U.S. patent application number 16/827977 was filed with the patent office on 2020-09-17 for internal ultrasound assembly fluid seal.
This patent application is currently assigned to Muffin Incorporated. The applicant listed for this patent is Muffin Incorporated. Invention is credited to Neal E. Fearnot, Peter S. McKinnis, Sarah Robbins, Yun Zhou.
Application Number | 20200289091 16/827977 |
Document ID | / |
Family ID | 1000004860153 |
Filed Date | 2020-09-17 |
United States Patent
Application |
20200289091 |
Kind Code |
A1 |
McKinnis; Peter S. ; et
al. |
September 17, 2020 |
INTERNAL ULTRASOUND ASSEMBLY FLUID SEAL
Abstract
There are disclosed embodiments of devices and methods for
imaging the inside of a body part, particularly a blood vessel. In
particular embodiments, a catheter has a tip chamber, within which
is an ultrasound transducer mounted on a pivot mechanism, a motor
for turning the transducer, and an implement for pivoting the
transducer. Examples of such an implement are a linear motor, a
shaft or filament, and the pivot mechanism may be biased to return
to a base position when the implement is not pivoting the
transducer. In other embodiments, a mirror reflecting ultrasound
signals from the transducer may be rotated and/or pivoted, using
similar mechanisms.
Inventors: |
McKinnis; Peter S.;
(Carrboro, NC) ; Zhou; Yun; (Eden Prairie, MN)
; Robbins; Sarah; (Lafayette, IN) ; Fearnot; Neal
E.; (West Lafayette, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Muffin Incorporated |
West Lafayette |
IN |
US |
|
|
Assignee: |
Muffin Incorporated
West Lafayette
IN
|
Family ID: |
1000004860153 |
Appl. No.: |
16/827977 |
Filed: |
March 24, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14211885 |
Mar 14, 2014 |
10595823 |
|
|
16827977 |
|
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|
61787357 |
Mar 15, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 8/0891 20130101;
A61B 8/445 20130101; A61B 8/12 20130101; A61B 8/4483 20130101 |
International
Class: |
A61B 8/00 20060101
A61B008/00; A61B 8/08 20060101 A61B008/08; A61B 8/12 20060101
A61B008/12 |
Claims
1. An apparatus, comprising: a housing, the housing having a
uniform-diameter chamber defined at least partially by an acoustic
window for transmission of ultrasound signals; a transducer for
emitting and/or receiving ultrasound signals, the transducer being
within the chamber; a shaft operatively connected to the
transducer, the shaft adapted to rotate with respect to the housing
so that the transducer rotates in response to rotation of the
shaft; and a seal partially bounding the chamber, a part of the
seal engaged with the housing across the chamber's diameter, the
seal having an opening through which the shaft extends, with a
portion of the seal around the opening engaging the outside of the
shaft to create a fluid-tight connection between the seal and the
shaft.
2. The apparatus of claim 1, wherein the seal includes a body
having a lip portion that is elastically bent with respect to the
rest of the body.
3. The apparatus of claim 2, wherein the lip portion includes a
rounded convex surface facing the opening, and wherein a portion of
the rounded convex surface engages the outside of the shaft to
create a fluid-tight connection between the seal and the shaft.
4. The apparatus of claim 2, wherein at least a portion of the body
is fixed substantially perpendicular to the housing.
5. The apparatus of claim 2, wherein the lip portion is
substantially annular.
6. The apparatus of claim 1, wherein the seal has a body including
a lip portion, and the seal has a first unstressed position when
the shaft does not extend through the opening in which the lip
portion is substantially planar with respect to the rest of the
body, and a second stressed position when the shaft extends through
the opening in which the lip portion is elastically bent with
respect to the rest of the body.
7. The apparatus of claim 1, wherein the seal is initially in the
shape of a disc with the opening having a diameter smaller than an
outer diameter of the shaft, and when the shaft extends through the
opening, the disc is elastically deformed.
8. The apparatus of claim 7, wherein the disc when elastically
deformed forms substantially a portion of a cone.
9. The apparatus of claim 7, wherein the disc when elastically
deformed is substantially uniformly deformed.
