U.S. patent application number 14/158723 was filed with the patent office on 2014-07-17 for high efficiency blood pump.
This patent application is currently assigned to EVERHEART SYSTEMS INC.. The applicant listed for this patent is EVERHEART SYSTEMS INC.. Invention is credited to Greg S. Aber, Neil H. Akkerman.
Application Number | 20140200664 14/158723 |
Document ID | / |
Family ID | 45925751 |
Filed Date | 2014-07-17 |
United States Patent
Application |
20140200664 |
Kind Code |
A1 |
Akkerman; Neil H. ; et
al. |
July 17, 2014 |
HIGH EFFICIENCY BLOOD PUMP
Abstract
A high efficiency blood pump includes a pump housing, wherein
the pump housing provides an inlet and outlet. The pump includes a
motor housing, wherein the motor housing contains a motor. An
impeller is housed in the pump housing, wherein the impeller is
radially supported by a hydrodynamic bearing providing at least one
row of pattern grooves. A diaphragm provided by the pump housing
separates the impeller chamber from the motor chamber. A magnetic
coupling is provided between the motor and the impeller, wherein
the magnetic coupling causes the impeller to rotate when the motor
rotates and provides axial restraint of the impeller.
Inventors: |
Akkerman; Neil H.; (Houston,
TX) ; Aber; Greg S.; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EVERHEART SYSTEMS INC. |
Webster |
TX |
US |
|
|
Assignee: |
EVERHEART SYSTEMS INC.
Webster
TX
|
Family ID: |
45925751 |
Appl. No.: |
14/158723 |
Filed: |
January 17, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12899748 |
Oct 7, 2010 |
|
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|
14158723 |
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Current U.S.
Class: |
623/3.14 |
Current CPC
Class: |
A61M 2205/8206 20130101;
A61M 1/1012 20140204; A61M 1/1017 20140204; A61M 2207/00 20130101;
A61M 1/122 20140204; A61M 1/1036 20140204; A61M 1/101 20130101;
A61M 1/1015 20140204 |
Class at
Publication: |
623/3.14 |
International
Class: |
A61M 1/10 20060101
A61M001/10 |
Claims
1-35. (canceled)
36. A blood pump comprising: a pump housing, wherein the pump
housing provides an inlet and outlet; a cylindrical bearing surface
facing radially outward from a central axis and housing a hub
configured to rotate about the central axis and the hub comprising
a first permanent magnet; an impeller housed in the pump housing
configured to rotate concentrically with respect to the cylindrical
bearing surface and comprising (i) a bore receiving the cylindrical
bearing surface and defining an internal surface concentric with
the central axis, a first hydrodynamic bearing configured to
radially support the impeller and being provided between the
cylindrical bearing surface and the internal surface; (ii) a
multi-lobe shape on the internal surface forming the first
hydrodynamic bearing; (iii) a second permanent magnet axially
aligned with and radially displaced from the first permanent magnet
of the hub, the first permanent magnet and the second permanent
magnet forming a magnetic coupling; and a motor axially displaced
from and rotationally connected to the hub.
37. The blood pump of claim 36, further comprising a
non-ferromagnetic diaphragm provided by the pump housing, wherein
the impeller is configured to rotate concentrically around the
diaphragm, and the diaphragm is intermediate to the magnetic
coupling between the motor and the impeller.
38. The blood pump of claim 36, further comprising: an impeller
chamber defined by the pump housing, wherein the impeller is housed
in the impeller chamber; a motor housing defining a motor chamber,
wherein the motor is housed in the motor chamber; and a diaphragm
provided by the pump housing and the diaphragm separates the motor
chamber and the impeller chamber.
39. The blood pump of claim 36, wherein the impeller is configured
to create high pressure zones, when the impeller is rotating,
between the internal surface of the impeller and the cylindrical
bearing surface.
40. The blood pump of claim 36, wherein the multi-lobe shape is
configured to create, when the impeller is rotating, high pressure
zones within the first hydrodynamic bearing, such that the
impeller, when rotating concentrically with respect to the
cylindrical bearing surface, is stabilized by radial stabilizing
forces created by the high pressure zones.
41. The blood pump of claim 36, wherein the motor is a brushless DC
motor having an efficiency equal to 85% or greater.
42. The blood pump of claim 36, wherein top surfaces of the
impeller provide a second hydrodynamic bearing that provides a top
set of pattern grooves for axial support of the impeller.
43. The blood pump of claim 42, wherein the grooves of the top set
are spiral grooves or spiral herringbone grooves.
