US3565296A

US3565296A - Power feeder mechanism having means for moving powder to a gas carrier

Info

Publication number: US3565296A
Application number: US773235A
Authority: US
Inventors: Stephen G Brush; Harold Gruen; John D Peterson; Charles H Piltzecker
Original assignee: Avco Corp
Current assignee: ABRASIVE INDUSTRIES Inc A DE CORP; Avco Corp
Priority date: 1968-11-04
Filing date: 1968-11-04
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23

Abstract

The disclosure shows a feeder for powdered metals, or the like, which are used in flame-spraying systems. Powdered metal is placed in a rotating, sealed drum. Pressurized gas is fed through a carburetor into the drum. A metered amount of material is entrained in gas entering an upwardly facing port. The entrained powder is carried through the carburetor to a conduit which conveys it to a plasma-type flame-spraying applicator. Gas enters the carburetor upstream of the metering port, through a downwardly opening, compensating port. This compensating gas supplements the flow of gas which carries the entrained powder through the carburetor after it enters the metering port. A central tube in the carburetor defines, in part, both the metering and compensating port. This tube is rotated to simultaneously change the feed rate of the powdered material and adjust the flow of supplemental gas to insure that powdered metal will flow uniformly at all feed rates.

Description

O United States Patent [111 3,565,296

[72] Inventors Stephen G. Brush 3,152,733 10/1964 Ross 222/193 Thompson, Conn.; 3,223,288 12/1965 Stern 222/369X Harold Gruen, Framingham; John D. Prima E S ry xammertanley H. Tollberg fi mz g g giz ggg Att0meys-Charles M. Hogan and Abraham Ogman 9 9 [211 App]. No. 773,235

:gfg 23: 3 ABSTRACT: The disclosure shows a feeder for powdered 73] A A fio metals, or the like, which are used in flame-spraying systems. I Ss'gnee y g g g gi Powdered metal is placed in a rotating, sealed drum. Pressurized gas is fed through a carburetor into the drum. A metered amount of material is entrained in gas entering an up- [54] ow FEEDER MECHANISM HAVING MEANS wardly facing port. The entrained powder is carried through FOR MOVING pow o A GAS CARRIER the carburetor to a condult which conveys 1t to a plasma-type 18 Claims, 7 Drawing Figs. flame-spraying applicator. Gas enters the carburetor upstream of the metering port, through a downwardly opening, compen- [52] US. Cl 222/193 gating port. This compensating gas supplements the fl ofgas [51] f 367d 5/54 which carries the entrained powder through the carburetor [50] of Search 222/193 after it enters the metering port. A central tube in the carbure- 369 tor defines, in part, both the metering and compensating port. This tube is rotated to simultaneously change the feed rate of [56] References cued the powdered material and adjust the flow of supplemental gas UNITED STATES PATENTS to insure that powdered metal will flow uniformly at all feed 3,093,268 6/1963 Smith et a1 222/193X rates.

PATENTEUFEBNIQYI 3,555,296

SHEET 1 OF 3 STEPHEN G. BRUSH HAROLD GRUEN JOHN D. PETERSON CHARLES H.PILTZECKER INVENTORS AT RNEYS.

Minnie-mm SHEET 2 BF 3 ELECTOR I I8 DRUM SPEED FEED RATE STEPHEN G. BRUSH HAROLD GRUEN JOHN DPETERSON CHARLES H. PILTZECKER INVENTORS ATTORNEYS.

PATENTED-FEB23 1971 SHEET 3 BF 3 \i. N9 3 mm A 8 POWER FEEDER MECHANISM HAVING MEANS FOR MOVING POWDER TO A GAS CR The present invention relates to improvements in powderfeeding devices.

There have been many devices for feeding various types of powdered material. Such devices generally feed powered materials to a dispensing mechanism. While the present invention has utility to such a broad class of powder-feeding systems, it particularly fulfills the unique and demanding requirements of feeding powdered metals, or the like, which are to be sprayed, in an essentially molten state, so as to surface coat a base material. In more particularity, the plasma system for such flame-spraying systems requires that the powdered materials be entrained in an inert gas stream as they are heated in a high energy field.

