Abstract:
A lawn mower having a cutter housing for receiving a cutter blade for cutting grass. To make the manufacture of molds easy, the cutter housing is divided into three members: a housing proper for receiving the cutter blade, a bottom member for forming a cut grass carrying passage, and a scroll guide member for forming a portion of a scroll part. The bottom member engages with the housing proper and the scroll guide member. The scroll guide member is co-fastened to the housing proper with an engine. As a result, molds needed for making the cutter housing can be made simple and the assembly of the lawn mower made easy.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to a lawn mower, and particularly to an improved cutter housing.  
       BACKGROUND OF THE INVENTION  
       [0002]     Lawn mowers in which a cutter blade is rotatably mounted in a cutter housing and grass cuttings are discharged to outside the cutter housing from a scroll part of the cutter housing through a cut grass carrying passage are known. In a lawn mower of this kind, the scroll part and the cut grass carrying passage are formed integrally with the cutter housing.  
         [0003]     A lawn mower in which a scroll part is formed integrally with a cutter housing like this and a bottom part of a cut grass carrying passage is formed separately is proposed in for example JP-UM-A-63-61223. This lawn mower will now be described on the basis of  FIG. 11  and  FIG. 12 .  
         [0004]     The lawn mower  220  shown in  FIG. 11  has an engine  222  mounted on top of a cutter housing  221  and a cutter blade  224  attached to the output shaft  223  of this engine  222 , and the cutter blade  224  is rotated inside the cutter housing  221  to cut grass.  
         [0005]     As shown in  FIG. 12 , the cutter housing  221  has a scroll part  225  which allows rotation of the cutter blade  224  and in which grass cuttings cut by the cutter blade  224  swirl, and a cut grass carrying duct  226  through which the grass cuttings are carried from the scroll part  225  to outside the cutter housing  221 .  
         [0006]     The cut grass carrying duct  226  is made up of an approximately U-shaped cut grass passage part  227  formed integrally with the cutter housing  221 , and a bottom plate  228  formed as a separate part covering the cut grass passage part  227 .  
         [0007]     However, in the lawn mower  220  of related art described above, because only the bottom plate  228  has been made a separate component from the cutter housing  221 , there has been the shortcoming that this is not enough to make the shape of the cutter housing  221  simple, and it is not possible to simplify the mold.  
         [0008]     Also, in this lawn mower  220 , because the cut grass passage part  227  and the scroll part  225  of the cut grass carrying duct  226  are formed integrally with the cutter housing  221  and the bottom plate  228  of the cut grass carrying duct  226  is formed as a separate piece, it is necessary for mounting parts  229  to be formed in three locations on the bottom plate  228 . Consequently, there has been the problem that the number of fixing components such as screws increases and ease of assembly deteriorates.  
         [0009]     Accordingly, a lawn mower has been awaited with which it is possible to form the cutter housing easily by split construction and it is possible to achieve improved ease of assembly of the pieces of the split construction and to achieve improved productivity.  
       SUMMARY OF THE INVENTION  
       [0010]     The invention provides a lawn mower having a motive power source; a cutter blade for cutting grass; and a cutter housing that receives the cutter blade and has a scroll part for guiding cut grass into a cut grass carrying passage, wherein the cutter housing is divided into a housing proper for receiving the cutter blade, a bottom member to be attached to the housing proper and form the cut grass carrying passage, and a scroll guide member to be attached to the housing proper and form the scroll part, a cut grass carrying passage exit side of the bottom member is engaged with the housing proper, a cut grass carrying passage entrance side of the bottom member is attached to the housing proper and engages with the scroll guide member, and the scroll guide member is co-fastened with the motive power source inside the housing proper.  
         [0011]     Because in this invention the cutter housing is divided into three members, simplification of dies for molding the members constituting the cutter housing is achieved and the manufacturability of the cutter housing can be improved.  
         [0012]     Also, because the cut grass carrying passage exit side of the bottom member is engaged with the housing proper and the cut grass carrying passage entrance side is attached to the housing proper and also engaged with the scroll guide member, the ease of assembly of the bottom member and the scroll guide member to the housing proper improves.  
