CA1146386A - Threaded fasteners with flexible flange - Google Patents

Abstract

THREADED FASTENERS WITH FLEXIBLE FLANGE

Abstract of the Disclosure A fastener such as a threaded nut, bolt or screw includes a body portion with a bearing surface at the workpiece engaging end defined at least in part by a flange. Segments of the bearing surface defined by the flange are flexible and resilient and other segments are rendered rigid by brace structure associated with the body portion of the fastener.
In one embodiment, upon tightening of the fastener against a workpiece or other element, deflection of the resilient segments provides a spring action to compensate for developed looseness or loss of tension. In another embodiment, locking teeth project from the bearing surface in the resilient segments of the flange located between the rigid segments.

Description

. The present invention relates to improvements in threaded fasteners having flanges.
An important aspect of the present invention relates to the provision of a threaded fastener having a flange with alternating flexible and rigid flange segments. A fastener of this character can be adapted to provide desirable spring characteristics for maintaining resilience in a threaded joint. Such a fastener can also be adapted to provide a locking characteristic having important advantages.
The desirability of providing resilience in a threaded joint is widely recognized. In the absence of sufficient flexibility, looseness can develop in the joint due to such factors as smoothing out or wearing of parts, thermal expansion, compression set of gaskets or other material, or the like. In order to compensate for developed looseness and to maintain clamp load or bolt tension in the joint, in the past it has been common practice to use washers having spring characteris-tics such as cone or bellville washers, or helical spring washers. For various reasons including the inconvenience, expense, and possibility of misassembly associated with the use of discrete washers, it has been proposed to provide fasteners having permanently associated therewith a washer or having an integral structure providing spring characteristics.
A first aspect of the present invention relates to improvements in the type of fasteners having integral structure for introducing flexibility or elasticity into a threaded joint. Among the important objects of the present invention are to provide a fastener having improved structure for providing a spring or flexible and resilient characteristic upon tightening of the fastener thereby to maintain tension in a threaded joint; to provide a fastener wherein flexibility is achieved without the sacrifice of the ability to apply substantial clamp loads and to provide a fastener wherein substantial spring forces are achieved.
A known type of locking fastener includes an array of locking teeth in the bearing surface of the fastener body.
The bearing surface may be defined on a flange formed on the body or head of a fastener such as a nut, bolt or screw. Upon tightening of a threaded joint, the teeth engage a workpiece, i.e., the surface of a structura~ member or the like in the joint, to provide a locking function. Locking fasteners of this type have in some instances performed well and in some installations are capable of achieving a ratio of "off torque"
to "on torque" well in excess of unity. On torque, also referred to as application torque, is the torque applied to the fastener in a threaded joint to tighten the fastener.
Off torque, also referred to as release torque, is the torque required to release or loosen the threaded joint.
Among the many factors which affect the off torque -on torque ratio, and thus the effectiveness of a locking fastener, are the bolt length or grip length of the joint and the hardness of the materials at the joint and particularly the hardness of the workpiece engaged by the locking teeth.
With known locking fasteners the off torque - on torque ratio falls if the bolt length, or thickness, of the joint is small and if a hard material is used in the joint. For example, in a joint having a bolt length in the neighborhood of one to two bolt diameters in which the workpiece is a hard material, the off torque to on torque ratio can be near unity. This means that under such adverse conditions, the locking fastener .~14~386 performs only marginally better than a conventional fastener having no locking teeth.
The difficulties experienced with joints of short bolt length arises from the relative absence of resilience in the joint. In a longer joint of, for example, four or five bolt diameters, when the joint is tightened and the bolt is subjected to tension to apply the clamp load, the bolt elongates resiliently. To a lesser extent, resilient compression may exist in the clamped part of the joint including the workpiece.
Consequently, the locking teeth are resiliently biased against the workpiece during the initial rotation of the fastener in the loosening direction. This resilient biasing effect is largely lost in a joint with a short bolt length and the desired locking effect is not obtained, particularly with a hard workpiece.
Another difficultly arises from working of the fastened joint due to vibrations or other cyclic loading. Such loading can cause progressive embedment of the locking teeth into the workpiece, with the result that the clamp load applied by the bolt is reduced. Similarly, in a static joint, tooth embedment can occur due to a phenomenon known as "creep". Extreme reduction in clamp load or bolt tension can result in loosening of the joint by rendering the locking teeth ineffective.
Moreover, if the clamp load decreases below the maximum actual load experienced in the joint, the variable loads to which the fastener system is then subjected can lead to fatigue and breakage.
While flanges are widely used in locking fasteners, such flanges are functionally rigid and serve to increase the area of the bearing surface thereby to avoid undesirable stress ti386 concentrations in the joint. Although fasteners having resilient flanges are known, it is not possible to overcome the difficulties discussed above by use of a resilient flange on a known toothed locking fastener because of the necessity for the fastener to apply substantial clamp loads. If the flange is sufficiently resilient to permit deflection of the teeth equivalent to bolt elongation in a joint of relatively long bolt length, then the rigidity of the flange is inadequate to apply the necessary clamp loads.
Conversely, if the flange is rigid enough to produce the desired clamp loads, sufficient resiliency cannot be achieved.
A second aspect of the present invention relates to improvements in locking fasteners of the type having locking teeth. Among the important objects of the present invention are to provide an improved locking fastener exhibiting good locking characteristics and a high off torque - on torque ratio even with joints of relatively short bolt lengths and hard materials;
to provide a locking fastener simultaneously achieving resilient deflection of its locking teeth upon tightening as well as ample clamp loads; to provide a locking fastener wherin fatigue of the fastener system and/or loosening of the joint due to locking tooth embedment into the workpiece is avoided; to provide a locking fastener wherein tooth embedment does not result in loss of clamp load; and to provide an improved locking fastener overcoming problems and disadvantages experienced with such fasteners in the past.
The present invention provides a fastener for use in a threaded joint having a workpiece and comprising a body portion having a workpiece engaging end, a thread structure generally located in a circular cylindrical region symmetrical about the central axis of the body portion, a flange integral with the body portion disposed at the workpiece engaging end of the body portion, said flange extending radially outward from the body portion and defining a workpiece engaging surface adjacent the workpiece engaging end of the body portion, and the improvement characterized by said flange including a plurality of axially resilient and flexible flange segments and a plurality of rigid flange segments extending radially outward from said body portion including a plurality of discrete reinforcements formed integrally with said body portion and flange, each reinforcement extending both radially and axially between said flange and said body portion for rendering rigid said rigid flange segments, said rigid flange segments alternating circumferentially with the flexible flange segments.
In a second embodiment of the invention, there is provided a locking fastener for a threaded joint, the fastener including a body portion and a flange formed integrally at an end of the body portion and defining a bearing surface engageable with a workpiece. The flange extends radially outward beyond the body portion, and a plurality of locking teeth project axially from the bearing surface for locking engagement with the workpiece upon tightening of the fastener. The teeth are disposed in a plurality of first circumferentially spaced apart regions of the flange. Second regions of the flange, interspersed between the first regions, are rendered substantially rigid by support or brace structure associated with the fastener body and reinforcing the flange in the second regions. The first regions are resiliently deflectable in the axial direction away from the workpiece as the locking teeth engage , ., , .

. - . . .

the workpiece upon tightening of the fastener. As a result, the first, relatively rigid regions are capable of applying substantial clamp loads to the threaded joint, while the second, relatively flexible regions provide resilient loading of the teeth to produce effective and reliable locking action.
~loreover, embedment of the teeth in the workpiece does not decrease the total clamp load applied by the fastener.
The present invention may be best understood by reference to the embodiments of the invention illustrated in the accompanying drawings wherein:
FIG. 1 is a perspective view of a fastener embodying the present invention;
FIG. 2 is a bottom plan view of the fastener of FIG. l;
FIG. 3 is a side view of a threaded joint including the locking fastener, shown partly in cross section, and showing the locking fastener in a snug-tight or finger-tight condition prior to tightening;
FIG. 4 is a side view of the threaded joint with the fastener in a tightened condition;
FIG. S is a top view of a threaded joint including a fastener comprising an alternative embodiment of the present invention;
FIG. 6 is a side view of the threaded joint of FIG.
5 showing the fastener of FIG. 5 in a snug-tight or finger-tight condition prior to tightening;
FIG. 7 is a perspective view of a locking fastener comprising a second embodiment of the invention;
FIG. 8 is another perspective view of the locking fastener of FIG. 7;
FIG. 9 is a top view of a threaded joint including the locking fastener;

