• Rotary Dobby




    From the researches on shedding methods and dobby machines, open shedding in modern weaving looms today. rotary dobbies appears to be preferred.

    In classical rotary dobbies, the programming-locking mechanism consists of spindle number 1 that makes a waiting rotation movement, 2 discs fixed on the spindle and 3 eccentrics placed in motion, lock mechanism #4, lever mechanism #6-7 and program unit #8.

    Working order of the machine as follows Seen.






    Position a: The main shaft l of the dobby is in the standby phase. Since the frame was required to shift in the next process, the pistons of the program were pulled inward and the hook of the locking mechanism was included in the slot opened on the disc of the locking mechanism and formed a connection between the disc 2 and the eccentric 2 with the effect of the closing spring. Pendulum 3 is in the left margin position.

    Position b: Its 1 shaft, 2 discs and 3 eccentrics rotate clockwise. The pendulum 3 arm 6 connected to the eccentric 7 rotates towards the right edge position. The frame attached to the pendulum moves from one edge state to the other.

    Position c: The number 1 shaft is waiting after turning 180°. Pendulum 7 has become the right side. If a program change is not desired, the 2nd position is repeated continuously. When the frame is asked to wait, the pistons turn the hook of the locking mechanism, eliminating the connection between the disc 2 and the eccentric 3, and the eccentric 3 is locked in this case.

    Position d: 1 shaft and 2 discs rotate. Since the 3 camshafts are locked, the pendulum 7 remains on the right edge. This will continue unless there is a program change.

    Rotary dobbies are generally regarded as advanced models of positive dobbies.

    In recent years, the speed of rotary dobbies has been developed by manufacturers and when the models exhibited at the fairs are examined, it has been observed that it reaches 1000 rpm and above. In this way, it is possible to work under high speeds in air-jet and water-jet weaving machines.

    Today, different types of rotary dobbies are found in various weaving machines. Since the drive systems of rotary dobbies are simple and rigid, they work without vibration and are durable. They take up little space. However, since the open mouth is formed and the construction structure from the selection unit, it additionally includes the units of recycling to the frames and centering the frames.

    Constantly connecting and wedges prevent the dobby from increasing speeds. Another feature of the rotary dobbies is that the parts are produced with very high precision and their costs are high. The basic working principle of the rotation type dobby machines is based on the conversion of the rotational movement to the forward-backward movement of the frames with the help of special clutches.

    A rotary dobby consists of three main parts. These parts are;

    • selection mechanism,
    • Frame drive mechanism including eccentrics
    • The part that produces the variable dobby shaft movement, that is, the modulator

    The task of the selection mechanism is is to determine the position of the frames by cutting the connection between the camshaft and the eccentric according to the knitting. modulator on the other hand, is the part that determines the movement and waiting angles of the frames. Since the construction structures of eccentrics and modulators do not differ from each other, rotary dobbies are classified depending on the type and structure of the selection mechanisms.






    In the figure above The basic parts that make up a dobby mechanism are shown schematically. Part A of the figure shows the eccentric part with a round shaft bearing. It is an eccentric rotating cam, the part designated by 2 and 3. The rotation axis of this cam rotates at the center Ao, not at the geometrically specified center A. Therefore, if the 2nd part makes a counterclockwise rotation, the movement is transmitted to the 3th arm by the 4 arm. In one complete revolution of number 2, lever 4 comes to the limit position. If A, Ao and B come to the same direction as a result of the movement, the 4 arms take their most forward position. If A, Ao and B return to the back position as a result of the movement, arm 4 returns to its most backward position. The movement transmission of the arm number 4 to the frames is given in the B part of the figure above. In the case where the arm 4 is in its most forward position, the frame, on the other hand, is in its lowest position. If the 4 arm is in its rearmost position, the frame, on the other hand, takes its highest position. The eccentric mechanism with this construction creates frame movement only for plain fabrics. This rotational movement in the rotary dobby necessarily includes the back and forth movement of the frames.

    Working principle of rotary dobbies in the figure below is seen. In the rotary dobby mechanism in the figure; 1 shaft special channel opened on the opposite direction to each other modulator It rotates intermittently with the help of a mechanism called When the 2 key, which is mounted on 4 eccentrics and can move in the radial direction, moves towards the rotation axis, when the 2 eccentrics and 1 shaft are combined, it makes a 180° rotation with the eccentric shaft and the frame connected to 5 limbs is brought from one state to another. When the wedge moves outward from its rotational center, its 3 limbs become clamped as its eccentric is combined with its 3 limbs. The movement of the wedge is governed by the selection mechanism. 






    Since the displacement of the frames from the lower position to the upper position or vice versa occurs during the 1º rotation of the 180 spindle, when the main shaft of the loom is made two full revolutions, the dobby shaft takes one full revolution rotation.

    Schematic view of RD 3000 type electronically controlled rotary dobby produced by Fimtextile company is seen as follows. The motion from the weaving machine is reduced by half and transmitted to the modulator input shaft (not shown in the figure).

