There is reasonable design of overflow slot.In order to swimmingly clean out dirt on surface, it needs enough area and the most axial length rate, to avoid overflow dead section.

• 有合理的溢流槽设计，为了保证顺畅地清除表面脏物不仅要有足够面积，更重要的要有最大的轴向长度比，以免产生溢流盲区。