US3688990A

US3688990A - Spray gun

Info

Publication number: US3688990A
Application number: US168855A
Authority: US
Inventors: Kurt Herman Liedberg
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1971-08-04
Filing date: 1971-08-04
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05
Also published as: GB1360551A; DE2237717C3; FR2144507A5; DE2237717A1; DE2237717B2; IT958548B

Abstract

An optionally electrostatic spray gun is of the type wherein a carrier pressure fluid is supplied to an axial passage having its mouth at the tip portion of the gun, a deflecting head is provided centrally in front of the mouth for deflecting the carrier fluid flow annularly outwardly in transverse relation to the passage when emerging therefrom, and spraying material is atomized and entrained by the carrier flow as it sweeps past an orifice in the gun supplied with spraying material. In such a gun the orifice is arranged circumferentially around the mouth and emits the spraying material as an annular film into the carrier fluid flow substantially in counter-direction to the resultant deflection thereof.

Description

United States Patent Sept. 5, 1972 Liedberg 1 SPRAY GUN [72] Inventor: 'Kurt Herman Liedberg, Skara,

, Sweden [73] Assignee: Atlas Copco Aktiebolag, Nacka 22 Filed: Aug. 4, 1971' 21 Appl.No.: 168,855

51 int. Cl. ..B05b1/26 58] FieldoiSearch; ..239/518,524,,15

56 References Cited v UNITED STATES PATENTS 1,165,240 12/1915 Gaultet'alnn; ..239/5-l8' 1,688,827 10/1928 Nelson ..239/52 4x' 2,089,673 8/1937 Steinmann ..239/518x 2,259,011 10/1941 Taylorn'i ...239/524x 2,586,34 2/1952 Kueblerl ..239/524x .1

3,000,574 9/1961 .Sedlacsik .239/524- 3,059,613- 10/1962 Nakaya....; ..'....'....239/524 3,233,831 2/1966 'Fraser ..239/15 FOREIGN PATENTS oR APPLICATIONS 1,476 4/1880 GreatBritain ..-,...239/524 5/ 1942 Great Britain ..239/524 9/1961 Netherlands ..239/ l 5 1571 ABSTRACT An optionally electrostatic spray gun is of the type wherein a carrier pressure fluid is supplied to an axial passage having its mouth at the tip portion of the gun, ,a deflecting head is provided centrally in front of the mouth for deflecting the carrier fluid flow annularly outwardly in transverse relation to the passage when emerging therefrom, and spraying material is atomized andentrained by the carrier flow as it sweeps past an orifice in the gun supplied with spraying materialnln such a gun the orifice is arranged circumferentially around the mouth and emits the spraying material as thereof.

7 Claims, 4 Figures WW/H/ SPRAY GUN This invention relates to spray guns and more particularly to spray guns of the type wherein a carrier pressure fluid is supplied to an axial passage having its mouth at the tip portion of the gun, a deflecting means is provided centrally in front of said mouth for deflecting the carrier fluid flow annularly outwardly in transverse relation to said passage when emerging therefrom, and spraying material is atomized and entrained by said carrier flow at an orifice in the gun supplied with spraying material and passed by said flow.

The annular spray pattern created by the above typed spray guns is utilized for spraying coating material on the interior surfaces of tubular articles and also on work pieces generally in connection with electrostatic spray coating systems. In the latter case the annular spray pattern serves to create a cloud of finally atomized liquid or powdered material particles around the tip portion of the gun whereupon the particles are transported to settle on the work piece by electrostatic forces. In connection therewith the annular spray pattern can be further directed towards the work piece by a controllable secondary pressure fluid flow from the gun directed generally forwardly of the gun across the annular spray pattern.

Present spray guns of the above type produce a satisfactory radial deflection of the spray but the circumferential particle distribution generally is uneven throughout the annular spray pattern and subject to haphazard variations due to movements of the gun. The resultant coating on the work piece therefore becomes unsatisfactory by the presence of unsufficiently coated spots. It is the main object of the invention to improve and to equalize the coating material distribution throughout the entire annular spray pattern in order to improve the coating produced on the work piece. A further object of the invention is to provide a more even distribution of the atomization process at the instant when the spraying material meets the carrier pressure fluid flow in the gun. A further object of the invention is to apply the secondary pressure fluid flow in a way to contract the annular spray pattern radially whereby the distribution of the spraying material particles within the carrier-flow is concentrated and equalized still further while the particles are in suspension.

