Analysis of the concentration criterion of spring force

About 90% of the manufacturers in the ring-pressurized cradle use SKF ring spring pressure cradle. The characteristic of the coil spring pressure cradle is that the pressing amount of the upper roller is not affected by the inclination angle of the roller seat; the locking operation is a four-bar linkage structure, the design is compact and the function is reliable; the pressing mechanism is connected with the top roller One body, easy to operate; the roller gauge has a large adjustment range, which can meet the process requirements of different lengths of fiber; when the gauge is adjusted, the pressure value is unchanged; the pressurizing component is designed with a self-adjusting center structure; the cradle pressure rod has A certain self-adjusting parallel action.

However, the force source of the cradle pressurization is a coil spring. Due to factors such as manufacturing precision, material and heat treatment of the spring element, the pressurization value has a certain error between the ingots. The spring is used for a long period of time, causing fatigue degradation, and the actual pressure value gradually decreases with the use time of the spring. This situation is not easy to detect in management, so the difference in fiber control between the roller jaws is formed, which affects the quality of the product.

Due to the limitation of the principle of “self-adjusting parallelism”, the inconsistency of the internal structure of the roller material and the requirements of the strips makes the gripping force and the drafting force of the roller jaws always change, resulting in a transient change of the self-adjusting turning moment. The pressure rod constantly moves, making the fiber shift point unstable. Therefore, in other drafting and pressing mechanisms, such as the Suessen HP cradle, the so-called "self-adjusting parallel" effect is negated, but the "parallelism" is ensured by improving the processing precision of the cradle.

Leaf spring pressure cradle The German drafting and pressing device introduced by the German Suessen Company in the 1980s adopts Hl]-A-320 leaf spring pressure cradle, the front end of the pressure plate spring A with a thickness of 2 and the top roller spring B and the top roller grip claw (aluminum alloy) C are riveted together. There are four symmetrical protruding positioning points a on the leaf spring, and the leaf spring is placed in the spring seat D to be positioned to form a holding pressure spring assembly. The top roller holds the point.

The arc is after the assembly is installed, and is regrind according to the working position of the vertical cradle body F, which coincides with the dZ axis. C has a grip width of 21, a large grip width, and high grip precision, which can improve the parallel precision between the upper and lower rollers and the top rollers, so that the leaf spring pressure is stable and reliable, and the draft quality is ensured. The spring assembly is mounted in the cradle body and fixed with a 呱 screw, and the screw head is exposed on the F surface to adjust the top roller gauge in a pressurized or depressurized state.

The locking of the cradle is also a four-bar linkage. However, this kind of cradle still has the following unique features: HP drafting device Shibo M. Teaching plate elastic structure diagram adopts three-roller double short apron structure, floating area length is 10.85<2>, than sKF drafting device Shortened by 4.52, it is particularly advantageous for processing cotton; the apron jaw is pressurized by the middle roller compression spring, and the jaw pressure and the middle and upper roller pressure are distributed in a ratio of 1:4. It is not affected by the installation position difference of the SKF cradle. The influence of unstable factors, the pressure-stabilized apron grip is beneficial to reduce the dispersion of the fiber shift point; although the apron is stamped, the front end is covered with engineering plastic PTFE, which can reduce the upper apron. The frictional resistance during the operation is beneficial to improve the apron of the apron, prevent the apron from vibrating and reduce the fine thick section of the yarn; the lower top surface and the three rollers form a common cut surface, and are placed on a 0.9-onon thick After the circle, the thickness of the apron is set on the bead, and the width of the upper support is 2, which can make up for the concave of the lower ring and stabilize the friction field in the middle of the apron; the lower apron and the middle and lower rollers The enveloping angle is about 105 more than the lower apron, which reduces the slip of the lower ring and stops momentarily. Advantageous; when the HP cradle is applied and released, the three-row top roller jaws are moved back or forward synchronously.

When the SKF cradle is released, the middle and upper roller aprons are moved backwards, and when pressed, they move forward, while the front and rear upper rollers are basically unchanged, which will destroy the arrangement of the original fibers in the drafting zone. The leaf spring is the same as the coil spring, and inevitably there is also a fatigue decay phenomenon, but the amount of pressure deformation (deflection) is smaller than that of the coil spring. Due to the short domestic use time and less experience, the pros and cons of leaf spring pressurization will remain to be seen.

Laminated Veneer Lumber (LVL) is another type of Plywood. It is made of multiple layers of thin wood (along the same direction of wood fiber), assembled with adhesives through hot-pressing. 

Currently, the core veneers are mainly Poplar, Eucalyptus, Eucalyptus and Poplar mixed, Paulownia and Poplar mixed etc.

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