Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02249929 1998-10-14
DEVICE FOR COMPACTING
TECHNICAL FIELD
The present invention relates to devices and techniques for compacting road
surfaces.
BACKGROUND ART
Though more and more urban roads are covered with pavement, most local rural
roads remain as 'gravel' roads. Vehicle tires tend to shift the gravel causing
bumps and
potholes. Part of the maintenance of these roads during summer months involves
grading
the road with a scrapper which smooths off the bumps and randomly distributes
the
scraped gravel to lower regions on the road surface such as potholes and then
is treated
with a dust suppressant. With continuing budget cuts, local governments, till
now, have
not bothered to incur the additional cost of manpower and machinery to
compress the
gravel on the freshly graded road surface to a denser form. As a result, the
fresh gravel is
easily shifted again by vehicle tires. The loose gravel is also easily
saturated by rain water
causing dangerous driving conditions, and a loss of gravel through splashing
of mud by
vehicle tires and run oil'
In those limited cases where these gravel roads are compacted, the compacting
machines normally used carry out the compacting procedure with a steel drum,
which has
the tendency to ride on the already dense relatively higher areas of the road
surface and
not compress the relatively lower areas such as in potholes.
A gravel road surface which has been graded but not compacted can create
hazardous visibility problems in view of blowing dust, hazardous driving
conditions due to
loose gravel, and a faster deteriorating road surface leading to pot holes,
wash boarding,
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and wheel rutting.
It would be desirable to provide a technique to compact the road surface after
it is
graded, without the expense of having a separate vehicle.
It is therefore an object of the present invention to obviate or mitigate
these
disadvantages.
DISCLOSURE OF THE INVENTION
Briefly stated, the present invention involves a device for compacting a road
surface, comprising a plurality of compression members, each being arranged to
be
displaced along a corresponding longitudinal path on said road surface and
under a
compacting load, wherein each of said compression members is capable of
following an
uneven road profile, while maintaining contact with said road surface, so as
to deliver said
compacting load thereto.
In another aspect of the present invention, there is provided a road grading
vehicle
comprising a motor-driven undercarriage supporting a road-scraping blade and a
road-
compacting assembly coupled with said undercarriage and trailing said blade,
said road-
compacting assembly including a number of compression members, each being
arranged to
deliver a compacting load to a road surface, each of said compression members
being
further arranged to follow the contour of said road substantially independent
of the other
compression members.
In still another aspect of the present invention, there is provided a device
for use
with a road grading vehicle comprising:
- a plurality of compression members to engage a road surface behind said
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vehicle along a road surface and under a compacting load,
- a frame for carrying said compression members; and
- displacement means for displacing said frame between an operative
position with said compression members delivering said compacting load to
said road surface and an inoperative position.
In yet a further aspect of the invention, there is provided a method for
compacting
a road surface, comprising the steps of
- providing a plurality of compression members,
- orienting each of said compression members to follow a longitudinal path
on said road surface;
- delivering a compacting load on each of said compression members, and
- arranging each of said compression members so that each is capable of
following an uneven road profile, while maintaining contact with said road
surface, so as to deliver said compacting load thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
Several preferred embodiments of the present invention will now be described,
by
way of example only, with reference to the appended drawings in which:
Figure 1 is a perspective view of a road grading vehicle including a device
for
compacting;
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Figure 2 is a perspective view of the device of figure 1;
Figure 3 is another perspective view of the device of figure I ;
Figure 4 is a side perspective view of the device of figure 1;
Figure 5 is a schematic view of one portion of the device of figure 1;
Figures 6, 7 and 8 are photographs of another device for compacting;
Figures 9a through 9c are schematic views of several devices for compacting.
Figure 10 is an exploded view of one portion of the device of figure 6; and
Figure 11 is a side view of a road grading vehicle of figure 6.
BEST MODE FOR CARRYING OUT THE INVENTION
The term 'compacting load' refers to the forces or pressures being exerted by
each
of the compression members on the road surface, which are sufficient to cause
the material
on the road surface to be compacted to a reasonable.
As will be described below, there is provided a device shown at 10 for
compacting
a road surface having an uneven profile, comprising a plurality of compression
members
in the form of load bearing wheels 12, each wheel having a pneumatic tire and
being
arranged to roll along a corresponding longitudinal path of the road surface
and under a
compacting Ioad. As will be described, the compacting load may be, if desired,
preset
according to the road surface, so that the load is sufficient to compact the
road surface,
wherein each of the wheels is capable of following the uneven profile and
maintaining
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contact with the road surface, so as to deliver the load thereto.
