Abstract:
Self-locking nuts help prevent the nut from backing off of a spindle or other type of threaded shaft. A single piece nut assembly is provided that is self-locking and comprises a nut subassembly and a washer subassembly. Nut and washer subassemblies are secured together, and do not require any special tools for installation or removal. The washer has an edge which is formed/rolled over a lip extending from the bottom edge of the nut when assembled to provide the unitized assembly. The nut and washer are held apart by a spring, such as a wave spring, until the washer contacts the face of the object to which the nut is being secured. At this point the spring is compressed to engage the nut with the washer, and engage holding elements located in the nut with a holding feature located on the washer and prevent movement between the washer and nut.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/230,688, filed on Jul. 31, 2009, the entire disclosure of which is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    Embodiments described herein generally relate to fastening mechanisms. Embodiments of the present invention more specifically relate to self-locking fastening mechanisms. 
       BACKGROUND 
       [0003]    Nuts are well known implements generally used to hold an object in place and may be used in numerous different application such as, for example, the ends of axles or spindles. For example, a nut may be used to hold the wheel-end of a truck in place by engaging with a spindle. A nut is generally a metal part with a circular, threaded bore through the middle, usually for engaging with a threaded spindle or similar implement. The nut is screwed onto the spindle and tightened against the object to be held in place. However, a problem with conventional nuts is that they may be prone to loosening during use, a failure known as “backing off.” For example, if a nut securing a truck&#39;s wheel-end backs off, the wheel-end may become loose or break apart from the vehicle. Such an incident poses a significant safety concern. 
         [0004]    To remedy this problem, there are nuts may be assembled with multiple components that are assembled as the nut is put into place that cause the nut to lock into place, reducing the likelihood of the nut backing off. 
       SUMMARY 
       [0005]    Embodiments of the present invention provide self-locking nuts that help prevent the nut from backing off of a spindle or other type of threaded shaft. For example, according to one embodiment, a single piece axle spindle nut assembly is provided that is self-locking and comprises a nut subassembly and a washer subassembly. The assembly of this embodiment is provided as a single piece, with the nut and washer subassemblies secured together, and does not require any special tools for installation or removal. The washer has an edge which is formed/rolled over a lip extending from the bottom edge of the nut when assembled to provide the unitized assembly. The nut and washer are held apart by a spring, such as a wave spring, until the washer contacts the face of the object to which the nut is being secured. At this point the spring is compressed to engage the nut with the washer. 
         [0006]    The washer also has holding features that are engaged when the spring is compressed. The holding features, in an embodiment, are spring loaded plungers inserted into the nut body and prevent rotation of the nut during service. The quantity of holding features depends on the retention force required per application. These holding features do not engage until the washer contacts the face of the object to which the nut is being secured. This allows the nut to be installed without resistance until the nut contacts the face of the object to which the nut is being secured. In an embodiment, the washer is hardened and features a wide tang area which mates with a keyway in a spindle. Such a wide tang allows for a large area to transfer any torque and would reduce spindle damage. The hardened washer would absorb all rotational forces. The nut would prevent axial movement and stop the assembly from unscrewing and maintain the bearing adjustment over time. The nut assembly may be installed using standard installation tools, and does not require any special tool for installation or removal. Furthermore, the tool, such as a standard socket, used for installation or removal is not required to engage any portion of locking or holding features in order to install or remove the nut assembly. 
         [0007]    The holding features act to retain the nut by themselves over time, but in one embodiment an additional locking feature is also incorporated into the assembly. The locking feature of this embodiment operates on a cam type system which locks the feature in a released or engaged state, and is operated by hand. The locking feature has to be disengaged in order for a socket to be installed on the nut for installation or removal. Once the nut is properly installed the locking feature of this embodiment is rotated out by hand and does not require any special tools. The locking feature locks the nut to the washer and provides additional safety over the holding features. The design of the engaging holes or slots for the locking pin depends on how much rotation is desired once locked. The nut can be used in both an end-play or pre-load installation. 
