Patent Publication Number: US-6668529-B2

Title: Operator control system for self-propelled vehicles

Description:
This is a continuation-in-part of U.S. patent application Ser. No. 09/893,193, filed Jun. 27, 2001, U.S. Pat. No. 6,557,331 which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to self-propelled, ground-working vehicles such as lawn mowers and, more particularly, to operator control systems for use with the same. 
     BACKGROUND OF THE INVENTION 
     Various types of lawn mowers are known. For example, small, walk-behind mowers are in general use by both homeowners and professionals alike. At the other end of the spectrum are large, riding mowers adept at mowing correspondingly large and typically unobstructed areas. Between these two categories lies what is commonly referred to as “mid-size” mowers. 
     Generally speaking, mid-size mowers are self-propelled units having a cutting width of approximately 32-60 inches. While they may be configured as either riding (including ride-on and ride-behind) or walk-behind units, walk-behind mowers potentially offer greater maneuverability. For example, walk-behind mowers are particularly efficient when mowing large lawns having numerous obstacles (e.g., trees, shrubs, flowerbeds, and the like) which necessitate intricate trimming, or when mowing lawns which may otherwise be ill-suited to high-speed riding mowers. Moreover, walk-behind mowers are often used in areas with steep slopes which may pose traction or tipping problems for riding mowers. Furthermore, mid-size, walk-behind mowers are also, in general, less expensive than riding mowers. While the present invention is directed to control systems for use with either riding or walk-behind vehicles, it will, for the sake of brevity, be described with respect to mid-size, walk-behind mowers. 
     One type of control system known for use with mid-size mowers uses two rearwardly extending handles each equipped with a scissors-type lever. Each lever operatively controls one of two drive wheels typically located at or near the rear corners of the cutting unit. Where the levers are configured as “normally engaged,” actuating (e.g., squeezing) one of the drive levers causes disengagement and/or braking of the corresponding drive wheel, permitting the mower to turn about that wheel. Alternatively, the levers may be “normally disengaged” such that actuating (e.g., squeezing) one of the drive levers causes engagement of the corresponding drive wheel. 
     While scissors-type lever control systems are more than adequate for their intended purpose, drawbacks remain. For instance, scissors-type levers, in general, may provide limited mechanical advantage in overcoming lever tension. Accordingly, when cutting a lawn with many trees, shrubs, or other obstacles that necessitate numerous turns, discomfort in the hands, wrists, and arms may occur. Scissors-type lever control systems may also be susceptible to variation in lever tension over the lever travel. Furthermore, depending on the position of each lever within its throw, the operator may not be able to grasp the respective lever with all fingers. 
     Other systems are also known. For example, U.S. Pat. No. 5,511,367 to Powers et al. and U.S. Pat. No. 5,809,755 to Velke et al. disclose control systems having a generally horizontal, transverse hand position. While addressing some of the above-identified problems, other issues with hand position and/or control actuation potentially remain. 
     SUMMARY OF THE INVENTION 
     Control systems of the present invention seek to overcome the above-identified drawbacks by providing natural hand positioning with conveniently located drive control levers. Control systems in accordance with the present invention further provide a hand position interior to the control system to reduce potential contact between the operator&#39;s hands and external objects during operation. The drive control levers of the present invention may additionally provide substantially constant tension throughout their range of motion, resulting in drive control lever forces which are more evenly distributed throughout the operator&#39;s hands. 
     In one embodiment, an operator control system for a self-propelled vehicle is provided. The operator control system includes a handle assembly including a first hand grip having a first grip axis and a second hand grip having a second grip axis. The first grip axis and the second grip axis extend upwardly and toward one another when the vehicle is in an operating configuration. A first control lever associated with the first hand grip is also included. The first control lever is pivotable about a first pivot axis, wherein the first pivot axis is substantially parallel to the first grip axis of the first hand grip. A latching device associated with the first control lever is also included and is adapted to latch the first control lever in two or more positions. 
     In another embodiment, an operator control system for a self-propelled vehicle is provided and includes a handle assembly including a first hand grip having a first grip axis and a second hand grip having a second grip axis. The first grip axis and the second grip axis extend upwardly, forwardly, and toward one another when the vehicle is in an operating configuration. Also provided is a first control lever associated with the first hand grip. The first control lever is pivotable about a first pivot axis, wherein the first pivot axis is substantially parallel to the first grip axis of the first hand grip. A latching device associated with the first control lever is also included. The latching device is operable to latch the first control lever in two or more positions. 
     In yet another embodiment, a method for controlling a self-propelled vehicle is provided. The method includes providing an operator control system including a handle assembly having a first hand grip with a first grip axis and a second hand grip with a second grip axis. The first grip axis and the second grip axis extend upwardly and toward one another when the vehicle is in an operating configuration. A first control lever associated with the first hand grip is also included. The first control lever is pivotable about a first pivot axis, wherein the first pivot axis is substantially parallel to the first grip axis of the first hand grip. The handle assembly also includes a first latching device associated with the first control lever, where the first latching device is operable to latch the first control lever in at least a first position and a second position. The method also includes: grasping the first control lever with an operator&#39;s first hand; manipulating the first control lever to the first position with the operator&#39;s first hand; and manipulating the first latching device to latch the first control lever in the first position. 