10-15. (canceled)
16. An apparatus for ultrasound procedures, comprising: a
transducer for emitting and/or receiving ultrasound signals, the
transducer being within a chamber, the chamber defined at least
partially by a wall forming an acoustic window for transmission of
ultrasound signals; a motor; a shaft operated by the motor and
operatively connected to the transducer, the shaft adapted to move
with respect to the wall in at least one of rotation and
translation; and a seal next to the motor and defining an end of
the chamber, the seal engaging the outside of the shaft to create a
fluid-tight connection between the seal and the shaft.
17. The apparatus of claim 16, further comprising a housing that
encloses the transducer, the motor, the shaft and the seal, the
housing having a wall to which the seal is fixed around the entire
circumference of the wall.
18. The apparatus of claim 17, wherein the seal includes an opening
smaller than the diameter of the shaft, through which the shaft
passes, at least a portion of the seal bending when the shaft
extends through the seal.
19. The apparatus of claim 18, wherein the seal includes a
substantially circular line around the opening, wherein when the
shaft extends through the seal the seal portion between the line
and the opening bends substantially around the line.
20. An apparatus, comprising: a housing, the housing having a
uniform-diameter chamber; a microminiature motor positioned within
the housing; a shaft operatively connected to the motor, wherein
the motor is configured to move the shaft relative to the housing,
the shaft having a first end; a stationary surface within the
housing; and a seal positioned between the first end and the motor,
the seal having an opening through which the shaft extends, wherein
a part of the seal is engaged with the stationary surface or the
shaft to create a fluid-tight connection.
21. The apparatus of claim 20, wherein the seal has a body
including a lip portion, and the seal has a first unstressed
position when the shaft does not extend through the opening in
which the lip portion is substantially planar with respect to the
rest of the body, and a second stressed position when the shaft
extends through the opening in which the lip portion is elastically
bent with respect to the rest of the body.
22. The apparatus of claim 20, wherein the seal is attached to the
housing, and wherein the seal includes a body having a lip portion
that is elastically bent with respect to the rest of the body, and
wherein the lip portion includes a rounded convex surface facing
the opening, and wherein a portion of the rounded convex surface
engages the outside of the shaft to create a fluid-tight connection
between the seal and the shaft.
23. The apparatus of claim 20, wherein the seal is initially in the
shape of a disc with the opening having a diameter smaller than an
outer diameter of the shaft, and when the shaft extends through the
opening, the disc is elastically deformed, wherein the disc when
elastically deformed forms substantially a portion of a cone.
24. The apparatus of claim 20, wherein the seal is an O-ring,
further comprising a holder having a space configured to accept the
O-ring, wherein the holder is a attached to the shaft and wherein
the O-ring engages the holder and the housing, wherein the shaft is
adapted to move longitudinally and wherein the O-ring moves with
the shaft.
25. The apparatus of claim 20, wherein the seal is an O-ring,
further comprising a holder having a space configured to accept the
O-ring, wherein the holder is attached to the stationary surface
and wherein the O-ring engages the holder and the shaft, wherein
the shaft is adapted to move longitudinally and wherein the shaft
moves relative to the O-ring.
Description
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 61/787,357, filed on Mar. 15, 2013, which is
incorporated herein by reference in its entirety.
[0002] The present disclosure relates to structure and methods in
medical uses of ultrasound. In particular, this disclosure relates
to seals around moving parts in medical ultrasound devices.
BACKGROUND
[0003] Commonly, devices for subcutaneous medical applications
require a motor to couple a moving part in a fluid environment.
Fluid environments can present hazardous conditions for certain
motors. One example is in the use of ultrasound for imaging,
therapy or other medical uses. In such use, ultrasound energy or
waves are transmitted through a medium and can reflect, scatter or
otherwise attenuate when they reach a surface or border having a
significant difference in acoustic impedance. For example, in
ultrasound imaging of the human body, ultrasound waves may be
applied externally (e.g. by placing a transducer on the skin) or
internally (e.g. by placing a transducer within a vessel or organ),
and travel through the body's internal fluids, which is a large
proportion of water. When the waves strike a bone, organ or other
body portion that provides an acoustic interface--i.e., a border of
two significantly different acoustic impedances--then the waves are
reflected or otherwise attenuated. A transducer (which may be the
same transducer that supplied the ultrasound waves or another)
receives the reflected or attenuated waves, and an image of a
portion of the body can be generated.
