Note: Descriptions are shown in the official language in which they were submitted.
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Title:
IMPROVED TRAILER AND TRAILER UNLOADING SYSTEM
Inventor:
E. Dale Fenton
SPECIFICATION
Field of the Invention-
This invention relates to transport trailers and is
especially concerned with a trailer uniquely adapted to
unload onto the ground large loads such as bundled building
trusses.
Background of the Invention:
When shipping goods to construction sites, especially
large loads such as bundled building trusses, there are
unloading problems. If a special "cradle" truss trailer or
a conventional flatbed trailer is used, on-site equipment
such as a crane or forklift must be available to unload the
trailer. ~ecause of scheduliny difficulties, often such
equi~pment is not ready when the trailer and its load arrives
at the site. The equipment needed to unload the trailer may
be busy with other more urgent tasks or it may not ha~e yet
arrived at the site itself. In such circumstances, the
truck driver has to choose between waiting (perhaps for
hours~ for the equipment to unload his trailer to be avail-
able or going about other tasks and returning later.
In either case, the result is a costly loss of equip-
ment use time and driver time.
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To overcome this problem, it has been proposed to make
trailers with a bed of rollers and to unload by untying the
load and "jerking" the trailer forward and, hopefully,
rolling and dropping the load on the ground off the rear of
the trailer. However, this involves subjecting the load to
a drop of at least two feet off the tail or back edge of ~he
trailer. While some loads can take such abuse, others are
damaged in the process.
Tilting trailer beds have been successfully used with
drive-off equipment. U. S. Patents No. 4,125l198;
2,717,707; 4,568,235; and 2,717,707 are examples of such
trailers. Such trailers are not well suited for unloading
loads which cannot be driven off of the trailer.' A similar
principle has been used for unloading containers. For ex-
ample, U. S. Patents 3,934,740 and 3,606,059. ~owever, all
such tilting-bed trailers require extra power units, such as
hydraulic rams and often a winch. The latter two examples
also require specialized containers which must be unloaded
and picked up later. Thus, these are not suitable for use
in unloading a "one-way" item such as a bundle of building
trusses. Such prior trailers also require special articu-
'lated pivoting sec-tions and special controls to operate the
power units so as to articulate the various sections. These
controls, extra power units, and articulated sections in-
crease the initial cost and complexity of the trailer,
require special tractors or power mover units, and are prone
to wear and break down, with the consequential increase in
maintenance costs and down-time.
Summarv of the Invention
In contrast to these prior art trailers, a
trailer constructed in accordance with the principles of
the present invention may be u~ed with any conventional
over-the-road tractor or prime mover unit, need not have
any special controls nor any extra power unit such as the
hydraulic rams or winches used before, and has no
articulated frame bed sections.
In accordance with an embodiment of the present
invention there is provided a trailer for use by a prime
mover unit for unloading a load on the ground, the prime
mover unit having means for receiving a trailer connection
which connection receiving means is maintained at a
substantially fixed height above the ground as the prime
mover moves over the ground, comprising: a longitudinal
frame having a tail end and a forward end, the longitudinal
frame being always inclined downward from the forward end
to the tail end; means on the forward end of the frame for
connection to the prime mover unit and allowing a tilt
upward and downward of the frame therefrom' a wheeled
under-carriage mounted to the frame so as to be shiftable
longitudinally along the frame, the frame and the under-
carriage being so arranged that a longitudinal shift of the
under-carriage in one direction tilts the frame downward
from the forward end connection means to the prime mover
and lowers the tail end to the ground level, while the
reverse shift tilts the frame upward from the forward end
connection means to the prime mover and raises the tail end
to an over-the-road height, the under-carriage having
brakes which are connected to be controlled from the prime
mover independently of the prime mover's brakes; and means
near the tail end of the frame for contacting the ground
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and for moving on the ground when the tail end is lowered
to the ground, whereby the tail end may be lowered to the
ground and raised therefrom solely by applying the brakes
of the under-carriage while moving the prime mover and the
frame relative to the under-carriage, and the trailer moved
along the ground on the tail-end ground contacting means.
