Medical tools having tension bands

A medical device, comprising:

• a first link, a second link, and a band;
• the first link comprising a proximal end portion and a distal end portion, the proximal end portion of the first link being coupled to a shaft, the first link comprising an inner guide surface and an outer guide surface, the inner guide surface and the outer guide surface collectively defining a first guide channel, a portion of the inner guide surface taken within a cross-sectional plane normal to a longitudinal center line of the first guide channel being a first linear portion, and a portion of the outer guide surface taken within the cross-sectional plane being a second linear portion;
• the second link comprising a proximal end portion and a distal end portion, the proximal end portion of the second link being rotatably coupled to the distal end portion of the first link, the second link being rotatable relative to the first link about a first axis, the distal end portion of the second link comprising a connector coupled to a tool member, the tool member being rotatable relative to the second link about a second axis, and the second axis being non-parallel to the first axis;
• and
• the band comprising a proximal end portion and a distal end portion, a first band portion of the distal end portion of the band being within the first guide channel, a second band portion of the distal end portion of the band being coupled to the tool member such that the second link rotates relative to the first link about the first axis as the distal end portion of the band is moved, a planar inner contact surface of the band directly contacts the inner guide surface of the first link as the second link rotates relative to the first link about the first axis in a first direction, a planar outer contact surface of the band directly contacts the outer guide surface of the first link as the second link rotates relative to the first link about the first axis in a second direction, and
• the planar outer contact surface of the second band portion directly contacts a pulley surface of the tool member as the second band portion bends about the second axis.

A medical device, comprising:

• a first link comprising a proximal end portion and a distal end portion, the proximal end portion of the first link being coupled to a shaft, and a first guide channel being defined within the first link;
• a second link comprising a proximal end portion and a distal end portion, the proximal end portion of the second link being rotatably coupled to the distal end portion of the first link, the second link being rotatable relative to the first link about a first axis, the distal end portion of the second link comprising a connector coupled to a tool member, the tool member being rotatable relative to the second link about a second axis, the second axis being non-parallel to the first axis, and a second guide channel being defined within the second link;
• and
• a band for transmitting force through the first guide channel and the second guide channel to rotate the second link relative to the first link about the first axis, the band having a planar inner contact surface and a planar outer contact surface, the planar inner contact surface faces a first direction and directly contacts an inner guide surface of the first guide channel as the second link rotates relative to the first link about the first axis in a first rotation direction, the planar outer contact surface faces a second direction opposite the first direction and directly contacts an outer guide surface of the first guide channel as the second link rotates relative to the first link about the first axis in a second rotation direction opposite the first rotation direction;
• and
• one of the planar inner contact surface or the planar outer contact surface of the band directly contacts a contact surface of the tool member and faces a third direction non-parallel to the first direction and the second direction.