Patent Publication Number: US-11653594-B2

Title: Walk power mower with transmission providing both forward and reverse propulsion

Description:
This application is a continuation of U.S. patent application Ser. No. 15/624,116, filed Jun. 15, 2017, which is a continuation-in-part of U.S. patent application Ser. No. 15/472,415, filed Mar. 29, 2017, both of which are incorporated herein by reference in their respective entireties. Moreover, U.S. patent application Ser. No. 15/195,648, filed Jun. 28, 2016 and issued as U.S. Pat. No. 10,039,229 B2 on Aug. 7, 2018, is also incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments of the present disclosure relate to a walk power mower for cutting grass and, more particularly, to a transmission providing both forward and reverse propulsion. 
     BACKGROUND 
     Walk power mowers are well known for cutting grass. For example, such mowers are commonly used by property owners, such as homeowners, to cut their lawns. Such mowers have a cutting deck that houses a rotary grass cutting blade. The deck is supported by a plurality of wheels for rolling over the ground. A handle extends upwardly and rearwardly from the deck. A user who walks on the ground behind the deck grips a handle grip of the handle to manipulate and guide the mower during a grass mowing operation. 
     It can be difficult or is undesirable for some users to manually push a walk power mower over the ground in order to cut one&#39;s lawn. It is tiring to do so, particularly when the area being mowed is either large, hilly, or both. Thus, many mowers have traction drive systems that utilize part of the power generated by the prime mover carried on the mower to drive at least one pair of the mower&#39;s wheels, either the front wheels or the rear wheels, in a forward direction. Such a self-propelled mower relieves the user of the necessity of having to bodily push the mower over the ground. This greatly eases the physical effort required from the user in mowing one&#39;s lawn. The user now primarily guides or steers the mower during the powered forward motion provided by the traction drive system and the prime mover. 
     There are times when mowing one&#39;s lawn when the user needs to pull the mower in reverse at least over short distances. For example, when a user cuts grass under the branches of a bush, the user will ordinarily drive the mower forwardly so that the cutting blade reaches under the branches sufficiently to cut whatever patch of grass lies beneath the branches. However, once this patch of grass is cut, the user must pull back on the handle to pull the mower out from under the branches of the bush. While the traction drive system is designed with a one-way clutch to allow the drive wheels to free-wheel during reverse motion so that the user is not pulling back against the resistance provided by the gearing in the traction drive system, the drive wheels of the mower are typically unpowered during this reverse motion. 
     As a result, many users end up having to manhandle or wrestle the mower back in this reverse motion scenario. This requires the user to expend physical energy and for some users accomplishing manual reverse motion of the mower may be difficult or impossible in some situations. This difficulty is exacerbated for those users in which trimming operations requiring reverse motions of the mower are numerous or are required on difficult terrain. For example, in trimming beneath a bush, pulling back on the mower is even more difficult if the user has to pull the mower back up a slope to get it out from under the branches of the bush. 
     Another problem sometimes present during reverse mower movement is unintentional lifting of the mower&#39;s front wheels. That is, when a pulling force is applied at the offset mower handle, a moment is produced that causes the mower to rotate about a line of contact between the ground and the rear wheels. As one can appreciate, this rotation may cause the mower&#39;s front wheels to lift. While such lifting of the front wheels may be beneficial for various mower operations (e.g., turning), maintaining front wheel engagement with the ground during reverse may be advantageous (e.g., to maintain quality of cut). 
     SUMMARY 
     On aspect of this disclosure relates to a walk power equipment unit having a housing supported upon the ground by at least a front wheel and a rear wheel, the housing adapted to traverse the ground in both a forward direction and an opposite, reverse direction. The power equipment unit further includes a handle having a handle member extending upwardly and rearwardly from the housing, wherein the handle member includes: an upper end; and a lower end, the lower end attached to the housing. A prime mover is carried by the housing, as is a variable speed traction drive system. The traction drive system includes: a bidirectional transmission operatively connected to a drive wheel selected from the group comprising the front wheel and the rear wheel, the transmission operable to selectively rotate the drive wheel to propel the housing over the ground; and a control system comprising a handle grip translatable along the handle member. The handle grip activates the transmission to power the drive wheel for movement of the housing in the forward direction when the handle grip is translated downwardly along the handle member from a neutral position, and the handle grip activates the transmission to power the drive wheel for movement of the housing in the reverse direction when the handle grip is translated upwardly along the handle member from the neutral position. 
     In another aspect of the present disclosure, a walk power mower is provided that includes a deck supported upon the ground by front wheels and rear wheels, the deck adapted to traverse the ground in both a forward direction and an opposite, reverse direction, wherein the front wheels and/or the rear wheels operate as powered drive wheels of the mower. The mower also includes a handle comprising a handle member extending upwardly and rearwardly from the deck, wherein the handle member includes: an upper end; and a lower end, the lower end attached to the deck. A prime mover is carried by the deck and operatively connected to a cutting member associated with the deck. A variable speed, bidirectional transmission is also carried by the deck, wherein the transmission selectively rotates at least one of the drive wheels to effect propulsion of the deck over the ground. A control system is provided and includes a handle grip positioned at or near the upper end of, and translatable along, the handle member. Translation of the handle grip activates the transmission to power at least one of the drive wheels for movement of the deck: in the forward direction when the handle grip is translated downwardly along the handle member from a neutral position; and in the reverse direction when the handle grip is translated upwardly along the handle member from the neutral position. 
     In still yet another aspect of the present disclosure, a walk power mower is provided that includes a deck supported upon the ground by front wheels and rear wheels, the deck adapted to traverse the ground in both a forward direction and an opposite, reverse direction, wherein one or more of the front wheels and the rear wheels operate as a powered drive wheel of the mower. The mower also includes a handle having a handle member extending upwardly and rearwardly from the deck, wherein the handle member has: an upper end comprising a grip area; and a lower end attached to the deck. A prime mover is also provided and carried by the deck, the prime mover being operatively connected to a cutting member. A variable speed, bidirectional traction drive system is also carried by the deck, wherein the traction drive system selectively rotates the drive wheel to effect propulsion of the deck over the ground. A control system is carried on the handle and operatively connected to the traction drive system, wherein the control system comprises a first control member and a second control member that are each independently movable between a neutral position corresponding to a neutral mode of the traction drive system, and a fully engaged position corresponding to a powered mode of the traction drive system. The first control member, when moved from the neutral position to the engaged position, is adapted to manipulate the traction drive system from: the neutral mode; to a forward powered mode wherein the traction drive system rotates the drive wheel in a first direction corresponding to the forward direction of the deck. Similarly, the second control member, when moved from the neutral position to the engaged position, is adapted to manipulate the traction drive system from: the neutral mode; to a reverse powered mode wherein the traction drive system rotates the drive wheel in a second direction corresponding to the reverse direction of the deck. 
     In yet another aspect, the present disclosure relates to a walk power mower including: a grass cutting deck surrounding a grass cutting member, wherein the cutting deck is adapted to travel over the ground in both a forward direction and a reverse direction; and a handle comprising an upwardly and rearwardly extending handle member. The handle member includes an upper end comprising a grip area, and a lower end pivotally attached to the cutting deck such that the handle member pivots about a transverse pivot axis within an operating range of pivotal motion defined by: an upper stop corresponding to the handle being in a first operating orientation; and a lower stop corresponding to the handle being in a second operating orientation, the operating range of pivotal motion being at least about 5 degrees. A resilient member is operatively positioned between the lower stop and the handle member, wherein the resilient member is adapted to bias the handle member to a location at or near the upper stop. 
