Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PROCESS FOR THREE-DIMENSIONAL MODELING
AND DESIGN OF OFF-HIGHWAY DUMP BODIES
FIELD OF THE INVENTION
The present invention relates generally to heavy-
duty off-highway trucks, and more particularly to a
process for designing an off-highway truck dump body.
BACKGROUND OF THE INVENTION
In mining and construction environments, heavy-duty
off-highway trucks are used to haul a variety of
materials such as, for example, coal, rock, ore, and
overburden materials. Such heavy-duty off-highway trucks
generally comprise a truck chassis or frame which
supports a dump body for receiving and carrying a load.
In order to ensure that the dump body is properly
balanced, the dump body should be designed based on an
anticipated load distribution of the material carried on
the truck chassis or frame. More specifically, the truck
chassis anticipates a particular optimal location on the
chassis where the center of gravity of the load carried
in the dump body should be positioned.
Trucks with dump bodies which are often sold by the
original equipment manufacturers have dump bodies
designed around an assumed load configuration or load
profile. In designing these dump bodies, however, the
load profile which is used to size the body is based on a
theoretical material angle of repose or load heap of the
material irrespective of material cohesiveness,
individual material heaping characteristics or material
gradation. For example, in designing a dump body for
hauling coal one theoretical material heap which is often
used is a 3:1 heap (corresponding to an angle of repose
of approximately 18 ). With bodies designed to haul
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overburden, a theoretical material heap of 2:1 (or a
different S.A.E. 2:1 heap) is often assumed.
Historically, off-highway truck manufacturers have
been unable to reach a consensus with regards to the
theoretical load heaps or configurations, let alone any
consensus on the individual hauled material
characteristics that should be used to design the dump
bodies. As evidenced by their commercially available
literature, some off-highway truck manufacturers use
theoretical material heap profiles based on standards
promulgated by the Society of Automotive Engineers
(S.A.E. J 1363 Jan. 1985) while others use their own heap
profiles. Moreover, many off-highway truck manufacturers
have over time alternated between using various different
theoretical load heap profiles or configurations to
design their dump bodies.
Off-highway truck manufacturers use these
theoretical load heap profiles so that they are able to
mass produce their dump bodies. However, the theoretical
load heap, and the resulting theoretical load profiles,
which the truck manufacturers use to design their dump
bodies ignore a number of factors. For example,
theoretical load profiles do not take into account the
particular material characteristics of the material being
loaded and hauled. In addition, theoretical load
profiles do not take into account the corner voids which
occur when a load is placed in the dump body. In
particular, since the material is loaded from overhead
into the dump body, the material tends to try to form a
generally conical shape in the dump body. Because the
load conforms to a generally conical shape, voids are
created in the corners of the dump body where no material
is present. The theoretical load profiles as used by
truck manufacturers ignore these corner voids.
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Additionally, field loading/haulage conditions
impact the actual angles of repose that the loaded
material forms in the dump body. In the loading process,
material on its own flows to a natural angle of repose,
however, in the loading process as the loading equipment
pushes/pulls and rests on the material being loaded an
imposed material angle of repose results. For instance,
the method by which the material is actually loaded into
the dump body, e.g. using a front-end loader or a shovel,
can impact the ultimate actual profile of the load in the
body. Other material characteristics such as the
cohesiveness, gradation, size and consistency of the
material (e.g., ore, overburden, clay, etc.) also impacts
the actual load profile. Accordingly, because of
differences in the materials and field loading and
haulage conditions, the actual load profile or
configuration of given materials in the dump body at
different sites can vary extensively.
As a result, the mass-produced dump bodies supplied
by off-highway truck manufacturers which are based on a
theoretical material load profile are often improperly
matched for a particular material haulage application.
For example, the dump body may be inadvertently designed
such that the dump body size and resultant load is either
undersized/underloaded or oversized/overloaded and that
the corresponding center of gravity of the actual load is
significantly offset from where it should be placed,
based on the design of the truck chassis. This causes
incorrect truck loading and improper truck utilization
with uneven loading of the truck chassis leading to
uneven or offset frame loading, which can potentially
result in truck chassis problems including uneven tire
wear which often requires premature replacement of the
tires; and potentially poor vehicle operating stability.
As will be appreciated, since the trucks themselves and
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the tires used on these types of off-highway trucks are
extremely costly, potential truck chassis repair and
premature replacement of tires significantly increases
the operating expenses associated with material haulage.