     In still yet another embodiment, an operator control system for a self-propelled power mower is provided. In this embodiment, the control system may include a handle assembly including a first hand grip having a first grip axis and a second hand grip having a second grip axis. The first grip axis and the second grip axis are substantially coplanar and extend upwardly, forwardly, and toward one another when the mower is in an operating configuration. The control system may also include a first control lever associated with the first hand grip, where the first control lever is pivotable about a first pivot axis, the first pivot axis being substantially parallel to the first grip axis of the first hand grip. A first latching device including a generally hook-shaped member pivotally coupled to the first hand grip is also included. The first latching device is operable to pivot about an axis generally coaxial with the first grip axis. The first latching device is adapted to latch the first control lever in at least a first position and a second position. 
    
    
     The above summary of the invention is not intended to describe each embodiment or every implementation of the present invention. Rather, a more complete understanding of the invention will become apparent and appreciated by reference to the following detailed description and claims in view of the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be further described with reference to the drawings, wherein: 
     FIG. 1 is a left front perspective view of a self-propelled vehicle, e.g., a mid-size, walk-behind mower, incorporating an operator control system in accordance with one embodiment of the present invention; 
     FIG. 2 is an enlarged, partial perspective view of the operator control system of FIG. 1; 
     FIG. 3 is a left rear perspective view of the operator control system of FIG. 1; 
     FIG. 4 is a top plan view of the operator control system of FIG. 1; 
     FIG. 5 is a partial perspective view of a right side portion of the control system of FIG. 1 with a left side portion removed for clarity; 
     FIGS. 6-10 are enlarged views of a neutral position latching device shown in various positions, (FIG. 6 illustrates a drive control lever secured in a first or neutral position by the latching device; FIG. 7 illustrates the latching device pivoted for release of the drive control lever; FIG. 8 illustrates the drive control lever in a second or forward position relative to the latching device; FIG. 9 illustrates the latching device relative to the drive control lever while the latter is in the second position; and FIG. 10 illustrates the latching device relative to the drive control lever while the latter is in a third or reverse position); 
     FIG. 11 is an enlarged section view taken along line  11 — 11  of FIG. 4 illustrating the cross-sectional shape of an operator presence control lever; 
     FIG. 12 is an enlarged end view of a portion of the operator presence control lever of FIG. 11; 
     FIG. 13 is a side elevation view of an operator control system in accordance with another embodiment of the invention; 
     FIG. 14 is a partial side elevation view of a mid-size, walk-behind power mower in accordance with another embodiment of the invention; and 
     FIGS. 15-19 are enlarged views of a latching device in accordance with another embodiment of the invention (FIG. 15 illustrates a drive control lever latched in a neutral position by the latching device; FIG. 16 illustrates the latching device pivoted for release of the drive control lever; FIG. 17 illustrates the drive control lever latched in a park position by the latching device; FIG. 18 illustrates the drive control lever in a forward position relative to the latching device; and FIG. 19 illustrates the latching device relative to the drive control lever while the latter is in the park position). 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In the following detailed description of the embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     FIG. 1 shows an operator control system  200  in accordance with one embodiment of the present invention as the latter may be incorporated on a self-propelled vehicle, e.g., a mid-size, walk-behind lawn mower  100 . While, for the sake of brevity, the invention is herein described with respect to a particular mid-size, walk-behind lawn mower (hereinafter generically referred to merely as “walk-behind mower,” or, more generally, as “mower”), those of skill in the art will realize that the invention is equally applicable to other walk-behind mowers, ride-behind mowers (e.g., such as those utilizing sulkies), and conventional ride-on mowers as well as to most any other walk-behind, ride-behind, or ride-on self-propelled, ground working vehicle, e.g., skid-steer loader, aerator, snow thrower, tiller, etc. 
     While the general construction of the mower  100  is not considered central to the invention, it will now be briefly described. FIG. 1 illustrates an exemplary mower  100  (shown primarily in broken lines) having a frame  102  supporting a prime mover, e.g., internal combustion engine  104 . A pair of transversely opposing, ground engaging drive wheels  106  (only left wheel visible) may support the rear of the mower  100  in rolling engagement with the ground. Each drive wheel  106  may be powered by a hydraulic motor (not shown) which receives hydraulic power from a hydraulic pump  107  (best shown in FIG. 3) under the control of various operator-controlled valves. The hydraulic pumps  107 , in turn, may be separately powered by the engine  104 . Other drive systems, e.g., gear or pulley driven systems (examples of which are described below), are also within the scope of the invention. 
