US2738234A

US2738234A - Powder dispensing apparatus

Info

Publication number: US2738234A
Application number: US324971A
Authority: US
Inventors: Nelson E Anderson
Original assignee: Air Reduction Co Inc
Current assignee: Airco Inc
Priority date: 1952-12-09
Filing date: 1952-12-09
Publication date: 1956-03-13
Anticipated expiration: 1973-03-13

Description

March 13, 1956 N. E. ANDERSON 2,738,234

POWDER DISPENSING APPARATUS Filed Dec. 9, 1952 4 Sheets-Sheet l 36 'lll W FIG. 2

INVENTOR NELSON E. ANDERSON MHW Q ATTORN March 13, 1 956 N. E. ANDERSON 2,738,234

POWDER DISPENSING APPARATUS Filed Dec. 9, 1952 4 Sheets-Sheet 2 INVENTOR NELSON E. AN DERSON ATTORNEY March 13, 1956 N. E. ANDERSON POWDER DISPENSING A'PPARATus 4 Sheets-Sheec 3 Filed Dec. 9, 1952 lOo.

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INVENTOR NELSON E. ANDERSON ATTORNEY March 13, 1956 ANDERSON 2,738,234

POWDER DISPENSING APPARATUS Filed Dec. 9, 1952 4 Sheets-Sheet 4 FIG! INVENTOR NELSON E. ANDERSON BY A. WWW

ATTORNEY United States Pate'ntfOfiYice Patented Mar. 13, 1956 POWDER DISPENSING APPARATUS Nelson E. Anderson, Berkeley Heights, N. J., assignor to Air Reduction Company, Incorporated, New York, N. Y., a corporation of New York Application December 9, 1952, Serial No. 324,971 Claims. (Cl. 302 56) This invention relates to apparatus for feeding powdered material into a flowing gas stream for mixing with and entrainment by the gas. i

There are many industrial applications in which it is necessary to entrain dry powdered material in a flowing gas stream. One such application is in oxyacetylene cut-' ting where it has been found advantageous to add a flux such as sodium bicarbonate or iron powder to the cutting gas to promote the cutting action on certain materials such as stainless steels or for certain cutting operations where the cut must be maintained across several reentrant sections. Such a process is disclosed in Linnert Patent No. 2,454,325 issued November 23, 1948. Another application of the use of apparatus of the type to be disclosed herein is in the treatment of molten metals such as the process of desulfurizing ferrous metals by the injection of pulverized calcium carbide into the molten metal bath with a carrier gas. Such a process is disclosed in Hulme Patent No. 2,577,764 issued December continuously in a uniform and regulated amount into a flowing gas stream.

Figure 2 is a sectional view of the dispensing unit proper, which unit forms a portion of the apparatus of Figure 1.

Figure 3 is a side view, partially in section, of the apparatus of Figure 2.

Figure 4 is a sectional view taken along line 4-4 of Figure 2.

Figure 5 is a view of the apparatus of the present invention as used with an auxiliary powder supply.

Referring to Figures 1-4 of the drawings, carrier gas may be suppliedto the systemfrom any suitable source such as compressed gas cylinder 10. Gas is admitted to the system through a cylinder valve 11, a pressure refine ing and regulating valve 12 and a down-stream'shutoft valve 13. The'gas, which serves as a carrier for the? powdered material, flows through conduit 15 to the dispensing unit generally designated as 16. The gas enters the dispenser at the bottomof a pressureve'ssel 17throughf pressure fitting 18. The gas circulates through thedisprising a tricycle support. The cylindrical pressure vessel 17 is mounted above the base 22 by means of angle iron supports 23 bolted to ears 25 welded to either side of the vessel 17. The cylindrical pressure vessel 17 is divided into upper and lower

pressuretight compartments

26 and 27 respectively by dividing wall 28. The volume 26 above the wall is the powdered material supply hopper. In the basic unit this hopper is closed at the top by a pressuretight lid 30 of suitable design. A powder drain 29 is provided in the side Wall of hopper 26 near the bottom. The volume 27 below the wall houses the powder feed motor mechanism and the actual feeding and mixing elements. This lower pressuretight compartment is closed by the pressure vessel bottom plate 31 which is held against the cylindrical wall by bolts 32 through the bottom plate 31 and an external flange 33 welded to the cylinder. In general the feeding is accomplished by vibrating the hopper 26 (pressure vessel 17) to permit the powdered material to fall by gravity onto a substantially horizontal delivery platform 35. This platform vibrates in such a manner that the powdered material walks across the platform and is dropped from the end of the platform into a vertical pipe 36 through which the carrier gas stream is flowing.

