Fastener joint with sealing gasket

Abstract

A joint comprising: a first component having a face and a bore defined by a bore wall; a second component; a fastener joining the first component to the second component, the fastener comprising a head and a shaft protruding from the head; and a polysulphide gasket comprising a ring which is compressed between the head of the fastener and the face of the first component; and a collar between the shaft of the fastener and the bore wall. The gasket comprises a ring of sealing material surrounding a hole for receiving a fastener, the sealing material comprising an at least partially cured polysulphide sealant. The gasket has a region of increased thickness positioned towards the inner periphery of the ring which flows to form the collar.

Claims

1. A joint comprising: a first component having a face and a bore defined by a bore wall, the bore having a tapered opening; a second component; a fastener joining the first component to the second component, the fastener comprising a tapered head and a shaft protruding from the head; and a gasket being substantially disk-shaped before installation, the gasket comprising a fully or partially cured polysulphide sealing material, a fabric impregnated with the sealing material and only a single protrusion which is positioned towards an inner periphery of the gasket and which contains substantially none of the fabric, wherein during assembly of the joint the shaft of the fastener is inserted through the first component and at least partially through the second component, and the sealing material of the gasket engages and is compressed between the head of the fastener and the tapered opening of the first component such that the protrusion engages the tapered opening before the gasket is compressed between the shaft of the fastener and the first component, whereby the sealing material in the protrusion flows along the shaft of the fastener and forms a collar between the shaft of the fastener and the bore wall.

2. The joint of claim 1, wherein the tapered head of the fastener is received in the tapered opening of the bore.

3. The joint of claim 1, wherein the sealing material forming the gasket is loaded with conductive particles.

4. An aircraft comprising a joint according to claim 1.

5. A method of manufacturing a joint, the method comprising: mounting a substantially disk-shaped gasket on a fastener; the fastener comprising a tapered head and a shaft protruding from the tapered head, and the gasket comprising a fully or partially cured polysulphide sealing material which is in contact with the head of the fastener, wherein the gasket further comprises a fabric impregnated with the sealing material, and a protrusion which is positioned towards an inner periphery of the gasket and contains substantially none of the fabric; inserting the shaft of the fastener through a first component and at least partially through a second component until the sealing material of the gasket engages the first component; compressing the gasket between the tapered head of the fastener and a tapered opening of the first component whereby the sealing material in the protrusion flows along the shaft of the fastener and forms a collar between the shaft of the fastener and the first component; and, wherein the protrusion engages the tapered opening of the first component before the gasket is compressed between the tapered head of the fastener and the first component.

6. The method of claim 5 wherein the protrusion extends around the entire circumference of the gasket.

7. The method of claim 5 wherein the polysulphide sealing material is filled with conductive particles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

(2) FIG. 1 is a plan view of a gasket;

(3) FIG. 2 is a cross-section through the gasket;

(4) FIG. 3 is an enlarged cross-section through part of the gasket;

(5) FIG. 4 is a cross-sectional view of a joint on an aircraft, before the sealant material has flowed along the shaft of the bolt;

(6) FIG. 5 shows the bolt being pushed into the joint; and

(7) FIG. 6 shows the joint after the sealant material has flowed along the shaft of the bolt.

DETAILED DESCRIPTION OF EMBODIMENT(S)

(8) A gasket 1 shown in FIGS. 1-3 comprises a ring of sealing material with an outer periphery 2, and an inner periphery 3 surrounding a hole 4.

(9) The sealing material comprising an at least partially cured polysulphide sealant 5, and a layer of fabric reinforcement 6 shown in cross-section in FIGS. 2 and 3. The gasket has a ring-shaped protrusion 7 which is positioned towards the inner periphery 3 of the ring, and extends around the entire circumference of the ring as shown in FIG. 1. The protrusion 7 contains substantially none of the reinforcing fabric as shown in FIGS. 2 and 3.

(10) The gasket is manufactured by the following process. First, a paste of polysulphide material is mixed with a curing agent such as manganese dioxide. Various suitable sealant materials are described in EP 1548083 A1, the contents of which is incorporated herein by reference. By way of example, the material may comprise Chemetall MC238-A1/2 or PRC-De Soto International PR1770C12. Optionally the paste of polysulphide material may be filled with conductive particles, most preferably carbon nanotubes, for purposes of lightning protection.

(11) A woven cloth of glass-fibre is then impregnated with the polysulphide sealant by a conventional calendering process. The calendering process produces matrix-rich regions 8,9 shown in FIG. 3. Then the sheet is stamped to cut out the ring-shaped profile of the gasket which is placed between a pair of mould tools shaped to give the required shape to the protrusion 7. The ring is compressed between the mould tools and heated to a lightly raised temperature (no greater than 60 C.) to fully or partially cure the polysulphide material. Completion of the curing process may occur before or after assembly of the joint.

(12) A method of sealing a fastener joint with the gasket 1 is shown in FIGS. 4-6. First, the gasket 1 is mounted on the tapered head 10 of a bolt. The shaft 11 of the bolt is then passed through a pair of components 12, 13 as shown in FIG. 4, and a nut 14 is screwed onto the threaded distal end 15 of the shaft 11. As the nut is screwed tight, the gasket engages a tapered opening 16 in the first component 12 as shown in FIG. 5. At this point the gasket is un-deformed. As the nut is tightened further; the gasket 1 becomes compressed between the tapered head 10 of the bolt and the wall of the tapered opening 16. Unexpectedly, this pressure causes the polysulphide sealing material in the matrix-rich regions 8,9 and the protrusion 7 to flow along the shaft 11 of the fastener to form a cylindrical collar 18 between the shaft 11 and the wall of the cylindrical bore 19 in the first component 12 as shown in the left-hand side FIG. 6. The right-hand side of FIG. 6 shows the gasket in its un-flowed state, for comparison purposes. This can be contrasted with gaskets formed with polytetrafluoroethylene (PTFE) which tend to flow outwardly instead of flowing along the shaft 11.

(13) Conceivably, if the first component 12 is thin then the sealing material may flow as far as the second component 13. After a period of time, the sealing material bonds to the opposing surfaces of the tapered head 10, tapered opening 16, shaft 11 and the wall of the cylindrical bore 19 to form a fluid-tight seal.

(14) Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.