Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02624994 2008-04-07
Title: INSULATED CONTAINER AND LINER
Field of Invention
This invention relates to the field of soft sided insulated containers. In
particular it relates to soft sided insulated containers having removable
impermeable
liners for discouraging or preventing the leakage of liquids.
Background of the Invention
In recent times soft sided insulated containers have become popular for
carrying
either articles that may best be served cool, such as beverages or salads, or
warm, such
as appetizers, hot dogs, and so on. Such containers are frequently used to
carry liquids,
whether hot liquids, such as soup containers, coffee or tea, or cold liquids
such as beer
pop, juices and milk. The containers are typically made in a generally cube
like shape,
whether of sides of equal length or not, having a base, four upstanding walls,
and a top.
The top is generally a lid which opens to permit articles to be placed in, or
retrieved
from, the container.
By the nature of their use, it is advantageous for the containers to be water
tight.
That is, whether to hold melted run-off from ice cubes or to hold spilled
liquids, the
container must be sufficiently liquid tight that it does not leave a trail of
drips, or
become moist or sticky to the touch of a person carrying the container.
The present inventor has found it disadvantageous to try to seal the container
itself. The type of insulating wall used by the present inventor is generally
sewn at its
seams. Sewn seams have a tendency to leak at the stitches. Another approach is
to fold
the insulated blanket from which the container is made, to present an assembly
that,
through folding, has no seams. This is also disadvantageous, in the present
inventor's
view, because the insulated blanket used to form the contairier walls is
relatively thick.
The thick material does not fold well, in the inventor's view. It would be
preferable to
form an impermeable layer that has a relatively thin wall thickness so that
the resulting
product does not look bulky and cumbersome.
It is also advantageous to be able to clean the inside of the insulated
container.
Spilt liquids may not always have the most attractive air when allowed to dry,
and may
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cause the inside of the container to become unsightly. It is possible to
provide a
plastic liner for soft sided insulated containers. A see through plastic liner
can be
made of the minimum amount of material by using only a single layer, and
forming
seams where the edges of the material meet. A common method of forming such a
seam is to weld two adjacent edges together by heating. However, an existing
liner of
this type is known to have had a tendency for the heat welded seams to develop
leaks
over time. It would be advantageous to reduce or eliminate the number of heat
welded
seams formed in areas of the liner that may need to be water tight.
In general, manufacture of an assembly of this type emphasizes cost reduction.
One common source of cost savings is a reduction of the raw material used.
However,
the present inventor has observed, counter-intuitively, that the overall
benefit an
increase in raw material use can outweigh the cost saving that would otherwise
be
achieved. Unexpectedly, the use of a greater amount of material in a folded
assembly
has been found to be advantageous, and has eliminated the need to have a heat
welding
station in manufacture.
Summary of the Invention
In an aspect of the invention there is a soft-sided insulated container, and a
removable liner for placement inside the container. The liner is folded from a
monolithic sheet of liner stock to define a chamber, capable of holding
liquids. The
liner is free of heat welded seams.
In another feature of that aspect of the invention the liner is made from a
water
impermeable plastic sheet. In an additional feature of that aspect of the
invention the
liner is made from a translucent static cling vinyl sheet. In another
additional feature of
that aspect of the invention the soft sided insulated container has a base,
sides and a
top. The liner has a base, sides for placement inside and adjacent to the base
and sides
of the container. The top of the container is moveable to an open position to
permit
articles to be placed in the chamber.
In still another additional feature of that aspect of the invention the
chamber has
an opening, the opening having a lip, and the liner is mated to the cooler
about the lip.
In yet another additional feature of that aspect of the invention the opening
has four
sides, the lip extends about the four sides opening and the liner is mated to
the
container on the four sides. In a further additional feature of that aspect of
the
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invention the liner has a rectangular base and four sides extending from the
base,
each of the sides having an edge adjoining the base and a distal edge distant
from the
base. The chamber has an opening defined between the distal edges of the
sides.
