US2920793A

US2920793A - Air-tight discharge valve for discharging fine solid materials

Info

Publication number: US2920793A
Application number: US655039A
Authority: US
Inventors: David D Munsell
Original assignee: Godfrey L Cabot Inc
Current assignee: Godfrey L Cabot Inc
Priority date: 1957-04-25
Filing date: 1957-04-25
Publication date: 1960-01-12
Anticipated expiration: 1977-01-12

Description

Jan. 12, 1960 MUNSELL 2,920,793

AIR-TIGHT DISCHARGE VALVE FOR DISCHARGING FINE SOLID MATERIALS Filed April 25, 1957 INVENTOR. DEV/D D. Mumsezj.

United States Patent Ara-Tram" nrscnARo'E VALVE FOR DISCHARG- SOLlD MATERIALS David D. Mun sell, Manchester, Mass., assignor to Godfrey L. Cabot, Inc., Boston, Mass., a corporation of Massachusetts a Application A rnzs, 1957, Serial No. 655,039 2 Claims. cL 222-58) gas stream. The separated material may then either be sent to further processing or be collected for packaging, depending on .the particular process being carried out.

In cyclone separation, it has been found that addition or removal of air from the lower portion of the hopper alfects the point at which separation of coarse from fine particles occurs.

Since in such processes the particle size is frequently critical, it is desirable to prevent air flow into or out of the lower portion of the hopper so that the separation of large from small particles occurs at the proper point.

The material settling in the bottom of the hopper must be removed while the cyclone is operating and for this purpose a valve is disposed on the bottom of the hopper to continuously or intermittently extract the precipitated material. A type in common use is known as a star valve which operates generally on the principle of a revolving door, and consists of a series of individual compartments mounted on a horizontal rotating shaft with a housing so arranged about the valve that precipitated material enters each compartment while facing the inside of the hopper and is discharged on the outside.

To prevent air leakage in or out of the hopper, which maybe operating either above or below atmospheric pressure, the moving portions of the valve must be closely fitted to the housing, which increases the cost of construction of the valve. Even if the valve is so closely fitted as to be completely airtight, such a valve necessarily permits the flow of a certain amount of air during operation.

It is customary to operate such valves continuously, because of the inconvenience of providing a means of measuring the amount of material in the hopper so as to permit intermittent operation. Consequently, during normal operation of the device, to insure that there is 'no build up of material in the hopper, the valve operates at a rate greater than necessary to discharge the exact amount of material being precipitated. Hence as the valve rotates, each compartment is filled to only a portion of its capacity, and if the hopper is being operated at a pressure greater than atmospheric each compartment also discharges a substantial quantity of gas from inside the hopper. If the hopper is operating at pressure less than atmospheric, which is the more usual case, the rotation of the valve continually releases air from the outside of the hopper to the inside.

For the reasons described above, such flow of gas into or out of the hopper is also undesirable since it tends to disturb the flow pattern inthe cyclone and alters the separation point between the large and small particles.

The object of this invention is to provide a substantially gas tight seal valve for discharging flowable material from a hopper.

A further object of the invention 'is to provide a valve oftbis type which is adapted for discharging precipitated material from a cyclone hopper without substantially affecting the air flow pattern in the hopper.

' A further object of the invention is to provide a valve assembly for the above purpose which has means responsive to the' amount of material in the hopper to control operation of the valve. i e I Other objects ofthe invention will be apparent to one skilled in the art from the following description of the specific embodiment thereof.

IIIl th d i Figure l is aview in side elevation partly in section of a cyclone separator'having a. discharge valve embodying the features of the invention,,with'the valve in the closed position. 1'

Figure2 is an enlarged view of the valve portion of the assembly of Figure l.

Figure 3 ,is an enlarged view of the valve illustrated in FigurelZ in which the valve is operating to discharge material from the hopper.

