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Патент USA US3093428

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June 11, 1963
Filed Sept. 22, 1960
2 Sheets-Sheet l
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June 11, 1963
Filed Sept. 22, 1960
2 Sheets-Sheet 2
FM. .3
nited States Patent
Patented June 11, 1963
Another object is to provide a means to stratify the
fluidized particles in a storage chamber into a con?ned
columnated area in that only the ?ne, uniform ?uidized
particles at the uppermost part of the columnated area
Allan M. Doble, 206 Poath Road, Melbourne,
are circulated to the blast gun.
Victoria, Australia
Filed Sept. 22, 1960, Ser. No. 57,792
2 Claims. (Cl. 302-—17)
Still another object of the invention is to provide an
abrasive ?uidizing and feeding system wherein the re
quired’ ?ow of air may be produced, either by applying
air under pressure through a porous plate to the container
This invention relates to the ?uidizing and feeding of
powdered, ?nely-ground and other ?nely divided ma 10 -or alternatively, by connecting the interior thereof to a
source of reduced pressure.
terials and refers especially, but is not limited to, the
Another important object of my invention is to pro
feeding of abrasive material to blast guns and the like.
vide a novel arrangement of components wherein a
simple yet reliable means can be utilized to regulate the
In the abrasive blasting art a system was proposed for
?uidizing and feeding ?nely-divided abrasive material
from a closed container having‘a horizontal porous bot 15 rate of feed of the abrasive particles in the air stream.
In carrying out the aforementioned objects, my inven
tom which provided for the entry of atmospheric air to
tion includes apparatus comprising a storage chamber
?uidize the material when the interior of the container
‘having a porous bottom, and a novel upstanding parti
was connected to a vacuum pump or the like. This sys
tion therein separating the storage chamber to form a
tem employed a vertical discharge pipe extending up
wardly through the porous bottom into the body of abra 20 feed chamber that is closed at its upper end and open at
its lower end. The lower edge of the partition is spaced
sive material in the chamberran'd this pipe, open at its
above the bottom of the storage chamber so that the
upper end, was connected at its lower end to an inter
coarse abrasive particles and debris may gravitate there
mediate portion of an air pipe which extends from the up
-below. .A discharge passage communicates with an up
per end of the closed container to a blast gun. The gun
was arranged Within‘ a sealed cabinet having a hopper 25 per portion of the feed chamber and restricted air pas
sage connecting the storage chamber above the material
bottom connected to the vacuum pump through a cyclone
therein to an upper’ part of the feed chamber.
‘separator. The solid material consisting of the abrasive
material and of particles removed from the workpieces
' Thus, when air or other‘ gas enters the storage cham
ber, it‘passes upwardly through the porous partition and
within the cabinet, was returned from the cyclone to the
container for re-circulation.
30 '?uidizes the abrasive material, and some of the air then
Thus, in the above described apparatus when the
passes through the restrict-ed air passage to the feed
vacuum pump was operating and the valve of the gun
chamber and thence into the ‘discharge passage.‘ When
the air ?ow to the feed chamber is restricted, the pressure
was open, air was continuously withdrawn from the top
therein is lower than in the top of the storage compart
of the sealed container and replaced by air which entered
through the porous bottom of the latter and which passed 35 ‘ment, with the unique result that the ?uidized material
rises within the feed chamber _to form a column. Since
upwardly through and so ?uidized the abrasive material
it is necessary for the fluidized material to rise a sub
therein. Also, the ?uidized material continuously entered
stantial distance within the air chamber, in order to enter
the upper end of the vertical discharge pipe and gravi
the discharge passage, the lighter abrasive particles rise
tated therefrom into the air pipe, whereby it was con
40 the highest within the feed chamber and an effective sep
veyed by the air stream to the blast gun.
aration of coarse particles is thereby obtained. When
In all such abrasive‘blasting operations, the debris re
the upper surface of this colurnn is disposed su?iciently
moved from the workpieces, and which consequently be
close to the entrance to the discharge passage, the ?uid
comes miXed wtih the abrasive, is generally of compara
ized material is then swept thereinto by an air stream
tively coarse particle size and thus it is undesirable that
this material should be re-circulated. For this reason, in 45 which flows substantially across the top of the column.
