1. Field of Invention
The present invention relates to a hinge unit. More particularly, the present invention relates to an auto-lock hinge unit.
2. Description of Related Art
Convertible tablet PCs (personal computer) integrate a normal notebook and tablet PC in a shell. FIG. 1 is a schematic diagram of a conventional convertible tablet PC. The convertible tablet PC 100 comprises a display unit 110, a base 130, a hinge unit 120 and a fastener unit wherein the fastener unit secures the display unit 110 to the base 130. The fastener unit is a latch or includes both a mortice 131 and a tenon 111, An easy way to convert the convertible tablet PC 100 from one operating status (such as normal notebook) to another operating status (such as tablet PC) is to directly rotate the display unit 110 in a preset rotation direction a of 180 degrees and then push the display unit 110 down to cover the base 130. To convert the convertible tablet PC 100 back to its original operation status (normal notebook), a user inverses the steps above.
During the rotation operation, while rotating the display unit 110 180 degrees, the display unit 110 can only be rotated in one direction, clockwise or counterclockwise, depending on the hinge unit 120 (for the foregoing example, rotation direction a is allowed while rotation direction b is not allowed). In other words, when rotating the display unit 110, the user has to remember the preset rotation direction, either a or b, or the hinge unit 120 may be damaged.