SURGICAL INSTRUMENT WITH INCREASED ACTUATION FORCE

Abstract

A surgical instrument with improved end-effector gripping force. The instrument comprises a shaft, which may be inserted into a body of a patient. The articulated end-effector is mounted on the distal extremity of the instrument shaft and comprises a plurality of links interconnected by a plurality of joints, whose movements are remotely actuated by the surgeon's hands. This remote actuation is accomplished through mechanical transmission, mainly along flexible elements, which are able to deliver motion from a set of actuation elements, placed at a proximal extremity of the shaft, to the instrument's articulated end-effector. The articulated end-effector further comprises one or more cam-and-follower mechanisms that are able to amplify the force transmitted by the flexible elements so that the actuation force at the instrument jaws is maximized and the tension on the transmission elements minimized, thus increasing the fatigue resistance and life of the instrument.

Claims

1. An articulated surgical instrument comprising: an end-effector comprising one or more end-effector links, the one or more end-effector links comprising first and second follower geometries; a first cam having a first spiral profile rotatably coupled to the first follower geometry; a second cam having a second spiral profile rotatably coupled to the second follower geometry; and flexible mechanical transmissions coupled to the first and second cams, the flexible mechanical transmissions configured to independently rotate the first and second cams in both directions about an axis of the first and second cams to thereby actuate the end-effector with an increased actuation force while reducing tension on the flexible mechanical transmissions via the one or more follower geometries.

2. The articulated surgical instrument of claim 1, further comprising two grooved surfaces coupled to the first and second cams, the two grooved surfaces configured to receive first and second flexible mechanical transmission to independently rotate the first and second cams in both directions about the axis of the first and second cams.

3. The articulated surgical instrument of claim 1, further comprising a longitudinal instrument shaft having a lumen configured to receive the flexible mechanical transmissions.

4. The articulated surgical instrument of claim 3, further comprising a proximal extremity, and wherein the flexible mechanical transmissions are configured to transmit motion from the proximal extremity to the end-effector through the lumen of the longitudinal instrument shaft.

5. The articulated surgical instrument of claim 1, wherein a first end-effector link of the one or more end-effector links is rotatably coupled to a second end-effector link of the one or more end-effector links via an end-effector joint.

6. The articulated surgical instrument of claim 5, wherein the end-effector joint is positioned distal to the first and second follower geometries and the first and second cams.

7. The articulated surgical instrument of claim 1, wherein the increased actuation force at the end-effector is higher than the reduced tension on the flexible mechanical transmissions.

8. The articulated surgical instrument of claim 1, wherein the reduced tension on the flexible mechanical transmissions increases fatigue performance of the articulated surgical instrument.

9. The articulated surgical instrument of claim 1, wherein the reduced tension on the flexible mechanical transmissions increases usage cycles of the articulated surgical instrument.

10. The articulated surgical instrument of claim 1, wherein the reduced tension on the flexible mechanical transmissions decreases overall friction of the articulated surgical instrument.

11. The articulated surgical instrument of claim 1, wherein rotation of the first and second cams by the flexible mechanical transmissions is configured to drive movement of the first and second follower geometries along the first and second spiral profiles of the first and second cams.

12. The articulated surgical instrument of claim 1, wherein the flexible mechanical transmissions comprise at least one of cables or metal ropes.

13. The articulated surgical instrument of claim 1, wherein variances in any of spiral pitch, initial spiral radius and spiral angle of the first and second spiral profiles influence a degree of the increased actuation force at the end-effector.

14. The articulated surgical instrument of claim 1, wherein the one or more end-effector links provide at least one orientational degrees of freedom and at least one actuation degree of freedom.

15. A method of actuating an end-effector of an articulated surgical instrument, the method comprising: actuating flexible mechanical transmissions to independently rotate a first cam comprising a first spiral profile rotatably coupled to a first follower geometry of one or more end-effector links of the end-effector and a second cam comprising a second spiral profile rotatably coupled to a second follower geometry of one or more end-effector links of the end-effector to thereby drive movement of the first and second follower geometries along the first and second spiral profiles of the first and second cams and actuate the end-effector with an increased actuation force while reducing tension on the flexible mechanical transmissions via the first and second follower geometries.