Figure 4 is a view similar to Figure 3 in which suific'ient material has been discharged from the hopper to stop the operation of the valve.

Referring to the drawing, there is illustrated in Figure 1 a cyclone separator of conventional design consisting of an upper cylindrical portion 10 and a lower conical portion 12 equipped with the discharge valve 14 of this invention as hereinafter described.

Supply conduit 16 is arranged to introduce gas and entrained finely divided material tangentially into the cylindrical portion 10 of the cyclone and discharge conduit 18 is connected axially thereinto in usual manner.

The discharge valve 14 shown in detail in Figures 2-4 comprises generally a frustoconical sleeve 20 aflixed around the bottom discharge spout of the cyclone and a rotatable closure member 22 of mating frusto-conical shape disposed below the sleeve 20.

Said bowl-like closure member 22 is mounted both for rotation and for vertical travel whereby to vary the spacing between its flared side and sleeve 20. In the illustrated embodiment this is accomplished by mounting the member 22 on a drive shaft 24 which has a slip sleeve 26 permitting axial movement of the member while it is rotating. The closure member 22 is normally held in a position such that it bears against the upper sleeve member 20 by means of a counterweighted lever arm 28 working on shaft 24 through bearing member 30. To insure that an air tight seal is maintained when the valve is in this position, a gasket 32 may be provided in the outer surface of the upper member 20.

To start and stop the rotation of the closure member 22, a switch 34 is advantageously provided which is operated by movement of the counterweighted arm 28 responsive to the change in weight on closure member 22 and controls the operation of drive motor 36 coupled to shaft 24.

In operation, gas carrying the finely divided material to be separated enters through conduit 16 and travels circumferentially in the hopper, with the heavier particles settling out in the bottom of the hopper and the finer particles passing out overhead in the gas stream through the closure member at a speed suflicient to throw the precipitated material over its flared wall by centrifugal force, where it is received by any convenient collecting system, such as a hood 38. As the material is discharged from the hopper the weight on the closure member decreases until the vcounterweight is again effective to lift the closure member and break the motor circuit at switch 34.

ltis evident that the exact manner of operation of the device may be varied, depending on the type ofmaterial being treated. If the precipitated material is dense enough to prevent the flowof gas, the cycle of operation can be so arranged that the switch shuts off the motor before the hopper is completely empty, and before the closure member has seated against the gasket. In this case the valve will always be slightly 'open, with-the gas seal being provided by the precipitated material remaining between the upper and lower-portions of the valve when the lowerportion has stopped rotating. (See Figure 4). 1 v A If the material being precipitated isso light andf 'flulfy as not to seal the valve when it is slightly ope'n, -the counterweight and the switch operating mechanism can beso adjusted that the-closuremember'is forced'against the gasket when rotation ceases.

It is also evident that the axial movement of theclosure member and the motor switch can be arranged for manual operation if desired.

Although the valve disclosed .herein is particularly adapted for use in processes in which the control of the gas flow is critical, it may be installed on any bottom discharging storage hopper. The valve is adapted for economical construction and provides a more effective gas seal than valves known heretofore.

Since certain obvious changes may be made in the device without departing from the scope of the invention, it is intended that all matter contained herein be inter preted in an illustrative and not in a limiting sense.

Having thus described my' invention, I claim:

1. A valve for controlling flow of solid materials comprising, in combination, a'vertically depending frustoconical discharge conduit, an axially movable, frustoconical closure member of congruous configuration and larger size rotatably mounted coaxially with and below said discharge conduit with its side wall extending adjacent and above the bottom of said discharge conduit,

means for rotating said closure member, and means responsive to the weight of the'material in the closure member for controlling the rotation thereof.

2. The discharge valve as defined in claim 1 including means for eifectingacseal between the outer wall of the discharge conduit: and .the inner wall of the closure member when the latter is most closely adjacent the discharge conduit. 1. i

References'Cite d in the file of this patent Germany June 15, 1953