Cable length conserving medical instrument
An apparatus includes a wrist, an end effector, a cable pair, and a transmission. A proximal wrist portion is coupled to a distal end portion of a shaft. Actuation of the wrist moves a distal wrist portion relative to the proximal wrist portion. The end effector is coupled to the distal wrist portion, and can be actuated to move relative to the wrist. The transmission is coupled to a proximal end portion of the shaft, and can move an end of the cable pair to actuate the end effector. The end of the cable pair is routed through a transmission cable path within the transmission. The transmission includes an adjustment mechanism having an input portion that receives a force exerted by the end of the cable pair. The adjustment mechanism is configured to change a length of the transmission cable path in response to a change in the force.
1. An apparatus, comprising:
a shaft comprising a proximal end portion and a distal end portion;
a wrist assembly comprising a proximal wrist portion and a distal wrist portion, the proximal wrist portion being coupled to the distal end portion of the shaft, actuation of the wrist assembly producing movement of the distal wrist portion relative to the proximal wrist portion, the wrist assembly defining a first wrist cable path, a second wrist cable path, and a length of the first wrist cable path changing when the distal wrist portion moves relative to the proximal wrist portion;
an end effector coupled to the distal wrist portion, actuation of the end effector producing movement of the end effector relative to the distal wrist portion, the end effector having a first tool and a second tool;
a first cable pair routed through the first wrist cable path, the first cable pair comprising a first end and a second end, and the first end of the first cable pair being coupled to the first tool of the end effector;
a second cable pair routed through the second wrist cable path within the wrist assembly, a length of the second wrist cable path changing when the distal wrist portion moves relative to the proximal wrist portion, and a first end of the second cable pair being coupled to the second tool of the end effector; and
a transmission coupled to the proximal end portion of the shaft, the transmission comprising a first capstan, a second capstan, a first transmission cable path, a second transmission cable path, and an adjustment mechanism,
the first capstan being configured to move the second end of the first cable pair to actuate the first tool of the end effector, the second end of the first cable pair being routed through the first transmission cable path within the transmission,
the second capstan being configured to move a second end of the second cable pair to cause the second cable pair to actuate the second tool of the end effector, the second end of the second cable pair being routed throuqh the second transmission cable path within the transmission,
the adjustment mechanism being configured to simultaneously change a first length of the first transmission cable path and a second length of the second transmission cable path in response to a change in the length of the first wrist cable path and the second wrist cable path, and
the adjustment mechanism being between the first capstan and the shaft.
2. The apparatus of claim 1 , wherein:
the adjustment mechanism comprises a movable member operably coupled to the first cable pair and the second cable pair; and
movement of the movable member increases the length of one of the first transmission cable path or the second transmission cable path and decreases the length of the other of the first transmission cable path or the second transmission cable path.
3. The apparatus of claim 2 , wherein:
the second end of the first cable pair exerts a first force on a first side of the movable member;
the second end of the second cable pair exerts a second force on a second side of the movable member; and
movement of the movable member is produced by a difference between the first force and the second force.
4. The apparatus of claim 2 , wherein:
the movable member comprises a first pulley and a second pulley;
a portion of the second end of the first cable pair is wrapped about and exerts a first force on the first pulley;
a portion of the second end of the second cable pair is wrapped about and exerts a second force on the second pulley; and
the movable member is configured to move within the transmission in response to a difference between the first force and the second force.
5. The apparatus of claim 2 , wherein:
the movable member is rotatable within the transmission about a pivot axis;
rotation of the movable member in a first direction about the pivot axis increases the length of the first transmission cable path and decreases the length of the second transmission cable path; and
rotation of the movable member in a second direction about the pivot axis decreases the length of the first transmission cable path and increases the length of the second transmission cable path.
6. The apparatus of claim 2 , wherein:
the first capstan comprises a first capstan portion about which the second end of the first cable pair is wound, the first capstan being configured to rotate about a first axle to move the second end of the first cable pair, and the first axle being configured to move within the transmission to change the length of the first transmission cable path;
the second capstan comprises a second capstan portion about which the second end of the second cable pair is wound, the second capstan being configured to rotate about a second axle to move the second end of the second cable pair, and the second axle being configured to move within the transmission to change the length of the second transmission cable path; and
the movable member is a link connecting the first capstan to the second capstan such that a first movement of the first axle causes a second movement of the second axle.