     Operator controls, as further described below, permit independent control of the speed and direction of each drive wheel  106 , allowing control of mower speed and direction from a walking or riding position generally aft, e.g., behind, the mower  100 . A pair of front swiveling caster wheels  108 , which are preferably connected to forwardly extending frame rails  102   a  and  102   b , may support the front of the mower  100  in rolling engagement with the ground. 
     As used herein, relative terms such as “left,” “right,” “fore,” “forward,” “aft,” “rearward,” “top,” “bottom,” “upper,” “lower,” “horizontal,” “vertical,” and the like are from the perspective of one operating the mower  100  while the mower is in an operating configuration, e.g., while the mower  100  is positioned such that the wheels  106  and  108  rest upon a generally horizontal ground surface as shown in FIG.  1 . These terms are used herein to simplify the description, however, and not to limit the scope of the invention in any way. 
     Although the illustrated mower  100  has the drive wheels  106  in the rear and the caster wheels  108  in front, this configuration is not limiting. For example, other embodiments may reverse the location of the wheels, e.g., drive wheels in front and caster wheels in back. Moreover, other configurations may use different wheel configurations altogether, e.g., a tri-wheel configuration. These and other embodiments are possible without departing from the scope of the invention. 
     A cutting deck  114  may be mounted to a lower side of the frame  102  generally between the drive wheels  106  and the caster wheels  108 . The cutting deck  114  includes one or more cutting blades (not shown) as known in the art which are operatively powered by the engine  104 . During operation, power is selectively delivered to the cutting deck  114 , whereby the blades rotate at a speed sufficient to sever grass and other vegetation passing underneath the cutting deck. The cutting deck  114  may optionally include deck rollers  115  to further support the cutting deck relative to the ground during operation. 
     As illustrated in FIGS. 2-3, the operator control system  200  may include a first hand grip  202   a  and a second hand grip  202   b . To support the operator control system  200 , one or more structural members such as arms  116  may extend between the frame  102  and the control system  200 , e.g., the arms  116  may extend upwardly and rearwardly from the frame  102  (best shown in FIG.  1 ). While shown and described as arms  116 , most any comparable structure is possible without departing from the scope of the invention. For example, plate and/or sheet metal structures may be used in place of, or in addition to, the arms  116 . 
     The suffixes “a” and “b” are used throughout this description to denote various left and right side parts/features, respectively. However, in most pertinent respects, the parts/features denoted with “a” and “b” suffixes are either substantially identical to, or mirror images of, one another. Therefore, such items may, where appropriate, be referred to generically or collectively without the suffix, e.g., “hand grip  202 ” may refer to either or both hand grip  202   a  and hand grip  202   b . It is understood that, unless otherwise noted, the description of an individual part/feature, e.g., the description of a part/feature identified with an “a” suffix, also applies to the opposing part/feature, e.g., the part/feature identified with a “b” suffix. Similarly, the description of a part/feature identified with no suffix applies to both the corresponding left and right part/feature, e.g., to both the part/feature identified with the “a” suffix and the “b” suffix. 
     In some embodiments, the hand grips  202  form ends of a continuous handle assembly  203  which may also include a substantially transverse tube member or portion  204  and curved portions  206  as shown in FIG.  3 . As the figures illustrate, the curved portions  206  and hand grips  202  may result in a generally bull-horn shaped handle assembly  203 . 
     The bull-horn shape of the handle assembly  203  yields hand grips  202  that are preferably generally inclined upwardly and toward one another. In other words, a first grip axis  201   a  of the first grip  202   a  may approach a second grip axis  201   b  of the second grip  202   b  at a point above the handle assembly  203  as shown in FIG.  2 . Preferably, although not necessarily, the hand grips  202  are generally straight and lie within a common plane (e.g., the grip axis  201   a  of the hand grip  202   a  may be coplanar with the grip axis  201   b  of the hand grip  202   b ). In embodiments where the hand grips  202  do lie within the same plane, the grip axis  201   a  may intersect the grip axis  201   b  at a point above the handle assembly  203 . While not limited thereto, the grip axis  201  of each hand grip  202  may be inclined at an angle  210  (see FIG. 3) of 30 degrees to 60 degrees and, more preferably, at an angle  210  of 30 to 40 degrees, measured from a respective line  205  formed by the intersection of the plane of the hand grips  202  and a vertical plane. 
     The hand grips  202  may also be inclined forwardly relative to a vertical plane passing through a lowermost portion of the handle assembly  203 , e.g., passing through a lowermost portion of the first hand grip  202   a , as generally indicated in the figures (see e.g., FIG.  13 ). While not limited thereto, some embodiments may be configured with the hand grips  202  inclined forwardly from the vertical plane at an angle  208  (see FIG. 13) of between 30 degrees and 60 degrees and, more preferably, at an angle  208  between 30 degrees and 40 degrees. 
