Patent Publication Number: US-2022234659-A1

Title: Sprocket locking segments

Description:
TECHNICAL FIELD 
     The present disclosure relates to a sprocket used to drive a track chain assembly of an endless undercarriage drive employed by earth moving, construction and mining equipment and the like. Specifically, the present disclosure relates to a sprocket that has sprocket locking segments that help to share the load exerted on the sprocket during use. 
     BACKGROUND 
     Earth moving, construction and mining equipment and the like are often used in rough, off-road terrain. These machines often employ an endless drive with track shoes that is better able to propel the machines in such environments over obstacles and uneven terrain, etc. The track chain assemblies, which include shoes, are held together by a series of interconnected track links, pins and bushings that are supported on the drive sprocket, idler and support rollers of the machine. The drive sprocket, is so called, as it may drive or convey power to the track chain assembly, causing it to revolve about the idler wheels, resulting in linear motion of the machine. 
     The drive sprocket includes lugs that fit between various inside and outside links of the track chain assembly and typically contact a track chain bushing that spans between the adjacent inside track links and outside track links. As the drive sprocket rotates, a first lug pushes the track chain assembly along a direction by pushing on the track chain bushing. Eventually, the first lug disengages the track chain bushing as a second lug disposed immediately behind the first lug contacts another track chain bushing, forcing the track chain assembly to continue to move along the same direction. 
     There can be a great deal of lateral force and vertical force exerted on the sprockets that may lead to one or more of the lugs wearing to a point that the sprocket needs to be replaced. Consequently, sprocket segments are often employed that contain a few of the lugs so that only the sprocket segment with the worn lug needs to be replaced rather than the entire sprocket assembly. This reduces the time and cost for fixing the sprocket assembly. However, these sprockets segments spread the load over fewer fasteners for each individual segment, which may cause the fasteners to wear quicker than desired, also necessitating replacement or maintenance. 
     Chinese Pat. No. CN 2706633Y discloses a sprocket that is used on a motorcycle that includes two halves that have two ends, with each end having a male and female feature that mates the corresponding female and male feature of the adjacent sprocket half. This patent does not disclose a sprocket that is designed with suitable strength or properties to be used on heavy equipment such as that described herein. Therefore, one skilled in the art of heavy equipment design as described herein would not look to this prior art for a solution to the aforementioned problems, nor would one skilled in the art expect the sprocket disclosed in this Chinese patent to work satisfactorily on heavy equipment. 
     SUMMARY 
     A sprocket assembly according to an embodiment of the present disclosure may comprise a cylindrical hub defining an axis of rotation, a radial direction, and a circumferential direction. A circumferential surface may extend about the axis, and the hub may define a plurality of mounting holes extending axially into the cylindrical hub, being disposed radially adjacent the circumferential surface. A first sprocket segment may include a first attachment web including a first circumferential end and a second circumferential end, and a first plurality of mounting apertures extending axially through the first attachment web in alignment with the plurality of mounting holes of the cylindrical hub. The first sprocket segment may include a first sprocket region extending radially outwardly from the first attachment web, including a first plurality of radially outwardly extending lugs, and the first circumferential end may include a single dovetail recess, while the first sprocket region defines a first sprocket region axial width, and the first attachment web defines a first web axial thickness that is less than the first sprocket region axial width. A second sprocket segment may include a second attachment web including a first circumferential extremity and a second circumferential extremity. A second plurality of mounting apertures may extend axially through the second sprocket segment that are in alignment with the plurality of mounting holes of the cylindrical hub. A second sprocket region may extend radially outwardly from the second attachment web, including a second plurality of radially outwardly extending lugs. The first circumferential extremity may include a single dovetail projection that mates with the single dovetail recess of the first sprocket segment, while the second sprocket region defines a second sprocket region axial width, and the second attachment web defines a second web axial thickness that is less than the second sprocket region axial width. 