Likewise, depending on how the actual material and
material heap varies from a theoretical material load
profile, the dump body can be either too large or too
small resulting in the truck chassis carrying loads which
are both improperly placed on the truck frame and
significantly heavier or lighter than intended. An
improperly designed body which is too small to carry the
intended load can lead to spillage of the load over the
sides and off the rear end of the body resulting in
significant under utilization of the truck. If side/rear
spillage occurs during transport, it can result in tire
damage and tire ruptures particularly on the following
trucks. While too large of a body for the intended load
can result in extreme truck overloads or if the load is
limited to the correct load amount in the dump body, the
load may often be improperly placed in the dump body
leading to poor truck stability and individual truck
chassis component overloads.
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SUMMARY OF THE INVENTION
In accordance with one aspect of the invention,
there is provided a method of loading material into a
dump body of a truck using four or less passes of a
loading bucket. For a first pass of the loading bucket
whose volume is approximately 1-4 or more than a
volumetric capacity of the dump body, the method
involves positioning the loading bucket over the dump
body so that material released from the loading bucket
is distributed on a floor of the body to be
approximately centered between opposing sidewalls of
the body. The method also involves lowering the loading
bucket while maintaining the position that allows the
distribution of the material in the body to be
approximately centered between the sidewalls when
released from the loading bucket, and releasing a door
of the bucket and freeing the material held in the
bucket to drop into the dump body when the bucket is at
a height above the floor that substantially minimizes a
distance the material in the loading bucket travels in
falling to the floor and also allows the door of the
loading bucket to swing downwardly toward the floor of
the body without interference with the sidewalls and
the floor of the dump body.
Second and subsequent passes of the loading bucket
may be positioned to drop material from the bucket (1)
at a location approximately centered between the
opposing sidewalls, (2) at a height over the floor that
substantially minimizes a distance the material falls,
and (3) without the side walls interfering with the
door when the door is released and the material freed
to fall.
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In accordance with another aspect of the
invention, there is provided a haulage body dimensioned
to be filled to capacity with earthen material in four
or less passes of a loading shovel whose loading bucket
includes a hinged gate that swings open and releases
the earthen material for loading into the haulage body.
The haulage body includes opposing sidewalls each
having a height (h), a floor having a width (w) that
defines with the height (h) and other dimensions of the
body a haulage volume that is four or less times a
volume capacity of the loading bucket, and a
dimensional relationship between the height (h) of each
of the opposing sidewalls and the width (w) of the
floor that allows the door of the loading bucket to
open and release the material into the body for at
least a first pass of the loading shovel without
colliding the door with either of the sidewalls when
the loading bucket is both (1) positioned such that the
released material is distributed on the floor to be
approximately centered between the opposing sidewalls
and (2) at an elevation over the floor that
substantially minimizes a height from which the
released material falls to the floor.
The dimensional relationship between the height
(h) of each of the opposing sidewalls and the width (w)
of the floor may allow the door of the loading bucket
to be positioned on second and subsequent passes of the
loading bucket to drop material from the bucket at a
location that (1) distributes the material into the
body to be approximately centered between the opposing
sidewalls and, (2) substantially minimizes a distance
the material falls when released from the loading
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bucket without the sidewalls or previously loaded
material interfering with the opened door.
In accordance with another aspect of the
invention, there is provided a system for moving
earthen material. The system includes a truck having a
dump body, a loading bucket having a volumetric
capacity that is approximately or more than the
volumetric capacity of the dump body such that the dump
body is loaded to capacity in four or less passes of
the loading bucket, and a door of the loading bucket
that swings between closed and opened positions which,
when opened, releases earthen material contained in the
loading bucket to fall freely from the bucket. The
system also includes opposing sidewalls each of a
height (h) and a floor of a width (w) comprising the
dump body whose relative dimensions of the height (h)
and width (w) enable the loading bucket to be
positioned when releasing material from the loading
bucket during a first pass of loading material into the
body such that the earthen material falls from the
loading bucket and into the body (1) at a location on
the floor that is approximately centered between the
opposing sidewalls and (2) at a height above the floor
that is minimized, without the position of the loading
bucket resulting in either of the opposing sidewalls
interfering with the opening of the door to release the
material.
The dimensional relationship between the height
(h) of each of the opposing sidewalls and the width (w)
of the floor may allow the door of the loading bucket
to be positioned on second and subsequent passes of the
loading bucket to drop material from the bucket (1) at
a location that (1) distributes the material into the
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body to be approximately centered between the opposing
sidewalls and, (2) substantially minimizes a distance
the material falls when released from the loading
bucket without the sidewalls or previously loaded
material interfering with the opened door.
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These and other features and advantages of the
invention will be more readily apparent upon reading the
following description of a preferred exemplary embodiment
of the invention and upon reference to the accompanying
5 drawings wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1-7 are side views and a rear view (FIG. 6) of
a heavy-duty, off-highway truck illustrating a portion of
an exemplary sequence of process steps for designing a
dump body for the truck in accordance with the present
invention.
