Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02744762 2011-06-30
VEHICLE-BED MOUNTED LIFTING SYSTEM
TECHNICAL FIELD
The current application relates to a system for lifting cargo, and in
particular to
lifting systems mounted on a bed of vehicle.
BACKGROUND
Loading and unloading cargo can require lifting heavy loads. Various systems
for
aiding in the loading and unloading of cargo from a bed of a vehicle have been
devised.
For example, in order to aid in loading or unloading a motorcycle from a
flatbed of a
pickup truck, ramps have been used. The motorcycle can be pushed or pulled up
the
ramps.
Previous attempted solutions for loading cargo, such as a motorcycle, onto a
bed
of a vehicle have included a platform that is pulled up a ramp into the bed.
The platform
is pulled onto the bed at an angle, which may be undesirable. Further,
previous
attempted solutions often require a component, such as a ramp or other
structure, that
extends past the end of the bed of the truck, which prevents a tailgate of the
bed from
being closed.
A loading and unloading system that can be mounted to a bed of a vehicle that
overcomes drawbacks of prior art attempted solutions is desired.
SUMMARY
In accordance with the present disclosure there is provided a vehicle-bed
mounted loading and unloading system comprising a lifting assembly and a lift
platform
releasably connected to the lifting assembly. The lifting assembly comprises a
support
frame to be mounted on the truck deck and providing front and rear pivot
points on first
and second sides of the truck deck; first and second lifting linkages each
coupled to a
respective side of the support frame and comprising a front lifting arm having
a lower
end pivotally connected to the respective front pivot point; a rear lifting
arm having a
lower end pivotally connected to the respective rear pivot point; and a
connecting arm
having a front end pivotally connected to an upper end of the front lifting
arm and a back
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r
end pivotally connected to an upper end of the rear lifting arm; and a
rotational driving
mechanism for providing a rotational force to at least one of the first and
second lifting
linkages. The lift platform comprises a lifting frame for supporting loads; a
lift support
connected to the lifting frame and providing a connection above the lifting
frame for
connecting to the lifting assembly proximate the upper ends of the front
lifting arms, the
lifting frame rotatable about the connection; and a rotation-limiting
connection for
coupling the lifting frame to the lifting assembly proximate the upper ends of
the rear
lifting arms to limit rotation of the lifting frame about the connection when
loading and
unloading loads.
In accordance with the present disclosure there is further provided a kit for
a
truck deck mounted loading and unloading system comprising first and second
support
structures to be mounted on or anchored to respective sides of the truck deck,
each
support structure providing front and rear pivot points on first and second
sides of the
truck deck; a pair of front lifting arms each having a lower end to be
pivotally connected
to a respective front pivot point; a pair of rear lifting arms each having a
lower end to be
pivotally connected to a respective rear pivot point; and a pair of connecting
arms each
having a front end to be pivotally connected to an upper end of a respective
one of the
front lifting arms and a back end to be pivotally connected to an upper end of
a
respective one of the rear lifting arms; a rotational driving mechanism for
providing a
rotational force to at least one of the first and second lifting linkages; and
a load platform
releasably connected to the lifting assembly comprising a platform for holding
loads; a
lift support of the platform to provide a connection above the platform for
connecting to
the lifting assembly proximate the upper ends of the front lifting arms; and a
rotation-
limiting connection for coupling the platform to the lifting assembly
proximate the upper
ends of the rear lifting arms to limit rotation of the platform about the
connection when
loading and unloading loads.
BRIEF DESCRIPTION OF THE DRAWINGS
A system for loading and unloading cargo will be described with reference to
the
appended drawings, in which:
Figure 1 is an isometric view of the lifting system mounted on a bed of a
truck;
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t
Figure 2 is a side view of a lifting system mounted on a bed of a truck;
Figure 3 is a top view of the lifting system mounted on a bed of a truck;
Figure 5 is a rear view of the lifting system mounted on a bed of a truck;
Figure 5 is a side view of the lifting system;
Figure 6 is a top view of the lifting system;
Figure 7 is an isometric view of the lifting system;
Figure 8 is an exploded view of the lifting system; and
Figure 9 is a side view of the lifting system mounted on a bed of a truck in
operation.
DESCRIPTION
The lifting system described herein provides easy loading and unloading of
heavy cargo in and out of a truck bed. The system is described in detail
herein as being
mounted in a flatbed of a pickup truck. It is contemplated that the lifting
system could
be adapted to be used in other applications such as trailer, flat beds, and
vans. The
lifting system is intended to remain in the truck with the cargo while in
transit.
Referring to the Figures, the lifting system 100 comprises a lifting assembly
102
and a load platform 150. The lifting assembly 102 includes a support frame
104,
linkages 106, 108, and a rotational driving mechanism 110. The lifting
assembly 102
may be assembled inside the box of a pickup truck 101 to reduce the need for
precise
manufacturing relating to the fit of the system 100.
The support frame 104 may comprise two support structures 112, 114 that are
substantially identical. Each support structure 112, 114 is located on a
respective side
of the truck bed. Each support structure 112, 114 may be separated from the
other by
bracing, which may include a front brace 116 and a rear brace 118. Respective
linkages
106, 108 are connected to each support structure positioned at each side of
the flatbed
box area. Each linkage comprises a front lift arm 120, a rear lift arm 122 and
a
connecting arm 124. The front lift arm and the rear lift arm are each
pivotally connected
to a respective support structure at pivot points 180,181,182,183. The
connecting arm
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connects the respective front lift arm to the rear lift arm. The linkages 106,
108 may be
connected to each other by a linkage brace 126, which may be located between
the top
ends of the front lift arms.
The rotational driving mechanism 110 may comprise driving sprockets 128 that
are attached to one of the arms of the linkages. As depicted , a drive
sprocket 128 is
attached to the front arm of each linkage 106, 108. By rotating the drive
sprockets, the
linkages rotate by a corresponding amount. The rotational driving mechanism
110
includes free-wheel sprockets 130 located on each support structure. Rolling
chains
132 connect each free-wheel sprocket 130 with each drive sprocket 128. A
sliding drive
134 is attached to the rolling chain 132 between the free-wheel sprocket 130
and the
drive sprocket 128. Movement of the sliding drive 134 towards either sprocket
causes
each sprocket to rotate. The sliding drive 134 may be attached to the rolling
chain by
way of one or more sprockets that are secured to the sliding drive so as to
prevent
rotation. The sliding drive 134 is connected to a means for providing linear
movement
such as a hydraulic cylinder 136. Each rotational driving mechanism 110 may
include a
chain guard 138.
The lifting system lifts a given load from ground level, up and into the truck
bed. It
can also lift the given load out of the truck bed down to ground level. The
load is placed
and secured onto the platform 150. Securing the load is accomplished using
restraining
methods chosen at the discretion of the user in a responsible manner. Although
the
platform 150 is depicted as a flat surface, it is possible to use other
lifting platforms. For
example a boxed platform may be used to lift materials such as sand or gravel.
Similarly a lifting frame/boom may be used to suspend loads to be used as a
hoist such
as an engine hoist.
The platform 150 is constructed to be attached to the upper brace by the use
of
lifting chains 152 and shackles 154, as well as a sliding locking hinge type
of connection
156 at the top of the ridged vertical member 158 located at the front end of
the platform.
The lift support connection 156 may allow the platform 150 to rotate when
being lifted.
The chains 152 and shackles 154 limit the rotation of the platform about the
lift support
156 when the platform 150 is lifted, in addition to providing support for the
platform.
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The platform 150 is lifted and loaded onto the truck bed via a push button
remote
control (not shown) using the "up" button. The remote control controls a
hydraulic pump
(not shown) that causes the pistons 136 to extend or retract as desired. The
hydraulic
pump may be mounted on a frame 174. The platform 150 initially lifts the front
of the
platform while the chains remain slack. As the platform continues to rise, the
platform
will rotate slightly until the chains 152 tighten, preventing further rotation
of the platform,
and begin to raise the rest of the platform. Figure 9 depicts this position as
902.
This tilting of the platform 150 benefits the operation. It slackens the
chains 152
when the platform is in the ground level position to enable easy unlatching of
the chains
152 from the shackles 154 by offloading the chain tension. It also ensures
that the rear
of the platform will contact the ground in the event of uneven ground level.
In order to
load and unload cargo on and off of the platform, the rear of the platform
must be as
close to ground level as possible.
As the platform continues to rise, it rises in an arched path inherently
designed
into the device by the combination of lift linkages 106, 108. The front lift
arms and rear
lift arms are linked to each other by the upper brace by bolts or pins. Their
motion is
commutative as all four arms are constrained to almost mimic each other's
motion. Due
to the orientation of the pivot points, the front vs. rear arm motion is not
quite identical to
each other, but rather provides the slight tilt action mentioned previously.
This arched motion continues to raise the platform to its peak height before
it
begins to descend onto the truck bed. Figure 9 depicts this peak height
position as 904.
As the platform passes this peak height, the direction of gravity now helps in
the rest of
the loading direction onto the truck bed. Once the platform is at rest on the
truck bed,
the "up" button can be released. Figure 9 depicts the transportation position
as 906. It
is noted that the load and the chains have been omitted from this position for
the clarity
of the Figure.
The platform is unloaded from the truck bed via the push button remote control
using the "down" button. When the platform is resting on the truck bed, it is
parallel to
the bed of the truck. The tilt action that was mentioned previously, works
during the
distance travelled between the loaded and ground level position of the
platform.
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Therefore the tilt effect is diminished in the resting position on the truck
bed. The lift
chains securing the platform are not slack in this position therefore will not
sway and
contact the cargo.
As the platform is raised, the front and rear of the platform will begin to
rise
simultaneously, but the front will rise faster, immediately initiating the
tilting action. The
platform will rise in the arched path governed by the lift arms and the manner
in which
they are all linked. The platform will continue along its arched path and
tilting to ensure
that the rear of the platform is lower than the front. As the platform passes
its peak
height, the direction of gravity now helps in the rest of the unloading
direction. The rear
of the platform will contact the ground first to ensure that there is minimal
elevation
change between the rear of the platform and the ground. The front of the
platform will
make contact as the "down" button is still depressed. The user shall then
release the
"down" button as the unloading is complete.
The platform is located within the majority of the inner box bed area. The
platform can be short to allow closure of the tailgate, or long to accommodate
longer
cargo items. There is guarding in place to help prevent injury from drive
components.
In a transport position 906, used while traveling, the lifting system 100
resembles
roll bars that are frequently installed on trucks. There is optional cargo
area 170 which
may be positioned over the cab of the truck. There is also an optional
auxiliary support
jack that can be attached to the bumper, bumper hitch, or receiver hitch of
the truck to
lessen the load on the truck suspension. The auxiliary support jack 172 would
only be
used during the loading or unloading process, and can be removed otherwise.
The lifting system 100 may be powered by an electrically operated, double
acting
hydraulic power pack (not shown). The electrical power may be delivered from
the
vehicle's electrical system. The hydraulic power pack requires 12VDC. The
power pack
utilises an electric motor to run a hydraulic pump capable of delivering
3000psi
pressure.
The flow required to lift and lower the lifting platform is low and may be
controlled
by 2 mechanisms. The flow to each piston is controlled by a throttle valve
which limits
the flow at the return end of the circuit. The throttle valve allows free flow
when the
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direction of flow is reversed. There is another throttle valve controlling
flow in this
reverse direction as well. Each valve limits flow in opposing directions, and
allows free
flow in the other. This controls the rate of decent as the platform is lowered
for both
directions (onto the ground and onto the truck bed) when gravity is helping in
the same
direction as the loading/unloading direction.
Another control mechanism affecting the flow is PO check valves (Pilot
Operated
Check Valve). Each flow direction has a PO check valve. This valve is in place
to only
allow free flow when there is pressure in the driving direction but not in the
opposite
direction. This enables the "up" or "down" button of the remote control to be
released
and the current position of the platform will be maintained. As each direction
has a PO
check valve this "hold in place" function will work in the loading and
unloading direction.
The hydraulic pressure provided by the power pack is delivered to two double
acting cylinders. There is a cylinder mounted on the driver side frame as well
as the
passenger side frame of the device. The cylinders are restrained by yokes at
both ends.
One yoke is fixed to the frame; the yoke at the other end is fixed to a
sliding
mechanism. The sliding mechanism is also slidingly attached to the frame, in
order to
provide a single degree of freedom. This sliding mechanism drives a roller
chain, where
the chain is anchored to it. As the sliding mechanism is forced to move by the
cylinder
rod, the roller chain is also forced to move. The driver side and passenger
side function
in the same manner.
The roller chain spans across two sprockets; a large sprocket and a smaller
sprocket. The large sprockets are fixed to the front lift arms. When the chain
is driven by
the cylinder/sliding mechanism, the sprockets rotate. As the large sprockets
are fixed to
the lift arms, the lift arms also rotate. The length of travel of the
cylinders is such that the
lift arms rotate in the arched path required to lift the platform onto or off
of the truck bed.
The motion of this arched path of the lift arms is described previously.
The structure described above, and in particular the rotational driving
mechanism
described above helps to eliminate, or at least reduce, bending moments on
components and keep all forces axial in the members. There is however a large
bending
moment on the front lift arm which cannot be avoided.
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The front lift arms are constructed in a triangular geometry to provide the
strength
to resist the large bending moment generated by the load. The rear lift arms
are not
subjected to a bending moment, but sustain a high compressive load. Because
the
compressive load on the rear arms is axial, they do not require a triangular
structure to
resist bending.
The front and rear lift arms are connected by a connecting arm, while a
linkage
brace links the driver side lifting linkage to the passenger side lifting
linkage. By linking
the driver and passenger sides, the hydraulic cylinders remain in
synchronisation. The
connecting arms are subjected to compressive loads as well as tensile loads
between
the front and rear lift arms. This load is axial within the structure between
the front and
rear lift arms. This axial loading leaves the upper brace inherently strong
due to the
reduction of bending moments.
By offsetting some of the pivot locations in the connecting arm and front lift
arms,
a slight increase in bending moments occurs in these members. This sacrifice
was
made to give the front and rear arms a nesting effect when the lifting
platform is fully
loaded to be transported. This nesting gives the structure an aesthetic appeal
while also
providing a well-defined stop in the motion. As the structure is nested in
this home
position there cannot be any further movement in the loading direction. The
assembly is
also designed such that hydraulic cylinders reach the end of their stroke at
this nested
home position. This eliminates the need for limit switches to prevent over
loading of any
of the components by the high forces applied by the hydraulic system.
As an effort to prevent over loading nearing the fully unloaded position
(platform
at ground level), there are spacers installed on the hydraulic cylinder rods.
In the
unloaded position, the cylinders are in a more retracted portion of their
stroke. The
spacers are installed to limit how much the cylinders can retract. This limit
prevents how
much the lifting device can travel in the unloading direction. This unloading
limit is in
place so that the cylinders can no longer retract when the rear lift arms
approach the
tailgate. The rear of the assembly is not to be anchored to the rear of the
truck bed so
that the assembly will lift in the event that the platform reaches the ground
before the
cylinders are at their limited retracted position. This is also to prevent
over loading of
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= components by the high forces applied by the hydraulic system.
The installation of the lifting system does not impede on other uses of the
truck.
The driver and passenger side frames are positioned over the wheel wells. This
takes
up space in the bed of the truck that is not as valuable as the rest of the
bed area. The
hydraulic power pack is positioned over the cab of the truck to also maximise
in keeping
the bed area free.
This lifting system does not use the receiver hitch or bumper hitch which
allows
the user to also haul a trailer while the lifting device is installed.
The lifting platform is detachable so that the bed of the truck can be used
for
other applications. The lifting platform can also be sized such that the
tailgate can be
closed when the lifting platform is in the loaded position to allow other
items that would
not require the advantages of this lifting device, and also be secure in the
box. If the
platform is sized in a longer length, the tailgate may have to remain open
while the
platform is installed.
There are no modifications to the truck required, with the exception of
electrical
wiring for the hydraulic power pack. This allows the lifting device to be
removed to
completely restore the truck to its original intent. The design is such that
it can be
disassembled in sections to make the installation and removal easier. This
sectional
design also allows the hydraulic plumbing to remain plumbed. The user does not
have
to disassemble hydraulic fittings to assemble or disassemble the lifting
device.
As the lifting system is beneficial for loading and unloading heavy cargo, it
is best
to design with safety factors included in the design. For example, the lifting
system may
include guards to protect the user from moving drive components. The framework
and
linkages can be designed with space in their relative positions to eliminate
crush/pinch
points. The hydraulic system can be adjusted to limit the capacity so that the
user
cannot lift a load that is heavier than the intended limit. The speed which
the hydraulics
drive the lifting device can also be adjusted so that it functions in a slow,
smooth and
predictable manner.
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