US3344992A

US3344992A - Spray gun

Info

Publication number: US3344992A
Application number: US340466A
Authority: US
Inventors: Edward O Norris
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-01-27
Filing date: 1964-01-27
Publication date: 1967-10-03
Anticipated expiration: 1984-10-03
Also published as: DE1425890A1; GB1049261A

Description

Oct. 3, 1967 E. o. NoRRls 3,344,992

SPRAY GUN Filed Jan. 27, 1964 5 Sheets-Sheet l mvENToR' bu/AED 0. NOR/@f5 Y B AIIC-RN EY 'v E. O. NORRIS Oct. 3, 1967 SPRAY GUN Filed Jan. 27, 1964 5 Sheets-Smet 2 oct. 3, 1967 .5o. NQRRIS 'Y 3,344,992

` SFRA? GUN Filed Jan. 2v, 1964 s sheets-Sheet s NIMH ATTORNEY United States Patent This invention relates to air spray guns of the type wherein a stream of liquid is atomized by a stream ofV compressed air, and has for an object to provide a spray gun of the above type having means, including controllable, rearwardly directed gas jets, to control the spray pattern and the spray particle velocity.

Another object is to provide a spray gun of the above type in which the width of the spray fan can be varied according to requirements.

Another object is to provide an electrostatic spray device of the above type having novel and improved characteristics.

Various other objects and advantages will be apparent las the nature of the invention is more fully disclosed.

In accordance with the present invention the spray gun includes a barrel having coaxial discharge means for the liquid to be sprayed and for the atomizing air which impinge as they are di-scharged from the nozzle to form a spray which iirst decreases -in cross sectional area to a zone otminimum diameter and thereafter increases in diameter to form a cone of Vspray having a circular crosssection. Means is provided to direct a pair of air jets inwardly and rearwardly against the spray cone at the zone of minimum diameter in a manner to retard the spray particles and to distort or flatten the spray pattern int-o elliptical form. This causes the spray to spread out into a fan in which the spray particles advance with low velocity so that they can be readily deflected electrostatically to the various parts of the work .piece to be coated. Means is also provided for reducing the velocity of the air jets when desired for decreasing the width of the spray fan and also for increasing the velocity of the spray particles as for coating recessed parts.

The nature of the invention will be better understood from the following description, taken in connection with the accompanying drawings in which a specic embodi- Vment has been set forth for purposes lof illustration.

In the drawings:

FIG. 1 is a longitudinal, vertical, cross section of the main portion of the spray gun; v

FIG. 1A is a similar -section of a portion ,of the handle of the gun which when joined to FIG. 1 along the line a-a illustrates the complete gun;

FIG. 2 is a detail illustrating one form of air horn;

FIG. 3 is a vertical, transverse section taken on the line 3 3 of FIG. 1;

FIG. 4 is a similar transverse section taken yon the line 4 4 of FIG. l;

FIG. 5 is a transverse section taken on the line 5-5 of FIG. 1 showing the upper portion of the handle;

FIG. 6 is a side elevation of a portion of the gun of FIG. 1;

FIG. 7 is a transverse section taken on the line 7 7 of FIG. 6;

FIG. 8 is a transverse section taken on the line 8 8 of FIG. 1 looking in the direction of the arrows;

FIG. 9 is a transverse section taken on the line 9-9 of FIG. 6;

FIG. 10 is an axial section taken on the line 10-10 of FIG. 9;

FIG. 11 is a `detail of the cam and cam follower;

FIG. 12 is a transverse section through the spray taken on the line 12-12 of FIG. l; showing the elliptical spray pattern;

ICCV

FIG. 13 is a similar section illustrating a spray pattern showing a substantially circular section;

FIG. 14 is a det-ail view, partly in section, on a reduced -scale illustrating a further embodiment of air horn support; and

FIG. l5 is a section taken on the line 15-15 of FIG. 14.

