Apparatus for controlling posture of front loader

An apparatus for controlling the posture of a front loader has booms attachable to a vehicle body which are pivotally movably upward and downward and has a work implement attached to the forward ends of the booms and pivotally movable in a scooping direction and a dumping direction. Each of the booms and the implement are pivotally movable by a single control lever independently of each other or movable simultaneously. The apparatus includes an actuating member for shifting the control lever from a boom raising position to a boom raising and dumping position when the booms are not positioned lower than a specified level. This eliminates the likelihood of the implement tilting rearwardly downward even if the booms are raised, precluding the implement from spilling the earth or sand scooped up.

FIELD OF THE INVENTION AND RELATED ART STATEMENT 
The present invention relates to an apparatus for controlling the posture 
of a front loader having booms and a work implement for use in operating 
the booms and the implement independently of each other and at the same 
time using a single control lever. 
Front loaders attached to tractors or like vehicles are adapted to scoop up 
earth or sand and carry the earth or sand to a site of higher level with a 
work implement by operating each boom and the implement independently of 
each other and also at the same time using a single control lever. 
When the booms of the front loader are raised with earth scooped up with 
its implement, the implement becomes tilted rearwardly downward as the 
booms rise, causing some earth to spill rearward from the implement at a 
raised position. 
To preclude such spillage, there arises a need to correct the posture of 
the front loader by turning the implement toward the dumping direction 
when raising the booms. However, this procedure requires skill when 
executed with the single control lever. 
OBJECT AND SUMMARY OF THE INVENTION 
The main object of the present invention is to provide a posture control 
apparatus for use with such front loaders for automatically turning the 
work implement toward the dumping direction before the implement tilts 
rearwardly downward the booms, permitting earth, sand or the like to spill 
from the implement, so as to prevent spillage without requiring a lot of 
skill. 
The invention will be summarized below. 
Actuating means is provided for shifting a control lever from a boom-up 
(boom raising) position to a boom-up and implement-dumping (implement 
unloading) position when each boom of the front loader is brought to a 
position not lower than a specified level, whereby when the booms are 
brought to the specified level, the implement is automatically pivotally 
moved toward the dumping direction and thereby precluded from tilting 
rearwardly downward to prevent spillage of earth without necessitating any 
skillful manipulation. 
Preferably, boom position detecting means is provided for detecting whether 
each boom is positioned not lower than the specified level. When the 
detecting means detects that the boom is positioned not lower than the 
specified level, the actuating means shifts the control lever from the 
boom-up position to the boom-up and implement-dumping position. 
Owing to the provision of the boom position detecting means, the actuating 
means is precluded from shifting the control lever until the boom is 
positioned not lower than the specified level. 
Preferably, implement position detecting means is provided for detecting 
whether the work implement is positioned as pivotally moved at least 
through a specified angle in the scooping direction relative to the boom. 
The actuating means shifts the control lever from the boom-up position to 
the boom-up and implement-dumping position upon the boom position 
detecting means detecting that the boom is positioned not lower than the 
specified level and upon the implement position detecting means detecting 
that the implement is positioned as pivotally moved at least through the 
specified angle in the scooping direction relative to the boom. 
When the implement position detecting means detects that the implement is 
not positioned as thus moved, the implement does not tilt rearwardly 
downward and does not permit spillage of earth even if the boom is raised 
beyond the specified level, so that the control lever is not shifted by 
the actuating means. 
Preferably, the boom position detecting means is operatively connected to 
the actuating means by a push-pull cable. When the boom is pivotally moved 
to the specified level or higher, the push-pull cable is operated in a 
direction to operate the actuating means. The implement position detecting 
means is operatively connected to a pivotal arm. The push-pull cable has 
an outer wire axially movably supported by the pivotal arm. The movement 
of the pivotal arm brings the outer wire selectively into a state 
involving an axial play or into a state involving no axial play. When the 
implement position detecting means detects that the implement is 
positioned as pivotally moved at least through the specified angle in the 
scooping direction relative to the boom, the pivotal arm is moved in a 
direction to eliminate the play of the outer wire. 
Thus, the outer wire of the push-pull cable operatively connecting the boom 
position detecting means to the actuating means no longer plays when the 
implement is positioned as pivotally moved at least through the specified 
angle in the scooping direction relative to the boom, whereas the wire 
plays when the implement is positioned otherwise. In the state of the 
outer wire involving no play, the actuating means shifts the control lever 
when the boom is positioned at the specified level or higher. In the state 
of the outer wire having play, there is no likelihood that the actuating 
means will shift the control lever even if the boom is positioned at the 
specified level or higher. 
Preferably, a control box having the boom position detecting means and the 
control lever is disposed in the vicinity of the pivot of the boom of the 
front loader. 
This positions the control lever close to the boom position detecting 
means, diminishes the movement thereof relative to each other and permits 
use of smaller members for operatively connecting one to the other. 
Further when the front loader is to be removed, the detecting means and 
the control lever are removable along with the front loader. 
Preferably, the implement position detecting means is provided on one side 
face of the boom above the pivot for the implement. 
This renders the implement position detecting means less likely to strike 
against obstacles and to be exposed to mud. 
Preferably, the actuating means comprises an actuating member which is 
pivotably disposed in the vicinity of the control lever. 
Preferably, the actuating means is provided with a slanting guide by which 
the control lever as shifted from the boom-up position to the boom-up and 
implement-dumping position is so guided as to move between the latter 
position and a neutral position. 
When the boom is positioned at the specified level or higher, the operator 
may attempt to shift the control lever from the neutral position to the 
boom-up position, but the slanting guide leads the control lever to the 
boom-up and implement-dumping position, whereby spillage of earth is 
prevented. 
Preferably, the boom position detecting means comprises a cam connected to 
the boom and a detecting arm connected to a member attachable to the 
vehicle body. The detecting arm is operatively connected to the actuating 
means. The detecting arm is moved by the cam in a direction to operate the 
actuating means when the boom is pivotally moved to the specified level or 
higher. 
Preferably, the detecting arm of the boom position detecting means is 
movable about a pivot, and the actuating member is movable about a pivot. 
The detecting arm is operatively connected to the actuating member by the 
push-pull cable. 
Preferably, the implement position detecting means comprises a cam 
connected to the implement and a detecting arm connected to the boom. This 
detecting arm is operatively connected to the pivotal arm. 
Preferably, the cam of the implement position detecting means is mounted on 
a rod, and the rod is pivoted to the implement by a pin and held by a 
guide sleeve pivoted to the boom by a pin and extending along the boom. 
The detecting arm is movable about a pivot, the pivotal arm is movable 
about a pivot, and the detecting arm is operatively connected to the 
pivotal arm by a push-pull cable. 
Further scope of applicability of the present invention will become 
apparent from the detailed description given hereinafter. However, it 
should be understood that the detailed description and specific examples, 
while indicating preferred embodiments of the invention, are given by way 
of illustration only, since various changes and modifications within the 
spirit and scope of the invention will become apparent to those skilled in 
the art from this detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The first preferred embodiment will be described with reference to FIGS. 1 
to 8. 
FIG. 4 shows a front loader of the bucket type as attached to a tractor for 
use. With reference to FIG. 4, the body 1 of the tractor has a driver's 
seat 2, and a mount 3 which is provided at each side of the tractor body 
1. 
The front loader 4 comprises an upright 5 removably attached to the mount 
3, a brace 6 extending forward from the upright 5 and removably fixed to 
the front end of the tractor body 1, a boom 8 supported by a pivot 7 on 
the upper end of the upright 5 and movable upward and downward, a boom 
cylinder 9 for moving the boom 8 upward and downward, a bucket (work 
implement) 11 supported by a pivot 10 on the forward end of the boom 8 and 
movable upward and downward in a scooping direction and a dumping 
direction, and a bucket cylinder (implement cylinder) 12 for pivotally 
moving the bucket 11. 
The upright 5, brace 6, boom 8, boom cylinder 9 and bucket cylinder 12 are 
disposed at each side of the tractor body 1. 
A control unit 13 is attached to the right upright 5, has a single control 
lever 14 and is of the construction shown in FIGS. 1 to 3. 
With reference to FIGS. 1 to 3, a boom control valve 15 for controlling the 
boom cylinders 9, and a bucket control valve 16 (implement control valve) 
for controlling the bucket cylinders 12 are shown. These control valves 15 
and 16 are three-way change-over valves of the spool type and are fixed to 
a mount plate 19 with spools 17 and 18 so arranged as to move vertically. 
The mount plate 19 is fixed to the upright 5. 
A control box 20 is positioned above the control valves 15, 16 and fixed to 
the mount plate 19. Housed in the control box 20 is an interlocking 
assembly 21 for rendering the control valves 15, 16 operable independently 
of each other or simultaneously operable by the single control lever 14. 
The interlocking assembly 21 includes a first pivot 22 and a second pivot 
23 positioned at right angles with respect to each other, a first pivotal 
member 24 movable about the axis of the first pivot 23, and a second 
pivotal member 25 movable about the axis of the second pivot 23. The 
control lever 14 is secured to the second pivotal member 25. The control 
lever 14 extends upward through an opening 27 formed in the top plate 26 
of the control box 20. 
The first pivotal member 24 is U-shaped when seen from above and has the 
first pivot 22 attached to its right side with its axis extending 
transversely of the loader. The first pivot 22 is rotatably inserted in a 
boss portion 29 secured to a bracket 28 on the mount plate 19. The first 
pivotal member 24 has an arm portion 30 projecting forward and connected 
to the spool 17 of the boom control valve 15 by a pin 31, rod 32 and pin 
33. 
The second pivotal member 25 is surrounded by the first pivotal member 24 
and rotatably supported by the second pivot 23 having an axis extending in 
the front-to-rear direction. The second pivot 23 is supported by the first 
pivotal member 24. The second pivotal member 25 has on its left side a 
projection 34 coaxial with the first pivot 22. The projection 34 is 
connected to the spool 18 of the bucket control valve 16 by a ball support 
member 35, rod 36 and pin 37. 
Because of the above arrangement, the control lever 14 is pivotally movable 
forward and rearward about the axis of the first pivot 22, moving the 
spool 17 of the control valve 15 therewith. The lever 14 lowers the booms 
8 when moved forward or raises the booms 8 when moved rearward. 
The control lever 14 is pivotally movable also rightward and leftward about 
the second pivot 23 to move the spool 18 of the control valve 16 
therewith. The leftward movement moves the bucket 11 in a scooping 
direction (direction of arrow X in FIG. 4). The rightward movement moves 
the bucket 11 in a dumping direction (direction of arrow Y in FIG. 4). 
Since the first pivotal member 24 is movable about the axis of the first 
pivot 22 and since the second pivotal member 25 is movable about the 
second pivot 23, the control lever 14 is pivotally movable in intermediate 
directions between the front-to-rear direction and the lateral direction. 
When moved in such an intermediate direction, the lever 14 moves the 
spools 17, 18 of the control valves 15, 16, thereby moving the booms 8 and 
the bucket 11 at the same time. 
A latch portion 38 is projected from the base portion of the control lever 
14 leftward slightly forward and has a left end which is hooked at its 
lower side. 
An engaging member 39, which is movable upward and downward about a pivot 
41, is supported by an inverted U-shaped bracket 40 attached to the lower 
side of the top plate 26 of the control box 20. The engaging member 39 has 
a stopper portion 43 and is biased upward by a coiled spring 42 to bring 
the stopper portion 43 into contact with the top plate 26. The engaging 
member 39 has at its free end a rearward projection 44. The latch portion 
38 releasably engages with the projection 44 from above when the control 
lever 14 is shifted to a scooping position for the bucket 11 by being 
forwardly moved from a neutral position N to a boom lowering (boom-down) 
position by a distance a and also moved leftward by a distance b as seen 
in FIG. 5. The engagement restrains the control lever 14 from shifting 
rightward under the action of a spring (not shown) for returning the spool 
18 to its neutral position. 
A push-pull cable 47 includes an inner wire 48 connected to the engaging 
member 39 by a pin 45 and a connector 46, and an outer wire 49 attached to 
a holder 50 provided on the control box 20 and disposed below the engaging 
member 39. The inner wire 48, when pulled, moves the engaging member 39 
downward about the pivot 41 out of engagement with the latch portion 38. 
The push-pull cable 47 is operatively connected to implement 
detecting-disengaging means 51. When the bucket 11 is detected as moved 
through a specified angle relative to the boom 8, the cable moves the 
engaging member 39 in a direction out of engagement with the latch portion 
38. 
The implement detecting-disengaging means 51 comprises a rod 53 extending 
along the boom 8 pivoted to a bracket 52 on the bucket 11 by a pin 53a 
above the pivot 10 as seen in FIG. 6. The means 51 further has a guide 
sleeve 54 slidably holding the free end portion of the rod 53, a cam 55 
provided on the rod 53, and an L-shaped detecting arm 56. 
The guide sleeve 54 and the detecting arm 56 are pivoted to the boom 8 by a 
pin 57. The detecting arm 56 is moved by the cam 55 when the bucket 11 is 
positioned at an angle with the boom 8 at which the bottom side 11a of the 
bucket 11 can be horizontally placed on the ground. For this purpose, the 
cam 55 is in contact with one end of the detecting arm 56. The detecting 
arm 56 is connected at the other end thereof to the other end of the inner 
wire 48 of the cable 47. The other end of the outer wire 49 of the cable 
47 is attached to a holder 58 secured to the guide sleeve 54. 
A stopper 59 is disposed behind the engaging member 39. The stopper 59 is 
supported by the pivot 41 to be upwardly and downwardly movable. The 
stopper 59 is engageable with the latch portion 38 in engagement with the 
projection 44 of the engaging member 39 to restrain the control lever 14 
from shifting rearward under the action of a spring (not shown) for 
returning the spool 17 to its neutral position. A push-pull cable 62 has 
an inner wire 63 connected to the stopper 59 and an outer wire 64 attached 
to a holder 65 on the control box 20. The push-pull wire 62 is operatively 
connected to boom detecting-disengaging means 66 to pivotally move the 
stopper 59 downward and release the latch portion 38 from the stopper 59 
upon the booms 8 lowering to a transport position A shown in FIG. 4 during 
their downward movement. 
With reference to FIG. 7, the boom detecting-disengaging means 66 has a cam 
67 attached to the rear end of the boom 8 on one side thereof, a detecting 
arm 68 resembling a bell crank and movably supported by a pivot 70, a cam 
roller 69 provided at the free end of the detecting arm 68, and a spring 
(not shown) for biasing the arm 68 to hold the cam roller 69 in contact 
with the cam 67. 
The inner wire 63 of the push-pull cable 62 is connected to the detecting 
arm 68, while the outer wire 64 of the cable 62 is attached to a holder 71 
secured to the upright 5. The face of the cam 67 in contact with the cam 
roller 69 is stepped so that the arm 68 moves counterclockwise to pull the 
inner wire 63 when the boom 8 lowers below the transport position A. 
Accordingly, when the boom 8 moves downward from the transport position A, 
the stopper 59 also moves downward out of engagement with the latch 
portion 38. 
As seen in FIG. 8, an actuating member 72 is provided on the top side of 
the control box 20. The actuating member 72 is adapted to forcibly shift 
the control lever 14 from a boom-up (boom raising) position U to a boom-up 
and bucket-dumping (bucket unloading) position UD. 
The actuating member 72 carries at its rear end a pivot 73, which is 
inserted in a tubular portion 74 of the control box 20, whereby the member 
72 can move about the pivot 73. Further as shown in FIG. 8, the actuating 
member 72 has an engaging portion 75 in the form of a circular-arc cutout. 
When the engaging portion 75 is positioned to the rear of the neutral 
position N, the control lever 14 in the boom-up position U is in 
engagement with the engaging portion 75. The actuating member 75 has a 
front face serving as a slanting guide 76a, whereby the control lever 14 
is guided to move between the positions N and UD. 
The actuating member 72 has a lever 76. With reference to FIG. 3, a 
push-pull cable 77 has an inner wire 78 connected to the lever 76 and an 
outer wire 79 attached to a holder 80 on the control box 20. The lever 76 
is operatively connected by the cable 77 to boom position detecting means 
81 for operating the actuating member 72 when detecting that the boom is 
positioned at a specified level or higher. 
With reference to FIG. 7, the boom position detecting means 81 has a 
detecting arm 82 movable by the upper end of the cam 67 and supported by a 
pivot 83 on the upright 5 to be upwardly and downwardly movable. The inner 
wire 78 of the cable 77 is connected to the detecting arm 82, and the 
outer wire 79 thereof to the upright 5 by a holder 87. The detecting arm 
82 carries a cam roller 88 at its forward end. 
The operation of the present embodiment will now be described. When the 
control lever 14 is positioned for dumping with the each boom 8 in its 
most raised position, the second pivotal member 25 moves about the second 
pivot 23, pulling up the spool 18 of the bucket control valve 16 through 
the projection 34 and the rod 36 and thereby extending the bucket 
cylinders 12, whereby the bucket 11 is moved about the pivot 10 toward the 
dumping direction to dump earth. 
From this state, the control lever 14 is returned to the neutral position N 
and then shifted from the neutral position N toward the lowering direction 
by the distance a and also toward the scooping direction by the distance 
b, whereby the lever 14 is brought to the boom-down and bucket-scooping 
(scooping with the bucket 11) position, whereupon the latch portion 38 
engages the projection 44 of the engaging member 39 from above, locking 
the control lever 14 in the shifted position. The shift of the lever 14 
moves the first pivotal member 24 about the axis of the first pivot 22, 
causing the arm portion 30 and the rod 32 to depress the spool 17 of the 
boom control valve 15 and thereby contract the boom cylinders 9, whereby 
the booms 8 are moved downward about the pivot 7. At the same time, the 
second pivotal member 25 moves about the second pivot 23, causing the rod 
36 to depress the spool 18 of the bucket control valve 16. Consequently, 
the bucket cylinders 12 are contracted, moving the bucket 11 about the 
pivot 10 toward the scooping direction. In this way, the booms 8 are 
lowered and the bucket 11 is moved for scooping at the same time. 
The engaging member 39 in engagement with the latch portion 38 locks the 
control lever 14 in the boomdown and bucket-scooping position. The forces 
of the return springs incorporated in the boom control valve 15 and the 
bucket control valve 16 are delivered through the spools 17, 18 to the 
control lever 14 thus locked, acting to return the lever to the neutral 
position N. Thus, with the return spring in the boom control valve 15 
biasing the control lever 14 rearward, the latch portion 38 acts to move 
out of engagement with the projection 44 of the engaging member 39 in the 
direction of arrow c in FIG. 5. However, the stopper 59 restrains the 
latch portion 38 from this movement. Further since the hooked end of the 
latch portion 38 is in engagement with the projection 44 from above, the 
lever 14 is prevented from moving rightward. Consequently, the control 
lever 14 can be reliably locked. 
Next, when the booms 8 reach the transport position A while lowering, the 
cam 67 moves the detecting arm 68 counterclockwise through the cam roller 
69, causing the inner wire 63 to pivotally move the stopper 59 downward 
out of engagement with the latch portion 38. As a result, the return 
spring of the boom control valve 15 forces the control lever 14 rearward, 
so that the lever 14 is shifted toward the direction of arrow c in FIG. 5 
with the latch portion 38 in engagement with the engaging member 39, 
whereby the spool 17 of the valve 15 is returned to its neutral position 
to stop the booms 8 at the transport position A. 
On the other hand, when the rod 53 is pushed rearward by the scooping 
movement of the bucket 11 about the pivot 10, the cam 55 is brought closer 
to the detecting arm 56. When the bucket 11 is positioned at an angle with 
the boom 8 at which the bottom side 11a of the bucket 11 is horizontally 
positioned in contact with the ground, the cam 55 rotates the detecting 
arm 56 about the pin 57 clockwise. The arm 56 in turn pulls the inner wire 
48 of the push-pull cable 47 to pivotally move the engaging member 39 
downward against the spring 42 out of engagement with the latch portion 
38. 
Consequently, the return spring of the bucket control valve 16 returns the 
control lever 14 rightward to the neutral position N, with the spool 18 
also returned to its neutral position, whereby the bucket 11 is halted. 
The control lever 14, when shifted toward the lowering direction, moves the 
first pivotal member 24 about the axis of the first pivot 22, causing the 
arm portion 30 and the rod 32 to depress the spool 17 of the boom control 
valve 15, whereby the boom cylinders 9 are contracted to lower the booms 
8. The bucket 11 is held stopped at the angle at which its bottom side 11a 
is horizontally positioned on the ground, so that the bucket 11 lowered 
can be placed on the ground with its bottom 11a invariably in horizontal 
contact with the ground. 
When sand or earth is to be scooped up with the bucket 11, the control 
valve 14 is shifted from the neutral position N to the scooping position, 
contracting the bucket cylinders 12 almost to the limit position and 
moving the bucket 11 about the pivot 10 toward the scooping direction. 
Next, the lever 14 is shifted from the neutral position N to the boom-up 
position U, whereby the first pivotal member 24 is moved about the axis of 
the first pivot 22 to pull up the spool 17 of the boom control valve 15 
through the arm portion 30 and the rod 32. The boom cylinders 9 therefore 
extend to raise the booms 8. At this time, the lever 14 is in engagement 
with the engaging portion 75 of the actuating member 72. 
Although the bucket 11 tilts rearwardly downward with the rise of the booms 
8, the cam 67 pushes up the detecting arm 82 (in the direction of arrow e 
in FIG. 7) before the bucket 11 reaches a position where the earth is 
liable to spill. The detecting arm 82 pushed up pulls the inner wire 78 of 
the push-pull cable 77, which in turn moves the lever 76 about the pivot 
73 in the direction of arrow d shown in FIG. 3. Consequently, the 
actuating member 72 moves from the solid-line position to the phantom-line 
position shown in FIG. 8, forcibly shifting the control lever 14 from the 
position U to the position UD. This moves the second pivotal member 25 
about the second pivot 23, thereby causing the projection 34 and the rod 
36 to pull up the spool 18 of the bucket control valve 16. The bucket 
cylinders 12 are extended to move the bucket 11 toward the dumping 
direction. Thus, when the booms 8 are raised beyond a predetermined level, 
the bucket 11 is moved toward the dumping direction with the rise of the 
booms 8, precluding the bucket 11 from spilling the earth. 
The rise of the booms 8 and the movement of the bucket 11 toward the 
dumping direction can be stopped by returning the control lever 14 from 
the position UD to the neutral position N along the slanting guide 76a of 
the actuating member 72. 
To further raise the booms 8 thus stopped, the control lever 14 is shifted 
rearward. Since the actuating member 72 is in the phantom-line position of 
FIG. 8 at this time, the lever 14 invariably moves toward the position UD. 
When the booms 8 start rising, therefore, the bucket 11 turns toward the 
dumping direction with the rise to prevent spillage of earth. 
FIGS. 9 to 15 show the second preferred embodiment, which will be described 
as to the differences thereof from the first embodiment. Throughout these 
drawings, like parts are designated by like reference numerals and will 
not be described. 
With reference to FIG. 12, the actuating member 72 has an L-shaped lever 76 
which is connected to the inner wire 78 of a push-pull cable 77 by a 
spring 90. 
The outer wire 79 of the cable 77 is axially slidably inserted in a bore 
93, having a stepped portion 92, of a holder 91 and is therefore adapted 
to have play. 
The outer wire holder 91 is fitted in and supported by a retaining portion 
95 at the forward end of pivotal arm 94 and is rotatable about a vertical 
axis. Through a pivot 96, the pivotal arm 94 is supported at its upper 
portion by a tubular portion 97 at the front end of the control box 20 and 
is movable forward and rearward. 
A push-pull cable 98 has an inner wire 101 connected to an intermediate 
portion of the pivotal arm 94 and an outer wire 102 attached to a holder 
103 projecting forward from the control box 20. 
The lever 76 is operatively connected to boom position detecting means 81 
by the push-pull cable 77. The pivotal arm 94 is operatively connected to 
bucket position detecting means 99 by the push-pull cable 98. 
With reference to FIG. 14, the bucket position detecting means 99 has an 
L-shaped detecting arm 106 movable by a cam 104 on the rod 53. The 
detecting arm 106 is supported by a pin 105 on the boom 8 and is pivotally 
movable upward and downward. The inner wire 101 of the push-pull cable 98 
is connected to the detecting arm 106. The outer wire 102 of the cable 98 
is attached to a holder 107 secured to the guide sleeve 54. 
The boom position detecting means 81 is the same as the one shown in FIG. 
7. The detecting arms 56, 106 carry cam rollers 111, 112, respectively, at 
their forward ends. 
The second embodiment operates in the following manner. 
To scoop up sand or earth with the bucket 11, the control lever 14 is 
shifted from the neutral position N to the scooping position, contracting 
the bucket cylinders 12 almost to the limit position to move the bucket 11 
about the pivot 10 in the scooping direction as indicated in phantom line 
in FIG. 14. This moves the rod 53 rearward, causing the cam 104 to 
pivotally move the detecting arm 106 counterclockwise to pull the inner 
wire 101 of the push-pull cable 98, which in turn moves the pivotal arm 94 
about the pivot 96 in the direction of arrow d in FIG. 12. Consequently, 
the outer wire 79 of the push-pull cable 77 comes into contact with the 
stepped portion of the outer wire holder 91 to eliminate the play of the 
outer wire 79 as seen in FIG. 15. 
Next, when the control lever 14 is shifted from the neutral position N to 
the boom-up position U, the first pivotal member 24 moves about the axis 
of the first pivot 22, causing the arm portion 30 and the rod 32 to pull 
up the spool 17 of the boom control valve 15, so that the boom cylinders 9 
extend to raise the booms 8. At this time, the control lever 14 engages 
the engaging portion 75 of the operating member 72. 
The bucket 11 tilts rearwardly downward with the rise of the booms 8, but 
before the bucket reaches a position where it is liable to spill the earth 
(phantom-line position B in FIG. 13), the cam 67 pushes up the detecting 
arm 82 (direction of arrow e in FIG. 7). The arm 82 pushed up pulls the 
inner wire 78 of the cable 77, which in turn moves the lever 76 about the 
pivot 73 in the direction of arrow f in FIG. 15. Consequently, the 
actuating member 72 forcibly shifts the control lever 14 from the position 
U to the position UD. This moves the second pivotal member 25 about the 
second pivot 23, causing the projection 34 and the rod 36 to pull up the 
spool 18 of the bucket control valve 16, whereby the bucket cylinders 12 
are extended to move the bucket 11 in the dumping direction. 
Accordingly, when the booms 8 rise beyond the phantom-line position B in 
FIG. 13, the bucket 11 turns toward the dumping direction (indicated by 
arrow g) with the rise of the booms 8. Thus, the bucket 11 is held with 
its opening up and with the plane of the opening approximately in a 
horizontal position without allowing spillage of the earth therefrom. 
When the booms 8 are raised without moving the bucket 11 in the scooping 
direction, the cam 104 of the bucket position detecting means 99 remains 
unmoved, with the result that the detecting arm 106 remains unmoved to 
hold the pivotal arm 94 in the position shown in FIG. 12, permitting the 
outer wire 79 of the push-pull cable 77 to have axial play. Accordingly, 
even if the boom position detecting means 81 pulls the inner wire 78 with 
the rise of the booms 8, the outer wire 79 sliding moves within the bore 
93 of the holder 91 without moving the lever 76. The actuating member 72 
is therefore held out of operation, obviating the likelihood that the 
control lever 14 will be forcibly shifted from the position U to the 
position UD. 
The invention being thus described, it will be obvious that the same may be 
varied in many ways. Such variations are not to be regarded as a departure 
from the spirit and scope of the invention, and all such modifications as 
would be obvious to one skilled in the art are intended to be included 
within the scope of the following claims.