Rieter

Spinning nozzle

Index

The spinning nozzle is basically the yarn formation element, i.e. the heart of the air-jet spinning process. Compressed air at up to 0.6 Mpa enters the actual spinning chamber through 4 small bores, thus creating a very strong air vortex (see Fig. 36). At the outlets of the bores, this air vortex has a rotation speed of up to 1 000 000 rpm. The vortex performs 2 functions through this high speed:

• generation of a vacuum and thereby an air flow through the fiber feed chanel,
• rotation of the free fiber ends around the spindle tip.

The vacuum is necessary in order to seize the fibers at the outlet nip of the drafting system and guide them securely through the fiber feed channel of the spinning nozzle toward the stationary spindle.

The fiber ends which have been split off from the main fiber flow between drafting unit and spindle entry eventually form a kind of fiber sun around the spindle tip (Fig. 36). In order to transform these fiber ends into wrapping fibers, they are rotated by the air vortex. The fibers thus reach a rotation speed of over 300 000 rpm. This speed is very high, but due to mechanical friction it is of course lower than the speed of the vortex.

In addition to generating twist, the rotation of the fiber ends also creates spinning tension in the yarn, i.e. tension in the yarn between nozzle and take-up rollers. This spinning tension Pspinn can be approximately calculated (Fig. 38). The shape of the fiber ends between spindle tip and nozzle housing is certainly curved. But with regard to the action of the centrifugal force acting on the fiber, it may be assumed that this fiber end f has a radial direction, as shown in Fig. 38. Under this assumption, force PA acting on the fiber at point A can be calculated by the formula for the spinning tension in rotor spinning, as it is the same physical situation, i.e. a rotating piece of fiber or yarn subjected to centrifugal forces [15]. The force in the fiber f at point A thus amounts to:

$P_A = \frac {1}{2}T_{fiber} {{ \omega_f}^2} {R^2}{e^{\mu \beta}$

where:

Tfiber = fiber count in tex
ωf = angular velocity in s-1
R = radius of the spinning housing in cm
ß = fiber deflection angle

From this follows the component of the fiber force in the direction of the yarn axis PAa:

PAa = PA sinß

$P_A = \frac {1}{2}T_{fiber} {{ \omega_f}^2} {R^2}{e^{\mu \beta} \sin \beta$

In order to obtain the spinning tension, the axial fiber force has to be multiplied by the number of wrapping fibers:

Pspinn = PAa n

$P_{spinn} = \frac {1}{2}T_{yarn}\ W{ \omega_f}^2} {R^2}{e^{\mu \beta} \sin \beta$