Waisted shank lockbolt

Abstract

A lockbolt pin comprises a lockbolt body extending from a first pin end to a second pin end along a longitudinal axis, and a shank extending between the first pin end and the second pin end. The shank comprises a blank portion having a substantially smooth outer surface and a grooved portion. The grooved portion of the shank is defined by a first diameter and the blank portion of the shank comprises a second diameter that is less than the first diameter.

Description

WAISTED SHANK LOCKBOLTTECHNICAL FIELD

[0001] This disclosure relates generally to a fastener and, more particularly, to a two-piece lockbolt with a waisted shank.BACKGROUND

[0002] Two-piece swaged fasteners, commonly referred to as lockbolts, are used to secure a plurality of workpieces together as a bolted joint. Typically, lockbolts comprise a pin member with lock grooves and a swage collar adapted to be swaged into the lock grooves by an installation tool. Fasteners in bolted joints with shorter clamping lengths may experience a loss of clamp as the bolted joint settles over time.SUMMARY

[0003] A lockbolt pin according to an exemplary aspect of the present disclosure includes, among other things: a lockbolt body extending from a first pin end to a second pin end along a longitudinal axis; and a shank extending between the first pin end and the second pin end, wherein the shank comprises a blank portion having a substantially smooth outer surface and a grooved portion, and wherein the grooved portion of the shank is defined by a first diameter and the blank portion of the shank comprises a second diameter that is less than the first diameter.

[0004] In a further non-limiting embodiment of the foregoing lockbolt pin, the first diameter comprises a nominal diameter.[0005| In a further non-limiting embodiment of any of the foregoing lockbolt pins, the second diameter is within a range of .7 to .9 of the nominal diameter.

[0006] In a further non-limiting embodiment of any of the foregoing lockbolt pins, the blank portion is defined by a length extending in a direction of the longitudinal axis, and wherein the length is 1.5 or less of the nominal diameter.

[0007] In a further non-limiting embodiment of any of the foregoing lockbolt pins, the grooved portion includes a plurality of grooves configured to receive a swaged portion of a lockbolt collar.

[0008] In a further non-limiting embodiment of any of the foregoing lockbolt pins, the grooved portion comprises a first grooved portion, and wherein the second pin end comprises a second grooved portion, wherein the first grooved portion is defined by a first inner groove diameter andthe second grooved portion is defined by a second inner groove diameter that is less than the first inner groove diameter.

[0009] In a further non-limiting embodiment of any of the foregoing lockbolt pins, the first pin end comprises a head comprising a largest outer dimension of the lockbolt body.

[0010] A multi-piece fastener according to an exemplary aspect of the present disclosure includes, among other things: a lockbolt pin extending from a first pin end to a second pin end along a longitudinal axis, wherein the lockbolt pin comprises a shank located between the first pin end and the second pin end, and wherein the shank comprises a blank portion having a substantially smooth outer surface and a grooved portion, and wherein the grooved portion of the shank is defined by a first diameter and the blank portion of the shank comprises a second diameter that is less than the first diameter; and a lockbolt collar comprising a center opening, wherein the grooved portion is received within the center opening in an interference fit with the lockbolt collar deformed onto the shank.

[0011] In a further non-limiting embodiment of the foregoing multi-piece fastener, the first diameter comprises a nominal diameter, and wherein the second diameter is within a range of .7 to .9 of the nominal diameter.

[0012] In a further non-limiting embodiment of any of the foregoing multi-piece fasteners, the blank portion is defined by a length extending in a direction of the longitudinal axis, and wherein the length is 1.5 or less of the nominal diameter.

[0013] In a further non-limiting embodiment of any of the foregoing multi-piece fasteners, the blank portion comprises a smooth outer surface and the grooved portion includes a plurality of grooves that receive a swaged portion of the lockbolt collar.

