Information
-
Patent Grant
-
6478724
-
Patent Number
6,478,724
-
Date Filed
Wednesday, June 3, 199825 years ago
-
Date Issued
Tuesday, November 12, 200221 years ago
-
Inventors
-
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 494 42
- 494 54
- 494 55
- 494 56
- 494 60
- 494 63
- 494 65
- 494 84
-
International Classifications
-
Abstract
An improved centrifuge apparatus comprising a spindle with an affixed bowl and a drive shaft passing through the spindle with a plurality of scraper blades affixed which rotate within the bowl. The spindle is driven by a pulley with a belt attached to a motor. The centrifuge has a clutch mechanism which provides a positive lock to insure synchronous blade and bowl rotation during processing. The clutch mechanism comprises a shifting coupling attached to the drive shaft with a bottom set of teeth and a top set of teeth. The bottom set of teeth interlockingly engage a matching set of teeth located on either the pulley or the top of the spindle. The top set of teeth interlockingly engage a matching set of teeth that are either immovably attached to a plate or attached to a sprocket which is rotatably attached to the plate. The scraper blades have recesses in their front face to allow a variable cutting edge geometry and the mixing and matching of cutting edge geometry while permitting the use of the same base blade. The centrifuge has a tangential outlet and an annular housing to minimize spray and misting in the exiting centrifuged liquid.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a centrifugal separation device and method of separating solids in liquids. The liquid has solid particles in suspension. Suspended solids removal can be achieved in many ways. Solids can be settled out in a tank, filtered out using cartridges or indexing paper or a filter press. Settling is a slow process and other alternatives generate an immense labor cost or a waste stream that may be greater than the solids alone.
Use of a centrifugal separation device allows the extraction of the solid particles from the liquid. In a centrifugal separator, the separation of the solid from the liquid is commonly accomplished by pumping the contaminated liquid or coolant into a high speed rotating chamber or bowl. The centrifugal forces created by high speed rotation of the chamber cause the contaminated fluid to conform to the interior surface of the rotating chamber. The centrifugal energy causes the heavier solids to concentrate in a solid cake form for easy removal, reclamation, reuse or disposal. Since the chamber or bowl is rotating at a high speed, the solid material adheres to the side of the bowl while a cleansed coolant or liquid exits through an opening or openings commonly located at the bottom or top of the bowl. Centrifugal separation is preferable to the more traditional medium of filtration because filtration does not allow for removal of submicron particles without extensive and very expensive filtering. When such filtering is performed, the filter paper or cartridges become clogged quickly and must be disposed of. Additionally, these filtration devices often cannot pass high viscosity fluid.
With the advent of computer controls, the horizon of activities to which centifugal separation may be applied, such as use as a waste separator, has been greatly expanded. For example, metal working coolants often become contaminated during grinding, wire drawing, machining, polishing, vibratory deburring or other metal working processes. Centrifugal separation allows fluid cleaning to increase coolant life and the solid discharge from centrifugation may have a marketable value or be disposable at minimal costs. The large spectrum of applications extends to contaminated fluids resulting from phosphate baths, dielectrics, glass grinding, EDM machining, water rinse baths, acid baths, all the way to food processing wherein oils can be contaminated by starches and other food products.
It is well known in the art that the efficiency of a centrifugal separator decreases when the scraper blades or stilling vanes do not rotate at the same speed as the bowl or chamber. It is desirable if the scraper blades inside the bowl rotate at the same speed as the bowl until such time as it is desired for them to scrape or plow the solids from the side of the bowl and expel them from the process chamber.
Current systems, as will be discussed in more detail later, use a frictional mechanism in an attempt to obtain equal rotational speeds between the blades and the bowl. This frictional mechanism does not provide the consistent synchronous blade and bowl rotation desired. In operation, a user will start the system up and direct a strobe light into the centrifuge to check whether the bowl and blade are rotating at the same speed. Since the frictional mechanism does not provide a positive lock between the bowl and the blade there is no way of knowing whether the bowl and blade are continuing to rotate together during processing. Furthermore, the frictional clutch mechanism possesses a great many parts, which increases the amount of time that must be spent for maintenance purposes.
Additionally, current systems are prone to spray or mist the fluids exiting the rotating bowl, which can be hazardous to human occupants in the room where centrifugation is occurring. Also, this spray or mist can collect and cause dripping which coats the centrifuge or surrounding machinery, and may contaminate the solids expelled from the centrifuge into a waiting receptacle.
