Patent Publication Number: US-2004045747-A1

Title: Drive for crawler track

Description:
[0001] The present application is based on and claims the benefit of U.S. Provisional Patent Application Serial No. 60/403,685, filed Aug. 15, 2002, the content of which is hereby incorporated by reference in its entirety. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] The present invention relates to a drive system for tracks on a crawler tractor that reduces the motor size necessary, and provides more efficient operation.  
       [0003] Traditional drives for crawler tractor tracks have used large drive motors directly driving the drive sprocket for a chain on the track along with large brakes needed for those motors. Large drive motors and large brakes are expensive, and difficult to mount.  
       [0004] Additionally, the large track drive sprocket that mounts onto the motor is expensive, and the loads involved require heavy bearing supports.  
       SUMMARY OF THE INVENTION  
       [0005] The present invention relates to a low cost, easily made track drive system for crawler tracks, as shown, molded rubber tracks. The drive system includes a main housing or drive case that mounts within the track enclosure formed by the endless track. A drive motor mounts on the housing or box drives, through a speed reduction chain and supporting the track drive sprocket.  
       [0006] The output shaft, rotated by the driven sprocket, has ends that extend out from opposite sides of the main housing or drive case. A track drive wheel is mounted on the opposite ends of the output shaft. The track drive wheel is split into separate drive wheel sections. A track drive wheel section is mounted on each of the ends of the output shaft on opposite sides of the housing. The track drive wheel sections together form a track drive wheel for the rubber tracks that are shown and utilized.  
       [0007] The track drive wheel sections can be cast wheels with drive bars at the periphery that engage drive lugs on the tracks. Also wheel sections stamped from metal can be used. Additionally, track drive wheel halves make it easy to mount the track on the drive because an outer track drive wheel section can be removed at a time.  
       [0008] Additionally, the drive case or housing output shaft driven by the motor that drives the drive sprocket on the input end of the drive case or housing has a spring applied pressure released brake mounted thereon at an end opposite from the motor. The brake is secured to the drive case or housing, and will provide a braking action for the drive shaft whenever pressure is released.  
       [0009] The drive motor is protected from dirt that may be ingested through the output shaft seals, because of the space from the drive shaft to the output shaft in the chain drive case or housing. The chain drive case or housing can be internally lubricated and continuously flushed with drive motor leakage or drain oil, after which the oil can be filtered. There can be a pressure return of the motor case drain oil.  
       [0010] The rubber tracks that are used and shown all have lugs that are driven and can be guided by idler wheels and bogie wheels and that keep the track centered on the drive wheel sections. The drive wheel sections or halves have positive lug drive bars to engage the track lugs, so that the drive wheel drive bars engage the drive lugs on the track.  
       [0011] Since the chain drive case or housing is located between the track drive wheel sections or halves, the drive case will tend to clear mud that might otherwise stick to the center parts of the track drive wheel. The stationary chain case or housing thus reduces the amount of mud that would be carried with the drive wheels and packed around or into the drive track.  
       [0012] The stationary chain case or housing can be made of fabricated material, or cast, and is generally made into two sections that would be secured together with bolts or cap screws. The drive wheel can be made also as a cast member, or in fabricated sections, as desired. The drive wheel is split into two drive wheel sections, with bars on the periphery that will engage the lugs on a rubber track, and will serve to drive the track much like teeth on a sprocket.  
       [0013] The track can have lugs that are arranged transversely parallel to each other, straight across the track, or the lugs for each drive wheel section can be one half pitch to provide for drives from one of the drive wheels to a first row of lugs, and from the other drive wheel section to another longitudinally offset row of lugs. Steel drive tracks also can be driven with this driver arrangement, using suitable lugs on tracks. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0014]FIG. 1 is a side elevational view of a portion of a drive track having a drive wheel and drive motor and chain case made according to the present invention installed thereon;  
     [0015]FIG. 2 is a sectional view taken as on line  2 -- 2  in FIG. 1;  
     [0016]FIG. 3 is a perspective view of a modified form of the drive wheel sections of the present invention with parts broken away to show a chain drive;  
     [0017]FIG. 4 is a side elevational view of a further modified form of the present invention showing a track which is used with the speed reduction chain case of the present invention;  
     [0018]FIG. 5 is a sectional view taken generally along line  5 -- 5  in FIG. 4;  
     [0019]FIG. 6 is a perspective view of the chain case of the present invention in the form used in FIG. 4;  
     [0020]FIG. 7 is an exploded view of the chain case of the present invention; and  
     [0021]FIG. 8 is a sectional view taken as on line  8 -- 8  in FIG. 4; and  
     [0022]FIG. 9 is a schematic perspective view of the track assembly from an opposite side from FIG. 4. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0023] Referring to FIG. 1, a crawler drive frame  10  is shown only schematically, and it is used to mount a chain drive case housing  12  that is suitably supported with ears or braces such as those shown at  14 , back to the frame  10 . The chain drive case  12  is long and narrow, as can be seen in FIG. 2, and has a first end portion forming a drive sprocket support indicated at  16 . The crawler drive frame  10  is mounted on a loader frame, such as a skid steer loader or tractor.  
