Abstract:
A sprocket assembly for a vehicle having a chassis and at least one endless track for engaging a ground surface. The track being movably coupled to the chassis and driven by the sprocket assembly. The sprocket assembly including at least one sprocket segment, a hub rotationally coupled to the chassis and a fastening system configured to displace some material portion of the sprocket segment when the sprocket segment is attached to the hub.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a non-provisional application based upon U.S. provisional patent application Ser. No. 61/525,040, entitled “TRACK TENSIONING SYSTEM”, filed Aug. 18, 2011, and U.S. provisional patent application Ser. No. 61/522,818, entitled “SEGMENTED SPROCKET ASSEMBLY”, filed Aug. 12, 2011, both of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to tracked vehicles, and, more particularly, to a segmented sprocket assembly method and system associated with the tracks of the vehicles. 
         [0004]    2. Description of the Related Art 
         [0005]    A crawler vehicle is typically has two endless tracks that serves to support and propel the vehicle. Each track is entrained about a drive sprocket, an idler roller and a series of track rollers. Typically the idler roller is adjustable to thereby alter the tension in the track to enable the track to function in a desired manner A tensioning mechanism is used to change the position of the idler roller to create the needed tension in the track so that the track is retained on the set of rollers. Wear in the track or stretching of the track creates slack in the track which needs to be removed for continued proper use of the track and this is accomplished by adjusting the tensioning mechanism. 
         [0006]    Associated with each track is a drive sprocket that is powered by way of a gearing system that is driven by an engine. The drive sprockets typically have teeth that interact with the track to drive the track. The tensioning system, the power delivered through the gearing system and the resistance in moving the track against a load all contribute to forces that are transmitted through the drive sprocket. These forces provide stress on the connecting mechanism between the sprocket and a drive hub to which the sprocket is connected. 
         [0007]    Drive sprockets may be segmented to provide for easier replacement. The sprocket may be composed of, for example, three segments that may be substantially similar. This would perhaps allow one of the segments to be disengaged from the track when it is rotated to a selected position, thereby allowing one segment at a time to be replaced without dismounting the track. Prior art systems have these segments bolted to the hub. 
         [0008]    What is needed in the art is a way of attaching segmented gears in a more cost effective and secure manner than is currently available. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides an apparatus and method for mounting a drive sprocket to a hub of a tracked vehicle. 
         [0010]    The invention in one form is directed to a sprocket assembly for a vehicle having a chassis and at least one endless track for engaging a ground surface. The track being movably coupled to the chassis and driven by the sprocket assembly. The sprocket assembly including at least one sprocket segment, a hub rotationally coupled to the chassis and a fastening system configured to displace some material portion of the sprocket segment when the sprocket segment is attached to the hub. 
         [0011]    The invention in another form is directed to a method of securing a sprocket segment to a hub of a tracked vehicle, the method including the steps of orienting the sprocket segment relative to the hub; passing a fastener through the hub and the sprocket segment; and displacing some material of the sprocket segment with a fastening system. 
         [0012]    An advantage of the present invention is that it the fastening system orients and secures the sprocket segment to the hub. 
         [0013]    Another advantage is that the present invention allows for an interference fit between the connecting hardware and the sprocket segment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0015]      FIG. 1  is a schematical side view of a tracked vehicle using a tensioning system according to the present invention; 
           [0016]      FIG. 2  is a schematical view of the tensioning system used on the vehicle of  FIG. 1 ; 
           [0017]      FIG. 3  is an exploded perspective view of the drive sprocket used on the vehicle of  FIG. 1 ; and 
           [0018]      FIG. 4  is a partial sectional view of the sprocket of  FIG. 3 . 
       
    
    
       [0019]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one embodiment of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown in schematical form a side view of a tracked vehicle  10  having a track  12  driven by a toothed sprocket  14 . Toothed sprocket  14  transfers rotational power from a power source (not shown) to track  12  thereby driving tracked vehicle  10  across the ground. An idler sprocket  16  is configured to tension track  12  by way of a tensioning system  18  that positions idler  16  such that excess slack in track  12  is removed. Additionally, when maintenance of the drive system is undertaken tensioning system  18  is used to back-off the tension on track  12  so that the drive components can be serviced. Toothed sprocket  14  is connected to a hub that is driven by way of a transmission and engine system. Toothed sprocket  14  may consist of one assembly or a series of segmented arcs that are arranged in a quasi-circular arrangement as they are connected to the hub. 
         [0021]    Now, additionally referring to  FIG. 2 , tensioning system  18  includes a control  20  and two tensioners  22 , one for each of the tracks on tracked vehicle  10 . Of course more tensioners  22  are contemplated for vehicles having additional tracks. Each tensioner  22  is shown schematically in  FIG. 2  and includes tensioning cylinder  24  and pressurizing cylinder  30 . Tensioning cylinder  24  has a rod that extends and retracts idler  16  as piston  26  moves dependent upon the amount of fluid  28  in cylinder  24 . Fluid  28  is an incompressible fluid, and may be in the form of grease. Cylinder  30  is fluidly connected with cylinder  24 , with fluid  32  being the same as fluid  28 . Piston  34  is a floating piston, which separates fluid  32  from fluid  36 . Fluid  36  may be a variety of fluids, such as air, nitrogen, oil or hydraulic fluid, which is kept separate from fluid  32 . As the pressure in fluid  36  is varied it causes a displacement of fluids  28  and  32  to thereby reposition piston  26  and hence idler  16 . 
