Note: Descriptions are shown in the official language in which they were submitted.
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PUMP DEVICE
FIBLD OF THE INVENTION
[0001] This invention relates to the field of centrifugal pumps.
BACKGROUND OF THE INVENTION
[0002] In the field of liquid transfer, it is common to provide power to the
impeller of a
centrifugal pump by means of a shaft coupled to an external motor. This
necessitates that a
form of dynamic seal be provided around the shaft, to minimize egress of
liquid, which seals
have associated maintenance issues. Dynamic shaft seals also add a frictional
resistance load to
the pump, which is not desired. Other pumps have been constructed wherein the
impeller is
rotated by an externally-created magnetic field. This type of pump avoids the
maintenance and
frictional resistance issues associated with dynamic shaft seals. However, in
order to ensure
that the impeller is properly indexed for rotation in the pump, submerged
bearings are generally
employed, which bearings have their own associated.maintenance and frictional-
resistance issues.
It has also been known to attempt to create pumps lacking both submerged
bearings and dynamic
shaft seals, by providing magnets which serve both to rotate the impeller and
support same in
spaced relation from the housing. However, known prior art pumps of this type
are not
completely successful in avoiding rubbing contact between the impeller and
housing; among
other things, wear continues to be an issue.
SUMMARY OF THE INVENTION
[0003] A centrifugal pump for use with a liquid forms one aspect of the
invention. This
pump comprises a housing and a rotor. The housing has an interior surface
defining an interior
cavity, an axis intersecting the cavity, an intake port for receiving liquid
and communicating
same to said cavity, and a discharge port in communication with said cavity.
The rotor has an
impeller, is positioned in said cavity and is rotatable in said cavity about
said axis in spaced
relation to the interior surface. The impeller is adapted to force said liquid
to flow through said
discharge port upon said rotation in use. The pump further comprises means for
balancing the
pressure in said cavity, adapted so as to avoid the creation of pressure
differentials in said cavity
that would otherwise in use tend to cause translation of said rotor in said
cavity. The pump
further comprises a rotating magnetic field generation device adapted to drive
rotation of said
rotor about said axis in use.
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r0004]' According to another aspect of the invention, the means for balancing
the pressure in
said cavity may be a liquid conduit.
[0005] According to another aspect of the invention, in use, the discharge
port may be
disposed above the impeller and the liquid conduit may extend between a first
terminus in the
cavity above the impeller and a second terminus in the cavity below the
impeller.
[0006] According to another aspect of the invention, the liquid conduit may be
defined at
least in part by an arc-shaped barrier.
[0007] According to another aspect of the invention, the rotor may include a
drive member
to which is coupled the impeller, for rotation therewith, the rotating
magnetic field generation
device being adapted to drive rotation of said rotor about said axis in use by
driving rotation of
said drive member.
[0008] According to another aspect of the invention, the impeller may be a
closed impeller
having axially-spaced sides and the drive member may comprise a metal tube
extending axially
from one of the sides of the impeller and arranged coaxial with the axis.
[0009] According to another aspect of the invention, the rotor and housing may
be adapted
such that, in use, said liquid supports said rotor for rotation substantially
about said axis in
spaced relation to said interior surface.
[0010] According to another aspect of the invention, said adaptation of the
rotor and housing,
such that, in use, said liquid supports said rotor for rotation substantially
about said axis in
spaced relation to said interior surface, may comprise: a balance tube
extending from the other of
the sides of the impeller in a direction coaxial with and opposite to the
drive member; and a
circular groove forming part of said cavity in which a rim of the balance tube
revolves in use.
[0011] According to another aspect of the invention, said adaptation of the
rotor and housing,
such that, in use, said liquid supports said rotor for rotation substantially
about said axis in
spaced relation to said interior surface, may comprise, for each side of the
impeller, a plurality of
protrusions defined by the interior surface such that the space between the
rotor and the housing,
in use, measured axially, undulates in magnitude around the impeller for
stabilizing the rotor
against axial movement.
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'[0012]' According to another aspect of the invention, measured axially, in
the direction of
rotation of the rotor, in each undulation the space between the rotor and the
housing may
gradually decrease and then quickly increase.
