Riding lawn mower

A riding lawn mower includes: a delivery passage for delivering cut grass from a housing to a receptacle; and a shutter mechanism provided on a lower portion of the delivery passage for switching the mower between a bagging mode in which cut grass is delivered from the housing to the receptacle and a mulching mode in which cut grass is discharged downward of the housing. The shutter mechanism includes a horizontal pivot shaft disposed on the lower portion of the delivery passage, and a shutter plate pivotable about the pivot shaft between a fully closed position where the shutter plate closes the delivery passage to place the mower in the mulching mode and a fully opened position where the shutter plate is laid down toward a discharge side of the delivery passage to place the mower in the bagging mode.

FIELD OF THE INVENTION

The present invention relates to an improvement of riding lawn mowers which include a shutter mechanism for switching between a bagging mode and a mulching mode.

BACKGROUND OF THE INVENTION

Among the conventionally-known riding lawn mowers is the so-called rotary lawn mower which cuts grass by rotating a cutting blade, accommodated in a downwardly-opening housing, along the surface of grass. Examples of such a rotary lawn mower include a type for use in a mulching mode and a type for use in a bagging mode. The lawn mower for use in the bagging mode collects grass cut by the cutting blade (i.e., cut grass or grass clippings) in a grass clippings receptacle, while the lawn mower for use in the mulching mode chops the grass clippings into finer pieces within the housing and discharges the thus-chopped glass clippings downward of the housing.

However, it is often inconvenient to use such two types of lawn mowers depending on intended purposes. So, recent years have seen development of a technique for allowing a single riding lawn mower to be used in both of the bagging and mulching modes. More specifically, such a riding lawn mower operable in both of the bagging and mulching modes is manually switchable between the bagging mode in which a shutter plate is placed in a fully opened position to allow grass clippings to be collected in the grass clippings receptacle and the mulching mode in which the shutter plate is placed in a fully closed position to allow glass clippings to be discharged downward of the housing.

A similar technique to the aforementioned is known from Japanese Patent Application Laid-Open Publication No. SHO-63-063306 (hereinafter referred to as “Patent Literature 1”), Japanese Patent Application Laid-open Publication No. 2000-050716 (hereinafter referred to as “Patent Literature 2”) and Japanese Patent No. 3418136. More specifically, from Patent Literatures 1 to 3, a riding lawn mower is known, in which a path for delivering grass clippings from the housing to the grass clippings receptacle is controlled via a shutter mechanism so as to discharge the grass clippings onto the ground surface.

The riding lawn mower known from Patent Literatures 1 to 3 includes the shutter mechanism provided on a grass clippings delivery passage over which grass cut by the cutting blade (i.e., grass clippings) is delivered from the housing to the grass clippings receptacle. The shutter mechanism includes a horizontal pivot shaft (hinge shaft) disposed on a lower portion of the grass clippings delivery passage, and the shutter plate pivotable about the pivot shaft for opening and closing the grass clippings delivery passage. More specifically, the shutter plate is pivotable between a fully closed position where it closes the grass clippings delivery passage and a fully opened position where it is laid down toward an entrance of the grass clippings delivery passage for opening the grass clippings delivery passage. Namely, the shutter mechanism employed in the riding lawn mower disclosed in Patent Literatures 1 to 3 is of a rear hinge type where the pivot point of the shutter plate is located at a rear portion of the shutter plate. In the so-called rear-hinge-type shutter mechanism, the shutter plate in the fully opened position is laid down in a direction opposite from a direction where grass clippings and delivering air flow from the housing to the grass clippings receptacle.

The delivering air for delivering grass clippings from the housing to the grass clippings receptacle flows along the grass clippings delivery passage. Such grass clippings delivering air differs in velocity or force (i.e., kinetic energy of the delivering air) between when the lawn mower is in the middle of a grass cutting operation and when the lawn mower is starting or stopping the grass cutting operation. More specifically, the force of the grass clippings delivering air when the lawn mower is starting or stopping the grass cutting operation is smaller than that when the lawn mower is in the middle of the grass cutting operation. When the force of the grass clippings delivering air is small, the grass clippings would fall onto the bottom surface of the grass clippings delivery passage halfway through the delivery. Particularly, a lot of heavy grass clippings (e.g., grass clippings containing much moisture content) would accumulate on the bottom surface of the grass clippings delivery passage. Generally, the shutter mechanism has a stepped section on or near the hinge section, and grass clippings would easily accumulate on the stepped section.

In the rear-hinge-type shutter mechanism, dispensing with the stepped section is one conceivable approach to avoid the aforementioned problem. Such an approach, however, is not advisable in that not only the shutter mechanism would become complicated in construction but also there would arise a need to greatly change the shape of the grass clippings delivery passage. Generally, because grass clippings delivering air of a relatively great pressure is generated when the operation of the lawn mower has been started again, it has been conventional to use such grass clippings delivering air of a relatively great pressure to blow away, to some extent, the grass clippings accumulated on the bottom surface of the grass clippings delivery passage.

However, in the rear-hinge-type shutter mechanism, the grass clippings delivering air flowing along the delivery passage would decrease in force at and around the hinge section. Thus, grass clippings falling on the bottom surface of the delivery passage would still accumulate on the stepped section formed on the hinge section. Besides, it is difficult for the grass clippings delivering air to reach a neighborhood behind the hinge section. Substances deposited on the neighborhood behind the hinge section may often remain deposited because the blowing-away force of the grass clippings delivering air applied to that neighborhood is weak. Besides, it is preferable to minimize the frequency of maintenance/inspection and cleaning operations to be performed on the shutter mechanism.

SUMMARY OF THE INVENTION

In view of the foregoing prior art problems, it is an object of the present invention to provide an improved technique which can minimize jamming of grass clippings in the shutter mechanism and thereby minimize the frequency of maintenance/inspection and cleaning operations to be performed on the shutter mechanism.

In order to accomplish the above-mentioned object, the present invention provides an improved riding lawn mower, which comprises: a housing opening downward and having a cutting blade accommodated therein; a cut grass receptacle disposed rearward of the housing; a cut grass (grass clippings) delivery passage for delivering grass, cut by the cutting blade, from the housing to the cut grass receptacle; and a shutter mechanism provided on a lower portion of the cut grass delivery passage for switching the lawn mower between a bagging mode in which grass cut by the cutting blade is delivered from the housing to the cut grass receptacle and a mulching mode in which grass cut by the cutting blade is discharged downward of the housing, the shutter mechanism including a horizontal pivot shaft disposed on the lower portion of the cut grass delivery passage, and a shutter plate pivotable about the pivot shaft between a fully closed position where the shutter plate closes the cut grass delivery passage in order to execute the mulching mode and a fully opened position where the shutter plate is laid down toward a discharge side of the cut grass delivery passage in order to execute the bagging mode.

According to the present invention, the shutter mechanism for switching the lawn mower between the bagging mode and the mulching mode includes the horizontal pivot shaft (or hinge shaft) disposed on the lower portion of the cut grass delivery passage, and the shutter plate pivotable about the pivot shaft for opening or closing the cut grass delivery passage. More specifically, the shutter plate is pivotable about the pivot shaft between the fully closed position where the shutter plate closes the cut grass delivery passage to execute the mulching mode and the fully opened position where the shutter plate is laid down toward the discharge side of the cut grass delivery passage to execute the bagging mode. The shutter mechanism employed in the present invention is of a so-called front hinge type where the pivot point of the shutter plate is disposed on a front portion of the shutter plate. Thus, in the fully opened position, the shutter plate is laid down in a direction along which cut grass delivering air and cut grass (grass clippings) flow from the housing to the cut grass delivery passage.

Because the shutter mechanism is of such a front hinge type, a hinge section and other component parts around the hinge section are located near an entrance of the cut grass delivery passage. Because the entrance of the cut grass delivery passage is connected to the housing, the cut grass delivering air has a relatively great force in the neighborhood of the entrance, so that grass clippings are less likely to fall on and around the hinge section. Further, even in case grass clippings have fallen and accumulated on and around the hinge section, they can be easily blown away by the cur grass delivering air. Thus, it is possible to effectively prevent unwanted jamming of grass clippings in the shutter mechanism, particularly in the hinge section, as a result of which the present invention can minimize the frequency of maintenance/inspection and cleaning operations to be performed on the shutter mechanism.

Preferably, the riding lawn mower of the present invention further comprises an operation section operable to switch the shutter plate between the fully closed position and the fully opened position, and the operation section is disposed away from the shutter mechanism. The shutter mechanism is constructed as a single unit integrally including: a base mounted on a lower portion of the cut grass delivery passage; the pivot shaft and the shutter plate assembled to the base; and an operating force transmission section for transmitting opening/closing operation force, given via the operation section, to the shutter plate. Because the shutter mechanism is a unitized mechanism (i.e., constructed as a single unit), it can be detachably attached together as the unit to the cut grass delivery passage. Thus, at the time of maintenance/inspection or cleaning operations, the shutter mechanism can be easily and simply detached and attached from and to the cut grass delivery passage. As a result, the maintenance/inspection and cleaning operations can be performed with ease on the shutter mechanism and the interior of the cut grass delivery passage.

Further, preferably, the pivot shaft and the shutter plate are disposed with a space from the bottom surface of the cut grass delivery passage. As the cutting blade stops rotating, the cut grass delivering air stops being generated, and thus, grass clippings would fall and accumulate on the bottom surface of the cut grass delivery passage and on and around the hinge section. However, by the provision of the above-mentioned space in the present invention, grass clippings are less likely to accumulate on the pivot shaft and the shutter plate and jam in the shutter mechanism.

Preferably, the riding lawn mower of the present invention further comprises a scroll guide provided in an entrance of the cut grass delivery passage for directing the cut grass and cut grass delivering air to the cut grass delivery passage while swirling the cut grass and the cut grass delivering air within the housing, and the scroll guide has, at the rear end thereof, a downwardly-recessed stepped section for accommodating therein the pivot shaft of the shutter mechanism. Thus, when the shutter plate is in the fully opened position where it is laid down toward the discharge side (output side) of the grass clippings delivery passage, the hinge section does not project into the grass clippings delivery passage. Namely, the shutter mechanism has no stepped section in and around the hinge section. Thus, even when grass cuttings have fallen on the bottom surface of the cut grass delivery passage, they do not accumulate on the bottom surface because they can be easily blown away by the cut grass delivering air. Thus, it is possible to effectively prevent jamming of grass clippings in the hinge section, as a result of which the present invention can even further minimize the frequency of maintenance/inspection and cleaning operations. Besides, because the shutter mechanism has no stepped section in and around the hinge section, any particular construction is not required to eliminate a stepped section from the hinge section.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, the terms “front”, “rear”, “left”, “right”, “upward”, “downward” etc. are used to refer to directions as viewed from a human operator of a riding lawn mower of the present invention.

Now, a description will be given about an embodiment of the riding lawn mower10of the present invention. As shown inFIGS. 1 and 2, the riding lawn mower10is a working machine of a type in which the human operator rides on a seat11and drives a grass cutting system while running the lawn mower10by means of a single power source12.

The power source12is, for example, in the form of an electric motor and provided on a front upper section of a machine frame13(vehicle body frame13) of the lawn mower10. The machine frame13has left and right front wheels14provided on left and right sides of a front section thereof and left and right rear wheels15provided on left and right sides of a rear section thereof. The left and right front wheels14are steered via a steering wheel16provided on a front section of the machine frame13, and the left and right rear wheels15are driven via the power source12.

As shown inFIGS. 2 to 5, the lawn mower10includes a housing20, a grass clippings delivery passage (cut grass delivery passage)22, left and right cutting blades31L and31R, left and right auxiliary fans40L and40R, a grass clippings receptacle (cut grass receptacle)51, and a chute52.

The housing20is disposed centrally on the underside of the machine frame13. As shown inFIGS. 3 to 5, the housing20is formed generally in a laterally-oriented “8” shape as viewed in top plan for accommodating therein left and right cutting blades31L and31R, and is open downwardly at its lower side.

Further, the housing20is formed in left-right symmetry respect to a centerline CL extending across the width of the housing20(i.e., widthwise centerline CL), and it includes a left-half housing section21L and a right-half housing section21R and a grass clippings delivery passage22extending along the widthwise centerline CL. The left-half housing section21L accommodates therein the left cutting blade31L and the left auxiliary fan40L, while the right-half housing section21R accommodates therein the right cutting blade31R and the right auxiliary fan40R.

Further, as viewed in top plan as inFIGS. 3,5and6, the left-half housing section21L has a scroll portion23L gradually protruding upward while winding spirally in a clockwise direction, and the right-half housing section21R has a scroll portion23R gradually protruding upward while winding spirally in a counterclockwise direction. Namely, the left-half housing section21L and the right-half housing section21R of the housing20are spiral cases or scroll cases which include the scroll portions23L and23R, respectively, for delivering grass cut by the left and right cutting blades31L and31R (grass clippings) toward the grass clippings delivery passage (cut grass delivery passage)22while swirling the grass clippings.

The grass clippings delivery passage (cut grass delivery passage)22is a passage for delivering the grass, cut by the left and right cutting blades31L and31R, from a position on the widthwise center CL to the grass clippings receptacle51via the chute52by use of grass clippings delivering air (cut grass delivering air), and it is formed in a generally rectangular sectional shape. More specifically, an entrance22aof the grass clippings delivery passage22is open, along the widthwise centerline CL, from a front portion20cto a rear portion20dof the inner peripheral surface20eof the housing20. Further, the grass clippings delivery passage22extends upwardly and rearwardly from the upper spirally-winding ends of the left and right scroll portions23L and23R and has, at its rear end, an exit22b(discharge outlet22b) connected to the chute52.

The grass clippings receptacle51is provided on a rear section of the machine frame13behind the housing20. The chute52connects from the exit22bat the rear end of the grass clippings delivery passage22to the grass clippings receptacle51. The chute52may be dispensed with as desired, in which case the exit22bof the grass clippings delivery passage22may be connected directly to the grass clippings receptacle51.

Further, as shown inFIGS. 5 and 6, the left and right cutting blades31L and31R are accommodated within the housing20and rotatable in generally the same plane. More specifically, the housing20rotatably supports, via bearings33L and33R, a pair of left and right drive shafts32L and32R disposed vertically along respective vertical centerlines HL and HR of the left- and right-half housing sections21L and21R. Power of the drive source13(FIG. 1) is transmitted to the left and right drive shafts32L and32R via a transmission member, such as a belt. Within the housing20, the two drive shafts32L and32R have the left and right cutting blades31L and31R mounted separately on their respective distal end portions.

Further, the left and right cutting blades31L and31R are disposed with a 90° phase difference from each other. The left cutting blade31L rotates in a counterclockwise direction (i.e., direction of arrow Ru) ofFIG. 6while the right cutting blade31R rotates in a clockwise direction (i.e., direction of arrow Rc) ofFIG. 6, as viewed in bottom plan.

The left cutting blade31L, which is an elongated blade formed in left-right symmetry with respect to the left drive shaft32L, has blade sections31aat its front edges in the rotational direction Ru and air lift sections31bat its rear edges in the rotational direction Ru. By the left cutting blade31L rotating in the rotational direction Ru, the blade sections31acan cut grass, and the air lift sections31bcan generate a flow of swirling air, i.e. swirling air flow Ws (or grass clippings delivering air Ws), in the left scroll portion23L.

Similarly to the left cutting blade31L, the right cutting flow31R has blade sections31aand air lift sections31b, and the air lift sections31bof the right cutting flow31R can generate a flow of swirling air, i.e. swirling air flow Ws (grass clippings delivering air Ws), in the right scroll portion23R.

The left and right auxiliary fans40L and40R are provided to increase the amount of the grass clippings delivering air Ws generated by the left and right cutting blades31L and31R and are disposed immediately over corresponding ones of the left and right cutting blades31L and31R within the housing20.

More specifically, the left auxiliary fan40L is disposed immediately over the left cutting blade31L within the left-half housing section21L and includes a fan rotor41. The fan rotor41includes a multiplicity of blades and is mounted on the left drive shaft32L. By rotating in the direction of arrow Ru, the left auxiliary fan40L absorbs external air through an air intake port42of the left-half housing section21L and emits auxiliary grass clippings delivering air Wa.

The right auxiliary fan40R, which is constructed similarly to the left auxiliary fan40L, is disposed immediately over the right cutting blade31RL within the right-half housing section21R and includes a fan rotor41. By rotating in the direction of arrow Rc, the right auxiliary fan40R absorbs external air through an air intake port42of the right-half housing section21R and emits auxiliary grass clippings delivering air Wa.

As shown inFIGS. 4 and 6, the housing20includes a delivering air guide section24disposed in the front portion20cof the inner peripheral surface2eand along the widthwise centerline CL. The delivering air guide section24is formed in a generally V shape tapering from a front portion20bof the inner surface20aof the housing20toward the entrance22aof the glass clippings delivery passage22as viewed in top plan, so as to direct auxiliary grass clippings delivering air Wa, emitted from the left and right auxiliary fans40L and40R, to the entrance22aof the grass clippings delivery passage22.

Grass clippings can be delivered to the grass clippings receptacle51by composite grass clippings delivering air Wt comprising grass clippings main delivering air Ws generated by rotation of the left and right cutting blades31L and31R and auxiliary grass clippings delivering air Wa generated by the left and right auxiliary fans40L and40R. Note that the left and right auxiliary fans40L and40R may be dispensed with as desired. Thus, the term “grass clippings delivering air Wt” may sometimes refer to only the main grass clippings delivering air Ws.

Further, as shown inFIG. 4, the grass clippings delivery passage22includes a bottom plate22chaving a flat surface slanting obliquely rearwardly and upwardly from a rear end portion of the housing20. The front end of the bottom plate22cis located in the entrance22aof the grass clippings delivery passage22. A scroll guide60and a shutter mechanism80are provided in the entrance22aof the grass clippings delivery passage22.

Further, as shown inFIGS. 3 and 4, the scroll guide60is a member for directing both grass cut by the left and right cutting blades31L and31R (grass clippings) and grass clippings delivering air to the grass clippings delivery passage22while swirling the grass clippings and the delivering air within the housing20. The scroll guide60is disposed along the widthwise centerline CL of the housing and in left-right symmetry with respect to the widthwise centerline CL. The scroll guide60is an integrally molded component that includes a base section61located in the entrance22aof the grass clippings delivery passage22and a guide body71extending forward from the base section61in a forward tapered shape.

Further, as shown inFIGS. 4,7and8, the base section61of the scroll guide60has a flat bottom surface62superposed on the bottom plate22cof the grass clippings delivery passage22. A nut63is embedded in the bottom surface62of the base section61. The base section61is fastened at the bottom surface62to the bottom plate22cof the grass clippings delivery passage22by means of the nut63and a bolt64. Thus, the scroll guide60is detachably attached to the bottom plate22cof the grass clippings delivery passage22.

The guide body71has an upper surface72slanting generally along the slant of the entrance22aof the grass clippings delivery passage22. An inclination angle of the upper surface72relative to the lower surface20aof the housing20is set such that the grass clippings delivering air can be smoothly introduced from the housing20to the grass clippings delivery passage22. For example, the inclination angle of the upper surface72is set such that the upper surface72extends substantially parallel to a top plate22dof the grass clippings delivery passage22slanting rearwardly and upwardly. Further, as shown inFIGS. 3 and 6, left and right side surfaces73L and73R are formed in a curved tapered shape generally along the inner surfaces of the left-half housing section21L and right-half housing section21R.

The following describe in detail, with reference toFIGS. 4,7,9and10, the scroll guide61. An overall shape of the scroll guide60as viewed in top plan is a substantial isosceles triangle extending into the housing20while tapering forward from the base section61(i.e., from the base section61toward the front of the lawn mower10). Further, an overall shape of the scroll guide60as viewed laterally in side elevation is a substantial triangle tapering forward from the base section61. Namely, the guide body71is formed in a substantial isosceles triangle as viewed in top plan and in a substantial triangle as viewed laterally in side elevation.

The left and right side surfaces73L and73R of the scroll guide60, i.e. the left and right side surfaces73L and73R of the guide body71, respectively comprise left and right lower slanting surfaces75and left and right upper slanting surfaces76below and above left and right substantial vertically-middle portions74. The “substantial vertically-middle portions74” are height portions near the distal end77of the guide body71.

The left and right lower slanting surfaces75and the left and right upper slanting surfaces76are each shaped to gradually increase in area in a direction from the distal end77of the scroll guide60, i.e. the distal end77of the guide body71, toward the base section61. The scroll guide60is constructed as follows.

Namely, with the scroll guide60attached to the grass clippings delivery passage22, the left and right lower slanting surfaces75extend generally normal to the lower surface20a(FIG. 4) and have curved surface portions arcuately recessed from the distal end77of the scroll guide60toward the base section61.

Further, the left and right upper slanting surfaces76slant upwardly from the distal end77of the scroll guide60toward the base section61. More specifically, the left and right upper slanting surfaces76have curved surface portions arcuately recessed toward the base section61while slanting upward from the distal end77of the scroll guide60toward the base section61.

The above-mentioned curved surface portions of the slanting surfaces75and76are each recessed toward the widthwise centerline CL in a generally arcuate shape corresponding to a rotating trajectory of a corresponding one of the left and right cutting blades31L and31R. Thus, in the mulching mode, it is possible to reduce a quantity of grass clippings, swirling within the housing20, falling downward (i.e., fall-down quantity of grass clippings), and thereby enhance the so-called grass retaining characteristic or performance.

As apparent from the foregoing, the scroll guide60projects forward from the base section61in a substantial isosceles triangle as viewed in top plan and in a substantial triangle as viewed laterally in side elevation. Therefore, when the lawn mower10is in the mulching mode, it is possible to prevent grass clippings, swirling within the housing20, from falling down onto undesired portions.

Namely, in the mulching mode, the left and right lower slanting surfaces75extend generally normal to the lower surface20aof the housing20in order to adjust the fall-down quantity of the grass clippings swirling within the housing20. Thus, in the mulching mode, the grass clippings swirling within the housing20can be caused to smoothly swirl by means of the left and right side surfaces73L and73R as well.

The left and right upper slanting surfaces76, on the other hand, slant upward from the distal end77of the scroll guide60toward the base section61. Namely, the left and right upper slanting surfaces76are twisted surfaces relative to the upper ends of the left and right lower slanting surfaces75. More specifically, the left and right upper slanting surfaces76formed as twisted surfaces in order to achieve both (1) enhancement of a grass delivery efficiency with which to discharge grass clippings from the housing20to the grass clippings delivery passage22in the bagging mode and (2) enhancement of the so-called grass retaining characteristic with which to adjust the fall-down quantity of the grass clippings swirling within the housing20in the mulching mode.

In the aforementioned manner, the instant embodiment of the lawn mower10can achieve an enhanced grass delivery efficiency in the bagging mode and an enhanced grass retaining characteristic in the mulching mode.

Of the base section61of the scroll guide60, surfaces65facing radially inward of the housing20, i.e. inwardly facing surfaces65, are shaped to extend along the circular inner peripheral surface20e(FIG. 10). The inwardly facing surfaces65are formed continuously or integrally with proximal end portions of the left and right side surfaces73L and73R, so that grass clippings are allowed to swirl even more smoothly within the housing20.

Further, of the scroll guide60, the lower surfaces78(inner bottom surfaces78) located within the housing20, more specifically at least rear half portions78rof the lower surfaces78of the guide body71, slant toward the base section61. More specifically, the lower surfaces78of the guide body71each include the rear half portion78radjacent to the base section61and a front half portion78flocated forward of the rear half portion78r. The front half portion78fextends substantially parallel to the lower surface20aof the housing20and located higher than the lower end66of the base section61. The rear half portion78rcurvingly slants rearwardly and downwardly from the rear end of the front half portion78fto the lower end66of the base section61.

Because at least the rear half portions78rof the lower surfaces78of the guide body71slant downward the lower end66of the base section61, a swirling current fo (air current fo) within the housing20is insusceptible to swirling resistance. Thus, grass clippings swirling within the housing20can smoothly swirl without meeting swirling resistance from the lower surface78of the scroll guide60.

Further, as shown inFIGS. 4,5and11, the distal end31cof each of the left and right cutting blades31L and31R (i.e., upper end31cof the air lift section) is located higher by a height Hi than the distal end77of the scroll guide60. Thus, grass clippings swirling within the housing20is less likely to be subjected to resistance by the distal end77of the scroll guide60, so that grass retaining performance or characteristic can be enhanced.

Further, in this case, turbulence is less likely to occur in a swirling flow Fo as compared to a case where no height difference is provided between the distal end31cof the left and right cutting blades31L and31R and the distal end77of the scroll guide60. Besides, a rising air current is generated by the air lift sections31bwithin the housing20as the left and right cutting blades31L and31R rotate. Namely, negative pressure is generated over the left and right cutting blades31L and31R, so that grass gr (FIG. 11) growing on the ground surface becomes easier to stand up by virtue of the negative pressure. Thus, the grass gr can be cut or clipped with an increased reliability, leaving fewer grass gr undesirably uncut. As a result, enhanced grass cutting performance can be achieved.

The following describe, with reference toFIGS. 4,7,12and13, the shutter mechanism80. The shutter mechanism80is an opening/closing mechanism which is detachably mounted on a lower portion of the grass clippings delivery passage22, and the shutter mechanism80is capable of opening and closing the grass clippings delivery passage22. More specifically, the shutter mechanism80is located immediately behind or rearward of the scroll guide60, i.e. adjacent to the rear end of the scroll guide60. The shutter mechanism80is constructed as a single unit that includes a base81, pivot shaft82, a shutter plate83and an operating force transmission section84as shown inFIG. 12.

The base81is a member mounted on a lower portion of the grass clippings delivery passage22and comprises left and right base halves91L and91R separable from each other in a width direction of the base81. In a front view of the shutter mechanism80, the left and right base halves91L and91R are each of a substantially L shape, and the substantially L shapes of the right base halves91L and91R are horizontally opposed to each other. Each of the left and right base halves91L or91R is a member formed by bending a steel plate and has a horizontal plate portion92elongated in the width direction of the base81, a flange portion93extending downward from the inner end, in the width direction, of the horizontal plate portion92and opposed to the flange portion93of the other base halve, and a vertical plate portion94extending upward from the outer end, in the width direction, of the horizontal plate portion92and opposed to the vertical plate portion94of the other base halve91R or91L. The base81is assembled together by the flange portions93of the left and right base halves91L and91R being superposed on each other and fastened together by means of a bolt95.

Preferably, the pivot shaft82comprises a pair of horizontal shaft members82disposed on a lower portion of the grass clippings delivery passage22and pivotably supported at its opposite end portions by the vertical plates94of the left and right base halves91L and91R. The pivot shaft members82are provided on opposite lower end portions of the shutter plate83.

The shutter plate83is a flat plate-shaped member pivotable about the pivot shaft82for opening or closing the grass clippings delivery passage22. Namely, the shutter plate83is pivotable between a fully closed position P1for closing the grass clippings delivery passage22to execute the mulching mode and a fully opened position P2where it is laid down toward the discharge side of the grass clippings delivery passage22to execute the bagging mode. The shutter plate83is operable between the fully closed position P1and the fully opened position P2via an operation section110(FIG. 1) located remote from the shutter mechanism80.

The operating force transmission section84is a mechanism for transmitting opening/closing operation force, given via the operation section110, to the shutter plate83. The operating force transmission section84includes: a pivot arm101mounted on one of the pivot shaft members82for limited relative pivoting movement; a return spring102normally urging the shutter plate83toward the opened position; and an engagement section103that hooks one end of the return spring102.

The swing arm101is a plate-shaped bar that, when the shutter mechanism80is assembled, is mounted on the one pivot shaft82to extend in opposite direction from the pivot shaft82. The other end of the return spring102is hooked by one end portion of the swing arm101. Further, an inner wire104aof a wire cable104is connected at one end portion to another end portion of the pivot arm101, and an outer tube104bcovering the inner tube104ais fixed at one end portion to a fastening portion103aof the engagement section103.

The return spring102is in the form of a tension spring. The engagement section103is integrally provided on one of the left and right vertical plates94, and the one vertical plate94has a stopper105. The stopper105is a member that defines the fully closed position P2of the shutter plate83, and, in the fully closed position P2of the shutter plate83, the other end portion of the swing arm101is abutted by the stopper105.

Further, as shown inFIG. 7, the pivot shaft82and the shutter plate83are disposed with a space Sp from the bottom plate22c(bottom surface) of the grass clippings delivery passage22. Namely, a height at which the pivot shaft82is supported by the base81is set in such a manner as to form the space Sp.

Further, when the shutter plate83is in the fully opened position, as shown inFIGS. 4 and 7, the shutter plate83extends generally in flush with the upper surface72of the scroll guide60, which allows the grass clippings delivering air to flow smoothly. A downwardly-recessed stepped section68for accommodating therein the pivot shaft82of the shutter mechanism80is formed at the rear end67of the base section61. More specifically, the stepped section68is formed by recessing an upper corner portion of the rear end67in a generally semi-circular shape.

Further, as shown inFIG. 8, the unitized shutter mechanism80is inserted onto the bottom plate22c, for example, from behind the passage, or superposed on the bottom plate22cfrom below or above the bottom plate22c. Then, the unitized shutter mechanism80can be assembled or attached to the grass clippings delivery passage22by the base81being fastened to the bottom plate22cby means of a bolt85. Then, the unitized shutter mechanism80can be disassembled or detached from the grass clippings delivery passage22by the base81being detached from the bottom plate22c. Therefore, a cleaning operation of the shutter mechanism80can be simplified.

Further, as shown inFIG. 1, the operation section110for operating the shutter mechanism80is disposed near the seat11of the riding lawn mower10. Namely, an operating lever115of the operation section110is disposed at a position operable by a hand, e.g. left hand, of the human operator seated in the seat11.

Further, as shown inFIGS. 14 and 15, the operation section110includes: a bracket111fixed to the machine frame13; a first shaft112rotatably supported at opposite ends on the bracket111; a pivot arm113mounted on the first shaft112; a second shaft114mounted at opposite ends on the pivot arm113; the operating lever115pivotably supported on the second shaft114; and a return spring116for normally urging the operating lever115.

The first shaft112is rotatable in a front-rear direction of the machine frame13, so that the pivot arm113is also rotatable in the front-rear direction of the machine frame13. The inner wire104aof the wire cable104is connected at its other end portion to one end portion of the pivot arm113, and the other end portion of the outer tube104bcovering the inner tube104ais fastened to the fastening portion117of the bracket111.

The operating lever115is pivotable relative to the pivot arm113in a direction perpendicular to the first shaft112, i.e. in a width direction (vertical direction inFIG. 14) of the machine frame13. The operating lever115has its proximal end portion covered with a cover119having a generally crank-shaped guide groove18as viewed in top plan. The return spring116is in the form of a torsion spring and normally urges the operating lever115inward in the width direction of the machine frame13.

Usually, the operating lever115is held in a generally upright or stand-up bagging position as shown inFIG. 14. In this state, the shutter plate83shown inFIG. 4is held in the fully opened position P2for fully opening the grass clippings delivery passage22, so that the lawn mower10is allowed to operate in the bagging mode.

Then, as necessary, the operating lever115is shifted forward and downward over to a mulching position Mu while being guided along the crank-shaped guide groove18. At that time, the pivot arm113pivots counterclockwise inFIG. 14to thereby pull the inner wire104a. Thus, the pivot arm101pivots counterclockwise inFIG. 12, so that the shutter plate83pivots counterclockwise inFIG. 12to thereby stand up. In this manner, the shutter plate83stands up to the fully closed position P1as indicated by imaginary line inFIG. 4, to thereby fully close the grass clippings delivery passage22. As a result, the lawn mower10can be switched from the bagging mode to the mulching mode.

Then, as necessary, the operating lever115shown inFIG. 14is shifted rearward and downward over to a bagging position Ba while being guided again along the crank-shaped guide groove18. Thus, the lawn mower10is switched to the bagging mode Ba, and the shutter plate83can be shifted back to the fully opened position P2as indicated by solid line inFIG. 4. As a result, the lawn mower10can be switched from the mulching mode back to the bagging mode.

The description about the shutter mechanism80constructed in the aforementioned manner can be summarized as follows. The shutter mechanism80employed in the instant embodiment is of a so-called front hinge type where the pivot point (pivot shaft82) of the shutter plate83is disposed on a front portion of the shutter plate83. Because the shutter mechanism80is of such a front hinge type, the hinge section (i.e., pivot shaft82and support portions for the pivot shaft members82) of the shutter mechanism80and other component parts around the hinge section are located near the entrance22aof the grass clippings delivery passage22. Because the entrance22ais connected to the housing20, the grass clippings delivering air Wt (Ws) has a relatively great force in the neighborhood of the entrance22a, so that grass clippings are less likely to fall on and around the hinge section. Even in case grass clippings have fallen and accumulated on and around the hinge section, they can be easily blown away by the strong grass clippings delivering air Wt (Ws). Thus, it is possible to effectively prevent unwanted jamming of grass clippings in the shutter mechanism80, particularly in the hinge section, as a result of which the instant embodiment can minimize the frequency of maintenance/inspection and cleaning operations to be performed on the shutter mechanism80.

Further, because the shutter mechanism80is a unitized mechanism (constructed as a single unit), it can be detachably attached together as the unit to the grass clippings delivery passage22. Thus, at the time of maintenance/inspection or cleaning operations, the shutter mechanism80can be easily and simply detached and attached from and to the grass clippings delivery passage22. As a result, maintenance/inspection and cleaning operations can be performed with ease on the shutter mechanism80and the interior of the grass clippings delivery passage22.

Furthermore, the pivot shaft82and the shutter plate83are disposed with the space Sp from the bottom plate22c(bottom surface22c) of the grass clippings delivery passage22. Generally, as the cutting blades31L and31R stop rotating, the grass clippings delivering air Wt (Ws) stops being generated, and thus, grass clippings would fall and accumulate on the bottom surface22cof the grass clippings delivery passage22and on and around the hinge section. However, by the provision of the above-mentioned space Sp, grass clippings are less likely to accumulate on the pivot shaft82and the shutter plate83and jam in the shutter mechanism80.

Furthermore, the downwardly-recessed stepped section68for accommodating therein the pivot shaft82of the shutter mechanism80is formed in the rear end67of the scroll guide60provided in the entrance22aof the grass clippings delivery passage22. Thus, when the shutter plate83is in the fully opened position P2where it is laid down toward the discharge side (output side) of the grass clippings delivery passage22, the hinge section does not project into the grass clippings delivery passage22. Namely, the shutter mechanism80has no stepped section in and around the hinge section. Thus, even when grass cuttings have fallen on the bottom surface22cof the grass clippings delivery passage22, they do not accumulate on the bottom surface22cbecause they can be easily blown away by the grass clippings delivering air Wt (Ws). Thus, it is possible to effectively prevent jamming of grass clippings in the hinge section, as a result of which the instant embodiment can even further minimize the frequency of maintenance/inspection and cleaning operations. Besides, because the shutter mechanism80has no stepped section in and around the hinge section, any particular construction is not required to eliminate a stepped section from the hinge section.

Now, a description will be given about behavior of the scroll guide60in the case where the lawn mower10is used selectively in any desired one of the bagging mode and mulching mode as necessary.

FIG. 16(a) shows flows of grass clippings delivering air and grass clippings in the case where the lawn mower10is used in the bagging mode, andFIG. 16(b) shows flows of grass clippings delivering air and grass clippings as viewed from the entrance22aof the grass clippings delivery passage22.

As shown inFIGS. 6,16(a) and16(b), the grass clippings delivery passage22is kept opened while the lawn mower10is in the bagging mode. Grass cut by the left and right cutting blades31L and31R (i.e., grass clippings) are directed to the upper surface72of the scroll guide60and the shutter plate83while swirling within the housing20and then flow along the grass clippings delivery passage22. Thus, the grass clippings swirling within the housing20can be efficiently delivered to the grass clippings delivery passage22.

FIG. 17(a) shows flows of grass clippings delivering air and grass clippings in the case where the lawn mower10is used in the mulching mode, andFIG. 17(b) shows flows of grass clippings delivering air and grass clippings as viewed from the entrance22aof the grass clippings delivery passage22.

As shown inFIGS. 6,17(a) and17(b), the grass clippings delivery passage22is kept closed while the lawn mower10is in the mulching mode. Grass clippings grc can be discharged downward of the housing20after being sufficiently chopped into finer pieces while swirling within the housing20.

The description about the scroll guide60constructed in the aforementioned manner can be summarized as follows. The left and right side surfaces73L and73R of the scroll guide60respectively comprise the left and right lower slanting surfaces75and the left and right upper slanting surfaces76below and above the left and right substantial vertically-middle portions74. By setting appropriate slant angles of the aforementioned individual slanting surfaces, it is possible to optimize flows of the grass clippings delivering air Wt (Ws) and grass clippings irrespective of whether the lawn mower10is in the mulching mode or in the bagging mode. Thus, grass clippings can be efficiently discharged downward of the housing20in mulching mode, while grass clippings can be efficiently collected in the grass clippings receptacle51in the bagging mode. Besides, when the lawn mower10has been switched from the bagging mode to the mulching mode or from the mulching mode to the bagging mode, there is no need to replace predetermined component parts of the previous or switched-from mode with component parts dedicated to the new or switched-to mode in order to optimize the flows of flows of the grass clippings delivering air Wt (Ws) and grass clippings.

In the mulching mode, the instant embodiment can prevent grass clippings, swirling within the housing20, from undesirably falling down in the neighborhood of the entrance22aof the grass clippings delivery passage22and thus can effectively retain the grass within the housing20(i.e., achieve an enhanced grass retaining characteristic). Therefore, the instant embodiment can discharge the grass clippings downward of the housing20after sufficiently chopping the grass clippings to finer pieces. Further, in the bagging mode, the instant embodiment can efficiently deliver grass clippings, swirling within the housing20, to the grass clippings delivery passage22.

Finally, the basic principles of the present invention are well suited for application to riding lawn mowers each of which includes left and right cutting blades and is capable of operating in both of a bagging mode and a mulching mode.