Another difficulty encountered is that some sticky solids refuse to let go of the blade during scraping. Different geometries are preferable to get the solid to peel off. However, each blade must be balanced to reduce vibration of the system, and it is expensive to produce and balance each blade properly. It would be advantageous if individual blades could be customized with different geometries for use in different applications.
The present invention meets the demand for a coupling mechanism ensuring synchronous blade and bowl rotation in the centrifuge. Additionally, it minimizes the occurrence of spray and misting upon exit from the apparatus. Furthermore, it provides a solution to the problem of obtaining variable geometries using a standard blade with inserts.
SUMMARY OF THE INVENTION
In one aspect of the invention the centrifuge comprises a spindle centered on a longitudinal axis with a top portion, a bottom portion, and a hollow interior extending along the longitudinal axis, a bowl attached to the bottom portion of the spindle and a drive shaft passing through the hollow interior with a plurality of scraper blades attached to the drive shaft. The centrifuge has a clutch mechanism comprising a shifting coupling attached to the blade drive shaft via a key locked in a rotary direction. The shifting coupling has a first set of teeth that interlockingly engage a second set of teeth. The second set of teeth are attached to the top of the spindle in one embodiment. In another embodiment the second set of teeth are attached to a pulley attached to the top portion of the spindle. The shifting coupling may be shifted upward and downward along the longitudinal axis between two positions. In the first position the first and second set of teeth are lockingly engaged so that the spindle and the scraper drive shaft rotate together. In the second position the first and second sets of teeth are disengaged.
In another aspect of this invention the centrifuge comprises a spindle configured to rotate about an axis. A bowl is attached to and rotates with the spindle. A drive shaft is received within a passageway of the spindle and rotates about the same axis. A scraper blade is attached to and rotates with the drive shaft. A mechanism is provided to selectively couple the drive shaft and spindle together to allow both to be driven by the same motor.
In another aspect of this invention the centrifuge scraping apparatus comprises blades with recesses on its front face adjacent the end of the blade next to the inner surface of the bowl. Inserts are placed in the recesses to give the scraper blade different cutting surfaces for contacting solids accumulated on the interior wall of the bowl.
In another aspect of the invention the centrifuge scraping kit comprises a rotatable scraper frame with a number of opposing ends. Each of the ends is adjacent the interior wall of the bowl and is also adjacent a front face of a blade in which a number of recesses are defined. A set of scraper inserts configured to plow solids accumulated on the interior wall of the bowl are placed in the recesses.
In another aspect of the invention the centrifuge comprises a housing with a rotatable bowl therein. The housing is cylindrical with a closed top end and an at least partially open bottom end. The housing has a tangential outlet which minimizes the entrainment of gas by a liquid exiting the bowl during processing.
In another aspect of the invention the centrifuge comprises a spindle attached to a bowl which rotate together. The centrifuge has a drive shaft which is received in a passageway defined by the spindle. The drive shaft is attached to scraper blades which rotate with the drive shaft. The centrifuge has means for selectively rotating the drive shaft and spindle together.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a partial cross-sectional side view of a centrifuge assembly of the prior art with a frictional clutch mechanism.
FIG. 2
is an exploded, partial cross-sectional side view of the frictional clutch assembly which comprises a part of the
FIG. 1
prior art centrifuge assembly.
FIG. 3
is a partial cross-sectional fragmentary view of the clutch mechanism and drive assembly according to a typical embodiment of the present invention.
FIG. 4
is a perspective view of the housing with bowl and blades of the present invention.
FIG. 5
is a perspective side view of the clutch mechanism and drive assembly according to a typical embodiment of the present invention.
FIG. 6
is another perspective side view of the clutch mechanism and drive assembly according to the same embodiment of the present invention.
FIG. 7
is a perspective side view of the clutch mechanism and drive assembly according to a second embodiment of the present invention.
FIG. 8A
is a top view of the blade assembly with recesses of the present invention.
FIG. 8B
is a side view of the blade assembly with recesses of the present invention in the
1
—
1
direction of FIG.
8
A.
FIG. 8C
is a side view of the blade assembly with recesses of the present invention in the
2
—
2
direction of FIG.
8
A.
FIG. 8D
is a side view of the blade assembly with recesses of the present invention in the
3
—
3
direction of FIG.
8
A.
FIG. 8E
is a side view of the blade assembly with recesses of the present invention in the
4
—
4
direction of FIG.
8
A.
FIGS. 9A-9D
are top views of examples of various inserts for placement in the recesses of the blade assembly of
FIGS. 8A-8E
.
FIG. 10
is a side view of the operation and exiting of fluid from within the centrifuge bowl of the prior art.
FIG. 11
is a top view of the operation of the prior art device of FIG.
10
.