The hopper and platform are vibrated by a magnetic vibratory motor having the electromagnet 37 rigidly secured to the hopper 26 and its armature 33 secured to the platform 35. The hopper and the platform are connected by

leaf springs

40, 41 and 42 in the following manner. An assembly plate 43 is bolted to the underside of the dividing wall 28 of the pressure vessel by bolts Three suspending brackets, 46, 47, and 48, are welded to the assembly plate 43 at an angle in such a manner that they project downwardly from the assembly plate at an acute included angle with the plate. In plan the three brackets are triangularly disposed and two of these brackets, 47, and 48, are considerably longer than the third. A leaf spring is bolted to each of the three brackets and projects downward from them at the same angle as the brackets. Two similar assembly brackets, and 51, are welded to the top of the delivery platform. Of these a single bracket 50 is bolted to the bottom of leaf spring 40 and a single long bracket 51 is bolted to the bottom of both

leaf springs

41 and 42. Appropriate notches are provided in the bottom of the brackets for the passage of the powder channel to be described more fully hereinafter. As a result of the above described construction the delivery platform 35 is suspended from the bottom of the dividing wall 28 of the pressure vessel 17 by these three inclined leaf springs. The electromagnet 37 of the vibratory motor is rigidly secured to the hopper through penser in amanner to be'hereinafter described and" emerges through another pressure fitting 20 in the bottom of the pressure vessel 17 into discharge conduit 21*with the powdered material entrained.

The dispenser unit is best described with reference'to' Figures' 2, 3 and The unit consists of a base 2200111- the medium of two downwardly extending

support brackets

52 and 53. The armature 38 of the vibratory motor is rigidly secured to the delivery platform 35 through the upwardly extending bracket 51. When the magnetic motor is energized by alternating current or pulsating direct current the armature 33 and magnet 37 are intermittently attracted toward one another against the restraining force of the leaf springs. The result is a vibratory motion of both the armature and the magnet in a direction at right angles to the axes of the leaf springs. Referring to Figure 2 the resultant motion of the platform is up and to the left and down and to the right. The hopper and delivery platform will both vibrate, the vibration of the platform exceeding that of the hopper approximately in the inverse ratio of their respective masses.

Powdered material is supplied to the delivery platform by gravity from the hopper 26 which constitutes the portion of the pressure vessel 17 above the dividing wall 23. One end of a length of rigid tubing 55 is secured within an appropriate opening 55 on the assembly plate 43 which opening is in alignment with a similar opening in the dividing wall. A resilient sealing ring 57 surrounds the opening between the assembly plate and the pressure vessel dividing wall 23 to assure a gastight seal between these elements. A short length of flexible tubing 58 such as rubber hose is connected to the lower end of the rigid tube 55 to link it to a circular fitting 60 onthe receiving end of the delivery platform 35. A gastight seal is affected at both ends of the resilient tube. A screen 61 is preferably placed across the hopper discharge to prevent ovcrsizcd powder particles from getting into the feed channels. An inverted U-shaped member 62 is welded to the delivery platform to form a gastight enclosure or channel for the powdered material to contain it as it is walked across the delivery platform from the receiving end to the delivery end. The edge of the delivery platform at the end of the powder channel is preferably of sawtooth configuration to promote uniform discharge of material from the platform.

The electromagnet 37 in the device illustrated is energized from an alternating current service line through an on-oif switch 63, a constant voltage transformer 65, and a variac 66. The rate of feed of powdered material may be controlled by varying the frequency of a constant voltage impressed on the magnet coil or preferably, as in the apparatus here shown, the amplitude of vibration may be varied by controlling the amplitude of the voltage impressed at a constant frequency. For this'reason a constant voltage transformer 65 is inserted in the line to absorb variations in line voltage and prevent these line voltage variations from being reflected in the delivery rate of the dispenser. The variac 66 (variable auto transformer) could be replaced by some other variable voltage dividing or reducing device.

