Rapier Loom

In a rapier loom, the rapier (a flexible or rigid rod or tape) carries the weft yarn from one side of the loom to the other, passing it through the shed created by the warp threads. The rapier is responsible for the transfer and insertion of the weft yarn across the warp threads to form the woven fabric.

Features:

  1. Weft Insertion by Rigid or Flexible Rapier:
    • Explanation: Rapier looms can employ either rigid or flexible rapiers for weft insertion. Rigid rapiers have a solid structure, while flexible rapiers use a tape-like structure. The choice between them can affect the loom’s performance in terms of shed geometry and versatility.
  2. Fancy & Costly Fabric is Produced:
    • Explanation: Rapier looms are capable of producing intricate and high-quality fabrics. The term “fancy” implies the creation of fabrics with complex patterns, and the ability to produce costly fabrics indicates the loom’s suitability for high-end textile production.
  3. Weft Patterning Maximum – 8:
    • Explanation: Rapier looms can achieve a maximum of 8 weft insertions for creating patterns in the fabric. This feature allows for a variety of designs and textures in the woven material.
  4. Power Consumption Medium:
    • Explanation: Compared to some other types of looms, rapier looms typically have a medium level of power consumption. This balance between power efficiency and weaving performance is a notable characteristic.
  5. Price Comparatively Lower:
    • Explanation: In comparison to certain advanced loom technologies, rapier looms are considered to have a relatively lower price. This can make them more accessible to a broader range of textile manufacturers.
  6. Standard Width of Rapier is 190 cm:
    • Explanation: The standard width of the rapier, referring to the effective weaving width of the loom, is 190 cm. This dimension defines the maximum width of the fabric that the loom can produce in a single pass.

Classification of Rapier Loom:

Rapier Loom Working Principle:

  1. Weft Supply:
    • The process begins with the supply of the weft yarn from a cone package.
  2. Tensioning:
    • The yarn passes through a tensioner that helps in maintaining proper yarn tension.
  3. Accumulator:
    • An accumulator stores a certain length of the yarn, providing a buffer for the weaving process.
  4. Leaf Tensioner:
    • The yarn then moves through a leaf tensioner, which further ensures the appropriate tension for smooth operation.
  5. Filling Detector:
    • As the yarn progresses, it passes through a filling detector. This device detects the presence or absence of the weft yarn, ensuring proper yarn insertion.
  6. Thread Guide:
    • The yarn is guided through a thread guide, aligning it for the next stages of the weaving process.
  7. Weft Selector:
    • In the weft selector, the loom determines which color of yarn to use. This is particularly relevant in multi-color fabric production, where a selector chooses the yarn color.
  8. Rapier Action:
    • The rapier, a flexible or rigid rod or tape, grips the selected yarn and swiftly carries it from one side of the loom to the other through the shed (the space created by the raised and lowered warp threads).
  9. Shedding:
    • Shedding is the controlled lifting and lowering of warp threads to create the shed. This allows the rapier to smoothly pass through and insert the weft yarn.
  10. Reed Beat-Up:
    • After the weft yarn is inserted, a reed, a comb-like structure, beats up the weft to the fell of the cloth. This action ensures proper alignment and density of the woven fabric.
  11. Weaving Completed:
    • With the completion of the beat-up, one weaving cycle is finished, and the process repeats for the next pick.

Rapier Driving System – Mechanism Explanation:

Rigid Rapier Drive from the Cam:

  1. Cam Off-Centered:
    • The cam is intentionally positioned off-center.
  2. Bowl Following Cam Profile:
    • The bowl tracks the profile of the off-centered cam.
  3. Bowl Lever and Triangular Mechanism:
    • The cam’s action on the bowl lever results in a downward movement of the bowl.
  4. Pivoting of Bowl Lever:
    • One side of the bowl lever is pivoted, allowing the bowl to move downward.
  5. Driving Lever with Link Connection:
    • A driving lever is fulcrum at the middle position and connected to the bowl lever via a link.
  6. Downward Movement of Driving Lever:
    • The right side of the driving lever moves downward.
  7. Drive to Rapier by Driving Arm:
    • The downward movement of the driving lever imparts drive to the rapier through the driving arm.
  8. Pivoting with Knuckle Joint:
    • The last end of the driving arm is pivoted with a knuckle joint.

Direct Drive from Eccentric:

  1. Eccentric Oscillation:
    • An eccentric component is designed to oscillate in unison with the main shaft.
  2. Connection with Main Shaft:
    • The eccentric is directly linked and synchronized with the rotation of the main shaft.
  3. Driving Arm and Connecting Arm:
    • A driving arm is engaged with a connecting arm in the mechanism.
  4. Pivoting with Knuckle Joint:
    • The driving arm is pivoted at one end, employing a knuckle joint.
  5. Main Shaft Rotation Effect:
    • When the main shaft rotates, the eccentric impels both the connecting arm and the driving arm on the right side.
  6. Smooth Straight Movement:
    • The design ensures that, due to the knuckle joint in the driving arm, the rapier experiences a smooth, straight movement through the warp shed.

Cycloidal Gear Drive (Epicyclic Gear Drive)

The cycloidal gear drive, also known as the epicyclic gear drive, is a sophisticated mechanism used in rapier looms for efficient weft insertion.

