Yarn Braking Body

Abstract

A yarn braking body is a flexible frustocone coat made from plastic material and has a circumferentially continuous braking surface which is defined by a part of the inner surface of the frustocone coat. The yarn braking body has a circumferentially continuous support part at the small diameter end. The support part is spherical and one piece with the frustocone coat and is made from the plastic material of the yarn braking body such that the centre of the sphere lies in the axis of the frustocone coat which axis is prolonged beyond the large diameter end.

Description

The invention relates to a yarn braking body according to the preamble of claim 1.

In knitting yarn feeding devices which are known in practice a yarn braking body is implemented which is a precise frustocone coat made from smooth vacuum-shaped plastic material. The support part is a support ring firmly gripping the small diameter end of the frustocone coat and is installed as a separate part which comprises anchoring openings serving to hook in tension springs which extend radially outwardly from the support part and which hold the braking body in the coaxial operational position in contact with the rounded withdrawal rim of the storage body of the knitting yarn feeding device. The holding construction with the tensioning springs is structurally complicated. Manufacturing and assembling the support part at the yarn braking body needs several working steps. The knitting yarn runs off the storage body over the withdrawal rim and along the yarn braking surface at the inner side of the frustocone coat and at the same time rotates like the hand of a clock while it is pulled off axially through the small diameter end. The tension springs allow a certain movability of the yarn braking body and centre the yarn braking body on the withdrawal rim of the storage body. The yarn braking body is a wear part which in some cases has to be replaced relatively frequently. Due to the holding construction replacements are time consuming. The support part increases the mass of the braking body.

It is an object of the invention to provide a yarn braking body of the type as mentioned at the beginning which has low mass, can be manufactured for fair costs, and which can be replaced and centred easily.

This object is achieved by the features of claim 1.

Since the support part is integrated as one piece into the frustocone coat the support part can be formed for fair costs during manufacturing the yarn braking body. The spherical support part is laid then with its spherical outer surface into a matching spherical pan for supporting the braking body. The support part is held by the contact pressure at the withdrawal rim of the storage body, and is centred by the spherical pan. The spherical support part forms so to speak a part of a spherical joint or a universal joint, respectively, which properly centres the yarn braking body on the withdrawal rim of the storage body. The yarn braking body can easily be replaced. The integrated spherical support part does not increase the mass of the braking body and also does not significantly influence the radial deformability of the frustocone coat in the region of the braking surface. The easily shapeable plastic material is used in order to form the spherical support part integrally with the frustocone coat. The rigidity of the support part which is slightly increased by the spherical form is sufficient for a stable suspension of the yarn braking body in the spherical pan without additional reinforcement measures.

Expediently, the same wall thickness is present in the yarn braking body in the frustocone coat and in the spherical support part. The wall thickness e.g. amounts to between 0.2 mm and 0.5 mm. In this way the yarn braking body can be manufactured from a simple blank. Alternatively, it is possible to provide, at least regionally, a different wall thickness in the support part than in the frustocone coat.

The sphere radius of the spherical support part may be designed such that it reacts in an expedient relationship with the diameter at the large diameter end of the yarn braking body. The sphere radius e.g. may amount to between about 30% to 60% of the diameter. By this measure a large contact surface is achieved in the ball joint while the radial deformability of the frustocone coat is not significantly influenced in the region of the braking surface.

The wall thickness expediently is smaller than 1.0 mm, preferably even smaller than 0.5 mm. In case of a yarn braking body having a diameter of about 150 mm at the large diameter end the wall thickness may be about 0.3 mm.

The cone angle of the regular frustocone coat should amount to between about 100° and about 130°. Expediently, the cone angle amount to 120°.

The plastic material from which the yarn braking body is made should be a thermoplast, e.g. a polyester, PET or PVC. Such materials can be shaped easily and allow to achieve high durability and excellent surface properties.

The yarn braking body expediently is made by, preferably thermal, vacuum shaping from a blank. In this case the blank even could be a planar blank. At least the die surface used when shaping the inner surface of the braking body in the region of the braking surface should be polished in order to produce an inner surface in the yarn braking body which is truly smooth.

In order to achieve a uniform deformation property in the yarn braking body the spherical support part should continue the frustocone coat without a transition or a step. The spherical curvature, so to speak, is nestled into the frustocone.

The height dimension of the spherical support part measured in the direction of the axis of the frustocone coat should measure between about 15% to 35%, preferably less than 30%, of the height dimension of the yarn braking body.

By the integration of the spherical support part into the frustocone coat the spherical support parts constitutes the small diameter end of the frustocone coat through which small diameter end the yarn will be withdrawn. The yarn may be withdrawn directly through the support part or, alternatively, with the help of a yarn eyelet which is placed at this location with or without a connection or a bonding to the yarn braking body.

The outer diameter of the spherical support part should amount to about 2.5 to 4.5 fold of the inner diameter of the smaller diameter end. Alternatively, the outer diameter of the spherical support part could amount to between about 25% and 45% of the diameter of the large diameter end. In this fashion a sufficiently large contact surface is achieved in the ball joint.

The inner surface of the frustocone coat, at least in the region of the braking surface, should have a smoothness which corresponds with a polished surface.

An embodiment of the invention is explained with the help of FIG. 1 which in the left half is a side view of a yarn braking body and in the right half is a radial section of the yarn braking body.

