Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
Field of the invention
The present invention relates to a system for use
on a load transportation vehicle, having an auxiliary axle
with a suspension of the pneumatic type, which system is
capable of automatically and accurately distributing the
load to be carried by the vehicle between at least one of
the main axle, preferably the front one, and the auxiliary
axle, whenever the latter is needed.
Description of the prior art
Vehicles to which the invention particularly
applies are those equipped with retractable auxiliary wheels
between the front steering wheels and the rear wheels; the
auxiliary retractable wheels being intended to carry a
surplus load when brought to ground-engaging position. Both
suspensions for the steering wheels and for the auxiliary
wheels include inflatable balloons either exclusively or in
combination with spring blades.
As is known, it is of prime importance that the
steering wheels not be overloaded or underloaded at any time
so that the driver may be able constantly to control
steering of the vehicle properly. This is particularly so
whenever the vehicle carries a surplus load at which time
the auxiliary wheels have to be used and the load
distributed so that the steering wheels are neither
overloaded or underloaded. Apart from difficulties in
driving, the driver may be penali~ed, at a load-measuring
station along the road, for having an overloaded axle.
At the present time, it is possible for the
vehicle driver to inflate or deflate the suspension balloons
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manually to try to reach the best possible load districution
between the steering and auxiliary wheels but this can only
be done manually, as aforesaid. There is indeed absolutely
no way for him to assess with any accuracy whether or not
the load distribution has been done properly except by means
of his own experienced perception of the vehicle behaviour
as sensed through the steering column. It will be
appreciated that such an adjustment is quite subjective and
therefore may lead to dangerous situations, not to mention
rendering driving more difficult.
SUMMARY OF THE INVENTION
An object of the invention is consequently to
provide a load distribution system wherein the distribution
can be made fully automatically and with accuracy, the
driver having no part to play in the operation.
With this object in view, the invention proposes a
load distribution system for a ~oad vehicle, which system
comprises a main suspension and an auxiliary suspension
including air-inflatable balloons fed by an air compressor.
A weight sensor constantly measures the weight carried by
the main suspension and sends corresponding signals to a
programmed computer. The system further comprises a control
assembly for the auxiliary wheels suspension constructed to
receive pressure air from the compressor and feed it to the
auxiliary suspension balloons. The control assembly is
connected to the computer which is programmed to respond to
the weight variations by correspondingly adjusting the
pressure in the balloons of the auxiliary suspension in
order to let the auxiliary suspension carry any extra weight
which exceeds a preselected weight to be carried by the main
suspension.
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More particularly, the invention proposees a load distribution system
for a road vehicle, said system comprising:
a main suspension;
an auxiliary-wheels suspension including air inflatable balloons;
an air compressor for feeding pressurized air to said balloons;
a weight sensor operatively connected to said main suspension, said
sensor being capable of constantly measuring the weight carried by said main
suspension and sending corresponding signals;
a programmed computer connected to said sensor to receive said
weight signals, said computer being programmed to compare said weight signals toa preselected weight to be carried by said main suspension and to establish weight
variations therefrom; and
a control assembly for controlling the auxiliary-wheels suspension, said
control assembly comprising an air pressure controller operatively connected to said
balloons of said auxiliary-wheels suspension, to said computer, and to said air
compressor for feeding pressurized air received from said air compressor to saidballoons of said auxiliary-wheels suspension under control of said computer;
wherein said computer is programmed to respond to said weight
variations and to monitor said control assembly to adjust the air pressure in said
balloons of said auxiliary-wheels suspension to a value commensurate to the weight
variations est~hlished by said computer in order to let the auxiliary-wheels
suspension carry only any extra weight which exceeds the preselected weight to be
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Preferably, the main suspension is the front
wheels suspension. Preferably also, the control assembly
comprises an air pressure controller operatively connected
to the balloons of the auxiliary suspension, to the computer
and to the air compressor for feeding pressure air to the
balloons under control of the computer.
The control assembly may also include lifting and
lowering means for moving the wheels of the auxiliary
suspension between a ground-engaging position of the wheels
and a retracted position.
According to a particular feature of the
invention, means are also proposed for feeding pressure air
to the air brakes of the auxiliary wheels up to a given
pressure that is proportional and preferably equal to the
pressure of the air fed to the balloons of the auxiliary
suspension. In this manner, the pressure applied by the
driver on the air brakes of the auxiliary suspension can
never exceed that corresponding to the load carried by the
wheels of the auxiliary suspension.
A description now follows of a preferred
embodiment of the invention having reference to the appended
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side elevation view of a load
transportation vehicle provided with a load-distribution
system made according to the invention, and
Figure 2 is a block diagram of the system.
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DESCRIPTION OF A PREFERRED EMBODIME,NT
Referring to Figure 1, there is shown a truck having front ~,leeli"g wheels 1, rear
wheels 3 and ret,~,1able auxiliary wheels 5 between the front and rear wheels, the
5 auxiliary wheels being intended for carrying any load in surplus of the usual load
carried by the truck and borne by the front and rear wheels.
The steering wheels 1 are mounted on a transverse axle beam 7
connected, at its ends, to a frame beam 9 of the truck by means of a pair of like
suspe"sions 21 which may be conver,Lional as long as it includes pneumatic
1 o balloons.
The f~ont suspensions 11 shown in Figure 1 are of the cor"b;.,ed
pneumatic and blade-spring type such as disclosed in Applicant's copending
Canadian a,Jplicalion No. 349,107 filed on May 9, 1989. The one ill~sll~led in Figure
1 comprises a blade spring 13 fixed to the axle beam 7 and pivoted at one end to15 a bracket 15 of the adjacent frame beam 9. The other end is slidably received in a
lever 17 pivoted at one end to a bracket 19 and fixed, at its other end, to an
inflatable air balloon 20 secured to and beneath the frame beam 9.