[0013] According to another aspect of the invention, each plurality of
protrusions may have
associated therewith a series of radial grooves forming part of the cavity,
the grooves separating
the protrusions from one another.
[0014] According to another aspect of the invention, each protrusion may
comprise a
wedge-shaped slope inclined in the direction of rotation of the rotor.
[0015] According to another aspect of the invention, the impeller may have
defined
therethrough, coaxial with the axis, an intake hole, and the housing may
comprise an inflow
regulation boss projecting into the cavity that extends, coaxially with the
axis, into the intake
hole.
[0016] According to another aspect of the invention, the inflow regulation
boss may be
shaped to direct flow impinging thereupon into the impeller.
[0017] According to another aspect of the invention, the inflow regulation
boss may have a
conical tip to direct flow impinging thereupon into the impeller.
[0018] According to another aspect of the invention, the pump may further
comprise a
tubular intake portion attached to the rim of the intake port and extending,
coaxially with the axis,
into the intake hole and towards the inflow regulation boss, to direct flow
thereupon.
[0019] According to another aspect of the invention, the impeller may have
defined.
therethrough, coaxial with the axis, an intake hole, and the pump may further
comprise a tubular
intake portion attached to the rim of the intake port and that extends,
coaxially with the axis, into
the intake hole.
[0020] According to another aspect of the invention, the impeller may have
axially-spaced
sides and the pump may further comprise extension plates attached around the
perimeter of the
impeller to increase the area of the impeller sides.
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10021]' According to another aspect of the invention, the pump may further
comprise a liquid
detection sensor, capable of detecting the existence of liquid within the
cavity and producing a
liquid detection signal, and a controller that uses the liquid detection
signal from said liquid
detection sensor to control the pump during startup.
[0022] A centrifugal pump for use with a liquid forms another aspect of the
invention. This
pump comprises a housing, a rotor, a liquid conduit and a rotating magnetic
field generating
device. The housing has an interior surface defining an interior cavity, an
axis intersecting the
cavity, an intake port for receiving liquid and communicating same to said
cavity, and a
discharge port in communication with said cavity. The rotor has an impeller,
is positioned in
said cavity and is rotatable in said cavity about said axis in spaced relation
to the interior surface.
The impeller is adapted to force said liquid to flow through said discharge
port upon said rotation
in use. The liquid conduit is for balancing the pressure in said cavity so as
to avoid the creation
of pressure differentials in said cavity that would otherwise in use tend to
cause translation of
said rotor in said cavity towards said discharge port. The magnetic field
generation device is
adapted to drive rotation of said rotor about said axis in use.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 is a cross sectional diagram of a pump constructed according
to a preferred embodiment of the invention
[0024] Figure 2 is an exploded, partially cut-away diagram of the pump shown
in
Figure 1
[0025] Figure 3 is an X1-Y1 direction cross-sectional diagram of Figure 1
[0026] Figure 4 is a side cross-sectional view of the liquid flow path inside
the casing
of a pump without a barrier inside the housing
[0027] Figure 5 is a front cross-sectional view of the pump shown in Figure 4,
showing
a contact condition of the impeller, drive member, housing and can
[0028] Figure 6 is a view similar to Figure 4, showing the liquid flow path
inside the
housing of the pump shown in Figure 1
[0029] Figure 7 is a cross-sectional diagram of part of the pump of Figure 1
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10030] ' Figure 8 is an X2-Y2 direction cross-sectional diagram of Figure 7
[0031] Figure 9 is a view showing the position relationship between the
impeller and
wedge surface of the pump shown in Figure 1
[0032] Figure 10 is a cross-sectional diagram of the structure of an
alternative
embodiment of the rotor
[0033] Figure 11 is a behavior characteristic diagram for the drive member in
the pump
device shown in Figure 1
DETAILED DESCRIPTION.
[0034] A pump constructed according to a preferred embodiment of the invention
is
described hereinafter with reference to Figures 1-3, 6-9 and 11. Figure 1 is a
cross-sectional
diagram of the pump. Figure 2 is a partial cut-away disassembly diagram of
Figure 1. Figure 3
is a X1-Y1 cross-sectional diagram of Figure 1. Figure 4 is a diagram showing
the behavior of
liquid within the housing in a pump with no barrier in the housing. Figure 5
is a diagram of a
contact condition between the impeller, drive member, housing and can oÃthe
pump device in
Figure 4. Figure 6 depicts the behavior of liquid within the housing of the
pump in Figure 1.
