Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates generally to semi-trailers,
and refers more particularly to a semi-trailer of low overall
height having an undercarriage with numerous wheels, the under-
carriage being so arranged that the several wheels all share
equally in supporting the load of the trailer body and its con-
tents so that none of the wheels is subjected to an excessive
load force.
In certain types of cargo transporting work it is
necessary to use a semi-trailer having a very low overall height.
Such a vehicle may be needed, for example, in dockside operations,
for the loading and unloading of package freighters, where the
trailer must be run in beneath a palletized load or a container
resting on a low frame, and must be capable of carrying the con-
tainer at a level just high enough to keep it clear of the deck
and not so high as to risk bringing it into collision with low
overhead structure.
For a semi-trailer to have the least possible overall
height, it must have small wheels. But a small wheel can support
only a limited load, and therefore a semi-trailer that has small
wheels and is intended for heavy cargo must have a large number
of such wheels, all of which must share in the support of a load.
It will be apparent that if a semi-trailer with numerous small
wheels has rigid connections between its wheel axles and its body,
it will be able to operate successfully only on relatively smooth,
flat surfaces, inasmuch as any irregularity in the surface will
throw the weight of the entire trailer and its cargo onto only
one or a few wh~els, overstressing and damaging them. It will
also be apparent that a trailer undercarriage having numerous
small wheels must not only be so arranged as to enable the wheels
to share equally in supporting the load but must not, in itself,
defeat the objective of achieving low overall height for the
trailer.
With these considerations in mind, it is an object of
the present invention to provide a trailer of the general type
that has its front portion supportable by a towing vehicle to
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which it can be attached and has its rear portion supported on
a wheeled undercarriage, which trailer has very low overall
height and has numerous very small wheels but nevertheless imposes
no excessive load on any of its wheels even when carrying a
heavy cargo over a bumpy or irregular surface.
Another and more specific object of the invention is
to provide a semi-trailer of low overall height having an under-
carriage with a large number of wheels, which undercarriage
enables all of the wheels to make constant contact with a
sur~ace over which the vehicle moves, and to share support of
the load equally, even though the surface may be bumpy or
irregular.
A further specific object of the invention is to
provide a semi-trailer having a wheeled undercarriage that
achieves the objects set forth above and having means by which
its body can be readily raised and lowered relative to its wheels,
so that the semi-trailer can be moved into position beneath a
palletized load or container that is supported on a low frame,
with the trailer body in lowered condition, and the body can then
by elevated relative to the wheels to supportingly engage the
load for transport of it.
In general, the objects of the invention are achieved
by means of a wheeled undercarriage for a semi-trailer that
comprises two symmetrically disposed undercarriage assemblies,
one at each side of the longitudinal centerline of the trailer,
each such assembly comprising a first generally horizontal beam
that is medially pivoted so that its ends can swing up and down
about a first tilting axis, and a pair of second generally
horizontal beams, each medially pivoted to an end portion of
the first beam to be bodily carried up and down by tilting of
the first beam and to have their end portions swingable about a
second tilting axis that is common to both of the second beams
and transverse to the first axis, one of said axes extending in
the fore-and-aft direction of the vehicle, and each of said
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second beams having at least one wheel rotatably connected to
each end thereof, the pivotal connections of said beams to the
body and to one another enabling all of the wheels to maintain
contact with a surface over which the trailer travels and to
share equally in the support of the body and any cargo that it
carries; and the arrangement being such that pivot axes can be
so disposed above and below respective beams as to maintain low
overall height of the vehicle.
The objects of the invention are further achieved by
connecting the first beams to a rigid frame member which is
in turn connected with the body by means of links that can swing
between a near-horizontal body-lowered position and a more or
less vertical body-raised position, and by means of extendable
and retractable motor means connected between the body and said
frame member to effect such swinging of the links.
With these observations and objectives in mind, the
manner in which the invention achieves its purpose will be
appreciated from the following description and the accompanying
drawings, which exemplify the invention, it being understood that
changes may be made in the specific apparatus disclosed herein
without departing from the essentials of the invention set forth
in the appended claims.
The accompanying drawings illustrate one complete
example of an embodiment of the invention constructed according
to the best mode so far devised for the practical application of
the principles thereof~ and in which:
Figure 1 is a top plan view of a semi-trailer embody-
ing the principles of this invention;
Figures 2 and 3 are longitudinal sectional views taken
on the plane of the line II, III-II, III in Figure l; Figure 2
showing the semi-trailer in its body-raised condition and
Figure 3 showing it in its body-lowered condition,
Figure 4 is a transverse sectional view through one
lateral half of the semi-trailer, taken on the plane of the line
IV-IV in Figure 1; and
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Figure 5 is a transverse sectlonal vlew taken on
the plane of the line V-V in Figure 1.
