Abstract:
A twin-lever drive wheel steering mower for a sitting operator with each lever independently controlling a brake and the speed of each drive wheel through a separate hydraulic pump and motor transmission. A brake assembly positioned on each drive wheel; a pair of pivotally mounted steering levers, each controlling one of said pumps mounted on the mower for longitudinal movement, each steering lever is connected independently to the swash plate of its controlled pump providing variable speeds forward, reverse, and a neutral zero flow position; linkage members connecting the steering levers for each wheel to a brake assembly on each wheel; a pair of T-shaped slots having a lateral leg in a cover plate surrounding each of the steering levers allowing the levers to move laterally outward in the lateral leg to engage the brakes only in the neutral position.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to drive wheel steering vehicles and more specifically to twin-lever drive wheel steering lawn mowers, wherein the steering levers also provide parking brakes.  
         DISCUSSION OF PRIOR ART  
         [0002]    Drive wheel steering is a concept where the two drive wheels on fixed axles are rotated at different speeds to achieve turning. The drive wheels can also be rotated in different directions for a very sharp turn or even a zero turn radius which is when the mower actually turns about the mid point of the drive wheel axis. The other wheels on the mower are free-wheeling and castered which merely follow the drive wheels.  
           [0003]    With drive wheel steering mowers, the mower becomes much more maneuverable than conventional vehicle steering. Hydraulically powered drive wheel mowers typically include a separate variable displacement axial piston hydraulic pump for each of the two fixed axle drive wheels. These variable displacement pumps include a tiltable swash plate which can vary the pump discharge rate from zero flow, referred to as neutral, up to a maximum flow or a reverse direction of flow. This variable flow rate takes the place of a transmission and a clutch. In drive wheel steering, the flow rates to the wheel motors control the turning speed of the wheels.  
           [0004]    Drive wheel steering type mowers, have been around for at least 40 years and are typically controlled by a pair of side-by-side levers which move forward and aft from a neutral position to achieve variable speed and steering. These two essentially vertically positioned levers can be positioned close together between the operator&#39;s knees or positioned out to the sides of the operator, as in the present invention, with horizontal gripping portions extending in toward the center of the mower for easy side-by-side gripping. Each lever independently controls the speed of one of the drive wheels which permits a variety of maneuvers including rotating one wheel forward while rotating the other backward, which causes the mower to turn within its own dimensions. These types of mowers are generally referred to as zero turning radius mowers or ZTR mowers.  
           [0005]    Parking brakes for hydraulically powered drive wheel steering mowers in the prior art are typically independent brakes of the nature of a hand brake in an automobile. If no power is being supplied to the pump, there is no braking action, so if the mower is on an incline, it will begin to roll. Prior art hydraulic drive wheel steering machines typically have a separate independent park brake lever which is either set by a pedal or by a locking hand lever. However, if the operator forgets to set the parking brake on an unpowered mower, there is a danger that the mower may roll if it is on a slight incline. If the engine is running in the neutral position, the motors are pressurized equally so the machine will not roll.  
         SUMMARY OF THE PRESENT INVENTION  
         [0006]    The present invention alleviates the potential rolling problem of the mower when the engine is not running with the provision of a parking brake on each drive wheel which is activated by moving the steering levers outward so that the operator can dismount the machine. The movement of each steering lever outward sets the brake on each drive wheel, thereby preventing a potential accident.  
           [0007]    The steering levers for both wheels are each connected through a series of linkages to the pump control for altering the flow rate from zero flow, either forward or backward, to a maximum flow rate or some speed in-between. Also connected to each steering lever is a second linkage which engages or releases a brake on each wheel. These two different functions which the steering levers perform are effected by two distinctive separate movements. To cause the mower to move forward or backward, the steering levers are moved longitudinally forward in a vertical plane from the neutral position or longitudinally backward in the same plane for moving in reverse.  
           [0008]    To engage the brake, the steering lever is moved laterally outward 45 degrees in a plane normal to the previously mentioned longitudinal plane. This lateral movement is only possible when the steering lever is in the neutral position. The hand engaging portions of the steering levers in the running position are horizontally positioned in front of the operator, thus blocking his egress from the mower. By rotating the steering levers laterally outward from the neutral position, the brakes on both wheels are engaged and the mower is safe to leave unattended.  
           [0009]    When engaging the brakes, the steering levers are rotated outward through 45 degrees of travel, thus causing the brake lever extension to rotate 13 degrees. By reason of the mechanical advantage of the moment arms and overall geometry of the linkage, a 10 to 1 mechanical advantage can be obtained when setting the brakes through manual rotation of the steering levers. When the steering levers are moved longitudinally for steering, there is no movement of the brake linkage.  