The pneumatic tire is particularly useful in the device 10 since it can
assists in
providing a relatively more even load or pressure over the area of the path
the wheel
follows and can better accommodate such things as small rocks and other
obstructions,
than with other compression members with inflexible or more rigid road-
contacting
surfaces. Nonetheless, there may be instances where more rigid road-contacting
surfaces
can nonetheless provide improved results over conventional techniques.
Examples include
sliding pads or blocks or members having partial rolling capability.
The device has a frame means 14 for carrying the wheels, the frame being
attachable to a road grading vehicle (also known as a 'grader').
A displacement means, in this case in the form of a pair of linear actuators,
in this
case hydraulic rams 18, are provided for displacing the frame between an
operative
position with the wheels in contact with the road surface, as shown in solid
lines in the
figure 3, and an inoperative position wherein the wheels are unable to deliver
a
compacting load to the road surface. In this latter case, the wheels are
spaced from and
above the road surface, as shown in dashed lines in figure 3. A plurality of
suspension
assemblies are provided as shown at 22, wherein each independently suspend a
group of
wheels, such as one or two wheels. In this case, each suspension assembly
supports a
pair of wheels, for example wheels 12a, 12b supported by suspension assemblies
22a as
shown in figure 2.
The frame has a laterally oriented beam member 24 and each of the suspension
assemblies, includes a spring arm arrangement 26 extending outwardly from the
beam.
Each of the arm arrangements has a distal end region 26a and an axle member 28
is
mounted on the distal end region, so as to form a pair of axle portions
outwardly
extending in opposing directions from each of the axle portions supporting a
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corresponding wheel. In this case, each suspension member includes a number of
stacked
leaf springs, wherein the longest thereof is secured to the axle portion at
its distal end. In
this case, the wheels are positioned parallel to one another and are spaced
apart to allow
the spring to be connected. The other end of the spring is secured to the
frame. When
assembled the tires are evenly spaced apart and in a substantially straight
line. A pair of
support members 30 extend outwardly from the beam member and each of the
hydraulic
rams is coupled to a corresponding one of the support members.
The frame means includes a harness assembly 36 fixed on the grader, and the
hydraulic rams are mounted between the support arms and the harness assembly.
The
harness is provided with pivot points allowing a frame to be raised or lowered
by the two
hydraulic rams or cylinders mounted parallel to each other on each side to the
rear of the
grader. One end of the frame, namely at the support arms, is pivoted to the
harness, with
another pivot location near a mid-point in the support arms, which is
connected to the
piston end of the ram. The barrel end of the ram is connected to a pivot point
on the
harness. When in use the tool will follow the path of the driven tool, the
grader,
compressing the loose gravel to a denser form by a controlled amount of
pressure
delivered through a valve to the cylinders.
As is shown in figure 5, the device also has a controller 50 for controlling
the
magnitude of the compacting load to be exerted by each of the wheels. In the
case of the
device 10, the controller works in conjunction with a hydraulic fluids source,
in this case
the hydraulic pump and reservoir 52, 54 on board the grader, a supply line 56
joining the
source with the hydraulic rams as well as a return line 58 to return the
fluids from the
supply line to the source. The controller functions to control the amount of
hydraulic
fluids being delivered to the hydraulic rams. To do this, the controller has a
monitoring
means 60 for monitoring pressure in the supply line and a diverter means, in
the form of a
diverter valve 62 is responsive to the monitoring means for diverting
hydraulic fluid from
the supply line to the barrel end of the hydraulic ram via line 64 (in the
case of extending
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the ram, as would be done, for instance to transfer the wheels to their
operative position,
according to a desired compacting load) and alternatively to the ram end as
shown at 66
(for retracting the ram, as would be done, for instance to transfer the wheels
to their
inoperative position). The monitoring means is also operable to maintain the
pressure in
the supply line below a predetermined maximum value and above a predetermined
minimum value, for reasons to be explained. The controller also has a switch,
for example
a three position toggle switch as shown at 68, which can be mounted in the cab
of the
grader and provide a first position 'A', corresponding to the inoperative
position, a second
position 'B' corresponding to the operative position and a central 'neutral'
position 'C',
corresponding to a 'operation constant' position.
A compacting load adjustment means is also provided which is in communication
with the diverter means for adjusting the compacting load, the adjustment
means including
a solenoid 72 for actuating the diverter and a power adjustment unit 74 for
adjusting
power being delivered to the solenoid. In this case, the adjustment means may
be
provided in the form of an adjustable scale, such as a linear or rotary scale,
which can be
placed adjacent the control switch.
