Patent Publication Number: US-2023160415-A1

Title: Track bolt stretch device with nut and spacer

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to track shoes and track bolts that are employed to assemble track chains used on endless track drive vehicles. More particularly, the present disclosure relates to such track shoes and track bolts that are less likely over time to loosen due to vibration, loads and wear. 
     BACKGROUND 
     Track type machines typically utilize track chains on each side of the machine that engage the ground surface during propulsion of the machine. A plurality of individual links are pivotably coupled via bushing and pin arrangements to form the track chain. A sprocket, driven by an engine of the machine, engages the bushings and translates the chain about one or more idlers. As the chain translates, the connected links engage a ground surface under the machine, for example, via coupled track shoes, and propel the machine on the surface. Track chains can be straight link chains with alternating inner and outer links or can be offset link chains where all the links are alike. The track shoes are typically connected to the links by a bolt and nut arrangement. Over time, these fastened connections may become loose due to vibration, loads, wear, etc. If the shoe becomes improperly positioned or falls of the track chain, damage to the undercarriage and/or undesirable downtime for maintenance is necessary. 
     One way to handle this problem is to adjust the bolt pattern, use spring washers, or provide a Loctite® or some other anti-loosening adhesive, solution, etc. 
     Another proposed solution is contained in U.S. Pat. Nos. 10,189,518 B2 that discloses a track nut with an increased surface area that significantly improves the clamp load retention during loading cycles. Of course, this could be also be achieved by increasing the size of the bolted connection by using a larger bolt and/or nut but this may not be feasible in all applications. Various embodiments of that patent include a track nut that has a reduced blend joining its bearing face to the side faces or flats of the nut. In many embodiments of that patent, this involves using a variable blend somewhere on the track nut to increase the bearing surface. In certain embodiments, the variable blend may be located between the corners of the track nut. In other embodiments, the variable blend may be located at the corner of the track nut. The blend may define a radius that is greater than or equal to the corresponding radius of the pocket in which the track nut is intended to sit. The radius may be varied such that the pocket radius may stay large enough to prevent track link cracking. At the same time, the radius of the blend of the track nut may be decreased to increase the bearing face of the track nut at appropriate locations. However, increasing the bearing surface area is not feasible in all applications. 
     Accordingly, there is a need for a device that reduces the likelihood of track bolt loosening that is feasible when the size of the nut or fastener cannot be increased. 
     SUMMARY 
     A track nut for use with a track assembly according to an embodiment of the present disclosure may have a body including a non-circular perimeter, a central internally threaded hole defining a minimum diameter, and a longitudinal axis, as well as a nut axial height measured along the longitudinal axis. A ratio of the nut axial height to the minimum diameter may be at least 1.20. 
     A track nut spacer for use with a track assembly according to an embodiment of the present disclosure may have a body including a central counterbore including a nut receiving portion, and a bolt shaft receiving portion. The central counterbore may also define a central axis and a radial direction. The body of the track nut spacer may also have a stepped periphery including a large external diameter defining portion, and a small diameter defining portion. The large external diameter defining portion may at least partially surround the nut receiving portion of the central counterbore. 
     A track link and track shoe bolted connection according to an embodiment of the present disclosure may include a track link with a clearance hole, a track bolt with a free end extending through the clearance hole, and a track nut with a top surface that is spaced away a minimum distance from the clearance hole. The track link may include a rail surface, a bottom surface, and a midplane between the rail surface and the bottom surface. The top surface of the track nut may be at or above the midplane. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of an exemplary machine such as a bulldozer or the like with an elevated track drive assembly. 
         FIG.  2    is an enlarged rear view of a portion of the elevated track drive assembly removed from the machine of  FIG.  1   , showing track bolts and track nuts attaching the track shoes to the track chain more clearly. 
         FIG.  3    is a side partial section view of one of the links of the track chain of  FIG.  2    showing a tall nut configured according to an embodiment of the present disclosure that is threaded onto the free end of a track bolt. 