The carrier gas which enters the device through conduit fills the entire lower pressuretight compartment 27 of the pressure vessel 17 in which compartment the above described vibrator and delivery platform and accessories are mounted. The gas discharges from this chamber through pipe 67 and check valve 68 into a vertical mixing and pressure equalizing conduit 36. The lower portion of this conduit, in conjunction with pressure fitting 20, etc., constitutes in effect the dispenser discharge outlet. This conduit extends through an appropriate opening in the dividing wall and is open ended near the top of the hopper 26. A gastight seal is formed between the outside of the conduit 36 and the dividing wall 28. Just below the point at which gas enters the conduit 36 from pipe 67 and check valve 68, and forming part of the conduit 36 a length of flexible tubing 70 is inserted connecting the upper portion of the conduit 36 to another rigid section 71 which makes a T-section gastight seal with the delivery platform and the inverted U-shaped member 62. Just below the rigid portion '71 into which the delivery platform feeds is another section of flexible tubing 72 which is hermetically sealed to the outlet fitting 20 which in turn is connected to the delivery tube 21 leading from the dispenser. The normal flow of gas through this apparatus is as follows. Gas enters the bottom of the pressure vessel 17 through tube 15 and circulates freely in lower chamber 27 from which it discharges through pipe 67 and check valve 625 into conduit 36. Pipe 67 is preferably horizontally disposed or has its open end slightly higher than the end attached to the check valve. From its entry into the mixing and pressure equalizing conduit 36 the gas flows downward past the delivery platform discharge and through the outlet fitting 2i) and outlet tube 21. Gas is free to fiow upwardly in conduit 36 and fill the powdered material hopper, but this flow ceases as soon as the pressure in the hopper reaches the system pressure. In normal operation the only flow of gas up into the hopper is that which is necessary to displace the powdered material that is being discharged from the hopper.

When the above described powder dispensing and gas supply systems are operated simultaneously a uniform supply of powder is dropped into the flowing gas stream as the gas passes the end of the powder channel of the delivery platform in the lower portion of the mixing and pressure equalizing conduit. The volume of gas delivered by the system is readily adjustable by manipulation of regulator 12 and valve 13. The quantity of powdered material fed into the preselected flow of gas may be controlled by adjusting the variable output auto transformer 66 which varies the amplitude of vibration of the vibratory motor and thus controls the rate of delivery of the powdered material to the gas stream.

A completely balanced pressure prevails in all parts of this dispensing device. This makes its dispensing feed rate completely independent of gas pressure. The pressure in the lower gastight compartment which houses the feeding mechanism is equal at all times during operation to the pressure above the powdered material in the hopper because of the pressure equalizing effect of the unrestricted pressure equalizing conduit. Furthermore, the pressure in the hopper and in the voids between solid powder particles in the hopper, in the delivery tube, and on the delivery platform is equal to the pressure surrounding the delivery tube and delivery platform. The hopper and the delivery platform vibrate in such a manner that they move in opposite directions creating a shearing action between the receiving fitting of the delivery platform and the hopper discharge pipe. This is a most desirable action to assure the powdered material flowing freely from the hopper to the delivery platform. As previously explained, a resilient tube 58 connects these two moving parts. Were it not for the'fact that the pressure inside and outside of this resilient tube are equal there would be a tendency for the tube to collapse and restrict the fiow of powder through it or to expand and perhaps blow ofi the hose clamps or other fittings used to secure it to the rigid members. This would be particularly true where considerable gas pressure was employed as it is in some commercial applications. For injecting powdered material into a metallurgical bath, for instance, gas pressures in excess of pounds per square inch may be required. Lengths of resilient tubing are also necessary to connect the rigid upper portion of the mixing and pressure equalizing. conduit to the T-fitting on the end of the delivery platform. Similarly another length of resilient tubing is required to connect the lower end of this T-fitting to the stationary outlet in the base of the pressure vessel. For the reasons described hereinbefore it is particularly advantageous to have the internal and external pressures equal on these resilient tubes. This is accomplished by the present device.

Another important feature of this dispenser is that the powdered material is completely enclosed and isolated in such a manner that it cannot accumulate in any part of the device except in the storage hopper and in the designated feeding channels. The powdered material is dispensed from the end of the feeding platform directly into the flowing gas stream in a confined passage such that the dispensing material cannot accumulate on any ledge or in the base of the'device or elsewhere to build up and eventually fall off in non-uniform amounts. With the construction of the present invention the powdered material is confined to those portions of the apparatus from which it may be moved by the vibratory action or by the gas fiow by virtue of being directly in the gas flow path. Thus should the gas fiow be interrupted and the powder feed continued the'powder will accumulate only in the gas outlet pipe and it will be'picked up immediately upon reestablishment of the gas flow. No powder can enter the lower pressure chamber that houses the vibrator mechanism because gas only flows outwardly from this chamber into the powder containing portion of the system. To be certain that gas only flows outwardly, the check valve 68 is provided at the point of gas exit. This prevents reverse flow; A minor exception gasses to this occurs when the gas is suddenly shut off down stream of the dispenser. This creates a pressure shock wave that travels upstream and which can carry a limited amount of powdered material back through the check valve before it closes. The length of substantially horizontal tubing 67 providing an entrance conduit for the check valve 68 accommodates this situation by retaining the small amount of powder carried through the check valve under the above conditions. When normal gas flow is resumed this powder is picked up by the gas and carried through the check valve and back into the normal channels. Confining the powdered material to the channels above described has the additional advantage of preventing powdered material from interfering with the normal operation of the vibrating mechanism. This is particularly important where the powdered material being fed is iron powder. Should the iron powder be permitted to come in contact with the vibratory motor it would adhere to the electromagnet and clog the air gap between the magnet and the armature and soon interrupt the normal operation of the vibrator.

With the apparatus thus far described the process for which this device is employed may be kept continuously operating only as long as the supply of powdered material in the dispenser hopper lasts. To increase the capacity of the system or to make it continuously operating for an indefinite length of time an auxiliary hopper may be supported above the dispensing unit in such a manner that the supply in the dispensing hopper can be replenished during operation. Such apparatus is illustrated in Figure 5. This apparatus is more fully disclosed and claimed in the Joseph F. Kiernan application, Serial Number 324,991, filed December 9, 1952, and assigned to the assignee of the present application. In Figure the dispensing unit and the gas supply system are similar in all respects to the unit illustrated in Figures 1 through 4. The elements of the apparatus shown in Figure 5 corresponding exactly to similar elements. in the preceding figures are designated by the same reference numbers as in the prior figures but with the postscript a. Thus the pressure vessel designated 17 in Figures 1 and 4 is designated 17a in Figure 5, etc.

Referring to Figure 5 an auxiliary hopper 75 is supported on a tripod base 76 above the dispensing unit heretofore described in detail. This auxiliary hopper 75 is a simple pressure vessel having a pressuretight head 77 and pressuretight discharge fittings 78 at the bottom which are terminated in a valve 90 of suitable construction. This valve should open wide and provide a straight run for material through it. Since this hopper 75 is not vibrated the hopper walls are inclined at an angle greater than the angle of repose of the material being fed in order to assure constant feeding of the entire hopper contents. The pressure lid 30 of the dispensing unit shown in Figures 1 and 4 is replaced by a pressure fitting 81 that is connected to the valve 80 by a length of flexible tubing 82. A gas conduit 83 connects the upper pressure compartment of the dispensing unit with the auxiliary hopper 75. A shutofli valve 85 is inserted in this interconnecting line 83. The pressure will equalize in the two hoppers when the valve 85 is open, and when the

valves

80 and 85 are closed the hoppers are isolated from one another. A pressure gage 86 indicates the pressure in the auxiliary hopper and pressure gage 87 indicates the pressure in the dispenser hopper. A blowofi valve 88 permits the pressure in the auxiliary hopper to be relieved. A relief valve 90 provides for the blowoif of excessive pressure in the entire system. An auxiliary gas supply pipe 91 is provided so that during the operation of the system should a large volume of gas be required to raise the pressure in the auxiliary hopper 75 there will be no danger of the flow of gas in the dispenser mixing and pressure equalizing conduit being reversed and therefore the feed of powdered material I .6 r from the system interrupted. A shutoif valve 92 may be provided in this line but is not required.