           [0010]    The principal advantage of the present invention is to provide a twin-lever drive wheel steering mower wherein the movement of the steering levers provides speed control as well as setting the park brake when the levers are locked in neutral.  
           [0011]    Another object of the present invention is to provide steering lever geometry which necessitates setting the brakes prior to egress from the mower.  
           [0012]    A further object of the present invention is to provide a riding mower with a high degree of safety when the operator dismounts the mower. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a right front perspective view of the twin-lever power mower of the present invention with the steering levers shown in dotted line when the parking brakes are set;  
         [0014]    [0014]FIG. 2 is a partial top plan view to an enlarged scale of a single steering lever and its connecting linkage, with the pump swash plate and the parking brake with portions of the mower removed;  
         [0015]    [0015]FIG. 3 is a partial top plan view similar to FIG. 2 with the steering arm in the brake set position;  
         [0016]    [0016]FIG. 4 is a forward perspective view of the same connecting linkage as shown in FIG. 2 with the steering arm neutrally positioned;  
         [0017]    [0017]FIG. 5 is a perspective view similar to FIG. 4 with the steering arm in the brake engaging FIG. 3 position;  
         [0018]    [0018]FIG. 6 is a plan view to an enlarged scale of the brake lever extension with its camming surfaces; and  
         [0019]    [0019]FIG. 7 is a perspective view of a modified version of the connecting linkage between the steering levers and the braking assembly of the hydraulic pump and motor transmission. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    The twin-lever drive wheel steering mower of the present invention is generally described by reference numeral  10  and as shown in FIG. 1. The mower includes a pair of drive wheels  12  and  13 , each of which are individually powered hydraulically by hydrostatic pumps  22  and  24  not shown in FIG. 1 through the movement of adjacent steering levers  14  and  15  rotatably attached to the mower. The mower  10  is built on a frame  16  which supports a conventional multi-blade deck  18  which in turn is supported by an adjustable height mechanism  21 , all of which is generally considered known in the art and therefore not described in detail. A pair of caster wheels  20  are located on the front of the mower frame which move as dictated by the drive wheels  12  and  13 . The remaining structure illustrated in FIG. 1 is also well known in the prior art and therefore not discussed. The pair of steering levers  14  and  15  control the direction and movement of the mower through a pair of similar axial piston variable displacement pumps  22  and  24 , as shown in FIGS. 2 through 5. FIGS. 2 through 5 are shown with substantial portions of the mower removed so that the portions of the mower illustrating the present invention are better seen.  
         [0021]    Axial piston variable displacement pumps are well known in the prior art as power sources which also function as transmissions. Variable flow pumps are controlled by swash plate positioning shaft  25  which positions a swash plate within the pump, not shown. When the swash plate is positioned normal to the pistons of the pump with the pump running, the flow rate of the pump is zero flow, also called neutral, and as the swash plate is tilted forward, the flow begins to increase up to a maximum level of tilt, and if the swash plate is tilted backward, the flow is reversed, thereby providing an infinite number of speeds for the vehicle being driven either forward or backward.  
         [0022]    In FIG. 4, swash plate positioning shaft  25  extending outwardly from pumps  24  and  22  are attached to a vertically positioned swash plate pivot arm  26 . Arm  26  is positioned by steering lever  14  through connecting rod  64 , ball joint  62 , and steering lever support base  30 . Steering lever  14  is pivotally mounted to support base  30  for movement in a lateral plane, as indicated by angle B in FIG. 5. Steering lever  14  is also rotatable in a vertical longitudinal plane about pivots  34  which pivotally mount support base  30  to the frame  16  of the mower. Steering lever  14 &#39;s longitudinal movement controls the fluid output from pump  24  by positioning swash plate pivot arm  26 . The fluid output from pump  24  is directed to a hydraulic wheel motor  74 , as shown in FIG. 2, which in turn drives wheel  12 .  
         [0023]    Steering lever  14  also controls the setting of a parking brake on the wheel  12  through the following linkage. Connected to the lower end of lever  14 , as seen in FIG. 4, is a connecting rod  36  with ball joints  38  at both ends which in turn is connected to brake pivot crank  40 . Crank  40  is pivotally mounted to the frame  16  of the mower at pivots  42  and includes an additional arm  44  which is pivotally connected to connecting rod  46  which in turn pivotally connects to brake lever  52 . Brake lever  52  rotates about pivot  54  through approximately 13 degrees when the brake is set which amounts to 1.5 inches of travel at the long end  83  of the lever  52 . The camming surfaces  78  and  80 , as shown in FIG. 6, surround pivot  54  and engage the brake shoes ends  82  of a conventional design and are not shown in detail. The wheel side plate  68 , as shown in FIGS. 4 and 5 attaches to the frame of the mower adjacent the axle wheel bearing and hydraulic motor  74  and are all concentrically aligned.  
