RU2309825C2 - Plasmatron - Google Patents

Abstract

FIELD: plasmatrons, possibly plasma surfacing, welding, cutting of ferrous and non-ferrous metals.

SUBSTANCE: in housing 1 of plasmatron ducts 5 for supplying shield gas 6 are formed. Sleeves 7 and 8 are mutually joined through lock joint 9 and hollow electrode 10 is arranged in them. Plasmatron has common cooling system for cooling housing 1, electrode 10, plasma generating nozzle 3 and casing 2. Cooling system includes pipeline 13; annular duct 15 between electrode 10 and pipeline 13; annular duct 16 between electrode 10 and inner insulation sleeves 7, 8 arranged in axial direction in turning on outer surface of electrode 10; annular duct 17 between insulation sleeves 7, 8 and housing 1; annular duct 18 between housing and casing; radial overflow ducts 19 in electrode 10 connecting ducts 15 and 16; radial overflow ducts 20 of upper insulation sleeve 8 for connecting ducts 16 and 17; radial overflow ducts 21 of housing for connecting ducts 17 and 18 and outlet duct 14 in casing 2.

EFFECT: improved operational reliability of plasmatron due to preventing electric breakdown between electrode and housing at igniting plasma arc by means of high-voltage HF discharge at keeping effective cooling of thermally loaded units without increasing cross size of plasmatron.

Description

The invention relates to the field of plasma processing of metals, and in particular to devices for plasma surfacing, welding, cutting of ferrous and non-ferrous metals.

Known plasma torch containing a hollow cylindrical electrode, a housing with a plasma-forming and protective nozzles mounted on it and channels made in the housing for supplying plasma-forming and protective gases and draining coolant, equipped with two insulating sleeves installed between the housing and the electrode at opposite ends of the housing, a cooling system with a central and coaxial annular channels connected to each other and located in the electrode, an annular channel formed by the outer surface of the electrode and the inner surface of the housing connected to the electrode cavity bypass radial channels made in the electrode near the working end (see RF patent No. 2060130, class B23K 10/60).

This plasmatron is quite simple in design, has small dimensions and weight, is technologically advanced and easy to operate, has high maintainability (it does not have welded and soldered joints). However, there are reserves to increase the power and reliability of the plasma torch by increasing the cooling efficiency. In addition, in the known plasmatron there is an electrical connection between the plasma-forming and protective nozzles, which increases the possibility of double arcing when the protective nozzle touches the product and creates an emergency mode during operation of the plasma torch.

Known plasmatron containing a hollow cylindrical electrode, a housing with a plasma-forming nozzle mounted on it and channels made therein for supplying a plasma-forming gas, equipped with two insulating sleeves mounted between the housing and the electrode at opposite ends of the housing. A casing with a protective nozzle mounted on it and channels made in it for supplying protective gas and draining coolant are mounted on the housing with two insulating sleeves. The cooling system includes a pipe installed in the cavity of the electrode, annular channels between the housing and the electrode, the electrode and the pipeline, the housing and the casing, respectively, bypass radial channels made in the electrode and the housing and connecting the annular channels (see RF patent No. 2198772, class B23K 10/60). The plasma torch has effective cooling and increased operational reliability due to the electrical isolation of the plasma-forming and protective nozzles by means of insulating sleeves installed between the housing and the casing.

However, when a plasma arc is ignited by a high-voltage high-frequency discharge, an electrical breakdown in the annular channel between the casing and the electrode is possible, which can lead to an emergency and failure of the plasma torch. The probability of breakdown increases when using sources of welding current with a high open circuit voltage, for example, during plasma cutting and spraying (open circuit voltage is more than 300 V).

The objective of the present invention is to increase the reliability of the plasma torch by eliminating the possibility of electrical breakdown between the electrode and the housing when igniting a plasma arc by a high-voltage high-frequency discharge while maintaining high cooling efficiency of heat-loaded units and without increasing the transverse dimensions of the plasma torch.

The problem is solved by improving the well-known plasmatron. The proposed plasma torch comprises a housing, a housing, a plasma forming and protective nozzle, channels for supplying a plasma forming gas made in the housing, a channel for supplying a protective gas and a channel for draining coolant made in the housing, front and rear insulating sleeves installed in the housing cavity. The bushings are interconnected by means of locking mating. A hollow electrode is installed in the bushings. The front and rear insulating sleeves, on which the casing is placed, are installed on the body. The plasma torch has a single cooling system for the housing, electrode, plasma forming nozzle and casing. The cooling system includes a pipe, annular channels: a channel between the electrode and the pipe, a channel between the electrode and the internal insulating sleeves, located in the axial direction in a groove made on the outer surface of the electrode, a channel between the internal insulating sleeves and the body, located in the axial direction in a groove on the inner surface of the housing, a channel between the housing and the casing, located in the axial direction between the outer insulating sleeves, radial bypass channels in the electrode, connecting the annular channels inside and outside the electrode, the bypass radial channels in the upper insulating sleeve installed in the cavity of the housing, connecting the annular channels on the outer surface of the electrode and inside the case, the bypass radial channels in the case, connecting the annular channels inside the case and inside the casing and outlet channel in the casing.

The proposed plasmatron differs from the plasmatron in the prototype in that the front and rear insulating sleeves installed in the body cavity are interconnected by means of locking mating. A groove is made on the outer surface of the electrode between the inner insulating bushings, forming an annular channel between the electrode and the bushings. A groove is made on the inner surface of the housing between the inner insulating bushings, forming an annular channel between the housing and the bushings. In the upper sleeve, radial bypass channels are made connecting the annular channels between the electrode and the bushings and between the housing and the bushings. Bypass radial channels made in the electrode and the housing are located at opposite ends of the annular channels relative to the bypass channels made in the upper part of the insulating sleeves.