Referring to the drawings more in detail, the spray gun is shown as comprising la barrel 13 Aof plastic material having a longitudinal bore 14 to constitute a passage for the paint or other material to be sprayed, a passage 15 for Iconducting air to the nozzle, and a passage 16 for conducting air to the horns t-o be described. The front end of the barrel 13 has a central bore 19 registering with the longitudinal passage 14 of the barrel 13 into which a tube 20 is threaded. A hollow annular horn ring 21 having an annular passage 22 therein is disposed against the end surface 23 of the barrel 13 (annular support member 17) and secured by a ring nut 24 carried by the barrel 13 (member). The annular passage 22 communicates with the air passage 16 in the barrel 13. A pair of hollow horns 25 in the form of J tubes are attached to the ring 21 in communication with the annular passage 22. The horns 25 taper in size toward their freeV ends which are bent inwardly to direct the airrtherefrom at an acute angle toward a predetermined zone 26 in the spray 27 to be described. The horns 25 and the ring 21 may be madeV of metal and coated with an insulating material 28 or maybe made of plastic.

The forward end of the tube 20 is threaded to receive a clamping nut 3'1 which secures tapered nozzle member 32.

An inner tube 33 is provided with a flange 34 seated within the tube 20 and is aligned within the tube 20 by iins 35 to provide an air space 36 therebetween. The lins 35 terminate in advance of the flange 34 to provide an annular air passage 37 between the tubes 20 and 33.

The barrel 13 has an annular passage 38 communicating with the air passage 15 in the barrel 13'. The tube 20 is formed with openings 40 to supply air from the annular passages 38 to the annular passage 37. The tube 33 is formed with the external rib 39 registering with the discharge end of the tapered nozzle member 32 to provide a concentric annular air discharge orice.

The tube 33 terminates in a conical valve seat 41 against which a valve head 42 seats. A valve stem 117 extends from the head 42 to sleeve 47. Nonconducting rods 44 extend from sleeve 47 through a spring pressed stuiiing gland 45 in the rear end of the barrel.

A compression spring 46 extends between the flange 34 and the sleeve 47 on the valve stem 117 to bias the valve to closed position. Suitable pins connect valve 117 to sleeve 47 and the sleeve to rod 44.

Handlemembers 50 are formed by sections 51 which are clamped around the rear portion of the barrel 13 and with handle portions 52 and are formed with flanges 53 which are clamped around the rear portion of the barrel 13 and with handle portions 52 and are formed with flanges 53 which -are clamped by bolts 54. A paint tube 55 extends through the handle 52 and is threaded into a -bore 56 in the bar-rel 13= which communicates with the axial passage 14. An air tube 58 extends through the 'handle 52 and is threaded into a bore 59 in the barrel 13 which communicates with the passage 15.

A high voltage wire 60 is connected to a spring 61 which is secured in the tube 58 and supports a resistor 62 centrally of the tube 58 to provide an annular passage for cooling air over the surface of the resistor. The resistor 62 is connected by a wire 63 which extends through the bore 59 and an axial bore 65 to a washer 66 which is clamped between the tube 20 and a shoulder in the central bore 19, to provide an electrical connection to the nozzle and to the horns. The washer 66 also serves to seal the paint passage 14 from the air passage around the tube 20. The axial bore 65 is lled with a hardened sealing compound. A grounded sheath 67 is disposed around the air tube 58 and is connected to the handle S2 by a screw 68.

The passage 16 from which air is supplied to the horns is connected by a transverse passage 70 (see FIGS. 6, 9 and to a longitudinal passage 71 of larger diameter which in turn is connected by a transverse passage 72 to the 4passage 15. A piston valve 73 slides in the passage 71 and is adapted to variably close the opening to the passage 72. The valve 73 is actuated by a stem 74 which projects through a packing gland 75 beyond the rear end of the barrel 13.

A trigger S0 is pivoted on a pivot 81 supported in ears 82 on the handle pieces 52 in a position to be gripped by the operator. The trigger 80 carries a cross arm 83 to which a bridge member 84 is pivoted and is adapted to be moved forwardly as the trigger is operated. A rotatable cam 8S is journalled between ears 86 from the sections 51 and has a depending arm 87 which is adjustably secured to the bridge member S4 by a screw 88 having a ball 89 and socket connection with the arm 87 and adjustable by a screw driver slot in ball 89. A compression spring 90 is interposed between the bridge piece 84 and the arm 87. A cam follower arm 91 is pivoted at 92 on the above mentioned section 51 and bears against a cam surface on the cam 85. This surface includes a sharp rise 93 (sce FIG. 11) followed by a slowly receding surface 94 which surfaces are successively engaged by the cam follower arm 91 as the trigger is actuated. An adjusting screw 96 is carried by the arm 91 in a position to engage and actuate the valve stem 44 for variably opening the paint supply Valve. The arrangement is Such that the paint valve is fully opened by a limited actuation of the trigger and is thereafter slowly closed as the trigger is further actuated.