     [0024] As shown in FIG. 2, suitable hubs  18  and  20  are formed on the chain housing at one end for supporting bearings  22  that in turn rotatably mount a sleeve or shaft  24  that supports a track drive sprocket  26 . The sleeve or shaft  24  is internally splined, and a drive hydraulic motor  28  has a splined output shaft that fits into the splined sleeve or shaft  24  and is mounted onto the outer exterior side of hub  20  using a suitable motor flange  30  and capscrews. The motor is controlled by an operator controlled valve  27  or by a variable displacement pump.  
     [0025] At the opposite end of the sleeve or shaft  24 , a spring applied, pressure released disc brake assembly  32  is secured to the chain case or housing in a suitable manner, and it has an input disc brake shaft that is splined, and fits into the opposite end of the sleeve or shaft  24  from the motor shaft.  
     [0026] The spring applied pressure released brake  32  is suitably controlled with a valve  31  from a pressure source or pump  29  as shown schematically. The valve  31  can be automatically operated with a controller  33  so that when the operator is properly positioned and secured with provided restraints, the brake would be pressurized and released. Otherwise, the brake is applied to prevent movement of the motor and track when the operator is not present or the engine is shut down. A manual operator switch can lock the brake as well.  
     [0027] The sprocket  26  can be a relatively small sprocket, for example, a 9-tooth sprocket. The opposite end  34  of the chain drive case or housing  12  also has hubs  36  and  38  thereon that mount bearings  40 . The bearings  40  are used for rotatably mounting drive wheel section hubs  42  and  44  that are drivably mounted on a center cross shaft  46 . The center cross shaft  46  passes through the hubs  42  and  44  and across the drive chain case or housing. The shaft also extends through the hub of a larger driven sprocket  48  (for example, a 17-tooth sprocket) that is drivably mounted on the shaft  46 .  
     [0028] The shaft  46  can be splined, so that there is a drive from the shaft  46  to the sprocket  48  and both of the hubs  42  and  44  are driven. As can be seen, suitable washers and capscrews  50  can be used for holding the hubs  42  and  44  and the sprocket  48  in an assembly.  
     [0029] The hub  42  mounts a first half of a drive track wheel, called a drive wheel section or segment  52 , which can be a metal stamping, and which has suitable openings for receiving lug bolts  54  for holding it onto the hub  42 . A second drive wheel section or segment  56  comprising a half of a drive wheel, is mounted on hub  44 , with lug bolts  54 , and will rotate with the hub  44 . Each of the drive wheel sections or segments  52  and  54  is provided with interior track drive lugs or bars  60  that can be formed from stamped metal, as can the rest of the drive wheel. The lugs  60  are used for effecting a drive to a rubber track  62  that is shown in FIG. 1. The rubber track  62  has centering lugs  64  that fit between the drive wheel sections or segments  52  and  54 , as shown schematically in FIG. 2 as well. These lugs  64  on the track are engaged and driven by the lugs  60  of the drive wheel section.  
     [0030] A chain  66  is used for drivably connecting the sprockets  26  and  48 , so that the track can be driven. The drive chain case or housing  12  can be made enclosed and sealed, and can be filled with oil that flows through the drive chain case in the desired manner.  
     [0031]FIG. 3 is a perspective view of a chain drive with the chain case broken away for illustrative purposes. A chain case base  70  is illustrated, and the chain case extends forwardly as shown in FIG. 2. In this instance, the drive motor  72  is provided on one side to drivably couple to an input shaft  74  that is rotatably mounted on this drive chain case in a suitable manner. The spring applied, pressure released brake  76  is mounted at the opposite end of the drive shaft  74 . The chain  78  is provided over a drive sprocket on the shaft  74 , driven in a suitable manner, and it in turn drives a driven sprocket  80  that is mounted onto a cross shaft and hub assembly  82  as previously shown. In this form of the invention, the drive wheel assembly is indicated at  84 , but only one of the drive wheel sections  86  is illustrated. The drive wheel section  86  is a wheel having a flange  86 A that runs against the interior surface of a track, and serves as a support for the track and also a guide to keep the track centered when the lugs on the track are engaging drive bars  88  that are extending inwardly from a radial plate  90  of the drive wheel section  86 .  
