Note: Descriptions are shown in the official language in which they were submitted.
~(31 ~ f85
This application relates to an improved air
cargo container and enabling method and means for the
construction th~reof. Also it pertains to an air cargo
container corner construction which facilitates advantage
in formation for assembly and disassembly of highly
desired transparent and tough polycarbonate panels, in
that it allows them for the first ~ime to be used
effectively in air cargo containers.
Prior art containers and container structures
have provided containers o* rigid and sturdy construction
to sa~eguard cargo items being transported or stored
therein. However, the side panels of the previous
containers have been attached to the container frame most
often using a bolt that passed through the panel. This
made the use of a polycarbonate panel undesirable because
of stress crazing and cracking that occurred around the
bolt holes through which the bolt passed when attaching
the panel. Additionally, the attempted use of nuts and
bolts, rivets, fixings or the like to attach the side
panel necessitated much effort to replace any side panel,
in that removing the panel required disassembly of the nut
and bolt combination. Special tools were often needed and
the individual nuts and bolts were lost, especially under
operating conditions for loading cargo containers into
airplanes, i.e., urgency and sometimes poor illumination.
Additionally, the commonly used panel material, aluminum,
is not transparent. Thus the cargo handlers cannot see
how or to what extent the cargo container is loaded. The
lack of transparency of prior panels also hid undesired
acts of pilferage from plain view.
The present invention provides containers
whereby the above noted disadvantages may be overcome.
The invention provides a cargo container having
a top, a bottom and a plurality of side walls defining an
enclosed interior, and having means defining peripheral
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corners of the cargo container comprising an elongated
corner strip with a channel formation thereon defining a
channel extending longitudinally of the strip, at least
one of the walls of the container panel comprising a sheet
of semi-rigid plastic material, preferably of
polycarbonate, said panel having a channel section
corrugation along a marginal edge, the corrugation being
in interengagement with the channel formation with one
side of the channel formation of the strip being received
in the channel of the corruyation and a portion of the
said marginal edge being received in the channel
formation, and means for removably maintaining the
interengagement between the corrugation and the channel
formation.
With the container o~ the invention there has
been eliminated any need to pass a bolt through the
polycarbonate or other plastic material panel, stress
crazing of the panel has been eliminated.
In one method for manufaciuring the cargo
container, the edges of a transparent polycarbonate panel
may be shape-formed into at least one corrugation by
proeheating the panel edges, for example to about 55C
(120F) and passing the preheated panel edge through one
or more roller dies disposed so as to progressively shape-
form corrugations into the panel edges. The panel maythen be introduced between an outer and inner corner
molding strip adapted to maXe lengthwise to form
peripheral edges of a container. Threaded bolts may be
inserted through aligned holes in inner and outer corner
molding strips, but not penetrating said panel. The bolt
is mated with a nut, the nut retained by non-rotatable
means, and tightening effected to press fit and releasable
retain the panel by the molding strips. Finally a door is
attached over an opening left without a side panel between
peripheral edges of the container.
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BRIEF DESCRIPTION OF THE DRAWINGS
Having thus described the invention in general
terms, reference will now be made to the accompanying
drawings in which:
FIG. 1 is an enlarged cross-sectional view of
the corner of an air cargo container.
FIG. 2 is the samé corner joint of the air cargo
container shown in a disengagement mode.
FIG. 3 is the same corner joint as shown in PIG.
1 with the upper nut removed to better illustrate details
of the invention.
FIG. 4 is a horizontal elevation of the shaping
apparatus.
FIG. 5 is a partially cut away vertical
elevation of the apparatus.
FIG. 6 is a partial horizontal cross-section of
the shaping apparatus taken along line 6-6 shown ln FIG.
4.
Fig. 7 is a partial horizontal cross-section of
the shaping apparatus taken along line 7-7 in FIG. 4.
FIG. 8 is a partial horizontal cross-section of
the shaping apparatus taken along line 8-8 in FIG. 4.