16. The method of claim 15, wherein the increased actuation force is higher than the reduced tension on the flexible mechanical transmissions.

17. The method of claim 15, wherein actuating flexible mechanical transmissions to independently rotate the first and second cams comprises actuating first and second flexible mechanical transmissions received by two grooved surfaces coupled to the first and second cams.

18. The method of claim 15, wherein actuating the flexible mechanical transmissions to independently rotate the first and second cams increases fatigue performance of the articulated surgical instrument.

19. The method of claim 15, wherein actuating the flexible mechanical transmissions to independently rotate the first and second cams actuates the end-effector in one or more orientational degrees of freedom or one or more actuation degrees of freedom.

20. The method of claim 15, further comprising varying any of spiral pitch, initial spiral radius and spiral angle of the first and second spiral profiles to influence a degree of increased actuation force at the end-effector.

Description

BRIEF DESCRIPTION OF FIGURES

[0016] The invention will be better understood according to the following detailed description of several embodiments with reference to the attached drawings, in which:

[0017] FIG. 1 shows a perspective view of a surgical instrument including an articulated end-effector according to an embodiment of the invention;

[0018] FIG. 2 shows a perspective view of an articulated end-effector of a surgical instrument according to an embodiment of the invention;

[0019] FIG. 3 shows the articulated end-effector of FIG. 2 in a first active position;

[0020] FIG. 4 shows the articulated end-effector of FIG. 2 in a second active position;

[0021] FIG. 5 shows the articulated end-effector of FIG. 2 in a third active position;

[0022] FIG. 6 shows the articulated end-effector of FIG. 2 in a fourth active position;

[0023] FIG. 7 shows the articulated end-effector of FIG. 2 in a sixth active position;

[0024] FIG. 8 shows the articulated end-effector of FIG. 2 in a seventh active position;

[0025] FIG. 9 shows a perspective view of the surgical instrument of FIG. 1 with a schematic cutout of an outer tube of the longitudinal shaft of the surgical instrument, through which is it possible to see the different flexible mechanical transmission elements;

[0026] FIG. 10 shows actuation topology for a distal end-effector link according to an embodiment of the invention;

[0027] FIG. 11 shows actuation topology for a second end-effector link according to an embodiment of the invention;

[0028] FIG. 12 shows actuation topology for a cam element of a cam-and-follower mechanism according to an embodiment of the invention;

[0029] FIG. 13 shows a side view of a cam-and-follower mechanism actuating a distal articulation of an instrument's end-effector according to an embodiment of the invention;

[0030] FIG. 14 shows the cam-and-follower mechanism of FIG. 13 in a first active position;

[0031] FIG. 15 shows the cam-and-follower mechanism of FIG. 13 in a second active position;

[0032] FIG. 16 illustrates the phenomenon of force amplification of a cam-and-follower mechanism with a single-pitch spiral-profile cam element according to an embodiment of the invention;

[0033] FIG. 17 illustrates the phenomenon of force amplification of a cam-and-follower mechanism with a dual-pitch spiral-profile cam element according to an embodiment of the invention;

[0034] FIG. 18 shows a perspective view of two cam elements (reverse and actuation) rigidly attached, according to an embodiment of the invention;

[0035] FIG. 19 shows a reverse cam-and-follower mechanism in a first active position according to the embodiment shown in FIG. 18;

[0036] FIG. 20 shows a reverse cam-and-follower mechanism in a second active position according to the embodiment shown in FIG. 19;

[0037] FIGS. 21 and 22 show an embodiment of the current invention with a spring element to reverse the actuation movement, in two different working positions;

[0038] FIG. 23 shows a perspective view of a surgical instrument previously disclosed by Applicants;

[0039] FIG. 24 shows a perspective view of an articulated end-effector of the surgical instrument shown in FIG. 23;

[0040] FIG. 25 shows the actuation topology for a first distal end-effector link of the surgical instrument shown in FIG. 23;

[0041] FIG. 26 shows the actuation topology for a second distal end-effector link of the surgical instrument shown in FIG. 23;

[0042] FIG. 27 shows a perspective views of the two distal end-effector links of the surgical instrument shown in FIG. 23;

[0043] FIG. 28 shows the articulated end-effector of the surgical instrument shown m FIG. 23 achieving an actuation by the movement of the distal end-effector links;

[0044] FIG. 29 shows a free body diagram of one of the distal end-effector members of the surgical instrument shown in FIG. 23.

