Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MIXER SYSTEMS
DescriPtion
The present invention relates to mixer systems, by
which is meant systems for suspending, agitating and/or
circulating materials, particularly liquids or liquid suspensions
and particularly to mixer systems for mixing aggressive
materials, by which is meant toxic, hazardous, corrosive or other
materials which need to be confined for proper handling,
processing or for environmental safety or health reasons.
In order to prevent the escape of aggressive materials
from the vessel in which they are mixed, confinement of the
mixing apparatus which contacts the material has necessitated the
use of magnet couplings which provide confinement shells or which
use the wall of the vessel to separate the driven impeller
apparatus from the motor and other drive elements. The spacing
of the impeller and other parts of its drive apparatus, for
example the impeller shaft, as well as the rotor of the magnet
coupling with respect to the confinement shell or the other
separating member (the wall of the tank) has necessitated the use
of bearings which control the run out of the shaft and the
impeller so that there is no interference with the confinement
shell. The conventional approach has been to protect the
bearings and to provide dynamic, running seals which prevent the
aggre3sive materials from leaking into regions where the bearings
are located. Such seals are undesirable since they have limited
lifetimes and must be replaced before failure. The life of the
seals is also subject to reduction because they are exposed to
the aggressive material.
It is a feature of this invention to eliminate such
seals thereby effectively providing a sealless miY.er system.
Instead of resorting to seals, the bearings themselves are made, ~
or at least surfaced, with material resistant to the aggressive ~ ;
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material being mixed. The invention, contrary to the
conventional technology, uses bearings or journals for the
impeller shaft which are confined with the aggressive material.
Notwithstanding, the conventional technology it has been found in
accordance with the invention that mixer systems having
acceptable lifetimes, in spite of their use with aggressive
materials, are not only possible but practicable.
It is necessary in accordance with certain processing
techniques, for example when the aggressive material is altered
from one type of material to another or has different ingredients
thereto and proportions are critical or the presence of materials
previously being mixed is detrimental to the proce~s, that all or
part of the region which is confined be purged or even
sterilized. In order to accommiodate such needs, and in other
applications where it is desirable to remove or replace the
bearings and other parts which are in confinement, a static seal
can be provided at a desired location and used when the impeller
shaft is stopped to isolate all or part of the region under
confinement, for example the part containing the rotor and inside
of the containment shell of the magnetic coupling or even the
aforementioned part including the bearings. It is a feature of
the invention to provide in the improved sealless mixer system an
expandable collar which defines a seal against the shaft thereby
isolating all or part of the region under confinement and
enabling it to be purged, say with nitrogen gas or even
sterilized, as when the purging agent is steam. When the
expanding collar is in sealing relationship with the shaft, the
shaft is stopped. During normal running conditions the collar
does not interfere with the shaft and the sealless condition
prevails.
The material which is subject to mixing may be under
pressure and the vessel in which it is located is pressurized.
This pressure may be used in accordance with the feat~re of the
invention to provide a secondary or back up static seal in
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addition to the seal provided by the expandable collar. Then a
flange on the shaft and a collar confines a seal member (2 . g ., a
O ring) between their opposed surfaces. The shaft may be biased
to separate the opposed surfaces so that under dynamic conditions
when the shaft is rotating no seal is formed between the opposed
surfaces. When the pressure is relieved, however, the bias is
counteracted by ~he pressure in the tank to enable the seal to be
formed between the opposed surfaces thereby providing even
further assurance that the aggressive material will not escape
from the vessel.
It is desirable for certain mixing applications that
the impeller rotate at lower speed and provide higher torque than
the motor which drives the impeller. The magnet coupling has
limited torque transfer capacity. Accordingly, mixing systems
with magnetic couplings have been limited in the amount of torque
and mixing power which can be delivered to the material being
processed. It is a feature of this invention to provide a gear
train in the confined region between the impeller shaft and the
inside or inner rotor of the magnet coupling. Preferably the
gear train is provided by a planetary gear set thereby enabling
~he torque to be multiplied in a volume which is available in the
confined region.
It is the principal object of the present invention to
provide improved mixing apparatus, and particularly an improved
mixer system which is adapted to be used for mixing aggressive
materials.
A more specific object of the present invention is to
provide an improved mixer system having one or more of the -
features discussed abo~e.