A trailPr constructed in accordance with the
principles of the present invention includes a wheeled
carriage which when unlocked can be shifted longitudinally
relative to the trailer's frame by simply applying the
brakes to its rear carriage wheels while driving the
tractor forward or backward. (This requires no
modification to the tractor, since such brakes are
conventionally controlled separately in tractor-trailer
rigs to prevent jack-knifing.) The mounting of the
carriage to the frame is such that shift of the carriage
causes the frame to pivot at its connection to the tractor
unit. (For a long bed (45 foot) trailer, this connection
may be entirely conventional, since such connections
already allow for a range of vertical pivoting of the
trailer - to accommodate hills and bumps.)
By this simple, unpowered arrangement, the tail
of the trailer may be lowered to the ground. The trailer
frame is so constructed that the tail end contacts ground
first and means, e.g., a pair of large-diameter rollers,
are there provided for contacting and moving the trailer
end over the ground in its tail-down configuration.
The trailer preferably has a bed of rollers and
is slanted so that when the trailer is in this tail-on-
ground state, the load can be unstrapped and unloaded by
moving the power unit forward out from under it. With
large loads, such as bundled building trusses, once the
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rear end of the load contacts the ground, the load itself tends to
propel the trailer out from under it. The final "drop" of the
front end of the load off oE the tail-down trailer is only a few
inches. This means little or no unloading damage to the freight.
Unlike prior trailers, the present trailer is designed to
and does roll along the ground on its tail-end rollers during the
unloading process. The provision of such ground-contacting rear
rollers prevents the tail end from tearing up the ground surface
(e.g., an asphalt parking lot next to a building site).
In accordance with another embodiment of the present
invention there is provided an elongated roller trailer having a
length several times its width for carrying a load, the trailer
comprising a pair of main longitudinal support members running
approximately the full length of the trailer and positioned
approximately parallel to one another but spaced apart so as to be
about one-quarter of the trailer's width and on either side of the
trailer's longitudinal center line, a pair of side secondary
longitudinal support members, one positioned at each side of the
trailer and extending for substantially the length of the trailer,
a plurality of cross supports between the main longitudinal support
members and between each of the main longitudinal support members
and their adjacent secondary longitudinal support members and means
connecting the main longitudinal support members to one another,
the main and secondary longitudinal support member and the cross
supports and the connecting means orming a framework, a wheel
carriage mounted to the framework, the carriage including a
plurality of ground contacting wheels and means for mounting these
wheels to the carriage, means for connecting the framework to a
tractor, the connecting means being at one end of the framework;
and a plurality of rollers, each of the rollers having extreme ends
and each of the rollers being mounted only at thP ends thereof to
one of the longitudinal support members and each of the rollers
spanning between adjacent longitudinal support members and each of
the rollers mounted at their ends to one of the longitudinal
support members, the rollers being positioned in an array such that
the roller array extends substantially across the width of the
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trailer and substantially along its length, with upper surfaces of
the rollers being approximately in a plane and above the support
members, whereby a large load may be placed on the rollers and that
load is transferred to the longitudinal support members during
transport and handling and wherein the rollers may aid in
longitudinally unloading the load from the trailer.
In accordance with a further embodiment of the present
invention there is provided a method fcr unloading a large load
from a long bed trailer onto a flat area of ground using a prime
mover as its sole source of power, wherein the trailer's bed is
connected to the prime mover at one end by a connection which
allows it to pivot downward at the connection from a position with
its tail end well off of the ground and maintains the bed at the
connection to the prime mover, a substantially fixed height above
the ground as the prime mover moves ovar the ground to a position
wherein the tail end is just off of the ground, and the trailer bed
has a wheeled carriage having brakes separately controlled from the
prime mover which is mounted at its bottom so as to move
longitudinally from a position wherein it supports the trailer with
its tail end well off of the ground to a position wherein the tail
end is ~ust off of the ground. The method comprising the steps of
(a) lowering the tail end of the bed by applying the brakes to the
wheeled carriage and moving the prime mover and the trailer bed
relative thereto and without the use of any other powered devices
and without articulating the trailer bed between the connection to
the prime mover and the carriage; (b) removing any securing devices
from between the load and the trailer; (c) advancing the trailer
and the bed, with the tail end down out from under the load, so
that it falls to the ground off of the tail of the bed; and (d)
raising the tail end of the bed by reapplying the brakes to the
wheeled carriage while moving the prime mover and the bed relative
thereto and without the use of any other powered devices and
without articulatiny the trailer bed between the connection to the
prime mover and the carriage.
