U.S. patent number 3,623,657 [Application Number 05/062,241] was granted by the patent office on 1971-11-30 for centrifuge apparatus.
This patent grant is currently assigned to Pennwalt Corporation. Invention is credited to Charles Edward Trump.
United States Patent |
3,623,657 |
Trump |
November 30, 1971 |
CENTRIFUGE APPARATUS
Abstract
A heavy-phase material and a light-phase material separate into
two concentric layers, the heavy-phase material accumulating
adjacent to the peripheral wall of the bowl. A control device
regulates the position of the interface or line of separation
between the layers, the control device including a conduit
extending inwardly from an opening in the bowl wall to the desired
position, and a detecting device. The conduit conducts a sample of
the material to the detecting device for sensing a change in
specific gravity at that position. Depending upon the direction of
change, the detecting device either temporarily closes a feed valve
controlling the introduction of feed mixture into the bowl, or
actuates a recycle pump for recycling extracted heavy-phase
material back into the bowl.
Inventors: |
Trump; Charles Edward (Bedford,
NY) |
Assignee: |
Pennwalt Corporation
(Philadelphia, PA)
|
Family
ID: |
26742019 |
Appl.
No.: |
05/062,241 |
Filed: |
August 6, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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743075 |
Jul 8, 1968 |
3560125 |
|
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Current U.S.
Class: |
494/5; 210/104;
494/11; 494/35; 494/57; 494/79; 494/10; 494/22; 494/42; 494/60 |
Current CPC
Class: |
B04B
11/04 (20130101); B04B 11/00 (20130101); B04B
11/043 (20130101) |
Current International
Class: |
B04B
11/00 (20060101); B04B 11/04 (20060101); B04b
011/00 () |
Field of
Search: |
;233/32,44,46,47R,19R,19A,2R,2A,9,27,28 ;210/104,105,78,377 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1,144,198 |
|
Feb 1963 |
|
DT |
|
1,142,137 |
|
Jan 1963 |
|
DT |
|
Primary Examiner: Boler; James R.
Assistant Examiner: Krizmanich; George H.
Parent Case Text
This application is a continuation-in-part of copending application
having U.S. Ser. No. 743,075, filed July 8, 1968, now U.S. Pat. No.
3,560,125.
Claims
What is claimed is:
1. A centrifuge including a rotatably mounted centrifuge bowl
having a separation chamber therein, said bowl having an annular
liquid overflow lip formed about the rotational axis at the upper
end of said bowl, means including valve means, for feeding a
mixture of at least two materials into said separation chamber
wherein the first material thereof has a higher specific gravity
than the second material thereof, and whereby said first material
builds up against the peripheral wall of said bowl, means for
continuously discharging said first material, means for receiving
said first material upon discharge, means including pump means,
operatively associated with said receiving means for recycling said
first material into the outer region of said separation chamber,
means for indicating when the line separation between said
materials has reached a predetermined level inward of said
peripheral wall and outward of said lip, said indicating means
including detecting means operatively associated with said valve
means and said pump means, said detecting means being adapted to
detect an increase above the specific gravity of said second
material for closing said valve means, and adapted to detect a
decrease in specific gravity below the specific gravity of said
first material for actuating said pump means.
2. A centrifuge according to claim 1 wherein said indicating means
includes a tubular passageway extending through the peripheral wall
of said bowl inwardly of the bowl to said predetermined level for
conducting material out of said bowl to said detecting means.
3. A centrifuge according to claim 1 wherein said bowl further
includes an annular ring dam formed about the rotational axis at
the bottom end of said bowl, and a passageway extending between the
inner edge of said ring dam and the outer region of said separation
chamber.
4. A centrifuge according to claim 3 wherein said means for
discharging said first material comprises a plurality of
circumferentially spaced peripheral outlets.
5. A centrifuge according to claim 4 wherein said recycling means
includes injection outlet means for recycling said first material
over said ring dam, and into the outer region of said separation
chamber.