Briefly described, a mixer system embodying the
invention is applicable for mixing aggressive material in a
vessel having an opening. A drive shaft for rotatably supporting
a mixing impeller is used. The drive shaft is rotatably
supported in bearings contained in an assembly which is located
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in the opening and closes the opening to confine the aggressive
material in the vessel. The assembly has an open passageway in
which the bearings and shaft are disposed. Since the passageway
is open the mixer system is sealless. The passageway connects
the bearings and the vessel in communicating relationship for the
aggressive material. There are no dynamic seals in the
passageway. The bearings have at least the surfaces thereof
which are exposed to the aggre sive material made of a material
resistant to the aggressive material. If desired, an expandable
collar may be used to provide a static seal when the drive shaft
is stopped. Passageways may be provided for releasing the
pressure behind the expanded collar in order to purge or
sterilize the parts of the assembly in confinement. For example
the bearings may be mounted in a cartridge which is removably
disposed in the assembly. If torque multiplication is desired,
the drive shaft may be connected via a gear train also in
confinement. This gear train may be driven at higher speed and
lower torque than desired to power the impeller through a magnet
couplingi the gear train being connected to the inside part of
the coupling. The term inner rotor should be taken to mean the
inside part of such a magnet coupling.
The foregoing and other objects, features and
advantages of the invention, as well as presently preferred
embodiments thereof will become more apparent from a reading of
the following description in connection with the accompanying
drawings in which:
FIG. l is a elevational view, partially in section, of
a mixer system embodying the invention;
FIG 2. is an enlarged fragmentary elevational view of
the region of the mixer system of FIG. l which is in confinement
and connected through a sealless open end thereof to the mi~ing
tank;
FIGs. 3, 4 and 5 are similar enlarged fragmentary
elevational views ~howing different arrangements of separator
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plates which may alternatively be used in the assembl~ shown in
FIGs. 1 and 2 to provide static sealing and purging or
sterilizing capabilities;
FIG. 6 is fragmentary elevational view similar to
FIG. 2 showing the portion of the assembly which provides the
confined region of the mixer system, but in accordance with
another embodiment of the invention.
FIG. 7 is a view similar to FIG. 6 which also shows the
flange and pedestal and outer rotor drive but is in accordance
with still another embodiment of the invention;
FIGs. 8 and 9 are respectiYely a view similar to
FIG. 7, and an elevational sectional view 90 about the axis of
the impeller drive shaft from the view shown in FIG. 8, both
views showing a mixer system in accordance with still another
embodiment of the invention; and
FIGs. 10 and 11 are ele~ational views illustrating a
mixer system which enters the vessel or tank from the side (side
entry) and which utilizes a planetary gear set, all in accordance
with still another embodiment of the invention.
Referring to FIGs. 1 and 2, there is shown a top entry
sealless mixer system 10 which embodies the invention.
Aggresisive material to be mixed is introduced into a vessel 12
having its inside walls coated or made with material which is
resistant to the aggressive characteristics of the material. An
impeller 14 is located in the vessel 12 and is connected to a
drive shaft 16. An assembly 18 has upper and lower bearings 20
and 22 which rotatably support the shaft and also rotatably
support an inner rotor 24 of a magnet coupling 26. This support
is provided by a cap nut 28 or bolt which is eccentrically
disposed on the shaft 16 as shown in greater detail in FIG. 2,
for torque transmission (acting like a cam~ between the inner
rotor 24 and the shaft 16.
The outer rotor 30 of the coupling 26 is connected ~ia
the flanged end 32 of a shaft 34 which extends from a motor gear-
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box assembly 36. The motor gear-box assembly is mounted on a
bearing support 38 which journals the shaft 34. The magnet
coupling 26 has circumferentially disposed arrays of permanent
magnets in its inner and outer rotors 24 and 30. The magnets in
the inner rotor 28 are aligned with the magnets in the outer
rotor 30 but are polarized oppositely (i.e., north-south, south-
north, north-south, south-north, etc.). The design of the
coupling 26 may be conventional and it may be of the type which
is commercially available. The assembly 18 has a flange 40 which
may be welded to a hub 42. The flange is bolted to a flange 44
of the nozzle 46 of the vessel 12 and closes the opening into the
vessel with the assembly 18. The motor 36 and its bearings
support 38 are mounted on the top of a pedestal 48 which has a
lower end flange 50 which is bolted to the flange 40. Openings
52 in the pedestal 48 provide access to the internals of the
mixer system (the bearing support 38, the outer rotor 30 and the
assembly 18). Ears 54 allow the mixer apparatus 10 to be lifted
and transported. The ears are 120 degrees apart; thus only one
ear appears in FIG. 1.
The assembly 18 also includes spacer plates 56 and 58
which are interchangeable with static seal plates 60 and purge
plates 62, as are shown and will be described in greater detail
hereinafter in connection with FIGs. 3 and 5. These plates 56
and 5~, either when used alone or in different arrangements with
the plates 60 and 62, are bolted together by a circumferentially
disposed array of bolts 64 to the flange 40. The magnet
coupling has a confinement shell (also known a~ a separator or
separating member) 66 having flange 68 which is bolted in the
assembly by the bolts 64. The shell 66 may also be called a
containment shell.
