Note: Descriptions are shown in the official language in which they were submitted.
CA 02409852 2008-06-12
PALLET CONTAINER
[0001] The invention relates to a pallet container having a thin-walled inner
receptacle made from thermoplastic material for the storage and transport of
fluid
or free-flowing goods, wherein the plastic container is closely surrounded by
an
outer cage jacket as a supporting casing of crossed pipe bars and a bottom
pallet
on which the thermoplastic receptacle is supported and which is firmly
connected
to the supporting casing.
Prior Art
[0002] Such pallet containers that have a welded pipe bar supporting casing
are generally known, as for example in EP 0 734 967 A (Sch). The pipe bar
supporting casing of the pallet container disclosed there consists of pipe
bars
having a circular profile, that are highly compressed at the welded
intersection
points. From EP 07 55 863 (F) another pallet container is known with pipe bars
having a square profiled cross section, that are partially slightly (each
about 1 mm)
compressed at four contact points only in the areas of intersections to
facilitate a
better welding action, while otherwise, along their entire length retaining a
cross
section without any indentations, respectively any cross section-reducing
dents
whatsoever. A further pallet container is known for example from the DE 196 42
242 A, with a cage that has an open trapezoid shaped pipe bars. There,
straight
surfaces laterally flanged outwards are welded together in the area where the
bars
intersect. The attachment of the cage jacket at the bottom pallet, which may
be
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CA 02409852 2002-11-22
configured as flat pallet from plastic or wood or as a steel tube frame, is
usually
realized by attachment means as for example, screws, brackets, clamps or grips
that engage with the lower horizontal and circumferentially extending cage
bars.
These attachment means are either nailed, riveted, screwed or welded to the
upper plate or the upper outer edge of the pallet.
[0003] For industrial use or when the pallet containers are utilized in the
chemical industry, they have to pass a governmental approval inspection and
fuffiN
various quality controls. For example, the filled pallet containers have to
undergo
interior pressure tests and drop tests from specific heights. Pallet
containers or
combination -IBCs (IBC=lntermediate Bulk Container) of the type discussed here
-with a filling volume of usually 1000 liters-, are preferably used in the
transport of
liquids. Particularly when transporting filled combination-lBCs by truck,
considerable gushing motions of the fluid container load occur that are due to
transport shocks and the movement of the transport vehicle- particularly, on
bumpy roads, thereby exerting constantly changing pressure forces on the
interior
receptacle walls which in turn lead to radial vibrational motion of the cage
jacket
(dynamic continuous vibrational stress). Depending on the configuration of the
cage jacket during long transports over bad roads, stress builds up so that
the
cage bars fatigue and break. Consequently, such pallet containers are not
suitable, for example for export to the USA, or for multiple usage.
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[0004] The drawbacks of the embodiment in the afore-described EP 0 734
967 A are such, that the circular pipe profile of the horizontal and vertical
cage
pipe bars, particularly in the area of the intersections, are prone to
considerable
deformation, specifically at the side of the welding points and thus exhibits
a
markedly reduced section modulus as compared to the other areas. The welding
of the pipe bars causes material brittleness precisely in the area of the
dented pipe
bar profile. Additionally, the pipe bar profile is still deeper indented next
to the
indentations for the welding points and thus, further weakened.
[00051 It is an object of the present invention to obviate the afore-described
drawbacks and to propose a pallet container with improved transport strength
that
provides a cage jacket with improved resistance against transport stress
respectively, against the long-term vibrational motion stress. The pallet
container
should thus be suitable for transporting dangerous fluids or free-flowing
loading
goods up to the class 6 (= highest standard of admissions quality).
