US2987221A - Powder ejector assembly - Google Patents

Description

June 6, 1961 c. B. MILTON POWDER EJECTOR ASSEMBLY Filed Aug. 29, 1957 uwz/vror? CHARLES B. MLTON arfi/l/M A TTORNEV United States Patent 2,987,221 POWDER EJECTOR ASSEMBLY Charles B. Milton, Matawan, NJ., assignor to Union Carbide Corporation, a corporation of New York Filed Aug. 29, 1957, Ser. No. 681,040 8 Claims. (Cl. 222-1) This invention relates to a powder dispensing device. More particularly it relates to a novel orifice-type powder ejector having improved flow characteristics.

Many industrial processes require the entrainment of a powder in a gas stream. The entraining gas may be either used as a simple carrier to transport a powder from one place to another where it is deposited and used in bulk form or it may be a critical agent in a process, as where the powder is entrained in the gas stream and then introduced into a pot of molten metal wherein the stream velocity carries the powder well into the melt and also greatly enhances mixing. Another widespread industrial use of gas entrained powders in recent years has been in the field of powder-flame cutting, lancing and scarfing operations. There are, of course, many other uses where the entraining of a finely divided or coarse material on a gas stream is necessary.

In all of the above mentioned processes a number of basic requirements must be met by the dispensing equipment to obtain satisfactory results. Plugging of the valves and tubes in such equipment is often a serious problem especially where the powders are extremely fine or where the powder is under pressure in the dispensing hopper. Such plugging may result in either complete failure of the equipment or in intermittent and erratic flow characteristics.

Where the powder is to be used in lancing operations it is often necessary to use pressures as high as 100 pounds per square inch in the top of the hopper to obtain suitable powder flow with the lancing operation. As stated previously, these pressures cause compacting and plugging in the ejector assembly. Further problems arise due to the back pressures created by long lengths of hose and the powder nozzles. This back pressure is also more acute in the 90 to 100 pounds per square inch range required for powder lancing.

In the ejectors of the prior art there were a number of undesirable features which resulted in frequent plugging of the apparatus and also in very uneven powder flow characteristics. All of these ejectors utilize complex powder flow paths requiring the powder to make a number of turns before entering the conveying air stream. Also, the small powder entry holes, often utilized, through which the powder had to flow very often became clogged. This required shut-down of the equipment and cleaning said holes.

The majority of the prior art devices utilized an entraining gas stream of large cross-sectional area which made it very diflicult to obtain uniform powder distribution across the entire gas stream. Also, the powder was introduced into the gas stream by pressure on the powder in the dispenser rather than by a positive pickup by the gas stream per se. Nor is provision made in any of these devices for a secondary air supply to facilitate unusually heavy powder flows as are required in some lancing operations.

It is accordingly an object of the present invention to provide a novel powder ejector for use in available dispensing equipment which is capable of producing a smooth and evenly metered powder flow.

It is a further object to produce such a metered flow in a high pressure system.

Another object is to provide an ejector which has a readily adjustable metering rate.

2,987,221 Patented June 6, 1961 Other objects and advantages will be apparent from the accompanying specification and claims in which:

FIGURE 1 is a general View of an exemplary powder dispensing system,

FIGURE 2 is a view of a longitudinal section of the novel powder ejector of the invention, and

FIGURE 3 is a perspective exploded View partly in section of the ejector showing the structural relationships of the parts.

According to this invention there is provided in a powder dispensing apparatus including a powder hopper, an improved ejector in the bottom thereof and convey ing hoses connected to the outlet means of said ejector, the ejector having means for metering a continuous flow of powder downwardly onto a substantially conical pile on a horizontally disposed plate, means for providing a substantially annular gas stream which continuously entrains powder from the lower peripheral edge of said conical pile, and apertures in the horizontally disposed plate for permitting the annular gas stream containing the powder to pass down through the plate member without otherwise disturbing the continuously supplied pile of powder thereon and means located below the horizontally disposed plate for directing the entrained powder stream into said conveying means.

Referring to FIGURE 1 there is shown an exemplary powder dispensing system including a covered hopper 10, a first conduit 12 entering gas tightly through the side thereof for maintaining pressure within the hopper and conduit means 14 which connects to the powder ejector within the hopper and supplies a conveying gas under appropriate pressure. Numeral 16 denotes generally the ejector assembly which, as may be seen, is located in the bottom of the hopper with suitable connection to conveying hoses 18 which in turn are connected to suitable cutting, lancing or scarfing torches and the like. It is to be understood that this over-all system is merely exemplary of a dispensing device as used with powderfiame operations and is not intended to limit the scope of the invention. Referring to FIGURES 2 and 3, the ejector assembly comprises a main body member 20 having an axial passageway 22 with a conical upper area which connects directly with the powder space in the hopper and serves as the flow path for conducting the powder to a metering shelf 24. There is also provided a second passageway 26 through the main body which is laterally disposed from the axial passageway and connects with a fitting 28 which is internally connected to a source of conveying gas. At the end of the main body member there is provided a metering nozzle 30 having an axial bore therethrough aligned with that of the main body member. This lower metering nozzle has an outside diameter substantially less than the outer diameter of the main body member 20'. This metering nozzle may be either insertable in the main body member as shown or constructed as one piece with said body member.