FIG. 8A is a side view of a dump body (outlined in
triple solid lines) and a material heap (outline in broken
lines) illustrating a process step in the sequence of
steps for developing a three-dimensional heaped material
load profile based on data collected from a specific
haulage environment for use in the dump body design
process of the present invention.
FIG. 8B is a rear view of the dump body (outlined in
triple solid lines) and the material heap (outlined in
broken lines) of FIG. 8A illustrating a process step in
the sequence of steps for developing the three-dimensional
heaped load profile.
FIG. 9 is top view of the dump body and material heap
of FIGS. 8A and 8B illustrating in part how the corners of
the heaped load are modeled based on an incremental
blending of the side angles of material repose to the
front and rear angles of material repose to develop the
three-dimensional modeled material heap profile.
FIGS. 10a and 10b are top views of the dump body and
material heap of FIGS. 8A and 8B illustrating in part how
the corners of the heaped load are modeled based on an
incremental blending of the side angles of material repose
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to the front and rear angles of material repose to develop
the three-dimensional modeled material heap profile.
FIGS. 10c and 11 are perspective views of the dump
body and material heap of FIGS. BA and 8B illustrating in
part how the corners of the heaped load are modeled based
on an incremental blending of the side angles of material
repose to the front and rear angles of material repose to
develop the three-dimensional modeled material heap
profile.
FIG. 12 is a side view of the dump body and material
heap of FIGS. 8A and 8B illustrating in part how the
corners of the heaped load are modeled based on an
incremental blending of the side angles of material repose
to the front and rear angles of material repose to develop
the three-dimensional modeled material heap profile.
FIG. 13 is a perspective view of the dump body and
material heap of FIG. BA and 8B illustrating how the
corners of the heaped load are modeled based on an
incremental blending of the side angles of material repose
to the front and rear angles of material repose to develop
the three-dimensional modeled material heap profile.
FIG. 14 is a perspective view of the final three-
dimensional modeled material heap profile for use in the
dump body design process of the present invention.
FIG. 15 is a perspective view of the three-
dimensional modeled material heap profile of FIG. 14 in
the dump body of FIGS. 8A and 8B.
FIG. 16 is a side view of the off-highway truck of
FIGS. 1-7 having the dump body and material heap profile
of FIG. 15 illustrating a further step in the dump body
design process of the present invention.
FIG. 17 is a side view illustrating the final design
of the dump body.
FIGS. 18a-b are a flow diagram of an exemplary
embodiment of the design process of the present invention.
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FIG. 19 is perspective drawing illustrating the
differences between the three-dimensional heaped load
profile of FIG. 15 and a load profile produced using a
S.A.E. J 1363 (Jan. 1985) 2:1 heap rating standard and a
:Load profile produced using a 2:1 straight heap rating.
FIG. 20 is a comparison diagram illustrating the
differences between the three-dimensional modeled material
heap load profile of FIG. 15 as carried in a dump body and
a straight 2:1 heap load profile and a S.A.E. 2:1 heap
load profile as carried in the same dump body.
FIG. 21 is a side view of an off-highway truck
carrying a load in an exemplary field operating
environment.
FIG. 22 is an end view of an off-highway truck
carrying a load in an exemplary field operating
environment.
FIG. 23 is an end view of a prior art off-highway
dump body being loaded by a large-capacity cable shovel or
bucket.
FIG. 24 is an end view of a dump body of the present
invention being loaded by a large-capacity cable shovel or
bucket.
FIG. 25 is a perspective view of an alternative
embodiment of dump body according to the present invention
have a curved rear edge.
While the invention will be described and disclosed
in connection with certain preferred embodiments and
procedures, it is not intended to limit the invention to
those specific embodiments. Rather it is intended to
cover all such alternative embodiments and modifications
as fall within the spirit and scope of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now more particularly to the drawings there
is shown in FIGS. 1-17 an illustrative sequence of process
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steps for designing a dump body 10 for an heavy-duty off-
highway truck 12 in accordance with the teachings of the
present invention. The truck 12 includes a chassis 14 to
which the dump body 10 is attached for pivotal movement
about an axis between a lowered position for receiving and
transporting a load of material and a raised position for
dumping a load of material. As shown in FIG. 17, the dump
body 10 is generally constructed of steel panels which
define the shape of the dump body and beams which form the
structural framework for the dump body. The dump body
Comprises, in this case, sidewalls 16, a front wall or
front slope 18, a floor 20 and a canopy 22 integrally
connected to the top end of the front slope 18 and
extending over the cab 24 of the truck 12. The truck
chassis 14 is supported by a plurality of tires 26.
In the illustrated embodiment, the truck 12 is
generally symmetrical about its longitudinal axis.
