Abstract:
A rear discharge mower comprising: a first shaft; a first blade that is rotated in unison with the first shaft; a second shaft that is configured to be rotated in a direction opposite from a rotational direction of the first shaft; a second blade that is rotated in unison with the second shaft, wherein a grass-clippings discharge path is formed through which grass clippings are discharged in a rearward direction from the area between the first shaft and second shaft; an enclosing casing that supports the blade shafts; and a power train that is accommodated in the enclosing casing and that transmits power to the first and second blade shafts.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an improvement of a rear discharge mower of a lawn mower, and a mid-mount type lawn mower that uses the rear discharge mower. 
         [0003]    2. Description of the Related Art 
         [0004]    This type of mid-mount type lawn mower that uses a rear discharge mower has, e.g., the following conventionally known structure. 
         [0005]    A lawn mower is known in which a power transmission pulley and a power transmission belt are used as means to transmit power to a plurality of adjacently positioned blade shafts, in which one of the blade shafts and the shaft of the power transmission pulley for providing input to the blade shaft are structured as separate shafts in order to drive the two shafts in mutually reverse directions, and in which a set of gears is provided to ensure reverse rotation between the two shafts (see Japanese Laid-Open Patent Application (JP-A) 2003-274728 (Patent Document 1), for example). 
         [0006]    A lawn mower is also known in which a power transmission pulley and a power transmission belt are used as means to transmit power to a plurality of adjacently positioned blade shafts, and in which a supplementary pulley is used convert the winding direction of the belt so that the internal peripheral surface side of the power transmission belt is wound around the power transmission pulley on one of the blade shafts, and the external peripheral surface side of the power transmission belt is wound around the power transmission pulley of another blade shaft, in order to drive the two shafts in mutually reverse directions (see Japanese Laid-Open Patent Application (JP-A) 2003-274729 (Patent Document 2), for example). 
         [0007]    A lawn mower is further known in which motive power transmitted from an input shaft is branched at a pair of power transmission shafts to provide input to a gearbox disposed in the upper portion of left and right blade shafts and to transmit shaft power via a bevel gear mechanism or the like as a means to pivotally transmit power to a plurality of blade shafts in adjacent positions (see Japanese Laid-Open Patent Application (JP-A) 2003-158907 (Patent Document 3), for example). 
         [0008]    In these kinds of rear discharge mowers, the blades are driven at a fairly high speed and high torque in order to discharge grass clippings in a rearward direction by generating airflow and producing a bouncing action that accompany the rotation of the blades. 
         [0009]    If an attempt is made to convey the grass clippings toward the grass catcher in the rearward and upward directions without while minimizing a reduction in the movement energy in the grass clippings discharge direction, it is desirable to gradually change the movement of the grass clippings upward from the conveyance start area in which a conveyance action is imparted by the rotation of the blades across to the location where discharge begins on the rearward side where the conveyance action is completed. In order to accomplish this, it would be advantageous to gradually change the movement direction by beginning an upward slope of the grass-clippings discharge path from a position as near the front end of the mower deck as possible. 
         [0010]    In models having a structure in which motive power is transmitted to the blade shafts using a belt as described in Japanese Laid-Open Patent Applications (JP-A) 2003-274728 and 2003-274729 noted above, the belt is used in a state of high belt tension. Therefore, the strength of the blade shaft support structure and the mower deck must be kept very high because the provision of a large distance between the mower deck and the power transmission pulley results in a situation in which a strong tension operates on the power transmission pulley in a position set at a distance from the mower deck, and there is a possibility that a bending moment will forcefully operate on the blade shaft. However) this is not practical in actual application in a mower deck composed of a thin metal plate because sufficient support strength cannot be obtained and the thickness of the mower deck must be unavoidably increased to assure strength, and other impractical structural modifications become necessary when attempting to set the power transmission pulley at a distance from the mower deck. 
         [0011]    For this reason, in the arts described in Japanese Laid-Open Patent Applications (JP-A) 2003-274728 and 2003-274729 noted above, measures are taken in which the power transmission pulley is not placed at a distance from the mower deck, but rather a supplementary pulley is used to bring the power transmission belt between adjacent blade shafts to the front side of the mower deck to the extent possible, and the location at which the grass-clippings discharge path portion on the mower deck begins an upward movement is set further forward. However, since there is no change in the fact that the power transmission pulley remains in close proximity on the surface of the mower deck, the location at which upward motion starts must be provided further rearward to avoid [close] placement of the power transmission pulley and belt, and the location at which upward motion starts cannot be brought sufficiently forward. 