The cylindrical hub 40 has an internal bore or
passageway 70 which defines a passageway through which the shaft
16 extends and in which the bearings 20 and 22 are located. This
passageway 70 is opened to the vessel 12 and therefore to the
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aggressive material confined therein which, especially if the
vessel is pressurized and the material can vaporize, is present
in the passage 70. The passage 70 is part of a confinement
region which includes cylindrical bores in the plates 56 and 58
and the inside of the confinement shell 66. The hub is
terminated at its open end by an end cap 72 but is otherwise open
and sealless.
The bearings 20 and 22 are bearings having rolling
elements, namely balls 74 and 76 and inner and outer races 78 and
80 (for the bearing 20 and 82 and 84 for the bearing 22). The
bearings are axially spaced from each other, with the bearing 82
closer to the open end 71 of the passageway 70 and the bearing 20
further from the open end 71, by spacer sleeves 86 and 88. The
shaft 16 has a shoulder 90 which references the inner race 82. ~-
The inner race and the bearing 22 is fixed in axial position by
the spacer sleeve 86 which sandwiches the inner race 78 of the
bearing 20 and is compressed against that inner race by force
applied from the bolt or nut 28 against the upper end of the
spacer sleeve 88 via a shoulder 92 which extends downwardly from
the hub 94 of the inner rotor 24. The outer race 22 is fixed
between a step 96 around the bore 70 and a shoulder 98 of the end
cap 72. The outer race 80 floats axially in the bore take up
thermal expansion and tolerances in manufacture.
The balls 74 and 76 of the ball bearings and the races
thereof are all exposed to the aggressive material. The surfaces
which are exposed are made of material resistant to the
aggressive material. Desirably the balls are made of entirely
such material so that their surfaces are resistant. The balls
may be a ceramic, for example silicon nitride. An alternative
material which may be suitable for other applications is
stellite. Stellite is a boron containing alloy. It has been
found that stellite, sold under the tradename Hanes 25 is
suitable. The races may be stellite of Rockwell C hardness of
about 60). For some applications, steel races having a
:,
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zirconium/zirconium nitride vapor deposition or sputtered coating
may be used. For other applications the races may be plated with
thin dense chromium, for example a 0.3 mil coating of chromium.
Other types of coatings may be applied by vapor deposition or
sputtering. The thin dense chromium material is sold under the
tradename Armalloy. Other materials which are resistant or more
preferably inert to the aggressive material being mixed may be
used.
FIGs. 3 and 5 illustrate a static seal which may be
provided by a pneumatically pressurized collar 100 of elastomeric
material, for example, such as viton, a elastomeric polymer. The
collar is a hollow annulus on a ring shaped metal core 102. Such
expandable seals are commercially available. Pressurized air is
introduced through a port 104 into a ring 106 which communicates
with the front end of the core through holes 108. Normally the
collar does not interfere with the shaft nor contact the sleeve
88. The collar is expanded only when the motor and the shaft 16
are stopped. Then access may be had to the magnet coupling. A
normally plugged opening may be provided in the purge ring or
plate 56 to relieve the pressure between the expandable collar
and the confinement shell. By locating the collar 100 above the
hub and above the bearings 20 and 22, the bearings and the
passageway 70 remain exposed to the aggressive material.
As shown in FIG. 5 the purge plate 62 has a port 108,
an annular manifold 110 and a plurality of circumferentially
disposed openings 112. The purge plate may have the port 108
plugged and then opened to relieve the pressure behind the
expanded collar 102. Alternatively, inert gas, such as nitrogen
or sterilizing vapors, such as steam, may be introduced through
the port 108, the manifold 110 and the openings 112 to purge
and/or sterilize the confinement region above the collar 102.
In the event that purging into the vessel 12 is desired
only the ring plate 58 is used together with the purge plate 62
as shown in FIG. 4. Then the vessel 12 as well ai the passageway ~ -
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g
and the entire confinement region can be purged and/or
sterilized. The exhaust from the vessel may be by suction
applied to the port 108 of the purge plate 62 or via an opening
(e.g., the fill opening) in the tank or vessel 12.
Referring to FIG. 6 there is shown an assembly 120
using a hub 122 and flange 124 connectable to an opening
(nozzle) of a tank, such as shown in FIG. 1, for closing that
opening. The hub 122 receives the bearings 20 and 22 in a
cartridge 126. The cartridge is a cylindrical tube having steps
130 and 132 against which the outer races of the bearings 20 and
22 are referenced and held in place by snap rings 134 and 136.