Solution
[0006] In accordance with the invention, this object is attained by providing
a
pallet container with a cage jacket of vertical and horizontal steel pipe bars
wherein the vertical and/or horizontal steel pipe bars lack any indentations,
or are
only very slightly indented at the contact plane in the area of the
intersecting bars
(wherein such a slight indentation in one of the bars is equal or less than
twice the
thickness of the width of the pipe bar, in concrete terms, about 2mm or less),
and
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CA 02409852 2008-06-12
each of the pipe bars have at least one indentation laterally next to the
intersection, respectively the welding point - a wanted bending point - each
of
which is located at a distance of about'one tenth of the pipe bar width (B)
from the
welding point. When the wanted bending points are transferred to a certain
distance away from the critical welding points to accommodate the varying
bending stresses, resulting from vibrations of the cage jacket, the continuous
bending stresses no longer occur at the brittle and thus critical welding
points, but
mainly only on the comparatively noncritical bars themselves, that is, at
points of
considerably higher bending elasticity and not directly at the stiffened
intersections. In order to improve the bending elasticity of the vertical
or/and
horizontal pipe bars, they can be kept indentations-free at the side opposite
the
contact plane in the area of the intersection, and each of the pipe bars can
be
provided with at least one indentation laterally next to the intersection,
that is, on
the other side of the welding points, as a wanted bending point, each of which
can
also be at a distance of at least one tenth of the pipe bar width (B).
One embodiment of the present invention provides a pallet container,
comprising:
a bottom pallet;
a thin-wailed rigid thermoplastic receptacle for storage and transport of a
liquid or
flowable contents; and
a cage jacket closely surrounding the thermoplastic receptacle and securely
connected with the bottom pallet; wherein the cage jacket includes horizontal
and
vertical hollow bars welded together in a contact area at points of
intersection,
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wherein the hollow bars are provided laterally next to each point of
intersection with
at least one dimple which is spaced from the point of intersection at a
distance of
about one tenth of a width of the hollow bar, and wherein the at least one
dimple is
located on a side of the bar opposite a plane of the contact area.
[0007] An excellent bending elasticity of the cage jacket is realized, when
the
vertical or horizontal pipe bars between two intersections, at the side of the
welding points, respectively at the contact plane or/and at the side opposite
the
contact plane, are provided with at least two indentations.
[0008] It is very advantageous to provide each of the vertical or/and
horizontal pipe bars at the side of the welding points between two
intersections, at
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their contact plane and the side opposite the side of the contact plane, with
at least
one indentation, such that the indentations are located precisely opposite
each
other and wherein the indentations are located at a distance from the
intersection
of at least one tenth of the pipe bar widths (B). Thereby, the neutral phase
of the
bending stress is located well in the middle of the pipe bar.
[0009] According to one feature of the invention, the depth (T) of one
indentation for reducing the height of the profile (H) is kept possibly small,
that is,
between about 15% and 50%, preferably about 33% of the height of the profile
(H). The longitudinal extension of an indentation - in longitudinal direction -
should
be in the range of one and one half times to three times of the profile width
(B),
preferably about twice the profile width (B). As a compromise, while least
weakening the flexural strength, a sufficiently high bending elasticity in the
wanted
bending points, respectively the indentations, is thereby realized.
[0010] Since the intensity of the vibrational stress which occurs in the cage
jacket of a pallet container filled with fluid varies, the indentations in
each of the
horizontal or/and vertical pipe bars can be formed with varying depth in
dependence of the intensity of the occurring vibrational stress in the various
areas
of the cage jacket or/and in the horizontal and vertical pipe bars.