         FIG.  4    is an enlarged detail view of the tall nut and track bolt of  FIG.  3   . 
         FIG.  5    depicts an alternate embodiment to that of  FIG.  4    where a spacer is used in conjunction with a nut to increase the clamping load of the bolted connection. 
     
    
    
     DETAILED DESCRIPTION 
     Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the features, as claimed. As used herein, the terms “comprises,” “comprising,” “having,” “including,” or other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such a process, method, article, or apparatus. In this disclosure, relative terms, such as, for example, “about,” “substantially,” and “approximately” are used to indicate a possible variation of ±10% in the stated value. 
     Reference will now be made in detail to embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In some cases, a reference number will be indicated in this specification and the drawings will show the reference number followed by a letter for example,  100   a ,  100   b  or by a prime for example,  100 ′,  100 ″ etc. It is to be understood that the use of letters or primes immediately after a reference number indicates that these features are similarly shaped and have similar function as is often the case when geometry is mirrored about a plane of symmetry. For ease of explanation in this specification, letters and primes will often not be included herein but may be shown in the drawings to indicate duplications of features, having similar or identical function or geometry, discussed within this written specification. 
       FIG.  1    illustrates a machine  10  with a track assembly  12  according to the present disclosure. Machine  10  may be a track-type tractor or any mobile machine that performs some type of operation with an industry, such as mining, construction, farming, transportation, or any other industry known in the art, for example, a dozer, an excavator, a loader, a backhoe, a motor grader, or any other earth moving machine. A work implement in the form of a blade  14  is shown, but other work implements may be used or may be omitted altogether. 
     In one aspect, machine  10  may be a bulldozer as shown. In other aspects, however, machine  10  may be a small track-type tractor or a large track-type tractor, etc. Track drive assembly  12 , which may have a track link assembly or a track chain assembly  13 , may be coupled to an undercarriage assembly of machine  10  and driven by a machine engine or other power source (not shown) via at least one drive gear or sprocket  15 . A separate track drive assembly  12  may be coupled to each side of machine  10 , with each having a track chain  13  forming separate endless loops. A plurality of track shoes  16  may be coupled to an outer surface of track chain  13  in order to aid in the engagement of the ground surface. 
     As best seen in  FIG.  2   , the track chain  13  may include multiple structurally similar link subassemblies, each of which may include a pair of links. A pair of links may include a link  18  and a respectively paired link that is parallel and spaced opposite from link  18 . Links  18  and their respectively paired links may be straight or offset links, and each include apertures at respective opposite ends (e.g., a first-end aperture and a second-end aperture). 
     Successive link subassemblies may be coupled by a pin  20  and a bushing (not shown). For example, to couple a first link subassembly with a successive a second link subassembly, pin  20  may be fixedly received in the first-end apertures of the links of the first link subassembly and bushing may be fixedly received in the second-end apertures of the links of the second link assembly. As such, pin  20  and bushing couple two link subassemblies together to form a portion of track chain  13 . 
     Each pin  20  may be a substantially cylindrical rod and may be sized to be slip fit through bushing. Each bushing may be generally cylindrical, with a cylindrical channel extending longitudinally through bushing as a bore. The bore and the pin may have a constant diameters, but not necessarily so. 
     Looking at  FIGS.  2 ,  3 , and  5   , the track shoes  16  are often fastened to the links of the assembly using a track bolt  24  that extends through a hole  26  of the track shoe  16  as alluded to earlier herein. The threaded end of the track bolt  24  is connected to a nut track  200 ,  200   a  found in a recess, aperture or void of the link as will be discussed in detail momentarily. 
     The particulars of various embodiments of a track nut and/or a track nut spacer may be configured to increase the amount of the track bolt is stretched increasing the clamp load, and reducing the likelihood of a bolted connection or other fastened connection between the track shoe, the track bolt, the nut, etc. from loosening. 
