Weaving Mechanisms Overview

The speed of the tappet shaft needs to be adjusted based on the number of cams used. For example, a 3/1 twill requires a 1/4 speed reduction from the main shaft, and 8-thread sateen needs an 1/8 reduction.

Cam design is influenced by the weave type, the heald frame's movement duration (dwell period) and range (stroke), and the treadle bowl's diameter and contact point.

The time the reed stays stationary at its extreme position, or the time taken for the heald frame to return to its original position. It is related to machine width and inversely related to speed.

A lever that moves up and down, driven by the cams, to control the up-and-down movement of the heald frames.

The distance a cam displaces the heald frame. It expresses the vertical movement.

Cams typically handle 8-12 picks per repeat due to increasing cam slope with more cams. More cams produce greater stress and force required for movement.

There are different ways of configuring the mechanism that makes use of cams to move other parts of the weaving machine.

To distribute the cams evenly, they are configured at a 45 degree angle to distribute force. More cams means a smaller angle for each cam.

The shape of the cam's surface, which dictates the motion produced.

A large amount of force generated by cams, leading to wear and tear.

Shedding mechanism where frames move (up/down) but return due to external forces (springs).

Shedding mechanism where frames are raised/lowered by double cams.

The mechanism (e.g., springs, pulleys) that returns the frames to their original position.

These cams control the motion of the heald frames.

The shaft driving the tappet cams.

The frames in a loom that raise/lower to create the shedding motion.

A versatile method of creating a shed, commonly designed to handle up to 32 heald frames. It allows for complex weave patterns like stripes, checks, and geometrical designs.

Dobbies are typically mounted at the bottom of the loom, except in water jet looms where they are mounted in the upper position to avoid water contact.

Dobby shedding offers several advantages, including a variety of designs, unlimited picks per repeat, easy design changes, and convenient settings.

Dobby shedding is more complicated, costly, prone to fabric faults, and slower compared to simpler shedding systems like crank or cam systems.

The shed opening can be increased by moving the fork lever upward with the clamp screw, and decreased by moving the lever downward.

The shed height can be increased by extending the link rods with the lock screw, and decreased by shortening them.

Dobby shedding systems can be classified based on various factors, allowing for differentiation and understanding of their specific characteristics.

Although dobby shedding offers flexibility, it has limitations in terms of speed and complexity, making it less suitable for high-speed production of simple fabrics.

A type of dobby that uses reciprocating knives and is classified as a double lift positive dobby.

A reciprocating dobby similar to the Hattersley dobby, but it's a double lift negative type.

Rigid components attached to the knives in a Hattersley dobby that move back and forth with the knives.

Fixed bars located opposite the push bars in a Hattersley dobby, used to stop the baulk.

Bars that engage or disengage hooks (H1 and H2) to hold the baulk in place during the weave selection.

A newer type of dobby that operates through rotation, allowing for much faster speeds compared to reciprocating dobbies.

Reciprocating dobbies have a maximum speed of around 500 rpm, while rotary dobbies can reach speeds of 1000 to 1500 rpm.

The method used by Hattersley and Keighly dobbies, where two knives are used to lift the heald frames.

The up-and-down motion of the harness in a loom, controlled by a double pulley system and knives.

Knives that can move both up and down, connected to hooks that determine the harness position.

Hooks that can latch onto the moving hooks, preventing them from moving further.

An electromagnet that controls the retaining hooks, determining whether they catch or release.

The state where the harness is at the bottom position, meaning no shed is created for the shuttle to pass through.

The state where the harness is at the top position, creating a shed for the shuttle to pass through.

The complete sequence of raising and lowering the harness to create a shed and allow the shuttle to pass through.

The pattern of interlacing warp and weft threads that determines the fabric's structure.

A type of Jacquard machine that uses hexagonal cylinders to facilitate high-speed operation.

A type of Jacquard machine that uses a single cylinder and can be either single lift or double lift.

A type of Verdol Jacquard that uses a single double hook for each harness and two sets of opposing knives to create a semi-open shed.

This method uses a continuous plastic pattern on the cylinder, selection needles, auxiliary needles, and a swing board to determine which hooks are lifted for weaving.

A needle in the Verdol Jacquard that is attached to a selection needle and can fall down or be pushed to the right, controlling the hook movement.

A board in the Verdol Jacquard that moves right and pushes auxiliary needles, determining whether a hook is lifted or not.

A hook attached to the bottom of a double hook in a double lift Verdol Jacquard, working with a supplementary knife to create a semi-open shed.

A knife carried by the fixed griffe in a double lift Verdol Jacquard that works in conjunction with the supplementary hook to create a semi-open shed.