Objects of weft changing mechanism

Objects of weft changing mechanism

The weft-changing mechanism is an essential component of weaving machines, which is responsible for inserting the weft yarn into the warp yarns at the right time and position. The weft yarn is the horizontal yarn that passes over and under the vertical warp yarns, forming the fabric. The weft-changing mechanism allows the weaver to change the weft yarn as necessary, to create different patterns, colors, and textures in the fabric. In this article, we will discuss the objects of the weft-changing mechanism in more detail.

Shuttle
The shuttle is a critical component of the weft-changing mechanism that carries the weft yarn across the loom. It is a small boat-shaped device that contains the weft yarn and travels across the loom during weaving. The shuttle has a pointed end and a bobbin that holds the weft yarn. When the shuttle moves across the loom, it leaves a trail of weft yarn behind it, creating the fabric.

There are different types of shuttles used in weaving machines, such as fly shuttles, projectile shuttles, and rapier shuttles. The fly shuttle is the most common type of shuttle used in modern weaving machines. It is propelled by a picking mechanism that moves it back and forth across the loom. The projectile shuttle is propelled by a gas or air pressure, while the rapier shuttle uses a flexible rod to insert the weft yarn into the warp yarns.

Picking mechanism
The picking mechanism is responsible for propelling the shuttle across the loom. It usually consists of a picking stick or a picking arm that moves the shuttle from one side of the loom to the other. The picking mechanism is powered by an electric motor or a manual lever.

The picking mechanism is timed to release the shuttle at the right moment, so it travels across the loom at the right speed and direction. The picking mechanism must also be accurate to ensure that the weft yarn is inserted into the warp yarns in the right place.

Shedding mechanism
The shedding mechanism is responsible for raising and lowering the warp yarns to create a shed or an opening through which the shuttle can pass. The shedding mechanism consists of a series of heddles, which are loops of wire or cord that hold the warp yarns.

The heddles are attached to the harnesses, which are raised and lowered by the treadles. The treadles are foot pedals that the weaver uses to control the shedding mechanism. By pressing on the treadles in a specific sequence, the weaver can create different patterns and designs in the fabric.

Beat-up mechanism
The beat-up mechanism is responsible for pressing the weft yarn into the fabric after each pass of the shuttle. It consists of a reed, which is a comb-like device that holds the warp yarns in place while the weft yarn is inserted.

The reed is attached to a beater, which is a bar that moves back and forth across the loom. The beater pushes the weft yarn into the fabric and then returns to its starting position, ready for the next pass of the shuttle.

Take-up mechanism
The take-up mechanism is responsible for winding the fabric onto the cloth beam as it is woven. The cloth beam is a large cylinder that holds the fabric as it is woven. The take-up mechanism consists of a series of rollers and gears that move the cloth beam forward as the fabric is woven.

The take-up mechanism must be synchronized with the other components of the weaving machine to ensure that the fabric is wound onto the cloth beam evenly and without tension.

Stop-motion mechanism
The stop-motion mechanism is a safety feature that stops the weaving machine if there is a problem with the weft yarn or the warp yarn. It

auxiliary motions of weaving
In weaving, there are several auxiliary motions that are used to create the pattern and structure of the fabric. These motions are used in addition to the primary motion of the weaving machine, which moves the warp and weft threads to create the basic fabric structure.

Some of the most common auxiliary motions used in weaving include:

Shedding: This motion involves lifting some of the warp threads to create a gap or "shed" through which the weft thread can be passed. Shedding is typically accomplished by using a device called a "heddle," which is used to raise and lower the warp threads.

Picking: Picking is the motion of passing the weft thread through the shed created by shedding. This is usually done by a shuttle, rapier, or air jet.

Beat-up: After the weft thread has been inserted into the shed, the reed or lay is used to push it up against the previous weft thread. This process is called "beating up," and it helps to pack the weft threads tightly together to create a stable fabric structure.

Take-up: The take-up motion is used to wind the finished fabric onto the cloth beam. As the fabric is woven, it is wound onto the cloth beam at a rate that is determined by the fabric design and the desired fabric density.

Other auxiliary motions that may be used in weaving include selvage formation, warp let-off, and warp stop motions. Each of these motions plays an important role in the weaving process, and they must be carefully controlled to ensure that the final fabric meets the desired specifications.

Secondary motion of weaving
The secondary motion of weaving refers to any movement or action that is not directly related to the primary motion of the weaving machine, which is the interlacement of warp and weft threads to create the fabric structure. These secondary motions are auxiliary to the primary motion and are used to control the various aspects of the weaving process, such as tension, pattern, and quality of the fabric.

Some of the common secondary motions in weaving include:

Let-off: The let-off motion controls the amount of warp yarn that is released from the warp beam to maintain a constant tension on the warp yarn as it is fed into the loom.

Take-up: The take-up motion controls the speed at which the woven fabric is wound onto the cloth beam, which affects the density and quality of the fabric.

Shuttle or rapier motion: This motion is used to insert the weft yarn through the shed created by the shedding motion. The shuttle or rapier carries the weft yarn across the loom to the opposite side, where it is inserted into the opposite shed.

Selvage formation: The selvage formation motion controls the formation of the edges of the fabric, which are used to prevent the fabric from unraveling and to facilitate further processing.

Beat-up: The beat-up motion is used to push each weft yarn firmly into place against the preceding yarns to form a dense, stable fabric structure.

Shedding: The shedding motion creates an opening in the warp yarns to allow the weft yarn to be inserted. It is achieved using heddles or other shedding devices.

These secondary motions are essential for producing a high-quality fabric with a consistent structure and appearance. Proper control of these motions is crucial for achieving the desired fabric properties and characteristics.