US3125296A

US3125296A - Attenuator spraying device

Info

Publication number: US3125296A
Authority: US
Publication date: 1964-03-17
Anticipated expiration: 1981-03-17

Description

March 1964 A. R. GOLD ETAL ATTENUATOR SPRAYING DEVICE 2 Sheets-Sheet 2 Filed July 12, 1962 United States Patent 3,125,296 ATTENUATGR SERAYING DEVICE Allen R. Gold, tChicago, and Gilbert M. Baumann, Glen Ellyn, Ill, assignors, by mesne assignments, to lift- Davis Publishing Company, New York, N.Y., a corporation of Delaware Filed July 12, 1962, Ser. No. 209,446 4 Claims. ((Ii. 239216) This invention relates to a spraying mechanism and more particularly to a rotary mechanism adapted to attenuate liquids, such as paint and the like, and to discharge the attenuated liquid therefrom.

Spraying mechanisms embodying the present invention are of general utility and may have any desired form and shape. An illustrative embodiment of the present invention in the form of a spray gun is described below in conjunction with the accompanying drawings, and with reference to its use for spraying paint, although it maybe used with any suitable liquid.

The spray gun has a can or other receptacle for holding the paint and a conveyor in the form of an open ended feed tube and a screw or screw conveyor having its outer peripheral surface contiguous to the inner surface of the tube to feed the paint upwardly from the can to a housing. An attenuator, which in this embodiment of the invention is a smooth surfaced inverted cone, is rotatably mounted in said housing and receives the paint fed upwardly through the feed tube by the screw conveyor. The close fit between the outer peripheral surface of the screw and the inner surface of the feed tube insures a positive feed of the paint to the attenuator and prevents paint from dripping down between the outer surface of the screw and the inner surface of the feed tube. A motor mounted above said housing rotates the screw conveyor for feeding paint upwardly from the can and also rotates the inverted cone to attenuate the paint. An adjustable shield controls the outlet through which the attenuated paint is discharged.

The inverted cone attenuator has a substantially fiat outer peripheral edge portion across which attenuated and filmed paint is discharged as a finely filmed spray substantially in the flat plane of the outer edge portion of the attenuator.

The screw conveyor comprises a stem having a screw thread projecting laterally therefrom. The upper end of the stem is provided with a threaded projection by means of which it is threaded into the drive shaft of the motor. The stem is tapered toward its lower end to provide maximum volume at the lower end of the conveyor for reception of paint that it feeds upwardly to the attenuator. The screw conveyor is mounted in an open ended feed tube with the outer peripheral surface of the screw thread contiguous to the inner surface of the tube throughout the length of said screw thread. A pivotally mounted plate positioned in slidable engagement with the lower end of the feed tube operates as a valve to regulate the flow of paint to the screw conveyor. The valve plate is provided with an opening defined by diverging side walls that varies the effective area of the cross sectional opening at the lower end of the feed tube as the valve plate is moved across the lower end of the feed tube, and thereby accurately controls the flow of paint from the can to the screw conveyor.

A flat disk, which may have a diameter substantially equal to or slightly larger than the diameter of the open top of the inverted cone attenuator, is spaced a short distance above the open top of the attenuator to cover the inverted cone attenuator and prevent excess discharged paint, expelled from the spraying mechanism as a whole, from rebounding or otherwise re-entering the attenuator 3,125,296 Patented Mar. 17, 1964 from the top. This prevents such excess paint from disturbingthe filming-out and attenuating action of the attenuator. By this means a smooth and uniform spray is obtained without interference from excess discharge from the attenuator and without spattering or other irreg ularities in the spray pattern.

The excess paint discharged from the attenuator is redirected and fed back to the can for reuse through communication openings between the housing and the can.

In addition to the valve assembly on the feed tube, the magnitude of the discharge from the spray gun, and the width of the spray pattern are controlled by a shield arrangement on the spray gun. An inner shield fixed to the top of the housing has a skirt depending below the space between the open top of the inverted cone and the flat disk. A portion of the skirt, however, is cut away to provide part of a discharge outlet. An outer shield or gate is rotatably mounted between the inner shield and the top of the housing and has a depending skirt substantially of the same size and shape as the skirt of the inner shield. A lever fixed to the outer shield projects outwardly through a slot in the housing and is accessible for manually rotating the outer shield to vary the length of the discharge outlet formed by the portions of the openingsin the two shields in registration with each other.