FIG~ 9 is a perspective view of a container
constructed in accordance with the invention herein
claimed.
:~31~
D~TAILED DESCRIPTION OF_THE PREFERRED ENBODIMENT
Referring to the drawings, l:ike numbers of
reference indicate like elements throughout. In FIG. 3,
peripheral corner 20 of container 10 is constructed with
an outer corner channel strip 18 having flanged edges 22
adapted to mate lengthwise with an inner corner molding
strip 24 and retaining side panel skins 26 thereinbetween
to form the peripheral corner 20 of container 10.
An outer panel skin 26 forms a side of container
10. Peripheral edges 28 of outer panel skin 26 are
adapted to be inserted and releasably retained between
outer channel strip 18 and inner molding strip 24.
The corrugated configuration of the peripheral
edges 28 of the outer panel skin 26 is formed by rolling
parallel ridges 29 and 30 (including corresponding grooves
or channels 30a, 30b) around the four edges of each panel.
The ridges are retained within corresponding longitudinal
grooves 25 and 19, in the inner and outer molding strips
24 and 18, respectively. A projecting lip 27 of the inner
molding strip 24 mates with ridge 29 and forces it into a
groove or channel 19 of the outer channel strip 18.
Simultaneously, the flanged sides or edges 22 of the outer
channel strip 18 mate with the ridge 30 of the two side
panel skins 26 and force them into opposite grooves 25 of
the inner corner molding 24. Projecting lips 23 on the
underside of the outer channel 18 mate with preferably
semicircular grooves 39 on the inner molding 24 and give
the joint integral strength when the two moldings are
clamped together. Thus, when threadably tightened, a bolt
and nut combination 34 and 32 will compress and retain in
a releasable lengthwise relation, the corrugated
peripheral edges 28 of the outer panel skins 26 inserted
between the inner and outer corner molding strips 24 and
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18 to form the structural corner 20 of the container 10.
It will be noted that, with this arrangement, a
side 22 of each channel formation 19 of the strip 18 is
received in a channel 3Oa of the corrugation of the panel
26, and an outer portion 28 or 29 of the panel is received
in the channel 19. The portions 27 and 25 remo~ably
maintain the interengagement.
The bolt 34 is inserted through aligned holes 36
in the inner and outer corner molding strips 24 and 18 and
hole 37 in a short channel piece 38. The nut 32 is held
rotationally immohile in the channel 38 which is slidably
inserted in the inner corner molding strip 24 and therein
held in place by channel-like extensions 35 protrud:ing
from the inner side o~ molding strip 24. The nut holding
channel 38 is therein retained by inwardly protruding
lips.
Thus, as best shown in FIG. 2, in the
replacement of damaged outer panel skins 26, the component
parts comprising the structural corner 20 are not totally
dismantled and the bolts and nuts 34 and 32 remain engaged
in the channel molding strip 18 and inner molding strip
24, thus preventing their separation and loss.
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The configuration of channel 38 shown in FIGo 3 is modified
by the addition of an integrally formed U-shaped extrusion 106,
as shown in FIGS. l and 2q In this embodiment, the projecting
end 108 of the bolt 34, when tightened in nut 32, is
protectively encapsulated by channel 38 with its U-shaped
extrusion 106, thus preventing damage to the extended end of
bolt 34 or the thread thereon and also the cargo stored within
the container. When the bolt 34 is tightened during the
assembly of the peripheral corner 20 of the container lO, its
length is such as to cause a dimple 107 in the U-shaped portion
106 of the channel 38. Thus, the mating of the bolt end 108 and
dimple 107 prevents the channel 38 from sliding from its
position encompassing the nut 32, especially on the veL~tical
corners. When the bolt 34 is rotatably retracted to the
position shown in FIG. 2, its end 1~8 remains threadably engaged
with the nut 32. This retracted position permits the
disengagement of the outer skin 26 which was retained between
the outer molding strip 18 and the inner molding strip 24.