For the above and-other purposes there is according to the invention provided an improved spray gun of the type wherein a carrier pressure fluid is supplied to an axial passage having its mouth at the tip portion of the gun, a deflecting means is provided centrally in front of said mouth for deflecting the carrier fluid flow annularly outwardly in transverse relation to said passage when emerging therefrom, and spraying material is atomized and entrained by said carrier-flow at an orifice in the gun supplied with spraying material and passed by said flow, the improvement comprising'a nozzle sleeve-on said gun coaxially around said tip portion thereof and extending forwardly beyond said mouth, passage means in said gun for supplying material into said sleeve, and an annular inwardly directed deflecting ridge on said sleeve spaced forwardly of said tip portion to provide said orifice between said ridge and tip portion annularly around the mouth of said passage.

The above and other purposes of the invention will become obvious from the following description and from the accompanying drawings in which three embodiments of the invention are illustrated by way of example. It should be understood that these embodiments are only illustrative of the invention and that further modifications thereof may be made within the scope of the appended claims.

In the drawings FIG. 1 shows a longitudinal section through the forward portion of a spray gun according to one embodiment of the invention, two alternative embodiments for electrostatic spraying being also included in the illustration.

FIG. 2 is a cross section on the line 2-2 in FIG. 1.

FIG. 3 is a cross section on the line 3-3 in FIG. 1.

FIG. 4 shows partly in section and on a slightly reduced scale a side view of the butt portion of the spray gun in FIG. 1, also optionally adaptable for electrostatic spraying.

The spray gun illustrated in the FIGS. 1 4 is used for distributing spraying material such as paint in liquid or powdery state. When used for spraying granular or pulverulent paint, the paint powder is maintained in a fluidized state by the aid of a flow of pressure fluid such as compressed air helping to keep the powder in movement along its path through the gun. The spray gun is provided with a barrel 10 comprising a spraying material chamber 11 to which spraying material is supplied via a passage 12. Chamber 11 is traversed axially by a needle valve 13 cooperating with a valve seat 14. Valve seat 14 is sealingly secured in the rear end of a nozzle plug 15 which in its turn is threaded fast to the barrel 10 and together with valve seat 14 closes off the forward end of the chamber 11. Centrally andforwardly plug 15 is provided with an axial passage 18 having its mouth 16 in a tubular forward portion 19 of plug 15. On nozzle plug 15 is threaded a frusto-conically shaped nozzle sleeve 20 screwed tight against and countered by a bevelled surface l7-of tubular portion 19. Portion 19 has circumferentially spaced grooves 22, FIG. 2, thereon extending along the generatrix of bevelled surface 17 and directed along the inner conical surface 21 of nozzle sleeve 20 towards an inner annular deflecting surface 23'terminating conical surface 21. Deflecting surface 23 is provided at the rear of an annular inwardly directed ridge 24 on sleeve 20 coaxial with passage 18 and having an inner orifice of substantially the same cross section as passage 18; Ridge 24 is spaced forwardly of the portion 19 providing an inner annular orifice 25 around mouth 16 of passage 18. Deflecting surface 23 adjacent orifice 25 is directed towards the axis of the passage 18 preferably being perpendicular thereto. An inner passage 26 is provided in plug 15 connecting the downstream end of valve plug 14 with the interior of nozzle sleeve 20.

A headed deflecting member 27 comprises a stem 29 supported with annular clearance in passage 18 by an end 34 in threaded engagement with nozzle plug 15 and by suitable supporting wings. Member 27,further comprises a head 28 on stem 29 centrally in front of mouth 16 and ridge 24 and having a suitable radius of curvature at the transition from stem 29. Head 28 has a groove whereby deflecting member 27 may be rotated by a tool such as a screw driver and the axial position of head 28 relative to mouth 16 may be adjusted thanks to the threads on end 34.

In barrel is provided a passage 31 through which a carrier pressure fluid, preferably compressed air, is supplied to a passage 32 in nozzle plug and thence via axial grooves 33 in threaded end 34 into the passage 18. The carrier pressure fluid flow follows annularly along stem 29, sweeps past orifice 25 and is then deflected by head 28v annularly outwardly in directions transverse and substantially perpendicular to passage 18. A clam-ping sleeve 35 is threaded on the end of barrel l0 sealingly engaging a flange on a frusto-conically converging secondary nozzle sleeve 36, thereby causing sleeve 36 to bear against radial lugs 37 on the nozzle plug 15. Secondary sleeve 36 is spaced around the sleeve '20 forming with the frusto-conical portion thereof an annular orifice 38 directed towards the outline of head 28. Secondary pressure fluid, normally compressed air, is supplied to the orifice 38 via a control valve 40 in the butt portion 39 of the gun, a passage 41 in the butt portion 39 and barrel l0, and the interior of clamping sleeve 35 and of secondary sleeve 36. The air flow leaves orifice 38 as an inwardly converging annular shroud directed towards the head 28.