The maximum length of the discharge outlet is limited to the size of the openings in the skirts of the shields, which, in this embodiment is about one-fourth the circumference of the skirts, respectively. Thus, in this embodiment of the invention, approximately seventy-five percent of the paint passing across the outer edge of the inverted cone strikes the inner surface of the inner shield, and a small additional portion of the paint may strike the inner surface of the portion of the outer skirt which may overlap the opening in the inner skirt such as when the openings in the two skirts are not in complete registration.

The skirts of the shields in addition to controlling the magnitude of the discharge from the spray gun, also are effective to redirect the excess paint issuing from the attenuator, toward the bottom of the housing for return through the communication openings to the can. For this purpose at least the upper portions of the skirts are formed as substantially 45 cones and are radially aligned with the outer edge portion of the attenuator so that excess paint issuing from the attenuator will strike the conical surfaces and be redirected as described.

Some of the excess paint may find its way onto the top and edge of the cover plate or disk. To prevent this portion of the excess from interferring with the spray pattern, the inner shield is provided with a doctoring blade having an edge closely adjacent the top surface and to the edge of the cover plate. The cover plate rotates with the inverted cone, and the doctoring blade scrapes the paint from the top of the cover plate and directs it to another doctoring blade which extends below the upper edge of the inverted cone and removes excess paint from the edges of the attenuator and the cover plate. The paint removed in this manner then flows back into the can along with the rest of the excess paint.

The structure by means of which the above-mentioned and other advantages of the invention are attained will be described in the following specification, taken in conjunction with the accompanying drawings forming a part of this specification, showing a preferred illustrative embodiment of the invention, in which like reference numerals refer to like parts and in which:

FIGURE 1 is a front elevational view of a spray gun embodying the invention;

FIG. 2 is a side elevational view of the spray gun;

FIG. 3 is an enlarged fragmentary vertical view, partly in elevation and partly in section, showing the interior construction of the spray gun;

FIG. 4 is an enlarged fragmentary vertical view, partly in elevation and partly in section, showing the pivotal mounting of the valve plate at the lower end of the feed tube;

FIG. is a fragmentary plan view, showing the valve plate in closed position;

FIG. 6 is a view similar to FIG. 5, showing the valve plate in partially open position;

FIG. 7 is a cross sectional view, taken along the line 77 of FIG. 3; and

FIG. 8 is a fragmentary cross sectional view, taken along the line 8-8 of FIG. 3.

Referring to the drawings, a motor casing 2 enclose-s a motor (not shown) having a drive shaft 3 (FIGURE 3) depending therefrom. A hollow handle 4, fixed to casing 2 in any suitable manner forms a conduit for electrical wiring 5 for connecting the motor to an electric current source. A switch (not shown) is mounted on the handle for controlling operation of the motor. A housing 6 having a cylindrical wall 7 fits against the bottom wall 8 of easing 2 and is secured thereto in any suitable manner. Bottom wall 8 is provided with an opening 9 through which drive shaft 3 extends. A portion of cylindrical wall 7 is cut away to provide a discharge outlet 10. The lower edge of outlet 10 is inclined downwardly toward the outer surface of wall 7, as indicated at 11, and is provided with a drain 12 for paint that may drip from the underside of the upper edge of the discharge outlet. Drain 12, extends downwardly from the inclined surface 11 throughout the length of the discharge outlet, and communicates with the interior of housing 6 through recesses 13. The recesses 13 extend downwardly and inwardly from the bottom of drain 12 adjacent each end of the drain, as shown in FIG. 8, to protect the outer surface of the spray gun from paint that might otherwise drip from the surface 11.

Housing 6 has a lower transverse wall 14 provided with communication openings 15 for the return of excess paint from the interior of the housing to a can or other receptacle 16. The upper edge portion :17 of can 16 may be secured to housing 6 in any suitable way. Preferably the upper edge portion 17 is threaded, as indicated at 18, to engage threads 19 in the outer surface of a cylindrical flange 20 depending from an annular member 21 that is secured to the underside of transverse wall 14 by screws 22. A skirt 23 depending from cylindrical wall 7 conceals the upper edge portion of can 16 to enhance the appearance of the spray device.