[0011] In a preferred embodiment, the vertical or/and horizontal pipe bars are
provided with a very specific pipe profile, that is, a closed profile having a
CA 02409852 2002-11-22
trapezoid shaped cross section with longer and shorter parallel extending side
walls and two straight side walls which extend obliquely relative to one
another,
and which, starting from the longer of the parallel side walls extend
obliquely
towards each other, connect to the shorter wall, and wherein the two straight
side
walls that are extending obliquely relative to each other form a crown angle
of
approximately 200 to 45 , preferably about 36 . The trapezoid shaped closed
profile of the pipe bar has a high bending section modulus and a high torsion-
section modulus due to the profile sidewalls being positioned relative to each
other
in a slightly oblique manner. This is realized particularly when the height to
width
(H/B) ratio of the trapezoid shaped tube profile is in the range of 0.8 to
1.0,
preferably about 0.86. In one embodiment of the invention, the longer parallel
side
wa!l of the pipe bar with the trapezoid shaped profile, partially in the area
the
intersection of two pipe bars, is indented inwardly along a length of
approximately
two width of a pipe profile in such a manner, that at each of the two outer
longitudinal edges they form an outward curvature (bulging), so that four
points are
formed at each intersection of the vertically and horizontally extending cage
bars
that are firmly joined after welding, whereby in each of the cage bar
intersections
the (longer) parallel walls facing each other are not in contact with each
other even
after being welded.
[0012] In a preferred embodiment, the longer of the parallel walls of the cage
bar with a trapezoid shaped profile is indented inwardly along its entire
length (=
continuous longitudinal indenting or profiling), such that the two outer
longitudinal
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CA 02409852 2002-11-22
edges are formed with an outwardly extending curvature (bulging), wherein at
each intersection of the horizontally and vertically extending cage bars four
contact
point are formed, which are firmly connected after being welded so that the
(longer) opposing parallel walls are at a distance from each other even after
being
welded and without contacting each other. In prototypes, the trapezoid shaped
cage bars, which are indented along their entire length have proven especially
outstanding in their use.
[0013] In a variation of the embodiment, the longer parallel wall of the
trapezoid profiled pipe bar may be inwardly indented only partially in the
area of an
intersection and the longer parallel wall of the other trapezoid shaped pipe
bar
inwardly indented along the entire length. This may prove already entirely
adequate for the average stress load.
[0014] The depth of the profiling indentation of the longer parallel wall is
about twice that of the wall thickness of the profiled pipe bar; in an actual
pallet
container, the profiled pipe bar wall thickness is 1 mm and the depth A of the
indentation is also 1 mm, so that after welding - whereby the contact points
of the
crossed cage bars melt into each other by about 1 mm - it is assured that at
each
intersection, the long parallel walls facing each other are spaced apart from
each
other by about 1 mm and are not in contact with each other, even after
welding.
This is particularly important because oftentimes pallet containers are stored
outdoors and are thus exposed to the elements of weather. By providing a
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CA 02409852 2002-11-22
distance between the cage bars at the points of welding, accumulating rain
water
can easily dry off and formation of rust is thereby substantially prevented.
If the
welding surfaces were in contact, the formation of rust would be unavoidable
leading to extensive rusting of the cage bars within a short time.
[0015] It is a special feature of the invention, that the pipe bar profile-as
compared to the known pipe bar profiles- is not partially indented at the
welding
points, but is provided with corresponding dents, respectively indentations at
a
certain distance next to the welding points at the same side or/and at the
opposite
side of the profile, in order to realize a reduced bending section modulus
relative to
the intersecting points, and to relieve the welding points of the cage bars of
static
and/or dynamic stress. The preferred trapezoid profile is configured such that
it
can be indented easily and without extensive material displacement. Only
specific
regions of the cage pipe bars (= indentation, respectively denting, as desired
formation of "vibration elements") are indented, whereby relief against
vibrational
stress and the fluctuating flexural tension peaks on the welded intersection
or the
four welding points is realized. When welding one pipe bar together with a
second
pipe bar, stiffening of the pipe with an attending material brittleness
results at that
location making the pipe bar particularly sensitive to vibrational stress at
that point.
Considerable vibrational stress, which is present, for example, during
transport by
truck can lead in the shortest time to breaking of the welding points or the
pipe bar
itself at the welding points.
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[0016] In accordance with the invention, the desired "wanted vibration points"
in the cage jacket-support casing are not provided precisely at the
intersecting
points or in the proximate zone thereof, but at least a short distance from
the
welding points of the intersection. The wanted vibration points, which are
provided
by forming the indentations, are in any event less than 50% of the cross
section of
the pipe bar. They are arranged in the range of 10 % to 45% of the height of
the
pipe bar cross section, preferably about 1/3 (33%). The flexural strength of
the
indented pipe bars is thereby somewhat reduced, but the proneness to fractures
due to fatigue is considerably reduced.