         [0024]    The steering lever  14  sets the parking brake by clockwise rotation of lever 14 through 45 degrees, which is shown in FIG. 5 as angle B, to set the brake. The rotational movement of steering lever  14  is restricted by a T-shaped slot  76 , shown in FIGS. 2 and 3. The slot  76  is in a stationary cover plate, not shown, which contains lever  14 . The parking brake can only be set with the steering lever  14  in the neutral position, which is defined by lateral leg  66  of the T-slot  76 . The adjustment of the neutral position is by an adjustable turn buckle  50  in connecting rod  46 .  
         [0025]    While FIGS. 2 through 5 only illustrate steering lever  14  and its associated linkages, steering lever  15  on the opposite side which controls drive wheel  13  is identical to all the parts illustrated with steering lever  14  and its connecting structure.  
         [0026]    A modified linkage between the steering lever  14 ′ and pump  24 ′ is illustrated in FIG. 7. Located at the lower end of steering lever  14 ′ is a fork  84  which engages a roller  85 . Roller  85  is mounted on the end of lug  86  which in turn is concentrically mounted on rotable shaft  87 . At the opposite end of shaft  87  is an offset lever  88  which in turn engages a spring mounted link  89 . Link  89  pivotally attaches to a locking pawl  91 . Pawl  91  is pivotally mounted on the transmission  93  and when pawl  91  is lifted upwards as seen in FIG. 7, it engages a gear  92  which in turn is tied to the rotation of wheel axle  94 . When the teeth of locking pawl  91  engage gear  92 , the wheel axle is locked against rotation and thereby forms a brake for that wheel.  
         [0027]    In viewing FIGS.  7 , when steering lever  14 ′ is rotated clockwise into its outward position so the operator can dismount the mower, fork  84  causes roller  85  to rotate shaft  87  in a counterclockwise direction which lifts locking pawl  91  into locking engagement with gear  92  thereby locking out wheel  12 ′ not shown.  
         [0028]    In FIGS. 2 through 5, the hydrostatic transmission includes a separate pump  24  and wheel motor  74  while in the FIG. 7 version, the pump and motor are combined in a single unit  93  which functions in the same manner as the separate pumps and motors disclosed in FIGS. 2 through 5.  
       Operation  
       [0029]    When the mower is in a storage, non-use position, the steering levers  14  and  15  are normally rotated outwardly 45 degrees to the dotted line positions shown in FIG. 1. In this position, the parking brakes are engaged, as illustrated in FIG. 5 or the wheel axle  94  is locked up in FIGS. 7. Before the engine can be started, microswtich  58  must be closed, as seen in FIG. 5 and microswitch  95  in FIG. 7. Since the parking brakes must be set before the engine will start, T-slot leg  66  of FIGS. 2 and 3 guarantees that the hydraulic pumps will be in their neutral position so as to prevent any possible movement of the mower. Once the engine has been started and the operator is in place, the two steering levers  14  and  15  are swung laterally inward to the full-line position illustrated in FIG. 1. Once in this position, the steering levers are out of the lateral slot  66  and are free to move longitudinally in leg  67  of T-shaped slot  76  for forward or backward movement. If the operator is not in the seat when the levers are moved to the full-line position, the engine will stop since a seat switch, not shown, has not been closed.  
         [0030]    To move the mower forward in a straight line, levers  14  and  15  are slowly rotated forward to the same degree, thus causing both drive wheels to turn at the same speed. To stop the movement, the levers are returned to neutral and the pumps&#39; flow reduction brakes the mower. If a right turn is desired, the left steering lever  15  must be advanced ahead of the right steering lever  14 . When it is desirous to back up the mower, both steering levers  14  and  15  are pulled backward the same degree, thus causing the mower to back up. If it is desirous to turn the mower about a zero radius turn to the right, the left steering lever  15  is moved forward while the right steering lever  14  is moved backward, both to the same degree, which causes the wheels to turn in opposite directions at the same speed, thus turning the mower about the center point between both drive wheels.  
         [0031]    When it is desirous to leave the mower, steering levers  14  and  15  are returned to the neutral position and then rotated laterally outward to the dotted line position, as seen in FIG. 1, thus setting the parking brake and also locking the pumps in their neutral no flow position. Since the horizontal extensions  17  and  19  of steering levers  15  and  14  are positioned in front of the operator, it is very difficult for the operator to leave the mower without setting the parking brakes.  
         [0032]    From the above description of the invention, those skilled in the art will perceive the improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims: