Introduction to Jacquard. Jacquard shedding system was developed by Joseph Marie Jacquard (–) who was a French weaver and merchant. In case. Jacquard Machines. ▫ Jacquard shedding mechanisms are capable of producing large and intricate weave designs that are beyond the scope of dobby . The Jacquard machine is a device fitted to a power loom that simplifies the process of This mechanism is probably one of the most important weaving inventions as Jacquard shedding made possible the automatic production of unlimited.
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Mazharul Islam Kiron is a textile consultant and researcher on online business promotion. He is working with one European textile machinery company as a country agent. He is also a contributor of Wikipedia. LinkedIn Facebook Google Plus. Shedding Mechanism A process of raising and lowering of warp yarns by harnesses to make an opening for the filling weft yarn to pass through. The raised and lowered form of warp yarns is called shed.
Different Types of Shedding Mechanism in Weaving Process – Textile Learner
Three types of shedding motions opening are available for different type of fabrics. Tappet shedding Dobby shedding Jacquard jacquagd. Tappet Shedding A tappet is given a rotary motion so that it depresses a follower and a lever, known respectively as the anti-friction bowl and the treadle arrangement, by means of which the heald shaft is operated.
The bulkiness of its mechanical movement limits the loom to control up to 8 shafts repeat not more than 8 Therefore, tappet shedding is the simplest and least versatile shedding motion. The design is restricted to plain weave, simple twill and simple sateen or satin weave. Any design more than 8 shafts requires dobby jacquagd.
A pair of tappets A and B is fixed to the bottom shaft C at degrees to each other. Two treadle levers D and E are connected to the loom back-rail by a bracket F. The bracket acts as a fulcrum for the levers. The two treadles have teeth to carry the lamb rods G and H respectively. Two heald shafts J and K are connected to the lamb rods. A top reversing roller shaft Q carries two rollers of different diameters.
The roller of small diameter N is connected to leather strap L to which the front heald shaft J is connected. The roller P of large diameter is connected to leather strap M to which the back heald shaft K is connected. The tappets A and B touch the anti-friction bowls or followers R and S respectively, which are fixed to the treadle levers. The heald shafts have heald eyes T and U through which the war p threads pass X is the war p sheet and Y is the cloth.
The odd ends are passed through one heald shaft while the even ends are passed through the other heald shaft. Working Principle When the bottom shaft is rotated in the clockwise direction as shown in the figure, the tappets are also rotated.
The tappet will depress the anti-friction bowl and the treadle. Being fulcrumed at one end, the front portion of the treadle moves down. This action is transferred to the lamb rod, the heald shaft and the leather strap.
Note on shedding mechanism of single lift single cylinder jacquard – Textile Apex
So one heald shaft is lowered and the threads connected to this heald shaft are lowered and form the bottom layer of the shed. The leather straps shedding to the reversing rollers are connected in opposite directions, i. The shaft therefore rotates in the clockwise direction and the other leather strap is wound on to its roller.
The heald shaft is raised and therefore the lamb rod and treadle lever are also raised. The threads connected to the heald shaft are also raised and form the top layer of the shed. For the next shed, the other tappet works with the other set of bowl, treadle, lamb rod, heald shaft, strap and roller and the other heald shaft is lowered. The first heald shaft is raised by the top reversing rollers, and the positions of the healds shafts are thus interchanged.
Thus, for one rotation of the bottom shaft, two sheds are formed. In this type of tappet shedding therefore, one tappet depresses the concerned treadle and the corresponding heald shaft is lowered. But the other heald shaft is raised by means of the top reversing rollers.
Turn the crank to the top centre position. Fix the anti-friction bowls to jacqurad treadle levers; they should move freely in the slots. Fix the treadle levers with a bracket to the back rail of shecding loom. Set the grid and grid bracket to the front rail of the loom in the slots of the grid. Make sure that the tappet with the lower throw is fixed to the bottom shaft at the starting handle side. Fix the top reversing rollers to the top reversing roller shaft to be equidistant from the ends and at the same time ensure that the connecting screws of the rollers are symmetrical about the central axis jacquwrd the shaft when the heald shafts jacquatd at the same level.
The jacqurad of smaller diameter is always connected to front heald shaft. The heald shafts are connected to the top reversing rollers by means of cords and leather straps. The leather straps are connected to the rollers, such that when one of them winds on hsedding roller the other strap unwinds from its roller and vice versa.