[0017] The invention is explained and described in greater detail hereinafter
with reference to embodiments, which are illustrated in the drawings. It is
shown
in:
[0018] FIG. 1 a front view of a pallet container according to the
invention;
[0019] FIG. 2 a side view of a testing-pallet container;
[0020] FIG. 3 an sectional illustration on an enlarged scale of the
trapezoid shaped pipe bar profile according to the invention at a pipe bar
intersecting point;
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CA 02409852 2002-11-22
10021] FIG. 4 a further sectional illustration on an enlarged scale of a
preferred trapezoid shaped pipe profile at a pipe bar intersecting point;
[0022] FIG. 5 a schematic sectional illustration of a hydro-dynamic
pressure effect of a fluid load on the container side- wall;
[0023] FIG. 6 a horizontal partial sectional illustration of a point of
greatest outward deflection of the cage;
[0024] FIG. 7 an enlarged illustration of an intersection of pipe bars
with indentations;
[0025] FIG. 8 a trapezoid shaped cross section of a pipe bar
according to view D of FIG. 7;
[0026] FIG. 9a an indentation of a trapezoid shaped cross section of a
pipe bar (narrow side) C-C;
[0027] FIG. 9b an indentation of a trapezoid shaped cross section of a
pipe bar (broad side) C-C;
[0028] FIG. 10 a square shaped profile of a cross section of a pipe bar
- unstressed;
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[0029] FIG. 11 the square shaped profile of a cross section of a pipe
bar according to FIG. 10- stressed-overstressed;
[0030] FIG. 12 a profile of a pipe bar according to the invention -
unstressed;
[0031] FIG. 13 the profile of a pipe bar according to the invention
according to FIG. 12 - stressed;
[0032] FIG. 14 another pipe bar profile according to the invention with
two indentations;
[0033] FIG. 15 a further pipe bar profile according to the invention with
four indentations;
[0034] FIG. 16 a partial top view of a comer arc of the pipe profile
according to the invention;
[0035] FIG. 17 a square shaped pipe bar profile with two indentations;
[0036] FIG. 18 another square shaped pipe bar profile with two-four
indentations;
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[0037] F1G.19 a circular cross section of a pipe bar with two
indentations;
[0038] F1G.20 an open trapezoid shaped pipe bar profile with two
indentations; and
[0039] FIG. 21 a further circular cross section of a pipe bar with two-
indentations.
[0040] In Figure 1 referenced with numeral 10, is a pallet container according
to the invention which shows a thin-walled blow-molded rigid inner receptacle
12
made of thermoplastic material (HD-PE) with an upper input opening and a cage
of intersected pipe bars 14 closely enveloping the inner receptacle, and which
is
firmly but detachably or interchangeably connected to the bottom pallet 16.
The
front view as depicted exhibits the narrow side of the pallet container 10
with an
exit valve disposed at the plastic receptacle 12 near the bottom. The lower
front
edge of bottom pallet 16, here shown in configuration as a wooden pallet (US
Runner), with the exit valve situated above, represents the most vunerable
point of the pallet container, which is exposed to the greatest stress during
approval testing, especially during the diagonal drop test. The special
configuration of the cage bars with indentations (cf. Fig. 7) are shown in the
circles.
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[0041] Prior to the development of the pallet container according to the
invention, five different pallet containers known and available on the market
were
submitted to the precise comparative stress tests (interior pressure test,
drop
tests, vibration tests, test for pressure capacity upset, respectively testing
stacking
capacity). In serial vibration tests during simulation of long haul truck
transport on
bad roads, certain particularly frequently occurring weak points in various
cage
jackets could be isolated.
