Spray discharge assembly
A spray discharge assembly is provided for use with an aerosol spray device comprising a pressurizable container holding a liquid to be discharged from the device by a propellant. The spray discharge assembly incorporates an approach channel having at least one inlet and an outlet, a flow conduit upstream of the approach channel in the direction of liquid discharge for supplying fluid to be discharged to the approach channel, at least one jetting orifice through which fluid from the conduit passes and issues as a jet into the approach channel through the inlet thereof, and a discharge orifice into which fluid from the approach channel passes via the outlet thereof to issue as a spray from the device. The outlet of the approach channel is surrounded by a sharp edge, and the jetting orifice is configured for directing the jet against the sharp edge.
1. A spray discharge assembly for an aerosol spray device comprising a pressurized container holding a liquid to be discharged from the device by a gaseous propellant that is a gas at a temperature of 25° C. and a pressure of at least 50 bar, the spray discharge assembly adapted to be inserted in a fluid flow path between fluid in the container and a nozzle, the spray discharge assembly comprising:
(i) an approach channel having at least one inlet and an outlet,
(ii) a flow conduit, located upstream of said approach channel in a direction of liquid discharge from the nozzle, for supplying fluid to be discharged to the approach channel,
(iii) at least one jetting orifice through which fluid from the conduit passes and issues as a jet into the approach channel through the inlet thereof, the jetting orifice being located between the flow conduit and the approach channel, and
(iv) a discharge orifice into which fluid from the approach channel passes via the outlet thereof to issue as a spray from the nozzle, the discharge orifice being located downstream of the approach channel,
wherein the flow conduit has at least one liquid inlet and at least one gas inlet configured to generate a bubble-laden flow in the flow conduit;
wherein the outlet of the approach channel is surrounded by a sharp edge and the jetting orifice is configured for directing the jet against said edge;
wherein the discharge orifice comprises a straight-sided cylindrical bore with a diameter defined by the outlet of the approach channel;
wherein the length of the straight-sided cylindrical bore is 4 to 15 times its diameter;
wherein the jetting orifice, sharp edge and discharge orifice are positioned to enable separation of the bubble-laden flow from an interior surface of the straight-sided cylindrical bore over an upstream region thereof; and
wherein the length of the straight-sided cylindrical bore is such that reattachment of the bubble-laden flow to the interior surface of the straight-sided cylindrical bore at a downstream region thereof is enabled.
2. An assembly according to claim 1 , wherein the approach channel is cylindrical and has a diameter of 0.5 to 3 mm and an axial length of 0.2 to 2 mm.
3. An assembly according to claim 2 , wherein the approach channel has a diameter equal to its axial length.
4. An assembly according to claim 3 , wherein the diameter and the axial length of the approach channel are both about 1 mm.
5. An assembly according to claim 1 , wherein the discharge orifice is cylindrical and has a uniform diameter of 0.1 to 0.75 mm and a length from 4 to 12 times its diameter.
6. An assembly according to claim 5 , wherein the discharge orifice has a diameter of 0.20 to 0.50 mm.
7. An assembly according to claim 6 , wherein the diameter of the discharge orifice is about 0.3 mm.
8. An assembly according to claim 1 , comprising a plurality of said jetting orifices.
9. An assembly according to claim 8 , comprising three to six of said jetting orifices.
10. An assembly according to claim 9 , comprising four of said jetting orifices.
11. An assembly according to claim 1 , wherein the at least one jetting orifice has a diameter of 0.1 to 0.5 mm.
12. An assembly according to claim 11 , wherein the jetting orifices have a diameter of 0.25 mm.
13. An assembly according to claim 1 , wherein said sharp edge presents a reflex angle of at least 270°.
14. An assembly according to claim 13 , wherein said sharp edge presents a reflex angle of 270° to 330°.
15. An assembly according to claim 14 , wherein said sharp edge presents an angle of about 270° to the interior of the approach channel.
16. An assembly according to claim 1 , wherein said sharp edge is provided at the apex of a conical projection within which the discharge orifice is at least partly formed.
17. An assembly according to claim 1 , wherein a radius of curvature at the sharp edge is less than 100 microns.
18. An assembly according to claim 17 , wherein the radius of curvature at the sharp edge is less than 25 microns.
19. An assembly according to claim 1 , wherein the discharge orifice is contiguous with, and defined by, the diameter of the outlet of the approach channel.