Locknut

Abstract

A locknut having a polygonal body portion with a frustoconical crown extension at one end. A plurality of indentations are provided in selected flat surfaces of the body portion to form a corresponding number of locking regions in the bore of the nut. Each indentation is curved so that the ends of the indentation are deeper than the crest. As a result, the locking regions also are curved but flatter than the initial curvature of the bore, whereby added contact is provided between the locking regions and a mating male member.

Parent Case Text

This application is a continuation of application Ser. No. 765,876, filed Oct. 8, 1968, which application has now been abandoned.

Description

The present invention relates, in general, to locknuts and, in particular, to nuts in which the thread is deformed over selected regions, whereby a nut and a mating bolt are held together in tightly fitted engagement.

Various locknuts are available at the present time in which the locking characteristic is derived by deforming or indenting the external surfaces of the nuts to develop deformed or distorted regions within the threaded bores of the nuts. The deformations are such that as the locknut engages a mating bolt, the nut is stressed elastically and grips the bolt tightly.

For the most part, locknuts of this type which are available at the present time fail to satisfy concurrently the requirements of sufficient, uniform and controllable locking action, retention of the desired locking characteristic after a number of applications and removals, simplicity of design, ease of manufacture and reasonable cost.

Accordingly, it is an object of the present invention to provide a new and improved locknut.

It is another object of the present invention to provide a locknut which derives its locking characteristic by being deformed at its surface and which overcomes the limitations and shortcomings of presently available, comparable devices.

These objects, as well as others, are achieved in accordance with a preferred embodiment of the present invention by providing a locknut having a polygonal body portion and frustoconical crown portion at one end of the body portion. The body portion has a plurality of indentations in selected flat surfaces thereof which form a corresponding number of locking regions in the threaded bore of the nut. The indentations intersect the body portion and the frusto-conical crown portion whereby each indentation is located partially within the body portion and partially within the frustoconical crown portion. The locking regions extend in a direction substantially perpendicular to the axis of the locknut and the magnitude of the indentations is such that the locking regions cause the locknut to be stressed elastically when the locknut threadably engages a mating threaded member. Each indentation includes an arcuate inner wall having a direction of curvature such that the ends of the arcuate wall are indented further than the crest. By shaping the indentations in this manner, the locking regions also remain curved, except these curves are flatter than the initial curvature of the bore of the nut. As a result, added contact is provided between the curved locking regions and a mating threaded member, whereby an improved locking characteristic is derived.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description, taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Referring to the drawing:

FIG. 1 is a perspective view of a locknut constructed in accordance with the present invention; and

FIG. 2 is a sectional view, on an enlarged scale, taken along line 2--2 of FIG. 1.

As shown in FIG. 1, a locknut 10, constructed in accordance with the present invention, includes a polygonal body portion 12 and a frustoconical crown portion 14. For the embodiment of the invention illustrated, the external surface of body portion 14 is hexagonal. A threaded bore 16 extends axially of nut 10 between upper end face 18 of crown portion 14 and lower end face 20 of body portion 12.

Locknut 10 is provided with a plurality of indentations 22 in selected flat surfaces 12a of body portion 12. For the embodiment of the invention illustrated, three indentations 22 are provided on alternate flat surfaces 12a. Indentations 22 preferably are located in the flat surfaces 12a at the juncture of body portion 12 and crown portion 14 so that each indentation in the body portion extends slightly into the crown portion.

As is clearly illustrated in FIG. 2, each indentation is defined by an arcuate vertical inner wall 22a, a pair of vertical sidewalls 22b, and a horizontal base surface 22c. Each arcuate inner wall 22a is a portion of a vertical cylinder having an axis which extends parallel to the axis of nut 10. The direction of curvature of each arcuate inner wall 22a is such that its cylinder either surrounds or intersects the threaded bore 16 of the locknut. As a result, the maximum depth of each indentation 22 occurs at the ends of the arcuate wall 22a and along the lines of juncture of the arcuate wall and vertical sidewalls 22b, while the minimum depth of each indentation exists near the middle of the indentation at the crest 22d of the arcuate inner wall. For the preferred embodiment of the invention being described, the height of each indentation 22 may be from 15 percent to 45 percent of the height of flat surfaces 12a with the height of these flat surfaces being defined as the distance from lower end face 20 of the nut to the midpoint of curved line 12b extending between the upper corners of flat surfaces 12a. The width of each indentation may be from 50 percent to 75 percent of the width of its associated flat surface 12a.

As indentations 22 are formed, a corresponding number of distorted locking regions 24 are formed in threaded bore 16. Locking regions 24 are in radial and axial alignment with indentations 22. It is seen from FIG. 2, that locking regions 24 are curved in generally the same direction as the direction of curvature of arcuate walls 22a and extend between relatively undistorted regions 25 of the threaded bore. The curvature of the locking regions is achieved by the curved configuration of indentations 22. The radius of curvature of locking regions 24 is greater than the radius of curvature of regions 25 of the threaded bore and the radius of the threaded bore prior to being distorted. As a result, the threaded bore 16 assumes what may be termed a tri-roundular configuration. The magnitude of indentations 22 is such that locking regions 24 cause locknut 10 to be stressed elastically as the locknut engages a mating bolt.

By developing curved locking regions, greater contact area is provided between the nut and a mating bolt than what may be achieved with a flat or oppositely curved indentation. The curved locking regions cause the distorted nut threads to conform more closely to the bolt threads, whereas a flat or oppositely curved indentation limits the contact area to a narrower region. Because of the greater contact area, the locking force is distributed more broadly to result in lower unit pressure in the contact area. This, in turn, reduces the wear inherent in repeated installations and removals of the nut onto and from the mating bolt and also reduces the tendency toward galling. As a result, the curved locking regions create an improved locking characteristic.

Indentations 22 are formed by correspondingly shaped tools (not shown). To achieve the desired result, the tools are moved inward radially to cause a corresponding radially inward deformation of the threaded bore at the selected locations. By having the indentations extend inwardly in a direction substantially perpendicular to the axis of the locknut so that there is little, if any, distortion of the threads in an axial direction, optimum prevailing torque retention is achieved.

The radius of curvature of arcuate inner walls 22a may vary from one application to another. It has been found that the radius of the arcuate walls may be either less than or greater than the radius of an imaginary circle centered on the axis of the nut and tangent to the flat surfaces 12a. The range of the radius of arcuate walls 22a may extend from one-half to twice the radius of this imaginary circle.

The angle of vertical sidewalls 22b is selected to facilitate removal of the forming tool after completion of formation of the indentations. For the embodiment of the invention illustrated, vertical sidewalls 22b of each indentation are disposed an angle of 45.degree. to the radius which bisects the arcuate segment. However, a considerably smaller angle, for example, 10.degree., may be used.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

Claims

What is claimed is:

1. A locknut having a body portion of polygonal external cross-section and a frusto-conical extension at one end of said body portion, said locknut also having a threaded bore extending throughout the axial extent thereof, said body portion having a plurality of radial indentations in selected flat surfaces thereof spaced from the corners of said polygonal external cross-section, and said threaded bore having a plurality of distorted locking regions in radial and axial alignment with said indentations and extending between relatively undistorted regions of said threaded bore, said indentations intersecting said body portion and said frustoconical extension whereby each of said indentations is located partially within said body portion and partially within said frusto-conical extension, said indentations being of a width and of a height less than those of said flat surfaces, the magnitude of said indentations being such that the locking regions cause said locknut to be stressed elastically when said locknut engages a mating threaded member, each indentation having an arcuate inner wall which is part of a cylinder that either surrounds or intersects said threaded bore and each locking region being curved in generally the same direction as the direction of curvature of said undistorted region, said inner wall being substantially parallel to the axis of said locknut throughout its axial extent, the radius of curvature of said locking regions being greater than the radius of curvature of said undistorted regions.

2. A locknut according to claim 1 wherein said arcuate inner walls extend parallel to the axis of said locknut.

3. A locknut according to claim 1 wherein:

a. said external cross-section of said body portion is hexagonal and said body portion has three indentations in alternate flat surfaces thereof at the juncture of said body portion and said frusto-conical section;

b. each of said indentations extends across 50 percent to 70 percent of the width of the flat surface in which it is located; and

c. each of said indentations extends along 15 percent to 45 percent of the height of said body portion of said locknut.

4. A locknut having a body portion of polygonal external cross-section and a frusto-conical crown portion at one end of said body portion, said locknut also having a threaded bore extending axially thereof between the top end of said crown portion and a second end of said body portion, said body portion having a plurality of indentations in selected flat surfaces thereof spaced from the corners of said polygonal external cross-section, and said threaded bore having a corresponding number of distorted locking regions in radial alignment with said indentations and extending between relatively undistorted regions in said threaded bore, said indentations intersecting said body portion and said crown portion whereby each of said indentations is located partially within said body portion and partially within said crown portion, said indentations being of a width and of a height less than those of said flat surfaces, said locking regions extending radially inward of said undistorted regions and substantially perpendicular to the axis of said locknut, the magnitude of said indentations being such that the locking regions cause said locknut to be stressed elastically when said locknut threadably engages a mating threaded member, each of said indentations having a convexly curved inner wall with ends indented further from the associated flat surface than is the crest of said curved inner wall, said inner wall being substantially parallel to said axis throughout its axial extent and said locking regions being curved in generally the same direction as the direction of curvature of said inner walls of said indentations, the radius of curvature of said locking regions being greater than the radius of curvature of said undistorted regions.

5. A locknut according to claim 4 wherein said external cross-section of said body portion is hexagonal and said body portion has three indentations in alternate flat surfaces thereof.

6. A locknut according to claim 4 wherein the curvature of said inner walls of said indentations is more flat than the curvature of said threaded bore prior to being distorted.

7. A locknut according to claim 5 wherein each of said indentations extends across 50 percent to 70 percent of the width of the flat surface in which it is located.

8. A locknut according to claim 7 wherein each of said indentations extends along 15 percent to 45 percent of the height of said body portion of said locknut.

9. A locknut having a body portion of polygonal external cross-section and a frustoconical extension at one end of said body portion, said locknut also having a threaded bore extending throughout the axial extent thereof, said body portion having a plurality of radial indentations in selected flat surfaces thereof spaced from the corners of said polygonal external cross-section, and said threaded bore having a plurality of distorted locking regions in radial and axial alignment with said indentations and extending between relatively undistorted regions of said threaded bore, said indentations intersecting said body portion and said frustoconical extension whereby each of said indentations is located partially within said body portion and partially within said frustoconical extension, said indentations being of a width and of a height less than those of said flat surfaces, the magnitude of said indentations being such that the locking regions cause said locknut to be stressed elastically when said locknut engages a mating threaded member, each indentation having an arcuate inner wall which is part of a cylinder that either surrounds or intersects said threaded bore and each locking region being curved in generally the same direction as the direction of curvature of said undistorted regions, the radius of curvature of said locking regions being greater than the radius of curvature of said undistorted regions.

10. A locknut having a body portion of polygonal external cross-section and a frustoconical crown portion at one end of said body portion, said locknut also having a threaded bore extending axially thereof between the top end of said crown portion and a second end of said body portion, said body portion having a plurality of indentations in selected flat surfaces thereof spaced from the corners of said polygonal external cross-section, and said threaded bore having a corresponding number of distorted locking regions in radial alignment with said indentations and extending between relatively undistorted regions in said threaded bore, said indentations intersecting said body portion and said crown portion whereby each of said indentations is located partially within said body portion and partially within said crown portion, said indentations being of a width and of a height less than those of said flat surfaces, said locking regions extending radially inward of said undistorted regions and substantially perpendicular to the axis of said locknut, the magnitude of said indentations being such that the locking regions cause said locknut to be stressed elastically when said locknut threadably engages a mating threaded member, each of said indentations having a convexly curved inner wall with ends indented further from the associated flat surface than is the crest of said curved inner wall, and said locking regions being curved in generally the same direction as the direction of curvature of said inner walls of said indentations, the radius of curvature of said locking regions being greater than the radius of curvature of said undistorted regions.