GB2171782A

GB2171782A - Spray gun with alternate pattern valve

Info

Publication number: GB2171782A
Application number: GB08602737A
Authority: GB
Inventors: Claude Senebier
Original assignee: DEVILBISS TOUSSAINT
Current assignee: DEVILBISS TOUSSAINT
Priority date: 1985-02-15
Filing date: 1986-02-04
Publication date: 1986-09-03
Also published as: GB2171782B; FR2577447B1; IT1204798B; IT8619415A0; GB8602737D0; AU571366B2; JPS61245860A; BR8600626A; FR2577447A1; BE904230A; AU5298686A; DE3604147A1

Abstract

For a paint spray gun of the type having an air cap (7, Fig. 1) defining orifices (9) for directing jets of pattern shaping air against a jet of atomized paint, a fluid flow regulating device for controlling the flow of compressed air to such orifices (9) to alternately select two different spray patterns. A cooperating fixed valve seat 14 and movable valve needle 11 are located in the spray gun for controlling the flow of compressed air to the orifices (9). The needle 11 has a first axial position (Fig. 3) which prevents passage of fluid between the needle 11 and the seat 14 and a second axial position (Fig. 5) spaced from the seat 14 to allow fluid flow through the device to the orifices (9). A push-button (24) actuated mechanism (12a) alternately positions the valve needle 11 in the first and second positions to permit the rapid alternate selection of two different spray patterns. Said mechanism comprises a rotary ratchet 17 (sic) moved by a push rod 18 on depression of button 24 to mesh with angularly displaced notches 16a and 16b on a fixed socket 15 in the closed and open positions respectively. When the needle 11 reaches the seat 14 during closing, continued depression of button 24 causes parts 18, 17 to move relative to the needle so that ratchet 17 meshes with notches 22 on rod 18 and is rotated. Biasing springs 20, 23 are provided. Socket 15 can be screwed further into or out of the gun body 1 to adjust the open position and thus the air flow. <IMAGE>

Description

SPECIFICATION Spray gun with alternate pattern valve technical field This invention relates to paint spray guns and more particularly to a paint spray gun of the type wherein compressed air is discharged from orifices in an air cap for shaping the pattern of the atomized paint. The spray gun of the invention includes a novel valve which alternately produces two different spray patterns.

Background Art Several methods are used for atomization of paint in spray guns. Compressed air is often used to atomize paint. In one type of spray gun, a stream of paint is discharged from a small diameter orifice in a nozzle or fluid tip.

An air cap which surrounds the fluid tip directs streams of air against and around the discharged paint to atomize the paint and to shape the spray pattern. When compressed air is directed uniformly around and against the discharged paint, a round spray pattern is achieved. The air cap typically has two projections or horns extending from its front surface for directing jets of air against opposite sides of the atomized paint to produce a flat or oval fan pattern. Normally, the horns are oriented either horizontally to produce a vertical fan pattern or vertically to produce a horizontal fan pattern. A needle valve is located in the spray gun for controlling the flow of pattern shaping air to orifices in the horns and thus to adjust the shape of the spray pattern.This valve can be rotated to a closed position to inhibit fan air and produce a round spray pattern for coating narrow parts and surfaces, or it can be gradually opened to flatten the spray pattern into a fan for coating large surfaces.

Whenever the valve is closed and reopened, it must be adjested to produce the desired fan shape. This takes time and wastes paint when portions of a particuair workpiece are most efficiently coated with a round spray pattern and other portions are most efficiently coated with a fan pattern.

Disclosure Of Invention According to the invention, the standard needle valve for controlling fan air in a spray gun is replaced with a needle valve which has two distinct valve positions. In one valve position, the valve is closed to inhibit fan air. In the second valve position, the valve is opened.

The valve is actuated by a push button which projects from the spray gun. By repeatedly pushing the button, the valve is alternately set to the closed position and the open position.

In operation, the valve button is pushed to close the valve to produce a round spray pattern when needed and is pushed again to open the valve to produce a preset fan pattern when needed. Thus, there is no time delay for readjusting the needle valve each time the spray gun operator desires to change between round and fan spray patterns and paint waste is reduced.

