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Патент USA US3021962

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Feb; 20, 1962
K. R. POWELL
3,021,952
CLASSIFYING APPARATUS
Filed May 29. 1958
FIG. |'
40% 7
r
48
INVENTOR.
>
KEITH
R.
POWELL
BY
WJZQ; a M
ATTORNEY
United States
‘
3,021,952
‘ Patented Feb. 20, 1962
1
2
3,021,952
as shown in FIG. 1 to provide both an upward lifting
.
and a horizontal conveying movement to the stock as
CLASSIFYING APPARATUS
Keith R. Powell, Minneapolis, Minn, assignor to
shown by the two-headed arrow 43, which extends per
pendicularly to the intermediate or rest position of the
General Mills, Inc., a corporation of Delaware
Filed May 29, 1958, Ser. No. 738,872
9 Claims. (Cl.'209-339)
hangers 36.
'
'
The desired vibrations of the sifting unit are provided
The‘present invention relates to improved classifying
through a drive shaft 44 having one end secured at 46
to the sifter body and having its other end driven by a
suitable eccentric 48-or other vibratory power sources.
or reciprocating sifter.
10 This eccentric, in turn, is driven by a suitable motor and
Classifying or sifting devices are known in the prior
gear box indicated generally at 50 and the frequency of
art in which stock is conveyed across ‘a sifting surface
vibration may be controlled by a suitable speed control
"by suitable reciprocation 0r vibration of the sifting unit.
handle 52.
Problems have been encountered in such sifters, particu
The stock 22 is fed into the inlet 24 through a ?exible
larly those in which the sifting surface is enclosed in 15 connection 54 from a supply spout 56. Similar ?exible
an outer box or frame, and particularly when the sifter
connections 62 and 64 connect the discharge ‘spouts 30
is subjected to rapid vibratory reciprocation to convey the
and 34 to appropriate subsequent apparatus; thus the
stock across the sifting surface. One of these problems
spout 30 is connected to a further conveying tube 66
is that of irregularity, or surging, in the sifting and con
which feeds the material to a receiving hopper or other
veying action of the stock on the surface. It is believed 20 processing unit 68, while the outlet 34 is connected by
that such surging may be due to variations in the in
its sleeve 64 to a suitable further processing unit or hop—
stantaneous pressure differentials above and below the
per 70.
'
sifting surface caused by rapid vibrations of the enclosure
As described up to ‘this point, the sifter 10 is essentially
in'which the sifting surface is mounted.
conventional. It has been observed, however, in connec'
With these problems of the prior art in view, it is 25 tion with such sifters, that the stock 22 does not always
one object of the present invention to provide improved
feed evenly along the sifting surface 28 and may, in fact,
classifying apparatus of the reciprocating type. 7
bunch up or collect at certain portions of the surface,
apparatus and more particularly to an improved vibratory
Another object is to provide an improved reciprocating
while leaving other portions of thesurface essentially
or vibratory sifter having novel means for equalizing or
bare. The present invention is based on the belief that
neutralizing pressure differentials above and below the 30 these di?iculties in feeding “and sifting of material may
sifting surface.
~
~
be due to the failure of prior Workers to recognize that
Other objects and advantages will be apparent from , an enclosed vibratory sifter of this type inherently creates
the following speci?cation, in which certain preferred
variable instantaneous pressure differentials above and
embodiments of the invention are described.
below the screen. Thus, when the sifter is moved to the
_- In general, the above objectives are accomplished ac 35 right in FIG. 1, the closed inlet end 18 of the sifter body
cording to the present invention by the use of suitable
tends to push the column of air below sifting surface 28
partitions, which are at least partially ?exible, at appro
toward the right to cause an increase in pressure along
priate locations in the sifter body. Such ?exible par
this 'air column or slug of air. The increase in dynamic
titions are particularly useful in sealing the upper cham
pressure at various points beneath the sifting surface 28
ber above the sifting surface and can be used either at 40 appears to depend on the total length of the air column
the inlet or discharge end of the sifter, and are particu
involved bet-weenjwalls 18 and 20 and on the relative
larly useful at the inlet end.
.
distancefrom end wall 18.
In the vdrawings forming a part of this application:
FIGURE 1 is a side view, partly in section, of a vi
: ‘Above the siftingsurface 28, there is less tendency to
generate dynamic pressures in the longitudinal column
bratory reciprocating sifter embodying features of the 45 of air ‘because the inlet opening 24 may dissipate some
of the pressures generated by end wall 18 above the
FIG. 2 ‘is a sectional view on the line 2—2 of FIG. 1;
screen. Thus, an instantaneous pressure differential ‘may
FIG. 3 is a partial perspective view, with certain por
be created as the sifter is moved upwardly and to the right
tions cut away for clarity, to show the details of one
and this pressure differential, particularly near the inlet
form of ?exible partition as used in FIG. 1; and
50 end, may lift the stock upwardly from the surface 28
present invention;
’
'
.
'
FIG. 4 is a partial perspective view of a modi?ed form
of partially ?exible partition.
As shown in FIG. 1, the invention is disclosed in
connection with a reciprocating vibratory sifter desig
just at the point when it should be in ‘contact with’such
surface to obtain the desired conveying'movement. Con
ditions may be reversed on the return stroke, when
movement
of end wall 18 to the leftin FIG. 1 may tend
nated generally at 10. This classifyingv unit includes a 55 to pull the respective air columns to the left and create
body portion having a bottom Wall 12, a top wall 14,
instantaneous decreases in dynamic pressure. Similar
side walls 16, and end walls 18 ~and 20‘. The stock to be
phenomena are believed to occur at the discharge end of
sifted is shownat 22 and is introduced through a suitable
the, sifter with respect to end wall 20 and the various
inlet 24 at one end of the sifter near end wall 18; The
stock is received on a conveying surface 26 which carries 60 wall portions of the discharge outlets 30 and 34.
According to one feature of the present invention an
the stock along‘ to a sifting or classifying screen 28. The
effort is made to equalize the pressure variations in the
stock is adapted to be fed across this screen 28 while
air slugs or columns above and below the sifting surface
desired particles are sifted through the surface 28 to the
by the introduction of suitable ?exible partitions at appro'
bottom 12 of the housing. The particles thus sifted are
discharged through an outlet 36, while the particles which 65 priate points in the sifter body. In connection with the
do not pass downwardly‘ through the sifting surface 28 ‘are
inlet of the sifter, it has been found particularly helpful
carried over the tail surface 32 and discharged through an
to introduce a ?exible partition 72 above the initial receiv
outlet 34 adjacent end wall 20.
_
ing surface 26 which receives the stock 22. This parti
The sifter is supported for suitable vibratory reciproca
tion 72 may be made of rubber, plastic, cloth, or other
tion on hangers 36 having their lower ends 38 pivoted to 70 relatively ?exible material, having its upper portion
the sifter body and their upper ends 49 pivoted to a
secured to a suitable cross member 74 secured to thetop
suitable frame member 42. The hangers may be inclined I wall v14 of the sifter body. This upper portion 76 of the
8,021,952
4
port 74.
.
for reciprocating said body chambers and sifting surface
?exible partition hangs generally vertically from its sup
as a unit longitudinally along a desired path and thereby
conveying stock from said receiving end to said discharge
end while classifying the stock by said surface, an inlet
'
The total vertical length of the ?exible partition is
somewhat greater than the vertical spacing between the
for stock at one end of said upper chamber, and an outlet
top wall 14 and the surface 26. Thus the lower end of
the flexible partition at 78 is inclined away from the inlet
toward the outlet end of the ‘sifter, as shown in FIG. 1,
for stock at the other end of each chamber, the improve
ment comprising an anti-surging partition located .in said
upper chamber between said inlet and the receiving end
of the sifting surface at a point adapted to provide desired
?exibility of the partition, and its own- inherent weight,
tend to hold the trailing end 78 of the partition in contact 10 dynamic air pressures above said sifting surface, said par
tition having its upper edge secured in air tight relation
with the stock and thus seal oft‘ the inlet end of the air
adjacent said top Wall and its upper portion extending
column above sifting surface 28 and effectively isolate it
downwardly across the entire ‘width of the upper cham
from the inlet opening 214.
ber toward said sifting surface and secured for longitu
In operation the partition 72 serves in a manner similar
to end wall 18 and is ‘believed to generate dynamic pres 15 dinal reciprocation with said body and sifting surface, at
least the lower portion of said partition consisting of ?ex
sures above the sifting surface which are in phase with
ible, airtight material extending toward said outlet and
reciprocation of the sifter and which can effectively
located to engage the ‘top of the stock on said sifting sur
equalize or neutralize the pressures generated below that
face and maintain a substantial air seal between the main
surface by end wall 18. Thus the contact of the stock
22 with sifting surface 28 and the ‘action of that surface 20 portion of said upper chamber and said inlet.
2 A classifying unit according to claim 1 in which both
on the stock will be essentially the result of the desired
the upper and lower portions of said partition consist of
vibration of the sifting surface and will not be substan
?exible material.
tially affected by undesired air pressures and differential
3. A classifying uni-t according to claim 1 in which said
pressures generated by the reciprocating movement.
According to a further feature of the invention it is 25 partition comprises a rigid, substantially vertical upper
portion extending downwardly from said top wall to a
possible to utilize a similar ?exible partition 80‘ supported
level spaced above the sifting surface and a lower portion
on a cross member 82 near the discharge end of ‘the sifter
of ?exible material extending downwardly toward said
and above the sifting surface 28. In some cases it may
surface and longitudinally toward said outlet.
be desirable to utilize a similar ?exible partition 84 be
4. A classifying unit according to claim 1 having a sec
neath the sifting surface 28 and between the end of that
ond partition of similar construction located adjacent the
surface and the discharge outlet 30. Such a partition may
outlet from said upper chamber and thereby providing a
be mounted on a cross member 86 to provide essentially
sealing wall between said upper chamber and outlet.
identical end wall conditions at the discharge ends of the
5. A classifying unit according to claim 4 having a
respective longitudinal air columns above and below the
35 third partition of similar construction located adjacent
sifting surface 28.
