Note: Descriptions are shown in the official language in which they were submitted.
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REINFORCED HOPPER CAR STRUCTURE
FIELD OF THE INVENTION
This invention relates to structures for railcars such as may be applicable,
for
example, to the reinforcement of hopper cars. One particular use for the
invention is the
reinforcement of hopper car roofs.
BACKGROUND OF THE INVENTION
The design of railway hopper cars is governed by three main requirements.
First, the
fully loaded weight of a 125 ton car must not exceed 315,000 lbs. Thus to
maximize useful
load, car designers try to minimize car weight. At present an empty grain
hopper steel car
may typically weigh about 63,000 lbs., such that lading in excess of 50,000
lbs. is
permissible. Second, the car must withstand a draft load of 630,000 lbs.
Third, the car must
not buckle under buff loads of 650,000 to 1,000,000 lbs. when slowing or
stopping. Under
the first, dead weight, loading condition the car may be modelled as a simply
supported
hollow beam carrying a distributed vertical load in excess of 50,000 lbs.,
with a
corresponding bending moment distribution. Under the second, tensile draft,
and third,
compressive buff, loading conditions the car is like a column, taking tensile
and compressive
loads.
The general structure of contemporary curved-sided hopper cars can be
idealized as a
load bearing monocoque in the form of a hollow, downwardly opening, generally
C-shaped,
thin walled, column. At each column end, the load is transferred through a
transition
structure from the shell into a stub sill and coupler by which the railcar is
connected to the
next rail car. The challenge in designing the structure for a hopper car, in
general, is to
reduce the mass of the thin shell, and any supporting structure, to a minimum
while still
maintaining the structural integrity required to withstand the given loads,
and to transfer those
loads between the couplers and the body shell. When the shell is made too thin
it fails in
compression due either to global buckling of the structure, or to the local
buckling
phenomenon of wrinkling. In such a hollow shell structure, the ability to
resist the
compressive buff load, without buckling, requires that the principle
longitudinal structural
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components of the car, those being the roof and side walls, work together as a
single
integrated structure.
One way to reduce the weight of the car is to reduce the thickness of the
roof. The
thickness of the roof of a typical hopper car is commonly less than 3/16".
Given a railcar
length of roughly 60 feet and width of roughly 10 feet, the roof may be
considered a thin shell
structure. Under vertical loading conditions of the car, this thin shell
structure is exposed to a
compressive load, with a consequent tendency toward buckling or wrinkling.
This tendency
is increased when a compressive longitudinal load is also applied to the car.
In the past, hopper car roofs have been given an outwardly bulging curved
panel
form to resist buckling, and have been supported by internal bulkheads or
partition sheets,
such as disclosed in United States patent 4,275,662 of Adler, issued June 30,
1981. For
example, a three hopper rail car generally has two end walls and two
intermediate partitions
leaving three roof spans each having a length of 15 to 20 feet. The roof is
supported along its
outboard edges by top chord members frequently in the form of a closed hollow
section as
depicted, for example, in Figure 2 of United States patent 4,275,662.
In United States patent 4,377,058 of Hallam et al., issued March 22, 1983
partial,
reinforced internal stiffeners, shown as web assemblies 34 and 36, extend
internally across
the full width of the car and maintain the curvature of the roof. In general,
internal fittings,
and particularly internal welds, tend to be avoided if possible. First,
internal welding tends to
be more difficult. Second, each additional fitting creates one or more niches
in which
foodstuffs may collect and rot. Third, it is generally better to leave the
inside of the hopper
free of obstructions. Where stiffeners are used a common goal is to obtain
adequate strength
without adding unnecessary weight.
The unsupported spans of hopper car roofs between end walls and bulkheads have
a
tendency to deflect. In particular, rapid unloading of grain hopper cars is
known to cause a
partial vacuum inside the car which tends to draw the roof inward. This is
more pronounced
in grain hopper cars having a continuous, central, longitudinally extending,
trough opening.