[0004] A gel is placed between the skin and transducer to reduce
reflection or other attenuation between the transducer and the
skin. When a transducer is placed within the body, commonly it is
inside a protective envelope, such as a tube, catheter or similar
housing or enclosure. The material of such an envelope may be
selected for its similarity in acoustic impedance to that of bodily
fluids, so that there is little or no attenuation as ultrasound
waves travel from that material to the fluids or tissues of the
body. The inner pocket or volume of the enclosure within which the
transducer is placed needs a coupling medium having an acoustic
impedance similar to that of the envelope material and the body's
fluids, to allow maximum transmission of the ultrasound signal.
Without such a medium, e.g. if the inside of the body simply
includes air or another gas, significant reflection or other
attenuation will occur when the ultrasound energy from the
transducer hits the boundary where the gas meets the material of
the envelope. Suitable coupling media include biocompatible fluids
such as saline, oils such as mineral oil, alcohols, and other
fluids.
[0005] In ultrasound devices in which the transducer can turn,
pivot or otherwise move, a seal between or around mechanisms to
move the transducer may be necessary to limit or prevent the
coupling medium from corroding, fouling or otherwise interfering
with performance of such mechanisms. For example, in mechanisms
using a motor that operates a turning or otherwise mobile shaft,
with the shaft connected to the transducer or its seat or other
holder, a seal may be needed between a chamber holding the
transducer and coupling medium and the motor. In another example, a
motor is combined with a tool to drill a bore through a clot or
plaque in a vein or artery. Corrosive and/or electrolytic coupling
media may be incompatible with electrical connections or other
parts of a motor, drive shaft or other mechanism. Piezoelectric
motors generally need dry conditions to operate, as they require a
high friction contact area between a stator and a clutch. If fluid
(whether generally corrosive or not) touches that contact area or
interface, the friction will be substantially reduced, thereby also
reducing the torque output of the motor.
[0006] Accordingly, to prevent fluid from contacting parts of such
devices, such as motors, a seal should be included between the
motor and the fluid environment, to prevent the fluid from gaining
access to the motor. Examples of such a structure are disclosed
below.
SUMMARY
[0007] Among other things, there are shown embodiments of apparatus
for ultrasound procedures that include a housing, the housing
having a chamber defined at least partially by an acoustic window
for transmission of ultrasound signals. The chamber may have a
uniform diameter in some embodiments. A transducer for emitting
and/or receiving ultrasound signals is within the chamber, and a
shaft is operatively connected to the transducer, the shaft adapted
to move with respect to the wall in at least one of rotation and
translation so that the transducer moves in response to movement of
the shaft. A seal partially bounds the chamber, with a part of the
seal fixed to the housing and the seal extending across the
chamber's diameter, and the seal has an opening through which the
shaft extends, with a portion of the seal around the opening
engaging the outside of the shaft to create a fluid-tight
connection between the seal and the shaft.
[0008] As exemplary embodiments, the seal can include a body having
a lip portion that is elastically bent with respect to the rest of
the body. The lip portion may have a rounded convex surface facing
the opening, e.g. with a portion of the rounded convex surface
engaging the outside of the shaft to create a fluid-tight
connection between the seal and the shaft. A portion of the body
can be fixed substantially perpendicular to the housing, and or the
lip portion may be substantially annular. If seal has a body
including a lip portion, the seal may have a first unstressed
position when the shaft does not extend through the opening in
which the lip portion is substantially planar with respect to the
rest of the body, and a second stressed position when the shaft
extends through the opening in which the lip portion is elastically
bent with respect to the rest of the body.
[0009] The seal may be initially in the shape of a disc with the
opening having a diameter smaller than an outer diameter of the
shaft. When the shaft extends through the opening, the disc is
elastically deformed. In such deformation, the disc can form
substantially a portion of a cone in particular examples, and/or be
substantially uniformly deformed.
[0010] In other embodiments, the seal may include an O-ring and an
O-ring holder. For example, such an O-ring holder may engage the
shaft with the O-ring fixed to the housing. The shaft is movable
with respect to the O-ring holder, and/or the O-ring holder is
movable with respect to the O-ring, in some instances. In
particular examples the O-ring does not move with the shaft.