         [0013]     Furthermore, because the scroll guide member is co-fastened to the motive power source and the housing proper, notwithstanding the increase in the number of parts arising from the division of the cutter housing into a plurality of members, there is no increase in the number of fixing screws. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     A preferred embodiment of the invention will be described below in detail on the basis of the accompanying drawings, in which:  
         [0015]      FIG. 1  is a perspective view of a lawn mower according to the invention;  
         [0016]      FIG. 2  is a side view of the lawn mower shown in  FIG. 1 ;  
         [0017]      FIG. 3  is a plan view of the lawn mower shown in  FIG. 1 ;  
         [0018]      FIG. 4  is a view in the direction of the arrow  4  in  FIG. 1 ;  
         [0019]      FIG. 5  is a view showing a mulching work state of the lawn mower shown in  FIG. 2 ;  
         [0020]      FIG. 6  is an exploded perspective view of a cutter housing according to the invention;  
         [0021]      FIG. 7  is a perspective view showing the cutter housing shown in  FIG. 6  in its assembled state;  
         [0022]      FIG. 8  is a sectional view on the line  8 - 8  in  FIG. 7 ;  
         [0023]      FIG. 9  is a view in the direction of the arrow  9  in  FIG. 7 ;  
         [0024]      FIG. 10A  to  FIG. 10F  are perspective views showing an assembly procedure of a cutter housing according to the invention;  
         [0025]      FIG. 11  is a side view showing a lawn mower of related art; and  
         [0026]      FIG. 12  is bottom view of a cutter housing shown in  FIG. 11 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]     A lawn mower  10  constituting a preferred embodiment of the invention shown in  FIG. 1  is of a self-propelling type. A cutter blade  14  for cutting grass is rotated by an engine  13 , which is a motive power source. Cut grass is collected by being carried from a cutter housing  12  by a carrying draft into a grass bag  24 . Rear wheels  17  are driven by the engine  13 .  
         [0028]     In the figure, the reference number  11  denotes a machine body;  16  front wheels;  18  handle stays;  19  a handle;  21  a handle cover extending across the handle  19 ;  22  a clutch lever for travel, which clutch-controls motive power transmission from the engine  13  to the rear wheels  17 ;  23  a grass cover;  25  a clutch lever for clutch-controlling rotational power to the cutter blade  14 ;  26  a lock lever;  27  a head cover; and  60  a lock mechanism.  
         [0029]     The clutch lever  25  is a lever that simultaneously performs an operation of applying a brake to the cutter blade  14  while stopping the driving of the cutter blade  14 , and is sometimes called a BBC control lever because it controls a blade, a brake and a clutch.  
         [0030]     As shown in  FIG. 2 , the engine  13  of the lawn mower  10  is mounted on the top of the cutter housing  12 . The cutter blade  14  is attached to the output shaft  28  of the engine  13  by way of a clutch mechanism  40 . The left and right front wheels  16  are disposed at side faces of the front part of the cutter housing  12 , and the left and right rear wheels  17  are disposed at side faces of the rear part of the cutter housing  12 . Left and right handle stays  18  are attached to the side faces of the rear part of the cutter housing  12 . The handle  19  extends rearward from the rear parts of these handle stays  18 ,  18 . The clutch lever  25  is mounted on this handle  19  and controls the clutch mechanism  40 . The lock lever  26  is mounted in front of the clutch lever  25  and bars an engaging function of the clutch lever. The grass bag  24  is removably attached to a rear wall  31  of the cutter housing  12 . A grass guard  23  is swingably attached to an upper part of the rear wall  31  of the cutter housing  12 .  
         [0031]     The grass bag  24  is made of a porous material having air holes (not shown) through which the carrying draft can pass but grass cuttings cannot pass.  
         [0032]     As shown in  FIG. 3 , with the engine  13  (see  FIG. 2 ) started, the clutch mechanism  40  (see  FIG. 2 ) is switched from an off state to an engaged state by a two-stage motion of shifting the clutch lever  25  to the handle  19  side and then shifting the lock lever  26  forward, to rotate the cutter blade  14 , and the clutch lever for travel  22  is shifted to the handle  19  side to rotate the rear wheels  17 ,  17 .  
