Note: Descriptions are shown in the official language in which they were submitted.
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SKIMMER/COALESCER SYSTEM FOR REMOVING AND
SEPARATING TRAMP OIL FROM AN AQUEOUS COOLANT
Field of the Invention
The background of U.S. Patent No. 5,053,145
provides a good description of the field to which this
invention relates. Namely, this field involves the removing
of tramp oil from aqueous solutions used as coolants in
machining centers and those used as cleaning fluids to wash
metal parts.
Background of the Invention
In many machining operations, an aqueous
coolant is sprayed or flowed at the location where a cutting
tool engages the workpiece, for lubrication and
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cooling purposes. The coolant is then collected in a tank
located below the machine and recycled for continuous use
for as long as possible.
Aqueous coolants of this type are fairly
expensive, so it is advantageous to maintain such aqueous
coolants in usable condition for as long as possible.
Typical machining operations also include lubricating oil
for lubricating movable parts. Eventually, this oil drips
or flows into the aqueous coolant tank, where it floats
upon the surface of the aqueous coolant due to its lighter
weight and lower density. This oil, referred to as "tramp
oil," will eventually also contribute to bacterial growth
within the aqueous coolant, resulting in a foul odor and
reducing the useful life of the aqueous coolant.
Due to environmental concerns, the oil-
contaminated aqueous coolant must be treated as hazardous
waste, and therefore represents an environmental and
economic concern. Thus, tramp oil represents a serious
environmental and economic problem with respect to
maintaining proper and cost effective aqueous coolant use
during machining operations.
A number of skimming devices have been developed
over the years to remove tramp oil from the surface of
aqueous coolant in a coolant tank for a machine. Disk
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skimmers include a disk which extends into the
aqueouscoolant and into contact with the tramp oil.
Rotation of the disk near the surface results in removal of
some oil from the surface, whereupon it is scraped by a
blade and removed. Belt type skimmers involve an endless
belt which removes tramp oil from the surface of the
aqueous coolant, whereupon it is also scraped therefrom for
removal. Disk and belt skimmers of this type are
relatively inefficient and have space limitations for
proper mounting and operation.
Floating tube skimmers and weir-type skimmers
adapt to liquid level fluctuations, and they generally
include a pump for pumping the skimmed liquid to a
separation device. Such skimmers have proved to be
acceptable in relatively large bodies such as lakes, ponds,
rivers or even oceans. However, their size typically
prevents their use in machining applications. In machining
operations, most coolant tanks are as shallow as five or
six inches, or as deep as 14 to 16 inches. Also, some
machining coolant tanks are located in relatively
inaccessible places without much spare space located
adjacent thereto.
Weir-type skimmers also have the disadvantage
of being too large to be readily adapted for machining
operations. With floating tube or weir-type skimmers,
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liquid is retrieved from the tank via a suction line
operatively connected to a suction pump. For most
operations of this type, a positive displacement pump
provides this suction force. Because the liquid removed
from the tank includes a mixture of two different liquid
components, and the proportions of these two liquid
components vary over a period of use, the volume pulled by
the pump is subject to variation. These volume variations
can adversely affect the efficient operation of the pump
and the entire system. Thus, while these relatively large
size skimming devices have proved effective in their
specific environment, i.e. large bodies of water, they
suffer from some disadvantages which would be aggravated if
the devices were to be adapted for use in relatively small
coolant tanks.
In summary, in machining operations it is
necessary to skim primarily tramp oil from the surface of
the aqueous coolant in the tank (though the skimmed liquid
will also include some coolant), to deliver the tramp oil
coolant mixture to a separation unit, to separate the tramp
oil from the aqueous coolant for collection, and to return
the aqueous coolant to the tank for reuse.
It is an object of this invention to optimize
the useful life of aqueous coolant used in conjunction
with the operation of a machine tool. As a corollary, it
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is also an object of this invention to minimize the
bacteria formation and hazardous waste conditions created
by tramp oil contamination of such aqueous coolant.
It is another object of this invention to
improve the skimming efficiency of an aqueous coolant
skimmer, for varying liquid levels in the tank.
It is still another object of the invention to
maintain consistency in liquid flow from a skimmer to a
coalescer; thereby to optimize the useful life of the pump
which causes the flow and to minimize the possibility of
damage to the pump.
It is still another object of the invention to
achieve the above-noted objects for a variety of
differently sized and shaped tanks for collecting and
holding aqueous coolant, to improve upon the versatility
and efficiency of present skimmer/coalescer systems.
Summary of the Invention
The present invention achieves the above-noted
objects by utilizing a skimmer with a submerged and
enclosed housing located below the liquid level in a
coolant tank, a vertically oriented, variable flow intake
extending above the submerged housing, which skims free
floating tramp oil from the surface of the liquid in the
tank and conveys the skimmed liquid to the inside of the
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housing, and an outlet for continuously removing
theskimmed liquid from the submerged housing to a compact,
portable coalescer, via pumping action. The intake
includes a float which moves vertically with respect to
the housing to accommodate variations in the liquid level
in the tank, so that skimming always occurs near the
surface. The housing also includes a sensor for
determining the level of the skimmed liquid contained
within the submerged housing, and this sensor controls the
rate of skimming in-flow at the intake, so that the
skimming rate is adjusted to compensate for fluctuations
in out-flow from the submerged housing via the outlet.
Such out-flow fluctuations generally result from pumping a
liquid mixture which, over a period of time, undergoes
viscosity changes due to variation in the relative
proportions of the two liquid components.
The coalescer of this invention utilizes gravity
flow operation through a circuitous flow path. This
assures efficient separation of free floating tramp oil
from aqueous coolant, aeration of the oil/coolant mixture
after such separation, and return of the coolant to the
tank so that it can be reused.