     A sprocket segment according to an embodiment of the present disclosure may comprise a body having an arcuate surface defining a circumferential direction, a radial direction, and an axis of rotation. The body may include an attachment web including a first circumferential end and a second circumferential end, and a plurality of mounting apertures extending axially through the body. A sprocket region may extend radially outwardly from the attachment web, including a plurality of radially outwardly extending lugs. The first circumferential end may include a dovetail recess including a first side flat surface extending circumferentially and radially from the first circumferential end, a second side flat surface extending circumferentially and radially from the first circumferential end, and an arcuate bottom surface extending radially between the first side flat surface and the second side flat surface. 
     A sprocket segment according to another embodiment of the present disclosure may comprise a body having an arcuate surface defining a circumferential direction, a radial direction, and an axis of rotation. The body may include an attachment web including a first circumferential end and a second circumferential end, and a plurality of mounting apertures extending axially through the body. A sprocket region may extend radially outwardly from the attachment web, including a plurality of radially outwardly extending lugs. The first circumferential end may include a dovetail projection including a first side straight surface extending circumferentially and radially from the first circumferential end, a second side straight surface extending circumferentially and radially from the first circumferential end, and an arcuate top surface extending radially between the first side straight surface and the second side straight surface, the arcuate top surface defining the first circumferential end. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure. In the drawings: 
         FIG. 1  is a side-view of a machine such a bulldozer that may use sprocket locking segments in its undercarriage according to various embodiments of the present disclosure. 
         FIG. 2  is a perspective view of a sprocket assembly that may be used in the undercarriage of the machine of  FIG. 1 . 
         FIG. 3  is a rear perspective view of the sprocket assembly of  FIG. 2 , revealing its mounting flange and mounting holes for attaching the sprocket locking segments to the hub. 
         FIG. 4  is a rear perspective view of the sprocket locking segments of the sprocket assembly of  FIG. 3 , shown in isolation from the hub. 
         FIG. 5  is enlarged detail view of the interface of two sprocket locking segments used in the sprocket assembly of  FIG. 4 . 
         FIG. 6  is a front view of a single instance of a sprocket locking segment shown in  FIG. 4 . 
         FIG. 7  is a rear oriented perspective view of the sprocket locking segment of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     An undercarriage assembly that may use a sprocket assembly or a sprocket segment according to various embodiments of the present disclosure will now be described. 
       FIG. 1  shows an embodiment of a tracked machine  100  in the form of a bulldozer that includes an embodiment of a sprocket assembly  200  constructed in accordance with principles of the present disclosure. Among other uses, a bulldozer may be used to break up ground using a rake, push ground using a blade, or pick up dirt or rocks using a bucket, etc. 
     While the arrangement is illustrated in connection with a bulldozer, the arrangement disclosed herein has universal applicability in various other types of machines that commonly employ track systems, as opposed to wheels. The term “machine” may refer to any machine that performs some type of operation associated with an industry such as mining, earth moving or construction, or any other industry known in the art. For example, the machine may be an excavator, a wheel loader, a cable shovel, a track type tractor, a hydraulic mining shovel, or dragline or the like. Moreover, one or more implements may be connected to the machine. Such implements may be utilized for a variety of tasks, including, for example, lifting and loading. 
     As shown in  FIG. 1 , the machine  100  may include a body  104 , with a track system  102  attached thereto, and also has a cab  106  to house a machine operator. The machine may also include a blade assembly  108  pivotally connected at one end to the body  104  and a rake assembly  110  at an opposing, distal end. In embodiments, the blade assembly or rake assembly can be any suitable implement, or may be omitted in other embodiments of the present disclosure. A control system can be housed in the cab  106  that can be adapted to allow a machine operator to manipulate and articulate the blade assembly and/or rake assembly for digging, excavating, or any other suitable application. 
     The track system  102  may include first and second track roller frame assemblies  116 , which are spaced from and adjacent respective first and second sides of the machine  100 . It will be appreciated that only one of the track roller frame assemblies  116  is visible in  FIG. 1 . 
