Force limiting assembly for surgical instrument
A force limiting assembly for a surgical instrument that has a handle and a lever pivotally mounted to the handle at a pivot point for movement of an internal drive shaft. The lever is coupled to the drive shaft by a cantilever spring that is positioned within the lever. The free end of the cantilever is spaced apart from the pivot point of the lever and coupled to the drive shaft via stops positioned on the drive shaft on either side of the free end of the cantilever spring. As the lever is pivoting by a user, the forces move the drive shaft and bias the cantilever spring, thereby reducing and ultimately limiting the amount of force that a user may apply to the drive shaft via operation of the lever.
1. A force limiting assembly for a surgical instrument, comprising:
a handle;
a lever pivotally mounted to the handle at a pivot point at a first end and extending out of the handle to define a trigger at an opposing end;
a cantilever spring positioned in the lever and having a free end spaced apart from the pivot point; and
a drive shaft coupled to the free end of the cantilever spring for axial movement in response to pivoting of the lever about the pivot point.
2. The force limiting assembly of claim 1 , wherein the first end of the lever has two spaced apart arms.
3. The force limiting assembly of claim 2 , wherein two spaced apart arms of the first end of the lever extend on opposite sides of the drive shaft.
4. The force limiting assembly of claim 3 , wherein the cantilever spring has two spaced apart plates.
5. The force limiting assembly of claim 4 , wherein the two spaced apart plates extend on either side of the drive shaft.
6. The force limiting assembly of claim 5 , wherein a pivot pin extends between the two spaced apart arms of the first end of the lever and the cantilever spring to hold the cantilever spring in a preload state where the cantilever spring is partially biased position.
7. The force limiting assembly of claim 6 , wherein the drive shaft includes a first stop fixed thereto and in engagement with the two spaced apart plates of the cantilever spring.
8. The force limiting assembly of claim 7 , wherein pivoting of the lever about the pivot pin causes the two spaced apart plates of the cantilever spring to push against the first stop so that the drive shaft moves axially.
9. The force limiting assembly of claim 8 , wherein pivoting of the lever about the pivot pin causes the cantilever spring to move into a flexed state where the cantilever spring is further biased than in the preload state.
10. A method of limiting an amount of force applied to a surgical instrument having a handle and a lever pivotally mounted to the handle, comprising the steps of:
positioning a cantilever spring within the lever so that the cantilever spring has a free end spaced apart from a pivot point of the lever relative to the handle; and
coupling the cantilever spring with a drive shaft of the surgical instrument so pivoting of the lever about the pivot point causes the cantilever spring to impart a force to the drive shaft to move the drive shaft axially.
11. The method of claim 10 , wherein the cantilever spring is partially biased prior to movement of the lever relative to the handle.
12. The method of claim 11 , wherein the cantilever spring is further biased when movement of the lever exceeds a predetermined amount of desired movement of the drive shaft.
13. The method of claim 12 , wherein the cantilever spring is positioned between two stops fixed to the drive shaft.