Patent ID: 8262002

Claim:
A pressure swirl atomizing nozzle for spraying a curable composition onto a surface ( 6 ) to produce a polymeric layer ( 9 ) thereon, which nozzle ( 5 ) comprises: an orifice piece ( 16 ) defining a funnel-shaped cavity and an exit orifice ( 17 ) which has a length L o and a diameter D o , the funnel-shaped cavity having a longitudinal axis (a) and ending at its downstream extremity in the exit orifice ( 17 ); and an injector piece ( 18 ) closing off said funnel-shaped cavity at its upstream extremity so that the funnel-shaped cavity forms a swirl chamber ( 19 ) between a front side of the injector piece ( 18 ) and the exit orifice ( 17 ), the injector piece ( 18 ) comprising at least two swirl ports ( 20 ), each of which has an inlet and an outlet and each of which end in the swirl chamber ( 19 ) for injecting the curable composition according to a predetermined overall direction ( 21 ) into the swirl chamber ( 19 ) and for thereby imparting swirl to the curable composition; wherein: each of said swirl ports ( 20 ) has a smallest cross-sectional area A sp , measured in a cross-sectional plane (C) perpendicular to said predetermined overall direction ( 21 ), the sum A sp,tot of the smallest cross-sectional areas A sp of the swirl ports ( 20 ) being smaller than 0.9 mm 2 , preferably smaller than 0.6 mm 2 ; wherein the swirl chamber ( 19 ) has a side wall ( 24 ) which has a surface area A so and which forms, in longitudinal sections through said longitudinal axis (a), an average angle α av with a transverse plane (B) perpendicular to said longitudinal axis (a), which average angle α av is comprised between 30 and 60°; and wherein the swirl ports ( 20 ) are oriented so that said predetermined overall directions ( 21 ), when projected at right angles onto a longitudinal plane (A) comprising said longitudinal axis (a) and being perpendicular to a straight line (b) which intersects said longitudinal axis (a) perpendicularly and which passes through the centre (c) of the outlet of the respective swirl port ( 20 ), form substantially an angle β with said transverse plane (B), the angle β being comprised between 30 and 60°; characterised in that, the injector piece ( 18 ) is situated at such a distance (H) from the exit orifice ( 17 ) that 6 ≤ A sc * cos ⁢ ⁢ β A sp , tot ≤ 17 and the ratio L o /D o is smaller than 1.