[0042] The test pallet container 10 (here shown without the elasticity
promoting indentations) shown in Figure 2, which for testing purposes was also
deliberately submitted to continuous overload testing, is shown with circles
drawn
to illustrate those points marked at the horizontal and vertical cage bars,
which fail
and begin to break first according to the comparative testing results during
dynamic vibration stress, (cf. FIG. 10, 11).
[0043] Figure 3 shows an area of intersection of a closed pipe bar profile 18
having a trapezoid shaped cross section in accordance with the invention, a
longer
wall and a shorter wall extending parallel to each other 20, 22 and the two
straight
walls 24 extending obliquely relative to each other, and beginning from the
longer
parallel wall 22 they extend obliquely and connect to the shorter wall 20,
whereby
the two straight side walls of profile 18 which extend obliquely relative to
each
other form a crown angle 26 in the range of 20 to 45 , preferably about 36 .
The
ratio of height to width of the trapezoid shaped profile of the pipe bar is in
the
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range from 0.8 to 1.0, - preferably about 0.86. Due to the relatively great
height of
the trapezoid shaped profile (without dents in the oblique side walls) a
correspondingly high flexural stiffness is realized, and due to the closed and
compact configuration of the trapezoid shaped profile, the pipe bars exhibit
an
improved torsional stiffness as compared to pipe bar profiles that are
configured
with a circular profile or those having an open profile. The distance of the
intersection of the extended horizontal axis of the walls 24 extending
obliquely
relative to each other at crown angle 26 is about the height H of the profile
or,
measured beginning from the longer parallel wall 20 is about 2H. The distance
can
be in the range of 0.75 and 2.5 H.
[0044] The trapezoid shaped profile 18, preferably utilized is depicted in
Figure 4. In a simple embodiment, the longer parallel wall 22 is only
partially
inwardly dented in the area of the intersection of two pipe bars in such a
manner
that at each of the two outer longitudinal edges a curvature 28 (bulge) is
formed
that bulges outwardly, so that at each intersection of the horizontally and
vertically
extending pipe bars, four contact points are formed, which after being welded,
are
firmly connected to each other, whereby the longer parallel walls 22 in each
pipe
bar intersection are still spaced apart from each other without any contact
even
after welding.
[0045] In an especially preferred embodiment, the longer parallel wall 22 is
dented inwardly along the entire length of the pipe bars, wherein the two
outer
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longitudinal edges are provided with an outwardly bulging curvature 28. The
pipe
bar having the indented trapezoid shaped profile 18 has proven outstanding and
is
being manufactured from a circular pipe template having a diameter of 18mm
(56.
55mm in circumference). The depth of indentation of the longitudinal profile
should
be about once or twice that of the wall thickness of the pipe bar (about 1 mm
to
2mm); in a fully formed pallet container the wall thickness of the pipe bar is
1 mm
and the depth of the indentation 1 mm. The welding at each of the four contact
points at each intersection of the pipe bars is carried out by means of
electrical
resistance pressure welding. When carrying out the four-point welding, the
crossing cage bars. are being pressed together about 1 mm, so that the
opposing
parallel walls 22 in each intersection are still distanced from each other by
about
0.5 mm to 2mm, preferably, about 1 mm and are not in contact with each other
even after being welded. (distance A= 1 mm). This is a particularly important
aspect, since pallet containers oftentimes are stored outdoors and are exposed
to
the weather. By distancing the cage bars from each other at the welding
points,
rain water which might accumulate there dries off by exposure to air and thus,
rusting is substantially prevented. Welding surfaces that are abutting each
other
are inevitably prone to formation of rust, which can lead to heavy rusting of
the
entire cage in the shortest time. Illustration of the cross section also
clearly shows
that the width of the (longer) parallel wall 22 that remains between the
outwardly
bulging edges 28 is approximately the same as the width B1 of the opposite
(shorter) parallel wall 20.
CA 02409852 2002-11-22
[0046] In Figure 5, the schematic representation of the changing deforming
deflection of the cage jacket due to dynamic vibrational stress is
illustrated. The
hydrostatic interior pressure of the fluid goods load - illustrated in the
right hand
side, causes the maximal cage deflection Da, Di occurring approximately at the
level of the center of gravity S of the loaded goods, which means at about 33%
of
the cage height, and at that level the vibration amplitude toward the outside
is
approximately two times that of the inside, which is the reason the greatest
danger
of crack formation in the cage pipe bars during vibrational stress is in the
area of
the lower half of the cage.
[0047] The schematic representation of a partial sectional view in Figure. 6
illustrates the horizontal cross section at the location of the maximal
deformation
effect D. and D. There is no interference of vibrational deflection directed
towards
the outside, while inside the fluid column encounters the opposite side wall.
The
lower circumferential horizontal cage bars 30 are thus submitted to great
bending
stresses particularly in the vicinity of the corner bends 38.
[0048] Figure 7 shows - in an interior view of the cage - the intersection 36
of a horizontal pipe bar 30 with that of a vertical pipe bar 32. In the
intersection 36,
the four welding points are indicated. The trapezoid shaped pipe profile of
horizontal bar 30 and that of the vertical bar 32 is provided each with one
indentation 34 at each side exactly next to the intersection 36, respectively
the four
welding points, wherein the indentations 34 are distanced to the point of
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CA 02409852 2002-11-22
intersection 36 by at least one tenth of the pipe bar width B. View D of the
non-
deformed trapezoid shaped profile 18 is shown in Figure 8 and a sectional
illustration of the indentation 34 along the line C-C is shown in Figure 9b.
The
indentations 34 in the pipe bar can be made on the side of the ("longer")
parallel
wall 22 (Fig. 9b) or/and on the side of the opposing ("shorter") parallel wall
20
according to Figure 9a. Numerous variations may thereby be realized, so that
between two cage bar intersections at least two indentations may be provided
at
the outer side of the trapezoid shaped profile or/and two indentations may
also be
provided at the inner side. It is however significant that the pipe bars in
these
embodiments are not indented or deformed directly at the point of intersection
or
respectively at the welding points, but only next to them.
[0049] When reducing the height H of the profile, the depth T of one
indentation 34 should be kept low if possible, i. e. in the range of 15% and
50%; in
a preferred embodiment, the depth T of the indentation is about 33% of the
height
H of the profile. The longitudinal extension of indentation 34 along the bar
should
be in the range of about one and one half to three times the width B of the
profile,
and in a preferred embodiment, the longitudinal extension of an indentation 34
is
about twice that of the profile width B.
[0050] Figure 10 shows an unstressed pipe profile of the known type having a
square shaped profile along the entire length of the bar. Already after a
relatively
short period of dynamic vibrational stress, formation of a crack is seen on
the
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CA 02409852 2002-11-22
horizontal bar 30' directly at the intersection, respectively at the welding
points, as
is illustrated in FIG. 11.
[0051] The formation of cracks or respectively, the tearing of the cage bars
always occurs in the area of highest pull tensions, or at the location where
the
greatest bulging of the cage jacket occurs. The vertical pipe bars are
arranged at
the inside of the cage jacket and the horizontal pipe bars are arranged at the
outside. Cracks and fracture points always occur in the area of the
intersection
directly next to the welding points (cf. circled views in FIG. 2). Cracks
start forming
at the vertical pipe bars - and relative to the jacket always travel from the
outside
to the inside and always start on the inside of the horizontal bars travelling
to the
outside. In comparative tests, it has been found that the cage jackets made
from
cage bars with an open profile and provided with flat outwardly angled edges
exhibit good stacking capacity because the welding points are relatively far
part
from each other within the intersection, but they react most unfavorable to
vibrational stress.
