Abstract:
A gang reel mower comprises a frame that carries a plurality of variable speed, electrically powered reel cutting units. Cutting units having different reel diameters may be installed on the frame. Upon system power up, a mower controller on the frame automatically acquires information identifying the reel size of the cutting units then installed on the frame and uses the acquired reel size information to properly set the speed of the electric motors driving the cutting units to a desired value, such as that needed to maintain a desired clip. Thus, the cutting units can be changed in size with the mower controller automatically recognizing the change in a plug and play manner.

Description:
TECHNICAL FIELD 
     This invention relates to a turf mower that carries one or more electrically driven reel cutting units for cutting grass. 
     BACKGROUND OF THE INVENTION 
     Turf mowers having one or more reel cutting units carried on a frame for cutting grass over a wide cutting swath are well known. In a gang mower configuration, a plurality of reel cutting units are usually arranged in front and rear rows with the cutting units in each row being laterally spaced from one another if there is more than one cutting unit in each row. The cutting units in the respective rows are laterally staggered relative to the cutting units in the other rows so that the gaps between the cutting units in one row are covered by the cutting unit(s) in another row. This allows the gang configuration of cutting units to cut an unbroken swath of grass during a single pass of the gang mower. Typically, gang mowers of this type comprise riding mowers that are operated by an operator carried on a seat provided on the mower. 
     Turf mowers of this type traditionally have been powered by an internal combustion engine carried on the frame of the mower, typically either a diesel engine or a gasoline powered engine. In many cases, the engine powers one or more hydraulic pumps that supply pressurized hydraulic fluid to a plurality of hydraulic motors that power the reel cutting units. The reel cutting units are available in different diameters, e.g. cutting units having a 5 inch diameter reel or cutting units having a 7 inch diameter reel. The reason for this is that different diameter reels are more effective in cutting different types of grass or at different times of the year. However, because of substantially different hydraulic requirements depending upon whether 5 inch or 7 inch reel cutting units are used, the traction unit that carry such cutting units had to be individually designed and manufactured for each sized reel cutting units. The same traction unit having the same hydraulic system could not be used to power both 5 inch reel cutting units and 7 inch cutting units, without significant changes to the hydraulic system. 
     The result of this fact meant that a manufacturer had to manufacture one traction unit to carry 5 inch hydraulic reel cutting units and a second separate traction unit to carry 7 inch hydraulic reel cutting units. A customer who wished to have both sizes of reel cutting units available for use had to purchase two different traction units each equipped with the size of reel cutting unit for which they were designed. Needless to say, this was expensive for the customer. It was also expensive for the manufacturer since a common traction unit platform could not be manufactured to carry both sizes of reel cutting units. 
     SUMMARY OF THE INVENTION 
     One aspect of this invention relates to a reel mower which comprises a frame supported for rolling over a turf surface having grass. Plural reel cutting units are carried on the frame. Each reel cutting unit comprises a cutting reel rotatable about a horizontal axis for pushing blades of grass against a cooperating bedknife to sever blades of grass on the turf surface in a shearing action between the cutting reel and the bedknife. The cutting reels of the cutting units are individually powered by separate variable speed electric motors such that a first electric motor drives the cutting reel of a first cutting unit, a second electric motor drives the cutting reel of a second cutting unit, a third electric motor drives the cutting reel of a third cutting unit, and so on. The cutting units that are carried on the frame are selected from a group of cutting units consisting of 1) cutting units having cutting reels of a first diameter and 2) cutting units having cutting reels of a second diameter that is different than the first diameter. Each electric motor that drives a cutting reel of a particular cutting unit includes an electronic motor controller. An electronic, microprocessor based, mower controller is carried on the frame and is operatively connected with the motor controllers of the electric motors of all the cutting units that are currently being carried on the frame. In addition, the mower controller is configured to 1) automatically acquire, prior to a mowing operation, reel size information that identifies whether the currently carried cutting reels being driven have the first or the second diameter, and to 2) automatically use the acquired reel size information to properly set the speeds of the cutting reels of all the currently carried cutting units during the mowing operation. 