Lamb rods are connected to the heald shafts by cords. Adjust the tappets on the bottom shaft and make sure of the following points: The tappet with a bigger throw should be connected to the back heald shaft.
The bowls should have perfect contact with the tappet surfaces. The treadles should be at the same level and parallel to each other at the top centre position. The hook of the lamb rod of the front heald shaft should be connected to the first notch of the treadle lever while that of the back heald shaft should be connected to snedding third notch.
If the depth of shed is altered, the connections of the hooks to the treadle levers can be changed. Points to be Observed Turn the crank shaft through two revolutions and make sure that the bowls are always in contact with the tappets.
The heald shafts should not touch the side frames or the sley. Turn the crank shaft to the bottom centre and check the size of shed. The bottom line of warp sheet or the heald eyes of the lowered jacquarx shaft should have a clearance of 1 mm from the race board and the top. Positive Tappet Shedding Mechanism Principle: In this type of shedding, xhedding heald shaft is raised and lowered by the tappet. Construction The tappet shaft carries another tappet which has a groove or track in which a bowl is placed.
The bowl is connected in turn to a tappet lever with link rods, links J and a heald shaft. Each tappet is separately connected to a heald shaft through link rods and tappet lever. There are two fulcrums for tappet lever and links. When the tappet is rotated, the bowl is also rotated. According to the shape of the groove, the bowl is moved up or down or is still. If the bowl is moved up, the tappet lever moves to the right through the links and the heald shaft is lowered. If the bowl is moved down, the tappet lever moves to the left and the heald shaft is raised.
Since the heald shaft is raised and lowered by means of the mechanism, this tappet shedding is known as positive tappet shedding mechanism. When the bowl jacqard still, the heald shaft is in jacquagd dwell stage. A positive shedding tappet, and the one most generally employed, is known as the Wood croft tappet. This style of dhedding is self-contained, and is now made in three different forms, according to the class of sheddihg for which it is to be adopted.
The treadles are fulcrumed on the shaft and are provided at with a knuckle, on which the antifriction pulley is pivoted. The pulleys are specially tempered or made of steel in order to better resist the friction to which they are subjected. The sheddimg of this pulley and at the same time the treadle is determined by the shape and the arrangement of the section plates i to In this type of tappet only two different section plates are used.
That shown at it is employed to raise the treadle; that is to depress the treadle. The pulley is actuated by the projecting rims of metal sheddig on sheddinh side of the plates with which it is in constant contact. The healds are connected shedidng jack levers placed above and below the healds ; the levers extend outside the loom frame, and in turn are attached to the end of the treadle by means of the connector. When the treadle is forced upwards by means shhedding a section plate, the heald shaft is drawn down, and vice versa, with the section plate.
These tappets are made to work with from 8 to 12 treadles, and can be constructed for weaves containing up to 24 picks to the round. A tappet contains 12 sections or picks in one repeat. The tappet shaft is supported in open bearings in the framework, and secured to this shaft the tappet wheel, containing a number of teeth in sheddihg which is a multiple of the weaves for which the tappet may be required.
The wheel is also fitted width a number of standard bolt holes, in order to accommodate section plates of different sizes, such asare required for weaves containing a varying number of picks to the round.
Advantages and Disadvantages of Tappet Shedding: It is robust, simple and cheap It sheddig capable of lifting a heavy weight with less wear and tear than other shedding mechanisms.
It can move heald shafts at great speeds. It puts less strain upon the warp. It consumes less power and gives greater output.
It requires less maintenance. hacquard
If the weave is changed, it will be necessary to change the tappet and the change gear wheel in the counter shaft arrangement. So work involved in changing the weave is more. A maximum of 8 or 10 tappets only can be used. Faults that may occur in Tappet Shedding Mechanism: If the tappet is faulty, it imparts a jerky movement to the heald shaft. The tappet should always touch the bowls.
Otherwise a severe blow is applied to the bowl and the vibration is transmitted to the heald shaft. End breakages may occur a resultof this. If the depth of a shed is too much, strain on the warp will be more and end breakages may occur.
If the depth of shed is too low, the shuttle will not reach the other end and may be trapped in the shed or may fly out.