Front loader with indicator rod

A front loader is provided with an indicator device. The indicator device is configured to indicate that the work implement is in an identical posture irrespective of a height position of the work implement, by aligning a rear end of the indicator rod with a rear end of the guide tube.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a front loader mounted in front of a travelling vehicle.

2. Description of the Related Art

One known example of such a front loader mounted in front of a travelling vehicle is a front loader described in JP 2006-028934 A (or U.S. Pat. No. 7,413,397 B2 corresponding thereto).

The front loader comprises:

a main frame standing erect in front of the travelling vehicle;

a boom having a rear end thereof pivotably supported at an upper portion of the main frame to be vertically movable; and

a work implement pivotably supported at a front end of the boom to effect scooping and dumping operations.

The front loader further comprises an indicator device for indicating that the work implement is in a horizontal posture (e.g. a posture where the bottom surface of the work implement is horizontal) while the work implement is contacted on the ground.

The indicator device has an indicator rod operable in association with the scoop and dumping operation of the work implement; and a guiding device for guiding an intermediate portion of the indicator rod to be movable in an axial direction thereof.

The indicator rod is arranged along a forward portion of the boom on a upper-forward side of the boom; and a front end thereof is pivotably supported by a pivot shaft for pivotably supporting a front end of a work implement cylinder for driving the work implement. In operation, the indicator rod is moved rearward in the axial direction by the scooping operation of the work implement, and is moved forward in the axial direction by the dumping operation of the work implement.

The guiding device is provided at a longitudinal intermediate portion of the boom, and has an insertion portion for receiving the indicator rod so that the indicator rod is movable in the axial direction.

An index portion is provided at the intermediate portion of the indicator. In operation, while the work implement is moved upward away from the ground, the work implement is pivoted to align the index portion of the indicator rod to the insertion portion of the guiding device; and in this state, bringing the work implement into contact with the ground causes the work implement to come into contact with the ground in a horizontal posture.

The indicator device of the conventional front loader indicates that the work implement is in a horizontal posture only when the work implement is in contact with the ground, and does not indicate that the work implement is in the same posture at any height position.

As such, when an operator has to manipulate the work implement while checking the posture of the work implement with his/her own eye in order to place the work implement in the same posture at any height position while operating the boom upward or downward. Therefore, it is difficult to perform a work in which an angle of the work implement is important, such as a work for vertically moving the boom while keeping the posture of the work implement at the same posture (e.g. a horizontal posture), such as a pallet fork work.

Further, the operator recognizes that the work implement is in a horizontal posture while contacted on the ground by visually checking that the index portion of the indicator rod is aligned with the insertion portion of the guiding device. However, with the aforementioned indicator device, since the indicator rod is disposed along the forward portion of the boom at the upper forward portion of the boom and the guiding device for receiving and guiding the indicator rod is provided at the longitudinal intermediate portion of the boom, the visually checking position by the operator is distant from the operator and is difficult to visually observe.

In view of these inconveniences, an object of the present invention is to provide a front loader provided with an indicator device whereby the foregoing problems are solved.

SUMMARY OF THE INVENTION

The above object is fulfilled according to a following configuration of the invention as under:

A front loader comprising:

a main frame standing erect in front of the travelling vehicle;

a boom having a rear end thereof pivotably supported at an upper portion of the main frame to be vertically movable;

a work implement pivotably supported at a front end of the boom to effect scooping and dumping operations; and

an indicator device for indicating a posture of the work implement, the indicator device including:a guide tube extending along a longitudinal direction of the boom on a rear portion of the boom;a tube support mechanism provided on the rear portion of the boom, the tube support mechanism supporting the guide tube so that the guide tube is movable in an axial direction thereof;a boom interlocking link having a rear end thereof pivotably supported by the main frame and a front end thereof operatively coupled to the tube support mechanism so that the guide tube moves in an axial direction thereof in association with vertical movement of the boom;an indicator rod inserted into the guide tube to be movable in the axial direction of the guide tube;a rod support mechanism provided at a longitudinal intermediate portion of the boom for supporting the indicator rod so that the indicator rod is movable in an axial direction thereof; anda work implement interlocking mechanism for interlocking the bucket and the rod support mechanism so that the indicator rod is movable in the axial direction thereof in association with the scooping operation and the dumping operation of the work implement;

wherein the indicator device is configured to indicate that the work implement is in an identical posture irrespective of a height position of the work implement, by aligning a rear end of the indicator rod with a rear end of the guide tube.

According to this configuration, vertical movement of the boom is accompanied by movement of the guide tube in the axial direction with respect to the indicator rod. Swinging the work implement causes the indicator rod to move in the axial direction with respect to the guide tube. As such, when the boom is moved vertically, scoop-operating or dump-operating the work implement aligns the rear end of the indicator rod with the rear end of the guide tube. Also, aligning the rear end of the indicator rod with the rear end of the guide tube indicates that the work implement is in the same posture at any height position. Whereby, aligning the rear end of the indicator rod with the rear end of the guide tube when the boom is vertically moved maintains the work implement at the same posture while the boom is moved vertically.

As described above, the indicator device is configured to align the rear end of the indicator rod with the rear end of the guide tube to thereby indicate that the work implement is at the same posture at any height. The operator visually checks for whether or not the rear end of the indicator rod is aligned with the rear end of the guide tube.

In the present configuration, the tube support mechanism for supporting the guide tube is provided on the rear side of the boom, the rod support mechanism for supporting the indicator rod is provided at the longitudinal intermediate portion of the boom, and the work implement and the rod support mechanism are interlocked by the work implement interlocking mechanism. Thus, the guide tube and the indicator rod can be arranged on the rear side of the boom along the longitudinal direction of the boom. Whereby, the visual check position of the indicator device can be brought closer to the operator, to facilitate the visual check by the operator.

According to one preferred embodiment, the front loader further comprises:

a boom cylinder for hydraulically operating the boom upward and downward;

a work implement cylinder for hydraulically effecting the scooping and dumping operations of the work implement; and

a spill guard control device for automatically dump-operating the work implement to prevent scooped object having scooped up by the work implement from falling out of the bucket to the rear side when the boom is being elevated without manually operating the work implement, the spill guard control device including:a spill guard valve for switching routes of hydraulic oil to automatically dump-operate the work implement;the work implement interlocking mechanism;an engaging portion provided at the work implement interlocking mechanism; anda valve operating mechanism for coming into engagement with the engaging portion and actuating the spill guard valve before the work implement reaches a posture in which the scooped object in the work implement will fall out to the rear side.

According to the above configuration, a portion (some components) of the configuration for the spill guard control device is shared with a portion of the configuration for the indicator device for maintaining the work implement posture. Thus, the number of components as well as resulting costs can be reduced and the outer appearance can be simplified, when providing the front loader with the indicator device for maintaining the work implement posture and the spill guard control device for preventing the spilling out of scooped object.

