Low-friction, small profile medical tools having easy-to-assemble components
A low-friction medical device includes a first link, a second link, and a tension member. The first link is coupled to an instrument shaft and a first guide path is defined in the first link. The second link is rotatable relative to the first link through an angular range. A distal end portion of the second link is rotatably coupled to a tool member. A curved guide path is defined within the second link between the tool member and the first guide path. A curved guide surface of the second link defines a portion of the second guide path. A first portion of the tension member is parallel to a centerline of the first guide path, and a second portion is coupled to the tool member. A third portion of the tension member between the first and second portions is in contact with the curved guide surface throughout a portion of the angular range.
1 . A method of assembling an apparatus, the apparatus including a tension member and a link, the tension member including a first tension member portion, a second tension member portion, and a retention member coupled to the second tension member portion, the link defining an assembly path, a guide path, and a retention pocket, the first tension member portion having a length that is longer than the guide path defined by the link, the method comprising:
positioning the tension member in a first position in which the first tension member portion is within the assembly path; and
rotating the entire tension member about a rotation axis to a second position to move the length of the first tension member portion from the assembly path to position a portion of the first tension member portion within the guide path and to position the retention member within the retention pocket.
2 . The method of claim 1 , wherein:
the assembly path lies on a plane extending through the link; and
the plane is orthogonal to a longitudinal axis of the link.
3 . The method of claim 1 , wherein:
the link is rotatable relative to an instrument shaft about a link rotation axis;
the assembly path lies on a plane extending through the link; and
the plane is parallel to and separated from the link rotation axis.
4 . The method of claim 3 , wherein:
the guide path lies on a plane that is normal to the link rotation axis.
5 . The method of claim 1 , wherein:
the guide path and a longitudinal axis of the link define a first plane;
the assembly path lies on a second plane; and
the second plane intersects the first plane.
6 . The method of claim 5 , wherein:
the second plane is normal to the first plane.
7 . The method of claim 1 , wherein:
rotating the tension member about the rotation axis includes rotating the tension member through an installation angle; and
the installation angle has a magnitude in a range of 60 degrees to 90 degrees.
8 . The method of claim 1 , wherein:
rotating the tension member about the rotation axis moves the first tension member portion from a plane that intersects a longitudinal axis of the link to extend parallel to the longitudinal axis of the link.
9 . The method of claim 1 , wherein:
the link includes a connection path extending through a portion of link between the guide path and the retention pocket; and
a centerline of the connection path and a centerline of the guide path define a first plane such that the connection path and the guide path are coplanar within the link.
10 . The method of claim 9 , wherein:
a centerline of the assembly path is nonparallel to the centerline of the connection path within a second plane that is nonparallel to the first plane.
11 . The method of claim 9 , wherein:
the assembly path lies on a second plane extending through the link; and
the centerline of the connection path is a line of intersection between the first plane and the second plane.
12 . The method of claim 11 , wherein:
rotating the tension member about the rotation axis includes rotating the tension member about the line of intersection between the first plane and the second plane.
13 . The method of claim 1 , wherein:
the link is rotatable relative to an instrument shaft about a link rotation axis; and
the rotation axis about which the tension member is rotated is nonparallel with the link rotation axis, with a longitudinal axis of the link, and with a longitudinal axis of the first tension member portion.
14 . The method of claim 1 , wherein:
the link includes an elongated slot in fluid communication with the retention pocket; and
rotating the tension member about the rotation axis passes the retention member through the elongated slot and into the retention pocket.
15 . The method of claim 14 , wherein:
positioning the tension member in the first position includes inserting the first tension member portion into the assembly path via the elongated slot and the retention pocket.
16 . A method of assembling an apparatus, the apparatus including a tension member and a link, the tension member including a first end portion, a second end portion, and a third portion coupled between the first end portion and the second end portion, the link defining an assembly path, a guide path, and a connection path, each of the first end portion in the second end portion having a length that is longer than the guide path defined by the link, the method comprising:
positioning the third portion of the tension member on a first side of the link;
positioning the first end portion and the second end portion of the tension member on a second side of the link within the assembly path while positioning the third portion of the tension member on the first side of the link, the second side of the link being opposite the first side of the link; and
rotating the tension member as a whole about a rotation axis to move the entire length of the first end portion and the entire length of the second end portion of the tension member from the assembly path and to position the third portion within the connection path.
17 . The method of claim 16 , wherein:
the link includes an elongated slot on the first side of the link in fluid communication with a retention pocket;
the assembly path and the connection path extend through a portion of the link and into the retention pocket; and
positioning the first end portion and the second end portion of the tension member on the second side of the link includes inserting the first end portion and the second end portion through the elongated slot on the first side of the link.
18 . The method of claim 17 , wherein:
the tension member includes a retention member coupled to the third portion; and
rotating the tension member about the rotation axis positions the retention member within the retention pocket.
19 . The method of claim 16 , wherein:
the guide path and a longitudinal axis of the link define a first plane positioned between the first side of the link and the second side of the link;
the assembly path lies on a second plane; and
the second plane intersects the first plane.
20 . The method of claim 16 , wherein:
a centerline of the connection path and a centerline of the guide path define a first plane such that the connection path and the guide path are coplanar within the link;
the assembly path lies on a second plane extending through the link;
the centerline of the connection path is a line of intersection between the first plane and the second plane; and
rotating the tension member about the rotation axis includes rotating the tension member about the line of intersection between the first plane and the second plane.