     Starting with  FIGS.  3 ,  4  and  5   , a track link and track shoe bolted connection  100 ,  100   a  may comprise a track link  18  with a clearance hole  28  that is in communication with the hole  26  of the track shoe  16 , and an aperture  30  that is in communication with the clearance hole  28 . The track bolt  24  may have a free end  32  that extends through the clearance hole  28  into the aperture  30 . The track nut  200 ,  200   a  may be disposed in the aperture  30  with a top surface  202 ,  202   a  that is spaced away a minimum distance  204 ,  204   a  from the clearance hole  28  (e.g., from the surface that defines the top extremity of the clearance hole  28 ). 
     Also, the track link  18  may include a rail surface  34  (so called since it contacts the rollers, idler, etc.), a bottom surface  36  (may also be referred to as the “shoe attachment surface”), and a midplane  38  that is disposed vertically (or axially as will be discussed later herein with respect to various holes) between the rail surface  34 , and the bottom surface  36  (or through the axes of rotation of the bushing and pin in use). As best seen in  FIGS.  4  and  5   , and the top surface  202 ,  202   a  of the track nut  200 ,  200   a  may be vertically (or axially) at or above the midplane  38 . This may not be the case for other embodiments of the present disclosure. 
     In  FIG.  4   , the track nut  200  may define a track nut height  206  that is equal to the minimum distance  204 . This may not be the case for other embodiments of the present disclosure. 
     In both  FIGS.  4  and  5   , a ratio of the minimum distance  204 ,  204   a  to a diameter  40  of the clearance hole  28  may range from 1.35 to 1.65 (e.g., about 1.50) in some embodiments of the present disclosure, but not necessarily so. In such a case, the minimum distance  204 ,  204   a  may range from 10. mm to 35.0. This may not be the case in other embodiments of the present disclosure. For example, the ratio may be 1.20 to 1.80 in some embodiments of the present disclosure, etc. 
     In  FIG.  5   , a track nut spacer  300  may be disposed in the aperture  30  between the track nut  200   a , and the clearance hole  28 . This may not be the case in other embodiments of the present disclosure (e.g., see  FIG.  4   ). 
     Referring now to  FIG.  4   , a track nut  200  that may be provided for use with the bolted connection  100  may be described as follows. The track nut  200  may have a body including a non-circular perimeter  208  (e.g., it is not cylindrical or conical, etc.), a central internally threaded hole  210  defining a minimum diameter  212 , and a longitudinal axis  214 . The track nut  200  may also define a nut axial height (see  206 ) measured along the longitudinal axis  214 . A ratio of the nut axial height (see  206 ) to the minimum diameter  212  may range from 1.53 to 1.87 in some embodiments of the present disclosure. More specifically, this ratio may range from 1.68 to 1.72 (e.g., about 1.70). In such a case, the nut axial height (see  206 ) may range from 15.0 mm to 40.0 mm. 
     In some embodiments of the present disclosure, the internally threaded hole has internal threads that extend at least partially along the entire nut axial height similar to what is shown in  FIG.  5   . This may not be the case in other embodiments such as when most or all of the hole is threaded, etc. Moreover, the non-circular perimeter  208  may include two parallel flats  216  defining a minimum dimension  218  between the two parallel flats  216 . This may not be the case for other embodiments of the present disclosure. 
     Also, the track nut  200  may include a flat top surface  220 , and a flat bottom surface  222  spaced along the longitudinal axis  214  from the flat top surface  220  by a distance equivalent to the nut axial height (e.g., see  206 ). A first blend  224  may connect the flat bottom surface  222  to the non-circular perimeter  208 . This first blend  224  may define a radius of curvature  226  measured in a plane containing a radial direction  228  and the longitudinal axis  214  (e.g., the cross-sectioned plane of  FIG.  4   ) that ranges from 2.0 mm to 6.0 mm in some embodiments of the present disclosure. 
     Referring now to  FIG.  5   , a track nut spacer  300  that may be provided for use with the bolted connection  100   a  may be described as follows. 