     Another aspect of this invention relates to a reel mower which comprises a frame that carries a plurality of variable speed, electrically powered reel cutting units. The cutting units carried on the frame may have either first or second reel diameters that are different from one another. A mower controller on the frame automatically acquires reel size information identifying the reel diameters of all the cutting units then carried on the frame and uses the acquired reel size information to properly set the speed of the electric motors driving the cutting units to a desired value to thereby permit the cutting units to be changed in size with the mower controller automatically recognizing the change in a plug and play manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This invention will be described more specifically 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 gang mower according to this invention; and 
         FIG. 2  is a flow chart of the automatic configuration process that takes place when electrically driven reel cutting units are installed on the gang mower of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a conventional gang mower as  2 . Mower  2  incorporates a plurality of cutting units  4  arranged in a 3-2 gang configuration. Such a configuration includes three laterally spaced front cutting units  4   f  placed in a front row thereof ahead of the front wheels  6  of mower  2 . A pair of laterally spaced rear cutting units  4   r  (one of which can be seen in  FIG. 1 ) is placed in a rear row between front wheels  6  and rear wheels  8  of mower  2 . Rear cutting units  4   r  are staggered to cover the gaps between front cutting units  4   f  to cut an unbroken swath of grass. Other gang configurations (e.g. a 2-3, 4-3, 3-4, 2-1 or 1-2) could be used. 
     Cutting units  4  shown in  FIG. 1  comprise reel cutting units each of which includes a rotatable cutting reel having a plurality of circumferentially spaced, helically twisted blades that may vary in number, e.g. five, eight, eleven, etc. blades. As the reel of the reel cutting unit rotates, the blades of the reels push standing blades of grass against a fixed bedknife to shear the grass between the reel and the bedknife.  FIG. 1  depicts a gang reel mower according to one embodiment of this invention. Cutting units  4  used in this embodiment of mower  2  will be powered by their own separate electric motors  20   a  or  20   b . Since there are five cutting units  4  shown in the embodiment of  FIG. 1 , there will be five electric motors  20   a  or  20   b  for powering such cutting units  4 , one motor  20   a  or  20   b  for each cutting unit  4 . 
     Mower  2  includes a seat  12  for carrying an operator who rides atop mower  2 . Mower  2  has a rear cowl  13  that encloses an internal combustion engine such as a diesel engine. An electrical generator/alternator (not shown) is operatively connected to the drive shaft of the engine for generating electrical power as the engine runs. In addition, an electrical storage device (not shown), such as a battery pack or an ultracapacitor, is provided on mower  2  for storing electrical power that has been generated by the generator/alternator. Together, the generator/alternator and the electrical storage device form a hybrid electric power supply system for powering electric motors  20   a  or  20   b  that are attached to the reel cutting units  4 . However, the electrical storage device could be deleted if so desired such that the generator/alternator is the sole source of electric power or the generator/alternator could be deleted such that an externally rechargeable battery pack could be the sole source of electric power. The electrical power supply system of mower  2 , whatever the system comprises, also provides electric power for powering components other than electric motors  20   a  or  20   b  on cutting units  4 , such as the main electrical supply system of mower  2  used to power the electronic controllers contained on modern mowers and other electrically powered components. 
     Referring now to the flow chart of  FIG. 2 , mower  2  has a main, microprocessor based, electronic controller  22  that is used to control the operation of mower  2 . Main controller  22  receives control inputs from various sources. This includes control inputs received from an information center (not shown) on mower  2 . The information center is used by the operator to input various user settable parameters into main controller  22  by the user manually entering information into various menus that may be pulled up on a display screen. The information center also uses the display screen to display information back to the operator, such as fault indications generated and displayed on the display screen by main controller  22 . The information center may comprise a display screen and an adjacent keypad for data entry or a touch screen that serves both as a display screen and a data entry device. 
     The reel cutting units  4  of this invention are preferably provided with cutting reels having different diameters, e.g. reels with a five inch diameter or reels with a seven inch diameter. In this invention, each of the five inch cutting units  4  is powered by a first electric motor  20   a  that is designed to mount only on a five inch cutting unit  4 . Each of the seven inch cutting units  4  is powered by a second electric motor  20   b  that is designed to mount only on a seven inch cutting unit  4 . Thus, the first electric motor  20   a  will not mechanically connect to the reel shaft of the seven inch cutting unit  4  and the second electric motor  20   b  will not mechanically connect to the reel shaft of the five inch cutting unit  4 . Consequently, the two different electric motors  20   a  and  20   b  cannot be mixed up and mounted on the wrong sized cutting unit  4 . However, both electric motors  20   a  and  20   b  are provided with a common wiring harness and common electrical connectors that permit either electric motor  20   a  or  20   b  to connect into the electrical power supply system and CANBUS  23  of mower  2 . 