         [0033]     The cutter blade  14  has blade parts  38 ,  38  on its leading sides in the rotation direction shown with the arrows A, A, and from these blade parts  38 ,  38  on its trailing sides in the rotation direction it has air-lifting parts  39 ,  39  formed so as to curve upward.  
         [0034]     That is, as the cutter blade  14  rotates, grass on the ground surface is caused to stand up by a negative pressure arising on the undersides of the air-lifting parts  39 ,  39 , and the grass is cut by the blade parts  38 ,  38 . The cut grass is hit by the upper sides of the air-lifting parts  39 ,  39  and caught by a swirling airflow created by the rotation of the cutter blade  14 , and with this swirling airflow as a carrying draft the grass cuttings are fed together with the carrying draft through a cut grass carrying passage  32  into the grass bag  24  as shown by the arrow B.  
         [0035]      FIG. 4  shows the underside of the lawn mower  10 .  
         [0036]     The cutter blade  14  is covered by the cutter housing  12 . The cut grass carrying passage  32  for guiding cut grass into the grass bag  24  (see  FIG. 2 ) is formed in the cutter housing  12 . This cut grass carrying passage  32  connects with the grass bag  24 .  
         [0037]     The reference number  29  denotes a power-transmitting part (a belt);  33  a scroll part provided in the cutter housing  12  for rotatably receiving the cutter blade  14 ;  52  a drive pulley;  34  a clutch for travel; and  35  a rear wheel axle.  
         [0038]     In the lawn mower  10 , the output of the engine  13  is transmitted from the drive pulley  52  of the output shaft  28  to a driven pulley  29   a  by the belt  29 , and by way of the driven pulley  29   a  and the clutch for travel  34  the output of the engine  13  is transmitted to the rear wheel axle  35  and drives the rear wheels  17 ,  17  (see  FIG. 3 ).  
         [0039]      FIG. 5  shows a mulching work state of the lawn mower. Mulching work (mulching mode) is a working mode in which two cutter blades are provided in the cutter housing, grass is cut with these cutter blades, and finely cut grass cuttings are dispersed on the lawn surface (ground surface) so that they are inconspicuous. Mulching work is an alternative mode of discharge work, discussed below.  
         [0040]     Discharge work (discharge mode) is a working mode in which grass is cut with one cutter blade, and the cut grass is made to pass through the cut grass carrying passage and discharged to outside through the grass cover.  
         [0041]     Bagging work (bagging mode) is a working mode in which grass is cut with one cutter blade and the cut grass is made to pass through the cut grass carrying passage and collected in the grass bag.  
         [0042]     That is, the lawn mower  10  of this preferred embodiment is capable of mulching work, discharge work and bagging work (see  FIG. 2 ). When mulching work is to be done, an upper cutter blade  15  for mulching work is fitted to the output shaft  28  of the engine  13  along with a cutter blade  14  for discharge work and bagging work, and a closing member (not shown) is placed in the cut grass carrying passage  32  (see  FIG. 4 ).  
         [0043]      FIG. 6  and  FIG. 7  show a cutter housing  12  according to the invention in an upside-down state.  
         [0044]     The cutter housing  12  is made up of a housing proper  131  for receiving the cutter blade  14 ; a bottom member  132 , attached to this housing proper  131 , for forming the cut grass carrying passage  32  (see  FIG. 4 ); and a scroll guide member  133 , attached to the housing proper  131 , for forming the scroll part  33  (see  FIG. 4 ). This cutter housing  12  is made of a resin material.  
         [0045]     The bottom member  132  is attached to the housing proper  131  by fixing screws  134 ,  135 . The scroll guide member  133  is co-fastened to the cutter housing  12  and the engine  13  (see  FIG. 1 ) with fixing screws  136 ,  136 .  
         [0046]     The reference numbers  137 ,  137  denote fixing screws for fixing the engine  13  to the cutter housing  12 .  
