Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TARP ROLLER LATCHI~G DEVICE
.
BACKGROUND OF THE INVENTIO~
This invention relates to a tarp roller latch-
ing device which is particularly but not exclusively
designed for use with a tarp for covering an open top of
a truck box.
Many truck boxes define upstanding walls which
leave a rectangular open top of the truck box. The rec-
tangular open top must generally be covered in accordance
with government regulations and generally a tarp has been
used as the covering member. It is highly desirable to
enable the tarp to be moved from a covering position to
an open position in a most convenient and quickly oper-
able manner so that the vehicle operator can simply
uncover the open top for loading and then roll the tarp
into place for transport.
One particular design has involved the mounting
of tarp along one edge of the truc~ box with a roller
mounted along an opposed edge of the tarp so that the
roller can be rolled across the open top away from the
first edge of the box toward an opposed edge with the
tarp being unrolled as the roller moves across the open
top. The initial design of this device required that the
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roller, once it reaches the opposed edge is strapped into
place to hold the tarp in tension. However this tech-
nique is generally unsatisfactory in that it requires
lengthy manual operation by the vehicle operator and it
is difficult to tension the tarp accurately.
Various arrangements for latching the tarp
roller at the opposed edge have therefore been proposed.
In United States patent no: 4,302,043 - Dimmer et al
propose an elongate plate which extends along the full
length of the truck box in an orientation which is canted
outwardly and downwardly so that the tarp roller and the
portion of the tarp are wedged up underneath the plate in
the V-shape area defined by the downwardly canted plate
and the side of the truck box.
In Canadian patent no: 1,132,168 - Michel pro-
poses an arrangement of a similar construction defined by
a flange which extends outwardly from the side of the
truck box in a horizontal plane and in which the bare
roller moves up underneath the flange and is tensioned in
that location by rotation of the roller which causes
tensioning on the tarp.
Neither of these devices is, however, entirely
satisfactory since it does not allow proper and accurate
tensioning of the tarp along its full length in a way
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which provides sufficient and equalized tension to hold
the tarp flat and free from wrinkles which can cause
flapping and damage.
SUMMARY OF THE INVENTION
It is one object of the present invention,
therefore, to provide an improved tarp latching device
which enables the roller to be latched in place while
allowing easier tensioning of the tarp in the latched
condition due to reduced friction.
According to the invention, therefore, there is
provided apparatus for covering a rectangular open top of
a truck box comprising a tarp shaped to cover the open
top, means for fastening one edge of the tarp along one
edge of the box, a roller attached to an opposed edge of
the tarp, means for rotating the roller such that it can
roll across the open top towards said one edge of the box
in a tarp winding direction and away from said one edge
to an edge of said box opposite to said one edge in a
tarp unwinding direction, and means for latching the tarp
roller at said opposite edge, said latching means com-
prising roller means, bracket means for mounting the
roller means on said opposite edge so as to lie parallel
to said tarp roller and so that the tarp roller can lie
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in engagement therewith and bearing means mounting said
roller means on said bracket means whereby said roller
means can rotate in contact with said tarp roller to
allow tensioning of said tarp on said tarp roller.
Preferably the roller means is divided into a
first and second roller assembly each arranged adjacent a
respective end of the tarp roller and having a length
significantly less than the length of the tarp roller.
In some cases where the tarp roller is for example great-
er than eighteen feet, a third roller assembly is posi-
tioned centrally of the tarp roller.
Preferably each roller assembly includes a
first roller and a second roller each lying parallel to
the tarp roller and each mounted on bushings projecting
coaxially into the roller from brackets at opposed ends
of the rollers. ~he brackets are arranged to support the
rollers on the outer edge of the open top of the truck
box so that the first or upper roller is positioned
slightly downwardly and outwardly of the outer edge and
the second roller is positioned downwardly and inwardly
relative to the first æo that the tarp roller can engage
in the spacing between the two rollers in engagement with
both of the rollers with the rollers thus providing bear-
ings to allow the tarp roller to freely rotate in a ten-
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sioning action. The position of the tarp roller in thespace between the two rollers allows it to contact both
rollers and be held at a position effectively overcenter
relative to the pull exerted by the tarp tension so that
the tarp roller is held latched in that position by the
tension in the tarp.
The contact of the bare tarp roller on the
roller assemblies allows very effective and accurate
tensioning of the tarp, with reduced physical effort, to
prevent any wrinkles which can cause flapping and eventu-
al damage.
With the foregoing in view, and other advan-
tages as will become apparent to those skilled in the art
to which this invention relates as this specification
proceeds, the invention is herein described by reference
to the accompanying drawings forming a part hereof, which
includes a description of the best mode known to the
applicant and of the preferred typical embodiment of the
principles of the present invention, in which:
DESCRIPTION OF THE DRAWINGS
Figure 1 is an isometric view of a truck box
showing a tarp roller and roller latching arrangement
according to the invention.
Figure 2 is a cross sectional view along the
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lines 2-2 of Figure 1 showing the tarp roller in a latch-
ed position and shown on an enlarged scale.
Figure 3 is a front elevational view showing
one of the roller assemblies of Figure 1.
In the drawings like characters of reference
indicate corresponding parts in the different figures.
DETAILED DESCRIPTIO~
A truck box is generally indicated at 10 in-
cluding upstanding sides defined by rails 11 and side
panels 12. Upper rails 13 lie along the uppermost edge
of the sides of the truck box and define a rectangular
open top of the truck box generally indicated at 14.
As shown in Figure 2, the side rails 13 of the
truck box are formed of tubular metal and carry the side
walls 12 which are connected to the tubular rail and
extend outwardly and downwardly to define a vertical side
portion 12A directly underlying the outermost edge of the
tubular rail 13.
The ends of the truck box indicated at 15 and
16 respectively are of a similar construction and include
gable ends 17 so the open top is constituted by two down-
wardly inclined portions which converge to an apex. The
gable ends are generally separate from the box itself and
supplied as part of the tarp system.
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A tarp is indicated at 18 and is attached to
the remote upper side rail indicated at 13A by suitable
connections schematically indicated at 19. The technique
of connecting the remote edge of the tarp to the remote
rail 13A is known in the art and accordingly the details
are not described here. The edge of the tarp remote from
the rail 13A is connected to a tarp roller 20 upon which
the tarp can be wound so that as shown in Figure 2, an
anticlockwise rotation of the roller 20 causes the tarp
to be rolled onto the roller as the roller 20 moves to-
wards the remote rail 13A. Conversely rotation of the
roller 20 in a clockwise direction causes the tarp to be
unrolled as the roller moves across the open top away
from the rail 13A toward the rail 13.
Wire guides can be positioned at the front and
rear edges of the tarp and wrapped around the tarp roller
20 so as to apply tension to the tarp roller as it winds
or unwinds and to ensure that it is pulled toward the
rail 13 at all times. The wires can be spring mounted so
as to tension them toward the rail 13. A construction of
this type is previously known and will be apparent to one
skilled in the art and therefore is not described in
detail here.
Rotation of the tarp roller 20 is obtained by a
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suitable mechanism again of a type which is known gener-
ally in the field and one example is indicated at 21 in
the form of a hand crank which is coupled by a universal
joint 22 to the end of the tarp roller 20.
A latching arrangement for the tarp roller is
formed by a plurality of roller assemblies each of which
is generally indicated at 23. Each roller assembly 23
comprises a pair of brackets 24 and 25 in the form of
angle brackets defining a base plate 26 and an upstanding
plate 27. The base plate 26 can be bolted to the outer
surface of the tubular rail 13 as indicated at 28. When
so bolted, the base plate 26 lies in a vertical plane and
the outstanding plate member 27 also lies in a vertical
plane at right angles to the side of the truck box. The
outstanding plate 27 is of triangular configuration as
shown best in Figure 2 and carries on an inner face
thereof projecting toward the opposed one of the brackets
a pair of tube bushings 29 and 30. The tube bushings are
welded to the plate so as to extend from the plate at
right angles thereto that is parallel to the side of the
truck box. The upper bushings 29 are aligned so as to
define a first axis of rotation for a tubular roller 31
with the axis lying horizontal and spaced outwardly from
the outer edge of the trucX box and downwardly from the
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uppermost edge thereof.
The bushings 30 are similarly aligned and
define an axis of rotation for a second roller 32 which
lies downwardly of the upper roller and slightly inwardly
therefrom.
In one example, the rollers 31 and 32 are of
two inches diameter with the ou~er periphery of the upper
roller 31 spaced one inch from the uppermost edge of the
rail 13 and outwardly one inch from the outer edge of the
rail 13. The second roller is spaced so that its axis
lies three inches downwardly from the axis of the roller
31 and an inch inwardly therefrom.
The length of the tarp 18 is chosen such that
when it is fully unwound from the tarp roller 20, it just
hangs over the upper roller 31 with the roller 20 depend-
ing downwardly in the area of the space between the roll-
ers 31 and 32. The distance between the outer surfaces
of the rollers 31 and 32 is less than the diameter of the
roller 20 so that it can move into contact with both of
the rollers when further rotated in the unrolling direct-
ion that is in a clockwise direction as shown in Figure
2. The rollers 31 and 32 thus act as bearings to allow
complete rotation of the roller 20 without any binding of
the roller 20 at any point along its length. This free
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or co~plete rotation thus acts to accurately tension the
tarp 18 along the full length of the truck box to avoid
wrinkles. The rotation is not however sufficient to draw
the tarp itself into contact with the rollers due to the
adjustment of the termination of the tarp.
It will be noted that a plane joining the axes
of the rollers 20 and 31 lies at an angle to the tarp 18
in a clockwise direction around the axis of the roller
31. This acts as an overcenter latch arrangement so the
tension in the tarp 18 pulls the tarp roller 20 into its
engagement with the rollers 31 and 32. This retains the
tarp roller 20 in its latched condition to hold the tarp
in the tensioned state.
The triangular shape of the outstanding plates
27 allows the roller 20 to engage into the space between
the roller 31 and 32 along the full length of the truck
box so the roller passes by each of the brackets 24 and
25 of the roller assemblies 23 from one end of the truck
box to the other end of the truck box.
In an alternative arrangement (not shown) the
rollers are fixed, that is not mounted on bearings, thus
defining cylindrical bodies having outer curved surfaces
which act as bearing members for rotation of the tarp
roller.
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Since various modifications can be made in my
invention as hereinabove described, and many apparently
widely different embodiments of same made within the
spirit and scope of the claims without departing from
such spirit and scope, it is intended that all matter
contained in the accompanying specification shall be
interpreted as illustrative only and not in a limiting
sense.