According to another preferred embodiment, the front loader further comprises:

a second indicator device for indicating that the work implement is at a horizontal posture where a bottom surface thereof is horizontal with the work implement being in contact with the ground, the second indicator device including:an index portion provided on the rod support mechanism for moving in unison with the indicator rod; anda mark member provided on the boom side;

wherein the work implement is in contact with the ground in a horizontal posture by scoop-operating or dump-operating the work implement until the index portion comes into alignment with the mark member in the longitudinal direction of the boom, and bringing the work implement into contact with the ground.

According to the above configuration, the second indicator device for indicating that the work implement is in a horizontal posture where the bottom surface thereof is horizontal when the work implement is brought into contact with the ground is shared with a portion (some components) of the configuration for the (first) indicator device for maintaining posture. Thus, the number of components can be reduced as well as resulting costs, and the outer appearance can be simplified, when providing to the front loader with the indicator device for maintaining the work implement posture and the second indicator device.

According to still another preferred embodiment,

a rear end surface of the guide tube forms an inclined surface with respect to an axis of the guide tube, and

a rear end surface of the indicator rod is forms an inclined surface with respect to an axis of the indicator rod, the inclined surface of the indicator rod being flush with to align the rear end surface of the guide tube.

According to the above configuration, the rear end surface of the guide tube and the rear end surface of the indicator rod forms inclined surfaces which are inclined with respect to the respective axes thereof. Thus, it is easier for the operator to visually observe a distal end of the rear end side of the indicator rod from behind, when the rear end surface of the indicator rod approaches the rear end surface of the guide tube from inside the guide tube. Further, it is easier to be known that the rear end side of the indicator rod approaches the rear end surface of the guide tube, and therefore it is easier to align the respective positions of the rear end surface of the indicator rod and the rear end surface of the guide tube.

According to still yet another preferred embodiment,

a notch portion is provided at the rear end of the guide tube by cutting away a portion in the peripheral direction thereof by a predetermined range, forwardly from the rear end.

According to the above configuration, the notch portion is formed by cutting out a predetermined range of a portion in the peripheral direction thereof from the rear end toward the front, on the rear end side of the guide tube; and that the rear end side of the indicator rod is exposed to the outside. This enhances visibility of the indicator device.

Other characteristic configurations and advantages and effects invited therefrom will be apparent by reading the following description with reference to accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIGS. 1 to 14show a first embodiment. With reference toFIG. 7, reference numeral “1” denotes a work vehicle, so-called a “TLB” (tractor, loader and backhoe) which is presented as one example of a work vehicle. The work vehicle (TLB) includes a tractor2acting as travelling vehicle, a front loader3mounted in front of the tractor2and a backhoe4mounted on a rearward portion of the tractor2.

The tractor2is a two-axle four-wheel tractor2having a vehicle body7supported for travelling by a right/left pair of front wheels5and a right/left pair of rear wheels6. The vehicle body7of the tractor2is formed by coupling a power transmission case9to the rearward portion of an engine8; and the power transmission case9is formed by directly interconnecting a clutch housing, a transmission case and a differential case, for example.

A driver's seat10is provided at the rearward portion of the vehicle body7. Rear wheel fenders14for covering the rear wheels6is provided on right/left sides of the driver's seat10; and a steering wheel11is provided on the front side of the driver's seat10. A hood12is provided on the front side of the steering wheel11for covering the engine8. In addition to the engine8, the hood12houses a radiator, a battery, a fuel tank and the like, which are supported by a front axle frame13extending forward from the bottom of the engine8.

Provided on the vehicle body7of the tractor2are a front loader mounting frame16for mounting the front loader3thereon, and a backhoe mounting frame17for mounting the backhoe4thereon.

The front loader mounting frame16is provided on a front right/left side of the vehicle body7. As shown inFIGS. 8 and 9, the front loader mounting frame16includes an attachment bracket18fixed by bolts to the front axle frame13and the vehicle body7; a support base19comprising a pipe member extending outwardly in the transverse direction from the attachment bracket18; and a mast20provided upright at the outer end of the support base19in the transverse direction.

As shown inFIG. 7, the backhoe mounting frame17extends from the forward portion to the rearward portion of the vehicle body7, and is arranged on the right/left side of the vehicle body7. The front end of the backhoe mounting frame17is fixed by bolts to the lower end of the mast20associated therewith in the transverse direction. A rear portion of the right/left backhoe mounting frame17is fixed to the rearward portion of the vehicle body7. The rear end of the right/left backhoe mounting frame17acts as a backhoe attaching section21for detachably attaching the backhoe4.

As shown inFIGS. 8 and 9, the front loader3has a right/left pair of main frames22, a right/left pair of booms23and a bracket24(a work implement).

The main frames22and the booms23are positioned on and extending across the right/left sides of the hood12of the tractor2; and the bucket24is positioned in front of the hood12.

The right/left main frame22is detachably attached to the mast20of the backhoe mounting frame17associated therewith in the transverse direction.

The rear end (proximal end) of the right/left boom23is pivotably supported to be rotatable about a transverse axis, via a boom support shaft25at an upper portion of the main frame22associated therewith in the transverse direction, thus enabling up/down swinging.

Each boom23includes, as primary components thereof, a front boom member26, a rear boom member27and a right/left pair of coupling plates28for coupling the front/rear boom members26,27.

As shown inFIG. 8, with the bucket24in contact with the ground, the rear boom member27extends forward from the upper portion of the main frame22, and from the front side of the hood12, the front boom member26extends downward toward a forward end thereof. Thus, the boom23describes a shape that is bent at an intermediate portion. The front boom members26of the right and left booms23are coupled by a boom coupling member29made of a pipe member.

A boom cylinder C1comprising double acting hydraulic cylinder is arranged under the right/left rear boom member27. The rear end of the boom cylinder C1is pivotably coupled to a lower portion of the main frame22, and the front end of the boom cylinder C1is pivotably coupled to a longitudinal intermediate portion of the boom23(the coupling plate28). Thus, the booms23are operated upward when the boom cylinders C1are extended, and the booms23are operated downward when the boom cylinders C1are retracted.

A work implement mounting frame30, having the transverse width spanning the right and left booms23, is detachably attached to the front end (distal end) of the right/left boom23. The work implement mounting frame30is pivotably coupled to the front end of the right/left boom23via a work implement pivot shaft32associated therewith, be rotatable about the transverse axis.

The bucket24is detachably attached to the work implement mounting frame30. The bucket24is swung up and down about the axis of the work implement pivot shaft32(an upward swinging operation of the bucket24will be also referred to as “a scooping operation”, and a downward swinging operation of the bucket24will be also referred to as “a dumping operation”).

In the front loader3of the present embodiment, work implements other than the bucket24(e.g. a distal end attachment such as a pallet fork) can be easily attached via the work implement mounting frame30.

A bucket cylinder C2(working implement cylinder), comprising a double acting hydraulic cylinder, is arranged above the right/left front boom member26. The rear end of the bucket cylinder C2is pivotably coupled to the longitudinal intermediate portion of the boom23(the coupling plate28) via a cylinder support shaft33(seeFIG. 4).

One end of a first work implement link34and one end of a second work implement link35are pivotably coupled to the front end of the bucket cylinder C2via a pivot shaft36. The other end of the first work implement link34is pivotably coupled to the work implement mounting frame30via a pivot shaft37. The other end of the second work implement link35is pivotably coupled to the booms23via a pivot shaft38, on the rear side of the work implement pivot support shaft32.

The front loader3includes an indicator device39for maintaining bucket posture (for maintaining work implement posture), whereby it is indicated that the bucket24is at the same posture when the booms23are positioned at any height.

As shown inFIG. 9, the indicator device39extends substantially along the right boom23inside of the boom23in the transverse direction, and close to an inner side of the right boom23in the transverse direction.

As shown inFIGS. 1 and 2, the indicator device39includes: a guide tube41arranged on the rear portion of the boom23; a tube support mechanism42for supporting the guide tube41so that the guide tube41is movable in the axial direction thereof; a boom interlocking link43having a rear end thereof pivotably supported by the main frame22and a front end thereof operatively coupled to the tube support mechanism42; an indicator rod44inserted into the guide tube41to be movable in the axial direction of the guide tube41; a rod support mechanism45for supporting the indicator rod44so that the indicator rod44is movable in the axial direction thereof; and a work implement interlocking mechanism46for interlocking the bucket24and the rod support mechanism45so that the indicator rod44is movable in association with vertical motion of the bucket24in association with the upward and downward swinging operations (i.e. the scooping operation and the dumping operation) of the work implement.

The guide tube41is formed of a cylindrical member having opened opposite ends in the axial direction. The guide tube41is arranged along the longitudinal direction of the boom23on top of the rearward portion of the boom23(of the rear boom member27).

As shown inFIG. 6(c), the rear end of the guide tube41is cut by a plane inclined with respect to the axial direction of the guide tube41, to thereby form an inclined surface with respect to the axial direction of the guide tube41. The rear end surface41aof the guide tube41is formed to provide a downward-facing.

As shown inFIG. 6(c) andFIG. 6(d), a notch portion47formed at the rear end of the guide tube41by partially cutting away in the peripheral direction by a predetermined range, forwardly from the rear end thereof. In the illustrated embodiment, a left half of the rear end of the guide tube41is cut away.

As shown inFIG. 1, the tube support mechanism42is arranged inside the rearward portion of the right boom23(the rear boom member27) in the transverse direction, and somewhat offset forward from a longitudinal center of the rearward portion of the right boom23.

As shown inFIGS. 4 and 5, the tube support mechanism42includes: a rotating support shaft48fixed to a lateral side of the boom23and having a transverse axis; a boss49externally fitted on and supported by the rotating support shaft48to be rotatable about the transverse axis; a support arm50extending radially outward and upward from the boss49; and a rotating arm51extending radially outward and downward from the boss49.

As shown inFIG. 1, a distal end (extending end) of the support arm50is pivotably coupled to the rearward portion of the guide tube41to be rotatable about a transverse axis. More specifically, as shown inFIGS. 5 and 6(b), a support shaft52having a transverse axis is fixed to a right surface of the guide tube41, and a distal end of the support arm50is pivotably coupled to the support shaft52.

As shown inFIG. 4, the rear end of the boom interlocking link43is pivotably supported by the main frame22to be rotatable about a transverse axis, via a rear pivot pin53which is provided below the boom support shaft25and fixed to the main frame22. The front end of the boom interlocking link43is pivotably coupled via a front pivot pin54to the distal end (the extending end) of the rotating arm51to be rotatable about the transverse axis.

As shown inFIG. 5, the indicator rod44comprises a cylindrical rod, and having a rear end thereof inserted into the guide tube41to be movable in the axial direction of the guide tube41. As shown inFIG. 6(c), a rear end surface44aof the indicator rod44forms an inclined surface cut by a plane extending parallel to the rear end surface41aof the guide tube41.

In the following description, the rear end surface44aof the indicator rod44will be referred to as a “posture indicating portion”, and the rear end surface41aof the guide tube41will be referred to as a “mark portion”.

When the posture indicating portion44ais aligned with the mark portion41a, the posture indicating portion44abecomes flush with the mark portion41a, to thereby indicate that the bucket24is at the same posture when the boom23is at any height position.

As shown inFIGS. 1 and 4, the rod support mechanism45is arranged at the longitudinal intermediate portion of the boom23. The rod support mechanism45includes: a rod support member55for fixing and supporting the forward portion of the indicator rod44; a rotating support shaft56provided on the boom23side and having a transverse axis; a boss57externally fitted on and supported by the rotating support shaft56to be rotatable about the transverse axis; and a swinging arm58extending radially outward from the boss57and having a distal end (extending end) thereof pivotably coupled to the rearward portion of the rod support member55to be rotatable about a transverse axis.

As shown inFIG. 5, the forward portion of the indicator rod44is inserted into the rod support member55to be movable in the axial direction thereof. A nut member59is fixed to the forward portion of the rod support member55. The nut member59is fixed to the rod support member55so that an axis of a screw hole thereof extends in a direction orthogonal to an axis of the rod support member55.

As shown inFIG. 6(a), a fixing bolt60is provided on the rod support member55to be threaded into the nut member59and extends through the rod support member55to abut against the indicator rod44.

By screwing and fastening the fixing bolt60, the indicator rod44is fixed to the rod support member55not to be movable in the axial direction thereof. By unscrewing and loosening the fixing bolt60, the indicator rod44becomes movable in the axial direction with respect to the rod support member55, whereby the indicator rod44is adjusted in position in the axial direction with respect to the rod support member55.

Further, a locknut61is provided between the nut member59and the head of the fixing bolt60for regulating the looseness of the fixing bolt60.

As shown inFIG. 4, the rotating support shaft56is provided concentric with the cylinder support shaft33for pivotably supporting the rear end of the bucket cylinder C2.

As shown inFIGS. 1 and 2, the work implement interlocking mechanism46includes: a detection link62arranged on the front end of the boom23for detecting a swinging action of the bucket24; a first interlocking arm64which rotatably swings about a transverse axis via a rotating support shaft63which is fixed to the boom23; a second interlocking arm65which swings in unison with the first interlocking arm64; a third interlocking arm66which swings in unison with the swinging arm58of the rod support mechanism45; and a coupling link67for operatively coupling the second interlocking arm65and the third interlocking arm66.

As shown inFIG. 3, the detection link62has a front end thereof pivotably supported by and coupled to the second work implement link35via a link pin68at a higher position than the pivot shaft38which pivotably supports the other end of the second work implement link35. On the other hand, the detection link62has a rear end thereof pivotably supported by and coupled to a distal end of the first interlocking arm64via a link pin69.

The rotating support shaft63is arranged on the rear side of the second work implement link35, and a boss70is externally fitted on the rotating support shaft63to be rotatable about the axis. A distal portion of the first interlocking arm64and a distal portion of the second interlocking arm65are fixed to the boss70.

As shown inFIG. 4, a distal portion of the third interlocking arm66is fixed to the boss57having the swinging arm58of the rod support mechanism45fixed thereto.

As shown inFIG. 3, the coupling link67has a forward end thereof pivotably supported by and coupled to a distal end of the second interlocking arm65via a link pin. As shown inFIG. 4, the coupling link67has a rear end thereof pivotably supported by and coupled to a distal end of the third interlocking arm66via a link pin72.

As shown inFIG. 1, in operation of the indicator device39configured as described above, when the bucket24is dump-operated, the detection link62is pulled forward (in the direction of the arrow a1). This causes the first interlocking arm64and the second interlocking arm65to swing in unison to push the coupling link67rearward (in the direction of the arrow a2). When the coupling link67is pushed in the direction of the arrow a2, the third interlocking arm66and the swinging arm58swing in unison and the rod support member55is pulled forward (in the direction of the arrow a3). This causes the indicator rod44to move forward in the axial direction thereof.

When the bucket24is scoop-operated, the detection link62is pushed rearward (in the direction of the arrow b1). This causes the first interlocking arm64and the second interlocking arm65to swing in unison and causes the coupling link67to be pulled forward (in the direction of the arrow b2). When the coupling link57is pulled in the direction of the arrow b2, the third interlocking arm66and the swinging arm58swing in unison and the rod support member55is pushed rearward (in the direction of the arrow b3), and this causes the indicator rod44to move rearward in the axial direction thereof.

Thus, swinging the bucket24moves the indicator rod44in the axial direction thereof relative to the guide tube41, whereby the posture indicating portion44aof the rear end of the indicator rod44can be aligned to the mark portion41aof the rear end of the guide tube41.

In the illustrated embodiment, when the posture indicating portion44aof the indicator rod44is aligned with the mark portion41aof the guide tube41, the bucket24is set to become in a horizontal posture (a posture where the bottom surface of the bucket24is horizontal).

In the indicator device39, the rear pivot support pin53for pivotably supporting the rear end of the boom interlocking link43is positioned below the boom support shaft25. Thus, as shown inFIG. 10, when the boom23is swung upward about the boom support shaft25from a state where the bucket24is contacted with the ground, the rotating support shaft48of the tube support mechanism42moves away from the rear pivot support pin53. Also, the rear end of the boom interlocking link43is pivotably supported by the main frame22, and thus the rotating arm51swings rearward and the support arm50swings forward. Whereby, the guide tube41moves forward in the axial direction.

When the bucket24is not swung in course of these operations, the upward swinging of the boom23is accompanied by an increasingly rearward tilt of the bucket24, and by the rear end of the indicator rod44projecting from the guide tube41.

In view whereof, when the boom23is swung upward, the bucket24is dump-operated, the indicator rod44is moved forward and, as shown inFIG. 5, the posture indicating portion44aof the indicator rod44is aligned with the mark portion41aof the guide tube41. Then, the bucket24becomes a horizontal posture.

When the boom23is swung downward from an elevated state, the guide tube41is conversely moved rearward in the axial direction, and therefore the bucket24is scoop-operated, the indicator rod44is moved rearward, and the posture indicating portion44aof the indicator rod44is aligned with the mark portion41aof the guide tube41.

In these manners, aligning the posture indicating portion44aof the indicator rod44with the mark portion41aof the guide tube41makes it possible to maintain the bucket24in a horizontal posture at any height position, and also makes it possible for the operator to easily maintain the horizontal posture of the bucket24by visually checking the posture indicating portion44a.

With the indicator device39, the position of the indicator rod44can be adjusted with respect to the rod support member55in the axial direction, and thus the bucket24can be set to maintain not only a horizontal posture but also an inclined posture (a posture where the bottom surface of the bucket24is inclined by a predetermined angle with respect to the horizontal).

To carry out this setting, for example, the bucket24is first swung vertically to reach a desired incline posture. In this state, the fixing bolt60is loosened to allow movement of the indicator rod44in the axial direction with respect to the rod support member55, and to align the posture indicating portion44aof the indicator rod44with the mark portion41aof the guide tube41so that the posture indicating portion44aof the indicator rod44becomes flush with the mark portion41aof the guide tube41. The fixing bolt60is fastened in this state, rendering the indicator rod44immovable in the axial direction with respect to the rod support member55.

Whereby, aligning the posture indicating portion44aof the indicator rod44with the mark portion41aof the guide tube41, regardless of whether the boom23is being raised or lowered, makes it possible to maintain the posture of the bucket24so that the bucket24will be at the same incline posture at any height position.

In the indicator device39, the guide tube41is arranged on the rearward portion of the boom23and along the longitudinal direction of the boom23, and therefore a mark position (visual check position) of the indicator device39can be placed close to the operator, thus allowing the operator to more easily perform the visual check.

The present invention is not limited to the foregoing embodiment. As shown inFIG. 11(b), the rear end surface44aof the indicator rod44and the rear end surface41aof the guide tube41may be cut on a plane orthogonal to the axial direction. However, in the illustration inFIG. 11(b), the posture indicating portion44aof the rear end of the indicator rod44is positioned inside the guide tube41, and it is difficult to know the position of the posture indicating portion44a, because the posture indicating portion44aapproaches the mark portion41aof the guide tube41from inside the guide tube41when the posture indicating portion44ais moved rearward from the guide tube41to be aligned with the position of the mark portion41aof the guide tube41. Also, when the posture indicating portion44aends up projecting from the mark portion41aof the guide tube41, it is then necessary to move the posture indicating portion44aforward, and in some cases the operation becomes cumbersome.

In view whereof, as shown inFIG. 11(a), if the rear end surfaces44a,41aof the indicator rod44and the guide tube41are cut on a plane inclined with respect to the axial direction, and if the posture indicating portion44ais positioned inside the guide tube41and approaches the mark portion41aof the guide tube41from inside the guide tube41, it is then possible for the operator to visually observe, from the rear side, the distal end of the rear end of the indicator rod44. This makes it easier to know that the rear end of the indicator rod44is approaching to the rear end surface of the guide tube41, and to align the positions of the posture indicating portion44aand the mark portion41a.

Also, compared with the embodiment inFIG. 11(a), visibility for the operator is further enhanced, when the rear end of the guide tube41is partially cut away and exposed as shown inFIG. 6(c) andFIG. 6(d) so that the indicator rod44is visible to the operator at the rear end of the guide tube41.

In the foregoing embodiment, the cutting plane of the rear ends of the indicator rod44and the guide tube41is downward facing, but this is not limitative. For example, as shown inFIG. 12(a), the cutting plane of the rear ends of the indicator rod44and the guide tube41may also be upward facing, or as shown inFIG. 12(b), the cutting plane of the rear ends of the indicator rod44and the guide tube41may be laterally facing.

With reference toFIG. 7, the backhoe4includes: a proximal base76detachably attached to the backhoe attaching section21of the backhoe mounting frame17; a swing bracket77supported at a rearward portion of the proximal base76to be swingable right and left about a vertical axis; a boom78supported by the swing bracket77to be rotatable about a transverse axis; an arm79supported by a distal end of the boom78to be rotatable about the transverse axis; a bucket80supported by a distal end of the arm79to be rotatable about the transverse axis; an outrigger81provided on a right/left side of the proximal base76; a maneuvering device82provided on the proximal base76; and a maneuver seat83.

The swing bucket77is driven by a swing cylinder C3. The boom78is driven by a boom cylinder C4. The arm79is driven by an arm cylinder C5. The bucket80is driven by a bucket cylinder C6. The outrigger is driven by an outrigger cylinder C7.

The maneuvering device82is adapted for manipulating each of the hydraulic cylinders C3to C7provided on the backhoe4, and includes a control valve for controlling any one of the hydraulic cylinders C3to C7.

The control valve receives hydraulic oil via a delivery hose84from a hydraulic pump provided on the tractor2. The hydraulic oil is returned toward a tank on the tractor2via a return hose85from the control valve.

The delivery hose84extends from the tractor2and is detachably connected to the maneuvering device82via a hydraulic joint86. The return hose85extends from the maneuvering device82and is detachably connected to a hydraulic joint87provided at the rear end of the tractor2.

When the backhoe4is dismounted from the tractor2, the return hose85remains on the backhoe4side, and the delivery hose84is dismounted from the maneuvering device82and is fixed to the tractor2side.

The fixation of the delivery hose84to the tractor2side involves a method of fixation using a clamp band, but clamp band fixation has problems such as that “removal is cumbersome” and “age-related (secular) degradation results in the clamp band tearing off.

In view whereof, in the TBL 1 in the present embodiment, as shown inFIGS. 7,13, and14, a hose holder88made of a metal plate is provided at the rear end of the tractor2, so that the delivery hose84is held by the hose holder88.

As shown inFIG. 14, the hose holder88includes a base portion89; a hooking portion90provided at an upper portion of the base portion89; and a regulation portion91provided to at a lower portion of the base portion89.

The base portion89is attached to a strut member93by a band92. The strut member93may be provided by a lower portion of a ROPS (rollover protection structure), for example (However, a member or a method for attaching the base portion89is not limited thereto).

The hooking portion90is constituted of a lower wall90aextending rearward from the upper end of the base portion89, and an upright wall90bextending upward from the rear end of the lower wall90a. The regulation portion91includes a side wall91aextending rearward from a side edge of the lower end of the base portion89, a rear wall91bextending laterally from the rear end of the side wall91a, and a locking wall91cextending forward from the extending side end portion of the rear wall91b. The rear wall91bjuts laterally from the strut member93, and the locking wall91cis formed with a narrower longitudinal width than the width of the side wall91a. As such, a clearance94for hose passage is formed between the rear portion of the locking wall91cand the strut member93.

To fix the delivery hose84to the hose holder88, as shown inFIG. 13, the front side of the delivery hose84is placed into the regulation portion91and hooked onto the hooking portion90. Thereafter, the rear side of the delivery hose84is placed into the regulation portion91, and the hydraulic joint86on the rear end of the delivery hose84is connected to the hydraulic joint87to which the return hose85is connected. In the illustrated embodiment, the delivery hose84is covered with a covering member.

With the hose holder88, the delivery hose84is easily fixed and is easily removed from the hose holder88; and moreover since the hose holder88is made of a metal plate, long-term usage is possible.

Second Embodiment

The second embodiment is different from the first embodiment in that the front loader3includes a spill guard control device96; and that a portion of the configuration for the spill guard control device96acts also as a portion of the configuration for the indicator device39.

The indicator device39and other configurations are configured substantially similar to those of the first embodiment.

The spill guard control device96is used when the operator elevates the boom23without operating (manually manipulating) the bucket24for preventing scooped object inside the bucket24, such as earth or sand having scooped by the bucket24, from falling (spilling) out of the bucket24on the rear side due to an automatic dumping operation (downward operation) of the bucket24effected before the scooped object falls out on the rear side.

The spill guard control device96includes, as primary components thereof, a spill guard valve SV for switching hydraulic oil routes to automatically dump-operate the bucket24; and a spill guard operating mechanism97for detecting the posture of the bucket24and activating the spill guard valve SV before the bucket24reached a posture whereby the scooped object in the interior thereof would fall out on the rear side.

As shown inFIGS. 15 and 16, the spill guard valve SV is attached and fixed to a left side surface of the right main frame22.

As shown inFIG. 19, the spill guard valve SV is disposed on a hydraulic route between the bucket cylinder C2, and a loader control valve CV for controlling the boom cylinder C1and the bucket cylinder C2.

The loader control valve CV is provided on the tractor2side. As shown inFIG. 19, the loader control valve CV includes a boom control valve V1for controlling the boom cylinder C1; and a bucket control valve V2(work implement control valve) for controlling the bucket cylinder C2. The control valves V1, V2are manually operated by a manipulating means such as a control lever.

As shown inFIG. 19, the spill guard valve SV comprises a two-position switching valve of a linear motion spool type, projecting a spool98upward (seeFIG. 18). Pushing down the spool98switches the spill guard valve SV from a neutral position99to a control position100; and a return spring returns the spill guard valve SV to the neutral position99.

A hydraulic pipe line101aextending from the boom control valve V1to a bottom side (upward side) of the boom cylinder C1, a hydraulic pipe line102aextending from the bucket control valve V2to a bottom side (dump side) of the bucket cylinder C2, and a hydraulic pipe line102bextending from the bucket control valve V2to a rod side (scoop side) runs through the spill guard valve SV; while a hydraulic pipe line101bextending from the boom control valve V1to a rod side (downward side) of the boom cylinder C1is disposed without running through the spill guard valve SV.

As shown inFIGS. 15 and 16, the spill guard operating mechanism97is provided on the left side of the right boom23, that is on one side of the boom23providing the indicator device39for maintaining the bucket posture.

The spill guard operating mechanism97comprises: the work implement interlocking mechanism46of the indicator device39for maintaining the bucket posture; an engaging portion103provided at the work implement interlocking mechanism46; and a valve operating mechanism104for operating the spill guard valve SV by coming into engagement with the engaging portion103. When the spill guard operating mechanism97detects that the bottom surface of the bucket24reaches a control angle inclined toward the scoop side by a predetermined angle with respect to the horizontal plane (an angle where further inclination of the bucket24would fall out the scooped object inside the bucket24on the rear side), the spill guard operating mechanism97actuates the spill guard valve SV so that the bucket24maintains the control angle.

As shown inFIG. 17the engaging portion103is formed of a plate material, and is provided on a back surface of the third interlocking arm66of the work implement interlocking mechanism46on the base portion side thereof.

As shown inFIGS. 15 and 16, the valve operating mechanism104includes: an engagement arm105supported to be rotatable about an axis of the rotating support shaft56which is provided on the cylinder support shaft33for pivotably supporting the rear end of the bucket cylinder C2; a transmission link106having a front end thereof pivotably coupled to the engagement arm105; a first operating arm107having a rear end thereof pivotably coupled to the transmission link106; a second operating arm108rotatable in usison with the first operating arm107; a spool operating member109pivotably coupled to the second operating arm108; and a spool attaching member110fixed to the spool operating member109.

As shown inFIG. 17, a boss111is externally fitted on the rotating support shaft56to be rotatable about the axis thereof, and the base portion side of the engagement arm105is fixed to the boss111to extend downward from the boss111.

The front end of the transmission link106is pivotably coupled to the extending end of the engagement arm105via a pin112. The engagement arm105is positioned on the front side of the engaging portion103.

As shown inFIG. 18, the first operating arm107extends downward with a forward inclination from a boss113, with the base portion side being fixed to the boss113which is supported on the boom support shaft25(or a shaft extending concentric with the boom support shaft25) to be rotatable about the axis thereof. The rear end of the transmission link106is pivotably coupled to the extending end of the first operating arm107via a pin114.

The second operating arm108extends forward from the boss113, with the base portion side thereof being fixed to the boss113. One end (the upper end) of the spool operating member109is pivotably coupled to the extending end of the second operating arm108via a pin115.

The spool attaching member110is fixed to the other end (the lower end) of the spool operating member109, and the spool attaching member110is pivotably coupled to the spool98of the spill guard valve SV.

In the spill guard control device96of the foregoing configuration, when the bucket24is scoop-operated (upwardly operated) in the course of scooping up earth or the like with the bucket24, then inFIG. 15the detection link62is pushed rearward (the direction of the arrow b1), the first interlocking arm64and the second interlocking arm65swing in unison, the coupling link67is pulled forward (in the direction of the arrow b2), the third interlocking arm66swings forward and the engaging portion103approaches the engagement arm105.

With the bucket24elevated after scooping earth or the like, when the boom23is upwardly operated without manually operating the bucket24, the bucket24inclines to the scoop side with respect to the horizontal plane (a bucket incline angle formed between the horizontal plane and the bottom surface of the bucket24is increased).

However, when the boom23is upwardly operated, the rotating support shaft56goes away from the pin114at the rear end of the transmission link106, and therefore the engagement arm105swings rearward (in the direction of the arrow d1) and the engagement arm105abuts against (comes into engagement with) the engaging portion103. After the engagement arm105has abutted against the engaging portion103, swinging motion of the engagement arm105in the direction of the arrow d1is regulated by the engaging portion103, and therefore upward swinging of the boom23is accompanied by forward pulling operation of the transmission link106(in the direction of the arrow d2). whereby, the first operating arm107swings upward and the second operating arm108swings downward to push down on a spool operating member109. This causes the spool98of the spill guard valve SV to be inwardly pushed on via the spool attaching member110.

When the spool98of the spill guard valve SV is pushed in, the spill guard valve SV is switched from the neutral position99to the control position100; and when the spill guard valve SV is switched to the control position100, a portion of the hydraulic oil supplied to the bottom side (upward side) of the boom cylinder C1is supplied to the rod side (scoop side) and the bottom side (dump side) of the bucket cylinder C2. Then, the difference in surface area between the rod side and the bottom side of the piston of the bucket cylinder C2causes the bucket cylinder C2to extend and causes the bucket24to be automatically dump-operated.

The automatic dump-operation of the bucket24in association with the upward operation of the boom23prevents scooped object, such as earth inside the bucket24, from falling out. More specifically, when the operator elevates the boom23without operating the bucket24, the elevating of the boom23is accompanied by a gradual rearward inclination of the bucket24. However, before the scooped object such as earth or sand inside the bucket24falls out rearward, the spill guard valve SV is actuated and the bucket24is automatically dump-operated (downward operated), thereby preventing the scooped object inside the bucket24from falling out.

On the other hand, when the upward operation of the boom23is stopped, the dumping operation of the bucket24is stopped also.

More specifically, when the bucket24is dump-operated, the detection link62is pulled forward (in the direction of the arrow a1), the first interlocking arm64and the second interlocking arm65swing in unison, the coupling link67is pushed rearward (in the direction of the arrow a2), and the third interlocking arm66swings rearward. When the third interlocking arm66swings rearward, the engaging portion103moves in the rearward direction away from the engagement arm105. Then, the engagement arm105can swing rearward, and therefore the force pushing in on the spool98is released, the spool98is pushed upward under the urging force of the return spring, the second operating arm108swings upward and the first operating arm107swings downward via the spool attaching member110and the spool operating member109, and the transmission link106is pulled rearward.

When the spool98of the spill guard valve SV is pushed upward and returns to the neutral position99, the supply of hydraulic oil to the bucket cylinder C2is stopped and the dumping operation of the bucket24stops.

On the other hand, when the bucket24is scoop-operated without swinging the boom23, the detection link62is pushed rearward in the direction of the arrow b1), the first interlocking arm64and the second interlocking arm65swing in unison, the coupling link67is pulled forward (in the direction of the arrow b2), the third interlocking arm66swings forward (in the direction of the arrow d3), and the engaging portion103approaches the engagement arm105and pushes on the engagement arm105. Then, the transmission link106is pulled forward (in the direction of the arrow d2); the spool98of the spill guard valve SV is pushed in on via the first operating arm107, the second operating arm108, the spool operating member109and the spool attaching member110; and the spool98is operated in the direction of switching from the neutral position99to the control position100.

The spill guard valve SV is completely switched to the control position100just before the bucket24rotates by a predetermined angle in the scoop direction and the incline angle of the bucket24with respect to the horizontal plane reaches an angle where the scooped object such as earth or sand would fall from the bucket24. When the spill guard valve SV is completely switched to the control position100, the flow passage of the hydraulic oil being supplied via the hydraulic pipe line102bto the rod side (upward side) of the bucket cylinder C2from the bucket control valve V2is shut off, and the scooping operation of the bucket24is stopped.

At this time, a dump-operation of the bucket24by the bucket control valve V2is allowed.

In the second embodiment, a portion of the spill guard control device96is used also as a portion of the indicator device39(i.e. the work implement interlocking mechanism46). Therefore, the number of components can be reduced as well as costs, and the exterior can be simplified when providing the front loader3with the indicator device39for maintaining the bucket posture and the spill guard control device96for preventing the spilling out of scooped object.

Third Embodiment

The third embodiment is different from the first embodiment in that: in addition to the above-described indicator device39for maintaining the bucket posture, the front loader3further includes a second indicator device116for indicating that the bucket24is in a horizontal posture only when the bucket24is at a position in contact with the ground, and that a portion of the configuration for the second indicator device116acts also as a portion of the configuration for the indicator device39for maintaining the bucket posture.

As shown inFIG. 20, in the front loader3according to the third embodiment, the front end of the bucket cylinder C2is pivotably coupled to the work implement mounting frame30.

Also, in the indicator device39for maintaining the bucket posture in the third embodiment, the front end of the detection link62is pivotably coupled to a portion upward of a work implement pivot support shaft31of the work implement mounting frame30.

The first interlocking arm64and the second interlocking arm65of the work implement interlocking mechanism46are integrally formed of a single sheet of a plate material, and the rotating support shaft63for supporting the first interlocking arm64and the second interlocking arm65is provided at a bracket117which is fixed to the boom coupling member29for coupling the right and left front boom members26.

The support arm50and the rotating arm51of the tube support mechanism42are also integrally formed of a single sheet of a plate material.

The notch portion (cutaway portion)47of the rear end of the guide tube41is formed longer in the axial direction of the guide tube41than that of the first embodiment.

The other configurations are substantially similar to those in the first embodiment.

As shown inFIG. 20, the second indicator device116includes: the work implement interlocking mechanism46, the rod support mechanism45, an index member118and a mark member119. Thus, the second indicator device116shares, with the (first) indicator device39, the work implement interlocking mechanism46and the rod support mechanism45of the indicator device39for maintaining the bucket posture.

The index member118is formed of a plate material. As shown inFIG. 22, the index member118comprises: an attachment wall121positioned above the rearward portion of the rod support member55of the rod support mechanism45; an index wall122(index portion) extending rearward and upward from the rear end of the attachment wall121; and a mating wall123extending downward from the front end of the attachment wall121. The index member118is formed by bending a single sheet of a plate material.

The attachment wall121is attached and fixed to the rod support member55by the fixing bolt60for fixing the indicator rod44. More specifically, the attachment wall121is inserted between the nut member59and the locknut61, and is fixed by screwing and inserting the fixing bolt60into the locknut61and also extending the fixing bolt60through a bolt insertion hole124formed in the attachment wall121to screw and insert the fixing bolt into the nut member59.

The bolt insertion hole124for receiving the fixing bolt60comprises an elongated slot which is elongated in the axial direction of the rod support member55, so that the position of the attachment wall121(the index member118) can be adjusted in the axial direction with respect to the rod support member55.

The index wall122is formed in an L-shape, where the transverse width of the upper portion122ais formed to be narrower than the transverse width of the lower portion122b, and where the upper portion122aextends inward in the transverse direction (toward the left) of the lower portion122b.

The mating wall123is formed in a forked shape for mating with the rod support member55from above so as to straddle the rod support member55, to prevent the index member118from rotating about the fixing bolt60.

The mark member119is formed of a plate material. The mark member119is fixed to a longitudinal intermediate portion of the left side surface of the right boom23and projecting leftward therefrom. The mark member119is formed in an L-shape where the transverse width of the upper portion119ais broader than the transverse width of the lower portion119b.

As shown inFIG. 20, the mark member119is provided so as to be positioned side by side (in juxtaposition) with the index wall122in the transverse direction (that is, the positions of the mark member119and the index wall122come into alignment with each other in the longitudinal direction of the boom23) when the bucket24becomes in a horizontal posture in contact with the ground. As shown inFIGS. 22 and 23, when the mark member119and the index wall122becomes arranged side by side with each other in the transverse direction, the upper portion of the mark member119enters a recessed portion on the upper portion of the index wall122.

As described above in the first embodiment, when the bucket24is swung, the rod support member55moves in the axial direction thereof, and therefore the index member118also moves in the axial direction together with the rod support member55. As such, moving the index member118together with the rod support member55in the axial direction to adjust the position thereof makes it possible for the index wall122of the index member118and the mark member119to be arranged side by side with each other in the transverse direction.

Arranging the index wall122and the mark member119side by side with each other in the transverse direction is carried out by the operator visually observing from behind the rear surface of the index wall122and the rear surface of the mark member119.

As shown inFIG. 24, when the operator is to lower the bucket24, which is elevated from the ground, into contact with the ground in a horizontal posture, this operation is carried out by using the second indicator device116.

More specifically, if the bucket24is in a horizontal posture as shown inFIG. 24when the bucket24is lifted upward from the ground, for example, then, the index wall122is deviated forward from the mark member119. Therefore, the bucket24is scoop-operated so as to move the index wall122rearward to align the index wall122with the mark member119in the longitudinal direction of the boom23. When the boom23is thereafter lowered to bring the bucket24into contact with the ground, the bucket24can be easily brought into contact with the ground in a horizontal posture.

When the operator is to use the indicator device39for maintaining the bucket posture when he/she lowers the bucket24from its elevated state from the ground and brings the bucket24into contact with the ground in a horizontal posture, the operator has to do this work at all times while viewing the rear end of the indicator rod44.

Further, since the position of the index member118can be adjusted in the axial direction with respect to the rod support member55, the index member118can be used also when another work implement (a distal end attachment) is attached instead of the bucket24. More specifically, if the index wall122and the mark member119are arranged side by side with each other in the transverse direction when another work implement is attached, and if the attached work implement is not brought into contact with the ground in a horizontal posture, then, the attached work implement is swung and adjusted into contact with the ground in a horizontal posture, and in this state, the position of the index member118is adjusted so as to be arranged side by side in the transverse direction with the mark member119.

In the third embodiment, the second indicator device116shares some components (i.e. the work implement interlocking mechanism46and the rod support mechanism45) with the indicator device39for maintaining the bucket posture. Therefore, the structure can be simplified and becomes inexpensive. Also, an inexpensive attachment structure is adopted, since the fixing bolt60, the nut member59and the like are used for the attachment for fixing the indicator rod44to the rod support member55.

Fourth Embodiment

FIGS. 25 to 30show the front loader3according to the fourth embodiment.

In the front loader3according to this embodiment, the indicator device39for maintaining the bucket posture, and the spill guard control device96are provided independently of each other.

In this embodiment, the work implement interlocking mechanism46is a component of the spill guard operating mechanism97, and does not form a component of the indicator device39.

As shown inFIGS. 27 and 28, first through third bosses126,127,128are arranged side by side in the transverse direction and externally fitted on the rotating support shaft56which is provided at the cylinder support shaft33for pivotably supporting the rear end of the bucket cylinder C2, so that the first through third bosses126,127,128are rotatable in the axial direction of the rotating support shaft56.

The support arm50and the rotating arm51of the tube support mechanism42for supporting the guide tube41are fixed to the first boss126; the engagement arm105is fixed to the second boss127; and the third interlocking arm66is fixed to the third boss128.

As shown inFIGS. 25 and 26, in the indicator device39for maintaining the bucket posture according to this embodiment, the guide tube41is provided at the longitudinal intermediate portion of the boom23. The guide tube41is tilted backward, when the boom23is lowered to bring the bucket24into contact with the ground.

A coupling piece130is fixed to the front end of the rod support member55which supports the indicator rod44. The coupling piece130is pivotably supported by the link pin68which pivotably supports the front end of the detection link62of the work implement interlocking mechanism46.

The rear end surfaces of the indicator rod44and the guide tube41are cut on respective planes which extend orthogonal to the axial directions thereof.

The spill guard control device96according to this embodiment is different from that in the second embodiment in that: the valve operating mechanism104of the spill guard operating mechanism97is different on the transmission route extending from the second operating arm108to the spill guard valve SV; and in that the spill guard valve SV is provided on the tractor2side. The other configurations are provided similarly to those in the second embodiment.

The transmission route extending from the second operating arm108of the valve operating mechanism104to the spill guard valve SV is configured as follows.

Namely, as shown inFIGS. 25,29and30, the transmission route extending from the second operating arm108to the spill guard valve SV includes: a transmission mechanism131provided on the main frame22side; and a relay mechanism132for transmission from the transmission mechanism131to the spill guard valve SV.

As shown inFIG. 29, the transmission mechanism131includes: a transmission link133having an upper end thereof pivotably coupled to the second operating arm108; and a transmission rod134having an upper end thereof pivotably coupled to a lower end of the transmission link133and extending therefrom downward.

An intermediate portion of the transmission rod134is supported and guided by a guide cylinder135which is fixed to the main frame22, so as to be movable up and down. Also, the transmission rod134per se is adjustable in its length.

The transmission rod134is urged upward by a return spring138which is interposed between a spring hook portion136provided on the transmission rod134, and a spring hook portion137provided on the main frame22.

Further, the lower portion of the transmission rod134projects downward from the guide cylinder135, and an abutting portion139formed by being bent rearward is provided at the lower end of the transmission rod134.

As shown inFIG. 30, the relay mechanism132includes: a relay bracket141fixed onto the support base19of the right front loader mounting frame16; a relay lever142pivotably supported by the relay bracket141so as to be rotatable about a transverse axis; and a relay arm143for rotating in unison with the relay lever142.

A boss145is provided at the forward portion of the relay bracket141, and is externally fitted on and supported by a support shaft144having an axis in the transverse direction, so as to be rotatable about the transverse axis. The intermediate lever142is fixed to the boss145so as to extend therefrom forward. The front end of the relay lever142is bent outward in the transverse direction to form an abutted portion146. The abutted portion146is positioned below the abutting portion139of the transmission rod134and is configured to abut against the abutting portion139.

The proximal end of the relay arm143is fixed to the boss145, and therefrom the relay arm143extends upward. A return spring148is interposed between the upper end of the relay arm143and a spring hook portion147which is provided on the relay bracket141. Under the force of the return spring148, the relay arm143is urged to swing rearward, and thus the relay lever142is urged to swing upward (into abutment against the abutting portion139).

One end of a transmission wire (not shown) is coupled to the relay lever142; and the other end of the transmission wire is operatively coupled to the spool of the spill guard valve SV via an interlocking mechanism.

With the spill guard control device96having the configuration as described above in operation, if the operator elevates the boom23without operating the bucket24and if the engagement arm105abuts against the engaging portion103to swing the second operating arm108downward, then, the transmission rod134is pushed downward via the transmission link133and the transmission rod134pushes the relay lever142downward. In response thereto, the relay arm143swings forward, and the spill guard valve SV is actuated via the transmission wire, so that the bucket24is automatically dump-operated.

The spill guard control device96according to the present embodiment as shown inFIGS. 25 to 30may also be adopted in the second embodiment.

Fifth Embodiment

FIG. 31shows a fifth embodiment which is another embodiment of an indicator device149for indicating a horizontal posture at a position where the bucket24is brought into contact with the ground.

The indicator device149comprises: a guide tube150; a support arm151for supporting the guide tube150; an indicator rod152having a rear end thereof inserted into the guide tube150; and a cylindrical rod support member153for supporting the indicator rod152.

The support arm151has one end thereof pivotably supported by a support shaft154which is provided at the cylinder support shaft33for pivotably supporting the rear end of the bucket cylinder C2, and has the other end thereof pivotably coupled to the guide tube150via a pin155.

The indicator rod44has a front end thereof inserted into and supported by the rod support member153. The indicator rod152is fixed to the rod support member153in a similar manner to that of the indicator device39according to the first embodiment.

A coupling piece156is provided at the front end of the rod support member153. The coupling piece156is pivotably supported by the cylinder support shaft which pivotably supports the front end of the bucket cylinder C2, so that the coupling piece156is rotatable about a transverse axis.

With this indicator device for indicating the horizontal posture in operation, too, the indicator rod152moves in the axial direction through and relative to the guide tube150in association with the swing operation of the bucket24, so as to align the rear end surface152aof the indicator rod152with the rear end surface150aof the guide tube150so that the rear end surface152abecomes flush with the rear end surface150a. Whereby, the bucket24adopts a horizontal posture in contact with the ground.

Further, the rear end surface152aof the indicator rod152and the rear end surface150aof the guide tube150are cut on planes inclined with respect to the axial direction, similarly to the indicator device39according to the first embodiment. Therefore, this is effective to easy alignment between the rear end surface152aof the indicator rod152and the rear end surface150aof the guide tube150.