         [0008]    One aspect of the present disclosure, in particular, provides a single piece locking nut assembly, comprising: (A) a nut having (i) a top surface, (ii) a bottom surface, (iii) a substantially cylindrical opening through the center thereof, at least a portion of which having threads that are adapted to engage with corresponding threads of a spindle, and (iv) one or more cavities that each receive a holding element that extends into the cylindrical opening; (B) a washer comprising (i) a substantially cylindrical opening through the center thereof, (ii) a washer base, (iii) an inner wall extending up from the washer base extending around at least a portion of the cylindrical opening and extending into the cylindrical opening of the nut, and (iv) a locking feature located on a side of the inner wall that is opposite the washer opening, the locking feature comprising a plurality of ridges that engage one or more holding elements; and (C) a biasing member located between the nut bottom surface and the washer base that prevents the holding element(s) from engaging the locking feature when the nut assembly is not fully engaged with a spindle. 
         [0009]    These illustrative embodiments are mentioned not to limit or define the invention, but to provide examples to aid understanding thereof. Illustrative embodiments are discussed in the Detailed Description, and further description of the invention is provided there. Advantages offered by various embodiments of this invention may be further understood by examining this specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    These and other features, aspects, and advantages of the present invention are better understood when the following Detailed Description is read with reference to the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a top perspective of an exploded view of a self-locking nut according to an embodiment; 
           [0012]      FIG. 2  is a bottom perspective of an exploded view of a self-locking nut according to an embodiment; 
           [0013]      FIG. 3  is a top perspective of an assembled a self-locking nut assembly according to an embodiment; 
           [0014]      FIG. 4  is a cross-sectional view of an assembled self-locking nut assembly according to an embodiment; 
           [0015]      FIG. 5  is a top perspective view of a self-locking nut assembly as installed according to an embodiment; 
           [0016]      FIG. 6  is a cross-sectional view of a self-locking nut assembly as installed according to an embodiment; 
           [0017]      FIG. 7  is a cross-sectional view of a holding feature in a pre-installed state according to an embodiment; 
           [0018]      FIG. 8  is a cross-sectional view of a holding feature in an installed state according to an embodiment; and 
           [0019]      FIG. 9  is atop perspective view of a washer of another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Embodiments of the present invention provide a variety of self-locking fasteners. Referring to the drawings,  FIGS. 1-8  illustrate various views of a single piece self-locking nut assembly  20  according to an embodiment.  FIGS. 1 and 2  illustrate an exploded view of a single piece self-locking nut assembly  20  according to one embodiment of the present disclosure. In the embodiment shown in  FIGS. 1 and 2 , self-locking nut  20  comprises a nut  24 , a washer  28 , and four holding features  32  that are assembled into corresponding through cavities  36  in the nut  24  to extend through to an interior portion of the nut  24 . The surface of nut  24  opposite the washer  28  is referred to as the top surface of the nut  24 , and the surface of the nut  24  that is adjacent to the washer  28  is referred to as the bottom surface of the nut  24 . The cavities  36 , in this embodiment, are through holes that extend from the outer perimeter of the nut  24  to the interior portion, although the cavities  36  do not necessarily have to extend completely through the nut  24 . In this embodiment, the holding features  32  are ball plungers that have a ball element that is biased outward by a spring located within the plunger housing such that, as will be described in more detail below, the ball element engages with the washer  28  to prevent movement between the nut  24  and washer  28 . In other embodiments, the holding feature  32  may comprise springs or other biased members that have a portion extending into the interior opening of the nut  24  so as to engage with the washer  28  engagement area. 