Thus, the component parts comprising the peripheral corner 20
are not totally dismantled during the attachment and/or
replacement of the outer skin panel 26.
In the second preferred embodiment as shown in FIGS. 1 and
2, it should be noted that a washer llO and supporting nut 112
are threadably mounted on bolt 34 in a counterbored recess 114
in the undexside of the molding strip 18. The self~locking nut
112, commercially known as a "nyloc-nut", has a nylon insert
which clinches the nut onto the threads of the bolt 34 in a
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relative position allowing a clearance space between the washer
110 and molding strip 18, thus permitting the bolt to rotate in
the hole 36 and in the outer mslding strip 18. Thus, when the
bolt 34 is rotatably retracted to its outer position as shown in
FIG. 2, the washer 110 and nut 112 rotate with the bolt and
remain in their relative position affixed upon the bolt 34. The
nut being held rotationally immobile in the channel 38 unscrews
from the bolt 34, thus forcing the outer molding strip 18 to
disengage from its locking position with inner molding 24 and,
thereby, releasing outer skin 26.
Referring now to FIG. 9, the invention is shown embodied in
the form of a cargo container 10, specifically, an air cargo
container. rr'he container comprises a top 12, a bottom 14, and a
plurality of exterior side walls 16. The actual exterior shape
of the container 10 can be contoured to occupy a particular
location as, for example, against the curved hull of a cargo
aircraft or a seagoing vessel, by the addition of angled and/or
shortened walls 16a. Through access opening 54 can be seen
hinged handles 74, gusset plates 78 and threshold channel 82 to
which a flexible door flap (not shown) may be attached and
secured. The peripheral corner 20 of the container 10 has bolts
34 accessible from the surface and penetrating the corner
thereof, as shown in FIGS. 1 - 3. The lower panel portions 58
of the side walls 16 are reinforced with peripheral hollow
stiffener members 60 forming a structural frame around the
bottom 14.
Referring now to FIG. 4, which is a horizontal elevation of
apparatus 212, the apparatus 212 can be composed of two
sections, the heating means 214 and shaping means 216. The
heating means 214 is composed of one or more heating lamps 218
enclosed as in a shroud 220. This shroud 220 can be mounted on
a pole 222 by clamp 224. Clamp 224 can be loosened and the
heating means 214 adjusted up ~nd down. This allows the
distance between the heating means 214 and the shaping means 216
to be varied.
The lamps 218 can be such as infra-red heat lamps.
Typically, these heating lamps draw 250 watts of electric
current. For example, a collection of 7 heating lamps, can
raise the temperature of a metal part up to around 110F (49C)
approximately when positioned 14 inches away.
The shaping means 216 is composed of a series of opposed
roller dies 226 and 228, wherein roller die 226 is disposed on
top of roller die 228. Although FIG. 4 shows eight such pairs
of roller di~s 226 - 226G and 228 - 228G, the number of opposed
roller die pairs can be varied depending upon the geometry
desired in the final edge of the plastic sheet to be
shape-formed. The roller dies 226 and 228 rotate in the same
direction, i.e., from right to left. Positioning means 230,
shown in FIGo 6, allows the sheets to be introduced into the
series of opposed roller dies. The sheet 236 travels from right
to left in FIG~ 4 encountering the roller die pairs in alpha-
betical order after roller die pairs 226 and 228. When the
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sheet 236 encounters the roller die pairs, and afterwards, the
roller dies with the third roller dies 238 - 238C, the sheet
edge is progressively shaped into the corrugations for inter-
nesting with a channel defined by the edges of the corner
molding strips.The roller dies 226 - 226G and 228 - 228G are
powered by electric motors.
FIG. 5 is a vertical elevation of apparatus 212. Heating
shroud 220 is shown in phantom to show its position in relation
to the top roller die 226. Alternatively, the heating assembly
could be configured to heat all the top roller dies or even all
the roller dies, bottom and top. As seen in FIG. 6, positioning
means 230 is composed of a horizontal table 232 with a guide 234
composed of angle iron mounted above the table 232. The angle
iron of guide 234 is mounted sufficiently far above the table
232 to allow a sheet of plastic material to slide along felt
webbing placed on top of the table 232. The positioning means
230 guides the sheets of thermoplastic material into the series
of opposed roller dies 226 - 226G and 228 - 228G.