[0035] The specifications for the pump device in Figure 1 are as below. The
aperture of the
external intake tube (the aperture of inflow mouth or intake port 26) is 32mm,
the discharge
aperture (the aperture of discharge mouth or port 27) is 20mm. The closed
impeller 20 is made
from PVC. The outer diameter of the impeller is 80mm. The aperture of the
intake hole 20a
is 32mm, and it has 5 blades. The drive member 30 consists of a metal tube,
specifically, an
aluminum cylinder, 3mm in thickness, the exposed surface of which is coated in
200 m thick
TeflonTM. The impeller 20 and drive member 30 together form a rotor 20,30. The
can 38, is a
2mm thick dual layer cylindrical structure consisting of an inner can 31 and
an outer can 32.
The gaps between the inner can 31, and outer can 32, and drive member 30, are
each 2mm. The
main casing 21 is a dual walled structure. The width of the liquid passage is
10mm.
[0036] Both the outer magnets 33 and inner magnets 34, that form part of the
rotating
magnetic field generation device, come in 4 pairs. These magnets are made of
neodymium. The
driving motor 37 is a 3-phase, 200V type, with an output of 0.4kW. Inclined
wedge-shaped
surfaces B1-B8 alternate with grooves 25-3, that are used to introduce water
onto the wedges, for
a total of 8 faces. Each inclined wedge-shaped surface has an angle of
inclination 0 of 2 . Also,
the pump has a discharge rate of 50 Umin, an 8m discharge head, and a pump
efficiency of 24%.
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100371' As seen in Figures 1, 2, the impeller casing 21 in the pump device is
formed by
sandwiching barrier 23-1 and the main casing plate 23 between intake side
casing plate 21-1, and
the can-side casing plate 21-2. These parts are fixed together by tightening
bolts 28.
[0038] The impeller 20 is installed within the impeller casing 21. Affixed to
one side of
this impeller (the drive side), along the same rotary axis A-A as the impeller
and casing 21, is the
aluminum drive member 30. Accordingly, by loosening and removing the
tightening bolts, it is
easy to remove or re-install the impeller 20 and drive member 30. As earlier
indicated, the
drive member 30 is a non-magnetic electrical conducting hollow aluminum
cylinder, the exposed
surface of which is coated in a Teflon TM resin.
[0039] The impeller 20 and drive member 30 (hereafter referred to individually
as rotating
parts or collectively as rotor) are installed such that they rotate freely in
the casing 21 and the can
38 (inner can 31, outer can 32). The casing 21 and the can 38 together define
a housing 21,38
having an interior surface 100 defining an interior cavity 102 in which the
rotor 20,3 0 is
positioned and rotatable about axis A-A in spaced relation to the interior
surface 100.
[0040] The can 38 (inner can 31, outer can 32) is a dual layer cylindrical
structure made
from a non-magnetic high electrical resistance material. The lower part of the
inner can 31 (the
part near the impeller 20) is closed, and the part at the other end (the part
near the drive motor
37) has the inner can 31 joined up with outer can 32, creating a closed form.
Arranged on the
inside of the inner can 31 and the outside of outer can 32 is a gap. Installed
into each gap are a
grouping of several magnets, the inner magnets 34 and outer magnets 33,
respectively. The
outer magnets and inner magnets, respectively, are attached to outer magnet
yoke 33-1 and inner
magnet yoke 34-1, said yokes 33-1,34-1 being formed by a dual layer
cylindrical magnet holder
35. This magnet holder 35 is connected to the output shaft (not shown) of the
drive motor 37 at
its axis A-A by a holder connective shaft 36.
[0041] As shown in Figure 3, the corresponding surfaces of the inner magnets
34, which are
attached to the inner magnet yoke 34-1, and the outer magnets 33, which are
attached to the inner
magnet yoke 33-1, are opposite in polarity. Regarding the inner magnets 34 and
outer magnets
33, they are arranged such that each adjacent magnet is also of opposite
polarity. These inner
magnets 34 and outer magnets 33 are synchronously rotated by the drive motor
37, which drives
the holder connective shaft 36, which in turn is fixed to the magnet holder
35.