A setting spring 97 is interposed between the screw head 96 and the arm 91 for maintaining the adjustment of the screw 96.

A screw 98 in an arm 99 carried by the bridge piece 84 is positioned to engage and actuate the valve stem 74 for controlling the air supply to the horns 25. The piston valve 73 is normally held in open position by a spring 100. The adjusting screw 98 is set to provide a clearance with the valve stem 74 so that the valve remains fully open when the trigger is actuated to an extent to fully open the paint valve 42 and to gradually close the air passage as the trigger is further retracted, so that the air to the horns through the passages is gradually reduced (71, 15, 72, 70, 16 and 22).

A tension spring 101 between an ear 102 on the bridge piece 84 and pivot pin 103 of the cam 85 biases the bridge member to its retracted position. A sliding pin 106 held outwardly by a spring 107 is slidably held in the bridge piece 84 and held in adjusted position by setting nuts 108. The pin 106 is set to engage a surface 109 on one of the clamp sections 51 to serve as a feeler to indicate the full open position of the paint valve. A screw 110 in the bridge piece S4 provides a stop to limit the movement of the trigger and the actuation of the valves.

In FIG. 1 the horns are shown in the form of tubes secured to the ring 21. In FIG. 2 the horns are shown as integral with the ring 21 and are provided with separate end pieces 111 which may be removed for cleaning or for varying the orifice size.

In the embodiment of FIGS. 14 and 15 air jets 125 are mounted on U-shaped tubes 126 which are supported on the horn ring 21 at diametrically opposite points. In this way each support is located out of the direct path of the air jet from the opposite nozzle so that build up of paint on these elements is avoided.

For manually opening the paint valve as for cleaning the nozzle -a bell crank lever 112 is pivoted to the sections 51 by a -pin 113 and is formed with a horizontal leg 114 adapted to engage the cam follower arm 91 to force the same into fully open position, and with an upstanding arm 115 positioned for manual actuation. A stop 116 limits the movement of the lever 112.

In operation atomizing air is supplied from the tube 58 through the passage bore 59 and passage 15, annular passage 38, and through openings 40 in the tube 20 to the annular orice 37 between the cap 32 and the tube 33 where it is discharged in a jet of cylindrical cross section. This air is supplied at all times whle the spray gun is in operation.

Paint or other liquid to be sprayed is supplied from the tube 55 through passages 56 and 14, to the nozzle formed by the valve head 42 and its seat 41. This valve is normally closed but is opened for spraying when the trigger is retracted to an extent to cause the sharp rise 93 of the cam S5 to engage and actuate the cam follower 91 to advance the valve 42 to an open position, the extent of which is determined by the setting of the

screws

89 and 96. The liquid is thus discharged from the oriiice around the valve 42 in the form of a cone which is immediately contracted by the air stream to form an atomized spray which rst decreases in cross-section to a zone 26 of minimum cross-section and thereafter diverges in an expanding cone 27 of spray of substantially circular crosssection.

The spray particles in the jet above described are discharged with a substantial velocity toward a work surface These particles are further directed to a work surface by an electrostatic charge which is supplied by the high voltage wire 60 through the resistor 62 and wire 63 to the metallic tube 20 through which the liquid passes.

In accordance with the present invention the velocity of the spr-ay particles is substantially reduced and the cross-sectional shape of the spray pattern is modified by air jets 119 `from the horns 25 which are ydirected to impinge on the spray cone in the zone 26 of minimum crosssection and at diametrically opposite points 120.

This horn air stream passes from the tube 58 through passages 59 and 15 to the annular passage 22 in the horn ring 21, thence to the horns 25 from which it is discharged angularly inward toward the zone 26 and rearwardly of the direction of the stream of the spray particles. The air valve 73 is normally retracted from the passage 72 when the trigger is in full spray position so that maximum air pressure is supplied to the horns.

This air stream, impinging on the spray cone at the zone 26, distorts the cross section of the spray to an elongated ellipse having reentrant sides at the points of impingement of the air jets and causes the `diverging spray cone to take the lform of an elongated ellipse as shown in FIG. 12. This ellipse may be closed to a predetermined extent to form a fan shaped spray pattern, the extent of the spread of the fan being determined by the air pressure and the velocity of the air discharge from the horns 25.

