An open and shut case for large enclosures

Large cases and enclosures frequently have heavy lids and doors. From a user point of view, this becomes an issue when the supported weight is too heavy for comfort; the weight is lighter, but the frequency of opening is high; or the application requires a lid to remain open without support. In these situations, gas struts offer an ideal solution in place of more traditional locking hinges, as they are able to counteract part, or all, of the load from the lid, plus they are also far cheaper than other powered alternatives, such as actuators or spring loaded return arms. Until recently, gas struts have been hampered by having a single fixed load rating. Different scenarios require different degrees of load to be taken by the gas strut, which can make specification difficult when choosing a suitable pressure, especially for single, variable or short-run applications. Manufacturers will fill struts with a bespoke gas pressure, but part costs or order numbers typically end up being very high, relative to the product value. Fortunately, adjustable gas struts are now available that allow users to tailor the product to their exact needs. Pressurised gas strut Large metal or composite enclosures are ideal for protecting valuable or delicate contents from external hazards, but, when access is required, it can prove extremely awkward to lift the lid and keep it open. Pioneered by the car industry for tailgates and often bonnets, in these situations a pressurised gas strut is the right solution to share a degree of the required opening force against the lid to reduce the apparent weight for the user. Depending on the applications, this may extend to supporting the entire weight or, in some cases that require self-opening lids, slightly more. As the range of possible requirements is so large, and a pressure difference of just a few Newton metres can make a gas strut unfit for purpose, many suppliers are now supplying self-adjusting gas struts that can be easily adjusted to suit individual requirements. Different forces at work Chris Putman, sales and marketing director for leading UK component supplier WDS, explained: "If you were to take a sample group of 100 applications where a gas strut was required to support an enclosure lid, I would happily bet that no two application required the same force. Some applications require the gas strut to simply reduce the weight of the lid, while others may require the lid to be held in place. In the first example, the accuracy of the force isn't as critical, so long as it does not exceed the closing force of the lid; however, the second requires the exact closing force of the lid to be matched. "Where an OEM may require many gas struts to perform the same function, then, once they have identified the ideal pressure for their application, we are able to supply them with fixed pressure products, which have been pre-loaded with the correct force," said Putman. "The products in our range are able to supply forces of between 20Nm and 2,500Nm. We use high quality materials for the adjusting valve and seals to ensure that constant and precise pressure is maintained, once adjustment is complete," he concluded.