PHOTO: The best type of single-use bottle is one that collapses on itself as the water is consumed, ending up as a flat disc
LARGE PET dispenser bottles are an excellent means of storing and dispensing water in the office and home. They are much lighter than traditional glass versions which weigh close to 20kg in their five-gallon versions. A regular multi-trip PET dispenser bottle — sometimes also called a water cooler bottle, when it sits on a dispensing unit that has a refrigeration system incorporated into it — weighs around 650g by contrast.
A recent trend has been to use single-use PET dispenser bottles, which weigh even less at 330g. This saves on materials and transport costs. But the bottles still take up a lot of space. The best type of single-use bottle is one that collapses on itself as the water is consumed, ending up as a flat disc that takes up much less room than the original.
But that is easier said than done. Bottles often collapse in an irregular manner, leaving lots of space inside, even when they are completely empty. SIPA has been putting a lot of effort, together with various customers, into developing designs for large PET dispenser bottles that are fit for purpose in transport and use, and which collapse on themselves as neatly as possibleas they empty.
Collapsing sequences were simulated on computer using Finite Element Method (FEM) analysis to find the buckling mechanism that would best suit the client’s requirement.
“FEM analysis accelerates the time of investigation and reduces the number of trials aiming at the correct solution,” said Dino Zanette at SIPA. “It also aids in determining a minimum weight at which the collapsing mechanism is still functional.”
Square and round bottle shapes were analysed along with the shape of the ribs and base. Graphs of volume vs. pressure and base centre displacement vs. pressure, together with photograms of the simulation, helped the SIPA experts to better understand the collapsing phenomena and how to modify the bottle structure to get the best performance. Physical prototypes were built to verify the virtual results.
Trials have proven the reproducibility of the collapsing mechanism that was studied during the development stages. Now, fully self-collapsible containers that require the application of no external mechanical forces to deflate are in industrial production.
www.sipa.it