     In still another aspect, the present disclosure relates to a walk power mower comprising: a grass cutting deck supported upon the ground by a front wheel and a rear wheel, the cutting deck surrounding a grass cutting member, wherein the cutting deck is adapted to traverse the ground in both a forward direction and a reverse direction; at least one transmission adapted to selectively provide driving power to at least one wheel of the front and rear wheels; and a handle comprising first and second laterally spaced-apart and parallel handle members each extending upwardly and rearwardly from the cutting deck. The first and second handle members each comprise: an upper end; and a lower end pivotally attached to the cutting deck such that the handle members pivot about a transverse pivot axis within an operating range of pivotal motion defined by: an upper stop corresponding to the handle being in a first operating orientation; and a lower stop corresponding to the handle being in a second operating orientation, the operating range of pivotal motion being about 5-20 degrees. A control member is carried at or near the upper ends of the first and second handle members, wherein the control member, when moved to a first engaged position, is adapted to place the transmission into operation so that the transmission propels the mower in the forward direction. First and second resilient members are provided and positioned between the deck and the first and second handle members, respectively, the first and second resilient members adapted to bias the first and second handle members to a location at or near the upper stop. 
     In still yet another aspect, a walk power mower is provided that includes: a grass cutting deck supported upon the ground by a pair of front wheels and a pair of rear wheels, the cutting deck surrounding at least one grass cutting blade; and a variable speed traction drive system carried on the cutting deck and adapted to selectively provide driving power to at least one wheel of the front and rear pairs of wheels to propel the mower over the ground in both a forward direction and a reverse direction. A handle is also provided and includes first and second laterally spaced-apart and parallel handle members extending upwardly and rearwardly from the cutting deck, wherein the first and second handle members each comprise: an upper end; and a lower end pivotally attached to a rear portion of the cutting deck such that the handle members pivot about a transverse pivot axis within an operating range of pivotal motion defined by an upper stop and a lower stop. The mower also includes a control system carried at or near the upper ends of the first and second handle members, the control system operable to engage the traction drive system to selectively propel the cutting deck in both the forward direction and the reverse direction. First and second resilient members are provided and positioned between the deck and the first and second handle members, respectively. The first and second resilient members are adapted to resiliently deform when the handle members pivot, about the transverse pivot axis, from a position at or near the upper stop toward a position at or near the lower stop. 
     Yet another aspect of this disclosure relates to a walk power mower which comprises a deck supported by a pair of front wheels and a pair of rear wheels. The deck has at least one grass cutting blade that rotates in a substantially horizontal plane about a substantially vertical axis to cut grass. The deck also has an upwardly and rearwardly extending handle that is gripped by a user who walks on the ground behind the deck to guide and manipulate the deck during motion of the deck over the ground. A prime mover is carried by the deck, the prime mover being operably coupled to the blade for effecting powered rotation of the blade. A variable speed traction drive system is carried on the deck, the prime mover being operably coupled to the traction drive system for effecting powered rotation of the front wheels and the rear wheels. The traction drive system comprises a rear transmission having a rear axle that is operatively connected to the rear wheels for powering the rear wheels to provide self-propelled motion of the deck in a first direction of motion over the ground, a front transmission having a front axle that is operatively connected to the front wheels for powering the front wheels to provide self-propelled motion of the deck in a second direction of motion over the ground that is opposite to the first direction of motion, and a control system carried on the handle that is selectively operable by a user for placing only one transmission at a time into operation so that the rear transmission is active to propel the deck in the first direction while the front transmission is inactive or the front transmission is active to propel the deck in the second direction while the rear transmission is inactive. 
     Yet another aspect of this disclosure relates to a walk power mower which comprises a traction drive system on a grass cutting deck having a pair of front wheels and a pair of rear wheels. A pair of transmissions power at least one pair of wheels on the deck. A first one of the transmissions provides forward motion of the mower when it is active and a second one of the transmissions provides rearward motion of the mower when it is active. A slidable handle grip is provided on a handle extending upwardly and rearwardly from the cutting deck. The handle grip has a cross bar long enough to be gripped by both hands of the user. The handle grip activates the first one of the transmissions when it is slid downwardly on a handle out of a neutral position thereof as a user walks forwardly holding the cross bar of the handle grip. The handle grip activates the second one of the transmissions when it is slid upwardly on the handle out of the neutral position as a user walks rearwardly holding the cross bar of the handle grip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of this disclosure will be described more fully in the following Detailed Description, when taken in conjunction with the following drawings, in which like reference numerals refer to like elements throughout. 
         FIG.  1    is a perspective view of one embodiment of a walk power mower according to this disclosure; 
         FIG.  2    is an enlarged perspective view of a portion of the handle of the mower of  FIG.  1   , particularly illustrating the return to neutral system that causes the slidable handle grip of the handle to return to a neutral position in which the traction drive system is disengaged once the user releases the handle grip; 
         FIG.  3    is a perspective view of the underside of the cutting deck of the mower of  FIG.  1   , particularly illustrating a dual transmission traction drive system; 
         FIG.  4    is a perspective view of a portion of a second embodiment of a walk power mower according to this disclosure; 
         FIG.  5    is an enlarged perspective view of a portion of the handle of the mower of  FIG.  4   , particularly illustrating a second embodiment of the return to neutral system that causes the slidable handle grip of the handle to return to a neutral position in which the traction drive system is disengaged once the user releases the handle grip; 
         FIG.  6    is a perspective view of the underside of a mower cutting deck in accordance with another embodiment of this disclosure, the mower shown with a bidirectional, single (forward and reverse) transmission traction drive system; 
         FIGS.  7 A- 7 C  illustrate various embodiments of a traction drive system in accordance with embodiments of the present disclosure, wherein:  FIG.  7 A  is a diagrammatic view of a bidirectional transmission powered by a belt connected to a prime mover of the mower; 
         FIG.  7 B  is a diagrammatic view of a bidirectional transmission powered by an independent motor separate from the mower&#39;s prime mover; and  FIG.  7 C  is a diagrammatic view of a bidirectional transmission(s) attached to a drive wheel of the mower, wherein each transmission is configured as an electric motor; 
         FIG.  8    is a perspective view of a portion of an exemplary handle for use with the mower of  FIG.  6   , the handle including a forward bail and a separate reverse bail; 
         FIG.  9    is a perspective view of a mower in accordance with another embodiment of the present disclosure, the mower including castering front wheels; 
         FIGS.  10 A- 10 B  illustrate a mower in accordance with another embodiment of this disclosure, the mower incorporating a biased or “floating” handle, wherein:  FIG.  10 A  is a rear perspective view; and  FIG.  10 B  is a front perspective view; 
         FIG.  11    is an enlarged view of a portion of the mower of  FIGS.  10 A- 10 B ; 
         FIG.  12    is an exploded perspective view of a portion of the mower of  FIGS.  10 A- 10 B ; 
         FIG.  13    is a perspective view of a resilient member for use with the mower of  FIGS.  10 A- 10 B ; and 
         FIG.  14    is a side elevation view of the mower of  FIGS.  10 A- 10 B . 
     
    
    
     The figures are rendered primarily for clarity and, as a result, are not necessarily drawn to scale. Moreover, various structure/components, including but not limited to fasteners, electrical components (wiring, cables, etc.), and the like, may be shown diagrammatically or removed from some or all of the views to better illustrate aspects of the depicted embodiments, or where inclusion of such structure/components is not necessary to an understanding of the various exemplary embodiments described herein. The lack of illustration/description of such structure/components in a particular figure is, however, not to be interpreted as limiting the scope of the various embodiments in any way. Still further, “Figure x” and “FIG. x” may be used interchangeably herein to refer to the figure numbered “x.” 
     DETAILED DESCRIPTION 
     One embodiment of a walk power mower  2  according to this disclosure is illustrated in  FIG.  1   . Mower  2  comprises a housing or cutting deck  4  that is formed with a generally toroidal cutting chamber  6  that faces downwardly and is open at its bottom. Deck  4  is supported for rolling over the ground by a pair of front wheels  8  and a pair of rear wheels  10 . A prime mover  12 , such as an internal combustion engine, is carried on top of deck  4 . Referring now to  FIG.  3   , the drive shaft  14  of the prime mover extends vertically downwardly with its lower end extending into cutting chamber  6 . A horizontal cutting member or blade  16  is positioned within cutting chamber  6  and is removably secured to the lower end of drive shaft  14  to rotate in a generally horizontal cutting plane to cut grass. 