FIG. 10 is a side view of the threaded joint of FIG.
9, partly in cross section, showing the locking fastener in a snug-tight condition prior to tightening;
FIG. 11 is a side view of the threaded joint ~lith the locking fastener in the tightened condition;
FIG. 12 iS a fragmentary sectional view on an enlarged scale taken along the line 12~12 of FIG. 9 in which the snug-tight condition is illustrated in full lines and the tightened condition is indicated in broken lines; and FIG. 13 iS a fragmentary sectional view taken along the line 13-13 of FIG. 12.
Having reference now to the drawings and initially to FIGS. 1-6 there is illustrated a one-piece, metal fastener generally designated by the reference numeral 10 and constructed in accordance with the principles of the present invention. The fastener 10 is illustrated as a nut, although it should be understood that the principles of the present invention are applicable as well to headed fasteners such as bolts and screws.
In general, the nut 10 is in the form of a hex flange nut having an hexagonal body portion 12 with corners 12A and flats 12B adapted to be engaged by a wrench for tightening of a threaded joint including the nut 10. One end of the nut is provided with a flange structure 14 and includes an axially directed bearing surface 16. A central axial opening 18 extends through the nut and is provided with a female thread structure 20 for mating with complementary threads on a cooperating fastener.
In accordance with the present invention, the fastener 10 includes structure providing a spring characteristic to compensate for developed looseness or loss of tension in a threaded joint thereby to maintain clamp load and bolt tension despite developed looseness due to thermal expansion and contraction, gasket set or the like. Moreover, substantial spring forces are achieved with a compact and inexpensively manufactured structure.
More specifically, and as best seen in FIG. 2, the bearin~ surface 16 defined at the workpiece engaging end of the fastener lO includes a plurality of flexible and resilient portions or segments 22. Flexibility of the segments 22 is effected by forming the flange structure 14 of the fastener lO
with a relatively thin cross-section as compared with the thicker flange cross-section of a standard hex flange nut wherein the flange is functionally rigid in use. As a result of the use of a relatively thin flange, the flexible and resilient bearing surface regions 22 are able resiliently to deflect in the axial direction under the loading experiensed in a threaded joint.
In addition to the flexible segments 22) the bearing surface 16 includes a central region 24 surrounding the threaded opening 18 and lying radially inward of the flexible segments 22. The central region 24 is effectively rigid due to the fact that it coincides with the hex body portion 12 of the fastener 10 as indicated in broken lines in FIG. 2.
Interspersed between the flexible segments 22 of the bearing surface 16 are a number of spoke-like relatively rigid regions 26. In order to render the regions 26 functionally rigid, the fastener is provided with supporting or reinforcing structure associated with the body portion 12 and aligned with the regions 26. In the embodiment illustrated in FIGS. 1-4, the fastener lO is provided with a number of brace or support 1~463~6 structures 28 in the form of gussets or strut-like braces extending radially outward and sloping axially from the body portion 12 of the fastener 10 to the flange structure 14.
The gussets 28 serve to brace or reinforce the regions 26 so that they are unable to axially deflect to a significant degree when subjected to clamp loads in a threaded joint.
In the illustrated arrangement, there are provided six gussets 34 aligned with six rigid bearing surface regions 26, these being aligned with the corners 12A of the hexagonal body portion 12. This configuration has the result that the flexible segments extend from the flats 12B and radial length of the flange 14 at the flexible segments 22 is maximized.
In order to permit the flexible segments 22 of the bearing surface 16 and the associated portions of the flange 14 to function collectively as a spring to maintain tension in a threaded joint, the flange 14 in the region of the flexible segments 22 is bowed axially in the workpiece engaging direction.
While the rigid central region 24 and spoke-like regions 26 all lie in a common plane normal to the axis of the fastener 10, the flexibIe segments 22 are axially displaced as by forming the periphery of the flange 14 in a wavy or undulating configuration.
Having reference now to FIGS. 3 and 4, there is illustrated a threaded joint generally designated 30 including the fastener 10 of the present invention. In addition to the fastener 10, the joint 30 includes a cooperating fastener in the form of a bolt 32 having a head 34 non-rotatably engaged with a structural member 36 to which another member or workpiece 38 is joined.
In FIG. 3 the joint 3Q is illustrated in a snug-tight or finger-tight condition prior to final tightening of the fastener lO. In this condition, the flexible segments 22 of the bearing surface 16 contact the workpiece 38 while the rigid bearing surface regions 24 and 26 are axially spaced from the wotkpiece by an appreciable distance.
In FIG. 4 the threaded joint 30 is illustrated in a tightened condition. As the fastener lO is tightened against the workpiece 38, the rigid bearing surface regions 24 and 26 approach the workpiece 38 and the flexible segments 22 resiliently deform in the manner of a spring to apply substantial clamp loads in the threaded joint. As a result, tension is maintained in the joint despite factors such as wearing of parts, vibrations, thermal contraction, compression set or the like.