         [0022]    Cylinders  24  and  30  may be of one construct so that the cavities in which fluids  28  and  32  occupy are one cavity. There is a spring (not shown) associated with each idler  16  that allows tensioners  22  to retract when pressure is removed from fluid  36 . 
         [0023]    Valves  38  are illustrated as contacts or connections with the contacts being normally open which is the equivalent of indicating that the valves are normally closed thereby preventing the flow of fluid to/from tensioners  22 . Valves  38  are only opened or used when there is a need to transfer fluid to/from the cavity where fluid  36  resides. Valves  38  can also be considered connections that automatically prevent the flow of fluid  36  when disconnected. This also illustrates a retrofit type of system of the present invention, where at least a part of control  20  is not part of tracked vehicle  10 . For example on legacy equipment it may be desirous to temporarily connect control valves  40  with a hydraulic source  42 , such as that already available on tracked vehicle  10 , and connect valves  40  to the two tensioners  22 . This allows legacy equipment to receive the benefits of the present invention, without the need to integrate an active and/or manual control system to vehicle  10 . In this scenario adjustments to the tension of tracks  12  are made while tracked vehicle  10  is stationary. Alternatively, control  20  can be integrated as illustrated in  FIG. 1  with new build or legacy equipment to thereby allow active adjustment of the tension of track  12 . 
         [0024]    As a further embodiment of the present invention, cylinders  30  may be disconnected from cylinders  24 , such as a legacy cylinder on current equipment, at the point shown as a flexible connection in  FIG. 2 . 
         [0025]    This also leads to another embodiment of a retrofit kit for legacy equipment with the addition of cylinders  30  to the legacy equipment to thereby utilize current grease cylinders  24  on tracked vehicle  10 . 
         [0026]    A substantial amount of torque is applied through sprocket assembly  14  and a problem encountered with the prior art toothed segments is the difficulty in aligning the segments and securing them in a manner to prevent movement and shifting of the segments once attached to the hubs. 
         [0027]    Now additionally referring to  FIGS. 3 and 4 , there is shown a toothed sprocket assembly  14  in an exploded form and in a cross-sectional form, having a hub  44  with splined studs  46 , multiple toothed segments  48  and nuts  50 . Splines  52  of splined studs  46  are arranged to extend through the thickness of hub  44  so that splines  52  additionally engage toothed segments  48 . Splines  52  engage the edges of the holes in toothed segments  48  and may displace some of the metal of toothed segments  48  as toothed segments  48  are drawn tight against hub  44 . Nuts  50  have a beveled extended surface that engages the hole in toothed segment  48 , which may have a corresponding angled surface to cooperatingly interact with nut  50  to help align toothed segment  48  during installation. 
         [0028]    As toothed segment  48  is being installed, splines  52  and the angled surfaces of nuts  50  and the holes in toothed segment  48  coact to align toothed segment  48  so that it is accurately positioned relative to hub  44  and thus to adjacent toothed segments  48 . The present invention advantageously provides for the alignment of toothed segments  48  as they are installed and to tightly secured toothed segments  48  to hub  44  so that they will not shift as the substantial forces associated with tracked vehicle  10  are endured by toothed sprocket assembly  14  during the operation of tracked vehicle  10 . 
         [0029]    Toothed sprocket  14  is configured by the interaction of splines  52  with hub  16  and toothed segments  20  to withstand the tension applied to track  12  by tensioning system  18 , as well as the forces applied during operation of the tracked vehicle. Although three segments  48  of sprocket  14  are illustrated other numbers of segments are also contemplated, including, but not limited to, 1, 2, 4, 5 and 6 segments. Also, although five splined studs  46  are illustrated as connecting each sprocket segment  48  to hub  44 , other quantities are also contemplated and since the present invention is more effective at holding sprocket segments  48  to hub  44 , fewer splined studs  46  may be needed than the bolt systems of the prior art. Advantageously the present invention may be easily adapted for use with legacy equipment with little or minimal modification of the hub and sprocket. 
         [0030]    Splined studs  46  have a head, splines  52 , and a threaded portion which nut  50  engages. The threaded portion is of a smaller diameter than the outer diameter of splines  52 , allowing the threaded portion to easily pass through the corresponding holes in hub  44  and sprocket segment  48 . As nut  50  is connected to the threaded portion of stud  46 , tapered portion  56  engages the conical or beveled portion  58  of the hole through sprocket segment  48 . This helps to orient and center sprocket segment  48  as it is being connected with hub  44 .  FIG. 4  illustrates that stud  46  is already connected to hub  44  and that splines  52  either have matched receiving grooves in hub  44  or that splines  52  have been forced into or drawn into hub  44 . Hub  44  has a thickness at the point which stud  46  extends therethrough, and this thickness is less than the overall length of splines  52  along stud  46 . Splines  52  extend beyond the surface of hub  44  by a distance  54 . Distance  54  is sufficient to engage the material of sprocket segment  48  and displace some of the material as sprocket segment  48  is drawn to hub  44 . It is also contemplated that distance  54  may approximate the thickness of sprocket segment  48 , making allowance for taper  56 . 
         [0031]    While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.