Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to improvements in dump trucks.
PRIOR ART
The load carrying capacity of a conven-tional dump
truck is limited by the fact that it is necessary to main-
tain the length of the container body at a length which
can be elevated for dumping without rendering the vehicle
unstable when the container body is in the elevated posi-
tion. It is for this reason that the fast majority of
dump truck which are presently available have a much shorter
container body than many other road going transportation
vehicles. Various attempts have been made to~overcome
this difficulty and one such proposal is contained in U.S
Patent 3,361,~77, dated January 2, 1968. This patent dis-.
closes a structure in which two container bodies are mounted
on a single frame. The two container bodies are separate
and distinct bodies each defining a separate and distinct
load carrying compartment. Both compartments are dis-
charged by elevating the front end thereof to discharge
the loead from the rear end. In order to discharge a
load, the rear compartment is elevated and then lowered
and the front compartment is telescoped within the rear
compartment and the combined assembly is then elevated to
unload the front compartment. When this structure is used,
it is essential to ensure that the front and rear container
bodies are separate and distinct from one another so that
the rear compartment can be tipped independently of the
front compartment. It is also necessary to ensure that
the front compartment is spaced a substantial distance for-
wardly of the rear compartment to permit the rear compart-
ment to move to its elevated position. For this reason
there must be a substantial space provided between the
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front and rear compartments when the vehicle is arranged
for transportation of the load. The space between these
compartments
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is, however lost space so far as the bay load is concerned
and conswquently the full length of the vehicle is not
loaded to its capacity.
Telescoping container bodies for trucks have previously
been proposed. ~lowever, despite the fact tha-t we have been
associated with the manufacture of dump -truck bodies for
a great many years, we have not previously encountered a
commercially accpetable vehicle which employed a tele-
scoping container body.
A dumping truck employing a telescoping container
body is described in U.S. Patent 2,663,439. In this struc-
ture the container body is made up of a large number of -
short lengths which are telescoped one within the other.
The forward section has a front wall which is rearwardly
and downwardly inclined so as to ensure that it will be
completely emptied when telescoped within the rearmost
section. This structure is extremely complex and requires
that the sections be telescoped one within the other in
sequence so that the forward section is tele~coped entirely
within the seconcd section before the second section is
telescoped wlthin the third section and so forth. This
requires an elaborate longitudinal drive mechanism. Phelps
indicates that this structure is necessary in order to en-
sure that the telescoping action will effectively remove
the load.
~ hile telescoping container bodies have not obtained
wide acceptance and the trucking industry has accepted
the dump trucks despite the limitations in load carrying
capacity, we have developed a con-tainer body structure
which when considered as a whole provides a container body
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which has a single load carrying compartment of greater
length than could normally be elevated for dumping and
which consists of only two sections capable of tele-
scoping one within the other to a length which is
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stabe when elevated for dumping purposes. The difficulties
associated with the lack of stabili-ty of dumping a long
container body have been eliminated by the fact tha-t the
length of the body is telescoped to a length which can
be easily and safely elevated for dumping.
The stabili-ty of the container body of -the present
invention~can be further improved by forming the front
section of the body with a length which is greater than
that of the back section so that when the front section
is telescoped within the back section, a portion of the
front section will project rearwardly from the back sec-
tion. This rearwardly projçcting portion will be located
below the rear end of the back portion when the container
body is in the elevated dumping position. By locating
a portion of the front section fo the container body below
the rear end of the back section, the centre of gravity of
the telescoped container body is lowered despite the fact
that the extended length of the container body is greater
than that available when the front and back sections are
of substantially equal length.
According to one aspect of the invention ~here is
provided in a dump truck having a longitudinally extending
support frame, the improvement of, the container body
con~isting of a front section and a back section telescoped
one within the other and having a common container compart
ment formed inwardly thereof, the front section is mounted
for longitudinal movement relative to the frame and the
back section whereby the front section to a first position
in which the common compartment is of substantially greater
length than either of the sec-tions taken alone and a second
position in which the front section is telescoped with res-
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pect to the back section to a stable tippable length,
the back section is pivotally
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mounted on said frame so as to be movable between a lower
position for transporting a load in an elevated position
for dumping a load and first drive means associated with
the front section for driving the front section longi~
tudinally of the frame between said first and second
positions thereby to effect a partial discharge of -the
load contained within the common container compartment
rearwardly from the back sect~on in response to movement
towards said second position in use, and second drive
means associated with said back section for moving said
back section from said lowered position to said elevated
position to complete the discharge of a load from the
common container by dumping action.
The invention will be more clearly unders-tood a~ter
reference to the following detailed specification read
in conjunction with the drawings wherein;
Fig. 1 is a side view of a dump truck according -to an
embodiment of the present invention,
Fig. 2 is a partial side view of the dump truck body
showing a first stage in the discharge of a load;
Fig 3 is a view similar to Fig. 2 showing a further
stage in the discharge of the load;
Fig. 4 is a plan view of a container body;
Fig. 5 is a plan view similar to Fig. 4 showing the
addit~on of a batch gate to the container body;
Fig. 6 is a side view of a dump truck trailer body in
which the front section of the body is longer tha~ the back
section;
Fig. 7 is a view similar to Fig. 6 showing the con-
tainer body inthe telescoped and dump position;
Fig. 8 is a side view of a drive mechanism for tele-
scoping the container body;
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Fig. 9 is a top view of the drive mechanism of Fig.
8; and
Fig 10 is a top view of a drive mechanism according
to a further embodiment of the present invention.
With reference to the drawings, the reference numeral
10 refers generally to a dump truck accoring'to an embodi-
ment of the present invention. The dump truck has a long-
i-tudinally extending frame 12 on which the container body
14 is mounted. The container body 14 consists of a front
section 16 and a back section 18. The front section 14
is adapted to slide telescopically within the back section
18 and is reciprocally driven with respect to-the frame
12 by means of a hydraulic drive unit 20. The back section
18 is mounted on a shaft 22 to pivot with respect to the
frame 12. Ine end of the reciprocating hydraulic drive
unit 20 is mounted on the shaft 22 and the other end is
secured to -the front section 14 by a bracket 24. As shown
in Fig. 3, a second hydraulic drive unit 26 has one end
secured to a support structure 28 mounted on the frame 12
and another end pivotally mounted on a pivot pin 30 which
is mounted on the under side of -the back sec-tion 18 of
the container body. This mechanism is the conventional
hydraulic tipping mechanism used to elevate the front-end
of a dump truck body.
As shown in Fig. 4 of the drawings, the front section
14 of the container body consists of a bottom wall 32, a
pair of oppositely disposed side walls 34 and a front wall
36. The back section 18 consists of a pair of opposi-tely
disposed side walls 38, a tailgate 40 and a bottom wall 42.
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The tailgate 40 i5 of the conventional type used on dump
trucks and is adapted to be releasably secured in the
closed position shown in Fig. 1 and is releasable to move
to the open positions sho~n in Figs. 2
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and 3 of the drawings. As shown in Fig. 4 of the drawing,
the back end of the front section 14 is open and the front
end of the back section 18 is open so that a common con~
tainer compartment is formed -thereby. In all positions
of the front section with respect to the back section,
the front section will be a-t least partially telescoped
within the back section, -the fron-t section is never ~ully
withdrawn from the back section, as -to do so would require
the closing of the back end of the front section and a
front end of the back section. If the back end of the
front section was clsoed by an end closure wall, consid-
erably difficulty would be experienced in attempting -to
move the closure wall aside in order to permit the re-
moval of the load from the back section by the tele-
scoping of the front section within the back section.
In use, the container body is filled with a dumpable
load when it is in the ex-tended configuration shown in
Fig. 1 of the drawings in whichposition the capacity of the
container body is at i-ts greates-t. It will be noted
that in -this construction a container body having substan-
tiallythe full length oE the support frame is employed.
The load may he distributed over the full length of the
frame. In order to discharge a load, the tailgate 40 is
released and the hydraulic drive unit 20 is activated
to cause the front section to telescope within the back
section and therby cause a portion of the load to be be
discharged at the back end of the back section as shown
in Fig. 2 of the drawings. The front section 14 will
be drawn inwardly of the back section 18 until the combined
lingth of the front and back sections is no-t greater
than the acceptable length of a conventional dump truck
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When the container has been e~fectively shortened by tele-
scoping as described above,
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the hydraulic cylinder 26 is activated to elevate the
front end of the telescoped container body to discharge
the remain~er of the load by means o~ a convent onal
dumping action. Af-ter the dumping has been completed the
container body is lowered to the horizontal position.
Af-ter the container body has been lowered to the horizon-
tal position, the vehicle may be driven forwardly at con-
ventional road going speeds during which the container
body may be extended by operaton of the drive mechanism
20. By reason of the fact th~t the container body has
been lowered to the horizontal position there is no loss
of stability by extending the container body while the
vehicle is in motion.
While the above description of the preferred embodi-
ment of the present invention does not include a detailed
description of all of the components necessary for mounting
the container body, i-t will be understood that these details
are well known .in the industry and are applied to conven-
tional dump truclcs.
The hydraulic drive unit 20 used for telescoping the
container body is pivoted above -the shaft 22 about which
the rear container body 18 also pi~vots to permit this
drive unit to be elevated with the contracted container
body as shown in Fig. 3.
Various modifications will be apparent to those
skilled in the art without departing from the scope of
the invention. For example, as shown in Fig. 5 of the
drawings a batch gate 50 may be located at any point along
the length of the front section 16 so as to separa-te two
distinct loads from one another within the container body.
This again is common practice in the industry.
With reference to Fig. 6 of the drawings, the refer-
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ence numbral 52 refers generally to a dump truclc trailer
body in which lilce numerals apply to like parts to those
iden-tified in ~igs. 1 through 5. In -this embodiment, the
front section 16
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of the container body is substantially longer than the back
section 18, wi-th the result that when the container body
is telescoped to the position shown in Gig. 7 a substantial
portion 16a of the front section 16 projects rearwardly
from the back section 18. The portion 16a is preferably
at least 10% of the length of the back section 18. When
the container body is in the position shown in Fig. 7,
the portion 16a has a centre of gravity which is lower
than the centre of gravity of the container body illus-
trated in Fig. 7 is lower than that illustrated in Fig. 3
The lowering of the cen-tre of gravity of a container body
of a dump truck when it is in the elevated position serves
to increase the stability of the container body and reduce
the likelihood of the body falling over during the dumping
operation. The lengthening of the front section 16 serves
to increase the load carrying capacity of the container
body and this increased capacity is obtained without
raising the centre of gravity of the container body as a
whole.
An alternative telescoping drive mechanism is illus-
trated in Figs. 8 and 9 of the drawings. As shown in
Figs. 8 and 9 of the drawings, a toothed rack 60 is mounted
on the underside of the front section 16 of the container
body. The rack consisits of a pair of longitudinally
extending rails 62 haiving a plurality of transverse teeth
members 64 located at uniformly spaced intervals along the
length thereof. A double ac~ting hydraulic cylinder 66 is
mounted on the frame 12 and has a reciprocating piston rod
68 projecting outwardly from one end thereof. A pawl
mechanism 70 is mounted at the outer end of the piston rod
68 and includes a frame 72 within which a pawl 74 is pivot-
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ally mounted on a transverse pivot pin 76. The pawl has
an arm 78 projec-~ing
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downwardl~ therefrom. The arm 78 is mounted on the reci-
procating shaft 80 of a double acting air cylinder 82.
Centering springs 84 and 86 serve to centre the arm on the
shaft 80. The pawl 74 has oppositely disposed pushing
faces 88 and 90. The air cylinder 82 is operative to move
the pawl 74 between the positions shown in solid lines and
in broken lines in Fig. 8 to selectively engage -the teeth
64 for movement of the rack 60 in opposite longitudinal
directions in response to movement of the connecting rod
68 of the double acting hydraulic cylinder 66. In use,
when it is necessary to move the container body 16 in the
direction of the arrow A, the air cylinder 82 is activated
to position in the pawl 74 in the position shown in solid
lines in Fig. 8. The double acting hydraulic cylinder 66
is then activated to move the pawl assembly 70 back and '
forth to engage successive teeth 64. The spring 86 yields
as the pawl 74 is drawn backwardly over the next tooth 64
and serves to return the pawl 74 to the elevated driving
position after it is drawn rearwardly over the tooth 64.
The stroke of the hydraulic cylinder 66 is at least equal
to the pitch of the ract teeth 64.
It will be apparent that the ratchet drive mechanism
described above will provide for intermittent movement of
th~firs-t section 16 with respect to the secondsec-tion 18.
In order to provide a substantially continuous movement,
two drive units are provided as shown in Fig. 10 of the
drawings. In this embodiment, the pawl assemblies 70a
and 70b are of the same structure as tha-t described
above with respect to Figs . 8 and 9 of the drawings.
The hydraulic cylinders 66a and 66b are connected to one
another by a conduit 92 so that the movement of the con-
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necting rod 68b with the pawl assemblies 70a and
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70b disposed 180 out of phase wi-th one ano-ther. This
mechanism provides for movement of the pawl 70a in the
direction of the arrow C when the pawl 70b is moving in
the same direction of the arrow and D and vice versa.
Wi-th this mechanism the pawl carried by the pawl assembly
70a is pushing the container body in the direction of the
arrow C when the pawl in -the assembly 70b is ratcheting in
the direction of arrow D to a position to engage the
next tooth 64. When the pawl assembly 70a is fully ext- ~i
ended and begins its return in the direction of the arrow
C, the pawl 70b is fully retracted to begin its extension
in the direction of the arrow D. The pitch of the rack
teeth 64 and the length of -the stroke of the double acting
hydraulic cylinders is such that a substantially con-tinuous
movement of the rack 60 and the container body 16 is ob-
tained.
It will be apparent from the foregoing that the drive
mechanism is such that it is not necessary to provide a
very long extending hydraulic cylinder. Hydraulic cylinders
which have a very long extension are expensive to manu-
facture and are prone to damage in use. The double acting
hydraulic cylinder of the present invention may have a
stroke of the order of about 2 to 4 feet. Such a cylinder
is subs-tantially less expensive thah that required to
move a telescoping container body over a length of about
15 feet as might be required in the embodiment of the in-
vention illustrated in Fig. 1.
In addition, the drive mechanism 20 of the present
invention may be replaced by a dr:ive mechanism similar to
that described in U.S. Paten-t 3,361,477 Pitts. The Pitts.
The Pitts mechanism is permanen-tly secured to the support
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frame and is not elevated with the container body during
the dumping operation.
It will be understood that while it is advantageous
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to telescope the front section within the back section
because it simplifies the location of the operating mech~
anism, it may also be possible to telescope the back section
with the front section. In addition, while the longitu-
dinal -telescoping drive mechanism is shown as being ~-
connected at one end to the frame and connected at the
other end to the front section, the drive mechanism
could consist of a rack and pinion drive mechanism in
which the rack is carried by the front section and the
driven~pinion is carried by either of the back section or
the f`rame. These and other modification will be apparent
to those skilled in the art.
A container body constructed according to the present
invention may have a total length of about 40 feet which
is far in excess of-the length of a dump truck container
body of the type which must be eleva-ted over the full
length to be un]oaded.
From the foregoing, it will be apparent thatlthe
pr-esent invention provides a simple and effective struc-
ture for increasing the load carrying capaci-ty of a vehicle
of the dump truck type while retaining the characteristic
of the dump truch which permits complete discharge of the
load from the container body. These and other advantages
of the present invention will be apparent to those
skilled in the art.
A further advantage of the drive mechanism of the
embodiments associated with the present invention resides
in the fact tha-t the double acting hydraulic cylinder may
be mounted with respect to the frame and the front section
of the container body~/so that the cylinder extends to push
the front section towards the contracted position. This
is in contrast -to the double acting hydraulic cylinder of
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of the embodiment illustrated in Figure 1 whereint the
:~ cylinder must be contracted to move the front section
to the contracted position. The efficiency of a double
acting
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hydraulic cylinder is greater when pressure is being applied to
the extension piston surface than it is when it is being applied
to the contraction piston because the area of the ContractiOn
piston is reduced by the diameter of the piston rod~ Thus, the
double acting hydraulic cylinder required for the mechanism of
Figure 8 of the drawings may be of a lighter weight than that
required for the embodiment illustrated in Figure 1. These
and other advantages will be apparent to those skilled in the
art.
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