Development of a pneumatic control circuit for weightless material handling with air hoists

Air hoists are widely used in handling of heavy materials in industry. Conventional air hoists necessitate the operation of manual switches for vertical motion, thus the operator has a difficulty in operating of the switches and handling of material at the same time. To overcome such difficulty, this study develops a pneumatic control circuit for weightless material handling with air hoists. The pneumatic circuit memorizes the weight of load in terms of a pneumatic pressure. The pressure is then used as a feedback signal to achieve weightless handling of materials. To demonstrate the effectiveness of the proposed pneumatic circuit, handling forces and the response of the system for various material weights are examined through a series of experiments. The results show that the proposed pneumatic circuit for air hoists can be used in material handling with small manual operation force.