Radius edge bell cup and method for shaping an atomized spray pattern

1. A method for shaping the pattern of coating sprayed from a rotary atomizing sprayer device in which coating is supplied to an interior surface of a rotary cup and caused to flow along the cup and to be discharged off a forward edge of the cup from centrifugal force acting on the coating as a result of spinning the cup about an axis of the cup, said method for shaping the pattern comprising:

providing the bell cup with a base and an outer surface extending outwardly and forwardly from the base, and a terminal portion at the forward edge of the bell cup transitioning from the outwardly and forwardly directed outer surface of the bell cup to a more forwardly and less outwardly directed segment adjacent the forward edge and parallel to the axis of the bell cup, the more forwardly less outwardly directed segment being of sufficient axial length for redirecting airflow of an air stream attached to and flowing along the outer surface of the bell cup to a forwardly directed airflow at the forward edge of the bell cup;

providing a plurality of air passage orifices near the base of the outer surface of the bell cup;

pressurizing air to a pressure above ambient air pressure and emitting the pressurized air from the air passage orifices in a first pattern of first shaping air streams against attached to and following the bell cup outer surface, from near the base to and including along the terminal portion;

redirecting the attached first shaping air streams with the shape of the bell cup outer surface at the terminal portion from generally outwardly directed flow relative to the bell cup axis to generally forwardly directed flow parallel to the axis at the forward edge of the bell cup; and

discharging the first shaping air streams from attachment to the outer surface of the bell cup at the forward edge of the bell cup in a generally forwardly directed flow parallel to the bell cup axis adjacent to the coating discharged off the forward edge of the bell cup.

2. The method of claim 1 , including providing the air passage orifices in evenly spaced locations around the base of the cup.

3. The method of claim 1 , including providing a second pattern of second shaping air streams at a pressure greater than ambient pressure, and directing said second pattern of second shaping air streams inwardly toward the forward edge of the bell cup without attachment to the bell cup outer surface.

4. The method of claim 3 , including directing the second pattern of second shaping air streams both inwardly and forwardly from outwardly of and behind the forward edge of the bell cup.

5. The method of claim 4 , including emitting the first pattern of first shaping air streams parallel to the axis of the bell cup.

6. The method of claim 1 , including emitting the first pattern of first shaping air streams parallel to the axis of the bell cup from outwardly of the base of the bell cup.

7. A rotary atomizing sprayer comprising:

a bell cup having a forward edge, said bell cup being rotatable about an axis of said cup;

a smooth inner surface of said bell cup along which coating flows to said forward edge;

a smoothly curved outer surface of said bell cup extending toward said forward edge;

a terminal portion of said smoothly curved outer surface converging with said inner surface at said forward edge, said terminal portion being smoothly curved from a significantly outwardly directed orientation to a forwardly directed segment parallel to said axis of said cup, said outer surface, including said terminal portion thereof, being of sufficient curvature and of sufficient length for redirecting air flow of an air stream attached to and flowing along the outer surface to forwardly directed air flow away from said bell cup parallel to the bell cup axis; and

a shaping air system including a first plurality of first shaping air orifices directed toward said outer surface at least one of at and rearward of said terminal portion, and a source of pressurized air supplying air pressurized above ambient pressure to said first plurality of first shaping air orifices.

8. The rotary atomizing sprayer of claim 7 , including a second plurality of second shaping air orifices connected to said source of pressurized air and directed at said forward edge.

9. The rotary atomizing sprayer of claim 8 , said second plurality of second shaping air orifices being positioned wider than and rearward of said forward edge, and said second plurality of second shaping air orifices directed inwardly and forwardly toward said forward edge.

10. The rotary atomizing sprayer of claim 7 , said first plurality of first shaping orifices being positioned behind said bell cup radially inwardly of said forward edge and directed parallel to said axis of said bell cup.

11. The rotary atomizing sprayer of claim 7 , said bell cup having a base, said forward edge being wider than said base, and said outer surface extending outwardly from said base to said forward edge.

12. The rotary atomizing sprayer of claim 11 , said terminal portion defining a smooth transition from outwardly expanding to forwardly directed, and said forwardly directed segment being adjacent said forward edge.

13. The rotary atomizing sprayer of claim 7 , said cup having a rearward portion, and said outer surface extending inwardly from said rearward portion to said forward edge.

14. The rotary atomizing sprayer of claim 7 , said outer surface being substantially cylindrical.