Torque limiting instrument

1. A torque limiting instrument comprising:

a shaft having a driving end;

a displaceable member disposed radially out from the shaft and rotatably fixed to the shaft,

a deformable gasket disposed between the shaft and the displaceable member; and

a cover that extends about the displaceable member such that the displaceable member is disposed between the cover and the deformable gasket,

wherein the cover is rotatably coupled to the displaceable member until a torque applied to the cover in a first direction of rotation reaches a predetermined threshold, at which point the cover causes the displaceable member to bias the deformable gasket to deform a sufficient distance such that the cover becomes rotatably decoupled from the displaceable member in the first direction of rotation.

2. The torque limiting instrument as recited in claim 1 , wherein the cover defines a pocket that receives the displaceable member when the applied torque force is below the predetermined threshold.

3. The torque limiting instrument as recited in claim 2 , wherein the cover includes a first leading surface that partially defines the pocket and the displaceable member includes a second leading surface, each of the first and second leading surfaces inclined in the first direction of rotation as they extend radially out with respect to a central axis of the shaft.

4. The torque limiting instrument as recited in claim 3 , wherein the first leading surface biases the displaceable member against the deformable gasket in response to the applied torque, and the deformable gasket deforms toward the central axis a sufficient distance so as to allows the displaceable member to travel out of the pocket when the torque reaches the predetermined threshold.

5. The torque limiting instrument as recited in claim 4 , wherein as the applied torque increases, the applied torque causes the first leading surface to ride along the second leading surface so as to bias the displaceable member toward the axis.

6. The torque limiting instrument as recited in claim 1 , wherein the deformable gasket elastically deforms toward a central axis of the shaft as the cover biases the displaceable member against the deformable gasket.

7. The torque limiting instrument as recited in claim 1 , wherein the deformable gasket comprises an elastomer that compresses when the cover biases the displaceable member against the deformable gasket in response to the applied torque in the first direction of rotation.

8. The torque limiting instrument as recited in claim 1 , wherein the cover defines a first trailing surface and the displaceable member defines a second trailing surface that abuts the first trailing surface, such that when a torque is applied to the cover in a second direction opposite the first direction, the cover causes the displaceable member to rotate in the second direction of rotation.

9. The torque limiting instrument as recited in claim 8 , wherein both of the first and second trailing surfaces have at least a portion that is inclined in the first direction of rotation as they extend radially out with respect to the central axis.

10. The torque limiting instrument as recited in claim 9 , wherein both of the first and second trailing surfaces extend radially with respect to the central axis along a direction that is perpendicular to the central axis.

11. The torque limiting instrument as recited in claim 1 , wherein the cover is rotatably coupled to the displaceable member until a torque applied to the cover in a second direction of rotation opposite the first direction of rotation reaches a predetermined threshold, at which point the cover causes the displaceable member to bias the deformable gasket to deform a sufficient distance such that the cover becomes rotatably decoupled from the displaceable member in the second direction of rotation.

12. The torque limiting instrument as recited in claim 11 , wherein the cover defines a first trailing surface and the displaceable member defines a second trailing surface that abuts the first trailing surface, wherein each of the first and second trailing surfaces are inclined in the second direction of rotation as they extend radially out with respect to a central axis of the shaft.

13. The torque limiting instrument as recited in claim 1 , further comprising a hub that is rotatably coupled to the shaft, wherein the displaceable member extends radially outward with respect to the hub so as to define a gap between the hub and the displaceable member, and the deformable gasket is disposed in the gap.

14. The torque limiting instrument as recited in claim 13 , wherein the hub is rotatably fixed to the displacement member.

15. The torque limiting instrument as recited in claim 1 , wherein the cover defines a plurality of first leading surfaces, the torque limiting instrument further comprising a plurality of displaceable members that define respective second leading surfaces that engage respective ones of the plurality of first leading surfaces, such that when the applied torque in the first direction of rotation is below the predetermined threshold, the second leading surfaces of the plurality of displaceable members engage respective ones of the first leading surfaces such that the cover drives the plurality of displaceable members to rotate in the first direction of rotation only until the applied torque in the first direction of rotation reaches the predetermined threshold, at which point the cover rotates in the first direction of rotation relative to the plurality of displaceable members.

16. The torque limiting instrument as recited in claim 15 , wherein the deformable gasket compresses against the hub.

17. The torque limiting instrument as recited in claim 15 , wherein the displaceable member comprises a spring member that is elastically deflectable with respect to the hub.

18. The torque limiting instrument as recited in claim 1 , wherein the displaceable member is a first displaceable member and the deformable gasket is a first deformable gasket, the torque limiting instrument further comprising:

a second displaceable member disposed adjacent the first displaceable member along the axis, the second displaceable member further disposed radially out from the shaft and rotatably fixed to the shaft;

a second deformable gasket disposed adjacent the first deformable gasket along the axis, the second deformable gasket further disposed between the shaft and the second displaceable member, such that the second displaceable member is disposed between the cover and the second deformable gasket,

wherein the cover is rotatably coupled to the second displaceable member until the torque applied to the cover in a first direction of rotation reaches the predetermined threshold, at which point the cover causes the second displaceable member to bias the deformable gasket to deform a sufficient distance such that the cover becomes rotatably decoupled from the second displaceable member in the first direction of rotation.

19. A torque limiting instrument comprising:

a grip member

a shaft having a driving end;

a torque transfer assembly having a first portion rotatably fixed with respect to the grip member, and a second portion including a gasket rotatably fixed with respect to the shaft,

wherein the second portion includes a deformable gasket that provides a force that rotatably couples the second portion to the first portion when a torque applied to the grip member in a first direction of rotation is below a predetermined threshold, and decouples the second portion from the first portion when the applied torque reaches the predetermined threshold.

20. The torque limiting instrument as recited in claim 19 , wherein the second portion is rotatably fixed to the first portion when a torque is applied to the grip member in a second direction of rotation that is opposite the first direction of rotation.