THREADED FLANGED BUSHING FOR FASTENING APPLICATIONS
A fastening system includes a first material having a first hole, a second material having a second hole, a bushing, and a threaded bolt. The bushing is located in the second hole and has a first end abutting the first material and a flanged second for securing the bushing to the second material. A threaded bolt extends through the first hole and into the bushing to secure the first material flush against the second material.
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This application is a divisional of U.S. patent application Ser. No. 12/501,608, filed Jul. 13, 2009, entitled “THREADED FLANGED BUSHING FOR FASTENING APPLICATIONS”.
STATEMENT OF GOVERNMENT INTERESTThe U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of N00019-02-C-3003 awarded by the U.S. Navy.
BACKGROUNDTwo materials can be joined together by a variety of different techniques, such as welding, adhesives, or fastening. Often times, materials are fastened together by one or more “fasteners”. In this context, a fastener is a piece of hardware that mechanically affixes two or more materials together. Known fasteners include nails, bolts, screws, and rivets. When joining materials with a fastener, it can be desirable to simultaneously distribute load. Known fastener and load distributor combinations include grommets and bushings.
Fastening composite materials creates a unique set of problems related to the thermal properties of the joined materials and the fastener system. Composite materials are desirable due to high strength-to-weight ratios and high temperature resistance, which allows them to be exposed to extreme environments. Composite materials, however, experience significant stresses when joined to metals with significantly different coefficients of thermal expansion. The disparity in thermal properties between composite materials and metals may mechanically strain fasteners as well as the surrounding composite material.
SUMMARYAn embodiment of the present disclosure is a fastening system including a bushing and a threaded bolt. The bushing is located within a first hole of a first material. The bushing has a first end substantially flush with a first surface of the first material, a second end having a flange for securing the bushing to the second surface of the first material, and an internally threaded bore extending along an inside surface of the bushing between the first end and second end. The threaded bolt extends through a second hole of a second material and into the bushing located within the first hole. The bushing and the threaded bolt secure the first material flush against the second material.
Another embodiment of the present disclosure is a method for fastening including aligning a first material having a first hole and a second material having a second hole so that the first hole and the second hole are coaxial and the first material and the second material are flush against one another. The method further includes inserting an internally threaded bushing into the first hole so that a first end of the bushing abuts the second material surrounding the second hole and a flanged second end extends out of the first hole to contact the first material surrounding the first hole. Additionally, the method includes securing the flanged second end of the bushing to the first material surrounding the first hole and inserting a bolt through the second hole into the bushing, thereby fastening the first material flush against the second material.
An internally threaded, flanged bushing for fastening applications, as well as systems and methods of use is provided. The bushing of the present disclosure can be advantageous where threads are required in a material which cannot, itself, be threaded. In addition, the bushing of the present disclosure can be advantageous where composite laminates or neat resin thermoplastics are subjected to thermal stresses.
First material 14 has top surface 11 and opposing, parallel bottom surface 13. First material 14 has first hole 18 extending perpendicularly from top surface 11, through first material 14, to bottom surface 13. Similarly, second material 16 has top surface 15 and opposing, parallel bottom surface 17. Second material 16 has second hole 20 extending perpendicularly from top surface 15, through second material 16, to bottom surface 17. Located on bottom surface 17, extending into second material 16 toward top surface 15, and generally surrounding second hole 20 is counter bore 19. Bottom surface 13 of first material 14 and top surface 15 of second material 16 are in physical contact so that the two surfaces 13, 15 lie flush against one another. First material 14 can be a composite laminate, neat resin thermoplastic, or metal. Likewise, second material 16 can be a composite laminate, neat resin thermoplastic, or metal. First material 14 and second material 16 are aligned so that first hole 18 is coaxial with second hole 20. In the embodiment depicted, first hole 18 and second hole 20 are simple circular holes, although the fastening system is not so limited. In order to accommodate fastener 10, a diameter of second hole 20 can be greater than a diameter of first hole 18.
Fastener 10 includes bushing 22, which has body 24, flange 26, and internally threaded bore 32. Body 24 can be further sub-divided into first end 28 and second end 30. Internally threaded bore 32 extends along an inside surface of body 24 between first end 28 and second end 30, and flange 26 is attached to second end 30. As a component of fastener 10, bushing 22 is located within second hole 20 such that first end 28 is abutting bottom surface 13 of first material 14 and flange 26 extends out of second hole 20 to rest within counter bore 19 second material 16. A light press fit between bushing 22 and second hole 20 will insure 360 degree contact, which can be desirable for load distribution. Although counter bore 19 is shown and described, in alternative embodiments counter bore 19 is absent so that flange 26 extends out of second hole 20 and attaches to bottom surface 17 of second material 16 to prevent pull-out. Without flange 26, a high-enough load directed from bolt 12 could cause fastener 10 to slide out of second hole 20. The perimeter of flange 26 is shaped like an oval, a race-track, or a truncated circle, so that additional bushings 22 can be inserted through first material 14 and second material 16 in close proximity to one another. In other words, bushing 22 has a smaller footprint than commercially available grommets and only minimally intrudes into second material 16, allowing more fasteners 10 to be inserted in a given area.
