The upper drafting rollers are negatively driven by frictional contact with the lower rollers. Hence the top rollers must be pressed against them to reach the same speed for better fiber control. There are three types of loading systems are used in ring spinning machines. in the exposure media used for the roles. These are 1. Spring loading: This system is used by most manufacturers in the conventional ring frame. Example: SKF PK 225, Sussen UT600 etc. 2. Pneumatic load: This system is used by most of the ring frames with high speed and high throw ratio. The most important manufacturers are Rieter and Texparts in this field. Example: Rieter FS 160 P 3. Magnetic charge: The manufacturer of this system is Saco Lowell. However, this is just the conceptual system that has not caught on in the commercial market.
The first two types require load brackets to mount the top rollers. These bearing arms are attached to continuous shafts or tubes that are mounted behind the rollers on the roller stand. They can be opened and closed by means of levers in order to The complete set is called the top arm. The upper arms are designed for one-handed operation. Their basic functions remain the same but differ in their design features.
Duties of the top arm
· The basic function of the top arm is to hold the upper rollers securely and precisely parallel and to align them with the lower rollers
- It should transfer the load to the lower rollers without undue friction.
- It should allow precise adjustment of the top roller.
- It must provide a reliable base to ensure fibre grip and guidance.
- It should allow easy opening and closing of the upper arm, but these upper arm movements must not adversely affect the positions of the upper roller in relation to the thread path.
Design features of the top arm
The entire bracket is made of sheet metal for conventional spring-loaded upper arms, but modern high-speed ring frames use lightweight, strong steel as a replacement. The structure of the upper arm invariably consists of three basic working elements; Bracket, frame and pressure lever, regardless of their type. However, its shape and support properties vary from manufacturer to manufacturer depending on the loading mechanism. However, its role in the stretching mechanism remains the same.
The following are the SKF spring loaded upper arm features as an example. Another mechanical upper arm from Sussen also has many identical features. But wherever they differ, it is enough to influence the performance. overcome the restrictive features of the classic and also convey simplicity. Therefore, the focus of the discussion in the procedural part is steered accordingly.
Working elements of the top arm
Bracket: It is a square with a rectangular hollow edge made of sheet metal with a rounded edge on mechanical upper arms. It is primarily used to hold the upper arm securely on the handrail. The support rod is the solid round rod that is mounted on the roller bracket behind the lower rollers in the bearing housing The bracket is drilled with a round hole near the bottom end The diameter of the round hole is larger than the hole diameter of the support rod, which allows for easy sliding on of the pendulum / upper arm in the desired position on the support rod. This loosely mounted upper arm is held in position by adjusting screws. The entire exercise makes the assembly and replacement of the mechanical upper arm too complicated.
To get around this limitation, the rectangular bracket is replaced by a hexagonal split bracket for the pneumatic upper arm. This change makes it easier to assemble and replace the upper arm on the handlebar for the two-part bracket. The fixation is done by two adjusting screws. It is punched from sheet steel and mounted on a continuous hexagonal profile tube behind the rollers, so the use of a hexagonal hollow bar instead of a solid cast iron bar reduces the load capacity when the roller beam is heavier.
The mechanical upper arm brackets are also equipped with a height adjustment for the front stretch roller. The vertical height of the front upper roller from the lower when loaded determines the extent of the load transfer. A set of height adjustment screws and locking screws is supplied for this purpose. With the height adjustment screw, the angular position of the bracket can be easily changed relative to the support rod. Therefore, the angular position of the support point of the frame on the support varies. This adjusts the height of the front roller back and forth around its bottom to change its load. This adjustment has to be done manually and with the head, which can lead to human errors. There are no such complications with the pneumatic arm.
Frame: It's a hollow channel frame with a lazy cut on its top. The load elements and their accessories, that is, the upper roller saddles, fit snugly into the body of the upper arm frame. This makes them strictly parallel and in perfect alignment with the lower rollers. The properties of the frames for mechanical and pneumatic upper arms differ greatly mainly due to their working concept. The roll is held securely in position by a leaf spring on the roll holder. unchanged for a smooth turning flow. Therefore, no provision is made for modifying the position of the front roller on the upper arms. Sussen's upper arm has a centimeter and millimeter scale parallel to the guide groove. This helps to read the roller setting values directly.
The pneumatic upper arm is equipped with two saddles, one with front and middle roll holders, while the second has rear roll holders. It is intended to change the positions of the middle and rear roller holders in the guide grooves of the saddles. This makes it easier to adjust different sizes. Both saddles have three equally sized holes in their surface and the saddles can be assembled by bringing these holes together and inserting the pin into one of the holes as needed. This pin acts as the pivot point for the front and rear rollers. These attached saddles are then attached to the frame via a second pin, this pin goes into one of the three holes drilled in both. This connection point becomes a pivot again, but now between the back roller and front roller group (front and back ). upper-intermediate rollers).
Loading element: It is only part of the frame in both categories The single roll is mechanically loaded, i.e. spiral spring (Texparts PK 225), leaf spring (Sussen UT 600) or pneumatic pressure (Rieter FS 160 P 3.1).
- Spiral spring loading: The SKF system uses a coil spring tensioning system. The springs load the roller carriers and, depending on the lever, the load is transferred to the roller shaft (Fig.13 (ii-iii)). Therefore it offers an indirect mode of charge transfer. front roller - pushes the top roller against the bottom roller. A special arrangement of the load selector is provided at SKF.
Only for the front roller. The loading pressure can be easily changed with the help of the three-stage eccentric load selector using a so-called wrench. The coloured markings indicate the set charging level. Spring pressure The idling of the rollers can be changed with a separate adjusting screw. The pressure can be increased or decreased by loosening or tightening the screw. But here, too, this is head-wise and in this additional manual setting in the sense of the roles, which is influenced purely by the experience of the people.
- Leaf spring loading: SUESSEN's upper arm uses a stainless steel I-spring curve on the front leading edge to form a plate for loading. This upper arm is known as the UT type. The spring pl exerts pressure directly on the roller shaft. acts like a roller vibration damper, usually occurring at high speeds, preventing the roller from becoming eccentric. Similar to SKF, the spring pressure c is changed with the help of an individual adjustment system for each saddle on the frame. ma restrictions are:
- Upper arm loading pressure can be changed through firm sale based solely on manual judgment and the influence of personal experience.
- The spring loses its strength over time and leads to pressure fluctuations and therefore affects the quality of the yarn.
- The head fit mode increases the spindle variations.
- The roll neck wears and roll
deflection also occurs due to abrasion in spring-loaded or loaded cages,
reducing roll life and the reliability of roll alignment.
Ref:-
- Engineering Techniques of Ring Spinning by Someshwar S. Bhattacharya and Tasnim N. Shaikh
- The Rieter Manual of Spinning volume 4
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