of rapier weaving machine covers a wide variety of fabric styles. Their present weaving speed of about 600-700 strokes/min is the result of the use of a state-of-the-art construction technique, characterized by the use of gear sets without plays and by minimum vibrations of the reed, the slay and the heald frames. Rapier loom has the advantages of high speed, stability, and good variety adaptability.

Features of Rapier Weaving Machines

1. Double flexible rapier machines are the standard machines, and they can be used to weave a wide range of fabrics with natural and synthetic fiber yarn.
2. In rapier weaving machines, the sley rocks on a shaft and complementary cams, with different sley dwells are used depending on the width of the loom.
3. Lightweight all-purpose grippers with few moving parts can be used for a wide range of yarns from 5tex to 1000tex.
4. Electronically controlled color selectors can be used for selecting eight colors in weft.
5. Tuck-in, leno or fused selvedges can be formed on rapier machines depend­ing on the requirement. The selvedge waste of weft yarn at both sides will be from 7cm to 14cm.
6. Rapier machines can be fitted with intermediate tucking units. This allows weaving several fabrics simultaneously.
7. Positive cam or positive dobby are mostly used for shedding.
8. Fabric take-up is controlled by a servomotor.
9. The weft insertion rate is up to 1100m/minute, and the width of the machine can be 220cm. The machine runs at 220ppm.

Types of Rapier Weaving Machines

Rapier weaving machine may have various types according to the weft insertion mechanism and number of pick such as insertion of double pick, insertion of single pick, two phase rapier etc. Rapier weaving machines are of two types. Rapier weaving machine that uses only one rapier head are called single rapier machines. Rapier weaving machines that use two rapier heads are called double rapier machines. Double rapier machines are further classified as double rigid rapiers and double flexible rapiers.

A. Single Rapier Machines:

A single rigid rapier is used in these machines for weft insertion. The rigid rapier is made of metal or composite with a round cross section. The rapier enters the warp shed from one side of the machine and, on reaching the other side, picks up the tip of the weft yarn and inserts the weft yarn in the warp shed while retracting. Figure 1 illustrates the weft insertion cycle of single rapier machines.

In Figure 1 at position A, rapier 1 is ready to enter the warp shed. At position B, the rapier head has entered the shed and reached the other end of the machine, and it catches the tip of weft yarn 3. At position C, the rapier head has retracted to the original position, laying the weft yarn inside the shed and is ready for the next cycle.

Single rapier carries the yarn in one way only, and half the movement is wasted. It is slow and occupies more space. The rapier requires high mass and rigidity. The maximum weft insertion rate of a single rapier weaving machine is 400mpm. For these reasons, single rapiers are not preferred. However, single rapier weaving machines can be used to weave weft yarns that are difficult to control.

B. Double Rigid Rapier Machines:

In double rigid rapier machines, two rapier heads are used, one on each side of the machine. Both rapiers start from both sides at the same time, meet at the midpoint and retreat backwards. The rapier, called a giver, takes the weft yarn from the accumulator, carries up to the center and transfers to the other rapier called the taker. The taker rapier retracts and brings the weft yarn to the other side. Because both rapiers extend outside the loom during withdrawal, the space requirement for double rigid rapier machines is high. Figure 2a illustrates a double rigid rapier machine. In the figure, mark A shows the width of the loom required for a rigid rapier.

C. Double Flexible Rapier Machines:

Since the double rigid rapiers occupy more space the rapier rigid rods are replaced by flexible metal or plastic tapes or bands which can be wound on a drum. These machines are called flexible rapiers machines. This saves space compared to rigid rapiers. Figure 2b shows a double flexible rapier machine. In the figure, mark B shows the width of the loom required for flexible rapier, which is less than that required for rigid rapiers.

Methods of Double Rapier Weft Insertion

There are two types of weft insertion in double rapier machines: tip transfer (Dewas) and loop transfer (Gabler) systems.

1. Tip Transfer or Dewas System:

In the Dewas system of weft insertion, the giver rapier grips the tip of the weft yarn, carries it to the center of the machine and transfers it to the taker, which takes the weft to the other side of the machine during its retraction. Figure 3 illustrates the tip transfer or Dewas system of rapier weft insertion.

In Figure 3 at position A, giver rapier head 2 grips the tip of weft yarn 4 and starts moving to the center of the machine. At the same time, taker rapier 1 also starts moving towards the center. At position B, both the rapiers, the giver and the taker, meet at the midpoint, and the giver transfers the tip of the weft yarn to the taker and the taker grips the tip. At position C, both rapiers retreated backwards to their original positions. But the taker brings the weft yarn to its side of the machine, thereby completing the weft insertion. The giver inserts the weft up to the midpoint, and the taker inserts the weft in the remaining portion of the warp. By travelling back and forth up to the midpoint of the machine, both rapiers complete one weft insertion cycle. In modern rapier weaving machines, the tip transfer of weft insertion is mostly used due to its simplicity and speed.

