Note: Descriptions are shown in the official language in which they were submitted.
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In the transportation industry, the use of tandem
trailer rigs has become very important, mainly because of its
cos-t~effectiveness. This is because such an arrangement uses
only one driver and one tractor at a time, while the load
carrying capacity is twice as great. The main difficulty
experienced in the past with the using two trailers in tandem
is the method by which they are joined together. If, for
instance, one uses a standard bogie, there are two arti:cul.ations,
one of which is under the rear end of the front trailer and
one of which is under the front end of the rear trailer. S:uch
a double articulation is dangerous, because it permits:several
kinds of buckling and similar motions between the two. tr.ai.lers,
thus leading to accidents. In my patents 3,933,374 and
4:,030,171, I suggested that a solution to this dangerous problem
could be brought about by use of an extension protruding
beyond the rear of the front trailer. While this arrangement
is generally satisfactory, it has the drawb.ack that.the
intermediate trailer is almost entirely committed to use in
tandem rigs and has very little use for running single. Further-
20 more, it is difficult to back. up to a loading dock even whenit is provided with the hinged platform shown in the patent..
These and other difficulties e~perienced wlth.the prior art
devices have been obviated in a novel manner by the present
invention.
It is, therefore, an outstanding obj:ect of:the
invention to provide a tandem trailer system in which .the
connection between the trailers provides a single point of
pivot or articulation.
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Another object of this invention is the provision
of a tandem trailer system in which the connection between
the trailers remains permanently with one of the trailers
and, therefore, is not subject to pilferage or vandalism,
as is true when a bogie is left by itself~
It is another object of the instant invention to
provide a tandem trailer system in a special forward trailer,
which special trailer can be used by itself.
It is another object of the instant invention to
provide a tandem trailer system in a special forward trailer,
which special trailer can be used by itself.
A still further object of the invention is the
provision of a tandem trailer system in which the connection
between the trailers remains permanently with the front
trailer, which front trailer, nevertheless, can be moved close
to a loading dock~
It is a further object of the invention to provide
a tandem trailer system which is simple in construction, which
is inexpensive to manufacture, and which is capable of a long
life of useful service with a minimum of maintenance.
With these and other obj.ects in view, as will be
apparent to..those skilled in the art, the invention resides
in the combination of parts set forth in the speci~ication
and covered by claims appended hereto.
In general, the invention consists of a trailer
unit adapted to be drawn behind a highway tractor and behind
which unit:can be drawn a second standard trailer. The unit
consists of a cargo. container and a chassis on which the
container is mounted. The.chassis has a first upper portion
and a second lower portion, the second portion being
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longitudinally slidable relative to the first portion from a
first position generally co-extensive with the firs-t portion
to a second position where it extends beyond the end of the
cargo container. A first attaching means is associated with
the front end of the container for connection to the highway
tractor and a second attaching means is associa-ted with -the
second portion of the chassis, so that, when the second portion
is in second position, another trailer can be attached to it.
Wheels are mounted on the said second portion of the chassis.
More specifically, a pair of locking pins are
mounted on the second portion for transverse movement to engage
apertures in the first portion when the second portion is in
the first or second position; the pins, thereforet serve -to
hold the first and second portions against relative sliding
movement in the first and second position. The wheels are
provided with pneumatic brakes and the locking pins are provided
with a pneumatic actuator cylinder. A selector valve is
provided to connect a source of pressure air selectively to
the brakes or the cylinder, so that the locking pins are
released when the brakes are locked and the pins are engaged
when the brakes are free. The lower portion is provided with
three pairs of wheels, the wheels being mounted so that one
pair is at the front end of the lower portion, one pair is at
the rear end, and one pair is in the middle; the second
attaching means is a fifth wheel located between the middle
and rear pair of wheels.
The character of the invention, however, may be best
understood by reference to one of its structural forms,
as illustrated by the accompanying drawings r in which:
FIG. 1 is a side elevational view of a trailer
unit embodying the principles of the present invention showing
two trailers operating in tandem,
FIG. 2 is side elevational view of a front
trailer at a loading dock,
FIG. 3 is a side evelational view of the trailer
unit using only one trailer,
FIG. 4 is a rear elevational view of the trailer
unit taken on the line IV IV of FIG. 3,
FIG~ 5 is a transverse vertical sectional view of the
trailer unit taken on the line V-V of FIG. 3,
FIG. 6 is an enlarged sectional view of a portion
of the apparatus,
FIG. 7 is a horizontal sectional view of the
apparatus,
FIGS. 8 and 9 are schematic cross-sectional views
of.the invention, showing locking means in two different
conditions,
FIG. lO is an enlarg.ed transverse sectional view of
a portion of the apparatus showing a locking pin in use,
FIG. 11 is a schematic circuit view of pneumatic
apparatus: used in the trailer unit.
