Tree Hash Under Concurrency Control.

A spinning unit for an open end spinning machine is disclosed. The unit includes a rotor having a short cylindrical portion defining a central aperture, a frustoconical portion connected at one end to and converging toward the cylindrical portion, and a portion connected to the other end of the frustoconical portion with air discharge openings. The unit further includes a casing having a first portion, and a second portion connected to the first portion of the casing and surrounding the portion of the rotor connected to the other end of the frustoconical portion to define an annular chamber into which air is discharged through the air discharge openings during rotation of the rotor. The first portion has an inner surface substantially surrounding both the cylindrical and frustoconical portions of the rotor in spaced relationship therewith thereby to provide a relatively long and narrow bent passage defined between the first portion of the casing and the cylindrical and frustoconical portions of the rotor and extending between the central aperture of the rotor and the chamber of the casing.