Friday, March 26, 2021

Double-lift and double-cylinder jacquard shedding mechanism

Double-lifts and double-cylinders jacquard shedding mechanism:


Structure of double-lifts and double-cylinders jacquard shedding mechanism:

There are two griffes used in this jacquard shedding mechanism. Eight knives are mounted on the first griffe and eight knives are mounted on the second griffe. The first griffe carries upward the odd number hooks and the second griffe carries even number hooks in the upward direction. In this jacquard shedding mechanism, two kinds of hooks are used. The upper ends of odd number hooks get inclined toward the pattern cylinder getting used for the selection of odd number hooks and the upper ends of even number hooks get inclined toward the pattern cylinder getting used for the selection of even number hooks. The number of hooks used in this mechanism is just double the figuring capacity of the jacquard. 800 hooks are used for 400 figuring capacity jacquard. Two sets of needles are used to control the hook selection in this jacquard. Needles E control the selection of odd number hooks while needles C control the selection of even number hooks. The front end A and B of each needle pass through the holes of respective needle boards. The spring boxes are mounted just behind the rear ends of the needles E and C. The pressure springs mounted at the rear end of each needle tend to push the needle toward the respective pattern cylinders. Two pattern cylinders are mounted in front of the needle boards. One pattern cylinder performs a selection of hooks for odd number picks and another pattern cylinder performs a selection of hooks for even number picks. One hook of an odd number and one hook of an even number get paired through the link. The doubled end of each hook rests upon the slotted grid. The upper end of the neck cord is connected with the pairing link. This neck cord passes through the hole of the tug board then the lower end of the neck cord gets connected with the upper end of the harness cord. Now the harness cord passes through the hole of the comber board. The lower end of this harness cord is connected to the upper end of the heald wire. A lingo is connected with the lower end of the heald wire.



Working principle of double-lift and double-cylinders jacquard mechanism:


This mechanism receives rotatory motion through the bottom shaft. One sprocket wheel is mounted on the bottom shaft while another sprocket wheel of the same number of teeth is mounted on the jacquard shaft. These sprocket wheels are connected to each other through an endless chain. The griffes receive the reciprocating motion through the eccentric cams mounted on the jacquard. When the first griffe reaches the top dead centre of the jacquard, the second griffe reaches the bottom dead centre of the jacquard. When the jacquard shaft rotates, both griffes cross to each other. When the griffe reaches the bottom dead centre position, it comes slightly down in comparison to the upper inclined end of the hook. Now the pattern cylinder pushes the front end of the needle. If there is a hole punched in the card, the front end of the needle gets entered into the hole of the perforated pattern cylinder and that hook gets engaged with a knife. If there is a blank portion in the design card, the needle gets pushed toward the spring box and the hook gets disengaged from the knife. When the griffe starts to travel from the bottom dead centre position to the top dead centre position, it carries the engaged hooks in the upward direction. The second griffe reaches at the bottom dead centre position now. The other pattern cylinder pushes the front end of the needle and hooks are selected. When the second griffe travels upward, it carries engaged hooks with it. The right-hand side pattern cylinder performs the selection of odd number picks while the left-hand side cylinder performs the selection of even number picks.

Since the upper end of the heald wire gets connected to hooks pairing link through the neck cord and harness cord so that the neck cord and harness cord lift the heald wire in an upward direction. The lingo brings the hook in a downward position. Two separate pattern chains are prepared in this jacquard. A chain of odd number picks is mounted on the right-side pattern cylinder while another chain of even number picks is mounted on the left side of the pattern cylinder. The number of picks in both chains should be equal.

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