44. The blood pump of claim 42, wherein the grooves of the top set
are rectangular, rectangular with a bevel, semi-circular, or
elliptical in cross section.
45. The blood pump of claim 36, further comprising a passive
magnetic axial bearing.
46. The blood pump of claim 45, wherein the passive magnetic axial
bearing comprises: a first set of one or more permanent magnets,
wherein the first set of permanent magnets is housed in blades of
the impeller and configured to rotate with the impeller; a second
set of one or more permanent magnets, wherein the second set of
permanent magnets is housed above the impeller in and fixed
relative to the pump housing; and a third set of one or more
permanent magnets, wherein the third set of permanent magnets is
housed below the impeller in and fixed relative to the pump
housing.
47. A blood pump comprising: a pump housing, wherein the pump
housing provides an inlet and outlet; an impeller chamber defined
by the pump housing, wherein an impeller is housed in the impeller
chamber; a motor housing defining a motor chamber, wherein a motor
is housed in the motor chamber; wherein the motor provides a shaft
with a hub mounted to the shaft; wherein the hub comprises a first
permanent magnet; a diaphragm provided by the pump housing, the
diaphragm separating the motor chamber and the impeller chamber;
the diaphragm defines cavity providing a region for hub to rotate
within; diaphragm also provides a cylindrical bearing surface for
impeller to rotate around with hydrodynamic radial support; wherein
the impeller is radially supported by a first hydrodynamic bearing
between the cylindrical bearing surface and an impeller internal
surface that provides a multi-lobe shape on the internal surface,
the multi-lobe shape being configured to create the first
hydrodynamic bearing and provide radial hydrodynamic support to
cause the impeller to rotate concentrically about the cylindrical
bearing surface, the impeller further comprising a second permanent
magnet providing a magnetic coupling between the impeller and the
hub.
48. The blood pump of claim 47, wherein the magnetic coupling
causes the impeller to rotate when the motor rotates, and the
diaphragm is a non-ferromagnetic diaphragm.
49. The blood pump of claim 47, wherein the impeller is an open
pressure balanced type impeller that minimizes axial thrust during
operation of the pump.
50. The blood pump of claim 47, wherein top surfaces of the
impeller provide a second hydrodynamic bearing that provides a top
set of pattern grooves for axial support of the impeller;
optionally wherein the top set of pattern grooves are spiral
grooves or spiral herringbone grooves; or wherein the top set of
pattern grooves are rectangular, rectangular with a bevel,
semi-circular, or elliptical in cross section.
51. The blood pump of claim 47, wherein at least a portion of the
impeller is conically shaped.
52. The blood pump of claim 51, wherein top surfaces of the
impeller are linear, convex, or concave.
53. The blood pump of claim 51, wherein top surfaces of the
impeller provide a top set of pattern grooves for axial and radial
support of the impeller; optionally wherein the top set of pattern
grooves are spiral grooves or spiral herringbone grooves; or
wherein the top set of pattern grooves are rectangular, rectangular
with a bevel, semi-circular, or elliptical in cross section.
54. The blood pump of claim 47, further comprising a passive
magnetic axial bearing comprising: a first set of one or more
permanent magnets, wherein the first set of permanent magnets is
housed in the impeller; a second set of one or more permanent
magnets, wherein the second set of permanent magnets is housed
above the impeller in the pump housing; and a third set of one or
more permanent magnets, wherein the third set of permanent magnets
is housed below the impeller in the pump housing.
55. The blood pump of claim 47, wherein the impeller is configured
to create a high pressure zone, when the impeller is rotating,
between the impeller internal surface and the cylindrical bearing
surface.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 12/899,748, filed Oct. 7, 2010, which is expressly incorporated
herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates to implantable rotary blood
pumps.
BACKGROUND OF INVENTION
[0003] Some blood pumps mimic the pulsatile flow of the heart and
have progressed to designs that are non-pulsatile. Non-pulsatile or
continuous flow pumps are typically rotary and propel fluid with
impellers that span the spectrum from radial flow centrifugal type
impellers to axial flow auger type impellers.
[0004] A common issue encountered by blood pumps is blood damage.
The causes of blood damage are mostly attributed to shear stress
and heat generated by the bearings supporting the impeller and/or
shaft seals of externally driven impellers. Shear stress and/or
heat may cause hemolysis, thrombosis, and the like.
[0005] A great deal of effort has been devoted to reducing or
eliminating blood damage in rotary blood pumps. One solution to
minimizing/eliminating blood damage is to provide total
hydrodynamic support of the impeller. For example, ramp, wedge,
plain journal, or groove hydrodynamic bearings may be utilized to
provide hydrodynamic support in blood pumps.