Barrel 10 is supported by butt portion 39 which carries a trigger 43 pivotally thereon adapted to retract the needle valve 13 against a spring bias and simultaneously to open a conventional similarly spring biased seat valve 44. Valve 44 opens access for a carrier pressure fluid, normally compressed air, delivered from a hose 45 and a butt bore 46 to an air chamber 47 within butt portion 39. Chamber 47 communicates with passage 31 of barrel 10 and also receives control valve 40. Control valve 40 has an outwardly projecting stem 42 thereon which is in threaded engagement with butt portion 39 and carries a knob 48 outwardly thereof. By knob 48 control valve 40 may be adjusted axially relative to its seat in chamber 47. Via a hose 49 connected to butt portion 39, spraying material is supplied to passage 12 in the spray gun.

When the gun is used for spraying the interior of tubular work pieces in which case the barrel 10 is formed sufficiently long in order to enable it to be moved along the interior of the work piece, carrier pressure supply hose 45 is connected to a supply of compressed air, while spraying material hose 49 is connected to a pressurized spraying material container or alternatively to a suitable pumping means. Let it be supposed that control valve 40 is closed. When trigger 43 is actuated, the needle valve 13 is opened simultaneously with valve 44. Compressed air is delivered to chamber 47 and thence to

passages

31, 32 and 18. Spraying material is passed from chamber 11 through seat 14 on into passage 26, nozzle sleeve and grooves 22, whereby the flow is divided into separate beams directed towards the outer boundary of deflecting surface 23. The spraying material beams are flattened out when impinging against surface 23 and united into a continuous fully circular and radially inwardly directed film of spraying material which emerges from the orifice 25. The carrier fluid flow simultaneously follows the annular clearance in passage 18 and sweeps past the orifice whereby the film emerging therefrom is atomized and the atomized particles are entrained by the carrier fluid through annular ridge 24 against head 28. Here the carrier fluid flow is deflected annularly outwardly transversely and substantially perpendicularly to passage 18 whereby an annular spray pattern is created. The barrel 10 is moved along the axis of the tubular work piece to be coated whereby the inner surfaces of the latter are coated as they are passed by the annular spray pattern emerging from the gun. The spraying material film created at the deflecting surface 23 assures even circumferential atomization and distribution of the spraying material particles regardless of the handling movements and inclinations of the gun. If it is desired to increase the axial width of the spray pattern, control valve 40 is opened to the desired extent by rotation of knob 48. A secondary pressure fluid flow of compressed air now issues from chamber 47 via passage 41,

clamping sleeve 35 and secondary nozzle sleeve 36 to orifice 38 from which is emitted a converging pressure fluid shroud towards head 28. This shroud influences the annular spray pattern by contracting itradially inwardly in forward direction as dictated by the setting of control valve 40. Such contraction brings the particles closer together equalizing their distribution around the axis and forwardly of the gun.

Another preferred use of the inventive spray gun is in conjunction with an electrostatic field created between the gun and the work piece to be sprayed, in this case an object of arbitrary form and not limited to tubular shape. To this end in one alternative embodiment depicted in FIGS. 1 4, an insulated high tension lead 50 is extended through butt portion 39 and barrel 10 to spraying material chamber 11 in which lead 50 is terminated by an electrode 51. The parts of the electrostatic spray gun are all made of insulating material except for the lead 50 and electrode 51. In use lead 50'is connected to a conventional electrostatic high tension generator, not shown, while spraying material and carrier and secondary pressure fluids are applied as before. The electrode 51 charges the spraying material in chamber 11 and the body of spraying material between the chamber 11 and the annular-orifice 25 passes on trated diagrammatically in FIG. 1 wherein the,el ectrode 51 and lead 50 may be substituted for three charging electrodes 52 protruding axially from secondary sleeve 36 at degrees angular distance from one another, united by a metallic ring 53 therein and connected to an outer insulated lead 54. The cloud of loaded discrete powder particles around the head 28 is charged by the electrodes 52 and subsequently urged towards the object to be coated by electrostatic forces if necessary supported by the axial impetus produced by the converging shroud emitted from orifice 38.

What I claim is:

1. An improved spray gun of the type wherein a carrier pressure fluid is supplied to an axial passage having its mouth at the tip portion of the gun, a deflecting means is provided centrally in front of said mouth for deflecting the carrier fluid flow annularly outwardly in transverse relation to said passage when emerging therefrom, and spraying material is atomized and entrained by said carrier flow at an orifice in the gun supplied with spraying material and passed by said flow, the improvement comprising:

a. a nozzle sleeve on said gun coaxially around said tip portion thereof and extending forwardly beyond said mouth;

b. passage means in said gun for supplying spraying material into said sleeve; and

c. an annular inwardly directed deflecting ridge on said sleeve spaced forwardly of said tip portion to provide said orifice between said ridge and tip portion annularly around the mouth of said passage.

2. Spray gun according to claim 1 in which said tip portion is tubular, said sleeve frusto-conical around said tip portion, and said ridge defines the orifice by a deflecting surface perpendicular to said passage.

3. A spray gun according to claim 2 in which said frusto-conical portion is countered by a cooperating bevelled surface on said tip portion, said tip portion having circumferentially spaced grooves, said bevelled surface directed towards said deflecting surface.

4. A spray gun according to claim 1 in which said deflecting means is a headed member comprising a stem portion supported with annular clearance in said passage and a head for deflecting the carrier flow emerging from said clearance.

5. A spray gun of the type wherein a carrier pressure fluid is supplied to an axial passage having its mouth at the tip portion of the gun, a deflecting head is provided centrally in front of said mouth for deflecting the carrier fluid flow annularly outwardly in transverse relation to said passage when emerging therefrom, a spraying material chamber rearwardly of said passage is' supplied with spraying material, the flow of spraying material from said chamber is controlled by an axially movable needle valve, and spraying material is atomized and entrained by said carrier flow at an orifice in said gun in communication with said chamber and passed by said flow, the improvement comprising: I

a. a nozzle plug on said gun providing a closure for the forward end of said chamber and having said tip portion and passage formed forwardly thereon;

b. a valve seat in said plug for said needle valve;

- c. a nozzle sleeve on said nozzle plug coaxially around said tip portion thereof and extending for-- wardly beyond said mouth;

d. passage means in said plug connecting said seat with the interior of said sleeve; and

e. an annular inwardly directed deflecting ridge on said sleeve spaced forwardly of said tip portion to provide said orifice between said ridge and tip portion annularly around the mouth of said passage.

6. A spray gun according to claim 5-in which said tip portion is tubular, said sleeve frusto-conical around said tip portion, and'said ridge defines the orifice by a deflecting surface perpendicular to said passage.

7. A spray gun according to claim 6 in which there is provided a frusto-conically converging secondary nozzle sleeve on said gun spaced around said sleeve to present an orifice therebetween directed towards said deflecting head, and means in said gun for supplying secondary pressure fluidim said secondary r iozzle sleeve whereby a converging ow of secondary uid is directed towards said head for modifying the annular shape of said carrier flow.

Claims

1. An improved spray gun of the type wherein a carrier pressure fluid is supplied to an axial passage having its mouth at the tip portion of the gun, a deflecting means is provided centrally in front of said mouth for deflecting the carrier fluid flow annularly outwardly in transverse relation to said passage when emerging therefrom, and spraying material is atomized and entrained by said carrier flow at an orifice in the gun supplied with spraying material and passed by said flow, the improvement comprising: a. a nozzle sleeve on said gun coaxially around said tip portion thereof and extending forwardly beyond said mouth; b. passage means in said gun for supplying spraying material into said sleeve; and c. an annular inwardly directed deflecting ridge on said sleeve spaced forwardly of said tip portion to provide said orifice between said ridge and tip portion annularly around the mouth of said passage.

5. A spray gun of the type wherein a carrier pressure fluid is supplied to an axial passage having its mouth at the tip portion of the gun, a deflecting head is provided centrally in front of said mouth for deflecting the carrier fluid flow annularly outwardly in transverse relation to said passage when emerging therefrom, a spraying material chamber rearwardly of said passage is supplied with spraying material, the flow of spraying material from said chamber is controlled by an axially movable needle valve, and spraying material is atomized and entrained by said carrier flow at an orifice in said gun in communication with said chamber and passed by said flow, the improvement comprising: a. a nozzle plug on said gun providing a closure for the forward end of said chamber and having said tip portion and passage formed forwardly thereon; b. a valve seat in said plug for said needle valve; c. a nozzle sleeve on said nozzle plug coaxially around said tip portion thereof and extending forwardly beyond said mouth; d. passage means in said plug connecting said seat with the interior of said sleeve; and e. an annular inwardly directed deflecting ridge on said sleeve spaced forwardly of said tip portion to provide said orifice between said ridge and tip portion annularly around the mouth of said passage.

6. A spray gun according to claim 5 in which said tip portion is tubular, said sleeve frusto-conical around said tip portion, and said ridge defines the orifice by a deflecting surface perpendicular to said passage.

7. A spray gun according to claim 6 in which there is provided a frusto-conically converging secondary nozzle sleeve on said gun spaced around said sleeve to present an orifice therebetween directed towards said deflecting head, and means in said gun for supplying secondary pressure fluid into said secondary nozzle sleeve whereby a converging flow of secondary fluid is directed towards said head for modifying the annular shape of said carrier flow.