         [0021]    The nut  24  comprises a generally octagonal outer perimeter and defines a substantially cylindrical opening through the center of the nut  24 . The substantially cylindrical opening is threaded over at least a portion thereof to correspond to threads of a spindle that receives the nut assembly  20 . While the nut  24  shown in  FIGS. 1 and 2  has a substantially octagonal outer perimeter, nuts according to other embodiments may have other suitable shapes. For example, in one embodiment, nut may comprise a substantially hexagonal outer perimeter. In other embodiments, nut may comprise other outer perimeter shapes, including without limitation circular, square, pentagonal, or any other suitable shape. 
         [0022]    In the embodiment illustrated in  FIGS. 1-8 , the nut  24  includes four cavities  36  configured to receive one holding feature  32  each. In a nut  24  having a substantially octagonal shape, four cavities  36  may be beneficial as it may provide a generally symmetric and evenly-spaced arrangement of cavities  36  around the perimeter of the nut  24 . However, other configurations are contemplated and within the scope of the present invention. For example, if symmetry and even spacing are desirable, two, four, or eight cavities  36  may be employed. Additionally, the shape of the nut  24  may affect the number and arrangement of cavities  36  in a symmetrical or otherwise evenly-spaced configuration. Alternate embodiments not having evenly-spaced or symmetrically-arranged cavities  36  may comprise other numbers holding features  32 . For example, a nut  24  may have one, three, or five cavities  36 . 
         [0023]    The washer  28  of this embodiment comprises an outer wall  40 , a washer holding feature engagement area  44 , an optional washer lock pin engagement area  48 , and a formed or rolled edge  52  (best viewed in  FIGS. 4 and 6 ). In other embodiments, the holding features  32  may be arranged in cavities  36  in the nut  24  so as to extend through the bottom of the nut  24  and engage with a holding feature engagement area located on the washer base to the interior, or exterior, side of the lock pin engagement area (if present). In this embodiment, the washer  28  comprises a substantially annular shape and defines a substantially cylindrical opening through the center of the washer  28 . The opening defined by washer  28  has substantially the same diameter as the opening defined by the nut  24 . 
         [0024]    In this embodiment, the washer  28  is hardened and features a wide tang area  56  which mates with a complementary spindle keyway. The wide tang  56  allows for a large area to transfer torque and acts to reduce spindle damage that may result from excessive torque being placed on the nut  24 . However, in some other embodiments, the washer  28  may define other sized or shaped openings. For example, in one embodiment, washer  28  may define an opening having a square cross-section or a D-shaped cross-section. In another embodiment, washer  28  may define an opening having any suitable cross-section, such as a cross-section complementary to a cross-section of a spindle that is to receive the nut assembly  20 . 
         [0025]    In the embodiment of  FIGS. 1-8 , the holding features  32  are ball plungers that are secured in place by an inner wall  60  that extends up from a washer base  64 . The washer  28  of the illustrated embodiment also comprises locking feature  44  located in the inside washer sidewall which is an engagement area that engages with the holding features  32  of the nut  24 . In this embodiment the locking feature  44  comprises an alternating series of peaks and valleys configured to engage with holding features  32  of the nut  24 . In the embodiment shown, the ridges of the locking feature  44  comprise alternating ‘U’ and inverted ‘U’ shapes. In other embodiments, the ridges may comprise a saw tooth or ‘V’ and inverted ‘V’ shape. Other suitable shapes for the locking feature  44  may be employed in other embodiments. The washer  28  in this embodiment, and best viewed in  FIGS. 4 and 6 , also comprises a formed or rolled lip  52  that is formed over a complementary lip  68  on the nut  24  to hold the assembly  20  together. 
