US2856010A - Device for pneumatic delivery of powder - Google Patents

Description

Oct. 14, 1958 E. F. BRILL ET AL DEVICE FOR PNEUMATIC DELIVERY OF POWDER Filed Feb. 29, 1956 viwvw:

vvlllilllllllllawlllllllllllllln m w A We Em m, AMY ML A T'TOEA/E VJ DEVICE FOR PNEUMATIC DELIVERY OF POWDER Edward F. Brill, Milwaukee, Wis., and Alden W. Hanson,

Midland, Mich, assignors to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Application February 29, 1956, Serial No. 568,551

7 Claims. (Cl. 169-9) This invention relates to a device for the pneumatic delivery of pulverulent dry particles such as fire extinguishing powders, flours, cement, sand and the like from a vessel having a uniform cross section such as a cylinder, which may be in any position, delivery therefrom being controlled by a discharge valve while the vessel and its contents remain under pressure.

The dry and pulverulent material may be'stored for indefinite periods in such a vessel, e. g., a cylinder, which, unlike the storage reservoirs of other systems, may be in any position whatever, including a horizontal position. In fact, the invention has been embodied in a system in which a cylinder eight inches in diameter and over twenty feet in horizontal length has been used for the storage of the dry material.

It is desirable that the pulverulent material stored in such a cylinder shall be thoroughly aerated with gas which is maintained under pressure throughout the material in advance of discharge. In fact, it has been found necessary to maintain upon the powder and the contained gas a pressure which continues effective notwithstanding the discharge of convective gas and powder from the cylinder. This objective is desirably achieved by the use of a piston provided with packing having wiping engagement with the interior wall of the cylinder while permitting some gas to by-pass the piston in the direction of movement of the piston, the piston being subject to sufiicient gas pressure to advance it in the cylinder as gas and powder are discharged, to maintain uniformly distributed pressure on, and aeration of, the powder. Piston advance continues automatically urging the aerated pulverulent material toward the discharge end of the cylinder without compacting the powder to the extent that it ceases to be fluidized by the gas.

The distribution and compression of the convective gas within the powder may be achieved in the following way. Without destroying the wiping engagement be tween the piston and the cylinder, it is possible to provide for suflicient leakage past the piston so that gas applied under pressure behind the piston will leak past the piston during storage periods to accumulate within and throughout the powdered material ahead of the piston until pressure is equalized on the opposite sides of the piston. When the discharge valve is opened, with consequent pressure reduction at the point of discharge from the cylinder, the expansion of the gases adjacent that point will render the pulverulent material fluid and provide convective gas for the propulsion thereof through the discharge pipe or hose. The discharge of convection gas from the cylinder when the discharge valve is opened also lowers the convection gas pressure ahead of the piston, thereby producing a differential pressure across the piston. The differential pressure then urges the piston forward as the fluidized pulverulent material is thus discharged from the cylinder with the convective gas.

Leakage past the piston must be so slight that it does not equalize pressures on the opposite faces of the piston during flow through the discharge hose. The piston atent 2,85,916 Patented Oct. 14, 1958 heads are identical and interchangeable, the couplings thereto are desirably interchangeable, whereby pressure discharge connections may be interchanged between the ends of the cylinder.

It has also been found very desirable to use a free floating piston within the cylinder which has a bearing against the cylinder wall of such axial extent that the piston cannot bind. In practice, the piston itself comprises a disk with marginal packing and the bearing is supported by radial wings having bearing surfaces engaging the piston some distance behind the disk. The free floating piston is particularly useful when the cylinder is of great length,-as it makes it unnecessary to provide a long piston rod or to retract the piston the whole length of the cylinder when it is desired to refill the cylinder. The piston is simply removed from the discharge end and either reinserted in that end for reverse movement or inserted in the end from which it started, if it is desired to retain the same supply and discharge connections to the cylinder. Otherwise these connections may be reversed and the cylinder may be charged from the end opposite to the discharge end.

Convective gas under pressure is supplied through the supply connections from behind the piston to fill the cylinder and interstitial space in the powder until pres sure ahead of the piston is more or less equalized with convective gas under pressure, the interstitial space receiving gas which bypasses the piston, whereupon the system is in readiness for use. The sole control is the discharge valve, the piston being subject to a differential pressure when the discharge flow is started by opening the valve at the point of discharge.

Various convective gases may be used for propelling purposes depending on the nature of the dry material, the use to which the apparatus is to be put and the gas pressure required. Pressures generally used in practice range, for example, from 360 p. s. i. downwardly. Typical gases usable are air, nitrogen and carbon dioxide, the latter being preferred for fire extinguishing purposes.

The invention has particular utility for a fire extinguisher and Will hereinafter be described with referference to an exemplification for that usage, it being understood that utility is by no means limited to the fire extinguisher field.

In the drawings:

Fig. 1 is a general view in side elevation of a physical apparatus suitable for the practice of the invention, the closure of the protective housing for the gas supply cylinder being omitted.

