Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02639719 2008-09-22
RETRACTABLE TARPING SYSTEM
FIELD OF THE INVENTION
[0002] The invention relates generally to a system for covering portions of
vehicles.
More particularly, the invention relates to a retractable tarping system.
BACKGROUND OF THE INVENTION
[0003] While many products are transported in packages or containers, many
other
products arc transported in bulk where the desired amount of product is placed
into the vehicle
that is to be used to transport the product. The vehicles typically used to
transport bulk products
include trucks, trailers, rail cars, carts, wagons, and other various
containers with open tops.
These vehicles typically include an open top to facilitate placing the bulk
product into the
vehicle.
[0004] To reduce the potential of product falling out of the vehicle as the
vehicle is
moved and to reduce the potential of the product being damaged by
environmental factors, it is
customary to place a cover over the open top of the vehicle. To facilitate
placing the bulk
product into the vehicle, the cover is typically retractable such as rolling
up.
[0005] An example of one such cover is marketed under the designation SRT-2 by
AgriCover such as is illustrated in Fig. 1. 'I1vs tarp system uses the tarp to
pull the roll tube
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across the hopper as it rolls up the tarp. An internal torsion spring in each
spool (similar to a
garage door spring) is preloaded to provide tarp tension in the closed
position. As the tarp is
being rolled up and begins to grow in diameter, the roll tube begins moving
faster than the cable
is unrolling and the spools begin to tum slightly on the roll tube, winding
the spring even tighter.
[0006] 'I'his increase in speed occurs because the tarp diameter becomes
larger than the
spools and the roll tube moves farther per revolution than the spools whose
circumference
remains the same. To close the tarp, the motor reverses and the torque
tensioned spools "reel in"
the cable, pulling the tube back across the hopper.
[0007] Other side roll-up tarp systems are marketed by Michel (Fig. 2) and
Shur-Co., the
assignee of this patent application, under the designation Super Duty Swing
Arm Electric System
(Figs. 3-4). Both of these tarp systems use extension springs and spools that
are rigidly mounted
to the roll tube.
[0008] Michel's tarp system uses a tapered grooved spool and Shur-Co uses a
narrow,
flat bottom, grooveless cable spool. Both systems pull cable from a side
mounted tube at a 90
angle as the roll tube moves across the caps. Both systems unroll cable from
their respective
spools as the tarp is opened. Both systems' roll tubes move further than the
amount of cable
unrolled, which results in extending the springs as the tarp moves to the open
position thus
giving the force needed to keep the cable tight allowing the spools to reel in
the cable which
closes the tarp.
SUMMARY OF TI-iE INVENTION
[0009] An embodiment of the invention is directed to a retractable tarp system
that
includes a shaft, a first and second cable, cable spools, a tarp, and a motor
or manual actuator.
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The shaft extends across the open top of the vehicle. The first and second
cables are wrapped
around the spools and tensioned with opposite ends thereof being secured to
the vehicle. The
spools are securely mounted over the ends of the shaft. The motor or manual
actuator is
operably attached to either shaft end to rotate the shaft which in turn moves
the shaft back and
forth across the box opening.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The accompanying drawings are included to provide a further
understanding of
embodiments and are incorporated in and constitute a part of this
specification. The drawings
illustrate embodiments and together with the description serve to explain
principles of
embodiments. Other embodiments and many of the intended advantages of
embodiments will be
readily appreciated as they become better understood by reference to the
following detailed
description. The elements of the drawings are not necessarily to scale
relative to cach other.
Like reference numerals designate corresponding similar parrs.
[0011] Fig. 1 is a perspective view of a prior art tarping system in a closed
configuration.
[0012] Fig. 2 is a perspective view of another prior art tarping system in a
partially closed
configuration.
[0013] Fig. 3 is a perspective view of still another prior art tarping system
in a closed
configuration.
[0014] Fig. 4 is a perspective view of the tarping system of Fig. 3 in a
partially closed
configuration.