[0006] Additionally, passive permanent magnetic and active
controlled magnetic bearings can be utilized to provide impeller
support in blood pumps. Magnetic bearings may be combined with
hydrodynamic bearings to provide total impeller support in blood
pumps.
[0007] Some blood pumps provide blood flow utilizing a motor that
has a shaft mechanically connected to an impeller. Shaft seals may
be utilized to separate the motor chamber from the pump chamber.
However, shaft seals can fail and generate excess heat allowing
blood to enter the motor and/or produce blood clots. Some blood
pumps incorporate electric motors into the pumping chamber, rather
than providing separate motor and pumping chambers. For example, a
stator may be provided in the pump housing and magnets can be
incorporated into an impeller to provide a pump impeller that also
functions as the rotor of the electric motor.
[0008] Heart pumps that are suitable for adults may call for
approximately 5 liters/min of blood flow at 100 mm of Hg pressure,
which equates to about 1 watt of hydraulic power. Some implantable
continuous flow blood pumps consume significantly more electric
power to produce the desired amount of flow and pressure.
[0009] High power consumption makes it impractical to implant a
power source in the body. For example, size restrictions of
implantable power sources may only allow the implantable power
source to provide a few hours of operation. Instead, high power
consumption blood pumps may provide a wire connected to the pump
that exits the body (i.e. percutaneous) for connection to a power
supply that is significantly larger than an implantable power
source. These blood pumps may require external power to be provided
at all times to operate. In order to provide some mobility,
external bulky batteries may be utilized. However, percutaneous
wires and external batteries can still restrict the mobility of a
person with such a blood pump implant. For example, such high power
consumption blood pumps have batteries that frequently require
recharging thereby limiting the amount of time the person can be
away from a charger or power source, batteries that can be heavy or
burdensome thereby restricting mobility, percutaneous wires that
are not suitable for prolonged exposure to water submersion (i.e.
swimming, bathing, etc.), and/or other additional drawbacks.
[0010] The various embodiments of blood pumps discussed herein may
be suitable for use as a ventricular assist device (VAD) or the
like because they cause minimal blood damage, are energy efficient,
and can be powered by implanted batteries for extended periods of
time. Further, these pumps are also beneficial because they may
improve the quality of life of a patient with a VAD by reducing
restrictions on the patient's lifestyle.
SUMMARY OF THE INVENTION
[0011] The discussion herein provides a description of a high
efficiency blood pump that is energy efficient, causes minimal
blood damage, and improves quality of life.
[0012] An embodiment of a blood pump includes a pump housing,
wherein the pump housing provides an inlet and outlet. The blood
pump also includes an impeller housed in the pump housing, wherein
the impeller is radially supported by a first hydrodynamic bearing
that provides at least one row of flow inducing pattern
grooves.
[0013] Another embodiment of a blood pump includes a pump housing,
wherein the pump housing provides an inlet and outlet. The blood
pump also includes an impeller housed in the pump housing, wherein
the impeller is axially supported by a first hydrodynamic bearing
that provides at least one row of flow inducing pattern
grooves.
[0014] Yet another embodiment of a pump includes a pump housing
providing an inlet and outlet and a motor housing, wherein the
motor housing houses a motor. The pump also includes an impeller
housed in the pump housing that is radially supported by a
hydrodynamic bearing that provides at least one row of pattern
grooves. The pump also provides a magnetic coupling between the
motor and the impeller, wherein the magnetic coupling causes the
impeller to rotate when the motor rotates.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a top view of an illustrative embodiment of a
pump;
[0016] FIG. 2 is a cross-sectional side view of an illustrative
embodiment of a pump;
[0017] FIG. 3 is a cross-sectional top view of an illustrative
embodiment of a pump;
[0018] FIG. 4 is a close up cross-sectional view of an area of an
illustrative embodiment of a pump;
[0019] FIG. 5 is a cross-sectional view of an illustrative
embodiment of an impeller;
[0020] FIG. 6 is a cross-sectional view of an illustrative
embodiment of a pump housing;
[0021] FIG. 7 is a cross-sectional view of an illustrative
embodiment of a motor housing of a pump;
[0022] FIG. 8 is an isometric view of an illustrative embodiment of
an impeller;
[0023] FIG. 9A-9K are illustrative embodiments of various types of
pattern grooves;
[0024] FIG. 10A-10D are cross-sectional views of various shapes of
pattern grooves;
[0025] FIG. 11 is a cross-sectional side view of an illustrative
embodiment of a pump with an axial hydrodynamic bearing;
[0026] FIG. 12A and 12B are top views of illustrative embodiments
of impellers with spiral herringbone grooves and spiral
grooves;
[0027] FIG. 13 is a close up cross-sectional view of an area of an
illustrative embodiment of a pump with an axial hydrodynamic
bearing;
[0028] FIG. 14A and 14B are isometric views of illustrative
embodiment of impellers with spiral herringbone grooves and spiral
grooves;
[0029] FIG. 15 is a cross-sectional side view of an illustrative
embodiment of a pump with a conically shaped impeller;
[0030] FIG. 16A-16E are isometric views of illustrative embodiments
of conically shaped impellers;
[0031] FIG. 17 is a close up cross-sectional view of an area of an
embodiment of a pump with a conically shaped impeller;
[0032] FIG. 18 is a cross-sectional side view of an illustrative
embodiment of a pump with passive magnetic axial bearings;
[0033] FIG. 19 is a cross-sectional top view of an illustrative
embodiment of a pump with passive magnetic axial bearings; and
[0034] FIG. 20 is a close up cross-sectional view of an area of an
illustrative embodiment of a pump with passive magnetic axial
bearings.