In a still further additional feature of that aspect of the invention one of
the sides
has a lid member extending therefrom, the lid member being moveable to close
the
opening of the liner. In yet another additional feature of that aspect of the
invention the
lid member is a flap formed integrally with the liner, the flap having four
lid edges, one
edge being a folded hinge edge adjoining one of the distal edges of the sides,
the
remaining three lid edges having a closure for mating with the remaining three
distal
edges.
In another aspect of the invention there is a removable liner for placement
inside the container. The liner is formed from a water impermeable plastic
sheet. The
sheet has a periphery. The liner has a quadrilateral base and four sides
extending from
the base to define a chamber therebetween capable of holding water. Each of
the sides
are joined to the base at a base edge. Each of the sides has a pair of lateral
edges each
meeting the base edge at a corner. Each of the sides has an edge opposed to
the base
edge and meets each of the lateral edges at a corner. The sheet has corner
portions
defined between adjacent lateral edges of two of the sides and the periphery
and the
corner positions are folded to lie against the sides.
In a further additional feature of that aspect of the invention the base is a
rectangle and two of the sides, joined to the base on opposite sides of the
rectangle, are
trapezoidal. In a still further additional feature of that aspect of the
invention the
chamber has the shape of an inverted, truncated rectangular based pyramid. In
yet
another additional feature of that aspect of the invention the container has
an internal
face made from a reflective material and the liner is transparent.
In another aspect of the invention there is a soft sided insulated container,
and a
removable liner for placement inside the container. The liner is formed from a
water
impermeable plastic sheet. The sheet has a periphery. The liner has a
rectangular base
and four sides extending from the base to form a chamber therebetween, each of
the
sides being joined to the base at a base edge. The sheet is folded on a first
pair of
parallel fold lines to define one pair of the base edges. The sheet is folded
on a second
pair of fold lines to define the remainder of the edges. The sheet has four
corner
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portions each defined between an end portion of one of the first pair of fold
lines,
an adjacent end portion of one of the second pair of fold lines and the
periphery, and
the corner portions are folded to lie against the sides.
In an additional feature of that aspect of the invention the sides have an
inside
face and an outside face and the corner portions are folded to lie against the
outside
faces. In another additional feature of that aspect of the invention each of
the corners is
folded to form a triangular flap, and each of the flaps is folded to lie
against one of the
sides. In still another additional feature of that aspect of the invention one
of the
triangular flaps is folded to lie against each of the sides of the liner. In
still yet another
additional feature of that aspect of the invention two of the triangular flaps
are folded to
lie against one side of the liner. In a further additional feature of that
aspect of the
invention two of the triangular flaps are folded to lie against one side of
the liner, and
the other two triangular flaps are folded to lie against another side of the
liner.
In still a further additional feature of that aspect of the invention each of
the
sides has a distal edge opposed to its respective base edge. The chamber has a
lip
defined by the distal edges. The corner portions are fastened to the sides
adjacent the
lip. In still yet a further additional feature of that aspect of the invention
one of the
sides has a cover flap formed integrally therewith, and joined thereto at a
cover fold,
the cover flap mating with the distal edges of the remaining sides of the
liner. In an
additional feature of that aspect of the invention the container has a
reflective inner
surface and the liner is transparent.
Brief Description of the Drawintis
These aspects and other features of the invention can be understood by with
the
aid of the following illustrations of a number of exemplary, and non-limiting,
embodiments of the principles of the invention in which:
Figure 1 is a three quarter view, general arrangement drawing of an insulated
container and liner assembly according to the present invention;
Figure 2 is a view of the liner of Figure 1 taken on an opposite angle;
Figure 3 is a developed view of a liner for use in the assembly of Figure 1;
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Figure 4 is a developed view of an alternative liner for an assembly analogous
to the liner of assembly of Figure 1 in which two sides are tapered;
Figure 5 is a developed view of an alternative liner for an assembly analogous
to the liner of assembly of Figure 1 in which four sides are tapered;
5 Figure 6 is a developed view of an alternative liner for an assembly
analogous
to the liner of assembly of Figure 1 in which the forward side of the assembly
is wider
than the rearward side;
Figure 7 is a front view of the assembly of Figure 1, in a collapsed position;
Figure 8 is a rear view of the assembly of Figure 1 in a collapsed position;
Figure 9 is a side view of the assembly of Figure 1 in a collapsed position;
Figure 10; is a section showing the wall construction of the assembly of
Figure
1 and
Figure 11 is a view of an alternative liner for the assembly of Figure 1.
