• Cam Shed Opening Systems



    Cam mechanisms, whose construction structures are simpler than other systems, are mostly used in the production of simple knitted fabrics. The construction structures of these mechanisms are simple, they take up little space due to their small size, they are light, their production costs are low, their working life is long and they are durable.


    The basis of formation of cam shedding mechanisms is that they consist of cams placed on the main shaft to transmit motion to the frames. Cam shedding mechanisms positive and negative divided into two groups. This diversification is adapted to the operating principle and machine conditions.


    Negative cam shedding mechanisms


    The basis of negative moving systems is that the frames move in only one direction (up or down) by means of a cam and that the movement in the opposite direction is provided by a spring or the frames' own weights.


    Negative cam shedding mechanisms according to the methods of transmitting motion to the frames. dependent and independent can be classified among themselves. Considering the dependent ones from these mechanisms, the movement of one frame is done by the other frame because of the inter-frame connections.





    When the mechanism seen in the figure above is examined; mechanism with limbs 1-2-3 and 1'-2'-3' in the mechanism C1 ve C2 It is connected by wheels. The 1 and 1' cams are located on the middle shaft. a double cam mechanism they form. These mechanisms are used in the production of twill and twill fabrics in old mechanical weaving looms.


    In independent action negative cam mechanisms On the other hand, since there is no connection between the frames, the frames gain freedom of movement and the displacements of the frames are independent of each other.






    When the 1st cam in the figure above rotates along its own axis, it moves the 2th frame downwards with the help of the 3nd arm and the 4 connection elements to which it is attached, and brings the frame to the lower position. The return movement is made by the spring number 6.


    However, since the spring connection in the upper position makes it difficult to eliminate the ends of the warp threads and to control the thread during the weaving process, the cam mechanisms with the spring system in the lower position are more preferred. Examples of these mechanisms are shown below.






    When the mechanism in the figure is examined; When the 1st cam is rotated on its own axis, the 2th frame moves vertically with the help of the 3nd and 4rd arms. Frame number 4 in the mechanism is guided by the guide and a more robust and vibration-free movement can be transmitted to the warp threads due to its placement on the slides. Mechanism dimensions have also been significantly reduced. The spring system numbered 6 in the mechanism is; It is designed in the lower position and in connection with the number 2 lever.


    In negative cam mechanisms, the backward movement of the frames and The use of springs to ensure contact creates a disadvantage for the mechanism.


    The springs in this type of mechanisms double the energy consumption and shorten the wear time of the cam pair. As the additional force is transmitted, the dimensions of the limbs and, accordingly, their mass increase, making it difficult for the mechanisms to operate under high speeds.


    positive cam shedding mechanisms


    In this type of mechanisms, both raising and lowering of the frames are provided by cams without return devices. Positive cam systems in weaving machines provide easier and smoother movements.


    In positive systems, the cams impart their movement to the followers, which are connected to the frame legs. Followers work with eccentrics with or without channels, depending on the construction. In non-channel eccentrics, the ball of the foot is on the eccentric, and in channeled ones, the ball of the foot is in the channel.







    When the sample positive cam shedding mechanism is examined in the figure below; When the cam number 2 is rotated around its axis, the follower number 3 receives the motion from the closed cam system and there is movement transmission to the frame number 4,5,6 through the arm connections indicated with the number 7. This system, which has a complex cam construction structure, provides the opportunity to work at high speeds.







     The figure below shows a positive cam muzzle opening mechanism using a closed double cam. The working principle of this mechanism is similar to the positive cam shedding mechanisms, and the mechanism is also used in Sulzer firm, STB firm and many shuttleless looms.






    Apart from these systems, eccentric and arm shedding mechanisms are also used in simple weaving and weaving machines where the frame does not have to wait. Two examples of these mechanisms are shown below.







    Posted by %PM, 29% 794% 2019 21%:%Jul in Weaving Read 2224 times

Cam Shed Opening Systems