GB1520000A - Plasma arc torches - Google Patents

Abstract

1520000 Plasma torch VSES N I PROEKTNOKONSTRUKT I TEKHNOLOGICHE INST ELEKTROSVAROCH OBORUDOV 3 Oct 1975 [10 Oct 1974 (2)] 40471/75 Heading H5H A plasma torch comprises two parts A and B detachably secured together in a fluid tight manner, the part A including an electrode holder 1, an electrode 2 with an active insert 3 mounted in the holder 1, a nozzle 4, a terminal 6 connected to the nozzle, an electrical insulator 7 between the holder 1 and nozzle 4, and passages 8, 9, 10,11 and 12 for plasma forming gas and coolant which terminate on a surface of part A which mates with a complementary surface of part B, and the part B including a terminal 16 for the electrode holder 1 and passageways 17, 18; 19, 20; 21, 22; 23, 24; 25, 26 for connection at the mating surfaces of the parts A and B to the corresponding passages 8, 9, 10, 11 and 12 of the part A. This arrangement enables the part A to be removed and replaced when it is worn simply by undoing nut 15. The nozzle 4 and electrode 2 are made of copper and the insert 3 is made of zirconium, tungsten, hafnium or alloys thereof. Passages 17, 18 and 8 cooperate for the supply of plasma gas to the torch. Passages 19, 20 and 9 cooperate to supply coolant (water) to the electrode 2 and passages 21, 22 and 10 cooperate to exhaust coolant from the electrode. Passages 23, 24 and 11 cooperate to supply coolant to nozzle 4 and passages 25, 26 and 12 cooperate to exhaust coolant from the nozzle 4. Fluid tight seals 13, 14 are provided between the mating surfaces of the parts A, B. Plasma forming gases may be compressed air, oxygen, carbon dioxide, argon, nitrogen, hydrogen, helium or mixtures thereof. The arc is initiated by an oscillator connected between the work 27 and the nozzle 4 via terminal 6. Once initiated the main arc is struck between the electrode insert 3 and the workpiece 27. The torch may operate under straight or reverse polarity. The plasma gas is given a vortex flow. Part B is held in a traversing mechanism. The specification gives dimensional criteria of the nozzle and electrode necessary for maximizing cutting speed when the torch is used for cutting. The insert 3 is inserted in a reentrant projection of the electrode 2 so that it may be efficiently cooled. Fins (Fig. 5, not shown) between the reentrant projection and the wall of the electrode 2 to improve cooling. The torch may be used for cutting metals on an automatic production line.