     The first electric motors  20   a  that drive the five inch cutting units  4  are physically smaller than the second electric motors  20   b  that drive the seven inch cutting units  4 . The first electric motors  20   a  used on the five inch cutting units have a relatively small gear reduction between their rotors and output shafts and are designed to rotate their output shafts in a first speed range of from 700 rpm to 1940 rpm. The second electric motors  20   b  used on the seven inch cutting units have a larger gear reduction between their rotors and output shaft and are designed to rotate their output shafts in a second lower speed range of from 500 to 1600 rpm. Thus, the seven inch cutting units have higher torque than the five inch cutting units and are accordingly better suited than the five inch cutting units to cutting certain types and lengths of grass. 
     One of the parameters an operator can set is the clip provided by reel cutting unit  4 . Clip is the distance traveled by mower  2  between successive contacts of the blades of the cutting reel with the same shear point on the bedknife. Clip is related to the ground speed of mower  2 , the rotational speed of the reel of cutting units  4 , and the number of blades on the reel. The operator can use the information center to input into main controller  22  a desired clip (e.g. a ½ inch clip), the mowing speed the operator intends to mow at (e.g. 6 mph), and the number of blades on the reel (e.g. 8 blades). Using this information, main controller  22  then determines the rotational speed that the reel must rotate at to provide the desired clip (e.g. 1584 rpm), either by a process of calculation or by pulling the necessary rotational reel speed from a look up table stored in the memory of main controller  22 . 
     As noted earlier, motors  20   a  and  20   b  have rotational speed ranges that begin and end at different rpms and that are different in size. Main controller  22  has look up tables for each motor  20   a  and  20   b  that splits the speed ranges for each motor into a discrete number of speed settings. For example, taking the 700 rpm to 1940 rpm speed range of motor  20   a  used on the five inch cutting units  4  and splitting that range into 9 increments, speed setting  1  will equal 700 rpm and speed setting  9  will equal 1940 rpm. Speed settings  2 - 8  will be spaced between 700 rpm and 1940 rpm. 
     However, this look up table would not be valid for motor  20   b  for the seven inch cutting units  4  since splitting its 500 to 1600 rpm speed range into the same 9 increments would yield a different look up table. When using such look up tables to set the rotational speed of the reel to achieve a particular clip, main controller  22  would use the speed setting from the look up table that is closest to the rotational reel speed that it has read out of the clip table as being required to achieve the desired clip. But, this would most likely mean that speed setting  6  would be the value read out of the look up table for motor  20   a  of the five inch cutting units while speed setting  8  would be the value that would be read out of the look up table for motor  20   b  of the seven inch cutting units. Thus, to properly set the reel speeds for achieving the desired clip, main controller  22  must know whether the five inch reel cutting units  4  or the seven inch reel cutting units  4  are installed on mower  2 , i.e. whether it should transmit speed setting  6  or speed setting  8 . This invention is intended to automatically supply the reel size information to main controller  2  upon system power up so that main controller  2  automatically configures itself to use the proper look up table for setting the reel speed. 
     Each reel motor  20   a  and  20   b  includes its own motor controller  24  as a part thereof. Such motor controller  24  has a non-volatile memory that stores a part number that identifies the corresponding motor as motor  20   a  of a five inch reel cutting unit  4  or as motor  20   b  of a seven inch reel cutting unit  4 . See block  30  of  FIG. 2  which is interrogated upon system power up to read the part number. Once the part number is read, motor controller  24  is able to determine which sized reel cutting unit is attached at block  32  and reports that information to main controller  22  along line  34 , CANBUS  23 , and line  36 . Motor controller  24  also uses that same information at blocks  35 ,  37  to know what gear reduction is present between the motor rotor and the motor output shaft as that gear reduction determines how fast the rotor must spin to achieve a commanded rotational speed of the motor output shaft. While the main controller  22  will determine what speed setting the motor controller  24  should use and transmit such speed setting to motor controller  24 , once a particular speed setting is received motor controller  24  will automatically regulate the motor  20   a  or  20   b  to maintain the speed corresponding to the speed setting it has received from main controller  22 . 
     When main controller  22  first receives the part number information identifying whether a five inch cutting unit  4  or a seven inch cutting unit  4  is attached, main controller first waits until all of the expected plurality of cutting units  4  have reported in. For example, if mower  2  is expected to have five reel cutting units  4  installed, all five reel cutting units  4  must be online to main controller  22 , as shown at block  38 . When all the expected reel cutting units  4  have come online to main controller, the process branches to block  40  which determines whether the part numbers identifying the reel cutting units  4  are all the same to signify that all of the attached reel cutting units  4  are the same size, i.e. all cutting units  4  are either five inch cutting units or seven inch cutting units. If a mismatch is detected at block  40  meaning one or more of the cutting units have a different size than the other cutting units, main controller  22  at block  42  displays a fault to the operator on the information center and prohibits or prevents operation of any of reel cutting units  4  until the mismatch issue is resolved. 