FIG. 12
is a top view of the operation of the fluid exiting the bowl of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, any alterations and further modifications in the illustrated device, and any further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
In order to more fully illustrate the advantages of the present invention, the device of the prior art will be described. With reference to
FIGS. 1 and 2
, a prior art centrifugal separator with a frictional mechanism to ensure synchronous bowl and blade rotation is illustrated. A portion of the prior art assembly
10
is shown in
FIG. 1
with more detail of the frictional clutch assembly
20
shown in FIG.
2
.
The assembly
10
comprises a spindle
60
with a lower and upper end. Bowl
85
is fixedly attached to the lower end of spindle
60
and pulley
43
is affixed to the upper end of spindle
60
. A scraper blade or stilling vane shaft
61
has an upper portion fixedly attached to a sprocket
40
and a lower portion affixed to a plurality of blades
70
by a nut
71
which holds blades
70
on shaft
61
. Spindle
60
and shaft
61
are concentric and spindle
60
defines an internal passage through which shaft
61
is received. The centrifuge has main bearings
50
, and bearing caps
52
located within bearing housing
51
.
During processing, pulley
43
is driven by a belt (not shown) attached to a first motor (not shown) which provides motive force for turning spindle
60
and fixedly attached bowl
85
as well as shaft
61
and blades
70
through frictional clutch assembly
20
. During the scraping mode motive force for the rotation of the shaft
61
and affixed blades
70
is accomplished by a chain (not shown) attached around sprocket
40
which is powered by a second motor (not shown). In the scraping mode only the sprocket
40
is being driven. The sprocket
40
is free floating until actuated by pneumatic clutch
42
which forces sprocket
40
to engage frictional clutch assembly
20
.
Frictional clutch assembly
20
consists of an adjusting nut
21
with external threading
22
. External threading
22
matches the internal threading
23
in adjusting plate
24
. Adjusting plate
24
sits on four springs
25
spaced evenly around the circumference of pressure plate
27
. The springs
25
are received in slots
26
defined by pressure plate
27
. Pressure plate
27
rests on top of a bronze bushing
28
. Bronze bushing
28
sits on friction disc
29
which sits on pulley
43
. The friction disc
29
resists differences in rotational speed and is intended to ensure synchronous bowl
85
and blade
70
rotation.
The difficulties associated with use of the frictional clutch assembly
20
are numerous. For one, it has numerous parts subject to wear and replacement. Additionally, friction disc
29
does not provide a positive lock to ensure synchronous bowl and blade rotation, but, instead, the system must be constantly monitored to ensure bowl and blade rotation are occurring at the same rotational speeds. In operation, whenever the centrifuge is in scraping mode the user is causing it to overcome friction forces causing wear to frictional clutch assembly
20
. Furthermore, as friction disc
29
wears, the difference in rotational speeds and the difficulty in obtaining synchronous blade and bowl rotation is increased.
With reference to
FIGS. 3-6
, an embodiment of the clutch mechanism for providing synchronous bowl and blade rotation of the present invention is illustrated. The centrifuge apparatus has a spindle
160
and scraper blade or stilling vane drive shaft
161
. Spindle
160
has a hollow interior defining a passageway extending along the longitudinal axis L around which spindle
160
and shaft
161
rotate. Shaft
161
is concentric with spindle
160
and passes through the passageway defined by the hollow interior of spindle
160
. The spindle
160
is journalled on main bearings
150
which are received in bearing caps
152
within bearing housing
151
. The shaft
161
is journalled on scraper bearings
153
which are held in place by bearing retainer rings
153
a
. Bowl
185
is held on spindle
160
by retainer ring
154
and nut
155
. Seals
156
and
156
a
aid in preventing fluid from escaping centrifuge bowl
185
and contacting bearings
153
or
150
. In one embodiment, centrifuge bowl
185
has an inverted cup shape and the centrifuge is an inverted bowl automatic self-discharging centrifuge. It is understood, however, that other types of centrifuges, including those with openings for exiting liquids at the top instead of the bottom of the bowl, are contemplated as within the scope of the invention.
Spindle
160
has a top portion to which pulley
143
is fixedly attached and a bottom portion to which bowl
185
is affixed. More specifically, the bottom portion of spindle
160
is affixed to bowl lid
186
. Motive force for rotating spindle
160
and bowl
185
is provided by a belt
208
on pulley
143
(See
FIGS. 5 and 6
) which in turn is driven by motor
207
. It is understood that throughout the entirety of this invention that alternative drive mechanisms such as a sprocket and chain combination may be used interchangeably with the pulley and belt combination.
