As shown in Figure 2, the yarn pulling device of a carpet tufting machine generally only has a pair of rollers. From the perspective of the installation method, it is an extrusion type, but the difference from the traditional extrusion type roller is that the two rollers of the device are both There are grooves instead of a rubber roller and a grooved roller. As shown in Figure 2(a), rollers A and B have the same structure, with 24 grooves (or teeth), shaped like arc teeth, the tooth top and tooth bottom are both arcs, and the radii are r and R, respectively. The arcs connect to form a roller groove. Roller A is driven by a dynamic force and is the active part; Roller B is supported at both ends and is a free roller. Roller A drives roller B to rotate through the engagement of the teeth, and only a pair of teeth participate in the engagement at a certain time. And there is a certain gap between the tooth top and the tooth bottom of the two rollers, let it be the center distance O. The difference between the diameter of the graduated circle and the roller. Figure 2(b) shows an enlarged view of the meshing area of the rollers. The yarn meshes with the two rollers respectively. Since the grooves of the rollers are connected by arcs, it can be seen that in the process of yarn drawing, there is always A number of moving slender rollers with a diameter of 2r pull the yarn downward in a non-extrusion manner, that is, when the yarn moves in the meshing area of the traction roller, it actually goes around several cylinders, and the yarn The bypassed cylinder has a circular cross-section. Rollers A and B mesh at the tangent point H of the small arc and the large arc. Since the yarn is relatively thin, its lateral compression is not considered, so it can be considered that the active roller A does not squeeze the yarn at point H, and the roller pressure is directly used To drive the driven roller B to rotate.
Therefore, the traction roller of the carpet tufting machine has the following characteristics: (1) Each roller has a groove, and the groove shape is an arc; (2) The structure is arranged in an extruded form, and the traction of the yarn is not adopted. The mechanism of the extrusion method, the threading process of the traction roller is equivalent to the non-extrusion threading of multiple small-diameter rollers; (3) Two rollers mesh with the yarn separately, and at the same time, the two rollers use a gear-like meshing method. Transmission; (4) Two rollers have and only a pair of teeth participate in meshing at any time, and the meshing point is in point contact.
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