Abstract:
A tracked multifunction work machine and tool carrier having bogie rollers. The machine includes an upper frame supported on an undercarriage. The upper frame includes a tool adapter and an operator station. The tool adapter supports a variety of work tools that can be selected for various operations. The operator station provides platform so the machine can be operated while walking behind or standing on the platform. The undercarriage includes a plurality of tracks for propelling the machine along the ground. Each track is associated with pairs of bogie rollers that engage the tracks as the tracks traverse the ground. The pairs of bogie rollers are pivotally mounted on the undercarriage, providing additional support of the tracks with the ground.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/689,242 filed Jun. 10, 2005, the contents of which are incorporated fully herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to apparatus and method for improving the ride characteristics of a compact, stand-on operated multipurpose work machine (also referred to as a multipurpose tool carrier), which utilizes a low-profile tracked undercarriage. More specifically, the present invention relates to the elements of the two endless tracks of the undercarriage that provide points of ground support to the compact stand-on operated machine. The end result is an improved “ride” for the stand-on operator in comparison to the conventional tracked undercarriages presently utilized on such compact multipurpose work machines. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]      FIG. 1  is a side view of a stand-on operated, multipurpose work machine (also referred to as a tool carrier) utilizing the low-profile undercarriage of the present invention.  
         [0004]      FIG. 2  is a side view depicting the right track drive arrangement of the low-profile undercarriage of the present invention.  
         [0005]      FIG. 3  shows the track drive of  FIG. 2  negotiating a raised obstacle such as a rock or concrete curb.  
         [0006]      FIG. 4  is an overhead sectional view of the track drive of  FIG. 2 .  
         [0007]      FIG. 5  is a partially sectional view of a rubber track suitable for use on the track drives ( FIGS. 2-4 ) of the stand-on operated, multipurpose work machine of  FIG. 1 .  
         [0008]      FIG. 6  is a sequence of side views depicting a machine with conventional undercarriage passing over an obstacle.  
         [0009]      FIG. 7  is a sequence of side views depicting a machine with an undercarriage of the present invention passing over an obstacle.  
         [0010]      FIG. 8  is a side view depicting the right track drive arrangement of the low-profile undercarriage of an alternative embodiment of the present invention.  
         [0011]      FIG. 9  shows the implements of the track drive of  FIG. 8  negotiating a raised obstacle.  
         [0012]      FIG. 10  is an overhead sectional view of the track drive of  FIG. 8 . 
     
    
     DESCRIPTION  
       [0013]     Turning to  FIG. 1 , shown in side view is a compact, stand-on operated multipurpose work machine (a.k.a., multipurpose tool carrier)  1 . The stand-on operated machine  1  is comprised of a compartment  10  housing an engine and hydraulic pumps that supply power to a plurality of independently controlled track drives  12 , of the machine-propelling undercarriage. The plurality of track drives  12  generally comprises a right track drive and a left track drive (not shown). An independent control  18  provides skid-steering for the stand-on operated machine  1 . A platform  16  is provided at the rear of the machine  1  for a standing operator. The multipurpose machine  1  pivotally supports a tool carrier assembly  20  comprised of at least one lift arm  22  and at least one pivotal actuator such as a lift cylinder  24 . A distal end of the lift arm(s)  22  may be equipped with one of a multitude of working tools  30 , such as: a rotary broom, a variety of loader buckets, pallet forks, stump grinder, backfill blade, auger backfiller, posthole auger, vibratory plow, shrub spade, jackhammer, and other useful tools. Their interchange may be enhanced by utilizing a conventional quick-attach adapter  28  pivotally mounted to the lift arm(s)  22 . The working tools  30  are held at or moved to one or more desired stowage and work positions by way of an orientation actuator such as a tilt cylinder  26 . The actuators  24  and  26  and auxiliary powered work tools  30  are activated by appropriate operator controls  18 .  
         [0014]     With reference now to  FIG. 2  and its horizontal cross-section  FIG. 4 , shown therein is the right track drive  12  of the work machine  1 . (The left track drive is a mirror image of the right, thus need not be separately described.) The track drive  12  comprises a track  40 , although the track  40  could be otherwise formed (e.g., a segmented steel track), preferably it is a one-piece molded rubber track (as shown in  FIG. 5 ). Such tracks  40  are commonly available with a selection of tread  42  types offering varying degrees of tractive capability (i.e., soil engaging aggressiveness). The endless track  40  is supported by (loops around) a drive sprocket  50  and a set of idlers  56 . For simplicity of illustration, the tread  42  is not shown in the area where the track  40  loops around the drive sprocket  50  and the idlers  56 . Although shown at the front end of the machine  1 , the position of the idlers  56  could be interchanged with that of the drive sprocket  50 . As best seen in  FIG. 4 , the front idlers  56  may comprise two outer rollers, of smooth circumference, laterally disposed about track guides  44  that are molded into the track  40 , along its central interior. The drive sprocket  50  is centrally positioned with respect to the lateral width of the track  40 , riding within the track guides  44 . The teeth  52  of the drive sprocket  50  engage segmented drive lugs  46  (shown in  FIG. 5 , but not individually illustrated in  FIGS. 1-4 ). The drive sprocket  50  and idlers  56  are supported by a track frame  62 , which attaches to the main frame (not shown) of the work machine  1 . A track tensioning arrangement  60  is comprised of the track frame  62 , a take-up slide  64  and a compression spring  66 . (The take-up slide  64  is also the supporting structure for the front idlers  56 .) Such commonly known tensioning arrangements are utilized, for instance, to allow the track  40  to jettison debris that might enter the drive system. In the present invention, the tensioning arrangement  60  also allows the track  40  to vertically flex along its ground-engaging interface for improved traction and ride on uneven ground ( FIG. 3 ).  
         [0015]     With continued reference to  FIG. 2 , the track drive  12  comprises a plurality of bogies  70 ,  80  supported on the frame  62 . In the preferred embodiment, the bogies  70 ,  80  are disposed on an inside and an outside of the frame  62 . The bogies  70 ,  80  are preferably paired to comprise a set of front  80  (i.e.,  80   a  and  80   b ) and rear  70  (i.e.,  70   a  and  70   b ) bogies individually pivotally supported on the track frame  62 . As best seen in  FIG. 4 , the inner  80   b  and outer  80   a  front bogies share a common pivot axis  81 , while being supported thereon independently. Likewise, the inner  70   b  and outer  70   a  rear bogies are independently supported on their pivot axis  71 . This allows the track  40  to flex laterally (interspatially twist between the drive sprocket  50  and the front idlers  56 ), to better maintain a ground-engaging interface across the width of the tread  42  while traversing uneven ground. Respective inner and outer bogies each have bearingly supported front and rear rollers. For instance, the outer rear bogie  70   a  has a rear roller  72  and a front roller  76 . The various inner ( 74 ,  78 ,  84 , and  88 ) and outer ( 72 ,  76 ,  82 , and  86 ) rollers straddle the track guides  44 , while being in approximate longitudinal alignment with the front idlers  56 . By straddling the track guides  44 , the rollers  72 - 78 ,  82 - 88  and the front idlers  56  work in combination to hold the track guides in alignment with the drive sprocket  50 .  
         [0016]     An alternative design of the drive track is shown in  FIGS. 8-10 . The endless track  40  is supported by the drive sprocket  50  and a single, center-mounted idler  56   b . This provides less wear on the drive track than a set of front idlers. The drive sprocket  50  and idler  56   b  are supported by the track frame  62 , which attaches to the main frame of the work machine  1 . The track drive  12  comprises a set of front  80  and rear  70  bogies pivotally supported on the track frame  62 . Each set of bogies  70 ,  80  comprises a common pivot axis  71 ,  81 . With the alternative design, the inner  70   d ,  80   d  and outer  70   c ,  80   c  bogies are not independent of each other. Each set of bogies are mounted on a support frame  90 , connecting the front inner  78 ,  88  and the front outer  76 ,  86  rollers together and connecting the rear inner  74 ,  84  and the rear outer  72 ,  82  rollers together. The single, center-mounted idler  56   b  and the alternative support frame  90  for the rollers offer a reduced cost in production while still maintaining a good ground-engaging surface and a smooth ride for the operator.  
         [0017]     The bogies  70 ,  80  and drive sprocket  50  are purposefully positioned for improved operator ride; i.e., to reduce vibration created at the dynamic interface between the track drives  12  and the ground. This is accomplished by four aspects of their position and operation: (1) nominal vertical location of the drive sprocket  50  with respect to the bogie rollers  72 - 78 ,  82 - 88 , (2) the spacing between adjacent bogie rollers  72 - 78 ,  82 - 88 , (3) fore and aft positioning of the bogies  70 ,  80  with respect to the rear drive sprocket  50  and idlers  56 , and by (4) an oscillation limit imposed upon the rear bogies  70 . In the first instance, the drive sprocket  50  is vertically positioned such that its rolling circumference is above those of the bogie rollers  72 - 78 ,  82 - 88  and the front idlers  56 . Thus, on a hard level surface, the bogie rollers  72 - 78 ,  82 - 88  and the front idlers  56  provide the ground support for the work machine  1 . That is, the track  40  to ground interface is substantially limited to the interval between the rearmost rollers  72 ,  74  and the front idlers  56 . Holding the drive sprocket  50  above ground contact eliminates or at least “feathers out” any ground contact impulse the teeth  52  of the sprocket  50  could otherwise interject as a vertical impulse at the rear end of the machine  1  each time one of them passes below the center of rotation of sprocket  50 . (With the drive sprocket  50  being almost directly under the operator  2  such an impulse can be bone-jarring for a conventional tracked undercarriage—see  FIG. 6 .) The proper amount by which the track  40  contacting points of the bogie rollers  72 - 78 ,  82 - 88  and the front idlers  56  are vertically positioned (offset) below those of the drive sprocket  50  depends upon a number of parameters, including: the overall length of the track drives  12 , the weight of the machine  1 , the diameters of the drive sprocket  50  and the front idlers  56 , and the tread  42  style of the track  40 . For a compact stand-on operated multipurpose work machine  1 , the vertical offset necessary to obtain the above-described benefits may be in the range of 0.2 to 1.0 inches. More preferably the offset is in the range of 0.2 to 0.5 inches. Given the goal of improved operator ride, one skilled in the art can make the necessary tradeoff decisions during an undercarriage design to determine the proper amount of vertical offset to be instituted. For some applications where the stand-on operated machine  1  is working almost exclusively on hard surfaces such as pavement, it may also be beneficial to raise the front idlers  56  a similar amount above the bogie rollers  72 - 78 ,  82 - 88 . This “feathers out” the ground contact impulse of the tread  42  that would normally occur below the center of rotation of the front idlers.  
         [0018]     Secondly, when defining the intervals between the contact points of adjacent sets of rollers ( 72 ,  74 ) to ( 76 ,  78 ); ( 76 ,  78 ) to ( 82 ,  84 ); and ( 82 ,  84 ) to ( 86 ,  88 ) and between rollers  86 ,  88  and the front idlers  56 , an important aspect is that these intervals preferably be equal to an odd multiple ( 1 ,  3 ,  5 , etc.) of approximately one-half the drive tooth  52  spacing. The drive tooth  52  spacing is also the pitch P of the rubber track, as illustrated in  FIG. 5 . The track guides  44  are comprised of embedded metal segments  46  spaced a distance P apart. A plurality of tooth grips  48  are disposed between the guides  44 , also at a distance apart, to accept the drive teeth  52  there between and transfer the rotational torque from the drive sprocket  50  into the rubber track  40 . The embedded metal segments  46  extend laterally across the track  40  such that the bogie rollers  72 - 78 ,  82 - 88  and the front idlers  56  roll over their extended flanges. The above purposeful interval spacing between the bogie rollers  72 - 78 ,  82 - 88  prevents all of them from rolling over embedded metal segments  46  simultaneously. This time-distributes the rolling contacts and reduces their potential jarring effect on the operator. One skilled in the art can appreciate that a lesser differential between the roller spacing and the pitch P of the track guides  44  than described above may provide noticeable benefit as well.  
         [0019]     In the third aspect, bogie positioning, the rear bogies  70  are positioned substantially closer to the drive sprocket  50  of the track drive  12  than are the front bogies  80  with respect to the front idlers  56 . As best seen in  FIG. 2 , the unsupported interval of track  40  between the drive sprocket  50  and the rear rollers  72 ,  74  of the rear bogies  70  is of length approximately equal to one diameter of the rollers  72 ,  74 . (Preferably this interval is less than 1½ diameters long.) Whereas, other unsupported track intervals between the contact points of adjacent sets of rollers—i.e.: ( 72 ,  74 ) to ( 76 ,  78 ); ( 76 ,  78 ) to ( 82 ,  84 ); and ( 82 ,  84 ) to ( 86 ,  88 )—and between rollers  86 ,  88  and the front idlers  56  may be as much as two to four times longer. Preferably these intervals are less than 3 diameters long and, although not required, may be approximately evenly spaced—so long as the previous consideration of roller spacing in relation to pitch P is also met. Purposeful close positioning of the rear bogies  70  improves their ability to hold the teeth  52  of the drive sprocket  50  from impinging the ground surface. That ability is further augmented by the oscillation limit imposed upon the rear bogies  70 .  
         [0020]     This—the fourth aspect—is best explained by referring to  FIG. 3  in conjunction with  FIG. 2 . The pivot-mounted bogies  70 ,  80  have a range of oscillatory motion to aid in traversing over rocks or other obstacles  100  protruding above the ground surface. The front bogies  80  are configured to have substantially the same clockwise (CW) and counterclockwise (CCW) oscillation limits—as displaced from the level or neutral position shown in  FIG. 2 . Although not limiting upon the present invention, the oscillation limits may be on the order of 15 degrees either side (i.e., CW and CCW) of the neutral position. The rear bogies  70  may have approximately the same CCW oscillation capability; however, they are prevented from having full CW displacement away from their  FIG. 2  illustrated neutral position by stops. For instance, their CW displacement may be limited to less than one-third of their CCW displacement. Preferably the stops are more limiting, to the point of permitting no CW displacement of the rear bogies. The benefit of this feature is that fewer teeth  52  of the drive sprocket  50  are able to contact the obstacle  100  when the rear of the track drive  12  passes over it. This is best explained by considering the various stages involved when the stand-on operated compact work machine  1  encounters an obstacle  100 .  