     Referring again to  FIG.  1   , mower  2  is a three-in-one mower having side discharge, rear bagging and mulching modes of operation. In the side discharge mode, a side discharge chute  18  can be mated with a side discharge opening to discharge grass clippings to the side of mower  2  when a side discharge door  20  is opened. In the rear bagging mode, a grass clipping collection bag  22  is mated with a rear discharge opening to collect grass clippings being discharged to the rear of mower  2  when a rear discharge door  24  is opened. While  FIG.  1    illustrates deck  4  as being both in the side discharge mode and the rear bagging mode, this is only for the purpose of illustration as these two modes would not be used simultaneously. When side discharge chute  18  is removed and side discharge door  20  is closed and when bag  22  is removed and rear discharge door  24  is closed, mower  2  is placed into its mulching mode in which grass clippings are driven downwardly out of cutting chamber  6  to discharge the clippings beneath mower  2 . However, mower  2  need not have multiple modes of operation, but could be built as a single purpose side discharge, rear bagger, or mulching mower. 
     An upwardly and rearwardly extending handle  26  comprising a pair of laterally spaced handle members or tubes  28  joined by a top cross member  30 . The lower ends of handle tubes  28  are attached to the rear of deck  4 . Handle  26  includes a U-shaped handle grip  32  that has a pair of laterally spaced legs  34  connected together by an upper cross bar  36 . Legs  34  of handle grip  32  are telescopically received on handle tubes  28  of handle  26  for sliding movement relative thereto. Thus, handle grip  32  is able to slide downwardly (translate along) on handle tubes  28  as a user walks forwardly while gripping cross bar  36  of handle grip  32  with both of the user&#39;s hands. 
     Handle grip  32  slides downwardly by an amount that depends upon how fast the user walks forwardly. As will be described in more detail hereafter, the extent or amount of downward travel of handle grip  32  controls a traction drive system  38  (see  FIG.  3   ) of mower  2  to vary the forward ground speed of mower  2  to correspond to the user&#39;s walking pace. This type of speed controlling, slidable handle grip is used on the Personal Pace® line of walk power mowers manufactured and sold by The Toro Company, the assignee herein. In addition, this type of slidable handle grip is disclosed more fully in U.S. Pat. No. 6,082,083 to Stalpes et al., which patent is hereby incorporated by reference and shall be referred to as “Stalpes” hereafter. 
     In Stalpes, handle grip  32  is in a neutral, i.e., a drive disengaged position, when handle grip  32  is at the top of handle  26  with handle grip  32  located adjacent to cross member  30  that joins handle tubes  28  together. The only control motion of handle grip  32  in Stalpes is the downward sliding motion that engages the traction drive system of Stalpes in forward and that varies the forward ground speed in concert with the user&#39;s forward walking pace. When the user lets go of handle grip  32  in Stalpes, handle grip  32  is spring biased to slide back up handle  26  to return to the top thereof at which point the traction drive system becomes disengaged once again. 
     In mower  2  of this disclosure, the Stalpes handle grip  32  has been modified so that the neutral position of handle grip  32  is no longer at the top of the range of motion of handle grip  32 . Now, the neutral position of handle grip  32  is displaced somewhat downwardly from cross member  30  of handle  26 . A return to neutral system  40  maintains handle grip  32  in its now lower neutral position relative to cross member  30  of handle  26 . 
     Handle grip  32  functions as it did in Stalpes when the user grips cross bar  36  of handle grip  32  and walks forwardly, i.e., handle grip  32  slides downwardly in the direction of the arrow A in  FIG.  1    to activate traction drive system  38  in forward and to vary the forward ground speed in concert with the user&#39;s forward walking pace. Now, however, if the user grips cross bar  36  of handle grip  32  and walks rearwardly, as when pulling mower  2  back, handle grip  32  is now also able to slide upwardly out of neutral rather than being held in neutral as in Stalpes. This upward sliding motion of handle grip  32  is shown by the arrow B in  FIG.  1   . This activates traction drive system  38  in reverse and varies the reverse ground speed of mower  2  in concert with the user&#39;s rearward walking pace. In either forward or reverse powered motion of mower  2 , when the user lets go of handle grip  32 , return to neutral system  40  causes handle grip  32  to slide back to its centered neutral position between the lower and upper limits of the range of motion of handle grip  32  to disengage traction drive system  38 . 
     Referring now to  FIG.  2   , return to neutral system  40  comprises a rod  42  having an upper end fixed by a bracket  44  to a laterally extending cross member  46  that is also part of handle grip  32 . Rod  42  has spaced upper and lower push nuts  48   u  and  48   l  fixed thereto to move with rod  42 . Push nuts  48  bear respectively against one end of cylindrical, upper and lower, push tubes  50   u  and  50   l  which are spaced along the length of rod  42  and through which rod  42  slides. Each push tube  50  has an annular thrust surface  52  that is formed as an integral part thereof. Push tubes  50  are assembled in an inverted relationship relative to each other along the length of rod  42  such that thrust surface  52  of upper push tube  50   u  is at the lowermost end of upper push tube  50   u  while thrust surface  52  of lower push tube  50   l  is at the uppermost end of lower push tube  50   l . 
     Return to neutral system  40  further includes a U-shaped clevis  54  fixed to handle  26  with the spaced, parallel side walls  56  of clevis  54  forming an upper wall  56   u  and a lower wall  56   l . Upper and lower push tubes  50   u  and  50   l  when assembled on rod  42  are arranged to pass through bores in upper and lower walls  56   u  and  56   l  of clevis  54  with thrust surfaces  52  on upper and lower push tubes  50   u  and  50   l  being inside clevis  54  immediately adjacent to upper and lower walls  56   u  and  56   l  of clevis  54 . A compression spring  58  is arranged inside clevis  54  with the ends of spring  58  bearing against thrust surfaces  52  of upper and lower push tubes  50   u  and  50   l . When return to neutral system  40  is properly adjusted and traction drive system  38  is in neutral, spring  58  will force upper and lower push tubes  50   u  and  50   l  apart until thrust surfaces  52  thereon abut against the upper and lower walls  56   u  and  56   l  of clevis  54  and the opposite ends of upper and lower push tubes  50   u  and  50   l  are immediately adjacent to upper and lower push nuts  48   u  and  48   l . 
     When the user pushes down on handle grip  32  to initiate powered forward motion of mower  2 , upper push nut  48   u  on rod  42  presses down on the upper end of upper push tube  50   u  to slide upper push tube  50   u  downwardly relative to clevis  54 . Note that lower push tube  50   l  remains stationary with rod  42  simply sliding through lower push tube  50   l  since the lower push nut  48   l  moves away from the lowermost end of lower push tube  50   l  and lower push tube  50   l  remains within clevis  54  since thrust surface  52  on lower push tube  50   l  is held in place by its engagement with lower wall  56   l  of clevis  54 . The downward motion of upper push tube  50   u  compresses spring  58  downwardly. Thus, when the user eventually releases handle grip  32 , the compressed spring  58  pushes back upwardly on upper push tube  50   u  to cause the uppermost end of upper push tube  50   u  to push the upper push nut  48   u  back upwardly, thereby returning handle grip  32  to its centered neutral position. 
     Return to neutral system  40  works the same way but in an opposite fashion when handle grip  32  is pulled upwardly in the direction of the arrow B to initiate reverse powered motion of mower  2 . This time it is lower push tube  50   l  that is pushed upwardly by lower push nut  48   l  with upper push tube  50   u  remaining stationary. Thus, spring  58  is compressed upwardly. When handle grip  32  is eventually released, the lowermost end of lower push tube  50   l  pushes downwardly on lower push nut  48   l  as the upward compression of spring  58  is released to slide handle grip  32  back downwardly to return handle grip  32  to its centered neutral position. 