Previous powder-feeding devices used in such plasma systems have had many shortcomings. For example, it has been extremely difficult to obtain accurately metered rates of powder flow which can be maintained at uniform flow rates. A further problem is that changing from one type of powder to another requires a great deal of cleaning effort to insure the previous material will not contaminate a new material which is to be sprayed.

Recently developed sprayable materials give further emphasis to these problems as well as making more critical other requirements for successful flame spraying. New powders in particular are formulated of a mixture of powders which individually vary greatly as to particle size, particle size distribution and density. It is essential that the feeder maintain the original formulation throughout the feeding of any batch of material.

Finer powder particle size makes more difficult the feeding of accurately metered amounts and maintaining uniform flow of entrained powdered material in the gas stream. Further, the wider selection of sprayable materials makes changing of the flame-spraying equipment more desirable and necessary in order that the coating which is applied will best suit the needs of a given job.

It should also be noted that powdered materials for these purposes are extremely hard and abrasive. This factor renders wholly impractical approaches which are suitable for feeding many other types of materials.

Accordingly, one object of the present invention is to overcome the shortcomings of presently existing feeders and otherwise meet the requirements of feeding powdered materials to flame-spraying equipment.

Another and broader object is to provide an improved feeder capable of maintaining the formulation of a batch of mixed powders and feeding accurately metered amounts of such powders at uniform flow rates.

Another object of the invention is to minimize cleaning requirements and provide for rapid changeover in feeding different types of powder.

A further object of the invention is to accomplish the above ends through the provision of a feeder which is simple and reliable in operation, as well as being inexpensive to manufacture.

These ends are attained through a feeder comprising a carburetor having an upwardly open metering port leading to a discharge passageway. Powder is tumbled over this port, preferably by disposing the carburetor within a rotating drum. Gas flows through the metering port and carries entrained powder along the discharge passageway, which, in turn, may be connected to a dispensing device.

Gas flow along the discharge passageway may be supplemented in accordance with another feature of the invention by additional gas. Preferably a compensating port provides this gas flow upstream of the metering port. It is also preferable to provide means for adjusting the effective openings of the metering ports and do so in a simultaneous, inverse fashion so that a substantially constant gas flow is maintained, particularly to facilitate uniform flow of low rates of powder feed.

Other features are found in sealing the drum relative to the carburetor, pressurizing the drum with gas flowing through the carburetor, and using this pressurized gas to increase the effectiveness of the drum-sealing means.

Further features are found in mounting the carburetor in cantilever fashion, joumaling the drum on the carburetor and providing a quickly detachable drum which readily exposes the minimum surface areas which require cleaning when changing from one powder to another.

The above and other related objects and features of the invention will be apparent from 'a reading of the following description of the disclosure found in the accompanying drawings and the novelty thereof pointed out in the appended claims.

In the drawings:

FIG. 1 is a side view, in section, of a powder feeder embodying the present invention;

FIG. 2 is a section, taken on line IIII in FIG. 1;

FIG. 3 is a section, taken on line III-III in FIG. I, with portions broken away;

FIG. 4 is a section, on an enlarged scale, taken on line V-V in FIG. I; I

FIG. 5 is a section, with portions broken away and on a further enlarged scale, taken on line V-V in FIG. 2;

FIG. 6 is a perspective view taken at arrow C in FIG. 5; and

FIG. 7 is a similar perspective view further illustrating operation of the feeder.

First referencing FIGS. 1 and 2, the present feeder comprises a supply drum 10 which is filled with powdered material, preferably to about one-third of its capacity. A pressurized gas source is connected to the feeder, at a rear connection port 12. This pressurized gas is fed, in a manner later described, into the dnim 10, being discharged therein from a carburetor 14 at a point indicated by arrow A in FIG. 1. The drum is rotated to tumble powdered material over the carburetor. A metering port, at the location of arrow B, passes pressurized gas from the drum 10 into the interior of the carburetor 14. The pressurized gas entering the carburetor at arrow B carries with it entrained powder. This feeding action is facilitated by gas entering the carburetor at arrow C. The entrained powder and gas are then discharged from the rear of the feeder through a tube 16. The tube 16 may be connected to an appropriate dispensing device, as for example, a plasma gun used in flame spraying.

