Note: Descriptions are shown in the official language in which they were submitted.
CA 02704239 2010-05-20
TANK FORMED FROM PANELS OF COMPOSITE MATERIAL
This invention relates to a tank formed from one or more panels of a
composite material.
This application relates to the panel disclosed and claimed in
Application Serial No: 12/355,827 filed January 19, 2009 which corresponds to
Canadian application 2,639,673 filed October 22nd, 2008. The panel used herein
can be of the type disclosed in the above application or other composite
panels can
be used.
BACKGROUND OF THE INVENTION
A number of prior proposals have been made for manufacturing a
composite core panel formed from a honeycomb panel formed with tubular cells
at
right angles to the panel where the panel is filled with a reinforcing foam
extending
through the cells so as to provide an enhanced compression strength of the
core in a
direction longitudinally of the cells. This strength is commonly significantly
greater
than the compression strength of the core and the foam separately. The core
panel
is then covered on top and bottom by reinforcing sheets of a fibrous
reinforcing
material which are then resin filled by a resin impregnation process, for
example
infusion, so as to attach the top and bottom sheets to the foam and honeycomb
core
panel. The compression strength of the core panel has a direct relationship to
the
shear strength of the finished panel so that it has been desirable to maximize
this
compression strength. Such panels have become widely used for many products.
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The materials commonly used for the honeycomb panel are phenolic
paper, aluminum and various types of plastic materials. The selection is made
in
part dependant on cost relative to the desired strength with the aluminum of
course
providing the highest strength at the highest cost. Phenolic paper is the
simplest
and cheapest option and is very widely used. The honeycomb, in many cases, is
formed by bonding strips side by side with the tubular cells formed around
rods or
simply by stretching the bonded strips longitudinally of the panel to open
them up.
Adhesive and heat sealing can be used for attaching the strips.
However there is always an ongoing requirement for yet further
increasing the strength of such panels to enable additional markets to be
entered or
for strength requirements to be met with a thinner panel of less material.
SUMMARY OF THE INVENTION
It is one object of the invention to provide a tank manufactured from
composite panels.
According to one aspect of the invention there is provided a tank
comprising:
a tank wall formed at least in part by at least one panel member;
the panel member comprising a honeycomb core panel having a first
face and a second opposite face with an array of generally hexagonal tubular
cells
defined by walls of the core panel extending between the first and second
faces;
a foam material filling the tubular cells;
a first fibrous reinforcing cover sheet extending over the first face of the
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core panel;
a second fibrous reinforcing cover sheet extending over the second
face of the core panel;
the first and second cover sheets being filled with a set resin material;
wherein the walls of the honey comb core panel are formed from a
porous fibrous material;
and wherein the set resin in the cover sheets extends from the cover
sheets into the porous fibrous material of the walls of the core panel so as
to form an
integral structure of the resin extending between the walls and the sheets.
In one arrangement the tank may be rectangular. In this case the tank
is formed from a plurality of panels arranged edge to edge.
The panel members can be connected edge to edge by an adhesive or
by channel members into which an edge of the panel is inserted.
In another arrangement the tank may have a cylindrical wall and at
least one circular end wall.
In this case the circular end wall can be formed of a single panel
member and the cylindrical wall is formed of one or more curved panel members.
Thus the cylindrical wall can be formed of a single peripheral panel
member with the first cover sheet defining an inner surface of the tank and
the
second cover sheet defining an outer surface of the tank.
Preferably the walls of the honey comb core panel are formed from a
porous fibrous material and the set resin in the cover sheets extends from the
cover
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sheets into the porous fibrous material of the walls of the core panel so as
to form an
integral structure of the resin extending between the walls and the sheets.
Preferably the resin substantially fills the material of the core walls and
preferably the resin extends through the core walls from the first sheet to
the second
sheet. However the first intention is that the resin acts firstly to form an
integral
connection between the layer defined by the face sheets and the core walls so
as to
provide and increased resistance to shear forces tending to delaminate the
structure
at the junction between the sheet and the core. Hence, it will be appreciated
that, in
order to achieve this requirement, the resin may not extend fully through the
structure to form the tubular reinforcement. Thus other resins can be used in
the
core material provided they do not interfere with the formation of the
integral
connection.
Secondly the intention is that the resin forms an increased
compression resistance in the core panel by forming a series of resin
reinforced
tubes through the panel at the walls. Hence, it will be appreciated that, in
order to
achieve this requirement, the resin may not extend fully into each and every
pore or
space in the walls but the resin will extend into the structure sufficiently
to form the
integral connection at the sheets and the tubular reinforcement extending
through
the panel.
It will be appreciated that the walls generally do not contain any
existing resin filling material when the resin introduction occurs since this
will prevent
or inhibit the penetration of the resin into the walls and the formation of
the tubular
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CA 02704239 2010-05-20
structures through the panel and the integral connection to the sheets.
However the
walls may contain some reinforcing resin provided it does not prevent the
formation
of the integral connection.
Preferably the resin is a thermosetting resin such as thermosetting
5 polyester. However other types of resin can be used such as polyurethane or
epoxy, vinyl ester, phenolic resin.
Preferably the walls are connected each to the next to form the
honeycomb panel by a heat seal. This is preferred as the heat seals are less
likely
to interfere with the entry of the resin during the resin introduction process
and are
easier to effect and less expensive. However adhesive connection may be used.
Preferably the walls are formed from a non-woven fibrous material
such as a spun bond fibrous plastics material. However the material selected
can
be of any construction provided it is porous so as to allow the penetration of
the
resin during the resin introduction step. Thus of course aluminum and plastics
film
cannot be used. The material should also bond to the foam during the foam
filling
step. The compressive strength of the material in the honeycomb construction
is of
less importance and can be quite low in comparison with other materials, such
as
those conventionally used, provided it is sufficient to allow the foam filling
step to
occur.
Preferably the sheets contain glass reinforcing fibers as these are
inexpensive and are known to provide the required strength characteristics.
However other reinforcing fibers can be used.
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While the term "honeycomb" is used generally and in this document it
will be appreciated that the tubular cells formed are generally not accurately
hexagonal in cross section, particularly where, as described herein, the cells
are
formed from a porous fibrous material without reinforcing resin available
during the
filling process to maintain a regular shape of the cells.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be described in conjunction
with the accompanying drawings in which:
Figure 1 is horizontal cross sectional view through a panel to be used
in the present invention.
Figure 2 is a vertical cross sectional view through the panel of Figure
1.
Figure 3 is an isometric view of a tank according to the present
invenion.
Figure 4 is a cross sectional view through one edge of the tank of
Figure 3.
Figure 4A is a cross sectional view through one edge of an alternative
arrangement of the tank of Figure 3.
Figure 5 is an isometric view of a second tank according to the present
invention.
DETAILED DESCRIPTION
The composite panel described in general above is shown in Figure 1
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and 2 and is formed by a honeycomb core panel 10 having a first face 11 and a
second opposite face 12 with an array of generally hexagonal tubular cells
defined
by walls 10A of the core panel extending between the first and second faces.
The
cells are formed from strips 15, 16 arranged side by side of a porous fibrous
material
which is heat sealed at a sealing line 14 to define the generally hexagonal
cells.
A foam material such as a polyurethane foam 18 fills the tubular cells.
A first fibrous reinforcing cover sheet such as a fiberglass mat (or
carbon fiber, aramid fiber, Kevlar fiber, polyester fiber, natural fiber --
e.g. hemp, flax,
straw) 19 extends over the first face 11 of the core panel and a second
fibrous
reinforcing cover sheet 20 extends over the second face of the core panel.
The first and second cover sheets are filled with a set resin material 21
which extends from the cover sheets 19, 20 into the porous fibrous material of
the
walls 15, 16 of the core panel so as to form an integral structure of the
resin
extending between the walls and the sheets.
In Figures 3 and 4 is shown a tank 10 which is rectangular and is
formed from a plurality of panels 11 to 14 arranged edge to edge. In the
example
shown, each side wall 11 to 14 is formed of a single panel, but in other
examples
(not shown) each side wall can be formed of a plurality of panels arranged in
rows or
arranged in rows and columns. The bottom panel 15 is also a single panel as
shown
but again more panels can be provided depending on dimensions.
The panel members are connected edge to edge by channel members
16 into which an edge of the panel is inserted. The channel members can be
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arranged at 90 degrees as shown in Figure 4 or can be at 180 degrees or at
other
angles as required.
As an alternative arrangement shown in Figure 4A, a corner is formed
by constructing the tank as an integral member without use of a separate
channel
member 16. In this arrangement the corner is formed by two portions of the
honey
comb material indicated at 30 and 30A where the portion 30 butts against the
side of
the portion 30A at its edge and the sheets 20 and 21 wrap around the corner so
that
the sheets form an integral structure at the corner. Thus the sheet 21 wraps
around
the outside surface of the honeycomb portions and the sheet 20 forms an inside
surface. The fact that the resin drawn through the structure integrates the
honeycomb and the sheets allows sufficient tensile strength to prevent
fracture at
the corner. Thus the joints between the honeycomb core panels 30 and 30A are
formed with the first and second cover sheets bridging the joints. These
joints can
lie in a common plane where necessary. However, also at corners which can be
at
right angles or at another angle different from 90 degrees, the joints between
the
honeycomb core panels are formed at an angle to one another so as to form a
corner of the tank with the first and second cover sheets bridging the joints.
In Figure 5, the tank has a cylindrical wall 18 and at least one circular
end wall 19.
The panel members are connected edge to edge by an adhesive layer
20. The circular end wall is formed of a single panel member and the
cylindrical wall
is formed of a cylindrical one or more curved panel members.
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Thus the cylindrical wall is formed of a single peripheral panel member
with the first cover sheet defining an inner surface of the tank and the
second cover
sheet defining an outer surface of the tank. In the alternative the tank can
be formed
from flat panels arranged as a polygonal arrangement.
Thus the circular end wall is formed of a single panel member.
The curved panels can be formed using the honeycomb as previously
described where the honeycomb material is laid into a mold and the
polyurethane
foam injected while the honeycomb is in the required shape. The inner and
outer
sheets are then applied and the resin introduced into the sheets and the walls
of the
honeycomb by a resin infusion system while the panel is shaped in its required
shape. The honeycomb material is shapable into required shapes by curving the
sheet so that the top and bottom surfaces curve to the required shape without
distorting the tubes.
Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
within the spirit and scope of the claims without department from such spirit
and
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
