Technical Articles

Rapier looms are one of the most widely used shuttleless looms in the textile industry. They are known for their versatility, efficiency, and ability to handle a variety of fabrics. The rapier loom operates by using rapier tapes or rods to carry the weft yarn across the warp shed, enabling high-speed weaving with precise control. Below is the main structure and characteristics of rapier loom.

1 Shedding Mechanism

The shedding mechanism includes negative dobby, positive dobby, cam (treadle) shedding mechanisms, and jacquard shedding mechanisms. Dobby mechanisms can be either bottom-mounted or top-mounted, typically accommodating 20 to 24 harness frames.

2 Main Drive System

The main drive system consists of a main motor transmitting power through an electromagnetic brake clutch to various mechanisms. This clutch is electrically controlled for precise loom operation, including starting, inching, positioning, and stopping. Some looms use variable-speed motors such as:

• Switched reluctance motors

• Variable reluctance motors

• Brushless DC motors

• Frequency-variable motors

These motors allow for direct drive operation.

3 Rapier Drive Methods

Rapier looms commonly use the following drive methods:

• Conjugate cams

• Eccentric linkages

• Spatial crank linkages

• Spatial screw mechanisms

The rapier stroke is adjustable to accommodate different fabric requirements.

4 Weft Insertion Methods

Most rapier looms adopt bilateral flexible rapier belts with central weft transfer. Some use rigid rapier rods for central handover, while a few employ single-sided rapier tapes or rods that traverse the entire shed directly.

5 Weft Supply

Weft supply in rapier looms is managed through independent bobbin frames and electronic weft accumulators, ensuring continuous and constant-tension unwinding of weft yarns.

6 Weft Yarn Color Selection

Rapier looms typically use electronic selectors controlled by microcomputers, which support up to 16 colors. In some models, mechanical selectors are also used.

7 Beat-Up Mechanism

The beat-up mechanism primarily employs conjugate cam mechanisms. In some cases, non-separable four-link or six-link beat-up mechanisms are used.

8 Warp Let-Off Mechanism

The warp let-off mechanism can be either mechanical or electronic, ensuring consistent warp tension throughout the weaving process.

9 Take-Up Mechanism

Rapier looms use either mechanical or electronic take-up mechanisms to regulate fabric winding.

10 Weft Density Adjustment

Weft density in rapier looms typically ranges from 20 to 1500 wefts per 10 cm. The adjustment methods include:

• Mechanical Feed Mechanisms: Utilize continuously variable density adjusters or interchangeable gears.

• Electronic Mechanisms: Adjust weft density by altering the take-up motor angle via the control panel.

11 Selvage Devices

Rapier looms commonly use leno edge-binding devices. Additionally, other selvage mechanisms include:

• Folding edges

• Hot-melt edges

• Electronic selvage mechanisms

12 Warp Stop Motion

The warp stop motion is based on an electrical contact type system, ensuring immediate response to warp breakages.

13 Weft Stop Methods

Weft stop detection uses a piezoelectric ceramic electronic sensor, which can detect broken or double wefts.

14 Starting and Braking

The starting and braking systems utilize electromagnetic clutch-brake mechanisms. Some rapier looms also employ variable-speed motors, such as:

• Switched reluctance motors

• Variable reluctance motors

• Brushless DC motors

• Frequency-variable motors

15 Control System

The control system in rapier looms is typically based on microcontrollers or PLCs (Programmable Logic Controllers). These systems provide various detection and control functions to optimize performance.

16 Rapier Head and Tape

• Rapier Heads: Available in both positive and passive types.

• Rapier Tapes: Can be flexible or rigid, with a trend towards smaller heads and narrower flexible tapes for enhanced efficiency.

17 Lubrication

The lubrication system in rapier looms involves:

• Primary Drive System: Uses oil bath or spray lubrication.

• Other Parts: Require manual pumps or grease lubrication.

18 Automatic Weft-Finding Methods

Three automatic weft-finding methods are used in rapier looms:

1. Motor-Driven Reverse Motion – Used in dobby looms.

2. Dedicated Slow-Motion Weft-Seeking Motors with Clutches.

3. Direct Main Motor Drive.

19 Selvage Yarn

Selvage yarns are supplied using either independent small warp beams or multiple bobbins to maintain consistent selvage quality.

20 Cleaning and Dust Removal

Rapier looms incorporate independent vacuum cleaning systems with dual-sided suction to ensure cleanliness and prevent weft shrinkage.

21 Machine Frame

The frame of a rapier loom can be of the following types:

• Wallboard-Type Frames

• Cast Iron Wall Panels

• Steel Frames (in some models)

22 Fabric Rolling

Fabric rolling in rapier looms is typically achieved through internal fabric winding, though external winding is also an option. Both methods maintain a constant linear speed.

23 Edge Cutters

Rapier looms may use either:

• Mechanical Edge Cutters

• Electronic Edge Cutters

24 Signal Processing

The signal processing system in rapier looms utilizes multicolor signal indicator lights for:

• Warp stop signals

• Weft stop signals

• Standby signals