[0035] FIG. 21 shows a cross-sectional top view of an illustrative
embodiment of a pump with an impeller internal surface having a
multi-lobe shape.
[0036] FIG. 22 shows a close up cross-sectional top view of an
illustrative embodiment of a pump with an impeller internal surface
having a multi-lobe shape.
DETAILED DESCRIPTION
[0037] Refer now to the drawings wherein depicted elements are not
necessarily shown to scale and wherein like or similar elements are
designated by the same reference numeral through the several
views.
[0038] The following detailed description provides an implantable,
energy efficient, small, sealess, and magnetically driven blood
pump. The blood pump is capable of operating for extended periods
of time on a single charge. For example, the energy efficient blood
pump may be suitable for use with an implanted rechargeable power
source or the like. The pump can be installed pericardially (i.e.
near the heart) with less complex surgical procedures. Those
skilled in the art will appreciate that the various features
discussed below can be combined in various manners, in addition to
the embodiments discussed below. The scope of the claims is in no
way limited to the specific embodiments discussed herein.
[0039] FIG. 1 is a top view of an illustrative embodiment of pump
10. Pump 10 is formed from pump housing 15 providing inlet 20 and
outlet 25 and motor housing 35. Pump housing 15 is composed of two
or more pieces and may be joined by welding. However, in other
embodiments, pump housing 15 may be joined by fusing, press fit,
threading, screw and elastomeric sealing, bonding, fasteners,
and/or any other suitable joining method or combinations of joining
methods. Motor housing 35 may be joined to pump housing 15 by
welding, fusing, press fit, threading, screw and elastomeric
sealing, bonding, fasteners, and/or any other suitable joining
method or combinations of joining methods. Line A-A passing through
pump housing 15 indicates the plane from which the cross-sectional
view in FIG. 2 is provided.
[0040] FIG. 2 is a cross-sectional side view of an illustrative
embodiment of pump 10. Pump housing 15 provides impeller chamber 30
for impeller 75. Impeller chamber 30 has inlet 20 for connection to
a fluid source and outlet 25 for providing fluid to a desired
location. Impeller chamber 30 is sealed and pressure tight to
prevent fluid from entering/exiting impeller chamber 30 from
locations other than inlet 20 and outlet 25.
[0041] Motor housing 35 is attached to pump housing 15 to form a
fluid and/or pressure tight chamber for motor 40. While motor
housing 35 is shown as a separate component from pump housing 15,
in other embodiments, pump housing 15 and motor housing 35 may be
combined to form a single combined housing. A cross-sectional view
of an illustrative embodiment of motor 40 and motor housing 35 of
pump 10 is shown in FIG. 7. In particular, motor housing 35 is
shown separate from pump 10. Motor 40 is entirely contained between
pump housing 15 and motor housing 35. A high efficiency electric
motor can be utilized, such as an electric motor with efficiency of
about 85% or greater. However, in other embodiments, any other
suitable driving means can be utilized. Motor 40 provides shaft 45
with hub 50 mounted to shaft 45. Hub 50 contains one or more
permanent magnets and/or magnetic materials 55. Motor 40 rotates
shaft 50 causing permanent magnets 55 placed in hub 50 to rotate.
In some embodiments, a motor with a useful life of greater than 10
years is utilized. Further, the motor may utilize hydrodynamic
bearings with fluid support provided by a fluid other than
blood.
[0042] A cross-sectional view of an illustrative embodiment of pump
housing 15 without impeller 75 is shown in FIG. 6. Pump housing 15
may provide a non-ferromagnetic and/or non-electrically conductive
diaphragm 60 separating impeller chamber 30 from the chamber
housing motor 40. Diaphragm 60 defines cavity 70 providing a region
for hub 50 to rotate within. Additionally, diaphragm 60 may provide
cylindrical bearing surface 65 for impeller 75 to rotate around
with hydrodynamic radial support. Impeller 75 includes one or more
permanent magnets and/or magnetic materials 80. Permanent magnets
80 allow impeller 75 to be magnetically coupled to hub 50. This
magnetic coupling allows motor 40 to cause impeller 75 to rotate
when motor 40 rotates hub 50.
[0043] Line B-B passing through pump housing 15 indicates the plane
from which the cross-section view in FIG. 3 is provided. FIG. 3 is
a cross-sectional top view of an illustrative embodiment of pump
10. Impeller 75 is composed of an array of arc shaped segments 90
joined by central ring 95. Pump housing 15 has volute 110 feeding
the outlet 25. In other embodiments, volute 110 could be omitted
from pump housing 15 and outlet 25 could have any suitable
orientation and shape. Pump housing 15 is designed in a manner
where impeller 75, when rotated, pressures and moves fluid received
from inlet 20 to outlet 25.
[0044] Permanent magnets 55 in hub 50 and permanent magnets 80 in
central ring 95 of impeller 75 form a magnetic coupling between the
impeller 75 and hub 50. In contrast to radial magnetic bearings
that are arranged to repel each other, permanent magnets 55 and 80
are arranged so that they are attracted to each other. In order to
minimize radial loads, permanent magnets 55 and 80 provide a
minimal magnetic coupling or just enough of a magnetic coupling to
rotate impeller 75 under load. The attractive force of the magnetic
coupling of permanent magnets 55 and 80 also provides axial
restraint of impeller 75. For example, axial movement of impeller
75 would misalign permanent magnets 55 and 80. The magnetic forces
of permanent magnets 55 and 80 would restrain and re-align the
magnets. Because of the magnetic forces caused by permanent magnets
55 and 80, axial movement of impeller 75 may cause axial force to
be exerted on shaft 45 and hub 50 of motor 40, which is then
transferred to bearing(s) (not shown) of motor 40.
[0045] Permanent magnets 80 may be sufficiently small in size that
they have no impact on the main fluid flow paths of impeller 75,
thereby allowing the design of impeller 75 to focus on fully
optimizing pump efficiency. These benefits can allow pumping
efficiencies of greater than 50% to be achieved.
[0046] Impeller internal surface 100 of central ring 95 is utilized
to form a hydrodynamic bearing between cylindrical bearing surface
65 and impeller internal surface 100. Impeller 75 is configured to
rotate within impeller chamber 30 with full radial hydrodynamic
support from the hydrodynamic bearing formed by cylindrical bearing
surface 65 and impeller internal surface 100. A cross section view
of an illustrative embodiment of impeller 75 is shown in FIG. 5 and
an isometric view of an illustrative embodiment of impeller 75 is
shown in FIG. 8, which more thoroughly illustrate the hydrodynamic
bearing.
[0047] Pattern grooves on impeller internal surface 100 of impeller
75 create a high pressure zone when impeller 75 is rotated, thereby
creating a hydrodynamic bearing. For example, symmetrical
herringbone grooves create a high pressure zone where the two
straight lines of the V-shape grooves meet or the central portion
of the symmetrical herringbone grooves. The pressure created by the
pattern grooves on impeller internal surface 100 acts as a radial
stabilizing force for impeller 75 when it is rotating
concentrically. While the embodiment shown provides symmetrical
herringbone grooves on internal surface 100 of impeller 75, a
variety of different groove patterns may be utilized on impeller
internal surface 100 to provide a hydrodynamic bearing, which is
discussed in detail below. Because low loads are exerted on
impeller 75, the radial hydrodynamic bearing formed between
cylindrical bearing surface 65 and impeller internal surface 100
can provide stable radial support of impeller 75.
[0048] Impeller 75 may be an open, pressure balanced type impeller
to minimize axial thrust. Impeller 75 is considered to be open
because there is no endplate on either side of arc shaped segments
90. Further, impeller 75 is considered to be pressure balanced
because it is designed to minimize axial thrust during the rotation
of impeller 75. However, other types of impellers may be suitable
in other embodiments. Impeller 75 could be any other suitable blade
shape, rotate in the opposite direction, or non-pressure balanced.