DETAILED DESCRIPTION OF THE INVENTION

[0045] With general reference to FIG. 1, a surgical instrument 1 for minimally invasive surgical procedures, with an articulated end-effector constructed in accordance with an embodiment of the present invention, is described herein. This instrument 1 includes a main shaft 2 with a distal end-effector 3 and a proximal extremity 4 or head. Referring to FIG. 2, the end-effector 3 is connected to the distal extremity 20 of the main shaft 2 by a proximal joint, which allows the rotation of a proximal end-effector link 6 around a proximal axis 7 in such a manner that the orientation of the proximal end-effector link 6 with respect to the main shaft axis 8 can be changed.

[0046] Referring to FIG. 2, a second end-effector link 9 is rotatably connected to the proximal end-effector link 6 by a second end-effector joint, which is represented by the second end-effector axis 10. This second end-effector axis 10 is substantially perpendicular and non-intersecting with the proximal axis 7 and substantially intersects the main shaft axis 8.

[0047] Referring to FIG. 2, the distal end-effector link 11 is rotatably connected to the second end-effector link 9 by a distal end-effector joint, which is represented by the distal end-effector axis 12. This distal end-effector axis 12 is substantially parallel to the second end-effector axis 10 and perpendicular and non-intersecting with the proximal end-effector axis 7.

[0048] By actuating the proximal joint, the proximal end-effector link 6 can be angulated over the proximal axis 7, in the range of up to ±90°, with respect to the plane containing the main shaft axis 8 and the proximal axis 7, thus providing a first orientational degree of freedom for the end effector 3. FIGS. 3 and 4 show a surgical instrument 1 according to an embodiment of the present invention with different angular displacements at the proximal joint.

[0049] By actuating the second end-effector joint, the second end-effector link 9 can be angulated, substantially up to ±90°, over the second end-effector axis 10, with respect to the plane containing the main shaft axis 8 and the second end-effector axis 10, thus providing a second orientational degree of freedom for the end effector 3 that is perpendicular to the aforementioned first orientational degree of freedom. FIGS. 5 and 6 show a surgical instrument 1 according to an embodiment of the present invention with different angular displacements at the second end-effector joint.

[0050] By actuating the distal end-effector joint, the distal end-effector link 11 can be angulated, over the distal end-effector axis 12, so that the surgical instrument is actuated in order to accomplish its function (for instance as a needle holder, scissors or forceps), thus providing an actuation degree of freedom at the end effector 3. FIGS. 7 and 8 show the surgical instrument 1 with different angular displacements at the distal end-effector joint.

[0051] With reference to FIG. 9, the main shaft 2 allows the passage of flexible elements 13, 14, 15 that are able to deliver motion to the different end-effector links 6, 9, 11, from the proximal extremity 4 or head of the instrument shaft 2. The flexible elements 13, 14, 15, may optionally take the form of metal ropes or cables which may be constructed of tungsten, steel or any other metal suitable for surgical applications.

[0052] As can be seen in FIG. 10, the flexible element 13 comprises two different segments, 13a, 13b, which form a closed cable loop between the proximal end-effector link 6 and an input element at the proximal extremity 4 of the instrument shaft 2. The proximal end-effector link 6 is operatively connected to the flexible members 13a and 13b so that it can be independently rotated in both directions along the proximal axis 7. The contact between the flexible elements 13a, 13b and the proximal end-effector link 6 is made in a grooved pulley 16, which is rigidly attached or operably connected to the proximal end-effector link 6.

[0053] As can be seen in FIG. 11, the flexible element 14 comprises two different segments, 14a, 14b, which form a closed cable loop between the proximal end-effector link 6 and an input element at the proximal extremity 4 of the instrument shaft 2. The second end-effector link 9 is operatively connected to the flexible members 14a and 14b so that it can be independently rotated in both directions along the second end-effector axis 10. The contact between the flexible elements 14a, 14b and the second end-effector link 9 is made in the grooved surfaces 9a, 9b, which have a pulley-like geometry and are part of the second end-effector link 9.