6. A centrifuge according to claim 4 wherein the radius of the
inner edge of said ring dam is larger than the radius of said
lip.
7. A centrifuge according to claim 4 wherein the radius of the
inner edge of said ring dam is equal to or less than the radius of
said lip.
8. A centrifuge according to claim 5, and further including delay
timer means operatively associated with said valve means and said
detection means, said delay timer means being adapted to reopen
said valve means after being closed a predetermined time.
9. A centrifuge according to claim 8 wherein said feed means
includes outlet means disposed within said separation chamber, and
further including annular wall structure formed about the
rotational axis, said wall structure being disposed between said
peripheral outlets and said outlet means.
10. A centrifuge including a rotatably mounted centrifuge bowl
having a separation chamber therein, said bowl having an annular
liquid overflow lip formed about the rotational axis at the upper
end of said bowl, means including valve means, for feeding a
mixture of at least two materials into said separation chamber
wherein the first material thereof has a higher specific gravity
than the second material thereof, and whereby said first material
builds up against the peripheral wall of said bowl, said bowl
having a plurality of circumferentially spaced peripheral outlets
for continuously discharging said first material, means including
pump means for injecting auxiliary material into the outer region
of said separating chamber, means for indicating when the line of
separation between said first and second materials has reached a
predetermined level inward of said peripheral wall and outward of
said lip, said indicating means including detecting means
operatively associated with said valve means and said pump means,
said detecting means being adapted to detect an increase above the
specific gravity of said second material for closing said valve
means, and adapted to detect a decrease in specific gravity below
the specific gravity of said first material for actuating said pump
means.
11. A centrifuge according to claim 10 wherein said bowl further
includes an annular ring dam formed about the rotational axis at
the bottom end of said bowl, a passageway extending between the
inner edge of said ring dam and the outer region of said separation
chamber, said injection means having injection outlet means
disposed adjacent to the inner edge of said ring dam for injecting
said auxiliary material over said ring dam and into the outer
region of said separation chamber, and wherein the radius of the
inner edge of said ring dam is larger than that of said lip.
12. A centrifuge according to claim 10 wherein said bowl further
includes an annular ring dam formed about the rotational axis at
the bottom end of said bowl, a passageway extending between the
inner edge of said ring dam and the outer region of said separation
chamber, said injection means having injection outlet means
disposed adjacent to the inner edge of said ring dam for injecting
said auxiliary material over said ring dam and into the outer
region of said separation chamber, and wherein the radius of the
inner edge of said ring dam is equal to or less than that of said
lip.
Description
BACKGROUND OF THE INVENTION
This invention relates to centrifuge apparatus having a bowl in
which light- and heavy-phase material are separated from one
another, the materials forming two concentric layers within the
bowl, and the bowl being provided with means for continuously
discharging each of the materials. The invention provides for
sampling from the interior of the bowl, and depending upon the
condition of the sample extracted, either interrupting the feed
into the bowl, or automatically recycling heavy-phase material
previously extracted.
The invention is applied to the separation of a light-phase
material, usually liquid, from a heavy-phase material, which may be
either a solid material, or another liquid of specific gravity
greater than the light phase. Therefore, although the invention
will be described herein as applied to the separation of solids or
sludge from a mixture with a light-phase liquid, it is to be
understood that it is equally applicable for two liquids of
different specific gravities that require separation. Also,
although the invention is described in connection with an
imperforate basket-type centrifuge bowl, it is equally applicable
to other types of centrifuge bowls such as a disc-type
centrifuge.
In prior art apparatus, feed is delivered to the bowl and clear
effluent is discharged over a lip at the upper end of the bowl.
