Circumferential strain rotary detent

1. A detent device comprising:

a first hub having an axis and comprising a plurality of protruding ridges having both a radial and an axial dimension relative to the hub axis, and having a first hub connection portion; and

a second hub located co-axially outside the first hub and comprising a plurality of receiving grooves having both a radial and an axial dimension relative to the hub axis, the plurality of receiving grooves of the second hub touching the plurality of protruding ridges of the first hub when the plurality of protruding ridges and plurality of receiving grooves are aligned, the second hub having a second hub connection portion;

wherein the plurality of protruding ridges and plurality of receiving grooves have complementary mating geometries;

wherein the detent device is configured such that relative movement of the first and second hub connection portions causes a circumferential strain energy of the second hub to change, providing a variable force between the two connection portions depending on their relative position;

wherein a surface of the first hub defines a diameter and the plurality of protruding ridges extend from the surface a distance that does not exceed 4% of the diameter of the first hub; and

wherein the circumferential strain in the second hub causes at least 2% strain on the material of the second hub.

2. The detent device of claim 1 , wherein one of the plurality of protruding ridges and plurality of receiving grooves causes bending strain energy on the second hub when the plurality of protruding ridges and plurality of receiving grooves are not aligned.

3. The detent device of claim 1 , wherein one of the first and second hub comprises an engineered plastic and characterized in that the detent device is free of a lubricant between the first and second hubs.

4. The detent device of claim 1 configured to produce substantially consistent force as the first and second hub connection portions are rotated relative to each other for at least two thousand cycles of relative rotation.

5. The detent device of claim 1 , wherein the first hub is rotationally grounded to an axis of a constant torque clutch.

6. A detent device comprising:

a first hub having at least two protruding ridges and a first hub connection portion; and

a second hub configured co-axially and adjacent the first hub and having at least two receiving grooves configured to receive and contact the respective two ridges of the first hub when the grooves and ridges are aligned, the second hub further configured with a second hub connection portion;

wherein relative movement of the first and second hub connection portions changes a circumferential strain energy of the second hub thereby providing a cyclical variable force between the first and second hub connection portions comprising a holding force when all ridges are within the grooves, followed by a maximum force when all ridges are moving out of the grooves, followed by a frictional force when all ridges are outside the grooves, followed by a negative force when all ridges are moving into the grooves, and wherein these forces repeat cyclically in sequence;

wherein a surface of the first hub defines a diameter and wherein the at least two protruding ridges extend from the surface a distance that does not exceed 4% of the diameter; and

wherein the circumferential strain in the second hub causes at least 2% strain on the material of the second hub.

7. The detent device of claim 6 , wherein the first hub is co-axially within the second hub.

8. The detent device of claim 6 , wherein the second hub is co-axially within the first hub.

9. The detent device of claim 6 further comprising the first hub having at least four protruding ridges and the second hub having at least four receiving grooves.

10. The detent device of claim 9 , wherein the second hub is configured to expand circumferentially when the at least four ridges move out of the at least four receiving grooves and wherein the second hub is further configured to create a bending strain between two adjacent ridges when the at least four ridges are out of the at least four receiving grooves.

11. The detent device of claim 6 , wherein one of the first and second hub comprises an engineered plastic and characterized in that the detent device is free of a lubricant between the first and second hubs.

12. The detent device of claim 6 configured to produce substantially consistent force as the first and second hub connection portions are rotated relative to each other for at least two thousand cycles of relative rotation.

13. A detent device comprising:

a first hub having an axis and comprising a plurality of grooves having both a radial and an axial dimension relative to the hub axis, and having a first hub connection portion; and

a second hub located co-axially outside the first hub and comprising a plurality of protruding ridges extending radially inward toward the first hub and having both a radial and an axial dimension relative to the hub axis, the plurality of protruding ridges of the second hub touching the plurality of grooves of the first hub when aligned, the second hub having a second hub connection portion;

wherein the plurality of grooves and plurality of protruding ridges have complementary mating geometries;

wherein the detent device is configured such that relative movement of the first and second hub connection portions causes a circumferential strain energy of the second hub to change, providing a variable force between the two connection portions depending on their relative position;

wherein an inner surface of the second hub defines an inner diameter and wherein the plurality of protruding ridges extend from the surface a distance that does not exceed 4% of the inner diameter; and

wherein the circumferential strain in the second hub causes at least 2 % strain on the material of the second hub.