[0014] In a further non-limiting embodiment of any of the foregoing multi-piece fasteners, the first pin end comprises a head comprising a largest outer dimension of the lockbolt pin, and wherein the grooved portion comprises a first grooved portion, and wherein the second pin end comprises a second grooved portion, wherein the first grooved portion is defined by a first inner groove diameter and the second grooved portion is defined by a second inner groove diameter that is less than the first inner groove diameter.[0015| In a further non-limiting embodiment of any of the foregoing multi-piece fasteners, the shank is configured to extend through aligned openings in at least two stacked workpieces, and wherein the blank portion is positioned immediately adjacent the head such that an entirety of the blank portion and at least a portion of the grooved portion is located within the aligned openings.

[0016] A method according to another exemplary aspect of the present disclosure includes, among other things: providing a lockbolt pin with a shank located between a first pin end and a second pin end, wherein the shank comprises a blank portion having a substantially smooth outer surface and a grooved portion; forming the grooved portion of the shank with a first diameter and forming the blank portion with a second diameter that is less than the first diameter; and swaging a lockbolt collar onto the grooved portion.

[0017] In a further non -limiting embodiment of the foregoing method, the first diameter comprises a nominal diameter, and wherein the second diameter is within a range of .7 to .9 of the nominal diameter.[0018| In a further non-limiting embodiment of any of the foregoing methods, the first diameter comprises a nominal diameter, and wherein the blank portion is defined by a length extending in a direction of a longitudinal axis defined by the lockbolt pin, and wherein the length is 1.5 or less of the nominal diameter.

[0019] In a further non-limiting embodiment of any of the foregoing methods, the first diameter comprises a nominal diameter, and wherein the second diameter is within a range of .7 to .9 of the nominal diameter, and wherein the blank portion is defined by a length extending in a direction of a longitudinal axis defined by the lockbolt pin, and wherein the length is 1.5 or less of the nominal diameter.

[0020] In a further non-limiting embodiment of any of the foregoing methods, the method includes inserting the shank into aligned openings in at least two stacked workpieces such that an entirety of the blank portion and at least a portion of the grooved portion is located within the aligned openings.

[0021] In a further non-limiting embodiment of any of the foregoing methods, the first diameter is a nominal diameter, and wherein subsequent to inserting the shank into the aligned openings and prior to swaging, the substantially smooth outer surface is spaced from inner surfaces of the aligned openings by a first gap defined by a dimension having a first size and the nominal diameter is spaced from the inner surfaces of the aligned openings by a second gap defined by a second size that is less than the first size.[0022| In a further non-limiting embodiment of any of the foregoing methods, the method includes swaging the lockbolt collar onto the shank to eliminate the first and second gaps while elongating the shank.

[0023] The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.BRIEF DESCRIPTION OF THE FIGURES

[0024] The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows:[0025| Figure 1 illustrates a side view of an example of a lockbolt pin with a waisted shank according to the disclosure.100261 Figure 2A illustrates is side view of the lockbolt of Figure 1 installed within corresponding openings of two workpieces, with a portion of the workpieces being removed such that the waisted shank can be viewed.[0027J Figure 2B is similar to Figure 2A but shows a subsequent assembly step of installing a collar.[00281 Figure 2C is similar to Figure 2B but shows a subsequent assembly step of the collar swaged to the pin.[0029[ Figure 3 is a magnified view of an identified portion of Figure 2C.DETAILED DESCRIPTION[0030J This disclosure details a lockbolt that can be used to secure a plurality of workpieces together as a bolted joint, wherein a pin of the lockbolt comprises a waisted shank to facilitate maintaining required clamping over time.[0031} A fastener comprises a lockbolt 10 that includes a lockbolt pin member 12, as shown in Figure 1, and a swage lockbolt collar 14 as shown in Figures 2B-C. In one example, the pin member 12 comprises a first pin end 16, a second pin end 18, and a shank 20 that extend along a longitudinal axis A.[0032J In one example, the first pin end 16 may comprise a head portion that includes the largest outer dimension, e.g., an outermost diameter, of the pin member 12.[0033J In one example, the shank portion 20 includes a smooth / blank cylindrical shank portion 22 and a lock groove portion 24 located adjacent to one end of the blank cylindrical shank portion22. The blank cylindrical shank portion 22 comprises a smooth outer surface without any grooves or interruptions. The lock groove portion 24 comprises a plurality of lock grooves 26. In one example, the lock grooves 26 are helical grooves; however, annular or other types of grooves could also be used.