In accordance with a still further embodiment of
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the present invention there is provided a method of
unloading a large load from a long trailer driven by a
prime mover, the trailer being of the type which has a
longitudinal frame having a tail end and a forward end, the
longitudinal frame being always inclined downward from the
forward end to the tail end; means on the forward end of
the frame for connection to the prime mover unit and
allowing a tilt upward and downward of the frame therefrom
and maintaining the frame at the connection to the prime
mover at a substantially fixed height above the ground as
the prime mover moves over the ground,; a wheeled under-
carriage mounted to the frame so as to be shiftable
longitudinally along the frame, the frame and the under-
carriage being so arranged that a longitudinal shift of the
under-carriage in one direction tilts the frame downward
from the forward end connection means to the prime mover
and lowers the tail end to the ground level, while the
reverse shift tilts the frame upward from the forward end
connection means to the prime mover and raises the tail end
to an over-the-road height, the undercarriage having brakes
which are connected to be controlled from the prime mover
independently of the prime mover's brakes, and means near
the tail end of the frame for contacting the ground and for
moving on the ground when the tail end is lowered to the
ground. The method comprising the steps of (a) lowering
the tail end of the trailer to the ground by applying the
brakes at the wheeled carriage and allowing it to move
relative to the frame by using the prime mover and to move
the trailer bed frame relative to the undercarriage; (b)
locking the undercarriage with the frame in its tail down
configuration; (c) releasing any restraints on the load;
and (d) moving the prime mover and trailer forward out from
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under the load.
The invention, together with the advantages
-thereof, may best be understood by reference to the
following description -taken in connection with the
accompanying drawings, in the several figures of which,
like reference numerals identify like elements.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a trailer constructed
in accordance with the principles of the present invention.
Fig. 2 is a top or plan view of the trailer of Fig. 1.
Fig. 3 is a side or elevational view oP the trailer of
Figs. 1 and 2 in its tail-down configuration.
Fig. 4 is an end view of the trailer of Figs. 1 - 3 as
seen from the line 4 - 4 in Fig. 3.
Fig. 5 is a sectional view as seen from the line 5 - 5
of Fig. 4, with a load shown in the process of being
unloaded.
Figs. 6 through 15 are each side views on a reduced
scale of a conventional tractor and the trailer of Figs. 1 -
4 with a load, showing successive steps in the unloading
process at a building site. These views are especially
useful in illustrating the distinctive manner of unloading
of the present invention.
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Detailed Description of a Preferred Embodiment
Referring now to the drawings and especially Fig. 1,
there is depicted a trailer constructed in accordance with
the principles of -the present invention and generally desig-
nated by the number 10. The trailer 10 is shown in Fig. 1
in its over-the-road configuration, coupled to a conven-
tional tractor or prime mover unit 12.
The trailer 10 is of ~he flatbed type but has a "bed"
comprised of a set of rollers 14, 14 , all of which are in
the same plane as better shown in Fig. 3, and are supported
on a frame 16. The frarne 16 includes a pair of main longi-
tudinal members or beams 18, 20 which run parallel to one
another at an equal distance from the longitudinal center
line (about one-quarter of the trailer width) of the
trailer. A number of cross members 22 are connected between
the main members. The frarne 16 also includes a pair of side
members 24, 26 which are connected to the main member by a
series of short cross members 28. The short cross members
28 may be formed as unitary extensions of the cross members
22, in which case, the main members 18 and 20 are cut to
receive them, and they are then welded in place to those
members. The frame 16 includes a front cross member 30
and has a conventional trailer-tractor connector unit 32
including a conven-tional kingpin for connecting to the con-
ventional tractor unit 12. This unit 12 is sometimes termed
a "fifth wheel" in this art.