FIG. 12 is a side elevational view of a portion of
the trailer unit,
FIG. 13 is a transverse vertical sectional view of a
portion of the trailer unit,
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FIG~ 14 is a side elevational view of a portion of
the trailer unit,
FIGa 15 is a plan view of the trailer unit during
turning, and
FIG~ 16 is a side elevational view of the trailer unit.
Referring first to FIG~ 1~ which best.shows the
general features of the invention, the trailer unit, indicated
generally by the reEerence numeral 10, is shown as being
drawn behind a highway tractor 11. The trailer unit in turn,
is drawing a second trailer unit 12 behind ltself. The trailer
unit 10 consists of a cargo container 13, at the rear end of
which is.carried a chassis 14~ The chassis has a first upper
portion 15 and a second lower portion 16. The second portion
16 is longitudinally slidable relative to the first portion 15
from a first position in which it is generally co-extensive
with the first portion to a second portion in which it extends
beyond the end of the.cargo container 13, as shown in FIG~ 1~
A first at-taching means 17 extends downwardly from the forward
portion of the container 13 for connection to the fifth wheel
.20 of the tractor 11. A second attaching means 18 in the form of
a fifth wheel is associated with the second portion 16 of the
chassis, so that, when the second portion is in the second
position, another trai.ler 12 can be attached to it. A set 19 of
whe~els is mounted on the said second portion of the: chassis.
FIG~ 2 shows the manner in which the container 13
can be unloaded. The second portion 16 remains in the .second
position, but a platform is provided to allow a l.ift truck or
similar unloading apparatus to be carried into the container.
FIG~ 3.shows the manner in which the container 13
can be moved over the road by its:elf behind the tractor 11.
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The second portion 16 is in the first position, that is to say,
is co-extensive with the first portion of the. chassis. At that
time the attaching means 18 lies under the container and the
wheels 19 are entirely beneath the container.
Referring next to FIGS. 4, 5, and 6, which shows
the details of the fi.rst portion 15 and the second porti~on 16,
it:can be seen that the first portion 15 is provided with
two spaced, parallel I-beams 21 and 22. The second portion
16 consists of two similar I-beams 23 and 24 held in spaced,
parallel relationship. As shown in FIG. 6, the undersurface
25~of:the I-beam 21 rests on the~ upper surface 26 of the
I-beam 16, while a similar relationship takes place between the
I-beams 22 and 24. Guides 27 are attached to the I-beams 23
and 24 and form part of the second portion 16; these guides
. envelope the bottom inner flanges of the upper I-beams.21
and.22.
.As shown in FIGS. 7, 8, and 9, a pair of lock.ing
pins.28 and.29 are mounted on the second portion 16 for
. transverse movement to engage apertures 31 of the first portion
15 when the .second portion 16 is in the first or s~econd position.
. These pin~ serve to hold the first and second portions against
relati.ve:sliding movement when in the said first or second
positions.
FIG. 10 shows the details of the locking pin:28
and.the manner in which.it engages an aperture 31.
Referring to FIG. 11, it can be seen that the wheels
19 are provided with pneumatic brakes 32, while the locking
pins:28 and:29 are provided with a pneumatic actuator cylinder
33. . A se:lector valve 34 is provided to conn~ect a source of
pressure air selectively to the brakes 32 or the cylinder 33
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so that the locking pins are released when the brakes are
locked and the pins are engaged when the brakes are free. The
brakes are provided with the conventional system, including a
valve 46, for use when running over the road.
FIG~ 6 shows the provision of slide pads, formed
preferably of Teflon, attached to the upper surface 26 of the
I-beams 23 and 24 to facilitate sliding motion between the first
and second portions. The ~uides:27 are also provided with side
pads 36 to facilitate relative sliding of the I-beams 26 and 22.
As is par-ticularly evident in FIG o 1~ the lower
portion 16 is provided with three pairs of wheels 37, 38 and
39, these making up the set 19 of wheels. The wheels are
mounted so that.the one pair 37 is located at the ront of the
lower portion 16, one pair 39 is at the rear end, and one pair
38 lies between them substantially closer to the set 37.
A second attaching means 18 in the form of a fifth wheel is
located between the middle and rear pair of wheels 3g and 39,
repectively.
As is particularly evident in FIG. 2, a platform 41
is provided between the. cargo container 13 and the rear end of
the chassis 14. The platform can be moved so that it extends
only a short distance beyond the rear end of the container.
The platform is hingedly. connected to the.chassis near the
rear end of the cargo container and normally lies against the
container door 42. A cable 43 is. connected to the platform
to.control its movement. Legs are provided to support the
platform against movement even if considerable weight is
placed on it.
FIG. 12 shows the manner in which a leaf spring 47
is mounted on the second portion 16 of the chassis. It overlies
and supports the axle 48 of the wheel set 39 in such a way that
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the axle underlies the pivotal axis of the second attaching means
18.