     As those of skill in the art will realize, the shape and orientation of the handle assembly  203 , e.g., the hand grips  202 , provide the operator with comfortable hand positioning during operation (see FIG.  2 ). Further, by positioning the operator&#39;s hands interior to the periphery of the handle assembly  203 , e.g., inboard or interior to the curved portions  206 , the chance of inadvertent contact between the hands and obstacles during operation may be reduced. 
     The handle assembly  203  may attach to the arms  116  in any number of ways. For example, the handle assembly  203  may be welded to the arms  116  as shown in FIG.  4 . Alternatively, the handle assembly  203  may be fastened to the arms  116  using, for example, mechanical fasteners, adhesives, or the like. In still other embodiments, the hand grips  202  may be integrally formed with the arms  116 , e.g., the ends of arms  116  may form the hand grips  202 . In the case of the latter, the transverse tube portion  204 , the curved portions  206 , or both, may be optional. 
     Various control devices are mounted on or in close proximity to the handle assembly  203  as illustrated in FIG.  3 . For example, a transmission lever  212  may be provided to allow drive parameter selection, e.g., forward speed, while a throttle  214  may be provided to control engine speed. Other controls not central to the invention, e.g., starter, choke, etc., although not illustrated, may also be provided. A cover  216  may be further included to offer a more aesthetically pleasing appearance as well as to shield various moving parts. 
     To control power delivery to the drive wheels  106 , the operator control system  200  preferably includes a first control lever, e.g., a first drive control lever  220   a , and a second control lever, e.g., a second drive control lever  220   b , as clearly illustrated in FIGS. 3 and 4. The drive control levers  220  are coupled to respective hydraulic pumps  107  via tie rods  222 . When a drive control lever  220  is manipulated as described below, the corresponding tie rod  222  pivots a lever arm  224  on the pump  107 , manipulating a hydraulic valve (not shown) which controls hydraulic flow to the respective drive wheel motor (also not shown). 
     Each drive control lever  220  preferably has a shape similar to the corresponding hand grip  202  as shown in FIG. 4, e.g., the drive control lever  220   a , similar to the drive control lever  220   b , may have a grip portion  226   a  defining a lever axis  227   a  substantially parallel to the grip axis  201   a  of the respective hand grip  202   a . Optionally, each drive control lever  220  may include a curved portion  228  having a shape that generally corresponds to the shape of the respective curved portion  206 , e.g., curved portion  228   a  may have generally the same radius of curvature as the respective curved portion  206 . While the grip portion  226  is described and illustrated as straight, other shapes are also possible without departing from the scope of the invention. 
     Each drive control lever  220  may pivotally couple to the mower  100  (e.g., to the handle assembly  203  or, as shown in FIG. 4, to the arms  116 ) via a pivot assembly  232 . Preferably, the pivot assembly  232  permits pivoting of the drive control lever  220  about an axis substantially parallel to the respective hand grip  202 , e.g., the drive control lever  220   a  pivots about a pivot axis  230   a  that is substantially parallel to the grip axis  201   a  of the hand grip  202   a . The tie rod  222  is coupled to the drive control lever  220  at a tie rod pivot  234  (see FIGS. 3 and 5) located a predetermined distance from the pivot axis  230  to provide the desired tie rod movement for a given drive control lever  220  movement. 
     Because of the substantially parallel orientation of the pivot axis  230  to the axes  201  and  227 , the lever axis  227  of the drive control lever  220  remains generally parallel to the grip axis  201  of the respective hand grip  202  throughout the range of motion of the drive control lever  220 , e.g., the grip portion  226   a  of the drive control lever  220   a  remains parallel to its respective hand grip  202   a . As a result, the force required to manipulate each drive control lever  220  is substantially uniform throughout the travel of the drive control lever  220 . Moreover, because the lever axis  227  of the drive control lever  220  is parallel to the grip axis  201  of the hand grip  202 , the operator is able to grasp the drive control lever  220  with most, if not all, fingers (see FIG. 2) regardless of the particular position of the drive control lever within its travel. 
     To further improve operator comfort during mower  100  use, each drive control lever  220  may have a cross section defined by one or more curved surfaces. For example, FIG. 5 illustrates an exemplary grip portion  226   b  with a curved, e.g., convex or semi-cylindrical, surface  236  and a generally planar surface  238 . Other embodiments may include a concave surface in place of the planar surface  238  such that the drive control lever  220  corresponds to the shape of the hand grip  202  when the drive control lever  220  is proximate thereto. Other embodiments may vary the shape or the radius of curvature of the curved surface  236 . Preferably, the curved surface  236  permits grasping by the operator without resulting in excessive pressure at any point along the operator&#39;s fingers. 