Referring now to the accompanylng drawings, the nu-
meral 1 deslgnate~ generally a seml-traller embodylng the prln-
clples of thls inventlon, comprlslng, ln general, a body 2 whlch
is in the nature of a substantially rectangular load ~upportlng
frame and an undercarriage 9 having a large number o~ rather
small wheels 11. The lntended dlrectlons of motlon of the vohi-
cle are as denoted by the arrow 3 ln Figure l. The wheeled under-
carriage supports the rear portlon of the semi-traller whlle it~
front portlon i~ supported by a towlng vehicle (not ~hown) to
whlch the semi-traller can be detachably connected by mcans Or a
goose-neck tow bar ~ that extends forwardly and upwardly from
the body 2.
The body of the particular semi-traller here lllu~-
trated i~ intended to carry relatlvely large and heavg cargo
contalners 29, each of which can extend across the ~ull width of
the body; and for such loads the body ¢an consist Or a ~lmple
rectangular frame of box girders having tran~versely extending
front and rear members 8 and 26, respectivoly, and longitudinally
extendlng slde members 32 and 33. A thlrd or lntermedlate tran~-
versely extending box glrder member 4 spaced from the ~ront and
rear members 8 and 26, affords rlgldlty to the body and provldes
for certain connection~ between the body and the wheels, as
descrlbed below. Between the front body member 8 and the lnter-
mediate member 4, the body has a front openlng or wlndow 5; and
it has a larger rear opening 6 between the lntermedlate member
and the rear member 26. The tow bar 7 ls of course rigidly con-
nected to the front body member 8.
The wheeled undercarrlage ls located between the two
side members 32, 33 and between the rear frame menber 26 and the
lntermediate frame member 4. As shown, it comprises elght bogie
units lO, each of whlch has two palrs of wheels ll, or a total
of sixteen wheels. The several bogle units lO are arranged ln
two undercarriage assemblies, one at each side of the longitudlnal
Centerline of the trailer, and those assemblies are of course
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disposed symmetrically with respect to that centerline.
For each undercarriage as~sembly there is a central
fore-and-aft extending supporting beam 22 which is confined to
bodily up and down motion relative to the body 2, as described
hereinafter, and which can be regarded as comprising a connection
between the undercarriage assembly and the body.
Each undercarriage assembly comprises a main tilting
beam 17 that extends transversely across the supporting beam 22,
intermediate the ends thereof, and is medially pivotally connected
with the supporting beam. The trunnion or pivot connection 19
between each main tilting beam 17 and its supporting beam 22
(best seen in Figure 4) is preferably located at the underside
of the supporting beam, and it allows the opposite ends of the
main tilting beam to swing freely up and down about a fore-and-
aft extending horizontal axis but otherwise confines the main
tilting beam against motion relative to the main supporting beam.
Across each end portion of each main tilting beam 17
there extends a longitudinal tilting beam 16. Each longitudinal
tilting beam is medially pivotally connected with its main
tilting beam, so that it moves bodily up and down with tilting
motion of the main tilting beam but its opposite ends can swing
up and down about an axis which extends lengthwise of the main
tilting beam, that is, transversely of the trailer. The pivotal
or trunnion connection 18 between each longitudinal tilting beam
16 and its main tilting beam 17 is at the upper side of the main
tilting beam, as best seen in Figures 1 and 4, so that the
longitudinal tilting beams are at about the level of the support-
ing beams 22.
A pair of bogie beams 14 extend across each end portion
of each longitudinal tilting beam 16. The two bogie beams of
each pair are spaced from one another lengthwise of the longitid-
inal tilting beam, with one bogie beam o~ the pair near the very
end of the longitudinal tilting beam and the other about midway
between the end of the longitudinal tilting beam and its trunnion
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connection 18. The distance between the two bogie beams of each
pair is thus somewhat greater than the diameter of a wheel. The
bogie beams of course extend transversely of the trailer, and
each has a medial pivotal connection to its longitudinal tilting
beam. The trunnion or pivot connection 15 between each bogie beam
and its longitudinal tilting beam is at the underside of the
latter and extends lengthwise thereof. Note that the bogie beams
are thus at about the level of the main tilting beams 17. The
four bogie beams connected with each longitudinal tilting beam 16
swing about coinciding axis, Each pair of bogie beams has con-
nections with two pairs of wheels and thus comprises a part of one
of the bogie units.
Each pair of bogie beams cooperates to support a pair
of rock shafts 13, each such rock shaft being connected with the
adjacent ends of the bogie beams of its pair and extending longi-
tudinally between them.- The rock shafts are confined to rotation
about their own axes relative to the bogie beams, and therefore
the two rock shafts that are connected with each pair of bogie
beams constrain those bogie beams to tilt in unison about their
coaxial trunnions 15. It will be apparent that each rock shaft
is in the nature of a longitudinally extending beam that is
rotatable about its own longitudinal centerline.