The carburetor 14 includes an elongated shaft 18 which is mounted in cantilever fashion by securing its enlarged rear end in a support 20, through the use of a set screw 22. The support 20 is mounted, as by welding on a port 24. The port 24 may be formed integrally with a cast frame 26 which includes a plate 28 supported by depending flanges 30 at its rear and side edges.

The drum 10 is secured to a hollow spindle 32 which is journaled for rotation on the cantilevered shaft 18 by ball bearings 34. The spindle 32 projects partially into the drum l0 and is provided thereat with a series of four seals 36 to isolate the bearings from the powder within the drum. The effectiveness of the seals is further enhanced by means later described. A seal 38, at the opposite end of the spindle 32, isolates the bearings 34, which are, themselves, of the sealed type, from any abrasive materials which might be in the atmosphere.

A belt 40 is trained around a wheel or pulley 42, secured to the spindle 32 and around a wheel 44 secured to the output shaft 46 of a geared, speed reduction unit 48. The speed reduction unit 48 is driven by a motor 50 mounted on the frame plate 28. Controls for the motor are mounted on a panel 52 extending between the side flanges 30 and secured to the frame by screws 54. A panel 55 is secured to the supporting flanges 30 and control panel 52 to seal off a compartment, below the plate 28, in which control mechanism is housed.

These controls include an off-on switch 56, a drum speed knob 53 and a timer knob 60. The switch 56, of course, controls the main current supply to the motor 50. The knob 58 may regulate a conventional speed control of the type common for DC motors. The knob 60 may set a timer to control the length of time the feeder is to be in operation.

The drum 10 is, by the described drive, rotated at a relatively slow and controllable rate on the shaft 18. The powder within the drum tumbles down onto the outer end of the carburetor 14 which projects within the drum. This tumbling action is facilitated by fins 62 projecting inwardly from the outer drum wall. Additionally, these fins and the tumbling action they produce effectively maintain a constant formulation of the various constituents of the powder.

A hood or cover 64 covers the moving parts of the feeder and conveniently rests in a peripheral groove 66 formed in the frame 26. A handle 68 is formed integrally with the support 20 and projects above the cover 64 to provide portability for the feeder.

A detailed description of the carburetor 14 will now be given with particular reference to FIGS. -7. As was previously noted, the carburetor comprises a cantilever mounted shaft 18. Within this shaft is a tube 70. The shaft 18 is relieved to form an annular passageway 72 surrounding the tube 70 from the point illustrated by arrow A to within the support 20. The passageway 72 is connected to the pressurized gas supply port 12 (FIG. 1) by a hole 74 (in shaft 18) which communicates with a tube 76 (FIG. 3). The tube is connected at its lower end to a passageway 78, through port 24, which extends to the supply port 12 (FIG. 1). Pressurized gas, thus supplied, is introduced into the drum through a fixed port 80 at the point indicated by arrow B.

The tube 70 provides a discharge passageway 82 extending from the interior of the drum 10 to the tube 16 which delivers powder to a dispensing device. Powder, entrained in gas, enters the discharge passageway 82, at arrow A, through a variable port formed by

radial holes

84, 86 in the shaft 18 and tube 70 respectively. Further gas enters the discharge passageway 82 through a variable compensating port, at arrow C, formed by

radial holes

88, 90 in the shaft 18 and tube 71 respectively.

The areas of the metering port and compensating port are varied by rotating the tube 70. To this end a sprocket 92 is secured to the rear end of the tube 70. A screw 94 is threaded into the forward end of the tube 70'and through a washer 96 draws the sprocket 92 against an O-ring 98 to seal the rear end of the gas supply passageway 72.

At this point it will also be noted that the seals 36 are rendered more effective by providing holes 100 from the passageway 72 to the spaces between adjacent seals. Vent holes 101 are also provided between the rear seal 36 and the forward bearing 34. In this fashion the pressure gradients across individual seals is minimized and migration of powder outwardly of the drum 10 is essentially eliminated. This not only increases seal life but also prevents the bearings 34 (FIG. 1) from being eroded by the powder. It will also be seen from FIG. 5 that the seals 36 are held in place by a snap ring 102 with rings 104 maintaining the spacing therebetween.