The air from the horns 25 passes in a direction having a large axial component and opposed to the advance of the spray particles. This component of the horn air serves to reduce the velocity of the spray particles to an extent such that they are readily deiiected by the electrostatic charge to the work surface. In this way maximum deposition efficiency is obtained. A

During the operation of the spray gun it may be desirable at times to increase the spray velocity, for example, in order to reach recessed parts.

This is accomplished by retracting the trigger 80 from the full-on position against the increased resistance of the spring pressed plunger 106. As the trigger is thus retracted the screw 9S engages the valve stem 74 to progressively advance the piston valve 73 for restricting the opening of the air passage 72 and thereby reduce the air flow to the horns 25. As the horn air iiow is decreased the retarding effect of the horn air on the spray is decreased and the velocity of the spray particles is correspondingly increased. At the same time the distortion of the horn airton the spray pattern is reduced and the spray pattern is altered from the eliptical form shown in FIG. 12 to the circular form shown in FIG. 13. Hence the width of the spray fan i is decreased as the velocity of the spray particles is increased.

In order to prevent excessive paint deposition in the narrowed spray pattern which results when the horn air is reduced, the rotation of the cam 85 causes the inclined surface 94 to engage the cam follower 91 and slightly close the spray valve so as to decrease the amount of liquid supplied to the spray nozzle. In this way both the spray pattern width and the spray volume can automatically be correlated.

The barrel 13, ring nut 24 and tubes 58 land 55 are made of plastic and the remaining parts may be made of metal and coated with an insulating material to protect the operator from the high Volt-age which is used for charging the spray particles. The resistor y62 prevents excessive current ow in the event of a,7 short circuit. The air ow over this resistor and over the connecting wires serves to provide cooling for these elements.

It is important that the handle be conductive and be grounded.

What is claimed is:

1. A spray gun of the -atomizing type, comprising:

(a) spray nozzle means for discharging spray liquid and atomizing gas under pressure and at a substantial -forward Velocity along a predetermined spray axis to achieve effective atomization -of said spray liquid,

(b) a plurality of gas jet nozzles disposed forwardly of said spray nozzle means,

(c) said jet nozzles being disposed in symmetrical opposed relation and being directed toward the spray axis and rearwardly relative to said spray, and

(d) means to supply gas under pressure to said jet v nozzles, to direct gas jets therefrom toward the spray axis and rearwardly in impinging relation to, and in a common zone of, the atomized spray issued from said spray nozzle means,

(e) said jet nozzles and jet gas supply being so related to the spray nozzle means that the forward velocity of said atomized spray is substantially reduced by the impingement of said gas jets, to achieve effective deposition of the spray liquid,

(f) said jet gas supply and jet nozzles being so balanced and related as to signicantly decelerate and shape said atomized spray while maintaining said spray substantially aligned with said spray axis.

2. The spray gun of claim 1, further characterized by:

V(a) said spray nozzle means including means to discharge gas from an annular outlet generally surrounding an annular outlet for spray liquid, in a manner to form an atomized spray which first converges and then diverges as it moves forward from said outlets, and

(b) said jet nozzles being disposed to direct said gas jets int-o impingement with said spray in a region of relatively maximum convergence.

3. The spray gun of claim '2, further characterized by:

(a) means for imparting an electrostatic charge to the particles of atomized spray liquid.

4. The spray gun of claim 1, further characterized by:

(a) valve means being provided for effecting fbalanced variation in the velocity of said gas jets relative to the velocity of said atomized spray issued by said spray nozzle means, whereby to variably control the decelerating elfect of said gas jets.

5. The spray gun of claim 1, further characterized by:

(a) a gas supply passage being provided for the flow of gas toward said jet nozzles and said spray nozzle means, and

(b) means being provided for applying a high voltage electric potential to said spray nozzle means, including a resistor,

(c) said resistor being mounted within said passage, in a position whereby air passing therethrough flows over and around said resistor in direct heat transfer relation,

(d) said passage having an enlarged portion to accommodate the presence of said resistor while permitting adequate flow of gas. Y

`6. The spray gun of claim 1, further characterized by:

(a) said gun having a gun body portion mounting said spray nozzle means at its forward end,

(b) support means projecting forward of said body portion and mounting a pair of said gas jet nozzles in an opposed relation, on opposite sides of said spray axis,

(c) said support means having enlarged open areas in the regions directly aligned with the discharge axes of said gas jet nozzles.