- "The problem of~ regulating the rate of feed of the
the aforesaid prior art system, the discharge pipe had its
abrasive material has been solved in my invention by
upper end located some distance above the bottom of the
varyirig'pthe position of the upper end of the column
container, whereby when the bed was ?uidized, it was in
relatively to the discharge opening ‘and thisis preferably
tended that the coarser particles gravitate to the bottom
of the container where they could not enter the discharge 50 effected by means of a valve for regulating the flow of
air through the restricted passage. Alternatively, provi
However, the aforesaid system proved to have several
sion may be made whereby the said discharge opening
disadvantages, one problem being that the coarse abra
sive material or debris was not separated to the desired
'may be raised or lowered to regulate the ?ow of abrasive
extent within the closed container. Thus, during the op 55 " ' According to a preferred arrangement of the present
invention, the novel feed chamber is formed by a more
eration of the apparatus a large number of the coarse
or less vertical duct which is arranged centrally within
abrasive particles and debris entered the vertical dis
charge pipe and were re-circulated to the blast gun, and
the storage compartment. The vertical duct is preferably
of a tapered formation so that it converges upwardly
this seriously reduced the quality of the surface treatment
60 whereby the velocity of the material increases as it rises
in these ?ne particle abrasive systems.
up the duct.
Another disadvantage of the prior art devices of the
Other objects and advantages of the invention will
aforementioned type was that they did not provide an
“appear from the following description of a preferred em
effective means to regulate the rate of feed of the abra
bodiment and description of the operation thereof, given
sive material. Such feed regulation is essential in order
to provide an efficient blasting operation under various 65 in accordance with 35 USC 112.
In the following description of preferred forms of the
conditions including the type of material being treated
invention reference is made to the accompanying drawings
and the surface ?nish desired.
Therefore, one principal objective of the present in
FIG. 1 is a view in elevation and in section showing
vention is to provide na improved ?uidizing and feeding
apparatus for ?nely divided materials which completely 70 apparatus according to one form of the invention;
FIG. 2 is a view in cross section taken along the line
separates out the coarse abrasive particles and debris and
re-circulates only the ?ne particles to the blasting gun. '
.2—2 of FIG. 1; and
FIG. 3 ‘is a view in elevation and in section of appara
tus according to a modi?ed form of the invention.
The apparatus 10 illustrated in FIGS. 1 and 2 of the
drawings is directed to one form of my invention for
11. A vacuum pump 33 is connected to the cyclone
separator 32 by a duct 34. A blast gun 35 of the conven
tional ejector type wherein a high velocity compressed air
jet induces a secondary ?ow of abrasive-laden air is
?uidizing and feeding ?nely divided abrasive particles.
located within a blast gun cabinet 37 which is connected
As shown, the apparatus 10 comprises a storage chamber
11 having an upper part of elongated vertical cylindrical
by a suction line 38 to the cyclone separator 32. Accord
ingly, the blast gun 35 is connected to the discharge pipe
form and a lower part of downwardly convergent conical
26 and to a source of compressed air controlled by a
shape. Attached to the lower end of the storage chamber
valve '36. The air inlet pipe 23 is preferably connected
11 is an integral ?ange 12 of annular formation. Near
the bottom of the storage chamber 11 are ?xed diametri
cally opposite lugs 13 which carry bolts 14 that are
pivotally connected thereto. The bolts 14 carry wing
to a silica-gel moisture trap 39 to dry the air entering
the storage chamber 11.
In the operation of the apparatus 10 when used in the
abrasive blasting system shown in FIGS. 1 and 2, a partial
nuts 15 and serve to retain in position a ?lter box 16.
vacuum is maintained in the blast gun cabinet 37 by
The ?lter box 16 comprises a plate 17 which is slotted 15 means of the suction pump 33 connected to the blast
to receive the bolts 14, and a ring 18 ?xed to the plate 17
gun cabinet 37 through the cyclone separator 32 located
so as to de?ne a circular space within the ?lter box. The
above the storage hopper 11. When the valve of the
ring 18 has a ?ange 19 adapted to engage the ?ange 12
blast gun 35 is open, air is induced to ?ow into the cabinet
with a gasket 20 interposed. A spacing ring 21 is in
37 from the discharge pipe 26 through the gun 35. Thus
serted within the ?lter box, and a disc 22 of porous stone 20 the pressure in the feed chamber 25 is reduced to cause
or some other suitable porous material such as a resin
a ?ow of air thereinto from the upper part of the sur
bonded quartz ?lter, is supported by the ring 21 so that
rounding storage chamber 11, but due to the restriction
of the air hole 27, there is an appreciable pressure drop
its upper surface is ?ush with the upper surface of the
flange 19. An inlet pipe 23 is provided to admit air into
from the storage chamber 11 to the feed chamber 25.
the ?lter box below the porous disc 22. It will be evident 25
The reduction in the air pressure due to the vacuum
that the ?lter box 16 is readily detachable to unload the
pump 33 within the storage chamber 11 causes air to pass
storage chamber 11 and provide access thereto. If de
into the bottom thereof through the inlet pipe 23 and the
sired, an opening (not shown) may be provided in the
porous disc 22 and then upwardly through the abrasive
side of the chamber 11 immediately above the ?lter 22,
material which is thereby ?uidized in the usual way.
and provided with closure means which can be removed 30
Due to the reduced pressure within the feed chamber
25 and to the ?uidized condition of the abrasive material,
tend to settle on the porous disc 22.
this material now rises within the chamber 25 in the form
To perform the novel columnating action the ?uidized
of a column as portrayed in FIG. 1 and when the surface
abrasive particles within the storage chamber 11, I utilize
of this column reaches a su?icient height, the air in flow
a novel vertical duct or feed chamber 25 which constitutes 35 ing across the chamber 25 and around the ba?le 30 from
an important feature of the invention. The feed chamber
the aperture 27 to the discharge pipe 26, sweeps over and
25, as shown in FIG. 2, is preferably a rectangular shape
erodes the surface of the column, so that the abrasive
in cross section and is arranged centrally within the
material is carried at a corresponding rate into the pipe
chamber 11 with its upper end disposed above the normal
26. The position of the upper surface of the column may
level of the abrasive material within the chamber 11, while 40 be varied, by controlling the pressure within the upper
its lower end is disposed a substantial distance above the
end of the feed chamber 25 by means of the regulating
top of the porous disc 22. The duct 25 is closed at its
‘needle valve 28, and thus the rate of feed of the material
upper end, while its lower end is open so as to communi
may be regulated as desired.
cate freely with the interior of the chamber 11.
As the lighter and smaller particles tend to rise higher
A discharge pipe 26 is arranged above the level of the ' than the heavier and coarser particles, a classifying action
material in the storage chamber 11, and it extends through
takes place. That is to say, the coarser particles do not
one wall of the feed chamber 25 through the storage
rise to the top of the column, so that an effective separa
chamber 11 and out one wall thereof. An air inlet hole
tion is produced. Thus the coarse particles tend to sink
27 is formed in the wall of the feed chamber 25 at ap
to the bottom of the storage chamber 11 and accumulate
proximately the same height as the discharge pipe 26 so 50 on the top of the ?lter box 16 in the form of a layer as
as to connect the feed chamber 25 to the upper portion
indicated in FIG. 1. This layer assists in uniformly dis
to permit the periodic removal of coarse particles which
of the storage chamber 11. A needle-type regulator valve
28 extends through the wall of the storage chamber 11
so as to provide for regulation of the effective size of the
tributing the incoming air in the body of the ?nely
divided material. However, if the amount of accumulated
coarse material becomes excessive, it may be removed
air hole 27 by turning the handle 29 thereof. Thus the 55 manually through the opening referred to above.
flow of air through the hole 27 may be restricted to any
Reference is now made to FIG. 3 of the drawings which
desired extent.
illustrates, partly in schematic fashion, abrasive blasting
As indicated in the drawings, the duct 25 is of oblong
apparatus including ?uidizing and feeding means accord
shape in plan view as shown in FIG. 2; and the discharge
ing to another form of the invention. The apparatus
pipe 26 extends centrally into one of the end walls thereof, 60 shown in FIG. 3 comprises a sand blasting cabinet 40 to
while the air hole 27 is arranged in one of the side walls
the bottom of which there is connected a conical storage
adjacent to the opposite end wall and on the opposite side
chamber 41. At the bottom of the storage chamber 41
of a shallow transverse baf?e 30 which depends from the
closed upper end 31 of the duct and has its lower edge
arranged slightly below the level of the discharge pipe 65
a filter box 42 is mounted with a porous block 43 of the
type previously described located therein.