Having described the manner in which the tube 70 is journaled and the carburetor is sealed for rotation of the drum as well, attention is directed to FIGS. 1 and 3, which show that the sprocket 92 is connected to a sprocket 106 by a chain 108. The latter sprocket is secured to the output of a Selsyn motor 109. The motor 109 is mounted on a flange 110 depending from the frame plate 28. The input shaft for the motor 109 is connected by a plastic tube 112 to the stem 114 of a feed control knob 116 journaled on the control panel 52. The described means for rotating the tube 70 enables high, accurate feed rates to be maintained. A selector knob 118 (FIG. 2) is also provided on the control panel 52 to enable remote operation of the feed rate control through appropriate switching means.

In operation the drum 10 is loaded with powder, preferably to about one-third of its capacity. A port may be provided in the drum to facilitate loading or the drum may be removed in a manner later described, for loading. As the drum rotates the powder is tumbled over the carburetor 14. There is a continuous flow of gas through the metering port at arrow A. The combined action results in an accurate metering of the powder which is entrained in the gas stream flowing through the discharge passageway 82. The rate of powder feed may be adjusted by turning knob 116 to rotate tube 70 and vary the degree of registration of the

holes

84, 86 which define the metering port.

It will be seen from FIG. 6, that when the

holes

84, 86 are fully registered, the compensating port, holes 88, are almost out of register. Thus the compensating gas flow is at a minimum. As the tube 70 is rotated in a counterclockwise direction from the FIG. 6 position to the FIG. 7 position, the metering port is progressively reduced as the compensating port opening is increased in inverse fashion. Compensating gas flow, thus provided from a point upstream of the metering port, maintains an essentially constant gas flow rate through the discharge passageway 82 and is of particular importance in assuring uniform flow of low rates of powder feed. The compensating port opens generally downwardly into the drum so that there will be essentially no powder entrained in the compensating gap.

The tube 82 may also be rotated further in a clockwise direction to completely close the metering port and thus shut off powder feed. The selector switch 118 provides for remote control of the feed rate.

The drum 10 not only provides the desired tumbling of powder over the carburetor 14, it also is highly effective in blending the powder so that the proportions of its constituents are maintained constant in feeding a given batch of powder. This is to say that there is a continuous mixing action which blends particles of different size, density or shape in a homogeneous fashion as they tumble over'the carburetor and are entrained in the gas flowingthrough the metering port. Thus there is no selective entrainment of any particular constituent of a mix of powders which would result in the last portion of a batch being different from that initially fed from the batch.

The drum 10 will be found to have a preferred, relatively slow rate of rotation for any given batch of powder, dependent on such factors as its specific gravity and particle size. The speed control which is adjusted by knob 58 enables the correct speed to be quickly and accurately set. The timer control, set by knob 60, can be used to limit the duration of drum rotation so that the drum will not be inadvertently left running for long periods of time.

The described feeder has further advantages in changing from one powder to another. The drum 10 is preferably mounted on the spindle 32 by a quick attachment connection. This is better shown in FIG. 4 where it will be seen that headed studs 120 project from a spindle flange 122 (see also FIG. I). These studs are received through keyhole slots in the drum, which is then rotated to its locked position on the spindle.

When the drum is removed, only the carburetor and a relatively small portion of the feeder has been in contact with the powder and requires cleaning. The drum also may be readily cleaned. However, the drum itself is a relatively inexpensive item and, therefore, it is contemplated that different drums will be used for different types of powder. This not only simplifies cleaning procedures, but facilitates storing of small quantities of powder normally remaining in the drum after feeding powder for a given application.

It will further be appreciated that the cantilever mounting of the carburetor, joumaling the drum on the cantilever, and the described sealing means are particularly adapted to the overcoming of problems normally inherent in handling highly abrasive powders as are used in flame spraying. This is particularly true, considering that it is desired to operate in a sealed chamber and with pressurized gases other than air.

