LOCKING FASTENER ASSEMBLY FOR THREADED JOINT

Abstract: A locking fastener assembly (10) for axle bearings and the like is free spinning during tightening and removal and is posi­ tively held against rotation after installation. The assembly (10) is engageable with an axially slottted male threaded mem­ ber (14) and includes a nut (40) with female threads and a flanged end. A retainer washer (42) includes spaced fingers (62) formed around the nut flange (48) for rotatably supporting the washer at the flange, and a tab (58) received in the slot (60) of the male threaded member (14) permitting the nut (40) to move axially but not to rotate on the male threaded member. When the nut (40) is engaged by a wrench, the wrench releases a flexible and resilient locking clip (44) to permit the nut freely to rotate. After the assembly (10) has been threaded onto the male threaded member (14), removal of the wrench frees the locking clip (44) and a lock finger (76) is received in a space (64) between fingers (62) of the retainer washer (42) po­ sitively to prevent further rotation of the nut (40).

Description: The present invention relates to locking fastener assemblies for threaded joints and more particularly to improvements in free-spinning locking fastener assemblies that are positively locked after installation. Background of the Invention Locking fasteners and locking fastener assemblies are used to prevent loosening of a threaded fastener in a fastener joint. There are many types of threaded joints in which loosening of a fastener is undesirable. One example to which the principles of the present invention may be applied is an axle assembly of an automotive vehicle. In a typical axle assembly, axle bearings are supported between an axle or spindle and a wheel hub or spindle support to permit rotation of a vehicle wheel. An axle bearing nut is used to hold the components together. In order to prevent premature bearing failure, the nut must be installed properly to avoid excessive axial bearing load or, alternatively, excessive free play. In addition, after assembly it is important to prevent loosening of the axle bearing nut to avoid bearing failure or even dangerous loss of a wheel. A conventional axle assembly includes a spindle with male threads having an axially extending slot. A washer received on the spindle has a tab in the slot to prevent rotation of the washer. After the nut is threaded onto the spindle and tightened to the desired degree, part of the washer is deformed to lock the washer to the nut and prevent further rotation of the nut. This conventional approach has disadvantages. One serious problem, especially in original mass production, is that installation of the washer and nut requires too many manual assembly steps. Another disadvantage is that the washer must be deformed both after installation of the nut and again when it is desired to remove the nut. The fact that the nut and washer are separate pieces makes it possible for the assembly to be installed improperly, for example without the washer or with an incorrect or damaged washer. Moreover, the locking of the nut against rotation is not as positive as desired because the washer can be deformed or broken. In order to overcome such disadvantages, in a prior art approach, a nut and a non-rotating retainer have been used normally separated by a spring and having interfacing teeth or similar locking structures. As the assembly is tightened, the spring force is overcome and the nut becomes locked to the retainer to prevent further rotation. In addition to complexity and expense, the arrangement has the disadvantage that as the nut reaches its final position, it is not free spinning. The ragged, uneven torque characteristic interferes with the use of torque detecting equipment that could otherwise detect a predetermined degree of tightening of the fastener assembly. Also, this assembly requires at least the amount of preload necessary to compress the spring normally separating the nut from the retainer. In another approach locking fastener assemblies have been proposed in which a washer and a nut are normally locked against rotation and in which the installation tool or wrench can be manipulated to free the nut for rotation. Examples of such proposals can be found in US-A-3 851 690 and US-A-3 942 570. While the assemblies disclosed in these patents overcome some disadvantages of the conventional nut and washer, they are subject in turn to other disadvantages. They include relatively delicate mechanisms requiring complex movements and are not well suited to the types of forces and environments encountered by automotive vehicles. In addition, they require special manipulation of an installation tool or wrench over and above the normal use of a wrench with a nut. More specifically, the fastener assembly of US-A-3 942 570 includes all of the