[0011] Embodiments of apparatus for ultrasound procedures as
disclosed below may include a transducer for emitting and/or
receiving ultrasound signals, with the transducer being within a
chamber that is defined at least partially by a wall forming an
acoustic window for transmission of ultrasound signals. The
apparatus further includes a motor and a shaft operated by the
motor and operatively connected to the transducer. The shaft is
adapted to move with respect to the wall in at least one of
rotation and translation. A seal is provided next to (e.g. abutting
or adjacent) the motor and around at least part of the shaft, the
seal engaging the outside of the shaft to create a fluid-tight
connection between the seal and the shaft.
[0012] Particular examples include a housing that encloses the
transducer, the motor, the shaft and the seal. The housing can
feature a wall to which the seal is fixed around the entire
circumference of the wall. The seal can include an opening smaller
than the diameter of the shaft, through which the shaft passes,
with at least a portion of the seal bending when the shaft extends
through the seal. The seal, in some embodiments, includes a
substantially circular line around the opening, wherein when the
shaft extends through the seal the seal portion between the line
and the opening bends substantially around the line. In other
embodiments, seals can include an O-ring and an O-ring holder, the
holder having an opening through which the shaft extends, and the
O-ring fixed with respect to the wall.
[0013] These and other embodiments are discussed further below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a part cross-sectional view of an application end
of an embodiment of an ultrasound device as disclosed herein.
[0015] FIG. 2 is a cross-sectional view of an embodiment of a
portion of the device of FIG. 1.
[0016] FIG. 3 is an end view of a portion of the embodiment shown
in FIG. 2.
[0017] FIG. 4 is a cross-sectional view of an embodiment of a
portion of the device of FIG. 1.
[0018] FIG. 5 is an end view of a portion of the embodiment shown
in FIG. 4.
[0019] FIG. 6 is a cross-sectional view of an embodiment of a
portion of the device of FIG. 1.
[0020] FIG. 7 is a part cross-sectional view of an application end
of an embodiment of an ultrasound device as disclosed herein.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0021] For the purposes of promoting an understanding of the
principles of the disclosure, reference will now be made to the
embodiments illustrated in the drawings and specific language will
be used to describe the same. It will nevertheless be understood
that no limitation of the scope of the claims is thereby intended,
such alterations and further modifications in the illustrated
embodiments, and such further applications of the principles of the
disclosure as illustrated therein being contemplated as would
normally occur to one skilled in the art to which the disclosure
relates.
[0022] Referring now generally to the drawings, there is shown an
embodiment of a device 20 for application of ultrasound internally
to a patient. Although the embodiment is described herein for use
in the context of ultrasound applications, device 20 and the
sealing apparatuses described can be used in any number of
structural applications in which a motor must be sealed from the
fluid environment. As particular examples, device 20 is or is part
of a device or system for imaging, such as for intravascular
ultrasound (IVUS) imaging. Other embodiments can include devices
for therapeutic or diagnostic uses within the body, or for
ultrasound devices used outside of the body. In the embodiment
indicated schematically in FIG. 1, device 20 is a catheter or other
flexible elongated or tubular housing or member 22, and in a
particular example is sized and configured for insertion into
and/or travel along the vascular system. Member 22 has an
application end 23 enclosed by a wall 24, with at least part of
wall 24 defining a boundary of internal chamber 26. Wall 24 may be
continuous (e.g. monolithic or one-piece), i.e. defining some or
all of catheter 22 and encircling or containing chamber 26, or in
other embodiments a portion of wall 24 surrounding chamber 26 may
be different from and fixed to the rest of catheter 22. Chamber 26
in this embodiment has a uniform diameter, with no steps, corners
or sharp irregularities that may undesirably attenuate ultrasound
waves. Within catheter 22 and chamber 26 in this embodiment is a
transducer 28 for sending and/or receiving ultrasound signals. One
or more motors 30 are connected directly or indirectly to
transducer 28 so as to turn transducer 28 around a longitudinal
axis of device 20, pivot transducer 28 around an axis substantially
perpendicular to that longitudinal axis, and/or provide other
motions to transducer 28.
