Basic investigation of a contactless air conveyor for flat products using viscous traction

Abstract

Thin, fragile products such as silicon wafers and large glass sheets are easily contaminated or damaged during transport and manipulation, and, air conveyors have been developed to bring them into contactless state during transportation process. In this study, a contactless air film conveyor for flat products is introduced. The air conveyor consists of a number of actuating cells, each of which has a square recess where two pairs of inlet and outlet ports are opened. The flat product is supported by a thin film formed between the product and the conveyor surface, and transported by the viscous traction, which is resulted from the air flow in the actuating cells. Experiments on the basic characteristics of the air conveyor are conducted. First, the results of flow measurement show that the relations between the flow rate and the varying upstream pressure keep unchangeable at different gap thicknesses. This means that the flow impedance is dependent on the valves but not the gap thickness. Then, a relatively flat pressure distribution is observed on the conveyor surface, and inversely, a wavy pressure distribution is observed in the actuating cells because pressure peak occurs at the inlet ports and pressure nadir occurs at the outlet ports. Finally, it is revealed that the viscous force decreases as the gap thickness increases when the suction flow rate is fixed. Moreover, at a fixed gap thickness, the viscous force increases if the suction flow rate is enlarged.