The auxiliary hopper makes possible continuous operation of this unit in the following manner. The dispenser hopper and'the auxiliary hopper are initially filled with powdered material. The dispenser hopper of course must not be filled in such a manner that the powdered material is permitted to overflow in the open end of the mixing and pressure equalizing conduit. In the preferred mode of operation, valve 80 is closed and the gas pressure is admitted to the entire system. This is done by opening

shutofi valves

13a and 92. When the supply of powdered material in the dispenser hopper begins to run low, valve 80 is opened and powdered material feeds down by gravity from the auxiliary hopper to replenish the supply in the dispenser hopper. When the dispenser hopper is again .filled to the desired level, valve 80 may be closed. If

shutoff valve 85 is then closed and blowoif valve 88 opened, the pressure in the auxiliary hopper may be relieved without effecting the continuing functioning of the dispensing system. When the pressure has been relieved from the auxiliary hopper 75 the pressure lid 77 may be opened and the supply of powdered material in the auxiliary hopper replenished. The pressure lid is then replaced and shutoff valve 85 reopened permitting the pressure to build up again in the auxiliary hopper to the pressure of the entire dispensing system. This sequence of operations may be performed as often as necessary to permit continuous feeding of powdered material to the molten metal bath. When the auxiliary hopper is being brought up to pressure after refilling, there may be considerable gas flow into the auxiliary hopper. Gas supply bypass 91 permits this required flow without upsetting the normal flow pattern in the dispensing unit.

I claim:

1. Apparatus for dispensing powdered material into a flowing gas stream at superatmospheric pressure comprising a cylindrical pressure vessel containing a transverse dividing wall to form an upper pressure chamber which constitutes a powder hopper and a lower pressure chamber which constitutes a gas inlet chamber, a vertical conduit within said pressure vessel placing the top of the interior of said upper pressure chamber in communication with a dispenser outlet fitting in the bottom of said pressure vessel, a powder delivery platform within said lower pressure chamber suspended by leaf springs from said transverse dividing wall, a wholly enclosed powder channel on said delivery platfom which communicates with said vertical conduit, a length of flexible tubing connecting a hopper discharge port in the transverse dividing wall of said pressure vessel with said powder channel, electromagnetic means within said lower pressure chamber for vibrating said delivery platform to feed powder from said hopper to said vertical conduit, means for admitting gas to said lower pressure chamber, and means including a check valve for permitting gas to flow from said lower pressure chamber into said vertical conduit at a point above the point of delivery of powder from said powder channel to said vertical conduit.

2. Apparatus for dispensing powdered material into a flowing gas stream at superatmospheric pressure comprising a first pressure retaining chamber adapted to retain a supply of powder to be dispensed, a second separate pressure retaining chamber below said first chamber, a discharge conduit through which said flowing gas stream passes and into which the powdered material is dispensed for mixing with and entrainment in said gas stream, powder feeding means including a vibrating mechanism and a wholly enclosed powder delivery conduit communicating only with said first chamber and said discharge conduit and vibrated by said vibrating mechanism, said powder feeding means being positioned within said second chamber, mean-s for admitting gas at superatmospheric pressure to said second chamber, means for discharging gas from said second chamber into said discharge conduit to form therein said flowing gas stream, and means for admitting gas to said first chamber above the powder therein from said second chamber to equalize the pressure in said first and second chambers.

3. Apparatus according to claim 2 in which the means for discharging gas from said second chamber into said discharge conduit includes a check valve.

4. Apparatus according to claim 3 in which the means for admitting gas to said first chamber from said second chamber includes a check valve.

5. Apparatus according to claim 2 in which the means References Cited in the file of this patent UNITED STATES PATENTS 2.375,766 Britcher May 15, 1945 2,533,331 Skinner Dec. 12, 1950 2,549,033 Tyrner Apr. 17, 1951