Centrifugal Filtering Apparatus

Abstract

Separating means rotating on an axis at a predetermined speed is provided with radial passages open at their outer ends and communicating at their inner ends with means for drawing fluid inwardly through them at a rate insufficient to overcome the centrifugal force acting on foreign particles carried into the passages by the fluid, whereby the fluid leaving the inner ends of said passages will be free of said particles.

Description

There are many methods and devices for the separation of entrained particulate matter from fluids. These include sieves, screens and porous filter elements through which the fluids pass. Inertial forces have also been used for this purpose by causing the fluid to change direction while moving at high velocity, thereby throwing out the foreign particles.

It is among the objects of this invention to provide filtering apparatus for fluids containing foreign particles, which is simple and inexpensive in operation, which makes use of differential inertial forces, and which by not requiring the fluid to move at high velocity avoids the expenditure of energy to overcome fluid flow resistance and other losses.

The invention is illustrated in the accompanying drawings, in which

FIG. 1 is a side view with parts broken away in vertical section;

FIG. 2 is a vertical section taken on the line II--II of FIG. 1; and

FIG. 3 is a plan view, partly in section, of a modification.

Referring to FIGS. 1 and 2 of the drawings, the shaft 1 of an electric motor 2 has an axial passage 3 extending through it. One end of the shaft projects from the motor housing and supports a cylindrical hub 4 rigidly mounted on it. The hub has a reduced diameter portion projecting a short distance beyond the end of the shaft and provided with a number of radial passages 5 extending inwardly from its periphery. The inner ends of these passages open into the adjacent open end of the shaft. The reduced outer end of the hub rigidly supports separating means provided with radial passages 6, the inner ends of which communicate with hub passages 5. The separating means may take different forms, including radial tubes, but preferably is a disc 7 in which the outer ends of passages 6 are at the periphery of the disc. When the motor is operated, the circular member formed by the disc and hub will be rotated on its axis by the hollow shaft at the desired speed.

The opposite end of the shaft is in communication with the inlet of a rotary pump 9 (shown at reduced scale) that will continuously draw fluid inwardly through the disc passages and then through the hollow shaft and toward the pump. The connection between the pump and the shaft can be made by a conduit 10, one end of which is enlarged and sealed around the projecting boss 11 of the motor housing. One end of the hollow shaft rotates in this boss.

In operation, the motor rotates disc 7 at a predetermined speed, which may be several hundred to several thousand revolutions per minute, depending upon the fluid. The pump operates continuously to draw in through the passages in the rotating disc the fluid from which foreign particles are to be separated. It is a feature of this invention that the rate at which the fluid is drawn through the disc and hollow motor shaft must be great enough to overcome the centrifugal force attempting to cause the fluid to flow in the opposite direction outwardly through the disc passages, but not sufficient to overcome the centrifugal force acting on the foreign particles carried into the passages by the fluid. Of course, this presumes that the particles are heavier than the fluid, which may be gas or liquid. The centrifugal force to which these particles are subjected by the rapidly revolving disc prevents them from moving inwardly through the disc passages far enough to enter the hollow shaft of the motor. Consequently, the fluid leaving the inner ends of those passages and entering the shaft is free of those particles. In other words, the fluid and the particles are separated from each other in the rotating disc so that the fluid leaving the pump outlet no longer contains particulate matter. This clean fluid can be conducted to whatever place it is to be used, such as to sampling apparatus.

In the modification shown in FIG. 3, a motor 13 with a hollow shaft 14 likewise is used, but the shaft projects from both ends of the motor. As before, a circular disc 15 or its equivalent is secured to a hub 16 rigidly mounted on one end of the shaft and is provided with radial passages 17 that open into hub passages connecting them with the open end of the shaft. Mounted on the opposite end of the shaft is a similar device in the form of an impeller. This, too, includes radial tubes or a disc 19 supported by a hub 20 attached to the shaft. This disc and hub are provided with radial passages 21 that communicate at their inner ends with the adjacent end of the hollow shaft.

The diameter of the impeller is greater than that of disc 15 at the other end of the motor, so that when the motor is operated, due to the greater peripheral velocity of the impeller the centrifugal force exerted by the impeller on the fluid in its passages exceeds the centrifugal force acting on the fluid in the passages of disc 15, whereby the fluid in the impeller is thrown outwardly away from it. This causes fluid to be drawn inwardly through the passages in the smaller disc continuously. The relative sizes of the two discs and the speed of the motor are such that the rate at which fluid is drawn inwardly through passages 17 of the smaller disc will be insufficient to overcome the centrifugal force acting on entrained particles carried into those same passages by the fluid. The result is that the fluid entering the adjoining end of the hollow shaft is free of those particles so that the fluid leaving the impeller 19 is clean.

The motor is sealed in a case 23 that is tightly mounted in a wall 24 of a chamber, with one end of the motor projecting from one side of the wall and the other end projecting from the opposite side. The transfer of fluid from one side of the wall to the other therefore must be through the hollow motor shaft. In other words, the apparatus takes unfiltered fluid from one side of the wall and delivers filtered fluid at the opposite side.

The apparatus described herein does not require the fluid to flow at high velocity as in other inertial systems. The apparatus never needs to be cleaned or back flushed to remove accumulated particles. It is self-cleaning. If desired, particles of different sizes or weights or other characteristics can be separated, depending upon mass, specific gravity, shape, viscosity of the fluid and the size and shape of the radial passages, so that some particles remain entrained in the fluid while others are rejected by the apparatus and do not pass through it.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

Claims

I claim:

1. Apparatus for separating foreign particles from a fluid, comprising separating means rotatable on an axis and provided with a plurality of radial passages open at their outer ends, means for rotating said separating means at a substantially constant speed, and means communicating with the inner ends of the passages for continuously drawing fluid inwardly through them at a rate insufficient to overcome the centrifugal force acting on foreign particles carried into the passages by the fluid, whereby the fluid leaving the inner ends of said passages will be free of said particles.

2. Filtering apparatus according to claim 1, in which said separating means is a circular member.

3. Filtering apparatus according to claim 2, in which said circular member is a disc.

4. Filtering apparatus according to claim 1, in which said fluid-drawing means includes a continuous flow pump and a conduit connecting the pump inlet with the inner ends of said passages.

5. Filtering apparatus according to claim 1, in which said rotating means include a hollow shaft with said separating means rigidly mounted on one end of it and with the inner ends of said passages opening into it, and means for rotating the shaft, said fluid-drawing means being connected with the opposite end of the shaft.

6. Filtering apparatus according to claim 5, in which said fluid-drawing means is an impeller rigidly mounted on said opposite end of the shaft and provided with radial passages open at the periphery of the impeller and communicating with the inside of the shaft, the diameter of the impeller being greater than the outer diameter of said separating means, whereby centrifugal force causes said fluid to flow outwardly through the impeller passages.

7. Filtering apparatus according to claim 6, in which said hollow shaft is the shaft of an electric motor and projects from both ends of the motor.