Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FLEXIBLE TORQUE TUBE FOR USE WITH ENDOSCOPE
[0001] Field of the Invention
[0002] The present invention is related generally to endoscopic devices. In
one embodiment, the
invention is directed to a hollow torque-transmitting shaft for an endoscopic
tacking device
which can be inserted into a working channel within an endoscope positioned
within a
human or animal body, such as the gastrointestinal (GI) tract of a human
patient.
[0003] Background of the Invention
[0004] An endoscope used in human surgical procedures typically has an
accessory with end
effector for removal of tissue, suturing of tissue, etc., within a body
cavity, such as in the
alimentary canal. The accessory is located at a distal end of the endoscope
and is remotely
operated by a surgeon from an opposite end of the endoscope. The distal end of
the
flexible endoscope is articulated by the surgeon to position the end effector
of the
accessory. The end effector is connected to a flexible cable which slides
through a hollow
channel within the endoscope. The flexible cable is typically a power
transmission style
cable of the type used for speedometers. Such cables are intended for low
torque and high
rotational speeds, but in an endoscope torques must sometimes be high and
rotational
speeds are normally very low. Hence, a phenomena known as windup occurs in the
cable.
Under higher torque situations such as in cutting tissue, windup within the
flexible cable
reduces control of the end effector, causing undesirable jerkiness.
[0005] Furthermore, the typical flexible cable is made of a substantially
solid radial buildup of
multiple layers of woven metal strands, which slide upon one another as the
cable is
articulated from side to side as the endoscope is steered. Such frictional
resistance and
general bending stiffness of a flexible cable inhibits delicate manipulations
of the end
effector. What is needed is a flexible cable which has low bending stiffness
and high
torsional stiffness compared to the conventional cable
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[0006] Summary of the Invention
[0007] The present invention provides a flexible torque tube to twist and
steer an end effector
within an endoscope. In one embodiment the invention provides a series of
interconnected
hollow tubular members which pivot on one another at their connection joints.
The hollow
design of the flexible torque tube enables one or more wires to pass
therethrough for
additional end effector functionality, such as for wire loop cutting, etc., or
for steering an
end effector independently of endoscope steering.
[0008] The present invention also provides a joint design and method of
construction such that
tubular member joints have minimal clearance between interlocking surfaces so
that slack
at each joint is minimized and the assembly acts as much as possible as a
solid torque tube,
both axially and rotationally, while having the flexibility to articulate
[0009] The present invention additionally provides tubular member joints that
behave similar to
Hooke's Joints. That is, two intersecting pivot planes are provided at 90
degrees to each
other at each joint. This arrangement provides maximum bending flexibility to
the torque
tube while providing maximum stiffness to torque tube windup, regardless of
the amount
of articulation along the length of the torque tube.
[0010] Brief Description of the Drawings
[0011] The invention is described further below with reference to the
accompanying drawings, in
which:
[0012] FIGURE 1 is a perspective view of a first member of a flexible torque
tube showing semi-
circular journal bearing surfaces at which second members may be joined to
form a chain
of members.
[0013] FIGURE 2 is a perspective view of a second member of a flexible torque
tube showing
trunnions which engage the journal bearings of the first member to form a
chain of
members.
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[0014] FIGURE 3 is a top plan view of the member of FIG. 2, showing the
trunnions at opposite
ends having perpendicular axes.
[0015] FIGURE 4 is a side elevation view of the member of FIG. 3, showing
complementary
features at one end rotated 90 degrees at the opposite end.
[0016] FIGURE 5 is a sectioned view of the member of FIG. 3, taken along
section line 12-12,
showing a hollow circular tubing cross-section.
[0017] FIGURE 6 is a top plan view of the member of FIG. 1, showing the
journal bearings
having intersecting perpendicular axes.
[0018] FIGURE 7 is a side elevation view of the member of FIG. 6, showing
complementary
features at one end rotated 90 degrees at the opposite end.
[0019] FIGURE 8 is a sectioned view of the member of FIG. 6, taken along
section line 14-14,
showing a hollow circular tubing cross-section.
[0020] FIGURE 9 is a side elevation view of a flexible torque tube formed by
linking first and
second members together in a repeated sequence.
[0021] FIGURE 10 is a side elevation view of the flexible torque tube of FIG.
