Expanded – threaded – driven – headed – tool-deformed – or locked-thr – With means to indicate application of predetermined... – Axially deformable member or portion
Reexamination Certificate
2000-04-04
2001-05-01
Wilson, Neill (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
With means to indicate application of predetermined...
Axially deformable member or portion
C411S034000, C411S055000, C411S183000
Reexamination Certificate
active
06224309
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to blind fasteners for securing sheet material together and, in particular, to a blind fastener that during installation is transformed into a solid shank fastener capable of withstanding high shear and tensile loads.
Blind fasteners have become particularly useful in securing sheet materials where it is impossible to access the underside of the material. Typically such fasteners are inserted into an aperture through the material and include a threaded stem for engaging the fastener. Rotation of the stem draws an expansion member into engagement with the underside of the material. Expansion may be aided by a nut body which forces the expansion member radially outwardly to engage the underside. Upon complete expansion to fully clamp the sheet material, the exterior end of the threaded stem may be broken away to eliminate any protrusions from the exterior surface.
Such fasteners have wide application in aircraft and space vehicle assembly. However, the vibrations and sonic fatigue such vehicles are subject to causes loosening of the fasteners.
Another problem with previously available blind fasteners, such as blind rivets, is that when the expansion member is drawn against the workpiece, the deformation of the expansion member causes a gap to exist between the expansion member and the stem. This gap limits the shear and tensile load capability for the fastener. An attempt to eliminate the space between the stem and the expansion member was through the use of a blind fastener arrangement wherein the stem member had an enlarged head which when drawn up through the expansion member caused the expansion member to expand only to the size of the enlarged head on the stem. The problem with this arrangement is that the footprint or surface area of the expansion member which engaged the backside of the workpiece is limited. A limited footprint also contributed to its inability to withstand high shear and tensile loads.
Other problems with previously available blind fasteners is that they do not provide a mechanism to visually determine if the fastener was installed, fails to provide a flush surface after installation, or incorporate frangible or loose pieces which could result in damage to internal damage to components of the vehicle. Other problems with previously available blind fasteners is that they require installation through the use of an expensive installation tool.
Consequently, a need exists for an improved blind fastener arrangement which can withstand high shear and tensile loads and eliminates the problems associated with previously available blind fasteners.
SUMMARY OF THE INVENTION
The present invention is directed to a structural blind fastener capable of withstanding high shear and tensile loads which has been designed to overcome the disadvantages of previous blind fasteners. The blind fastener of the present invention includes an externally threaded core bolt which is positioned within a hollow bolt or sleeve body which is positioned within an aperture extending through two or more sheets of material to be fastened together. An internally threaded pull-up nut is positioned below the sleeve body and is threaded onto the core bolt. A portion of the pull-up nut has a smaller outside diameter so that the sleeve body partially overlaps the pull-up nut. A spring washer is positioned below the head of the core bolt and adjacent the sleeve body which provides a means of visually determining if the fastener is installed.
Following insertion of the fastener into the apertures in the overlapping sheet material the core bolt is rotated relative to the pull-up nut drawing the pull-up nut towards the head of the core bolt. As the pull-up nut is drawn towards the sleeve body, a portion of the sleeve body expands outwardly. The core bolt and pull-up nut continue to compress the sleeve body as it engages the interior surface of the sheet material. Further movement of the pull-up nut axially compresses and radially expands the sleeve body against the interior wall surrounding the aperture and the smaller diameter portion of the nut fills the gap between the core bold and the disrupted sleeve body thereby resulting in a solid shank fastener when installed. Simultaneously, the spring washer is compressed by the head of the core bolt against a head portion of the sleeve body providing a visual indication that the fastener has successfully been installed.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.
REFERENCES:
patent: 2409352 (1946-10-01), Gill
patent: 2850937 (1958-09-01), Ralston
patent: 2914106 (1959-11-01), Boyd
patent: 3136203 (1964-06-01), Davis
patent: 4007659 (1977-02-01), Stencel
patent: 4875815 (1989-10-01), Phillips, II
patent: 5498110 (1996-03-01), Stencel et al.
patent: 5919016 (1999-07-01), Smith et al.
Christie Parker & Hale LLP
Fairchild Holding Corp.
Wilson Neill
LandOfFree
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