Abstract: A yarn treatment jet is provided having a venturi member with a venturi shaped bore, and an inlet member with a yarn passage therethrough located in the mouth of the bore, in which the inlet member is in contact with the mouth of the bore to locate the inlet member positively relative to the venturi member and is configured to provide a passage for air into the venturi bore between the inlet member and the venturi member. The inlet member may be formed of a core and a needle so that to change the configuration of the air passage only the core need be changed. The air passage is formed by one or more grooves or bores in the inlet member or core.

Abstract: A yarn treatment jet has a yarn passage extending through the body of the jet and a fluid inlet intersecting the yarn passage transversely. In cross-section the yarn passage has a main part and a substantially parallel sided yarn controlling part which is of lesser width than the main part. The width of the fluid inlet is greater than that of the controlling part but less than that of the main part. The yarn is guided to run in the yarn controlling part which the fluid inlet intersects and the fluid is directed past the running yarn in the direction of the main part. The yarn guides are movable towards and away from the inlet and outlet ends of the yarn passage. A curved threading slot connects the controlling part with the outside of the jet.