Detailed Description of a Best Mode for Practicinti the Invention
The description which follows, and the embodiments described therein, are
provided by way of illustration of an example of a particular embodiment, or
examples
of particular embodiments, of the principles of the present invention. These
examples
are provided for the purposes of explanation, and not of limitation, of those
principles
and of the invention. In the description which follows, like parts are marked
throughout the specification and the drawings with the same respective
reference
numerals. The drawings are not necessarily to scale and in some instances
proportions
may have been exaggerated in order more clearly to depict certain features of
the
invention.
Referring to the general arrangement illustration of Figures 1 and 2, an
example
of a preferred embodiment of an insulated container and liner assembly
according to
the principles of the present invention is indicated generally as 20. It has
two major
elements, those being an outer casing in the nature of a soft-sided insulated
container
22, and a removable, impermeable liner 24 for placement inside container 22.
An
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optional moveable bulkhead, or baffle, in the nature of a partition wall 25
seats
within line 24 for dividing the interior space into two sub-compartments 27
and 29.
Looking at these major elements in detail, it can be seen that container 22
has a
bottom 26, a front pane128, a rear pane130, and a pair of left and right hand
side panels
32 and 34. In this preferred embodiment the choice of front and rear, left and
right,
orientations is arbitrary. Each of front panel 28, rear panel 30, and left and
right hand
side panels 32 and 34 is joined at sewn seams to bottom 26 at bottom vertices
36, 37,
38, or 39 respectively. Similarly, front panel 28 and side panels 32 and 34
have top
edges 40, 41 and 42, distant from their base edges. Rear panel 30 is joined by
a folded
hinge 44 at its top edge to a top panel in the nature of a lid 46. Lid 46 has
a closure
member in the nature of a zipper 48 extending in a U-shape around the three
free edge
portions of its periphery to mate with the other portions of zipper 48
positioned about
the three top edges 40, 41 and 42 of panels 28, 32 and 34. Lid 46 is moveable
between
a closed position, in which zipper 48 may be zipped closed, and an open
position in
which lid 46 is folded back to permit entry and exit of objects to and from an
internal
cavity 50 defined between bottom 26 and panels 28, 30, 32 and 34. A generally
rectangular insulated auxiliary pouch 52 is mounted to the front face of front
panel 28.
In the preferred embodiment, lid 46 has an extent substantially equal to that
of
bottom panel 26. This need not be the case. Lid 26 could be a small opening
set in a
larger top panel, or could be an opening of half, or some other portion of the
panel.
The opening need not extend fully along three sides of lid 26, but could
extend along
part of one or two sides as may be found suitable in a particular use.
Top edges 40, 41, and 42 form the rim 54 of cavity 50. On the inside of rim 54
is a liner securing means, or liner attachment mounting, in the nature of a
zipper 56,
which, in the embodiment illustrated, includes portions 57, 58, and 59 mounted
respectively to panels 28, 32, and 34 near their upper margins, and a hook and
eye
fabric fastener strip 60 mounted to panel 30. Although this arrangement is
preferred, in
an alternative embodiment all of strip portions 57, 58, 59 and 60 (or some
other
combination of them) could be hook-and-eye fabric fasteners. Other types of
mounting
could be used, in addition to zippers, such as interlocking seal strips,
snaps, clips,
grommets or other means.
