Torque-limiting device
View Patent ↗A torque-limiting driver has a handle, a body, a torque-limiting assembly and a work-piece engaging tip. The torque-limiting assembly includes an upper and lower shank that have a plurality of teeth circumferentially spaced. The teeth have a vertical face, an inclined face and a flat peak. The inclined face is defined by a radius of curvature that transitions to the flat peak. There is a spring for applying pressure across the upper and lower shank. The teeth engage for relative rotation when the handle is turned and disengage when a predetermined value of torque is exceeded.
1. A disposable torque-limiting driver comprising:
a handle and an axially extending cylindrical body;
a torque-limiting assembly within the axially extending cylindrical body, the assembly comprising:
an upper cylindrical shank;
a lower cylindrical shank;
wherein the upper cylindrical shank and the lower cylindrical shank have a plurality of teeth and an axial bore;
a spring for applying pressure across the upper cylindrical shank and the lower cylindrical shank, wherein the teeth of the upper cylindrical shank and the lower cylindrical shank engage for relative rotation, and wherein the teeth disengage when a predetermined value of torque is exceeded;
a locking screw extending through the axial bore of the upper cylindrical shank and mated with the lower cylindrical shank;
a work piece-engaging tip connected to the lower cylindrical shank; and
at least one radially extending axial protrusion extending inward on an inner surface of an axially extending hollow shaft;
wherein the upper cylindrical shank has at least one recess for receiving the at least one radially extending protrusion for locking the upper cylindrical shank relative to the lower cylindrical shank;
wherein the at least one recess is wider than the at least one radially extending protrusion, allowing the driver to rotate in reverse a predetermined distance without reverse rotation of the work piece engaging tip.
2. The disposable torque-limiting driver of claim 1 , wherein the predetermined torque is at least 1 inch pounds.
3. The disposable torque-limiting driver of claim 1 , wherein the predetermined torque is at least 30 inch pounds.
4. The disposable torque-limiting driver of claim 1 , wherein the predetermined torque is at least 60 inch pounds.
5. The disposable torque-limiting driver of claim 1 , wherein the teeth have a vertical face, an inclined face and a substantially flat peak, wherein the inclined face is defined by a first radius of curvature that transitions to the substantially flat peak and wherein the teeth spiral around the axial bore.
6. The disposable torque-limiting driver of claim 5 , wherein the vertical face terminates in a second radius of curvature that transitions to the substantially flat peak and wherein the second radius of curvature is smaller than the first radius of curvature.
7. The disposable torque-limiting driver of claim 5 , wherein the substantially flat surface is wider at the outer radius than at the inner radius and wherein the substantially flat surface is perpendicular to an axis of the upper and lower shank.
8. The disposable torque-limiting driver of claim 6 , wherein the transition from the first radius of curvature and second radius of curvature to the substantially flat peak is smooth.
9. The disposable torque-limiting driver of claim 1 , wherein the locking screw further extends through the spring and is threaded within the axial bore of the lower cylindrical shank.