     Referring now to  FIG.  3   , traction drive system  38  comprises a first rear transmission  60   r  which powers rear wheels  10  of mower  2  and a second front transmission  60   f  which powers front wheels  8  of mower  2 . Transmissions  60  preferably comprise, but are not limited to, mechanical gear drive transmissions that use various speed reduction stages to reduce the relatively high rotational speed of drive shaft  14  of prime mover  12  to a lower speed suitable for self-propelling mower  2  at ground speeds that match the walking pace of the user. Some of these speed reduction stages are built into the gearing inside the housings of transmissions  60 . However, the final speed reduction stage is formed by a small diameter drive gear  62  on each end of an axle  64  of each transmission  60  that drives a larger diameter driven gear  66  fixedly attached to one of wheels  8 ,  10 . 
     Drive gears  62  on the opposite ends of axle  64  of rear transmission  60   r  engage the backsides of driven gears  66  of rear wheels  10 . The reverse is true for drive gears  62  for front transmission  60   f  which engage the front sides of driven gears  66  of front wheels  8 . Thus, when axles  64  of transmissions  60  are rotated in opposite directions by the operation of prime mover  12 , front and rear drive wheels  8  and  10  will be rotated in opposite directions relative to each other. For example, if rear drive wheels  10  are rotated in a forward direction to propel mower  2  forwardly, front drive wheels  8  will be rotated in a rearward direction to propel mower  2  in reverse. As a consequence, it should be apparent that only one transmission  60  is active at any given time while the other transmission  60  remains inactive. Either transmission  60  can be selected to be the one that provides forward motion while the remaining transmission  60  will then be the one that provides reverse motion. 
     Rear transmission  60  preferably has a split axle  64  and provides a differential action to permit rear wheels  10  to be driven at different speeds during a turn, such as when the user swings mower  2  around 180° at the end of a pass when mowing his or her lawn, to avoid tearing or scuffing the grass. Rear wheels  10  may rotate at different speeds during turns using either an unpowered or powered differential. For example, in an unpowered differential which is preferred due to somewhat lower cost, the portion of split axle  64  powering whichever rear wheel  10  is on the outside of the turn simply overruns the rotational speed of the portion of split axle  64  powering the rear wheel  10  on the inside of the turn to create the difference in wheel speed. Since front wheels  8  of mower  2  are typically lifted up off the ground during such a turnaround of mower  2 , front transmission  60  preferably has a solid axle and lacks any differential action, thereby reducing overall cost of mower  2 . 
     Each transmission  60  is provided with a one-way clutch that permits the wheels driven by that transmission  60  to free wheel when mower  2  is being propelled in a direction opposite to the direction transmission  60  is designed to operate. In the example where one transmission is active and is driving mower  2  forwardly while the other reverse drive transmission is inactive and is not in operation, the one-way clutch in the inactive reverse drive transmission permits the drive wheels coupled to that transmission to rotate freely with respect to the internal gearing of the reverse drive transmission to avoid the drag or resistance such internal gearing would otherwise provide when mower  2  moves forwardly. 
     Each front and rear transmission  60   f  and  60   r  is separately driven by its own independent belt drive  68   f  and  68   r  from drive shaft  14  of prime mover  12 . Each transmission  60  is a rocking transmission of the type disclosed in Stalpes. When handle grip  32  is in neutral and both transmissions  60  are inactive, belts  70  in belt drives  68  are sufficiently slack so that the input pulleys on transmissions  60  are stationary even though drive shaft  14  of prime mover  12  is rotating. Effectively, mower  2  is at rest even with the engine running when handle grip  32  is not being pushed or pulled by the user. 
     However, as the user slides handle grip  32  up or down on handle  26  in either the downward direction A or the upward direction B, this motion rocks one transmission  60  in a direction (rearwardly about its axle  64  for rear transmission  60   r  and forwardly about its axle  64  for front transmission  60   f ) to tighten drive belt  70  to the rocking transmission while leaving drive belt  70  to other transmission slack. As drive belt  70  to the rocking transmission becomes taut, the transmission becomes active to begin rotating the pair of wheels powered by the rocking transmission. The speed of rotation of axle  64  of the rocking transmission, and thus the ground speed of mower  2 , progressively increases as handle grip  32  is moved ever further in the selected direction and the tautness of belt  70  progressively increases. Thus, the ground speed of mower  2  progressively increases from zero to a maximum speed as handle grip  32  travels out of neutral to the end of its range of motion in the selected direction A or B. This enables the ground speed of mower  2  to be matched to the walking pace of the user whether mower  2  is being propelled in forward or reverse. 
     First and second Bowden cables (not shown) having inner wires carried within outer conduits operably couple handle grip  32  to transmissions  60 . The first Bowden cable has a “live cable” setup in which a rear end of the outer conduit is fixed or clamped to handle  26  and the front end of the outer conduit is fixed or clamped to a lower end of one handle tube  28  or to a rear end of deck  4 . The rear end of the inner wire of the first Bowden cable is secured to an opening  72  in a pivotal tab  74  (see  FIG.  2   ) that is rotated rearwardly when handle grip  32  is moved downwardly in the direction of arrow A. The front end of the inner wire of the first Bowden cable is then attached to rear transmission  60   r  to rock rear transmission  60   r  rearwardly during downward motion of handle grip  32  in the direction of arrow A. In this “live cable” setup of the first Bowden cable, the downward motion of handle grip  32  causes the “live” inner wire of the first Bowden cable to slide rearwardly within the outer conduit in order to rock rear transmission  60   r  rearwardly while the outer conduit remains fixed in place. The “live cable” setup of the first Bowden cable and its interaction with pivotal tab  74  is shown and described in more detail in the Stalpes patent which has previously been incorporated by reference herein. 
     The second Bowden cable has a “live conduit” setup in which the front end of the inner wire is fixed or clamped in place to deck  4  and the rear end of the inner wire is fixed or clamped in place to handle grip  32 . The rear end of the conduit in the second Bowden cable is fixed or clamped in place to an upper portion of one handle tube  28  adjacent the place where the rear end of the inner wire of the second Bowden cable attaches to handle grip  32 . The front end of the conduit in the second Bowden cable is clamped or fixed to front transmission  60  to rock front transmission  60  forwardly during upward motion of handle grip  32  in the direction of arrow B. In this “live conduit” setup, the upward motion of handle grip  32  in the direction of arrow B deforms the shape of the clamped inner wire of the second Bowden cable. This deformation in the shape of the inner wire causes the “live” conduit of the second Bowden cable to slide forwardly over the inner wire to push against front transmission  60   f  to rock front transmission  60   f  forwardly. Only one Bowden cable applies force to only one transmission at any given time with the other Bowden cable not applying force to the other transmission so that only one transmission at a time is activated. 
     Mower  2  equipped with traction drive system  38  of this disclosure has powered operation of rear transmission  60   r  to propel mower  2  forwardly in a variable speed manner as handle grip  32  is gripped by the user and the user walks forwardly, thereby sliding handle grip  32  downwardly on handle  26  in an amount proportional to the walking pace of the user. However, when trying to pull mower  2  back during a trimming operation or when trying to mow a small patch of grass in reverse, the user no longer has to use manual force to manhandle mower  2  in the reverse direction. Instead, the user merely maintains his or her grip on cross bar  36  of handle grip  32  and walks rearwardly at any desired pace. This will slide handle grip  32  upwardly on handle  26  to initiate powered operation of front transmission  60  to propel mower  2  rearwardly at a variable ground speed commensurate to the walking pace of the user. Thus, the task of operating mower  2  is greatly eased since mower  2  is self-propelled both in forward and reverse while maintaining the functionality of the Personal Pace® control system of The Toro Company that had previously been used only on mowers that were self-propelled in forward only. 
     The advantages of a mower that is self-propelled in both forward and reverse is achieved in a cost-effective manner by using mechanical, gear drive transmissions that are both durable and inexpensive in comparison to using hydraulic motor/pump combinations or electric motor/drive combinations. Moreover, since transmissions  60  used to drive front and rear wheels  8 ,  10  are different from one another and are mounted on separate front and rear axles, this allows rear transmission  60   r  to have a split axle/differential action configuration while front transmission  60   f  has a solid axle/non-differential action configuration. The manner of driving front and rear wheels  8 ,  10  using the same size drive gears  62  on the ends of the axles of the front and rear transmissions and the same size driven gears  66  on the wheels, but simply reversing which sides of driven gears  66  are engaged by drive gears  62 , leads to increased part commonality and thus reduced cost. This allows a powered, reversible mower to be manufactured and sold at a reasonable cost. 