Fig. 2 is an enlarged view in axial section of the powder storage cylinder, portions of the cylinder and the connections thereto being broken away.

Fig. 3 is a view taken in transverse section through the cylinder behind the piston on the line 33 of Fig. 2.

Fig. 4 is a fragmentary detail view showing a portion of the piston in section to illustrate the optional provision of an orifice therethrough.

The propellent gas is carried in the conventional container 5 which may conveniently be mounted in bracket 6 and enclosed by housing '7. From the high pressure source, the gas passes through a reducing valve and pressure regulator 8 into the pressure line 9 which leads through the normally open main shutoff valve 10 to the cylinder 15 in which dry powder or chemical in pulverulent form is stored.

The cylinder 15 is shown in detail in Fig. 2. It is desirably of circular cross section to facilitate manufacture. At its ends, it preferably has identical coupling rings 16 which are internally threaded to receive the annular retainers 17 by which the identical cylinder heads or closures 18 are clamped to the ends of the cylinder. Each. head 18 has a radial flange 19 confined between the retainer 17 and a shoulder 20 of the coupling ring 16. O-ring packing at 21 is used to provide a seal between flange 19 and the coupling ring 16, the latter being welded to the cylinder.

Opening through the respective heads are identical nipples 22. To one of these the pressure supply pipe 23 is secured by a standard coupling. To the other, a dischargepipe 24 is secured by a like coupling. The discharge pipe 24 has a normally open shutoff valve 25, beyond which a hose 26 extends to the nozzle 27 or other delivery outlet controlled by valve 30. In practice, 500.pounds of dry chemical stored in cylinder 15 have been delivered through a one inch hose 26, fifty feet in length, delivery being started and stopped by the control valve 30 at the nozzle 27. The figures given are, of course, by way of example and not by way of limitation.

The piston generically designated by reference character 35 may conveniently comprise a disk 36 to which an annular clamping ring 37 is anchored by bolts 38 in clamping engagement with inner peripheral portions of an annular packing 39. The radius of this packing is such that its free marginal portions 40 are in wiping radial pressure engagement with the inner wall of the storage cylinder 15. It has been found to be broadly immaterial whether the outer margin of the packing is directed forwardly or rearwardly with respect to the direction of piston movement in the cylinder.

In actual practice, a properly designed .packingwill direct convective gas along the wall of the cylinder and wipe all such material ahead of it, thereby tending to preclude wedging or cylinder scoring. However, scoring of the cylinder, should it occur, does not preclude continued successful operation since, during the storage period preliminary to and during the ejection of the pulverulent material it is necessary to permit some of the convective gas to by-pass the piston. It is possible, as suggested in Fig. 4, to provide one or more small orifices 41 opening through piston disk 36, thereby to assist in fiuidizing the pulverulent material by allowing convective gas to pass from one side of the piston to the other through such orifices.

For piston guidance, to prevent the floating piston from canting and binding in the cylinder, the piston bearing on the cylinder is desirably extended axially. This is conveniently done by the provision of generally radial wings 43 welded or otherwise secured to the piston face 36 and provided with marginal bearing portions at 44 enengaging the cylinder wall at a point axially remote from the face to maintain the piston in axial alignment with thecylinder.

The dry powder which is to be stored pending pneumatic delivery to the point of use is inserted in the cylinder ahead of piston 35. Due to the fact that the two cylinder heads and couplings are identical, the powder may be loaded from either end and discharged from the opposite end, the piston being inserted from the pressure end of the cylinder behind the powder.

After placing the powder in the cylinder, it will be necessary to aerate and pressurize the powder as by allowing gas from a source such as tank to enter the cylinder and seep past the piston packing 39 to effect the desired aeration. Alternatively, the orifices 41 in the piston may be relied upon for this purpose. There will be a tendency for much of the hose 26 to remain free of powder but subject to the pressure-of gas confined therein by the valve 30 which controls discharge from the hose.

The cylinder. being provided with'powder and connected with the gas supply tank 5 through the. pressure.

regulator 8 and the open valve 10, valve likewise being open, it will be evident that only the valve 30 at the discharge nozzle 27 will control flow from the cylinder. When valve 30 is opened, there will be a sharp drop of pressure at the delivery end of the cylinder. The gas diffused throughout the powder will expand in the vicinity of the discharge port because of the pressure drop in the hose. This will locally fluidize the powder. A flow of powder with the convective gas will occur through the hose 26 to thepoint of discharge, which may be a nozzle such as that shown at 27.

However, as fast as gas and powdered material are discharged from the cylinder, the piston 35 moves forwardly in the cylinder to maintain the remaining material and gas under'continued pressure because the fluid pressure is greater behind the piston than on the discharge side. The wiping, but not complete fluid sealing, engagement of the packing 39 with the interior of the cylinder permits some flow of gas past the ,piston tomaintain the powder in fluidized condition during discharge.