9, showing the
members of FIG. 2 and FIG. 6, whereby the member of FIG. 6 has its journal
bearings
pivoted on the trunnions of the member of FIG. 2 where the two members are
connected.
[0022] FIGURE 11 is a perspective view of a portion of an endoscope and a
flexible torque tube
operated by a handle to independently drive an end effector in both
articulation and
rotation modes relative to the endoscope.
[0023] Detailed Description
[0024] With reference to FIGS. 1-2, a first member 20 and a second member 22
of a flexible
torque tube 24 (illustrated in FIGS. 9 and 10) are shown. First member 20 is a
hollow tube
having a wall 26 between outer surface 28 and inner surface 30. First member
20 has a
constant cross-section along its length and such cross-section is shown as
circular in shape,
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having a longitudinal axis 32. Other constant and/or variable cross-sectional
shapes are
possible to achieve the functional benefits of the present invention, however.
First member
20 is sculpted with various interlocking surfaces located at each end thereof.
At one end,
first member 20 has two similar keyhole-shaped cutouts 34 through wall 26,
which are
equally spaced about surface 28. Cutouts 34 provide two semi-circular holes 36
having
wall surfaces which are parallel to an axis 38 extending through both holes.
Axis 38
intersects and is perpendicular to longitudinal axis 32. At an opposite end,
first member
20 has two similar keyhole-shaped cutouts 40 through wall 26, which are
equally spaced
about surface 28. Cutouts 40 provide two semi-circular holes 42 having wall
surfaces
which are parallel to an axis 44 extending through both holes. Axis 44
intersects and is
perpendicular to both longitudinal axis 32 and axis 38. Surfaces 36 and 42
have a precise
fit with similarly shaped male surfaces on second member 22 to form trunnion
journal
bearings.
[0025] As used herein, a trunion is either of two opposite pivots which can be
supported by
bearings to provide a means of swiveling or turning. A journal bearing is a
cylindrical
bearing which supports a rotating shaft.
[0026] Located at 90 degrees around surface 28 from cutouts 34, first member
20 has a pair of
longitudinal rectangular notches 46 extending through wall 26. Pair of notches
46 have
wall surfaces which are parallel to an axis 48 extending therethrough. Axis 48
is
perpendicular to and intersects axis 32. Located at 90 degrees around surface
28 from
cutouts 40, first member 20 has a pair of longitudinal rectangular notches 52
extending
through wall 26. Pair of notches 52 have wall surfaces which are parallel to
an axis 56
extending therethrough. Axis 56 is perpendicular to and intersects axis 32.
The wall
surfaces have a precise fit with similarly shaped male surfaces on second
member 22 to
form locks to prevent disassembly of members 20 and 22, once assembled, as is
described
hereinafter.
[0027] In FIG. 2, second member 22 is shown as a hollow tube having a wall 70
between outer
surface 72 and inner surface 74. Hollow tube wall 70 has the same curvature
and thickness
of hollow tube wall 26. Second member 22 has a constant cross-section along
its length,
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and such cross-section is shown as circular in shape, having a longitudinal
axis 76. Other
constant and/or variable cross-sectional shapes are possible to achieve the
functional
benefits of the present invention, however. Second member 22 is sculpted with
various
interlocking surfaces located at each end thereof. At one end, second member
22 has two
similar trunnions 78 extending therefrom, equally spaced about surface 72.
Trunnions 78
are cut from the hollow tubing and have the same thickness as wall 70.
Trunnions 78 have
semi-circular surfaces which are parallel to an axis 82 extending through both
semi-circles.
Axis 82 intersects and is perpendicular to longitudinal axis 76. At an
opposite end, second
member 22 has two similar trunnions 84 extending therefrom, equally spaced
about surface
72. Trunions 84 are cut from the hollow tubing and have the same thickness as
wall 70.
Trunnions 84 have semi-circular surfaces which are parallel to an axis 86
extending
through both semi-circles. Axis 86 intersects and is perpendicular to
longitudinal axis 76
and axis 82. Trunnions 78 and 84 are shaped to have a rotationally sliding fit
when
engaged with journal bearing surfaces 36 and 42 of first member 20. The fit
can be such
that no more than 0.0002 to 0.0003 inch total surface to surface clearance
exists between
trunnions and journal bearings.
[0028] Located at 90 degrees around surface 72 from trunnions 78, second
member 22 has a pair
of rectangular cantilever beams 88 having a thickness of tubing wall 70 and
extending
longitudinally. Pair of beams 88 have wall surfaces which are parallel to an
axis 92
extending therethrough. Axis 92 is perpendicular to and intersects axis 76.
