Abstract:
A tamper-resistant fastener such as a nut for a bicycle has a smoothly rounded generally dome-shaped body and one or more recesses formed into the body. Each recess has a first and open ended portion which is bounded on radially inward side but not on the radially outward side, and a second and closed ended portion which is bounded on both the radially inward side and the radially outward side. Additionally, each recess can have an additional notch formed therein, the recess and notch together forming a major and minor recess. A wall which bounds the radially inward side of the recess decreases in radial distance from the central axis of the nut as the recess proceeds in the circumferential direction. A mating wrench has teeth that match the recesses and, if present, the notches.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit U.S. Provisional Patent Application No. 62/010,125 filed Jun. 10, 2014 which is incorporated by reference as if set forth fully herein. This application is also related to U.S. Design patent application No. 29/529,126 filed Jun. 4, 2015 and U.S. Design patent application No. 29/529,127 filed Jun. 4, 2015. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to the field of fasteners. More particularly, this invention relates to the field of a tamper-resistant nut for bicycle axles. 
         [0004]    2. Description of Related Art 
         [0005]    To keep an object fixed and locked in place, threaded fasteners such as nuts and bolts are commonly used. Common tools, such as a wrench or variations on a wrench, are used to install and remove fasteners. Understandably, as simple as it is to secure an object with a fastener, it is just as simple to remove the fastener with a common tool. Therefore, anyone from the owner of the property to a thief who has access to these basic tools will be able to disassemble the object effortlessly. Essentially, this opens the door for unwanted removal and theft. As a result of this problem, tamper-resistant fasteners have been suggested offering elements of security against unwanted tampering. Some fasteners are shaped spherically making it difficult to grasp onto them using common tools. Others include a smooth outer surface to the product in order to reduce leverage, preventing unloosening. Also, some provide a special key so that only the owner will be able to tighten and loosen the fastener. 
         [0006]    U.S. Pat. No. 5,097,686 entitled “Security Locking System for Vehicle Wheel Nuts” describes a cover cylinder that covers a vehicle&#39;s lug nuts and has a locking mechanism over it. Although this prevents unwanted tampering and unfastening of the nut, it requires two parts: the original nut as well as the cover cylinder as opposed to one nut with a special unfastening configuration. 
         [0007]    U.S. Pat. No. 5,199,838 entitled “Nut for Use on Roadways, Runways, in Reinforced Concrete Construction, and the Like” describes a primarily spherical nut for use on roadway apparatuses. The spherical shape of the nut makes removal with the most common tools difficult. The nut, however, is still vulnerable to being opened with certain tools such as a spanner wrench. 
         [0008]    U.S. Pat. No. 4,674,306 entitled “Vehicle and Assembly Locking and Wrenching Apparatus” describes a specific device for a vehicle lock, where that device is used in conjunction with a tamper-proof fastener. The apparatus provided is tailored to the unique lock. The nut has an “incised front face and arcuate sides parallel to the face, surrounded by cylindrical, annual rings that prevent the gripping and turning of the nuts.” However, a universal socket wrench will be able to compromise this device. 
         [0009]    U.S. Pat. No. 5,033,501 entitled “Fire Hydrant Cap and Actuating Tool Therefor” describes a dome shaped fire hydrant cap that provides enhanced security against removal. The cap has cutouts on the front of the dome surface to work with a special tool for fastening/removal. However, similar to EP patent 1203164, the cap is still vulnerable to unwanted tampering/removal by using a universal socket wrench as the cutouts are not hidden and are on the face of the cap. 
         [0010]    U.S. Pat. No. 4,302,137 entitled “Anti-Tamper Fastening Means” describes a nut with a curved surface and circular openings for pins to grab and rotate the nut. This nut is covered by a sleeve to further prevent tampering. However, this adds a second component to be used with the nut and thus makes it more difficult, complicated, and slower to unfasten the nut. 
         [0011]    U.S. Pat. No. 4,125,051 entitled “Tamperproof Fastener” describes a fastener in which the “upper surface of the head is configured to include a very short cylindrical boss, coaxial of the fastener and a plurality of ribs extending radially outward.” This device uses a low profile headed design. It protects against high-profile tools; therefore, it is still susceptible to unwanted removal, just with “harder-to-find” tools. 