Shaft
161
is affixed to blades
170
at the bottom end of shaft
161
. It is understood that the centrifuge may possess two or more blades. The blades
170
are held by a nut
171
on shaft
161
. The shaft
161
has threading upon which nut
171
is screwed and possesses further threading below nut
171
upon which impeller or accelerator
172
is screwed. The impeller
172
may have a nut welded on it, so that in an alternative embodiment blades
170
are held on shaft
161
by impeller or accelerator
172
alone. Centrifuge bowl
185
has an exterior surface
179
and an interior surface
180
. Centrifuge bowl
185
at the top portion has a lid
186
with external surface
181
and internal surface
182
. Gaskets or O-rings
183
are provided to prevent leakage of liquid from the lid
186
of bowl
185
.
With reference to
FIGS. 3 and 4
, centrifuge bowl
185
and blades
170
rotate within a housing
189
with a top
192
and a cylindrical portion with exterior surface
190
and interior surface
191
. The housing
189
has an inlet tube
195
which provides liquid with solids in suspension to the bottom injector (not shown) which injects it upward into rotating blades
170
and bowl
185
. It is understood that alternative injection arrangements, including top injectors wherein liquid is provided through a passageway defined within the interior of drive shaft
161
are within the scope of the invention. An outlet port
196
from a tangential outlet
197
exits the housing
189
to a storage location or a drain for the liquid from which solids have been centrifuged. In some cases, the exiting liquid may be immediately injected back into whatever application it becomes contaminated in.
Each of blades
170
has an edge
173
. In one embodiment, the clearance or gap
184
between blade edges
173
and bowl interior surface
180
is on the order of 2 mm. Solids may coat the bowl interior surface
180
, thus reducing wear, and fill the gap
184
. It is understood that clearance
184
may be greater or lesser than 2 mm.
The clutch assembly
120
is moved upward and downward by a pneumatically driven shifter
144
. Shifter
144
is affixed at bottom portion
139
(
FIG. 3
) to the top of housing
192
. In an alternative embodiment, the bottom portion
139
of shifter
144
may be affixed to the exterior surface of bearing housing
151
. It is understood that the bottom portion
139
of shifter
144
may be affixed to any convenient non-rotating surface. The top portion
146
of shifter
144
engages a bar
145
which is pivotally connected to shifter
144
by a clevis pin
146
a
. Bar
145
is affixed to mating structure
147
which encircles or otherwise surrounds jaw or shifting coupling
122
. Shifting coupling
122
is attached to shaft
161
by a key
121
(FIG.
3
). Coupling
122
may possess any geometry which will mate with shaft
161
and not allow it to slip in a rotating fashion. That is, coupling
122
has a geometrical mating surface that does not permit rotational motion relative to shaft
161
, but coupling
122
can slide up and down along the longitudinal axis L of shaft
161
. While it is preferable that the upward and downward movement of shifting coupling
122
be accomplished with shifter
144
, it is understood that bar
145
may be moved manually or by any actuating device such as a ball screw, electric actuator or spring loaded device.
It is contemplated that alternative geometrical mating surfaces for coupling
122
other than a circular profile are within the scope of the invention. It is understood that almost any geometry such as square, pentagonal, hexagonal, etc. may be used. It is further understood that spindle
160
and shaft
161
are also not limited to a circular profile. In a similar manner, mating structure
147
is not limited to a geometry that conforms to or encircles shifting coupling
122
and may be any structure that will allow shifting of shifting coupling
122
, including, but not limited to, a fork structure. Mating structure
147
is affixed to shifting coupling
122
by bolts or screws
148
. It is understood that alternative fastening mechanisms such as welding, adhesives, and other means known in the art may be used to affix mating structure
147
to shifting coupling
122
.
On the opposite side of mating structure
147
from bar
145
is a second bar
206
which is pivotally connected by bolt or screw
149
to plate
205
. The triangular plate
205
is part of support structure
199
. Support structure
199
has a longitudinally extending portion
200
generally parallel to the longitudinal axis L of spindle
160
and shaft
161
. Support structure
199
is L-shaped and further possesses a portion
201
attached to the top of longitudinal portion
200
and extending in a radial direction. Radial portion
201
has a top surface
202
and a bottom surface
203
. Triangular portion
205
extends between longitudinal portion
200
and radial portion
201
of support structure
199
. It is understood that the support structure may be made out of materials such as metal, ceramics, and composites so long as the material selected possesses sufficient strength to withstand the stresses put on it. It is further understood that support structure
199
may have geometries other than the L-shape described herein.