The fastener 10 is capable of imposing large spring forces despite its compact size and readily manufactured configuration. Each flexible segment 22 is bounded at its radially inward edge by the relatively rigid central region 24 aligned with the body 12 of the fastener. Each flexible segment 22 is also bounded at its sides by the rigid spoke-like regions 26. Because each flexible segment 22 is partially surrounded by rigid portions of the bearing surface, each segment 22 forms a relatively heavy or strong spring.
Having reference now to FIGS. 5 and 6, there is illustrated a threaded joint 40 similar to the joint 30 of FIGS. 3 and 4 except that it includes a unitary, metal fastener generally designated as 42 and comprising an alternative embodiment of the present invention. The same reference numerals are used for those components of the joint 40 which are similar to the components described above with reference to FIGS. 3 and 4. While the fastener 42 is illustrated as a nut, it should be understood that the principles of the present invention are applicable as well to headed fasteners such as bolts and screws.
In general, the nut 42 is in the form of a hex nut having a partially hexagonal body portion 44 with corners 44A
defined by partial flats adapted to be engaged by a wrench for tightening of a threaded joint including the nut 42. One end of the nut is provided with a flange structure 46 having a generally circular periphery coinciding with corners 44A. The flanged end of the fastener 42 includes an axially directed bearing surface 48.
In accordance with the present invention, the fastener 42 includes structure providing a spring characteristic to compensate for developed looseness or loss of tension in a threaded joint thereby to maintain clamp load and bolt tension despite developed looseness due to thermal expansion and contraction, gasket set or the like. ~oreover, substantial spring forces are achieved with a compact and inexpensively manufactured structure.
More.specifically, the bearing surface 48 includes a plurality of flexible and resilient portions or segments 50.
Segments 50 are located between the corners 44A around the periphery of the flange 46. Flexibility of the segments 50 is effected by forming the flange structure 46 of the fastener 42 with a relatively thin cross-section able resiliently to deflect in the axial direction under the loading experienced in a threaded joint.
The ability of the segments 50 to flex is enhanced by means of recesses 52 formed in the flats of the body portion 44 in order to increase the area of the flange 46 and of the segments 50. Use of the recesses 52 may be desirable if the ~1~6386 diameter of the flange is not appreciably larger than the corner-to-corner dimension of the body portion. Because the recesses 52 leave portions of the flats adjacent the corners 44A
undisturbed, the fastener 42 is able to be tightened with a conventional wrench.
In addition to the flexible segments 50, the bearing surface 48 includes a central region surrounding the threaded opening 18 and lying radially inward of the flexible segments 50. The central region is effectively rigid due to the fact that it coincides with the body portion 44 of the fastener 42.
The rigid central region, which is not seen in FIGS. 5 and 6, is similar to but relatively somewhat smaller than the region 24 shown in FIG. 2.
Interspersed between the flexible segments 50 of the bearing surface 48 are a number of spoke-like relatively rigid regions 54. The regions 54 are functionally rigid because they are aligned with the corners 44A of the body portion 44. In the embodiment illustrated in ~IGS. 5 and 6, the corners 44A
thus serve as brace or support structures serving to brace or reinforce the regions 54 so that they are unable to axially deflect to a significant degree when subjected-to clamp loads in a threaded joint.
In order to permit the flexible segments 50 of the bearing surface 48 and the associated portions of the flange 46 to function collectively as a spring to maintain tension in a threaded joint, the flange 46 in the region of the flexible segments 50 is bowed axially in the workpiece engaging direction.
While the rigid central region and the spoke-like regions 54 all lie in a common plane normal to the axis of the fastener 42, the flexible segments 50 are axially displaced as by forming the periphery of the flange 46 in a wavy or undulating configuration.
In FIG. 6 the joint 40 is illustrated in a snug-tight or finger-tight condition prior to final tightening of the fastener 42. In this condition, the flexible segments 50 of the bearing surface 48 contact the workpiece 38 while the rigid bearing surface regions including the spoke-like regions 54 are axially spaced from the workpiece by an appreciable distance.
When the fastener 10 is tightened against the work-piece 38, the rigid bearing surface regions approach the workpiece 38 and the flexible segments 50 resiliently deform in the manner of a spring to apply substantial clamp loads in the threaded joint. As a result, tension is maintained in the joint despite factors such as wearing of parts, vibrations, thermal contraction, compression set or the like.
The fastener 42 is capable of imposing large spring forces despite its compact size and readily manufactured configuration. Each flexible segment 50 is bounded at its radially inward edge by the relatively rigid central region aligned with the body 12 of the fastener. Each flexible segment 50 is also bounded at its sides by the rigid spoke-like regions 54. Because each flexible segment 50 is partially surrounded by rigid portions of the bearing surface, each segment 50 forms a relatively heavy or strong spring.
Having reference now to FIGS. 7-13 of the drawings, there is illustrated a locking fastener generally designated by the reference numeral 60 and comprising another embodiment of the present invention. The fastener 60 is illustrated in the form of a nut, although it should be understood that the principles of the invention are applicable as well to headed fasteners such as bolts and screws.