    The delayed output movement obtained from the modulator is transmitted to the dobby shaft (2). By combining the dobby shaft (2) and the eccentric (3) with the part no. 4, the eccentric no. 3 moves between the two end positions (forward and backward).





    If 2 shafts and 3 camshafts are separated in any of these positions, the camshaft stays in its current position. The movement of the eccentric from one position to the other means that the frame that it drives changes position and the eccentric waits in one position, which means that the frame is also waiting in this position. The rotational movement of the eccentric is transformed into the swing movement of the 5 arm in the clockwise or counterclockwise direction by means of the 6th limb. As mentioned before, there are roller bearings between 2 and 3 and 3 and 5 limbs. The combination of the 3 parts, which are connected to the 4 eccentrics by a rotary joint, by entering the channels opened on the 2 shafts, or combining these two parts by leaving the channels and separating these two parts, is provided by the oscillating movement produced by the 9 electromagnet, through the 8 arms, by the 7 arm.

    In the eccentric position shown in the figure, if the frame is above, the frame moves to the lower position in 4° rotation of the 2 shafts from this position, since 2 parts are clamped with the 180 shafts. As long as the part 7 stays in this position, the 180 parts of the eccentric are separated from the 4 shafts in the 2 degrees rotated position. In the next rotation of the 2 shaft, it does not transmit movement to the eccentric and the frame remains in the lower position.

    If the arm 7 changes position under the influence of the magnet, part 4 is clamped with the shaft 2 and returns the eccentric to the position shown in the figure. Thus, the frame returns to the upper position again. As long as the position of the arm no. 7 is not changed by the magnet, in this position, the part 4 is separated from the shaft 2 and the eccentric does not transmit motion. The frame remains in the up position. In the case of plain knitting, the eccentric changes position in each weaving machine cycle, since its 2 spindles and 4 parts will remain constantly clamped. So the frame moves up and down.

    Staubli company produces rotary dobbies with different selection mechanisms for different weaving applications. 2668 model rotary dobby machine is seen in the figure below.





    The disc number 4, on which two channels have been opened, rotates intermittently with the dobby shaft. Part 5 is connected to part 6 with a spring (not shown in the figure) at one end, and is clamped to the disc number 1 by the pressure exerted by the 1 and 4' arms from one end, and the clamping is released when there is no pressure. When piece 5 is clamped with disc 4, the disc and piece 6 rotate as well.

    Part 6 is also eccentric, and its rotational movement is converted into the rotational movement of the 7 arm by means of the connecting arm shown with the number 8. When clamped with piece 5, every 4º rotation of disc 180 moves the frame from one position to another. The clamping or unclamping of the piece 5 with the disc number 4 is accomplished by rotating the arms 2 and 3' of the arm 1, which is moved by the electromagnet indicated with the number 1. The movements of arms 1 and 1' in one direction are produced by the electromagnet, while the movement in the other direction is provided by springs.

    In the above way In the first position, the number 1 arm rotates a little clockwise, so the pressure on the 5 piece is removed. Therefore, with the effect of the spring, its 5 parts and 4 discs are clamped. This position corresponds to the upper nozzle position of the frames. The frame is moved to the lower position with the following 4º rotation of the number 180 disc.

    In the figure above In the second position, it shows the position corresponding to the 4º rotation of the disc 90 . This position corresponds to the center nozzle position of the frame. In the third position, the 4 discs have completed their 180º rotation and the frame has reached the lower nozzle position. In this position, the 1' piece is rotated a little clockwise and by pressing the end of the 5 piece, it has released the clamping with the 4 disc. As long as parts 1 and 1' remain in this position, the frame rests in the lower nozzle position. When the l and 1' arms rotate a little counterclockwise under the influence of the magnet

    In the figure above In the third position, the pressure of the 1' arm on the 5 piece is removed and the 5 piece is clamped with the 4 disc. With the 4º rotation of the 180 disc, the frame moves to the upper mouth position. Since the 1 arm is turned counterclockwise, the clamping between the piece 5 and the disc 4 is released. The position of arms 1 and 1' corresponds to the top mouth positions of the frames. The 9 and 9' supports limit the rotational movements of the 1 and 1' arms. Consequently, some clockwise rotation of the arms 1 and XNUMX' corresponds to the lower position of their bezel. The counter-clockwise rotated positions correspond to the upper mouth positions of the bezels.

    Since the drive systems of rotary dobbies are simple and rigid, they are vibration-free and long-lasting. However, due to the fact that they form open mouthpieces and the construction structure of the selection unit, they additionally need units to center the frames in the mouthpiece search and stops. The use of wedges for clamping at the time of selection limits the operating conditions of the selection unit and prevents high weaving speeds.



    Posted by %AM, 31% 374%2019 10%:%Jul in Weaving Read 2245 times

Rotary Dobby