According to a preferred embodiment of the
invention, the skimmer, or skimming unit, includes a
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substantially enclosed plexiglass housing adapted to be
mounted to the inside wall of a coolant tank via magnets.
An outlet tube connects to the housing, and a bottom end
thereof extends into the housing to a position adjacent the
bottom wall thereof. An intake structure also connects to
the housing. The intake structure includes an inner tube
which is fixed in vertical position relative to the
housing, but which is vertically rotatable with respect
thereto, about its vertical axis. An upper end of the
inner tube includes a vertically oriented, elongated
opening. An outer sleeve surrounds an upper end of the
inner tube, and the outer sleeve also includes an opening
partially aligned with the opening in the inner tube. The
aligned portions of the two openings define an inlet for
the skimmer. An external float connects to the outer
sleeve, and the external float causes the outer sleeve to
move vertically with respect to the inner tube, so that the
inlet adjusts vertically with respect to the liquid level
in the tank, thereby to skim adjacent the surface of the
liquid and to obtain a liquid mixture which is
predominantly tramp oil. Preferably, one end of the
external float connects to the outlet, to prevent
rotational movement of the outer sleeve about its vertical
axis.
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The skimmer also includes an inner float, located
inside the submerged housing. The inner float connects to
one end of a pivotal lever, the other end ofwhich connects
to the inner tube. The inner float moves vertically with
respect to the liquid in the submerged housing, and this
vertical movement pivots the lever to cause rotation of the
inner tube about its vertical axis with respect to the outer
sleeve, thereby changing the size of the inlet. When the
inner float moves vertically downward, the lever pivots the
inner sleeve to increase the size of the inlet, thereby
increasing the flow rate into the submerged housing to
compensate for the lower liquid level in the housing.
Conversely, if the inner float raises upwardly, the lever
pivots the inner tube to reduce the size of the inlet,
thereby reducing the flow rate of the skimmed liquid into
the submerged housing. The system includes a pump
which pumps the skimmed liquid from the submerged housing,
whereupon it is fed to a coalescer for gravity separation of
the tramp oil from the aqueous coolant. This separation
occurs via flow through a circuitous flow path. The
coalescer filters the mixture prior to flow along the flow
path, and the coalescer also aerates the mixture at the last
stage
of the flow path. If desired, the mixture may be treated
with ultraviolet radiation prior to entry into the flow path
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of the coalescer, thereby to kill bacteria which may have
formed while in the tank.
According to one preferred embodiment of the
invention, the coalescer includes a housing having an entry
port and a first exit port and a flow path therebetween. A
pump causes the liquid mixture to flow into the entry port,
and gravity then causes the mixture to flow along the flow
path to the first exit port. The coalescer preferably also
includes a filter upstream of the pump to filter debris from
the liquid mixture. Preferably, a flow-regulating orifice
is included between the pump and the entry port, or
alternatively between the filter and the pump, to promote
more-constant volumetric flow rate over a range of mixture
temperatures. The pump may be mounted within a portion of
the housing that is removable from the remainder of the
housing to facilitate servicing of the coalescer. The
housing may also have a removable top panel or member to
facilitate cleaning of the unit.
Within the flow path is a grid that includes a
plurality of parallel inclined plates which promote
separation of the tramp oil from the mixture by causing the
oil to rise upwardly in the housing. The housing has a
second exit port in fluid communication with the flow path
via an outlet located above the grid. The vertical level of
the outlet is above the first exit port. Oil which has
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risen upward in the housing moves upwardly through the
outlet and then flows out through the second exit port as
the liquid mixture flows along the flow path during
operation of the pump.
Advantageously, this coalescer also includes a dam
located immediately upstream of the first exit port, with
the top edge of the dam located below the vertical level of
the outlet. The coalescer further includes an aperture in a
side wall of the housing upstream of the entry port. The
liquid mixture from the skimmer first enters the coalescer
through the aperture and from there flows into the entry
port. Mounting of the coalescer within a confined space and
routing of fluid lines to and from the coalescer are
promoted by locating the first exit port adjacent the
aperture in the same side wall of the coalescer housing.
The coalescer is mounted to any vertical and
magnetically permeable surface by magnets secured to the
housing. Each magnet is spaced apart from the housing by a
spacer to permit a person to insert fingers between the
housing and the mounting surface when mounting or removing
the coalescer. The magnets permit the coalescer to be
mounted without drilling holes in and securing brackets to
the mounting surface. The magnets also allow adjustments in
the leveling of the coalescer to be made quickly and
easily.
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With this invention, the useful life of aqueous
coolant used in conjunction with the operation of a machine
tool is prolonged, due to efficient removal and separation
of tramp oil therefrom. This minimizes bacteria formation
in aqueous coolant retained in the coolant tank, and it also
minimizes the need to dispose of liquid hazardous waste, a
need which arises when the aqueous coolant in the tank has
been contaminated beyond useful life and therefore must be
disposed of. As a corollary to the longer useful life of
the aqueous coolant, this invention also significantly
reduces the need to dispose of aqueous coolant which has
become contaminated beyond possible use, and reduces the
total quantity of hazardous waste produced during machining.
Because the skimmer of this invention always skims
at or near the surface of the liquid level in the tank, this
invention improves skimming efficiency regardless of varying
liquid levels in the tank. This improved skimming
efficiency, in combination with the efficiency of the
coalescer, also presents the opportunity of cycling the
system off and on, so that it does not have to be operated
continuously. This results in energy savings and longer
pump life compared to prior continuously operating systems.
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Because the skimmer includes structural components
which vary the size of the inlet to compensate for liquid
level fluctuations within the submerged housing, this
invention maintains consistent liquid flow from the skimmer
to the coalescer and consistent flow through the entire
system. This optimizes the useful life of the pump used in
conjunction with the coalescer, by minimizing the
possibility of air intake to the pump.
