Openability of vacuum lug closures.

The Vacuum Lug Closure system, or VLC, is found on many widely available
products such as jam, sauces and pickles. The closure has many useful advantages
over other closure systems, and it is popular with both manufacturers and consumers.
However, there are large groups ofpeople that have great difficulty opening products
packaged in jars with vacuum lug caps.
The goal of this project is to understand both the way in which consumers interact
with the closure, and also how the closure system works. The torque that users can
apply to ajar lid was measured using a torque sensor embedded in a modified jar.
This was then compared to a calcula~ed torque derived from grip measurements. This
second type oftest can be used to predict openability for any kind of closure by
utilising simple and quick tests and mathematically adapting strength test data. By
eliminating the need to perform more extensive tests, costs are kept to a minimum
whilst ensuring that the results are still relevant to the problem. The results from both
tests were compared with the measured forces required to open examples ofconsumer
packaging found on sale.
The results from both tests agree reasonably well, but more data is required regarding
the interaction between human skin and packaging materials. However the current
required opening torques were found to be far too high for many users. It is suggested
that a limit of 1Nm torque should be used for future packaging designs to allow over
97% ofthe UK population to openjars. The optimal diameter ofjar lid was found to
be 73 mm.