A circular conduit member or annular gas distributor 32 is connected with the secondary passageway 26 through the main body member and completely encircles the lower portion or metering nozzle 30 of the main body portion. As may be seen, the outside diameter of this annular gas distributor is also less than the outer di ameter of the main body member. Gas distributor 32 is provided with a plurality of downwardly directed openings 34 through which the conveying gas is ejected. It should be stated that any means for obtaining an annular gas stream may be provided such as an annular distribution chamber having a continuous annular opening in the bottom thereof.

A second body member 36 is attached to the main body member by such means as threads 38 and is provided I l 3 with suitable slideable sealing means such as the O-ring 40. As may be seen from the drawing, the inner diameter of the second body member corresponds approximately to the outer diameter of the upper portion of the main body member 20 this leaving an annular cavity 42 between the inner surface of the second body member and the outer surface of the metering nozzle 30. The gas distributor 32 is thus located in the upper portion of this annular cavity and above the lower end of the metering nozzle 30.

The lower end of the cylindrical passage in the second body member is closed by a horizontal metering plate or shelf 24. This shelf is so constructed that a portion in the center thereof under the opening in the metering nozzle 30 is continuous while openings 44 are provided around the periphery of the continuous portion. The diameter of the continuous surface in the center of the horizontal metering shelf is determined by the angle of incline or repose of the powder being entrained so that the powder resting on the shelf as fed by the metering nozzle 30 will not fall through the openings when there is no gas flow and the hopper pressure is shut ofi. This diameter is of course, limited by the maximum operable distance between the metering nozzle 30 and shelf 24. The openings 44 in the metering shelf are shown as arcnate in form; however, they may be of other shapes providing the continuous area of the shelf is left undisturbed and that sufficient total cross-sectional area of the openings themselves is provided.

A third body member 46 is provided which is securely fastened to the lower end of the second body member 36 which serves to direct powder flow into the suitable conveying means 18. There is also provided in this third body member a tube 48 which is connected to the secondary conveying gas source 50 and which is disposed with its irmer end downwardly directed to direct the secondary gas flow along the axis of the bore of said third body member.

FIGURE 3 shows the relative positions of the various elements in perspective from which the adjustability of the main body 20 and the second body member 36 may be seen. The distance (A) between the edge of the metering nozzle and the metering shelf 24 may thus be readily adjusted to obtain varying powder flows.

In operation, powder flows through the axial passageway 22 in the main body member 20 and metering nozzle 30 both under gravity and whatever gas pressure, if any, may be present in the hopper. The powder falls upon the metering shelf 24 and forms an essentially conical pile between the metering shelf and the lower end of the metering nozzle. The main conveying gas stream passes through the openings 34 in the annular gas distributor 32 which surrounds the metering nozzle 30 above the lower end thereof and forms a substantially tubular or annular stream which passes down over the edges of the conical pile of powder and through the openings 44 in the metering shelf 24. This annular gas stream entrains powder from the exposed lower edges of the conical pile and due to the relatively thin wall section of the gas stream and to the continuous contact said stream makes with the pile of powder around the entire periphery thereof an extremely uniform amount of powder is entrained in the gas stream for any given velocity of conveying gas. The gas entrained powder is directed into the suitable conduit means 18 by means of the funnel shaped upper part of the third body member 46 located below the metering shelf 24.

When it is desired to change the powder flow rate either the hopper pressure may be altered and/or the distance (A) between the lower end of the metering nozzle 39 and the metering shelf 24 may be varied. Increasing either of these parameters will increase powder flow.

It has been found that when unusually heavy powder flows are required, the annular gas stream as limited by the discharge openings, by itself, is often insufiicient to carry the powder stream for substantial distances although it will initially entrain almost any desired amount of powder in the stream; therefore, a secondary conveying gas inlet 48 has been provided and placed in operation. This secondary conveying gas source is necessary only during such severe powder iiow requirements as for lancing, and since it is introduced below the metering and entraining area it in no way affects the entrainment mechanism. It increases the gas flow, and thus the velocity in the conveying means 18 and prevents any tendency of the powder to settle out and clog said means.

The instant ejector has proved far superior to any tried for the specific applications to which it has been put. The improved operating characteristics are attributed to the following features:

(1) Stream-lined flow path. The powder flow path through the ejector from the dispenser hopper to the conveying member is straight and unrestricted except for the powder metering orifice. This is the one place that the flow must be restricted in order to control quantity.

(2) The sharpened edge of the powder metering member 30. The area of restriction through which the powder must flow is thus held to a This reduces the tendency to plug when larger than usual powder particles are encountered.

(3) Replaceable powder metering member 30. The said member screws into the main body of the ejector and may be easily replaced when worn. Also, different metering members are available for the different ranges of operation.