         [0012]    Moreover, insofar as a belt is used as the transmission mechanism, some sort of blade reversal mechanism must be used between adjacent blade shafts, necessitating a dedicated set of gears or a redundant supplementary pulley for that purpose. 
         [0013]    A structure is also conventionally known in which power transmission is branched by using a pair of power transmission shafts, a bevel gear mechanism, or the like in place of a structure using a belt and power transmission belt, as described in Japanese Laid-Open Patent Application (JP-A) 2003-158907. 
         [0014]    In a structure that drives a bevel gear about the center of a horizontal shaft using a power transmission shaft in this manner, there are no drawbacks such as the generation of high tension between adjacent blade shafts, but the following problems arise because placement of a bevel gear with a rather large diameter is difficult on a mower deck that has little extra space. 
         [0015]    The power transmission mechanism itself, which involves the meshing of bevel gears with each other, produces a relatively high level of noise in comparison with a power transmission mechanism composed of flat gears. In addition, there is a drawback when the bevel gear itself has a small diameter in that the noise in the gear meshing portion increases further due to the load that operates in a concentrated fashion on the meshing portion that has a small number of teeth. Also, a separate reverse rotation mechanism naturally becomes necessary. 
       SUMMARY OF THE INVENTION 
       [0016]    An object of the present invention is to provide an improvement of this kind of conventional rear discharge mower. 
         [0017]    The rear discharge mower according to the present invention comprises the following: 
         [0018]    a first shaft; 
         [0019]    a first blade that is rotated in unison with the first shaft; 
         [0020]    a second shaft that is configured to be rotated in a direction opposite from a rotational direction of the first shaft; 
         [0021]    a second blade that is rotated in unison with the second shaft, wherein a grass-clippings discharge path is formed through which grass clippings are discharged in a rearward direction from the area between the first shaft and second shaft as viewed from above; 
         [0022]    an enclosing casing that pivotally supports the blade shafts; and 
         [0023]    a power train that is accommodated in the enclosing casing and that transmits power to the first and second blade shafts. 
         [0024]    In accordance with configuration described above, a mower blade drive casing that supports adjacent blade shafts is provided. Therefore, a configuration is formed so as to have sufficient strength in order to support the two blade shafts, whereby the mower deck itself can be composed of a thin member that has strength in order to shape the intended blade rotation space. 
         [0025]    In this embodiment, it is preferred that the enclosing casing have a first cylindrical shaft casing portion that at least partially encloses the first shaft, a second cylindrical shaft casing portion that at least partially encloses the second shaft, and a connecting casing portion that connects the first and second cylindrical shaft casings. 
         [0026]    Since the connecting casing portion of the mower blade drive casing connects together the cylindrical shaft casing portions that support the blade shafts, the connecting casing portion can be disposed in a position that is set at a sufficient distance from the mower deck by suitably setting the length of the cylindrical shaft casing portions. Therefore, a starting end of the grass-clippings discharge path can be set nearer to the front end in the direction of the grass clippings conveyance on the top surface side of the mower deck without being affected by the existence of the connecting casing portion, and a grass-clippings discharge path with good grass clipping discharge performance can be formed. 
         [0027]    In this embodiment, it is preferred that the enclosing casing enclose the first shaft, the second shaft, and the power train, from a front side, lateral sides, a rear side, and a top side. 
         [0028]    In this embodiment, it is preferred that the power train be configured with a plurality of flat gears disposed in the connecting casing portion of the enclosing casing. 
         [0029]    In this embodiment, it is preferred that the plurality of flat gears be disposed in the same plane. 
         [0030]    In this embodiment, it is preferred that one of the flat gears be positioned above the grass-clippings discharge path, and the one flat gear be configured with a smaller diameter than the other flat gears in the power train. 
         [0031]    In this embodiment, it is preferred that one of the flat gears be positioned above the grass-clippings discharge path, and the position of the axial center of rotation of the one flat gear be set to be more frontward than the axial center of rotation of the other flat gears in the power train. 
         [0032]    In this embodiment, it is preferred that a flat gear to which external power is input be disposed in the connecting casing portion, an odd number of flat gears be provided to transmit power to the first blade shaft among the flat gears to which power is transmitted by meshing with the flat gear to which external power is input, and an even number of flat gears be provided to transmit power to the second blade shaft. 