Because of the compact nature of the skimmer, it
may be mounted readily to the inside of a coolant tank by
magnets. Also, the vertical dimensions of the intake may be
varied to accommodate different standard operating levels in
the tank. In other words, the skimmer may be readily
adapted for use with tanks of various shapes and sizes, and
for a variety of different standard liquid operating levels.
Similarly, the compact nature of the coalescer
enables it to be mounted readily to any adjacent metal wall,
as by magnets, thereby facilitating the step of assuring
level orientation. The shape and configuration of the
coalescer facilitates interconnection of the inlet and
outlet hoses, and it also facilitates filtering and
radiating the liquid mixture prior to conveyance along the
circuitous flow path.
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These and other features of the invention will be
more readily understood in view of the following detailed
description and the drawings.
Brief Description of the Drawings
Fig. 1 is a schematic perspective view which
schematically shows a skimmer/coalescer system for removing
and separating tramp oil from an aqueous coolant, in
accordance with a first preferred embodiment of the
invention.
Fig. 2 is a longitudinal cross-sectional view
taken on lines 2-2 of Fig. 1, showing a skimmer which forms
part of the system.
Fig. 3 is a transverse side view of the skimmer
shown in Fig. 2.
Fig. 3A is a bottom view of one end of the skimmer
showing securement of the intake structure to the housing.
Fig. 4 is a transverse side view, similar to Fig.
3, but with the inner tube of the skimmer rotated from the
position shown in Fig. 3.
Fig. 5 is a front view in partial cross-section of
a first preferred coalescer which forms part of the system
shown in Fig. 1.
Fig. 6 is an enlarged cross-sectional view of an
oil outlet which is part of the coalescer.
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Fig. 7 is a top plan view of a second preferred
embodiment of the skimmer of this invention, with the
skimmer located in a tank.
Fig. 8 is a side view of the skimmer shown in
Fig. 7, as viewed along lines 8-8 of Fig. 7.
Fig. 9 is a front view in partial cross section,
similar to Fig. 5, of a coalescer constructed in accordance
with a second preferred embodiment of the invention.
Fig. 10 is a front view in partial cross section,
similar to Fig. 5, of a coalescer constructed in accordance
with a third preferred embodiment of the invention.
Fig. 11 is a side view of the coalescer shown in
Fig. 10.
Fig. 12 is an enlarged view of the flow regulator,
shown located between the filter and the pump of the
coalescer depicted in Fig. 10.
Detailed Description of the Invention
Fig. 1 shows a preferred embodiment of a
skimmer/coalescer system 10 for separating free floating
tramp oil from an aqueous coolant of the type typically used
in machine tool cutting operations. The system 10 prolongs
the useful life of the aqueous coolant. This reduces
coolant costs, which is relatively expensive, and it
minimizes the number Of times it is necessary to shut down
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the machine tool to change or clean the coolant. The system
may also be used in conjunction with a parts washing
system, to separate oil washed off of parts from the top of
an aqueous solution, or in any other situation where a
5 lighter, surface residing liquid must be removed and
separated from a heavier liquid located below.
Generally, the system 10 includes a skimming unit,
or skimmer 12, which skims the top surface of a liquid
within a tank 14. If the system 10 is used in connection
10 with a machine tool, the tank 14 holds a water-based coolant
into which some quantity of machine tool lubricating oil
inevitably leaks. Reference numeral 16 identifies the
liquid level in the tank 14, and this usually represents a
mixture of coolant and oil. If system 10 is used with a
parts washer, liquid level 16 refers to a mixture of water
and washed off oil. For a machine tool, the tank 14 may
vary in height, ranging from as low as 5 inches to as high
as 14 inches.
The system 10 removes the skimmed liquid from the
tank 14 via a hose 18, and this liquid removal occurs via
operation of a conventional positive displacement pump 20,
such as a Gorman Rupp pump sold under Model No. 92462-000.
For the system 10, as shown in Fig. 1, the pump 20
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is preferably mounted to a coalesces, or coalescing unit 22.
The coalesces 22 separates the two components of the liquid
mixture. The coalesces 22 returns the purified or cleaned
coolant to the tank 14 via a return line 24, and the
coalesces 22 conveys the separated oil outwardly therefrom
along an oil outlet line 26, which terminates in an oil
collection container 28.
Fig. 2 shows the skimmer 12 in greater detail.
More specifically, Fig. 2 shows that the skimmer 12 includes
a rigid substantially enclosed housing 30, preferably of
plexiglass, to which a magnet 32 is secured, as by a bolt
33, to mount the skimmer 12 to a sidewall of the tank 14,
which is typically metal. This enables the housing 30 to be
mounted at any height in the tank 14. If the tank 14 is
not metal, a metal piece may be secured thereto so as to
span the range of normal mounting heights. The housing 30
is mounted at a level within the tank 14 such that it will
be submerged well below the liquid level 16 in the tank 14.
For some applications, the housing 30 may rest on the bottom
of the tank 14.
The housing 30 includes an upper wall 34 with a
pair of spaced holes formed therethrough. Reference numeral
36 refers to the first of the holes, while reference numeral
38 refers to the second of the holes. An outlet tube 40
extends through the first hole 36, with
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an optional surrounding gasket 39 providing a fluid tight
interconnection therebetween. The outlet tube 40 may be
formed of rigid plastic. A fitting 42 secures to an upper
end 41 of the outlet tube 40 to secure hose 18 thereto. A
lower end 43 of the outlet tube 40 extends downwardly toward
a bottom wall 35 of the housing 30, with sufficient
clearance therebetween to allow unobstructed outward fluid
flow via hose 18 when the pump 20 is operating. If desired,
the skimmer 12 may include a screen 44 located adjacent the
bottom end 43 of the outlet tube 40, to minimize the
possibility of particulate flow into the outlet tube 40
during operation. The bottom end 43 may include a depth
stop 43a to allow accurate positioning with respect to the
bottom wall 35.