     Referring now to  FIGS.  4  and  5   , a second embodiment of a mower according to this disclosure is illustrated generally as  2 ′. The same reference numerals used in  FIGS.  1 - 3    to refer to components will be used in  FIGS.  4  and  5    to refer to the same or corresponding components with a prime designation being used to refer to those components in the second embodiment, e.g. mower  2 ′ in  FIGS.  4  and  5    as opposed to mower  2  in  FIGS.  1 - 3   . 
     Referring now to  FIG.  4   , in mower  2 ′ front transmission  60   f ′ and its axle  64 ′ have been relocated from the front to the back of mower  2 ′ so that only rear wheels  10 ′ are reversibly driven by the dual transmissions  60   f ′ and  60   r ′ with such transmissions and their axles being disposed on opposite sides of the axis of rotation of rear wheels  10 ′. In this embodiment, front wheels  8 ′ are present but unpowered with only rear wheels  10 ′ serving to self-propel mower  2 ′. As in the first embodiment concerning mower  2 , only one transmission  60 ′ (driven by belt  70 ′ and having a drive gear  62 ′ engaged with driven gear  66 ′) is active at any given time while the other transmission  60 ′ (driven by another belt  70 ′ and also having a drive gear  62 ′ engaged with driven gear  66 ′) remains inactive. Propelling rear wheels  10 ′ in opposite directions may yield better traction than using front wheels  8 ′ to drive mower  2 ′ in the direction that is opposite to the direction that rear wheels  10 ′ drive mower  2 ′. This is due to the fact that more of the weight of a mower like mower  2 ,  2 ′ is over rear wheels  10 ′ as compared to front wheels  8 ′. In addition, the filling of a grass clipping collection bag at the rear of mower  2 ′ with grass clippings during a mowing operation only accentuates this rearward weight distribution. 
     In mower  2 ′ as shown in  FIG.  4   , whichever transmission  60 ′ is used to produce forward motion of mower  2 ′ is preferably one having a split axle/differential feature as described earlier with respect to rear transmission  60   r  in mower  2 . The other transmission  60 ′ that is used to produce reverse motion of mower  2 ′ could also be one having a split axle/differential feature since both transmissions are now being used to power rear wheels  10 ′. However, since the times at which reverse motion is needed and the distances over which mower  2 ′ would travel in reverse are much more limited than what is required for forward motion, whichever transmission  60 ′ propels the mower in reverse could remain a transmission having a solid axle without any differential ability. 
     In addition to the use of both transmissions  60 ′ to drive rear wheels  10 ′, a simplified Bowden cable coupling setup is used in mower  2 ′ as shown in  FIG.  5   . In mower  2 ′, pivotal tab  74 ′ now has a second opening  76  that is disposed on an opposite side of a horizontal axis of rotation, illustrated as x in  FIG.  5   , of a pivot rod  78  compared to the location of first opening  72 ′ in tab  74 ′. As taught in more detail in Stalpes, tab  74 ′ is rigidly attached to rod  78  to pivot by virtue of the pivoting motion of rod  78  caused by journaling the ends of rod  78  in the mower handle tubes  28 ′ while a middle U-shaped portion  79  of rod  78  is captured within a channel  80  in cross member  46 ′ of slidable handle grip  32 ′. Again, rod  78  and its interaction with cross member  46 ′ are detailed more fully in the Stalpes patent which has been incorporated by reference herein. 
     When the user slides handle grip  32 ′ downwardly on handle tubes  28 ′, the portion of tab  74 ′ having opening  72 ′ is pivoted rearwardly as described in connection with the operation of mower  2 . This pulls rearwardly on the “live cable” setup of the first Bowden cable that is connected to whichever transmission  60 ′ is arranged to drive mower  2 ′ forwardly to actuate the forward drive transmission  60 ′. Whichever transmission  60 ′ is arranged to drive mower  2 ′ in reverse is now connected by a “live cable” setup of the second Bowden cable to the newly added second opening  76  in tab  74 ′. Thus, when the user pulls handle grip  32 ′ upwardly on handle tubes  28 ′ as he or she walks in reverse, the portion of tab  74 ′ having opening  76  is now pivoted rearwardly to actuate the reverse drive transmission  60 ′. Since both transmissions  60 ′ are now at the rear of mower  2 ′, the length of the second Bowden cable run is shortened compared to the length required in mower  2 , and a “live cable” rather than a “live conduit” setup of the Bowden cable is used. This simplifies the routing and arrangement of the Bowden cables. However, the operation of mower  2 ′ is the same as mower  2 , namely pushing handle grip  32 ′ downwardly as the user walks forwardly powers mower  2 ′ in a forward direction at a speed commensurate to the user&#39;s walking pace while pulling handle grip  32 ′ upwardly as the user walks rearwardly powers mower  2 ′ in a rearward direction at a speed commensurate to the user&#39;s walking pace. 
     Referring still further to  FIG.  5   , the use of the double headed tab  74 ′ as described above to activate both transmission  60   f′  and  60   r ′ in mower  2 ′ permits a simplified return to neutral system  40 ′. All that is required now is the use of one or more torsion springs  82 , preferably two such springs  82 , surrounding the ends of rod  78  that lie along and define the rotational axis x of rod  78  with such springs being anchored at one end on rod  78  and at the other end on a portion of the adjacent handle tube  28 ′. When handle grip  32 ′ is located in its centered, neutral, drive disengaging position, torsion springs  82  are in their unstressed state such that handle grip  32 ′ is retained in neutral. As rod  78  is rotated about axis x in either one direction or the other due to motion of handle grip  32 ′ relative to handle tubes  28 ′, torsion springs  82  get coiled up or twisted in one direction or the other to resist the motion of handle grip  32 ′ out of neutral. When the user subsequently releases handle grip  32 ′, the biasing force built up in the coiled torsion springs  82  is now free to act on handle grip  32 ′ to move it back to neutral. 
     The return to neutral system  40 ′ as shown in  FIG.  5    is simpler and thus less costly than system  40  shown in  FIGS.  1 - 3    and takes up less space on mower  2 ′. Thus, the cable coupling setup and return to neutral system  40 ′ shown in  FIG.  5    could be used with mower  2  shown in  FIGS.  1 - 3    if so desired. 
     While traction drive systems are shown in  FIGS.  1 - 5    as utilizing discrete forward and reverse transmissions, such a construction is exemplary only as other traction drive systems are contemplated. For example,  FIG.  6    illustrate a power equipment unit (e.g., self-propelled, walk power mower  300 ) that utilizes a traction drive system having a single, variable speed, bidirectional transmission  360  carried by the deck that alternatively powers one or more drive wheels (e.g., two rear wheels  310 ) to selectively propel the deck over the ground in both forward and reverse directions. While shown as being used to power the rear wheels  310 , the mower  300  could, in addition or alternatively, include a bidirectional transmission (see broken line rendering of front transmission  360  in  FIG.  6   ) powering the two front wheels  308 . In still other embodiments, only one of the front and rear transmissions may be bidirectional, while the other transmission provides driving power in only a single (e.g., forward) direction. Other aspects of the mower  300  may be similar to the mower  2  (or  2 ′) already described herein (e.g., the mower  300  may include the deck  4 , engine  12  (see  FIG.  1   ), blade  16 , and handle (not shown, but see handles described elsewhere herein). Accordingly, further description of these features of the mower  300  is not provided herein. 
     Utilizing a power equipment unit incorporating a singular, bidirectional transmission  360  may provide various benefits over dual transmission configurations including, for example, reduced cost and weight. Moreover, a single transmission may also benefit from a comparatively simplified control system. For example, cables (e.g., such as the Bowden cables described above connecting the handle grip  32 / 32 ′ to the transmissions) may require connection to only a single transmission, thereby simplifying cable routing/adjustment. 
