Suitable Interhandle Distance on a Roll Box Pallet during Turning Task

Abstract

Roll box pallets (RBPs) are manual material-handling equipment with four swivel wheels, used in Japan. Although they are widely used in almost all industries, many RBP-related operator accidents have occurred in the transportation industry, usually involving injuries to the hands or feet. To decrease the likelihood of hand injuries, it is important to install special handles situated toward the inside of the frames. This study aimed to determine a suitable RBP interhandle distance for turning movements. Six healthy young males were asked to move the RBP (height, 170 cm; depth, 80 cm; width, 60 cm) by 90° at a normal speed using handles with four different interhandle distances (40, 50, 60, and 80 cm) and two loading conditions (0 and 50 kg) for approximately 1.4 m. A three-axis accelerometer attached to the lower part of the RBP was used to measure motion. Then maximum combined values of the longitudinal and lateral directions (horizontal plane) and maximum upward values were analyzed during the initial response phase. Operability was evaluated by the acceleration data, handling process duration, and subjective evaluation. Operating duration was approximately 5 s. It was longer for the 50-kg loading condition for all interhandle distances, and significant differences between interhandle distances were not observed with both loads; however, the duration tended to be shorter with wider interhandle distances in the 50-kg loading condition. Subjective evaluation ratings were similar in RBP movement durations. The maximal acceleration on the horizontal plane showed varied with different interhandle distances, probably because horizontal acceleration tends to affect RBP movement in tasks combining lateral movement and rotation. In contrast, maximum upward acceleration increased with increased loads, but was not affected by an increase in the interhandle distance. This indicates that the upward acceleration probably corresponded to the lifting of the handles while applying lateral force. The results suggest that a wider interhandle distance, e.g., 80 cm, would be suitable for RBP movements, including lateral movement and rotation.

Keywords: Roll Box Pallets (RBP), Interhandle Distance, Acceleration, Motion Analysis

DOI: 10.54941/ahfe100068