         [0021]     Prior art machines with conventional undercarriage of fixed-position rollers would climb over the obstacle  100  in a “teeter-totter” fashion, as shown in the sequential views of  FIG. 6 . The front idlers  56  continue to rise after they cross the obstacle (View A), until the machine reaches a balance point directly over the obstacle (View B). Then the machine tilts forward (View C) to rapidly drop the front idlers  56  back to the ground. Finally (View D), the drive sprocket  50  passes over and drops off the obstacle  100 . This teeter-totter motion can impart substantial upward and downward acceleration into the standing operator  2 .  
         [0022]     The present invention is the application of a novel track suspension on small stand-on operated multipurpose work machines  1 . Until now, machines of this nature have not been equipped with such undercarriages. The sequence of passing over an obstacle  100  is shown in  FIG. 7 . The obstacle  100  is first engaged by the tread  42  wrapping around the front idlers  56 . Assuming the tread  42  does not slip on the obstacle  100 , continued rotation of the drive sprocket causes the idlers  56  to raise and “walk” onto, then over the obstacle (View A). In the meantime, the front bogies  80  begin to oscillate CCW about their pivot axis  81 . This softens the lowering of the front idlers  56  (slows the rate at which they fall back toward the ground). The track suspension also prevents them from being lifted so high above the ground (compare  FIG. 6  View A to  FIG. 7  Views A and B). The concentrated reactionary load of the obstacle  100  on the unsupported span of track  40  between the front idlers  56  and the front rollers  86 ,  88  of the front bogies  80  may also increase the track tension sufficiently to move the front idlers  56  and take-up slide  64  rearward, further compressing the spring  66 . (In the  FIG. 7  sequences, the take-up slide  64  will move back and forth in response to changing track tension brought about by the respective position of the obstacle along the track to ground interface.) For a machine  1  of approximately balanced fore and aft center of gravity location, the idlers  56  will again be lifted when the front bogies  80  pass directly over the obstacle  100  (View B). The front bogies  80  rotate CW back toward their neutral position and then continue that rotation as dictated by the size and shape of the obstacle  100 , or until their CW oscillation limits are reached. During this time, the front idlers  56  lower and the rear bogies  70  begin to rotate CCW about their pivot axis  71 . The rear bogies  70  will continue that rotation as dictated by the size and shape of the obstacle  100 , or until their CCW oscillation limits are reached (View C). The obstacle  100  is now in the same location as depicted in  FIG. 3 . When the rear bogies  80  pass directly over the obstacle  100 , the drive sprocket  50 —because of its close proximity—raises to approximately the same level. The rear bogies  70  have rotated CW back toward their neutral position. However as the machine  1  continues forward, the rear bogies  70  are purposefully prevented by stops from rotating clockwise beyond their neutral position (View D). The obstacle  100  is thereby prevented from causing more than incidental deflection of the short track  40  interval between the rear rollers  72 ,  74  and the drive sprocket  50 . Essentially only those teeth  52  of the drive sprocket  50  fitting within an angle of departure of the obstacle  100  have the potential for creating contact with it. Thus, as stated earlier, the present invention limits the number of teeth  52  able to contact the obstacle  100  when the rear of the track drive  12  passes over it—thereby also limiting the number of machine jarring tooth impulses associated with such contact. The result is a smoother ride for the stand-on operator.  
         [0023]     The present invention not only reduces the “pitching” acceleration going over large obstacles (as described above), it also makes higher speed operation smoother for the operator and improves stability on side slopes. With respect to side slope operation, the obstacle negotiating sequences described above clearly show that there will be less “lifting” of the up slope track drive  12  of the present invention when it encounters an obstacle  100  than would be the case for a conventional ( FIG. 6 ) undercarriage. Other benefits of the present invention include improved track  40  life and less turf damage, especially on moderately firm surfaces, due to improve load distribution and less scuffing at the ends of the track drives  12 .  
         [0024]     Although the above benefits have been described in relation to a compact, stand-on operated multipurpose work machine, this bogie undercarriage configuration is also suitable for larger, ride-on operated work machines. Various modifications can be made in the design and operation of the present invention without departing from the spirit thereof. Thus, while the principal preferred construction and modes of operation of the invention have been explained in what is now considered to represent its best embodiments, which have been illustrated and described, it should be understood that the invention may be practiced otherwise than as specifically illustrated and described.