Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
The present invention relates generally to separable
blade agitators and more particularly to a glass coated agitator
and the apparatus and method for assembling the agitator within
a mixing vessel.
Separable blade agitators are well known in the art
and are described for example in U.S. Patent Nos. 2,811,339 ~hich
issued October 29, 1957 to Alec V. Osborne and CharIes W. Webster
and U.S. Patent 3,494,708 which issued February 10, 1970 to
Erwin J. Nunlist and John S. Eyster. Briefly, a separable blade
agitator includes a drive shaft and a separable impeller. The
impeller includes a hub for attachment to the drive shaft and
two or more blades extending outwardly from the hub. The entire
surface of the drive shaft, hub and blades exposed to the contents
; of-the vessel is glass coated to resist corrosion, adherence andk abrasion. Such separable blade agitators are used in vessels for mixing various corrosive, adhesive, abrasive or easily
contaminated ingredients such as acids, polymers, pharmaceuticals,
dyes and the like.
These agitators especially have great value in
closed vessels because they eliminate the need for large vessel
openings normally used for agitator removal and admittance. In
this respect, the separable impeller portions can be passed into
a pressure vessel through a relatively small manhole opening
and assembled within the vessel to the drive shaft.
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Separable blade agitators are useful in either closed or
open vessels in that they permit replacement of damaged impellers or
changing the size or type of Lmpeller without the need to remove the entire
agitator (i.e. drive shaft and impeller) from the vessel or to disconnect
the drive shaft from the drive motor and seals.
Separable blade agitators having gaskets between the shaft
and impeller are known. Such agitators are not entirely satisfactory
because any gasket used must be made from tantalum or other exotic metal
or from a fluro-carbon in order to resist the highly corrosive environments
to which these gaskets may ke expos d. Another drawback with gaskets is
that they take a set due to repeated heating and cooling and eventually
leak. Normally, leaking gaskets can be resealed by tightening, but this is
- difficult to do in separable blade agitators and often a leak is not noticed
until leakage into the shaft has caused damage.
Separable blade agitators æ e also known in which no gaskets
.
are used, as shown for example in U.S. Patent No. 3,494,708 which issued
February 10, 1970 to Erwin J. Nunlist and John S. Eyster. Here, a gasketless
connection is made by forcing near optically flat glass coated surfaces
together with considerable force. m e prImary drawback of the construction
shown in this prior art is that relatively complicated, expensive components,
which themselves are not glass coated, æe needed to hold the shaft and
agitator portion together in a fluid tight gasketless connection capable
of transmitting torque from the drive shaft to the impeller blades.
Thus, prior art separable blade agitators used gaskets or
optically flat surfaces between joints to seal the jounts between the
separable me~bers and isolate non-corrosive resistant surfaces from the
vessel contents. m e present invention, however, does not rely on sealed
joints because all surfaces exposed to the vessel contents
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are protected hy non-corrosive ~oatings such as glass or
. plastic. .
In the present invention, the configura~ion o~ both
the drive shaft an~ separable impellers is such that
they can be quickly and easily joinea in an in~erference
itted, gas~etless connection. The in~ention not only
pro~ides a safe connection because all exposed surfaces
axe glass coated~ but also provides for relatively hi~h
~or~ue transmission because o~ the cross sec~ional
configuration of the hub of the impeller an~ a portion
. . .. .
. : o the shaft t~ which the hub is attached. .-
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. Su~mary of the Invention - - .- .
- . In the present in~ention, the agitator shaft is
flattened alo~g a portion of its length to form ~wo
. generally parallel sides for recei~inS the separable
impellers. There are at least two separable impellers.
The fixst impeller includes a flat sided mountin5 m.e~.ber
. aisposed in acing relationship with one o~ the iat
: 20 shaft sides an at least one blaae extending ra~ially from
the mounting me~ber. Shims are positioned bet~Jeen tne :
mounting me~ber ana.the shaft and a mechanical clamp
. appliea across the bla~e ana shaft.to bow the ~.ounting
. me~ber ~owara the shaft there~y decreasing the space
therebet~7een. A second impeller has a hub with a genexally
squaxe opening and at least one blade extending ra~ially .
~rom the hub. The hub is then slippea ~ver the shaft ana
the mounting mem~er o~ the firs~ impeller so that upon
release of the clamping force from the first impeller, the .-
~ounting me~ex will spxiny outwara against the cl~lping-
hub to loc~ the first and second impellers fir~ly to the
sha~t. .
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Therefore, in accordance with one aspect of
the present inven'tion there is provided a separable blade
agitator comprising: a glass coated shaft terminating as an
axially extending mounting shaft, a first glass coated impeller
mounted to the mounting shaft and including an axially extending
mounting base portion corresponding with the axially extending
mounting shaft; a second glass coated impeller mounted to the
mounting shaft and including a hub defining an axia,l bore
embracing the mounting shaft and the mounting base portion of
the first impeller; and spacer means disposed between the
mounting shaft and the ends of the mounting base portion of
the first impeller to space the mounting shaft and the mounting
base portion apart by an amount to effect an interference it
of the hub over the mounting shaft and the mounting base portion,
whereby the hub compresses the mounting base portion and the
i' mounting shaft toward each other, between the spacer means to ''
rigidly clamp the shaft and the first and second impellers
together.
According to a second aspect there is provided
a method of ioining separable impéller to a drive shaft in
- an interference fitted connection to provide a separable blade
; agitator. The method comprises the steps of: providing
(i) a first impeller having a part with a surface complementary
to an axially extending surface on the shaft and ~ii) a second
impeller with a hub having a bore capable of receiving there-
through both the first impeller part and a portion of the shaft
including the axially extending surface; moving the second
impeller onto the shaft so that the shaft surface extends through
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the bore; supporting the first impeller so that the
complementary surfaces on the first impeller part and shaft
are in face-to-face relationship; placing shims between the
surfaces to create a space therebetween and sufficiently
i.ncrease the distance across the first impeller part and shaft
portion to prevent passage of the hub; applying a force across
the first impeller part and shaft to bow the first impeller
part towards the shaft and reduce the space to permit passage
of the hub over the first impeller part, and releasing the
force to permit the first impeller part to spring away from the
shaft and against the hub for locking the hub, shaft and first
impeller together in an interference fit.
Description of the Drawings
Figure 1 is a side elevation view partly broken
away and
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in section showing the co~ponen~s of the separable blade
agitator prior to connection;
Figure 2 is a view taken along lines 2-2 of Figure l;
Figure 3 is a view on an enlarged scale of the
agitator corpone~nts in an assemkled condition; and
Figure 4 is a view taken alony lines 4-4 of Figure 3.
Description of the Preferred Embodirlents
Referring to the drawing, Figure 1 shows the lower
poxtion of a vertically orientecl a~itator drive shaft 12.
It should be appreciated that shaft 12 when in use, is
suspended within a mixing vessel and that the upper end
(not shown) of the shaft is attached by any suitable
means to a motor and gear system for rotating the agitator
shaft to mix the contents of the vessel.
It is not uncommon for agitators of this type to
have a span equal to 40-60% of the of the vessel diameter.
Consequently, a relatively lar~e vessel opening woul~ be
required in order to allow the assemblecl agitator to pass
into the vessel.
In order to avoid larse vessel openings separa~le blade
agitators are used so that the impeller bla~es can be
carried separately through a small vessel opening into the
vessel and then asse~bled to the agitator drive shaft
25 within the vessel. Typical of those separable blade
agitators known in the art are as described in the t~o
U.S. patents set out hereinabove.
Referriny again to Figure 1, shaft 12 is round in
cross section for the major portion of its len~th. However,
the 10~7er por~ion 14 is flattened to provide two yenerally
flat parallel faces 16 and 18 and a generally rectangular
cross section wherein the distance between the two faces
16 and 18 is less than the diameter of shaft 12.
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The loJer most end of the shaft is provided with a
stop 20 adjacent face 18. Face 18, bet~ieen stop 20 and
the normal diameter of shaft 12, defines a mounting
sur~ace for one of the impellers as set out hereinbelow.
S It should be appreciated that the entire outer surface
of shat 12 exposed to the contents of the mixing vessel
is glass coated. For this purposel it is important that
all of the edges of shaft portion 1~ be slightly rouncled to
accon~odate a glass coating.
A first impeller for attachment to the shaft is
identified at 22. This first impeller 22 includes an
axially extending mountiny foot 2A and an agitatox blade
26 attached to and extending radially from the mounting
foot. ~lounting foot 2~ is generally rectangular in cross
section ~Figure 2) with a relatively flat surface 28 that
can be disposed in face-to-~ace relationship with the
mounting surface on the shaft provided by face 1~. The
' upper end of the mounting foot has a reduced thickness so
as to form a toe 25 for purposes set out hereinbelow.
It should be appreciated that the length of foot 24 is
such that it can easily fit against face 18 between stop
20 and the normal diameter of shaft 12. All of the edges
of i~peller 22 are, of course, rounded so that its entire
surface can be provided with a glass coating.
A secona impeller for attachment to the shaft is
identified at 30. Second impeller 30 has one or more '
impeller blades 32 (see Figure 4) extending radially
outward rom a central hub 3~. rxtending axially through
the hub is a generally square opening or bore 36. The
size and shape of opening 36 is sufficient to accomrodate
the lower portion 14 of shaft 12 and the mounting foot 2A
of first impeller 22 for purposes of clamping the shaft
and impellers 22, 30 togeth~r in a manner set out
hereinbelow.
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Completing the structure of the separable blade
agitator as shown in Figure 1 are shims 38 positioned between shaft
mounting surface 18 and the flat surface 28 of first impeller 22.
,These shims preferably are made of a high corrosion resistant
material such as tantalum or the like.
The shims are used to avoid the need to maintain close
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tolerances between the mating parts for an interference fit
assembly (as described below) and reduces the cost of manufacture.
However, in applications where exposure to any metal cannot be
tolerated, (i.e, where shims 38 cannot be used), the surfaces that
control the dimension across foot 24 and shaft portion 14 and the
inside dimension of bore 36 can be ground to provide the close
tolerances needed for an interference fit assembly. In such a
case surface 28 of mounting foot 24 would be under cut so as to
provide the mounting foot with thicker ends as is now provided by
shims 38. , ' ,
'- Referring now to Figures 1 and 2, a special tool 40 îs
' shown for use in assembiing the two separable impellers 22 and
30 to the agitator, shaft 12. Tool 40 is in the shape of a
,20 elongated U. The ends 42 of each of the elongated legs of the U-
, shape are threaded. A cross bar 44 extends across the elongated
- legs of the tool and has openings 46, to permit the free movement
of the legs through ~e cross piece. Completing the structure of ',
the U-shaped tool are nuts 48 threaded to the ends 42 of each leg.
~ he ffsemb~ly of the first and second impellers 22, 30 to
agitator shaft 12 is acoomplished in the following manner. Second impeller 30
is moved onto the shaft first by lifting the impeller above the position shown
in Figure 1 so as to allow shaft portion 14 to pass thrcugh the ~ore opening
36. The seoond impeller 30thenistemporarily supported in this elevated
posi~ion manually or with a suit~ble mechanical means not shown.
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The first i~peller 22 is then lifted into position
with its flat surface 28 resting against the m~ounting
sur~ace of face 18. Second impeller 30 is then dropped
over the toe 25 of mounting foot 24 as sho~m in Figure 1.