At an opposite end of the housing 30, an intake
structure 46 extends vertically through the second hole 38.
This intake structure 46 includes an inner tube 48,
preferably of rigid plastic, which is secured to the bottom
wall 35 of the housing 30 by a mechanical fastener 50 and
bracket 51, as shown in Fig. 3A. The inner tube 48 is
secured in a manner which prevents vertical raising or
lowering with respect to the housing 30, but which allows
rotational movement about a longitudinal axis 52 extending
therethrough. In normal operation, this longitudinal axis
52 is oriented vertically.
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As with the outlet tube 40, a bottom end 54 of the
inner tube 48 is spaced from the bottom wall 35 of the
housing 30, thereby to enable unobstructed flow of liquid
into the housing 30 via the intake structure 46. An upper
portion 55 of the inner tube 48 includes an elongated
opening 56, preferably oriented vertically.
Within the housing 30, the skimmer 12 includes an
internal float 58 which is buoyed by liquid therein, at a
level which is indicated by reference numeral 60. The
float 58 may be of any suitable buoyant material, such as
Styrofoam or cork. Preferably, a plurality of pins 59
extend upwardly from the float 58, to prevent surface
contact, and hence surface tension, with the upper wall 34.
A rigid pin 61 pivotally secures a first leg 62 of
a lever 64 to the internal float 58. An apex 65 of the
lever 64 is secured to the housing 30 by a horizontally
oriented pin 67 so that the lever 64 is rotatable about a
fixed, vertical pivot axis 66 (Fig. 2 and 3). More
particularly, the pin 67 pivotally connects the apex 65 of
the lever 64 to a vertical wall 70 located within the
housing 30. Preferably, the wall 70 is made of the same
components as the rest of the walls of the housing 30, and
it is rigidly secured to the upper wall 34. This allows
all of the components of the housing 30 to be removed for
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cleaning, simply by lifting upper wall 34. A second leg 72
of the lever 64 is connected to the inner tube 48 at a
predetermined distance above the bottom end 54 thereof. The
second leg 72 has a slot 68 which receives a pin 69, which
is fixed to the inner tube 48. Rotation of lever 64 about
axis 66 causes leg 72 to move left and right arcuately in a
vertical plane (as viewed in Fig. 2) which causes rotational
movement by inner tube 48.
Via rotation of lever 64 about axis 66, raising
or lowering of the liquid level 60 in the housing 30 causes
a corresponding rotation of the inner tube 48 with respect
to its longitudinal axis 52. Preferably, the horizontal
clearance between the inner tube 48 and the upper wall 34 of
the housing 30, at the second hole 38, is about 0.007
inches. This allows rotation of the inner tube 48 with
respect to the housing 30, but minimizes inflow of liquid
into the housing 30 through the opening therebetween. The
inner tube 48 also includes a shoulder 48a to further
minimize leakage.
An outer sleeve 74 telescopes over the upper
portion 55 of the inner tube 48, with a preferable clearance
therebetween of 0.040 inches. The sleeve 74 is preferably
of rigid plastic, and is slidable with respect to the inner
tube 48. A float 76 secures to the outer sleeve 74, and the
float 76 preferably extends toward the
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outlet tube 40. The float 76 moves upwardly and downwardly
within the tank 14, depending upon the liquid level 16
therein. Accordingly, the outer sleeve 74 moves upwardly
and downwardly with the float 76. A pair of spaced rods 78
extend horizontally from the float 76 toward the outlet tube
40, and the rods 78 preferably have a spacing slightly
greater than the diameter of the outlet tube 40. As shown
in Fig. 7, alternatively, this function can be performed by
extending the float 76 around the outlet tube 40. This
prevents rotational movement of the outer sleeve 74 during
rotation of the inner tube 48 about axis 52. Thus, the only
movement permitted of the outer sleeve 74 is upward and
downward, along the inner tube 48.
The outer sleeve 74 includes a vertically oriented
opening 80 formed therein. The opening 80 extends below the
bottom of the float 76, and the opening 80 preferably
includes an angled bottom 82. These features are best shown
in Figs. 3 and 4. The opening 80 in the outer sleeve 74
and the opening 56 in the inner tube 48 have some portions
thereof which are in horizontal registration, or alignment,
if viewed horizontally. These aligned portions are
indicated by reference numeral 86, representing a shaded
area. This shaded area 86 represents a fluid inlet for the
intake structure 46.
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Because of the curve in the inner tube 48, the inlet 86 is
actually a curved region.
Depending upon the liquid level 16 in the tank 14,
and hence the position of the float 76, there will always
exist some inlet 86 which represents the aligned portions of
the opening 80 and the opening 56. As the float 76 raises
and lowers with the liquid level 16, the inlet 86 raises and
lowers. Because of the shape of the opening 80, and
particularly the angled bottom 82 which extends below liquid
level 16, liquid from the tank 14 flows into the inlet 86,
through the intake structure 46 and into the housing 30.
Because of the relative position of the inlet 86 with
respect to the float 76, the liquid which flows into the
intake structure 46 always comes from just below the top
surface. Stated another way, the intake structure 46 skims
the liquid just below the liquid level 16. This optimizes
the efficiency of the skimming operation because all of the
oil resides at or near the surface.
If desired, the skimmer 12 may include an
adjustable screw 83 to vertically adjust the position of the
float 76 with respect to the opening, to obtain the optimum
position of angled bottom 82 in relation to the liquid level
16.
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All other things being equal, the size of inlet 86
will remain the same, with the liquid intake to housing 30
being constant, regardless of the vertical level 16 and the
position of the float 76. Depending on the depth of tank 14
and the typical liquid level 16 therein, the lengths of the
inner tube 48 and the outer sleeve 74 may be shortened or
lengthened as needed to accommodate the particular
situation, without affecting the manner of operation or the
efficiency of the system 10. However, the vertical drop
between the inlet 86 and the housing 30 provides beneficial
aeration of the skimmed liquid.
When inner tube 48 rotates with respect to outer
sleeve 74, the rotation changes the cross-sectional area of
alignment, i.e. the size of the inlet 86. As shown in Fig.
4, in comparison to Fig. 3, when the inner tube 48 rotates
to the left, the size of inlet 86 increases, resulting in
increased flow of liquid into the housing 30 via the intake
structure 46. Correspondingly, if the inner tube 48 rotates
to the right from the original position shown in Fig. 3,
the size of the intake 86 decreases, resulting in decreased
flow of liquid into the housing 30 via the intake structure
46.
Because rotation of the inner tube 48 depends upon
the vertical level 60 of the internal float 58 with respect
to the housing 30, the skimmer 12 compensates for
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raising or lowering of the liquid level 60 by decreasing or
increasing, respectively, the flow of liquid into the
housing 30 via the intake structure 46. This raising or
lowering of the level 60 is caused by fluctuations in the
overall viscosity of the liquid mixture pumped from the
skimmer 12 to the coalescer 22. Despite the fluctuations in
the rate of outflow from housing 30, the skimmer 12
automatically maintains a desired liquid level 60 in the
tank 30, a level 60 which is well above the lower end 43 of
the outlet tube 40. This optimizes operation of the pump 20
and minimizes the possibility of air flow into the hose 18
and subsequently to the pump 20 (Fig. 1), a
problem to which pumps 20 of this type are susceptible over
a period of time.
Thus, the skimmer 12 simultaneously provides the
features of: 1) skimming the liquid from the tank 14
adjacent a top surface thereof, regardless of variations in
the liquid level 16; 2) aerating the skimmed liquid
immediately after intake; and 3) preventing the admission
of air into the hose 18 or the pump 20. This results in
delivery of an oil-rich liquid mixture to the coalescer 22,
with optimum pump 20 operation.
As a corollary, because of the efficiency of the
skimming and coalescing operations performed by the skimmer
12 and the coalescer 22, respectively, operation
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of the pump 20 may be cycled on and off by a timer 85 (Fig.
9), so that it does not have to run continuously. For
instance, it may only be necessary to operate for fifteen
minutes every hour. This represents a tremendous energy
savings compared to continuous operation.
Fig. 5 shows the structural details of the
coalesces 22, which separates free floating tramp oil from
the aqueous coolant after it has been skimmed from the tank
14 by the skimmer 12. More particularly, the coalesces 22
includes a box-shaped housing 87 which may be made of
plexiglass or any other rigid material. Use of plexiglass
at least on the front side thereof provides the advantage of
allowing the user to observe the effectiveness of the unit
22, if that is desired. A plurality of magnets 84 mount to
a rear surface of the housing 87 to enable easy and properly
aligned mounting to a metal surface at a convenient
location. Alternate mounting methods may be substituted,
depending upon the circumstances and the space
considerations. However, the mounting must assure level
orientation during operation.
The hose 18 connects to the housing 87 at an
isolated bottom region 89, in which a screen filter 90 spans
the cross-sectional flow area. This filter 90 provides
another degree of protection from the flow of particulates
to the pump 20. An additional hose 91
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interconnects the outlet of the bottom region 89 to the
intake of the pump 20, and this additional hose 91 may be
routed upwardly beyond the pump 20 to connect thereto from
above. Yet another hose 92 extends from the pump 20 to an
inlet 94 of the housing 87 (Fig. 1).
The housing 87 includes a plurality of angled
baffles 95 which define a flow path therebetween, from the
inlet 94 to an outlet 97 at the end of the flow path. The
flow path is designated generally by directional arrows 96.
The outlet 97 connects to the return line 24 via a fitting
93, to return cleaned coolant to the basin 14. To reach the
outlet 97, the coolant must flow over a weir, or dam 98.
While en route to the outlet 97, oil contained within the
liquid mixture tends to move upwardly because it is lighter
than the aqueous coolant. Because of the upward angling of
the baffles 95 and the overlapping center sections of the
flow path 96, most of the oil in the liquid mixture remains
within the center of the housing 87, or on the right side of
an internal panel 88 in the housing 87.
The oil gradually moves upwardly along the bottom
surfaces of the baffles 95, and it eventually accumulates
beneath a central upper panel 99 of the housing 87. A
cylindrical fitting 100 mounts to the upper panel 99 within
a port formed therethrough, preferably by
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a press fit connection. This fitting 100 serves as an oil
outlet from the flow path. An upper end 102 of the fitting
100 is located vertically above the weir 98, preferably at a
vertical distance of 0.010" above the weir 98.
When the housing 87 is filled with liquid, the
combination of fluid pressure flowing along the flow path 96
and upward floating movement of the oil causes the oil to
move further upwardly inside the fitting 100, and eventually
over the edge thereof. Stated another way, the upwardly
flowing oil displaces the oil already located adjacent the
top of fitting 100. Because of the manner in which the oil
is displaced, it is critical that the coalescer 22 be
mounted in a level orientation, with the top of fitting 100
located only slightly above, i.e. 0.010" above, the level of
the weir 98. As the oil spills over the outer end of the
fitting 100, it flows downwardly along a top surface of an
angled portion 104 of the panel 99, and eventually to an oil
outlet 106. A fitting 107 in the outlet 106 connects the
oil outlet line 26 thereto, with a fluid tight connection.
Reference numeral 103 represents a vertical level, above
which during use, the liquid is predominantly oil.
