Method and device for generating a jet of fluid for material processing and fluid nozzle for use in said device

Abstract

The invention relates to a method and a device for generating a jet of liquid which is suitable, in the manner of a waveguide, to carry a laser beam injected into it and which is used to process a work piece. Said device comprises a liquid nozzle for generating a jet of liquid and a gas outlet nozzle, disposed at a distance from the liquid nozzle and producing a flow of gas enclosing the jet of liquid on the exterior thereof. A gas storage is defined between the liquid nozzle and the gas outlet nozzle. The jet of liquid is passed or ejected through the gas outlet nozzle. The jet of liquid has a diameter of preferably 60 m or less and the flow of gas has a diameter of 1-2 mm.

1 . A method for generating a jet of fluid which is suitable for guiding, in the manner of a waveguide, a laser beam which is injected into it, for the purpose of processing a workpiece, wherein the jet of fluid is generated with a fluid nozzle, and wherein the jet of fluid is surrounded on the outside by a gas stream, characterized in that the jet of fluid is guided through a gas outlet nozzle which is arranged at a distance from the fluid nozzle and forms the gas stream. 
     
     
         2 . The method as claimed in  claim 1 , characterized in that the jet of fluid is generated with a diameter of 200 μm or less and in that the gas stream has a diameter of 0.5-2 mm. 
     
     
         3 . The method as claimed in one of  claim 1 , characterized in that the gas of the gas stream has a kinematic gas viscosity which is less than that of a surrounding atmospheric gas. 
     
     
         4 . The method as claimed in  claim 1 , characterized in that gas for generating the gas stream flows into a first flow region without affecting the jet of fluid and is deflected into a second flow region, adjoining said first flow region, so as to flow around the jet of fluid, a junction between said first and second flow regions being at a predefined radial distance from the jet of fluid, and the gas being fed into said first flow region at a plurality of locations which are placed at regular angles around an axis of the jet of fluid. 
     
     
         5 . The method as claimed in  claim 4 , characterized in that in a third flow region a direction of flow counter to the gas outlet nozzle is impressed on the gas, wherein in the third flow region a gas stream which accelerates in the outflow direction of the jet of fluid is produced. 
     
     
         6 . A device for generating a jet of fluid which is suitable for guiding, in the manner of a waveguide, a laser beam which is injected into it, for the purpose of processing a workpiece, comprising
 a fluid nozzle for generating the jet of fluid,   having a gas outlet nozzle which is arranged at a distance downstream from the fluid nozzle and forms a gas stream surrounding the jet of fluid on the outside with a gas stream   wherein he jet of fluid can be directed through the gas outlet nozzle.   
     
     
         7 . The device as claimed in  claim 6 , characterized in that a gas retaining space is provided between the fluid nozzle and the gas outlet nozzle. 
     
     
         8 . The device as claimed in  claim 6 , characterized in that the fluid nozzle forms a circular passage through which the jet of fluid can pass together with the gas stream. 
     
     
         9 . The device as claimed in  claim 6 , characterized in that a jet axis which is assigned to the fluid nozzle and an axis which is assigned to the gas outlet nozzle essentially coincide. 
     
     
         10 . The device as claimed in  claim 6 , characterized in that the fluid nozzle has a diameter in the range from 20 μm to 200 μm, and the diameter of the gas outlet nozzle has a diameter in the range from 0.5 mm to 2 mm. 
     
     
         11 . The device as claimed in  claim 6 , characterized in that the gas outlet nozzle has an internal diameter which is essentially 10 to 20 times as large as the internal diameter of the fluid nozzle. 
     
     
         12 . A device for optimizing the coherence of a jet of fluid which is generated with a fluid nozzle, as a jet director for processing a workpiece, characterized by a housing with a circumferential wall which holds the fluid nozzle, and with at least one gas inlet for the applied gas, wherein the gas inlet is arranged downstream of the fluid nozzle in terms of flow. 
     
     
         13 . The device as claimed in  claim 12 , characterized in that the at least one gas inlet defines an inflow direction into the housing for the applied gas and the wall has a circular cross section in the region of the at least one gas inlet and the inflow direction impacts on this wall tangentially, in a way which does not affect the fluid jet directly. 
     
     
         14 . The device as claimed in one of  claim 12 , characterized in that the housing is embodied as a double cone, wherein the fluid nozzle is arranged in one of the cone tips and the other cone tip has the gas outlet nozzle, and the at least one gas inlet is arranged in a direct vicinity of the largest diameter of the double cone. 
     
     
         15 . A fluid nozzle for a device as claimed in  claim 12  having a nozzle duct which generates a jet of fluid, characterized by a sharp-edged transition from a nozzle surface at a nozzle inlet into the nozzle duct, the sharp-edged transition having a radius of less than 10 micrometers, preferably less than 2 micrometers. 
     
     
         16 . The fluid nozzle as claimed in  claim 15 , characterized in that the nozzle duct has a length which is less than five times, preferably three times, a diameter of the nozzle duct. 
     
     
         17 . The fluid nozzle as claimed in  claim 15 , characterized in that the length of the nozzle duct and thus the thickness of the fluid nozzle is selected to be just so thick that the nozzle just withstands the fluid inlet pressure loading it, wherein, in order to mechanically reinforce the stability, a slope is formed running outward in the manner of a cone on the underside of the nozzle, starting from a cylindrical nozzle duct inner wall at the nozzle duct outlet, and the slope is constructed so that it extends at an angle between 90° and 150° with respect to a longitudinal axis of the nozzle duct. 
     
     
         18 . A method for generating a jet of fluid guiding a laser beam in the manner of a waveguide, for the purpose of processing a workpiece, comprising the steps of:
 generating the jet of fluid with a fluid jet nozzle,   injecting the laser beam into the fluid jet at the fluid jet nozzle,   directing the jet of fluid, which guides the laser beam, through a gas outlet nozzle which is arranged at a distance downstream from the fluid nozzle, said gas outlet nozzle forming a gas stream surrounding the jet of fluid on the outside by a gas stream.