The wheels are arranged in pairs, with each pair mounted
for rotation on opposite end portions of a relatively short axle
member 12. Each axle member is in turn medially secured to one
of the rock shafts 13, with the axle member midway between the
two bogie beams 14 that support the rock shaft and with the axis
of the two wheels transverse to that of the rock shaft and with
the wheels of the pair disposed at opposite sides of the rock
shaft. In this case, since the rock shafts are rotatable rela-
tive to the bogie beams that carry them, each axle member can be
rigidly secured to its rock shaft and the rotatable mounting of
the rock shafts relative to the bogie beams will provide for up
and down tilting of the axle members about their midpoints.
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~bviously the same results could be obtained if the rock shafts
were replaced by beam members rigidly connected to their respect-
îve bogie beams and the axle members were medially pivotally
connected to their respective beam members. However, with rock
shafts 13 that are journalled in the bogie beams, as shown, the
rigid connection of each axle member 12 to its rock shaft can be
either at the upper side of the rock shaft or at the bottom
thereof, depending upon the arrangement that obtains the least
distance between the wheel axes and the top surface of the trailer
body 2.
It will be evident that by reason of the above described
pivotal connections of the several beams to one another and to
the trailer body 2, every one of the wheels 11 can maintain con-
tact with a surface over which the trailer travels, notwithstand-
ing bumps or irregularities in tha~ surface, and every wheel will
always carry its proportiona*e share of the load of the trailer
and its cargo, so that no wheel wili ever be overloaded.
To enable the trailer to be used with palletized loads,
its body 2 is arranged to be raised and lowered through a limited
distance relative to the wheeled undercarriage. As an example
of one form of palletized load, Figure 5 shows stacked large cargo
containers 29 that are stored on low supports comprising a pair
of parallel sills 31 which are spaced apart by a distance slightly
less than the width of a container. With the trailer body in
lowered condition, it is run in between the sills and under the
containers resting on them. The body is then raised to its
elevated position, thereby lifting the containers off of the sills
and causing them to be supported solely by the trailer, so that
they can be transported by it to a new location.
Each of the main supporting beams 22 of the semi-trailer
comprises one leg of a generally U-shaped rigid frame 20 that also
includes a transversely extending bight member 21 to which the
beams 22 are rigidly attached at their forward ends. At its rear
end each of the longitudinally extending supporting beams is
bifurcated, and a heavy link 23 is received between the
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bifurcations and has its lower end swingably connected to them.
At its upper end each of the links 23 has a swinging connection
to brackets 25 that are fixed on the rear body member 26 and
project a short distance forwardly from it.
Near its front end each of the longitudinal supporting
beams 22 is similarly connected with the body 2 by links 24.
There is a link 24 on each side of each supporting beam 22, and
the lower ends of those links are swingably connected to the
supporting beams while their upper ends are pivotally connected
to brackets 27 that project a short distance rearwardly from the
intermediate body member 4. The pivot axes of all of the links
23 and 24 extend transversely of the body so that those links
swing in vertical fore-and-aft extending planes.
A pair of double acting hydraulic cylinder mechanisms
28 are connected between the front body member 8 and the trans-
verse member 21 that forms the bight of the U-shaped frame 20.
When those hydraulic motors are retracted, the body 2 is in its
lowered condition shown in Figure 3, and the several links are
in near-horizontal orientations but extend obliquely ~earwardly a
and slightly upwardly from their pivoted lower ends. As shown
in Figure 2, extension of the hydraulic motors 28 causes the
body 2 to move forwardly relative to the U-shaped frame 20,
swinging the upper ends of the links forwardly and upwardly and
thus raising the body 2 relative to the frame 20 that carries
the undercarriage assemblies. The links swing to defined posi-
tions a little past the vertical so that the body is locked in
its raised position without the need for maintaining extending
force upon the hydraulic motors 28.
The body is ol course lowered by retracting the
hydraulic motors. Note that when the body is in lowered position
the upper portions of the wheels are received in the large rear
opening S in the body 2 so that the upper surface of the body is
at a level only slightly above that of the tops of the wheels.
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Wheel diameter is thus the dimension that substantially controls
the overall height of a semi-trailer of this invention.
From the foregoing description taken with the accompany-
ing drawings, it will be apparent that this invention provides
an undercarriage for a semi-trailer whereby the vehicle can be
equipped with numerous very small wheels, to enable it to have
a low overall height, and whereby assurance is had that all of
the wheels will share equally in supporting the load of the
trailer and its cargo. It will also be apparent that the semi-
trailer ofthis invention has simple means for raising and lower-
ing its body to enable it to lift and carry palletized loads.
Those skilled in the art will appreciate that the
invention can be embodied in forms other than as herein disclosed
for purposes of illustration.
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