[0023] Catheter 22 in the illustrated embodiment is an elongated
device of plastic or other sturdy flexible material that is
substantially transparent to or presenting a minimal barrier to
passage of ultrasound signals. For example, when used within a
blood vessel containing body tissues and blood, it is preferable
for catheter 22 (or at least some or all of wall 24) to be
constructed of a material which has acoustic impedances similar to
that of body fluids such as blood. Possible materials could
include, for example, a polymer material such as high density
polyethylene, polymethylpentene (PMP), or acrylonitrile butadiene
styrene (ABS). It has been determined that a preferred thickness of
at least the portion of catheter 22 which serves as the viewing
window should be at least 1/2 of the wavelength of the center
frequency. Alternatively, the thickness can be N*1/2 of the
wavelength, where N is a positive integer.
[0024] Wall 24 surrounds chamber 26, which is at the distal end of
device 20 in the illustrated embodiment, and extends proximally.
Wall 24 is a monolithic part of a catheter 22 in some embodiments,
and in others wall 24 is at the application end surrounding all or
part of chamber 26. Wall 24 may extend toward the control end of
device 20 beyond chamber 26 in some examples. The proximal end of
wall 24 and/or catheter 22 may extend outside of the patient during
use, and the control end may include a handle or other operating
portion (e.g. an imaging system and/or a maneuvering system (not
shown)). Particular embodiments of catheter 22 or at least chamber
26 are cylindrical, and are sized for insertion into and passage
through blood vessels, such as insertion into the femoral artery
and passage through it toward the heart.
[0025] Transducer 28 is indicated schematically in the drawings.
The term "transducer" should be understood to include an assembly
of two or more parts as well as a single piece. For instance,
transducer 28 can include a body or backing 40, a transducer
element 42 attached to one side of body 40, and a matching layer
(not shown) attached to one side of element 42. The matching layer
is attached to one side of element 42 and may be focused or
non-focused. The matching layer has acoustic impedance generally
between that of element 42 and the medium surrounding transducer 28
in order to minimize mismatched acoustic impedance between
transducer 28 and the medium surrounding transducer 28 (e.g.
mineral oil). In some embodiments, transducer 28 includes an
element 42 and matching layer but no body 40. In this embodiment,
transducer 28 is pivotable and/or rotatable through action or
influence of motor 30, so that with element 42 on the side of body
40 as indicated, a generally lateral (i.e. away from the
longitudinal axis) and forward ultrasound beam direction is
possible depending on the motion of transducer 28. Body 40 may be
substantially opaque to or reflective of ultrasound signals, so
that such signals are effectively only projected in one general
direction outward from element 42, e.g. to one side or in a limited
angular range radially from body 40. Embodiments of transducer 28
may be capable in particular examples of sending and receiving
ultrasound waves in a range of frequencies which are typically used
in medical ultrasound procedures, such as, for example, in the
range from 2 MHz to 50 MHz.
[0026] Transducer 28 is electronically connected to a power source
and to an imaging system (not shown). Examples of connections
include conductors (e.g. wires or cables) along wall 24, through a
central lumen of a motor shaft, via slip ring connections, and/or
via metallic film(s) along wall 24. Transducer 28 may be mounted in
a pivoting mechanism or otherwise linked to motor 30 or a shaft
(which rotates, travels longitudinally, or otherwise moves) to
permit transducer 28 to turn, pivot, or otherwise move. Embodiments
of such examples are discussed and shown in Application Ser. Nos.
61/713,135; 61/713,172; 61/714,275; and 61/748,773, all of which
are incorporated by reference in their entireties.
[0027] Motor 30 may be a rotary or linear motor and includes a
shaft 44 for connecting or linking to transducer 28 or a mechanism
connected to it. Multiple-motor embodiments are also considered
(e.g. FIG. 7), which shows an example of a rotary motor 30a and a
linear motor 30b with respective shafts 44a and 44b. In this
example, motor 30a turns hollow shaft 44a about a longitudinal axis
L of device 20, and shaft 44a is linked to transducer 28 as
schematically indicated so that transducer 28 likewise turns around
axis L. Motor 30b moves shaft 44b forward and backward along axis L
and through shaft 44a in this example, with shaft 44b engaging or
linked to transducer 28 off-center. Forward motion of 44b tends to
pivot transducer 28 clockwise about an axis into the page
(perpendicular to axis L), and rearward motion of shaft 44b tends
to pivot or allow pivoting of transducer 28 counterclockwise around
an axis into the page.
