Iranian Journal of Ergonomics

Introduction: Nine percent of all available packaging are jars with steel lids. However, some consumers have trouble with jar opening. The aim of the current research was to analyze the exerting force on jar lids regarding the torque input to the anthropometric and physiological characteristics of the consumers.

Methods: In this study, the force distributed on the fingers and the palm was examined using a special tester consisting of Force Sensing Resistors (FSR). This tester included 19 sensors, 14 of which were installed on the fingers and 5 on the palm. Each sensor was connected to a driver via 2 wires and then to a computer by a USB port. A full jar with 1100 g weight and 85 mm lid outer diameter was used and the forces exerted by 20 participants, including 10 male and 10 female students, was recorded. Next, the Minitab 17 software was used and the mathematical relationship between the torque and anthropometric and physiological characteristics was investigated.

Results: It was found that the force is mainly exerted by the index finger. The calculation of the torque based on the force measurements showed that the maximum torque applied by males was 10.63 Nm and by females was 7.66 Nm. Statistical F test for the torque (response variable) at a significance level of 0.05 resulted in P values equal to 0.011 and 0.008 for male and female participants, respectively. Therefore, it can be concluded that the measured values are statistically significant.

Conclusions: Statistical analysis revealed that hand dimensions and grip strength play major roles in applying torque. Additionally, the results indicated that packaging conditions for the particular jar in this study must be adjusted such that the consumers with the lowest physical ability (5.11 Nm torque) could open them.