Application nozzle, application unit and method
An application nozzle, an application unit, and a method are used for applying a liquid or pasty coating medium onto a running surface, in particular onto a running surface in a machine for producing or processing a fibrous web. The application nozzle contains a fluid head which is configured to produce a film from a coating medium or a curtain from a coating medium, and the application also additionally contains a blowing head which is configured to generate a linear jet of gaseous medium. An impact line is additionally provided on which the linear jet of gaseous medium impacts the film or curtain made of the coating medium, thereby forming a spray curtain. The blowing head is arranged such that the spray curtain is oriented in the direction of the running surface.
1 . An application nozzle for an application of a coating medium being a liquid coating medium or a pasty coating medium onto a running surface, the application nozzle comprising:
a fluid head formed to generate a fluid film composed of the coating medium or a curtain composed of the coating medium;
a blow head formed to generate a linear jet of a gaseous medium, wherein an impact line is formed where the linear jet of the gaseous medium impacts the fluid film or the curtain composed of the coating medium, thereby forming a spray curtain, said blow head is disposed so that the spray curtain is directed in a direction of the running surface, wherein said blow head further has a wall; and
a support surface disposed so that the coating medium is discharged from said fluid head onto said support surface, and is guided as the fluid film along said support surface, wherein said support surface is provided at least partially by said wall of said blow head, wherein said support surface has a lower end forming a breaking edge, and the impact line is provided at said breaking edge or at a distance of less than 5 mm from said breaking edge.
2 . The application nozzle according to claim 1 , wherein said breaking edge is provided with a structure.
3 . The application nozzle according to claim 1 , wherein said support surface is provided entirely by said wall of said blow head.
4 . The application nozzle according to claim 1 , wherein a length of the spray curtain from the impact line to the running surface is at most 50 mm.
5 . The application nozzle according to claim 1 , wherein the direction of the spray curtain has a component which is directed counter to a direction of movement of the running surface.
6 . The application nozzle according to claim 1 , wherein the spray curtain has an opening angle δ being less than 30°.
7 . The application nozzle according to claim 6 , wherein said blow head has an outlet with a lip being suitable for influencing the direction and/or the opening angle of the spray curtain.
8 . The application nozzle according to claim 1 , wherein the running surface is a running surface in a machine for producing or processing a fibrous web.
9 . The application nozzle according to claim 2 , wherein said structure of said breaking edge is an undulating structure or a saw tooth structure.
10 . The application nozzle according to claim 1 , wherein a length of the spray curtain from the impact line to the running surface is at most 20 mm.
11 . An application unit for an application of a coating medium being a liquid coating medium or a pasty coating medium onto a running surface, the application unit comprising:
a rotatable transfer roller having a surface functioning as the running surface;
at least one application nozzle, containing:
a fluid head formed to generate a fluid film composed of the coating medium or a curtain composed of the coating medium; and
a blow head formed to generate a linear jet of a gaseous medium, wherein an impact line is formed where the linear jet of the gaseous medium impacts the fluid film or the curtain composed of the coating medium, thereby forming a spray curtain, said blow head is disposed so that the spray curtain is directed in a direction of the running surface.
12 . The application unit according to claim 11 , wherein the application unit defines an application space which is formed and delimited by:
the running surface;
a wall of said blow head;
the spray curtain; and
a point of a narrowest gap between the running surface and said blow head, and wherein the coating medium from said fluid head is applied onto said wall of said blow head such that an entirety of said wall of said blow head inside said application space is covered with the coating medium.
13 . The application unit according to claim 12 , wherein said narrowest gap between the running surface and said blow head is between 2 mm and 20 mm wide.
14 . The application unit according to claim 12 , further comprising a nozzle for generating an air flow, wherein the air flow is directed from outside said application space to said narrowest gap.
15 . The application apparatus according to claim 12 , wherein said application space is shaped so that a tangent of the transfer roller intersects with said wall of said blow head inside said application space at a point of impact of the spray curtain.
16 . A method for applying a coating medium onto a running surface, which comprises the steps of:
providing the application unit according to claim 11 ; and
applying the coating medium to the running surface by means of the application unit.
17 . The method according to claim 16 , wherein the linear jet of the gaseous medium at an output of the blow head has a speed of more than 5 m/s.