         [0012]    U.S. Pat. No. 4,018,111 entitled “Tamper Resistant Fastener and Tool for Operating Same” describes a fastener with a head having a flat top surface and a smooth circular sidewall. The head has an offset opening to be filled with a complementary pin on a special key. This type of fastener is tamper resistant and prevents theft as when it is secured, it works in conjunction with a circular washer having a smooth frustoconical sidewall that covers the head. 
         [0013]    U.S. Pat. No. 3,818,731 entitled “Nut Lock” describes a lock for preventing unauthorized removal of a nut. In a single casing, a plate having a flange at one edge is locked in a housing. The nut is threaded on a stud and the housing locked in place to prevent access to the nut. In a separate embodiment, such as where a cable having a coupling member is to be protected, the plate has an aperture shaped to receive the coupling member. 
         [0014]    U.S. Pat. No. 7,673,482 entitled “Wheel Lock” describes an anti-theft device for preventing removal of a wheel from an axle. The wheel lock includes a cup shaped base piece with an opening to receive a wheel stud for threaded interaction with a lug nut, which will clamp the base portion to the wheel. A cup shape encloses the stud and lug nut. The cover piece interlocks with the locking portion to prevent tampering and rotation of the cover piece. The cover piece may include a flange that bears against the rim of the base portion giving the wheel lock an exterior surface that is hard to pry apart. 
         [0015]    U.S. Pat. No. 4,645,397 entitled “Tire Theft Prevention Device” describes a device that purports to prevent theft of items having threaded nuts or the like, particularly truck tires. It includes a tamper-proof fastener having a locking cap which engages the underlying lug bolt and a seal which surrounds the locking cap and the lug nut of the tire to be secured. The seal moves freely about the locking cap and the lug nut, preventing anyone from loosening the lug nut without first breaking the seal. This invention is based on covering the lug nut thereby preventing access to the threaded nuts. 
         [0016]    U.S. Pat. No. 4,880,344 entitled “Device for Preventing Loosening of a Member” describes a device for preventing tampering or loosening of a prismatic member such as a nut, screw head or bolt, or particularly a lock nut of a wheel of an automobile vehicle. The cap includes a transverse bottom and a cylindrical skirt in one piece with the bottom and a mechanism means for locking the prismatic member received in the cap in order to prevent the loosening of the respective member. 
         [0017]    U.S. Pat. No. 4,825,669 entitled “Wheel Lug Nut Cover” describes a lug nut cover on a vehicle wheel secured to a vehicle. A mounting bracket and a lug nut cover both have elongated holes which makes them universal and allows them to fit a substantial number of lug bolt spacings. The cover is fitted onto special lug nuts as an extension. This mounting bracket works with the locking mechanism to hold the lug nut cover firmly in place. 
         [0018]    U.S. Pat. No. 6,341,927 entitled “Tamper Resistant Fastener” describes a tamper resistant device that has a head with two or more tear-shaped cutouts having discontinuous sidewalls. A key having downwardly projecting pins mate into corresponding slots in the device. The specification claims that these tear-shaped cutouts prevent a tool other than the specific key provided from engaging the device and thus rotating it in a counter clockwise direction. However, other tools such as a gator grip socket wrench are able to gain leverage on the cutouts and rotate the fastener count-clockwise. The shape of the cutouts and the slope in the cutouts open the door to other tools compromising the device as well. 
         [0019]    U.S. Pat. No. 5,863,166 entitled “Anti-Theft Locking Device” describes a device for attaching bicycle components to the bicycle frame. The device includes a threaded bolt with a matching nut. The nut has a rotatable casing around the outer surface. The key engages with the nut giving the user access. The key and the nut share at least one spigot and at least one hole in order to engage with each other. 
       SUMMARY OF THE INVENTION 
       [0020]    The present invention is of a tamper-resistant fastener which is particularly useful as a bicycle axle nut, and a mating wrench for tightening and removing the nut. 
