Patent GB-818144-A (GB)
Title: Improvements in or relating to detachable sealed joints for securing pliant sheet material to a support structure
Inventor: TATOM RAYMOND F
IPC: B64D37/06
Filed: 1955-11-10
Abstract: 818,144. Fuel tanks on aircraft. BOEING AIRPLANE CO. Nov. 10, 1955, No. 32206/55. Class 4. [Also in Groups XXV and XXIX] A detachable sealed joint between a pliant sheet material and a support structure comprises a securing part 28 extending along an edge of said sheet, a seating 26 formed in said support structure in which said securing part is continuously in contact, means 30 carried by said support structure which means extends at a uniform short spacing from said seating and thrust means located between said means 30 and the seating to press said securing part into sealing engagement with said seating. In the construction shown in Fig. 3 the pliant sheet material forms the wall or one of the walls of a sectional fuel tank in the wing of an aeroplane. The tank is divided into a plurality of sections the end sections being in the form of bags with one open end and the intermediate sections being in the form of sleeves. Adjacent open ends are secured to the rib structure of the wing. Each rib structure is made of sections 10 forming a generally rectangular frame with mitred butt joints. The sections 10 are held together by means of a central bulkhead plate 14 riveted to webs 16 of the sections 10 and by reinforcing plates 18 riveted to the outer margins of the webs 16. Apertures 20 are provided for the passage of liquid. Each section 10 has a pair of oppositely projecting flanges 22 and these flanges extend all round the periphery of the rib frame. To the margins of these flanges metal sheets are secured for backing the pliant walls of the tank sections. The seating 26 is a groove which extends continuously around the frame and such a groove is formed the root portion of each of the flanges 22. The means 30 is also a grooved flange having its groove facing the seating 26 and extending all round the frame. The securing part is a bead formed at the open edge or each edge of each tank section the thickness of the bead being greater than that of the adjoining wall of the tank unit. It is formed by providing a round core rod of rubber encircled by overlapping marginal edges of vulcanised rubber which form the outer layers of the tank wall and between which, in each wall, is an unvulcanised soft rubber inner layer. In Fig. 3 the bead is pressed into the groove 26 by a plurality of presser elements in the form of cam plates 36. These cam plates are of generally rectangular shape with two opposite corners rounded and the other two corners substantially right angled. Each has one or more apertures by which it can be rotated through approximately 90 degrees. Each cam plate 30 is inserted between the flange 30 and a bearing strip 34 which is substantially incompressible and which on one side bears uniformly against the bead 28 and at its opposite side had a groove 35 facing the groove in the flange 30. The cam plate is received between the groove in the flange 30 and the groove 34 and when each is rotated the bearing strip is pressed against the bead 28 and its narrow outer edge portion constricts the neck of rubber adjoining the bead against the edge of the groove 26. The diagonal dimension of the cam plate is made slightly greater than the length dimension so that once the cam plate has been rotated it remains firmly in its installed position. In a modification Fig. 6 substantially non-resilient metal clips 38 are substituted for the cam plates. Each metal clip initially has a substantial angular set and it is inserted between the groove in the flange 30 and the bead. In this construction the bearing strip 34 is unnecessary. The clip is straightened or flattened by striking it with a hammer to remove the angular set and the resultant transverse expansion of the clip compresses the bead and holds it firmly in the groove 26. Each clip has a rolled edge for engaging the bead which is of a diameter somewhat smaller than the width of the groove 26 so that the bead is deformed and the edge wedges into the groove 26 adjacent the web 16. The clips cannot therefore work loose. The clips are placed in a row so that they form a substantially continuous line and for ease of removal are provided with tabs 40. For extending the joint round sharply re-entrant corners such as the mitre joint of the frame sections 10 a rubber corner fillet 44, Fig. 11, is inserted in the corner intersection of adjoining runs of the groove 26. The fillet is grooved to receive the bead 28. The bead 28 is pressed into the groove in the fillet 44 by an L-shaped bearing member 50 pressure on which is imparted by two wedges 52 which can be driven lengthwise of the bearing member legs towards the corner and which are guided between inclined edges of the bearing member and the flanges 30. A deep notch 53 in the inside corner of the bearing member enables it to bend so that it can press uniformly on the bead. Each wedge is fixed in position by means of a serrated block 56 which engages transverse serrations on the outer face of the wedge. The block 56 is secured to the structural section 10 by means of a bolt 58 which passes through slots in the block wedge and section 10. To help to prevent seepage through the crack at the mitred butt joint between adjoining sections 10 the crack is blocked by a rubber rat-tail 48 which passes through apertures extending at the joint, through the side walls of two opposite grooves 26 and the webs 16 of the sections 10. It also passes through an aperture near the apex of the fillet 44. The rat-tail stretches as it is drawn into position and when it is released it expands in crosssection and engages the walls of the apertures and in conjunction with the fillets prevents the seepage. It also serves to hold the fillet in place during assembly.