[0042] By rotating the inner magnets 34 and outer magnets 33 together with the
magnet
holder 35 in this way, a rotating magnetic field is established in the space
between the inner
magnets 34 and outer magnets 33; the magnetic flux between the inner magnets
34 and the outer
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inagnets 33 intersect the drive member 30, generating an induced current and
generating a
rotational force and repulsive force in the drive member 30. These rotational
and repulsive
forces serve as the rotational driving force for the impeller 20.
[0043] Since the drive member 30 is attached to the impeller 20 only on one
surface (the
drive side surface), the center of gravity of the rotating part or rotor
composed by joining the
impeller 20 and the drive member 30 is positioned in the part of impeller 20
close to the drive
member 30, such that there is a possibility that the impeller could swing to
the left and right.
To minimize the likelihood of this outcome, attached to the intake surface of
impeller side plate
20-1, which constitutes the side of the impeller positioned opposite the drive
side surface (the
surface to which the drive member 30 is attached) of impeller 20, is a
cylindrical balance tube
20-3 that projects out to the side opposite the drive member 30. The balance
tube 20-3 is
positioned about the same rotational axis A-A as the impeller 20. The rim of
the balance tube
20-3 fits into a circular groove 21 a in the corresponding inner surface of
the intake casing side
plate 21-1. By placing a balance tube 20-3 and a groove 21a like this, a
radial wedge effect,
that occurs from the existence of liquid in the gap between the balance tube
in 20-3 and 21 a,
causes the balance tube 20-3 to be forced away from the inner wall of groove
21 a and to rotate in
a suspended state inside groove 21 a. Consequently, by coupling the wedge
effect that occurs in
the gap between the drive member 30 and can 38, and the wedge effect that
occurs between the
balance tube 20-3 and groove 21a, stability of the drive member 30 and the
impeller 20 is
provided in operation.
.[0044] As a result, contact and rubbing between the impeller 20 and impeller
casing 21, and
the drive member 30 and can 38, is minimized, and it is possible to limit the
chance of
breakdown flowing from rubbing contact of these parts. In the case of the
illustrated preferred
embodiment, the inner diameter and outer diameter of the balance tube 20-3 are
identical to the
inner diameter and outer diameter of the drive member 30, providing
exceptional stability to the
drive member 30 and the impeller 20.
[0045] Also, as shown in Figure 2, and later shown in Figure 6, an intake hole
20a is
established in the impeller 20 that penetrates through the center of
impeller's rotary axis.
Attached to the rim of the liquid intake mouth 26, on the impeller casing side
plate 21-1 that
corresponds intake surface of the impeller 20, is an auxiliary intake tube 21-
1-1 that protrudes
out into the intake hole 20a.
100461 By attaching the auxiliary intake tube 21-1-1, it is possible to
mitigate movement in
the impeller 20's thrust direction due to liquid intake into the impeller 20
when the pump starts
rotating, or during operation. As a result, it is possible to prevent rubbing
and contact of the
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irnpellor 20 and iinpeller casing 21 during operation, or when the pump starts
rotating.
[0047] Also, an inflow regulation 'boss' 31-1 that protrudes out into the
intake hole 20a, is
attached onto inner surface in the center (the lower part of the inner can 31)
of the impeller
casing side plate 21 that faces the impeller 20 drive surface. By attaching
this inflow regulation
boss 31-1 as above, it is possible to mitigate movement in the impeller 20's
thrust direction due
to liquid intake into the impeller 20 when the pump starts rotating, or during
operation. As a
result, it is possible to prevent rubbing and contact of the impeller 20 and
impeller casing 21
during operation, or when the pump starts rotating.
[0048] Furthermore, a tip of one end of the inflow regulation boss 31-1, the
top of which is
positioned into the center of the impeller 20's rotary axis, has attached to
or formed thereon a
conical protrusion 31-1a. By having this protrusion 31-la, it becomes possible
to evenly guide
the dispersion of fluid flowing along the impeller 20 rotary shaft and into
the inflow hole 20a, by
radiating it along the perimeter of the protrusion 31-1a. This eases the
movement of the
impeller 20 thrust direction, and further increases the stability of the
impeller 20 during startup
and during operation.