features mentioned in the preamble of claim 1. In this case the resilient locking means consist of a solid toothed ring engaging, with its teeth, either spaced apart axial slots of the washer and aligned grooves of the nut and is displaceable axially against a spring force thus to free the nut for rotation relative to the washer. Though this displacement can be effected by a wrench at the same time engaged with the wrench surfaces of the nut it requires application of an additional force in an additional, unusual direction thus rendering this assembly impractical. In DE-A-593 758 another locking fastener assembly including a threaded spindle, a grooved nut and a washer having spaced apart apertures for engagement with a wrench releasable locking means is disclosed where the latter consists of a resilient locking clip mainly received in a groove of the nut. In this case the groove extends into the area of the wrench engaging surfaces of the nut, and the locking clip, in its normal or locking condition, protrudes radially outward form the groove. Thus, when the nut is engaged by a wrench, the locking clip can be depressed without requiring an additional movement or force to release the washer for allowing rotation of the nut. However, this assembly is designed to prevent rotation of the nut relative to the part to be secured rather than to the spindle on which it is threaded and thus cannot be used where the part to be secured can itself rotate relative to the spindle. Moreover, to obtain the desired release operation for rotation of the nut, some wrenches such as ordinary open-mouthed wrenches must be applied in a specific angular position to releasingly engage the locking clip. Starting from this basis, the invention as claimed aims at providing a locking fastener assembly of the kind specified in the preamble of claim 1 in which the nut can be released simply by applying a wrench - any wrench that fits to the wrench surfaces of the nut - in the usual way and, in case of applying a ring wrench or an annular nut wrench, even in any angular position to effect rotation of the nut. This is achieved by the characterizing features of claim 1 in that a resilient locking clip provided at the intersection of two wrench surfaces will automatically be depressed by any ordinary wrench engaging the nut, no matter in which angular position with regard to the position of the locking clip the wrench is applied. The invention is adventageous particularly in providing improvements in axle bearing fastener assemblies and in overcoming difficulties encountered with axle bearing nut installations known in the past. In the following, for better understanding, a preferred embodiment of the invention is described in detail in connection with the accompanying drawings wherein FIG. 1 is a simplified, somewhat diagrammatic, fragmentary side elevational view of an axle assembly provided with a locking fastener assembly embodying the present invention; FIG. 2 is an enlarged end view taken from the line 2-2 of FIG. 1; FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2; FIG. 4 is an enlarged sectional view taken along the line 4-4 of FIG. 2; FIG. 5 is a fragmentary sectional view taken along the line 5-5 of FIG. 3; FIG. 6 is a view like FIG. 5 showing the released condition of the fastener assembly; FIG. 7 is a view like part of FIG. 4 showing the released condition of the fastener assembly; and FIG. 8 is a perspective view showing the components of the locking fastener assembly prior to assembly. Detailed Description Having reference now to the drawings and initially to FIG. 1, there are illustrated in somewhat simplified and diagrammatic fashion certain components of a threaded joint designated as a whole by the reference character 10. The threaded joint includes a locking fastener assembly generally designated as 12 and constructed in accordance with the principles of the present invention. In the preferred embodiment of the invention illustrated in the drawings, the threaded joint 10 is typical of an axle bearing assembly for an automotive vehicle such as a truck, automobile or the like. However, the principles of the present invention are applicable to locking fastener assemblies for a wide variety of threaded joints including axle assemblies of different configurations as well as others. Axle assembly 10 includes a spindle 14 provided with a suitable flange 16 for supporting the spindle suspended from the frame of an automotive vehicle. A wheel hub 18 supports studs 20 for mounting a wheel on the hub. A caliper brake disc 22 is carried by the hub, although a drum brake might be employed instead. The wheel hub 18 is mounted for rotation around the spindle 14 by an inner bearing assembly 24 and an outer bearing assembly 26 held in position by the locking fastener assembly 12 of the present invention. While FIG. 1 illustrates