         [0033]    In this embodiment, it is preferred that each of the first and second blades be disposed so that a rotational trajectory of the first blade and a rotational trajectory of the second blade overlap each other, and respective rotational phases be mutually different. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  is a diagram showing an overall side view of a mid-mount type lawn mower; 
           [0035]      FIG. 2  is a diagram showing an overall plan view of a mid-mount type lawn mower; 
           [0036]      FIG. 3  is a diagram showing a plan view of a rear discharge mower; 
           [0037]      FIG. 4  is a longitudinal sectional view in the lateral direction showing a power transmission system of a rear discharge mower; 
           [0038]      FIG. 5  is a transverse sectional view in the horizontal direction showing the power transmission system of a rear discharge mower; 
           [0039]      FIG. 6  is a longitudinal sectional view in the longitudinal direction showing the power transmission system of a rear discharge mower; 
           [0040]      FIG. 7  is a perspective view showing the housing of a rear discharge mower; 
           [0041]      FIG. 8  is an explanatory diagram showing another embodiment of the housing of a rear discharge mower; 
           [0042]      FIG. 9  is an explanatory diagram in a plan view showing another embodiment of the power transmission system of a rear discharge mower; 
           [0043]      FIG. 10  is an explanatory diagram in a plan view showing another embodiment of the power transmission system of a rear discharge mower; and 
           [0044]      FIG. 11  is an explanatory diagram in a plan view showing another embodiment of the power transmission system of a rear discharge mower. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0045]    An example of an embodiment of the present invention will be described below in detail with reference to the diagrams. A plurality of embodiments will be described below. It is to be understood that the combination of characteristics of one embodiment with the characteristics of another embodiment is included within the scope of the present invention. 
         [0046]    [Configuration of the Lawn Mower] 
         [0047]      FIGS. 1 and 2  show a riding-type, mid-mount type lawn mower as an example of a lawn mower provided with a rear discharge mower according to the present invention. 
         [0048]    The lawn mower is configured with a mower  2  that is mounted in suspended fashion so as to be able to be raised and lowered between the front wheels  11  and the rear wheels  12  of a riding running carriage  1 , while a grass catcher  6  is connected so as to be able to be raised and lowered to the rear section of the carriage via parallel four-point linking mechanisms  13 . 
         [0049]    An engine  5  is installed in the front of the running carriage  1 , power taken from an output shaft  50  at the front portion of the engine  5  is transmitted via a belt transmission device  51  to an operating power take-off shaft  52  that is disposed below the front portion of the carriage, and power from the operating power take-off shaft  52  is transmitted by a shaft to the mower  2 . 
         [0050]    The rear wheels  12  are configured so that the right and left rear wheels  12  are each separately pivotably supported in a cantilevered state at the lower end of a pair of left and right rear wheel shaft casings  15  that protrude facing in the rearward downward direction from both the left and right sides of a transmission casing  14  that is secured to the carriage frame  10 , and a duct  16  for discharging grass clippings is secured to a space that is formed between the left and right rear wheel shaft casings  15 . 
         [0051]    The grass catcher  6  is composed of a container main body  60  that is formed in the overall shape of a box and is provided with an entrance opening  61  that faces the running carriage  1  in the grass-catching position and is externally fitted and connected to the rear end of the duct  16 , and an exit opening  62  that faces the opposite side of the entrance opening. The grass catcher is further composed of a rear portion lid  63  that can open and close the exit opening  62  formed in the container main body  60 . 
         [0052]    The grass catcher  6 , which is connected by a linking mechanism  13  as described above, is configured to be able to change position between a grass-catching position connected to the duct  16  for conveying grass clippings from the running carriage  1  so as to collect grass clippings that are conveyed by the power of the airflow from the mower  2 , which is installed on the running carriage  1 , and a discharge position that is set at a distance from the duct  16 . 
         [0053]    [Mower Configuration] 
         [0054]    The mower  2  has a structure in which two rotating blades  21  are arranged in a row to the left and right within a mower housing  20 , as shown in  FIGS. 2 and 3 , and is formed as a rear discharge mower in which the left blade  21  is driven in a clockwise direction, and the right blade  21  is driven in a counterclockwise direction, whereby grass clippings ride on a conveying airflow generated by the rotation of the blades  21  and are discharged from an exit  20 A formed near the rear center portion of the mower housing  20 . The grass clippings discharged from the exit  20 A are brought to the grass catcher  6  via the duct  16  disposed between the left and right rear wheels  12 . 
