Spray Guns

Abstract

This invention relates to electropneumatic spray guns, particularly paint spray guns having an electrostatic generator incorporated in the barrel of the gun. According to this invention, the air supply which is fed to the gun to atomize the material to be sprayed is also used to drive the rotor of an electrostatic generator for applying an electric charge to the atomized particles of the material to be sprayed. The said rotor is provided with blades on which the air impinges to cause it to rotate.

Description

The present invention relates to electropneumatic spray guns, particularly paint spray guns, having an electrostatic generator incorporated in the barrel of the spray gun. Various types of spray guns incorporating a generator have already been proposed, in which the generator is of the electrostatic type with a rotor placed in a chamber from which extends a drive shaft connected to an electric driving motor. This type of electrostatic motor usually has the drawback of being heavy and cumbersome which results therefore in a spray gun which is difficult to handle.

The present invention relates to an electropneumatic spray gun wherein the electrostatic generator of the type having an insulating rotor with excitation ionizers and output ionizers, comprises a rotor caused to rotate by the direct action of air derived, in the spray gun, from the atomization air passage, this driving air acting on blades integral with the rotor and flowing through the rotor space.

By reason of this construction, it is not necessary to have a separate motor for driving the generator, the air supply to the spray gun for atomization being used both as a motor fluid for driving the rotor and as a continuously renewed insulating medium flowing over the rotor and the electric elements producing the charge and discharge of the rotor. There is thus obtained a compact spray gun, relatively light and easy to handle and which is reliable in operation.

The invention will now be further described, by way of example, with reference to the accompanying drawings, win which:

FIG. 1 is a schematic view in section of an embodiment of spray gun according to the invention, and

FIG. 2 is a plan view from above, of this same spray gun.

Referring to the drawings, the spray gun comprises a hand grip 1, a barrel 2, a paint supply pipe 3, an air supply pipe 4 and an electric cable 5. The latter is used for the excitation of the electrostatic generator and carries a current of several milliamperes at a voltage between approximately 4-6 kv.

The electrostatic generator is formed from a rotatable disc 8 positioned in a detachable casing 9 wherein it is mounted to rotate on a shaft 10 carried in bearings 11 an 12. This rotatable disc has an annular peripheral groove 13 in which are arranged, at diametrically opposite positions, on the one hand excitation ionizers 14 cooperating with inductors 15 and 16, on the other hand output ionizers 17 cooperating with output inductors 18 and 19. The excitation ionizers 14 are connected to the cable 5 by contact studs 20 whilst the excitation inductors 15 and 16 are connected by studs and by conductors 21 and 22 to the casing 23, earthed by the cable 5. The output inductors 18 and 19 are connected to ionizers 17. In a manner known per se, the excitation ionizers deposit, under the action of the excitation inductors 15 and 16, ions on the two faces of the groove 13, these ions being recovered by the output ionizers 17 situated adjacent an atomization nozzle 24. The atomization nozzle 24 causes the atomization of the paint by a jet of air fed through the passage 4, whilst the charge of the atomized particles is effected, by reason of the energizing of the nozzle by a conductor 25 connected to the output ionizers 17. It can be seen that the rotor 8 of the electrostatic generator is driven by air impinging on the blades 26 arranged on a lower face of the rotor disc. This air is fed through a passage 27 connected to the air passage 4.

A trigger 28 controls a valve 29 for the air input and a valve 30 for the input of the paint under pressure, the supply of the air inducing the electric supply over the cable 5.

The device described produces the atomization of paint with electric charges due to the high voltage output from the generator. Instead of using a rotor disc, an insulating cylinder can be used which gives similar results.

Such a spray gun has been produced having a cylinder 55 mm. in diameter rotating at 10,000 r.p.m. and having a consumption of drive air of the order of several cubic meters per hour, usually not exceeding 2 cubic meters per hour. Such a generator has an output current of 5 to 10 microamperes at a voltage of 30 to 50 kilovolts. Such power is sufficient to electrically charge a normal flow of atomized paint and to feed it to the object to be coated which is itself carried at earth potential.

It will be noted that in the embodiment described, the driving air for the electrostatic generator is obtained from the air passage 4 and evacuated by a valve 31 adjusted for an overpressure of 0.5 of an atmosphere, for example, and arranged in an area which does not disturb the atomization phenomenon. In this way, the pressure of the air about the generator is higher than the atmospheric pressure, which considerably improves its electrical functioning. In place of this arrangement air which has passed through the generator may also be used for the atomization. It is noted that the air which is supplied to the generator ensures not only the driving in rotation of this generator, but also forms a dielectric medium which is constantly renewed adjacent the rotor and electric excitation and flow elements and of which the pressure may be higher than the atmospheric pressure, which ensures a good electric resistance of the insulating medium.

Claims

I claim:

1. Electropneumatic spray gun having an electrostatic generator incorporated in the barrel of the spray gun characterized in that the electrostatic generator has a insulating rotor with excitation and output ionizers and is driven in rotation by the action of the air obtained from the atomization air passage, this driving air acting on blades integral with the rotor and flowing through the rotor space.

2. Electropneumatic spray gun as claimed in claim 1, characterized in that the output ionizers are arranged adjacent the atomization nozzle.

3. Electropneumatic spray gun as claimed in claim 1, characterized in that the rotor is located in a casing incorporating not only the excitation ionizers and the output ionizers but also the drive blades of the said rotor, so that the drive air flows around all the electric elements located in the said housing.

4. Electropneumatic spray gun as claimed in claim 1, characterized in that the electrostatic generator is placed flat on the barrel of the spray gun.

5. Electropneumatic spray gun as claimed in claim 4, characterized in that the rotor is the shape of a disc.

6. Electropneumatic paint spray gun as claimed in claim 5, characterized in that the ionizers are located in an annular groove extending around the disc.

7. Electropneumatic spray gun as claimed in claim 1, characterized in that the air escapes to the atmosphere through a valve in the casing of the generator.