Abstract:
A system for notifying the operator of a reel-type greens mower, or any blade-based cutting system, of the relative sharpness of the blades. A controller receives at least one input from the mowing unit such as current draw of the mowing unit, driving energy input to the mowing unit, or rotational speed of the reel, for example, and monitors that input in comparison with the forward cutting speed of the mower to make a determination as to the relative sharpness of the blades. A display may be provided to alert the operator of the condition of the blades, including when maintenance of the blades in necessary. A speed control circuit may also be provided to maintain the speed of the greens mower below the maximum effective cutting speed of the mower.

Description:
FIELD  
       [0001]     The present disclosure relates to sharpness monitors and to reel-type turf mowers.  
       BACKGROUND  
       [0002]     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.  
         [0003]     As is known in the art, reel-type turf mowers are useful for mowing golf course fairways and greens. Golf courses typically require that grass in these areas be cut to exacting standards, and in some cases, such as the putting green areas, to very short lengths. Reel-type turf mowers are well-suited for these applications as they are capable of cutting grass to very short lengths and maintaining a consistent cut. These reel-type mowers can be of the walk-behind or riding variety.  
         [0004]     The quality and consistency of the cut of the grass is very important in golf course environments where the play is greatly affected by the length and cut of the grass. The blades will become dull over time, with a corresponding decrease in the ability of the reel-type mower to cut the turf neatly and efficiently. The mower will need to be operated at a slower forward speed to maintain a similar quality of cut if the blade is not sharp, which leads to lengthier lawn maintenance times. It is therefore important that the reel blade cutting elements be well-maintained. The operator must constantly be aware of the relative sharpness of the cutting elements, and sharpen, recondition, or even replace the blades when necessary to prevent poor cut quality. However, it is difficult for the operator to realize exactly when the blades have become dull without first cutting a tract of grass with the dull blade to observe the quality of the cut. It is unlikely that an operator will be able to tell simply by looking at or touching the blades precisely how dull the blades are, or how much life the blades have left before they will require sharpening. Simply sharpening or replacing the blades frequently can also be time-consuming, and may require the inconvenience of increased mower downtime, a decided disadvantage for golf course maintenance crews with short windows of time for lawn maintenance on the course.  
         [0005]     Accordingly, there exists a need to provide a reel-type turf mower capable of notifying the operator of the condition or relative sharpness of the blades, when those blades need to be replaced or sharpened, and how much longer the operator can use the blades before they will require sharpening or replacing. In this manner maintenance schedules can be optimized for these types of mowers.  
       SUMMARY  
       [0006]     According to the principles of the present invention, a walk-behind reel-type mower having an advantageous construction is provided. It should be noted that the present invention is also applicable to ride-on reel-type mowers, rotary mowers, or any other type of mower or blade-based cutting system, and these other embodiments should not be construed as beyond the scope of the present invention. The walk-behind reel-type mower includes a mobile structure and a ground engaging traction member rotatably coupled to the mobile structure for imparting traction movement to the mobile structure for movement on the ground. An electric motor or gas engine is supported on the mobile structure and outputs a driving force at an output shaft. A bed knife is supported by the mobile structure having a cutting edge that cooperates with a grass cutting reel rotatably supported on the mobile structure. The grass cutting reel includes cutting blades being in grass cutting relationship with the bed knife. A drive system is operably coupled between the output shaft and at least one of the ground engaging traction member and the grass cutting reel for transmitting the driving force thereto.  
         [0007]     A control system supported by the mobile structure measures the forward speed of the mobile structure, and also the current or driving energy input to the reel-type cutting elements. The control system may also measure other parameters of mower performance that implicate blade wear, such as the rotational speed of the cutting elements. The control system calculates blade wear from an algorithm using these or other inputs, based upon the principle that as the blade becomes more dull, more electric current (for electric reel mowers) or driving energy (for hydraulic reel mowers) must be supplied to the reel or reels to cut similar tracts of grass at similar forward cutting speeds. The control system can thus determine the blade condition by comparing the current draw or driving energy input of the reels with the forward cutting speed of the turf mower over time.  
         [0008]     Different lawns will dull the blade at varying rates due to differences in the density of the grass, the height of the uncut grass, moisture level of the soil, etc. Therefore a calibration program may be programmed in the control system for use by the operator on a new tract of grass. The mower would be run over the tract of grass to determine mower performance upon that tract. This effect would then be used by the control system to determine blade wear, along with the aforementioned parameters implicating blade wear. This calibration program would thus adapt the blade wear logic to the various tracts of grass which may be cut.  
         [0009]     The control system then relays the blade condition to a display, which can be mounted on the handle or in an otherwise convenient location for the operator to observe, ideally while mowing. An audible or visible alarm may be provided to alert the operator when the blade is reaching certain milestones regarding blade wear, indicating to the operator how worn the blade is, and how much longer the operator may be able to mow until blade maintenance is required. Because the blade wear also impacts the maximum speed at which the mower is effective, a speed control system supported by the mobile structure may also be provided which limits the allowable maximum speed of the turf mower in accordance with the condition of the cutting elements determined by the control system.  