The device has proven to be extremely practical for fire extinguishing purposes,,particularly since the storage cylinder may be operated at any angle. Most, if not all, fire extinguishers which handle powder fail to operate dependably unless the storage cylinders are vertical.

-In the present device, the powder not only does not pack ,but it actually flows like water even when the cylinderis horizontal .or vented in any other manner. For this reason, .itis possible to incorporate the cylinder structurally into a fire truck or the like without impairing. its use in. any way. The'shutoff valve at the point of discharge may be opened and closed to start and stop the flow of the powder and the propellant gas as desired.

It will be observed that the disclosed embodiment of piston 35 floats freely in the storage cylinder, requiring no rod or;guiding means other than its own fins 43 or equivalent axial extension. This is a great advantage since it permits the, piston to be removed bodily from one end of the cylinder and either replaced in reverse position inthe same cylinder (in the event that the connections to the. cylinder are to be reversed) or taken to the same end from which it started and re-inserted in that end. In-other words, no elongated rod and no return of the piston through the cylinder to the starting point are required.

The piston is propelled forwardly by the pressurizing gas and followsthe'pulverulent material, urging it toward thedischarge end of rthe .cylinder as it empties, thereby promoting uniformity of discharge. In operation,-it has been observed1that .thespace for about two inches ahead of the piston is substantially free of powder, tending to remain so by reason of leakage past the piston. Pressurizing gas by-passing the piston maintains the desired convectivegas pressure ahead of, as well as behind, the piston and produces localized powder diffusing expansion substantiallysolely at the outlet. The convective gas used in delivering material pneumatically through the hose is, of course, gas which has by-passed the piston and filled the interstices between the pulverulent particles stored in the cylinder. The expansion of such gas from between the particles as particles approach the delivery nipple at the discharge end of the cylinder keeps the particles free-flowing and precludes stoppages.

Merely by way of illustrating preferred practices, and without intending to indicate any limitation on the range of pressures which maybe used, it is noted that we have successfully employed pressures of approximately sixty pounds per square inch above atmospheric.

We claim:

1. A device for 'thestorage and pneumatic delivery of pulverulent material, said device comprising the combination with a cylinder and a piston movable therein and ahead of which such material'is stored dry and aerated with convective gas under pressure, a high pressure gas sourcehaving a. reducing valve connection with the cylinder behind the piston for supplying gas under pressure which remains substantially constant in all piston positions, a discharge connection opening from the cylinder ahead of the piston and a valve controlling the discharge connection, said piston having a wiping bearing with said cylinder and being suificiently fluid tight so that, upon the opening of the valve controlling the discharge connection, the difierential pressure thereby generated of convective gas on the piston advances it in substantial pressure contact with the material and the continuing flow of convective gas and entrained material through the discharge connection will be effected substantially solely by the convective gas in the interstitial spaces in the material ahead of the advancing piston.

2. The device of claim 1, the convection gases under pressure ahead of the piston being derived from the gas admitted to the cylinder behind the piston, the piston having means afiording restricted leakage of such gas to the front of the piston.

3. The device of claim 1 in which the piston is a free floating piston having unitary means for maintaining it co-axial with the cylinder independently of any rod.

4. The device of claim 3 in which the piston comprises a head portion having packing means engaged with the interior of the cylinder and having guide flanges mounted unitarily to the head portion and projecting axially therefrom and having marginal edges in bearing engagement with the cylinder wall behind the head portion.

5. A fire extinguisher comprising a cylinder having an axial length very greatly exceeding its transverse width and provided adjacent one end with a discharge hose having a control valve and adjacent the other end with a convective gas pressure supply connection, of a fire extinguishing powder confined within the cylinder adjacent the end first mentioned, convective gas under pressure permeating the powder, and a floating piston reciprocable in the cylinder and disposed between the gas permeated powder and the second mentioned end of the cylinder, said second end being permanently open to fluid pressure, whereby the piston is maintained in intimate contact with the powder, discharge of powder and permeating convective gas being controlled solely by the valve controlling flow through said hose, said piston including means for by-passing convective gas at a rate too low to interfere with the advance of the piston by pressure of such gas when said valve is open, whereby continued pressure on the powder and convective gas ahead of the piston is maintained when the valve is open.

6. The device of claim 5 in which the piston is provided with a head, an annular packing, and guide means connected to the head and extending rearwardly from the piston and away from the powder, said guide means including bearing surfaces engaged with the cylinder remote from the head to maintain the piston head axially aligned with the cylinder.

7. The device of claim 5 in which the cylinder comprises a tube having heads provided with substantially identical coupling means affording the fluid pressure and discharge hose connections aforesaid, each of the heads being in detachable connection with the cylinder and each being freely removable therefrom for the withdrawal and replacement of the floating piston.

References Cited in the file of this patent UNITED STATES PATENTS 1,939,333 Bronander Dec. 12, 1933 2,001,207 McManamma et a1. May 14, 1935 2,021,493 Trueblood Nov. 19, 1935 2,577,744 Faust Dec. 11, 1951

Images