FIG. 7, which is a partial horizontal cross-section of the
apparatus 212, shows a sheet 236 of thermoplastic material going
through the first pair of roller dies 226 and 228. The roller
dies are deforming the thermoplastic material sheet 236 as
shown.
FIG. 8, which is a partial horizontal cross-section,,taken
along lines 8-8 in FIG. 4, shows the thermoplastic material
sheet 236 as it emerges from the last set of roller dies 226 and
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228. Also impinging upon the thermoplastic sheet 236 is a third
roller die 238, the last in a series of third roller dies 238 -
238C. As can be seen, the set of three roller dies 226G, 228G
and 238 are beyond the range of heating means 214. However, due
to the pre-heating of the panel and the heating of the ~irst
series of roller dies, the thermoplastic material is still
amenable to shaping. Also illustrated in FIG. 8 is the complex
shape with the minimal radius of curvature for the ridges formed
in the edge of sheet 236.
The apparatus and method of the present invention ~aintains
enough heat in the edge of the sheet 236 of plastic material so
that the edge may be shaped into the desired geometry by the
series of roller dies 226 - 226G, 228 - 228G and, if needed, 238
- 238C. The heat is transferred into the sheet 236 by first
heating the panel separately to 120F before putting the sheet
into the apparatus. The top roller die 226 is heated, in turn,
by the heating means 214O The heat transfer from the roller die
226 to the sheet 236 is accomplished by direct contact and is to
maintain the sheet temperature near 120F. The heat transfer
from the heating means 214 to the top roller die 226 is
accomplished by radiation heating where heat lamps 218 are used.
In the case of infra-red heat lamps, in an assembly of 7 heat
lamps together, the temperature of the top roller die 226
reaches 110F (49C). This is sufficient to maintain enough
heat in the plastic sheet 236 to make it amenable to shaping by
the roller die 226 and 228. Thus, the sheet 236 is pliable
enough to be reshaped into the desired geometry.
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One specific use of the apparatus and method for shaping
the edges of thermcplastic material sheets is in manufacture of
advanced air cargo containers. It is desirable that the side
panels of air cargo containers be light, yet strong enough to
withstand rough handling and other abuses. Polycarb~nate
material, such as polycarbonate produced by General Electric
Company, meets this requirement. In one specific type of air
cargo container, the geometry required for the edges of the side
panel skins consists of a series of corrugations. The radius of
curvature is typically the thickness of the sheet material. In
the case of polycarbonate, cold forming techniques are not
recommended where the radius of curvature is less than 100 times
the thickness of the sheet material. If the radius of curvature
is less/ stress crazing can result.
In particular, it has been found that a collection of
infra-red heat lamps, positioned in a shroud assembly about 14
inches from the top roller die, was sufficient to raise the
temperature of the top roller die to 110~F ~49C~. In
particular, when a sheet of l/16th inch thick of polycarbonate
is introduced into the shaping means containing the roller dies,
above which the heating assembly described hereinbefore is
mounted 14 inches away from the initial top roller dies, the
complicated geometry required for side panels of air cargo
containers can be shaped-formed into the edges of the sheet.
