The electric fan is a very important machine in our daily life. Computers, air conditioners, hair-blowers and the like all have electric fans inside. The blades of most electric fans are disc blades. When the disc blades are rotated, a columnar current vertical to the surface of blades will be generated. However, there are other kinds of electric fans, such as cross fan. The cross fan is substantially columnar and rotated along its axial direction of the column. When the cross fan is rotated, a planar surface of air current, a so-called air wall, will be generated. The cross fan is usually disposed on the top of the automatic door of a convenience store.
Conventionally, the blades are sleeved on a rotary shaft and a rubber cap is set at the end of the shaft to support the blades to be rotated together. However, because the surface of the rotary shaft is smooth, the rubber cap can easily slide from one place to another so that the rotation of the blades will be retarded and blocked by other elements.
To solve this problem, the rubber cap usually is agglutinated with the rotary shaft by an adhesive agent to ensure that the rubber is properly fixed on the rotary shaft, but this method is not good enough. The adhesive agent cannot be effectively attached on the smooth surface of the rotary shaft and after the shaft is rotated for a while, the heat generated by rotation will undo the adhesive agent, resulting in that the rubber cap cannot be fixed on the shaft. Consequently, the blades cannot rotate effectively and the cross fan will fail.
It is therefore attempted by the applicant to deal with the above situation encountered with the prior art.