[0052] As compared to the square shaped pipe profile, in Figure 12, a closed
trapezoid shaped pipe profile 18 in accordance with the invention, is shown
with
two indentations 34 in a horizontal bar 30. As illustrated in exaggerated
manner in
Figure 13, crack formation does not occur even after prolonged exposure to
vibrational stress. On the one hand, this is due to the intersecting area at
the
welding points lacking weakness-inducing indentations and therefore is very
18
CA 02409852 2002-11-22
stable, while on the other hand, the indentations 34 reduce the bending
section
modulus and function as a kind of "bending hinge" when located at least at a
small
distance from the intersection thereby acting to prevent the peak tensions
impacting upon the sensitive welding points and deflecting them towards more
distant flexible areas.
[0053] An indentation, which acts as a wanted bending point represents a
reduction in the height of the pipe bar profile H and serves as a stress
reduction
against the occurring vibrational stress at the sensitive welding points at
critical
stress peaks during changing bending stresses. Thus, during occurrence of the
dynamic vibrational stress, the critical tension peaks are shifted away from
the
welding points to adjacent areas at a distance thereto. By means of this
special
configuration, a substantial reduction in static or dynamic stress on the
welding
connections is realized by means of the indentations on the pipe bars, which
are
provided laterally next to the welding points and which reduce the peak-
stress, so
that the welding points are provided not in a deformation zone, thus retaining
their
high flexural strength.
[0054] The special problems in constructing a particular embodiment of a
cage jacket is that the vertical and horizontal cage bars should be as stable
and
rigid as possible in order to prevent excessive bulging of the pallet
container which
is, for example, exerted by interior pressure; and on the other hand, a high
bending section modulus should be provided to counteract constant dynamic
19
CA 02409852 2002-11-22
vibrational stress, wherein the two afore-mentioned criteria operate in
opposite
directions. While considering favorable, i.e. low production costs, an optimal
solution must be found. Thus, known pallet containers having cage bars with an
even profile along the length of bar, as for example according to DE 297 19
830
U 1, according to latest trends in the present invention, are not suitable as
containers for carrying dangerous fluid loads submitted to dynamic vibrational
stress; but may be suitable as storage containers, not as a transport
container
undergoing dynamic vibration stresses. The afore-cited patent publication is
based
on the prior art insofar as the known pallet container has a cage jacket made
from
pipes with a circular cross section that are provided with indentations at
least at
the welded pipe intersections. A statement on page 2 of that patent disclosure
which states "....by using a profiled pipe (there) according the invention
(without
any localized indentations) local tension accumulation is avoided...." does
not
correctly state the latest trends in the present invention and simply shows
that the
effect of the opposite connection between flexural strength and vibration
elasticity
have not been taken into account when such cage jackets of pallet containers
are
submitted to transport stress.
[0055] The depth T of the indentations 34 in the trapezoid shaped profile
according to the invention are approximately 25% and 50%, preferably
approximately 33% of the height H of the pipe bar profile. An indentation by
5mm
(=33%) is generally sufficient for a pipe having a height of 15mm, whereby the
vibrational stress at the welding points is either kept low or is eliminated
while
CA 02409852 2002-11-22
retaining a sufficiently high rigidity in the pipe. This rigidity is important
in order to
keep the vibration amplitude of the lateral bulging of the vibrating cage at a
low
level.
[0056] Figure 14 illustrates an embodiment having two indentations 34 at the
side of the pipe bar profile facing away from the welding points with the
short
parallel wall 20, and which - as is shown in Figure 15 - illustrates a
modified and
particularly useful variation of that embodiment. The trapezoid shaped pipe
profile
18 is provided with indentations 34, each at the side of the shorter parallel
wall 20
and on the side of the longer parallel wall 22 laterally next to an
intersection 36, so
that the indentations are exactly opposite each other. The indentations are
spaced
here at a distance of approximately one tenth of the width B of the pipe bar
profile
from the intersecting point 36. Placing the indentations 34 in each of the
parallel
extending side walls 20, 22, particularly enhances the "hinge effect" or the
elasticity of the pipe profile.