7. A spray gun of the gas atomizing type, comprising:

(a) a barrel having concentric passages forming a nozzle adapted to discharge a liquid to be sprayed and an atomizing gas in the form of a cone of spray which advances forwardly along a predetermined spray axis and tapers inwardly to a zone of minimum cross section and then outwardly in a diverging cone,

(b) members carried by said barrel having passages terminating in jet nozzles positioned to direct jets of gas onto said cone of spray from opposite sides at said zone of minimum cross section in a rearwardly inclined direction relative to the spray and adapted to distort the spray pattern and to significantly retard the velocity of the spray particles,

(c) said gun having passages for said liquid and for the gas to said jets,

(d) a valve to control the supply of liquid to said nozzle,

(e) a second valve to control the supply of gas to said jets,

(f) the gas control valve being normally open and the liquid control valve being normally closed, and

(g) interconnected control means operative upon movement in one direction to open said liquid control valve to full open position for spraying and, in response to further movement in said direction, to gradually close both of said valves for decreasing the gas velocity and the quantity of liquid.

8. A spray gun as set forth in claim 7, including:

(a) manual means disposed to open said liquid control valve for cleaning purposes.

9. A spray gun as set forth in claim 7, in which:

(a) said control means comprises a trigger connected to control said valves, and

(b) feeler means is provided to be engaged prior to closing of said Valves.

10. The method of spraying a liquid which comprises projecting said liquid and atomizing air from a nozzle in the form of a cone of spray decreasing in size to a zone of minimumV cross section and then diverging in a cone, and distorting said cone by directing opposed symmetrically disposed jets of air rearwardly and inwardly onto said Icone at the zone of minimum cross section in a direction to cause the spray to form a diverging fan shape and to retard the Velocity of the spray particles.

11. The method of spraying a liquid which comprises projecting said liquid and atomizing air from a nozzle in the form of a cone of spray decreasing in size to a zone of minimum cross section and then diverging in a cone, and distorting the spray pattern by directing a pair of symmetrically disposed air jets onto said cone from opposite sides at said zone of minimum cross section in an inwardly and rearwardly inclined direction adapted to cause the cone of spray to fan out into an eliptical pattern and to markedly reduce the velocity of the spray particles.

(References on following page) 7 References Cited 3,111,266

UNITED STATES PATENTS 8/ 1920 Holton 239-290 10/ 1934 Gretschel 239-543 5 4/ 1943 Bleakley 239-290 29,349

8/ 1944 Junkins 239-8 54,231

4/ 1947 Nagel 239-8 3 54,376

7/1949 Beach 239-300 9/1952 Thompson 239-295 11/1953 Meltzer 2/ 1957 Asbeck et a1 239-290 2/1957 Sedlacski 239-290 8 11/.1963 Axelson et al 239-15' 2/1965 Juvinall et al. 239-3 6/1966 Cody 239-543 FOREIGN PATENTS 19/ 1909 Great Britain. 11/1923 Sweden.

6/ 1961 Switzerland.

EVERETT W. KIRBY, Primary Examiner.

239-132 10 M. HENSON WOOD, JR., ROBERT B. REEVES,

Examiners.

R. S. STROBEL, Assistant Examiner.

Claims

10. THE METHOD OF SPRAYING A LIQUID WHICH COMPRISES PROJECTING SAID LIQUID AND ATOMIZING AIR FROM A NOZZLE IN THE FORM OF A CONE OF SPRAY DECREASING IN SIZE TO A ZONE OF MINIMUM CROSS SECTION AND THEN DIVERGING IN A CONE, AND DISTORTING SAID CONE BY DIRECTING OPPOSED SYMMETRICALLY DISPOSED JETS OF AIR REARWARDLY AND INWARDLY ONTO SAID CONE AT THE ZONE OF MINIMUM CROSS SECTION IN A DIRECTION TO CAUSE THE SPRAY TO FORM A DIVERGING FAN SHAPE AND TO RETARD THE VELOCITY OF THE SPRAY PARTICLES.