     FIG. 5 also illustrates the range of motion of the drive control lever  220 . In this figure, the drive control lever  220   b  is illustrated in solid lines in a forward position identified as “F.” Preferably, the drive control levers  220  are biased toward the forward position F. The forward position F corresponds to the respective hydraulic pump  107  (see FIG. 3) providing maximum hydraulic flow for forward motion of the mower  100 . Each drive control lever  220  may also be movable to a reverse position “R” by squeezing the drive control lever  220 , e.g., drive control lever  220   b , toward the hand grip  202 , e.g., hand grip  202   b . The reverse position R corresponds to the respective hydraulic pump  107  (see FIG. 3) providing maximum hydraulic flow for reverse motion of the mower  100 . 
     Each drive control lever  220  may also be movable to any position between the forward position F and the reverse position R. In some embodiments, the drive control lever  220 , when in an intermediate or neutral position, e.g., a position identified as N in broken lines in FIG. 5, may place the respective hydraulic pump  107  (see FIG. 3) in a static configuration. That is, when the drive control lever  220  is in the neutral position N, differential flow output from the pump  107  may be effectively terminated such that no driving power is delivered to the respective drive wheel  106 . In some embodiments, the neutral position N could configure internal valving of the respective hydraulic pump  107  into a cross-ported configuration such that the respective drive wheel  106  could freewheel without substantial hydraulic resistance. As a result, the mower  100  could, when both drive control levers  220  are in the neutral position N, be moved without starting the engine. 
     Accordingly, drive control systems in accordance with the present invention provide intuitive control of the mower  100 . For instance, incremental forward movement of both drive control levers  220  from the neutral position N to the forward position F results in forward propulsion of the mower  100  at incrementally increasing speed. Similarly, incremental rearward motion of both drive control levers  220  from the neutral position N to the reverse position R results in incrementally increasing reverse speed. By manipulating the drive control lever  220   a  and drive control lever  220   b  independently between the forward position F and the reverse position R, the operator can control both speed and direction of the mower  100 . For example, while one drive control lever, e.g.,  220   a , may be commanded for mower movement in a first direction at a first speed, the opposite drive control lever, e.g.,  220   b , may be commanded for mower movement in the same or opposite direction at the same or different speed. 
     Some embodiments of the present invention may optionally include a latching device, e.g., a neutral lock  270 , of which one configuration is shown in FIG.  5 . The neutral lock  270  permits the operator to temporarily lock the drive control lever  220  in at least one predetermined position, e.g., in the neutral position N. By permitting locking of each drive control lever  220  in the neutral position N, the operator may suspend operation and release one or more secondary levers, e.g., an operator presence control (hereinafter “OPC”) lever  240  further described below, without inadvertently stopping the engine  104 . 
     FIGS. 6-10 illustrate end views of the hand grip  202   b  showing the neutral lock  270  in various positions relative to the drive control lever  220   b . The hand grip  202   a  also preferably includes a neutral lock  270  (see e.g., FIG. 3) which operates in a manner generally identical to that described below. 
     In the embodiments illustrated herein, the neutral lock  270  is pivotable about an end of the hand grip  202   b , e.g., about a latch pivot axis  272  which may be generally parallel and preferably coaxial to the grip axis  201   b  of the hand grip  202   b  (see FIG.  4 ), between a locked position (see FIG. 6) and an unlocked position (see FIG.  7 ). 
     The neutral lock  270  may include a hook portion  274  for capturing the drive control lever  220   b  when the latter is in the first or neutral position N as generally shown in FIG.  6 . To disengage the neutral lock  270  from the locked position of FIG. 6, it may be manually pivoted about the latch pivot axis  272  in a direction  275  to the unlocked position illustrated in FIG.  7 . While the neutral lock  270 , as illustrated in FIGS.  5  and  6 - 10 , may be configured with an outwardly opening mouth, other embodiments may utilize a neutral lock  270  having an inwardly opening mouth as generally shown in FIGS. 1 and 2. To assist the operator with pivoting the neutral lock  270 , thumb tabs  276  and  278  may be included. Optionally, a friction-reducing member/device, e.g., a roller  280 , may be provided to assist with moving the neutral lock  270  relative to the drive control lever  220   b.    
     To provide rotational resistance to the neutral lock  270 , a friction device (not shown) may be incorporated. For example, the neutral lock  270  may be fastened to the hand grip  202   b  with a fastener and one or more spring disc washers as known in the art. By controlling the installation torque of the fastener, the axial clamping force applied to the neutral lock  270  by the spring washers may be varied, thus altering the resistance of the neutral lock  270  to rotational movement. Other friction devices may also be used without departing from the scope of the invention. 
     Once the neutral lock  270  is moved to the unlocked position illustrated in FIG. 7, the drive control lever  220   b  is free to move to the forward position F as shown in FIG. 8. A pivot limiting device, e.g., ear  282  as shown in FIG. 9, may be included with the neutral lock  270  to prevent engagement of the neutral lock  270 , e.g., rotation of the neutral lock  270  in the direction  284 , when the drive control lever  220   b  is in the forward position F. FIG. 10 illustrates the relative locations of the drive control lever  220   b  and the neutral lock  270  when the drive control lever  220   b  is in the reverse position R. 
