Abstract:
A lawn mower comprises an operation arm, a driven shaft rotatably supported inside the operation arm and having two opposite ends, a cutter operatively connected to one end of the driven shaft, a power source operatively connected to the other end of the driven shaft for generating a drive power to be transmitted to the cutter through the driven shaft, wherein said power source is selective from an engine and an electric motor, an arm side joint case provided on the end of the operation arm, a power source side joint case provided on a housing of the power source and detachably and selectively connected to the arm side joint case, and a centrifugal clutch incorporated in the arm side joint case and having a first member connected to the driven shaft, a second member detachably and selectively connected to the power source and a third member provided to engage the first member and the second member according to the centrifugal force applied thereto.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     The disclosure of Japanese Application No. 2004-301988 filed on Oct. 15, 2004 including the specification, drawing and abstract is incorporated herein by reference in its entirety.  
       FIELD OF THE INVENTION  
       [0002]     This present invention is related to a lawn mower, preferably the lawn mower having a structure to be selectively attached one of an engine and an electric motor as a power source.  
       BACKGROUND OF THE INVENTION  
       [0003]     A lawn mower, also referred to as a grass mower, is used to mow a weed of a footpath in the fields, bottom weed of the forest or pasture grass. There are two types of the lawn mower, one is an arm coupling type and the other is a direct acting type. As for the arm coupling type, a cutter is attached to one end of an operation arm and a power source is attached to the other end of the operation arm. On the other hands, as for the direct acting type, a cutter is directly attached to an axis of a power source. These lawn mowers use either an engine or an electric motor as the power source.  
         [0004]     As the lawn mower which uses the electric motor as the power source, as shown in Japanese Utility Model Laid-Open No. 5-2620, the direct acting type lawn mower, where an electric motor is attached to a tip of an operation arm, and a cutter is directly attached to a shaft of the electric motor, is mainly used.  
         [0005]     As the lawn mower which uses the engine as the power source, the arm coupling type lawn mower, as shown in Japanese Patent Laid-Open No. 2004-8054, where a cutter is attached to one end of an operation arm and an engine is attached to the other end of the operation arm, is mainly used.  
         [0006]     Examples of the arm coupling type lawn mowers include, but are not limited to, a carrying type lawn mower in which an engine is carried on the back puck mount, a shoulder type lawn mower in which a loop-like belt is attached to the operation arm for shouldering and a handle type lawn mower in which a handle, either looped or two-handed type, is attached on the operation arm for manipulation.  
         [0007]     The lawn mower which has the electric motor as the power source can be used where a commercial power supply outlet is placed close to the place of use, It is necessary to use an electric generator when the lawn mower with the electric motor is used where there is no power supply outlet.  
         [0008]     In contrast, the lawn mower which has the engine as the power source has the advantage that it can be used even if there is no power supply outlet close to the place of use. However, engine noise at the time of work is louder than a motor drive.  
         [0009]     Thus, the lawn mower which has the electric motor as the power source does not generate a loud noise, however, the place where the lawn mower is used is limited to around a house. For this reason, it is not suitable for mowing work on a footpath in fields where there is no supply outlet.  
         [0010]     In contrast, the lawn mower which has the engine as the power source can be used even if there is no power supply outlet close to the working place for mowing weeds and grass, however, when mowing work is carried out in the city, the noise problem may bother the neighbors.  
         [0011]     For those reasons, the user has to select one of the lawn mowers between the lawn mower having the engine power source and the lawn mower having the electric motor power source according to the use environment.  
       SUMMARY OF THE INVENTION  
       [0012]     An object of the invention is to address the problem discussed above, a preferred embodiment of the invention includes a lawn mower comprising a main body, a driven shaft rotatably supported in the main body and having two opposite ends, a cutter member operatively connected to one end of the driven shaft, a power source operatively connected to the other end of the driven shaft for generating a drive power to be transmitted to the cutter member through the driven shaft, wherein said power source is selective from an engine and an electric motor, and joint means for detachably and selectively connecting the main body and a housing of the power source. Accordingly, both of the engine as the power source and the electric motor as the power source are selectively attached to the main body by joint structures so that a user can select one of the power sources based on the working circumstance. The joint means includes a main body side joint case incorporating a centrifugal clutch therein and a power source side joint case connected to the housing of the power source. The centrifugal clutch can be placed in the housing of the engine instead. The main body is accompanied by a handle for an user to carry the lawn mower durg inowing.  