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Container 22, with liner 24 installed, can be folded to a collapsed
position, as shown in Figures 7, 8 and 9. In this collapsed, or storage
position, side
panels 32 and 34 fold inward, and bottom 26 folds upward. This permits front
panel 28
to move toward rear panel 30. Lid 46 is then drawn forward and downward in
front of
front panel 28 and auxiliary pouch 52. Lid 46 has, on its inner face, spaced
inwardly
from zipper 48, a retainer in the nature of another hook and eye fastener
strip 62 that
engages a mating hook and eye fastener strip 64 located on a lower portion of
the front
face of auxiliary pouch 52. In addition, left and right hand side retainers 66
and 68
mounted to the left and right hand edges of auxiliary pouch 52 of front panel
28 are
drawn around to fasten to fastening strips 70 and 72 located on the outer,
rearward face
of rear panel 30. (When container 22 is in its open position, strips 66 and 68
engage
storage strips 74 and 76 located on side panels 32 and 34 respectively).
Other features of container 22 are visible in Figures 1 and 2. Front and rear
carrying handles 78 and 80 with reinforced bails are attached to both front
pane128 and
rear panel 30 to permit two people to carry assembly 20 between them. In the
preferred
embodiment assembly 20 has a maximum capacity of 24 quarts. Smaller
embodiments,
include a twelve quart container. A single shoulder strap 79 is attached to
side panels
32 and 34. An elasticized retaining matrix 82 permits other materials, such as
cups,
plates, serving utensils or other objects to be carried on top of assembly 20.
Above
strip 64, auxiliary pouch 52 has a see-through mesh pocket 84, such as may be
convenient for carrying knives, forks, spoons or other objects.
Figure 10 shows a cross section of front pane128 with liner 24 in place. A
scab
section of panel 34 is also shown to reveal its layers of construction. With
the exception
of auxiliary pouch 52, this section is typical not only of front panel 28 but
also,
generally, of rear panel 30, side panels 32 and 34, bottom panel 26 and lid
46. The
outer facing layer of front panel 28 is a canvas covering layer 88 for
resisting abrasion.
It overlays a closed cell foam insulation layer 90. The inner face of
insulation layer 90
is covered by flexible plasticised metallic foil sheeting 92 that is shiny and
reflective.
The material is sold under the name Therma-Flect (T.M.). Liner 24 lies inside
sheeting
92, and is pressed against it by the objects it contains. The inside of pouch
52 is lined
with white vinyl sheeting, 93 on its forward and bottom sides.
Liner 24, is shown in Figures 2 and 3. It is made from a membrane, or web, in
the nature of a sheet 100 of flexible, transparent plastic stock, in
particular, static cling
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vinyl. The shiny, reflective surface of sheeting 92 is visible through liner
24 in
use. Liner 24 has a base 102 and four sides, front, rear, left hand and right
hand
respectively, 104, 106, 108, and 110 extending upwardly from base 102. Each of
sides
104, 106, 108 and 110 is joined to base 102 at a base edge, 112, 114, 116 or
118, as
indicated, and each has an opposite, distal edge 120, 122, 124 or 126 distant
from its
respective base edge. The sides meet at respective upstanding corners 128,
130, 132
and 134. A chamber 136 is defined between base 102 and sides 104, 106, 108 and
110.
Chamber 136 has an opening 138 defined by the peripheral lip 140 formed
collectively
by the distal edges 120, 122, 124 and 126 of sides 104, 106, 108 and 110.
Immediately
below lip 140 liner support fasteners, in the nature of hook and eye strips,
are mounted
to sheet 100. This mounting may be by heat welding or by use of a bonding
agent or
adhesive. In the preferred embodiment lip 140 is folded over to form a hem,
and
fasteners 141, 144, 143 are of the nature of a continuous zipper around three
sides of lip
140, and a fastener 142 in the nature of a fabric hook-and-eye strip are sewn
in place
with stitching 145 that is at a height relative to base 102 that is expected
to be well
above the liquid level in liner 24.