in simplified fashion one type of axle assembly, many different types are also used. In some arrangements, inner and outer bearing assemblies may be interposed between a driven spindle or axle upon which a wheel is mounted and a support suspended from a vehicle frame. In other arrangements, for example as employed on four-wheel drive vehicles, the spindle may be a tube interposed between a drive axle and a wheel hub. The locking fastener assembly 12 of the present invention may be employed in any of the various types of axle assemblies for fastening the components of the assembly together and avoiding excessive loading or end play of the bearings. Inner bearing assembly 24 is captured between a shoulder 28 on the spindle 14 and a shoulder 30 on the wheel hub 18. Outer bearing assembly 26 is captured between a shoulder 32 on the wheel hub 18 and the locking fastener assembly 12. In different types of assemblies, spacers or the like may also be used to assist in positioning the bearing assemblies. Assembly 12 is threaded onto a threaded portion 34 of the spindle 14 to take up any looseness or play and hold the components in place. If fastener assembly 12 is threaded too far onto the threaded portion 34, the bearing assemblies 24 and 26 are excessively loaded or compressed and their operating life is reduced. If fastener assembly 12 is not threaded far enough onto the threaded portion 34, the bearings have excessive free play and their operating life is also decreased. Thus, it is important that the fastener assembly 12 is threaded onto the portion 34 to a carefully determined position and that thereafter the fastener assembly 12 is prevented from rotating. Having reference now more specifically to FIGS. 2-8, the locking fastener assembly 12 of the present invention includes a nut 40 associated with a retainer washer 42 and a locking clip 44. The washer is permitted to move axially upon but cannot rotate relative to the threaded portion 34 of the spindle 14. The clip 44 permits the nut 40 to rotate freely relative to washer 42 when a tool is used to thread the nut 40 onto or off of the threaded portion 34 of the spindle. When the tool is removed, the locking clip 44 achieves a positive locking action by preventing the nut 40 from rotating relative to the washer 42. Nut 40 includes a female thread structure 46 sized to mate with the male threads formed on the threaded portion 34 of the spindle 14. The load bearing end of the nut 40 is provided with a flange 48 of increased diameter. The remainder of the nut body is provided with a tool receiving wrenching structure 50 preferably of hexagonal shape to mate with a standard wrench socket. At one point along the periphery of the nut 40, there is provided an axially extending groove 52 recessed into the flange 48 and into the wrenching structure 50. At the flange end of the nut 40, the groove 52 intersects a radially extending groove 54 formed in the end of the nut. Washer 42 is preferably stamped and formed from flat metal stock and includes a central axial opening 56 slightly larger in diameter than the female thread structure 46 of nut 40. A restraining tab 58 extends radially inward into the central opening 56 of the washer 42. The threaded portion 34 of spindle 14 includes a cooperating axially extending slot 60 (FIGS. 4-6) serving to receive tab 58 and prevent rotation of washer 42 around the threaded portion 34. In threaded joints of other configurations, different restraining structures might be provided for preventing rotation of a retainer. The outer circumference of retainer washer 42 is provided with numerous fingers 62 separated by spaces or slots 64. In order to hold the washer 42 in assembly with nut 40, the washer is received against the flange end of the nut 40 and the fingers 62 are first formed axially (FIG. 8) and then formed radially inward around the outer circumference of the flange 48. In the assembled condition, clearance is provided to permit the nut 40 and the washer 42 to rotate relative to one another. Locking clip 44 is a unitary, one-piece stamped and formed element fabricated of spring steel or similar resilient and flexible material. It includes a base portion 66 joined to a foot portion 68 received respectively in the grooves 52 and 54 of the nut 40 (FIG. 4). The end of base portion 66 opposite foot portion 68 is bounded by a loop or hinge segment 70 leading to an elongated latch release segment 72 disposed at an acute angle relative to the base portion 66. The opposite end of segment 72 defines a pair of stop shoulders 74. A locking finger 76 extends outwardly between the stop shoulders 74. Locking clip 44 may be installed in the locking fastener assembly 12 after mounting of the retainer washer 42 on the nut 40. Segment 72 can be flexed toward the base portion 66 and the clip 44 can then be moved to the installed position best seen in FIG. 4. When the segment 72 is released, the base portion 66 is seated in the bottom of the axial groove 52 and the clip is captured against axial movement by engagement of the foot 68 in the groove 54 and engagement of the loop 70 with the nonflanged end of the nut 40. The components of the completed assembly 12 are not easily disassembled because the washer 42 is captured on the flange 48 of nut 40 and because the locking clip 44 cannot be removed from grooves 52 and 54 without great difficulty. As a result, improper use of only portions of the assembly 12 and improper installation of the assembly are prevented. In the normal condition of the fastener assembly 12 shown in FIGS. 4 and 5, the locking finger 76 is resiliently urged in the radially outward direction. Finger 74 is sized to fit in any of the spaces 64 between fingers 62 with stop surfaces 74 in engagement with the fingers 62 on opposite side of the space 64. In this position, the locking clip 44 positively prevents rotation of the nut 40 relative to the retainer washer 42. When the latch release segment 72 is moved radially inwardly as seen in FIGS. 6 and 7, the locking finger 76 moves inwardly clear of the fingers 62. In this released condition, nut 40 can rotate or spin freely relative to the retainer washer 42. In accordance with an important feature of the invention, when a wrench socket 78 (see FIGS. 6 and 7) is engaged with the wrenching structure 50 of the nut 40, the socket 78 engages the latch release segment 72 of the locking clip 44 and moves it to the released position. No special manipulation of the socket 78 is required since the normal engagement of the socket itself frees the locking clip 44. Conversely, when a wrench is not present on the wrenching structure 50, the locking finger 76 is resiliently biased radially outward to be received in a space 64 between adjacent fingers 62. Since the locking clip 44 is located at a corner of the hex shaped wrenching structure 50, release of the latch is assured regardless of whether a six point or a twelve point socket is used. In use of the locking fastener assembly 12 in the threaded joint 10, the threaded portion 34 of the spindle together with the slot 60 may be considered to be a relatively fixed structure, while the fastener assembly 12 may be considered as moving relative thereto. To install the fastener, the wrench socket 78 is engaged with the hex shaped wrenching structure 50 of the nut 40 in the normal manner. As the socket is placed on the nut 40, it contacts the latch release segment 72 of the locking clip 44 and forces the segment 72 as well as the locking finger 76 radially inward. This action is enhanced by the angular orientation of the segment 72 providing the mechanical advantage of a cam action. When the wrench is engaged sufficiently to drive the fastener assembly 12, the locking finger 76 is completely clear of fingers 62 to achieve a free spinning action of the nut 40 relative to the retainer washer 42. At this point, the locking fastener assembly 12 may be installed on the threaded portion 34 of the spindle 14. The tab 58 of the washer 42 is received in the slot 60 in the threaded portion 34. The nut 40 is rotated by the wrench socket 78 and is threaded onto the threaded portion 34. Threading of the nut continues until a predetermined position is reached in which the inner and outer bearing assemblies 24 and 26 are neither too tight nor too loose. This point may be determined by detecting an increase in the torque required to rotate the nut 40. An accurate determination is enabled because the nut turns freely without a prevailing torque or an uneven torque characteristic until the wrench socket 78 is removed. At the properly installed position of the fastener assembly 12, the wrench socket 78 is removed. This frees the latch release segment 72 together with the locking finger 76 for radially outward movement. Depending upon the relative circumferential positions of fingers 62 and clip 44, the locking finger 76 may immediately enter a space 64 between two adjacent fingers 62. In this case, the nut 40 is interlocked to the retainer washer 42 and positively locked from further rotation since the retainer washer 42 is rotationally locked by tab 58 to the threaded portion 34. Alternatively, in a slightly different position of the clip 44 relative to fingers 62, the locking finger 76 may strike a finger 62 rather than a space 64 when the wrench socket 78 is removed. Nevertheless, positive locking is assured because if nut 40 rotates a maximum of only a few degrees, the locking finger 76 becomes aligned with a space 64 and moves outwardly to a locked position. While the invention has been described with reference to details of the preferred embodiment, these details are not intended to limit the scope of the invention as defined in the following claims.