The upper bearing 20 is fixed since its inner race is referenced
against a step 138 on the shaft and held against that step 138 by
a tubular sleeve 141 which may be compressed by the hub shoulder
of the inner rotor as discussed in connection with FIGs. 1 and 2.
The inner race of the lower bearing 22 is allowed to float. The ~;
bearings 20 and 22 may be made of materials similar to those
diqcussed above.
Below the bearings, in a ring plate 140 which is
sandwiched against the bottom end of the hub 122 by a grooved end
cap 142, i~ an expandable collar 144. A split collar or neck 146
which is clamped to the shaft and located in the grooyed end cap -~
142 provides shoulders to limit the axial movement of the shaft,
particularly the downward mo~ement of the shaft into the tank 12.
Since the expandable collar 144 is disposed at the
bottom of the passageway defined in the cartridge 126 around the
shaft and then upwardly into the confinement region which is
closed by the confinement shell 66, substantially the entire ~
confined region in the assembly 120 may be statically sealed. ;
~ purge plate 150 is sandwiched between the flange 68
of the confinement or containment shell and the hub 122 at the
upper end thereof. This plate has normally plugged inlet and
outlet ports 152 and 154 to which holes 156 and 158 extend. When
the plugged port 154 is opened the confined region may be
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depressurized. The confined region may be purged or sterilized
by introducing gas or sterilizing vapors through the inlet port
152 and exhausting the gas or vapors (e.g., nitrogen and/or
steam) through the outlet port 154.
The expandable collar 144 is connected via a passage
160 for pressurized air or gas to a control line from a pump (not
shown). The bore in the hub in which the cartridge 126 is
disposed may have an annular groove or relief 162 which
facilitates the insertion and removal of the cartridge 126 and
decreases the area of the bore in the hub 122 and the outside of
the cartridge 126 which needs to be precisely machined.
FIG. 7 illustrates an assembly 170 with a hub 172 and a
cartridge 174 carrying bearings 178 and 180. The bearings 178
and lB0 may respectively float downwardly and upwardly on the
shaft at their inside races. The outside races of the bearings
are both fixed by spacers and snap rings. Passages 184 and 186
bypass the bearings 178 and 180.
The mixer shown in FIG. 7 has a magnet coupling 188
with outer and inner rotors 190 and 192 separated by a
confinement shell 194. This coupling may be somewhat different
in design from the coupling 26, but is functionally identical
therewith. The inner rotor 192 is connected to the shaft 182 by
a cap nut 196 which holds-the hub of the rotor 192 against a
spacer sleeve 198 which acts as a shoulder against the inner rac,e
of the bearing 178.
The shaft 182 has a flange 200 which extends
riadially into a groo~e defined by the lower surface of a
pneumatically pressurized collar 202 and an end cap 204. This
groove also captures an expandable elastomeric collar 206 which
is normally clear of the flange 200, but when expanded by
compressed air which eY.tends to the collar through a line (not
shown~ defines a seal against the circumfere~tial rim 208 of the
flange 200. The flange 200 has a groove which locates an O-ring
seal member 210. The gap between the opposed surface~ of the
ROCll/11956
flanae 200 and the collar 202 where the O-ring 210 is located is
spaced apart sufficiently to prevent a seal from being formed by
the O-ring during normal running operation of the shaft. This is
because the shaft is biased downwardly by a wave spring 212 (an
annular spring member) which is captured between the foot 214 of
the confinement shell 194 and the top of the hub 172 and extends -~
radially inward. The bias of this spring is transferred through
a ring shaped plate 216 which is bolted to the top of the
cartridge 174. The force then is transferred via the lower
bearing 180 to the shaft 182 in a downward direction thereby
creating the gap of sufficient size to prevent the formation of
the seal by the O-ring 210.
When the collar 206 is expanded and a port 218 which
extends via a conduit 220 in the hub through the collar 202 is
opened, the flange 202, acting as a piston, counteracts the
bias of the wave spring 212 and enables the seal to be formed by
the O-ring 210. The O-ring therefore provides a double or
secondary seal in addition to the expandable collar 206. The
flange 200 provides a stop when it engages the end cap 204.
The bypasses around the bearings 178 and 180 assure
that the pressure in the confined region is relieved when the
port 218 is opened. The port 218 may also be used for purging,
sterilizing, etc. when the static seals are in place.