The valve has a needle which is axially moved by an alternate action actuating mechanism towards and away from a seat in the spray gun. In the closed position, the needle rests against the seat to inhibit air flow, while in the open position the needle is spaced from the seat. The actuating mechanism is of the rotary ratchet type moved by a rectilinear sliding push rod. The mechanism includes a compensating mechanism which permits operation of the mechanism in spite of the stopping of further movement of the valve needle when the needle meets the seat. The compensating mechanism comprises an elastic or spring connection between the needle and the rotary ratchet.

Brief Description of the Drawings Figure 1 is a cross sectional elevational view of a conventional spray gun including an adjustable valve operated by a screw and nut mechanism for controlling pattern shaping air; Figure 2 is an enlarged cross sectional view through the alternate action valve for use in the spray gun of Fig. 1 and showing the valve in an open position; Figure 3 is an enlarged cross sectional view through the alternate action valve similar to Fig. 2, but showing the valve in a closed position; Figure 4 is an exploded perspective view of the valve ratchet mechanism; and Figure 5 is an enlarged perspective cross sectional view through the assembled valve ratchet mechanism.

Best Mode For Carrying Out The Invention Referring to Fig. 1, an external air atomization type paint spray gun 1 of a known type is shown. The spray gun 1 includes a nozzle of fluid tip 2 through which paint or other fluid to be sprayed is discharged. The paint is supplied from an external source (not shown), such as a conventional paint cup, through a connector 3. Paint flows to the gun 1 when a user squeezes a trigger 4 to move a needle 5 from a seat in the fluid tip 2. The spray gun 1 also is attached through a connector 6 to a conventional source of compresses air (not shown).

The fluid tip 2 is surrounded by an air cap 7 which has a central opening 8 encircling a paint outlet orifice 8a in the fluid tip 2 with a clearance. In this manner, compressed air escapes through the annular space delimited between the fluid tip 2 and the walls of the opening 8 and atomizes the paint or other material to be sprayed.

The air cap 7 includes a pair of projections or horns 7a and 7b which have orifices 9 arranged on diametrically opposite sides of the axis of the fluid tip 2. The orifices 9 are supplied with compressed air from a duct 10, in which a valve needle 11 can move lengthwise, under the action of a screw and nut mechanism 12 controlled by a rotary button or knob 13. Under the action of the button 13, the end of the needle 11 can come in contact with a valve seat 14 (as shown in Fig. 1) or be moved away from the seat 14. When the end of the needle 11 rests on the seat 14, the duct 10 is closed, so that the orifices 9 are not supplied with compressed air and the jet of atomized paint has a circular section.

When the end of the needle 11 is separated from the seat 14, compressed air flows from the duct 10 to the orifices 9 and air jets discharged therefrom act on the jet of atomized paint to give it a flattened cross section.

As explained above, operating the rotary button 13 is inconvenient and does not permit a fast and easy change of the shape of the atomized paint jet, particularly during a spray operation. To eliminate these problems, the screw and nut mechanism 12 which position the valve needle 11 are replaced with a ratchet mechanism 12a, as shown in Figs.

2-5.

The ratchet mechanism 1 2a includes a threaded socket 15 which is closed with a cap 27. The socket 15 has an external configuration adapted for mounting in the body of the spray gun 1 where the screw and nut mechanism 12 were mounted. At the end of the threaded socket 15 which faces the duct 10, a system of notches 16 (see Fig. 4) are distributed on two radial planes, with some of the notches 1 6a located on the front face of the socket 15 and other notches 1 6b recessed in relation to the notches 16a. Thus, a star ratchet 17 can occupy either of two axial positions.Depending on its angular position in relation to the socket 15, four branches 17a on the ratchet 17 will mesh either with the notches 1 6a or with the notches 1 6b and can therefore occupy either of two axial positions in relation to the needle 11.

According to an important feature of the invention, a compensating mechanism is provided for permitting operation of the ratchet mechanism 1 2a when the valve needle 11 is in the closed position and stopped against the seat 14. The ratchet mechanism 12a includes the valve needle 11, one end of which is conic to mate with the seat 14. The other end of the valve needle 11 telescopically slides in an end of a push rod 18 and is stopped in rotation relative to the socket 15 by a pin 19 which is attached to the needle 11. The pin 19 is located to project through and move in an oblong hole 21 in the push rod to allow only axial movement between the needle 11 and the push rod 18. A spring 20 located concentric about the push rod 18 maintains the assembly in position. The push rod 18 has an enlarged end defining notches 22.A spring 23 is located concentric about the needle 11 and acts between the needle 11 and the ratchet 17 to maintain the ratchet branches 1 7a in contact with the push rod notches 22.