For example, other suitable impellers may be semi-open type (i.e.
end plate on one side of impeller) or closed type (i.e. end plate
on both sides of impeller).
[0049] FIG. 4 is a close up cross-sectional view of an area C (see
FIG. 2) of an illustrative embodiment of pump 10. The magnetic
coupling transmits torque from shaft 45 of the motor 40 to impeller
75. In the embodiment shown, permanent magnets 55 and 80 are
radially distributed around hub 50 and impeller 75. The poles of
permanent magnets 55 and 80 are arranged to attract to each other.
The attractive force of the magnetic coupling of permanent magnets
55 and 80 provides axial restraint of impeller 75. While permanent
magnets 55 and 80 are shown as arc shaped like quadrants of a
cylinder, it should be recognized that permanent magnets 55 and 80
may be shaped in a variety of different manners to provide the
magnetic coupling. For example, one or more ring shaped magnets
polarized with arc shaped magnetic regions, square/rectangular
shaped, rod shaped, disc shaped, or the like may be utilized. In
the magnetic coupling arrangement shown, permanent magnets 80 are
shown in the internal portion of impeller 75. Internal magnetic
couplings, similar to the arrangement shown, can be more efficient
than face or external type magnetic couplings that place the
magnets in the blades of an impeller or rotor because they have a
smaller diameter and less eddy current losses. Diaphragm 60,
intermediate the coupling, is non-ferromagnetic and/or
non-electrically conductive to minimize eddy current losses. For
example, couplings with non-electrically conducting diaphragms such
as bio-compatible ceramic, glass or the like, would exhibit less
eddy current losses than those with electrically conducting
diaphragms.
[0050] In one embodiment, motor 40 is of the brushless DC,
sensorless, iron core type electric motor with fluid dynamic
bearings. However, in other embodiments, any suitable type of motor
including one or more features such as, but not limited to,
brushed, hall-effect sensored, coreless, and Halbach array or any
type of bearing such as ball or bushing may be used. Motor housing
35 may include motor control circuitry or be configured to operate
with remotely located control circuits.
[0051] Separating motor 40 from impeller chamber 30 may allow a
high efficiency motor to be utilized. For example, incorporating
components into a pump impeller to form the rotor of an electric
motor may compromise the design of the pump impeller resulting in
reduced efficiency. Further, designing a rotor and stator that is
incorporated into the design of a pump may result in an electric
motor with large gaps between components of the rotor and stator,
thereby decreasing the efficiency of the motor. The magnetic
coupling arrangements utilized in the embodiments discussed herein
allow a highly efficient motor design to be utilized without
compromising the design of an efficient pump impeller.
[0052] FIGS. 9A-9K and 10A-10D illustrate various embodiments of
pattern grooves that may be implemented on impeller internal
surface 100. As discussed previously, impeller internal surface 100
provides a hydrodynamic journal bearing. For example, impeller
internal surface 100 may utilize patterned grooves. The pattern
grooves may be of any type including, but not limited to, half
herringbone (FIG. 9A), dual half herringbone (FIG. 9B), symmetrical
herringbone (FIG. 9C), dual symmetrical herringbone (FIG. 9D), open
symmetrical herringbone (FIG. 9E), open dual symmetrical
herringbone (FIG. 9F), asymmetrical herringbone (FIG. 9G),
continuous asymmetrical dual herringbone (FIG. 9H), asymmetrical
dual herringbone (FIG. 9I), asymmetrical open herringbone (FIG.
9J), asymmetrical open dual herringbone (FIG. 9K), or the like.
Flow inducing pattern grooves, such as half herringbone patterns
and asymmetrical herringbone patterns, have the added benefit of
producing a substantial secondary flow, particularly along the axis
of impeller rotation between cylindrical bearing surface 65 and
impeller 75, thereby minimizing stagnant flow between cylindrical
bearing surface 65 and impeller 75. Because stagnant areas may
cause blood clots to form in blood pumps, the secondary flow
reduces the chances of blood clots forming. Further, asymmetrical
herringbone patterns have the additional benefit over half
herringbone patterns in that they provide similar radial stiffness
as symmetrical herringbone patterns. As shown in FIG. 10A-10D, each
of the pattern grooves of internal surface 100 can be shaped in a
variety of different manners, such as, but not limited to,
rectangular grooves, rectangular grooves with a bevel,
semi-circular grooves, elliptical grooves, or the like. In other
embodiments, impeller internal surface 100 may also be a plain
journal bearing without pattern grooves or a multi-lobe shape, as
shown in FIGS. 21 and 22, that creates a hydrodynamic bearing. In
alternative embodiments, the pattern grooves or multi-lobe shapes
may be located on the surface of cylindrical bearing surface 65
facing impeller 75 rather than impeller internal surface 100 or the
pattern grooves may be located on an outer radial surface of
impeller 75 or internal radial surface of pump housing 15 facing
the impeller 75.
[0053] FIG. 11 provides a cross-sectional side view of an
illustrative embodiment of housing 150 for pump 120. Similar to the
embodiment shown in FIG. 2, pump 120 provides pump housing 150,
impeller 125, shaft 130, hub 132, permanent magnets 135 and 140,
motor housing 142, motor 145, and impeller chamber 160, which all
provide a similar function to the components discussed previously.
These common elements may operate in substantially the same manner
as previously described. The substantial differences in the
embodiments are discussed below.
[0054] The embodiment shown in FIG. 2 provided radial support of
impeller 75 utilizing a hydrodynamic bearing. However in FIG. 11,
in addition to a radial hydrodynamic bearing, one or more external
planar surfaces or top surfaces 165 of impeller 125 include pattern
grooves providing partial axial hydrodynamic support.
[0055] FIG. 13 is a close up cross-sectional view of an area D of
an illustrative embodiment of pump 120. Each arc shaped segment 127
of impeller 125 includes one or more pattern grooves on top
surfaces 165. The pattern grooves on top surface 165 of impeller
125 and internal surface 155 of housing 150 form a hydrodynamic
bearing providing partial axial hydrodynamic support that prevents
or minimizes contact between impeller 125 and housing 150. The
pattern grooves on top surface 165 are considered to be interrupted
because they are separated by the flow channels of impeller
125.
[0056] Pattern grooves on top surface of impeller 125 may be any
suitable type of grooves including, but not limited to, spiral
herringbone and spiral grooves shown in FIGS. 12A and 12B. FIGS.
14A and 14B respectively provide an isometric view of impeller 125
with spiral herringbone and spiral grooves. The arrangement of the
pattern grooves on top surfaces 165 is balanced so that instability
during rotation of impeller 125 is prevented or minimized. For
example, all of the top surfaces 165 have pattern grooves in the
embodiment shown. However, it should be recognized that in other
embodiments a balanced arrangement of top surfaces 165 that have
pattern grooves and do not have pattern grooves may be utilized. A
balanced arrangement of top surfaces 165 prevents or minimizes the
instability of impeller 125. Examples of balanced arrangements for
the embodiment shown may include, but are not limited to, all top
surfaces 165 with grooves or three alternating top surfaces 165
with grooves and three without grooves. Flow inducing pattern
grooves, such as spiral and spiral herringbone grooves, have the
added benefit of producing a substantial secondary flow,
particularly between top surface 165 of impeller 75 and internal
surface 155 of housing 150. Additionally, various pattern groove
types including symmetrical, asymmetrical, open, and/or dual groove
patterns and various groove shapes including rectangular,
rectangular with a bevel, semi-circular, and elliptical shown in
FIGS. 9A-9K and 10A-10D may be utilized. An additional benefit of
the hydrodynamic bearing on top surface 165 of impeller 125 is that
it increases impeller stability during rotation by restraining
angular motion along axes normal to the axis of impeller
rotation.
[0057] FIG. 15 is a cross-sectional side view of an illustrative
embodiment of pump 170 with a conically shaped impeller 175. Many
of the components of pump 170 are substantially similar to the
components of the previously discussed illustrative embodiments.
These similar components may operate in substantially the same
manner as previously described. As in the previously discussed
embodiments, impeller 175 is magnetically coupled to shaft 180 of
motor 182. Permanent magnets 185 and 190 couple motor 182 to
impeller 175. However, in the embodiment shown, impeller 175 is
formed in a generally conical shape. Top surfaces 195 of impeller
175 facing internal surface 200 of the pump housing 202 are shaped
in a manner that provides a hydrodynamic bearing between impeller
top surfaces 195 and internal surface 200.
[0058] FIG. 17 is a close up cross-sectional view of an area E of
an illustrative embodiment of pump 170. As in the other embodiments
previously discussed, internal surface 205 of impeller 175 may
include pattern grooves for a hydrodynamic bearing providing radial
support. Top surfaces 195 of impeller 175 are angled to provide a
generally conical shaped impeller 175. FIGS. 16A-16E are views of
various embodiments of impeller 175. Impeller 175 has multiple
blade segments 210 that each have a top surface 195. Top surfaces
195 of blade segments 210 may be linear (FIG. 16A), convex (FIG.