In an alternate embodiment, fasteners 141, 142, and 143 are all fabric hook
and
eye fasteners each mounted on one side of lip 140, and which mate with
corresponding
hook-and-eye fastener strips mounted to container 22. These fastener strips
are
commonly sold under the name Velcro (T.M.). Optional partition 25 is variably
positionable. About the upper portion of its periphery it has a strip engaging
material
146 that catches on mating strips 147 and 148 located on the inner face of
liner 24.
These strips can be hook and eye fastener strips. The range of the strips
permits the
division of sub compartments 27 and 29 of chamber 136 into equal, half-and
half
portions, or into some other portions, such as 1/4 to 3/4, 1/3 to 2/3, 2/5 to
3/5 and so
forth as may be found desirable given the objects to be contained in chamber
136.
In Figure 3 sheet 100 is shown in developed view, as it would be before being
folded to form liner 24. A first pair of parallel fold lines 150 and 152
extend across
sheet 100, and a second pair of parallel fold lines 154 and 156, perpendicular
to lines
150 and 152 extend along sheet 100, thus dividing it into nine portions within
the
rectangular periphery, 158, of sheet 100. It will also be noted that each of
lines 150,
152, 154 and 156 has two intersections, and is thus divided into a central
sector
between the parallel lines it intersects, and a pair of end sectors between
each of the
parallel lines it intersects and the line's termination at periphery 158.
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The central portion of sheet 100, bounded by the central sector of each of
lines 150, 152, 154 and 156, defines base 102, each of those sectors defining
one of
base edges 112, 114, 116 and 118. Front side 104 is defined between the
central sector
160 of line 150, two parallel forward end sectors 162 and 164 of lines 154 and
156,
and a mid-edge sector 166 of periphery 158. Rear side 106 is defined by the
central
sector 168 of line 152, two parallel rearward end sectors 170 and 172 of lines
154 and
156, and a mid edge sector 174 of periphery 158. Left hand side 108 is defined
by
central sector 176 of line 154, two left end sectors 178 and 180 of lines 150
and 152,
and a mid-edge sector 182 of periphery 158. Right hand side 110 is defined by
central
sector 184 of line 156, two right end sectors 186 and 188 of lines 150 and
152, and a
mid-edge sector 190 of periphery 158.
The remaining four portions of sheet 100 are corner portions 192, 194, 196 and
198 defined by a pair of adjacent end sectors of a pair of perpendicular
lines, and a
corner sector of periphery 158, indicated respectively as 202, 204, 206 and
208. Corner
portions 192, 194, 196 and 198 are bisected by diagonal bisectors 212, 214,
216 and
218 which extend from the intersection of the respective perpendicular lines
to
periphery 158.
Having thus defined the geometry of sheet 100, liner 24 is formed by folding
sides 104, 106, 108 and 110 upwardly such that sectors 162 and 178, 164 and
186, 170
and 180, and 172 and 186 lie adjacent to each other to form corners 128, 130,
132 and
134 respectively. This folding necessitates folding of corner portions 192,
194, 196
and 198, and this is done along their respective diagonal bisectors.
When folded along bisectors 202, 204, 206, and 208 corner portions 192, 194,
196 and 198 form triangular flaps 220, 222, 224 and 226. In the preferred
embodiment
flaps 220 and 222 are folded to lie against the outside face of front side
104, the corner
of flap 220 lying most distant from corner 128 overlapping the corner of flap
204 lying
most distant from corner 130. Similarly flaps 224 and 226 are folded to lie
against the
outside face of rear side 106 the most distant corner of flap 224 overlapping
the most
distant corner of flap 226. One edge of each flap lies roughly flush with lip
140, which
is folded over and the entire periphery of opening of chamber 136 sewn as a
hem 228
having a double row of stitches. In this way liner 24 is formed from sheet 100
such that
it is not only free of welded seams, but free of any seams below hem 228 of
lip 140.
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In the preferred embodiment the folding process is purely mechanical, and
can be performed relatively quickly, in contradistinction to heat welding or
adhesive
bonding processes which require a time interval for heating and cooling or for
adhesive
curing. Inasmuch as the preferred embodiment uses a relatively thick static
cling vinyl,
5 sheet 100 can be folded over a cube form of the desired dimensions, and held
in place
by its own clinging properties in preparation for the sewing of hem 228. The
overlap of
the tips of flaps 202 and 204, and flaps 206 and 208, and subsequent sewing
makes it
doubly improbable that liner 24 will unfold.