Many variations in the described, preferred embodiment, within the spirit and scope of the present inventive concepts, will occur to those skilled in the art. The claims, therefore. encompass other structure beyond what is specifically described.

We claim:

1. A feeder comprising:

a carburetor having an upwardly open metering port and a discharge passageway maintained at a lesser pressure than at the entrance to said metering port, said port opening into said passageway whereby there is gas flow through said metering port into the discharge passageway;

port means for introducing compensating gas into said discharge passageway to maintain constant gas flow through said discharge passageway to facilitate flow of entrained powder through said metering port and discharge passageway; and

means for tumbling powder over said metering port whereby a metered quantity of powder will be entrained in the gas flowing through said discharge passageway for delivery from said feeder.

2. A feeder as in claim 1 wherein the tumbling means comprises a drum rotatable about an axis having a sufficient horizontal component for powder therein to be carried above the metering port and then fall thereon.

3. A feeder as in claim 2 further comprising:

means for sealing the drum relative to the carburetor; and

means for introducing pressurized gas into said drum whereby the pressure in the discharge passageway is maintained at said lesser pressure.

4. A feeder as in claim 3 further including:

port means for introducing compensating gas into said discharge passageway, upstream of said metering port, to facilitate flow of entrained powder through said metering port and discharge passageway and means for adjusting the openings of said metering port and said compensating port means.

5. A feeder as in claim 4 wherein, the adjusting means simultaneously and inversely vary the openings of said metering port and compensating port means to increase gas flow through the compensating port means as the opening of the metering port is decreased. I

6. A feeder as in claim 5 wherein:

the carburetor includes an outer shaft mounted in cantilever fashion with its free end projecting into said drum, and a tube telescoped therein, the interior of the tube forming said discharge passageway, said tube and shaft having registerable holes forming said'metering port and compensating port means; and

the adjusting means comprise means for rotating said tube within said shaft to vary the registration of said holes.

7. A feeder as in claim 6 wherein, an annular passageway surrounds said tube to a point spaced'from said metering port, said shaft having a hole extending from said annular passageway to the interior of said drum, whereby said annular passageway may be connected to a source of pressurized gas to pressurize said drum.

8. A feeder as in claim 7 wherein:

the drum axis is essentially horizontal; and

further including a spindle joumaled on said carburetor shaft, said drum being secured to said spindle.

9. A feeder as in claim 2 wherein:

the drum axis is essentially horizontal;

the carburetor is mounted in cantilever fashion with its free end projecting into said drum; and

the drum is joumaled on the carburetor.

10. A feeder as in claim 8 wherein:

the drum sealing means comprise a plurality of annular sealing elements disposed between the spindle and carburetor and axially spaced apart; and

the carburetor shaft has holes extending from said annular passageway to the spaces between said sealing elements to pressurize said spaces and isolate the spindle journal means from powder carried in said drum; and

means providing a vent between the sealing means and the journaling means.

11. A feeder as in claim 8 further including means for detachably mounting said drum on said spindle. 12. A feeder as in claim 9 further including:

a spindle stcilpported by bearings on said carburetor; and means for e achably mounting said drum on said spindle to provide means for joumaling the drum which will permit its removal in changing to another type of powder.

13. A feeder as in claim 8 further including means for varying the rate of drum rotation.

14. A feeder as in claim 8 wherein the drum includes fins projecting inwardly from its inner circumferential surface to facilitate the tumbling action and blend the powder in operatron.

15. A feeder as in claim 2 wherein the drum includes fins projecting inwardly from its inner circumferential surface to facilitate the tumbling action and blend the powder in operation.

16. A feeder comprising:

a feeding unit including gas input means and gas discharge means;

means supporting the feeding unit at one end in cantilever fashion;

a spindle;

means rotatably supporting said spindle on said feeding unit;

a drum detachably secured to said spindle whereby said drum may be removed from said spindle; and

means for rotating said spindle for rotating said drum.