Each auxiliary wheel 5 is similarly mounted on the beam 9 of the truck
body frame through a suspension 21 of conventional type including an air i"rlalable
2 0 balloon 23 and air brakes 25. The suspensions 21 further include conventional lifting
and lowering means 27 (Fig. 2) capable of moving the wheels 5 between a ground-
engaging position and a rel,actecl position. Such means 27 can be pneumatic and
part of the system of the inven-
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tion or hydraulic and connected to the hydraulic circuitryof the truck.
A computarized pneumatic circuit 29 connected to
the front and auxiliary suspensions 11, 21, integrates the
various components of the load distribution system, as made
according to the invention and illustrated in Figure 2 to
which reference is now made.
As shown, an air compressor 31 sends pressure air
to the balloons 20.
A weight sensor 37 operatively connected to the
balloons 20 and to the computer 35 constantly assesses the
weight supported by the steering-wheels suspension. It may
include a conventional pressure gauge capable of measuring
the air pressure in the balloons 20 or it may include a
ruler device measuring the linear lag or deflection of the
suspension. It may also include sensor means for
evaluating the effective load and calculating its
distribution over the axles. In all cases, the measures
made are directly proportional to the weight supported by
the steering-wheels suspension 11 and are transformed into
corresponding weight signals sent to the computer 35 which
compares them to thepreselected weight, acceptable to the
steering wheels; the computer establishing weight variations
from these signals with respect to the acceptable weight.
The system in Figure 2 further comprises an
assembly 39 for controlling the action of the auxiliary-
wheels suspension 21. It is operatively connected to the
computer 27, to the air compressor 31 and to the balloons 23
of the auxiliary-wheels suspension through pipings 41, 43.
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air from the air compressor 31 and for feeding it to
the balloons 23. The computer 35 is programmed for
responding to the weight variations in the balloons 20
by correspondingly adjusting the pressure in the balloons
23 in order to maintain constant t he p re se le c te d
weight to be carried by the steering wheels 1 of the
suspension 11. For this purpose, the control assembly
has an air pressure controller 45 which is operatively
connected to the balloons 23, through pipings 41, 43,
so as to transfer, under the control of the computer
35, pressure air to the balloons 23 at a pressure commen-
surate to the weight variations in the balloons 20.
The control assembly 39 additionally comprises
the aforesaid means 27 for lifting and lowering the auxi-
liary wheels 5 between a ground-engaging position and
a retracted position as aforesaid. Where these means,
which could involve power jacks, are pneumatic, they
are connected to the air compressor 31 and to the computer
for complete computer-controlled operation. They
may, on the other hand, be hydraulically operated and
be part of the hydraulic circuit of the vehicle.
Where the means 27 are pneumatic and a surplus
load is detected on the steering wheels by the weight
sensor 37, the computer orders their actuation to apply
the auxiliary wheels to the ground and pressure air to
be sent to the balloons 13, 15, which, by their inflation,
lift the vehicle so that the auxiliary wheels 5 gradually
pick up the surplus load thereby gradually reducing the
load on the steering wheels 1 until the preselected load
thereon is reestablished. In this manner, the computer
9 is able constantly to keep the load on the steering
wheels at the preselected weight by shifting any overload
thereon to the auxiliary wheels. There is no longer
any need for the driver to make approximate and hazardous
adjustments.
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Let us assume, for instance, that the proper load,
for good driving condition, to be supported by the steering
wheels corresponds to a pressure of 80 psi in the balloons
20. Suppose now that a surplus load is added which brings
the total load to an equivalent of 145 psi which load is
distributed to all wheels including the steering wheels 1
and the rear wheels 3. The steering wheels 1 are thus
overloaded. The sensor 11 then sens signals to the computer
9 which orders actuation of the control assembly 39 causing
the means 27 to lower the auxiliary wheels 5 to the ground
and inflation of the balloons 23. As the latter lifts the
vehicle, the auxiliary wheels 5 gradually pick up part of
the surplus load reducing, by the same token, that applied
to the front wheels 1 until the load on them is finally
reduced to the acceptable one corresponding to 80 psi in the
balloons 20. Any further addition of load on the steering
wheels over the acceptable one is immediately removed from
them by corresponding inflation of the balloons 23.
As an added feature, the system of the invention
may provide for supplying air to the air brakes 25 at a
pressure that is always proportional to the one
corresponding to the load carried by th~ auxiliary wheels to
prevent freezing of the brakes and skidding of the vehicle.
For this purpose, and as shown in the embodiment of Figure
2, a control valve 51 is connected to the piping 41 to
receive air from it which will be at the same pressure as
that in the balloons 23. This valve 51 is mounted in line
onto a pressurized air supply line 47 leading from the air
compressor to the air brakes 25, just upstream the pedal-
operated air-brake control valve 53 of said air brakes 25.
In this manner, the braking force allowed by the vehicle
operator can never exceed the pressure allowed by the
control valve 51 in the line 47, which pressure is
proportional to force carrying the load in the balloons 23.
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Although, in the above description of a preferred
embodiment of the invention, reference has been made to the
front wheels suspension as "main" suspension whose load is
to be controlled, the invention as claimed hereinafter is of
broader application. Indeed, use could also be made of the
rear suspension or of any intermediate suspension in the
case of multiaxles vehicle as "main" suspension, the basic
aim of the invention being exclusively to balance the weight
over the axles.
Although in the above description and appended
claims, reference has been made exclusively to air-
inflatable balloons supplied by an air compressor, the
invention is intended also to encompass any similar
suspension using another fluid instead of air.