Claims: A locking fastener assembly (12) for positively securing the longitudinal position of an annular ring member mounted on a spindle (14), said locking fastener assembly being of the type including an externally threaded outer surface portion (34) of said spindle (14) provided with an axially extending slot (60), an annular locking washer (42) mounted on said spindle (14), abutting an end face of said ring member and including a radially inwardly extending restraining tab (58) slidably engaged in said slot (60) for preventing relative rotation between said spindle (14) and said washer (42) and a plurality of spaced apart open-ended slots (64) around a periphery of said washer (42), and a nut (40) internally threaded for threaded engagement with said spindle (14) and including a plurality of intersecting wrench surfaces spaced equilaterally around said spindle (14) for engagement with a wrench means (78), and an axially extending groove (52) in an outer surface of said nut (40), and resilient locking means normally engaged with said groove (52) of said nut and one of said slots (64) of said washer (42) to lockingly interconnect said nut (40) and said washer (42) yet displaceable by said wrench means (78) when this is engaged with said wrench surfaces to free the nut (40) for rotation relative to said washer (42), characterized in that said open-ended slots (64) are provided in a radially outward portion of said washer (42) bent around a radially outwardly extending flange (48) of said nut (40) for securing said washer to said nut and in that said locking means comprise a resilient locking clip (44) mounted in said groove (52) of said nut (40) and including a radially outwardly directed locking finger (76) adapted to be engaged in a selected one of said open-ended slots (64) of said washer (42) for securing said nut (40) and said washer (42) against relative rotation, said locking clip (44) also including lock release means (72) adapted to be engaged by said wrench means (78) for retracting said locking finger (76) radially inwardly from engagement with said selected one of said slots (64) of said washer (42) when said wrench means (78) is applied for turning said nut (40) relative to said spindle (14), and in that said axial groove (52) of said nut (40) is positioned between a pair of adjacent wrench surfaces for engagement by said wrench means (78) when this engages either or both of said adjacent wrench surfaces. The locking fastener assembly (12) of claim 1, wherein said lock release means (72) are biased to urge said locking finger (76) radially outwardly to engage one of the slots (64) of said washer (42) when this is aligned therewith, the wrench means (78) being disengaged. The locking fastener assembly (12) of claim 1 or 2, wherein said locking clip (44) is formed of metal and includes an inner base portion (66) seated in said groove (52) of said nut (40), and an outer portion (72) extending radially outwardly thereof beyond at least one of said wrench surfaces to form said lock release means. The locking fastener assembly (12) of claim 3, wherein said locking finger (76) is formed on said outer portion of said locking clip (44), and said outer portion is deflectable radially inwardly by engagement of said wrench means (78) with at least one of said pair of wrench surfaces adjacent said groove (52) for turning said nut (40) relative to said spindle (14). The locking fastener assembly (12) of claim 3 or 4, wherein said nut (40) further includes a radially extending groove (54) intersecting said axially extending groove (52) adjacent said flange (48), and said inner base portion (66) of said locking clip (44) includes a radially inwardly directed foot portion (68) extending into said radial groove (54) for retaining said locking clip in said axial groove (52). The locking faster assembly (12) of anyone of the claims 3 to 5, wherein said locking clip (44) comprises a unitary member formed of spring metal and said inner and outer portions (66, 72) are joined integrally at one end thereof whereas said locking finger (76) is formed on the free end of said outer portion (72). The locking fastener assembly (12) of claim 6, wherein said inner and outer portions (66, 72) are joined by a loop segment (70) and spread away from one another away from said loop segment.

Inventors: GRUBE, WILLIAM L.
Applicants: MACLEAN-FOGG COMPANY
Application year: 1988
Main classification: F16C35
IPC codes: F16B39, F16C35, F16C25