The coalescer 22 effectively separates free
floating oil particles from aqueous coolant, and the
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coalescer 22 requires no movable or adjustable parts. The
only adjustment necessary is to set the flow rate, which is
dependent upon the pressure of the pump 20, so that a first
compartment 109 of the housing 87, located adjacent the
inlet 94, does not overflow in the direction of the oil
outlet 106. Nevertheless, if by chance the flow rate is too
high, the mixture will spill from compartment 109 onto
angled portion 104 and through outlet 106, rather than
spilling onto the floor.
The space 112 between an end wall 114 of the
housing 87 and a first baffle plate 115 bounding the
compartment 109 may be varied, depending on the desired flow
rate and/or operating pressure for the pump 20. Preferably,
the first compartment 109 remains open-ended during
operation, to remove any pump pulsations in the liquid
mixture as it enters the housing 87 at the beginning of the
flow path 96. Such pulsations could have an adverse effect
on oil separation at the upper end 102 of fitting 100. In
short, the open-ended first compartment 109 dampens the
fluid pulses caused by the pump 20.
The coalescer 22 is located above the tank 14, so
that the remaining coolant returns to the tank 14 via return
line 24 by gravity, and the oil also flows along oil outlet
line 26 to collection container 28 by gravity.
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If desired, the outlet 97 may be moved downwardly along one
end wall 118 of the housing 87. This would enable both hose
connections to the housing 87 to be located adjacent one
another, thereby to better accommodate convenient routing of
the hoses within given space requirements.
In operation, the skimmer 12 is mounted inside the
tank 14 via magnets 32, thereby submerging the housing 30 at
a desired position well below the normal operating liquid
level 16. This mounting may be done with the tank 14
filled, or in an empty condition. The coalescer 22 is
connected to the skimmer 12, via hose 18 and return line 24,
with lines 91 and 92 in place. The oil outlet line 26 and
the oil collection container 28 are also connected to the
coalescer 22. The pump 20 is then activated. This
initially causes the pump 20 to suck air for a short period
of time, i.e. ten seconds, followed by skimmed withdrawal of
liquid from the housing 30. Preferably, the pump 20
operates in the range of about 20-26 gallons per hour, and
applicant has had success with a rate of 24 gallons/hour.
During skimming, the intake structure 46
continuously skims the top surface of the liquid in the tank
14, just below liquid level 16. Stated another way, the
liquid from the tank 14 continuously flows into intake
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structure 46 via inlet 86, and the inlet 86 is always
located just below the liquid level 16, regardless of the
vertical position of liquid level 16. If the liquid level
60 in the housing 30 recedes, which may occur due to changes
in pressure and/or flow in line 18, the internal float 58
lowers and pivots lever 64 about its horizontal pivot axis
66, thereby rotating the inner tube 48 with respect to the
outer sleeve 74 and expanding the size of the inlet 86.
This increases the liquid flow into the housing 30 to
compensate for the receding of the liquid level 60.
Conversely, if the liquid level 60 rises, the lever 64
pivots in the opposite direction, thereby rotating inner
tube 48 with respect to outer sleeve 74 and reducing the
size of the inlet 86. This slows the flow rate of liquid
into the housing 30 to compensate for the raising of the
liquid level 60.
As the liquid level 60 raises or lowers with
fluctuations in pressure or flow, the skimmer 12 compensates
with a corresponding decrease or increase, respectively, in
liquid flow through inlet 86. Thus, the liquid level 60
remains relatively constant, and at a desired level above
the bottom end 43 of the outlet tube 40. Because the liquid
level 60 is always above the bottom end 43 of the outlet
tube 40, the skimmer 12 prevents any sucking of air into the
hose 18 or the pump
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20. In summary, the skimmer 12 effectively skims liquid
from adjacent top surface, to optimize the efficiency of the
system 10, and it actively prevents air intake to the pump
20, which would cause damage if the pump pumped air for an
extended amount of time, i.e., 30 to 60 minutes.
Additionally, the skimmer 12 provides another
level of safety. If the liquid level 16 in the tank 14
recedes below a predetermined caution level 125 (see Fig.
3), a bottom end 124 of the outer sleeve 74 contacts a lever
126 mounted to the upper wall 34 of the housing 30 and
causes the lever 126 to pivot about a horizontal axis
aligned with a pivot point 122. This pivotal motion of the
level 126 about pivot point 122 unseats a normally closed
plug valve 127 from a port 128 formed in the upper wall 34.
The plug valve 127 is hingedly connected to the lever 126 by
a pin 129. The unseating of plug 127 allows liquid to flow
directly into the housing 30, from a level well below the
inlet 86. Although this liquid will predominately be
coolant, the main concern in this instance is to prevent air
intake to the pump 20. This immediate concern outweighs the
efficiency concern of skimming a predominately oil-rich
liquid mixture from the top. This latter concern will
become important again after normal operation resumes.
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The system 10 itself does not include any
additional safety features if the liquid level 16 should by
chance recede below the level of the upper wall 34.
However, because there is no limitation as to how low the
housing 30 may be placed within the tank 14, this should not
really present a problem for the operator. If desired,
separate safety controls may be connected to the tank 14 to
determine an extremely low liquid level condition. However,
for the most part, if the liquid level 16 recedes to such an
extremely low depth, there most likely will be other
problems with operation of.the coolant system and/or the
machine tool which will draw the attention of the operator.
Because of the manner in which the skimmer 12
operates, it can accommodate tanks 14 of virtually any
depth, so long as the lengths of the inner tube 48 and the
outer sleeve 74 are chosen to accommodate the normal range
of liquid levels 16 for the particular tank 14 selected.
The skimmed liquid flows from the skimmer 12 to
the coalescer 22. More specifically, the skimmed liquid
flows into the bottom region 89 for an additional stage of
filtering, into the pump 20 and eventually to the inlet 94.