[0028] Embodiments of piezoelectric or electromagnetic micromotors
of a size and configuration suitable for containment within
catheter 22 may be used. For example, a particular embodiment of a
rotary motor (e.g. motor 30a) is a two-phase, coreless, brushless
DC electromagnetic motor, which has few components, small size and
minimal complexity. A piezoelectric micromotor is of a small size,
such as having a diameter in the range from 0.3 mm to 4 mm in
particular embodiments, and can exhibit a high torque-to-size
ratio. An example of a linear motor (e.g. motor 30b) is an
electromagnetic motor similar to a voice coil, used extensively for
loudspeakers, which operate by creating a high static magnetic flux
(e.g. by a permanent magnet) in the lateral direction (e.g.
perpendicular to the longitudinal axis of the motor). An
electrically conductive coil is placed through this flux and when
current is applied to the coil a force in the axial direction is
created, pulling or pushing shaft 44b.
[0029] A seal 50 is provided forward of motor 30 (e.g. engaging or
adjacent to the forward-most part of motor 30a in the illustrated
embodiment) to separate chamber 26 from motor 30. Seal 50 in the
illustrated embodiment is a wall or membrane that extends across
the entire diameter or width of chamber 26, e.g. contacting wall 24
around a full circumference and forming an end of chamber 26 toward
the control end of device 20. Seal 50 may be unitary, formed with
or as part of wall 24 and of the same material as wall 24, or may
be separately formed and inserted into and joined with the inside
of wall 24. For example, seal 50 may be formed concurrently with
wall 24, as by molding, or may be separately formed or prepared and
fixed to or within wall 24, as by adhesive joining or welding.
Outermost portion of seal 50 (e.g. its outer diameter) is attached
to wall 24, either in the acoustic window or in the catheter behind
it. The attachment may be to an inner surface of wall 24, or to
different component such as an end surface of motor 30 so that
chamber 26 is isolated from the rest of device 20. In any case, the
attachment is to a stationary surface with respect to the movable
shaft 44. As indicated in the drawings, one or more shafts (e.g.
shafts 44a and/or 44b, associated with motors 30a and/or 30b)
extend through seal 50 in order to link or connect to transducer
28. In such embodiments, seal 50 thus provides not only a general
wall bounding chamber 26, but also inhibits or prevents flow of
fluid out of chamber 26 around shaft(s) 44 extending through seal
50.
[0030] A particular embodiment of seal 50 is shown in FIGS. 2-3
which is configured to provide a seal between chamber 26 and motor
30 during rotating motion of shaft 44. Seal 50 is in the form of a
disc seal. Seal 50 is a disc of low-friction polymer or elastomer
material, and in a particular embodiment of silicone. An opening 54
is in seal 50, and in the illustrated embodiment is in the middle
of seal 50 (i.e. along the central longitudinal axis of device 20).
Opening 54 is slightly smaller than the outer diameter of shaft 44.
Opening 54 is a hole smaller than the diameter of shaft 44 in
particular embodiments, and in other embodiments could be a hole
combined with a slit, a slit itself, or otherwise configured. In
the illustrated embodiment, shaft 44 is centrally located, i.e.
along the central longitudinal axis of device 20, and therefore
opening 54 is also centrally located. It will be understood that
other embodiments may have the location of shaft 44 and opening 54
off-center.
[0031] As seal 50 is pulled over shaft 44 (or shaft 44 is inserted
through seal 50), opening 54 is elastically deformed, enlarging or
stretching out over the circumference of shaft 44. The elastic
properties of the stretched material of seal 50 causes seal 50 to
exert a compressive force or stress on shaft 44 to create a seal
between seal 50 and shaft 44. As indicated in the embodiment of
FIG. 4, seal 50 may stretch along the length of shaft 44 while
remaining attached to wall 24, so that much or all of seal 50
becomes substantially conical and/or reduces in thickness when
shaft 44 is forced through it. The low-friction nature of the
material of seal 50 permits shaft 44 to turn with minimal hindrance
even under some pressure from fluid in chamber 26.
[0032] Seal 50 may be formed concurrently with wall 24, or may be
separately formed or prepared and fixed to or within wall 24. In
other embodiments, seal 50 is attached to other components of
device 20 so that chamber 26 is isolated from the rest of device
20, or particularly from motor 30. For example, seal 50 can be
attached to an end surface or other portion of the motor 30, or it
may be attached to a sheath extending within catheter 22. In any
case, the attachment is to a stationary surface with respect to the
movable shaft 44. Generally seal 50 is attached to a component
which is stationary with respect to wall 24. In any case, the
outermost portion of seal 50 (e.g. its outer diameter) is attached
either in the acoustic window or in the catheter behind it.