A yarn braking body B in FIG. 1, expediently for a not shown knitting yarn feeding device, is provided for a co-action with a rounded withdrawal rim of a drum-shaped storage body of a knitting yarn feeding device, in order to actuate or load the yarn with a relatively low braking force while the yarn is withdrawn inwardly over the withdrawal rim and at the same time is rotating like the hand of a clock. For this reason, the yarn braking body is laid coaxially with the storage body from the front side against the withdrawal rim and is held in a suspension such that it is centred at the withdrawal rim but nevertheless remains somewhat movable. The yarn braking body B is a one-piece plastic material shaped part, e.g. made from a thermoplastic material P like polyester, PET or PVC. The yarn braking body B e.g. is manufactured by vacuum shaping on a forming die, in some cases even by thermal vacuum shaping.

The yarn braking body B consists of a regular frustocone coat K and a spherical support part S which is integrated in one piece into the frustocone part K. The yarn braking body B has a large diameter circular end 1 having an opening 5 of a diameter D and a small diameter circular end 2 with an opening 4 of an inner diameter d. The frustocone coat K has a linear generatrice 3 and an axis Y. The spherical support part S is a stepless continuation of the generatrice 3 and has a sphere radius R e.g. between 30% to 60% of the diameter D. The centre Z of the sphere is situated on the axis Y of the frustocone coat K which axis Y is prolonged beyond the large diameter end 1.

In a concise embodiment of a yarn braking body B with a diameter D of about 110 mm and a cone angle α of 120° the sphere radius R is about 590 mm.

The wall thickness x of the yarn braking body B is the same in the frustocone coat K and in the spherical support part S and amounts to between 0.2 mm and maximally 1.0 mm, preferably amounts to about 0.3 mm (in the case of a yarn braking body having a diameter D of 150 mm). Alternatively, the wall thickness in the spherical support part at least in part could be different from the wall thickness in the frustocone coat K.

The respective edges in the openings 5, 6 in the large diameter end 1 and in the small diameter end 2 could be rounded. The inner surface of the frustocone coat constitutes at least in a region a ring-shaped, circumferentially continuous braking surface F. At least in the region of the braking surface F the inner surface should be very smooth, e.g. with a smoothness corresponding to a polished surface.

The height h of the yarn braking body B in direction of the axis Y e.g. amounts in case of a diameter D of 110 mm to about 46 mm. The height h2 of the spherical support part S amounts to somewhat less than 30% of the height h and may amount to between about 15% to about 35% of the height h. The outer diameter dS of the spherical support part S amounts to about 2.5 to 4.5 fold of the inner diameter d of the small diameter end 2, or may be about 25% to 45% of the diameter D, respectively. The cone angle α in general may amount to between about 100° and 135°. A tangent drawn at the edge 6 of the opening 4 along the outer side of the spherical support part S either may be perpendicular to the axis Y or may include an angle with the axis Y which angle is smaller than 90°. The height h1 of the frustocone coat K in each case is larger than the height h2 of the spherical support part S. In no case should the yarn braking surface F reach towards the spherical support part S. Expediently, the outer surface of the spherical support part S also has a smoothness which corresponds to a polished surface.

Claims

1. Yarn braking body for a yarn feeding device, in particular for a knitting yarn feeding device, the yarn braking body being a flexible frustocone coat made from plastic material and having a large diameter end of substantially circular form, a small diameter end of substantially circular form and a circumferentially continuous braking surface defined by a part of the inner surface of the frustocone coat, and having a circumferentially continuous support part at the small diameter end, wherein the support part is integrally made spherical and in one piece with the frustocone coat from the plastic material of the yarn braking body such that the center of the sphere lies in the axis of the frustocone coat which axis is prolonged beyond the large diameter end.

2. Yarn braking body as in claim 1, wherein the wall thickness of the yarn braking body is continuously the same in the frustocone coat and in the spherical support part.

3. Yarn braking body as in claim 1, wherein the sphere radius of the spherical support part is between 30%,and 60%, preferably about 43%, of the diameter of the large diameter end of the frustocone coat.

4. Yarn braking body as in claim 2, wherein the wall thickness is smaller than 1.0 mm, preferably is between 0.2 mm and 0.5 mm.

5. Yarn braking body as in claim 1, wherein the cone angle of the frustocone coat amounts to between about 100° and 135°.

6. Yarn braking body as in claim 1, wherein the plastic material is a thermal plastic material, e.g. polyester, PET or PVC.

7. Yarn braking body as in claim 1, wherein the yarn braking body is shaped by, preferably thermal, vacuum shaping of a blank, preferably of a planar blank.

8. Yarn braking body as in claim 1, wherein the spherical support part is a stepless continuation of the frustocone coat.

9. Yarn braking body as in claim 1, wherein the height of the spherical support part measured in the direction of the axis of the frustocone coat measures between about 15% to 35%, preferably less than 30%, of the height of the yarn braking body.

10. Yarn braking body as in claim 1, wherein the spherical support part forms the small diameter end of the frustocone coat.

11. Yarn braking body as in claim 1, wherein the outer diameter of the spherical support part amounts to about 2.5 to 4.5 fold of the inner diameter of the small diameter end.

12. Yarn braking body as in claim 1, wherein the outer diameter of the spherical support part amounts to about 25% to 45% of the diameter of the large diameter end.

13. Yarn braking body as in claim 1, wherein the inner surface of the frustocone coat has a smoothness at least in the region of the braking surface corresponding to a polished surface.