Lubricating cap, fastener comprising this type of cap and interference assembly process

Patent metadata

Field	Value
Publication number	US-11187259-B2
Application number	US-201716324854-A
Country	US
Kind code	B2
Filing date	Aug 11, 2017
Priority date	Aug 12, 2016
Publication date	Nov 30, 2021
Grant date	Nov 30, 2021

Abstract

The object of the invention is a cap to lubricate an inner wall of a perforation going through at least two elements of the structure. The cap comprises a tubular body and at least one lubricant reserve, and before installation in the structure said cap has a largest external diameter larger than an internal diameter (DS) of the perforation, and the cap lubricates the internal surface of the perforation when its largest external diameter is radially compressed by a wall of the perforation. The invention also concerns a fastener comprising this type of cap, and an interference assembly process for the fastener equipped with the cap. The invention is applicable to the assembly of aircraft structures.

First claim

The invention claimed is:

1. A cap for a fastener wherein when the cap is placed on the fastener, the cap is configured to lubricate an internal wall of a perforation or a sleeve with internal diameter (D S ) when part of the fastener passes through at least two structural elements characterized by the fact that the cap comprises a tubular body having an internal wall configured to encircle a portion of a body of the fastener and at least one external wall extending outwardly from the internal wall and where the internal wall and the at least one external wall are configured to form at least one reservoir containing lubricant, wherein before insertion in the perforation or in the sleeve, the cap is configured to have a largest external diameter larger than a smallest internal diameter (D S ) of said perforation or sleeve with which the cap is to be used, and by the fact that the lubricant and the cap are configured such that the lubricant of said cap will be distributed over an internal surface of the perforation or the sleeve when said cap is on said fastener and inserted into the perforation or the sleeve and is radially compressed by the internal wall of said perforation or sleeve.

2. The cap according to claim 1 in which the at least one external wall has the largest external diameter of the cap, before insertion into the perforation or the sleeve.

3. The cap according to claim 1 in which the internal wall and the external wall form, within a radial plane of the cap, a U-shaped section; this U-shaped section determines a cavity that forms the reservoir for the lubricant; the cap also features an annular piston feature able to slide with clearance into said cavity, and the piston element has at least one skirt with the largest exterior diameter of the cap before insertion.

4. The cap according to claim 1 in which the internal wall and the external wall form, in a radial plane of said cap, a U-shaped section, which determines a cavity that forms the reservoir for the lubricant, the cap also comprises an annular piston element which is able to slide into said cavity, and the piston element comprises a skirt with the largest external diameter of the cap before insertion, wherein the external wall forming an external branch of the U-section comprises at least one opening allowing said lubricant to pass through to the outside of said cavity via said opening.

5. The cap according to claim 1 in which the internal wall and the external wall form, in a radial plane of said cap, a U-shaped section, which defines a cavity that forms the reservoir for the lubricant, the cap also comprises an annular piston element which is able to slide into said cavity, and the piston element comprises a skirt having the largest external diameter of the cap before insertion, wherein the external wall forming an external branch of the U-section, or a wall of an external surface of the piston, comprises at least a channel allowing said lubricant to pass through to the outside of said cavity via said channel.

6. The cap according to claim 1 comprising at least one circumferential rib on an exterior surface of the external wall, the rib has the largest external diameter of the cap before insertion; a holding space between the rib and the tubular body, or between several ribs, forming the reservoir for the lubricant.

7. The cap according to claim 1 , in which the lubricant is in a pasty state.

8. The cap according to claim 7 , in which the lubricant comprises a blend of cetyl alcohol and fats.

9. The cap according to claim 7 in which the lubricant is covered with a solid envelope designed to self-destruct when the fastener is inserted into the perforation to release the lubricant.

10. A fastener configured to assemble at least two structural elements comprising a perforation wherein a portion of the fastener can extend into the perforation, the fastener having an enlarged head and a smooth shaft configured with, before installation, an external diameter (D 1 ) larger than an internal diameter (D S ) of the perforation or the sleeve inserted into said perforation, characterized by the fact that said fastener comprises a cap according to claim 1 , positioned on said fastener opposite the enlarged head of one distal end of the smooth shaft.

11. The fastener according to claim 10 such that the distal end of the fastener has a recess and such that the cap also has a protruding holding element matching said recess.

12. The fastener according to claim 10 such that the distal end of the fastener features traction grooves or a threading, and such that the tubular body of the cap is placed on said grooves or threading.

13. A process for assembling at least two structural elements comprising a perforation; the process involves the following steps:
assembling a cap according to claim 1 on a fastener featuring an enlarged head and a smooth shaft with, before installation, an external diameter (D 1 ) larger than an internal diameter (D S ) of the perforation or of a sleeve inserted into the perforation;
inserting the fastener and the cap into the perforation or the sleeve, the cap enters the perforation or sleeve first and lubricates the interior surface of the perforation or the sleeve when its largest external diameter is radially compressed by a wall of the perforation or of the sleeve.

14. The assembly process according to claim 13 , comprising a subsequent step in which the cap is removed from the fastener, and the fastener is configured relative to the at least two structural elements to include an end portion suitable for receiving a nut or a collar.

Assignees

• Lisi Aerospace

Inventors

• Berthou Alexandre
• Broucke Martial

Classifications

• F16B33/06

  Surface treatment of parts furnished with screw-thread, e.g. for preventing seizure {or fretting (corrosion preventing means F16B33/008; settable coatings for locking threaded members F16B39/225; deformable coatings for locking threaded members F16B39/34)} · CPC title

• F16N1/00

  Constructional modifications of parts of machines or apparatus for the purpose of lubrication · CPC title

• F16B19/05 Primary

  Bolts fastening by swaged-on collars (F16B19/08 takes precedence) · CPC title