     The track nut spacer  300  may have a body including a central counterbore  302  including a nut receiving portion  304 , and a bolt shaft receiving portion  306 . Also, the central counterbore  302  may define a radial direction  308 , and a central axis  310 . The body of the track nut spacer  300  may have a stepped periphery  312  including a large external diameter defining portion  314 , and a small external diameter defining portion  316 . 
     The large external diameter defining portion  314  of the stepped periphery  312  may at least partially radially surround the nut receiving portion  304  of the central counterbore  302 . Similarly, the small external diameter defining portion  316  of the stepped periphery  312  at least partially radially surrounds the bolt shaft receiving portion  306  of the central counterbore  302 . 
     The body of the track nut spacer  300  may maintain a minimum wall thickness for strength. To that end, a difference of the large external diameter D 314  minus the internal diameter D 304  may at least 8.0 mm in some embodiments of the present disclosure. This would be equal to about half of the minimum wall thickness  318  locally (e.g., 4.0 mm). Similarly, a difference of the small external diameter D 316  minus the small internal diameter D 306  is at least 8.0 mm in some embodiments. Again, this would be equal to about half of the minimum wall thickness (e.g., 4.0 mm) locally. 
     Put another way, the internal diameter may be large to provide 0.1 mm clearance on a side with respect to the nut, but no greater than 1.0 mm on a side with respect to the nut so that it can fit in the aperture of the link. Similarly, the small internal diameter may be large enough to provide 0.25 mm clearance on a side with respect to the bolt to allow it to pass through the spacer. 
     The stepped periphery  312  may be hexagonal, polygonal or have parallel flats in some embodiments of the present disclosure. This may allow the track nut spacer  300  to engage the anti-rotation feature  42  of in the aperture  30  of the link. Similarly, the central counterbore may have a nut receiving portion that is also hexagonal, polygonal or has parallel flats to help prevent the rotation of the track nut  200   a  when the track bolt  24  is being tightened. In such embodiments, the aforementioned diameters would be measured via inscribing circles that are tangent to the flat sides, etc. In other embodiments, these various features may be cylindrical, conical, etc. 
     In order to position the nut height enough to get the desired elongation of the track bolt and its associated clamping force, the body of the track nut spacer may define a spacer axial height  320  measured along the central axis  310 , and a ratio of the spacer axial height  320  to the small internal diameter D 306  may range from 1.08 to 1.32 (e.g., about 1.20) in some embodiments of the present disclosure. This may not be the case in other embodiments of the present disclosure. 
     Likewise, the nut receiving portion  304  may define an internal diameter D 304 , and a nut receiving portion axial height H 304  measured along the central axis  310 . A ratio of the large internal diameter D 304  to the large internal diameter portion axial height H 304  may range from 3.825 to 4.675 (e.g., about 4.25) in some embodiments of the present disclosure. This may not be the case in other embodiments of the present disclosure. 
     In general, any component discussed herein may be made from any suitable material, including, but not limited to, iron, steel, cast-iron, grey-cast iron, white iron, etc. Also, any component discussed herein may be heat treated, induction hardened, carburized, coated, etc. 
     INDUSTRIAL APPLICABILITY 
     A track nut, a track nut spacer, or any assembly including one or more of these components according to any embodiment discussed herein may be provided as a replacement part in the field or in an OEM (Original Equipment Manufacturer) context. 
     The components may be manufactured using any suitable process including forging, casting, tapping, machining, etc. 
     As used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has”, “have”, “having”, “with” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. 
     Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the apparatus and methods of assembly as discussed herein without departing from the scope or spirit of the invention(s). Other embodiments of this disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the various embodiments disclosed herein. For example, some of the equipment may be constructed and function differently than what has been described herein and certain steps of any method may be omitted, performed in an order that is different than what has been specifically mentioned or in some cases performed simultaneously or in sub-steps. Furthermore, variations or modifications to certain aspects or features of various embodiments may be made to create further embodiments and features and aspects of various embodiments may be added to or substituted for other features or aspects of other embodiments in order to provide still further embodiments.