     Various embodiments of operator control systems in accordance with the present invention may further include one or more operator presence control (OPC) devices as shown in FIGS. 4 and 5. OPC devices are typically configured to terminate mower operation, e.g., stop the engine  104 , in some circumstances unless operator presence is detected. In the instant invention, the OPC device may be configured as one or more secondary or OPC levers  240  positioned proximate the respective hand grips  202  opposite the drive control lever  220 , e.g., aft of the hand grip. Like the drive control lever  220 , each OPC lever  240  may include a generally straight gripping portion  242  and a curved portion  244 . The gripping portion  242  and the curved portion  244  have shapes that may generally correspond to that of the hand grip  202  and the curved portion  206 , respectively. 
     OPC levers  240  in accordance with the present invention may operatively couple to an interlock switch  249  (as known in the art and diagrammatically represented in FIG. 4) and manipulate the same between an open configuration and a closed configuration. Generally speaking, mower, e.g., engine  104 , operation is disabled when the interlock switch  249  is in its open configuration and enabled when the interlock switch  249  is in its closed configuration. 
     The OPC levers  240  are preferably biased toward a disengaged, normally open position identified as “O” in broken lines in FIG.  5 . The open position O preferably corresponds to the interlock switch  249  being in its open configuration (mower disabled). To operate the mower  100 , at least one of the OPC levers  240  may be squeezed toward the respective hand grip  202  to a closed, e.g., engaged, position identified as “C” in solid lines in FIG.  5 . The closed position C preferably corresponds to the interlock switch  249  being in its closed configuration (mower enabled). 
     In some embodiments, the OPC lever  240  may be movable between the open position O and the closed position C by pivoting about an OPC pivot  246  having a pivot axis  248  that is generally transverse to a longitudinal axis  150  of the mower  100  as shown in FIG.  4 . The gripping portions  242  may each, in some embodiments, define a secondary lever axis  243  (see e.g., axis  243   b  in FIG. 5) which is substantially parallel to the grip axis  201  of the respective hand grip  202  when the OPC lever  240  is in the closed position C. 
     Preferably, one OPC lever  240  is associated with each hand grip  202 , e.g., OPC levers  240   a  and  240   b  may be provided as shown in FIG.  4 . The OPC levers  240  may further be configured such that they form a single lever. As a result, the operator may engage the interlock switch  249  with one OPC lever  240 , e.g., the interlock switch may be engaged by holding either one or both OPC levers  240   a  and  240   b  in the closed position C (see FIG.  5 ). However, should the operator release both levers  240   a  and  240   b , they will return to their open position O, opening the interlock switch  249  and thus disabling the mower  100 , e.g., engine  104 , from further operation. 
     Like the drive control levers  220 , the OPC levers  240  may be configured to assist in reducing operator fatigue. For example, the cross-sectional shape of at least the gripping portion  242  (see e.g.,  242   b  in FIG. 5) may be configured to generally correspond to the exterior profile of the hand grip  202  as shown in FIG.  11 . 
     As illustrated in FIG. 1, each hand grip  202  may include a rigid or semi-rigid core portion  286  which, in one embodiment, is made from steel or aluminum. To provide more comfortable gripping, the core portion  286  of the hand grip  202  may optionally be surrounded, at least in part, by a gripping layer  288 . While not limited thereto, the gripping layer  288  may preferably be made from a compressible material such as foam rubber. As FIG. 11 illustrates, the gripping layer  288  defines an outer radius  290  of the hand grip  202 . 
     The OPC lever  240  may define a cross-sectional shape having a surface  292  which preferably conforms to a cross-sectional shape of the hand grip  202  when the OPC lever  240  is in the closed position C (as shown in FIG.  11 ). In the illustrated embodiment of FIGS. 11 and 12, the surface  292  is concave having an inner radius  291  generally equal in size to the outer radius  290 . As a result, the OPC lever  240  contacts the hand grip  202  along most, if not all, of the surface  292 . 
     The OPC lever  240  may be further defined by a convex surface  294  having a radius  296 . Preferably, the radius  296  of the convex surface  294  is less than the radius of the concave surface  292 , e.g., the radii  291  and  296  have different centers. This geometry yields a crescent-shaped cross-section as shown in FIG.  12 . To avoid sharp edges and to provide a smooth transition to the gripping layer  288 , the two surfaces  292  and  294  may blend together at a radius  298 . 
     Providing an OPC cross-sectional shape as described above and shown in FIGS. 11 and 12 results in generally smooth transition zones from the edges of the gripping portion  242  of the OPC lever  240  to the hand grips  202 . Also, the eccentric surfaces  292  and  294  result in the OPC lever gripping portion  242  having a non-uniform thickness, e.g., being somewhat thicker near its middle than near its edges (see FIG.  12 ). The thicker middle portion provides the operator with a protrusion to grip during operation while the thinner edges provide a gradual transition from the gripping portion  242  to the hand grip  202 . As a result, the transition from the OPC lever  240  to the hand grip  202  produces relatively few pressure points. 