       FIG.  7 A  diagrammatically represents a forward/reverse transmission  360  in accordance with one embodiment of this disclosure. While illustrated with some specificity, the transmission  360  illustrated in  FIG.  7 A  is exemplary only as other bidirectional transmissions are certainly contemplated within the scope of this disclosure. 
     The transmission  360  may be carried by the deck  4  and may include an input sheave  362  powered by a belt  70  (belt is not illustrated in  FIG.  6    as it is beneath cover  71 , but see  FIG.  3   ) connected to the drive shaft (see  14  in  FIG.  3   ). The sheave  362  is fixed to a journaled shaft  364  having a bevel gear  366  such that, when the sheave  362  rotates, the bevel gear  366  rotates in the same direction. 
     The bevel gear  366  meshes with first (forward) and second (reverse) bevel gears  368 ,  370 , which are each journaled for rotation about an axis  305  perpendicular to an axis of the shaft  364 . As a result, when the input sheave  362  rotates, the first and second bevel gears  368 ,  370  also rotate about their axis  305 , albeit in opposite directions. 
     A cone gear  372  may be located between the first and second bevel gears  368 ,  370 . The cone gear may be selectively translatable between: contact with the first bevel gear  368 ; and contact with the second bevel gear  370 . The cone gear  372  may include friction surfaces  374  on each side, the friction surfaces adapted to alternatively engage associated friction surfaces  376  of the first and second bevel gears. More specifically, when the cone gear  372  is displaced to the right in  FIG.  7 A  such that its right-side friction surfaces  374  engage the friction surfaces  376  of the first bevel gear  368 , the cone gear will rotate in a first direction ultimately corresponding to propulsion of the mower in the forward direction. Similarly, displacement of the cone gear to the left in  FIG.  7 A  such that its left-side friction surfaces  374  engage the friction surfaces  376  of the second bevel gear  370  will cause the cone gear to rotate in a second opposite direction ultimately corresponding to propulsion of the mower in the opposite, reverse direction. 
     The cone gear  372  includes gear teeth that mesh with an axle gear  378  operatively connected to the drive wheel axle  364 . As already described above, the axle  364  may include a differential  380  (diagrammatically illustrated) that allows each drive wheel to rotate independent of the other, i.e., during turns. While shown as incorporating the differential  380 , other embodiments may use a solid axle without departing from the scope of this disclosure. 
     The cone gear  373  may be connected, via Bowden cables  382 ,  384  to the mower&#39;s control system. For example, with the control system shown in  FIG.  5   , the cable  382  may be connected between the cone gear  372  and the opening  72 ′, while the cable  384  may be connected between the cone gear and the opening  76 . As a result, when the operator moves the handle  36 ′ (see  FIG.  5   ) downwardly, the tab  74 ′ may pivot such that the opening  72 ′ moves rearwardly, displacing the cable  382  and causing the cone gear  372  to slide to the right in  FIG.  7 A . As the friction surfaces  374  of the cone gear engage the friction surfaces  376  of the first bevel gear  368 , the cone gear will rotate in the first direction, causing the mower to be propelled in the forward direction. 
     Similarly, when the operator moves the handle  36 ′ upwardly in  FIG.  5   , the tab  74 ′ may pivot such that the opening  76  moves rearwardly, displacing the cable  384  and causing the cone gear  372  to slide to the left in  FIG.  7 A . As the friction surfaces  374  of the cone gear engage the friction surfaces  376  of the second bevel gear  370 , the cone gear will rotate in the second direction, causing the mower to be propelled in the reverse direction. 
     Engagement of the cone gear  372  with either of the bevel gears  368 ,  370  may be proportional to the movement of the handle  36 ′. Accordingly, the speed of mower propulsion may be associated with the degree of movement of the handle  36 ′. That is to say, the speed of the mower  300  (in both forward and reverse directions) may be dependent upon how much force the operator applies to the handle  36 ′. 
     The forward/reverse transmission  360  shown in  FIG.  7 A  may be powered, via belt  70 , by the mower&#39;s prime mover  12  (see, e.g.,  FIG.  1   ), the latter of which may be an internal combustion engine, an electric motor, or another power source. That is to say, the transmission  360  may be powered by the same power source used to rotate the cutting member  16  (see, e.g.,  FIG.  6   ). 
     However, such a configuration is not limiting. For example,  FIG.  7 B  illustrates a bidirectional transmission  1360  that is similar in many respects to the transmission  360  described above. Instead of receiving power from the prime mover  12 , however, the transmission  1360  includes an independent propulsion motor  1362  connected to or integral with the transmission to provide power to the same. For instance, the motor  1362  may be an electric motor that is powered by an onboard battery system  1364  that may also provide power to the prime mover  12  (assuming the latter is configured as an electric motor). While the actual construction of the battery system  1364  may vary, it may in some embodiments include one or more lithium-based battery cells as is known in the art. Alternatively, the motor  1362  and prime mover  12  could be powered by separate and independent battery systems. Still further, one or both of the motor  1362  and prime mover  12  could receive AC power from an external power source. 
     In yet another potential drive system, the transmission may be configured as one or more, e.g., two, independent electric motors  1462  directly coupled to the mower drive wheels (e.g., one to each of the rear wheels  310 ) as shown in  FIG.  7 C . As with the motor  1362 , the motors  1462  may be powered by a battery system  1364  that is either dedicated to mower propulsion, or is shared with the prime mover  12  (not shown in  FIG.  7 C ). Each electric motor  1462  and  1362  may, as is known in the art, be reversible to provide the desired forward/reverse propulsion. 
     One benefit of the electric transmissions  1360 ,  1462  is that no mechanical interconnection is required between the handle and the transmission. Instead, a cable or wire harness adapted to carry electrical signals (or an equivalent wireless protocol) may be used to provide a command signal to the electric motors based upon a position of the handle. For example, the handle may include a position sensor (e.g., linear variable differential transducer) or similar device that may convert a physical position of the handle into an appropriate electrical signal that is ultimately provided to the electric motors. In some embodiments, a microcontroller may be provided to receive, as inputs, the signals representing the position of the handle. The microcontroller may then process these inputs and produce corresponding output commands to the electric motor(s). 
     Accordingly, various bidirectional transmission configurations, now known or later developed, are certainly contemplated within the scope of this disclosure. 
     While described above in the context of the handle  36 ′ of  FIG.  5   , those of skill in the art will recognize that the handle  36  of  FIG.  2    could also be utilized with slight modification with the mower  300 . Moreover, control systems other than the handles  36  and  36 ′ are also contemplated. For example,  FIG.  8    illustrates a mower  400  having a handle  426  that incorporates two independently movable control members, e.g., first and second bails  435  and  436 . The bails  435  and  436  are each movable between a neutral position (corresponding to a neutral mode of the drive system), and an engaged position (corresponding to a powered mode of the drive system). The bails may be connected by cables  382  and  384 , respectively, to the transmission  360  (not shown in  FIG.  8   , but see  FIG.  7 A ). As a result, movement of the bail  435  from its neutral position to its engaged position translates the cone gear  372  to the right in  FIG.  7 A , resulting in forward mower propulsion (e.g., forward powered mode), while movement of the bail  436  from its neutral position to its engaged position translates the cone gear  372  to the left in  FIG.  7 A , resulting in reverse mower propulsion (e.g., reverse power mode). In one embodiment, the engaged position of both bails is achieved by pivoting the bail (about the handle) until it rests against the cross member  430  as indicated in broken lines in  FIG.  8   . 
     The bails  435 ,  436  may include an interlock that prevents engagement of one bail unless the other is in a neutral position. In other embodiments, the diametrically opposing forces applied to the cone gear  372  by the cables  382  and  384  (see  FIG.  7 A ) may effectively negate the need for such an interlock as the bail with the highest operator engagement force will determine the direction/speed of mower propulsion. 