~he thickness of foot 24 and shaft portion 14 are together,
smaller than the dimension across hub opening 36 so that if
the second impeller 30 were released, it would merely
slide down on to foot 24 and shaft portion 14 and would
not clamp foot 24 to the shaft.
In order to provide a clamping actionl second impeller
30 is held in the position shown in Figure 1 while shims 38
are positioned between shaft portion 14 and foot 26. The
thickness of the shims can be selected and adjusted to
increase the spacing between foot 2~ and sha~t portion 14
so that the dimension across these components is greater
than the insi~e dimension of hub opening 36. With the
arrange~.ent as described, the second i~peller part 30 now
will not be able to slide down ove~ the foot an~ shaft
portion to effect a clamping relationship and instead, will
sinply be held in the position shown in Figure 1.
After shims 38 have been put in position, tool 40 is
put into the position as shown in Figures 1 and 2 and bolts
48 are tightened. This dri~es cross piece 44 to the right
as shown in the figures. As bolts 48 are turned still
further, the force e~erted by the tool causes mounting
~oot 24 to bow inwards towards ~ace 18 as shown in dotted
~ine in Figure 3. ~his decreases the space between t~
shaft and the mounting foot and reduces the dimension
across the foot and shat portion 14 to a distance which
is less than the width of hub opening 36. Hub 34 can now
~ own over the mounting foot 24 to the position shown
in Figure 3.
As bolts ~8 are no~ loosened so that tool 40 can be
i g foot 24 sprin~s outwar
the hub, mounting foot a
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together ~nd locks the entire asse~kly together in a
rigid connection. The contac~ pressures between hub 34,
foot 2~ and shaft portion 1~ are suficient to prevent
movement of the components when subjected to the forces
applied to the impeller blades 26, 32 during a ~ixing
operation ~oreover, the connection provi~ed by the
present invention is effected without the use of any
permanent mechanical fasteners such as screws, bolts or
the li~.e which can become loosened or damaged during use.
Thus, the present invention provides a means of
furnislling a streamlined separable blade mi~ing agitator
that can be installed through small vessel openings such
as a manhole. The design allows a variety of spans and
bla~e configurations to be applied without restrictions
and provides mechanical stability without the need for
any fasteners that could corme loose.
While a three blade design has been described with
one blade on the first impeller and two blades on the
second, other blade combinations can be used. For exa~ple,
a hub, without agitator blades could be used to fix one or
more impellers to the shaft. Thus, the present invention
allows considerable flexibility for changing the nun~er,
size and shape of agitator blades without the neea to
change or disturb the main drive shaft 12.
All surfaces of the im.pellers and shaft are provided
with a corrosion resistant glass coating and although
the design is pri~arily to be used in applications
requiring such a coating, the design can also be applied
to agitators with other coatings such as plastic, ru~ber,
etc. where coating conventional fasteners i9 not practical.
Accordingly, the design of the present invention is well
suited to applications where agitators, r.~ade fro~ any
materials of construction, must be install~d through small
openings and where the use of conventional mechanica
fasteners could be a disadvantage.
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~ ile all the mounting and clampin~ surfaces are
shown to be flat, it should be appreciated that they
also could be concave, convex or some other con~enient
shape capable of receiving a glass coating. The important
thing is that the suxface 28 be complementary to surface
18 and that the inside profile of bore 36 match the
proile formed by the mounting foot 24 and shaft portion
14 together.
It should be readily apparent that from a design
standpoint, the length and thic~ness of mounting foot 24
should be such that the desired amount of flexure can be
obtained with tool 40 without exceeding the co~.pression
factor of the glass coating. Such design criteria would be
within the skill of the art. Also, while a particular
tool ~0 has been described fox effecting the interference
fit it should be obvious that any suitable mechanical or
hydraulic means can be used which is able to exert
- sufficient force across foot 24 to deform it towaxds shaft
surface 18.
Having thus described the invention in detail, what is
claimed as new is:
