WO2008118609A1

WO2008118609A1 - Flexible torque tube for use with endoscope

Info

Publication number: WO2008118609A1
Application number: PCT/US2008/055402
Authority: WO
Inventors: David Stefanchik
Original assignee: Ethicon Endo-Surgery, Inc
Priority date: 2007-03-23
Filing date: 2008-02-29
Publication date: 2008-10-02
Also published as: CA2681693A1; BRPI0809097A2

Abstract

A flexible torque tube is disclosed. The torque tube can be used with an endoscope. For instance, the torque tube can be part of an endoscopic accessory having an end effector which is manipulated through the working channel of an endoscope. The torque tube can include a series of interconnected hollow tubular members extending proximally from the end effector. The tubular members can be interconnected to provide a flexible torque tube have substantially zero bending stiffness and a torsional stiffness sufficient for manipulating the end effector through the working channel of an endoscope.

Description

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 factional 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 [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 semicircular 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. [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, 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, 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 coUinear axes 32 and 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, alternative 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 defined 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. [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 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. 1 1 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 normally on the outer surface of a flexible cable. The hollow flexible torque tube permits the steering cables to be located internally as well as externally. Alternative 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.

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.

Claims

Wh at is claimed:

1. An apparatus for use with an endoscope, the apparatus comprising:

an end effector; and

a series of hollow tubular members operatively associated with the end effector and extending proximally from the end effector, the series of tubular members interconnected to provide a flexible torque tube have substantially zero bending stiffness and torsional stiffness sufficient for manipulating the end effector through the working channel of an endoscope.

2. An endoscopic flexible torque tube comprising a series of interconnected hollow tubular members, the series of tubular members comprising:

a plurality of first members, each first member having oppositely facing pairs of female features for providing journal bearing surfaces; and

a plurality of second members, each second member having oppositely facing pairs of trunions shaped to have a rotatationally sliding fit with a journal bearing surface of an adjacent first member;

wherein the first and second members are disposed in alternate fashion adjacent to each other along the length of the flexible torque tube.