[0057] According to the technical teaching of the present invention, the
configuration of the indentations 34 in the horizontal and vertical pipe bars
30, 32
can be of different depth depending on the intensity of the dynamic stress
expected to bear on the cage jacket 14. Thus, in accordance with a specific
demand or need, while retaining sufficient flexural strength, the optimal
vibrational
elasticity in the horizontal and vertical pipe bars can be controlled in
various areas
21
CA 02409852 2002-11-22
of the cage jacket, for example in the longer side walls, or the shorter front
and
rear walls of the pallet container.
[0058] Figure 16 illustrates a further important embodiment for reducing the
bad effects of the dynamic vibrational stress of the horizontal pipe bars. In
the
region of the corner areas, bent 90 and parallel to the vertical, the
horizontal pipe
bars 30 of the cage jacket 14 are flattened, such that they also act as a
hinge-type
"bending joint". In the corner areas, the horizontal pipes need not possess a
high
bending resistance, of greater importance here is a higher elasticity.
Particularly
favorable test results were realized with pallet containers that have
horizontal pipe
bars 30 which are flattened in the corner areas 38 of support jacket 14 from
the
inside andlor from the outside by at least one fourth of the height H of the
diameter
of the profile 18. In one of the embodiments actually built, the horizontal
pipes in
the lower region of the cage jacket are flattened from the inside by about 20
% and
form the outer comer arch by about 35%, while of flattenings in the upper
region of
the cage jacket are configured so they are incrementally reduced.
[0059] In Figure 17 an intersection of two pipe bars with a special square
shaped profile 42 is depicted. There, the pipe walls are slightly indented
along the
entire length if the bar, so that at the intersection of the pipe bars a four-
point
contact is realized, by which the pipe bars are welded to each other. In
section
along plane C-C an indentation is shown. Figure 18 shows a similar pipe bar
profile 44 with a square shaped cross section of the vertical and horizontal
pipe
22
CA 02409852 2002-11-22
bars, wherein here, a partial indentation of one of the pipe walls was only
formed
in the area of the intersection such, that a four-point contact by which the
two
crossing pipe bars are welded to each other was likewise realized. Section
along
plane B-B also shows an indentations 34.
[0060] The vertical or/and horizontal pipe bars can have a closed profile with
a round, respectively circular cross section. Such a circular profile 46 with
an
indentation 34 along section line A-A is shown in Figure 19. In another
embodiment, the vertical and horizontal pipe bars can have an open profile
with a
trapezoid shaped cross section. Figure 20 illustrates such an open trapezoid
shaped profile 48 with an indentation 34 along section line D - D.
[0061] Finally, in Figure 21, a further circular pipe profile 50 is shown,
wherein
the crossing pipe bars are only partially indented in the area of the
intersection 52,
so that a preferred four point contact is realized by which the two pipe bars
are
welded to each other. Here, the wanted bending points, respectively the
indentations 34 are provided at the side opposite the welding point.
[0062] It is understood that the variations as shown can be combined in
various ways and that other combinations are also within the ambit of the
invention.
23
CA 02409852 2002-11-22
[0063] The above-presented possible variations, particularly the lower region
of the cage jacket can be provided with different means for realizing
sufficient
flexural strength with an optimal suitable pipe bar elasticity.
24
CA 02409852 2002-11-22
REFERENCE NUMERAL LIST
pallet container A distance (22-22)
12 inner receptacle HD-PE B width pipe profile
14 cage jacket Bi reduced width (22)
16 bottom pallet H height pipe profile
18 trapezoid profile S load-point of gravity
short parallel wall T depth indentation (34)
22 long parallel wall Da outer deformation
24 straight slanted wall Di inner deformation
26 crown angle
28 convexity (bulging)
horizontal bar
32 vertical bar
34 indentation (30, 32)
36 intersection (30, 32)
38 corner arc (30)
flattening (38)
42. square profile 1
44. square profile II
46 circular profile 1
48 open trapezoid profile
circular pipe bar profile II
52 intersection (50)