In one embodiment, support structure
199
is affixed at the bottom portion of longitudinal portion
200
to the exterior surface of bearing housing
151
. In an alternative embodiment, support structure
199
is attached to the housing top
192
. It is understood that support structure
199
may be attached to any non-rotating portion of the centrifuge in a variety of manners. It is further understood that support structure
199
may also be attached to something other than the centrifuge, such as a plate of another larger outer housing containing the entirety of the centrifuge or even the ceiling of the room in which the centrifuge is located.
Shifting coupling
122
has a set of teeth or other geometrical mating or engagement means
163
on its bottom end facing downward. Additionally, shifting coupling
122
has a set of teeth
164
on its top end facing upward. The set of teeth
163
on shifting coupling
122
facing downward are sized for interlocking engagement with an equal number of teeth
159
facing upward on the top portion of spindle
160
. It is understood that set of upward facing teeth
159
may be affixed directly to pulley
143
instead of spindle
160
. In a similar manner, set of teeth
164
are sized for interlocking engagement with an equal number of teeth
204
facing downward affixed to the bottom surface
203
of radial portion
201
of support structure
199
. In one embodiment, set of teeth
163
and set of teeth
164
are identical. It is contemplated as within the scope of the invention, however, that set of teeth
163
and set of teeth
164
may be of different sizes and possess a different number of teeth or other engagement or interlocking means. In one embodiment, set of teeth
163
and
164
each possess three rectangular shaped teeth formed on the circumference of shifting coupling
122
. It is understood that each set of teeth may possess between one to more than twenty teeth. It is further understood that the set of teeth or other engagement or interlocking means may have a profile other than rectangular, including, but not limited to, triangular, trapezoidal, or even an arc of a circle.
It is contemplated as within the scope of the invention that the directions set of teeth
163
and
159
, and sets of teeth
164
and
204
, respectively, extend toward may be varied so long as the directions used permit interlocking engagement. For example, set of teeth
163
could face radially outward and set of teeth
159
could face radially inward or vice-versa. Additionally, set of teeth
163
could extend along the longitudinal axis and engage set of teeth
159
extending in a radial direction or vice-versa. Additional variations as would occur to a person of ordinary skill in the art are contemplated as within the scope of the invention and may be applied to sets of teeth
164
and
204
as well. These variations may include placing sets of teeth
163
,
164
on the sides of shifting coupling
122
instead of the bottom and top surfaces respectively.
With reference to
FIG. 7
, an alternative embodiment of the invention is illustrated. In
FIG. 7
, like objects are labeled as previously. The difference in this embodiment is that instead of having stationary or immovable set of teeth
204
, a sprocket
210
is attached to the bottom surface
203
in such a manner that it may rotate. Sprocket
210
is affixed to set of teeth
204
which are sized for interlocking engagement with the set of teeth
164
on the top of shifting coupling
122
. Sprocket
210
is driven by chain
211
. Motive force is provided to chain
211
by a second motor
212
. In operation, this embodiment allows the scraper blades to be driven in a direction opposite that of the bowl during the scraping mode of centrifugal separation. Since the bowl and the blades rotate in opposite directions, the time necessary to effectively scrape the interior of the bowl of solids is correspondingly reduced. Alternatively, the scraper blades may be driven in the same direction as the bowl but at a different speed so that bowl and blades rotate relative to one another, and scraping occurs.
The advantages of this clutch or coupling mechanism are numerous. This clutch mechanism positively locks the scraper blades or stilling vanes with the drive mechanism that drives the bowl. This ensures the same rotational speed for both bowl and blade, and keeps the liquid within the bowl from slipping, resulting in higher efficiencies during operation. This design also allows the centrifuge to be operated with one motor as opposed to two. Even in the embodiment described above with two motors, the second motor need only be run during scraping time. As a result, the design of the present invention is a much less complicated assembly and the change-out time for replacing parts is greatly lowered. For example, the GLASSLINE prior art devices such as DL 75, DL 175, or DL 275 manufactured by GLASSLINE Corporation, of Perrysburg, Ohio previously described takes 4-6 hours to change-out by an experienced mechanic familiar with the system. In contrast, in the embodiment described above where set of teeth
204
are stationary, it took less than 30 minutes for the same mechanic to change-out the second time it was done.
