Note: Descriptions are shown in the official language in which they were submitted.
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LARGE DUMP TRUCK SUSPENSION
Field of the Invention:
This invention i-elates to suspension systems and configurations for the main
structural components of very large trucks of the type used in mining
operations.
Background of the Invention:
There is much commonality between currently available large mining
trucks made by different manufacturers and the following observations are
generally applicable regardless of the truck manufacturer:
- The empty vehicle weight is a high proportion of the maximum gross
vehicle weight. Typically the ratio of payload to empty vehicle weight is
only about 1.4:1. This means that much of the cost of operating such
trucks is related to moving the empty vehicle weight rather than the
payload.
- The total width of the four rear tyres is large compared to the total width
of the truck. Typically 65% of the total width of a truck is taken up by the
four rear tyres. With present designs of truck this leads to a very narrow
main frame for the truck and very high bending loads on the rear axle and
rear wheel support systems. The narrow main frame causes shortage of
space for maintenance of some components, high stress changes during
cornering manoeuvres, the need for vertically stiff rear suspension springs
and design restrictions on the body. The nett effect is high weight and cost
for the main frame, the rear axle, the rear wheel support assemblies and
the body.
- The travel of the rear suspension system of a fully loaded truck is very
limited compared to the scale of the truck. Typically the maximum travel
in the compression direction of the rear axle relative to the main frame is
only of the order of 50 mm when loaded. This limited travel is a result of
the need to achieve adequate roll stiffness from the two narrowly spaced
rear spring units.
- The main franaes of these trucks are complex welded steel structures that
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are heavy (e.g. 16.5 tonnes for the main frame of a truck with a payload
rating of 172 tonnes), expensive to design, develop and manufacture, and
prone to fatigue cracking.
- The main load carrying member (the body) of the trucks is a very strong
and generally stiff member. This strength and stiffness is a consequence of
the need for the body to withstand the shock loads applied during loading
of large rocks by large excavators.
- The body is generally supported by the main frame of the truck at
numerous points. For example at the rear pivot points, at two, four, six or
eight points along the underside of the body and in some trucks also at
forward extensions of the body which contact the main frame at points
which are close to being above the line joining the centres of the front
wheels. This system of supporting the stiff body causes high variation of
stress levels in the main frame of the truck and the body as the truck
traverses over uneven ground and during cornering. This feature causes
fatigue problems, high design and fabricating costs and the need for
considerable expenditure to limit the unevenness of the ground on which
the trucks travel.
- The body is tipped (hoisted) by hydraulic cylinders which react against the
main frame of the truck at points near to midway between the front and
rear wheels. This causes very large bending loads to be applied to the main
frame of the truck and requires that the main frame be very massive at the
mid sections. It can also cause large stress changes in the body.
- The dual rear tyres are rotationally locked together. During short radius
turning manoeuvres (frequent occurrences in typical mining operations),
this causes severe scrubbing type wear of the tyres due to the differential
travel distance effect. Relative scrubbing between the two tyres of a dual
set is considered to contribute significantly to total wear of rear tyres on
large mining trucks.
- The combination of four wide tyres on a solid beam type rear axle causes
large variations in individual tyre loads as the truck traverses uneven
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ground conditions. This arrangement also means that it is necessary to take
considerable care in matching tyre outside diameters and inflation
pressures to minimise the unevenness in tyre loads on level ground
conditions.
In general with currently available truck designs, the transfer of forces
between the body and the ground is through a very indirect path which
involves high bending loads in the body, the main frame of the truck, the
rear axle housing and the rear wheel support systems. Furthermore these
bending loads fluctuate greatly as the truck travels over uneven ground,
during cornering and when the dump body is raised during unloading.
A typical very large mining truck is shown in Figure 1 of the drawings of
US Patent No. 5,385,391, and it will be noted that the frame structure is
quite
substantial and this results from the frame being required to bear the load
supported by the body of the truck by contact between the body and the upper
surfaces of the frame, and by virtue of the body hoisting rams being connected
to
the frames as shown. The substantial size of the rear axle is also apparent.
While many truck frame design improvements have been suggested over the
years, no one design has successfully addressed more than a few of the
difficulties which have been outlined above. For example, United States Patent
No. 3,704,040 Davis et al discloses a frame arrangement in which the front and
rear wheel pairs are centrally supported, the independent frame members
arrangement which is described as addressing many of the problems created by
uneven terrain is extremely complex and consequently expensive and heavy. This
patent and the related United States Patent No. 3,773,348 also disclose a rear
suspension arrangement suitable for use with centrally supported rear wheel
pairs.
Centrally supported rear wheel pairs provide the potential to overcome some of
the problems inherent in currently available large mining trucks, but to date
no
successful method of exploiting this potential has been established.
In addition to the above, most truck body designs have remained
essentially unchanged for many years, being characterized by extremely heavy
structures reinforced by means of relatively closely spaced transverse beams
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assisted by limited longitudinal beams, thereby resulting in a body structure
of
extremely high weight.
Similarly, most conventional truck bodies have a sloping floor and
vertical longitudinal sides arranged at a constant width spacing. In one
departure
from this approach, a body having a flat floor and vertical sides which are
wider
apart at the rear of the body than at the front of the body was designed.
Although
in this arrangement, the wear on the sides of the body is reduced, the flat
body
floor is not compatible with most truck main frame designs and it increases
the
height of the centre of gravity of the truck unless the overall width and/or
length
of the truck is increased.
At least some of the problems outlined above are overcome in the very
large vehicle described in US patent no. 5,476,285.
Summary of Invention and Objects:
It is an object of the present invention to provide a further improved
suspension system and configuration for a very large vehicle in which at least
some of the problems outlined above are ameliorated.
In one aspect the invention provides a suspension system for a very large
vehicle, comprising a substantially rigid main frame having a forward section
carrying front wheels and a rear section, said rear section being
substantially
rigidly attached to said front section and including spaced frame members each
associated with a wheel mounting hub, each hub independently supporting a pair
of rear wheels one either side of the hub, said suspension system comprising a
forward attachment means for said hub pivotally mounted on said frame
members to allow limited rotation of said hub about a longitudinal and a
transverse axis relative to each frame member, and a substantially vertically
compliant suspension means.
Certain exemplary embodiments can provide a suspension system for a
very large vehicle, comprising a substantially rigid main frame having a
forward
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section carrying front wheels and a rear section, said rear section being
substantially rigidly attached to said forward section and including spaced
frame
members each associated with a wheel mounting hub, each hub independently
supporting a pair of rear wheels one either side of the hub and a body
pivotally
mounted on said main frame, said suspension system comprising a forward
attachment means for each hub pivotally mounted on said frame members to
allow limited rotation of said hubs about a longitudinal and a transverse axis
relative to the frame member, and a substantially vertically compliant
suspension
spring unit, wherein each substantially vertically compliant suspension spring
unit is pivotally mounted to the hubs to allow rotation of said hub about a
longitudinal axis and a transverse axis relative to the frame member and that
each
substantially vertically compliant suspension spring unit is also pivotally
mounted to the frame member by a suspension support member comprising a
pivot mounting for constraining rotation of the substantially vertically
compliant
suspension spring unit to rotate about an axis through the pivot mounting and
normal to the vehicle's longitudinal vertical plane thereby preventing
sideways
movement of the hub relative to the frame member.
Certain exemplary embodiments can provide a large vehicle including a
substantially rigid main frame having a forward section carrying front wheels
and a rear section, said rear section being substantially rigidly attached to
said
front section and including spaced frame members, each associated with a wheel
mounting hub, each hub independently supporting a pair of rear wheels, one
either side of the hub, a suspension system including a forwarding attachment
means for each hub pivotally mounted to said frame member to allow limited
rotation about a longitudinal axis and a transverse axis relative to the frame
members and a substantially vertically compliant suspension spring unit,
a substantially rigid load supporting body, means for pivotally mounting said
body with respect to said main frame in proximity to the pivotal mounting of
the
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substantially vertically compliant suspension spring unit to said frame
member,
and means for maintaining transverse spacing between said rear wheels, wherein
said substantially vertically compliant suspension spring unit is pivotally
attached to said hub to allow limited rotation of said hub about a
longitudinal
axis and a transverse axis relative to said frame member, and that each
substantially vertically compliant suspension spring unit is also pivotally
mounted to the frame member by a suspension support member comprising a
pivot mounting for constraining rotation of the substantially vertically
compliant
suspension spring unit to rotate about an axis through the pivot mounting and
normal to the vehicle's longitudinal vertical plane thereby preventing
sideways
movement of the hub relative to the frame member.
The substantially vertically compliant suspension means is pivotally
connected to said hub to allow relative rotation of said hub about a
longitudinal
axis and a transverse axis relative to the frame member. The suspension means
is also pivotally connected to the frame member to thereby limit relative
rotation
of the hub about a transverse axis relative to the frame member.
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In a preferred form, the invention provides a main frame forward section
which is relatively narrow and extends between said front wheels, said rear
section being wideir than said front section, said spaced frame members
including
elongate frame poi-tions which extend gradually inwardly from said wider rear
section to said nanrower front section such that the transition between said
front
and rear sections is gradual rather than abrupt.
The said forward attachment means is preferably, pivotally mounted on
mounting means extending laterally outwardly from said frame members, said
main frame further comprising a cross member extending between said spaced
frame members and secured thereto to minimise twisting loads imposed on said
rear frame section by said mounting means for said forward attachment means.
The cross section preferably comprises a shaft passing through portions of
said frame members and having end portions extending laterally outwardly from
said frame members to provide said mounting means for said forward attachment
means.
The forward attachment member may be substantially tubular and the
pivotal mounting may have a passage through it to convey cooling air to
electric
traction motors supported by the rear wheel mounting hub.
In another aspect of the invention there is provided a large vehicle
comprising a suspension system as defined above, a substantially rigid load
supporting body, means for pivotally mounting said body with respect to said
main frame, and means for maintaining transverse spacing between said rear
wheel pairs.
By provid'uig the principal reinforcement of the body by means of
longitudinally exteiading strengthening beams, the necessary body strength can
be
achieved with significant reductions in the weight and the manufacturing cost
of
the body.
The body is pivotally mounted on the main frame of the truck and it is
preferably supported only at the pivot points and at one or two points near
the
front of the body, these forward support(s) lying close to above the line
between
the centres of the front wheels of the truck. The hydraulic cylinder(s) used
for
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tipping the body about its pivot points preferably react onto the main frame
of the
truck at one or two points which are also close to above the line between the
centres of the front wheels of the truck. By these means the body is prevented
from exerting large bending moments in the main longitudinal members of the
main frame of the truck. The forward body supports may include a positive
location system between the body and the main frame of the truck so that the
body can provide a significant proportion of the strength that is required
between
the front and rear wheels when it is in the 'down' position.
The use of rear wheel mounting hubs positioned between each pair of wheels
suits the use of electric motor systems to drive the rear wheels. The use of
such
motors has the inherent advantage of enabling the problems associated with a
solid rear axle to be easily overcome thereby reducing the weight of the rear
wheel supporting systems, improving load sharing between the rear tyres and
reducing the rear tyre wear effects of such axles. However, mechanical drive
systems may be utilized with acceptable results. Advantages may be taken of
the
rear wheel mounting arrangement to incline one or both of the wheels which are
mounted on the hub at an angle other than vertical so as to improve the
stability
of the vehicle during cornering manoeuvres and when operating on cross
(transverse) slopes. The location of the rear wheel mounting hubs between each
pair of wheels allows independent rotation of each wheel thereby avoiding tyre
wear caused by short radius turning.
In another aspect of the invention, there is provided a large vehicle
including a substantially rigid main frame having a forward section carrying
front
wheels and a rear section, said rear section being substantially rigidly
attached to
said front section and including spaced frame members each associated with a
wheel mounting hub, each hub independently supporting a pair of rear wheels,
one either side of the hub and a suspension system,
said suspension system including a forwarding attachment means for said
hub pivotally mounted to said frame member to allow limited rotation about a
longitudinal and transverse axis relative to each frame member and a
vertically
compliant suspension means, and
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a substantiially rigid load supporting body, means for pivotally mounting
said body with respect to said main frame in proximity of the pivotal mounting
of
the suspension means to said frame member, and means for maintaining
transverse spacing between said rear wheels.
The verticailly compliant suspension means is pivotally attached to said hub
to allow limited relative rotation of said hub about a longitudinal and a
transverse
axis relative to said frame member. The suspension means is also pivotally
connected to the frame member to allow relative rotation of said hub about a
transverse axis relative to the frame member.
The suspension means preferably includes a suspension support member
which is mounted for pivotal movement on said frame member. In one preferred
form, the suspension support mounting is in proximity to or coincidental with
the
pivot mounting of the body to the main frame.
In a preferred form of the invention, the pivotal connection of the
suspension means to the frame member permits rotation of said suspension means
only about an axis which is parallel to the body pivoting axis. The body pivot
may include a cylindrical bearing which engages with the frame members and the
support of the suspension means.
In an alternate form of the invention, the pivotal connection of the
suspension means to the frame member, or the frame member itself, allows
limited rotation of the hub in a transverse-vertical plane relative to the
frame
member. The suspension support of the suspension means may be provided
with a yoke for supporting a spherical bearing, said spherical bearing
engaging
bearing surfaces formed in the respective frame member. The yoke may be
provided with a transversely extending bush into which is journalled an inner
sleeve for pivotal mounting of the body support.
Alternatively, the pivotal mounting of the body support may provide the
support for the spherical bearing, said bearing engaging bearing surfaces
formed
in the respective frame member and eliminating torsional loading on the frame
member between the spherical bearing housing on the frame member and the
forward attachment means for the hub on the frame member.
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The pivotal mounting of the suspension means and the body allows the
main frame, the body support and the suspension means to each pivot
independently relative to the other two. This enables side loads generated in
the
tyre/road interface to be transferred directly into the dump body supports
substantially by-passing the frame.
In addition to substantially direct transfer of the dump body loads onto the
suspension means, the need for a device such as a anti-sway bar, Panhard rod
or
similar device for transferring cornering loads between the rear axle and the
dump body is eliminated.
The forward attachment means is preferably, pivotally mounted on a
mounting arm mounted on mounting means extending laterally outwardly from
said frame members, the mounting means allowing pivotal movement of the
mounting arm about the transverse axis and the longitudinal axis.
While having the pivotal mounting of the body coincidental with the pivot
mounting of the suspension means has a number of advantages, it is preferable
in
some instances to have the pivot mounting of the body displaced a short
distance
from the pivot mounting of the suspension means. The short intervening section
of the main frame is then used to transfer side loading between the dump body
and the suspension means.
Accordingly, the pivotal mounting of said body on to said frame member
may be spaced from the pivot mounting of the suspension means to the frame
members and preferably spaced rearwardly and/or upwardly from the pivot
mounting of the suspension means to the frame member.
Brief Description of the Drawings:
The foregoing and other features, objects and advantages of the present
invention will become more apparent from the following description of the
preferred embodiment and the accompanying drawings in which:
Figure 1 is a side elevation of a truck incorporating an embodiment of a
suspension system in accordance with an earlier invention;
Figure 2 is a side elevation similar to Figure 1 with the truck. body
elevated;
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Figure 3 is a rear end elevation of the truck of Figure 1 showing details of
an earlier embodiment of the rear suspension and partly illustrating the truck
body construction;
Figure 4 is a fragmentary sectional end elevation with parts removed to
show the extent of transverse rotation of one of the two rear wheel mounting
hubs in one direction;
Figure 5 is a fragmentary plan view of the truck frame with the body
removed;
Figure 6 is an enlarged sectional side elevation of one rear wheel mounting
and suspension,
Figure 7 is a plan view of the truck body showing its construction.
Figure 8 is a side elevational view of an embodiment of the suspension
system of the present invention, which replaces the suspension system in the
truck shown in Figure 1.
Figure 9 is a rear sectional view of the embodiment shown in figure 8,
Figure 10 is a fragmentary plan view of the truck frame in accordance
with the embodiment of figure 8 with the body removed,
Figure 11 is a rear sectional view of a second embodiment of the
suspension system of the present invention,
Figure 12 is ai side view of the improved truck construction incorporating
the suspension systems of Figures 8, 9 and 11 of the present invention,
Figure 13 is a side view of the improved truck construction incorporating a
suspension system/body attachment in accordance with a third embodiment of the
invention,
Figure 14 is a side view of the embodiment of Figure 13 showing the body
tilted about the connection to the main frame, and
Figure 15 is a sectional view along line 15-15 of Figure 13.
Description of Preferred Embodiment:
Referring to Figures 1 to 5 of the drawings, the truck frame comprises a
pair of relatively lightweight longitudinal members 10 and 11 suspending rear
wheel mounting hubs 12 and 13 towards their rear ends. The longitudinal
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members 10 and 11 are connected at their forward ends by a substantial cross
member 14, such as a mounting collar which generally includes mounting points
for the front suspension (not shown) for the front wheels Wf, at the front by
a
bumper 60 and at the rear, forwardly of the rear wheels, by a cross member
60a,
which forms part of the support means for the rear wheel mounting hubs 12 and
13, as will be described further below. The front suspension may take the form
described in greater detail in US Patent No. 5,385,391 or in any other
suitable
form.
As shown in Figures 3, 4 and 5, the wheel mounting hubs 12 and 13
support drive means for the rear wheels W, such as electric traction motors
16,
17, 18 and 19, which are in turn connected to the rear wheels W, with each
wheel being mounted one on either side of the hubs 12 and 13. The location of
the rear wheel mounting hubs 12 and 13 between each pair of rear wheels W,
allows independent rotation of each wheel thereby avoiding tyre wear caused by
short radius turning.
The rear suspension system of figures 1-6 includes rear wheel mounting
hubs 12 and 13 mounted to the longitudinal frame members 10 and 11 by means
of hollow forwardly extending attachment members 20 which are attached to
pivotal mountings 21 which are in turn pivotally secured to a cross member 60a
which is rigidly secured to the frame members 10 and 11. The attachment
members 20 and the rear wheel mounting hubs 12 and 13 may be formed
separately or as an integral unit, and the hollow attachment members 20
operate
to convey cooling air to the motors 16 to 19 attached to the hubs 12 and 13.
Each pivotal mounting 21 includes a top transverse journal 22 and a
bottom longitudinal journal 23 which allow two rotational degrees of freedom
for
the hubs 12 and 13. The transverse journal 22 engages spindle sections on the
ends of a shaft 24 (Fig. 5) which forms part of the rear cross member 60a for
the
frame members 10 and 11, which, as shown in Figures 1 and 2, are of increased
depth in this region to allow the cross member 60a to penetrate the side
plates of
the frame members 10 and 11, to which the cross member 60a is rigidly secured
in some suitable manner. Each lower journal 23 receives the end portion of one
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of the attachment members 20, within which journal 23 this end portion is free
to
rotate, the end portion of the attachment member 20 being restrained within
the
journal by a flange 23a formed on the attachment member 20 and a nut 23b
engaging the end portion of the attachment member 20, as shown most clearly in
Figure 6 of the drawings.
The frame members 10 and 11 also provide a journal for a mounting
member 26 for vertically compliant suspension means or spring unit 27, the
mounting member 26 also having an integrally formed journal 28 which receives
pivot pins 29 about which the body B of the truck also pivots. The spring unit
27
includes a cylinder housing 41 rigidly attached to the mounting means 26 and
receiving a piston unit 40 which is attached to the mounting hubs 12,13 by a
rearward extension 42. The spring effect may be obtained by the compression of
a gas within the cylinder or by other suitable means.
The mounting means 26 has downwardly extending rigid flanges 30 which
are adapted to be engaged by a projection 31 extending from each hub 12,13 at
a
position closely adjacent the flanges 30 whereby transverse rotation of the
hubs
12 and 13 is limited.
Rotation of the attachment member 20 and its connected hub 12,13 in the
other direction is confined to the vertical longitudinal plane by its
attachment to
the piston 40 and the confinement of the piston 40 by the cylinder of the
spring
means 27 to travel along the axis of the cylinder. The attachment of the
piston
40 to the rearward extension 42 is by a restrained spherical bearing 45
between
the piston 40 and the rearward extension 42.
The above described coupling and spring unit for the rear wheel mounting
hubs 12 and 13 allows the hubs 12 and 13 to pivot about both longitudinal and
transverse axes to facilitate greater flexibility in the movement of each hub
12,13
with respect to the frame and truck body B. One such movement is illustrated
in
Figure 4 of the drawings.
In the first entbodiment of the present invention shown in figures 8, 9 and
10, the rear wheel mounting hubs 112 and 113 are shown mounted to the
longitudinal frame members 110, 111 by means of forwardly extending
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attachment members 120. The attachment members 120 are attached to pivotal
mountings 121 which in turn are pivotally secured to respective frame members
110 and 111. The attachment members 120 and the rear wheel mounting hubs
112, 113 may be formed separately or as an integral unit.
Each pivotal mounting 121 includes a transverse journal 123 which
engages spindle sections on the ends of a shaft 124 which is attached to frame
members 110, 111. Rear cross member 160 is formed by connecting the inside
ends of shaft 124. Connection 125 at each end of rear cross member 160 can be
either a rigid joint, a pin joint or a suitable flexible joint.
Cross member 160 is optional but is useful in that it helps to maintain
constant separation between the end portion of attachment members 120 which
would otherwise tend to increase under tractive effort if cross member 160
were
not present and cause small amounts of "toe out". Cross member 160 also
reduces the torsional loading about the frame long-axis under tractive effort
on
frame members 110, 111. During cornering cross member 160 acts as an
equaliser spreading the unequal cornering loads transmitted through attachment
members 120 to pivotal mountings 121 across frame members 110, 111. Rear
cross member 160 is also useful for mounting ancillary equipment such as
pumps,
valves, etc.
The bottom transverse journal 123 is received within a spherical bearing
123a on the end portion of attachment member 120. The journal 123 allows
rotation of the hub about a transverse axis and a longitudinal axis.
Rotation of the attachment member 120 and respective connected hub 112,
113 about a transverse axis is confined by a vertically compliant suspension
means 127. The lower end 129 of the suspension means 127 engages a
longitudinal extension 128 of the hub 112, 113. The longitudinal extension 128
is preferably received within a spherical bearing 130 in the lower end 129 of
the
suspension means so as to enable rotation of the hub about the vehicle's
longitudinal and transverse axes. The spherical bearing also allows limited
relative rotation between the suspension means and the hub about a transverse
axis.
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The suspension means 127 which is preferably a spring consisting of a
cylinder 127a and piston 150, is received at its upper eind within a mounting
member 126 and is secured by bolts 119. The mounting member 126 pivotally
engages the body pivot 131 and the ends 143 of frame members 110 and 111.
The mounting memiber is provided with a yoke 132 for receiving a suspension
pivot 133 which allows independent relative movement between the body pivot
131, suspension means 127 and frame members 112, 113 about an axis through
the suspension pivot and normal to the vehicle's vertical plane.
The suspension pivot 133 includes a cylindrical bush 134 which extends
through both arms 135, 136 of the yoke and into which is journalled an inner
sleeve 137. The inner sleeve extends beyond the cylindrical bush and is
received
within apertures fonned in the body pivot arms 138, 139. The inner sleeve 137
is secured in position by a retainer 140 and retaining bolts 141. To reduce
frictional forces between the cylindrical bush and the inner sleeve, a
cylindrical
bearing 142 may be provided, preferably in the form of a bronze bearing. In
this
way movement of the inner sleeve 137 relative to the cylindrical bush 134
corresponds to pivotal movement of the body pivot relative to the suspension
means.
The ends 143 of the frame members 110, 111 engage the cylindrical bush
through a spherical bearing 144 located on the centre of the outer surface of
the
cylindrical bush in the vicinity of the space between the arms 135, 136 of the
yoke 132. The ends 143 of the frame members 110 and 111 are received within
the space between the yoke arms and are provided with a bearing which
encircles
the spherical bearing surface 144 located on the cylindrical bush 134.
Since the position of the cylindrical bush 134 is fixed relative to the
mounting member 126 of the suspension means 127, relative movement between
= the suspension means 127 and frame members 110 and 111 is accommodated by
relative movement about spherical bearing 144.
When the ends 143 of the respective frame members are received within
the yoke 132, a small gap 145, 146 between the frame member ends and the yoke
132 exists to allow limited rotation of the mounting member 126 about the
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vehicle's longitudinal axis.
Since the yoke 132 of the mounting member 126 of the suspension means
is received within the arms 138, 139 of the body pivot, side loads generated
in
the ground plane are transferred directly between the rear axle and the dump
body and torsional moments about the long axis of frame members 110, 111 are
minimised.
As a further refinement, it is thought that by laterally off-setting the
vertical axis of the vertically compliant suspension means from the vertical
axis
of the yoke, enhanced distribution of the torsional moments on the body can be
accomplished.
In Figures 11 and 12, an alternative second embodiment of the
suspension/body pivot mounting 233 is illustrated. This embodiment of
suspension/body pivot mounting may be substituted for the mounting 133 shown
in Figure 9.
In the alternate embodiment, the arms 235, 236 of the suspension
mounting member 126 are positioned either side of the frame member 210, and a
cylindrical shaft 237 extends through apertures in both arms and the frame
member 210. The cylindrical shaft is received within apertures formed in the
body pivot arms 238, 239 and secured in position by a retainer 240 and
retaining
bolts 241.
To reduce frictional forces between the cylindrical shaft, arms 235, 236,
frame member 210 and body pivot arms 238, 239, bushings 234 and 244 may be
provided.
The bushings 234 fit within the aperture of the frame member 210, and
between the arms 235 and 236 of the suspension mounting member 126. Each
bushing 234 may be shaped to provide journal bearing sections 231 and spacer
bearing sections 232. Bushing 234 may be secured to the frame member 210
using pins 245 which are received within aligned holes in abutting faces of
spacers 232 and frame member 210 to prevent relative movement and associated
frictional wear between the bushing 234 and the frame member.
Bushings 244 fit within the apertures in the arms 235 and 236 of the
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suspension mounting member 126. The bushings 244 may be shaped to provide
journal bearing sections 243 and spacer or thrust bearing sections 242.
The arrangeinent of Figure 11 functions similar to the arrangement of
Figures 8, 9 and 10 except that no rotation of the mounting member 226 about
the vehicle longitudinal axis is provided for. For some vehicle configurations
this restriction may be acceptable. This arrangement is a much simpler
construction and replacement of the bearings is easier and less expensive
compared with replacement of the spherical bearing of Figure 9.
A further arrangement of body pivot mounting and suspension system
mounting to the miain frame is shown in Figures 13, 14 and 15. In this
arrangement, the rearward mounting of the attachment member 120 to the main
frame 310 is similar to that shown by the combination of Figures 8 and 11.
The suspension means includes spring unit 127 attached to a support 126.
The support 126 is pivotally connected to the frame members 310 which allows
limited rotation of the suspension means relative to the frame member about a
transverse axis. Tb.e pivotal connection is typically a cylindrical bearing
which
does not permit rotation of the suspension means in the transverse-vertical
plane.
As shown in Figure 15, the pivotal connections 200, 250 of the body 238
to the frame member 310 and the suspension support 126 is within section 255
of
the frame member. The body pivot connection 200 comprises a cylindrical shaft
337 which is received within apertures in body pivot arms 238,239 and secured
in
position by a retainer 340 and retaining bolts 341. The bushings 334 of the
body
pivot connection 200 fit within an aperture of section 255 of the frame member
310. Each bushing 334 may provide journal bearing surfaces 331 and spacer
bearing surfaces 332.
The pivotal connection 250 of the suspension member 126 also includes a
cylindrical shaft 357 received within apertures in the suspension member 126
and
secured in position by a retainer 360 and retaining bolts 361. Bushings 354
fit
within the aperture in section 255 of frame member 310 and between the arms of
the suspension mounting member 126. Each bushing 354 may provide journal
bearing sections 351 and spacer bearing sections 352. To prevent relative
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movement and associated frictional wear between bushing 354 and section 255 of
frame member 310, spacer section 352 is secured to section 255 using pins 355
which are received within aligned holes formed in the abutting surfaces of
spacer
section 352 and section 255.
Bushings 342 may be provided to fit within apertures in the arms of
suspension mounting member 126. Bushings 344 preferably includes journal
bearing sections 343 and spacer or thrust bearing sections 342.
The pivotal connection 200 of the body to the frame member 310 of this
arrangement is displaced rearwardly along the frame member 310 from the
suspension system mounting to the main frame as shown in the drawings. The
frame members 310,311 may slope upwardly from the front of the vehicle to the
rear. Consequently, if the distance from the suspension pivot to the rear end
251 of the body remains the same, by displacing the body pivot mounting 200
rearwardly from the suspension system mounting 250, the height hi of the body
rear end from the rear wheels is greater than height h2 when the body pivot
mounting and suspension system mounting are coincidental as shown in Figure
12. Additionally, the distance from the body rear end 251 to the wheels is
increased when the body is raised.
This is particularly advantageous in mine site situations where a guide
mound may be used to indicate the edge of a pit or some other embankment and
the driver of a large mining vehicle reverses up to the mound until the rear
wheels contact before tipping the contents from the body.
Furthermore, while the suspension means is described as being vertically
compliant, the applicants have found some advantages in having the suspension
means slightly inclined from the vertical towards the rear of the vehicle. In
this
way, it is possible to simultaneously achieve an increase in the height of the
rear
end of the dump-body above ground when the body is in the raised position, and
an increase in the distance from the rear of the dump-body to the wheels, with
the preferred embodiment shown in Figure 8 by simply moving the pivotal
connection between the dump-body, the frame and the suspension rearwardly and
upwardly by an appropriate amount. This has many advantages, including
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making more space for a suspension unit with longer stroke. By increasing the
angle between the frame members 110,111 and the horizontal there would be
more clearance between the front section of the rear-axle housing and the
frame
to accommodate relative movement between rear-axle housing and the frame
member. Furthermore, by moving the pivotal connection between the dump-
body, the frame and the suspension means shown in Figure 8 rearwardly, and
thereby angling the rear suspension unit slightly rearward, it is possible to
apply a
preload on the rear-axle end cap 128, this has some advantages over the
general
embodiment shown nn Figure 8.
It can be seen. that the arrangement and the strength of the,body pivot 200,
the suspension member pivot 250 and the section of the main frame 255 which
contains these two pivots is such that most of the transverse twisting loads
from
the supports 126 is transferred into the body pivots 238 rather than into the
forward sections of the frame members 310. In this way compared with prior art
designs, enhanced absorption of the torsional forces can be accomplished.
While the above described suspension systems are suitable for trucks
having frames of the type described above, or of the type otherwise described
in
US Patent No. 5,385,391, it should be appreciated that the suspension system
is
equally applicable to other forms of truck having independent rear axles
supported in a different manner to that described above.
Referring additionally to Figures 1,2,3,4,6 and 7 of the drawings, the truck
body B according to a particularly preferred embodiment comprises side walls
61
and 61a, a floor 62, a front wall 63 and a forwardly extending cabin-
protecting
extension 64. The truck body B has a number of novel features, including that
the
main reinforcing beains under the floor 62, front wall 63 and extension 64
extend
longitudinally of the body, as shown at 65 to 70, and only one transverse
reinforcing beam 72, located close to or on a line between brackets 73 formed
to
receive the pivot pin 29 engaging the journals 28, as previously described.
Two
additional beams 74, 75 and 76, 77 extend along each side 61 and 61a as shown
most clearly in Figure 3 of the drawings. The transverse beam 72 extends the
full width of the floor 62, and preferably extends up the sides 61, 61a of the
body
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as shown.
As mentioned earlier in US Patent No. 5,476,285, conventional truck body
designs rely on numerous transverse beams, and generally only two longitudinal
beams running above the main frame of the truck or along the sides of the body
floor. The principal advantages of the new body design described above include
a significant reduction in the body weight, and a significant reduction in the
manufacturing cost of the body, the body still having sufficient strength to
allow
it to be supported only at the front and at the body pivots, thereby allowing
the
weight and cost of the main frame of the truck to be reduced as described in
greater detail in US Patent Application No. 5,385,391.
In additional to the above, the floor 62 and the sides 61 and 61a are sloped
in the manner shown in Figures 1,3,4 and 7 of the drawings whereby the width
of
the floor 62 of the body B increases from the front of the body to the rear of
the
body, as shown most clearly in Figure 7 of the drawings. The advantage of this
design feature is that wear on the sides of the body is reduced, because when
the
body is raised to the tipping position as shown in Figure 2, the load slides
into a
widening space, rather than being confined to a constant width as for a
conventional body design. Furthermore, the weight of the body can be reduced
and there is no increase of the overall width of the truck.
As described in US Patent Nos. 5,385,391 and 5,476,285 referred to above,
the body is elevated by a pair of extendible rams 51 carried by mounting
points
50 on the frame close to the cross member 14 and at 52 on the truck body B.
It will be appreciated that the truck body features described in greater
detail above are equally applicable to trucks of designs other than the design
described in greater detail above.
Details of the attachment of the traction motors 16 to 19, the front wheel
assemblies, the engine and the construction of the truck ancillaries including
the
driver's cab has not been included in this specification since each of these
items
can be of relatively standard construction and is within the existing
knowledge of
a person of skill in the art. It will, however, be noted that the rear axles
are
independent short axles with one tyre on either side. Whilst the three cross
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members 14, 60 and 60a provide substantial strength and rigidity between the
two
main longitudinal members of the main frame, the transverse spacing of the
frame
members 10 and 11 is also maintained to a significant extent by the direct
attachment of the body B to the longitudinal frame members at the pivot mounts
= 73. This use of the inherent strength of the body B enables a further
reduction in
the frame strength, xveight and cost.