     As noted above, the embodiments described and illustrated herein are exemplary only. Other configurations are certainly possible without departing from the scope of the invention. For example, the hand grips  202  may have different cross-sectional shapes, e.g., an oval. When so configured, various corresponding surfaces, e.g., the surface  292  of the OPC lever  240  (see FIG. 12) and/or the surface  238  of the drive control lever  220  (See FIG. 5) may be reconfigured to correspond to the new cross-sectional shape of the hand grip  202 . 
     The OPC lever  240  may also be configured to pivot about an axis generally parallel to the grip axis  201  of the hand grip  202  (see FIG. 4) rather than about the transverse axis  248  (see also FIG. 4) described herein. 
     In still other embodiments, an operator control system  300  may be configured such that a drive control lever  320  is located aft of, i.e., behind, the hand grip  202  as shown in FIG.  13 . The drive control lever  320  may still pivot about a pivot assembly  322  having a pivot axis substantially parallel to an axis of the hand grip  202 . Movement of the drive control lever  320  may reposition the tie rod  222  as described above. While not shown, neutral locks and OPC levers may be reconfigured to accommodate this revised drive control lever structure. 
     While described above specifically with application to hydraulically-powered mowers, the present invention is equally applicable to vehicles utilizing other drive systems. For example, a walk-behind power mower  500  using a gear drive system, an exemplary embodiment of which is partially illustrated in FIG. 14, may also utilize a control system  400  in accordance with the present invention (for clarity, only the right side of the mower  500  is illustrated in this view). 
     The control system  400  may be similar in many respects to the control system  200  described and illustrated herein. For example, it may include hand grips  402 , drive control levers  420 , and OPC levers  440  having generally the same configuration and functionality as that of the respective corresponding hand grips  202 , drive control levers  220 , and OPC levers  240  of the control system  200 . 
     The exemplary gear drive system illustrated in FIG. 14 uses a driving pulley  504  powered by a prime mover (not shown) which is supported by a frame  502  of the mower  500 . An endless belt  506  may transmit power from the driving pulley  504  to a driven pulley  508 , the latter being attached to the respective drive wheel  509  (right drive wheel removed for clarity in FIG.  14 ). A gear selector (not shown) may be provided to permit selection of driving speed and direction (forward, reverse) of the driving pulley  504 . 
     An idler pulley  510  selectively tensions the belt  506  in response to operator manipulation of the drive control lever  420 . For example, when the drive control lever  420  is manipulated to a forward position F (see FIG.  18 ), e.g., a position generally similar to the forward position F of lever  220  shown in FIG. 5, a tie rod  422  causes a bell crank  512  (see FIG. 14) to pivot about a pivot  514  in a first direction  516 . Movement of the bell crank  512  in the first direction  516  causes the idler pulley  510  to tension the belt  506 , providing driving power to the drive wheel. Thus, the forward position F of the drive control lever  420  corresponds to the respective drive wheel of the mower being configured for driving operation (either forward or rearward movement, depending on the position of the transmission gear selector). 
     The bell crank  512  is preferably biased in the first direction  516  by a spring (not shown) or other similar device such that the drive control lever  420  is biased toward the forward position F (see FIG.  18 ). 
     When the drive control lever  420  is moved from the forward position F to a first or neutral position N (shown in FIGS.  15  and  16 ), e.g., to a position generally similar to the neutral position N of lever  220  shown in FIG. 5, the tie rod  422  causes the bell crank  512  to pivot about the pivot  514  in a second direction  518 . Motion of the bell crank  512  in the second direction  518  causes the idler pulley  510  to move away from the belt  506 . With belt tension relaxed, power to the drive wheel  509  is reduced or terminated. Thus, the neutral position N of the drive control lever  420  corresponds to the respective drive wheel  509  of the mower  100  being in a neutral configuration, i.e., providing substantially no power or braking. 
     Preferably, further movement of the bell crank  512  in the direction  518 , e.g., movement of the drive control lever  420  to a second or “park” position “P” (shown in FIGS.  17  and  19 ), may engage a wheel brake  520 . While not limited to any particular configuration, the wheel brake  520  may be a friction band brake or other brake mechanism known in the art, e.g., a disk brake. To engage the wheel brake  520 , the bell crank  512  may be coupled thereto, e.g., via a linkage  522 , such that movement of the drive control lever  420  to the park position P results in braking of the respective drive wheel  509 . Thus, the park position P of the drive control lever  420  corresponds to the respective drive wheel  509  of the mower  100  being in a park (e.g., braked) configuration. 