         [0021]    In a generally preferred embodiment, the bicycle wheel axle nut has a generally dome-shaped body having what will be called a top surface and a bottom surface, the bottom surface being the one that will rest against the bicycle fork when the axle nut is installed on a bicycle. As is conventional, the bottom surface can contain a friction surface to help keep the nut from vibrating loose during use. The top surface can be flattened. 
         [0022]    The generally dome-shaped body of the nut includes a generally smooth, curved exterior surface that make it difficult for a conventional tool such as a crescent wrench, pliers, channel locks, or a pipe wrench, to grip. 
         [0023]    The body has one or more, and three in the exemplary embodiment, recesses formed into the exterior surface. The recess generally increases in depth from the exterior surface of the nut and toward the central axis as the recess extends circumferentially around the nut. Preferably, the recess increases in depth as the recess extends in the nut-tightening direction, which is clockwise for typical threaded fasteners in virtually every country. Thus, as the recess extends clockwise around the fastener, the recess increases in depth toward the central axis. A mating wrench or key having curved teeth that match the curved recess(es) will be able to both tighten and loosen the nut; at the same time, however, standard tools such as crescent wrench or pliers will be unable to effectively grip the nut and thus will be unable to easily loosen it. 
         [0024]    The recess is defined in part by a curved inner wall, the curved inner wall curving closer to the central axis as that wall extends circumferentially around the nut in a clockwise direction as described. Preferably the recess has two portions: a first and open-ended portion defined on the radially inward side by the curved inner wall and being unbounded on the radially outward side; and a second and closed-ended portion that is defined on the radially inward side by the curved inner wall including its end point, and is defined on the radially outward side by an exterior wall whose exterior surface defines in part the smooth, curved, generally dome-shaped exterior surface of the nut. Within that second section of the recess, the inner wall and outer wall are angled toward each other at an angle of preferably less than 45°, defining a channel that narrows in the clockwise direction. 
         [0025]    Optionally, the curved inner wall that defines in part the recess has a notch formed therein, the notch being smaller than the recess. The notch can be thought of as being part of the recess. Preferably the notch has a volume that is less than one quarter of a volume of the recess including the notch. The nut thus has both a major (larger) recess and a minor (smaller) recess. The notch extends inwardly from the curved inner wall, and can optionally extend circumferentially as well such that its directional vector includes both a radially inward component and a circumferentially clockwise component. The walls that define the notch define a narrowing channel as one moves from the opening of the notch to its innermost extent. The minor recess, taken together with its mating tooth on the associated wrench, provides for additional grip of the wrench on the nut. 
         [0026]    Preferably the recesses are open at their top sides, and the walls that define the recess are generally vertical, so that the wrench can be slid downward directly onto the nut for ease of use. The recesses including the notches can be substantially identically shaped and evenly spaced such as at three evenly spaced locations around the nut, or the recesses including the notches can be differently shaped from one another, and/or placed at differing locations around the nut. 
         [0027]    The recess is generally bounded on the bottom by a floor of the recess, the floor of the recess being located above the bottom surface of the nut. Preferably the floor of the recess is generally flat. 
         [0028]    A threaded central bore for the wheel axle preferably extends all the way through the nut. However, for applications in which the wheel axle is not long enough to extend all the way through the nut when installed, it is not strictly necessary that the central bore and thread extend all the way through the nut. Preferably the nut is at least 50% as high as it is wide at its widest point, i.e., its greatest diameter which is generally at its bottom surface. 
         [0029]    A manufacturer can manufacture various nuts and mating wrenches in which the following parameters are varied slightly from one nut-and-wrench set sold to a consumer to the next: the position, shape, and number of major recesses; and the position, shape, and number of minor recesses. The nuts, together with their mating wrench, would be sold as a unit. Generally speaking the wrench from one set of nuts will not mate with a different set of nuts. The wrench therefore acts as a unique key for a particular set of nuts, the key working for that set of nuts and that set of nuts only. In this way, a large number of uniquely mating nut-and-wrench sets can be manufactured and sold, with each set of nuts being removable with only its mating wrench. A would-be bicycle wheel thief would therefore need to purchase or form and carry a large number of wrenches in order to effectively remove bicycle wheels protected by a set of axle nuts according to the invention, and even then, the additional time that it would require for the thief to find the correct wrench for a particular axle nut set would greatly deter the would-be thief. 
         [0030]    The nut and/or the wrench of the present invention can be used in, or applied to, other applications than merely bicycle axles, although bicycle axles are foreseen as being particularly well suited for use with the invention. 
         [0031]    Exemplary embodiments of the invention will be further described below with reference to the drawings, in which like numbers refer to like parts. The drawing figures might not be to scale, and certain components may be shown in generalized or schematic form and identified by commercial designations in the interest of clarity and conciseness. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1  is an exploded oblique view of a bicycle wheel having a conventional solid axle, with two of the nuts of the present invention being used to secure the axle. 
           [0033]      FIG. 2  is an exploded oblique view of a bicycle wheel having a replacement skewer and a quick release mechanism, with one of the nuts of the present invention being used to secure the axle. 
           [0034]      FIG. 3  is an oblique view of a bicycle axle having a nut according to a first embodiment of the present invention installed thereon to secure the axle, and showing in exploded form how the mating wrench would be used on the nut. 
           [0035]      FIG. 4  is an oblique view of the bicycle axle, nut, and wrench of  FIG. 3 , but showing the wrench being applied to the nut. 
           [0036]      FIG. 5  is a top plan view of just the nut according to the first embodiment shown in  FIG. 3 . 
           [0037]      FIG. 6  is a bottom plan view of the nut of  FIG. 5 . 
           [0038]      FIG. 7  is a top plan view of the wrench shown in  FIG. 3 , and which mates with the nut of  FIG. 5 . 
           [0039]      FIG. 8  is an end elevation view of the wrench shown in  FIG. 7 . 
           [0040]      FIG. 9  is an oblique view of a bicycle axle having a nut according to a second embodiment of the present invention installed thereon to secure the axle, and showing in exploded form how the mating wrench would be used on the nut. 
           [0041]      FIG. 10  is an oblique view of the bicycle axle, nut, and wrench of  FIG. 9 , but showing the wrench being applied to the nut. 
           [0042]      FIG. 11  is a top plan view of just the nut according to the second embodiment shown in  FIG. 9 . 
           [0043]      FIG. 12  is a bottom plan view of the nut of  FIG. 11 . 
           [0044]      FIG. 13  is an oblique view of the nut of  FIG. 11 . 
           [0045]      FIG. 14  is a top plan view of the wrench shown in  FIG. 9 , and which mates with the nut of  FIG. 11 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0046]      FIG. 1  is an exploded oblique view of a bicycle wheel having a conventional solid axle  19 , with two of the bicycle axle nuts  10  of the present invention being used to secure the axle. Nut  10  has a threaded central bore that screws onto threaded bicycle axle  19  to secure axle  19  and hence secure the bicycle wheel to the bicycle wheel fork  18 . 
         [0047]      FIG. 2  is an exploded oblique view of a bicycle wheel having a replacement skewer  17  for a quick release mechanism, with one of the nuts  10  of the present invention being used to secure the replacement skewer  17 . 
         [0048]      FIG. 3  is an oblique view of a bicycle axle  19  having a nut  10  according to a first embodiment of the present invention installed thereon to secure the axle, and showing in exploded form how the mating wrench  20  would be used on nut  10 . In this first embodiment, nut  10  has three recesses  6 / 7 / 8  generally evenly spaced around the circumference of the nut. Each recess  6 / 7 / 8  defines only a major recess, or simple recess. The shape of recesses  6 / 7 / 8  will be discussed in greater detail below with reference to  FIGS. 5 and 6 , and further with references to  FIGS. 8 ,  10 , and  12  in which the second embodiment of the nut contains similar recesses as recesses  6 / 7 / 8  but also include minor recesses. 
         [0049]    Mating wrench  20  has a first and working end  21  ( FIG. 7 ) which mates with nut  10 . A second and handle end  25  of wrench  20  may also mate with nut  10 , and/or may have decorative elements such as decorate cutouts  26  and  27 , and/or an unrelated functional structure such as bottle opener  28 . Teeth  3 / 4 / 5  extend both radially inwardly and circumferentially clockwise from a generally circular outer periphery of working end  21 . In this preferred embodiment because teeth  3 / 4 / 5  extend only radially inwardly, and not downwardly as in some prior art solutions, wrench  20  can be kept flat and thin as seen in  FIG. 8 . As an example, the wrench can have a thickness of 5 mm or less, or even 4 mm or less. This is an advantage because for bicycle riders, their tools should be as small, lightweight, and compact as possible. This is especially true for tools used for removing and reinstalling wheels and tires, which bicycle riders need to do when repairing flat tires which are unfortunately all too common occurrences on bicycle rides due to thorns, broken glass, and other small road hazards. Bicycle riders must therefore generally carry those tools with them at all times. 
         [0050]      FIG. 4  is an oblique view of the bicycle axle  19 , nut  10 , and wrench  20  of  FIG. 3 , but showing wrench  20  being applied to nut  10 . Teeth  3 / 4 / 5  mate with recesses  6 / 7 / 8 , respectively. Because the walls that define recesses  6 / 7 / 8  are generally vertical walls (or horizontal walls in the particular orientation shown in the figure), wrench  20  slides directly downward onto nut  10 . Wrench  20  can now be used to tighten nut  10  onto axle  19  or to remove it. 
         [0051]      FIG. 5  is a top plan view of just the nut according to the first embodiment shown in  FIG. 3 . Nut  10  includes a threaded central bore  13  along its central longitudinal axis  16  in order to threadingly engage threaded bicycle axle  19  or quick release replacement skewer  17 . In the embodiment shown nut  10  also has a flat top surface  11 . In general, the top surface of the nut could be either flattened as shown or smoothly rounded. The flattened top surface  11 , however, helps to prevent the very top of nut  10  from being accidentally damaged and bent inwardly, which would interfere with its ability to thread smoothly onto axle  19 . 
         [0052]    Each recess  6 / 7 / 8  preferably has a first and open-ended portion  36 , and a second and closed-ended portion  37 . In the open-ended portion  36 , recess  6  is bounded on its radially inward side by convexly curved inner wall  6 A, and on its bottom side by floor  6 C. Floor  6 C of recess  6  is preferably mostly or completely flat, i.e., parallel to bottom surface  14  ( FIG. 6 ). Thus, the open-ended portion  36  of recess  6  is bounded on its radially inward side by curved inner wall  6 A, and on its bottom by floor  6 C, and is not otherwise bounded. Curved inner wall  6 A becomes gradually closer to central axis  16  as it extends circumferentially, preferably as it extends circumferentially in the tightening direction which is nearly universally the clockwise direction. Thus, recess  6  increases in radial depth as the recess extends circumferentially in the tightening direction. 
         [0053]    Floor  6 C is located preferably in the lower half of nut  10 , and more preferably approximately less than or equal to approximately one quarter of the way from bottom surface  14  to top surface  11  of nut  10 . 
         [0054]    The second and closed-ended portion  37  of recess  6  is also bounded on the radially inward side by curved inner wall  6 A of decreasing radius, and by floor  6 C. It is further bounded on its radially outward side by exterior wall  6 B having a concavely shaped inwardly-facing wall Inner curved wall  6 A and exterior wall  6 B are angled toward each other at an angle φ of preferably less than 45°, and even less than 30°, meeting at a clockwise-most and inner-most extent of recess  6 . Preferably curved inner wall  6 A and the inner surface of external wall  6 B extend vertically or generally vertically, so that wrench  10  including tooth  3  can slide straight up and down over nut  10  for ease of use. Recesses  7  and  8 , including their inner curved walls  7 A and  8 A, their exterior walls  7 B and  8 B, and their floors  7 C and  8 C, can be identical to the corresponding features in recess  6 . Alternatively, they can be different to allow for more unique variations of nut  10  and wrench  20 . Each unique recess pattern for nut  10  and its corresponding wrench  20  constitutes a unique security signature for that nut-and-wrench set. 
         [0055]    The recesses  6 / 7 / 8  including the notches  67778 ′ described later with respect to  FIGS. 9-14  can be substantially identically shaped and evenly spaced such as at three evenly spaced locations (e.g., at the 0°, 120°, and 240° positions) around the nut in which case the wrench can be applied to the nut at any one of three different yet functionally identical positions on the nut. Alternatively, the recesses  6 / 7 / 8  including the notches  6 ′/ 7 ′/ 8 ′ can be different from one another, and/or placed at non-uniform spacings around the nut (e.g., at the 0°, 100°, and 240° positions) such that the spacings between the recesses are non-uniform, in which case the wrench can be applied at only a single position on the nut, thus making the nut and wrench combination slightly more difficult to use but increasing the number of unique combinations available and thus increasing the security of the nut and wrench system. 
         [0056]      FIG. 6  is a bottom plan view of the nut  10  of  FIG. 5 . Bottom surface  14  can include an area  15  that is raised and/or knurled, shingled or otherwise roughened to increase the grip of nut  10  onto the bicycle&#39;s wheel fork  18  to help prevent unintended loosening of nut  10 . 
         [0057]      FIG. 7  is a top plan view of the key or wrench  20  shown in  FIG. 3 , and which mates with nut  10  of  FIG. 5 . Working end  21  of wrench  20  has a central hole  22 , and inwardly projecting teeth  3 / 4 / 5  that extend from generally circular peripheral wall  24 . When wrench  20  is installed on nut  10 , inward surface  3 A of tooth  3  abuts curved inner wall  6 A of recess  6 , and outer surface  3 B of tooth  3  abuts the interior surface of exterior wall  6 B. Corresponding tooth surfaces  4 A/ 4 B and  5 A/ 5 B perform corresponding functions relative to recesses  7  and  8 , respectively. When wrench  10  is turned counter-clockwise to loosen the nut, inward surfaces  3 A/ 4 A/ 5 A of the wrench tighten and push counter-clockwise against corresponding curved walls  6 A/ 7 A/ 8 A of the nut, thus unscrewing the nut. 
         [0058]      FIG. 8  is an end elevation view of the wrench shown in  FIG. 7 . The wrench is flat having no upward or downward projections. In the exemplary embodiment the wrench is less 5 mm thick, and can be made less than 4 mm thick, or even 3 mm thick or thinner depending on the strength of the metals chosen. 
         [0059]      FIG. 9  is an oblique view of a bicycle axle having a nut  110  according to a second embodiment of the present invention installed thereon to secure the bicycle axle  19 , and showing in exploded form how the mating wrench  120  would be used on nut  110 . Nut  110  includes three major recesses  6 / 7 / 8 . The three recesses may be evenly spaced about nut  110 , or they may be unevenly spaced, as discussed above with respect to the first embodiment. 
         [0060]      FIG. 10  is an oblique view of the bicycle axle, nut, and wrench of  FIG. 9 , but showing the wrench  120  being applied to the nut  110 . 
         [0061]      FIG. 11  is a top plan view of just the nut  110  shown in  FIG. 9 . In recesses  6 / 7 / 8 : inner curved walls  6 A/ 7 A/ 8 A generally have similar shapes and functions as inner curved walls  6 A/ 7 A/ 8 A in the first embodiment; exterior walls  6 B/ 7 B/ 8 B generally have similar shapes and functions as exterior walls  6 B/ 7 B/ 8 B in the first embodiment; and floors  6 C/ 7 C/ 8 C generally have similar shapes and functions as floors  6 C/ 7 C/ 8 C in the first embodiment. The prior description of nut  10  of the first embodiment, including potential variations thereon, therefore also generally applies to nut  110  of this second embodiment. 
         [0062]    In this second embodiment, however, in addition to recess  6  which defines a major recess, curved inner wall  6 A also has a notch  6 ′ formed therein which defines a minor recess, and which will be referred to herein as being a part of major recess  6 . Notch  6 ′ is defined in part by notch walls  6 E and  6 D, with those notch walls meeting at a farthest and radially inward-most extent of notch  6 ′. Notch wall  6 E and thus notch  6 ′ can extend in a purely radially inward direction, or can extend both radially inwardly as well as circumferentially such as circumferentially clockwise. Notch wall  6 D can be either curved or flat. Minor recess  6 ′ preferably has a volume that is less than one quarter of the total volume of major recess  106  including minor recess  6 ′. 
         [0063]      FIG. 12  is a bottom plan view of the nut of  FIG. 11 . As in the first embodiment, bottom surface  14  can include an area  15  that is raised and/or knurled, shingled or otherwise roughened to increase the grip of nut  110  onto the bicycle&#39;s wheel fork to help prevent unintended loosening of nut  110 . 
         [0064]      FIG. 13  is an oblique view of the nut of  FIG. 11 , providing perhaps the clearest view of major recess  6  including floor  6 C, inner curved wall  6 A, exterior wall  6 B, and notch or minor recess  6 ′ defined in part by notch walls  6 E and  6 D. 
         [0065]      FIG. 14  is a top plan view of the wrench  120  shown in  FIG. 9 , and which mates with the nut  110  of  FIG. 11 . Major teeth  3 / 4 / 5  slide into and thus mate with corresponding major recesses  6 / 7 / 8 , and minor teeth  3 ′/ 4 ′/ 5 ′ slide into and thus mate with corresponding minor recesses  67778 ′. 
         [0066]    Because the walls that define recesses  6 / 7 / 8  and the walls that define notches  6 ′/ 7 ′/ 8 ′ are generally vertical walls, wrench  120  slides directly downward onto nut  110 . 
         [0067]    Together, major recess  6  and minor recess  6 ′ in nut  110 , together with the corresponding mating major tooth  3  and minor tooth  3 ′ in wrench  120 , provide a superior grip for the wrench on the nut than the recess  6  and single tooth  3  in the first embodiment of nut  10  and wrench  20 , according to tests conducted by the inventors. 
         [0068]    As in the first embodiment, the recesses including the notches can be substantially identically shaped and evenly spaced such as at three evenly spaced locations (e.g., at the 0°, 120°, and 240° positions) around the nut in which case the wrench can be applied to the nut at any one of three different positions on the nut. Alternatively, the recesses  6 / 7 / 8  including the notches  6 ′/ 7 ′/ 8 ′ can be different from one another, and/or placed at non-uniform spacings around the nut (e.g., at the 0°, 100°, and 240° positions) such that the spacings between the recesses are non-uniform, in which case the wrench can be applied at only a single position on the nut, thus making the nut and wrench combination slightly more difficult to use but increasing the number of unique combinations available and thus increasing the security of the nut and wrench system. 
         [0069]    It will be understood that the terms “generally,” “approximately,” and “substantially,” as used within the specification and the claims herein allow for a certain amount of variation from any exact dimensions, measurements, and arrangements, and that those terms should be understood within the context of the description and operation of the invention as disclosed herein. 
         [0070]    It will further be understood that terms such as “top,” “bottom,” “above,” and “below” as used within the specification and the claims herein are terms of convenience that denote the spatial relationships of parts relative to each other rather than to any specific spatial or gravitational orientation. Thus, the terms are to be understood as applying to parts that are oriented in the particular orientations shown in the drawings and described in the specification, upside down from that orientation, or any other rotational variation. 
         [0071]    It will be appreciated that the term “present invention” as used herein should not be construed to mean that only a single invention having a single essential element or group of elements is presented. Although the present invention has thus been described in detail with regard to the preferred embodiments and drawings thereof, it should be apparent to those skilled in the art that various adaptations and modifications of the present invention may be accomplished without departing from the spirit and the scope of the invention. Accordingly, it is to be understood that the detailed description and the accompanying drawings as set forth hereinabove are not intended to limit the breadth of the present invention, which should be inferred only from the following claims and their appropriately construed legal equivalents.