Mechanically Locked Nut Assembly

1. Field of the Invention

This invention relates to a nut assembly having a nut element that is integrally connected to and movable rotationally and longitudinally relative to a washer so as to deform the washer and thereby mechanically lock the nut assembly to an associated bolt to prevent the inadvertent removal of the bolt from the nut assembly due to vibration and similar mechanical forces.

2. Background Art

The conventional two-piece fastener assembly 1 comprising a separate collar 2 and washer 4 is briefly described when referring to FIGS. 1 and 2 of the drawings. In the as-packaged configuration before installation, and is best shown in FIG. 1, the collar 2 includes a hollow body 6 having an internally threaded, hex-shaped head 8 at one end thereof and a relatively thin cylindrical shank 10 at the opposite end. The washer 4 also includes a hollow body 12 having a dish-shaped cavity 14 formed in one end thereof.

FIG. 2 shows the fastener assembly 1 of FIG. 1 after installation for securing a pair of sheet metal panels 60 and 70 together. More particularly, the collar 2 and washer 4 are first axially aligned with one another, and a commercially available (e.g. titanium) bolt or pin 16 is then inserted through holes in sheet metal panels 60 and 70 and into the hollow bodies 6 and 12 of collar 2 and washer 4 to connect said collar and washer together. The bolt 16 is of the type having a series of screw threads 18 at the forward end thereof, a flat head 20 at the opposite end, and a relatively narrow annular groove 22 located between the threaded end 18 and head 20. During tightening of the fastener assembly 1, the collar 2 is pulled towards washer 4 by bolt 16. Accordingly, the shank 10 of collar 2 is received within the cavity 14 of washer 4. A compressive force applied by washer 4 to shank 10 causes said shank to be bent or deflected inwardly towards the intermediate groove 22 of bolt 16. The position of the deflected shank 10 relative to the groove 22 forms a stop to prevent the bolt from withdrawing past shank 10 and inadvertently rotating out of engagement with threaded collar 2 as a consequence of vibration and similar mechanical forces to which the fastener assembly 1 is subjected.

The conventional two-piece fastener assembly 1 illustrated in FIGS. 1 and 2 is characterized by several shortcomings. First, there are a plurality of separate members (i.e. a collar 2 and a washer 4) to be handled which increases the assembly time and the possibility that fastener members may be lost or misplaced. Moreover, the washer 4 must first be oriented relative to collar 2 such that the shank 10 of collar 2 and the dish-shaped cavity 14 of washer 4 are aligned end-to-end one another during installation. Sometimes, the washer 4 is incorrectly installed with the cavity 14 facing away from shank 10, whereby to reduce the locking ability of the fastener assembly and the reliability for preventing removal of the bolt 16. What is more, it is relatively difficult to remove the bolt 16 and separate the washer 4 from the collar 2 when it is necessary to disconnect fastener assembly 1 from the panels 60 and 70 after installation.

In general terms, this invention relates to a nut assembly that is adapted to be mechanically locked to a threaded bolt or pin of the type having an annular groove formed therein for securing a pair of sheet metal panels, or the like. The nut assembly comprises a threaded nut element to engage the bolt and a washer connected to the nut element such that the nut element is movable relative to the washer. The washer has a pair of coaxially aligned, inner and outer cylindrical walls extending longitudinally therefrom.

In the as-packaged configuration of the nut assembly, the outer cylindrical wall of the washer is deflected radially inward to engage the nut element and prevent disconnection of the nut element from the washer. The nut element rests upon the inner cylindrical wall of the washer at a counterbore formed in the nut element such that a longitudinal gap is established between the washer and the nut element.

During installation of the nut assembly at the fastened structure, the bolt draws the nut element towards the washer to eliminate the gap therebetween. A compressive force is applied to the inner wall of the washer to correspondingly deflect the inner wall radially inward into the annular groove of the bolt. Accordingly, the deflected inner wall functions as a lock or stop which prevents the bolt from inadvertently rotating out of engagement with the nut assembly as a consequence of vibration and similar mechanical forces.

FIG. 1 is a partial cross section of a conventional multi-piece fastener assembly in the as-packaged configuration;

FIG. 2 shows the installation of the conventional fastener assembly of FIG. 1 with a bolt for securing two panels together;

FIG. 3 is a perspective view of the nut assembly of the present invention aligned for receipt of a bolt;

FIG. 4 is a partial cross section of the nut assembly of FIG. 3 in the as-packaged configuration; and

FIG. 5 shows the installation of the nut assembly of FIG. 3 mechanically locked to the bolt of FIG. 3 for securing two panels together.

An integral, nut assembly 30 which forms the present invention and which overcomes the problems inherent to the conventional fastener assembly 1 of FIGS. 1 and 2 is shown in FIGS. 3-5 of the drawings. That is to say, the nut assembly 30 is adapted to be more conveniently mated to the same commercially available bolt or pin 16 that has heretofore been associated with the conventional fastener assembly 1.

More particularly, and referring to FIG. 4, the nut assembly 30 is shown in the as-packaged configuration before installation comprising the interconnection of a nut element 32 and a washer 34. The nut element 32 includes a hollow body 36 that is preferably manufactured from steel, stainless steel, aluminum, or the like. The body 36 has an internally threaded, hex-shaped wrench pad 38 at one end thereof and a cylindrical base 40 at the opposite end. The diameter of base 40 of nut element 32 is slightly larger than the cross-corner dimension of the wrench pad 38. It is important to note that the base 40 is provided with contiguous, coaxially aligned upper and lower counter bores 42 and 44. The lower counter bore 44 of nut element 32 has a slightly larger diameter than the diameter of upper counter bore 42.

The washer 34, which is interconnected with nut element 32 in the as-packaged configuration of nut assembly 30, is preferably manufactured from steel, stainless steel, or the like. The washer 34 has a hollow body 46 and cylindrical inner and outer walls 48 and 5 projecting upwardly from body 46. Inner and outer walls 48 and 50 are spaced radially from one another, and the outer wall 50 is longer than inner wall 48. In the as-packaged configuration of nut assembly 30, the base 40 of nut element 32 is received between the radially spaced inner and outer walls 48 and 50 of washer 34, such that the inner wall 48 is received in the lower counter bore 44 of base 40, and the outer wall 50 surrounds and embraces base 40. Thus, it can be seen that the nut element 32 rests upon the top of washer 34 (i.e. on inner wall 48), such that a small, longitudinally extending gap 52 of approximately 0.03 inches is created between the body 46 of washer 34 and the base 40 of nut element 32. The nut assembly 30 is completed when the top of the cylindrical outer wall 50 of washer 34 is deflected radially inward during manufacture around the base 40 of nut element 32 to form a captive washer-type assembly. The foregoing may be accomplished by means of a well-known staking, crimping or similar technique.

FIG. 5 of the drawings shows the integral nut assembly 30 of FIG. 4 after installation for securing a pair of sheet metal panels 60 and 70 together. More particularly, the bolt 16 of FIG. 3 is inserted through holes in a pair of sheet metal panels 60 and 70 and into the hollow bodies 36 and 46 of nut element 32 and washer 34. As was described when referring to FIG. 2, the bolt 16 has a series of screw threads 18 at the forward end thereof to engage the screw threads of nut element 32, a flat head 20 at the opposite end, and a relatively narrow angular groove 22 located between the threaded end 18 and head 20.

During tightening of the nut assembly 30 against panels 60 and 70, the nut element 32 is rotated towards the washer 34 by bolt 16. Accordingly, the base 40 of nut element 32 moves through and eliminates the longitudinally extending gap (designated 52 in FIG. 4) between nut element 32 and washer 34, whereby a space 54 is formed between the deflected top of outer wall 50 of washer 34 and nut element 32. Moreover, the inner wall 48 of washer 34 is received within the lower counter bore 44 of nut element 32, such that a compressive force is applied by nut element 32 to inner wall 48 to cause inner wall to be bent or deflected through the upper counter bore 42 and into the intermediate groove 22 of bolt 16. The position of deflected inner wall 48 within the groove 22 forms a mechanical lock of washer 34 to bolt 16 to prevent the bolt from withdrawing past deflected wall 48 and inadvertently rotating out of engagement with the threaded nut element 32 as a consequence of vibration, and the like. Therefore, if the nut assembly 30 is used on a jet aircraft the probability is greatly reduced that the bolt 16 could become free of nut assembly 30 and ingested into a jet engine.

The integral nut assembly 30 of the present invention is an improvement over the multi-piece fastener assembly 1 of FIGS. 1 and 2. That is, the integral nut assembly 30 is easier to handle than the multi-piece assembly 1 having separate fastener members. The nut element 32 and washer 34 of the integral nut assembly 30 require no manual alignment by a workman, making installation relatively quick and easy and assuring a reliable connection with bolt 16 to prevent loosening of the bolt and separation of the fastened structure (of FIG. 5). Accordingly, the cost of installing the nut 30 herein disclosed is significantly less than the cost incurred to install the conventional fastener assembly 1 of FIGS. 1 and 2.

It will be apparent that while a preferred embodiment of the invention has been shown and described, various modifications and changes may be made without departing from the true spirit and scope of the invention.