Conformal clearance fit fastener, fastener system, and method for composite structures

Patent metadata

Field	Value
Publication number	US-10385908-B2
Application number	US-201615087841-A
Country	US
Kind code	B2
Filing date	Mar 31, 2016
Priority date	Mar 31, 2016
Publication date	Aug 20, 2019
Grant date	Aug 20, 2019

Abstract

A fastener includes an elongated shaft having a first end, a second end, and a shaft body, a head portion, and a threaded portion. At least one inner feed channel extends through the head portion and the shaft body and terminates proximal to the threaded portion. The fastener has a plurality of flutes formed along and circumferentially spaced around an outer surface of the shaft body and an outer surface of the head portion. Each flute has a first end and extends from a first location proximal to the threaded portion, along the outer surface of the shaft body, and radially outward along the outer surface of the head portion. The fastener further has one or more lateral feed channels formed laterally through the shaft body and connecting the inner feed channel to at least two opposing flutes on the outer surface of the shaft body.

First claim

What is claimed is:

1. A fastener comprising:
an elongated shaft having a first end, a second end, and a shaft body disposed between the first end and the second end;
a head portion disposed at the first end;
a threaded portion disposed at the second end;
at least one inner feed channel extending from an opening in the head portion, through the head portion and the shaft body, along a longitudinal central axis of the elongated shaft, and terminating proximal to the threaded portion;
a plurality of flutes formed along and circumferentially spaced around an outer surface of the shaft body and an outer surface of the head portion, each flute having a first end extending from a first location proximal to the threaded portion, along the outer surface of the shaft body, and radially outward along the outer surface of the head portion; and
one or more lateral feed channels formed laterally through the shaft body, each lateral feed channel connecting the inner feed channel to at least two opposing flutes on the outer surface of the shaft body.

2. The fastener of claim 1 wherein the shaft body has a substantially straight outer profile.

3. The fastener of claim 1 wherein the shaft body has a tapered outer profile.

4. The fastener of claim 1 wherein when the fastener is installed into a corresponding fastener hole, the at least one inner feed channel, the one or more lateral feed channels, and the plurality of flutes are configured to transport and deposit a conductive fluid injected into the fastener, to one or more areas between an outer surface of the fastener and inner surface of the corresponding fastener hole.

5. The fastener of claim 1 wherein the elongated shaft has at least two sets of the one or more lateral feed channels formed laterally through the shaft body, the at least two sets being spaced apart from each other.

6. The fastener of claim 1 wherein each flute extends radially outward along the outer surface of the head portion and terminates at a second end, the second end comprising one of a second location proximal to an outer periphery of the head portion, and a periphery opening at the outer periphery of the head portion.

7. A fastener system for providing improved electrical contact with a composite structure, the fastener system comprising:
one or more fasteners configured for installation in one or more corresponding fastener holes formed in the composite structure, each fastener comprising:
an elongated shaft having a first end with a head portion, a second end with a threaded portion, and a shaft body disposed between the first end and the second end;
at least one inner central feed channel extending from an opening in the head portion, through the head portion and the shaft body, along a longitudinal central axis of the elongated shaft, and terminating proximal to the threaded portion;
a plurality of flutes formed along and circumferentially spaced around an outer surface of the shaft body and an outer surface of the head portion, each flute extending from a first location proximal to the threaded portion, along the outer surface of the shaft body, and radially outward along the outer surface of the head portion; and
one or more lateral feed channels formed laterally through the shaft body, each lateral feed channel connecting the inner central feed channel to at least two opposing flutes on the outer surface of the shaft body;

an injection tool assembly configured for coupling to each of the one or more fasteners installed in the one or more corresponding fastener holes; and
a conductive fluid injected via the injection tool assembly into each fastener installed in the composite structure, the conductive fluid transported and deposited via the at least one inner central feed channel, the one or more lateral feed channels, and the plurality of flutes of each fastener, to one or more areas between an outer surface of the fastener and an inner surface of a corresponding fastener hole of the composite structure,
wherein the conductive fluid provides electrical contact between carbon fibers of the composite structure and the one or more fasteners installed in the one or more corresponding fastener holes of the composite structure, resulting in the fastener system providing electrical contact with the composite structure.

