Opening mechanism opening movement cycle
The function of the shedding mechanism is to drive the warp yarns in sequence and timely according to the changing pattern of warp and weft staggered on the machine diagram of the fabric, and divide the warp yarns into upper and lower layers to form a shed channel for the weft yarns to pass through.
1. Shedding shedding cycle
Shedding shedding can generally be divided into the following three stages:
(1) Shedding period: the two warp yarns leave the heald flat position, separate up and down to form a shed, and then fully open. This stage The warp yarn is in a relaxed state, and the warp yarn tension gradually increases from small to large;
(2) Stationary period: after the shed is fully opened, the warp yarn is stationary at the upper and lower extreme positions, which is conducive to the weft yarn passing through the shed;
(3) Closing period: The warp yarn returns to the heald flat position from full opening to close the shed. At this stage, the warp tension gradually decreases from large to small.
The above three stages form an opening cycle and are continuously circulated to enable continuous weaving. The angles corresponding to the three stages of opening, rest and closing in turn are called opening angle, rest angle and closing angle.
Figure 3-13 is the opening cycle diagram. Since the heald frame is in a continuous resting state during the closing and opening stages, the closing period and the opening period are collectively called the heald frame resting period. The distribution of shedding angle, rest angle, and closing angle varies with factors such as the effective width of the loom, fabric type, weft insertion method, and shedding mechanism form. For example, if a four-link opening mechanism is adopted on a water-jet loom, due to the structure of the rods, the opening angle and closing angle are larger, but the angle of repose is smaller. For high-speed looms that adopt cam openings, in order to make the heald frame rest smoothly and reduce the uneven friction of the cam, the opening angle is often larger than the closing angle. The time allocation of the three periods during the shedding process must not only provide good conditions for weft insertion, but also prevent the warp yarns from being excessively damaged during the shedding process, which must be considered comprehensively.
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