It tends to cause the arcuate shape of the roof section to flatten. This
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problem worsens as the thickness of the roof material decreases. The central
trough may be
bordered by a coaming, and the deflection of the roof may tend not only to
cause the coaming
to deflect, but may also tend to twist the coaming and reduce its ability to
strengthen the
structure. Consequently as roof thickness is reduced to lower the weight of
the car it is
desirable to reinforce the roof so that it provides resistance to buckling and
to deflection
under internal vacuum comparable to a thicker un-reinforced roof. It is also
advantageous
to provide stiffening to maintain a natural frequency comparable to previous
roofs, as
vibration remains a significant factor in railcar design generally.
In general, it would be advantageous to have, and there has been a long felt
need for,
an improved hopper car shell structure. To that end, it would be advantageous
to have
improved reinforcement of a hopper car roof.
SUMMARY OF THE INVENTION
The present invention provides, in one aspect, a reinforcement for an
unsupported
span of an hopper car roof structure subject to compressive forces applied in
a longitudinal
direction relative to the hopper car, the span having a desired cross-
sectional profile, the
reinforcement chosen from the set of reinforcement consisting of (a) a
longitudinal beam for
forming a border along an unsupported edge of the span, the beam having a
first leg rooted
to the edge and extending away from the span; said first leg having a distal
portion distant
from the edge, and a depending leg joined to the distal portion and extending
therefrom back
toward said span; and (b) an outwardly standing web attachable to the
unsupported span,
the web having a footprint for mating with at least a portion of the profile
of the unsupported
span.
In a further feature of that aspect of the invention, the reinforcement is the
longitudinal beam extending along the unsupported edge of the span. The beam
has a first
leg rooted to the edge and extending away from the span. The first leg has a
distal portion
distant from the edge, and a depending leg joined to the distal portion and
extending
therefrom back toward the span. The first and second legs are parts of a
continuous roll
formed section.
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In yet a further feature, the longitudinal beam is a roof coaming formed
integrally
with the roof span. The first leg is an upstanding leg folded upwardly from
the span. A
rounded coaming is lip formed at the uppermost end of the upstanding leg, and
the depending
leg is folded downwardly from the lip.
In a second aspect of the invention there is a hopper car roof assembly having
a
desired roof profile, and having at least one unsupported roof span and a
reinforcement
attached to the span, the reinforcement having a web upstanding from the span
and a
footprint attached to at least a portion of the span for maintaining the
profile over at least a
portion said span.
In an additional feature of that aspect of the invention, the reinforcement
has a toe
for location adjacent to a longitudinal roof stiffening section, and a heel
for location in a
position to receive support from a top chord of the hopper car. The footprint
is of a length
for reinforcing the span between the beam and the section and of a pattern to
mate with the
roof profile in an orientation chosen from the set of orientations consisting
of (i)
perpendicularly to the beam; and (ii) at an oblique angle to the beam.
In an alternative feature of that aspect of the invention, the assembly
comprises at
least two webs attached to the roof in spaced relationship from each other.
The webs, in plan
view, are oriented transversely to the longitudinal direction in an
orientation chosen from the
set of orientations consisting of a) parallel to each other and perpendicular
to the
longitudinal direction; b) parallel to each other and angled obliquely to the
longitudinal
direction; c) one perpendicular to the longitudinal direction, and the other
angled obliquely
thereto; and d) one angled obliquely to the longitudinal direction at one
angle, and the other
angled obliquely at another angle.