[0049] Figure 4 depicts a form of the pump device of Figure 1 lacking an arc-
shaped barrier
and showing the relationship between the pump impeller 20 and the impeller
casing 23, when the
discharge 27 is vertical. If the center of the impeller 20 is set to 01, the
impeller 20 is rotating,
and the liquid discharge out of the discharge 27 has started, then the
pressure at position P 1,
facing towards the discharge 27 on the inside of the impeller casing 23 is
less than the pressure at
position P2, symmetrically opposite the intake 26. At this time, the impeller
20, which is still in
a state of non-contact with the impeller casing 23, rises upwards towards the
discharge port due
to the pressure differential between P2 and P1, such that the drive member 30
touches the inner
can 31 and outer 32, and the impeller 20 and drive member 30 end up rotating
at an incline, as
shown in Figure 5. At this time, drive member 30 is touching the inner can 31
at point Ql and the
outer can 32 at point Q2, and the impeller 20 is touching the intake side
impeller casing plate
21-1 at point Q3 and the can side casing plate 21-2 at point Q4.
[0050] The construction shown in Figure 6 resolves this type of contact and
rubbing
phenomenon. As shown in Figure 6, an arc shaped barrier 23-1 is attached
parallel to the
impeller 20's rotary locus, on the impeller casing 21, in the outer perimeter
area inside the
impeller casing 21, and outside the impeller, such that it divides the
impeller outer perimeter area
into an inner area and outer area, with one end facing the inner opening of
the discharge 27 that
is within the impeller casing 21, and the other end of the barrier 23-1
positioned opposite the
discharge 27.
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[0051] By these means, the barrier 23-1 and the outer wall 23-2 form a dual-
walled arc
shape. Positioned opposite this dual wall is a closed arc-shaped wal123-5.
Also, established
between each end of the barrier 23-1, at one end 23-la and the other 23-lb,
and the closed wall
23-5, connecting each through to the impeller 20's outer perimeter, are
discharge holes 23-3, and
23-4, whose widths are roughly identical. The liquid flow that passes thorough
the lower facing
discharge hole 23-4 flows along the liquid discharge pathway, between the
outer wall 23-2 and
the barrier 23-1, and merges with the liquid flow that passes through the
upward facing discharge
hole 23-3 that faces the discharge 27. To restate, the barrier in combination
with the casing 21
defines a liquid flow conduit 108 that extends between a first terminus 106 in
the cavity above
the impeller and a second terminus 104 in the cavity below the impeller. By
attaching arc
shaped barrier 23-1 onto the impeller casing 21, in the outer perimeter area
inside the impeller
casing 21, and outside the impeller 20, with one end 23-1a facing the inner
opening of the
discharge 27 and the other end of the barrier 23-lb positioned opposite the
discharge 27, the
pressure at the discharge hole 23-3, P1 is made to roughly equal P2, the
pressure at discharge
hole 23-4. As a result, the impeller 20 is no longer urged towards the
discharge, away from the
axis of rotation, and can rotate in a stable position. Also, the rotating
parts will not tilt, thus
eliminating the phenomenon, due to tilting of the impeller, of rubbing and
contact between the
rotor 30 and the inner can 31 and outer can 32, and of the impeller 20 rubbing
and contacting the
casing 21, as shown in Figures 4 and 5.
[0052] With this barrier in place, there exists a thrust force against the
impeller 20 (the force
along the axis of rotation = the force along the holder connective shaft 36),
whose magnitude
depends on the pump discharge head, and discharge quantity. All things being
equal, this thrust
force would tend to force the impeller 20 to tilt to the left and right, which
would result in wear.
