Dobby Shedding Systems
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- Created on Monday, 29 July 2019 23:50
- Last Update: Saturday, 05 February 2022 21:35
- Published on Monday, 29 July 2019 23:50.
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- Dobby Shedding Systems writer Faik KeserPosted by %PM, 29% 899% 2019 23%:%Jul in Weaving Read 2738 times
When the publications and patents related to dobby mechanisms are examined, dobby mechanisms that work with mechanical, electronic and electromagnetic principles especially stand out.
When the patents are examined, the point where the patent studies for weaving looms are most concentrated is the dobby shed opening mechanisms.
The reason for this is the intense use of dobby mechanisms in jet and rapier weaving machines, which allow working at high speeds today.
Dobby is one of the shedding devices that are used to create sheds in weaving machines and provide the movements of the frames for this purpose. Cam shedding mechanisms are used for the production of simple knit fabrics that do not require more than 10 frames. Programmable dobby mechanisms are also used in weaving looms in the production of fabrics with complex patterns and higher weft patterns.
Dobby mechanisms have a more complex structure than cam mechanisms. Patterning possibilities with dobby mechanisms are more than eccentric shedders and less than jacquard shedders. Dobby mechanisms can be considered as the starting point of jacquard mechanisms in terms of control systems. There are basically two separate processes of dobby mechanisms. These; is the motion transmission and the creation and interruption of the motion transmission with the harnesses at the appropriate time.
Dobby machines nowadays;
- Negative,
- Positive
- Rotary
It is classified as
However, it is possible to make a broader classification under this classification. Dobby machines can be classified in detail according to shedding methods, stroke numbers, type of program mechanisms, construction structures and motion transmission methods to frames.
Dobby machines according to shedding methods;
- Dobby forming a mouthpiece that closes at the bottom,
- Dobby forming a mouthpiece that closes in the middle,
- Dobbies forming a semi-open mouth,
- Open mouth forming dobbies
- asymmetrical mouthpiece
They are classified as forming dobbies.
Dobbies are divided into two according to the number of strokes;
- single stroke
- double stroke
They are dobby.
The oldest of these single stroke they are dobbies. This type of dobby only has a lifting blade and a set of levers. After each weft insertion, all levers and frames return to the same, original position. Thus, the frames of the shed, which the new hooks will open for the next weft, are selected. For this reason, after each weft is thrown and finished, the mouthpiece is closed and teeing is done while the mouthpiece is closed.
It has been understood that this situation has provided a great advantage in the wool weaving sector for many years. When the weft thread is tamped in the closed shed, there are no undesired tension increases in the warps and all warp threads are tensioned uniformly in one plane. As a result, warp breaks are minimized and weaving is done in a soft manner.
If double stroke dobbies They managed to increase the speed limit to higher revolutions by dividing the shed change course into two revolutions of the weaving machine. In two full revolutions of the main shaft of the weaving machine, the dobby mechanism makes one full revolution.
According to the programming mechanisms, dobbies are basically divided into two groups;
- mechanically operated
- electronically controlled
They are dobby.
In mechanically controlled dobbies they are divided into two subgroups, which are controlled by punch card and controlled by pattern chain.
Dobby mechanisms controlled by punched card;
- Pieced cardboard to cardboard type
- Endless strip cardboard
They are divided into two.
Dobby controlled by pattern chain;
- tree spiked
- With steel relay
They are of two kinds.
The first dobby mechanisms and today many modern dobby machines are mechanically controlled. Programming in this type of dobbies is done with the help of wheeled, spherical or perforated cardboard apparatuses, depending on the type of control element. In modern mechanical dobbies, the cardboard control element is more common.
In electronic dobby machines On the other hand, programming is done by means of computer-aided units.
Dobby machines according to their construction structures;
- Single blade dobby machines,
- Double-knife dobby machines,
- Gear driven dobby machines,
- Rotation type dobby machines,
- Arm mechanism dobby machines,
- Hydraulic driven dobby machines,
- Servo motor dobby machines
- Hydro-mechanical driven dobby machines
They are classified as
Dobby machines according to the motion transmission method to the frames;
- Negative,
- Positive
- Rotary
They are divided into three types.
negative dobbies because they are simpler, they have found more widespread use than positive dobbies and are mostly suitable for light to medium warp tensions. positive dobbies on the other hand, they are widely used in the weaving of heavy fabrics and high-speed looms, and they are preferred in worsted and woolen weaving. They are suitable mechanisms for medium and high warp tension.
Similar to cam shedding systems, The negative dobby only lifts the frames, a spring-loaded return device is used to lower them. In case of positive dobby and mouthpiece formation, the dobby both raises and lowers the frames.
In rotary dobbies On the other hand, the rotational movement is converted into the forward-backward movement of the frames with the help of special clutches. Rotary dobbies can be structurally included in the positive dobby class.
It is known that dobby constructions with many different structures have been invented during the period from the first dobby machine to the present day. However, very few of them are practically applicable.