FEATURE FASTENINGS & ADHESIVES
Shielding medical teams during COVID-19 patient care
Fir Tree Buttons – fastenings which are often used in
furniture manufacture – and Plastic Screw Cover Clips are playing an important role in the development of a new device designed to protect medical teams caring for COVID-19 patients, as JET PRESS explains
A
s an airborne disease, just being close to someone with COVID-19 can be fatal.
However, many healthcare workers in the NHS and overseas have to be close to patients for procedures such as intubation and extubation (inserting and removing breathing tubes) and, as a result, many catch the virus. So to help with the situation, JET PRESS is working with Rolls-Royce, Aston Martin, Multimatic, the Manufacturing Technology Centre (MTC) and the NHS on the development of the Aerosol Generating Procedure (AGP) Shield. The AGP Shield is designed to provide a high
level of protection to the medical team. Following trials in hospitals including St Bartholomew’s, The Royal London Hospital and the Royal Derby Hospital, medical teams are happy they can use the shields for patients on ventilators. They are, however, also suitable for use in Intensive Care Units and Operating Theatres, and in the future dentists may also be able to use them. Computerised Fluid Dynamics (CFD)
testing of the shield showed the spread of airborne particles is reduced by almost 90%. Furthermore, as the patients’ breath condenses on the inner surface of the shield, rather than into the room, this reduces the cleaning time in areas where procedures are undertaken.
DEVELOPING THE PROTOTYPE Rolls-Royce and MTC engineers worked closely with NHS teams to develop the first prototype
which was ready in just one week. According to Danny McGee of MTC, they used WhatsApp to get feedback from medics using the prototypes. After the initial trials, engineers from
Aston Martin and their supplier Multimatic were brought in to refine the design. The next iteration was made from Polyethylene terephthalate glycol (PET G) which allows the shield to be vacuum formed. This not only meets the high optical requirements of the medical teams but is also very strong. Silicone sheets over apertures allow the
medics to get their hands and equipment inside the shield so they can care for the patient without significant exposure to the virus. The challenge, however, was working out how to fix silicone to PET G, as Alan Pardoe of Rolls-Royce explained to Martin Critchley, group sales director of JET PRESS: “The design started off by using metal nuts and bolts to hold the silicone sheets in position; however these made the shield heavy and difficult to clean so we have been hunting for solutions. We have tried bonding the silicone directly to the shield, and have also tried various plastic fasteners, but unfortunately all of our current attempts have failed for various reasons.” For this
application, the fastener needed to be simple and quick to use, with a smooth finish on the inside to allow for easy
cleaning. It also needed to be able to cope with varying thicknesses of material as the shield itself is vacuum formed and therefore the material thickness varies from around 5mm to 2mm. While it could be single use, the main requirement was that once used it must provide a tight fit. “Some of the plastic
fasteners we have tried pull apart too easily and so
16 SEPTEMBER 2020 | DESIGN SOLUTIONS
when the medics have lifted the shield by the front silicone flaps the fasteners have ‘popped’ apart, which is obviously not a good solution,” explained Pardoe.
THE SOLUTION The answer turned out to be Fir Tree fasteners (also called Fir tree Clips or even Christmas Tree clips), which are often used in furniture manufacture – including seats on trains and planes. These small plastic studs holding the fabric on are the top of the Fir Tree Button. These were selected as they provided an easy to use, reliable, lightweight and cost effective solution. However, as the sharp end of the Fir Tree
button was exposed on the inside of the shield, it could snag on gloves and make cleaning more difficult. So, JET PRESS paired the Fir Tree Button with a Screw Cover Clip to provide a smooth finish inside. The result is an AGP shield that is strong, easy to clean, and stacks neatly. The final challenge the team faced was how
to transport the shields back and forth to the hospitals for testing. Fortunately, Aston Martin needed to road test its latest DBX model so they used moving the shields as road tests.
MAKING IMPROVEMENTS Although this solution is working well, McGee and his team at MTC believe it can still be improved so they are working on a bespoke Fir Tree Button and clip that will make the manufacturing process simpler. JET PRESS will then look at the implications of manufacturing the new fastener designs. Once this stage is complete the AGP will be
ready for mass manufacturing for use in the NHS – and potentially around the world.
Jet Press
www.jetpress.com
/ DESIGNSOLUTIONS
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