초록 ▼

A torque limiting instrument is disclosed configured to drive a shaft to rotate in a select direction in response to an applied torque until the applied torque reaches a predetermined threshold. Thus, when the torque limiting instrument drives a bone screw into bone, the bone screw is advanced into

A torque limiting instrument is disclosed configured to drive a shaft to rotate in a select direction in response to an applied torque until the applied torque reaches a predetermined threshold. Thus, when the torque limiting instrument drives a bone screw into bone, the bone screw is advanced into the bone until the torque applied to the torque limiting instrument reaches the predetermined threshold, at which point the torque limiting instrument will no longer communicate the applied torque to the bone screw.

대표청구항 ▼

1. A torque limiting instrument comprising: a shaft having a driving end;a cover that supports a first inclined leading surface, the cover spaced radially outward from the shaft, wherein the cover supports a plurality of pockets;a rocker member that includes a biasing member, the biasing member disp

1. A torque limiting instrument comprising: a shaft having a driving end;a cover that supports a first inclined leading surface, the cover spaced radially outward from the shaft, wherein the cover supports a plurality of pockets;a rocker member that includes a biasing member, the biasing member disposed between the shaft and the cover, the biasing member defining a second inclined leading surface, wherein the biasing member is rotatably coupled to the shaft; andan expansion member supported by the cover and disposed between the rocker member and the cover, the expansion member defining the plurality of pockets,wherein when a torque that is applied to the cover in a first direction of rotation is less than a predetermined threshold, the biasing member extends into a respective one of the pockets, such that the first inclined leading surface abuts the second inclined leading surface so as to rotatably couple the biasing member to the cover with respect to the first direction of rotation, and when the applied torque increases to the predetermined threshold, the first inclined leading surface rides along the second inclined leading surface, which causes the biasing member to urge the expansion member to expand radially outward toward the cover, until the biasing member moves out of the respective one of the pockets whereby the first inclined leading surface no longer abuts the second inclined leading surface, thereby rotationally decoupling the cover from the biasing member, andwherein the expansion member is rotatably coupled to the cover both before and after the applied torque reaches the predetermined threshold. 2. The torque limiting instrument as recited in claim 1, wherein each of the first inclined leading surface and the second inclined trailing surface is inclined in the first direction of rotation as it extends radially outward. 3. The torque limiting instrument as recited in claim 1, wherein the first inclined leading surface partially defines a respective one of the pockets and rides along the second inclined leading surface of the biasing member when the applied torque reaches the predetermined threshold, such that the biasing member is removed from the respective one of the pockets. 4. The torque limiting instrument as recited in claim 3, wherein the expansion member defines a plurality of engagement teeth that project radially outward, and the cover defines a plurality of recesses configured to receive respective ones of the engagement teeth so as to rotatably fix the expansion member to the cover, wherein the engagement teeth move radially outward within the recesses when the torque increases to the predetermined threshold. 5. The torque limiting instrument as recited in claim 1, wherein the rocker member comprises a hub that receives the shaft so as to rotatably couple the hub to the shaft, and the biasing member is rotatably fixed to the hub. 6. The torque limiting instrument as recited in claim 1, wherein the biasing member comprises a bearing that is configured to roll along the first inclined leading surface so as to urge the expansion member to expand toward the cover. 7. The torque limiting instrument as recited in claim 1, wherein the shaft extends axially out with respect to the cover. 8. The torque limiting instrument as recited in claim 1, wherein the driving end is configured to support a bone anchor and drive the bone anchor into bone. 9. The torque limiting instrument as recited in claim 1, wherein the driving end is configured to support or define a drill bit that is configured to create an opening in bone. 10. A torque limiting instrument comprising: a shaft having a driving end;a cover; andan expansion member disposed between the shaft and the cover, such that the cover is disposed radially outward with respect to the expansion member, wherein the expansion member is rotatably fixed to the cover, and is configured to expand radially outward relative to the cover from a first position whereby the expansion member is rotatably coupled to the shaft to a second position whereby the expansion member is rotatably decoupled from the shaft such that the expansion member is rotatable about the shaft; anda biasing member disposed between the shaft and the expansion member, the biasing member rotatably fixed to the shaft, wherein when the expansion member is in the first position, the expansion member is rotatably coupled to the biasing member, and when the expansion member is in the second position, the expansion member is rotatably decoupled from the biasing member such that the expansion member is rotatable about the biasing member,wherein the expansion member is in the first position when a torque is applied to the cover in a first direction of rotation below a predetermined threshold, and an increase of the applied torque to the predetermined threshold causes the expansion member to move from the first position to the second position, andwherein the applied torque causes the cover to rotate the expansion member in the first direction of rotation, such that the biasing member provides a force that urges the expansion member to expand radially outward. 11. The torque limiting instrument as recited in claim 10, wherein the expansion member defines a first inclined leading surface, the biasing member defines a second inclined leading surface configured to abut the first inclined leading surface when the applied torque is less than the predetermined threshold. 12. The torque limiting instrument as recited in claim 11, wherein the expansion member defines a plurality of first inclined leading surfaces, and a corresponding plurality of pockets partially defined by the plurality of first inclined leading surfaces, wherein the biasing member is disposed in a respective one of the plurality of pockets when the expansion member is in the first position. 13. The torque limiting instrument as recited in claim 12, wherein movement of the expansion member to the second position removes the biasing member from the respective one of the plurality of pockets. 14. The torque limiting instrument as recited in claim 12, wherein the expansion member defines a torque transfer ring that includes a flexible annular torque transfer ring body, and the pockets extend radially outward into the annular torque transfer ring body. 15. The torque limiting instrument as recited in claim 11, wherein the first inclined leading surface rides along the second inclined leading surface so as to move the expansion member from the first position to the second position when the applied torque in the first direction of rotation reaches the predetermined threshold. 16. The torque limiting instrument as recited in claim 11, wherein the biasing member comprises a bearing that is configured to roll along the first inclined leading surface so as to move the expansion member from the first position to the second position. 17. The torque limiting instrument as recited in claim 10, further comprising a hub that is rotatably fixed to the shaft and rotatably coupled to the biasing member. 18. The torque limiting instrument as recited in claim 10, wherein the expansion member is in the first position when a torque is applied to the cover below a second predetermined threshold in a second direction of rotation opposite the first direction of rotation, and an increase of the applied torque in the second direction of rotation to the second predetermined threshold causes the expansion member to move from the first position to the second position. 19. The torque limiting instrument as recited in claim 10, wherein the expansion member defines a plurality of engagement teeth that project radially outward, the cover defines a plurality of recesses configured to receive respective ones of the engagement teeth so as to rotatably fix the expansion member to the cover, and the engagement teeth move radially outward within the recesses as the expansion member moves from the first position to the second position.