Accumulated solids form a cake against the peripheral wall of the
centrifuge bowl. After a predetermined period of time, based on
experience, which approximates the time required for sludge to
build up to the maximum desired level, feed is shut off by a timer,
and the sludge is discharged. Sludge discharge may be accomplished
by a skimmer which first penetrates the inner layer of effluent,
and discharges the same while the bowl is still rotating; and then
as the skimmer reaches the sludge effluent interface, the operator
manually diverts the discharge to waste so not to comingle the
sludge with the effluent already collected. Thereafter, with the
sludge removed from the bowl to the extent practicable, the skimmer
is returned to its inward rest position and feed to the bowl is
resumed.
The foregoing manual or semiautomatic process of the prior art is
disadvantageous because the concentration of sludge in the feed is
variable, and it is therefor not possible to predict with accuracy
the time required to accumulate the maximum desired amount of
sludge within the bowl. Thus, if the solids accumulation period is
too short, the operation of the machine will be inefficient; and if
the same period is too long, sludge will contaminate the effluent.
In the interest of efficiency, it is also desired to provide
apparatus which discharges solids automatically so that an operator
will not be required.
The prior art discloses means for sampling from the interior of the
bowl, and in response to the sample obtained, automatically
interrupting the feed into the bowl and actuating a skimmer tube to
automatically discharge the accumulated solids. While this method
has the advantage of automatically interrupting the feed, and
actuating the skimmer tube by means responsive to the sample
obtained, it still requires the provision of a skimming tube, and
requires a considerable period of time to extract the heavy-phase
material or solids because the skimmer tube must first extract the
light-phase material from within the bowl.
According to the present invention, separate means are provided for
discharging in a continuous manner, each of the materials, i.e. the
light-phase material and the heavy-phase material. This continuous
discharge occurs even after automatic control means has interrupted
the feed into the bowl. Thus, after feed is interrupted, both the
light-phase and heavy-phase materials continuously discharge
simultaneously. This not only eliminates mechanical skimming tubes,
but also reduces the mechanical desludging time required to extract
heavy-phase material from the interior of the bowl, because both
phases are simultaneously discharging.
SUMMARY OF THE INVENTION
According to the present invention, there is provided inwardly of
the bowl at least one overflow conduit extending radially inwardly
from an opening in the bowl wall to the desired level or position
of the interface or line of separation between the separated
materials within the bowl. With this arrangement a sample of the
material or "control material" within the bowl at that level will
flow through the conduit and out of the bowl to a detecting device
or apparatus. This detecting device or apparatus senses the
specific gravity of the control material and provides the means for
automatically maintaining the interface or line of separation at
the desired level. Depending upon the direction of change of the
specific gravity of the extracted control material, the detecting
means will either actuate a delay timer which then closes a feed
control valve for a predetermined period of time, or actuate a
recycle pump which either returns previously extracted heavy-phase
material back into the bowl, or injects a suitable auxiliary liquid
into the bowl. If the interface between the separated materials
moves inwardly within the bowl, increasing amounts of the
heavy-phase material will be conducted to the overflow conduits,
thereby increasing the specific gravity of the control material
being extracted. The detecting means will then actuate the delay
timer to close the feed valve for a predetermined amount of time
during which time the heavy-phase material is being continuously
discharged, thereby moving the interface outwardly to its desired
position. As the interface moves outwardly within the bowl,
increasing amounts of light-phase material will be conducted
through the overflow conduit to the detecting device, thereby
decreasing the specific gravity of the control liquid being
extracted. In response to this decrease, the detecting means
actuates a recycle pump to recycle extracted heavy-phase material
back into the outer region of the separating chamber of the bowl,
thereby building up the accumulation of heavy-phase material, and
moving the interface inwardly within the bowl to restore it to its
desired position. Thus, means are provided for automatically
controlling the position or level of the interface within the
interior of the centrifuge bowl by either closing the feed valve
for a predetermined amount of time during which time the
heavy-phase material is being continuously discharged and thereby
moving the interface outwardly within the bowl, or by recycling
heavy-phase material back into the bowl and thus moving the
interface inwardly within the bowl.