Bushing 22 is “low-profile” in that it lies just above, flush with, or below the surface of a parent material to which it attaches. For example, first end 28 is depicted as substantially flush with top surface 15 of second material 16 and adjacent or abutting bottom surface 13 of top material 14. This low-profile configuration allows first material 14 and second material 16 to be fastened flush against one another. Second material 16 can also include counterbore 19 so that flange 26 is substantially flush with bottom surface 17 of second material 16. When a fastener protrudes through the parent material, it can change the aerodynamics of the parent material and/or interfere with the interior structure of the parent material and/or complicate the mounting of additional exterior materials. A low-profile bushing, such as bushing 22 of the present disclosure, is advantageous because it does not significantly alter the surface of the parent material.
Bushing bore 32 includes bushing threads 34 for receiving bolt and/or insert 36. In the depicted embodiment, fastener 10 includes commercially available insert 36 where both external threads 38 and internal threads 40 are unified national coarse (UNC) threads, therefore having fewer threads per inch than unified national fine (UNF) threaded inserts. When insert 36 is disposed within bore 32, external threads 38 engage bushing threads 34 and internal threads 40 engage bolt threads 42. One or more stakes 44 can be positioned within bore 32 between insert 36 and bushing 22. Bore 32 has one or more internal slots 46 running vertically through bushing threads 34 for receiving stakes 44 Likewise, insert 36 has one or more external slots 48 running vertically through external threads 38 for receiving stakes 44. Stakes 44 prevent inadvertent rotation of insert 36 relative to bushing 22. Insert 36 can also include internal thread-locking ring 50 and annular groove 52 in internal threads 40 for receiving thread-locking ring 50. Thread-locking ring 50 comprises plastic, which is configured to crush when bolt threads 42 engage internal threads 40 of insert 36. When thread-locking ring 50 is crushed, the inner diameter of insert 36 is slightly reduced, thereby creating an engagement between insert 36 and bolt 12 that can withstand prolonged vibrations. Equivalents of thread-locking ring 50 include, but are not limited to, self-locking threads, self-locking features, adhesives, or self-locking inserts.
Bushing body 24 has internally threaded bore 32 for receiving a bolt and/or an insert. Internal bushing threads 34 receive external threads 38 of insert 36, or in alternative embodiments, for directly receiving a bolt (see
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. A method for fastening, the method comprising:
- aligning a first material having a first hole and a second material having a second hole so that the first hole and the second hole are coaxial and the first material and the second material are flush against one another;
- inserting an internally threaded bushing into the first hole so that a first end of the bushing abuts the second material surrounding the second hole and a flanged second end extends out of the first hole to contact the first material surrounding the first hole;
- securing the flanged second end of the bushing to the first material surrounding the first hole; and
- inserting a threaded bolt through the second hole into the bushing, thereby fastening the first material flush against the second material.
2. The method of claim 1, wherein securing the flanged second end of the bushing to the first material surrounding the first hole includes using sufficient force to deform the first material.
3. The method of claim 1, wherein inserting the threaded bolt through the second hole into the bushing includes inserting the threaded bolt all the way through the bushing so that the bolt extends out an opening in the second end of the bushing.
4. The method of claim 3, further comprising:
- threadingly engaging the internally threaded bushing with external threads of a threaded insert; and
- threadingly engaging the threaded bolt with internal threads of the threaded insert.
5. The method of claim 4, further comprising:
- inserting at least one stake between the insert and the bushing to prevent rotation of the insert relative to the bushing.
6. The method of claim 1, wherein the second end of the bushing is closed.
7. The method of claim 1, wherein the first hole is larger than the second hole such that the first end of the bushing abuts a second surface of the second material located around the second hole.
8. The method of claim 1, further comprising:
- a counterbore located in the second surface of the first material and extending around the first hole.
9. The method of claim 1, wherein the first material is a neat resin thermoplastic.
10. The method of claim 1, wherein the first material is a composite laminate.
11. The method of claim 1, wherein the bushing is formed of metal.
12. The method of claim 1, wherein the bushing is formed of nickel-alloy.
13. The method of claim 1, wherein the flange has an oval shape.
14. The method of claim 1, wherein the threaded bolt extends out through the second end of the bushing.
15. The method of claim 1, wherein the insert includes at least one thread-locking ring.
Type: Application
Filed: Aug 29, 2012
Publication Date: Dec 20, 2012
Applicant: UNITED TECHNOLOGIES CORPORATION (Hartford, CT)
Inventors: Francis R. Moon (Granby, CT), John F. Corini (Barkhamsted, CT), Gianfranco D. Conti (Ellington, CT)
Application Number: 13/597,794
International Classification: B23P 17/00 (20060101);