The complete separation of the electrode and the casing by insulating bushings interconnected by means of interlocking eliminates the possibility of electrical breakdown in the annular channel between the casing and the electrode when a plasma arc is ignited by a high-voltage high-frequency discharge. The implementation of the annular channels between the electrode and the insulating sleeves and between the housing and the insulating sleeves due to the grooves in the corresponding elements avoids the increase in the radial dimensions of the plasma torch. The location of the bypass channels in the upper insulating sleeve, the electrode and the housing at the opposite ends of the annular channels provides the maximum contact surface of the cooled nodes with the liquid, which increases the efficiency of the cooling system.

Figure 1 shows a General view of the plasma torch with a longitudinal section through the system of supply and removal of coolant and the supply of protective gas.

Figure 2 shows a plasmatron with a longitudinal section through a plasma gas supply system and a cooling system (to increase the clarity of the drawing, individual details are shown on an enlarged scale).

The plasma torch comprises a housing 1, a housing 2, a plasma forming nozzle 3 mounted on the housing 1, a protective nozzle 4 mounted on the housing 2, channels 5 for supplying a plasma forming gas made in the housing 1, a channel 6 for supplying a protective gas made in the housing 2, installed in body cavities 1 front 7 and rear 8 insulating sleeves interconnected by means of locking mating 9. In the sleeve 7, the hollow electrode 10 is installed with its head part “a”, the back part “b” of which (shank) is installed in the sleeve 8. On the case 1 installed The front 11 and rear 12 insulating sleeves on which the casing 2 is placed. The plasma torch contains a single water cooling system for the electrode 10, the housing 1, the plasma forming nozzle 3 and the casing 2. The cooling system includes a pipe 13 located along the axis of the plasma torch for supplying coolant into the cavity "D" of the electrode 10 and the channel 14 made in the casing 2 for the removal of coolant. The pipe 13 forms an annular channel 15 with the electrode 10. The electrode 10 forms, with the bushings 7, 8, the housing 1 and the casing 2, annular channels 16, 17 and 18. The channel 16 is formed by a groove made on the outer surface of the electrode 10, the channel 17 by a groove on the inner the surface of the housing 1. The annular channels 15 and 16 are connected bypass radial channels 19, made in the electrode 10 and located in the lower part of the annular channel 16. The annular channels 16 and 17 are connected bypass radial channels 20, made in the upper insulating sleeve 8 and placed female in the upper part of the channel 17. The annular channels 17 and 18 are connected bypass radial channels 21, made in the housing 1 and located in the lower part of the channels 17 and 18. Water is supplied through the channel 22. The electrode 10 is fixed and the ring channels 16 and 17 are sealed nut 23. The casing 2 is mounted on the housing 1 and the annular channel 18 is sealed by the nut 24 through the insulator washer 25.

When the plasma torch is operating, the cooling liquid is supplied through the channel 22 of the pipeline 12 to the working area of the electrode 10 (cavity "d"), fills the annular channel 15, while cooling the electrode 10 from the inside. From channel 15, through channels 19, coolant enters the annular channel 16, cooling the electrode 10 from the outside, then through the channels 20, the liquid enters the annular channel 17, cooling the housing 1 from the inside. Through channels 21, coolant is supplied to the annular channel 18, cooling the casing 1 from the outside and the casing 2, and is discharged to the drain via channel 14. The nozzles 3 and 4 are cooled through reliable thermal contact into the casing 1 and the casing 2, respectively, as well as by plasma-forming and protective gases.

The plasma forming gas through the channels 26 and 5 enters the cavity of the plasma forming nozzle 3, the protective gas through the channel 6 enters under the protective nozzle 4.

Laboratory tests of a prototype plasmatron with dimensions equal to D29 × 70 mm and a mass of 0.3 kg at a flow rate of coolant (water) of 2.5 l / min showed high reliability at a welding current of up to 450 A. At the same time, the possibility of electrical breakdown between the electrode and the plasma torch case during ignition of a plasma arc by a high-voltage high-frequency discharge when using a welding current power source with an open-circuit voltage of 300 V.

Claims (1)

A plasma torch comprising a hollow cylindrical electrode, a housing in which channels for supplying plasma-forming gas are made, a plasma-forming nozzle mounted on the housing, two insulation bushings mounted on opposite ends of the housing and the electrode mounted on the housing using two insulation bushings located on the outside housing at opposite ends, a casing with a protective nozzle mounted on it and channels made therein for supplying protective gas and draining coolant, a system cooling with central and coaxial annular channels connected to each other and located in the electrode, annular channels formed between the outer surface of the housing and the inner surface of the casing and in the axial direction between the external insulating sleeves, and radial bypass channels made in the electrode and the housing characterized in that the insulating sleeves installed between the housing and the electrode are interconnected by means of locking mating, the annular channels of the cooling system in the form of points formed between the insulating sleeves, the electrode and the housing are made on the outer side of the electrode and the inner side of the housing and in the axial direction between the insulating sleeves and connected in the upper part bypass radial channels made in the upper insulating sleeve, and radial bypass channels made in the electrode and the housing are located at opposite ends of the annular channels relative to the bypass channels made in the upper part of the insulating sleeves.

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