     [0032] As shown, a mounting hub  92  that has a bolt circle for bolting on the radial flange  90  is provided. The drive wheel section that would mount onto the hub  92  is not shown.  
     [0033]FIG. 3 is an illustrative example of a different type of drive wheel section that can be utilized with the drive chain case of the present invention for driving lugs on a track.  
     [0034]FIG. 4 illustrates another embodiment of the track assembly illustrated generally at  110 . Track assembly  110  mounts onto the sides of a vehicle frame, such as a loader frame or tractor frame, and will provide a track drive for the vehicle to which it is attached. It includes a track frame shown partially at  112 , that supports bogie wheels  114  at the ground engaging lower length  153 A of the track  153 . The bogie wheels  114  are rotatably mounted and provide guides for holding the track centered as the track is driven. The track assembly also includes a front lower idler wheel  116 , a rear lower idler wheel  118 , and an upper front idler track tension adjusting wheel  120 . A track drive wheel assembly of this embodiment is shown at  122 .  
     [0035] The track tensioning idler  120  is mounted onto a frame  108  that is pivotally mounted as at  109  to the track frame  112 , and includes a hydraulic actuator  111  that can be utilized for creating a force to pivot the frame  108  to provide an adequate tension in the track. The hydraulic actuator is anchored at the frame  112  on a bracket and pin  111 A.  
     [0036]FIG. 6 is a perspective view of a drive chain drive case  123 , and the drive chain case has a motor  124  mounted on one side thereof. As shown in FIGS. 7 and 8, a drive shaft  125  which mounts a drive sprocket  126  in the center of the drive chain case is rotatably mounted on the chain case  123  on suitable bearings  128 . The bearings  128  are on opposite sides of the chain case.  
     [0037] The sprocket  126  drives a chain  130  that extends through the drive chain case and in turn chain  130  drives a larger sprocket  132  that is drivably mounted onto a shaft assembly  134 . The shaft assembly is mounted on suitable bearings  136  in the chain case  123 . It should be noted in FIG. 7 that the chain case is a split chain case and includes sections  123 A and  123 B that are bolted together for use.  
     [0038] Shaft assembly  134  has the sprocket  132  fixed thereon (welded or machined with the shaft) for driving, and sprocket  126  is also machined in place on shaft  125 . As shown in FIG. 6, the end of shaft  125  outside of the drive chain case  123  and opposite from motor  124  has a spring applied, pressure released brake  140  drivably mounted thereon with the outer housing of the brake bolted to the chain case section  123 B. The spring applied brake is released by pressurizing a hydraulic actuator port  141 . The spring applied, pressure released brake is a known brake assembly. In addition to the friction brake shown, a positive mechanical stop can be utilized. A plunger that acts to intercept lugs on a rotating wheel on the motor drive shaft can be used.  
     [0039] The shaft  134  protrudes from the chain case assembly  123  on opposite sides thereof, as can be seen in FIGS. 5 and 8, and the outer ends of shaft  134  mount a drive wheel assembly  142 . The drive wheel assembly includes two separate drive wheel sections, including a section  144  that is on the side of the drive chain case section  123 A, and a drive wheel section  146  which is on the side of the drive chain case section  123 B. The drive wheel sections have hubs that are drivably mounted onto the tapered ends of the shaft  134  so that they will be rotationally driven when the sprocket  132  is driven.  
     [0040] The drive wheel sections have outer transversely extending drive bars  148 A and  148 B thereon. The drive bars  148 A are on the drive wheel section  144  and the drive bars  148 B are on the drive wheel section  146 . These drive bars are positioned so that they will engage lugs shown at  150  and  152  in FIG. 5 on the track  153  that is used. The track  153  in the form shown, has the drive lugs  150  and  152  in longitudinal rows, and the lugs in one row are offset one-half the pitch from the other. The track lugs can be directly aligned transversely. Other types of drives shown can be used with the drive chain case speed reduction shown. The split set two drive wheel sections of a drive wheel assembly permit the drive chain case to be mounted on the interior of the track periphery.  
