Key assembly used in an electronic device

1. A key assembly used in an electronic device, comprising:

a printed circuit board (PCB) comprising two optical couplers;

a key body, rotatably supported on the PCB, and comprising a circular disk and a plurality of teeth extending from periphery edge of the circular disk toward the PCB and spaced apart from each other; and

a supporting assembly to support the key body on the PCB;

wherein when the key body is rotated, the plurality of teeth interact with the two optical couplers so as to generate one or more control signals to control corresponding one or more operations of the electronic device.

2. The key assembly as claimed in claim 1 , wherein the circular disk comprises a plurality of direction key portions distributed centrosymmetrically, and the PCB further comprises a switch unit, which comprises a plurality of first dome switches corresponding to the plurality of direction key portions.

3. The key assembly as claimed in claim 2 , wherein the key body further comprises a center key received in a hole defined at center of the key body and supported on the supporting assembly, and the switch unit comprises a second dome switch corresponding to the center key.

4. The key assembly as claimed in claim 3 , wherein the key body further comprises a positioning ring disposed around the hole and extending from the circular disk toward the PCB, and the positioning ring comprises a step portion extending inward from an inner surface thereof to install the key body on the supporting assembly.

5. The key assembly as claimed in claim 4 , wherein the positioning ring comprises a plurality positioning pins, and the supporting assembly comprises a touch ring rotatably disposed around the positioning ring and a fixing plate defining a plurality of positioning holes, wherein the touch ring is positioned between the key body and the fixing plate fixed on the key body via the positioning holes engaging with the positioning pins.

6. The key assembly as claimed in claim 5 , wherein the touch ring further comprises a plurality of touch portions corresponding to the plurality of direction key portions respectively, and the supporting assembly further comprises a supporting member comprising plurality of elastic hooks engaged with the step portion of the key body and defining a plurality of through holes receiving the plurality of touch portions.

7. The key assembly as claimed in claim 6 , wherein the supporting member further comprises at least one fixing post defining a screw hole to match with a screw to fix the supporting member on the PCB.

8. The key assembly as claimed in claim 7 , wherein the supporting assembly further comprises a rubber disk located between the supporting member and the PCB, and the at least one fixing post extends through the rubber disk, the switch unit and to the PCB to match with the screw to fix the supporting member on the PCB.

9. The key assembly as claimed in claim 8 , wherein the supporting member defines a central hole, and the rubber disk comprises a central convex stage extending from one side of the rubber disk and inserted into the central hole to engage with the center key.

10. The key assembly as claimed in claim 9 , wherein the rubber disk further comprises a plurality of first padding blocks corresponding to the plurality of first dome switches respectively, and a second padding block corresponding to the second dome switch, on the other side of the rubber disk.

11. The key assembly as claimed in claim 10 , wherein the plurality of touch portions of the touch ring pass through the plurality of through holes of the supporting member and are supported on the rubber disk.

12. The key assembly as claimed in claim 11 , wherein the touch ring and the rubber disk are made of elastic rubber material.

13. The key assembly as claimed in claim 12 , wherein the supporting assembly further comprises a sliding plate disposed between the touch ring and the circular disk of the key body.

14. The key assembly as claimed in claim 13 , wherein the key body is in frictional engagement with the supporting assembly to damp rotation of the key body.