A vehicle-mounted air purifier 1 includes a main unit incorporating an ion generator. With very good water reduction power, the copolymers according to the invention scarcely retard the hardening of the concrete and ensure long processability of the concrete. The explosion resistant panels comprise a plurality of layers of explosion resistant sheets. The handle of the cane holds the batteries which drive the motor and the switch starts the motor in forward or reverse drive. A battery seat with battery is laterally inserted into the space for providing power to the circuit board. The ball drive assembly for one of the supports has a ball wheel housing containing a spherical, rigid ball, a drive shaft extending into the ball, a first driver for initiating rotating movement of the ball with respect to the ball wheel housing, and a second driver for initiating swiveling left and right movement of the ball so that it twists laterally of the ball wheel housing.