         [0055]    The mower  2  is configured so that the upper end side is elevatably suspended and connected to the lower end side of a pair of front and rear swinging links  23  that are pivotally connected to the carriage frame  10 , and so that the mower will run with gauge wheels  24 , which are provided to the lower end portion of the mower housing  20 , in a state of contact with the ground in when operated to clip grass. 
         [0056]    Among the swinging links  23 , a portion of the rear swinging link  23  is connected and interlocked via a connecting rod  26  to a raising and lowering operation lever  25  located to the side of a driver seat  7  that is provided to the top of the carriage frame  10 , and is configured to allow manual raising or lowering operation by swingably operating the raising and lowering operational lever  25 . 
         [0057]    Blade shafts  22  that support the right and left blades  21  of the mower  2  are mutually connected and interlocked via a power train  4  composed of a set of gears that is composed of flat gears  40  housed in a mower blade drive casing  3 , as shown in  FIGS. 3 through 5 . The mower blade drive casing  3  is an example of an enclosing casing. 
         [0058]    The mower blade drive casing  3  is composed of cylindrical shaft casings  30  that enclose the blade shafts  22 , and a connecting casing  31  that connects the top end sides of the cylindrical shaft casings  30 . The flat gears  40  for power transmission are housed in the interior space of the connecting casing  31 . 
         [0059]    A gear box  32  is secured to an intermediate portion of the connecting casing  31 . The gear box  32  is provided with a bevel gear  33  that is formed on the end of the power train shaft  53 , which is connected to the operating power take-off shaft  52  on the front side of the carriage, and an input shaft  35  in which a bevel gear  34  that meshes with the bevel gear  33  is provided to the end of the shaft. 
         [0060]    A boss section  41   a  of an input flat gear  41  fitted over a spline formed on the portion of the power input shaft  35  that projects from the gear box  32  is supported by a shaft via ball bearings  44  in an intermediate section of the connecting casing  31 , and an odd number of relaying flat gears  43 , i.e., a single such gear, is disposed between the input flat gear  41  and the output flat gear  42  fitted over a spline on the shaft ends of one of the blade shafts  22 . An even number of flat gears  43 , i.e., two such gears, are disposed between the input flat gear  41  and the output flat gear  42  fitted over a spline on the end of the other blade shaft  22 . 
         [0061]    The flat gears  40  that constitute the power train  4  are composed of the flat gears  41 ,  42 , and  43 . The right and left blades  21  that are connected and interlocked using the power train  4 , which is composed of the flat gears  40  in this manner, are disposed so that the rotating track of each blade partially overlaps the other, but the blades are mutually offset in phase in the manner shown in  FIG. 3  and assembled so that collision between the blades  21  is avoided. 
         [0062]    Among the flat gears  41 ,  42 , and  43 , the flat gears  41  and  42  for input and output have boss sections  41   a  and  42   a  that are each rest on bearings inside the connecting casing  31  via ball bearings  44 . Also, splines are formed at the input locations and the output locations on the internal peripheral side of the boss sections  41   a  and  42   a  of the power input and output flat gears  41  and  42 , and the boss sections are configured to be able to be inserted and removed with respect to the power input shaft  35  in which splines are formed and the upper end section of the blade shaft  22 . 
         [0063]    The boss sections  41   a ,  42   a , and  43   a  and the teeth sections  41   b ,  42   b , and  43   b  of the flat gears  41 ,  42  and  43 , are formed to be thick, but the hub portions between these sections are formed to be thin. 
         [0064]    A pivot support shaft  45  for the relaying flat gears  43  has a maximum diameter at the upper end portion, the medial portion of the shaft supported by bearings has a smaller diameter than the upper end portion, and the lower end side is formed to a smaller diameter smaller than the internal diameter of the bearing, and is configured to be able to be inserted and removed from above. 
         [0065]    The cylindrical shaft casings  30  that house the blade shafts  22  and the connecting casing  31  are separately formed, but are configured to be integrally connected by bolts at the connecting flange sections  30 A and  31 A formed at the ends of each casing. The lower ends of the cylindrical shaft casings  30  are formed so that the diameter of the corresponding portions of the cylindrical shaft casings is greater than that of the upper end side; even larger flange parts  30 B are formed integrally with the lower ends; and the assembly is connected by bolts to the mower deck  20 B. 
         [0066]    The mower blade drive casing  3  is thus easy to assemble because the mower deck  20 B need only be bolted together in a completely assembled state. 
