Tool with end effector force limiter
The invention provides surgical or diagnostic tools and associated methods that offer user control for operating remotely within regions of the body: In some embodiments these tools include a proximally-located actuator for the operation of a distal end effector, as well as proximally-located actuators for articulational and rotational movements of the end effector. Control mechanisms and methods refine operator control of end effector actuation and of these articulational and rotational movements. A force limiter mechanism protects the end effector and manipulated objects from the harm of potentially excessive force applied by the operator. A multi-state ratchet for end effector actuation provides enablement-disablement options with tactile feedback. An articulation lock allows the fixing and releasing of both neutral and articulated configurations of the tool and of consequent placement of the end effector. A rotation lock provides for enablement and disablement of rotatability of the end effector.
1. A surgical or diagnostic tool comprising:
an end effector at a distal end of the tool;
an end effector actuator at a proximal end of the tool, the end effector actuator being rotatable about a rotation axis, the end effector actuator being operatively connected to the end effector through a linkage to deliver an actuation force from the end effector actuator to the end effector in response to movement of the end effector actuator, the linkage comprising a rod actuator, the rod actuator being independently rotatable about the same rotation axis as the end effector acuator; and
a force limiter using a leaf spring adapted to establish an upper limit on the actuation force delivered to the end effector by the end effector actuator, the leaf spring having a first end portion attached to one of the end effector actuator and the rod actuator and having a second end portion slidably engaged with and bendable away from an engagement surface at the other of the end effector actuator and the rod actuator.
2. The tool of claim 1 further comprising a handle supporting the end effector actuator, the end effector actuator being movable with respect to the handle.
3. The tool of claim 1 wherein the force limiter comprises a stop element engagable with the end effector actuator to stop its motion.
4. The tool of claim 1 wherein the force limiter is adapted to deform in response to actuation force delivered by the end effector actuator.
5. The tool of claim 1 wherein the leaf spring is preloaded to a pre-determined stress within the linkage.
6. The tool of claim 5 wherein the spring is formed from a superelastic shape memory material treated so as to bend when the upper limit of the actuation force is applied to the end effector by the end effector actuator.
7. The tool of claim 6 wherein the superelastic shape memory material has a plateau stress level, the spring bang disposed within the linkage so at to be pre-loaded at about the plateau stress level.
8. The tool of claim 1 wherein the force limiter further comprises a stop element engagable with the end effector actuator to stop its motion.
9. The tool of clam 1 wherein the end effector is operably connected to the end effector actuator at least in part through the force limiter.
10. The tool of claim 9 wherein the force limiter is disposed between the end effector actuator and the linkage.
11. The tool of claim 9 wherein the end effector actuator is operably connected to the linkage wherein a movement of the end effector actuator moves the linkage and the movement of the end effector actuator with respect to the linkage varies when the upper limit of the actuation force is reached.
12. The tool of claim 1 where the force limiter comprises a tension bearing member in the linkage, the member comprising a superelastic shape memory material.
13. The tool of claim 1 wherein the upper limit on the actuation force is a predetermined stress applied to the end effector by the end effector actuator.
14. The tool of claim 1 wherein the end effector comprises a movable force delivery surface.
15. The tool of claim 14 wherein the end effector comprises a pair of jaws.
16. The tool of claim 1 further comprising:
a shaft disposed between the end effector and the end effector actuator, and
an articulation mechanism for manipulating angular orientation of the end effector with respect to the shaft, the articulation mechanism comprising a proximal link and a distal link spaced apart from the proximal link, wherein movement of the proximal link causes corresponding relative movement of the distal link.
17. A method of operating a surgical or diagnostic tool, the tool comprising an end effector in a distal portion and an end effector actuator in a proximal portion, the method comprising:
placing the end effector at a target site;
applying an actuation force to the end effector actuator;
delivering at least some of the actuation force through the end effector to the target site using a leaf spring;
slidably engaging an end portion of the leaf spring with an engagement surface on one of the end effector actuator and the rod actuator; and
limiting a magnitude of a delivered actuation force to an upper limit through the leaf spring by bending the leaf spring away from the engagement surface;
wherein the limiting of the delivered actuation force comprises rotating the end effector actuator about a rotation axis and independently rotating a rod actuator about the same rotation axis as the end effector actuator.
18. The method of claim 17 wherein the tool further comprises a handle supporting the end effector actuator, and moving the end effector actuator comprises moving the end effector actuator with respect to the handle.
19. The method of claim 17 wherein the tool further comprises a stop element, and engaging the end effector actuator with the stop element.
20. The method of claim 17 wherein the tool further comprises a force limiter, and limiting the magnitude of the delivered actuation force further comprises deforming the force limiter.
21. The method of claim 20 wherein the force limiter comprises the leaf spring, and limiting the magnitude of the delivered actuation force comprises deforming the leaf spring.
22. The method of claim 21 wherein deforming the leaf spring comprises increasing strain of the leaf spring without substantially increasing stress of the leaf spring.
23. The method of clam 17 wherein the delivering at least some of the actuation force comprises moving the end effector, and limiting the magnitude of the delivered actuation force comprises ceasing movement of the end effector despite continued movement of the end effector actuator.
24. The method of claim 17 wherein the delivering at least some of the actuation force to the target site comprises moving the end effector.
25. The method of claim 24 wherein the end effector comprises jaws, and delivering at least some of the actuation force to the target site comprises moving the end effector jaws.
26. The method of claim 17 wherein the tool further comprises a handle supporting the end effector actuator and a shaft disposed between the handle and the end effector, the method further comprising moving the handle angularly with respect to the shaft to move the end effector angularly with respect to the shaft.