[0034] In one example, the second pin end 18 comprises another, second grooved portion 28 having a plurality of grooves 30. In one example, the grooves 30 are annular grooves; however, other types of grooves could also be used. In one example, the grooves 30 are formed perpendicular to the longitudinal axis A of the pin member 12.

[0035] In one example, the second grooved portion 28 is defined by a smaller diameter than a diameter of the first grooved portion 24. For example, the first grooved portion 24 is defined by a first inner groove diameter 32 and the second groove portion 28 is defined by a second inner groove diameter 34 that is less than the first inner groove diameter 32.

[0036] In one example, the lockbolt pin member 12 extends from the first pin end 16 to the second pin end 18 along the longitudinal axis A. The blank cylindrical portion 22 of the shank 20 is immediately adjacent the head at the first pin end 16, and the first grooved portion 24 immediately follows the blank cylindrical shank portion 22. In one example, the shank 20 is defined by a first diameter DI and the blank cylindrical portion 22 of the shank 20 comprises a second diameter D2 that is less than the first diameter DI . Thus, the shank 20 at the blank cylindrical portion 22 has a smaller cross-sectional area than at the grooved portion 24.[0037[ In one example, the first diameter DI comprises a nominal diameter and the second diameter D2 is within a range of .7 to .9 of the nominal diameter, e.g. .7 x DI < D2 < .9 x DI. A nominal is the diameter as measured from crest to crest of the threads as best shown in Figure 3.

[0038] In one example, the blank cylindrical portion 22 is defined by a length Ls extending in the direction of the longitudinal axis A, and the length is 1.5 or less of the nominal diameter, e.g. 0< Ls< 1.5 x DI.

[0039] In one example, the swage lockbolt collar 14 is sized and shaped to mate with, and be swaged onto, the pin member 12. Figures 2A-C shown an example installation process. The shank 20 is configured to extend through aligned openings 40, 42 in at least two stacked workpieces 44, 46 as shown in Figure 2A. The head at the first pin end 16 is sized to prevent the pin member 12 from falling through the openings. In one example, the blank cylindrical portion 22 is positioned immediately adjacent the head at the first pin end 16 such that an entirety of the blank cylindrical portion 22 and at least a portion of the grooved portion 24 is located within the aligned openings40, 42. It should be noted that portions of the workpieces 44, 46 and collar 14 are shown as removed in Figures 2A-C and 3 such that the relationship between the shank, the collar, and the openings in the workpieces can be seen and understood.

[0040] Next, as shown in Figure 2B, the lockbolt collar 14 is inserted over the second pin end 18. The lockbolt collar 14 comprises a center opening 48 that extends from a first collar end 50 to a second collar end 52. In one example, near the second collar end 52, the center opening 48 gradually increases, e.g. tapers, in size (see 56) as best shown in Figure 3. In one example, the second collar end 52 comprises a flange 54 having a greater diameter than the rest of the collar body. At least a portion of the grooved portion 24 is received within the center opening 48 in an interference fit with the lockbolt collar 14 being deformed, e.g. swaged, onto the shank 20 as shown in Figure 2C to form a bolted joint. As known, a tool (not shown) is used to deform the collar 14 onto the shank 20.

[0041] For standard lockbolts, there can be a loss of clamp in a bolted joint with shorter clamping lengths, e.g., typically less than one times the nominal diameter of the bolt. The waisted, e.g. reduced cross-sectional area, of the blank cylindrical portion 22 reduces elastic stiffness k (Figure 3) as compared to standard lockbolts. Further, lockbolt tension F (Figure 3) causes increased elongation of the shank compared to a standard lockbolt. Increased elongation reduces preload losses leading to increased clamp in the bolted joint at shorter clamping lengths. Thus, the reduced diameter shank allows the lockbolt to elongate further during installation, reducing the amount of clamp loss after the joint has settled.

[0042] As shown in Figure 1, the blank cylindrical portion 22 of the shank 20 is immediately adjacent the head at the first pin end 16 and extends from a first end 60 to a second end 62. The first end 60 transitions from the head and comprises a tapered portion 64 that tapers inwardly in a direction toward the axis A. A first curved portion 66 transitions from the tapered portion 64 into a waisted portion 68 of the blank cylindrical portion 22. The first curved portion 66 is defined by a first radius of curvature Rl. The waisted portion 68 comprises the narrowest, i.e. the smallest cross-sectional area, portion of the blank cylindrical portion 22. The waisted portion 68 is defined by a constant outer diameter, which comprises the second diameter D2. A second curved portion 70 transitions from the waisted portion 68 to the grooved portion 24. The second curved portion 70 is defined by a second radius of curvature R2. In one example, R2 is greater than Rl. The grooved portion 24 immediately follows the second curved portion 70 of the blank cylindrical shank portion 22 and defines the first diameter DI of the shank 20.

[0043] In one example, a method for forming a lockbolt 10 comprises forming the grooved portion 24 of the shank 20 with a first diameter DI, forming the blank portion 22 with a second diameter D2 that is less than the first diameter DI, inserting the shank 20 into aligned openings 40, 42 in at least two stacked workpieces 44, 46 such that an entirety of the blank portion 22 and at least a portion of the grooved portion 24 are located within the aligned openings 40, 42, and swaging a lockbolt collar 14 onto the grooved portion 24.[0044[ In one example, subsequent to inserting the shank 20 into the aligned openings 40, 42 and prior to swaging, the substantially smooth outer surface of the blank portion 22 is spaced from inner surfaces of the aligned openings 40, 42 by a gap G1 defined by a dimension having a first size and the nominal diameter is spaced from the inner surfaces of the aligned openings 40, 42 by a gap G2 defined by a second size that is less than the first size (see Figure 3). In one example, the method further includes swaging the lockbolt collar 14 onto the shank 20 to eliminate the first and second gaps Gl, G2 while elongating the shank 20.

[0045] During installation, the reduced shank diameter at the waisted portion 68 allows for the lockbolt to elongate further than with a standard shank. The additional elongation reduces the effect of settling within the joint which can cause significant loss in clamp in applications where shorter clamping lengths are used. In one example, the reduced shank has a machined profile; however, the reduced shank could also be cold formed onto the blank at the same time the lock grooves are formed. Cold forming provides for a weight reduction and material savings as compared to machining.

[0046] The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of protection given to this disclosure can only be determined by studying the following claims.

Claims

CLAIMSWhat is claimed is:

1. A lockbolt pin comprising: a lockbolt body extending from a first pin end to a second pin end along a longitudinal axis; and a shank extending between the first pin end and the second pin end, wherein the shank comprises a blank portion having a substantially smooth outer surface and a grooved portion, and wherein the grooved portion of the shank is defined by a first diameter and the blank portion of the shank comprises a second diameter that is less than the first diameter.

2. The lockbolt pin of claim 1, wherein the first diameter comprises a nominal diameter.

3. The lockbolt pin of claim 2, wherein the second diameter is within a range of .7 to .9 of the nominal diameter.

4. The lockbolt pin of claim 2, wherein the blank portion is defined by a length extending in a direction of the longitudinal axis, and wherein the length is 1.5 or less of the nominal diameter.

5. The lockbolt pin of claim 1, wherein the grooved portion includes a plurality of grooves configured to receive a swaged portion of a lockbolt collar.

6. The lockbolt pin of claim 1, wherein the grooved portion comprises a first grooved portion, and wherein the second pin end comprises a second grooved portion, wherein the first grooved portion is defined by a first inner groove diameter and the second grooved portion is defined by a second inner groove diameter that is less than the first inner groove diameter.

7. The lockbolt pin of claim 1, wherein the first pin end comprises a head comprising a largest outer dimension of the lockbolt body.

8. A multi-piece fastener comprising: a lockbolt pin extending from a first pin end to a second pin end along a longitudinal axis, wherein the lockbolt pin comprises a shank located between the first pin end and the second pin end, and wherein the shank comprises a blank portion having a substantially smooth outer surface and a grooved portion, and wherein the grooved portion of the shank is defined by a first diameter and the blank portion of the shank comprises a second diameter that is less than the first diameter; and a lockbolt collar comprising a center opening, wherein the grooved portion is received within the center opening in an interference fit with the lockbolt collar deformed onto the shank.

9. The multi-piece fastener of claim 8, wherein the first diameter comprises a nominal diameter, and wherein the second diameter is within a range of .7 to .9 of the nominal diameter.

10. The multi-piece fastener of claim 9, wherein the blank portion is defined by a length extending in a direction of the longitudinal axis, and wherein the length is 1.5 or less of the nominal diameter.

11. The multi-piece fastener of claim 8, wherein the blank portion comprises a smooth outer surface and the grooved portion includes a plurality of grooves that receive a swaged portion of the lockbolt collar.

12. The multi-piece fastener of claim 8, wherein the first pin end comprises a head comprising a largest outer dimension of the lockbolt pin, and wherein the grooved portion comprises a first grooved portion, and wherein the second pin end comprises a second grooved portion, wherein the first grooved portion is defined by a first inner groove diameter and the second grooved portion is defined by a second inner groove diameter that is less than the first inner groove diameter.

13. The multi-piece fastener of claim 12, wherein the shank is configured to extend through aligned openings in at least two stacked workpieces, and wherein the blank portion is positioned immediately adjacent the head such that an entirety of the blank portion and at least a portion of the grooved portion is located within the aligned openings.

14. A method compri sing : providing a lockbolt pin with a shank located between a first pin end and a second pin end, wherein the shank comprises a blank portion having a substantially smooth outer surface and a grooved portion; forming the grooved portion of the shank with a first diameter and forming the blank portion with a second diameter that is less than the first diameter; and swaging a lockbolt collar onto the grooved portion.

15. The method of claim 14, wherein the first diameter comprises a nominal diameter, and wherein the second diameter is within a range of .7 to .9 of the nominal diameter.

16. The method of claim 14, wherein the first diameter comprises a nominal diameter, and wherein the blank portion is defined by a length extending in a direction of a longitudinal axis defined by the lockbolt pin, and wherein the length is 1.5 or less of the nominal diameter.

17. The method of claim 14, wherein the first diameter comprises a nominal diameter, and wherein the second diameter is within a range of .7 to .9 of the nominal diameter, and wherein the blank portion is defined by a length extending in a direction of a longitudinal axis defined by the lockbolt pin, and wherein the length is 1.5 or less of the nominal diameter.

18. The method of claim 14, including inserting the shank into aligned openings in at least two stacked workpieces such that an entirety of the blank portion and at least a portion of the grooved portion is located within the aligned openings.

19. The method of claim 18, wherein the first diameter is a nominal diameter, and wherein subsequent to inserting the shank into the aligned openings and prior to swaging, the substantially smooth outer surface is spaced from inner surfaces of the aligned openings by a first gap defined by a dimension having a first size and the nominal diameter is spaced from the inner surfaces of the aligned openings by a second gap defined by a second size that is less than the first size.

20. The method of claim 19, including swaging the lockbolt collar onto the shank to eliminate the first and second gaps while elongating the shank.

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