Patent ID: 6098904
Filing Date: 2000-08-08
Classification: B05B,F26B,Y10S

Abstract:
Apparatus for blowing a jet of air at a workpiece, the apparatus being configured to project the jet a long distance of penetration, wherein:the apparatus includes a means for supplying pressurised air at a pressure not more than 2 psi;the apparatus includes a nozzle unit;the apparatus includes an air-supply pipe, for supplying the pressurised air to the nozzle unit;the nozzle unit has a mouth, which is open to the atmosphere, and which is so configured that the jet of air emerges therefrom into the atmosphere at a high velocity;the nozzle unit is so configured, in relation to the air-supply pipe, that air passing through the nozzle unit is caused to undergo a substantial increase in velocity;walls of the nozzle unit are defined by the following parameters:(a) axial locations A,B,C,D are present along the axial length of the nozzle unit, in order from upstream to downstream, the axial location D lying at the mouth of the nozzle unit;(b) the nozzle unit has respective diameters at the axial locations, designated DiaA, DiaB, DiaC, DiaD;(c) between axial locations A and D, the nozzle unit has an inward-facing surface, which is smooth and substantially without any sudden change in diameter;(d) an air-entry portion of the nozzle unit lies between axial locations A and B; and(i) between axial locations A and B, the diameter of the nozzle unit is not less than DiaB;(ii) the axial distance LenAB between axial locations A and B is more than 50% of DiaB;(e) a convergence-transition portion of the nozzle unit lies between axial locations B and C; and(i) DiaC is smaller than about 75% of DiaB; and(ii) the convergence-transition portion has walls that define a smoothly convergent air-flow-transition between DiaB and DiaC;(f) a nose portion of the nozzle unit lies between axial locations C and D; and(i) the axial distance LenCD between axial locations C and D differs from DiaD by less than 50% of DiaD; and(ii) the nose portion is right-cylindrical, to the extent that DiaD differs from DiaC by less than 10%;the apparatus includes a bullet, and a bullet-mounting-means, which is effective to mount the bullet in the nozzle unit, in close adjacency to the mouth;the size of the bullet in relation to the nozzle unit, and the disposition of the bullet as mounted in the nozzle, are such as to create, aerodynamically, a reduced-pressure-region inside the jet of air emerging from the nozzle, downstream of the mouth, and to create, in the said reduced-pressure-region, a pressure reduction of such magnitude as to give rise to a substantial force acting upon the jet from the inside thereof, being a force tending to inhibit the jet from spreading outwards;the bullet is aerodynamically faired, to the extent that the bullet is thereby effective to aerodynamically create the reduced-pressure-region inside the jet with minimum turbulence and drag;the bullet is defined by the following parameters:(a) axial locations Q,R are present along the axial length of the bullet, in order from upstream to downstream;(b) the bullet has an outer surface which is smooth, aerodynamically-faired, and substantially without any sudden change in diameter;(c) DiaQ is the maximum overall diameter of the bullet downstream of axial location C, and the axial location Q is the downstream extremity at which the diameter of the bullet is 50 more than 90% of DiaQ;(d) DiaR is the diameter of the bullet at axial location R, DiaR being 25% of DiaQ;(e) axial location R on the bullet lies downstream of an axial location M on the nozzle unit, axial location M being a distance LenMD upstream of axial location D, LenMD being 25% of DiaD;(f) axial location Q on the bullet lies downstream of an axial location N on the nozzle unit, axial location N being a distance LenND upstream of axial location D, LenND being 75% of DiaD.