16B), or concave (FIG. 16C) surfaces. Additionally, FIGS. 16D-16E
are views of impeller 175 with convex and concave top surfaces
195.
[0059] One or more of the top surfaces 195 of impeller 175 may
incorporate interrupted pattern grooves of any type including, but
not limited to, spiral or spiral herringbone grooves. For example,
the interrupted pattern grooves may be similar to the pattern
grooves shown in FIGS. 12A and 12B. The arrangement of the pattern
grooves on top surfaces 195 is balanced so that instability during
rotation of impeller 175 is prevented or minimized. For example,
all of the top surfaces 195 have pattern grooves in the embodiment
shown. However, it should be recognized that in other embodiments a
balanced arrangement of top surfaces 195 that have pattern grooves
and do not have pattern grooves may be utilized. Flow inducing
pattern grooves, such as spiral and spiral herringbone grooves,
have the added benefit of producing a substantial secondary flow,
particularly between top surface 195 of impeller 175 and internal
surface 200 of pump housing 202. Additionally, various pattern
groove types including symmetrical, asymmetrical, open, and/or dual
groove patterns and various groove shapes including rectangular,
rectangular with a bevel, semi-circular, and elliptical may
alternatively be utilized as shown in FIGS. 9A-9K and 10A-10D. In
some embodiments, top surfaces 195 of impeller 175 do not utilize
pattern grooves. For example, the conical shaped impeller 175 may
be a pressure balanced type impeller where the magnetic coupling
formed by magnets 185 and 190 provides sole axial restraint of
impeller 175.
[0060] In addition to the axial restraint provided by the magnetic
coupling discussed previously, the hydrodynamic bearing provided by
top surfaces 195 of impeller 175 partially restrains axial movement
in the direction along the axis of rotation. Because top surfaces
195 are angled, the hydrodynamic bearing of top surfaces 195 also
partially restrains radial motion of impeller 175. Thus, the
hydrodynamic bearing of top surfaces 195 provides partial radial
and axial support for impeller 175. The hydrodynamic bearings of
top surface 195 and impeller internal surface 205 and the partial
restraint provided by the magnetic coupling increase impeller
stability during rotation by restraining axial and radial
motion.
[0061] FIG. 18 is a cross-sectional side view of an illustrative
embodiment of pump housing 215 for pump 212. Many of the components
of pump 212 are substantially similar to the components of the
previously discussed illustrative embodiments. These similar
components may operate in substantially the same manner as
previously described. As in the previously discussed embodiments,
impeller 220 is magnetically coupled to shaft 225. Permanent
magnets 230 and 235 couple the motor to impeller 220.
[0062] Impeller 220 contains permanent magnets 240 and pump housing
215 contains permanent magnets 245, 250 thereby forming a magnetic
thrust bearing for minimizing axial movement of impeller 220.
Permanent magnets 245, 250 in housing 215 may be one or more
magnets formed into a ring. FIG. 20 is a close up cross-sectional
view of an area H of an illustrative embodiment of pump 212.
Permanent magnets 240 in impeller 220 and permanent magnets 245 in
the top portion of pump housing 215 are arranged to provide a
repulsive force between impeller 220 and pump housing 215.
Permanent magnets 240 in impeller 220 and permanent magnets 250 in
the bottom portion of pump housing 215 are also arranged to provide
a repulsive force between impeller 220 and pump housing 215. The
axial restraint forces generated by magnets 240, 245, 250 are
significantly greater than the attractive forces generated by the
permanent magnets 230 and 235 and thereby provide sole axial
support with greater stiffness for impeller 220 during rotation.
Magnets 240 in impeller 220 and magnets 245, 250 in pump housing
215 provide large axial restraint forces to allow for increased
clearances between impeller 220 and pump housing 215 during
rotation. The increased clearances reduce damage to blood and allow
for increased flow through the clearances during impeller
rotation.
[0063] FIG. 19 is a cross sectional top view of an illustrative
embodiment of pump 212. Magnets 240 are arranged radially around
impeller 220. Each blade segment 255 of impeller 220 may provide an
opening/region for receiving one or more magnets 240. Additionally,
in some embodiments, the top and/or bottom surfaces of impeller 220
may incorporate various pattern groove types including spiral,
spiral herringbone, symmetrical, asymmetrical, open, and/or dual
groove patterns. Further, various groove shapes including
rectangular, rectangular with a bevel, semi-circular, and
elliptical may also be utilized as shown in FIGS. 9A-9K and
10A-10D.
[0064] While the invention has been disclosed with respect to a
limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations can be made to
those embodiments without departing from the scope of the appended
claims.
* * * * *