1. Field of the Invention
The present invention relates to an umbrella and, more particularly, to an opening/closing structure for an automatic umbrella which is opened and closed completely.
2. Description of the Prior Art
A conventional umbrella is employed to shield rains in a rainy day and contains a frame manually pushed to a certain position to expand the umbrella. To improve over manually expanding the umbrella, an automatic umbrella is developed and contains a button fixed on a handle to be pressed to expand the automatic umbrella automatically. However, such an automatic umbrella cannot be retracted automatically, i.e., the automatic umbrella is retracted manually, so a user will get wet during manually retracting the automatic umbrella.
However, when a driving structure drives a first tube to move upwardly relative to a second tube, a shaft assembly causes vibration, so a user cannot hold the automatic umbrella comfortably. In other words, when a screw rod of the driving mechanism drives a push post to move upwardly toward a complete opening position, inner threads on a lower end of the push post actuate the first tube to rotate relative to the second tube. Then, the shaft assembly vibrates after receiving a rotating force of the first tube, thus reducing the service life of the automatic umbrella.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.