[0054] In order to increase the actuation (or gripping) force at the distal jaws 9, 11, while decreasing the tension in the flexible transmission elements, a cam-and-follower mechanism is used at the instrument's articulated end-effector 3. It comprises a cam element 17 (FIG. 12), having 2 grooved surfaces 17a, 17a, with pulley-like geometry, to which the flexible members 15a and 15b are attached, so that it can be independently rotated in both directions along the second end-effector axis 10. Rigidly attached or operably connected to these pulley-like geometries 17a, 17b (or components), a cam-profile geometry 17c (or component) is also able to rotate in both directions along the second end-effector axis 10. Another element of the cam-and-follower mechanism is the follower geometry 11a (or component), which is part of (or rigidly attached to) the distal end-effector link 11 (FIG. 13). By being in contact with the cam-profile geometry 17c of the cam element 17, the follower geometry 11a (and therefore, necessarily, the distal end-effector link 11) is driven to rotate against the second end-effector element 9 when the cam element 17 is rotating (shown in counterclockwise rotation in FIGS. 14 and 15). This movement of the distal jaws 9, 11 moving against each other corresponds to the actuation of the surgical instrument 1, wherein the actuation force can be maximized by a careful selection of the profile of the cam element 17.

[0055] In some embodiments of the current invention, by way of example but not limitation, the cam element 17 may have a spiral profile (FIG. 16), whose rotation is able to drive the movement of the follower geometry 11a or component with a force that is much higher than the tension in the flexible element 15 that is driving the rotation. As a consequence, the instrument will be able to deliver high actuation forces at the jaws, while keeping the tension in the cables at more minimal values, which increases the fatigue performance and available usage cycles of the instrument and decreases the overall friction in the system.

[0056] This aforementioned force multiplication phenomenon can be better understood with the example of the wedge analogy of FIG. 16. With reference to the above embodiment, the rotation of the spiral cam element 17 so that the point of contact with the follower geometry 11a or component is traveling from point A to point B, is equivalent to driving along a y vector a follower geometry 11a or component by moving a wedge along an x vector and having the point of contact travelling from point A to point B. The angle α of the wedge is optimally a function of the pitch of the spiral and its initial radius. The smaller the angle of the wedge, the higher the multiplication of forces, from cable tension to actuation force. Thus, variation of the wedge angle (by varying spiral pitch and initial spiral radius) can be used to ultimately control the degree of force multiplication and, consequently, the degree of reduction in cable tension.

[0057] FIG. 17 shows an alternate embodiment of the current invention, where the cam profile 17a comprises different spiral profiles (from A to C and from C to B), with different pitches p1, p2. In the same way, in other embodiments of the current invention, a wide variety of shapes and profiles can be used in the cam element 17 to drive the follower geometry 11a to move according to different movement and force patterns.

[0058] In a further alternate embodiment, and in order to reverse the movement of the jaws, a second cam-and-follower mechanism can be used. FIG. 18 shows how a reverse cam element 18 can be fixed to the actuation cam element 17 so that both cam profiles are able to rotate about the same axis 10. By being in contact with the cam element 18, the follower geometry 11b (and therefore the distal end-effector link 11) is driven to rotate away from the second end-effector element 9 when the cam element is rotating (shown rotating in a clockwise direction in FIGS. 19 and 20).

[0059] In yet another embodiment of the current invention, the reverse movement can be achieved not by a second cam-and-follower mechanism but by a spring element 19, which is able to rotate (about the axis 12) the distal end-effector link 11 back to its open position, when the cam element 17 rotates back (shown rotating clockwise in FIGS. 21 and 22) and the follower geometry 11a loses contact with the cam-profile geometry 17c of the cam element 17.

[0060] While this invention has been shown and described with reference to particular embodiments thereof, one of skill in the art will readily realise that various changes in form and details will be possible without departing from the spirit and scope of the invention as defined by the appended claims. Solely by way of example, one of skill in the art will understand that various geometries are possible for the cam-and-follower elements and that various angles are possible for the wedge element, thus impacting the force multiplication effect of the inventive system.