FIG, 13 shows the manner in which the second attaching
means 18 is located within the space defined by the first portion
15 of the chassis. This feature permits it to reside under.the
container 13 when the second portion i5 nested under the
container, as shown in FIG. 3.
FIG. 14 shows the manner in which the second portion 16
o~ the chassis is provided with a leaf spring 49 to support the
axle 51 of the front wheels 37. A leaf spring 52 with a
stabilizer.53 is used to support the axle 54 associa-ted with the
intermediate wheels 38.
In FIGS. 15 and 16 are shown the cables 55 carried
by the second portion 16 to supply electrical current and pressure
air to the rear trailer 12. These cables are carried on a rod 56
which is connected to the second portion 16 through a flexible
spring 57. The dimensions of the cables 55, rod 56, and
spring 57 are selected to permit them to lie between the
I-beams.23 and 24 of the second portion 16 when it is in the
first position under the first portion 15, as indicated in
broken lines. FIG. 15 shows the manner in which the location
of the s.econd attaching means 18 is selected to allow the
forward corners o.f the rear trailer 12 to avoid contact during
turning with the rear o~ the front railer 13.
.The operation and advantages of the present invention
will now be readily understood in view of the above description.
In FIG. 1, which shows two trailers 12 and 13 in tandem, it
can be seen that the only connection between them is at the
at-taching means 18, which means that a single pivot joins the
trailers and the dangers of articulation about two pivots is
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not present, There is no bogie that would be left behind when
the rear trailer is dropped off at its destination or when a
portion of the highway is reached in which tandem operation is
forbidden. Normally~ the unloading of the container 13 wouId
take place in the manner shown in FIG. 2 with the platform 41
in horizontal position, having been lowered to that position by
means of a cable 43. A plate 44 rests on the fifth wheel 18
and legs 45 are provided to give additional support for the
platform. This allows a forklift truck to enter the. container
from -the dock.
At the time when the rear trailer has been dropped
off it is possible to use the trailer 13 and the tractor 11
by themselves. At that time, the apparatus takes the
condition shown in FIG. 3.
In order to move.the lower portion 16 from one
position to another, it is possible to use the braking system
shown in FIG. 11. If the valve 34 is operated to move the
actuating cylinder 33, the locking pins 28 and.29 are in l:ocked
position and the brakes 32 are free, so that the apparatus
20 can roll on the wheels 37, 38 and 39 without difficulty. When
it is necessary to move the lower portion 16 from one position
to the other, this is done also by means of the valve 34.
If, for instance, the portion 16 is shown in the condition
shown in FIG. 1 and it is desired to move it to the first
position shown in FIG. 3, i-t is only necessary to move the valve
34 to a second position in which the brakes 32.receive
pressure air, thus locking them against rolling. At .that time
the cylinder 33 is released, thus allowing the springs in the
system to pull the locking pins.28 and 29 out of their position
31. .When this is done, the tractor and the container 13 are
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moved backwardly. Since the wheels brakes 32 in the wheels 19
are locked in place this causes the firs-t portion 15 of the
chassis 14 to slide rearwardly over the second portion 16.
~ventually, a limiting position is reached, as shown in FIG. 3,
and the valve 34 is changed back to the position shown in
FIG. 11 where the actuating cylinder 33 causes the locking pin
to move into place and lock them in the first or front
condition, the wheels are, therefore, free. Tractor ll and
the container 13 are then free to move over the road as a
single unit. The normal brake system is operative on the
brakes 32 at that time.
As shown in FIGS. 12 and 14, the axles 48,.51 and.54
are mounted above their respective springs by use of shackles.
This allows the use of standard size wheels, even though the
second attaching means 18 is located at a low enough level to
permit the rear trailer 12 to be a standard trailer unit.
FIG. 15 indicates the manner in which the entire unit,
incl~l~;ng the tractor 11, the front trailer 13, and the rear
trailer 12,. can turn on a very small radius. More specif.ically,
the front corners of the rear trailer 12 clear the rear end of
the front trailer 13 by substantial amounts during turning.
FIG. 16 shows clearly the way in which the cables 55
on their support rod.56 and spring.57 are pressed downwardly into
a storage position when the second portion 16 slides from its
rear, s.econd position to. its front, first position. When.the
rever:se movement ta]~es place, the cables spring upwardly into
the.functional position for: connection to the.coupling element
on.the front end of the:rear trailer 12. An alarm is provided
that .is. energized when .the pins are released and r~m~'n~
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operative when moving the sliding elements from one posi-tion
to the other.
It is obvious that minor changes may be made in the
form and construction of the invention without departing from
the material spirit thereof. I-t is not, however, desired to
confine the invention to the exact form herein shown and
described, but it is desired to include all such as properly
. come within the scope: claimed~
. The invention having been thus de.scribed, what is
claimed as new and desired to s.ecure by Letters Patent is:
