Method and apparatus for forming a braided yarn coating over a product, and product thus obtained

1. A method of forming a braided yarn coating over a product having a longitudinal axis, wherein the product, while leaving a coating zone of a braiding apparatus, is submitted to a continuous unidirectional or bidirectional rotation about its longitudinal axis, wherein said product is a flexible product, and in that said rotation, at least in case of a unidirectional rotation, is accompanied by a corresponding and synchronized rotation of the product along a whole path thereof between means feeding the braiding apparatus with the product to be coated and the coating zone and between the latter and means collecting the coated product.

2. The method according to claim 1 , wherein a rotation speed of the product and a translation speed of the same through the braiding apparatus are adjusted so that the angle formed by a rightward-twisted weft or a leftward-twisted weft with the axis of the product is substantially zero.

3. The method according to claim 1 , wherein the rotation speed of the product is variable and, in case of bidirectional rotation, the rotation speeds in the first and second direction are different from each other.

4. The method according to claim 1 , wherein the bidirectional rotation is obtained by alternating, at programmed levels, a rotation in a first direction and a rotation in a second direction opposite to the first.

5. The method according to claim 4 , wherein the bidirectional rotation is accompanied by a corresponding and synchronized rotation of the product along the whole path thereof between the means feeding the braiding apparatus with the product to be coated and the coating zone and between the latter and the means collecting the coated product when the distance between a point of entrance of the product into the apparatus and the coating zone is limited.

6. An apparatus for forming a braided yarn coating over a product having a longitudinal axis, including a mechanism, placed along the path of the coated product at an exit from a coating zone of the apparatus, for imparting a continuous unidirectional or bidirectional rotation to the product about its longitudinal axis, wherein said mechanism includes:

a worm screw reducer with speed and direction control, which is programmed to make the worm screw rotate either according to a continuous unidirectional rotary movement or according to a bidirectional rotary movement obtained by alternating, at programmed intervals, a rotation in a first direction and a rotation in a second direction opposed to the first; and

means for radially positioning the product leaving the coating zone.

7. The apparatus according to claim 6 , wherein the radially positioning means include:

a toothed wheel, which is coaxially passed through by the product and with which the worm screw meshes in order to make it rotate about its axis; and

a set of pulleys, which follow one another along the path of the product leaving the coating zone and between which said product passes, the pulleys being carried by a support fixedly connected for rotation to said toothed wheel and fastened to the latter in an off-axis position.

8. The apparatus according to claim 6 , wherein said product is a flexible product, and wherein motors with speed and direction control are further provided in order to impart to means feeding the braiding apparatus with the product to be coated and to means collecting the coated product, at least in case of a unidirectional rotation of the product, a rotation corresponding to the rotation imparted by said mechanism and synchronized therewith.