Additionally, it will be noted that this clutch assembly has fewer parts than the prior art frictional clutch assembly and requires no lubrication leading to a longer lifetime. Moreover, the design of the clutch assembly of the present invention allows the user to shift on-the-fly reducing scraping time correspondingly. To illustrate the advantages of shifting on the fly, the operation of the centrifuge will be discussed briefly. During processing shifter
144
is shifted downward so that set of teeth
163
on shifting coupling
122
are in interlocking engagement with set of teeth
159
located on either spindle
160
or pulley
143
. Thus, pulley
143
is driving both spindle
160
and affixed bowl
185
as well as shaft
161
and affixed scraper blades or stilling vanes
170
. When shifting on the fly, shifter
144
is shifted upward so that set of teeth
164
on top of shifting coupling
122
are in interlocking engagement with set of teeth
204
which are stationary and affixed to support structure
199
. Thus, stilling vanes
170
are stationary while bowl
185
continues to rotate, and scraping occurs since stilling vanes
170
are moving relative to bowl
185
. This is advantageous because when scraper blades
170
rotate to scrape, they can fling the solid out past the receptacle. Because the bowl
185
rotates as opposed to scraper blades
170
, the solid falls under the influence of gravity down into a waiting receptacle (not shown).
Furthermore, the present design minimizes the amount of unsupported shaft
161
from approximately seven inches in the prior art devices to on the order of two inches in the present device. Even the two inches in the present invention possess support from the teeth which are affixed to the support assembly in one embodiment. The minimization of the amount of unsupported shaft reduces the possibility for vibration and potentially destructive oscillation. Additionally, this design does not require any parts to be hanging on the unsupported portion of shaft
161
.
Centrifugal separation operating in the low to mid range of zero to two thousand g's allows the extraction of solid particles from a contaminated liquid containing a liquid and solid particle in suspension. Motor
207
need only produce 7.5 to 10 hp to operate one embodiment of the centrifuge, in which bowl
185
has a processing volume of 6 gallons, in this range. One motor used is the 10 hp, 3600 max rpm motor manufactured by Lincoln Electric Part No. LM16243TF6255/1, of Cleveland, Ohio. Different size centrifuges, however, will have different power requirements of motor
207
. Another added benefit of this invention is that the reduction in the amount of unsupported shaft
161
, as well as the minimization or lack of parts hanging from it, allow the use of larger centrifugal forces in excess of 2000 g's. Filtration of smaller particles is possible with larger centrifugal forces.
Additionally, the use of larger centrifugal forces lowers the residence time for a particular size solid, which is the amount of time the liquid is in the bowl and under centrifugal force so that the solids in the liquid are forced out to the wall. Thus, because of the reduction in residence time available using larger centrifugal forces and the reduction in scraping time available from shifting on the fly, total processing time is reduced. This allows the use of a smaller system to process the same amount of liquid in the same amount of time. As a result, a wide variety of centrifuges and motor sizes are contemplated as within the scope of the invention. Similarly, a correspondingly wide variety of centrifugal forces extending from the zero to two thousand g's previously used to more than two thousand g's as now possible with this invention are contemplated as within the scope of this invention.
With reference to
FIGS. 8A-8E
and
9
A-
9
D, another aspect of the present invention is illustrated. The solids in suspension in the liquid are often sticky and refuse to let go of the scraper blade. In this situation, different scraping edge geometries are often necessary to get the solids to peel off the scraper blade. The scraper blades, however, are expensive and must be individually balanced to reduce the potential for destructive oscillation. Illustrated in
FIGS. 8A-8E
is a scraper blade assembly
300
. Blade assembly
300
has blades
310
,
320
,
330
, and
340
which are affixed to plate
301
on their top portion and which are further affixed to ring
303
on their bottom portion. Plate
301
has an opening
302
in its center through which the bottom portion of the centrifuge drive shaft (not shown) passes. Blades
310
,
320
,
330
, and
340
have front faces
311
,
321
,
331
,
341
, back faces
312
,
322
,
332
,
342
, and ends
313
,
323
,
333
, and
343
, and recesses
314
,
324
,
334
, and
344
, respectively. The recesses
314
,
323
,
334
,
344
are defined on the front faces
311
,
321
,
331
,
341
adjacent ends
313
,
323
,
333
,
343
, respectively. Into recesses
314
,
324
,
334
,
344
, different inserts
315
and
316
,
325
and
326
,
335
and
336
,
345
and
346
, respectively, are attached by screws or bolts for different applications such as oil, water, acid and other liquids with solids in suspension. The use of recesses with inserts received therein for the blade assembly
300
allows the cutting geometry of blade assembly
300
to be easily customized based on the liquid-solid combination being separated. It is understood that blade assembly
300
may have as few as two or more than four blades.
The base scraper blade assembly
300
is the same for each centrifuge. The base blade assembly
300
may be balanced and the inserts added afterward. As long as the inserts
315
and
335
,
316
and
336
,
325
and
345
,
326
and
346
, respectively, have the same mass, the blade assembly
300
will remain balanced. This eliminates the need to rebalance the blade assembly
300
for vibration control. This invention permits the use of easily varied geometries along a single blade cutting edge of blade assembly
300
. Even greater efficiencies may be obtained by mixing and matching geometries on the same blade since heavier solids may accrete in different places on the bowl than the lighter solids. For example, the geometry of insert
315
and that of insert
316
and correspondingly the geometry of insert
325
and insert
326
may be varied on one edge to provide the most effective cutting surface for the different solids at different elevations along the longitudinal axis of the bowl.
FIGS. 9A-9D
illustrate top views of four examples for cutting surface profiles for the inserts. It is understood that other cutting surface profiles are within the scope of the invention.
It is contemplated as within the scope of the invention that if geometry permits, a single insert might be placed within recesses
314
,
324
,
334
, and
344
of blade assembly
300
. It is understood that more than two inserts may be placed within any recess
314
,
324
,
334
, and
344
if more than two different cutting edge geometries are necessary. It is also understood that any single insert may be formed to have a varying scraping edge profile along its length. In a preferred embodiment, inserts
315
and
335
, inserts
316
and
336
, inserts
325
and
345
, and inserts
326
and
346
, respectively, have not only the same mass, but are also mirror images of one another around the centerline
309
which scraper blade
300
rotates.
This aspect of the invention is useful because it solves the problems previously discussed. Each base scraper blade assembly
300
costs approximately $1500.00 to $2000.00. The use of the same base scraper blade assembly permits the varying of the cutting edge geometry in a much simpler and more economical fashion. Simpler because it is much easier to machine the inserts then the blade assembly, and more economical because it allows the use of the same base scraper blade assembly.
With reference to
FIGS. 10 and 11
, there is illustrated the design by which liquid exits the centrifuge after processing. Contaminated liquid enters the housing
402
through inlet port
404
and is injected upward into the rotating bowl
401
by bottom injector
405
. The injected liquid stays within the bowl
401
until the shaded regions (
FIG. 10
) illustrating the processing volume
403
are full. After processing volume
403
is full continued injection of liquid into bowl
401
results in the overflow of centrifuged liquid at the bottom lip of bowl
401
as indicated by arrow
406
in FIG.
10
. Since the bowl is rotating as indicated by the arrow in
FIG. 11
, the centrifuged liquid has both tangential and radial velocity components. This results in the spray path
406
as illustrated in FIG.
11
. The liquid exits the housing
402
through outlet port
407
.
In the devices of the prior art, housing
402
was square and outlet port
407
was positioned on one side of housing
402
. In the improvement of the present invention, as illustrated in
FIG. 12
, housing
502
is circular and has a tangential outlet port
507
. The tangential outlet in this design results in less splash. It is understood that this aspect of the invention may be used with a top feed injector or a top fluid exiting centrifuge or both. The tangential outlet takes advantage of liquid rotation, as opposed to simply falling out under the influence of gravity, it generates an exit velocity. This reduced splash prevents the formation of a mist or spray that could cloud the room and endanger human occupants when toxic materials are being centrifuged. Another advantage of this tangential outlet that has been noted by the inventor is that when liquid is being injected into the system and exiting during processing, its exit through the tangential outlet creates a suction/vacuum. Thus, any misting that occurs does not flow up between the exterior surface of the bowl and the interior surface of the housing. This aids in the prevention of buildup of deposits or crusting on the exterior surface of the bowl and the interior surface of the housing.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.
Claims
- 1. A centrifuge comprising:a spindle centered on a longitudinal axis, said spindle having a first end portion and a second end portion, and a hollow interior extending along the longitudinal axis; a bowl affixed to said second end portion of said spindle; a plurality of scraper blades within said bowl with a drive shaft affixed to said blades, said drive shaft extending along the longitudinal axis and passing through said hollow interior of said spindle; and, a clutch mechanism comprising: a shifting coupling attached to said drive shaft, said shifting coupling having a first set of teeth; and, a second set of teeth on said first end portion of said spindle, wherein said second set of teeth are sized for interlocking engagement with said first set of teeth, and wherein said shifting coupling is movable along the longitudinal axis between a first position to interlock said first and second sets of teeth and a second position to disengage said first and second sets of teeth.
- 2. The centrifuge of claim 1, further including a first pulley affixed to said first end portion of said spindle at a position below said second set of teeth, wherein said first pulley is driven by a first belt attached to a first motor.
- 3. The centrifuge of claim 1, further including a first pulley affixed to said first end portion of said spindle, wherein said second set of teeth are affixed to said first pulley, and wherein said first pulley is driven by a first belt attached to a first motor.