(4) The conveying gas stream issues from a circular member 32 having openings 34 contained therein thus completely contacting the powder to be conveyed. Because of the design and positioning of the powder metering nozzle 30 and shelf 24 a conical pile of powder is formed on a round shelf. The conveying gas which encircles the orifice blows directly down onto the powder cone. As a result, the powder is blown or sheared off the shelf and is picked up by the gas in a smooth and continuous manner. As this occurs, the dispenser hopper pressure assists in moving the hopper powder down through the axial passageway 22 and maintains the powder cone on the metering shelf. Thus, a tendency for erratic or pulsating powder pickup from the pile is eliminated since the pile is maintained at a uniform size and the conveying gas continues to flow at a constant velocity.

(5) The secondary conveying gas supply. The external fitting 48 downstream from the metering orifice permits adding more conveying gas to the gas-powder-stream which thereby prov-ides the increased gas velocity necessary for the conveyance of unusually large powder flows.

In summary, the powder rate may be determined by either the hopper pressure or the distance A between the lower end of the metering member 33 and the metering shelf 24 while the gas-powder stream velocity is dependent primarily on the pressure of the main conveying gas source and if used, the pressure supplied at the secondary conveying gas inlet means 48. In the instant example the system gas pressures must either be equal or provided from the same gas source to prevent arculatory flow within the system when the downstream end of the conveying means is shut off.

It can thus be seen that there is provided a novel and useful powder ejector for use in powder dispensing systems which gives results heretofore unobtainable.

The above description and drawings are to be taken as merely exemplary, the only limitations intended are those set forth in the following claims.

What is claimed is:

1. An orifice type powder ejector comprising a body having a passage therethrough with a horizontally dis posed plate therein, means for providing a continuous flow of powder on said horizontally disposed plate so as to form a substantially conical pile whose vertex extends opposite to the direction of powder flow, means for providing a substantially annular gas stream which continuously entrains powder from the lower peripheral surface of said conical pile, aperture means in the horizontally disposed plate for permitting the annular gas stream containing the entrained powder to pass down through the plate member without otherwise disturbing the continuously supplied, conical pile of powder thereon, and means located below the horizontally disposed plate for directing the entrained powder stream into suitable conduit means.

2. A powder ejector as set forth in claim 1 wherein said means located below the horizontally disposed plate includes an additional means for introducing further gas into the gas entrained powder flow.

3. An orifice type powder ejector comprising a first body member with upper and lower portions having an axial passageway and a secondary passageway therethrough, said secondary passageway being laterally displaced from said axial passageway, the lower portion of said first body having a reduced diameter so that the lower opening of the secondary passageway extends without said lower portion and is displaced both laterally and vertically from the lower opening of the axial passageway, an annular gas distributor connecting with the lower end of the secondary passageway and disposed in a plane perpendicular to the axis of and above the lower end of the first body whereby it encircles said first body, said annular gas distributor having a plurality of downwardly disposed discharge openings therein, a second body member engaging the first body member and having an axial passageway therethrough having a diameter larger than the outer diameter of the lower portion of the first body member whereby an annular chamber is formed which contains said annular gas distributor member, a horizontally disposed shelf in the lower end of said second body member, said shelf having a continuous surface whose diameter is greater than the diameter of said axial passageway of said first body member spaced from and centered below said lower end of said first body member and said shelf having at least one opening located about the periphery of said continuous surface, and a third body member attached to the bottom of the second body member below the horizontally disposed shelf adapted to direct material flowing through the ejector into a subsequent conduit means.

4. A powder ejector as set forth in claim 3 wherein the second body member is in axially movable engage ment with said first body member whereby the spacing between the lower end of the first body member and the horizontally disposed shelf may be varied.

5. In a process for forming a gas borne powder stream, the steps comprising providing a supply body of powder; causing a continuous flow of said powder from said body onto an essentially horizontal support so as to form a substantially conical pile whose vertex extends in the opposite direction of powder flow; providing an annular gas stream to flow in continuous contact with the lower peripheral edge of said conical pile so as to entrain the powder therein and thereby forming the gas and entrained powder into a gas borne powder stream.

6. A process as set forth in claim 5 wherein the continuous powder flow from said body onto said horizontal support is regulated by pressurizing said body of powder.

7. A process as set forth in claim 5 wherein the rate of powder entrainment is regulated by adjusting the diameter of the base of said conical pile.

8. A powder ejector as set forth in claim 1 in which said means for providing a continuous flow of powder onto a substantially conical pile whose vertex extends opposite to the direction of powder flow comprises means defining a substantially vertical passage with a lower end spaced above said horizontally disposed plate and means for adjusting the spacing of said lower end above the horizontal plate for regulating the powder entrainment rate.

References Cited in the file of this patent UNITED STATES PATENTS 2,011,133 Yoss Aug. 13, 1935 2,120,003 Schanz June 7, 1938 2,577,550 Wahlin Dec. 4, 1951 2,594,476 Miller Apr. 29, 1952 FOREIGN PATENTS 549,435 France Nov. 20, 1922

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