Double-shell lightning protection cap with improved assembly
A lightning protection cap is for sealing an attachment element attached to the structure of an aircraft. The lightning protection cap includes an inner shell defining an interior volume for receiving the attachment element and an outer shell configured to cover the inner shell. The inner and outer shells include complementary first and second attachment devices capable of cooperating to enable engagement of the outer shell on the inner shell. First and second attachment devices are configured to angularly lock the outer shell relative to the inner shell when the outer shell is rotated relative to the inner shell.
1 . A lightning protection cap for sealing an attachment element attached to the structure of an aircraft, the lightning protection cap comprising: an inner shell defining an interior volume for receiving the attachment element and an outer shell configured to cover the inner shell, the inner and outer shells comprising complementary first and second attachment means configured for cooperating to enable engagement of the outer shell on the inner shell;
wherein one of the inner shell or the outer shell comprises the second attachment means, said second attachment means comprising at least one lug; and
wherein the other of the inner shell and the outer shell comprises the first attachment means, including a ramp and a protuberance separated from the ramp to form a housing between the ramp and the protuberance, said ramp, said housing and said protuberance being circumferentially and consecutively arranged with said housing intermediate said ramp and said protuberance, said ramp being configured to allow the lug to slide until reaching the housing when the outer shell is rotated relative to the inner shell, in order for the housing to angularly lock the outer shell relative to the inner shell.
2 . The lightning protection cap according to claim 1 , wherein the first attachment means comprises a single assembly formed by the protuberance and the ramp, the protuberance being separated from the ramp to form the housing.
3 . The lightning protection cap according to claim 1 , wherein the housing comprises an upper stop and said at least one lug comprises an edge bearing against said stop when the outer shell is locked angularly relative to the inner shell, to lock the outer shell axially relative to the inner shell.
4 . The lightning protection cap according to claim 1 , wherein the second attachment means comprise a plurality of lugs distributed around the circumference of an inner surface of the outer shell.
5 . The lightning protection cap according to claim 1 , wherein the shell comprising the first attachment means further comprises a plurality of protuberances distributed around the circumference of an outer surface of said shell.
6 . The lightning protection cap according to claim 1 , wherein the inner shell and the outer shell are made of polyethyleneimine (PEI).
7 . The lightning protection cap according to claim 1 , wherein the outer shell is bell-shaped, said outer shell comprising a flared portion and a dome surmounting the flared portion, said at least one lug being located at the flared portion.
8 . The lightning protection cap according to claim 1 , wherein the inner shell comprises a cylindrical portion and a dome surmounting the cylindrical portion, the sliding ramp, the protuberance, and the housing being located at the cylindrical portion.
9 . The lightning protection cap according to claim 1 , wherein the shell comprising the first attachment means further comprises an annular protuberance delimiting the ramp, the protuberance, and the housing.
10 . An attachment device configured to attach to an aircraft structure comprising an attachment element and the lightning protection cap according to claim 1 , wherein said lightning protection cap is mounted on the attachment element to cover said attachment element.
11 . The lightning protection cap according to claim 1 , wherein the first attachment means consists of a single assembly formed by the protuberance and the ramp, the protuberance being separated from the ramp to form the housing.