A most important feature of this invention is the joint as
used with the particular polycarbonite material~ The joint is a
continuous joint so that every piece of the joint is providing
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strength. When there is a riveted or bolted or any mechanical
joint, the strength is provided by the rivet, and if the rivets
are at half-inch, one inch, two inch, or whatever pitch that
they are, the strength is only provided at those points and
pitches. If high strength is desired, a very high number of
fixings, rivets, bolts, or whatever have to be employed. ~or
the present container with the polycarbonate panel, tests have
shown tha~ loads of 500 lbs. per inch were obtained. The area
of the joint or the linear length of the joint on top of the
present container is 160 inches plus 120 inches which gives
approximately 280 inches and, at 500 lbs. per inch, it gives the
staggering load of approximately 150lO00 lbs. Without use of
the herein described joint, it would need probably a treble line
of rivets every half inch to approach the load which is obtained
from this joint. The cost of doing that would be prohibitive,
The added weight would be prohibitive. The maintenance costs
would be prohibitive. With the present design, one man with a
power screwdriver can remove or replace a panel in five minutes.
Thus, a massively high level of strength equal to the tensile
strength of these polycarbonate sheets is achieved, coupled with
ease of assembly and disassembly are achieved.
Another feature of this design is that the joint creates
its own hollow section which provides greater stiffness of the
frame. In either of these materials, aluminum or polycarbonate,
the container structure produces a diaphragm effect as with
drums where the skin of the drum is in tension against a strong
outside periphery. There is still flexibility so that, when it
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receives a blow, it absorbs a tremendous amount of energy
before breaking. The strong frame is achieved by way of
the extrusions ~inner and outer corner molding strips3
which are made stronger because the clamping extrusion
forms a hollow section as two independent clamping
extrusions come together to form a hollow extrusion, which
means that the stiffness of the frame is very much greater
than it would otherwise be.
The joint that has been disclosed herein enables
polycarbonate panels to be used. Polycarbonate has been
around for many years, but it has never been able to be
used in this application, because the only way of fixing
it to any box is by way of fixing it by rivets, or
whatever, which would inevitably fail due to stress
corrosion. As noted, there are no holes in the instant
design; therefore, the disclosed joints make polycarbonate
useable and it cannot be used without this type of joint.
Referring to FIG. 3, in the preferred form the two inner
legs of the capping extrusion have small b~ads 23. The
small beads fit into the recesses marked 39 on the
structural extrusion by driving past rims 21 which go back
to the position shown in FIG. 3 once the beads have passed
by. ~hen these two beads are connected and home, the two
extrusions become as if they were one integral extrusion.
The force required to make them and to disengage them is
very, very significant.
The jackbolt, which is item 108 (FIG. 3), is the
means of forceably removing the capping extrusion (outer
corner molding strip) from the structural extrusion (outer
corner molding strip). When these two legs 23 are
connected to the structural extrusion, the capping is
fixed and the fixing joint, which is shown on the panel,
is sufficient to prevent the panel from coming out. It
should be noted that the grooves are deep. It therefore
means that if the snap-fit is to pull out, the leg 23 must
bend. And when the leg bends, it comes into the side and
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the more it comes into the side the more it jams. The
same eff~ct is experienced on the insicle area about the
number 39. So this becomes absolutely fixed because the
two legs are fixed in the center at 23, 39.
The bolts 34 themselves are not necessary from a
structural point of view. The bolts enable the capping to
be put on and taken off. It therefore, in effect,
produces a joint which requires no bolt for the purpose of
the joint. After pressure is put on by the bolt, the two
middle legs 23 bend inwards and as they get past the cam-
like rims 21, they spring back (as little as .020"), which
makes a firm snap and a permanent connection between the
capping and structural extrusions until forced apart, as
by the jackbolt 108 (Fig. 3).
Preferably, the outside capping leg fits into a
U-section. The yap in that U-section is preferably
designed to be no more than 1/16th of an inch. The
polycarbonate panel is preferably 1/16th of an inch
throughout (including its formed edges). The more load
that goes on the panel the more it tends to cram or jam
into the adjacent structural extrusion.
The invention described above is susceptible to
many variations, modifications and changes, all of which
are within the skill of the art. It should be understood
that all such variations, modifications and changes are
within the spirit and scope of the invention and the
appended claims. Similarly, it will be understood that it
is intended to cover all changes, modifications and
variations of the example of the invention herein
disclosed for the purpose of illustration which do not
constitute departures from the spirit and scope of the
invention.