8. The system of claim 7 wherein the shaft body has an outer profile, the outer profile comprising one of a substantially straight outer profile, and a tapered outer profile.

9. The system of claim 7 wherein the injection tool assembly comprises a vessel containing the conductive fluid, the vessel configured for coupling to the opening in the head portion of the fastener, and wherein the injection tool assembly further comprises a pressure injector coupled to the vessel and to the opening in the head portion of the fastener, the pressure injector configured to inject the conductive fluid, under pressure, into the fastener.

10. The system of claim 7 wherein the conductive fluid comprises a resin material mixed with a conductive material that is electrically conductive.

11. The system of claim 7 wherein the conductive fluid is selected so that a coefficient of thermal expansion of the conductive fluid substantially matches a coefficient of thermal expansion of the composite structure in contact with the conductive fluid.

12. The system of claim 7 wherein each flute extends radially outward along the outer surface of the head portion and terminates at a second end, the second end comprising one of a second location proximal to an outer periphery of the head portion, and a periphery opening at the outer periphery of the head portion.

13. The system of claim 7 wherein the composite structure comprises an aircraft composite structure, and wherein each of the one or more fasteners comprises a conformal clearance fit fastener, that when used with the conductive fluid, provides electrical contact with composite joints of the aircraft composite structure.

14. A method for providing to a composite structure of an aircraft improved electrical conductivity and dissipation of current energy resulting from lightning strikes to the aircraft, the method comprising the steps of:
installing one or more fasteners into one or more corresponding fastener holes formed in the composite structure, each fastener comprising:
an elongated shaft having a first end with a head portion, a second end with a threaded portion, and a shaft body disposed therebetween;
at least one inner feed channel extending from an opening in the head portion, through the head portion and the shaft body, along a longitudinal central axis of the elongated shaft, and terminating proximal to the threaded portion;
a plurality of flutes formed along and circumferentially spaced around an outer surface of the shaft body and an outer surface of the head portion, each flute extending from a first location proximal to the threaded portion, along the outer surface of the shaft body, and radially outward along the outer surface of the head portion; and
one or more lateral feed channels formed laterally through the shaft body, each lateral feed channel connecting the inner feed channel to at least two opposing flutes on the outer surface of the shaft body;

torquing the one or more fasteners in place in the one or more corresponding fastener holes;
injecting, under pressure, a conductive fluid into the opening in the head portion of each fastener, and through the at least one inner feed channel and through at least one of the one or more lateral feed channels;
depositing the conductive fluid to one or more areas between an outer surface of each fa

Assignees

• Boeing Co

Inventors

• Greegor Robert B
• Le Quynhgiao N
• Whiting Brent A
• Mittleider John A

Classifications

• F16B35/06

  Specially-shaped heads (special shape in order to rotate the bolt F16B23/00 {; separate hook adaptors for bolts F16B43/025}) · CPC title

• F16B35/041

  Specially-shaped shafts (shape of thread F16B33/02) · CPC title

• F16B5/02

  by means of fastening members using screw-thread ({F16B5/0004 takes precedence}; construction of screw-threaded connections F16B25/00 - F16B39/00) · CPC title

• F16B35/00 Primary

  Screw-bolts; Stay-bolts; Screw-threaded studs; Screws; Set screws ({F16B33/008 takes precedence; joining sheets or plates using screws with two separate threads F16B5/0275; using screws with adjustment sleeves F16B5/0283}; thread cutting screws F16B25/00) · CPC title

• F16B39/021 Primary

  by injecting a settable material after the screwing down · CPC title