In one mode, the control unit thus functions to direct a predetermined portion
of
the hydraulic fluid from the supply line to the barrel end of the hydraulic
rams. The
greater the pressure to be exerted, or the greater the displacement of the
ram, the greater
the quantity of fluid to be diverted. The magnitude of the compacting force
will be related
to the pressure in the ram multiplied by the operative cross sectional area of
the ram,
multiplied by the number of hydraulic rams (in this case two) and divided by
the number of
wheels. The compacting force will of course depend on the geometry of the
support arms
and the suspension assemblies. The pressure being exerted by each wheel will
thus equal
the force being exerted by the wheel over area of the 'foot print' of the
wheel on the road
surface.
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The device functions as follows. First, assuming the device is in its a
position with
the wheels resting on the ground surface, the operator activates the hydraulic
system
causing pressure to be established in the supply line. The operator then
toggles the switch
from its neutral position to its 'inoperative' position, which in this case
causes the diverter
to redirect hydraulic fluid from the supply line to the ram end of the
hydraulic rams, in this
case causing the rams to retract and bring the wheels to their inoperative
position. The
operator may then proceed to a particular road surface, select the compacting
load to be
delivered by the wheels, that is by adjusting the rotary dial, and then
transferring the
toggle switch to its first position, causing the diverter to divert fluids to
the barrel end of
the ram, thereby causing it to be extended and thus bringing the wheels to
their operative
position. The monitoring means functions to bring the wheels to within a
predetermined
range of compacting load as represented, say, by a range of pressures being
present in the
supply line, say to within a few percent, or more or less depending on the
sensitivity
required. The operator may then operate the grader in the normal fashion,
meanwhile
causing the wheels to roll, under load, along their respective longitudinal
paths and
compacting the road surface as a result. The degree of the compacting can of
course
depend on the magnitude of the compacting load and the number of passes of the
wheels
along the road surface.
Figure 9a) shows, schematically, four groups of two wheels each on a
relatively
flat road surface. Figure 9b) shows, schematically, eight groups of one wheel
each, that is
each independently suspended along and, in this case, traveling over a
relatively irregular
road surface. Figure 9c) shows, schematically, four groups of two wheels each,
traveling
over a relatively irregular road surface. This case be seen by a combination
of the
torsional rotation of the suspension along with varying degrees of vertical
translation of
each axle relatively to the others.
Although, the spring assemblies in the device 10 support a pair of wheels,
they
nonetheless allow the wheels to follow the road contour in a substantially
independent
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manner, since the spring assemblies have a torsional and vertical resiliency,
as shown by
arrows Rt and Rv in figure 3. Of course, this independence can be enhanced by
providing
a suspension assembly for each individual wheel, if desired. Should the wheels
encounter
a substantial obstruction, such as a large rut or hump, or should the vehicle
pass over a
relatively sharp or pronounced crest or valley in the road surface, the wheels
may in fact
cause a momentary change or fluctuation in the pressure in the supply lines.
In this case,
the monitoring means detects the pressure change and, should the change exceed
the
predetermined range of allowable fluctuations, the monitoring means
communicates with
the diverter to adjust the quantity of hydraulic fluid being present in the
supply line
accordingly.
A particular feature of the control system is that the hydraulic fluid is
constantly
flowing through the supply line and the return line, the proportion actually
being returned
to the reservoir depending on the particular operating phase of the device.
This allows the
controller to constantly monitor and tailor the position of the wheels and the
compacting
loads exerted thereby on the road surface.
The device is useful in that it is able to utilize the weight of the grader
to, in effect,
pre-load the suspension assemblies, thereby increasing the applied pressure,
and thus the
compacting load, to the gravel on the road surface. The device may have an
extension to
be used for a wider area to be rolled. The device also utilizes the grader's
hydraulic system
to supply to the valve pressure, and thus the compacting load to the wheels,
by action of
the hydraulic rams. The valve is controlled from within the cab of the grader
by means of a
switch and a control knob.
Thus, when used with a grader, the device 10 provides a modified road grading
comprising a motor-driven undercarriage supporting a road-scraping blade and a
road-
compacting assembly coupled with said undercarriage and trailing said blade,
said road-
compacting assembly including a number of compression members, each being
arranged to
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deliver a compacting load to a road surface, each of said compression members
being
further arranged to follow the contour of said road substantially independent
of the other
compression members.
It will be seen that, in the case of device 10, the wheels have collinear
rolling axes
and are independently mounted on the frame and with substantially collinear
axes in the
operative position shown in figure 9a. The frame is movable relative to the
undercarriage
in order to adjust the compressive force, the higher the force, the greater
its ability of
compressing loose gravel or dirt to a higher density, thereby to lengthen the
useful life of a
road between repairs.
