Apparatus and method for chemical deposition on a rod member in an optical fibre manufacturing process

1. A method for chemical deposition on a rod member, comprising:

supporting the rod member with its longitudinal axis substantially coaxial to a deposition axis, including

applying a radial constraint to a first end portion of the rod member with a first support member rotatively coupled to the first end portion of the rod member, and

applying a radial constraint to a second end portion of the rod member with a second support member rotatively coupled to the second end portion at a first axial position on the second end portion of the rod member;

coupling the second end portion of the rod member to a handling member having a handling axis with the handling member coupled to the rod member at a second axial position on the second end portion of the rod member, the second axial position being spaced axially from the first axial position;

transmitting a torque generated about a motor axis to the rod member via the handling member, including transmitting the torque from a joint member to the handling member and further transmitting the torque from the handling member to the rod member, for rotating the rod member about the deposition axis; and

depositing chemical substances on the rod member during rotation of the rod member;

wherein transmitting the torque comprises redirecting the torque whenever a misalignment occurs between the motor axis and the handling axis or between the handling axis and the longitudinal axis of the rod member, wherein redirecting the torque includes compensating the misalignment with the joint member acting with an axis inclined with respect to the longitudinal axis of the rod member in order to allow the handling axis or the motor axis to lie inclined with respect to the rod axis without deforming the rod member;

wherein the handling member is a gripper, and the coupling of the second end portion of the rod member to the handling member includes gripping the second end portion of the rod member with the handling member; and

wherein gripping the second end portion of the rod member with the handling member comprises protecting the rod member by interposing an elastic sleeve between the gripper and rod member.

2. The method of claim 1 , wherein supporting the rod member further includes applying a further radial constraint to the first end portion of the rod member at an axial position spaced from the radial constraint applied by the first support member.

3. The method of claim 1 , further including applying a further radial constraint to the second end portion of the rod member with an auxiliary support member at a position spaced from the first support member along the deposition axis.

4. The method of claim 1 , wherein the joint member comprises a universal joint.

5. The method of claim 1 , wherein the joint member comprises a double joint.

6. The method of claim 5 , wherein the double joint comprises a universal double joint.

7. The method of claim 6 , wherein the universal double joint comprises a double Hooke's joint.

8. The method of claim 1 , wherein supporting the rod member with its longitudinal axis substantially coaxial to the deposition axis further includes supporting the first end portion with an auxiliary support member, the first support member and the auxiliary support member being spaced from one another along the first end portion along the deposition axis.

9. The method of claim 1 , wherein supporting the rod member with its longitudinal axis substantially coaxial to a deposition axis includes supporting the first end portion of the rod member only with the first support member.