         [0047]     The housing proper  131  has a housing concavity  141  forming the cut grass carrying passage  32  and the scroll part  33  shown in  FIG. 4 . A front guard part  142  is formed at the front of this housing concavity  141 . A rear wall  31  is formed at the rear of the housing concavity  141 . Left and right side guard parts  145 ,  146  are formed at the left and right sides of the housing concavity  141 .  
         [0048]     The output shaft  28  of the engine  13  and the dutch mechanism  40  shown in  FIG. 2  are passed through a top opening  147  formed in the center of the housing concavity  141 .  
         [0049]     An engine mount part  148  for the engine  13  to be mounted to is formed around the top opening  147 . The engine  13  is mounted to the engine mount part  148  using the fixing screws  136 ,  137  and a plurality of fixing holes  149  formed in the engine mount part  148 .  
         [0050]     An inner mounting boss  151  for mounting the bottom member  132  to the housing proper  131  is formed in the housing concavity  141 . Also, an outer mounting boss  152  for mounting the bottom member  132  to the housing proper  131  is formed on the right side guard part  146 .  
         [0051]     Multiple internal pressure control holes  153  for controlling the internal pressure of the cut grass collecting unit  24  (see  FIG. 2 ) are formed in the left side of the rear wall  31 . A cut grass carrying passage exit  154  (exit-side opening) is formed in the right side of the rear wall  31 . Engaging holes  155 ,  155  for engaging with the bottom member  132  are also formed in the right side of the rear wall  31 .  
         [0052]     The bottom member  132  has a body part  161  for forming the bottom of the cut grass carrying passage  32  (see  FIG. 4 ); an entrance-side reinforced part  163  formed at the front of the body part  161  so that it forms a flange in the shape of an arc of the circle of the scroll part  33  (see  FIG. 4 ) and completes a cut grass carrying passage entrance  162  (see  FIG. 7 ); an inner mounting part  165 , formed at the inner end of this entrance-side reinforced part  163 , to be fixed to the inner mounting boss  151 ; an outer mounting part  166 , formed at the outer end of the entrance-side reinforced part  163 , to be fixed to the outer mounting boss  152 ; and projections  167 ,  167 , formed at the rear of the body part  161 , to fit in the engaging holes  155 ,  155  formed in the rear wall  31 .  
         [0053]     The entrance-side reinforced part  163  has the function of completing the vertical wall of the scroll part  33 .  
         [0054]     The scroll guide member  133  has an arcuate scroll channel  171  through which an approximate sectional U-shape forming the scroll part  33  (see  FIG. 4 ) continues. The scroll guide member  133  is co-fastened to the housing proper  131  along with the engine  13  through co-fastening parts  172 ,  172  formed at the inner periphery of this scroll channel  171 . A flange part  173  formed on the outer periphery of the scroll channel  171  forms an arcuate flange of the scroll part  33 . The flange part  173  has a boss part  174  formed at one end  176  of it. The boss part  174  is fitted (press-fitted) in the inner mounting part  165  of the bottom member  132 . A carrying passage side face part  175  forming a part of a side face of the cut grass carrying passage  32  is formed at the end  176  of the scroll channel  171 .  
         [0055]     The reference number  177  denotes the other end of the flange part  173 .  
         [0056]     Also, to obtain the ideal (desired) shape of the scroll part  33 , the scroll guide member  133  is positioned at the lowest position of the cut grass carrying passage entrance  162  of the cut grass carrying passage  32  and is formed-in a shape continuous with the housing proper  131  at the vicinity of the maximum width of the cutter housing  12 .  
         [0057]     Because the cutter housing  12  is divided into the housing proper  131 , the bottom member  132  and the scroll guide member  133  like this, simplification of dies for molding the members constituting the cutter housing  12  is achieved and the manufacturability of the cutter housing  12  can be improved.  
         [0058]     Because the projections  167 ,  167  formed on the bottom member  132  are engaged with the engaging holes  155 ,  155  formed in the rear wall  31  of the housing proper  131 , the ease of assembly of the bottom member  132  to the housing proper  131  is improved.  
         [0059]     And because the scroll guide member  133  is co-fastened to the engine  13  and the housing proper  131 , notwithstanding the increase in the number of parts arising from the division of the cutter housing  12  into a plurality of members, as mentioned above, there is no increase in the number of fixing screws.  
