Development and validation of a technique to measure and compare the opening characteristics of tamper-evident bottle closures

Large sections of the population encounter difficulty in opening consumer packaging of many kinds. Screw-caps in particular can cause problems for a range of people with a variety of impairments. This paper describes the development and initial testing of a novel multi-axial force and torque transducer, designed for the study of loading conditions when tamper-evident bottle closures are opened manually. The transducer, which comprises seven beams that are sensitive to direct forces and torques in each of three axes, can provide comprehensive information on the loading conditions that occur when an instrumented bottle is opened. Importantly, the transducer has been designed to fit inside a typical 500?ml capacity plastic soft drinks bottle so that it does not interfere with the way in which the subject grips the bottle and cap, or applies forces and torques, in order to open the bottle. The method to obtain load data from the calibration matrix, along with initial opening force and torque test data from two user groups, elderly and young, is described. It is clear from the results of these tests that the elderly and young groups exhibit significantly different torque and force profiles to open bottles. It is anticipated that the transducer will be a valuable tool in future studies of opening strategies.