Water-vapor plasma torch, and wear-detection and process-control method to be used with such a water-vapor plasma torch

Abstract

The invention relates to a water-vapor plasma torch ( 7 ) for cutting a workpiece ( 21 ), comprising a feed line ( 8 ) for a liquid ( 9 ), a heating device ( 22 ), and an evaporator ( 23 ) for forming a gas ( 20 ) from the liquid ( 9 ), a cathode ( 24 ) detachably connected to a movably mounted piston rod ( 25 ), and a nozzle ( 26 ) with an outlet opening ( 27 ) for the gas ( 20 ), as well as to a wear-detection and process-control method to be used with such a water-vapor plasma torch ( 7 ). To create such a water-vapor plasma torch ( 7 ) including wearing-part detection, at least one temperature sensor ( 28 ) is arranged within the piston rod ( 25 ), said temperature sensor being connected to a control unit ( 4 ), so that a wear of the cathode ( 24 ) and the nozzle ( 26 ) can be concluded from the temperature values detected, and that the control of the water-vapor plasma cutting process is influenceable.

What is claimed is: 
     
         1 . A method of detecting the wear of the anode of a water-vapor plasma torch ( 7 ), said anode being designed as a nozzle ( 26 ) with an outlet opening ( 27 ), wherein a gas ( 20 ) escapes through the outlet opening ( 27 ) formed by evaporation of a liquid ( 9 ), fed via a feed line ( 8 ), by means of a heating device ( 22 ), and an evaporator ( 23 ), wherein the nozzle ( 26 ) is worn out by enlarging the outlet opening ( 27 ), thus increasing the flow rate of the liquid ( 9 ), wherein the flow rate of the liquid ( 9 ) is measured in the feed line ( 8 ), and wherein the change in the flow rate is consulted as a measure for the wear of the nozzle ( 26 ). 
     
     
         2 . The wear-detection method according to  claim 1 , wherein the flow rate is compared with a threshold value of the flow rate, which threshold value preferably ranges 60% above the flow rate of a new nozzle, and wherein a change of the nozzle ( 26 ) is requested when the threshold value is reached. 
     
     
         3 . The wear-detection method according to  claim 1 , wherein the wear of the nozzle ( 26 ) is displayed on a display. 
     
     
         4 . The wear-detection method according to  claim 1 , wherein the flow rate detected is compared to the flow-rate reference values deposited in the control unit ( 4 ). 
     
     
         5 . The wear-detection method according to  claim 4 , wherein the flow-rate reference values are deposited as a function of current strength, and wherein the current strength is taken into consideration when assessing wear of the nozzle ( 26 ). 
     
     
         6 . A method of detecting the wear of the anode of a water-vapor plasma torch ( 7 ), said anode being designed as a nozzle ( 26 ) with an outlet opening ( 27 ), wherein a gas ( 20 ) escapes through the outlet opening ( 27 ) formed by evaporation of a liquid ( 9 ), fed via a feed line ( 8 ), by means of a heating device ( 22 ), and an evaporator ( 23 ), wherein the nozzle ( 26 ) is worn out by enlarging the outlet opening ( 27 ), thus increasing the flow rate of the liquid ( 9 ), wherein the output of the heating element ( 22 ) is detected, and wherein the heating output which is a function of the flow rate of the liquid ( 9 ) is consulted when assessing wear of the nozzle ( 26 ). 
     
     
         7 . The wear-detection method according to  claim 6 , wherein the heating output is determined via the electric power fed to the heating device ( 22 ). 
     
     
         8 . The wear-detection method according to  claim 6 , wherein the heating output of the heating device ( 22 ) is controlled as a function of at least one temperature. 
     
     
         9 . The wear-detection method according to  claim 8 , wherein the heating output of the heating device ( 22 ) is controlled as a function of the temperature within a piston rod ( 25 ), and the temperature within the evaporator ( 23 ). 
     
     
         10 . The wear-detection method according to  claim 6 , wherein the wear of the nozzle ( 26 ) is displayed on a display. 
     
     
         11 . The wear-detection method according to  claim 6 , wherein the heating output of the heating device ( 22 ) detected is compared to the heating-output reference values deposited in the control unit ( 4 ). 
     
     
         12 . The wear-detection method according to  claim 6 , wherein the heating-output reference values are deposited as a function of the current strength, and wherein the current strength is taken into consideration when assessing wear of the nozzle ( 26 ) 
     
     
         13 . A method of controlling a cutting process conducted by means of a water-vapor plasma torch ( 7 ), wherein a liquid ( 9 ) is fed to the torch ( 7 ) via a feed line ( 8 ), and wherein the liquid ( 9 ) is evaporated into a gas ( 20 ) by means of a controlled heating device ( 22 ) and an evaporator ( 23 ), wherein the temperature within a piston rod ( 25 ) of the torch ( 7 ) is detected by at least one temperature sensor ( 28 ) arranged within the piston rod ( 25 ), and wherein the heating device ( 22 ) is controlled as a function of the temperature within the piston rod ( 25 ) in a manner to ensure the complete evaporation of the liquid ( 9 ) fed via the feed line ( 8 ). 
     
     
         14 . The process-control method according to  claim 13 , wherein the temperature values detected are processed by the control unit ( 4 ) which is connected to the heating device ( 22 ), the control unit ( 4 ) thus controlling the heating device ( 22 ). 
     
     
         15 . The process-control method according to  claim 13 , wherein the heating device ( 22 ) is controlled as a function of the temperature values detected, taking into consideration the reference values deposited in the control unit ( 4 ). 
     
     
         16 . The process-control method according to  claim 13 , wherein the output of the heating device ( 22 ) is correspondingly increased when the temperature values are decreasing. 
     
     
         17 . The process-control method according to  claim 13 , wherein the output of the heating device ( 22 ) is correspondingly decreased when the temperature values are increasing. 
     
     
         18 . The process-control method according to  claim 13 , wherein the heating device ( 22 ) is controlled only when an appropriate signal is sent by a protective-cap monitoring means. 
     
     
         19 . The process-control method according to  claim 13 , wherein also a power element is started by the control unit ( 4 ) substantially at the same time the control process is started.