A regular floor fan, as shown in FIG. 1, generally comprises a fan head x1, a support shank x2 used for adjusting the upright height of the fan head, and a base x3, which sequentially connected with each other. However, the adjustable range of height of the fan head x1 is restricted, because the retractable length of the support shank x2 is limited, such an electric fan can be arranged into a floor fan only, and cannot be arranged in to a desk fan. Moreover, the fan head x1, the support shank x2 and the base x3 need to be detached during package and transportation, and the user has to reassemble them together before using. The process of detachment is time-consuming, and the operation is complicated. A risk of losing some tiny parts may also exist. Further, influenced by the size of the base which is usually a regular disc-like base and the length of the support shank, the electric fan after detachment also occupies a large space even if it can be detached into several parts and packed up separately, which greatly increase the cost of package and transportation. Besides, the user has to reassemble the floor fan every time when using it, which requires using extra tools. This is inconvenient for immediate usage of the fan while increasing the operation burden of the users.
Aiming at overcoming the shortcomings in the above-mentioned floor fan, the invention with U.S. Pat. No. 8,734,109 disclosed a foldable electric fan, which enables the folding and storage of the fan by adding a turnover mechanism in it and enables the folding of the fan base by a transforming the structure of the base. This invention has overcome the shortcomings mentioned above by enabling the folding and storage of the floor fan.
Specifically, referring to FIGS. 2-10, the said foldable electric fan comprises a fan head X1, a turnover mechanism X4 that is used to turn the fan head up and down, a support tube X2 and a base X3. The support tube X2 comprises two erect tubes X21 and two height adjusting tubes X22 which engaging with the two elect tubes X21 respectively. The turnover mechanism X4 comprises a connecting block X41 connected on the top of the two height-adjusting tubes X22, an automatic position-limit and locking mechanism X42 for limiting and locking the connecting block X41 on the support tube X2, and a fan head joining tube X43 connected on the middle part of the top of the connecting block. The both sides of the connecting block X41 are movably hanged to the two height-adjusting tubes X22 through axes (X411 and X412); the said automatic position-limit and locking mechanism X42 is arranged in the hanging position of the connecting block X41 and one of the height-adjusting tubes X22. Referring to FIG. 5, the automatic position-limit and locking mechanism X42 is able to tightly lock the connecting block X41 by a spring bolt X421 arranged on the top of one side of the connecting block X41 and a locating hole 42 on the top of one of the height-adjusting tube. Or, referring to FIG. 6, the automatic position-limit and locking mechanism X42 is able to lock the connecting block X41 by a pawl ratchet assembly X′421 installed between the end of the connecting block X41 and one of the height-adjusting tube. The said fan head joining tube X43 is connected to the said fan head X1 on the top.
Referring to FIG. 4 and FIG. 7, the structures enabling the folding of the base X3 include a stationary base X31, a vertical moveable base X32 and a horizontal moveable base X33. The vertical moveable base X32 is articulated with the stationary base 31 by a first door hinge and thus can be turned upward to be folded and restored. The horizontal moveable base X33 is articulated with the middle part of the stationary base X31 by a vertical second door hinge and can be horizontally folded toward one side of the stationary base X31. Meanwhile, referring to FIG. 4 and FIG. 8, in order to ensure the supporting stability of the base X3 in normal use, by the locking bolts (X7 & X8) arranged on the stationary base X31 respectively working with the locking hole X9, the vertical moveable base X32 and the horizontal moveable base X33 can be locked tightly on the stationary base X31. Or referring to FIG. 9 or FIG. 10, the base X′3 can be folded in another way: the base X′3 comprises a stationary base X′31 and a rotatable base X′32. The rotatable base X′32 is in detachable joint with the stationary base X31 by a lock nut X′7, a fastening bolt X′8 and a lock screw X′9 (as referred in FIG. 9) or just by the screw X″7 (as referred in FIG. 10).
Although the structure of the above foldable electric fan has overcome the shortcomings of the floor fan, however, certain defects remain in the said foldable electric fan:    1) The upward and downward turnover of the fan head X1 is enabled by the turnover mechanism X4 through the vertical rotation of connecting block X41, the two sides of which are movably articulated with the top of two height-adjusting tubes X22, around the axis between the top of two height-adjusting tubes X22, and the said connecting block X41 is in flat bar shape, and tend to be influenced by the weight of the fan head X1 which will lead to deformation when the force is too strong. Beside, the turnover flexibility of the turnover mechanism X4 will be decreased because the two sides of the connecting block X41 tend to be influenced by the force exerted by the fan head X1, and thus reduces the working life of the turnover mechanism X4;    2) The locking and locating to the turnover mechanism X4 depends on the automatic position-limit and locking mechanism X42 arranged at the articulating position of the one side of the connecting block X41 and the corresponding height-adjusting tubes, therefore, either the automatic position-limit and locking mechanism X42 of the spring bolt X421 structure or the automatic position-limit and locking mechanism X42 of pawl ratchet assembly X′421 structure, is enabling the locking and locating the turnover mechanism X4 through one direction, which may lead to the instability of the turnover mechanism X4 and increase the burden of the automatic position-limit and locking mechanism X42.    3) It can be known from the structure of the base that it has two embodiments: dividing into two part (stationary base X′31 and rotatable base X′32) or dividing into three parts (a stationary base X31, a vertical moveable base X32 and a horizontal moveable base X33) to enable the folding of the base. When the structure of the base is divided into stationary base X′31 and rotatable base X′32, the separation of the stationary base X′31 and rotatable base X′32 requires disassembling a lock nut, a fastening bolt and a lock screw when packing or folding, thus increase the complexity of the operation and the time for folding and produce many scattered components that is easily lost. Meanwhile, when the structure of the base is divided into a stationary base X31, a vertical moveable base X32 and a horizontal moveable base X33, because it requires locking the three locking bolts by hands to enable the locking when the vertical moveable base X32 and horizontal moveable base X33 is in normal use, and because the fulcrum is on the locking bolts, deformation of the moveable base and movement of position of the locking hole may occur during long-term usage, which may provide difficulty of installation in repeated folding and reduce the utility of the fan.