Low-friction, small profile medical tools having easy-to-assemble components

An apparatus, comprising:

• an instrument shaft, a tool member, a first link coupled to the instrument shaft, a second link, and a tension member;
• the instrument shaft having an axial centerline;
• the first link comprising a first guide path having a centerline, the centerline of the first guide path being offset from the axial centerline of the instrument shaft by an offset distance;
• the second link comprising a proximal end portion, a distal end portion, a second guide path, and a curved guide surface,
• the proximal end portion being coupled to the first link,
• the second link being rotatable relative to the first link about a first axis through an angular range,
• the distal end portion of the second link being coupled to the tool member, the tool member being rotatable relative to the second link about a second axis,
• the second guide path being located between the tool member and the first guide path,
• the curved guide surface defining a portion of the second guide path, the curved guide surface being characterized by a radius about the first axis, and the radius being equal to the offset distance;
• and
• the tension member comprising a first tension member portion, a second tension member portion, and a third tension member portion between the first tension member portion and the second tension member portion,
• the first tension member portion being within the first guide path,
• the second tension member portion being coupled to the tool member, and
• the third tension member portion being in contact with the curved guide surface throughout at least a portion of the angular range of the second link.

An apparatus, comprising:

• an instrument shaft, a tool member, a first link coupled to the instrument shaft, a second link, and a tension member;
• the instrument shaft having an axial centerline;
• the first link comprising a first guide path having a centerline offset from the axial centerline of the instrument shaft by a first distance;
• the second link comprising a proximal end portion, a distal end portion, and a second guide path, and a curved guide surface,
• the proximal end portion being coupled to the first link,
• the second link being rotatable relative to the first link about a first axis through an angular range,
• the distal end portion of the second link being coupled to the tool member, the tool member being rotatable relative to the second link about a second axis,
• the second guide path being located between the tool member and the first guide path,
• the curved guide surface defining a first portion of the second guide path, the curved guide surface being characterized by a radius of curvature, a center of the radius of curvature being offset from the axial centerline of the instrument shaft by a second distance, and the second distance being equal to a sum of the radius of curvature and the first distance;
• and
• the tension member comprising a first tension member portion, a second tension member portion, and a third tension member portion located between the first tension member portion and the second tension member portion,
• the first tension member portion being within the first guide path,
• the second tension member portion being coupled to the tool member, and
• the third tension member portion being in contact with the curved guide surface throughout at least a portion of the angular range of the second link.