     Each of the track roller frame assemblies  116  carries a front idler wheel  118 , a rear idler wheel  120 , a drive sprocket assembly  200 , and a plurality of track guiding rollers  124 . The drive sprocket assembly  122 , is powered in forward and reverse directions by the machine  100 . An endless track chain assembly  126  encircles each drive sprocket assembly  200 , the idler wheels  118  and  120 , and the track guiding rollers  124 . The track chain assembly  126  includes a plurality of interconnected track links  114  with a plurality of track shoes  128  attached thereto. The track guiding rollers  124  guide the track links  114  as the track chain assembly  126  is driven by the drive sprocket wheel assembly  200 . The track chain assembly  126  may have any track chain member, track pin retention device, and/or track chain assembly. A power source  130  supplies the power to drive the track chain assembly  126  via the sprocket assembly  200 , as the lugs (discussed in more detail later herein) of the drive sprocket assembly  200  engage the various track bushings (not shown in  FIG. 1 ), propelling the movement of the track chain assembly  126  as described earlier herein. While an elevated track drive is illustrated, other drives without an elevated sprocket are contemplated to be with the scope of the present disclosure. 
     Power source  130  may drive the sprocket assembly  200  of machine  100  at a range of output speeds and torques. Power source  130  may be an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-powered engine, or any other suitable engine. Power source  130  may also be a non-combustion source of power such as, for example, a fuel cell, a power storage device, or any other source of power known or that will be devised in the art. 
     Turning now to  FIGS. 2 and 3 , details of the sprocket assembly  200  according to an embodiment of the present disclosure will now be discussed in further detail. 
     Such a sprocket assembly  200  may comprise a cylindrical hub  202  (i.e., that hub has at least partially a cylindrical configuration) defining an axis of rotation  204 , a radial direction  206 , and a circumferential direction  208 . A circumferential surface  210  may extend about the axis of rotation  204 , while a plurality of mounting holes  212  may extending axially into the cylindrical hub  202  (see  FIG. 3 ). These mounting holes  212  may be threaded to receive fasteners (e.g., cap screws) that attach the sprocket segments that will be described herein momentarily. Or, these mounting holes may be clearance holes that allow a fastener  214  (e.g., a bolt as shown in  FIG. 2 ) to pass through a flange  213  of the hub  202 , exposing a free threaded end of the fastener to which a nut may be tightened to retain the sprocket segment to the hub. To that end, these mounting holes  212  may be disposed radially adjacent the circumferential surface  210 , and allowing the sprocket segments  300  to extend radially past the circumferential surface  210  so the lugs  312  may engage the bushings of the track chain assembly. 
     A first sprocket segment  300  may be attached to the cylindrical hub  202 . The first sprocket  300  may include a first attachment web  302  that includes a first circumferential end  304 , and a second circumferential end  306  (as best seen in  FIG. 6 ), and a first plurality of mounting apertures  308  extending axially through the first attachment web  302  that are in alignment with the plurality of mounting holes  212  of the cylindrical hub  202  for receiving the fasteners  214  as just described above herein. 
     A first sprocket region  310  extends radially outwardly from the first attachment web  302 , including a first plurality of radially outwardly extending lugs  312 . The first circumferential end  304  may include a single dovetail recess  314 . Also, the first sprocket region  310  may define a first sprocket region axial width W 310 , and the first attachment web  302  may define a first web axial thickness T 302  that is less than the first sprocket region axial width W 310  (see also  FIG. 4 ). 
     With continued reference to  FIGS. 4 and 7 , a second sprocket segment  300   a  may include a second attachment web  302   a  including a first circumferential extremity  316 , and a second circumferential extremity  318 . A second plurality of mounting apertures  308 a may extend axially through the second sprocket segment  300   a  that are in alignment with the plurality of mounting holes  212  of the cylindrical hub  202  for fastening as previously described herein. 
     The second sprocket segment  300   a  may include a second sprocket region  310   a  that extends radially outwardly from the second attachment web  302   a,  including a second plurality of radially outwardly extending lugs  312   a.  The first circumferential extremity  316  may include a single dovetail projection  320  that mates with the single dovetail recess  314  of the first sprocket segment  300  (being disposed therein as shown in  FIG. 5 ). The second sprocket region  310   a  defines a second sprocket region axial width W 310   a,  and the second attachment web  302   a  defines a second web axial thickness T 302   a  that is less than the second sprocket region axial width W 310   a  (see  FIG. 4 ). 