     As indicated above, the mower  300  may include the single forward/reverse transmission  360  (or  1360 ,  1462 ) at the rear axle to effectively provide driving power to the rear wheels  310 . Providing both forward and reverse operation at the rear axle is beneficial as, for example, the rear wheels typically bear a substantial portion of the mower weight and further allow for both forward and reverse propulsion even when the front wheels  308  are lifted off the ground (e.g., during a turn). However, the forward/reverse transmission  360  (or  1360 ,  1462 ) could alternatively be located at the front axle in other embodiments. Still further, the mower  300  could provide a forward/reverse transmission at both front and rear axles (see, e.g., broken line transmission  360  in  FIG.  6   ), or a forward/reverse transmission at one (e.g., rear) axle, and a forward-only transmission at the other (e.g., front axle). The latter configuration would provide not only powered forward and reverse propulsion, but also all-wheel drive when operating in the forward direction. 
       FIG.  9    illustrates a mower  500  in accordance with another embodiment of this disclosure. The mower  500  may be similar in many respects to the mower  2 ,  2 ′,  300 , and  400  already described herein. However, the mower  500  differs in that the two front wheels  508  each form part of a caster assembly  509  having a caster arm rotationally connected to the deck so that each front wheel assembly, and thus, its associated front wheel, is permitted to caster or rotate about a vertical caster axis  511  relative to the deck  6 . With forward/reverse propulsion provided by the rear wheels  510 , castering front wheels  508  may provide the mower  500  with improved maneuverability by, for example, reducing or even eliminating the need to lift the front wheels during turns. The mower  500  may include any one of the handles described elsewhere herein. 
     While various traction drive configurations are described and illustrated in  FIGS.  1 - 9   , those of skill in the art will understand that other embodiments are certainly possible without departing from the scope of this invention. Moreover, features of the various embodiments described may be combined/substituted with one another to produce yet even additional embodiments. Accordingly, the embodiments described and illustrated herein are exemplary only. 
     During reverse mower operation, the force vector applied by the operator to the mower handle (e.g., which results in an applied moment to the handle about the handle/deck attachment point) may reverse. This reversal may ultimately result in a downward force being applied to the mower handle. In some instances, this downward force may cause the front of the deck to lift upwardly. As described below, embodiments of the present disclosure may address such lifting by utilizing a handle that provides a degree of float during mower operation. 
       FIGS.  10 A- 14    illustrate a walk power mower  200  in accordance with another embodiment of the present disclosure. With the exceptions noted below, the mower  200  may be mostly identical to the mower  2  (or  2 ′ or  300 ) already described herein. For example, the mower  200  may include a cutting deck  204  that may be self-propelled, i.e., it may include a variable speed traction drive system having one or more transmission(s) carried by the deck as described herein. The drive system may be capable of selectively providing driving power to one or more of the wheels in both a forward and a reverse direction. Alternatively, the mower  200  may incorporate a conventional transmission (e.g., rear-wheel drive, front-wheel drive, or all-wheel drive) that is capable of selectively providing driving power to one or more of the wheels in only a single (e.g., forward) direction. For brevity, aspects of the mower  200  that are either commonly known in the art, or that are already described herein above, are not further described below. 
     As shown in  FIGS.  10 A- 10 B , the grass cutting deck  204  is supported upon the ground  203  by a front wheel (e.g., a pair of ground-engaging front wheels  208 ) and a rear wheel (e.g., a pair of ground-engaging rear wheels  210 ). Again, the traction drive system may drive at least one of the front wheels and/or rear wheels forwardly to propel the mower  200  as it traverses the ground  203  in a forward direction, while the same or different wheel(s) may optionally be driven rearwardly to propel the mower in the reverse direction as already discussed herein. In other embodiments, the wheels of the mower may be undriven, i.e., the mower may move under operator push-power only. 
     The deck  204  may further support a prime mover  212  such as an electric motor or gasoline-powered engine. The prime mover may power not only the drive wheels of the mower, but also a cutting blade  16  (see  FIG.  3   ) operable to rotate within the deck. 
     A handle  226  extends upwardly and rearwardly from the deck  204  as shown in  FIGS.  10 A- 10 B . As with the handle  26  of the mower  2 , the handle  226  may include a pair of laterally spaced-apart and parallel handle members or tubes  228  extending upwardly and rearwardly from the cutting deck. Each handle tube includes an upper end forming a grip area, e.g., cross member  230  and/or handle grip  232 . Lower ends of each handle tube  228  may be pivotally attached to the deck  204 , e.g., to a rear portion of the deck. While shown as incorporating two parallel handle tubes, mowers with handles formed from a single handle member or tube are also contemplated. 
     The handle  226  of the exemplary mower  200  may include a U-shaped handle grip  232  having a pair of laterally spaced legs  234  connected by an upper cross bar  236  at or near the upper ends of the handle members. As with the mower  2 , legs  234  of the handle grip  232  may be telescopically attached near the upper ends of the handle tubes  228  for sliding movement (translation) relative thereto. Thus, handle grip  232 , like the grip  32  described above, forms a control system or member slidable downwardly (and optionally upwardly) on the handle tubes  228  as the user walks forwardly (and optionally, rearwardly) while gripping the cross bar  236  with the user&#39;s hands. That is to say, the control member of the handle  226  is operable to engage the variable speed traction drive system to selectively propel the cutting deck  204  in one or both of the forward and reverse directions in a manner already described herein with respect to the mowers  2  and  2 ′. 
     Of course, in other embodiments, the handle  226  may include an alternative control member for interfacing with the traction drive system to control mower propulsion, or it may completely lack any such control member/traction drive system (i.e., when configured as a push-powered mower). 
     The lower ends of the handle tubes  228  may pivotally attach to the deck  204  such that the handle  226 /handle tubes  228  may pivot about a horizontal transverse pivot axis  250  (e.g., an axis that is transverse to a direction of forward or reverse travel of the deck) as shown in  FIG.  11   . To accommodate this pivotal connection, the mower  200  may include left and right upright float plates  252  associated with the left and right handle tubes  228 , respectively. The plates  252  may each define an aperture operable to receive a fastener (e.g., pin/nut  254 ) passing through an aligned aperture in its associated handle tube  228 . The pins/nuts  254  thus define the pivot axis  250  about which the handle (e.g., handle tubes) may pivot. 
     Each handle tube  228  may also include a handle latch  256 . Each latch may include a lever  258  that is rotatable (e.g., 90 degrees) to allow extension and retraction of a latch pin  260 . In the operating position illustrated in  FIG.  11   , each pin  260  may be engaged with a slot  264  formed in the associated plate  252 . The slots constrain the handle  226  (handle members  228 ) not to a singular position like the notches  262  (described below), but rather allow the handle  226 /tubes  228  to pivot, relative to the deck  204 , between: an upper stop  266   a  (upper end of the slot  264 ) corresponding to the handle being in a first operating orientation R (see  FIG.  14   ); and a lower stop  266   b  (lower end of the slot) corresponding to the handle being in a second operating orientation B (see also  FIG.  14   ). The upper and lower stops  266   a ,  266   b  thus define an operating range of pivotal motion of the handle (i.e., of the handle tubes). In one embodiment, the operating range of pivotal motion is at least about 5 degrees (i.e., about 5 degrees or more) of rotation about the pivot axis  250 . For example, in some embodiments, a range of about 5-20 degrees, or a range of about 8-12 degrees, is contemplated. 
     By retracting the latch pins  260 , the handle  226 /handle members  228  may also be moved from the operating orientations to a third or storage orientation S shown in broken lines in  FIG.  14   . In the storage orientation S, the handle  226 /handle tubes  228  is positioned generally vertically to reduce the footprint of the mower during non-use. The handle  226  may be latched in the storage orientation by extending the pins  260  into engagement with associated notches or openings  262  formed on the plates  252  (see  FIG.  11   ). As one can appreciate, the storage orientation S is outside of the operating range of pivotal motion defined by the slots  264  and stops  266   a ,  266   b . While shown as placing the handle  226 /handle members  228  in a generally vertical storage position, such a configuration is not limiting. For instance, other embodiments may locate the notches  262  (or, alternatively, provide an additional set of notches  262 ) to allow for handle  226 /handle member  228  storage at a different angular orientation. One such orientation may place notches  262  such that the handle  226 /handle members  228  extend forwardly and generally parallel to the ground  203  (see  FIG.  14   ) when in a storage orientation S′. 
