Abstract: Process for controlling the flow of a fluid through a valve having a given section and a movable valve member, in which the pressures of the fluid which are upstream P.sub.upstream and downstream P.sub.downstream of the valve and the position d of the valve member are measured, then the real flow Q.sub.real of the fluid is calculated and compared with a set value Q.sub.0, the difference signal Q.sub.real -Q.sub.0 commanding the displacement of the valve member in the desired direction, said process comprising effecting the real flow calculation by measuring the ratio R=P.sub.upstream /P.sub.downstream which is compared with a predetermined value R and calculating the product Q.sub.sonic =k.times.P.sub.upstream .times.d so that when R>R.sub.0, the product Q.sub.sonic is directly compared with a set value Q.sub.0, the difference signal Q.sub.sonic -Q.sub.0 commanding the displacement of the valve member in the desired direction whereas, when R<R.sub.

Abstract: This nozzle includes an outer case (1) and a core (2) which define in succession: a series of passageways (15) having a zone for the injection of fuel gas and comburent gas, a mixing zone of small section and a primary homogenization zone of larger section; an annular secondary homogenization zone (16) whose section is substantially equal to the total section of the preceding zone; a single acceleration passage (17) having a decreasing section; and a single outlet conduit (18) having a constant section. Application in oxyacetylene torches consuming a few cubic meters per hour acetylene.

Abstract: In order to improve electric arc penetration of an arc welding torch, the angles of convergence .alpha. and .beta. of a sleeve and a nozzle of the torch are selected within an area which is inscribed in a quadrangular figure defined by the coordinates (.alpha., .beta.) with corners, or apices, at the four following points:______________________________________ .alpha. = 17.5 degrees S'.sub.1 : .beta. = 27.5 degrees .alpha. = 7.2 degrees S'.sub.2 : .beta. = 20 degrees .alpha. = 7.5 degrees S'.sub.3 : .beta. = 15 degrees .alpha. = 17.5 degrees S'.sub.4 : .beta. = 7.5 degrees ______________________________________The disclosed arc welding torch is favorably employed in an inert gas welding process.

Abstract: An arc welding process and apparatus utilising an electrode and a counter-electrode between which a column of plasma forms. A first unidirectional current source is located between the electrode and the counter-electrode, and a second unidirectional current source is located between the counter-electrode and the member to be welded. These two sources simultaneously pass the two unidirectional currents.