Abstract
The present report investigates consumers' gripping postures of caps when they unscrew the cap of aluminum beverage bottles so as to evaluate opening ease of the cap. We have investigated the effect of the cap diameter and the sizes of consumers' hand on gripping postures. Results from a survey on gripping postures, most of subjects have gripped the cap with two kinds of gripping postures, i.e., two-finger gripping and three-finger gripping. It is found that the gripping posture of subjects shifts from the two-finger gripping to the three-ginger gripping when the diameter reaches about φ37. In addition, the sizes of palm correlate with the transition diameter from the two-finger gripping to the three-finger gripping. Similarly, the magnitude of maximum gripping torque of the two gripping postures is inversed. Therefore, it is necessary to consider the shift of gripping postures of consumers caused by the cap diameter and individual differences in order to evaluate openability.