17. A feeder as in claim 16 further including means for sealing said drum relative to said feeding unit.

18. A feeder as in claim 16 further including multiple spaced sealing means between said spindle and said feeder unit to seal said drum, the spaces between said spaced seals being in fluid communication with said gas input means for maintaining a higher gas pressure than the gas pressure in the gas discharge means.

g;;g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3, 565, 296 Dated February 23, 1971 Inventor(s) Stephen G. Brush, et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 7, for "powered" read--powdered--; Column 3, line 35, for "71" read--70--; Column 4, line 71, after "described" insert the following paragraph--Having thus described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States Signed and sealed this 6th day of July 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,J'R. WILLIAM E. SCHUYLER, JR Attesting Officer Commissionerof Patent:

Claims

2. A feeder as in claim 1 wherein the tumbling means comprises a drum rotatable about an axis having a sufficient horizontal component for powder therein to be carried above the metering port and then fall thereon.
3. A feeder as in claim 2 further comprising: means for sealing the drum relative to the carburetor; and means for introducing pressurized gas into said drum whereby the pressure in the discharge passageway is maintained at said lesser pressure.
4. A feeder as in claim 3 further including: port means for introducing compensating gas into said discharge passageway, upstream of said metering port, to facilitate flow of entrained powder through said metering port and discharge passageway and means for adjusting the openings of said metering port and said compensating port means.
5. A feeder as in claim 4 wherein, the adjusting means simultaneously and inversely vary the openings of said metering port and compensating port means to increase gas flow through the compensating port means as the opening of the metering port is decreased.
6. A feeder as in claim 5 wherein: the carburetor includes an outer shaft mounted in cantilever fashion with its free end projecting into said drum, and a tube telescoped therein, the interior of the tube forming said discharge passageway, said tube and shaft having regisTerable holes forming said metering port and compensating port means; and the adjusting means comprise means for rotating said tube within said shaft to vary the registration of said holes.
7. A feeder as in claim 6 wherein, an annular passageway surrounds said tube to a point spaced from said metering port, said shaft having a hole extending from said annular passageway to the interior of said drum, whereby said annular passageway may be connected to a source of pressurized gas to pressurize said drum.
8. A feeder as in claim 7 wherein: the drum axis is essentially horizontal; and further including a spindle journaled on said carburetor shaft, said drum being secured to said spindle.
9. A feeder as in claim 2 wherein: the drum axis is essentially horizontal; the carburetor is mounted in cantilever fashion with its free end projecting into said drum; and the drum is journaled on the carburetor.
10. A feeder as in claim 8 wherein: the drum sealing means comprise a plurality of annular sealing elements disposed between the spindle and carburetor and axially spaced apart; and the carburetor shaft has holes extending from said annular passageway to the spaces between said sealing elements to pressurize said spaces and isolate the spindle journal means from powder carried in said drum; and means providing a vent between the sealing means and the journaling means.
11. A feeder as in claim 8 further including means for detachably mounting said drum on said spindle.
12. A feeder as in claim 9 further including: a spindle supported by bearings on said carburetor; and means for detachably mounting said drum on said spindle to provide means for journaling the drum which will permit its removal in changing to another type of powder.
13. A feeder as in claim 8 further including means for varying the rate of drum rotation.
14. A feeder as in claim 8 wherein the drum includes fins projecting inwardly from its inner circumferential surface to facilitate the tumbling action and blend the powder in operation.
15. A feeder as in claim 2 wherein the drum includes fins projecting inwardly from its inner circumferential surface to facilitate the tumbling action and blend the powder in operation.
16. A feeder comprising: a feeding unit including gas input means and gas discharge means; means supporting the feeding unit at one end in cantilever fashion; a spindle; means rotatably supporting said spindle on said feeding unit; a drum detachably secured to said spindle whereby said drum may be removed from said spindle; and means for rotating said spindle for rotating said drum.
17. A feeder as in claim 16 further including means for sealing said drum relative to said feeding unit.
18. A feeder as in claim 16 further including multiple spaced sealing means between said spindle and said feeder unit to seal said drum, the spaces between said spaced seals being in fluid communication with said gas input means for maintaining a higher gas pressure than the gas pressure in the gas discharge means.