- 4. The centrifuge of claim 1, wherein said first set and said second set of teeth each have three teeth.
- 5. The centrifuge of claim 1, wherein said first set and said second set of teeth extend along the longitudinal axis.
- 6. The centrifuge of claim 1, wherein said centrifuge has two scraper blades.
- 7. The centrifuge of claim 1, wherein said centrifuge has four scraper blades.
- 8. The centrifuge of claim 1, further including an accelerator, wherein said accelerator fastens said scraper blades on said drive shaft, and a liquid injector below said bowl for injecting a liquid with solids in suspension upward, the liquid being injected upward when said first set and said second set of teeth are in locking engagement, and said liquid impacts upon said accelerator which imparts a first rotational speed to said liquid about the same as a second rotational speed at which said scraper blades and said bowl are rotating.
- 9. The centrifuge of claim 1, wherein each of said scraper blades has a front face and an end, said end adjacent an interior wall of said bowl, said front face and said end defining a recess therein, said recess receiving a scraping insert, said scraping insert defining a cutting surface configured to plow solids accumulated on the interior wall of the bowl.
- 10. The centrifuge of claim 1, further including a housing, said housing receiving said bowl and said blades therein, said housing having a cylindrical portion and a closed top end and an at least partially open bottom end, wherein said housing has a tangential outlet which minimizes the entrainment of gas by a liquid exiting said bowl when said bowl is rotating.
- 11. A centrifuge comprising:a spindle centered on a longitudinal axis, said spindle having a first end portion and a second end portion, and a hollow interior extending along the longitudinal axis; a bowl affixed to said second end portion of said spindle; a plurality of scraper blades within said bowl with a drive shaft affixed to said blades, said drive shaft extending along the longitudinal axis and passing through said hollow interior of said spindle; and, a clutch mechanism comprising: a shifting coupling attached to said drive shaft, said shifting coupling having a first set of teeth; and, a second set of teeth on said first end portion of said spindle, wherein said second set of teeth are sized for interlocking engagement with said first set of teeth, and wherein said shifting coupling is movable along the longitudinal axis between a first position to interlock said first and second sets of teeth and a second position to disengage said first and second sets of teeth; and a third set of teeth, said third set of teeth sized for interlocking engagement with a fourth set of teeth, said third set and fourth set of teeth being engaged when said shifting coupling is in said second position, and said third set and said fourth set of teeth being disengaged when said shifting coupling is in said first position.
- 12. The centrifuge of claim 11, wherein said forth set of teeth are immovable and are mounted on a bottom surface of a plate.
- 13. The centrifuge of claim 11, further including a first pulley affixed to said first end portion of said spindle at a position below said second set of teeth, wherein said first pulley is driven by a first belt attached to a first motor, wherein said fourth set of teeth are affixed to a second pulley rotatably attached to a bottom surface of a plate, and wherein said second pulley is driven by a second belt attached to a second motor.
- 14. A centrifuge comprising:a spindle centered on a longitudinal axis, said spindle having a first end portion and a second end portion, and a hollow interior extending along the longitudinal axis; a bowl affixed to said second end portion of said spindle; a plurality of scraper blades within said bowl with a drive shaft affixed to said blades, said drive shaft extending along the longitudinal axis and passing through said hollow interior of said spindle; a first pulley affixed to said first end portion of said spindle, and a clutch mechanism comprising: a shifting coupling attached to said drive shaft, said shifting coupling having a first set of teeth; and, a second set of teeth on said first end portion of said spindle wherein said second set of teeth are affixed to said first pulley and are sized for interlocking engagement with said first set of teeth and wherein said shifting coupling is movable along the longitudinal axis between a first position to interlock said first and second sets of teeth and a second position to disengage said first and second sets of teeth; and a third set of teeth, said third set of teeth sized for interlocking engagement with a fourth set of teeth, said third set and fourth set of teeth being engaged when said shifting coupling is in said second position, and said third set and said fourth set of teeth being disengaged when said shifting coupling is in said first position.
- 15. The centrifuge of claim 14, wherein said fourth set of teeth are immovable and are mounted on a bottom surface of a plate.
- 16. The centrifuge of claim 14, wherein said fourth set of teeth are affixed to a second pulley rotatably attached to a bottom surface of a plate, and wherein said second pulley is driven by a second belt attached to a second motor.
US Referenced Citations (46)
Foreign Referenced Citations (3)
Number |
Date |
Country |
39-27707 |
Mar 1990 |
DE |
59-066367 |
Apr 1984 |
JP |
59-225761 |
Dec 1984 |
JP |