2. Loop Transfer or Gabler System:

In the Gabler system, the giver rapier does not grip the weft; instead, it extends the weft yarn in the form of “U”-shape (loop) to the center of the machine. The tip of the weft yarn is still held by the stopper. At the midpoint, the giver transfers the loop to the taker, and at the same time, the stopper releases the tip of the yarn. When the taker retracts, the loop of yarn straightens itself, and no further yarn is released by the accumulator. This makes straightening of the loop without slag. Figure 4 shows the Gabler system of weft insertion.

Important Parts of Rapier Weaving Machine

Rapier Heads:

In modern rapier weaving machines, rapier heads are called grippers. Figure 5 shows the left-hand and right-hand rapier heads of a dornier loom.

In Figure 5, lever 1 is pivoted at point 2 in both the right-hand and left-hand rapier heads. The lever carries yarn clamp 3 at one end, and at the other end, it car­ries protrusion 4. Between the pivot and protrusion, a hardened plate 7 is secured. Under lever 1, a set of leaf springs 5 is fastened, and it applies a clamping force to the yarn clamps. Both the rapier heads are fastened to tape 8. The yarn clamp plates are made of different materials according to the requirement.

During operation, the weft yarn is presented to the left-hand rapier clamp, and the yarn is seized. When the weft yarn is held by the clamp, it is cut off by a cutter between the selvedge and the yarn clamp. Then weft is inserted in the warp shed.

Rapier Drives:

The to-and-fro movement of the rapier heads is derived from the main shaft either by a linkage mechanism or by a cam. Different makers have different designs for rigid rapier drives and flexible rapier drives. Figure 6 shows a flexible rapier drive system. The continuous rotary motion of main shaft 2 is converted into an oscillat­ing motion of quadrant 4 by cam assembly 1 and connecting arm 3. The oscillating motion of the quadrant is transferred to rapier drive wheel 6 by pinion 5. When the quadrant oscillates, it makes rapier tape 7 move forwards and backwards. The gear­ing of the rapier tape with the drive wheel is achieved by engaging the perforations of the tape with the sprockets of the driving wheel. The rapier movement can be adjusted by adjusting the distance between fulcrum 10 and rapier adjustment point 9.

The principle of operation of the dornier rigid rapier drive is shown in Figure 7. By means of a pair of cams, rocking shaft 1 is rocked in its center. This rocking is transmitted to rocking arm 4 via arm 2 and slide 3. Quadrant 5 is fastened to rocking arm 4. The quadrant is engaged with pinion 6, which, in turn, is engaged with bevel gear 10. The bevel gear transmits its movement to rapier drive spur wheel 7, which, in turn, moves rapier rod 8 forwards and backs. The relative position of the slide and the rocking arm will adjust the stroke of the rapiers.

Rapier Motion:

The rapier heads in the rapier weaving machines are accelerated twice and deceler­ated twice for every pick cycle. Starting from rest at 0° (beat-up), the rapier reaches a speed of about 15m/sec at 90° and slows down to stop immediately at transfer point at 180°. In modern machines, the maximum rapier velocity is as high as 60m/sec. The rapiers have to be accelerated up to a quarter of the reed space and decelerated up to the middle. Figure 8 shows the rapier motion with respect to machine angle of rotation for normal rapier weaving machines.

In Figure 8, both left- and right-hand rapiers start at 0° (beat-up position) At point 2, the weft yarn is presented to the left-hand rapier. At point 3, the left-hand rapier seizes the weft yarn. At point 4, the weft yarn between the rapier head and the selvedge is cut by the cutter. At point 5, which is about 90° of machine rotation, the left-hand rapier reaches maximum velocity. At point 6, which is at 180° of machine rotation, the weft is transferred. At point 7, the right-hand rapier reaches maximum velocity. At point 8, weft yarn is released by the right-hand rapier, and the rapier movement stops. This makes one complete weft insertion cycle of rapiers.

Conclusion

The rapier loom are emerging as weaving machines of the future. In shuttleless weaving machines, the rapier method of weft insertion has been the most widely adopted. The rapier is a weft insertion device which avoids the need for a moving weft package or pirn, by maintaining constant kinematic communication with a drive. The rapier weaving machines are the most flexible machines on the market. I have tried to discuss rapier loom and its salient features, types, weft insertion methods and various parts. If you have any query about rapier weaving machine then comment below. I will try to give answer.

References:

1. Fabric Manufacturing Technology: Weaving and Knitting by K. Thangamani and S. Sundaresan
2. Reference Books of Weaving (ACIMIT) by Giovanni Castelli, Salvatore Maietta, Giuseppe Sigrisi, Ivo Matteo Slaviero
3. Handbook on Fabric Manufacturing: Grey Fabrics: Preparation, Weaving to Marketing by B. Purushothama
4. Mechanisms of Flat Weaving Technology By Valeriy V. Choogin, Palitha Bandara and Elena V. Chepelyuk