An annular ring dam is provided at the bottom of the bowl, the ring
dam being formed about the axis of rotation. The recycled or
injected material is directed over the ring dam to the outer
regions of the separating chamber. The recycled material may also
be injected into the top of the bowl and appropriately channeled to
the outer region of the separation chamber. When used as a
liquid-liquid separator wherein the heavy-phase material is a
liquid having a specific gravity greater than that of the
light-phase material, recycled material which is not accepted by
the bowl will be discharged downwardly over the inner edge of this
ring dam. On the present embodiment there may be only a few nozzles
discharging the heavy-phase material around the periphery of the
bowl, and thus incoming feed material will tend to be channeled
toward these nozzles before separation. To prevent the same an
annular wall is located within the separation chamber between the
outlets of the feed tubes and the nozzles. By providing a plurality
of generally radially extending accelerator vanes, the feed
introduced into the bowl is quickly brought up to the peripheral
speed of the bowl. Thus, the feed mixture is more efficiently
separated into its component parts, and any channeling effect would
then occur after separation and beneath the annular wall structure
en route to the nozzles.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of the centrifuge embodying the
invention, and showing in schematic form some of the controls
thereof;
FIG. 2 is an enlarged sectional view of the bottom portion of the
centrifuge shown in FIG. 1, and illustrating the form of the
recycling arrangement;
FIG. 3 is a transverse sectional view taken through line 3--3 of
FIG. 2 showing the radially extending accelerator vanes;
FIG. 4 is a sectional view of a modification of the present
embodiment and showing the controls in schematic form.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, the centrifuge is designated generally by the
numeral 10, the centrifuge including a base with a plurality of
upright standards (not shown) for supporting or suspending the
centrifuge housing. At the lower end of the housing 12 is a bearing
14 which is mounted with a centrifuge bowl 16 on a shaft, the
latter having a lower end extending downwardly through the bearing
for reception in a pulley 18 driven by motor 20 by suitable pulley
means.
Preferably, the centrifuge bowl is a cylindrical shell, including
an imperforate bottom wall 22 and a peripheral wall 24, the
peripheral wall having a plurality of circumferentially spaced
outlets or nozzles 26, each of these nozzles being formed to
discharge in a tangential direction. The centrifuge bowl includes
an upper end wall 28, this upper end wall having an inner annular
liquid overflow lip 30. The radial position of this lip may be made
adjustable if desired. Arranged within the centrifuge bowl is a
plurality of radially extending accelerator vanes 32 utilized for
bringing the mixture introduced into the bowl up to the peripheral
speed of the bowl.
A feed slurry or mixture is introduced into the separation chamber
34 of the bowl through feed means comprising a stationary feed tube
36 having valve means 38 therein. The feed tube is mounted and
spaced in coaxial relationship with the upper end of the bowl. At
the top of the bowl is provided a feed-receiving cup 40 which
rotates with the bowl, and receives the feed mixture for
distribution downwardly and outwardly toward the bottom of the bowl
through a plurality of feed conduits 42 each having feed outlet
means 44 at the remote ends thereof. Located between the outlet
ends 44 and the peripheral nozzles 26 is an annular inner wall
extending around the interior of the bowl. As the feed mixture is
introduced into the bowl through the feed means, it is quickly
brought up through the speed of the bowl, thus separating the
mixture into two concentric layers, the heavy-phase or sludge
material being that layer immediately adjacent to the inner annular
surface of the bowl. This sludge or heavy-phase material will be
continuously discharged through discharge nozzles 26 disposed about
the periphery of the bowl. The inner or liquid layer will be
discharged from the bowl over liquid overflow lip 30. Where there
are only a small number of discharge nozzles 26, feed mixture being
introduced into the separation chamber 34 will tend to be channeled
toward these nozzles before the mixture can separate into its
respective concentric layers. To prevent this, the inner annular
wall 45 is located between outlets 44 and nozzles 26, the
accelerator vanes 32 serving to quickly bring the mixture up to the
rotating speed of the bowl. Thus, any channeling effect would occur
underneath this annular wall in route to the nozzle 26 after the
material or mixture has separated into its heavy and light
phases.