     As shown in the exploded view of  FIG.  12   , each plate  252  may rotatably attached to an upright flange  253  of the mower deck via its associated pin/nut  254  such that it may rotate about the transverse pivot axis  250 . To rotationally secure each plate  252  in place relative to its associated flange  253 , a fastener  255  and threaded knob  257  may be provided. The fastener  255  may be inserted through an aperture  259  in the flange  253  and into one of two (or more) holes  261   a ,  261   b  formed in the bracket  252 . By pivoting the plate until the appropriate hole  261   a ,  261   b  aligns with the aperture  259 , the mower may provide varying handle operating heights to accommodate a broad range of users. Once the fastener  255  is inserted through the desired hole  261   a  or  261   b  of each plate  252 , the threaded knob  257  may be secured to the fastener  255  to lock the plate  252  in place. 
     With reference now to  FIGS.  11 - 14   , the mower  200  may also include a handle float system adapted to bias the handle (e.g., the handle members) toward the upper stop  266   a . In one embodiment, the float system includes a resilient member, e.g., left and right resilient members  272 , operatively positioned between each lower stop  266   b  of the cutting deck and its respective handle member  228 . For example, in the illustrated embodiment, the left and right resilient members  272  may be positioned such that they abut a lower side of the left and right handle tubes  228 , respectively, when the handle is at rest (when the handle is in the operating orientation R (see  FIG.  14   ) and no user loads are applied to the handle). In some embodiments, the resilient members  272  may bias the tubes  228  against their respective upper stops  266   a . However, in other embodiments, the resilient members may be configured to bias the handle members to a location that is at or near (e.g., slightly short of) the upper stops when the handle is at rest. 
     The term “resilient member,” as used herein, includes most any device that is able to deform, displace (e.g., displace a contained fluid), distort, or contract under load, and then spontaneously return to (or near) its original configuration when the load is removed. Thus, in addition to the neoprene cylinder configuration described below, other resilient members, e.g., a pneumatic spring, a mechanical or fluidic shock absorber, etc., are also contemplated within the scope of this disclosure. 
     To secure each resilient member  272  in place, the mower deck  204 , e.g., the plates  252 , may each define a seat  274 . In the illustrated embodiment, each seat is formed by a bent tab of its associated plate  252  (see  FIG.  12   ). The seat  274  may define an aperture adapted to receive an integral threaded stud  276  of the member  272  as shown in  FIGS.  12  and  13   . The stud  276  may pass through the aperture in the seat  274  and be secured relative to the plate  252  with a nut  278 . 
     Each member may be constructed of a resilient elastomeric material. For example, while not wishing to be bound to any specific configuration, each member  272  may be a neoprene disk or cylinder having a durometer of 60 Shore A. In the illustrated embodiment (see, e.g.,  FIG.  13   ), the cylinder may have a height of about one inch and a diameter of about 1.25 inches. However, members of other materials, hardness, size, and geometry are certainly contemplated. 
     During operation of the mower  200  over the ground  203 , the handle  226  may be used to control forward propulsion at already described above with reference to the mower  2  and  2 ′. For example, as shown in  FIG.  14   , the user may apply a force  280  that either: displaces the handle grip  232  downwardly along the handle tubes  228  to engage the traction drive system; or, where the mower is push-powered, pushes against the cross member  230  sufficiently to move the mower forwardly. In the case of the former, as the user walks forwardly and applies this input force  280  to the handle grip  232 , the handle grip moves from a neutral position (wherein the traction drive system is inactive), to a first engaged position, causing one of the transmissions to engage and propel the mower in the forward direction. 
     As this user-applied force  280  is offset from the deck  204 , it may also produce a pivoting force on the handle  226 /handle tubes  228  (about the axis  250  (see also  FIG.  11   )) in a clockwise direction  282  as shown in  FIG.  14   . However, the upper stop  266   a  of the slot  264  (see also  FIG.  11   ) will effectively limit this pivotal movement of the handle (relative to the deck  204 ). As stated above, however, some minimal pivotal movement in the direction  282  may be accommodated before contact occurs between the pin  260  and the upper stop  266   a . However, once the hard stop  266   a  is contacted, further movement of the handle  226  (relative to the deck) in the direction  282  may be constrained. 
     When the user instead applies a pulling input force  284  to the mower handle  226  (e.g., directly to the handle grip  232 ) in a reverse direction, the handle grip  232  may move upwardly along the handle members from the neutral position to a second engaged position. In the second engaged position, the traction drive system may activate for propulsion in the reverse direction. Moreover, as this reverse motion occurs, the handle  226 /handle members  228  may pivot (about the pivot axis  250 ) in a counterclockwise direction  286 , i.e., toward the lower stop  266   b  (see  FIG.  11   ) corresponding to the second operating orientation B of the handle. As this pivotal movement occurs, each handle tube  228  may compress and resiliently deform its associated member  272 . As a result, the moment of the handle  226  is reacted, at least initially, by compression of the members  272 , allowing substantial downward movement of the handle (e.g., cross member  230 /hand grip  232 ) to occur and be isolated (at least initially) from corresponding upward movement of the mower&#39;s front wheels  208 . Of course, once the members bottom out on the hard stop  266   b  (see  FIG.  11   ), further movement of the handle  226  in the direction  286  may begin to elevate the mower&#39;s front wheels  208 . 
     With a mower  200  like that described herein incorporating two neoprene members  272  as described above, the handle  226  may pivot about its pivot axis  250  (in the direction  286 ) about 10 degrees from its at rest position R (shown in solid lines in  FIG.  14   ) to a bottom position B before the front wheels  208  would begin to rise. While varying geometries are possible, one embodiment of the mower  200  may use a handle that is roughly 32 inches long (measured from a centerline of the cross member  230  to the pivot axis  250 ). With this construction, the cross bar  230  may move a linear distance (e.g., along an arc  288 ) of approximately 5-10 inches, e.g., 6 inches, as the handle tubes move from the upper stop  266   a  to the lower stop  266   b  (see  FIG.  11   ). Of course, depending on the stiffness/configuration of the members, the weight and weight distribution of the mower, and the magnitude of the force  284 , the members may effectively form the lower stops. That is to say, the members  272  may reach a maximum deflection before the pins  260  contact the lower stops  266   b . However, in other embodiments, the members may continue to compress up and until the lower stops  266   b  are contacted by their respective pins  260 . 
     Floating handles such as those described herein may thus allow at least some degree of downward movement of the handle to occur without causing associated lifting of the front wheels. As a result, mowers that utilize a sliding control member to initiate rearward propulsion (e.g., like the handle  226  described herein) may permit rearward/downward handle movement without causing front wheel lifting (at least during typical and expected operation). This advantage may be especially useful for mowers that incorporate reverse drive at the front wheel axle. However, even for mowers that provide no powered reverse operation, floating handles in accordance with embodiments of the present disclosure may still assist in keeping the front wheels in contact with the ground during reverse pulling of the mower. 
     While described herein in the context of a four-wheel mower, such a configuration is exemplary only. For instance, it is contemplated that embodiments of the present disclosure may find application to mowers having tri-wheel configurations (e.g., having only a single front wheel and/or a single rear wheel), as well as to most any other multi-wheel/multi-axle configuration. Yet further, mowers using ground-engaging members other than wheels (e.g., a rear roller) are also possible. Still further, embodiments of the present disclosure may find application to mowers entirely lacking physical ground-engaging members. For example, hover mowers, which float above the ground on a cushion of air generated by the mower, may benefit from the concepts (e.g., the biased handle) described herein. Those of skill in the art will further realize that embodiments of the present disclosure may also find application to walk-behind power equipment other than lawn mowers having a ground-traversing tool housing other than a cutting deck including, for example, aerators, wheeled debris blowers, cultivators, and the like. 
     Various modifications will be apparent to those skilled in the art. Thus, the scope of this invention is not to be limited to the details of the various embodiments described herein, but shall be limited only by the appended claims, and equivalents thereof.