[0015] Fig. 5 is a perspective view of a tarping system according to an
embodiment of
the invention.
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[0016] Fig. 6 is an enlarged perspective view of the tarping system of Fig. 5.
[0017] Fig. 7 is a top view of the tarping system of Fig. 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] In the following Detailed Description, reference is made to the
accompanying
drawings, which form a part hereof, and in which is shown by way of
illustration specific
embodiments in which the invention may be practiced. In this regard,
directional terminology,
such as "top," "bottom," "front," "back," "leading," "trailing," etc., is used
with reference to the
orientation of the Figure(s) being described. Because components of
embodiments can be
positioned in a number of different orientations, the directional terminology
is used for purposes
of illustration and is in no way limiting. It is to be understood that other
embodiments may be
utilized and structural or logical changes may be made without departing from
the scope of the
present invention. The following detailed description, therefore, is not to be
taken in a limiting
sense, and the scope of the present invention is defined by the appended
claims.
[0019] An embodiment of the invention is directed to a retractable tarping
system, as
illustrated at 10 in Figs. 5-7. The retractable tarping system 10 may be used
in conjunction with
a vehicle, container, or box that is used for transporting products. One
application that the
retra.ctable tarping system 10 is particularly suited for is open top trucks,
trailers, rail cars, carts,
wagons, and other various containers 12 that are used for transporting bulk
products.
[0020] There are several features that are unique to this system. These
features are: (1)
the spools and cable propel the shaft in both the opening and closing
directions. The tarp is not
used to move the shaft and is simply along for the ride. (2) There is no
torque arm required.
Torque wheels on the motor mounting plate in conjunction with the cable
tension keep the motor
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from turning. (3) "Unrolling tensioning," this feature allows the shaft to
apply tension gradually
when closing the tarp with a significant increase in torque at the shaft
without sacrificing speed.
(4) There is no additional "stored energy" device such as a spring that is
used to assist in closing
the tarp. This makes for a safer system, especially if being manually
operated.
[0021] The retractable tarping system 10 enables a tarp 14 to be moved between
an open
configuration and a closed configuration. When the tarp 14 is in the closed
configuration, the
tarp 14 substantially covers the box opening 12 to which it is attached to
thereby protect products
placed in the box 12 from blowing out of the box 12 as well as from being
damaged by
environmental elements such as snow or rain. When the tarp 14 is in the open
configuration, a
substantial portion of the open top of the box 12 is not covered to facilitate
placing products in
the box 12.
[0022] While the retractable tarping system 10 is described and illustrated as
rolling the
tarp from side to side across the box 12, it is possible to use the concepts
of the invention to
rolling the tarp from front to back across the opening of the box. The front
end 20 and the back
end 22 of the box 12 may each include a support surface 24 over which the
retractable tarping
system 10 is rollable. These support surfaces 24 may be substantially flat,
angled or convex.
These support surfaces 24 may be included in the box 12 when manufactured or
may be attached
to the box 12 with the other components of the retractable tarping system 10.
[0023] The retractable tarping system 10 generally includes a shaft 30, a
first cable 32, a
second cable 34, a tarp 14 and a motor 36. The shaft 30 extends between the
support surfaces 24
and is formed with a diameter and wall thickness to provide the shaft 30 with
sufficient rigidity
to support not only the shaft 30 but also the tarp 14 operably attached
thereto. Rotating the shaft
30 thereby causes the tarp 14 to be rolled onto or off of the shaft 30.
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[0024] A spool 40 is provided proximate each end of the shaft 30. Each spool
40 may
have a plurality of spiral grooves formed in a surface thereof to reduce the
potential of the cable
32, 34 slipping with respect to the spool 40 and provide the necessary
distance of cable travel
length to allow the cable to track across the face of the spool 40 as it opens
and closes the tarp
14.