In a further aspect of the invention there is a hopper car roof assembly
wherein the
roof assembly has a pair of opposed outboard edges. The roof is reinforced at
each
outboard edge by a top chord beam, and has a central trough bounded by a
coaming. The
roof assembly includes at least two of the reinforcements oriented, in plan
view, to extend
inwardly of one of the outboard edges toward the coaming in a manner chosen
from the set
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of orientations consisting of (a) perpendicularly to the outboard edge in
parallel spaced
relationship to each other; (b) obliquely to the outboard edge in offset
parallel relationship to
each other; (c) one extending perpendicularly to the outboard edge and the
other lying
obliquely thereto; and (d) one lying obliquely at a first angle to the
outboard edge and the
5 other lying obliquely at a second angle to the outboard edge, the webs being
surmounted by
horizontally extending flanges; and running boards mounted to the flanges.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention and to show more clearly
how
it may be carried into effect, reference is made by way of example to the
accompanying
drawings, which show an apparatus according to the preferred embodiment of the
present
invention and in which:
Figure 1 is a general arrangement view of a hopper car incorporating the
present
invention;
Figure 2 is a longitudinal centre-line cross-section of the hopper car of
Figure 1
taken on section '2 - 2';
Figure 3 is a plan section of the hopper car of Figure 1 taken on section '3 -
3';
Figure 4 is a lateral cross section of the hopper car of Figure 1 taken on
section '4 -
4' =
,
Figure 5 shows a sectional view of a roof of the hopper car of Figure 1;
Figure 6a shows a developed view of a carline for the roof of Figure 5;
Figure 6b shows a profile view of the carline of Figure 6a;
Figure 6c shows an end view of the carline of Figure 6a;
Figures 7a shows an alternative carline to that shown in Figure 6b;
Figures 7b shows an alternative carline to that shown in Figure 6b;
Figures 7c shows an alternative carline to that shown in Figure 6b;
Figures 7d shows an alternative carline to that shown in Figure 6b;
Figures 7e shows an alternative carline to that shown in Figure 6b;
Figure 8a shows a plan view of the roof of the hopper car of Figure 1;
Figures 8b shows a plan view of an alternative roof for the hopper car of
Figure 1;
Figures 8c shows a plan view of an alternative roof for the hopper car of
Figure 1;
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Figure 9a shows an enlarged detail of a coaming section for the roof of Figure
5;
Figure 9b shows an alternative embodiment of the coaming section of Figure 9a.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The description of the invention is best understood by commencing with
reference to
Figure 1, in which some proportions have been exaggerated for the purposes of
conceptual
il l ustration.
Referring to the preferred embodiment of Figures 1, 2, 3 and 4, a hopper car
of all
steel construction is shown generally as 20. It has trucks 22 in the customary
manner, upon
which a railcar body 24 rests. The body has end structures 26 and 28 supported
on trucks 20.
Three hoppers 30, 32 and 34 are defined by a combination of left and right
main side walls 36
and 38, respectively; left and right hand, foremost, middle and rearmost
inwardly
downwardly sloping side sheets, 40, 42, 44, 46, 48, and 50, respectively; end
wall 52 and 54;
internal bulkhead partitions 56 and 58; and foremost and rearmost sloped
sheets 60, 62, 64,
66, 68, and 70, tied together and reinforced by left and right hand side sills
72 and 74 and top
chords beams 76 and 78 all of which are attached to end structures 26 and 28
and covered by
a roof assembly 80.
In general terms, roof assembly 80 and sidewalls 36 and 38 form a three sided,
downwardly opening, thin shelled structure, similar to a monocoque. This thin
shell is, in
effect, wrapped around endwalls 52 and 54 and bulkhead partitions 56 and 58
and extends
downwardly to the level of side sills 72 and 74. End walls 52 and sloped sheet
60, endwall
54 and slope sheet 70, and bulkhead partitions 56 and 58 act in general terms
as frames, or
formers, forming a skeleton to which the monocoque-like structure is attached
like a skin.
The individual members of the structure are relatively thin and flexible
alone, but when
assembled work together mutually to stiffen each other and the entire
structure. The ability of
such a structure to bear service loads generally depends on the ability of the
unsupported
spans between the formers to maintain their desired shape. The formers shown
are all
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upstanding, but need not be vertically upstanding, and need not be parallel to
give a desired
stiffening effect when the skins are welded in place.
In the embodiment shown the distance between each adjacent pair of formers
defines
the fore-and-aft length of one of hoppers 30, 32, or 34. Generally speaking
sidewalls 36 and
38 extend along the formers between the discharge assemblies of the hopper car
and the
superstructure which is typically a roof assembly.
Butt welded roof assembly 80 has predominantly longitudinally extending left
and
right hand roof panels 222 and 224, and predominantly laterally extending end
region panels
226 and 228. Left and right hand roof panels 222 and 224 extend inwardly from
top chord
beams 76 and 78, nominally following the curve of the arcuate upper edges 230
and 232 of
bulkhead partitions 56 and 58 to terminate at upstanding left and right hand,
rounded-lip
coamings 236 and 238. U-shaped end coaming styles 240 and 242 are let into end
region
panels 226 and 228 to mate with the coamings 236 and 238 to form a continuous
periphery,
the gap bounded thereby defining a trough 244 through which grain may be
introduced to
hoppers 30, 32 and 34.
