To address labor shortages in retail stores, the automation of tasks, such as product display and disposal, using industrial robots is actively being promoted. These robots use suction grippers to grasp the products. However, conventional suction grippers often experience pad curling due to grasping pose errors, leading to air leaks and failed grasps. In this study, we proposed a curling prevention structure for suction pads to improve the grasping performance of suction grippers. Our solution focuses on a spring structure that reacts only to the parts where the force is applied. The proposed curling prevention structure consists of a ring that connects the cylinders with an elastic string. The cylinders passively applied force to the areas where curling occurred, thereby preventing curling. The design is highly versatile, as it is independent of the suction pad type. We performed experiments to evaluate the success or failure of grasping by varying the grasping angles of the robot arm for five types of products. The results showed that the range of grasping was expanded by up to 15° compared with that of conventional suction grippers. In addition, we performed experiments in which the robot grasped and conveyed products placed on store shelves using our gripper. The results showed improvements in both grasping and conveyance success rates.

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