[0053] Arresting this, as seen in Figure 1, defined by each of the inner
surfaces of the
impeller casing plate 21-1, 21-2, opposite impeller side plates 20-1, 20-2,
are a set of wedge
faces 25-1, 25-2 respectively. As shown in Figure 8, wedge faces 25-1 and 25-2
are formed and
separated from one another by series of 8 radial grooves 25-3 arranged about
the impeller 20's
rotary axis, and a series of wedge shaped slopes B 1-B8 or protrusions that
are set within each of
the 8 areas divided by the grooves 25-3, which are inclined in the direction
of rotation of the
impeller R. Through this arrangement, the space between the rotor and the
housing, measured
axially, undulates in magnitude around the impeller. More specifically, in the
direction of
rotation of the rotor, in each undulation, the space between the rotor and the
housing gradually
decreases and then quickly increases, due to the wedge shapes.
[0054] By placing these kinds of wedge faces 25-1, 25-2, when the impeller 20
approaches
the casing side plate 21-1 or 21-2 due to the aforementioned thrust force, the
wedge effect due to
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the flow of liquid through the gap between the impeller 20 and the wedge face
25-1, 25-2 will
force the impeller sides and housing away from one another.
[0055] Without intending to be bound by theory, here follows a detailed
explanation of the
wedge effect referenced in Figures 7-9. Figure 7 is a partial cross-sectional
diagram of part of the
pump device. Figure 8 is an X2-Y2 directional diagram, and Figure 9 shows the
relationship
between the impeller side plate 20-1 (20-2) and the wedge face 25-1 (25-2). As
shown in
Figure 8, the wedge face 25-2 in casing side plate 21-2, is divided into
several wedge-shaped
slopes B 1-B8 by a series of groves 25-3. In Figure 8 there are a series of
arrows: arrow 39
indicates the direction of inclination of the wedge-shaped slopes B 1-B8;
arrow R indicates the
direction of rotation of the impeller 20; and arrow W indicates the flow
direction for liquid that
has entered wedge-shaped slopes B1-B8. In Figure 9, when R> 0, 0 is the angle
of inclination
of B1-B8 and gl, g2 are the gaps between the wedge face 25-1 (25-2) of casing
side plate 21-1
(21-2), and the impeller side plate 20-1 (20-2). The repulsive force FA that
occurs due to
wedge face 25-1 (25-2) is summarized below. If the liquid viscosity, and the
speed of liquid
entering the wedge face 25-1 (25-2) (it is assumed that this is proportional
to the rpm of the
impeller 20), are fixed, then FA can be expressed by:
FAa (b2X L X n) /g12
(b: wedge shaped slope width, L: wedge shaped slope length, n: number of wedge
shaped slope)
[0056] Here, g2 is the gap at the liquid entry side towards the wedge-shaped
slopes B1-B8,
gi is the gap at the discharge side, and g2/gl nonnally has a value from 2-4.
Therefore, L and 0
can be determined.
[0057] From above, when the diameter of the impeller 20 is small, the
corresponding area of
the wedge face 25-1 (25-2) (b x L) becomes narrow and the wedge effect is
decreased, and
especially as the width b decreases, the wedge effect tends to decrease
dramatically. To avoid
suppression of the wedge effect when the outer diameter of the impeller is
small, it may be
preferable to provide for the area of the impeller and wedge faces to be
larger than the area of the
impeller. This can be done by increasing the impeller 20 side plate, and also
expanding the
corresponding wedge faces 25-1, 25-2 of the casing side plate 21-1, 21-2. In
other words, just
as seen in Figure 7, by attaching the extension plates 20-1-1 and 20-2-1 to
the perimeter of
impeller side plates 20-1, 20-2 which compose impeller 20, and also expanding
the
corresponding wedge faces 25-1, 25-2 of the casing side plate 21-1, 21-2, it
is possible to provide
a desired wedge effect even in the context of a relatively small diameter
impeller.
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--[0058] The only liquid-contacting component of the illustrated pump that
must utilize metal
is the drive member 30. To prevent corrosion (including galvanic corrosion) of
the drive member
30, it is advantageous to apply a sufficient coating of a resin, etc., or
apply a lining to surface in
contact with liquid. However, when coatings and the like are applied to the
drive member 30,
and it is attached to the impeller 20, it becomes troublesome to directly
attach them together by
screws etc., and thus it may be preferable to indirectly attach them. In other
words, just as
shown in Figure 10, rather than attaching the drive member 30 directly to the
impeller 20, it can
be advantageous to attach it via a resin auxiliary attachment plate 30-1. This
is because if there
are screw holes in the drive member 30, it is difficult to apply a coating
completely inside the
screw holes, and if the interior of the screw holes are improperly coated,
galvanic corrosion can
result.