6;386 In general, the nut 60 is in the form of a hex flange nut having an hexagonal body portion 62 adapted to be engaged by a wrench for tightening of a threaded joint including the nut 60. One end of the nut is provided with a flange structure 64 defining an axially directed bearing surface 66. A central axial opening 68 extends through the nut and is provided with a female thread structure 70 for mating with complementary threads on a cooperating fastener.
A plurality of locking teeth 72 are formed upon the bearing surface 66 to provide a locking action. Each tooth includes a crest 74 (FIG. 12) defined on one side by a sloping tooth side surface 76 defining a relatively small angle, such as approximately ten degrees or so with a plane normal to the fastener axis. The other side of each tooth is defined by an abrupt or steep surface 78 which may be parallel or nearly parallel with the fastener axis. The sloping surfaces 76 permit the fastener to be rotated in the tightening direction, and the steep or abrupt surfaces 78 resist rotation of the fastener 60 in the loosen ng direction.
In accordance with the present invention, the flange structure 64 is provided with first segments 80 which are resiliently and axially deflectable, and with second rigid flange segments 82 alternating with the resilient regions 80.
The locking teeth 72 are disposed only in the resilient regions 80. As appears in more detail below, this arrangement permits the fastener 60 to apply substantial clamp loads to a threaded joint, provides for effective locking action even in a joint of short bolt length, and avoids loss of clamp load or loosening of the fastener due to tooth embedment.
More specifically, flexibility of flange regions 80 is effected by forming the flange structure 64 of the fastener 60 3~6 with a relatively thin cross section. For example, a standard hex flange nut of 5/16 inch nominal size has a flange cross section with a thickness at its periphery of approximately 0.04 inch and a maximum flange thickness in the neighborhood of O. JO/
about-0.~75-inch. In contrast, the locking fastener 60 constructed in accordance with the present invention and illustrated in the drawing in a 5/16 inch size may have a 0~~ s~
peripheral flange thickness of about 4~ inch and a maximum flange thickness in the neighborhood of about 0.035 inch. As a result of the use of a relatively thin flange, the resilient flange regions 80 are able resiliently to deflect in the axial direction under the loading experienced in a threaded joint.
This is in marked contrast to a standard hex flange nut wherein the flange is effectively rigid in normal use.
In order to render the flange regions 82 functionally rigid, the fastener is provided with supporting or reinforcing structure associated with the body portion 62 and aligned with the regions 82. In the illustrated embodiment of the invention, fastener 60 is provided with a number of brace or support struc-tures 84 in the form of gussets or strut-like braces extending radially outwardly and sloping axially from the body portion 62 of the fastener 60 to the flange structure 64. The gussets 84 serve to brace or reinforce the rigid flange regions 82 so that they are unable to axially deflect to a significant degree when subjected to clamp loads in a threaded joint. In the illus-trated arrangement, there are provided six gussets 84 aligned with six rigid flange regions 82, these being aligned with the corners of the hexagonal body portion 62. This configuration has the beneficial result that ~he radial length of the flange in the resilient regions 80 is maximized for maximum flexibility.

1~46386 As best illustrated in FIG. 9, the locking teeth 72 in accordance with the invention are disposed only in the resilient flange regions 80 and no locking teeth are provided in the rigid flange regions 82. Moreover, the locking teeth 72 are disposed adjacent the periphery of the bearing surface 66 at the radially outer portion of the flange structure 64.
Having reference now to FIGS. 3-7, there is illustrated a threaded joint generally designated as 90 including the fastener 60 of the present invention. In addition to the fastener 60, the joint 90 includes a cooperating fastener in the form of a round head square neck bolt 92 having a head 98 nonrotatably engaged with a structural member 94 to which another member or workpiece 96 is jointed.
In FIGS. 9, 10, 12 and 13 the joint 90 is illustrated in a snug-tight or finger-tight condition prior to final tightening of the fastener 60. In FIG. 11, joint 90 is illus-trated in the tightened condition achieved by rotation of the nut 60 in the tightening direction. In the tightened condition tension in the bolt between bolt head 98 and nut 60 is applied as a compressive load, termed a clamp load or preload, to the member 94 and workpiece 96.
The illustrated joint 40 represents an extremely adverse installation for a locking fastener because the bolt length of the joint - i.e., the axial distance between the head 98 of the bolt 92 and the bearing surface 66 of the fastener 60 is relatively small in that it is in the neighborhood of a single diameter of the bolt shank. Because of the short bolt length, only minimal bolt elongation can occur upon tightening of the joint 90, and the inherent flexibility of the joint is slight.

1~46386 In accordance with the present invention, the structure of the fastener 60 itself provides resilient flexibility for proper locking operation of the locking teeth 72 in engagement with the workpiece 96. More specifically, as shown in FIG. 11, upon tightening of the joint 90, engagement of the teeth 72 against the workpiece 96 causes the resilient flange regions 80 axially to deflect or bow away from the workpiece 96. As a result, the axial force with which the teeth 72 engage the workpiece 96 under full preload can be controlled and is a function of the resiliency or effective spring constant of the resilient flange regions 80.
While the regions 80 are capable of resilient deflec-tion upon engagement of the teeth 72 with the workpiece, the regions 82 are incapable of significant deflection because they are effectively rigid. Regions 82 are consequently capable of applying substantial clamp loads in the joint 90. As shown in FIG. 11 and as indicated in the broken lines in FIGS. 12 and 13, the bearing surface 66 in the regions 82 reinforced by the gussets 84 bottom out in flush engagement against the workpiece 96. This is best illustrated in FIG. 11 of the drawings wherein the regid regions 82 are firmly engaged with the workpiece 96, the resilient regions 80 are deflected or bowed upwardly away from the workpiece 96, and the crests 74 of the teeth 72 are firmly held in contact with the workpiece 96.
After the joint has been tightened, the clamp load applied by the fastener 60 is shared by the rigid regions 82 and by the teeth 72 in cooperation with the resilient regions 80.
Thus, a certain part of the clamp load is applied directly by the rigid regions 82 and the remainder of the total clamp load is applied by engagement of the teeth 72 against the workpiece 96.

~L463~6 It is typical of threaded joints including toothed fasteners that the teeth further embed into the workpiece over a period of time. An advantage of the fastener 60 of the present invention is that such further tooth embedment does not decrease the clamp load of the joint. As the teeth 72 become further embedded in the workpiece 96, the portion of the clamp load applied by the teeth 72 decreases as the extent of deflec-tion of the resilient flange regions 80 becomes less. However, the total clamp load remains substantially the same and a portion of the total clamp load applied by the rigid regions 82 increases an equivalent amount.
Since the total clamp load is not significantly decreased by embedment of the teeth 72 in the workpiece 96, the fastener 60 does not exhibit a tendency to become loose due to vibrations, cyclic loading or the like. Moreover, the initial clamp load or preload remains greater than the actual loads to which the joint 90 is subject so that fatigue to the fasteners in the joint is avoided.
An extremely important advantage of the fastener 60 is realized when the threaded joint is loosened by rotation of the fastener 60 in the release direction. In the initial increment of loosening rotation of the fastener 60, the locklng teeth 72 are continuously and resiliently biased toward the workpiece by the spring-like characteristic of the resilient flange regions 80. Thus, the locking teeth 72 are capable of performing an anti-rotation locking function equivalent to that achieved with known locking fasteners in joints characterized by long bolt lengths and substantial bolt elongation. Even with short bolt lengths and workpiece materials not substantially softer than the teeth 72, the crests 74 and steep surfaces 78 11~6386 are urged toward the workpiece 96 to dig or bite against the workpiece to achieve substantial off torque throughout the initial loosening rotation of the fastener 10.
In the illustrated embodiment of the invention, there are provided three individual locking teeth 72 in association with each resilient flange region 80. More or fewer teeth might be provided depending upon factors including, among others, the size of the fastener, the intended use of the fastener, the hardness of the material of the workpiece, and the like. It is preferred that where a number of teeth are associated with each resilient region 80 as in the illustrated arrangement, the teeth have relative heights such as to encourage even distribution of the axial tooth loading forces among the various teeth.
In the illustrated arrangement, the three teeth 72 of each grouping are of the same overall shape, but the tooth height (i.e., the axial distance from the bearing surface 66 to the tooth crest 74 in the nontightened condition) of the center tooth is slightly larger than the tooth height of the two flanking outer teeth. Consequently, when the resilient flange region 80 is flexed or bowed upon tightening of the fastener 60 against workpiece 96 as seen in broken lines in FIG. 12, the crests 74 of the three teeth 72 becomes substan-tially coplanar against the workpiece 96.
In addition, in the preferred embodiment of the invention, each tooth 72 has a nonuniform height to the end that the tooth crest 74 becomes flush with the workpiece 96 upon tightening of the fastener 60. As illustrated in FIG. 13, in the nontightened condition of the fastener the tooth height is greatest at the periphery of the flange 64 and decreases to a minimum at the radially inner end of the tooth. ~hen the .

11~6386 fastener 60 is tightened as indicated in broken lines in FIG.
13, the deflection of the flexible flange segment 80 is accompanied by tilting or cocking of the tooth 72 bringing its crest 74 into substantial alignment with the surface of the ~ 5 workpiece.
The principles of the present invention are applicable to fasteners other than the illustrated nut 60, such as flange head bolts and screws. Thus the term "body" as used herein is intended to encompass not only the body of a nut, but also equivalent structures such as the head of a shanked fastener.
Moreover, various head or nut body configurations including both external and internal wrenching configurations, may be provided with the locking construction of the present invention.

Claims (17)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A fastener for use in a threaded joint having a workpiece and comprising a body portion having a workpiece engaging end, a thread structure generally located in a circular cylindrical region symmetrical about the central axis of the body portion, a flange integral with the body portion disposed at the workpiece engaging end of the body portion, said flange extending radially outward from the body portion and defining a workpiece engaging surface adjacent the workpiece engaging end of the body portion, and the improvement characterized by said flange including a plurality of axially resilient and flexible flange segments and a plurality of rigid flange segments extending radially outward from said body portion including a plurality of discrete reinforcements formed integrally with said body portion and flange, each reinforcement extending both radially and axially between said flange and said body portion for rendering rigid said rigid flange segments, said rigid flange segments alternating circumferentially with the flexible flange segments.

2. The fastener of claim 1 wherein said body portion is generally hex-shaped and wherein said reinforcing means is aligned with the corners of said body portion and said resilient and flexible flange segments are aligned with the flats of said body portion.

3. The fastener of claim 2 wherein said flange means is generally circular and wherein the periphery of said flange means is radially spaced outwardly from said corners.

4. The fastener of claim 3, said reinforcing means comprising brace structure extending between said body portion and said flange.

5. The fastener of claim 4, said brace structure comprising a gusset extending radially outwardly and sloping axially between said body portion and said flange.

6. The fastener of claim 2 wherein said flange means is generally circular and wherein the periphery of said flange means generally coincides with said corners.

7. The fastener of claim 6 further comprising recesses in said flats overlying said flexible flange segments, said corners and the nonrecessed portions of said flats constituting said reinforcing means.

8. A fastener as claimed in claim 1 wherein first segments of said workpiece engaging surface defined by the rigid flange segments lie in a flat plane substantially perpendicular to the fastener axis, and second segments of said workpiece engaging surface defined by the flexible flange segments extend axially outward from said flat plane.

9. The fastener of claim 1 further comprising locking projections extending axially from said workpiece engaging surface; said locking projections being restricted to said flexible flange segments.

10. A fastener as claimed in claim 9 wherein said locking projections comprise teeth.

11. A fastener as claimed in claim 10 wherein each tooth includes a crest comprising a line defined at the junctions of abrupt and sloping tooth sides, said line having a substantial component in the radial direction.

12. A fastener as claimed in claim 10 wherein a plurality of teeth are located at each said flexible flange segment.

13. A fastener as claimed in claim 12 wherein the height of said teeth is nonuniform.

14. A fastener as claimed in claim 13 wherein the height of those teeth at the center of each said flexible flange segment is greater than the height of adjacent teeth.

15. A fastener as claimed in claim 11 wherein each tooth has a maximum tooth height at its radially outward end and a minimum height at its radially inner end.

16. The fastener of claim 1 wherein said rigid flange segments extend radially outward from said body portion substantially to the periphery of said flange, said rigid flange segments being spaced apart from one another around the circumference of said flange for rendering relatively rigid a plurality of spoke-like regions of said flange, said spoke-like regions extending from said body portion substantially to the periphery of said flange, said spoke-like regions lying in a plane normal to a central longitudinal axis of said fastener, said flexible and resilient flange segments extending radially outward from said body portion in the interstices between said rigid flange segments to the periphery of said flange and defining spring regions of said flange, each said spring region being bounded at its radially inner extent by said body portion, at its sides by an adjacent pair of said spoke-like regions, and at its radially outer extent by the periphery of said flange, and said flange means being bowed in the axial direction away from said body portion, and said spring portions being engageable with the workpiece while said body portion and spoke-like regions are spaced from the workpiece.

17. The fastener of claim 16 wherein said flange is connected through-out its inner periphery to said body portion.