a shaft base comprising a shaft, a restraining rod, and a restraining member, wherein the shaft and the restraining rod have different rod diameters, and the restraining member is disposed on a side of the restraining rod opposite to the shaft; and

a driving mechanism assembled on the shaft base, and comprising a sleeve surrounding the shaft and the restraining rod of the shaft base, and a pressing unit movably assembled inside the sleeve, wherein the sleeve comprises an accommodation space formed therein and configured to receive the pressing unit, and a shaft hole formed in the accommodation space and configured for insertion of the shaft and the restraining rod, wherein the pressing unit comprises an inner sliding channel formed on a bottom thereof, and the restraining member and the restraining rod are slidably disposed in the inner sliding channel, the inner sliding channel has at least one through hole respectively formed on at least one side thereof and outwardly cut therethrough, wherein at least one locating member is disposed in the at least one through hole, respectively, and axially movable along the restraining member, and the at least one locating member is radially moved to restrain with or depart from the restraining rod in the at least one through hole, and the pressing unit comprises an elastic part disposed and reciprocated between the bottom of the pressing unit and the accommodation space;

the pressing unit comprising a releasing button base, a pressing base, a first elastic member and a second elastic member of the elastic part, wherein the releasing button base and the pressing base each extend out of an end of the sleeve such that they can be engaged by a user from an outside of the sleeve;

wherein a pressing member of the pressing unit can be pressed by the user to vertically downwardly move the pressing base along a sliding space of the releasing button base, and downwardly slide along the restraining member and the restraining rod, allowing the at least one locating member to engage with the restraining member, to thereby fasten the shaft base to the driving mechanism;

wherein when the user presses the releasing button base against an elastic force of the first elastic member, the releasing button base will downwardly move toward the accommodation space of the sleeve, allowing the at least one locating member to disengage from the restraining member, and then the pressing base is pushed by an elastic recovering force of the second elastic member to achieve releasing and separation of the shaft base from the driving mechanism.