Conduit, useful in plasma arc torch used for cutting metal part, comprises external envelope and removable internal element, where external surface of internal element covers specific percentage of internal surface of external envelope

摘要

The conduit comprises an external envelope (10) and a removable internal element (11), where each of the external envelope and the removable internal element comprises an axial recess including an inner surface, an input orifice and an output orifice. The internal element is positioned in a removable manner in the axial recess of the external envelope to form a sleeve around the removable internal element. An external surface of the removable internal element covers 70% of an internal surface of the external envelope. The external envelope is made of a first material. The conduit comprises an external envelope (10) and a removable internal element (11), where each of the external envelope and the removable internal element comprises an axial recess including an inner surface, an input orifice and an output orifice. The internal element is positioned in a removable manner in the axial recess of the external envelope to form a sleeve around the removable internal element. An external surface of the removable internal element covers 70% of an internal surface of the external envelope. The external envelope is made of a first material and the removable internal element is made of a second material, where a melting point of the second material is greater than the melting point of the first material. The external envelope and the removable internal element are revolution parts whose axes of symmetry are aligned along a same axis. A profile of the external surface of the removable internal element forms a complementary portion of a profile of the internal surface of the external envelope. A profile of an internal surface (11a) of the removable internal element includes a cylindrical or quasi-cylindrical upstream portion having a first internal diameter of 8-25 mm, a cylindrical downstream portion defining a conduit channel and having a second internal diameter of 0.4-5 mm, and an intermediate portion that is located between the upstream portion and the downstream portion and including a truncated convergent portion forming an aperture with the axis at 25-75[deg] . The internal and external surfaces of the removable internal element define a peripheral wall having a thickness of 1-2 mm. The conduit further comprises a unit for mechanical assembly of the removable internal element in the external envelope by threading, clamping or hafting. The external envelope includes a unit for obstinate the removable internal element against the external envelope. A first sealing component (20) such as joint elastomer, is arranged between the external envelope and the removable internal element and in a first peripheral groove (21) in the internal surface of the external envelope and/or the external surface of the removable internal element. A second peripheral groove is formed in the external surface of the external envelope and formed to accommodate a second sealing component. An independent claim is included for a method for cutting a metal part by plasma arc.