Between the housing 12 and the peripheral wall 24 of the bowl,
there are plurality of annular spaces partially defined by annular
partitions 46, 48, and 50.
With this arrangement the upper annular space 52 receives the
liquid or light-phase material flowing over the overflow lip 30,
the material being conducted away from the space by a conduit 54,
and into an effluent-receiving tank 56. The sludge or heavy-phase
material is discharged through nozzles 26 into the lower annular
space 58, and is conducted out of housing 12 through a conduit 60,
and into a sludge-receiving means or tank 62. Connected between the
sludge-receiving tank 62 and the bottom of the centrifuge bowl, is
a recycle or injection means for recycling extracted sludge or
heavy-phase material back into the bowl in response to conditions
to be hereinafter described.
Referring more particularly to the inventive subject matter, it can
be seen that the feed mixture separates into two concentric layers
having an interface A between the layers. It is particularly
important that this interface or line of separation be maintained
at a desired level or position, or at least maintained within a
desired range for efficient separation.
To accomplish this, the centrifuge includes two control tubes 66
and 68, each leading from an opening in the peripheral wall 24 in
which it is sealed, securely mounted as by a threaded connection,
and oriented in a radial and horizontal direction to extend
inwardly of the bowl 16. The inner end of each tube may be threaded
and fitted, as shown, with nozzles 70 and 72 respectively. It is
contemplated that nozzles 70 and 72 will be provided in various
lengths and orifice sizes so that the peripheral radial extent of
the tubes 66 and 68, and also their flow areas, can be accurately
adjusted.
There may be one or a plurality of each of these control tubes
located around the peripheral wall of the centrifuge bowl. As will
appear more fully, adjustment of the radial inward extent of each
of the tubes 66 and 68 is to a level setting the maximum desired
range which is desired for the interface A. Since such maximum
range can vary from application to application, this means of
adjustment is believed to be economical, convenient, and effective.
Thus, each of these tubes 66 and 68 acts as an indicating means to
indicate the position of the interface A within the separation
chamber. With this arrangement, tube 66 conducts a sample of
material taken from the inner end of nozzle 70 and discharges it
into annular space 74. This sample material, which may also be
termed "control material," is conducted to control tank 76 by means
of a conduit 78 connected between the centrifuge housing 12 and the
tank 76. Tube 68 will conduct the sample material into annular
space 80 from which it is ultimately conducted to a control tank 82
via conduit 84 extending between the housing 12 and the control
tank 82.
Each of the control tanks 76 and 82 can be provided with a valve
opening in the bottom thereof (not shown) which may be used to
recover the samples of material deposited within each of these
tanks. The samples may then be returned to the feed supply tank
(not shown), or to a sludge-receiving tank 62 as desired.
Connected between the annular space 74 and tank 76, and between
annular space 80 and control tank 82 are two detecting devices 86
and 88 respectively. Each of these detecting devices is identical
to the detecting device 72 set forth in the drawing of the
above-mentioned patent application having U.S. Ser. No. 743,075,
filed July 8, 1968. Each of these detecting devices 86 and 88 and
their respective control tanks 76 and 82 comprise a detecting means
represented by the dotted line, and designated generally by the
numeral 90.
Each of the detecting devices 86 and 88 are responsive to changes
in specific gravity of the control liquid flowing therethrough.