     Looking more closely at  FIG. 5 , the single dovetail recess defines a recess outline  322 , while the single dovetail projection  320  defines a projection perimeter  324  that is at least partially offset from the recess outline  322 , creating one or more gaps  326  between the projection perimeter  324  and the recess outline  322 . 
     More specifically, the single dovetail recess  314  includes a concave arcuate surface  328  that extends predominantly radially, and the single dovetail projection  320  includes a convex arcuate surface  330  that may also extend predominantly radially, and that defines the first circumferential extremity  316 . As shown in  FIG. 3 , the convex arcuate surface  330  may be offset from the concave arcuate surface  328  a first offset distance  332  that ranges from greater than 0 mm to 10.0 mm (e.g., may range from 2.0 mm to 4.7 mm with a nominal value of 3.7 mm) in some embodiments of the present disclosure. 
     Likewise, the first circumferential end  304  of the first sprocket segment  300  may be spaced circumferentially away from the second sprocket segment  300   a  a second offset distance  334  that ranges from greater than 0 mm to 10.0 mm (e.g., may range from 1.5 mm to 3.5 mm with a nominal value of 2.5 mm) in certain embodiments of the present disclosure. 
     The single dovetail recess  314  includes a first undercut surface  336 , whereas the single dovetail projection  320  includes a first side face  338  that contacts the first undercut surface  336 . As a result, radial and circumferential loads may be shared between the first sprocket segment  300 , and the second sprocket segment  300   a.    
     Some symmetry may be provided about a cylindrical surface that radially splits the single dovetail projection  320 , and the single dovetail recess  314 . As a result, the single dovetail recess  314  includes a second undercut surface  340 , and the single dovetail projection  320  includes a second side face  342  that contacts the second undercut surface  340 . This provides another interface for sharing loads. 
     In the embodiments shown, the first undercut surface  336 , the second undercut surface  340 , the first side face  338 , and the second side face  342  are all flat in order to help maximize the surface area through which these loads are transmitted. For that purpose, the first side face  338  may be parallel to the first undercut surface  336 , and the second side face  342  may be parallel to the second undercut surface  340 . This might not be the case in other embodiments of the present disclosure. 
     In addition, the first side face  338  may form an acute angle  340  with the radial direction  206  that ranges from 2.0 degrees to 20.0 degrees (e.g., may range from 5.0 degrees to 15.0 degrees with a nominal value of 10.0 degrees) in some embodiments of the present disclosure. 
     To maximize design flexibility and reduce manufacturing cost, the first sprocket member  300 , and the second sprocket member  300   a  may have identical configurations as shown in  FIGS. 2  thru  4 . So, sets of segments may be arranged as a circular array to about the hub to form the assembly. This may not be the case for other embodiments of the present disclosure. 
     Next, a sprocket segment that may be used to assemble the sprocket assembly  200  as just described herein, or as a replacement part will now be described with reference to  FIGS. 5 and 6 . The sprocket segment  300  may comprise a body having an arcuate surface (e.g. a cylindrical surface, a conical surface, etc.) defining a circumferential direction (e.g. may be the same as  208  once the sprocket assembly  200  is assembled), a radial direction (e.g. may be the same as  206  once the sprocket assembly  200  is assembled), and an axis of rotation (e.g. may be the same as  204  once the sprocket assembly  200  is assembled). The body may include an attachment web (e.g., see  302 ) including a first circumferential end  304 , and a second circumferential end  306 . A plurality of mounting apertures  308  may extend axially through the body. A sprocket region  310  may extend radially outwardly from the attachment web, including a plurality of radially outwardly extending lugs  312  as previously described herein. 
     The first circumferential end  304  may include a dovetail recess (e.g., see  314 ) including a first side flat surface (e.g., see  336 ) extending circumferentially and radially from the first circumferential end  304 , a second side flat surface (e.g., see  340 ) extending circumferentially and radially from the first circumferential end  304 , and an arcuate bottom surface (e.g., see  328 ) extending radially between the first side flat surface and the second side flat surface. 