[0059] Figure 11 shows, from the time this pump embodiment starts operating
until it
achieves full operating speed, the characteristics of the applied torque and
repulsive force to the
drive member 30 from the rotating magnetic field generation device (outside
magnets 33, inside
magnets 34, magnet holder 35), and the repulsive force due to liquid flow
between the can 38
and the drive member 30 due to the wedge effect. In Figure 11, the graph shown
is for R>2, the
drive member 30's speed (slip S) is drawn along the horizontal axis, the
vertical axis shows the
characteristic of the applied rotor 30's torque T, the repulsive force Fm
received by the magnetic
field on the drive member 30, and the repulsive force FA due to the wedge
effect.
[0060] In Figure 11, curve Cl shows the Torque T, curve C2, the repulsive
force Fm due to
the magnetic field, C3, and the repulsive force FA due to the wedge effect. If
the rpm of the
outside magnets 33 and inner magnets 34 are no, and the rpm of the rotor 30 n,
then S=(no-n)/no.
Since the applied torque T to the drive member 30 from the rotating magnetic
field is
approximated by the speed characteristic of a general purpose drive motor with
an extremely
large gap, it is roughly the same as C 1.
[0061] The applied repulsive force Fm to the drive member 30 due to the
rotating magnetic
field is a repulsive force when S*Rm > 1, and is an attractive force when
S*Rm<l. Here, Rm,
is a value determined by the magnetic gap between magnets 33, 34 and the
thickness and
material of drive member 30, etc. It is called the Magnetic Reynolds' number.
[0062] As can be understood from the graph shown in Figure 11, when S is at
its maximum
point, in other words when S=1 at startup, the repulsive force is at maximum.
Conveniently
therefore, substantial rubbing will not occur between the drive member 30 and
the can 38 at
startup.
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[0063] On the other hand, as the rpm of the drive member 30 increases, in
other words, the
rpm of the impeller 20 increases, S=O, that repulsive force becomes 0.
However, the repulsive
force due to the wedge effect that occurs between the can 38 and the drive
member 30 becomes
proportionally larger as the rpm of the drive member 30 increases, so long as
there is liquid. If
S 1 is the slip when the drive member 30, i.e. the impeller 20, reaches normal
rotation, the
applied repulsive force to the drive member 30 becomes FmS 1+ FAS 1, and the
drive member 30
has risen and stabilized. However, if there is no liquid, FA=O, the rpm of the
drive member 30
further increases, Fm becomes extremely small, and the repulsive force almost
disappears. This
fact shows that when there is no liquid, the repulsive force becomes extremely
small, and
rubbing occurs between the drive member 30 and the can. Accordingly, in this
pump, an empty
operation preventative counter-measure is advantageous, to prevent operation
of the drive motor
37 when the inside of casing 21 is empty or liquid.
[0064] Therefore, in the illustrated preferred embodiment, as shown in the
aforementioned
Figure 1, a liquid sensor 29 capable of detecting the existence of liquid is
placed close to the
discharge 27. The liquid detection signal from liquid sensor 29 acts as the
startup condition for
the pump device. In other words, it becomes impossible to operate the drive
motor 37 when there
is no liquid detection signal from the liquid sensor 29. In this manner, it is
possible to prevent
dry operation of the pump. Also, as a method of preventing empty pump
operation, it is also a
way of ensuring there will be sufficient liquid in the pump casing at
shutdown.
[0065] In the preferred embodiment, wedge effects provided by the balance
tube/groove,
drive member/can, impeller/protrusion, intake regulation boss/intake hole and
intake
portion/intake hole combinations support the rotor for rotation substantially
about the axis in
spaced relation to the interior surface of the housing. In testing, absolutely
no trace of rubbing
between the rotating parts (drive member 30, impeller 20) and the surrounding
walls (casing 21,
can 38) were observable, during startup, operation, and shutdown, for every
condition starting
with a completely open discharge valve to completely closed. Inspection for
the existence of
rubbing was conducted by coating the rotating parts in an inspection coating,
and after operating
the pump, inspecting the inspection coating for the existence of peeling.