7. The apparatus of claim 6 , wherein:
the transmission further comprises a first drive coupling, a second drive coupling, a first drive spindle and a second drive spindle;
the first drive coupling couples the first drive spindle to the first capstan so that rotation of the first drive spindle causes the first capstan to rotate about a first axis; and
the second drive coupling couples the second drive spindle to the second capstan so that rotation of the second drive spindle causes the second capstan to rotate about a second axis.
8. The apparatus of claim 1 , wherein:
the adjustment mechanism comprises a movable member operably coupled to at least the second end of the first cable pair;
the movable member is configured to move within the transmission in response to a change in a tension force exerted by the first cable pair on the movable member; and
the length of the first transmission cable path changes in response to movement of the movable member.
9. An apparatus, comprising:
a shaft comprising a distal end portion and a proximal end portion;
a wrist assembly comprising a proximal wrist portion and a distal wrist portion, the proximal wrist portion being coupled to the distal end portion of the shaft, and actuation of the wrist assembly producing movement of the distal wrist portion relative to the proximal wrist portion;
an end effector coupled to the distal wrist portion, actuation of the end effector producing movement of the end effector relative to the distal wrist portion, the end effector comprising a first tool and a second tool;
a first cable pair comprising a first end and a second end, the first end being coupled to the first tool of the end effector;
a second cable pair comprising a first end and a second end, the first end being coupled to the second tool of the end effector; and
a transmission coupled to the proximal end portion of the shaft, the transmission comprising a first capstan, a second capstan, and an adjustment mechanism,
the first capstan being configured to move the second end of the first cable pair to cause the first cable pair to actuate the end effector,
the second capstan configured to move the second end of the second cable pair to cause the second cable pair to actuate the second tool of the end effector;
a first transmission cable path being defined within the transmission,
a second transmission cable path is defined within the transmission,
the second end of the first cable pair being routed through the first transmission cable path,
the second end of the second cable pair is routed through the second transmission cable path;
the adjustment mechanism comprising a movable member that comprises a first input portion and a second input portion, the first input portion receiving a first force exerted by the second end of the first cable pair and the second input portion receiving a second force exerted by the second end of the second cable pair, wherein
movement of the movable member simultaneously increases one of the length of the first transmission cable path or the length of the second transmission cable path and decreases the other of the length of the first transmission cable path or the length of the second transmission cable path in response to a change in the first force or the second force, and the adjustment mechanism being between the first capstan and the shaft.
10. The apparatus of claim 9 , wherein movement of the movable member is produced by a difference between the first force and the second force.
11. The apparatus of claim 9 , wherein:
the first input portion comprises a first pulley, and the second input portion comprises a second pulley;
a portion of the second end of the first cable pair is wrapped about and exerts the first force on the first pulley;
a portion of the second end of the second cable pair is wrapped about and exerts the second force on the second pulley; and
the movable member is configured to move within the transmission in response to a difference between the first force and the second force.
12. The apparatus of claim 9 , wherein:
the adjustment mechanism comprises a bearing;
the movable member is configured to translate within the transmission and comprises a bearing surface in sliding contact with the bearing;
translation of the movable member in a first direction along the bearing surface increases the length of the first transmission cable path and decreases the length of the second transmission cable path; and
translation of the movable member in a second direction along the bearing surface decreases the length of the first transmission cable path and increases the length of the second transmission cable path.
13. The apparatus of claim 12 , wherein:
the bearing is a first roller bearing;
the adjustment mechanism comprises a frame and a second roller bearing;
the frame is positioned within the transmission;
the first roller bearing is coupled to the frame about a first pin;
the second roller bearing is coupled to the frame about a second pin; and
the movable member is configured to translate along a linear path defined between a centerline of the first pin and a centerline of the second pin.
14. The apparatus of claim 12 , wherein:
the adjustment mechanism comprises a frame positioned within the transmission; and
the frame comprises a stop surface configured to engage the movable member to limit movement of the movable member.
15. The apparatus of claim 12 , wherein:
the movable member is configured to translate along a linear path substantially collinear with a longitudinal centerline of the movable member;
the bearing surface of the movable member is a first bearing surface in contact with a first side of the bearing; and
the movable member comprises a second bearing surface in contact with a second side of the bearing.
16. The apparatus of claim 9 , wherein:
the second end of the first cable pair is wound about the first capstan;
the first capstan is configured to rotate about an axle to move the second end of the first cable pair; and
the axle is configured to move within the transmission to change the length of the first transmission cable path.