The Role of Settling Plates and Sinker Jaws in Knitting Machine

In the intricate world of single jersey circular knitting machines, the movement and precision of components like the settling plate and sinker jaws play a pivotal role in determining the quality and efficiency of fabric production. These machines operate with a delicate balance, where the triangular mechanism of the settling plate and the controlled action of the sinker's jaws orchestrate the formation and closure of yarn loops during each weaving cycle. Understanding their function and optimal positioning is essential for achieving smooth, flawless fabric production across various textile applications.

Function of the Settling Plate and Sinker Jaws

The movement of a single jersey machine's settling plate is governed by its triangular mechanism, instrumental in forming and closing loops during the weaving process. The settling plate acts as an auxiliary tool, while the sinker's jaws function similarly to the lateral walls of a needle groove on a double jersey knitting machine, controlling the yarn to facilitate loop formation and removal of the old loop by the shuttle.

Role of Sinker Jaws in Loop Management

As the shuttle opens or closes loops, the sinker's jaws must push the old loop away from the needle's tip to prevent it from sticking when the shuttle retracts. They must maintain this action throughout the shuttle's movement to ensure complete loop removal. The position of the sinker's jaws is crucial for the sinker's technical position during weaving, influencing the entire process. Before the shuttle rises to retrace its loop, the jaws should push the old loop away from the needle's tip, avoiding interference with the warp when the needle rises.

Optimal Positioning for Smooth Weaving

The sinker's jaws should ideally touch the needle's back line as it ascends, allowing for a smooth descent without disrupting the settling arc of the new loop. However, in practice, selecting the position of the settling cam involves more than just aligning the jaws with the needle line; various factors can affect this positioning.

Types of Settling Plates and Their Characteristics

The most common types of single jersey machine settling plates with curved corners can be divided into two categories. For the curve depicted, the sinker plate's arc intersects the angle S, with its center coinciding with the needle's center. The sinker plate's jaws should align with the needle bar line throughout the loop formation and unwinding process.

Impact on Fabric Quality

Microscopically, the new coil's sagging arc consistently exceeds the needle-back line in the tiger's mouth, causing tension during weaving. While this tension is less noticeable with delicate fabrics due to larger thread loops, it can lead to defects like holes in thicker fabrics with smaller loops. Therefore, the selection of the curve's drafting cam technique should not be based solely on aligning the tiger mouth with the needle and thread. During installation, a slight outward adjustment from the tiger's mouth and needle line is recommended.

Practical Considerations and Machine Adjustments

If the gauge is set to align with the needle back line at point T, it should remain in this position as the shuttle moves up from loop formation until it reaches its highest point. During this ascent, the gauge's mouth should be positioned outside the needle back line, except for the initial alignment at the start of the shuttle's rise. Even if the new coil's sagging arc is momentarily loaded, it does not significantly affect weaving due to the force transfer between strands. Thus, for the curve, the position of the trapezoidal plates' entry and exit should be based on aligning them with the needle's back line when adjusted at the workshop.

Shape of the Settling Plate and Its Influence

The shape of the tiger's mouth in the settling plate forms a semicircular net arc, with one end coinciding with the blade jaw. During weaving, the yarn follows a curve on the plate jaw. Before the shuttle completes its loop and rises to the level of the plate jaw, if the sinker plate is pushed down to align with the needle line, the new loop's descent arc does not lie at the deepest point of the sinker plate but along the curved surface between the sinker plate and the plate jaw. This positioning is distant from the needle line, and the settling of the new coil is subjected to load unless the cleft shape is rectangular, in which case it may align with the needle line.

Variations in Machine Number and Impact on Fabric Characteristics

A change in the machine number indicates a variation in the needle pitch, which affects the weft thread's sagging arc on the fabric. A longer settling arc length corresponds to a higher machine number, while a shorter length corresponds to a lower machine number. As the machine number increases, the line density allowed for weaving decreases, with the yarns being weaker and shorter. Even slight forces can alter the loop shape, especially when weaving polyurethane fabrics.

Conclusion

The careful calibration of the settling plate and sinker jaws in single jersey machines underscores their critical role in modern textile manufacturing. From ensuring the precise formation and removal of yarn loops to accommodating different fabric types and machine configurations, these components embody the fusion of mechanical precision and textile expertise. As technology evolves, so too does the sophistication of these mechanisms, continuously refining the art and science of weaving for industries worldwide.