[0033] A further embodiment is shown in FIGS. 4-5. In that
embodiment, seal 50' is configured to provide a seal between
chamber 26 and motor 30 during rotation of shaft 44. Seal 50' is a
lipped seal made of a low-friction polymer or elastomer. Seal 50'
includes a body portion 52, and an opening 54' having a diameter
smaller than the shaft 44. Body portion 52 is substantially planar
or disc-shaped in this embodiment, extending substantially
perpendicular to the longitudinal axis and joining wall 24 so as to
form part of the enclosure of chamber 26. The thickness of body
portion 52 is preferably uniform, so that the contact between body
portion 52 and shaft 44 will be uniform around the circumference of
shaft 44.
[0034] An annular inner part 56 of body portion 52 surrounds
opening 54' and forms a lip. In this embodiment, the lip or annular
center 56 is a part that elastically bends as shaft 44 is pressed
through it. A line, score or other feature 57 may be placed in body
portion 52, for example concentric with opening 54', that promotes
bending or provides a particular bending location. An inward
surface 58 of annular center 56 that borders or defines opening 54'
is rounded in the embodiment illustrated in FIG. 2, to ease
insertion of shaft 44 through opening 54' and to ensure that a
portion of surface 58 will press evenly and without the potential
for gaps on shaft 44 as shaft 44 turns. Surface 58 may describe
part of a torus, be convex, and/or describe a semicircle or other
part of a curve in cross-section, in specific examples.
[0035] In some embodiments, body portion 52 is substantially planar
prior to inserting shaft 44 through opening 54'. When device 20 is
being assembled, shaft 44 is pressed against body portion 52 at
opening 54', and annular part 56 bends away from shaft 44 (e.g. at
line or feature 57) to allow shaft 44 to pass through opening 54',
without tearing body portion 52. While the part of body portion 52
between annular part 56 and wall 24 of device 20 remains
substantially perpendicular to wall 24, as indicated in the
embodiment of FIG. 2, annular part 56 angles toward chamber 26 so
as to be substantially conical or having a concave surface (e.g. at
location C) facing chamber 26. A portion of rounded or convex
surface 58 engages shaft 44 around the entire circumference of
shaft 44.
[0036] Body portion 52 is prepared with annular part 56 already
bent to an extent as it is formed or attached in device 20.
Insertion of shaft 44 through opening 54' bends annular part 56 at
least slightly more (i.e. through elastic deformation) so that
surface 58 applies a force to shaft 44 which creates a fluid seal
at the engagement of surface 58 and shaft 44. The force effectively
seals surface 58 against the outer surface of shaft 44. In some
embodiments, fluid pressure from coupling medium in chamber 26 will
tend to press annular part 56 against shaft 44, maintaining or
strengthening the seal against fluid escaping chamber 26 between
annular part 56 of seal 50' and shaft 44.
[0037] FIG. 6 shows an embodiment of seal 50'' that is configured
for shaft(s) 44 that move longitudinally, including reciprocating
longitudinal movement. Seal 50'' includes an O-ring 60 and an
O-ring holder or gland 62, which together form a fluid-tight
barrier between shaft 44 and wall 24. O-ring 60 in the illustrated
embodiment is a circular torus of elastomeric or other sealing
material, having an outer diameter that engages or abuts against
the inner diameter of wall 24.
[0038] O-ring holder or gland 62, in the particular illustrated
embodiment, is a round, spool-shaped piece having a longitudinal
opening 64 for shaft 44 through a body 66. A central groove or
space 68 around body 66 is between side flanges 70. The unstressed
(i.e. natural) outer diameter of ring 60 is slightly larger than an
inner diameter of wall 24, so that when ring 60 is inserted into
device 20 a press or interference fit exists between ring 60 and
wall 24. The inner diameter of the torus of ring 60 is at least
slightly larger than the outer diameter of shaft 44 and at least
slightly smaller than the diameter of opening 64. In that way, ring
60 is slightly oversized so that when the ring is placed in space
68 between holder 62 and wall 24, ring 60 is compressed, and the
compression force creates a fluid seal between chamber 26 and motor
30.