         [0013]     It is another object of the present invention to provide a lawn mower comprising an operation arm, a driven shaft rotatably supported inside the operation arm and having two opposite ends, a cutter operatively connected to one end of the driven shaft, a power source operatively connected to the other end of the driven shaft for generating a drive power to be transmitted to the cutter through the driven shaft, wherein said power source is selective from an engine and an electric motor, an arm side joint case provided on the end of the operation arm, a power source side joint case provided on a housing of the power source and detachably and selectively connected to the arm side joint case, and a centrifugal clutch incorporated in the arm side joint case and having a first member connected to the driven shaft, a second member detachably and selectively connected to the power source and a third member provided to engage the first member and the second member according to the centrifugal force applied thereto. The first member comprises a clutch drum, the second member comprises a clutch input shaft rotatably supported by the arm side joint case and the third member comprises a rotor plate fixed to the clutch input shaft, a pivot member rotatably supported on the rotor plate and an extension spring applying the spring force to the pivot member so as to leave the pivot member from the clutch drum, whereby when the rotational speed of the clutch input shaft increases, the centrifugal force moves the pivot member toward the clutch drum against the spring force of the extension spring to have the centrifugal clutch engaged. The arm side joint case and the power source side joint case are fastened by a fasten member. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1 (A) is a perspective view to show the lawn mower according to the present invention, in which an engine is attached to a main body as the power source.  
         [0015]      FIG. 1 (B) is a perspective view to show the lawn mower according to the present invention, in which an electric motor is attached to a main body as the power source.  
         [0016]      FIG. 2  is an expanded cross-sectional view of  FIG. 1  (A) along the line  2 - 2  .  
         [0017]      FIG. 3  is a cross-sectional view of FIGC  2 .  
         [0018]      FIG. 4  is an expanded crosssectional view of  FIG. 1 (B) along line  44 .  
         [0019]      FIG. 5  is a cross-sectional view, of the other embodiment of the lawn mower according to the present invention, which is equivalent to  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     A preferred embodiment of the present invention is explained with figures.  
         [0021]     However, the scope of the invention is not limited by the illustrated embodiments of the figures.  
         [0022]     A lawn niower shown in FIGS.  1 (A) and  1 (B), which is the arm coupling type, comprises an operation ann  10  as a main body, a driven shaft  11  rotatably provided inside the operation arm  10  as shown in FIG,  2 , a discoid metal cutter  13  installed on the driven shaft  11  at one end of the operation arm  10 , an arm side joint case  16  provided at the other end of the operation arm  10  with a large diameter than the operation arm  10  and either one of an engine  17  and an electic motor  18  selectively installed on the operation arm  10  through the joint case  16 . The operation arm  10  is formed of a hollow shaft. A holder  12  is attached to the one end of the operation arm  10 . The metal cutter  13  has a plurality of saw-edged cutting tooth on its outer peripheral and is rotatably attached to the holder  12 . The cutter  13  is connected to the end of the driven shaft  11  through a pair of bevel gears (not shown). The operation arm  10  has a cover  14  at its end to partially cover the cutter  13  so that the safety of work is secured. In addition, the cutter  13  may be replaced by a cutter composed of one or more strings extending radially from the center of rotation  
         [0023]     Two handles  15  are installed on a center part of the operation arm  10  so that the user can work on mowing grass by grpping the handles  15  with both hands. In place of the two-handed type handles  15  as shown in FIGS.  1 (A) and  1 (B), a looped type handle may be used. Furthermore, a loop-like belt can be attached to the operation arm  10  for shoulder carrying the mower.  
         [0024]     The arm side joint case  16 , as a main body side joint case, is provided on the opposite end of the operation arm  10  from the cutter  13 . The arm side joint case  16  is constructed by a cylindrical member of a large diameter than the operation arm  10 . Either an engine  17  as shown in  FIG. 1 (A) or an electric motor  1 S as shown in  FIG. 1 (B) is selectively attached to the operation arm  10  through the arm side joint case  16 . The electric motor  18  has a power supply cable  20  with an electrical plug  19  which is inserted into the power supply outlet so as to supply electric power to the electric motor  18 . Otherwise, a battery may be used as the power supply instead of the commercial power supply. By using the battery as the power supply, the lawn mower can be quietly driven by the motor in the outdoors with no power supply outlet.  
         [0025]     The engine  17  is a single cylinder 4-stroke cycles engine. Inside of an engine cover  21 , there are engine coxnponents such as a crankcase for rotatably supporting an engine output shaft  22  connected to a crankshaft shown in  FIG. 2 , and a cylinder in which a piston tavels reciprocally is provided in the crankcase. Also, the engine  17  is equipped with a fuiel tank  23  storing fuel of gasoline. A cooling fan  24  generating engine cooling air is installed on the output shaft  22 . The cooling fan  24  comprises a disk  25  connected to the output shaft  22  and a plurality of fan blades  26  fixed to the disk  25 . Further, the engine  17  is equipped with a recoil starter for turning the output shaft  22  manually so that the engine  17  can be started by pulling a recoil knob  27  as shown in  FIG. 1 (A).  
         [0026]     An engine side joint case  28 , as a power source side joint case, which can be attached to and removed from the arm side joint case  16 , is provided on the engine cover  21 . As shown in  FIG. 2 , this engine side joint case  28  is partly fitted to the arm side joint case  16 . On the outer surface of the arm side joint case  16 , one end of a link  32  is swingably connected to a supporting point  31  of the outer surface of the arm side joint case  16  and the other end of the link  32  is swingably connected to a middle portion of a tightening lever  33 . A detent projection  34  is provided at one end of the tightening lever  33  as a fastener member, so as to be selectively engaged with a projection  29  formed on the engine side joint case  28 . When the tightening lever  33  is pushed down to the arm side joint case  16  after engaging the detent projection  34  with the projection  29 , the tightening lever  33  tightly couples the joint case  16  of the operation arm  10  and the joint case  28  of the engine  17 .  
         [0027]     In addition, regarding the fastener member, it is not limited to the structure shown in  FIG. 2 . For example, bolts can be used to couple the joint cases  16  and  28  of the operation arn  10  and the engine  17 . Furthermore, a connecting sleeve is rotatably attached to the outside of the arm side joint case  16 , and the engine side joint case  28  may be provided with a male screw to be coupled with a female screw which is provided inside the connect sleeve so that the operation arm  10  and the engine  17  can be screwed.  
         [0028]     The arm side joint case  16 , which is formed of a cylindrical member, incorporates a centrifugal clutch  35  inside. This centrifugal clutch  35  comprises a clutch drum  36  fixed to the driven shaft  11  and a clutch input shaft  38  rotatably supported by a supporting wall  37 . As shown in  FIG. 3 , a plurality of pivot members  42  are rotatably supported by a pin  41  on a rotor plate  39  fixed to the clutch input shaft  38 . Spring force of an extension spring  43  is applied to each pivot member  42  so as to leave a frictional contact region  44  of the pivot member  42  from an internal surface of the clutch drum  36 . Thus, when the rotational speed of the clutch input shaft  38  increases, the centrifugal force applied to the pivot members  42  moves the pivot members  42  toward the internal surface of the clutch drum  36  against the spring force of the extension springs  43 , whereby the clutch input shaft  38  and the driven shaft  11  are connected through the pivot members  42 . On the other hand, when the engine  17  is started by pulling the recoil knob  27 , the centrifugal clutch  35  has not been engaged so that the recoil knob  27  can be pulled without a big resistance being applied.  
         [0029]     An engaging groove  45  is provided across the end of the clutch input shaft  38  of the centriflgal clutch  35  in a diametrical direction An engaging projection  46  to be engaged with the engaging groove  45  is provided on the side of the disk  25  of the cooling fan  24  opposite to the fan blades  26 . Thus, the driven shaft  11  and the engine output shaft  22  are coupled through the centrifugal clutch  35  with the engagement of the engaging groove  45  and the engaging projection  46 . In addition, it is also suggested that the engaging groove and the engaging projection can be provided vice versa  
         [0030]     As shown in  FIG. 2 , in order to attach the engine  17  to the operation arm  10 , first the engaging groove  45  and engaging projection  46  are engaged each other, then the engine side joint case  28  of the engine cover  21  is fitted to the arm side joint case  16  of the operation arm  10 , and fially the tightening lever  33  as the fastenmg member is manipulated to tighten the joint cases  16  and  28 . According to this structure, the lawn mower drives the cutter  13  by the driving force of the engine  17  so that grass can be mowed.  
         [0031]     As shown in  FIG. 1 (B), the electric motor  18  has motor cover  47  shown in  FIG. 4 , a cylindrical motor side joint case  48 , as the power source side joint case, which is the same size as the engine side joint case  28  is attached to this motor cover  47 . The mnotor side joint case  48  has a projection  49  with which a detent projection  34  of a tightening lever  33  installed in the arm side joint case  16  is adapted to engage. An engaging projection  51  is provided on the end of a motor output shaft  50  so as to engage with the engaging groove  45  provided across the end of the clutch input shaft  38 . According to this structure, the driven shaft  11  and the motor output shaft  50  are coupled through the centrifugal clutch  35  with the engagement of the engaging groove  45  and the engaging projection  46 .  
         [0032]     Thus, as shown in  FIG. 4 , in order to attach the electric motor  18  to the operation arm  10 , first the engaging groove  45  and the engaging projection  51  are engaged each other, then the motor side joint case  48  of the motor cover  47  is fitted to the arm side joint case  16  of the operation arm I 0 , and finally the tightening lever  33  as the fastening member is manipulated to tighten the joint cases  16  and  48 . According to this structure, the lawn mower drives the cutter  13  by the driving power of the electric motor  18  so that grass can be mowed.  
         [0033]     According to the above disclosure, the user can selectively install either one of the engine  17  and the electric motor  18  on the operation arm  10  with the preparation of both the engine  17  and the electric motor  18  as attachments to a lawn mower. That is, the lawn mower can be used as whichever with an engine drive type and a motor drive type on the basis of the mowing environment For example, the engine  17  would be used as the power source in the situation where there is no power supply outlet or at the place where silence is not required. On the other hands, the electric motor  18  would be used as the power source in the situation where there is a power supply outlet. That is, the user can select either the engine  17  or the electric motor  18  as the power source based on the working environment. In addition, even if the user has purchased the lawn mower comprising the operation arm  10  and the engine  17  as a set, the lawn mower can be changed to the electric motor operation by purchasing the electric motor  18 , additionally.  
         [0034]      FIG. 5  is a sectional view of a second embodiment of the lawn mower of the present invention. This view shows the same portion as  FIG. 2 . In this lawn mower, the centrifugal clutch  35  is incorporated inside the joint case  28  of the engine cover  21 . A large-diameter flange  52  having the engaging groove  45  is provided on the end of the driven shaft  11 . And, a large-diameter flange  54  having the engaging projection  46  is provided on the end of a clutch output shaft  53  secured to the clutch drum  36  of the centrifugal clutch  35 . The engaging projection  46  is adopted to couple with the engaging groove  45 .  
         [0035]     In this embodiment, the motor output shaft  50  of the electric motor  18  is coupled with a large diameter flange  52  of the driven shaft  11  directly. Furthermore, the centrifugal clutch  35  may be installed to the extent of the operation arm  10  or may be installed inside the engine  17 .  
         [0036]     The present invention is not limited by the abovedescribed preferred embodiment; it can be changed in various ways in the range that does not deviate from the subject matter. For example, this invention can be applied to such a lawn mower that the power source and the cutter are installed on a carriage.