Since coamings 236 and 238 are formed integrally with roof panels 224 and 226
respectively in a roll forming process, they are made from the same thickness
of material, i.e.
0.125 inch thick steel. The relatively deep, folded over sections of coamings
236 and 238, act
like inboard longitudinal beams running along the otherwise unsupported inner
edge of panel
222 or 238, and extend to reach across the longitudinal gap between partitions
56 and 58. To
obtain a thicker coaming section, as illustrated in Figure 9a, one may fold
over a double
thickness of sheet, and then pass it through rolls to form the coaming
profile. Coaming 236
has a main leg 245 rooted to, and bent upwardly and outwardly away from, panel
222, a
bulbous lip 246, curled back upon itself, and a depending leg 248 which
extends
approximately two thirds of the distance down the outside face of main leg 245
back toward
panel 222. This unequal, double-leg design permits a stiffer coaming to be
formed without
additional welding.
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Typical unsupported span 252 of roof panel 222 is bounded by end wall 52,
bulkhead
partition 56 and top chord beam 76. Typical unsupported span 254 is bounded by
bulkhead
partitions 56 and 58 and top chord beam 76. Typical unsupported span 256 is
bounded by
bulkhead partition 58, end wall 54, and top chord beam 76. Right and left hand
carlines 260
and 262 surmount roof assembly 80, and provide a convenient support upon which
to mount
running boards 264 and 266. They replace the rung-like, 3/8 inch thick bent
bar running
board support brackets previously used for this purpose.
Carline 260, shown Figures 4 and 5, and in greater detail in Figures 6a, 6b,
and 6c,
has a web 268 oriented to stand upright, and to extend across roof panel 222
perpendicular to
the longitudinal axis centreline 110 of hopper car 20 generally. Web 268 has a
heel 272
welded to roof panel 222 near the juncture of roof panel 222, top chord beam
76, and main
side wall 36. The web 268 has a gusset-like toe 274 having a first edge welded
to the more or
less horizontal arcuate portion of roof panel 222 and a web portion 276
extending roughly
halfway up the height of, and welded to, leg 248 of the coaming 236. Further,
the web 268
has a footprint 278 with a desired arcuate profile for mating with roof
pane1222 and a number
of reliefs 280, 282, 284, 286 and 288 therein. Web 268 also has a mid-web
lightening hole
290, and a folded over flange 292, forming a stiffened spine for web 268.
Running board 264
is attached to the web 268 by for example, a threaded fasteners as in the
embodiment
illustrated. The running boards also serve to stabilize neighbouring carlines
260 by
maintaining them in fixed mutually parallel relationship to each other.
As shown, each carline 260 provides a stiff section between top chord beam 76
and
coaming 236 and tends to reduce sagging at that section, not merely by virtue
of its own
stiffness but by tending to extend the range of influence of the torsional
stiffness of the
hollow section of top chord beam 76 further out into roof panel 222. Further,
carline 260 also
tends to maintain the orientation of coaming 242, that is it reduces the
tendency of coaming
242 to twist. Further still, it tends to maintain the desired sectional
profile of roof panel 222
and hence tends to maintain its resistance to buckling. The stiffness of
carline 260 is such
that, as illustrated in Figure 8a, unsupported span 252 in the illustrated
embodiment, roughly
fifteen feet in length between bulkhead partitions 56 and 58, tends to have
vibration
properties similar to shorter panels 294, 296, 298 and 300.
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In the preferred embodiment described above, roof panel 222 is 0.125 inches
thick, as
opposed to the 0.177 inch thickness butt welded roof panels currently used.
Carlines 260 and
262 are made from 0.177 inch thick steel .
Other embodiments of hopper roof reinforcement carline are shown in Figures
7a, 7b,
7c, and 7d. In Figure 7a, a carline 320 has a continuous arc 322 without
reliefs for fillet
welding to roof panel 222. The carline 320 also has two lightening holes 324
and 326
bridged by a brace 328, and a toe 330 which does not extend fully to coaming
236.