         [0060]     As shown in  FIG. 8 , the inner mounting part  165  of the bottom member  132  has a through hole  168  for a fixing screw  134  to pass through and a mating tubular part  169  for the boss part  174  of the scroll guide member  133  to mate with.  
         [0061]     As a result of the entrance-side reinforced part  163  of the bottom member  132  being fixed to the housing proper  131  and the boss part  174  of the scroll guide member  133  being mated with the mating tubular part  169 , the ease of assembly of the bottom member  132  and the scroll guide member  133  improves.  
         [0062]     As shown in  FIG. 9 , by the inner mounting part  165  of the bottom member  132  being fixed to the inner mounting boss  151  of the housing proper  131  and the boss part  174  of the scroll guide member  133  being fitted (press-fitted) into the mating tubular part  169  (see  FIG. 8 ) of this inner mounting part  165 , the two members that are the bottom member  132  and the scroll guide member  133  can be supported on the one inner mounting boss  151 . Also, the entrance-side reinforced part  163  of the bottom member  132  and the scroll guide member  133  are assembled in a continuous circular arc shape so as to allow rotation of the cutter blade  14  (see  FIG. 4 ).  
         [0063]     An assembly procedure of the cutter housing  12  described above will now be described, on the basis of  FIG. 10A  to  FIG. 10F .  
         [0064]     As shown in  FIG. 10A , the housing proper  131  is set in an upside-down state, and the bottom member  132  is brought preparatorily to above the housing proper  131 .  
         [0065]     As shown in  FIG. 10B , the projections  167 ,  167  of the bottom member  132  are inserted into the engaging holes  155 ,  155  in the housing proper  131  as shown by the arrows d 1 , d 1 .  
         [0066]     In  FIG. 10C , the inner mounting part  165  of the bottom member  132  is set on the inner mounting boss  151  of the housing proper  131  and the outer mounting part  166  of the bottom member  132  is set on the outer mounting boss  152  of the housing proper  131 . Then, the fixing screw  134  is passed through the inner mounting part  165  and screwed into the inner mounting boss  151  of the fixing screw  134  as shown by the arrow d 2  and the fixing screw  135  is passed through the outer mounting part  166  and screwed into the outer mounting boss  152  as shown by the arrow d 3  and the bottom member  132  is thereby fixed to the housing proper  131 .  
         [0067]     In  FIG. 10D , the boss part  174  of the scroll guide member  133  is fitted (press-fitted) into the inner mounting part  165  of the bottom member  132  as shown by the arrow d 4 , and the co-fastening parts  172 ,  172  of the scroll guide member  133  are set on the fixing holes  149 ,  149  of the housing proper  131  as shown by the arrows d 5 , d 5 .  
         [0068]     In  FIG. 10E , the engine  13  (see  FIG. 2 ) is made ready and the fixing screws  136 ,  136  for co-fastening the scroll guide member  133  to the housing proper  131  together with the engine  13  are made ready. The fixing screws  137 ,  137  for fixing the engine  13  to the housing proper  131  are also made ready.  
         [0069]     As shown in  FIG. 10F , the engine  13  is placed on the engine mount part  148  of the housing proper  131  and the fixing screws  136 ,  136  and the fixing screws  137 ,  137  are screwed into the engine  13  from the inner side of the housing proper  131 , whereby the engine  13  is fixed to the housing proper  131 . As a result, the scroll guide member  133  is also fixed to the housing proper  131 .  
         [0070]     That is, by the scroll guide member  133  being co-fastened together with the housing proper  131  and the engine  13 , it is possible to keep down the number of fixing screws. As a result, the assembly time of the cutter housing  12  can be shortened.  
         [0071]     Whereas the lawn mower of this preferred embodiment has been described using an example in which the boss part  174  of the scroll guide member  133  is fitted (press-fitted) to the inner mounting part  165  of the bottom member  132  as shown in  FIG. 6 , the invention is not limited to this, and alternatively for example the inner mounting part  165  and the boss part  174  may be co-fastened to the inner mounting boss  151  with the fixing screw  134 .  
         [0072]     Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.