         [0010]     It should be noted that this control system can be made to work with a reel-type turf mower with reels powered electrically or hydraulically. The electrically powered reels may be monitored for blade wear by measuring the current draw of the reels compared with the forward cutting speed of the mower, assuming similar tracts of grass are cut. Similarly, hydraulically powered reels will also work with this control system. Instead of an electric current, the driving energy input to the reels is monitored and compared with the forward cutting speed of the mower, again assuming similar tracts of grass are cut.  
         [0011]     Further areas of applicability will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     DRAWINGS  
       [0012]     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.  
         [0013]      FIG. 1  is a perspective view illustrating a reel-type turf mower according to various embodiments;  
         [0014]      FIG. 2  is a block diagram of a sharpness monitor system according to various embodiments;  
         [0015]      FIG. 3  is a plot illustrating current draw of a reel-type mower versus the feed rate of a turf mower; and  
         [0016]      FIG. 4  is a flow diagram for determining the cutting element condition of a turf mower according to the various embodiments. 
     
    
     DETAILED DESCRIPTION  
       [0017]     The following description is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Throughout the specification, like reference numerals will be used to refer to like elements.  
         [0018]     With reference to the figure,  FIG. 1  illustrates a greens mower  10  according to various embodiments. Greens mower  10  is a reel-type mower having a base portion  12  and a floating or articulating mowing unit  14 . Mowing unit  14  is preferably articulately coupled to base portion  12  through a pivoting mechanism  16 . It will be understood by one skilled in the art that the sharpness monitor will be described with respect to a reel mower; however, the present disclosure is equally applicable to other blade-based cutting systems. Such systems include woodworking tools, rotary mowers, and any of a number of various cutting tools.  
         [0019]     Mowing unit  14  includes a rotatable greens mower reel  18  having helical blades  20  equally spaced around a reel shaft  22 . Reel shaft  22  is generally elongated and defines a rotation axis  24  extending along the length of reel shaft  22 . A conventional fixed bed knife (not shown) is operably mounted to mowing unit  14 . Blades  20  orbit relative to shaft  22  and move past the fixed bed knife for the usual and well-known function of cutting the grass. Mowing unit  14  further includes a pair of non-driven ground engaging rollers  26  rotatably mounted along a forward and rearward portion of mowing unit  14 . The pair of ground engaging rollers  26  serve to support mowing unit  14  for movement on the ground. The pair of ground engaging rollers  26  can be adjustable to define a cutting height. Ground engaging rollers  26  are also equipped with a speed sensor (not shown in  FIG. 1 ) which detects the forward cutting speed of greens mower  10 .  
         [0020]     Base portion  12  generally includes a gas engine or electric motor  32 , a frame  34 , a lawn roller  36 , a drive system  38 , and a handle assembly  40 . For the sake of brevity only the electric motor configuration will be discussed herein. However, various embodiments using an internal combustion engine and a hydraulically powered mowing unit  14  are equally applicable. Motor  32  is of conventional design and is mounted on frame  34 . A controller (not shown in  FIG. 1 ) is mounted with motor  32  on base portion  12 .  
         [0021]     Lawn roller  36  is rotatably mounted to frame  34  through a roller axle  46 . Lawn roller  36  supports base portion  12  on the ground and serves as the traction drive for greens mower  10 . Other ground-supporting traction members could be substituted. Drive system  38  is operably coupled between an output shaft  48  and lawn roller  36 . Drive system  38  generally includes a drive pulley (not shown) mounted to output shaft  48  for rotation therewith and an idler pulley (not shown) mounted to lawn roller  36  for rotation therewith. A drive belt (not shown) extends between the drive pulley and the idler pulley to transfer drive force from motor  32  to lawn roller  36 . This configuration provides a traction drive train from motor  32  to the ground-engaging lawn roller  36  capable of driving greens mower  10  in at least a forward direction.  
         [0022]     With reference to  FIG. 2 , controller  60  communicates with mowing unit  14 . Although only one mowing unit  14  is shown, it will be understood that one or a plurality of secondary mowing units  70  and  72  shown in phantom may be included in various embodiments without departing from the scope of the invention. Controller  60  is shown receiving signals from mowing unit  14  for sensing current draw and reel speed, and from non-driven ground engaging rollers  26  for sensing the speed of greens mower  10 . Controller  60  determines the condition of the reel blades  20  from these inputs, and then communicates signals to display  62  to indicate the determined condition. Controller  60  may optionally receive other inputs that vary in accordance with the condition of blades  20 . Display  62  shows the condition of the blades at LED  64  for observation by the operator. Reset button  66  may be provided for resetting a data stored in controller  60  after blades  20  have been reconditioned, sharpened, or replaced. Reset button  66  may be provided at locations to minimize inadvertent activation by the operator or bystanders, such as the back of display  62 , or as part of controller  60  itself, for example.  