As best shown in Fig. 2I the frame 16 is open and the
rollers 14, 14' are staggered, with the outside rollers 14
being somewhat shorter than the center rollers 14'. Three
sets or rows of rollers are thus provided. The use of
staggered rollers and shorter than full-width rollers (as is
commonly done in prior roller bed trailers) provides bet-ter
support and less bending of the rollers under load. Ir.
should be no-ted that the outside rollers 14 overlap the ends
of the center rollers 14' to leave no part of the transverse
extent of the trailer load surface unsupported.
As is also shown in Fig. 2, the frame 16 includes
triangular bracing members 29, as is conventional for flat-
bed trailer frames. The tail end of the trailer 10 is
formed by a single large roller 19T which does extend across
the width of the -trailer. As will be explained below, this
is the last roller which contacts and supports a load during
unloading and thus is constructed in a substantial manner so
as to support up to half or more of the expected load during
the unloading process.
As best shown in Fig. 3, the main frame members i8, 20
are shaped to taper toward the tail and also each support on
their bottom a track 34 which is part of the mounting for a
tandem-wheeled carriage 36. The carriage 36, itself, may be
entirely conventional and thus need not be described in
detail. It may be, for example, the carriage currently
commercially available and known as a hitch sliding axle,
single leaf spring carriage employing 5" round*Rockwell
brand #TKN4670-Q axles with*Stenco brand grit guard oil
sales and 12-1/2 x 8-5/8 non~asbestos brakes. Such unlts
conventionally include rollers for contacting a flat surface
of the track 34 and manually-releasable locking pins that
project into holes in the track. The height of the carriage
36 is less than that of a conventional drive wheel carriage
*Trade mark
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12C ~Fig. 3) of a conventional tractor 12. Thus, the
trailer "bed" of rollers 14, 14 , 14T slants rearward
slightly in the over-the-road configuration.
Unlike conventional trailers which of-ten allow a limi-
ted shift in their carriages, the track or slide rails 34
extends for a considerable portion of the length o~ the
frame 16, and the carriage may be shifted along the truck
from the position shown in Fig. 2 to that of Fig. 3. The
construction of the frame members and the height of the
carriage 36 relative to that of the connector unit 32 causes
the frame 16 to pivot downward about the unit 12 to allow
its tail to contact the ground.
Although a double-axle carriage unit 36 is shown and
described, another prototype using a single-axle unit has
been built and tested and also shown to work well. The use
of a double-axle unit allows for a greater load-carrying
capacity and thus is currently preferred.
A novel arrangement is provided for contacting and
moving the tail on the ground. This is a pair of rollers
40, one on each side of the tail just forward and below the
las-t roller 14R. ~hese ground rollers 40 are, as shown in
Fig. 4, situated between the main frame members 18, 20 and
the outer side members 24, 26 and project below the level of
the frame 16. As explained below, during the unloading
process, these rollers and the main tractor unit 12 provide
the support for the trailer 10 and its load, and thus it is
desirable -to place these rollers at the tail end of the
trailer 10. (Although they could be placed further toward
the front, if desired, just so long as they contact the
ground first when the carriage advances and sufficient sup-
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port is provided to the tail roller 14R and the tail toprevent it from bending down and con-tacting the ground.)
As shown in Fig. 5, the height "h" of the roller 14T
off of the ground when-the trailer is in its tail-down
position is much less than the over-the-road height. In a
45 -long trailer prototype, this is only 12 inches above a
flat unloading surface. For a long load (such as the
trusses 50 shown in Fig. 5 and Figs. 6 - 15), the e~ective
drop is less than even this height, since its other end is
already on the ground, its center of gravity typically drops
only half of this distance. For wood trusses and like loads
50, this has been demonstrated to be entirely acceptable
(being typically less of a shock than the conventional drop
by a t-vpical crane operator) and to no-t result in any damage
to the load.
Figs. 6 through 15 illustrate the successive steps in
unloading a load of trusses 50 from the trailer 10. In Fig.
6, the tractor 12 with a loaded trailer 10 has arrived at a
building site. As is often the case, the equipment 60 and
personnel which might be used to unload the trailer 10 are
not readily available. With conventional cradle or flatbed
trucks, the driver would have to wait or come back again.
With a prior art rolle~bed truck, the driver could attempt
to "jerk" and drop off the load several feet and risk load
damage. With the trailer 10, the driver need only align and
point the tail of the trailer toward an area~ such as the
area 62 where it is desired to leave the load 50. He then
unlocks the carriage 36 and, as shown in Fig. 7, applies the
brakes to its wheels while backing up the tractor 10. This
lowers the tail end to have the tail rollers 40 contac~ the
ground ~Fig. 8).
The driver can back up or move forward the trailer in
this arrangement so as to "place" -the load almost exac~ly
where he wants it. When so placed, he removes the straps
(Fig. 9) and then drives the rig 10 - 12 forward from a
standing stop. The natural inertia of the load causes it to
tend to remain in place, and the trailer 10 rolls out from
under it. In some cases, some forward momentum may be
transferred to the load, but in any case, as soon as the
load makes contact with the ground, that contact tends to
brake and hold the load from going forward. (Fig. 10)
The load 50 then actually propels or pushes the trailer
forward (Figs. 11 and 12) until the forward end of the load
50 rides over the tail roller 14T and drops to the ground
(Fig. 13).
At this point, it should be noted that, contrary to
prior art pivoting trailers, the trailer 10 has run on the
tail rollers 40 on the ground for a considerable distance.
The driver may next apply the brakes to the wheels of
the carriage 36 while driving forward (Figs. 13 and 14) to
raise the tail and return the trailer to its over-the-road
state. He then stops and re-locks the carriage 36 in place
and drives off to pick up a new load (Fig. 15).
This entire unloading process can be done by one man,
the truck driver, in as little as ten minutes.
A prototype trailer was constructed substantially in
accordance with the drawings. This trailer was tested and
shown to perform well.
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For purposes of definiteness and not limitation, the
following details of the prototype are given, it being
understood that the principles of the invention may be
incorporated into many variations. Also, the inventor and
his firm may choose to make changes in the future from the
following, for reasons of econom~ or as experience may indi-
cate are desirable.
The prototype was about 45 feet long, with side members
24, 26 formed of 1-3/4-inch by 6-inch steel channels. The
main members 18, 20 were about 45-feet-long specially-fabri-
cated I-beams substantially as shown, with a 6-inch wide
top and bottom and being a maximum height of l9 inches. The
cross members 22, 28 were formed of 4-inch Jr. I-beams. The
rollers 14 were 47-inch long rollers, 2 inches in diameter,
supported by ~PR ~estron brand end supports, with longitudi-
nal and transverse bracing~ The rollers 14 were 24 inches
long and 2 inches in diameter and similarly supported. Both
rollers 14 and 14 employed section 80 steel machine tubing
at their outer surfaces. The roller 14T was 7 inches in
diameter. The rollers 40 were 12 inches in diameter.
The carriage 36 was that previously identified.
The track 34 was formed of conventional track material
for such a carriage but was made 26 feet long by adding an
extension of 11 feet to the front of the conventional track.
The brake air hose for the carriaye was run between the
members 28, 2~, and three 36-inch coil springs used to hold
the hose in position and so as to prevent it from tangling
or kinking as the carriage moves relative to the frameO
Conventional lighting and conventional front supports
for the trailer for use when the trailer is not connected to
*Tracle mark 11
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a tractor were employed as shown in the drawings.
The conventional trailer connector stands at about 34
inches off the ground, so with the carriage 36 being about
17 inches high, the over-the-road pitch of the rollexs 14,
14 , 14T was about three degrees from the horizontal when on
flat ground. When in its tail-down configuration ~Fig. 3),
the pitch is about seven degrees to the horizontal.
While one particular embodiment of the invention
has been shown and described, it will be obvious to those
skilled in the art that changes and modifications may be
made without departing from the invention and, therefore,
the aim in the appended claims is to cover all such changes
and modifications as fall within the true spirit and scope
of the invention.