An attenuator 24, rotatably mounted within housing 6, comprises an inverted cone 25 having a fiat upper edge 26, and a centrally disposed upstanding boss 27. The upper end of boss 27 extends slightly above the horizontal plane of the edge 26 of the inverted cone. The attenuator is fixed to drive shaft 3 in any suitable manner, as, for example, by a press fit between the boss and the outer surface of the drive shaft, to hold the attenuator in place. Boss 27 is counterbored from its lower end, as indicated at 28, to provide an annular shoulder 29, and the lower end of counterbore 28 is cut away, as indicated at 30, to shorten the passageway for the flow of paint from the feeding mechanism 31 to the attenuator. A plurality of openings 32, extending through the boss from the cut away surface 36 to the interior of the inverted cone define the passageway for paint flowing from the feeding mechanism to the inverted cone. The inverted cone is provided with a depending annular flange 33 surrounding the upper end of the feeding mechanism.

The feeding mechanism 31 comprises a feed tube 33, preferably of glass, and a screw conveyor 34. The screw conveyor may be of any suitable material, but is preferably made of nylon, which is inert and nonco-ntaminating to liquids to be conveyed thereby. The screw conveyor comprises a stem 35, tapering toward its lower end 35, and a screw thread 36 extending laterally from the stem along approximately half the length of the stem. The

screw thread is on the lower portion of the stem and its outer peripheral surface is contiguous to the inner surface of the feed tube throughout the length of the thread.

The amount of space between the stem and the tube increases toward the lower end of the stem because of the taper, and therefore, when the screw is rotated, its lower end lifts more paint than it could lift if the stem were not tapered. The upper portion of the stem does not require a screw thread because the paint being lifted from the can by the thread at the lower end of the stem forces the paint upwardly through the upper portion of the tube. The close fit between the outer peripheral surface of the screw thread and the inner surface of the tube permits rotation of the screw in the tube, but prevents any of the paint from dripping downwardly along the outer edge of the screw. Any paint dripping downwardly in the tube would obviously impair the efficiency of the feeding mechanism.

The feed tube 33 is protected against breakage by a metal protective tube 37 coextensive in length with tube 33 and having an upper end portion threaded, as indicated at 38, into an annular collar 39 depending from transverse wall 14. Collar 39 is preferably integral with wall 14, but may be formed separately and secured thereto in any suitable manner.

The screw conveyor is fixed to the drive shaft 3 by means of a threaded stud 40 secured to the upper end of the stem 35 in any suitable manner and screwed into a threaded axial bore 41 provided therefor in the lower end of the drive shaft. The threaded stud is preferably metal, but may be integral with stem 35, if desired. Stud 40 has a lateral flange 42 abutting the upper end of stem 35 and fitting within counterbore 28. When the annular shoulder 29 is flat against flange 42, the inverted cone 25 must be disposed with its fiat upper edge 26 in a horizontal plane perpendicular to drive shaft 3.

The screw conveyor 34 is rotated in a direction to cause the screw thread 36 to lift the paint or other liquid in which it is immersed. The screw conveyor terminates slightly above the lower end of feed tube 33 which is spaced a short distance above the bottom of can 16. The amount of paint fed to the attenuator is regulated by varying the cross sectional area of the opening at the lower end of the feed tube that is immersed in the paint. The size of the opening is varied by means of a valve in the form of a plate 43 that is pivotally mounted to swing across the lower end of the tube 33.

Plate 43 is fixed to the lower end of a link 44, as indicated at 45. The upper end of link 44 is fixed to a rotatable rod 46, as indicated at 47. Rod 46 is rotatably mounted in a cylindrical recess 48 in housing 6. Transverse wall 14 is slotted, as indicated at 49, to permit pivotal movement of link 44. A knob 50 is secured, by a set screw 51, to a reduced end portion 52 projecting outwardly from cylindrical wall 7. The knob 50 may be manually turned to move plate 43 transversely across the lower end of the feed tube 33. Plate 43 is curved, as shown in FIG. 4, to conform to the arc of a circle having a radius equal to the distance from the axis of rod 46 to plate 43, and the lower edges of feed tube 33 and protective tube 37 are similarly curved, to provide a close fit between plate 43 and the lower end of the feed tube.

The plate 43 is provided with an opening 53 defined by diverging sides 54. Opening 53 is preferably of triangular shape with its apex 55 spaced from one end of the plate far enough so that the plate can completely close the lower end of the feed tube 33. As knob 50 is turned in one direction, plate 43 is moved pivotally about the axis of rod 46 to move the apex of opening 53 toward feed tube 33. After apex 55 moves into registration with the open lower end of tube 33, continued turning of knob 50 in the same direction progressively increases the cross sectional area of the opening through which paint can flow into the lower end of the feed tube. The triangular shape of opening 53 and the rigid connections between knob 50 and plate 43 permit positive regulation of the size of the exposed opening to accurately control the amount of paint fiowing into the lower end of the feed tube.