Figs. 2 and 5 show the needle 11 in the rear or valve open position. In this position, the ratchet 17 meshes with the recessed notches 1 6b due to the action of the return spring 20. Moving the push rod 18 axially towards the seat 14 by pushing the button 24 causes the push rod 18, ratchet 17 and needle 11 assembly to move axially forward, guided by the pin 19. The pin 19 slides in a groove 25 provided in th socket 15. As soon as the end of the needle 11 comes to rest on the seat 14, air no longer flows to the orifices 9 in the air cap horns 7a and 7b. As the user continues to press the button 24, only the push rod 18 and the ratchet 17 maintained by the spring 24 continue to move since the needle is stopped by the seat 14. This axial movement enables the ratchet 17 to clear the notches 16 of the socket 15 and to mesh with the notches 22 of the push rod 12.The push rod notches 22 are offset angularly in relation to the socket notches 16 so that the ratchet 17 slightly rotates.

When the user relaeses the button 24 as shown in Fig. 3, the branches 17a on the ratchet 17 return into the front face notches 1 6a on the push rod 18, under the action of the return spring 23. When the pressure on the button 24 ceases, the spring 20 returns the assembly toward the back until the ratchet 1 7 is blocked on the notches 1 6a of the front part of the valve body and the spring 23 then prevents the assembly from continuing to move and maintains a certain force on the needle 11 in order to keep the needle 11 at rest against the seat 14. The tightness of the needle 11 on its seat 14 is therefore assured.

At the rear of the mechanism, an O-ring 26 guarantees that the mechanism operates without air leakage along the push rod 18.

To return to a flat spray pattern, the user merely presses the button 24 again. The ratchet 17 moved by the push rod 18 can then clear the notches 16a of the socket 15 and make a small rotation according to the same principle as previously described. When the button 24 is released, the ratchet branches 1 7a can nest again in the notches 1 6b in the rear part of the socket 15. The needle 11 will then move clear of the seat 14 to open the passage between the duct 10 and the air horn orifices 9.

Therefore, two types of paint patterns, round and flat, are readily obtained successively by this invention, merely by pressing the button 24 located at the rear of the spray gun. The user can select these two types of spraying without the need for any movement other than that of a finger that will be pressed on the button. This invention permits the easy and very quick change between a flat pattern and a round pattern. The two extreme positions of the needle 11 are fixed by the mechanism, which is therefore fool-proof. If desired, the mechanism can be easily modified to enable the end positions of the needle 11 to be adjusted. The amount of air flowing through the valve when the needle 11 is in the second or open position can be adjusted by screwing the socket 15 further into the spray gun body to reduce the air flow or screwing the socket further out of the spray gun body to increase the air slow.

Claims

1. For a paint spray gun of the type having an air cap defining orifices for directing jets of pattern shaping air against a jet of atomized paint, a fluid flow regulating device for controlling the flow of compressed air to such orifices comprising a cooperating fixed valve seat and moveable valve needle located in th spray gun for controlling the flow of compressed air to such orifices, said needle having a first axial position which prevents passage of fluid between said needle and said seat and a second axial position spaced from said seat to allow fluid flow through said device to such orifices, and a linearly actuated action mechanism for alternately positioning said needle in said first and second positions to permit the rapid alternate selection of two different spray patterns.

2. The fluid flow regulating device for a paint spray gun of claim 1, wherein said alternate action mechanism includes a rotary ratchet moved by a push rod sliding in a linear fashion.

3. The fluid flow regulating device for a paint spray gun of claim 2, wherein said alternate action mechanism further includes compensating means for permitting the operation of said mechanism when the valve needle is in the first position stopped against said valve seat.

4. The fluid flow regulating device for a paint spray gun of claim 3, wherein said valve needle slides axially relative to said push rod, and wherein said compensating means includes a first compression spring positioned to urge said valve needle and said push rod toward said valve and a second compression spring positioned between said valve needle and said rotary ratchet.

5. The fluid flow regulating device for a paint spray gun of claim 4, wherein said alternate action mechanism includes means for adjusting the second position of said valve needle.

6. A fluid flow regulating device for a paint spray gun substantially as hereinbefore described with reference to Figures 2 to 5 of the accompanying drawings.