         [0067]    A protruding section  20 C that protrudes upward in a gradual fashion from the vicinity of the point a in  FIG. 3  is formed on a deck  20 B portion of the mower housing  20  in the vicinity of the external peripheral edge of the mower deck  2013 , as shown in  FIGS. 3 ,  6 , and  7 . Assuming that an imaginary line x that connects the axial centers of the two blade shafts  22  together is the start location of grass clippings discharge, the protruding section  20 C forms a gradually upward-sloping surface across about ¾ of the circumference and is configured to smoothly hand off grass clippings to the duct  16  that trails the exit  20 A. 
       Other Embodiments 
       [0068]    Other embodiments of the present invention will be listed next. 
         [0069]    In regard to the configuration of the mower blade drive casing  3 , the cylindrical shaft casings  30  and the connecting casing  31  may be integrally formed overall and may be configured using a partially open section or an opening and closing lid as a structure for removing and inserting the flat gears  40  as well as various shafts and other components of the power train  4 , though these possibilities are not depicted in the diagrams. 
         [0070]    In  FIG. 8A , the internal height of the mower housing  20  is set to be greater, e.g., about 1.2 times to 1.5 times greater than in the ordinary configuration shown in  FIG. 8B . When the height of the mower housing  20  is set greater in this manner, the grass clippings can be more finely shredded because the grass clippings are carried about inside the housing  20  for a long period of time. 
         [0071]    The layout of the flat gears  40  is not limited to a configuration in which all the flat gears  40  have substantially the same diameter in the manner of the embodiment described above. For example, the flat gears  40  that are positioned above the overlapping location of the rotating track of the two blades  21  may be configured as flat gears  40  that have a smaller diameter than the flat gears  40  of the blade shaft  22  portion, as shown in  FIG. 9 . 
         [0072]    When the flat gears  40  positioned above the overlapping location of the rotating track of the two blades  21  are configured in this manner by using a flat gear  40  that has a smaller diameter than the flat gears  40  of the blade shaft  22  portions, the connecting casing  31  portion of the location in which the smaller diameter flat gear  40  is housed can be formed in a shape in which the outside peripheral wall of the casing is brought inward so as to be moved closer to the small diameter flat gear  40  as viewed from above. It then follows that the connecting casing  31  is arranged so that the portion that has been brought inward is positioned above the grass-clippings discharge path in which grass clippings are discharged in a rearward direction through a space between the right and left blade shafts  22 . As a result, the rear end of the connecting casing  31  can be shifted as far forward as possible so that the slope start end portion of the grass-clippings discharge path can be brought as far forward as possible and disposed in the direction in which grass clippings are conveyed. 
         [0073]    The layout of the flat gears  40  is not limited to one in which the entire configuration is arranged in a single straight line as viewed from above, as described above in embodiment [3]. For example, the entire configuration may be arranged along a curved line segment so that the flat gears  40  that are positioned forward of the overlapping location of the rotating track of both blades  21  are positioned further forward than the flat gears  40  of the of the blade shaft  22  portion, as shown in  FIG. 10 . 
         [0074]    In this case as well, the rear end edge of the connecting casing  31  can be brought as far forward as possible so that the connecting casing  31 , which is disposed so as to be positioned above the grass-clippings discharge path in which grass clippings are discharged in a rearward direction through a space between the right and left blade shafts  22 , can, as a result, be disposed so that the slope start end portion of the grass-clippings discharge path is brought as far forward as possible in the grass clippings conveyance direction. 
         [0075]    The layout of the flat gears  40  is not limited to one in which the entire configuration is composed of flat gears  40  having substantially the same diameter and is arranged in a single straight line as viewed from above, as in the embodiment described above. For example, the flat gears  40  that are positioned forward of the overlapping location of the rotating track of the two blades  21  may have a smaller diameter than the other flat gears  40 , and may be disposed along a curved line segment so as to be positioned further forward than the flat gears  40  of the blade shaft  22  portions, as shown in  FIG. 11 . 
         [0076]    In this case as well, the rear end edge of the connecting casing  31  can be shifted as far forward as possible. 
         [0077]    The layout of the flat gears  40  is not limited to one in which the entire configuration is disposed in a single plane, as described in the embodiments above, and the set of gears constituting the power train  4  may, e.g., be provided in a plurality of upper and lower levels, though this possibility is not depicted in the diagrams. 
         [0078]    The power drive  4  disposed in the mower blade drive casing  3  is not limited to one in which flat gears  40  are used as described in the embodiments above, and power transmission belts and power transmission shafts may be used.