[0025] Tbe first and second cables 32, 34 are pulled tight over the support
surfaces 24
and attached at opposite ends thereof. To further reduce the potential of the
first and second
cables 32, 34 slipping with respect to the spool 40, the first and second
cables 32, 34 may be
wrapped at least once around the spool 40. In a preferred configuration, the
first and second
cables 32, 34 are wrapped around the spool 40 two or more times. The spools 40
thereby use the
first and second cables 32, 34 as a track and pull both ends of the shaft 30
in substantial unison
across the box 12.
[0026] To prevent slipping and keep both sides of the tarp 14 even, the cables
32, 34
should be maintained tight. To enhance the ability to maintain cables 32, 34
tight, a tension
means such as a spring may be used to insure the cables 32, 34 are always
tensioned.
[0027] The motor 36 or manual actuator may be attached to either the front or
back end
of the shaft 30. The motor 36 may be selected with a variety of sizes and
configurations
depending on the size of the vehicle and the available power sources. The
tarping system 10
may be of such design that in the event of a motor 36 failure, a single bolt
may be removed from
the spool 40 that will allow the shaft 30 to be manually operated from the
other end. This may
be accomplished without removing a still securely mounted inoperable motor 36
from the shaft
30.
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[0028] An end plate assembly 50 may be operably attached to the motor 36. The
end
plate assembly 50 may include two rollers 52 that resist the torque of the
motor 36, which in turn
causes the shaft 34 to turn and move. Alternatively, it is possible to
fabricate end plate assembly
50 and the support surface 24 with at least one of the adjacent surface
fabricated from a low
friction material such that the end plate assembly 50 slides with respect to
the support surface 24.
[0029] Because of the structure described herein, the retractable tarping
system 10 of the
invention is operable without energy storing devices such as springs to assist
in returning the
shaft 30 to the closed position. Additionally, because the spool 40 rolls on
the support surface
24, the retractable tarping system 10 rolls and unrolls at a constant rate
across the entire width of
the box 12 and moves the same distance for cach revolution.
[0030] On the other hand, the tarp 14 rolls and unrolls at a variable rate
depending on
how much fabric is on the shaft 30. If the spools 40 are properly sized, the
tarp 14 can start out
in the open position fully rolled up neatly on the shaft 30. As you begin to
close a fully open tarp
14, the tarp 14 first is unrolling at a faster rate than the shaft 30 is
moving. This situation creates
a slight amount of slack in the tarp 14.
[0031] As the shaft 30 approaches the closed position, most of the tarp 14 has
unrolled
and the now smaller diameter roll is unrolling at a slower rate than the shaft
30 is moving. The
previous slack is now taken up and as the shaft 30 goes ovcr the side of the
box 12, the tarp 14 is
pulled tight. This all occurs while the shaft 30 is moving in the same
direction. This
phenomenon is called "unrolling tensioning"
[0032] A distinct advantage of the retractable tarping system 10 is that the
tensioning of
the tarp 14 is not abrupt as on every other system, but gradual. This is due
to the fact that the
tensioning occurs during the unrolling of the tarp 14 when it is being
unrolled at a slower rate
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than the shaft 30 is moving. 'Ihis gives the motor 36 an additional mechanical
advantage of up
to 3 or 4 times the motor 36 torque rating. This configuration allows for a
much smaller, less
powerful, and less expensive motor to tension the tarp 14 as tight or tighter
as the largest, most
powerful motors currently used.
[0033] Other advantages of the retractable tarping system 10 include the
absence of a
torque ann, which allows for the entire system to be installed behind the
front edge of the box.
This is extremely useful when space is minimal. The retractable tarping system
10 also does not
require the use of a latch plate. The configuration of the retractable tarping
system 10 provides
easy and safer manual operation with no springs to overpower and "load up"
creating a
potentially dangerous storage of energy. Because tensioned cables are provided
at the front and
back ends of the retractable tarping system 10, the system is extremely wind
resistant at any
point during its travel from open to closed position.
[0034] It is contemplated that features disclosed in this application, as well
as those
descnbed in the above applications incorporated by reference, can be mixed and
matched to suit
particular circumstances. Various other modifications and changes will be
apparent to those of
ordinary skill.
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