The liquid is removed of any pump pulsations in the first
compartment 109 of the coalescer 22. Thereafter,
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the liquid mixture flows along the flow path 96, which
extends snakelike back and forth through the central portion
of the housing 87, before reaching the vertically oriented
internal panel 88. While en route to the outlet 97, oil
within the liquid mixture tends to raise upwardly because it
is lighter than the aqueous coolant, and it eventually
contacts the bottom surfaces of the angled baffles 95. The
angling of the baffles 95 causes the collected oil to move
upwardly in a desired direction, and eventually, the oil
collects adjacent upper wall 99.
As the aqueous coolant spills over the weir 98 and
out the outlet 97, fluid pressure in the housing 87 builds
and more oil accumulates adjacent the bottom of wall 99.
Eventually, the oil moves upwardly through the inside of the
fitting 100, as best shown in Fig. 6. The oil then flows
downwardly from the fitting 100, and onto the top of the
upper plate 99. It then flows through the oil outlet 106,
along the oil outlet line 26 and to the oil collection
container 28.
During pump 20 operation, the skimmer 12
continuously skims the oil/coolant liquid mixture from the
tank 14, while the coalescer 22 separates the free floating
tramp oil from the mixture and simultaneously returns the
coolant to the tank 14 and conveys the separated oil to the
container 28. So long as the system
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operates, the proportion of oil to coolant in the tank 14
becomes lower.
Fig. 7 shows a second preferred embodiment of the
skimmer 12 of this invention. In this embodiment, the
5 external float 176 is extended horizontally to encompass, or
surround, the outlet 40. With this structure, the float 176
itself serves the purpose of the brackets 78 shown in the
other preferred embodiment, in Fig. 2.
Fig. 7 also shows the benefits of the overall
10 shape of the skimmer 12 in accordance with this invention.
More specifically, Fig. 7 shows that the skimmer 12 may be
mounted adjacent two sidewalls, designated 14a and 14b, of
the tank 14. In this mounting arrangement, the sides of the
float 176 are spaced from the walls 14a and 14b, so that
surface contact therebetween is prevented. Such surface
contact would adversely affect the ability of the float 176
to move vertically with respect to fluctuations in the
liquid level i6 in the tank 14.
Fig. 8 shows a side view of the skimmer 12 shown
in Fig. 7. Fig. 8 also shows a preferred manner of
returning the filtered aqueous coolant to the tank 14. This
is done via return line connector 24a and return line outlet
24b. Preferably, return line outlet 24b includes a
plurality of vertically spaced holes 24c formed
therethrough, and the bottom end of the return line outlet
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24b is also open. The external float 176 does not contact
the outlet 24b, but return line outlet 24b is secured to
outlet 40 in any suitable manner, as by glue.
With this structure, coolant returned to the tank
14 may flow out of any of the holes 24c or from the bottom
end of the return line outlet 24b, depending upon the liquid
level 16 in the tank 14. Applicant learned that it became
necessary to mount the return line 24 to the tank 14, to
assure that filtered coolant would be returned thereto and
not spilled outside the tank 14. However, if the end of the
return line 24 became submerged below the liquid level 16,
liquid gravity flow through the coalescer 22 was inhibited
and system 10 operation was also therefore inhibited.
The outlet structure shown in Fig. 8 solves this
problem, by letting the filtered aqueous coolant flow into
the tank 14 from any one of a plurality of different
vertical levels. This solution also provides another
corollary benefit, which is more readily appreciated when
viewing Fig. 7. Because of the location of this return line
outlet 24b relative to the rest of the skimmer 12, the
return coolant will flow into the tank 14 adjacent the wall
14b. This creates a flow of coolant around the elongated
sides of the float 176, and this flow effectively prevents
accumulation of tramp oil along the
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walls 14a and 14b of the tank 14, and it promotes movement
of the tramp oil toward the intake.
Another benefit which results from this structure
relates to convenience in interconnection and cleaning the
system 10, because connections for the outlet and the intake
of the skimmer 12 are located right next to each other.
Similarly, Fig. 9 shows a second preferred
embodiment of the coalescer 22. With this embodiment, the
flow path is reconfigured somewhat to increase the vertical
length of the weir 198 at the end of the flow path. This
increases the dimension of the vertical column of liquid
adjacent the outlet 97, thereby to better accommodate normal
liquid level fluctuations during operation. It also enables
the inlet and outlet for the coalescer 22 to be connected at
convenient and adjacently located positions. Preferably,
the weir 198 includes a horizontally extending removable lip
199, which under certain desired conditions helps to aerate
the separated aqueous coolant as it flows or spills toward
the outlet 97.
The coalescer 22 shown in Fig. 9 also includes a
removably connected filter 131 which is easily removable for
cleaning. The filter 131 includes a bottom cup which
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threadably connects to an upper inline portion. This allows
easy disconnection and removal of debris.
The coalescer configuration shown in Fig. 9 is
somewhat more compact, and due to the location of the pump
20, it makes more efficient use of space. The timer 85 is
also located adjacent to the pump 20, to provide cycled
operation during a predetermined duration of time, at
regularly occurring intervals. As stated previously, this
is made possible by the efficient skimming operation of the
skimmer and the efficient coalescing operation of a
coalescer. Because both of these units operate so
efficiently, there is no need to continuously run the pump
20.
Fig. 9 also shows that the coalescer may be
equipped with yet another feature. This involves the
mounting of a radiation device 132, such as a UV light,
along the outside of the coalescer 22, with a U-shaped
reflective mirror 134 spaced therefrom, with the feedline
for the coalescer 22 located therebetween. By radiating
the liquid mixture prior to flow into the coalescer 22,
bacteria within the mixture are killed or neutralized.
Again, this promotes longer useful life of the aqueous
coolant.
Fig. 10 depicts a third preferred embodiment of a
coalescer according to the present invention. The
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coalescer 200 includes a housing 202 having an entry port
204 and a first exit port 206 and a flow path therebetween.