     If block  40  determines that all of the reel cutting units  4  are the same size, main controller  22  at block  44  correlates the part number for such motors  20   a  or  20   b  to the size of the motor to determine whether the five inch reel cutting units  4  are installed on mower  2  or the seven inch reel cutting units  4  are installed. Depending upon the answer, main controller  22  loads the configuration data, primarily the speed setting look up tables, required for the size of reel cutting units that are present, i.e. either the configuration data for the five inch cutting reels  4  as shown at block  46  or the seven inch cutting reels  4  as shown at block  48 . This configuration data is then used thereafter during operation of mower  2  to set an appropriate rotational speed of the installed size of reel cutting units  4 . This subroutine ends after blocks  46  or  48  and main controller  22  proceeds on to its main control loop for controlling other functions of mower  2 . 
     This invention permits an operator of mower  2  to purchase a single traction unit designed to electrically power the plurality of reel cutting units  4  that are to be attached to such traction unit, a set of five inch reel cutting units all powered by motors  20   a , and a set of seven inch reel cutting units all powered by motors  20   b . If an operator wishes to use the five inch size at a particular time, the cutting units  4  having motors  20   a  are installed on the traction unit. The control process shown in  FIG. 2  automatically detects which size cutting units have been installed and automatically loads and uses the configuration data for such size, all without the operator having to do anything. If the operator later wishes to switch over and use the larger seven inch reel cutting units  4  on the traction unit, he or she can do so by removing the five inch cutting units  4  and motors  20   a  and installing the seven inch cutting units  4  and motors  20   b . Again, the control process shown in  FIG. 2  automatically detects this change and thereafter loads and uses the configuration data for the newly installed cutting units  4  and motors  20 , again without the operator having to do anything other than change out the cutting units  4  and motors  20 . 
     Accordingly, the operator need not purchase two entirely separate traction units for five inch or seven inch cutting, but just one traction unit and two sets of cutting units  4  and motors  20 . The manufacturer of mower  2  need not manufacture two separate traction units, but can manufacture a single common traction unit platform. The economic advantages to all concerned are apparent. 
     The scope of this invention is not to be limited to the details of the embodiment of the invention disclosed herein. For example, main controller  22  will remember the clip and the resulting reel speed settings that were last input into main controller  22  for the size of reel cutting units  4  that had been installed on mower  2  and use such settings upon system power-up. If main controller  22  receives information indicating that the size of reel cutting units  4  has been switched from one size to another size (e.g. from the five inch size to the seven inch size), main controller  22  will use the information center to display to the operator the previously stored clip and reel speed settings for the previously installed cutting units  4  (e.g. the previously installed five inch cutting units  4 ) as well as the reel speed settings required for the newly installed cutting units  4  (e.g. the newly installed seven inch cutting units  4 ). Then, main controller  22  will require the operator to verify or confirm that he or she wishes to use the reel speed settings for the newly installed cutting units  4  as an alternative to simply automatically using such reel speed settings without requiring operator verification. If the verification step described herein is optionally implemented in main controller  22 , such step is preferably used only upon detection of a change in the size of the reel cutting units  22 . Once the operator has verified which reel speed settings are to be used, the verification step will disappear and not reappear until the next change in reel size is reported to main controller. 
     Various modifications of this invention will be apparent to those skilled in the art. For example, while it is preferred that the reel size information be stored in the memory of motor controllers  24  and transmitted to the main controller  22  using two-way communication, this need not necessarily be the case. For example, main controller  22  could use digital or analog inputs to distinguish between the two different reel motors  20   a  and  20   b  that respectively drive the five inch or seven inch cutting reels, respectively. A simple alternative would be to provide main controller  22  with five designated inputs for the five reel motors  20  of the five cutting units carried on mower  2 . If the motor connected to a particular input is a reel motor  20   a  of a five inch cutting reel, the wiring harness for such reel motor  20   a  could be designed to simply ground that input. Conversely, if the motor connected to a particular input is a reel motor  20   b  of a seven inch cutting reel, the wiring harness for such reel motor  20   b  would be somewhat differently designed to leave that input powered. Accordingly, in acquiring the reel size information in this alternative situation, main controller simply monitors the status of the five inputs for each of the motors  20  connected thereto to determine if such inputs are grounded (i.e. those cutting units would have a five inch cutting reel) or powered (i.e. those cutting units would have a seven inch cutting reel). 
     Thus, the scope of this invention shall be limited only by the appended claims.