         [0026]    The nut  24 , in this embodiment, also includes an optional further locking feature in the form of a manually rotated spring loaded locking pin  72 . In embodiments employing the manually rotated locking pin  72 , the uninstalled state is illustrated in  FIGS. 3 and 4 , where the locking pin  72  is turned such that no portion of the locking pin  72  extends beyond the edge of the nut  24 . When the nut  24  is installed, such as illustrated in  FIGS. 5 and 6 , the locking pin  72  may be turned to engage a lock pin  76  with the lock pin engagement area  48  in the washer. The lock pin  76  of an embodiment includes a cam type feature that engages/disengages the lock pin  76  with the washer  28  when the locking pin  72  rotated. This provides an additional locking feature beyond the holding features  32  of this embodiment. The design of the engaging holes or slots for the locking pin  72  depends on how much rotation is desired once locked, with an alternate design for such slots illustrated in the washer  80  illustrated in  FIG. 9 , in which lock pin engagement area  84  elongated slots  88  rather than the circular areas of engagement area  48  of the embodiment of  FIGS. 1-8 . A locking pin stop  96  may be used to prevent rotation of the locking pin  72  beyond certain limits, and in one embodiment the lock pin engages with an inclined groove in a bottom surface of a lever  98  causing a spring-loaded lock pin  76  to engage with the lock pin engagement area  48  on the washer. 
         [0027]    The self-locking nut  20  of the embodiment of  FIGS. 1-8  includes a biasing member that in this embodiment is a wave spring  92  that is assembled between the washer  28  and the nut  24 . The nut  24  and washer  28  are held apart by the wave spring  92  until the washer  28  contacts the bearing face, or other face to which the nut assembly  20  is being secured. At this point the wave spring  92  is compressed, engaging the nut  24  with the washer  24 . As the nut  24  is tightened, the holding features  32  slide down into the grooves of the washer holding feature engagement area  44 . Of course, one of skill in the art will readily recognize that other types of biasing members may be used to hold the nut  24  and washer  28  apart as described, such as a number of separate springs or resiliently deformable members. The uninstalled and installed state of the holding features  32  and washer  28  are illustrated in  FIGS. 7 and 8 . This allows the nut  24  to be rotated on the spindle with little resistance until the washer  28  contacts resistance when the nut  24  is almost completely tightened. In embodiments such as illustrated in  FIGS. 1-8 , the washer  28  includes a tang  56  that engages with a key in the spindle, and thus the nut  24  is able to rotate relative to the washer  28  until the washer  28  encounters resistance at, for example, a bearing face. 
         [0028]    When the locking pin  72  is rotated into the unlocked position, the nut  24  and the washer  28 , including the wave spring  92  form a unitary self locking nut assembly  20  suitable for use with conventional sockets. Further, the nut  24  will be free to rotate with respect to the washer  28  because the holding features  32  are not engaged with the holding feature engagement area  44  of washer  28  in an uninstalled state. 
         [0029]    When the holding features  32  engage with the washer  28 , the nut  24  is continued to be rotated causing the holding features  32 , such as the illustrated ball plungers, to yield and move over a peak of one of the ridges in the engagement area  44 . In some embodiments, the contact between the locking end of the holding feature  32  and the washer  28  may result in more resistance in one direction of rotation than for rotation in the opposite direction. Some embodiments may comprise additional features to increase the resistance between the holding feature  32  and the washer  28 , such as through sawtooth features formed on the engagement area  44  of the washer  28 . When the nut  24  is tightened to the desired torque, the holding features prevent relative movement of the nut  24  and washer  28  to prevent the nut  24  from backing off the spindle. As mentioned, some embodiments include a locking pin  72  that engages with a separate lock pin engagement area  48  on the washer base  64 , and further prevents any substantial relative movement between the washer  28  and nut  24 . The washer  28  in such embodiments absorbs substantially all rotational forces, while the nut  24  prevents axial movement of the assembly, and together prevent the assembly from unscrewing to maintain, for example, the bearing adjustment over time. 
         [0030]    Although the present invention has been described with reference to particular embodiments, it should be recognized that these embodiments are merely illustrative of the principles of the present invention. Those of ordinary skill in the art will appreciate that the present invention may be constructed and implemented in other ways and embodiments. Accordingly, the description herein should not be read as limiting the present invention, as other embodiments also fall within the scope of the present invention.