Dobby Shedding Mechanism and its types

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3 years ago

Dobby Shedding Mechanism | Classification | Types | Working

To know regarding the various elements shaped this shedding.
To learn the mechanism of dobby shedding.What is Dobby and Dobby Shedding?Dobby may be a compact, electronically or automatically guided shedding motion. Dobbies unremarkably area unit capable of getting up to twenty-eight shafts.Dobby may be a shedding mechanism placed on the highest of the loom so as to supply patterned patterns by victimization sizable amount of healds than the capability of a tappet. Dobby is additionally called a “witch or “wizard”. Dobby shedding is additional advanced and versatile shedding motion.

Fig: Dobby shedding in loomDobby shedding is 2 types; negative dobby shedding and positive dobby shedding.Scope of a Dobby:
The scope of dobby is restricted between a lever and a jacquard. the quantity of shafts which will be motivated by a dobby varies between half dozen and forty. in theory dobby will management forty eight shafts (maximum). However, much it will management thirty six shafts just in case of wool and allied fibers. Again, for cotton and allied fibers, it will management most twenty four heald shafts. In these case healds area unit operated by jacks and levers.
Main elements of Dobby Shedding:
Bottom shaft
L-lever
Upright shaft
T-lever
Upper draw knife
Lower draw knife
Upper hook
Lower hook
S-lever
Bulk lever
Thumb lever
Jack lever
Heald shaft
Returning spring
Motor
Crank shaft
Pattern cylinder
Pattern chain
Classification of Dobby:

INTRODUCTION: –Dobby is a shedding device connected to loom to augmented the coming up with capability. The dobby unremarkably controls twelve to twenty four hold shafts the dobbies area unit classified as negative or positive, single raise, double raise, crank driven, cam driven etc.
The dobby forms bottom closed, center closed, semi open and open style of shed. The dobby is additionally classified as left and mitt.
The right-hand dobby is one that is placed at the left-hand facet of the left. It gets drive from left finish loom.
The left-hand dobby is one placed at mitt facet of left-hand loom. left dobby gets its drive from right finish of the loom.
Climax Dobby

The Climax Dobby is double acting machine controlled from bottom shaft , it forms the open shade. The lifting of heald is finished by lifting of jacks. The healds area unit lowered as a result of of springs used on the lowest facet. It has a pair of jacks. Dobby runs at 0.5 the speed. within the mitt dobby, cylinder rotates in dextral direction. within the left Dobby, cylinder rotates in anticlockwise direction.
Working

Dobby gets its drive from the lowest shaft through rod. The T- lever gets oscillation and thereby knives move forward and backward within the framing machine slot. once the knives area unit towards the set of hooks selection of engagement hook and knife is formed feller. The feelers are activated attributable to wood pegs. once the hooks and knives area unit engaged, then the hook is force, whereas the another hook and also the lever rest on the stop bar. currently the heald is upraised up.

Timing and setting of Climax Dobby:

1- At 270 degree The heald shaft is levelled, knives area unit middle approach position.2- The T- lever is horizontal. At sixty to a hundred and twenty degree is that the dwell amount of the dobby
Heald area unit writing paper
shed shed is open3- At ninety degree, one arm of the t— lever is outside and another is within.4- The bottom shaft is at prime or on bottom center .At a hundred and twenty To 360 degree To sixty degree is that the amendment amount of the heald shaft.Settings:1- The driving rod connecting to the crank connected to the lowest shaft off the loop and T-lever should be set to applicable length. If the rod is simply too short or long, one set of the hook can cosmopolitan then additional distance than the opposite.2- The length of driving rod is adjusted such T-Lever is horizontal once the crank connected to the lowest shaft is in horizontal plane either within the front or back of rotary its stroke.
3- Crank and T-lever area unit unbroken within the horizontal position and currently 2 knives area unit Adjusted by draw bolts, in order that they’re equidistance from their slots. The pattern cylinder is turned by wheel. Cylinder is turned by 1/8th revolution for each a pair of decide. the cylinder is command steady purchase flat steady star wheel. The detent regulate through of the star wheel. The T-lever is lifting knives area unit extreme position there ought to be a qurter in. clearance between the tip of the detent and also the teeth of the cylinder ratchet.

For mitt Dobby visible outer feeler that operate bottom drawer hook , pattern cylinder rotate dextral. In the left Dobby, the primary feeler may be a straight feeler acts on the highest hook. In pegging, the higher row of holes within the lug represents initial decide.

Cross Border Fabrics:

Many materials wants border within the warp yet as within the woof approach. for making the woof approach border style. the quantity of pegleg needed area unit high. therefore to make a border style, special cross border Dobby is employed. the materials which require the cross border area unit sarees, carpets ,Chadar, tapestries, handkerchiefs, table covers.

Cross border Dobby

Cross border Dobby is employed once 2 different weaves are needed to plain woven victimization same variety of healds.Cross border Dobby eliminates high variety of wood legs that area unit needed in traditional dobbies.

Types of cross border dobbies:

1- 2 cylinder cross border Dobby

2- 3 cylinder cross border Dobby

Dobby Faults:

The common downside within the dobby is Jack missing. The heald shaft isn’t raised once needed and woof floats across the warp finish giving rise the material result referred to as handicraft.

Stitching is usually caused by shuttle flying. Warp thread get break occur due to shuttle fly inflicting a serious cloth defect.

The causes of Jack missing (Heald not lifted) are:

1) Bent picket peg in a very lag.

2) picket peg is done in because of frequent use.

3) The spacing between the lag ought to be uniform and cylinder ought to be positioned below the feeler within the perpendicular manner. if the lags don’t seem to be spaced properly additional feelers is also raised inflicting lifting of improper jack.

4) The pattern barrel during which picket lag rotate shouldn’t move laterally.

5) Needle operative hook might mire and jack is incomprehensible , sensible oiling is critical.

6) picket peg are broken and so jack is incomprehensible .

7) The hook might come back aloof from the knife within the middle of stroke, inflicting missing jack.

Ruti Cam Dobby:-

The ruti cam dobby is negative in action i.e the heald square measure lowered due to the spring during this dobby. The knives square measure pushed forward by the combine of cams. The knive can return and forever within the contact with the cams due to the spring. Here dwell of regarding 1/3 pic is achieved. the choice of the hook square measure created by paper pattern rather than picket pegs.

Dobby Shedding Mechanism:

Fig: Diagram of Dobby Shedding Mechanism

Here a climax dobby is represented to clarify the dobby shedding mechanism. Climax dobby may be a double carry double jack-lever negative dobby. Here 2 jack levers square measure operated by one bulk lever. they’re joined with the majority lever by a timber lever and a link. The double lever is pin MEd at some extent and is connected with S-lever. The S-lever controls 2 hooks, one higher hook and one lower hook. The hooks square measure controlled by feelers. One hook is controlled by hooked feeler and alternative by a connecting needle. {the 2|the 2} hooks management two knives that square measure joined with a T-lever. The T-lever is pin MEd associated is controlled by associate upright shaft and an L-lever. They get motion from motor and machine simple machine. once the feeler comes in-tuned with a peg and once it’s not within the contact it goes down.

Fig: Dobby peg set upDobby loom is vital for its use. we are able to use 8-12 heald border tappet loom but if we wish to use additional heald frame for additional ornamental style then we should always use dobby loom. This sensible helps ME to grasp regarding the dobby loom and its mechanism. i believe this can facilitate ME in my future life.