Accordingly, as will be appreciated, many of the elements
identified in the side views of FIGS. 1-7 have
complementary elements arranged on the opposite side of
the truck 12. As will be appreciated, reference to plural
elements where only one is shown indicate that a
complementary element is disposed on the side of the truck
12 not shown (e.g., sidewalls 16).
In accordance with an important aspect of the present
invention, the dump body 10 is designed so that the
volumetric capacity of the dump body matches the truck
hauling capacity and that loads in the dump body have a
center of gravity that best matches the intended load
center of gravity/corresponding load distribution
contemplated by the design of the truck chassis 14. More
specifically, the dump body 10 is shaped and dimensioned
to accommodate the correct volumetric load as well as to
maintain a load distribution that results in the center of
gravity of the load being proximate a predetermined
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location, in this case, the preferred position for the
load center of gravity based on the truck manufacturer's
designed chassis loading/weight distribution. Unlike
previous dump body design methods, the dump body design of
the present invention is not based on an assumed
theoretical or universal load profile/load material heap.
Instead, the present invention utilizes a load profile
that is based on a detailed analysis of the actual
material characteristics and loading conditions present in
specific field haulage environments thereby taking into
account factors such as the cohesiveness of the material
to be hauled and the size, shape and gradation of the
pieces of material.
For example, U.S. Patent No. 5,887,914 issued to
LeRoy G. Hagenbuch on March 30, 1999 discloses a dump body
design process which can be used to produce a dump body
that is capable of hauling both overburden and coal. This
design process assumes a theoretical 2:1 heap for
overburden and a theoretical 3:1 heap for coal. It has
been found that these theoretical load profile assumptions
do not always provide an accurate body design of the
actual haulage operating conditions which are encountered
at specific job sites. Such theoretical body load
profiles, are used without any consideration of the actual
material, loading and hauling conditions that exist at
actual locations of use. Thus, in many cases the dump
body can be improperly sized and designed or matched to
the material to be hauled and accordingly to the truck
chassis.
In order to more accurately take into account actual
field conditions, the first step in the design process of
the present invention is to collect field data relating to
the material characteristics and load configurations
currently being hauled by trucks at the site at which the
dump body 10 will be used. In particular, data should be
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collected with regard to the actual angles of material
repose, the size and shape of any plateau formed at the
top of the load and loading voids that are formed by the
material when it is loaded and carried in existing dump
5 bodies. The angles of material repose are dependent upon
a number of factors including the cohesiveness of the
material being hauled and the size, shape and gradation of
the material pieces. With respect to analyzing the angles
of repose, load plateau and loading voids of the loaded
10 material, one method by which this can be accomplished is
to photograph (or videotape) from various different angles
the loads 72 presently being hauled by one or more
existing off-highway trucks 74 at a site (see, e.g., FIGS.
21 and 22). More specifically, photographs should be
taken of loads 72 carried by several different existing
trucks 74 with photographs being taken from the front,
back, corners (front and rear) and sides of those trucks.
In order to help identify any shifting of the load that
may effect load profiles and which may occur during
transport, photographs can be taken of the loaded trucks
as they are leaving the loading area as well as when they
are traveling on the haul roads.
Furthermore, since the method by which material is
loaded into the truck 12 can also impact the loaded
material profile, it can also be useful to collect data,
via photographs or otherwise, regarding truck loading
techniques and the equipment used to load the dump bodies.
For example, front-end loaders generally have a wide
bucket relative to the dump body length and typically load
material into the dump body from the side of the truck.
Accordingly, when front end-loaders will be used to load
the dump body, the length of the dump body can be an
important factor. Likewise, cable and hydraulic shovels
tend to have narrower buckets and are also used to load
material into the body typically from the side of the
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truck. Since cable shovels typically have a door which
swings toward the shovel when dumping (i.e. towards the
side of the body), the width of the body may be an
:important factor when shovels will be used to load the
dump body.Additionally, information should be collected
giving an accurate material density. The types of
information which can be relevant to determining the
density of the load material include visual examinations
of the load material, the taking of weight samples of
known volumes of the load material and consultations with
the end user of the proposed dump body.
In some circumstances, such as in the case of a new
mine, it may not be possible or desirable to collect
material and loading data from the site at which the dump
body 10 will be used. In these situations, data from a
similar field haulage environment should be used. As will
be appreciated by those skilled in the art, a similar
field haulage environment would have conditions that
parallel as closely as possible the conditions which are
anticipated at the new site. This could include, for
example, a nearby site or mine in which the same or
similar material is hauled, a site hauling similar
materials and using similar hauling equipment and/or a
site using similar loading equipment. Once the new mine
or site is operational, the design of future dump bodies
for that site can be refined as needed and as information
is developed about the material and loading conditions at
the site. Of course, the material and loading conditions
at sites will, in most cases, evolve over time which could
necessitate further analysis of these parameters prior to
the design of new additional dump bodies for that site.
Once the appropriate load heap pictorial information
has been collected, the information is then analyzed to
determine what are the actual angles of material repose of
the loaded material and the dimensions of the top plateau
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of the material heap. In one presently preferred
embodiment, this is accomplished by blowing up at least
select representative photographs of off-highway trucks
with loaded material. From these blown up photographs,
the size of the plateau of the heap, the angles of
material repose and the corner voids of the loaded
materials are then measured. In most cases, the angles of
material repose that run to the front, rear and sides of
the dump body will all be somewhat different namely due to
the natural and imposed angles of repose occurring as a
result of the loading process. Accordingly, using the
photographs, values should be determined for each of these
angles repose. The various values for the front, rear and
side angles of repose which are measured from the
photographs are compiled and averaged respectively in
order to produce a composite front angle of repose, a
composite rear angle of repose and a composite side angle
of repose which can then be used to create a three-
dimensional load profile as described in greater detail
:below. Of course, as will be appreciated by those skilled
in the art, other methods may be used to collect and
analyze the data on actual dump body field haulage
conditions including, for example, actual hands-on
:measurements of the relevant angles of repose and corner
voids.
Using the values of the empty and loaded weights of
the truck 12 provided by the off-highway truck
manufacturer, the ideal position along the chassis 14 for
the load center of gravity is then determined. As
illustrated in FIG. 1, the correct load center of gravity
on the chassis 14 (represented by arrow 28 in the
drawings) is located using conventional moment diagrams.
To begin designing the body 10, as shown in FIG. 2, a
line 30 is established to represent the plane of the dump
body floor. Generally, the angle of the floor line 30 is
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established to provide an incline with respect to the
horizontal plane as illustrated in FIG. 3 and is
established at a set minimum distance above the chassis 14
at the front of the body and a set minimum distance above
the chassis and/or tires at the rear of the body. A
proposed line 32 for the front slope of the dump body is
also established, as shown in FIG. 3, at a set minimum
distance back from the chassis deck/engine compartment at
the bottom end of the front slope and at a set minimum
distance back from the chassis cab 24 at the upper portion
of the front slope. To minimize the vertical height of
the center of gravity of the load, it is preferable to set
the initial front slope line 32 as far forward and the
initial floor line 30 as low as possible while still
maintaining the appropriate clearances for the truck cab
24 and chassis 14. As shown in FIG. 4, the initial
proposed inside body width of the body 10 is then set
based on 90-115% of the overall rear axle tire width or as
set by the truck chassis manufacturer.
As shown in FIGS. 5 and 6, using the angles of
material repose (i.e. front, rear and sides) data
obtained from the analysis of the actual field haulage
conditions, an approximate heap profile 33 of the
material to be hauled is then generated utilizing the
individual average values for the front, rear and sides
angles of material repose 34, 36, 40 (e.g., 24 , 30 and
32 respectively in the illustrated embodiment) taken
from the field data. Additionally, as shown in FIG. 5,
an initial dump body side height (referenced as line 37)
is established at the point where the front angle of
material repose 34 contacts the front slope line 32. The
placement of the center of gravity of the approximate
heap profile 33 along the truck chassis 14 is then
determined and compared with the optimal location along
the chassis for the load center of gravity (arrow 28).
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The angle of the floor line 30, the lengths of the
front slope line and floor line and the line defining the
height of the sidewalls are adjusted as indicated by the
arrows in FIG. 7 so that through an iterative process, the
center of gravity of the load can be located as close as
possible to the correct truck chassis 14 load center of
gravity while maintaining the desired body volume. In
adjusting the various parameters, it is preferable to keep
the center of gravity of the load as low as possible in
order to provide the best truck chassis stability.
Accordingly, in the iterative process used to locate the
center of gravity of the load in the desired position, it
is generally preferable to focus on adjusting the height
of the sidewalls and the length of the floor, versus
rotating the rear of the floor. For example, either
lowering the sidewalls and lengthening the floor to move
the center of gravity rearward relative to the chassis 14
or raising the sidewalls and shortening the floor to move
the center of gravity forward relative to the chassis 14.
Using an iterative process, the width of the body 10 may
also be adjusted with the slopes and lengths (within given
parameters) of the floor and front slope in order to
minimize the overall load height profile. While overall
loading height of the dump body influences the size of the
loading equipment that is required, lower overall dump
body loading heights improve truck stability and lessen
the need for larger loading equipment. Lower overall dump
body loading heights also necessarily allow the load
material to be dropped into the dump body from a lower
point, thereby minimizing the impact force of the load
material on the dump body. Obviously, the wider the body
10, the lower the center of gravity. As a practical
limit, however, the body 10 generally should not be
significantly wider than the overall width of the rear
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axle measured from the outer edges of the rear tires or as
preset by the truck chassis manufacturer.
Next, based upon this approximate load profile 33
(e.g., shown in FIG. 6) and the data on the actual field
5 haulage conditions, a three-dimensional model 38 (e.g.
shown in FIGS. 8-15) of the load heap is developed which
incorporates corner voids and the actual side angles of
material repose 40 (e.g., 32 ), front and rear angles of
material repose 34, 36 (e.g. 24 and 30 ) and a top of
10 heaped load plateau 48 as measured from the actual field
collected data. The process/steps used to develop the
three-dimensional modeled heaped material load profile 38
are generally shown in FIGS. 8-15 with the outline of the
truck body 10 shown in triple solid lines and the outline
15 of the three-dimensional model 38 shown in broken lines.
To account for corner voids (corners of the body where no
.hauled material is located) in the three-dimensional
modeled load profile 38, the transition areas between the
sides and the front and the rear of the load are modeled
:based on a gradual incremental blending of the side angle
of material repose 40 to the front and rear angles of
repose 34, 36 (which angles of repose may or may not be
different. After the corner voids are so modeled, the
modeled voids are then compared to the information
collected in the field and the corner voids may then be
adjusted so as to as closely as possible match the
modeled corner voids with the actual field corner voids.
As will be appreciated, the steps described in FIGS. 5-7
are used only to expedite the design process and are not
necessary to the present invention. In particular, one
can move directly to using the three-dimensional model 38
of the load heap (with the corner voids) and eliminate
the steps shown in FIGS. 5-7.
To this end, in one preferred embodiment, the
transition areas between the front 42 and the sides 44,
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and the rear 46 and the sides 44 of the three-dimensional
load model 38 are divided into a number of equal segments
as shown in FIG. 9. In the illustrated embodiment, the
,creation of the corner voids (e.g., FIG. 15) through the
transitional blending of the angles of repose is only
shown with respect to one of the front corners and one of
the rear corners of the load. Of course, it will be
appreciated that the same methodology described herein
can be used to model the voids in the other corners of
the load. In the illustrated embodiment, the boundaries
of the transition areas between the sides 44 and the
front 42 and rear 46 portions of the three-dimensional
load model 38 form 90 angles defined by the flat top or
plateau 48 (FIG. 8 and 9), as defined by actual field
operating data, of the load model 38, with each of the
transition areas being divided into nine equal 10
segments. Planes 50 (FIG. 9) are established in each of
these segments which extend at a respective angle of
repose that allows, if required, an incremental change in
the angle of repose through the corners from the sides 44
to the front 42 and rear 46 of the three-dimensional load
model 38. In particular, the difference between the side
and rear angles of repose, in this case 2 , and the side
and front angles of repose, in this case 8 is divided
into nine equal incremental segments as shown in FIG. 9.
Each of these planes 50 is then extended using
standard geometric principles until it intersects a
portion of the dump body 10 such as the floor, side
walls, front slope or canopy as shown in FIGS. lOa-c and
11. Specifically, as shown in FIGS. lOa-c, end points
are established for each of these planes by using the
values of the angles of material repose for each of the
segments and the horizontal distance for each respective
segment from the appropriate corner of the load plateau
48 to the perimeter of the dump body 10 to calculate the
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horizontal and vertical positions for the end points of
the planes. Each plane 50 is then extended to its
respective end points (FIG. 11). Next, any portion of
the planes 50 which extends beyond the boundaries of the
dump body 10 (referenced as 62, 64 and 66 in FIGS. 12-13)
is then "cut-off" at the point at which it intersects the
dump body to define the corner edges of the three-
dimensional load model 38 as shown in FIGS. 12 and 13.
The completed three-dimensional load heap profile 38 is
shown in FIG. 14 and arranged in the dump body 10 in FIG.
15.
Once the three-dimensional modeling of the material
heap is completed, including the modeling of the corner
'voids along with a subsequent comparison with the field
gathered information, the center of gravity of the
.resulting three-dimensional load model 38 is then
determined. This center of gravity is then compared to
the center of gravity location (arrow 28) contemplated by
the chassis design as shown in FIG. 16. If the center of
gravity of the three-dimensional load model 38 is in
close proximity to the center of gravity location
contemplated by the chassis design then the design of the
dump body 10 is complete. It is generally desirable to
have the load center of gravity as close as is practical
to the desired chassis location. While the distance will
vary depending upon the relative length of the wheelbase
of the truck, in one preferred embodiment the center of
gravity will be considered sufficiently close to the
desired location if it is within less than one inch (plus
or minus) from the desired location. Due to the inherent
design characteristics of off-highway trucks (in an empty
condition an inordinate amount of the net weight of the
'truck is carried on the front axle), in most
circumstances, the center of gravity of the three-
dimensional load profile should not be allowed to be
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positioned forward of the center of gravity location
contemplated by the chassis design.
In the event that the center of gravity of the
three-dimensional load model 38 is not close enough to
the desired location, in an iterative process a new
three-dimensional profile of the heaped load is generated
based on the data collected from the field
loading/haulage environment. Through adjustment of the
parameters of the dump body (e.g., the dump body floor
angle, floor length and side height), the center of
gravity of this new three-dimensional heaped load profile
is moved through the iterative process until it is in
close proximity to the desired location. These steps
being repeated in an iterative fashion as necessary until
the center of gravity of the three-dimensional load model
is adjusted to be approximately coincident with the
anticipated center of gravity contemplated by the design
of the truck chassis 14.
The final design of the dump body 10 is shown in FIG.
17. In accordance with the present invention, the body 10
is custom modeled/designed based on specific field
material, loading and hauling conditions and thus when the
body is used in the field it will carry the desired
volumetric hauling capacity and the center of gravity of
the load will be in closer proximity to the desired center
of gravity location than bodies designed using theoretical
heap load profiles (see, e.g., FIG. 20).
FIGS. 18a-b are a flow diagram which illustrates the
individual steps in the design process of the present
invention which are described herein and shown in the
drawings of FIGS. 1-17. For ease of reference, the steps
in the flow diagram of FIGS. 18a-b are numbered to
correspond with the numbering of the steps in FIGS. 1-17.
As will be appreciated by those skilled in the art, steps
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6 and 7 shown in FIGS. 18a-b can be considered optional in
the design process.
As will be appreciated, the use of actual angles of
repose gathered from data taken from the actual field
haulage conditions in which the dump body 10 will be
employed can have a significant impact on the model of
the load and thus ultimately on the design of the dump
body. For example, as shown in FIG. 19, in the
illustrated example of a load having actual 32 side, 24
front and 30 rear angles of repose, the three-
dimensional load modeling process of the present
invention results in a significant amount of material
being removed from the front and rear and through part of
the corners of the three dimensional load model 38 as
compared to a standard 2:1 heap model 54 and a S.A.E. 2:1
heap model 52 as defined by S.A.E. Standard No. J 1263
(Jan. 1985) (with the profiled three-dimensional model
created using the present invention shown in broken lines
and the S.A.E. 2:1 heaped model and standard 2:1 heaped
model shown in solid lines). In this case, the three-
dimensional load modeling process of the present
invention also results in a significant amount of load
material being added to the sides in the three-
dimensional load model 38 as compared to the S.A.E. 2:1
heap and the standard 2:1 heap.
An example of how these differences in the load
model can impact the location of the center of gravity of
the load as it is carried in a dump body and the rated
capacity or yardage of the dump body is shown in FIG. 20
(which is a side view of the load models shown in FIG.
19). More particularly, in FIG. 20, the location of the
center of gravity and capacity of the three dimensional
load model 38 as carried in a dump body is compared to
the center of gravity and rated capacity of load models
using the S.A.E. 2:1 heap standard model 52 or the 2:1
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heap model 54 in the same dump body. As can be seen, the
use of the S.A.E. 2:1 standard heap model 52 and the 2:1
heap model 54 results in the center of gravity being
offset from the ideal location and in an overstatement of
5 the truck body capacity. Of course, FIGS. 19 and 20
provide just one illustrative example of the differences
between the three dimensional modeled heaped load
profiles which result from using the process of the
present invention as compared to heaped load models
10 created using theoretical load profiles. Since the load
modeling process of the present invention is dependent
upon angle of repose data collected from the actual field
haulage environment, the differences which result from
using the load modeling process of the present invention
15 as compared to the theoretical load profiling will vary
on a case-by-case basis.
In view of the foregoing, it will be appreciated
that, unlike the theoretical load profiling currently
being done, the body and design process of the present
20 invention takes into account the field material, loading
and hauling conditions in which the dump body will be used
and provides a method by which this information can be
used in a meaningful manner in designing the dump body.
Thus, a much more accurately designed dump body is
produced resulting in improved body capacity and
corresponding load retention, and proper placement of the
load on the truck chassis and tires.
In accordance with a further aspect of the present
invention, the floor 20 of the dump body 10 can be
configured so as to help ensure that the load is placed in
the proper position in the dump body 10 during the loading
process. In particular, the rear edge 90 of the floor 20
of the dump body can have a rounded or curved
configuration, as shown in FIG. 25, in which the length of
the floor 20 is less near the sidewalls 16 than in the
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middle. The rear edge 9C of the floor 20 can be curved
inward adjacent the side-:;alls because of the rear corner
voids in the heaped load as shown for example in FIG. 1S.
