Winding glass tube into double helix

摘要

In the bifilar winding of a heat-softened glass tube to a double helix shape on a winding mandrel moving in the direction of its rotational axis, the mandrel and the wound glass tube are subsequently enclosed by a multipart (esp. at least 3-part) mould and pressurised gas is fed into the hot glass tube to effect tube expansion into contact with the mandrel and the inside of the mould. Also claimed are: (i) a method of bending the free ends of a glass coil, esp. produced by the above process; and (ii) an appts. for carrying out the above process and method.