     The control system  400  may also include a latching device  470  (shown in FIGS. 14-19) similar in most respects to the latching device  270  described herein and illustrated in FIGS. 5-10. In the illustrated embodiments, the latching device  470  includes a pivoting, generally hook-shaped latch member  473 . However, other shapes are certainly possible. In fact, the term “latching device” may include most any device operable to substantially retain the drive control lever  420  in a predetermined position until intentionally released (or otherwise manipulated) by the operator. 
     FIGS. 15-19 illustrate end views of one hand grip  402  showing the latching device  470  and drive control lever  420  in various configurations. While only the latching device  470  associated with one hand grip (the right-hand grip) of the control system  400  is illustrated in FIGS. 15-19, the latching device  470  for the opposite hand grip (the left-hand grip) is substantially the same, e.g., a mirror image, unless otherwise described herein. 
     The latching device  470  is pivotable about a latch pivot axis  472  that is preferably parallel and coincident (coaxial) to a grip axis of the hand grip  402  (much like the latch pivot axis  272  of the neutral lock  270  and the grip axis  201  as shown in FIGS.  5 - 6 ). The latching device  470  may include a first lever seating surface  474  to assist in securely latching the drive control lever  420  when the latter is in the neutral position N as generally shown in FIG.  15 . That is, when the latching device is engaged as shown in FIG. 15, the drive control lever  420  is latched in the neutral position N. 
     To disengage the drive control lever  420  from the neutral position N, the latching device  470  may be pivoted about the pivot axis  472  in a direction  475  to a disengaged (unlatched) position illustrated in FIG.  16 . To assist the operator with pivoting the latching device  470 , tabs, e.g., thumb tabs  476  and  478 , which may be manipulated with the operator&#39;s thumb or other finger, may be included. An optional, friction-reducing member/device, e.g., a roller  280  (see FIG.  15 ), may be provided to assist with moving the latching device  470  relative to the drive control lever  420 . Similarly, as with the neutral lock  270 , a device (not shown) may be included to provide rotational resistance of the latching device  470  about the axis  472 . 
     Once again, while illustrated in FIGS.  14  and  15 - 19  with an outwardly opening mouth  471  (i.e., the opening formed by the latching device  470  opens toward the outside of the mower  500 ), other embodiments may utilize a latching device  470  having an inwardly opening mouth  471  similar to the embodiment of the neutral lock  270  illustrated in FIGS. 1 and 2. 
     Once the latching device  470  is moved to the disengaged position illustrated in FIG. 16, the drive control lever  420  is free to move from the neutral position N toward either the park position P of FIG. 17 or toward the forward position F of FIG. 18 (the drive control lever  420  may also be moved between the neutral position N of FIG.  15  and the park position P of FIG. 17 while the latching device  470  remains in the engaged position shown in FIG.  15 ). 
     To improve latching of the drive control lever  420  when the latter is in the park position P, the latching device  470  may include a second lever seating surface  481  as identified in FIGS. 15 and 17. A discontinuity, e.g., raised portion  483 , preferably exists between the first seating surface  474  and the second seating surface  481 . The discontinuity adequately isolates the two seating surfaces  474 ,  481  and provides more positive latching of the drive control lever  420  in either of the selected positions. 
     When the drive control lever  420  is moved to the forward position F as shown in FIG. 18, an optional pivot limiting device, e.g., ear  482 , may prevent engagement of the latching device  470 , e.g., limit rotation of the latching device  470  in the direction  484 . FIG. 19 illustrates the relative locations of the drive control lever  420  and the latching device  470  when the drive control lever  420  is in the park position P and the latching device  470  is disengaged. 
     Thus, the latching device  470  permits latching of each drive control lever  420  in two or more positions, e.g., in a neutral position N (see FIG. 15) and in a park position P (see FIG.  17 ). Identifying indicia  486   a  and  486   b  (see FIG. 19) may be included on each latching device  470  to assist the operator in quickly identifying latching device positions. For example, indicia  486   a  may include the letter “N” or the word “NEUTRAL” (or some equivalent) while indicia  486   b  may include the letter “P” or the word “PARK” (or some equivalent). 
     Different indicia may be used to indicate other positions. For example, some embodiments may utilize latching devices having additional (e.g., three) or different latching positions. In this case, specific identifying indicia corresponding to these additional/different latching positions may be provided without departing from the scope of the invention. 
     The invention is not limited to the embodiments described above as other configurations are certainly also possible within the scope of the invention. For example, other embodiments may have hand grips configured to extend downwardly and outwardly rather than upwardly and inwardly. That is, the hand grips may couple to the mower at or near their uppermost end and extend downwardly and outwardly therefrom. However, such embodiments may still result in grip axes, e.g., axes  201   a  and  201   b  (see FIG.  2 ), that approach and/or intersect one another above the grip assembly  203 . 
     Exemplary embodiments of the present invention are described above. Other variations, modifications, and combinations of the various parts and assemblies can certainly be made and still fall within the scope of the invention. Thus, the invention is limited only by the following claims, and equivalents thereto.