Curving the rear edge 90 of the floor 20 limits the space
available at the rear of the dump body 10 for retaining
the load and thereby helcs prevent an off-center loading
condition. If an operator attempts to load material too
far rearward in the dump body 10, the material will simply
fall off rear edge 90. The degree to which the rear edge
90 of the floor 20 can be curved is determined by
examining the curve of the rear edge of the three
dimensional heaped load irofile 38 (see, e.g., FIG. 15).
Specifically, the curve of the rear edge 90 can be
configured to correspond with the curve of the rear edge
of the three dimensional heaped load profile 38 (see FIG.
25). As will be appreciated, if a curved rear edge 90 is
used for the floor 20, the sidewalls 16 are then modified
to follow the curve of the floor 20.
According to another aspect of the present invention,
for situations in which a relatively large capacity cable
shovel bucket will be used to load material into the dump
body, the dump body 10 can be designed with a relatively
wider inside body width than conventional dump bodies in
order to substantially reduce the impact force of the
falling load and ensure that the load is properly placed
within the dump body. Specifically, as the size and
capacity of the buckets on cable shovels has increased, it
has become possible to fill a dump body to capacity in
four or less passes with the shovel bucket. However,
using such large capacity loading buckets to load dump
bodies has led to loads being improperly placed within the
dump body and substantial increases in the impact force
caused by the material as it drops into the dump body.
As explained above, cable shovel buckets 60 (FIGS.
23-24) have a swinging door or gate 62 which will swing
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towards one sidewall of the dump body when opened to allow
the material contained in the bucket to drop into the dump
body. Accordingly, during a loading operation, the shovel
operator must be careful to give sufficient clearance to
the sides of the dump body 10 so that the gate 62 will not
collide with the sidewall of the dump body when the gate
is released. Because conventional dump bodies provided by
off-highway truck manufacturers are relatively narrow,
operators of large capacity loading buckets must position
the bucket relatively close to one of the sidewalls of the
clump body to ensure that the swinging gate does not swing
into the opposing sidewall when it is released. For
example, FIG. 23 is a scaled drawing showing one of the
new large-capacity buckets 60 being used to load a
conventional relatively narrower dump body 100. As will
be appreciated, it is very difficult and time consuming to
properly position a large-capacity bucket 60 with respect
to a conventional dump body 100. Moreover, since the
bucket 60 must be positioned relatively close to one of
the sidewalls 102 of the dump body 100, the material is
discharged in an off-center position relative to the dump
body leading to improper loading of the dump body and
truck chassis. However, if the bucket operator attempts
to the place the load in the center of the dump body 100,
the gate when it is released 62 will swing into the
sidewall 102 of the dump body.
Additionally, when loading conventional dump bodies
with large capacity buckets, the clearance between the
floor 104 of the dump body 100 and the swinging gate 62 in
the freed position cannot be minimized because the
operator must ensure that the bucket does not come into
contact with the sidewalls 102 of the dump body. As a
result, the load must be dropped from the bucket 60 at a
relatively large distance above the floor 104 of the dump
body 100. Because of the extremely large capacity of
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these large buckets, the dropping material produces a very
substantial impact force when it contacts the floor of the
dump body. This impact force significantly increases the
wear on the dump body and can severely jar the operator of
the truck.
In contrast to conventional loading operations
involving prior art dump bodies and large capacity
buckets, the present invention provides a method by which
material can be loaded from a minimal height substantially
into the center of a dump body 10 using a large capacity
bucket 60 whose volumetric capacity is approximately 1/4
or more than that of the dump body 10. As shown in FIG.
24, this is accomplished by using a relatively wider dump
body 10 that has relatively lower sidewalls 16 than the
similar capacity dump bodies conventionally provided by
off-highway truck manufacturers. This allows a bucket
operator to bring the bucket 60 into a substantially lower
position in which just enough clearance is provided from
the floor 20 of the dump body for operation of the
swinging gate 62 before discharging the load from the
bucket. In particular, using a relatively wider dump body
10, enables a shovel operator to lower the bucket 60 to a
position that: (1) substantially minimizes the clearance
between the floor 20 of the dump body 10 and the swinging
gate 62 so as to minimize the impact force of the dropping
load and (2) allows the material to be discharged
substantially in the center of the dump body 10 while (3)
allowing the swinging gate 62 to clear the sidewalls 16 of
the dump body as it swings through an arc after it is
freed. Thus, the method of the present invention results
in a more balanced load on the dump body and a
substantially reduced impact force from the discharge of
the bucket load.
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While this invention has been described with an
emphasis upon preferred embodiments, it will be obvious
to those of ordinary skill in the art that variations of
the preferred embodiments may be used and that it is
intended that the invention may be practiced otherwise,
than as specifically described herein. Accordingly, this
invention includes all modifications encompassed within
the spirit and scope of the invention as defined by the
following claims.
24
