Note: Descriptions are shown in the official language in which they were submitted.
CA 02297499 2000-O1-31
TITLE OF THE INVENTION
Lifting device for lateral displacement of the trailing end of road
vehicles.
FIELD OF THE INVENTION
The present invention relates to a lifting device and more
specifically a device to lift the trailing end of a road vehicle and allow for
its lateral
displacement when towed by a tractor or the like.
BACKGROUND OF THE INVENTION
It is known that tractor-trailer units often have steering difficulties,
especially when the trailer is long and the road narrow, causing the rear
wheels
of the trailer to either hit the corner of the sidewalks or go over to corner
ditch,
thereby causing the trailer to dangerously tilt sideways, when not tilting
over and
falling off.
In order to avoid the above problems, most of the tractor-trailer
units need to take much wider turns, whenever possible, and go over opposite
side traffic lanes that may cause road accidents. Also, the tractor-trailer
units
need to go through much longer road paths to avoid any narrow roads to get to
their final destination, thus increasing travel time and reducing the
efficiency of
the cargo delivery network.
To obviate the above problems, many mechanisms provide for a
self steering of the rear wheel train. Such mechanisms, as shown in U.S.
Patents
3,930,669 to Kollander et al, 5,197,751 to Rankel, 5,213,353 to Williams and
5,246,242 to Penzotti, are expensive and require special rear wheel trains
since
they are built-in the latter. Also, in case of breakage of the mechanism, the
rear
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wheel train must be fixed before the trailer can move again, thus causing more
problems of towing the trailer away for repair.
OBJECTS OF THE INVENTION
It is therefore a general object of the present invention to provide a
lifting device for lateral displacement of the trailing end of road vehicles
that
obviates the above noted disadvantages.
Another object of the present invention is to provide a lifting device
for lateral displacement of the trailing end of road vehicles that allows for
lifting of
the trailing end of the trailer, or the like, and lateral displacement of the
same
when it is towed by a tractor.
It is a further object of the present invention is to provide a lifting
device for lateral displacement of the trailing end of road vehicles that is
easily
adaptable to most of the trailers without having to change the existing rear
wheel
train.
It is yet another object of the present invention is to provide a lifting
device for lateral displacement of the trailing end of road vehicles that can
be
easily mounted in dismounted, in case of breakage, to any trailer.
SUMMARY OF THE INVENTION
The present invention is directed to a lifting device for lifting a
trailing end of a road vehicle and used for laterally displacing said trailing
end,
said lifting device comprises a main body including a fixed section for
rigidly
securing to said trailing end, a first mobile section substantially vertically
movable
relative to said fixed section between an elevated non-operative position and
a
lowered operative position lifting said trailing end, and a second mobile
section
rotatably mounting on said first mobile section, a first actuator device
linearly
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moving said first mobile section relative to said fixed section, a second
actuator
device rotatably moving said second mobile section relative to said first
mobile
section, a rolling device securing to said second mobile section for rollingly
engaging a road surface, a blocking mechanism temporarily blocking said second
actuator device from rotating when in said operative position, and a power
source
activating both said first and second actuator devices.
Preferably, the rolling device freely pivotally mounts on said second
mobile section.
Preferably, the lifting device further includes a control device to
control the application of power from said power source to both said first and
second actuator devices.
Preferably, the first actuator device includes a reversible hydraulic
linear actuator and a guide to prevent any rotational displacement of said
first
mobile section relative to said fixed section, said power source being a
hydraulic
pump connected to an electrical motor and said control device includes a
hydraulic network.
Preferably, the second actuator device includes a reversible
hydraulic rotary actuator, said blocking mechanism holding said rotary
actuator at
a plurality of predetermined rotated positions, all angles between two
adjacent
positions being equal to each other.
Preferably, the hydraulic network includes a regeneration circuit
connected to said linear actuator, said regeneration circuit includes a
hydraulic
valve and check valves used for rapid raising of said first mobile section
from said
operative position to said non-operative position.
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Preferably, the first mobile section includes an attachment device
adapted to be removably engaged by a linear actuator backup device, said
hydraulic network includes a pressure relief valve connected to said linear
actuator whereby said first mobile section can be raised by said actuator
backup
and activation of said pressure relief valve upon failure of said linear
actuator.
Preferably, the rolling device includes a plurality of wheels, said
wheels are mounted with their respective axis of rotation parallel to each
other,
and a track rotatably engaging and covering all of said wheels.
The present invention is also directed to a combination of two lifting
devices, wherein each one of said lifting device for securing to a respective
side
of said trailing end, both said power sources being linked together to
simultaneously activate both first actuator devices and both second actuator
devices respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
In the annexed drawings, like reference characters indicate like
elements throughout.
Figures 1 a and 1 b are schematic illustrations of the trailer being
towed, showing the paths that would be taken without and with an embodiment of
the lifting device of the present invention respectively;
Figures 2a and 2b are side elevation views of the tractor-trailer units
with an embodiment of the lifting device of the present invention in a non-
operative and in an operative position respectively;
Figure 3 is a rear view taken along line 3-3 of Fig. 2a;
Figure 4 is a partial section view taken along line 4-4 of Fig. 3;
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Figure 4a is a view similar to Fig. 4 showing the lifting device in an
operative position;
Figure 5 is a top plan view of the lifting device of Fig. 4;
Figure 6 is an enlarged partial section view taken along line 6 of
Fig. 3;
Figure 7 is a section view taken along line 7-7 of Fig. 4;
Figure 8 is a partial section enlarged view taken along line 8-8 of
Fig. 4; and
Figure 9 is a diagrammatic representation of the hydraulic control
network used in conjunction with the preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Figs. 1 a to 8, there is shown a lifting device 20 for
lateral displacement of the trailing end of road vehicles, preferably for
trailers T,
semi-trailers and the like. The lifting device 20 lifts the trailing end of
the trailer T
such that the rear wheels W loose contact from the road, then, the trailing
end of
the trailer is forced to move in a predetermined direction set to the device
20
when the trailer T is being towed by the tractor A.
As shown in Fig. 1 a, without any lifting device 20, the trailer T,
especially of a certain length, tends to take short corners and go over the
sidewalks corner C of a road R, as represented in dashed lines, when towed by
the tractor A that makes a 90 degree angle turn.
When lifting devices 20 are used, as shown in Fig. 1 b, close to the
rear wheel train, the latter being forced to follow a predetermined direction
imposed by the orientation of the portion of the lifting devices 20 in contact
with
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the road R. Consequently, the trailing end tends to move away from the corners
C without having the tractor A taking very large corners and possibly hit
other
vehicles V stopped in the opposite direction lane.
According to Figs. 2a and 2b, the lifting device 20 is adapted to be
rigidly secured to the walking beams B at the trailing end of the trailer T.
Preferably, the lifting device 20 is located inbetween to rear wheels W, even
though it could be located at the front or the back of the latter. In Fig. 2a,
the
lifting device 20 is in its non-operative retracted position, when the trailer
T is
towed by the tractor A. While in Fig. 2b, the lifting device 20 is in its
operative
extended position, supporting the weight of the trailing end of the trailer T
since
the rear wheels W are slightly lifted up away from the surface of the road R.
As seen in Figs. 3 to 4a, the lifting device 20 comprises a main
body 22 that generally includes a fixed section 24 rigidly secured to the
walking
beam B, a first mobile section 26 and a second mobile section 28. The first
mobile section 26 is substantially vertically moving relative to the fixed
section 24
via a first actuator device, preferably a reversible hydraulic linear actuator
30.
The fixed section 24 is the outer cylinder 32 of the actuator 30. The external
free
end of the inner piston 34 of the actuator 30 is generally formed of a plate
36
supporting the second actuator device, preferably a reversible hydraulic
rotary
actuator 38.
The rotary actuator 38 is adapted to drive a pinion 42 that slidably
engages a sprocket gear 44 itself secured to the upper part 46 of the second
mobile section 28 of the lifting device 20. That second mobile section 28
generally co-axially rotates around the axis of the sprocket gear 44 and the
first
mobile section 26, and is supported at the base 48 of the piston 34. The lower
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part 50 of the second mobile section 28 includes a rolling device, preferably
two
adjacent tracks 52, pivotally free mounted thereon. The tracks 52 are
preferably
on each side and diametrically opposed of the rotational axis of the second
mobile section 28. The two tracks 52 rollingly engage the surface of the road
R
when the device is in operative position.
The fixed section 24 is preferably secured to the walking beam B
using six mounting bolts 54 on a flat mounting plate 56, as well as through a
plurality of reinforcing braces (not shown), as required. The mounting bolts
54
are easily accessible for dismounting of the lifting device 20 whenever
required.
The fixed section 24 also includes guides, preferably two sleeves 58 adjacent
and parallel to the cylinder 32 and located diametrically apart from the
latter. The
two sleeves 58 generally have a rounded square cross-section adapted to
slightly
receive two bars 60 also with rounded square cross-section secured to the
first
mobile section 26. These two bars 60 prevent any rotational movement of the
first mobile section 26 around the fixed section 24.
As pictured in Fig. 6, the base 48 of the piston 34 is adapted to co-
axially receive the upper part 46 of the second mobile section 28 and provides
a
shoulder 62 as an abutment support for a radial flange 64 at the extremity of
the
upper part 46 when the lifting device 20 is in the non-operative position,
under the
gravity weight of the second mobile section 28.
The plate 36 supporting the rotary actuator 38 also includes a
blocking mechanism to prevent the second mobile section 28 from rotating about
the first mobile and fixed sections 26, 24 when the lifting device 20 is in
operative
position. The blocking mechanism preferably includes a plurality of short pins
66,
generally cylindrical and located at the lower edge of the plate 36,
circularly
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positioned around the axis of the sprocket gear 44 and sized to tightly and
releasably engage corresponding holes 68 located on the sprocket gear 44, see
Figs. 6 and 7. When tracks 52 engage the road R under activation of the linear
actuator 30, the pins 66, preferably having chamfered extremities for final
self-
alignment, start engaging the corresponding holes 68 until the sprocket gear
44
abuts against the plate 36, thus locking the second mobile section 28 of the
lifting
device 20 in place ready for operation. Upon retraction of the lifting device
20,
the blocking mechanism automatically releases the pins 66 from the
corresponding holes 68 to allow for repositioning of the second mobile section
28
to its non-operative zero degree angle position.
Essentially, the pins 66 and their corresponding holes 68 are
equally distributed at predetermined rotational angle positions, preferably
every
degrees form one to another, to rotationally position the second mobile
section
28 and its tracks 52 around its rotational axis, with respect to the fixed
section 24
15 and the trailer T. The rotational angle is set by the controlled
displacement of the
rotary actuator 38.
As shown in Figs. 4 and 8, each tracks 52 preferably covers three
wheels 70 free to rotate about and with their respective axis of rotation,
preferably
via standard ball bearings, all co-linear and parallel to each other. Out of
the six
wheels 70, the two central ones 72 have a common shaft 74 that is preferably
pivotally mounted on bearings onto the lower part 50 of the second mobile
section 28 to allow for the tracks 52 to easily adapt to and roll onto any
deformation of the surface of the road R. The four remaining wheels 70 are
independent from each other and held in place by sidebars 76.
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To drive the two reversible hydraulic actuators 30, 38, a power
source, preferably a hydraulic network including a control device 78 and
hydraulic
pumps 80, 80a pressurizing the hydraulic fluid from a reservoir 82 is used.
The
fluid is directed to the proper actuator via standard bi-directional valve
controls
84. The pumps 80, 80a are driven by the electrical motors 85 powered by the
standard 12 volt direct current tension source available from the
alternator/battery
86 of the road vehicle. The hydraulic network is preferably closely located to
the
lifting devices 20 connected thereto and, is preferably remotely controlled
via the
control device 78 by the tractor driver, while seated in the tractor A.
Preferably, a
first pump 80 is used to supply the large quantity of hydraulic fluid required
for the
extended displacement of the pistons 34 of linear actuators 30 and, a second
pump 80a is series connected to the first one to ensure proper fluid pressure
as
required for the heavy weight being lifted by the lifting devices 20, when the
trailer
T carries heavy loads.
Fig. 9 shows the diagram of the hydraulic network including its
control device 78 formed of the different bi-directional valve controls 84.
Preferably, in order to accelerate the displacement of the linear actuator
from the
lowered operative position to the raised non-operative position using the two
pumps 80, 80a, a regeneration circuit is used via a hydraulic valve 87 and its
corresponding check valves 89. When two lifting devices 20 are used, one on
each side of the trailing end of the trailer T, their respective actuators 30,
38 are
similarly and simultaneously activated by the same pumps 80, 80a.
Preferably, pressure relief valves 88 are provided for emergency
cases when the lifting device 20 undergoes some problems and the linear
actuator 30 needs to be manually retracted using a linear actuator backup
device,
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preferably in the form of a hook 90 connected to a cable 92 and a common
manual hitch 94. The hook 90 then removably engages an attachment device,
preferably an eyelet 96 provided on plate 36 of the first moving section 26
(see
Figs. 2b and 7) to allow for easy manual retraction of the latter. In general,
hitch
94 is already available since many hitches are typically slidably mounted on
the
longitudinal edges of the trailer T for securing the trailer load.
Although embodiments have been described herein with some
particularity and details, many modifications and variations of the preferred
embodiment are possible without deviating from the scope of the present
invention.