     Also, the dovetail recess may include a first blend  344  (e.g., a concave radius) tangentially connecting the first circumferential end  304  to the first side flat surface (e.g., see  336 ), and a second blend  346  (e.g., a concave radius) tangentially connecting the first circumferential end  304  to the second side flat surface (e.g., see  340 ). 
     The dovetail recess may include a third blend  348  (e.g., a convex radius) tangentially connecting the first side flat surface (e.g., see  336 ) to the arcuate bottom surface (e.g., see  328 ), and a fourth blend  350  (e.g., a convex radius) tangentially connecting the second side flat surface (e.g., see  340 ) to the arcuate bottom surface. 
     On the other hand, the second circumferential end  306  may be defined by a dovetail projection (e.g., see  320 ). As alluded to earlier herein, the first circumferential end  304  may lack a dovetail projection, while the second circumferential end  306  may lack a dovetail recess. This may not be the case in other embodiments of the present disclosure. 
     A sprocket segment  300   a  (see  FIG. 7 ) according to another embodiment of the present disclosure may also comprise a body with an arcuate surface including an attachment web  302   a  including a first circumferential end (e.g., see  316 ), and a second circumferential end (e.g., see  318 ), and a plurality of mounting apertures  308 a extending axially through the body. 
     A sprocket region  310   a  may extend radially outwardly from the attachment web  302   a,  including a plurality of radially outwardly extending lugs  312   a.  The first circumferential end includes a dovetail projection (e.g., see  320 ) including a first side straight surface (e.g., see  338 ) extending circumferentially and radially from the first circumferential end, a second side straight surface (e.g., see  342 ) extending circumferentially and radially from the first circumferential end, and an arcuate top surface (e.g., see  330 ) extending radially between the first side straight surface and the second side straight surface. The arcuate top surface may define the first circumferential end. 
     Moreover, the dovetail projection (e.g., see  320 ) may include a first transitional surface  352  (e.g., a radius, a chamfer, etc.) connecting the arcuate top surface (e.g., see  330 ) to the first side straight surface (e.g., see  338 ), and a second transitional surface  354  connecting the arcuate top surface (e.g., see  330 ) to the second side flat surface (e.g., see  342 ). 
     More particularly, the first transitional surface  352  may be a first radius that tangentially connects the arcuate top surface to the first side straight surface (e.g., see  338 ), and the second transitional surface  354  may be a second radius that tangentially connects the acuate top surface (e.g., see  330 ) to the second side straight surface (e.g., see  342 ). The dovetail projection (e.g., see  320 ) may include a third radius  356  that tangentially connects the first side straight surface (e.g., see  338 ) to a first radially extending surface  358 , and a fourth radius  360  that tangentially connects the second side straight surface (e.g., see  342 ) to a second radially extending surface  362 . 
     As alluded to earlier herein, the second circumferential end (e.g., see  316 ) may be defined by a dovetail recess (e.g., see  314 ) and may lack a dovetail projection, while the first circumferential may lack a dovetail recess. 
     Any of the aforementioned features may be differently configured or dimensioned than what has been specifically described herein in various embodiments of the present disclosure. 
     For many embodiments, the sprocket segment and/or hub may be cast using iron, grey-iron, steel or other suitable materials. Other manufacturing processes may be used such as any type of machining, forging, etc. For example, steel or “tough steel” may be used to create the lugs. Lugs may also be coated, heat treated, etc. to provide suitable characteristics for various applications. 
     INDUSTRIAL APPLICABILITY 
     In practice, a sprocket assembly, a sprocket segment, and an undercarriage assembly according to any embodiment described herein may be sold, bought, manufactured or otherwise obtained in an OEM (original equipment manufacturer) or after-market context. 
     The various embodiments of the interlocking sprocket segments may help to share the loads between adjacent segments, reducing the load borne by any single segment or its fasteners, 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. 
     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. 
     Accordingly, it is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention(s) being indicated by the following claims and their equivalents.