The present invention relates to a yarn brake, especially for two-for-one twisting spindles, having a tubular brake housing into which an abutment extends in the radially inward direction and in which a brake cartridge in the form of a capsule rests at a lower brake ring and at an upper brake ring. The upper brake ring is positioned in a spring-loaded brake ring carrier that is rotatable about its axis and is axially displacable. The brake ring carrier has distributed about its circumference a plurality of support shoulders that have an axial spacing relative to one another whereby one of the support shoulders, depending on the rotational position of the brake ring carrier, rests on the abutment.
Especially in connection with two-for-one twisting spindles yarn brakes are known which are comprised of a brake housing through which the yarn is guided in the axial direction. The inlet and outlet openings are formed by brake rings with conical brake surfaces. These brake rings, in general, are made of a material with high wear resistance. Between the brake rings at the inlet and the outlet side, the actual brake body extends which is, in general, a brake cartridge made of two cylindrical sleeves that are telescopically inserted into one another and have semi-spherical, respectively, cup-shaped ends. The sleeves enclose a pressure spring that upon insertion of the brake cartridge into the brake housing is tensioned by compressing the two sleeves so that the semi-spherical ends of the sleeves exert that braking pressure onto the brake rings that is required for the yarn guided through the yarn brake. Depending on the magnitude of the required braking pressure, stronger or weaker springs are inserted into the brake cartridge.
With a yarn brake disclosed in German Patent 15 10 860 it is possible, by changing rotational position of the brake ring carriers, to bring into contact a different support shoulder on the abutment so that it is possible to change the braking force without exchanging the brake cartridge.
German Patent 31 34 763 discloses a yarn brake with a capsule-shaped brake cartridge that is clamped between the lower and upper brake rings. A pin which is radially adjustable against the force of a spring is supported within the upper brake ring. The adjustable pin can be inserted into one of a plurality of axially spaced bores of the brake housing in order to change the braking force of the yarn brake. This yarn brake allows, as a function of the number of individual bores and the axial distance of these bores relative to one another, to provide for certain braking force levels comparable to the solution disclosed in German Patent 15 10 860.
Such yarn brakes, which are also called capsule yarn brakes, are limited with respect to their radial extension, especially when they are to be inserted into the hollow shaft of a two-for-one twisting spindle. This is partially due to the very small inner diameters of the spool carrier sleeves. As a consequence of these small dimensions, the periphery of the upper brake ring carrier can be provided only with a limited number of support shoulders, especially when in the form of axial slots. In practice, the upper brake ring carrier is generally provided with four to six support shoulders distributed over the circumference so that accordingly there is also only a limited number of adjustment options for the braking force. It is not possible to vary the adjustment range by providing a greater difference between the axial slots (groove depth) because then the individual steps are spaced too far from one another.
It is therefore an object of the present invention to improve a yarn brake of the aforementioned kind such that the number of adjustment possibilities for the braking force is increased.