Also, in tests with fine
slurries, and liquid limestone, no obstacles were observed. Also, by attaching
a reflux valve
(not shown) to the inflow tube (not shown) to the inflow 26, it was possible
to confirm the
possibility of ordinary restart.
[0066) In the illustrated preferred embodiment, which has a no-seal
construction, no
submerged bearings, and rotating parts (drive member 30, impeller 20) that can
rotate in an
extremely stable floating state without contacting the surrounding walls
(casing 21, can 38), in
testing there was found to be no contamination due to rubbing, etc.
CA 02541550 2006-03-31
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[0067) Also, since it is possible to manufacture the liquid-contacting parts
but for the drive
member entirely from plastic, resin coating, or ceramic materials, there is no
necessity to use
metal materials in the liquid-contacting surfaces. This fact shows that it is
possible to eliminate
or minimize the elution of metal ions into the transported liquid. Also, the
fact that there are no
rubbing parts in operation provides a relatively maintenance-free pump having
a relatively long
lifespan and a relatively low breakdown risk.
[0068] The pump in this invention has a wide variety of possible uses, in
various fields,
transporting, drawing, etc., all kinds of liquids, in addition to pure liquids
and corrosive liquids,
fine slurries, mixed liquids, etc.
[00691 The various parts of the pump described are listed below.
PARTS LIST
2 0 Impeller
2 0 a Inflow hole
2 0- 1, 2 0- 2 Impeller side plate
2 0 -1- 1, 2 0- 2- 1 Extension side plate
2 0 - 3 Balance tube
2 1 Impeller casing
2 1 a, 2 5- 3 Groove
2 1- 1, 2 1- 2 Casing Side plate
2 1 - 1- 1 Auxiliary inflow tube
2 2 Drive Casing
2 3 Casing main plate
2 3 - 1 Barrier
2 3 - 2 Outer wall
2 3-1 a Discharge end of the barrier
2 3-1 b Opposite end of the barrier
2 3 - 3 Upward discharge hole
2 3 - 4 Downward discharge hole
2 3- 5 Closed Wall
2 4 Liquid discharge path
2 5 - 1, 2 5 - 2 Wedge Faces
2 6 Inflow
2 7 Discharge
2 8 Tightening bolt
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2 9 Liquid detection sensor
3 0 Rotor
3 0 - 1 Auxiliary attachment plate
3 0-2 Screw
3 1 Inner Can
3 1 - 1 Inflow regulation boss
3 1 - 1 a Protrusion on the inflow regulation boss
3 2 Outer Can
3 3 Outer magnets
3 3 - 1 Outer magnetic yoke
3 4 Inner magnets
3 4 - 1 Inner magnetic yoke
3 5 Magnet holder
3 6 Holder connective shaft
3 7 Drive motor
3 8 Can
3 9 Directional arrow
100 interior surface
102 cavity
104 second terminus of flow conduit
106 first terminus of flow conduit
108 flow conduit
A-A axis
P I, P 2 Pressure
o1 Center of the impeller
Q 1 Point of contact between the rotor and can
Q Z Point of contact between the rotor and can
Q3 Point of contact between the impeller and casing
Q4 Point of contact between the impeller and casing
B 1~- B 8 wedge shaped slope
R Direction of rotation for the impeller
W Direction of liquid flow
0 Angle of inclination for wedge-shaped slope
g t, g 2 The gap between the impeller side plate and the wedge-shaped slope
b Width of the wedge-shaped slope
L Length of the wedge-shaped slope
S Slip
T Torque
CA 02541550 2006-03-31
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F Attractive force
F m Repulsive force
F A Repulsive force due to the wedge effect
C 1 T-S characteristic curve
C 2 Fm-S characteristic curve
C 3 FA-S characteristic curve
S 1 Slip during normal operation
[0070] Finally, it is to be understood that while but a single preferred
embodiment of the
pump, and a single alternative embodiment of the rotor, have been herein shown
and described, it
will be understood that various changes in size and shape of parts may be
made. These
modifications, and others which may be routine to persons of ordinary skill in
the art, may be
made without departing from the spirit or scope of the invention, which is
accordingly limited
only by the claims appended hereto, purposively construed.