Liner 24 is formed from a single integral sheet, and, absent punctures of that
10 sheet is not intended to leak below the level of the sewn seam at lip 140.
The body of
base 102 and sides 104, 106, 108 and 110 is seamless, being free of heat welds
or other
joints. In general use the liquid level in chamber 136 is not expected to be
greater than
one half of the height of the sides, and still less commonly to be more than
three
quarters of the height. There are no seams below either of these levels, heat
welded or
otherwise.
Liner 24 is also thin enough that it can be folded inside container 22 when
container 22 is compressed to its collapsed position as illustrated in Figures
7, 8, and 9.
Liner 24 need not be transparent, but could be translucent or opaque. A
transparent
liner is preferred since it permits the reflection of sheeting 92 to be seen.
In an optional embodiment, a liner 224 can have its own closure, or lid, 230,
to
provide a double closure with lid 46 of container 22 in Figure 11. As shown in
Figure
11, optional lid 230 extends on a folding plastic hinge 232 that is an
integral part of
sheet 234 from rear side 236 of sheet 234, and mates at front, left hand and
right hand
side edges 238, 240 and 242 along a U-shaped closure interface such as may be
held
closed by a closure member in the nature of a seal, a zipper, a hook and eye
fabric
fastener, or a similar device. It is not necessary that the opening of the
container, or the
liner, form a parallel plane to the respective base or bottom sides. The
opening could
be in a skewed plane, or could be something other than a plane.
In alternative embodiments, one of each of corner flaps 220, 222, 224 and 226
can be folded against each of sides 104, 106, 108 and 110, or a pair (220,
224) can be
folded against left hand side 108 and another pair (222, 226) against right
hand side
110, rather than against front and rear sides 104 and 106 as illustrated in
Figure 11. It
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is not necessary that the corner portions have one edge lying flush with lip
146.
However, if the corner portions are cut down, the height at which a liquid
tight barrier
is provided may not necessarily be as high as shown in the preferred
embodiment of
Figure 1. It is also not necessary that corner portions 192, 194, 196, and 198
be folded
against the outside faces of the sides, but could be folded to lie along the
inside faces.
It would also be possible to fold each flap to lie partially against one side
and partially
against another side by using more than one fold line and by cutting the
periphery of
the corner portions differently. There is simplicity in using a single fold
and to fold the
flaps against the outside of one side of the liner, as shown in the preferred
embodiment
of Figure 1.
As shown in the developed views of the alternate embodiments of Figures 4, 5,
and 6, the liner need not be a cube or cuboid, but could be a tapered,
trapezoidal, or
truncated pyramidal shape. In the embodiment of Figure 4 a developed sheet 300
has
fold lines for forming a liner having a pair of opposed trapezoidal sides 304
and 306
which rise at right angles from a base 308, and a pair of opposed rectangular
sides that
are folded upward at an angle corresponding to the rake angle I of trapezoidal
sides 304
and 306. It can be seen that there is one pair of parallel fold lines 310 and
312, each
line having a central sector 314, 316 and a pair of left and right end sectors
318, 320 or
322, 324. There is also a pair of fold line sectors 326 and 328 which define
the
remaining two sides of base 308 (perpendicular to sectors 314 and 316). The
intersections of sectors 326, 314, 328, and 316 define the corners of base
308.
Extending away from those corners to periphery 330 are left and right hand
canted
trapezoidal side sectors 332, 334, 336, and 338 to define the remaining
vertices of
trapezoidal sides 304 and 306. At the angular bisector of the included angle
between
adjacent pairs of rectangular side lateral sectors and trapezoidal side
sectors, as, for
example between sectors 318 and 332, are corner portion fold lines 340, 342,
344, and
346. Corner portions 348, 350, 352 and 354, each defined between one
trapezoidal side
end sector, one rectangular side end sector and periphery 330, have been
trimmed along
periphery 330 to lie flush with the resulting lip. When sheet 300 is folded in
a manner
analogous to the folding of sheet 100, a cradle shaped liner will result, for
mating use
with a similarly cradle shaped container analogous to container 22.
In the embodiment of Figure 5 a developed sheet 400 has fold lines for forming
a liner 402 having a first pair of opposed trapezoidal sides 404 and 406 which
rise at a
non-perpendicular angle I from a base 408, and a second pair of opposed
trapezoidal
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sides 410, 412 that are folded upward at an angle corresponding to the
vertical
projection of the rake angle J of the first pair of trapezoidal sides 404 and
406. It can
be seen that there is one pair of fold line sector 414, 416 pairs of left and
right hand end
sectors 418, 420 or 422, 424 and a perpendicular pair of fold line sectors 418
and 420
which define the remaining two sides of base 408. The intersections of sectors
418,
414, 420, and 416 define the corners of base 408. Extending away from those
corners
to periphery 430 are left and right hand trapezoidal side lateral sectors 422,
424, 426
and 428. Similarly, left and right hand canted trapezoidal side sectors 432,
434, 436,
and 438 extend from those intersections toward periphery 430 to define the
remaining
vertices of the trapezoidal sides. At the angular bisector of the included
angle between
adjacent pairs of rectangular side lateral sectors and trapezoidal side
sectors, as, for
example between sectors 418 and 432, are corner portion fold lines 440, 442,
444, and
446 of corner portions 448, 450, 452 and 454.
Sectors 422, 424, 426, 428, 432, 434, 436 and 438 all have the same true
length,
indicated as 1. The distance that sectors 422, 424, 426 and 428 are splayed
outward
from square is indicated as M. Similarly, the distance that sections 432, 434,
436 and
438 are splayed outward from square is indicated as L. Angle I satisfies the
condition
that Sin I=[M/(12-LZ)]'/z. Similarly Angle J satisfies the condition that Sin
J=[L/(12-
L2)]'/z.
When folded in a manner analogous to the folding of sheet 100, sheet 400 will
form a truncated, inverted rectangular shaped pyramid. It should be noted that
the pairs
of opposed slanted pyramid sides need not rise at the same angle, but could be
at
different angles. In the most general case, each side could rise at a
different angle, and
to a different height. The upper edges of the sides need not be level, but
could have a
slant, or, alternatively, need not be linear but could be curved as may suit
the desired
geometry. However, it is expected that the sides will, most often, have
straight and
level edges.
In the embodiment of Figure 6, a developed sheet 500 has fold lines for
forming
a liner 502 having a trapezoidal base 504 such as might be desired in a
knapsack having
a large rearward face for placement against a person's back, and a narrower
outer or
forward face. A pair of parallel lines of unequal length, being a short front
fold line
506 and a longer rear fold line 508, define the parallel sides of the
trapezoidal base 504.
A pair of left and right hand side fold lines 510 and 512 extend between lines
506 and
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508 at angles to define the splayed sides of trapezoidal base 504. Front side
514,
rear side 516, left side 518 and right side 520 are all hinged along
respective fold lines
506, 508, 510 and 512 to base 504. Corner portions 522, 524, 526 and 528 are
defined
between the periphery 530 and respective pairs of side sectors 532 and 534,
536 and
538, 540 and 542, and 544 and 546. Each of portions 522, 532, 526 and 528 has
a fold
line 548, 550, 552 or 554 on which the respective corner portion is folded,
those
portions being trimmed along their peripheral edges to lie flush with the
peripheral
edges of the respective sides against which they are folded, similar to the
manner
described above in connection with the preferred embodiment.
A preferred embodiment has been described in detail and a number of
alternatives have been considered. As changes in or additions to the above
described
embodiments may be made without departing from the nature, spirit or scope of
the
invention, the invention is not to be limited by or to those details, but only
by the
appended claims.