The flow path with this embodiment is reconfigured and
furthermore includes a grid 208 having a plurality of
inclined plates to improve oil separation efficiency. Good
separation efficiency is achieved, for example, with 25 to
30 such inclined plates. The plates are preferably spaced
0.170 inch apart. The grid 208 is mounted beneath a baffle
210 having an outlet 212 therein. The vertical level of the
top of the outlet 212 is at a first vertical level above the
first exit port 206. Because the plates of the grid 208
slant downwardly in the flow direction, the oil in the
mixture flowing through the grid 208 has less tendency to
remain entrained with the mixture flow, but rather
accumulates on the under surfaces of the plates. The close
spacing of the plates means that oil within the liquid
mixture flowing through the grid 208 only has to rise a
maximum of 0.170 inch before encountering a substantially
horizontal surface upon which it can accumulate. This
improves separation efficiency relative to a design with
more widely spaced baffles or plates. The buoyancy force
exerted on the oil by the aqueous coolant causes the oil to
move upwardly so that
the oil migrates along the under surfaces of the plates in
the general direction of the outlet 212. The oil reaching
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the edges of the plates then rises upwardly and accumulates
beneath the baffle 210, and from there the oil moves
upwardly through the outlet 212 and onto the upper surface
of the baffle 210. The oil exits the housing through a
second exit port 214. Thus, the liquid exiting the housing
through the first exit port 206 is primarily aqueous coolant
while the liquid exiting via the second exit port 214 is
primarily tramp oil.
The coalescer 200 preferably includes a dam or
weir 216 immediately upstream of the first exit port 206,
which is located in the side wall 218. The top edge of the
dam 216 advantageously is located slightly below the first
vertical level of the outlet 212 so that the column of
liquid retained by the dam 216, which is primarily aqueous
coolant, exerts a greater pressure than the column of liquid
beneath the outlet 212, which contains a substantial amount
of less-dense oil. The pressure difference between the two
columns of liquid causes the oil to move upwardly through
the outlet 212. When the coalescer includes the dam 216,
the first exit port 206 can be located anywhere along the
side wall 218, so long as it is below the dam 216. If no
dam 216 is provided, then the first exit port 206 should be
slightly below the first vertical level of the outlet 212.
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The side wall 218 also has an aperture 220 which
serves as the fluid inlet for liquid mixture coming from a
skimmer. The first exit port 206 and aperture 220
preferably are located adjacent one another to facilitate
routing of fluid lines 222 and 224.
The pump 226 and filter 228 are preferably mounted
in a portion 230 of the housing 202 that is removable from
the remainder of the housing in order to facilitate
servicing of the coalescer. An elbow section or joint 232
resides between the filter 228 and the pump 226 and is
resiliently connected at one or both ends. The resilient
connection damps vibrations of the pump to prevent pump
oscillations which can impair the proper functioning of the
pump.
As shown in Fig. 11, the housing 202 has magnets
234 secured to the rear surface 236 of the housing 202 for
mounting the coalescer on a vertical metal surface.
Preferably, the magnets 234 are spaced apart from the rear
surface 236 by spacers 238 so that a person can insert
fingers between the rear surface 236 and the metal mounting
surface when mounting or removing the coalescer.
The flow rate of liquid delivered to the flow
path by the pump 226 may vary depending on the temperature
of the liquid. More specifically, the flow rate becomes
slower when the mixture is colder because the pump 226
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slows down. One solution to this problem is to set the
pump rate to a higher setting. However, too high of a
setting may be disadvantageous to consistent coalescing
action, and it is undesirable to have to change the pump
setting with temperature fluctuations.
Accordingly, the coalescer 200 further includes a
flow-regulator 240 between the pump 226 and the entry port
204. Alternatively, a regulator 240a may be located
between the filter 228 and the pump 226 within the joint
232. Fig. 12 shows details of the regulator 240a when it
is located between the filter and the pump, with the flow
direction indicated. Regulator 240a is substantially
identical to regulator 240, so only the details of
regulator 240 are described herein. The flow regulator 240
has an orifice with a diameter in the range of about 0.100
to 0.400 inch, and preferably about 0.157 inch (the line
within which it resides being approximately 0.5 inch
diameter). The regulator 240 restricts flow into the
housing 202, particularly at relatively high pump settings,
so that a higher pump setting does not result in a
proportional increase in the flow rate into the housing
202. Thus, the regulator 240 helps assure a more-constant
volumetric flow rate into the housing 202 regardless of the
temperature of the liquid mixture. Preferably, the pump
226 is then set at the highest possible setting. If
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more than one skimmer 12 is connected to the coalescer 200,
the internal diameter of the regulator 240 may be increased
to permit higher flow rates. This is advantageous, for
instance, when the tank l4 comprises two or more separate
compartments each requiring its own skimmer 12. A single
coalescer 200 may be used simply by inserting a
larger-diameter regulator and joining the two or more
separate supply lines into a single line upstream of the
regulator.
To facilitate cleaning of the coalescer 200, the
housing 202 also includes a removable top panel 242. A
removable side panel 244 may also be included to provide
easy access to the fluid line connecting the pump 226 to
the entry port 204.
While these and other features of a
skimmer/coalescer system 10 in accordance with a preferred
embodiment of the inventions have been described, it is to
be understood that the invention is not limited thereby
and in light of the present disclosure, various other
alternative embodiments will be apparent to one of
ordinary skill in the art without departing from the scope
of the invention. For instance, the invention has been
described with respect to use in conjunction with a
machine tool, for skimming and separating tramp oil from
aqueous coolant. As noted at the outset, this same
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structure and operation may also be used in conjunction
with a parts washer. Accordingly, applicant intends to be
bound only by the following claims.
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