Located at 90
degrees around surface 72 from trunnions 84, second member 22 has a pair of
rectangular
cantilever beams 94 having a thickness of tubing wall 70 and extending
longitudinally.
Pair of beams 94 have wall surfaces which are parallel to an axis 98 extending
therethrough. Axis 98 is perpendicular to and intersects axis 76. Beams 88
engage
notches 46 of first member 20 when members 20 and 22 are assembled.
[0029] At assembly of first member 20 with second member 22, an outer tip of
each beam 88 is
deflected outward from axis 76 an amount slightly greater than the thickness
of wall 70 as
trunnions 78 are slid radially into journal bearings formed by surfaces 36 of
first member
20, by aligning axis 82 with axis 38. Once members 20 and 22 have collinear
axes 32 and
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76, respectively, tips of beams 88 are released to snap into notch 46 to
prevent members 20
and 22 from being disassembled.
[0030] Members 20 and 22 can be made of 300 series stainless steel for high
torsional stiffness;
however, alterna.tive materials compatible within an endoscopic surgery
environment can
also be used, including composite materials. When member 20 is made from
stainless
steel tubing, its interlocking surfaces can be formed by a wire EDM (electro
discharge
machining) process, which is commonly known in the metalworking art. Tubing
can be
employed which tubing is sized with an outside diameter of about 0.120 inches,
and inside
diameter of about 0.080 inches and a wall thickness of about 0.020 inches. The
lengths of
members 20 and 22 can be selected such that the shorter the length of the
members, the
smaller the effective radius of bend of a chain of members can be.
[0031.] Trunnions can be about 0.030 inches in diameter, with a minimum neck
width where they
are connected to the body of the tubing of about 0.015 inches, for structural
integrity.
Notches and beams can be about about 0.025 inches wide.
[0032] FIGS. 3-5 show member 22 in more detail. FIG. 5 is a sectioned view of
tubular member
22 through trunnions 84, which are on opposite sides and at one end of the
tube. The body
of tubular member 22 is defmed by outer surface 72, inner surface 74, and
constant cross-
section wall 70. Edge surfaces of trunnions 84 are parallel to radial axis 86.
Trunnions 84
are semi-circular and are connected to a necked down body of the tube.
Rectangular
beams 94, which are on opposite sides and at the same end of the tube as
trunnions 84, are
cantilevered from the body of the tube inboard of the trunnions. Edge surfaces
of beams
94 are parallel with radial axis 98 passing through the center of the beams.
As indicated in
FIGS. 3 and 4, member 22 has a side elevation view which is a horizontally
flipped top
plan view. Thus, trunnions 78 and beams 88 are substantially identical to
trunnions 84 and
beams 94, but are rotated 90 degrees therefrom around the body of the tube. At
one end of
member 22 a journal bearing of a first member 20 may pivot vertically about
trunnions 84
while a second member 22 may pivot in a horizontal plane about trunnions 78.
The angle
of pivot rotation at each pair of trunnions is limited by the width of the
necked base of each
trunnion, which can be designed for structural integrity.
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[0033] Beams 88 and 94 serve to lock the members together once assembled. As
seen in FIGS. 6-
8, member 20 has rectangular notches 46 and 52 into which the ends of beams 88
and 94
fit with a clearance of about 0.00025 inches. FIG. 8 shows that the edges of
journal
bearings 42 and 36, as well as notches 46 and 52 are parallel to their
respective radial axes.
Similar to member 22, FIGS, 6 and 7, the top plan view and side elevation view
of
member 20, show that journal bearings 36 and 42, and notches 46 and 52 can be
substantially identical, but each end of member 20 is rotated 90 degrees from
the other end.
[0034] FIGS. 9 and 10 show members 20 and 22 connected to form a chain of
members for
providing a flexible torque tube 24. Torque tube 24 is shown straight in FIG.
9 and
articulated in FIG. 10. The limit of articulation of each member relative to
the other is
limited by interference at point 100. This interference point is established
by a clearance
102 between members 20 and 22. This interference point is preferred to contact
with the
neck of a trunnion so that stress at the weakest point of the trunnions is
minimized.