A disk-shaped cover plate 56 having a centrally disposed opening fitting around drive shaft 3 is seated on the upper end of boss 27. The upper end of boss 27 is fiat and supports plate 56 in parallel spaced relationship to the horizontal plane of the upper edge 26 of the inverted cone 25. A collar 57 is mounted on drive shaft 3 above cover plate 56 and is held thereagainst by a block 58 secured in a recess provided therefor in bottom wall 8 of easing 2 by screws or bolts 60. The diameter of the cover plate 56 may be substantially equal to or slightly greater than the diameter of the upper end of inverted cone 25. The cover plate is spaced from the upper end of inverted cone 25 to provide a continuous opening 61 between the upper end of the inverted cone and the cover plate throughout the circumference thereof, for flow of attenuated paint across the flat outer edge portion 26 of the attenuator.

An inner shield 62 is rigidly secured to the bottom of motor casing 2 by screws 63 and has an annular skirt 64 depending into housing 6 below opening 61. An outer shield 65 is rotatably mounted between inner shield 62 and the bottom of motor casing 2. Shield 65 has a depending skirt 66 of approximately the same size and shape as skirt 64. A finger operated lever 67, secured to outer shield 65, projects through a slot 68 in casing 2. Lever 67 may be manually manipulated to rotate outer shield 65.

Each of

skirts

64 and 66 has an opening which in this embodiment of the invention is approximately one-fourth of the circumference of the skirts to provide openings 69 and 69', respectively. When lever 67 is positioned to make opening 69' coincide with opening 69, the discharge outlet, which comprises the portions of openings 69 and 69' that are in registration with each other, has a length equal to about one-fourth of the circumference of either skirt. This is the maximum length of the discharge outlet. As lever 67 is moved from said position, the length of the discharge outlet is gradually reduced by movement of lever 67 in the same direction, until the discharge outlet is closed by the continued rotation of outer shield 65 until opening 69' is completely out of registration with opening 69.

The

skirts

64 and 66 of the shields 62 and 65, in addition to controlling the magnitude of the discharge from the spray gun, also are effective to redirect the excess paint issuing from the attenuator toward the bottom 14 of the housing 6 for return through the communication openings to the can 16. For this purpose at least the upper portions 70 and 71 of the

skirts

64 and 66 are formed as substantially 45 cones and are radially aligned with the outer edge portion 26 of the attenuator 24 so that excess paint issuing from the attenuator will strike the conical surfaces 70 and 71 and be redirected as described.

In the operation of the spray gun, the screw 36 is rotated counter-clockwise, as viewed in FIG. 3. This direction of rotation of the screw causes the screw 36 to move the paint upwardly until it reaches the top of the screw. The paint then flows through openings 32 and is attenuated, filmed-out and spread outwardly on the surface of the rotating inverted cone. The paint moves upwardly on the surface of the cone and is filmedout and increasingly attenuated until it moves outwardly across or over the flat peripheral edge 26 of the inverted cone 25. The distribution of the paint around the circumference of attenuator 24 is substantially uniform, and the paint is centrifugally sprayed across edge portion 26 as a finely filmed spray.

The paint that impinges on the conical portions 70 and 71 of the shields 62 and 65 is directed thereby to flow through openings 15 into the can 16. Inner shield 62 6 is provided with doctoring blades 72 and 73 that have edges arranged radially and axially of the plate 56 so close to its upper surface and edge, respectively, that they scrape excess paint therefrom as the plate is rotated. Blade 72 terminates adjacent to blade 73 that extends downwardly past the outer upper edges of the plate 56 and the inverted cone 25 to remove excess paint therefrom and guide the paint downwardly into casing 6, from which it flows through openings 15 along with the excess paint from the inner surface of the skirts and from the drain 12. Paint passing through openings 15 falls directly into the can 16 from which it is again fed by screw conveyor 34.

The size of the pattern of paint sprayed may be regulated by adjusting the length of the discharge outlet. This is done by rotating outer shield 65 by means of lever 67. The amount of paint sprayed is affected by two factors, namely the distance between plate 43 and the bottom of feed tube 33, and by the speed of the motor. Paint may be sprayed from the gun continuously until the can 16 is substantially empty, because the paint from the can will be fed upwardly into inverted cone 25 as long as there is enough paint in the lower chamber to be engaged by screw 36.