With the appropriate change in specific gravity, detecting device
86 will transmit an electrical signal through line 92 to actuate
the recycle means 64, thus returning extracted heavy-phase material
from receiving tank 62 back into the outer region of separation
chamber 34. Upon the appropriate change in specific gravity for
detecting device 88 an electrical signal will be transmitted
through the line 94, and through a relay timer 96 to close the feed
valve 38, the feed valve automatically reopening after a
predetermined time has elapsed. The relay timer is adjusted so that
the sludge or heavy-phase material will not be completely removed
from the bowl through discharge nozzles 26 before valve 38 is
reopened. Thus, as interface A moves inwardly beyond the end of
tube 68, increasing amounts of heavy-phase material will be
conducted through tube 68 to detecting device 88 which in turn
temporarily closes the feed valve 38 in response to the increase in
specific gravity of the control material. Thus, the feed is
momentarily stopped allowing the nozzles 26 to lower the sludge or
heavy-phase level, thus moving the interface A outwardly. If the
interface A moves outwardly beyond the end of tube 66, increasing
amounts of light-phase material will be conducted through detecting
device 86. Density detection device 86 senses the decrease in
specific gravity of the control material being transmitted
therethrough, thus, actuating recycle means 64 to recycle
discharged sludge or heavy-phase from the receiving tank 62 back
into the outer region of separation chamber 34. This recycled
material would then enrich the content of the bowl, thus satisfying
the nozzles 26. To satisfy the nozzles means to supply sufficient
discharged sludge or heavy phase material on a recycled basis, so
that the flow through the nozzles, determined by the size of the
nozzles and the pressure at the same, will be satisfied by
heavy-phase material rather than light-phase material. As the
interface A begins to move inwardly once more, the flow of
heavy-phase material through tube 66 would deenergize the recycle
means 64 via the detecting device 86. By adjusting the length of
each of the tubes 66 and 68 it is possible to control the location
of the interface A within the separation chamber under all
conditions of feed concentration. This applies whether or not
separation involves liquid-solids or liquid-liquid separation.
Thus, as can be seen, detection device 88 senses high specific
gravity, and device 86 senses low specific gravity to actuate the
valve 38 and recycle means 64 respectively.
Referring to FIG. 2, the recycle or injection means 64 will be
described in more detail. Upon actuation of the recycle means 64,
the recycle pump 98 will begin to remove discharged sludge or
heavy-phase material from the tank 62 returning it to the bottom of
the centrifuge bowl via injection conduit 100 having an injection
outlet 102. Mounted to the bottom of the centrifuge bowl 16 beneath
the imperforate bottom 22 is an annular ring dam 104 formed about
the axis of rotation, and secured to the centrifuge bowl by means
of bolts 106. Attached to the upper surface of the ring dam 104, is
a plurality of radially positioned accelerator vanes 108 which
serve to pick up and accelerate material being injected into the
bowl via injection outlet 102. The position of the inner edge of
the annular ring dam 104 with respect to the overflow lip 30 is
important, and dependent upon the materials being separated.
Overflow lip 30 has an inner circular opening having a radius, or
in other words, a radial distance from the axis of rotation
indicated by the letter a. This distance may be made adjustable if
desired. Annular ring dam 104 has an inner circular opening or edge
105 having a radius, or in other words, a radial distance from the
axis of rotation indicated by the letter b. It is contemplated that
ring dams will be made available in various sizes so that the
radial distance b can be varied between being something less than a
to being something greater than a. Thus material injected into the
bottom of the bowl via injection openings 102 will be accelerated
by accelerator vanes 108, and directed toward the outer peripheral
wall 24 of the centrifuge bowl. The recycled or injected material
will enter the outer region of the separation chamber 34 via
openings 110 in the bottom 22 of the bowl.
Since a plurality of ring dams will be made available in various
sizes the present invention can be used for liquid-solids
separation as in the present example where the dimension b is less
than dimension a, or in a liquid-liquid separation where dimension
b may be somewhat greater than dimension a.