the outlet from said lower chamber and thereby providing
FIG. 4 shows a modi?ed form of partially ?exible
a sealing wall between said lower chamber and outlet.
partition for use according to the present invention. Here
6. A reciprocatory classifying device comprising a sift
‘ the partition 88 includes a relatively rigid upper portion
ing chamber enclosed by a plurality of wall members,
90, which may be secured to a suitable cross member 92
means for reciprocating said device including said cham
in the sifter body by bolts 94. This portion 90 provides
' to permit the stock 22 to pass beneath this partition. The
ber and wall members along a given path, inlet means
a solid wall portion throughout a. major part of the cross
in said chamber for feeding stock to be classi?ed thereto,
section between the sifting surface and top of the sifter.
outlet means for discharging the classi?ed stock, a sifting
The lower portion of partition 88 is made of ?exible mate
surface intermediate said inlet and outlet means for classi- ‘
rial 96, secured at 98 to the portion 90’.
Just as in the case of the completely ?exible partition 45 fying said stock during said reciprocation, a substantially
imperfo-rate receiving plate at one end of said sifting sur
of FIGS. 1 to 3, the flexible portion 96 of partition 88 in
FIG. 4 will tend to accommodate itself to the surface of
face below said inlet means, a relatively airtight discharge
the stock received by the sifter. Theserflexible portions
plate at the opposite end of said sifting surface adjacent
said discharge means and ?exible anti-surging partition
will thus maintain a suitable air seal regardless of varia
tions in the rate of feed of the stock beneath the parti
tion. At the same time the angular orientation of these
?exible portions toward the discharge end of the sifter
will permit them to increase or decrease their spacing
above the sifting surface in accordance with the rate of
stock feed.
means disposed above at least one of said plates and re
ciprocable with said chamber, said partition having a
substantial area transversely of said path located and ar
ranged to move the volume of air withinsaid chamber in
55 phased relation to the reciprocation of said chamber and
’ ‘;
thereby provide improved sifting and conveying.
According to the.’ foregoing description, this invention
contemplates the use of at least partially ?exible parti
tions at appropriate locations to equalize the variations
7. An improved classifying device, ‘the combination
' comprising a rectangular sifting chamber enclosed by a
plurality of Wall members, and provided with a classi
in a vibratory sifting unit. While ‘these partitions have 60 fying surface therein, inlet means for admitting stock
to said classifying surface, means for moving said cham
particular utility in connection with vibratory reciprocat
ber and said classifying surface as a unit relative to said
ing sifters of the type shown in FIG. 1, they are believed
stock along a desired path, said stock being classi?ed by
to have applicatiton to certain other types of sifters in
said movement, outlet means in said chamber for dis
which similar surging problems may be encountered.
charging the classi?ed stock, and ?exible anti-surging parti
The foregoing speci?cation includes a description of the
in dynamic pressures above and below a sifting surface
principles which are believed to be involved in the present
invention, together with some of the ways in which the"
invention may be practiced.
Now, therefore, I claim:
_ 70
1. In a vibratory classifying unit comprising a sifting
surface having receiving and discharge ends, a body por
tion having top, bottom, side and end walls enclosing said
sifting surface and providing substantially closed upper
tion means located between said classifying surface and
said outlet means and extending substantially normal to
said path and movablewith said chamber and surface
thereby moving a'volume of air within said chamber in
correlation to the movement of said classifying surface.
8. An improved classifying device, the combination
comprising a rectangular sifting chamber enclosed by a
plurality of wall, members, and provided with a sub
and lower chambers aboveand below said surface, means 75 stantially horizontal classifying surface therein, inlet means
5
3,021,952
for admitting stock to said classifying surface, means for
moving said chamber and said classifying surface as a
unit relative to said stock along a desired path, said stock
being classi?ed by said movement, outlet means in said
chamber for discharging the classi?ed stock, and ?exible
partition means located adjacent each of said inlet and
outlet means and extending transversely of said path, said
partition means moving with said chamber and moving
air within the chamber thereby generating dynamic aid
pressures o? setting undesired pressure differentials result 10
ing from movement of the volume of air within said
chamber.
9. The device of claim 8 wherein each ?exible parti
tion means is positioned generally perpendicular to the
direction of ?ow of the stock and has at least one yield
able longitudinal edge in engagement with said stock and
5
yieldable in’a direction toward the discharge end of said
chamber.
References Cited in the ?le of this patent
UNITED STATES PATENTS
398,692
Bittinger ____________ __ Feb. 26, 1889
418,587
11,214,506
Prinz ______ _.. _______ __ Dec. 31, 1889
Brasack ______________ __ Feb. 6, 1917
1,629,244
1,686,107
WillcoX ______________ __ May 17, 1927
Sewell ________________ __ Oct. 2, 1928
2,047,713
2,903,135
Simpson _____________ __ July 14, 1936
Dryg ________________ __ Sept. 8, 1959
7 3,646
Germany ______________ __ Apr. 5, 1893
FOREIGN PATENTS
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