Although we have described a preferred embodiment of the invention in considerable detail, it will be understood that the description thereof is intended to be illustrative, rather than restrictive, as many details may be modified or changed without departing from the spirit or scope of the invention. Accordingly, we do not desire to be restricted to the exact construction described.

We claim:

1. In a spraying mechanism, a rotatably mounted attenuator apertured to provide an inlet, a housing enclosing said attenuator and defining a discharge outlet, means for directing liquid to said attenuator, said means comprising a tube and a screw conveyor positioned in said tube and having its outer peripheral surface contiguous to the inner surface of said tube to provide for positive feeding of said liquid, said tube and said screw conveyor each having its lower end adapted to be immersed in a supply of liquid, said tube having its upper end in communication with said inlet, a valve plate mounted for pivotal movement transversely across the lower end of said tube, said plate having an opening defined by diverging side walls whereby the cross sectional area of the opening at the lower end of said tube will vary in accordance with the position of said plate, means for adjusting the position of said plate relative to the lower end of said tube to control the flow of liquid to said screw conveyor, and means to rotate said screw conveyor and said attenuator to feed the liquid to said attenuator from where it is discharged in the form of a spray.

2. In a spraying mechanism, a rotatably mounted attenuator apertured to provide an inlet, a housing enclosing said attenuator, a portion of said housing being cut away to provide a discharge outlet, means for carrying liquid to said attenuator, said means comprising an open ended tube and a screw conveyor positioned in said tube with its outer peripheral surface contiguous to the inner surface of said tube to provide a positive feed of said liquid, said tube and said screw conveyor each having its lower end adapted to be immersed in a supply of liquid, said tube having its upper end in communication with said inlet, a shaft mounted in said housing for pivotal movement about a horizontal axis, a rod fixed to said shaft at right angles thereto, and a plate fixed to the lower end of said rod at right angles to the longitudinal axis of said rod, said plate being movable across the lower end of said tube and having an opening therein adapted to register with the open lower end of said tube, said opening varying in width from one end to the other, means for rotating said shaft to adjust the position of said plate relative to the lower end of said tube to control the flow of liquid to said screw conveyor, and means to rotate said screw conveyor and said attenuator to feed the liquid to said attenuator and to discharge it therefrom in the form of a spray.

3. In a spraying mechanism, a rotatably mounted attenuator apertured to provide an inlet, a housing enclosing said attenuator, a portion of said housing being cut away to provide a discharge outlet, means for carrying liquid to said attenuator, said means comprising an open ended tube and a screw conveyor positioned in said tube with its outer peripheral surface contiguous to the inner surface of said tube to provide a positive feed of said liquid, said tube and said screw conveyor each having its lower end adapted to be immersed in a supply of liquid, said tube having its upper end in communication with said inlet, a shaft mounted in said housing for pivotal movement about a horizontal axis, a rod fixed to said shaft at right angles thereto, and a plate fixed to the lower end of said rod for movement across the lower end of said tube as said shaft is pivotally moved, said plate being curved to conform to the arc of a circle having a radius equal to the length of said rod, the lower end of said tube being curved to conform to the curvature of said plate to provide a snug fit between said plate and the lower end of said tube, said plate having an opening therein to vary the cross sectional area of the opening at the lower end of said tube in accordance with the position of said plate to control the flow of liquid to said screw conveyor, and means to rotate said screw conveyor and said attenuator to feed the liquid to said attenuator and to discharge it therefrom in the form of a spray.

4. In a spraying mechanism comprising a housing defining an outlet opening, a rotatably mounted attenuator in said housing apertured to define an inlet, means for feeding liquid into the inlet of said attenuator including a tube depending therefrom and a screw conveyor positioned in said tube having its outer peripheral surface contiguous to the inner surface of said tube, the lower end of said tube and screw conveyor extending toward the bottom of said housing and the tube having its upper end in communication with said attenuator inlet, a closure member defining a variable opening for controlling the flow of liquid into the lower end of said tube, means for setting said closure member to maintain a fixed opening into the bottom of said tube, said last-mentioned means including an adjustable member positioned exteriorly of the housing and a linkage interconnecting said adjustable member and closure member and pivotally moveablc about the horizontal axis of said adjustable member, whereby the opening into said tube can be changed whenever desired, and means to rotate the screw conveyor and attenuator to supply liquid to the attenuator from where it is discharged through the housing outlet in the form of a spray.

References Cited in the file of this patent UNITED STATES PATENTS