When utilizing the present invention for a liquid-liquid
separation, the inner edge 105 of the ring dam 104 is located
outwardly of the liquid overflow lip 30, i.e., the b dimension is
greater than the a dimension. All other factors remaining constant,
the interface A moves radially inwardly or outwardly depending upon
the a and b dimensions. A skilled centrifuge engineer can resort to
simple calculations to determine the exact dimensions. When using
the centrifuge as a liquid-liquid separator, recycled material not
accepted by the bowl flows downwardly over the inner edge 105 of
the annular ring dam and back to the recycle tank 62. When the
nozzle demand has been satisfied, the bowl automatically rejects
recycled material.
Referring to FIG. 4, a modification of the present embodiment is
illustrated. The centrifuge is alike in all respects except as to
the means utilized for detecting changes in specific gravity of the
control material. This can be seen in FIG. 4. A single control tube
66' having an adjustable nozzle 70' on the end thereof extends
inwardly to the desired level or position of the interface A'. A
sample of the material within the bowl 16' is conducted through
tube 66', into annular area 74', to a detecting means designated
generally by the numeral 112. In the embodiment illustrated in FIG.
1 it was necessary to have two detecting devices, 86 and 88, the
first being utilized to detect low specific gravity, the second or
latter being used to detect high specific gravity. The present
detecting means 112 can be utilized to detect either high or low
densities or specific gravities. This device is commercially
available from Automation Products, Incorporated, and as described
in their Bulletin No. J-8/D is responsive to changes in specific
gravity of the sample material flowing therethrough. The product or
sample to be measured flows through U-tube 114 and is ultimately
conducted to a control tank 76', from which tank the sample liquid
or material may be later recovered if desired. A driver coil 116 is
electrically excited by a pulsating current which drives the U-tube
114 into mechanical vibration. The vibration becomes a function of
the mass of the material contained in the U-tube. If the density or
specific gravity of this sample is increased the effective mass of
the U-tube increases; if the density decreases the effective mass
of the U-tube decreases.
The vibration is sensed in a pickup coil 118 which consists of an
armature and coil arrangement similar to that of the driver coil
116. The vibration of the pickup armature induces an AC voltage in
the pickup coil, the output in the pickup coil 118 being a function
of the density or specific gravity of the material being conducted
therethrough. Thus, depending upon the direction of change the
specific gravity being conducted through the U-tube either the
delay timer 96' and ultimately the feed valve is actuated, i.e.,
closed, or the recycle means 64' is actuated to return heavy phase
material from the receiving tank 62' back into the centrifuge bowl
16'.
Thus as the interface A' moves inwardly or outwardly of the end of
tube 66' more or less of heavy-phase material will be conducted
through the U-tube 114. Thus, as stated, depending upon the
direction of the change, i.e., an increase or a decrease in the
specific gravity, either the feed valve will be temporarily closed,
or the recycle means 64' will be actuated.
In either of the above-described embodiments, multipositioning or
fully variable control adjustments on either the feed valve or the
recycle means to smooth out the operation permits the system to be
finely tuned. It is also within the scope of the resent invention
to inject a suitable auxiliary material to control the position of
the interface, rather than recycle discharged heavy-phase material.
Thus, pumps 98 or 98' would be connected to a separate supply of
the auxiliary material rather than tanks 62 or 62'. The means for
controlling the injection of the auxiliary material would be
identical to that disclosed herein for controlling recycled
material.
It can be seen that with the present invention skimming pipes or
tubes are eliminated and mechanical desludging time is greatly
reduced. With relatively solids in the feed, this can multiply the
effective rate of the centrifuge by two to 10 times while at the
same time providing maximum concentration of sludge or heavy-phase
material, as this is removed from the maximum diameter of the bowl.
Sizing of the nozzles, and the number of nozzles is determined by
the feed perimeters, and approximate prestraining can be provided
to preclude possible pluggage of the nozzles.
Although I have described my invention with a certain degree of
particularlity, it is understood that the present disclosure has
been made only by way of example, and that numerous changes in the
details of construction and combination and arrangement of parts
may be resorted to without departing from the spirit and scope of
the invention as hereinafter claimed.
* * * * *