Flexible wrist for surgical tool
The present invention is directed to a tool having a wrist mechanism that provides pitch and yaw rotation in such a way that the tool has no singularity in roll, pitch, and yaw. In one embodiment, a minimally invasive surgical instrument includes an elongate shaft having a working end, a proximal end, and a shaft axis between the working end and the proximal end; and an end effector. A wrist member has a flexible tube including an axis extending through an interior surrounded by a wall. The wall of the flexible tube includes a plurality of lumens oriented generally parallel to the axis of the flexible tube. The wrist member has a proximal portion connected to the working end of the elongate shaft and a distal portion connected to the end effector. A plurality of actuation cables have distal portions connected to the end effector and extend from the distal portion through the lumens of the wall of the wrist member toward the elongate shaft to proximal portions which are actuatable to bend the wrist member in pitch rotation and yaw rotation.
1. An apparatus comprising:
an elongate shaft having a working end and a proximal end;
an end effector;
a flexible tube including a proximal portion connected to the working end of the elongate shaft and a distal portion connected to the end effector;
a plurality of actuation cables extending from the proximal end of the shaft to the flexible tube, the plurality of actuation cables comprising proximal portions which are actuatable to bend the flexible tube in pitch and yaw; and
at least one end effector actuation cable extending from the proximal end of the shaft to the end effector through a lumen formed by the flexible tube to allow actuation of the end effector; wherein the plurality of actuation cables comprises pairs of cables, each pair of cables comprising a single cable having two ends coupled to the proximal end of the elongate shaft, each pair further comprising a segment forming a U-turn around the end disk.
2. The apparatus of claim 1 , the flexible tube comprising a plurality of annular disks.
3. The apparatus of claim 2 , the plurality of annular disks comprising an end disk closest to the end effector and a middle disk, the end disk having a greater thickness than the middle disk.
4. The apparatus of claim 2 , the plurality of annular disks comprising an end disk closest to the end effector and a middle disk, the end disk including a counter bore into which an inner spring fits.
5. The apparatus of claim 2 , the end effector comprising at least one of a gripper, a cautery connection, and a tether to hold a tip thereon.
6. The apparatus of claim 2 , the annular disks comprising pairs of oppositely disposed inner tabs captured by the inner spring.
7. The apparatus of claim 2 , each annular disk comprising twelve evenly spaced holes for receiving the plurality of actuation cables.
8. The apparatus of claim 2 , further comprising a gimbal plate coupled to the proximal end of the shaft, the gimbal plate driving the plurality of actuation cables to bend the flexible tube at arbitrary angles relative to the pitch and yaw axes.
9. The apparatus of claim 2 , the flexible tube further comprising an inner spring disposed inside an interior cavity of the flexible tube, the plurality of annular disks surrounding the inner spring.
10. The apparatus of claim 9 , the plurality of annular disks threaded onto the inner spring.
11. The apparatus of claim 10 , each annular disk spaced apart from another by four coils of the inner spring.
12. The apparatus of claim 9 , the inner spring comprising edge wound flat wire.
13. The apparatus of claim 9 , the at least one end effector actuation cable further extending through a lumen formed by the inner spring.
14. A method for operating an apparatus comprising an elongate shaft having a working end and a proximal end, an end effector, and a flexible tube including a proximal portion connected to the working end of the elongate shaft and a distal portion connected to the end effector, the method comprising:
actuating a plurality of actuation cables extending from the proximal end of the shaft to the flexible tube, the plurality of actuation cables comprising proximal portions which are actuatable to bend the flexible tube in pitch and yaw; and
actuating the end effector by pushing and pulling least one end effector actuation cable extending from the proximal end of the shaft to the end effector through a lumen formed by the flexible tube; wherein the plurality of actuation cables comprises pairs of cables, each pair of cables comprising a single cable having two ends coupled to the proximal end of the elongate shaft, each pair further comprising a segment forming a U-turn around the end disk.