The storage chamber 41 is provided with a central feed
26. Thus the air must pass below the ba?ie 30 in ?owing
chamber 44, but instead of being of uniform cross section
from the air inlet hole 27 to the discharge pipe 26.
the feed chamber 44 is made of conical or pyramidal
The apparatus 10 illustrated in FIGS. 1 and 2 would
form so that its cross section diminishes towards the top.
normally be used for supplying powdered abrasive mate
The upper end of the feed duct or chamber 44 is con
rial to a blast gun in a system similar to the type described 70 nected to a discharge pipe 45 which may extend outwardly
above. Thus, to illustrate my invention as it would be em
through the wall of the chamber 41 or may be connected
ployed in a complete blasting system, I have shown the
directly to a sand blasting gun 46 as shown in FIG. 3.
storage chamber 11 arranged below a cyclone separator 32
The junction of the feed chamber 44 with the outlet pipe
or other equivalent means, from which the abrasive and
45 is effected by means of a T-joint 47, and a pivot tube
other solid material descends into the storage chamber 75 48 is mounted within the T-joint 47 so that it faces
gest themselves without departing from the spirit and
scope of the invention. The disclosures and the descrip
towards the outlet pipe 45. A pipe 49 provided with a
control valve 50 leads from the interior of the cabinet 40
tion herein are purely illustrative and are not intended
to be in any sense limiting.
I claim:
and is connected to the other arm of the T-piece 47. The
valve 50 operates in a similar manner to the needle valve
28 shown in FIGS. 1 and 2, i.e. it serves to control the
pressure differential between the chamber 41 and the top
of the feed duct '44 and so controls the height of the
column of ?uidized material in the feed duct 44.
The apparatus also includes a pressure air-line 51 hav
ing one branch 52 which is connected to the ?lter box 412
through a valve 53, and a second branch 54 which is
connected to the blast gun 46 through a valve 55.
In the operation of this form of the invention, com
pressed air supplied by a compressor 57' and admitted
through the valve 53 to the ?lter box 42 causes the mate
rial within the chamber 44 to be ?uidized, while the com
pressed air admitted through the valve 55 to the blast
gun 46 induces a flow of air and suspended material
through the outlet pipe 45 to the blast gun 46. The blast
ing gun 46 may be manipulated manually within the cab 2 0
inet 40 using a ?exible protective shield 58 in the well
1. Apparatus for ?uidizing and feeding ?nely divided
materials comprising: a storage chamber having a porous
bottom; a feed chamber mounted within said storage
chamber, said feed chamber comprising a vertically ex—
tending duct open at its lower end and closed at its upper
end, said duct having a frusto-conical form with a cross
section that diminishes towards its upper end; the lower
edge of said duct being spaced above the bottom of said
storage chamber whereby the material may gravitate
therebelow; a restricted air passage connecting the storage
chamber above the material therein to an upper part of
said feed chamber; and a discharge passage communicat
ing with an upper portion of said feed chamber.
2. Apparatus for ?uidizing and feeding ?nely divided
materials comprising: a storage chamber having a porous
bottom; a feed chamber mounted within said storage
chamber, said feed chamber comprising a vertically ex
known manner.
tending duct open at its lower end and closed at its upper
By closing the valve 50 to restrict the ?ow through the
end, said duct having a cross section that diminishes
pipe 49 and by opening valve 53 to increase the ?ow of
?uidizing air, the amount of abrasive particles carried 2 5 towards its upper end and a lower edge spaced above
the bottom or" said storage chamber whereby the material
through the pipe 45 can be increased, whereas if the valves
may gravitate therebelow; a T-joint conduit having a
50 and 53 are operated in the reverse manner the amount
stem and two branches, said stern being connected to the
of abrasive particles in the air carried through the pipe 45
upper end of said duct; a pipe having a restricted air pas
can be reduced.
An important feature of the construction of FIG. 3 is 3 0 sage connecting the storage chamber above the material
therein to one said branch of the T-joint; and a dis
that at the bottom of the duct 44 the vertical travel of
charge conduit connected to the other said branch and
the abrasive particles is comparatively slow whereas at
thereby also communicating with an upper portion of said
the top of this duct the speed of travel of the particles is
feed chamber.
considerably greater in view of the smaller cross sectional
area. It is found in practice that this arrangement leads 3 5
References Cited in the ?le of this patent
to an even rate of feeding at both high and low concen
trations of the abrasive particles in the air stream.
To those skilled in the art to which this invention re
lates, many changes in construction and widely differing
embodiments and applications of the invention will sug
Baresch ______________ __ Apr. 26, 1955
Randall ______________ __ Aug. 14, 1956
Beckmann _____________ __ Feb. 9, 1960
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