[0035] In one embodiment, member 20 can be relatively short with an overall
length of about
0.150 inches. The centerlines of the four journal bearings can be coplanar, as
in a Hookes
Joint. This permits articulation of two members 22 at the journal bearings of
each member
20 in any of two perpendicular directions. That is, in the elevation view of
FIG. 9, for
example, right hand member 22 may pivot at trunnions 84 in a vertical plane
while left
hand member 22 pivots in a horizontal plane about trunnions 78. The minimum
radius of
curvature at which a flexible torque tube 24 may be articulated depends
primarily on the
length of each member 22. At a minimum member 22 length of about 0.450 inches,
flexible torque tube 24 may be articulated to a radius of curvature of about 2
inches.
[0036] Torsional stiffness of a chain of members 20 and 22 is roughly
equivalent to that of a solid
piece of tubing the same length as the chain of members. Bending resistance of
the chain
of members is a function of the surface friction between journal bearing and
trunnion
surfaces for each member connection. Although minimal, this can be reduced
further with
lubrication.
[0037] Instron tests comparing torsional stiffness and bending stiffness of a
flexible torque tube
versus a cable having the same general outside diameter, such as a common
flexible cable
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part number B-MCX- 125 having diameter 0.125 inches, available from Small
Parts Inc. of
Miami Lakes, FL, can be used to illustrate how the flexible torque tube is
suited for
endoscopic use. Torsional stiffness for the flexible torque tube can be at
least about 0.018
pound inches per degree of twist per inch of tubing, compared to torsional
stiffness for a
flexible cable of about 0.010 pound inches per degree of twist per inch of
cable. The
higher the torsional stiffness the better in order to minimize windup over the
approximate
one meter length of an endoscope. Bending stiffness for the flexible torque
tube is
substantially zero pounds force per millimeter of deflection because the tube
just falls
down under its own weight. Bending stiffness for the comparison flexible cable
is about
4.3 pounds force per millimeter of deflection when the force is applied to a
cantilevered
segment at a location of 0.5 inches away from its fixation point. The lower
the bending
stiffness the better in order to minimize force to steer an end effector.
[0038] FIG. 11 shows a distal end 110 of a portion of an endoscope 112 having
a working channel
114 with an articulated flexible torque tube 116 extending therethrough.
Connected to the
end of flexible torque tube 116 is an end effector 118 which releasably grips
a conical
spring-shaped screw 120. Conical screw 120 is intended to be twisted into
tissue to cinch
tissue to stop bleeding therein. Flexible torque tube 116 is first articulated
to position
conical screw 120 substantially perpendicular to the tissue surface, not
shown. Then
flexible torque tube 116 is twisted through several rotations to secure
conical spring 120 in
the tissue. Finally, end effector 118 releases conical spring 120. In
performing this action
it is important to rotate flexible torque tube 116 with precision and without
windup during
transmission of motion through endoscope 112. Flexible torque tube 116 is
articulated
and twisted by a handle 122 at an operating end of endoscope 112. Handle 122
is rotated
laterally as indicated by arrow 124 or axially as indicated by arrow 126 to
twist flexible
torque tube 116 or operate three cables, not shown, within hollow torque tube
116. The
three cables are connected to the distal end of flexible torque tube 116 and
to handle 122.
Cables are spaced approximately 120 degrees apart and are slidably connected
to each
interconnected member 128 of flexible torque tube 116. Articulation of
flexible torque tube
116 occurs when lateral rotation of handle 122 pulls one cable tighter than
the others. This
method of articulation is well known in the endoscopic art.. However, steering
cables are
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normally on the outer surface of a flexible cable. The hollow flexible torque
tube permits
the steering cables to be located interna.lly as well as externally.
Alterna.tive accessories
used with endoscopes include suturing devices, gripping devices, loop cutting
devices, etc.
All such accessories may benefit by having their end effectors connected to a
flexible
torque tube of the present invention.
[0039] While the present invention has been illustrated by description of
several embodiments, it
is not the intention of the applicant to restrict or limit the spirit and
scope of the appended
claims to such detail. Numerous other variations, changes, and substitutions
will occur to
those skilled in the art without departing from the scope of the invention.
Moreover, the
structure of each element associated with the present invention can be
alternatively
described as a means for providing the function performed by the element. It
will be
understood that the foregoing description is provided by way of example, and
that other
modifications may occur to those skilled in the art without departing from the
scope and
spirit of the appended Claims.
