US2961581A - Electrostatic coating means and apparatus - Google Patents

Description

Nov. 22, 1960 G. GRAVE ETAL ELECTROSTATIC COATING MEANS AND APPARATUS Filed Feb. 14. 1955 2 Sheets-Sheet 1 Nov. 22, 1960 G. GRAVE ETAL 2,961,581

ELECTROSTATIC COATING MEANS AND APPARATUS Filed Feb. 14, 1955 2 Sheets-Sheet 2 United States Patent ELECTROSTATIC COATING MEANS AND APPARATUS ttlistatic Company, Cleveland, Ohio, a corporation of Filed Feb. 14, 1955, Ser. No. 488,094

4 Claims. (Cl. 317-3) The invention is concerned with an electrostatic coating means and apparatus consisting of a rotating disk connected to a high voltage source. The combination of centrifugal and electrostatic forces disperses from the disk a coating medium such as paint, lacquer, liquid or powder. The medium is brought to the disk by means of a pipe connected to a distributing tank or pump. Between atomizing disk and the surface to be coated is created an electrical high tension field through which the atomized particles of the coating medium are migrating in a known manner to the surface to be coated.

It is an object of the present invention to provide a handy device allowing to coat the whole surface of an article from all sides.

It is a further object of the invention to have the power pack together with the electrostatic atomizing device on movable means in contrast to conventional stationary equipment.

It is another object of the invention to have an electrostatic generator together with the electrostatic atomizer device in a handy casing.

A further object of the invention is to have an atomizing device which can be handled and operated without electrocution.

According to the invention the electrostatic atomizing device has a shape similar to a pneumatic drilling hammer or a spray gun. In order to avoid fatigue for the worker, the weight of the apparatus may be suspended by springs or wires attached to supports either stationary or movable. The supporting wires may also have counterweights in connection with a pulley.

According to another feature of the invention the high voltage may be furnished by a small electrostatic generator of the band or drum type mounted inside the casing of the atomizing device.

When a power pack is used, its power may be fed to the atomizing device via the suspension wires or springs holding the atomizing device in working position.

Further features of the invention are shown in the drawings representing by way of example two types of the atomizing device according to the invention without limitation in scope.

Fig. 1 is an elevation of the electrostatic atomizing device with a casing made of plastics or the like and having the contours similar to a pneumatic drilling hammer.

Fig. 2 is an elevation of the electrostatic atomizing device mounted together with the power pack on a movable column.

Fig. 3 is the same device as Fig. 2 but seen from the rear.

In lieu of the column, the electrostatic atomizing device may also be carried either on a truck or be sus pended on a monorail.

1 denotes a mushroom shaped rotating disk (of a diameter of about 50 to 100 millimeters) with an electrically conducting dismountable shaft 3 and one or more electrically non-conductive feeding tubes 2 for the coat- 2361,1581 Patented Nov. 22, 1960 ing medium such as paint, lacquer, powder or liquid. Shaft 3 is connected by an intermediate shaft to motor shaft 5. When working shaft 3 with the rotating disk (approximately 900 to 2000 revolutions per minute) is under high voltage just the same as the intermediate shaft which is supported on two bearings 4. The high voltage is fed to the atomizing device by an electrically insulated line 12 with slip ring 13. Shaft 5 is made of plexiglass or other convenient insulating material. A combination 6 of electrical generator plus electrical motor rotates shaft 5, intermediate shaft, shaft 3 and disk 1. An electrically insulated casing 7 with handle 8 contains combination generator-motor 6, shaft 5, slip ring 13, bearing 4 and line 12. The whole length of the atomizing device is about 500 millimeters. Electrical feed lines connected to the motor are not shown. Eye 9 is a suspension means for an expansible suspender like spring 10 attached to ceiling 11. The suspension means 10 plus casing 7 are electrically grounded. Articles to be coated are not shown in the drawing.

For the combination 6, the generator used may be the Van de Graalf type with self-excitation (Patent 808,355 of the Federated Republic of Germany). This kind of generator has a height of about 7 inches for a delivered high voltage of kilovolts or more.

Also may be used a conventional drum type generator as disclosed in the Patent 811,595 of the Federated Republic of Germany.

The generator of combination 6 may also be placed outside the casing 7 of the atomizing device and may have the form of a conventional power pack.

In such cases where the high voltage is available by a known power pack, the latter may be mounted together with the atomizing device on a column 14 as shown in Figs. 2 and 3. 18 denotes the known power pack (transformer and selenium rectifier) furnishing the high voltage e.g. via feed line 17, suspension means 16, shaft 3 to disk 1. The coating material is fed to the pipe 2 by a feed tank or pump 15 adjustable in height for regulation of pressure in pipe 2.

Since each atomizing device has its own power pack or generator, the electric current necessary for the hand spray disk can be limited to less than one milliampere.

The device allows to use a hand operated spraying apparatus for the coating of single items of difficult configuration without exposing the operator to electrocution. During spray operation, the disk can be held very close to the surface to be coated without arc-overs.

What we claim is:

1. In an electrostatic-spraying equipment, means for supporting an article to be coated, means to support a spray head, said head comprising a disk lying in a general plane parallel to the general plane of the article to be coated, a drive shaft perpendicular to said disk and extending rearwardly from the front side of said disk facing toward the article support means, means connecting the rear side of said disk to said drive shaft so that the axis of said drive shaft extends through the center of said disk, means for driving said drive shaft, and a tube feeding a coating medium to the rear side of said disk and terminating adjacent said rear side, means for establishing electrical tension between said disk and said article support means, and means for electrically insulating said disk and at least the end of said paint tube from the article support, whereby, when said disk is rotated and said electrical tension is established, coating medium fed to said disk will be atomized and dispersed centrifugally and the so atomized and dispersed particles of said coating medium will converge upon external surfaces of the article to coat the same.

2. Equipment as defined in claim 1 including a commutator on said drive shaft adjacent said disk electrically connecting said disk to the source of electrical tension and in which said means to insulate said disk include a non-conductive section in said drive shaft between said disk and the driving means for said shaft and a nonconductive section in said paint tube adjacent said disk.

3. Equipment as defined in claim 2 in which said means for driving said drive shaft is a motor in said head, and including a bearing supporting said drive shaft adjacent said disk and commutator, a casing extending from said motor to said bearing for supporting said bearing, and a non-conductive section in said casing between said motor and said bearing.

4. Equipment as defined in claim 1 in which said disk comprises a mushroom-shaped member having a convex face directed toward the article to be coated and the means for connecting said disk to said drive shaft comprises a rearwardly extending stern centrally attached to the rear side of said disk, said rear side being adapted to receive a coating medium from said feeding tube to dis tribute a coating medium to points on the periphery of said disk, whereby, but for the electrical tension between said disk and the article to be coated, said coating medium would leave said disk in a plane perpendicular to said stem as said disk is rotated.

References Cited in the file of this patent UNITED STATES PATENTS

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