FIGs. 8 and 9 show a mixer system 230 which is similar
in design to the embodiment shown in FIG. 7 except that sleeve
bearings instead of ball bearings are used. There are upper and
lower sleeve or journal bearings 232 and 234 and thrust bearings
238. These thrust bearings are plates on opposite sides of a web
240 or flange which is appertured, like the journal bearings 232
and 234 at holes 242 and 244 so as to spring all parts of the
confined region into communicating relationship. The thrust
bearingq 238 are pressed into the cartridge 174 and a cap 246
which holds the upper pad of the thrust bearing 238 in place.
I The wave spring 212 bears against this cap 246 to open the gap
.:
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where the O-ring 210 is located during normal running operation.
When the pneumatically pressurized collar seal is formed by air
pressure applied to lines 248 and 250 and the pressure behind the
piston 200 is released via the conduit 220 and the plug 218, the
spring 212 is further compressed, counteracting its bias by the
pressùre in the vessel and enabling the seal to be formed by the
O-ring 210. The formal and thrust bearings may be of material
resistant or inert to the aggressive material being mixed. A
sintered graphite material (e.g. Graphalloy) or a polyamidimid
(e.g. Vespel) are suitable. for this purpose.
FIGs. 10 and 11 show a side entry mixer 260 which
enters through the side wall 262 of a tank 264. The side wall
has a flange nozzle 266 which forms the opening into the tank.
This nozzle is sealed by the assembly 268 including ball bea~ings
270 and 272 in a cartridge 274 in the bore of a hub 276. The hub
is sealless and has an open end which may have a bushing 278.
This bushing does not form a seal so that the mixer 268 is
sealless as was the case with the mixer system described above.
The mixer 268 has an impeller 280 and an impeller shaft
282 which is journaled in the bearings 270 and 272. The shaft
has a flange 284, against the rim of which an expandable collar
286 may be expanded to form a static seal. A double seal is not
used in this embodiment of the invention. Pressurized air to the
collar 286 is applied via a conduit 288.
The impeller shaft 282 is connected to a gear box 290
containing a gear train in the form of a planetary gear set 292.
This gear train as well as the passageway in the cartridge 274
which carries the bearings 270 and 272 are contained in the gear
train housing 290.
The gear train is driven by a shaft 294 which is
connected to the inner rotor 296 of a magnet coupling 298 by a
shaft 300 connected to a motor 302 via an adapter 304. The
magnet coupling 298 has an outer rotor 306 which is connected to
the shaft 300. The motor 302 is supported on a table 306. The
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motor front end is mounted on a pedestal 308 which is bolted to a
flange 310 which extends radially from the hub 276 of the
assembly 268. The flange and pedestal are bolted to the
nozzle flange 266.
The planetary gear set 292 has a sun gear 310 which
engages planet gears 312 mounted on roller bearings to a planet
carrier 314. The planet gears engage a ring gear 316 which is
mounted on the housing 290. The output of the planetary gear set
292 is taken at an adapter 316 connected to the upper end of the
impeIler shaft 282 by one or more splines 320. The planet gear
is continuously lubricated by oil in the housing which is
circulated by blades 322 on a sleeve 324 connected to the shaft
294 as by a set screw. The oil circulateQ through ball bearings
326 and 332 which support the shaft 294 against thrust and radial
movement and thence through the planet gears 312 and the sun gear
to a splash guard 328. There are holes 330 for the circulation
of oil backward to another bearing 332, the impeller 324 and back
to the bearing 326 and the planetary gear set 292. The oil may
be admitted into the housing 290 via a top plug 334 and drained
via a drain plug 336. ~
Planet gear set 292 provides a reduction in shaft speed ~:
and multiplication in torque delivered to the impeller shaft 282.
If additional speed reduction and torque multiplication is
desired another planetary gear set may be mounted in series and
coaxially with the gear set 292 shown in FIG. 11. In the event
that the tank 262 contains oil or other lubricating material
which does not interact with the oil in the confinement region of
the assembly, then it may be desirable to fill the confinement
region with oil and to arrange conduits and a piston to equalize
the preqsure in the confinement region of the assembly 288 with
the pressure in the tank thereby preventing leakage into the tank
of the oil in the confinement region or leakage of oil from the
tank into the confinement region. The planet gear set may be dry
running, and the use of such dry running gears may be preferred, ~ :
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especlally in the top entry mi:~er systems, such as shown in FIGS.
1-9 . .
From the foregoing description it will be apparent that
there has been provided improved mixer systems, and especially
systems using magnet couplings and sealless entry into a vessel .
in which mixing occurs. Variations and modifications of the
herein described mix.er system, in accordance with the invention,
will undoubtedly suggest themselves to those skilled in this art.
According the foregoing description should be taken as
illustrative and not in a limiting sense. :~
ROCll/11956