[0039] Holder 62 is of a low-friction material, perhaps similar to
the materials noted above with respect to seals 50, 50' to permit
easy movement, sliding, or rolling motion of holder 62 with respect
to ring 60. In particular embodiments, holder 62 is attached to
shaft 44 so that longitudinal movement of shaft 44 moves holder 62
as well. The low-friction material of holder 62 allows ring 60 to
move within space 68 (or at least rotate with respect to holder
62). During such movement, the inner diameter of ring 60 engages
the diameter of opening 64 as the outer diameter of ring 60 engages
the inner diameter of wall 24, preserving the seal. Similarly, ring
60 is able to move longitudinally along wall 24 while preserving
the seal. In that way, ring 60 follows holder 62 as holder 62 moves
in unison with longitudinal movement of shaft 44. It will be
understood that the size of holder 62 and/or the size of space 68
measured along the length of shaft 44 may be related or tailored to
the length of travel of shaft 44. That is, the longer space 68 is,
the longer ring 60 can move within it and the longer the amount of
longitudinal travel of shaft 44 is allowed for, and conversely a
shorter distance of travel by shaft 44 may need only a relatively
short holder 62 and space 68.
[0040] In an alternative embodiment (not shown), holder 62 is
shaped in an opposite fashion with respect to axis L. In that
embodiment, holder 62 is attached to wall 24 with a space and
flanges that are directed inward toward axis L. In that embodiment,
the unstressed (i.e. natural) outer diameter of ring 60 is slightly
larger than the inner diameter of the space between the flanges of
holder 62. The inner diameter of the torus of ring 60 is at least
slightly smaller than the outer diameter of shaft 44. In that way,
similar to the embodiment of FIG. 6, ring 60 is slightly oversized
so that when the ring is placed in the space between holder 62 and
shaft 44, ring 60 is compressed, and the compression force creates
a fluid seal between chamber 26 and motor 30. In this embodiment
ring 60 may move with the longitudinal movement of shaft 44, but
holder 62 will remain stationary relative to wall 24 while shaft 44
moves. Ring 60 can move around in holder 62 and still maintain the
seal as was explained in the above example.
[0041] Specific embodiments of device 20 may have seal(s) 50, 50'
and/or 50'' having an outer diameter of approximately 2.5 mm, i.e.
about the inner diameter of wall 24 and/or chamber 26. An inner
diameter of about 0.8 mm for seal(s) 50, 50' and/or 50'' is
proposed, in light of the expected outer diameter of embodiments of
shaft 44. Of course, it will be understood that size and
configuration of the outer and inner diameters of seal embodiments
may depend on geometry and size of shaft(s) 44, and of wall 24
and/or chamber 26.
[0042] It will be understood that features or attributes noted with
respect to one or more specific embodiments may be used or
incorporated into other embodiments of the structures and methods
disclosed. Multiple seals 50, 50' and/or 50'' may be used in
particular embodiments, as where a first seal is placed at a
boundary of chamber 26 and around a first shaft 44a, and a second
seal is placed between motor 30a that turns shaft 44a and motor 30b
which operates shaft 44b. For example, where shaft 44a is a hollow
shaft and shaft 44b operates through the lumen of shaft 44a, a
first seal 50 (or other embodiment(s)) is around shaft 44a at the
boundary of chamber 26, as discussed above. A second seal 50'' (or
other embodiment(s)) is between motor 30a and 30b (e.g. attached to
or adjacent the rear of motor 30a) and sealingly fitted around
shaft 44b. In such a configuration, some liquid from chamber 26 may
escape through hollow shaft 44a, i.e. between the inner diameter of
shaft 44a and the outer diameter of shaft 44b. Motor 30a in this
example can be an electromagnetic motor that is not significantly
susceptible to small amounts of escaping coupling medium, which is
in any case largely or entirely contained within shaft 44a. The
second seal, around shaft 44b and otherwise fixed to catheter 22
(e.g. wall 24), maintains any such escaped coupling medium away
from motor 30b.
[0043] While the embodiments have been illustrated and described in
detail in the drawings and foregoing description, the same is to be
considered as illustrative and not restrictive in character, it
being understood that only particular embodiments have been shown
and described and that all changes and modifications that come
within the spirit of the disclosure are desired to be
protected.
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