Apparatus For Electric Field Curtain Of Contact Type

Abstract

A tubular duct of insulating material has three elongated electrodes spirally wound along it on its outer surface, uniformly spaced from one another. The electrodes are connected with the terminals of an alternating current source having a voltage of the order of 5-10 KV to produce a wave-like electric field within the duct by which particles are repelled from the inner duct surface and repulsively propelled in one lengthwise direction along the duct.

Description

This invention relates to apparatus for controlling the motion of powder or dust particles. The particles of powders of sulphur, plastics and carbon black, etc., are electrified by means of contact electrification and those electrified particles are made to float by an electrodynamical repulsive action due to an alternating unequal electric field and, while floating, are caused to be shifted in a desired direction.

The present inventors have heretofore devised a method of this kind of transportation in a closed space of dust particles and invented an apparatus for controlling the motion of particles without any contact by an electrodynamic action by means of an alternating unequal electric field, the particles being given beforehand electric charges by corona discharge, or the like (refer to Japanese Patent Application No. 62,935,1967).

The object of the present invention is to simplify the apparatus for electrifying dust particles.

Another object is to obtain not merely an apparatus for the utilization in transportation of dust particles, but also for application broadly to be used in electrostatic printing, electrostatic painting or collecting the materials, etc.

According to the present invention, the apparatus by which powdered or powder-like material is guidingly transported comprises a tubular duct of insulating material around the exterior of which three elongated electrodes are spirally wound, with a small, uniform spacing between adjacent electrodes, and the three electrodes are connected to the respective three terminals of a three-phase a.c. source of substantially high voltage to thus cooperate in producing an electric field within the tube or duct. As a particle contacts the surface of the duct, the electric field imparts a charge to it whereby it is repelled from the tube surface and thus levitated or caused to float in the interior of the tube; and since the field moves wave-like in one direction lengthwise of the tube, the levitated particles are propelled (or, more accurately, repelled) in said direction along the tube by the electric field.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawing, which exemplifies the invention, it being understood that changes may be made in the specific apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims.

The accompanying drawing illustrates one complete example of an embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

There is shown a side-view of an embodiment of the present invention, a part being cut away and shown in longitudinal section.

In the FIGURE, there are shown a cylindrical insulator 1, electrodes 2, 3 and a 4, and three-phase power source 7.

In the FIGURE, there is a tubular cylinder 1 comprising an insulator of high electrical resistivity and high contact electrifying effect prepared from a material such as fluorine resin, having, for example, 20mm in inner diameter, 800mm in length and 1mm in wall thickness. There are also electrodes 2, 3 and 4 formed of three electrical wires covered with, for example, fluorine resin and wound spirally around the cylinder 1, spaced from one another at intervals of 1cm. A hopper 5 is made from a material such as fluorine resin and serves as a source of supply for the dust 6. There is also a three-phase alternating current power source 7 which applies an alternating voltage of the order of 5 - 10 KV to the electrodes 2, 3 and 4 and forms a traveling electric field in the direction of the arrow A in the interior of the cylinder 1. This electric field travels in rotating spirally in a direction perpendicular to the electrodes and the traveling velocity in the axial direction (synchronous velocity in axial direction) V is

V = fp/[ 1 + (P/2.pi.R).sup.2 ]

where

f : frequency of the power source,

p : pitch of electrodes (3 .times. electrode interval), and

2R: outer diameter of the cylinder.

The dust particles supplied into the cylinder 1 from the hopper 5 are electrified by contact electrification between each particle and the inner surface of the cylinder 1, or by contact of uncharged particles with particles that have already been so charged. Particles in contact with the inner surface of the tubular cylinder are then gradually peeled off from the piled surface layer and thus made to float in air space, thus shifting in direction of progression of the electric field without any contact or repeating the collision with the inner surface of the cylinder 1, and thus are ejected from the end of the cylinder 1. In a trial by utilizing lycopodium powder of average diameter of 15/u and of average weight of 1.5/u/ug, the particles are transported at a velocity of 15 cm/sec. Moreover, by an observation in detail, it is acknowledged that the particles travel spirally in the interior of cylinder 1.

The transporting action on the particles in the above-mentioned apparatus of traveling wave electric field curtain of contact type is quite equally effective in upward and downward directions and regardless of whether a part or whole of the cylinder is oblique or vertical.

The shape of the electrodes is not limited to that shown in the above embodiment. For example, a plurality of ring electrodes may well be arranged on the circumference of the cylinder and each electrode may be connected to the three-phase power source by conductors.

Further, the insulator for contact electrification is not limited to a cylindrical shape and may well be of angular cylindrical shape or a flat plate. In these latter cases the rod-like substances may be arranged in parallel as electrodes.

The apparatus of electric field curtain of contact type of the present invention works effectively to prevent sticking of dust on the walls which surround the works where production of dust is active or in case of collection of raw materials. That is, a coating of insulating material for contact electrification can be provided on the surface of walls, a plurality of rod-like electrodes can be disposed near or embedded in this coating, and three-phase alternating voltage can be applied to the electrodes to peel the sticking substances from the coating, then transfer these downward, thus letting them drop into a duct provided in the lower part.

In this case as the peeled-off sticking substances are also let fall by gravity, then an apparatus of stationary wave electric field curtain forming a stationary wave alternating unequal electric field by the application of single-phase alternating voltage on the neighboring electrode may do as well.

The material of the insulator to be utilized is not limited to fluorine resin, but inorganic or organic materials may also be used, and its shape may be tubular, tabular or clothlike, so long as it is capable of electrifying by contact the particles coming into contact with it.

The particles now possible to be dealt with are such as sulphur powder, plastics powder, carbon black, etc., despite of its electric resistance, but the particles having poor adhesive and cohesive properties are suitable.

As stated above the apparatus of electric field curtain of contact type of the present invention becomes simpler inasmuch as the electrification of particles is due to the contact with the insulator or the contacts between the particles themselves and so it is not limited to mere transportation of particles but has further characteristics for application for such as electrostatic printing, electrostatic painting or the collection of materials, etc.

It is to be understood that the invention is not limited to the precise embodiment described above and that minor modification may be made within the scope of the invention.

Those skilled in the art will appreciate that the invention can be embodied in forms other than as herein disclosed for purposes of illustration.

Claims

The invention is defined by the following claims:

1. Apparatus for effecting the guided transportation of material in powder-like particulate form, said apparatus comprising:

A. a tubular duct of electrical insulating material through which particles of said material can guidedly move;

B. three elongated electrodes, each arranged in a spiral along a substantial length of the duct and substantially in contact with the outer surface thereof, said electrodes being spaced from one another by substantially uniform distances axially and circumferentially with respect to the duct; and

C. means connecting each of said electrodes with a different one of the terminals of a three phase alternating current source having a voltage on the order of 5 to 10 KV so that an electric field is produced between each pair of electrodes that are axially adjacent along the duct and the several turns of the several electrodes cooperate to produce an electric field that travels lengthwise in one direction along the duct at its interior, said field producing a repulsive action upon particles of said material.

2. The apparatus of claim 1, for the guided transport of powders such as sulphur, plastics and carbon black, further characterized by:

1. said duct being of a high dielectric material and having

a. an inside diameter on the order of 20 mm and

b. a wall thickness on the order of 1 mm; and

2. said electrodes being spaced from one another by a distance on the order of 1 mm.