AUTOMATIC HVLP PAINT SPRAY GUN

Abstract

An automatic HVLP paint spray gun utilizes turbine air atomizing the paint as it is discharged from a central nozzle, as well as for fanning the paint. The turbine air for fanning or the fanning turbine is directed at the paint after it issues through a paint discharge port disposed centrally of the gun. The utilization of turbine air for both atomizing and fanning provides a paint spray gun which operates between psi up to about 10 psi.

Claims

1. An HVLP paint spray gun, comprising: (a) a housing; (b) a tubular extension mounted onto the housing and having a first passageway; (c) an air cap mounted on the tubular extension for discharging paint, the air cap having a nozzle in communication with the first passageway; (d) a central paint discharge opening for directing turbine air at the discharging paint; (e) a first source of turbine air for delivering atomizing turbine air to the air cap for the discharging paint; and (f) a second source of turbine air for delivering fanning air to the air cap and being directed at the discharged paint.

2. The HVLP paint spray gun of claim 1, which further comprises: a trigger and a source of compressed air; the compressed air for regulating the trigger; the trigger for controlling paint delivered through the first passageway to the air cap.

3. The HVLP paint spray gun of claim 1 wherein: the nozzle has a plurality of radially projecting wings having outer ends disposed on a cylindrical surface; the surface being coaxial with the axis of the nozzle.

4. The HVLP paint spray gun of claim 1 wherein: the tubular extension includes a turbine air chamber in fluid communication with the air cap, turbine air passing from the chamber through the air cap atomizes paint discharged through the central opening.

5. The HVLP paint spray gun of claim 1, which further includes: a passageway for delivering compressed fanning turbine air to the already atomized paint.

6. The HVLP paint spray gun of claim 5, wherein: the fanning air passageway is provided at the forward end of the tubular extension proximate the air cap at a location on the tubular extension to a position opposite to that of the atomizing turbine air.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0036] FIG. 1 is a perspective view of an automatic HLVP paint spray gun embodying the present invention hereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Referring to FIG. 1, a spray gun 200 embodying the present invention comprises an improvement on the spray gun embodiments shown and described in the aforementioned Toth U.S. Pat. No. 5,080,285. The spray gun 200 according to this invention includes certain of the features shown and described in the embodiments of the Toth '285 patent and the same numbers will be used herein to refer to or describe common structure and function incorporated into the spray gun 200.

[0038] In a preferred embodiment according to this invention, the spray gun 200 includes a main housing designated generally at 10, a generally cylindrical or tubular extension 12 secured to the forward end of the housing 10, the extension including a forwardly projecting hollow tubular member 34, and an air cap 14 having a rearward end mounted on the front end of the extension 12.

[0039] As will be detailed herein, the air cap 14 is adapted to receive and discharge paint from the spray gun and direct turbine air at the spray both for atomizing and forming the paint discharged into a conical spray and fanning the conical shape into a thin elliptical configuration.

[0040] The forward end of the air cap 14 includes a nozzle 24 and a central or discharge opening 26, the nozzle projecting coaxially through the central or discharge opening 26. The nozzle 24 is formed with a forwardly convergent tapered or conical bore 28 which terminates at an orifice 30 at the front end thereof. The nozzle 24 includes a threaded shank 32 which is threadably received within the forward end of tubular member 34 of the extension 12.

[0041] The tubular member 34 includes a central passage 36 that communicates with a bore 35 formed in the main housing 10.

[0042] Paint under pressure is supplied to the central passage 36 via a first fitting 38 threadably connected to the housing 10.

[0043] The rear or right hand end of the central passage 36 is closed by a packing 43. A threaded plug 42 slidably supports and guides an elongate rod-like needle valve 44 having a tapered forward end 46, which may be seated in the tapered or conical bore 28 of nozzle 24, to close the orifice 30.

[0044] The gun hereof, also, includes a trigger which is regulated by compressed air, as described below. The trigger includes a piston 150 axially mounted within the housing 10 to engage an enlarged diameter portion of an adjustable locknut 48 threaded on needle valve 44 to draw the valve to the right as viewed in FIG. 1 when air pressure is applied in a conventional manner. The needle valve 44 extends rearwardly past the piston 150 and continues through the housing 10 to be coupled to an adjustment knob 50 mounted within the housing.

[0045] A spring loaded coupling 47 is disposed between the needle valve 44 and the adjusting knob 50, such as spring 49, of conventional construction which acts to continuously bias needle valve 44 in a forward manner to its closed seated position within the nozzle 24. The adjustment knob 50 essentially locates the end limit of the movement of the needle valve 44 in a rearward manner to establish a maximum opening of the nozzle 24 when the piston 150 is fully moved rearwardly via the compressed air source, against the force of spring 49.

[0046] The nozzle 24 is formed with a plurality of radially projecting wings 52 having radially outer ends lying on a cylindrical surface coaxial with the axis of the nozzle 24. The rearward side of the air cap 14 is formed with a counter bore 54 of a diameter such that the outer ends of the wings 52 of the nozzle are slidably received within the counter bore 54. The inner end of the counter bore 54 merges with an inclined conical bore 56, which extends from the counter bore 54 to pierce the front side of the air cap 14, thereby establishing a central or discharge opening 26 surrounding the forward tip of the nozzle 24. The inclination of the wall of the conical bore 56 and the inclination of the forward side of the nozzle 24 and the axial dimensions of the air cap 14 and the nozzle 24 define an air passage.

[0047] The nozzle 24 and the air cap 14 are assembled in the gun between the central or discharge opening 26 and a chamber 60 having an enlarged diameter counter bore at the rearward side of the air cap 14. The air passage extends from the central or discharge opening 26 through the space between the opposed incline of the conical bore 56 of the air cap 14 and into the nozzle 24, and thereafter through the spaces between adjacent wings 52 of the nozzle 24. This construction is more particularly described in U.S. Pat. No. 4,744,518, issued May 17, 1988 to Toth, the disclosure of which is hereby incorporated by reference, including the drawings.

[0048] The tubular housing extension 12 is formed with an annular wall 64 in its forward end of the same diameter as the mating member 62 in the air cap 14, and the wall 64 and the mating member 62 define the turbine air chamber 60. The turbine air chamber 60 is of a diameter larger than the outer diameter of bores 54 and 56 and is in communication therewith such that air passes through the chamber 60, into the bores 54, 56 and exits via the air cap 14 through an orifice 30.

[0049] Turbine air under pressure is supplied to the chamber 60 via an air supply passage of a second fitting 76 threaded into the extension 12. This turbine air provided via the second fitting 76 is used for atomizing paint discharged from the central or discharge opening of the air cap and generally into a conical spray. Preferably, the second fitting 76 is at the forward end of the spray gun and proximate the air cap 14.

[0050] According to a preferred embodiment of this invention, turbine air under pressure is supplied from the extension 12 to the air cap 14 for fanning the conical paint spray from the discharge bores 52, 54. Preferably, the turbine air is introduced at a forward end of the extension 12, proximate to the air cap 14, and opposite to the fitting 76 that receives turbine air for atomizing. This turbine air is used exclusively for directing air to the atomized paint being discharged from the discharge ports 106 of the air cap 14 whereby to effect a desired fanning of a conical spray.

[0051] In this regard, a passage 91 is formed between an outer annular ring 110 of the extension 12 and the internal annular wall 64.

[0052] According to this preferred embodiment of this invention, a third fitting 176 is threadably attached to the tubular extension 12 and delivers compressed turbine air through a passage 170 of the fitting 176 to the passage 91.

[0053] The forward location of the third fitting 176 operates to increase the velocity of air through the passage 104.

[0054] Unexpectedly, by the configuration of the passageway 91 and location of the third fitting 176 herein, the fan dimension can be increased by as much as four inches, without splattering or developing paint droplets and obviates poor surface appearance or paint waste. This is a significant cost reduction in a typical paint situation.

[0055] It is to be appreciated that the preferred embodiment of the paint spray gun of the present invention utilizes turbine air both for atomizing as well as for fanning, to provide a low pressure, high volume system.

[0056] Likewise, paint and turbine air are admixed in the nozzle 24 and delivered. However, in accordance with this embodiment, turbine air is employed both to control atomizing and fanning. The turbine air is heated to a high volume and a low pressure and delivered from a remote source (not shown) into the chamber 60 and passageway 91.

[0057] In this embodiment, no adjustment rod is used to control the amount of turbine air delivered through the port 106 after passing through the passageway 91 of the tubular extension 12. Rather, only a turbine at high volume and low pressure is employed, which is regulated by a simple ball valve (not shown).

[0058] By employing all turbine air in this embodiment, there is still further provided a low pressure, high volume paint spray gun. For example, the turbine air at about 7 psig entering passage 91 will exit port 106 at about 6 psi, but at a volume of about 5-6 cfm.

[0059] It should be noted that the axial movement of the trigger piston 150 is accomplished with compressed air which is delivered through a fitting 71. However, it is solely turbine air which controls the atomizing and fanning of the paint discharged. The construction hereof enables a paint spray gun to operate efficiently between about psi and up to about 10 psi.

[0060] Operating Parameters: This is a typical example of the operating parameters for the automatic paint spray gun of the present invention, wherein turbine air is used for both atomizing and fanning.

TABLE-US-00001 Atomizing Air Supply Fanning Air Supply Pressure Range 1-10 psi 1-10 psi Flow Rate 1-20 cfm 1-10 cfm Temp. Range Ambient 5 F.-160 F. Ambient 5 F.-160 F. Discharge Orifice - inch ID 2 mm-5 mm Hose Length Range 4-60 feet 4-60 feet Control Means High Flow Ball Valve High Flow Ball Valve

[0061] Atomizing air and fanning air are flowing at all times independent of fluid discharge. Additional solenoid valves can be placed upstream from the pressure control ball valve to prevent the constant air bleeding if required. These must be opened just prior to triggering the fluid flow from the nozzle to inside adequate atomization of paint at the beginning of discharge from the nozzle orifice.

[0062] While the paint spray gun of the present invention has been described in conjunction with a specific embodiment, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the disclosure herein. It is intended that the metes and bounds of the invention be determined by the appended claims, rather than by the language of the above specification, and that all such alternatives, modifications, and variations which form a functional or conjointly cooperative equivalent are intended to be included within the spirit and scope of these claims.

LIST OF REFERENCE NUMERALS

[0063] 10 Housing [0064] 12 Tubular Extension [0065] 14 Air Cap [0066] 24 Nozzle [0067] 26 Central or Discharge Opening [0068] 28 Tapered Bore or Conical bore [0069] 30 Orifice [0070] 32 Threaded Shank [0071] 34 Tubular Member [0072] 35 Bore [0073] 36 Central Passage [0074] 38 First Fitting [0075] 42 Threaded Plug [0076] 43 Packing [0077] 44 Needle Valve [0078] 47 Spring loaded coupling [0079] 48 Locknut [0080] 49 Spring [0081] 50 Adjustment knob [0082] 52 Wings [0083] 54 Counter bore [0084] 56 Conical bore [0085] 60 Air chamber [0086] 62 Mating member [0087] 64 Annular wall [0088] 71 Fitting [0089] 76 Fitting [0090] 91 Passage [0091] 104 Passage [0092] 106 Port [0093] 110 Annular ring [0094] 150 Piston [0095] 170 Passage [0096] 176 Fitting