Blind tack bolt with higher clamp-up strength

{
  "publication_number": "US9931688B2",
  "country": "US",
  "kind": "B2",
  "title": "Blind tack bolt with higher clamp-up strength",
  "abstract": "A blind tack fastener includes a pull stem having an elongated shaft with an extended tail portion. The blind tack fastener also includes a crush-initiating washer, a crush sleeve, and a swage collar, surrounding the elongated shaft of the pull stem. The elongated shaft has a breakaway groove configured to create a predictive fracture point below the head-end surface of the swage collar, such that a hole in the swage collar serves as a centering lead-in for a drill that can be used to remove the blind tack fastener.",
  "claims": [
    "1. A blind tack fastener comprising: a pull stem having an elongated shaft with an extended tail portion, the elongated shaft having a first outer surface with a first outer diameter, the extended tail portion having a second outer surface with a second outer diameter larger than the first outer diameter, the extended tail portion also having a fillet; a crush-initiating washer surrounding the pull stem, the crush-initiating washer having a head-end surface, a fillet engagement surface in contact with the fillet of the extended tail portion of the elongated shaft, an inner surface in contact with the first outer surface of the elongated shaft, and an outer surface with an outer diameter equal to the second outer diameter of the extended tail portion of the elongated shaft; a crush sleeve surrounding the pull stem, the crush sleeve having a head-end surface, a tail-end surface in contact with the head-end surface of the crush-initiating washer, an inner surface in contact with the first outer surface of the elongated shaft, and an outer surface with an outer diameter equal to the second outer diameter of the extended tail portion of the elongated shaft; a swage collar surrounding the pull stem, the swage collar having a tail-end surface in contact with the head-end surface of the crush sleeve, an inner surface in contact with the first outer surface of the elongated shaft, and an outer surface with an outer diameter larger than the second outer diameter of the extended tail portion of the elongated shaft; and a breakaway groove in the elongated shaft of the pull stem, the breakaway groove being located within an inner bore of the swage collar.",
    "2. The blind tack fastener of claim 1, further comprising a plurality of lock grooves on the outer surface of the elongated shaft of the pull stem, the lock grooves being located within an inner bore of the swage collar.",
    "3. The blind tack fastener of claim 1, wherein the pull stem comprises aluminum or an aluminum alloy having a yield strength greater than about 60 ksi and a machinability rating greater than about 40%.",
    "4. The blind tack fastener of claim 1, wherein the crush-initiating washer comprises high-alloy steel having a yield strength greater than about 150 ksi.",
    "5. The blind tack fastener of claim 1, wherein the crush sleeve comprises aluminum, copper or an alloy having a yield strength less than about 20 ksi and a ductility greater than about 15%.",
    "6. The blind tack fastener of claim 1, wherein the swage collar comprises aluminum or an aluminum alloy having a yield strength less than about 20 ksi.",
    "7. The blind tack fastener of claim 1, wherein the head-end surface of the crush-initiating washer and the tail-end surface of the crush sleeve are tapered relative to the elongated shaft.",
    "8. A system comprising: a workpiece comprising a first part and a second part, the workpiece having a first hole extending through both the first part and the second part; a blind tack fastener comprising: a pull stem having an elongated shaft with an extended tail portion, the elongated shaft having a first outer surface with a first outer diameter, the extended tail portion having a second outer surface with a second outer diameter larger than the first outer diameter, the extended tail portion also having a fillet, a crush-initiating washer surrounding the pull stem, the crush-initiating washer having a head-end surface, a fillet engagement surface in contact with the fillet of the extended tail portion of the elongated shaft, an inner surface in contact with the first outer surface of the elongated shaft, and an outer surface with an outer diameter equal to the second outer diameter of the extended tail portion of the elongated shaft; a crush sleeve surrounding the pull stem, the crush sleeve having a head-end surface, a tail-end surface in contact with the head-end surface of the crush-initiating washer, an inner surface in contact with the first outer surface of the elongated shaft, and an outer surface with an outer diameter equal to the second outer diameter of the extended tail portion of the elongated shaft; a swage collar surrounding the pull stem, the swage collar having a tail-end surface in contact with the head-end surface of the crush sleeve, an inner surface in contact with the first outer surface of the elongated shaft, and an outer surface with an outer diameter larger than the second outer diameter of the extended tail portion of the elongated shaft; and a breakaway groove in the elongated shaft of the pull stem, the breakaway groove being located within an inner bore of the swage collar, wherein the blind tack fastener exerts a clamp-up force of at least 300 pounds on the workpiece.",
