SU1005939A1 - Ac electrostatic depositing of powder materials - Google Patents

Abstract

1. A DEVICE FOR ELECTROSTATIC DUSTING OF POWDER MATERIALS, containing a powder bin, a powder supply unit and a screen installed under it, and an electrode grid connected to a high voltage source, and a vibrator characterized in that. rG7} w schjj11, 1 /. that in order to increase the powder deposition coefficient, ensure uniform coating thickness and improve the fire and explosion safety of the device, it is equipped with an additional electrode grid, which is grounded, rigidly connected to the main electrode grid through an insulator and installed above it with a gap equal to the distance from the main electrode grid to the product to be coated or at least half of this distance. 2. The device according to claim 1, characterized in that additional electrodes, made in the form of needles of the same length, are fixed on the inner surface of the main electrode grid. 3. The device according to claim 1, characterized by the fact that the electrode grids are connected to a vibrator. (L ate with 00 l / -igg

Description

11, the art relates to a technique for coating electrically charged powder materials.

A device for electrostatic spraying of powder materials is known, which contains a metering hopper made in the form of screens cleaned by a rotating brush, one of which is grounded and installed at the exit of the collector, and the second is connected to the high voltage source and installed at the outlet of the dispenser 1.

However, the deposition coefficient of the powder is unsatisfactory, since the particles are charged directly when they touch the electrode. grids, so not all particles get enough charge to hold onto the surface of the product. In addition, the deposited coating is uneven in thickness, since the distribution of the powder on the electrode grid is uneven.

The closest to the invention in technical essence and the achieved result is a device for electrostatic spraying of powder materials, containing a powder bin, a powder feed unit and a screen installed under it, and an electrode grid connected to a high voltage source and a vibrator 2.

However, the powder deposition coefficient is low, since the particles acquire a charge only when the electrode grid is touched, and particles that do not receive a sufficient charge do not settle on the metal surface.

In addition, the known device does not provide a uniform coating thickness, since the charging electrode does not create a uniform electric field of high strength and the largest thickness of the coating is formed in the zone of maximum voltages.

The reliability of the device is low due to the fact that the field strength between the electrode grid and the product changes as the distance between them changes, which can lead to electrical breakdown and, consequently, to a fire and explosion.

The aim of the invention is to increase the deposition rate of the powder, ensure uniform coating thickness and increase the fire and explosion safety of the device.

The goal is achieved by the fact that a device for electrostatic spraying of powder materials, containing a powder dL bin, a powder supply unit and an under-installed sieve and an electrode grid connected to a high voltage source, and a vibrator, are provided with an additional electrode grid that is grounded and rigidly connected with the main electrode grid through the insulator and installed above it with a gap equal to the distance from the main electrode grid to the product to be coated or at least half of this distance.

At the same time, the electrode grids are connected to the vibrator, and additional electrodes are mounted on the inner surface of the main electrode grid,

0 in the form of needles of the same length.

Introduction to the device of an additional electrode grid and placing it from the main electrode grid with a gap equal to the distance from the product to be coated to the main electrode grid or not less than half of it, and, in addition, installing additional needle electrodes on the inner surface of the main electrode grid equal length provides a corona discharge between the electrode grids, in which

0 particles get the largest charge.

The location of the main electrode grid from the coated product at a distance equal to or greater than the gap between the 5 DN electrode grids, allows to obtain a uniform electric field that ensures uniform distribution of particles over the coated surface, and in addition, this eliminates the possibility of electrical breakdown between the grid and product leading to fire or explosion.

The presence of oscillations of electrode grids connected to a vibrator also contributes to the uniform charging of particles.

The drawing shows the proposed

device.

The device contains a hopper 1 with powder material 2, a screw feeder 3 with an electric motor 4, an electrode grid 5 connected to a high voltage source and connected through insulator 6

 With an additional grounded electrode grid 7, the electrode grid 5 has on the inner surface additional electrodes 8 in the form of needles of the same length, a vibrator 9.

g The device operates as follows.

The powder material 2 from the hopper 1 with a screw feeder 3, driven by the electric motor 4, is fed to a grounded additional electrode grid 7, which oscillates under the action of the vibrator 9. The powder is distributed over the surface of the additional grid J) one grid 7, wakes up through it and gets into the charge gap between the grounded grid 7 and the 5 tires of the needles 8. Here, the particles get the main charge and then pass through the main electrode grid 5, where they are additionally charged when they touch

with her. Under the action of a uniform electric field between the main electrode grid 5 and the grounded coated product 10, the charged particles are deposited on. covered surface of the product.

Example The device was mounted on a fixed stack-iHe above a pipe to be covered, which was located on a wheel conveyor table. The distance between the main electrode grid and the product to be coated was 200 mm and remained constant, and the distance between the electrode grids was alternately 80, 100, 150, 200 and 220 mm. Needles of equal length were installed on the inner surface of the main electrode grid.

From a high voltage source of the ERG-150 type, a voltage of 40 kV was applied to the main electrode grid. After that, the electric motor of the screw metering unit, the vibrator and the wheel roller table, which sets the rotational-translational motion of the tube, were turned on. The tube passed successively under the device at a linear speed of 200 mm / min at a rotational speed of 30 rpm. The powder consumption of the sprayed glass enamel was 850 g / m. After spraying, the pipe entered the ring inductor, where the powder melted at 920 ° C.

In the coating process using the proposed device, the powder deposition coefficient and the uniformity of distribution of the resulting coating over the thickness were determined.

When the gap between the electrode weave is less than half the distance from the main electrode grid to the surface to be coated, the powder deposition coefficient was 92-94% (in the known device 85%), the variation in thickness over the coating was ± 0.020-0.025 mm. When the gap between the electrode grids is equal to the distance from the main electrode grid to the surface to be coated or at least half of this distance, the coefficient of powder deposition is 96-99% (in the known device 85%).

Thus, the invention makes it possible to increase the deposition rate of the powder by 11-14%, to obtain a more uniform thickness in the coating — the deviation spread decreases by a factor of 2-3, and to increase the reliability of the device.

Claims (3)

1. DEVICE FOR ELECTROSTATIC SPRAYING OF POWDER MATERIALS, containing a powder hopper, a powder supply unit and a sieve and an electrode grid mounted under it connected to a high voltage source, and a vibrator, characterized in that in order to increase the powder deposition coefficient, to ensure uniform coating thickness and to increase the fire and explosion safety of the device, it is equipped with an additional electrode grid, which is grounded, rigidly connected to the main electrode grid through an insulator and installed above it with a gap equal to the distance from the main grid electrode to be coated article or at least half of this distance. 2. The device according to π. 1, characterized in that on the inner surface of the main electrode grid attached additional electrodes made in the form of needles of the same length. 3. The device according to π. 1, characterized in that the electrode grid is connected to a vibrator.