In Figure 7b, a carline 340 has a heel 342 extending outboard over top chord
76, and
a flange 344 running along the back of heel 342. A finger 346 extends for
welding to the
outside face of top chord beam 76.
In Figure 7c, a carline 350 is shown having a foot print 352 which extends
over only a
partial arc of roof panel 222, but maintains the sectional profile of roof
panel 222 over that
arc.
In Figure 7d, a further alternative carline 354 is shown having a footprint
356 for
mating with a roof panel 358 having corrugations 360. These corrugations are
shown as
having the section of shallow, taper sided channels or ribs, but could be
rectangular,
triangular, or sinusoidal sections, or of some other chosen readily
manufactured profile. The
corrugations may have more or less ribs, of greater or lesser depth. In each
case, the carline
serves not only to stiffen roof assembly 80 but also supports running board
264.
An alternative internal brace is shown in Figure 7e as 362, having a web 364,
lightening holes 366, 368 and 370, a web flange 372, and a heel 374 welded to
main side
wall 36 in a position next to the top chord beam 76. Internal fittings are
less favoured by the
inventors, for the reasons noted above, and also because brace 362 does not
also serve the
second function of supporting running board 264, which must still be carried
on a running
board support 348.
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While the illustrated, preferred, embodiment of Figure 6c shows carline 260
having a
web 268, which extends perpendicularly away from the roof panel 222, web 268
may extend
away at an oblique upstanding angle. Figure 8a shows a plan view of the
preferred
embodiment in which carlines 260 extend in parallel spaced relationship from
each other
5 perpendicularly to, and between, top chord beam 76 and coaming 236. Figure
8b shows
carlines 376 and 3781ocated at the diagonal at the corners of hopper car 20.
Figure 8c shows
carlines 380 deployed in a diagonal pattern about roof assembly 382 leaving
roughly
triangular panels 384, 386, 388, 390.
Similarly, although the preferred embodiment employs specific arcuate
footprint on a
10 constant 130 inch radius of curvature, a different curvature, an arbitrary
curve, a corrugated
section, or a flat profile may be chosen to mate with the specific roof
profile desired. Further
still, although web 262 has been shown in a linear form it may, as seen from
above, have a
dog-leg, zig-zag, single arc, corrugated, or other chosen sectional profile.
Flange 292 need
not be folded over, but can alternatively be formed by, for example, welded
fabrication.
= Similarly, while an all-welded car roof structure has been described other
forms of fabrication
could also be used including threaded fasteners, rivets, or bonding
techniques.
Figure 9b illustrates an alternative form of longitudinal roof coaming
reinforcement.
Rather than the integrally formed, bulbous-lipped folded embodiment shown in
Figure 9a, a
curved coaming liner 302 is welded inside the folded curve of coaming 304.
Liner 302 has an
outer lip 306 which extends past the end of coaming lip 308 such that they may
be fillet
welded together more easily. Liner 302 also has a shank 310 extending down and
stitch
welded to the face of coaming 304. It will be appreciated that liner 302 can
be mounted
within the curve of coaming 304, or on the back side of coaming 304. Similarly
in the
embodiment of Figure 9a, the material could be folded back on itself to give a
depending
shank lying on the hopper trough opening side of main leg 245.
Notably, while reinforcements in the nature of flutes have been described
primarily in
the context of main side walls 36 and 38, and reinforcements in the nature of
transversely
extending carlines have been described in the context of roof panels, while
maintaining the
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overall envelope of the car, transverse stiffeners may be used to reinforce
unsupported side
wall panels, and longitudinal flutes may be used to stiffen the roof
unsupported roof panels.
While a longitudinal reinforcement in the nature of longitudinally extending
coamings
236 and 238 is provided along the free edge of the otherwise unsupported spans
of roof
panels 224 and 226 it would also be possible to deform the sections of those
panels to
provide longitudinal flutes or corrugations at intermediate locations relative
to the arc
between the respective side sills and coamings.
A particular preferred embodiment of the invention, and a number of
alternative
embodiments, have been described herein and illustrated in the figures. Those
embodiments
are described by way of illustration, and not of limitation, of the invention.
The principles
of the present invention are not limited to those specific embodiments, but
are defined by the
claims which follow, and equivalents thereof.
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