Abstract: A plasma torch includes a torch main unit and a nozzle. The torch main unit has a nozzle seat member on which the nozzle is mounted. The nozzle is arranged to move toward or away from the nozzle seat member in a direction substantially parallel to a center axis of the nozzle when the nozzle is mounted on or removed from the nozzle seat member. The nozzle has an electroconductive surface facing the nozzle seat member. The torch main unit has an elastic electric contact portion contacting with the electroconductive surface of the nozzle to form an electroconductive path for a pilot arc to the nozzle. The electroconductive surface of the nozzle presses the electric contact portion in the direction substantially parallel to the center axis when the nozzle is moved toward the nozzle seat member to mount the nozzle on the nozzle seat member.

Abstract: A plasma torch includes a torch main unit and a nozzle. The torch main unit has a nozzle seat member on which the nozzle is mounted. The nozzle is arranged to move toward or away from the nozzle seat member in a direction substantially parallel to a center axis of the nozzle when the nozzle is mounted on or removed from the nozzle seat member. The nozzle has an electroconductive surface facing the nozzle seat member. The torch main unit has an elastic electric contact portion contacting with the electroconductive surface of the nozzle to form an electroconductive path for a pilot arc to the nozzle. The electroconductive surface of the nozzle presses the electric contact portion in the direction substantially parallel to the center axis when the nozzle is moved toward the nozzle seat member to mount the nozzle on the nozzle seat member.

Abstract: A plasma cutting machine cuts stainless steel with good quality. An inactive gas (nitrogen) is supplied as a plasma gas, and a combustible gas (propane) having a specific gravity higher than that of air and having a reducing ability or a mixed gas of the combustible gas (propane) and an inactive gas (nitrogen) is supplied as an assist gas to a plasma torch. The combustible gas (propane) contained in the assist gas is not supplied in the pre-flow interval and after-flow interval, and is supplied only in the plasma arc generation interval.

Abstract: A plasma cutting machine is provided in which a dross adhesion inhibitor is jetted from a plasma torch toward the cutting start position (piercing position) of the object material. A dross adhesion inhibitor supply flow path for feeding the dross adhesion inhibitor is connected to an assist gas feeding line in which an assist gas for assisting cutting of the object material with the plasma arc flows.

Abstract: With reliable application of a necessary amount of dross adhesion inhibitor to a cutting start position of an object material, adhesion and deposition of dross is prevented, improved productivity is attained by reducing the cycle time, and a reduction in the running cost as well as man power and improved reliability are achieved. To this end, a plasma cutting machine has a jetting means for jetting the dross adhesion inhibitor toward the cutting start position (piercing position) of the object material W from a plasma torch used for generating the plasma arc. This jetting means is constructed such that a dross adhesion inhibitor supply flow path for feeding the dross adhesion inhibitor is connected to an assist gas feeding line in which an assist gas for assisting cutting of the object material W carried out with the plasma arc flows after jetted along the plasma arc.

Abstract: The invention prolongs the electrode lifetime of plasma machining electrodes having a hafnium or zirconium insert. A hafnium or zirconium insert 21 inserted into the tip of a copper holder 22 protrudes from the tip of the copper holder 22. The protrusion length L is not larger than the diameter D of the insert, preferably not larger than 0.5 mm. The protruding portion 21a of the insert has a rounded section without sharp angles. The rear surface 21 of the insert is exposed to the flow of the cooling water inside the electrode. At least during the generation of the pilot arc, a plasma gas containing at least 5 mol % nitrogen is used.

Abstract: The object is to facilitate replacement of consumable parts, such as the electrode, nozzle, or the like, in a plasma torch, whilst suppressing any increase in structural complexity or cost. An electrode 103, insulating guide 105 and nozzle 107 are fit together installed in a retainer cap 113. By means of O-rings 193, 195, 197, the electrode 103, insulating guide 105, nozzle 107 and retainer cap 113 are coupled together by a coupling force which allows the components to be pulled apart and separated manually. By attaching the retainer cap 113 to the torch main unit and detaching the retainer cap 113 from same, the electrode 103, insulating guide 105 and nozzle 107 can be attached and detached to and from the torch main unit, simultaneously.

Abstract: An object is to provide a plasma torch having a function to achieve fully satisfactory cooling of the nozzle and shield cap. A plasma torch 1 comprises a nozzle 17 positioned at the front end portion of the torch 1 so as to cover an electrode 13, with a plasma gas passage 37 interposed therebetween. A shield cap 21 is mounted at the front end of the nozzle 17, and these components 13, 17 and 21 are accommodated in a retainer cap 23. Assist gas passages 45, 55 are formed in the wall of the retainer cap 23, and feed assist gas to the vicinity of the plasma arc 81. A space enclosed by the retainer cap 23, nozzle 17 and shield cap 21 is a cooling water passage 63. The retainer cap 23, nozzle 17 and shield cap 21 faces the cooling water passage 63, and hence directly and powerfully water-cooled.