         [0023]     Controller  60  may be integrated with or function cooperatively with speed control circuit  78  for controlling the speed of greens mower  10  in accordance with the condition of blades  20 . Controller  60  determines the condition of blades  20  as described above, and determines a maximum allowable speed of greens mower  10 . Speed sensor  68  may be positioned adjacent or on non-driven ground-engaging roller  26  to measure the speed of greens mower  10 . Controller  60  will then vary the output speed of motor  32  and, consequently, drivetrain  74  if the ground speed of greens mower  10 , as determined by speed sensor  68 , exceeds the maximum allowable speed. Controller  60  can monitor the speed of greens mower  10  and determine a maximum allowable speed continuously during operation of greens mower  10 .  
         [0024]      FIG. 3  shows an example graph of the current draw of mowing unit  14  versus the feed rate of greens mower  10 . Generally, as the volumetric feed rate of greens mower  10  increases, electric current supplied to mowing unit  14  increases in a generally linear manner in order to maintain an even cut of the grass. As such, when the current draw of mowing unit  14  is plotted against the forward cutting speed of greens mower  10  (which is proportional to the volumetric feed rate of the mower since the width of reel  18  is constant), an approximately straight line  84  results. As the blade becomes less sharp over time through use, more current will be necessary to cut grass at the same speed, for a similar cutting path. Line  90  indicates a plot of current draw versus feed rate for a greens mower cutting a similar path with a worn blade. Controller  60  monitors the current draw of mowing unit  14  and the forward cutting speed of greens mower  10 , and determines blade wear accordingly. In some embodiments, other parameters may be measured to determine the wear of reel  18 . By way of example, rotational speed of reel  18  is proportional to blade wear over time, similarly as described above. Greater rotational speed requirements of reel  18  to cut similar paths at the same general forward mower speeds indicate blade wear.  
         [0025]     A calibration algorithm based upon the principle illustrated by  FIG. 3  may also be programmed into or determined by controller  60  as another input for determining blade wear. This may be useful as different strains, mixes, thicknesses, textures, or other characteristics of grass may cause blades  20  to wear at different rates. Greens mower  10  may be programmed at the beginning of each use to be run a set distance at a generally constant speed over a tract of representative grass to be cut. Current draw of mowing unit  14  can be monitored while traveling over the tract of representative grass. Controller  60  can additionally monitor the ground speed or feed rate of greens mower  10 . Controller  60  can thus extrapolate a grass density index for the relevant tract of representative grass at the initial blade wear percentage by plotting the current draw observed by controller  60  over the representative tract of grass versus the feed rate. Upon replacement or sharpening of blades  20 , the blade life will initially be 100% or, conversely, the blade wear will be at 0%. The condition of blades  20  at the end of any period of use or calibration run may be stored in a memory of controller  60  for retrieval upon the next calibration or use of greens mower  10  on another tract of grass. Current draw and feed rate may subsequently be monitored during use of the mower over similar tracts of grass to calculate wear of blades  20  over time using the memorized blade condition as an initial starting point.  
         [0026]     Controller  60  determines the condition of blades  20  from the inputs measured at mowing unit  14  according to an algorithm illustrated in  FIG. 4 . Input blocks  100  and  102  show the two primary inputs to controller  60 , the forward speed  100  of greens mower  10  and the current draw  102  of mowing unit  14 . Optional inputs shown in phantom include a grass calibration algorithm  104  and the rotational speed of the reel  106 , as described above. At block  108 , controller  60  generates a blade wear percentage in accordance with these inputs. This blade wear percentage can then be output to display  62 , shown at output block  110 . The blade wear percentage is also output to decision block  112 , which determines whether the blade wear percentage exceeds a certain predetermined value, representing a condition where the operator should consider or plan to sharpen the blades. This predetermined value may be preset by the manufacturer and adjusted or set by the operator. If the blade wear percentage does exceed a predetermined value, an audible or visible alarm may be triggered at display  62 , as shown at block  114 . If the blade wear percentage does not exceed the predetermined value, then the process begins again at block  108 . Thus, controller  60  constantly monitors the wear of blades  20  and alerts the operator if the blade wear percentage exceeds a predetermined value.  
         [0027]     In some embodiments, controller  60  can also include logic to control the speed of greens mower  10  based upon the condition of blades  20 . A maximum allowable speed for greens mower  10  is determined by controller  60  at block  108  from the inputs described above. At decision block  116  this maximum allowable speed is compared with the actual speed of greens mower  10  as determined by speed sensor  68 . If the actual speed of greens mower  10  does exceed the maximum allowable speed as determined by controller  60 , block  118  directs controller  60  to decrease the output speed of motor  32 . Other methods of decreasing the speed of greens mower  10  may be utilized. This cycle continues, thus continuously comparing the actual speed of greens mower  10  with the maximum allowable speed as continuously adjusted by controller  60 .  
         [0028]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of that which is described are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.