Referring to figures 7 to 10, there is provided another device shown at 100
for
compacting a road surface having an uneven profile, comprising a plurality of
compression members in the form of load bearing wheels 112 carried by a frame
means
14, the frame being attachable to a grader. A displacement means, in this case
in the form
of a pair of linear actuators, in this case hydraulic rams 118, are provided
for displacing
the frame between an operative position with the wheels in contact with the
road surface
and an inoperative position wherein the wheels are unable to deliver a
compacting load to
the road surface, the inoperative position being one wherein the wheels are
spaced from
the road surface as shown by figure 7. As with the earlier device 10, a
plurality of
suspension assemblies are provided as shown at 122, wherein each independently
suspend
a group of wheels, such as one or two wheels, again in this case two wheels
112a, 112b
supported by suspension assemblies 22a as shown in figure 6.
The frame has a laterally oriented beam member 124 and each of the suspension
assemblies, includes a spring arm arrangement 126 extending outwardly from the
beam.
Each of the arm arrangements has a distal end region 126a and an axle member
128 is
mounted on the distal end region, so as to form a pair of axle portions
outwardly
extending in opposing directions from each of the axle portions supporting a
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corresponding wheel.
The detail of the suspension members is shown in figure 9 and includes a
number
of stacked spring plates 126b held at one end by a ring clamp 126c which
includes a pair
of U-bolts 126d and mating nuts 126e, themselves engaging a base plate 126f.
The distal
end 126a of the longest of the plates has mounted thereon another ring clamp
127 to
embrace the axle portion 128 and is similar in construction to the ring clamp
126c, apart
from the use of a central bolt 127a extending through the spring plate to
secure the clamp
127 in position. The piston end of each of the two hydraulic rams 118 are
pivoted to a
flange shown at 114a which is welded to the upper face of the frame member.
The devices are believed to be particularly useful because the series of load-
bearing compression members, preferably wheels, more preferably with pneumatic
tires,
follow the grader while grading a road. During use, the grader will be driven
over the
road surface a number of times to provide an optimum profile. This allows the
wheels to
run into the pot-holes and wheel ruts many times, thereby improving the
compression of
the road surface, particularly in these depressions, still further. It is
believed that the use
of the device will greatly increase the span between road grading treatments
and will
decrease the need for dust suppressants, while still achieving a longer
lasting road surface
and decreasing the negative effects on the environment. It could be said that
the device is
an 'environmentally friendly' tool.
While the above embodiments make use of compression members in the form of
load bearing wheels, it will be understood that other wheels can also be used
including
those filled with other fluids such a water for are solid wheels, for example.
In addition,
compression members may also be used such as rollers, or load bearing skid
pads that are
arranged to slide along the road surface. In addition, other suspension
arrangements are
envisaged for supporting the wheels such as in the use of other springs such
as
compression springs, pneumatic bladders or other arrangements which allow each
of the
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compression members to follow the contour of the road substantially
independent of the
others.
Thus, the device provides an attachment which can be secured to the rear of a
grader. It may be hydraulically operated by two cylinders in order to raise or
lower it to
the ground, or alternatively operated with pneumatic or electrical circuits
instead of the
hydraulic circuit above mentioned. The device 10 is compact and uses the
weight of the
grader to pre-load springs connected to tires which roll the road surface to a
higher
density. Also the amount of weight applied to the device can be adjusted
simply by the
turn of a dial. In addition, while the device 10 makes use of a controller
capable of
controlling the compacting load, other controllers are contemplated which do
not
necessarily do so, including those used in standard hydraulic, pneumatic and
electronic
control systems.
When used with a grader, the device allows for the compaction of gravel roads
to
be carried out simultaneously while being graded. Among its advantages, the
device 10
can be relatively easy to operate and be used the same time the grader is
being operated.
The device can have relatively low maintenance costs, and can be made to
attach easily to
the grader.
The device can in some cases be made to be compact, easy to use, cost
effective,
require relatively little maintenance. Furthermore, the device may be
configured to rely on
the hydraulic system on the grader in order to operate it between its
operative and
inoperative positions, thereby to achieve the compaction necessary for
improving the life
of gradable road surfaces. The device can be made to be relatively adaptable
to fit a
number of different models of grader and can be made with relatively
accessible materials.
It is also believed that there may be some road surfaces where the device 10
may
not be as useful as in others. For example, the device may not show
significant results
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when used on roads covered with larger aggregate such as that known
colloquially as "rip
rap".
While the device 10 is movable to an inoperative position which is
characterized by
the compression members actually being physically spaced from the road
surface, there are
other positions available for the compression members which can be considered
to be
inoperative, such as the position where the wheels are still in contact with
the road
surface, but are essentially 'floating' on the road surface because the load
being exerted on
them is essentially zero, or nonzero but still clearly not sufficient to
compact the road
surface by any reasonable measure.
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