  1. Direct Connection to Rapier:
    • The rapier, the component responsible for carrying and inserting the weft yarn, is directly connected to a cycloidal gear driving cam.
  2. Cycloidal Gear and Driving Gear:
    • The cycloidal gear, linked to the driving cam, plays a crucial role. It is intricately attached to a driving gear, forming a connected system.
  3. Revolution Around Main Gear:
    • The driving gear is designed to revolve around a larger gear known as the main gear. This main gear is, in turn, driven by the main shaft of the loom.
  4. Elimination of Intermediate Components:
    • Unlike some other drive systems, the cycloidal gear drive eliminates the need for certain intermediate components. There’s no requirement for an intermediate driving arm, a pivot arm, or an oscillating fulcrum.
  5. Simplified Design for Harmonic Movement:
    • The elimination of intermediate components streamlines the design, contributing to a more straightforward and efficient system. The movement achieved by this mechanism closely approaches simple harmonic motion, ensuring a smooth and controlled operation of the rapier.

Telescopic Rapier Driving System

The telescopic rapier driving system is a specialized mechanism employed in certain looms, such as the Versomat loom. This system utilizes the telescopic expansion principle to save space and enhance the efficiency of the rapier movement.

  1. Main Outer Body and Inner Body:
    • The rapier, the component responsible for carrying and inserting the weft yarn, consists of two main parts: the outer body and the inner body.
  2. Drive from Eccentric:
    • The main outer body of the rapier is primarily driven by an eccentric mechanism through connecting and driving arms. This eccentric is typically connected to the loom’s machinery.
  3. Attachment to Tape:
    • The inner body of the rapier is fastened to a tape at its outer end. This tape plays a crucial role in the telescopic movement of the rapier.
  4. Fixed Point Attachment:
    • The tape is attached to a fixed point on the loom. This fixed point serves as an anchor for the telescopic movement mechanism.
  5. Pulley System:
    • The tape passes around four pulleys, with two mounted at each end of the outer rapier body. These pulleys facilitate the controlled movement of the tape during the rapier’s operation.
  6. Telescopic Expansion Principle:
    • When the rapier is out of the shed (not actively engaged in the weaving process), the inner rapier is withdrawn inside the outer rapier. However, as the outer rapier is driven towards the center of the loom, the tape is designed to slide around the pulleys. This action causes the inner rapier to move in the same direction but at an even faster rate.
  7. Space-Saving Design:
    • The telescopic expansion principle allows for a space-saving design. The inner rapier can be retracted when not in use, optimizing the spatial efficiency of the loom.

Dewas Double Rapier Weft Insertion and Transfer Mechanism:

Description: In the Dewas double rapier system, each rapier head grips the yarn during the weaving process. The gripping unit typically consists of a fixed point against which a spring-loaded clamp presses to trap the yarn.

  1. Gripping Unit:
    • Each rapier head has a gripping unit with a fixed point and a spring-loaded clamp. The fixed point may be located on the loom or the sley mounting.
  2. Clamp Operation:
    • The clamps open and close based on the weaving requirements. They open when the weft is to be picked up or released outside the selvedge.
  3. Weft Trapping and Transfer:
    • The right-hand rapier head traps the weft at point A and pulls it through the shed until the rapiers meet.
  4. Guided Movement:
    • The head is then guided around point B, and as the left-hand rapier head withdraws, the thread is trapped at point C.
  5. Completion of Insertion:
    • The left-hand rapier head pulls the weft across the loom to complete the insertion process.
  6. Spring Operation during Transfer:
    • In some looms, the spring in the delivery head is opened at the time of transfer. This is achieved through the specially shaped profile of the left-hand rapier head. This feature helps minimize weft breaks at the transfer point.
  7. Advantages:
    • Minimization of weft breaks at transfer points.
    • Prevention of wefts being pulled out of the receiving spring.
    • Enhanced reliability and efficiency in weft insertion.

Gabler Double Rapier Weft Insertion System:

  1. No Gripping of Weft:
    • In the Gabler system, the weft is not gripped by the rapier heads during the insertion process.
  2. Initial Placement:
    • The weft yarn is initially placed opposite the cut-out A in the right-hand rapier head.
  3. Advance Toward the Center:
    • As the rapier advances toward the center of the loom, the yarn passes from its initial clamped position.
  4. Yarn Passage and Meeting Heads:
    • The yarn passes around the rapier head and moves toward the center until the heads meet at the center of the loom.
  5. Entry of Left-Hand Rapier Head:
    • The smaller left-hand rapier head enters the space occupied by the right-hand rapier head carrying the yarn.
  6. Repositioning the Weft:
    • At this point (C), the thread at the initial cut-out position (A) is passed under the spring-loaded cover guide. This action repositions the weft.
  7. Sliding Through and Straightening:
    • The yarn can then slide through the left-hand rapier head as it is withdrawn. This sliding action straightens out the yarn in a hairpin-like manner.

Advantages:

  • The Gabler double rapier system offers a unique approach by avoiding direct gripping of the weft.
  • The repositioning mechanism with the spring-loaded cover guide ensures proper alignment and control of the weft yarn during the insertion process.

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