Nut Cap with Deformable Skirt
Publication Date: 2017-Jul-25
The IP.com Prior Art Database
NUT CAP WITH DEFORMABLE SKIRT One of the challenges when developing these caps was to enable them to be fitted in close proximity to ribs and other features inside the aircraft wing as positioning fasteners in close proximity to ribs etc. is advantageous in terms of the strength of joints and the number and size of fasteners required. On the other hand caps need to be robustly adhered to the aircraft structure and resist the rigors of fuel exposure pressure and temperature cycling over the service life of the aircraft for which a reasonable width of bonding area is required. In order to maximise adhesion of the cap and enable fitment of caps in close proximity to ribs etc. the present caps were designed with an outer skirt that is offset from the base of the cap which enables sealant (adhesive) to conform to the surface of the aircraft structure (shown below).
The single walled injectable cap which is currently being developed and has advantages in terms of cost weight and installation but the concept requires an outer skirt that is in contact with the AC structure. This contact of the skirt to the panel surface forms a seal which contains the adhesive / sealant as it flows around the skirt cavity. In order to enable fitment close to ribs a 5mm radius plane is cut at the skirt base radially opposite to the inlet nozzle, this cut also forms a ‘mouse-hole’ which also creates an exit port. This is a reasonably successful concept but the amount that the skirt can be cut away is limited or else it can compromise sealant flow when the cap is installed to a flat panel.
A later iteration of the single walled cap has an elastomer skirt that is adhered or co-moulded to the (rigid) cap (below right). This concept optimises installation and sealant flow of the cap both on a flat panel and in close proximity to a rib. Although this design...