     [0041] The chain drive case  123  is mounted on the interior of the periphery of the track, as shown, that is, within the track enclosure. The drive chain case is mounted on the track frame  112 . The track frame  112  includes an inverted channel  160  that supports the bogie wheels and idler wheels for track  153 . Cross members  162  are secured to the inverted channel  160  (see FIG. 4 also) and extend laterally so they mount to a frame of a vehicle  164  in a suitable manner. The drive chain case can be bolted to the inverted channel  160  or attached to the channel, and thus supported relative to the frame of the vehicle, using suitable brackets.  
     [0042] The chain drive permits speed reduction, and a much smaller, but high speed, motor can be utilized and still obtain the necessary torque for driving, when compared to the motors used for a direct track wheel drive. Also, a smaller brake can be used.  
     [0043] The motor  124  is a hydraulic motor controlled by a controller  170  that controls a valve  172  to obtain the desired speed of the motor, as shown. A wheel speed sensor  174  can be used primarily to sense inadvertent actuation of the drive motor. If motor is secured when not demanded by the operator, the controller will lock the parking brake. The speed of drive wheel  142  also can be secured. The controller also controls a valve  176  for the brake actuator port  141  so when the operator is not stationed or the loader on other vehicle is parked, the brake is applied or on. The brake is a parking brake only.  
     [0044] While the drawings show a track with the drive wheel at the top of the track, the chain drive case with the chain speed reduction can also be utilized where the drive wheel or wheels are at the lower side of the track. Any desired location for the drive wheel can be accommodated with the present drive chain case design.  
     [0045] The drive chain case mounted within the track does require the use of a split drive wheel, with lugs that are matching the position of the drive wheels on the track. However, tracks that have bars or lugs that go all the way across the track can be utilized as well, because the wheels are still capable of being split and driving on a continuous lug that extends laterally across the track.  
     [0046] The guide wheels for holding the track in position can be mounted at the edges of the track, that is, one on each side, for bogie wheels and guide wheels, and a roller that has a central wheel that would also serve as a guide between the lower lugs can be utilized when the lugs are split into two rows as shown herein. The illustrations herein show the drive with an all rubber positive drive track, but the speed reduction drive chain case also can be used with the embedded iron core crossbar tracks as well as friction drive tracks. However, the drive chain case would be mounted along the center plane of the track and the drive wheel sections are on the sides of this case.  
     [0047] When the motor  28  or  124  is driven, and drives sprocket  26  or  126 , it can be seen that a speed reduction takes place to the drive hubs  42  and  44  and shaft  134 . That means that a smaller motor, which rotates at a higher speed than the drive wheel, can be used.  
     [0048] The spring applied pressure release brake will be used for stopping the track whenever it is desired, either by a manual input, or automatically, as shown. The drive chain case can be pivoted to the frame  112  in a manner that will permit using it for track tensioning by using a pivot and springs that urge the chain case to move to a position increasing the track tension.  
     [0049] It can be seen that the drive chain case itself is between the track drive wheel sections, so that the drive chain case acts as a block or scraper to remove mud from the track drive wheel sections as the drive wheel rotates.  
     [0050] The motor shaft is spaced from the track drive wheel shaft where dirt and debris may be ingested, so that the motor is not susceptible to ingest dirt that comes directly from the track drive wheel.  
     [0051] It can be seen that track drive wheel sections can be removed, as shown in dotted lines in FIG. 2, for installation and removal of the track. The track also has exterior traction lugs as is conventional.  
     [0052] The sprockets and chain in the drive chain case can be replaced with V-belts and pulleys, or cogged belts and pulleys, if desired. Sprockets and pulleys are both drive wheels, and chains and belts are endless flexible drive members between the input and output shafts of the drive chain case.  
     [0053] Also schematically shown in FIGS. 7 and 8 is a flow through oil arrangement for the drive chain case. The hydraulic motor has normal leakage of hydraulic oil and this leakage oil  189  is directed through a bore  186  in shaft  125 . Also, the low pressure line or return line from the motor represented at  186  can have a shuttle valve  187  therein (integral with the motor) that directs a low flow, for example, 1 to 2 gallons per minute to the bore  182 . The oil flows out the end of shaft  125  into the case for the brake  140  as shown by arrow  183  and back to the case  123  through bearings  128  or suitable ports. The oil in the case  123  can be kept at the desired level (to ensure oil in the case  123  for the chain and sprockets) by location of a drain port  185 . The oil then flows back to the hydraulic oil tank. The oil also lubricates the spline drive from the motor  124  to shaft  125 . Other oil flow through arrangements can be made as well.  
     [0054] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.