    "9. The system of claim 8, wherein the pull stem is recessed within an inner bore of the swage collar.",
    "10. The system of claim 8, wherein the aluminum pull stem has a yield strength greater than about 60 ksi and a machinability rating greater than about 40%.",
    "11. The system of claim 8, wherein the blind tack fastener comprises a crush-initiating washer made of high-alloy steel having a yield strength greater than about 150 ksi.",
    "12. The system of claim 8, wherein the aluminum crush sleeve has a yield strength less than about 20 ksi and a ductility greater than about 15%.",
    "13. The system of claim 8, wherein the swage collar comprises aluminum or an aluminum alloy having a yield strength less than about 20 ksi.",
    "14. The blind tack fastener of claim 1, incorporated into a workpiece comprising a first part and a second part, the blind tack fastener inserted into a first hole extending through both the first part and the second part, wherein the swage collar is in contact with the first part and a bulb formed in a portion of the aluminum crush sleeve is in contact with the second part.",
    "15. The blind tack fastener of claim 14, wherein the blind tack fastener exerts a clamp-up force of at least 300 pounds on the workpiece.",
    "16. The blind tack fastener of claim 1, wherein the crush sleeve is configured to form a bulb in response to the pull stem being pulled.",
    "17. The blind tack fastener of claim 1, wherein the pull stem is configured to form a hole relative to the swage collar upon breaking of the pull stem at the breakaway groove.",
    "18. The system of claim 8, wherein the head-end surface of the crush-initiating washer and the tail-end surface of the crush sleeve are tapered relative to the elongated shaft.",
    "19. The system of claim 8, wherein the crush sleeve is configured to form a bulb in response to the pull stem being pulled.",
    "20. The system of claim 8, wherein the pull stem is configured to form a hole relative to the swage collar upon breaking of the pull stem at the breakaway groove."
  ],
  "description_excerpt": "The present disclosure relates generally to tack fasteners and, in particular, to blind tack fasteners utilized to fasten components of a workpiece together to perform manufacturing operations on the workpiece.\n\nIn many environments it is desirable to temporarily hold and clamp parts together while other operations, such as drilling and riveting operations, are performed. For example, in the aircraft industry, it is becoming increasingly desirable to perform the drilling of holes and insertion of fasteners using a one-up assembly process. Traditionally, many parts are subject to disassembly after drilling to clean and deburr the parts, resulting in increased labor hours, and often creating damage to the components induced during disassembly and rework associated with mismatched holes after disassembly.\n\nA one-up assembly process, by contrast, involves drilling and fastening multiple layers of a workpiece at one time, without having to disassemble the parts for other operations, such as deburring, cleaning, sealing, and other suitable operations. The layers may be parts of a workpiece that are to be fastened to each other, such as, for example, a skin panel to be fastened to a spar or spar cap, or a skin panel to be attached to a frame of a fuselage. Future production strategies contemplate a “lights out” one-up assembly process, which involves more automation and less human involvement than traditional manufacturing processes.\n\nTack fasteners are widely used in the aircraft industry to attach the parts of a workpiece together temporarily to perform operations on a workpiece.",
  "cpc": [
    "B21J 15/043",
    "B23P 25/00",
    "F16B 19/1054",
    "Y10T 29/49799"
  ],
  "ipc": [
    "B21J 15/04",
    "B23P 25/00",
    "F16B 19/05",
    "F16B 19/10"
  ],
  "assignees": [
    "Boeing Co"
  ],
  "inventors": [
    "Scott William Gunther",
    "Edward John Batt",
    "Farahnaz Sisco"
  ],
  "filing_date": "2015-03-30",
  "publication_date": "2018-04-03",
  "grant_date": "2018-04-03",
  "priority_date": "2014-04-01",
  "application_number": "US-201514672794-A",
  "family_id": "52807686",
  "cited_by_count": 0,
  "citations": [
    "US2114493A",
    "US2787932A",
    "US4810142A",
    "GB2202293A",
    "US5651649A",
    "US6077009A"
  ]
}