Surgical cutting instrument for robotic surgery and method
A surgical cutting instrument including a connection link connected to the distal end of a shaft having a body including integral convex ruled surfaces of connection, a first distal connecting portion; a support link articulated to the connection link and having convex ruled surfaces. A proximal connecting portion articulated to the first connection link defines a proximal rotational joint. A second distal connecting portion includes a blade holder link articulated to the support link. A blade holder link attachment root has a pulley portion, a drag portion, a blade link, a bendable cutting edge and a drag counter-portion. A reaction link articulates to the support link and to the blade/blade holder link, having a body including a pulley portion formed by convex ruled surfaces of the reaction link root. First and second distances between the first and second termination seats of the root are constant for any cutting condition.
1 . A surgical cutting instrument comprising a rod having a distal end and an articulated end-effector connected to the distal end of the rod, wherein said articulated end-effector comprises:
a connection link connected to the distal end of the rod having a body comprising in a single piece:
one or more convex ruled surfaces of connection links with parallel generator lines,
a first distal connecting portion;
a support link articulated to the connection link and having a body comprising in a single piece:
one or more convex ruled surfaces of support links with parallel generator lines;
a proximal connecting portion articulated to the first distal connecting portion of the first connection link, defining a proximal rotational joint for the connection link and the support link so that the connection link and the support link are rotatable relatively about a common proximal rotation axis;
a second distal connecting portion;
a blade holder link articulated to the support link having a body comprising in a single piece:
a blade holder link attachment root having a pulley portion formed by one or more convex ruled surfaces of blade holder root with parallel generator lines,
a drag portion
a blade link, integral in rotation with said blade holder link, having a body comprising in a single piece a cutting edge and a drag counter-portion engaged with said drag portion of the blade holder link;
a reaction link articulated to the support link and to the group formed by the blade link and the blade holder link, having a body comprising in a single piece an attachment root having a pulley portion formed by one or more convex ruled surfaces of reaction link root, with parallel generator lines; wherein:
the blade holder link attachment root and the attachment root of the reaction link define with the second distal connecting portion of the support link a distal rotational joint for the blade holder link, the reaction link and the support link, so that the blade holder link, the reaction link and the support link are relatively rotatable about a common distal rotation axis, orthogonal to said common proximal rotation axis;
a counter-blade portion which is integral in rotation with said attachment root of the reaction link; and wherein said surgical cutting instrument further comprises:
a first pair of antagonistic tendons extending along the rod and connected to the blade holder link to move the blade link about said common distal rotation axis,
a second pair of antagonistic tendons extending along the rod and connected to said reaction link to move the counter-blade portion about said common distal rotation axis,
each tendon having a longitudinal extension; and wherein:
the attachment root of the blade holder link comprises in a single piece at least a first termination seat which receives said first pair of antagonistic tendons;
the attachment root of the reaction link comprises in a single piece at least a second termination seat which receives said second pair of antagonistic tendons; and wherein:
said one or more convex ruled surfaces with parallel generator lines of the connection link are parallel to said common proximal rotation axis;
at least one of said one or more convex ruled surfaces with parallel generator lines of the support link is parallel to said common proximal rotation axis;
said one or more convex ruled surfaces of blade holder root with parallel generator lines of the blade holder link and said one or more convex ruled surfaces of further root with parallel generator lines of the reaction link are parallel to the common distal rotation axis;
the first pair of antagonistic tendons and the second pair of antagonistic tendons are adapted to slide longitudinally on said one or more convex ruled surfaces of the connection link and on said one or more convex ruled surfaces of the support link and are adapted to wind/unwind without sliding on the respective convex ruled surface of the root of the blade holder link or of the reaction link, to move the blade link and the counter-blade portion respectively in opening/closing; and wherein
the cutting edge of the blade link is adapted to abut against said counter-blade portion during the movement of the degree of freedom of opening/closing in a mechanical interference contact condition to exert a cutting action;
the cutting edge of the blade link is elastically bendable in a direction parallel to the common distal rotation axis;
a first distance in a direction parallel to the common distal rotation axis between the first termination seat of the root of the blade holder link and a surface of said one or more convex ruled surfaces of the support link is constant for any cutting condition;
a second distance in a direction parallel to the common distal rotation axis between the second termination seat of the root of the reaction link and a surface of said one or more convex ruled surfaces of the support link is constant for any cutting condition.
2 . The surgical instrument according to claim 1 , wherein the overall sliding friction force exchanged between each tendon and all the ruled surfaces of the links on which the tendon slides, when in operating conditions, is much less than the tensile force transmitted by the same tendon to achieve the elastic bending deformation of the blade portion of the blade link when the degree of freedom of opening/closing is moved in closing to exert a cutting action.
3 . The surgical instrument according to claim 1 , wherein said distal rotational joint is a rigid rotational joint in an axial direction.
4 . The surgical instrument according to claim 1 , wherein all the convex ruled surfaces of the connection link, the support link, the pulley portion of the blade holder link and the pulley portion of the reaction link lack longitudinal channels.
5 . The surgical instrument according to claim 1 , wherein the attachment root of the blade holder link comprises a first surface facing axially outwards, and wherein the root of the reaction link comprises a second surface facing axially outwards, and wherein a distance in an axial direction between said first surface of the attachment root of the blade holder link and said second surface of the attachment root of the reaction link is constant for any cutting condition.
6 . The surgical instrument according to claim 1 , wherein the blade holder link comprises in a single piece a first cantilevered drag leg extending from the root of the blade holder link forming a free first leg end, said first cantilevered drag leg axially delimiting said first termination seat; and
wherein the reaction link comprises in a single piece a second cantilevered drag leg extending from the root of the reaction link forming a free second leg end, said second cantilevered drag leg axially delimiting said second termination seat; and
wherein said first and second cantilevered legs each comprise abutment and drag walls placed undercut with respect to the respective termination seats acting as dragging abutments for the respective tendon termination;
wherein
a first distance in an axial direction between the first cantilevered leg of the blade holder link and a surface of said one or more convex ruled surfaces of the support link is constant for any cutting condition;
a second distance in a direction parallel to the common distal rotation axis between the second cantilevered leg and a surface of said one or more convex ruled surfaces of the support link is constant for any cutting condition.
7 . The surgical instrument according to claim 1 , wherein at least one of the blade holder link and the blade link comprises a free distal end in a single piece.
8 . The surgical instrument according to claim 1 , wherein the counter-blade portion protrudes axially internally.
9 . The surgical instrument according to claim 1 , further comprising a third pair of antagonistic tendons for moving the support link about said common proximal rotation axis with respect to the connection link;
wherein the support link comprises at least a third termination seat which receives the tendon terminations of said third pair of antagonistic tendons.
10 . The surgical instrument according to claim 1 , wherein the counter-blade portion protrudes axially internally, and comprises an internally curved protruding surface having a concavity facing axially inwards.
11 . The surgical instrument according to claim 1 , further comprising a third pair of antagonistic tendons for moving the support link about said common proximal rotation axis with respect to the connection link;
wherein the support link comprises at least a third termination seat which receives the tendon terminations of said third pair of antagonistic tendons; and
wherein actuation tendons of said third pair of antagonistic tendons wind/unwind without longitudinally sliding on said one or more convex ruled surfaces of the support link, which act as pulley surfaces for the actuation tendons of the third pair of antagonistic tendons.