Load handling vehicle with a bucket side tilt mechanism

A load handling vehicle includes a bucket side tilt mechanism with a supporting H-framework comprised of first and second side frame members and a cross-frame member. The side frame members are each coupled at a first end to the body of the vehicle and at a second end to the bucket, while the cross-frame member is pivoted at each end to a respective one of the side frame members so that the cross-frame member pivots during tilting of the bucket and relieves stress on the framework. A pair of dump cylinders coupled between the framework and bucket are provided for emptying the bucket. In addition, a hoist cylinder extends between the framework and the body of the vehicle, at each side of the vehicle, for raising and lowering the framework and thereby the bucket. A tilt cylinder is tandem with one of these hoist cylinders is extended and retracted to tip the framework and in turn tilt the bucket relative to horizontal as desired. A low-pressure relief mechanism is provided for relieving hydraulic pressure at the bucket side of the dump cylinders to minimize stresses applied to the bucket as the tilt cylinder operates.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to load handling vehicles, and in particular 
to such vehicles with a bucket and a mechanism for tilting the bucket with 
respect to horizontal. 
2. Description of the Prior Art 
A number of prior art load handling vehicles having buckets or blades are 
known to have a mechanism for tilting the bucket with respect to 
horizontal. 
Among such tilt mechanisms are those of the type having a pair of side arms 
rigidly connected together by a crossbar to form a fixed H-frame 
framework. The arms are each pivoted at a first end to the body of the 
vehicle and pivoted at their opposite or second end to the bucket. A short 
stroke hydraulic cylinder is connected at one end to the bucket and at its 
other end to one of the arms. Also, a rigid link is connected at one end 
to the bucket and its other end to the other arm. With this construction, 
operation of the short stroke cylinder applies a torsional load to the 
bucket and physically twists it. This racking or twisting of the bucket 
tilts it with respect to horizontal. However, because of the repeated 
physical twisting, such buckets are subject to breakage and fatigue 
failure. Furthermore, the buckets are relatively expensive to construct 
because reinforcing and heavier components must be utilized to withstand 
the torsional stresses applied to the bucket during tilting. 
In another known type of prior art tilt mechanism, a bucket is pivotally 
connected to the body of a vehicle by an H-frame framework which includes 
a pair of arms and a cross-member. In addition, a hoist cylinder is 
connected at one end to a first of the arms and at its other end to the 
vehicle body while another hoist cylinder extends between the other arm 
and vehicle body. Simultaneous extension and retraction of these hoist 
cylinders respectively lowers and raises the framework and hence, the 
bucket. Also, in this device, the bucket is tilted by extending one hoist 
cylinder while simultaneously retracting the other hoist cylinder. This 
physically twists both the H-frame framework and the bucket and causes the 
bucket to tilt. A cam actuated air switch is provided to control the hoist 
cylinders to limit the maximum tilt of the bucket. In addition, the 
cross-member is pivoted at its respective ends to the side arms to twist 
as the bucket is tilted to partially take up stresses applied to the 
framework during tilting. 
However, in common with the other prior art devices, this particular 
mechanism highly stresses the bucket. Consequently, the bucket is subject 
to failure and must be heavily constructed to withstand the torsional 
loading applied to it during tilting. Furthermore, vehicles of this type 
are often used in dusty areas. This dust easily clogs air actuated 
switches and prevents such switches from effectively limiting the twisting 
of the bucket. As a result of failure of such limit switches, buckets on 
these vehicles are frequently damaged because of stresses from excess 
tilting. 
Therefore, a need exists for a load handling vehicle having a side tilt 
mechanism for a bucket which minimizes the stresses applied to the bucket 
during tilting. 
SUMMARY OF THE INVENTION 
In accordance with the invention, a load handling vehicle includes a bucket 
pivoted to a supporting framework, which in turn is pivoted to a body 
portion of the vehicle. Plural hydraulic spaced-apart hoist cylinder means 
are provided for raising and lowering the framework and thus the bucket. 
Hydraulic tilt cylinder means in tandem with at least one of such hoist 
cylinder means is provided to vary the effective length of one such hoist 
cylinder means relative to the other such hoist cylinder means to thereby 
tilt the bucket relative to horizontal. 
As another feature of the invention, hydraulic dump cylinder means are 
provided for pivoting the bucket relative to the framework to empty it 
and, a low pressure relief mechanism is provided for relieving the 
hydraulic pressure at the bucket side of said dump cylinder means during 
tilting of the bucket to minimize stresses applied to the bucket during 
tilting. 
As a more specific feature of the invention, the framework comprises a pair 
of generally parallel spaced-apart side arm members interconnected by a 
cross-member to form an H-frame, a first hydraulic cylinder extends 
between one of said side arm members and the body of the vehicle and a 
second hydraulic cylinder extends between the other of said arms and the 
body of the vehicle, and a hydraulic tilt cylinder is provided in tandem 
with one of said hoist cylinders to tip the frame and tilt the bucket as 
desired. 
As still another feature of the invention, the cross-frame member is 
pivoted at one end to a first of said sidearm frame members and pivoted at 
its opposite end to the other of said side frame members, such that the 
cross-frame member pivots about its axis during tilting of the bucket to 
minimize stresses on the frame. 
As a further, more specific feature of the invention, the dump cylinder 
means comprises a first dump cylinder extending between the first of said 
side arm members and the bucket and a second dump cylinder means extending 
between the other of said side arm members and the bucket, and the 
low-pressure relief mechanism comprises means for relieving hydraulic 
pressure on the bucket side of each of such dump cylinder means during 
tilting of the bucket. 
As a still more specific feature of the invention, such dump cylinders each 
have their rod or stem ends pivoted to the bucket and said low-pressure 
relief mechanism comprises a means for relieving hydraulic pressure at 
such rod ends. 
It is accordingly a broad object of the invention to provide a load 
handling vehicle with a side tilt mechanism for a bucket which minimizes 
stresses applied to the bucket during tilting. 
It is a further object of the invention to provide a bucket side tilt 
attachment for a load handling vehicle in which the stresses applied to 
the bucket during tilting are minimized. 
It is still another object of the invention to provide a hydraulically 
operated side tilt mechanism for a vehicle which is easily and reliably 
controlled, and which is long lasting as well as relatively trouble-free. 
It is still another object of the invention to provide a bucket side tilt 
mechanism which is relatively low cost, mechanically simple, and which 
requires little maintenance. 
Another object of the invention is to provide a side tilt mechanism for a 
load handling vehicle with a bucket of relatively low cost construction 
with a minimum of reinforcing components. 
These and other objects, features, and advantages of the invention will 
become apparent with the following description, which proceeds with 
reference to the accompanying drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
Overall Description of Vehicle 
With reference to FIGS. 1 and 2, a load handling vehicle in accordance with 
the invention includes an articulated frame 10 comprising a rear or main 
body 12 and a steerable forward body or bogie portion 14. The vehicle also 
includes a forwardly projecting load handling attachment 16 which, in the 
illustrated embodiment includes a bucket 18. Although the term bucket is 
used throughout the specification, it is not to be construed as a 
limitation. That is, the term bucket is intended to include any suitable 
load handling device, whether it be a blade, scoop or other member. 
Main body 12 is supported by a pair of driven wheels 20 operable in a 
conventional manner and controlled by controls conveniently located in a 
cab 22 carried by body 12. Steerable body 14 includes a pair of driven and 
steerable wheels 24 mounted on a conventional wheel supporting framework 
26. The steerable body also includes an upright, generally rectangular, 
rigid mounting block or support 28 to which wheel supporting framework 26 
is journaled by a conventional pivot tube and bearing assembly 30. Thus, 
steerable body 14 is free to oscillate about the axis of pivot 30 as the 
vehicle travels over uneven terrain. 
An upper, generally horizontal, plate-like body connecting flange 34 
projects rearwardly from an upper portion of mounting block 28 while a 
similar lower flange 36 projects rearwardly from a lower portion of the 
mounting block. Flanges 34, 36 are pivoted by respective pins 38, 40 to 
main body 12. Therefore, the portion of the vehicle forward of pins 38, 40 
is free to pivot about a generally vertical steering axis 42 (represented 
by dashed lines in FIG. 1) through the pins. First and second rigid 
steering flanges or ears 44, 46 project rearwardly of mounting block 28 on 
opposite sides of steering axis 42. A hydraulic steering cylinder 48 is 
connected at one end to ear 44 and at its other end to main body 12 while 
a similar hydraulic steering cylinder 50 is connected at its respective 
ends to the body 12 and ear 46. Extension and retraction of cylinders 48, 
50, in response to controls located in cab 22, pivots the front end of the 
vehicle about steering axis 42 to steer the vehicle in a well-known 
manner. 
SIDE TILT MECHANISM 
As shown in FIG. 3, the side tilt mechanism includes a bucket supporting 
framework 50 comprising first and second rigid, elongated, generally 
parallel spaced-apart side arm members 52, 54. Side arm 52 includes a 
sleeve defining block portion 56 projecting generally normal to the 
longitudinal axis of the side arm and inwardly toward side arm 54. 
Similarly, side arm 54 includes an inwardly projecting sleeve defining 
block portion 58. A pivot tube 60 interconnects side arm 52 and side arm 
54. More specifically, one end portion of tube 60 is pivotally received 
within a sleeve 57 defined by block portion 56 while the other end portion 
of tube 60 is pivotally received within a sleeve 59 defined by block 
portion 58. Suitable bushings or bearings are disposed between tube 60 and 
members 56, 58. Therefore, sleeve 60 is free to pivot relative to side 
arms 52, 54 to relieve stress otherwise applied to framework 50 during 
tilting of the mechanism, as explained below. Thus, in its preferred form, 
framework 50 comprises an H-shaped frame supporting structure having side 
arms 52, 54 and a cross-member or pivot tube 60. 
A first end portion 64 of framework 50 is pivoted to mounting block 28 such 
that the framework may be raised and lowered relative to the body 12 of 
the vehicle about a generally horizontal pivot axis indicated at 66 in 
FIG. 3. More specifically, a first end portion of arm 52 is pivoted at 68 
to a lower side edge portion of mounting block 28 while a corresponding 
end portion of arm 54 is pivoted at 70 to the opposite lower side edge 
portion of the mounting block. In addition, the outer end portion 72 of 
framework 50 is pivoted to bucket 18 such that the bucket is free to move 
about a generally horizontal axis 74 for dumping purposes. More 
specifically, the second end portion of arm 52 is pivoted at 76 to one 
lower side portion of the bucket while the corresponding end portion of 
arm 54 is pivoted at 78 to a lower opposite side portion of the bucket. 
Fluid hoist means are provided for pivoting the framework 50 about axis 66 
to raise and lower the bucket. Such fluid hoist means preferably comprises 
plural hydraulic hoist cylinder means. More specifically, as shown in FIG. 
3, such hoist means may comprise a first hydraulic hoist cylinder 
mechanism 80 extending between a midsection portion of arm 52 and an upper 
side edge portion of mounting block 28 and a second hydraulic hoist 
cylinder mechanism 82 extending between a mid-section portion arm 54 and 
an opposite upper side edge portion of mounting block 28. For purposes 
explained below, at least one of the cylinder mechanisms 80, 82, in the 
illustrated embodiment cylinder mechanism 80, comprises a conventional 
tandem hydraulic cylinder which includes a hydraulic hoist cylinder 
portion 84 and a tilt cylinder portion 86 separated by a fixed plate 88. 
Hoist cylinder portion 84 and tilt cylinder portion 86 extend and retract 
along a common axis or line. Hoist cylinder 82 is pivoted at 90 to arm 54 
and at 92 to mounting block 28. In addition, hoist cylinder mechanism 80 
is pivoted at 94 to arm 52 and at 96 to mounting block 28. 
Hoist cylinder portion 84 of the tandem cylinders and hoist cylinder 82 are 
preferably of the same stroke and are supplied with hydraulic fluid 
through a commercially available flow-splitter mechanism such that they 
operate together to raise and lower framework 50, and hence the bucket 18, 
about axis 66. That is, with tilt cylinder portion 86 of the cylinder 
mechanism 80 in a fixed or locked position, cylinders 82, 84 will raise 
and lower both sides of the framework together in unison. 
The side tilt mechanism is also provided with a hydraulically controlled 
dumping means for pivoting bucket 18 about axis 74 to empty its contents. 
Preferably, such dumping means comprises a plural hydraulic cylinder means 
such as a hydraulic cylinder 100 and a hydraulic cylinder 102. As shown in 
FIG. 3, the rod or stem end of cylinder 100 is pivoted at 104 to an upper 
side edge portion of bucket 18 while the piston end of this cylinder is 
pivoted at 106 to a mid-section portion of arm 52. Although not required, 
preferably the rod or stem ends of the dump cylinders are connected to the 
bucket because during dumping, it is desirable to apply fluid to the 
piston side of these cylinders as this produces more available power for 
dumping purposes. In addition, the stem end of cylinder 102 is pivoted at 
108 to an upper side edge portion of bucket 18 opposite pivot 104 and the 
piston end of cylinder 102 is pivoted at 110 to a mid-section portion of 
arm 54. It will be appreciated that extension of cylinders 102, 104 causes 
bucket 18 to pivot forwardly about axis 74 to empty its contents, while 
retraction of these cylinders pivots the bucket in the opposite direction. 
As previously mentioned, hydraulic cylinder mechanism 80 includes a side 
tilt cylinder portion 86 in tandem with hoist cylinder portion 84. Side 
tilt cylinder 86 preferably comprises a short stroke hydraulic cylinder 
operable to vary the distance between points 94-96 relative to the 
distance between points 90-92. That is, in its neutral or non-tilt 
position, the distance between points 94-96 is identical to the distance 
between points 90-92 such that arms 52 and 54 are parallel to one another 
and bucket 18 is generally horizontal, assuming for discussion purposes 
that the vehicle is being operated on level ground. On the other hand, as 
explained in greater detail in connection with the operation of the 
vehicle, extension of tilt cylinder portion 86 increases the distance 
between points 94-96 while the distance between points 90-92 remains 
constant. This in turn forces point 76 and the corresponding portion of 
bucket 18 downwardly relative to point 78 at the opposite side of the 
bucket and thereby tilts the bucket. In addition, retraction of cylinder 
86 shortens the distance between points 94-96 while the distance between 
points 90-92 remains constant. This raises point 76 and the corresponding 
portion of the bucket relative to point 78 so that the bucket is tilted in 
the opposite direction with respect to horizontal. 
As a specific example, in one embodiment of the invention having a tilt 
cylinder with a total stroke of eight inches, four inches in each 
direction from its neutral position, actuation of tilt cylinder 86 causes 
point 76 to tilt a maximum of approximately a total of thirty four inches, 
seventeen inches in each direction from horizontal. Also, as cylinder 86 
is extended and retracted, pivot tube 60 pivots and relieves stress that 
otherwise would be applied to framework 50. 
To further reduce stresses applied to bucket 18 during tilting, as 
explained more fully below in connection with the discussion of the 
hydraulic circuit of the invention, a low-pressure relief mechanism is 
provided for relieving pressure at the bucket side of cylinders 100, 102. 
Hence, with cylinders 100, 102 mounted as shown in FIG. 3, this pressure 
relief mechanism relieves pressure at the stem side of such cylinders 
during tilting. In particular, as the cylinder 86 is extended, a tensile 
force is applied to cylinder 100 and it is permitted by the pressure 
relief mechanism to elongate and reduce the stress on the bucket. In 
contrast, a compressive force is applied to cylinder 102 and it remains 
locked. Conversely, retraction of tilt cylinder 86 applies a tensile force 
to cylinder 102 and a compressive force on cylinder 100. In this 
situation, cylinder 102 is permitted by the low-pressure relief mechanism 
to elongate and thereby relieve stress on the bucket. 
The extent of tilting is positively limited by the length of the stroke of 
the cylinder 86 and does not depend upon failure prone air actuated 
switches. Furthermore, by selecting a tilt cylinder of a desired stroke, 
the maximum degree of tilting of the bucket with respect to horizontal is 
controlled. 
Each of the connections between the cylinders and other structural members 
preferably comprises a conventional ball-type pivot connection permitting 
some rotation as well as pivoting. Similar ball-type pivot connections 
join framework 50 to bucket 18 and main body 12. 
Thus, a bucket tilt mechanism in accordance with the invention is reliable 
and minimizes stresses applied to the bucket during tilting. 
HYDRAULIC CIRCUIT 
With reference to FIG. 4, a hydraulic circuit for operating the side tilt 
mechanism of FIG. 3 includes a dump cylinder control valve 116, a tilt 
cylinder control valve 118, a main hoist cylinder control valve 120 and a 
steering cylinder control valve (not shown). Each of these control valves 
has six ports respectfully labelled 116a-116f, 118a-118f, and 120a-120f. 
Furthermore, each of these valves comprises a conventional three-way valve 
having a neutral position, a forward flow position, and a reverse flow 
position. An air controlled hydraulic actuation cylinder 122 is provided 
to shift valve 116 between its operating positions. Similar actuating 
cylinders 124, 126 are provided for controlling the respective valves 118, 
120. Actuation cylinders 122, 124 and 126 are controlled from the cab of 
the vehicle for convenience and operate to shift the respective valves 
against a suitable spring biasing mechanism. 
When valves 116, 118 and 120 are in their neutral position, a flow path is 
provided between ports b and e and the remaining ports are blocked. In 
addition, when each valve is in its forward position, ports b and e are 
blocked, a flow path is provided between ports a and d, and a flow path 
exists between ports c and f. Also, when each valve is in its reverse flow 
position, ports b and e are blocked, a flow path exists between ports a 
and f, and a flow path exists between ports c and d. 
Port 116a is connected by a hydraulic line to the piston side of each of 
the dump cylinders 100, 102 and also through a conventional pressure 
relief valve 130 to a return line 132 which leads to a filter 134 and in 
turn to the hydraulic fluid supply tank 136. A check valve 134 permits 
fluid to flow from line 132 back to port 116a and hence to the cylinder 
side of dump cylinders 100, 102. Ports 116b and 116f are connected to 
return line 132. In addition, port 116c is connected through a hydraulic 
line to the stem or rod side of the respective dump cylinders 100, 102 and 
also through a conventional pressure relief valve 138 to line 132. A check 
valve 140 permits fluid to flow from line 132 to the rod side of cylinders 
100, 102. Port 116e is coupled through a check valve 142 to port 116d and 
also through a conventional pressure relief valve 144 to line 132. When 
valve 122 is in its neutral position, fluid returning from the steering 
cylinders on a line 146 is fed through the valve ports 116e, 116b, through 
filter 135 and to tank 136. 
When valve 118 is in its neutral position, a pump 148 supplies hydraulic 
fluid from tank 136 through ports 118b and 118e to a steering fluid supply 
line 150, which is connected to the steering cylinder control valve. Port 
118b is also connected through a check valve 152 to port 118c and, in 
addition, is coupled through a conventional pressure relief valve 154 to 
line 132 and hence to the tank. Port 118a is connected to line 132. Port 
118d is connected by a hydraulic fluid supply line to the piston side of 
tilt cylinder 86 and also through still another pressure relief valve 156 
to line 132. Also, port 118f is coupled both to the stem side of tilt 
cylinder 86 as well as through a pressure relief valve 158 to line 132. 
A pair of parallel pumps 160, 162 supply fluid from tank 136 to port 120b 
of valve 120. When this valve is in its neutral position, this fluid 
passes through port 120e to a return line 164, a filter 168, and to tank 
136. Port 120b is also coupled by a pressure relief valve 170 to line 164 
and through a check valve 172 to port 120a. Port 120c is coupled to return 
line 164. Port 120d is connected to an input 175 of a conventional flow 
divider mechanism 174 which evenly divides the fluid it receives from port 
120d between a pair of output lines 176, 178. Preferably, flow-splitter 
174 comprises a pair of hydraulic motors 180, 182 physically 
interconnected by a shaft 184 such that they operate at the same speed. As 
motors 180 and 182 are restricted so as to operate together, the fluid 
from line 175 is divided equally between lines 176 and 178. Line 176 is 
connected to the stem side of hoist cylinder 82 and also through a 
conventional variable pressure relief valve 188 to line 170. In addition, 
line 178 is connected to the stem side of hoist cylinder 84 and also 
through a variable pressure relief valve 190 to line 176. Relief valves 
188, 190 equalize the pressure at the stem side of the respective 
cylinders 82, 84 when the system is initially started to synchronize the 
cylinders. Port 120d is also coupled through a pressure relief valve 192 
to return line 164 and hence to tank 136. Finally, port 120f is connected 
to the piston side of cylinders 82, 84 and through still another pressure 
relief valve 194 to the tank. 
Pressure relief valves 130, 144, 154, 156, 158, 170, 188, 190, 192 and 194 
are each set in a conventional manner at a level to relieve excess 
pressures in their respective lines. Typically, such settings will range 
at on the order of from 1,800 to 2,300 pounds per square inch depending on 
the particular valve in question. In contrast, pressure relief valve 138 
is set at a relatively low pressure level, for example within the range of 
from 300 to 400 psi or thereabout, to permit fluid from the stem side of 
cylinders 100, 102 to bleed through it as the bucket is tilted. 
OPERATION OF THE LOAD HANDLING VEHICLE 
As indicated above, bucket 18 is raised and lowered by hoist cylinders 82, 
84. More specifically, to raise the bucket, valve 120 is shifted from its 
neutral position shown in FIG. 4 to its forward flow position so that 
hoist cylinders 82, 84 retract. When the valve is in this position, pumps 
160, 162 supply fluid through check valves 172, ports 120a, 120d, 
flow-splitter 174 and to the stem side of the cylinders 82, 84. Also, 
fluid from the piston side of these cylinders is fed through ports 120f 
and 120c to the tank. Thus, the hoist cylinders retract and the bucket is 
raised. Conversely, to lower the bucket, valve 120 is shifted to its flow 
reversal position and the hoist cylinders elongate. When valve 120 is in 
this flow reversal position, pumps 160, 162 supply fluid through check 
valve 172, port 120a and port 120f to the piston side of cylinders 82, 84. 
This in turn causes these cylinders to elongate and lower the bucket. 
Cylinders 100, 102 operate to dump bucket 18 as follows. To dump the 
bucket, valve 116 is shifted to its forward flow position to elongate the 
dump cylinders. When in this position, fluid returning from the steering 
portion of the hydraulic circuit is fed from port 116e through check valve 
142, port 116d to port 116a and hence to the piston side of the cylinders 
100, 102. In addition, fluid from the stem side of these cylinders is 
returned through ports 116b and 116f to the tank. As a result, cylinders 
100, 102 elongate and pivot bucket 18 forwardly about axis 74. A 
conventional latching mechanism 128, unless interrupted by the operator in 
the cab, latches control valve 116 in its forward position until the 
cylinders 100, 102 bottom out and the bucket is completely empty. At this 
time, mechanism 128 becomes unlatched. Conversely, to pivot the bucket in 
the opposite direction about axis 174, valve 116 is shifted to its flow 
reversal position to cause dump cylinders 100, 102 to retract. When in 
this latter position, fluid is supplied from line 146, through check valve 
142 to port 116d, and hence to port 116b and to the stem side of cylinders 
100, 102. At the same time, fluid from the piston side of these cylinders 
is fed through port 116a and port 116f to the tank. 
More importantly, the side tilt cylinder operates to tilt the bucket as 
follows. To raise the bucket portion 76 relative to horizontal, valve 118 
is shifted to its flow reversal position to cause tilt cylinder 86 to 
elongate. When valve 118 is in this position, fluid passes from pump 148 
through check valve 152, port 118c, port 118d and to the piston side of 
side tilt cylinder 86 causing it to elongate. This in turn increases the 
distance between points 94, 96 of the mechanism relative to distance 
between points 90, 92 and drives bucket portion 76 upwardly relative to 
the opposite side of the bucket. Conversely, to tilt the bucket in the 
opposite direction, valve 118 is shifted to its forward flow position to 
cause tilt cylinder 86 to retract. When valve 118 is in this latter 
position, fluid from pump 148 is fed through check valve 152, port 118f 
and hence to the stem side of tilt cylinder 86. At the same time, fluid 
from the piston side of this cylinder is returned through port 118d and 
118a to the tank. As a result, the portion of the bucket at location 76 is 
raised with respect to horizontal. 
More specifically, with reference to FIGS. 3, 5 and 6, the side tilt 
mechanism operates as follows. With the blade in its horizontal position 
as shown in FIG. 3, and the tandem side tilt cylinder 86 and hoist 
cylinder 84 at the lefthand side of the vehicle relative to the driver, 
lengthening tilt cylinder 86 causes the following to occur. The lefthand 
portion of the blade is tilted downwardly and, in fact, pivots about 
location 78 at the opposite side of the blade. Both the hoist cylinders 82 
and 84 remain locked in their respective positions. In addition, pivot 
tube 60 permits arm 52 to move downwardly relative to arm 54 and thereby 
relieves stress on the supporting framework 50. In addition, the lefthand 
dump cylinder 100 elongates as fluid is forced from the stem side of this 
cylinder through the low pressure relief valve 138 (FIG. 4) to the tank. 
At the same time, the righthand dump cylinder 102 remains locked as the 
forces applied to it are opposite to those applied to the cylinder 100. 
That is, excess pressure is not applied to the stem side of cylinder 100. 
This sequence of events is represented in FIG. 5 wherein the distance 
between points 94 and 96 has increased relative to the distance between 
points 90 and 92, and the distance between points 104 and 106 has 
increased relative to the distance between points 108 and 110. 
Conversely, to tilt the blade in the opposite direction with respect to 
horizontal, again with the tilt cylinder at the lefthand side of the 
vehicle, the following occurs. Tilt cylinder 86 is shortened to raise 
location 76 of the bucket with respect to horizontal. That is, location 76 
pivots upwardly about point 78 at the other side of the bucket. Again, 
both hoist cylinders 82, 84 remain fixed as, under the example being 
discussed, the bucket is not being raised or lowered at this time. 
Furthermore, the righthand dump cylinder 102 elongates and relieves stress 
on the bucket as an excess pressure is present at the stem side of this 
cylinder, which is relieved through low-pressure relief valve 138. The 
force applied to cylinder 100 during tilting is opposite to that on 
cylinder 102 so that cylinder 100 remains locked. This sequence of events 
is represented in FIG. 6 in which the distance between points 94, 96 has 
shortened relative to the distance between points 90, 92 while the 
distance between points 110, 108 has increased relative to the distance 
between points 104, 106. 
Therefore, as a result of this construction, a side tilt mechanism is 
provided in which the stresses applied to a bucket during tilting are 
minimized. 
Of course, many modifications may be made to the specific preferred 
embodiment discussed above. For example, it has been found that the side 
tilt mechanism will function without a low-pressure relief mechanism such 
as valve 138. However, without such a low-pressure relief at the bucket 
side of the dump cylinders, additional stresses would be applied to the 
bucket. 
Also, it has been found that the side tilt mechanism will function with a 
rigid member interconnecting side arms 52, 54 instead of a pivoting member 
such as 60. However, with such an alternate construction, additional 
stresses are applied to the frame. 
In addition, tandem cylinder mechanism 80 can be positioned at either side 
of the vehicle as desired. For that matter, a similar tandem cylinder may 
be provided at each side of the vehicle for additional tilting 
capabilities of the bucket. However, in such a case, the mechanism is more 
difficult to hydraulically control. Also it has been found that a single 
tandem cylinder provides more than enough tilting capability for most 
applications. 
While I have shown and described a preferred embodiment of my invention, it 
will be apparent to those skilled in the art that many additional changes 
and modifications may be made without departing from my invention in its 
broader aspects.